Fault-tolerant quantum coding Noise and imperfections in a quantum system can result in the presence and propagation of errors through the system. A reliable quantum processor will need to be able to correct for these errors and error syndromes. Rosenblum et al. used higher quantum states of a superconducting-based quantum circuit to demonstrate a method for the fault-tolerant measurement of an error-correctable logical qubit. Such fault-tolerant measurements will allow more frequent interrogations of the state of the logical qubit, ultimately leading to the implementation of more quantum operations and more complex entangled quantum circuits. Science, this issue p. 266 A fault-tolerant measurement protocol is demonstrated with an error-correctable logical qubit. A critical component of any quantum error–correcting scheme is detection of errors by using an ancilla system. However, errors occurring in the ancilla can propagate onto the logical qubit, irreversibly corrupting the encoded information. We demonstrate a fault-tolerant error-detection scheme that suppresses spreading of ancilla errors by a factor of 5, while maintaining the assignment fidelity. The same method is used to prevent propagation of ancilla excitations, increasing the logical qubit dephasing time by an order of magnitude. Our approach is hardware-efficient, as it uses a single multilevel transmon ancilla and a cavity-encoded logical qubit, whose interaction is engineered in situ by using an off-resonant sideband drive. The results demonstrate that hardware-efficient approaches that exploit system-specific error models can yield advances toward fault-tolerant quantum computation.

中文翻译：

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量子错误的容错检测

容错量子编码 量子系统中的噪声和缺陷会导致错误的存在和通过系统传播。一个可靠的量子处理器需要能够纠正这些错误和错误综合症。罗森布鲁姆等人。使用基于超导的量子电路的更高量子态来演示一种对可纠错逻辑量子位进行容错测量的方法。这种容错测量将允许更频繁地询问逻辑量子位的状态，最终导致实现更多的量子操作和更复杂的纠缠量子电路。科学，这个问题 p。266 使用可纠错逻辑量子位演示了容错测量协议。任何量子纠错方案的一个关键组成部分是使用辅助系统检测错误。然而，发生在辅助装置中的错误会传播到逻辑量子位上，不可逆转地破坏编码信息。我们展示了一种容错错误检测方案，可将辅助错误的传播抑制 5 倍，同时保持分配保真度。相同的方法用于防止辅助激发的传播，将逻辑量子位移相时间增加一个数量级。我们的方法是硬件高效的，因为它使用单个多级 transmon ancilla 和腔编码逻辑量子位，其交互是通过使用非谐振边带驱动器原位设计的。