论文标题

连贯的保利检查减轻单次错误

Single-shot error mitigation by coherent Pauli checks

论文作者

Berg, Ewout van den, Bravyi, Sergey, Gambetta, Jay M., Jurcevic, Petar, Maslov, Dmitri, Temme, Kristan

论文摘要

从量子电路的输出分布中生成样品是一项无处不在的任务,用作许多量子算法的构件。在这里,我们展示了如何在缺少Clifford Gates主导的特殊类别量子电路的嘈杂量子处理器上完成此任务。我们的方法是基于连贯的Pauli检查(CPC),该检查通过验证随机的Pauli-Type检查操作员和所考虑的电路之间的换向规则来检测Clifford电路中的错误。我们的主要贡献如下。首先,我们得出了一个简单的公式,即受CPC保护的Clifford电路包含逻辑误差的概率。在大量检查的限制中,逻辑错误概率显示为接近值$ {\ ot}7εn/5 $,其中$ n $是Qubits的数量,而$ε$是去极化错误率。我们的公式几乎与数值模拟结果完全吻合。其次,我们证明CPC非常适合具有有限量子连接性的量子处理器。例如,全能和线性量子置换连接之间的差异仅增加了实现CPC所需的CNOT门数3倍。第三,我们描述了简化的单方面CPC,非常适合减轻单一设置中的测量误差。最后,我们报告了具有多达10个逻辑QPIT和100多个逻辑CNOT门的CPC的实验证明。我们的实验结果表明,CPC为考虑对量子电路的输出分布的考虑任务的逻辑误差概率提供了明显的改善。

Generating samples from the output distribution of a quantum circuit is a ubiquitous task used as a building block of many quantum algorithms. Here we show how to accomplish this task on a noisy quantum processor lacking full-blown error correction for a special class of quantum circuits dominated by Clifford gates. Our approach is based on Coherent Pauli Checks (CPCs) that detect errors in a Clifford circuit by verifying commutation rules between random Pauli-type check operators and the considered circuit. Our main contributions are as follows. First, we derive a simple formula for the probability that a Clifford circuit protected by CPCs contains a logical error. In the limit of a large number of checks, the logical error probability is shown to approach the value ${\approx}7εn/5$, where $n$ is the number of qubits and $ε$ is the depolarizing error rate. Our formula agrees nearly perfectly with the numerical simulation results. Second, we show that CPCs are well-suited for quantum processors with a limited qubit connectivity. For example, the difference between all-to-all and linear qubit connectivity is only a 3X increase in the number of CNOT gates required to implement CPCs. Third, we describe simplified one-sided CPCs which are well-suited for mitigating measurement errors in the single-shot settings. Finally, we report an experimental demonstration of CPCs with up to 10 logical qubits and more than 100 logical CNOT gates. Our experimental results show that CPCs provide a marked improvement in the logical error probability for the considered task of sampling the output distribution of quantum circuits.

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