Classical system boundaries cannot be determined within quantum Darwinism

TL;DR

Quantum Darwinism fails to establish a purely quantum-mechanical basis for classicality emergence because multiple observers cannot independently verify the classical boundary of a system without prior assumptions.

Contribution

The paper demonstrates that quantum Darwinism cannot define classical system boundaries solely through quantum mechanics, challenging its explanatory power for classical emergence.

Findings

Observers cannot jointly verify system boundaries without prior assumptions

Quantum Darwinism does not provide a purely quantum explanation for classicality

Classical boundaries require a priori classical assumptions

Abstract

Multiple observers who interact with environmental encodings of the states of a macroscopic quantum system S as required by quantum Darwinism cannot demonstrate that they are jointly observing S without a joint a priori assumption of a classical boundary separating S from its environment E. Quantum Darwinism cannot, therefore, be regarded as providing a purely quantum-mechanical explanation of the "emergence" of classicality.