The models we use, habitually, to describe quantum nonlinear optical processes have been remarkably successful yet, with few exceptions, they each contain a mathematical flaw. We present this flaw, show how it can be fixed and, in the process, suggest why we can continue to use our favoured Hamiltonians.
@article{arxiv.1806.05732,
title = {Is there a problem with our Hamiltonians for quantum nonlinear optical processes?},
author = {Stephen M. Barnett},
journal= {arXiv preprint arXiv:1806.05732},
year = {2018}
}