Optimization and characterization of a differential quantum gravimeter

Measuring the acceleration of the Earth’s gravity g and the gravity gradient simultaneously and at the same location promises to provide enhanced information about the distribution of underground masses, especially at shallow depths [1]. Quantum sensors relying on Atom Interferometry with laser cooled-atoms [2,3] is a technology of choice to implement such new sensing capability and an industry-grade demonstrator has been recently developed [4] by iXblue.

This Differential Quantum Gravimeter (DQG) has been operational for more than two years and has demonstrated state-of-the-art sensitivity mainly limited by Quantum Projection Noise down to a noise floor at about 40E/sqrt(tau). We will present as well a 21 day long run with the demonstration of a resolution below 1E for the measurement of the vertical gravity gradient (1E = 10^-9 s^-2 = 0.1 µGal/m) and 0.5 µGal for the measurement of g. Moreover in order to illustrate the potential for mass balance monitoring and gravity survey we will present a proof-of-principle experiment with realistic masses and measurement duration. We will provide insight on an previsional accuracy budget and main biases.

The compactness of the instrument and the field-tested technology [5] on which it is based, allows to consider the deployment of this new sensor in real environment as a future short-term outcome to investigate both spatial and temporal mass balance in the field. Promising case studies will be discussed, as this type of sensor can sense mass changes that are not detected by gravimeters.

[1] G. Pajot, O. de Viron, M. M. Diament, M. F. Lequentrec-Lalancette, V. Mikhailov, GEO-PHYSICS 73, 123 (2008).

[2] R.Geiger, A.Landragin, S.Merlet, F.P.D.Santos, AVS QuantumScience 2, 024702(2020).

[3] V. Ménoret et al., "Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018)

[4] A compact differential gravimeter at the quantum projection noise limit, to be published in Physical Review A

[5] A.-K. Cooke, C. Champollion, N. Le Moigne, Geoscientific Instrumentation, Methods and

Data Systems Discussions 2020, 1 (2020).