Polarization based discrete variables quantum key distribution via conjugated homodyne detection

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Optical Communication

Background:

• Optical homodyne detection is crucial for continuous-variable quantum key distribution (CV-QKD) and quantum tomography.
• Existing DV-QKD systems can benefit from enhanced speed and polarization stability.

Purpose of the Study:

• To propose and demonstrate a high-speed discrete-variable quantum key distribution (DV-QKD) system.
• To integrate phase modulators for rapid state of polarization (SOP) generation with conjugate homodyne detection.
• To enable effective polarization drift compensation and high-rate secure key generation.

Main Methods:

• Utilized phase modulators for high-speed SOP generation.
• Implemented a conjugate homodyne detection scheme with a detection threshold for channel discretization (click/no-click).
• Employed a time-multiplexed pilot tone-quantum signal architecture with a locally generated local oscillator at Bob's side.

Main Results:

• Achieved a low quantum bit error rate (QBER) with higher detection threshold values.
• Demonstrated a secure key rate of approximately 46.9 Mbps over 40 km of optical fiber at a 500 MHz symbol generation clock.
• Showcased effective polarization drift compensation capabilities.

Conclusions:

• The proposed DV-QKD scheme effectively combines high-speed SOP generation and conjugate homodyne detection.
• Optimizing the detection threshold is critical for balancing QBER and secure key length.
• The system offers a promising approach for high-rate, secure quantum communication over optical fiber.