A prototype quantum radar has the potential to detect objects that are invisible to conventional systems. The new breed of radar is a hybrid system that uses quantum correlation between microwave and optical beams to detect objects of low reflectivity, such as cancer cells or aircraft, with a stealth capability. Because the quantum radar operates at much lower energies than conventional systems, it has the long-term potential for a range of applications in biomedicine including non-invasive NMR scans.

A conventional radar antenna emits a microwave to scan a region of space. Any target object would reflect the signal to the source, but objects of low reflectivity immersed in regions with high background noise are difficult to spot using classical radar systems. In contrast, quantum radars operate more effectively and exploit quantum entanglement to enhance their sensitivity to detect small signal reflections from very noisy regions.

The radar could be operated at short distances to detect the presence of defects in biological samples or human tissues in a completely non-invasive fashion, thanks to the use of a low number of quantum-correlated photons.