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Phoenix666 writes:

The hissing sound you hear in the background when you turn up the volume of your music player is called "noise". Most of this hiss is due to the thermal motion of electrons in the music-player circuitry. Just like molecules in a hot gas, electrons in the circuitry are constantly jiggling about in a random fashion, and this motion this gives rise to an unwanted noise signal.

But there is another type of noise that only comes into play when we have an electrical current flowing. This noise is known as shot noise. Obstacles that generate shot noise in this way are found in many electronic components, such as diodes and some transistors, and electronic engineers take great efforts to try to get rid of the effects of all sources of noise, including shot noise, in their designs.

Now a new study has shown that shot noise can be eliminated at its microscopic origin. And to do so, they have borrowed an idea from an unlikely source – the early days of the steam engine.

[...] In the 18th century, James Watt was struggling to get his steam engine to run at a constant speed. To solve this problem, he came up with the "centrifugal governor" in 1788, a contraption that consisted of two metal balls rotating on a vertical spindle driven by the steam engine. If the engine ran too fast, the balls would move upwards under the centrifugal force (a force acting on a body moving in a circular path is directed away from the centre around which the body is moving).

[...] The new experiment focuses on an ultra-small electronics device known as the single-electron transistor, which... [is] somewhat like ordinary transistors, which switch electronic signals, but taken to the extreme limit of miniaturisation such that electrons move through them one at a time. This happens via quantum tunneling, which means the current through a single-electron transistor suffers from the randomness of shot noise.

Using sensitive charge measurements, the researchers were able to detect exactly when an electron had tunnelled through the transistor. Based on this electron counting, they then adjusted the voltages of the transistor, following Watt's recipe for the centrifugal governor: if more electrons than normal had tunnelled, they changed the voltages to reduce the flow; if fewer had tunnelled, the voltages were changed to increase the flow.

Original Submission