Establishing the quasi-inertial reference system based on free-falling atom and its application on gravity experiments

We construct a quasi-inertial reference system for the atom interferometer in terms of the light-field compensation, which is equivalent to the establishment of a quantum drag-free system. The compensation considered in our approach involves feedbacks of both classical and quantum nature. As a result, it may significantly reduce the dependence of the interferometric phase shift on the atomic initial position and velocity. As the error bound for gravity experiments originates primarily from the uncertainties in the initial conditions, the proposed quasi-inertial reference system might lead to substantial improvement in this regard. To be specific, the refined process introduced in the present study gives rise to the possibility of the measurement of the Newtonian gravitational constant G beyond the precision level of 10−6, as well as the test of the weak equivalence principle beyond 10−14. Moreover, when compared with the conventional quasi-inertial reference based on macroscopic objects, additional quantum feedback plays an essential role concerning both theoretical rigor and practical performance enhancement. We further explore the possibility of implementing the proposed quasi-inertial reference system in ongoing experimental developments.