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We introduce a measure of the compatibility between quantum states--the likelihood that two density matrices describe the same object. Our measure is motivated by two elementary requirements, which lead to a natural definition. We list some…

Quantum Physics · Physics 2009-11-07 David Poulin , Robin Blume-Kohout

The structure of quantum theory assures the discrimination of any possible orthogonal set of states. However, the scenario becomes highly nontrivial in the limited measurement setting and leads to different classes of impossibility, viz.,…

While all bipartite pure entangled states are known to generate correlations violating a Bell inequality, and are therefore nonlocal, the quantitative relation between pure-state entanglement and nonlocality is poorly understood. In fact,…

Quantum Physics · Physics 2018-08-14 Victoria Lipinska , Florian Curchod , Alejandro Máttar , Antonio Acín

Two distant systems can exhibit quantum nonlocality even though the correlations between them admit a local model. This nonlocality can be revealed by testing extra correlations between successive measurements on one of the systems which do…

Quantum Physics · Physics 2014-11-20 Adan Cabello

Local or nonlocal character of quantum states can be quantified and is subject to various bounds that can be formulated as complementarity relations. Here, we investigate the local vs. nonlocal character of pure three-qubit states by a…

Quantum Physics · Physics 2008-11-19 Xinhua Peng , Jingfu Zhang , Jiangfeng Du , Dieter Suter

We consider a quantum system subject to superselection rules, for which certain restrictions apply to the quantum operations that can be implemented. It is shown how the notion of quantum-nonlocality has to be redefined in the presence of…

Quantum Physics · Physics 2009-11-10 F. Verstraete , J. I. Cirac

Characterization and categorization of quantum correlations are both fundamentally and practically important in quantum information science. Although quantum correlations such as non-separability, steerability, and non-locality can be…

There is a commonly recognized paradigm in which a multipartite quantum system described by a density matrix having no product eigenbasis is considered to possess nonclassical correlation. Supporting this paradigm, we define two entropic…

Quantum Physics · Physics 2008-05-02 Akira SaiToh , Robabeh Rahimi , Mikio Nakahara

We introduce a fresh scheme based on the local hidden variable models to quantify nonlocality for arbitrarily high-dimensional quantum systems. Our scheme explores the minimal amount of white noise that must be added to the system in order…

Quantum Physics · Physics 2009-11-09 Dong-Ling Deng , Jing-Ling Chen , Zi-Sui Zhou

It is well known that entangled quantum states can be nonlocal: the correlations between local measurements carried out on these states cannot always be reproduced by local hidden variable models. Svetlichny, followed by others, showed that…

Quantum Physics · Physics 2009-11-10 Nick S. Jones , Noah Linden , Serge Massar

Nonlocality is a distinctive feature of quantum theory, which has been extensively studied for decades. It is found that the uncertainty principle determines the nonlocality of quantum mechanics. Here we show that various degrees of…

Quantum Physics · Physics 2023-06-14 Ma-Cheng Yang , Jun-Li Li , Cong-Feng Qiao

The locality issue of quantum mechanics is a key issue to a proper understanding of quantum physics and beyond. What has been commonly emphasized as quantum nonlocality has received an inspiring examination through the notion of Heisenberg…

Quantum Physics · Physics 2024-06-11 Otto C. W. Kong

Recently, there is growing interest in the study of genuine nonlocality, which serves to explore the local accessability of global information encoded in orthogonal multipartite quantum states under scenarios where not all subsystems are…

Quantum Physics · Physics 2026-04-14 Zong-Xing Xiong , Mao-Sheng Li , Bing Yu , Zhu-Jun Zheng , Lvzhou Li

Any bipartite quantum state has quasi-probability representations in terms of separable states. For entangled states these quasi-probabilities necessarily exhibit negativities. Based on the general structure of composite quantum states, one…

Quantum Physics · Physics 2015-05-13 J. Sperling , W. Vogel

Contextuality is a fundamental manifestation of nonclassicality, indicating that for certain quantum correlations, sets of jointly measurable variables cannot be pre-assigned values independently of the measurement context. In this work, we…

Quantum Physics · Physics 2026-01-12 Chellasamy Jebarathinam , R. Srikanth

The construction of nonlocal sets of quantum states has attracted much attention in recent years. We first introduce two Lemmas related to the triviality of orthogonality-preserving local measurements. Then we propose a general construction…

Quantum Physics · Physics 2023-01-02 Xiao-Fan Zhen , Shao-Ming Fei , Hui-Juan Zuo

Many experiments have shown that locality-realism theory is at variance with quantum mechanics predictions. Although locality and realism, which are two different conceptions, are given respective definition, the descriptions of the both…

Quantum Physics · Physics 2007-11-12 Ping-Xing Chen , Shi-Yao Zhu

Complementarity principle is one of the central concepts in quantum mechanics which restricts joint measurement for certain observables. Of course, later development shows that joint measurement could be possible for such observables with…

Quantum Physics · Physics 2013-05-28 Manik Banik , M. D. Rajjak Gazi , Sibasish Ghosh , Guruprasad Kar

We define nonlocal predictability as how well one observer can predict another's measurement outcomes without classical communication, given full knowledge of the shared quantum state and measurement settings. The local bound on nonlocal…

Quantum Physics · Physics 2026-02-19 Chirag Srivastava , Aparajita Bhattacharyya , Ujjwal Sen

We analyze the general nonclassicality of correlations of a composite quantum systems as measured by the negativity of quantumness. The latter corresponds to the minimum entanglement, as quantified by the negativity, that is created between…

Quantum Physics · Physics 2013-07-31 Takafumi Nakano , Marco Piani , Gerardo Adesso