Single holes confined in semiconductor quantum dots are a promising platform for spin-qubit technology, due to the electrical tunability of the g factor of holes. However, the underlying mechanisms that enable electric spin control remain unclear due to the complexity of hole-spin states. Here, we study the underlying hole-spin physics of the first hole in a silicon planar metal-oxide-semiconductor (MOS) quantum dot. We show that nonuniform electrode-induced strain produces nanometer-scale variations in the heavy-hole-light-hole (HH-LH) splitting. Importantly, we find that this nonuniform strain causes the HH-LH splitting to vary by up to 50% across the active region of the quantum dot. We show that local electric fields can be used to displace the hole relative to the nonuniform strain profile, allowing a mechanism for electric modulation of the hole g tensor. Using this mechanism, we demonstrate tuning of the hole g factor by up to 500%. In addition, we observe a potential sweet spot where dg (110) /dV = 0, offering a configuration to suppress spin decoherence caused by electrical noise. These results open a path towards a technology involving engineering of nonuniform strains to optimize spin-based devices.

We demonstrate that a lightly strained germanium channel ([Formula: see text]) in an undoped Ge/Si0.1Ge0.9 heterostructure field effect transistor supports a two-dimensional (2D) hole gas with mobility in excess of [Formula: see text] cm2/Vs and percolation density less than [Formula: see text] cm−2. This low disorder 2D hole system shows tunable fractional quantum Hall effects at low densities and low magnetic fields. The low-disorder and small effective mass ([Formula: see text]) defines lightly strained germanium as a basis to tune the strength of the spin–orbit coupling for fast and coherent quantum hardware.

This is a repository copy of Gate voltage dependent Rashba spin splitting in hole transverse magnetic focusing.

We perform magnetic focussing of high mobility holes confined in a shallow GaAs/ Al 0.33 Ga 0.67 As quantum well grown on a (100) GaAs substrate. We observe ballistic focussing of holes over a path length of up to 4.9 μm with a large number of focussing peaks. We show that additional structure on the focussing peaks can be caused by a combination of the finite width of the injector quantum point contact and Shubnikov-de Haas oscillations. These results pave the way to studies of spin-dependent magnetic focussing and spin relaxation lengths in twodimentional hole systems without complications of crystal anisotropies and anisotropic gtensors.