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- In what represents another step toward a new age in computing,
IBM researchers have demonstrated an effect that could be used to transmit
information within electronic circuits too small to accommodate wires.
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- Research into the phenomenon, known as a quantum mirage,
fits into a decades-long drive toward smaller and smaller computing devices.
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- The push toward smaller circuitry is a key factor behind
the steady doubling and redoubling of computational power. But scientists
say that traditional silicon-based chip technology is approaching its theoretical
limit, which is fueling the search for new nanometer-scale technologies.
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- IBM researcher Donald Eigler estimates that the push
toward miniaturization is nearing the 100-nanometer mark - that is, circuitry
at a scale of 100 billionths of a meter, or the width of 500 atoms. "By
the time you get down to 10 nanometers or so, there may be circumstances
where you would begin to look for alternatives to the way you do things,"
he said.
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- The research conducted by Eigler and his colleagues at
IBM's Almaden Research Center may open the way toward some of those alternatives.
The latest work on quantum mirages, published in Thursday s issue of the
journal Nature, hints at a fundamentally new way to transport information
through a solid, Eigler said.
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- The researchers were able to manipulate individual cobalt
atoms so that electron waves introduced at one point were focused and mirrored
at another point all within a quantum corral about 20 nanometers wide.
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- In the future, Eigler said, the trick may enable the
creation of nanometer-size circuits with characteristic dimensions that
might be 10 to 100 atoms across.
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- HOW IT WORKS
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- The corral was an ellipse made up of several dozen cobalt
atoms, positioned on a copper surface. Those atoms served as a reflector
for the copper s surface electrons, creating a wave pattern like ripples
in an elliptical pool. Using a scanning tunneling microscope, the researchers
placed a magnetic cobalt atom at a focus of the ellipse and that disrupted
the wave pattern in a characteristic way.
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- Here's the extra twist: The electronic signature of the
disruption showed up not only where the cobalt atom was placed, but also
at the other focus of the ellipse the effect of a ghostly atom that wasn
t really there.
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- IBM researcher Donald Eigler calls himself a "quantum
mechanic."
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- The phenomenon could be compared to one of those specially
built rooms that can reflect a whisper from one spot so it could be heard
clearly at another spot (IBM cited the example of Statuary Hall at the
U.S. Capitol), or a mirrored elliptical room that can create trick lighting
effects. But in this case, the quantum corral focuses electron waves rather
than sound waves or light waves.
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- Researchers noted that the electronic mirage had about
a third the intensity of the effect around the real atom.
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- WHAT IT MEANS
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- The quantum mirage technique permits us to do some very
interesting scientific experiments, such as remotely probing atoms and
molecules, studying the origins of magnetism at the atomic level, and ultimately
manipulating individual electron or nuclear spins, Hari Manoharan, a colleague
of Eigler s and the study s lead author, said in a written statement.
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- But we must make significant improvements before this
method becomes useful in actual circuits. Making each ellipse ... is currently
impractically slow, Manoharan cautioned
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- Eigler agreed that quantum corrals won t replace printed
circuits anytime soon: We have a very long way to go from the demonstration
of a principle to a product we can ship, and it s by no means clear that
we can include it in our future products, he said. But he said faster
techniques for making nanoscale circuitry could be developed as the years
go by.
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- "I don t think it s that tough a trick, he said
half-jokingly. If I can do it, how tough can it be?
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- He cautioned that the quantum mirage effect isn t directly
related to quantum computing, which seeks to harness the properties of
ions or subatomic particles to solve particular classes of intractable
problems. But the effect could be used to transfer data within a quantum
computer, he said. Eigler said he found it truly exciting to put the
often-abstract field of quantum mechanics to use in real mechanisms, paving
the way for future nanotechnicians.
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- We re quantum mechanics, he quipped. We re engineers
in the sense of designing electron states. ... We actively engineer these
systems to do what we want them to do. .
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