Defining the local part of a hidden variable model: a comment

TL;DR

This paper clarifies the definition of the local part in hidden variable models, emphasizing the importance of physicality and addressing misconceptions caused by non-physical counterexamples.

Contribution

It refines the notion of the local part in hidden variable models, emphasizing physicality and clarifying misunderstandings in recent literature.

Findings

Recent counterexamples are based on non-physical definitions of local hidden variables.

The notion of local part is grounded in Bell's principles and physical plausibility.

The clarification resolves confusion about the limitations of hidden variable explanations for quantum theory.

Abstract

In [Physical Review Letters 101, 050403 (2008)], we showed that quantum theory cannot be explained by a hidden variable model with a non-trivial local part. The purpose of this comment is to clarify our notion of local part, which seems to have caused some confusion in the recent literature. This notion is based on Bell's and demands that local hidden variables are physical, the idea being that, if discovered, they would not contradict basic physical principles. We explain why the recent supposed "counterexamples" that have appeared are not counterexamples to our theorem--in fact they are based on a definition of local hidden variables which would allow signalling and is therefore not physical.