Transient dynamics of open quantum systems

TL;DR

This paper introduces a renormalization group method for analyzing the transient dynamics of open quantum systems across all time scales, revealing new insights into long-time behavior and deviations from previous models.

Contribution

The paper develops an RG approach that analytically studies transient dynamics in open quantum systems, highlighting differences in long-time behavior and scaling.

Findings

Significant deviations from previous long-time predictions in the ohmic spin boson model.

Long-time behavior linked to scaling near fixed points and inverse time cutoffs.

Weak coupling problems may become strong coupling issues for long-time analysis.

Abstract

We present a renormalization group (RG) method which allows for an analytical study of the transient dynamics of open quantum systems on all time scales. Whereas oscillation frequencies and decay rates of exponential time evolution follow from the fixed point positions, the long-time behavior of pre-exponential functions is related to the scaling behavior around the fixed points. We show that certain terms of the RG flow are only cut off by inverse time, which leads to a difference between infrared and ultraviolet scaling. An evaluation for the ohmic spin boson model at weak damping reveals significant deviations from previous predictions in the long-time regime. We propose that weak coupling problems for stationary quantities can in principle turn into strong coupling ones for the determination of the long-time behavior.