# Truly unentangled photon pairs without spectral filtering

## TL;DR

This paper demonstrates an integrated silicon microring resonator capable of producing unentangled photon pairs with high purity, crucial for heralded single photon sources, by independently tuning quality factors to achieve near-perfect unentanglement.

## Contribution

It introduces a dual-channel interferometric coupling scheme that allows independent control of quality factors, enabling generation of nearly unentangled photon pairs without spectral filtering.

## Key findings

- Photon pairs with Schmidt number close to 1
- High purity heralded single photon states possible
- Efficient unentangled photon pair generation

## Abstract

We demonstrate that an integrated silicon microring resonator is capable of efficiently producing photon pairs that are completely unentangled; such pairs are a key component of heralded single photon sources. A dual-channel interferometric coupling scheme can be used to independently tune the quality factors associated with the pump and signal and idler modes, yielding a biphoton wavefunction with Schmidt number arbitrarily close to unity. This will permit the generation of heralded single photon states with unit purity.