Infrared Ion-Photon Entanglement with a Metastable Strontium-Ion Qubit

Photonic interconnects are a promising method for linking remote ion trap quantum processors in a quantum network, with applications in quantum sensing and distributed quantum computing. Operating quantum networks in the low-loss infrared band of telecom fiber allows for easy integration with pre-existing fiber infrastructure. The strontium ion has an atomic transition near this band, at 1092 nm, eliminating the need for lossy photon conversion processes and making it an excellent candidate for direct quantum networking at the kilometer scale. In this talk, we present the design and characterization of a trapped-ion system using strontium for remote entanglement. The qubit states in our photon-generation scheme lie in the metastable D_3/2 level and differ by Δm_j=2 in magnetic quantum number. We report on results demonstrating ion-photon entanglement in this system including methods for coherent operations and electron shelving of the qubit. Additionally, a network of telecom fiber connecting our laboratory to other facilities in the Durham, NC downtown has been installed in the field. We show initial results for characterization of that network, especially regarding polarization stability, and discuss progress towards ion photon entanglement across kilometer length deployed fiber.