Weekly Papers on Quantum Foundations (26)

上午10:14 | Sabine Hossenfelder | quant-ph updates on arXiv.org

We here put forward a simple argument for Born’s rule based on the requirement that the probability distribution should not be a function of the number of degrees of freedom.

上午10:14 | Nicolás Mirkin, Diego Wisniacki | quant-ph updates on arXiv.org

The environment of an open quantum system is usually modelled as a large and complex many-body quantum system. However, the question of how large and complex this many-body quantum system must be in order to play the role of a genuine environment and thus generate decoherence is an often elusive key-point in the literature. In this work, by studying the reduced dynamics of a spin connected to a 1D Ising spin chain, we show that the physical mechanism responsible for generating decoherence on the reduced spin relies mostly on the chaotic behaviour of the chain. More interestingly, even in the case of an extremely short spin chain composed of two spins, by analyzing the decoherence dynamics of the reduced system we are able to reproduce the whole integrable to chaos transition. Finally, we discuss implications on quantum control experiments and show that quantum chaos reigns over the best degree of control achieved, even in small chains.

上午10:14 | Basil S. Davis | quant-ph updates on arXiv.org

Zitterbewegung of a Dirac electron is an oscillation between positive and negative energy states, and is thus distinct from the analogous phenomena exhibited by spin half charged particles in electric and magnetic fields. Quantum field theory offers an insight into the velocity operator and provides an interpretation of zitterbewegung. Applying stationary perturbation theory to these results the electron $g$ factor is obtained analytically up to the Schwinger correction ($g = 2 + \alpha/\pi $).

上午10:14 | Caitlin Jones, Tommaso Guaita, Angelo Bassi | quant-ph updates on arXiv.org

Spontaneous collapse models are proposed modifications to quantum mechanics which aim to solve the measurement problem. In this article we will consider models which attempt to extend a specific spontaneous collapse model, the Ghirardi-Rimini-Weber model (GRW), to be consistent with special relativity. We will present a condition that a relativistic GRW model must meet for three cases: for a single particle, for N distinguishable particles, and for indistinguishable particles. We will then show that this relativistic condition implies that one can have a relativistic GRW model for a single particles or for distinguishable non-interacting, non-entangled particles but not otherwise.

上午10:14 | Iwo Bialynicki-Birula, Zofia Bialynicka-Birula | quant-ph updates on arXiv.org

In our Comment we question the validity of the claim made by the authors of \cite{cc} that their solutions of the Dirac equation in an external {\em time-dependent} electromagnetic field describe beams of electrons. In every time-dependent field, no matter how weak, which has {\em infinite} time duration, there is a continuous electron-positron pair creation and annihilation. Without the proper accounting for these processes, the mathematical solutions of the Dirac equation are not directly applicable to realistic physical situations. In particular, the time evolution of the average values $\langle x\rangle$ and $\langle y\rangle$ does not describe the electron trajectory but the motion of some combination of the electron and positron charge distributions with pathological properties (zitterbewegung).

Authors: Andrei G. Lebed

We review our recent theoretical results about inequivalence between passive gravitational mass and energy for a composite quantum body at a macroscopic level. In particular, we consider macroscopic ensembles of the simplest composite quantum bodies – hydrogen atoms. Our results are as follows. For the most ensembles, the Einstein’s Equivalence Principle is valid. On the other hand, we discuss that for some special quantum ensembles – ensembles of the coherent superpositions of the stationary quantum states in the hydrogen atoms (which we call Gravitational demons) – the Equivalence Principle between passive gravitational mass and energy is broken. We show that, for such superpositions, the expectation values of passive gravitational masses are not related to the expectation values of energies by the famous Einstein’s equation, i.e, $m_g \neq \frac{E}{c^2}$. Possible experiments at the Earth’s laboratories are briefly discussed, in contrast to the numerous attempts and projects to discover the possible breakdown of the Einstein’s Equivalence Principle during the space missions.

Authors: Yasunori Nomura

We study microscopic operators describing the experience of an observer falling into the horizon of a unitarily evaporating black hole. For a young black hole, these operators can be taken to act only on the degrees of freedom in the black hole region: the soft—or stretched horizon—modes as well as the semiclassical modes in the zone region. On the other hand, for an old black hole, the operators must also involve radiation emitted earlier; the difference between the two cases comes from statistics associated with the coarse-graining performed to obtain the effective theory of the interior. We find that the operators relevant for the interior theory can be defined globally as standard linear operators throughout the microstates, which obey the correct algebra up to corrections exponentially suppressed in the ratio of excitation energy to the Hawking temperature. We conjecture that the existence of such global operators is required for the emergence of the semiclassical picture. We also elucidate relation between the present construction and entanglement wedge reconstruction of the interior.

2020年6月26日 星期五 上午10:27 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
O’Connor, Cailin (2020) Measuring Conventionality. Australasian Journal of Philosophy.
2020年6月25日 星期四 下午3:00 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
Icefield, William (2020) Making string theory empirical: defending unitary incompatibility between effective theories. [Preprint]
2020年6月25日 星期四 下午2:52 | Philsci-Archive: No conditions. Results ordered -Date Deposited.
Huggett, Nick and Lizzi, Fedele and Menon, Tushar (2020) Missing the point in noncommutative geometry. [Preprint]
2020年6月25日 星期四 上午8:00 | Latest Results for Foundations of Physics

Abstract

Bohm developed the Bohmian mechanics (BM), in which the Schrödinger equation is transformed into two differential equations: a continuity equation and an equation of motion similar to the Newtonian equation of motion. This transformation can be executed both for single-particle systems and for many-particle systems. Later, Kuzmenkov and Maksimov used basic quantum mechanics for the derivation of many-particle quantum hydrodynamics (MPQHD) including one differential equation for the mass balance and two differential equations for the momentum balance, and we extended their analysis in a prework (K. Renziehausen, I. Barth in Prog. Theor. Exp. Phys. 2018:013A05, 2018) for the case that the particle ensemble consists of different particle sorts. The purpose of this paper is to show how the differential equations of MPQHD can be derived for such a particle ensemble with the differential equations of BM as a starting point. Moreover, our discussion clarifies that the differential equations of MPQHD are more suitable for an analysis of many-particle systems than the differential equations of BM because the differential equations of MPQHD depend on a single position vector only while the differential equations of BM depend on the complete set of all particle coordinates.

2020年6月23日 星期二 上午8:00 | Latest Results for Synthese

Abstract

Classic inductive skepticism–the epistemological claim that we have no good reason to believe that the unobserved resembles the observed–is plausibly everyone’s lot, whether or not they embrace Hume’s metaphysical claim that distinct existents are “entirely loose and separate”. But contemporary advocates of a Humean metaphysic accept a metaphysical claim stronger than Hume’s own. I argue that their view plausibly gives rise to a radical inductive skepticism–according to which we are downright irrational in believing as we do about the unobserved–that we don’t otherwise have reason to accept. The Metaphysical Neo-Humean is in an epistemological quagmire all her own.

2020年6月22日 星期一 下午6:00 | M. J. Kewming, S. Shrapnel, A. G. White, and J. Romero | PRL: General Physics: Statistical and Quantum Mechanics, Quantum Information, etc.

Author(s): M. J. Kewming, S. Shrapnel, A. G. White, and J. Romero

The absence of information—entirely or partly—is called ignorance. Naturally, one might ask if some ignorance of a whole system will imply some ignorance of its parts. Our classical intuition tells us yes, however quantum theory tells us no: it is possible to encode information in a quantum system s…

[Phys. Rev. Lett. 124, 250401] Published Mon Jun 22, 2020

2020年6月22日 星期一 上午8:00 | John Preskill | Nature Physics – Issue – nature.com science feeds

Nature Physics, Published online: 22 June 2020; doi:10.1038/s41567-020-0932-7

An efficient method has been proposed through which the properties of a complex, large-scale quantum system can be predicted without fully characterizing the quantum state.

2020年6月22日 星期一 上午8:00 | Bruce W. Drinkwater | Nature Physics – Issue – nature.com science feeds

Nature Physics, Published online: 22 June 2020; doi:10.1038/s41567-020-0954-1

An elegant experiment showing that acoustic waves are amplified after scattering by a rotating body demonstrates an effect predicted in 1971 by Yakov Zel’dovich. This result has implications for the understanding of scattering from black holes.

2020年6月22日 星期一 上午8:00 | Latest Results for Foundations of Physics

Abstract

This paper argues that the path integral formulation of quantum mechanics suggests a form of holism for which the whole (total ensemble of paths) has properties that are not strongly reducible to the properties of the parts (the single trajectories). Feynman’s sum over histories calculates the probability amplitude of a particle moving within a boundary by summing over all the possible trajectories that the particle can undertake. These trajectories and their individual probability amplitudes are thus necessary in calculating the total amplitude. However, not all possible trajectories are differentiable, thus suggesting that they are not physical possibilities, but only mathematical entities. It follows that if the possible differentiable trajectories are taken to be part of the physical system, they are not sufficient to calculate the total probability amplitude. The conclusion is that the total ensemble is weakly non-supervenient upon the physically possible trajectories.

Article written by

editor