Einselection

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Einselection is short for environmentally-induced superselection, a nickname coined by Wojciech H. Zurek.^[1] Einselection is the quantum thermodynamic process whereby the environment persistently monitors a quantum system, causing decoherence between states of the quantum system. 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).

[edit] Definition

Zurek has defined einselection as follows "Decoherence leads to einselection when the states of the environment $|\epsilon_i \rangle$ corresponding to different pointer states become orthogonal: $\langle \epsilon_i|\epsilon_j \rangle = \delta_{ij}$ "^[1],