A new look at quantum radar suggests it might boost accuracy more than thought

 

Contour plot of mean-squared range-delay accuracy advantage (in dB) at SNRQthresh assuming range uncertainty ΔR=R/100 at range R. Credit: DOI: 10.1103/PhysRevLett.128.010501

According to a team of researchers from the University of Arizona and MIT, quantum radar may be able to improve radar system accuracy more than previously imagined. The team discusses a new strategy to building quantum radar, as well as the challenges that it faces, in a study published in the journal Physical Review Letters.

Radar operates by directing microwave radiation towards an object and measuring the signals that return. And, while it works well for many purposes, it falls short when it comes to long-distance communication. As scientists learned more about quantum entanglement over the last few decades, some speculated that it could be utilized to improve radar systems. Sending just one of two paired photons to a target does, in fact, improve the signal's confidence. Unfortunately, the benefit (about 2 to 4 times) did not justify the additional cost of adding quantum capabilities to a radar system. The researchers discovered that exploiting entanglement in a different method could improve accuracy by up to 500 times that of current systems in this new study.

Researchers discovered that extending the pulses (bunches of photons) transmitted to a target could enhance accuracy. As the pulse was formed and sent, the radar frequency was swept from high to low, stretching the photon in time and allowing its frequency to be better determined. This improved the definition of its companion, resulting in increased signal certainty. This strategy may work because statistical variation is exploited in detection, narrowing detection variations, according to the researchers.

Unfortunately, despite their efforts, the researchers concede that one more hurdle must be crossed before quantum radar can become a reality: a way to produce more photons from a source (current systems generate photons at a rate of around 1 million per second). A device capable of producing photons at a pace several orders of magnitude faster would be required for a quantum radar system.

References:

Quntao Zhuang et al, Ultimate Accuracy Limit of Quantum Pulse-Compression Ranging, Physical Review Letters (2022). DOI:10.1103/PhysRevLett.128.010501