Block Locally Optimal Preconditioned Eigenvalue Xolvers (BLOPEX) in hypre and PETSc

We describe our software package Block Locally Optimal Preconditioned Eigenvalue Xolvers (BLOPEX) publicly released recently. BLOPEX is available as a stand-alone serial library, as an external package to PETSc (``Portable, Extensible Toolkit for Scientific Computation'', a general purpose suite of tools for the scalable solution of partial differential equations and related problems developed by Argonne National Laboratory), and is also built into {\it hypre} (``High Performance Preconditioners'', scalable linear solvers package developed by Lawrence Livermore National Laboratory). The present BLOPEX release includes only one solver--the Locally Optimal Block Preconditioned Conjugate Gradient (LOBPCG) method for symmetric eigenvalue problems. {\it hypre} provides users with advanced high-quality parallel preconditioners for linear systems, in particular, with domain decomposition and multigrid preconditioners. With BLOPEX, the same preconditioners can now be efficiently used for symmetric eigenvalue problems. PETSc facilitates the integration of independently developed application modules with strict attention to component interoperability, and makes BLOPEX extremely easy to compile and use with preconditioners that are available via PETSc. We present the LOBPCG algorithm in BLOPEX for {\it hypre} and PETSc. We demonstrate numerically the scalability of BLOPEX by testing it on a number of distributed and shared memory parallel systems, including a Beowulf system, SUN Fire 880, an AMD dual-core Opteron workstation, and IBM BlueGene/L supercomputer, using PETSc domain decomposition and {\it hypre} multigrid preconditioning. We test BLOPEX on a model problem, the standard 7-point finite-difference approximation of the 3-D Laplacian, with the problem size in the range $10^5-10^8$.Comment: Submitted to SIAM Journal on Scientific Computin

Interfacing single photons and single quantum dots with photonic nanostructures

Photonic nanostructures provide means of tailoring the interaction between light and matter and the past decade has witnessed a tremendous experimental and theoretical progress in this subject. In particular, the combination with semiconductor quantum dots has proven successful. This manuscript reviews quantum optics with excitons in single quantum dots embedded in photonic nanostructures. The ability to engineer the light-matter interaction strength in integrated photonic nanostructures enables a range of fundamental quantum-electrodynamics experiments on, e.g., spontaneous-emission control, modified Lamb shifts, and enhanced dipole-dipole interaction. Furthermore, highly efficient single-photon sources and giant photon nonlinearities may be implemented with immediate applications for photonic quantum-information processing. The review summarizes the general theoretical framework of photon emission including the role of dephasing processes, and applies it to photonic nanostructures of current interest, such as photonic-crystal cavities and waveguides, dielectric nanowires, and plasmonic waveguides. The introduced concepts are generally applicable in quantum nanophotonics and apply to a large extent also to other quantum emitters, such as molecules, nitrogen vacancy ceters, or atoms. Finally, the progress and future prospects of applications in quantum-information processing are considered.Comment: Updated version resubmitted to Reviews of Modern Physic

Center for Space Microelectronics Technology

The 1991 Technical Report of the Jet Propulsion Laboratory Center for Space Microelectronics Technology summarizes the technical accomplishments, publications, presentations, and patents of the Center during the past year. The report lists 193 publications, 211 presentations, and 125 new technology reports and patents

Optical Forces Generated by Plasmonic Nanostructures

For millennia, scientists have sought to uncover the secrets of what holds the world together. Optical physicists are often at the forefront, unraveling material properties through investigations of light-matter interactions. As the field has progressed, the smallest unit at which matter can be probed and manipulated has subsequently decreased. The resulting sub-field nanophotonics- which reflects the processing of light at the nanoscale- has blossomed into a vast design space for both applied and theoretical researchers. Plasmonics, the phenomena by which the electron-density of a material oscillates in response to incident electromagnetic radiation, is a subject that has excited nanophotonics researchers for two reasons. The first is that plasmonic excitations are able to couple light to sub-wavelength dimensions, circumventing the diffraction limit and concentrating electromagnetic fields, leading to significantly enhanced light-matter interactions. The second is that the advances in nanofabrication methods, driven by the silicon microelectronics industry, has allowed for the fabrication and development of metallic structures at the nanoscale, a requirement for the excitation of plasmons with visible light. This thesis explores some aspects of how plasmonics can be used to exploit the design, fabrication and applications of nanostructures that result in materials with highly tailored optical properties. In particular, this thesis will demonstrate the understanding of how high electromagnetic field density that plasmons create produce optically-generated forces. Applications of the optically-generated forces presented here include the advanced control of nanoparticles that form the building blocks of metamaterials, as well as metasurface designs that vary polarization and encode information. Ultimately, it is hoped that this work furthers the research on how metasurfaces and metamaterials are designed, fabricated, and applied

Real-space electronic structure calculations for nanoscale systems

In this thesis, basic research focused on quantum systems relevant for the future nanotechnologies is presented. The research is modeling based on electronic structure calculations using the density-functional theory. For the solution of the ensuing Kohn-Sham equations, we have developed a new numerical scheme based on the Rayleigh quotient multigrid method. While an important part of the thesis is formed by software development for three-dimensional first-principles real-space electronic structure calculations, we use axially symmetric model systems in the study of nanostructures. This approximation reduces the computational demands and allows studies of rather large nanoscale systems encompassing hundreds or thousands of electrons. In addition, by restricting the geometry to the axial symmetry and resorting to jellium models, many random effects related to the detailed ionic structure are absent, and the relevant physics is easier to extract from the simulations. Nanowires can be considered as the ultimate conductors in which the atomistic confinement of electrons perpendicular to the wire and the atomistic length of the wire lead to quantum mechanical effects in cohesive and transport properties. The breaking process of a nanowire is studied using the ultimate jellium model, in which the positive background charge compensates in every point the electronic charge. Thereby, the shape of the narrowing constriction is free to vary so that the total energy is minimized. The prospect of molecular electronics is to use single molecules as circuit components. The electronic transport in atomic chains of a few Na atoms between cone-shaped leads is investigated in the thesis. Electrons residing in a Na island on the Cu(111) surface form a quantum dot system, in which the quantum mechanical confinement in all directions determines the electronic properties. We have developed a simple jellium model system which reproduces the characteristics of the confined electron states seen in scanning tunneling microscope experiments.reviewe