Zurek mentions in http://arxiv.org/pdf/quant-ph/9805065v1.pdf : "It is amusing to speculate that a truly quantum observer (i.e., an observer processing quantum information in a quantum computer-like fashion) might be able to perceive superpositions of branches which are inaccessible to us, beings limited in our information processing strategies to the record states “censored” by einselection." Isn't it that the density matrix makes it impossible to have superpositions. This begs the question. Is the density matrix created by humans just to make classical output? In order to turn improper mixture to proper? This means somewhere out there other improper mixture branches or even pure state combination of system plus environment is still in superposition? Hence a quantum observer can still theoretically perceive the superpositions?