single atom wants to meet single photon · 2011. 1. 6. · deterministic source of single neutral...

Copyright Research Group of Dieter Meschede, University of Bonn, Feb. 2002

Single Atom wants to meet Single PhotonControlled Processes with Neutral Atoms

D. Meschede,

Institut für Angewandte Physik

Collège de FranceParis, Fevriér 26, 2002

Universität Bonn


Single Atoms Crew

Dr.Victor GomerStephan KuhrWolfgang AltDominik SchraderMartin MüllerYephen Miroshnyshenko

Daniel Frese (`00)Bernd Ueberholz (`01)


1. Experimenting with Single Neutral Atoms in a MOT

2. Deterministic Source ofSingle Neutral atoms

3. Single Atom Dynamics4. Towards entanglement

Overview


Ernst Mach (1838-1916)

1867 Professor for Experimental Physics Prague1895 Professor for Philosophy Vienna

„Atome können wir nirgends wahrnehmen, sie sind wie alle Substanzen Gedankendinge.“

(„Atoms themselves cannot be perceived anywhere, like all substances they are abstractions.“ 1912)


2002:Physics/Quantum Optics is moving

towards Quantum Engineering!





Overview


Strong magnetic field helpsto better localise atoms

Magneto-optical Trap (MOT)

1. Experimenting with Single Neutral Atoms


Cesium atom „sixpack“

10 µm




Clock 1

Detectors: APD (EG&G), 200ns dead time, Q.E. > 50%

Clocks: 50 ns resolution, ~ 1 MHz dyn. range




Dynamics of trapped atoms

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10

12

14

16

18

5 Atoms

Minutes

103 counts/100ms


Clock 1Clock 2


Hanbury-Brown & Twiss setupImproves time resolution!


1. Presto Internal Dynamics @ nano seconds2. Allegro Magnetic Bistability @ micro seconds3. Andante Global trap motion @ milli seconds4. Adagio Cold collisions @ seconds/minutes

Photon correlationsreveal atomic dynamics

at all relevant time scales!


For a review see: V. Gomer and D. Meschede, Ann.Phys.(Leipzig)10, 9 –18 (2001) and refs. therein


1 atom

0

1

2

3

Time [ns]0 40 80-40-80

Photon Antibunching – a Classic of Quantum Optics

Coi

ncid

ence

s/m

in„Prepares“ atom in ground state

Shows Rabi oscillation1. Photon

2. Photon



3 atoms

10

0

5

coin

cid

en

ces/

min

0

4

8

2 atoms

1 atom

0

1

2

3

Time [ns]0 40 80-40-80

0 20 40 600,0

0,5

1,0ρ22

N = 1

N = 10

0 20 40 600,0

0,5

1,0

22



Polarisation analysis

Clock 1Clock 2

Use linearly polarized light only!

PBS

l

r



Strong circular correlations!

No linear correlations !

t [µs]0 20 40 60 80 100

1300

1400

1500

1600C

oinc

iden

ces/

100

ms l l

0 20 40 60 80 1000,0

0,2

0,4

0,6

0,8

1,0

t [µs]

lr

0 20 40 60 80 1000,0

0,2

0,4

0,6

0,8

1,0

1,2

g(2

)(τ

)vh

t [µs]

h v



r

Magnetic Bistability(Optical pumping in „real time“, µs time scale)



h



∆m = 1

∆m = 0

h

r






Overview


2. Deterministic Source of Cold Atoms

Controlling atomic dynamics:

• Impossible in the MOT• Use off resonant dipole trap!

SetupMOT

Nd:YAG laser


Optical dipole potential = AC Stark effect

ground state

excited state



500 nm

U0=1.3 mK

z

Ωz




Laser SequenceMOTDipole Trap

N=0

N=2

N=4

N=3

0 10 20 30 40 50

Time [s]

Phot

on C

ount

s [1

00 k

Hz]



Controlling theEXACT NUMBERof atoms

!!

SetupMOT

Nd:YAG laser



F=4

F=3

CesiumHyperfine structure

Controlling the internalQUANTUM STATEof single atoms !!

SetupMOT

Nd:YAG laser



Towards controlling theEXACT POSITIONof single atoms !!



AOM

AOM

Loading Station for Single Atom Conveyor Belt


Photoncounter

Imaging optics

Nd:YAG-laser

MOTlaser beams


M OTr e gion

fix ed

detectio n

optic s

pro be

las er

di spl ace d

dete ctio noptics

a b

flu

ore

sc

en

ce

[co

un

ts/

20

ms]

0 50 100 15 0 20 0

0

10

20

30

tim e [ m s]

pr obe las er

Detection of relocated atoms



-2-4 0 2 4 6 8 100.0

0.2

0.4

0.6

0.8

1.0

Fluorescence-DetectionRayleigh-Zone

Separation (mm)

Eff

icie

ncy

Transport Efficiency of Single Atoms (1)



Laser sequence

0 100 200 300 400 500 600 7000

100

200

300

400

500

600

700

fluor

esc

ence

[cou

nts

/100

ms]

time [ms]

MOTdipole trap

MOT

mut

ual

detu

ning

oneatom

+∆ω

-∆ω

forward

backward

motion of thestanding wave0

1 ms

Laser sequence

0 100 200 300 400 500 600 7000

100

200

300

400

500

600

700

fluor

esc

ence

[cou

nts

/100

ms]

time [ms]

MOTdipole trap

MOT

mut

ual

detu

ning

oneatom

+∆ω

-∆ω

forward

backward


1 ms

Laser sequence

0 100 200 300 400 500 600 7000

100

200

300

400

500

600

700

fluor

esc

ence

[cou

nts

/100

ms]

time [ms]

MOTdipole trap

MOT

mut

ual

detu

ning

oneatom

+∆ω

-∆ω

forward

backward


1 ms



distance [mm]

eff

icie

ncy

-4 -2 0 2 4 6 8 100.0

0.2

0.4

0.6

0.8

1.0

Fluorescent Detection

MOT-Recapture

Transport Efficiency of Single Atoms (2)



0

0.02

0.04

0.06

0.08

10 12 14 16 18 20z [mm]

U [m

K] ρ

Utot

Ueff

U (z)eff

U (z)

0



“Moving standing wave”

atom

1, 2, 3, ... Atoms0, 1, 2, ... Photons

Delivery of atomsON DEMAND !!


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

Refs:





Overview


3. Single Atom Dynamics

Spectroscopyof a single neutral atom


Photon Bursts of Individual Trapped Atoms

Time [ms]

1 Atom

Phot

ons/

20m

s

Time [ms]

No Atom

Phot

ons/

20m

s



Spectroscopy of atoms in dipole trap

0 20 40 60 80 1000

20

40

60

80

100F

luor

esce

nce

[cou

nts/

ms]

Probe laser detuning [MHz]

0,50 W1,05 W2,15 W



σ-polarisiert

π-polarisiert

0 20 40 60 80 1000.0

0.2

0.4

0.6

0 20 40 60 80 1000.0

0.2

0.4

0.6

Detuning [MHz]

Detuning [MHz]

Flu

ores

cenc

e[a

.u.]

Flu

ores

cenc

e[a

.u.]

0 20 40 60 80 1000

500

1000

0 20 40 60 80 1000

1000

2000

Detuning [MHz]

Detuning [MHz]

Pho

tons

Pho

tons

∆mF=0

∆mF=1



ground state

excited state



Bound excited states!



Acceleratinga single neutral atom


10 100 1000 10000 100000 10000000.0

0.2

0.4

0.6

0.8

1.0

a [m/s2]

Effi

zien

z

δν

tt / 20

vmax


aspontaneous


Axial oscillation frequencyExcitation mechanism

dipole traplaser

dipole traplaser

vacuumwindow

resonant excitation ifparametric excitation if



200 400 600 800 1000 1200 1400 1600 1800 2000 2200 24000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Model: GaussChi^2 = 1.23

frequency1 330 ±5 kHzwidth1 66 ±10 kHz

frequency2 660 ±15 kHzwidth2 112 ±24 kHzd

ete

ctio

ne

ffic

ien

cy

∆ω [kHz]

resonantexcitation

parametricexcitation

Frequency measurement




„Temperature“ (E/kB)of a single neutral atom


UE

x0U1 E1=U1

x0

∫ == const.dxpSAdiabatic Cooling:

x

U0

E0

0

V(U,x)



0.0 0.1 0.2 0.3 0.40.0

0.2

0.4

0.6

0.8

1.0

Initial energy of atom E0/U0

surv

ival

pro

babi

lity

p(E) ~ E2exp(-E/kT)


T ~ TDoppler





Overview


Creation of entangled and fully controlled atoms

( )12

4. Towards Entanglement


Next technical implementation:Raman cooling to dipole trap ground state

0

T=E/kB

U(x)U0

x



top view:

Nd:YAGlaser

MOT laserresonator

side view:

MOT laser Nd:YAGlaser

resonator200 µm

1 mm



Conclusion

We can or will control neutral atoms:

Atoms are excellent quantum memories ... Photons make good transmitters, switches ...

Exact number UUQuantum state (internal) UUPosition (global) UU

Trapping oscillator stateNumber of photons in cavity.....


Merci beaucoup pour votre attention !

single atom wants to meet single photon · 2011. 1. 6. · deterministic source of single neutral...

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