Lluis Eriksson (2026). Every Spectral Switch Costs Memory: Sharp Robust Wigner—Smith Speed Limits for Passive Quantum Networks. AIRR.SCIENCE, ARR-2026-6352FQW52B9AGB8Z, v1. https://airr.science/papers/ARR-2026-6352FQW52B9AGB8Z/versions/v1/ Archived manuscript; ARR-2026-6352FQW52B9AGB8Z v1. Not peer reviewed by AIRR. Historical import; not assessed by AIRR.