The indeterminism of quantum mechanics generally permits the independent specification of both an initial and a final condition on the state. Quantum pre-and-post-selection of states opens up a new, experimentally testable, sector of quantum mechanics, when combined with statistical averages of identical weak measurements. Recently I applied the theory of weak quantum measurements combined with pre-and-post-selection to cosmology. The novel feature is post-selection: the additional specification of a condition on the quantum state in the far future. I studied “natural” final conditions, and showed how they may lead to potentially large and observable effects at the present cosmological epoch.
See Davies chapter HERE