Quantum circuit detects individual radio photons

Radio technology does not normally fall under photonics, but single-photon detection certainly does.

Quantum circuit detects individual radio photons
Quantum circuit detects individual radio photons
This 1 x 1 cm superconducting quantum chip cooled to near its ground state can detect individual radio-frequency photons. (Photo: Delft University of Technology)

Researchers at Delft University of Technology have created a quantum circuit that enables them to listen to the weakest radio signal allowed by quantum mechanics: single photons.1 The device opens the door to possible future applications in areas such as radio astronomy and medicine (particularly MRI). It also enables researchers to do experiments that can shed light on the interplay between quantum mechanics and gravity.

Using a superconducting qubit, researchers in professor Gary Steele's group at Delft observed the quantization of a megahertz radio-frequency resonator at cryogenic temperatures; the device could even be cooled to its ground state. The detection of quanta (photons) could be done at megahertz rates.

From quantum radio to quantum gravity?
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 on how to fit gravity into quantum mechanics.

"Using our quantum radio, we want to try to listen to and control the quantum vibrations of heavy objects, and explore experimentally what happens when you mix quantum mechanics and gravity," Gely says. "Such experiments are hard, but if successful we would be able to test if we can make a quantum superposition of space-time itself, a new concept that would test our understanding of both quantum mechanics and general relativity."

Source: https://www.tudelft.nl/en/2019/tnw/listening-to-quantum-radio/


1. Mario F. Gely et al., Science, 7 March 2019; doi: 10.1126/science.aaw3101

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