  In quantum illumination, the signal mode of light, entangled with an idler
mode, is dispatched towards a suspected object bathed in thermal noise and the
returning mode, along with the stored idler mode, is measured to determine the
presence or absence of the object. In this process, entanglement is destroyed
but its benefits in the form of classical correlations and enlarged Hilbert
space survive. Here, we propose the use of probe state hyperentangled in two
degrees of freedom - polarization and frequency, to achieve a significant 12dB
performance improvement in error probability exponent over the best known
quantum illumination procedure in the low noise regime. We present a simple
receiver model using four optical parametric amplifiers (OPA) that exploits
hyperentanglement in the probe state to match the performance of the
feed-forward sum-frequency generator (FF-SFG) receiver in the high noise
regime. By replacing each OPA in the proposed model with a FF-SFG receiver,
further 3dB improvement in the performance of a lone FF-SFG receiver can be
seen.
