The sound of silence: One excited atom is so quiet that the human ear cannot detect it

Listen! Could this be a Quantum Communications Leap?

Boffins believe they have successfully demonstrated the sound a single atom makes when excited - even though it is completely inaudible to the human ear.

The researchers at the University of Columbia and Sweden's Chalmers University of Technology "captured" the very soft sound, according to a paper published in Science journal on Thursday.

The discovery could eventually unlock the basic science for new quantum computing devices, reported Motherboard, which spoke to the paper's co-author Göran Johansson.

"Basically, when you excite the atom, it creates a sound, one phonon at a time, according to theory. It's the weakest possible sound possible at the frequency [that it vibrates]," Johansson said.

The Propagating phonons coupled to an artificial atom paper explained in its abstract:

Quantum information can be stored in micromechanical resonators, encoded as quanta of vibration known as phonons. The vibrational motion is then restricted to the stationary eigenmodes of the resonator, which thus serves as local storage for phonons.

In contrast, we couple propagating phonons to an artificial atom in the quantum regime and reproduce findings from quantum optics with sound taking over the role of light. Our results highlight the similarities between phonons and photons but also point to new opportunities arising from the unique features of quantum mechanical sound.

The low propagation speed of phonons should enable new dynamic schemes for processing quantum information, and the short wavelength allows regimes of atomic physics to be explored that cannot be reached in photonic systems.

The artificial atom was created using a semiconducting circuit, such as those found in small quantum computers.

Johansson told Motherboard that a series of long metallic "fingers" on the chip captured and measured the acoustic waves made by the atoms vibrations, which are said to be too small to see. The waves then propagate to a second set of fingers that transform them into microwaves.

"These can then be detected using low-temperature microwaving amplifiers. It's the same technology we use to read out superconducting qubits," Johansson was quoted as saying.

He added: "We thought this would be some nice curiosity-driven basic research. It's kind of neat to see what happens when you replace light with sound."

Apparently, that one little excited artificial atom could help to reveal new possibilities for quantum communications. ®

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