Quantized Embedding Approaches for Collective Strong Coupling -- Connecting ab initio and macroscopic QED to Simple Models in Polaritonics

TL;DR

This paper introduces a simplified ab initio quantum embedding method for collective light-matter interactions, enabling efficient and rigorous modeling of molecular systems coupled to quantized fields, bridging microscopic and macroscopic descriptions.

Contribution

It presents a novel quantum embedding approach that combines ab initio quantum chemistry with macroscopic QED for collective systems, maintaining simplicity and including quantum fluctuations.

Findings

The method accurately reproduces collective coupling effects.

It offers a practical framework for ab initio polaritonic chemistry.

Comparison with Tavis--Cummings model validates the approach.

Abstract

Collective light-matter interactions have been used to control chemistry and energy transfer, yet accessible approaches that combine ab initio methodology with large many-body quantum optical systems are missing due to the fast increase in computational cost for explicit simulations. We introduce an accessible ab initio quantum embedding concept for many-body quantum optical systems that allows to treat the collective coupling of molecular many-body systems effectively in the spirit of macroscopic QED while keeping the rigor of ab initio quantum chemistry for the molecular structure. Our approach fully includes the quantum fluctuations of the polaritonic field and yet remains much simpler and more intuitive than complex embedding approaches such as dynamical mean-field theory. We illustrate the underlying assumptions by comparison to the Tavis--Cummings model. The intuitive application of the quantized embedding approach and its transparent limitations offer a practical framework for the field of ab initio polaritonic chemistry to describe collective effects in realistic molecular ensembles.