Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Quantum Routing”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Facile fabrication of highly ordered poly(vinylidene fluoride-trifluoroethylene) nanodot arrays for organic ferroelectric memory

Nano-patterned ferroelectric materials have attracted significant attention as the presence of two or more thermodynamically equivalent switchable polarization states can be employed in many applications such as non-volatile memory. In this work, a simple and effective approach for fabrication of highly ordered poly(vinylidene fluoride–trifluoroethylene) P(VDF-TrFE) nanodot arrays is demonstrated. By using a soft polydimethylsiloxane mold, we successfully transferred the 2D array pattern from the initial monolayer of colloidal polystyrene nanospheres to the imprinted P(VDF-TrFE) films via nanoimprinting. The existence of a preferred orientation of the copolymer chain after nanoimprinting was confirmed by Fourier transform infrared spectra. Local polarization switching behavior was measured by piezoresponse force microscopy, and each nanodot showed well-formed hysteresis curve and butterfly loop with a coercive field of ∼62.5 MV/m. To illustrate the potential application of these ordered P(VDF-TrFE) nanodot arrays, the writing and reading process as non-volatile memory was demonstrated at a relatively low voltage. As such, our results offer a facile and promising route to produce arrays of ferroelectric polymer nanodots with improved piezoelectric functionality.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Surfactant-induced chemical ordering of GaAsN:Bi

In this study, we have examined the influence of an incorporating surfactant on chemical ordering in GaAsN:Bi alloys. Epitaxy with a (2 x 1) reconstruction leads to the formation of GaAsN alloys, while the introduction of a Bi flux induces long-range chemical ordering of the {111} planes of GaAsN:Bi. We propose a mechanism in which Bi enhances the alignment of dimer rows along the [110] direction, facilitating N incorporation beneath surface dimers and Bi incorporation between dimer rows to form alternating N-rich and Bi-rich {111} planes. In conclusion, these findings suggest a route to tailoring the local atomic environment of N and Bi atoms in a wide range of emerging dilute nitride-bismide alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Bifurcations and degenerate periodic points in a three dimensional chaotic fluid flow

Analysis of the periodic points of a conservative periodic dynamical system uncovers the basic kinematic structure of the transport dynamics and identifies regions of local stability or chaos. While elliptic and hyperbolic points typically govern such behaviour in 3D systems, degenerate (parabolic) points also play an important role. These points represent a bifurcation in local stability and Lagrangian topology. In this study, we consider the ramifications of the two types of degenerate periodic points that occur in a model 3D fluid flow. (1) Period-tripling bifurcations occur when the local rotation angle associated with elliptic points is reversed, creating a reversal in the orientation of associated Lagrangian structures. Even though a single unstable point is created, the bifurcation in local stability has a large influence on local transport and the global arrangement of manifolds as the unstable degenerate point has three stable and three unstable directions, similar to hyperbolic points, and occurs at the intersection of three hyperbolic periodic lines. The presence of period-tripling bifurcation points indicates regions of both chaos and confinement, with the extent of each depending on the nature of the associated manifold intersections. (2) The second type of bifurcation occurs when periodic lines become tangent to local or global invariant surfaces. This bifurcation creates both saddle–centre bifurcations which can create both chaotic and stable regions, and period-doubling bifurcations which are a common route to chaos in 2D systems. We provide conditions for the occurrence of these tangent bifurcations in 3D conservative systems, as well as constraints on the possible types of tangent bifurcation that can occur based on topological considerations.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Superconductivity in dilute SrTiO 3 : A review

Doped SrTiO 3 , one of the most dilute bulk systems to display superconductivity, is perhaps the first example of an unconventional superconductor, as it does not fit into the standard BCS paradigm. More than five decades of research has revealed a rich temperature-carrier concentration phase diagram that showcases a superconducting dome, proximity to a putative quantum critical point, Lifshitz transitions, a multi-gap pairing state and unusual normal-state transport properties. Research has also extended beyond bulk SrTiO 3 , ushering the new field of SrTiO 3 -based heterostructures. Because many of these themes are also featured in other quantum materials of contemporary interest, recent years have seen renewed interest in SrTiO 3 . Here, we review the challenges and recent progress in elucidating the superconducting state of this model system. At the same time that its extreme dilution requires to revisit several of the approximations that constitute the successful Migdal–Eliashberg description of electron–phonon superconductivity, including the suppression of the Coulomb repulsion via the Tolmachev–Anderson–Morel mechanism, it opens interesting routes for alternative pairing mechanisms whose applicability remains under debate. For instance, pairing mechanisms involving longitudinal optical phonons have to overcome the hurdles created by the anti-adiabatic nature of the pairing interaction, whereas mechanisms that rely on the soft transverse optical phonons associated with incipient ferroelectricity face challenges related to the nature of the electron–phonon coupling. Proposals in which pairing is mediated by plasmons or promoted locally by defects are also discussed. In conclusion, we finish by surveying the existing evidence for multi-band superconductivity and outlining promising directions that can potentially shed new light on the rich problem of superconductivity in SrTiO 3 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Highly Textured Tin(II) Sulfide Thin Films Formed from Sheetlike Nanocrystal Inks

Highly textured tin(II) sulfide thin films are prepared from a nanocrystal ink comprised of high-aspect-ratio nanosheets. The orthorhombic nanosheets are synthesized colloidally to isolate lateral growth and minimize the presence of alternate crystal phases. The tin sulfide films deposited from the nanosheets exhibit pure elemental composition, micrometer-sized grains, and a remarkable degree of texturing. The films consist of lamellar stacking of nanosheets with some intercalation, and the average sheet thickness is ~30 nm. The SnS films have an indirect band gap of 1.23 eV, and density functional theory calculations indicate minimal quantum confinement contributions. The anisotropic electronic properties of tin sulfide are greatly intensified in films formed by this process, yielding an in-plane mobility of 5.7 cm 2 /(V s) but an out-of-plane resistivity as high as 30 kΩ cm. This work represents a new strategy for nanocrystal inks in which the nanocrystal morphology is tailored to direct film orientation, grain size, and transport properties. The method provides a route for the deposition of high-quality, layered semiconductor thin films with applications in photovoltaics and two-dimensional (2-D) electronics.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Imaging an aligned polyatomic molecule with laser-induced electron diffraction

Laser-induced electron diffraction is an evolving tabletop method that aims to image ultrafast structural changes in gas-phase polyatomic molecules with sub-Ångstro¨m spatial and femtosecond temporal resolutions. Here we demonstrate the retrieval of multiple bond lengths from a polyatomic molecule by simultaneously measuring the C–C and C–H bond lengths in aligned acetylene. Our approach takes the method beyond the hitherto achieved imaging of simple diatomic molecules and is based on the combination of a 160 kHz mid-infrared few-cycle laser source with full three-dimensional electron–ion coincidence detection. Our technique provides an accessible and robust route towards imaging ultrafast processes in complex gas-phase molecules with atto- to femto-second temporal resolution.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Systems and methods for vehicle speed management

Controlling a speed of a vehicle based on at least a portion of a route grade and a route distance divided into a plurality of route sections, each including at least one of a section grade and section length. Controlling the speed of the vehicle is further based on determining a cruise control speed mode for the vehicle for each of the plurality of route sections and determining a speed reference command of the vehicle based on at least one of the cruise control speed mode, the section length, the section grade, and a current speed.

42 ENGINEERING↗
DOE OSTI2024

Characterization of lignin-degrading enzyme PmdC, which catalyzes a key step in the synthesis of polymer precursor 2-pyrone-4,6-dicarboxylic acid

Pyrone-2,4-dicarboxylic acid (PDC) is a valuable polymer precursor that can be derived from the microbial degradation of lignin. The key enzyme in the microbial production of PDC is 4-carboxy-2-hydroxymuconate-6-semialdehyde (CHMS) dehydrogenase, which acts on the substrate CHMS. We present the crystal structure of CHMS dehydrogenase (PmdC from Comamonas testosteroni) bound to the cofactor NADP, shedding light on its three-dimensional architecture, and revealing residues responsible for binding NADP. Using a combination of structural homology, molecular docking, and quantum chemistry calculations, we have predicted the binding site of CHMS. Key histidine residues in a conserved sequence are identified as crucial for binding the hydroxyl group of CHMS and facilitating dehydrogenation with NADP. Mutating these histidine residues results in a loss of enzyme activity, leading to a proposed model for the enzyme's mechanism. These findings are expected to help guide efforts in protein and metabolic engineering to enhance PDC yields in biological routes to polymer feedstock synthesis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Anyon superconductivity from topological criticality in a Hofstadter–Hubbard model

We argue that the combination of strong repulsive interactions and high magnetic fields can generate electron pairing and superconductivity. Inspired by the large lattice constants of moiré materials, which make large flux per unit cell accessible at laboratory fields, we study the triangular lattice Hofstadter-Hubbard model at one-quarter flux quantum per plaquette, where previous literature has argued that a chiral spin liquid separates a weak-coupling integer quantum Hall phase and a strong-coupling topologically trivial antiferromagnetic insulator at a density of one electron per site. We argue that topological superconductivity emerges upon doping in the vicinity of the integer quantum Hall to chiral spin liquid transition. We employ exact diagonalization and density matrix renormalization group methods to examine this theoretical scenario and find that electronic pairing indeed occurs on both sides of criticality over a remarkably broad range of interaction strengths. On the chiral spin liquid side, our results provide a concrete model realization of the long-hypothesized mechanism of anyon superconductivity. Our study thus establishes a beyond-Bardeen-Cooper-Schrieffer route to electron pairing in a well-controlled limit, relying crucially on the interplay between electron correlations and band topology.

Hubbard model↗
DOE OSTI2014

Preparation and characterization of nanocrystalline CuO powders with the different surfactants and complexing agent mediated precipitation method

Highlights: • CuO nanostructures by surfactants mediated method. • Structural and optical properties of CuO nanostructures changes under the effect of surface modifier. • Citric acid assisted is the best, in terms of size, morphology and optical properties than that of CTAB, SDS and PEG-400. - Abstract: Nanostructures of copper oxide (CuO) was synthesized into crystallite sized ranging from 20 to 50 nm in the presence of different surfactants, and complex agent such as cityl tri methyl ammonium bromide (CTAB), sodium do decyl sulfate (SDS), poly ethylene glycol (PEG-400) and citric acid via a precipitation route. Variations in several parameters and their effects on the structural and optical properties of CuO nanostructures (crystallite size, morphology and band gap) were investigated by XRD, FTIR, SEM and UV analysis. The UV–visible absorption spectra of the different surfactants and complexing agent assisted CuO nanostructures indicates that the estimated optical band gap energy value (1.94–1.98 eV) is higher than that of the bulk CuO value (1.4 eV), which is attributed to the quantum confinement effect. The formation mechanism of different surfactants and complexing agent assisted CuO nanostructures is also proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Directed-Assembly of Block Copolymers for Large-Scale, Three-Dimensional, Optical Metamaterials at Visible Wavelengths. Final LDRD Report

Metamaterials are composites with patterned subwavelength features where the choice of materials and subwavelength structuring bestows upon the metamaterials unique optical properties not found in nature, thereby enabling optical applications previously considered impossible. However, because the structure of optical metamaterials must be subwavelength, metamaterials operating at visible wavelengths require features on the order of 100 nm or smaller, and such resolution typically requires top-down lithographic fabrication techniques that are not easily scaled to device-relevant areas that are square centimeters in size. In this project, we developed a new fabrication route using block copolymers to make over large device-relevant areas optical metamaterials that operate at visible wavelengths. Our structures are smaller in size (sub-100 nm) and cover a larger area (cm 2 ) than what has been achieved with traditional nanofabrication routes. To guide our experimental efforts, we developed an algorithm to calculate the expected optical properties (specifically the index of refraction) of such metamaterials that predicts that we can achieve surprisingly large changes in optical properties with small changes in metamaterials’ structure. In the course of our work, we also found that the ordered metal nanowires meshes produced by our scalable fabrication route for making optical metamaterials may also possibly act as transparent electrodes, which are needed in electrical displays and solar cells. We explored the ordered metal nanowires meshes’ utility for this application and developed design guidelines to aide our experimental efforts.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Architectural scaling tradeoffs in modular 3D bosonic quantum processors

We propose a modular three-dimensional bosonic quantum processor built from repeatable coupled-cavity modules linked by configurable interconnect networks. Using hardware-motivated graph-theoretic measures, we compare nearest-neighbor, hub-based, and hybrid architectures in terms of interconnect count, communication distance, resource concentration, and implementation complexity. Rather than identifying a universally optimal topology, our analysis shows how these architectures redistribute the costs of scaling, including wiring and port requirements, nonlocal communication distance, exposure to shared resources, routing bottlenecks, and scheduling overhead. Case studies of a \(3\times3\) processor and a larger hierarchical architecture further distinguish finite-size performance from asymptotic scaling. The resulting framework provides a systematic basis for evaluating modular three-dimensional bosonic processors and for identifying the device-level parameters required for quantitative hardware design.

Zhu, Shaojiang [Fermilab] (ORCID:0000000293180092)↗
DOE OSTI2018

Large Deviations for Gaussian Diffusions with Delay

Dynamical systems driven by nonlinear delay SDEs with small noise can exhibit important rare events on long timescales. When there is no delay, classical large deviations theory quantifies rare events such as escapes from metastable fixed points. Near such fixed points, one can approximate nonlinear delay SDEs by linear delay SDEs. Here, we develop a fully explicit large deviations framework for (necessarily Gaussian) processes X{sub t} driven by linear delay SDEs with small diffusion coefficients. Our approach enables fast numerical computation of the action functional controlling rare events for X{sub t} and of the most likely paths transiting from X{sub 0}=p to X{sub T}=q. Via linear noise local approximations, we can then compute most likely routes of escape from metastable states for nonlinear delay SDEs. We apply our methodology to the detailed dynamics of a genetic regulatory circuit, namely the co-repressive toggle switch, which may be described by a nonlinear chemical Langevin SDE with delay.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Structure-Properties Correlation in Si Nanoparticles by Total Scattering and Computer Simulations

High-energy synchrotron X-ray diffraction coupled to atomic pair distribution function analysis and computer simulations is used to determine the atomic-scale structure of silicon (Si) nanoparticles obtained by two different synthetic routes. Results show that Si nanoparticles may have significant structural differences depending on the synthesis route and surface chemistry. In this case, one method produced Si nanoparticles that are highly crystalline but surface oxidized, whereas a different method yields organic ligand-passivated nanoparticles without surface oxide but that are structurally distorted at the atomic scale. Particular structural features of the oxide-free Si nanoparticles such as average first coordination numbers, length of structural coherence, and degree of local distortions are compared to their optical properties such as photoluminescence emission energy, quantum yield, and Raman spectra. A clear structure–properties correlation is observed indicating that the former may need to be taken into account when considering the latter.

Petkov, Valeri↗
DOE OSTI2025

Mixed quantum-classical methods for polaron spectral functions

In this work, using two distinct semiclassical approaches—namely, the mean-field Ehrenfest method and the mapping approach to surface hopping—we investigate the spectral function of a single charge interacting with phonons on a lattice. This quantity is relevant for the description of angle-resolved photoemission experiments. Focusing on the one-dimensional Holstein model, we compare the performance of these approaches across a range of coupling strengths and lattice sizes, exposing the relative strengths and weaknesses of each. We demonstrate that these approaches can be efficiently applied with reasonable accuracy to ab initio polaron models. Furthermore, our work provides a route to the calculation of spectral properties in realistic electron–phonon-coupled systems in a computationally inexpensive manner with encouraging accuracy.

Atomic and molecular spectra↗
DOE OSTI2019

Preparation of RE(DBM){sub 3}·Phen (RE=Eu{sup 3+},Tb{sup 3+}) Plate-Loading Fe{sub 3}O{sub 4} Nanospheres and their Magnetic-Optic Bifunctional Property

A facile wet chemical method has been used to synthesize bifunctional core-shell nanoparticles of Fe{sub 3}O{sub 4}@RE(DBM){sub 3}·Phen (RE=Eu{sup 3+},Tb{sup 3+}) showing an interesting combination of magnetic and luminescent properties. This method is convenient, cheap, and efficient. The morphology, structure, luminescent, and magnetic properties of the nanoparticles were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption, fluorescence emission, and superconducting quantum interference device magnetometer (SQUID-VSM). The maximum emission peaks of novel Eu{sup 3+} and Tb{sup 3+} nanocomposites are at 618 nm and at 514 nm, respectively. And their corresponding special saturation magnetization Ms. are 25.853 emu/g and 24.015 emu/g, respectively. For the nanoparticles, it is shown that there have better magnetic behavior and they may act as red- and green-emitting material with potential application for fluorescent magnetic particle testing. Moreover, this chemical route could be used to obtain the development of several bifunctional systems of other rare earth ions for practical application.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

How to realize the spin-Seebeck effect with a high spin figure of merit in magnetic boron–nitrogen nanoribbon and nanotube structures?

The spin-Seebeck effect (SSE) has been regarded as one of the core topics in spin caloritronics. To realize the SSE together with high spin thermoelectric conversion efficiency (TCE), two nanoscale structures referred to as nanoribbons and nanotubes have long been regarded as potential candidates. To illustrate their advantages to the above end, we construct magnetic boron–nitrogen nanoribbons (BNNRs) and nanotubes (BNNTs) by substituting some B atoms with carbon, and the BNNTs can be rolled from the BNNRs. To unify the magnetism origins, the edge magnetisms in BNNRs are cancelled by hydrogen passivation. Our theoretical results show that although these two different structures display similar spin semiconducting states, the BNNRs have lower lattice thermal conductance due to the phonon scattering at edges, contributing to the enhancement of the spin figure of merit; while the BNNTs can generate a better SSE and larger spin thermopower, due to the rotational symmetry. Moreover, we remove the hydrogen passivation from the BNNRs to construct another typical class of magnetic BNNRs, the electronic state which is changed to a magnetic metallic one, which suppresses the spin thermopower and the SSE largely. Systematic and comparative studies help us to choose feasible routes to improve and design the SSE with a high spin figure of merit in nanoscale structures, and give us deep understanding into the device applications of spin caloritronics based on nanoribbon and nanotube materials.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗