Lensing of Vacuum Entanglement near Schwarzschild Black Holes

TL;DR

This paper investigates how strong gravitational lensing effects near Schwarzschild black holes influence the distribution of vacuum entanglement in quantum fields, revealing amplification of entanglement harvesting near caustics.

Contribution

It demonstrates that gravitational lensing in Schwarzschild spacetime significantly enhances vacuum entanglement harvesting, even at lightlike separations, using the entanglement harvesting method.

Findings

Vacuum entanglement harvesting is amplified near caustics.

Lensing effects enable entanglement harvesting at lightlike separations.

Pre-existing vacuum entanglement can be accessed through lensing effects.

Abstract

An important feature of Schwarzschild spacetime is the presence of orbiting null geodesics and caustics. Their presence implies strong gravitational lensing effects for matter and radiation, i.e., for excitations of quantum fields. Here, we raise the question whether the lensing manifests itself also in the vacuum of quantum fields, namely by lensing the distribution of vacuum entanglement. To explore this possibility, we use the method of entanglement harvesting, where initially unentangled localized quantum systems are temporarily coupled to the field at different locations. We find that for the Boulware, Hartle-Hawking and Unruh vacua in 3+1 dimensional Schwarzschild spacetime, the harvesting of vacuum entanglement is indeed greatly amplified near caustics. In particular, we establish that pre-existing vacuum entanglement can be harvested also for lightlike separations.