Increasing the sensitivity of light-pulse atom interferometers demands precise control over light–matter interactions and quantum states. In this seminar, we present recent advances across three key areas: First, we demonstrate dichroic mirror pulses enabling selective reflection of resonant atomic paths in Bragg diffraction, effectively isolating desired interferometric signals and enhancing scalability to large-momentum transfers. Second, we explore quantum-enhanced Bragg interferometry using entangled or squeezed atomic ensembles, highlighting the interplay between loss mechanisms, velocity selectivity, and achievable sensitivity beyond the shot-noise limit. Finally, we discuss atom interferometers as precision probes for fundamental physics, including their role as quantum detectors of gravitational waves and as correlated sensors for differential phase measurements. Together, these developments showcase how quantum engineering can advance the frontier of quantum sensing and fundamental physics experiments.