Non-Markovian Quantum State Diffusion for Temperature-Dependent Linear Spectra of Light Harvesting Aggregates

TL;DR

This paper demonstrates that for temperature-dependent linear spectra of light-harvesting aggregates, a stochastic approach is unnecessary, allowing spectra to be computed efficiently via a single trajectory using a thermofield mapping.

Contribution

The paper introduces a method to compute temperature-dependent linear spectra without stochastic simulations by mapping finite temperature environments to zero temperature using thermofield techniques.

Findings

Spectra can be obtained from a single trajectory without stochastic averaging.

The thermofield method effectively maps finite temperature environments to zero temperature.

Efficient numerical solutions are achieved using standard integrators.

Abstract

Non-Markovian Quantum State Diffusion (NMQSD) has turned out to be an efficient method to calculate excitonic properties of aggregates composed of organic chromophores, taking into account the coupling of electronic transitions to vibrational modes of the chromophores. NMQSD is an open quantum system approach that incorporates environmental degrees of freedom (the vibrations in our case) in a stochastic way. We show in this paper that for linear optical spectra (absorption, circular dichroism) no stochastics is needed, even for finite temperatures. Thus, the spectra can be obtained by propagating a single trajectory. To this end we map a finite temperature environment to the zero temperature case using the so-called thermofield method. The resulting equations can then be solved efficiently by standard integrators.