Pseudomodes and the corresponding transformation of the temperature-dependent bath correlation function

TL;DR

This paper investigates how the temperature-dependent bath correlation function transforms when inserting or removing pseudomodes in non-Markovian open quantum systems, revealing significant effects on system dynamics under strong coupling.

Contribution

It provides analytic formulas for the temperature-dependent transformation of the bath correlation function during pseudomode manipulation, incorporating initial state considerations.

Findings

Differences in BCFs lead to notable variations in system dynamics.

Strong coupling amplifies the impact of initial state differences.

Analytic expressions enable better modeling of temperature effects in pseudomode approaches.

Abstract

In open system approaches with non-Markovian environments, the process of inserting an individual mode (denoted as "pseudomode") into the bath or extracting it from the bath is widely employed. This procedure, however, is typically performed on basis of the spectral density (SD) and does not incorporate temperature. Here, we show how the - temperature-dependent - bath correlation function (BCF) transforms in such a process. We present analytic formulae for the transformed BCF and numerically study the differences between factorizing initial state and global thermal (correlated) initial state of mode and bath, respectively. We find that in the regime of strong coupling of the mode to both system and bath, the differences in the BCFs give rise to pronounced differences in the dynamics of the system.