Shau-Yu Lan 藍劭宇. University of California, Berkeley Department of Physics

Transcription

1 Atom Interferometry Experiments for Precision Measurement of Fundamental Physics Shau-Yu Lan 藍劭宇 University of California, Berkeley Department of Physics

2 Contents Principle of Light-Pulse Atom Interferometer Fine Structure Constant Large Momentum Transfer Systematic Effects Matter Wave Source- Cold Atomic Fountain Outlook

3 Optical Interferometry 19 th Century : Young s Experiment 1 st Century : Large Interferometry Space Antenna (LISA) Image from Wikipedia

4 Matter Wave Louis de Broglie 194 h mv C. Davisson and L. H. Germer 197

5 Laser cooling and trapping Room Temperature Liquid Helium 300K 3K Doppler Limit 300K Recoil Limit Evaporative Cooling 3K 100nK Absolutely Zero

6 Light-Pulse Atom Interferometer g π π π free laser 1 free classical L( z( t), z( t)) dt L mz V ( z) Interferometer in time domain

7 Light-Pulse Atom Interferometer Mach Zehnder interferometer Symmetric interferometer MZ free laser free 0 MZ laser n( kgt L) g π π π ( ) ( ) ( ) L t0 t0 T t0 T k is the wavenumber and the number of photons. n is The sensitivity scales with the interferometer enclosed area

8 de Broglie Wave Beam Splitter Off Resonant Two Photon Transition Coherent Control of Atomic State Effective Two Photon Rabi Frequency g e eff gg 1 1 g e

9 Measurements Using Light-Pulse AI Gravity g : 3x10-9 g A. Peters et al. Nature 400, (1999). 9 Gravity gradient : 410 g Hz J. B. Fixler et al, Science 315, 74 (007). : 4.6 ppb M. Cadoret et al., Phys. Rev. Lett. 101, (008). Newton s constant G : 4 ppt J. B. Fixler et al, Science 315, 74 (007). UFF : S. Fray, and M. Weitz - Space Science Reviews, 009 Springer Gravitational redshift : H. Mueller et al. Nature 463, 96 (010) Sagnac effect : rad/sec Hz T. L. Gustavson et al. Class. Quantum Grav. 17 (000)

10 Fine Structure Constant 1 e CODATA 4 c (94) Current Status of Electron's magnetic moment anomaly g- : 0.37 ppb D. Hanneke et al. PRL 100, (008 ) g 1 C C C C... a a a 4 6 8, hadronic weak Photon Recoil Measurement (Rb) : 4.6 ppb M. Cadoret et al. PRL 101, (008) Photon Recoil Measurement(Cs) : 7.4 ppb A. Wicht et al., Phys. Scr. T 10, 8 (00).

11 Contributions to g- Best h/m g-

12 Alpha in Atom Recoil Frequency R u M h c m u M e 1 Rydberg Constant ppb P. J. Mohr et al., Rev. Mod. Phys. 80, 633 (008). Electron mass in atomic mass units u 0.18 ppb P. J. Mohr et al., Rev. Mod. Phys. 80, 633 (008). Cs mass in u 0.43ppb M. P. Bradley et al., Phys. Rev. Lett. 83, 4510 (1999). Lowest : 0.3ppb Determined by the atom recoil frequency h 4c r M

13 Photon Recoil Measurement L b a b a 1 v k L ab i rec L ab L L a a b ( a ) ( b ) L L rec L khz For Cs D1 recoil frequency rec, accuracy in part per billion need to pinpoint the resonance to Hz range!!!

14 Ramsey Borde Interferometer g n nkg n RB ' 8 rt+ (T+T )T+ ( ) ( ) beamsplitter beamsplitter

15 Ramsey Borde Interferometer g n nkg n RB ' 8 rt+ (T+T )T+ ( ) ( ) beamsplitter beamsplitter

16 Conjugate Interferometer g g n nkg n RB ' 8 rt+ (T+T )T+ beamsplitter beamsplitter n nkg n RB ' 8 rt+ (T+T )T+ beamsplitter beamsplitter 16n rt+ n ( ) ( ) beamsplitter beamsplitter

17 Simultaneous Conjugate Interferometer g S.-w. Chiow et al. Phys. Rev. Lett. 103, (009) 16n T+ n r beamsplitter ( ) ( beamsplitter ) Common Mode Rejection

18 Large Momentum Transfer Multi-photon Bragg Diffraction g p p g p n k, 0, eff external field insensitive Energy Conservation: H. Mueller et al. Phys. Rev. Lett. 100, (008) 4 n r n ( 1 ) Effective Rabi Frequency n eff n n1 n1 8 ( n 1)! r eff 1

19 Flourescense Flourescense Flourescense Flourescense Flourescense Flourescense Flourescense Flourescense Flourescense Multi-Photon Bragg Diffraction Beam Splitter k k k Time[s] Time[s] Time[s] k k k Time[s] Time[s] Time[s] k k k Time[s] Time[s] Time[s] Required power for Cs 3,0 : I 5n mw/cm with 5GHz detuning 5GHz one photon detuning, 1.5cm diameter beam

20 Bloch Oscillation Matter Wave Accelerator E. Peik et al., Phys. Rev. A 55, 989 (1997). 1 t Bloch Period 8 B r H. Mueller et al. Phys. Rev. Lett. 10, (009)

21 Systematic Effects Guoy Phase kz 0 zr 1 z ( z) tan ( ) k 1 k z k 0 z0 0 k For =85nm and 0=1cm, 0.15ppb k Larger Beam Waist

22 Systematic Effects Zeeman Effect No linear Zeeman Shift Quadratic Zeeman Shift for m F =0 ( gj gi ) B f B (430Hz/G ) B f Magnetic field gradient gives the shift B B B( z) ( B0 z ) B0 B0 z z z Assume T=500ms, n=10 and give error 0.14ppb B z 15mG

23 Systematic Effects Beam Misalignment k 1 k k k eff keff 1 4 ( k) (1 ) k Active stabilization can be done to 5.1rad which corresponds to 0.03ppb

24 Systematic Effects AC Stark Shift Same internal state, differential Shift is negligible The laser frequencies used for addressing the upper interferometer may cause an AC Stark shift in the lower one Adding extra frequencies to the laser beam with the appropriate detuning to cancel the effect

25 Wavefronts Sagnac Effect Speckle Clipping Mean Field Shift Missed Recoils Gravity Gradient More Systematic Effects

26 Experimental Setup Atomic Fountain : Cs de Broglie Wave Source Mirror λ/4 3-Layer Magnetic Shielding 1.5 m molesses cooling~ ms adiabatic cooling~ 0.5 ms T~ K Lattice Cooling / Detection 3 m 3D MOT / Molasses g D MOT Bragg / Bloch Beams

27 Experimental sequence State selection using Doppler insensitive Raman transition v k k 1

28 Flourescense Flourescense Experimental sequence Velocity selection using Doppler sensitive Raman transition k Kof atoms has velocity spread v cm/s After 1s of time of flight, atoms will drift out of interferometer beams v 100 S selection pulse selects about 1/10 of atoms in hundreds of nk t 6.8ms ms t k Time[s] Time[s]

29 Norm. Flourescense Norm. Flourescense Norm. Flourescense Norm. Flourescense Mach Zehnder Interferometer fringe First atomic inertia sensor in Berkeley 0.10 k k Phase[deg] 4 k Phase[deg] k Phase[deg] Period=360 o /4n Single shot, T=1ms, no vibration isolation -0.3 Phase[deg]

30 Cold Atomic Fountain

31 Outlook Implementing Raman sideband cooling to further increase signal by an order of magnitude Working on large momentum transfer to further boost the sensitivity Expecting the uncertainty of fine structure constant to be less than 1 ppb in 10 mins with T=500 ms and p=0 k

32 Our Team Principal Investigator: Holger Mueller Postdocs: Shau-Yu Lan Michael Hohensee Paul Hamilton Graduate Students: Pei-Chen Kuan Brian Estey Geena Kim Francisco J. Monsalve Undergrads: Cheong Chan