H-Theorem for Systems with an Interaction Invariant Distribution Function

H-theorem gives necessary conditions for a system to evolve in time with a non-diminishing entropy. In a quantum case the role of H-theorem plays the unitality criteria of a quantum channel transformation describing the evolution of the system’s density matrix under the presence of the interaction with an environment. Here, we show that if diagonal elements of the system’s density matrix are robust to the presence of interaction the corresponding quantum channel is unital.