<http://www.technologyreview.com/articles/04/11/rnb_110804.asp?trk=nl> Technology Review Single Field Shapes Quantum Bits November 8, 2005 Quantum computers, which tap the properties of particles like atoms, photons and electrons to carry out computations, could potentially use a variety of schemes: individual photons controlled by optical networks, clouds of atoms linked by laser beams, and electrons trapped in quantum dots embedded in silicon chips. Due to the strange nature of quantum particles, quantum computers are theoretically much faster than ordinary computers at solving certain large problems, like cracking secret codes. Chip-based quantum computers would have a distinct advantage - they could leverage the manufacturing infrastructure of the semiconductor industry. Controlling individual electrons, however, is extremely challenging. Researchers have recently realized that it may be possible to control the electrons in a quantum computer using a single magnetic field rather than having to produce extremely small, precisely focused magnetic fields for each electron. Researchers from the University of Toronto and the University of Wisconsin at Madison have advanced this idea with a scheme that allows individual electrons to serve as the quantum bits that store and process computer information. Electrons have two magnetic orientations, spin up and spin down, which can represent the 1s and 0s of computing. The researchers' scheme relies on the interactions of pairs of electrons. Tiny electrodes positioned near quantum dots -- bits of semiconductor material that can trap single electrons - can draw neighboring electrons near enough that they exchange energy. The researchers' scheme takes a pair of electrons through eleven incremental steps that involve the electron interaction and a global magnetic field to flip one of the bits from a 0 to a 1 or vice versa. The technique could be used practically in 10 to 20 years, according to the researchers. The work appeared in the July 15, 2004 issue of Physical Review Letters. Technology Research News -- ----------------- R. A. Hettinga <mailto: rah@ibuc.com> The Internet Bearer Underwriting Corporation <http://www.ibuc.com/> 44 Farquhar Street, Boston, MA 02131 USA "... however it may deserve respect for its usefulness and antiquity, [predicting the end of the world] has not been found agreeable to experience." -- Edward Gibbon, 'Decline and Fall of the Roman Empire'