Simulating quantum vibronic dynamics at finite temperatures with many body wave functions at 0K

TL;DR

This paper introduces a method to simulate finite-temperature quantum vibronic dynamics efficiently using zero-temperature many-body wave functions, enabling more practical studies of complex molecular systems.

Contribution

The authors demonstrate a numerical approach that extracts finite-temperature effects from a single zero-temperature wave function simulation using time-dependent variational matrix product states.

Findings

Efficient extraction of finite-temperature dynamics from zero-temperature simulations.

Application of the method to vibronic tunneling systems.

Identification of numerical challenges at high temperatures.

Abstract

For complex molecules, nuclear degrees of freedom can act as an environment for the electronic `system' variables, allowing the theory and concepts of open quantum systems to be applied. However, when molecular system-environment interactions are non-perturbative and non-Markovian, numerical simulations of the complete system-environment wave function become necessary. These many body dynamics can be very expensive to simulate, and extracting finite-temperature results - which require running and averaging over many such simulations - becomes especially challenging. Here, we present numerical simulations that exploit a recent theoretical result that allows dissipative environmental effects at finite temperature to be extracted efficiently from a single, zero-temperature wave function simulation. Using numerically exact time-dependent variational matrix product states, we verify that this approach can be applied to vibronic tunneling systems and provide insight into the practical problems lurking behind the elegance of the theory, such as the rapidly growing numerical demands that can appear for high temperatures over the length of computations.