A team of researchers from Austria, the U.S., the UK, and Italy has demonstrated a new technology called microwave quantum illumination that uses entangled microwave photons as a method of detection. Their prototype device is able to detect objects in noisy thermal environments where classical radar systems often fail.
“What we have demonstrated is a proof of concept for microwave quantum radar,” said Dr. Shabir Barzanjeh, a researcher in the Institute for Quantum Science and Technology at the University of Calgary and the Institute of Science and Technology Austria.
“Using entanglement generated at a few thousandths of a degree above absolute zero, we have been able to detect low reflectivity objects at room-temperature.”
Instead of using conventional microwaves, Dr. Barzanjeh and colleagues entangle two groups of photons: ‘signal’ and ‘idler’ photons.
The signal photons are sent out towards the object of interest, whilst the idler photons are measured in relative isolation, free from interference and noise.
When the signal photons are reflected back, true entanglement between the signal and idler photons is lost, but a small amount of correlation survives, creating a signature or pattern that describes the existence or the absence of the target object — irrespective of the noise within the environment.
While quantum entanglement in itself is fragile in nature, the device has a few advantages over conventional classical radars.
For instance, at low power levels, conventional radar systems typically suffer from poor sensitivity as they have trouble distinguishing the radiation reflected by the object from naturally occurring background radiation noise.
Quantum illumination offers a solution to this problem as the similarities between the signal and idler photons — generated by quantum entanglement — makes it more effective to distinguish the signal photons from the noise generated within the environment.
“The main message behind our research is that quantum radar or quantum microwave illumination is not only possible in theory but also in practice,” Dr. Barzanjeh said.
“When benchmarked against classical low-power detectors in the same conditions we already see, at very low-signal photon numbers, that quantum-enhanced detection can be superior.”
The team’s device is described in a paper in the journal Science Advances.
S. Barzanjeh et al. 2020. Microwave quantum illumination using a digital receiver. Science Advances 6 (19): eabb0451; doi: 10.1126/sciadv.abb0451
This article is based on text provided by the Institute of Science and Technology Austria.
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