半导体中受主空穴量子比特的电学调控理论研究

硅中的自旋比特是有吸引力的量子计算平台，因其比特具有长相干时间、与传统半导体加工工艺相匹配、全固态的芯片化电学体系等优势。近年来该领域受到各国大力支持，发展迅速。尤其是针对空穴自旋比特的研究正在积极进行中，因为它们具有弱核自旋噪声耦合和强自旋轨道耦合（Spin-Orbit Coupling，简称SOC）的优点，在构建高保真量子门方面具有优势。然而，对于只需要低金属电极密度的单受主原子中的空穴自旋量子比特的研究还相对匮乏。尤其是，利用可控应变的灵活可调性实现容错量子门方面的探究仍处于空缺，需要建立详细理论框架。本篇论文中，我们通过理论推导、计算和分析，研究了可控应变下，基于受主空穴自旋比特的电偶极自旋共振（Electric Dipole Spin Resonance，简称EDSR）的可调性。重空穴-轻空穴劈裂和自旋空穴耦合（Spin-Hole Coupling，简称SHC）在两种应变下的灵活可调性可以避免“甜点”的高电场，受主自旋比特的操控性能可以得到优化。在低电场下，自旋比特可以得到更长的弛豫时间或更强的EDSR耦合。此外，在非对称的应变下，两个“甜点”会被诱导出现并可能合并在一起，形成一个二阶“甜点”。因此，单比特操控的品质因子Q可以达到10⁴，同时对电场变化有高容忍度。此外，为实现高保真两比特门，基于电偶极-偶极相互作用的受主比特的两比特操控被论证。可调应变下，单比特门和两比特门的品质因子分别能被增强100和7倍。通过应变带来的受主自旋比特性质可调性为自旋量子计算提供了具有希望的实现路径。

Spin qubits in silicon is an attractive platform for quantum computing, owing to their advantages such as long coherence time and compatibility with conventional semiconductor fabrication processes, and fully solid-state chip-scale electrical systems. In recent years, this field has received strong support from various countries and has developed rapidly. In particular, hole spin qubits are being actively researched as they have the advantages of weak coupling to nuclear spin noise and strong spin-orbit coupling (SOC), in constructing high-fidelity quantum gates. However, there are relatively few studies on the hole spin qubits in a single acceptor, which requires only low density of the metallic gates. In particular, the investigation of flexible tunability using controllable strain for fault-tolerant quantum gates of acceptor-based qubits is still lacking, and a detailed theoretical framework needs to be established. Here, we study the tunability of electric dipole spin resonance (EDSR) of acceptor-based hole spin qubits with controllable strain by theoretical derivation, calcuating and analyzing. The flexible tunability of heavy hole-light hole splitting and spin-hole coupling (SHC) with the two kinds of strain can avoid high electric field at the "sweet spot", and the operation performance of the acceptor spin qubits could be optimized. Longer relaxation time or stronger EDSR coupling at low electric field can be obtained. Moreover, with asymmetric strain, two "sweet spots" are induced and may merge together, and form a second-order "sweet spot". As a result, the quality factor Q can reach 10⁴ for single-qubit operation, with high tolerance for the electric field variation. Furthermore, the two-qubit operation of acceptor qubits based on electric dipole-dipole interaction is discussed for high-fidelity two-qubit gates. The quality factors of single-qubit gates and two-qubit gates can be enhanced by 100 and 7 times respectively with tunable strain. The tunability of spin qubit properties in an acceptor via strain could provide promising routes for spin-based quantum computing.

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