TESTING A BELL-TYPE INEQUALITY WITH A MICROMASER

We propose a phase-sensitive micromaser setup to demonstrate experimen tally a violation of a Bell-type inequality. The interaction of atoms with the cavity field produces entanglement between the atoms and the cavity photons and therefore also between the atoms. We derive a Bell- type inequality for the atom-atom correlations and show that it can be violated not only in an idealized model but also under realistic circ umstances when various sources of additional randomness are accounted for. Among them are the energy dissipation in the resonator and the Po issonian arrival statistics of the atoms.