RT Journal Article T1 Fundamental limitations in the purifications of tensor networks A1 De las Cuevas, G. A1 Cubitt, J.L. A1 Wolf, M.M. A1 Pérez García, David AB We show a fundamental limitation in the description of quantum many-body mixed states with tensor networks in purification form. Namely, we show that there exist mixed states which can be represented as a translationally invariant (TI) matrix product density operator valid for all system sizes, but for which there does not exist a TI purification valid for all system sizes. The proof is based on an undecidable problem and on the uniqueness of canonical forms of matrix product states. The result also holds for classical states. PB American Institute of Physics Inc. SN 0022-2488 YR 2016 FD 2016 LK https://hdl.handle.net/20.500.14352/24628 UL https://hdl.handle.net/20.500.14352/24628 LA eng NO European Commission NO Ministerio de Economía y Competitividad (España) NO Comunidad de Madrid DS Docta Complutense RD 21 dic 2025