Here, only the electronically adiabatic state energies E α and transition dipole matrix elements µ αβ are required as input. As has been known for many decades, solving the many-body electronic system is not trivial, while the harmonic oscillator problem is an easy text book problem. The purpose of this pQED procedure is to make use of the simplicity of the photonic sub-system, while still relying on complicated many-body methods to extract the necessary information from the electronic sub-system as input.