Quantum Teleportation

In quantum teleportation, the object transferred is a quantum state—the information that describes a quantum system—not the particle or other matter itself. A receiving system is prepared in the state that the sender's original system had, while the sender's measurement changes that original state. The protocol is therefore not a way to make a duplicate of an unknown quantum state.

The sender and receiver first share an entangled pair of quantum systems. The sender combines the unknown system with their half of the pair and performs a joint measurement. The measurement yields classical bits, which the sender communicates to the receiver. The receiver uses those results to choose a correction operation on their half of the entangled pair. With the appropriate shared entanglement and classical message, that system becomes the state that was initially held by the sender.

Entanglement alone cannot let the receiver recover the state immediately. The sender's measurement outcome determines which correction the receiver must apply, so those classical results must reach them. Since this message is ordinary classical communication, quantum teleportation cannot be used to send usable information faster than light. The protocol also consumes the shared entangled resource and does not leave the original unknown state intact.

Charles H. Bennett, Gilles Brassard, Claude Crépeau, Richard Jozsa, Asher Peres and William K. Wootters introduced the protocol in a 1993 paper. Later experiments realized teleportation using different physical systems. In a 2015 NIST-reported demonstration, researchers teleported quantum information carried by photons over 102 kilometres of optical fibre in a laboratory. Such demonstrations transfer states under carefully controlled experimental conditions; they do not teleport people or objects.

Quantum teleportation is a protocol for quantum communication and is also related to methods for carrying out operations on quantum systems. It is relevant to research on quantum networks, where entanglement can be shared between distant nodes. Practical use depends on reliably creating, distributing and preserving entanglement, as well as communicating classical measurement results. It is one component of quantum information science, not a standalone faster-than-light communications technology.