# On-chip quantum interference with heralded photons from two independent micro-ring resonator sources in silicon photonics

## TL;DR

This paper demonstrates high-visibility quantum interference between heralded photons from two independent micro-ring resonator sources on a silicon photonics chip, advancing integrated quantum photonics for quantum computing.

## Contribution

First on-chip measurement of indistinguishability of heralded photons from independent micro-ring resonators using an integrated Mach-Zehnder interferometer.

## Key findings

- Measured 72% interference fringe visibility, consistent with a detailed model.
- Identified multi-pair emissions as the main limit to visibility.
- Proposed methods to improve visibility towards near unity in future work.

## Abstract

High visibility on-chip quantum interference among indistinguishable single-photons from multiples sources is a key prerequisite for integrated linear optical quantum computing. Resonant enhancement in micro-ring resonators naturally enables brighter, purer and more indistinguishable single-photon production without any tight spectral filtering. The indistinguishability of heralded single-photons from multiple micro-ring resonators has not been measured in any photonic platform. Here, we report on-chip indistinguishability measurements of heralded single-photons generated from independent micro-ring resonators by using an on-chip Mach-Zehnder interferometer and spectral demultiplexer. We measured the raw heralded two-photon interference fringe visibility as 72 +/- 3%. This result agrees with our model, which includes device imperfections, spectral impurity and multi-pair emissions. We identify multi-pair emissions as the main factor limiting the nonclassical interference visibility, and show a route towards achieving near unity visibility in future experiments.