Although we have remarked that the reference determinant in the coherent state basis includes an infinite number of photonic states by virtue of Eq. 6, this does not automatically guarantee that the photon basis for the subsequent QED-CASCI problem is complete. One reason for this is that the specific form of the coherent state transformation (i.e., the value of z in Eq. 3) is derived selfconsistently from the QED-HF procedure, which is variationally optimized for the direct product of the coherent state wavefunction for the photon and a single Slater determinant for the electrons.