# Interference between independent photonic integrated devices for quantum key distribution

## TL;DR

This paper demonstrates Hong-Ou-Mandel interference between independent integrated photonic devices, advancing the feasibility of scalable quantum key distribution systems for secure communication networks.

## Contribution

It experimentally shows interference between independent integrated photonic transmitters, a key step for scalable measurement-device-independent QKD.

## Key findings

- Achieved 46.5% interference visibility at 431 MHz
- Demonstrated interference between indium phosphide transmitters
- Lowered barriers for integrated QKD deployment

## Abstract

Advances in quantum computing are a rapidly growing threat towards modern cryptography. Quantum key distribution (QKD) provides long-term security without assuming the computational power of an adversary. However, inconsistencies between theory and experiment have raised questions in terms of real-world security, while large and power-hungry commercial systems have slowed wide-scale adoption. Measurement-device-independent QKD (MDI-QKD) provides a method of sharing secret keys that removes all possible detector side-channel attacks which drastically improves security claims. In this letter, we experimentally demonstrate a key step required to perform MDI-QKD with scalable integrated devices. We show Hong-Ou-Mandel interference between weak coherent states carved from two independent indium phosphide transmitters at $431$ MHz with a visibility of $46.5 \pm 0.8\%$. This work demonstrates the feasibility of using integrated devices to lower a major barrier towards adoption of QKD in metropolitan networks.