Fast, high-fidelity addressed single-qubit gates using efficient composite pulse sequences

We use electronic microwave control methods to implement addressed single-qubit gates with high speed and fidelity, for ${}^{43}{\text{Ca}}^{+}$ hyperfine “atomic clock” qubits in a cryogenic (100K) surface trap. For a single qubit, we benchmark an error of $1.5$ $\times$ ${10}^{-6}$ per Clifford gate (implemented using $600\text{ ns}$ $\pi \mathrm{/}2$-pulses). For two qubits in the same trap zone (ion separation $5\mu \text{m}$), we use a spatial microwave field gradient, combined with an efficient 4-pulse scheme, to implement independent addressed gates. Parallel randomized benchmarking on both qubits yields an average error $3.4$ $\times$ ${10}^{-5}$ per addressed $\pi \mathrm{/}2$-gate. The scheme scales theoretically to larger numbers of qubits in a single register.