Single atom edge-like states via quantum interference

We demonstrate how quantum interference may lead to the appearance of robust edge-like states of a single ultracold atom in a two-dimensional optical ribbon. We show that these states can be engineered either within the manifold of local ground states of the sites forming the ribbon, or of states carrying one unit of angular momentum. In the former case, we show that the implementation of edge-like states can be extended to other geometries, such as tilted square lattices. In the latter case, we suggest to use the winding number associated to the angular momentum as a synthetic dimension.Comment: 5 pages, 5 figure

Interaction-induced topological properties of two bosons in flat-band systems

In flat-band systems, destructive interference leads to the localization of non-interacting particles and forbids their motion through the lattice. However, in the presence of interactions the overlap between neighbouring single-particle localized eigenstates may enable the propagation of bound pairs of particles. In this work, we show how these interaction-induced hoppings can be tuned to obtain a variety of two-body topological states. In particular, we consider two interacting bosons loaded into the orbital angular momentum $l=1$ states of a diamond-chain lattice, wherein an effective $\pi$ flux may yield a completely flat single-particle energy landscape. In the weakly-interacting limit, we derive effective single-particle models for the two-boson quasiparticles which provide an intuitive picture of how the topological states arise. By means of exact diagonalization calculations, we benchmark these states and we show that they are also present for strong interactions and away from the strict flat-band limit. Furthermore, we identify a set of doubly localized two-boson flat-band states that give rise to a special instance of Aharonov-Bohm cages for arbitrary interactions

The ocean, our climate and the earth's health

The ocean is the major element controlling the long-term stability of the earth´s climate. It involves a complex pattern of interrelations between its physical, geological, chemical and biological components: the greater the complexity and diversity of these links the more robust is the stability of the system, and the healthier the earth. A set of papers that resulted from communications presented at a workshop held in Las Palmas on November 1998 emphasises the need for an interdisciplinary approach to the ocean.No disponibl

Few-body bound topological and flat-band states in a Creutz Ladder

We investigate the properties of few interacting bosons in a Creutz ladder, which has become a standard model for topological systems, and which can be realised in experiments with cold atoms in optical lattices. At the single-particle level, this system may exhibit a completely flat energy landscape with non-trivial topological properties. In this scenario, we identify topological two-body edge states resulting from the bonding of single-particle edge and flat-band states. We also explore the formation of two- and three-body bound states in the strongly-interacting limit, and we show how these quasi-particles can be engineered to replicate the flat-band and topological features of the original single-particle model. Furthermore, we show that in this geometry perfect Aharonov-Bohm caging of two-body bound states may occur for arbitrary interaction strengths, and we provide numerical evidence that the main features of this effect are preserved in an interacting many-body scenario resulting in many-body Aharonov-Bohm caging

Physical and biogeochemical forcing of oxygen and nitrate changes during El Niño/El Viejo and La Niña/La Vieja upper-ocean phases in the tropical eastern South Pacific along 86° W

Temporal changes in the water mass distribution and biogeochemical signals in the tropical eastern South Pacific are investigated with the help of an extended optimum multi-parameter (OMP) analysis, a technique for inverse modeling of mixing and biogeochemical processes through a multidimensional least-square fit. Two ship occupations of a meridional section along 85°50' W from 14° S to 1° N are analysed during relatively warm (El Niño/El Viejo, March 1993) and cold (La Niña/La Vieja, February 2009) upper-ocean phases. The largest El Niño–Southern Oscillation (ENSO) impact was found in the water properties and water mass distribution in the upper 200 m north of 10° S. ENSO promotes the vertical motion of the oxygen minimum zone (OMZ) associated with the hypoxic equatorial subsurface water (ESSW). During a cold phase the core of the ESSW is found at shallower layers, replacing shallow (top 200 m) subtropical surface water (STW). The heave of isopycnals due to ENSO partially explains the intrusion of oxygen-rich and nutrient-poor antarctic intermediate water (AAIW) into the depth range of 150–500 m. The other cause of the AAIW increase at shallower depths is that this water mass flowed along shallower isopycnals in 2009. The shift in the vertical location of AAIW reaching the OMZ induces changes in the amount of oxygen advected and respired inside the OMZ: the larger the oxygen supply, the greater the respiration and the lower the nitrate loss through denitrification. Variations in the intensity of the zonal currents in the equatorial current system, which ventilates the OMZ from the west, are used to explain the patchy latitudinal changes of seawater properties observed along the repeated section. Significant changes reach down to 800 m, suggesting that decadal variability (Pacific decadal oscillation) is also a potential driver in the observed variability

Multipartite entanglement measures via Bell basis measurements

We show how to estimate a broad class of multipartite entanglement measures from Bell basis measurement data. In addition to lowering the experimental requirements relative to previously known methods of estimating these measures, our proposed scheme also enables a simpler analysis of the number of measurement repetitions required to achieve an $\epsilon$-close approximation of the measures, which we provide for each. We focus our analysis on the recently introduced Concentratable Entanglements [Beckey et al. Phys. Rev. Lett. 127, 140501 (2021)] because many other well-known multipartite entanglement measures are recovered as special cases of this family of measures. We extend the definition of the Concentratable Entanglements to mixed states and show how to construct lower bounds on the mixed state Concentratable Entanglements that can also be estimated using only Bell basis measurement data. Finally, we demonstrate the feasibility of our methods by realistically simulating their implementation on a Rydberg atom quantum computer.Comment: 5+19 pages. 4+3 figure

Predicting the Batteries' State of Health in Wireless Sensor Networks Applications

[EN] The lifetime of wireless sensor networks deployments depends strongly on the nodes battery state of health (SoH). It is important to detect promptly those motes whose batteries are affected and degraded by ageing, environmental conditions, failures, etc. There are several parameters that can provide significant information of the battery SoH, such as the number of charge/discharge cycles, the internal resistance, voltage, drained current, temperature, etc. The combination of these parameters can be used to generate analytical models capable of predicting the battery SoH. The generation of these models needs a previous process to collect dense data traces with sampled values of the battery parameters during a large number of discharge cycles under different operating conditions. The collected data allow the development of mathematical models that can predict the battery SoH. These models are required to be simple because they must be executed in motes with low computational capabilities. The paper shows the complete process of acquiring the training data, the models generation and its experimental validation using rechargeable batteries connected to Telosb motes. The obtained results provide significant insight of the battery SoH at different temperatures and charge/discharge cycles.This work was supported in part by the Spanish MINECO under Grant BIA2016-76957-C3-1-R and in part by the I+D+i Program of the Generalitat Valenciana, Spain, under Grant AICO/2016/046.Lajara Vizcaino, JR.; Perez Solano, JJ.; Pelegrí Sebastiá, J. (2018). Predicting the Batteries' State of Health in Wireless Sensor Networks Applications. IEEE Transactions on Industrial Electronics. 65(11):8936-8945. https://doi.org/10.1109/TIE.2018.2808925S89368945651

Water mass pathways to the North Atlantic oxygen minimum zone

23 pages, 14 figures, 1 table, supporting information http://dx.doi.org/10.1002/2014JC010557The water mass pathways to the North Atlantic Oxygen Minimum Zone (naOMZ) are traditionally sketched within the cyclonic tropical circulation via the poleward branching from the eastward flowing jets that lie south of 10°N. However, our water mass analysis of historic hydrographic observations together with numerical Lagrangian experiments consistently reveal that the potential density level of σθ = 26.8 kg m-3 (σ26.8, approximately 300 m depth) separates two distinct regimes of circulation within the Central Water (CW) stratum of the naOMZ. In the upper CW (above σ26.8), and in agreement with previous studies, the supply of water mainly comes from the south with a predominant contribution of South Atlantic CW. In the lower CW (below σ26.8), where minimal oxygen content is found, the tropical pathway is instead drastically weakened in favor of a subtropical pathway. More than two thirds of the total water supply to this lower layer takes place north of 10°N, mainly via an eastward flow at 14°N and northern recirculations from the northern subtropical gyre. The existence of these northern jets explains the greater contribution of North Atlantic CW observed in the lower CW, making up to 50% of the water mass at the naOMZ core. The equatorward transfer of mass from the well-ventilated northern subtropical gyre emerges as an essential part of the ventilation of the naOMZ. © 2015. American Geophysical Union. All Rights ReservedThis research has been funded by the Spanish Ministerio de Economía y Competitividad through projects MOC2 (CTM2008–06438-C02-01) and TIC-MOC (CTM2011–28867). J. Peña- Izquierdo has been supported through a FPI predoctoral grant linked to MOC2. E. van Sebille was supported by the Australian Research Council via grant DE130101336 and P. J. Llanillo was partly funded by CONICYT/FONDECYT de Postdoctorado through project 3150229. The authors acknowledge the NODC and Argo Program for making hydrographic data freely available (http://www.nodc.noaa.gov and http://www.coriolis.eu.org). We also thank the ECCO2/NASA program for providing the numerical assimilative simulation via their web page (http://ecco2.jpl.nasa.gov/products/)Peer Reviewe