Sending-or-not-sending twin-field quantum key distribution in practice.

Area of Science:

• Quantum Information Science
• Cryptography
• Quantum Communication

Background:

• Twin Field Quantum Key Distribution (TF-QKD) protocols are extensively researched for secure communication.
• Previous work established efficient TF-QKD protocols using a sending-or-not-sending (SNS) approach.
• Real-world implementations face constraints like finite intensity choices, phase slice size, and statistical fluctuations.

Purpose of the Study:

• To present practical implementations of the SNS-TF-QKD protocol.
• To address real-world constraints in TF-QKD by adapting the decoy-state method.
• To analyze the security and efficiency of practical SNS-TF-QKD.

Main Methods:

• Developed a decoy-state method accommodating a few discrete intensity levels and a finite phase slice.
• Performed statistical fluctuation analysis for the decoy-state method in SNS-TF-QKD.
• Conducted numerical simulations to evaluate protocol performance.

Main Results:

• The practical SNS-TF-QKD method achieves performance comparable to ideal asymptotic cases.
• The proposed method surpasses the Persistent Loss-Bound (PLOB) limit for secret key capacity.
• Demonstrated that practical SNS-TF-QKD can be both secure and efficient.

Conclusions:

• Practical implementations of SNS-TF-QKD are feasible and secure.
• The developed decoy-state method effectively handles real-world limitations.
• This work advances the practical deployment of high-security quantum communication systems.