标题： 多轮量子过程层析术：精度和准确性的提升 显示英文标题

标题： Multipass Quantum Process Tomography: Precision and Accuracy Enhancement

摘要： 我们引入一种方法，通过减轻状态制备和测量（SPAM）、读出和量子噪声引起的误差，来提高量子过程层析成像（QPT）的精度和准确性。与其仅对单个门进行QPT，我们提出对同一门的多次应用序列进行QPT。该方法涉及通过标准QPT测量多通过程的泡利转移矩阵（PTM），然后通过两种替代方法推导单通过程的PTM：一种是迭代方法，在理论上对于小误差可以得到精确结果；另一种是基于求解西尔维斯特方程的线性化方法。我们通过在IBM量子上使用ibmq_qasm_simulator的模拟来检验这两种方法的效率。与随机基准测试类型的 方法相比，所提出的方法提供整个PTM而不是一个单一数值（保真度）。与标准QPT相比，我们的方法由于大大减少了SPAM、读出和量子噪声误差，因此提供了更高精度和准确性的PTM。我们使用所提出的方法在量子处理器ibmq_manila（Falcon r5.11L）上实验确定CNOT门的PTM和保真度。 显示英文摘要

摘要： We introduce a method to enhance the precision and accuracy of Quantum Process Tomography (QPT) by mitigating the errors caused by state preparation and measurement (SPAM), readout and shot noise. Instead of performing QPT solely on a single gate, we propose performing QPT on a sequence of multiple applications of the same gate. The method involves the measurement of the Pauli transfer matrix (PTM) by standard QPT of the multipass process, and then deduce the single-process PTM by two alternative approaches: an iterative approach which in theory delivers the exact result for small errors, and a linearized approach based on solving the Sylvester equation. We examine the efficiency of these two approaches through simulations on IBM Quantum using ibmq_qasm_simulator. Compared to the Randomized Benchmarking type of methods, the proposed method delivers the entire PTM rather than a single number (fidelity). Compared to standard QPT, our method delivers PTM with much higher accuracy and precision because it greatly reduces the SPAM, readout and shot noise errors. We use the proposed method to experimentally determine the PTM and the fidelity of the CNOT gate on the quantum processor ibmq_manila (Falcon r5.11L).