# Asymmetric Protocols for Mode Pairing Quantum Key Distribution with Finite-Key Analysis

## TL;DR

This paper improves the security and performance of quantum key distribution over long distances by analyzing an asymmetric protocol with realistic assumptions.

## Contribution

The paper introduces a finite-key analysis for asymmetric MP-QKD without ideal decoy state assumptions.

## Key findings

- Improved secure key rates and transmission distances were achieved compared to additional attenuation strategies.
- The relationship between signal, decoy, and vacuum state intensities and transmission distance was investigated.
- A modified particle swarm optimization method was used to optimize 10 independent protocol parameters.

## Abstract

The mode pairing quantum key distribution (MP-QKD) protocol has attracted considerable attention for its capability to ensure high secure key rates over long distances without requiring global phase locking. However, ensuring symmetric channels for the MP-QKD protocol is challenging in practical quantum communication networks. Previous studies on the asymmetric MP-QKD protocol have relied on ideal decoy state assumptions and infinite-key analysis, which are unattainable for real-world deployment. In this paper, we conduct a security analysis of the asymmetric MP-QKD protocol with the finite-key analysis, where we discard the previously impractical assumptions made in the decoy state method. Combined with statistical fluctuation analysis, we globally optimized the 10 independent parameters in the asymmetric MP-QKD protocol by employing our modified particle swarm optimization. Through further analysis, the simulation results demonstrate that our work achieves improved secure key rates and transmission distances compared to the strategy with additional attenuation. We further investigate the relationship between the intensities and probabilities of signal, decoy, and vacuum states with transmission distance, facilitating their more efficient deployment in future quantum networks.