  Witnessing quantum effects in the gravitational field is found to be
exceptionally difficult in practice due to lack of empirical evidence. Hence, a
debate is going on among physicists whether gravity has a quantum domain or
not. There had been no successful experiments at all to show the quantum nature
of gravity till two recent independent works by Bose et al. [Phys. Rev. Lett.
119, 240401 (2017)] and by Marletto and Vedral [Phy. Rev. Lett. 119, 240402
(2017)]. The authors have proposed schemes to test the quantumness of gravity
in two small test masses by entangling two spatially separated objects using
gravitational interactions. They provide a method to witness the entanglement
using spin correlation measurements, which could imply evidence for gravity
being a quantum coherent mediator. Here we propose a simulational model by
providing a new quantum circuit for verifying the above schemes. We simulate
the schemes for the first time in IBM's 5-qubit quantum chip 'ibmqx4' by
developing a quantum system which shows effects analogous to quantum gravity
and calculates the degree of entanglement of the spin correlation. The
entanglement witness over a range is obtained for different experimental
parameters.
