Characterizing Control of Superconducting Qutrits by Randomized Benchmarking

We present experimental results for control of a qutrit implemented in the lowest three levels of a capacitively-shunted flux-biased superconducting circuit. Using randomized benchmarking over the qutrit Clifford group, we measure an average fidelity of 99.0 +/- 0.2% over the elements of the qutrit Clifford group. For a subset of this group, we characterize the fidelity using quantum process tomography and by observing the behaviour of repeated gate sequences. The gate decomposition used in this experiment can generate any unitary gate, given resonant control of two-level subspaces in the qutrit. Analysis of the results shows that errors are dominated by driving-induced level shifts, with leakage and decoherence playing a role as well. This work demonstrates a benchmark for high-fidelity control of qutrits, and outlines interesting avenues for future work on controlling single and multiple superconducting qudits.