Australian scientists have created the world's smallest transistor, measuring just four billionths of a metre long.

It consists of just seven atoms in a single silicon crystal and, despite its infinitesimal size, the transistor is a working electronic device and the first to be made by deliberately placing individual atoms.

Prior to this discovery, nobody had been able to make atomic-precision devices that could process electronic inputs from more standard-sized devices.

The technology, produced by a team of researchers from the University of New South Wales' Centre for Quantum Computer Technology (CQCT) and the University of Wisconsin-Madison, can control electrical current flow like an everyday transistor.

This development is a step towards a new era of atomic-scale minituarisation and new super-computers, according to the scientists.

"The Australian team has been able to fabricate an electronic device entirely out of crystalline silicon where we have replaced just seven individual silicon atoms with phosphorus atoms. That is amazing exactness," said Professor Michelle Simmons, director of the CQCT and leader of the research.

"This is a huge technological achievement and it is a critical step to demonstrating that it is possible to build the ultimate computer - a quantum computer in silicon," she added in a statement.