NICOLAS GISIN* AND ROB THEW Group of Applied Physics, University of Geneva, 1211 Geneva 4, Switzerland. Quantum communication is the art of transferring a quantum state from one place to another. Traditionally, the sender is named Alice and the receiver Bob. The basic motivation is that quantum states code quantum information — called qubits in the case of two-dimensional Hilbert spaces — and that quantum information allows tasks to be performed that could only be achieved far less efficiently, if at all, using classical information. The best known example is quantum key distribution (QKD)1–3. In fact, there is another motivation, at least equally important to most physicists, namely the close connection between quantum communication and quantum non-locality 4,5, as illustrated by the fascinating process of quantum teleportation 6.