DOCSLIB.ORG

Testing Quantum Mechanics: a Statistical Approach

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Testing Quantum Mechanics: a Statistical Approach Quantum Measurements and Quantum Metrology Mini Review • DOI: 10.2478/qmetro-2013-0007 • QMTR • 2013 • 84-109 Testing quantum mechanics: a statistical approach Abstract As experiments continue to push the quantum-classical Mankei Tsang1,2∗ boundary using increasingly complex dynamical systems, the interpretation of experimental data becomes more and more 1 Department of Electrical and Computer Engineering, challenging: when the observations are noisy, indirect, and National University of Singapore, 4 Engineering Drive 3, limited, how can we be sure that we are observing quan- Singapore 117583 tum behavior? This tutorial highlights some of the difficulties 2 Department of Physics, National University of Singapore, in such experimental tests of quantum mechanics, using op- 2 Science Drive 3, Singapore 117551 tomechanics as the central example, and discusses how the issues can be resolved using techniques from statistics and insights from quantum information theory. Received 8 August 2013 Accepted 28 November 2013 Keywords PACS: 42.50.Pq, 42.65.Ky, 42.65.Lm, 42.79.Hp © 2013 Mankei Tsang, licensee Versita Sp. z o. o. This work is licensed under the Creative Commons Attribution-NonCommercial- NoDerivs license, which means that the text may be used for non-commercial pur- poses, provided credit is given to the author. 1. Introduction tomechanics is used as the main example. Optomechanics refers to the physics of the interactions between optical Once thought to be a theory confined to the atomic do- beams and mechanical moving objects. A moving mirror, main, quantum mechanics is now being tested on increas- for example, will introduce varying phase shifts depending ingly macroscopic levels, thanks to technological advances on its position to an optical beam reflected by it. The mo- and the ingenuity of experimentalists [1–6]. As experi- tion of the mirror can then be inferred from measurements ments continue to push the quantum-classical boundary of the optical phase, while the change in momentum of the using increasingly complex dynamical systems, the inter- reflected optical beam also means that the mirror experi- pretation of experimental data becomes more and more ences a force, namely, radiation pressure. Optomechanics challenging: when the observations are noisy, indirect, technology has advanced so rapidly in recent years [4–6] and limited, how can we be sure that we are observing that quantum effects are becoming observable in mechan- quantum behavior? The goal of this tutorial is to high- ical devices with unprecedented sizes [7–10]. Such de- light some of the difficulties in such experimental tests of vices thus serve as promising testbeds for new concepts quantum mechanics and discuss how the issues can be re- in macroscopic quantum mechanics [11]. Sec. 4.4 in par- solved using techniques from statistics and insights from ticular studies the optomechanics experiment reported by et al. quantum information theory. Apart from quantum physi- Safavi-Naeini [12, 13] and demonstrates how statis- cists, another target audience of this tutorial is statis- tics can be applied to the experimental data. For the mo- ticians and engineers, who might be interested to learn tivated reader, the Appendices also introduce some of the more about quantum physics and how statistics can be more advanced techniques in classical and quantum prob- useful for the new generation of quantum experiments. ability theory that can facilitate the experimental design and signal processing. The tutorial starts off in rather basic and general terms, introducing the basic concepts of quantum mechanics in 2. Quantum mechanics Sec.2 and statistical hypothesis testing in Sec.3. Sec.4 2.1. Origin of quantum is the centerpiece of this tutorial, discussing in detail why and how quantum mechanics should be tested. To illus- The word “quantum” in quantum mechanics refers to the trate the concepts in the context of recent experiments, op- fact that certain physical quantities, such as energy and angular momentum, exist only in discrete levels, or quanta. ∗ E-mail: [email protected] This assumption, together with classical mechanics, are 84 Testing quantum mechanics: a statistical approach able to explain many phenomena; for example, screen, the experimentalists themselves, and, by exten- sion, the whole universe. 1. Planck’s model of electromagnetic fields with dis- This viral nature of the Hilbert-space theory is nowadays crete energy can explain the blackbody spectrum taken more seriously among some theorists. On a prag- and, later by Einstein, the photoelectric effect. matic level, it makes the theory, by itself, impossible to test experimentally, as the experimentalists would have to 2. Bohr’s model of bound electrons with discrete en- take into account the universe, including themselves, ev- ergy and orbital angular momentum can explain the ery time they would like to generate a prediction from the spectral lines of hydrogen. Hilbert-space theory and perform an experiment to test it. Despite its success, the seemingly ad-hoc nature of the To test the Hilbert-space theory, we must therefore find quantal assumption motivated theorists to find a deeper a way to divorce the test object from the rest of the uni- model. The result is Schrödinger’s wave mechanics and verse and extract reproducible experimental results from Heisenberg’s matrix mechanics. the model. Fortunately, for experimentalists, the von Neu- mann measurement theory provides a way out. 2.2. The Hilbert-space theory 2.3. Quantum probability The Schrödinger and Heisenberg pictures of quantum me- The von Neumann measurement theory provides a defini- chanics are equivalent theories, which are able to explain tion of quantum measurement with respect to an observ- the quantal model as a consequence of deeper axioms able, known as the von Neumann measurement. The def- based on Hilbert-space algebra. The central quantities inition allows one to model a test object using a Hilbert of the theory is the quantum state, which is a complex space, but still describe the rest of the universe as an vector denoted by |ψi, observables, which are Hermitian observer that follows the classical rules of probability. matrices, and a unitary matrix U for time evolution. The probabilities of measurement outcomes are deter- The Hilbert-space theory produces many predictions be- mined from a Hilbert-space model using Born’s rule. Al- yond the quantal hypothesis. Perhaps the most outra- though each measurement outcome is random, the Born geous one is the “uncertainty” relation, which states that probability values are deterministic and can be estimated the product of the variances of a pair of incompatible with increasing accuracy by repeated experiments. As the observables, such as the position and momentum of an probabilities depend on the Hilbert-space model being electron, cannot be zero but is instead lower-bounded by assumed, one can then obtain asymptotically reproducible a certain positive value. The word “uncertainty” is put results that verify the validity of the Hilbert-space theory. in quotes because, at this stage, the “uncertainty” rela- The combined theory of Hilbert space and von Neumann tion is nothing more than a mathematical statement in measurement is referred to as the quantum probability the Hilbert-space theory. Although Ehrenfest’s correspon- theory. dence principle tells us that the Hilbert-space average of With the quantum probability theory, the Hilbert-space an observable obeys classical mechanics and gives us a moments and the uncertainty relation acquire operational rough sense of how observables correspond to physical meanings: one can define Hilbert-space averages in an quantities, it is unclear how the Hilbert-space variance is unambiguous fashion by specifying the measurements and related to the common sense of uncertainty, which is best asking how the averages are related to the expected val- described using probability theory. ues for the measurements. Most importantly, the theory This problem becomes more apparent when one wishes to enables experimentalists to stay safely in the realm of define the correlation of incompatible observables. Cor- classical logic and still test the Hilbert-space theory by relation is a well defined concept in probability, but in considering smaller models. the Hilbert-space theory its definition is ambiguous, with We now have a quantum theory that predicts probabilities infinitely many ways of combining the observables that as verifiable deterministic numbers, but it is very clumsy result in different Hilbert-space moments. to use, as it provides no rule that specifies which part of An even more troubling problem with the theory is how the experiment should be included in the Hilbert space to test it in an experiment. In the Stern-Gerlach experi- and which part should be defined as the observer. This ment, for example, an electron beam interacts with mag- dichotomy is known as the Heisenberg cut. An empirical netic fields, before being detected on a screen. If we are way of deciding on a cut is as follows: to believe that the Hilbert-space theory is a fundamental theory that governs all the interacting objects involved in 1. Make a guess of how the cut should be made and an experiment, then we must include in the Hilbert space compute the quantum probabilities based on the not only the electrons, but also the magnetic field, the cut. 85 Mankei Tsang 2. The validity of the cut can be checked by making a 2. Signal processing. After the results are obtained, larger cut: include more experimental objects in a statistical signal processing techniques can be used larger Hilbert space, do the calculation again, and to optimize their accuracy further and compute their see if the predictions match. errors. Universality 3. Alternatively, one can also attempt to find smaller 3. By using standard error measures, it cuts with smaller Hilbert spaces (by using certain is easier to compare and communicate the signifi- tricks known as the open quantum system theory).
Load more

Recommended publications
  • Arxiv:1511.01069V1 [Quant-Ph]
    To appear in Contemporary Physics Copenhagen Quantum Mechanics Timothy J. Hollowood Department of Physics, Swansea University, Swansea SA2 8PP, U.K. (September 2015) In our quantum mechanics courses, measurement is usually taught in passing, as an ad-hoc procedure involving the ugly collapse of the wave function. No wonder we search for more satisfying alternatives to the Copenhagen interpretation. But this overlooks the fact that the approach fits very well with modern measurement theory with its notions of the conditioned state and quantum trajectory. In addition, what we know of as the Copenhagen interpretation is a later 1950’s development and some of the earlier pioneers like Bohr did not talk of wave function collapse. In fact, if one takes these earlier ideas and mixes them with later insights of decoherence, a much more satisfying version of Copenhagen quantum mechanics emerges, one for which the collapse of the wave function is seen to be a harmless book keeping device. Along the way, we explain why chaotic systems lead to wave functions that spread out quickly on macroscopic scales implying that Schr¨odinger cat states are the norm rather than curiosities generated in physicists’ laboratories. We then describe how the conditioned state of a quantum system depends crucially on how the system is monitored illustrating this with the example of a decaying atom monitored with a time of arrival photon detector, leading to Bohr’s quantum jumps. On the other hand, other kinds of detection lead to much smoother behaviour, providing yet another example of complementarity. Finally we explain how classical behaviour emerges, including classical mechanics but also thermodynamics.
    [Show full text]
  • Demnächst Auch in Ihrem Laptop?
    The Measurement Problem Johannes Kofler Quantum Foundations Seminar Max Planck Institute of Quantum Optics Munich, December 12th 2011 The measurement problem Different aspects: • How does the wavefunction collapse occur? Does it even occur at all? • How does one know whether something is a system or a measurement apparatus? When does one apply the Schrödinger equation (continuous and deterministic evolution) and when the projection postulate (discontinuous and probabilistic)? • How real is the wavefunction? Does the measurement only reveal pre-existing properties or “create reality”? Is quantum randomness reducible or irreducible? • Are there macroscopic superposition states (Schrödinger cats)? Where is the border between quantum mechanics and classical physics? The Kopenhagen interpretation • Wavefunction: mathematical tool, “catalogue of knowledge” (Schrödinger) not a description of objective reality • Measurement: leads to collapse of the wavefunction (Born rule) • Properties: wavefunction: non-realistic randomness: irreducible • “Heisenberg cut” between system and apparatus: “[T]here arises the necessity to draw a clear dividing line in the description of atomic processes, between the measuring apparatus of the observer which is described in classical concepts, and the object under observation, whose behavior is represented by a wave function.” (Heisenberg) • Classical physics as limiting case and as requirement: “It is decisive to recognize that, however far the phenomena transcend the scope of classical physical explanation, the
    [Show full text]
  • Advanced Quantum Theory AMATH473/673, PHYS454
    Advanced Quantum Theory AMATH473/673, PHYS454 Achim Kempf Department of Applied Mathematics University of Waterloo Canada c Achim Kempf, September 2017 (Please do not copy: textbook in progress) 2 Contents 1 A brief history of quantum theory 9 1.1 The classical period . 9 1.2 Planck and the \Ultraviolet Catastrophe" . 9 1.3 Discovery of h ................................ 10 1.4 Mounting evidence for the fundamental importance of h . 11 1.5 The discovery of quantum theory . 11 1.6 Relativistic quantum mechanics . 13 1.7 Quantum field theory . 14 1.8 Beyond quantum field theory? . 16 1.9 Experiment and theory . 18 2 Classical mechanics in Hamiltonian form 21 2.1 Newton's laws for classical mechanics cannot be upgraded . 21 2.2 Levels of abstraction . 22 2.3 Classical mechanics in Hamiltonian formulation . 23 2.3.1 The energy function H contains all information . 23 2.3.2 The Poisson bracket . 25 2.3.3 The Hamilton equations . 27 2.3.4 Symmetries and Conservation laws . 29 2.3.5 A representation of the Poisson bracket . 31 2.4 Summary: The laws of classical mechanics . 32 2.5 Classical field theory . 33 3 Quantum mechanics in Hamiltonian form 35 3.1 Reconsidering the nature of observables . 36 3.2 The canonical commutation relations . 37 3.3 From the Hamiltonian to the equations of motion . 40 3.4 From the Hamiltonian to predictions of numbers . 44 3.4.1 Linear maps . 44 3.4.2 Choices of representation . 45 3.4.3 A matrix representation . 46 3 4 CONTENTS 3.4.4 Example: Solving the equations of motion for a free particle with matrix-valued functions .
    [Show full text]
  • Perceived Reality, Quantum Mechanics, and Consciousness
    7/28/2015 Cosmology About Contents Abstracting Processing Editorial Manuscript Submit Your Book/Journal the All & Indexing Charges Guidelines & Preparation Manuscript Sales Contact Journal Volumes Review Order from Amazon Order from Amazon Order from Amazon Order from Amazon Order from Amazon Cosmology, 2014, Vol. 18. 231-245 Cosmology.com, 2014 Perceived Reality, Quantum Mechanics, and Consciousness Subhash Kak1, Deepak Chopra2, and Menas Kafatos3 1Oklahoma State University, Stillwater, OK 74078 2Chopra Foundation, 2013 Costa Del Mar Road, Carlsbad, CA 92009 3Chapman University, Orange, CA 92866 Abstract: Our sense of reality is different from its mathematical basis as given by physical theories. Although nature at its deepest level is quantum mechanical and nonlocal, it appears to our minds in everyday experience as local and classical. Since the same laws should govern all phenomena, we propose this difference in the nature of perceived reality is due to the principle of veiled nonlocality that is associated with consciousness. Veiled nonlocality allows consciousness to operate and present what we experience as objective reality. In other words, this principle allows us to consider consciousness indirectly, in terms of how consciousness operates. We consider different theoretical models commonly used in physics and neuroscience to describe veiled nonlocality. Furthermore, if consciousness as an entity leaves a physical trace, then laboratory searches for such a trace should be sought for in nonlocality, where probabilities do not conform to local expectations. Keywords: quantum physics, neuroscience, nonlocality, mental time travel, time Introduction Our perceived reality is classical, that is it consists of material objects and their fields. On the other hand, reality at the quantum level is different in as much as it is nonlocal, which implies that objects are superpositions of other entities and, therefore, their underlying structure is wave-like, that is it is smeared out.
    [Show full text]
  • 1 Does Consciousness Really Collapse the Wave Function?
    Does consciousness really collapse the wave function?: A possible objective biophysical resolution of the measurement problem Fred H. Thaheld* 99 Cable Circle #20 Folsom, Calif. 95630 USA Abstract An analysis has been performed of the theories and postulates advanced by von Neumann, London and Bauer, and Wigner, concerning the role that consciousness might play in the collapse of the wave function, which has become known as the measurement problem. This reveals that an error may have been made by them in the area of biology and its interface with quantum mechanics when they called for the reduction of any superposition states in the brain through the mind or consciousness. Many years later Wigner changed his mind to reflect a simpler and more realistic objective position, expanded upon by Shimony, which appears to offer a way to resolve this issue. The argument is therefore made that the wave function of any superposed photon state or states is always objectively changed within the complex architecture of the eye in a continuous linear process initially for most of the superposed photons, followed by a discontinuous nonlinear collapse process later for any remaining superposed photons, thereby guaranteeing that only final, measured information is presented to the brain, mind or consciousness. An experiment to be conducted in the near future may enable us to simultaneously resolve the measurement problem and also determine if the linear nature of quantum mechanics is violated by the perceptual process. Keywords: Consciousness; Euglena; Linear; Measurement problem; Nonlinear; Objective; Retina; Rhodopsin molecule; Subjective; Wave function collapse. * e-mail address: [email protected] 1 1.
    [Show full text]
  • The Minimal Modal Interpretation of Quantum Theory
    The Minimal Modal Interpretation of Quantum Theory Jacob A. Barandes1, ∗ and David Kagan2, y 1Jefferson Physical Laboratory, Harvard University, Cambridge, MA 02138 2Department of Physics, University of Massachusetts Dartmouth, North Dartmouth, MA 02747 (Dated: May 5, 2017) We introduce a realist, unextravagant interpretation of quantum theory that builds on the existing physical structure of the theory and allows experiments to have definite outcomes but leaves the theory's basic dynamical content essentially intact. Much as classical systems have specific states that evolve along definite trajectories through configuration spaces, the traditional formulation of quantum theory permits assuming that closed quantum systems have specific states that evolve unitarily along definite trajectories through Hilbert spaces, and our interpretation extends this intuitive picture of states and Hilbert-space trajectories to the more realistic case of open quantum systems despite the generic development of entanglement. We provide independent justification for the partial-trace operation for density matrices, reformulate wave-function collapse in terms of an underlying interpolating dynamics, derive the Born rule from deeper principles, resolve several open questions regarding ontological stability and dynamics, address a number of familiar no-go theorems, and argue that our interpretation is ultimately compatible with Lorentz invariance. Along the way, we also investigate a number of unexplored features of quantum theory, including an interesting geometrical structure|which we call subsystem space|that we believe merits further study. We conclude with a summary, a list of criteria for future work on quantum foundations, and further research directions. We include an appendix that briefly reviews the traditional Copenhagen interpretation and the measurement problem of quantum theory, as well as the instrumentalist approach and a collection of foundational theorems not otherwise discussed in the main text.
    [Show full text]
  • 8.051: Quantum Physics II Introduction 1 February 3, 2020
    8.051: Quantum Physics II Lecturer: Professor Barton Zwiebach Notes by: Andrew Lin Spring 2020 Introduction An MITx page for this class will be up by this afternoon. That’s where most of the content for this class will come from (regular class meetings are recitations). Lecture videos on the MITx page are divided into 7 to 25 minute sections, each covering some particular topic. After each block, there are some “lecture exercises:” this class is structured in a way so that before each recitation, we should have finished going over the material designated for it. We’ll also have real problems in problem sets – there are about 11 of these over the semester, and they’re also going to be online. Homework is the best predictor of how we’re going to do in this course – if we basically understand the homework completely, we’re extremely likely to do very well. Homework on the MITx page is given to us problem by problem, part by part, but we’ll also be given a PDF of the problems that we can complete like a regular problem set. And we’ll have some tests in the evenings of the exams instead of recitations on those days. This class also has a graduate TA (Matt Hodel) and an MITx site administrator (Michelle Tomasik), and we should ask them if we have questions. Grading is 10 percent lecture questions, 30 percent online homework, 15 percent for each of the two midterms (March 11 and April 22), and 25 percent from the final. It’s pretty likely we’ll be able to drop one problem set.
    [Show full text]
  • Advanced Quantum Theory AMATH473/673, PHYS454
    Advanced Quantum Theory AMATH473/673, PHYS454 Achim Kempf Department of Applied Mathematics University of Waterloo Canada c Achim Kempf, October 2016 (Please do not copy: textbook in progress) 2 Contents 1 A brief history of quantum theory 9 1.1 The classical period . 9 1.2 Planck and the \Ultraviolet Catastrophe" . 9 1.3 Discovery of h ................................ 10 1.4 Mounting evidence for the fundamental importance of h . 11 1.5 The discovery of quantum theory . 11 1.6 Relativistic quantum mechanics . 12 1.7 Quantum field theory . 14 1.8 Beyond quantum field theory? . 16 1.9 Experiment and theory . 18 2 Classical mechanics in Hamiltonian form 19 2.1 Newton's laws for classical mechanics cannot be upgraded . 19 2.2 Levels of abstraction . 20 2.3 Classical mechanics in Hamiltonian formulation . 21 2.3.1 The energy function H contains all information . 21 2.3.2 The Poisson bracket . 23 2.3.3 The Hamilton equations . 25 2.3.4 Symmetries and Conservation laws . 27 2.3.5 A representation of the Poisson bracket . 29 2.4 Summary: The laws of classical mechanics . 30 2.5 Classical field theory . 31 3 Quantum mechanics in Hamiltonian form 33 3.1 Reconsidering the nature of observables . 34 3.2 The canonical commutation relations . 35 3.3 From the Hamiltonian to the Equations of Motion . 38 3.4 From the Hamiltonian to predictions of numbers . 41 3.4.1 A matrix representation . 42 3.4.2 Solving the matrix differential equations . 44 3.4.3 From matrix-valued functions to number predictions .
    [Show full text]
  • De Broglie's Double Solution Program: 90 Years Later
    de Broglie's double solution program: 90 years later Samuel Colin1, Thomas Durt2, and Ralph Willox3 1Centro Brasileiro de Pesquisas F´ısicas,Rua Dr. Xavier Sigaud 150, 22290-180, Rio de Janeiro { RJ, Brasil Theiss Research, 7411 Eads Ave, La Jolla, CA 92037, USA 2Aix Marseille Universit´e,CNRS, Centrale Marseille, Institut Fresnel (UMR 7249), 13013 Marseille, France 3Graduate School of Mathematical Sciences, the University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8914 Tokyo, Japan Abstract RESUM´ E.´ Depuis que les id´eesde de Broglie furent revisit´eespar David Bohm dans les ann´ees'50, la grande majorit´edes recherches men´eesdans le domaine se sont concentr´eessur ce que l'on appelle aujourd'hui la dynamique de de Broglie-Bohm, tandis que le programme originel de de Broglie (dit de la double solution) ´etaitgraduellement oubli´e. Il en r´esulteque certains aspects de ce programme sont encore aujourd'hui flous et impr´ecis. A la lumi`ere des progr`esr´ealis´esdepuis la pr´esentation de ces id´eespar de Broglie lors de la conf´erence Solvay de 1927, nous reconsid´erons dans le pr´esent article le statut du programme de la double solution. Plut^otqu'un fossile poussi´ereux de l'histoire des sciences, nous estimons que ce programme constitue une tentative l´egitime et bien fond´eede r´econcilier la th´eoriequantique avec le r´ealisme. ABSTRACT. Since de Broglie's pilot wave theory was revived by David Bohm in the 1950's, the overwhelming majority of researchers involved in the field have focused on what is nowadays called de Broglie-Bohm dynamics and de Broglie's original double solution program was gradually forgotten.
    [Show full text]
  • Wave-Packet Reduction'' and the Quantum Character of The
    entropy Article “Wave-Packet Reduction” and the Quantum Character of the Actualization of Potentia Gregg Jaeger Quantum Communication and Measurement Laboratory, Department of Electrical and Computer Engineering and Division of Natural Science and Mathematics, Boston University, Boston, MA 02215, USA; [email protected]; Tel.: +1-617-353-3251 Received: 1 September 2017; Accepted: 21 September 2017; Published: 24 September 2017 Abstract: Werner Heisenberg introduced the notion of quantum potentia in order to accommodate the indeterminism associated with quantum measurement. Potentia captures the capacity of the system to be found to possess a property upon a corresponding sharp measurement in which it is actualized. The specific potentiae of the individual system are represented formally by the complex amplitudes in the measurement bases of the eigenstate in which it is prepared. All predictions for future values of system properties can be made by an experimenter using the probabilities which are the squared moduli of these amplitudes that are the diagonal elements of the density matrix description of the pure ensemble to which the system, so prepared, belongs. Heisenberg considered the change of the ensemble attribution following quantum measurement to be analogous to the classical change in Gibbs’ thermodynamics when measurement of the canonical ensemble enables a microcanonical ensemble description. This analogy, presented by Heisenberg as operating at the epistemic level, is analyzed here. It has led some to claim not only that the change
    [Show full text]
  • About Wigner Friend's and Hardy's Paradox in a Bohmian Approach
    About Wigner Friend’s and Hardy’s paradox in a Bohmian approach: a comment of “Quantum theory cannot consistently describe the use of itself” Aurélien Drezet To cite this version: Aurélien Drezet. About Wigner Friend’s and Hardy’s paradox in a Bohmian approach: a comment of “Quantum theory cannot consistently describe the use of itself”. International journal of quantum foundations, Research Center for Philosophy of Science and Technology, Shanxi University, 2019, 5 (2), pp.80 - 97. hal-02380166 HAL Id: hal-02380166 https://hal.archives-ouvertes.fr/hal-02380166 Submitted on 26 Nov 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution| 4.0 International License International Journal of Quantum Foundations 5 (2019) 80-97 Original Paper About Wigner Friend’s and Hardy’s paradox in a Bohmian approach: a comment of “Quantum theory cannot consistently describe the use of itself” Aurélien Drezet Institut NEEL, CNRS and Université Grenoble Alpes, F-38000 Grenoble, France. E-mail: [email protected] Received: 9 November 2018 / Accepted: 31 March 2019 / Published: 2 April 2019 Abstract: This is an analysis of the recently published article ‘Quantum theory cannot consistently describe the use of itself’ by D.
    [Show full text]
  • On Quantum Theory
    Eur. Phys. J. D (2013) DOI: 10.1140/epjd/e2013-40486-5 THE EUROPEAN PHYSICAL JOURNAL D Colloquium On quantum theory Berthold-Georg Englerta Centre for Quantum Technologies and Department of Physics, National University of Singapore, Singapore Received 9 August 2013 / Received in final form 24 August 2013 Published online (Inserted Later) – c EDP Sciences, Societ`a Italiana di Fisica, Springer-Verlag 2013 Abstract. Quantum theory is a well-defined local theory with a clear interpretation. No “measurement problem” or any other foundational matters are waiting to be settled. Quantum theory had essentially taken its final shape by 1 Physical theories: phenomena, formalism, the end of the 1920s and, in the more than eighty years interpretation; preexisting concepts since then, has been spectacularly successful and reliable – there is no experimental fact, not a single one, that con- tradicts a quantum-theoretical prediction. Yet, there is a In physics, a theory has three defining constituents: the steady stream of publications that are motivated by al- physical phenomena, the mathematical formalism, and the leged fundamental problems: We are told that quantum interpretation. The phenomena are the empirical evidence theory is ill-defined, that its interpretation is unclear, that about physical objects gathered by passive observation, it is nonlocal, that there is an unresolved “measurement typical for astronomy and meteorology, or by active ex- problem”, and so forth1. perimentation in the laboratory. The formalism provides the adequate mathematical description of the phenomena It may, therefore, be worth reviewing what quantum and enables the physicist to make precise quantitative pre- theory is and what it is about.
    [Show full text]