By Roland Piquepaille
It's an antenna, it's a nanomachine, and it's a macroscopic quantum system. This antenna, made of 50 billion atoms, is so far the largest structure to display quantum mechanical movements. It's also the fastest device of its kind in the world, oscillating about 1.5 billion times per second. Such technology might soon be used in our cell phones. But more importantly, this nanomechanical device bridges classic and quantum physics. Such "mechanical/quantum mechanical hybrids could be used for quantum computing" in the future. Read more...Here is the introduction from this Boston University news release.
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.
Please note that this is the second appearance of Mohanty's team in this space. I already mentioned their works back in October 2004 in "Nanomechanical Memory Outstrips Chip Technology."
Now, let's look at some -- impressive -- numbers.
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, 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.
The above image shows different views of this nanomechanical structure. The center, (a), is a scanning electron micrograph of the suspended antenna oscillator. The nanomechanical antenna consists of a central silicon beam, 10.7 microns long and 400 nm wide, that bears a "paddle" array 500 nm long and 200 nm wide along each side. In (b), you can see a modal simulation of the antenna structure, showing the low frequency fundamental resonance mode. And in the high order collective mode (c), the paddles vibrate at their own natural frequency. (Credit: Pritiraj Mohanty, Boston University)
The research work has been published in a recent issue of Physical Review Letters on January 25, 2005 under the name "Evidence for Quantized Displacement in Macroscopic Nanomechanical Oscillators." Here is a link to the abstract.
We report the observation of discrete displacement of nanomechanical oscillators with gigahertz-range resonance frequencies at millikelvin temperatures. The oscillators are nanomachined single-crystal structures of silicon, designed to provide two distinct sets of coupled elements with very low and very high frequencies. With this novel design, femtometer-level displacement of the frequency-determining element is amplified into collective motion of the entire micron-sized structure. The observed discrete response possibly results from energy quantization at the onset of the quantum regime in these macroscopic nanomechanical oscillators.
And here is a link to the full article (PDF format, 4 pages, 955 KB). The above illustration comes from this article.
Finally, for explanations written in -- almost -- plain English, you might read the news release quoted above.
Sources: Boston University, via EurekAlert!, February 9, 2005; and various websites
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