Silicon quantum chips offer a promising path toward scalable, fault-tolerant quantum computing, with the potential to host millions of qubits. However, scaling up dense quantum-dot arrays and enabling qubit interconnections through shuttling are hindered by uncontrolled lateral variations of the valley splitting energy Eₕₒ. We map Eₕₒ across a 40 \, nm x 400 \, nm region of a ^28Si/Si₀. ₇Ge₀. ₃ shuttle device and analyze the spin coherence of a single electron spin transported by conveyor-belt shuttling. We observe that the Eₕₒ varies over a wide range from 1. 5 \, μeV to 200 \, μeV and is dominated by SiGe alloy disorder. In regions of low Eₕₒ and at spin-valley resonances, spin coherence is reduced and its dependence on shuttle velocity matches predictions. Rapid and frequent traversal of low-Eₕₒ regions induces a regime of enhanced spin coherence explained by motional narrowing. By selecting shuttle trajectories that avoid problematic areas on the Eₕₒ map, we achieve transport over tens of microns with coherence limited only by the coupling to a static electron spin entangled with the mobile qubit. Our results provide experimental confirmation of the theory of spin-decoherence of mobile electron spin-qubits and present practical strategies to integrate conveyor-mode qubit shuttling into silicon quantum chips.
Volmer et al. (Sat,) studied this question.