Nonadiabatic \textit{ab initio} Quantum Dynamics without Potential Energy Surfaces

TL;DR

This paper introduces an efficient abab initiobb quantum dynamics method that avoids potential energy surfaces, using a stochastic wavefunction approach for accurate simulations of complex interacting quantum systems.

Contribution

It develops a stochastic wavefunction ansatz based on conditional wavefunctions, providing a practical alternative to traditional quantum-classical methods for many-body systems.

Findings

Achieves quantitative accuracy in proton-coupled electron transfer simulations

Requires two orders of magnitude fewer trajectories than mean field methods

Highly parallelizable and efficient for interacting fermion and boson systems

Abstract

We present an efficient \textit{ab initio} algorithm for quantum dynamics simulations of interacting systems that is based on the conditional decomposition of the many-body wavefunction [Phys. Rev. Lett. 113, 083003 (2014)]. Starting with this formally exact approach, we develop a stochastic wavefunction ansatz using a set of interacting conditional wavefunctions as a basis. We show that this technique achieves quantitative accuracy for a photo-excited proton-coupled electron transfer problem and for nonequilibrium dynamics in a cavity bound electron-photon system in the ultra-strong coupling regime, using two orders of magnitude fewer trajectories than the corresponding mean field calculation. This method is highly parallelizable, and constitutes a practical and efficient alternative to available quantum-classical simulation methods for systems of interacting fermions and bosons.