A new theoretical study challenges the assumption that particles crossing a black hole's event horizon cannot dynamically entangle with external particles. Using a gravitational retarded-potential model, researchers have demonstrated that quantum entanglement can be created from scratch between freely falling spatial superpositions, even when one particle has already crossed the horizon. This finding suggests a more complex quantum interaction between the interior and exterior of a black hole than previously thought.

However, the radial extraction of this entangled state presents significant challenges. It requires non-inertial deceleration, which in turn triggers soft-graviton bremsstrahlung. This process imposes a strict dephasing bound, Γ ≥ (729/160π)Φ, leading to the decoherence of the entangled state, making it practically unobservable if one attempts to extract it directly from the interior.

In contrast, the study explores an analogous scenario with macroscopic optical masses. In this case, entanglement can be locally harvested tangentially via quantum erasure. This reveals a remarkable geometric duality: spacetime irreversibly degrades entanglement the moment the localized mass is dragged away from the horizon, while allowing the transverse teleportation of its entangled state to infinity. This result opens new avenues for understanding the interaction between gravity and quantum mechanics in extreme environments.