We show that it is possible to add or subtract many photons from a cavity field by interacting it resonantly with a two-level atom. The atom, after entangling with the field inside the cavity and exiting it, may be measured in one of the Schmidt states, producing a multiphoton process (in the sense that can add or annihilate more photons than a single transition allows), i.e., adding or subtracting several photons from the cavity field.
@article{arxiv.1703.07635,
title = {Multiphoton processes by conditional measurements in the atom-field interaction},
author = {Jorge A. Anaya-Contreras and Arturo Zúñiga-Segundo and Francisco Soto-Eguibar and H. Moya-Cessa},
journal= {arXiv preprint arXiv:1703.07635},
year = {2017}
}