where the photonic position operator qc = ℏ/(2ω c )(â † + â) and momentum operator pc = i ℏω c /2(â † -â) are expressed in terms of the photonic creation operator â † and annihilation â for a given cavity mode, with ω c as the cavity frequency. A generalization of this term with many cavity modes will be discussed at the end of the paper. Further, η c is the light-matter coupling strength expressed as follows