The measure of PBR's reality

TL;DR

This paper revisits the Pusey-Barret-Rudolph theorem, arguing that the reality of a quantum state depends on whether it has been measured, thus linking measurement to the physical reality of quantum states.

Contribution

It provides a reinterpretation of the PBR theorem, emphasizing the role of measurement in defining the reality of quantum states.

Findings

Measured states are physical properties with reality.

Unmeasured states are regarded as pure information.

The statement of PBR's theorem is significantly modified.

Abstract

We review the Pusey-Barret-Rudolph (PBR) theorem\cite{PBR} and their setup, and arrive to the conclusion that the reality of a quantum state $\psi$ is intrinsically attached to the measurement the system described by $\psi$ has undergone. We show that a state that has not been measured can be regarded as pure information, while a state that has been measured has to be regarded as a physical property of a certain system, having a counterpart in reality. This demonstration implies that the statement of PBR's theorem changes in a meaningful way.