Emergence of the Classical from within the Quantum Universe

TL;DR

This paper discusses how classical reality emerges from quantum systems through decoherence, environment-induced superselection, and quantum Darwinism, which explains the dissemination of information in the environment leading to objective classical states.

Contribution

It provides a comprehensive explanation of the emergence of classicality from quantum mechanics via environment interactions and information dissemination mechanisms.

Findings

Decoherence suppresses quantum superpositions in open systems.

Quantum Darwinism explains the proliferation of information in the environment.

Objective classical states arise without direct measurement, through environmental monitoring.

Abstract

Decoherence shows how the openness of quantum systems -- interaction with their environment -- suppresses flagrant manifestations of quantumness. Einselection accounts for the emergence of preferred quasi-classical pointer states. Quantum Darwinism goes beyond decoherence. It posits that the information acquired by the monitoring environment responsible for decoherence is disseminated, in many copies, in the environment, and thus becomes accessible to observers. This indirect nature of the acquisition of information by observers who use the environment as a communication channel is the mechanism through which objective classical reality emerges from the quantum substrate: States of the systems of interest are not subjected to direct measurements (hence, not perturbed) by the agents acquiring information about them. Thus, they can exist unaffected by the information gained by observers.