Experimental AMO eets meets M odel Model Building: Part I (Precision Atom Interferometry)

Transcription

1 Experimental AMO meets Model Building: Part I (Precision Atom Interferometry)

2 Interference of Rb atoms Chiow, et. al, PRL, 2011

3 Young s double slit with atoms Young s 2 slit with Helium atoms Interference fringes Slits One of the first experiments to demonstrate de Broglie wave interference with atoms, 1991 (Mlynek, PRL, 1991)

4 (Light-pulse) atom interferometry Resonant optical interaction Recoil diagram Momentum conservation between atom and laser light field (recoil effects) leads to spatial separation of atomic wavepackets level atom Resonant traveling wave optical excitation, (wavelength ) )

5 Semi-classical approximation Three contributions to interferometer phase shift: Propagation shift: Laser fields (Raman interaction): Wavepacket separation at detection: See, for example, Bongs, et al., App. Phys. B, 2006.

6 Differential accelerometer ~ 1 m l d d Applications in precision navigation, geodesy and precision gravitational physics

7 Laser cooling Laser cooling techniques are used to achieve the required velocity (wavelength) control for the atom source. Laser cooling: Laser light is used to cool atomic vapors to temperatures of ~10-6 deg K. Image source: se/physics

8 Gravity gradiometer Demonstrated accelerometer resolution: ~1x10-11 g.

9 Measurement of G Systematic error sources dominated by initial position/velocity of atomic clouds. G/G ~ 0.3%. Next Generation: <1e-4 4, exp t in progress at AOSense, Inc. in colloboration with LLNL. Fixler, et al., Science, 2007.

10 Gravity gradiometer/mass tomography Sample mass configurations: Data: A2 Gra avity grad dient A4 AOSense Vertical distance AOSense.com (cm) Sunnyvale, CA 10

11 Test Newton s Inverse Square Law Using new sensors, we anticipate G/G < This will also test for deviations from the inverse square law at distances from ~ 1 mm to 10 cm. (J. Wacker)

12 Physical sensitivity limits (10 m apparatus) Quantum limited accelerometer resolution: ~ 7x10-20 g Assumptions: 1) Wavepackets (Rb) separated by z = 10 m, for T = 1 sec. For 1 g acceleration: ~ mgzt/ ~ 1.3x10 11 rad 2) Signal-to-noise for read-out: SNR ~ 10 5 :1 per second. 3) Resolution to changes in g per shot: g ~ 1/( SNR) ~ 7x10-17 g 4) 10 6 seconds data collection We will exploit this sensitivity for: Gravity wave detection, tests of General Relativity, new atom charge neutrality tests, tests of QED (photon recoil measurements), searches for anomalous forces

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

14 Status update Image of cold atom cloud launched in 10 m fountain.

15 Post-Newtonian gravitation Light-pulse interferometer phase shifts for Schwarzchild metric: Geodesic propagation for atoms and light. Path integral formulation to obtain quantum phases. Atom-field interaction at intersection of laser and atom geodesics. laser atom Post-Newtonian trajectories for classical particle: 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.

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

17 Atom charge neutrality Apparatus will support >1 m wavepacket separation Enables ultra-sensitive search for atom charge neutrality through h scalar Aharonov-Bohm h effect. e/e ~ for mature experiment using scalar Aharonov-Bohm effect Current limit: e/e ~ (Unnikrishnan et al., Metrologia 41, 2004) Impact of a possible observed imbalance currently under investigation. Phase shift: Theory collaborators: A. Arvanitaki, S. Dimopoulos, A. Geraci, PRL 2008.

18 Gravity waves Atoms provide inertially decoupled references Gravity wave phase shift through propagation of optical fields Evades quantum measurement noise (photon scattering regularized by nonlinear 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). This work: S. Dimopoulos, et al., Phys. Rev. D 78, (2008). Possible satellite configuration

19 Possible sensitivity J. M. Hogan, et. al, Gen. Rel. and Grav. (2011); PRD (2011).

20 (2012) Laser frequency noise insensitive detector Use single photon transitions to suppress laser frequency noise. Dramatically eases experimental requirements. Fundamentally new GW detection paradigm. adigm (Graham, Hogan, Kasevich, Rajendran, in preparation)

21 Future questions Can sensitivity be improved with new classes of atom optics? Can precision atom interferometric methods be extended d to massive particles? Can quantum metrology approaches be used to improve interferometer sensitivity?

22 Massive particle interferometry with atomic solitons ~100 atom solitons produced by forced evaporation of (attractively interacting) 7 Li Under appropriate conditions solitons behave as single particles. In principle, 100x improved sensitivity for interferometers

23 Soliton lifetime Soliton lifetime ~ 10 s. Enables precise force sensing applications.

24 Soliton center-of-mass wavefunction dynamics Center-mass-wavefunction spreading for single solitons released from tight traps. Sequence of images of solitons (100 atoms in each) suddenly released from a tight optical trap. Dashed: Expected behavior from Heisenberg uncertainty principle. Control: soliton adiabatically released from trap. Histogram of observed soliton positions at a 60 msec time of flight following release from the trap.. Precursor to soliton interferometry experiments

25 Acknowledgements THANKS SAVAS!