Design and Optimization of Spin Dynamics in Ge Quantum Dots: g-Factor Modulation, Geometry-Induced Dephasing Sweet Spots, and Phonon-Induced Relaxation
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| Autores principales: | , |
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| Formato: | Preprint |
| Publicado: |
2025
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| _version_ | 1866913052594536448 |
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| author | Duong, Ngoc Vashaee, Daryoosh |
| author_facet | Duong, Ngoc Vashaee, Daryoosh |
| contents | Gate geometry and bias asymmetry can be used to engineer spin dynamics in gate-defined Ge hole quantum dots by reshaping the confinement potential and driving transitions between distinct confinement regimes. In this work, we show that these transitions strongly modify wavefunction localization, heavy-hole/light-hole mixing, and the effective vertical electric field, leading to pronounced g-factor modulation and geometry-induced dephasing sweet spots where the qubit becomes first-order insensitive to vertical electric-field fluctuations. We further find that phonon-induced spin relaxation exhibits a strong dependence on device size and bias, with T1 following a magnetic-field scaling close to B-9, consistent with Rashba-dominated heavy-hole spin dynamics. These results are obtained using a comprehensive three-dimensional simulation framework for strained Si0.2Ge0.8/Ge gate-defined hole spin qubits, combining realistic electrostatics with a four-band Luttinger-Kohn Hamiltonian. Unlike simplified symmetric confinement models, this approach captures asymmetric wavefunction redistribution, g-tensor anisotropy, and the coupled electrostatic and spin response of realistic devices. Our results establish gate pattern and bias design as practical tools for optimizing spin coherence in Ge hole-spin qubits. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_10731 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Design and Optimization of Spin Dynamics in Ge Quantum Dots: g-Factor Modulation, Geometry-Induced Dephasing Sweet Spots, and Phonon-Induced Relaxation Duong, Ngoc Vashaee, Daryoosh Mesoscale and Nanoscale Physics Quantum Physics Gate geometry and bias asymmetry can be used to engineer spin dynamics in gate-defined Ge hole quantum dots by reshaping the confinement potential and driving transitions between distinct confinement regimes. In this work, we show that these transitions strongly modify wavefunction localization, heavy-hole/light-hole mixing, and the effective vertical electric field, leading to pronounced g-factor modulation and geometry-induced dephasing sweet spots where the qubit becomes first-order insensitive to vertical electric-field fluctuations. We further find that phonon-induced spin relaxation exhibits a strong dependence on device size and bias, with T1 following a magnetic-field scaling close to B-9, consistent with Rashba-dominated heavy-hole spin dynamics. These results are obtained using a comprehensive three-dimensional simulation framework for strained Si0.2Ge0.8/Ge gate-defined hole spin qubits, combining realistic electrostatics with a four-band Luttinger-Kohn Hamiltonian. Unlike simplified symmetric confinement models, this approach captures asymmetric wavefunction redistribution, g-tensor anisotropy, and the coupled electrostatic and spin response of realistic devices. Our results establish gate pattern and bias design as practical tools for optimizing spin coherence in Ge hole-spin qubits. |
| title | Design and Optimization of Spin Dynamics in Ge Quantum Dots: g-Factor Modulation, Geometry-Induced Dephasing Sweet Spots, and Phonon-Induced Relaxation |
| topic | Mesoscale and Nanoscale Physics Quantum Physics |
| url | https://arxiv.org/abs/2509.10731 |