Stealth Bombers and Cancer Cells Be Warned: Quantum Radar Has Gone Microwave

Image: S. Barzanjeh et al., Phys. Rev. Lett.
Like a lot of things with „quantum“ in their name, quantum radar picks up where its classical analog ends. Stealth fighters? Cancer cells? Quantum radar can spot them with relative ease. But, again, like most things with quantum in their name, the technology is only now coming into reach.

By Michael Byrne|MOTHERBOARD

Researchers at the University of York have developed a new system that promises to open up quantum radar technology in a new, practical way. As described by ​a paper in the current Physical Review Letters, their system depends on a new sort of electromagnetic frequency converter, one allowing the coupling (or entanglement) of beams in optical wavelengths with beams in the microwave spectrum.

The result is a radar system that can both generate entangled microwave-optical beams, as during signal emission, and convert the received microwave beams back into optical wavelengths.

Quantum radar is still fairly out-there idea. Lockheed Martin holds ​a generic patent in Europe on the theorized technology, but the defense contractor doesn’t offer much in the way of possible implementations. Using „entangled quantum particles,“ Lockheed’s would-be system, should allow its users to „visualise useful target details through background and/or camouflaging clutter, through plasma shrouds around hypersonic air vehicles, through the layers of concealment hiding underground facilities, [and find] IEDs [improvised explosive devices], mines and other threats–all while operating from an airborne platform.“ That’s not a particularly modest declaration.

The gist of the idea (also known as „quantum illumination“) is that, through quantum entanglement, beams of extremely high-frequencies, like microwaves, might be used to image cloaked objects very far away. Currently, this is an impossibility as beams like this don’t travel so well across big distances.

That is, a microwave radar beam might do well enough when it’s reflecting against some well-defined, conventional surface, where the returning beam is sufficiently strong to persist through atmospheric thermal background noise. But a stealth surface, where this reflection is minimized, reflects a radar beam only very weakly. A detection is made, but the returning signal isn’t powerful enough to make the trip back. That’s the whole idea of stealth technology: not invisibility, but good-enough dampening.

The concept behind quantum radar is quantum entanglement. This is where one or more particles or particle collections are put into the same quantum state, such that they’re „sharing“ the state or even becoming indistinguishable from each other, with the effect being that a distant particle can influence (in a sense) its nearby entangled partner. It gives the illusion (at least) of a sort of superliminal communication.

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