# Weekly Papers on Quantum Foundations (10)

This is a list of this week’s papers on quantum foundations published in various journals or uploaded to preprint servers such as arxiv.org and PhilSci Archive.

A novel quantum-mechanical interpretation of the Dirac equation. (arXiv:1411.2296v5 [math-ph] UPDATED)

on 2016-3-05 8:55am GMT

A novel interpretation is given of Dirac’s “wave equation for the relativistic electron” as a quantum-mechanical one-particle equation. In this interpretation the electron and the positron are merely the two different “topological spin” states of a single more fundamental particle, not distinct particles in their own right. The new interpretation is backed up by the existence of such bi-particle structures in general relativity, in particular the ring singularity present in any spacelike section of the maximal analytically extended, topologically non-trivial, electromagnetic Kerr-Newman spacetime in the zero-gravity limit (here, “zero-gravity” means the limit $G\to 0$, where $G$ is Newton’s constant of universal gravitation). This novel interpretation resolves the dilemma that Dirac’s wave equation seems to be capable of describing both the electron and the positron in “external” fields in many relevant situations, while the bi-spinorial wave function has only a single position variable in its argument, not two – as it should if it were a two-particle equation! A Dirac equation is formulated for a ring-like bi-particle which interacts with a static point charges located elsewhere in the topologically non-trivial physical space associated with the moving ring bi-particle, the motion being governed by a de-Broglie-Bohm type law extracted from the Dirac equation. As an application, the pertinent general-relativistic zero-gravity Hydrogen problem is studied in the usual Born-Oppenheimer approximation. Its spectral results suggest that the zero-$G$ Kerr-Newman magnetic moment be identified with the so-called “anomalous magnetic moment of the physical electron,” not with the Bohr magneton, so that the ring radius is only a tiny fraction of the electron’s Compton wave length.

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From Weyl to Born–Jordan quantization: The Schrödinger representation revisited

ScienceDirect Publication: Physics Reports

on 2016-3-04 8:25pm GMT

Publication date: Available online 27 February 2016
Source:Physics Reports
Author(s): Maurice A. de Gosson
The ordering problem has been one of the long standing and much discussed questions in quantum mechanics from its very beginning. Nowadays, there is more or less a consensus among physicists that the right prescription is Weyl’s rule, which is closely related to the Moyal–Wigner phase space formalism. We propose in this Report an alternative approach by replacing Weyl quantization with the less well-known Born–Jordan quantization. This choice is actually natural if we want the Heisenberg and Schrödinger pictures of quantum mechanics to be mathematically equivalent. It turns out that, in addition, Born–Jordan quantization can be recovered from Feynman’s path integral approach provided that one used short-time propagators arising from correct formulas for the short-time action, as observed by Makri and Miller. These observations lead to a slightly different quantum mechanics, exhibiting some unexpected features, and this without affecting the main existing theory; for instance quantizations of physical Hamiltonian functions are the same as in the Weyl correspondence. The differences are in fact of a more subtle nature; for instance, the quantum observables will not correspond in a one-to-one fashion to classical ones, and the dequantization of a Born–Jordan quantum operator is less straightforward than that of the corresponding Weyl operator. The use of Born–Jordan quantization moreover solves the “angular momentum dilemma”, which already puzzled L. Pauling. Born–Jordan quantization has been known for some time (but not fully exploited) by mathematicians working in time-frequency analysis and signal analysis, but ignored by physicists. One of the aims of this Report is to collect and synthesize these sporadic discussions, while analyzing the conceptual differences with Weyl quantization, which is also reviewed in detail. Another striking feature is that the Born–Jordan formalism leads to a redefinition of phase space quantum mechanics, where the usual Wigner distribution has to be replaced with a new quasi-distribution reducing interference effects.

Automated Search for new Quantum Experiments

PRL Editors’ Suggestions

on 2016-3-04 3:00pm GMT

Author(s): Mario Krenn, Mehul Malik, Robert Fickler, Radek Lapkiewicz, and Anton Zeilinger

Quantum weirdness is hard for humans to grasp, so researchers wrote a program to suggest experimental setups.

[Phys. Rev. Lett. 116, 090405] Published Fri Mar 04, 2016

Delayed-choice gedanken experiments and their realizations

Recent Articles in Rev. Mod. Phys.

on 2016-3-03 3:00pm GMT

Author(s): Xiao-song Ma, Johannes Kofler, and Anton Zeilinger

Wave-particle duality lies at the root of quantum mechanics and is central in the description of interferences observed with elementary objects. In a delayed-choice experiment, the decision to observe the particle or wave character of a quantum system is delayed with respect to the time at which the system enters the interferometer. This paper reviews the history of the delayed-choice idea, introduced as a challenge to a realistic explanation of the wave-particle duality. It also describes recent experimental realizations of this idea and discusses intriguing extensions, such as the duality between separability and entanglement in multiple quantum systems.

[Rev. Mod. Phys. 88, 015005] Published Thu Mar 03, 2016

Quantum Worlds

PhilSci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-3-02 8:08pm GMT

Barrett, Jeffrey Alan (2016) Quantum Worlds. [Preprint]

Upper Bounds on Spontaneous Wave-Function Collapse Models Using Millikelvin-Cooled Nanocantilevers

PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

on 2016-3-02 3:00pm GMT

Author(s): A. Vinante, M. Bahrami, A. Bassi, O. Usenko, G. Wijts, and T. H. Oosterkamp

Collapse models predict a tiny violation of energy conservation, as a consequence of the spontaneous collapse of the wave function. This property allows us to set experimental bounds on their parameters. We consider an ultrasoft magnetically tipped nanocantilever cooled to millikelvin temperature. T…

[Phys. Rev. Lett. 116, 090402] Published Wed Mar 02, 2016

Niels Bohr on the wave function and the classical/quantum divide

PhilSci-Archive: No conditions. Results ordered -Date Deposited.

on 2016-3-02 1:42am GMT

Zinkernagel, Henrik (2016) Niels Bohr on the wave function and the classical/quantum divide. [Published Article]

Simple method for experimentally testing any form of quantum contextuality

PRA: Fundamental concepts

on 2016-3-01 3:00pm GMT

Contextuality provides a unifying paradigm for nonclassical aspects of quantum probabilities and resources of quantum information. Unfortunately, most forms of quantum contextuality remain experimentally unexplored due to the difficulty of performing sequences of projective measurements on individua…

[Phys. Rev. A 93, 032102] Published Tue Mar 01, 2016

Quantum Mechanics and the Principle of Maximal Variety

Latest Results for Foundations of Physics

on 2016-3-01 12:00am GMT

Abstract

Quantum mechanics is derived from the principle that the universe contain as much variety as possible, in the sense of maximizing the distinctiveness of each subsystem. The quantum state of a microscopic system is defined to correspond to an ensemble of subsystems of the universe with identical constituents and similar preparations and environments. A new kind of interaction is posited amongst such similar subsystems which acts to increase their distinctiveness, by extremizing the variety. In the limit of large numbers of similar subsystems this interaction is shown to give rise to Bohm’s quantum potential. As a result the probability distribution for the ensemble is governed by the Schroedinger equation. The measurement problem is naturally and simply solved. Microscopic systems appear statistical because they are members of large ensembles of similar systems which interact non-locally. Macroscopic systems are unique, and are not members of any ensembles of similar systems. Consequently their collective coordinates may evolve deterministically. This proposal could be tested by constructing quantum devices from entangled states of a modest number of quits which, by its combinatorial complexity, can be expected to have no natural copies.

The dynamics of the Schrödinger–Newton system with self-field coupling

Classical and Quantum Gravity – latest papers

on 2016-3-01 12:00am GMT

We probe the dynamics of a modified form of the Schrödinger–Newton (SN) system of gravity coupled to single particle quantum mechanics. At the masses of interest here, the ones associated with the onset of ‘collapse’ (where the gravitational attraction is competitive with the quantum mechanical dissipation), we show that the Schrödinger ground state energies match the Dirac ones with an error of ##IMG## [http://ej.iop.org/images/0264-9381/33/7/075002/cqgaa1113ieqn1.gif] {$\sim 10\%$} . At the Planck mass scale, we predict the critical mass at which a potential collapse could occur for the self-coupled gravitational case, ##IMG## [http://ej.iop.org/images/0264-9381/33/7/075002/cqgaa1113ieqn2.gif] {$m\approx 3.3$} Planck mass, and show that gravitational attraction opposes Gaussian spreading at around this value, which is a factor of two higher than the one predicted (and verified) for the SN system. Unlike the SN dynamics, we do not find…

Spontaneously Emitted X-rays: An Experimental Signature of the Dynamical Reduction Models

Latest Results for Foundations of Physics

on 2016-3-01 12:00am GMT

Abstract

We present the idea of searching for X-rays as a signature of the mechanism inducing the spontaneous collapse of the wave function. Such a signal is predicted by the continuous spontaneous localization theories, which are solving the “measurement problem” by modifying the Schrödinger equation. We will show some encouraging preliminary results and discuss future plans and strategy.

Quantum Theory is an Information Theory

Latest Results for Foundations of Physics

on 2016-3-01 12:00am GMT

Abstract

In this paper we review the general framework of operational probabilistic theories (OPT), along with the six axioms from which quantum theory can be derived. We argue that the OPT framework along with a relaxed version of five of the axioms, define a general information theory. We close the paper with considerations about the role of the observer in an OPT, and the interpretation of the von Neumann postulate and the Schrödinger-cat paradox.