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In the context of the decoherent histories approach to quantum theory, it is shown that a class of macroscopic configurations consisting of histories of local densities (number, momentum, energy) exhibit negligible interference. This…

Quantum Physics · Physics 2009-10-31 J. J. Halliwell

We present a decomposition of the general quantum mechanical evolution operator, that corresponds to the path decomposition expansion, and interpret its constituents in terms of the quantum Zeno effect (QZE). This decomposition is applied…

Quantum Physics · Physics 2009-11-06 I. L. Egusquiza , J. G. Muga

We propose a novel approach to the problem of a transition from quantum to classical behavior in mesoscopic spin systems. This paper is intended to demonstrate that main cause of such transitions is quantum decoherence which appear as a…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 V. V. Makhro

A model quantum cosmology is used to illustrate how arrows of time emerge in a universe governed by a time-neutral dynamical theory constrained by time asymmetric initial and final boundary conditions represented by initial and final…

General Relativity and Quantum Cosmology · Physics 2020-02-18 James B. Hartle

Why do quantum evolutions occur and why do they stop at certain points? In classical thermodynamics affinity was introduced to predict in which direction an irreversible process proceeds. In this paper the quantum mechanical counterpart of…

Quantum Physics · Physics 2018-12-11 B. Ahmadi , S. Salimi , F. Kheirandish , A. S. Khorashad

Quantum backflow is a counterintuitive effect in which the probability density of a free particle moves in the direction opposite to the particle's momentum. If the particle is electrically charged, then the effect can be viewed as the…

Quantum Physics · Physics 2024-03-05 Arseni Goussev , Jaewoo Joo

The predictions of the Bohmian and the decoherent (or consistent) histories formulations of the quantum mechanics of a closed system are compared for histories -- sequences of alternatives at a series of times. For certain kinds of…

Quantum Physics · Physics 2009-11-07 James B. Hartle

We illustrate the crucial role played by decoherence (consistency of quantum histories) in extracting consistent quantum probabilities for alternative histories in quantum cosmology. Specifically, within a Wheeler-DeWitt quantization of a…

General Relativity and Quantum Cosmology · Physics 2011-05-26 David A. Craig , Parampreet Singh

The quantum teleportation protocol can be used to probabilistically simulate a quantum circuit with backward-in-time connections. This allows us to analyze some conceptual problems of time travel in the context of physically realizable…

Quantum Physics · Physics 2012-03-06 George Svetlichny

Usual quantum mechanics predicts probabilities for the outcomes of measurements carried out at definite moments of time. However, realistic measurements do not take place in an instant, but are extended over a period of time. The assumption…

Quantum Physics · Physics 2009-10-30 Richard J. Micanek , James B. Hartle

Frauchiger and Renner recently cast doubt on the universal applicability of Quantum Mechanics [1]. In the following, it is pointed out that their conclusion of one of three common-sense conditions, demanded for Quantum Mechanics, being…

General Physics · Physics 2020-04-23 Knud Thomsen

The outcome of a single quantum experiment is unpredictable, except in a pure-state limit. The definite process that takes place in the apparatus may either be intrinsically random or be explainable from a deeper theory. While the first…

Quantum Physics · Physics 2015-06-22 Theo M. Nieuwenhuizen

In the quantization of simple cosmological models (minisuperspace models) described by the Wheeler-DeWitt equation, an important step is the construction, from the wave function, of a probability distribution answering various questions of…

General Relativity and Quantum Cosmology · Physics 2010-04-30 J. J. Halliwell

The consistent histories approach to quantum mechanics is traditionally based on linearly ordered sequences of events. We extend the histories formalism to sets of events whose causal ordering is described by directed acyclic graphs. The…

General Relativity and Quantum Cosmology · Physics 2007-05-23 R. F. Blute , I. T. Ivanov , P. Panangaden

The problem of time in quantum gravity occurs because `time' is taken to have a different meaning in each of general relativity and ordinary quantum theory. This incompatibility creates serious problems with trying to replace these two…

General Relativity and Quantum Cosmology · Physics 2012-07-23 Edward Anderson

We consider the quantum first detection problem for a particle evolving on a graph under repeated projective measurements with fixed rate $1/\tau$. A general formula for the mean first detected transition time is obtained for a quantum walk…

Statistical Mechanics · Physics 2020-07-29 Q. Liu , R. Yin , K. Ziegler , E. Barkai

A system of quantum reasoning for a closed system is developed by treating non-relativistic quantum mechanics as a stochastic theory. The sample space corresponds to a decomposition, as a sum of orthogonal projectors, of the identity…

Quantum Physics · Physics 2009-10-30 Robert B. Griffiths

The question of how long a particle takes to pass through a potential barrier is still a controversial topic in quantum mechanics. Arguably, the main theoretical problem in obtaining estimates for measurable times is the fact that…

Quantum Physics · Physics 2018-09-19 Ricardo Ximenes , Fernando Parisio , Eduardo O. Dias

A curious effect is uncovered by calculating the it time evolving probability of reflection of a Gaussian wave packet from a rectangular potential barrier while it is perturbed by reducing its height. A time interval is found during which…

Quantum Physics · Physics 2009-11-07 S. Bandyopadhyay , A. S. Majumdar , D. Home

A fundamental issue for any quantum cosmological theory is to specify how probabilities can be assigned to various quantum events or sequences of events such as the occurrence of singularities or bounces. In previous work, we have…

General Relativity and Quantum Cosmology · Physics 2013-10-02 David A. Craig , Parampreet Singh