Quantum Antennas

Due to the recent groundbreaking developments of nanotechnologies, it became possible to create intrinsically quantum systems able to serve as high‐directional antennas in terahertz, infrared, and optical ranges. In fact, the quantum antennas, as devices shaping light on the level of single quanta, have already become key elements in nanooptics and nanoelectronics. The quantum antennas are actively researched for possible implementations in quantum communications, quantum imaging and sensing, and energy harvesting. However, the design and optimization of these emitting/receiving devices are still rather undeveloped in comparison with the well‐known methods for conventional radio‐frequency antennas. This review provides a discussion of the recent achievements in the concept of the quantum antenna as an open quantum system emitting via interaction with a photonic reservoir. The review is focused on bridging the gap between quantum antennas and their macroscopic classical analogues. Furthermore, the way of quantum‐antenna implementation is discussed for different configurations, based on such materials as plasmonic metals, carbon nanotubes, and semiconductor quantum dots. Quantum antennas are promising tools for imaging and sensing that allow reaching super‐directivity of emission and super‐resolution. They shape not only a spatial distribution of the emitted field amplitude, but also its quantum correlations. This review summarizes theoretical advances related to the emerging field of quantum antennas and experimental implementations.