Dynamic attenuation scheme in measurement-device-independent quantum key distribution over turbulent channels

TL;DR

This paper proposes a dynamic attenuation scheme for MDI QKD over turbulent free-space channels, improving key rates by real-time channel transmittance monitoring and adaptive attenuation.

Contribution

It introduces a real-time transmittance monitoring and adaptive attenuation method to enhance MDI QKD performance over turbulent channels.

Findings

Significant improvement in secret key rate with the proposed scheme.

Enhanced performance especially with short raw keys.

Simulation results demonstrate the effectiveness of dynamic attenuation.

Abstract

Measurement-device-independent quantum key distribution (MDI QKD) offers great security in practice because it removes all detector side channels. However, conducting MDI QKD over free-space channels is challenging. One of the largest culprits is the mismatched transmittance of the two independent turbulent channels causing a reduced Hong-Ou-Mandel visibility and thus a lower secret key rate. Here we introduce a dynamic attenuation scheme, where the transmittance of each of the two channels is monitored in real time by transmitting bright light pulses from each users to the measurement device. Based on the measured channel transmittance, a suitable amount of attenuation is introduced to the low-loss channel at the measurement device. Our simulation results show a significant improvement of QKD performance, especially when using short raw keys.