AI 中文总结
研究有偏噪声量子比特，基于保偏操作集合分析容错协议。无保偏 CX 门时，噪声偏差好处被抵消；有保偏 CX 门时，误差层次可反映在码结构中，还能实现魔术态制备。此外提出基于测量的架构，扩展开销降低范围。
AI 中文摘要
具有强偏置噪声的量子比特，其中相位翻转误差比比特翻转频繁几个数量级，自然存在于电子和核自旋中，也可通过工程手段实现，如稳定的猫态量子比特。这种噪声结构有望降低容错量子计算令人生畏的硬件开销，但利用它需要不将频繁相位翻转转换为罕见比特翻转的物理操作。在本综述中，我们根据此类保偏操作的可用集合，分析了用于有偏噪声量子比特的最突出的容错协议。当该集合限于 CZ 门以及在 X 基下的制备和测量时，我们表明所需的错误症候提取小工具的复杂性基本上抵消了噪声偏差的好处：在实验相关的错误率下，人们不妨忽略偏差并依赖为去极化噪声设计的标准纠错。当有保偏 CX 门可用时，情况会发生巨大变化：误差层次然后可以反映在码的结构中，频繁的相位翻转由专用的高阈值码校正，罕见的比特翻转通过与高速率码级联校正。相同的层次结构还实现了魔术态的硬件高效制备。最后，由于在自然有偏平台中禁止保偏 CX 门且在工程平台中具有挑战性，我们提出了一种基于测量的架构，其中多量子比特泡利 Z 算符的高保真量子非破坏读出取而代之，将这些开销降低扩展到更广泛的物理平台。
英文摘要
Qubits with strongly biased noise, in which phase-flip errors are orders of magnitude more frequent than bit-flips, arise both naturally, as in electron and nuclear spins, and by engineering, as in stabilized cat qubits. This noise structure holds the promise of reducing the daunting hardware overhead of fault-tolerant quantum computing, but exploiting it requires physical operations that do not convert frequent phase-flips into rare bit-flips. In this review, we analyze the most prominent fault-tolerant protocols for biased-noise qubits, organized according to the available set of such bias-preserving operations. When this set is restricted to the CZ gate together with preparation and measurement in the X basis, we show that the complexity of the required syndrome extraction gadgets essentially cancels the benefit of the noise bias: at experimentally relevant error rates, one may as well ignore the bias and rely on standard error correction designed for depolarizing noise. The situation changes drastically when a bias-preserving CX gate is available: the hierarchy of errors can then be reflected in the structure of the code, with frequent phase-flips corrected by a dedicated high-threshold code and rare bit-flips by concatenation with a high-rate code. The same hierarchy also enables hardware-efficient preparation of magic states. Finally, as a bias-preserving CX is forbidden in naturally biased platforms and challenging in engineered ones, we present a measurement-based architecture in which a high-fidelity quantum non-demolition readout of multi-qubit Pauli Z operators takes its place, extending these overhead reductions to a much broader range of physical platforms.
Comments27 pages, 26 figures
