  We review Unruh-DeWitt detectors and other models of detector-field
interaction in a relativistic quantum field theory setting as a tool for
extracting detector-detector, field-field and detector-field correlation
functions of interest in quantum information science, from entanglement
dynamics to quantum teleportation. We in particular highlight the contrast
between the results obtained from linear perturbation theory which can be
justified provided switching effects are properly accounted for, and the
nonperturbative effects from available analytic expressions which incorporate
the backreaction effects of the quantum field on the detector behaviour.
