Phys.org  January 10, 2022 Despite the many proposals for quantum radar, none have delineated the ultimate quantum limit on ranging accuracy. A team of researchers in the US (University of Arizona, MIT) has derived that limit through continuous-time quantum analysis. They showed that quantum illumination ranging—a quantum pulse-compression radar that exploits the entanglement between a high time-bandwidth product transmitted signal pulse and a high time-bandwidth product retained idler pulse—achieves that limit. They also showed that quantum illumination ranging offers mean-squared range-delay accuracy that can be tens of dB better than that of a classical pulse-compression radar of the same pulse […]