Field-state measurement in a micromaser using retrodictive quantum theory

Injected two-level atoms, prepared and measured in various states, make an effective measurement of the cavity field of a micromaser prior to the injection of the atoms. In contrast to other existing literature on the micromaser, we have used the unconventional retrodictive quantum theory which allows us to calculate, in particular, the phase properties of the field state at an earlier time prior to the interaction with the injected atoms.