Improving quantum gate fidelities by using a qubit to measure microwave pulse distortions

TL;DR

This paper introduces a method using a qubit to detect and correct microwave pulse distortions, significantly enhancing the fidelity of single-qubit gates in superconducting qubits.

Contribution

A novel technique for reconstructing and compensating microwave pulse distortions to improve quantum gate fidelity in superconducting qubits.

Findings

Achieved single-qubit gate fidelity above 99.8%

Demonstrated effective pulse shape correction using qubit-based measurements

Enhanced gate performance by compensating microwave pulse distortions

Abstract

We present a new method for determining pulse imperfections and improving the single-gate fidelity in a superconducting qubit. By applying consecutive positive and negative $\pi$ pulses, we amplify the qubit evolution due to microwave pulse distortion, which causes the qubit state to rotate around an axis perpendicular to the intended rotation axis. Measuring these rotations as a function of pulse period allows us to reconstruct the shape of the microwave pulse arriving at the sample. Using the extracted response to predistort the input signal, we are able to improve the pulse shapes and to reach an average single-qubit gate fidelity higher than 99.8%.