Stable and deterministic quantum key distribution based on differential phase shift

TL;DR

This paper introduces a stable, efficient, and secure quantum key distribution system using differential phase shift with cascaded interferometers, automatic compensation for fiber effects, and simplified classical communication.

Contribution

It proposes a novel QKD system with improved key creation efficiency, enhanced security features, and practical advantages over existing phase-coding systems.

Findings

Key creation efficiency of 7/8 achieved

Automatic compensation for birefringence and polarization effects

Enhanced security with added eavesdropping check

Abstract

We present a stable and deterministic quantum key distribution (QKD) system based on differential phase shift. With three cascaded Mach-Zehnder interferometers with different arm-length differences for creating key, its key creation efficiency can be improved to be 7/8, more than other systems. Any birefringence effects and polarization-dependent losses in the long-distance fiber are automatically compensated with a Faraday mirror. Added an eavesdropping check, this system is more secure than some other phase-coding-based QKD systems. Moreover, the classical information exchanged is reduces largely and the modulation of phase shifts is simplified. All these features make this QKD system more convenient than others in a practical application.