September 27, 2010 Gauging High-Speed Spin Inside a Lilliputian World By JOHN MARKOFF NY Times
http://www.nytimes.com/2010/09/28/science/28atom.html?_r=1&ref=technology&pagewanted=print SAN FRANCISCO — I.B.M. scientists have modified a scanning-tunneling microscope, making it possible to observe dynamic processes inside individual atoms on a time scale one million times faster than has previously been possible. The researchers have perfected a measurement technique in which they use an extremely short voltage pulse to excite an individual atom and then follow with a lower voltage to read the atom’s magnetic state, or spin, shortly afterward. The resulting data produces the equivalent of a high-resolution, high-speed movie of the atom’s behavior. The advance, reported Thursday in the journal Science, has potential applications in fields including solar energy technology, computer data storage and quantum computing. The scanning-tunneling microscope was invented by I.B.M. researchers in 1981 in Switzerland. The systems are now in wide use, and make it possible to make images of individual atoms. While they have attained astounding spatial resolutions, however, they have been less precise in detailing physical processes that occur so quickly that their duration is measured in nanoseconds. A nanosecond — a billionth of a second — is to a second as one second is to 30 years, roughly. “This technique is really nice because it allows us to measure how things change in time,” said Michael Crommie, a physicist at the University of California, Berkeley. “Obviously people have been doing this with other techniques for many years, but it has proven hard to do at very small time scales.” The researchers said that the actual rate of change in the magnetic orientation of the atoms they were able to measure is several orders of magnitude faster than even the new technique. But they are able to slow down aspects of the process, which is described as “spin,” so that they are able to observe it at the nanosecond scale. Spin can be likened to the constantly changing orientation of an atomic-scale bar magnet, said Andreas J. Heinrich, a physicist at the I.B.M. Almaden Research Center in San Jose, Calif. “Before we had the scanning-tunneling microscope that allowed us to follow things down to the atomic scale,” he said, “but we did not have the ability to follow these fast processes. Now we can offer a combination of high time and spatial resolution; we’re trying to speed up nanoscience.” He said that one of the questions the researchers are trying to answer is how many atoms are required to store a single bit of magnetic information. The new technique will allow scientists to peer into a Lilliputian world where magnetic ones and zeros are read and written by modern digital computers. That ability should lead to a better understanding of the remarkably small structures that are at the heart of both magnetic and digital memory systems. It will also give them a tool for building a generation of computers based on quantum mechanical effects. While the basic unit of today’s digital computers is a bit — a one or a zero — researchers are now designing systems in which a quantum bit, or qubit, will be able to represent one and zero simultaneously. “With quantum computing the idea is to break out of the paradigm of normal computing, which uses ones and zeros to compute,” said Sebastian Loth, an I.B.M. scientist. “Quantum computing is interesting because it offers the ability to perform calculations that are not possible with any supercomputer that is around right now.” -- ======================================== George Antunes, Political Science Dept University of Houston; Houston, TX 77204 Voice: 713-743-3923 Fax: 713-743-3927 Mail: antunes at uh dot edu _______________________________________________ Medianews mailing list [email protected] http://lists.etskywarn.net/mailman/listinfo/medianews
