Strong atom-light interactions along nanostructures

158 Pages·2015·62.09 MB·English

Strong atom-light interactions along nanostructures:
Transition from free-space to nanophotonic interfaces
Thesisby
AkihisaGoban
InPartialFulfillmentoftheRequirements
fortheDegreeof
DoctorofPhilosophy
CaliforniaInstituteofTechnology
Pasadena,California
2015
(SubmittedMay20,2015)
ii
c 2015
(cid:13)
AkihisaGoban
AllRightsReserved
iii
Tomyfamily,
iv
Acknowledgments
Firstandforemost,IwouldliketothankmyadvisorJeffKimbleforhissupportandencouragementduring
thecompletionoftheworkpresentedinthisthesis. Hiskeenscientificinsightandrelentlesscuriosityhave
neverceasedtobeinspiringandhavekeptmechallengedduringthoseyearsthatIhadtheprivilegetobehis
student.Needlesstosay,histirelesseffortshaveplayedakeyroleintheprogresswehavemadethesepastfew
years. Oneofthemostmemorablemomentsoutsidethelabwas“QuantumOpticsFrontier”symposiumin
celebrationofJeff’s65thbirthday.Ienjoyedcatchingaglimpseofthehistoryofquantumopticsandquantum
information science, and felt excited about the future of these fields. I have also been fortunate to interact
with Oskar Painter, whose creativity and perspective opened a new opportunity to investigate atom-photon
interactioninthephotonicscrystalwaveguide.
The work described in this thesis is a result of contributions of many people that I would like to ac-
knowledge here. During the completion of this work, I have had the privilege to work with many talented
colleagues, in particular, Kyung Soo Choi and Chen-Lung Hung. From day one in Lab 2, Kyung was my
mentor. He taught me all the details of complicated experiments patiently, and how critical it is to set the
highstandardsformakingthingsworkwellinthelab. IadmireKyungforhisprecise,thoroughapproachto
physics,andhisextremelyhardworkdrivenbyhisunquenchablecuriosityinphysics. Chen-Lung’sarrival
in Quantum optics group triggered another exciting journey. Taking apart the historic cavity QED experi-
mentsinLab11andbuildingupthenewlabwithhimwasagreatexperience. Overthenextthreeyears, I
learnedatremendousamountfromhimandenjoyedworkingwithhimgreatly. JonathanHoodandSu-Peng
Yu’srelentlesseffortsondevicefabricationacceleratedourprogressdramatically. Withouttheirhardwork
and dedication, this project would not have taken off as of today. I owe them a special debt of gratitude. I
havenodoubtthatitsfuturewillbebrightinthehandsoftheLab11crewofJonathanHood,Su-PengYu,
v
andMingwuLu. IhavealsobeenfortunatetointeractwithDarrickChang,whohasbroughtabroadrange
ofexcitingproposalsandgrandchallengesforourexperiments. Ihavealsoworkedwithanamazingsetof
colleaguesonthisnewproject: JuanAndre´sMuniz,AndrewMcClung,JaeHoonLee,MichaelMartin,and
LucasPenginLab2, andRichardNorte, JustinCohen, andSea´nMeenehaninPaintergroup. Particularly,
Juanhasbeenagoodfriendandco-worker,andaseparateparagraphofgratitudecouldbewrittenabouthim.
It was great to have so many other graduate students and postdocs to talk to and learn from over the past
years,includingDalzielWilson,DanielAlton,DingDing,ScottPapp,CindyRegal,Kang-KuenNi,Cle´ment
Lacrouˆte,MartinPototshcnig,andPolForn-Diaz.
IwouldalsoliketoacknowledgetheNakajimaFoundationfortheirfinancialsupportthroughoutmyPhD
research.
Finally,IdeeplyappreciatethesupportIhavereceivedfrommyfamily. Theirunquestioningsupporthas
beenessentialtothecompletionofthiswork.
vi
Abstract
An exciting frontier in quantum information science is the integration of otherwise “simple” quantum ele-
mentsintocomplexquantumnetworks. Thelaboratoryrealizationofevensmallquantumnetworksenables
the exploration of physical systems that have not heretofore existed in the natural world. Within this con-
text,thereisactiveresearchtoachievenanoscalequantumopticalcircuits,forwhichatomsaretrappednear
nano-scopicdielectricstructuresand“wired”togetherbyphotonspropagatingthroughthecircuitelements.
Single atoms and atomic ensembles endow quantum functionality for otherwise linear optical circuits and
therebyenablethecapabilityofbuildingquantumnetworkscomponentbycomponent. Towardthesegoals,
we have experimentally investigated three different systems, from conventional to rather exotic systems :
free-space atomic ensembles, optical nano fibers, and photonics crystal waveguides. First, we demonstrate
measurement-inducedquadripartiteentanglementamongfourquantummemories. Next,followingtheland-
markrealizationofananofibertrap,wedemonstratetheimplementationofastate-insensitive,compensated
nanofibertrap. Finally, wereachmoreexoticsystemsbasedonphotonicscrystaldevices. Beyondconven-
tionaltopologiesofresonatorsandwaveguides,newopportunitiesemergefromthepowerfulcapabilitiesof
dispersion and modalengineering in photonic crystal waveguides. We have implemented anintegrated op-
ticalcircuitwithaphotonicscrystalwaveguidecapableofbothtrappingandinterfacingatomswithguided
photons, and have observed the collective effect, superradiance, mediated by the guided photons. These
advances provide an important capability for engineered light-matter interactions, enabling explorations of
novelquantumtransportandquantummany-bodyphenomena.
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Contents
Acknowledgments iv
Abstract vi
1 Introduction 1
1.1 Quantumnetworks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Conventionalstrongatom-photoninteraction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 CavityQEDwithasingleatom . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.2 Collectiveatom-photoncouplingwithatomicensembles . . . . . . . . . . . . . . . 3
1.3 Integrationofatomsandnanophotonics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3.1 CavityQEDwithmicro-andnanoscopiccavities . . . . . . . . . . . . . . . . . . . 4
1.3.2 WaveguideQED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.4 Newavenuewithphotoniccrystalwaveguides . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.4.1 Many-bodyphysicswithstronglyinteractingphotons . . . . . . . . . . . . . . . . . 6
1.5 Thesisoutline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Entanglementofspinwavesamongfourquantummemories 9
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 GenerationandcharacterizationofW-state . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.1 Experimentalprocedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.2 W-stateamongfouratomicensembles . . . . . . . . . . . . . . . . . . . . . . . . 13
2.3 Dissipativedynamicsofatomicentanglement . . . . . . . . . . . . . . . . . . . . . . . . . 16
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2.4 Conclusionandoutlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.5 Experimentaldetails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.5.1 Preparationofcoldatomicensembles . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.5.2 Quantuminterface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.5.3 Spin-wavequantummemories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
2.5.4 Quantumuncertaintyrelationsandgenuinemultipartiteentanglement . . . . . . . . 20
2.5.5 Generationandcharacterizationofa‘crossed’quantumstate . . . . . . . . . . . . . 20
2.5.6 Relationshipbetweenquantumuncertaintyandoff-diagonalcoherences. . . . . . . . 21
2.5.7 Derivationofentanglementfidelity . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.5.8 Prospectsforimprovingmemorytimeandmatter-lighttransferefficiency . . . . . . 22
2.5.9 Quantum-enhancedparameterestimationwithentangledspin-waves . . . . . . . . . 23
3 Atom-lightinteractions: waveguideQED 26
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2 Singleatomcoupledtoa1Dwaveguide . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.1 SystemHamiltonian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.2.2 Basicratesofasingleatom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.2.3 Coherentfieldtransport. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.2.4 Photoncorrelationforcoherentincidentfield . . . . . . . . . . . . . . . . . . . . . 30
3.2.5 Transfermatrixintheweakexcitationlimit . . . . . . . . . . . . . . . . . . . . . . 32
3.3 Multipleatomscoupledtothe1Dwaveguide . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.3.1 InteractingspinHamiltonian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.3.1.1 Twoatoms: superradianceattheseparationϕ=π . . . . . . . . . . . . . 35
3.3.1.2 Twoatoms: dipole-dipoleinteractionattheseparationϕ=π/2 . . . . . . 35
3.3.2 Fieldresponseintheweak-excitationlimit . . . . . . . . . . . . . . . . . . . . . . 35
3.3.2.1 Superradianceattheseparationϕ=π . . . . . . . . . . . . . . . . . . . 36
3.3.2.2 Dipole-dipoleinteractionattheseparationϕ=π/2 . . . . . . . . . . . . 37
3.4 Photoniccrystalwaveguidenearthebandedge . . . . . . . . . . . . . . . . . . . . . . . . 37
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3.4.1 Outsidethebandgap: Superradiance . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.4.2 Insidethebandgap: Finite-rangedipole-dipoleinteraction . . . . . . . . . . . . . . 39
4 Designofastate-insensitive,compensatednanofibertrap 40
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
4.2 Astate-insensitivenanofibertrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.2.1 ACStarkshiftHamiltonian. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4.2.2 HE mode-Electricfielddistributionandpolarization . . . . . . . . . . . . . . . 44
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4.2.3 3Dnanofibertrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.2.4 Cancellationofthevectorshifts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
4.2.5 Magicwavelengthsforanevanescentfieldtrap . . . . . . . . . . . . . . . . . . . . 49
4.3 Numericalresults: Trappingpotentials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.3.1 Totalpotential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
4.3.2 State-insensitivetrappingpotential . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
4.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
5 Demonstrationofastate-insensitive,compensatednanofibertrap 55
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
5.2 Trappotentialwithstate-insensitive,compensatedscheme . . . . . . . . . . . . . . . . . . 56
5.3 Experimentalprocedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
5.4 Transmissionspectroscopyoftrappedatoms . . . . . . . . . . . . . . . . . . . . . . . . . . 59
5.5 Reflectionspectroscopyoftrappedatoms . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
5.6 Conclusionandoutlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.7 Experimentaldetails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.7.1 Polarizationcharacterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
5.7.2 Opticaldepthestimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.7.3 Atomnumberestimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
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6 Atom-lightinteractionsinphotoniccrystals 68
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
6.2 Designandcharacterizationof1Dphotonicscrystalwaveguide . . . . . . . . . . . . . . . . 69
6.3 Atom-lightcouplingintheAPCW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
6.3.1 Reflectionmeasurementsaton-andoff-resonantcavity . . . . . . . . . . . . . . . . 72
6.3.2 Reflectionmeasurementsandtheoreticalfit . . . . . . . . . . . . . . . . . . . . . . 76
6.3.3 Saturationmeasurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
6.4 Conclusionandoutlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.5 Experimentaldetails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.5.1 Designprinciple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.5.2 Atom-photoncoupling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
6.5.3 Devicecharacterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
6.5.4 Devicemodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
6.5.5 Simulationsofrelativedensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
6.5.6 Experimentalprocedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.5.7 Modelofreflectionspectrumofatoms . . . . . . . . . . . . . . . . . . . . . . . . . 87
7 Superradianceforatomstrappedalongaphotoniccrystalwaveguide 90
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
7.2 TrappingatomsalongtheAPCW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
7.3 Observationofsuperradiancefortrappedatoms . . . . . . . . . . . . . . . . . . . . . . . . 95
7.3.1 Superradiantemissionintimedomain . . . . . . . . . . . . . . . . . . . . . . . . . 95
7.3.2 Superradiantemissioninfrequencydomain . . . . . . . . . . . . . . . . . . . . . . 98
7.4 Conclusionandoutlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
7.5 Experimentaldetails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
7.5.1 Devicecharacterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
7.5.2 Finitedifferenttimedomaincalculationsforcollectivecouplingrates . . . . . . . . 103
7.5.3 LifetimeoftrappedatomsalongtheAPCW . . . . . . . . . . . . . . . . . . . . . . 105