A key challenge in realizing practical quantum networks for long-distance quantum communication involves robust entanglement between quantum memory nodes connected via fiber optical infrastructure. Here, we demonstrate a two-node quantum network composed of multi-qubit registers based on silicon-vacancy (SiV) centers in nanophotonic diamond cavities integrated with a telecommunication (telecom) fiber network. Remote entanglement is generated via the cavity-enhanced interactions between the SiV's electron spin qubits and optical photons. Serial, heralded spin-photon entangling gate operations with time-bin qubits are used for robust entanglement of separated nodes. Long-lived nuclear spin qubits are used to provide second-long entanglement storage and integrated error detection. By integrating efficient bi-directional quantum frequency conversion of photonic communication qubits to telecom frequencies (1350 nm), we demonstrate entanglement of two nuclear spin memories through 40 km spools of low-loss fiber and a 35 km long fiber loop deployed in the Boston area urban environment, representing an enabling step towards practical quantum repeaters and large-scale quantum networks.
@article{arxiv.2310.01316,
title = {Entanglement of Nanophotonic Quantum Memory Nodes in a Telecom Network},
author = {Can M. Knaut and Aziza Suleymanzade and Yan-Cheng Wei and Daniel R. Assumpcao and Pieter-Jan Stas and Yan Qi Huan and Bartholomeus Machielse and Erik N. Knall and Madison Sutula and Gefen Baranes and Neil Sinclair and Chawina De-Eknamkul and David S. Levonian and Mihir K. Bhaskar and Hongkun Park and Marko Lončar and Mikhail D. Lukin},
journal= {arXiv preprint arXiv:2310.01316},
year = {2024}
}