A non-local hidden-variable model that violates Leggett-type inequalities

TL;DR

This paper presents a contextual, realistic non-local hidden-variable model that reproduces quantum predictions and violates Leggett-type inequalities, challenging the notion that such inequalities rule out all non-local realistic theories.

Contribution

The paper introduces an explicit non-local hidden-variable model that reproduces quantum mechanics and violates Leggett-type inequalities, showing these inequalities do not exclude all realistic models.

Findings

The model reproduces quantum correlations.

Leggett-type inequalities are not universally valid.

Realistic, contextual models remain plausible.

Abstract

Recent experiments of Groeblacher et al. proved the violation of a Leggett-type inequality that was claimed to be valid for a broad class of non-local hidden-variable theories. The impossibility of constructing a non-local and realistic theory, unless it entails highly counterintuitive features, seems thus to have been experimentally proved. This would bring us close to a definite refutation of realism. Indeed, realism was proved to be also incompatible with locality, according to a series of experiments testing Bell inequalities. The present paper addresses the said experiments of Groeblacher et al. and presents an explicit, contextual and realistic, model that reproduces the predictions of quantum mechanics. It thus violates the Leggett-type inequality that was established with the aim of ruling out a supposedly broad class of non-local models. We can thus conclude that plausible contextual, realistic, models are still tenable. This restates the possibility of a future completion of quantum mechanics by a realistic and contextual theory which is not in a class containing only highly counterintuitive models. The class that was ruled out by the experiments of Groeblacher et al. is thus proved to be a limited one, arbitrarily separating models that physically belong in the same class.