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

Margarida Almeida, Daniel Pereira, Nelson J Muga

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    Discrete modulation continuous variable quantum key distribution (DM-CV-QKD) using M-symbol amplitude and phase shift keying (M-APSK) constellations can approximate Gaussian modulation. This advancement enhances transmission distances and key rates for practical quantum communication systems.

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    Area of Science:

    • Quantum Information Science
    • Quantum Communication Security
    • Cryptography

    Background:

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

    Purpose of the Study:

    • To investigate the potential of M-symbol amplitude and phase shift keying (M-APSK) constellations in DM-CV-QKD systems.
    • To determine if M-APSK constellations can approximate the performance of Gaussian modulation (GM).
    • To enhance the practical reach and key generation rates of CV-QKD systems.

    Main Methods:

    • Theoretical analysis and simulation of DM-CV-QKD systems employing M-APSK constellations.
    • Comparison of M-APSK performance against GM and M-PSK constellations, considering finite-size effects.
    • Evaluation of key generation rates and transmission distances for various M-APSK configurations.

    Main Results:

    • M-APSK constellations can effectively approximate the performance of GM in DM-CV-QKD.
    • A 4-ring 64-APSK constellation demonstrated a transmission distance of 52.0 km, only 7.2 km less than GM.
    • This represents 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 approach significantly improves the practical feasibility of long-distance quantum key distribution.
    • This research paves the way for more robust and longer-range quantum communication networks.