where ω c is the cavity mode frequency, â † and â are the photon creation and annihilation operators of the cavity mode, respectively. Here, we consider only a single cavity mode interacting collectively with N molecules. For the light-matter interaction term ĤLM , we assume the long-wavelength approximation, that is, each molecule is coupled to the quantized radiation field with the same light-matter coupling strength g c . Under the rotating wave approximation (RWA), ĤLM is expressed as