# Indistinguishable and efficient single photons from a quantum dot in a planar nanobeam waveguide

## TL;DR

This paper presents a highly efficient, on-chip source of indistinguishable single photons from a quantum dot in a nanophotonic waveguide, achieving high purity and indistinguishability suitable for quantum photonic applications.

## Contribution

It demonstrates a near-unity coupling efficiency and high photon indistinguishability using a planar nanobeam waveguide with advanced excitation and filtering techniques.

## Key findings

- Single-photon purity >99.4%
- Photon indistinguishability up to 94%
- Efficient off-chip photon coupling

## Abstract

We demonstrate a high-purity source of indistinguishable single photons using a quantum dot embedded in a nanophotonic waveguide. The source features a near-unity internal coupling efficiency and the collected photons are efficiently coupled off-chip by implementing a taper that adiabatically couples the photons to an optical fiber. By quasi-resonant excitation of the quantum dot, we measure a single-photon purity larger than 99.4% and a photon indistinguishability of up to 94+-1% by using p-shell excitation combined with spectral filtering to reduce photon jitter. A temperature-dependent study allows pinpointing the residual decoherence processes notably the effect of phonon broadening. Strict resonant excitation is implemented as well as another mean of suppressing photon jitter, and the additional complexity of suppressing the excitation laser source is addressed. The study opens a clear pathway towards the long-standing goal of a fully deterministic source of indistinguishable photons, which is integrated on a planar photonic chip.