Single-Hole Spin Qubit Optimization in SOI Quantum Dots via $\boldsymbol {k}\cdot \boldsymbol {p}$ Simulations and Perturbative Analysis

Abstract

Hole spin qubits in silicon nanostructures offer fast, all-electrical control through electric dipole spin resonance, yet their performance strongly depends on device geometry. In this work, optimization criteria of Rabi frequency of single-hole spin qubits in silicon-on-insulator quantum dots are identified by combining electrostatic and $\boldsymbol {k}\cdot \boldsymbol {p}$ simulations with a perturbative model of the Rabi frequency linear in the magnetic field magnitude. Starting from a reference device deeply studied in the literature, the dominant terms governing the Rabi frequency are recalled, remarking the key role of the component of the RF electric field parallel to the long axis of the nanowire cross section. Guided by such insights, two alternative devices designed to enhance this field component are proposed, leveraging the gate geometries and the crystal orientation. In the strain-free case, a more than fourfold improvement in the peak Rabi frequency over the reference device is achieved, partially offset by a shorter dephasing time, yet still providing an improvement of more than 10% in the quality factor $Q_{2}^{*}$.The analyses are then repeated with uniform in-plane biaxial strain. Again, higher Rabi frequenciesare generally obtained, accompanied by shorter dephasing times, resulting in improvements in $Q_{2}^{*}$ that can approach one order of magnitude, although strongly dependent on the strain value.