Revealing Hidden Non n-Locality In n-Local Star Network

TL;DR

This paper explores how filtering operations in star-shaped quantum networks can reveal hidden non n-local correlations, surpassing traditional Bell nonlocality constraints, and highlights the advantage of nonseparable filters in such networks.

Contribution

It introduces a framework for sequential n-local networks with filtering operations, demonstrating the ability to reveal non n-locality without Bell nonlocality and showing the advantage of nonseparable filters.

Findings

Sequential networks can generate non n-local correlations without Bell nonlocality.

Separable filters cannot reveal non n-locality in networks with Bell local states.

Nonseparable multi-qubit filters offer advantages due to network topology.

Abstract

Keeping pace with technological advancement, in the past decade, use of scalable networks have extended the study of quantum non-classicality beyond the regime of Bell-CHSH nonlocality. Present work provide characterization of non n-locality that can be exploited by incorporating filtering operations in star-shaped n-local networks. This in turn provide a framework of sequential n-local networks capable of generating non n-local correlations by involving some suitable form of stochastic local operations assisted with classical communications(SLOCC). It is observed that for effectiveness of such sequential networks, Bell-CHSH nonlocality(upto SLOCC operations) of every individual two-qubit state, distributed in the network, is not mandatory. However, there does not exist any separable local filter, which when applied in n-local network involving only Bell local states(upto SLOCC operations), can reveal non n-locality. Interestingly, instances revealing advantage of nonseparable mutli-qubit local filters over separable mutli-qubit local filters(by central node) are obtained. Such an advantage is attributable to the specific topology of star-shaped n-local networks and thus can never be reflected in Bell scenario.