Deterministic photon source of genuine three-qubit entanglement

• Published in: Nature communications 2024-09, Vol.15 (1), p.7774-7, Article 7774
• Main Authors: Meng, Yijian, Chan, Ming Lai, Nielsen, Rasmus B., Appel, Martin H., Liu, Zhe, Wang, Ying, Bart, Nikolai, Wieck, Andreas D., Ludwig, Arne, Midolo, Leonardo, Tiranov, Alexey, Sørensen, Anders S., Lodahl, Peter
• Format: Article
• Language: English
• Subjects: 639/766/483/3925; 639/766/483/481; Electron spin; Electrons; Emitters; Emitters (electron); Entangled states; Humanities and Social Sciences; multidisciplinary; Nuclear spin; Optics; Photonics; Photons; Quantum computing; Quantum dots; Quantum entanglement; Quantum optics; Qubits (quantum computing); Science; Science (multidisciplinary); Single electrons; Waveguides
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-024-52086-y

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 T 2 * ≃ 33 ns, which enables high-fidelity coherent optical spin rotations, and realize a spin-echo pulse sequence for sequential generation of spin-photon and spin-photon-photon entanglement. The emitted photons are highly indistinguishable, which is a key requirement for scalability and enables 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. Entanglement between single photons and solid-state emitters is a key component for photonic quantum computing and networks. Here, using a single electron spin in a quantum dot, the authors present a deterministic photon source achieving three-qubit entanglement of one electron spin and two photons.