Long-distance practical quantum key distribution by entanglement swapping

TL;DR

This paper presents a practical model for long-distance quantum key distribution using entanglement swapping, optimizing resource parameters with existing technology to maximize secret key rates over lossy channels.

Contribution

It introduces an optimized framework for entanglement-based QKD over long distances, balancing detector efficiency, dark counts, and source brightness with practical components.

Findings

Optimal trade-off between detector efficiency and dark counts identified

Maximum secret key rate achieved by tuning source brightness

Effective long-distance QKD feasible with current off-the-shelf technology

Abstract

We develop a model for practical, entanglement-based long-distance quantum key distribution employing entanglement swapping as a key building block. Relying only on existing off-the-shelf technology, we show how to optimize resources so as to maximize secret key distribution rates. The tools comprise lossy transmission links, such as telecom optical fibers or free space, parametric down-conversion sources of entangled photon pairs, and threshold detectors that are inefficient and have dark counts. Our analysis provides the optimal trade-off between detector efficiency and dark counts, which are usually competing, as well as the optimal source brightness that maximizes the secret key rate for specified distances (i.e. loss) between sender and receiver.