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Forty-five years after the discovery of the peculiar quantum effect known as `probability backflow', and twenty years after the greatest possible size of the effect was characterized, an experiment has been proposed recently to observe the…

Quantum Physics · Physics 2015-11-19 A. J. Bracken , G. F. Melloy

As quantum computing approaches the threshold where certain tasks demonstrably outpace their classical machines, the need for a precise, clear, consensus-driven definition of quantum advantage becomes essential. Rapid progress in the field…

Recent advancements in quantum technologies have opened new horizons for exploring the physical world in ways once deemed impossible. Central to these breakthroughs is the concept of quantum advantage, where quantum systems outperform their…

We introduce the concept of a quantum walk with two particles and study it for the case of a discrete time walk on a line. A quantum walk with more than one particle may contain entanglement, thus offering a resource unavailable in the…

Quantum Physics · Physics 2007-05-23 Y. Omar , N. Paunkovic , L. Sheridan , S. Bose

Quantum backflow refers to the appearance of negative probability current in a state whose momentum distribution is essentially positive. We propose a scheme to prepare such states in a noninteracting Bose-Einstein condensate using…

Quantum Physics · Physics 2026-05-22 Yuchong Chen , Yijun Tang

It is argued from several points of view that quantum probabilities might play a role in statistical settings. New approaches toward quantum foundations have postulates that appear to be equally valid in macroscopic settings. One such…

Quantum Physics · Physics 2025-06-26 Inge S. Helland

We study the quantum backflow problem in the noncommutative plane. In particular, we have considered a charged particle with and without an oscillator interaction with noncommuting momentum operators and examined angular momentum backflow…

High Energy Physics - Theory · Physics 2020-12-29 V. D. Paccoia , O. Panella , P. Roy

In its standard formulation, quantum mechanics presents a very serious inconvenience: given a quantum system, there is no possibility at all to unambiguously (causally) connect a particular feature of its final state with some specific…

Quantum Physics · Physics 2013-09-10 A. S. Sanz , S. Miret-Artes

We study a special kind of semiclassical limit of quantum dynamics on a circle and in a box (infinite potential well with hard walls) as the Planck constant tends to zero and time tends to infinity. The results give detailed information…

Quantum Physics · Physics 2013-04-18 A. S. Trushechkin , I. V. Volovich

Quantum theory makes the most accurate empirical predictions and yet it lacks simple, comprehensible physical principles from which the theory can be uniquely derived. A broad class of probabilistic theories exist which all share some…

Quantum Physics · Physics 2012-04-17 Borivoje Dakic , Caslav Brukner

We compare the classical and quantum mechanical position-space probability densities for a particle in an asymmetric infinite well. In an idealized system with a discontinuous step in the middle of the well, the classical and quantum…

Quantum Physics · Physics 2007-05-23 M. A. Doncheski , R. W. Robinett

Significant advances in the development of computing devices based on quantum effects and the demonstration of their use to solve various problems have rekindled interest in the nature of the "quantum computational advantage." Although…

Quantum Physics · Physics 2024-11-01 Aleksey K. Fedorov , Evgeniy O. Kiktenko , Nikolay N. Kolachevsky

We investigate the orgin of ``quantum superarrivals'' in the reflection and transmission probabilities of a Gaussian wave packet for a rectangular potential barrier while it is perturbed by either reducing or increasing its height. There…

Quantum Physics · Physics 2009-11-07 Md. Manirul Ali , A. S. Majumdar , Dipankar Home

We remark that the often ignored quantum probability current is fundamental for a genuine understanding of scattering phenomena and, in particular, for the statistics of the time and position of the first exit of a quantum particle from a…

Quantum Physics · Physics 2008-02-03 M. Daumer , D. Duerr , S. Goldstein , N. Zanghi

The time of flight distribution for a cloud of cold atoms falling freely under gravity is considered. We generalise the probability current density approach to calculate the quantum arrival time distribution for the mixed state describing…

Quantum Physics · Physics 2009-11-13 Md. Manirul Ali , Dipankar Home , A. S. Majumdar , Alok K. Pan

We show how a potential that is well-defined everywhere on the positive half-line, but diverges to $-\infty$ as $x\rightarrow 0^+$, may still be able to dynamically confine a particle to the (positive) half-line. We shall call this effect…

Quantum Physics · Physics 2024-07-17 Rodrigo Andrade e Silva

The position density of a "particle" performing a continuous-time quantum walk on the integer lattice, viewed on length scales inversely proportional to the time t, converges (as t tends to infinity) to a probability distribution that…

Quantum Physics · Physics 2013-05-29 Alex D. Gottlieb

We study a phenomenon occuring in various areas of quantum physics, in which an observable density (such as an energy density) which is classically pointwise nonnegative may assume arbitrarily negative expectation values after quantisation,…

Mathematical Physics · Physics 2007-05-23 Simon P. Eveson , Christopher J. Fewster , Rainer Verch

A key issue of current quantum advantage experiments is that their verification requires a full classical simulation of the ideal computation. This limits the regime in which the experiments can be verified to precisely the regime in which…

Quantum Physics · Physics 2025-10-08 Abhinav Deshpande , Bill Fefferman , Soumik Ghosh , Michael Gullans , Dominik Hangleiter

It is often stated that quantum mechanics only makes statistical predictions and that a quantum state is described by the various probability distributions associated with it. Can we describe a quantum state completely in terms of…

Quantum Physics · Physics 2007-05-23 E. C. G. Sudarshan