  We study quantum steering and Bell nonlocality harvested by the local
interaction of two Unruh-DeWitt detectors with the vacuum massless scalar
field, both in the presence of gravitational waves and in Minkowski spacetime.
It is shown that quantum steerability under the influence of gravitational
waves can be greater than or less than quantum steerability in Minkowski
spacetime, which means that the gravitational waves can amplify or degrade the
harvested steering. In particular, a resonance effect occurs when the energy
gap of the detector is tuned to the frequency of the gravitational wave. We
also find that the harvesting-achievable separation range of vacuum steering
can be expanded or reduced by the presence of gravitational waves, which
depends on the energy gap, the gravitational wave frequency, and the duration
of the gravitational wave action. It is interesting to note that two detector
systems that satisfy the Bell inequality in most parameter spaces, regardless
of the existence of gravitational waves, indicating that steering harvesting
cannot be considered to be nonlocal.
