Silicon quantum dot devices for scalable quantum computing*

Silicon (Si) quantum dot (QD) spin qubits have great potential for application in large-scale quantum circuits as they share many similarities with classical transistors that represent the prototypical example for scalable electronic platforms. However, for QD formation and control, additional gates are required that add to device complexity and thus hinder upscaling. Here, we meet this challenge by demonstrating the scalable integration of a multilayer-gate-stack in Si QD devices using self-alignment, which allows for ultra-small gate lengths and intrinsically perfect layer-to-layer alignment [Geyer et al., arXiv:2007.15400 (2020)]. We study hole transport through a double QD and observe Pauli spin blockade (PSB). Application of a small magnetic field leads to lifting of PSB and reveals the presence of spin-orbit interaction. From the magnitude of a singlet-triplet anticrossing at high magnetic field we estimate a spin-orbit energy of 37µeV, which corresponds to a spin-orbit length of just 48nm. This work paves the way for scalable spin-based quantum circuits with fast, all-electrical qubit control and operation temperatures above 1K.