# Long-distance continuous-variable measurement-device-independent quantum key distribution with discrete modulation

## TL;DR

This paper introduces a discrete-modulated, long-distance CV-MDI-QKD protocol that enhances security and implementation simplicity, achieving greater transmission distances than previous Gaussian-modulated schemes.

## Contribution

It presents a novel discrete modulation scheme for CV-MDI-QKD that improves distance and efficiency, with proven security against collective attacks.

## Key findings

- Higher maximal transmission distance achieved
- Enhanced reconciliation efficiency at low SNR
- Secure against arbitrary collective attacks

## Abstract

We propose a long-distance continuous-variable measurement-device-independent quantum key distribution (CV-MDI-QKD) protocol with discrete modulation. This kind of discrete-modulated schemes have good compatibility with efficient error correction code, which lead to higher reconciliation efficiency even at low signal-to-noise ratio (SNR). Security analysis shows that the proposed protocol is secure against arbitrary collective attacks in the asymptotic limit with proper use of decoy states. And with the using of discrete modulation, the proposed CV-MDI-QKD protocol has simpler implementation and outperform previous protocols in terms of achievable maximal transmission distance, which precisely solve the bottleneck of the original Gaussian-modulated CV-MDI-QKD protocol.