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Boston University's World's Fastest Moving Nanostructure

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  • RemyC
    From: http://www.physorg.com/news2996.html Nanomechanical device bridges classic and quantum physics February 09, 2005 Nanotechnology leapt into the realm of
    Message 1 of 1 , Feb 13, 2005

      Nanomechanical device bridges classic and quantum physics

      February 09, 2005

      Nanotechnology leapt into the realm of quantum mechanics this past winter
      when an antenna-like sliver of silicon one-tenth the width of a human hair
      oscillated in a lab in a Boston University basement. With two sets of
      protrusions, much like the teeth from a two-sided comb or the paddles from a
      rowing shell, the antenna not only exhibits the first quantum nanomechanical
      motion but is also the world's fastest moving nanostructure.

      A team of Boston University physicists led by Assistant Professor Pritiraj
      Mohanty developed the nanomechanical oscillator. Operating at gigahertz
      speeds, the technology could help further miniaturize wireless communication
      devices like cell phones, which exchange information at gigahertz
      frequencies. But, more important to the researchers, the oscillator lies at
      the cusp of classic physics, what people experience everyday, and quantum
      physics, the behavior of the molecular world.

      Comprised of 50 billion atoms, the antenna built by Mohanty's team is so far
      the largest structure to display quantum mechanical movements.

      "It's a truly macroscopic quantum system," says Alexei Gaidarzhy, the paper's
      lead author and a graduate student in the BU College of Engineering's
      Department of Aerospace and Mechanical Engineering. The device is also the
      fastest of its kind, oscillating at 1.49 gigahertz, or 1.49 billion times a
      second, breaking the previous record of 1.02 gigahertz achieved by a
      nanomachine produced by another group.

      According to Gaidarzhy, during the past several decades engineers have made
      phenomenal advances in information technology by shrinking electronic
      circuitry and devices to fit onto semiconductor chips. Shrinking electronic
      or mechanical systems further, he says, will inevitably require new
      paradigms involving quantum theory. For example, these mechanical/quantum
      mechanical hybrids could be used for quantum computing.

      Because Mohanty's nanomechanical oscillator is "large," the research team
      was able to attach electrical wiring to its surface in order to monitor tiny
      discrete quantum motion, behavior that exists in the realm of atoms and

      At a certain frequency, the paddles begin to vibrate in concert, causing the
      central beam to move at that same high frequency, but at an increased and
      easily measured amplitude. Where each paddle moves only about a femtometer,
      roughly the diameter of an atom's nucleus, the antenna moves over a distance
      of one-tenth of a picometer, a tiny distance that still translates to a
      100-fold increase in amplitude.

      When fabricating and testing the nanomechanical device, the researchers
      placed the entire apparatus, including the cryostat and monitoring devices,
      in a state-of-the-art, copper-walled, copper-floored room. This set-up
      shielded the experiment from unwanted vibration noise and electromagnetic
      radiation that could generate from outside electrical devices, such as cell
      phone signals, or even the movement of subway trains outside the building.

      Even with these precautions, performing such novel experiments is tricky.
      "When it's a new phenomenon, it's best not to be guided by expectations
      based on conventional wisdom," says Gaidarzhy. "The philosophy here is to
      let the data speak for itself."

      The group carries out the experiments under extremely cold conditions, at a
      temperature of 110 millikelvin, which is only a tenth of a degree above the
      absolute zero. When cooled to such a low temperature, the nanomechanical
      oscillator starts to jump between two discrete positions without occupying
      the physical space in between, a telltale sign of quantum behavior.

      In addition to Gaidarzhy, Mohanty's team consists of Guiti Zolfagharkhani, a
      graduate student, and Robert L. Badzey, a post-doctoral fellow in BU's
      Physics Department. Their paper appears in the January 28, 2005 issue of
      Physical Review Letters. The research was supported by grants from the
      National Science Foundation, U.S. Department of Defense, the American
      Chemical Society's Petroleum Research Fund, and the Sloan Foundation.

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