Restricted Connectivity Research Articles

Improved rate-distance trade-offs for quantum codes with restricted connectivity

Abstract For quantum error-correcting codes to be realizable, it is important that the qubits subject to the code constraints exhibit some form of limited connectivity. The works of Bravyi and Terhal (2009 New J. Phys. 11 043029) (BT) and Bravyi et al (2010 Phys. Rev. Lett. 104 050503) (BPT) established that geometric locality constrains code properties—for instance [ [ n , k , d ] ] quantum codes defined by local checks on the D-dimensional lattice must obey k d 2 / ( D − 1 ) ⩽ O ( n ) . Baspin and Krishna (2022 Quantum 6 711) studied the more general question of how the connectivity graph associated with a quantum code constrains the code parameters. These trade-offs apply to a richer class of codes compared to the BPT and BT bounds, which only capture geometrically-local codes. We extend and improve this work, establishing a tighter dimension-distance trade-off as a function of the size of separators in the connectivity graph. We also obtain a distance bound that covers all stabilizer codes with a particular separation profile, rather than only LDPC codes.

Linear circuit synthesis using weighted Steiner trees

CNOT circuits are a common building block of general quantum circuits. The problem of synthesizing and optimizing such circuits has received a lot of attention in the quantum computing literature. This problem is especially challenging for quantum devices with restricted connectivity, where two-qubit gates can only be placed between adjacent qubits. The state-of-the-art algorithms for optimizing the number of CNOT gates are heuristic algorithms that are based on Gaussian elimination and that use Steiner trees to connect between different subsets of qubits. In this article, we suggest considering \emph{weighted} Steiner trees, and we present a simple low-cost heuristic to compute weights. The simulated evaluation shows that the suggested heuristic is almost always beneficial and reduces the number of CNOT gates by up to 10%.

Hydrologic Versus Biogeochemical Control of Nutrient Dynamics in a Shallow Hypersaline Coastal Lagoon: Insight From a Coupled Hydrodynamic‐Water Quality Model

AbstractShallow coastal lagoons with restricted connection to the ocean are often productive but can also be sensitive to nutrient enrichment and hydrologic changes. Resolving nutrient dynamics is important for their sustainable management, yet being able to accurately resolve nutrient budgets has remained a challenge due to their complex hydrological regimes and habitat heterogeneity. In this study, we undertake a systematic nutrient budget of a large shallow hypersaline lagoon (Coorong, South Australia), with assistance of a high‐resolution coupled hydrodynamic‐biogeochemical model, to demonstrate the conditions that lead to nutrient retention. Under current conditions, high rates of evapo‐concentration and limited water connectivity have led to a persistent accumulation of nutrients and poor water quality in substantial areas of the lagoon. The interplay between hydrological drivers and biogeochemical processes was quantified using an adjusted Damköhler number, comparing the timescales of nutrient flushing versus processing. This showed a general transition from hydrologic control to biogeochemical control with increasing distance from the main ocean connection, modified by episodes of increased flows and external loads. Whilst water age was a useful indicator of the factors controlling rates of nutrient retention, interannual variability in retention between areas of the lagoon was explained based on river flows and changes in mean sea level. As the system has been affected by reduced flows over past decades, the results provide evidence that increasing river flow to the lagoon would reduce the nutrient retention, and we discuss the potential for net nutrient export to the ocean under sustained high flows.

Super (Edge-)connectivity of the Folded Petersen Network

Reliability evaluation of an interconnection network is of great significance for construction and maintenance of the network. The super (edge-)connectivity, restricted (edge-)connectivity and cyclic (edge-)connectivity are important parameters to evaluate network reliability. Compared with the hypercube [Formula: see text], the folded Petersen network [Formula: see text] has better properties, including strong connectivity, symmetry. Besides, it has smaller diameter and more vertices than [Formula: see text] with the same degree and connectivity. In this paper, based on the symmetric properties of [Formula: see text], we prove that [Formula: see text] is super (edge-)connected, super restricted edge-connected and super cyclically edge-connected. In addition, we obtain the restricted edge-connectivity and the cyclic edge-connectivity of [Formula: see text].

Maximizing UAV fog deployment efficiency for critical rescue operations: A multi-objective optimization approach

In disaster scenarios and high-stakes rescue operations, integrating Unmanned Aerial Vehicles (UAVs) as fog nodes has become crucial. This integration ensures a smooth connection between affected populations and essential health monitoring devices, supporting the Internet of Things (IoT). Integrating UAVs in such environments is inherently challenging, where the primary objectives involve maximizing network connectivity and coverage while extending the networks lifetime through energy-efficient strategies to serve the maximum number of affected individuals. In this paper, we decomposed our problem into two subproblems. Connectivity, coverage subproblem and network lifespan optimization subproblem. For the Connectivity and coverage subproblem, the optimal connectivity and coverage are optimized by strategically deploying UAV fog nodes in a manner that maximizes network coverage, thoughtfully considering the distinctive constraints that emerge in these high-pressure situations where lives are at stake. We shape our UAV fog deployment problem as a multi-objective optimization and introduce a specialized UAV fog deployment algorithm tailored specifically for UAV fog nodes deployed in rescue missions. For the network lifespan subproblem, after determining the optimal connectivity and coverage of UAV nodes and users within the entire network, the network lifespan optimization subproblem is greatly simplified and efficiently solved via a one-dimensional swapping method. After conducting thorough experiments using our proposed architecture across diverse scenarios, our method consistently surpasses existing approaches. It effectively tackles issues like restricted connectivity and potential node failures. This advancement in deployment efficiency notably enhances rescue operations, enabling us to aid the maximum number of affected individuals swiftly during critical and time-pressing situations.

Between conformity and individuality: Psychologists in Czechoslovakia during normalization (1968-1989).

The study examines the development of psychology in former Czechoslovakia during the period of "normalization" (1968-1989) and the challenges it faced under the communist regime. The restricted connection to Western psychology and the regime's control over all aspects of human activity negatively influenced the continuity of development in psychology. The regime demanded conformity, leaving individuals, including psychologists, in recurring states of internal conflict and intellectual discomfort when deciding how much to compromise in their personal and professional lives. The study identifies three groups of psychologists based on their adaptability to regime demands. The first group consists of those who aligned themselves with the regime, allowing them to hold positions of leadership and shape the conceptualization of the field. The second group comprises individuals who actively opposed the regime, facing significant limitations in their educational and career opportunities, and mostly being forced to leave the profession. The third group of psychologists belongs to the apolitical gray zone. A significant portion of individuals in this largest group passively complied with established norms and constraints, accepting the restrictions imposed on the development of Czechoslovak psychology. Fortunately, thanks to the persistent efforts of the proactive members of the gray zone and their willingness to endure significant discomfort, an even deeper decline of psychology during the normalization period was prevented. The study provides insights into the topics of education, research, Western influences, and adaptation to the communist regime within Czechoslovak psychology, illuminating the intricacies of living in that historical period. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Thing Artifact-based Design of IoT Ecosystems

This paper sheds light on the complexity of designing Internet of Things (IoT) ecosystems where a high number of things reside and thus must collaborate despite their reduced size, restricted connectivity, and constrained storage limitations. To address this complexity, a novel concept referred to as thing artifact is devised abstracting the roles that things play in an IoT ecosystem. The abstraction focuses on 3 crosscutting aspects, namely functionality in terms of what to perform, life cycle in terms of how to behave, and interaction flow in terms of with whom to exchange. Building upon the concept of data artifact commonly used in data-driven business applications design, thing artifacts engage in relations with peers to coordinate their individual behaviors and hence avoid conflicts that could result from the quality of exchanged data. Putting functionality, life cycle, interaction flow, and relation together contributes to abstracting IoT ecosystems design. A system implementing a thing artifact-based IoT ecosystem along with some experiments is presented in the paper as well.

The regular edge connectivity of regular networks

Classical connectivity is a vital metric to assess the reliability of interconnection networks, while it has defects in the defective assumption that all neighbours of one node may fail concurrently. To overcome this deficiency, many new generalizations of traditional connectivity, such as g-component (edge) connectivity, restricted (edge) connectivity, g-extra (edge) connectivity and so on, have been suggested. For any positive integer a, the a-regular edge connectivity of a connected graph G is the minimum cardinality of an edge cut, whose deletion disconnects G so that each component is a a-regular graph. In this work, we investigate the a-regular edge connectivity of some regular networks, which provides a novel idea for further exploring the reliability of networks. Finally, simulations are carried out to compare the a-regular connectivity with other types of connectivity in some regular networks. The comparison results imply that the a-regular edge connectivity has its superiority.

Earliest styliolinids from the Wenlock of Saaremaa Island (Estonia): paleoecological and evolutionary implications

The new tentaculitoid Styliolina giga n. sp. is described from the Wenlock of Saaremaa Island, Estonia. It is the earliest definite styliolinid as other known species are all reported from the Devonian. The peculiarities of the accompanying fauna indicate that Styliolina giga n. sp. could have inhabited a marginal marine environment, which had restricted connections to the ocean. The occurrence of Styliolina in the Homerian could indicate that styliolinids were first to evolve from benthic tentaculitoids and were ancestors of nowakiids, but the annulated shells of nowakaiids resemble more closely those of ancestral Choniconarida. Presumably still nowakiids gave rise to styliolinids and Silurian records of nowakiids are missing due to a sampling bias or because they were too rare to be preserved. The earliest large styliolinids probably inhabited only in restricted marginal marine environments and later (Devonian) colonization of open marine environments led to increased predation pressure that favoured evolution of small forms.

Time Series Compression for IoT: A Systematic Literature Review

Time series are widely used to record information in applications developed with Internet of Things (IoT) devices, where sensors are used to collect large amounts of data. These devices, even with the exponential technological evolution of the last years, present limitations for the handling of this data given the enormous volume of data collected. Low storage or processing capacity and environments with restricted connection resources make it difficult to manipulate and transmit information. In this context, compression of information collected in the format of time series can be an alternative to reduce the amount of data handled by devices. However, given the peculiarities of IoT devices and applications, the compression process cannot be more costly than handling raw data. To identify the existing solutions to compress time series for IoT applications. In this paper, we present a descriptive systematic literature review on this topic. Based on a well-defined protocol, 40 papers were selected for review to analyze the strategies used, as well as performance and limitations. In this review, we aim to identify different approaches to solving the problem of data compression in the context addressed, as well as identifying directions for future research. The use of performance metrics in the reviewed papers was also reported in detail, to better understand how the authors compare their solutions to others. Additionally, the relationship between time series compression and machine learning (ML) techniques was highlighted. Being aware of the state-of-the-art in time series compression solutions for IoT can help us project future trends and challenges regarding this process and also to identify which algorithms, methods, and techniques can best be used in combination with ML models, the purpose inherent to the IoT context.

Shallow waters as critical habitats for fish assemblages under eutrophication-mediated events in a coastal lagoon

Eutrophication is a major driver of the degradation of transitional waters worldwide, especially in environments with a restricted connection to the sea, such as coastal lagoons. In recent decades, intensive agriculture and urban water inputs around the Mar Menor coastal lagoon (Western Mediterranean) have disturbed this originally oligotrophic aquatic system. The nutrient input into the lagoon has triggered its eutrophication, leading to dystrophic crises and mass mortality events for aquatic biota, transforming it into one of the most eutrophication-impacted transitional waters in the Mediterranean basin. In this study, we applied a fish-based indicator to assess the ecological quality of shallow waters under different eutrophication-mediated environmental stress scenarios (from pre-eutrophic reference periods to critical eutrophic periods), as well as to explore the role of confinement (i.e., water renewal time) and shoreline anthropogenic pressure as factors modulating the indicator response. Despite the high magnitude of the eutrophication impact on the lagoon, the ecological quality of the shallow waters decreased only slightly after the mass mortality events. The level of confinement also had slight effects on the ecological quality of the most confined shallow areas in the summer during eutrophic periods. Hence, shallow waters could play a critical role as refuge habitats, both for fish assemblages and other aquatic taxa, by buffering euxinic conditions during eutrophication processes.”. In fact, shallow waters could act as critical habitats, allowing for the recolonisation of aquatic biota from more impacted areas in the lagoon. This attribute further reinforces the need to properly manage and protect the shoreline areas of transitional waters, particularly under eutrophication scenarios.

Increasing Extractable Work in Small Qubit Landscapes.

An interesting class of physical systems, including those associated with life, demonstrates the ability to hold thermalization at bay and perpetuate states of high free-energy compared to a local environment. In this work we study quantum systems with no external sources or sinks for energy, heat, work, or entropy that allow for high free-energy subsystems to form and persist. We initialize systems of qubits in mixed, uncorrelated states and evolve them subject to a conservation law. We find that four qubits make up the minimal system for which these restricted dynamics and initial conditions allow an increase in extractable work for a subsystem. On landscapes of eight co-evolving qubits, interacting in randomly selected subsystems at each step, we demonstrate that restricted connectivity and an inhomogeneous distribution of initial temperatures both lead to landscapes with longer intervals of increasing extractable work for individual qubits. We demonstrate the role of correlations that develop on the landscape in enabling a positive change in extractable work.

Implication of middle Eocene to early Miocene ostracodes from the N. El Faras-1X Well, Qattara Depression, Egypt, for paleobathymetry and paleobiogeographic reconstruction

The subsurface middle Eocene - early Miocene succession in the N. El Faras - 1X Well, drilled in the Qattara Depression at the northern part of the Western Desert, Egypt (Southern Tethyan Province, STP), was studied for its ostracode content to infer changes in paleobathymetry as well as paleobiogeographic reconstructions. This succession is composed mainly of three lithostratigraphic units, as the upper part of the Apollonia Formation (middle to late Eocene), the Dabaa Formation (late Eocene and Oligocene) and the lower part of the Moghra Formation (early Miocene). The stratigraphical distribution, paleoenvironmental and paleobiogeographical significance of the ostracode faunas from the Oligocene interval of the study area are documented for the first time. Fifty seven ostracode species belonging to 36 genera were identified in this succession. Among them, two new species were described. The vertical distribution of these ostracode species enabled the recognition of seven local biozones. Qualitative and quantitative statistical analysis of ostracode associations revealed a depositional depth ranging from the inner to outer neritic setting. Considering the CONISS cluster analysis, six ecozones were established. During the middle and late Eocene, the paleobiogeographical affinities of the Egyptian ostracodes from N. El Faras-1X× Well succession with that of the Southern Tethyan countries suggest a direct connection between Egypt and the countries of the Southern Tethyan Province. This connection facilitated the dispersal and exchange within this province. The low ostracode similarity between the STP and the Northern Tethyan Province (NTP) suggests a slight connection and exchange between them. The in common occurrence of these ostracodes with that of Somalia is attributed to the connection between the STP and Somalia via the Tethyan Seaway, which facilitated the dispersal and exchange of the middle Eocene ostracodes. The similarity between the Egyptian ostracodes (STP) and that of South America and the Caribbean Sub-Province indicates a direct connection between those provinces across the Gibraltar Strait and through the North Equatorial Oceanic Water Current during that time. During the Oligocene, the low ostracode similarity between the STP and the NTP may be attributed to a more or less restricted connection. Also, the low similarity indicates a continuation of the mild connection between the STP and the South America and Caribbean Sub-Province across the Gibraltar Strait and through the North Equatorial Current. During the early Miocene, the similarity of the recorded ostracodes of the STP with that of the NTP suggests a continuous connection between the two provinces. Also, there was a connection between the South America and Caribbean Sub-Province and the North American Province through the North Equatorial Current and the warm Gulf Stream within the Caribbean Sea.

Restricted connectivity of Cayley graph generated by transposition trees

Restricted connectivity of Cayley graph generated by transposition trees

Mitochondrial haplotypes reveal low diversity and restricted connectivity of the critically endangered batoid population in a Marine Protected Area

Stability and long-term persistence of a species rely heavily on its genetic diversity, which is closely allied to its capacity for adaptation. In threatened species, population connectivity can play a major role in maintaining that diversity, and genetic assessments of their populations can be crucial for the design of effective spatial conservation management. Not only is it worth evaluating the amount of diversity in a candidate population for protection, but the magnitude of outgoing gene flow can provide insight into its potential to replenish others via emigrants. The critically endangered flapper skate Dipturus intermedius receives protection in the Loch Sunart to the Sound of Jura Marine Protected Area (MPA) in Scotland. However, there is insufficient knowledge of genetic diversity and connectivity across its range. Recent tagging studies in the MPA suggest the presence of animals with high levels of site fidelity and residency, as well as transient individuals, raising concerns of limited connectivity to populations beyond the MPA. In this study, a newly developed mitochondrial haplotype marker allowed use of DNA sourced from fin clips, mucus and egg cases to investigate population structure and mitochondrial variability across several sites around the British Isles, including the MPA. Unfortunately, results characterized the MPA as having particularly low haplotype diversity and significant population differentiation from other sample sites. More than a quarter of its individuals carry a haplotype rarely observed elsewhere, leaving outgoing gene flow questionable. The MPA appears unlikely to sustain the species’ existing mtDNA genetic diversity or act as an effective source population.

Quantum Optimization with Arbitrary Connectivity Using Rydberg Atom Arrays

Programmable quantum systems based on Rydberg atom arrays have recently been used for hardware-efficient tests of quantum optimization algorithms [Ebadi et al., Science, 376, 1209 (2022)] with hundreds of qubits. In particular, the maximum independent set problem on so-called unit-disk graphs, was shown to be efficiently encodable in such a quantum system. Here, we extend the classes of problems that can be efficiently encoded in Rydberg arrays by constructing explicit mappings from a wide class of problems to maximum-weighted independent set problems on unit-disk graphs, with at most a quadratic overhead in the number of qubits. We analyze several examples, including maximum-weighted independent set on graphs with arbitrary connectivity, quadratic unconstrained binary optimization problems with arbitrary or restricted connectivity, and integer factorization. Numerical simulations on small system sizes indicate that the adiabatic time scale for solving the mapped problems is strongly correlated with that of the original problems. Our work provides a blueprint for using Rydberg atom arrays to solve a wide range of combinatorial optimization problems with arbitrary connectivity, beyond the restrictions imposed by the hardware geometry.5 MoreReceived 14 September 2022Revised 14 December 2022Accepted 4 January 2023DOI:https://doi.org/10.1103/PRXQuantum.4.010316Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBoolean satisfiability problemNP-hard problemsQuantum information architectures & platformsQuantum softwarePhysical SystemsAtomsRydberg atoms & moleculesQuantum InformationAtomic, Molecular & OpticalStatistical Physics

On k-restricted connectivity of direct product of graphs

Let [Formula: see text] be a graph. A vertex-cut [Formula: see text] of [Formula: see text] is said to be k-restricted if every component of [Formula: see text] has at least [Formula: see text] vertices, and cyclic if [Formula: see text] has at least two components which contain a cycle. The minimum cardinality over all [Formula: see text]-restricted vertex-cuts of [Formula: see text] is called the k-restricted connectivity of [Formula: see text] and is denoted by [Formula: see text]. Also the minimum cardinality over all cyclic vertex-cuts of [Formula: see text] is called the cyclic connectivity of graph [Formula: see text] and is denoted by [Formula: see text]. In this paper, the [Formula: see text]-restricted connectivity and cyclic connectivity of the direct product of two graphs [Formula: see text] and [Formula: see text] is obtained for some [Formula: see text], where [Formula: see text] is a complete graph, and [Formula: see text] is a complete graph, a complete bipartite graph or a cycle.

Segregation of fluids with polymer additives at domain interfaces: a dissipative particle dynamics study.

This paper investigates the phase separation kinetics of ternary fluid mixtures composed of a polymeric component (C) and two simple fluids (A and B) using dissipative particle dynamics simulations with a system dimensionality of d = 3. We model the affinities between the components to enable the settling of the polymeric component at the interface of fluids A and B. Thus, the system evolves to form polymer coated morphologies, enabling alteration of the fluids' interfacial properties. This manipulation can be utilized across various disciplines, such as the stabilization of emulsions and foams, rheological control, biomimetic design, and surface modification. We probe the effects of various parameters, such as the polymeric concentration, chain stiffness, and length, on the phase separation kinetics of the system. The simulation results show that changes in the concentration of flexible polymers exhibit perfect dynamic scaling for coated morphologies. The growth rate decreases as the polymeric composition is increased due to reduced surface tension and restricted connectivity between A- and B-rich clusters. Variations in the polymer chain rigidity at fixed composition ratios and degrees of polymerization slow the evolution kinetics of AB fluids marginally, although the effect is more pronounced for perfectly rigid chains. Whereas flexible polymer chain lengths at fixed composition ratios slow down the segregation kinetics of AB fluids slightly, varying the chain lengths of perfectly rigid polymers leads to a significant deviation in the length scale and dynamic scaling for the evolved coated morphologies. The characteristic length scale follows a power-law growth with a growth exponent ϕ that shows a crossover from the viscous to the inertial hydrodynamic regime, where the values of ϕ depend on the constraints imposed on the system.

BCCC Disjoint Path Construction Algorithm and Fault-Tolerant Routing Algorithm under Restricted Connectivity

Connectivity in large-scale data center networks is a critical indicator to evaluate network state. A feasible and performance-guaranteed algorithm enables us to find disjoint paths between network vertices to ensure effective data transfer and to maintain the normal operation of network in case of faulty nodes. As an important data center network, BCube Connected Crossbars (BCCC) has many excellent properties that have been widely studied. In this paper, we first propose a vertex disjoint path algorithm with the time complexity of O(nk) in BCCC, where n denotes a switch connected to n servers and k denotes dimension. Then, we prove that the restricted connectivity of BCCC(n,k). Finally, we present an O(knκ1(G)) fault-free algorithm in BCCC, where κ1(G) is the restricted connectivity. This algorithm can obtain a fault-free path between any two distinct fault-free vertices under the condition that each vertex has at least one fault-free neighbor in the BCCC and a set of faulty vertices F with |F|<κ1(G).

Oceanographic consequences of the Bransfield Strait (Antarctica) opening

Abstract The Bransfield Strait (Antarctica) is an important region for evaluating changes in Weddell Sea shelf waters on geological time scales because of its restricted connections to the surrounding ocean. However, the detailed oceanographic consequences of the opening of the strait remain unclear. We present bottom-current-related sedimentary features in the Bransfield Strait and examine the impact of the strait’s opening on deep-water circulation. Our findings show that the ocean circulation started to resemble that of the present day after a period of volcanic activity, possibly around the Middle Pleistocene. Coeval changes in Bransfield Strait morphology and an increase in seafloor irregularities due to the formation of volcanic chains finally determined new pathways for the Bransfield deep and bottom waters, enhanced due to the new climatic scenario of 100 k.y. cycles. The fact that “modernlike” oceanic circulation occurred only during previous interglacial periods demonstrates the significant impact of 100 k.y. climate cycles on the thermohaline changes of Antarctic deep waters. Hence, establishing a modern-day circulation model would enable researchers to assess paleoproductivity and local upwelling that have profoundly influenced the marine ecosystem of the Antarctic Peninsula after the Middle Pleistocene.