  This report is about contradiction between fidelity needed to determine the
entanglement and concomitant noise that always accompanies precise measurement.
  Account of quantum properties of field leads to additional noise caused by
multiple particle creation through nonunitarity of quantum field representation
in embedded sections of space (Unruh noise).
  Causes of quantum noise vanish at leaving off assumption about statistical
independence of detectors. Smearing of detector leads to elimination of causes
of Unruh noise and to emergence of imaginary entanglement of few mode states
caused by overlap of detector sections.
