Diagrams and symmetry in polaritonic coupled cluster theory

Abstract: We present a diagrammatic notation to derive the quantum-electrodynamic coupled cluster (QED-CC) equations needed for the description for polaritonic ground and excited states. Our presented notation is a generalization of the existing diagrammatic notation of standard electronic coupled-cluster theory. Further, we discuss point-group symmetry inside a cavity and its exploitation within a QED-CC code for efficiency and the targeted treatment of excited states.