Testing gravity with atomic quantum sensors

In this article, three experiments aimed at the detection of grav- itational effects with atomic sensors are reported. In the first experiment, a gradiometer is used to perform a precision measurement of the Newtonian gravitational constant G. In the second experiment, a similar apparatus is used to provide a test of the Weak Equivalence Principle for atoms in different internal states and in a coherent superposition of internal states. Finally, in the third experiment, a new kind of interferometer operating on a single-photon transition is described. This sensor is a promising candidate for the detection of low-frequency gravitational waves.