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Experimental tests of the weak equivalence principle. Susannah Dickerson, Kasevich Group, Stanford University 2 nd International Workshop on Antimatter and Gravity November 13, 2013. The Weak Equivalence Principle. - PowerPoint PPT Presentation
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Experimental testsof the weak equivalence principle
Susannah Dickerson, Kasevich Group, Stanford University2nd International Workshop on Antimatter and Gravity
November 13, 2013
The Weak Equivalence Principle
Independent of mass or composition, all bodies locally fall under gravity at the same rate rate.
The Weak Equivalence Principle
Independent of mass or composition, all bodies locally fall under gravity at the same rate rate.
Testing WEP for antimatter
• Direct measurements– Matter v. antimatter particles under gravity
• Semi-direct measurements– Matter v. antimatter particles, indirectly under gravity
• Indirect measurements via matter– Couplings to gravitoscalar/vector force– Contributions of antimatter to mass energy of
conventional matter
Testing WEP for antimatter
• Direct measurements– Matter v. antimatter particles under gravity
• Semi-direct measurements– Matter v. antimatter particles, indirectly under gravity
• Indirect measurements via matter– Couplings to gravitoscalar/vector force– Contributions of antimatter to mass energy of
conventional matter
Testing WEP for antimatter
• Direct measurements– Matter v. antimatter particles under gravity
• Semi-direct measurements– Matter v. antimatter particles, indirectly under gravity
• Indirect measurements via matter– Couplings to gravitoscalar/vector force– Contributions of antimatter to mass energy of
conventional matter
Historical trend
Historical trend
LLR = Lunar Laser Ranging
Current Limits of the WEP
• Lunar Laser Ranging:
• Torsion Balance:
Earth-Moon v. SunWilliams et al, Class. Quant. Grav. 29, 2012
Wagner et al, Class. Quant. Grav. 29, 2012
Be-Ti v. Earth
Be-Al v. Earth
Bounds on antimatter EP from matter
Alves et al, arXiv:0907.4110 (2009)
Based on LLR, Torsion Balance, and pulsar timing results:
(virtual antimatter)
(extra forces)
Based on Eot-Wash Torsion Balance results:
Fifth force vector force coupled to B – L # ~ 10-9-10-11
Wagner et al. Class. Quantum Grav. 29 (2012)
Isotopic sensitivity to antimatter EP
Hohensee, PRL 111, 2013
(anomalous fractional acceleration)
(ano
mal
ous f
racti
onal
acc
eler
ation
)
Bounds on antimatter EP violation: 10-6 – 10-8
(based on torsion balance, clock comparison and matter waves)
Ground-based tests (matter only)Experiment Precision Material
Atom interferometry
Stanford 10-15 85Rb-87Rb
Berkeley 10-14 6Li-7Li
Hannover (QUANTUS-II) 10-11 40K-87Rb
Paris (ICE) 10-11 39K-87Rb; parabolic flight
Macroscopic proof masses
Torsion Balance (Eot-Wash) 10-14 Be-Polyethylene
LLR 10-14 Earth-moon
Galileo Galilei on Ground 10-16 Rapidly-rotating concentric masses
SR-POEM 10-17 Sounding rocket;
Space-based tests (matter only)Experiment Precision Material
Atom interferometry
STE-QUEST 10-15 85Rb-87Rb
Macroscopic proof masses
MICROSCOPE 10-15 (rotating) concentric masses, Pt-T
STEP 10-18 Rotating concentric masses; Be, Nb, Pt-Ir
Galileo Galilei 10-17 Rapidly-rotating concentric masses
Direct antimatter testsExperiment Precision Material
Already performed
ALPHA 102 Free fall of Ħ
Operating/planned
AEGIS 10-2 Moiré deflectometry of Ħ
ALPHA 10-2 Atom interferometry of Ħ
GBAR 10-2 Free fall of Ħ
AGE 10-2 Grating atom interferometry of Ħ
Semi-direct (already performed)
CP LEAR 10-9 K0 – anti-K0 oscillations
ATRAP 10-4 p – anti-p cyclotron frequencies
Supernova 1987A 10-2-10-6 ν – anti-ν arrival times
Towards testing the WEP with atom
interferometry
Atom Interferometry
Atom Interferometry
Atom Interferometry
Influences on phase shift:• Acceleration• Rotation• Gravity gradients• Magnetic fields
Atom Interferometry
Influences on phase shift:• Acceleration• Rotation• Gravity gradients• Magnetic fields
~ 10
m
2.3 s
Atom Interferometry
Sensitivity to phase shift:
~ 10
m
2.3 s
Precision Measurements of…• Equivalence Principle• Gravity curvature/tidal term
• General Relativity
• Gravitational waves (future)• Antimatter?
Hogan et al. Proceedings of Enrico Fermi (2009) Dimopoulos et al. PRL 98, 111102 (2007)
Apparatus• Ultracold atom source
– 107 at 50 nK– 105 at 3 nK
• Optical Lattice Launch– 13.1 m/s with 2386 photon
recoils to 9 m
• Atom Interferometry– 2 cm 1/e2 radial waist– 500 mW total power– Dyanmic nrad control of laser
angle with precision piezo-actuated stage
• Detection– Spatially-resolved
fluorescence imaging– Two CCD cameras on
perpendicular lines of sight
Atom Interferometry~
10 m
2.3 s
t = T: Image at apex
1.5 cm
F=1 F=2
F=1
F=2(pushed)
1 cm
t = 2T = 2.3s: Images of Interferometry
Atom Interferometry
3 nK, 105 atoms 50 nK, 4 x 106 atoms
F=2(pushed)
F=1
Dickerson, et al., PRL 111 (2013)
Dickerson, et al., PRL 111 (2013)
Atom Interferometry
3 nK, 105 atoms 50 nK, 4 x 106 atoms
F=2(pushed)
F=1
Acceleration sensitivity:
Precision measurement of
Earth’s rotation
Coriolis Effect
Gustavson et al. PRL 78, 1997McGuirk et al. PRA 65, 2001
Hogan et al. Enrico Fermi Proceedings, 2009Lan et al. PRL 108, 2012
Coriolis acceleration:
Atom phase:
Uncompensated Compensated
Point Source Interferometry– Long time of flight x-p correlation– Velocity-dependent phase phase gradient
Phase:Ballistic expansion
Dickerson, et al., PRL 111 (2013)
Phase ShearsInterferometer output atom population:
Contrast Interferometer phase
Sugarbaker, et al., PRL 111 (2013)
Phase ShearsInterferometer output atom population:
No gradient Small gradient(displacement)
Large gradient(fringes)
F = 2(pushed)
F = 1
Sugarbaker, et al., PRL 111 (2013)
Phase Shears
No gradient Small gradient(displacement)
Large gradient(fringes)
Interferometer output atom population:
F = 2(pushed)
F = 1
Sugarbaker, et al., PRL 111 (2013)
Dual-Axis Gyroscope
Rotation phase shift:
CCD2
CCD1
y
xz
CCD1:
CCD2:
Mirror
Rotation vector
Dual-Axis Gyroscope
Rotation phase shift:
CCD2
CCD1
y
xz
CCD1:
CCD2:
CCD1
CCD2
Precision:Noise Floor:
Mirror
Gyrocompassing
Beam Angle + Coriolis Error:
g True north:
Precision:Repeatability:Correction to axis:
Sugarbaker, et al., PRL 111 (2013)
Large-momentum transfer(Current line of research)
Near-term goal: with …wavepacket separation, in a shot
LMT Atom Interferometry
Sensitivity increase:
102ħk demonstration: Chiow et al. PRL 107, 2011
Wavepacket separation at the top:
4 cm
LMT with long interrogation time6 ħk sequential Raman in 10 meter tower2T = 2.3 seconds
CollaboratorsStanford University: PI:
Mark KasevichEP:
Jason HoganSusannah DickersonAlex SugarbakerTim Kovachy
Former members:Sheng-wey ChiowDave JohnsonJan Rudolph (Rasel Group)
Also:Philippe Bouyer (CNRS)
Supported by:SD: Gerald J. Lieberman Fellowship AS: National Science Foundation GRF TK: Hertz Foundation
