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Center for Nonlinear Studies |
A quantum system in contact with its surroundings (environment) is said to be open. One of the main goals of the theory of open systems is to describe generic effects of environments on the system, such as thermalization and decoherence. The general approach is to remove the degrees of freedom of the environment ("tracing it out") and to obtain a description of the reduced dynamics of the open system only. This leads to a non-hamiltonian dynamics.
In this talk, we present a method of quantum resonances which allows us to obtain the reduced dynamics of open systems, starting from a true hamiltonian dynamics of the system plus the environment. Our method is valid for small couplings between the system and the environment, and it holds uniformly for all times. We present an application to a not explicitly solvable model of a qubit register coupled to a thermal environment through an interaction having both energy conserving and energy-exchange parts. We obtain in particular the decay rates of the register density matrix elements in the energy basis (decoherence rates).
The results presented are based on collaborations with G.P. Berman and I.M. Sigal.
Host: Gennady Berman, T-13