(ResourcesAltium) Quantum radar is unique and relies on the same phenomenon (which Einstein called “spooky action at a distance”) that is used in quantum communication. Quantum radar with entanglement received an early US patent in 2008, and the technology is still being pursued by the US, Europe, and China.
There are really two versions of quantum radar, although the version involving quantum entanglement has received a lot of recent attention, probably due to the esoteric nature of this phenomenon. The second version of quantum radar relies on quantum homodyne detection.
The high sensitivity in both methods means that the radar can run at lower power, and the systems will not expose themselves when being used to detect distant targets. In addition, detecting oncoming entangled or coherent photons on a moving craft without a reference oscillator is difficult as they will be masked by background microwave radiation. As such, the targets won’t know they’ve been detected by a distant quantum radar station.
It remains to be seen which type of radar will win the day. The esoteric nature of quantum entanglement causes everyone to focus on its use in new technology, so it is not surprising that everyone is obsessed with entanglement quantum radar. However, existing systems could be adapted for use with quantum radar. Bringing quantum radar online represents a huge scientific advance in practical uses of quantum physics outside of lasers, semiconductors, and quantum computing.