Nonlinear Ringdowns as Sources and Detectors of Quantum Gravitational Waves

TL;DR

This paper proposes that nonlinear effects in black hole ringdowns, like second harmonic generation, could serve as detectors for quantum gravitational waves, providing a novel approach to exploring quantum gravity.

Contribution

It introduces the idea that nonlinear gravitational wave phenomena can be used as detectors for quantum gravitational signals, a novel concept inspired by quantum optics.

Findings

Nonlinear ringdowns can generate non-classical gravitational wave states.

These nonlinear effects could be used as strongly coupled detectors for quantum gravity.

Detecting quantum features of gravitational waves remains extremely challenging.

Abstract

Is gravity quantum mechanical? If so, we argue that nonlinear effects in black hole ringdowns - notably second harmonic generation - generates gravitational waves in non-classical states. While quantum features of these states such as sub-Poissonian statistics or entanglement could in principle be measured at interferometric detectors, the tiny coupling of gravity to matter makes this extremely challenging. Drawing on ideas from quantum optics, we instead propose that the nonlinearities in ringdowns could be used as strongly coupled detectors of quantum gravitational radiation, potentially offering a new route to probing the quantum nature of gravity.