Mapping g-factors and complex intervalley coupling in Si/SiGe by conveyor-mode shuttling

TL;DR

This paper presents a high-resolution 2D mapping of electron g-factors in Si/SiGe quantum dots, revealing valley-related properties and complex intervalley coupling, crucial for silicon quantum computing development.

Contribution

It introduces a novel conveyor-mode shuttling technique for mapping g-factors and valley coupling in Si/SiGe quantum dots with nanometer precision, advancing qubit material characterization.

Findings

Two g-factors per quantum dot site with symmetry and bimodal distribution.

Correlation between g-factors and valley states consistent with theoretical models.

Extraction of complex intervalley coupling parameters along shuttle trajectories.

Abstract

As silicon spin qubit chips are increasing in qubit number and area, methods for the screening of qubit related material parameters become vital. Here we demonstrate the two-dimensional mapping of small variations of the electron g-factor of quantum dots formed in planar Si/SiGe quantum wells with precision better than $10^{-3}$ and with nanometer lateral resolution. We scan the electron g-factor across a 40 nm $\times$ 400 nm area and observe two g-factors per QD site which obey a striking symmetry and bimodal distribution across the area. These two g-factors relate to valley states of the electron in the quantum dot in agreement with a recent theoretical model. Using conveyor-belt shuttling of entangled electron spin pairs, complementary to the mapping of the local valley-splitting, we map the g-factor. We compare g-factor and valley splitting maps measured on the same device, and extract the complex intervalley coupling parameter along the shuttle trajectories applying a theoretical model of g-factor dependence on intervalley coupling. These maps will allow unprecedented insights into the spin-valley dynamics during qubit manipulation, readout and shuttling and serve as a benchmark for the engineering of Si/SiGe heterostructures for large-scale quantum chips.