Teleportation - the instantaneous transportation of an object (like Captain Kirk in Star Trek) across space - may seem to be solely the stuff of science fiction. However, at the quantum level, the dream has already become a reality.

Experiments in Austria and Italy pioneered "teleported" information about photon polarization (not the photon itself) from a sender to a receiver using the trick of "entanglement" - a deep quantum mechanical connection between particles that was first pointed out by Einstein, Podolsky and Rosen.

For example, with two entangled photons (A and B), determining the polarization of one of them (say, 0°) automatically defines the polarization of the other _ the second photon must "collapse" into the complementary state (90°). Therefore to teleport the information "45° polarization", a messenger photon of 45° polarization is made to entangle with photon A, thus obliging A then to be in the complementary polarization state. This in turn means that photon B now has the same polarization as the messenger photon, which is complementary to that of A. Then measuring the 45° polarization of B means "message received".

Experimenting with entangled photons is quite difficult, however. Now UK researchers are proposing a much simpler technique of conveying information - by teleporting the quantum state of an atom trapped in a cavity to a second atom in a distant cavity.