Characterization of Qubit Control Pulse Distortions in Superconducting Quantum Hardware

Abstract

Input qubit control signals from an arbitrary waveform generator (AWG) operating at room temperature undergo linear dynamical distortions as it traverses various electrical components on the control line connecting to the quantum device.
If uncompensated for, such distortions can have detrimental effects on gate performance, affecting fidelity and even repeatability. Distortions introduced by components at room temperature (e.g., AWG bandwidth, high-pass filtering of a bias tee, and skin effect in instrumentation cable) are easily characterized using a fast oscilloscope. However, distortions introduced by components inside the refrigerator (e.g., low-pass filters, impedance mismatch, skin effect in semi-rigid coaxial cable, and chip packaging) are generally temperature-dependent and are thus best characterized in the cold. Additionally, the on-chip response varies across devices and even between different qubits on the very same device. Evidently, the ideal strategy for characterizing pulse distortion is to use the controlled qubit itself.
The aim of the thesis project is to implement the various, available protocols for the characterization of control pulse distortions on a superconducting quantum hardware and evaluate their individual performances.