Nature Communications, Published online: 08 September 2026; doi:10.1038/s41467-026-77397-0 Spatial-light computing is limited by the lack of compact, non-volatile, rewritable analog devices. Wen et al. report a ferroelectric crystal that converts lanthanide emission into a rewritable, multilevel memory, allowing stored optical states to be read and used as persistent weights for neuromorphic computing.