gravitational physics with atom interferometry
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Gravitational Physics with Atom Interferometry
Prof. Mark KasevichDept. 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
Phase shifts: Semi-classical approximationThree 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.
Gyroscope, Measurement of Earth rotation rate
Gyroscope output vs.orientation.
200 mdeg/hr1/2
Interior view F=3
F=4
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
AOSense, Inc. DARPA DSO
+30 min
Gyroscope output necessary to disambiguate tilt from horizontal motion (navigation problem).
Honduras/offshore 7.3
Differential accelerometer
Applications in precision navigation and geodesy
~ 1 m
Gravity gradiometer
Demonstrated accelerometer resolution: ~10-11 g.
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.
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
Error ModelUse 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)
Earth rotation compensation
Related work: Howell, PRL 102, 173601 (2009); Howell, Phys. Rev. A 81, 033813 (2010).
~ 1 prad/Hz1/2 performance achieved
Angle pick-off:Optical lever + Sagnac interferometer for precision angle measurement
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).
Required 1 nrad angular stability in beam-steering axis achieved by controlling orientation of retro-reflecting mirror.
Top view of mirror
Magnetic shields
Magnetic shielding specifications require joint-free shields over 10 m.
Achieved 100 mG axial uniformity over 10 m.
Shields at annealing facility
atom
laser
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.
Prior work, de Broglie interferometry: Post-Newtonian effects of gravity on quantum interferometry, Shigeru Wajima, Masumi Kasai, Toshifumi Futamase, Phys. Rev. D, 55, 1997; Bordé, et al.
Atom and photon geodesics
Tests of General RelativitySchwarzschild metric, PPN expansion:
Corresponding AI phase shifts:
Projected experimental limits:
Steady path of apparatus improvements include:
• Improved atom optics
• Longer baseline• Sub-shot noise
interference read-out
(Dimopoulos, et al., PRL 2007; PRD 2008)
Gravity waves
Atoms provide inertially decoupled referencesGravity wave phase shift through propagation of optical fieldsEvades 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
AGIS free-flying satellite concept
In collaboration with GSFC (Bernie Seery, Babak Saif and co-workers)
Considering ISS, free-flyer LEO configurations
Possible instrument configuration
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.
Error models
Wavefront distortion: temporal variationsTime varying wavefront inhomogeneities 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
See also, P. Bender, to be published.
J. M. Hogan, et al., 1009.2702 (2010), submitted; arXiv.
Atom cloud kinematic constrainsShot-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
See also, P. Bender, to be published.
J. M. Hogan, et al., 1009.2702 (2010), submitted, arXiv
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– Chetan Mahadeswaraswamy, PhD, Mechanical engineering– David Johnson, Graduate student, Physics– Geert Vrijsen, 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