Deterministic photon sources allow long-term advancements in quantum optics. A single quantum emitter embedded in a photonic resonator or waveguide may be triggered to emit one photon at a time into a desired optical mode. By coherently controlling a single spin in the emitter, multi-photon entanglement can be realized. We demonstrate a deterministic source of three-qubit entanglement based on a single electron spin trapped in a quantum dot embedded in a planar nanophotonic waveguide. We implement nuclear spin narrowing to increase the spin dephasing time to T2∗≃33 ns, which enables high-fidelity coherent optical spin rotations, and realize a spin-echo pulse sequence for sequential generation of high-fidelity spin-photon and spin-photon-photon entanglement. The emitted photons are highly indistinguishable, which is a key requirement for subsequent photon fusions to realize larger entangled states. This work presents a scalable deterministic source of multi-photon entanglement with a clear pathway for further improvements, offering promising applications in photonic quantum computing or quantum networks.
@article{arxiv.2310.12038,
title = {Deterministic photon source of genuine three-qubit entanglement},
author = {Yijian Meng and Ming Lai Chan and Rasmus B. Nielsen and Martin H. Appel and Zhe Liu and Ying Wang and Nikolai Bart and Andreas D. Wieck and Arne Ludwig and Leonardo Midolo and Alexey Tiranov and Anders S. Sørensen and Peter Lodahl},
journal= {arXiv preprint arXiv:2310.12038},
year = {2024}
}