A new criteria for zero quantum discord

We propose a new criterion to judge zero quantum discord for arbitrary bipartite states. A bipartite quantum state has zero quantum discord if and only if all blocks of its density matrix are normal matrices and commute with each other. Given a bipartite state with zero quantum discord, how to find out the set of local projectors, which do not disturb the whole state after being imposed on one subsystem, is also presented. A class of two-qubit X-state is used to test the criterion, and an experimental scheme is proposed to realize it. Consequently, we prove that the positive operator-valued measurement can not extinguish the quantum correlation of a bipartite state with nonzero quantum discord.Comment: 10 pages, 1 figur

Implementing the PIE (Person, Interaction and Environment) programme to improve person-centred care for people with dementia admitted to hospital wards: a qualitative evaluation

Background Improving person-centred care for people with dementia in hospitals is a UK policy priority. The PIE (Person, Interaction, Environment) programme comprises cycles of observations of care by staff, identification of areas for improvement and plans for practice change and evaluation. The aim of the research reported here was to describe and evaluate PIE implementation in three UK NHS regions. Methods A qualitative design was adopted in ten case study sites (wards). Site selection was based on readiness for change criteria. Following a training workshop, PIE cycles were introduced into each ward. Data collection comprised observation, interviews, documentary analysis and an events log. Normalisation Process Theory provided a guiding framework for analysis. Results PIE was fully adopted in two study wards over 18 months, which resulted in sustained practice change and increased awareness of person-centredness. Partial implementation of PIE took place in a further two wards but progress stalled before significant action. The remaining six wards failed to implement PIE. Factors influencing implementation were: salience of PIE, collective team involvement, fit with strategic priorities, adequate resources, effective clinical leadership, good facilitation and organisational stability. Conclusions PIE has the potential to help staff improve person-centred care for people with dementia admitted to hospital wards. However, the evidence is limited to ten wards of which only two fully implemented the programme. Implications for practice • A programme for improving person-centred care for people with dementia in acute hospital wards requires sustained commitment from both the organisation and the ward. • Successful practice change depends on multiple key factors, including effective clinical leadership and good facilitation. • Contextual factors at various levels of an organisation need to be considered. • Use of the PIE tool has the potential to enable staff’s attention to focus on person centred care for older people with dementia in acute settings

Classical, quantum and total correlations

We discuss the problem of separating consistently the total correlations in a bipartite quantum state into a quantum and a purely classical part. A measure of classical correlations is proposed and its properties are explored.Comment: 10 pages, 3 figure

Foundations of Quantum Discord

This paper summarizes the basics of the notion of quantum discord and how it relates to other types of correlations in quantum physics. We take the fundamental information theoretic approach and illustrate our exposition with a number of simple examples.Comment: 3 pages, special issue edited by Diogo de Oliveira Soares Pinto et a

The elusive source of quantum effectiveness

We discuss two qualities of quantum systems: various correlations existing between their subsystems and the distingushability of different quantum states. This is then applied to analysing quantum information processing. While quantum correlations, or entanglement, are clearly of paramount importance for efficient pure state manipulations, mixed states present a much richer arena and reveal a more subtle interplay between correlations and distinguishability. The current work explores a number of issues related with identifying the important ingredients needed for quantum information processing. We discuss the Deutsch-Jozsa algorithm, the Shor algorithm, the Grover algorithm and the power of a single qubit class of algorithms. One section is dedicated to cluster states where entanglement is crucial, but its precise role is highly counter-intuitive. Here we see that distinguishability becomes a more useful concept.Comment: 8 pages, no figure

Profiles in Science: John Bennett Fenn

“Don’t ever try to be a scientist or engineer!” Had John Bennett Fenn listened to this advice given by his ninth grade teacher, he might not have gone on to pursue a career in analytical chemistry which would culminate in the attainment of the Nobel Prize in 2002. Gathered from interviews, publication analyses, glowing tributes, and his reminiscences, this paper outlines the academic and professional life of John Fenn from childhood through the end of his career in 2010

Crystal structures of K2[XSi5O12] (X = Fe2+, Co, Zn) and Rb2[XSi5O12] (X = Mn) leucites: comparison of monoclinic P21/c and Iad polymorph structures and inverse relationship between tetrahedral cation (T = Si and X)—O bond distances and intertetrahedral T—O—T angles

The leucite tectosilicate mineral analogues K X Si O (X = Fe , Co, Zn) and Rb X Si O (X = Mn) have been synthesized at elevated temperatures both dry at atmospheric pressure and at controlled water vapour pressure; for X = Co and Zn both dry and hydrothermally synthesized samples are available. Rietveld refinement of X-ray data for hydrothermal K X Si O (X = Fe , Co, Zn) samples shows that they crystallize in the monoclinic space group P2 /c and have tetrahedral cations (Si and X) ordered onto distinct framework sites [cf. hydrothermal K MgSi O ; Bell et al. (1994a), Acta Cryst. B50, 560-566]. Dry-synthesized K X Si O (X = Co, Zn) and Rb X Si O (X = Mn) samples crystallize in the cubic space group Ia{\overline 3}d and with Si and X cations disordered in the tetrahedral framework sites as typified by dry K MgSi O . Both structure types have tetrahedrally coordinated SiO and XO sharing corners to form a partially substituted silicate framework. Extraframework K and Rb cations occupy large channels in the framework. Structural data for the ordered samples show that mean tetrahedral Si-O and X-O bond lengths cover the ranges 1.60 Å (Si-O) to 2.24 Å (Fe -O) and show an inverse relationship with the intertetrahedral angles (T-O-T) which range from 144.7° (Si-O-Si) to 124.6° (Si-O-Fe ). For the compositions with both disordered and ordered tetrahedral cation structures (K MgSi O , K CoSi O , K ZnSi O , Rb MnSi O and Cs CuSi O leucites) the disordered polymorphs always have larger unit-cell volumes, larger intertetrahedral T-O-T angles and smaller mean T-O distances than their isochemical ordered polymorphs. The ordered samples clearly have more flexible frameworks than the disordered structures which allow the former to undergo a greater degree of tetrahedral collapse around the interframework cavity cations. Multivariant linear regression has been used to develop equations to predict intertetrahedral T-O-T angle variation depending on the independent variables Si-O and X-O bond lengths, cavity cation ideal radius, intratetrahedral (O-T-O) angle variance, and X cation electronegativity

YbtT is a low-specificity type II thioesterase that maintains production of the metallophore yersiniabactin in pathogenic enterobacteria

Clinical isolates of Yersinia, Klebsiella, and Escherichia coli frequently secrete the small molecule metallophore yersiniabactin (Ybt), which passivates and scavenges transition metals during human infections. YbtT is encoded within the Ybt biosynthetic operon and is critical for full Ybt production in bacteria. However, its biosynthetic function has been unclear because it is not essential for Ybt production by the in vitro reconstituted nonribosomal peptide synthetase/polyketide synthase (NRPS/PKS) pathway. Here, we report the structural and biochemical characterization of YbtT. YbtT structures at 1.4-1.9 Å resolution possess a serine hydrolase catalytic triad and an associated substrate chamber with features similar to those previously reported for low-specificity type II thioesterases (TEIIs). We found that YbtT interacts with the two major Ybt biosynthetic proteins, HMWP1 (high-molecular-weight protein 1) and HMWP2 (high-molecular-weight protein 2), and hydrolyzes a variety of aromatic and acyl groups from their phosphopantetheinylated carrier protein domains. In vivo YbtT titration in uropathogenic E. coli revealed a distinct optimum for Ybt production consistent with a tradeoff between clearing both stalled inhibitory intermediates and productive Ybt precursors from HMWP1 and HMWP2. These results are consistent with a model in which YbtT maintains cellular Ybt biosynthesis by removing nonproductive, inhibitory thioesters that form aberrantly at multiple sites on HMWP1 and HMWP2