Silicon-Germanium Heterostructures with Enhanced Valley Splitting for Spin Qubits

• URL: http://arxiv.org/abs/2607.09652v1
• Date: Fri, 10 Jul 2026 17:50:38 GMT
• Title: Silicon-Germanium Heterostructures with Enhanced Valley Splitting for Spin Qubits
• Abstract summary: We present a device-level optimization strategy for pushing valley splittings to between 1 and 5 meV.<n>If realized experimentally, we effectively eliminate valley splitting as an existential problem for large scale SiGe-based quantum processors.
• Score: 0.9332987715848714
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Achieving valley splittings well in excess of the thermal energy of electrons and avoiding valley excitations is essential for the consistent initialization, operation and readout of gate-defined Si spin qubits. In this work, we present a device-level optimization strategy for pushing valley splittings to between 1 and 5 meV, well beyond values reported in nearly all previous theoretical studies. Using device-scale simulations that incorporate atomistic alloy disorder through a 1D tight-binding theory, we demonstrate that our proposed approach yields large valley splittings with a tight distribution across disorder realizations, a key requirement for reproducible qubit performance at scale. The approach rests on an unorthodox Si/SiGe heterostructure design combining a narrow quantum well, a small Ge spike, and a pure-Ge cap. We corroborate these predictions with targeted atomistic density functional theory calculations. These results offer a clear path forward for scalable Si/SiGe spin qubit devices and, if realized experimentally, effectively eliminate valley splitting as an existential problem for large scale SiGe-based quantum processors.

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