Precision gate characterization in the presence of low-frequency noise on a superconducting processor

Coherent amplification, the primary tool for precision quantum estimation, remains elusive for many tasks because the necessary coherence is scrambled by noise processes. One such noise process in superconducting-qubit platforms is flux noise, which causes slow fluctuations of the qubit frequency. In addition to making the qubit frequency itself ill defined for estimation purposes, these fluctuations mask deviations in other well-defined parameters in the system. We present a characterization technique that allows us to precisely target select unitary parameters for controlled-Z gates in the presence of such low-frequency noise, obtaining up to 20 times precision improvement in these parameters. The simplicity and directness of this method makes it a robust and reliable tool for precision characterization of noisy quantum devices.