Secret key rate of multi-ring M-APSK continuous variable quantum key distribution

Area of Science:

• Quantum Information Science
• Quantum Communication Security
• Applied Physics

Background:

• Discrete modulation continuous variable quantum key distribution (DM-CV-QKD) is preferred for practical systems over Gaussian modulation (GM) due to reduced complexity.
• Current DM-CV-QKD systems often utilize M-symbol phase shift keying (M-PSK) constellations, which limit achievable transmission distances and key rates compared to GM.

Purpose of the Study:

• To investigate the potential of M-symbol amplitude and phase shift keying (M-APSK) constellations to approximate the performance of Gaussian modulation in DM-CV-QKD systems.
• To enhance the practical implementation of continuous variable quantum key distribution (CV-QKD) by improving distance and key rate.

Main Methods:

• Theoretical analysis and simulation of DM-CV-QKD systems employing M-APSK constellations.
• Evaluation of system performance considering finite-size effects.

Main Results:

• M-APSK constellations can effectively approximate the performance of Gaussian modulation in DM-CV-QKD.
• A 4-ring 64-APSK constellation achieved a transmission distance of 52.0 km, only 7.2 km less than GM.
• The 4-ring 64-APSK constellation demonstrated a 282% increase in maximum achievable transmission distance compared to 8-PSK.

Conclusions:

• M-APSK constellations offer a viable approach to bridge the performance gap between complex GM and simpler M-PSK in CV-QKD.
• The proposed M-APSK constellations significantly improve the practical reach and key generation rates for secure quantum communication.