  Quantum gravity between masses can produce entangled states in thought
experiments. We extend the experiments to tripartite case and construct states
equivalent to Greenberger- Horne-Zeilinger states and W states under stochastic
local operations and classical communication. The entanglement relates to the
evolution phases induced by gravitational interaction. When we involve more
masses in the experiments, multipartite entangled states can be constructed in
a similar way. We measure the degree of multipartite entanglement by
calculating the geometric measure. We describe the relationship between
geometric measure and the evolution phases. It helps in searching out the
states with robust entanglement.
