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The quantum theory of black holes has opened up a window to study theintersection of general relativity and quantum field theory, but perceivedparadoxes concerning the fate of classical information directed at a black holehorizon, as well as concerning the unitarity of the evaporation process, haveled researchers to question the very foundations of physics. In thispedagogical review I clarify the ramifications of the fact that black holes notonly emit radiation spontaneously, but also respond to infalling matter andradiation by emitting approximate clones of those fields in a stimulatedmanner. I review early purely statistical arguments based on Einstein'streatment of black bodies, and then show that the Holevo capacity of the blackhole (the capacity to transmit classical information through a quantum channel)is always positive. I then show how stimulated emission turns the black holeinto an almost optimal quantum cloning machine, and furthermore discuss thecapacity of black holes to transmit quantum information. Taking advantage of ananalogy between black hole physics and non-linear optics I show that acalculation of the evolution of a black hole over time, using a discretizationof the black hole $S$-matrix path integral, yields well-behaved Page curvessuggesting that black hole evaporation is unitary. Finally, I speculate aboutpossible observable consequences of stimulated emission of radiation in blackholes.

Stimulated Emission of Radiation and the Black Hole Information Problem