NOTHING sits still. Even at absolute zero, when the thermal jiggling of matter is frozen, all things must still buzz to the tune of quantum mechanics. Now this subtle jittering has been detected in a small silicon bar, the first solid object ever to reveal its quantum vibrations.
This phenomenon, called zero-point fluctuation, is a consequence of Heisenberg's uncertainty principle, which says that we can never pin down the precise position and motion of any object. So far zero-point energy has only been seen directly in single atoms or small collections of particles.
The new experiment uses a silicon bar about 12 micrometres long and less than a micrometre across. Oskar Painter at the California Institute of Technology in Pasadena and colleagues cooled the bar to within half a degree of absolute zero and then used a laser to detect its motion.
Some photons from this laser got a shift in energy when they hit the vibrating bar. Ordinary thermal vibrations can either boost or reduce photon energy, but the zero-point quantum vibration is different. Because it is the lowest energy state possible, it can only absorb energy. Painter's group detected this bias towards lower-energy scattered light, a clear signature of a quantum twang (Physical Review Letters, DOI: 10.1103/physrevlett.108.033602).
"Seeing these effects in large objects can provide us with a way to probe the foundations of quantum mechanics," says Caltech team member Amir Safavi-Naeini.