Understanding decoherence by comparing classical and quantum irreversibility

OLIMPIA LOMBARDI; MANUEL HERRERA

Utrecht

Congreso; 19th European Conference on Foundations of Physics; 2018

University of Utrecht

If decoherence is an irreversible process, its physical meaning might be clarified by comparing quantum and classical irreversibility. In this talk we carry out this comparison, from which a unified view of the emergence of irreversibility arises, applicable both to the classical and to the quantum case. According to this unified view, in the two cases the relation between the irreversible macro-level and the reversible micro-level is a kind of generalized coarse-graining, mathematically defined as a projection. This position supplies an understanding of the phenomenon of decoherence different from that implicit in most presentations: the reduced state is not the quantum state of the open system, but a coarse-grained state of the closed composite system; as a consequence, decoherence is not a phenomenon resulting from the interaction between an open system and its environment, but rather it is a coarse-grained evolution that emerges from disregarding certain degrees of freedom of the whole closed system.