Implications of the Pusey-Barrett-Rudolph quantum no-go theorem

TL;DR

This paper analyzes the Pusey-Barrett-Rudolph quantum no-go theorem, clarifying its assumptions, constructing models that evade it, and exploring implications for hidden-variable theories and measurement inefficiencies.

Contribution

It precisely defines the class of models targeted by the theorem, constructs equivalent models that avoid it, and identifies the weakest assumptions needed for the theorem's applicability.

Findings

Identifies 'compactness' as the weakest assumption for the theorem.

Constructs models that evade the no-go theorem.

Shows some measurements must have built-in inefficiencies.

Abstract

Pusey, Barrett, and Rudolph introduce a new no-go theorem for hidden-variables models of quantum theory. We make precise the class of models targeted and construct equivalent models that evade the theorem. The theorem requires assumptions for models of composite systems, which we examine, determining "compactness" as the weakest assumption needed. On that basis, we demonstrate results of the Bell-Kochen-Specker theorem. Given compactness and the relevant class of models, the theorem can be seen as showing that some measurements on composite systems must have built-in inefficiencies, complicating its testing.