Long distance measurement-device-independent quantum key distribution without reference calibration*

Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) can reduce the complexity of practical systems caused by the alignment of the reference frame. Lengthening the transmission distance and improving the system clock rate are essential in practical applications of QKD. Herein, in an asymptotic case, we report the results of RFI-MDI-QKD over a distance of 160 km at a clock rate of 50 MHz. By considering the statistical fluctuation of a finite key, we experimentally implemented a four-intensity decoy-state RFI-MDI-QKD protocol with biased bases at transmission distances of 100 km and 120 km. In addition, we compare the RFI-MDI-QKD protocol with the original MDI-QKD protocol when different isalignments of the reference frame are deployed. The results demonstrate the robustness of our scheme and that the key rate of RFI-MDI-QKD can be improved for a large misalignment of the reference frame.

Please see the Referece [H.-W. Liu,et al., Optica 5, 902 (2018)] for mor information about the results of our paper.