Silicon spin qubits: Exploring an epitaxial materials platform for controllable valley splitting and charge noise mitigation

硅自旋量子位：探索用于可控谷分裂和电荷噪声缓解的外延材料平台

• 批准号: 289786932
• 负责人: Professor Dr. Dominique Bougeard
• 金额: --
• 依托单位: Institut für Experimentelle und Angewandte Physik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/289786932?language=en
• 关键词: Silicon; spin; qubits; Exploring; epitaxial

The spin of single electrons is one of the most promising candidates to define qubits in a highly integrated and scalable semiconductor environment. Spins localized in silicon-germanium by means of gate-defined quantum dots have recently seen major advances in manipulation fidelities and ideas for scalable quantum computing architectures. In our previous project, we, ourselves, have demonstrated a state-of-the-art qubit in highly enriched 28Si/SiGe, longest echo coherence time and high valley splitting. However, there is a consensus that charge noise, potential disorder and valley splitting of these Si/SiGe-based qubits need to be improved in terms of reproducibility to implement further scalability. The material physics of the qubit devices has been scarcely addressed so far, although it is foreseeable that it contributes significantly to the currently observed limits.With respect to charge noise and potential fluctuations, our previous experiments point to the special role of the interface between the Si/SiGe heterostructure and the oxide dielectric. We propose here to replace the amorphous aluminum oxide - with all its charged defects - currently used worldwide by alternative oxides. Our focus will lie on an oxide that is grown by molecular beam epitaxy, in-situ, epitaxially and monocrystalline on the Si/SiGe heterostructure. This should minimize impurities and defects at the interface and in the dielectric and be significantly reflected in our noise analyses of single qubits. The valley splitting for spin qubits in Si/SiGe is currently dominated by local short-range atomic impurities such as steps. Here, we want to exploit that an electric field perpendicular to the Si/SiGe quantum well can, additionally, significantly contribute to the valley splitting. Therefore, we will extend our surface gate controlled qubit devices by a global backgate. This will enable us to apply considerably higher electric fields to the heterostructure than is possible in the current state of research. Experimentally, a significant increase of the valley splitting is expected, which on the one hand will considerably facilitate the manipulation of spin qubits and at the same time - due to the global backgate - promises lower fluctuations of the splitting in the local space. Within the project we will also introduce locally strongly localized annealing for the activation of implanted donors in the Ohmic contacts of the qubit components by means of an in house-designed laser scanner to replace the currently worldwide used high temperature annealing step of the entire component. The resulting significant reduction of volume diffusion in the Si/SiGe/dielectric qubit structure will result in reduced charge noise and potential fluctuations as well as in reproducibly high valley splitting.

单电子的自旋是在高度集成和可扩展的半导体环境中定义量子比特的最有希望的候选者之一。通过栅极定义的量子点在硅锗中局域化的自旋最近在可扩展的量子计算架构的操纵能力和想法方面取得了重大进展。在我们之前的项目中，我们自己已经在高度富集的28 Si/SiGe中展示了最先进的量子位，最长的回波相干时间和高谷分裂。然而，有一个共识，这些Si/SiGe基量子比特的电荷噪声，潜在的无序和谷分裂需要在再现性方面进行改进，以实现进一步的可扩展性。到目前为止，量子比特器件的材料物理几乎没有得到解决，尽管可以预见的是，它对目前观察到的极限有很大的贡献。关于电荷噪声和电势波动，我们以前的实验指出了Si/SiGe异质结构和氧化物电介质之间的界面的特殊作用。我们建议在这里取代无定形氧化铝-其所有的带电缺陷-目前在世界范围内使用的替代氧化物。我们的重点将在于通过分子束外延生长的氧化物，在原位，外延和单晶的Si/SiGe异质结构。这应该最大限度地减少界面和电介质中的杂质和缺陷，并在我们对单量子位的噪声分析中得到显着反映。Si/SiGe中自旋量子比特的谷分裂目前主要由局部短程原子杂质如台阶所控制。在这里，我们想要利用垂直于Si/SiGe量子阱的电场可以另外显著地有助于谷分裂。因此，我们将通过全局背栅来扩展我们的表面栅控量子位器件。这将使我们能够施加相当高的电场的异质结构比可能在目前的研究状态。从实验上看，预计谷分裂会显着增加，这一方面将大大促进自旋量子比特的操纵，同时由于全局后门，有望降低局部空间分裂的波动。在该项目中，我们还将通过内部设计的激光扫描仪引入局部强局部退火，用于激活量子位组件欧姆接触中的植入供体，以取代目前全球使用的整个组件的高温退火步骤。在Si/SiGe/电介质量子位结构中所得到的体积扩散的显著减少将导致减少的电荷噪声和电势波动以及可再现的高谷分裂。