Electrical control of a long-lived spin qubit in a Si/SiGe quantum dot
Electrical control of a long-lived spin qubit in a Si/SiGe quantum dot
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DOI：
10.1038/nnano.2014.153
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发表时间：
2014-09-01
影响因子：
38.3
通讯作者：
Vandersypen, L. M. K.
中科院分区：
文献类型：
--
作者：
Kawakami, E.;Scarlino, P.;Vandersypen, L. M. K.
纳米制造的量子比特允许大规模集成，但由于与固态环境的相互作用，通常会受到短相干时间的影响（1）。突出的挑战是设计环境，使其对量子位的影响最小，但仍然允许量子位控制和可扩展性。在这里，我们展示了一个长寿命的单电子自旋量子比特在Si/SiGe量子点与全电双轴控制。自旋由来自局部微磁体（2）的横向磁场梯度中的谐振微波电场驱动，并且自旋状态以单次激发模式（3）读出。电子自旋共振发生在两个紧密间隔的频率，我们归因于两个谷态。由于硅中的弱超精细耦合，观察到1 μ s的Ramsey衰减时间尺度，几乎比GaAs量子点中的本征时间尺度长两个数量级（4，5），而栅极操作时间与GaAs中报道的时间相当6 -8。自旋回波衰减时间类似于40 μ s，具有一个和四个回波脉冲，可能受到谷间散射的限制。这些进展极大地改善了基于量子点的量子信息处理的前景。
Nanofabricated quantum bits permit large-scale integration but usually suffer from short coherence times due to interactions with their solid-state environment(1). The outstanding challenge is to engineer the environment so that it minimally affects the qubit, but still allows qubit control and scalability. Here, we demonstrate a long-lived single-electron spin qubit in a Si/SiGe quantum dot with all-electrical two-axis control. The spin is driven by resonant microwave electric fields in a transverse magnetic field gradient from a local micromagnet(2), and the spin state is read out in the single-shot mode(3). Electron spin resonance occurs at two closely spaced frequencies, which we attribute to two valley states. Thanks to the weak hyperfine coupling in silicon, a Ramsey decay timescale of 1 mu s is observed, almost two orders of magnitude longer than the intrinsic timescales in GaAs quantum dots(4,5), whereas gate operation times are comparable to those reported in GaAs6-8. The spin echo decay time is similar to 40 mu s, both with one and four echo pulses, possibly limited by intervalley scattering. These advances strongly improve the prospects for quantum information processing based on quantum dots.