探测$^{28}$Si/SiGe自旋量子比特退相干甜点处的残余噪声
Probing Residual Noise at a Decoherence Sweet Spot in a $^{28}$Si/SiGe Spin Qubit
查看机构详情
- Seoul National University（首尔国立大学）
- The University of Tokyo（东京大学）
- Delft University of Technology（代尔夫特理工大学）
机构由 AI 辅助整理，请以论文原文为准。
浏览论文内容
中文总结 AI 辅助
该研究通过比较同一器件中甜点与非甜点位置的量子比特，发现甜点处残余频率噪声接近$^{29}$Si核自旋噪声预测水平，且电荷噪声转换被显著抑制，从而大幅提升相干时间。
中文摘要 AI 辅助
在带有微磁体的$^{28}$Si/SiGe自旋量子比特中，纵向杂散场梯度将电荷噪声转换为量子比特频率噪声并限制相干性。我们比较了同一器件中两个相邻的量子比特，其残余$^{29}$Si浓度为800 ppm，一个位于退相干甜点附近（梯度局部最小化），另一个位于梯度较大的位置。在甜点处，$T_2^*$达到67 $\mu\mathrm{s}$，Carr-Purcell-Meiboom-Gill相干时间达到4.6 ms，而相邻量子比特的$T_2^*$为5.2 $\mu\mathrm{s}$。在接近1 Hz时，甜点处的频率噪声功率谱密度比相邻量子比特低近两个数量级。残余频谱的幅度和低频衰减与$^{29}$Si核自旋噪声的预测相符，而量子比特间较弱的互相关性表明，在甜点处局域噪声对退相干变得重要。尽管与电荷传感器存在有限的相关性，甜点操作显著降低了电荷噪声的转换，使残余频率噪声接近$^{29}$Si核自旋涨落预测的水平。
英文摘要
In $^{28}$Si/SiGe spin qubits with micromagnets, the longitudinal stray field gradient transduces charge noise into qubit frequency noise and limits coherence. We compare two neighboring qubits in the same device with 800 ppm residual $^{29}$Si, one near a decoherence sweet spot where the gradient is locally minimized and the other at a position with a larger gradient. At the sweet spot, $T_2^*$ reaches 67 $μ\mathrm{s}$ and the Carr-Purcell-Meiboom-Gill coherence time reaches 4.6 ms, whereas $T_2^*$ is 5.2 $μ\mathrm{s}$ at the neighboring qubit. Near 1 Hz, the frequency noise power spectral density at the sweet spot is nearly two orders of magnitude lower than at the neighboring qubit. The magnitude and low-frequency decay of the residual spectrum are compatible with the prediction for $^{29}$Si nuclear spin noise, and the weak interqubit correlation indicates that local noise becomes important for dephasing at the sweet spot. Despite a finite correlation with the charge sensor, sweet-spot operation strongly reduced the transduction of charge noise, bringing the residual frequency noise close to the level predicted for $^{29}$Si nuclear spin fluctuations.
