Single Atom wants to meet Single Photon Controlled Processes with Neutral Atoms

Transcription

1 Single Atom wants to meet Single Photon Controlled Processes with Neutral Atoms Collège de France Paris, Fevriér 26, 2002 Universität Bonn D. Meschede, Institut für Angewandte Physik

2 Single Atoms Crew Dr.Victor Gomer Stephan Kuhr Wolfgang Alt Dominik Schrader Martin Müller Yephen Miroshnyshenko Daniel Frese (`00) Bernd Ueberholz (`01)

3 Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement

4 Atome können wir nirgends wahrnehmen, sie sind wie alle Substanzen Gedankendinge. ( Atoms themselves cannot be perceived anywhere, like all substances they are abstractions. 1912) Ernst Mach ( ) 1867 Professor for Experimental Physics Prague 1895 Professor for Philosophy Vienna

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8 2002: Physics/Quantum Optics is moving towards Quantum Engineering!

9 Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement

10 1. Experimenting with Single Neutral Atoms Magneto-optical Trap (MOT) Strong magnetic field helps to better localise atoms

11 1. Experimenting with Single Neutral Atoms Magneto-optical Trap (MOT) Cesium atom sixpack 10 µm

12 1. Experimenting with Single Neutral Atoms Magneto-optical Trap (MOT) Clock 1 Detectors: APD (EG&G), 200ns dead time, Q.E. > 50% Clocks: 50 ns resolution, ~ 1 MHz dyn. range

13 Dynamics of trapped atoms 10 3 counts/100ms Atoms Minutes

14 1. Experimenting with Single Neutral Atoms Clock 1 Clock 2 Hanbury-Brown & Twiss setup Improves time resolution!

15 1. Experimenting with Single Neutral Atoms Photon correlations reveal atomic dynamics at all relevant time scales! 1. Presto Internal nano seconds 2. Allegro Magnetic micro seconds 3. Andante Global trap milli seconds 4. Adagio Cold seconds/minutes For a review see: V. Gomer and D. Meschede, Ann.Phys.(Leipzig)10, 9 18 (2001) and refs. therein

16 1. Experimenting with Single Neutral Atoms Photon Antibunching a Classic of Quantum Optics Prepares atom in ground state Coincidences/min Photon atom Time [ns] Shows Rabi oscillation 2. Photon

17 1. Experimenting with Single Neutral Atoms 1,0 ρ 22 N = atoms 0,5 co i n ci d e n ce s/mi n atoms 0, ,0 22 0,5 0, N = atom Time [ns]

18 1. Experimenting with Single Neutral Atoms Polarisation analysis Clock 1 Clock 2 PBS l Use linearly polarized light only! r

19 1. Experimenting with Single Neutral Atoms Coincidences/ 100 m s l l t [µs] 1,0 0,8 0,6 0,4 0,2 0,0 r l t [µs] Strong circular correlations! No linear correlations! g ( 2) ( τ ) vh 1,2 1,0 0,8 0,6 0,4 0,2 0,0 h v t [µs]

20 1. Experimenting with Single Neutral Atoms r Magnetic Bistability (Optical pumping in real time, µs time scale)

21 1. Experimenting with Single Neutral Atoms h

22 1. Experimenting with Single Neutral Atoms r m = 1 m = 0 h

23 Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement

24 2. Deterministic Source of Cold Atoms Controlling atomic dynamics: Impossible in the MOT Use off resonant dipole trap! Setup MOT Nd:YAG laser

25 2. Deterministic Source of Cold Atoms Optical dipole potential = AC Stark effect excited state ground state

26 2. Deterministic Source of Cold Atoms Optical dipole potential = AC Stark effect 500 nm U 0 = 1.3 mk Ω z z

27 2. Deterministic Source of Cold Atoms Photon Counts [100 khz] Laser Sequence MOT Dipole Trap N=4 N=3 N=2 N= Time [s]

28 2. Deterministic Source of Cold Atoms Controlling the EXACT NUMBER of atoms!! Setup MOT Nd:YAG laser

29 2. Deterministic Source of Cold Atoms F=4 F=3 Cesium Hyperfine structure Controlling the internal QUANTUM STATE of single atoms!! Setup MOT Nd:YAG laser

30 2. Deterministic Source of Cold Atoms Towards controlling the EXACT POSITION of single atoms!!

31 2. Deterministic Source of Cold Atoms Loading Station for Single Atom Conveyor Belt AOM MOT laser beams Imaging optics Photon counter AOM Nd:YAG-laser

32 2. Deterministic Source of Cold Atoms

33 2. Deterministic Source of Cold Atoms Detection of relocated atoms a di spl ace d det e ctio n optics M O T r e gion pro be las er fix ed det ectio n optic s b f luore sce nc e [ co unt s / 2 0 m s] pr obe las er tim e [ m s]

34 2. Deterministic Source of Cold Atoms Transport Efficiency of Single Atoms (1) Efficiency Rayleigh-Zone Fluorescence-Detection Separation (mm)

35 2. Deterministic Source of Cold Atoms f lu o r e sce n ce [ co u n t s/ m s] mutual detuning ω 0 - ω Laser sequence MOT MOT dipole trap forward backward time [ms] 1 ms motion of the standing wave one atom

36 2. Deterministic Source of Cold Atoms Transport Efficiency of Single Atoms (2) e ffi ci e n cy Fluorescent Detection MOT-Recapture distance [mm]

37 2. Deterministic Source of Cold Atoms U tot 0.08 U eff U [mk] ρ U (z) 0.02 U (z) eff z [mm]

38 2. Deterministic Source of Cold Atoms Moving standing wave atom Delivery of atoms ON DEMAND!! 1, 2, 3,... Atoms 0, 1, 2,... Photons Refs: D. Frese, B. Ueberholz, S. Kuhr, W. Alt, D. Schrader, V. Gomer, and D. Meschede, Phys. Rev. Lett., (2000) S. Kuhr, W. Alt, D. Schrader, M. Müller,V. Gomer,D. Meschede, Science 293, p , (2001) D. Schrader, S. Kuhr, W. Alt, M. Mueller, V. Gomer, D. Meschede, Appl Phys B 73 (2001) 8,

39 Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement

40 3. Single Atom Dynamics Spectroscopy of a single neutral atom

41 3. Single Atom Dynamics Photon Bursts of Individual Trapped Atoms Photons/20ms 1 Atom Photons/20ms No Atom Time [ms] Time [ms]

42 3. Single Atom Dynamics Spectroscopy of atoms in dipole trap Fluorescence [counts/ms] ,50 W 1,05 W 2,15 W Probe laser detuning [MHz]

43 3. Single Atom Dynamics Fluorescence [a.u.] Detuning [MHz] π-polarisiert m F =0 Photons Detuning [MHz] Fluorescence [a.u.] Detuning [MHz] σ-polarisiert m F =1 Photons Detuning [MHz]

44 3. Single Atom Dynamics Optical dipole potential = AC Stark effect excited state Bound excited states! ground state

45 3. Single Atom Dynamics Accelerating a single neutral atom

46 3. Single Atom Dynamics

47 3. Single Atom Dynamics δν a spontaneous v max t / 2 t 0.8 Effizienz a [m/s 2 ]

48 3. Single Atom Dynamics Axial oscillation frequency Excitation mechanism dipole trap laser vacuum window dipole trap laser resonant excitation if parametric excitation if

49 3. Single Atom Dynamics 1.0 Frequency measurement det ect i on ef f i ci ency resonant excitation parametric excitation Model: Gauss Chi^2 = 1.23 frequency1 330 ±5 khz width1 66 ±10 khz frequency2 660 ±15 khz width2 112 ±24 khz ω [khz]

50 3. Single Atom Dynamics

51 3. Single Atom Dynamics Temperature (E/k B ) of a single neutral atom

52 3. Single Atom Dynamics V(U,x) U 0 E 0 U 0 x U E 1 E 0 x 1 =U 0 1 x Adiabatic Cooling: S = p dx = const.

53 3. Single Atom Dynamics 1.0 survival probability p(e) ~ E 2 exp(-e/kt) T ~ T Doppler Initial energy of atom E 0 /U 0

54 Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement

55 4. Towards Entanglement 1 2 ( ) Creation of entangled and fully controlled atoms

56 4. Towards Entanglement U(x) U 0 T=E/k B 0 x Next technical implementation: Raman cooling to dipole trap ground state

57 4. Towards Entanglement top view: side view: MOT laser Nd:YAG laser 1 mm Nd:YAG 200 µm laser resonator MOT laser resonator

58 Conclusion We can or will control neutral atoms: Exact number U Quantum state (internal) U Position (global) U Trapping oscillator state Number of photons in cavity... Atoms are excellent quantum memories... Photons make good transmitters, switches...

59 Merci beaucoup pour votre attention!