Characterizing Coherent Errors using Matrix-Element Amplification

• URL: http://arxiv.org/abs/2404.12550v2
• Date: Tue, 03 Dec 2024 00:58:25 GMT
• Title: Characterizing Coherent Errors using Matrix-Element Amplification
• Authors: Jonathan A. Gross, Elie Genois, Dripto M. Debroy, Yaxing Zhang, Wojciech Mruczkiewicz, Ze-Pei Cian, Zhang Jiang,
• Abstract summary: Matrix-Element Amplification using Dynamical Decoupling (MEADD)<n>We experimentally demonstrate that MEADD surpasses the accuracy and precision of existing characterization protocols for estimating systematic errors in single- and two-qubit gates.<n>We also use it to characterize coherent crosstalk in the processor which was previously too small to detect reliably.
• Score: 0.27907340310431333
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Repeating a gate sequence multiple times amplifies systematic errors coherently, making it a useful tool for characterizing quantum gates. However, the precision of such an approach is limited by low-frequency noises, while its efficiency hindered by time-consuming scans required to match up the phases of the off-diagonal matrix elements being amplified. Here, we overcome both challenges by interleaving the gate of interest with dynamical decoupling sequences in a protocol we call Matrix-Element Amplification using Dynamical Decoupling (MEADD). Using frequency-tunable superconducting qubits from a Google Sycamore quantum processor, we experimentally demonstrate that MEADD surpasses the accuracy and precision of existing characterization protocols for estimating systematic errors in single- and two-qubit gates. In particular, MEADD yields factors of 5 to 10 improvements in estimating coherent parameters of the $\mathrm{CZ}$ gates compared to existing methods, reaching a precision below one milliradian. We also use it to characterize coherent crosstalk in the processor which was previously too small to detect reliably.

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