  Different procedures have been developed in order to recover entanglement
after propagation over a noisy channel. Besides a certain amount of noise,
entanglement is completely lost and the channel is called entanglement
breaking. Here we investigate both theoretically and experimentally an
entanglement concentration protocol for a mixed three-qubit state outgoing from
a strong linear coupling of two-qubit maximally entangled polarization state
with another qubit in a completely mixed state. Thanks to such concentration
procedure, the initial entanglement can be probabilistically recovered.
Furthermore, we analyse the case of sequential linear couplings with many
depolarized photons showing that thanks to the concentration a full recovering
of entanglement is still possible.
