Hiroyasu Koizumi (1962–) is a Japanese theoretical physicist and theoretical chemist. After graduating from the University of Tokyo’s Department of Pure and Applied Sciences, he earned a master’s degree there and a Ph.D. from Northwestern University. He is an associate professor at the Center for Computational Sciences, University of Tsukuba. His research encompasses the Berry phase, the Jahn–Teller effect, high-temperature cuprate superconductivity, and quantum computing. He has proposed quantum bits based on cuprate materials and is named as an inventor on quantum-computing patents in Japan and the United States. “Ryoshi konpyuta ni nani ga dekiru ka: Chishiki zero kara rikai dekiru genri to shikumi” explains principles such as quantum superposition, entanglement, and quantum gates, as well as possible applications in cryptography, drug discovery, materials development, and artificial intelligence.