  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.
