How inhomogeneities enhance the manipulability of Ge spin qubits
Talk given at the Quantum Matter conference in 2023 & SiQEW 23
Abstract of the talk: In recent years, there has been a growing interest in utilizing hole spins in silicon and germanium for quantum information processing. One reason for this is the strong spin-orbit interaction present in the valence band of these materials, which allows for versatile interactions with electric fields. As a result, there have been demonstrations of fast electrical manipulation of hole spin qubits [1] and strong spin-photon interactions [2], which are useful for generating long-range entanglement. While these experimental advances are well-established, there is still much to learn on the theoretical side. For example, Ge hole qubits can be operated with in-plane magnetic fields [3], which cannot be easily explained by the expected spin-orbit mechanisms like cubic Rashba or g-tensor modulation resonance. In this work, we go beyond the usual models for electrical spin manipulation in semiconductor quantum dots. We perform simulations of realistic Ge devices and find that both the electrostatics [4] and the strain [5] display inhomogeneities that heavily affect the performance of hole spin qubits. In particular, we identify overlooked spin-orbit mechanisms that enable manipulation under in-plane magnetic fields and enhance the expected Rabi frequencies. Our simulations show that these mechanisms are dominating the physics of isotropic hole spin qubits.
Related to the publications Phys. Rev. B 106, 235426 (2022), Phys. Rev. Lett. 131, 097002 (2023). BTW, the animations are exaggerated and not meant to be understood literally!