Quantum Antennas

Due to the recent groundbreaking developmentsof nanotechnologies,it became possible to create intrinsically quantum systems able to serve as high-directional antennas in THz, infrared and optical ranges. Actually, the quantum antennas,as devices shaping light on thelevel of single quanta,havealreadybecomethe key elements in nanooptics and nanoelectronics. The quantum antennas are actively researched for possible implementations in quantum communications, quantum imaging and sensing,andenergy harvesting. However, the design and optimization of these emitting/receivingdevices arestill rather undevelopedin comparisonwith 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 systememitting via interaction with a photonic reservoir. We focuson bridging the gap between quantum antennas and their macroscopic classical analogues. We also discuss the ways of quantum-antennaimplementation for different configurations basedon such materials, as plasmonic metals, carbon nanotubes, and semiconductor quantum dots.