The holographic principle posits a radical way to quantify gravitational physics. It claims that all information of a gravitational theory in a region of space can be encoded by a quantum theory at the boundary of this region. During this colloquium, I will discuss holography from an engineering perspective. We will see how one can engineer—i.e., design and build—gravity through this relationship, using possible quantum theories on the boundary as materials for the undertaking. The concrete advances will be presented for AdS_3/CFT_2: an instance of holography that relates three-dimensional gravity with a negative cosmological constant (AdS_3) to a two-dimensional conformal field theory (CFT_2).

In this talk I will describe holographic properties of near-AdS_2 spacetimes that arise within spherically symmetric configurations of N=2 4D supergravity, for both gauged and ungauged theories. These theories pose a rich space of AdS_2xS^2 backgrounds, and their responses in the near-AdS_2 region are not universal. I will show that the spectrum of operators dual to the matter fields, and their cubic interactions, are sensitive to properties of the background and the theory it is embedded in. The properties that have the most striking effect are whether the background is BPS or non-BPS, and if the theory is gauged or ungauged. The resulting differences will have an imprint on the quantum nature of the microstates of near-extremal black holes, reflecting that not all extremal black holes respond equally when kicked away from extremality.