Stanford physicists observed a tiny vibrating structure lose a single unit of sound energy in a sudden quantum jump. The finding could help advance quantum computing and precision sensing.
A tiny mechanical resonator, a structure that vibrates like a tuning fork, has given Stanford researchers a close look at how sound disappears at the quantum scale. They watched it lose a single phonon, the smallest discrete unit of sound, in the first direct observation of a quantum jump of sound.
A phonon represents the coordinated movement of a large group of atoms, just as a photon is a quantum of light. Although a ringing bell seems to fade smoothly, a resonator’s vibrational energy changes in discrete steps. These sudden transitions between energy states are called quantum jumps.
Quantum jumps can signal computing errors
The team, led by Stanford physicist Amir Safavi-Naeini, reported its findings in Science. Detecting these jumps could help researchers address a persistent problem in quantum computing: recognizing when something has gone wrong during a calculation.
Quantum computers have the potential to handle some complex calculations beyond the capabilities of conventional computers, but their fragile quantum states can develop errors before the work is finished. In many proposed quantum computing architectures, a quantum jump represents an error. Pinpointing when those jumps occur has been difficult, so tracking them in sound offers a step toward correcting them.
Two milliseconds to track one phonon
Making that measurement required a detector that could repeatedly check the resonator without disrupting its fragile quantum state. Study co-first authors Takuma Makihara and Erik Szakiel developed a way to connect the resonator to a superconducting qubit, an electrical circuit that can store quantum information and act as a detector.
“We had to continually develop new processes to make this extremely long-lived, vibrating object and then integrate it with the qubit, which is our little electrical detector—without ruining either subsystem,” said Makihara, a recent Stanford doctoral graduate.
The resonator’s ability to keep vibrating gave the detector enough time to work. It could ring for two milliseconds, a duration that would correspond to several hours of ringing in a regular-sized tuning fork with the same capability. This unusually long “ringdown time,” the time over which the vibration fades, allowed the researchers to take hundreds of readings.
During those repeated checks, the qubit distinguished between a state containing one phonon and a state containing none. By following the readings over time, the researchers could identify the moment the resonator jumped from the state labeled 1 to the state labeled 0.
The result extends an experimental history stretching back more than a century. Quantum jumps were theorized in the early 1900s, first demonstrated in trapped ions in 1986, and later observed in photons in 2007. Earlier sound experiments had provided evidence of quantum jumps, but had not directly tracked individual jumps in real time.
Toward detecting proteins inside cells
“What this study shows will allow us to move forward with developing new quantum technologies with sound,” said Safavi-Naeini, an associate professor of applied physics in Stanford’s 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.”
The resonator was made using chipmaking techniques and is small enough that many could fit on a single chip to carry out complex functions. Its small size, combined with the sensitivity of the resonator and qubit system, could also support extremely precise sensing. Safavi-Naeini’s team is already working with physicist Michael Roukes’ team at Caltech to pursue a way to detect and identify proteins within cells using the platform.
Szakiel, a doctoral student in Safavi-Naeini’s lab, said the advance could eventually help improve smartphones and other everyday devices that rely on sound.
“This shows we can have incredibly fine-tuned control of sound, which might mean that devices that use sound as a fundamental technology can get much better,” he said.
Reference: “Quantum jumps of sound” by Takuma Makihara, Erik Szakiel, Matthew P. Maksymowych, Oliver A. Hitchcock, Kaveh Pezeshki, Rachel G. Gruenke-Freudenstein, Mihir Pendharkar, Shannon P. Harvey, David I. Schuster and Amir H. Safavi-Naeini, 17 September 2026, Science.
DOI: 10.1126/science.aeh7535
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.