How Quantum Mechanics can consistently describe the use of itself

TL;DR

This paper analyzes the Frauchiger-Renner no-go theorem using an extended Wigner's friend thought experiment, demonstrating that inconsistencies arise only when descriptions are incomplete, and explores implications for relativity and nonlocality.

Contribution

It clarifies how a complete quantum description resolves apparent contradictions in the Frauchiger-Renner theorem and discusses implications for interpretations like Bohmian mechanics.

Findings

No inconsistency with complete descriptions

Tension between relativity and quantum nonlocality

Implications for Bohmian mechanics

Abstract

We discuss the no-go theorem of Frauchiger and Renner based on an "extended Wigner's friend" thought experiment which is supposed to show that any single-world interpretation of quantum mechanics leads to inconsistent predictions if it is applicable on all scales. We show that no such inconsistency occurs if one considers a complete description of the physical situation. We then discuss implications of the thought experiment that have not been clearly addressed in the original paper, including a tension between relativity and nonlocal effects predicted by quantum mechanics. Our discussion applies in particular to Bohmian mechanics.