Local quantum mechanics and superquantum correlations imply superluminal signaling

TL;DR

This paper demonstrates that combining local quantum mechanics with superquantum correlations inevitably leads to superluminal signaling, challenging the consistency of such theories.

Contribution

It provides a specific example showing that local quantum mechanics plus superquantum correlations imply superluminal signaling, highlighting inconsistencies in generalized non-signaling theories.

Findings

Superquantum correlations can cause superluminal signaling when combined with local quantum mechanics.

Replacing local dynamics in GNST with local unitaries can lead to signaling violations.

The results challenge the consistency of certain generalized non-signaling theories.

Abstract

It has been shown that local quantum measurements and no-signaling imply quantum correlations (Barnum et al. Phys. Rev. Lett., 104, 140401 (2010)). This entails that superquantum correlations will be superluminaly signaling if we admit the validity of local quantum mechanics. We present a specific, simple instance of this situation. Our result also has the interpretation that replacing the local (trivial) dynamics in a generalized non-signaling theory (GNST) by one that admits local unitaries, results in a probability distribution that may be positive and normalization-preserving but violates no-signaling, and is thus inconsistent within the formalism.