Characterization of control in a superconducting qutrit using randomized benchmarking

Abstract

We characterize control of a qutrit implemented in the lowest three energy levels of a capacitively shunted flux-biased superconducting circuit. Randomized benchmarking over the qutrit Clifford group yields an average fidelity of 98.89±0.05%. For a selected subset of the Clifford group, we perform quantum process tomography and observe the behavior of repeated gate sequences. Each qutrit gate is generated using only two-state rotations via a method applicable to any unitary. We find that errors are due primarily to decoherence and have a significant contribution from level shifts. This work demonstrates high-fidelity qutrit control and outlines avenues for future work on the optimal control of superconducting qudits.