Fig. 3: Apparatus and performance.

a Schematic representation of the trapped-ion QC. The qubit register is implemented in a linear chain of \(^{171}\)Yb\(^{+}\) ions residing inside an ultra-high vacuum chamber (not shown), and high-NA imaging optics enable individual addressing and readout of the ion qubits. The Raman beams (shown in red and purple) are generated from a pulsed laser at 355 nm and drive a two-photon transition between \(\left|0\right\rangle\) and \(\left|1\right\rangle\). Full control of the amplitude, frequency, and phase of the individual addressing beams enables implementations of arbitrary single- and two-qubit operators. b SPAM characterization on a three-ion chain. From top to bottom, we show the SPAM error of each three-qubit state, the per-qubit SPAM error for \(\left|0\right\rangle\) and \(\left|1\right\rangle\), and a bar plot of the full SPAM matrix where the color is log-scaled for visibility. We see no indication of measurement crosstalk between qubits. c Characterization of the small-angle XX(\(\theta\)) gate performance. The state fidelity after 50 consecutive small-angle XX gates is \(\approx 78 \%\), and we estimate the per-gate error to be \(\epsilon \lesssim \ 4\times 10^{-3}\).