Quantum Ontology in the Laboratory: A Tabletop Test of Gravity-Induced Collapse, Stochastic Localization, and Unitarity

This work tackles the quantum measurement problem with a fully falsifiable experimental program. We propose a tabletop protocol that reduces the debate to a single operational quantity: the coherence time τ of a mesoscopic spatial superposition at fixed mass m and separation Δx. Using optically levitated silica nanospheres (m ≈ 10⁻¹⁴ kg, Δx ≈ 1 μm) operated in ultra-high vacuum and cryogenic conditions, τ can be measured with precision sufficient to discriminate among competing ontologies: • Gravity-induced collapse (Diósi–Penrose): τ scales as m⁻² with absolute timescales in the 10–20 ms range at m ≈ 10⁻¹⁴ kg.• Objective-collapse models (GRW/CSL): τ scales as m⁻¹, implying hour-scale lifetimes at mesoscopic masses for canonical parameters.• Unitary quantum mechanics with environmental decoherence: no fundamental collapse; τ is set by bath interactions and often scales as m⁻²╱³. Only the unitary case permits engineered coherence revivals. We also introduce the Perera Hybrid Model (PHM), a dissipative synthesis of gravitational self-energy instability and CSL-type localization, predicting an intermediate scaling τ ∝ m⁻¹⋅⁵ and an experimentally accessible crossover regime. The framework is expressed in a unified Lindblad master equation, validated numerically, and paired with a Bayesian pipeline that converts visibility data into model evidence. Monte Carlo studies show that two to three well-chosen mass points suffice for 5σ discrimination. The result is a concrete roadmap that translates questions of quantum ontology into chronometric verdicts, with implications for quantum gravity, macroscopic quantum technologies, and foundational physics.