Refrence-Frame-Independent Quantum Key Distribution over 250 km of Optical Fiber

TL;DR

This paper demonstrates a reference-frame-independent quantum key distribution system over 250 km of optical fiber, achieving high secret key rates and significantly extending practical secure communication distances.

Contribution

We developed a high-repetition-rate RFI QKD system that extends transmission distance and improves secret key rates compared to previous systems.

Findings

Secure key distribution over 250 km fiber

Finite-key secret key rate of 49.65 bit/s at 200 km

Key rate more than three times higher than previous systems

Abstract

The reference-frame-independent quantum key distribution (RFI QKD) protocol enables QKD systems to function effectively despite slowly varying reference frames, offering a distinct advantage in practical scenarios, particularly in mobile platforms. In this study, we successfully distribute secure key bits over a 250-km optical fiber distance by developing an RFI QKD system with a repetition rate of 150 MHz. Benefiting from high repetition rate, we achieve a finite-key secret key rate of 49.65 bit/s at a distance of 200 km, which is more than three times higher than state-of-the-art systems. Our work dramatically extends the transmission distance and enhances the secret key rate of RFI QKD, significantly promoting its practical application.