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 spatiallysymmetric Mach-Zehnder geometry. Using a biased interferometer we demonstrate the ability to measure small residual forces in our system and discriminate between magnetic and intertial effects.. These are a residual ambient magnetic field gradient of 15±2 mG/cm and an inertial acceleration of 0.08±0.02 m/s 2 . Our method has important applications in the calibration of precision measurement devices and the reduction of systematic errors.

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We present a new framework to study the time variation of fundamental constants in a model-independent way. Model independence implies more free parameters than assumed in previous studies. Using data from atomic clocks based on 87 Sr, 171 Yb + and 133 Cs, we set bounds on parameters controlling the variation of the fine-structure constant, α, and the electron-to-proton mass ratio, µ. We consider variations on timescales ranging from a minute to almost a day. In addition, we use our results to derive some of the tightest limits to date on the parameter space of models of ultralight dark matter and axion-like particles.