High-fidelity quantum logic operations using linear optical elements.

Knill, Laflamme, and Milburn [Nature (London) 409, 46 ((2001))]] have shown that quantum logic operations can be performed using linear optical elements and additional ancilla photons. Their approach is probabilistic in the sense that the logic devices fail to produce an output with a failure rate that scales as 1/n, where n is the number of ancilla. Here we present an alternative approach in which the logic devices always produce an output with an intrinsic error rate that scales as 1/n(2), which may have several advantages in quantum computing applications.

Electro-optic measurement of the wake fields of a relativistic electron beam.

When a relativistic electron bunch traverses a structure, strong electromagnetic fields are induced in its wake. For a 12 nC bunch of duration 4.2 ps FWHM, the peak field is measured >0.5 MV/m. Time resolution of approximately 5 ps is achieved using electro-optic sampling with a lithium tantalate (LiTaO3) crystal and a short-pulse infrared laser synchronized to the beam. We present measurements for both the longitudinal and radial components of the field and relate them to the wall impedance.

Outcome of a cooperatively funded children's day-treatment program.

Emotionally disturbed children participated in a cooperatively funded day-treatment program. The philosophy of the program, designed to facilitate understanding and cooperation among the three funding agencies, the parents, and interdisciplinary team members, was a variant of social learning theory. In this article the program is described, as well as the results of a follow-up study which indicated successful therapeutic intervention. Finally, a discussion of the success, problems, and dissolution of the program is presented. A suggestion is made that future programs which are funded cooperatively include a buffer fund to allow the program to survive temporary financial shortfalls.

Child abuse. Its relationship to birthweight, apgar score, and developmental testing.

Fifty-two abused and 23 nonabused children from a low socioeconomic group were studied with respect to birthweight, five-minute Apgar score, and developmental quotients. An association was found between low Apgar scores, low birthweight, poor performance on developmental testing, and child abuse. Furthermore, it was found that among children with normal birthweights, abused children tended to have lower Apgar scores and significantly lower developmental quotients. This study suggests that among this group of children, abuse and subsequent poor performance may be related not only to the socioeconomic status of the children but also to the characteristics the child brings to the parent-child relationship and to the abusive environment.

Nonaccidental trauma and failure to thrive.

Charts were reviewed of 140 children who were discharged from Denver General Hospital (DGH) with diagnoses of nonaccidental trauma or failure to thrive. These children were all enrolled in a neighborhood health program. It was found that boys and girls were affected equally and that most of these children were under 3 years of age. In relation to their representation in the Neighborhood Health Program, more white children were abused or failed to thrive than children from other racial groups. A disproportionate number of children had birth weights under 2,500 gm as compared to children born at DGH. Young parents who were raised in disrupted families were involved in child abuse more frequently than were individuals from more stable families. Bruising was the most frequent injury and was most prevalent among boys under 3 years of age. Fractures were the second most common injury and occurred equally among boys and girls. There appeared to be a seasonal variation in the incidence of abuse.