It is well-known that the $(1+1)$ dimensional Schwarzschild and spatially
flat FLRW spacetimes are conformally flat. This work examines entanglement
harvesting from the conformal field vacuums in these spacetimes between two
Unruh-DeWitt detectors, moving along outgoing null trajectories. In $(1+1)$
dimensional Schwarzschild spacetime, we considered the Boulware and Unruh
vacuums for our investigations. In this analysis, one observes that while
entanglement harvesting is possible in $(1+1)$ dimensional Schwarzschild and
$(1+3)$ dimensional de Sitter spacetimes, it is not possible in the $(1+1)$
dimensional de Sitter background for the same set of parameters when the
detectors move along the same outgoing null trajectory. The qualitative results
from the Boulware and the Unruh vacuums are alike. Furthermore, we observed
that the concurrence depends on the distance $d$ between the two null paths of
the detectors periodically, and depending on the parameter values, there could
be entanglement harvesting shadow points or regions. We also observe that the
mutual information does not depend on $d$ in $(1+1)$ dimensional Schwarzschild
and de Sitter spacetimes but periodically depends on it in $(1+3)$ dimensional
de Sitter background. We also provide elucidation on the origin of the
harvested entanglement.
