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Here we discuss a phenomenon of sharp increase in the photon number noise at initial stages of propagation in tight-binding bosonic chains with off-diagonal disorder. Such a "noise avalanche" occurs under classical coherent excitation of waveguides and leads to high super-thermal photon bunching. Additional classical excitation slows but cannot quench this noise avalanche. However, an additional single-photon excitation stops the avalanche., Comment: 23 pages, 3 figures. Comments welcome and appreciated

In this paper, we develop a theory of edge effects in graphene for its applications to nanoantennas in the terahertz, infrared, and visible frequency ranges. Its characteristic feature is selfconsistence reached due the formulation in terms of dynamical conductance instead of ordinary used surface conductivity. The physical model of edge effects is based on using the concept of Dirac fermions. The surface conductance is considered as a general susceptibility and is calculated via the Kubo approach. In contrast with earlier models, the surface conductance becomes nonhomogeneous and nonlocal. The spatial behavior of the surface conductance depends on the length of the sheet and the electrochemical potential. Results of numerical simulations are presented for lengths in the range of 2.1-800 nm and electrochemical potentials ranging between 0.1-1.0 eV. It is shown that if the length exceeded 800 nm, our model agrees with the classical Drude conductivity model with a relatively high degree of accuracy. For rather short lengths, the conductance usually exhibits spatial oscillations, which absent in conductivity and strongly affect the properties of graphene based antennas. The period and amplitude of such spatial oscillations, strongly depend on the electrochemical potential. The new theory opens the way for realizing electrically controlled nanoantennas by changing the electrochemical potential may of the gate voltage. The obtained results may be applicable for the design of carbon based nanodevices in modern quantum technologies., Comment: 24 pages, 8 figures; typos corrected

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., Comment: It is a review paper (70 pages, 20 figures, 299 references)

In this article, we review the basic concepts of quantum radars as such types of the devices while highlighting differences with their classical analogs. We discuss how several concepts from traditional radars technology, e.g., target detection sensitivity, noise resilience and ranging accuracy can be translated to quantum radars. We examine such new far-field sensing protocols as quantum illumination (QI), and engineering opportunities enabled by its different realizations. We consider possibilities of achieving super-sensitivity and super-resolution using quantum correlations, and discuss possibilities to create quantum correlated states in practice., Comment: It is a brief popular review (11 pages, 7 figures, 77 references)