Engineered spin-electric coupling enables spin qubits in semiconductor nanostructures to be manipulated efficiently and addressed individually. While synthetic spin-orbit coupling using a micromagnet is widely investigated for driving and entangling qubits based on single spins in silicon, the baseband control of encoded spin qubits with a micromagnet in isotopically purified silicon has been less well investigated. Here, we demonstrate fast singlet-triplet qubit oscillation (~100 MHz) in a gate-defined double quantum dot in ²⁸Si/SiGe with an on-chip micromagnet with which we show the oscillation quality factor of an encoded spin qubit exceeding 580. The coherence time T₂* is analyzed as a function of potential detuning and an external magnetic field. In weak magnetic fields, the coherence is limited by frequency-independent noise whose time scale is faster than the typical data acquisition time of ~100 ms, which limits the T₂* below 1 μs in the ergodic limit. We present evidence of sizable and coherent coupling of the qubit with the spin states of a nearby quantum dot, demonstrating that appropriate spin-electric coupling may enable a charge-based two-qubit gate in a (1,1) charge configuration.

工程自旋电耦合使得半导体纳米结构中的自旋量子位能够被有效地操纵并单独寻址。虽然使用微磁体的合成自旋轨道耦合被广泛研究用于驱动和纠缠硅中基于单自旋的量子位，但使用同位素纯化硅中的微磁体对编码自旋量子位进行基带控制的研究较少。在这里，我们利用片上微磁体在²⁸ Si/SiGe 中的门定义双量子点中演示了快速单重态-三重态量子位振荡（~100 MHz），并显示编码自旋量子位的振荡品质因数超过 580。相干时间T ₂ * 被分析为潜在失谐和外部磁场的函数。在弱磁场中，相干性受到与频率无关的噪声的限制，其时间尺度比~100 ms的典型数据采集时间更快，这将遍历极限中的T ₂ * 限制在1 μs以下。我们提供了量子位与附近量子点的自旋态之间存在相当大且相干耦合的证据，证明适当的自旋电耦合可以在 (1,1) 电荷配置中实现基于电荷的双量子位门。