Reproducing entanglement through local classical resources with no communication

TL;DR

This paper demonstrates that classical resources, without communication, can reproduce quantum entanglement correlations and even surpass quantum limits, challenging the notion that such correlations are exclusively quantum.

Contribution

It provides a classical realization of models reproducing quantum correlations using only local resources, without any communication, and exceeds quantum bounds.

Findings

Classical resources can reproduce quantum correlations.

Stronger correlations than quantum maximum violation achieved.

No communication needed for reproducing entanglement-like correlations.

Abstract

Entanglement is one of the most intriguing features of quantum mechanics. It gives rise to peculiar correlations which cannot be reproduced by a large class of alternative theories, the so-called hidden-variable models, that use parameters in addition to the wave-function. This incompatibility was quantified through the celebrated Bell inequalities, and more recently through new inequalities due to Leggett. Experiments confirm the predictions of quantum mechanics. However, this does not imply that quantum mechanics is the ultimate theory, unsusceptible of improvement, nor that quantum mechanics is essentially non-local. The theories ruled out by Bell and Leggett inequalities are required to satisfy some hypotheses, none of which is implied by locality alone. By dropping one or more hypotheses, it is possible not only to violate said inequalities, but to reproduce the quantum mechanical predictions altogether. So far, the models proposed were only mathematical constructs. In this paper we provide a classical realization of two of these models, using local classical resources, without recurring to any type of communication among the involved parties. The resources consist in two baseballs, two bats, and a number of synchronized watches. Our results demonstrate the possibility of reproducing the quantum mechanical correlations, and even creating stronger correlations which provide the maximum violation of the Bell inequality, beyond the Cirel'son bound for quantum mechanics.