Escaping decoherence

Decoherence is the bane of quantum information, and putting states into decoherence-free subspaces is one strategy to avoid this destruction of quantum information. The bad news is that we have found that decoherence-free subspaces do not exist for extended systems in more than one dimension for a broad class of realistic reservoirs, but the good news is that we have discovered that in some cases the environment protects certain states by disallowing them from decohering via a nudging process from the unitary part of the open system dynamics. Examples given from cavity quantum electrodynamics and squeezed light.