  We present a method of directly obtaining the parity of a Gaussian state of
light without recourse to photon-number counting. The scheme uses only a simple
balanced homodyne technique, and intensity correlation. Thus interferometric
schemes utilizing coherent or squeezed light, and parity detection may be
practically implemented for an arbitrary photon flux. Specifically we
investigate a two-mode, squeezed-light, Mach-Zehnder interferometer and show
how the parity of the output state may be obtained. We also show that the
detection may be described independent of the parity operator, and that this
"parity-by-proxy" measurement has the same signal as traditional parity.
