Polarization entanglement over 100 km optical fiber for quantum key distribution
Michael Ross Vanner, Hannes Hübel, Andreas Poppe, Anton Zeilinger · 2007
We demonstrate distribution of polarization entangled photons over 100 km of optical fiber. Measurements of the two-photon visibility, without dark count subtraction, have shown that the quantum correlations (raw visibility 89%) allow secure quantum cryptography after 100 km of non-zero dispersion shifted fiber using commercially available single photon detectors. In addition, quantum tomography has revealed little degradation of entangled state indicating minimal loss in fidelity during the transmission.