In the continuous-variable quantum key distribution with real local oscillators, the reference pulses transmitted in the insecure quantum channel results in phase compensation noises on the homodyne detection of quantum signals. Traditionally, the phase compensation noise is modelled as a zero-mean Gaussian distribution for simplicity. However, it is more likely to be the one with non-zero mean in the actual environment. In this paper, the phase compensation noise is considered to be with a non-zero mean, and then the secure bound is analyzed according to the imperfect phase compensation noise model. The actual transmittance and excess noise are compared between the evaluation values derived from the theoretical analysis and the estimation values calculated by training signals. Simulation results show that the security analysis is consistent with the practical implementation, and the secret key rate decreases with the increasing mean value and noise variance.
Continuous-variable quantum key distribution (CVQKD) with a real local oscillator (LO) is confronted with new security issues attributed to the reference pulses transmitted together with quantum signals over the insecure quantum channel. This paper proposes a method of phase attack on reference pulses of the CVQKD with real LOs. Under the phase attack, the phase drifts of reference pulses are manipulated by eavesdroppers so that the phase compensation error is increased. Consequently, the secret key rate is reduced because of the imperfect phase compensation for quantum signals. Based on the noise model of imperfect phase compensation, both the parameters of actual transmittance and actual excess noise are deduced from the phase compensation accuracy, and then they are compared with those estimated by training signals. The simulation results show that the secret key rate calculated from the theoretical parameters is consistent with the one estimated by training signals.
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