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The outstanding performance of superconducting nanowire single-photon detectors (SNSPDs) has expanded their application areas from quantum technologies to astronomy, space communication, imaging, and LiDAR. As a result, there has been a surge in demand for these devices, that commercial products cannot readily meet. Consequently, more research and development efforts are being directed towards establishing in-house SNSPD manufacturing, leveraging existing nano-fabrication capabilities that can be customized and fine-tuned for specific needs. We report on the implementation of an end-to-end workflow for SNSPD fabrication and characterization, from superconducting film growth to meander nanowire fabrication and their integration with electrical readout circuits and optical testbeds. An essential aspect of this research involved identifying the key parameters of our workflow and developing reliable procedures for their optimization. As an outcome, the ab initio development of SNSPD technology yielded devices with characteristics comparable to commercial devices at a wavelength of 1550 nm, making them well-suited for telecommunication and integrated quantum systems. This report aims to provide useful insights to those entering the field and accelerate the establishment of superconducting detector technology and its application across various domains. [ABSTRACT FROM AUTHOR]

Significant progress has been achieved in leveraging atomic systems for the effective operation of quantum networks, which are essential for secure and long-distance quantum communication protocols. The key elements of such networks are quantum nodes that can store or generate both single and entangled photon pairs. The primary mechanisms leading to the production of single and entangled photon pairs revolve around established techniques such as parametric down-conversion, four-wave mixing, and stimulated Raman scattering. In contrast to solid-state platforms, atomic platforms offer a more controlled approach to the generation of single and entangled photon pairs, owing to the progress made in atom manipulation techniques such as trapping, cooling, and precise excitation schemes facilitated by the use of lasers. This review article delves into the techniques implemented for generating single and entangled photon pairs in atomic platforms, starting with a detailed discussion of the fundamental concepts associated with single and entangled photons and their characterization techniques. The aim is to evaluate the strengths and limitations of these methodologies and offer insights into potential applications. Additionally, the article will review the extent to which these atomic-based systems have been integrated into operational quantum communication networks. [ABSTRACT FROM AUTHOR]

Quantum phenomena, including entanglement, superposition, tunneling, and spin-orbit interactions, among others, are foundational to the development of recent innovations in quantum computing, teleportation, encryption, sensing, and new modalities of electronics, such as spintronics, spinorbitronics, caloritronics, magnonics, twistronics, and valleytronics. These emerging technologies provide disruptive influences to global commercial markets. These remarkable advances in quantum technologies are nearly always enabled by the discovery of materials and their quantum behaviors. Such advances are governed by quantum principles that are strongly influenced by environmental, physical, topological, and morphological conditions such as very small length scales, short time durations, ultrahigh pressures, ultralow temperatures, etc., which lead to quantum behaviors that manifest as quantum tunneling, entanglement, superpositioning, superfluidity, low-dimensional, high-temperature and high-pressure superconductivity, quantum fluctuations, Bose-Einstein condensates, topological effects, and other phenomena that are not yet fully understood nor adequately explored. Here, we provide a review of quantum materials developed up to 2023. Remarkable advances in quantum materials occur daily, and therefore, by the time of publication, new and exciting breakthroughs will have occurred that are regrettably not covered herein. [ABSTRACT FROM AUTHOR]

A dynamic numerical model is developed considering in-plane and out-of-plane behaviour and their interaction for the novel energy dissipating hysteretic infill and conventional brick infill system. The response of three-story infilled buildings under earthquake excitations shows a significant performance improvement in the energy dissipating hysteretic infilled building. The novel infill system resists the formation of the soft-story mechanism with enhanced overall structural performance, and a reduced number of infill failures compared with the conventional infilled buildings. This is mainly due to its low stiffening effect, better post-peak response in the in-plane direction and improved out-of-plane deformation capacity and bi-axial stability. [ABSTRACT FROM AUTHOR]

Simple Summary: Canine cancer is a leading cause of dog mortality. In this study, we examine the hypothesis that the structure of keratin changes when cancer develops in the patient. We use X-ray diffraction of dog claws to detect these changes, finding that the modifications of the intermolecular distances are the most significant. Machine learning algorithms are utilized for cancer/non-cancer diagnostics, achieving a balanced accuracy of 85% for the blind group. Our research suggests that the changes in keratin structure can be tracked by X-ray diffraction, offering a potential tool for non-invasive cancer diagnostics. This could have significant implications for the early detection and treatment of canine cancer, potentially saving many lives. Moreover, this approach can be extended to human cancer detection. We report the results of X-ray diffraction (XRD) measurements of the dogs' claws and show the feasibility of using this approach for early, non-invasive cancer detection. The obtained two-dimensional XRD patterns can be described by Fourier coefficients, which were calculated for the radial and circular (angular) directions. We analyzed these coefficients using the supervised learning algorithm, which implies optimization of the random forest classifier by using samples from the training group and following the calculation of mean cancer probability per patient for the blind dataset. The proposed algorithm achieved a balanced accuracy of 85% and ROC-AUC of 0.91 for a blind group of 68 dogs. The transition from samples to patients additionally improved the ROC-AUC by 10%. The best specificity and sensitivity values for 68 patients were 97.4% and 72.4%, respectively. We also found that the structural parameter (biomarker) most important for the diagnostics is the intermolecular distance. [ABSTRACT FROM AUTHOR]

The object of research is seismic design, and the subject of the study is the determination of the reduction coefficient. One of the important problems of earthquake-resistant design is to determine the effect of low-cycle fatigue of reinforced concrete on the reduction coefficient and determine its optimal value. This problem is not disclosed and is not specifically taken into account in the standards for earthquake engineering when determining the maximum bearing capacity of types of structures due to the lack of study of the issue. To solve the problem, a series of experimental studies were carried out on low-cycle fatigue of reinforced concrete bending elements and frame units. The range of results of the reduction coefficient values and the degree of influence of monocyclic fatigue on the properties of the reduction coefficient are obtained. A feature and characteristic of the results obtained is that the reduction coefficient Rμ depends on the nature of the hysteresis deformation pattern and the plastic life of structural elements estimated by the plasticity coefficient μ, which is significantly influenced by low-cycle fatigue manifested at peak accelerations of strong seismic impacts. The above test algorithm, the feature and characteristics of the results obtained made it possible to solve the problem under study. The results obtained are accepted for practical use in the action of seismic loads: on the calculation of strength taking into account new low-cycle coefficients, reduction coefficients for determining the spectra of design reactions and seismic loads, taking into account energy absorption. New reduction coefficients are proposed for determining the spectra of calculated reactions and seismic loads. [ABSTRACT FROM AUTHOR]

We study a quantum-enhanced differential measurement scheme that uses quantum probes and single-photon detectors to measure a minute defect in the absorption parameter of an analyte under investigation. For the purpose, we consider two typical non-classical states of light as a probe, a twin-Fock state and a two-mode squeezed vacuum state. Their signal-to-noise ratios (SNRs) that quantifies the capability of detecting the defect are compared with a corresponding classical imaging scheme that employs a coherent state input. A quantitative comparison is made in terms of typical system imperfections such as photon loss and background noise that are common in practice. It is shown that a quantum enhancement in SNR can be described generally by the Mandel Q-parameter and the noise-reduction-factor, which characterize an input state that is incident to the analyte. We thereby identify the conditions under which the quantum enhancement remains and can be further increased. We expect our study to provide a guideline for improving the SNR in quantum imaging experiments employing a differential measurement scheme with time-integrated single-photon detectors., (© 2022. The Author(s).)

Quantifying aleatory and epistemic uncertainty in nonlinear structural response simulation is key to robust performance-based seismic assessments. This paper focuses on the modeling parameters that are used to describe the nonlinear force-deformation response of the equivalent infill struts used in models of reinforced concrete frames with infills. The variability in several parameters is characterized by developing empirical and theoretical multivariate probability distributions based on the deduced-to-predicted ratios derived using data from 113 physical experiments. The effect of the uncertainty in the infill strut modeling parameters on maximum story drift ratios and associated limit state fragility functions is investigated for a 3-story reinforced concrete frame building with infills. Multiple stripe analysis is performed using hazard-consistent ground motions. Relative to when only record-to-record variability is considered, modeling parameter uncertainty has a non-negligible effect on the dispersion of the maximum story drift ratios, and affects both the median and dispersion of the limit state fragilities. [ABSTRACT FROM AUTHOR]

Unique soils of the chalk polygons in the steppe zone of Obshchii Syrt and the Sub-Ural Plateau have been studied. They are characterized by a combination of uneven-aged features formed in contrasting environments. Modern features are the result of biogenic-accumulative processes, structuring, salinization, and crust formation. Relict features are associated with paleocryogenesis and include paleo-permafrost block–pseudomorph complexes, cryoturbations, paleo-permafrost wedges, accumulations and sorting of coarse fraction, etc. The good conservation of relict cryogenic features and modern cryogenic processes determine the uniqueness of these steppe soils. Such horizons and profile formula are not found in the existing diagnostic scheme for the classification and diagnostics of soils in Russia (CDSR). In order to represent the features, modern image, and genesis of these soils in the terminology of CDSR, a new diagnostic BCM cryostructural-metamorphic horizon was proposed. The soils were diagnosed as cryostructural-metamorphic on microhighs, protohumic and light-humus cryostructural-metamorphic on microslopes, and light-humus and light-humus cryometamorphic in microdepressions of the chalk polygons. Relict cryogenic features are proposed to be taken into account in the classification of these soils at the level of soil genus with the prefix 'paleo'. According to the WRB, soils were classified as Rendzic Endoleptic Calcaric Phaeozems (Relictiturbic, Tonguic) in microdepressions, Skeletic Calcaric Regosols (Relictiturbic, Ruptic, Nudiyermic) on microhighs, and (Relictiturbuc, Raptic, Ochric) on microslopes. [ABSTRACT FROM AUTHOR]

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The paper aims at the design of a digital tool for analyzing the impact of scientific and technological progress on socioeconomic problems and sustainable development of the region. The research focuses on the consistent development of a digital platform for analyzing and visualizing digital data on regional innovation development, as well as predicting the sustainable development of regions based on the available regional infrastructure of innovation systems and the Russian regions' cluster structure. When designing the digital platform, we gave special attention to ensuring efficient data collection, processing, and analysis processes required for studying the socio-economic system. In the course of the work, an automated process of working with data was developed. The digital platform is being developed as a flexible tool for a wide range of users, from research centers, investors, and private enterprises to individual users interested in regional innovation development models. As part of the work, the process of selecting technical tools for the software implementation of the platform in terms of tasks and technical features of designing digital platforms is presented. The result of the work is a prototype of the Russian regional innovation system digital platform with the implemented functionality of a personal account, a module of simulation experiments, and various approaches to data analysis and visualization. The research is carried out as part of a project to develop a digital model of the regional innovation system of the Russian Federation as a driver of sustainable development. [ABSTRACT FROM AUTHOR]

The feasibility of the detection of electromagnetic response in the upper ionosphere to ground large‐scale ultra‐low‐frequency (ULF) and extremely‐low‐frequency (ELF) transmitters by low‐Earth‐orbit (LEO) satellites is considered. As an example of such transmitters, we consider the ZEVS 82 Hz transmitter, FENICS installation driven by 0.5–150 Hz generator, and industrial 50 Hz unbalanced power transmission lines. We numerically model the ULF/ELF wave energy leakage into the upper ionosphere from an oscillating grounded linear power line of a finite length suspended above a ground with a finite resistivity. The numerical scheme is based on the theoretical formalism developed to describe the excitation of an electromagnetic field by a horizontal grounded dipole. A realistic altitudinal profile of the plasma parameters has been reconstructed with the use of the IRI ionospheric model. For the ZEVS transmitter powered by 200 A current the modeled amplitudes of electromagnetic response can reach in the upper nightside ionosphere up to 60 µV/m and 6 pT. The assumption of an infinite source scale overestimates the ionospheric response by a factor of ∼7 as compared with realistic scale 60 km of the ZEVS transmitter. Unbalanced 50 Hz current of 10 A in large‐scale (>100 km) power transmission lines can produce the electric response in the upper ionosphere that is sufficient to be detected by electric sensors at LEO satellite. The stimulation of artificial Pc1 pulsations (0.5 Hz) with amplitudes ∼1 pT and ∼10 µV/m by large‐scale (>100 km) power lines is possible with driving current >100 A. The use of decommissioned power lines can be a cheap and efficient tool to stimulate Pc1 pulsations in the ionosphere. Plain Language Summary: Our planet was found to exist in an electromagnetic environment, at least in some frequency bands, created by rather industrial activity than by natural processes. The electromagnetic response in the ionosphere to thunderstorms and radio transmitters has been well studied in the very‐low‐frequency range (>1 kHz), but much less attention has been paid to the extremely‐low‐frequency (ELF) (≪1 kHz) and ultra‐low‐frequency (ULF) (<1 Hz) bands. Any noticeable ULF/ELF emission efficiency may be expected only for extremely large‐scale emitting systems. Such man‐made transmitters do exist. Powerful ELF aerials for communication with submarines with a length of about several tens of km were constructed. Special experiments with controlled sources of electromagnetic fields of ULF/ELF bands were carried out using decommissioned power lines as a horizontal radiating antenna. Transportation systems can also be extended ULF antenna. Finally, unbalanced networks of electric power transmission 50/60 Hz lines become large‐scale emitters. Our numerical modeling has proved that manmade ULF/ELF electromagnetic activity near the ground can be monitored by low‐Earth‐orbit satellites. The large‐scale decommissioned power lines can be used to stimulate artificial Pc1 pulsations with frequency ≤1 Hz in the ionosphere‐magnetosphere system. These experiments open the possibility to stimulate a loss of relativistic electrons from the radiation belt. Key Points: New numerical model of ultra‐low‐frequency/extremely‐low‐frequency emission generation in the ionosphere by a near‐ground linear current of a finite length has been elaboratedThe model gives the possibility to estimate electromagnetic response of the ionosphere to current sources of different lengthsArtificial Pc1 pulsations can be generated in the upper ionosphere by a large‐scale power line system [ABSTRACT FROM AUTHOR]

Discrete-variable (DV) and continuous-variable (CV) schemes constitute the two major families of quantum key distribution (QKD) protocols. Unfortunately, since the setup elements required by these schemes are quite different, making a fair comparison of their potential performance in particular applications is often troublesome, limiting the experimenters' capability to choose an optimal solution. In this work we perform a general comparison of the major entanglement-based DV and CV QKD protocols in terms of their resistance to the channel noise, with the otherwise perfect setup, showing the definite superiority of the DV family. We analytically derive fundamental bounds on the tolerable channel noise and attenuation for entanglement-based CV QKD protocols. We also investigate the influence of DV QKD setup imperfections on the obtained results in order to determine benchmarks for the parameters of realistic photon sources and detectors, allowing the realistic DV protocols to outperform even the ideal CV QKD analogs. Our results indicate the realistic advantage of DV entanglement-based schemes over their CV counterparts and suggests the practical efforts for maximizing this advantage. [ABSTRACT FROM AUTHOR]

The present study is focused on the formation of a superconducting niobium coating on cryogyroscope rotors. The application of a superconducting coating onto a cryogyroscope rotor can significantly improve the orientation accuracy of a moving object in space. Electrometallurgical processes, necessary to form a superconducting niobium coating on a cryogyroscope rotor, are considered. An electrochemical unit for applying electrolytic coatings onto spherical substrates was developed. An original cathode design for obtaining smooth continuous niobium coatings on spherical samples is proposed. Niobium coatings were electrodeposited on carbositall rotors in NaCl–KCl–NaF(10 wt%)–K2NbF7(8 wt%)–Nb melt at 750°C using galvanostatic electrolysis. The conditions for the electrodeposition of niobium coatings were selected. A unit for the electrochemical polishing of niobium was developed. The parameters of electrochemical polishing for niobium coatings on spherical samples in H2SO4:HF (9:1) electrolyte were identified. A protective insulating layer of niobium pentaoxide was applied to Nb-coated rotors by anodizing in 1% orthophosphoric acid solution. The modes of the potentiostatic electrolysis for anodizing spherical samples were established. [ABSTRACT FROM AUTHOR]

In this study we make use of the closely spaced Swarm A and C spacecraft to determine the main wave parameters of micro‐pulsation in the Pc1 range. Generally, the interpretation of wave events in satellite recordings suffers from the spatial/temporal ambiguity of such data. To resolve that problem, we use for the first time in the 0.2–5 Hz apparent frequency range high‐resolution magnetic field data from the Swarm A/C spacecraft pair. Particularly suitable for this analysis is the period of Counter Rotating Orbit Phase in 2021. During that period the along‐track distance between the spacecraft was varied from 2 to 40 s. Surprisingly many of the wavy signals at middle latitudes were identified as small‐scale (order of 10s km) quasi‐static field‐aligned current (FAC) structures. Some of the events turned out to be medium‐scale (100–200 km) waves oscillating at 1 Hz or less. A number of published electromagnetic ion cyclotron (EMIC) waves were checked on their consistency. One characteristic is their long wavelength (∼1,000 km). About half of the cases passed the check, the other did not satisfy the spatial homogeneity. The small‐scale FAC structures we believe to be driven by atmospheric gravity waves. While the medium‐scale waves we prefer to relate to the effects of the ionospheric Alfvén resonator. Key Points: Resolving for the first time the spatial/temporal ambiguity in satellite wave signals within the Pc1 range by the Swarm constellationSmall‐scale (10s km) quasi‐static current features are frequently detected, also medium‐scale (100s km) waves with less than 1 Hz are foundElectromagnetic ion cyclotron waves exhibit long wavelengths (∼1,000 km). This has to be verified for their identification [ABSTRACT FROM AUTHOR]

One of the main characteristics of optical imaging systems is spatial resolution, which is restricted by the diffraction limit to approximately half the wavelength of the incident light. Along with the recently developed classical super-resolution techniques, which aim at breaking the diffraction limit in classical systems, there is a class of quantum super-resolution techniques which leverage the non-classical nature of the optical signals radiated by quantum emitters, the so-called antibunching super-resolution microscopy. This approach can ensure a factor of n improvement in the spatial resolution by measuring the n -th order autocorrelation function. The main bottleneck of the antibunching super-resolution microscopy is the time-consuming acquisition of multi-photon event histograms. We present a machine learning-assisted approach for the realization of rapid antibunching super-resolution imaging and demonstrate 12 times speed-up compared to conventional, fitting-based autocorrelation measurements. The developed framework paves the way to the practical realization of scalable quantum super-resolution imaging devices that can be compatible with various types of quantum emitters. Quantum super-resolution techniques take advantage of the non-classical nature of the quantum emitters, but are time-consuming. Here, the authors present a machine learning-assisted approach for fast antibunching-based super-resolution imaging, with a 12-fold speed up over the conventional approach [ABSTRACT FROM AUTHOR]

Single photon emitters (SPEs) are extensively utilized in quantum technologies, single photon emission computed tomography, and quantum key distribution. The present, efficient robust materials used as SPEs would be insufficient. Some photoresist polymers are employed in secondary applications of single photon emission for enhancing optical properties such as transmittance and life span. Polymers becomes conductive by doping and they demonstrate a wide range of optoelectronic applications. Although conductive polymers are now primarily employed in secondary applications of single photon emission, they could directly emit a single photon in the future in consideration of their promising structural and optical properties. [ABSTRACT FROM AUTHOR]

The ducting of whistler waves by systems of small‐scale field‐aligned plasma density depletions is studied. Similarly to our previous paper (Zudin et al., 2019, https://doi.org/10.1029/2019ja026637), we carry out analytical calculations and numerical simulations for the parameters of an active experiment in which very low frequency whistler waves emitted by a ground‐based transmitter at a frequency of 18 kHz were received onboard the DEMETER satellite at 700 km above the SURA heating facility. Random‐sized density depletions with a level around 10%–20% and perpendicular sizes ranging from 10 m up to about 300 m are considered. The properties of ducted waves are determined by the perpendicular size of individual depletions. Particularly, depletions with a width of more then d0 ∼ 100 m form separate ducting structures, that is, coupled waveguides capable of exchanging energy by means of mode overlap. Depletions with a width of less than d0 ∼ 100 m form a common waveguide structure, whose properties are equivalent to those of a wider irregularity with a smoothed density profile. Two important differences are revealed in ducting properties of density depletions compared to density enhancements considered in Zudin et al. (2019, https://doi.org/10.1029/2019ja026637). First, depletions support highly oblique Gendrin mode waves, rather than quasi‐longitudinal whistlers as in the case of density enhancements. Second, the characteristic perpendicular size d0 ∼ 100 m of density depletions separating the regimes of "coupled waveguides" and of "equivalent ducting structure" with smoothed density profile is by an order of magnitude smaller than for density enhancements of the same 10–20% relative level. Key Points: Small‐scale field‐aligned ionospheric plasma density depletions can serve as specific ducting structures for very low frequency whistlersThe ducting properties of systems from multiple small‐scale density depletions are studied both analytically and numericallyThe ducting properties of density depletions and enhancements are compared [ABSTRACT FROM AUTHOR]

This work deals with the derivation of a receiver structure for the quantum detection of information-carrying coherent states used in photonic communications systems, that employ the degrees of freedom of both the complex amplitude and the state of polarization in the quantum state, producing a high dimensional modulation in the form of a constellation of quantum composite coherent states to be transmitted in the optical channel. Our receiver is based on the extension of the positive operator value measurements (POVM) in the constellation Hilbert space, towards projective measurements in a larger Hilbert space. Starting from the measurement vectors obtained from an optimum detection/discrimination strategy-the square root method (SRM) in our case-, and basing our analysis on the Naimark extension, we present a procedure for building those projectors for a received modulation format of composite coherent states. We analytically derive the orthogonal and idempotent projectors, arriving at closer form expressions for the considered modulation format, their decomposition in unitary rotations, and suggest a receiver configuration for its physical realization. Finally, an error probability analysis of our modulation formats is presented. [ABSTRACT FROM AUTHOR]

The quantum internet is envisioned as the ultimate stage of the quantum revolution, which surpasses its classical counterpart in various aspects, such as the efficiency of data transmission, the security of network services, and the capability of information processing. Given its disruptive impact on the national security and the digital economy, a global race to build scalable quantum networks has already begun. With the joint effort of national governments, industrial participants, and research institutes, the development of quantum networks has advanced rapidly in recent years, bringing the first primitive quantum networks within reach. In this work, we aim to provide an up-to-date review of the field of quantum networks from both theoretical and experimental perspectives, contributing to a better understanding of the building blocks required for the establishment of a global quantum internet. We also introduce a newly developed quantum network toolkit to facilitate the exploration and evaluation of innovative ideas. Particularly, it provides dual quantum computing engines, supporting simulations in both the quantum circuit and measurement-based models. It also includes a compilation scheme for mapping quantum network protocols onto quantum circuits, enabling their emulations on real-world quantum hardware devices. We showcase the power of this toolkit with several featured demonstrations, including a simulation of the Micius quantum satellite experiment, a testing of a four-layer quantum network architecture with resource management, and a quantum emulation of the CHSH game. We hope this work can give a better understanding of the state-of-the-art development of quantum networks and provide the necessary tools to make further contributions along the way. [ABSTRACT FROM AUTHOR]