  During many years since the birth of quantum mechanics, instrumentalist
interpretations prevailed: the meaning of the theory was expressed in terms of
measurements results. But in the last decades, several attempts to interpret it
from a realist viewpoint have been proposed. Among them, modal interpretations
supply a realist non-collapse account, according to which the system always has
definite properties and the quantum state represents possibilities, not
actualities. However, the traditional modal interpretations faced some
conceptual problems when addressing imperfect measurements. The
modal-Hamiltonian interpretation, on the contrary, proved to be able to supply
an adequate account of the measurement problem, both in its ideal and its
non-ideal versions. Moreover, in the non-ideal case, it gives a precise
criterion to distinguish between reliable and non-reliable measurements.
Nevertheless, that criterion depends on the particular state of the measured
system, and this might be considered as a shortcoming of the proposal. In fact,
one could ask for a criterion of reliability that does not depend on the
features of what is measured but only on the properties of the measurement
device. The aim of this article is precisely to supply such a criterion: we
will adopt an informational perspective for this purpose.
