Single atom transistor to improve quantum computing
20 Dec 2009 by Evoluted New Media
A transistor with an active region of a single phosphorus atom in silicon has been built by researchers, and they think it will give the field of quantum computing boost.
A transistor with an active region of a single phosphorus atom in silicon has been built by researchers, and they think it will give the field of quantum computing boost.
Development of computers has been based on reducing the size of transistors. In this study – recently published in Nano Letters – researchers developed a transistor where all the electric current passes through a single atom of phosphorous and studied the effects arising in the extreme limit of the transistor size.
“Our purpose was not to build the tiniest transistor for a classical computer, but a quantum bit which would be the heart of a quantum computer that is being developed worldwide,” said Dr Möttönen, one of the 11 study authors from Helsinki University of Technology, University of New South Wales and University of Melbourne.
The working principles of the device are based on sequential tunnelling of single electrons between the phosphorous atom and the source and drain leads of the transistor. This tunnelling can be controlled by altering the voltage on a nearby metal electrode with the width of a few tens of nanometres.
When the transistor is shrunk towards the ultimate limit, problems arise due to the emergence of quantum mechanical effects. One the one hand, it is expected to challenge the usual transistor operation, but on the other it allows classically irrational behaviour which could be harnessed for quantum computing. The idea is to utilise the spin degree of freedom of an electron of the phosphorous donor as a qubit or quantum bit.
Researchers observed in their experiment the spin up and down states of the phosphorous for the first time, which is a crucial step towards the control of these states and the realisation of a qubit.
