Tripartite non-classical correlations without backwards in time signalling

TL;DR

This paper explores the limitations of no backwards in time signaling in three-party quantum correlations, showing it does not always imply classical causal order, unlike in two-party cases, with explicit examples and generalizations.

Contribution

It reveals that no backwards in time signaling is insufficient for classical causality in three-party scenarios and extends linear two-time state results to multiple parties.

Findings

No backwards in time signaling does not guarantee classical causality for three parties.

Explicit example demonstrating non-classical correlations without backwards signaling.

Generalization of two-time state results to multi-party scenarios.

Abstract

We investigate the relationship between no backwards in time signaling and classically causal correlations. We discover that unlike the case for two parties, the no backwards in time signaling paradigm for three parties is not enough to ensure that correlations can be reproduced with a classical causal ordering. We demonstrate this with an explicit example. We also generalise some existing results for linear two-time states to multi-party scenarios.