N ov 2 00 6 Can there be a Fock state of the radiation field ?

We plan to answer this question with the Munich micromaser in mind [1]. It consists of a superconducting cavity maintained at T = 0.3K. Hence, the average thermal photons present in the cavity is n̄th = 0.033. The cavity dissipation parameter κ = ν/2Q stands at 3.146 Hz with the cavity Q = 3.4× 10 and ν being the masing frequency. A clever velocity selector sends Rb atoms in the upper of its two Rydberg levels into the cavity at such a rate that at most one atom is present there at a time. Also, the velocity selector maintains a constant flight time for each and every atom through the cavity. This is crucial for the Jaynes-Cummings [2] interaction between the single mode of the cavity and the atom present there. The attempt is to generate a Fock state of the cavity radiation field. To start with, the cavity is in thermal equilibrium having the normalized variance