Probing Gravity using Quantum Information
In this talk I will explain recent progress in quantum gravity using quantum information theory and AdS/CFT correspondence. AdS/CFT correspondence tells us that quantum gravity on Anti de Sitter space is equivalent to QFT on the spacetime boundary. The crucial observation here is that various interesting gravity observables in AdS/CFT can be nicely analyzed by quantum information theoretic observables of the boundary QFT. One of the most important quantity is the entanglement entropy, which corresponds to the area of extremal area surface in the gravity side. I will show that other quantum information theoretic quantities such as Fisher information, also correspond to bulk geometric quantities. Then I will explain the recent resolution of (a version of) black hole information paradox via the computation of the entropy of Hawking radiation by the replica wormhole. A drawback of this computation is that it only gives the answer for ensemble average of theories, thus being ignorant about whether each member of the ensemble gives a unitary Page curve or not. I will argue that the typical error of the entropy is exponentially suppressed by the black hole entropy, thus showing the computed unitary Page curve is indeed typical.