Quadrature Space Research Articles

On the performance of wireless sensor networks with QSSK modulation in the presence of co-channel interference

This paper proposes the use of quadrature space shift keying (QSSK) modulation for wireless sensor networks (WSNs). QSSK is a multiple input multiple output communication protocol that attracted substantial interest due to several promised inherent advantages. It has been shown in literature that QSSK scheme achieves high spectral efficiency with low average error probability, high energy efficiency, and very simple transmitter and receiver architectures. Hence, its use in WSNs is very promising to ameliorate the major limitations of such networks. The performance of a WSN with QSSK modulation and in the presence of co-channel interference is studied in this paper. A closed form expression for the average pair wise error probability is derived and used to obtain a tight upper bound on the overall average bit error ratio. Obtained results verified the superiority of QSSK scheme as compared to traditional modulation techniques especially for high spectral efficiency.

Three dimensional thermal diffusion in anisotropic heterogeneous structures simulated by a non-dimensional lattice Boltzmann method with a controllable structure generation scheme based on discrete Gaussian quadrature space and velocity

A new Controllable Structure Generation Scheme (CSGS) based on discrete Gaussian quadrature space and velocity is presented and used to generate multiple-phase random isotropic homogenous and shape-constrained anisotropic heterogeneous structures. The primary advantage of the new CSGS over the existing random structure generation growth method is the ability to model a wide variety of structures by controlling the shape through relatively simple constraint indexes. The growth speed probability function is introduced to control the mesoscopic porosities and mixture/separation of material phases. The model is applied to generate four packed structure types (shapeless random, separated solid shapes, separated random-filled shapes, and random-mixture-filled shapes). Three-dimensional steady and transient thermal diffusion are simulated by Non-Dimensional Lattice Boltzmann Method (NDLBM). The steady state results are compared to measured data available in the published literature. The transient results reveal how the mesoscopic shape of a structure impacts thermal diffusion. With equivalent macroscopic volume fractions, structures with higher mesoscopic volume fractions of high conductivity phases possess higher effective thermal conductivity/diffusivity because there is greater connectivity of the higher conductive material at mesoscopic scale.

Generating a perfect quantum optical vortex

In this article we introduce a novel quantum state, the perfect quantum optical vortex state which exhibits a highly localised distribution along a ring in the quadrature space. We examine its nonclassical properties using the Wigner function and the negativity volume. Such a quantum state can be a useful resource for quantum information processing and communication.

Cavity Femtochemistry: Manipulating Nonadiabatic Dynamics at Avoided Crossings.

Molecular potential energy surfaces can be actively manipulated by light. This is usually done by strong classical laser light but was recently demonstrated for the quantum field in an optical cavity. The photonic vacuum state of a localized cavity mode can be strongly mixed with the molecular degrees of freedom to create hybrid field-matter states known as polaritons. We simulate the avoided crossing of sodium iodide in a cavity by incorporating the quantized cavity field into the nuclear wave packet dynamics calculation. The quantized field is represented on a numerical grid in quadrature space, thus avoiding the limitations set by the rotating wave approximation (RWA) when the field is expanded in Fock space. This approach allows the investigation of cavity couplings in the vicinity of naturally occurring avoided crossings and conical intersections, which is too expensive in the fock space expansion when the RWA does not apply. Numerical results show how the branching ratio between the covalent and ionic dissociation channels can be strongly manipulated by the optical cavity.

BER-driven synthesis for directional modulation secured wireless communication

Directional modulation (DM) is a recently introduced technique for secure wireless transmission using direct physical layer wave-front manipulation. This paper provides a bit error rate (BER)-based DM array synthesis method. It is shown for the first time that the standard constellation mappings in In-phase and Quadrature (IQ) space to a pre-specified BER can be exactly achieved along a given specified spatial direction. Different receiver capabilities are investigated and different assessment metrics for each case are discussed. The approach is validated for a1 × 4element dipole array operating at 1 GHz.

Preparing quantum vortex states with odd Schrödinger cat states through a coupled waveguide system

A scheme is proposed for preparing a quantum vortex state with a coupled waveguide, in which a single-mode odd cat state with weak intensity and a single-mode coherent state are inserted in the input ports, respectively. The analytical wavefunction of the resulting state in the quadrature space is derived, and the vortex structure of the output state is analyzed. It is found that the obtained states, which may carry a vortex with topological charge index one, are entangled and nonclassical, depending only on the scaled propagation time and the weak intensity of the input odd cat state instead of the displacement parameter of the input coherent state. The phase distribution, however, in the quadrature space, depends on the displacement parameter of the input coherent state

Engineering Two-Mode Non-Gaussian States with Vortex Structures Using a Beam Splitter

Vortex structure and entanglement properties of output field from a beam splitter are investigated. With a n-photon Fock state and a coherent state as the inputs, it is found that the output state before a beam splitter bears a vortex structure in quadrature space and is always entangled and non-classical based on the linear entropy criterion and the P-function analysis in phase space.

The Partial Revival of the Quadrature Variance Product in the Dynamics of the Squeezed Vacuum Field in the Jaynes-Cummings Model

We consider the time evolution of a squeezed vacuum cavity field interacting with an initially excited two-level atom via the Jaynes-Cummings model in the Rotating Wave approximation. For large enough initial squeezing, we recognize a new partial revival phenomenon in terms of the quadrature variance product. We show the time evolution of the field quasiprobability Q-function, which provides a quadrature space picture of the partial revival phenomenon. An interpretation of the phenomenon in terms of a certain kind of first momentum of the photon distribution function is given.

Analysis Of Machine Foundations On Undrained(incompressible) Soils

A boundary element formulation, incorporating an infinite element approach to describe the far-field behaviour outside the immediate vicinity of the loaded area and coupled with the asymptotic form of the full-space Green's function for harmonic point loading in incompressible media, is used to analyse the machine foundation problem. The infinite elements assumed in the analysis are based on Rayleigh wave attenuation away from a source located at the centroid of the loaded area, while in the finite regions, tractions and displacements are described by quadratic interpolation functions between the element nodes, and the integrations are carried out by means of triangular subelement mappings into Gauss quadrature space to reduce the order of the singularities. A combined analytical/numerical approach is used to evaluate the integrals over the infinite free surface. Illustrative impedance plots for shallow foundations are presented in order to illustrate the potential of the formulation for incompressible media. The results for vertical loading can be described accurately using the simple, participating mass concept.