Persistency of entanglement and nonlocality in multipartite quantum systems

TL;DR

This paper explores how entanglement and nonlocality in multipartite quantum systems persist under particle loss, introducing a new measure called persistency of nonlocality and analyzing its relation to state symmetry.

Contribution

It defines and investigates the concept of persistency of nonlocality, providing insights into how symmetry affects quantum correlations and proposing device-independent methods to estimate state asymmetry.

Findings

States with maximal persistency exhibit strong nonlocal correlations.

High symmetry in states tends to reduce correlation strength.

The work introduces a device-independent approach to estimate state asymmetry.

Abstract

The behaviour under particle loss of entanglement and nonlocality is investigated in multipartite quantum systems. In particular, we define a notion of persistency of nonlocality, which leads to device-independent tests of persistent entanglement. We investigate the persistency of various classes of multipartite quantum states, exhibiting a variety of different behaviours. A particular attention is devoted to states featuring maximal persistency. Finally we discuss a link between the symmetry of a state and its persistency, illustrating the fact that too much symmetry reduces the strength of correlations among subsystems. These ideas also lead to a device-independent estimation of the asymmetry of a quantum state.