Boundary duals of bulk detectors

Abstract

What is the boundary dual of an Unruh-DeWitt detector in anti-de Sitter space? We argue that this question is naturally answered by the HKLL reconstruction program. A local detector in the bulk can be associated with a smeared detector in the boundary, where the choice of smearing depends on the choice of HKLL kernel. We use this formalism to analyze entanglement harvesting in the Poincaré patch of AdS$_{3}$ for a bulk Unruh-DeWitt detector paired either with a boundary detector or with a second bulk detector. We compute the amount of harvesting in the standard way, namely by evaluating the two-detector density matrix to quadratic order in the coupling $λ$. Additionally, we address an apparent tension between microcausality for spacelike-separated bulk detectors and the fact that the dual HKLL detectors may directly overlap in the boundary theory.