QI In the literature: contested

Detect single-graviton absorption in a massive acoustic resonator

In plain words

A heavy resonator cooled to its lowest vibration state could absorb a single quantum of a passing gravitational wave, called a graviton, and jump up by one vibration quantum. Detecting such jumps is argued to be within reach, but whether they would prove that gravity is quantum is disputed.

Precise statement

Tobar, Manikandan, Beitel and Pikovski (Nature Communications 2024) propose a resonant-mass detector with a kHz-band mode cooled near its ground state and continuously monitored for single-phonon transitions coincident with gravitational waves detected by LIGO. Determine whether such transitions can be detected, and which observable (counting statistics or correlations that no classical wave drive reproduces) would exclude a classical gravitational-wave explanation, which Carney, Domcke and Rodd (PRD 2024) argue a record of single transitions alone cannot do.

What would settle it

Resonator quantum jumps coincident with a LIGO event together with a statistical signature excluded for every classical gravitational-wave drive.

Status in the literature

Unverified note

Proposed in 2024 (doi:10.1038/s41467-024-51420-8); the interpretive objection is doi:10.1103/PhysRevD.109.044009, and a 2026 follow-up by the proposing group analyzes stimulated absorption (Annals of Physics 489, doi:10.1016/j.aop.2026.170448).