In-situ characterization of microwave pulse distortions using a superconducting qubit

Unaccounted pulse distortions in the qubit control lines lead to coherent errors that can limit the fidelity of diverse quantum operations. These distortions are due to frequency-dependent attenuations in the lines and to the presence of non-ideal components such as microwave filters, attenuators, and IQ-mixers. Here, we characterize the full transfer function capturing these distortions using the transmon qubit as an in-situ probe for the microwave fields it receives. Following this characterization, we show that we can deconvolve the microwave controls in software and account for more than 99 percent of these distortions. Using a set of simple but carefully designed qubit experiments, we can additionally characterize the IQ-mixer transfer function individually and use it to accurately deconvolve our controls using different local oscillator frequencies without needing further calibrations. Such an efficient and scalable characterization protocol will be essential in achieving rapid, coherence-limited microwave operations in large quantum devices.