September 26, 2007 | Patrick Hayden, John Preskill
The paper explores the retrieval of information from evaporating black holes, assuming that the black hole's internal dynamics are unitary and rapidly mixing, and that the retriever has unlimited control over the emitted Hawking radiation. The authors find that if the black hole has already radiated away more than half of its initial entropy, additional quantum information deposited in the black hole is revealed in the Hawking radiation very quickly. Information deposited before this point remains concealed until the halfway point and then emerges rapidly. These conclusions are based on the efficiency of typical local quantum circuits as encoders for quantum error-correcting codes, which nearly achieve the capacity of the quantum erasure channel. The authors estimate that the black hole's information retention time is just barely compatible with the black hole complementarity hypothesis, which posits that no violations of quantum physics can be detected by any observer. The paper also discusses the thermalization time of the black hole and the efficiency of the quantum circuits used to model the black hole's dynamics.The paper explores the retrieval of information from evaporating black holes, assuming that the black hole's internal dynamics are unitary and rapidly mixing, and that the retriever has unlimited control over the emitted Hawking radiation. The authors find that if the black hole has already radiated away more than half of its initial entropy, additional quantum information deposited in the black hole is revealed in the Hawking radiation very quickly. Information deposited before this point remains concealed until the halfway point and then emerges rapidly. These conclusions are based on the efficiency of typical local quantum circuits as encoders for quantum error-correcting codes, which nearly achieve the capacity of the quantum erasure channel. The authors estimate that the black hole's information retention time is just barely compatible with the black hole complementarity hypothesis, which posits that no violations of quantum physics can be detected by any observer. The paper also discusses the thermalization time of the black hole and the efficiency of the quantum circuits used to model the black hole's dynamics.