In this installment of Science Not Fiction’s Codex Futurius project, we pose the question:

I want to have a teleporter in my story. How would one work?

The good news is that a working teleportation device already exists. The bad news is that it won’t work for you if you happen to be bigger than a rubidium atom—but scientists are toiling away to fix that. As physicist Michio Kaku noted last year in DISCOVER, we could be teleporting things as big as a virus within a few decades, which means we would be ready teleport a person around the 23rd century, just in time for the predicted construction date of Captain Kirk’s Enterprise.

The key to teleportation is to realize that we don’t want to use it as some kind of “matter transporter.” The kind of everyday matter that makes up you, me, and the planet, is made up of protons, neutrons and electrons. Quantum physics tells us that every proton is identical to every other proton, every neutron is identical to every other neutron, and the same holds for electrons too. What’s important are not the particular particles that make up our bodies, but the way those particles are arranged into atoms, molecules, and cells. Duplicate the arrangement, and you duplicate the person.

The situation is analogous to what happens when a scene is captured by a TV camera and transmitted to a screen somewhere else. We’re not interested in somehow transporting the actual photons that entered the camera’s lens to the eyes of the viewer. Instead, the camera records the pattern the incoming light makes. Information that describes this pattern is transmitted to viewer’s screen, where a brand new set of photons are produced with the desired color and intensity. These convey the image of the scene to the eye. What’s important is preserving and transmitting the pattern of information, not the original photons.

The key to transmitting the information pattern of solid matter, as opposed to an two-dimensional image made of photons, is a spooky phenomenon known as quantum entanglement. It turns out that particles can be in a number of different states, and big part of the weirdness of quantum mechanics is that these states are undefined until they are somehow measured. Imagine tossing a coin and catching it. In the quantum world, not until you peek at the coin does it decide to be heads up or tails up! Entanglement means taking two particles and treating them together in such a way that their states become mingled. The states of the particles are still undefined until measured, but now making a measurement of one particle’s state will instantly determine the state of both particles, not just one. This holds true, even if you took one of the entangled particles and moved it to the other side of the solar system before performing the measurement.

Incidentally, Einstein loathed this idea, and it was one of the things that turned him away from quantum mechanics and towards a more-or-less dead end approach to physics in his later years. But thanks to a piece of quantum theory known as “Bell’s inequalities” along with entanglement experiments conducted in Paris in the 1980’s, Einstein was proved to be wrong.

Entanglement makes teleportation possible like this: first create an entangled pair of particles, say two atoms. We’ll call one atom “the pitcher,” and the other “the catcher” (This is not standard physics terminology). Now move the catcher to wherever you want to teleport to. This must be done very carefully to avoid destroying the entanglement. Now let’s take an atom that we want to teleport. This atom has a particular internal arrangement of electrons, neutron and protons that somehow makes it special to us—we’ll call it the Scotty atom. We put the Scotty atom into a chamber containing the pitcher atom. The states of the Scotty and pitcher atoms are combined and then measured. This combination process scrambles the state of the Scotty and pitcher atoms, putting them into random states.

So far, it looks like all you’ve done is put a perfectly good Scotty particle into a quantum shredder—the arrangement that made it special has been destroyed. But now you take the measurements of those scrambled random states and transmit them (in theory this could be done by radio, or any other method you can think of) to wherever the catcher atom is located. A regular, run-of-the-mill, atom is pushed into a chamber with the catcher atom. We’ll call this new, boring, atom the Tabula Rasa atom. The information about the random states that we measured after the Scotty and pitcher atoms were combined is also fed into the chamber. Presto—the Tabula Rasa atom takes on all the attributes of the Scotty atom. To all intents and purposes it is the Scotty atom.

Scientists are working on scaling up the process so that it works on larger and larger scales, hoping to move up from atoms to molecules, molecules to cells, and maybe one day, entire people. But the basic process is the same as for a single atom.

Note that in some ways the process is similar to what happens on Star Trek—teleporting someone requires disintegrating their body. There’s no way to teleport someone and leave their original body intact—the person can’t exist at the pitcher and catcher ends at the same time. Teleportation cannot be used to make copies of a person. In quantum mechanics this restriction is known as the “no cloning theorem.” In some ways however, teleportation is quite different to Star Trek—it requires quite a bit of preparation and equipment at both ends of the process—you can’t just appear on the surface of a planet you’ve never visited before.

But you could imagine this being used as a way to travel to distant solar systems—a robot probe with a supply of entangled particles could be sent out on the decades, or centuries long, journey required to travel between stars. Once it arrived at it destination, explorers would step into a teleportation chamber on Earth containing the entangled pairs of the particles sent with the probe. Their bodies would be destroyed, but information about them would be transmitted by radio at the speed of light to the probe. The probe would receive the information, and reconstitute the explorers. Of course, if anything happened to break the chain of transmission, or to disturb the entangled particles before the right time, the explorers would be killed. But if everything worked, to them it would feel like going from Earth to an alien world in the blink of an eye.

March 19th, 2009 Tags: quantum entanglement, Star Trek, Teleportation
by Stephen Cass in Codex Futurius, Physics, Transportation | 8 comments | RSS feed | Trackback >