A quantum-coherent photon-emitter interface in the original telecom band

Quantum dots have set benchmarks that far surpass other quantum emitters owing to their ability to deliver high-quality, high-rate and pure photons. However, achieving these exceptional capabilities at telecom wavelengths, bridging the gap to fibre-optic infrastructure and scalable silicon photonics, remains a challenge. Overcoming this difficulty demands high-quality quantum materials and devices that, despite extensive efforts, have not yet been realized. Here we demonstrate waveguide-integrated InAs quantum dots and realize a fully quantum-coherent photon-emitter interface operating in the original telecommunication band (or O-band, 1,260-1,360 nm). We record transform-limited linewidths only 8% broader than the inverse lifetime and bright 41.7-MHz emission rate under 80-MHz π-pulse excitation. These findings showcase the potential of quantum dots for scalable quantum networks.