Consensus About Classical Reality in a Quantum Universe

Quantum Darwinism explains how the environment redundantly encodes information about certain preferred quasi-classical states, leading to consensus between observers which can be referred to as objective reality. To capture this, we propose an information-theoretic measure that gauges the level of agreement on what exists in the records available to observers. We then test the proposed measure with numerical simulations of many-body systems. Our focus is on how consensus identifies stable, effectively classical pointer states, which serve as the foundation of a collective classical world. In particular, we demonstrate that, in the quantum universe, objective classical reality emerges through the widespread dissemination of amplified information about these pointer states.