A Diffusion Quantum Monte Carlo Approach to the Polaritonic Ground State

TL;DR

This paper develops a diffusion quantum Monte Carlo method to accurately compute the polaritonic ground state of molecules, providing insights into electron-photon interactions during molecular dissociation.

Contribution

It introduces a formally exact DQMC approach for polaritonic states, enabling precise modeling of electron-photon interactions in chemical systems.

Findings

DQMC accurately predicts polaritonic ground states.

Electron-photon properties vary during dissociation.

Results differ from approximate coupled cluster methods.

Abstract

Making and using polaritonic states (i.e., hybrid electron-photon states) for chemical applications have recently become one of the most prominent and active fields that connects the communities of chemistry and quantum optics. Modeling of such polaritonic phenomena using ab initio approaches calls for new methodologies, leading to the reinvention of many commonly used electronic structure methods, such as Hartree-Fock, density functional, and coupled cluster theories. In this work, we explore the formally exact diffusion quantum Monte Carlo approach (DQMC) to obtain numerical solutions to the polaritonic ground state during the dissociation of the H$_2$ molecular system. We examine various electron-nuclear-photon properties throughout the dissociation, such as changes to the minimum of the cavity Born-Oppenheimer surface, the localization of the electronic wavefunction, and the average mode occupation. Finally, we directly compare our results to that obtained with state-of-the-art, yet approximate, polaritonic coupled cluster approaches.