Seminar: Frederik vom Ende
We invite all colleagues interested in open quantum systems and quantum information to the upcoming seminar by Frederik vom Ende from Freie Universität Berlin (please see the title and abstract below). The seminar will take place next Thursday, October 10th, at 13:00 in P35-PS439. Lunch will be provided on-site.
Quantum-Dynamical Semigroups and the Church of the Larger Hilbert Space
The idea underlying open systems theory is to describe the evolution of non-isolated systems—at least approximately—via a differential equation ρ'(t)=Lρ(t) with L of a special form, called Lindblad- or GKSL-form. This is, however, not the only way to tackle this problem; another successful approach is to consider the system coupled to its environment, and then extract the system’s dynamics by tracing out the environment from the combined unitary evolution. While the physics literature features well-known approximations which guarantee when these two descriptions are compatible, in this talk we will investigate under what conditions they can match precisely: Our main result is that GKSL-dynamics can be written exactly as the reduced evolution of system plus some environment if and only if the environment is infinite-dimensional with an overall unbounded Hamiltonian. In doing so we obtain a second-order Taylor-approximation for bounded system-environment Hamiltonians, with some familiar coefficients.