Experimental realization of free-space continuous-variable quantum key distribution based on fiber Sagnac...

Area of Science:

• Quantum Information Science
• Optics and Photonics
• Cybersecurity

Background:

• Continuous-variable quantum key distribution (CV-QKD) using Gaussian-modulated coherent states (GMCS) offers robustness against noise.
• Existing polarization coding schemes face challenges in practical free-space CV-QKD implementation.
• Ambient light suppression and background noise resilience are key advantages of GMCS CV-QKD.

Purpose of the Study:

• To propose and experimentally demonstrate a novel polarization coding structure for GMCS CV-QKD.
• To overcome the implementation difficulties of GMCS CV-QKD in free space using polarization coding.
• To develop a compact and efficient polarization modulation system suitable for mobile applications.

Main Methods:

• Development of a polarization coding structure based on a self-compensating fiber Sagnac interferometer.
• Achieving significant reduction (by two orders of magnitude) in required modulation voltage.
• Experimental demonstration of polarization coding-based GMCS CV-QKD.

Main Results:

• The proposed structure enables fast and arbitrary polarization modulation.
• The system utilizes off-the-shelf fiber components, ensuring simplicity and compactness.
• Successful experimental demonstration of polarization coding-based GMCS CV-QKD for the first time.

Conclusions:

• The developed polarization coding structure is a significant advancement for practical free-space GMCS CV-QKD.
• The system's compact and simple design makes it suitable for mobile terminals, including aerial platforms.
• This work paves the way for more accessible and widespread quantum communication networks.