  A systematic procedure is proposed for better understanding the evolution
laws of black holes in terms of pure quantum states. We start with the two
opposed regions I and II in the Penrose diagram, and study the evolution of
matter in these regions, using the algebra derived earlier from the Shapiro
effect in quantum particles. Since this spacetime has two distinct asymptotic
regions, one must assume that there is a mechanism that reduces the number of
states. In earlier work we proposed that region II describes the angular
antipodes of region I, the `antipodal identification', but this eventually
leads to contradictions. Our much simpler proposal is now that all states
defined in region II are exact quantum clones of those in region I. This
indicates more precisely how to restore unitarity by making all quantum states
observable, and in addition suggests that generalisations towards other black
hole structures will be possible. An apparent complication is that the wave
function must evolve with a purely antisymmetric, imaginary-valued Hamiltonian,
but this complication can be well-understood in a realistic interpretation of
quantum mechanics.
