Modelling Non-Markovian Quantum Processes with Recurrent Neural Networks

Quantum systems interacting with an unknown environment are notoriously difficult to model, especially in presence of non-Markovian and non-perturbative effects. Here we introduce a neural network based approach, which has the mathematical simplicity of the Gorini-Kossakowski-Sudarshan-Lindblad master equation, but is able to model non-Markovian effects in different regimes. This is achieved by using recurrent neural networks for defining Lindblad operators that can keep track of memory effects. Building upon this framework, we also introduce a neural network architecture that is able to reproduce the entire quantum evolution, given an initial state. As an application we study how to train these models for quantum process tomography, showing that recurrent neural networks are accurate over different times and regimes.Comment: 10 pages, 8 figure

Learning hard quantum distributions with variational autoencoders

Studying general quantum many-body systems is one of the major challenges in modern physics because it requires an amount of computational resources that scales exponentially with the size of the system.Simulating the evolution of a state, or even storing its description, rapidly becomes intractable for exact classical algorithms. Recently, machine learning techniques, in the form of restricted Boltzmann machines, have been proposed as a way to efficiently represent certain quantum states with applications in state tomography and ground state estimation. Here, we introduce a new representation of states based on variational autoencoders. Variational autoencoders are a type of generative model in the form of a neural network. We probe the power of this representation by encoding probability distributions associated with states from different classes. Our simulations show that deep networks give a better representation for states that are hard to sample from, while providing no benefit for random states. This suggests that the probability distributions associated to hard quantum states might have a compositional structure that can be exploited by layered neural networks. Specifically, we consider the learnability of a class of quantum states introduced by Fefferman and Umans. Such states are provably hard to sample for classical computers, but not for quantum ones, under plausible computational complexity assumptions. The good level of compression achieved for hard states suggests these methods can be suitable for characterising states of the size expected in first generation quantum hardware.Comment: v2: 9 pages, 3 figures, journal version with major edits with respect to v1 (rewriting of section "hard and easy quantum states", extended discussion on comparison with tensor networks

The 'feeling of what happens' in fourth year : exploring the emotive dimensions of learning in a communication design programme

Includes bibliographical references (leaves 93-97).Includes abstract.This is a story of discovery and renewal in my approach to teaching, learning and research. The research is a product of insights gained through the holistic theories of cognition offered by enactivism and complexity thinking. Some of the more established learning theories have clarified areas of concern I encountered in interpreting the data. Among my aspirations for the education of fourth year design graduates are those that tend toward transformational learning, critical learning and lifelong learning. As such, I undertook this research in an attempt to understand the kind of learning environment that would best support creativity, and the self-development of a designer in their fourth year

Hypertension Knowledge, Expectation of Care, Social Support, and Adherence to Prescribed Medications of African Americans with Hypertension Framed by the Roy Adaptation Model

Hypertension (HTN) prevalence in African Americans contribute to higher rates of disabilities and deaths from stroke, myocardial infarction, and end stage renal disease than all other racial groups in the United States. The major reason documented for these poor health outcomes is related to lower HTN control rates among African Americans compared to other racial/ethnic groups. Though overall HTN awareness, pharmacological treatments and control have significantly improved for all populations, studies found that rates of HTN control and adherence with anti-hypertensive medications are lower for African Americans compared to other subgroups. Study Aims The primary aim was to determine whether hypertension knowledge, expectation of care, and social support are predictors of adherence to prescribed medications while controlling for socioeconomic factors in the context of hypertension among African Americans. Methods A cross sectional quantitative approach was used. A secondary data analysis was conducted with 387 hypertensive African Americans. The Morisky Medication Adherence scale was used to measure adherence, internal consistency was established, (r=.61). The Roy Adaptation Model (RAM) was used to link HTN knowledge, expectations of care, social support, and socioeconomic factors with adherence to medications to provide an understanding of the process of adaptation. Logistic regressions were used to determine the relationships among the variables. Results The sample (N=387) was primarily female (76%) and men (24%). On average, participants scored high in knowledge about hypertension; mean knowledge score was .91 (SD = .09). Controlling for patient covariates, hypertension knowledge was not found to be a predictor of adherence to prescribed medications (p=.469). Expectation of care was found to be a predictor of adherence to prescribed medications (p=.008); social support was found to be a predictor of adherence to medications (p=.006). Conclusion and Implications This study supports findings regarding expectations of care, social support, and adherence to medication in African American patients with hypertension. The findings are useful for planning patient management initiatives specific to chronic disease such as hypertension

1855 and 1991 Surveys of the San Andreas Fault: Implications for Fault Mechanics

Two monuments from an 1855 cadastral survey that span the San Andreas fault in the Carrizo Plain have been right-laterally displaced 11.0 ± 2.5 m by the 1857 Fort Tejon earthquake and associated seismicity and afterslip. This measurement confirms that at least 9.5 ± 0.5 m of slip occurred along the main fault trace, as suggested by measurements of offset channels near Wallace Creek. The slip varied by 2 to 3 m along a 2.6-km section of the main fault trace. Using radiocarbon dates of the penultimate large earthquake and measurements of slip from the 1857 earthquake, we calculate an apparent slip rate for the last complete earthquake cycle that is at least 25% lower than the late-Holocene slip rate on the main fault trace. Comparison of short-term broad-aperture strain accumulation rates with the narrow-aperture late-Holocene slip rate indicates that the fault behaves nearly elastically over a time scale of several earthquake cycles. Therefore, slip in future earthquakes should compensate the slip-rate deficit from the 1857 earthquake

Analysis of the SEA-OWC-Clam wave energy device part B:structural integrity analysis

In this paper the dynamic loads determined for the SEA-OWC-Clam wave energy device, treated as a floating offshore structure with six degrees-of-freedom with partial internal sealed-off channels, are applied to assess its structural integrity. This task necessitates the matching of the boundary element determined dynamic pressures to the corresponding Finite Element Analysis (FEA) to determine the effective von Mises stress levels. A decomposition of the total load to permit attribution to different aspects of radiation and diffraction loading is presented. Possible modification of structural details is identified by undertaking a more local stiffened plate analysis to improve structural detail

An independent evaluation of The Filter

Existing Research In 2009, a comprehensive review of evidence relating to young people and smoking was published. Few studies were identified which focused specifically on smoking prevention or cessation interventions for young people, and the majority of the existing evidence focused on school-based programmes. We searched for Cochrane reviews and peer reviewed literature from 2009-2015. There was little research on the acceptability and effectiveness of training professionals who work with young people to deliver smoking prevention and cessation messages. There was also a dearth of evidence regarding the effectiveness of direct youth involvement in smoking prevention and cessation programmes. Evidence relating to online health promotion and young people focused primarily on educational programmes involving highly structured content, with very little evidence regarding a less formal approach. Research design A multi-faceted process evaluation of The Filter was undertaken. First, tweets sent to or from The Filter Twitter account were subjected to thematic analysis. Second, semi-structured interviews were undertaken with The Filter staff, professionals who had undergone training from The Filter and young people who had either interacted with The Filter online or as part of face-to-face workshops. Finally, surveys were developed based on the findings of the interview study, which asked professionals and young people about their experiences of all elements of The Filter programme. Results: Training for professionals working with young people The Filter training team reported that initially they designed and delivered training based on the key tobacco topics identified in Wales. This was later amended, to include smoking cessation training, and bespoke training packages. Professionals who took part in interviews reported that they valued this flexible approach to training courses and had put some of the techniques they had learnt into practice in their work with young people. This was found to be the case by professionals who took part in the online survey. Professionals also reported that the training was relevant, enjoyable and gave them new knowledge about smoking. 5 Results: Youth development, education and smoking cessation support The Filter developed a workshop-based approach to transmitting tobacco control and smoking cessation messages, which was delivered to small groups of young people in their own communities. The Filter staff reported that delivering these sessions was unproblematic, and all respondents identified a very strong rapport between The Filter staff and young people. The range of activities included in workshops was also identified as a key way of sustaining interest from young people, and visual aids were identified as particularly engaging. Some young people suggested that their interaction with The Filter had changed their planned behaviour in relation to smoking, or encouraged them to cut down or quit if they were existing smokers. Results: Online health promotion The Filter team shared tobacco control messages via a wide range of online platforms. They have achieved some level of success in terms of reach on The Filter website and potential reach on Twitter and Facebook. However, it was not possible within the confines of this research to understand if these users fit within the target demographic for the intervention, and how much overlap there was between The Filter face-to-face services and online services. The Filter staff reported that the intervention was deliverable by using a flexible approach, including the use of multiple and changing online platforms. It was not possible to understand how acceptable this intervention was to young people, as only one of The Filter’s followers agreed to take part in an online interview, and only 11 respondents to the online survey had interacted with the online resources. The evaluation of social media based interventions has been acknowledged to be a challenging area (Bailey et al., 2015) and this low response does not mean that the intervention is not reaching the targeted individuals, but that the individuals were not willing to take part in a brief evaluation. Conclusion To carry out this evaluation, we were given full access to The Filter team and their contacts in order to gather samples for the interviews and surveys. The Filter team were adaptable in their approaches to training and the use of social media over the course of the project, ensuring smoking cessation and prevention information was maintained as up to date and relevant. Professionals noted the rapport the Filter Team developed with young people was excellent. Training was high quality and professionals were able to use what they had learned from The Filter when working directly with young people. Young people liked the visual aspects of The Filter and they preferred the informal youth work approach to school based sessions on smoking. The use of The Filter social media platforms and online resources was encouraging, showing maintained growth over the course of evaluation period. Online resources were reported to be used by the majority of professionals taking part in the evaluation, however, engaging young people in the evaluation of The Filter via social media proved challenging. The data in this evaluation suggests that The Filter is a service which is feasible to deliver. The methodology of this evaluation did not allow us to examine the effectiveness of The Filter in terms of smoking prevention or cessation