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The emergence of classicality is fundamentally driven by the interaction between a quantum system and its environment. Foundational open-system approaches, notably the Caldeira-Leggett model, successfully captured how these interactions…

Quantum Physics · Physics 2026-04-28 Arthur C. R. Dutra , Roberto D. Baldijão , Marcelo Terra Cunha

It is a fundamental prediction of quantum theory that states of physical systems are described by complex vectors or density operators on a Hilbert space. However, many experiments admit effective descriptions in terms of other state…

Quantum Physics · Physics 2023-10-04 Markus P. Mueller , Andrew J. P. Garner

For a two-particle two-state system, sets of compatible propositions exist for which quantum mechanics and noncontextual hidden-variable theories make conflicting predictions for every individual system whatever its quantum state. This…

Quantum Physics · Physics 2009-01-23 Adan Cabello , Guillermo Garcia-Alcaine

Randomness is a key feature of quantum physics. Heisenberg's uncertainty principle reveals the existence of an intrinsic noise, usually explored through Gaussian squeezed states. Due to their insufficiency for quantum advantage, the focus…

Quantum Physics · Physics 2025-11-20 Vojtěch Kala , Jiří Fadrný , Michal Neset , Jan Bílek , Petr Marek , Miroslav Ježek

Self-testing of quantum devices based on observed measurement statistics is a method to certify quantum systems using minimal resources. In Ref. [Phys. Rev. \textbf{A} 101, 032106 (2020)], a scheme based on observing measurement statistics…

Quantum Physics · Physics 2024-12-03 Chellasamy Jebarathinam , Gautam Sharma , Sk Sazim , Remigiusz Augusiak

We derive inequalities for $n$ spin-1/2 systems under the assumption that the hidden-variable theoretical joint probability distribution for any pair of commuting observables is equal to the quantum mechanical one. Fine showed that this…

Quantum Physics · Physics 2015-06-26 Koji Nagata

In this paper, we extend the standard formalism of quantum mechanics to a quantum theory for a total system including one internal measuring apparatus. The internality of the measuring apparatus implies that different decomposition of a…

Quantum Physics · Physics 2012-05-17 Wen-ge Wang

When a measurement is compatible with each of two other measurements that are incompatible with one another, these define distinct contexts for the given measurement. The Kochen-Specker theorem rules out models of quantum theory that…

Quantum Physics · Physics 2018-02-06 Anirudh Krishna , Robert W. Spekkens , Elie Wolfe

The engine that powers quantum cryptography is the principle that there are no physical means for gathering information about the identity of a quantum system's state (when it is known to be prepared in one of a set of nonorthogonal states)…

Quantum Physics · Physics 2007-05-23 Christopher A. Fuchs

We show that three unsharp binary qubit measurements are enough to violate a generalized noncontextuality inequality, the LSW inequality, in a state-dependent manner. For the case of trine spin axes we calculate the optimal quantum…

Quantum Physics · Physics 2014-05-15 Ravi Kunjwal , Sibasish Ghosh

Bell-Kochen-Specker theorem states that a non-contextual hidden-variable theory cannot completely reproduce the predictions of quantum mechanics. Asher Peres gave a remarkably simple proof of quantum contextuality in a four-dimensional…

Quantum Physics · Physics 2026-03-16 Md Manirul Ali , Sovik Roy

The Kochen-Specker theorem shows the impossibility for a hidden variable theory to consistently assign values to certain (finite) sets of observables in a way that is non-contextual and consistent with quantum mechanics. If we require…

Quantum Physics · Physics 2012-12-19 Alastair A. Abbott , Cristian S. Calude , Jonathan Conder , Karl Svozil

Quantum contextuality describes situations where the statistics observed in different measurement contexts cannot be explained by a measurement independent reality of the system. The most simple case is observed in a three-dimensional…

Quantum Physics · Physics 2024-08-28 Holger F. Hofmann

Recently, an inequality satisfied by non-contextual hidden-variable models and violated by quantum mechanics for all states of a four-level system has been derived based on information-theoretic distance approach to non-classical…

Fully revealing the mathmatical structure of quantum contextuality is a significant task, while some known contextuality theories are only applicable for rank-1 projectors. That is because they adopt the observable-based definitions. This…

Quantum Physics · Physics 2025-01-17 Songyi Liu , Yongjun Wang , Baoshan Wang , Yunyi Jia

Quantum mechanics has been subject to logical scrutiny since its inception. The behavior of quantum systems, which are fundamentally dissimilar from classical systems, often appears to point to a logical inconsistency in quantum mechanics,…

Mathematical Physics · Physics 2026-04-01 Felipe Dilho Alves , João Carlos Alves Barata

It is well known that in quantum mechanics we cannot always define consistently properties that are context independent. Many approaches exist to describe contextual properties, such as Contextuality by Default (CbD), sheaf theory, topos…

Quantum Physics · Physics 2017-07-18 J. Acacio de Barros , Federico Holik , Decio Krause

For any state in four-dimensional system, the quantum violation of an inequality based on the Peres-Mermin proof for testing noncontextual realist models has experimentally been corroborated. In the Peres-Mermin proof, an array of nine…

Quantum Physics · Physics 2015-05-19 Alok Kumar Pan

We show that there are Bell-type inequalities for noncontextual theories that are violated by any quantum state. One of these inequalities between the correlations of compatible measurements is particularly suitable for testing this…

Quantum Physics · Physics 2009-07-28 Adan Cabello

Kochen-Specker (KS) theorem denies the possibility for the noncontextual hidden variable theories to reproduce the predictions of quantum mechanics. A set of projection operators (projectors) and bases used to show the impossibility of…

Quantum Physics · Physics 2015-06-17 S. P. Toh