Building and using an atom interferometer to measure time-dependent gravitational potentials.*

A Foucault pendulum hangs in an unused elevator shaft at the physics department of the U.S. Naval Postgraduate School in Monterey, CA. The quantum sensing team is building a 30-meter atom interferometer in an adjacent elevator shaft to measure the pendulum’s motion. Atom interferometers have proven to be highly capable instruments for capturing precision measurements. In this interferometer we use strontium atoms to take advantage of a low magnetic dipole moment. Between laser pulses, the cold strontium atoms evolve freely and take in information about their surroundings. We anticipate the sensitivity to measure the small changes in the gravitational potential field due to the oscillating mass of the pendulum. Not only are we interested in the sensitivity of this interferometer, but also that the measurements are completed within time scales that are operationally relevant in a defense context. In this talk we present an update on the construction efforts and review the pertinent theoretical calculations for this sensor. Specifically, we highlight the Feynman path integrals associated with closing the interferometer and time-dependent phase calculations.  Additionally, we show how initial calculations in 1D are altered to fit the 3D geometry of the experiment. We also discuss the anticipated next steps and review our experimental methodology.