Nonlocal memory effects allow perfect teleportation with mixed states
  We show that perfect quantum teleportation can be achieved with mixed photon polarization states when nonlocal memory effects influence the dynamics of the quantum system. The protocol is carried out with a pair of photons, whose initial maximally entangled state is destroyed by local decoherence prior to teleportation. It is demonstrated that the presence of strong nonlocal memory effects, which arise from initial correlations between the environments of the photons, allow to restore perfect teleportation. We further analyze how the amount of initial correlations within the environment affects the fidelity of the protocol, and find that for a moderate amount of correlations the fidelity exceeds the one of the previously known optimal teleportation protocol without memory effects. Our results show that memory effects can be exploited in harnessing noisy quantum systems for quantum communication and that non-Markovianity is a resource for quantum information tasks. 
Elsi-Mari Laine, Heinz-Peter Breuer and Jyrki Piilo
quant-ph