Nano-watch: an environmental sensor of stunning precision

"It is amazing that we can take an electronic signal, and use it to perfectly drive the motion of a physi-cal object, without any loss of stability. Our clock only lost one-millionth of a second over four days", says co-author James Millen.

Other such tiny mechanical devices are limited in precision through contact with their environment, but when levitated the nano-rotor remains extremely stable for very long times.

Preparing such nanomechanical devices relies on the art of making pristine silicon pillars on a chip, as done in the group of Fernando Patolsky at Tel Aviv University. The Vienna team uses a "laser hammer" to knock out individual rods and traps them in tweezers made of light.

Describing the ensuing dynamics is a theoretical challenge that has been solved by the theoretical physicists Benjamin Stickler and Klaus Hornberger at the University of Duisburg-Essen. The motion of the spinning nano-rod is chaotic, a behaviour also found in weather patterns and road traffic.

This may not sound promising for technological application, but it is possible to find islands of calm in the chaos, where the ticking of the nano-hands of the clock become ultra-stable.

The ticking of a material, rather than electronic, clock is very sensitive to its environment. This high-ly accurate, tiny hand of a watch can be used to precisely measure properties of the world on the nanoscale, for instance pressure variations over sub-millimetre distances.

The levitated cylinder could be moved through a gas flow to measure turbulence, or through a beam of atoms or light to discern its properties. It may one day even be possible to use this method to test the limits of quantum physics: "At high rotation rates, this is an environmental sensor of stunning precision. At low frequencies it can open a new range of experiments on the quantum mechanics of rotation", says Markus Arndt.