For the first time, scientists watch sound jump between quantum states

Stanford researchers have directly observed quantum jumps of sound in a mechanical resonator for the first time, marking the latest milestone in a line of quantum physics research that stretches back more than a century.

Quantum jumps -- sudden transitions from one energy state to another -- have been part of quantum theory since the early 1900s. Researchers first demonstrated them in trapped ions in 1986, followed by photons, the fundamental particles of light, in 2007. Sound, however, remained a more difficult target. A team led by Stanford physicist Amir Safavi-Naeini has now recorded these jumps directly, with the findings published in Science.

"What this study shows will allow us to move forward with developing new quantum technologies with sound," said Safavi-Naeini, associate professor of applied physics in the Stanford School of Humanities and Sciences. "We have seen that vibrating objects can exhibit quantum behavior, which is the prerequisite for many of the operations needed by quantum computing and sensing."

Watching Sound Behave Quantum Mechanically

The smallest discrete unit of light is a photon. The quantum equivalent for sound is a phonon, which represents the coordinated motion of many atoms.