Pushing the stability of a Differential Quantum Gravimeter below 1Eötvös/1µGal

One year after the first signals were obtained with the Differential Quantum Gravimeter (DQG) developed by muquans, we report on the new performances of the instrument. DQG is a unique instrument that combines the ability of simultaneously measuring the local gravity acceleration and its vertical gradient with an industry-grade geophysics-oriented design. Relying on a similar physical principle and same technologies developed for our absolute quantum gravimeters (AQG) [1], a single vertical laser beam simultaneously measures the vertical acceleration experienced by two sets of free-falling laser-cooled atoms from different heights. The vertical acceleration gives a direct access to g, and the difference of both measurements yields to vertical gravity gradient . [2,3]. 

Our demonstrator has been operational for a year and demonstrated best sensitivities of 53 E/√t, and 360nm/s²/√t, on the second floor of a university building. Long term stabilities below 1E and 10nm/s² levels have been obtained on 60 hours long measurements. After presenting the instrument and results, the talk will present the studies led to further improve the capabilities and performances. We will finally present ongoing works on mass detection experiments. Such experiments aim at assessing the accuracy of the instrument as well as its ability to detect and monitor underground density variations, opening new perspectives for applications in geodesy and hydrology.

This work has been supported by the DGA, the French Department of Defense, and the ANR GRADUS.

 

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

[2] M. J. Snadden et al. “Measurement of the Earth's Gravity Gradient with an Atom Interferometer-Based Gravity Gradiometer” , Phys. Rev. Lett. 81, 971 (1998)

[3] R. Caldani et al. "Simultaneous accurate determination of both gravity and its vertical gradient", Phys. Rev. A 99, 033601 (2019)