Experimental Purification of Single Qubits
  We report the experimental realization of the purification protocol for single qubits sent through a depolarization channel. The qubits are associated with polarization encoded photon particles and the protocol is achieved by means of passive linear optical elements. The present approach may represent a convenient alternative to the distillation and error correction protocols of quantum information. 
M. Ricci, F. De Martini, N.J. Cerf, R. Filip, J. Fiurasek and C.   Macchiavello