Einstein-Podolsky-Rosen correlations of photons: Quantum-field-theory approach

We formulate a description of Einstein-Podolsky-Rosen-type experiments with photons which is especially convenient in the discussion of questions concerning Lorentz covariance. We classify all Lorentz-covariant two-photon states with sharp momenta and define observables corresponding to measurements of the linear polarization of photons. We also calculate explicitly the Einstein-Podolsky-Rosen correlation function and coincidence rate in the scalar two-photon state.