number of noise photons detected per second (Hz)
  $\eta_p$   total transmission of the probe light
  $\eta_r$   total transmission of the reference light
  $T_c$      coincidence window
  $\tau$     detection time (s)

  : table list of variables

\[TAB\]

SYSTEM DEMONSTRATION
====================

To date, most of the prior work on quantum illumination and correlation enhanced target detection work has been using bulk optics. While notable in terms of demonstrating a certain type of quantum advantage, they employed intensity correlation. The correlation enhancement has been shown in terms of the ROC metric, which is fundamental in radar detection theory. However, for it to be of interest to radar practitioners, advantage has to be demonstrated in the regime where the $P_\text{fa}$ is of the order of $10^{-6}$. No prior work has demonstrated this in experimental investigations, be it optical or microwave. In this section, we provide an overview of the first such demonstration [@trans; @liu2019enhancing] based on the QTC protocol in a setup that lends itself to be a scalable solution.

Experimental Setup
------------------

As shown in the schematic plot Figure. \[SETUP\], the QTC experimental setup consists of three sections: the non-classical photon-pair source, the free-space transceiver, and the detection system. The photon pair source is 