Searching for MHz gravitational waves from harmonic sources

A MHz gravitational wave search for harmonic sources was conducted using a 704 h dataset obtained from the Holometer, a pair of 40 m power recycled Michelson interferometers. Our search was designed to look for cosmic string loops and eccentric black hole binaries in an entirely unexplored frequency range from 1 to 25 MHz. The measured cross-spectral density between both interferometers was used to perform four different searches. First, we search to identify any fundamental frequencies bins that have excess power above 5σ. Second, we reduce the per-bin threshold on any individual frequency bin by employing that a fundamental frequency and its harmonics all collectively lie above a threshold. We vary the number of harmonics searched over from n = 4 up to n = 23. Third, we perform an agnostic approach to identify harmonic candidates that may have a single contaminated frequency bin or follow a power-law dependence. Lastly, we expand on the agnostic approach for individual candidates and search for a potential underlying population of harmonic sources. Each method was tested on the interferometer dataset, as well as a dark noise, photon shot-noise-limited, and simulated Gaussian-noise datasets. We conclude that these four different search methods did not find any candidate frequencies that would be consistent with harmonic sources. This work presents a new way of searching for gravitational wave candidates, which allowed us to survey a previously unexplored frequency range

Searching for MHz gravitational waves from harmonic sources

A MHz gravitational wave search for harmonic sources was conducted using a 704 h dataset obtained from the Holometer, a pair of 40 m power recycled Michelson interferometers. Our search was designed to look for cosmic string loops and eccentric black hole binaries in an entirely unexplored frequency range from 1 to 25 MHz. The measured cross-spectral density between both interferometers was used to perform four different searches. First, we search to identify any fundamental frequencies bins that have excess power above 5σ. Second, we reduce the per-bin threshold on any individual frequency bin by employing that a fundamental frequency and its harmonics all collectively lie above a threshold. We vary the number of harmonics searched over from n = 4 up to n = 23. Third, we perform an agnostic approach to identify harmonic candidates that may have a single contaminated frequency bin or follow a power-law dependence. Lastly, we expand on the agnostic approach for individual candidates and search for a potential underlying population of harmonic sources. Each method was tested on the interferometer dataset, as well as a dark noise, photon shot-noise-limited, and simulated Gaussian-noise datasets. We conclude that these four different search methods did not find any candidate frequencies that would be consistent with harmonic sources. This work presents a new way of searching for gravitational wave candidates, which allowed us to survey a previously unexplored frequency range

The [Ne III]/[Ne II] line ratio in NGC 253

We present results of the mapping of the nucleus of the starburst galaxy NGC 253 and its immediate surroundings using the Infrared Spectrograph on board the Spitzer Space Telescope. The map is centered on the nucleus of the galaxy and spans the inner 800 × 688 pc^2. We perform a brief investigation of the implications of these measurement on the properties of the star formation in this region using theories developed to explain the deficiency of massive stars in starbursts

Full-Stack Optimization for CAM-Only DNN Inference

The accuracy of neural networks has greatly improved across various domains over the past years. Their ever-increasing complexity, however, leads to prohibitively high energy demands and latency in von Neumann systems. Several computing-in-memory (CIM) systems have recently been proposed to overcome this, but trade-offs involving accuracy, hardware reliability, and scalability for large models remain a challenge. Additionally, for some CIM designs, the activation movement still requires considerable time and energy. This paper explores the combination of algorithmic optimizations for ternary weight neural networks and associative processors (APs) implemented using racetrack memory (RTM). We propose a novel compilation flow to optimize convolutions on APs by reducing their arithmetic intensity. By leveraging the benefits of RTM-based APs, this approach substantially reduces data transfers within the memory while addressing accuracy, energy efficiency, and reliability concerns. Concretely, our solution improves the energy efficiency of ResNet-18 inference on ImageNet by 7.5x compared to crossbar in-memory accelerators while retaining software accuracy.Comment: To be presented at DATE2

The Landscape of Compute-near-memory and Compute-in-memory: A Research and Commercial Overview

In today's data-centric world, where data fuels numerous application domains, with machine learning at the forefront, handling the enormous volume of data efficiently in terms of time and energy presents a formidable challenge. Conventional computing systems and accelerators are continually being pushed to their limits to stay competitive. In this context, computing near-memory (CNM) and computing-in-memory (CIM) have emerged as potentially game-changing paradigms. This survey introduces the basics of CNM and CIM architectures, including their underlying technologies and working principles. We focus particularly on CIM and CNM architectures that have either been prototyped or commercialized. While surveying the evolving CIM and CNM landscape in academia and industry, we discuss the potential benefits in terms of performance, energy, and cost, along with the challenges associated with these cutting-edge computing paradigms

Flat-band localization and interaction-induced delocalization of photons

Advances in quantum engineering have enabled the design, measurement, and precise control of synthetic condensed matter systems. The platform of superconducting circuits offers two particular capabilities: flexible connectivity of circuit elements that enables a variety of lattice geometries, and circuit nonlinearity that provides access to strongly interacting physics. Separately, these features have allowed for the creation of curved-space lattices and the realization of strongly correlated phases and dynamics in one-dimensional chains and square lattices. Missing in this suite of simulations is the simultaneous integration of interacting particles into lattices with unique band dispersions, such as dispersionless flat bands. An ideal building block for flat-band physics is the Aharonov-Bohm cage: a single plaquette of a lattice whose band structure consists entirely of flat bands. Here, we experimentally construct an Aharonov-Bohm cage and observe the localization of a single photon, the hallmark of all-bands-flat physics. Upon placing an interaction-bound photon pair into the cage, we see a delocalized walk indicating an escape from Aharonov-Bohm caging. We further find that a variation of caging persists for two particles initialized on opposite sites of the cage. These results mark the first experimental observation of a quantum walk that becomes delocalized due to interactions and establish superconducting circuits for studies of flat-band-lattice dynamics with strong interactions.Comment: 8 + 9 pages, 4 + 12 figures, 0 + 2 tables; modified title, added a supplementary figure, and modified the definition used for tunneling tim

Engineering the reciprocal space for ultrathin GaAs solar cells

III-V solar cells dominate the high efficiency charts, but with significantly higher cost than other solar cells. Ultrathin III-V solar cells can exhibit lower production costs and immunity to short carrier diffusion lengths caused by radiation damage, dislocations, or native defects. Nevertheless, solving the incomplete optical absorption of sub-micron layers presents a challenge for light-trapping structures. Simple photonic crystals have high diffractive efficiencies, which are excellent for narrow-band applications. Random structures a broadband response instead but suffer from low diffraction efficiencies. Quasirandom (hyperuniform) structures lie in between providing high diffractive efficiency over a target wavelength range, broader than simple photonic crystals, but narrower than a random structure. In this work, we present a design method to evolve a simple photonic crystal into a quasirandom structure by modifying the spatial-Fourier space in a controlled manner. We apply these structures to an ultrathin GaAs solar cell of only 100 nm. We predict a photocurrent for the tested quasirandom structure of 25.3 mA/cm$^2$, while a planar structure would be limited to 16.1 mA/cm$^2$. The modified spatial-Fourier space in the quasirandom structure increases the amount of resonances, with a progression from discrete number of peaks to a continuum in the absorption. The enhancement in photocurrent is stable under angle variations because of this continuum. We also explore the robustness against changes in the real-space distribution of the quasirandom structures using different numerical seeds, simulating variations in a self-assembly method

Productivity of three sugarcane cultivars under dry and drip irrigated management

O objetivo neste trabalho foi estudar o efeito da tecnologia de irrigação por gotejamento, em cultivares de cana-de-açúcar, em dois ciclos de produção (cana-planta e cana-soca). O delineamento experimental utilizado foi o de blocos ao acaso, com quatro repetições, constituídos pela combinação de três cultivares de cana-de-açúcar: RB867515; RB855536 e SP80-3280, e dois manejos da cultura: sistema de irrigação por gotejamento subterrâneo e sistema de sequeiro, totalizando seis tratamentos. O primeiro ciclo teve duração de 336 dias, ocorrendo precipitação de 1.480 mm. O volume de água disponibilizado pelo sistema de irrigação por gotejamento foi de 400 mm, totalizando 1.880 mm. O segundo ciclo teve duração de 365 dias, cujo volume de água por meio de precipitação foi de 1.394 mm; somados aos 320 mm fornecidos pelo sistema de irrigação, totalizaram 1.714 mm. Ocorreu interação entre manejo e cultivar para as variáveis: produtividade de colmos (TCH) e produtividade de açúcar (TPH) em que a maior diferença foi observada para a cultivar SP80-3280. As cultivares apresentaram respostas diferenciadas na eficiência de utilização da água. No manejo irrigado por gotejamento houve elevação de 24% na produtividade de colmos e de 23% na produtividade de açúcar, em relação ao manejo de sequeiro.This study aimed to evaluate the effect of drip irrigation technology in different sugarcane varieties in two crop cycles (plant cane and ratoon). The experimental design was in completly randomized blocks, in split-plot with four replications, constituted by three sugarcane genotypes: RB867515; RB855536 and SP80-3280 and two crop management: drip irrigation system and rainfed system, totalizing six treatments. The first cycle lasted for 336 days, with rainfall of 1,480 mm. The volume of water provided by the system of drip irrigation was 400 mm, totaling 1,880 mm. The second cycle lasted for 365 days, the volume of water through rainfall was 1,394 mm, added to 320 mm provided by the system of irrigation, totaled 1,714 mm. Interaction between management and cultivars was found significant for the variables: productivity of stalks (TCH) and sugar yield (TPH), in which the largest difference was observed for cultivar SP80-3280. There was significant response to drip irrigation, on average the increase of production of stalks and sugar was 24 and 23%, respectively