Sensitive absolute-gravity gradiometry using atom interferometry

We report the demonstration of a sensitive absolute-gravity gradiometer based on light-pulse atom-interference techniques. The gradiometer consists of two absolute accelerometers operated in a differential mode. We report a differential acceleration sensitivity of 4x10(-9) g/Hz(1/2) and an inferred differential acceleration accuracy of less than 10(-9) g. This corresponds to a gravity-gradient sensitivity of 4E/Hz(1/2) (1E =10(-9) s(-2)) and an accuracy of better than 1E for a 10-m separation between accelerometers. We demonstrate that the instrument can be used to detect nearby masses in a vibrationally noisy environment and characterize instrument sensitivity to spurious acceleration and rotation noise.