Abstract

We have shown that all "single-photon" and "photon-pair" states, produced in atomic transitions, and in parametric down conversion by nonlinear optical crystals, may be represented by positive Wigner densities of the relevant sets of mode amplitudes. The light fields of all such states are represented as a real probability ensemble (not a pseudoensemble) of solutions of the unquantized Maxwell equation. The local realist analysis of light-detection events in spatially separated detectors requires a theory of detection which goes beyond the currently fashionable single-mode photon theory. It also requires us to recognize that there is a payoff between detector efficiency and signal-noise discrimination. Using such a theory, we have demonstrated that all experimental data, both in atomic cascades and in parametric down conversions, have a consistent local realist explanation based on the unquantized Maxwell field. Finally we discuss current attempts to demonstrate Schroedinger-cat-like behaviour of microwave cavities interacting with Rydberg atoms. Here also we demonstrate that there is no experimental evidence which cannot be described by the unquantized Maxwell field. We conclude that misuse of the Photon Concept has resulted in a mistaken recognition of "nonlocal" phenomena.