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Physics may lead to revolution in computing, says UA scientist

By Sean McLachlan
Arizona Daily Wildcat
April 5, 1999
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Nicholas Valenzuela
Arizona Daily Wildcat

Physics graduate student David Haycock explains a network of laser beams that hold atoms suspended and frozen. The device is the first step to making the atomic latticework needed to develop a quantum computer.

If a UA scientist's theories are correct, the next generation of computer technology could make microchips obsolete with lasers and rapidly changing patterns of atoms.

Poul Jessen, an assistant professor of optical sciences at the University of Arizona, believes that a "quantum computer" using hyper-cooled atoms suspended within lasers would be radically better at solving problems than conventional machines.

Jessen and his colleague, physicist Ivan Deutsch of the University of New Mexico, published their concept of a quantum computer last month in Physical Review Letters.

Computers currently use microscopic chips to store binary information, a series of zeros and ones that when strung together symbolize information.

A quantum computer would replace chips with a series of individual atoms trapped in a lattice of lasers like "eggs in an egg carton," Jessen said.

"Each atom is going to be a bit," he said. "They are going to play the role of individual transistors."

Every atom has a tiny magnetic charge - positive or negative - which would replicate the zeros and ones of a binary system in the new wave of technology, he said.

Jessen said quantum computing is "a whole new paradigm for what information is and how it is processed."

Because of the nature of quantum physics, which deals with concepts in the microscopic world, a quantum computer would be much faster than traditional technology.

In a normal binary system using transistors, a series of zeros and ones are placed in different combinations to produce a result. Each transistor has to switch from zero to one repeatedly to make all the different combinations required to come up with an answer - which takes time.

For most applications, a few seconds or minutes isn't a problem, but the duration required for intricate equations by physicists and other researchers can take prohibitively long.

Quantum physics allows a way beyond this limitation, postulating that an atom can be in two states at the same time.

Jessen's atomic "bits" can be positive and negative, representing zero and one, simultaneously. When each bit is able to be both zero and one at the same time, all possible combinations of bits can be created at once.

"This is the mystery of quantum mechanics. There is nothing in our common experience that permits that to happen. It's unique to the microscopic world," Jessen said.

A quantum computer with only 100 bits would be able to process two to the power of 100 - a thousand billion billion billion - different computations in the same instant.

Problems that would take billions of years to solve with traditional computers could be solved in a matter of seconds, Jessen said.

But don't expect to see quantum computers on your desktop anytime soon. Jessen stressed that the project is still in the theoretical stage. He estimates that quantum computers won't be practical until the middle of the next century.

The network of lasers that would hold the atoms has already been developed, however.

Physics graduate student David Haycock has helped Jessen create a laser network that suspends atoms in a vacuum chamber. The atoms are pushed by opposing laser beams from several directions so they are held suspended in the middle of the chamber, he said.

The lasers act to freeze the atoms in place, slowing their vibrations and cooling them down to a billionth of a degree Fahrenheit above absolute zero. At that temperature, the atoms are colder than liquid helium by the same amount that liquid helium is colder than the center of the sun.

"This is the coldest spot in Arizona," Jessen joked.

With the atoms motionless and frozen, they can theoretically be made to form a latticework - the fundamental building block of a quantum computer. Atoms can then be superimposed to create combinations of bits.

"We are working on the technology to allow us to do that," Haycock said.

Despite a number of theoretical and engineering hurdles, Jessen remains confident that his dream will be realized someday.

"I think, as a physicist, there is no basic fundamental law that says this cannot be done," he said "Still, it's going to be very hard."