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Quantum contextuality refers to the impossibility of assigning a predefined, intrinsic value to a physical property of a system independently of the context in which the property is measured. It is, perhaps, the most fundamental feature of…

High Energy Physics - Phenomenology · Physics 2025-04-18 M. Fabbrichesi , R. Floreanini , E. Gabrielli , L. Marzola

A recent concept in theoretical physics, motivated in string duality and M-theory, is the notion that not all quantum theories arise from quantising a classical system. Also, a given quantum model may possess more than just one classical…

Quantum Physics · Physics 2007-05-23 J. M. Isidro

The existence of contextuality in quantum mechanics is a fundamental departure from the classical description of the world. Currently, the quest to identify scenarios which cannot be more contextual than quantum theory is at the forefront…

Quantum Physics · Physics 2019-08-14 Dileep Singh , Jaskaran Singh , Kavita Dorai , Arvind

Contextuality is a fundamental property of quantum theory and a critical resource for quantum computation. Here, we experimentally observe the arguably cleanest form of contextuality in quantum theory [A. Cabello \emph{et al.}, Phys. Rev.…

Quantum Physics · Physics 2014-12-24 Breno Marques , Johan Ahrens , Mohamed Nawareg , Adan Cabello , Mohamed Bourennane

Quantum theory has the intriguing feature that is inconsistent with noncontextual hidden variable models, for which the outcome of a measurement does not depend on which other compatible measurements are being performed concurrently. While…

Quantum Physics · Physics 2015-08-20 Hong-Yi Su , Jing-Ling Chen , Yeong-Cherng Liang

We present a logical type of proof of contextuality for a two-qubit state. We formulate a paradox that cannot be verified by a two-qubit system with local measurements while it is possible by using entanglement measurements. With our scheme…

Quantum Physics · Physics 2019-08-21 Adel Sohbi , Jaewan Kim

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

We study the contextuality of a three-level quantum system using classical conditional entropy of measurement outcomes. First, we analytically construct the minimal configuration of measurements required to reveal contextuality. Next, an…

Quantum Physics · Physics 2013-05-30 Pawel Kurzynski , Ravishankar Ramanathan , Dagomir Kaszlikowski

The CHSH inequality is an inequality used to test locality in quantum theory and is recognized as one of Bell's inequalities. In contrast, the KCBS inequality is employed to test noncontextuality in quantum theory. While certain quantum…

Quantum Physics · Physics 2025-07-10 Yuichiro Kitajima

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

Quantum correlations are contextual yet, in general, nothing prevents the existence of even more contextual correlations. We identify and test a noncontextuality inequality in which the quantum violation cannot be improved by any…

In quantum cosmology, one applies quantum physics to the whole universe. While no unique version and no completely well-defined theory is available yet, the framework gives rise to interesting conceptual, mathematical and physical…

General Relativity and Quantum Cosmology · Physics 2015-01-21 Martin Bojowald

As a phenomenon encompassing measurement incompatibility and Bell nonlocality, quantum contextuality is not only central to our understanding of quantum mechanics, but also an essential resource in many quantum information processing tasks.…

Quantum Physics · Physics 2024-03-19 Xiao-Dong Yu , Isadora Veeren , Otfried Gühne

Classical chaos is marked by an extreme sensitivity to initial conditions, where infinitesimally close trajectories separate exponentially over time. In quantum mechanics, however, unitary evolution and the uncertainty principle preclude…

Quantum Physics · Physics 2025-03-19 Sanchit Srivastava , Shohini Ghose

Measurement incompatibility is the most basic resource that distinguishes quantum from classical physics. Contextuality is the critical resource behind the power of some models of quantum computation and is also a necessary ingredient for…

Quantum Physics · Physics 2019-02-20 Zhen-Peng Xu , Adán Cabello

Quantum contextuality is a key nonclassical feature underlying advantages in quantum computation and communication. We introduce a new method to study contextuality in quantum information-processing tasks and protocols, relying solely on…

Quantum Physics · Physics 2026-03-03 Mina Doosti , Theodoros Yianni , Farid Shahandeh

Contextuality is a central feature of quantum theory, traditionally understood as the impossibility of reproducing quantum measurement statistics using noncontextual ontological models. We study classical ontological descriptions in which a…

Artificial Intelligence · Computer Science 2026-04-16 Song-Ju Kim

Contextuality is a phenomenon at the heart of the quantum mechanical departure from classical behaviour, and has been recently identified as a resource in quantum computation. Experimental demonstration of contextuality is thus an important…

Quantum Physics · Physics 2019-03-26 Xiang Zhan , Eric G. Cavalcanti , Jian Li , Zhihao Bian , Yongsheng Zhang , Howard M. Wiseman , Peng Xue

Quantum mechanics provides a statistical description about nature, and thus would be incomplete if its statistical predictions could not be accounted for some realistic models with hidden variables. There are, however, two powerful theorems…

Random numbers represent an indispensable resource for many applications. A recent remarkable result is the realization that non-locality in quantum mechanics can be used to certify genuine randomness through Bell's theorem, producing…

Quantum Physics · Physics 2013-01-28 D. -L. Deng , C. Zu , X. -Y. Chang , P. -Y. Hou , H. -X. Yang , Y. -X. Wang , L. -M. Duan