Finite-key analysis for twin-field quantum key distribution with composable security.

Area of Science:

• Quantum Information Science
• Cryptography
• Quantum Communication

Background:

• Long-distance quantum key distribution (QKD) traditionally relies on trusted relays or quantum repeaters, posing security risks or facing implementation challenges.
• Existing security proofs for advanced QKD protocols often lack simplicity or only guarantee security against collective attacks, with full proofs requiring asymptotic assumptions.
• Twin-field (TF) QKD and its variants have emerged as promising solutions for long-distance QKD, but require robust security analyses.

Purpose of the Study:

• To provide a composable finite-key security analysis for coherent-state-based twin-field (TF) QKD.
• To develop rigorous security proofs against general quantum attacks, moving beyond collective attack limitations.
• To enhance the practical feasibility and performance of long-distance QKD.

Main Methods:

• Implemented a composable finite-key security analysis framework.
• Developed rigorous security proofs applicable to general quantum attacks.
• Introduced an optimal statistical fluctuation analysis method to improve performance in high-loss scenarios.

Main Results:

• Achieved a rigorous security proof against general attacks for coherent-state-based TF-QKD.
• Significantly improved the secret key rate, especially in high-loss conditions, through optimal statistical fluctuation analysis.
• Demonstrated the practical feasibility of coherent-state-based TF-QKD.

Conclusions:

• Coherent-state-based TF-QKD offers a practical and secure solution for long-distance quantum communication.
• The developed security analysis and optimization methods pave the way for QKD deployment over extended ranges, potentially up to one thousand kilometers.
• This work advances the field of quantum cryptography by providing a simplified yet robust security framework for practical QKD systems.