  We propose a hetero-homodyne receiver for quantum illumination (QI) target
detection. Unlike prior QI receivers, it uses a cascaded positive
operator-valued measurement (POVM) that does not require a quantum interaction
between QI's returned radiation and its stored idler. When used without
sequential detection its performance matches the 3 dB quantum advantage over
optimum classical illumination (CI) that Guha and Erkmen's [Phys. Rev. A 80,
052310 (2009)] phase-conjugate and parametric amplifier receivers enjoy. When
used in a sequential detection QI protocol, the hetero-homodyne receiver offers
a 9 dB quantum advantage over a conventional CI radar, and a 3 dB advantage
over a CI radar with sequential detection. Our work is a significant step
forward toward a practical quantum radar for the microwave region, and, more
generally, emphasizes the potential offered by cascaded POVMs for quantum
radar.
