Classical simulation of commuting quantum computations implies collapse of the polynomial hierarchy

We consider quantum computations comprising only commuting gates, known as IQP computations, and provide compelling evidence that the task of sampling their output probability distributions is unlikely to be achievable by any efficient classical means. More specifically we introduce the class post-IQP of languages decided with bounded error by uniform families of IQP circuits with post-selection, and prove first that post-IQP equals the classical class PP. Using this result we show that if the output distributions of uniform IQP circuit families could be classically efficiently sampled, even up to 41% multiplicative error in the probabilities, then the infinite tower of classical complexity classes known as the polynomial hierarchy, would collapse to its third level. We mention some further results on the classical simulation properties of IQP circuit families, in particular showing that if the output distribution results from measurements on only O(log n) lines then it may in fact be classically efficiently sampled.Comment: 13 page

A multifrequency evaluation of active and passive microwave sensors for oil spill detection and assessment

An evaluation is given of how active and passive microwave sensors can best be used in oil spill detection and assessment. Radar backscatter curves taken over oil spills are presented and their effect on synthetic aperture radar (SAR) imagery are discussed. Plots of microwave radiometric brightness variations over oil spills are presented and discussed. Recommendations as to how to select the best combination of frequency, viewing angle, and sensor type for evaluation of various aspects of oil spills are also discussed

A Parametric Study of Tillage Effects on Radar Backscatter

Radar backscatter data for different field configurations and modulation function curves for angular and frequency variations are presented. A simplistic approach to modeling this effect is presented. It is concluded that: (1) row direction is a significant contributor to radar backscatter from cropland and must be considered when making radar measurements over bare or sparsely vegetated fields; (2) while the effect decrease with increasing frequency, it is still large (5 dB) at 13.3 GHz; (3) row effects are independent of linear polarization; (4) there is a strong aspect angle sensitivity which is a function of the scene and radar system parameters

An unconventional approach to imaging radar calibration

An unconventional approach to imaging radar calibration was considered for the entire system, including the imaging processing as a measurement instrument. The technique made use of a calibrated aircraft scatterometer as a secondary standard to measure the backscatter (sigma zero) of large units of constant roughness. These measured roughness units when viewed by an imaging radar system can be used to provide gray scale level, corresponding to known degrees of roughness. To obtain a calibrated aircraft scatterometer, a homogeneous smooth surface was measured by both the aircraft scatterometer and a sphere calibrated ground system. This provided a measure of the precision and accuracy of the aircraft system. The aircraft system was then used to measure large roughness units in the Death Valley, California area. Transfer of the measured roughness units to radar imagery was demonstrated

Case of Ununited Fracture of the Humerus. Failure of Brainardʼs Operation, and of the Scton:

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Lived experiences of mental health recovery in persons of culturally and linguistically diverse (CALD) backgrounds within the Australian context

Lived experience research related to mental health recovery is advancing, but there remains a lack of narrative material from the perspectives of people from under-represented, non-dominant cultural backgrounds in this domain. This study aimed to explore the lived experiences of mental health recovery in people of culturally and linguistically diverse (CALD) backgrounds in the Australian context. The current study involved a secondary analysis of audio and visual data collected during the digital storytelling project Finding our way in Melbourne, Australia. Thematic analysis was used to understand the lived experience narratives of nine participants in relation to mental health recovery. Five themes were identified through an iterative process of analysis, including Newfound opportunities and care, Family as key motivators and facilitators, Coping and generativity, Cultivating self-understanding and resilience, and Empowerment through social engagement. First person lived experience narratives offer deep insight into understanding the ways in which individuals of marginalised communities conceptualise and embody recovery. These findings further the literature and understanding on how to better serve the needs of people with mental health challenges from CALD communities through informed knowledge of what may be helpful to, and meaningful in, individuals’ recoveries

A stochastic model for the evolution of the web allowing link deletion

Recently several authors have proposed stochastic evolutionary models for the growth of the web graph and other networks that give rise to power-law distributions. These models are based on the notion of preferential attachment leading to the ``rich get richer'' phenomenon. We present a generalisation of the basic model by allowing deletion of individual links and show that it also gives rise to a power-law distribution. We derive the mean-field equations for this stochastic model and show that by examining a snapshot of the distribution at the steady state of the model, we are able to tell whether any link deletion has taken place and estimate the link deletion probability. Our model enables us to gain some insight into the distribution of inlinks in the web graph, in particular it suggests a power-law exponent of approximately 2.15 rather than the widely published exponent of 2.1