COHERENCE OF ATOMIC MATTER-WAVE FIELDS

In analogy to Glauber's analysis of optical coherence, we adopt an ope rational approach to introduce different classes of atomic coherence a ssociated with different types of measurements. For the sake of concre teness we consider specifically fluorescence, nonresonant imaging, and ionization. We introduce definitions of coherence appropriate to them , which we call electronic, density, and field coherence, respectively . We illustrate these concepts in various descriptions of Bose-Einstei n condensation, showing that each of these descriptions makes differen t implicit assumptions on the coherence of the system. We also study t he impact of elastic collision on the field and density coherence prop erties of atom lasers.