标题： 高保真翻转模式单自旋操作与量子点轨道能级调节 显示英文标题

标题： High fidelity flopping-mode single spin operation with tuning inter-dot orbital levels

摘要： 快速自旋操控和长自旋相干时间是高保真度半导体自旋量子比特的关键特性。然而，通常尚未明确如何同时优化这两个特性，因为这两个特性通常不是相互独立的。因此，一种不依赖于材料相关的强自旋-轨道耦合和限制其可扩展性的局部磁场梯度的高保真操作方案，受到强烈需求。在这里，我们展示了一种通过调节GaAs三量子点（TQD）中的点间自旋-轨道耦合来实现高保真自旋控制的方法，其中第三个量子点提供了对轨道能级的精确控制。在电稳定电荷状态下，通过优化隧穿耦合，我们实现了超过100 MHz的拉比频率，同时通过适当调节TQD的点间轨道能级保持相干性。通过实施基于机器学习的反馈控制，有效地利用过去测量数据估计量子比特频率，我们以最小的测量开销表征并减轻了低频噪声对量子比特相干性的影响。最后，我们通过随机基准测试演示了在GaAs量子点器件中，即使电子自旋相干性通常受核自旋的强超精细相互作用限制，也实现了99.7%的$\pi$/2门保真度，门时间为4 ns。我们的方法通过利用器件特定参数而不是依赖材料特性或外部场梯度，为半导体量子点阵列中的高保真自旋控制提供了一种可扩展的策略。 显示英文摘要

摘要： Fast spin manipulation and long spin coherence time in quantum dots are essential features for high fidelity semiconductor spin qubits. However, generally it has not been well established how to optimize these two properties simultaneously, because these two properties are usually not independent from each other. Therefore, the scheme for high fidelity operation by simultaneous tuning Rabi frequency and coherence time, which does not rely on the material-dependent strong spin-orbit interaction and the local magnetic field gradient limiting their scalability, are strongly demanded. Here, we demonstrate an approach to achieve high-fidelity spin control by tuning inter-dot spin-orbit coupling in a GaAs triple quantum dot (TQD), where the third dot provides precise control over orbital energy levels. In an electrically stable charge state with optimized tunnel coupling, we achieve Rabi frequencies exceeding 100 MHz while maintaining coherence through proper tuning of the inter-dot orbital levels of the TQD. By implementing a machine learning-based feedback control that efficiently estimates qubit frequency using past measurement data, we characterize and mitigate the impact of low frequency noise on qubit coherence with minimal measurement overhead. Finally, we demonstrate a $\pi$/2 gate fidelity of 99.7\% with a gate time of 4 ns through randomized benchmarking, even in a GaAs quantum dot device where electron spin coherence is typically limited by strong hyperfine interaction with nuclear spins. Our approach provides a scalable strategy for high-fidelity spin control in semiconductor quantum dot arrays by utilizing device-specific parameters rather than relying on material properties or external field gradients.