Lluis Eriksson (2026). Complete contraction of unital qubit channels and order-constrained depolarization. AIRR.SCIENCE, ARR-2026-77DGRYDGXD8MDSY2, v4. https://airr.science/papers/ARR-2026-77DGRYDGXD8MDSY2/versions/v4/ Research preprint; ARR-2026-77DGRYDGXD8MDSY2 v4. Not peer reviewed by AIRR. Working paper; not admitted to the AIRR accepted collection.