ADVANCE MAY LEAD TO PRACTICAL QUANTUM COMPUTING

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ADVANCE MAY LEAD TO PRACTICAL QUANTUM COMPUTING
23 July 2002 - University of Wisconsin-Madison

For the first time, University of Wisconsin-Madison scientists have designed a semiconductor-based device that can trap individual electrons and line them up, an advance that could bring quantum computing out of the gee-whiz world of scientific novelty and into the practical realm.

Professors Mark Eriksson and Bob Joynt ( physics), Max Lagally (materials science and engineering), and Dan van der Weide (electrical and computer engineering) have developed a new type of "quantum dot" device for holding electrons that can be scaled up to build a working quantum computer.

Made from tiny amounts of the same semiconductor materials used in today's computer chips, each quantum dot device contains just one infinitesimally small electron. When many of the devices are aligned, the electrons they house become usable quantum bits, or qubits, for computing.

"The first prerequisite to building a large computer is to have a lot of bits, and we think we have a way to get a lot of them," says Eriksson. "We've done some sophisticated simulations with this device that show the concept is very likely to work, and we're in the beginning stages of actually making the device."

Unlike the bits of classical, serial computers, which exist in either the 0 or 1 state, qubits can exist in more than one state at once. This elusive quality of their components frees quantum computers to calculate all the possible solutions to a problem simultaneously, instead of running through them one-by-one like their slower, serial counterparts.

This ability to "parallel process" means quantum computers hold tremendous number-crunching potential for certain tasks, such as highly sophisticated data encryption and code-breaking, that now defy even the most powerful computers.

The team's device uses layers of semiconductor materials and electrostatic forces, the same forces that build up when you scuff across a carpet in winter, to squeeze a single electron into place within each quantum dot. The design allows the alignment of a large number of dots, their captured electrons separated by a distance only one-one thousandth the width of a human hair. Eriksson emphasizes that researchers worldwide are trying to find the best way to harness subatomic particles for quantum computing. In fact, others have realized success in stringing a few quantum dots together.

"People often talk about quantum computing in the future tense, but that's not really right, it exists today. People have solved simple problems with it, but in the future we want to address problems that can't be solved by any other means," says Eriksson.

With its potential for coupling hundreds of electrons, Eriksson believes the team's device could provide a quantum leap in that direction. "Our invention makes it more likely that quantum computing might actually be useful someday instead of a curiosity," he says.

Collaborators include postdoctoral researcher Mark Friesen (physics theory), staff scientist Don Savage and graduate student Paul Rugheimer (materials growth).

To read a preprint paper describing the technology, visit: http://xxx.lanl.gov/abs/cond-mat/0204035.

A patent on the technology has been filed by the Wisconsin Alumni Research Foundation, a non-profit organization that manages the intellectual property of the UW-Madison.

http://www.wisc.edu

About: University of Wisconsin-Madison
In achievement and prestige, the University of Wisconsin-Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW-Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Many of its programs are hailed as world leaders in instruction, research and public service.

The university traces its roots to a clause in the Wisconsin Constitution, which decreed that the state should have a prominent public university. In 1848, Nelson Dewey, Wisconsin’s first governor, signed the act that formally created the university, and its first class, with 17 students, met in a Madison school building on February 5, 1849.

From those humble beginnings, the university has grown into a large, diverse community, with about 40,000 students enrolled each year. These students represent every state in the nation, as well as countries from around the globe, making for a truly international population.

UW-Madison is the oldest and largest campus in the University of Wisconsin System, a statewide network of 13 comprehensive universities, 13 freshman-sophomore transfer colleges and an extension service. One of two doctorate-granting universities in the system, UW-Madison’s specific mission is to provide "a learning environment in which faculty, staff and students can discover, examine critically, preserve and transmit the knowledge, wisdom and values that will help insure the survival of this and future generations and improve the quality of life for all."

The university achieves these ends through innovative programs of research, teaching and public service. Throughout its history, UW-Madison has sought to bring the power of learning into the daily lives of its students through innovations such as residential learning communities and service-learning opportunities. Students also participate freely in research, which has led to life-improving inventions from more fuel-efficient engines to cutting-edge genetic therapies.

Students, faculty and staff are motivated by a tradition known as the "Wisconsin Idea," described by UW President Charles Van Hise in 1904 as the compelling need to carry "the beneficent influence of the university ... to every home in the state." The Wisconsin Idea permeates the university’s work and helps forge close working relationships among university faculty and students and the state’s industries and government.

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