Dr. Marko Žnidarič: Many-body physics of open quantum systems

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      Many-body physics of open quantum systems

      Dr. Marko Žnidarič, Fakulteta za matematiko in fiziko, Univerza v Ljubljani

Perfectly isolated quantum systems, governed by unitary evolution, are often an idealization. To describe the evolution of the reduced density matrix, ignoring environmental degrees of freedom, one has to resort to either generalized master equations, or, in general, to quantum maps. I will give a short overview of different types of evolutions possible in quantum mechanics. The structure of quantum maps can be rather complicated -- a complete classification is known only for a single two-level system.

Fortunately, much simpler description in terms of the Lindblad master equation is often sufficient. The Lindblad equation is the most general form of a master equation without memory effects permissible in quantum mechanics. It has been used in quantum optics since '70, in recent years though it proved to be useful also in other fields like statistical physics, condensed matter and quantum information. I will present some of these recent findings, like preparation of states or transformations and properties of nonequilibrium states of many-body systems.