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Gravitational Physics with Atom Interferometry

Gravitational Physics with Atom Interferometry. Prof. Mark Kasevich Dept. of Physics and Applied Physics Stanford University, Stanford CA. Atom interferometric inertial sensors. Pulses of light are used to coherently manipulated the center-of-mass motion of atomic wavepackets.

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Gravitational Physics with Atom Interferometry

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  1. Gravitational Physics with Atom Interferometry Prof. Mark Kasevich Dept. of Physics and Applied Physics Stanford University, Stanford CA

  2. Atom interferometric inertial sensors Pulses of light are used to coherently manipulated the center-of-mass motion of atomic wavepackets

  3. Phase shifts: Semi-classical approximation Three contributions to interferometer phase shift: Propagation shift: Laser fields (Raman interaction): Wavepacket separation at detection: See Bongs, et al., quant-ph/0204102 (2002), also App. Phys. B, 2006.

  4. Gyroscope, Measurement of Earth rotation rate F=4 Interior view F=3 Gyroscope output vs.orientation. 200 mdeg/hr1/2

  5. Gravimeter, Measurement of g Fabricated and tested at AOSense, Inc., Sunnyvale, CA. Sensors designed for precision navigation. AOSense, Inc. DARPA DSO

  6. Gyroscope mode/Rotational Seismology Honduras/offshore 7.3 +30 min Gyroscope output necessary to disambiguate tilt from horizontal motion (navigation problem). AOSense, Inc. DARPA DSO

  7. Differential accelerometer ~ 1 m Applications in precision navigation and geodesy

  8. Gravity gradiometer Demonstrated accelerometer resolution: ~10-11 g.

  9. Test Newton’s Inverse Square Law Using new sensors, we anticipate dG/G ~ 10-5. This will also test for deviations from the inverse square law at distances from l ~ 1 mm to 10 cm. Theory in collaboration with S. Dimopoulos, P. Graham, J. Wacker.

  10. Equivalence Principle Co-falling 85Rb and 87Rb ensembles Evaporatively cool to < 1 mK to enforce tight control over kinematic degrees of freedom Statistical sensitivity dg ~ 10-15 g with 1 month data collection Systematic uncertainty dg ~ 10-16 limited by magnetic field inhomogeneities and gravity anomalies. 10 m drop tower

  11. Error Model • Use standard methods to analyze spurious phase shifts from uncontrolled: • Rotations • Gravity anomalies/gradients • Magnetic fields • Proof-mass overlap • Misalignments • Finite pulse effects • Known systematic effects appear controllable at the dg ~ 10-16 g level. • (Hogan, Johnson, Proc. Enrico Fermi, 2007)

  12. Earth rotation compensation Earth rotation induces systematic phase shift which needs to be compensated. Strategy is to keep atom-optics axis inertially stabilized over interferometer pulse sequence duration (~ 2.8 s). Angle pick-off: Optical lever + Sagnac interferometer for precision angle measurement Required 1 nrad angular stability in beam-steering axis achieved by controlling orientation of retro-reflecting mirror. ~ 1 prad/Hz1/2 performance achieved Related work: Howell, PRL 102, 173601 (2009); Howell, Phys. Rev. A 81, 033813 (2010). Top view of mirror

  13. Magnetic shields Shields at annealing facility Magnetic shielding specifications require joint-free shields over 10 m. Achieved 100 mG axial uniformity over 10 m.

  14. laser atom General Relativity/Phase shifts • Light-pulse interferometer phase shifts in GR: • Geodesic propagation for atoms and light. • Path integral formulation to obtain quantum phases. • Atom-field interaction at intersection of laser and atom geodesics. Atom and photon geodesics Prior work, de Broglie interferometry: Post-Newtonian effects of gravity on quantum interferometry, Shigeru Wajima, Masumi Kasai, ToshifumiFutamase, Phys. Rev. D, 55, 1997; Bordé, et al.

  15. Tests of General Relativity Schwarzschild metric, PPN expansion: • Steady path of apparatus improvements include: • Improved atom optics • Longer baseline • Sub-shot noise interference read-out Corresponding AI phase shifts: Projected experimental limits: (Dimopoulos, et al., PRL 2007; PRD 2008)

  16. Gravity waves Atoms provide inertially decoupled references Gravity wave phase shift through propagation of optical fields Evades quantum measurement noise (photon scattering regularized by non-linear atom/photon interaction; prepare fresh atom ensemble each shot) Previous work: B. Lamine, et al., Eur. Phys. J. D 20, (2002); R. Chiao, et al., J. Mod. Opt. 51, (2004); S. Foffa, et al., Phys. Rev. D 73, (2006); A. Roura, et al., Phys. Rev. D 73, (2006); P. Delva, Phys. Lett. A 357 (2006); G. Tino, et al., Class. Quant. Grav. 24 (2007). Possible satellite configuration

  17. AGIS free-flying satellite concept In collaboration with GSFC (Bernie Seery, BabakSaif and co-workers) Considering ISS, free-flyer LEO configurations Recent analysis for Earth orbiting configurations: J. M. Hogan, D. M. S. Johnson, S. Dickerson, T. Kovachy, A. Sugarbaker, S. Chiow, P. W. Graham, M. A. Kasevich, B. Saif, S. Rajendran, P. Bouyer, B. D. Seery, L. Feinberg, and R Keski-Kuha, 1009.2702 (2010), submitted. Possible instrument configuration

  18. Error models

  19. Wavefront distortion: temporal variations • Time varying wavefrontinhomogeneities will lead to non-common phase shifts between distant clouds of atoms • High spatial frequencies diffract out of the laser beam as the beam propagates between atom clouds • - Limit for temporal stability of wavefronts determined by stability of final telescope mirror Mirror: Be at 300K J. M. Hogan, et al., 1009.2702 (2010), submitted; arXiv. See also, P. Bender, to be published.

  20. Atom cloud kinematic constrains Shot-to-shot jitter in the position of the atom cloud with respect to the satellite/laser beams constrains static wavefront curvature Wavefront error vs. spatial frequency, assuming 10 nm/Hz1/2 position jitter J. M. Hogan, et al., 1009.2702 (2010), submitted, arXiv See also, P. Bender, to be published.

  21. Acknowledgements • Grant Biedermann, PhD, Physics • Ken Takase, PhD, Physics • Igor Teper, Post-doctoral fellow • John Stockton, Post-doctoral fellow • Louis Delsauliers, Post-doctoral fellow • Xinan Wu, PhD, Applied physics • Jongmin Lee, Graduate student, Applied physics • ChetanMahadeswaraswamy, PhD, Mechanical engineering • David Johnson, Graduate student, Physics • GeertVrijsen, Graduate student, Applied physics • Jason Hogan, Post-doctoral fellow, Physics • Sean Roy, Graduate student, Physics • Tim Kovachy, Graduate student, Physics • Alex Sugarbaker, Graduate student, Physics • Susannah Dickerson, Graduate student, Physics • + THEORY COLLABORATORS: • S. Dimopolous, P. Graham, S.Rajendran • + GSFC COLLABORATORS: • B. Saif, B. Seery, L. Feinberg, R. Keski-Kuha • + CNRS • P. Bouyer (See talk, MIGA terrestrial GW detector) • + AOSENSE TEAM

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