Stanford scientists directly observe quantum jumps of sound for the very first time

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Researchers at Stanford University have directly recorded quantum jumps of sound for the first time, tracking individual phonons, the fundamental quantum units of sound, as they abruptly transitioned between distinct energy states inside a mechanical resonator. Similar quantum jump behaviour has previously been observed in ions back in 1986 and in photons in 2007, but sound itself presented genuinely unique technical challenges that had kept this particular milestone out of reach until now.

The team, led by associate professor of applied physics Amir Safavi-Naeini alongside co-first authors Takuma Makihara and Erik Szakiel, achieved the breakthrough by coupling a microscopic mechanical resonator to a superconducting qubit, allowing them to repeatedly measure the resonator's vibration state without disrupting its delicate quantum behaviour, a longstanding and genuinely difficult challenge in quantum measurement generally. The resonator's vibrations were tracked across a two millisecond ringdown time, an interval Stanford compares to the equivalent of an ordinary tuning fork ringing continuously for several hours once properly scaled.

Safavi-Naeini described the significance of the result plainly, saying the study will allow the field to move forward with developing new quantum technologies built specifically around sound, while Szakiel added that the level of fine tuned control demonstrated here could mean devices already built around sound as a fundamental technology stand to get significantly better. Potential applications flagged by the team include improved quantum error correction for future quantum computers, ultra sensitive protein detection systems, and meaningful improvements to sound based consumer devices more broadly.

For the first time, scientists watch sound jump between quantum stateswww.sciencedaily.com