During the years, we have watched Captains Kirk, Picard, and others in the Star Trek universe step onto a transporter platform, fade into shimmering motes of light, then instantaneously reappear on the surface of an unexplored planet. This is teleportation, surely the coolest possible way to travel through space – no need to squirm into a spacesuit or navigate a spaceship; just step up and away you go!
Except that in the real world, away nobody goes, because teleportation has just been pure fantasy. Long before the term was invented in 1931, instantaneous or at least extremely rapid travel was a magical favorite. In European folklore, seven-league boots enable their wearer to cover that much ground, 21 miles or nearly 35 kilometers, per step. In the tale of Aladdin and the lamp, a jinn instantly transports himself and an entire palace from China to Morocco. Likewise, Siegfried in Wagner’s Ring cycle travels long distances in an eye-blink via the Tarnhelm, a magical helmet.
However, in dozens of science-fiction scenarios, not just Star Trek, people are dematerialized, beamed elsewhere, and reassembled not by magic but by technology. Still, there is the danger that the pattern representing you might become distorted as it is transmitted, or worse yet, become confused with someone or something else. That is the awful fate of the researcher in the film The Fly (1958, with Vincent Price; 1986, with Jeff Goldblum), who has the bad luck to start teleporting just as a random fly buzzes into the chamber. What emerges is a repulsive combination that neither a human Mom nor a mother fly could love.
Though we do not yet need to worry about this grisly outcome, astonishingly teleportation is now known to truly work at least at the level of elementary particles. It arises from the strange but real quantum effect of “entanglement,” in which two submicroscopic particles emerging from a process at the same time remain forever linked thereafter, no matter how widely separated. That is, measuring the properties of one immediately determines the state of the other as if they are somehow communicating by some unknown means, even if many kilometers apart.
To see where the weirdness enters, think of two electrons, A and B. Electrons behave like tiny bar magnets and two of them can be correlated to have net zero magnetic field so that whatever direction the North pole of A points, B points oppositely, cancelling it out. So far, so good; but according to entanglement if you measure the North pole of A as pointing straight up, electron B, no matter how far away, responds by pointing its North pole down; and if you measure A as pointing down, B would be found pointing up. For a simple analogy, imagine pairs of socks correlated to always have the same color; then entanglement predicts that if you randomly pick a sock from a pile of black and white ones, a second sock randomly chosen from a different pile always matches the original color. But how does the second sock “know” the color of the first sock? How does electron B know, and respond to, the state of electron A?
No one understands what lies behind this apparent violation of ordinary space and time. It deeply troubled Einstein, who called it “spooky action at a distance”; but it is absolutely confirmed by experiments using pairs of photons, atoms, and electrons separated by up to dozens of kilometers. Equally perplexing, measurements show that any communication between the two members of the pair travel at multiples of the speed of light and maybe even instantaneously. This would upset Einstein as well, because his theory of relativity establishes that nothing can go faster than light.
Nevertheless, in 1993, physicist Charles Bennett at IBM and his colleagues embraced the weirdness to theorize that entanglement could enable what they aptly called “teleportation” as a “term from science fiction meaning to make a person or object disappear while an exact replica appears somewhere else.” Instead of electrons, they considered photons, the quantum particles of light. These carry electric fields that can be pointed in specific directions, or “polarized,” and polarized photons can be made in correlated pairs. Bennett’s group showed that the link between entangled A and B photons could transmit the polarization of a third “X” photon located near A to a distant B photon, turning it into a perfect copy of X, which itself disappears in the process – the very definition of teleportation.
A photon was actually teleported for the first time in 1997, followed by other experiments that confirm the process for pairs of photons and also of atoms separated by several kilometers. Now the mysteries of entanglement and teleportation contribute to technology. They can be used to send photons through optical fiber telecommunications lines to represent digital data in an absolutely unbreakable code. This ability is already being used to securely transfer financial information. You might soon encounter teleportation technology that guarantees the security of messages from your smartphone to your bank or your Facebook friends. Down the road, researchers foresee powerful new computers based on these quantum principles.
Still, these applications are only microscopic versions of beaming Captain Picard through space. We may never be able to teleport people or big objects because it is theoretically impossible to transmit the necessary huge mass of information without distortion. The last thing anyone wants is hi-tech quantum teleportation that reproduces the hybrid horror of The Fly; but then, if banks were to teleport photons to protect their customer’s financial data, you might be lucky enough to have your account mistakenly merged with that of some random billionaire.
Sidney Perkowitz is the Candler Professor of Physics at Emory University. Readers can learn more about teleportation in his latest book Slow Light: Invisibility, Teleportation, and Other Mysteries of Light. He can be reached at http://sidneyperkowitz.net.
