The fate of classical information incident on a quantum black hole has been the subject of an ongoing controversy in theoretical physics, because a calculation within the framework of semi-classical curved-space quantum field theory appears to show that the incident information is irretrievably lost, in contradiction to time-honored principles such as time-reversibility and unitarity. Within this framework embedded in quantum communication theory that signaling from past to future infinity in the presence of a Schwarzschild black hole can occur with arbitrary accuracy, and thus that classical information is not lost in black hole dynamics. The calculation relies on a treatment that is manifestly unitary from the outset, where probability conservation is guaranteed because black holes stimulate the emission of radiation in response to infalling matter. This stimulated radiation is non-thermal, and contains all of the information about the infalling matter, while Hawking radiation contains none of it.
Lenny Susskind writes in his book "The Black Hole War" that he proposed (in front of Sid Coleman and Stephen Hawking) that the problem would be solved if "the region just outside the horizon is occupied by a lot of tiny invisible Xerox machines" [6, p. 227]. But he then immediately retreated from this idea, because he thought it would violate the no-cloning theorem (Which we now know it does not). Susskind later revived the idea in his "black hole complementarity" proposal, claiming that somehow information would both fall into the black hole and be reflected at the horizon, but that the no-cloning theorem would not be violated because nobody would ever know (as you can't make an experiment both inside and outside of the black hole). This idea is based on a profound misunderstanding of quantum cloning, and in particular its relation to stimulated emission of radiation.