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DOE OSTI2020

Experimental Passive-State Preparation for Continuous-Variable Quantum Communications

In the Gaussian-modulated coherent state quantum key distribution (QKD) protocol, the sender first generates Gaussian-distributed random numbers and then encodes them on weak laser pulses actively by performing amplitude and phase modulations. Recently, an equivalent passive QKD scheme has been proposed by exploring the intrinsic field fluctuations of a thermal source [B. Qi, P. G. Evans, and W. P. Grice, Phys. Rev. A 97, 012317 (2018)]. This passive QKD scheme is especially appealing for chip-scale implementation since no active modulation is required. In this paper, we conduct an experimental study of the passively encoded QKD scheme using an off-the-shelf amplified spontaneous emission source operated in continuous-wave mode. Our results show that the excess noise introduced by the passive state preparation scheme can be effectively suppressed by applying optical attenuation and a secure key can be generated over metro-area distances.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2024

4-Clique network minor embedding for quantum annealers

Quantum annealing is a quantum algorithm for computing solutions to combinatorial optimization problems. This study proposes a method for minor embedding optimization problems onto sparse quantum annealing hardware graphs called 4-clique network minor embedding. This method is in contrast to the standard minor embedding technique of using a path of linearly connected qubits in order to represent a logical variable state. The 4-clique minor embedding is possible on Pegasus graph connectivity, which is the native hardware graph for some of the current D-Wave quantum annealers. The Pegasus hardware graph contains many cliques of size 4, making it possible to form a graph composed entirely of paths of connected 4-cliques on which a problem can be minor-embedded. The 4-clique chains come at the cost of additional qubit usage on the hardware graph, but they allow for stronger coupling within each chain, thereby increasing chain integrity, reducing chain breaks, and allow for greater usage of the available energy scale for programming logical problem coefficients on current quantum annealers. The 4-clique minor embedding technique is compared with the standard linear path minor embedding with experiments on two D-Wave quantum annealing processors with Pegasus hardware graphs. We show proof-of-concept experiments where the 4-clique minor embeddings can use weak chain strengths while successfully carrying out the computation of minimizing random all-to-all spin glass problem instances. Published by the American Physical Society 2024

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2022

Dark Energy Survey Year 3 results: Cosmology with moments of weak lensing mass maps

We present a cosmological analysis using the second and third moments of the weak lensing mass (convergence) maps from the first three years of data (Y3) data of the Dark Energy Survey. The survey spans an effective area of 4139 square degrees and uses the images of over 100 million galaxies to reconstruct the convergence field. The second moment of the convergence as a function of smoothing scale contains information similar to standard shear 2-point statistics. The third moment, or the skewness, contains additional non-Gaussian information. The data is analyzed in the context of the Λ CDM model, varying five cosmological parameters and 19 nuisance parameters modeling astrophysical and measurement systematics. Our modeling of the observables is completely analytical, and has been tested with simulations in our previous methodology study. We obtain a 1.7% measurement of the amplitude of fluctuations parameter S 8 ≡ σ 8 ( Ω m / 0.3 ) 0.5 = 0.784 ± 0.013 . The measurements are shown to be internally consistent across redshift bins, angular scales, and between second and third moments. In particular, the measured third moment is consistent with the expectation of gravitational clustering under the Λ CDM model. The addition of the third moment improves the constraints on S 8 and Ω m by ∼ 15 % and ∼ 25 % compared to an analysis that only uses second moments. We compare our results with Planck constraints from the cosmic microwave background, finding a 2.2 – 2.8 σ tension in the full parameter space, depending on the combination of moments considered. The third moment, independently, is in 2.8 σ tension with Planck, and thus provides a cross-check on the analyses of 2-point correlations.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2024

Random singlet-like state in the dimer-based triangular antiferromagnet Ba 6 Y 2 Rh 2 Ti 2 O 17 − δ

We present the magnetic, thermodynamic, and muon spin relaxation ( μ SR ) results of the dimer-based triangular antiferromagnet Ba 6 Y 2 Rh 2 Ti 2 O 17 − δ . The magnetic susceptibility data show the sub-Curie-Weiss behavior χ ( T ) ∝ T − α χ below 100 K, suggesting random magnetism. The isothermal magnetization results reveal the presence of weakly interacting structural orphan spins about 6.1 % at 2 K, arising from the oxygen deficiency. The comprehensive μ SR experiments exhibit the coexisting relaxing and nonrelaxing components along with the thermally activated behavior in the muon spin relaxation rate, reflecting the fluctuating orphan spins in the dimer singlet background. In addition, we observe the scaling behavior of M ( H , T ) in H / T and P z ( t ) in t / H LF with the scaling exponents α χ = α M = 0.75 and α μ = 0.72 , respectively, but not for the magnetic specific heat data. The failure of the scaling relation in C m ( H , T ) / T implies low-energy excitations dressed by the conventional orphan spins. Based on these observations, we find that the magnetic ground state resembles random singlets and discuss the possible configurations of the spin dimer unit Rh 2 O 9 . Our results shed light on the role of quenched disorder in the dimer-based frustrated magnets. Published by the American Physical Society 2024

Lee, Wonjun (ORCID:000000034848852X)↗

DOE OSTI2022

LOKI

LOKI is a simulation code that models weakly-coupled plasma evolution using Eulerian kinetic models in four phase space dimensions. The code is useful to understand basic plasma nonlinear plasma physics phenomena - in particular, wave-particle and wave-wave resonances that occur in laser plasma interactions. LOKI can simulate fundamental physical process in low-density plasmas on a scale of hundreds of light wavelengths. It does so by solving the relativistic Vlasov and Valsov-Fokker-Planck differential transport equations describing the collision less and low-collisionality evolution of charged particles in electromagnetic fields in two configuration space and two velocity space dimensions. Two principle electromagnetic models are provided: electrostatic (Poisson's Equation) and electromagnetic (Maxwell's equations).

DIMITS, ANDRIS↗

DOE OSTI2020

Are Supercells Resistant to Entrainment because of Their Rotation?

This research investigates a hypothesis posed by previous authors, which argues that the helical nature of the flow in supercell updrafts makes them more resistant to entrainment than nonsupercellular updrafts because of the suppressed turbulence in purely helical flows. It was further supposed that this entrainment resistance contributes to the steadiness and longevity of supercell updrafts. A series of idealized large-eddy simulations were run to address this idea, wherein the deep-layer shear and hodograph shape were varied, resulting in supercells in the strongly sheared runs, nonsupercells in the weakly sheared runs, and variations in the percentage of streamwise vorticity in updrafts among runs. Fourier energy spectrum analyses show well-developed inertial subranges in all simulations, which suggests that the percentages of streamwise and crosswise vorticity have little effect on turbulence in convective environments. Additional analyses find little evidence of updraft-scale centrifugally stable flow within updrafts, which has also been hypothesized to limit horizontal mass flux across supercell updrafts. Results suggest that supercells do have smaller fractional entrainment rates than nonsupercells, but these differences are consistent with theoretical dependencies of entrainment on updraft width, and with supercells being wider than nonsupercells. Thus, while supercells do experience reduced fractional entrainment rates and entrainment-driven dilution, this advantage is primarily attributable to increased supercell updraft width relative to ordinary convection, and has little to do with updraft helicity and rotation.

Peters, John M.↗

DOE OSTI2024

ALP-Assisted Electroweak Phase Transition and Baryogenesis

Axion-like particles (ALPs) can be naturally lighter than the electroweak scale. We consider an ALP that couples to the Standard Model Higgs to achieve the strong first-order electroweak phase transition. We discuss the two-field dynamics of the phase transition and the associated computation in detail and identify the viable parameter space. The ALP mass can be from the MeV to GeV scale. Baryon asymmetry can be explained by local baryogenesis without violating the electron electric dipole moment bound. The viable parameter space can be probed through Higgs exotic decay, rare kaon decay, the electron electric dipole moment, and the effective number of neutrinos in the cosmic microwave background. The gravitational-wave signal is too weak to be detected.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2021

Ocean Energy Systems Wave Energy Modeling Task 10.4: Numerical Modeling of a Fixed Oscillating Water Column

This paper reports on an ongoing international effort to establish guidelines for numerical modeling of wave energy converters, initiated by the International Energy Agency Technology Collaboration Program for Ocean Energy Systems. Initial results for point absorbers were presented in previous work, and here we present results for a breakwater-mounted Oscillating Water Column (OWC) device. The experimental model is at scale 1:4 relative to a full-scale installation in a water depth of 12.8 m. The power-extracting air turbine is modeled by an orifice plate of 1–2% of the internal chamber surface area. Measurements of chamber surface elevation, air flow through the orifice, and pressure difference across the orifice are compared with numerical calculations using both weakly-nonlinear potential flow theory and computational fluid dynamics. Both compressible- and incompressible-flow models are considered, and the effects of air compressibility are found to have a significant influence on the motion of the internal chamber surface. Recommendations are made for reducing uncertainties in future experimental campaigns, which are critical to enable firm conclusions to be drawn about the relative accuracy of the numerical models. It is well-known that boundary element method solutions of the linear potential flow problem (e.g., WAMIT) are singular at infinite frequency when panels are placed directly on the free surface. This is problematic for time-domain solutions where the value of the added mass matrix at infinite frequency is critical, especially for OWC chambers, which are modeled by zero-mass elements on the free surface. A straightforward rational procedure is described to replace ad-hoc solutions to this problem that have been proposed in the literature.

16 TIDAL AND WAVE POWER↗

NASA NTRS1976

Ballistic range experiments on the superboom generated at increasing flight Mach numbers

Ballistic range experiments for the study of the propagation of converging shocks are described and the similarity between the observed phenomenon and that expected for superbooms created by accelerating supersonic aircraft is discussed. For weak shocks (shock Mach numbers of about 1.03), a structure resembling that of a folded shock predicted by geometrical acoustics theory is observed while for stronger shocks, a concave front with enhanced overpressure is recorded. Other results are in general accord with the basic concepts of shock propagation and in conjunction with some theoretical scaling laws indicate that the peak magnification of sonic booms due to aircraft flight acceleration in the real atmosphere should be in the range of 6 to 13.

Sanai, M.↗

NASA NTRS1980

Current understanding of the physics of type III solar radio bursts

One of the most exciting plasma physics investigations of recent years has been connected with the understanding of a new strong turbulent plasma state excited by propagating electron beams. This new state is initiated on the linear level by parametric instabilities (OTS, modulational, etc.) and results in a very dynamic state composed of collective clusters of modes called solitons, cavitons, spikons, etc. Introduction of these concepts into the classic beam-plasma interaction problem has rendered quasi-linear and weak turbulence theories inapplicable over most of the interesting parameter range, and helped explain many paradoxes connected with the propagation of beams in the laboratory and space. Following a brief review of these nonlinear notions, the means by which their application to type III solar radiobursts has revolutionized understanding of their propagation, radioemission and scaling properties and has guided the in situ observations towards a more complete understanding are demonstrated. A particular burst (May 16, 1971) is analyzed in detail and compared with numerical predictions.

Papadopoulos, K.↗

NASA NTRS1986

Rainfall over oceans inferred from Nimbus 7 SMMR - Application to 1982-83 El Nino

Nimbus 7 Scanning Multichannel Microwave Radiometer (SMMR) measurements at five frequencies in the region 6.6 to 37 GHz, at a resolution of 155 km, are analyzed to infer precipitation over the global oceans. The microwave data show, on this spatial scale, that the combined liquid water in the clouds and rain increases the brightness temperature almost linearly with frequency in the 6.6-18-GHz region, while at 37 GHz such a simple relationship is not noticed. Further, as the atmospheric water-vapor absorption and the effects of scattering by precipitation particles are relatively weak at 6.6 and 10.7 GHz, a technique to remotely sense the liquid water content in the atmosphere is developed based on the brightness measurements at these two frequencies. Seasonal mean patterns of liquid water content in the atmosphere derived from SMMR over global oceans relate closely to climatological patterns of precipitation. Based on this, an empirical relationship is derived to estimate precipitation over the global oceans, with an accuracy of about + or - 30 percent, on a seasonal basis from satellite measurements made during the three years (1979-81) before the recent El Nino event. The deviations from these three-year means, in the precipitation, produced by the 1982-83 el Nino event are then deduced from the SMMR measurements. In the Pacific, the precipitation over the ITCZ in the north, the South Pacific Convergence Zone, and the oceans around Indonesia is drastically reduced. At the same time a substantial increase in precipitation is observed over the normally dry central and eastern equatorial Pacific Ocean.

Prabhakara, C.↗

NASA NTRS1988

Energy transfer in isotropic turbulence at low Reynolds numbers

Detailed measurements were made of energy transfer among the scales of motion in incompressible turbulent fields at low Reynolds numbers generated by direct numerical simulation. It was observed that although the transfer resulted from triad interactions that were non-local in k space, the energy always transferred locally. The results are consistent with the notion of non-uniform advection of small weak eddies by larger and stronger ones, similar to transfer processes in the far dissipation range at high Reynolds numbers.

Domaradzki, J. A.↗

NASA NTRS1994

Nonthermal accretion disk models around neutron stars

We consider the structure and emission spectra of nonthermal accretion disks around both strongly and weakly magnetized neutron stars. Such disks may be dissipating their gravitational binding energy and transferring their angular momentum via semicontinuous magnetic reconnections. We consider specifically the structure of the disk-stellar magnetospheric boundary where magnetic pressure balances the disk pressure. We consider energy dissipation via reconnection of the stellar field and small-scale disk turbulent fields of opposite polarity. Constraints on the disk emission spectrum are discussed.

Tavani, M.↗

DOE OSTI2020

Metal oxide-organic hybrid materials for heterogeneous catalysis and methods of making and using thereof

Catalysts prepared from abundant, cost effective metals, such as cobalt, nickel, chromium, manganese, iron, and copper, and containing one or more neutrally charged ligands (e.g., monodentate, bidentate, and/or polydentate ligands) and methods of making and using thereof are described herein. Exemplary ligands include, but are not limited to, phosphine ligands, nitrogen-based ligands, sulfur-based ligands, and/or arsenic-based ligands. In some embodiments, the catalyst is a cobalt-based catalyst or a nickel-based catalyst. The catalysts described herein are stable and active at neutral pH and in a wide range of buffers that are both weak and strong proton acceptors. While its activity is slightly lower than state of the art cobalt-based water oxidation catalysts under some conditions, it is capable of sustaining electrolysis at high applied potentials without a significant degradation in catalytic current. This enhanced robustness gives it an advantage in industrial and large-scale water electrolysis schemes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2024

Dynamic Shaping of Grid Response of Multi-Machine Multi-Inverter Systems Through Grid-Forming IBRs

We consider the problem of controlling the frequency response of weakly-coupled multi-machine multi-inverter low-inertia power systems via grid-forming inverter-based resources (IBRs). In contrast to existing methods, our approach relies on dividing the larger system into multiple strongly-coupled subsystems, without ignoring either the underlying network or approximating the subsystem response as an aggregate harmonic mean model. Rather, through a structured clustering and recursive dynamic shaping approach, the frequency response of the overall system to load perturbations is shaped appropriately. We demonstrate the proposed approach for a three-node triangular configuration and a small-scale radial network. Furthermore, previous synchronization analysis for heterogeneous systems requires the machines to satisfy certain proportionality property. In our approach, the effective transfer functions for each cluster can be tuned by the IBRs to satisfy such property, enabling us to apply the shaping control to systems with a wider range of heterogeneous machines.

frequency-shaping control↗

DOE OSTI2025

The "Fake" Supernova Neutrinos of SBND: Using Muons Decaying at Rest to Study the Charged Current MeV-Scale $V_e$-Ar Cross Section

In a Type-II core collapse supernova, 99% of the total amount of energy is released in the form of neutrinos. However, the nearest supernova explosion in the last few hundred years was in 1987, over thirty years ago. It was also the first from which particle detectors around the world managed to detect the neutrino flux, yielding important information about their properties and the explosion mechanism. Neutrinos are the most weakly interacting subatomic fundamental particles known to date, and they act as a cooling mechanism for the star. Out of the six neutrino flavours currently known, the majority exiting the explosion are electron neutrinos, ve. Neutrino experiments using liquid argon (LAr) as their detector medium are unique at probing this specific channel. In the meantime, however, until the next explosion, we can still practise for the big event. With the Short Baseline Near Detector (SBND) experiment at Fermilab, we can study how electron neutrinos of the same energy coming from the Booster Neutrino Beam (BNB) interact in LAr, and measure the cross section. As BNB measurements are mostly tailored to higher energy neutrinos, I will present an overview of how SBND is aiming to select the low-energy neutrino candidates from muons Decaying At Rest (DAR) in the absorber and target within the BNB beam pipe. This is not a straightforward feat, encompassing special difficulties that include beam and flux systematic uncertainty simulation, system trigger needs and particular reconstruction efforts, and so I will present how each challenge is being addressed in SBND. This will be a novel measurement in the neutrino particle physics community, and will prove fundamental for the next generation of supernova neutrino detectors.

Kotsiopoulou, Lucy [Edinburgh U.]↗

DOE OSTI2023

Weak Gravitational Lensing of Low Surface Brightness Galaxies in the DES Year 3 Catalog

We present galaxy-galaxy lensing measurements of a sample of low surface brightness galaxies (LSBGs) drawn from the Dark Energy Survey Year 3 (Y3) data. LSBGs are diffuse galaxies with a surface brightness dimmer than the ambient night sky. Given their faintness, the use of standard observational techniques proves challenging. Weak gravitational lensing probes both the baryonic and dark matter content of galaxies, rendering it a powerful technique to estimate LSBG masses. The LSBG lens sample consists of 23, 790 total extended galaxies separated into red and blue color types at $g-i\ge 0.60$ and $g-i\le 0.60$, respectively. We use the Y3 \metacal\ shape catalog as the source sample, with a number density of {\color{red}$5.59 \mathrm{gal}/\mathrm{arcmin}^2$}. We measure the tangential shear around the lens galaxies across angular scales of $0.25-400$ arcmin and find a signal-to-noise of 6.67 for red galaxies, 2.17 for blue galaxies, and 5.30 for the total sample. W e fit a model built from two NFW profiles corresponding to the LSBG dark matter subhalo and host halo to the red LSBG shear measurements with an MCMC. We estimate the host halo mass at $7.3 ^{+2.0}_{-1.6}\times 10^{12} M_\mathrm{\odot}$. We place a 95\% upper bound on the subhalo mass at $2.8\times 10^{11} M_\mathrm{\odot}$. We utilize the lens sample photometry to obtain an estimate of the red LSBG stellar mass distribution. We compare the ratio between the stellar mass and the subhalo mass to the parameterized, satellite-specific SHMR \citep{Moster2010}. This work represents the first example of an attempted constraint on the masses of LSBGs using weak gravitational lensing.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2025

Collisionless conduction in a high-beta plasma: a collision operator for whistler turbulence

The regulation of electron heat transport in high-β, weakly collisional, magnetized plasma is investigated. A temperature gradient oriented along a mean magnetic field can induce a kinetic heat-flux-driven whistler instability (HWI), which back-reacts on the transport by scattering electrons and impeding their flow. Previous analytical and numerical studies have shown that the heat flux for the saturated HWI scales as β$^{-1}_{e}$. These numerical studies, however, had limited scale separation and consequently large fluctuation amplitudes, which calls into question their relevance at astrophysical scales. To this end, we perform a series of particle-in-cell simulations of the HWI across a range of β$_e$ and temperature-gradient length scales under two different physical set-ups. The saturated heat flux in all of our simulations follows the expected β$^{-1}_{e}$ scaling, supporting the robustness of the result. We also use our simulation results to develop and implement several methods to construct an effective collision operator for whistler turbulence. The results point to an issue with the standard quasi-linear explanation of HWI saturation, which is analogous to the well-known 90° scattering problem in the cosmic-ray community. Despite this limitation, the methods developed here can serve as a blueprint for future work seeking to characterize the effective collisionality caused by kinetic instabilities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗