Efficient calculation of open quantum system dynamics and time-resolved spectroscopy with Distributed Memory HEOM (DM-HEOM)

TL;DR

This paper introduces DM-HEOM, a scalable distributed memory implementation of the hierarchical equations of motion, enabling efficient and accurate simulation of open quantum system dynamics and spectroscopy in large molecular complexes.

Contribution

The authors develop a scalable, distributed memory version of HEOM, allowing for the simulation of larger and more complex open quantum systems without extensive computational resources.

Findings

DM-HEOM accurately computes time- and frequency-resolved signals.

It handles arbitrary system-environment couplings across various temperatures.

The method enables simulations of large molecular complexes previously infeasible.

Abstract

Time- and frequency resolved optical signals provide insights into the properties of light harvesting molecular complexes, including excitation energies, dipole strengths and orientations, as well as in the exciton energy flow through the complex. The hierarchical equations of motion (HEOM) provide a unifying theory, which allows one to study the combined effects of system-environment dissipation and non-Markovian memory without making restrictive assumptions about weak or strong couplings or separability of vibrational and electronic degrees of freedom. With increasing system size the exact solution of the open quantum system dynamics requires memory and compute resources beyond a single compute node. To overcome this barrier, we developed a scalable variant of HEOM. Our distributed memory HEOM, DM-HEOM, is a universal tool for open quantum system dynamics. It is used to accurately compute all experimentally accessible time- and frequency resolved processes in light harvesting molecular complexes with arbitrary system-environment couplings for a wide range of temperatures and complex sizes.