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Secrets of Almaden 

An elegant experiment at a Bay Area lab echoes through the world of quantum physics

Wednesday, Apr 5 2000
One of the world's most advanced science laboratories lies nestled in the coastal hills a few miles south of San Jose. An English lord would be hard pressed to inherit a finer estate for his countryseat. The road into the lab traverses grassy meadows, squeezes through a high-tech security gate, and neatly curls into the parking lot of a turquoise building at IBM Corp.'s Almaden Research Center, which sits alone in its corporate majesty on 690 acres of IBM-owned wildlife preserve.

In the lobby, exhibits present IBM's corporate self-truths in low-key patter -- the first disk drive, invented in the 1950s, weighed 500 pounds. As the age of vacuum tube transistors gave way to the age of microchips and, now, atomic scale devices, IBM scientists remained on the cutting edge ... blah, blah, blah.

Locked within the walls of the securely situated Almaden lab are, no doubt, industrial secrets potentially worth billions of dollars: new inventions and bright ideas worth guarding, possibly even with human lives.

There are also discoveries worth revealing to the public at large, in a controlled, image-conscious way that allows IBM to appear competitive in the computer hardware markets without, of course, giving away trade secrets.

In February, one such secret of the Almaden lab was unveiled. A paper written by three IBM physicists, Donald M. Eigler, Christopher P. Lutz, and Hari C. Manoharan, was published as the cover story in Nature, one of Western science's most prestigious publications. The paper explained the discovery of what the physicists call a quantum mirage. Simultaneous with publication of the Nature story, IBM's public relations division issued press releases heralding the quantum mirage as a new way to transport information using electron waves, rather than solid metal wires. In some ways, the quantum mirage sounds like a miracle of science fiction come true: teleportation.

While the quantum mirage promises to make multiple contributions to computer technology, Eigler, the lead scientist on the project, insists that it is not a form of teleportation, which is the instantaneous transportation of matter across space. That engineering feat has yet to be accomplished.

But the quantum mirage is, according to physicists with no connection to IBM, a technical tour de force, an elegant piece of work. In the world of physics and mathematics, "elegance" is often used to describe a relatively simple solution to a complex problem. Einstein's famous summation of the unity of mass and energy -- E=MC2 -- is the epitome of elegance. Not to equate the importance of Eigler's work with Einstein's earth-shaking theories, but Eigler's peers say that producing the quantum mirage was simply that. Elegant.

Surrounded by racks of machines lining his closely packed laboratory, Eigler takes obvious pleasure in tackling the difficult task of translating the physics behind the quantum mirage into a language comprehensible to a layperson. A sign over the lab door reads: "Just get the data -- a modern philosopher." A kind of modest American seat-of-the-pants-backyard-inventor pragmatism is being deliberately projected into this small room by one of the richest and most powerful multinational corporations to ever thread a screw.

The temptation to take the cues and to reproduce the images that IBM dangles before the source-dependent journalist is hard to resist. It is not shameful, after all, to be overawed by the mostly inaccessible technicalities of modern physics. The normal-brained reporter can choose to reprint, or rephrase, the well-written press release from IBM about the quantum mirage (which is exactly what dozens of newspapers did do).

And there is no harm in that, because the press release is true. On the other hand, visiting Eigler in his lab provides a more potent dose of reality than the surface spin of a press release.

The quest for the quantum mirage began with a Volkswagen-sized tool called a scanning tunneling microscope, which Eigler and his colleagues use regularly to visit -- and manipulate -- atomic scale terrains. When drawn by computers, these minute landscapes resemble preternaturally ancient deserts stripped of life. Under Eigler's electronic looking glass, cobalt atoms rise like mountains from seas of electrons, which slosh about in the shape of probability waves made sluggish -- and therefore visible -- by temperatures pushed to 4 degrees above absolute zero.

For more than a decade, Eigler and his custom-built microscope have been at the epicenter of nanotechnology, that is, the building of molecule-sized devices measured in billionths of a meter, or "nanometers." In 1989, Eigler and his collaborators learned how to use the tip of his microscope to pick up individual atoms and move them. Ultimately, they were able to arrange single atoms into shapes. (Not surprisingly, the first shape they made spelled out "IBM.") Closed geometric shapes, such as circles and ellipses, became known as quantum corrals. "Quantum" because the tiny energies in play can only be described with the mathematical language of quantum mechanics; "corrals" because the geometric structures have walls made up of individual atoms that trap electrons inside like a gas. The electron gas is the medium through which waves -- electron waves -- can travel.

To construct a corral, says Eigler, "We blast a copper surface with argon atoms, until it's superclean and superthin -- about 30 to 40 atoms thick. Then we supercool the smooth metal sheet inside a vacuum chamber and drop a dust of cobalt atoms on top of it." Eigler and his labmates then use the microscope tip to form the loose cobalt atoms into a quantum corral.

One particularly useful shape for a corral is an ellipse, or slightly elongated circle. Since the beginning of the 19th century, scientists have known that elliptically shaped materials possess a peculiar property. Equidistant from the center of an ellipse are two points -- two focuses, or foci. These foci share a remarkable link.

Imagine that an elliptically shaped pan is filled with water. Drop a pebble at one of the foci. Waves of water will ripple out from the splash and bounce off the walls of the dish, thereby creating a wave pattern that repeatedly doubles back on itself. Due to the nature of the ellipse, the pattern of intersecting waves will soon look as if there were two spots where the pebble dropped -- two foci. This phenomenon occurs because the shape of an ellipse perfectly focuses bouncing waves at two points; it reproduces the physical appearance of the first focal point at the second one.

About The Author

Peter Byrne


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