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Quantum optics

Quantum optics

The decay route to teleportation

16 Dec 1999

A new way to "teleport" a quantum state has been proposed by physicists from Imperial College, London and Oxford University. The proposed technique teleports the quantum state of an atom trapped in a cavity to a second atom in a distant cavity (Phys. Rev. Lett. 83 5158). The technique is simpler than current methods that rely on "entangled" pairs of photons.

In quantum teleportation the quantum state of an object held by “Alice” is instantaneously sent to “Bob”. The new technique works by having two optical cavities that both contain a single trapped atom with three energy levels – two ground states and one excited state. The cavities are designed so that the photon emitted when the atom spontaneously decays from the excited state to one of the ground states can only escape from one side of the cavity. Alice also has a beam splitter and two detectors.

Alice teleports her quantum state to Bob in three stages. In the first stage Alice “maps” her atomic state to the cavity state while Bob simultaneously creates an “entangled” state consisting of his atom and cavity. Alice then waits for a finite time for one of her detectors to see a photon, indicating that the protocol is successful. The success of the transfer is then transmitted to Bob who can recreate the quantum state of Alice’s atom. The technique can, in principle, work over vast distances and could be ideal for linking up distant quantum processors.

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