Entanglement Revivals and Scrambling for Evaporating Black Holes

TL;DR

This paper studies how black hole scrambling affects entanglement revival and mutual information spikes in 2D conformal field theories on evaporating black hole backgrounds, revealing a transition from quasiparticle to maximal scrambling behavior.

Contribution

It demonstrates how increasing black hole scrambling time suppresses entanglement spikes, showing a smooth transition between different entanglement dynamics in two gravity models.

Findings

Entanglement revival is driven by island-induced purification.

Increasing scrambling time smooths out and suppresses mutual information spikes.

At a critical scrambling scale, spikes disappear, indicating a transition in entanglement behavior.

Abstract

We investigate the spreading of entanglement, and entanglement memory effects, in two-dimensional conformal field theory (CFT) propagating on evaporating black hole backgrounds. Memory effects leading to late-time spikes in mutual information for widely separated intervals are well known in CFTs admitting a quasiparticle description. In this work we examine the effect of black hole scrambling on late time mutual information spikes for disjoint intervals in free fermion CFT prepared in a thermofield double state. Late-time entanglement revival is driven by island-induced purification of modes in the union of the intervals. We show across two distinct 2d gravity models, Jackiw-Teitelboim (JT) gravity and the Russo-Susskind-Thorlacius (RST) model, that parametrically dialing up black hole scrambling time smooths out and suppresses entanglement spikes until they disappear at a critical scale, interpolating between free quasiparticle and maximal scrambling pictures. At the critical point, the interval lengths are exponential in black hole scrambling time. We further find a very closely related effect manifest as an entanglement dip for a single interval in a single-sided evaporating RST black hole.