Impact of the local valley splitting on the coherence of conveyor-belt spin shuttling in <sup>28</sup>Si/SiGe.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 42321194.
- Also identified by DOI 10.1038/s41467-026-74382-5 and PMC identifier 13282485.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Electron spins in silicon 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 E<sub>VS</sub>. We map E<sub>VS</sub> across a 40 nm × 400 nm region of a <sup>28</sup>Si/Si<sub>0.7</sub>Ge<sub>0.3</sub> shuttle device and analyze the spin coherence of a single electron spin transported by conveyor-belt shuttling. We observe that the E<sub>VS</sub> varies over a wide range from 1.5 μeV to 200 μeV and is dominated by SiGe alloy disorder. In regions of low E<sub>VS</sub> and at spin-valley resonances, spin coherence is reduced and its dependence on shuttle velocity matches predictions. Rapid and frequent traversal of low-E<sub>VS</sub> regions induces a regime of enhanced spin coherence explained by motional narrowing. By selecting shuttle trajectories that avoid problematic areas on the E<sub>VS</sub> map, we achieve transport over tens of microns with coherence limited 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.