Memory-assisted measurement-device-independent quantum key distribution

TL;DR

This paper proposes a memory-assisted measurement-device-independent quantum key distribution protocol that leverages quantum memories to extend communication distances and improve performance over existing QKD systems, accounting for real-world imperfections.

Contribution

It introduces a novel QKD scheme combining quantum memories with measurement-device independence, enabling longer distances and higher rates with current technology.

Findings

Memory-assisted QKD can outperform current systems at practical distances.

Fast quantum memories reduce coherence time requirements.

The framework accounts for various non-idealities in realistic settings.

Abstract

A protocol with the potential of beating the existing distance records for conventional quantum key distribution (QKD) systems is proposed. It borrows ideas from quantum repeaters by using memories in the middle of the link, and that of measurement-device-independent QKD, which only requires optical source equipment at the user's end. For certain fast memories, our scheme allows a higher repetition rate than that of quantum repeaters, thereby requiring lower coherence times. By accounting for various sources of nonideality, such as memory decoherence, dark counts, misalignment errors, and background noise, as well as timing issues with memories, we develop a mathematical framework within which we can compare QKD systems with and without memories. In particular, we show that with the state-of-the-art technology for quantum memories, it is possible to devise memory-assisted QKD systems that, at certain distances of practical interest, outperform current QKD implementations.