An operational framework for nonlocality

TL;DR

This paper proposes an operational framework for nonlocality in quantum systems, highlighting inconsistencies in existing definitions and suggesting alternatives to ensure nonlocality cannot be generated by local operations and classical communication.

Contribution

It introduces a new operational framework for nonlocality, aligning it with principles similar to those used for entanglement, and critiques Svetlichny's definition for inconsistency.

Findings

Svetlichny's definition allows creation of genuine tripartite nonlocality by two parties.

The proposed framework ensures nonlocality cannot be generated by local operations and classical communication.

Alternative definitions are discussed to restore consistency in nonlocality characterization.

Abstract

Due to the importance of entanglement for quantum information purposes, a framework has been developed for its characterization and quantification as a resource based on the following operational principle: entanglement among $N$ parties cannot be created by local operations and classical communication, even when $N-1$ parties collaborate. More recently, nonlocality has been identified as another resource, alternative to entanglement and necessary for device-independent quantum information protocols. We introduce an operational framework for nonlocality based on a similar principle: nonlocality among $N$ parties cannot be created by local operations and allowed classical communication even when $N-1$ parties collaborate. We then show that the standard definition of multipartite nonlocality, due to Svetlichny, is inconsistent with this operational approach: according to it, genuine tripartite nonlocality could be created by two collaborating parties. We finally discuss alternative definitions for which consistency is recovered.