Matrix diagonalization and exact solution of the k-photon Jaynes–Cummings model Enrique Choreño, Didier Ojeda-Guillén and Víctor David Granados Eur. Phys. J. D, 72 8 (2018) 142 Published online: 28 August 2018 DOI: 10.1140/epjd/e2018-90106-y