High-speed Gaussian-modulated continuous-variable quantum key distribution with a local local oscillator based on...

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Optical Communications

Background:

• Continuous-variable quantum key distribution (CVQKD) offers enhanced security.
• Traditional CVQKD methods face challenges with phase noise and basis reconciliation.
• Local local oscillator (LLO) based CVQKD can simplify detection.

Purpose of the Study:

• To experimentally demonstrate a high-speed Gaussian-modulated CVQKD system with LLO.
• To implement pilot-tone-assisted phase compensation for real-time noise mitigation.
• To achieve a high secure key rate over a standard optical fiber channel.

Main Methods:

• Utilized frequency and polarization multiplexing for separate quantum signal and pilot tone transmission.
• Employed heterodyne detection for simultaneous measurement of X and P quadratures.
• Implemented real-time phase compensation to counteract fast and slow phase drifts.

Main Results:

• Achieved a secure key rate of 7.04 Mbps in the asymptotic regime.
• Obtained a secure key rate of 1.85 Mbps for finite-size blocks (10^7).
• Demonstrated effective phase noise compensation over a 25 km optical fiber with 5 dB loss.

Conclusions:

• The LLO-CVQKD scheme with pilot-tone-assisted phase compensation is a viable approach for high-speed quantum key distribution.
• The system effectively mitigates phase noise, enabling practical secure communication.
• This work advances the development of secure and high-performance quantum communication networks.