# High efficiency 'plug & play' source of heralded single photons

## TL;DR

This paper presents a compact, stable, and alignment-free photon pair source in the telecom band that maintains high heralding efficiency and brightness, suitable for real-world quantum applications without the need for alignment.

## Contribution

It introduces a 'plug & play' waveguide-based photon source with over 50% heralding efficiency that is easy to integrate with fiber networks and operable outside laboratory settings.

## Key findings

- Heralding efficiency > 50% after fiber pigtailing
- High brightness and spectral tunability
- Operates without alignment outside lab environment

## Abstract

Reliable generation of single photons is of key importance for fundamental physical experiments and to demonstrate quantum technologies. Waveguide-based photon pair sources have shown great promise in this regard due to their large degree of spectral tunability, high generation rates and long photon coherence times. However, for such a source to have real world applications it needs to be efficiently integrated with fiber-optic networks. We answer this challenge by presenting an alignment-free source of photon pairs in the telecommunications band that maintains heralding efficiency > 50 % even after fiber pigtailing, photon separation, and pump suppression. The source combines this outstanding performance in heralding efficiency and brightness with a compact, stable, and easy-to-use 'plug & play' package: one simply connects a laser to the input and detectors to the output and the source is ready to use. This high performance can be achieved even outside the lab without the need for alignment which makes the source extremely useful for any experiment or demonstration needing heralded single photons.