《通信工程专业英语（第二版）》课件Unit 6

Unit6TextAQuantumCommunicationsLeapoutoftheLabQuantumCommunicationsLeapoutoftheLab

——Chinabeginsworkonsuper-securenetworkas‘real-world’trialsuccessfullysendsquantumkeysanddata.TextTextWordsNotesDiscussionHomeCybersecurityisastepclosertothedreamofsendingdatasecurelyoverlongdistancesusingquantumphysics—spurredbytwodevelopments.TextTextWordsNotesDiscussionHomeThisweek,Chinawillstartinstallingtheworld’slongestquantum-communicationsnetwork,whichincludesa2,000-kilometrelinkbetweenBeijingandShanghai.AndastudyjointlyannouncedthisweekbythecompaniesToshiba,BTandADVA,withtheUKNationalPhysicalLaboratoryinTeddington,reports“encouraging”resultsfromanetworkfieldtrial,suggestingthatquantumcommunicationscouldbefeasibleonexistingfibre-opticinfrastructure.TextTextWordsNotesDiscussionHomeIsthereanydisadvantageinconventionaldata-encryptionsystems?Whatisit?TextTextWordsNotesDiscussionHomeConventionaldata-encryptionsystemsrelyontheexchangeofasecret‘key’—inbinary0sand1s—toencryptanddecryptinformation.Butthesecurityofsuchacommunicationchannelcanbeunderminedifahacker‘eavesdrops’onthiskeyduringtransmission.Quantumcommunicationsuseatechnologycalledquantumkeydistribution[1](QKD),whichharnessesthesubatomicpropertiesofphotonsto“removethisweakestlinkofthecurrentsystem”,saysGrégoireRibordy,co-founderandchiefexecutiveofIDQuantique,aquantum-cryptographycompanyinGeneva,Switzerland.TextTextWordsNotesDiscussionHomeThemethodallowsausertosendapulseofphotonsthatareplacedinspecificquantumstatesthatcharacterizethecryptographickey.Ifanyonetriestointerceptthekey,theactofeavesdroppingintrinsicallyaltersitsquantumstate—alertinguserstoasecuritybreach.BoththeUS$100-millionChineseinitiativeandthesystemtestedinthelateststudyuseQKD.TextTextWordsNotesDiscussionHomeTheChinesenetwork“willnotonlyprovidethehighestlevelofprotectionforgovernmentandfinancialdata,butprovideatestbedforquantumtheoriesandnewtechnologies”,saysJian-WeiPan,aquantumphysicistattheUniversityofScienceandTechnologyofChinainHefei,whoisleadingtheChineseproject.TextTextWordsNotesDiscussionHomePanhopestotestsuchideasusingthenetwork,alongwithaquantumsatellitethathisteamplanstolaunchnextyear.Together,hesays,thetechnologiescouldperformfurthertestsoffundamentalquantumtheoriesoverlargescales(around2,000kilometres),suchasquantumnon-locality[2],inwhichchangingthequantumstateofoneparticlecaninfluencethestateofanothereveniftheyarefarapart,saysPan.TextTextWordsNotesDiscussionHomeSendingsinglephotonsoverlongdistancesisoneofthegreatestproblemsinQKDbecausetheytendtogetabsorbedbyopticalfibers,makingthekeystrickytodetectonthereceiver’send.TextTextWordsNotesDiscussionHomeThisis“abigchallengeforconventionaldetectors”,saysHoi-KwongLo,aquantumphysicistattheUniversityofTorontoinCanada.Buttechnologicalbreakthroughsinrecentyearshavesignificantlyreducedthenoiselevelofdetectorswhileincreasingtheirefficiencyindetectingphotonsfromjust15%to50%.TextTextWordsNotesDiscussionHomeVastimprovementshavealsobeenmadeintherateatwhichdetectorscan‘count’photonpulses—crucialindeterminingtherateatwhichquantumkeyscanbesent,andthusthespeedofthenetwork.Countingrateshavebeenraised1,000-fold,toabout2gigahertz,saysLo.TextTextWordsNotesDiscussionHomeThebreakthroughsarepushingthedistanceoverwhichquantumsignalscanbesent.Trialsusing‘darkfibers’—opticalfiberslaiddownbytelecommunicationscompaniesbutlyingunused--havesentquantumsignalsupto100kilometers,saysDonHayford,aresearcheratBattelle,atechnology-developmentcompanyheadquarteredinColumbus,Ohio.TextTextWordsNotesDiscussionHomeTogofartherthanthat,quantumsignalsmustberelayedat‘nodepoints’—thequantumnetworksbetweenBeijingandShanghai,forinstance,willrequire32nodes.Totransmitphotonsoverlongerdistanceswithouttheuseofnodeswouldrequireasatellite.TextTextWordsNotesDiscussionHomeChinaisnotaloneinitsquantum-communicationefforts.AteamledbyHayford,togetherwithIDQuantique,hasstartedinstallinga650-kilometrelinkbetweenBattelle’sheadquartersanditsofficesinWashingtonDC.ThepartnershipisalsoplanninganetworklinkingmajorUScities,whichcouldexceed10,000kilometers,saysHayford,althoughithasyettosecurefundingforthat.TextTextWordsNotesDiscussionHomeTheChineseandUSnetworkswillbothusedarkfiberstosendquantumkeys.Butthesefibers“arenotalwaysavailableandcanbeprohibitivelyexpensive”,saysAndrewShields,aquantumphysicistatToshibaResearchEuropeinCambridge,UK.Onewaytosidesteptheproblemistopiggybackthephotonstreamsontothe‘lit’fibersthattransmitconventionaltelecommunicationsdata.However,thoseconventionaldatastreamsareusuallyaboutamilliontimesstrongerthanquantumstreams,sothequantumdatatendtobedrownedout.TextTextWordsNotesDiscussionHomeIntheresultsannouncedthisweek,ShieldsandhiscolleaguesweresuccessfulinachievingthestableandsecuretransmissionofQKDsalongalivelitfiberbetweentwostationsoftheUKtelecommunicationscompanyBT,26kilometersapart.Thequantumkeysweresentoverseveralweeksatahighratealongsidefourchannelsofstrongconventionaldataonthesamefiber.TheresearchbuildsonpreviousworkinwhichShieldsandhisteamdevelopedatechniquetodetectquantumsignalssentalongsidenoisydataina90-kilometrefiber,butincontrolledlaboratoryconditions.TextTextWordsNotesDiscussionHome“ImplementingQKDinthe‘realworld’ismuchmorechallengingthaninthecontrolledenvironmentofthelab,duetoenvironmentalfluctuationsandgreaterlossinthefibre,”saysShields.TextTextWordsNotesDiscussionHomeThequantumkeysinthelateststudyweresentalongsideconventionaldatatravellingat40gigabitspersecond.“AsfarasIamaware,thisisthehighestbandwidthofdatathathasbeenmultiplexedwithQKDtodate,”addShields.TextTextWordsNotesDiscussionHomeHecalculatesthatitwouldbepossibletosendQKDsignalsalongside40conventionaldatachannels.Opticalfibersusuallycarrybetween40and160telecommunicationschannels,meaningthatquantumcommunicationcouldbecarriedoutwithexistinginfrastructure.TextTextWordsNotesDiscussionHome“Ifinditanimpressivepieceofworkthatdemonstratesthemultiplexingofstrongclassicalsignalswithquantumsignalsinthesamefiberforthefirsttime”inafieldtrial,saysLo.Removingtheneedfordarkfibers,hesays,isanimportantstepinshowingthatQKDhasthepotentialtobeusedin“reallife”.ByJaneQiu,23April2014,fromNatureTextTextWordsNotesDiscussionHomespurv.促进，加速，推动feasibleadj.可行的；可实行的conventionaladj.传统的；依照惯例的encryptv.编密码；加密decryptv.译（电文），解释明白underminev.逐渐削弱；破坏WordsWordsTextWordsNotesDiscussionHomeharnessvt.利用；控制interceptvt.&n.拦截，拦住；截球；截击subatomicadj.小于原子的，亚原子的cryptographyn.密码使用法，密码系统photonn.<物>光子，光量子eavesdropv.偷听；窃听WordsTextWordsNotesDiscussionHomeintrinsicadj.固有的，本质的breachn.破坏；破裂；缺口initiativen.积极的行动；主动localityn.位置，地区；产地trickyadj.复杂的；棘手的gigahertzn.千兆赫WordsTextWordsNotesDiscussionHomeprohibitiveadj.禁止的；抑制的sidestepvi.绕开；向侧方跨步piggybackvt.背负式装运fluctuationn.波动，涨落，起伏multiplexvt.[通信]多路传输spurv.促进，加速，推动feasibleadj.可行的；可实行的WordsTextWordsNotesDiscussionHome1.quantumkeydistribution(QKD)：量子密钥分配是1984年物理学家Bennett和密码学家Brassard提出了基于量子力学测量原理的BB84协议，量子密钥分配从根本上保证了密钥的安全性。例如天宫二号上的载荷"量子密钥分配专项"就是以实现空地间实用化的量子密钥分配为目标，通过天上发射一个个单光子并在地面接收，生成"天机不可泄露"的量子密钥。TextWordsNotesDiscussionNotesHome2.quantumnon-locality：量子的非定域性又称“测不准原理”、“不确定关系”，是量子力学的一个基本原理，由德国物理学家海森堡（WernerHeisenberg）于1927年提出。该原理表明，一个微观粒子的某些物理量（如位置和动量，或方位角与动量矩，还有时间和能量等），不可能同时具有确定的数值，其中一个量越确定，另一个量的不确定程度就越大。TextWordsNotesDiscussionHomeQuestionsfordiscussion1.Isthereanydisadvantageinconventionaldata-encryptionsystems?Whatisit?2.HowcanQKDpreventhackersfromeavesdroppingduringtransmission?3.Whatisthedisadvantageofdarkfibers?Howcanitbeavoided?4.DoyouthinkitispossiblethatQKDwillbeemployedin“reallife”?TextWordsNotesDiscussionHomeAnswerstoquestionsfordiscussionTextWordsNotesDiscussionHome1.Isthereanydisadvantageinconventionaldata-encryptionsystems?Whatisit?Conventionaldata-encryptionsystemsrelyontheexchangeofasecret‘key’—inbinary0sand1s—toencryptanddecryptinformation.Butthesecurityofsuchacommunicationchannelcanbeunderminedifahacker‘eavesdrops’onthiskeyduringtransmission.TextWordsNotesDiscussionHome2.HowcanQKDpreventhackersfromeavesdroppingduringtransmission?Quantumcommunicationsuseatechnologycalledquantumkeydistribution(QKD),whichharnessesthesubatomicpropertiesofphotonstoremovethisweakestlinkofthecurrentsystem,which,therefore,allowsausertosendapulseofphotonsthatareplacedinspecificquantumstatesthatcharacterizethecryptographickey.Ifanyonetriestointerceptthekey,theactofeavesdroppingintrinsicallyaltersitsquantumstate—alertinguserstoasecuritybreach.TextWordsNotesDiscussionHome3.Whatisthedisadvantageofdarkfibers?Howcanitbeavoided?Theproblemwithdarkfibersisthattheyarenotalwaysavailableandcanbeprohibitivelyexpensive.Onewaytosidesteptheproblemistopiggybackthephotonstreamsontothe‘lit’fibersthattransmitconventionaltelecommunicationsdata.TextWordsNotesDiscussionHome4.DoyouthinkitispossiblethatQKDwillbeemployedin“reallife”?Yes.Aslongasdarkfiberscanbereplacedwithopticalfibers,itcanbeusedin“reallife”.Infact,Shields’researchhasshownthemultiplexingofstrongclassicalsignalswithquantumsignalsinthesamefiberforthefirsttime,whichindicatesitispossibletoremovetheneedfordarkfibers.TextWordsNotesDiscussionHomeThankyou!Unit6TextBChina’sLatestLeapForwardIsn’tJustGreat—It’sQuantumChina’sLatestLeapForwardIsn’tJustGreat—It’sQuantum——Beijinglaunchestheworld’sfirstquantum-communicationssatelliteintoorbitTextTextWordsNotesDiscussionHomeBEIJING—ArocketthatshotskywardfromtheGobiDesertearlyTuesdayisexpectedtopropelChinatotheforefrontofoneofscience’smostchallengingfields.TextTextWordsNotesDiscussionHomeItalsoissettolaunchBeijingfaraheadofitsglobalrivalsinthedrivetoacquireahighlycovetedassetintheageofcyberespionage:hack-proofcommunications.TextTextWordsNotesDiscussionHomeStatemediasaidChinasenttheworld’sfirstquantum-communicationssatelliteintoorbitfromalaunchcenterinInnerMongoliaabout1:40a.m.Tuesday.Fiveyearsinthemaking,theprojectisbeingcloselywatchedinscientificandsecuritycircles.TextTextWordsNotesDiscussionHomeThequantumprogramisthelatestpartofChina’smultibillion-dollarstrategyoverthepasttwodecadestodrawwithorevensurpasstheWestinhard-sciences[1]research.TextTextWordsNotesDiscussionHome“There’sbeenaracetoproduceaquantumsatellite,anditisverylikelythatChinaisgoingtowinthatrace,”said

NicolasGisin,

aprofessorandquantumphysicistattheUniversityofGeneva.“ItshowsagainChina’sabilitytocommittolargeandambitiousprojectsandtorealizethem.”TextTextWordsNotesDiscussionHomeScientistsintheU.S.,Europe,Japanandelsewherearerushingtoexploitthestrangeandpotentiallypowerfulpropertiesofsubatomicparticles,butfewwithasmuchstatesupportasthoseinChina,researcherssay.Quantumtechnologyisatopstrategicfocusinthecountry’sfive-yeareconomicdevelopmentplan,releasedinMarch.TextTextWordsNotesDiscussionHomeBeijinghasn’tdisclosedhowmuchmoneyithasallocatedtoquantumresearchortobuildingthe1,400-poundsatellite.Butfundingforbasicresearch,whichincludesquantumphysics,was$10.1billionin2015,upfrom$1.9billionin2005.TextTextWordsNotesDiscussionHomeU.S.federalfundingforquantumresearchisabout$200millionayear,accordingtoacongressionalreportinJulybyagroupofscience,defense,intelligenceandotherofficials.Itsaiddevelopmentofquantumsciencewould“enhanceU.S.nationalsecurity,”butsaidfluctuationsinfundinghadsetbackprogress.TextTextWordsNotesDiscussionHomeBeijing,meanwhile,hastriedtolureChinese-born,foreign-educatedexpertsinquantumphysicsbacktoChina,includingPanJianwei,thephysicistwhoisleadingtheproject.TextTextWordsNotesDiscussionHome“We’vetakenallthegoodtechnologyfromlabsaroundtheworld,absorbeditandbroughtitback,”Mr.PantoldChinesestateTVinaninterviewthatairedonMonday.TextTextWordsNotesDiscussionHomeWithstatesupport,Mr.PanwasabletoleapfroghisformerPh.D.adviser,UniversityofViennaphysicist

AntonZeilinger,

whosaidhehastriedsince2001topersuadetheEuropeanSpaceAgencytolaunchasimilarsatellite.TextTextWordsNotesDiscussionHome“It’sadifficultprocess,whichtakesalotoftime,”saidMr.Zeilinger,whoisnowworkingonhisformerstudent’ssatellite.TextTextWordsNotesDiscussionHomeNeitherMr.PannortheChineseAcademyofSciences,whichisdirectingtheproject,respondedtorequeststocomment.TheEuropeanSpaceAgencydidn’trespondtorequestsforcomment.TextTextWordsNotesDiscussionHomeTheNationalScienceFoundation,whichprovidesfederalfundingforbasicAmericanscienceresearch,saidquantumsciencewasoneofsix“bigideas.”Ithadidentifiedforlong-termresearchtoaddresscriticalsocietalchallenges,accordingtoC.DeniseCaldwell,headofthegroup’sphysicsdivision.ShesaidtheNSFalsorecentlyestablishednewresearchawardsthatwillhaveadirectimpactonquantuminformationresearch.TextTextWordsNotesDiscussionHomeChina’sinvestmentinthefieldislikelybeingdriveninpartbyfearofU.S.cybercapabilities,said

JohnCostello,

afellowatWashington,D.C.-basedNewAmericaspecializinginChinaandcybersecurity,pointingto2013disclosuresthattheU.S.hadpenetrateddeeplyintoChinesenetworks.HealsonotedthatU.S.institutionsareresearchinghowtobuildpowerfulquantumcomputerstheoreticallycapableofshatteringthemath-basedencryptionnowusedworld-wideforsecurecommunication.TextTextWordsNotesDiscussionHome“TheChinesegovernmentisawarethattheyaregrowingparticularlysusceptibletoelectronicespionage,”Mr.Costellosaid.TextTextWordsNotesDiscussionHomeHowever,quantumcommunicationisdefensiveinnature,henoted,andwouldn’tbenefitfromwhattheU.S.hasidentifiedasChina’sstate-sponsoredhackingprogram.TextTextWordsNotesDiscussionHomeQuantumencryptionissecureagainstanykindofcomputingpowerbecauseinformationencodedinaquantumparticleisdestroyedassoonasitismeasured.

GregoirRibordy,

co-founderofGeneva-basedquantumcryptographyfirmIDQuantique,likenedittosendingamessagewrittenonasoapbubble.“Ifsomeonetriestointerceptitwhenit’sbeingtransmitted,bytouchingit,theymakeitburst,”hesaid.TextTextWordsNotesDiscussionHomeQuantumphysicistshaverecentlyadvancedtheuseofphotonstocommunicatesecurelyovershortdistancesonearth.Thesatellite,ifsuccessful,wouldvastlyexpandtherangeofun-hackablecommunication.Totestwhetherquantumcommunicationscantakeplaceataglobalscale,Mr.PanhastoldstatemediathatheandhisteamwilltrytobeamaquantumcryptographickeythroughspacefromBeijingtoVienna.“Inevitablythesekindsoftechnologieshaveproblemsandthingsgetmessedupbythepeopleusingthem,unlesstheyhavegonethroughextensivetraining,”said

PeterMattis,

afellowattheJamestownFoundation[2]whostudiesChina’sintelligenceservices.“IthinkChinahasanobligationnotjusttodosomethingforourselves—manyothercountrieshavebeentothemoon,havedonemannedspaceflight—buttoexploresomethingunknown,”hesaid.TextTextWordsNotesDiscussionHome“Itwouldbeenormousifthetestsucceeded,”saidMaXiaosong,aVienna-trainedquantumphysicistatNanjingUniversitywhoworkedonearlyphasesofthesatelliteproject.TextTextWordsNotesDiscussionHomeQuantumencryptionisn’tfoolproof.It’spossibleforhackerstotrickanincautiousrecipientbyshininganintenselaserintoaquantumreceptor,said

AlexanderLing,

principalinvestigatorattheCenterforQuantumTechnologiesinSingapore.TextTextWordsNotesDiscussionHomeU.S.securityexpertsalsoquestionwhetherintricaciesofquantumcommunicationcanbesimplifiedenoughforuseinaconflictsituation.TextTextWordsNotesDiscussionHomeWhateverthechallenges,theUniversityofVienna’sMr.Zeilingersaid,thesatelliteputsChinaandthefieldofquantummechanicsonthevergeofasignificanttechnologicalbreakthrough.“Inthelongrun,thereisagoodchancethatthiswillreplaceourcurrentcommunicationstechnology,”hesaid.“Iseenobasicreasonwhyitwon’thappen.”TextTextWordsNotesDiscussionHomeInaJanuaryinterviewwiththejournalNature,Mr.PansaidthesatelliteshowedChina’sscientistshadstoppedfollowinginthefootstepsofothers.Todrivethepointhome,ChinesestatemediaonMondaysaidthesatellitehadbeennamedMic