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Experimental tests of the weak equivalence principle

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.

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Experimental tests of the weak equivalence principle

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  1. Experimental testsof the weak equivalence principle Susannah Dickerson, Kasevich Group, Stanford University 2nd International Workshop on Antimatter and Gravity November 13, 2013

  2. The Weak Equivalence Principle Independent of mass or composition, all bodies locally fall under gravity at the same rate rate.

  3. The Weak Equivalence Principle Independent of mass or composition, all bodies locally fall under gravity at the same rate rate.

  4. 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

  5. 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

  6. 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

  7. Historical trend

  8. Historical trend LLR = Lunar Laser Ranging

  9. Current Limits of the WEP • Lunar Laser Ranging: • Torsion Balance: Williams et al, Class. Quant. Grav. 29, 2012 Earth-Moon v. Sun Wagner et al, Class. Quant. Grav. 29, 2012 Be-Ti v. Earth Be-Al v. Earth

  10. Bounds on antimatter EP from matter Based on LLR, Torsion Balance, and pulsar timing results: (virtual antimatter) (extra forces) Alves et al, arXiv:0907.4110 (2009) 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)

  11. Isotopic sensitivity to antimatter EP (anomalous fractional acceleration) (anomalous fractional acceleration) Bounds on antimatter EP violation: 10-6 – 10-8 (based on torsion balance, clock comparison and matter waves) Hohensee, PRL 111, 2013

  12. Ground-based tests (matter only)

  13. Space-based tests (matter only)

  14. Direct antimatter tests

  15. Towards testing the WEP with atom interferometry

  16. Atom Interferometry

  17. Atom Interferometry

  18. Atom Interferometry • Influences on phase shift: • Acceleration • Rotation • Gravity gradients • Magnetic fields

  19. Atom Interferometry • Influences on phase shift: • Acceleration • Rotation • Gravity gradients • Magnetic fields ~ 10 m 2.3 s

  20. Atom Interferometry Sensitivity to phase shift: • Precision Measurements of… • Equivalence Principle • Gravity curvature/tidal term • General Relativity • Gravitational waves (future) • Antimatter? ~ 10 m 2.3 s Hogan et al. Proceedings of Enrico Fermi (2009) Dimopoulos et al. PRL 98, 111102 (2007)

  21. 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 • Dyanmicnrad control of laser angle with precision piezo-actuated stage • Detection • Spatially-resolved fluorescence imaging • Two CCD cameras on perpendicular lines of sight

  22. Atom Interferometry t = 2T = 2.3s: Images of Interferometry t = T: Image at apex F=2 F=1 1 cm 1.5 cm F=1 ~ 10 m F=2 (pushed) 2.3 s

  23. Atom Interferometry 3 nK, 105 atoms 50 nK, 4 x 106 atoms F=1 F=2 (pushed) Dickerson, et al., PRL 111 (2013)

  24. Atom Interferometry 3 nK, 105 atoms 50 nK, 4 x 106 atoms F=1 F=2 (pushed) Acceleration sensitivity: Dickerson, et al., PRL 111 (2013)

  25. Precision measurement of Earth’s rotation

  26. Coriolis Effect Coriolis acceleration: Atom phase: Uncompensated Compensated Gustavson et al. PRL 78, 1997 McGuirk et al. PRA 65, 2001 Hogan et al. Enrico Fermi Proceedings, 2009 Lan et al. PRL 108, 2012

  27. Point Source Interferometry • Long time of flight x-p correlation • Velocity-dependent phase phase gradient Ballistic expansion Phase: Dickerson, et al., PRL 111 (2013)

  28. Phase Shears Interferometer output atom population: Contrast Interferometer phase Sugarbaker, et al., PRL 111 (2013)

  29. Phase Shears Interferometer output atom population: Large gradient (fringes) Small gradient (displacement) No gradient F = 2 (pushed) F = 1 Sugarbaker, et al., PRL 111 (2013)

  30. Phase Shears Interferometer output atom population: Large gradient (fringes) Small gradient (displacement) No gradient F = 1 F = 2 (pushed) Sugarbaker, et al., PRL 111 (2013)

  31. Dual-Axis Gyroscope Rotation phase shift: CCD1: CCD2: Rotation vector CCD2 CCD1 y x z Mirror

  32. Dual-Axis Gyroscope Rotation phase shift: Precision: Noise Floor: CCD1: CCD2: CCD2 CCD2 CCD1 CCD1 y x z Mirror

  33. Gyrocompassing Beam Angle + Coriolis Error: Precision: Repeatability: Correction to axis: g True north: Sugarbaker, et al., PRL 111 (2013)

  34. Large-momentum transfer(Current line of research)

  35. LMT Atom Interferometry Sensitivity increase: Near-term goal: with … wavepacket separation, in a shot 102ħk demonstration: Chiow et al. PRL 107, 2011

  36. LMT with long interrogation time 6 ħk sequential Raman in 10 meter tower 2T = 2.3 seconds Wavepacket separation at the top: 4 cm

  37. Collaborators Stanford University: PI: Mark Kasevich EP: Jason Hogan Susannah Dickerson Alex Sugarbaker Tim Kovachy Former members: Sheng-weyChiow Dave Johnson Jan Rudolph (Rasel Group) Also: Philippe Bouyer (CNRS) Supported by: SD: Gerald J. Lieberman Fellowship AS: National Science Foundation GRF TK: Hertz Foundation

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