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Completeness of Quantum Theory: Still an Open Question

A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Quantum Information".

Deadline for manuscript submissions: closed (30 October 2022) | Viewed by 15990

Special Issue Editor


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Guest Editor
Département d'informatique et d'ingénierie, Université du Québec en Outaouais, Gatineau, QC J8X 3X7, Canada
Interests: foundations of quantum mechanics; quantum information; violation of Bell inequalities; completeness of quantum mechanics; high-energy particle physics; optical theorem; statistical analysis of the experimental data; stochastic processes

Special Issue Information

Dear Colleagues,

The success of quantum information and computer technologies is not dependent on quantum magic and or nonlocality, which are both misleading notions, but on the correct understanding of quantum mechanics (QM) and its foundations. It is a relatively easy task, on a paper, to manipulate entangled states of qubits, switch on and off interactions, apply a sequence of unitary operators, or perform a particular measurement leading to the instantaneous collapse of a quantum state. To do so in a meaningful and controllable way in experiments and in industry is far more difficult, because the quantum states are only mathematical entities, which are not the attributes of individual quantum systems, and may be changed instantaneously.

 QM has led to spectacular technological developments. However, there is still no consensus regarding its interpretation and limitations. It provides abstract probabilistic descriptions of physical phenomena. Bohr claimed that quantum probabilities are irreducible, and that more detailed locally causal subquantum description of quantum phenomena is impossible, though this has not been proven. Einstein disagreed with this idea: "Is there really any physicist who believes that we shall never get any insight into these important changes in the single systems, in their structure and their causal connections... To believe this is logically possible without contradiction; but, it is so very contrary to my scientific instinct that I cannot forego the search for a more complete description". It has been incorrectly believed that the violation of various Bell inequalities (BI) allows closure of the Bohr–Einstein quantum debate. However, it has been demonstrated that the violation of (BI) has little to say about the completeness of QM and nonlocality of Nature. Imperfect correlations in Bell Tests may be explained using a locally causal contextual probabilistic model in which setting-dependent parameters describing measuring device are correctly introduced. This Special Issue aims to act as a forum for the presentation of articles of physicists and philosophers who believe that quantum probabilities are emergent and who have been searching for a more intuitive and detailed explanation of quantum phenomena. As Bohr wisely said, no theory can claim to be complete or definite: “Knowledge presents itself within a conceptual framework adapted to previous experience and . . . any such frame may prove too narrow to comprehend new experiences”.

Contributors should share their ideas, experimental results, beliefs, untested conjectures, and doubts, without unnecessary mathematical details. This Special Issue will accept unpublished original papers and comprehensive reviews focused on (but not limited to) the following areas:

  • Which sense models, which we create to quantitatively describe our observations and experiments, may be considered as a complete description of the physical reality?
  • Quantum phenomena and experiments produce time series of data. We should answer an important question: Is QM is predictably complete (whether quantum probabilities grasp all reproducible fine details of these time-series of data)?
  • Despite erroneous belief, the violation of BI does not justify speculations about nonlocality, super-determinism, or retro-causality in nature.
  • Contextuality is the key to understanding quantum paradoxes and is a resource for quantum information.
  • Two slit experiments with larger and larger molecules suggest that to explain these experiments in an intuitive way we need both waves and particles.
  • Recent experiments with bouncing droplets, the continuation of pioneering research of Couder et al., provide an intuitive understanding of various quantum phenomena.
  • There are successful subquantum theoretical causal models and computer simulations of some quantum phenomena.
  • In QM and in the standard model, semi-empirical inputs containing several free parameters are often needed in order to explain experimental data. In some sense quantum theory becomes unfalsifiable!

Prof. Dr. Marian Kupczynski
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Entropy is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (9 papers)

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Research

14 pages, 517 KiB  
Article
Notions of Completeness in the EPR Discussion
by Gerd Christian Krizek and Lukas Mairhofer
Entropy 2023, 25(4), 585; https://doi.org/10.3390/e25040585 - 29 Mar 2023
Viewed by 872
Abstract
We explore the different notions of completeness applied in the EPR discussion following and amending the thorough analysis of Arthur Fine. To this aim, we propose a classification scheme for scientific theories that provides a methodology for analyzing the different levels at which [...] Read more.
We explore the different notions of completeness applied in the EPR discussion following and amending the thorough analysis of Arthur Fine. To this aim, we propose a classification scheme for scientific theories that provides a methodology for analyzing the different levels at which interpretive approaches come into play. This allows us to contrast several concepts of completeness that operate on specific levels of the theory. We introduce the notion of theory completeness and compare it with the established notions of Born completeness, Schrödinger completeness and bijective completeness. We relate these notions to the recent concept of ψ-completeness and predictable completeness. The paper shows that the EPR argument contains conflicting versions of completeness. The confusion of these notions led to misunderstandings in the EPR debate and hindered its progress. Their clarification will thus contribute to recent debates on interpretational issues of quantum mechanics. Finally, we discuss the connection between the EPR paper and the Einstein–Rosen paper with regard to the question of completeness. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
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16 pages, 769 KiB  
Article
Models for Quantum Measurement of Particles with Higher Spin
by Theodorus M. Nieuwenhuizen
Entropy 2022, 24(12), 1746; https://doi.org/10.3390/e24121746 - 29 Nov 2022
Cited by 2 | Viewed by 914
Abstract
The Curie–Weiss model for quantum measurement describes the dynamical measurement of a spin-12 by an apparatus consisting of an Ising magnet of many spins 12 coupled to a thermal phonon bath. To measure the z-component [...] Read more.
The Curie–Weiss model for quantum measurement describes the dynamical measurement of a spin-12 by an apparatus consisting of an Ising magnet of many spins 12 coupled to a thermal phonon bath. To measure the z-component s=l,l+1,,l of a spin l, a class of models is designed along the same lines, which involve 2l order parameters. As required for unbiased measurement, the Hamiltonian of the magnet, its entropy and the interaction Hamiltonian possess an invariance under the permutation ss+1 mod 2l+1. The theory is worked out for the spin-1 case, where the thermodynamics is analyzed in detail, and, for spins 32,2,52, the thermodynamics and the invariance are presented. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
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8 pages, 272 KiB  
Article
On the Complete Description of Entangled Systems Part II: The (Meta)Physical Status and Semantic Aspects
by Karl Svozil
Entropy 2022, 24(12), 1724; https://doi.org/10.3390/e24121724 - 25 Nov 2022
Cited by 1 | Viewed by 1072
Abstract
We review some semantical aspects of probability bounds from Boole’s “conditions on possible experience” violated by quantum mechanics. We also speculate about emerging space-time categories as an epiphenomenon of quantization and the resulting breakdown of relativity theory by non-unitary and non-linear processes. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
16 pages, 346 KiB  
Article
The Electromagnetic Vacuum Field as an Essential Hidden Ingredient of the Quantum-Mechanical Ontology
by Ana Maria Cetto and Luis de la Peña
Entropy 2022, 24(12), 1717; https://doi.org/10.3390/e24121717 - 24 Nov 2022
Cited by 4 | Viewed by 1733
Abstract
This paper provides elements in support of the random zero-point radiation field (zpf) as an essential ontological ingredient needed to explain distinctive properties of quantum-mechanical systems. We show that when an otherwise classical particle is connected to the zpf, a [...] Read more.
This paper provides elements in support of the random zero-point radiation field (zpf) as an essential ontological ingredient needed to explain distinctive properties of quantum-mechanical systems. We show that when an otherwise classical particle is connected to the zpf, a drastic, qualitative change in the dynamics takes place, leading eventually to the quantum dynamics. In particular, we demonstrate that in parallel with the evolution of the canonical variables of the particle into quantum operators satisfying the basic commutator x^,p^=i, also the field canonical variables are transformed, giving rise to the corresponding creation and annihilation operators a^,a^, satisfying a^,a^=1. This allows for an explanation of quantum features such as quantum fluctuations, stationary states and transitions, and establishes a natural contact with (nonrelativistic) quantum electrodynamics. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
16 pages, 345 KiB  
Article
Quantum Mechanics: Statistical Balance Prompts Caution in Assessing Conceptual Implications
by Brian Drummond
Entropy 2022, 24(11), 1537; https://doi.org/10.3390/e24111537 - 26 Oct 2022
Viewed by 2249
Abstract
Throughout quantum mechanics there is statistical balance, in the collective response of an ensemble of systems to differing measurement types. Statistical balance is a core feature of quantum mechanics, underlying quantum mechanical states, and not yet explained. The concept of “statistical balance” is [...] Read more.
Throughout quantum mechanics there is statistical balance, in the collective response of an ensemble of systems to differing measurement types. Statistical balance is a core feature of quantum mechanics, underlying quantum mechanical states, and not yet explained. The concept of “statistical balance” is here explored, comparing its meaning since 2019 with its original meaning in 2001. Statistical balance now refers to a feature of contexts in which: (a) there is a prescribed probability other than 0 or 1 for the collective response of an ensemble to one measurement type; and (b) the collective response of the same ensemble to another measurement type demonstrates that no well-defined value can be attributed, for the property relevant to the original measurement type, to individual members of the ensemble. In some unexplained way, the outcomes of single runs of a measurement of the original type “balance” each other to give an overall result in line with the prescribed probability. Unexplained statistical balance prompts caution in assessing the conceptual implications of entanglement, measurement, uncertainty, and two-slit and Bell-type analyses. Physicists have a responsibility to the wider population to be conceptually precise about quantum mechanics, and to make clear that many possible conceptual implications are uncertain. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
16 pages, 457 KiB  
Article
A Proposed Interpretation of the Wave–Particle Duality
by Kurt Jung
Entropy 2022, 24(11), 1535; https://doi.org/10.3390/e24111535 - 26 Oct 2022
Cited by 1 | Viewed by 1393
Abstract
Within the framework of quantum mechanics, the wave function squared describes the probability density of particles. In this article, another description of the wave function is given which embeds quantum mechanics into the traditional fields of physics, thus making new interpretations dispensable. The [...] Read more.
Within the framework of quantum mechanics, the wave function squared describes the probability density of particles. In this article, another description of the wave function is given which embeds quantum mechanics into the traditional fields of physics, thus making new interpretations dispensable. The new concept is based on the idea that each microscopic particle with non-vanishing rest mass is accompanied by a matter wave, which is formed by adjusting the phases of the vacuum fluctuations in the vicinity of the vibrating particle. The vibrations of the particle and wave are phase-coupled. Particles move on continuous approximately classical trajectories. By the phase coupling mechanism, the particle transfers the information on its kinematics and thus also on the external potential to the wave. The space dependence of the escorting wave turns out to be equal to the wave function. The new concept fundamentally differs from the pilot wave concept of Bohmian mechanics. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
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8 pages, 431 KiB  
Article
Observations of Bell Inequality Violations with Causal Isolation between Source and Detectors
by Marc Jean Jose Fleury
Entropy 2022, 24(9), 1230; https://doi.org/10.3390/e24091230 - 01 Sep 2022
Cited by 1 | Viewed by 1874
Abstract
We report the experimental observations of Bell inequality violations (BIV) in entangled photons causally separated by a rotating mirror. A Foucault mirror gating geometry is used to causally isolate the entangled photon source and detectors. We report an observed BIV of CHSH- [...] Read more.
We report the experimental observations of Bell inequality violations (BIV) in entangled photons causally separated by a rotating mirror. A Foucault mirror gating geometry is used to causally isolate the entangled photon source and detectors. We report an observed BIV of CHSH-S=2.30±0.07>2.00. This result rules out theories that explain correlations with traveling communication between source and detectors, including super-luminal and instantaneous communication. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
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27 pages, 9519 KiB  
Article
Classical, Quantum and Event-by-Event Simulation of a Stern–Gerlach Experiment with Neutrons
by Hans De Raedt, Fengping Jin and Kristel Michielsen
Entropy 2022, 24(8), 1143; https://doi.org/10.3390/e24081143 - 17 Aug 2022
Cited by 2 | Viewed by 1718
Abstract
We present a comprehensive simulation study of the Newtonian and quantum model of a Stern–Gerlach experiment with cold neutrons. By solving Newton’s equation of motion and the time-dependent Pauli equation for a wide range of uniform magnetic field strengths, we scrutinize the role [...] Read more.
We present a comprehensive simulation study of the Newtonian and quantum model of a Stern–Gerlach experiment with cold neutrons. By solving Newton’s equation of motion and the time-dependent Pauli equation for a wide range of uniform magnetic field strengths, we scrutinize the role of the latter for drawing the conclusion that the magnetic moment of the neutron is quantized. We then demonstrate that a marginal modification of the Newtonian model suffices to construct, without invoking any concept of quantum theory, an event-based subquantum model that eliminates the shortcomings of the classical model and yields results that are in qualitative agreement with experiment and quantum theory. In this event-by-event model, the intrinsic angular momentum can take any value on the sphere, yet, for a sufficiently strong uniform magnetic field, the particle beam splits in two, exactly as in experiment and in concert with quantum theory. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
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8 pages, 226 KiB  
Article
There Is No Spooky Action at a Distance in Quantum Mechanics
by Stephen Boughn
Entropy 2022, 24(4), 560; https://doi.org/10.3390/e24040560 - 16 Apr 2022
Cited by 7 | Viewed by 2695
Abstract
Einstein became bothered by quantum mechanical action at a distance within two years of Schrödinger’s introduction of his eponymous wave equation. If the wave function represents the “real” physical state of a particle, then the measurement of the particle’s position would result in [...] Read more.
Einstein became bothered by quantum mechanical action at a distance within two years of Schrödinger’s introduction of his eponymous wave equation. If the wave function represents the “real” physical state of a particle, then the measurement of the particle’s position would result in the instantaneous collapse of the wave function to the single, measured position. Such a process seemingly violates not only the Schrödinger equation but also special relativity. Einstein was not alone in this vexation; however, the dilemma eventually faded as physicists concentrated on using the Schrödinger equation to solve a plethora of pressing problems. For the next 30 years, wave function collapse, while occasionally discussed by physicists, was primarily a topic of interest for philosophers. That is, until 1964, when Bell introduced his famous inequality and maintained that its violation proved that quantum mechanics and, by implication, nature herself are nonlocal. Unfortunately, this brought the topic back to mainstream physics, where it has remained and continues to muddy the waters. To be sure, not all physicists are bothered by the apparent nonlocality of quantum mechanics. So where have those who embrace quantum nonlocality gone wrong? I argue that the answer is a gratuitous belief in the ontic nature of the quantum state. Full article
(This article belongs to the Special Issue Completeness of Quantum Theory: Still an Open Question)
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