Abstract – Sina Loriani

Gravity gradient cancellation in space-borne quantum tests of the universality of free fall

Sina Loriani, Sven Abend, Holger Ahlers, Wolfgang Ertmer, Franck Pereira Dos Santos, Dennis Schlippert, Christian Schubert, Peter Wolf, Ernst M Rasel and Naceur Gaaloul

In tests of the weak equivalence principle (WEP) [1], the free fall acceleration of objects of different composition is compared, usually by dropping them simultaneously. However, any deviation from from a homogeneous gravitational field couples to the position and velocity of the two test masses upon release. As a consequence, these initial kinematics need to be well-controlled, since any uncertainties induce spurious differential accelerations, which, a priori, can not be distinguished from a possible WEP violating signal. Indeed, this problem displays a major limitation for quantum tests of the WEP in terms of required integration time and achievable accuracy [2].
In this work, we present a two-fold strategy to mitigate the detrimental effect of gravity gradients, which is based on a compensation mechanism as proposed in [3] together with a demodulation of the differential acceleration signal. To this end, we propose a scheme to reduce the gravity gradient induced uncertainties in an atom interferometric test of the WEP in a dedicated satellite mission and study the experimental feasibility. We find that with moderate parameters, the requirements on the initial preparation of the two sources can be relaxed by three orders of magnitude. This does not only imply a significantly reduced mission time but also allows to reduce the differential acceleration uncertainty caused by gravity gradients below the 10e-18 level.

References
[1] C.M. Will, Living Rev. Relativ. 17:4 (2014)
[2] D. N. Aguilera et al., Class. Quantum Grav. 31, 115010 (2014)
[3] A. Roura, Phys. Rev. Lett. 118, 160401 (2017)