Fig. 1. Distribution of modulated coherent states in phase space. (a) 4PSK; (b) 8PSK

Fig. 2. Modulation representation of KNN classification algorithm in phase space. (a) QPSK; (b) 8PSK

Fig. 3. Phase coded CVQKD based on KNN

Fig. 4. Performance of KNN algorithm under different K values in 4PSK and 8PSK modulated coherent states

Fig. 5. Performance of KNN algorithm under different modulation variances

Fig. 6. Performance of KNN algorithm at different transmission distances

Fig. 7. Performance of KNN algorithm under different excess noises

Fig. 8. Performance comparison of different protocols

Fig. 9. Security key rates for protocols with different modulation variances