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It is proposed to give up the description of physical states in terms of ensembles of state vectors with various probabilities, relying instead solely on the density matrix as the description of reality. With this definition of a physical…

Quantum Physics · Physics 2015-06-19 Steven Weinberg

Density-dependent potentials are frequently used in materials simulations due to their approximate description of many-body effects at minimal computational cost. However, in order to apply such models to multi-component systems, an…

Chemical Physics · Physics 2020-09-14 Peter Vanya , James A. Elliott

A set of quantum states is said to be antidistinguishable if, upon being given a randomly chosen state, it is possible to identify a state that the system was definitively not prepared in. In this work, we begin with a study of quantum…

Quantum Physics · Physics 2026-05-12 Biswadeep Chatterjee , Tathagata Gupta , Pratik Ghosal , Samrat Sen

A new quantum mechanical notion -- Conditional Density Matrix -- is discussed and is applied to describe some physical processes. This notion is a natural generalization of von Neumann density matrix for such processes as divisions of…

Quantum Physics · Physics 2007-05-23 V. V. Belokurov , O. A. Khrustalev , V. A. Sadovnichy , O. D. Timofeevskaya

In a recent work, arXiv:2503.05884, we proposed a unified notion of nonclassicality that applies to arbitrary processes in quantum theory, including individual quantum states, measurements, channels, set of these, etc. This notion is…

Quantum Physics · Physics 2025-04-07 Yujie Zhang , Yìlè Yīng , David Schmid

One notion of non-locality in quantum theory is the fact that information may be encoded in a composite system in such a way that it is not accessible through local measurements, even with the assistance of classical communication. Thus,…

Quantum Physics · Physics 2022-10-05 Sarah Croke

Generalized measurement schemes on one part of bipartite states, which would leave the set of all separable states insensitive are explored here to understand quantumness of correlations in a more general perspecitve. This is done by…

Quantum Physics · Physics 2012-01-04 A. R. Usha Devi , A. K. Rajagopal , Sudha

In a full theory of quantum gravity, local physics is expected to be approximate rather than innate. It is therefore important to understand how approximate locality emerges in the semiclassical limit. Here we show that any notion of…

High Energy Physics - Theory · Physics 2017-11-09 Netta Engelhardt , Sebastian Fischetti

Recent works in foundations of quantum (field) theory and relativistic quantum information try to better grasp the interplay between the structure of quantum correlations and the constraints imposed by causality on physical operations.…

Quantum Physics · Physics 2015-10-14 Issam Ibnouhsein

Quantum nonlocality is presented often as the most remarkable and inexplicable phenomenon known to modern science which was confirmed in the experiments proving the violation of Bell Inequalities (BI). It has been known already for a long…

Quantum Physics · Physics 2021-06-09 Marian Kupczynski

The nonlocality of certain quantum states can be revealed by using local filters before performing a standard Bell test. This phenomenon, known as hidden nonlocality, has been so far demonstrated only for a restricted class of measurements,…

Quantum Physics · Physics 2013-10-23 Flavien Hirsch , Marco Túlio Quintino , Joseph Bowles , Nicolas Brunner

Motivated by Popescu's example of hidden nonlocality, we elaborate on the conjecture that quantum states that are intuitively nonlocal, i.e., entangled, do not admit a local causal hidden variables model. We exhibit quantum states which…

Quantum Physics · Physics 2009-10-30 Stefan Teufel , Karin Berndl , Detlef Dürr , Sheldon Goldstein , Nino Zangh\`ı

We propose a single-particle experiment that is equivalent to the conventional two-particle experiment used to demonstrate a violation of Bell's inequalities. Hence, we argue that quantum mechanical nonlocality can be demonstrated by…

Quantum Physics · Physics 2013-05-29 G. Bjork , P. Jonsson , L. L. Sanchez-Soto

Non-locality, or quantum-non-locality, are buzzwords in the community of quantum foundation and information scientists, which purportedly describe the implications of Bell's theorem. When such phrases are treated seriously, that is it is…

Quantum Physics · Physics 2015-01-23 Marek Zukowski

Nonlocality without entanglement and its subsequent generalizations offer deep information-theoretic insights and subsequently find several useful applications. Concept of genuinely nonlocal set of product states emerges as a natural…

Quantum Physics · Physics 2023-03-31 Sumit Rout , Ananda G. Maity , Amit Mukherjee , Saronath Halder , Manik Banik

We introduce, for any bipartite Bell scenario, a measure that quantifies both the amount of nonlocality and the efficiency in device-independent quantum key distribution of a set of measurement outcomes probabilities. It is a proper measure…

Quantum Physics · Physics 2020-11-30 S. Camalet

Quantum nonlocality is typically assigned to systems of two or more well separated particles, but nonlocality can also exist in systems consisting of just a single particle, when one considers the subsystems to be distant spatial field…

Quantum Physics · Physics 2015-03-13 Libby Heaney , Adan Cabello , Marcelo F. Santos , Vlatko Vedral

We study emerging notions of quantum correlations in compound systems. Based on different definitions of quantumness in individual subsystems, we investigate how they extend to the joint description of a composite system. Especially, we…

Quantum Physics · Physics 2017-06-12 J. Sperling , E. Agudelo , I. A. Walmsley , W. Vogel

Employing a procedure called monitoring---via a completely positive trace-preserving map that is able to interpolate between weak and projective measurements---we investigate the resilience of the recently proposed realism-based nonlocality…

Quantum Physics · Physics 2019-01-23 V. S. Gomes , R. M. Angelo

We consider the problem of quantum-state tomography under the assumption that the state is pure, and more generally that its rank is bounded by a given value. In this scenario, new notions of informationally complete POVMs emerge, which…

Quantum Physics · Physics 2016-05-11 Charles H. Baldwin , Ivan H. Deutsch , Amir Kalev