Realization of a universal two-qubit register for a QCCD-based quantum processor

Single-qubit rotations and two-qubit entangling gates form a universal set of quantum operations. In this work, we realize such a two-qubit register compatible with the quantum CCD architecture. Quantum logic operations are implemented using embedded microwave conductors. Single-qubit gates in a two-ion crystal are performed by addressing each ion individually via a micromotion sideband [1]. The entanglement operation is implemented using an MS-type interaction, where we measure an infidelity approaching 10^-3 using partial state tomography. In addition, we characterize the single-qubit gates using a randomized benchmarking protocol and obtain an infidelity of 3.8(4)*10^-3. Finally, we characterize the quantum processor in a computational context using the cycle benchmarking protocol [3]. As a preliminary result, we obtain a composite process fidelity of 96.6(4)%.

    [1] U. Warring et al.,  Phys. Rev. Lett. 17, 173002 (2013)

    [2] M. Duwe et al., Quantum Sci. Technol. 7, 045005 (2022)

    [3] A. Erhard et al.,  Nat. Commun. 10, 5347 (2019)