Shape of things to comeQuantum computers near: Scientists rotate electron spin with electric field
Researchers succeed in controlling the spin of a single electron merely by using electric fields; this clears the way for a much simpler realization of the building blocks of a (as yet theoretical) super-fast quantum computer
Yesterday we wrote about two Singaporean researchers showing the outline of a third type of computer: Phononic computers, that is, computers relying on heat for operation. In addition to electronic computers and (theoretical) optical computers, phononic computers are based on logic gates in which inputs and outputs are represented by different temperatures; in run-of-the-mill electronic computers, inputs and outputs are represented by different voltages. Now let’s go back to optical, or quantum, computers. Question: What is the essential building block of a future quantum computer? Answer: Controlling the spin of a single electron. An electron not only has a charge but, because of its spin, it also behaves as a tiny magnet. In a magnetic field, the spin can point in the same direction as the field or in the opposite direction, but the laws of quantum mechanics also allow the spin to exist in both states simultaneously. As a result, the spin of an electron is a very promising building block for the yet-to-be-developed quantum computer — a computer which, for certain applications, is far more powerful than a conventional computer.
It may be surprising that the spin can be rotated by an electric field. The theory of relativity, however, tells us that a moving electron can “feel” an electric field as though it were a magnetic field. Researchers Katja Nowack and Dr. Frank Koppens therefore forced an electron to move through a rapidly changing electric field. Working in collaboration with Professor Yuli Nazarov, theoretical researcher at the Delft University of Technology’s Kavli Institute of Nanoscience, they showed that it was indeed possible to turn the spin of the electron by doing so. The advantage of controlling spin with electric fields rather than magnetic fields is that the former are easy to generate. It will also be easier to control various spins independently from one another — a requirement for building a quantum computer — using electric fields. The team, led by Dr. Lieven Vandersypen, is now going to apply this technique to a number of electrons.
-read more in K. C. Nowack et al., “Coherent Control of a Single Electron Spin with Electric Fields,” ScienceExpress (1 November 2007) (10.1126/science.1148092) (sub. req.)
