The Optical and Quantum Communications Group develops impactful classical and quantum technologies and system prototypes for use in a wide range of challenging environments including terrestrial, space and underwater applications. Primary areas of research include the development of novel modulation and coding approaches; multi-format modems; sensitive, single-photon receivers; robust and compact optical beam directors; precision beam pointing, link acquisition and tracking systems; and novel entangled-photon source technologies. The group is leveraging these technologies for use in prototype systems that are deployed in the field to inform next-generation classical and quantum optical system capabilities. Examples of near-term field tests include terabit-per-second direct-to-Earth small-satellite constellations, near-Earth wideband relay laser communication terminal hardware for space and ground, and next-generation beam-director prototypes inherently scalable to deep-space systems...