Progress toward quantum networking with ⁴⁰Ca⁺ ions in a cryogenic surface-electrode trap with integrated fiber cavity

Quantum networks are a promising new infrastructure to accelerate scalability in quantum computing, remotely share entanglement, improve secure communication, and propel a wide range of distributed sensing applications. Trapped ions are nearly ideal stationary qubits in quantum network nodes because of their long coherence time, precise state preparation and control, and reconfigurable interconnectivity, while telecom-wavelength photons are an optimal choice for non-stationary qubits travelling between nodes with low loss. Here we show progress toward long-distance entanglement distribution between ion qubits in separate network nodes. We aim to integrate a fiber Fabry-Perot optical cavity into a surface-electrode ion trap to generate high-fidelity, high-rate entanglement between Ca⁺ ions and 854 nm photons, which are then coherently converted to 1550 nm photons by difference frequency generation. I will present our progress in evaluating and addressing the challenges of coherently controlling a trapped ion in an integrated ion trap/microcavity system at cryogenic temperatures.