Measurement-device-independent quantum key distribution with quantum memories

TL;DR

This paper extends measurement-device-independent quantum key distribution to include heralded quantum memories, providing analytical formulas for key rates and demonstrating potential for improved secure communication despite decoherence.

Contribution

It introduces a generalized protocol incorporating quantum memories into MDI-QKD with analytical formulas for key metrics, advancing quantum repeater development.

Findings

Significant performance improvement over original MDI-QKD with quantum memories.

Analytical formulas account for device imperfections and decoherence effects.

Protocol feasible with single-photon or decoy-state sources.

Abstract

We generalize measurement-device-independent quantum key distribution [ H.-K. Lo, M. Curty, and B. Qi, Phys. Rev. Lett. 108, 130503 (2012) ] to the scenario where the Bell-state measurement station contains also heralded quantum memories. We find analytical formulas, in terms of device imperfections, for all quantities entering in the secret key rates, i.e., the quantum bit error rate and the repeater rate. We assume either single-photon sources or weak coherent pulse sources plus decoy states. We show that it is possible to significantly outperform the original proposal, even in presence of decoherence of the quantum memory. Our protocol may represent the first natural step for implementing a two-segment quantum repeater.