Environment as a witness: the inevitable emergence of classicality

Understanding our everyday observations of the classical universe from the underlying quantumness of nature is a major open problem. Therefore, we study quantum Darwinism in the example of a central spin undergoing decoherence in a spin environment. The system-environment interactions are modeled by imperfect CNOT operations. As main results, we derive analytic expressions for discord between the central spin and an arbitrary partition of the environment, where measurements are applied either on the system or environment spins. In the more realistic case of imperfect measurements, we show that we inevitably reach the classical plateau for a large environment size.