delayed commutation in quantum computer networks

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1、Delayedcommutationinquantumcomputernetworks.JuanCarlosGarc´ia-Escart´in∗andPedroChamorro-PosadaDepartamentodeTeor´iadelaSe˜nalyComunicacioneseIngenier´iaTelem´atica.UniversidaddeValladolid.Spain.(Dated:February1,2008)Inthesamewaythatclassicalcomputerne

2、tworksconnectandenhancethecapabilitiesofclassicalcomputers,quantumnetworkscancombinetheadvantagesofquantuminformationandcommuni-cations.Weproposeanon-classicalnetworkelement,adelayedcommutationswitch,thatcansolvetheproblemofswitchingtimeinpacketswitchi

3、ngnetworks.Withthehelpofsomelocalancillaryqubitsandsuperdensecodeswecanroutetheinformationafterpartofithasleftthenetworknode.I.INTRODUCTIONQuantuminformationoffersnewpossibilitiesinthefieldsofcommunicationandcomputation[1].Therearequantumalgorithmscapabl

4、eofperformingcertaintaskswithanefficiencythatnoknownclassicalalgorithmcanmatch.ExamplesareShor’salgorithmforpolynomialtimefactorization[2],Grover’salgorithmforunstructureddatabasesearch[3],andtheDeutsch-Jozsaalgorithm,thatgivesinformationonglobalproperti

5、esofafunctionwithoutanexplicitevaluationofallthepossiblevalues[4,5].Quantuminformationtheoryextendsclassicalinformationtheory[6]andincludesanaloguestoclassicalHuffmancodes[7],anderrorcorrectioncodes[8,9,10].Applicationstoquantumcommunicationareespeciall

6、yinteresting.Quantumcryptographyproposals[11]giveschemesforsecuredatatransmission,andsuperdensecoding[12]allowstosendmorethanoneclassicalbitpertransmittedqubit.Thedevelopmentofopticalcommunicationnetworksandtheadvancedstateofthecurrentphotonictechnolog

7、yhavepermittedtheexperimentalrealizationofcryptography[13],transmissionofinformationinsuperdensecodes[14],andtheteleportationofqubits[15].Ontheotherhand,classicalcomputernetworkshavewitnessedanimpressiveprogressinthelastdecades.Theadventofmultimediadat

8、aapplicationsandtheincreaseduseoftheInternet,telephoneandothernetworkserviceshavebroughtanincreasingbandwidthdemand.Theneedforfastertransmissionrateshasledtotheprogressiveimplantationofopticalnetworks.Opticalfibretechnologyisnowusedinthe