Active switching in long distance quantum state teleportation

Summary form only given. Quantum state teleportation is a fundamental scheme of quantum communication and computation. A full implementation of the protocol requires to actively perform a unitary transformation on the teleported quantum state, depending on the outcome of a Bell-state measurement on Alice's side. Up to now, only "passive" schemes for teleporting arbitrary qubits exist, i.e. three out of four teleportation events have to be rejected. We present a scheme where the distinction of two Bell-states is combined with an active control over the mandatory unitary transformation at Bob's side. By transmitting the entangled pair through a long fibre while broadcasting Alice's result one can achieve that the classical signal overtakes the quantum signal allowing Bob to switch before the teleported photon arrives. This is another important step towards the implementation of quantum teleportation as a tool in quantum communication schemes.