Transverse quantum correlations in the active microscopic cavity

A microcavity technique is adopted to investigate, we believe for the first time, the process of transverse interatom quantum correlations taking place after photon emission, according to the plane-wave QED photon-delocalization model. We find that the QED model is indeed verified, but that it is generally limited by the nonideal cavity properties. The concept introduced here of ``transverse quantum-correlation length'' is of fundamental relevance to all kinds of Casimir-type vacuum-confinement processes, including ``anomalous'' QED effects in spontaneous emission. It also sets a fundamental limitation on the performance of the ``thresholdless laser,'' a device of actual scientific and technological interest.