Network Nonlocality Without Entanglement Of All Sources

TL;DR

This paper investigates how entanglement in independent sources affects nonlocal correlations in quantum networks, revealing that entanglement is necessary in linear networks but not in star networks, with specific conditions for nonlocality detection.

Contribution

It provides a detailed analysis of entanglement requirements for nonlocality in linear and star quantum networks, introducing new criteria for nonlocality detection based on source entanglement.

Findings

Entanglement of all sources is necessary for nonlocality in linear networks.

Not all sources need to be entangled for nonlocality in star networks.

Nonlocality detection is guaranteed if the product of source concurrences exceeds 1/2.

Abstract

Entanglement and nonlocality are two important nonclassical features of quantum correlations. Recently the study of quantum correlations in networks has undergone remarkable progress owing to technological development towards scalable quantum networks. However, compared to standard Bell scenario, manifestation of the interplay between these two aspects has received less attention in network scenarios featuring independent sources. In this work we have analyzed the relation between entanglement content of the sources and detectable non n-locality in two distinct network topologies(linear and star). We have studied the extremal violations of n-local inequalities(compatible with linear and star network) for any fixed amount of entanglement(in terms of concurrence) of the independent sources. It is observed that each of the sources must be entangled for detecting non n-locality in linear network. However, the same is not true for star n-local network. Present analysis is revealing that entanglement of all the independent sources is not a necessity for generation of non n-local correlations in star topology. Characterization of sources in terms of minimum entanglement requirement for any fixed violation amount of the n-local inequalities is also provided. Interestingly, detection of non n-locality is ensured in the network if product of concurrence of all the sources involved exceeds 1/2. .