Modeling a measurement-device-independent quantum key distribution system

TL;DR

This paper introduces a comprehensive mathematical model for measurement-device-independent quantum key distribution systems, validated through experiments, enabling optimization and performance projection of such quantum communication systems.

Contribution

The paper provides a detailed, validated mathematical model for MDI-QKD systems that aids in optimizing key rates and understanding system limitations.

Findings

Model predictions closely match experimental data.

Optimization of photon numbers improves secret key rates.

System performance remains stable over deployed fiber environments.

Abstract

We present a detailed description of a widely applicable mathematical model for quantum key distribution (QKD) systems implementing the measurement-device-independent (MDI) protocol. The model is tested by comparing its predictions with data taken using a proof-of-principle, time-bin qubit-based QKD system in a secure laboratory environment (i.e. in a setting in which eavesdropping can be excluded). The good agreement between the predictions and the experimental data allows the model to be used to optimize mean photon numbers per attenuated laser pulse, which are used to encode quantum bits. This in turn allows optimization of secret key rates of existing MDI-QKD systems, identification of rate-limiting components, and projection of future performance. In addition, we also performed measurements over deployed fiber, showing that our system's performance is not affected by environment-induced perturbations.