In macroscopic oscillators. Physicists at Boston University have performed an experiment in which 500-nm-long silicon paddles sprouting from a 10.7-µm-long central spine of Si (see the figure) oscillate collectively. With the device in an external magnetic field, a current is applied to a gold-film electrode on top of the spine. The resulting Lorentz force causes the structure to vibrate at frequencies up to 1.5 GHz, which makes it the fastest macroscopic oscillator to date. At a temperature of 1 K, the device responds continuously to a changing drive force. However, at 110 mK, precisely where the researchers expect quantum effects to set in, the oscillator responds discretely. Confirmation that this system of about 50 billion Si atoms is quantized will require more work, both theoretical and experimental. (A. Gaidarzhy et al. , Phys. Rev. Lett. 94, 030402, 2005 https://doi.org/10.1103/PhysRevLett.94.030402 .)
