  We report a bulk optics experiment demonstrating the possibility of restoring
the entanglement distribution through noisy quantum channels by inserting a
suitable unitary operation (filter) in the middle of the transmission process.
We focus on two relevant classes of single-qubit channels consisting in
repeated applications of rotated phase damping or rotated amplitude damping
maps, both modeling the combined Hamiltonian and dissipative dynamics of the
polarization state of single photons. Our results show that interposing a
unitary filter between two noisy channels can significantly improve
entanglement transmission. This proof-of-principle demonstration could be
generalized to many other physical scenarios where entanglement-breaking
communication lines may be amended by unitary filters.
