What is it about?

The robustness of quantum illumination (QI) against environmental noise led to intense research for building quantum radar. However, QI is experimentally implemented through joint measurement between probe and idler. A joint measurement is not possible in ranging applications where the target's location is unknown. We proposed a new technique to implement QI without joint measurement, which paves the way for building ranging technologies with quantum advantage.

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Why is it important?

Light is well-known as a powerful tool for precision measurement; for example, Gravitational Waves are detected in a highly precise giant optical interferometer. While an interferometer measures small changes in the length of one of its arms relative to the other, ranging application measures the entire optical path length. A well-known example of ranging technology is radar. Unlike an interferometer, ranging equipment is deployed in an open environment. So the signal received contains not only the input probe field but also a lot of environmental noise. In fact, the received signal contains only noise when the target is not present. Designing measurements that can preserve quantum advantage is challenging in such scenarios. Our work proposes a new method that performs ranging with quantum advantage while eliminating the need for joint measurement and quantum storage.

Perspectives

While QI is a promising idea, there is also a significant amount of criticism about its application in ranging technologies. We believe this article addresses most of such concerns and takes quantum mechanics closer to radar applications.

Sankar Davuluri
Birla Institute of Technology and Science Pilani, Hyderabad Campus

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This page is a summary of: Optical ranging with quantum advantage and anti-stealth, Applied Physics Letters, September 2025, American Institute of Physics,
DOI: 10.1063/5.0276647.
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