Horizons and Soft Quantum Information

TL;DR

This paper extends quantum field theory tools to analyze how black holes decohere quantum states via soft radiation, revealing new insights into the quantum information dynamics near horizons.

Contribution

It develops a generalized framework for soft radiation states and applies it to demonstrate black hole decoherence and information loss mechanisms.

Findings

Black holes decohere quantum superpositions through soft radiation.

New relations for state distinguishability and quantum information content are established.

Black horizons act as optimal observers, causing environment decoherence.

Abstract

It was recently shown that black holes decohere any quantum superpositions in their vicinity. This decoherence is mediated by soft radiation through the horizon, and can be understood as the result of the fact that quantum states in the exterior source distinguishable states of long-range fields in the interior. To study this phenomenon and others, we extend Tomita-Takesaki theory to accommodate states of soft radiation such as arise in the electromagnetic and gravitational memory effects, and provide a general framework for computing the distinguishability of general coherent states. Applying these tools, we use the methods of unambiguous state discrimination and approximate quantum error correction to prove some new relations regarding the distinguishability of quantum states, and the quantum information content of soft radiation, and thereby show that a black hole (or any horizon) decoheres its environment as though its interior were full of optimal observers.