Composition rules for quantum processes: a no-go theorem

Funding

We thank Ilya Kull, Ding Jia, Fabio Costa, Paolo Perinotti, and Lucien Hardy for useful discussions and comments. We acknowledge the support of the Austrian Science Fund (FWF) through the Doctoral Programme CoQuS, the projects I-2562-N27 and I-2906, the project M2107 (Meitner-Programm) and the research platform TURIS, as well as support from the European Commission via Testing the Large-Scale Limit of Quantum Mechanics (TEQ) (No. 766900) project. PAG acknowledges support from the Fonds de Recherche du Quebec-Nature et Technologies (FRQNT). This publication was made possible through the support of a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation.