Fig. 1. Satellite to ground channel model

Fig. 2. Geometric losses at different wavelengths and its relationship with the distance from the satellite to the ground observation station

Fig. 3. Relationship between Rytov variance at different wavelengths and effective atmospheric thickness

Fig. 4. Scintillation losses at different wavelengths and receiver aperture diameters related with the effective atmospheric thickness

Fig. 5. Constellation diagrams of the 8-DM-CV-QKD, 16-DM-CV-QKD, d16-DM-CV-QKD protocols on the optical phase space. (a) 8-DM-CV-QKD; (b) 16-DM-CV-QKD; (c) d16-DM-CV-QKD

Fig. 6. Relationship diagram between z and VA

Fig. 7. Graph of the relationship between SKR and VA at different amplification factors

Fig. 8. Variation of the secure key rate with distance for 8-DM-CV-QKD system under heterodyne detection with different amplification factors

Fig. 9. Variation of the secure key rate with distance for d16-DM-CV-QKD system under heterodyne detection with different amplification factors

Fig. 10. Graph of the relationship between the improvement ratio and communication distance for 8-DM-CV-QKD

Fig. 11. Effect of channel excess noise on communication distance and improvement ratio in the 8-DM-CV-QKD system

Fig. 12. Graph of the relationship between the improvement ratio and communication distance for d16-DM-CV-QKD

Fig. 13. Graph of the relationship between the improvement ratio and communication distance distance under different channel excess noise conditions for d16-DM-CV-QKD

Fig. 14. Graphs of the secure key rate as a function of satellite-to-ground distance under weak turbulence strength and horizontal elevation angle φ=90°. (a) λ=850 nm; (b) λ=1550 nm; (c) λ=3800 nm

Fig. 15. Graphs of the secure key rate as a function of satellite-to-ground distance under weak turbulence strength and horizontal elevation angle φ=30°. (a) λ=850 nm; (b) λ=1550 nm; (c) λ=3800 nm

Fig. 16. Graphs of the secure key rate as a function of satellite-to-ground distance under strong turbulence strength and horizontal elevation angle φ = 30°. (a) λ=850 nm; (b) λ=1550 nm; (c) λ=3800 nm