Crosstalk and several sources of operational interference are invisible when qubit or a gate is calibrated or benchmarked in isolation. These are unlocked during the execution of full quantum circuit applying entangling gates to several qubits simultaneously. Unwanted Z-Z coupling on superconducting cross-resonance CNOT gates, is a commonly occurring unitary crosstalk noise that severely limits the state fidelity. This work presents (1) method of tracing unitary errors, which exploits their sensitivity to the arrangement of CNOT gates in the circuit and (2) correction scheme that modifies original circuit by inserting carefully chosen compensating gates (single- or two-qubit) to possibly undo unitary errors. On two vastly different types of IBMQ processors offering quantum volume 8 and 32, our experimental results show up to 25% reduction in the infidelity of [[7, 1, 3]] code |+> state. Our experiments aggressively deploy forced commutation of CNOT gates to obtain low noise state-preparation circuits. Encoded state initialized with fewer unitary errors marks an important step towards successful demonstration of fault-tolerant quantum computers.

中文翻译：

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用于校正相干噪声的量子电路工程

当量子位或门被隔离校准或基准测试时，串扰和几个操作干扰源是不可见的。这些在执行完整的量子电路期间解锁，同时将纠缠门应用于几个量子位。超导交叉谐振 CNOT 门上不需要的 ZZ 耦合是一种常见的单一串扰噪声，严重限制了状态保真度。这项工作提出了 (1) 跟踪单一错误的方法，它利用了它们对电路中 CNOT 门排列的敏感性和 (2) 通过插入精心选择的补偿门（单或两个量子位）来修改原始电路的校正方案可能会撤消单一错误。在提供量子卷 8 和 32 的两种截然不同类型的 IBMQ 处理器上，我们的实验结果表明 [[7, 1, 3]] 代码 |+> 状态的不忠减少了 25%。我们的实验积极部署 CNOT 门的强制换向以获得低噪声状态准备电路。以较少的单一错误初始化的编码状态标志着成功演示容错量子计算机的重要一步。