Sending-or-Not-Sending Twin-Field Quantum Key Distribution with Light Source Monitoring

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Optical Communication Systems

Background:

• Twin-field quantum key distribution (TF-QKD) offers secure communication over long distances (over 500 km).
• Existing TF-QKD protocols, like the sending-or-not-sending (SNS) protocol, often assume ideal light sources (coherent states).
• This assumption is not met in practice, posing security risks in real-world quantum key distribution (QKD) systems.

Purpose of the Study:

• To investigate the security of the SNS protocol when the photon number distribution (PND) of the light source is unknown.
• To demonstrate the validity of the security analysis for the SNS protocol under non-ideal source conditions.
• To assess the impact of light source monitoring on the performance of the SNS protocol.

Main Methods:

• Theoretical analysis of the SNS protocol under an unknown photon number distribution (PND).
• Security analysis incorporating practical limitations of real-world light sources in QKD.
• Simulation or experimental validation of the SNS protocol's performance with and without source monitoring.

Main Results:

• The security analysis of the SNS protocol remains valid even when the photon number distribution (PND) of the light source is unknown.
• The performance of the SNS protocol is shown to be largely unaffected by the unknown PND when employing light source monitoring.
• Practical security concerns related to non-ideal light sources in TF-QKD are addressed.

Conclusions:

• The SNS protocol offers robust security for TF-QKD, even with practical light sources exhibiting unknown photon number distributions (PNDs).
• Implementing light source monitoring is an effective strategy to maintain the performance and security of the SNS protocol.
• This research contributes to the practical implementation of secure long-distance quantum key distribution systems.