Posted at 11:00 p.m. PDT Monday, April 27, 1998

Breakthrough made on new era of computing

Prototype quantum transistor offers huge potential

Mercury News Staff Writer

A team of researchers that includes scientists from IBM's Almaden Valley Research Center and the Bay Area's two top universities have turned molecules of chloroform into the world's first quantum computer.

The breakthrough uses a variation of medicine's magnetic resonance imaging to manipulate the core of the two elements in chloroform -- carbon and hydrogen. By doing so, the researchers were able to perform a simple database query at the molecular level.

A quantum computer has the advantage of being blindingly fast and could prove thousands or even millions of times faster than anything in use today. Any practical application is many years away, but theoretically the device or its descendants could be used for two important applications -- cryptography and complex database queries.

``This will reshape the face of science,'' said Stanley Williams, a Hewlett-Packard Co. physicist who is coordinating his company's quantum computing research in Palo Alto but was not part of the discovery team.

The development takes computing a step away from the stable, binary world of silicon with its ones and zeros, toward the bizarre world of quantum physics, where reality sometimes seems to defy logic. In the quantum world, a particle is neither a one nor a zero -- it's both.

The study of quantum physics over the last few decades has taught researchers the arcane rules of the subatomic road. Trying to describe these rules to the uninitiated, theorists inevitably use the word ``counter-intuitive'' -- one way of saying it just doesn't make sense.

For example, in our world, you can only be in one place at one time and particles are simply bits of matter.

But in the quantum world, elementary particles can be in every possible place at the same time.

Because a quantum computer does its figuring in the subatomic world, it could take a question and examine all possible answers -- the right ones and the wrong ones -- virtually at once. That explains the lightning speed.

``It is very exciting,'' said Isaac Chuang of IBM's Almaden Research Center in San Jose, who began his work at Stanford University. ``I think we are poised to do this kind of research in the valley because we have an excellent combination of multidisciplinary people, physicists and engineers.''

But, said Chuang, who was a member of the successful research team, ``I want to emphasize it is still basic research.''

Simple problem

The problem solved by the quantum computer -- finding a piece of data from four possible answers -- would be trivial for any modern computer. But the way the researchers' quantum computer did it was impossible by conventional computing.

A standard computer would analyze each of the four possibilities, one after the other, until it found the answer. On average, it would take the standard computer two and a quarter tries. The quantum computer analyzes all four possible answers with a single query.

``You can be in four places at the same time,'' Chuang said.

Two years ago, many researchers thought the latest accomplishment was impossible. The practical problem was maintaining the molecule in a coherent state long enough to do the computing.

``The trick of making a quantum computer is being able to understand these strange rules of physics and being able to map your problem onto these strange rules,'' said Chuang.

Chuang and Neal Gershenfeld, a physicist at the Massachusetts Institute of Technology, developed a way to do this, working with researchers at MIT, Oxford University, the University of California at Berkeley and Stanford.

The nuclear spin

The researchers used nuclear magnetic resonance techniques to study the structure of the molecule and control the orientation of its nucleus before manipulating it with a radio wave. ``We represent a zero and one by the state of a nucleus, the nuclear spin,'' said Chuang. ``Is the spin pointing up or is it pointing down?''

The spin can also be halfway between zero and one, an impossibility in conventional computers and a fact which gives quantum computing so much more potential power.

Nuclear magnetic resonance techniques also overcame the fundamental stumbling block of how to read information into and out of a quantum computer.

According to ordinary quantum rules, observation tends to alter the outcome of a quantum event. But by using magnetic resonance techniques to observe observe vast numbers of molecules at once, the effect of quantum measurements are canceled.

Chloroform was used because it is one of the simplest organic molecules and is highly stable, said Mark Kubenic, a UC-Berkeley chemist and staff scientist who worked on the project. It has a carbon atom in the middle and three chlorine atoms and one hydrogen atom attached to it.

`Organic molecules are easy to make, and we're looking down the future for making these molecules, for mass production,'' said Kubenic. There is also a voluminous literature on synthesizing organic molecules, he said, ``so if we want to design a molecule for a computing task, organic molecules are ideally suited for building a quantum computer.''

James Harris, a Stanford professor of electrical engineering, compared the successful experiment with another group's effort. ``The beauty of (ours) is it is done at room temperature with commercially available equipment,'' Harris said. The other approach involves cooling the quantum computing device to extremely low temperatures.

Harris said he thinks a quantum computer would be useful for running exhaustive searches of databases and for finding prime numbers, which are used in code-breaking.

In search of more powerful tools for code breaking or searching large databases, large computer companies such as IBM and Hewlett-Packard are already assembling teams of researchers in an effort to work on a generation of quantum computing systems which may come into their own sometime in the second decade of the next century.

One practical application might be to speed the hunt for a single word hidden all the data stored in the Internet's World Wide Web.

Not long ago IBM researchers took a snapshot of the entire web, more than eight trillion bytes of data. Searching for the word using a conventional computer would take a full month, Chuang said. However using a simple quantum computer would reduce the search time to 27 minutes.

The New York Times contributed to this report.