Paving the way for a technologically viable prototype of a quantum radar involves the resolution of a number of experimental challenges as discussed in some review articles,[1][2][3] the latter of which pointed out "inaccurate reporting" in the media.
Current experimental designs seem to be limited to very short ranges, of the order of one meter,[4][5][6] suggesting that potential applications might instead be for near-distance surveillance or biomedical scanning.
Using a suitable quantum detection scheme, the system can pick out just those photons that were originally sent by the radar, completely filtering out any other sources.
Review articles that delve more into the history and designs of quantum radar, in addition to the ones mentioned in the introduction above, are available on arXiv.
For instance, storing the idler pulse in a delay line by using a standard optical fiber would degrade the system and limit the maximum range of a quantum illumination radar to about 11 km.
Other limitations include the fact that current quantum designs only consider a single polarization, azimuth, elevation, range, Doppler bin at a time.
The main limitations of microwave Quantum Radar concerning the detection of conventional and stealth targets have been recently analysed in the paper "Range Limitations in Microwave Quantum Radar" by G. Pavan and G. Galati,https://www.mdpi.com/2865432 There is media speculation that a quantum radar could operate at long ranges detecting stealth aircraft, filter out deliberate jamming attempts, and operate in areas of high background noise, e.g., due to ground clutter.
[17] Stealth aircraft are designed to reflect signals away from the radar, typically by using rounded surfaces and avoiding anything that might form a partial corner reflector.
This so reduces the amount of signal returned to the radar's receiver that the target is (ideally) lost in the thermal background noise.