The intense simulation efforts on hole-spin qubits in germanium have so far focused primarily on singly occupied quantum dots. Here, we theoretically investigate three-hole qubits in germanium and demonstrate that their performance can rival that of single-hole qubits in both strained and unstrained systems. In particular, we find that -- in the widely used quasi-circular geometry -- a three-hole qubit encoding can yield enhancements of the Rabi frequencies of up to two orders of magnitude and a large advantage also in terms of quality factors.
@article{arxiv.2505.02449,
title = {Hole-spin qubits in germanium beyond the single-particle regime},
author = {Andrea Secchi and Gaia Forghieri and Paolo Bordone and Daniel Loss and Stefano Bosco and Filippo Troiani},
journal= {arXiv preprint arXiv:2505.02449},
year = {2026}
}