Source and transmitter Tracking laser TransmitterICCD telescope BBO High-power aser La gomera Alice on La alma Bob on Tenerife Polarization compensation Polarization compensation BN因 Time 4、团B ggang 岛心 Polarization analyser Polarization analyser R Ursin et al, Entanglement-based quantum communication over 144km University of vienna, Nature Physics 3: 481-484(2007)R. Ursin et al，Entanglement-based quantum communication over 144km， University of Vienna，Nature Physics 3：481-484 (2007)