John Preskill is a prominent theoretical physicist known for his work in quantum information science. He is a professor at the California Institute of Technology and has made significant contributions to the understanding of quantum computing and quantum error correction. His research has helped lay the groundwork for the development of practical quantum computers. In addition to his research, Preskill is known for coining the term "quantum supremacy," which refers to the point at which a quantum computer can perform tasks that classical computers cannot. He is also involved in educating the next generation of scientists and promoting the field of quantum mechanics.