【Seminar】"Master Equations and the Mean Force Gibbs State"

Speaker

James Cresser, University of Glasgow

Title

"Master Equations and the Mean Force Gibbs State"

Abstract

The master equation is central to theory of open quantum systems. It has a history that dates back to 1927, but exploded into prominence in the 1970s with applications in quantum optics and elsewhere, along with developments of the formal theory of these equations. Nevertheless there are still issues that are incompletely understood, or misunderstood regarding these equations. In the first part of the talk a brief overview of the master equation will be given, with a focus on its steady state. The Gibbs state is often taken as the `thermodynamically correct’ steady state, but in fact it turns out not to be the true steady state of a master equation. That is instead believed to be a generalised version, the mean force Gibbs state. Useful expressions for this state are hard to come by, but can be found in two limiting cases: when the system-reservoir coupling is very weak, and when it is very strong. These two limiting cases will be considered, with a connection of the ultrastrong case to the quantum Zeno effect also given a passing mention.