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TT: Fachverband Tiefe Temperaturen

TT 18: Focus Session: Relaxation Timescales in Open Quantum Systems (joint session TT/DY)

TT 18.5: Topical Talk

Monday, March 9, 2026, 17:15–17:45, CHE/0089

Connecting time-nonlocal and time-local quantum master equations — •Maarten Wegewijs — Peter Grünberg Institut, Forschungszentrum Jülich, 52425 Jülich, Germany — Institute for Theory of Statistical Physics, RWTH Aachen, 52056 Aachen, Germany

A perhaps puzzling feature of open-system dynamics is that it admits both a retarded description via a time-nonlocal memory-kernel K and an equivalent time-convolutionless description by a time-local generator G. This leads to a split in approaches to the problem of time scales in open quantum systems.

In this talk I discuss an elegant fixed-point relation G = K(G) that connects these two approaches directly, without first solving the respective quantum master equations for the dynamics ultimately of interest. As applications, I connect the distinct results (!) obtained when expanding in the same perturbation parameter and relate distinct time-scales (!) obtained by approximations approaching the same, exact stationary state. The fixed-point relation is also explicitly related to quantum Markovianity as defined by completely-positive divisibility of the dynamics (Huelga, Rivas, Plenio): What generates the retardation of the memory kernel turns out to be precisely what defines the Markovian divisibility of the dynamics. Exact solutions of simple models of electron transport (resonant level) and atomic-decay (dissipative Jaynes-Cummings) illustate these findings.
[1] SciPost Phys. 7, 012 (2019)
[2] Phys. Rev. X 11, 021041 (2021)
[3] Phys. Rev. B 104, 155407 (2021)
[4] SciPost Phys. 12, 121 (2022)
[5] J. Chem. Phys. 161 (2024)

Keywords: memory; master equation; open system; transport; quantum