Heavy-Hole--Light-Hole Mixing and Spin--Photon Coupling in Germanium Flopping-Mode Qubits

• URL: http://arxiv.org/abs/2608.29325v1
• Date: Sat, 29 Aug 2026 15:12:27 GMT
• Title: Heavy-Hole--Light-Hole Mixing and Spin--Photon Coupling in Germanium Flopping-Mode Qubits
• Abstract summary: Intrinsic spin--orbit interaction in germanium provides electrically active flopping-mode qubits without requiring magnetic-field gradients.<n>We study double quantum dots (DQDs) with a multiband Luttinger--Kohn framework that retains heavy-hole (HH) and light-hole (LH) states on equal footing.
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• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Intrinsic spin--orbit interaction in germanium provides electrically active flopping-mode qubits without requiring magnetic-field gradients to generate spin--charge hybridization. We study double quantum dots (DQDs) with a multiband Luttinger--Kohn framework that retains heavy-hole (HH) and light-hole (LH) states on equal footing. Modeling vertical confinement with a finite confinement potential along the growth direction brings selected subbands into a regime of appreciable HH--LH mixing. This admixture activates electric-dipole spin-coupling through LH--LH and LH--HH transitions, complementing the conventional HH--HH pseudospin-flip resonance. For the parameter sets considered, these additional channels can produce larger spin--photon figures of merit than the HH--HH transition. HH--LH mixing thus supplies a tunable ingredient for qubit--cavity coupling in germanium hole-spin qubits and extends the operating regimes available to circuit-QED architectures.

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