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Helvetica Physica Acta (Switzerland)

On the problem of non-locality in quantum mechanics

Diederik Aerts, Reignier, J.

Published Jul 5, 1991• 13 citations
Publisher

Abstract

Many experimental results and theoretical reasonings on gedanken experiments suggest that quantum entities behave in a non-local . In order to make the discussion more precise, we propose an operational definition of non-locality . We discuss two examples of spin superposition experiments which illustrate the use of this definition. They show that quantum entities like a neutron or an atom are non-local. We make an analysis of the difficulty to imagine such non-local entities and to conciliate this non-locality with the locality of classical entities

DOI
10.5169/seals-116311

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Many experimental results and theoretical reasonings on gedanken experiments suggest that quantum entities behave in a non-local . In order to make the discussion more precise, we propose an operational definition of non-locality . We discuss two examples of spin superposition experiments which illustrate the use of this definition. They show that quantum entities like a neutron or an atom are non-local. We make an analysis of the difficulty to imagine such non-local entities and to conciliate this non-locality with the locality of classical entities
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Starting from the late 60’s many experiments have been performed to verify the violation Bell’s inequality by Einstein-Podolsky-Rosen (EPR) type correlations. The idea of these experiments being that: (i) Bell’s inequality is a consequence of locality, hence its experimental violation is an indication of non locality; (ii) this violation is a typical quantum phenomenon because any classical system making local choices (either deterministic or random) will produce correlations satisfying this inequality. Both statements (i) and (ii) have been criticized by quantum probability on theoretical grounds (not discussed in the present paper) and the experiment discussed below has been devised to support these theoretical arguments. We emphasize that the goal of our experiment is not to reproduce classically the EPR correlations but to prove that there exist perfectly local classical dynamical systems violating Bell’s inequality. The conclusions of the present experiment are: no contradiction between quantum theory and locality can be deduced from the violation of Bell’s inequality. The Copenhagen interpretation of quantum theory becomes quite reasonable and not metaphyisic if interpreted at the light of the chameleon effect. One can realize quantum entanglement by classical computers. In section (7) we prove that our experiment also provides a classical analogue of the type of logical (i.e. independent of statistics) incompatibilities pointed out by Greenberger, Home and Zeilinger. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.
The quantum interference of de Broglie matter waves is probably one of the most startling and fundamental aspects of quantum mechanics. It continues to tax our imaginations and leads us to new experimental windows on nature. Quantum interference phenomena are vividly displayed in the wide assembly of neutron interferometry experiments, which have been carried out since the first demonstration of a perfect silicon crystal interferometer in 1974. Since the neutron experiences all four fundamental forces of nature (strong, weak, electromagnetic, and gravitational), interferometry with neutrons provides a fertile testing ground for theory and precision measurements. Many Gedanken experiments of quantum mechanics have become real due to neutron interferometry. Quantum mechanics is a part of physics where experiment and theory are inseparably intertwined. This general theme permeates the second edition of this book. It discusses more than 40 neutron interferometry experiments along with their theoretical motivations and explanations. The basic ideas and results of interference experiments related to coherence and decoherence of matter waves and certain post-selection variations, gravitationally induced quantum phase shifts, Berry's geometrical phases, spinor symmetry and spin superposition, and Bell's inequalities are all discussed and explained in this book. Both the scalar and vector Aharonov-Bohm topological interference effects and the neutron version of the Sagnac effect are presented in a self-contained and pedagogical way. Interferometry with perfect crystals, artificial lattices, and spin-echo systems are also topics of this book. It includes the theoretical underpinning as well as connections to other areas of experimental physics, such as quantum optics, nuclear physics, gravitation, and atom interferometry. The observed phase shifts due to the Earth's gravity and rotation indicate a close connection to relativity theory. Neutron interferometry can be considered as a central technique of quantum optics with massive particles. It has stimulated the development of interferometry with atoms, molecules and clusters. The book is written in a style that will be suitable at the senior undergraduate and beginning of graduate level. It will interest and excite many students and researchers in neutron, nuclear, quantum, gravitational, optical, and atomic physics. Lecturers teaching courses in modern physics and quantum mechanics will find a number of interesting and historic experiments they may want to include in their lectures.
Within the framework of Aristotelian philosophy, the author presents an analysis of the exchange of energy by photons. These massless particles exhibit the most pronounced quantum behavior and pose serious challenges to classical physics. The arguments are based on the Heisenberg Uncertainty Principle and a number of Gedanken experiments on single photons. For illustration, experimental and numerical work on optical microresonators is discussed. These allow to assess the validity of Maxwell’s equations and to verify some of the Gedanken experiments. As a result of the discussion, one has to accept that the photon trajectory is causally influenced by the final state, which is separated in time and space from the initial state: non-locality and non-temporality.