quantum physics of light and matter a modern intr
rs create and annihilate photons within these modes, obeying bosonic commutation relations: \[ [a_{k,\lambda}, a_{k',\lambda'}^\dagger] = \delta_{k,k'} \delta_{\lambda,\lambda'} \] where \( a_{k,\lambda} \) and \( a_{k,\lambda}^\dagge
