Simple Quantum Key Distribution using a Stable Transmitter-Receiver Scheme

TL;DR

This paper presents a simple, stable, and low-cost quantum key distribution system that maintains stability over 48 hours and over 75 km fiber, suitable for practical and space applications.

Contribution

The authors introduce a stable transmitter-receiver scheme that simplifies alignment and environmental robustness, advancing practical QKD deployment.

Findings

System remains stable for 48 hours without feedback control.

Achieves a secure key rate of 7.32k bits/sec over 75 km fiber.

Maintains an average quantum bit error rate below 1%.

Abstract

Quantum Key Distribution (QKD) is a technology that allows secure key exchange between two distant users. A widespread adoption of QKD requires the development of simple, low-cost, and stable systems. However, implementation of the current QKD requires a complex self-alignment process during the initial stage and an additional hardware to compensate the environmental disturbances. In this study, we have presented the implementation of a simple QKD with the help of a stable transmitter-receiver scheme, which simplifies the self-alignment and is robust enough to withstand environmental disturbances. In case of the stability test, the implementation system is able to remain stable for 48 hours and exhibits an average quantum bit error rate of less than 1\% without any feedback control. The scheme is also tested over a fiber spool, obtaining a stable and secure finite key rate of 7.32k bits per second over a fiber spool extending up to 75 km. The demonstrated long-term stability and obtained secure key rate prove that our method of implementation is a promising alternative for practical QKD systems, in particular, for Cubesat platform and satellite applications.