Researchers Use Quantum Mechanics to Detect Very Weak Radio Signals

Researchers at Delft University, have developed a new quantum circuit that allows them to listen to the weakest radio signal possible in quantum mechanics. This new circuit opens the door to possible future applications in areas such as radio astronomy and medicine (MRI). It will also enable researchers to do experiments that can shed light on the interplay between quantum mechanics and gravity. The circuit was developed by researchers at Delft University of Technology.

We have all been annoyed by weak radio signals at some point in our lives, most often when we do not get cell reception in an area of the house or we are too far away from our Wi-Fi router to check our email. The usual solution is to make the signal stronger, by going closer to the source. However, what if, we could just listen more carefully?

Weak radio signals are not just a challenge for people trying to get better cell reception, but also for magnetic resonance imaging (MRI) scanners at hospitals, as well as for the telescopes scientists use to peer into space. In a quantum ‘leap’ in radio frequency detection, a research group led by Prof. Gary Steele in Delft demonstrated the detection of photons or quanta of energy, the weakest signals allowed by the theory of quantum mechanics.

One of the strange predictions of quantum mechanics is that energy comes in tiny little chunks called ‘quanta’. Lead researcher, Mario Gely explains, “Say I am pushing a kid on a swing. In the classical theory of physics, if I want the kid to go a little bit faster I can give them a small push, giving them more speed and more energy. Quantum mechanics says something different: I can only increase the kid’s energy one ’quantum step’ at a time. Pushing by half of that amount is not possible.”

For a kid on a swing these ’quantum steps’ are so tiny that they are too small to notice. Until recently, the same was true for radio waves. However, the research team in Delft has developed a circuit that can actually detect these chunks of energy in radio frequency signals, opening up the potential for sensing radio waves at the quantum level.

Beyond applications in quantum sensing, the group in Delft is interested in taking quantum mechanics to the next level: mass. While the theory of quantum electromagnetism was developed nearly 100 years ago, physicists are still puzzled today on how to fit gravity into quantum mechanics. Using their quantum radio, they want to try to listen to and control the quantum vibrations of heavy objects, and explore experimentally what happens when quantum mechanics and gravity are mixed. Such experiments are hard, but if successful, researchers would be able to test if they can make a quantum superposition of space-time itself, a new concept that would test their understanding of both quantum mechanics and general relativity.