Relative descriptors for quantum agents

TL;DR

This paper explores the use of the Heisenberg picture in Everettian quantum mechanics to analyze the Frauchiger-Renner thought experiment, revealing non-sharp foliations and histories of quantum agents, thus clarifying paradoxes.

Contribution

It introduces a novel analysis of quantum agents using the Heisenberg picture, showing non-sharp memory registries and resolving paradoxes in Everettian mechanics.

Findings

No paradox within the thought experiment in Everettian mechanics

Decoherence-free setup reveals a branching tree with non-sharp foliations

Quantum agents have histories with non-sharp memory registries

Abstract

We use the Heisenberg picture of Everettian quantum mechanics to work out the relative descriptors for the Frauchiger-Renner thought experiment. While Everettian mechanics reveals no paradox within the thought experiment, the decoherence-free setup offers an instructive branching tree. Traditionally, branching structures derived from the Schr\"odinger picture suggest that foliations are always sharply defined. However, the Heisenberg picture demonstrates that the tree contains regions with inherently non-sharp foliations, leading to the conclusion that, in Everettian mechanics, quantum agents possess a history with a non-sharp memory registry.