Abstract
This volume contains the proceedings of the 20th International Conference on Quantum Physics and Logic (QPL 2023). The aim of the QPL conference series is to bring together academic and industry researchers working on mathematical foundations of quantum computation, quantum physics, and related areas. The main focus is on the use of algebraic and categorical structures, formal languages, type systems, semantic methods, as well as other mathematical and computer scientific techniques applicable to the study of physical systems, physical processes, and their composition.