Molecular Computing

This is amazing, even to a non-geek, non-'puter guy.
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Scientists Shrink Computing to Molecular Level
By KENNETH CHANG, New York Times

Using a novel computing technique that resembles an elaborately staged billiards trick shot, I.B.M. scientists have created what they say is not only the world's smallest logic circuit, but also possibly the smallest that could ever be made.

The entire circuit covers less than a trillionth of a square inch. The equivalent circuit made from state-of-the-art silicon transistors takes up 260,000 times as much space.

"That gives you an idea for what incredible potential there is for miniaturization," said Dr. Andreas J. Heinrich, a physicist at I.B.M.'s Almaden Research Center in San Jose, Calif., and the lead author of a paper that appears today on the Web site of the journal Science.

Instead of using the transistors and wires of traditional electronics, the scientists stuck individual molecules of carbon monoxide onto a flat copper surface at specific locations. Then, using the tiny tip of one of their instruments as a cue stick, they knocked some of the molecules, setting off a cascade of collisions. The final positions of the molecules provided the answer of the calculation.

The technique is far from practical. The calculations are performed in a vacuum at ultralow temperatures, a few degrees above absolute zero. Setting up the molecules to perform the calculation and then reading out the answer are slow, laborious tasks. For each calculation, the molecules must be nudged to the correct starting positions.

Still, scientists marveled.

"The beauty of this experiment is opening our eyes," said Dr. Wolf-Dieter Schneider, a professor of physics at the University of Lausanne in Switzerland. "There might be new possibilities in computing. This is a totally different approach."

Dr. Donald M. Eigler, leader of the I.B.M. team, has performed a series of increasingly sophisticated molecular tricks using a scanning tunneling microscope, which produces images of an object by measuring the amount of current that flows between a very sharp metal tip and the object. It can even make out the shapes of individual atoms.

In 1989, Dr. Eigler and Dr. Erhard Schweizer, a colleague, nudged 35 atoms of xenon with the tip of a scanning tunneling microscope to spell "IBM." Two years later, Dr. Eigler made a switch whose only moving part was a single xenon atom hopping between a metal surface and a tunneling microscope tip. But the nonmoving parts of that switch — the microscope, in particular — were too large for any practical use.

The latest work shows that entire calculations can be performed at the molecular scale, a considerable advance in the field of nanotechnology. Nanotechnology derives its name from nanometer, a billionth of a meter, or about one 25-millionth of an inch, which is about the width of 10 hydrogen atoms placed side by side.

"Here we've got the whole show at the nanometer length scale," said Dr. Eigler. "It hints at what our future has in store for us."

Current silicon technology will hit fundamental physical barriers in the next decade or two. Most earlier efforts in the emerging field of molecular electronics have focused on finding ways to continue the miniaturization of transistors.

For I.B.M.'s molecular trick shot, the surface of a crystal of copper serves as the billiards table. Unlike billiard balls, the carbon monoxide molecules do not roll smoothly along the surface. The copper atoms, which are lined up in neat rows, form tiny hollows where the carbon monoxide molecules can settle, somewhat like tennis balls sitting in an egg carton.

The carbon monoxide molecules are considerably larger than the indentations, so two molecules in neighboring indentations push up against each other. When three molecules form a V-shape, pressure from the two outside molecules inevitably shove the center one to the next space over.

While colliding carbon monoxide molecules will never be a practical method of computing, there might be other ways of using such cascade calculations, the scientists said. One possibility might be a lattice of tiny magnets, with the flipping of one causing one or more of its neighbors to flip. The magnets could be easily reset by an external magnetic field.

"It's just a really interesting demonstration of how small you can get and still manipulate information," said Dr. James Heath, a professor of chemistry at the University of California at Los Angeles. "It's a beautiful piece of work. Don Eigler and his group work at the boundary between art and science."