Bounds on Atomistic Disorder for Scalable Electron Shuttling

Electron shuttling is emerging as a key enabler of scalable silicon spin-qubit quantum computing, but fidelities are limited by atomistic disorder. We introduce a multiscale simulation framework combining time-dependent finite-element electrostatics and atomistic tight-binding to capture the impact of random alloying and interface roughness on the valley splitting and phase of shuttled electrons. We find that shuttling fidelities are strongly suppressed by interface roughness, with a sharp anomaly near the atomic-layer scale, setting quantitative guidelines to realize scalable shuttling.