Stealth technology may not be very stealthy in the future thanks to a US$2.7-million project by the Canadian Department of National Defence to develop a new quantum radar system. The project, led by Jonathan Baugh at the University of Waterloo's Institute for Quantum Computing (IQC), uses the phenomenon of quantum entanglement to eliminate heavy background noise, thereby defeating stealth anti-radar technologies to detect incoming aircraft and missiles with much greater accuracy.

Ever since the development of modern camouflage during the First World War, the military forces of major powers have been in a continual arms race between more advanced sensors and more effective stealth technologies. Using composite materials, novel geometries that limit microwave reflections, and special radar-absorbing paints, modern stealth aircraft have been able to reduce their radar profiles to that of a small bird – if they can be seen at all.

This stealthiness is compounded by modern radar jamming and deception technologies and by natural phenomena. In fact, one reason the Canadian Department of National Defence is pursuing the quantum radar project is that, in addition to Canada being at the frontier of any incoming strategic attacks directed against the West, it's also in a region that is extremely hostile to conventional radar.

"In the Arctic, space weather such as geomagnetic storms and solar flares interfere with radar operation and make the effective identification of objects more challenging," says Baugh. "By moving from traditional radar to quantum radar, we hope to not only cut through this noise, but also to identify objects that have been specifically designed to avoid detection."

Conventional radar suffers from a universal problem of all radio communications and detection, which is the signal to noise ratio. That is, if there is too much random noise mixed in with the signal you're trying to detect, it doesn't' matter how much you turn up the volume. That only turns up the noise as well.

Quantum radar, on the other hand, gets around this using something called quantum illumination to filter out the noise by making the outgoing photons that make up the radar signal identifiable. It does this by means of the principle of quantum entanglement. This is when two photons are generated or made to interact in such a way that their properties are linked together. When this happens, if you can determine the position, momentum, spin, or polarization of one photon, you can ascertain the complementary position, momentum, spin, or polarization of its partner.

The upshot of this is that by shooting one photon out of the radar dish and retaining its pair, it's possible to filter out unpaired photons from the returning beam. This way, background noise and electronic jamming is eliminated and the radar image becomes clear enough to detect even the most advanced stealth craft.

The quantum radar under development at the IQC is currently confined to the laboratory under the Department of National Defence's All Domain Situational Awareness (ADSA) Science & Technology program, but it is hoped that it will one day be mature enough to replace the North American Aerospace Defense Command's (NORAD) current 54 North Warning System (NWS) radar stations in the Arctic, which may need to be replaced from 2025.

"This project will allow us to develop the technology to help move quantum radar from the lab to the field," says Baugh. "It could change the way we think about national security."

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