Quantum teleportation

“Beam me up, Scotty, there’s no intelligent life here!” How often have you wished you could escape unpleasant situations just by flipping open a communicator and asking to be instantaneously whisked away? (Using your cell phone to have yourself paged doesn’t count.) Well, teleportation of human beings–causing them to vanish in one location and instantaneously appear in another, a la Star Trek–may still be a pipe dream, but teleportation itself is not: it’s been achieved.

A team at the Institute for Experimental Physics in Innsbruck, Austria, has succeeded in transferring the properties of a photon–a single particle of light–to another photon, instantly and without any connection between the two. In their ground-breaking experiment, the first photon disappeared and an exact duplicate appeared three metres away.

To understand how, you need to understand a couple of basic principles.

First, quantum mechanics states that elementary particles such as photons don’t have precise properties until they are measured–before that, they exist solely as a set of probabilities. Second, something called the Heisenberg uncertainty principle prevents you from ever measuring the state of an elementary particle with precision: the very act of measuring it disturbs it. The more accurately you measure it, the more disturbed it becomes; before you achieve complete accuracy, you’ve disrupted the particle.

Since teleportation involves making an exact, particle-by-particle replica of an object, and you can’t measure particles that precisely due to the uncertainty principle, teleportation was long assumed to be impossible. But a couple of years ago six scientists figured out how to get around the uncertainty principle.

The method they came up with, and which the Austrian group used, uses an aspect of quantum mechanics so bizarre Einstein refused to believe it was real, even though he first discussed it in a 1930 paper cowritten by Boris Podolsky and Nathan Rosen. Certain pairs of particles have a mysterious linkage called the “Einstein-Podolsky-Rosen (EPR) correlation,” or “entanglement.” Measuring one particle of an entangled pair instantaneously determines the state of the other particle of the pair.

It doesn’t matter if the particles are three metres apart, three kilometres apart, three light years apart or at the opposite ends of the universe. Einstein rejected this as “spooky action at a distance,” but it was confirmed in a dramatic experiment just last May. Physicist Nicolas Gisin and colleagues at the University of Geneva sent two entangled photons along fiber optic cables to opposite sides of the city, 11 kilometres apart. Each was then fed into a detector–and their states were found to still be linked. Gisin said it was as if he had flipped a coin at one end of the city, and his colleague had flipped one at the other end, and each time Gisin grabbed his coin out of the air and saw it was heads up, his colleague’s coin simultaneously stopped spinning and also landed heads up–thousands of times in a row.

This entanglement is the key to quantum teleportation. Here’s how it works: two photons (B and C) are entangled, then separated. B is sent to a scanning station along with the particle that is to be transported (A). C is sent to the receiving station. A and B are scanned together, which disrupts them. The information gleaned from that scan, although incomplete, is sent to the receiving station and used to alter C, which becomes an exact replica of A. The information that the scan of A could not reveal was provided by the entanglement of B and C.

Zeilinger says teleportation could lead to revolutionary advances in computing, producing machines able to process information faster than the speed of light and providing an absolutely secure way to send and receive information. He figures we’ll be able to teleport entire atoms within a few years, and small molecules within 10 or 20.

But humans won’t be beaming from place to place any time soon, even if this breakthrough makes it theoretically possible. The biggest problem is the sheer amount of information involved. One scientist estimates that the information necessary to reconstruct a human being on the atomic level would fill enough CD-ROMS to pack a cube a thousand kilometres on a side and would take longer than the age of the universe to transmit.

But if quantum teleportation does give us computers almost infinitely faster than those we have now, maybe our ancestors really will be able to “beam” from place to place.

Einstein might not approve–but Captain James T. Kirk most definitely would.

Permanent link to this article: https://edwardwillett.com/1998/01/quantum-teleportation/

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Easy AdSense Pro by Unreal