Continuous-variable quantum key distribution with time-division dual-quadrature homodyne detection

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Optical Physics

Background:

• Continuous-variable quantum key distribution (CVQKD) enables secure communication.
• Traditional heterodyne detection requires complex setups.
• Polarization drift in optical fibers hinders secure key distribution.

Purpose of the Study:

• To propose a novel heterodyne detection scheme for CVQKD.
• To simplify CVQKD systems by using a single homodyne detector.
• To improve the robustness of CVQKD against polarization fluctuations.

Main Methods:

• A novel heterodyne detection scheme measuring both quadrature components.
• Time-division multiplexing to emulate heterodyne detection with a single homodyne system.
• A Faraday-Michelson interferometer to mitigate polarization drift.

Main Results:

• Experimental demonstration of the proposed scheme using the Gaussian-modulated coherent-states (GMCS) protocol.
• Successful transmission over a 20.06 km optical fiber channel.
• Achieved an expected secret key rate of up to 0.187 Mbps.

Conclusions:

• The proposed scheme offers a simplified and robust approach to CVQKD.
• It achieves performance comparable to conventional heterodyne detection.
• The system is resilient to polarization drift, reducing hardware complexity.