Local Quantum Measurement and No-Signaling Imply Quantum Correlations

TL;DR

This paper demonstrates that assuming local quantum mechanics and finite information speed constrains all correlations to be quantum mechanical, implying nonlocal correlations beyond quantum theory would challenge the validity of quantum mechanics itself.

Contribution

It establishes that local quantum mechanics combined with finite information speed limits correlations to quantum bounds without assuming tensor product structure.

Findings

Nonlocal correlations beyond quantum mechanics would invalidate quantum theory locally.

Local quantum mechanics and finite information speed imply quantum correlations.

The tensor product formalism is not assumed in the analysis.

Abstract

We show that, assuming that quantum mechanics holds locally, the finite speed of information is the principle that limits all possible correlations between distant parties to be quantum mechanical as well. Local quantum mechanics means that a Hilbert space is assigned to each party, and then all local positive-operator-valued measurements are (in principle) available; however, the joint system is not necessarily described by a Hilbert space. In particular, we do not assume the tensor product formalism between the joint systems. Our result shows that if any experiment would give nonlocal correlations beyond quantum mechanics, quantum theory would be invalidated even locally.