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IBM questions the performance of D-Wave's quantum computer

IBM charges that a D-Wave quantum computer run by Google actually relies on good old-fashioned classical physics

By Joab Jackson, IDG News Service
February 04, 2014 06:08 PM ET

IDG News Service - Researchers at IBM and the University of California are questioning whether a closely watched experimental computer used by Google actually relies on quantum mechanics as its manufacturer, D-Wave, claims.

At the heart of the battle is a question about the validity of quantum computing, which some predict may offer a road forward after Intel and other chip manufacturers exhaust "and reach the physical limits" of how powerful they can make their processors.

D-Wave claims it does. D-Wave charges that the IBM and university researchers confined their study to only one aspect of what its computer can do.

"A successful theory needs to explain all the existing experimental results, not just a narrowly selected subset of them," said Colin Williams, the business development director for D-Wave, of the researchers' work. "The right theory has to explain all of the data, not just some of the data."

D-Wave is a closely watched company in that it is perhaps the most advanced in terms of commercializing quantum computing, though even its founders acknowledge that they exploit only a subset of quantum mechanics, called quantum annealing.

Quantum computing is the practice of harnessing the laws of quantum mechanics, or how matter behaves at the subatomic level. Advocates claim quantum computing could be more powerful than standard silicon processing in that its small scale of operations can simulate problems too large to be represented in traditional computing systems.

D-Wave markets its machines, which it started selling in 2011, as very large co-processors, handy for solving complex optimization and machine-learning problems that could overwhelm classically designed computers. Google has invested in one of D-Wave's computers and is evaluating the results.

The researchers, from the IBM T.J. Watson Research Center and from the University of California, developed a model showing that, for a given problem solved by a D-Wave computer, a similar level of computation could be achieved through equipment that relied on classical mechanics. They used actual results from a problem solved on Google's D-Wave computer.

The researchers' paper kick-started debate over the validity of D-Wave's computer in a number of online forums.

Williams said the charge from IBM and University of California is a pretty common one for D-Wave. Researchers will typically try to match the results of a quantum computer to what could be achieved by using classical physics. However, they usually just confine their study to one aspect of quantum computing.

"Whenever there is an experiment claiming to report quantum mechanical -- or any non-classical -- effects, researchers look for classical models that predict the same results. This is a very common practice in the history of science," Williams said.

The researchers examined a problem solved by Google's D-Wave computer that involved finding the ground state of an erratically operating magnet called a spin glass. The researchers came up with a model of a hypothetical system that could solve the problem equally as well just using components that operated by the laws of classical physics.

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