Electrometry Using Coherent Exchange Oscillations in a Singlet-Triplet-Qubit

Two level systems that can be reliably controlled and measured hold promise in both metrology and as qubits for quantum information science (QIS). When prepared in a superposition of two states and allowed to evolve freely, the state of the system precesses with a frequency proportional to the splitting between the states. In QIS,this precession forms the basis for universal control of the qubit,and in metrology the frequency of the precession provides a sensitive measurement of the splitting. However, on a timescale of the coherence time, $T_2$, the qubit loses its quantum information due to interactions with its noisy environment, causing qubit oscillations to decay and setting a limit on the fidelity of quantum control and the precision of qubit-based measurements. Understanding how the qubit couples to its environment and the dynamics of the noise in the environment are therefore key to effective QIS experiments and metrology. Here we show measurements of the level splitting and dephasing due to voltage noise of a GaAs singlet-triplet qubit during exchange oscillations. Using free evolution and Hahn echo experiments we probe the low frequency and high frequency environmental fluctuations, respectively. The measured fluctuations at high frequencies are small, allowing the qubit to be used as a charge sensor with a sensitivity of $2 \times 10^{-8} e/\sqrt{\mathrm{Hz}}$, two orders of magnitude better than the quantum limit for an RF single electron transistor (RF-SET). We find that the dephasing is due to non-Markovian voltage fluctuations in both regimes and exhibits an unexpected temperature dependence. Based on these measurements we provide recommendations for improving $T_2$ in future experiments, allowing for higher fidelity operations and improved charge sensitivity

Using tasks to explore teacher knowledge in situation-specific contexts

This article was published in the journal, Journal of Mathematics Teacher Education [© Springer] and the original publication is available at www.springerlink.comResearch often reports an overt discrepancy between theoretically/out-of context expressed teacher beliefs about mathematics and pedagogy and actual practice. In order to explore teacher knowledge in situation-specific contexts we have engaged mathematics teachers with classroom scenarios (Tasks) which: are hypothetical but grounded on learning and teaching issues that previous research and experience have highlighted as seminal; are likely to occur in actual practice; have purpose and utility; and, can be used both in (pre- and in-service) teacher education and research through generating access to teachers’ views and intended practices. The Tasks have the following structure: reflecting upon the learning objectives within a mathematical problem (and solving it); examining a flawed (fictional) student solution; and, describing, in writing, feedback to the student. Here we draw on the written responses to one Task (which involved reflecting on solutions of x+x−1=0 of 53 Greek in-service mathematics teachers in order to demonstrate the range of teacher knowledge (mathematical, didactical and pedagogical) that engagement with these tasks allows us to explore

Demonstration of Entanglement of Electrostatically Coupled Singlet-Triplet Qubits

Quantum computers have the potential to solve certain interesting problems significantly faster than classical computers. To exploit the power of a quantum computation it is necessary to perform inter-qubit operations and generate entangled states. Spin qubits are a promising candidate for implementing a quantum processor due to their potential for scalability and miniaturization. However, their weak interactions with the environment, which leads to their long coherence times, makes inter-qubit operations challenging. We perform a controlled two-qubit operation between singlet-triplet qubits using a dynamically decoupled sequence that maintains the two-qubit coupling while decoupling each qubit from its fluctuating environment. Using state tomography we measure the full density matrix of the system and determine the concurrence and the fidelity of the generated state, providing proof of entanglement

Differences in SpeB Protease Activity Among Group A Streptococci Associated With Superficial, Invasive, and Autoimmune Disease

The secreted cysteine proteinase SpeB is an important virulence factor of group A streptococci (GAS), whereby SpeB activity varies widely among strains. To establish the degree to which SpeB activity correlates with disease, GAS organisms were recovered from patients with pharyngitis, impetigo, invasive disease or acute rheumatic fever (ARF), and selected for analysis using rigorous sampling criteria; \u3e300 GAS isolates were tested for SpeB activity by casein digestion assays, and each GAS isolate was scored as a SpeB-producer or non-producer. Highly significant statistical differences (p \u3c 0.01) in SpeB production are observed between GAS recovered from patients with ARF (41.5% SpeB-non-producers) compared to pharyngitis (20.5%), invasive disease (16.7%), and impetigo (5.5%). SpeB activity differences between pharyngitis and impetigo isolates are also significant, whereas pharyngitis versus invasive isolates show no significant difference. The disproportionately greater number of SpeB-non-producers among ARF-associated isolates may indicate an altered transcriptional program for many rheumatogenic strains and/or a protective role for SpeB in GAS-triggered autoimmunity

Inhibition of immunoglobulin production by parathyroid hormone. Implications in chronic renal failure

Inhibition of immunoglobulin production by parathyroid hormone. Implications in chronic renal failure. Available data indicate that B cell proliferation is inhibited in chronic renal failure and this is due to excess blood levels of PTH. This defect may also affect immunoglobulin production. We examined production of IgG, IgM and IgA by B cells stimulated with Staphylococcus aureus Cowan I (SAC) or with pokeweed mitogen (PWM) after eight days of culture and evaluated the effect of PTH on this process in 34 hemodialysis patients and 44 normal subjects. IgG, IgM and IgA production by B cells from patients was lower (P < 0.01) than by B cells from normal subjects. Both 1-34 and 1-84 PTH inhibited (P < 0.01) immunoglobulin production by B cells from normal subjects and dialysis patients. However, this inhibitory effect was evident in dialysis patients only with the higher dose of PTH. The inhibition of immunoglobulin production by PTH occurred only when the hormone was added at the initiation of the B cell culture. Inactivation of PTH abolished its inhibitory effect on immunoglobulin production. Agents that stimulate cAMP production (forskolin, cholera toxin) and the cAMP analogue, 8-bromoadenosine 3′,5′ cyclic monophosphate inhibited immunoglobulin production by B cells from both normal and dialysis patients, and the degree of inhibition was not different between the two groups. The calcium inophore A23187 also inhibited IgG, IgA and IgM production by B cells from normal subjects and dialysis patients; there was no significant difference in the degree of inhibition between the two groups. The resting levels of cytosolic calcium in B cells of dialysis patients was significantly (P < 0.01) higher than that of B cells from normal subjects. The data show that: (1) immunoglobulin production is impaired in dialysis patients; (2) B cells of dialysis patients have elevated resting levels of cytosolic calcium; (3) PTH inhibits IgG, IgA and IgM production and this effect is at least partly mediated by PTH-induced cAMP production and alterations in cytosolic calcium into B cells; (4) this inhibitory effect is mediated by events that affect initial stages of B cell proliferation and maturation; (5) the requirement for high dose of PTH for its inhibitory effect on B cells from dialysis patients is probably due to desensitization and/or down-regulation of PTH receptors on B cells. The results are consistent with the proposition that impaired immunoglobulin production by B cells from dialysis patients is at least partly due to the state of secondary hyperparathyroidism in these patients

Systematic review and consensus definitions for the Standardised Endpoints in Perioperative Medicine initiative: patient-centred outcomes

BACKGROUND: Patient-centred outcomes are increasingly used in perioperative clinical trials. The Standardised Endpoints in Perioperative Medicine (StEP) initiative aims to define which measures should be used in future research to facilitate comparison between studies and to enable robust evidence synthesis. METHODS: A systematic review was conducted to create a longlist of patient satisfaction, health-related quality of life, functional status, patient well-being, and life-impact measures for consideration. A three-stage Delphi consensus process involving 89 international experts was then conducted in order to refine this list into a set of recommendations. RESULTS: The literature review yielded six patient-satisfaction measures, seven generic health-related quality-of-life measures, eight patient well-being measures, five functional-status measures, and five life-impact measures for consideration. The Delphi response rates were 92%, 87%, and 100% for Rounds 1, 2, and 3, respectively. Three additional measures were added during the Delphi process as a result of contributions from the StEP group members. Firm recommendations have been made about one health-related quality-of-life measure (EuroQol 5 Dimension, five-level version with visual analogue scale), one functional-status measure (WHO Disability Assessment Schedule version 2.0, 12-question version), and one life-impact measure (days alive and out of hospital at 30 days after surgery). Recommendations with caveats have been made about the Bauer patient-satisfaction measure and two life-impact measures (days alive and out of hospital at 1 yr after surgery, and discharge destination). CONCLUSIONS: Several patient-centred outcome measures have been recommended for use in future perioperative studies. We suggest that every clinical study should consider using at least one patient-centred outcome within a suite of endpoints

The Middle Urals distributed power generation formation

This paper presents formation of local power systems based on high efficiency combined-cycle cogeneration plant as a depressed towns of the region problem solving technique. The proposed conception benefits are denoted.В статье рассматриваются вопросы формирования локальных энергосистем на базе высокоэффективных когенерационных парогазовых установок ПГУ-ТЭЦ как способ решения комплекса проблем депрессивных городов региона. Обозначены преимущества предлагаемой концепции

The Middle Urals Distributed Power Generation Formation Based on CCCPP

Irbit and Kamyshlov (as the examples of little towns in the Middle Urals) power systems state is analyzed in this paper and conclusions about the probable way of problems overcoming by means of distributed power generation formation in this region by medium sized high-performance CHP (Central Heating and Power) plants locating in these towns are drawn on the basis of perceived disadvantages of the systems. Highly efficient combined-cycle cogeneration power plant (CCCPP) able to provide high fuel combustion efficiency, flexibility and ecological compatibility are considered as energy providers in the proposed conception of the local power systems formation in the Middle Urals. The significance of this conception for the social and economic development of Irbit and Kamyshlov towns and Sverdlovsk region generally is described.В статье проанализировано состояние энергосистем малых городов Среднего Урала на примере городов Ирбит и Камышлов, на основе выявленных недостатков систем сделаны выводы о возможном способе преодоления проблем с помощью формирования распределённой генерации в регионе путём размещения в этих городах приближенных к потребителям высокоэкономичных ТЭЦ. В качестве генераторов энергии в предложенной концепции создания локальных энергетических структур на Среднем Урале выступают высокоэффективные когенерационные парогазовые установки ПГУ-ТЭЦ, способные обеспечить высокую эффективность использования топлива, маневренность и экологичность. Описано значение данной концепции для социально-экономического развития городов Ирбит, Камышлов и Свердловской области в целом

CCCP FOR THE MIDDLE URALS DISTRIBUTED POWER GENERATION

This paper presents variations of CCCP (combined-cycle cogeneration plant) technological schemes and major equipment for the local power systems in the Middle Urals formation. The article contains examples of different decisions using at power assets of our country. An inference is drawn about possibility of home-grown technology of power plant engineering application for the conception realization.В статье изложены варианты технологических схем ПГУ-ТЭЦ и основного оборудования для формирования комплекса локальных энергосистем на Среднем Урале. Рассмотрены примеры использования различных решений на энергетических объектах страны. Сделаны выводы о возможности применения оборудования отечественного энергомашиностроения для реализации концепции