High fidelity manipulation of a qubit built from a synthetic nucleus

Abstract

The recently demonstrated trapping and laser cooling of ${}^{133}$Ba${}^{+}$ has opened the door to the use of this nearly ideal atom for quantum information processing. However, before high fidelity qubit operations can be performed, a number of unknown state energies are needed. Here, we report measurements of the ${}^2$P${}_{3/2}$ and ${}^2$D${}_{5/2}$ hyperfine splittings, as well as the ${}^2$P${}_{3/2}$$\leftrightarrow$ ${}^2$S${}_{1/2}$and ${}^2$P${}_{3/2}$ $\leftrightarrow$ ${}^2$D${}_{5/2}$ transition frequencies. Using these transitions, we demonstrate high fidelity ${}^{133}$Ba${}^{+}$ hyperfine qubit manipulation with electron shelving detection to benchmark qubit state preparation and measurement (SPAM). Using single-shot, threshold discrimination, we measure an average SPAM fidelity of $\mathcal{F}=0.99971(6)$, a factor of $\approx$ 2 improvement over the best reported performance of any qubit.