title: Quantum information cannot be completely hidden in correlations: implications for the black-hole information paradox.
abstract: Can quantum-information theory shed light on black-hole evaporation? By entangling the in-fallen matter with an external system we show that the black-hole information paradox becomes more severe, even for cosmologically sized black holes. We rule out the possibility that the information about the in-fallen matter might hide in correlations between the Hawking radiation and the internal states of the black hole. As a consequence, either unitarity or Hawking's semiclassical predictions must break down. Any resolution of the black-hole information crisis must elucidate one of these possibilities.
authors.affiliation: Computer Science, University of York, York YO10 5DD, United Kingdom.
authors.forename: Samuel L
authors.initials: SL
authors.lastname: Braunstein
authors.forename: Arun K
authors.initials: AK
authors.lastname: Pati