From: John Devers ® 28/05/2001 12:57:27 Subject: Quantum computer. post id: 308974 Looks like other ways of making QCs are chellenging IBMs 5 bit QC. How is Australia's challenge from the league of Uni's going? From the email to a friend section. http://www.nature.com/nsu/010531/010531-5.html New wave machine http://www.nature.com/nsu/010426/010426-11.html physics: New wave machine PHILIP BALL A new computer design uses interfering light beams to speed up database searches. The computer could perform some tasks a billion times faster than existing electronics-based machines, claim its inventors, Ian Walmsley of the University of Rochester, UK, and his colleagues. Walmsley's team unveiled a simple prototype that searches a record of 50 items encoded in laser beams at the Conference on Lasers and Electro-Optics/Quantum Electronic and Laser Science in Baltimore, Maryland earlier this month. The device did not execute this modest task any faster or more efficiently than a conventional computer. But the same principles could give rise to a kind of wave computing that leaves electronic systems standing. The approach is a kind of intermediate between classical electronic information processing and quantum computing. Quantum computing, which has so far been demonstrated only in the most rudimentary of systems, makes use of the wave properties of particles such as individual atoms, or photons, the particles of light. This wave nature gives rise to interference effects. Two waves with peaks and troughs that are perfectly in step enhance one another when they interact; two out-of-step waves cancel each other out. Some proposed designs for quantum computers use quantum interference to add and subtract signals and thus to perform computations. Walmsley and colleagues' wave-computing scheme is easier to implement than true quantum computing. Their database is an acousto-optic modulator — it alters light waves with sound waves. It consists of a block of tellurium dioxide vibrated by an acoustic transducer, rather like a loudspeaker. The acoustic waves compress some parts of the material and expand others, locally altering the way it interacts with light. Information is encoded in this pattern of expansion and compression. The database is searched using a light beam that is split in two. One half passes through a prism that splits it into its component frequencies. Different colours pass through different parts of the acousto-optic modulator — that is, different portions of the database. So each bit of encoded information is probed by a different colour. Depending on the contents of the database, some of these beams are shifted in-phase, so that the peaks and troughs of the light waves coincide. This altered rainbow is recombined by another prism and interacts with the other half of the original beam. Because of interference effects, the parts of the beam that have been shifted in-phase travel in a different direction to the others, revealing which parts of the database altered the incoming signal. So the researchers can locate the bits of information they are looking for. This offers the ability to search every part of the database simultaneously, rather than looking through each entry one at a time as a normal computer does. That is not so laborious for a 50-item database, but if the entries run into millions, the economy of performing a single search, rather than millions of consecutive ones, is considerable. This forum is un-moderated. The views and opinions expressed are those of the individual poster and not the ABC. The ABC reserves the right to remove offensive or inappropriate messages.