Black holes as mirrors

          @misc{ pirsa_PIRSA:09010031,
            doi = {10.48660/09010031},
            url = {https://pirsa.org/09010031},
            author = {Hayden, Patrick},
            keywords = {Quantum Gravity, Quantum Fields and Strings},
            language = {en},
            title = {Black holes as mirrors},
            publisher = {Perimeter Institute},
            year = {2009},
            month = {jan},
            note = {PIRSA:09010031 see, \url{https://pirsa.org}}
          }
          

Abstract

I'll discuss information retrieval from evaporating black holes, assuming that the internal dynamics of a black hole is unitary and rapidly mixing, and assuming that the retriever has unlimited control over the emitted Hawking radiation. If the evaporation of the black hole has already proceeded past the 'half-way' point, where half of the initial entropy has been radiated away, then additional quantum information deposited in the black hole is revealed in the Hawking radiation very rapidly. Information deposited prior to the half-way point remains concealed until the half-way point, and then emerges quickly. These conclusions hold because typical local quantum circuits are efficient encoders for quantum error-correcting codes that nearly achieve the capacity of the quantum erasure channel. The resulting estimate of a black hole's information retention time, based on speculative dynamical assumptions, is just barely compatible with the black hole complementary hypothesis. (Joint work with John Preskill).