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| A Quantum Leap for
Computers IBM's experimental machine turns physics theories into reality Carl T. Hall, Chronicle Science Writer |
Tuesday, August 15, 2000
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Tapping into a bizarre realm of nuclear spin and subatomic entanglements, scientists at IBM Corp. showed yesterday that a so-called quantum computer can actually work in the real world -- and may outdistance even the fastest supercomputers. Experimenters at IBM's Almaden Research Center in San Jose said they had used ``the world's most advanced quantum computer'' to solve in a single step a mathematical problem that would take a conventional computer up to four distinct steps to handle. It was described as the first experiment to confirm theoretical predictions earlier this year that such a feat was possible. The research is aimed at surpassing current silicon-based computer architecture by taking advantage of some of the seminal findings of 20th century physics, in particular the notion that the same subatomic particle can exist in two seemingly opposite ``quantum states.'' The IBM prototype was not the pocket-sized supercomputer of science fiction but rather an unwieldy collection of magnets, spectrometers and probes big enough to fill half a room and built around a room-temperature ``magnetic spin system.'' The machinery's core computational engine consisted of five atoms of fluorine -- each representing a single ``quantum bit,'' or ``qubit,'' of information-holding capacity -- suspended in a specially designed molecule. When subjected to a magnetic field, the nuclei at the centers of the atoms can be made to spin like tops in a way that can be controlled and detected, using MRI (magnetic resonance imaging) devices commonly used in hospitals. Unlike the children's toys, each spinning nucleus interacts with the others, creating a logic-defying quantum ``entanglement'' that computer designers can harness to perform calculations at blinding speeds. IBM scientist Isaac Chuang, leader of the quantum computing project, outlined the latest results yesterday, previewing a presentation scheduled for today at Hot Chips 2000, a computer-engineering conference being held at Stanford University. Findings have also been submitted to the scientific journal Physical Review Letters. ``This was the first time anyone has done a computation using a 5-qubit molecule,'' Chuang said. ``The trend is that the theoretical projections about quantum computing are being realized, one by one.'' The latest experiments offered a glimpse at the working guts of what many predict could become a critical computing technology of the future, particularly suited to handling elaborate security codes and solving certain types of mathematical problems that tend to stymie conventional computers. The mathematical trick IBM chose for its latest demonstration was just such a problem -- an ``order-finding experiment'' that involved finding the ``period of a function,'' which can be likened to figuring out how to return through a series of rooms to a starting point by following a series of one-way passages. The abstract quality of the puzzle highlighted the widespread belief -- shared by IBM scientists, in fact -- that the earliest commercial applications of quantum computers appear to be at least 20 years or so away. Nor can anyone predict which of several early design concepts will eventually bear fruit. Stan Williams, head of a competing team of computer architects at Hewlett-Packard in Palo Alto, called the latest IBM results ``very encouraging and impressive progress'' when he was apprised of them yesterday. But he also noted that quantum computing comes with some built-in problems, including data instability and capacity constraints, that have yet to be solved. H-P, meanwhile, is pursuing a more conventional type of superfast, low-power computing expected to yield results in as little as five years. Other computer-of-the-future possibilities include computers built around DNA molecules or which use chemical reactions to assemble tiny components. None of it is anywhere near ready for prime time. IBM's announcement is ``an important proof of principle demonstration,'' Williams said, ``but I don't think this will be the primary way of doing computing in the future.'' E-mail Carl Hall at cthall@sfgate.com. |
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