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
Single Atoms Crew Dr.Victor Gomer Stephan Kuhr Wolfgang Alt Dominik Schrader Martin Müller Yephen Miroshnyshenko Daniel Frese (`00) Bernd Ueberholz (`01)
Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement
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 (1838-1916) 1867 Professor for Experimental Physics Prague 1895 Professor for Philosophy Vienna
2002: Physics/Quantum Optics is moving towards Quantum Engineering!
Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement
1. Experimenting with Single Neutral Atoms Magneto-optical Trap (MOT) Strong magnetic field helps to better localise atoms
1. Experimenting with Single Neutral Atoms Magneto-optical Trap (MOT) Cesium atom sixpack 10 µm
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
Dynamics of trapped atoms 10 3 counts/100ms 18 16 14 12 10 8 6 4 2 0 0 1 2 3 4 5 6 7 8 9 10 5 Atoms Minutes
1. Experimenting with Single Neutral Atoms Clock 1 Clock 2 Hanbury-Brown & Twiss setup Improves time resolution!
1. Experimenting with Single Neutral Atoms Photon correlations reveal atomic dynamics at all relevant time scales! 1. Presto Internal Dynamics @ nano seconds 2. Allegro Magnetic Bistability @ micro seconds 3. Andante Global trap motion @ milli seconds 4. Adagio Cold collisions @ seconds/minutes For a review see: V. Gomer and D. Meschede, Ann.Phys.(Leipzig)10, 9 18 (2001) and refs. therein
1. Experimenting with Single Neutral Atoms Photon Antibunching a Classic of Quantum Optics Prepares atom in ground state Coincidences/min 3 2 1 0-80 1. Photon -40 1 atom 0 40 80 Time [ns] Shows Rabi oscillation 2. Photon
1. Experimenting with Single Neutral Atoms 1,0 ρ 22 N = 1 10 5 3 atoms 0,5 co i n ci d e n ce s/mi n 0 8 4 0 3 2 atoms 0,0 0 20 40 60 1,0 22 0,5 0,0 0 20 40 60 N = 10 2 1 0-80 -40 1 atom 0 40 80 Time [ns]
1. Experimenting with Single Neutral Atoms Polarisation analysis Clock 1 Clock 2 PBS l Use linearly polarized light only! r
1. Experimenting with Single Neutral Atoms Coincidences/ 100 m s 1600 1500 1400 1300 l l 0 20 40 60 80 100 t [µs] 1,0 0,8 0,6 0,4 0,2 0,0 r l 0 20 40 60 80 100 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 0 20 40 60 80 100 t [µs]
1. Experimenting with Single Neutral Atoms r Magnetic Bistability (Optical pumping in real time, µs time scale)
1. Experimenting with Single Neutral Atoms h
1. Experimenting with Single Neutral Atoms r m = 1 m = 0 h
Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement
2. Deterministic Source of Cold Atoms Controlling atomic dynamics: Impossible in the MOT Use off resonant dipole trap! Setup MOT Nd:YAG laser
2. Deterministic Source of Cold Atoms Optical dipole potential = AC Stark effect excited state ground state
2. Deterministic Source of Cold Atoms Optical dipole potential = AC Stark effect 500 nm U 0 = 1.3 mk Ω z z
2. Deterministic Source of Cold Atoms Photon Counts [100 khz] Laser Sequence MOT Dipole Trap N=4 N=3 N=2 N=0 0 10 20 30 40 50 Time [s]
2. Deterministic Source of Cold Atoms Controlling the EXACT NUMBER of atoms!! Setup MOT Nd:YAG laser
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
2. Deterministic Source of Cold Atoms Towards controlling the EXACT POSITION of single atoms!!
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
2. Deterministic Source of Cold Atoms
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] 3 0 2 0 1 0 0 0 5 0 1 0 0 1 5 0 2 0 0 pr obe las er tim e [ m s]
2. Deterministic Source of Cold Atoms Transport Efficiency of Single Atoms (1) 1.0 0.8 Efficiency 0.6 0.4 Rayleigh-Zone Fluorescence-Detection 0.2 0.0-4 -2 0 2 4 6 8 10 Separation (mm)
2. Deterministic Source of Cold Atoms f lu o r e sce n ce [ co u n t s/ 1 0 0 m s] mutual detuning 700 600 500 400 300 200 100 0 + ω 0 - ω Laser sequence MOT MOT dipole trap 0 100 200 300 400 500 600 700 forward backward time [ms] 1 ms motion of the standing wave one atom
2. Deterministic Source of Cold Atoms Transport Efficiency of Single Atoms (2) 1.0 0.8 e ffi ci e n cy 0.6 0.4 Fluorescent Detection MOT-Recapture 0.2 0.0-4 -2 0 2 4 6 8 10 distance [mm]
2. Deterministic Source of Cold Atoms U tot 0.08 U eff U [mk] 0.06 0.04 0 ρ U (z) 0.02 U (z) eff 0 10 12 14 16 18 20 z [mm]
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., 85 3777 (2000) S. Kuhr, W. Alt, D. Schrader, M. Müller,V. Gomer,D. Meschede, Science 293, p. 278-280, (2001) D. Schrader, S. Kuhr, W. Alt, M. Mueller, V. Gomer, D. Meschede, Appl Phys B 73 (2001) 8, 819-824
Overview 1. Experimenting with Single Neutral Atoms in a MOT 2. Deterministic Source of Single Neutral atoms 3. Single Atom Dynamics 4. Towards entanglement
3. Single Atom Dynamics Spectroscopy of a single neutral atom
3. Single Atom Dynamics Photon Bursts of Individual Trapped Atoms Photons/20ms 1 Atom Photons/20ms No Atom Time [ms] Time [ms]
3. Single Atom Dynamics Spectroscopy of atoms in dipole trap Fluorescence [counts/ms] 100 80 60 40 0,50 W 1,05 W 2,15 W 20 0 0 20 40 60 80 100 Probe laser detuning [MHz]
3. Single Atom Dynamics Fluorescence [a.u.] 0.6 0.4 0.2 0.0 0 20 40 60 80 100 Detuning [MHz] π-polarisiert m F =0 Photons 1000 500 0 0 20 40 60 80 100 Detuning [MHz] Fluorescence [a.u.] 0.6 0.4 0.2 0.0 0 20 40 60 80 100 Detuning [MHz] σ-polarisiert m F =1 Photons 2000 1000 0 0 20 40 60 80 100 Detuning [MHz]
3. Single Atom Dynamics Optical dipole potential = AC Stark effect excited state Bound excited states! ground state
3. Single Atom Dynamics Accelerating a single neutral atom
3. Single Atom Dynamics
3. Single Atom Dynamics δν a spontaneous v max 1.0 0 t / 2 t 0.8 Effizienz 0.6 0.4 0.2 0.0 10 100 1000 10000 100000 1000000 a [m/s 2 ]
3. Single Atom Dynamics Axial oscillation frequency Excitation mechanism dipole trap laser vacuum window dipole trap laser resonant excitation if parametric excitation if
3. Single Atom Dynamics 1.0 Frequency measurement 0.9 0.8 det ect i on ef f i ci ency 0.7 0.6 0.5 0.4 0.3 0.2 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 0.1 0.0 200 400 600 800 1000 1200 1400 1600 1800 2000 2200 2400 ω [khz]
3. Single Atom Dynamics
3. Single Atom Dynamics Temperature (E/k B ) of a single neutral atom
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.
3. Single Atom Dynamics 1.0 survival probability 0.8 0.6 0.4 0.2 p(e) ~ E 2 exp(-e/kt) T ~ T Doppler 0.0 0.0 0.1 0.2 0.3 0.4 Initial energy of atom E 0 /U 0
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. Towards Entanglement 1 2 ( ) Creation of entangled and fully controlled atoms
4. Towards Entanglement U(x) U 0 T=E/k B 0 x Next technical implementation: Raman cooling to dipole trap ground state
4. Towards Entanglement top view: side view: MOT laser Nd:YAG laser 1 mm Nd:YAG 200 µm laser resonator MOT laser resonator
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...
Merci beaucoup pour votre attention!