Long-distance quantum key distribution using concatenated entanglement swapping with practical resources

TL;DR

This paper explores long-distance quantum key distribution using concatenated entanglement swapping, analyzing practical resource limitations and trade-offs affecting key rate and distance.

Contribution

It introduces a model incorporating realistic resource constraints for assessing four-photon visibility and key rates in long-distance QKD.

Findings

Concatenated entanglement swapping enables quantum communication over large distances.

Trade-offs exist between run-time, pair-production rate, and detector efficiency.

Long distances are achievable at the cost of lower key generation rates.

Abstract

We present our approach for sharing photons and assessing resultant four-photon visibility between two distant parties using concatenated entanglement swapping. In addition we determine the corresponding key generation rate and the quantum bit-error rate. Our model is based on practical limitations of resources, including multipair parametric down-conversion sources, inefficient detectors with dark counts and lossy channels. Through this approach, we have found that a trade-off is needed between experimental run-time, pair-production rate and detector efficiency. Concatenated entanglement swapping enables huge distances for quantum key-distribution but at the expense of low key generation rate.