Optimized electrical control of a Si/SiGe spin qubit in the presence of an induced frequency shift
Optimized electrical control of a Si/SiGe spin qubit in the presence of an induced frequency shift
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DOI：
10.1038/s41534-018-0105-z
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发表时间：
2018-10-29
影响因子：
7.6
通讯作者：
Tarucha, S.
中科院分区：
文献类型：
--
作者：
Takeda, K.;Yoneda, J.;Tarucha, S.
量子点内的电子自旋具有较长的相干时间，是实现高保真量子比特的理想系统。然而，随着自旋相干时间的延长，控制保真度可能受到系统误差而不是退相干的限制，因此表征和抑制其影响对于进一步改进至关重要。本文报道了Si/SiGe自旋量子比特的控制保真度会受到微波引起的电偶极子自旋共振频移的限制，可以通过优化控制脉冲来提高控制保真度。随着控制微波振幅的增加，我们观察到除了拉比频率增加外，量子比特共振频率也发生了移位。我们发现，这限制了传统调幅微波脉冲的控制保真度低于99.8%。为了达到99.9%的门保真度，我们引入了一种正交控制方法，并通过随机基准测试实验验证了该方法。我们的发现有助于在量子点中实现具有电子自旋的超高保真量子比特。
Electron spins confined in quantum dots are an attractive system to realize high-fidelity qubits owing to their long coherence time. With the prolonged spin coherence time, however, the control fidelity can be limited by systematic errors rather than decoherence, making characterization and suppression of their influence crucial for further improvement. Here we report that the control fidelity of Si/SiGe spin qubits can be limited by the microwave-induced frequency shift of electric dipole spin resonance and it can be improved by optimization of control pulses. As we increase the control microwave amplitude, we observe a shift of the qubit resonance frequency, in addition to the increasing Rabi frequency. We reveal that this limits control fidelity with a conventional amplitude-modulated microwave pulse below 99.8%. In order to achieve a gate fidelity >99.9%, we introduce a quadrature control method, and validate this approach experimentally by randomized benchmarking. Our finding facilitates realization of an ultra-high-fidelity qubit with electron spins in quantum dots.