Newswise — In physics textbooks, an atom is drawn as a tiny solar system with the nucleus uniformly orbited by electrons. It's a good illustration of a neat and predictable Newtonian world. But in the real world, atoms are a cloud of swirling electron motion around the nucleus. Any electron can be anywhere at any time and -- here's the strange thing -- at all places simultaneously. This is quantum mechanics in action. But it's also chaos.
Humans want and need a predictable, reliable world where the lights turn on with the flip of a switch and computers hum without a glitch. That's why Newton's physics is so appealing.
Now, science is one step closer to bringing order to that swirling cloud of electrons, and with that, obtaining a new perspective to quantum control of atoms, molecules, nano-devices and, dare it be said, quantum information storage and computing. Three University of Virginia physicists have made the textbook ideal of the classic solar-system atom a reality by manipulating an electron with a microwave.
The finding will be featured online Feb. 10, 2005, on Science Express, the rapid electronic publication forum of the journal Science (http://www.sciencexpress.org). The paper also will appear in a future print issue of the journal.
The scientists first "excited" the atom with lasers, causing the electron to swirl about more slowly and farther out from the nucleus, according to Haruka Maeda, a senior research scientist at U.Va. and the project's main investigator. Then they brought predictable order to the orbit with a "periodic force" from a microwave, This is the first time scientists have been able to manipulate electrons into a classical orbit for an extended period of time. Maeda said the classical orbit can be nearly infinitely maintained.
"In the classic model of the atom, the electron moves decisively along a specific orbit, so we know where it is at," Maeda said. "But in the real world of quantum mechanics, we don't know exactly where the electron is. But in this experiment we have been able to create the classic atom. We know where the electron is, and we can sustain and manipulate its orbit for a long duration of time."
U.Va. physicists Maeda, Don V.L. Norum and Thomas F. Gallagher were able to increase or decrease the speed of the orbits of the electrons by shortening or lengthening the wavelength of the microwave bombarding the atom.
"The electron oscillates smoothly back and forth along its classical trajectory eternally, obeying our manipulations through microwave frequency control," Maeda said. He noted that about 17 years ago pioneering experiments using short optical pulses had created quasi-classical atoms, but the state could be maintained for only several tens of picoseconds before disappearing. A picosecond — 1 x 10-12 seconds — is an infinitesimally short period of time.
"In this new experiment, we are able to synchronize the electron's oscillations with the microwave cycles, creating the well-controlled classic atom," Maeda said. "This manipulation and long-life control will possibly allow a chance to do some future applications with the atom."
Applications could include quantum information storage, for example, which has been demonstrated at the University of Michigan; and also quantum computing, which, while still a dream, could possibly be used for such highly complex tasks as transmission of unbreakable codes and bringing order to chaotic meteorological data.
Quantum computers would have capabilities far beyond the level of anything available today, but will require the engineering of incredibly tiny circuitry, measured in atom widths. Thus, atom manipulation and deeper insights into quantum-classical correspondence in the atom will be crucial.
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