  In this paper, we are exploring the feasibility of observing non-classical
features of gravity in a low-energy regime in a quantum optomechanical
experiment. If gravity is to have an underlying quantum nature, it should hold
the most fundamental quantum characteristics such as the superposition
principle and entanglement. Despite the weakness of gravity, in principle there
is a chance, to observe such a quantum signature of the gravity by exploiting
the quantum optomechanical techniques, without direct observation of graviton.
We are investigating a new dynamical scheme called, gravitational quantum
regime, in which the source of gravity is a quantum particle, and its centre of
mass is subject to the spatial superposition. In a Gedankenexperiment, a test
particle is gravitationally interacting with a quantum nanoparticle in a
double-slit setup. Possible entanglement or superposition of the fields is
investigated. We are looking for the corresponding deviation of the classical
description of gravity despite being far from the Planck scale. Any
experimental interrogation which reveals that gravitational field obeys the
quantum superposition principle would be the first recognition of quantumness
of gravity. This study will show how feasible it is to search for a
non-classical feature of gravity in such a regime of motion. Moreover, this
proposal would be an attempt to test the objectivity of the quantum
superposition principle and its contribution to the microstructure of
space-time.
