Integrated silicon qubit platform with single-spin addressability, exchange control and robust single-shot singlet-triplet readout

Silicon quantum dot spin qubits provide a promising platform for large-scale quantum computation because of their compatibility with conventional CMOS manufacturing and the long coherence times accessible using $^{28}$Si enriched material. A scalable error-corrected quantum processor, however, will require control of many qubits in parallel, while performing error detection across the constituent qubits. Spin resonance techniques are a convenient path to parallel two-axis control, while Pauli spin blockade can be used to realize local parity measurements for error detection. Despite this, silicon qubit implementations have so far focused on either single-spin resonance control, or control and measurement via voltage-pulse detuning in the two-spin singlet-triplet basis, but not both simultaneously. Here, we demonstrate an integrated device platform incorporating a silicon metal-oxide-semiconductor double quantum dot that is capable of single-spin addressing and control via electron spin resonance, combined with high-fidelity spin readout in the singlet-triplet basis.Comment: 10 pages, 4 figure

Megafauna communities from abyssal sites along the Gloria Fracture Zone (NE Atlantic)

Fracture zones are areas of poorly known abyssal landscapes and benthic faunal communities. During the R/V Meteor M162 cruise several imagery surveys were performed using a TV-CTD guided camera system along four main areas of the Gloria fault system, between the Terceira ridge and the Madeira Tore Rise. Based on these records, we were able to characterize - for the first time - the megafaunal composition, their abundance and diversity along the sub-basin of the Gloria fault at depths between 3500 and 4500m. Quantitative annotations of the observed fauna, as well as evidence of animal traces on the seafloor were explored in relation to topography, substrate type, and geochemical data acquired during surveys. Preliminary observations revealed a total of 121 morphospecies, of which Holothuroidea is the most diverse group, with 12 morphospecies. Deepest transects carried out along the main trace of Gloria Fault system showed the highest similarity among dives, predominantly characterised by soft sediment areas with Elpidiidae holothurians frequently observed. In contrast, the survey carried out at the Terceira ridge showed more diverse communities, which is likely due to a larger variability in substrate and topography. Specifically, soft-sediment sections showed a higher proportion of holothurians, ophiuroids and acorn worms, while unique Anthozoan and Porifera morphospecies were observed in areas with presence of hard substrates. The findings of this study provide unique knowledge of abyssal fauna associated with the Gloria Fault System, including areas inside of national jurisdiction and of relevance for management and conservation actions

Occurrence of marine litter along abyssal areas of the Gloria Fracture Zone (NE Atlantic).

Marine litter pollution is a recognized form of anthropogenic disturbance that affects widely the marine environment, particularly near the continental margins, although also present at abyssal and bathyal depths. This study reports the occurrence of marine litter distribution and abundance in four abyssal basins along the Gloria fracture zone in the NE Atlantic. Litter items occurrences were analysed using TV-CTD video surveys carried out during the multidisciplinary activities of the R/V Meteor M162 cruise. The surveys reached depths between 3500-4500m and covered 16 km of seafloor, between the Terceira ridge and the Madeira-Tore Rise. Litter items were annotated and categorized by type (i.e., plastic, fishing gear, metal, glass, other unknown items). Results revealed that litter was exclusively found on soft sediment habitats across all areas, i.e. depositional areas, with the overwhelming dominance of plastics items (71%), such as plastic containers, cups and bag fragments. Although less common (6-8%), metal, glass and lost fishing gear were also observed. Litter density was on average 9 times higher in the easternmost area near the Madeira-Tore ridge, when compared to the other areas. Higher litter densities are likely explained due to the proximity to the Madeira-Tore seamount complex targeted by the fishing industry and nearimportant corridors of marine traffic between various Atlantic and Mediterranean locations

Greenhouse gas observations from Cabauw Tall Tower (1992–2010)

Since 1992 semi-continuous in-situ observations of greenhouse gas concentrations have been performed at the tall tower of Cabauw (4.927° E, 51.971° N, −0.7 m a.s.l.). Through 1992 up to now, the measurement system has been gradually extended and improved in precision, starting with CO<sub>2</sub> and CH<sub>4</sub> concentrations from 200 m a.g.l. in 1992 to vertical gradients at 4 levels of the gases CO<sub>2</sub>, CH<sub>4</sub>, SF<sub>6</sub>, N<sub>2</sub>O, H<sub>2</sub>, CO and gradients at 2 levels for <sup>222</sup>Rn. In this paper the measurement systems and measurement results are described for the main greenhouse gases and CO, for the whole period. The automatic measurement system now provides half-hourly concentration gradients with a precision better than or close to the WMO recommendations. <br><br> The observations at Cabauw show a complex pattern caused by the influence of sources and sinks from a large area around the tower with significant contributions of sources and sinks at distances up to 500–700 km. The concentration footprint area of Cabauw is one the most intensive and complex source areas of greenhouse gases in the world. Despite this, annual mean trends for the most important greenhouse gases, compatible with the values derived using the global network, can be reproduced from the measured concentrations at Cabauw over the entire measurement period, with a measured increase in the period 2000–2009 for CO<sub>2</sub> of 1.90 ± 0.1 ppm yr<sup>−1</sup>, for CH<sub>4</sub> of 4.4 ± 0.6 ppb yr<sup>−1</sup>, for N<sub>2</sub>O of 0.86 ± 0.04 ppb yr<sup>−1</sup>, and for SF<sub>6</sub> of 0.27 ± 0.01 ppt yr<sup>−1</sup>; for CO no significant trend could be detected. <br><br> The influences of strong local sources and sinks are reflected in the amplitude of the mean seasonal cycles observed at Cabauw, that are larger than the mean Northern Hemisphere average; Cabauw mean seasonal amplitude for CO<sub>2</sub> is 25–30 ppm (higher value for lower sampling levels). The observed CH<sub>4</sub> seasonal amplitude is 50–110 ppb. All gases except N<sub>2</sub>O show highest concentrations in winter and lower concentrations in summer, N<sub>2</sub>O observations show two additional concentration maxima in early summer and in autumn. <br><br> Seasonal cycles of the day-time mean concentrations show that surface concentrations or high elevation concentrations alone do not give a representative value for the boundary layer concentrations, especially in winter time, but that the vertical profile data along the mast can be used to construct a useful boundary layer mean value. The variability at Cabauw in the atmospheric concentrations of CO<sub>2</sub> on time scales of minutes to hours is several ppm and is much larger than the precision of the measurements (0.1 ppm). The diurnal and synoptical variability of the concentrations at Cabauw carry information on the sources and sinks in the footprint area of the mast, that will be useful in combination with inverse atmospheric transport model to verify emission estimates and improve ecosystem models. For this purpose a network of tall tower stations like Cabauw forms a very useful addition to the existing global observing network for greenhouse gases

COMET: a Lagrangian transport model for greenhouse gas emission estimation ? forward model technique and performance for methane

International audienceThe Lagrangian transport model COMET has been developed to evaluate emission estimates based on atmospheric concentration observations. This paper describes the model and its application in modelling the methane concentrations at the European stations Cabauw and Macehead. The COMET model captures in most cases both synoptic and diurnal variations of the concentrations as a function of time and in absolute size quite well. The explained variability by COMET of the mixed layer concentration for Cabauw varies from 50% to 84%; for all hourly observations in 2002 the explained variability is 71% with a RMSE of 112 ppb. The explained variability for Macehead is 48%. The most important model parameters were tested for their influence on model performance, but in general the model is not very sensitive to variations within acceptable limits. For a regionally and locally polluted continental site the COMET model shows only a small bias and a moderate random error, and therefore is considered to capture the influence of the sources on the concentration variations quite well. It is therefore concluded that inverse methods and more specifically the COMET model is suitable to be applied in deriving independent estimates of greenhouse gas emissions using Source-Receptor relationships