Status of gravimetric measurements and modelling along a 10m atom interferometer

Abstract

Transportable quantum sensors become more common especially in gravimetry and measurements on longer timescales or field campaigns are carried out. Large scale atom interferometers are much rarer and mostly used for experiments in fundamental physics but can also be operated as gravimeter. The extended free fall time of atoms compared to transportable devices paves the way towards a new measurement standard in absolute gravimetry with a potential stability of better than 1 nm/s² at 1 second integration time. In contrast, the reference values at gravimetric key comparisons, which provide the highest accuracy today, achieve an accuracy of 10 nm/s². At the Leibniz University Hannover, we are currently building a very long baseline atom interferometer (VLBAI) with a 10 m vertical free fall zone. The impact of the instrument on the local gravity field and vice versa was determined by gravimetric measurements during the construction. A 3D model of the VLBAI and its environment was created to calculate the gravitational effect of the masses on experiments of the atom interferometer. The model is then compared to episodic gravimetric measurements. The knowledge of local gravity and its gradient is required to establish the instrument´s uncertainty budget and enable the transfer of gravimetric measurements to nearby devices for comparison. We report on the progress of the gravimetric measurements and modelling in parallel to the construction of the VLBAI.