Practical Security Analysis of Self-Referenced CV-QKD System in the Presence of Polarization Aberration
How to remove local oscillator (LO) side channel attacks has been a notoriously hard problem in continuous-variable quantum key distribution (CV-QKD). In the self-referenced CV-QKD schemes, the LO signal is locally generated at the receiver by an independent laser so that it is not co-transmitted with the quantum signal. This simple solution removes all LO side channels. However it also introduces some other practical vulnerabilities. Especially the polarization states of the quantum signal and LO signal may not be identical across the detector because of the presence of the polarization aberrations. Thus, the detection efficiency which is arguably the most critical experiment parameter of the practical implementation will be impaired. In this paper, we analyze the impact of polarization aberrations on the detection efficiency for CV-QKD and propose a self-referenced CV-QKD scheme in the presence of polarization aberrations by using an off-axis optical system. In the proposed scheme, the polarization states of the quantum signal would change with the off-axis optical system, thus impairing the heterodyne efficiency. Our security analysis shows a gap between the theory and practice of CV-QKD.
KeywordsLocal oscillator Polarization states Polarization aberrations Detection efficiency Security
This work was supported by the Fundamental Research Funds for the Central Universities of Central South University (Grant No. 2018zzts533), the National Natural Science Foundation of China (Grant Nos. 61871407, 61572529), and the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 18KJB510045).
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