Quantum Gravity and Entanglement in Particle Physics and Gravitation

TL;DR

This paper explores how quantum gravity might cause decoherence affecting entangled states, and discusses novel effects like modified EPR correlations and entangled gravitons from black hole superradiance, revealing new quantum-gravitational phenomena.

Contribution

It introduces potential observable effects of quantum gravity-induced decoherence on entanglement and proposes mechanisms for graviton entanglement via black hole superradiance and axion-like fields.

Findings

QG-induced decoherence can modify EPR correlations in meson experiments.

Axion clouds around black holes can produce entangled gravitons through superradiance.

Different gravitational effective actions lead to distinct entangled graviton states.

Abstract

Some approaches to Quantum Gravity (QG) entail decoherence of quantum matter propagating in it, due to an ``environment'' of QG degrees of freedom inaccessible to low-energy observers. In the first part of this talk, I discuss potential, and rather unique, effects of QG-induced decoherence on entangled particle states, specifically an induced modification of Einstein-Podolsky-Rosen (EPR) correlations of entangled neutral-meson states in meson factories ($\omega$-effect). In the second part, I summarise a recent work in which axion-like fields, forming a kind of condensate clouds surrounding rotating (Kerr-type) astrophysical black holes, can lead to superradiant instabilities, and, through these, to the production of EPR-like entangled states of gravitons, with the entanglement pertaining to (left, right) polarisation degrees of freedom. In the presence of axions and Kerr geometries, there are non-trivial gravitational Chern-Simons (gCS)-type anomalous terms in the respective low-energy gravitational effective actions. Depending on whether the graviton entanglement is due to the non-anomalous terms (of General-Relativity type) in the effective action, or to the gCS terms, one obtains different structures of the resulting entangled squeezed-graviton states, which resemble somewhat the $\omega$-effect.