A simulational model for witnessing quantum effects of gravity using IBM quantum computer

Abstract: 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.