用于噪声偏置量子计算的耗散稳定0-n Fock量子比特
Dissipatively Stabilized 0-n Fock Qubits for Noise-Biased Quantum Computing
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中文总结 AI 辅助
该研究提出耗散稳定的0-n Fock量子比特架构，通过非线性多能级系统编码信息维持噪声偏置，可实现极低比特翻转概率，在重复码中仅d=9即可达到兆量子位级逻辑错误率，助力噪声偏置量子计算发展。
中文摘要 AI 辅助
噪声偏置量子比特的比特翻转错误相对相位翻转错误呈指数级抑制，为容错量子计算提供了有前景的途径。然而，在使用非偏置控制量子比特进行门操作时，这种偏置可能会受损。为解决这一局限，我们提出一种“0-n”Fock量子比特架构，该架构通过在非线性多能级系统（如transmon）的基态和第n激发态中编码信息，维持噪声偏置。这种编码通过耗散稳定实现，该稳定分别对较低和较高中间能级起衰减和增益作用。我们首先通过分析证明，比特翻转错误随能级数量呈指数级抑制。接着，我们提出一种利用多模损耗滤波器实现频率选择性耗散的实际方案。最后，我们通过数值模拟证明，在实际实验参数下，当n≥9（即十个或更多能级）时，使用0-n量子比特作为辅助比特对猫量子比特执行受控-X门，可实现接近10⁻⁸的比特翻转概率。在此基础上，我们对重复码中的校正子提取进行模拟，在仅距离d=9的情况下，达到了兆量子位（megaquop）范围内的逻辑错误率。
英文摘要
Noise-biased qubits have bit-flip errors that are exponentially suppressed relative to phase-flip errors, and offer a promising route toward fault-tolerant quantum computing. However, this bias can be compromised during gate operations with non-biased control qubits. To address this limitation, we propose a "0-n" Fock qubit architecture that maintains the noise bias by encoding information in the ground state and n-th excited state of a nonlinear multi-level system, such as a transmon. This encoding is achieved via a dissipative stabilization that acts as decay and gain for lower and upper intermediate levels, respectively. We first analytically demonstrate that bit-flip errors are exponentially suppressed with the number of levels. Then, we present a practical implementation using a multi-mode lossy filter to achieve the frequency-selective dissipation. Finally, we numerically demonstrate that bit-flip probabilities approaching $10^{-8}$ are achievable for controlled-X gates on cat qubits using the 0-n qubit as an ancilla with $n \geq 9$ (i.e. ten or more levels), for realistic experimental parameters. Building on this, we simulate syndrome extraction in a repetition code, achieving logical error rates in the megaquop regime with only a distance of $d=9$.
