A Closed-System Perspective for Decoherence

SEBASTIAN FORTIN

Washington

Conferencia; New Directions in the Foundations of Physics; 2014

University of Maryland

 According to the works of Zurek et al., decoherence is a process resulting from the interaction between an open quantum system and its environment (environment-induced decoherence, EID). This process determines the privileged basis, which defines the observables that will behave classically. However, this approach still has to face conceptual difficulties, e.g. it cannot be applied to closed systems like the universe as a whole, and it does not supply a criterion for deciding where to place the cut between system and environment.On the other hand, there are other approaches to describe both the decoherence and the relaxation of quantum systems. For example, in the works of Castagnino et al., decoherence is a process resulting from the dynamics of a closed quantum system governed by a Hamiltonian with continuous spectrum (self-induced decoherence, SID). This process also determines the privileged basis, that is, defines the classical observables that can be interpreted as Boolean properties.In this talk we will focus our attention on a closed-system perspective based on expectation values. This will lead us to a general theoretical framework for decoherence, which shows that decoherence is relative to the choice of a set of relevant observables (observables of the open system in EID, van Hove observables of the closed system in SID), and unifies previous approaches from the perspective of the closed system. This general framework describes relaxation and decoherence in quantum systems and solves the conceptual difficulties of the EID approach.