Regular Article

Everett’s theory of the universal wave function

¹ International Center for Quantum Materials, School of Physics, Peking University, 100871, Beijing, China
² Wilczek Quantum Center, School of Physics and Astronomy, Shanghai Jiao Tong University, 200240, Shanghai, China
³ Collaborative Innovation Center of Quantum Matter, 100871, Beijing, China

^a wubiao@pku.edu.cn

Received: 21 May 2020
Accepted: 20 November 2020
Published online: 24 February 2021

Abstract

This is a tutorial for the many-worlds theory by Everett, which includes some of my personal views. It has two main parts. The first main part shows the emergence of many worlds in a universe consisting of only a Mach–Zehnder interferometer. The second main part is an abridgment of Everett’s long thesis, where his theory was originally elaborated in detail with clarity and rigor. Some minor comments are added in the abridgment in light of recent developments. Even if you do not agree to Everett’s view, you will still learn a great deal from his generalization of the uncertainty relation, his unique way of defining entanglement (or canonical correlation), his formulation of quantum measurement using Hamiltonian, and his relative state.