I. Introduction
The Matter-wave Atomic Gradiometer Interferometric Sensor (MAGIS-100), currently under construction at Fermilab, is a 100-m tall atomic fountain that will be used to explore fundamental physics on a macroscopic scale. Functioning as a high-precision quantum sensor, it will search for ultralight dark matter and exotic forces, as well as test quantum mechanics in a new regime. MAGIS-100 will also serve as a testbed for new technologies required to eventually develop a km-scale atomic interferometer capable of detecting gravitational waves in the currently unexplored midband region, corresponding to 0.3 to 3 Hertz, bridging the gap between the peak sensitivities of LIGO and LISA [1].