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. Scientists from the Institute of Science and Technology Austria (IST Austria) — along with collaborators from the Massachusetts Institute of Technology (MIT), the University of York (UK), and the University of Camerino, Italy — have demonstrated a new type of detection technology called “microwave quantum illumination” that utilizes entangled microwave photons as a method of detection. The prototype, also known as a “quantum radar,” is able to detect objects in noisy thermal environments where classical radar systems often fail.
Quantum Entanglement as a Form of Detection
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, while 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 — regardless of the noise within the environment.
“What we have demonstrated is a proof-of-concept for microwave quantum radar,” said lead researcher and Assistant Professor at the University of Calgary, Shabir 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 (-273.14 °C), we have been able to detect low-reflectivity objects at room temperature.”
Outperforming Classical Radar
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 — make it more effective to distinguish the signal photons (received from the object of interest) 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,” said Barzanjeh. “When bench-marked against classical low-power detectors in the same conditions we already see, at very low-signal photon numbers, quantum-enhanced detection can be superior.”
Throughout history, basic science has been one of the key drivers of innovation, paradigm shift, and technological breakthrough. While still a proof-of-concept, the research has effectively demonstrated a new method of detection that, in some cases, may already be superior to classical radar.
A proof-of-concept, such as the one demonstrated by the research team, “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,” said Barzanjeh.
“This scientific result was only possible by bringing together theoretical and experimental physicists who are driven by the curiosity of how quantum mechanics can help to push the fundamental limits of sensing,” said group leader, Professor Johannes Fink. “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.”