Spatial variations of the valley splitting in a quantum well present a key challenge for conveyor-mode shuttling of electron spins in Si/SiGe, giving rise to Landau-Zener-like excitations that cause leakage outside the qubit subspace. Here, we propose an unconventional two-electron qubit encoding, based on valley-singlet states, that is largely immune to Landau-Zener leakage processes. In contrast to single-electron spins, the shuttling fidelity actually improves for small valley splittings, in this case. We show that high fidelities can be achieved without applying any special procedures, such as fine-tuning of the shuttling path.
@article{arxiv.2605.12687,
title = {Using a spin-triplet encoding to enhance shuttling fidelities in Si/SiGe quantum wells},
author = {Merritt P. R. Losert and S. N. Coppersmith and Mark Friesen},
journal= {arXiv preprint arXiv:2605.12687},
year = {2026}
}