Loschmidt's paradox-II: Quantum Decoherence

[Dmitry67]

So if you remember, Loschmidt's paradox is about "Loschmidt's paradox, also known as the reversibility paradox, is the objection that it should not be possible to deduce an irreversible process from time-symmetric dynamics" ( http://en.wikipedia.org/wiki/Loschmidt's_paradox )

My question is, how time-assymetric Quantum Decoherence emerges from time-symmetric Quantum Mechanics?

P.S. I dont think weak CP violation (which leads to T-symettry violation) plays any role in it.

[cesiumfrog]

Isn't it simply that the wave-function of the universe/multiverse as a whole is time reversible, even though we can inspect it from a basis in which each part is not reversible? In other words, there's nothing preventing the SE from back-evolving a superposition of "observed dead cat" plus "observed live cat" into "haven't yet opened the box"; apparent asymmetry arises from our (self-centred) choices to ignore/drop part of the final superposition.

(And classicaly, there is no paradox in time-symmetric laws predicting that if the universe had low entropy at its lower bound of time then it will have entropy increasing with time.)

[Demystifier]

My question is, how time-assymetric Quantum Decoherence emerges from time-symmetric Quantum Mechanics?

Essentially, the same way how time-asymmetric second law of thermodynamics emerges from classical time-symmetric equations of motion:
Special initial conditions + coarse graining -> time-asymmetry