Ultrashort light-pulse-induced vibrations of atoms in a lattice, called optical coherent phonons, have been controlled in various materials. However, different experiments demonstrating such control have been explained through multiple empirical theories, and a unified theory based on quantum mechanics is lacking. Scientists at Tokyo Institute of Technology successfully formulated a unified theory for this phenomenon and experimentally verified it in diamond, the optical phonons of which have great potential for application in quantum information technology.