This page intentionally left blank QuantumComputationandQuantumInformation 10thAnniversaryEdition Oneofthemostcitedbooksinphysicsofalltime,QuantumComputationandQuantum Informationremainsthebesttextbookinthisexcitingfieldofscience.This10th AnniversaryEditionincludesanewIntroductionandAfterwordfromtheauthors settingtheworkincontext. Thiscomprehensivetextbookdescribessuchremarkableeffectsasfastquantum algorithms,quantumteleportation,quantumcryptography,andquantum error-correction.Quantummechanicsandcomputerscienceareintroduced,before movingontodescribewhataquantumcomputeris,howitcanbeusedtosolveproblems fasterthan“classical”computers,anditsreal-worldimplementation.Itconcludeswith anin-depthtreatmentofquantuminformation. Containingawealthoffiguresandexercises,thiswell-knowntextbookisidealfor coursesonthesubject,andwillinterestbeginninggraduatestudentsandresearchersin physics,computerscience,mathematics,andelectricalengineering. MICHAELNIELSENwaseducatedattheUniversityofQueensland,andasaFulbright ScholarattheUniversityofNewMexico.HeworkedatLosAlamosNational Laboratory,astheRichardChaceTolmanFellowatCaltech,wasFoundationProfessor ofQuantumInformationScienceandaFederationFellowattheUniversityof Queensland,andaSeniorFacultyMemberatthePerimeterInstituteforTheoretical Physics.HeleftPerimeterInstitutetowriteabookaboutopenscienceandnowlivesin Toronto. ISAACCHUANGisaProfessorattheMassachusettsInstituteofTechnology,jointly appointedinElectricalEngineering&ComputerScience,andinPhysics.Heleadsthe quantaresearchgroupattheCenterforUltracoldAtoms,intheMITResearch LaboratoryofElectronics,whichseekstounderstandandcreateinformationtechnology andintelligencefromthefundamentalbuildingblocksofphysicalsystems,atoms,and molecules. Inpraiseofthebook10yearsafterpublication Tenyearsafteritsinitialpublication,“MikeandIke”(asit’saffectionatelycalled)remainsthequantum computingtextbooktowhichallothersarecompared.Nootherbookinthefieldmatchesitsscope: fromexperimentalimplementationtocomplexityclasses,fromthephilosophicaljustificationsforthe Church-TuringThesistothenitty-grittyofbra/ketmanipulation.Adog-earedcopysitsonmydesk; thesectionontracedistanceandfidelityalonehasbeenworthmanytimesthepriceofthebooktome. ScottAaronson,MassachusettsInstituteofTechnology Quantuminformationprocessinghasbecomeahugeinterdisciplinaryfieldattheintersectionofboth, theoreticalandexperimentalquantumphysics,computerscience,mathematics,quantumengineering and,morerecently,evenquantummetrology.ThebookbyMichaelNielsenandIsaacChuangwas seminal in many ways: it paved the way for a broader, yet deep understanding of the underlying science,itintroducedacommonlanguagenowwidelyusedbyagrowingcommunityanditbecame thestandardbookinthefieldforawholedecade.Inspiteofthefastprogressinthefield,evenafter 10yearsthebookprovidesthebasicintroductionintothefieldforstudentsandscholarsalikeand the 10th anniversary edition will remain a bestseller for a long time to come. The foundations of quantumcomputationandquantuminformationprocessingareexcellentlylaidoutinthisbookand italsoprovidesanoverviewoversomeexperimentaltechniquesthathavebecomethetestingground forquantuminformationprocessingduringthelastdecade.Inviewoftherapidprogressofthefield thebookwillcontinuetobeextremelyvaluableforallenteringthishighlyinterdisciplinaryresearch areaanditwillalwaysprovidethereferenceforthosewhogrewupwithit.Thisisanexcellentbook, wellwritten,highlycommendable,andinfactimperativeforeverybodyinthefield. RainerBlatt,Universtita¨tInnsbruck Mywell-perusedcopyofNielsenandChuangis,asalways,closeathandasIwritethis.Itappears thatthematerialthatMikeandIkechosetocover,whichwasalot,hasturnedouttobealargeportion ofwhatwillbecometheeternalveritiesofthisstill-youngfield.Whenanotherresearcherasksmeto giveheraclearexplanationofsomeimportantpointofquantuminformationscience,Ibreatheasigh ofreliefwhenIrecallthatitisinthisbook–myjobiseasy,Ijustsendherthere. DavidDiVincenzo,IBMT.J.WatsonResearchCenter Ifthereisanythingyouwanttoknow,orremindyourself,aboutquantuminformationscience,then looknofurtherthanthiscomprehensivecompendiumbyIkeandMike.Whetheryouareanexpert,a studentoracasualreader,tapintothistreasurechestofusefulandwellpresentedinformation. ArturEkert,MathematicalInstitute,UniversityofOxford NearlyeverychildwhohasreadHarryPotterbelievesthatifyoujustsaytherightthingordothe rightthing,youcancoercemattertodosomethingfantastic.Butwhatadultwouldbelieveit?Until quantum computation and quantum information came along in the early 1990s, nearly none. The quantumcomputeristhePhilosopher’sStoneofourcentury,andNielsenandChuangisourbasic bookofincantations.Tenyearshavepassedsinceitspublication,anditisasbasictothefieldasit everwas.Matterwilldowonderfulthingsifaskedto,butwemustfirstunderstanditslanguage.No bookwrittensince(therewasnobefore)doesthejobofteachingthelanguageofquantumtheory’s possibilitieslikeNielsenandChuang’s. ChrisFuchs,PerimeterInstituteforTheoreticalPhysics NielsenandChuangisthebibleofthequantuminformationfield.Itappeared10yearsago,yeteven thoughthefieldhaschangedenormouslyinthese10years-thebookstillcoversmostoftheimportant conceptsofthefield. LovGrover,BellLabs QuantumComputationandQuantumInformation,commonlyreferredtoas“MikeandIke,”continues tobeamostvaluableresourceforbackgroundinformationonquantuminformationprocessing.Asa mathematically-impairedexperimentalist,Iparticularlyappreciatethefactthatarmedwithamodest backgroundinquantummechanics,itispossibletopickupatanypointinthebookandreadilygrasp thebasicideasbeingdiscussed.Tome,itisstill“the”bookonthesubject. DavidWineland,NationalInstituteofStandardsandTechnology,Boulder,Colorado Endorsementsfortheoriginalpublication ChuangandNielsenhaveproducedthefirstcomprehensivestudyofquantumcomputation.To developarobustunderstandingofthissubjectonemustintegratemanyideaswhoseoriginsare variouslywithinphysics,computerscience,ormathematics.Untilthistext,puttingtogetherthe essentialmaterial,muchlessmasteringit,hasbeenachallenge.OurUniversehasintrinsiccapa- bilitiesandlimitationsontheprocessingofinformation.Whatthesearewillultimatelydetermine thecourseoftechnologyandshapeoureffortstofindafundamentalphysicaltheory.Thisbookis anexcellentwayforanyscientistorgraduatestudent–inanyoftherelatedfields–toenterthe discussion. MichaelFreedman,FieldsMedalist,Microsoft Nielsen and Chuang’s new text is remarkably thorough and up-to-date, covering many aspects of this rapidly evolving field from a physics perspective, complementing the computer science perspectiveofGruska’s1999text.Theauthorshavesucceededinproducingaself-containedbook accessibletoanyonewithagoodundergraduategroundinginmath,computerscienceorphysical sciences.Anindependentstudentcouldspendanenjoyableyearreadingthisbookandemergeready totacklethecurrentliteratureanddoseriousresearch.Tostreamlinetheexposition,footnoteshave beengatheredintoshortbutlivelyHistoryandFurtherReadingsectionsattheendofeachchapter. CharlesHBennett,IBM Thisisanexcellentbook.Thefieldisalreadytoobigtocovercompletelyinonebook,butNielsen andChuanghavemadeagoodselectionoftopics,andexplainthetopicstheyhavechosenvery well. PeterShor,MassachusettsInstituteofTechnology Quantum Computation and Quantum Information 10th Anniversary Edition Michael A. Nielsen & Isaac L. Chuang CAMBRIDGE UNIVERSITY PRESS Cambridge,NewYork,Melbourne,Madrid,CapeTown,Singapore, Sa˜oPaulo,Delhi,Dubai,Tokyo,MexicoCity CambridgeUniversityPress TheEdinburghBuilding,CambridgeCB28RU,UK PublishedintheUnitedStatesofAmericabyCambridgeUniversityPress,NewYork www.cambridge.org Informationonthistitle:www.cambridge.org/9781107002173 (cid:1)C M.NielsenandI.Chuang2010 Thispublicationisincopyright.Subjecttostatutoryexception andtotheprovisionsofrelevantcollectivelicensingagreements, noreproductionofanypartmaytakeplacewithoutthewritten permissionofCambridgeUniversityPress. Firstpublished2000 Reprinted2002,2003,2004,2007,2009 10thAnniversaryeditionpublished2010 PrintedintheUnitedKingdomattheUniversityPress,Cambridge AcatalogrecordforthispublicationisavailablefromtheBritishLibrary ISBN978-1-107-00217-3Hardback CambridgeUniversityPresshasnoresponsibilityforthepersistenceor accuracyofURLsforexternalorthird-partyinternetwebsitesreferredtoin thispublication,anddoesnotguaranteethatanycontentonsuchwebsitesis, orwillremain,accurateorappropriate. To our parents, and our teachers