# A fiber coupled cavity QED source of identical single photons

## TL;DR

This paper presents a fiber-coupled quantum dot single-photon source with high purity, indistinguishability, and brightness, suitable for integration into quantum networks and quantum gates.

## Contribution

It introduces a novel micropillar cavity design and a fiber-based cross-polarization technique enabling high-quality single photons in a fiber-integrated setup.

## Key findings

- Purity of 97% achieved
- Indistinguishability of 90% demonstrated
- Brightness of 17% realized

## Abstract

A high-fidelity source of identical single photons is essential for numerous quantum technologies such as quantum repeaters and optical quantum information processing. Hallmarks thereof are a near-unity single-photon purity, near-unity indistinguishability of consecutively emitted photons, and high brightness through a near-unity number of photons per time bin. In order to embed such sources in quantum networks, optical fiber integration is essential but complicated by cryogenic compatability and noise. Here we demonstrate a resonantly pumped, quantum dot (QD) based, transmission operated, single-mode fiber coupled single photon source with a purity of 97%, indistinguishability of 90%, and a brightness of 17%. This is achieved by deploying a unique micropillar cavity design in a closed-cycle cryostat, which is operated using a through-fiber cross-polarization technique to remove the pump laser light from the resonantly scattered single photons. These results pave the way for fully fiber integrated photonic quantum networks, as our technology is equally applicable for cavity-QED based photonic quantum gates.