SpaceTime: Probing for 21st Century Physics with Clocks Near the Sun Lute Maleki Quantum Sciences and Technology Group Jet Propulsion Laboratory California Institute of Technology Pasadena, CA, USA
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
Fundamental Physics and Space Space investigations and fundamental physics play complementary roles: – As a challenging endeavor, extremely sensitive instrumentation is required for space with features of high performance, low power, low mass, and low cost. – As a benign environment (micro gravity, low vibration, high isolation, space and time spans, etc.) space offers the opportunity to perform exacting tests of physics.
Fund. Phys.
Space environment for tests of fundamental physics
Space Space based measurements enhanced by advance technology
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
Cosmology: Pathway to Fundamental Physics in Space • In the past decade observations from space has opened new vistas to the universe, and also has created new puzzles: – – – – –
The horizon problem The accelerating universe The fine tuning problem The fate of the universe Planck-scale physics
• New theoretical models are being developed – – – –
String theories, M-theory, quantum gravity Modified gravity theories Non-commutative quantum mechanics VSL Theories
• These are all hints point that point to the emergence of new physics! Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
Sacred ideas in Physics are open to question
• Constancy of “constants” • Robustness of fundamental symmetries • The truism “all theories in physics will breakdown at some limit…” is no longer an alien notion in mainstream physics! This climate requires experimental tests of fundamental physics more urgently than ever! This is a golden opportunity for fundamental physics in space!
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
But…Challenges remain • Climate at NASA and other space agencies • Priorities (lack thereof) for space research • General view of the value in “tests of theoretical models” • “Unrealistic” view of “priorities” amongst us, the scientists • All of the above translating into high cost/benefit ratio
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
How to deal with reality ?
• Hope that space agencies come to their senses! • Hope that time will improve funding of science • Seek and identify sensible, low cost/benefit experiments with multiple functions to be used in already planned missions
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
JPL’s Quantum Sciences and Technology Projects 1.
2.
3.
4. 5.
CLOCKS: - experiments in atomic physics are routinely sensitive to sub-mHz energy shifts - expressed in GeV, this is a larger sensitivity than 4 x 10-27 GeV. - testing variation of fundamental constants and the validity of string theory - testing Einstein relativity theories ATOM INTERFEROMETERS - testing the equivalence principle - gravity mapping in space - inertial navigation and drag-free control - atom chips BEC - exploring quantum gas/fluid in absence of gravity - studying matter wave coherence and decoherence - accessing Planck scale physics and the structure of space-time - atom interferometer enhancement EIT Others ….
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
e2 α= hc
Webb, et al. PRL, 87, 0191301 (2001)
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
There are also clock comparison tests Astronomy Tests: Low resolution determined by spectroscopy of distant gas clouds over 1010 yr period. Clock Tests: Ultrahigh resolution determined by clock accuracy over a few year baseline - can be repeated, and improved
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
Hyperfine Transitions
Prestage, Tjoelker, Maleki PRL, 74, 3511(1995)
Hydrogen hyperfine splitting scales as:
1 As (I + ) = 2
2.35 2.20 2.05
Clock frequency
F Z)α ( rel
8 2 me As = α g p R∞ c 3 mp
2.50
Alkali atoms and alkali-like ions scale as hydrogen but with relativistic corrections Frel(αZ):
1.90 1.75 1.60 1.45 1.30 1.15 1.00
0
10
20
30
40
50
60
70
80
Z
8 2 z2 dΔ m As = α g I Z 3 (1 − n ) Frel (αZ )(1 − δ )(1 − ε ) e R∞ c 3 n* dn mp Relativistic corrections to wavefunction at the nucleus
Finite Size nuclear charge 4% Cs,…, 12% Hg
Quantum Science and Technology Group
Finite Size nuclear Magnetic Moment 0.5% Cs,…., 3% Hg
PQE 2005, Snowbird, Utah
90
α Dependence of Hyprefine Transitions Hyperfine Transitions The frequency of transition: m mc 2 f =α F(αZ ) M h 4
Rb Yb+
α sensitivity comparison
H-maser
H
Rb
Cs
Hg+
H
0
0.3
0.74
2.2
Rb
-0.3
0
0.45
1.9
Cs
-0.74 -0.45 0
1.4
Hg+
-2.2
0
-1.9
-1.4
Hg+
Cs
Cd+
. .
Quantum Science and Technology Group
PQE 2005, Snowbird, Utah
Summary of Clock Comparison Tests SCSO
vs Cs hfs
Hg+ vs H-Maser (hfs) Rb vs Cs (hfs) Optical Hg+ vs Cs Optical/hfs
g Cs
me 3.74 α mp
µ Hg µH
α 2.2
µ Rb −0.44 α µ Cs me g Cs m p
6.0 α
