Macroscopically nonlocal quantum correlations

TL;DR

This paper demonstrates that in the non-IID scenario, quantum correlations can persist at the macroscopic level, leading to Bell violations and challenging the principle of macroscopic locality.

Contribution

It extends the understanding of quantum correlations to non-IID cases, showing that macroscopic locality can be violated without the IID assumption.

Findings

Quantum correlations can survive coarse-graining in non-IID scenarios.

Bell violations occur at the macroscopic level for collective measurements.

The Hilbert space structure of quantum theory is preserved macroscopically.

Abstract

It is usually believed that coarse-graining of quantum correlations leads to classical correlations in the macroscopic limit. Such a principle, known as macroscopic locality, has been proved for correlations arising from independent and identically distributed (IID) entangled pairs. In this letter we consider the generic (non-IID) scenario. We find that the Hilbert space structure of quantum theory can be preserved in the macroscopic limit. This leads directly to a Bell violation for coarse-grained collective measurements, thus breaking the principle of macroscopic locality.