Decoherence and the (non)emergence of classicality

TL;DR

This paper argues that decoherence alone does not account for the emergence of classicality in quantum systems, as typical universes do not exhibit classical behavior despite decoherence effects.

Contribution

It demonstrates that classicality does not naturally emerge from decoherence in generic quantum states, challenging common assumptions in quantum foundations.

Findings

Decoherence does not guarantee classical behavior in typical quantum states.

Most universes with decoherence do not show classicality in macroscopic subsystems.

Special, non-generic quantum states are required for classicality to emerge.

Abstract

We consider the claim that decoherence explains the emergence of classicality in quantum systems, and conclude that it does not. We show that, given a randomly chosen universe composed of a variety of subsystems, some of which are macroscopic and subject to decoherence-inducing interactions, and some of which are microscopic, the macroscopic subsystems will not display any distinctively classical behavior. Therefore, a universe in which macroscopic and microscopic do display distinct behavior must be in a very special, highly nongeneric quantum state.