Reduction of the impact of the local valley splitting on the coherence of conveyor-belt spin shuttling in $^{28}$Si/SiGe

• URL: http://arxiv.org/abs/2510.03773v1
• Date: Sat, 04 Oct 2025 10:45:30 GMT
• Title: Reduction of the impact of the local valley splitting on the coherence of conveyor-belt spin shuttling in $^{28}$Si/SiGe
• Authors: Mats Volmer, Tom Struck, Jhih-Sian Tu, Stefan Trellenkamp, Davide Degli Esposti, Giordano Scappucci, Łukasz Cywiński, Hendrik Bluhm, Lars R. Schreiber,
• Abstract summary: We map $E_VS$ across a $40, $nm x $400, $nm region of a $28$Si/Si$_0.7$Ge$_0.3$ shuttle device.<n>We analyze the spin coherence of a single electron spin transported by conveyor-belt shuttling.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: 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 $E_{VS}$. We map $E_{VS}$ across a $40 \, $nm x $400 \, $nm region of a $^{28}$Si/Si$_{0.7}$Ge$_{0.3}$ shuttle device and analyze the spin coherence of a single electron spin transported by conveyor-belt shuttling. We observe that the $E_{VS}$ varies over a wide range from $1.5 \, \mu$eV to $200 \, \mu$eV and is dominated by SiGe alloy disorder. In regions of low $E_{VS}$ and at spin-valley resonances, spin coherence is reduced and its dependence on shuttle velocity matches predictions. Rapid and frequent traversal of low-$E_{VS}$ regions induces a regime of enhanced spin coherence explained by motional narrowing. By selecting shuttle trajectories that avoid problematic areas on the $E_{VS}$ 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.

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