Decoherence of measurement outcomes

[Johny Boy]

Suppose we have a quantum system $Q$ with an initial state $\rho^{(Q)}$. The measurement process will involve two additional quantum systems: an apparatus system $A$ and an environment system $E$, hence giving the initial state of the system $\rho^{(AEQ)} = \rho_{0}^{(AE)}\otimes \rho^{(Q)}$.

Given the above, can anyone provide an explanation to the following statement which appears in a quantum information theory paper: "Coherences between different measurement outcomes do not remain in the joint state of systems A (apparatus) and Q (quantum system to measured). Any such coherences have “leaked away” into the environment during the dynamical evolution. The pointer states are in fact determined by the requirement that different measurement outcomes decohere via interaction with the environment. "

Thanks for any assistance.

 

[Nugatory]

can anyone provide an explanation to the following statement which appears in a quantum information theory paper:

Please please please provide a link to the paper. You will get better answers that way.

 

[Johny Boy]

@Nugatory Okay will do. The PDF of the referenced paper can be found here. Question refers to statement on page 6.