A method based on integrals of motion for collective processes has been introduced to achieve physical schemes in which one of the systems is insensitive to interaction. Decoherence-free quantum channels that allow sending any state of light, particulary the Fock states, through an absorbing medium are considered as an example.
@article{arxiv.quant-ph/0603242,
title = {Quantum channel for light based on integrals of motion},
author = {V. N. Gorbachev and A. I. Trubilko},
journal= {arXiv preprint arXiv:quant-ph/0603242},
year = {2009}
}