Description of the non-Markovian dynamics of atoms in terms of a pure state

The quantum master equation (QME), used to describe the Markov process of interaction between atoms and field, has a number of significant drawbacks. It is extremely memory intensive, and also inapplicable to the case of long-term memory in the environment. An iterative algorithm for modeling the dynamics of an atomic system in the extended Tavis-Cummings model in terms of a pure state is proposed. The correctness of this algorithm is shown on the example of the interaction of an atomic system with the environment through the exchange of photons with the preservation of coherence. This algorithm is applicable to a wide class of processes associated with photonic machinery, in particular, to chemical reactions.