We discuss the latest insights gained from the modelling of hole spin qubits in silicon and germanium quantum dots. We highlight, in particular, the existence of "reciprocal sweet spots" with the magnetic field orientation, where the Rabi frequency (transverse spin-electric coupling) is maximal and dephasing (longitudinal spin-electric coupling) minimal, or vice-versa [1]. As a consequence, a careful design of the devices and an appropriate choice of magnetic field orientation can make hole spin qubits much more resilient to longitudinal noise and to disorder [2, 3]. We also discuss how higher-order longitudinal interactions can be harvested for readout and long-range spin coupling [1]. The models support recent experimental data on highly coherent hole spins [3] and strong spin-photon coupling [4] in silicon nanowire MOS devices. We show, in particular, how microscopic modelling unveils the fingerprints of residual disorder, strains, and Coulomb interactions [5] in these devices. We finally discuss the relevance of these results for spin circuit QED experiments.

__Authors__: J. C. Abadillo-Uriel, V. P. Michal, B. Martinez, E. Rodriguez Mena, M. Filippone and Y.-M. Niquet.

__References__:

[1] *Tunable hole spin-photon interaction based on g-matrix modulation*, V. P. Michal, J. C. Abadillo-Uriel, S. Zihlmann, R. Maurand, Y.-M. Niquet, M. Filippone, arXiv:2204.00404.

[2] *Variability of electron and hole spin qubits due to interface roughness and charge traps*, B. Martinez and Y.-M. Niquet, Phys. Rev. Applied **17**, 024022 (2022).

[3] *A single hole spin with enhanced coherence in natural silicon*, N. Piot, B. Brun, V. Schmitt, S. Zihlmann, V. P. Michal, A. Apra, J. C. Abadillo-Uriel, X. Jehl, B. Bertrand, H. Niebojewski, L. Hutin, M. Vinet, M. Urdampilleta, T. Meunier, Y.-M. Niquet, R. Maurand, S. De Franceschi, arXiv:2201.08637.

[4] *Strong photon coupling to a hole spin in silicon*, C. X. Yu, S. Zihlmann, J. C. Abadillo-Uriel, V. P. Michal, N. Rambel, H. Niebojewski, T. Bedecarrats, M. Vinet, E. Dumur, M. Filippone, B. Bertrand, S. De Franceschi, Y.-M. Niquet, R. Maurand, to be submitted.

[5] *Two-body Wigner molecularization in asymmetric quantum dot spin qubits*, J. C. Abadillo-Uriel, B. Martinez, M. Filippone, Y.-M. Niquet, Phys. Rev. B **104**, 195305 (2021).