Page "Quantum Darwinism" Paragraph 2

Along with Zurek ’ s related theory of envariance, quantum Darwinism explains how the classical world emerges from the quantum world and proposes to answer the quantum measurement problem, the main interpretational challenge for quantum theory.

The measurement problem arises because the quantum state vector, the source of all knowledge concerning quantum systems, evolves according to the Schrödinger equation into a linear superposition of different states, predicting paradoxical situations such as “ Schrödinger's cat ”; situations never experienced in our classical world.

Quantum theory has traditionally treated this problem as being resolved by a non-unitary transformation of the state vector at the time of measurement into a definite state.

It provides an extremely accurate means of predicting the value of the definite state that will be measured in the form of a probability for each possible measurement value.

The physical nature of the transition from the quantum superposition of states to the definite classical state measured is not explained by the traditional theory but is usually assumed as an axiom and was at the basis of the debate between Bohr and Einstein concerning the completeness of quantum theory.