Quantum Measurement Division, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
Joint Quantum Institute, University of Maryland and National Institute of Standards and Technology , Gaithersburg, Maryland 20742, United States.
Nano Lett. 2017 Jul 12;17(7):4461-4465. doi: 10.1021/acs.nanolett.7b01677. Epub 2017 Jun 28.
With any roughness at the interface of an indirect-bandgap semiconducting dot, the phase of the valley-orbit coupling can take on a random value. This random value, in double quantum dots, causes a large change in the exchange splitting. We demonstrate a simple analytical method to calculate the phase, and thus the exchange splitting and singlet-triplet qubit frequency, for an arbitrary interface. We then show that, with lateral control of the position of a quantum dot using a gate voltage, the valley-orbit phase can be controlled over a wide range, so that variations in the exchange splitting can be controlled for individual devices. Finally, we suggest experiments to measure the valley phase and the concomitant gate voltage control.
在间接带隙半导体点的界面处存在任何粗糙度时，谷轨道耦合的相位都可能取一个随机值。在双量子点中，这个随机值会导致交换分裂发生很大的变化。我们提出了一种简单的分析方法来计算任意界面的相位，从而计算出交换分裂和单重态-三重态量子比特频率。然后我们表明，通过使用栅极电压对量子点的位置进行横向控制，可以在很宽的范围内控制谷轨道相位，从而可以控制各个器件的交换分裂变化。最后，我们建议进行实验来测量谷相位和随之而来的栅极电压控制。
