\documentclass[12pt]{article} \usepackage{amssymb,amsmath,amscd,concmath} \pagestyle{empty} \begin{document} \begin{equation*}|\Psi\rangle=|\psi\rangle_{1}\otimes|\psi\rangle_{2}\otimes\ldots\otimes|\psi\rangle_{n}\end{equation*} \end{document}