Coherent States and Fock States at Very High Average Photon Numbers

Abstract

A laser field may be idealized as a coherent state, but it is often more convenient to use Fock states fQr quantum electrodynamical calculations. A Fock state implies fluctuations in the field intensity, aptl a constant field intensity (coherent state) implies fluctuations in the photon number. Both these effects are discussed rigorously. When the average photon number tends to infinity, these different states become asymptotically indistinguishable.