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Thursday, April 8, 1999 Published at 21:57 GMT 22:57 UK


Computers that run without electricity

Computers could run entirely on small internal batteries

Powerful computers that run without electric power could be possible in the future.

Research shows that computer circuits can be built to work without electricity. A tiny initial charge is all that is needed.

Charles Smith explains how the new computers would work
The new "logic gates" exploit the charge of captured electrons to set off a domino-like cascade of change in stored information.

They have been developed by scientists at the University of Notre Dame in Indiana, USA.

Most experts believe that standard computer processors can only be miniaturised so far, before classical physics fails and strange quantum effects take over. This new technology could be a replacement as it can in theory be shrunk to the molecular scale.

Dr Charles Smith, in the Physics Department at the University of Cambridge, UK, told BBC News Online: "It is very nice work to show that you can make a gate using single electrons which move around. This has the advantages of switching very quickly and using very low power."

Quantum dots

The key to the new technology is a cell with four tiny dots of material which can capture electrons. They are arranged as a square. When two electrons are put into the cell, they repel one another and end up positioned across one diagonal or the other.

These two positions correspond to the binary "0" and "1" used in computing. Today's computers use on and off transistors for zeroes and ones.

By placing another quantum-dot cell next to the first, the repulsive electrical charge of the electrons allows the information to be passed on without needing an electrical current.

Possible in principle

Chains of the cells would be the "wires" in the new computers and could be arranged to make logic gates. The researchers at Notre Dame built a simple type of gate to show that the principle of this kind of computing is sound. Their work is published in Science magazine.

However, Dr Smith comments: "Other research shows you probably have to control the size of the quantum dot which holds your electron to such tiny resolution that it may well turn out to be rather impractical.

"But there is a chance that the same architecture might work with something other than electrons, such as tiny magnets."

In addition to these, another major obstacle will need to be overcome. At the moment, the circuits only work at -272.9 degrees Centigrade, just above absolute zero.

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