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The presence of Bell-nonlocality in the correlations arising from measuring spatially-separated systems guarantees that the sets of measurements used are necessarily incompatible. Not all sets of incompatible measurements can however lead…

Quantum Physics · Physics 2025-08-21 Andrés F. Ducuara , Patryk Lipka-Bartosik , Cristian E. Susa , Paul Skrzypczyk

Measurement incompatibility describes two or more quantum measurements whose expected joint outcome on a given system cannot be defined. This purely non-classical phenomenon provides a necessary ingredient in many quantum information tasks…

Quantum Physics · Physics 2020-04-01 Francesco Buscemi , Eric Chitambar , Wenbin Zhou

Quantum incompatibility, referred as the phenomenon that some quantum measurements cannot be performed simultaneously, is necessary for various quantum information processing tasks, such as nonlocality and steering. When these applications…

Quantum Physics · Physics 2024-11-19 Xiaolin Zhang , Rui Qu , Zehong Chang , Yunlong Wang , Zhenyu Guo , Min An , Hong Gao , Fuli Li , Pei Zhang

Nonlocality, manifested by the violation of Bell inequalities, indicates entanglement within a joint quantum system. A natural question is how much entanglement is required for a given nonlocal behavior. Here, we explore this question by…

Quantum Physics · Physics 2025-06-23 Yuwei Zhu , Xingjian Zhang , Xiongfeng Ma

The view exists that Bell-tests would only be about local incompatibility of quantum observables and that quantum non-locality would be an unnecessary concept in physics. In this note, we emphasize that it is not incompatibility at the…

Quantum Physics · Physics 2024-04-10 Diederik Aerts , Massimiliano Sassoli de Bianchi

The certification of Bell nonlocality or quantum steering implies the use of incompatible measurements. Here we make this connection quantitative. We show how to strengthen robustness-based steering and nonlocality quantifiers in order that…

Quantum Physics · Physics 2016-06-07 Daniel Cavalcanti , Paul Skrzypczyk

In quantum mechanics, joint measurements of non-commuting observables are only possible if a minimal unavoidable measurement uncertainty is accepted. On the other hand, correlations between non-commuting observables can exceed classical…

Quantum Physics · Physics 2019-07-24 Holger F. Hofmann

We argue that the conclusion of Bell theorem, namely, that there must be spatial non-local correlations in certain experimental situations, does not apply to typical individual measurements performed on entangled EPR pairs. Our claim is…

General Physics · Physics 2015-10-22 Victor Romero-Rochin

Bell tests---the experimental demonstration of a Bell inequality violation---are central to understanding the foundations of quantum mechanics, underpin quantum technologies, and are a powerful diagnostic tool for technological developments…

We consider the question of characterising the incompatibility of sets of high-dimensional quantum measurements. We introduce the concept of measurement incompatibility in subspaces. That is, starting from a set of measurements that is…

This paper is aimed to dissociate nonlocality from quantum theory. We demonstrate that the tests on violation of the Bell type inequalities are simply statistical tests of local incompatibility of observables. In fact, these are tests on…

Quantum Physics · Physics 2021-01-01 Andrei Khrennikov

A well-known manifestation of quantum entanglement is that it may lead to correlations that are inexplicable within the framework of a locally causal theory --- a fact that is demonstrated by the quantum violation of Bell inequalities. The…

Quantum Physics · Physics 2012-12-07 Yeong-Cherng Liang , Lluis Masanes , Denis Rosset

One of the hallmarks of quantum theory is the realization that distinct measurements cannot in general be performed simultaneously, in stark contrast to classical physics. In this context the notions of coexistence and joint measurability…

Quantum Physics · Physics 2013-11-26 David Reeb , Daniel Reitzner , Michael M. Wolf

It is one of the most remarkable features of quantum physics that measurements on spatially separated systems cannot always be described by a locally causal theory. In such a theory, the outcomes of local measurements are determined in…

Quantum Physics · Physics 2016-09-08 Yeong-Cherng Liang

Bell's inequalities are defined by sums of correlations involving non-commuting observables in each of the two systems. Violations of Bell's inequalities are only possible because the precision of any joint measurement of these observables…

Quantum Physics · Physics 2021-11-17 Kengo Matsuyama , Holger F. Hofmann , Masataka Iinuma

Quantum theory is inconsistent with any local hidden variable model as was first shown by Bell. To test Bell inequalities two separated observers extract correlations from a common ensemble of identical systems. Since quantum theory does…

Quantum Physics · Physics 2011-01-19 Shmuel Marcovitch , Benni Reznik

Bell's theorem is a fundamental theorem in physics concerning the incompatibility between some correlations predicted by quantum theory and a large class of physical theories. In this paper, we introduce the hypothesis of accountability,…

Quantum Physics · Physics 2014-11-27 Nicola Vona , Yeong-Cherng Liang

Incompatibility of quantum measurements is of fundamental importance in quantum mechanics. It is closely related to many nonclassical phenomena such as Bell nonlocality, quantum uncertainty relations, and quantum steering. We study the…

Quantum Physics · Physics 2020-01-01 Lin Zhang , Hua Xiang , Xianqing Li-Jost , Shao-Ming Fei

The characterization of a quantum system can be complicated by non-ideal measurement processes. In many systems, the underlying physical measurement is only sensitive to a single fixed state, complementary outcomes are inferred by…

Quantum Physics · Physics 2014-12-24 Kaila C. S. Hall , Daniel K. L. Oi

One of the central features of quantum theory is that there are pairs of quantum observables that cannot be measured simultaneously. This incompatibility of quantum observables is a necessary ingredient in several quantum phenomena, such as…

Quantum Physics · Physics 2016-04-28 Teiko Heinosaari