Stanford physicists observe quantum jump of sound in real time

September 22, 2026 at 02:52 PM1 min

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Stanford University researchers have directly observed a quantum jump of a phonon, the smallest unit of sound energy, in real time. The team used a microscopic mechanical resonator coupled to a superconducting qubit to detect the transition from energy level 1 to level 0. The findings were published in the journal Science.

Key Facts

The experiment used a microscopic mechanical resonator built with standard microchip manufacturing techniques.
The resonator can sustain vibration for two milliseconds, which is exceptionally long for a quantum system.
A superconducting qubit served as a non-invasive detector, continuously monitoring the resonator's state without disturbing it.
The observed phonon jumped from energy level 1 to level 0, a discrete transition characteristic of quantum behavior.
The results were published in the scientific journal Science.

Experimental Setup

The Stanford team fabricated a microscopic mechanical resonator using standard microchip production methods. The device functions as a miniature tuning fork and can maintain vibration for two milliseconds. To observe the quantum jump without disturbing the fragile system, the researchers coupled the resonator to a superconducting qubit. The qubit acted as an ultra-sensitive detector, continuously checking the vibration state without collapsing it.

Quantum Sound Behavior

In the macroscopic world, sound decays smoothly, like a fading bell. At the quantum level, sound energy decreases in discrete steps called phonons, which are collective motions of millions of atoms. The experiment captured the exact moment a phonon made an instantaneous jump from energy level 1 to level 0. Previous direct observations of quantum jumps were limited to ions in 1986 and photons in 2007.

Implications

The ability to detect quantum jumps of sound could improve error correction in quantum computers by pinpointing the moment of information failure. The sensitivity of the resonator-qubit combination may enable new detectors capable of identifying individual protein molecules inside living cells.