Precision measurement of the gravitational constant with atom interferometry

We report on the current performance of our atom interferometry gravity gradiometer. After careful elimination of the main sources of fluctuations and biases in the atom interferometer, we achieve a sensitivity of 3×10
^-9
g per second to differential gravity; by modulating the position of a set of source masses, we achieve a relative statistical uncertainty of 1.1 × 10
^-4
to the gravitational constant G.