Gravitational decoherence for mesoscopic systems

•An extension of gravitationally induced decoherence is proposed.•The decoherence effect is conveniently expressed in terms of the energy variance.•A proof that the interferometric visibility is bounded from below is given.•The competition between gravitational and collisional decoherence is studied.

We extend the recent gravitational decoherence analysis of Pikovski et al. to an individual mesoscopic system with internal state characterized by a coherent superposition of energy eigenstates. We express the Pikovski et al. effect directly in terms of the energy variance, and show that the interferometric visibility is bounded from below. Hence unlike collisional decoherence, the visibility does not approach zero at large times, although for a large system it can become very small.