Is contextuality about the identity of random variables?

TL;DR

This paper compares two approaches to contextuality in quantum theory, highlighting limitations of the context-dependent method and clarifying the role of random variable identity in understanding contextuality.

Contribution

It provides a critical analysis contrasting context-independent and context-dependent treatments of random variables in contextuality theories.

Findings

Context-independent approach treats identical measurements uniformly.

Context-dependent approach associates contextuality with joint distributions.

Limitations of the context-dependent approach as a physical theory are identified.

Abstract

Recent years have seen new general notions of contextuality emerge. Most of these employ context-independent symbols to represent random variables in different contexts. As an example, the operational theory of Spekkens [1] treats an observable being measured in two different contexts identically. Non-contextuality in this approach is the impossibility of drawing ontological distinctions between identical elements of the operational theory. However, a recent collection of work seeks to exploit context-dependent symbols of random variables to interpret contextuality [2, 3]. This approach associates contextuality with the possibility of imposing a particular joint distribution on random variables recorded under different experimental contexts. This paper compares these two different treatments of random variables and highlights the limitations of the context-dependent approach as a physical theory.