发表机构
Alice & Bob; Laboratoire de Physique de l’École Normale Supérieure, Inria, ENS, Mines ParisTech, Université PSL, Sorbonne Université; RIKEN Center for Quantum Computing (RQC)（爱丽丝与鲍勃; 巴黎高等师范学院物理实验室、法国国家信息与自动化研究所、巴黎高等师范学院、巴黎矿业学院、巴黎文理研究大学、索邦大学; 理化学研究所量子计算中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文提出连续变量标志方法，通过辅助振荡器检测并纠正辅助量子比特衰减引起的连续误差，显著降低玻色子码逻辑错误率，为混合振荡器-量子比特处理器容错计算开辟新途径。
AI 中文摘要
玻色子量子纠错代表了实现容错量子计算中显著硬件开销降低的一条途径。然而，控制编码量子信息的量子谐振子本身也带来了挑战。在超导电路和捕获离子等许多平台中，玻色子自由度由一个辅助量子比特控制，该辅助量子比特在量子比特-振荡器门操作期间的衰减会作为连续误差传播到振荡器。这类误差通常超出了玻色子码能够纠正的误差范围。我们引入了连续变量标志：一个与辅助量子比特耦合的辅助振荡器，其相空间位置编码了污染存储模式的连续误差。在门操作之后，对标志的外差测量估计了这一连续变量误差，随后反馈控制将其抵消，直至玻色子码稳定子。该方案不需要新的组件，因为标志由与实现其要保护的门相同的色散耦合、位移和旋转驱动。我们构造了序列，用一个标志保护条件旋转到辅助量子比特衰减的所有阶，用一个标志保护条件位移到一阶，用两个标志保护到所有阶。使用现实电路量子电动力学参数的模拟预测，四分量猫码的奇偶校验测量的逻辑误差减少了三个数量级以上，并且有限能量高斯-克劳德态逻辑寿命接近其无噪声辅助量子比特界限。通过离散化连续变量误差，本工作中引入的标志对于任何混合振荡器-量子比特处理器都是有用的工具，并为玻色子模式的容错模拟和计算开辟了道路。
英文摘要
Bosonic quantum error correction represents a route towards significant hardware overhead reduction for fault-tolerant quantum computation. However, controlling quantum harmonic oscillators that encode the quantum information comes with its own challenges. In many platforms such as superconducting circuits and trapped ions, the bosonic degree of freedom is controlled by an ancillary qubit whose decay during a qubit-oscillator gate propagates to the oscillator as a continuous error. Such errors generally lie beyond the scope of errors that the bosonic code is capable of correcting. We introduce the continuous-variable flag: an auxiliary oscillator coupled to the ancilla whose phase-space position encodes the continuous error corrupting the storage mode. After the gate, a heterodyne measurement of the flag estimates this continuous-variable error and a subsequent feedback control undoes it up to a bosonic code stabilizer. The scheme requires no new ingredients, as the flag is driven by the same dispersive coupling, displacements and rotations that implement the gates it is supposed to protect. We construct sequences protecting conditional rotations to all orders in ancilla decay with one flag, and conditional displacements to first order with one flag and to all orders with two. Simulations with realistic circuit-QED parameters predict more than three orders of magnitude fewer logical errors for the parity measurement of a four-component cat code, and a finite-energy GKP logical lifetime near its noiseless-ancilla bound. By discretizing continuous-variable errors, the flags introduced in this work are a useful tool for any hybrid oscillator-qubit processor, and open the route towards fault-tolerant simulation and computation with bosonic modes.
Comments37 pages, 12 figures
