Spin shuttling in silicon: avoiding valley-state excitations

Spin shuttling is a leading platform for intermediate-range communications between quantum dot qubits, providing new opportunities for computing at scale. However, in silicon-based implementations, long-range shuttlers greatly increase the chance of encountering sites with low valley splittings, causing leakage outside the logical subspace via Landau-Zener tunneling. Here, I summarize the physics of valley splitting variability and valley-state excitations, and I discuss methods for suppressing leakage, especially by allowing for lateral motion in the shuttling channel, to detour around dangerous locations.