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Robust twin-field quantum key distribution through sending or not sending
Cong Jiang1,2, Zong-Wen Yu3, Xiao-Long Hu4
1Jinan Institute of Quantum Technology, Jinan 250101, China.
National Science Review
|April 24, 2023
Summary
The sending-or-not-sending (SNS) protocol in quantum key distribution (QKD) is robust against source errors. Our new method ensures secure key rates even with intensity fluctuations in practical experiments.
Area of Science:
- Quantum Information Science
- Quantum Cryptography
- Experimental Physics
Background:
- The twin-field (TF) quantum key distribution (QKD) protocol, specifically the sending-or-not-sending (SNS) variant, has achieved record distances (511 km).
- Practical implementations face challenges with unavoidable, potentially non-random source errors in decoy-state methods, compromising security.
- Existing TF-QKD security analyses often assume perfect control over source intensity, which is not realistic.
Purpose of the Study:
- To develop a general and efficient method for calculating the secure key rate of the SNS protocol under practical source errors.
- To demonstrate the robustness of the SNS protocol against real-world imperfections in quantum key distribution experiments.
- To provide a security framework for TF-QKD that accounts for uncontrollable source intensity fluctuations.
Main Methods:
- Introduced equivalent protocols using virtual attenuation and a tagged model to handle source errors.
- Developed a general approach for calculating secure key rates in the presence of source intensity fluctuations.
- Explored combining the method with two-way classical communication techniques like active odd-parity pairing for enhanced key rates.
Main Results:
- Presented the first security analysis for practical TF-QKD where source intensity is not precisely controlled.
- Demonstrated that moderate intensity errors (within a few percent) lead to only marginal decreases in secure key rate and distance.
- Showed that the SNS protocol maintains a positive key rate even with significant intensity fluctuations (e.g., [Formula: see text]) in long-distance experiments.
Conclusions:
- The proposed method provides a robust framework for analyzing the security of SNS-based TF-QKD under realistic source errors.
- The SNS protocol exhibits significant resilience to source intensity fluctuations, making it suitable for practical, long-distance quantum key distribution.
- This work bridges the gap between theoretical security and practical implementation challenges in TF-QKD.
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