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Experimental exclusion of a generalized Károlyházy gravity-induced decoherence model

Nicola Bortolotti, Kristian Piscicchia, Matthias Laubenstein, Simone Manti, Antonino Marcianò, Federico Nola, Catalina Curceanu

TL;DR

The paper addresses gravity-induced decoherence models, specifically a generalized Károlyházy framework with a Gaussian spatial correlation length $R_K$. It uses the VIP germanium detector data from the LNGS underground laboratory and a Bayesian spectral analysis to search for spontaneous radiation signatures predicted by the model, incorporating detailed background modeling and material-dependent emission rates. The main result is a 95% CL lower bound of $R_K>4.64$ m, which, when considered alongside a theoretical upper bound $R_K<1.98$ m, excludes the entire generalized model and its non-Markovian CSL equivalence. This demonstrates the power of low-background underground experiments to constrain foundational quantum-mechanics modifications linked to gravity, and it highlights the potential for future, more stringent tests of non-Markovian collapse and gravity-related decoherence scenarios.

Abstract

We report new experimental constraints on the generalized version of the gravity-induced decoherence model originally proposed by Károlyházy. 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 Károlyházy 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.

Experimental exclusion of a generalized Károlyházy gravity-induced decoherence model

TL;DR

The paper addresses gravity-induced decoherence models, specifically a generalized Károlyházy framework with a Gaussian spatial correlation length . It uses the VIP germanium detector data from the LNGS underground laboratory and a Bayesian spectral analysis to search for spontaneous radiation signatures predicted by the model, incorporating detailed background modeling and material-dependent emission rates. The main result is a 95% CL lower bound of m, which, when considered alongside a theoretical upper bound m, excludes the entire generalized model and its non-Markovian CSL equivalence. This demonstrates the power of low-background underground experiments to constrain foundational quantum-mechanics modifications linked to gravity, and it highlights the potential for future, more stringent tests of non-Markovian collapse and gravity-related decoherence scenarios.

Abstract

We report new experimental constraints on the generalized version of the gravity-induced decoherence model originally proposed by Károlyházy. 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 characterizing metric fluctuations in the model. We obtain a bound m (95\% C.L.), which exceeds by more than an order of magnitude the previous experimental limit. When combined with the theoretical upper bound m derived from macroscopic localization requirements, our result excludes the generalized Károlyházy 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.
Paper Structure (7 sections, 23 equations, 4 figures, 1 table)

This paper contains 7 sections, 23 equations, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. Brief review of the Károlyházy model and its generalization
  3. Experimental apparatus
  4. Data analysis and results
  5. Expected signal shape and prior on $Y$
  6. Posterior distributions and novel bound on the correlation length of the generalized Károlyházy model
  7. Conclusion

Figures (4)

  • Figure 1: The previously allowed region for the correlation length parameter of the generalized károlyházy model, according to the analysis figurato2024testability is shown in green. The updated bound $R_K > 4.64$ m obtained in this work is also shown. This new lower value belongs to the forbidden region, thus falsifying the generalized károlyházy mechanism.
  • Figure 2: Schematic render of the germanium detector. From inside out, (1) germanium crystal, (2) electric contact, (3) plastic insulator, (4,5,6) Copper cup, end-cup and block, (7) inner Copper shield and (8) Lead shield.
  • Figure 3: The measured spectrum is represented as a blue distribution. The MC distribution is also shown in red.
  • Figure 4: Posterior probability density functions for $Y = 1/R_K^2$. A dotted line indicates the local mode, the dashed line shows the global mode. The green, yellow and red areas represent the ranges corresponding to probabilities of 0.66, 0.90 and 0.95 respectively.