We implemented, optimized and fully tested over multiple runs a superconducting Josephson junction fabrication process tailored for the integrated digital circuits that are used for control and readout of superconducting qubits operating at millikelvin temperatures. This process was optimized for highly energy efficient single flux quantum (ERSFQ) circuits with the critical currents reduced by factor of ~10 as compared to those operated at 4.2 K. Specifically, it implemented Josephson junctions with 10 uA unit critical current fabricated with a 10 uA/um2 critical current density. In order to circumvent the substantial size increase of the SFQ circuit inductors, we employed a NbN high kinetic inductance layer (HKIL) with a 8.5 pH/sq sheet inductance. Similarly, to maintain the small size of junction resistive shunts, we used a non-superconducting PdAu alloy with a 4.0 ohm/sq sheet resistance. For integration with quantum circuits in a multi-chip module, 5 and 10 um height bump processes were also optimized. To keep the fabrication process in check, we developed and thoroughly tested a comprehensive Process Control Monitor chip set.

The Sustainable Development Goals (SDGs) adopetd by the United Nations in 2016 include the SDG 15.3 „Land Degradation Neutrality (LDN)“, which aims to reduce land degradation by national efforts of the member states. Three indicators for land degradation were gloablly identified: landcover, land productivity and soil organic carbon stocks (SOC). In particular, the assessment of SOC is challenging in countries where (a) spatial digital data is largely missing and (b) SOC mapping is difficult due to remotness typical for high mountain regions . Global data provided by the Secretariat of the United Nations Convention to Combat Desertification (UNCCD) may be used for reporting, but experience from various countries indicates inaccuracies due to generalisation. This is especially the case for SOC. Moreover, to report on changes in SOC stocks, a comprehensive baseline is mandatory. In order to approach these challenges, Kirgistan, which has signed the SDG’s but still lacks a baseline for SOC, has been chosen for a case study.In a multinational project we developed a scientifically based method to map and assess SOC stocks enabling a nationwide upscaling of SOC data (baseline). Using globally available data on landcover, elevation, climate and national soil data, „representative SOC units“ were identified prior to sampling. We assume that mainly these factors determine the spatial variability of SOC and that similar SOC stocks can be expected at comparable site conditions. More than 90% of the surface area, that potentially store SOC, is coverd by only 20 representative units, which were sampled 3-fold in the field. Sampling location within a single unit was determined using a drone to identify a representative location. Using the drone was especially helpful as sampling sites in a high mountain region were often extremely remote. During sampling small-scale variability of SOC was considered in the field. To determine SOC stocks, bulk density of the fine soil, coarse fragments and amount of roots were measured in the laboratory. Furthermore, pH, clay, silt and sand content were analysed to identify further drivers for SOC distribution.Results show that spatial distribution of SOC in such a high mountain region is mainly controlled by landcover (cropland, grassland, forest), elevation, bulk density and clay content. Within single landcover classes topographic indices, such as aspect, further determine SOC distribution. This is especially the case for grassland, which is the dominant landcover in Kirgistan (53%). For the assessment of SOC stocks different approaches were compared. For instance, precise assessment of stocks using the bulk density of the fine soil corrected for coarse fragments leads to significantly lower SOC stocks when compared to the global data provided by the UNCCD.

ABSTRACT The application of electrical resistivity tomography to peatlands supports conventional coring by providing data on the current condition of peatlands, including data on stratigraphy, peat properties and thickness of organic deposits. Data on the current condition of drained peatlands are particularly required to improve estimates of carbon storage as well as losses and emissions from agriculturally used peatlands. However, most of the studies focusing on electrical resistivity tomography surveys have been conducted on natural peatlands with higher groundwater levels. Peatlands drained for agriculture have not often been studied using geophysical techniques. Drained sites are characterized by low groundwater levels and high groundwater fluctuations during the year, which lead to varying levels of water saturation. To validate better electrical resistivity tomography surveys of drained peatlands, the aim of this laboratory study is to investigate the influence of varying water saturation levels on electrical conductivity (reciprocal of resistivity) for a variety of peat and gyttja types, as well as for different degrees of peat decomposition. Results show that different levels of water saturation strongly influence bulk electrical conductivity. Distinct differences in this relationship exist between peat and gyttja substrates and between different degrees of peat decomposition. Peat shows an exponential relationship for all degrees of decomposition, whereas gyttja, in particular organic‐rich gyttja, is characterized by a rather unimodal relationship. The slopes for the relationship between electrical conductivity and water content are steeper at high degrees of decomposition than for peat of low degrees of decomposition. These results have direct implications for field electrical resistivity tomography surveys. In drained peatlands that are strongly susceptible to drying, electrical resistivity tomography surveys have a high potential to monitor the actual field water content. In addition, at comparable water saturations, high or low degrees of decomposition can be inferred from electrical conductivity.

An approach for scalable quantum computing infrastructure based on the use of low-power digital superconducting single flux quantum (SFQ) circuits is described. Rather than replicating the room-temperature microwave control and measurement infrastructure solutions dominating the current systems, we use the inherent to superconducting technology methods - the use of SFQ pulses directly at the base temperature. For qubit control, we irradiate qubits with the coherent SFQ pulse sequences computed using optical control theory. For qubit measurement, Josephson photon counter performs projective quantum measurement, the result of which is converted to digital SFQ output. These operations are aided by a high-speed digital SFQ coprocessor located at higher temperature stage (e.g., 3 K) to process the measurement results and load new control sequences to 20 mK SFQ quantum-classical interface circuits.

We present test results for parallel data communication ERSFQ circuits with clock recovery. We experimentally study on-chip and chip-to-chip parallel data communication circuits with 4-, 8- and 16-bit word lengths. The largest circuit is a 16-bit chip-to-chip communication test circuit embedded into a testbed with clock distributed over a combination of active and passive transmission lines with transmitter/receiver pairs, and is comprised of 3464 Josephson junctions in total. All ERSFQ circuits are fabricated using MITLL 10-kA/cm 2 SFQ5ee process. For the chip-to-chip communication experiment, a multi-chip module (MCM) is assembled using Hypres' MCM flip-chip bonding process which connected the MIT-LL-made flip-chip to the Hypres-made MCM carrier using 220 signal bumps with 50 um pitch. We experimentally confirmed correct functionality of 4-, 8- and 16-bit circuits and measured their current bias margins. For the 16- bit chip-to-chip communication circuit mounted to a MCM, we measured ±12% dc bias margins similar to the margins measured for the on-chip version of the same circuit. The MCM circuit is also evaluated at high clock speed generated by an external source, while the data words are changed at low speed. The correct functionality is observed without significant reduction in the bias margins using average-voltage test approach.

Inland salt meadows are particularly valuable ecosystems, because they support a variety of salt-adapted species (halophytes). They can be found throughout Europe; including the peatlands of the glacial lowlands in northeast Germany. These German ecosystems have been seriously damaged through drainage. To assess and ultimately limit the damages, temporal monitoring of soil salinity is essential, which can be conducted by geoelectrical techniques that measure the soil electrical conductivity. However, there is limited knowledge on how to interpret electrical conductivity surveys of peaty salt meadows. In this study, temporal and spatial monitoring of dissolved salts was conducted in saline peatland soils using different geoelectrical techniques at different scales (1D: conductivity probe, 2D: conductivity cross-sections). Cores and soil samples were taken to validate the geoelectrical surveys. Although the influence of peat on bulk conductivity is large, the seasonal dynamics of dissolved salts within the soil profile could be monitored by repeated geoelectrical measurements. A close correlation is observed between conductivity (~salinity) at different depths and temperature, precipitation and corresponding groundwater level. The conductivity distribution between top- and subsoil during the growing season reflected the leaching of dissolved salts by precipitation and the capillary rise of dissolved salts by increasing temperature (~evaporation). Groundwater levels below 0.38cm resulted in very low conductivities in the topsoil, which is presumably due to limited soil moisture and thus precipitation of salts. Therefore, to prevent the disappearance of dissolved salts from the rooting zone, which are essential for the halophytes, groundwater levels should be adjusted to maintain depths of between 20 and 35cm. Lower groundwater levels will lead to the loss of dissolved salts from the rooting zone and higher levels to increasing dilution with fresh rainwater. The easy-to-handle conductivity probe is an appropriate tool for salinity monitoring. Using this probe with regressions adjusted for sandy and organic substrates (peat and organic gyttja) additional influences on bulk conductivity (e.g. cation exchange capacity, water content) can be compensated for and the correlation between salinity and electrical conductivity is high.

Fur die Erstellung von flachenhaften thematischen Auswertungskarten fur organische und mineralische Boden sind Informationen zu dem Ausgangssubstrat an ausgewahlten Punkten, sowie die dort auftretenden Pedogenesen wesentlich. Basis sind dabei die bodenchemischen und bodenphysikalischen Analysedaten zu den Horizonten. Die Schnittstelle bilden hierbei die Horizont-Substrat-Kombinationen (HSK) fur die Flachenbodenformen. Diese Klassifizierung geht mit der Auspragung von ganz spezifischen Bodeneigenschaften einher. Die Erhebung von Analysedaten ist zeit- und kostenaufwendig. Um diese Aufwendungen zu optimieren ist das Ziel dieser Untersuchung, mit Hilfe einer Hauptkomponentenanalyse (Principal Component Analysis – PCA) zu prufen, inwieweit dieser methodische Ansatz statistisch begrundbar ist. Dabei warenim Besonderen folgende Fragestellungen zu beachten: (i) welche physikalischen und/oder chemischen Variablen fur die HSK merkmalsbestimmend sind, (ii) welche Variablen weniger relevant sind fur die Einteilung und Abgrenzung der HSK und damit ggf. prioritar nicht analysiert werden mussen und (iii) welche alternativen Merkmalsgruppierungen sich ggf. ergeben wurde. Da sich die Eigenschaften von organischen und mineralischen Boden fundamental voneinander unterscheiden wurden sie jeweils gesondert analysiert. Fur die organischen Horizonte wurde in Erganzung zu den HSK-Gruppierungen der Zersetzungsgrad der organischen Substrate berucksichtigt, da aufgrund bisheriger eigener als auch internationaler Forschungen auf Moorboden zu erwarten war, dass dieser im Gelande bestimmbarer Parameter einen zusatzlichen merkmalsbestimmenden Einfluss haben wird. Der Vortrag beinhaltet die Auswertungsergebnisse und gibt Empfehlungen fur kunftige Kartier- und Untersuchungsziele vergleichbarer Boden.

The determination of the total carbon storage of peatlands is of high relevance in the context of climate-change mitigation efforts. This determination relies on data about stratigraphy and peat properties, which are conventionally collected by coring. Ground-penetrating radar (GPR) and electrical resistivity imaging (ERI) can support these point data by providing subsoil information in two-dimensional cross-sections. In this study, GPR and ERI were conducted at two groundwater-fed fen sites located in the temperate zone in north-east Germany. The fens of this region are embedded in low conductive glacial sand and are characterised by thick layers of gyttja, which can be either mineral or organic. The two study sites are representative of this region with respect to stratigraphy (total thickness, peat and gyttja types) and ecological conditions (pH-value, trophic condition). The aim of this study is to assess the suitability of GPR and ERI to detect stratigraphy and peat properties under these characteristic site conditions.Results show that GPR clearly detects the interfaces between (i) Carex and brown-moss peat, (ii) brown-moss peat and organic gyttja, (iii) organic- and mineral gyttja, and (iv) mineral gyttja and the parent material (glacial sand). These layers differ in bulk density and the related organic matter content. ERI, however, does not delineate these layers; rather it delineates regions of varying properties. At our base-rich site, pore fluid conductivity and cation.exchange capacity are the main factors that determine peat electrical conductivity (reverse of resistivity), whereas organic matter and water content are most influential at the more acidic site. Thus the correlation between peat properties and electrical conductivity are driven by site-specific conditions, which are mainly determined by the solute load in the groundwater at fens. When the total organic deposits exceed a thickness of 5 m, the depth of investigation by GPR is limited due to increasing attenuation. This is not a limiting factor for ERI, where the transition from organic deposits to glacial sand is visible at both sites. Due to these specific sensitivities, a combined application of GPR and ERI meets the demand for up-to-date information on carbon storage of peatlands, which is, moreover, very site-specific because of the inherent variety of ecological conditions and stratigraphy between peatlands in general and between fens and bogs in particular. (C) 2016 Elsevier B.V. All rights reserved.

SummaryPeatlands store large amounts of carbon. This storage function has been reduced through intensive drainage, which leads to the decomposition of peat, resulting in a loss of carbon. Measurements of the real (σ′) and imaginary part (σ″) of electrical conductivity can deliver information on peat properties, such as the pore fluid conductivity (σw), cation exchange capacity (CEC), bulk density (ρb), water content (WC) and soil organic matter (SOM) content. These properties change with the peat's degree of decomposition (DD). To explore the relationships between the peat properties, σ′, σ″ and DD, we focused on three different types of survey and scales. First, point measurements were made with a conductivity probe at various locations over a large area of northeast Germany to determine the degree of correlation between σ′ and DD. Second, nine of these locations were selected for sampling to determine which of the properties σw, CEC, ρb, WC and SOM predominantly influence σ′ and σ″. This multisite dataset includes the entire range of DD and was analysed in the laboratory. Third, one site was selected for a survey of σ′ including sampling, to identify which properties mainly control σ′ in a single‐site approach. Statistical analysis revealed that for the multisite laboratory dataset, σw has the strongest effect on σ′, followed by CEC, whereas σ″ is mainly determined by CEC. In a single‐site approach, WC followed by CEC had a dominant effect on σ′. No clear correlation could be observed between (i) DD and peat properties and (ii) DD and σ′ or σ″. This is because of the complex changes in properties with increasing DD.

Data of soil organic matter (SOM) content can be used for the assessment of stocks and changes of soil organic carbon (SOC) in peatland soils. Therefore, it is essentially necessary to convert SOM contents into SOC contents by SOM/SOC ratios (“conversion factors”). Various substrates of peatland soils in Northeastern Germany (n = 311) were analyzed in SOM/SOC ratios. Sphagnum peats showed significantly higher SOM/SOC ratios (2.05 ± 0.09) than peats of vascular plants (1.73 ± 0.09) and amorphous peats (1.93 ± 0.29). Amorphous peats and humic sands (2.41 ± 0.46) showed a high variability. The classification using WRB qualifiers featured significant differences (***P < 0.001) between humic, sapric, hemic and fibric substrates, except hemic and fibric peats of vascular plants. Moreover, impacts of drainage on pedogenesis could be proved in different SOM/SOC ratios of drained topsoils and water-saturated subsoils. Due to the high dependency of SOM/SOC ratios on the botanical origin, the implementation of peat type-related conversion factors is most suitable. In contrast, the application of one single conversion factor causes considerable conversion errors. As a consequence, many SOC assessment studies referring to peats should be reviewed.