AI 中文总结
研究在 p 轨道-谷谱中编码量子比特，利用谷-轨道耦合实现单比特控制，找到对电荷噪声不敏感的‘甜点’，估计相关参数，还表明可通过磁场诱导甜点，且双量子比特门可电调，为可扩展量子计算提供新途径。
AI 中文摘要
我们提出在由各向异性量子点激发谷中的最低 p 轨道态和基态谷中的激发 p 轨道所跨越的两能级子空间中编码一个量子比特，我们将其称为 pOv 量子比特。由于合金无序引起的谷-轨道耦合（VOC），这些态之间存在避免交叉，可通过对量子点各向异性的基带电控制实现完整的单量子比特控制。我们发现特定量子点取向存在‘甜点’，其瞬时本征态对电荷噪声一阶不敏感。使用现象学两能级涨落器（TLF）偶极噪声模型，我们估计平均退相时间\(T_2^*\approx 10\,\mu\text{s}\)和品质因数\(Q\sim 10^4\)。在各向同性量子点附近的基态谷中的 p 轨道态中编码，可通过面外磁场诱导类似甜点。最后，我们发现 pOv 量子比特的双量子比特门由四极-四极库仑相互作用介导，通过调整各向异性量子点的相对取向可将其从零电调到\(\sim 1~\text{GHz}\)，为可扩展量子计算提供了一条新途径。
英文摘要
We propose encoding a qubit in a two-level subspace spanned by the lowest $p$-orbital state in the excited valley of an anisotropic quantum dot and the excited $p$-orbital in the ground valley, which we dub the $pOv$ qubit. There is an avoided crossing between these states due to valley-orbit coupling (VOC) induced by alloy disorder, enabling complete single-qubit control using baseband electrical control of the dot anisotropy. We find that `sweet spots' exist at specific dot orientations where the instantaneous eigenstates are first-order insensitive to charge noise. Using a phenomenological two-level fluctuator (TLF) dipole noise model, we estimate an average dephasing time of $T_2^*\approx 10\,μ\text{s}$ and a quality factor of $Q\sim 10^4$. Alternatively, encoding in the $p$-orbital states in the ground valley near the isotropic dot point, we show that one can induce a similar sweet spot via an out-of-plane magnetic field. Finally, we find that two-qubit gates for the $pOv$ qubit are mediated by the quadrupole-quadrupole Coulomb interaction and can be electrically tuned from zero to $\sim 1~\text{GHz}$ by adjusting the relative orientation of the anisotropic dots, providing a novel pathway towards scalable quantum computation.
Comments16 pages, 8 figures
