Researchers from the Technical University Delft, Holland have built a quantum circuit that enables them to listen to the weakest radio signal that is permitted by quantum mechanics. This new quantum circuit could lead to future applications in areas such as radio astronomy and medicine (MRI). It also enables researchers to carry out experiments that could shed light on the interaction between quantum mechanics and gravity.
Everyone will, at some time, have been annoyed by weak radio signals. Our favourite song in the car turns into noise, or we are too far from our WiFi router to be able to check our email. The usual solution is to make the signal stronger, for example by selecting a different radio station or by moving to a room closer to the router. But what if we just listened harder?

Quantum leap

Weak radio signals are not only a challenge for people who are trying to find their favourite radio station, but also for MRI scanners in hospitals and for the radio telescopes that scientists use to detect signals from space.

In a ‘quantum leap’ in the detection of signals, researchers in the group from professor Gary Steele in Delft have now detected photons or ‘quanta’ of energy. These are the weakest signals allowed by the theory of quantum mechanics.

Quantum chunks

One of the strange predictions of quantum mechanics is that energy comes in tiny chunks. These chunks are called ‘quanta’. What does this mean? ‘Say I am pushing a child on a swing”, says lead researcher Mario Gely. “If I want the child to go a little faster, then, according to the classical physics, I can give a small push on the back, which results in a little bit more speed and energy. But the quantum mechanics says something different: I can only increase the energy of the child by one quantum step at a time. Half of that quantity is not possible.”

For a child on a swing these ‘quantum steps’ are too small to notice. And until recently this was also true for radio waves. However, the research team from Delft have now developed a ‘quantum circuit’ that can actually detect these energy quanta in radio signals, which enables the possibility of detecting radio waves at the quantum level.

Quantum gravity?

Besides applications in quantum detection, the researchers also would like to take quantum mechanics to a new level: mass. Although the theory of quantum mechanics was developed nearly 100 years ago, physicists today still do not know how to unite gravity with quantum mechanics.

“Using our quantum radio we don't want to only listen to quantum vibrations of heavy objects, but also control them, so that we can experimentally explore what happens when you mix quantum mechanics and gravity”, says Gely. “Such experiments are very complicated, but if we succeed we could try to make a quantum superposition of space-time. This is a completely new concept that would test our understanding of both quantum mechanics as well as general relativity.”
The research has been published in Science.
SourceTU Delft