People may be familiar with the soft sound of the breeze, the chirping of the birds and the annoying ring of the alarm clock in the morning but no one knows what the sound of an atom is like until a group of researchers embarked in an experiment that involved the interaction of an artificial atom and light.

In an experiment conducted at the Chalmers University of Technology in Sweden and which was described in a study published in the journal Science on Sept. 11, Martin Gustafsson from the Department of Chemistry of the Columbia University in New York, and colleagues made an artificial atom with length of 0.01 millimeters and then charged this with energy.

The researchers designed their experimental atom to absorb and emit energy in the form of sound, also known as phonon, instead of photon, or energy in the form of light, which atoms normally emit, so they can better understand the world of quantum sound.

"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," the researchers wrote. "Our results highlight the similarities between phonons and photons but also point to new opportunities arising from the unique features of quantum mechanical sound."

In theory, the sound that the atom released is made up of quantum particles and study researcher Göran Johansson, from the Chalmers University of Technology, said that such particle is also the weakest detectable sound. The researchers likewise revealed that the sound produced by the artificial atom in their experiment is a D-note although it is too high-pitched for anybody to hear.

"The sound amplitude, or strength, is very weak," said  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]."

Scientists noted of the possible implications of the experiment particularly in the field of quantum physics as sound is 100,000 times slower than light and has a short wavelength, which mean that it is easier to manipulate compared with light. One of the problems with using photons in quantum experiments is that they are hard to manipulate because they are too fast.

"Due to the slow speed of sound, we will have time to control the quantum particles while they travel. This is difficult to achieve with light, which moves 100,000 times more quickly," Gustafsson said.

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