The Problem of Identifying the System and the Environment in the Phenomenon of Decoherence

Abstract

The term “decoherence” generally refers to the quantum process that supposedly turns a pure state into a mixed state, which is diagonal in a well-defined basis. The orthodox explanation of the phenomenon is given by the so-called environment-induced decoherence (EID) approach (Zurek 1982, 1993, 2003; Paz and Zurek 2002), according to which decoherence results from the interaction of an open quantum system and its environment. The study of different physical models shows that, under certain circumstances, the reduced state of the open system rapidly diagonalizes in a basis that identifies the candidates for classical states. By contrast to non-dissipative accounts to decoherence, the EID approach is commonly understood as a dissipative approach: “if one believes that classicality is really an emergent property of quantum open systems one may be tempted to conclude that the existence of emergent classicality will always be accompanied by other manifestations of openness such as dissipation of energy into the environment” (Paz and Zurek 2002, 6).