Physicists capture the sound of an atom
On the right, an artificial atom generates sound waves that ripple on the surface of a solid. The sound is picked up on the left by a 'microphone' of interlaced metal fingers.
Image: Philip Krantz, Krantz NanoArt

For many years, scientists have been studying the interaction between atoms and light, but getting sounds to do the same thing is an entirely new feat. 

Artificial atoms can come in the form of a quantum electrical circuit, and like regular atoms, they can be charged with energy to emit particles. While scientists know how to get them to emit particles of light, called photons, a team of scientists from Chalmers University of Technology in Sweden has figured out how to get their artificial atom to emit and absorb energy in the form of sound particles.

According to Science 2.0, the sound waves used in the experiment were surface acoustic waves (SAWs), which can be visualised on the surface of a solid. The team performed the experiments at super-low temperatures of almost absolute zero (20 millikelvin), so that even the tiniest amounts of heat energy did not disturb the atom.

"We have opened a new door into the quantum world by talking and listening to atoms", said Per Delsing, head of the experimental research group, in a press release. "Our long term goal is to harness quantum physics so that we can benefit from its laws, for example in extremely fast computers. We do this by making electrical circuits which obey quantum laws, that we can control and study.”

Because sound waves move more slowly than light, discovering how to interact with an atom using sound waves completely changes the way scientists can control minuscule quantum phenomena. For example, it gives them the time to control quantum particles while they’re traveling from one point to the next. "This is difficult to achieve with light, which moves 100,000 times more quickly,” says physicist Martin Gustafsson, the article's first author in the journal Science.

The frequency the team used in the experiment was 4.8 gigahertz, which is close to the microwave frequencies that are used in modern wireless networks. Once frequencies get as high as this, the wavelength of sound emitted becomes so short that it can be guided along the surface of a microchip. So team researchers placed their artificial atom on a microchip to make a superconducting material. Superconducting materials can conduct electricity with no resistance, which means that they can carry a current indefinitely without losing any energy, which is the next step in improving electrical technology in the future.