Contents - Max-Planck-Institut für Physik komplexer Systeme
Contents - Max-Planck-Institut für Physik komplexer Systeme
Contents - Max-Planck-Institut für Physik komplexer Systeme
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manipulationofchargequbits.TakingCoulombinteractionsintoaccount,wehavealsoinvestigatednonadiabaticchargepumpingthroughsingle-levelquantumdotswhichmaybeusedtoproducequantized<br />
currentsformetrologicalpurposes.<br />
UltracoldRydbergdynamics AnultracoldenvironmentharmonizesperfectlywithRydbergdynamics<br />
withitsinherentlysmallenergyscale.Consequently,thisfieldhasgainedenormousmomentumrecently,<br />
holdinghopesforinformationscienceandofferingveryflexiblepossibilitiestodesignandinvestigate<br />
condensedmatterlikesystemsofverydifferentcharacter.Inmostapplicationsthefocusisonelectron<br />
dynamicswiththeatomicmotionasanannoyingbutunavoidablefact. Incontrastweconcentrateon<br />
theinterplayofelectronicandatomicmotionakintochemicaldynamics.<br />
WehavefoundthatthisinterplayproducessurprisingdynamicalfeaturessuchasinternalquantumreflectioninRydbergdimers(boundsystemsformedwithagroundstateandaRydbergatom),orabundantconicalintersectionsinanultracoldRydberggas.WithRydbergdressingonlyasmalladmixtureofRydbergcharacterisaddedtotheelectronicgroundstatewavefunction,producingverystablepoly-atomic<br />
systemswithwelldefinedgeometriesinatrap.Thisallowsonetostudyarchetypicalmolecularsituations,<br />
e.g.,aconicalintersectionnotinfluencedbyotherchannelsasinastandardmolecule.Ultracoldtrapped<br />
Rydbergatomsmayalsobepreparedtogetherwithgroundstateatomssuchthattheyformasystem<br />
withpropertiesofquantumaggregates. Whileintraditionalaggregates,thepositionoftheatomsis<br />
hardlycontrollable,thiscanbeachievedintheultracoldrealizationbyentanglingatomicmotionand<br />
electronicexcitation.Thereby,wehavefoundanefficientwaytotransportelectronicentanglementand<br />
coherencealonganatomicchain,akintoNewton’scradleintheclassicalcase.<br />
Quantumaggregates Self-organizedaggregatesofdyemoleculesareversatilequantumsystemswith<br />
applicationsinphotography,opto-electronics,solarcells,photo-biologyandassupra-molecularfibers.In<br />
addition,newtypesofquantumaggregatehaveemerged:e.g.assembliesofultra-coldRydbergatoms,as<br />
discussedabove,“molecules”and“crystals”composedofquantumdotsorarraysofnano-sizemetallic<br />
particles.<br />
Foraggregatesembeddedinaglassyhostwehavefoundthatstaticdisorderstronglyinfluencesthe<br />
opticalandtransferproperties(Andersonlocalization). Abroadeningoftheabsorptionspectrumupon<br />
aggregationoccursforstableLevydisorder.Thisisincontrasttoastrongnarrowingwhichfollowsfrom<br />
thecommonlyassumedGaussiandisorder.<br />
ForaHelium-nanodropletasanenvironmentithasturnedoutthataproperinclusionofinternalvibrational<br />
modesisessentialtoexplainmeasuredaggregatespectraoftheorganicsemiconductorPTCDA.<br />
Perspectivesforthefuture<br />
WithadditionalFELsourcescomingonlineandmoreusersgettinginterested,thegeneralemphasisin<br />
theoreticalresearchshiftstowardssimulationofspecificsituationsandexperiments. Incontrasttothis<br />
trendwewillcontinuetoconcentrateongeneralprinciplesofinteractionandtheirsimpleformulation<br />
forlight-matterinteractionintheattosecond-andXUV-aswellasX-ray-shortpulseparameterregime,<br />
includingthedevelopmentofsimplifiedmodelsforabetterunderstanding,suchastheconceptofCoulomb<br />
complexes.<br />
Ourapproachtodescribelargemoleculesorclustersundershortpulseshasbeensofarbasedonthe<br />
classicalmotionofallchargedparticleswheretheactivationoftheseparticlesthroughphotonsismodeled<br />
byratessinceduetothewavelength,thelightdoesnotresolveboundorbitalstructureforIRdownto<br />
VUVradiation. ThischangesforXUVtoX-rayradiationwhereweplanamoredetailedformulation<br />
withthehelpofthecoherentstateapproach.Itoffersformallyaquantumframeworkbutstillbasedon<br />
classicaltrajectories.<br />
Weareonlybeginningtounderstandthephenomenaofexcitondynamicscoupledtoatomicmotionin<br />
thecontextofultracoldRydbergaggregates.ThegreatflexibilityofultracoldRydbergsystemsandthe<br />
possibilityforexperimentalrealizationofferawidepotentialwhichcanbedevelopedinvariousdirections,<br />
severalofwhichwefollowinthedepartmentwithThomasPohlandhisresearchgroupaswellasparts<br />
oftheFiniteSystemsresearchgroup. Inthelatterwewillconcentrateondevelopinganunderstanding<br />
howtransportofcoherenceandentanglementcanproceedovermanysitesinlargeultracoldRydberg<br />
networks. Duetotheuniversalcharacterofdipole-dipoleforces,suchanunderstandingwillgiveusa<br />
1.8. DepartmentsandResearchGroups 9