Meyer, David HenryThis work encompasses two projects employing coherent probing of neutral rubidium atom vapors for sensing applications: 1) observing and characterizing new ``twists'' within Nonlinear Magneto-Optical Rotation (NMOR) signals in laser-cooled atoms. Using these features an in-situ, multi-directional characterization of magnetic fields and gradients at the sub-mG (and mG/mm) level in a compact cold-atom system is demonstrated; 2) high-bandwidth, phase-sensitive electrometry via Electromagnetically Induced Transparency (EIT) with a warm vapor of Rydberg atoms is employed as a digital communication receiver of free-space, modulated RF carrier electric fields. Channel capacities in excess of 10 Mbit/s are measured. Performance limitations due to EIT probing and fundamental quantum noise are explored in detail.enDissertationAtomic physicsQuantum physicsDigital CommunicationElectromagnetically Induced TransparencyElectrometryMagnetometryNonlinear Magneto-Optical RotationRydberg