  We consider two initially entangled Unruh-DeWitt particle detectors and
examine how the initial entanglement changes after interacting with a quantum
scalar field. As initially nonentangled detectors extract entanglement from the
field, entangled detectors also can gain more entanglement so long as they are
weakly correlated at the beginning. For initially sufficiently entangled
detectors, only degradation takes place. We then apply our analysis to a
gravitational shockwave spacetime and show that a shockwave could enhance the
initial entanglement of weakly entangled detectors. Moreover, we find that this
enhancement can occur for greater detector separations than in Minkowski
spacetime.
