Decoherence due to gravitational time dilation: Analysis of competing decoherence effects

Recently the Earth gravitational field was proposed as a new source of decoherence [1]. We study the conditions under which, at least in principle, it becomes the dominant decoherence effect in a typical matter-wave or optomechanical experiment aiming at testing quantum coherence for massive systems. The following competing sources of decoherence are considered: spontaneous emission of light, absorption, scattering with the thermal photons and collisions with the residual gas. The conclusion is that the gravitational decoherence cannot be observed using the present experimental technology.