Facts So Romantic

The Trouble With Teleportation

One of my favorite scenes in the film Galaxy Quest—a satirical love letter to Star Trek and its rabid fans—is when Jason, an actor on a fictional TV series within the movie, ends up stranded on a real alien planet facing off against a monstrous “pig lizard.” His crew, back on board the ship, can only save him by using the “digital conveyer”—although it has not yet been tested (successfully, that is). Before attempting to beam Jason aboard, they decide to first try the conveyor on something else, which doesn’t go so well for the pig lizard:

What went wrong? Chalk it up to the intricacies of quantum physics.

Whenever the geekerati gather, a popular topic of discussion centers on people’s preferred choice of superpower. Would you want to walk through walls? Have X-ray vision or super strength? Do you hanker for a bit of telepathy? For me, there has never been any question: I’d opt for teleportation. The prospect of dispensing with traffic jams, airport security lines, and jostling crowds in favor of instantly being transported to the destination of choice is thrilling.

Teleportation typically involves dematerializing an object at one point and sending the details of its precise atomic configuration to another location, where that information can then be used to construct an exact replica. In one sense, we teleport information at the macroscale using classical mechanics all the time—think your average fax machine. Alas, things get a bit more complicated once we get down to the quantum level.

For a long time, physicists assumed quantum teleportation wasn’t possible. In order to teleport an object, like our pig lizard, we must scan it to obtain precise information about its atomic structure. However, the more accurately an object is scanned, the more it is disturbed by the process of being scanned. We can’t measure a particle without altering it in some way, never mind every single subatomic particle that makes up a full-sized pig lizard. So how could we extract all the information we would need to create an exact copy in another location via teleportation?

In 1993, an IBM physicist named Charles Bennett and his colleagues figured out a way to work around this fundamental limitation using quantum entanglement, a strange connection between particles that even Einstein called “spooky.” Their method involves three particles: the particle to be teleported (A) and an entangled pair of other particles (B and C). First, B and C are entangled and sent to separate locations. B then interacts with A, and A’s information is transferred to B. Since B is still entangled with C, any information transferred to B is also transferred automatically to C without any need to transmit that information across physical space-time. C essentially turns into A, in the new location.

Ah, but there is a catch: The original object must be destroyed in the process. When B scans A, that interaction alters the latter’s properties. A no longer exists in the exact same state as it did. C is now the only particle in that original state. I’ll let Sheldon Cooper of The Big Bang Theory explain:

In 1997, Austrian physicists “teleported” a single photon (technically, information about that photon) across a tabletop, recreating an exact copy on the other side. By 2003, the technique had been sufficiently developed that scientists at the University of Geneva in Switzerland managed to teleport photons 1.2 miles through fiber optic cable. (The current distance record, set last year, is 89 miles.) Last month Danish physicists successfully teleported information between two clouds of gas atoms via laser light.

This is great for things like quantum cryptography, the use of entangled photons as a secure method of communication between two distant parties. Not only is there no solid copy of the “messages” being transmitted, and thus no chance of them being intercepted, but if someone tries to eavesdrop on the data stream, it alters the photons’ quantum states, alerting the two parties that their communication channel has been compromised

In 2001, researchers in Denmark succeeded in entangling a pair of gas clouds containing about a trillion atoms each, separated by a few millimeters. This is tricky because any entanglement only lasts as long as nothing else interacts with the system. If there is even the slightest interaction—one collision with a single nitrogen molecule in the air, for example—the system “decoheres” and the entanglement is lost. That’s why quantum teleportation systems must take great pains to isolate their entangled pairs.

Here’s the reality check: the average human body contains roughly 1028 atoms, or more than a trillion trillion. It takes a great deal of effort to keep two particles entangled. It is extremely difficult to get more than a few atoms to vibrate together, perfectly synchronized, because of interference. In the real world, objects interact constantly with the environment, and decoherence occurs instantaneously. If I tried to teleport information about every single atom in my body via quantum entanglement, decoherence would scramble things in an instant. I’d be lucky to fare as well as the pig lizard.

And that’s why my dream of teleporting to Paris for fresh croissants each morning will probably never come true.


Jennifer Ouellette is a science writer and the author of The Calculus Diaries and the forthcoming Me, Myself and Why: Searching for the Science of Self. Follow her on Twitter @JenLucPiquant.


Most Recent Entries

See All

Current Issue

See Full Issue

SP_Nature_THUMB
14 Comments - Join the Discussion