Quantum nonlocality based on finite-speed causal influences leads to superluminal signaling

TL;DR

This paper demonstrates that models with finite-speed causal influences explaining quantum nonlocality inevitably allow superluminal signaling, thus challenging their validity and reinforcing the nonlocal nature of quantum correlations.

Contribution

It proves that any finite-speed causal influence model for quantum nonlocality leads to superluminal communication, excluding such models as explanations for quantum correlations.

Findings

Finite-speed influence models predict superluminal signaling.

Superluminal communication can be achieved without hidden variables.

Quantum nonlocality cannot be explained by finite-speed causal influences.

Abstract

The experimental violation of Bell inequalities using spacelike separated measurements precludes the explanation of quantum correlations through causal influences propagating at subluminal speed. Yet, any such experimental violation could always be explained in principle through models based on hidden influences propagating at a finite speed v>c, provided v is large enough. Here, we show that for any finite speed v with c<v<infinity, such models predict correlations that can be exploited for faster-than-light communication. This superluminal communication does not require access to any hidden physical quantities, but only the manipulation of measurement devices at the level of our present-day description of quantum experiments. Hence, assuming the impossibility of using nonlocal correlations for superluminal communication, we exclude any possible explanation of quantum correlations in terms of influences propagating at any finite speed. Our result uncovers a new aspect of the complex relationship between multipartite quantum nonlocality and the impossibility of signalling.