Edge local complementation for logical cluster states

A method is presented for the implementation of edge local complementation in graph states, based on the application of two Hadamard operations and a single controlled-phase (CZ) gate. As an application, we demonstrate an efficient scheme to construct a one-dimensional logical cluster state based on the five-qubit quantum error-correcting code, using a sequence of edge local complementations. A single physical CZ operation, together with local operations, is sufficient to create a logical CZ operation between two logical qubits. The same construction can be used to generate any encoded graph state. This approach in concatenation may allow one to create a hierarchical quantum network for quantum information tasks.Comment: 15 pages, two figures, IOP styl

Psychometric qualities of the Educational Identity Processes Scale (EIPS)

In the educational domain, the development of identity becomes especially salient during school transition phases. To assess the specific identity processes that match the adolescents' experiences before and after the school transition, the Educational Identity Processes Scale (EIPS) was developed. The present study aimed to test the psychometric qualities of the EIPS by examining its factor structure, the internal and convergent validity of the identity dimensions, and whether the questionnaire was measurement invariant over time. The pre-transition version was tested in a Dutch sample (N = 242 early adolescents) and the post-transition version was tested in a Lithuanian sample (N = 1,268 mid-adolescents). Findings indicated good psychometric qualities for both the pre- and post-transition versions of the EIPS. Additionally, context dependencies were observed, as distance to the transition influenced the meaning of specific identity processes and determined whether specific processes could be considered as part of normative development

Maximally entangled mixed states of two qubits

We consider mixed states of two qubits and show under which global unitary operations their entanglement is maximized. This leads to a class of states that is a generalization of the Bell states. Three measures of entanglement are considered: entanglement of formation, negativity and relative entropy of entanglement. Surprisingly all states that maximize one measure also maximize the others. We will give a complete characterization of these generalized Bell states and prove that these states for fixed eigenvalues are all equivalent under local unitary transformations. We will furthermore characterize all nearly entangled states closest to the maximally mixed state and derive a new lower bound on the volume of separable mixed states

Conductance Quantization at zero magnetic field in InSb nanowires

Ballistic electron transport is a key requirement for existence of a topological phase transition in proximitized InSb nanowires. However, measurements of quantized conductance as direct evidence of ballistic transport have so far been obscured due to the increased chance of backscattering in one dimensional nanowires. We show that by improving the nanowire-metal interface as well as the dielectric environment we can consistently achieve conductance quantization at zero magnetic field. Additionally, studying the sub-band evolution in a rotating magnetic field reveals an orbital degeneracy between the second and third sub-bands for perpendicular fields above 1T

Amazon deforestation alters small stream structure, nitrogen biogeochemistry and connectivity to larger rivers

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 105 (2011): 53-74, doi:10.1007/s10533-010-9540-4.Human activities that modify land cover can alter the structure and biogeochemistry of small streams but these effects are poorly known over large regions of the humid tropics where rates of forest clearing are high. We examined how conversion of Amazon lowland tropical forest to cattle pasture influenced the physical and chemical structure, organic matter stocks and N cycling of small streams. We combined a regional ground survey of small streams with an intensive study of nutrient cycling using 15N additions in three representative streams: a second-order forest stream, a second-order pasture stream and a third-order pasture stream that were within several km of each other and on similar soils and landscape positions. Replacement of forest with pasture decreased stream habitat complexity by changing streams from run and pool channels with forest leaf detritus (50% cover) to grass-filled (63% cover) channel with runs of slow-moving water. In the survey, pasture streams consistently had lower concentrations of dissolved oxygen and nitrate (NO3-) compared with similar-sized forest streams. Stable isotope additions revealed that second-order pasture stream had a shorter NH4+ uptake length, higher uptake rates into organic matter components and a shorter 15NH4+ residence time than the second-order forest stream or the third-order pasture stream. Nitrification was significant in the forest stream (19% of the added 15NH4+) but not in the second-order pasture (0%) or third-order (6%) pasture stream. The forest stream retained 7% of added 15N in organic matter compartments and exported 53% (15NH4+ =34%; 15NO3- = 19%). In contrast, the second-order pasture stream retained 75% of added 15N, predominantly in grasses (69%) and exported only 4% as 15NH4+. The fate of tracer 15N in the third-order pasture stream more closely resembled that in the forest stream, with 5% of added N retained and 26% exported (15NH4+ = 9%; 15NO3- = 6%). These findings indicate that the widespread infilling by grass in small streams in areas deforested for pasture greatly increases the retention of inorganic N in the first- and second-order streams, which make up roughly three-fourths of total stream channel length in Amazon basin watersheds. The importance of this phenomenon and its effect on N transport to larger rivers across the larger areas of the Amazon Basin will depend on better evaluation of both the extent and the scale at which stream infilling by grass occurs, but our analysis suggests the phenomenon is widespread.This work was supported by grants from the NASA Large-Scale Biosphere and Atmosphere Experiment (NCC5-686), the National Science Foundation (DEB-0315656) and the Fundação de Ámparo à Pesquisa do Estado de São Paulo

The crater lake of Ilamatepec (Santa Ana) volcano, El Salvador: insights into lake gas composition and implications for monitoring

We here present the first chemical characterization of the volcanic gas plume issuing from the Santa Ana crater lake, a hyper-acidic crater lake (pH of − 0.2 to 2.5) in north-western El Salvador. Our results, obtained during regular surveys in 2017 and 2018 using a Multi-GAS instrument, demonstrate a hydrous gas composition (H2O/SO2 ratios from 32 to 205) and SO2 as the main sulfur species (H2S/SO2 = 0.03–0.1). We also find that gas composition evolved during our investigated period, with the CO2/SO2 ratio decreasing by one order of magnitude from March 2017 (37.2 ± 9.7) to November 2018 (< 3). This compositional evolution toward more magmatic (SO2-rich) compositions is interpreted in the context of the long-term evolution of the volcano following its 2005 and 2007 eruptions. We find that, in spite of reduced (background-level) seismicity, the magmatic gas supply into the lake was one order of magnitude higher in March 2017 (total volatile flux: 20,200–30,200 t/day) than in the following periods (total volatile flux: 900–10,167 t/day). We propose that the elevated magmatic/hydrothermal transport in March 2017, combined with a 15% reduction in precipitation, caused the volume of the lake to decrease, ultimately reducing its sulfur absorbing and scrubbing capacity, and hence causing the gas plume CO2/SO2 ratio to decrease. The recently observed increases in temperature, acidity, and salinity of the lake are consistent with this hypothesis. We conclude that the installation of a continuous, fully-automated Multi-GAS is highly desirable to monitor any future change in lake plume chemistry, and hence the level of degassing activity