# Time-domain characterization and correction of on-chip distortion of control pulses in a quantum processor

## TL;DR

This paper presents Cryoscope, a method for characterizing and correcting on-chip control pulse distortions in quantum processors, enhancing the fidelity of qubit operations through real-time digital filtering.

## Contribution

Cryoscope enables precise measurement of control pulse distortions and introduces a correction technique to improve quantum gate fidelity in superconducting qubits.

## Key findings

- Cryoscope accurately samples on-chip control pulses with high temporal resolution.
- Iterative filtering significantly reduces control line distortions.
- Enhanced gate fidelity achieved through distortion correction.

## Abstract

We introduce Cryoscope, a method for sampling on-chip baseband pulses used to dynamically control qubit frequency in a quantum processor. We specifically use Cryoscope to measure the step response of the dedicated flux control lines of two-junction transmon qubits in circuit QED processors with the temporal resolution of the room-temperature arbitrary waveform generator producing the control pulses. As a first application, we iteratively improve this step response using optimized real-time digital filters to counter the linear-dynamical distortion in the control line, as needed for high-fidelity, repeatable one- and two-qubit gates based on dynamical control of qubit frequency.