We entangle two co-trapped atomic barium ion qubits by collecting single visible photons from each ion through in-vacuo 0.8 NA objectives, interfering them through an integrated fiber-beamsplitter and detecting them in coincidence. This projects the qubits into an entangled Bell state with an observed fidelity lower bound of F > 94%. We also introduce an ytterbium ion for sympathetic cooling to remove the need for recooling interruptions and achieve a continuous entanglement rate of 250 1/s.
@article{arxiv.2404.16167,
title = {Fast photon-mediated entanglement of continuously-cooled trapped ions for quantum networking},
author = {Jameson O'Reilly and George Toh and Isabella Goetting and Sagnik Saha and Mikhail Shalaev and Allison Carter and Andrew Risinger and Ashish Kalakuntla and Tingguang Li and Ashrit Verma and Christopher Monroe},
journal= {arXiv preprint arXiv:2404.16167},
year = {2025}
}