Better Late than Never: Information Retrieval from Black Holes

TL;DR

This paper proposes that in unitarily evaporating black holes, information is stored as entanglement entropy across the horizon and is only released late in the evaporation process, aligning with quantum information principles.

Contribution

It demonstrates that black hole entropy is primarily entanglement entropy and shows how information is encoded in a tripartite quantum state, emerging only at late times.

Findings

Black hole entropy is mainly entanglement entropy.

Information is encoded in a tripartite quantum state.

Information is released very late in black hole evaporation.

Abstract

We show that, in order to preserve the equivalence principle until late times in unitarily evaporating black holes, the thermodynamic entropy of a black hole must be primarily entropy of entanglement across the event horizon. For such black holes, we show that the information entering a black hole becomes encoded in correlations within a tripartite quantum state, the quantum analogue of a one-time pad, and is only decoded into the outgoing radiation very late in the evaporation. This behavior generically describes the unitary evaporation of highly entangled black holes and requires no specially designed evolution. Our work suggests the existence of a matter-field sum rule for any fundamental theory.