Gravitationally Induced Entanglement Across an Event Horizon

Abstract

It has long been assumed that a particle--having crossed a black hole event horizon unentangled with another particle in the exterior universe--can no longer dynamically entangle with that particle. Here, we first establish the possibility of post-crossing entanglement via an electromagnetic mediator. We then show within a gravitational time-delayed-potential model that entanglement can be created between freely falling spatial superpositions across an event horizon. Radial escape, however, triggers bremsstrahlung emission--imposing a dephasing bound that grows with entangling phase, $\Gamma>\frac{6}{11\pi}\Phi$, within a constrained leading-quadrupole model--and is ultimately ruled out by macroscopic which-path leakage. By contrast, equivalent macroscopic optical masses in principle allow local harvesting of entanglement tangentially, via quantum erasure, thus revealing a remarkable geometric duality: Spacetime irreversibly degrades entanglement under radial escape, while allowing the transverse teleportation of the entangled qubit to infinity, independent of Hawking evaporation.