Entanglement of nanophotonic quantum memory nodes in a telecom network

TLDR

Robust entanglement between quantum memory nodes connected by fibre optical infrastructure is a key challenge for practical long‑distance quantum networks. The authors demonstrate a two‑node quantum network of multi‑qubit registers based on silicon‑vacancy centres in nanophotonic diamond cavities integrated with a telecommunication fibre network. Entanglement is generated via cavity‑enhanced interactions between SiV electron spin qubits and optical photons, using serial, heralded spin‑photon entangling gates with time‑bin qubits and long‑lived nuclear spin qubits for second‑long storage and error detection. Efficient bidirectional quantum frequency conversion to 1,350 nm enables entanglement of two nuclear spin memories over 40 km of low‑loss fibre and a 35‑km Boston‑area fibre loop, marking a step toward practical quantum repeaters and large‑scale networks.

Abstract

Abstract A key challenge in realizing practical quantum networks for long-distance quantum communication involves robust entanglement between quantum memory nodes connected by fibre optical infrastructure 1–3 . Here we demonstrate a two-node quantum network composed of multi-qubit registers based on silicon-vacancy (SiV) centres in nanophotonic diamond cavities integrated with a telecommunication fibre network. Remote entanglement is generated by the cavity-enhanced interactions between the electron spin qubits of the SiVs 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 bidirectional quantum frequency conversion of photonic communication qubits to telecommunication frequencies (1,350 nm), we demonstrate the entanglement of two nuclear spin memories through 40 km spools of low-loss fibre and a 35-km long fibre loop deployed in the Boston area urban environment, representing an enabling step towards practical quantum repeaters and large-scale quantum networks.