Stanford researchers directly observed a single phonon dropping from energy state 1 to 0 in real time, marking the first confirmed quantum jump of sound in a mechanical resonator.
A chip-scale resonator that vibrates for about 2 milliseconds let the team take hundreds of measurements, while a superconducting qubit repeatedly read the resonator without collapsing its fragile quantum state.
The result closes a gap left after quantum jumps were shown in trapped ions in 1986 and photons in 2007, turning earlier indirect evidence in sound into a direct observation published in Science.
The platform could aid quantum-computing error correction by flagging jump events as they happen and could also support ultrasensitive sensing, including efforts to identify proteins inside cells.
Because the resonator is fabricated with chipmaking techniques and many could fit on one chip, the work also points to future sound-based components for devices such as smartphones.