Atomic Test of the Equivalence Principle in a 10-meter Tower

We aim to explore and expand the limits of atom interferometry in a 10-meter tower at Stanford University. Atom interferometry uses the coherent splitting and recombination of atoms to make precision measurements of environmental parameters such as gravity, acceleration, or magnetic field. The apparatus has been designed to test Einstein's Equivalence Principle to a precision of $10^{-15}$g by simultaneously launching ultracold atoms of different mass (specifically $^{85}$Rb and $^{87}$Rb) and accurately observing their free-fall motion in a vacuum chamber. Although we will perform the measurements with low-density clouds of cold atoms, we have demonstrated our ability to cool the atoms by forming Bose-Einstein condensates of $^{87}$Rb. Cold, dilute clouds can be launched with an optical lattice into the interferometer region. Splitting the atoms with Bragg pulses allows for the creation of a Mach-Zehnder interferometer for the Equivalence Principle measurement.