Beam Me Up

Thursday, December 11, 1997

Scientists Report Primitive Step in Teleportation Physics: It won't be beaming up Capt. Kirk any time soon. But scientists say the breakthrough may lead to faster computers.
-- Article by K.C. COLE, Times Science Writer

Austrian researchers have taken a primitive first step toward creating a perfect copy of matter instantaneously over long distances. The feat, reported today in the journal Nature, involved replicating the exact properties of one light particle, or photon, in another three feet away.

This first experimental confirmation of so-called quantum teleportation is not likely to produce "Star Trek"-like transporter systems. But physicists do consider it an important confirmation of the "spooky" action-at-a-distance possible through quantum mechanics, the bizarre rules that govern the behavior of all subatomic articles.

"It's not going to lead to teleporting people," said Case Western Reserve University physicist Lawrence Krauss, who wrote "The Physics of Star Trek." "But it's one of those important first steps," perhaps toward a new technology enlisting quantum mechanics to make much faster computers.

Until a few years ago, physicists thought teleportation would be impossible, because merely measuring the properties of delicate atomic systems is enough to destroy them. And it's impossible to make a perfect copy of something that can't be precisely measured.

The only way for "Star Trek's" Scotty to "beam up" Capt. Kirk, in other words, was to scan the exact characteristics of all Kirk's atoms, then send that information instantaneously to another locale. But measuring Kirk's atoms would also distort them beyond recognition.

In 1993, however, IBM physicist Charles Bennet devised a scheme for using a third "object" to transmit information from one object to another without actually knowing the exact nature of the first object. But Bennet's contribution was theoretical--he did not actually achieve such a transmission.

Now, Viennese physicist Anton Zeilinger and his colleagues report that they were able to accomplish this feat with photons. Without measuring the properties of a first photon, they induced another photon three feet away to exactly replicate the first photon's polarization, or orientation of vibration.

"It's exciting that it's been realized in the laboratory," said Bennet. The achievement is possible because light particles--like other subatomic entities--can be linked to each other in a mysterious relationship known in physics jargon as "entanglement." In effect, it means the two particles mirror each other's behavior instantaneously through any distance in space, even though they are not in contact.

The team at the University of Innsbruck was able to entangle three light particles so that the polarization of the third matched that of the first.

Transporting people--or even bacteria--is not feasible because of the immense amount of information needed to replicate a living being. By the time Scotty beamed up Kirk, the universe would be dead and gone.

However, the fact that quantum information can be moved around and manipulated has enormous potential benefit for computing. That's because any quantum entity, like a light particle or an atom, can exist in an infinite number of overlapping states at once. Each of those states can be used like a miniature parallel computer to work on one aspect of a difficult problem, creating a massive cooperative network of sub-computers all working on the same problem.

Until now, the obstacle had been that the states of a particle couldn't be measured without being destroyed. The beauty of teleportation is that it acts on the information even if you don't know exactly what it is, said Caltech physicist John Preskill, who is also working on quantum computers. That makes it possible to "divide up a problem into pieces, and move a piece over here so another one of your quantum processors can work on it," he said. Beyond such practical aspects, however, "the concept of teleportation is really cool," Preskill said. "And this is the closest thing to an experimental realization of it so far."

Several critical fundamental differences make teleportation unlike everyday copying or faxing of documents. For one thing, the original is destroyed in teleportation. Indeed, the original can't even be scanned to extract information about it. Only the relationship between the original and some third entangled object can be extracted.

Bennet likens the situation to an FBI investigator who wants to interrogate a witness--call her Alice--about a crime, but doesn't want to ask her questions directly for fear of putting ideas into her head and distorting her memory. Instead, the agent calls on the FBI's in-house pair of "entangled" twins, Romulus and Remus. Romulus and Remus hate each other, and what one says is always the exact opposite of whatever his twin says. In this scenario, Alice contains the original information and Romulus gains the copy of that information. The FBI sends Remus to meet Alice--not to question her about the crime, but merely to find out whether she likes or hates him. Alice calls the FBI and says she hates Remus. The FBI then knows that even though she conveys no information about the crime, it can ask Romulus any question about the crime and get Alice's truthful answer. This is possible, says Bennet, because through the entanglement, Romulus is Remus' "predestined opposite." And much like the teleported properties of the photon, Romulus is now a copy of Alice, "even though he's never been anywhere near her," Bennet says.

If this all sounds unbelievable, it is. Even Einstein called communicating action at a distance "spooky," and Preskill calls teleportation "staggering" and "amazing." At heart, the experiment is a concrete demonstration of the magical richness of quantum reality. In the words of the 19th century physicist Michael Faraday, in nature, it seems, "nothing is too wonderful to be true."

* * *

Quantum Teleportation -- In the popular understanding of teleportation, an object or person disintegrates in one place and reappears unchanged somewhere else. No one is going to teleport a human any time soon, but scientists have announced a "first step" in teleportation in which a photon three feet away replicated a first photon's polorization exactly. Here is a fanciful interpretation of the process--based on the real quantum mechanics principles: Objects exhibiting "entanglement," whereby two particles mirror each other's behavior instantaneously through any distances in space. Other half of entangled pair exactly mirrors properties of the original, completing the teleporation. Original is exposed to one half of entangled pair. Original destroyed.

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