Black Holes are about Quantum Information

Abstract

We review and analyse quantum information-theoretic approaches to black hole evaporation that purport to bring us closer to a resolution of the black hole information paradox. Our focus is on the Page-time paradox and on the contribution of the Hayden-Preskill model to understanding information release under the assumption of unitary evaporation. In this model, the black hole is taken to be a finite-dimensional quantum system whose dynamics can be represented by a quantum circuit, and its information-processing and communication abilities are studied. We identify the assumptions underlying this modelling and highlight two key features, fast scrambling dynamics and entanglement as a resource, that underpin the information release in the model. We argue that this reasoning exemplifies a broader change in how information is used in black hole physics, in which quantum information theory now provides a useful operational modelling framework. This application avoids earlier philosophical objections insofar as it is not based on epistemic ignorance and does not regard information as a substance. This line of reasoning has become central to the debate and, as such, warrants greater attention from the philosophy of physics community.