Wigner's argument inferring a Bell-type inequality for the Einstein--Podolsky--Rosen--Bohm entangled state is generalized here for any $N$ -partite state. This is based on assuming for the relevant dichotomic observables the existence of the overall joint probability distributions, satisfying the locality condition, which would yield the measurable marginal probabilities. For any $N$ , such a generalized Wigner inequality (GWI) is violated by quantum mechanics for all pure entangled states. The efficacy of GWI is probed, comparing with the Seevinck--Svetlichny multipartite Bell-type inequality, by calculating threshold visibilities for the quadripartite Greenberger--Horne--Zeilinger, Cluster, and $W$ states that determine their respective robustness with respect to the quantum-mechanical violation of GWI in the presence of white noise.Wigner's argument inferring a Bell-type inequality for the Einstein--Podolsky--Rosen--Bohm entangled state is generalized here for any $N$-partite state. This is based on assuming for the relevant dichotomic observables the existence of the overall joint probability distributions, satisfying the locality condition, which would yield the measurable marginal probabilities. For any $N$, such a generalized Wigner inequality (GWI) is violated by quantum mechanics for all pure entangled states. The efficacy of GWI is probed, comparing with the Seevinck--Svetlichny multipartite Bell-type inequality, by calculating threshold visibilities for the quadripartite Greenberger--Horne--Zeilinger, Cluster, and $W$ states that determine their respective robustness with respect to the quantum-mechanical violation of GWI in the presence of white noise.

arXiv:1410.7936Physical Review AJan 9, 201519 citations

Locality and Bell's Theorem

Willy De Baere, A. Mann, M. Revzen

Foundations of PhysicsJan 1, 199919 citations

Connecting extended Wigner's friend arguments and noncontextuality

Laurens Walleghem, Yìlè Yīng, Rafael Wagner +1 more

The Local Friendliness argument is an extended Wigner's friend no-go theorem that provides strong constraints on the nature of reality – stronger even than those imposed by Bell's theorem or by noncontextuality arguments. In this work, we prove a variety of connections between Local Friendliness scenarios and Kochen-Specker noncontextuality. Specifically, we first show how one can derive new Local Friendliness inequalities using known tools and results from the literature on Kochen-Specker noncontextuality. In doing so, we provide a new derivation for some of the facets of the Local Friendliness polytope, and we prove that this polytope is equal to the Bell polytope in a wide range of extended Wigner's friend scenarios with multipartite agents and sequential measurements. We then show how any possibilistic Kochen-Specker argument can be mathematically translated into a related proof of the Local Friendliness no-go theorem. In particular, we construct a novel kind of Local Friendliness scenario where a friend implements several compatible measurements (or joint measurements of these) in between the superobserver's operations on them. We illustrate this with the well-known 5-cycle and Peres-Mermin contextuality arguments.The Local Friendliness argument is an extended Wigner's friend no-go theorem that provides strong constraints on the nature of reality – stronger even than those imposed by Bell's theorem or by noncontextuality arguments. In this work, we prove a variety of connections between Local Friendliness scenarios and Kochen-Specker noncontextuality. Specifically, we first show how one can derive new Local Friendliness inequalities using known tools and results from the literature on Kochen-Specker noncontextuality. In doing so, we provide a new derivation for some of the facets of the Local Friendliness polytope, and we prove that this polytope is equal to the Bell polytope in a wide range of extended Wigner's friend scenarios with multipartite agents and sequential measurements. We then show how any possibilistic Kochen-Specker argument can be mathematically translated into a related proof of the Local Friendliness no-go theorem. In particular, we construct a novel kind of Local Friendliness scenario where a friend implements several compatible measurements (or joint measurements of these) in between the superobserver's operations on them. We illustrate this with the well-known 5-cycle and Peres-Mermin contextuality arguments.

arXiv:2409.07537QuantumJul 31, 20252 citations

Quantum Locality

Robert B. Griffiths

arXiv:0908.2914Foundations of PhysicsOct 19, 201037 citations

Wigner's argument inferring a Bell-type inequality for the Einstein--Podolsky--Rosen--Bohm entangled state is generalized here for any

N

-partite state. This is based on assuming for the relevant dichotomic observables the existence of the overall joint probability distributions, satisfying the locality condition, which would yield the measurable marginal probabilities. For any

N

, such a generalized Wigner inequality (GWI) is violated by quantum mechanics for all pure entangled states. The efficacy of GWI is probed, comparing with the Seevinck--Svetlichny multipartite Bell-type inequality, by calculating threshold visibilities for the quadripartite Greenberger--Horne--Zeilinger, Cluster, and

W

states that determine their respective robustness with respect to the quantum-mechanical violation of GWI in the presence of white noise.