  Real world quantum systems are open to perpetual influence from the wider
environment. Quantum gravitational fluctuations provide a most fundamental
source of the environmental influence through their universal interactions with
all forms of energy and matter causing decoherence. This may have subtle
implications on precision laboratory experiments and astronomical observations
and could limit the ultimate capacities for quantum technologies prone to
decoherence. To establish the essential physical mechanism of decoherence under
weak spacetime fluctuations, we carry out a sequence of analytical steps
utilizing the Dirac constraint quantization and gauge invariant influence
functional techniques, resulting in a general master equation of a compact
form, that describes an open quantum gravitational system with arbitrary
bosonic fields. An initial application of the theory is illustrated by the
implied quantum gravitational dissipation of light as well as (non)relativistic
massive or massless scalar particles. Related effects could eventually lead to
important physical consequences including those on a cosmological scale and for
a large number of correlated particles.
