We integrate a long-lived memory qubit into a mixed-species trapped-ion quantum network node. Ion-photon entanglement first generated with a network qubit in Sr-88 is transferred to Ca-43 with 0.977(7) fidelity, and mapped to a robust memory qubit. We then entangle the network qubit with a second photon, without affecting the memory qubit. We perform quantum state tomography to show that the fidelity of ion-photon entanglement decays ~70 times slower on the memory qubit. Dynamical decoupling further extends the storage duration; we measure an ion-photon entanglement fidelity of 0.81(4) after 10s.
@article{arxiv.2210.11447,
title = {Robust Quantum Memory in a Trapped-Ion Quantum Network Node},
author = {P. Drmota and D. Main and D. P. Nadlinger and B. C. Nichol and M. A. Weber and E. M. Ainley and A. Agrawal and R. Srinivas and G. Araneda and C. J. Ballance and D. M. Lucas},
journal= {arXiv preprint arXiv:2210.11447},
year = {2023}
}