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Arxiv:1911.07386V2 [Quant-Ph] 25 Nov 2019
Ideas Abandoned en Route to QBism Blake C. Stacey1 1Physics Department, University of Massachusetts Boston (Dated: November 26, 2019) The interpretation of quantum mechanics known as QBism developed out of efforts to understand the probabilities arising in quantum physics as Bayesian in character. But this development was neither easy nor without casualties. Many ideas voiced, and even committed to print, during earlier stages of Quantum Bayesianism turn out to be quite fallacious when seen from the vantage point of QBism. If the profession of science history needed a motto, a good candidate would be, “I think you’ll find it’s a bit more complicated than that.” This essay explores a particular application of that catechism, in the generally inconclusive and dubiously reputable area known as quantum foundations. QBism is a research program that can briefly be defined as an interpretation of quantum mechanics in which the ideas of agent and ex- perience are fundamental. A “quantum measurement” is an act that an agent performs on the external world. A “quantum state” is an agent’s encoding of her own personal expectations for what she might experience as a consequence of her actions. Moreover, each measurement outcome is a personal event, an expe- rience specific to the agent who incites it. Subjective judgments thus comprise much of the quantum machinery, but the formalism of the theory establishes the standard to which agents should strive to hold their expectations, and that standard for the relations among beliefs is as objective as any other physical theory [1]. The first use of the term QBism itself in the literature was by Fuchs and Schack in June 2009 [2]. -
Physical Vacuum Is a Special Superfluid Medium
Physical vacuum is a special superfluid medium Valeriy I. Sbitnev∗ St. Petersburg B. P. Konstantinov Nuclear Physics Institute, NRC Kurchatov Institute, Gatchina, Leningrad district, 188350, Russia; Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, Berkeley, CA 94720, USA (Dated: August 9, 2016) The Navier-Stokes equation contains two terms which have been subjected to slight modification: (a) the viscosity term depends of time (the viscosity in average on time is zero, but its variance is non-zero); (b) the pressure gradient contains an added term describing the quantum entropy gradient multiplied by the pressure. Owing to these modifications, the Navier-Stokes equation can be reduced to the Schr¨odingerequation describing behavior of a particle into the vacuum being as a superfluid medium. Vortex structures arising in this medium show infinitely long life owing to zeroth average viscosity. The non-zero variance describes exchange of the vortex energy with zero-point energy of the vacuum. Radius of the vortex trembles around some average value. This observation sheds the light to the Zitterbewegung phenomenon. The long-lived vortex has a non-zero core where the vortex velocity vanishes. Keywords: Navier-Stokes; Schr¨odinger; zero-point fluctuations; superfluid vacuum; vortex; Bohmian trajectory; interference I. INTRODUCTION registered. Instead, the wave function represents it existence within an experimental scene [13]. A dramatic situation in physical understand- Another interpretation was proposed by Louis ing of the nature emerged in the late of 19th cen- de Broglie [18], which permits to explain such an tury. Observed phenomena on micro scales came experiment. In de Broglie's wave mechanics and into contradiction with the general positions of the double solution theory there are two waves. -
Conformal Field Theory out of Equilibrium: a Review Denis Bernard
Conformal field theory out of equilibrium: a review Denis Bernard| and Benjamin Doyon♠ | Laboratoire de Physique Th´eoriquede l'Ecole Normale Sup´erieurede Paris, CNRS, ENS & PSL Research University, UMPC & Sorbonne Universit´es,France. ♠ Department of Mathematics, King's College London, London, United Kingdom. We provide a pedagogical review of the main ideas and results in non-equilibrium conformal field theory and connected subjects. These concern the understanding of quantum transport and its statistics at and near critical points. Starting with phenomenological considerations, we explain the general framework, illustrated by the example of the Heisenberg quantum chain. We then introduce the main concepts underlying conformal field theory (CFT), the emergence of critical ballistic transport, and the CFT scattering construction of non-equilibrium steady states. Using this we review the theory for energy transport in homogeneous one-dimensional critical systems, including the complete description of its large deviations and the resulting (extended) fluctuation relations. We generalize some of these ideas to one-dimensional critical charge transport and to the presence of defects, as well as beyond one-dimensional criticality. We describe non-equilibrium transport in free-particle models, where connections are made with generalized Gibbs ensembles, and in higher-dimensional and non-integrable quantum field theories, where the use of the powerful hydrodynamic ideas for non-equilibrium steady states is explained. We finish with a list of open questions. The review does not assume any advanced prior knowledge of conformal field theory, large-deviation theory or hydrodynamics. March 24, 2016 Contents 1 Introduction 1 2 Mesoscopic electronic transport: basics 3 2.1 Elementary phenomenology . -
Pilot-Wave Theory, Bohmian Metaphysics, and the Foundations of Quantum Mechanics Lecture 6 Calculating Things with Quantum Trajectories
Pilot-wave theory, Bohmian metaphysics, and the foundations of quantum mechanics Lecture 6 Calculating things with quantum trajectories Mike Towler TCM Group, Cavendish Laboratory, University of Cambridge www.tcm.phy.cam.ac.uk/∼mdt26 and www.vallico.net/tti/tti.html [email protected] – Typeset by FoilTEX – 1 Acknowledgements The material in this lecture is to a large extent a summary of publications by Peter Holland, R.E. Wyatt, D.A. Deckert, R. Tumulka, D.J. Tannor, D. Bohm, B.J. Hiley, I.P. Christov and J.D. Watson. Other sources used and many other interesting papers are listed on the course web page: www.tcm.phy.cam.ac.uk/∼mdt26/pilot waves.html MDT – Typeset by FoilTEX – 2 On anticlimaxes.. Up to now we have enjoyed ourselves freewheeling through the highs and lows of fundamental quantum and relativistic physics whilst slagging off Bohr, Heisenberg, Pauli, Wheeler, Oppenheimer, Born, Feynman and other physics heroes (last week we even disagreed with Einstein - an attitude that since the dawn of the 20th century has been the ultimate sign of gibbering insanity). All tremendous fun. This week - we shall learn about finite differencing and least squares fitting..! Cough. “Dr. Towler, please. You’re not allowed to use the sprinkler system to keep the audience awake.” – Typeset by FoilTEX – 3 QM computations with trajectories Computing the wavefunction from trajectories: particle and wave pictures in quantum mechanics and their relation P. Holland (2004) “The notion that the concept of a continuous material orbit is incompatible with a full wave theory of microphysical systems was central to the genesis of wave mechanics. -
Stochastic Hydrodynamic Analogy of Quantum Mechanics
The mass lowest limit of a black hole: the hydrodynamic approach to quantum gravity Piero Chiarelli National Council of Research of Italy, Area of Pisa, 56124 Pisa, Moruzzi 1, Italy Interdepartmental Center “E.Piaggio” University of Pisa Phone: +39-050-315-2359 Fax: +39-050-315-2166 Email: [email protected]. Abstract: In this work the quantum gravitational equations are derived by using the quantum hydrodynamic description. The outputs of the work show that the quantum dynamics of the mass distribution inside a black hole can hinder its formation if the mass is smaller than the Planck's one. The quantum-gravitational equations of motion show that the quantum potential generates a repulsive force that opposes itself to the gravitational collapse. The eigenstates in a central symmetric black hole realize themselves when the repulsive force of the quantum potential becomes equal to the gravitational one. The work shows that, in the case of maximum collapse, the mass of the black hole is concentrated inside a sphere whose radius is two times the Compton length of the black hole. The mass minimum is determined requiring that the gravitational radius is bigger than or at least equal to the radius of the state of maximum collapse. PACS: 04.60.-m Keywords: quantum gravity, minimum black hole mass, Planck's mass, quantum Kaluza Klein model 1. Introduction One of the unsolved problems of the theoretical physics is that of unifying the general relativity with the quantum mechanics. The former theory concerns the gravitation dynamics on large cosmological scale in a fully classical ambit, the latter one concerns, mainly, the atomic or sub-atomic quantum phenomena and the fundamental interactions [1-9]. -
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. -
Quantum Retrodiction: Foundations and Controversies
S S symmetry Article Quantum Retrodiction: Foundations and Controversies Stephen M. Barnett 1,* , John Jeffers 2 and David T. Pegg 3 1 School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK 2 Department of Physics, University of Strathclyde, Glasgow G4 0NG, UK; [email protected] 3 Centre for Quantum Dynamics, School of Science, Griffith University, Nathan 4111, Australia; d.pegg@griffith.edu.au * Correspondence: [email protected] Abstract: Prediction is the making of statements, usually probabilistic, about future events based on current information. Retrodiction is the making of statements about past events based on cur- rent information. We present the foundations of quantum retrodiction and highlight its intimate connection with the Bayesian interpretation of probability. The close link with Bayesian methods enables us to explore controversies and misunderstandings about retrodiction that have appeared in the literature. To be clear, quantum retrodiction is universally applicable and draws its validity directly from conventional predictive quantum theory coupled with Bayes’ theorem. Keywords: quantum foundations; bayesian inference; time reversal 1. Introduction Quantum theory is usually presented as a predictive theory, with statements made concerning the probabilities for measurement outcomes based upon earlier preparation events. In retrodictive quantum theory this order is reversed and we seek to use the Citation: Barnett, S.M.; Jeffers, J.; outcome of a measurement to make probabilistic statements concerning earlier events [1–6]. Pegg, D.T. Quantum Retrodiction: The theory was first presented within the context of time-reversal symmetry [1–3] but, more Foundations and Controversies. recently, has been developed into a practical tool for analysing experiments in quantum Symmetry 2021, 13, 586. -
Towards a Categorical Account of Conditional Probability
Towards a Categorical Account of Conditional Probability Robert Furber and Bart Jacobs Institute for Computing and Information Sciences (iCIS), Radboud University Nijmegen, The Netherlands. Web addresses: www.cs.ru.nl/~rfurber and www.cs.ru.nl/~bart This paper presents a categorical account of conditional probability, covering both the classical and the quantum case. Classical conditional probabilities are expressed as a certain “triangle-fill-in” condition, connecting marginal and joint probabilities, in the Kleisli category of the distribution monad. The conditional probabilities are induced by a map together with a predicate (the condition). The latter is a predicate in the logic of effect modules on this Kleisli category. This same approach can be transferred to the category of C∗-algebras (with positive unital maps), whose predicate logic is also expressed in terms of effect modules. Conditional probabilities can again be expressed via a triangle-fill-in property. In the literature, there are several proposals for what quantum conditional probability should be, and also there are extra difficulties not present in the classical case. At this stage, we only describe quantum systems with classical parametrization. 1 Introduction In the categorical description of probability theory, several monads play an important role. The main ones are the discrete probability monad D on the category Sets of sets and functions, and the Giry monad G , for continuous probability, on the category Meas of measurable spaces and measurable functions. The Kleisli categories of these monads have suitable probabilistic matrices as morphisms, which capture probabilistic transition systems (and Markov chains). Additionally, more recent monads of interest are the expectation monad [8] and the Radon monad [5]. -
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. -
Quantum Foundations 90 Years of Uncertainty
Quantum Foundations 90 Years of Uncertainty Edited by Pedro W. Lamberti, Gustavo M. Bosyk, Sebastian Fortin and Federico Holik Printed Edition of the Special Issue Published in Entropy www.mdpi.com/journal/entropy Quantum Foundations Quantum Foundations 90 Years of Uncertainty Special Issue Editors Pedro W. Lamberti Gustavo M. Bosyk Sebastian Fortin Federico Holik MDPI • Basel • Beijing • Wuhan • Barcelona • Belgrade Special Issue Editors Pedro W. Lamberti Gustavo M. Bosyk Universidad Nacional de Cordoba´ & CONICET Instituto de F´ısica La Plata Argentina Argentina Sebastian Fortin Universidad de Buenos Aires Argentina Federico Holik Instituto de F´ısica La Plata Argentina Editorial Office MDPI St. Alban-Anlage 66 4052 Basel, Switzerland This is a reprint of articles from the Special Issue published online in the open access journal Entropy (ISSN 1099-4300) from 2018 to 2019 (available at: https://www.mdpi.com/journal/entropy/special issues/90 Years Uncertainty) For citation purposes, cite each article independently as indicated on the article page online and as indicated below: LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. Journal Name Year, Article Number, Page Range. ISBN 978-3-03897-754-4 (Pbk) ISBN 978-3-03897-755-1 (PDF) c 2019 by the authors. Articles in this book are Open Access and distributed under the Creative Commons Attribution (CC BY) license, which allows users to download, copy and build upon published articles, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. The book as a whole is distributed by MDPI under the terms and conditions of the Creative Commons license CC BY-NC-ND. -
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News 6/2013 Physics H. Friedrich, TU München, Germany R. Gendler, Rob Gendler Astropics, Avon, CT, USA G. Ghisellini, The Astronomical Observatory of Brera, Scattering Theory (Ed) Merate, Italy Lessons from the Masters Radiative Processes in High This book presents a concise and modern coverage of scattering theory. It is motivated by the fact that Current Concepts in Astronomical Image Energy Astrophysics experimental advances have shifted and broad- Processing This book grew out of the author’s notes from his ened the scope of applications where concepts course on Radiative Processes in High Energy from scattering theory are used, e.g. to the field of There are currently thousands of amateur astrono- Astrophysics. The course provides fundamental ultracold atoms and molecules, which has been mers around the world engaged in astrophotogra- definitions of radiative processes and serves as a experiencing enormous growth in recent years, phy at a sophisticated level. brief introduction to Bremsstrahlung and black largely triggered by the successful realization of Features body emission, relativistic beaming, synchrotron Bose-Einstein condensates of dilute atomic gases 7 Written by a brilliant body of recognized emission and absorption, Compton scattering, in 1995. In the present treatment, special atten- leaders 7 Contains the most current, sophisti- synchrotron self-compton emission, pair creation tion is given to the role played by the long-range cated and useful information on astrophotogra- and emission. The final chapter discusses the ob- behaviour of the projectile-target interaction, phy 7 Covers all types of astronomical image served features of Active Galactic Nuclei and their and a theory is developed, which is well suited processing, including processing of events such interpretation based on the radiative processes to describe near-threshold bound and continuum as eclipses, using DSLRs, and deep sky, planetary, presented in the book. -
Arxiv:2105.05054V2 [Cond-Mat.Stat-Mech] 1 Sep 2021 2
Exact entanglement growth of a one-dimensional hard-core quantum gas during a free expansion Stefano Scopa1, Alexandre Krajenbrink1, Pasquale Calabrese1;2 and Jer´ omeˆ Dubail3 1 SISSA and INFN, via Bonomea 265, 34136 Trieste, Italy 2 International Centre for Theoretical Physics (ICTP), I-34151, Trieste, Italy 3 Universite´ de Lorraine, CNRS, LPCT, F-54000 Nancy, France Abstract. We consider the non-equilibrium dynamics of the entanglement entropy of a one- dimensional quantum gas of hard-core particles, initially confined in a box potential at zero temperature. At t = 0 the right edge of the box is suddenly released and the system is let free to expand. During this expansion, the initially correlated region propagates with a non-homogeneous profile, leading to the growth of entanglement entropy. This setting is investigated in the hydrodynamic regime, with tools stemming from semi-classical Wigner function approach and with recent developments of quantum fluctuating hydrodynamics. Within this framework, the entanglement entropy can be associated to a correlation function of chiral twist-fields of the conformal field theory that lives along the Fermi contour and it can be exactly determined. Our predictions for the entanglement evolution are found in agreement with and generalize previous results in literature based on numerical calculations and heuristic arguments. arXiv:2105.05054v2 [cond-mat.stat-mech] 1 Sep 2021 2 Contents 1 Introduction3 2 Setup and main result5 2.1 The model: free expansion of a lattice hard-core gas . .5 2.2 Previous results in the literature . .6 2.3 Main result of this paper . .7 3 Classical and quantum fluctuating hydrodynamic description8 3.1 Continuum limit and regularization of the problem .