On-chip interference of single photons from an embedded quantum dot and an external laser

TL;DR

This paper demonstrates on-chip two-photon interference between a quantum dot and an external laser, using a directional coupler to assess photon indistinguishability and device performance in a quantum photonic circuit.

Contribution

It introduces an integrated on-chip method for observing two-photon interference between dissimilar sources, combining quantum dot emission and laser light.

Findings

Successful on-chip Hong-Ou-Mandel interference verification

Use of classical laser to evaluate quantum device performance

Assessment of quantum dot photon indistinguishability

Abstract

In this work, we demonstrate the on-chip two-photon interference between single photons emitted by a single self-assembled InGaAs quantum dot and an external laser. The quantum dot is embedded within one arm of an air-clad directional coupler which acts as a beam-splitter for incoming light. Photons originating from an attenuated external laser are coupled to the second arm of the beam-splitter and then combined with the quantum dot photons, giving rise to two-photon quantum interference between dissimilar sources. We verify the occurrence of on-chip Hong-Ou-Mandel interference by cross-correlating the optical signal from the separate output ports of the directional coupler. This experimental approach allows us to use classical light source (laser) to assess in a single step the overall device performance in the quantum regime and probe quantum dot photon indistinguishability on application realistic time scales.