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MIT, HP to build quantum computer

By Gillian Law

(IDG) -- Hewlett-Packard Co. (HP) and the Massachusetts Institute of Technology (MIT) have announced a joint $2.5 million quantum computing project to advance computing development beyond its current physical limits.

The project, announced last week, is part of a $25 million, five-year alliance launched in June 2000. Researchers at HP Labs in Palo Alto, California and Bristol, England will work with their counterparts in MIT's Media Lab, including Neil Gershenfeld and Isaac Chuang. Gershenfeld and Chuang are described as pioneers by HP in its press release, because of their past work in actually building and operating a simple quantum computer. INFOCENTER
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Quantum computing development is necessary because the current classical computing model is reaching its limit, said an HP spokesman Friday.

"Moore's Law is going to reach its natural conclusion because of the physical limitations of present technology. When you get to the atomic scale you can't take it much further," the spokesman said. "So we have to use the laws of quantum physics, as far as they are understood, to take computing further," he said.

Quantum computing research is farsighted, and it may take 10 years to develop a fully operational quantum computer, "but if you want to keep using computers in the way we have been, and to keep Moore's Law working, then we have to keep moving forward," the spokesman concluded.

Quantum computing uses the properties of quantum physics to perform calculations. The basic unit of computation used is the qubit, or quantum bit. Unlike classical bits the qubit is not just 0 to 1 but is in a superposition of both. In other words, it is both on and off at the same time.

While the classical digital byte can store any number between 0 and 255 using all of its eight bits, it can only represent one of those numbers at a time. But a qubyte can be all of the numbers between 0 and 255 simultaneously.

This allows much more information to be stored on a quantum bit than a classical bit, and allows massively parallel processing on a quantum scale. One calculation can give the answer for all the numbers on the byte at the same time, according to an explanation posted on the MIT Web site. In other words, for each clock cycle a quantum computer could perform 256 calculations in the same time a digital computer can perform just one.

However, problems arise when it comes to reading the information back. Any interactions with the environment -- including trying to read the information stored -- affect the qubits so that they change from a pure quantum state to a mixed state. This is known as decoherence and any reading taken from this state will be wrong. Various techniques have been developed to avoid decoherence including one by Gershenfeld and Chuang that makes use of a chemistry technique called nuclear magnetic resonance (NMR) spectroscopy.

• Hewlett-Packard

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