  The black-hole information paradox has fueled a fascinating effort to
reconcile the predictions of general relativity and those of quantum mechanics.
Gravitational considerations teach us that black holes must trap everything
that falls into them. Quantum mechanically the mass of a black hole leaks away
as featureless (Hawking) radiation, but if the black hole vanishes, where is
the information about the matter that made it? We treat the states of the
in-fallen matter quantum mechanically and show that the black-hole information
paradox becomes more severe. Our formulation of the paradox rules out one of
the most conservative resolutions: that the state of the in-falling matter
might be hidden in correlations between semi-classical Hawking radiation and
the internal states of the black hole. As a consequence, either unitarity or
Hawking's semi-classical predictions must break down. Any resolution of the
black-hole information crisis must elucidate one of these possibilities.
