While not actually teleporting matter from place to place as in Star Trek, physicists have now plucked a quantum property from one atom and transmitted it to another. That feat of quantum teleportation, reported independently by teams in Austria and the United States in the June 17 Nature, moves scientists nearer to building a class of so-called quantum computers that’s expected to be astonishingly speedy at certain tasks, such as scouring databases for specific information.
The new achievements “represent a magnificent confluence of experimental advances,” H. Jeff Kimble of the California Institute of Technology in Pasadena, Calif., and Steven J. van Enk of Bell Labs’ Lucent Technologies in Murray Hill, N.J., say in a commentary in the same issue.
Starting in the early 1980s, physicists have realized that aspects of quantum mechanics—the physics of minuscule specks of matter and energy such as atoms and photons—could be exploited to greatly improve some types of computing and communications.
In particular, researchers have been devising ways to use an individual charged atom, or ion, as a quantum bit of information. Differing from the bit that represents either 1 or 0 in a conventional computer, the qubit can simultaneously represent multiple numbers.
Moreover, qubits can be entangled, meaning that they can maintain a correlation between their quantum states—for instance, the energy levels of particular electrons—across even vast reaches of space (SN: 3/27/04, p. 206: Available to subscribers at http://www.sciencenews.org/articles/20040327/note16.asp). Scientists expect entanglement to open a route to shuttling information among quantum computer components (SN: 4/3/99, p. 220).
In the new experiments, groups at the University of Innsbruck and the National Institute of Standards and Technology (NIST) in Boulder, Colo., used electric fields at near–absolute zero temperatures to suspend three ions in a line. The Innsbruck team, led by Rainer Blatt, used calcium ions; the NIST researchers, led by David J. Wineland, worked with beryllium ions.
By means of a choreographed sequence of laser pulses, the scientists in each group set the stage for teleportation by tweaking one of the three ions so that it would have a particular quantum state and by entangling the second and third ions. With additional laser pulses, both groups showed that they could transfer the laser-dictated quantum state, by way of the entangled pair, from the first ion to the third.
In the Innsbruck work, the scientists focused their lasers so tightly that they could carry out operations on individual ions as the particles floated about 5 micrometers apart. In the NIST experiment, the researchers made only certain ions targets for the laser by nudging them apart or together with selectively energized gold electrodes.
Several years ago, other research teams demonstrated quantum teleportation using various quantum entities: photons, light beams, and multitudes of atoms within molecules of a liquid (SN: 1/17/98, p. 41).
The new teleportation achievements are “very different than what’s been shown so far,” Blatt says. For one thing, teleportation between individual ions opens the way to systems containing more ions, which would be a step toward practical quantum computers. Also, in past work, those quantum transfers took place only when certain random processes, such as photons arriving simultaneously at a detector, happened to occur. By contrast, the Innsbruck and NIST teams can produce teleportation on demand. “This is push-button teleportation,” Blatt says. Still, Wineland notes, even the simplest, useful quantum computers remain at least a decade away.
In principle, Blatt conjectures, similar teleportation procedures in the more distant future could lead to moving all the defining properties of a complex object, say a virus, from that object’s original atoms to a new pile of atoms. This might fulfill the Star Trek vision in a down-to-Earth way.
06/19/2004 Peter Weiss, sciencenews.org