Fault-tolerant control of an error-corrected qubit
Fault-tolerant control of an error-corrected qubit
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DOI：
10.1038/s41586-021-03928-y
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发表时间：
2021-10-04
期刊：
影响因子：
64.8
通讯作者：
Monroe, Christopher
中科院分区：
文献类型：
--
作者：
Egan, Laird;Debroy, Dripto M.;Monroe, Christopher
量子纠错通过将脆弱的量子信息编码成更大的量子系统(1，2)来保护脆弱的量子信息。这些额外的自由度使得能够检测和纠正错误，但也增加了编码逻辑量子比特的控制复杂性。容错电路在控制逻辑量子比特的同时包含错误的传播，并且对于在实践中实现错误抑制是必不可少的(3-6)。虽然容错设计在原理上是可行的，但它以前还没有在具有本机噪声特性的纠错物理系统中得到验证。在这里，我们用13个俘获的离子量子比特实验演示了用于培根-肖尔逻辑量子比特的制备、测量、旋转和稳定器测量的容错电路。当我们将这些容错协议与非容错协议进行比较时，我们发现在存在噪声的情况下，逻辑原语的错误率显著降低。容错设计的结果是，经过离线误差修正后，平均状态准备和测量误差为0.6%，Clifford门误差为0.3%。此外，我们准备了保真度超过蒸馏阈值(7)的魔术状态，展示了通用容错控制所需的所有关键单量子比特成分。这些结果表明，容错电路能够在当前的量子系统中实现高精度的逻辑原语。通过改进的双量子比特门和使用中间测量，可以实现稳定的逻辑量子比特。
Quantum error correction protects fragile quantum information by encoding it into a larger quantum system(1,2). These extra degrees of freedom enable the detection and correction of errors, but also increase the control complexity of the encoded logical qubit. Fault-tolerant circuits contain the spread of errors while controlling the logical qubit, and are essential for realizing error suppression in practice(3-6). Although fault-tolerant design works in principle, it has not previously been demonstrated in an error-corrected physical system with native noise characteristics. Here we experimentally demonstrate fault-tolerant circuits for the preparation, measurement, rotation and stabilizer measurement of a Bacon-Shor logical qubit using 13 trapped ion qubits. When we compare these fault-tolerant protocols to non-fault-tolerant protocols, we see significant reductions in the error rates of the logical primitives in the presence of noise. The result of fault-tolerant design is an average state preparation and measurement error of 0.6 per cent and a Clifford gate error of 0.3 per cent after offline error correction. In addition, we prepare magic states with fidelities that exceed the distillation threshold(7), demonstrating all of the key single-qubit ingredients required for universal fault-tolerant control. These results demonstrate that fault-tolerant circuits enable highly accurate logical primitives in current quantum systems. With improved two-qubit gates and the use of intermediate measurements, a stabilized logical qubit can be achieved.