  We calculate exactly the quantum mechanical, temporal second-order coherence
function for a single-mode, degenerate parametric amplifier for a system in the
Gaussian state, viz., a displaced-squeezed thermal state. The calculation
involves first the generation of the Gaussian state and subsequent measurements
of two photons a time $\tau \geq 0$ apart. The generation of the Gaussian state
by the parametric amplifier insures that the temporal second-order coherence
function depends only on $\tau$.
