Experimental exclusion of a generalized K\'arolyh\'azy gravity-induced decoherence model

TL;DR

This study uses underground low-background experiments to set new, stringent constraints on a gravity-induced decoherence model, effectively excluding the generalized Károlyházý model and related CSL formulations.

Contribution

It provides the first experimental exclusion of the generalized Károlyházý gravity-induced decoherence model by improving bounds on the spatial correlation length R_K.

Findings

Lower bound on R_K > 4.64 m (95% C.L.)

Excludes the generalized Károlyházý model

Constraints also apply to related CSL models

Abstract

We report new experimental constraints on the generalized version of the gravity-induced decoherence model originally proposed by K\'arolyh\'azy. Using data collected by the VIP Collaboration at the INFN Gran Sasso National Laboratory with a high-purity germanium detector, we derive an improved lower bound on the spatial correlation length $R_K$ characterizing metric fluctuations in the model. We obtain a bound $R_K > 4.64$ m (95\% C.L.), which exceeds by more than an order of magnitude the previous experimental limit. When combined with the theoretical upper bound $R_K <1.98$ m derived from macroscopic localization requirements, our result excludes the generalized K\'arolyh\'azy model. The same conclusion applies to an associated non-Markovian formulation of the Continuous Spontaneous Localization (CSL) model. Our findings significantly tighten experimental constraints on gravity-related decoherence scenarios and demonstrate the sensitivity of underground low-background experiments to foundational modifications of quantum mechanics.