Performance evaluation of twin-field quantum key distribution using avalanche photodiode single-photon detectors

Area of Science:

• Quantum Communication
• Quantum Cryptography
• Photonics

Background:

• Twin-field quantum key distribution (TF-QKD) offers a path to secure long-distance communication beyond the repeaterless bound.
• Avalanche photodiodes (APDs) are practical single-photon detectors for QKD due to their size, cost, and room-temperature operation.
• Imperfections in APDs, such as afterpulse, dead time, and dark counts, can significantly hinder TF-QKD system performance.

Purpose of the Study:

• To develop a detailed simulation model for TF-QKD that accounts for APD imperfections.
• To quantitatively analyze the impact of individual APD non-idealities on TF-QKD performance.
• To compare the performance of different TF-QKD protocols under realistic APD conditions.

Main Methods:

• Development of a comprehensive TF-QKD simulation model.
• Inclusion of key APD imperfections: afterpulse probability, dead time, and dark counts.
• Comparative analysis of three representative TF-QKD protocols (including SNS) using the simulation model.

Main Results:

• Afterpulse probability, particularly from high-intensity reference pulses, emerges as the primary factor limiting TF-QKD performance.
• Under identical APD conditions, the sending-or-not-sending (SNS) protocol exhibits superior performance for long-distance quantum communication.
• The SNS protocol's advantages stem from its higher signal photon count and improved noise resilience.

Conclusions:

• APD imperfections critically affect the performance of compact, practical TF-QKD systems.
• Afterpulse mitigation strategies are crucial for optimizing APD-based TF-QKD.
• The SNS protocol is a promising candidate for robust, long-distance quantum key distribution with APD detectors.