  Employing a non-perturbative approach based on an instantaneous interaction
between a two-level Unruh-DeWitt detector and a massive scalar field, we
investigate the ability of the field to generate or destroy coherence in the
detector by deriving the cohering and decohering power of the induced quantum
evolution channel. For a field in a coherent state a previously unnoticed
effect is reported whereby the amount of coherence that the field generates
displays a revival pattern with respect to the size of the detector. It is
demonstrated that by including mass in a thermal field the set of maximally
coherent states of the detector decoheres less compared to a zero mass. In both
of the examples mentioned, by making a suitable choice of detector radius,
field energy and coupling strength it is possible to infer the mass of the
field by either measuring the coherence present in the detector in the case of
an interaction with a coherent field or the corresponding decoherence of a
maximally coherent state in the case of a thermal field. In view of recent
advances in the study of Proca metamaterials, these results suggest the
possibility of utilising the theory of massive electromagnetism for the
construction of novel applications for use in quantum technologies.
