The study of black holes has revealed a deep connection between

quantum information and spacetime geometry. Its origin must lie

in the quantum theory of gravity, which offers a valuable hint in

our search for a unified theory. Precise formulations of this relation

recently led to new insights in Quantum Field Theory, some of which

have been rigorously proven. An important example is our discovery

of the first universal lower bound on the local energy density. The

energy near a point can be negative but it is bounded below by a

quantity related to the information flowing past the point.