The measurement problem is the measurement problem is the measurement problem

TL;DR

This paper discusses the measurement problem in quantum mechanics, highlighting that contradictions arise from subjective application of the measurement-update rule, and clarifies that these do not invalidate any interpretation.

Contribution

It clarifies that apparent contradictions in Wigner's-friend experiments stem from the incompatibility of collapse and unitarity, not from the invalidity of interpretations.

Findings

Contradictions arise from subjective application of measurement rules.

The incompatibility of collapse and unitarity explains the contradictions.

No interpretation of quantum theory is dismissed by these contradictions.

Abstract

Recently, it has been stated that single-world interpretations of quantum theory are logically inconsistent. The claim is derived from contradicting statements of agents in a setup combining two Wigner's-friend experiments. Those statements stem from applying the measurement-update rule subjectively, i.e., only for the respective agent's own measurement. We argue that the contradiction expresses the incompatibility of collapse and unitarity - resulting in different formal descriptions of a measurement - and does not allow to dismiss any specific interpretation of quantum theory.