Quantum gyroscope

A quantum gyroscope is a very sensitive device to measure angular rotation based on quantum mechanical principles. The first of these has been built by Richard Packard and his colleagues at the University of California, Berkeley. The extreme sensitiveitivity means that theoretically a larger version could detect effects like minute changes in the rotational rate of the Earth.

Principle

In 1962, Cambridge University physicist Brian Josephson hypothesized that an electrical current could travel between two superconducting materials even when they were separated by a thin insulating layer.The term "Josephson effect" has come to refer generically to the different behaviors that occur in any two weakly connected macroscopic quantum systems—systems composed of molecules that all possess identical wavelike properties. Among other things, the Josephson effect means that when you connect two superfluids (zero friction fluids) using a weak link and pressure is applied to the superfluid on one side of a weak link, the fluid will oscillate from one side of the weak link to the other.

Take any pipe shaped in the form of a torus (donut shape), containing a superfluid (liquid helium-3) that has at two places along the loop with weak connections (thin membranes of silicon nitride each perforated with 4,225 small apertures, each of which is about 1/500 the size of a human hair). Apply a small amount of pressure and a wave is created that oscillates from one side of the link to the other.While the frequency of the wave is determined by the pressure applied, the magnitude of the wave depends on what, if any, rotation the torus had. This magnitude can be measured using electricity.So if the donut is spun, the wave gets broader, and it is possible to measure the size of the wave, making sensitive measurements of rotation.

References

Simmonds, R. et al., "Quantum interference of superfluid 3He". Nature, 412 (July 5, 2001): 55-58.