专业英语翻译 16.docx
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专业英语翻译 16.docx
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专业英语翻译16
Quantuminformationscience
英文原稿:
Informationscienceandtechnologyhaspenetratedintoallaspectsofsociety,inwhichtheprotagonist--thedevelopmentofcomputerscienceandtechnologyandapplication,itisgreatlypromotestheprogressofhumancivilization.
Currentcomputersarebasedontheclassicalphysicallaws,isaclassicalcomputer.Overtheyears,ithasbeenrecognizedclassiccomputerhassomeunconquerablelimitations.Forexample,couldnotproduceatruerandomnumbersequence,notinalimitedtimetosimulateaconventionalquantummechanicssystem,notpossibleinacceptabletimefactorizationoflargenumbers.
Fromatpresentthedevelopmentofmicroelectronicstechnologyinlightofthedegree,peoplehavetofacesuchaproblem:
whenthesilicasurfaceelectriclineofsmalltoatomicscales,electroniccircuitsbehaviorwillnolongerobeythelawofclassicalmechanics,replacesb.Isquantummechanics.Thatistosay,peoplehavetointhequantumtheoryundertheframeworkofinformationscienceandinformationsystemconstruction.
Whenthescienceisstill
Quantuminformation(quantuminformation,QI)science,basedonthesuperpositionprincipleofquantummechanics,basedonstudiesofinformationprocessinganewcutting-edgescience,thebasictheoryofmodernphysicsandinformationscienceandtechnologyintersectandproduceafullvitalityofthediscipline.Quantuminformationscience,includingquantumcomputers,quantumstatetransferfromthematerial,quantumcryptographycommunicationandquantumnon-destructivemeasurementofotheraspects.
1980,Feynman[1]andBennett(C.Bennett)[2]hadcarriedoutsuchasquantuminformationsciencetheory.Theypointedoutthatthetwoorthogonalpolarizationstatesofphotons,atomsoratomsintwospinstates,theappropriatelevelofthesetwoorthogonalquantumstates(forexample:
|0>,|1>)canbeexpressedabitofquantuminformation,calledquantumbit(qubit).Bitdifferentfromtheclassical,quantumbitsintheparticles(photonsoratoms)notonlyinthe|0>orstate|1>state,andcanat|0>and|1>ofanykindofsuperpositionstate.Itisthisstrangecharacteristic,sothatquantumbitscannotbecomparedwithaclassicbitofadvantage
Inthestudyofquantuminformation,inadditiontoquantumalgorithms,quantumcomputersandquantumlogicgatesinquantumcommunicationquantumstatetransferfromthematerial,isthatpeoplearemostconcernedabout,themostinterestingresearchtopics,hasreceivedapreliminaryexperimentalstudytheresults.
Inaddition,toexploremethodsofquantuminformationprocessingdonebytheprocessofquantummechanicsexperiments,inturn,helppeopletoverifyanddeepenunderstandingofthelawsofthequantumworld,theanswertothosestillremainingcontroversialissues.Quantuminformationscienceresearch,notonlyhasimportantpotentialapplicationsbutalsohasfar-reachingscientificsignificance.
Powerfulandefficientcomputationaltools
In1985,OxfordUniversity,morethantheodd(D.Deutsch)[3]establishedthetheoreticalbasisofquantumcomputers,andpromotethedevelopmentofquantumcomputers.Similartotheclassiccomputers,quantumcomputing,butalsodependsontherealizationofthecorrespondingbasiclogiccomponents-quantumlogicgates(quantumlogicalgate,QLD).Therearefourpossibleexperimentalschemeofquantumlogicgates,whicharebasedoncavityquantumelectrodynamics(CQED),iontrap(iontrap),nuclearmagneticresonance(NMR)andquantumdots(quantumdot).
(1)cavityquantumelectrodynamics
Cavityquantumelectrodynamics(CQED)Thebasicideaisthattheverysmallnumberofatomsplacedinahigh-qualitymicro-cavity,thecavityelectromagneticfields(includingthevacuumfield)canbecontrolledtochange,thusaffectingtheprocessofatomicradiation.CQEDmostsuccessfulistostudyasmallnumberofparticles(photons,atoms)betweentheTheinteraction.Themethodispossibletomakeasinglephotonoftheelectricfieldenhancement,sothatitcanmakeasingleatomresponsesaturation.Toachievethisobjective,wemustachievesingle-atomandsinglephotoninthecavityofthestrongcoupling.
AsforquantumlogicelementsCQEDquantuminformationprocessing,firstbyPeiLizhain(T.Pellizzari),andothersmade.CaliforniaPolytechnicUniversity,Kimble(J.Kimble)groupdemonstratedtheuseoftheprograminitialquantumlogicgates.Thebasicapproachistocaptureanumberofneutralatomsinthehigh-qualitymicro-opticalcavity,thequantuminformationstoredintheatomswithinthestate,thatisthegroundstateofneutralatomsandonametastablestate.Containsthequantumstateofaqubitisintheatomicgroundstate|g>andalong-livedmetastablestate|e>ofthelinearcombination.Thestatequantumbitscanbestoredalongtime,whiletheatomicenergyinthecavitywellwiththeoutsideworld.
CQEDquantumlogicgateisidealtoachieveoneoftheoptions.However,high-qualitycavity,theconnectionbetweenmultiplequantumgatesstillhavesometechnicaldifficulties.
(2)iontraptechnology
Ion-trapquantumlogicgateprogramfirstbyCirac(J.Cirac),whosuggestedthatthecurrentinthepreliminaryexperimenthasbeenachieved.Intheexperiment,eachqubitisassignedinthecaptureinalinearPaul(Paul)trapsingleions.Containsaqubitquantumstate,isintheiongroundstate|g>andacertainlong-livedmetastablestate|e>ofthelinearcombination.Therefore,thesameatoms,italsoenablesqubitstorage.
Theadvantageofiontrap,ionCoulombinteractionbetweenthefardistancebetweentheions,sotheenergyofasinglelaserpulsetunedtoaparticularionof|g>stateand|e>stateenergydifference,wecanachievequantuminformationtoreadandchange.
Iontrapisthelargestprograminordertoestablishtheiontrapquantumcomputingspeedwillberestricted.Thereasonistime-energyuncertaintyrelationdeterminetheuncertaintyofthelaserpulseenergyshouldbehigherthanthecharacteristicfrequencyofthevibrationcenterofmassissmall,thedurationofeachpulseshouldbelongerthanthereciprocalofthecharacteristicfrequency;thephononvibrationfrequencyisgenerallylowertheexperimentthecharacteristicfrequencyofabout100kHz,sotheslowerspeed.InCQED,becauseoftheroleofthelightfieldandatomictimesoon,sothereisnoiontrapintheproblemsofslowresponse.
(3)NMRtechniques
NMR-basedquantumcomputingschemeinrecentyearsdevelopedanewmethodofquantuminformationprocessing.InNMR,quantumbitsareassignedcertainspecificmoleculesonthenuclearspinstates.Ataconstantexternalmagneticfield,eachnuclearspiniseitherupordown.Systemandspindecoherenceindegradedstatecanbekeptforalongertimebefore,sothequbitcanbestored.
Byapulsedmagneticfieldactingonthespin-spinRabioscillationstatetoachievetheselectedmagneticpulsecanalsobeappropriatetoachievethetransformationofasinglemagneticspinstates,becauseonlythosewhoareinresonancewiththespinstateoftheexternalmagneticfieldwillproducetherole.Meanwhile,thespinstate,therearealsodipole-dipoleinteraction,thiseffectcanbeusedtoimplementlogicgates.
NMRforquantumcomputation,butnotaseasilyacceptedasthefirsttwooptions.BecausetheNMRsystemis"hot"nuclearspintemperature(roomtemperature)isgenerallycausedbyfluctuationsinenergythanthedifferencebetweentheupperandlowerlevelsofnuclearspinhundredsoftimeshigher.Thismeansthat,fromasinglemoleculeinthecompositionofthenuclearspinquantumcomputerquantumstateinaverylargethermalnoiseinto.Thenoisewilldrownoutthequantuminformation.Further,theactualprocessisnothandledasinglemolecule,butincludes1023"quantumcomputer"macrosamples.
Readfromthisdevicethesignalisactuallyalargenumberofmoleculesoftheensembleaverage,butthequantumalgorithmisprobabilistic,itcomesfromtherandomnessofquantumcomputingitself,andpeopletookadvantageofthisrandomness.Ensembleaveragedoesnotmeanasingleunitonquantumcomputing.Peoplehadputforwardsomeexplanationsofthesedifficulties,thatthecalculatedaveragewillnoteliminatemanyusefulquantuminformation.Accordingtoreports,theuseofNMRmethodshaveproduced
Multi-qubitlogicgate,andusethistoachieveaquantumstatetransferfromthematerial.
ManyscholarsbelievethattheexistingNMRsystemcouldnotproduceentanglement;arisingfromentanglementinquantuminformationisthekey.NMRasaquantuminformationhardwarewillencountermanydifficulties,fromtheprinciplelimitationsare:
coherentsignalandbackgroundnoiseratiowillbewiththenuclearspinofeachmoleculeincreasesthenumberofexponentialdecay.Inarealsystem,completewitha10-qubitNMRcalculationswillfaceseriouschallenges.Ofcourse,somescholarsholddifferentviewsontheabovearguments,theNMRquantumlogicgatestobeoptimistic.However,NMRwillhelppeopleunderstandsomeofthenuclearspinofthings.
(4)quantumdots
Relatedtonano-scalequantum-dotsemiconductorregion.Theseregionsshowedasmallnumberofelectronicstates,thesingle-electronquantumdotcanbechangedintoelectronicstate,whichmaybeusedforquantuminformationprocessing,quantumdotsplacedCQEDtheymaycontrolthematerialsinthespontaneousemission,enhancedlightmatterinteractiontherole.Ifthematuresemiconductortechnologycombinedwithquantumdevices,mayhaveapracticalquantuminformationsystems.However,howtoensurethepurityofquantumdotmaterialsremainsachalle
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