Extraction of entanglement from quantum fields with entangled particle detectors

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.