Long-distance continuous-variable quantum key distribution over 100-km fiber with local local oscillator.

Area of Science:

• Quantum Information Science
• Telecommunications Engineering
• Applied Physics

Background:

• Continuous-variable quantum key distribution (CV-QKD) offers enhanced security by leveraging quantum mechanics for key sharing.
• Existing long-distance CV-QKD schemes often require transmitting the local oscillator, introducing security vulnerabilities.
• Integration with telecommunication networks is crucial for practical CV-QKD deployment.

Purpose of the Study:

• To demonstrate a secure, long-distance CV-QKD system with a locally generated local oscillator.
• To overcome security loopholes associated with transmitted local oscillators in previous CV-QKD experiments.
• To achieve a high loss budget for robust quantum communication networks.

Main Methods:

• Implemented a 100-kilometer fiber channel CV-QKD experiment.
• Utilized a locally generated local oscillator to enhance security.
• Employed a machine learning framework for carrier recovery to manage phase noise.
• Optimized modulation variance for improved performance.

Main Results:

• Achieved a record-breaking 100 km distance for CV-QKD with a locally generated local oscillator.
• Demonstrated secure key generation against collective attacks in the finite-size regime.
• Successfully managed phase noise-induced excess noise using machine learning.

Conclusions:

• This work represents a significant advancement for CV-QKD, enabling secure communication over high-loss channels.
• The developed system paves the way for large-scale deployment of secure quantum access networks.
• The integration of machine learning enhances the robustness and practicality of CV-QKD systems.