Exclusivity principle and unphysicality of Garg-Mermin correlation

TL;DR

This paper investigates the physical plausibility of certain quantum correlations using the exclusivity principle, revealing that Garg-Mermin correlations are unphysical and highlighting differences from the no-signaling condition.

Contribution

It demonstrates that the local orthogonality principle at the single-copy level cannot reproduce the no-signaling condition for Garg-Mermin correlations, challenging previous assumptions.

Findings

Garg-Mermin correlations are shown to be unphysical.

The local orthogonality principle differs from no-signaling in the GM scenario.

The study clarifies the limitations of simple principles in quantum foundations.

Abstract

The question concerning the physical realizability of a probability distribution is of quite importance in Quantum foundations. Specker first pointed out that this question cannot be answered from Kolmogorov's axioms alone. Lately, this observation of Specker has motivated simple principles (exclusivity principle/ local orthogonality principle) that can explain quantum limit regarding the possible sets of experimental probabilities in various nonlocality and contextuality experiments. We study Specker's observation in the simplest scenario involving three inputs each with two outputs. Then using only linear constraints imposed on joint probabilities by this principle, we reveal unphysical nature of Garg-Mermin (GM) correlation. Interestingly, GM correlation was proposed to falsify the following suggestion by Fine: if the inequalities of Clauser and Horne (CH) holds, then there exists a deterministic local hidden-variable model for a spin-1/2 correlation experiment of the Einstein-Podolsky-Rosen type, even when more than two observables are involved on each side. Our result establishes that, unlike in the CH scenario, the local orthogonality principle at single copy level is not equivalent to the no-signaling condition in the GM scenario.