Efficient characterization of noise during quantum gate operations is an essential step to building and scaling up a quantum computer. One such protocol is averaged circuit eigenvalue sampling (ACES) which efficiently characterizes a noisy gate set by reconstructing a Pauli noise model for a each gate. Here we utilize the ACES protocol to characterize two coupled superconducting qubits. For accurate reconstruction, we tailor the noise via Pauli twirling and account for measurement errors. We verify the accuracy of the protocol by comparing the predicted gate fidelities to that extracted from conventional benchmarking approaches, such as interleaved randomized benchmarking. Furthermore, we demonstrate the efficacy of ACES in accurately identifying specific noise sources by reconstructing injected phase errors in the two-qubit gates.
Characterizing quantum channels from local-unitary invariants
Institute for Quantum Inspired and Quantum Optimization, Hamburg University of Technology（汉堡工业大学量子启发与量子优化研究所）；University of Tsukuba（筑波大学）；Center for Artificial Intelligence Research (C-AIR), University of Tsukuba（筑波大学人工智能研究中心）
Strongly trapped space-inhomogeneous quantum walks in one dimension
定域化是一维空间非均匀量子行走的一个特征现象，其中粒子保持在其初始位置附近。时间演化算子特征值的存在是局部化发生的充分必要条件，其相关特征向量与局部化量有着深刻的关系，即，步行者在长时间限制内停留在起始位置附近的概率。在作者先前的研究中，使用转移矩阵研究了具有一个缺陷的两相量子行走的本征值，该转移矩阵专注于局域化的发生（Quantum Inf. Process 20（5），2021）。在本文中，我们介绍了分析方法来计算本征向量使用的传输矩阵，也扩展了我们的结果来表征本征值不仅为两相量子行走的一个缺陷，但也为更一般的空间非均匀模型。利用这些结果，我们定量地评估本地化和研究强捕获性能，通过推导的时间平均极限分布的五个模型研究以前。
