Entanglement-swapping chains for general pure states - art. no. 052315

We consider entanglement-swapping schemes with general (rather than maximal ly) entangled bipartite states of arbitary dimension shared pairwise betwee n three or more parties in a chain. The intermediate parties perform genera lized Bell measurements with the result that the two end parties end up sha ring an entangled state which can be converted into maximally entangled sta tes. We obtain an expression for the average amount of maximal entanglement concentrated in such a scheme and show that in a certain reasonably broad class of cases this scheme is provably optimal and that, in these cases, th e amount of entanglement concentrated between the two ends is equal to that which could be concentrated from the weakest link in the chain.