# Efficient passive measurement-device-independent quantum key distribution

## TL;DR

This paper introduces a passive decoy-state MDI-QKD protocol that enhances security by avoiding intensity modulation, using heralded single-photon sources, and demonstrating advantages over existing schemes even with finite key sizes.

## Contribution

The paper proposes a novel passive decoy-state MDI-QKD protocol that eliminates the need for intensity modulation, improving security and practicality in quantum key distribution.

## Key findings

- Avoids modulation leakage of decoy states
- Enhances security against eavesdroppers
- Shows advantages over existing MDI-QKD schemes

## Abstract

The measurement-device-independent quantum key distribution (MDI-QKD) possesses the highest security among all practical quantum key distribution protocols. However, existing multi-intensity decoy-state methods may cause loopholes when modulating light intensities with practical devices. In this paper, we propose a passive decoy-state MDI-QKD protocol based on a novel structure of heralded single-photon sources. It does not need to modulate the light source into different intensities and thus can avoid leaking modulation information of decoy states to eavesdroppers, enhancing the security of practical MDI-QKD. Furthermore, by combining the passive decoy states and biased basis choices, our protocol can exhibit distinct advantages compared with state-of-the art MDI-QKD schemes even when the finite key-size effect is taken into account. Therefore, our present passive decoy-state MDI-QKD seems a promising candidate for practical implementation of quantum key distributions in the near future.