QI In the literature: open

Close the decoherence-diffusion window for classical gravity

In plain words

If gravity is classical while matter is quantum, consistency requires gravity to both blur superpositions and make the gravitational pull jitter randomly. Measuring both effects together can exclude such theories.

Precise statement

In classical-quantum gravity (Oppenheim and coworkers), the decoherence coefficient $D_2$ for mass superpositions and the diffusion coefficient $D_0$ of the Newtonian potential obey a trade-off with $D_0D_2$ bounded below (Oppenheim, Sparaciari, Soda, Weller-Davies, Nature Communications 2023). Determine whether coherence times from matter-wave interferometry combined with acceleration-noise data (torsion balances, Cavendish-type experiments, LISA Pathfinder) exclude the entire allowed $(D_0,D_2)$ region for each choice of kernel.

What would settle it

Joint bounds from interferometric coherence and gravitational acceleration noise leaving no allowed $(D_{0}, D_{2})$ for the model class.

Status in the literature

Unverified note

The trade-off was derived in 2022-2023 (arXiv:2203.01982); 2025 proposals test it via classical diffusion of probe masses (arXiv:2501.13030).