Researchers announce single atom transistor

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Researchers claim to have built a working transistor with a region composed only of a single phosphorus atom in silicon.

The team is comprised of researchers from Helsinki University of Technology, Finland, University of New South Wales and University of Melbourne. According to the team, the working principles of the device are based on sequential tunneling of single electrons between the phosphorus atom and the source and drain leads of the transistor. The tunneling can be suppressed or allowed by controlling the voltage on a nearby metal electrode with a width of a few tens of nanometers. All the electric current in the transistor passes through the same single atom, allowing the researchers to study the effects arising in the extreme limit of the transistor size. Part of the research was spent attempting to address problems when the size of a transistor is shrunk towards the ultimate limit and the resulting quantum mechanical effects. While the phenomena are expected to challenge the usual transistor operation, they allow irrational behaviour which can, in principle, be harnessed for conceptually more efficient computing - quantum computing. Working from the new measurements, the development team plans to utilise the spin degree of freedom of an electron of the phosphorus donor as a qubit. The researchers claim to have observed spin up and down states for a single phosphorus donor for the first time - a crucial step towards the control of these states and the realisation of a qubit.