Probabilistic shaped 128-APSK CV-QKD transmission system over optical fibres

Area of Science:

• Quantum Information Science
• Secure Communication Technologies
• Optical Engineering

Background:

• Quantum key distribution (QKD) offers unparalleled security based on quantum mechanics principles.
• Continuous-variable (CV) QKD systems are essential for long-distance secure key generation.
• Challenges remain in implementing robust and practical CV-QKD systems using accessible components.

Purpose of the Study:

• To present a novel discrete modulated, continuous variables quantum key distribution (CV-QKD) implementation.
• To demonstrate the system's security against collective attacks.
• To showcase the system's long-term operational capability and performance over extended distances.

Main Methods:

• Utilizing two probabilistically shaped, 128-symbol, amplitude and phase shift keying (PSK) constellations.
• Implementing a polarization-diverse, true heterodyne receiver architecture for symbol recovery at the detection side.
• Conducting experimental validation of the CV-QKD system.

Main Results:

• The system achieves security against collective attacks.
• The implementation uses accessible, telecom-grade materials.
• The system demonstrated reliable functioning for extended periods at distances exceeding 185 km in the asymptotic regime.

Conclusions:

• The presented CV-QKD system offers a practical and secure solution for long-distance key distribution.
• The use of standard telecom components enhances the feasibility of widespread deployment.
• The system's robust performance over 185 km signifies a significant advancement in secure communication technology.