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.
This phenomenon, known as quantum whistling, occurs when pressure is applied to push a superfluid through a very small hole, somewhat as sound is produced by blowing air through an ordinary whistle. A ring-shaped tube full of superfluid, blocked by a barrier containing a tiny hole, could in principle be used to detect pressure differences caused by changes in rotational motion of the ring, in effect functioning as a sensitive gyroscope. Superfluid whistling was first demonstrated using helium-3, which has the disadvantage of being scarce and expensive, and requiring extremely low temperature (a few thousandths of a Kelvin). Common helium-4, which remains superfluid at 2 Kelvin, is much more practical, but its quantum whistling is too weak to be heard with a single practical-sized hole. This problem was overcome by using barriers with thousands of holes, in effect a chorus of quantum whistles producing sound waves that reinforced one another by constructive interference.
Read more about this topic: Quantum Gyroscope
Famous quotes containing the word principle:
“Look through the whole history of countries professing the Romish religion, and you will uniformly find the leaven of this besetting and accursed principle of action—that the end will sanction any means.”
—Samuel Taylor Coleridge (1772–1834)
“The principle of the brotherhood of man is ... narcissistic ... for the grounds for that love have always been the assumption that we ought to realize that we are the same the whole world over.”
—Germaine Greer (b. 1939)
“Custom, then, is the great guide of human life. It is that principle alone, which renders our experience useful to us, and makes us expect, for the future, a similar train of events with those which have appeared in the past.”
—David Hume (1711–1776)