Multipartite quantum nonlocality under local decoherence

TL;DR

This paper investigates how multipartite quantum states maintain nonlocal correlations under local decoherence, revealing that entanglement resilience does not always align with Bell-inequality violations or nonlocal content, impacting quantum communication protocols.

Contribution

It provides a detailed analysis of nonlocality behavior under local decoherence, highlighting anomalies and their effects on quantum protocol efficiency, especially for GHZ states.

Findings

Entanglement resilience does not always match Bell-inequality violation resilience.

Examples of anomalous nonlocal behaviors in bipartite and multipartite states.

Quantum gains in communication complexity can increase despite exponential decay of entanglement.

Abstract

We study the nonlocal properties of two-qubit maximally-entangled and N-qubit Greenberger-Horne-Zeilinger states under local decoherence. We show that the (non)resilience of entanglement under local depolarization or dephasing is not necessarily equivalent to the (non)resilience of Bell-inequality violations. Apart from entanglement and Bell-inequality violations, we consider also nonlocality as quantified by the nonlocal content of correlations, and provide several examples of anomalous behaviors, both in the bipartite and multipartite cases. In addition, we study the practical implications of these anomalies on the usefulness of noisy Greenberger-Horne-Zeilinger states as resources for nonlocality-based physical protocols given by communication complexity problems. There, we provide examples of quantum gains improving with the number of particles that coexist with exponentially-decaying entanglement and non-local contents.