Fibre polarisation state compensation in entanglement-based quantum key distribution

Area of Science:

• Quantum Information Science
• Optical Communications
• Quantum Cryptography

Background:

• Polarization-encoded Quantum Key Distribution (QKD) is susceptible to birefringence and routing in deployed telecom fibers.
• Fiber-induced polarization alterations lead to basis mismatch and increased Quantum Bit Error Rate (QBER).

Purpose of the Study:

• To demonstrate a novel technique for dynamically compensating fiber-induced polarization state alterations in QKD systems.
• To improve the reliability and performance of polarization-encoded QKD over deployed optical fiber infrastructure.

Main Methods:

• Implementation of a feedback loop for real-time QKD system monitoring and adjustment.
• Utilization of a stochastic optimization algorithm to minimize QBER by actively compensating for polarization drifts.
• Experimental verification in a polarization-entangled QKD system over a deployed telecom fiber link.

Main Results:

• Successful dynamic compensation of fiber-induced polarization state alterations was achieved.
• The QBER was significantly minimized, demonstrating the effectiveness of the stochastic optimization feedback loop.
• The technique proved viable for polarization-entangled QKD systems operating in real-world telecom fiber networks.

Conclusions:

• Dynamic compensation is a crucial technique for overcoming polarization instability in fiber-based QKD.
• The developed feedback loop and optimization algorithm effectively reduce QBER, enhancing QKD system robustness.
• This method enables more practical and widespread implementation of polarization-encoded QKD over existing fiber infrastructure.