- Physicists build a new circuit that can detect very tiny quantum steps (photons) in radio frequency signals.
- This new quantum circuits could have a number of applications, from nuclear magnetic resonance imaging to radio astronomy.
Detection of weak radio-frequency electromagnetic fields plays an important role in several fields, including nuclear magnetic resonance imaging to radio astronomy.
In quantum optics, the weakest signal is a single photon. It’s really hard to detect and manipulate individual photons at megahertz frequencies because you cannot stop thermal fluctuations even at cryogenic temperatures.
Now, physicists at the Delft University of Technology have developed a system that makes such detection possible. They have built a quantum circuit for detecting the weakest signals — photons or quanta of energy — allowed by the theory of quantum mechanics.
Tiny Quantum Steps
In quantum mechanics, energy comes in a form of tiny chinks known as ‘quanta’. Allow me to explain this with an example: let’s say you’re pushing a shopping cart. As per classical physics, if you want to go faster you can give the cart an extra push, providing more energy and more speed.
However, laws of quantum mechanics are quite different: You can only increase the energy of cart one ‘quantum step’ at a time. These ‘quantum steps’ are too weak to push the cart. In fact, there is hardly any device to detect a single quantum step accurately. The same is true for radio waves.
Reference: ScienceMag | doi:10.1126/science.aaw3101 | Delft University of Technology
What researchers built in this study can actually detect these tiny quantum steps in radio frequency signals. The new circuit quantum electrodynamics architecture enables the readout and manipulation of a radio-frequency resonator at the quantum level.
The Quantum chip (1*1 cm) developed in this study | Source: TU Delft
The architecture can also be used to interface circuit quantum electrodynamics with other physical systems in the megahertz frequency range, for example, macroscopic mechanical oscillators or spin systems.
Interplay Between Quantum Gravity and Quantum Mechanics
The team aims to take quantum mechanisms beyond applications in quantum sensing: they want to explore quantum gravity. Although quantum electromagnetism theory was first formulated in the 1920s, physicists haven’t been able to figure out how to fit gravity into quantum mechanics.
Researchers plan to listen to and manipulate the quantum vibrations of large objects, using the quantum radio. They will also try to combine quantum gravity and mechanics and see what happens.
Of course, such experiments won’t be easy to carry out, but if successful they might be able to create a quantum superposition of space-time itself, which would require a great understanding of both general relativity and quantum mechanics.