Rate-Adaptive Information Reconciliation for CV-QKD Systems at Low Signal-to-Noise Ratios.

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Information Theory

Background:

• Information reconciliation (IR) is vital for continuous-variable quantum key distribution (CV-QKD) secret key rate (SKR).
• Fixed-rate error-correcting codes in IR struggle with varying signal-to-noise ratios (SNRs), limiting reconciliation efficiency in practical CV-QKD.
• Existing methods lack adaptability to dynamic channel conditions.

Purpose of the Study:

• To develop rate-adaptive IR protocols for CV-QKD systems.
• To improve reconciliation efficiency and maintain SKR under fluctuating SNRs.
• To offer solutions for practical CV-QKD implementations.

Main Methods:

• Proposed Threshold-based IR (TIR) protocol using low-density parity-check (LDPC) codes with adjustable code rates.
• Developed Sorting-based IR (SIR) protocol for dynamic code rate adjustment based on SNR.
• Analyzed protocols for code rate, reconciliation efficiency, and complexity.

Main Results:

• TIR and SIR protocols demonstrate superior performance compared to existing rate-adaptive IR protocols.
• Achieved reconciliation efficiency exceeding 98.5% for SNRs below -20 dB.
• Maintained a stable SKR in simulations, indicating suitability for long-distance CV-QKD.

Conclusions:

• The proposed TIR and SIR protocols effectively address the limitations of fixed-rate codes in CV-QKD IR.
• These rate-adaptive strategies significantly enhance reconciliation efficiency across a broad SNR range.
• The developed protocols offer a practical solution for robust and efficient CV-QKD systems.