Quantum teleportation in noisy environments

Teleportation of an unknown quantum state is an interesting issue in quantu m information processing. Unit fidelity is achieved if sender and receiver share a maximally entangled state corresponding to the Hilbert space of the quantum state to be teleported. Realistic experiments necessarily make use of passive optical devices such as beam splitters and optical fibers which show losses. Losses however, are known to degrade the entanglement content , and hence the teleportation fidelity, of any given quantum state. This is due to the interaction with a noisy environment, say, an optical fiber. We combine two methods, multiparticle entanglement and appropriate filtering, to 'restore' some of the entanglement lost during the transmission process . The filtering parameter and the basis used in the projective measurement of the multiparticle-entangled state can be optimized for given material pr operties (refractive index, fiber length).