FIELD-THEORETICAL VIEW OF THE ANGULAR-CORRELATION OF PHOTONS

We give a field-theoretical derivation of the explicit probability distribution of photon emission by identical N noninteracting atoms (sources), which has been applied to study the tendency of photons to form collimated beams. More precisely, given that each source emits one photon with some given energy, due to the same atomic transition, we derive the conditional probability that the N photons have momenta in arbitrary directions. Each source is assumed separately to emit photons of momenta with uniform distribution for their directions, and no assumption is made on the sources being pointlike.