The Quantum Illumination Story

TL;DR

Quantum illumination leverages entanglement to improve radar target detection despite decoherence, demonstrating potential benefits and inspiring further research in quantum radar technology.

Contribution

This paper narrates the development and understanding of quantum illumination, highlighting its ability to enhance radar detection even after entanglement is destroyed by noise.

Findings

Quantum illumination improves target detection over classical radar.

The utility of quantum advantage is limited by practical noise and loss.

Entanglement remains valuable even on channels that break entanglement.

Abstract

Superposition and entanglement, the quintessential characteristics of quantum physics, have been shown to provide communication, computation, and sensing capabilities that go beyond what classical physics will permit. It is natural, therefore, to explore their application to radar, despite the fact that decoherence---caused by the loss and noise encountered in radar sensing---destroys these fragile quantum properties. This paper tells the story of "quantum illumination", an entanglement-based approach to quantum radar, from its inception to its current understanding. Remarkably, despite loss and noise that destroy its initial entanglement, quantum illumination does offer a target-detection performance improvement over a classical radar of the same transmitted energy. A realistic assessment of that improvement's utility, however, shows that its value is severely limited. Nevertheless, the fact that entanglement can be of value on an entanglement-breaking channel---the meta-lesson of the quantum illumination story---should spur continued research on quantum radar.