# Highly indistinguishable single photons from incoherently and coherently excited GaAs quantum dots

## TL;DR

This paper investigates the indistinguishability of single photons emitted by GaAs quantum dots under various excitation schemes, finding that phonon-assisted excitation yields high indistinguishability and practical advantages for quantum photonics.

## Contribution

It compares different excitation methods for GaAs quantum dots and demonstrates that phonon-assisted excitation achieves high photon indistinguishability with practical benefits.

## Key findings

- Conventional excitation shows poor indistinguishability due to a phonon bottleneck.
- Resonant and phonon-assisted excitation achieve over 90% indistinguishability.
- Optical phonon-assisted excitation allows laser rejection without reducing brightness.

## Abstract

Semiconductor quantum dots are converging towards the demanding requirements of photonic quantum technologies. Among different systems, quantum dots with dimensions exceeding the free-exciton Bohr radius are appealing because of their high oscillator strengths. While this property has received much attention in the context of cavity quantum electrodynamics, little is known about the degree of indistinguishability of single photons consecutively emitted by such dots and on the proper excitation schemes to achieve high indistinguishability. A prominent example is represented by GaAs quantum dots obtained by local droplet etching, which recently outperformed other systems as triggered sources of entangled photon pairs. On these dots, we compare different single-photon excitation mechanisms, and we find (i) a "phonon bottleneck" and poor indistinguishability for conventional excitation via excited states and (ii) photon indistinguishablilities above 90% for both strictly resonant and for incoherent acoustic- and optical-phonon-assisted excitation. Among the excitation schemes, optical phonon-assisted excitation enables straightforward laser rejection without a compromise on the source brightness together with a high photon indistinguishability.