  In recent years an increasing number of papers attempt to mimic or supplant
quantum field theory in discussions of issues related to gravity by the tools
and through the perspective of quantum information theory, often in the context
of alternative quantum theories. In this essay, we point out three common
problems in such treatments. First, we show that the notion of interactions
mediated by an information channel is not, in general, equivalent to the
treatment of interactions by quantum field theory. When used to describe
gravity, this notion may lead to inconsistencies with general relativity.
Second, we point out that in general one cannot replace a quantum field by that
of classical stochastic sources, or mock up the effects of quantum fluctuations
by classical noises, because in so doing important quantum features such as
coherence and entanglement will be left out. Third, we explain how under
specific conditions semi-classical and stochastic theories indeed can be
formulated from their quantum origins and play a role at certain regimes of
interest.
