Quantum Teleportation of a Moving Atom

Quantum teleportation involves transmitting all of the information contained in a quantum-mechanical particle (such as a photon or atom) to another particle, even if the two are completely separated by a large distance. Experimentally demonstrated with photons in numerous labs, quantum teleportation schemes have up to now focused on transmitting a particle's internal states, such as photon polarization.

Exploring quantum teleportation with atoms, an Israel-Germany-Czech Republic collaboration (Tomas Opatrny, Weizmann Institute/F. Schiller University, pto@tpi.uni-jena.de) has come up with an experimental proposal for transmitting an atom's full information including its "external" states, such as its energy of motion. This procedure replicates the quantum features of the external motion of a particle.

For example, if particle-to-be-teleported C yielded a diffraction pattern after passing through two slits, then the same pattern would be produced by particle B, which receives the teleported information. The researchers propose the following idea: Dissociate a very cold molecule with a laser pulse into two atoms (called A and B). Then, manipulate the two atoms so that they become entangled: each one is in a fuzzy state individually but has a precisely defined relationship with its partner. Then, let one of the entangled particles (such as A) collide with particle C, whose unknown state should be teleported. After their collision, the momentum values of the collision partners A and C are measured.

With that information, the researchers know how to "kick" and deflect atom B so that the motion of B precisely emulates that of particle C. Teleportation is extremely demanding, but the authors say that state-of-the-art equipment for studying atomic collisions and quantum effects makes this experiment "hard but feasible." (Opatrny and Kurizki, Phys. Rev. Lett., 2 April 2001; text at Physics News Select.)