  Noiseless subsystems were proved to be an efficient and faithful approach to
preserve fragile information against decoherence in quantum information
processing and quantum computation. They were employed to design a general
(hybrid) quantum memory cell model that can store both quantum and classical
information. In this paper, we find an interesting new phenomenon that the
purely classical memory cell can be super-activated to preserve quantum states,
whereas the null memory cell can only be super-activated to encode classical
information. Furthermore, necessary and sufficient conditions for this
phenomenon are discovered so that the super-activation can be easily checked by
examining certain eigenvalues of the quantum memory cell without computing the
noiseless subsystems explicitly. In particular, it is found that entangled and
separable stationary states are responsible for the super-activation of storing
quantum and classical information, respectively.
