Making Sense of Bell's Theorem and Quantum Nonlocality
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Arxiv:2002.00255V3 [Quant-Ph] 13 Feb 2021 Lem (BVP)
A Path Integral approach to Quantum Fluid Dynamics Sagnik Ghosh Indian Institute of Science Education and Research, Pune-411008, India Swapan K Ghosh UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai, Kalina, Santacruz, Mumbai-400098, India ∗ (Dated: February 16, 2021) In this work we develop an alternative approach for solution of Quantum Trajectories using the Path Integral method. The state-of-the-art technique in the field is to solve a set of non-linear, coupled partial differential equations (PDEs) simultaneously. We opt for a fundamentally different route. We first derive a general closed form expression for the Path Integral propagator valid for any general potential as a functional of the corresponding classical path. The method is exact and is applicable in many dimensions as well as multi-particle cases. This, then, is used to compute the Quantum Potential (QP), which, in turn, can generate the Quantum Trajectories. For cases, where closed form solution is not possible, the problem is formally boiled down to solving the classical path as a boundary value problem. The work formally bridges the Path Integral approach with Quantum Fluid Dynamics. As a model application to illustrate the method, we work out a toy model viz. the double-well potential, where the boundary value problem for the classical path has been computed perturbatively, but the Quantum part is left exact. Using this we delve into seeking insight in one of the long standing debates with regard to Quantum Tunneling. Keywords: Path Integral, Quantum Fluid Dynamics, Analytical Solution, Quantum Potential, Quantum Tunneling, Quantum Trajectories Submitted to: J. -
Bachelorarbeit
Bachelorarbeit The EPR-Paradox, Nonlocality and the Question of Causality Ilvy Schultschik angestrebter akademischer Grad Bachelor of Science (BSc) Wien, 2014 Studienkennzahl lt. Studienblatt: 033 676 Studienrichtung lt. Studienblatt: Physik Betreuer: Univ. Prof. Dr. Reinhold A. Bertlmann Contents 1 Motivation and Mathematical framework 2 1.1 Entanglement - Separability . .2 1.2 Schmidt Decomposition . .3 2 The EPR-paradox 5 2.1 Introduction . .5 2.2 Preface . .5 2.3 EPR reasoning . .8 2.4 Bohr's reply . 11 3 Hidden Variables and no-go theorems 12 4 Nonlocality 14 4.1 Nonlocality and Quantum non-separability . 15 4.2 Teleportation . 17 5 The Bell theorem 19 5.1 Bell's Inequality . 19 5.2 Derivation . 19 5.3 Violation by quantum mechanics . 21 5.4 CHSH inequality . 22 5.5 Bell's theorem and further discussion . 24 5.6 Different assumptions . 26 6 Experimental realizations and loopholes 26 7 Causality 29 7.1 Causality in Special Relativity . 30 7.2 Causality and Quantum Mechanics . 33 7.3 Remarks and prospects . 34 8 Acknowledgment 35 1 1 Motivation and Mathematical framework In recent years, many physicists have taken the incompatibility between cer- tain notions of causality, reality, locality and the empirical data less and less as a philosophical discussion about interpretational ambiguities. Instead sci- entists started to regard this tension as a productive resource for new ideas about quantum entanglement, quantum computation, quantum cryptogra- phy and quantum information. This becomes especially apparent looking at the number of citations of the original EPR paper, which has risen enormously over recent years, and be- coming the starting point for many groundbreaking ideas. -
Many Worlds Model Resolving the Einstein Podolsky Rosen Paradox Via a Direct Realism to Modal Realism Transition That Preserves Einstein Locality
Many Worlds Model resolving the Einstein Podolsky Rosen paradox via a Direct Realism to Modal Realism Transition that preserves Einstein Locality Sascha Vongehr †,†† †Department of Philosophy, Nanjing University †† National Laboratory of Solid-State Microstructures, Thin-film and Nano-metals Laboratory, Nanjing University Hankou Lu 22, Nanjing 210093, P. R. China The violation of Bell inequalities by quantum physical experiments disproves all relativistic micro causal, classically real models, short Local Realistic Models (LRM). Non-locality, the infamous “spooky interaction at a distance” (A. Einstein), is already sufficiently ‘unreal’ to motivate modifying the “realistic” in “local realistic”. This has led to many worlds and finally many minds interpretations. We introduce a simple many world model that resolves the Einstein Podolsky Rosen paradox. The model starts out as a classical LRM, thus clarifying that the many worlds concept alone does not imply quantum physics. Some of the desired ‘non-locality’, e.g. anti-correlation at equal measurement angles, is already present, but Bell’s inequality can of course not be violated. A single and natural step turns this LRM into a quantum model predicting the correct probabilities. Intriguingly, the crucial step does obviously not modify locality but instead reality: What before could have still been a direct realism turns into modal realism. This supports the trend away from the focus on non-locality in quantum mechanics towards a mature structural realism that preserves micro causality. Keywords: Many Worlds Interpretation; Many Minds Interpretation; Einstein Podolsky Rosen Paradox; Everett Relativity; Modal Realism; Non-Locality PACS: 03.65. Ud 1 1 Introduction: Quantum Physics and Different Realisms ............................................................... -
Simulation of the Bell Inequality Violation Based on Quantum Steering Concept Mohsen Ruzbehani
www.nature.com/scientificreports OPEN Simulation of the Bell inequality violation based on quantum steering concept Mohsen Ruzbehani Violation of Bell’s inequality in experiments shows that predictions of local realistic models disagree with those of quantum mechanics. However, despite the quantum mechanics formalism, there are debates on how does it happen in nature. In this paper by use of a model of polarizers that obeys the Malus’ law and quantum steering concept, i.e. superluminal infuence of the states of entangled pairs to each other, simulation of phenomena is presented. The given model, as it is intended to be, is extremely simple without using mathematical formalism of quantum mechanics. However, the result completely agrees with prediction of quantum mechanics. Although it may seem trivial, this model can be applied to simulate the behavior of other not easy to analytically evaluate efects, such as defciency of detectors and polarizers, diferent value of photons in each run and so on. For example, it is demonstrated, when detector efciency is 83% the S factor of CHSH inequality will be 2, which completely agrees with famous detector efciency limit calculated analytically. Also, it is shown in one-channel polarizers the polarization of absorbed photons, should change to the perpendicular of polarizer angle, at very end, to have perfect violation of the Bell inequality (2 √2 ) otherwise maximum violation will be limited to (1.5 √2). More than a half-century afer celebrated Bell inequality 1, nonlocality is almost totally accepted concept which has been proved by numerous experiments. Although there is no doubt about validity of the mathematical model proposed by Bell to examine the principle of the locality, it is comprehended that Bell’s inequality in its original form is not testable. -
Hidden Variables and the Two Theorems of John Bell
Hidden Variables and the Two Theorems of John Bell N. David Mermin What follows is the text of my article that appeared in Reviews of Modern Physics 65, 803-815 (1993). I’ve corrected the three small errors posted over the years at the Revs. Mod. Phys. website. I’ve removed two decorative figures and changed the other two figures into (unnumbered) displayed equations. I’ve made a small number of minor editorial improvements. I’ve added citations to some recent critical articles by Jeffrey Bub and Dennis Dieks. And I’ve added a few footnotes of commentary.∗ I’m posting my old paper at arXiv for several reasons. First, because it’s still timely and I’d like to make it available to a wider audience in its 25th anniversary year. Second, because, rereading it, I was struck that Section VII raises some questions that, as far as I know, have yet to be adequately answered. And third, because it has recently been criticized by Bub and Dieks as part of their broader criticism of John Bell’s and Grete Hermann’s reading of John von Neumann.∗∗ arXiv:1802.10119v1 [quant-ph] 27 Feb 2018 ∗ The added footnotes are denoted by single or double asterisks. The footnotes from the original article have the same numbering as in that article. ∗∗ R¨udiger Schack and I will soon post a paper in which we give our own view of von Neumann’s four assumptions about quantum mechanics, how he uses them to prove his famous no-hidden-variable theorem, and how he fails to point out that one of his assump- tions can be violated by a hidden-variables theory without necessarily doing violence to the whole structure of quantum mechanics. -
Violation of Bell Inequalities: Mapping the Conceptual Implications
International Journal of Quantum Foundations 7 (2021) 47-78 Original Paper Violation of Bell Inequalities: Mapping the Conceptual Implications Brian Drummond Edinburgh, Scotland. E-mail: [email protected] Received: 10 April 2021 / Accepted: 14 June 2021 / Published: 30 June 2021 Abstract: This short article concentrates on the conceptual aspects of the violation of Bell inequalities, and acts as a map to the 265 cited references. The article outlines (a) relevant characteristics of quantum mechanics, such as statistical balance and entanglement, (b) the thinking that led to the derivation of the original Bell inequality, and (c) the range of claimed implications, including realism, locality and others which attract less attention. The main conclusion is that violation of Bell inequalities appears to have some implications for the nature of physical reality, but that none of these are definite. The violations constrain possible prequantum (underlying) theories, but do not rule out the possibility that such theories might reconcile at least one understanding of locality and realism to quantum mechanical predictions. Violation might reflect, at least partly, failure to acknowledge the contextuality of quantum mechanics, or that data from different probability spaces have been inappropriately combined. Many claims that there are definite implications reflect one or more of (i) imprecise non-mathematical language, (ii) assumptions inappropriate in quantum mechanics, (iii) inadequate treatment of measurement statistics and (iv) underlying philosophical assumptions. Keywords: Bell inequalities; statistical balance; entanglement; realism; locality; prequantum theories; contextuality; probability space; conceptual; philosophical International Journal of Quantum Foundations 7 (2021) 48 1. Introduction and Overview (Area Mapped and Mapping Methods) Concepts are an important part of physics [1, § 2][2][3, § 1.2][4, § 1][5, p. -
Lessons of Bell's Theorem
Lessons of Bell's Theorem: Nonlocality, yes; Action at a distance, not necessarily. Wayne C. Myrvold Department of Philosophy The University of Western Ontario Forthcoming in Shan Gao and Mary Bell, eds., Quantum Nonlocality and Reality { 50 Years of Bell's Theorem (Cambridge University Press) Contents 1 Introduction page 1 2 Does relativity preclude action at a distance? 2 3 Locally explicable correlations 5 4 Correlations that are not locally explicable 8 5 Bell and Local Causality 11 6 Quantum state evolution 13 7 Local beables for relativistic collapse theories 17 8 A comment on Everettian theories 19 9 Conclusion 20 10 Acknowledgments 20 11 Appendix 20 References 25 1 Introduction 1 1 Introduction Fifty years after the publication of Bell's theorem, there remains some con- troversy regarding what the theorem is telling us about quantum mechanics, and what the experimental violations of Bell inequalities are telling us about the world. This chapter represents my best attempt to be clear about what I think the lessons are. In brief: there is some sort of nonlocality inherent in any quantum theory, and, moreover, in any theory that reproduces, even approximately, the quantum probabilities for the outcomes of experiments. But not all forms of nonlocality are the same; there is a distinction to be made between action at a distance and other forms of nonlocality, and I will argue that the nonlocality needed to violate the Bell inequalities need not involve action at a distance. Furthermore, the distinction between forms of nonlocality makes a difference when it comes to compatibility with relativis- tic causal structure. -
Quantum Nonlocality Explained
Quantum Nonlocality Explained Ulrich Mohrhoff Sri Aurobindo International Centre of Education Pondicherry 605002 India [email protected] Abstract Quantum theory's violation of remote outcome independence is as- sessed in the context of a novel interpretation of the theory, in which the unavoidable distinction between the classical and quantum domains is understood as a distinction between the manifested world and its manifestation. 1 Preliminaries There are at least nine formulations of quantum mechanics [1], among them Heisenberg's matrix formulation, Schr¨odinger'swave-function formu- lation, Feynman's path-integral formulation, Wigner's phase-space formula- tion, and the density-matrix formulation. The idiosyncracies of these forma- tions have much in common with the inertial reference frames of relativistic physics: anything that is not invariant under Lorentz transformations is a feature of whichever language we use to describe the physical world rather than an objective feature of the physical world. By the same token, any- thing that depends on the particular formulation of quantum mechanics is a feature of whichever mathematical tool we use to calculate the values of observables or the probabilities of measurement outcomes rather than an objective feature of the physical world. That said, when it comes to addressing specific questions, some formu- lations are obviously more suitable than others. As Styer et al. [1] wrote, The ever-popular wavefunction formulation is standard for prob- lem solving, but leaves the conceptual misimpression that [the] wavefunction is a physical entity rather than a mathematical tool. The path integral formulation is physically appealing and 1 generalizes readily beyond the domain of nonrelativistic quan- tum mechanics, but is laborious in most standard applications. -
PROPOSED EXPERIMENT to TEST LOCAL HIDDEN-VARIABLE THEORIES* John F
VOLUME 23, NUMBER 15 PHYSI CA I. REVIEW I.ETTERS 13 OcToBER 1969 sible without the devoted effort of the personnel ~K. P. Beuermann, C. J. Rice, K. C. Stone, and R. K. of the Orbiting Geophysical Observatory office Vogt, Phys. Rev. Letters 22, 412 (1969). at the Goddard Space Flight Center and at TR%. 2J. L'Heureux and P. Meyer, Can. J. Phys. 46, S892 (1968). 3J. Rockstroh and W. R. Webber, University of Min- nesota Publication No. CR-126, 1969. ~Research supported in part under National Aeronau- 46. M. Simnett and F. B. McDonald, Goddard Space tics and Space Administration Contract No. NAS 5-9096 Plight Center Report No. X-611-68-450, 1968 (to be and Grant No. NGR 14-001-005. published) . )Present address: Department of Physics, The Uni- 5W. R. Webber, J. Geophys. Res. 73, 4905 (1968). versity of Arizona, Tucson, Ariz. GP. B. Abraham, K. A. Brunstein, and T. L. Cline, (Also Department of Physics. Phys. Rev. 150, 1088 (1966). PROPOSED EXPERIMENT TO TEST LOCAL HIDDEN-VARIABLE THEORIES* John F. Clauserf Department of Physics, Columbia University, New York, New York 10027 Michael A. Horne Department of Physics, Boston University, Boston, Massachusetts 02215 and Abner Shimony Departments of Philosophy and Physics, Boston University, Boston, Massachusetts 02215 and Richard A. Holt Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (Received 4 August 1969) A theorem of Bell, proving that certain predictions of quantum mechanics are incon- sistent with the entire family of local hidden-variable theories, is generalized so as to apply to realizable experiments. A proposed extension of the experiment of Kocher and Commins, on the polarization correlation of a pair of optical photons, will provide a de- cisive test betw'een quantum mechanics and local hidden-variable theories. -
Cosmic Bell Test Using Random Measurement Settings from High-Redshift Quasars
PHYSICAL REVIEW LETTERS 121, 080403 (2018) Editors' Suggestion Cosmic Bell Test Using Random Measurement Settings from High-Redshift Quasars Dominik Rauch,1,2,* Johannes Handsteiner,1,2 Armin Hochrainer,1,2 Jason Gallicchio,3 Andrew S. Friedman,4 Calvin Leung,1,2,3,5 Bo Liu,6 Lukas Bulla,1,2 Sebastian Ecker,1,2 Fabian Steinlechner,1,2 Rupert Ursin,1,2 Beili Hu,3 David Leon,4 Chris Benn,7 Adriano Ghedina,8 Massimo Cecconi,8 Alan H. Guth,5 † ‡ David I. Kaiser,5, Thomas Scheidl,1,2 and Anton Zeilinger1,2, 1Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria 2Vienna Center for Quantum Science & Technology (VCQ), Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria 3Department of Physics, Harvey Mudd College, Claremont, California 91711, USA 4Center for Astrophysics and Space Sciences, University of California, San Diego, La Jolla, California 92093, USA 5Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA 6School of Computer, NUDT, 410073 Changsha, China 7Isaac Newton Group, Apartado 321, 38700 Santa Cruz de La Palma, Spain 8Fundación Galileo Galilei—INAF, 38712 Breña Baja, Spain (Received 5 April 2018; revised manuscript received 14 June 2018; published 20 August 2018) In this Letter, we present a cosmic Bell experiment with polarization-entangled photons, in which measurement settings were determined based on real-time measurements of the wavelength of photons from high-redshift quasars, whose light was emitted billions of years ago; the experiment simultaneously ensures locality. Assuming fair sampling for all detected photons and that the wavelength of the quasar photons had not been selectively altered or previewed between emission and detection, we observe statistically significant violation of Bell’s inequality by 9.3 standard deviations, corresponding to an estimated p value of ≲7.4 × 10−21. -
Quantum Nonlocality As an Axiom
Foundations of Physics, Vol. 24, No. 3, 1994 Quantum Nonlocality as an Axiom Sandu Popescu t and Daniel Rohrlich 2 Received July 2, 1993: revised July 19, 1993 In the conventional approach to quantum mechanics, &determinism is an axiom and nonlocality is a theorem. We consider inverting the logical order, mak#1g nonlocality an axiom and indeterminism a theorem. Nonlocal "superquantum" correlations, preserving relativistic causality, can violate the CHSH inequality more strongly than any quantum correlations. What is the quantum principle? J. Wheeler named it the "Merlin principle" after the legendary magician who, when pursued, could change his form again and again. The more we pursue the quantum principle, the more it changes: from discreteness, to indeterminism, to sums over paths, to many worlds, and so on. By comparison, the relativity principle is easy to grasp. Relativity theory and quantum theory underlie all of physics, but we do not always know how to reconcile them. Here, we take nonlocality as the quantum principle, and we ask what nonlocality and relativistic causality together imply. It is a pleasure to dedicate this paper to Professor Fritz Rohrlich, who has contributed much to the juncture of quantum theory and relativity theory, including its most spectacular success, quantum electrodynamics, and who has written both on quantum paradoxes tll and the logical structure of physical theory, t2~ Bell t31 proved that some predictions of quantum mechanics cannot be reproduced by any theory of local physical variables. Although Bell worked within nonrelativistic quantum theory, the definition of local variable is relativistic: a local variable can be influenced only by events in its back- ward light cone, not by events outside, and can influence events in its i Universit6 Libre de Bruxelles, Campus Plaine, C.P. -
Is Emerging Science Answering Philosopher: Greatest Questions?
free inquiry SPRING 2001 • VOL. 21 No. Is Emerging Science Answering Philosopher: Greatest Questions? ALSO: Paul Kurtz Peter Christina Hoff Sommers Tibor Machan Joan Kennedy Taylor Christopher Hitchens `Secular Humanism THE AFFIRMATIONS OF HUMANISM: LI I A STATEMENT OF PRINCIPLES free inquiry We are committed to the application of reason and science to the understanding of the universe and to the solving of human problems. We deplore efforts to denigrate human intelligence, to seek to explain the world in supernatural terms, and to look outside nature for salvation. We believe that scientific discovery and technology can contribute to the betterment of human life. We believe in an open and pluralistic society and that democracy is the best guarantee of protecting human rights from authoritarian elites and repressive majorities. We are committed to the principle of the separation of church and state. We cultivate the arts of negotiation and compromise as a means of resolving differences and achieving mutual under- standing. We are concerned with securing justice and fairness in society and with eliminating discrimination and intolerance. We believe in supporting the disadvantaged and the handicapped so that they will be able to help themselves. We attempt to transcend divisive parochial loyalties based on race, religion, gender, nationality, creed, class, sexual ori- entation, or ethnicity, and strive to work together for the common good of humanity. We want to protect and enhance the earth, to preserve it for future generations, and to avoid inflicting needless suf- fering on other species. We believe in enjoying life here and now and in developing our creative talents to their fullest.