Search

Photonics offers unique capabilities for quantum information processing (QIP) such as room-temperature operation, the scalability of nanophotonics, and access to ultrabroad bandwidths and consequently ultrafast operation. Ultrashort pulse sources of quantum states in nanophotonics are an important building block for achieving scalable ultrafast QIP; however, their demonstrations so far have been sparse. Here, we demonstrate a femtosecond biphoton source in dispersion-engineered periodically poled lithium niobate nanophotonics. We measure 17 THz of bandwidth for the source centered at 2.09 µm, corresponding to a few optical cycles, with a brightness of 8.8 GHz/mW. Our results open new paths toward realization of ultrafast nanophotonic QIP.

This article highlights some of Katalin Marton's main contributions to rate distortion theory, probability theory, and multiuser information theory and their lasting impact on the work of many other researchers.

In recent years, the computational demands of deep learning applications have necessitated the introduction of energy-efficient hardware accelerators. Optical neural networks are a promising option; however, thus far they have been largely limited by the lack of energy-efficient nonlinear optical functions. Here, we experimentally demonstrate an all-optical Rectified Linear Unit (ReLU), which is the most widely used nonlinear activation function for deep learning, using a periodically-poled thin-film lithium niobate nanophotonic waveguide and achieve ultra-low energies in the regime of femtojoules per activation with near-instantaneous operation. Our results provide a clear and practical path towards truly all-optical, energy-efficient nanophotonic deep learning.

Optical nonlinear functions are crucial for various applications in integrated photonics, including all-optical information processing1, photonic neural networks2,3and on-chip ultrafast light sources4,5. However, the weak native nonlinearity of most nanophotonic platforms has imposed barriers for such functions by necessitating large driving energies, high-Qcavities or integration with other materials with stronger nonlinearity. Here we effectively utilize the strong and instantaneous quadratic nonlinearity of lithium niobate nanowaveguides for the realization of cavity-free all-optical switching. By simultaneous engineering of the dispersion and quasi-phase matching, we design and demonstrate a nonlinear splitter that can achieve ultralow switching energies down to 80 fJ, featuring a fastest switching time of ~46 fs and a lowest energy–time product of 3.7 × 10−27J s in integrated photonics. Our results can enable on-chip ultrafast and energy-efficient all-optical information processing, computing systems and light sources.

Histogram equalization refers to contrast enhancement techniques that distribute intensity over an entire image and remaps pixels to an intensity proportional to its rank among other pixel intensities. These techniques were performed on the code-book of a tree-structured vectro quantizer to generate compression and contrast enhancements. The study shows that global histogram equalization using the histogram of the training images can be carried out off-line on a vector quantizer's codebook.

The Pennsylvania Department of Transportation (PennDOT) original and innovative program that introduces local governments to new products and processes through the use of its liquid fuels funds is presented, and other departments of transportation are encouraged to adapt it. Liquid fuels funds may be used on locally owned and maintained roads with approved PennDOT products and processes. PennDOT's Bureau of Municipal Services (BMS) initiated the program, the New Products Evaluation Program for Lower-Volume Local Roads, to give stakeholders a wider selection of quality products and processes to choose from. Pennsylvania maintains an interest in reducing costs for local governments by providing access to high-quality products that are eligible for liquid fuels funds expenditures. These products are designed for lower-volume roads rather than high-volume highways. PennDOT also initiated this streamlined program to allow manufacturers of innovative products and processes for lower-volume local roads to submit their applications to PennDOT for evaluation. The manufacturers contract with the testing facilities and are responsible for all costs incurred in the testing and evaluation process. The objectives of this program are to (a) increase the number of available high-quality new products and processes for low-volume local roads, (b) create strong communication channels among various stakeholders and BMS about new product offerings for low-volume local roads, (c) provide manufacturers with a more expedient process for testing their products locally, and (d) develop a products evaluation process that is more cost-effective for local governments and PennDOT.

The present study extends our previous work characterizing the behavioral features of autistic‐spectrum disorder (ASD) in Down syndrome (DS) using the Aberrant Behavior Checklist (ABC) and Autism Behavior Checklist (AutBehav). We examined which specific behaviors distinguished the behavioral phenotype of DS + ASD from other aberrant behavior disorders in DS, by determining the relative contribution of ABC and AutBehav subscales and items to the diagnosis of ASD. A total of 127 subjects (aged 2–24 years; mean age: 8.4 years; ∼70% male), comprising: a cohort of 64 children and adolescents with DS and co‐morbid ASD (DS + ASD), 19 with DS and stereotypic movement disorder (DS + SMD), 18 with DS and disruptive behaviors (DS + DB), and 26 with DS and no co‐morbid behavior disorders (DS + none) were examined using the aforementioned measures of aberrant behavior. We found that subjects with DS + ASD showed the most severe aberrant behavior, especially stereotypy compared to DS + none and lethargy/social withdrawal and relating problems compared to DS + SMD. Specifically, relatively simple stereotypic behavior differentiated DS + ASD from DS + DB, whereas odd/bizarre stereotypic and anxious behavior characterized DS + ASD relative to DS + SMD and DS + none. Additionally, in a subset of subjects with DS + ASD and anxiety, social withdrawal was particularly pronounced. Overall, our findings indicate that a diagnosis of DS + ASD represents a distinctive set of aberrant behaviors marked by characteristic odd/bizarre stereotypic behavior, anxiety, and social withdrawal. © 2006 Wiley‐Liss, Inc.

The present study extends our previous work on social behavior impairment in young males with fragile X syndrome (FraX). Specifically, we evaluated whether the autistic phenomenon in FraX is expressed as a range of behavioral impairments as in idiopathic autism (Aut). We also examined whether there are behaviors, identified as items of the Autism Diagnostic Interview‐Revised (ADI‐R), that in FraX predispose to or differentiate subjects with autism spectrum disorder (ASD) diagnosis. Finally, regression models were utilized to test the relative contribution of reduced communication and socialization skills to ADI‐R scores and diagnoses. A cohort of 56 boys (3–8 years) with FraX was examined in terms of scores on measures of cognition (IQ was a co‐variate in most analyses.), autistic behavior, problem/aberrant behavior, adaptive behavior, and language development. We found that, indeed, in terms of problem behavior and adaptive skills, there is a range of severity from FraX + Aut to FraX + PDD (Pervasive Developmental Disorder) to FraX + none. ADI‐R items representing “Play” types of interaction appear to be “susceptibility” factors since they were abnormal across the FraX cohort. Integrated regression models demonstrated that items reflecting complex social interaction differentiated the FraX + ASD (Aut + PDD) subgroup from the rest of the FraX cohort, while abnormalities in basic verbal and non‐verbal communication distinguished the most severely affected boys with FraX + Aut from the milder FraX + PDD cohort. Models incorporating language, adaptive communication, and adaptive socialization skills revealed that socialization was not only the main influence on scores but also a predictor of ASD diagnosis. Altogether, our findings demonstrate that the diagnosis of ASD in FraX reflects, to a large extent, an impairment in social interaction that is expressed with variable severity in young males with FraX. © 2004 Wiley‐Liss, Inc.

This study presents a data set for a reference group on the Reitan-In-diana Neuropsychological Test Battery for Young Children. The data set is based on a sample of 224 children, ages 5 to 8 years, referred to a special services cooperative for academic or behavioral concerns during the years 1980 through 1993. Data are presented in terms of sample size, means, standard deviations, diagnostic classifications, and population characteristics. Previously published data sets are reviewed in comparison to this newly acquired data set. Potential advantages of this data set include the larger sample, contemporary data collection, and a sample drawn from a United States school-referred population.

The Reitan-Indiana Neuropsychological Battery (RINB) was administered to a sample of children referred for educational and behavioral problems (N = 130). Subtest scores were standardized by age at 1-year intervals (6, 7, and 8 years). A principal components analysis (PCA) with promax rotation of 18 subtest scores produced a five-factor solution. Factor 1 emphasizes tactile/spatial functions, Factor 2 emphasizes concept formation and visual/spatial abilities, Factor 3 reflects motor strength, Factor 4 emphasizes sensory perception, and Factor 5 reflects motor speed. Principal factor analysis (PFA) of these data was performed to permit comparison with the PCA solutions. The PFA and PCA solutions were similar and major conclusions about factor structure were consis tent.

The internal consistency of three neuropsychological tests was examined in a sample of 334 referred children (9-14 years of age). Coefficient alpha was calculated to estimate reliability on the Seashore Rhythm Test (SRT), two forms of the Speech Sounds Perception Test (SSPT), and the Aphasia Screening Test (AST). The standard SSPT appears to have relatively good internal consistency with an average coefficient of .81. The average coefficient for the abbreviated form of the SSPT was considerably lower (i.e., .73), highlighting the superiority of the standard form in clinical practice. Internal consistency of the SRT was relatively low (i.e., .67). This level of reliability may be acceptable in group research and for component tests, but is marginal for independent clinical use. Coefficient alpha for the AST was moderate (i.e., .77), suggesting adequate reliability for a screening test. These reliability estimates are compared to those obtained in previous studies using these tests in adult samples and with other tests commonly used with children.

This study examined the factor structure of the six subtests of the Intermediate Category Test in a heterogeneous sample of school-referred students, age 9 to 14 years. A three-factor solution emerged that accounted for approximately 72% of the total variance. This indicates that the test measures multiple underlying constructs in this school-referred sample. Clinical and educational interpretations may be enhanced by utilizing factor scores that reflect the multiple abilities assessed. Recommendations for developing factor/index scores are provided.

A sample of 645 school-age children, ages 9 to 14 years, were administered independent forms of the Speech Sounds Perception Test for older children. 328 subjects took the complete test (SSPT-60) and 317 were administered only the first 30 items (SSPT-30). Comparison of mean errors indicated that significantly more errors were made by subjects given the SSPT-30. Decisions regarding the use of each form for school-age children are discussed.

Utilizing the 22-ltem Mental Health Scale developed by the staff of the Midtown Manhattan Project, the mental health status of a sample of 900 married women residing in a Western state is examined. The concern is with further investigation of prior research findings regarding associations between anomia, social class variables, and psychiatric impairment. The findings indicate that subjects' feelings of anomia maintain a significant relationship with psychiatric impairment within each socioeconomic category investigated. Data further reveal that the proportion of subjects reporting psychiatric symptomatology decreases with increasing status but that the relative risk of such symptoms for highly anomic respondents (compared to nonanomic subjects within each category) is much higher for the highest status groups than for the lower groups.

The construct validity of the Verbal Comprehension, Perceptual Organization, and Freedom from Distractibility factor scores was examined in a sample of school-aged referred children. Examination of correlations between factor scores and neuropsychological and achievement tests generally supported the construct validity of the factors. The Verbal Comprehension factor was associated with verbal, quantitative, and concept-formation abilities. The Perceptual Organization factor was related to nonverbal concept formation, tactual performance, and visual attention. The Freedom from Distractibility factor demonstrated a complex pattern of correlations and appeared to reflect a range of abilities including quantitative, language, attentional, and concept formation.