Extended Wigner's friend paradoxes do not require nonlocal correlations

TL;DR

This paper demonstrates that extended Wigner's friend paradoxes can be constructed without relying on nonlocal quantum correlations, instead using noncontextuality failure and a new metaphysical assumption called Commutation Irrelevance.

Contribution

It introduces a no-go theorem based on noncontextuality failure, expanding the understanding of measurement problems beyond Bell inequality violations.

Findings

Extended Wigner's friend paradoxes do not require Bell nonlocality.

A new metaphysical assumption called Commutation Irrelevance is proposed.

The theorem shows paradoxes can arise from noncontextuality failure alone.

Abstract

Extended Wigner's friend no-go theorems provide a modern lens for investigating the measurement problem, by making precise the challenges that arise when one attempts to model agents as dynamical quantum systems. Most such no-go theorems studied to date, such as the Frauchiger-Renner argument and the Local Friendliness argument, are explicitly constructed using quantum correlations that violate Bell inequalities. In this work, we show that such correlations are not necessary for having extended Wigner's friend paradoxes, by constructing a no-go theorem utilizing a proof of the failure of noncontextuality. The argument hinges on a novel metaphysical assumption (which we term Commutation Irrelevance) that is a natural extension of a key assumption going into the Frauchiger and Renner's no-go theorem.