QuantumInformation

FundamentalQuantumPhysics

QNDmeasurements

Cavity

QEDExperimentatLKBS.Haroche,J.M.Raimond

Complementarity

Outline

Aimandordersofmagnitude

Apparatus

RabiOscillations

RamseyInterferometry

Conclusion

Interaction:lightfield↔atom

Strongcouplingregime:

JaynesCummingsmodel

Howtoaccessthestrongcouplingregime

Groundstateτ=100ns

Γ~10MHz

Rydbergstateτ=30msΓ~30Hz

Optical300THz

0.1- 1μmκ~MHz

g=3GHzg/Γ=300

g/ϰ=300

g=400MHz

Microwaves51GHz

6cmκ~10Hz

g=3kHz g=200kHzg/Γ=60000

g/ϰ=20000

Howtoaccessthestrongcouplingregime

Groundstate RydbergAtoms

g=400MHz

g=200kHzg/Γ=60000

g/ϰ=20000

Circularstate:

● maximuml,m

● most“classical”state

● longlifetime

● verygood2-level-system(in

directingel.field)

→uniquedecaychannel

● “sensitiveandselectivedetection”

Overviewofthesetup LaboratoireKastler

Brossel,

Paris

Stepbystep

87Rbthermalbeam

Velocity(Doppler)selectiveexcitation

SuperconductingFabry-Pérotcavity

shiftablemirrors

VoltageforStarkshift

State-selectivefieldionization

ClassicalmicrowavesourceRamseyinterferometer:2lowQcavites

Classicalmicrowavesource

CircularStatePreparation

2)

1)

RFLaser

(n,l,m)=(50,49,49)

Stepbystep

87Rbthermalbeam

Velocity(Doppler)selectiveexcitation

SuperconductingFabry-Pérotcavity

shiftablemirrors

VoltageforStarkshift

State-selectivefieldionization

ClassicalmicrowavesourceRamseyinterferometer:2lowQcavites

Classicalmicrowavesource

● Diameter50mm● Curvature40mm

● Length27mm

9antinodes

SuperconductingHighlypolished

Niobiummirrors

Cryostat→0.8K

LiquidNitrogen

LiquidHelium-4

Liquid

Helium-3

SuperconductingFabry-PérotCavity

Stepbystep

87Rbthermalbeam

Velocity(Doppler)selectiveexcitation

SuperconductingFabry-Pérotcavity

shiftablemirrors

VoltageforStarkshift

State-selectivefieldionization

ClassicalmicrowavesourceRamseyinterferometer:2lowQcavites

Classicalmicrowavesource

Detection

• Electricfieldionizesatoms

dependingontheirmainquantum

numbern

• adjustable

• circularstatepurity98%

• Upto80%detectionefficiency

90%fidelityafterselection

Stateevolution

Ramsey Interferometry

Microwave field (51 GHz)

Ramsey Interferometry

Microwave field (51 GHz)

Ramsey InterferometryAcquired phase shift

Transition probability

Ramsey Interferometry

Quantum Non-Demolition measurement of light

• count photons without destruction

• 1. Ramsey zone: !/2 pulse → superposition

• Cavity: phase shift

• 2. Ramsey zone: !/2 pulse →photon number

Rabi Oscillations

Rabi Oscillations

Rabi Oscillations

Coherent field

Large number of photons: Collapse and Revival

Coherent state:

Coherent state

Photon number <n>

Prob

abilit

y

So what?Where are the difficulties?

Problems to solve

• Quality/finesse of cavity

• Decoherence time

• Control Rydberg states

• Strong Coupling

• Screen room-temperature blackbody field

• Selection mechanism for velocity

References

J.M.Raimond,M.BruneandS.Haroche,Manipulating quantumentanglement withatomsandphotonsinacavityRev.Mod.Phys.73,565

T.F.Gallagher.Rydbergatoms.CambridgeUniversityPress,1994

B.Peaudecerf,C.Sayrin,X.Zhou,T.Rybarczyk,S.Gleyzes, I.Dotsenko, J.M.Raimond,M.Brune,andS.Haroche,Quantumfeedbackexperiments stabilizing Fockstatesoflight inacavity,Phys.Rev.A87,042320

C.Sayrin,I.Dotsenko,X.Zhou,B.Peaudecerf,T.Rybarczyk,S.Gleyzes,P.Rouchon,M.Mirrahimi,H.Amini,M.Brune,J-M.

Raimond&S.Haroche,Real-timequantum feedbackpreparesandstabilizesphoton numberstates,Nature,477,73(2011)

X.Zhou,I.Dotsenko,B.Peaudecerf,T.Rybarczyk,C.Sayrin,S.Gleyzes, J.M.Raimond,M.Brune,andS.Haroche,FieldLocked toaFockStatebyQuantumFeedback withSinglePhotonCorrections ,Phys.Rev.Lett.108(2012)

http://www.cqed.org,[Online],April2016

S.Haroche, J.M.Raimond.Exploring theQuantum.OxfordUniversityPress,2006