Stanford physicists have directly observed a quantum jump in sound for the first time, watching a single phonon abruptly switch energy states in real time. The century-old prediction, first demonstrated with trapped ions in 1986 and with photons in 2007, had never been captured for units of sound until now.
The team, led by physicist Amir Safavi-Naeini with co-first authors Takuma Makihara and Erik Szakiel, built a microscopic mechanical resonator using chip-fabrication techniques and paired it with a superconducting qubit as a detector. The resonator vibrates for about two milliseconds — a comparatively enormous "ringdown time" that let the qubit take hundreds of measurements per run, repeatedly checking whether the vibrational energy sat at state 1 or 0 to pinpoint the exact moment of transition.
The result, published in Science, opens paths toward quantum error correction for quantum computers, ultra-sensitive biological sensors capable of detecting individual proteins in cells, and finer control over sound-based technology in everyday devices. "This shows we can have incredibly fine-tuned control of sound," the researchers said, "which might mean that devices that use sound as a fundamental technology can get much better."