Bibliographic Guide to the Foundations of Quantum Mechanics and Quantum Information

Total Page:16

File Type:pdf, Size:1020Kb

Bibliographic Guide to the Foundations of Quantum Mechanics and Quantum Information Bibliographic guide to the foundations of quantum mechanics and quantum information Ad¶an Cabello¤ Departamento de F¶³sica Aplicada II, Universidad de Sevilla, 41012 Sevilla, Spain (Dated: January 22, 2007) PACS numbers: 01.30.Rr, 01.30.Tt, 03.65.-w, 03.65.Ca, 03.65.Ta, 03.65.Ud, 03.65.Wj, 03.65.Xp, 03.65.Yz, 03.67.-a, 03.67.Dd, 03.67.Hk, 03.67.Lx, 03.67.Mn, 03.67.Pp, 03.75.Gg, 42.50.Dv \[T]here's much more di®erence (. ) be- Most of this work was developed for personal use, and tween a human being who knows quantum is therefore biased towards my own preferences, tastes mechanics and one that doesn't than between and phobias. This means that the selection is incom- one that doesn't and the other great apes." plete, although some e®ort has been made to cover some gaps. Some closely related subjects such as quantum M. Gell-Mann chaos, quantum structures, geometrical phases, relativis- at the annual meeting of the American Association for tic quantum mechanics, or Bose-Einstein condensates the Advancement of Science, Chicago 11 Feb. 1992. have been deliberately excluded. Reported in [Siegfried 00], pp. 177-178. Please note that this guide has been directly written in LaTeX (REVTeX4) and therefore a corresponding Bib- \The Copenhagen interpretation is quan- TeX ¯le does not exist, so do not ask for it. tum mechanics." Please e-mail corrections to [email protected] (under sub- ject: Error). Indicate the references as, for instance, [von R. Peierls. Neumann 31], not by its number (since this number Reported in [Khal¯n 90], p. 477. may have been changed in a later version). Suggestions \Quantum theory needs no `interpreta- for additional (essential) references which ought to be in- tion'." cluded are welcome (please e-mail to [email protected] under subject: Suggestion). C. A. Fuchs and A. Peres. Title of [Fuchs-Peres 00 a]. Acknowledgments \Unperformed experiments have no re- sults." The author thanks those who have pointed out er- rors, made suggestions, and sent copies of papers, lists of A. Peres. personal publications, and lists of references on speci¯c Title of [Peres 78 a]. subjects. Special thanks are given to T. D. Angelidis, J. L. Cereceda, R. Onofrio, A. Peres, E. Santos, C. Serra, M. Simonius, R. G. Stomphorst, and A. Y. Vlasov for Introduction their help on the improvement of this guide. This work was partially supported by the Universidad de Sevilla This is a collection of references (papers, books, grant OGICYT-191-97, the Junta de Andaluc¶³aProjects preprints, book reviews, Ph. D. thesis, patents, web FQM-239 (1998, 2000, 2002, 2004), and the Spanish Min- sites, etc.), sorted alphabetically and (some of them) isterio de Ciencia y Tecnolog¶³aProjects BFM2000-0529, classi¯ed by subject, on foundations of quantum me- BFM2001-3943, and BFM2002-02815. chanics and quantum information. Speci¯cally, it cov- ers hidden variables (\no-go" theorems, experiments), \interpretations" of quantum mechanics, entanglement, quantum e®ects (quantum Zeno e®ect, quantum era- sure, \interaction-free" measurements, quantum \non- demolition" measurements), quantum information (cryp- tography, cloning, dense coding, teleportation), and quantum computation. For a more detailed account of the subjects covered, please see the table of contents in the next pages. ¤Electronic address: [email protected] 2 Contents 3. Local immeasurability or indistinguishability (\nonlocality Introduction 1 without entanglement") 9 I. Experiments on Bell's theorem 9 Acknowledgments 1 1. Real experiments 9 2. Proposed gedanken experiments 9 I. Hidden variables 4 3. EPR with neutral kaons 9 A. Von Neumann's impossibility proof 4 4. Reviews 10 B. Einstein-Podolsky-Rosen's argument of 5. Experimental proposals on GHZ proof, incompleteness of QM 4 preparation of GHZ states 10 1. General 4 6. Experimental proposals on Hardy's 2. Bohr's reply to EPR 4 proof 10 C. Gleason theorem 4 7. Some criticisms of the experiments on D. Other proofs of impossibility of hidden Bell's inequalities. Loopholes 10 variables 5 E. Bell-Kochen-Specker theorem 5 II. \Interpretations" 11 1. The BKS theorem 5 A. Copenhagen interpretation 11 2. From the BKS theorem to the BKS B. De Broglie's \pilot wave" and Bohm's with locality theorem 5 \causal" interpretations 11 3. The BKS with locality theorem 5 1. General 11 2. Tunneling times in Bohmian mechanics 12 4. Probabilistic versions of the BKS theorem 5 C. \Relative state", \many worlds", and \many minds" interpretations 12 5. The BKS theorem and the existence of D. Interpretations with explicit collapse or dense \KS-colourable" subsets of dynamical reduction theories (spontaneous projectors 5 localization, nonlinear terms in SchrÄodinger 6. The BKS theorem in real experiments 6 equation, stochastic theories) 12 7. The BKS theorem for a single qubit 6 E. Statistical (or ensemble) interpretation 13 F. Bell's inequalities 6 F. \Modal" interpretations 13 1. First works 6 G. \It from bit" 13 2. Bell's inequalities for two spin-s H. \Consistent histories" (or \decoherent particles 6 histories") 13 3. Bell's inequalities for two particles and I. Decoherence and environment induced more than two observables per particle 6 superselection 14 4. Bell's inequalities for n particles 6 J. Time symmetric formalism, pre- and 5. Which states violate Bell's inequalities? 7 post-selected systems, \weak" 6. Other inequalities 7 measurements 14 7. Inequalities to detect genuine n-particle K. The transactional interpretation 14 nonseparability 7 L. The Ithaca interpretation (\correlations 8. Herbert's proof of Bell's theorem 7 without correlata") and the observation 9. Mermin's statistical proof of Bell's that correlations cannot be regarded as theorem 7 objective local properties 14 G. Bell's theorem without inequalities 7 1. Greenberger-Horne-Zeilinger's proof 7 III. Composite systems, preparations, and 2. Peres' proof of impossibility of recursive measurements 14 elements of reality 8 A. States of composite systems 14 3. Hardy's proof 8 1. Schmidt decomposition 14 4. Two-observer \all versus nothing" 2. Entanglement measures 15 proof 8 3. Separability criteria 15 5. Other algebraic proofs of no-local 4. Multiparticle entanglement 15 hidden variables 8 5. Entanglement swapping 16 6. Classical limits of no-local hidden 6. Entanglement distillation variables proofs 8 (concentration and puri¯cation) 16 H. Other \nonlocalities" 8 7. Disentanglement 16 1. \Nonlocality" of a single particle 8 8. Bound entanglement 16 2. Violations of local realism exhibited in 9. Entanglement as a catalyst 17 sequences of measurements (\hidden B. State determination, state discrimination, nonlocality") 8 and measurement of arbitrary observables 17 3 1. State determination, quantum 5. Quantum random walks 29 tomography 17 6. General and others 29 2. Generalized measurements, positive C. Quantum logic gates 29 operator-valued measurements D. Schemes for reducing decoherence 29 (POVMs), discrimination between E. Quantum error correction 29 non-orthogonal states 17 F. Decoherence-free subspaces and subsystems 30 3. State preparation and measurement of G. Experiments and experimental proposals 30 arbitrary observables 18 4. Stern-Gerlach experiment and its VII. Miscellaneous 30 successors 18 A. Textbooks 30 5. Bell operator measurements 18 B. History of quantum mechanics 31 C. Biographs 31 IV. Quantum e®ects 18 D. Philosophy of the founding fathers 31 6. Quantum Zeno and anti-Zeno e®ects 18 E. Quantum logic 31 7. Reversible measurements, delayed F. Superselection rules 31 choice and quantum erasure 19 G. Relativity and the instantaneous change of 8. Quantum nondemolition measurements 19 the quantum state by local interventions 32 9. \Interaction-free" measurements 19 H. Quantum cosmology 32 10. Quantum-enhanced measurements 20 VIII. Bibliography 33 V. Quantum information 20 A. 33 A. Quantum cryptography 20 B. 58 1. General 20 C. 115 2. Proofs of security 21 D. 147 3. Quantum eavesdropping 21 E. 166 4. Quantum key distribution with F. 175 orthogonal states 21 G. 194 5. Experiments 21 H. 223 6. Commercial quantum cryptography 22 I. 253 J. 256 7. Quantum detectable Byzantine K. 265 agrement |or broadcast| and liar L. 289 detection 22 M. 310 B. Cloning and deleting quantum states 22 N. 338 C. Quantum bit commitment 23 O. 344 D. Secret sharing and quantum secret sharing 23 P. 352 E. Quantum authentication 23 Q. 380 F. Teleportation of quantum states 23 R. 381 1. General 23 S. 396 2. Experiments 24 T. 437 G. Telecloning 25 U. 449 H. Dense coding 25 V. 451 I. Remote state preparation and measurement25 W. 465 J. Classical information capacity of quantum X. 481 channels 25 Y. 483 K. Quantum coding, quantum data Z. 488 compression 26 L. Reducing the communication complexity with quantum entanglement 26 M. Quantum games and quantum strategies 26 N. Quantum clock synchronization 27 VI. Quantum computation 27 A. General 27 B. Quantum algorithms 28 1. Deutsch-Jozsa's and Simon's 28 2. Factoring 28 3. Searching 28 4. Simulating quantum systems 28 4 I. HIDDEN VARIABLES 91]; [Deltete-Guy 91] (Einstein on EPR), [H¶ajek- Bub 92] (EPR's argument is \better" than later argu- A. Von Neumann's impossibility proof ments by Einstein, contrary to Fine's opinion), [Com- bourieu 92] (Popper on EPR, including a letter by Ein- [von Neumann 31], [von Neumann 32] stein from 1935 with containing a brief presentation of (Sec. IV. 2), [Hermann 35], [Albertson 61], [Komar EPR's argument), [Bohm-Hiley 93] (Sec. 7. 7, analy- 62], [Bell 66, 71], [Capasso-Fortunato-Selleri 70], sis of the EPR experiment according to the \causal" in- [Wigner 70, 71], [Clauser 71 a, b], [Gudder 80] terpretation), [Schatten 93] (hidden-variable model for (includes an example in two dimensions showing that the EPR experiment), [Hong-yi-Klauder 94] (common the expected value cannot be additive), [Selleri 90] eigenvectors of relative position and total momentum of (Chap.
Recommended publications
  • Information and Entropy in Quantum Theory
    Information and Entropy in Quantum Theory O J E Maroney Ph.D. Thesis Birkbeck College University of London Malet Street London WC1E 7HX arXiv:quant-ph/0411172v1 23 Nov 2004 Abstract Recent developments in quantum computing have revived interest in the notion of information as a foundational principle in physics. It has been suggested that information provides a means of interpreting quantum theory and a means of understanding the role of entropy in thermodynam- ics. The thesis presents a critical examination of these ideas, and contrasts the use of Shannon information with the concept of ’active information’ introduced by Bohm and Hiley. We look at certain thought experiments based upon the ’delayed choice’ and ’quantum eraser’ interference experiments, which present a complementarity between information gathered from a quantum measurement and interference effects. It has been argued that these experiments show the Bohm interpretation of quantum theory is untenable. We demonstrate that these experiments depend critically upon the assumption that a quantum optics device can operate as a measuring device, and show that, in the context of these experiments, it cannot be consistently understood in this way. By contrast, we then show how the notion of ’active information’ in the Bohm interpretation provides a coherent explanation of the phenomena shown in these experiments. We then examine the relationship between information and entropy. The thought experiment connecting these two quantities is the Szilard Engine version of Maxwell’s Demon, and it has been suggested that quantum measurement plays a key role in this. We provide the first complete description of the operation of the Szilard Engine as a quantum system.
    [Show full text]
  • Notes on the Theory of Quantum Clock
    NOTES ON THE THEORY OF QUANTUM CLOCK I.Tralle1, J.-P. Pellonp¨a¨a2 1Institute of Physics, University of Rzesz´ow,Rzesz´ow,Poland e-mail:[email protected] 2Department of Physics, University of Turku, Turku, Finland e-mail:juhpello@utu.fi (Received 11 March 2005; accepted 21 April 2005) Abstract In this paper we argue that the notion of time, whatever complicated and difficult to define as the philosophical cat- egory, from physicist’s point of view is nothing else but the sum of ’lapses of time’ measured by a proper clock. As far as Quantum Mechanics is concerned, we distinguish a special class of clocks, the ’atomic clocks’. It is because at atomic and subatomic level there is no other possibility to construct a ’unit of time’ or ’instant of time’ as to use the quantum transitions between chosen quantum states of a quantum ob- ject such as atoms, atomic nuclei and so on, to imitate the periodic circular motion of a clock hand over the dial. The clock synchronization problem is also discussed in the paper. We study the problem of defining a time difference observable for two-mode oscillator system. We assume that the time dif- ference obsevable is the difference of two single-mode covariant Concepts of Physics, Vol. II (2005) 113 time observables which are represented as a time shift covari- ant normalized positive operator measures. The difficulty of finding the correct value space and normalization for time dif- ference is discussed. 114 Concepts of Physics, Vol. II (2005) Notes on the Theory of Quantum Clock And the heaven departed as a scroll when it is rolled together;..
    [Show full text]
  • Engineering Ultrafast Quantum Frequency Conversion
    Engineering ultrafast quantum frequency conversion Der Naturwissenschaftlichen Fakultät der Universität Paderborn zur Erlangung des Doktorgrades Dr. rer. nat. vorgelegt von BENJAMIN BRECHT aus Nürnberg To Olga for Love and Support Contents 1 Summary1 2 Zusammenfassung3 3 A brief history of ultrafast quantum optics5 3.1 1900 – 1950 ................................... 5 3.2 1950 – 2000 ................................... 6 3.3 2000 – today .................................. 8 4 Fundamental theory 11 4.1 Waveguides .................................. 11 4.1.1 Waveguide modelling ........................ 12 4.1.2 Spatial mode considerations .................... 14 4.2 Light-matter interaction ........................... 16 4.2.1 Nonlinear polarisation ........................ 16 4.2.2 Three-wave mixing .......................... 17 4.2.3 More on phasematching ...................... 18 4.3 Ultrafast pulses ................................. 21 4.3.1 Time-bandwidth product ...................... 22 4.3.2 Chronocyclic Wigner function ................... 22 4.3.3 Pulse shaping ............................. 25 5 From classical to quantum optics 27 5.1 Speaking quantum .............................. 27 iii 5.1.1 Field quantisation in waveguides ................. 28 5.1.2 Quantum three-wave mixing .................... 30 5.1.3 Time-frequency representation .................. 32 5.1.3.1 Joint spectral amplitude functions ........... 32 5.1.3.2 Schmidt decomposition ................. 35 5.2 Understanding quantum ........................... 36 5.2.1 Parametric
    [Show full text]
  • Notes on the Theory of Quantum Clock
    NOTES ON THE THEORY OF QUANTUM CLOCK I.Tralle1, J.-P. Pellonp¨a¨a2 1Institute of Physics, University of Rzesz´ow,Rzesz´ow,Poland e-mail:[email protected] 2Department of Physics, University of Turku, Turku, Finland e-mail:juhpello@utu.fi (Received 11 March 2005; accepted 21 April 2005) Abstract In this paper we argue that the notion of time, whatever complicated and difficult to define as the philosophical cat- egory, from physicist’s point of view is nothing else but the sum of ’lapses of time’ measured by a proper clock. As far as Quantum Mechanics is concerned, we distinguish a special class of clocks, the ’atomic clocks’. It is because at atomic and subatomic level there is no other possibility to construct a ’unit of time’ or ’instant of time’ as to use the quantum transitions between chosen quantum states of a quantum ob- ject such as atoms, atomic nuclei and so on, to imitate the periodic circular motion of a clock hand over the dial. The clock synchronization problem is also discussed in the paper. We study the problem of defining a time difference observable for two-mode oscillator system. We assume that the time dif- ference obsevable is the difference of two single-mode covariant Concepts of Physics, Vol. II (2005) 113 time observables which are represented as a time shift covari- ant normalized positive operator measures. The difficulty of finding the correct value space and normalization for time dif- ference is discussed. 114 Concepts of Physics, Vol. II (2005) Notes on the Theory of Quantum Clock And the heaven departed as a scroll when it is rolled together;..
    [Show full text]
  • The Boundaries of Nature: Special & General Relativity and Quantum
    “The Boundaries of Nature: Special & General Relativity and Quantum Mechanics, A Second Course in Physics” Edwin F. Taylor's acceptance speech for the 1998 Oersted medal presented by the American Association of Physics Teachers, 6 January 1998 Edwin F. Taylor Center for Innovation in Learning, Carnegie Mellon University, Pittsburgh, PA 15213 (Now at 22 Hopkins Road, Arlington, MA 02476-8109, email [email protected] , web http://www.artsaxis.com/eftaylor/ ) ABSTRACT Public hunger for relativity and quantum mechanics is insatiable, and we should use it selectively but shamelessly to attract students, most of whom will not become physics majors, but all of whom can experience "deep physics." Science, engineering, and mathematics students, indeed anyone comfortable with calculus, can now delve deeply into special and general relativity and quantum mechanics. Big chunks of general relativity require only calculus if one starts with the metric describing spacetime around Earth or black hole. Expressions for energy and angular momentum follow, along with orbit predictions for particles and light. Feynman's Sum Over Paths quantum theory simply commands the electron: Explore all paths. Students can model this command with the computer, pointing and clicking to tell the electron which paths to explore; wave functions and bound states arise naturally. A second full year course in physics covering special relativity, general relativity, and quantum mechanics would have wide appeal -- and might also lead to significant advancements in upper-level courses for the physics major. © 1998 American Association of Physics Teachers INTRODUCTION It is easy to feel intimidated by those who have in the past received the Oersted Medal, especially those with whom I have worked closely in the enterprise of physics teaching: Edward M.
    [Show full text]
  • Time and Frequency Division Report
    Time and Frequency Division Goal The broad mission of the Time and Frequency Division is to provide official U.S. time and related quantities to support a wide range of uses in industry, national infrastructure, research, and among the general public. DIVISION STRATEGY The division’s research and metrology ac- tivities comprise three vertically integrated components, each of which constitutes a strategic element: 1. Official time: Accurate and precise realization of official U.S. time (UTC) and frequency. 2. Dissemination: A wide range of mea- surement services to efficiently and effectively distribute U.S. time and frequency and related quantities – pri- marily through free broadcast services available to any user 24/7/365. 3. Research: Research and technolo- gy development to improve time and frequency standards and dissemination. Part of this research includes high-impact programs in areas such as quantum information processing, atom-based sensors, and laser development and applications, which evolved directly from research to make better frequency standards (atomic clocks). Overview These three components – official time, dissemination, and research – are closely integrated. For example, all Division dissemination services tie directly to the Division’s realization of official time (UTC), and much of the Division’s research is enabled by the continual availability of precision UTC. Our modern technology and economy depend critically on the broad availability of precision timing, frequency, and synchronization. NIST realization and dissemination of time and frequency – continually improved by NIST research and development – is a crucial part of a series of informal national timing infrastructures that enable such essential technologies as: • Telecommunications and computer networks • Utility distribution • GPS, widely available in every cell phone and smartphone as well as GPS receivers • Electronic financial transactions 1 • National security and intelligence applications • Research Strategic Goal: Official Time Intended Outcome and Background U.S.
    [Show full text]
  • Quantum Physics in Space
    Quantum Physics in Space Alessio Belenchiaa,b,∗∗, Matteo Carlessob,c,d,∗∗, Omer¨ Bayraktare,f, Daniele Dequalg, Ivan Derkachh, Giulio Gasbarrii,j, Waldemar Herrk,l, Ying Lia Lim, Markus Rademacherm, Jasminder Sidhun, Daniel KL Oin, Stephan T. Seidelo, Rainer Kaltenbaekp,q, Christoph Marquardte,f, Hendrik Ulbrichtj, Vladyslav C. Usenkoh, Lisa W¨ornerr,s, Andr´eXuerebt, Mauro Paternostrob, Angelo Bassic,d,∗ aInstitut f¨urTheoretische Physik, Eberhard-Karls-Universit¨atT¨ubingen, 72076 T¨ubingen,Germany bCentre for Theoretical Atomic,Molecular, and Optical Physics, School of Mathematics and Physics, Queen's University, Belfast BT7 1NN, United Kingdom cDepartment of Physics,University of Trieste, Strada Costiera 11, 34151 Trieste,Italy dIstituto Nazionale di Fisica Nucleare, Trieste Section, Via Valerio 2, 34127 Trieste, Italy eMax Planck Institute for the Science of Light, Staudtstraße 2, 91058 Erlangen, Germany fInstitute of Optics, Information and Photonics, Friedrich-Alexander University Erlangen-N¨urnberg, Staudtstraße 7 B2, 91058 Erlangen, Germany gScientific Research Unit, Agenzia Spaziale Italiana, Matera, Italy hDepartment of Optics, Palacky University, 17. listopadu 50,772 07 Olomouc,Czech Republic iF´ısica Te`orica: Informaci´oi Fen`omensQu`antics,Department de F´ısica, Universitat Aut`onomade Barcelona, 08193 Bellaterra (Barcelona), Spain jDepartment of Physics and Astronomy, University of Southampton, Highfield Campus, SO17 1BJ, United Kingdom kDeutsches Zentrum f¨urLuft- und Raumfahrt e. V. (DLR), Institut f¨urSatellitengeod¨asieund
    [Show full text]
  • 1 Temporal Arrows in Space-Time Temporality
    Temporal Arrows in Space-Time Temporality (…) has nothing to do with mechanics. It has to do with statistical mechanics, thermodynamics (…).C. Rovelli, in Dieks, 2006, 35 Abstract The prevailing current of thought in both physics and philosophy is that relativistic space-time provides no means for the objective measurement of the passage of time. Kurt Gödel, for instance, denied the possibility of an objective lapse of time, both in the Special and the General theory of relativity. From this failure many writers have inferred that a static block universe is the only acceptable conceptual consequence of a four-dimensional world. The aim of this paper is to investigate how arrows of time could be measured objectively in space-time. In order to carry out this investigation it is proposed to consider both local and global arrows of time. In particular the investigation will focus on a) invariant thermodynamic parameters in both the Special and the General theory for local regions of space-time (passage of time); b) the evolution of the universe under appropriate boundary conditions for the whole of space-time (arrow of time), as envisaged in modern quantum cosmology. The upshot of this investigation is that a number of invariant physical indicators in space-time can be found, which would allow observers to measure the lapse of time and to infer both the existence of an objective passage and an arrow of time. Keywords Arrows of time; entropy; four-dimensional world; invariance; space-time; thermodynamics 1 I. Introduction Philosophical debates about the nature of space-time often centre on questions of its ontology, i.e.
    [Show full text]
  • Gravitational Redshift in Quantum-Clock Interferometry
    PHYSICAL REVIEW X 10, 021014 (2020) Gravitational Redshift in Quantum-Clock Interferometry Albert Roura Institute of Quantum Technologies, German Aerospace Center (DLR), Söflinger Straße 100, 89077 Ulm, Germany and Institut für Quantenphysik, Universität Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany (Received 29 September 2019; revised manuscript received 12 February 2020; accepted 5 March 2020; published 20 April 2020) The creation of delocalized coherent superpositions of quantum systems experiencing different relativistic effects is an important milestone in future research at the interface of gravity and quantum mechanics. This milestone could be achieved by generating a superposition of quantum clocks that follow paths with different gravitational time dilation and investigating the consequences on the interference signal when they are eventually recombined. Light-pulse atom interferometry with elements employed in optical atomic clocks is a promising candidate for that purpose, but it suffers from major challenges including its insensitivity to the gravitational redshift in a uniform field. All of these difficulties can be overcome with the novel scheme presented here, which is based on initializing the clock when the spatially separate superposition has already been generated and performing a doubly differential measurement where the differential phase shift between the two internal states is compared for different initialization times. This scheme can be exploited to test the universality of the gravitational redshift with delocalized coherent superpositions of quantum clocks, and it is argued that its experimental implementation should be feasible with a new generation of 10-meter atomic fountains that will soon become available. Interestingly, the approach also offers significant advantages for more compact setups based on guided interferometry or hybrid configurations.
    [Show full text]
  • Arxiv:Quant-Ph/0412146V1 19 Dec 2004 (Ukraine)
    Tunnelling Times: ( ) An Elementary Introduction † Giuseppe Privitera Facolt`adi Ingegneria, Universit`adi Catania, Catania, Italy; e-mail: [email protected] Giovanni Salesi Facolt`adi Ingegneria, Universit`adi Bergamo, Dalmine (BG), Italy; and I.N.F.N.–Sezione di Milano, Milan, Italy. Vladislav S. Olkhovsky Institute for Nuclear Research, Kiev-252028; Research Center ”Vidhuk”, Kiev, Ukraine. Erasmo Recami Facolt`adi Ingegneria, Universit`adi Bergamo, Dalmine (BG), Italy; and I.N.F.N.–Sezione di Milano, Milan, Italy; e-mail: [email protected] Abstract In this paper we examine critically and in detail some existing definitions for the tunnelling times, namely: the phase-time; the centroid-based times; the B¨uttiker and Landauer times; the Larmor times; the complex (path-integral and Bohm) times; the dwell time, and finally the generalized (Olkhovsky and Recami) dwell arXiv:quant-ph/0412146v1 19 Dec 2004 time, by adding also some numerical evaluations. Then, we pass to examine the equivalence between quantum tunnelling and “photon tunnelling” (evanescent waves propagation), with particular attention to tunnelling with Superluminal group- velocities (“Hartman effect”). At last, in an Appendix, we add a bird-eye view of all the experimental sectors of physics in which Superluminal motions seem to appear. (†) Work partially supported by INFN and MURST (Italy); and by I.N.R., Kiev, and S.K.S.T. (Ukraine). 1 1 Introduction Let us consider a freely moving particle which, at a given time, meets a potential barrier higher than its energy. As it is known, quantum mechanics implies a non-vanishing prob- ability for the particle to cross the barrier (i.e., the tunnel effect).
    [Show full text]
  • Feynman Clocks, Causal Networks, and the Origin of Hierarchical 'Arrows of Time' in Complex Systems from the Big Bang To
    Feynman Clocks, Causal Networks, and the Origin of Hierarchical ’Arrows of Time’ in Complex Systems from the Big Bang to the Brain’ Scott M. Hitchcock National Superconducting Cyclotron Laboratory (NSCL) Michigan State University, East Lansing, MI 48824-1321 E-mail: [email protected] A theory of time as the ‘information’ created in the irreversible decay process of excited or unstable states is proposed. Using new tools such as Feynman Clocks (FCs) [1], [2], [3], Feynman Detectors (FDs), Collective Excitation Networks (CENs), Sequential Excitation Networks (SENs), Plateaus of Complexity (POCs), Causal Networks, and Quantum Computation Methods [4], [5], [6] previously separate ’arrows of time’ describing change in complex systems ranging from the Big Bang to the emergence of consciousness in the Brain can be ’unified’. The ’direction’ and ’dimension’ of time are created from clock ordered sets of real number ’labels’ coupled to signal induced states in detectors and memory registers. The ’Problem of Time’ may be ’solved’ using the fundamental irreversible Quantum Arrow of Time (QAT) and reversible Classical Arrows of Time (CATs) to ’map’ information flow in causal networks. A pair of communicating electronic Feynman Clock/Detector units were built and used to demonstrate the basic principles of this new approach to a description of ‘time’. 1 Introduction Should we be prepared to see some day a new structure for the foundations of physics that does away with time?...Yes, because “time” is in trouble.-John Wheeler [7]. It has been suggested by Julian Barbour that ’time’ does not exist [8] thus adding one more complication to the ‘Problem of Time’.
    [Show full text]
  • Arxiv:2105.02304V1 [Quant-Ph] 5 May 2021 Relativity and Quantum Theory
    Page-Wootters formulation of indefinite causal order Veronika Baumann,1, 2, 3, ∗ Marius Krumm,1, 2, ∗ Philippe Allard Gu´erin,1, 2, 4 and Caslavˇ Brukner1, 2 1Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria 2Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria 3Faculty of Informatics, Universit`adella Svizzera italiana, Via G. Buffi 13, CH-6900 Lugano, Switzerland 4Perimeter Institute for Theoretical Physics, 31 Caroline St. N, Waterloo, Ontario, N2L 2Y5, Canada (Dated: May 7, 2021) One of the most fundamental open problems in physics is the unification of general relativity and quantum theory to a theory of quantum gravity. An aspect that might become relevant in such a theory is that the dynamical nature of causal structure present in general relativity displays quantum uncertainty. This may lead to a phenomenon known as indefinite or quantum causal structure, as captured by the process matrix framework. Due to the generality of that framework, however, for many process matrices there is no clear physical interpretation. A popular approach towards a quantum theory of gravity is the Page-Wootters formalism, which associates to time a Hilbert space structure similar to spatial position. By explicitly introducing a quantum clock, it allows to describe time-evolution of systems via correlations between this clock and said systems encoded in history states. In this paper we combine the process matrix framework with a generalization of the Page-Wootters formalism in which one considers several observers, each with their own discrete quantum clock. We describe how to extract process matrices from scenarios involving such observers with quantum clocks, and analyze their properties.
    [Show full text]