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Contextuality is a key distinguishing feature between classical and quantum physics. It expresses a fundamental obstruction to describing quantum theory using classical concepts. In turn, understood as a resource for quantum computation, it…

Quantum Physics · Physics 2024-08-30 Markus Frembs

The violation of Bell, CHSH and CH inequalities indicates only that the assumption of "conterfactual definiteness" and/or the probabilistic models used in proofs were incorrect. In this paper we discuss in detail an intimate relation…

Quantum Physics · Physics 2015-08-26 Marian Kupczynski

It is known that "quantum non locality", leading to the violation of Bell's inequality and more generally of classical local realism, can be attributed to the conjunction of two properties, that we call here elementary locality and…

Quantum Physics · Physics 2022-01-04 Philippe Grangier

Quantum non-demolition measurements facilitate various quantum technologies, including quantum communication. Notably, their operational structure can be replicated by a classical model--referred to as a noncontextual model--making it…

Quantum Physics · Physics 2026-03-31 Min Namkung , Ilhwan Kim , Hyang-Tag Lim

Contextuality is a natural generalization of nonlocality which does not need composite systems or spacelike separation and offers a wider spectrum of interesting phenomena. Most notably, in quantum mechanics there exist scenarios where the…

Quantum Physics · Physics 2022-03-16 Matthias Kleinmann , Costantino Budroni , Jan-Åke Larsson , Otfried Gühne , Adan Cabello

Contextuality and nonlocality are two fundamental properties of nature. Hardy's proof is considered the simplest proof of nonlocality and can also be seen as a particular violation of the simplest Bell inequality. A fundamental question is:…

Quantum Physics · Physics 2013-11-01 Adan Cabello , Piotr Badziag , Marcelo Terra Cunha , Mohamed Bourennane

Quantum contextuality is one of the most recognized resources in quantum communication and computing scenarios. We provide a new quantifier of this resource, the rank of contextuality (RC). We define RC as the minimum number of…

Contextuality is a key distinguishing feature between classical and quantum physics. It expresses a fundamental obstruction to describing quantum theory using classical concepts. In turn, when understood as a resource for quantum…

Quantum Physics · Physics 2025-01-17 Markus Frembs

Contextuality is a fundamental feature of quantum theory and a necessary resource for quantum computation and communication. It is therefore important to investigate how large contextuality can be in quantum theory. Linear contextuality…

Quantum Physics · Physics 2015-12-21 Barbara Amaral , Marcelo Terra Cunha , Adán Cabello

It is explained on a physical basis how contextuality allows Bell inequalities to be violated, without bringing an implication on locality or realism. The point is that the initial values of the hidden variables of the detectors are…

Quantum Physics · Physics 2016-12-01 Th. M. Nieuwenhuizen

We introduce a contextual quantum system comprising mutually complementary observables organized into two or more collections of pseudocontexts with the same probability sums of outcomes. These pseudocontexts constitute non-orthogonal bases…

Quantum Physics · Physics 2024-04-05 Mirko Navara , Karl Svozil

Quantum correlations in Bell and prepare-and-measure experiments are central resources for probing nonclassicality and enabling device-based quantum information protocols. In the absence of shared public randomness (i.e., without run-to-run…

Quantum Physics · Physics 2026-04-21 Liang-Liang Sun , Xiang Zhou , Chengjie Zhang , Zizhu Wang , Yong-Shun Song , Sixia Yu

The task of conclusive exclusion for a set of quantum states is to find a measurement such that for each state in the set, there is an outcome that allows one to conclude with certainty that the state in question was not prepared. Defining…

Quantum Physics · Physics 2026-01-28 Yìlè Yīng , David Schmid , Robert W. Spekkens

Many protocols and tasks in quantum information science rely inherently on the fundamental notion of contextuality to provide advantages over their classical counterparts, and contextuality represents one of the main differences between…

Quantum Physics · Physics 2026-01-01 Carles Roch I Carceller , Jonatan Bohr Brask

The quantum predictions for a single nonrelativistic spin-1/2 particle can be reproduced by noncontextual hidden variables. Here we show that quantum contextuality for a relativistic electron moving in a Coulomb potential naturally emerges…

Quantum Physics · Physics 2013-02-18 Jing-Ling Chen , Hong-Yi Su , Chunfeng Wu , Dong-Ling Deng , Adan Cabello , L. C. Kwek , C. H. Oh

Studying the extent to which realism is compatible with quantum mechanics teaches us something about the quantum mechanical universe, regardless of the validity of such realistic assumptions. It has also recently been appreciated that these…

Quantum Physics · Physics 2007-09-28 Nicholas Harrigan , Terry Rudolph

Exploring quantum phenomena beyond predictions of any classical model has fundamental importance to understand the boundary of classical and quantum descriptions of nature. As a typical property that a quantum system behaves distinctively…

In this paper I demonstrate that the quantum correlations of polarization (or spin) observables used in Bell's argument against local realism have to be interpreted as {\it conditional} quantum correlations. By taking into account…

Quantum Physics · Physics 2018-07-18 Andrei Khrennikov

For any Bell locality scenario (or Kochen-Specker noncontextuality scenario), the joint Shannon entropies of local (or noncontextual) models define a convex cone for which the non-trivial facets are tight entropic Bell (or contextuality)…

Quantum Physics · Physics 2012-03-15 Rafael Chaves , Tobias Fritz

There are two powerful arguments against the possibility of extending quantum mechanics, the violation of Bell inequalities and the Kochen-Specker theorem, but the connection between the two remains confused. Following the distinctive…

Quantum Physics · Physics 2025-01-08 Jianqi Sheng , Dongkai Zhang , Lixiang Chen