Temperature Controlled Open Quantum System Dynamics using Time-dependent Variational Method

TL;DR

This paper introduces a thermalization algorithm integrated into a variational method to simulate open quantum system dynamics, enabling temperature control and faster computations by thermalizing bath vibrational modes.

Contribution

The authors extend the Dirac-Frenkel variational method with a thermalization algorithm for open quantum systems, allowing temperature control and improved computational efficiency.

Findings

Thermalization controls bath temperature via stochastic scatterings.

The method accelerates calculations by reducing vibrational modes needed.

Numerical results show effective exciton relaxation simulation.

Abstract

Dirac-Frenkel variational method with Davydov D2 trial wavefunction is extended by introducing a thermalization algorithm and applied to simulate dynamics of a general open quantum system. The algorithm allows to control temperature variations of a harmonic finite size bath, when in contact with the quantum system. Thermalization of the bath vibrational modes is realised via stochastic scatterings, implemented as a discrete-time Bernoulli process with Poisson statistics. It controls bath temperature by steering vibrational modes' evolution towards their canonical thermal equilibrium. Numerical analysis of the exciton relaxation dynamics in a small molecular cluster reveals that thermalization additionally provides significant calculation speed up due to reduced number of vibrational modes needed to obtain the convergence.