Black holes, quantum information, and unitary evolution

Understand

The unitary crisis for black holes indicates an apparent need to modify local quantum field theory.

• This paper explores the idea that quantum mechanics and in particular unitarity are fundamental principles, but at the price of familiar locality.
• Thus, one should seek to parameterize unitary evolution, extending the field theory description of black holes, such that their quantum information is transferred to the external state.
• This discussion is set in a broader framework of unitary evolution acting on Hilbert spaces comprising subsystems.