June 17, 2004
Scientists Teleport Not Kirk, but an Atom
By KENNETH CHANG
nd the beryllium atom said to the Starship Enterprise, beam me up!
Two teams of scientists report today that for the first time they have teleported individual atoms, taking characteristics of one atom and imprinting them on a second.
In physics, teleportation means creating a replica of an object, or at least some aspect of it, at some distance from the original. The act of teleporting always destroys the original - not entirely unlike the transporters of the "Star Trek" television shows and movies - so it is impossible produce multiple copies.
The prospect of using teleportation to move large objects or people remains far beyond the current realm of possibility. But it could prove an important component of so-called quantum computers. Scientists hope that one day such computers will tap quantum mechanics to solve complex problems quickly by calculating many different possible answers at once; computers today must calculate each possibility separately.
The two teams, one at the National Institute of Standards and Technology in Boulder, Colo., and one at the University of Innsbruck in Austria, worked independently, but the experiments were similar, using a process proposed by Dr. Charles H. Bennett, a scientist at I.B.M., and others in 1993.
"This will be an important part of attempts to build quantum computers," said Dr. H. Jeff Kimble, a professor of physics at the California Institute of Technology. He co-wrote a commentary accompanying the two research papers on the experiments, which appear today in the journal Nature.
"This is a complicated thing that begins to work," Dr. Kimble said. "We've reached this point on our journey and it's really quite significant."
Several scientific groups, including one led by Dr. Kimble, previously teleported photons, and scientists at the University of Aarhus in Denmark reported in 2001 that they had teleported the magnetic field produced by clouds of atoms.
In the new experiments, both teams of scientists worked with triplets of charged atoms trapped in magnetic fields. The Colorado team used beryllium; the Innsbruck researchers used calcium.
The feat of teleportation is transferring information from atom A to atom C without the two meeting. The third atom, B, is an intermediary.
The three atoms can be thought of as boxes that can contain a 1 or a zero, a bit of information like that used by a conventional computer chip. The promise of quantum computers is that both a zero and a 1 can exist at once, just like the perplexing premise described by the Austrian physicist Erwin Schrödinger in which a cat in a box can be simultaneously alive and dead until someone looks inside.
First, atoms B and C were brought together, making them "entangled" and creating an invisible link between the two atoms no matter how far apart they were. Atom C was moved away. Next, A and B were similarly entangled.
Then the scientists measured the energy states of A and B, essentially opening the boxes to see whether each contained a 1 or a zero. Because B had been entangled with C, opening A and B created an instant change in atom C, what Albert Einstein called "spooky action at a distance," and this, in essence, set a combination lock on atom C, with the data in A and B serving as the combination.
For the final step, the combination was sent and a pulse of laser light was applied to atom C, almost magically turning it into a replica of the original A. Atom A was teleported to atom C.
"It's a way of transferring the information," Dr. Rainer Blatt, leader of the Innsbruck team, said.
A quantum computer could use teleportation to move the results of calculations from one part of the computer to another. "Teleportation in principle could be done pretty quick," said Dr. David J. Wineland, head of the Colorado team, noting that directly moving atoms containing intermediate results would almost certainly be too slow.
In the current experiments, the teleportation distances were a fraction of a millimeter, but in principle, the atoms could be teleported over much longer distances. The teleportation was also not perfect, succeeding about three-quarters of the time.
"We're not doing very well yet," Dr. Wineland said. "All of these operations have to be improved."
Teleporting a much larger object, like a person, appears unlikely, if not entirely impossible, because too much information would have to be captured and transmitted.
"It's certainly not useful for any beaming in the 'Star Trek' sense," Dr. Blatt of the University of Innsbruck said. "Consider even some molecules or something small like a virus. I cannot imagine it. As far as I can see, it's not going to happen."