Towards building and controlling large registers of ¹³³Ba⁺ trapped-ion qubits

The synthetic ¹³³Ba⁺ isotope has unique properties useful for trapped-ion quantum information processing. It offers long-lived magnetically-insensitive `clock' qubits in the 6S_1/2 and 5D_5/2 manifolds that can be manipulated with visible and near-IR light [1]. Thus, advanced qubit control schemes can be realised with high fidelity using off-the-shelf optics. We demonstrate an all-fibre Raman system using low noise lasers at 532nm, standard fibre modulators, and a custom laser-written waveguide beam delivery system.

Loading methods involving metallic barium, such as conventional electric ovens, are inappropriate for use with ¹³³Ba⁺. Its radioactive nature limits the maximum sample size, increasing its surface-to-mass ratio and speeding up the oxidation rate. Here we present our work towards loading ¹³³Ba⁺ by ablating barium salt targets. To build isotopically pure crystals, we load and then confirm the species of each ion before merging into a storage zone.

[1] D. Hucul, et al. Phys. Rev. Lett. 119, 100501 (2017).