Relativistic Quantum Measurement and Decoherence: Lectures of a Workshop Held at the Istituto Italiano per gli Studi Filosofici Naples, April 9–10, 1999 PDF
Preview Relativistic Quantum Measurement and Decoherence: Lectures of a Workshop Held at the Istituto Italiano per gli Studi Filosofici Naples, April 9–10, 1999
Lecture Notes in Physics EditorialBoard R.Beig,Wien,Austria J.Ehlers,Potsdam,Germany U.Frisch,Nice,France K.Hepp,Zu¨rich,Switzerland W.Hillebrandt,Garching,Germany D.Imboden,Zu¨rich,Switzerland R.L.Jaffe,Cambridge,MA,USA R.Kippenhahn,Go¨ttingen,Germany R.Lipowsky,Golm,Germany H.v.Lo¨hneysen,Karlsruhe,Germany I.Ojima,Kyoto,Japan H.A.Weidenmu¨ller,Heidelberg,Germany J.Wess,Mu¨nchen,Germany J.Zittartz,Ko¨ln,Germany 3 Berlin Heidelberg NewYork Barcelona HongKong London Milan Paris Singapore Tokyo TheEditorialPolicyforProceedings TheseriesLectureNotesinPhysicsreportsnewdevelopmentsinphysicalresearchandteaching–quickly, informally,andatahighlevel.Theproceedingstobeconsideredforpublicationinthisseriesshouldbelimited toonlyafewareasofresearch,andtheseshouldbecloselyrelatedtoeachother.Thecontributionsshouldbe ofahighstandardandshouldavoidlengthyredraftingsofpapersalreadypublishedorabouttobepublished elsewhere.Asawhole,theproceedingsshouldaimforabalancedpresentationofthethemeoftheconference includingadescriptionofthetechniquesusedandenoughmotivationforabroadreadership.Itshouldnot beassumedthatthepublishedproceedingsmustreflecttheconferenceinitsentirety.(Alistingorabstracts ofpaperspresentedatthemeetingbutnotincludedintheproceedingscouldbeaddedasanappendix.) 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Westronglyrecommendthatyoumakeuseofthisoffer,sincetheresultwillbeabookofconsiderably improvedtechnicalquality.Toavoidmistakesandtime-consumingcorrespondenceduringtheproduction periodtheconferenceeditorsshouldrequestspecialinstructionsfromthepublisherwellbeforethebeginning oftheconference.Manuscriptsnotmeetingthetechnicalstandardoftheserieswillhavetobereturnedfor improvement. ForfurtherinformationpleasecontactSpringer-Verlag,PhysicsEditorialDepartmentII,Tiergartenstrasse17, D-69121Heidelberg,Germany Serieshomepage–http://www.springer.de/phys/books/lnpp Heinz-Peter Breuer Francesco Petruccione (Eds.) Relativistic Quantum Measurement and Decoherence Lectures of a Workshop Held at the Istituto Italiano per gli Studi Filosofici Naples, April 9–10, 1999 1 3 Editors Heinz-PeterBreuer FrancescoPetruccione UniversityofFreiburg FacultyofPhysics Hermann-Herder-Strasse3 79104Freiburg,Germany LibraryofCongressCataloging-in-PublicationDataappliedfor. DieDeutscheBibliothek-CIP-Einheitsaufnahme Relativisticquantummeasurementanddecoherence:lecturesofa workshopheldattheIstitutoItalianopergliStudiFilosofici, Naples,April9-11,1999/Heinz-PeterBreuer;Francesco Petruccione(ed.).-Berlin;Heidelberg;NewYork;Barcelona;Hong Kong;London;Milan;Paris;Singapore;Tokyo:Springer,2000 (Lecturenotesinphysics;Vol.559) (Physicsandastronomyonlinelibrary) ISBN3-540-41061-9 ISSN0075-8450 ISBN3-540-41061-9Springer-VerlagBerlinHeidelbergNewYork Thisworkissubjecttocopyright.Allrightsarereserved,whetherthewholeorpartofthe materialisconcerned,specificallytherightsoftranslation,reprinting,reuseofillustra- tions, recitation, broadcasting, reproduction on microfilm or in any other way, and storageindatabanks.Duplicationofthispublicationorpartsthereofispermittedonly undertheprovisionsoftheGermanCopyrightLawofSeptember9,1965,initscurrent version,andpermissionforusemustalwaysbeobtainedfromSpringer-Verlag.Violations areliableforprosecutionundertheGermanCopyrightLaw. Springer-VerlagBerlinHeidelbergNewYork amemberofBertelsmannSpringerScience+BusinessMediaGmbH ©Springer-VerlagBerlinHeidelberg2000 PrintedinGermany Theuseofgeneraldescriptivenames,registerednames,trademarks,etc.inthispublication doesnotimply,evenintheabsenceofaspecificstatement,thatsuchnamesareexempt fromtherelevantprotectivelawsandregulationsandthereforefreeforgeneraluse. Typesetting:Camera-readybytheauthors/editor Coverdesign:design&production,Heidelberg Printedonacid-freepaper SPIN:10783595 57/3141/du-543210 Preface The development of a consistent picture of the processes of decoherence and quantum measurement is among the most interesting fundamental problems with far-reaching consequences for our understanding of the physical world. A satisfactory solution of this problem requires a treatment which is com- patiblewiththetheoryofrelativity,andmanydiverseapproachestosolveor circumvent the arising difficulties have been suggested. This volume collects the contributions of a workshop on Relativistic Quantum Measurement and Decoherence held at the Istituto Italiano per gli Studi Filosofici in Naples, April 9-10, 1999. The workshop was intended to continue a previous meeting entitledOpenSystemsandMeasurementinRelativisticQuantumTheory,the talks of which are also published in the Lecture Notes in Physics Series (Vol. 526). The different attitudes and concepts used to approach the decoherence andquantummeasurementproblemledtolivelydiscussionsduringthework- shopandarereflectedinthediversityofthecontributions.Inthefirstarticle themeasurementproblemisintroducedandthevariouslevelsofcompatibility withspecialrelativityarecriticallyreviewed.Inothercontributionstheroˆles of non-locality and entanglement in quantum measurement and state vector preparation are discussed from a pragmatic quantum-optical and quantum- information perspective. In a further article the viewpoint of the consistent histories approach is presented and a new criterion is proposed which refines the notion of consistency. Also, the phenomenon of decoherence is examined from an open system’s point of view and on the basis of superselection rules employing group theoretic and algebraic methods. The notions of hard and softsuperselectionrulesareaddressed,aswellasthedistinctionbetweenreal andapparentlossofquantumcoherence.Furthermore,theemergenceofreal decoherence in quantum electrodynamics is studied through an investigation of the reduced dynamics of the matter variables and is traced back to the emission of bremsstrahlung. It is a pleasure to thank Avv. Gerardo Marotta, the President of the Is- tituto Italiano per gli Studi Filosofici, for suggesting and making possible an interesting workshop in the fascinating environment of Palazzo Serra di Cassano. Furthermore, we would like to express our gratidude to Prof. An- tonio Gargano, the General Secretaty of the Istituto Italiano per gli Studi Filosofici, for his friendly and efficient local organization. We would also like to thank the participants of the workshop. Freiburg im Breisgau, Heinz-Peter Breuer July 2000 Francesco Petruccione List of Participants Albert, David Z. Department of Philosophy Columbia University 1150 Amsterdam Avenue New York, NY 10027, USA [email protected] Braunstein, Samuel L. SEECS, Dean Street University of Wales Bangor LL57 1UT, United Kingdom [email protected] Breuer, Heinz-Peter Fakulta¨t fu¨r Physik Universita¨t Freiburg Hermann-Herder-Str. 3 D-79104 Freiburg i. Br., Germany [email protected] Giulini, Domenico Universita¨t Zu¨rich Insitut fu¨r Theoretische Physik Winterthurerstr. 190 CH-8057 Zu¨rich, Schweiz [email protected] Kent, Adrian Department of Applied mathematics and Theoretical Physics University of Cambridge Silver Street Cambridge CB3 9EW, United Kingdom [email protected] Petruccione, Francesco Fakulta¨t fu¨r Physik Universita¨t Freiburg Hermann-Herder-Str. 3 D-79104 Freiburg i. Br., Germany and VIII Istituto Italiano per gli Studi Filosofici Palazzo Serra di Cassano Via Monte di Dio, 14 I-80132 Napoli, Italy [email protected] Popescu, Sandu H. H. Wills Physics Laboratory University of Bristol Tyndall Avenue Bristol BS8 1TL, United Kingdom and BRIMS, Hewlett-Packard Laboratories Stoke Gifford Bristol, BS12 6QZ, United Kingdom [email protected] Unruh, William G. Department of Physics University of British Columbia 6224 Agricultural Rd. Vancouver, B. C., Canada V6T1Z1 [email protected] Contents Special Relativity as an Open Question....................... 1 David Z. Albert 1 The Measurement Problem.................................... 1 2 Degrees of Compatibility with Special Relativity ................. 3 3 The Theory I Have in Mind ................................... 8 4 Approximate Compatibility with Special Relativity............... 10 References ..................................................... 13 Event-Ready Entanglement................................... 15 Pieter Kok, Samuel L. Braunstein 1 Introduction................................................. 15 2 Parametric Down-Conversion and Entanglement Swapping ........ 17 3 Event-Ready Entanglement ................................... 21 4 Conclusions ................................................. 25 Appendix: Transformation of Maximally Entangled States............ 26 References ..................................................... 28 Radiation Damping and Decoherence in Quantum Electrody- namics........................................................ 31 Heinz–Peter Breuer, Francesco Petruccione 1 Introduction................................................. 31 2 Reduced Density Matrix of the Matter Degrees of Freedom........ 33 3 The Influence Phase Functional of QED ........................ 35 4 The Interaction of a Single Electron with the Radiation Field...... 41 5 Decoherence Through the Emission of Bremsstrahlung............ 51 6 The Harmonically Bound Electron in the Radiation Field ......... 60 7 Destruction of Coherence of Many-Particle States ................ 61 8 Conclusions ................................................. 62 References ..................................................... 64 Decoherence: A Dynamical Approach to Superselection Rules? 67 Domenico Giulini 1 Introduction................................................. 67 2 Elementary Concepts......................................... 69 3 Superselection Rules via Symmetry Requirements ................ 79 4 Bargmann’s Superselection Rule ............................... 81 5 Charge Superselection Rule ................................... 85 References ..................................................... 90 VI Quantum Histories and Their Implications.................... 93 Adrian Kent 1 Introduction................................................. 93 2 Partial Ordering of Quantum Histories.......................... 94 3 Consistent Histories .......................................... 95 4 Consistent Sets and Contrary Inferences: A Brief Review.......... 97 5 Relation of Contrary Inferences and Subspace Implications ........ 101 6 Ordered Consistent Sets of Histories............................ 102 7 Ordered Consistent Sets and Quasiclassicality ................... 104 8 Ordering and Ordering Violations: Interpretation ................ 108 9 Conclusions ................................................. 110 Appendix: Ordering and Decoherence Functionals................... 111 References ..................................................... 114 Quantum Measurements and Non-locality .................... 117 Sandu Popescu, Nicolas Gisin 1 Introduction................................................. 117 2 Measurements on 2-Particle Systems with Parallel or Anti-Parallel Spins............................. 118 3 Conclusions ................................................. 123 References ..................................................... 123 False Loss of Coherence....................................... 125 William G. Unruh 1 Massive Field Heat Bath and a Two Level System ............... 125 2 Spin-1 System............................................... 126 2 3 Oscillator ................................................... 131 4 Spin Boson Problem.......................................... 133 5 Instantaneous Change ........................................ 136 6 Discussion .................................................. 138 References ..................................................... 140 Special Relativity as an Open Question David Z. Albert Department of Philosophy, Columbia University, New York, USA Abstract. Thereseemstometobeawayofreadingsomeofthetroublewehave lately been having with the quantum-mechanical measurement problem (not the standard way, mind you, and certainly not the only way; but a way that nonethe- lessbeworthexploring)thatsuggeststhattherearefairlyprosaicphysicalcircum- stances under which it might not be entirely beside the point to look around for observableviolationsofthespecialtheoryofrelativity.ThesuggestionIhaveinmind is connected with attempts over the past several years to write down a relativistic field-theoretic version of the dynamical reduction theory of Ghirardi, Rimini, and Weber [Physical Review D34, 470-491 (1986)], or rather it is connected with the persistentfailure ofthoseattempts,itisconnectedwiththemostobviousstrategy for giving those attempts up. And that (in the end) is what this paper is going to be about. 1 The Measurement Problem Letmestartout(however)byremindingyouofpreciselywhatthequantum- mechanical problem of measurement is, and then talk a bit about where things stand at present vis-a-vis the general question of the compatibility of quantum mechanics with the special theory of relativity, and then I want to present the simple, standard, well-understood non-relativistic version of the Ghirardi, Rimini, and Weber (GRW) theory [1], and then (at last) I will get into the business I referred to above. First the measurement problem. Suppose that every system in the world invariablyevolvesinaccordancewiththelineardeterministicquantum-mecha- nicalequationsofmotionandsupposethatM isagoodmeasuringinstrument for a certain observable A of a certain physical system S. What it means for M to be a “good” measuring instrument for A is just that for all eigenvalues a of A: i |ready(cid:2) |A=a (cid:2) −→|indicates that A=a (cid:2) |A=a (cid:2) , (1) M i S i M i S where |ready(cid:2) is that state of the measuring instrument M in which M M is prepared to carry out a measurement of A, “−→” denotes the evolution of the state of M + S during the measurement-interaction between those two systems, and |indicates that A = a (cid:2) is that state of the measuring i M instrument in which, say, its pointer is pointing to the the a -position on its i dial. That is: what it means for M to be a “good” measuring instrument for A is just that M invariably indicates the correct value for A in all those states of S in which A has any definite value. H.-P.BreuerandF.Petruccione(Eds.):Proceedings1999,LNP559,pp.1–13,2000. (cid:1)c Springer-VerlagBerlinHeidelberg2000
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