Experimental investigation of the robustness of partially entangled   photons over 11km
  We experimentally investigate the robustness of maximal and non-maximal Time-Bin entangled photons over distances up to 11 km. The entanglement is determined by controllable parameters and in all cases is shown to be robust, in that the photons maintain their degree of entanglement after transmission. 
R. T. Thew, S. Tanzilli, W. Tittel, H. Zbinden and N. Gisin