Search

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., It is a brief popular review (11 pages, 7 figures, 77 references)

An adaptive multilevel non-uniform grid (MLNG) algorithm is developed for the accelerated computation of fields radiated through composite metallic-dielectric radomes as well as antenna-radome interactions. The MLNG approach is applied to the mixed potential formulation of the coupled surface and volume electric field integral equations. The radome is decomposed into a hierarchy of subdomains (SDs) by an adaptive algorithm that closely follows the radome geometry, allowing significant savings in memory and CPU time. In the MLNG algorithm, only local generalized impedance matrices of the finest level SDs are evaluated. Far-zone potentials and fields are indirectly evaluated through a multilevel aggregation involving phase and amplitude compensated interpolation on non-uniform grids (NGs), requiring considerably fewer calculations as compared with the classical Method of Moments (MoM). The MLNG algorithm is incorporated in a preconditioned iterative solver. Accuracy as well as memory consumption and computation times of the algorithm are studied on realistic examples. The radome effect on the antenna input impedance and electric current density distribution is demonstrated. The method is validated by comparison with a commercial MoM software and shown to exhibit a computational complexity (CC) of O(NlogN), N being the number of unknowns.

A backprojection-based synthetic aperture radar (SAR) processing approach for fast and accurate imaging of moving objects and stationary background is proposed. This divide-and-conquer backprojection approach allows for efficient detection of moving objects, estimation of their positions and velocities, and overlaying their focused images over the stationary background. Two algorithms are presented to exploit the tradeoff between the complexity and performance. The full 4-D phase space imaging algorithm provides the optimal performance under low signal-to-clutter conditions, while the adaptive detection and imaging leads to reduced complexity in more favorable scenarios. We show that in a single-channel SAR the conventional straight-line data collection path does not resolve the target’s velocity, therefore a curved path is assumed in the formulation and numerical examples.

A numerical model facilitating fast analysis of acoustic scattering by thin shells immersed in fluids is presented. The shell is simulated by an effective boundary condition, in which the inertial properties of the shell are taken into account while the elastic ones are neglected. The problem reduces to a hypersingular surface integral equation, which is solved using the boundary element method accelerated by the multilevel nonuniform grid approach. The validity of the numerical method and the adopted physical approximations were tested by comparison with a water tank experiment on acoustic scattering from cylindrical metallic shells filled with water.

The quantum framework of the time-dependent density functional theory (TDDFT) for analyzing nanostructured devices is reviewed, and alternative methods for incorporating induced electromagnetic fields into the theory are discussed. To capture the retardation effects in larger electronic structures, the TDDFT equations can be formulated by applying the Lorenz gauge-fixing condition to the induced scalar and vector potentials (analogous to macroscopic formulations used in antenna theory). Evaluating the retarded potentials via radiation integrals, however, rapidly becomes the computational bottleneck within the TDDFT time-marching framework if done in a brute-force manner. This article demonstrates that 3D space or 4D space-time fast Fourier transform (FFT) schemes can be adopted to accelerate these computations and reduce the costs of evaluating the potentials below the typical computational bottleneck of TDDFT. Thus, FFT-accelerated Lorenz gauge retarded potentials become an attractive candidate for replacing the conventionally used electrostatic-induced scalar potential within TDDFT.

Presents information on the 2019 IEEE International Conference on Microwaves, Communications, Antennas, and Electronic Systems.

A class of inherently compressible integral equation formulations for problems of scattering by impenetrable objects, which makes use of generalized directional sources, is presented. The new formulation effectively reduces the problem’s dimensionality and, thus, allows for efficient low-rank compression of moment matrices’ off-diagonal blocks. When the formulation is used with a hierarchical matrix compression and factorization algorithm, a fast direct solver is obtained. The computational bottlenecks introduced by the proposed generalized formulation, in both the matrix-fill and matrix compression stages, are alleviated by using nonuniform sampling-based techniques. These techniques are described in detail for one choice of generalized sources, which use absorbing equivalent source shields, and can be extended to other shield types. The formulation’s properties and limitations are studied and its enhanced compressibility is used for the development of a fast direct solver.

An asymptotic model of acoustic scattering by a thin elastic shell is developed. The shell is replaced with effective boundary conditions involving surface differential operators. The shell thickness is considered a small parameter. Analytical solutions within asymptotic approximations in the spherical case are compared with the exact solution for an elastic spherical layer. Resonance effects of the first and third order in the shell thickness are distinguished.

We consider transformation of quantum states of electromagnetic field by scattering from a perfectly conducting cylinder with a circular cross-section. We introduce a quantization technique for the scattered field, and demonstrate how quantumness (in particular, entanglement) of field states is transferred to the scattered field. The obtained results may be useful for designing quantum antennas and for quantum-enhanced far-field sensing, i.e., quantum lidars/radars.

A direct solver for quasi-planar electromagnetic scattering problems is developed. The algorithm consists of a multilevel domain decomposition, a rank revealing procedure (RRP), and a direct solution of the resulting compressed system of linear algebraic equations. The RRP is performed step by step from the bottom to top levels and is based on the singular value decomposition (SVD) using the interpolation grids of the Multilevel Nonuniform Grid (MLNG) approach. The efficiency of the solver is demonstrated by numerical experiments.

Low loss electromagnetic energy transport over long distances motivates the development of different types of waveguiding systems. Requirements of high quality optically polished waveguide surfaces needed in high-frequency applications and low-cost manufacturing are practically incompatible in current realizations. Here we demonstrate a new paradigm solution, based on surface functionalization with subsequent electroless plating of conductive micron smooth copper layer on the inner surface of flexible non-conducting poly-carbonate tubes. The structure was shown to support reasonable guiding performances (∼5·10−3 cm−1) at Ku-band. The mechanically flexible design of the system allows shaping the waveguide network almost on demand. In particular, an efficient energy guiding over a closed loop with 8 lambda radius was demonstrated. The new platform of high quality metalized flexible waveguiding systems opens new opportunities in designs of cheap and efficient networks, operating over a broad spectral range, approaching tens of GHz and even higher.

Artificially created media allow employing material parameters as additional valuable degrees of freedom in tailoring electromagnetic scattering. In particular, metamaterials with either negative permeability or permittivity allow creating deeply subwavelength resonant structures with relatively high scattering cross-sections. However, the equivalence principle allows replacing volumetric structures with properly designed curved impedance surfaces, ensuring the same electromagnetic properties. Here, we examine this statement from a practical standpoint, considering two structures, having a dipolar electric resonance at the same frequency. The first realization is based on arrays of inductively loaded electric dipoles printed on stacked circuit boards (a volumetric metamaterial), while the second structure utilizes a 4-wire spiral on a spherical surface (surface impedance realization). An intermediate conclusion is that the surface implementation tends to outperform the volumetric counterparts in the scenario when a single resonance is involved. However, in the case where multiple resonances are overlapping and lossy materials are involved, volumetric realization can have an advantage. The discussed structures are of significant importance to the field of electrically small antennas, superdirective antennas, and superscatterers, which find use in wireless communications and radar applications, to name just a few.

We propose a numerical technique for modeling the quantum multimode light scattering by a perfectly conducting body. Using the novel quantization technique, we give the quantum adaptation of the characteristic mode approach widely used in the classical electrodynamics. The method is universal with respect to the body's configuration, as well as its dimensions relative to the wavelength. Using this method and calculating the first- and the second-order field correlation functions, we demonstrate how scattering affects quantum-statistical features of the field. As an example, we consider scattering of the two single-photon incident Gaussian beams on the cylinder with circular cross-section. We show that the scattering is accompanied by the two-photon interference and demonstrates the Hong-Ou-Mandel effect. It is shown, that the scattered two-photon field and its correlations are able to manifest a varying directive propagation, which is controllable by various means (angles of incidence, configuration of the body, relations between its sizes with the frequency). We expect that this method will be useful for designing quantum-optical devices.

The scattering theory for two crossing metallic single-walled carbon nanotubes of finite length exposed to an electromagnetic field has been developed based on a synthesis of the quantum transport formalism and classical electrodynamics. The model of the point contact has been developed to be incorporated into the Hall\'en and Pocklington equations for crossing carbon nanotubes. The influence of the contact conductance and position as well as the angle between the tube axes on the tube polarizability has been analyzed in the range of 1 GHz to 10 THz. The physical mechanisms responsible for the electromagnetic interaction between crossing tubes with zero and nonzero intertube contact conductance are shown and discussed. The influence of the coupling between the tubes on the localized plasmon resonance in them has been demonstrated.

A fast solver based on the multilevel nonuniform grid approach and an asymptotic approximation designed for scattering by strongly elongated spheroids are mutually validated. Good agreement between the numerical and asymptotic solutions is observed over a wide frequency range for spheroids with various aspect ratios. Numerical noise of the numerical solution is estimated.

A periodic array of dual-Vivaldi antennas integrated with metal-insulator-metal (MIM) plasmonic waveguides was designed and investigated for its infrared light absorbance efficiency. Full-wave analysis was used to optimize MIM waveguides compatible with parallel and series connected DC leads without sacrificing radiation efficiency. Free-space to MIM waveguide in-coupling efficiency as high as 41% has been obtained in a sub-wavelength unit cell geometry at a wavelength of 1373 nm. Higher efficiency, up to 85%, is predicted with a modified design including a backplane reflector. A nanofabrication process was developed to realize test devices and far-field optical spectroscopy was used as experimental evidence for antenna-waveguide matching.

A shadow-radiation-based fast iterative physical optics (IPO) scheme, for the analysis of the scattering from large complex geometries involving multiple reflection and occlusion effects, is proposed. By employing a “shadow-radiation” mechanism, the scheme alleviates the need for expensive computation and storage of a geometric visibility function. In a nested fashion, shadow radiation iterations are performed for each “bounce” in the conventional multiple reflection IPO scheme. The resulting method makes use of simple field integrals which are all accelerable using a multilevel nonuniform grid-based field evaluation algorithm, with a modification tailored to the scheme’s integral kernels. The proposed scheme is also shown analytically to be a more stable (faster converging) equivalent of existing IPO schemes. The method is studied in terms of accuracy and performance for representative examples and compared with alternative physical optics and numerically exact solution techniques.

Employment of modern 3D-printing technologies allow efficient exploration of the third space dimension, providing advantages over conventional planar architectures. In particular, volumetric electromagnetic antennas can outperform their planar counterparts. Here a new approach to fabrication of electromagnetic devices is developed and applied to antennas, implemented on b-spline surfaces. The antenna skeleton and the support were simultaneously printed with different polymer materials - PLA mixed with graphene flakes and pure PLA, respectively. Weakly dc-conductive graphene PLA-based skeleton was post-processed and high quality conductive layer was selectively electrochemically deposited on it. The antenna devices were found to demonstrate radiation performance, similar to that achievable with conventional fabrication approaches. However, additive manufacturing of RF antennas provides superior capabilities of constructing tailor-made devices with properties, pre-defined by non-standardized end users.