Description
In this talk, two gravitationally induced decoherence models are analysed that compare different formulations of quantum gravity. The first model discusses decoherence induced by horizons with classical and quantum geometries. In a recent series of papers following arXiv:2205.06279, it was shown that classical horizons constantly induce decoherence on spatial quantum superpositions, which increases linearly with the time during which the superposition is kept open. In this talk, possible effects of black hole quantisation are discussed, the latter being effectively described in terms of a quantisation of the area of its horizon with a minimal value for area variations, i.e., a quantum of the horizon area $\Delta A$, which induces a low frequency cutoff on the modes that can enter the horizon. Focusing on a charged particle and the electromagnetic field accompanying it, it is shown that the quantisation of the horizon can be expected to affect the decoherence of the spatial superposition. More specifically, the resulting decoherence exhibits a constant saturation value, the magnitude of which depends on the assumed value of the quantum of area, and turns out to be quite small for $\Delta A$ of the order of the Planck length squared. In the second part of the talk, a quantum-mechanical toy model describing a neutrino propagating in flat space through an environment of gravitational waves is analysed. The interaction term is motivated by the way in which Fock-quantised linearised gravity couples to matter fields. Within this framework, gravity induces a decoherence effect that damps neutrino oscillations, providing insight into the physical properties of the model. In a subsequent step, the coupling is modified in a Loop Quantum Gravity–inspired manner to mimic certain features of a loop quantisation, leading to a modified decoherence rate compared to the Fock-quantisation–inspired model.