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<p>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 <i>E</i><sub>VS</sub>. We map <i>E</i><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 <i>E</i><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 <i>E</i><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-<i>E</i><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 <i>E</i><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&#xa0;decoherence of mobile electron spin-qubits and present practical strategies to integrate conveyor-mode qubit shuttling into silicon quantum chips.</p>

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Impact of the local valley splitting on the coherence of conveyor-belt spin shuttling in 28Si/SiGe

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月19日

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  • Mats Volmer,
  • Tom Struck,
  • Arnau Sala,
  • Jhih-Sian Tu,
  • Stefan Trellenkamp,
  • Davide Degli Esposti,
  • Giordano Scappucci,
  • Łukasz Cywiński,
  • Hendrik Bluhm,
  • Lars R. Schreiber

摘要

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 EVS. We map EVS across a 40 nm × 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 EVS varies over a wide range from 1.5 μeV to 200 μeV and is dominated by SiGe alloy disorder. In regions of low EVS and at spin-valley resonances, spin coherence is reduced and its dependence on shuttle velocity matches predictions. Rapid and frequent traversal of low-EVS regions induces a regime of enhanced spin coherence explained by motional narrowing. By selecting shuttle trajectories that avoid problematic areas on the EVS 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.