Dutch physicists get a grip on the spin of a single electron

Researchers of the Kavli Institute of Nanoscience at Delft University of Technology and the Foundation for Fundamental Research on Matter (FOM, both from The Netherlands) have succeeded in controlling the spin of a single electron in a nanostructure. They are able to rotate the spin to every possible direction and to record it accordingly. This achievement makes it possible to use the electron's spin as a ‘'quantum bit'', the basis of a (still theoretical) future quantum computer. Usually, the rotation of the spin is being executed by switching on and off a magnetic field that oscillates very fast during some billionths of a second. The interfering side effects of a locally generated magnetic field made it hard to rotate the electron spin and yet to keep it locked up at the same time, explain the researchers. But the Delft team get around these side effects. Their approach was to lock up a second electron in another quantum dot alongside the first one and to use it to read out the spin direction of the first electron. A basic principle of quantum mechanics tells that two electrons that have identically oriented spins cannot stay together, while two electrons that have different spins can. Each time after the spin was rotated, a check was made to see whether two electrons were able to reside close together or not. This then defined to what extend the spin direction was changed. At the moment further research is being executed by combining the materialized basic ingredients to get a quantum bit.