Einselection

Einselection is short for environmentally-induced superselection, a nickname coined by Wojciech H. Zurek. Einselection is the quantum process whereby the environment persistently monitors a quantum system, causing decoherence between its states. The decoherence process selects a certain subset of states from the enormous Hilbert space. These 'pointer states' are stable despite environmental interaction, which explains the emergence of a preferred basis in quantum measurement. The einselected states lack coherence, and therefore do not exhibit the quantum behaviours of entanglement and superposition. Since only quasi-local, essentially classical states survive the decoherence process, einselection can in many ways explain the emergence of a (seemingly) classical reality in a fundamentally quantum universe (at least to local observers).