The emergence of classical properties through interaction with the environment

Robert C. Bishop, George Ellis

Paul Duruisseau, Akram Touil, Sebastian Deffner

Quantum Darwinism explains the emergence of classical objectivity within a quantum universe. However, to date most research in quantum Darwinism has focused on specific models and their stationary properties. To further our understanding of the quantum-to-classical transition it appears desirable to identify the general criteria a Hamiltonian has to fulfill to support classical reality. To this end, we categorize all models with 2-body interactions, and we show that only those with separable interaction of system and environment can support a pointer basis. We further show that "perfect" quantum Darwinism can only emerge if there are no intra-environmental interactions. Our analysis is complemented by the solution of the ensuing dynamics. We find that in systems that exhibit information scrambling, the dynamical emergence of classical objectivity is in direct competition with the non-local spread of quantum correlations. Our rigorous findings are illustrated with the numerical analysis of four representative models.

L. E. Ballentine

Mario Castagnino, Olímpia Lombardi

In this paper we argue that the emergence of the classical world from the underlying quantum reality involves two elements: self-induced decoherence and macroscopicity. Self-induced decoherence does not require the openness of the system and its interaction with the environment: a single closed system can decohere when its Hamiltonian has continuous spectrum. We show that, if the system is macroscopic enough, after self-induced decoherence it can be described as an ensemble of classical distributions weighted by their corresponding probabilities. We also argue that classicality is an emergent property that arises when the behavior of the system is described from an observational perspective.

Alberto Cordero

Claus Kiefer, Joos, E

We give a pedagogical introduction to the process of decoherence - the irreversible emergence of classical properties through interaction with the environment. After discussing the general concepts, we present the following examples: Localisation of objects, quantum Zeno effect, classicality of fields and charges in QED, and decoherence in gravity theory. We finally emphasise the important interpretational features of decoherence.