Quantum Darwinism — Pointer Basis & Objectivity
How classical reality emerges from quantum entanglement with environment
Quantum Darwinism (Zurek) explains why we observe a classical world: a system S interacts with environment E, which fragments into N_E sub-environments. Only pointer states — the eigenstates of the system-environment interaction — survive decoherence. The mutual information I(S:F_k) between S and fraction F_k of E forms a plateau: even a tiny fraction reveals all classical info. This redundancy is the signature of objectivity. The coherence decays as ρ_off ~ e^{-γt·N_E}.