Quantum electrodynamics configuration interaction theory for molecular polaritonic dynamics

Strong coupling between molecules and cavities is being considered as a route to control chemical reactivity as well as for applications in quantum information science. As a number of experiments have shown the impact of cavities upon molecular processes, theoretical methods can be used to provide explanation and guidance. For example, quantum electrodynamics (QED) electronic structure methods can be used to model light-matter interactions by combining rigorous electronic structure methods with a quantized light-matter coupling Hamiltonian. QED configuration interaction (QED-CI) theory, in particular, treats the electronic states using CI methods, and the coupling of the molecule to the cavity photon is included using the Pauli-Fierz Hamiltonian. QED-CI also serves as the foundation for real-time polaritonic dynamics using QED time-dependent CI (QED-TDCI). Here, we overview recent developments in the QED-CI method for applications in polaritonic dynamics, focusing on how truncation of the electronic subspace impacts the accuracy of QED-CI energies and properties.