Detection of Applied and Ambient Forces with a Matterwave Magnetic-Gradiometer

An atom interferometer using a Bose-Einstein condensate of ${}^{87}$Rb atoms is utilized for the measurement of magnetic field gradients. Composite optical pulses are used to construct a spatially symmetric Mach-Zehnder geometry. Using a biased interferometer we demonstrate the ability to measure small residual forces in our system at the position of the atoms. These are a residual magnetic field gradient of 15$\pm$2 mG/cm and and an inertial acceleration of 0.08$\pm$0.02 m/s${}^2$. Our method has important applications in the calibration of precision measurement devices and the reduction of systematic errors.