从双量子比特系统的腔发射中重构噪声关联谱密度
Reconstruction of the noise correlation spectral density from the cavity emission in a two-qubit system
AI总结：
研究双量子比特系统中噪声关联问题，通过描述腔耦合量子比特动力学，利用腔发射表征噪声关联，给出不同噪声情况及谱密度重构方法，还提出未知噪声类型时提取谱密度的方法。
AI中文摘要：
大规模容错量子计算领域面临的重大挑战是噪声影响。除了噪声对单个量子比特的影响，噪声关联的较小附加效应也很重要，因为相关误差对量子纠错构成挑战。我们描述了受相关噪声影响的两个腔耦合量子比特的动力学，假设量子比特受纵向噪声影响且无直接耦合。发现腔发射能表征噪声关联，描述了白噪声、准静态噪声和奥恩斯坦 - 乌伦贝克噪声的情况。对于已知频谱，通过对多种不同噪声实现进行平均，可从腔发射中重构噪声关联谱密度。证明了在白噪声情况下，噪声关联效应与腔 - 量子比特耦合常数的五次方成正比，比准静态噪声情况（与耦合常数的三次方成正比）受到更强抑制。还提出了一种在潜在噪声类型未知时从腔发射中提取噪声关联谱密度的方法，可通过应用卷积定理实现。
英文摘要：
A significant challenge in the field of large-scale fault-tolerant quantum computation is the influence of noise. In addition to the influence of noise on individual qubits, the smaller additional effect of noise correlations is also of high significance because correlated errors pose a challenge for quantum error correction. We describe the dynamics of two cavity-coupled qubits that are subject to correlated noise, assuming that the qubits are affected by longitudinal noise and not coupled directly. We find that the cavity emission enables the characterization of the noise correlations and describe the cases of white noise, quasi-static noise, and Ornstein-Uhlenbeck noise. For a known frequency spectrum, the reconstruction of the noise correlation spectral density from the cavity emission is possible by averaging over many different noise realizations. We demonstrate that, in the case of white noise, the noise correlation effects scale with the fifth order of the cavity-qubit coupling constant and are thus strongly suppressed compared with the case of quasi-static noise, where they scale with the third order. Furthermore, we present a method for extracting the noise correlation spectral density from the cavity emission in the case where the underlying noise type remains unidentified. This can be achieved by applying the convolution theorem.
