In particle physics, the Pontecorvo–Maki–Nakagawa–Sakata matrix, Maki–Nakagawa–Sakata matrix, lepton mixing matrix, or neutrino mixing matrix is a unitary mixing matrix that contains information on the mismatch of quantum states of neutrinos when they propagate freely and when they take part in weak interactions. It is a model of neutrino oscillation. This matrix was introduced in 1962 by Ziro Maki, Masami Nakagawa, and Shoichi Sakata, to explain the neutrino oscillations predicted by Bruno Pontecorvo.