  Quantum illumination uses a quantum state of the electromagnetic field to
detect the presence of a target against a bright background more sensitively
than any classical state. Most often, the quantum state is a two-mode squeezed
vacuum consisting of signal and idler modes with a non-zero phase-sensitive
cross correlation, which serves as the signature for target detection, and a
zero phase-insensitive cross correlation, which means the modes produce no
fringes in second order interference. Here it is shown that applying
phase-sensitive amplification to the idler modes of a two-mode squeezed vacuum
results in a non-zero phase-insensitive cross correlation enabling reception by
a simple beam splitter and photodetectors. It is shown that quantum
illumination with a parametrically amplified idler has a lower probability of
error than an asymptotically optimal classical-state scheme in discriminating
between a present target and an absent target with equal prior probabilities.
