A simple minimax estimator for quantum states

Quantum tomography requires repeated measurements of many copies of the physical system, all prepared by a source in the unknown state. In the limit of very many copies measured, the often-used maximum-likelihood (ML) method for converting the gathered data into an estimate of the state works very well. For smaller data sets, however, it often suffers from problems of rank deficiency in the estimated state. For many systems of relevance for quantum information processing, the preparation of a very large number of copies of the same quantum state is still a technological challenge, which motivates us to look for estimation strategies that perform well even when there is not much data. In this article, we review the concept of minimax state estimation, and use minimax ideas to construct a simple estimator for quantum states. We demonstrate that, for the case of tomography of a single qubit, our estimator significantly outperforms the ML estimator for small number of copies of the state measured. Our estimator is always full-rank, and furthermore, has a natural dependence on the number of copies measured, which is missing in the ML estimator.Comment: 26 pages, 3 figures. v2 contains minor improvements to the text, and an additional appendix on symmetric measurement

Average transmission probability of a random stack

The transmission through a stack of identical slabs that are separated by gaps with random widths is usually treated by calculating the average of the logarithm of the transmission probability. We show how to calculate the average of the transmission probability itself with the aid of a recurrence relation and derive analytical upper and lower bounds. The upper bound, when used as an approximation for the transmission probability, is unreasonably good and we conjecture that it is asymptotically exact.Comment: 10 pages, 6 figure

Heterogeneous characters modeling of instant message services users’ online behavior

Research on temporal characteristics of human dynamics has attracted much attentions for its contribution to various areas such as communication, medical treatment, finance, etc. Existing studies show that the time intervals between two consecutive events present different non-Poisson characteristics, such as power-law, Pareto, bimodal distribution of power-law, exponential distribution, piecewise power-law, et al. With the occurrences of new services, new types of distributions may arise. In this paper, we study the distributions of the time intervals between two consecutive visits to QQ and WeChat service, the top two popular instant messaging services in China, and present a new finding that when the value of statistical unit T is set to 0.001s, the inter-event time distribution follows a piecewise distribution of exponential and power-law, indicating the heterogeneous character of IM services users’ online behavior in different time scales. We infer that the heterogeneous character is related to the communication mechanism of IM and the habits of users. Then we develop a combination model of exponential model and interest model to characterize the heterogeneity. Furthermore, we find that the exponent of the inter-event time distribution of the same service is different in two cities, which is correlated with the popularity of the services. Our research is useful for the application of information diffusion, prediction of economic development of cities, and so on.National Natural Science Foundation (China) (61201153)National Basic Research Program of China (973 Program) (Grant 2012CB315805)CCF Venus Research Project (CCF-VenustechRP2016004)Jiangsu Industrial Technology Research Institute. Institute of Future Networks Technology (BY2013095-2-16

Education Program for Improved Water Quality in Copano Bay Final Report

The Copano Bay watershed covers approximately 1.4 million acres encompassing portions of Karnes, Bee, Goliad, Refugio, San Patricio and Aransas counties. Copano Bay and its main tributaries, the Mission and Aransas rivers, were placed on the Texas Commission on Environmental Quality (TCEQ) 303(d) list in 1998 due to levels of bacteria that exceed water quality standards established to protect oyster waters use. A Total Maximum Daily Load (TMDL) program was initiated in September 2003 to identify and assess sources of these bacteria. The Center for Research in Water Resources at the University of Texas at Austin (UT CRWR) was funded by TCEQ to conduct computer-based modeling to determine the bacterial loading and reductions necessary to attain water quality standards. Subsequently Texas A&M University-Corpus Christi (TAMU-CC) conducted bacterial source tracking (BST) with funding from Texas General Land Office (TGLO) and the Coastal Bend Bays and Estuaries Program (CBBEP) to determine actual sources of bacteria. Due to the findings of the initial efforts of the TMDL and concerns voiced by stakeholders in the watershed, Texas AgriLife Extension Service was awarded a Clean Water Act § 319(h) Nonpoint Source Grant from the Texas State Soil and Water Conservation Board (TSSWCB) and the U.S. Environmental Protection Agency. The overall goal of this project was to improve water quality in Copano Bay and its tributaries by increasing awareness of water quality issues throughout the watershed. This increased awareness was to be accomplished by providing education and demonstrations for land and livestock owners in the watershed on best management practices (BMPs) to decrease or prevent bacteria from entering waterways. Through creation of a project website, 52 educational programs, and nine one-on-one consultations over the span of the project, we have reached 5,408 residents in and around the Copano Bay watershed. Additionally, through this project all data collected for the initial TMDL efforts was re-evaluated and findings were presented in the “Task 2 Report.” Project members developed a curriculum for horse owners, “A Guide to Good Horsekeeping” that addressed BMPs specific to horse operations. Land and livestock owners who had already implemented BMPs or were interested in implementing BMPs were given a participation certificate

Off-nadir antenna bias correction using Amazon rain forest sigma deg data

The radar response from the Amazon rain forest was studied to determine the suitability of this region for use as a standard target to calibrate a scatterometer like that proposed for the National Ocean Satellite System (NOSS). Backscattering observations made by the SEASAT-1 scatterometer system show the Amazon rain forest to be a homogeneous, azimuthally-isotropic, radar target which is insensitive to polarization. The variation with angle of incidence may be adequately modeled as sigma deg (dB) = alpha theta + beta with typical values for the incidence-angle coefficient from 0.07 dB deg to 0.15 dB/deg. A small diurnal effect occurs, with measurements at sunrise being 0.5 dB to 1 dB higher than the rest of the day. Maximum likelihood estimation algorithms are presented which permit determination of relative bias and true pointing angle for each beam. Specific implementation of these algorithms for the proposed NOSS scatterometer system is also discussed

Cell number and transfection volume dependent peptide nucleic acid antisense activity by cationic delivery methods

Efficient intracellular delivery is essential for high activity of nucleic acids based therapeutics, including antisense agents. Several strategies have been developed and practically all rely on auxiliary transfection reagents such as cationic lipids, cationic polymers and cell penetrating peptides as complexing agents and carriers of the nucleic acids. However, uptake mechanisms remain rather poorly understood, and protocols always require optimization of transfection parameters. Considering that cationic transfection complexes bind to and thus may up-concentrate on the cell surface, we have now quantitatively compared the cellular activity (in the pLuc705 HeLa cell splice correction system) of PNA antisense oligomers using lipoplex delivery of cholesterol- and bisphosphonate-PNA conjugates, polyplex delivery via a PNA-polyethyleneimine conjugate and CPP delivery via a PNA-octaarginine conjugate upon varying the cell culture transfection volume (and cell density) at fixed PNA concentration. The results show that for all delivery modalities the cellular antisense activity increases (less than proportionally) with increasing volume (in some cases accompanied with increased toxicity), and that this effect is more pronounced at higher cell densities. These results emphasize that transfection efficacy using cationic carriers is critically dependent on parameters such as transfection volume and cell density, and that these must be taken into account when comparing different delivery regimes

Attitudes Concerning Postmortem Organ Donation : A Multicenter Survey in Various German Cohorts

BACKGROUND The aim of this study was to characterize postmortem organ donation attitudes in various German cohorts. MATERIAL AND METHODS Employees of 2 German cities and 2 German university hospitals, employees of a German automobile enterprise, and members of a German Medical Society were administered a questionnaire about postmortem organ and tissue donation attitudes. Demographic data and general attitudes were questioned and focused on: I) willingness to donate organs, II) holding a donor card, and III) having discussed the topic with the family. RESULTS Of 5291 participants, 65.2% reported favoring postmortem organ donation. Missing negative experiences, the idea that donation is helpful, a non-medical professional environment, excellent general health, gender, agreement with the brain-death paradigm, and age significantly influenced the participants’ attitudes. Participants were more likely to possess donor cards and had discussed more often with family members if they agreed with the brain-death paradigm and considered donation to be helpful. Males and older participants were the most likely to neglect donor cards, and Catholics, Protestants, and participants with poor health were the least likely to donate organs. Interest in receiving more information was expressed by 38.1% and 50.6% of participants refusing donation of all or of specific organs, respectively, and suggested the internet (60.0%) and family doctors (35.0%) as preferred sources of information. CONCLUSIONS Public campaigns in Germany should focus on males and older people as regards donor cards, and females, younger, and religiously affiliated persons as regards the general willingness to donate organs postmortem

Revisiting Fara: Comparison of merged prospection results of diverse magnetometers with the earliest excavations in ancient Suruppak from 120 years ago

Ancient Suruppak, today Fara, was one of the major Sumerian cities in Mesopotamia. It was situated along one of the ancient watercourses of the Euphrates River. Findings date it back to the Jemdet Nasr period around 3000 bc with a continuous occupation until the end of the Ur III period around 2000 bc. Fara was first explored and excavated by the Deutsche Orient-Gesellschaft in the years 1902 and 1903 under the direction of Walter Andrae. Multiple excavation trenches with lengths up to 900 m transect the 1 km(2) wide mound and are still visible today which enables us to georeference the excavation maps. Today, the 2.2 km(2) wide archaeological area is dry and without any vegetation. Thousands of deep looting pits are covering the majority of mound which not only destroyed its upper metres but also challenge the application of geophysical prospection methods and their interpretation. The magnetometer prospecting of selected areas on and around the mound was carried out with three devices, two total field magnetometers and one gradiometer. The individual survey areas were combined in post-processing by applying a high-pass filter on the total field data sets and multiplying the vertical gradiometer data sets by a factor of two. This approach provides visually uniform magnetograms, despite being obtained by different devices, which simplifies subsequent visual interpretation. These magnetograms enable us to review, and to extend the results of the old excavations. The comparison show a good correlation in accuracy to the old drawings and positive identification of the already excavated features with magnetometry. Highlights of the survey are the discovery of the city wall confirming its existence, the layout of a unique building complex in the centre of the mound, likely a temple, traces of canals inside the city and an evaluation of magnetometer prospection over a looted area