The GRA Beam-Splitter Experiments and Particle-Wav

arXiv:quant-ph/0503201v329Aug2006TheGRABeam-SplitterExperimentsandParticle-WaveDualityofLightP.N.KaloyerouDeptartmentofPhysics,SchoolofNaturalSciences,UniversityofZambia,POBox32379,Lusaka10101,Zambia∗†February1,2008AbstractGrangier,RogerandAspect(GRA)performedabeam-splitterexperimenttodemonstratetheparticlebehaviouroflightandaMach-Zehnderinterferometerexperimenttodemonstratethewavebehaviouroflight.Thedistinguishingfeatureoftheseexperimentsistheuseofagatingsystemtoproducenearidealsinglephotonstates.Withthedemonstrationofbothwaveandparticlebehaviour(intwomutuallyexclusiveexperiments)theyclaimtohavedemonstratedthedualparticle-wavebehaviouroflightandhencetohaveconfirmedBohr’sprincipleofcomple-mentarity.Thedemonstrationofthewavebehaviouroflightisnotindispute.Butwewanttodemonstrate,contrarytotheclaimsofGRA,thattheirbeam-splitterexperimentdoesnotcon-clusivelyconfirmtheparticlebehaviouroflight,andhencedoesnotconfirmparticle-waveduality,nor,moregenerally,doesitconfirmcomplementarity.OurdemonstrationconsistsofprovidingadetailedmodelbasedontheCausalInterpretationofQuantumFields(CIEM),whichdoesnotinvolvetheparticleconcept,ofGRA’swhich-pathexperiment.WewillalsogiveabriefoutlineofaCIEMmodelforthesecond,interference,GRAexperiment.1IntroductionTherearecountlessexperimentswhichdemonstratethewavebehaviouroflight.Twotypicalexper-imentsarethetwo-slitandMach-Zehnderarrangements.Thatsuchexperimentsdemonstratethewavebehaviouroflight,evenwherethelightisfeeble1[1],isnotindispute.Whatisquestionableistheexperimentalevidencefortheparticlebehaviouroflight.Toavoidlatermisunderstandingoftheessentialpointofthisarticle,itisnecessaryformetomakeclearthatIusetheterm‘particlebehaviour’torefertothedescriptionpriortothefinaldetectedresultbutnottothecharacterofthefinaldetectedresult.Thisisamorerestrictiveusagethanisusualintheliteraturewheretheterm‘particlebehaviour’alsoencompassesthecharacterofthefinaldetectedexperimentalresult.Ialsousetheterm‘particlebehaviour’intwocontextdependentways:InthecontextofBohr’sprincipleofcomplementarityIusetheterm‘particlebehaviour’torefertothedescriptionoftheexperimentintermsofthecomplementaryparticleconcept(understandingthataccordingtoBohrtheparticleconcept,alongwithothercomplementaryconcepts,isanabstractiontoaidthoughttowhichphysicalrealitycannotbeattached).InthecontextofthecausalinterpretationItaketheterm‘particlebehaviour’tobesynonymouswith‘particleontology’.Similarconsiderationsapplytotheterm‘wavebehaviour’,butthedistinctionhereisnotsocrucialsinceamainpointofthisarticleistodemonstratethatafinaldetectedresultshowingaparticlecharacterdoesnotforceaparticledescriptionorparticleontologypriortothefinaldetectedresult.Morerecentandinterestingexperimentsconcerningparticle-wavedualityandcomplementarityhavebeensuggestedandsubsequentlyperformed.Ghoseetal[2]proposedanexperimentinvolving∗emailaddress:[e-mail]†Alternativeaddress:TheUniversityofOxford,WolfsonCollege,LintonRoad,OxfordOX26UD,UK.1Byfeeblelightwemeanlightofsuchlowintensitythatonaverageonlyonephotonatatimeisintheapparatus.1tunnelingbetweentwocloselyspacedprismswhichhassincebeencarriedoutbyMizobuchietal[3](althoughthestatisticalresultsoftheexperimenthavebeenquestionedby[4,5,6]).Later,Bridaetal[6]realizedanexperimentsuggestedbyGhose[5]inwhichtunnelingatatwinprismarrangementisreplacedbybirefringence.AlsoofinterestisAfshar’sexperiment[7].Alloftheseexperimentsuselightandaimtodisproveorgeneralize2complementarity(whereasGRA’saimwastoconfirmcomplementarity)byclaimingtohavedemonstratedparticleandwavebehaviourinthesameexperiment.Inalloftheseexperiments,thefinaldetectionresultisattributedbytheauthorstowhich-pathinformationand,therefore,toparticlebehaviour(accordingtotheusualcriteriaacceptedintheliterature),buttheexperimentsaresoarrangedthatthelightundergoesaprocess(tunnelinginthecaseofMizobuchietal’sexperiment,birefringenceinBridaetal’sexperiment,andinterferenceinAfshar’sexperiment)whichtheauthorsclaimnecessarilyrepresentswavebehaviour.Hence,theyclaimtoobservewaveandparticlebehaviourinthesameexperiment.WedonotagreewiththemforthesamereasonsthatwedonotagreewithGRA’sclaimtohaveprovedcomplementarity,aclaimwewillargueagainstinthisarticle.Generally,wetaketheviewthatcomplementarityissoimprecisethatitcanneitherbeprovednordisproved.WewillelaboratefurtheronthisintherestofthearticlewithregardtotheGRAexperiments,butwewillalsobrieflydescribeandcommentfurtheronMizobuchietal’s,Bridaetal’sandAfshar’sexperimentsinsection6.WehavechosentofocusontheGRAexperimentsinthisarticlebecausetheywerethefirsttointroduceagatingsystemforproducinggenuinesinglephotonstatesandbecausetheirexperimentslendthemselvestoillustratingimportantfeaturesofCIEM.Further,thedetailedtreatmentofthisexperimentservesasamodelthatcanbeeasilyadaptedtothelaterexperiments,therebyprovidingargumentsagainsttheclaimsofobservingsimultaneouswaveandparticlebehaviourintheseexperiments.ThequantumeraserexperimentofKimetal[11]isavariantoftheWheelerdelayed-choiceidea[12,13].Theuseofparticle-wavedualityandcomplementarityinthisexperiments