Inflationary GWs, being of quantum mechanical origin, possess non-trivial dynamics representing quantum-to-classical transition. We discuss the process of classicalization in two different ways: One is the interaction between the modes of GWs on observable and unobservable scales, leading to the change of the density matrix of the observable, long-wavelength GWs. The other is based on the simple commutation relation, which exhibits non-trivial decaying solution on large-scale that is related to the observationally relevant growing mode.
