  Understanding the quantum nature of the gravitational field is undoubtedly
one of the greatest challenges in theoretical physics. Despite significant
progress, a complete and consistent theory remains elusive. However, in the
weak field approximation -- where curvature effects are small -- we can explore
some expected properties of such a theory. Particularly relevant to this study
is the quantum nature of gravitational waves, which are represented as small
perturbations in flat spacetime. In this framework, a quantum description of
these perturbations, as a quantum field, is feasible, leading to the emergence
of the graviton. Here we consider a non-relativistic quantum system interacting
with such a field. We employ the consistent histories approach to quantum
mechanics, which allows us to frame classical questions in a quantum context,
to define a fluctuation relation for this system. As a result, thermodynamic
entropy must be produced in the system due to its unavoidable interaction with
the quantum fluctuations of spacetime.
