and

ABSTRACT BOOK

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Local Organizing and Program Committee Salomon S. Mizrahi (UFSCar, Chairman) Vanderlei Bagnato (IFSC-USP) Viktor V. Dodonov (UnB) Miled H.Y. Moussa (IFSC-USP) Paulo Nussenzveig (IF-USP) Marcos C. de Oliveira (UNICAMP) Gustavo G. Rigolin (UFSCar) José A. Roversi (UNICAMP) Celso J. Villas-Bôas (UFSCar)

International Organizing Committee Young S. Kim (College Park, USA) Vladimir Man’ko (Moscow, Russia) Jan Perina Jr (Olomouc, Czech Rep.) Apostolos Vourdas (Bradford, UK)

International Advisory Board Marco Bellini (Florence, Italy) Mario Bertolotti (Roma, Italy) Akira Furusawa (Tokyo, Japan) Guan-Can Guo (Beijing, China) Mark Hillery (New York, U.S.A.) Andrei Klimov (Guadalajara, Mexico) Gershon Kurizki (Rehovot, Israel) Ulf Leonhardt (St. Andrews, U.K.) Gerd Leuchs (Erlangen, Germany) Luigi Lugiato (Como, Italy) Margarita Man´ko (Moscow, Russia) Antonino Messina (Palermo, Italy) Miguel Orzsag (Santiago, Chile) Saverio Pascazio (Bari, Italy) Juan Pablo Paz (Buenos Aires, Argentina) Martin Plenio (Ulm, Germany) Luis L. Sánchez-Soto (Madrid, Spain) Ryszard Tanaś (Poznan, Poland) Malvin Carl Teich (Boston, U.S.A.) Werner Vogel (Rostock, Germany) Dirk Gunnar Welsch (Jena, Germany) Edited by Daniel Z. Rossatto (UFSCar, Brazil).

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The Conferences: brief historical retrospective International Conferences on Squeezed States and Uncertainty Relations (ICCSUR) The ICSSUR conferences occur every two years, alternating roughly the location between Europe and North America. The name of the ICSSUR says it all about the range of themes of the presentations, although it has incorporated many more, in realm of experimental as well as theoretical physics. The first ICSSUR occurred at the University of Maryland, Campus of College Park (UMCP) in March 1991, and was organized as a Workshop by Professor Young S. Kim, in collaboration with Dr. D. Han (NASA) and Prof. W. Zachary from Howard University. The duration of the workshop was three days, and it gathered about 50 leading researchers from different countries. The majority of talks were devoted to "squeezed states of photons," that was already a hot subject in quantum optics. Animated by the success of the first meeting and impressive results obtained by many groups in Europe, Professor Kim suggested making the second workshop in 1992 in Moscow. It was, indeed, organized in May 1992 by the team of the Lebedev Physical Institute of the Russian Academy of Sciences (V.V. Dodonov, V.A. Isakov, M.A. Man’ko, V.I. Man’ko, A.V. Vinogradov and V.N. Zaikin). The third episode of the series happened again in the University of Maryland, but now in Campus of Baltimore County (UMBC), in 1993, having been organized by Professors N.H. Rubin and Y.-H. Shih with the help of D. Han, Y.S. Kim and W.W. Zachary. From then on, it became unequivocal that this sequence of meetings had acquired a respectable level of maturity that could permit the continuation not only in theoretical and experimental quantum optics. So, it embraced other frontier themes as fundamental problems in quantum mechanics, mathematical physics methods, old and new experimental methods in light and matter, and so on. After 1993 the status of the workshop was raised to the status of International Conference and establishing a periodicity of two years. Subsequently, the fourth ICSSUR occurred in China, in 1995, at Shanxi University, organized by Professor Kunchi Peng. The fifth ICSSUR happened in 1997, in the city of Balaton, Hungary, having been organized by Professor Janszki. A sixth ICSSUR was in 1999, the chosen location being the University of Naples, Italy. It was organized by professor S. Solimeno. The seventh ICSSSUR occurred in 2001 at the University of Boston (MA, EUA), having been organized by Professors M.C. Teich, A.V. Sergienko and B.E.A. Saleh. In 2003 the eighth ICSSUR happened in Mexico, held at the University of Puebla, Mexico, and organized by Professors H. Moya-Cessa, R. Jáuregui, S. Hacyan, and O. Castaños. A ninth ICSSUR was in 2005 held at the University of Besançon, France, organized by Professor M. Planat. The tenth ICSSUR was in 2007 at the University of Bradford, UK, organized by Professor A. Vourdas. The eleventh ICSSUR occurred in 2009 at Palacký University, Olomouc, Czech Republic and was organized by Professor Jan Perina Jr. This series of events was maintained during 20 years due to enthusiasm and efforts of three persons participated in all 11 conferences: Young S. Kim, Vladimir I. Man’ko, and Margarita A. Man’ko. And now the twelfth chapter of ICSSUR is being held for the first time not only in South America but in the South Hemisphere, in a five star hotel, the Mabu Resort, in Foz do Iguaçu, state of Paraná, Brazil, nearby the famous Iguaçu (Iguassu or Iguazu) falls. For more information and accessing the lists of participants of the previous ICSSUR go to the site http://www2.physics.umd.edu/~yskim 3

The Feynman Festivals (FEYNFEST) The first three FEYNFEST were held at the University of Maryland, Campus of College Park (UMCP), in the years 2002, 2004, and 2006. They were organized by Professor Young S. Kim. The fourth FEYNFEST occurred in 2009 at Palacký University, Olomouc, Czech Republic, simultaneously with the ICSSUR. The FEYNFEST was idealized to honor Richard P. Feynman and to remember his scientific legacy. In principle, the contributions are devoted to themes along the lines of research approached by Richard Feynman, a quite wide variety of subjects, going from particle physics to quantum computation. By doing a retrospective of the works presented in the previous three FEYNFEST, one finds out that the dominant themes are: quantum computing, fundamentals of quantum mechanics and quantum optics. For more information and to have access to lists of participants of the previous FEYNFEST go to the site http://www2.physics.umd.edu/~yskim

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Registered participants Adiga, Veena, Department of Physics, Yuvaraja's College, University of Mysore, Mysore-05, INDIA Aguiar, Leandro S., Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas, SP, Brazil Alcalde, Augusto M., Instituto de Física, Universidade Federal de Uberlândia, Uberlândia – MG, Brazil Alekseev, Pavel S., Ioffe Institute, Saint Petersburg, Russia Angelo, Renato M., Universidade Federal do Paraná, Curitiba, PR, Brazil Auccaise, Ruben, EMBRAPA, Brazil Avelar, Ardiley T., Instituto de Física, Universidade Federal de Goiás, Goiânia, Goiás, Brazil Bagnato, Vanderlei S., Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil Barbosa, Felippe A. S., Universidade de São Paulo – USP, São Paulo – SP, Brazil Batalhão, Tiago B., Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil Beckwith, Andrew, Chongquing University, Dept. of physics, Chongquing, PRC Bellini, Marco, Istituto Nazionale di Ottica - CNR, Florence, Italy and Department of Physics, University of Florence, Italy Boscá, María C., University of Granada. Facultad de Ciencias. Dpto. Física Atómica y Nuclear, Spain Braga, Helena, Departamento de Física, Universidade Federal de São Carlos, São Carlos, SP, Brazil Brasil, Carlos A., Instituto de Física de São Carlos (IFSC) / Universidade de São Paulo (USP), Brazil Brod, Daniel J., Instituto de Física, Universidade Federal Fluminense, Niteroi, Brazil Caldeira, Amir O., IFGW – Universidade Estadual de Campinas, Campinas, SP, Brazil Canosa, Norma, Departamento de Física, IFLP, Universidad Nacional de La Plata - CONICET - CIC – Argentina Cardoso, Wesley B., Instituto de Física, Universidade Federal de Goiás, Goiânia, Goiás, Brazil Caruso, Filippo, Institute of Theoretical Physics, Ulm University, Ulm, Germany Céleri, Lucas, Universidade Federal do ABC, Santo André – SP, Brazil Chew, Lock Y., Nanyang Technological University, Singapore Cirac, Juan I., Max-Planck Institute of Quantum Optics, Hans-Kopfermann- Str. 1 - Garching – Germany 5

Cornelio, Marcio F., Universidade Estadual de Campinas - IFGW/DFMC, Campinas - SP, Brazil Costa, Ana C. S., Universidade Federal do Paraná, Curitiba, PR, Brazil da Cruz, Luciano S., Universidade Federal do ABC, Santo André – SP, Brazil da Silva Jr., Milton A., Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Brazil da Silva, Luciano F., Instituto de Física, Universidade Federal de Goiás, Goiânia (GO), Brazil da Silva, Raphael Dias, Universidade Federal Fluminense, Brazil Davidovich, Luiz , Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil de Almeida, Norton G., IF/UFG- Universidade Federal de Goiás, Goiânia – GO, Brazil de Castro, Leonardo A., Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil de Lima, João P. C., Universidade Tecnológica Federal do Paraná ,Toledo - PR – Brazil de Miranda, Marcio H. G., JILA, NIST and University of Colorado at Boulder, USA de Oliveira, Marcos C., Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas SP, Brazil de Oliveria, Thiago R., Universidade Federal Fluminense, Niterói – RJ, Brazil de Sá Neto, Olímpio P., Universidade Estadual de Campinas, Brazil De Siena, Silvio, DMI, Università di Salerno, Fisciano (SA), Italy de Souza, Douglas D., DEQ - IFGW - UNICAMP, Campinas - SP – Brazil Dehesa, Jesus S., University of Granada, Spain Delsing, Per, Chalmers University of Technology, Goteborg, Sweden Di Lorenzo, Antonino, Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, Brazil Dodonov, Viktor V., Instituto de Fisica, Universidade de Brasília, Brasília, Brazil dos Reis, Paulo J., Universidade Estadual de Londrina, Londrina – PR, Brazil Dusek, Miloslav, Department of Optics, Palacky University, Olomouc, Joint Laboratory of Optics of Palacky University and Institute of Physics of Academy of Sciences of the Czech Republic Escher, Bruno M., Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro (RJ), Brazil Fanchini, Felipe, Universidade Federal de Ouro Preto, Ouro Preto – MG, Brazil Farias, Osvaldo J., Instituto de Fisica, Universidad Federal do Rio de Janeiro , Brazil 6

Farias, Reginaldo J. C., Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, Campinas - SP, Brazil. Figueroa, Eden, Max-Planck-Institut für Quantenoptik, Garching, Germany Filgueiras, Jefferson G., Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro/RJ – Brazil Freitas, Nahuel, Departamento de Física, FCEyN, UBA, Buenos Aires, Argentina Fresneda, Rodrigo, UFABC, Santo André, Brazil Furuya, Kyoko, Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas, SP, Brazil Gabriel, Christian, Max Planck Institute for the Science of Light, Erlangen, Germany and Institute of Optics, Information and Photonics, University Erlangen, Erlangen, Germany Gallego, María A., Pontificia Universidad Católica de Chile, Santiago, Chile Galvão, Ernesto F., Instituto de Física, Universidade Federal Fluminense, Niterói – RJ, Brazil Gatti, Alessandra, IFN-CNR and Dept. Of Physics and Mathematics, Insubria University, Como, Italy Gavenda, Miroslav, Dept. Of Optics & Joint Laboratory of Optics, Palacky University & Academy of Sciences of the Czech Republic, Olomouc - Czech Republic Gitman, Dmitri, Institute of Physics, USP, Brazil Gomes, Raphael F. I., UFSCAR, São Carlos, SP, Brazil González, Julio C., Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas, SP, Brazil Herrera, Alba M., Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, Santo André, SP, Brazil Johansson, Göran, Microtechnology and Nanoscience, MC2, Chalmers University of Technology, Göteborg, Sweden Jonathan, Daniel, Instituto de Física, Universidade Federal Fluminense, Niterói, Brazil Khoury, Antonio Z., Instituto de Fisica - Universidade Federal Fluminense, Niteroi - RJ – Brazil Kim, Young S., Center for Fundamental Physics, University of Maryland, College Park, Maryland, USA Lassen, Mikael, Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark Lavoie, Jonathan, Institute for Quantum Computing and Department of Physics & Astronomy, University of Waterloo, Waterloo, Canada

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Lemos, Gabriela B., Instituto de Fisica/Universidade Federal do Rio de Janeiro, Brazil Lemr, Karel, Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Sciences of the Czech Republic, Czech Republic Leuchs, Gerd, Max Planck Institute for the Science of Light, Erlangen, Germany and Department of Physics, University of Erlangen-Nuremberg, Germany Lobo, Augusto C., Department of Physics, Federal University of Ouro Preto, Brazil López, Raquel, Arizona State University, Physical Sciences, Tempe, Arizona, USA Lopez-Ruiz, Francisco F., Institute of Astrophysics of Andalusia – CSIC, Glorieta de la Astronomia - Granada – Spain Lozada, Alejandro C., Universidade Estadual de Campinas, Campinas – SP, Brazil Luiz, Fabricio S., Federal University of São Carlos, São Carlos – SP, Brazil Lunardi, José T. T., Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, Brazil Luthra, Jagdish, Departamento de Fisica, Universidad de Los Andes, Bogota, Colombia Maciel, Thiago O., Departamento de Física - ICEx - Universidade Federal de Minas Gerais, Belo Horizonte MG - Brazil Mandilara, Aikaterini, Universite Libre de Bruxelles, Quantum Information and Communication, Ecole Polytechnique, Bruxelles, Belgium Man'ko, Margarita A., P.N. Lebedev Physical Institute, Moscow ,Russia Man'ko, Vladimir I., P.N. Lebedev Physical Institute, Moscow, Russia Mann, Ady, Technion, Physics Department, Technion City - Haifa - Israel Manzoni, Luiz A., Concordia College, Moorhead, USA Marchiolli, Marcelo A., Instituto de Física Teórica, Universidade Estadual Paulista, São Paulo, SP, Brazil Marek, Petr, Department of Optics, Palacky University, Czech Republic Marino, Alberto M., Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, USA Marques, Breno, Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG – Brazil Martinelli, Marcelo, IF-USP, São Paulo, Brazil Maziero, Jonas, Universidade Federal do ABC, Brazil

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Mendonça, José T., IPFN, Instituto Superior Técnico, Lisboa, Portugal Meneguele, Hugo L. O., Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, Campinas, SP, Brazil Messina, Antonino, Dipartimento di Fisica, Università di Palermo, Palermo, Italy Milburn, Gerard J., The Univerity of Queensland, Brisbane, Australia Militello, Benedetto D., Dipartimento di Fisica dell'Università di Palermo, Palermo, Italy Mitchell, Morgan W., ICFO - Institute of Photonic Sciences, Castelldefels (Barcelona) – Spain Mizrahi, Salomon S., Federal University of São Carlos, São Carlos, SP, Brazil Moussa, Miled H. Y., Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil Mueller, Markus, University of Innsbruck, Austria Muschik, Christine A., Max-Planck-Institut fuer Quantenoptik, Garching, Germany, and Niels Bohr Institute, Danish Quantum Optics Center – QUANTOP, Copenhagen University, Copenhagen, Denmark Napolitano, Mario, ICFO-Institut of photonic sciences, Castelldefels – Spain Nemes, Maria C., Universidade Federal de Minas Gerais, Belo Horizonte, Brazil Neto, Gentil D. M., Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil Neves, Leonardo, Center for Optics and Photonics, Universidad de Concepción, Chile Nicacio, Fernando, Instituto de Física "Gleb Wataghin'', Universidade Estadual de Campinas, Campinas, SP, Brazil Nussenzveig, Paulo, IF-USP, São Paulo, Brazil Oberthaler, Markus, University of Heidelberg, Kirchhoff-Institute of Physics, Heidelberg, Germany Paz, Juan P., Departamento de Física, FCEyN, Universidad de Buenos Aires, Argentina Pedraza-Saavedra, Luis-Gerardo, Pontificia Universidad Javeriana, Cali, Colombia Peixoto de Faria, José G., Departamento de Física e Matemática, Centro Federal de Educação Tecnológica de Minas Gerais, Belo Horizonte - MG, Brazil Peřina Jr., Jan, Palacky University, RCPTM, Joint Laboratory of Optics, Olomouc, Czech Republic Poulios, Konstantinos,Centre for Quantum Photonics, School of Physics, University of Bristol, UK Pramanik, Tanumoy, Bose Institute, University of Oxford, S. N. Bose National Centre For Basic Science, Kolkata, India Ribeiro, Alexandre D., Departamento de Física, Universidade Federal do Paraná, Curitiba, PR, Brazil 9

Richardson, Chris D., Department of Physics and Astronomy, Louisiana State University, Baton Rouge, USA Rigolin, Gustavo, Federal University of São Carlos, São Carlos, SP, Brazil Romera, Elvira, Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Granada, Spain Rossatto, Daniel Z., Department of Physics, Federal University of São Carlos, São Carlos - SP, Brazil Rossignoli, Raul, Depto. de Física-IFLP, Universidad Nacional de La Plata, CIC-CONICET, Argentina Roversi, José A., Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas - SP, Brazil Ruby, V. Chithiika, Research Scholar, Centre for Nonlinear Dynamics, School of Physics, Bharathidasan University, Tamilnadu, India Rudnicki, Lukasz, Center for Theoretical Physics PAS, Warsaw, Poland Rulli, Clodoaldo C., Instituto de Física, Universidade Federal Fluminense, Niterói - RJ, Brazil Ruzzi, Maurizio, Instituto de Física Teórica – UNESP, São Paulo - SP, Brazil Samblowski, Aiko, Institut für Gravitationsphysik, Leibniz Universität Hannover and Max-Planck Institut für Gravitationsphysik, Hannover, Germany Sanders, Barry C., University of Calgary, Canada Santos, Marcelo F., Universidade Federal de Minas Gerais, Belo Horizonte, Brazil Sanz, Liliana, Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, Brazil Schnabel, Roman, Albert-Einstein-Institut, Leibniz Universität Hannover, Hannover, Germany Schreiber, Andreas, Max Planck Institute for the Science of Light, Erlangen, Germany Semenov, Andrii A., Institut fuer Physik, Universitaet Rostock, Germany and Institute of Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine Serra, Roberto M., Federal University of ABC (UFABC), Santo André, São Paulo, Brazil Shaterzadeh-Yazdi, Zahra, Institute for Quantum Information Science, University of Calgary, Calgary, Alberta, Canada Simon, Rajiah, The Institute of Mathematical Sciences, Tharamani - Chennai – India Solomon, Allan, Open University (UK) and University of Paris VI, France Souza, James A., Federal University of São Carlos, São Carlos – SP, Brazil Sperling, Jan, Arbeitsgruppe Quantenoptik, Institut fuer Physik, Universitaet Rostock, Rostock, Germany 10

Summer, Ilyssa, Arizona State University,Tempe Tempe, USA Suslov, Sergei, School of Mathematical and Statistical Sciences, Arizona State University, Tempe, USA Svozilík, Jiří, Joint Laboratory of Optics, RCPTM, Palacky University, Olomouc, Czech Republic Sych, Denis, Max Planck Institute for the Science of Light, Erlangen, Germany Taketani, Bruno G., Universidade Federal do Rio de Janeiro (Brazil), and Universität Freiburg, Germany Tanatar, Bilal, Bilkent University, Department of Physics, Ankara, Turkey Tapia, Ramon M., Dept. of Physics, Universitat Autonoma Barcelona, Bellaterra (Barcelona), Spain Tollaksen, Jeff, Chapman University, Orange, USA Toscano, Fabricio, Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, - RJ, Brazil Traina, Paolo, INRIM, Turin, Italy Vallejos, Raul O., CBPF, Rio de Janeiro, Brazil Vega-Guzman, Jose M., Arizona States University, Tempe, USA Vera, John L., Instituto de Física Gleb Wataghin, UNICAMP, Brazil Vidiella-Barranco, Antonio, Universidade Estadual de Campinas, Campinas, SP, Brazil Villas-Boas, Celso J., Departamento de Física, Universidade Federal de São Carlos, São Carlos, Brazil Vourdas, Apostolos, University of Bradford, UK Walborn, Stephen, Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil Wallentowitz, Sasha, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Santiago, Chile Wang, Jingbo, The University of Western Australia, Perth, Australia Weber, Paulo E. R., UnB, Brasília – DF, Brazil Werlang, Thiago, Federal University of São Carlos, São Carlos, SP, Brazil Yabu-uti, Bruno F. C., Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas SP, Brazil Zagury, Nicim, Universidade Federal do Rio de Janeiro, Brazil Zambrano, Eduardo, Centro Brasileiro de Pesquisas Fisicas – CBPF, Rio de Janeiro, Brazil Znidaric, Marko, ICF, UNAM, Mexico and FMF, University of Ljubljana, Slovenia

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Zurek, Wojciech H., Theory Division, Los Alamos National Laboratory, Los Alamos, USA Zypman, Fredy, Department of Physics, Yeshiva University, New York, USA

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PLENARY TALKS

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Quantum process tomography with coherent states Barry C. Sanders University of Calgary, Canada Abstract A general quantum optical process can be fully characterized by injecting coherent states and performing optical homodyne tomography on the output states: nonclassical input states are surprisingly not required, even for nonclassical quantum processes [1,2]. As the Hilbert space is infinite dimensional, representations of states and processes must be regularized, e.g. truncated. I discuss and compare two of our approaches: a filtered Glauber–Sudarshan method vs a truncated Fock representation. Our method is applicable to multi-mode processes and to non-trace-preserving optical processes. [1] M. Lobino, D. Korystov, C. Kupchak, E. Figueroa, B. C. Sanders and A. I. Lvovsky, Complete characterization of quantum-optical processes, Science 322(5901): 563-566, 2008. [2] S. Rahimi-Keshari, A. Scherer, A. Mann, A. T. Rezakhani, A. I. Lvovsky and B. C. Sanders, Quantum process tomography with coherent states, New Journal of Physics 13: 013006 (17 pp.), 2011.

Quantum measurement and control in optomechanical systems Gerard J. Milburn The Univerity of Queensland, Brisbane, Australia Abstract The emerging field of quantum optomechanics combines quantum optics and new fabrication techniques to control the quantum state of macroscopic mechanical resonators. This now provides a new approach for controlling the mutual interaction between light and mesoscopic structures, which is one of the eminent goals in quantum information science and of importance for fundamental experiments at the quantum-classical boundary. I will give an overview of this new field and discuss some specific models. These include a scheme to conditionally prepare a macroscopic mechanical resonator in an energy eigenstate by measurement, single photon optomechanics, and quantum entanglement in optomechanical networks.

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Efficient descriptions of quantum many-body systems Juan Ignacio Cirac Max-Planck Institute of Quantum Optics, Hans-Kopfermann-Str. 1 - Garching – Germany Abstract Quantum many-body systems are very hard to describe, since the number of parameters describing their quantum state increases exponentially with the number of particles. In practice, even for spin ½ particles, one can only treat the exact dynamics and equilibrium properties of up to 30 of them with the help of the most powerful computational methods. In this talk I will report on ideas and methods coming from the field of Quantum Information Theory to treat many-body systems. They are useful for problems where particles lie on regular lattices and are subjected to short-range interactions. They are based on the so called projected entangled-pair states (PEPS), which is a family of states that provides us with a very efficient description of certain classes of states that naturally appear in condensed matter systems.

Ultimate precision limits in noisy quantum-enhanced metrology B. M. Escher, R. L. de Matos Filho, and Luiz Davidovich* Instituto de Física, Universidade Federal do Rio de Janeiro, 21941-972 Rio de Janeiro, RJ, Brazil Abstract The estimation of parameters characterizing dynamical processes is central to science and technology. The estimation error decreases with the number N of resources employed in the experiment (which could quantify, for instance, the number of probes or the probing energy). Typically, it scales as one over the square root of N. Quantum strategies may improve the precision, for noiseless processes, so that it scales with 1/N. For noisy processes, it is not known in general if and when this improvement can be achieved. Here we propose a general framework for obtaining attainable and useful lower bounds for the ultimate limit of precision in noisy systems. We apply this bound to lossy optical interferometry and atomic spectroscopy in the presence of dephasing, showing that it captures the main features of the transition from the 1/N to the one over square root of N behavior as N increases, independently of the initial state of the probes, and even with use of adaptive feedback. B. M. Escher, R. L. de Matos Filho, and L. Davidovich, Nature Physics (2011).

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Quantum Atom Optics: Atomic spin squeezed and Einstein – Podolsky – Rosen entangled states Markus Oberthaler University of Heidelberg, Kirchhoff-Institute of Physics, Heidelberg, Germany Abstract Bose Einstein condensates allow the experimental implementation of very different routes for the deterministic generation of atomic entanglement. Here we report on two different routes to generate highly entangled states with this experimental system employing inter-species Feshbach enhanced interactions as well as spin changing collisions. For the generation of spin squeezed states we employ two hyperfine ground states of Rubidium which can be coupled via a two photon transition. By tuning a magnetic field close to a Feshbach resonance the system can be realized in the miscible regime with significant interaction between the two species. With that system 8.3dB spin squeezing [1] has been realized. The high level of experimental control leads to an almost Heisenberg limited squeezed state which implies strong many particle entanglement. Employing the entanglement witness for the depth of entanglement developed by Sørenson and Mølmer [2] one can claim that at least 80 particles out of 400 are entangled within three sigma confidence level. With this massive quantum resource it was possible to demonstrate explicitly the improvement of a Ramsey type matterwave interferometer beyond the classical precision limit. Since the squeezing is realize within the first beamsplitter of the interferometer while the input stat e is a classical coherent state we refer to this setup as nonlinear matterwave interferometer. For the generation of mode entangled states we have employed spin changing collisions in a situation where the single external mode approximation can be applied. Beside the observation of 12dB suppression below shot noise of particle number difference fluctuations we have also extracted information about the sum of the phases of the fields in the two modes. This has been achieved by implementing a novel homodyning technique allowing for measuring one of the di-atom quadratures. The observations reveal that continuous variable entanglement classified as Einstein-Podolsky-Rosen entanglement is present. [1] C. Gross, T. Zibold, E. Nicklas, J. Esteve and M. K. Oberthaler, “Nonlinear atom interferometer surpasses classical precision limit” Nature 464, 1165 (2010). [2] A. Sørensen, and K. Mølmer, “Entanglement and extreme spin squeezing” Phys. Rev. Lett. 86, 4431 (2001).

Squeezed states, uncertainty relations, and quantum information science Rajiah Simon The Institute of Mathematical Sciences, Tharamani - Chennai – India Abstract Quantum information science of canonical (continuous variable) systems is dominated by Gaussian states on the one hand and channels which preserve Gaussianity (Bosonic Gaussian channels) on the other. Nonclassicality of two-mode squeezed states forms the primary source of entanglement in this scenario. The generalized multimode uncertainty relations formulated in a symplectically covariant manner is the bedrock on which most of the analysis in this field is built, phase space methods of quantum optics and symplectic groups acting as principal tools. The talk will review the enormous progress that has become possible in recent years, thereby setting the stage for presenting some new results.

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Quantum Theory of the Classical Wojciech H. Zurek Theory Division, Los Alamos National Laboratory, Los Alamos, USA Abstract I will discuss three insights into the transition from quantum to classical. I will start with (i) a minimalist (decoherence-free) derivation of preferred states. Such pointer states define events (e.g., measurement outcomes) without appealing to Born's rule that relates probabilities with amplitudes. Probabilities and (ii) Born’s rule can be derived from the symmetries of entangled quantum states. With probabilities at hand one can analyze information flows from the system to the environment in course of decoherence. They explain how (iii) the robust “classical reality” arises from the quantum substrate by accounting for objective existence of pointer states of quantum systems through redundancy of their records in the environment. Taken together, and in the right order, these three insights elucidate quantum origins of the classical. W. H. Zurek, Quantum Darwinism Nature Physics 5, 181-188 (2009).

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INVITED SPEAKERS

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Exploring the spatio-temporal correlation of twin photons via sum frequency generation Alessandra Gatti*1,2, E.Brambilla2, O. Jedrkiewicz2, J.L. Blanchet2 and L. Lugiato2 1

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IFN-CNR, Dept. Of Physics and Mathematics, Insubria University, Via Valleggio 11, Como, Italy Abstract

The entangled photon pairs (biphotons) produced by parametric down-conversion (PDC) are the key elements for several quantum information and communication schemes. Recent theoretical investigations by some of us [1-3] revealed the peculiar structure of the biphoton correlation characterizing the entanglement of twin photons in the space-time domain. In type I PDC, the spatiotemporal correlation is indeed characterized by a X-shaped geometry, which turns out to be nonfactorable in space and time, offering thus the relevant possibility of manipulating the temporal bandwidth of biphoton entanglement by acting on their spatial degrees of freedom. The name "Xentanglement" was coined to describe this geometry. A key feature emerged is the extreme spatial and temporal localization of the biphoton correlation, in the micrometer and femtosecond range, which is present only when biphotons are detected in the near field at the crystal exit face. From an experimental point of view, exploring the highly localized X-shape of the biphoton correlation is extremely challenging because i) it requires a temporal resolution in the femtosecond range, as well as the detection of a huge temporal bandwidth of PDC, and ii) both the spatial and the temporal degrees of freedom of twin photons have to be carefully controlled independently. We concentrate on a scheme where the PDC correlation is measured trough the inverse process of sum-frequency generation (SFG) occurring in a second crystal identical to the first one. Such a technique has been used to study the temporal correlation of twin photons, by introducing a controlled delay between them. We aim to implement it in the full spatiotemporal domain, by inserting both a temporal delay and a spatial shift between the twin beams generated from the PDC crystal, thus enabling us to investigate the full spatio-temporal correlation of twin photons. We present a careful analysis of a such a scheme: we discuss the crucial issue of the visibility of the biphoton correlation against the incoherent SFG background, originating from the random up-conversion of uncorrelated PDC photons, and we study the spatio-temporal properties of the SFG light, showing that both spectral and far-field measurements allow us to isolate the coherent component containing the information on the PDC correlation, thereby improving drastically its visibility. We shall present preliminary experimental results that confirm this prediction. Contrary to the HOM interferometry, the SFG scheme is sensitive to dispersion. Therefore, due to the huge bandwidth involved, an achromatic imaging of the PDC light onto the SFG crystal has to be implemented. By reproducing the narrow spectrum of the pump beam in the coherent SFG component, we give evidence that the phase conjugation of twin beams can be preserved over a huge bandwidth. [1]A. Gatti, E. Brambilla, L. Caspani, O. Jedrkiewicz, and L.A. Lugiato, Phys. Rev. Lett. 102, 223601 (2009) [2]L. Caspani, E. Brambilla and A. Gatti, Phys. Rev A, 81, 033808 (2010). [3]E. Brambilla, L. Caspani, L. A. Lugiato and A. Gatti, Phys. Rev. A 82, 013835 (2010)

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Links to Entanglement Allan Solomon Open University and University of Paris VI Abstract We elaborate on the relation between topological links and entanglement for multi-partite systems. We exemplify by the case of tri-partite systems, for which we exhibit the topological links corresponding to two states which are locally unitarily transformable. Nevertheless, these states have obviously different quantum entanglement properties. We find explicit unitary representations of the appropriate braid group (B3) which implement the quantum state transformations, and also describe the associated links. We indicate generalizations of this approach to higher order multipartite systems.

Quantum dynamics of two Brownian particles Amir O. Caldeira IFGW – Universidade Estadual de Campinas, Campinas, SP, Brazil Abstract In this talk we present a generalization of a well-known “system-plus-reservoir” model – which has been used for describing the quantum Brownian motion of a single particle – in order to deal with the problem of the quantum dynamics of two such particles immersed in a common medium. This new model predicts that the two particles perform independent Brownian motion if they are placed far away from one another. One the other hand, if they are brought closer together, an effective interaction mediated by the environment may result. The Feynman – Vernon approach for dealing with the dynamics of the reduced density operator of the two particles is then applied to the situation at which the initial state of this system is described by a two mode squeezed state and the subsequent dynamics of the initial entanglement present in the system is numerically analyzed. The final equilibrium state and the possibility it still stores finite entanglement is also discussed.

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Quantum systems with variables in GF(pn) Apostolos Vourdas University of Bradford, UK Abstract A quantum system in which the positions and momenta take values in the ring Zd (the integers modulo d), is considered. The Heisenberg-Weyl group HW(Zd) of displacements in the Zd x Zd phase space, the symplectic group Sp(2,Zd), and Wigner and Weyl functions, are studied. When d is equal to a prime number p, the Zp is a field and the system has stronger properties. For example, the number of mutually unbiased bases is equal to the maximum possible value p+1. Also the order of the symplectic group is in general |Sp(2,Zd)|=dJ2(d)≤ d3-d (where J2(d) is the Jordan totient function) and when d is equal to a prime number p, the inequality becomes equality. Motivated by this we also study a quantum system in which the positions and momenta take values in the Galois field GF(pn). Such a system is comprised of n component systems, each of which has positions and momenta in Zp, and which are coupled in a particular way. In general such a system is described with variables in Zpn, but due to the special coupling (described by a certain class of Hamiltonians), we can express the entire formalism, in terms of variables in GF(pn). We say that these Hamiltonians are compatible with GF(pn). We partition the set of all Hamiltonians of the n-partite system into two subsets which contain the Hamiltonians which are compatible with GF(pn) and the rest of them. Systems with variables in GF(pn) are not readily available in nature, but they can be engineered by coupling the n component systems as described by one of the Hamiltonians which are compatible with GF(pn). The Heisenberg-Weyl group HW[GF(pn)] of displacements in the GF(pn)×GF(pn) phase space, the symplectic group Sp(2, GF(pn)), and Wigner and Weyl functions, are studied in this context. Frobenius symmetries (which are based on Frobenius automorphisms in the theory of Galois fields) are a unique feature of these quantum systems (for n ≥ 2). A. Vourdas, J. Phys A40, R285 (2007). A. Vourdas, J. Math. Phys., 51, 052102 (2010).

Aharonov-Bohm effect and coherent states in magnetic-solenoid field Dmitri Gitman*, V. G. Bagrov, S. Gavrilov, D. Meira Institute of Physics USP, Brazil Abstract We construct coherent states (CS) and semiclassical states (SS) in magnetic-solenoid field. The main idea is based on the fact that the AB solenoid breaks the translational symmetry in the xy-plane, this has a topological effect such that there appear two types of trajectories which embrace and do not embrace the solenoid. Due to this fact, one has to construct two different kinds of CS/SS, which correspond to such trajectories in the semiclassical limit. Following this idea, we construct CS in two steps, first the instantaneous CS (ICS) and the time dependent CS/SS as an evolution of the ICS. The construction is realized for nonrelativistic and relativistic, spinning and spinless particles both in (2+1)- and (3+1)- dimensions and gives a non-trivial example of SS/CS for systems with a nonquadratic Hamiltonian. It is stressed that CS depending on their parameters (quantum numbers) describe both pure quantum and semiclassical states.

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Investigating the dynamical Casimir effect in superconducting circuits Göran Johansson Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Göteborg, Sweden Abstract Recently, there has been tremendous progress in using superconducting circuits for quantum information processing. One particular result is the demonstration of ultrafast tunability of circuit parameters, such as the frequency of a microwave cavity with high quality factor [1]. I will discuss how this technology can be used to investigate the dynamical Casimir effect (DCE) in a single mirror configuration, using a coplanar waveguide (CPW) terminated by a superconducting quantum interference device (SQUID). Changing the magnetic flux through the SQUID parametrically modulates the boundary condition of the CPW, and thereby, its effective length. Effective boundary velocities comparable to the speed of light in the CPW result in broadband photon generation which is identical to the one calculated in the dynamical Casimir effect for a single oscillating mirror. [2] In experiments, it is challenging to create a microwave waveguide with a completely flat density of states over tens of GHz. Thus we have also analyzed the effects of weak resonances on the DCE spectrum, and characterized the photon correlations, in terms of broadband squeezing and photon bunching [3]. Finally, I will discuss the current status of experiments. [1] "Tuning the field in a microwave resonator faster than the photon lifetime", M. Sandberg, C. M. Wilson, F. Persson, G. Johansson, V. S. Shumeiko, T. Duty, P. Delsing App. Phys. Lett. 92, 203501 (2008). [2] "Dynamical Casimir Effect in a Superconducting Coplanar Waveguide", J. R. Johansson, G. Johansson, C. M. Wilson, F. Nori, Phys. Rev. Lett. 103, 147003 (2009). [3] "Dynamical Casimir effect in superconducting microwave circuits", J. R. Johansson, G. Johansson, C. M. Wilson, and Franco Nori, Phys. Rev. A 82, 052509 (2010).

Nonlinear layered media as promising sources of entangled photon pairs Jan Peřina Jr. Palacky University, RCPTM, Joint Laboratory of Optics 17. listopadu 12, 772 07 Olomouc, Czech Republic Abstract The vectorial quantum model of spontaneous parametric down-conversion in nonlinear layered media pumped by cw or pulsed fields will be discussed. Relation between transmissivity of a nonlinear structure and ability to efficiently generate entangled photon pairs will be elucidated using several structures made of GaN/AlN and operating in the visible spectral range. Both spectral and temporal characteristics of photon pairs will be analyzed together with the attanable enhancement of the nonlinear process. Also transverse intensity profiles of the down-converted fields and correlation areas of the signal and idler beams will be mentioned. The generation of photon pairs at boundaries between different dielectrics and its contribution to the photon-pair generation rate will be discussed. As special cases, the emission of photon pairs from random 1D structures and emission of entangled photon pairs anti-symmetric in frequencies will be mentioned. Temporal anti-bunching and anti-coalescence on a beam splitter are typical properties of the states anti-symmetric in frequencies.

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Time refraction in perturbed quantum vacuum José Tito Mendonça IPFN, Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal Abstract The concept of time refraction is introduced, using both classical and quantum descriptions. It is shown that time refraction is a universal and first order process. The associated temporal Fresnel laws are discussed. Possible connections with sonoluminiscence is established. Photon pair production and the generation of entangled photon states are considered. The influence of boundary conditions, temporal beam-splitters and temporal cavities are also considered. Comparison with the dynamical Casimir effect in oscillating cavities is given. Similarities and differences with the Unruh radiation are stressed. The concept of effective Unruh acceleration is introduced. We show that time refraction leads to radiation by non-accelerated but superluminal dielectric boundaries. Finally, the concept is extended to the case of plasmons and phonons. In the case of plasmons, implications to inertial confinement fusion are shown as an illustration. In the case of phonons, time refraction is applied to Bose Einstein condensates and to ultra-cold plasmas.

Gouy phase in matter waves and the role of the uncertainty relation Maria Carolina Nemes Universidade Federal de Minas Gerais, Belo Horizonte, Brazil Abstract We study theoretical and experimental aspects of the Gouy Phase in matter waves. We show that this phase is related to the covariance between position and momentum and that interferometric studies with fullerens are consistent with the existence of the phase. An experimental proposal for a direct measurement is given using Ramsey interferometry of Rydberg atoms with parameters available to present day technology.

Unitary perturbative expansion of the time evolution operator: applications Nicim Zagury Universidade Federal do Rio de Janeiro, Brazil Abstract In ref. [1] it was shown that it is possible to express the time evolution operator as a product of unitary operators of the form U(t)= exp[-iZ1(t)]exp[-iZ2(t)] ...exp[-iZN(t)], where Zj(t), j=1,…, (N-1), are hermitian operators proportional to the j-th power of a suitable perturbation parameter λ, and ZN(t) is an hermitian operator which is at least of order O(λN).$ We apply this formalism to discuss the multiphoton transitions in a cavity assisted by a strong classical field. [1] N. Zagury, A. Aragão, J. Casanova, E. Solano, Phys. Rev. A, 82, 042110 (2010)

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Photon generation in an electromagnetic cavity with a timedependent boundary Per Delsing Chalmers University of Technology, Goteborg – Sweden Abstract We report the observation of photon generation in a microwave cavity with a time-dependent boundary condition. Our system is a microfabricated quarter-wave coplanar waveguide cavity. The electrical length of the cavity is varied by using the tunable inductance of a superconducting quantum interference device. It is measured at a temperature significantly less than the resonance frequency. When the length is modulated at approximately twice the static resonance frequency, spontaneous parametric oscillations of the cavity field are observed. Time-resolved measurements of the dynamical state of the cavity show multiple stable states. The behavior is well described by theory. Our results may be considered a preliminary step towards demonstrating the dynamical Casimir effect. Work done in collaboration with C.M. Wilson, T. Duty, M. Sandberg, F. Persson and V. Shumeiko.

The first application of squeezed light in a gravitational wave detector Roman Schnabel Albert-Einstein-Institut, Leibniz Universität Hannover, Hannover, Germany Abstract Around the globe several observatories are seeking the first direct detection of gravitational waves (GWs). These waves are predicted by Einstein’s General Theory of Relativity and are generated by accelerated mass distributions, e.g., by black-hole binary systems. Current GW detectors are Michelson-type kilometer-scale laser interferometers measuring the distance changes between in vacuum suspended mirrors. Although very high light powers are used, the sensitivity of these detectors at frequencies above several hundred Hertz is limited by quantum shot-noise resulting from the vacuum (zero-point) fluctuations of the electromagnetic field. This contribution reports on the squeezed-light enhancement of GEO600, which will be the GW observatory operated by the LIGO Scientific Collaboration in its search for gravitational waves for the next 3-4 years.

Dynamical invariants for variable quadratic Hamiltonians Sergei Suslov School of Mathematical and Statistical Sciences, Arizona State University, Tempe, USA Abstract We review classification of dynamical invariants (quantum integrals of motion) for generalized harmonic oscillators in terms of solutions of certain Riccati and Ermakov-type systems. Group theoretical approach and applications to coherent states and uncertainty relations are also discussed.

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Quantum turbulence in an atomic superfluid: generation and properties Vanderlei S. Bagnato Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil Abstract In this presentation we review our technique to generate turbulence in a Bose-Einstein Condensate of trapped Rb atoms. A perturbation in the trapping potential produces displacement, rotation and deformation of the atomic cloud, inducing the formation of vortices and their evolution. The generation of quantized vortices is investigated as a function of the amplitude of oscillation as well as time of excitation. The results allow the construction of a diagram for stable structures justified based on numerical simulations using the Gross-Pitaevskii equation. The necessity of having the presence of dissipation is obtained during the numerical simulation. Hydrodynamic considerations allow us to understand the occurrence of an anomalous expansion behavior for the cloud within the turbulent regime. Concepts of thermodynamic are applied to understand the variation of pressure during the occurrence of turbulence in the condensate. The existence of a critical number of vortices as a threshold for turbulence is also discussed. ( Experimental part with Financial fupport from FAPESP and CNPq – Brazilian agencies) . (Work done in collaboration with the following students and PD: E. Henn, J. Seman, P. Castilho, G. Roati, K. Magalhaes, R. Shiozaki, E. Ramos, M. Caracanhas, C. Castelo-Branco, P.Tavares , G. Bagnato, F. Jackson, F. Poveda, G. Telles,M. A. Fandino and the participation of external collaborators: A. Fetter, V. Yukalov , V.Romero-Rochin, M. Kobayashi, K. Kasamatsu and M. Tsubota)

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Homodyne quadrature statistics and probability representation of quantum states Vladimir I. Man'ko P.N. Lebedev Physical Institute, Leninskii Prospect 53, Moscow 119991, Russia Abstract The probability description as an alternative of the density-matrix description of quantum states is discussed. The optical tomograms of quantum states and the evolution and energy-level equations for the tomograms are obtained in explicit forms using integral Radon transform of the Moyal equation for the Wigner function. The connection with known symplectic tomographic quantum equations is established. The list of bounds including the homodyne-quadrature uncertainty relations for measurable optical tomograms is presented. The optical tomogram (symplectic tomogram) is proposed to be a primary object describing the quantum states, and all the state characteristics are expressed in terms of the measurable tomograms, avoiding the reconstruction procedure of the Wigner function. The example of such a characteristic as the purity is considered in detail. The homodyne-quadrature statistics is suggested as a test for both the fundamentals of quantum optics an d the accuracy of the experiments with measuring the photon quantum states. The purity-dependent bound in the photon-quadrature uncertainty relation is considered as one of the possible targets to be checked in the experiments with homodyne photon detection.

Dirac and Feynman bonded by squeezed states Young S. Kim Center for Fundamental Physics, University of Maryland, College Park, Maryland 20742, U.S.A . Abstract It is shown that, in their late years, both Dirac and Feynman were approaching the formalism of squeezed states. Dirac used two coupled oscillators to construct a representation of the deSitter group O(3,2) isomorphic to the symplectic group S(4), which constitutes the basic scientific language for two-mode squeezed states. Feynman on the other hand attempted to construct Lorerentzcovariant harmonic oscillators in order to explain hadronic mass spectra and other hadronic phenomena in the quark model. Feynman's formalism can be modified and extended to coincide with Dirac's two-oscillator formalism. This result allows us to transplant the physics of two-mode squeezed states to the quantum mechanics of bound system in the Lorentz-covariant world. It is now possible to give a physical interpretation to the time-separation variable which is thoroughly hidden to the Copenhagen school of quantum mechanics.

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ORAL PRESENTATIONS

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Non-Gaussianity bounded uncertainty relation Aikaterini Mandilara*, E. Karpov and N. J. Cerf Universite Libre de Bruxelles, Quantum Information and Communication, Ecole Polytechnique, CP 165/59, 50 av. F. D. Roosevelt, Bruxelles, Belgium Abstract We present a new uncertainty relation for one-dimensional mixed states given its purity and degree of non-Gaussianity. This relation extends the purity-bounded uncertainty relation for mixed states derived by V. V. Dodonov and V. I. Man'ko. For the special case of pure states it provides us with an extended version of the Robertson-Schrödinger uncertainty relation, saturated by a set of states which includes all the eigenstates of the quantum harmonic oscillator. We represent our results as a bound in a three-dimensional parametric space of mixed states and identify the regions of the bound realized by states with non-negative Wigner function. This takes us closer to a proper extension of Hudson's theorem to mixed states and permits us to visualize and compare the set of states with non-negative Wigner function and the set of states which minimize the newly derived uncertainty relation.

Unconditional preparation of bound entanglement Aiko Samblowski*1, J. DiGuglielmo1, B. Hage1, C. Pineda2,3, J. Eisert3,4 and R. Schnabel1 1

Institut für Gravitationsphysik, Leibniz Universität Hannover and Max-Planck Institut für Gravitationsphysik, 30167 Hannover, Germany; 2 Instituto de Física, Universidad Nacional Autónoma de México, México; 3 Institute of Physics and Astronomy, University of Potsdam, 14476 Potsdam, Germany; 4 Institute for Advanced Study Berlin, 14193 Berlin, Germany Abstract

Among the possibly most fascinating aspects of quantum entanglement is that it comes in "free" and "bound" instances. In contrast to free entanglement is it not possible to distill bound entangled states, although free entanglement is needed for their preparation. Their existence hence certifies an intrinsic irreversibility of entanglement in nature and suggests a connection with thermodynamics [1-4]. A first experimental unconditional preparation and detection of a bound entangled state of light [5] will be presented in this talk. The focus will be set on the realization and results of our experiment that continuously produced a continuous-variable (CV) bound entangled state with an extraordinary significance of more than ten standard deviations away from both separability and distillability. This platform allows the efficient preparation of multi-mode entangled states of light with various applications in quantum information, quantum state engineering and metrology. [1] M. Horodecki, P. Horodecki, and R. Horodecki, Phys. Rev. Lett. 80, 5239 (1998) [2] M. Horodecki, J. Oppenheim, and R. Horodecki, Phys. Rev. Lett. 89, 240403 (2002) [3] R. Horodecki, P. Horodecki, and M. Horodecki, Rev. Mod. Phys. 81, 865 (2009) [4] F. Brandao and M. B. Plenio, Nature Physics 4, 873 (2008) [5] J. DiGuglielmo, A. Samblowski, B. Hage, C. Pineda, J. Eisert and R. Schnabel, arXiv:1006.4651 (2010)

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Multi-spatial mode properties of squeezed light from four-wave mixing Alberto M. Marino*, Neil V. Corzo Trejo, and Paul D. Lett Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, USA Abstract The study of the spatial degree of freedom of the quantum correlations present in optical fields has led to the field of quantum imaging. These quantum spatial correlations hold the promise of improved optical resolution, quantum holographic teleportation, and parallel quantum information encoding, to name a few. In order to take advantage of the many predictions that have emerged from the field of quantum imaging, a system that can produce highly multi-spatial mode quantum states of light is needed. We show that non-degenerate four-wave mixing (4WM) in rubidium atomic vapor can be used to generate both single-mode and two-mode squeezed beams of light that contain a large number of spatial modes. The generation of both types of squeezed states is implemented with a 4WM process in a single pass configuration and based on a double-lambda system in Rb 85. For the case of the two-mode squeezed state a phase-insensitive process (PIP) is used. In this process a strong pump is mixed at a small angle with a weak probe. This results in the emission of a pairs of photons, such that the input probe gets amplified and a new beam, which we call the conjugate, gets generated. With this configuration we have measured relative-intensity squeezing greater than 8 dB and have shown that there is continuous-variable entanglement between the quadratures of the probe and conjugate fields. The absence of a cavity combined with a weak phase-matching condition makes it possible for the process to support a large number of spatial modes. We have characterized the spatial quantum correlations by measuring the intensitydifference squeezing between different spatial regions of the probe and the conjugate and have estimated that the process can support about 100 spatial modes. As a result of the multi-spatial mode nature of the fields this process can be used to generate entangled images. For the generation of a single-mode squeezed state a phase sensitive process (PSP) is needed. In order to implement such a process we interchange the roles of the pump and the probe and conjugate beams used in the PIP, such that the process is now pumped with two different frequencies. This leads to the emission of a pair of photons at a single frequency and into a single beam, the probe, thus generating a single-mode squeezed state. With this configuration we have measured up to 3 dB of quadrature squeezing. As is the case for the PIP, the PSP also results in the generation of a large number of spatial modes. We verify the multi-spatial mode nature of the quantum field by performing similar measurements to the ones done for the two-mode squeezed state. In addition to the generation of squeezed light, such a multi-spatial mode PSP should make it possible to implement noiseless image amplification.

Entanglement dynamics via coherent-state propagators Alexandre D. Ribeiro* and R. M. Angelo Departamento de Física, Universidade Federal do Paraná, Curitiba, PR, Brazil Abstract The dynamical generation of entanglement in closed bipartite systems is investigated in the semiclassical regime. We consider a model of two particles, initially prepared in a product of coherent states, evolving in time according to a generic Hamiltonian, and derive a formula for the linear entropy of the reduced density matrix using the semiclassical propagator in the coherent-state representation. The formula is explicitly written in terms of quantities that define the stability of classical trajectories of the underlying classical system. The formalism is then applied to the problem of two nonlinearly coupled harmonic oscillators and the result is shown to be in remarkable agreement with the exact quantum measure of entanglement in the short-time regime. An important byproduct of our approach is a unified semiclassical formula which contemplates both the coherent-state propagator and its complex conjugate. 29

Decoherence and disorder in quantum walks: from ballistic spread to localization Andreas Schreiber Max Planck Institute for the Science of Light, Günther-Scharowsky-Str. 1 / Bau 24, 91058 Erlangen, Germany Abstract Quantum walks serve as a standard model to describe the dynamics of quantum particles in a discretized environment. Their coherent evolution is highly influenced by quantum interference effects, which leads to significantly different expansion properties compared to classical particles. In recent years quantum walks have become an established framework to study many different physical scenarios. They do not only offer a new way for designing quantum algorithms, but also built a foundation for theoretical simulations of complex physical systems, like the energy transfer in photosynthesis. The occurring quantum propagation in these scenarios is highly dependent on the environmental conditions. We experimentally implemented 28 steps of a one-dimensional photonic quantum walk [1], corresponding to a network of over four hundred beam splitters, by using a timemultiplexed setup in a loop geometry [2]. Our experimental data confirms a full preservation of the coherence properties during the entire propagation. By including a fast operating modulator, we achieved full control over the photons' dynamics. The provided flexibility allows systematic studies of quantum walks in an environment with decoherence and static disorders. The different conditions result in a ballistic spread in a coherent quantum walk, a diffusive behavior in a classical random walk and the first Anderson localization in a quantum walk scenario with discrete steps. In particular, we demonstrated in our setup the propagation of a quantum particle in a coherent and homogeneous environment. By artificially inducing random fluctuations in the system, we suppressed the occurring quantum interference, which led to a diffusive spread of the particle. This can be understood as a breakdown of the quantum evolution to a classical random propagation. For more detailed studies, we modified the strength of decoherence, simulating a controlled transition between both scenarios. In contrast to the behavior induced by dynamic variations, we also investigated a system of static disorders. For this purpose we fixed random variations at the discrete positions in the walk. This situation results in a exponential localization of the wave packet at its initial position, thus completely suppressing the spatial expansion of the photons. The flexibility and scalability of our setup makes it a perfect test-bed for simulations of mesoscopic systems and investigations of biophysical processes. Additionally, the possibility of applying position dependent operations opens new routes for the implementation of quantum walk-based algorithms. [1] A.Schreiber et al., arXiv:1101.2638 (2011). [2] A.Schreiber et al., Phys. Rev. Lett. 104, 050502 (2010).

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Can a massive graviton be a stable particle? Andrew Beckwith Chongquing University, Dept of physics. Chongquing, PRC Abstract This document is due to a question asked in the Dark Side of the Universe conference, 2010, in Leon, Mexico, when a researcher from India asked the author about how to obtain a stability analysis of massive gravitons. The answer to this question involves an extension of the usual Pauli-Fiertz Lagrangian, with non-zero graviton mass contributing to a relationship between the trace of a re done GR stressenergy tensor (assuming non zero graviton mass) , and the trace of a re done symmetric tensor , times a tiny mass for a 4 dimensional graviton. The resulting analysis makes use of Visser’s treatment of a stress energy tensor, with experimental applications discussed in the resulting analysis. If the square of frequency of a massive graviton is real valued and greater than zero, stability can be possibly confirmed experimentally.

Quantum channels in the atmosphere: theoretical treatments and unexpected properties Andrii A. Semenov*1,2 and W. Vogel1 1

2

Institut fuer Physik, Universitaet Rostock, Germany, and Institute of Physics, National Academy of Sciences of Ukraine, Kiev, Ukraine Abstract

Long-distance quantum communications are connected with serious difficulties due to high-level losses in transmission channels. There are no chances for a direct elimination of losses in standard attenuating channels, such as fibers. Instead, experiments in free space demonstrate reasonable results even in the presence of extremely high losses, see [1]. Our explanation for this surprising fact is that standard postselection procedures in quantum measurements may also select such events when the atmosphere randomly is rather transparent [2]. In the framework of a general approach for fluctuating-loss channels, we discuss different configurations of experiments with quantum light transmitting through the turbulent atmosphere: Bell-type experiments [1], homodyne detection with an independent source of the local oscillator [3], and homodyne detection with the local oscillator also passing through the atmosphere [4]. [1] A. Fedrizzi et al., Nature Physics 5, 389 (2009). [2] A. A. Semenov and W. Vogel, Phys. Rev. A 81, 023835 (2010); see also D. Monroe, Phys. Rev. Focus 25, st. 7 (http://focus.aps.org/story/v25/st7). [3] A. A. Semenov and W. Vogel, Phys. Rev. A 80, 021802(R) (2009). [4] D. Elser et al., New J. Phys. 11, 045014 (2009).

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Nonlocal and local hidden-variables models violating Bell and Leggett inequality Antonino Di Lorenzo Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, Brazil Abstract Leggett formulated an inequality which generalizes the Bell theorem to non-local hidden variable theories. Leggett inequality is violated by Quantum Mechanics, as was confirmed by experiment. However, the inequality applies only to a special class of nonlocal theories. In this paper a counterexample is presented which reproduces the predictions of quantum mechanics for spin 1/2. The counterexample discussed here does not satisfy one hypothesis which was implicitly made in the derivation of Leggett inequality and which is analysed in the conclusions. Furthermore, a family of local models is presented which violate both Bell and Leggett inequality. These models, however, fail to reproduce the predictions of Quantum Mechanics, and thus are experimentally testable. Even if the models are disproved by experiment, as the author believes, they prove that Bell and Leggett inequality do not capture fully the counterintuitive aspects of Quantum Mechanics. This work was supported by FAPEMIG through process APQ-02804-10.

Continuous variable hyperentanglement in a parametric oscillator Antonio Z. Khoury*, B. Coutinho dos Santos, and K. Dechoum Instituto de Fisica - Universidade Federal Fluminense, 24210-346 Niteroi - RJ – Brazil Abstract We describe continuous variable hyperentanglement in polarization and orbital angular momentum modes of an optical parametric oscillator. The quantum stochastic equations for the multimode parametric interaction are derived and solved allowing for calculation of the quadrature noise spectra that characterize continuous variable entanglement. As a main result, we predict simultaneous entanglement between different combinations of amplitude and phase quadratures of the interacting modes. We also propose experimental setups to access the different kinds of entanglement.

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Modular variables and Schwinger's finite phase space Augusto C. Lobo*¹ and C. A. Ribeiro² 1

Department of Physics, Federal University of Ouro Preto, Brazil. Department of Physics, Federal University of Minas Gerais, Brazil.

2

Abstract We propose to explain in a natural manner, the mathematical structure behind the modular variable concept introduced in 1969 by Aharonov, Pendleton and Petersen to explain certain non-local dynamical properties of quantum mechanics as like the celebrated Bohm-Aharonov effect. The original definition of a modular variable is that of the phase of the eigenvalue of certain unitary operators such as the translation operators VL=exp(iPL) and U2π/L=exp(Q2πi/L) (with units such that h-bar is one) that act respectively upon the position and momentum basis. It is easy to see that these operators commute for all L and consequently they have simultaneous eigenstates which describe some quantum mechanical experiments as the state of a diffracting particle beam emerging from a lattice of slits (with L being the distance between nearby slits.) Aharonov et al argued convincingly that the slits and the particles exchange modular momentum in a non-local way. We advance a mathematical formalism based on Schwinger's finite quantum kinematics which offers a clear understanding of this phenomenon. We present a finite dimensional "toy model" where the particle beams transversal degree of freedom is described by the product of two finite dimensional spaces, where one of them will be interpreted as the modular variable space after an appropriate "continuum limit" is conducted. This same mathematical structure has shown up before in many applications of quantum mechanics (the so called Zak states) mainly for systems where periodicity is a fundamental feature. Yet, as far as we know, we suggest here for the first time that the mathematical structure of these states describe correctly Aharonov's modular variable concept. We believe that the kind of understanding we address here contributes to one of the most widespread and ongo ing discussions in quantum information theory and the foundations of quantum mechanics which is the (still elusive) precise grasping of the so called non-locality of quantum phenomena. Aharonov and collaborators have coined the kind of non-locality described above as being dynamical instead of the more usual kinematical kind of non-locality exhibited by EPR-like phenomena, because the authors believe that it can be only grasped if described within the Heisenberg picture, following from the manifest non-locality of the equation of motion for the relevant operators. Yet, are construction indicates that one can distinguish directly (in the Schrödinger picture) the space of modular variables through the proper decomposition of the degree of freedom as two “pseudodegrees” of freedom. This seems to mean that the dynamical kind of quantum mechanical nonlocality is not so different from the kinematical kind after all.

STIRAP in the presence of quantum noise: a case of time-dependent Hamiltonian under environmental effects Benedetto D. Militello Dipartimento di Fisica dell'Università di Palermo, Palermo, Italy Abstract Stimulated Raman Adiabatic Passage (STIRAP) has been studied in a variety of physical scenarios and in different situations, including the presence of environmental effects. Following a standard master equation approach valid for systems governed by time-dependent Hamiltonians, I describe the STIRAP process in the presence of quantum noise in different physical situations [Scala, M, Messina, Vitanov, PRA 81, 053847 (2010); PRA 83, 012101 (2011)].

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Popper's thought experiments reinvestigated Chris D. Richardson* and Jonathan P. Dowling Department of Physics and Astronomy, Louisiana State University, Baton Rouge, USA Abstract Karl Popper posed an interesting thought experiment in 1934. With it, he meant to question the completeness of quantum mechanics (QM). He claimed that the notion of quantum entanglement leads to absurd scenarios that cannot be true in real life and that an implementation of his thought experiment would not give the results that QM predicts. Unfortunately for Popper, it has taken until recently to perform experiments that test his claims. However, the results of the experiments do not refute QM as Popper predicted, but neither do they confirm what Popper claimed QM predicted. Kim and Shih implemented Popper's thought experiment in the lab. The results of the experiment are not clear and have instigated many interpretations of the results. The results show some correlation between entangled photons, but not in the way that Popper thought, nor in the way a simple application of QM might predict. A ghost-imaging experiment by Strekalov, et al. sheds light on the physics behind Popper's thought experiment and the results found by Kim and Shih, but does not try to directly test Popper's thought experiment. These two experiments are almost identical, but give different and unexplained results. I will use QM to build the physics of Popper's thought experiment from the ground up and show how the results of both of these experiments agree with each other and the theory of QM, but disprove Popper. Popper proposed an experiment in which two photons entangled in position and momentum were sent in opposite directions. The photon on the left passes through a slit. The result of many of those photons passing through the slit would produce an interference pattern on a screen behind the slit. The action of the slit can be thought of as a measurement of the position of the photon. The diffraction of the photon can be thought of as a direct consequence of Heisenberg's uncertainty principle. Since the photon's position was measured, then its momentum is uncertain. Since we are dealing with an entangled source, Popper claimed that QM tells us that if one photon's position is measured, then the other photon's position is also known. Therefore, the momentum of the other photon must also be uncertain even though it did not pass through a slit. Then this photon too, when measured over many trials, should produce an identical interference pattern compared to the photon that pa sses through the real slit. Popper did not think that this would happen in an experiment. He thought that this sort of instantaneous action at a distance was incorrect. He argued that the diffraction of the right side photon by a ghost slit is what the theory of quantum mechanics predicts, but when the experiment was performed, no diffraction of the undisturbed photon would appear and this would therefore prove that QM is wrong or at least incomplete. The analysis of the following two experiments will show that Popper's qualms with QM are unfounded.

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Generation of multi-partite entanglement between different degrees of freedom by squeezing cylindrically polarized modes Christian Gabriel*1,2, A. Aiello1,2, P. van Loock1,2, U. L. Andersen1,2,3, Ch. Marquardt1,2 and G. Leuchs1,2 1

Max Planck Institute for the Science of Light, Guenther-Scharowsky-Str. 1, 91058 Erlangen, Germany; 2 Institute of Optics, Information and Photonics, University Erlangen-Nuremberg, Staudtstr. 7/B2, 91058 Erlangen, Germany; 3 Department of Physics, Technical University of Denmark, 2800 Kongens Lyngby, Denmark. Abstract

Entanglement is one of the most intriguing features of quantum mechanics. It plays a major role in quantum information science [1] and finds applications in quantum teleportation, quantum computation and quantum cryptography. Therefore the creation and control of such entangled states has been of great interest in both the single photon and continuous variable regime. In continuous variables various methods have been developed to generate, inter alia, quadrature, polarization and spatial entanglement [2]. Normally such states contain only entanglement between two modes. This can also be extended to systems where entanglement between several modes exists, these are often referred to as multi-partite entangled states. Such systems can be exploited to achieve so-called cluster states, which form the basis of one-way quantum computers [3]. We present theoretical and experimental results of non-classical states of light generated in modes which have a complex spatial as well as a complex polarization structure, namely radially and azimuthally polarized modes. These modes have the peculiar feature that already in a classical picture their polarization and spatial field variables cannot be separated. We show that this property can be exploited to generate entanglement between these two degrees of freedom by squeezing one of these cylindrically polarized modes [4]. Such a state is experimentally realized by exploiting the non-linear Kerr-effect in a specially tailored fiber which directly supports these modes [5]. An azimuthally polarized mode can be described in the Hermite-Gaussian basis as a superposition of a horizontally polarized TEM01 and a vertically polarized TEM10 mode. Analogously a radially polarized mode can be described as a superposition of a vertically polarized TEM01 and a horizontally polarized TEM10 mode. We will present schemes which show how one can exploit a squeezed radially and a squeezed azimuthally polarized mode to generate entanglement between all four of these basis modes. Such multi-partite entangled states potentially can be used for the production of cluster states and might have many attractive applications in quantum information protocols as well as quantum computing. [1] S. L. Braunstein and P. van Loock, Rev. Mod. Phys. 77, 513-577 (2005). [2] Z. Ou et al., Phys. Rev. Lett. 68, 3663-3666 (1992); C. Silberhorn et al., Phys. Rev. Lett., 86 (19), 4267 - 4270 (2001); W. P. Bowen et al., Phy. Rev. Lett 89, 253601 (2002); V. Boyer et al., Science 321, 544 (2008); K. Wagner et al., Science 321, 541 (2008). [3] R. Raussendorf et al., Phys. Rev. A 68, 022312 (2003). [4] C. Gabriel et al., Phys. Rev. Lett. 106, 060502 (2011). [5] T. G. Euser et al., J. Opt. Soc. Am. B 28, 193-198 (2011).

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Entanglement generated by dissipation Christine A. Muschik*, H. Krauter, K, Jensen, W. Wasilewski, J. M. Petersen, J. I. Cirac, and E. S. Polzik Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Str. 1, D-85748 Garching, Germany, and Niels Bohr Institute, Danish Quantum Optics Center – QUANTOP, Copenhagen University, Blegdamsvej 17, 2100 Copenhagen, Denmark. Abstract Entanglement is not only one of the most striking features of Quantum Mechanics but also an essential ingredient in most applications in the field of Quantum Information. Unfortunately, this property is very fragile. In experiments conducted so far, coupling of the system to a quantum mechanical environment, either inhibits entanglement or prevents its generation. Therefore, entangled states are created under strict isolation conditions. In contrast, new approaches harness the coupling of the system to the environment, which drives the system into the desired state. Following these ideas, we present a robust method for generating steady state entanglement between two distant atomic ensembles and report on an experiment in which dissipation induces entanglement between two atomic objects rather than impairing it. This counter-intuitive effect is achieved by engineering the dissipation by means of laser- and magnetic fields, and leads to longlived entanglement. Our system consists of two distant macroscopic ensembles containing about 1012 atoms coupled to the environment composed of the vacuum modes of the electromagnetic field. The two atomic objects are kept entangled by dissipation at room temperature for 0.04s. By combining the dissipative mechanism with continuous measurements, we demonstrate steady state entanglement observed for up to an hour.

Random quantum circuits from locally invariant gates Daniel Jonathan*1 and Igor Tuche Diniz1,2 1

Instituto de Física, Universidade Federal Fluminense, Niterói, Brazil; 2 Institut Néel, Grenoble, France Abstract

The ability to generate random states and/or random unitary operators is a crucial requirement for many quantum information protocols. Although generating truly random n-qubit unitaries requires physical resources that scale exponentially with n, it is believed that only poly(n) resources are needed in order generate a quantum unitary k-design: a pseudo-random ensemble of n-qubit gates whose k-th order moments equal those of the truly random ensemble. Random quantum circuits (RQCs) provide a conceptually and experimentally feasible way to generate such pseudo-random ensembles. We study the convergence of RQCs composed of 2-qubit gates drawn from gate ensembles that are invariant under local, but not necessarily global, rotations. We show that, for all such gate ensembles, the RQC converges to an ε-approximate quantum 2-quantum design in at most O[n ln(n/ε)] steps. We are also able to show which physical features of the gates contribute to a faster convergence of the circuit.

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Quantum uniqueness and objective randomness generation from quantum uncertainty Denis Sych* and Gerd Leuchs Max Planck Institute for the Science of Light, Guenther-Scharowsky-Strasse 1 / Bau24, 91058 Erlangen, Germany Abstract One of the most amazing aspects of quantum theory is the prediction of phenomena which do not exist in the classical world. In the area of quantum information, the well–known examples are the special superposition states called entangled states, the violation of Bell’s inequality, teleportation, the “no–cloning” theorem, etc. In this work, we have found another new phenomenon of purely quantum origin. In the classical world one can construct two absolutely identical systems. For an external observer who performs measurements to get any information, identical systems must give identical measurement results. They can be regarded as perfect copies, since they have identical properties, have identical behavior and can perfectly substitute each other. We show that the existence of such perfect copies is impossible in the quantum domain. Particularly, we prove that one cannot construct two quantum systems, whatever their bipartite state is, such that both systems always yield absolutely the same sequence of results after the same sequence of non orthogonal quantum measurements. This is interpreted as quantum uniqueness - a quantum feature which has no classical analog [1]. This idea of quantum uniqueness has interesting applications. A particularly interesting example is generation of random numbers. We introduce the notion of objectively random numbers which are 1) completely random in a statistical sense, i.e. they have no regular statistical patters, 2) provably secure and private, i.e. a priori unknown and unpredictable for any potential eavesdropper, and 3) asymptotically unique, i.e. an infinitely long sequence of these numbers can be obtained in only one copy [1]. One can generate such numbers with the help of relatively simple optical measurements that exploit quantum uncertainty and verify purity of the measured quantum states. A working experimental realization based on homodyne detection of the coherent vacuum state is shown to comply with the above conditions for objective randomness generation [2]. [1] D. Sych and G. Leuchs, Quantum uniqueness, arXiv:1003.1402 (2010) [2] Ch. Gabriel, Ch. Wittmann, D. Sych, R. Dong, W. Mauerer, U. L. Andersen, Ch. Marquardt, and G. Leuchs, A Generator for Unique Quantum Random Numbers Based on Vacuum States, Nature Photonics 4, 711 (2010)

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A single-atom quantum memory Eden Figueroa*, Holger Specht, Christian Nölleke, Andreas Reiserer, Manuel Uphoff, Stephan Ritter and Gerhard Rempe Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany. Abstract We show the implementation of the most fundamental quantum memory by mapping arbitrary polarization states of light into and out of a single atom trapped inside an optical cavity. The memory performance is analyzed through full quantum process tomography. The average fidelity is measured to be 93% and low decoherence rates result in storage times exceeding 180 microseconds. The implementation of quantum networks requires the development of quantum interconnects, featuring the coherent and reversible mapping of quantum information between light and matter. So far, these interfaces have been based upon the engineered exchange of information between photons and collective atomic excitations [1]. A promising alternative is the development of interfaces between photons and single particles of matter [2]. This approach has fundamental advantages as it allows for the individual manipulation of the stored atomic qubit. The storage of photons is achieved by a vacuum-stimulated Raman adiabatic passage [3] with a control laser. The polarization state of the photon is thereby mapped onto a superposition of internal states of the atom. After a variable storage time, the atomic state can be read out using the inverse procedure, producing a single photon and thereby reproducing the initial polarization state. To test the performance of the quantum memory we store six different input polarizations and analyze each output state in three orthogonal bases, allowing for a full reconstruction of the retrieved photon’s density matrix. The fidelity is defined as the overlap between the ideal input state and the density matrix of the measured output. When tested with single photons, a fidelity larger than 2/3 unambiguously proves the quantum nature of the memory. For coherent input pulses, this value has to be adapted, as a classical memory could gain additional information by measuring more than one photon. In that case, the fidelity threshold for a quantum memory with our characteristics (efficiency: 9%, input mean photon number: 1) is increased to 80%. Our measure fidelity (93%) is well above both of these thresholds, thus proving the quantum nature of the memory. *This work has been accepted for publication in Nature, and is now available online: arXiv:1103.1528) [1] A. I. Lvovsky, B. C. Sanders, and W. Tittel. Nature Photonics 3, 706 (2009). [2] A. D. Boozer et al., Phys. Rev. Lett. 98, 193601 (2007). [3] M. Hennrich, T. Legero, A. Kuhn, and G. Rempe. Phys. Rev. Lett. 85, 4872 (2000).

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Semiclassical approach to blind spots Eduardo Zambrano Centro Brasileiro de Pesquisas Fisicas – CBPF, Rio de Janeiro, Brazil Abstract The overlap of a large quantum state with its image under tiny translations, oscillates swiftly. We here show that complete orthogonality occurs generically at isolated points, so-called blind spots. On the other hand, characteristic functions contain complete information about all the moments of a classical distribution and the same holds for the Fourier transform of the Wigner function: a quantum characteristic function, or the 'chord function'. However, knowledge of a finite number of moments does not allow for accurate determination of the chord function. This provides the overlap of the state with all its possible rigid translations (or displacements). We here present a semiclassical approximation of the chord function for a Bohr-quantized states, which is accurate right up to a caustic, beyond which the chord function becomes evanescent. It is verified to pick out blind spots. These occur even for translations within a Planck area of the origin. We derive a simple approximation for the closets blind spots, depending on the Schrödinger covariance matrix, which is verified for Bohr-quantized states.

Revivals, classical periodicity, and zitterbewegung of electron currents in monolayer grapheme Elvira Romera Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada, Spain Abstract Revivals of electric current in graphene in the presence of an external magnetic field are described. It is shown that when the electrons are prepared in the form of wave packets assuming a Gaussian population of only positive or negative energy Landau levels, the presence of the magnetic field induce revivals of the electron currents, besides the classical cyclotron motion. When the population comprises both positive and negative energy Landau levels, revivals of the electric current manifest simultaneously with zitterbewegung and the classical cyclotron motion. We relate the temporal scales of these three effects and discuss to what extent these results hold for real graphene samples.

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Time travel in measurement-based quantum computation Ernesto F. Galvão Instituto de Física, Universidade Federal Fluminense, Niterói – RJ, Brazil Abstract Many results have been recently obtained regarding the power of hypothetical closed time-like curves (CTC’s) in quantum computation. Most of them have been derived using Deutsch’s influential model for quantum CTCs [D. Deutsch, Phys. Rev. D 44, 3197 (1991)]. Deutsch’s model demands selfconsistency for the time-travelling system, but in the absence of (hypothetical) physical CTCs, it cannot be tested experimentally. In this paper we test Deutsch's CTC model against predictions arising from the one-way model of measurement-based quantum computation (MBQC). Using a simple example we show that Deutsch’s formalism leads to predictions conflicting with those of the one-way model. There exists an alternative, little-discussed model for quantum time-travel due to Bennett and Schumacher (in unpublished work, see http://bit.ly/cjWUT2) and also Svetlichny [arXiv:0902.4898v1] . This model uses quantum teleportation to probabilistically simulate what would happen if one sends quantum states back in time. We show how the Bennett/ Schumacher/ Svetlichny (BSS) model for CTCs fits in naturally within the formalism of MBQC. We identify a class of CTC’s in this model that can be simulated deterministically using techniques associated with the stabilizer formalism. We also identify the fundamental limitation of Deutsch's model that accounts for its conflict with the predictions of MBQC and the BSS model. This work was done in collaboration with Raphael Dias da Silva and Elham Kashefi, resulting in the publication Phys. Rev. A 83, 012316 (2011).

The conservation law between entanglement and quantum discord Felipe Fanchini Universidade Federal de Ouro Preto, Morro do Cruzeiro, Ouro Preto – MG, Brazil Abstract We present a direct relation between entanglement of formation and quantum discord and show how they are distributed in an arbitrary tripartite system following a conservative rule. By extending the relation to a paradigmatic situation of a bipartite system coupled to the environment we show that in the deterministic quantum computer with one pure qubit the protocol has the ability to rearrange the entanglement and the quantum discord. This implies that quantum computation can be understood in a different ground -as a coherent dynamics where quantum correlations are distributed between the qubits of the computer. Moreover the balance between distributed entanglement and discord in general imposes strong bounds on the subsystems entropies additivity.

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Mapping Gaussians and Qubits Fernando Nicacio Instituto de Física "Gleb Wataghin'', Universidade Estadual de Campinas, 13083-970, Campinas, São Paulo, Brazil Abstract We consider a plausible manipulation of qubits states via a mapping into gaussians continuous variables systems. This mapping is constructed using the generators of the canonical transformations acting into gaussian states and the generators of the unitary transformation on Bloch sphere. We propose a experimental scheme to implement quantum computation algorithms manipulating the quadratures of the electromagnetic field.

Noise-enhanced transfer of energy and quantum information in complex networks Filippo Caruso Institute of Theoretical Physics, Ulm University, Albert Einstein Allee 11, D-89069 Ulm, Germany Abstract Noise and memory effects may have a huge impact on transport phenomena in complex networks, a very fascinating topic of continual interest in many areas of physics, sociology, biology, and others. In particular, in quantum information science this has been rejuvenated recently by the prospect of transfer of quantum information in quantum networks, and in biology recurring interest in understanding the fundamental processes influencing the remarkable efficiency well above 90% for excitation energy transfer in photosynthetic complexes. In particular, very recently we have identified the key mechanisms through which noise, such as dephasing, perhaps counter intuitively, may actually aid transport through a dissipative network by opening up additional pathways and suppressing the ineffective ones. Here, we propose: 1) a quantum optical simulator of noise-assisted transport, 2) an experimental test for these mechanisms by optimally controlling the dynamics of real systems, 3) an application of these ideas to quantum communication. Firstly, we show an experimentally realizable optical network scheme for the demonstration of the basic mechanisms underlying noise-assisted transport. The proposed system consists of a network of coupled quantum optical cavities, injected with a single photon, whose transmission efficiency can be measured. Introducing dephasing in the photon path, this system exhibits a characteristic enhancement of the transport efficiency that can be observed with presently available technology [1]. Secondly, we apply open-loop quantum optimal control techniques under realistic experimental conditions to verify the relevance of the transport mechanisms in natural and artificial light-harvesting complexes. We demonstrate that optimally shaped laser pulses allow to faithful prepare the photosystem in specified initial states and to probe efficiently the dynamics, providing a way towards the discrimination of the different transport paths and to the characterization of the environmental properties, enhancing our understanding of coherent processes in biological complexes [2]. Finally, we show how noise, in terms of dephasing, may enhance the capability of transmitting not only classical but also quantum information, encoded in quantum systems, through communication networks. In particular, we find analytically and numerically the quantum and classical capacities for a large family of quantum channels and show that these information transmission rates can be strongly enhanced by introducing dephasing noise in the complex network dynamics, e.g. getting almost perfect quantum state transfer, while the noiseless system has vanishing capacity [3]. [1] F. Caruso, N. Spagnolo, C. Vitelli, F. Sciarrino, M.B. Plenio, Phys. Rev. A 83, 013811 (2011). [2] F. Caruso, S. Montangero, T. Calarco, S.F. Huelga, M.B. Plenio, in preparation (2011). [3] F. Caruso, S.F. Huelga, M.B. Plenio, Phys. Rev. Lett. 105, 190501 (2010).

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The Quantum Arnold Transformation Francisco F. Lopez-Ruiz Institute of Astrophysics of Andalusia – CSIC, Glorieta de la Astronomia - Granada – Spain Abstract Using a quantum version of the Arnold transformation of classical mechanics, all quantum dynamical systems whose classical equations of motion are non-homogeneous linear second-order ordinary differential equations (LSODE), including systems with friction linear in velocity, can be related to the quantum free-particle dynamical system. This implies that symmetries and simple computations in the free particle can be exported to the LSODE-system. Application to obtaining Hermite-Gauss and Laguerre-Gauss wave packets, as well as some possible further applications in the theory of open quantum systems will be outlined.

Entanglement conditions and quasi-probabilities Jan Sperling* and W. Vogel Arbeitsgruppe Quantenoptik, Institut fuer Physik, Universitaet Rostock, D-18051 Rostock, Germany Abstract The characterization and identification of quantum entanglement nowadays plays an increasing role. With modern experimental techniques it becomes feasible to use the quantumness of a systems as a resource for quantum technologies, which represent a rapidly developing field of research. In composed quantum systems, the most classical pure states are the product states. For a deep understanding of entanglement the consideration of pure states is too simple. In practice any kind of losses unavoidably leads to mixed quantum states. Here we will present an formally unified approach to a general identification of entanglement by necessary and sufficient conditions with Hermitian test operators and quasi-probabilities of entanglement. This unified approach is given in terms of the ''Separability Eigenvalue Equations'' (SEE). These equations are the algebraic form of optimization problems for separable quantum states. A general construction scheme of entanglement witnesses will be presented. This scheme allows to formulate optimized, necessary and sufficient conditions for entanglement in terms of arbitrary Hermitian operators [1]. The optimization of these conditions will be given in terms of SEE. We apply this approach to identify the entanglement of phase-randomized two-mode squeezed-vacuum states in continuous variable systems. Any mixed quantum state can be decomposed in terms of factorizable states and an optimized quasiprobability [2]. These quasiprobabilities yield the optimal decomposition of mixed states in terms of separable ones. Therefore, it overcomes ambiguities of other decompositions in a similar form. We obtain a positive decomposition, if and only if the state is separable. Negativities in this optimized form directly visualize the entanglement of the state. We obtain this decomposition by solving the SEE for the state under study and we apply them to some examples. Acknowledgment. The authors gratefully acknowledge support by the Deutsche Forschungsgemeinschaft through SFB 652. [1] J. Sperling and W. Vogel, Phys. Rev. A 79, 022318 (2009). [2] J. Sperling and W. Vogel, Phys. Rev. A 79, 042337 (2009).

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Polarization squeezing for macroscopic Bell states Gerd Leuchs*1,3, Timur Sh. Iskhakov1,3, and Maria V. Chekhova1,2 1

Max Planck Institute for the Science of Light, Günther-Scharowsky-Strasse 1/Bau 24, 91058 Erlangen, Germany 2 Department of Physics, M.V.Lomonosov Moscow State University, Leninskie Gory, 119991 Moscow, Russia 3 Institute of Optics, Information and Photonics, University Erlangen-Nuremberg, Staudtstrasse 7/B2, 91058 Erlangen, Germany Abstract

Two-photon Bell states are among the basic tools of quantum optics and quantum information. Currently, there is a growing interest in their macroscopic analogues in connection with macroscopic entanglement. In particular, conditions for non-separability (entanglement) can be formulated in terms of polarization (Stokes) observables [1]. In this work, we produce four macroscopic Bell states in a high-gain travelling-wave four-mode optical parametric amplifier and study their polarization properties. We show that each of the three macroscopic triplet states has fluctuations of a single Stokes observable suppressed below the shot-noise level and therefore manifests hidden polarization [2]. The first order degree of polarization is zero, but the second order degree is not zero [2-5]. The macroscopic singlet state has fluctuations in all Stokes observables equally suppressed. Similarly to the two-photon singlet Bell state, it is invariant to any polarization transformations and thus manifests no hidden polarization, i.e. the second order degree of polarization is likewise zero. One can say that the state is completely non-polarized, at the same time being pure. Because of this, it is known in the literature as ‘polarization-scalar light’ [6]. [1] Ch. Simon and D. Bouwmeester, Phys. Rev. Lett. 91, 053601 (2003). [2] D.N. Klyshko, Phys. Lett. A 163, 349 (1992). [3] D.N. Klyshko, JETP 84, 1065 (1997) [4] A.P. Alodjants and S.M. Arakelian, J. Mod. Opt. 46, 475 (1999) [5] A.B. Klimov, G. Björk, J. Söderholm et al., Phys. Rev. Lett. 105, 153602 (2010) [6] V.P. Karasev, A.V. Masalov, Opt. Spectrosc. 74, 551 (1993).

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A new approach to quantum interference Jeff Tollaksen Chapman University, Orange, USA Abstract Aharonov-Bohm effects have significantly impacted the development of physics since their discovery more than 50 years ago. Nevertheless, the (arguably) most profound implication, namely dynamical non-locality, though originally introduced by Aharonov some decades ago, is still new to the physics community. Dynamical non-locality is evident in the interactions between quantum systems, particularly for quantum phenomenon without a classical analog. This contrasts with classical mechanics where the equations of motion are local. For example, when quantum mechanical interference is analyzed with states which are more `non-classical,' namely with states comprised of multiple lumps, then a new type of dynamical variable (called modular variables) reveals physical features of dynamical nonlocality. This suggests a physical explanation for the different behaviors of a single particle in a double-slit setup, helping us shift from a picture involving a quantum wave that passes through all slits, to one with more `localized' particles which interact non-locally} with the other slit(s). Feynman stated that such phenomena "..have in it the heart of quantum mechanics. In reality, it contains the only mystery." Although particles localized around one slit can interact nonlocally with the ``barrier" at the other slit, the uncertainty in quantum mechanics appears to be just right to protect causality. Nevertheless, our proposed experiment to measure this non-locality has been successfully carried out. This new approach has lead to new insights, new intuitions, new experiments and even the possibility of new devices that were missed from the old perspective.

Fisher-information-based uncertainty relations and physical implications Jesus Sanchez Dehesa University of Granada, Spain Abstract The locality property of the Fisher information allows it to occupy a very special place among the wide class of information-theoretic measures (Shannon, Rényi, Tsallis,...). Numerous scientific and tecnological applications have been published in the literature[1]. In this talk we will present and discuss the position-momentum uncertainty relation based on this quantity, which has been recently obtained for general D-dimensional quantum systems[2]. Then, we show the improvement of this relation for general central potentials in arbitrary dimensions. Finally, we give and discuss the values of the Fisher information of the ground and excited hydrogenic states in both position and momentum spaces explicitly in terms of the space dimensionality and the D quantum numbers of the states, as well as the corresponding uncertainty product[3]. Some physical and chemical implications [4] will be also shown. This is a joint work with R. Gonzalez-Ferez, S. Lopez-Rosa, D. Manzano, A.R. Plastino and P. Sanchez-Moreno. [1] See e.g., B.R. Frieden, Science from Fisher Information. Cambridge Univ. Press, Cambridge, 2004. [2] P. Sanchez-Moreno, A.R. Plastino and J.S. Dehesa, J. Phys. A: Math. Theor. 44 (2011) 065301. [3] P. Sanchez-Moreno, R. Gonzalez-Ferez and J.S. Dehesa, New J. Phys. 8 (2006) 330. [4] J.S. Dehesa, S. Lopez-Rosa and D. Manzano, Entropy and complexity analysis of D-dimensional quantum systems. In K.D. Sen (editor), Statistical Complexities: Application to Electronic Structure. Springer, Berlin, 2011.

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Evolution of quantum correlations (entanglement and discord) for quantum open systems Juan Pablo Paz* and Nahuel Freitas Departamento de Física, FCEyN, Universidad de Buenos Aires, Argentina Abstract I will describe recent results concerning the evolution of quantum correlations for a system of two oscillators coupled with the same bosonic environment. The long time evolution of entanglement is characterized by three qualitatively different phases: the entanglement may disappear after a finite time, it may persist forever or it may periodically disappear and reappear. Other quantum correlations, quantified by discord, behave in a different way. We fully characterize the evolution of discord as a function of the initial temperature of the environment and the initial squeezing of system. As it never undergoes sudden death, the fate of discord is simpler than the one of entanglement. However, the long time evolution of discord is also characterized by different dynamical phases, that will be described in this work.

Atomic spin squeezing with cold atomic ensembles Morgan W. Mitchell ICFO - Institute of Photonic Sciences, Castelldefels (Barcelona) – Spain Abstract Quantum metrology uses quantum features such as entanglement and squeezing to improve the sensitivity of quantum-limited measurements. Long established as a valuable technique in optical measurements such as gravitational-wave detection, quantum metrology is increasingly being applied to atomic instruments such as matter-wave interferometers, atomic clocks, and atomic magnetometers. Several of these new applications involve dual optical/atomic quantum systems, presenting both new challenges and new opportunities. I will describe an optical magnetometry system which achieves both shot-noise- and projection-noise-limited performance, allowing study of optical magnetometry in a fully-quantum regime. The versatility of this system allows us to design both linear and non-linear atom-light couplings, with potential application in generation of squeezing and sub-projection- noise measurement. I will briefly discuss applications to quantumenhanced magnetometry and generation of exotic many-atom entangled states.

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Quantum walks and graph characterization Jingbo Wang The University of Western Australia, Perth, Australia Abstract The strikingly different behavior of quantum walks from their classical counterparts has already been harnessed in the formulation of quantum-walk-based algorithms that outperform corresponding classical algorithms [1-6]. In this talk, we present further study of single and two-particle discretetime quantum walks, their potential algorithmic applications and actual physical implementation. In particular, we study the quantum-walk-based search for a marked vertex on a graph. By considering various structures in which not all vertices are equivalent, we investigate the relationship between the successful search probability and the location of the marked vertex within the structure, such as its centrality. We find that the maximum value of the successful search probability does not necessarily increase as the marked vertex becomes more central and we investigate an interesting relationship between the frequency of the successful search probability and the centrality of the marked vertex. We also study two-particle quantum walks with both interacting and non-interacting particles. We show that a simple interaction scheme leads to diverse probability distributions, which depend on the entanglement of the initial state, and this interaction generates entanglement between the particles. We introduce two-particle discrete-time quantum walks on graphs and use them to formulate a polynomial-time algorithm for the graph isomorphism problem. The algorithm is tested on strongly-regular graphs, where it is found that interactions between particles crucially increase the graph distinguishing power of the algorithm. What remains a major challenge is a physical realization of the above proposed algorithmic applications with discrete-time quantum walk, which needs to be experimentally viable, readily scalable, and not limited to specific connectivity criteria. In the last part of my talk, I will present an implementation scheme for discretetime quantum walks on arbitrarily complex graphs. This scheme is particularly elegant since the walker is not required to physically step between the nodes; only flipping coins is sufficient. In addition, by taking advantage of the inherent structure of the CS decomposition of unitary matrices, we are able to implement all coin operations necessary for each step of the walk simultaneously. This scheme can be physically realized using a variety of quantum systems, such as cold atoms trapped inside an optical lattice or electrons inside coupled quantum dots [7, 8]. [1] J. Kempe, Contemp. Phys. 44, 307 (2003). [2] A. Childs and J. Goldstone, Phys. Rev. A 70, 022314 (2004) [3] M. Santha, Lect. Notes Comput. Sci. 4978, 31 (2008). [4] B. L. Douglas and J. B. Wang, J. Phys. A 41, 075303 (2008). [5] D. Reitzner, M. Hillery, E. Feldman, V. Buzek, Phys. Rev. A 79, 012323 (2009) [6] S. Berry and J. B. Wang, Phys. Rev. A 82, 042333 (2010) [7] K. Manouchehri and J. B. Wang, J. Phys. A 41, 065304 (2008) [8] K. Manouchehri and J. B. Wang, Phys. Rev. A 80, 060304R (2009)

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Intense emission of entangled photon pairs in randomly poled nonlinear crystals Jiří Svozilík* and Jan Peřina Jr. Joint Laboratory of Optics, RCPTM, Palacky University, 17. listopadu 12, 772 07 Olomouc, Czech Republic Abstract Randomly poled nonlinear crystals are presented as ultra-broadband intensive sources of photon pairs [1]. Their properties are comparable to those coming from chirped periodically-poled crystals [2]. The high efficiency of photon-pair generation is reached due to the stochastic quasi-phasematching [3], similarly as in the process of second-harmonic generation. The photon-pair generation rate scales linearly with the number of poled domains [4]. The larger the randomness in the domain lengths, the broader the emitted spectra of the down-converted fields. When properly phase compensated the spectrally ultra-broadband photons in a pair can be temporally correlated at the fs timescale. Thus the detection times of the two photons occur in a temporal window with the width comparable to that characterizing an optical cycle. Similarities between the randomly poled and chirped periodically-poled crystals have been found also in the transverse profiles of the downconverted fields as well as correlation areas of two photons comprising a pair. Properties of photon pairs coming from randomly poled structures are temperature dependent, in contrast to those belonging to chirped periodically-poled crystals. Easy fabrication represents a great advantage of randomly poled crystals that allow high fabrication tolerances. [1] J. Svozilik and J. Perina Jr., Opt. Express 18, 27130 (2010). [2] J. Svozilk and J. Perina Jr., Phys. Rev. A 80 (2009). [3] J. Perina Jr. and J. Svozilik: Randomly poled crystals as a source of photon pairs, Phys. Rev. A, in press. [4] M. M. Fejer, G. A. Magel, D. H. Jundt, and R. L. Byer, IEEE J. Quant. Electr. 28, 2631 (1992).

Experimental implementation of the optimal linear-optical controlled phase gate Karel Lemr*, A. Černoch, J. Soubusta, K. Kieling, J. Eisert and M. Dušek Joint Laboratory of Optics of Palacký University and Institute of Physics of Academy of Sciences of the Czech Republic, 779 07 Olomouc, Czech Republic Abstract We report on the first experimental realization of optimal linear-optical controlled phase gates for arbitrary phases. The realized scheme is entirely flexible in that the phase shift can be tuned to any given value. All such controlled phase gates are optimal in the sense that they operate at the maximum possible success probabilities that are achievable within the framework of postselected linear-optical implementations with vacuum ancillas. The quantum gate is implemented by using bulk optical elements and polarization encoding of qubit states. We have experimentally explored the remarkable observation that the optimum success probability is not monotone in the phase. For further reference please see Phys. Rev. Lett. 106, 013602 (2011).

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Integrated quantum photonics Konstantinos Poulios Centre for Quantum Photonics, School of Physics, University of Bristol, Tyndall Avenue, BS8 1TL, UK Abstract Quantum information science aims to harness uniquely quantum mechanical properties to enhance measurement and information technologies, and to explore fundamental aspects of quantum physics. Of the various approaches to quantum computing, photons are particularly appealing for their low-noise properties and ease of manipulation at the single qubit level [1]. Encoding quantum information in photons is also an appealing approach to quantum communication, metrology and other quantum technologies [2]. However, the implementation of optical quantum circuits with bulk optics has reached practical limits. We have developed an integrated waveguide approach to photonic quantum circuits for high performance, miniaturisation and scalability [3]. Here we report high-fidelity silica-on-silicon integrated optical realisations of key quantum photonic circuits, including two-photon quantum interference and a controlled-NOT logic gate [4]. We have demonstrated controlled manipulation of up to four photons on-chip, including high-fidelity single qubit operations, using a lithographically patterned resistive phase shifter [5]. We have used this architecture to implement a small-scale compiled version of Shor’s quantum factoring algorithm [6] and demonstrated heralded generation of tunable four photon entangled states from a six photon input [7]. We have combined waveguide photonic circuits with superconducting single photon detectors [8]. Finally, we describe complex quantum interference behavior in multi-mode interference devices with up to eight inputs and outputs [9], and quantum walks of correlated particles in arrays of coupled waveguides [10]. [1] J. L. O’Brien, Science 318, 1567 (2007); [2] J.L.O’Brien, A.Furusawa, and J.Vuckovic, Nature Photon. 3, 687 (2009); [3] A. Politi, M. J. Cryan, J. G. Rarity, S. Yu, and J. L. O’Brien, Science 320, 646 (2008); [4] A. Laing, A. Peruzzo, A. Politi, M. R. Verde, M. Halder, T. C. Ralph, M. G. Thompson, and J. L. O’Brien, Appl. Phys. Lett. 97, 211109 (2010); [5] J. C. F. Matthews, A. Politi, A. Stefanov, and J. L. O’Brien, Nature Photon. 3, 346 (2009); [6] A. Politi, J. C. F. Matthews, and J. L. O’Brien, Science 325, 1221 (2009); [7] J. C. F. Matthews, A. Peruzzo, D. Bonneau, and J. L. O’Brien, arXiv:1005.5119; [8] C. M. Natarajan, A. Peruzzo, S. Miki, M. Sasaki, Z. Wang, B. Baek, S. Nam, R. H. Hadfield, and J. L. O’Brien, Appl. Phys. Lett. 96, 211101 (2010); [9] A. Peruzzo, A. Laing, A. Politi, T. Rudolph, and J. L. O’Brien, Nature Comm. 2, 224 (2011); [10] A. Peruzzo, M. Lobino, J. C. F. Matthews, N. Matsuda, A. Politi, K. Poulios, X.-Q. Zhou, Y. Lahini, N. Ismail, K. Worhoff, Y. Bromberg, Y. Silberberg, M. G. Thompson, and J. L. O’Brien, Science 329, 1500 (2009).

All-optical generation of states for “Encoding a qubit in an oscillator” H. M. Vasconcelos, Liliana Sanz*, and S. Glancy Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, Brazil Abstract Most quantum computation schemes propose encoding qubits in two-level systems. Others exploit the use of an infinite-dimensional system. In “Encoding a qubit in an oscillator” [Phys. Rev. A 64, 012310 (2001)], Gottesman, Kitaev, and Preskill (GKP) combined these approaches when they proposed a fault-tolerant quantum computation scheme in which a qubit is encoded in the continuous position and momentum degrees of freedom of an oscillator. One advantage of this scheme is that it can be performed by use of relatively simple linear optical devices, squeezing, and homodyne detection. However, we lack a practical method to prepare the initial GKP states. Here we propose the generation of an approximate GKP state by using superpositions of optical coherent states (sometimes called “Schrödinger cat states”), squeezing, linear optical devices, and homodyne detection. Optics Letters, Vol. 35, Issue 19, pp. 3261-3263 (2010).

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Quantum entanglement and squeezing in coupled harmonic and anharmonic oscillator systems Lock Yue Chew Nanyang Technological University, 21 Nanyang Link SPMS-PAP-04-04, Singapore 637371 Abstract In this talk, I will present our recent work on quantum squeezing and its relation to quantum entanglement. Our systems of interest are two-mode interacting bosonic systems protected from the decohering environment. The consideration of isolated quantum systems allows us to optimally exploit entanglement as a resource for quantum computation through selecting the maximal entangled state during the unitary time evolution. This motivation has led us to explore different coupled harmonic and anharmonic oscillator systems. First, I will present the link between entanglement entropy and quantum squeezing in the ground states of two-coupled anharmonic oscillator systems. The coupling and the anharmonicities in the oscillator have the effect of enhancing the squeezing in the state without any significant change in the uncertainty product[1]. While the increase in squeezing implies an increase in the entanglement entropy, our studies found that the relation between them is not unique. It depends on the type of anharmonic oscillators. On the other hand, the relation between entanglement entropy and the local uncertainty product is found to be unique when the former become large. However, this robust relationship is formerly altered by a quantum catastrophe[2]. Second, we explore the generation of entanglement by coupled harmonic and anharmonic oscillator systems. By studying the connections between the entanglement dynamics and the underlying classical trajectories in coupled oscillator systems, we found that the dynamics is dependent on the global classical dynamical regime instead of the local classical behavior for both integrable and non-integrable models. Thus, we have found “non-local” models that are stable against any errors in the preparation of the initial coherent states. This is significant in the design of robust quantum information processing protocol[3]. Finally, I will present our recent results on how entanglement can be dynamically enhanced through local squeezing of initial separable Gaussian states in coupled harmonic oscillator systems. In particular, I will show that an appropriate allocation of local squeezing to each initial mode is important. Otherwise, less or no entanglement will be generated[4]. [1] N. N. Chung and L. Y. Chew, Physical Review A 76, 032113 (2007). [2] N. N. Chung, C. H. Er, Y. S. Teo and L. Y. Chew, Physical Review A 82, 014101 (2010). [3] N. N. Chung and L. Y. Chew, Physical Review E 80, 016204 (2009). [4] C. H. Er, N. N. Chung and L. Y. Chew, Manuscript in Preparation.

Entropic uncertainty relations including experimental accuracies Lukasz Rudnicki Center for Theoretical Physics PAS (Al. Lotnikow 32/46, 02-668 Warsaw Poland) Abstract During my presentation I would like to get the participant's attention to entropic uncertainty relations for binned probability distributions of position and momentum variables, and their recent improvements. At the beginning I will briefly introduce the BBM (Bialynicki-Birula, Mycielski) uncertainty relation for continuous Shannon entropies in quantum mechanics (for position and momentum probability distributions) and its connection with Heisenberg uncertainty relation. Later I will introduce Shannon (Renyi) entropies of binned (due to finite experimental accuracies) position and momentum probability distributions and the corresponding uncertainty relation [Phys Rev A 74, 052101 (2006)]. The main part of my presentation shall be the recent improvement of this uncertainty relation. I will present the complete derivation and the discussion which compares my new results with older ones. 49

Distant entanglement protected through artificially increased local temperature Marcelo França Santos Universidade Federal de Minas Gerais, Belo Horizonte, Brazil Abstract In composed quantum systems, the presence of local dissipative channels causes loss of coherence and entanglement at a rate that grows with the temperature of the reservoirs. However, here we show that if temperature is artificially added to the system, entanglement decay can be significantly slowed down or even suppressed conditioned on suitable local monitoring of the reservoirs [1]. We propose a scheme for implementing joint reservoir monitoring applicable in different experimental setups, such as trapped ions, circuit and cavity QED or quantum dots coupled to nanowires, and we analyze its general robustness against detection inefficiencies and the non-zero temperature of the natural reservoir. Typically, a two level system ({|0>,|1>}) coupled to a zero temperature dissipative reservoir loses coherence exponentially in time. If such qubit is entangled with another decohereing qubit, then the system as a whole loses entanglement as well at an equivalent rate. Earlier works show that if the reservoirs acting on each qubit can be locally monitored, then the average loss of entanglement can be slowed down [2]. This change of pace derives from the information about the qubits gathered from reading out the reservoirs. Nonetheless, entanglement is eventually lost, either immediately if a photon is detected in any local reservoir, hence projecting the corresponding qubit onto its ground state, or asymptotically by driving the system as a whole to its global ground state. Our scheme relies on adding an extra decoherence channel to each qubit, i.e. another reservoir, that pumps the system back into its excited state |1> and to do so through a third level that is adiabatically eliminated but whose decay into level |1> emits a photon at the same propagation mode but of orthogonal polarization of that created by spontaneous emission. The direct detection of each photon can identify which channel acted on the system, hence separating the local qubit from the rest of the network. However, the combination of both propagation modes in a suitably oriented polarized beam splitter (PBS) produces detections that represent local unitaries on the respective qubit what necessarily preserves the entanglement of the system as a whole. Furthermore, because one can keep track of which detector clicked (through which port of the PBS the photon left), then one knows which unitary affected the system and, if necessary, the evolution can be locally corrected at any time to bring the system back to its original state. Finally, we present schemes to simulate this in cavity QED with the atoms and field interchanging the roles of qubits and reservoirs [3]. [1] A.R.R. Carvalho, MFS, New J. Phys. 13 013010 (2011) - IOP Select. [2] A. Sales, et. Al., Phys. Rev. A 78, 022322 (2008), E. Mascarenhas, et. Al., Phys. Rev. A 81, 032310 (2010), S. Vogelsberger, et. Al., Phys. Rev. A., 82, 052327, E. Mascarenhas, et. Al., Phys. Rev. A, [3] MFS, A.R.R. Carvalho, arXiv:1102.1047 (2011).

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Complete reconstruction of the spectral covariance matrix Marcelo Martinelli IF-USP, São Paulo, Brazil Abstract Photodetection of a light beam is the usual tool for probing the state of the electromagnetic field. In the continuous variables domain, we often perform a homodyning measurement of the studied field with the help of a reference field, the local oscillator, and their interference on a beam splitter, to convert phase and amplitude fluctuations into correlated intensity fluctuations in the outputs of this interferometer. These correlations can be recovered by the subtraction of the photocurrent measured at these outputs. Alternatively, one can use an empty cavity to convert phase into amplitude fluctuations, through a self-homodyning technique. With these techniques, we can observe the light fluctuations of any quadrature of the field at a given analysis frequency, and use the outcome of these measurements to characterize squeezing of one field, entanglement between two modes, or look for a complete reconstruction of the spectral covariance matrix of the fields involved, allowing the analysis of entanglement among many different modes. Nevertheless, the outcome of this process may return only part of the spectral covariance, the measurement being, therefore, incomplete : on the one hand, in the evaluation of the noise matrix from the Langevin equations, off-diagonal terms in the spectral matrix can be indeed complex numbers; on the other hand, detection of this field by usual techniques results in a real-valued covariance matrix for the noise. For example, the evaluation of this matrix for all the interacting modes of a lossless OPO results in a final state with non-unity purity [1]. In contrast, if we consider the complete complex values of the matrix elements, the purity is one, as expected from unitary operations acting on input vacuum or coherent states, as those performed by the OPO. In this presentation, we will discuss some measurement techniques that can give us full access to these terms. In this case, we will be able to perform a complete tomography of the quantum state, and recover all the information in the field. We will study the case of the OPO above threshold, and show that these complex terms are present in the cross correlations between pump, signal and idler modes. Entanglement in this picture should consider six fields, providing a rich source of Gaussian entangled states. [1] T. Golubeva, Yu. Golubev, C. Fabre, and N. Treps, Eur. Phys. J. D 46, 179–193 (2008).

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Entanglement irreversibility from quantum discord and quantum deficit Marcio F. Cornelio*, Marcos C. de Oliveira, Felipe F. Fanchini Universidade Estadual de Campinas - IFGW/DFMC, Rua Sergio Buarque de Holanda, 777, Campinas - SP, CEP 13083-859, Brazil Abstract We relate the problem of irreversibility of entanglement with the recently defined measures of quantum correlation - quantum discord and one-way quantum deficit. We show that the entanglement of formation is always strictly larger than the coherent information and the entanglement cost is also larger in most cases. We prove irreversibility of entanglement under LOCC for a family of entangled states. This family is a generalization of the maximally correlated states for which we also give an analytic expression for the distillable entanglement, the relative entropy of entanglement, the distillable secret key and the quantum discord.

Suppression of dipolar collisions in quantum regime Marcio H. G. de Miranda*, A. Chotia, B. Neyenhuis, D. Wang, G. Quemener, S. Ospelkaus, J. L. Bohn, D. Jin, J. Ye JILA, NIST and University of Colorado at Boulder, USA Abstract The creation of ultracold polar molecular gases near quantum degeneracy opens novel research prospects ranging from dipolar quantum many-body physics to ultracold chemistry. With a near quantum degenerate gas of fermionic KRb polar molecules, this work presents studies on dipolar collision and chemical reaction dynamics, exhibiting long range interactions and spatial anisotropy. With full control over the internal quantum state (electronic, vibrational, rotational and hyperfine states) of the molecules, we show how quantum statistics of the molecule determines the rate of chemical reactivity in the limit of vanishing collisional energy. Combining control over the molecular dipole moment and the dimensionality of the spatial confinement, we suppress inelastic collisions between polar molecules by up to two orders of magnitude. The suppression of inelastic collisions is achieved by changing the geometry of the confinement from three-dimensional to two-di mensional optical trapping. With the combination of a sufficiently tight 2D confinement and Fermi statistics of the molecules, two polar molecules approach each other only in a ``side-by-side'' collision, where the inelastic collisions are suppressed by the repulsive dipole-dipole interaction. This suppression requires quantum state control of internal and external (harmonic oscillator levels of the optical lattice) degrees of freedom of the molecules.

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Experimental coherent superpositions of quantum operators for noiseless amplification and advanced state manipulation A. Zavatta, M. Locatelli, C. Polycarpou, and Marco Bellini* Istituto Nazionale di Ottica - CNR, L.go E. Fermi, 6, I-50125, Florence, Italy + LENS and Department of Physics, University of Florence, Italy Abstract Conditional single-photon addition and subtraction have been demonstrated by different experimental groups, and sequences of these operations have also been used to test fundamental quantum rules. However, only recently it was shown that arbitrary coherent superpositions of these basic quantum operators can be realized in a laboratory. The basic experimental scheme includes a parametric amplifier (performing conditional single-photon addition) placed between two lowreflectivity beam-splitters (performing conditional single-photon subtractions) in the path of a generic quantum light state. The reflected modes of the two subtracting beam-splitters are then interferometrically combined by means of another beam-splitter, and a single-photon detector is placed at one of its outputs. In the event of a coincident click from this detector and the one placed in the idler mode of the parametric crystal, one is left with the ambiguity as to the order of the sequence of single-photon addition and subtraction, and has therefore implemented a coherent superposition of the two alternated sequences. Both the amplitudes and the relative phase of the two terms of the superposition can be arbitrarily adjusted by changing the beam-splitter reflectivity and the optical paths, thus allowing the implementation of arbitrary super positions. In the first experiment of this kind, a superposition of alternated sequences of creation and annihilation operations with equal weights were used for the first direct test of quantum commutation rules. Later, it was found that this setup can lead to a variety of other interesting tools for quantum state engineering. A particularly interesting example is the realization of noiseless linear amplification of quantum light states. The possibility of amplifying light states (although in a non-deterministic way) without introducing additional noise and without large distortions could be used to distill and concentrate entanglement and could form part of a quantum repeater, or it could improve the performance of phase-estimation schemes and enable high-fidelity probabilistic cloning and discrimination of coherent states. If the interferometric scheme above is adopted to produce a welldefined superposition of opposite sequences of photon addition and subtraction, an amplifier with a completely adjustable gain can be realized, and the same setup can be used to emulate Kerr nonlinearity. However, a particularly simple case is obtained when the amplitude gain is fixed to 2, such that the scheme reduces to a simple sequence of photon addition and subtraction. The application of this non-determinist ic scheme for noiseless amplification has already shown that, for a given input coherent state amplitude, its effective gain and fidelity greatly outperform those of other existing approaches. Other recent results will be presented in this context.

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Probabilistic and information characteristics of photon states Margarita A. Man'ko P.N. Lebedev Physical Institute, Leninskii Prospect 53, Moscow 119991, Russia Abstract The probabilistic characteristics of quantum states like entropy, information, and inequalities associated with these characteristics are discussed. The probability distributions describing the photon quantum states within the framework of tomographic approach, where the state tomograms are used as an object providing complete information on the properties of the quantum states, are considered. For photon number tomograms and optical tomograms of two- and three-mode electromagnetic fields, the entropic subadditivity and strong subadditivity conditions related to tomographic Shannon entropy are studied. The example of squeezed states is considered in detail. The talk presents, in particular, the results of [13]. [1] M.A. Man'ko, V.I. Man'ko, and Rui V. Mendes, J. Russ. Laser Res., Vol. 27, 507-532 (2006). [2] M.A. Man'ko, Phys. Scr., Vol. 82, 0381009 (2010). [3] M.A. Man'ko and V.I. Man'ko, Found. Phys., Vol. 41, 330-344 (2011).

Interaction-based quantum metrology showing scaling beyond the Heisenberg limit Mario Napolitano ICFO-Institut of photonic sciences, Castelldefels – Spain Abstract Quantum metrology studies the use of entanglement and other quantum resources to improve precision measurement. An interferometer using N independent particles to measure a parameter χ can achieve at best the “standard quantum limit” (SQL) of sensitivity δχ ∝ N-1/2. The same interferometer using N entangled particles can achieve in principle the “Heisenberg limit” δχ ∝ N-1, using exotic states, e.g., NooN states. Recent theoretical work argues that interactions among particles may be a valuable resource for quantum metrology, allowing scaling beyond the Heisenberg limit. Specifically, a k-particle interaction will produce sensitivity δχ ∝ N-k with appropriate entangled states and δχ ∝ N-(k-1/2) even without entanglement. Here we demonstrate this “super-Heisenberg” scaling in a nonlinear, non-destructive measurement of the magnetisation of an atomic ensemble. We use fast optical nonlinearities to generate a pairwise photon-photon interaction (k = 2) while preserving quantum-noise-limited performance, to produce δχ ∝ N-3/2. We observe super-Heisenberg scaling over two orders of magnitude in N, limited at large N by higherorder nonlinear effects, in good agreement with theory. The experiment, uses pulses of nearresonant light to measure the collective spin F of an ensemble of NA ∼ 106 cold rubidium-87 atoms, probed on the (5S1/2 → 5P3/2) D2 line. The on-axis atomic magnetisation Fz, which plays the role of χ in this measurement, is prepared in the initial state Fz = NA by optical pumping with resonant circularly polarised light propagating along the trap axis z. Polarised, but not entangled, photons pass through the ensemble and experience polarization rotation proportional to Fz. Two regimes of probing are used by selecting different light intensities and detunings: the linear probe, giving linear estimation, provides a projection-noise-limited quantum-non-demolition (QND) measurement of Fz, with uncertainty at the parts-per-thousand level. Conversely, the nonlinear probe consists of a single τNL = 54 ns FWHM, Gaussian-shaped, high-intensity pulse with NNL photons and the detuning ∆0 where symmetry in the excited state manifold suppresses the linear susceptibility. Crucially, having two probes allows us to precisely calibrate the nonlinear measurement using a highly sensitive and well characterised independent measurement of the same sample. The experiment demonstrates the use of interparticle interactions as a new resource for quantum metrology. While possible applications to precision measurement will require detailed study, this first experiment shows that interactions can produce super-Heisenberg scaling and improved precision in a quantum-limited measurement. Ref. M. Napolitano, M. Koschorreck, B. Dubost, N. Behbood, R. J. Sewell, and M. W. Mitchell, “Interactionbased quantum metrology showing scaling beyond the Heisenberg limit,” arXiv:1012.5787.

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A solvable quantum diffusive model Marko Znidaric ICF, UNAM, Mexico and FMF, University of Ljubljana, Slovenia Abstract Understanding quantum transport from microscopic equations of motions is one of the unsolved problems of theoretical physics. For instance, it is not known what are the necessary requirements to observe diffusive transport. Close to equilibrium, where linear response theory is expected to be valid, one can study transport by calculating an equilibrium correlation function. To access a true nonequilibrium situation though one must either couple a system to a very large (an infinite) reservoir or take the coupling with baths into account in an effective way, for instance by means of a master equation. Analytic results are clearly preferred, unfortunately however all known solvable systems display ballistic transport. I shall present an analytical solution for a one dimensional spin chain under nonequilibrium driving described by the Lindblad master equation. Exact expressions for one and two-point correlation functions indicate diffusive transport. This is a first example of an exactly solvable diffusive quantum model. In the nonequilibrium steady state long-range correlations are present. We also identify a nonequilibrium phase transition between diffusive and ballistic transport regimes. In a special case, corresponding to a ballistic XX chain with boundary driving, an exact solution is expressed in terms of matrix product ansatz with matrices if fixed dimension 4. The solution shows some similarity with classical exclusion processes.

Open-system quantum simulation with Rydberg atoms and ions Markus Mueller University of Innsbruck, Austria Abstract A universal quantum simulator is a controlled quantum device that reproduces the dynamics of any other many-particle quantum system with short-range interactions. This dynamics can refer to both coherent Hamiltonian and dissipative open-system time evolution. We propose and analyze a novel simulation scheme, where laser-excited Rydberg atoms in optical lattices provide an efficient implementation of a universal quantum simulator for complex spin models involving n-body interactions and constraints, such as, e.g., Kitaev's toric Hamiltonian. In addition, the approach provides the ingredients for dissipative preparation of entangled states based on engineering multiparticle reservoir couplings. The basic building blocks of the simulation architecture are efficient and high-fidelity multi-qubit entangling gates using auxiliary Rydberg atoms, including a possible dissipative time step through optical pumping. This enables mimicking the time evolution of the many-particle quantum system by a sequence of fast, parallel and high-fidelity multi-particle coherent and dissipative Rydberg gates. We also present an open-system quantum simulation architecture with trapped ions. For an ion-trap quantum computing architecture, we show how a combination of multi-qubit entangling gates and optical pumping enables the implementation of coherent operations and dissipative processes. We finally present the results of a collaboration, where we have demonstrated the elementary building blocks of such an open-system quantum simulator in an experiment with up to five ions.

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Quantum averaging of squeezed quadratures Mikael Lassen Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark Abstract Squeezing has been recognized as the main resource for quantum information processing and an important resource for beating classical detection strategies and also for fundamental test of quantum mechanics. It is therefore of high importance to reliably generate stable squeezing over longer periods of time. The averaging procedure for a single quadrature can be realized using a single beam splitter followed by homodyne measurement and feed-forward as shown in the figure. If the input squeezing variances are known, the protocol can be deterministic where all quadrature measurement outcomes are used to drive a displacement operation in the other output. However, since the input states have unknown squeezing degrees the deterministic protocol cannot be used. By resorting to a probabilistic protocol, where the output state is selected based on the quadrature measurement outcomes, it is however possible to construct the harmonic mean without knowing the input variances as explained above. The strategy is to interfere the two squeezed light states on a beam splitter and probabilistically herald one output based on the homodyne measurement result of the other output: If the measurement outcome of the homodyne measurement lies within a certain interval the state is kept, otherwise it is discarded.

Linear-optical quantum information processing: a few experiments Miloslav Dusek*, L. Celechovska, A. Cernoch, J. Eisert, H. Fikerova, J. Fiurasek, M. Jezek, K. Kieling, K. Lemr, M. Micuda, M. Mikova, J. Soubusta Department of Optics, Palacky University, Olomouc, Joint Laboratory of Optics of Palacky University and Institute of Physics of Academy of Sciences of the Czech Republic, Institute of Physics and Astronomy, University of Potsdam, Institute for Advanced Study, Berlin Abstract Quantum information processing requires precise manipulation and measurement of states of quantum systems. Even if linear-optical implementations of quantum operations are mostly probabilistic, they have a potential for practical realization of many quantum information processing tasks. In this contribution we review some our recent experiments in this field. Namely, linearoptical implementations of a Programmable discriminator of non-orthogonal weak coherent states, Programmable gate for an arbitrary rotation of a single qubit along the z axis, Partial-SWAP gates including entangling square-root of SWAP, Partial symmetrization and anti-symmetrization of twoqubit states (applicable for optimal universal asymmetric quantum cloning), Optimal linear-optical controlled-phase gate with an arbitrary phase shift (its probability of success is a non-monotonous function of phase), and Programmable phase gate with the probability of success increased to the theoretical limit (using electronic feed-forward). Some of these experiments were built from bulk optical elements and the information was encoded into polarization states of photons. The others were based on fiber optics. In these cases the information was encoded into spatial modes (each photon could propagate through two or more optical fibers).

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How much does a distinguishable particle destroy coherence of a quantum bit? Miroslav Gavenda*, Lucie Bartuskova, Jan Soubusta, Miloslav Dusek, Radim Filip Dept. Of Optics & Joint Laboratory of Optics, Palacky University & Academy of Sciences of the Czech Republic, Olomouc - Czech Republic Abstract We investigate how distinguishability of a "noise" particle degrades interference of the "signal" particle. The signal, represented by an equatorial state of a photonic qubit, is mixed with noise, represented by another photonic qubit, via linear coupling on the beam splitter. We report on the degradation of the "signal" photon interference depending on the degree of indistinguishability between "signal" and "noise" photon. When the photons are principally completely distinguishable but technically indistinguishable the visibility drops to the value 1/√2. As the photons become more indistinguishable the maximal visibility increases and reaches the unit value for completely indistinguishable photons. We have examined this effect experimentally using setup with fiber optics two-photon Mach-Zehnder interferometer.

Experimental investigation of dynamical invariants in bipartite entanglement Osvaldo Jimenez Farias Instituto de Fisica, Universidad Federal do Rio de Janeiro Abstract The non-conservation of entanglement, when two or more particles interact, sets it apart from other dynamical quantities like energy and momentum. It does not allow the interpretation of the subtle dynamics of entanglement as a flow of this quantity between the constituents of the system. Here we show that adding a third party to a two-particle system may lead to a conservation law that relates the quantities characterizing the bipartite entanglement between each of the parties and the other two. We provide an experimental demonstration of this idea using entangled photons, and generalize it to N-partite GHZ states.

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Experimental QKD based on orthogonal states Paolo Traina INRIM, strada delle cacce 91 10135 Turin – Italy Abstract We report on the experimental implementation of QKD with orthogonal states. In general, it is not possible to clone non-orthogonal states, thus any eavesdropping attempt in a non-orthogonal states-based Quantum Communication scheme induces errors in the key transmission, which can lead to the detection of the the spy. In the most common applications, orthogonal states are not used in QKD schemes because they can be faithfully copied without spoiling the transmitted information. Nevertheless, a protocol has been proposed by L. Goldberg and L. Vaidman (GV), in which even if the data exchange is realized using only two orthogonal states, any eavesdropping attack is detectable by the legal users. In this case, the orthogonal states are superpositions of two localized wave packets travelling along separate channels. Here we show the first experimental realization of QKD based on GV protocol and we characterize it in terms of the main parameters related to the stability and security of our system. We show the possibility of achieving a Quantum Bit Error Rate comparable with more common secure QKD systems. Our work provides a significant hint to the discussion on the minimal quantum resources necessary for the implementation of quantum tasks overcoming classical limits.

Symplectically invariant multidimensional uncertainty relations Pavel S. Alekseev* and F. V. Moroseev Ioffe Institute, Politekhnicheskaya 26, Saint Petersburg, Russia Abstract It is of interest to derive multidimensional uncertainty relations for canonically conjugate variables (for example, for the components of coordinates and momentums), which would not change its form under a change of basis in the space of the canonically conjugate variables. Due to the symplectic geometry of phase space, it is logical to consider only the symplectic bases, i. e., the case when a change of variables is the canonical linear transform. A problem of constructing of the uncertainty relations being invariant in this sense was discussed for the first time in paper [1]. In that paper, starting from the commutation relations for coordinates and momentums, some inequalities for the coefficients of the characteristic equation of the correlation matrix of a set of coordinates and momentums were obtained (the correlation matrix corresponds to the quantum mechanical averaging over the state under consideration). We have derived other symplectically invariant inequalities, which, in our opinion, with more reason can be called multi-dimensional analogue of the Schrödinger-Robertson inequality. Feature of our inequalities is the fact that, unlike paper [1] and other studies, we started not from the correlation matrix for the coordinates and momentums , but from a certain expressions quadratic by the correlation matrix. Specifically, we examined the product of the correlation matrix on its symplectically conjugate matrix, and it was shown that the eigenvalues of this product matrix pairwise coincide and are all equal or greater than the square of Planck's constant divided by 4 [2]. The choice of the symplectic basis by the method of paper [1], in which the correlation matrix is diagonalized, demonstrates that our inequalities are equivalent to the Heisenberg inequalities for each pair of the transformed coordinates and momenta. But it was shown that our inequalities are more stringent than those obtained in [1]. Equal sign in the obtained inequalities is achieved on the most common form of the multidimensional squeezed states. A twomode light in an entangled state close to the two-mode squeezed state may serve as a physical system for which the uncertainty relation obtained can manifest. [1] E.C.G. Sudarshan, C.B. Chiu, and G. Bhamathi, Phys. Rev. A 52, 43 (1995). [2] P. S. Alekseev and F. V. Moroseev, Journal of Experimental and Theoretical Physics 108 , 571, (2009).

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Noiseless amplification powered by noise Petr Marek Department of Optics, Palacky University, 17. listopadu 12, Olomouc 771 46, Czech Republic Abstract Uncertainty is inherent to quantum mechanics. It has long been considered more than a nuisance, as it allows for applications going well beyond the possibilities of classical physics, empowering the quantum key distribution, for example. However, next to the “necessary uncertainty” that cannot be reduced, there is a “noise” - classically random fluctuations which serve only to deteriorate the quantum state and reduce its usability. or so it would seem at the first glance. Surprisingly, there are situations, in which the noise is not only harmless, but in which it is necessary! An example of such the situation appears when we take interest in amplification of signals of light. Phase properties of a classical signal of light can be improved by amplification, approach that is problematic in its application on quantum states of light, mostly because amplification also introduces additional noise. However, there is a way around this problem. The `noiseless' amplification can work if reduced probability of success is accepted. There are several possible approaches to amplification, most of them relying on fine control of the light field at the single photon level. But noiseless amplification can be also achieved by substituting the expensive single photon resources with addition of noise. And this will be the story of that rather counter-intuitive result.

No quantum memory for programmable discrimination Ramon Muñoz Tapia Dept. of Physics, Universitat Autonoma Barcelona, Bellaterra (Barcelona) – Spain Abstract Discrimination between given hypothesis is one the most basic tasks in our everyday lives. In the quantum realm it amounts to discriminate between quantum states. A programmable machine is a device able to discriminate between any unknown states. The device has program ports loaded with the states to be discriminated, which act as analogic programs. At the data port one has the state one wishes to identify. These devices can be viewed as learning machines. In this talk I will consider two states discrimination and focus on qubit states, although most of the results can be generalised to higher dimensional systems. I first study the performance of such devices for pure states. I compute the unambiguous and minimum error probabilities for any number of pure qubit states at the input ports. I show that when the program ports are loaded with an infinitely large number of copies of the states, the usual state discrimination problem is recovered while when the number of copies at the data port is infinitely large we recover the state comparison problem. I then extend the applicability of the device when the ports are fed with mixed states. In this case no unambiguous answers can be given, but the minimum error probability can be readily computed. The asymptotic cases are also studied. I obtain the very non trivial subleading term of the error probability when the number of states at the program is asymptotically large. Finally, I compare the performance of these devices with measure-and-discriminate (MAD) machine, i.e., one that first measures the program states and then tries to identify the nature of the input states. I show that, rather surprisingly, in some cases these MAD machines are in fact optimal.

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Generalized entropic measures of quantum correlations Raul Rossignoli*, N. Canosa, L. Ciliberti Depto. de Física-IFLP, Universidad Nacional de La Plata, CIC-CONICET, Argentina Abstract The exponential speedup achieved in certain quantum algorithms based on mixed states with negligible entanglement has renewed the interest on alternative measures of quantum correlations for mixed states. In this contribution we discuss a general measure of non-classical correlations for bipartite systems based on generalized entropic functions, defined as the minimum information loss due to a local measurement. In the case of pure states it reduces to the generalized entanglement entropy, i.e., to the generalized entropy of the reduced state. However, in the case of mixed states it can be nonzero in separable states, vanishing just for states diagonal in a general product basis, like the quantum discord. Simple quadratic measures of quantum correlations arise as a particular case of the present formalism. The minimum information loss due to a joint local measurement is also considered. The evaluation of these measures in some relevant cases will also be discussed, together with comparison with the corresponding entanglement monotones.

Physics within a quantum reference frame Renato M. Angelo Universidade Federal do Paraná, PO Box 19044, 81531-990, Curitiba, PR, Brazil Abstract We investigate the physics of quantum reference frames. Specifically, we study some simple scenarios involving a small number of quantum particles, whereby we promote one of these particles to the role of a quantum observer and ask what is the description of the rest of the system, as seen by this observer? In this context, we present and unravel some apparent paradoxes which reveal fundamental aspects underlying the physics within quantum reference frames.

Quantization of the damped harmonic oscillator revisited Rodrigo Fresneda UFABC, Santo André, Brazil Abstract We return to the description of the damped harmonic oscillator by means of a closed quantum theory with a general assessment of previous works, in particular the Bateman-Caldirola-Kanai model and a new model recently proposed by one of the authors. We show the local equivalence between the two models and argue that latter has better high energy behavior and is naturally connected to existing open-quantum-systems approaches.

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Phonon-induced disentanglement in a semiconductor quantum register F. Lastra1, S. Reyes2, Sasha Wallentowitz*2 1

2

Departamento de Fisica, Universidad de Santiago, Santiago, Chile; Facultad de Fisica, Pontificia Universidad Catolica de Chile, Santiago, Chile Abstract

A quantum bit can be implemented in a semiconductor substrate as a single electron shared by two charge-based donor sites. Below room temperature one of the principal sources of decoherence of such a qubit is the off-resonant scattering of acoustic phonons. It leads to a strongly non-Markovian dynamics with temporary recoherence and stationary non-vanishing coherence [1]. In this contribution we generalize our previous results to the case of a N-qubit quantum register. We show how the acoustic phonon scattering generates a disentanglement dynamics within the quantum register by showing the dynamics or the concurrence of two selected qubits. Moreover, we discuss its dependence on the geometrical arrangement of the donor sites that constitute the quantum register. [1] F. Lastra, S. Reyes, S. Wallentowitz, Analytic model of non-Markovian decoherence in donor-based charge quantum bits, J. Phys. B 44, 015504 (2011).

Engineering of non Gaussian resources with high performance in Quantum Information Silvio De Siena DMI, Università di Salerno, via Ponte Don Melillo, 84084 Fisciano (SA), Italy Abstract The engineering of entangled resources to be exploited in quantum protocols, as for example teleportation, are a crucial step in the framework of Quantum Information. Both high performance and experimental achievability with current technology of the entangled resources are required. Despite Gaussian states are the most common and easily achievable resources in continuous variable Quantum Information, in the last years it has been realized that non Gaussian resources are significantly more effective, and indispensable for the implementation of the universal quantum computation. We present schemes for the generation of a class of non Gaussian entangled states, realized by linear optics and post-selection strategies. The scheme introduces an external parameter which can be tuned in such a way to span the whole class of states, and which can be exploited to optimize the teleportation performance for various choices of input states. We show that the optimized resources are sensibly more effective in teleportation and in entanglement swapping protocols in comparison with Gaussian resources and with other non Gaussian resources, both in ideal and in realistic conditions. We also discuss the characteristic of a “good” resource, involving a careful balance of different aspects.

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An entropic Einstein – Podolsky – Rosen steering criteria Stephen Walborn Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brasil Abstract We propose an EPR inequality based on an entropic uncertainty relation for complementary continuous variable observables. This inequality is more sensitive than the previously established EPR inequality based on inferred variances, and opens up the possibility of EPR tests of quantum nonlocality in a wider variety of quantum states. We experimentally test the inequality using spatially entangled photons. For a particular quantum state, our experimental results show a violation of the entropic EPR inequality, while the variance EPR inequality is not violated. We show theoretically that our inequality identifies the non-local steering phenomenon, and is directly connected to security bounds in quantum cryptography. In 1935, Einstein, Podolsky and Rosen published the famous “EPR” paper, in which they concluded that quantum theory must be incomplete, since it is in conflict with either realism or locality [1]. In the continuous variable regime, it has been shown by Reid that one can identify an “EPR paradox” when the inequality Var(XA)Var(PA) ≥ 1/4, is violated [2]. Here Var(XA) is the minimum variance in inferring property XA of system A given measurement of property XB on system B. Moreover, it has been recently shown that the Reid-EPR inequality identifies steering, a distinct classification of quantum non-locality for states whose quantum correlation strength lies between entanglement and Bell non-locality [3, 4]. This shows that there exists a hierarchy of quantum correlations that has only been sparsely explored. Recently, we derived an entropic EPR-steering criterion [5]: h(XA|XB) + h(PA|PB) ≥ ln(πe), where h(XA|XB) is the conditional Shannon entropy. Violation of this inequality indicates a physical situation for which local realism is inconsistent with the completeness of quantum mechanics. The entropic inequality is in general more sensitive than the variance inequality. To illustrate the utility of the entropic criterion, we experimentally tested it for a pair of spatially entangled photons. [1] A. Einstein, D. Podolsky, and N. Rosen, Phys. Rev. 47, 777 (1935). [2] M. D. Reid, Phys. Rev. A 40, 913 (1989). [3] H. M. Wiseman, S. J. Jones, and A. C. Doherty, Phys. Rev. Lett. 98, 140402 (2007). [4] E. G. Cavalcanti, S. J. Jones, H. M. Wiseman, and M. D. Reid, Phys. Rev. A 80, 032112 (2009). [5] S. P. Walborn, et al., To appear in Physical Review Letters (2011).

Typicality in random matrix product states Thiago R. de Oliveria Universidade Federal Fluminense, Niterói – RJ, Brazil Abstract Recently it has been suggested that the use of ensembles in Statistical Mechanics may not be essential, since most of the states of the Hilbert space would have properties similar to the ones of the ensemble; typically the system looks as if it is described by a ensemble [1,2]. This seems to be a potential new way to understand why physics statistics work. Nevertheless it is often argued that most of the states of the Hilbert space are unphysical and not good descriptions of systems we encounter in nature. Therefore an important question arises: Can we have typicality for a set of physical relevant states? In this letter we make a attempt to address this is- sue studying if and how typicality emerges in the set of Matrix Product States. We show analytical that it can occur at the level of observables acting on a small subsystem, when the dimension of the Matrix Product State scales with the size of the system with a power greater than two. We then illustrate this result numerically and, present some indications that typicality can appears already for a linear scaling of the Matrix Product State dimensions and, furthermore, at the level of states. [1] S. Popescu, A. Short and A. Winter, Nature Physics 2, 754 (2006) [2] S. Goldstein, J. L. Lebowitz, R. Tumulka and N. Zanghi, Phys. Rev. Lett. 96, 050403 (2006)

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Certified optimal lower bound estimation of quantum properties using incomplete information: variational quantum tomography Thiago O. Maciel*, André T. Cesário and Reinaldo O. Vianna Departamento de Física - ICEx - Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627 - Belo Horizonte - MG - Brazil - 31270-901. Abstract It is assumed partial knowledge about the state of a quantum system. This knowledge is represented by the results of some measurements, spanning a certain subspace. We refer to this subspace as the known subspace, and to its complement as the unknown one. Then we introduce a variational method to estimate the expectation value of every observable. This estimate is optimal and reliable, in the sense that it is always smaller, in absolute value, than the true expectation value (the one that would be obtained if directly measured, of if the quantum state were known exactly). As a byproduct of this approach, we obtain a method of reconstruction of the quantum state, using incomplete information. We also mention that we have extended our method to the problem of process tomography . Our results make clear that it is typically not necessary to perform an informationally complete set of measurements, which grows exponentially with the Hilbert space size, in order to obtain certified optimal lower bounds to properties of a quantum system. The algorithm that implements our method is a linear convex problem, which has exact solution in terms of well known semidefinite programs.

Theoretical model of the Dynamical Casimir Effect in cavities with laser excited semiconductor mirrors Viktor V. Dodonov Instituto de Fisica, Universidade de Brasília, Brasília, Brazil Abstract I consider a "microscopic" model of a quantum oscillator with time-dependent frequency and timedependent damping. This model is elaborated in connection with experiments on simulating the dynamical Casimir effect in a cavity with a periodically photo-excited semiconductor mirror. It is shown that the most general bilinear time-dependent coupling of a selected oscillator (field mode) to a bath of harmonic oscillators results in two {\em equal\/} friction coefficients for the both quadratures, provided all the coupling coefficients are proportional to a single arbitrary function of time whose duration is much shorter than the periods of all oscillators. The choice of coupling in the rotating wave approximation form leads to the "mimimum noise" model of the quantum damped oscillator, introduced earlier in a phenomenological way. The consequences of the model are compared with recent experimental results obtained by the MIR group in Padova (Italy).

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On the construction of generalized intelligent states and certain nonclassical states of a nonlinear oscillator and its position dependent mass counterpart V. Chithiika Ruby Research Scholar, Centre for Nonlinear Dynamics, School of Physics, Bharathidasan University, Tiruchirappalli - 620024, Tamilnadu, India. Abstract We construct generalized intelligent states and certain nonclassical states for a nonpolynomial nonlinear oscillator [1]. This nonlinear oscillator can be considered as placed in the middle between harmonic oscillator and isotonic oscillator. To construct the nonlinear coherent states, one needs the deformed annihilation and creation operators. We obtain these deformed annihilation and creation operators from the solution of the underlying Schrödinger equation. From these operators we construct the generalized intelligent states, nonlinear coherent states and even-odd nonlinear coherent states in the number basis. To study the photon statistical properties of these nonlinear coherent states we calculate Mandel parameter and second order correlation function. We also construct nonlinear coherent states for the position dependent mass Schrödinger equation associated with this solvable nonlinear oscillator [2,3]. Finally, we consider a mass profile which is often used to study transport properties in semiconductors and give explicit expressions of all these nonlinear coherent states. [1] J. F. Cariñena, A. M. Perelomov, M. F. Ranada and M. Santander J. Phys. A: Math. Theor. 41 085301 (2008). [2] V. Chithiika Ruby and M. Senthilvelan J.Phys.A: Math. Theor. 43 415301 (2010). [3] V. Chithiika Ruby and M. Senthilvelan J. Math. Phys. 51 052106 (2010).

On measuring dangling-bond charge-qubit dynamics Zahra Shaterzadeh-Yazdi* and Barry C. Sanders Institute for Quantum Information Science, University of Calgary, 2500 University Drive NW, Calgary, Alberta, Canada, T2N 1N4 Abstract Recently we showed that charge qubits formed from two silicon-surface dangling bonds sharing one excess charge should overcome the high-decoherence drawbacks of larger-scale quantum-dot charge qubits [1]. However, decoherence of this charge qubit is speculative as the dynamics has not yet been measured. Here we propose using an atomic force microscope to characterize the fast tunneling rate and decoherence of the charge qubit. In our scheme the dynamics are studied by observing frequency changes to an atomic force microscope cantilever. This cantilever is capacitively coupled to the dangling-bond pair, which is being driven by a Terahertz electromagnetic field. Our scheme is analogous to previous studies of slow measurements to determine fast qubit dynamics [2,3]. [1] L. Livadaru et al., New Journal of Physics 12, 083018 (2010) [2] J. R. Petta et al., Physical Review Letters 93, 186802 (2004) [3] S. D. Barrett and T. M. Stace, Physical Review Letters 96, 017405 (2006)

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POSTER PRESENTATIONS

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Quantum bit commitment under Gaussian constraints Aiketarini Mandilara* and N. J. Cerf Quantum Information and Communication, Ecole Polytechnique, CP 165/59, Universite Libre de Bruxelles, 1050 Brussels, Belgium Abstract Quantum bit commitment has long been known to be impossible. Nevertheless, just as in the classical case, imposing certain constraints on the power of the parties may enable the construction of asymptotically secure protocols. We present a quantum bit commitment protocol using currently available quantum optical components and prove that it is asymptotically secure if the cheating operations of the party who commits the bit is restricted to Gaussian operations. This protocol exploits continuous-variable quantum optical carriers, for which such a Gaussian constraint is experimentally relevant since the high optical nonlinearity needed to effect deterministic nonGaussian cheating is inaccessible.

Quantum correlations in superconducting charge qubits Alba M. Herrera*¹, R.M. Serra¹ , J.H. Reina² ¹Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, R. Santa Adélia 166, Santo André, 09210-170, SP, Brazil; ² Universidad del Valle, Departamento de física, A.A. 25360, Cali, Colombia Abstract Entanglement is an important resource to quantum computation and communication. However, some authors have pointed out, recently, that there exist other kinds of non-classical correlations, which may be present even in separable states. The so-called Quantum Discord may be employed to quantify such a quantum correlation. We report on the dissipative dynamics of two coupled superconducting charge qubits. The coupling between the superconducting quantum register and the environment is modelled considering two different mechanisms. i.e.: collective and independent decoherence. By means of the Bloch-Redfield formalism, we compute the quantum master equation and we show a fundamental contrast between the entanglement and the quantum discord dynamics.

Non-Markovian characterization of dynamical regimes in a microcavity quantum dot system Alejandro Carrillo Lozada Universidade Estadual de Campinas, Campinas – SP, Brazil Abstract The quantum dot-microcavity system is studied under the light of a non-markovian timeconvolutionless master equation. The different dynamical regimes reached (weak and strong coupling between the quantum dot exciton and a mode of light trapped inside the cavity) are related to the entanglement. Concurrence and negativity are used to identify each regime, as well as the Wigner function. Previous results available are confirmed, in particular sudden death in entanglement in strong coupling. Comparisons between markovian and non-markovian results are made as an attempt to answer the questions about the need to consider long-term correlations between the system and the bath.

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Dynamics of entanglement and quantum discord in a two-qbit system Ana Cristina Sprotte Costa Universidade Federal do Paraná, Curitiba, PR, Brazil Abstract In the last years very much attention has been given to the understanding of the quantum discord, a resource which encapsulates quantum correlations beyond entanglement. In this work we study the dynamical generation of quantum correlations in a system composed of two interacting qubits. The system is initially prepared in a mixed state and evolves under a bilinear interaction. Both the initial state and the interaction are parametrized by vectors in a solid sphere. We present some results comparing the dynamics of entanglement and quantum discord for a class of bilinear interactions. Finally, as the system evolves in time we search for violations of the CHSH-Bell inequality and assess the results in terms of the quantum correlations.

Strong correspondence principle for joint measurement of conjugate observables Antonino Di Lorenzo Instituto de Física, Universidade Federal de Uberlândia, Uberlândia – MG, Brazil Abstract It is demonstrated that the statistics for a joint measurement of two conjugate variables in Quantum Mechanics are expressed through an equation identical to the classical one, provided that joint classical probabilities are substituted by Wigner functions and that the interaction between the system and the detectors is accounted for. This constitutes an extension of Ehrenfest correspondence principle, and it is thereby dubbed strong correspondence principle. Furthermore, it is proved that the detectors provide an additive term to all the cumulants, and that if they are prepared in a Gaussian state they only contribute to the first and second cumulant. This work was supported by FAPEMIG through process APQ-02804-10.

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Controlled generation of multipartite entanglement in Josephson architectures Antonino Messina*1, Rosanna Migliore2, Matteo Scala1, Anna Napoli1 1

Dipartimento di Fisica, Università di Palermo, Via Archirafi 36, 90123, Palermo 2 IBF-CNR, Via Ugo La Malfa153, 90146 Palermo Abstract

The recent progress during the last decade in the context of superconducting solid-state devices, whose system parameters can be controlled in situ to manipulate quantum states coherently, has strengthened the idea that Josephson architectures are among the best candidates both for the search of experimental evidence of non classical features at mesoscopic level and for the practical implementation of logic gates and circuits. So far, experimental research in this field has mostly focused on the behaviour of a single isolated qubit while in the last few years, significant achievements on superconducting two-qubit systems were reported, i.e., the generation of entangled states in systems of coupled flux and phase qubits, as well as the observation of quantum coherent oscillations and conditional gate operations using two coupled superconducting charge qubits. The controlled generation of entanglement in multipartite nanostructured architectures will be the next significant and very challenging step towards quantum information processing based on these scalable superconducting systems. Within this framework the performances of theoretical coupling schemes for the controlled generation and manipulation of entangled states and of non classical superposition in a system of three Josephson junction based qubit will be discussed.

A quantum harmonic oscillator coupled to a composite bath Antonio Vidiella-Barranco Universidade Estadual de Campinas, Campinas, SP, Brazil Abstract A quantum harmonic oscillator prepared in a coherent state is considered to be interacting with a composite bath, constituted by another harmonic oscillator (small system, initially in a thermal state) coupled to a thermal reservoir (large system, collection of harmonic oscillators) at finite temperature. An analysis of the decoherence process in the oscillator is presented, and the results are compared with the case in which the system is directly coupled to a thermal reservoir.

Modulation of breathers in cigar-shaped Bose-Einstein condensates W. B. Cardoso, Ardiley T. Avelar*, D. Bazeia Instituto de Física, Universidade Federal de Goiás, 74.001-970, Goiânia, Goiás, Brazil, and Departamento de Física, Universidade Federal da Paraíba, 58.059-900, João-Pessoa, Paraíba, Brazil. Abstract We present new solutions to the nonautonomous nonlinear Schrödinger equation that may be realized through convenient manipulation of Bose-Einstein condensates. The procedure is based on the modulation of breathers through an analytical study of the one-dimensional Gross-Pitaevskii equation, which is known to offer a good theoretical model to describe quasi-one-dimensional cigarshaped condensates. Using a specific Ansatz, we transform the nonautonomous nonlinear equation into an autonomous one, which engenders composed states corresponding to solutions localized in space, with an oscillating behavior in time. Numerical simulations confirm stability of the breathers against random perturbation on the input profile of the solutions. 68

Slow light effect in semiconductor quantum dots coupled by tunneling H. Borges, L. Sanz, Augusto M. Alcalde* Instituto de Física, Universidade Federal de Uberlândia, Uberlândia – MG, Brazil Abstract The coherent control of carriers confined in semiconductor quantum dots have been extensively studied due to several applications in quantum information processing and quantum computation. In this work, we study the optical linear properties of asymmetric double quantum dot coupled by tunneling. By solving the Liouville-Von Neumman-Lindblad equation, considering the Markovian approximation, we calculate the optical susceptibility considering spontaneous exciton decay and pure dephasing process as source of decoherence. We investigate the optical response of the system analyzing the dispersive properties and absorption of the incident field in the regime of low optical excitation. We demonstrate that sob certain conditions the tunneling coupling establishes an e±cient destructive quantum interference path, which creates a dip transmission region in the absorption spectra. This effect is analogous to the electromagnetic induced transparency observed in atomic systems, where the role of the optical pump field is replaced by a strong tunneling coupling parameter between quantum dots. Numerical calculations allow us determine a wide and precise regime of parameters where the tunneling induced transparency effect can be experimental observed. We consider physical parameters as tunneling coupling, external electric field detuning and laser intensity rigorously compatible with current experiments in III-V coupled quantum dots spectroscopy. In this framework, we also calculate the refraction index and group velocity of the radiation pulse and suggest a possibility of slow light effects produced by tunneling and externally controlled by an electric field which modifies the level detuning.

Dimensional crossover in two dimensional boson-fermion mixtures Bilal Tanatar Bilkent University, Department of Physics, Bilkent 06800, Ankara, Turkey Abstract Using mean-field theory, we study the equilibrium properties of boson-fermion mixtures confined in a harmonic pancake-shaped trap at zero temperature. When the modulus of the $s$-wave scattering lengths are comparable to the mixture thickness, two-dimensional scattering events introduce a logarithmic dependence on density in the coupling constants, greatly modifying the density profiles themselves. We show that for the case of a negative boson-fermion three-dimensional $s$-wave scattering length, the dimensional crossover stabilizes the mixture against collapse and drives it towards spatial demixing. Our numerical calculations are done for 6Li-7Li and 87Rb-40K mixtures which have positive and negative s-wave scattering lengths, respectively.

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Spatial light modulator in quantum optics Breno Marques Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG – Brazil Abstract Liquid-crystal displays (LCD) are optoelectronic devices that can modulate a light beam. These devices, so called Spatial Light Modulator (SLM) can be useful in Quantum Optics [1]. This work shows two experimental implementation using Spatial Light Modulator and Spontaneous Parametric Down Conversion (SPDC): Deutsch Algorithm [2] and Minimal quantum state tomography [3]. To implement the Deutsch Algorithm we used the SLM as oracle and the Minimal state tomography the SLM are used to implement the POVM. In both cases we used two-qubit transversal momenta as quantum state. [1] S. Cialdi, D. Brivio, and M. G. A. Paris; “Demonstration of a programmable source of two-photon multiqubit entangled states”; http//www.arxiv.org/abs/quantph/0912.2975v3 [2] David Deutsch (1985), “The Church-Turing principle and the universal quantum computer”; Proceedings of the Royal Society of London A 400,97. [3] W. Pimenta, B. Marques, M. A. Carvalho, M. R. Barros, J. G. Fonseca, J. Ferraz, M. Terra Cunha, S. Pádua; “Minimal state tomography of spatial qubits using a spatial light modulator”; Optics Express, Vol. 18 Issue 24, pp.24423-24433.

Optimal teleportation with a noisy source Bruno G. Taketani*, Fernando de Melo, Ruynet L. de Matos Filho Universidade Federal do Rio de Janeiro, Universität Freiburg, K.U. Leuven Abstract Several studies have tackled the problem of teleportation when Alice and Bob share a nonmaximally entangled state. Be that a pure or mixed state, protocols that aim to maximize the input/output fidelity have been suggested. Realistic experimental situations will nonetheless present decoherence not only in the quantum channel but also in the state to be teleported. We consider the problem of realistic teleportation of d-dimensional quantum states where neither the bipartite quantum channel nor the unknown input state are in a pure state. In the case of maximally entangled bipartite quantum channel a protocol that gives unit fidelity for pure and mixed input states can be easily established, but when the bipartite state undergoes a decoherence process knowledge of the space of states to be teleported is crucial to determine the optimal protocol. We study the case where this space of states is generated by a decoherence map applied to the space of pure states and we aim to maximize the fidelity between the teleportation output state and the original pure state. Our protocol only requires knowledge of the bipartite state and the decoherence channel that acts on the input states. Numerical results show that by taking this into account our protocol outperforms other protocols and the increase in fidelity can reach 10-20% in many cases. Surprisingly we find that for several experimentally relevant decoherence processes, the standard teleportation can achieve the maximum fidelity. Quantum information is disturbed by the environment even before its transmission. Our results show that this disturbance cannot in general be accommodated as a faulty communication channel. Recognizing this is not only of conceptual importance, but has also practical implications. The teleportation protocol proposed appeals to this mindset shift in order to obtain sizable gains in communication quality.

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Implementation of controlled-U gate in the atom-coupled cavities system Bruno F. C. Yabu-uti* and J. A. Roversi Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas - SP, Brazil Abstract For a distributed quantum information processing, the coupling between different sub-systems is essential to implement controllable and distributed quantum gates in a scalable quantum computing. Cavity quantum electrodynamics systems (cQED), which combine atomic and photonic quantum bits together, have attracted much attention because of both its low decoherence rate and promising feasibility to scale up. Coupled cavities array has the advantage of easily addressing individual lattice sites with optical lasers. Furthermore, the atoms trapped in the resonators can have relatively long-lived atomic levels for encoding quantum information. In this work, we investigated the implementation of a Controlled-U gate in the hybrid system atom-CCA (coupled cavities array). The proposal is based on single qubit operations and unconventional geometric phase on two identical three-level atoms in a CCA, strongly driven by a resonant classical field. A qubit-bus coupling (atom resonator) adjustable lets you specify a particular transformation U on the target qubit. In our view, the most promising candidate to implement our proposal is made combining fiber-based cavities with atom-chip technology. In such a system, the atom can be positioned deterministically anywhere within the cavity that gives rise to a controlled, tunable coupling rate. On the other hand, circuit QED (analogous to a 1−D waveguide) and superconduc‚ng qubits with tunable coupling would be another important implementation. However, as far as we know an independent control of the coupling rate as well as qubit-resonator detuning is difficult to obtain. Such a fact is a backdraw to our protocol.

Quantum limits for lossy optical interferometry Bruno M. Escher*, R. L. de Matos Filho, L. Davidovich Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro (RJ), Brazil Abstract Modern optical interferometry has attained a high degree of precision regarding phase shift estimation, such that limitations stem from the quantum nature of the measurement process itself. Special quantum states of light may beat the shot-noise limit, attained with standard light sources, leading, for lossless interferometers, to the ultimate quantum limit for the precision, the so-called Heisenberg limit. The unavoidable interaction with the environment introduces however extra noise. An open question is what is the fundamental quantum limit for optical interferometry in the presence of photon losses. Here we derive an analytical lower bound for this limit, which implies, for any state of light, with use of adaptive feedback and, and even for arbitrarily small losses, that this uncertainty scales asymptotically with the number of photons at best as the shot noise. Our bound captures the main features of the transition from the Heisenberg limit, valid for sufficiently small photon numbers, to the asymptotic shot-noiselike behavior.

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Electromagnetically induced transparency in cavity QED M. Mücke1, E. Figueroa1, J. Bochmann1, C. Hahn1, K. Murr1, S. Ritter1, Celso J. Villas-Boas*1,2, G. Rempe1 1

2

Max-Planck-Institut für Quantenoptik, Garching, Germany Departamento de Física, Universidade Federal de São Carlos, São Carlos, Brazil Abstract

The Quantum Information Theory (QIT) is a rapidly developing area. Much of the future progress of this area depends on the ability to manipulate and store quantum information. In this context, electromagnetically induced transparency (EIT)-based techniques are promising because they allow to store and manipulate information using stable atomic states [1]. The EIT phenomenon has been intensively investigated since, besides the applications in QIT, it also allows to control the propagation of the light field, reduce the group velocity of light to few meters per second, giant nonlinear interactions for electromagnetic fields, etc. Scaling such experiments into the quantum domain with one (or just a few) particles of light and matter will allow for the implementation of quantum computing protocols with atoms and photons, or the realization of strongly interacting photon gases exhibiting quantum phase transitions of light. Reaching these aims is challenging and requires an enhanced matter–light interaction, as provided by cavity quantum electrodynamics. Here we demonstrate EIT with a single atom quasi-permanently trapped inside a high-finesse optical cavity [2]. The atom acts as a quantum-optical transistor with the ability to coherently control the transmission of light through the cavity. We investigate the scaling of EIT when the atom number is increased one-by-one. The measured spectra are in excellent agreement with a theoretical model. We also analyze some extensions of this work, for example how to control the statistical properties of light. In this quantum model, the properties of the cavity field depend on the number of atoms inside the cavity. For example, we show that changing the number of atoms we can store different number of photons, i.e., for an incoming coherent pulse (coherent state), one atom allows us to store one photon; two atoms allow us to store up to two photons, and so on. [1] M. Fleischhauer, A. Imamoglu, and J. P. Marangos, Rev. Mod. Phys. 77, 633 (2005). [2] M. Mücke, E. Figueroa, J. Bochmann, C. Hahn, K. Murr, S. Ritter, C. J. Villas-Boas, and G. Rempe, Nature 465, 755 (2010).

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Analysis of the environmental influence on the measurement process of a qubit system using the Lindblad equation Carlos Alexandre Brasil* and Reginaldo de Jesus Napolitano Instituto de Física de São Carlos (IFSC) / Universidade de São Paulo (USP) Abstract The aim of this work is to explore a model for finite-time measurement based on the Lindblad equation [1], with analysis of a system consisting of a qubit coupled to a thermal reservoir. The observable to be measured may either or not commute with the unperturbed Hamiltonian of the system. The analytical solution of the Lindblad equation in the absence of environmental interactions is relatively simple to obtain [2,3]. However, the inclusion of the environment into the description requires the use of techniques for supressing its degrees of freedom, involving the projection operators of Nakajima-Zwanzig [2,4] and super-operators relating to each term of the Liouvillian (that is, the term for the system, the reservoir, and the interaction between them) and the Lindbladian. Analytical and numerical calculations are under way. Besides representing a fundamental problem in quantum mechanics, a realistic description of quan- tum measurements is crucial in the practical context of irreversible quantum computation [5], whose realization intrinsically relies on measurements. [1] G. Lindblad, On the generators of quantum dynamical semigroups, Comm. Math. Phys. 48, 119 (1976). [2] Breuer, H-P. and Petruccione, F. The theory of open quantum systems. Oxford: Oxford university press, 2002. 650 p. [3] Percival, I. Quantum state diffusion. Cambridge: Cambridge university press, 1998. 190 p. [4] Nakajima, S. On quantum theory of transport phenomena. Progress of theoretical physics, Kyoto, v. 20, n. 6, 948 (1958). [5] R. Raussendorf, D.E. Browne and H.J. Briegel, Measurement-based quantum computation with cluster states, Phys. Rev. A 68, 022312 (2003).

Quantum Discord in Multipartite Systems Clodoaldo C. Rulli* and M. S. Sarandy Instituto de Física, Universidade Federal Fluminense, Niterói - RJ, Brazil Abstract Quantum discord (QD) has attracted a great deal of attention in recent years as a measure of the nonclassical contribution for correlations in quantum systems. It has been associated with a wide range of applications, such as quantum computation without entanglement, quantum phase transitions in many-body systems, and open-system dynamics. QD has been originally defined for bipartite systems as the difference between quantum mutual information and the mutual information of the same system after a non-selective Von Neumann measurement in one part of the system. In this work, by expressing QD in terms of a distance measure, we consider its extension for multipartite systems. This extension for a global measure of QD is symmetrically defined, with nonselective Von Neumann measurement performed in all parts of the systems. As an illustration, we provide applications in the GHZ-Werner state as well as in quantum spin chains.

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Extending Matchgates to Full Quantum Universality Daniel J. Brod*, Ernesto F. Galvão Instituto de Física, Universidade Federal Fluminense, Niteroi, Brazil Abstract In 2002, Valiant showed [1] that quantum circuits composed only of matchgates are simulatable classically, if the gates are restricted to act only on nearest-neighbour qubits. This result was reobtained in the context of fermionic linear optics by Terhal and DiVincenzo [2] and Knill [3]. In 2008, Josza and Miyake showed [4] that, by relaxing the nearest-neighbour condition slightly to allow for next-nearest neighbour interactions - or, equivalently, by allowing a limited use of the SWAP gate - the power of matchgates is boosted to full universal quantum computation. The group of all parity-preserving two-qubit gates is characterized by 7 real parameters, of which matchgates form a 6-parameter subgroup. We extend the construction in [4] to show that matchgates, together with any non-matchgate parity-preserving unitary are sufficient for universal quantum computation. We identify the parameter that interpolates between matchgates and non-matchgate paritypreserving unitaries as one of the three nonlocal parameters of two-qubit gates, as described by Zhang et al in 2003 [5]. This single non-local parameter is a phase induced between even and oddparity subspaces, and brings about an abrupt change in computational power, from classical simulability to full quantum computation. [1] L. G. Valiant, SIAM J. Comput. 31(4), 1229-1254 (2002). [2] D. DiVincenzo and B. Terhal, Phys. Rev. A 65, 032325 (2002). [3] E. Knill arXiv:quant-ph/0108033 [4] R. Jozsa and A. Miyake, Proc. R. Soc. A 464, 3089–3106 (2008). [5] J. Zhang, J. Vala, S. Sastry, and K. B. Whaley, Phys. Rev. A 67, 042313 (2003).

Non-classical behavior of an intense cavity field revealed by quantum discord Daniel Z. Rossatto*1, T. Werlang1, E. I. Duzzioni2, C. J. Villas-Boas1 1 2

Department of Physics, Federal University of São Carlos, São Carlos - SP, Brazil Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, MG, Brazil. Abstract

We investigate the quantum-to-classical crossover of a dissipative cavity mode based on measurement of the correlations (entanglement of formation and quantum discord) between two atoms which do not interact with each other, but interact with the cavity mode. Firstly, we note that there is a time window where the mode has a classical behavior, which depends on the cavity decay rate, the atom-field coupling strength and the number of atoms. Then, considering only two atoms inside the cavity and analyzing the steady state of the system, we note that the entanglement between the atoms disappears when increasing the mean number of photons of the cavity field (n). However, the quantum discord reaches an asymptotic non-zero value even in the limit of n -> ∞, either by increasing n coherently or incoherently. Therefore, the cavity mode always preserves some quantum character in the asymptotic limit, which is revealed by the quantum discord.

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A new protocol for QKD using squeezed coherent states of light Douglas Delgado de Souza* e Antonio Vidiella Barranco DEQ - IFGW - UNICAMP, Campinas - SP – Brazil Abstract In this work, we introduce a new protocol for Quantum Key Distribution which makes use of three squeezed coherent states of light: two bit states, used for transmission of information, and a Decoy state, used for eavesdropping detection. Its development was based on the protocol for squeezed coherent states suggested by P. Horak, which in turn consists of a generalization of the protocol by R. Namiki and T. Hirano for coherent states. We analyze its security by considering two kinds of attack: simultaneous quadrature measurement attack and superior channel attack. For this analysis we use a description in terms of the Wigner function, obtaining from it some joint and marginal probability distributions. From the distribution for the Decoy states we define an Eavesdropping Measure M, and discuss its usefulness in calculating the rate of information leaked to Eve in each attack. Finally, for the superior channel attack, we analyze the influence of a post-selection threshold over the Bob and Eve informations, showing that, by raising this parameter, larger transmission distances (smaller trasmissivities) can be handled by the protocol at the expense of lower bit acceptance rates.

Quantum logic gates with coupled Bose-Einstein condensates Fabricio Souza Luiz Federal University of São Carlos, São Carlos – SP, Brazil Abstract It is well established that the dynamics of two coupled Bose-Einstein condensates (BECs) can be described by using the two-mode Hamiltonian. This model takes into account the trap confinement and the effects of collisions associated with each condensate. Other effects, as collision between atoms that belong to different BECs and detuning has been included in this approach. In this work, we are interested in atoms condensed on different hyperfine levels, coupled by a two photons transition. First, we demonstrate that this particular system can be considered a feasible candidate for a qubit. Then, we show the necessary conditions for the implementation of the six most important one-qubit quantum logic gates (NOT, Y, Z, S, T and Hadamard) for quantum information processing.

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Entropic criteria to detect entanglement in continuous variable quantum systems Fabricio Toscano Instituto de Física, Universidade Federal do Rio de Janeiro, Rio de Janeiro, - RJ, Brazil Abstract Several entanglement criteria for bipartite continuous variable quantum systems based on the Shannon entropy of complementary distributions are introduced. These criteria are more sensitive than the usual one involving only second-order moments, and are equivalent to well-known variance product tests in the case of Gaussian states. We then generalize these criteria using the Rényi entropy and we show that they are even more sensitive that the particular case using the Shannon entropy. Some of our entropic entanglement criteria are based on the entropic uncertainty relation for Rényi (or Shannon) entropy of complementary distributions and we show that these particular criteria below to the class of PPT (Positive Partial Transpose) criteria. We provide several numerical results which show that our criteria can be used to identify entanglement in a number of experimentally relevant quantum states. Because our criteria only involve a pair of quadrature m easurements they are very useful in the experimental identification of entanglement.

Robustness under losses for continuous variable bipartite states Felippe Alexandre Silva Barbosa Universidade de São Paulo – USP, São Paulo – SP, Brazil Abstract We experimentally analyzed the robustness of continuous-variable bipartite states possessing Gaussian statistics under losses. We used an above threshold optical parametric oscillator (OPO) to generate entangled twin beams. Such states are fully characterized by the covariance matrix of the phase space operators. In our case, the action of the environment is limited to dissipation only, which is implemented by losses in a beam-splitter. In this context, we call robust those states that maintain their entanglement until total loss. We observed both regions of robust and non-robust entanglement. The later can be accessed by adding phase noise to and robust ones. Which is done by increasing the pump power. We also theoretically studied the robustness of entanglement in continuous-variable two-mode bipartite system. We derived, from the PPT criterion, a sufficient condition that attests the robustness, which becomes also necessary for Gaussian states. We show that it is an optimized form of the Duan criterion, which gives it an operational meaning connecting it with the resilience of entanglement under transmission losses. As a consequence, we showed that it is possible to transit between robust and non-robust states by local squeezing. Consequently, the robustness under losses is a property that can be independent of the quantity of entanglement no matter what entanglement measure one uses.

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Entropic uncertainties for coherent states Fredy Zypman Department of Physics, Yeshiva University, New York, USA Abstract We establish lower bounds for the position and momentum entropies in coherent and squeezed states. We review the supersymmetric case [C. Aragone and F. Zypman, J. Phys. A: Math. Gen. 19 (1986) 2267-2279].

Decoherence, entanglement decay and equilibration produced by chaotic environments. Gabriela Barreto Lemos Instituto de Fisica/Universidade Federal do Rio de Janeiro Abstract We investigate decoherence in quantum systems coupled via dephasing-type interactions to na arbitrary environment with chaotic underlying classical dynamics. The coherences of the reduced state of the central system written in the preferential energy eigenbasis are quantum Loschmidt echoes, which in the strong coupling regime are characterized at long times scales by fluctuations around a constant mean value. We show that due to the chaotic dynamics of the environment, the mean value and the width of the Loschmidt echo fluctuations are inversely proportional to the quantity we define as the effective Hilbert space dimension of the environment, which in general is smaller than the dimension of the entire available Hilbert space. Nevertheless, in the semiclassical regime this effective Hilbert space dimension is in general large, in which case even a chaotic environment with few degrees of freedom produces decoherence without revivals. Moreover we show that in this regime the environment leads the central system to equilibrate to the time average of its reduced density matrix, which corresponds to a diagonal state in the preferential energy eigenbasis. For the case of two uncoupled, initially entangled central systems that interact with identical local quantum environments with chaotic underlying classical dynamics, we show that in the semiclassical limit the equilibration state is arbitrarily close to a separable state. We confirm our results with numerical simulations in which the environment is modeled by the Quantum Kicked Rotor in the chaotic regime.

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Dissipative unconditional tunnelling teleportation through a local quantum channel Gentil D. M. Neto*, M. A. de Ponte, and M. H. Y. Moussa Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil Abstract In this letter we demonstrate how to achieve tunneling teleportation of a quantum state by virtually populating the only required local quantum channel connecting Alice's to Bob's lab. In order to counteract the effects of the channel nonidealities, we build on our process within a decoherence quasi-free subspace. A recipe or the emergence of such a subspace is also presented together with an analyzes of the role played by local channel topology.

Distance of entanglement as signature of quantum phase transitions Helena Braga*, Simone Souza and Salomon S. Mizrahi Departamento de Física, Universidade Federal de São Carlos, São Carlos, SP, Brazil Abstract Entanglement of different degrees of freedom or of subsystems is a purely quantum phenomenon, and for certain simple systems (few degrees of freedom) there exist several criteria to detect the existence of entanglement as well as measures of its extent. Although the expressions are mathematically sound, their physical explanation is not quite clear and is subject to different interpretations. The older criterion for two qubits system is based in looking for negative eigenvalues in the partially transposed density matrix, that is no longer a physical state. This criterion is also known as Peres-Horodecki criterion (PHC) [1]. It is a non-unitary transformation on the density operator that can indicate if a state is entangled or separable. Here we shall use the method of distances in a hyperbolic space (in a form quite similar to the spacetime squared distance having a Minkowski metric, s² = t² - r²) to identify and measure the degree of entanglement of a twoqubit state, as presented in [2]; it is closely associated to the PHC. The t vs. r space is divided by a conic shaped surface, at 45 degree, where inside reside the separable states and outside lay the entangled ones. In this work we study the symmetry breaking and criticality in the two-qubit Heisenberg Models, looking for signatures of quantum phase transitions in s² and its derivatives. [1] A. Peres, Phys. Rev. Lett. 77, 1413 (1996); M. Horodecki, P. Horodecki, and R. Horodecki, Phys. Lett. A 223, 1 (1996). [2] Phys. Rev. A. 81, 042310 (2010).

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Discord, entanglement and non-Markovian behavior in 2-qubit systems with dipolar interaction and structured reservoirs Hugo L. O. Meneguele*, José A. Roversi Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, Campinas, SP, Brazil Abstract In this work we focus on the behavior of classical and quantum correlations in 2-qubit systems interacting with structured reservoirs and with each other through dipolar coupling. In our analysis of correlations, we consider quantum mutual information as a measure of total correlations, concurrence and quantum discord as measures of quantum correlations, and try to account for their distinct dynamics. Our two 2-qubits systems, besides interacting with each other, interact with Lorentzian reservoirs; they can be independent reservoirs, each one attached to a single system, or a shared reservoir which interacts with both systems. This two possible arrangements have very distinct dynamics; we also investigate the in influence of the reservoirs' markovianity in the structure and survival of the correlations, associating it with the reservoirs' bandwidth (Mazzola et al., Phys. Rev. A 79 042302 2009). We can arrive at the dynamics of both systems by using the pseudomodes approach (Garraway, Phys. Rev. A 55 2290 1997), which reduce our problem to simple sets of coupled differential equations. With the dynamics in hand, we are able to describe the correlations dynamics and their interplay.

Initial value problems of diffusion-type equations related to quantum systems Ilyssa Summer Arizona State University,Tempe Tempe, USA Abstract Connections of initial value problems to diffusion-type equations with corresponding quantum systems will be discussed. Non-autonomous and inhomogeneous diffusion-type equations will be solved by eigenfunction expansion methods similar to quantum quadratic systems via the Riccatiequation type.

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Intelligent and Squeezed States for Angular Momentum and SU(n) groups Jagdish Luthra Departamento de Fisica, Universidad de Los Andes, Bogota, Colombia Abstract In this paper we study the properties of Angular Momentum Squeezed States using the Schwinger Boson Operator construction. We use the harmonic oscillator boson operators to construct angular momentum intelligent states. The symmetry of angular momentum and the SU(2) group connection is generalized to construct intelligent and squeezed states for the group SU(n). Interesting applications to interferometry are also presented.

Electromagnetically induced transparency in different physical systems James A. Souza*, Daniel Z. Rossatto and Celso J. Villas-Boas Federal University of São Carlos, São Carlos – SP, Brazil Abstract The electromagnetically induced transparency (EIT) is a phenomenon where the transmission of a probe beam through an optically dense medium is manipulated by means of a control beam. Under appropriate conditions, the medium becomes effectively transparent (zero absorption). EIT is an example of optical nonlinearity that offers unique possibilities for the control of light with light. Recent progress on EIT based on cavity quantum electrodynamics with single quanta of matter is promising for novel applications, such as dynamic control of the photon statistics of propagating light fields or the engineering of Fock state superposition of flying light pulses. Our purpose in this work is to demonstrate the equivalences and differences of EIT phenomena in different physical systems such as three level atoms, coupled oscillators, two-level atoms plus cavity mode and transparency induced by tunneling in quantum dots. The importance of recognizing the EIT in other physical systems concerns in achieving experimental facilities for the implementation of quantum computing protocols with atoms and photons and the realization of strongly interacting photon gases exhibiting quantum phase transitions of light.

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Photoelectron ionization spectra in a system interacting with a neighbor atom Jan Peřina Jr.*1, A. Luks1, V. Perinova1 and Wieslaw Leonski2 1

2

Palacky University, RCPTM, Joint Laboratory of Optics,Olomouc, Czech Republic Quantum Optics and Engineering Division, Institute of Physics, University of Zielona Gora Abstract

Long-time photoelectron ionization spectra of a system interacting with a neighbor two-level atom are investigated using the Laplace-transform method. Also auto-ionization levels are considered. These spectra are typically composed of several peaks. Conditions for the occurrence of Fano zeros are revealed. Photoelectron ionization spectra conditioned by the measurement on the two-level atom show oscillations at the Rabi frequency. The presence of spectral zeros occurring in the conditioned spectra periodically with the Rabi period is predicted.

Experimental implementation of a NMR etanglement witness for Bell-diagonal states Jefferson G. Filgueiras*, R. Auccaise, R. S. Sarthour and I. S. Oliveira Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro/RJ – Brazil Abstract Entanglement witnesses (EW) are important quantum information tools for testing the presence of entanglement by directly measuring a thermodynamic observable. Whereas EWs have been established for magnetic systems for some time [1,2,3], only recently a proposal for a EW has been made for Nuclear Magnetic Resonance (NMR) quantum information processing experiments [4]. In this work we implement an experimental determination of a NMR EW, in a two-qubit system, 1H and 13C in liquid-state chloroform sample. The experiment has been performed in a Varian 500 MHz Shielded spectrometer at the Brazilian Center for Research in Physics. We study various examples of entangled states which are detectable and not by the same EW. [1] Wiesniak, M., Vedral, V. and Brukner, C., New Journal Of Physics 7, 258 (2005). [2] Rappoposrt, T. G., et al., Physical Review B 75, 054422 (2007). [3] Souza, A. M., et al., Physical Review B 77, 104402 (2008). [4] Rahimi, R. et al., Journal of Physics A 39, 2151 (2006).

Squeezed states of a generalized f-oscillator João Paulo Camargo de Lima Universidade Tecnológica Federal do Paraná ,Toledo - PR – Brasil Abstract In this work a class of nonlinear squeezed states [1,2] are introduced from f-deformed oscillators and generalized deformed algebras of quantum harmonic oscillator[3]. Some statistical properties are investigated and the behavior of the obtained expressions in terms of deformation parameters the algebras used. [1] L. C. Kwek and D. Kiang, Journal of Optics B: Quantum ans Semiclassical Optics 5, 383 (2003) [2] M. Darwish. European Physical Journal D 41, 547 (2007) [3] S. S. Mizrahi, J. P. Camargo Lima, V. V. Dodonov, Journal of Physics A 37, 3707 (2004).

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Atomic localization of a Bose-Einstein condensate using an oscillatory modulated scattering length John Lozada Vera* and Marcos Cesar de Oliveira Instituto de Física Gleb Wataghin, UNICAMP Abstract Atomic localization process of a Bose-Einstein condensate in an optical lattice is studied for the case where the scattering length has not only a constant but also an oscillatory part, by management of Feshbach resonances. Using a mean field approach (numerically solving the Gross-Pitaevskii equation) and a local mode approximation, we explore how through the variation of the amplitude and frequency of the magnetic field drive we could induce, in a controlled way, a macroscopic selftrapping and fragmentation of the condensate. [1]. Pollack, S.E. et al. PRA 81, 053627 (2010) [2]. Holthaus, M. & Stenholm, S. Eur. Phys. J. B 20, 451 (2001) [3]. Raghavan et al. PRA 59, 620 (1999) [4]. Viscondi et al. Ann. Phys. 324, 1837 (2009) [5]. Albiez et al. PRL 95, 010402 (2005)

On the symmetry of quantum correlations quantifiers Jonas Maziero Universidade Federal do ABC Abstract The quantum discord (QD) reveals the nonclassical correlations presented in a bipartite quantum state. It is well known that the value of QD can be different depending on the bipartition we choose to compute it. As recently this quantifier for quantum correlation has been applied to several scenarios, it is important to analyze this symmetry issue in more depth. In this work we obtain an analytical formula for a symmetric version of the QD (SQD) and show that, for two-qubit states with maximally mixed marginals, the symmetric and asymmetric versions of QD coincide. We note yet that, if correlation is regarded as a property shared by the parts constituents of the whole system, one should expect a measure of correlation to be independent of the choice of partition from which it is computed. In this direction, we present examples of classes of states for which the QD is asymmetric and argue that the SQD can be more appropriate to quantify quantum c orrelations in general. We also consider the implications of this symmetry issue in the identification of the resources behind the speedup in the model of deterministic quantum computation with one qubit.

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Measurement-based quantum computation with a simulated valence-bond solid Jonathan Lavoie Institute for Quantum Computing and Department of Physics & Astronomy, University of Waterloo, Waterloo, Canada Abstract In the measurement-based model for quantum computation, information is processed by sequentially measuring individual spins (qubits) on an entangled resource state. It remains a challenge, however, to efficiently produce such resource states. One route to creating resources is to cool a strongly-correlated quantum many-body system to its ground state, provided the system contains the right kind of interactions. An appealing candidate is a valence-bond-solid state first described by Affleck, Kennedy, Lieb, and Tasaki (AKLT). It is the unique, gapped ground state for a two-body Hamiltonian on a spin-1 chain, and can be used as a resource for measurement-based quantum computing. We generated a photonic AKLT state, using biphoton polarization as the spin-1 element, and implemented single-qubit quantum logic gates. This constitutes the first demonstration of quantum logic gates in measurement-based quantum computing without cluster states.

Experimental Bound Entanglement in Photonic Quantum States Jonathan Lavoie Institute for Quantum Computing and Department of Physics & Astronomy, University of Waterloo, Waterloo, Canada Abstract Entangled states can be classified into two categories: those that can be distilled into pure entangled states and those that cannot. Undistillable entangled states are called bound entangled and have recently attracted a great deal of theoretical interest. Recently, they have showed up in the breakthrough proof of non-additivity of quantum capacities and new results in quantum cryptography. We report the experimental demonstration of bound entanglement encoded in the polarization of four optical photons. We aimed to create a family of noisy Smolin states. We characterized our experimentally produced states using state tomography, and quantitatively show that, in a narrow parameter regime, they are entangled and undistillable, exhibiting robust bound entanglement. We then use our bound entangled state to demonstrate unlocking of entanglement, one of the key features of these states.

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Average clock times for the tunneling of a Dirac wave packet José Tadeu Teles Lunardi Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa Abstract We address the tunneling time problem for a localized Dirac wave packet scattering by a localized potential. By coupling a quantum clock to the system we are able to define average transmission and reflection clock times by taking a post-selection of the final state (together with a pre-seletion of the initial state) and then tracing out the particle’s degrees of freedom. We discuss the role of the negative energy components of the wave packet when the barrier is opaque. We obtain the average transmission time for the special case of a rectangular barrier potential and show that such a time never saturates with the barrier width, thus showing no evidence of the Hartman effect, similarly to what is observed in the non relativistic case. Finally, we address the interpretation of superluminal velocities associated with the average transmission time, which can emerge even in the relativistic approach.

Gaussian states: a geometrical viewpoint José G. Peixoto de Faria*1, I. G. da Paz2, M. C. Nemes3 1

Departamento de Física e Matemática, Centro Federal de Educação Tecnológica de Minas Gerais, Belo Horizonte - MG, Brazil; 2 Departamento de Matemática, Universidade Federal do Piauí, Picos - PI, Brazil; 3 Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte - MG, Brazil Abstract Methods of the differential geometry, applied in the treatment of the distinguishability between classical probability distributions, can be extended to deal with the distinguishability of quantum states as well. In particular, the determination of the degree of distinguishability between two quantum states, pure or mixed, through a set of suitably prepared measurements, and related problems, has received special attention in Quantum Information Theory. We present an application of these methods to construct a geometrical description of Gaussian states of a single mode of the electromagnetic field. In order to do this, we start from the Robertson- Schroedinger uncertainty relation for the determint of the covariance matrix. In the unidimensional case, we found that these states "live" in an abstract ray space with constant and negative (guassian) curvature, which can be modelled by the Poincaré upperplane (or semiplane). This model allows us to determine, e.g., the geometric phase associated to the free evolution of a Gaussian state.

Diffusion-type equations Jose M. Vega-Guzman Arizona States University, Tempe, USA Abstract We discuss a method of constructing solution of the initial value problem for diffusion-type equations in terms of solutions of certain Riccati and Ermakov-type systems. A nonautonomous Burgers-type equation is also considered.

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Two-qubits state transfer between trapped ions in the coupled cavities system in the presence of spontaneous emission for T≠0 Julio C. González* and J. A. Roversi Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas, SP, Brazil Abstract The study of systems, where it is possible to transmit quantum information, i.e. the transmission of quantum states of one qubit to another, is important in different fields of physics. Moreover, systems in which it is possible transmit maximally entangled states (commonly called Bell states) are of great interest. Such a states play an important role in quantum computing, information and cryptography. In this work, we studied the transmission of quantum states (in particular an entangled state of the vibrational and internal degrees of freedom of the ions) between two twolevel ions in Paul traps inside different optical cavity. We investigated two types of coupling between the cavities, in the first one the cavities are very close to allow a direct coupling between them and, in the second one, they are connected by an optical fiber (indirect coupling). In both cases we analytically studied the use of one or two collective modes of the coupled cavities for the transmission of information. For the indirect coupling, we will include the spontaneous emission of the ions using a thermal reservoir model at T≠0. We then calculate the fidelity and purity to determine the degree of entanglement of the qubits.

Probing the quantum phase transition in the Dicke model through a movable mirror Kyoko Furuya*1, Jader P. Santos2 and Fernando L. Semião3 1

Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas, SP, Brazil 2 3

UEPG UFABC

Abstract What happens when we allow one of the mirrors of the cavity in a Dicke [1] system to be movable? We show that the electromagnetic field inside the cavity couples to the movable mirror through radiation pressure [2]. It comes as a surprise, however, that as a result of this coupling, in the thermodynamical limit and in the superradiant phase of the Dicke system [3], a classical nonfluctuating driving force proportional to the number of photons appears on the movable mirror [4]. This does not cause decoherence. That result substantially differs from the usual open system case where the presence of the reservoir causes a fluctuating driving force responsible for the decoherence of the system. This illustrates how the coupling to a critical reservoir may reveal interesting dynamics in the scope of quantum optomechanics. [1] R. H. Dicke, Phys. Rev. 93, 99 (1954). [2] S. Gröblacher, K. Hammerer, M. R. Vanner, and M. Aspelmeyer, Nature (London) 460, 724 (2009). [3] T. Brandes, Phys. Rep. 408, 315 (2005). and references there in. [4] J. P. Santos, F. L. Semião and K. Furuya, Phys. Rev. A 82, 063801 (2010).

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Mutual information in global and separated quantum measurements on a quaternary-state signal Leandro S. Aguiar*, L. F. M. Borelli, A. Vidiella-Barranco and J. A. Roversi Instituto de Física ”Gleb Wataghin”, Universidade Estadual de Campinas, Campinas, SP, Brazil Abstract In this work we have studied the accessible information in two symmetric sets of equiprobable quaternary states signal [1, 2]. These two sets are represented by a tetrahedral and cross symmetry in a Bloch Sphere. We can formulate the task as following: one prepares (Alice) two quantum systems identically, that is to say with redundancy ( ψ ⊗ ψ ), and another one (Bob) performs a measurement, that can be a global or separated (two step) measurement. Bob’s aim is to carry out a measurement that provides as much information as possible. To do this, he is allowed to perform either local measurements and classical communication or a combined measurement on both systems. In the case studied by Ban et al. [3], the set of binary states are linearly independent (considering one or two particles); in the system studied by Peres and Wootters [4, 5] the trine states are linearly dependent and the double trine states are linearly independent. In this work, however, the systems are linearly dependent in both cases, when one considers one or two particles. The amount of information is calculated using the well-known Shannon mutual information [6]. We have computed the mutual information for the two sets considering both cases, global and separated measurements. The POVMs are checked using the Holevo test [7] in order to verify the necessary condition for the optimum measurement. [1] E. D. Davies, IEEE Trans. Inf. Theory. 24, 596 (1978). [2] C. W. Helstrom, Quantum Detection and Estimation Theory (Academic Press, New York, 1976). [3] M. Ban, Yamazaki, K. and O. Hirota, Phys Rev. A. 55, 22 (1997). [4] A. Peres and W. K. Wootters, Phys. Rev. Lett. 66, 1119 (1991). [5] W. K. Wootters, Int. J. of Quantum Information. 4, 219 (2006). [6] C. E. Shannon, Bell Syst. Tech. J. 27, 379 (1948). [7] A. S. Holevo, J. Multivariate Analysis, 3, 337 (1973).

Quantum error correction theory during logical gates and finite syndrome measurements Leonardo A. de Castro* and R. d. J. Napolitano, Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil Abstract Quantum error correction methods are one the main theoretical techniques of preventing the loss of information during quantum computation. These methods, however, are usually presented under ideal conditions, where no logical gates are being applied (i.e., memory qubits) and the syndrome measurement is perfect. The objective of this work is twofold: to present a method of correcting errors that occur during the application of quantum gates and to consider the effects of external noise and finite time on syndrome measurements. The first aim is achieved by considering which kinds of noise do not affect the process of correction, and by applying the gate in short steps if the coupling with the environment does not allow a direct recovery of the qubits. The second part requires a solution of the Lindblad equation for the syndrome measurement, taking into account the environmental noise.

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Spatial correlations in parametric down-conversion measured by an electron multiplying charged-coupled device Leonardo Neves Center for Optics and Photonics, Universidad de Concepción, Chile Abstract The capabilities and limits of an electron multiplying charge-coupled device (EMCCD) as a singlephoton-detector array for applications in quantum optics have been recently established. Here we use such a device to measure the spatial correlations of degenerate photon pairs produced by type-I spontaneous parametric down-conversion (SPDC). We operate the EMCCD in the photon counting mode, and illuminate it with the light from SPDC in the far-field regime. By applying a thresholding technique to each collected frame and convolving it with itself, one can measure the overlap between this frame and its shifted mirror version. The individual frame convolutions are added together to give the total correlation. We investigate the dependence of the measured correlations on the characteristics of a Gaussian pump laser beam.

The spectrum and dynamics for electrons in coupled quantum molecules P. A. Oliveira and Liliana Sanz* Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, Brazil Abstract Nowadays, the study of quantum information processing attracted a lot of attention due to the advantages provided by the resources of Quantum Mechanics such as entanglement. Among all candidates for quantum computing, solid state systems (where quantum bits are defined using the electric charge and spin) are pointed out as promised systems in order to obtain scalability. Once a quantum bit is defined in a specific physical system, it is necessary to perform operations involving one and two qubits, which are known as quantum logic gates. An example of quantum gate is the controlled rotation (CROT), where the state of a target qubit is conditioned by the state of a control qubit. The implementation of this gate and others has been demonstrated experimentally in a quantum system consisting of two quantum molecules. A quantum molecule is defined as two quantum dots coupled by tunneling where a charge qubit, a single electron, that can tunnel into the molecule. Coupling between the two subsystems is given by a Coulomb interaction between the electrons of each molecules. Few theoretical works about this systems are found in literature. In this work, we studied two aspects associated with the system described above. First, we analyze the behavior of the energy spectrum as a function of the coupling parameters which describe tunneling, Coulomb interaction and the detuning between the electronic levels. Then, we explore the coherent dynamics that can be used to define quantum logic gates of one or two qubits.

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Redfield and master equation approaches for a time-dependent quantum system and coherence control Lucas Céleri Universidade Federal do ABC, Santo André – SP, Brazil Abstract We present a derivation of the Redfield formalism for treating the dissipative dynamics of a timedependent quantum system coupled to a classical environment. We compare such a formalism with the master equation approach when the environments are treated quantum mechanically. Focusing on a time-dependent spin-1/2 system we demonstrate the equivalence between both approaches by showing that they lead to the same Bloch equations and, as a consequence, to the same characteristic times T1 and T2 (associated with the longitudinal and transversal relaxations, respectively). These characteristic times are shown to be related to the operator-sum representation and the equivalent phenomenological-operator approach. Finally, we present a protocol to circumvent the decoherence process due to the loss of energy (and thus, associated with T1). To this end, we simply associate the time-dependence of the quantum system to an easily achieved modulated frequency. A possible implementation of the protocol is also proposed in the context of the nuclear magnetic resonance (NMR) context.

Coherence freeze in an optical lattice investigated via twodimensional pump-probe spectroscopy Luciano Soares da Cruz Universidade Federal do ABC, Santo André – SP, Brazil Abstract Motivated by our observation of fast echo decay and a surprising coherence freeze, we have developed a two-dimensional pump-probe spectroscopy technique for vibrational states of ultracold 85Rb atoms in a 1D optical lattice to gain information on the memory dynamics of the system. In the 1D lattice, transverse motion of atoms through an inhomogeneous distribution of lattice depths gives rise to many frequency trajectories. We use pump-probe spectroscopy to characterize the probability distribution of these trajectories, and show that the inferred distribution, unlike a naive microscopic model of the lattice, correctly predicts the main features of the observed echo decay. Such techniques should be broadly useful for understanding (and subsequently correcting) decoherence in quantum information systems. [This work was published in Phys.Rev.Lett, 105, 193001(2010)].

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Preparing superposition of squeezed coherent states under thermal reservoir J. S. Sales, Luciano F. da Silva* and N. G. de Almeida Instituto de Física, Universidade Federal de Goiás, Goiânia (GO), Brazil; UnUCETUniversidade Estadual de Goiás, Anápolis (GO), Brazil and Instituto Federal Campus-Ceres, Ceres (GO), Brazil Abstract We propose a scheme for engineering a superposition of squeezed coherent states into a lossy cavity and study its evolution under the influence of a thermal reservoir, providing analytical results for the Wigner function as well as for the Glauber–Sudarshan P function. To characterize this state, we study both the fidelity and the atomic inversion for several parameters, including some parameters taken out from recent experiments in cavity QED.

The vacuum fluctuations on the charge-current uncertainty relations Luis-Gerardo Pedraza-Saavedra Pontificia Universidad Javeriana, Cali, Colombia Abstract Recently it has been demonstrated by the author that the Corinaldesi’s finding of Bohr and Rosenfeld’s flaw in their seminal paper on the measurability of the free quantum electromagnetic field components does not affect their conclusions. That it is possible to make a completion of the aforementioned article with pseudo realistic graphics of the thought experiments they designed in spite of Compagno and Persico’s critics which, according to Hnizdo, are dubious. That along Bohr and Rosenfeld’s own lines of reasoning, especially using spring compensating mechanisms, it is possible to treat the pending measurement cases. Also it has been shown that the treatment of Corinaldesi’s untreated correction on Bohr and Rosenfeld’s untreated cases does not affect the conclusions that could have been obtained by them. That a reaction from Bohr and Rosenfeld to Corinaldesi’s finding was not strictly necessary. That the measurement of an electromagnetic quantum fiel d component is not prevented by any commutation relation or vacuum fluctuations and that the subsequent studies in the measurement of a particle’s momentum and in the measurement of the free quantum gravitational field, based on Bohr and Rosenfeld’s pioneering article have been thoroughly justified. In this article the author completes and justifies the Bohr and Rosenfeld’s extension of their seminal work to the formal pseudo realistic measurement of charge-current uncertainty relations and the quantum control of vacuum fluctuations.

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Average traversal time for non-relativistic quantum tunneling Luiz A. Manzoni Concordia College, 901 8th St. S., Moorhead, MN 56562, USA Abstract We consider the longstanding problem of defining the time for a particle, represented by a wave packet, to tunnel through a potential. The approach used is to couple the particle with a quantum clock, namely the Salecker-Wigner-Peres clock, such that the particle-clock system becomes entangled by the interaction. We show that by performing a post-selection of the final state, in addition to the pre-selection of the initial state, an average traversal time can be obtained after tracing out the particle's degrees of freedom. The average time obtained is then explicitly used to calculate the tunneling time for one dimensional non-relativistic problems and it is shown to yield sensible results. In particular, the average traversal time does not saturate for opaque barriers (i.e., it does not suffer from the Hartman effect).

First considerations on the generalized uncertainty principle for finite-dimensional spaces Marcelo A. Marchiolli* and Maurizio Ruzzi Instituto de Física Teórica, Universidade Estadual Paulista, São Paulo, SP, Brazil Abstract Generalized uncertainty principle and breakdown of the spacetime continuum represent two important results derived of certain mathematical approaches related to quantum gravity and black hole physics near the Planck scale. The discreteness of space suggests, in particular, that all measurable lengths are quantized in units of a fundamental scale (in such a case, the Planck length). We propose a self-consistent theoretical framework for physical systems characterized by a finite space of states, and show that this enlarges previous knowledge about generalized uncertainty principles, as border effects in finite-dimensional discrete phase spaces come into play. In addition, we also investigate under what circumstances the generalized uncertainty principle works well and its inherent limitations.

Quantum correlation measurements for two qubits in a common squeezed bath María de los Angeles Gallego Pontificia Universidad Católica de Chile, Santiago, Chile Abstract For many years the entangled systems have been associated to the quantum world, while the separable systems with the classical world. Recently quantum discord showed that some separable states posses quantum correlation even when the entanglement is zero. In this work, we compare different features of quantum discord and entanglement of formation for two qubits in a common squeezed reservoir. We relate the quantum correlations with the ”distance” of our initial condition from the decoherence free subspace where the system is not affected by environment. While for some initial conditions, the entanglement presents sudden death and revival, quantum discord does not. Still, is not clear the relation between these two measurements of ”quantumness”.

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New experiments in quantum foundations and the epistemological debate María C. Boscá University of Granada. Facultad de Ciencias. Dpto. Física Atómica y Nuclear, Spain Abstract In this poster we display a recapitulation of some recent experiments whose consequences have a deep impact on the foundations of Quantum Physics, discussing the profound conceptual revolution involved. Additionally, we intend to clarify the epistemological consequences derived, specially the concerning to our conceptions of “reality” and which of them can remain consistently assumed today, when the new essential quantum ingredient, the entanglement, has forced us to abandon the local realism. The topics covered would include: · Updates of the concept of Bohr’s complementarity, which must become understood as a continuous concept[1] after experimental intermediate observational situations in some double slit experiments[2], or when we have experiments where complementarity is not due to an unavoidable disturbance during observation[3] or, also, experiments in which a contradiction with the notion of mutual exclusiveness of classical wave and particle pictures emerges[4]. · Delayed choice experiments that demonstrate that the behaviour of the photon in the interferometer depends on the choice of the observable that is measured, even when that choice is made at a position and a time such that it is separated from the entrance of the photon into the interferometer by a space-like interval[5]. · Experiments in quantum teleportation involving two distant experimenters, that “demonstrates some of the salient features of entanglement and quantum information and raises deep questions about the nature of reality in the quantum world”.[6] · Experiments that have shown that realism and certain types of non-locality are also incompatible[7]. [1] P.D.D. Schwindt, P.G. Kwiat and B-G. Englert, Phys. Rev. A60 (1999) 4285-4290; Y. Abranyos, M. Jacob and J. Bergou, Phys. Rev. A61 (1999) 013804; A. Zeilinger, Rev. Mod. Phys. 71,2 (1999) S292. [2] F. Bardou, Am. J. Phys. 59 (1991) 458-461. [3] M.O. Scully, B-G. Englert y H. Walther, Nature 351 (1991) 111-116. [4] P. Ghose and D. Home, Found. Phys. 22,12 (1992) 1435-1447.G. Brida et al, Phys. Let. A328 (2004) 313-318. [5] V. Jacques et al, Science 315 (2007) 966-968. [6] A. Zeilinger, Rev. Mod. Phys. 71,2 (1999) S295. [7] A. Aspect, Nature 446 (2007) 866-867.

Quantum discrete phase space: symmetry phases, coherent sates and quasi-probabilitiy distributions Maurizio Ruzzi Instituto de Física Teórica – UNESP, São Paulo - SP, Brazil Abstract In recent years it has been developed an approach to quantum discrete phase space on which all the main quasi-probability distributions known may be defined. It started from the work of Galetti and Piza, where the idea of operator bases constructed out of Discrete Fourier Transforms of unitary displacement operators was first introduced, passing through the introduction of discrete coherent states, constructed following Klauder's prescription, with the use of a reference state particularly well suited to the discrete context, and finally s-parametrized distributions -- which include Wigner, Husimi and Glauber-Sudarshan distributions functions as particular cases -- were obtained. In the present work, besides summarizing the above formalism, we adapt its formulation so as to encompass some discrete symmetries which has been studied in the literature. Once we accomplished that, an elegant yet physically sound formalism is achieved, which allows us to, on a following contribution, obtain very interesting results regarding the possible discrete structure of space-time. 91

Observer invariance of the collapse postulate of quantum mechanics Milton A. da Silva Jr.* , Roberto M. Serra, Lucas C. Céleri Centro de Ciências Naturais e Humanas, Universidade Federal do ABC Abstract We analyze the wave function collapse as seen by two distinct observers (detectors) in relative motion. Imposing that the measurement process demands information transfer from the system to the detectors, we find that although different observers will acquire different amount of information from their measurements, all of them will agree about the orthogonality of the outcomes, as defined by their own reference frame. So, in this sense, we conclude that such a postulate is observer invariant, however the collapse occurs in a different basis for each observer.

Dynamics of the Gaussian Quantum Discord between two oscillators interacting with a common environment Nahuel Freitas* and Juan Pablo Paz Departamento de Física, FCEyN, UBA, Buenos Aires, Argentina Abstract In this work we analyze the evolution of the quantum correlations, quantified by the Gaussian quantum discord, between two oscillators coupled to a common environment. Following a previous work (J.P. Paz and A. Roncaglia, Phys. Rev. Lett. 100(2008)), in which the evolution of the entanglement was analyzed for the same system, we characterize, for several temperatures and initial states, the asymptotic value of the Gaussian discord and the type of measurement involved (homodyne or heterodyne). We found that for high temperatures the Gaussian quantum discord is a growing function of the temperature, reaching asymptotically a value of one unit of information. This is in clear contrast with the behaviour of the entanglement, which vanishes for sufficiently high temperatures.

Evaluation of entanglement observables in spin systems Norma Canosa*, R. Rossignoli, J.M. Matera Departamento de Física, IFLP, Universidad Nacional de La Plata - CONICET - CIC – Argentina Abstract The study of quantum entanglement in many-body systems is of great importance for both quantum information science and condensed matter physics. In this contribution we describe some recent developments for evaluating entanglement observables in general interacting quantum many-body systems and in particular in quantum spin systems. Based on the path integral representation of the partition function obtained through the Hubbard-Stratonovich transformation and a proper treatment of the different contributions to the path integral, a robust yet tractable general approximation scheme is derived, which contains as a particular case the so-called random phase approximation. This allows to relate the entanglement properties of general systems to those in more simple and solvable systems, where they can be more easily evaluated, like bosonic systems with quadratic interactions. Results for different entanglement observables such as the pairwise concurrence, the block entropy and the negativity between arbitrary subsystems are shown for different spin systems and compared with exact results when available.

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Accuracy of a teleported squeezed coherent-state superposition trapped into a high Q cavity Norton G. de Almeida IF/UFG- Universidade Federal de Goiás, Goiânia – GO, Brazil Abstract We propose a scheme to teleport a superposition of squeezed coherent states (SCSS) from one mode of a lossy cavity to one mode of a second lossy cavity. Based on current experimental capabilities, we present a calculation of the fidelity demonstrating that accurate quantum teleportation can be achieved for some parameters of the SCSS. The signature of successful quantum teleportation is present in the negative values of the Wigner function.

Hybrid qubit gates in circuit QED: a scheme of quantum bit encoding and information processing Olímpio Pereira de Sá Neto Universidade Estadual de Campinas Abstract We propose a specic hybrid two-quantum bit gate encoding involving a quantum electromagnetic field state prepared in a coplanar transmission line capacitively coupled to a single superconducting device. We analyze the efficiency of the encoding under the action of an ohmic bath, and show that this encoding can be actually implemented with present day technology. We also show how the proposal can be extended to generate entanglement between several the solid state qubits and the cavity field in a form of a cluster state through the action of external classical magnetic pulses.

Three atom entanglement dynamics in two mode squeezed field Paulo J. dos Reis* and S. Shelly Sharma Universidade Estadual de Londrina, Londrina – PR, Brazil Abstract We have examined the effect of two mode squeezed field on dynamics of three atom entanglement. Two atoms (A1 and A2) trapped in a cavity held by Alice and one atom (B) in a remote cavity owned by Bob are initially prepared in a W state. These atoms interact with two mode squeezed light injected into the cavities by a beam splitter. In our previous proposal [P. J. dos Reis and S. Shelly Sharma, Phys. Rev. A 79, 012326 (2009).], three atoms prepared in a separable state at t=0, become entangled through interaction with squeezed light and phenomenon of entanglement sudden death (ESD) and revival had been observed. In this article it is shown that for an appropriate choice of squeeze parameter, the entanglement sudden death is delayed while the peak value entanglement between remote atoms is of the same order as in the case of initially separable atoms.

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Photon statistics for thermalized superposition of displaced squeezed states Paulo E. R. Weber*, L. M. Silva, A. E. Santana UnB, Brasília – DF, Brazil Abstract We present a study of the photon statistics for thermalized superposition of displaced squeezed states making use of Thermofield Dynamics formalism. In particular the Photon distribution and Mandel's Q-parameter are presented and the thermal effects over the statistics are analysed. A fidelity comparison is made to the non-thermalized superposition. A subtraction photon state is also considered.

Translating measurement-based quantum computation patterns into compact quantum circuits Raphael Dias da Silva* and Ernesto F. Galvão Universidade Federal Fluminense

Abstract We consider the task of translating measurement-based quantum computation (MBQC) patterns into the circuit model. A method that has been proposed for the task (the Star Pattern translation [1]) in general results in circuits with anachronical gates, i.e., time travel. We analyze the reasons for this problem and clarify the limitations of this method. We propose a new method to translate MBQC patterns into compact circuits, based on the unique way that information is processed in MBQC patterns and how it relates to the way information is processed in quantum circuits. Although the translation procedure that we develop has not been proved to be general, it provides a framework that serves to highlight the similarities and differences between the circuit model and MBQC. [1] Daniel E. Browne, Elham Kashefi, Mehdi Mhalla and Simon Perdrix, Generalized flow and determinism in measurement-based quantum computation, New J. Phys. 9, 250 (2007).

Quantum teleportation using directly partially entangled states Raphael Fortes Infante Gomes* and Gustavo Rigolin UFSCAR, São Carlos, SP, Brazil Abstract We want to study quantum entangled states from a conceptual and a practical perspective. In particular, we wish to investigate partially entangled states, i.e., states whose entanglement content are below the maximum value allowed by quantum mechanics. In this work, we will show the main protocols using partially entangled states wich give the best results for probabilistic teleportations. Our central goal is to study the viability of using directly such states for the implementation of quantum communication tasks so far devised for maximally entangled states. We will be mostly concerned to the utility of partially entangled states for quantum teleportaion and quantum cryptography.

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Exact wave functions of a generalized harmonic oscillator Raquel López Arizona State University, Physical Sciences, Tempe, Arizona, USA Abstract Several approaches or methods of solving the nonlinear Schrödinger equation (NSE) exist and have been proposed by many authors. Variants of the NSE are almost impossible to solve analytically in the general case. That is to say, the exact solution of the NSE can be found only in a comparatively small number of the simplest cases, because the majority of problems in quantum mechanics lead to equations too complex to be solved exactly. In this work our approach to solving a Schrödinger equation is by means of an elegant method for the wave function. We propose the Hermite Gaussian Transform based on an Ansatz of the wave function, along with non-autonomous Hamiltonian mechanics. Exact wave functions of a generalized driven harmonic oscillator in terms of Hermite polynomials are constructed by means of non-autonomous mechanics to transform the equations back into autonomous form. The non-autonomous Schrödinger equation presented has a variable time dependent quadratic Hamiltonian and the corresponding exact wave functions are constructed in terms of a Riccati-type system.

Entanglement and the Mott insulator–superfluid phase transition in bosonic atom chains Reginaldo de Jesus Costa Farias Instituto de Física Gleb Wataghin, Universidade Estadual de Campinas, 13.083-859, Campinas - SP, Brazil. Abstract We analyze the developing of bipartite and multipartite entanglement through the Mott-Insulator Superfluid quantum phase transition. Starting from a Mott insulator state, where a filling factor ν = N/M = 1 per lattice site is considered, we derive an expression for a completely connected graph configuration of bosons and show how bipartite and multipartite entanglement evolve through the phase transition predicted in previous works. Moreover, we show how, through the transition, bipartite entanglement is distributed through the system respecting monogamous relations.

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Experimentally witnessing the quantumness of correlations Roberto M. Serra Federal University of ABC (UFABC), Santo André, São Paulo, Brazil Abstract Nonlocality and entanglement of composed systems are distinguishing features of the quantum domain. Nevertheless, it is the possibility of locally broadcast the state of a multiparticle system that broadly defines the nature of its correlations. Remarkably even separable (disentangled) states can be quantum correlated in this sense. And this kind of quantumness of correlations has an important role not only related to fundamental physical aspects but also concerning applications in quantum information processing and communication, thermodynamics, quantum phase transitions, and biological systems. The quantification of quantum correlations usually involves hard numerical optimization procedures and demanding reconstruction methods. So, it is interesting to have a laboratory friendly witness for the character of correlations. Here we report a direct experimental implementation of such a witness in a room temperature system by using a nuclear magnetic re sonance setup. In our experiment the nature of correlations is revealed performing only few local magnetization measurements.

Generalized Gaussian cat states Raul O. Vallejos CBPF, Rio de Janeiro Abstract We analyse generalized Gaussian cat states obtained by superposing arbitrary Gaussian states, e.g., a coherent state and a squeezed state. The Wigner function of such a state exhibits the typical pair of Gaussian hills plus an interference term which presents a novel structure, as compared with the standard superposition of coherent states (degenerate case). We prove that, in general, the phase structure of the interference term is hyperbolic. This structure survives the action of a thermal reservoir. We also discuss certain superpositions of mixed Gaussian states (generated by conditional Gaussian operations on thermal states).

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Dynamics of non-classical correlations under thermal environment Ruben Auccaise*1, L. C. Céleri2, D. O. Soares-Pinto3, E. R. de Azevedo3, J. Maziero2, A. M. Souza4, T. J. Bonagamba3, R. S. Sarthour4, I. S. Oliveira4 and R. M. Serra2 1

EMBRAPA, 2UFABC, 3IFSC, 4CBPF Abstract

The concept of non-classical correlation is pointed out as a more general than entanglement. The study of such kind of correlation turns out to be very important both from the point of view of fundamental Physics as well as for technological applications. Many authors proposed different measures for the quantification of this non-classical correlation, as, for example, the so called quantum discord [1,2]. The study of the dynamics of non-classical correlation under the action of decoherence lead to the discovery of the sudden-change phenomenon [3]. In this poster we discuss this interesting phenomenon and its experimental implementation in a two qubit system using Nuclear Magnetic Resonance technique. Beyond describing the experimental procedures we theoretically describe the action of the natural thermal environment, leading to the phase and amplitude damping channels. Moreover, this experiment permits us to verify the immunity against decoherence of the classical correlation (the counterpart of the non-classical one) under certain conditions. [1] Ollivier, H. and Zurek, W. H., Phys. Rev. Lett. 88, 017901 (2001). [2] Henderson, L. and Vedral, V., J. Phys. A: Math. Gen. 34, 6899 (2001). [3] Maziero, J., et al., Phys. Rev. A 80, 044102 (2009).

Entanglement and separabilty of states belonging to the the D-7 manifold class Helena Braga*, Simone Souza, and Salomon S. Mizrahi Departamento de Física, CCET, Universidade Federal de São Carlos Rodovia Washington Luis km 235, 13565-905, São Carlos, SP, Brazil. Abstract The entanglement properties of two qubits can be envisaged from the point of view of geometry and, in particular, the representation of a class of 4×4 matrices belonging called D-7 manifold, whose reshuffled elements fit within a hyperspherical geometry, with metric of the spacetime geometry of the theory of relativity, However, the parameters have compact support. This character of the twoqubit states has been appointed previously for a particular subclass of states of the D-7 manifold, called X-states. Their entanglement can be measured using a squared distance with Minkowski metric, s2=t2-V2, associated to the eigenvalues of a new matrix obtained from special symmetry operations done on the original one. Here we show that this same analysis can be applied to any matrix of D-7 manifold that has symmetries, such that it can be expanded in terms of the generators of the u(1)⊗⋃kSUk(2) algebra, a subalgebra of SU(4).

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Generalized uncertainty relation as a tool for measuring mixedness of two qubit states D. Home, Peter Holland, A. S. Majumdar, Tanumoy Pramanik*, N. Ganguly Bose Institute, University of Oxford, S. N. Bose National Centre For Basic Science, Kolkata, India Abstract A hitherto unexplored line of study is initiated in this paper by invoking the Generalized Uncer- tainty Relation (GUR) for the purpose of quantitatively testing the mixedness (purity) of two qubit states. To this end, GUR is recast in a suitable form in order to define an appropriate quantity (Z) involving the mean values and variances of observables that correspond to what may be called the mixedness witness operators. Calculated values of Z for different types of two qubit states pro- vide testable measures of the mixedness of such states, in agreement with the standard measure of mixedness of states using linear entropy (SL) which is not a measurable quantity.

Spotlighting quantum critical points via quantum correlations at finite temperatures Thiago Werlang*, C. Trippe, G. A. P. Ribeiro, and Gustavo Rigolin Federal University of São Carlos, São Carlos, SP, Brazil Abstract We compute the quantum correlation (quantum discord (QD)) and the entanglement (EoF) between nearest neighbor qubits (spin-1/2) in an infinite chain described by the XXZ model with an external field at finite temperatures. The chain is in the thermodynamic limit and thermalized with a reservoir at temperature T (canonical ensemble). We compare the ability of quantum discord, entanglement, and some thermodynamic quantities to spotlight the quantum critical points for several different temperatures. Furthermore, we furnish a more quantitative description of how good all these quantities are in spotlighting critical points of quantum phase transitions at finite T, bridging the gap between experimental data and those theoretical descriptions solely based on the unattainable absolute zero assumption.

An exact treatment for the system-reservoir interaction: beyond the Wigner-Weisskopf approximation. Tiago Barbin Batalhão*, Mickel A. de Ponte and Miled H. Y. Moussa Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brasil Abstract In this work we present an exact treatment of the system-reservoir interaction, which goes beyond the usual Markov approximations. To this end we consider a network of interacting oscillators, one of which is considered to be the system of interest and the others play the role of the reservoir. We verify that the decay rate of the system excitation goes quadratically in the short time regime, instead of the exponential behavior predicted by the Wigner-Weisskopf approximation. Moreover, our approach enables us to account for the reservoir effect when their oscillators are coupled to each other. Our treatment is part of a program where the dissipative system of interest is considered to be a network of interacting oscillators, by which collective damping and diffusion effects lead to interesting phenomena such as decoherence-free subspaces.

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SU(2) invariants of symmetric qubit states Veena Adiga* and Swarnamala Sirsi Department of Physics, Yuvaraja's College, University of Mysore, Mysore-05, INDIA Abstract The problem of enumeration of local invariants of quantum state described by a density matrix ρ is important in the context of quantum entanglement. Nonlocal correlations in quantum systems reflect entanglement between its parts. Genuine non- local properties should be described in a form invariant under local unitary operations. Two N-qubit states are said to be locally equivalent if one can be transformed into the other by local operations. i.e., ρ′ = UρU† where U ∈ SU(2)×N and the two quantum states ρ and ρ´ are said to be equally entangled. In this paper we will focus on “entanglement invariants” of symmetric states which exhibit exchange symmetry. Symmetric states offer elegant mathematical analysis as the dimension of the Hilbert space reduces drastically from 2N to (N + 1), when N qubits respect exchange symmetry. Such a Hilbert space is considered to be spanned by the eigen states { J, M ; − J ≤ M ≤ + J} of angular momentum operators J2 and Jz, where J =

N . The standard expression for the most general 2

symmetric N-qubit density matrix in terms of Fano statistical tensor parameters

r Tr (ρ ) 2 J ρ (J ) = ∑ ( 2 J + 1 ) k =0 where

τ

k† q

k

tq =

Tr ( ρτ qk ) Tr( ρ )

= ( −) q τ − q , k

t

k q

+k

k ( Jv) , ∑ t q τq q=−k

and

τ

k

k q

t

k q

’s is given by

†

(1)

’s are the irreducible tensor operators. Since ρ is hermitian and

satisfy the condition

t

k∗ q

k = (−1) q t −q . In general

t

k ±k

can be made zero for any k

by a suitable rotation. i.e.,

k

(t ± k ) R = 0 =

+k

∑D

q′= − k

k q′, ± k

k

(φ , θ ,ψ ) t q′ .

(2)

Using the well known Wigner expression for the rotation matrix Dk, the above equation can be written as 2k

(t ± k ) R = 0 = [±cos (θ / 2)]2 k exp[ik (φ + ψ )]∑ C r Z r , k

sin

(3)

r =0

where the complex variable

Z = tan (θ / 2 )e

− i (φ + π )

Z = cot (θ / 2 ) e

t

in the case of (

k −k

− iφ

in the case of

k

(t + k ) R = 0 and

) R = 0 . The expansion coefficients Cr in the polynomial 1

1

2k 2k 2 2 are the same in both the cases and is given by C r =   t kq =   t kr − k . By solving the above r  k+q  polynomial equation, it has been shown that there exists in general two sets of k-coordiante frames

in which

(t

k ±k

) = 0 [G.Ramachandran and V.Ravishankar, J. Phys.G: Nucl.Phys. 12(1986)]. One set is

obtained by the other by inverting the Z-axis. Thus a spin-J density matrix is characterized by J (2J+1) axes and 2J real scalars. Using this multiaxial parametrization of density matrix, we enumerate the total number of SU(2) invariants characterizing an N-qubit symmetric state. We consider the well known case of two qubit and three qubit states for a detailed analysis.

99

Unidimensional reduction of the 3D Gross-Pitaevskii equation with two- and three-body interactions Wesley B. Cardoso*, A. T. Avelar, and D. Bazeia Instituto de Física, Universidade Federal de Goiás, 74.001-970, Goiânia, Goiás, Brazil, and Departamento de Física, Universidade Federal da Paraíba, 58.059-900, João-Pessoa, Paraíba, Brazil. Abstract We deal with the three-dimensional Gross-Pitaevskii equation, which is used to describe a cloud of dilute bosonic atoms that interact under competing two- and three-body scattering potentials. We study the case where the cloud of atoms is strongly confined in two spatial dimensions, allowing us to build an unidimensional nonlinear equation, controlled by the nonlinearities and the confining potentials that trap the system along the longitudinal coordinate. We focus attention on specific limits, dictated by the cubic and quintic coefficients, and we implement numerical simulations to help us to quantify the validity of the procedure.

100

AUTHOR INDEX Adiga, V., 99 Aguiar, L. S., 86 Aiello, A., 35 Alcalde, A. M., 69 Alekseev, P. S., 58 Andersen, U. L., 35 Angelo, R. M., 29, 60 Auccaise, R., 81, 97 Avelar, A. T., 68, 100 Bagnato, V. S., 25 Bagrov, V. D., 21 Barbosa, F. A. S., 76 Bartuskova, L., 57 Batalhão, T. B., 98 Bazeia, D., 68, 100 Beckwith, A., 31 Bellini, M., 53 Blanchet, J. L., 19 Bohn, J. L., 52 Bonagamba, T. J., 97 Borelli, L. F. M., 86 Borges, H., 69 Boscá, M. C., 91 Braga, H., 78, 97 Brambilla, E., 19 Brasil, C. A., 73 Brod, D. J., 74 Caldeira, A. O., 20 Canosa, N., 60, 92 Cardoso, W. B., 68, 100 Caruso, F., 41 Celechovska, L., 56 Céleri, L., 88, 92, 97 Cerf, N. J., 28, 66 Cernoch, A., 56 Černoch, A., 47 Cesário, A. T., 63 Chew, L. Y., 49 Chotia, A., 52 Ciliberti, L., 60 Cirac, J. I., 15, 36 Cornelio, M. F., 52 Corzo Trejo, N. V., 29 Costa, A. N. S., 67 Coutinho dos Santos, B., 32 da Cruz, L. S., 88 da Paz, I. G., 84 da Silva Jr, M. A., 92 da Silva, L. F., 89 da Silva, R. D., 94

Davidovich, L., 15, 71 de Almeida, N. G., 89, 93 de Azevedo, E. R., 97 de Castro, L. A., 86 de Lima, J. P. C., 81 de Matos Filho, R. L., 15, 70, 71 de Melo, F., 70 de Miranda, M. H. G., 52 de Moraes Neto, G. D., 78 de Oliveira, M. C., 52, 82 de Oliveria, T. R., 62 de Ponte, M. A., 78, 98 de Sá Neto, O. P., 93 De Siena, S., 61 de Souza, D. D., 75 Dechoum, K., 32 Dehesa, J. S., 44 Delsing, P., 24 Di Lorenzo, A., 32, 67 DiGuglielmo, J., 28 Diniz, I. T., 36 Dodonov, V. V., 63 dos Reis, P. J., 93 Dowling, J. P., 34 Dusek, M., 56, 57 Dušek, M., 47 Duzzioni, E. I., 74 Eisert, J., 28, 47, 56 Escher, B. M., 15, 71 Fanchini, F., 40, 52 Farias, O. J., 57 Farias, R. J. C., 7, 95 Figueroa, E., 38 Fikerova, H., 56 Filgueiras, J. G., 81 Filip, R., 57 Fiurasek, J., 56 Freitas, N., 45, 92 Fresneda, R., 60 Furuya, K., 85 Gabriel, C., 35 Gallego, M. A., 90 Galvão, E. F., 40, 74, 94 Ganguly, N., 98 Gatti, A., 19 Gavenda, M., 57 Gavrilov, S., 21 Gitman, D., 21 Glancy, S., 48 Gomes, R. F. I., 94 101

González, J., C., 85 Hage, B., 28 Herrera, A. M., 66 Holland, P., 98 Home, D., 98 Jedrkiewicz, O., 19 Jensen, K., 36 Jezek, M., 56 Jin, D., 52 Johansson, G., 22 Jonathan, D., 36 Karpov, E., 28 Khoury, A. Z., 32 Kieling, K., 47, 56 Kim, Y. S., 26 Krauter, H., 36 Lassen, M., 56 Lavoie, J., 83 Lemos, G. B., 77 Lemr, K., 47, 56 Leonski, W., 81 Lett, P. D., 29 Leuchs, G., 35, 37 Lobo, A. C., 33 Locatelli, M., 53 López, R., 95 Lopez-Ruiz, F. F., 42 Lozada A. C., 66 Lugiato, L., 19 Luiz, F. S., 75 Luks, A., 81 Lunardi, J. T. T., 84 Luthra, J., 80 Maciel, T. O., 63 Majumdar, A. S., 98 Mandilara, A., 28, 66 Man'ko, M. A., 54 Man'ko, V. I., 26 Manzoni, L. A., 90 Marchiolli, M. A., 90 Marek, P., 59 Marino, A. M., 29 Marquardt, C., 35 Marques, B., 70 Martinelli, M., 51 Matera, J. M., 92 Maziero, J., 82, 97 Meira, D., 21 Mendonça, J. T., 23 Meneguele, H. L. O., 79 Messina, A., 68 Micuda, M., 56 Migliore, R., 68 Mikova, M., 56 Milburn, G. J., 14 Militello, B. D., 33 Mitchell, M. W., 45

Mizrahi, S. S., 78, 97 Moroseev, F. V., 58 Moussa, M. H. Y., 78, 98 Mueller, M., 55 Muschik, C., 36 Napoli, A., 68 Napolitano, M., 54 Napolitano, R. J., 73, 86 Nemes, M. C., 23, 84 Neves, L., 87 Neyenhuis, B., 52 Nicacio, F., 41 Nölleke, C., 38 Oberthaler, M., 16 Oliveira, I. S., 81, 97 Oliveira, P. A., 87 Ospelkaus, S., 52 Paz, J. P., 45, 92 Peixoto de Faria, J. G., 84 Perina Jr., J., 22, 47, 81 Perinova, V., 81 Petersen, J. M., 36 Pineda, C., 28 Polycarpou, C., 53 Polzik, E. S., 36 Poulios, K., 48 Pramanik, T., 98 Quemener, G., 52 Reina, J. H., 66 Reiserer, A., 38 Rempe, G., 38 Reyes, S., 61 Ribeiro, A. D., 29 Ribeiro, C. A., 33 Ribeiro, C. A. P., 98 Richardson, C. D., 34 Rigolin, G., 94, 98 Ritter, S., 38 Romera, E., 39 Rossatto, D. Z., 74, 80 Rossignoli, R., 60, 92 Roversi, J. A., 71, 79, 85, 86 Ruby, V. C., 64 Rudnicki, L., 49 Rulli, C. C., 73 Ruzzi, M., 90, 91 Saavedra, L. G. P., 89 Sales, J. S., 89 Samblowski, A., 28 Sanders, B. C., 64 Sanders, B.C., 14 Santana, A. E., 94 Santos, J. P., 85 Santos, M. F., 50 Sanz, L., 48, 69, 87 Sarandy, M. S., 73 Sarthour, R. S., 81, 97 102

Scala, M., 68 Schnabel, R., 24, 28 Schreiber, A., 30 Semenov, A. A., 31 Semião, F. L., 85 Serra, R. M., 66, 92, 96, 97 Sharma, S. S., 93 Shaterzadeh-Yazdi, Z., 64 Silva, L. M., 94 Simon, R., 16 Sirsi, S., 99 Soares-Pinto, D. O., 97 Solomon, A., 20 Soubusta, J., 47, 56, 57 Souza, A. M., 97 Souza, J. A., 80 Souza, S., 78, 97 Specht, H., 38 Sperling, J., 42 Summer, I., 79 Suslov, S., 24 Svozilik, J., 47 Sych, D., 37 Taketani, B. G., 70 Tanatar, B., 69 Tapia, R. M., 59 Tollaksen, J., 44 Toscano, F., 76

Traina, P., 58 Trippe, C., 98 Uphoff, M., 38 Vallejos, R. O., 96 van Loock, P., 35 Vasconcelos, H. M., 48 Vega-Guzman, J. M., 84 Vera, J. L., 82 Vianna, R. O., 63 Vidiella-Barranco, A., 68, 75, 86 Villas-Boas, C. J., 72, 74, 80 Vogel, W., 31, 42 Vourdas, A., 21 Walborn, S., 62 Wallentowitz, S., 61 Wang, D., 52 Wang, J., 46 Wasilewski, W., 36 Weber, P. E. R., 94 Werlang, T., 74, 98 Yabu-uti, B. F. C., 71 Ye, J., 52 Zagury, N., 23 Zambrano, E., 39 Zavatta, A., 53 Znidaric, M., 55 Zurek, W. H., 17 Zypman, F., 77

103