Robust and parsimonious realisations of unitaries in the one-way model

We present a new set of generators for unitary maps over \otimes^n(C^2) which differs from the traditional rotation-based generating set in that it uses a single-parameter family of 1-qubit unitaries J(a), together with a single 2-qubit unitary controlled-Z. Each generator is implementable in the one-way model using only two qubits, and this leads to both parsimonious and robust implementations of general unitaries. As an illustration, we give an implementation of the controlled-U family which uses only 14 qubits, and has a 2-colourable underlying entanglement graph (known to yield robust entangled states).Comment: 8 pages, 2 figures, keywords: unitary transformations, measurement-based quantum computin

Pseudo-Random Number Generators for Vector Processors and Multicore Processors

Large scale Monte Carlo applications need a good pseudo-random number generator capable of utilizing both the vector processing capabilities and multiprocessing capabilities of modern computers in order to get the maximum performance. The requirements for such a generator are discussed. New ways of avoiding overlapping subsequences by combining two generators are proposed. Some fundamental philosophical problems in proving independence of random streams are discussed. Remedies for hitherto ignored quantization errors are offered. An open source C++ implementation is provided for a generator that meets these needs

Hybrid Biomass-Wind Power Plant For Reliable Energy Generation

[EN] Massive implementation of renewable energy resources is a key element to reduce CO2 emissions associated to electricity generation. Wind resources can provide an important alternative to conventional electricity generation mainly based on fossil fuels. However, wind generators are greatly affected by the restrictive operating rules of electricity markets because, as wind is naturally variable, wind generators may have serious difficulties on submitting accurate generation schedules on a day ahead basis, and on complying with scheduled obligations in real-time operation. In this paper, an innovative system combining a biomass gasification power plant, a gas storage system and stand-by generators to stabilize a generic 40 MW wind park is proposed and evaluated with real data. The wind park power production model is based on real data about power production of a Spanish wind park and a probabilistic approach to quantify fluctuations and so, power compensation needs. The hybrid wind-biomass system is analysed to obtain main hybrid system design parameters. This hybrid system can mitigate wind prediction errors and so provide a predictable source of electricity. An entire year cycle of hourly power compensations needs has been simulated deducing storage capacity, extra power needs of the biomass power plant and stand-by generation capacity to assure power compensation during critical peak hours with acceptable reliability.Pérez-Navarro, A.; Alfonso-Solar, D.; Álvarez, C.; Ibáñez, F.; Sánchez-Diaz, C.; Segura Heras, I. (2010). Hybrid Biomass-Wind Power Plant For Reliable Energy Generation. Renewable Energy. 35(7):1436-1443. https://doi.org/10.1016/j.renene.2009.12.0181436144335

Towards cooperative software verification with test generation and formal verification

There are two major methods for software verification: testing and formal verification. To increase our confidence in software on a large scale, we require tools that apply these methods automatically and reliably. Testing with manually written tests is widespread, but for automatically generated tests for the C programming language there is no standardized format. This makes the use and comparison of automated test generators expensive. In addition, testing can never provide full confidence in software—it can show the presence of bugs, but not their absence. In contrast, formal verification uses established, standardized formats and can prove the absence of bugs. Unfortunately, even successful formal-verification techniques suffer from different weaknesses. Compositions of multiple techniques try to combine the strengths of complementing techniques, but such combinations are often designed as cohesive, monolithic units. This makes them inflexible and it is costly to replace components. To improve on this state of the art, we work towards an off-the-shelf cooperation between verification tools through standardized exchange formats. First, we work towards standardization of automated test generation for C. We increase the comparability of test generators through a common benchmarking framework and reliable tooling, and provide means to reliably compare the bug-finding capabilities of test generators and formal verifiers. Second, we introduce new concepts for the off-the-shelf cooperation between verifiers (both test generators and formal verifiers). We show the flexibility of these concepts through an array of combinations and through an application to incremental verification. We also show how existing, strongly coupled techniques in software verification can be decomposed into stand-alone components that cooperate through clearly defined interfaces and standardized exchange formats. All our work is backed by rigorous implementation of the proposed concepts and thorough experimental evaluations that demonstrate the benefits of our work. Through these means we are able to improve the comparability of automated verifiers, allow the cooperation between a large array of existing verifiers, increase the effectiveness of software verification, and create new opportunities for further research on cooperative verification

Practical Volume Estimation by a New Annealing Schedule for Cooling Convex Bodies

We study the problem of estimating the volume of convex polytopes, focusing on H- and V-polytopes, as well as zonotopes. Although a lot of effort is devoted to practical algorithms for H-polytopes there is no such method for the latter two representations. We propose a new, practical algorithm for all representations, which is faster than existing methods. It relies on Hit-and-Run sampling, and combines a new simulated annealing method with the Multiphase Monte Carlo (MMC) approach. Our method introduces the following key features to make it adaptive: (a) It defines a sequence of convex bodies in MMC by introducing a new annealing schedule, whose length is shorter than in previous methods with high probability, and the need of computing an enclosing and an inscribed ball is removed; (b) It exploits statistical properties in rejection-sampling and proposes a better empirical convergence criterion for specifying each step; (c) For zonotopes, it may use a sequence of convex bodies for MMC different than balls, where the chosen body adapts to the input. We offer an open-source, optimized C++ implementation, and analyze its performance to show that it outperforms state-of-the-art software for H-polytopes by Cousins-Vempala (2016) and Emiris-Fisikopoulos (2018), while it undertakes volume computations that were intractable until now, as it is the first polynomial-time, practical method for V-polytopes and zonotopes that scales to high dimensions (currently 100). We further focus on zonotopes, and characterize them by their order (number of generators over dimension), because this largely determines sampling complexity. We analyze a related application, where we evaluate methods of zonotope approximation in engineering.Comment: 20 pages, 12 figures, 3 table

Transition Support Mechanisms for Communities Facing Full or Partial Coal Power Plant Retirement in New York

New York State is undergoing a rapid and unprecedented energy transformation, particularly in the electricity sector. As new resources and technologies emerge to meet the demands of 21st century life, regulators must balance the need for cost effective and equitable participation in wholesale power markets while maintaining reliability on the grid. Furthermore, it is critical that all New Yorkers participate fully in the promise of a revitalized and equitable energy future. Such a transformation requires that the needs of all communities are factored into the polices and regulations that move New York toward the bold goals set forth under its Reforming the Energy Vision (REV) initiative. The precipitous drop in natural gas prices, the decreased costs of wind and solar energy, and the rise in the cost of coal, have contributed to the mothballing or retiring of coal-fired and nuclear energy generators across the country, including in New York. Communities that have been home to the electric generation units of the past, particularly struggling coal-fired power plants, are especially vulnerable during this transformation, because these communities often rely on the generators for tax revenues, such as through Payments in Lieu of Tax agreements. New York has the opportunity to ensure a just transition for these communities by adopting new, clean energy resources, technologies, and markets while fostering a trained and skilled workforce to support its ambitious goals. For all New Yorkers to enjoy the new energy future, leadership must address the impact of lost jobs, declining economic activity and lost tax revenue, and must support essential services in impacted communities with the same level of urgency and expansive vision needed to balance the integration of new technologies in the most cost effective manner to maintain grid reliability. At the same time, state and federal funding must be allocated to communities in transition for the remediation and redevelopment of shuttered power plant sites, and to provide the necessary support, training and tools for impacted communities to actively participate in the transition and implementation of clean energy resources. The first section of this report examines the lessons learned from other jurisdictions in when and how to address the fiscal challenges of retiring electric generation units (EGU’s). The challenges New York faces are not unlike the challenges faced by communities, legislators, and plant owners during periods of deindustrialization of the late 1960’s through 1980’s, described in Section One below, which additionally provides: 1. An evaluation of case studies that address the process of retirement, decommissioning, remediation and preparation for redevelopment for future use, along with the state and federal policies and funding sources that made revitalization possible. 2. An overview of case studies that illustrate local government fiscal and workforce support to communities during periods of plant transformation. These periods encompass three historical phases: a. Deindustrialization of the 1960’s to1980’s; b. Federally Mandated Social Programs to Support Enforcement of Federal Regulations 1990’s to 2000; and c. Coal Plant Closures and Community Transition in the Age of Carbon Emissions Reductions: Federal and State Initiatives between 2000 to 2015; and Section Two examines four New York coal-fired generators, some of which are currently mothballed, retired, or struggling financially. In addition to providing profiles of each generator, Section Two also describes the Payment in Lieu of Taxes (PILOT) agreements that these generators have entered into with the towns, school boards, and counties in whose jurisdictions they are located. Due to the plants’ finances, several of the generators have made reduced PILOT payments in recent years, creating “budget gaps” for some of the communities. Finally, Section Three describes state and federal funding and support mechanisms that may be available to the New York communities described in Section Two. Because each community faces unique challenges and opportunities, this report does not attempt to provide specific recommendations for any of the communities. Rather, Section Three lists a number of support mechanisms that each community could consider in developing its own transition plan. New York State leadership can capitalize on the legislative legacy of prior eras and develop comprehensive approaches to reinvest in communities with obsolete industrial facilities that were once the primary source of jobs and economic activity, and revenue to local budgets

A Comparative Study of Some Pseudorandom Number Generators

We present results of an extensive test program of a group of pseudorandom number generators which are commonly used in the applications of physics, in particular in Monte Carlo simulations. The generators include public domain programs, manufacturer installed routines and a random number sequence produced from physical noise. We start by traditional statistical tests, followed by detailed bit level and visual tests. The computational speed of various algorithms is also scrutinized. Our results allow direct comparisons between the properties of different generators, as well as an assessment of the efficiency of the various test methods. This information provides the best available criterion to choose the best possible generator for a given problem. However, in light of recent problems reported with some of these generators, we also discuss the importance of developing more refined physical tests to find possible correlations not revealed by the present test methods.Comment: University of Helsinki preprint HU-TFT-93-22 (minor changes in Tables 2 and 7, and in the text, correspondingly

Some comments on C. S. Wallace's random number generators

We outline some of Chris Wallace's contributions to pseudo-random number generation. In particular, we consider his idea for generating normally distributed variates without relying on a source of uniform random numbers, and compare it with more conventional methods for generating normal random numbers. Implementations of Wallace's idea can be very fast (approximately as fast as good uniform generators). We discuss the statistical quality of the output, and mention how certain pitfalls can be avoided.Comment: 13 pages. For further information, see http://wwwmaths.anu.edu.au/~brent/pub/pub213.htm