Black Hole Encryption

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Science  17 Mar 2006:
Vol. 311, Issue 5767, pp. 1525
DOI: 10.1126/science.311.5767.1525a

What happens to the quantum information ingested by a black hole? In 1997, Thorne and Hawking argued that information swallowed by a black hole is forever hidden, despite the fact that these dense objects do emit a peculiar kind of radiation and eventually evaporate. Preskill countered that for quantum mechanics to remain valid, the theory mandates that the information has to be released from the evaporating black hole in some fashion. Although Hawking conceded in 2004, the disagreement between Preskill and Thorne still stands.

Smolin and Oppenheim now find that one of the main assertions made about black holes may be flawed. It is often assumed that as the black hole evaporates, all of the information gets stored in the remnant until the very end, at which point the information is either released or else disappears forever. Instead, Smolin and Oppenheim suggest that the information is distributed among the quanta that escape during evaporation, but is encrypted and thus effectively locked away.

The catch is that it can only be accessed with the help of the quanta released when the black hole disappears, in much the same way as a cryptographic key unlocks a coded message. The result offers a link between general relativity and quantum cryptography. — DV

Phys. Rev. Lett. 96, 081302 (2006).

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