Calibration of Drive Non-Linearity for Arbitrary-Angle Single-Qubit Gates Using Error Amplification

TL;DR

This paper introduces a measurement-based method to calibrate and correct non-linear distortions in single-qubit gate control lines, significantly improving gate fidelity by addressing drive non-linearity effects.

Contribution

The work presents a novel error amplification technique for characterizing and correcting drive non-linearity in quantum gates, applicable across different hardware setups.

Findings

Control errors reach 2×10⁻⁴, accounting for half of total gate error.

Arbitrary-angle single-qubit gates achieved with coherence-limited errors of 2×10⁻⁴.

Leakage below 6×10⁻⁵ demonstrates high gate fidelity.

Abstract

The ability to execute high-fidelity operations is crucial to scaling up quantum devices to large numbers of qubits. However, signal distortions originating from non-linear components in the control lines can limit the performance of single-qubit gates. In this work, we use a measurement based on error amplification to characterize and correct the small single-qubit rotation errors originating from the non-linear scaling of the qubit drive rate with the amplitude of the programmed pulse. With our hardware, and for a 15-ns pulse, the rotation angles deviate by up to several degrees from a linear model. Using purity benchmarking, we find that control errors reach $2\times 10^{-4}$, which accounts for half of the total gate error. Using cross-entropy benchmarking, we demonstrate arbitrary-angle single-qubit gates with coherence-limited errors of $2\times 10^{-4}$ and leakage below $6\times 10^{-5}$. While the exact magnitude of these errors is specific to our setup, the presented method is applicable to any source of non-linearity. Our work shows that the non-linearity of qubit drive line components imposes a limit on the fidelity of single-qubit gates, independent of improvements in coherence times, circuit design, or leakage mitigation when not corrected for.