Quantum Networking with Trapped ⁸⁸Sr⁺ and ⁴³Ca⁺ Ions

By interfering photons from two network nodes separated by 2 m, we create remote entanglement between two ⁸⁸Sr⁺ ions with 96.9(1)% fidelity at a rate of ∼100 s⁻¹. This remote entanglement enabled demonstrations of device-independent quantum key distribution [1] and a network of entangled optical atomic clocks [2]. Additionally, the integration of robust quantum memory qubits in ⁴³Ca⁺ [3] has enabled demonstrations of distributed quantum computing [4] and deterministic and verifiable blind quantum computing through adaptive polarisation measurements [5]. Here, we present extensions of the distributed quantum computing architecture, with applications in quantum error detection, entanglement distillation, and a 200-m network link. We also show remote entanglement storage for up to 10 s, and a variety of remotely entangled states that we create between the modules.

[1] D. P. Nadlinger et al., Nature 607, 682-686 (2022)

[2] B. C. Nichol et al., Nature 609, 689-694 (2022)

[3] P. Drmota et al., Phys. Rev. Lett. 130, 090803 (2023)

[4] D. Main et al., Nature, accepted for publication (2025)

[5] P. Drmota et al., Phys. Rev. Lett. 132, 150604 (2024)