High-Fidelity Two-Qubit Gates in a Surface Ion Trap*

Microfabricated surface traps are capable of supporting a variety of exotic trapping geometries and provide a scalable system for trapped ion Quantum Information Processing (QIP). However, the feasibility of using surface traps for QIP has long been a point of contention because the close proximity of the ions to trap electrodes increases heating rates and might lead to laser-induced charging of the trap. As surface traps continue to evolve at a remarkable rate, their performance is rapidly approaching that of macroscopic electrode traps. Using Sandia's High-Optical-Access surface trap, we demonstrate robust single-qubit gates, both laser- and microwave-based. Our gates are accurately characterized by Gate Set Tomography (GST) and we report the first diamond norm measurements near the fault-tolerance threshold\footnote{P. Aliferis and A. W. Cross, Phys. Rev. Lett. 98, 220502 (2007)}. Extending these techniques, we've realized a M{\o}lmer-S{\o}rensen two-qubit gate\footnote{A. S{\o}rensen and K. M{\o}lmer, Phys. Rev. Lett. 82, 1971 (1999)} that is stable for several hours. This stability has allowed us to perform the first GST measurements of a two-qubit gate, yielding a \textit{process} fidelity of 99.58(6){\%}.