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Detecting the spin

February 2002

STM image shows four BDPA molecules adsorbed on a graphite substrate - a typical sample used by Durkan and Welland to demonstrate their technique for detecting spin.

Researchers in the Department's Laboratory for Nanoscale Science have made a significant advance towards the goal of developing a so-called 'quantum computer' following the development of a new technique for detecting a single electron spin.

Dr Colm Durkan,a lecturer in the Department of Engineering explains:

"At a simple level, all computers work by detecting some signal that can either be' on' or 'off'. That is all you need. The computers that are used at present read data by detecting changes in magnetism. Electrons have a fundamental property of spin which determines magnetic properties.Up to now it has only been possible to detect electronic spins of the order 10¹⁰, but we have developed a technique for detecting the magnetism of a single atom by detecting a single electron spin. Obviously once that is possible, then it becomes possible to use magnetic properties of a single atom as the 'on/off' signal that is required for computing, bringing us much nearer to our ultimate goal of creating a quantum computer."

The measurements have been made using the technique of scanning tunneling microscopy, using an organic molecule that contains free radicals which give rise to a large spin signal.

The paper describing this research has recently been published in Applied Physics Letters (Volume 80, Number 3, January 2002) and enquiries are flooding in. It was also heralded by the journal Nature as a significant advance.

The research to-date has been funded jointly by the EPSRC and in part by an EU grant. Proposals for the next stage of the work which is to implement the findings in a quantum computer are currently being submitted.

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