Accelerated key generation and distribution using polarization scrambling in optical fiber

Area of Science:

• Quantum Information Science
• Optical Communications
• Cybersecurity

Background:

• Classical optical fiber channels offer inherent physical-layer properties suitable for secure key generation and distribution (SKGD).
• Existing SKGD schemes often suffer from low key generation rates (KGR), typically below kbit/s, limiting practical applications.
• The unique birefringence and reciprocal nature of optical fibers are foundational for secure key exchange.

Purpose of the Study:

• To propose and demonstrate an accelerated SKGD scheme in classical optical fiber channels.
• To enhance the key generation rate (KGR) beyond conventional limits.
• To analyze the security robustness of the proposed scheme against fiber-tapping attacks.

Main Methods:

• Implementation of an active polarization scrambling technique combined with the inherent birefringence of the optical fiber channel.
• Utilizing fast and random fluctuations in the state of polarization (SOP) to securely share randomness between legitimate users.
• Experimental demonstration over 24-km of standard single-mode fiber (SSMF).

Main Results:

• Achieved a high KGR of 200-kbit/s with error-free operation after post-processing.
• Demonstrated the feasibility of accelerated SKGD through active polarization scrambling.
• Provided theoretical and experimental analysis confirming the scheme's security against fiber-tapping.

Conclusions:

• Active polarization scrambling effectively accelerates SKGD in classical optical fiber channels.
• The proposed scheme offers a significant improvement in KGR while maintaining security.
• Incorporating active polarization scrambling is a viable strategy for developing faster and more secure key distribution systems.