Quantum Gravity Gradiometer Using Atom Interferometers for gravity Mapping

Quantum gravity gradiometers based on atom-wave interferometry hold the promise for greater sensitivity and suitability for space applications. These instruments can provide not only high-resolution mapping of mass distribution both above and below the surface of planets, but also temporal monitoring of dynamical processes. Funded in part by NASA, we have been developing an atom interferometer-based gravity gradiometer for Earth science application. The inertial sensors use atomic particles as free fall test mass and the matter-wave interferometry to measure inertial forces acting upon the test masses. The overall approach is based on the recent development of laser cooling and manipulation of atoms in fundamental physics and high precision measurements. Atom interferometers have been demonstrated in research laboratories for gravity and gravity gradient measurements, and the scheme is specially suited for applications in space where atoms are truly drag-free and microgravity makes long interaction time possible for achieving high sensitivity and precision. In this paper, we will review the underlying principles of the atom interferometers as inertial force sensors and describe the instrument design and operation. We will also report the progress in the technology developments towards a portable and eventually a flyable system.