Abstract:
For the purpose of improving the performance of discrete modulation-continuous variable quantum key distribution (CVQKD) protocols, the amplitude phase-shift keying(APSK) modulation format method was used, proposed to use Gaussian mixed model (GMM) classification algorithm at the receiver side to identify quantum states to enhance the performance of the system, dividing the key transmission system into two stages: state learning and state prediction. In the state learning stage, the classifier based on GMM was trained for known classes of quantum states, learning the amplitude-phase distribution of different classes of quantum states. The state prediction stage then used the minimum Euclidean distance to calculate the posterior probability that the quantum state to be measured belongs to each class, thus determining the class of the quantum state to be measured, and generating the final key by parameter estimation, reverse coordination and secrecy enhancement. Numerical simulation results show that the 128-APSK discrete modulation continuous-variable quantum key distribution protocol can effectively generate secure keys under reverse coordination and collective attack, and the transmission distance can approach 60 km when the secure code rate is 10
-6 bit/symbol. This study provides a reference for further improving the system performance of discrete modulation continuous-variable quantum key distribution protocols.