Wave function collapse is a process of losing the superposition information to the environment.
The remaining problem is that we still cannot predict which part of the information will be lost.
In quantum mechanics, quantum decoherence is the loss of coherence or ordering of the phase angles between the components of a system in a quantum superposition. A consequence of this dephasing leads to classical or probabilistically additive behavior.
Decoherence can be viewed as the loss of information from a system into the environment (often modeled as a heat bath), since every system is loosely coupled with the energetic state of its surroundings.
That is, components of the wavefunction are decoupled from a coherent system, and acquiring phases from their immediate surroundings.
— Wikipedia on Quantum decoherence
2011.11.23 Wednesday (c) All rights reserved by ACHK