On-Chip Hong-Ou-Mandel Interference from Separate Quantum Dot Emitters in an Integrated Circuit

Scalable quantum photonic technologies require the low-lossintegrationof many identical single-photon sources with photonic circuitry ona chip. Relatively complex quantum photonic circuits have alreadybeen demonstrated; however, sources used so far relied on parametricdown-conversion which has a probabilistic nature that intrinsicallylimits its efficiency and scalability. Quantum emitter-based single-photonsources are free of this limitation, but frequency matching of multipleemitters within a single circuit remains challenging. In this work,we demonstrate a key component in this regard in the form of a fullymonolithic GaAs circuit combining two frequency-matched quantum dotsingle-photon sources interconnected with a low-loss on-chip beamsplitterconnected via single-mode ridge waveguides. This device enabled usto perform a two-photon interference experiment on-chip with a visibilityreaching 66%. Our device could be further scaled up, providing a clearpath to increasing the complexity of quantum circuits toward fullyscalable integrated quantum technologies.