World Year of Physics 2005

Under the right circumstances almost anything can be quantized, and many such quantities have been observed directly in experiments. Now it seems that a new quantity may have joined the list: displacement. Researchers at Boston University used silicon to construct a comb-like structure with "teeth" some 500 nm long and 200 nm wide. They then equipped it with a current-carrying gold strip so that it could be made to oscillate in a magnetic field.

What they have observed is quite remarkable. At millikelvin temperatures, where quantum effects dominate over thermal ones, they have seen preferences for distinct amplitudes of the displacement, just as one would expect for a quantum simple harmonic oscillator. The actual displacements due to the driving force are only femtometres, but the mechanical structure amplifies them up to the level where they become observable. The displacements reach frequencies up to 1 GHz, which makes this the highest frequency bulk mechanical oscillator to date.

Further reading

Alexei Gaidarzhy et al. 2005 Phys. Rev. Lett. 94 030402.