In papers on primary state diffusion (Percival 1994, 1995), numerical estimates suggested that fluctuations in the spacetime metric on the scale of the Planck time (ca.10–44s) could be detected using atom interferometers. In this paper we first specify a stochastic metric obtained from fluctuations that propagate with the velocity of light, and then develop the non–Markovian quantum state diffusion theory required to estimate the resulting decoherence effects on a model matter interferometer. Both commuting and non–commuting fluctuations are considered. The effects of the latter are so large that if they applied to some real atom interferometry experiments they would have suppressed the observed interference. The model is too crude to conclude that such fluctuations do not exist, but it does demonstrate that the small numerical value of the Planck time does not alone prevent experimental access to Planck–scale phenomena in the laboratory.
We develop a mathematically rigorous theory of quantum measurement within Entanglement-Weighted Operator Gravity (EWOG), in which spacetime geometry is an operator-valued entity weighted by quantum entanglement. We show that quantum measurement corresponds to a localized, transient fluctuation of spacetime curvature induced by rapid redistribution of entanglement. We prove that competing measurement outcomes correspond to competing semiclassical geometries whose stability is governed by curvature variance. Minimization of curvature fluctuations leads uniquely to probability weights proportional to
∣ψ∣2, yielding the Born rule as an emergent geometric law rather than an axiom. This framework unifies quantum measurement, decoherence, and classical spacetime emergence within a single gravitational-informational principle. We further derive the spectral density of measurement-induced curvature fluctuations and establish experimental bounds on their detectability.
With recent developments in high-precision quantum measurements, the question of whether observations of decoherence from spacetime fluctuations are accessible experimentally arises. Here we investigate the dynamics of bound states interacting with an environment of gravitons under the Markov approximation. The corresponding Lindblad master equation is presented that enables gravitational decoherence and dissipation due to zero-point spacetime fluctuations to be analyzed. Specifically, we consider a one-dimensional cavity of massless scalar particles that models a light beam with negligible spin polarizations being reflected between two free masses. Numerical simulations have been performed to illustrate the wave-modal dependent decoherence and dissipation of such a configuration. We further demonstrate the existence of nontrivial collective effects akin to superradiance, providing amplifications of gravitational decoherence for a large number of identical bosonic particles.