  When a quantum system interacts with an external environment, it undergoes
the loss of quantum correlation (decoherence) and the loss of energy
(relaxation) and eventually all of the quantum information becomes classical.
Here we show a general principle to use unitary operations to establish and
preserve particular non-equilibrium states in arbitrary relaxing quantum
systems. We elucidate these concepts with examples of state preservation in
one-spin and two-spin entangled systems.
