Granular Aluminum is a superconductor known for more than eighty years, which recently found its application in qubits, microwave detectors and compact resonators, due to its high kinetic inductance, critical magnetic field and critical current. Here we report on the nonlinear dependence of granular Aluminum inductance on current, which hints towards parametric amplification of the microwave signal in granular Aluminum films. The phase shift of the microwave signal reached 4 radians at a frequency of 7 GHz, which makes it possible to estimate the nonlinearity of the system as Δϕ/ϕ = 1.4% and the potential gain of the order of 17 dB.

Superconducting qubits are considered as a promising platform for implementing a fault tolerant quantum computing. However, surface defects of superconductors and the substrate leading to qubit state decoherence and fluctuations in qubit parameters constitute a significant problem. The amount and type of defects depend both on the chip materials and fabrication procedure. In this work, transmons produced by two different methods of aluminum etching: wet etching in a solution of weak acids and dry etching using a chlorine-based plasma are experimentally studied. The relaxation and coherence times for dry-etched qubits are more than twice as long as those for wet-etched ones. Additionally, the analysis of time fluctuations of qubit frequencies and relaxation times, which is an effective method to identify the dominant dielectric loss mechanisms, i-ndicates a significantly lower impact of two-level systems in the dry-etched qubits compared to the wet-etched ones.

The artificial neuron proposed earlier for use in superconducting neural networks is experimentally studied. The fabricated sample is a single-junction interferometer, part of the circuit of which is shunted by an additional inductance, which is also used to generate an output signal. A technological process has been developed and tested to fabricate a neuron in the form of a multilayer thin-film structure over a thick superconducting screen. The transfer function of the fabricated sample, which contains sigmoid and linear components, is experimentally measured. A theoretical model is developed to describe the relation between input and output signals in a practical superconducting neuron. The derived equations are shown to approximate experimental curves at a high level of accuracy. The linear component of the transfer function is shown to be related to the direct transmission of an input signal to a measuring circuit. Possible ways for improving the design of the sigma neuron are considered.

Polycrystalline films of Pr1−xSrxMnO3 (x = 0.2 and 0.4) and La0.7Sr0.3MnO3 deposited on YSZ substrates represent a special case for the formation of the AFM-CO phase in manganite at temperatures close to and above room temperature.

Several new approaches to the measurement of intrinsic noise and dynamic characteristics of superconducting bolometers based on the RFTES technology are demonstrated. The developed methods were tested with an experimental 550–750 GHz sample at reading frequency of 1.5 GHz at a temperature of 400 mK. The absorption of thin-film resistive coatings on sapphire and quartz substrates was studied, and the emissivity of the experimental heat source was estimated as 14 √(Hz) ± 30

Several new approaches to the measurement of intrinsic noise and dynamic characteristics of superconducting bolometers based on the RFTES technology are demonstrated. The developed methods were tested with an experimental 550–750 GHz sample at reading frequency of ~1.5 GHz at a temperature of 400 mK. The absorption of thin-film resistive coatings on sapphire and quartz substrates was studied, and the emissivity of the experimental heat source was estimated as ~14%. A shot noise source based on Al/AlOx/Al tunnel junction was developed, and the noise temperature of the 1.35–1.6 GHz buffer amplifier referred to the detector output was determined as ~20 K. The response time of RFTES with a hafnium film sized 6 µm × 2 µm × 0.08 µm was evaluated as ~3 µs via microwave heat modulation at the second resonance at ~4.2 GHz; the dynamic range at a modulation frequency of 10 kHz was more than 23 dB. The data obtained made it possible to determine the RFTES sensitivity as 1∙10-17 W/√Hz ± 30%, that coincided with the theoretical value up to the measurement error.

The magnetoresistance of a planar microbridge based on a three layer Pd0.99Fe0.01–Nb–Pd0.99Fe0.01 FSF sandwich near its superconducting transition is studied. We previously showed that the magnetoresistance curve of such samples is hysteretic and contains dips (negative peaks of the resistance) in the coercive fields. In this work, it is found that the low-resistance state has a memory effect. Functioning of such a sample as a superconducting memory element is demonstrated. The effect of the ferromagnetic Pd0.99Fe0.01 layer on the superconducting transition temperature of the proposed memory element is studied by measuring the dep-endence of the critical temperature of bilayer Pd0.99Fe0.01–Nb FS structures on the thickness of the Pd0.99Fe0.01 layer.

The detection of a terahertz optical signal using a bolometric detector with a planar niobium resonator loaded with a hafnium micromotor using the nonlinearity of the impedance of an electron gas at a frequency of 1.5 GHz near the critical temperature of the micromotor is demonstrated for the first time. The temperature of the electron gas was shifted by the resonator current, and the superconducting transition of the micromotor occurred under the action of a terahertz signal. The test thermodynamic signal from a thin-film Fe-Cr-Ni absorber heated in the range of 1-10 K was focused from a distance of 10 mm with an immersion lens made of sapphire onto a planar antenna matched with a micro-bridge in the range of 600-700 GHz. The measured power transmission coefficient of the bolometer was +5.5 dB with a saturation power of ~1 pW and a threshold sensitivity of the receiving system (3±1)·10-17 W/sqrt(Hz)sqrt sqrt, which is close to the theoretical values for the investigated bridge with a size of 2.5x2.5x0.08 μm. The tested detector can be used to create imaging terahertz matrices with frequency multiplexing in sorption-type cryostats. Keywords: RFTES bolometer, superconducting micro bridge, high-frequency impedance of superconductor, hafnium film, electron gas, planar resonator, frequency multiplexing, planar antenna, black body, thermodynamic noise. Keywords: RFTES bolometer, superconducting microbridge, high-frequency impedance, hafnium film, electron gas, coplanar resonator, frequency-division multiplexing, planar antenna, blackbody, noise.

Behavior of magnetic susceptibility and electronic magnetic resonance of polycrystalline Pr 1-x Sr x MnO 3 /YSZ films (x = 0.2 and x = 0.4) in a wide temperature range has been studied. The typical signs of martensitic transformation in the films at temperatures exceeding room temperature have been detected. This phenomenon is associated with internal strain in the samples and a formation of charge-ordering domains in them. The reasons for the appearance of such strain lie in the crystallites size and the boundary between them. The data obtained attract attention to new research and technological opportunities for the study and practical use of rare earth-doped manganites.

In this paper, we propose new kind nonradiating state appearing in high Q planar toroidal THz metamaterial. So-called pseudo-anapole regime arises when the trivial solution to the non-radiating state condition is met. Here, both toroidal and electric dipole intensities are suppressed at resonance frequency while their far-field zone intensities tend to zero. The proposed effect is quite different from well-known anapole regime that is established by the condition p =− ikT that leads to nonradiating state [1] . The fundamental difference of pseudo-anapole state is that suppression of both electric and toroidal multipoles providing an opportunity for study of higher order multipoles from different families. This effect has been confirmed both numerically and experimentally in terahertz frequency range.

We explore the concept of the Josephson magnetic memory element based on a multilayer two-barrier SIsFS Josephson junction storing the digital state by means of the orientation of magnetization in the F-layer. A diluted PdFe alloy with 1% magnetic atoms is used as a ferromagnet (F), and a tunnel AlOx layer (I) ensures a high voltage in the resistive state. We have studied two junctions of a rectangular shape in which two digital states are defined by the orientation of the residual F-layer magnetization set along or across the junction in the plane of the ferromagnetic barrier. Implementations of both binary and ternary logic elements are demonstrated. A scalability of rectangular memory elements is analyzed using micro-magnetic modeling.

We present the numerical, theoretical, and experimental study of a terahertz metasurface supporting a pseudo-anapole. Pseudo-anapole effect arises when electric and toroidal dipole moments both tend to a minimum, instead of destructive interference between electric and toroidal dipole moments in conventional anapole mode. Such overlap allows resonance suppression of electric type radiation. Thus it becomes possible to study the multipoles of other families and higher order excitations. We estimate multipole contribution to the metasurface response via the multipole expansion method. The series is extended with such terms as mean-square radii and multipole interference. We also study the metasurface geometrical tunability. Via scaling, we demonstrate that it is possible to control the metasurface toroidal and electric responses independently. This in turn proves the fact that these multipoles have different physical origin. Moreover, we demonstrate that the proposed metasurface allows excitation of coherent magnetic dipole and electric quadrupole modes, which is crucial for planar cavities and lasing spasers in nanophotonics.

The transport properties of two types of quasi-one-dimensional superconducting microstructures were investigated at ultra-low temperatures: the narrow channels close-packed in the shape of meander, and the chains of tunneling contacts “superconductor-insulator-superconductor.” Both types of the microstructures demonstrated high value of high-frequency impedance and-or the dynamic resistance. The study opens up potential for using of such structures as current stabilizing elements with zero dissipation.

Express analysis of the dependence of the critical temperature of different superconducting films on its thickness was proposed, developed, and tested. The technique is based on a mathematical analysis of an integral equation that describes a one-time measurement of the electrical resistance temperature dependence of a sufficiently long superconductor film with variable thickness. The dependence of the film thickness and width along its longitudinal coordinate (film geometry) is set or measured using known methods. The express analysis has significant advantages over the more labor-consuming method of time-shared measurement of the critical temperature of film segments with different thicknesses.

The ability to control Josephson vortices is instrumental for development of superconducting cryoelectronics. However, direct visualization of multivortex states in Josephson junctions is a challenging task. Here, we employ a magnetic force microscopy (MFM) for the analysis of planar Josephson junctions. We observe a specific MFM response, seen as a chain of small rings. By changing the applied field, we show that the number of rings is equal to the number of flux quanta in the junction. Therefore, each ring represents an individual vortex in a one-dimensional vortex chain within the junction. Our observation demonstrates that the MFM technique can be used for visualization of Josephson vortices and for probing their spatial configurations and mutual interaction.

A negative magnetoresistive effect has been observed for ferromagnet/superconductor/ferromagnet (FSF) microbridges based on diluted ferromagnetic PdFe alloy containing as small as 1% of magnetic atoms. The effect is represented by sharp negative peaks in magnetoresistance at magnetic fields opposite in sign to the initial saturated magnetizations. Microstructuring of the FSF trilayers does not suppress the effect: the most pronounced dips were obtained for the smallest bridges 6–8 µm wide and 10–15 µm long. The negative magnetoresistance peak was observed at temperatures within the superconducting transition and reaches a noticeable value of up to 1.3% of the normal state resistance.

Abstract The transport properties of two types of quasi-one-dimensional superconducting microstructures were investigated at ultra-low temperatures: the narrow channels close-packed in the shape of meander, and the chains of tunneling contacts “superconductor-insulator-superconductor.” Both types of the microstructures demonstrated high value of high-frequency impedance and-or the dynamic resistance. The study opens up potential for using of such structures as current stabilizing elements with zero dissipation.