Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:2105.12341 · Physical Review A

Genuine network quantum nonlocality and self-testing

Ivan Šupić, Jean-Daniel Bancal, Yu Cai, Nicolas Brunner

Published Feb 9, 2022• 46 citations
arXivHTMLPDF

Abstract

The network structure offers in principle the possibility for novel forms of quantum nonlocal correlations, that are proper to networks and cannot be traced back to standard quantum Bell nonlocality. Here we define a notion of genuine network quantum nonlocality. Our approach is operational and views standard quantum nonlocality as a resource for producing correlations in networks. We show several examples of correlations that are genuine network nonlocal, considering the so-called bilocality network of entanglement swapping. In particular, we present an example of quantum self-testing which relies on the network structure; the considered correlations are nonbilocal, but are local according to the usual definition of Bell locality.

DOI
10.1103/physreva.105.022206

Related papers

Genuine Quantum Nonlocality in the Triangle Network

Marc-Olivier Renou, Elisa Bäumer, Sadra Boreiri +3 more

Quantum networks allow in principle for completely novel forms of quantum correlations. In particular, quantum nonlocality can be demonstrated here without the need of having various input settings, but only by considering the joint statistics of fixed local measurement outputs. However, previous examples of this intriguing phenomenon all appear to stem directly from the usual form of quantum nonlocality, namely via the violation of a standard Bell inequality. Here we present novel examples of "quantum nonlocality without inputs," which we believe represent a new form of quantum nonlocality, genuine to networks. Our simplest examples, for the triangle network, involve both entangled states and joint entangled measurements. A generalization to any odd-cycle network is also presented.

arXiv:1905.04902•Physical Review Letters•Sep 30, 2019•175 citations

Self-testing nonlocality without entanglement

Ivan Šupić, Nicolas Brunner

Quantum theory allows for nonlocality without entanglement. Notably, there exist bipartite quantum measurements consisting of only product eigenstates, yet they cannot be implemented via local quantum operations and classical communication. In the present work, we show that a measurement exhibiting nonlocality without entanglement can be certified in a device-independent manner. Specifically, we consider a simple quantum network and construct a self-testing procedure that is robust to noise. This result also demonstrates that genuine network quantum nonlocality can be obtained using only nonentangled measurements. From a more general perspective, our work establishes a connection between the effect of nonlocality without entanglement and the area of Bell nonlocality.

arXiv:2203.13171•Physical Review A•Jun 30, 2023•13 citations

Full Network Nonlocality

Alejandro Pozas-Kerstjens, Nicolas Gisin, Armin Tavakoli

Networks have advanced the study of nonlocality beyond Bell's theorem. Here, we introduce the concept of full network nonlocality, which describes correlations that necessitate all links in a network to distribute nonlocal resources. Showcasing that this notion is stronger than standard network nonlocality, we prove that the most well-known network Bell test does not witness full network nonlocality. In contrast, we demonstrate that its generalization to star networks is capable of detecting full network nonlocality in quantum theory. More generally, we point out that established methods for analyzing local and theory-independent correlations in networks can be combined in order to systematically deduce sufficient conditions for full network nonlocality in any network and input-output scenario. We demonstrate the usefulness of these methods by constructing polynomial witnesses of full network nonlocality for the bilocal scenario. Then, we show that these inequalities can be violated via quantum elegant joint measurements.

arXiv:2105.09325•Physical Review Letters•Jan 7, 2022•83 citations

Activation of Genuine Tripartite Nonlocality

Biswajit Paul, Kaushiki Mukherjee, Debasis Sarkar

Nonlocal correlations arise from measurements on tripartite entangled states can be classified into two types, one genuinely $3-$way nonlocal and other local with respect to some bipartition. Still, whether a genuine tripartite entangled quantum state can exhibit genuine $3-$way nonlocality, remains a challenging problem so far as measurement context is concerned. Here we introduce a novel approach in this regard. We consider three genuine tripartite mixed entangled quantum states none of which is genuinely $3-$way nonlocal in original Bell scenario, but they can exhibit genuine $3-$way nonlocality when distributed in some suitable multiple entanglement swapping network. So, genuine $3-$way nonlocality is a nonadditive resource, which can be activated. Our result implies that genuine $3-$way nonlocality of quantum states strongly depends on the measurement context contrary to the belief that genuine $3-$way nonlocality can be exhibited only in original Bell scenario.

•Dec 26, 2015•1 citation

Genuine Bell locality and nonlocality in the networks

Li‐Yi Hsu

In the literature on $K$-locality ($K\geq2$) networks, the local hidden variables are strictly distributed in the specific observers rather than the whole ones. Regarding genuine Bell locality, all local hidden variables, as classical objects that allow for perfect cloning in classical physics, should be cloned and then spread throughout the networks. More correlators are involved in the proposed linear and non-linear Bell-type inequalities, where their upper bounds are specified by the pre-determined output probability distribution. As for the quantum version, the no-clone theorem limits the broadcast of quantum correlations. To explore genuine Bell nonlocality in variant particle distributions in the networks, the Pauli operators stabilizing the two-qubit Bell states or multi-qubit Greenberger--Horne--Zeilinger states (GHZ states) play an essential role in designing the proposed linear and non-linear Bell tests and assigning the local incompatible measurements for the spatially separated observers. We prove the maximal violations of the proposed Bell-type inequalities quantum networks. In the end, how entanglement swapping replaces the joint measurements in the Bell tests is demonstrated.

arXiv:2209.11402•Sep 23, 2022•0 citations

Genuine quantum nonlocality in the quadrangle network

Yu Fan, Qing Yang, Arif Ullah +2 more

Abstract Given the inherent complexity of network scenarios, quantum nonlocality in networks has gained renewed significance, motivating research into the subsequent fundamental challenges. Specially, networks with independent quantum sources enable the demonstration of quantum nonlocality in networks without measurement inputs–characterized by all parties performing fixed joint measurements. Here, we propose a quadrangle network scenario without inputs and demonstrate quantum nonlocality genuine to it. It is by a logical contradiction rather than the violation of some Bell-type inequality that this kind of quadrangle network nonlocality is identified, so it can not be traced back to the standard Bell nonlocality. The detailed conditions for identifying the genuine quantum nonlocality in the quadrangle network are presented in terms of the measurement entanglement and the channel entanglement, which indicates that the precise compatibility between the measurement entanglement and the channel entanglement is essential for demonstrating the quantum nonlocality genuine to the quadrangle network.

Laser Physics•May 7, 2026•0 citations
The network structure offers in principle the possibility for novel forms of quantum nonlocal correlations, that are proper to networks and cannot be traced back to standard quantum Bell nonlocality. Here we define a notion of genuine network quantum nonlocality. Our approach is operational and views standard quantum nonlocality as a resource for producing correlations in networks. We show several examples of correlations that are genuine network nonlocal, considering the so-called bilocality network of entanglement swapping. In particular, we present an example of quantum self-testing which relies on the network structure; the considered correlations are nonbilocal, but are local according to the usual definition of Bell locality.
Quantum networks allow in principle for completely novel forms of quantum correlations. In particular, quantum nonlocality can be demonstrated here without the need of having various input settings, but only by considering the joint statistics of fixed local measurement outputs. However, previous examples of this intriguing phenomenon all appear to stem directly from the usual form of quantum nonlocality, namely via the violation of a standard Bell inequality. Here we present novel examples of "quantum nonlocality without inputs," which we believe represent a new form of quantum nonlocality, genuine to networks. Our simplest examples, for the triangle network, involve both entangled states and joint entangled measurements. A generalization to any odd-cycle network is also presented.
Quantum theory allows for nonlocality without entanglement. Notably, there exist bipartite quantum measurements consisting of only product eigenstates, yet they cannot be implemented via local quantum operations and classical communication. In the present work, we show that a measurement exhibiting nonlocality without entanglement can be certified in a device-independent manner. Specifically, we consider a simple quantum network and construct a self-testing procedure that is robust to noise. This result also demonstrates that genuine network quantum nonlocality can be obtained using only nonentangled measurements. From a more general perspective, our work establishes a connection between the effect of nonlocality without entanglement and the area of Bell nonlocality.
Networks have advanced the study of nonlocality beyond Bell's theorem. Here, we introduce the concept of full network nonlocality, which describes correlations that necessitate all links in a network to distribute nonlocal resources. Showcasing that this notion is stronger than standard network nonlocality, we prove that the most well-known network Bell test does not witness full network nonlocality. In contrast, we demonstrate that its generalization to star networks is capable of detecting full network nonlocality in quantum theory. More generally, we point out that established methods for analyzing local and theory-independent correlations in networks can be combined in order to systematically deduce sufficient conditions for full network nonlocality in any network and input-output scenario. We demonstrate the usefulness of these methods by constructing polynomial witnesses of full network nonlocality for the bilocal scenario. Then, we show that these inequalities can be violated via quantum elegant joint measurements.
Nonlocal correlations arise from measurements on tripartite entangled states can be classified into two types, one genuinely 3−3-3−way nonlocal and other local with respect to some bipartition. Still, whether a genuine tripartite entangled quantum state can exhibit genuine 3−3-3−way nonlocality, remains a challenging problem so far as measurement context is concerned. Here we introduce a novel approach in this regard. We consider three genuine tripartite mixed entangled quantum states none of which is genuinely 3−3-3−way nonlocal in original Bell scenario, but they can exhibit genuine 3−3-3−way nonlocality when distributed in some suitable multiple entanglement swapping network. So, genuine 3−3-3−way nonlocality is a nonadditive resource, which can be activated. Our result implies that genuine 3−3-3−way nonlocality of quantum states strongly depends on the measurement context contrary to the belief that genuine 3−3-3−way nonlocality can be exhibited only in original Bell scenario.
In the literature on KKK-locality (K≥2K\geq2K≥2) networks, the local hidden variables are strictly distributed in the specific observers rather than the whole ones. Regarding genuine Bell locality, all local hidden variables, as classical objects that allow for perfect cloning in classical physics, should be cloned and then spread throughout the networks. More correlators are involved in the proposed linear and non-linear Bell-type inequalities, where their upper bounds are specified by the pre-determined output probability distribution. As for the quantum version, the no-clone theorem limits the broadcast of quantum correlations. To explore genuine Bell nonlocality in variant particle distributions in the networks, the Pauli operators stabilizing the two-qubit Bell states or multi-qubit Greenberger--Horne--Zeilinger states (GHZ states) play an essential role in designing the proposed linear and non-linear Bell tests and assigning the local incompatible measurements for the spatially separated observers. We prove the maximal violations of the proposed Bell-type inequalities quantum networks. In the end, how entanglement swapping replaces the joint measurements in the Bell tests is demonstrated.
Abstract Given the inherent complexity of network scenarios, quantum nonlocality in networks has gained renewed significance, motivating research into the subsequent fundamental challenges. Specially, networks with independent quantum sources enable the demonstration of quantum nonlocality in networks without measurement inputs–characterized by all parties performing fixed joint measurements. Here, we propose a quadrangle network scenario without inputs and demonstrate quantum nonlocality genuine to it. It is by a logical contradiction rather than the violation of some Bell-type inequality that this kind of quadrangle network nonlocality is identified, so it can not be traced back to the standard Bell nonlocality. The detailed conditions for identifying the genuine quantum nonlocality in the quadrangle network are presented in terms of the measurement entanglement and the channel entanglement, which indicates that the precise compatibility between the measurement entanglement and the channel entanglement is essential for demonstrating the quantum nonlocality genuine to the quadrangle network.