Physicists at Stanford University have directly observed quantum jumps in sound in real time for the first time. Their findings were published in the journal Science.
The researchers worked with phonons, which are quanta of mechanical vibrations. In the macroscopic world, sound fades gradually, but at the quantum level, energy changes in discrete amounts.
The team successfully observed the moment when a system abruptly transitioned from one energy level to another.
Quantum jumps were predicted in the early 20th century. They were first observed in trapped ions in 1986 and in photons in 2007. For phonons, previous experiments provided indirect evidence, but individual transitions in real time had not been recorded until now.
How the Jump Was Observed
For the experiment, the team created a microscopic mechanical resonator, akin to a tiny tuning fork, using chip manufacturing techniques.
The key feature of the device was its long vibration decay time—about 2 milliseconds. During this interval, researchers could conduct hundreds of measurements to pinpoint the moment when a phonon’s energy transitioned from level 1 to 0.
To observe this, the resonator was connected to a superconducting qubit, which acted as a sensor, repeatedly checking the system’s state without disrupting it with each measurement.
“We observed that vibrating objects can exhibit quantum behavior. This is essential for many operations in quantum computing and sensors,” said lead researcher Amir Safavi-Naeini.
Why Observe Quantum Jumps
One potential application is in error correction for quantum computers. Quantum states are unstable, and a system’s transition between levels can indicate an error in some architectures. To correct it, the moment of occurrence must first be identified.
According to the researchers, the ability to track such changes in real time lays the groundwork for systems based on mechanical resonators. However, the current experiment is a fundamental study, not a ready method for error correction.
Another area is ultra-sensitive sensors. The Stanford team, along with scientists from the California Institute of Technology, is exploring the use of a resonator-qubit combination to detect and identify proteins within cells.
The authors also see potential applications in electronics. Mechanical vibrations are used in smartphones and other devices, and more precise control could lead to new acoustic components.
In June, Microsoft Quantum and Quantinuum reported a reduction in logical errors in a quantum processor by 11 to 800 times compared to comparable physical circuits. At the same time, IBM introduced a system for discovering new error correction codes using AI.
