A New Quantum Radar Prototype

Illustration of a quantum radar prototype. (Source: P. Krantz, IST Austria)

Quantum entangle­ment is a physical phenomenon where two particles remain inter-connected, sharing physical traits regardless of how far apart they are from one another. Now, scientists from the research group of Johannes Fink at the Institute of Science and Technology Austria (IST Austria) along with colla­borators Stefano Pirandola from the Massa­chusetts Institute of Technology (MIT) and the University of York, UK, and David Vitali from the University of Camerino, Italy – have demons­trated a new type of detection tech­nology. The microwave quantum illu­mination utilizes entangled microwave photons as a method of detection. The prototype of a quantum radar is able to detect objects in noisy thermal environ­ments where classical radar systems often fail. The tech­nology has potential appli­cations for ultra-low power biomedical imaging and security scanners.

The working principles behind the device are simple: Instead of using conven­tional microwaves, the researchers entangle two groups of photons, which are called the ‘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.

“What we have demons­trated is a proof of concept for Microwave Quantum Radar,” says lShabir Barzanjeh, whose previous research helped advance the theo­retical notion behind quantum enhanced radar tech­nology. “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.” 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 photon from the noise generated within the environ­ment. Barzanjeh says: “The main message behind our research is that ‘quantum radar’ or ‘quantum microwave illu­mination’ is not only possible in theory but also in practice. 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.”

Throughout history, basic science has been one of the key drivers of innovation, paradigm shift and techno­logical break­through. Whilst still a proof of concept, the group’s research has effec­tively demons­trated a new method of detection that, in some cases, may already be superior to classical radar. “Throughout history, proof of concepts such as the one we have demons­trated here have often served as prominent milestones towards future techno­logical advance­ments. It will be interes­ting to see the future implications of this research, particularly for short-range microwave sensors”, says Barzanjeh.

Johannes Fink adds “This scientific result was only possible by bringing together theo­retical and experi­mental physicists that are driven by the curiosity of how quantum mechanics can help to push the fundamental limits of sensing. But to show an advantage in practical situa­tions we will also need the help of experienced elec­trical engineers and there still remains a lot of work to be done in order to make our result appli­cable to real-world detection tasks.” (Source: IST Austria)

Reference: S. Barzanjeh et al.: Microwave quantum illumination using a digital receiver, Sci. Adv. 6, eabb0451 (2020); DOI: 10.1126/sciadv.abb0451

Link: Integrated Quantum Systems (J. Fink), Institute of Science and Technology Austria, Klosterneuburg, Austria

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