AI 中文总结
本文提出并研究一种与锗晶格匹配的轻穴自旋量子比特异质结构，其自旋响应更具各向同性、品质因子更高，还可实现重穴与轻穴基态的电切换。
AI 中文摘要
基于变质SiGe缓冲层上的应变锗（ε-Ge）量子阱已实现先进的空穴型自旋量子比特器件。另一种方案是采用与晶格匹配的应变硅锗（ε-SiGe）势垒的未应变锗，可完全省去变质缓冲层。上述两种平台的基态特性以重穴（HH）为主，自旋响应各向异性显著。本文提出并研究了一种与锗晶格匹配的替代异质结构，其中SiGe量子阱和势垒均受张应变，其组分差提供限域带offset，张应变稳定轻穴（LH）基态。研究显示该结构具有大的线性和立方自旋轨道耦合（SOC），且自旋响应比应变HH量子比特显著更具各向同性；还研究了该器件的退相干特性，显示其品质因子相比HH对应器件有可观提升；最后提出一种双层异质结构，可实现HH与LH基态特性的电切换。
英文摘要
Strained germanium ($\varepsilon$-Ge) quantum wells on metamorphic SiGe buffers have enabled advanced hole-based spin qubit devices. Alternatively, unstrained Ge with lattice-matched strained silicon-germanium ($\varepsilon$-SiGe) barriers eliminates the need for metamorphic buffers altogether. The ground state character of both these platforms is predominantly heavy-hole (HH) with a largely anisotropic spin response. We propose and study an alternative heterostructure, lattice-matched to Ge, in which both the SiGe quantum well and barriers are tensile strained, with their composition contrast providing the band offset for confinement and the tensile strain stabilizing a light-hole (LH) ground state. We show large spin-orbit coupling (SOC), both linear and cubic, along with a significantly more isotropic spin response compared to strained HH qubits. We also study the decoherence properties of the proposed device, showing an appreciable gain in the quality factor compared to their HH counterparts. Finally, we propose a bilayer heterostructure that allows for electrical switching between HH and LH ground state character.
