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DY: Fachverband Dynamik und Statistische Physik

DY 12: Quantum Dynamics, Decoherence, and Quantum Information II

DY 12.8: Vortrag

Dienstag, 15. März 2011, 12:15–12:30, ZEU 255

Dissipative quantum mechanics: Taming the sign problem — •Jürgen T. Stockburger — Universität Ulm, Institut für Theoretische Physik, 89069 Ulm

Influence functionals are a straightforward non-perturbative approach to open quantum systems in the path integral formalism. Numerical work based on this approach suffers from the dynamical sign problem, a severe degradation of sampling statistics for long time intervals. However, influence functionals can be formally re-interpreted as generating functionals of c-number-valued quantum noise. This immediately leads to an equivalent non-Markovian stochastic dynamics in terms of pure or mixed quantum states, allowing numerical simulation in the Schrödinger picture. Since the noise forces are complex-valued, a new (typically milder) sign problem arises from the non-unitary propagation of stochastic samples. For friction kernels with finite effective support, this simulation method is modified such that stochastic variances remain bounded in the long-time limit, thus curing the sign problem. Hybrid stochastic approaches which preserve hermiticity of individual samples are also discussed.