Once a black hole forms, it starts losing mass by radiating energy, called Hawking radiation. This Hawking radiation contains no information about the matter inside the black hole and once the black hole evaporates, all information is lost. The Hawking paradox (or the black hole information paradox) suggests that physical information could permanently disappear in a black hole, allowing many physical states to devolve into the same state. It is well known that the Hawking radiation is completely independent of the material entering the black hole but if the material entering the black hole were a pure quantum state, the transformation of that state into the mixed state of Hawking radiation would destroy information about the original quantum state. On the other hand, according to the quantum mechanics, the complete information about a system is encoded in its wave function up to when the wave function collapses.

The evolution of the wave function is determined by a unitary operator, and unitarity implies that information is conserved in the quantum sense. This is the strictest form of quantum determinism. The Hawking paradox is controversial because it violates the quantum determinism and presents a physical paradox.

The present paper presents the physical aspects of the black hole loss information paradox but the conflicts with the laws of quantum physics, which say that such information can never be completely wiped out, are also discussed.