We introduce the detailed comparison of meta-heuristic and reinforcement learning algorithms implementation in the area of quantum computations on the example of effective optimization of quantum control scheme to produce quantum logic gates with maximum fidelity to their theoretical counterpart. In particular, we compare the decision making process of the Genetic Algorithm (GA) as a meta-heuristic algorithm and Proximal Policy Optimization (PPO) as a reinforcement learning algorithm. We provide the comparison via the t-SNE and UMAP dimensionality reduction algorithms and analyze solution exploration process for each algorithm based on the reduced representation of generated solutions during training. Besides, a detailed review of the investigated problems and the algorithms used in the paper is given.

The longitudinal electron transport in a multilayer superconducting structure SF1S1F2sN, where S is a superconductor, F is a ferromagnet, s is a thin superconducting layer, and N is a normal metal, has been theoretically studied. Calculations have shown that the rotation of the magnetization of ferromagnetic layers relative to each other makes it possible to smoothly change the kinetic inductance of the structure by several times. A feature of the electronic state of the structure in the region of system parameters corresponding to its transition from a state with the 0 stable Josephson phase to a state with the π stable phase (0–π transition) has been discovered. This feature leads to the decrease in the singlet component of the pairing amplitude and to an increase in the kinetic inductance of the entire structure. The study of the effect of the finite longitudinal current on the charge transport has shown that the destruction of superconductivity in different layers occurs step-by-step, and the dependence of the kinetic inductance Lk on the total transport current J exhibits several plateaus with an almost constant inductance.

The transport properties of a nanobridge superconducting quantum interference device made of Al/Pt bilayer have been studied. Measurement and approximation of the voltage-field dependencies allow to estimate the inductance of the structure. It is found that this value significantly exceeds the expected geometric inductance and exhibits an atypical temperature dependence. To explain this effect, a microscopic model of electron transport in SN bilayers is developed, considering the proximity effect, and the available regimes of the current distribution are described. The measured properties may be indicative of the formation of high-resistance aluminum with high values of kinetic inductance during the fabrication of Al/Pt bilayers.

The supercurrent in a Josephson SF1S1F2sIS spin valve (“S” is for superconductor, “F” is for ferromagnet, and “I” is for insulator) is studied theoretically. It is found that by rotating the magnetization of one of the ferromagnetic layers, a smooth switching of the system between two states with different critical currents is possible. The operating range of the device can be adjusted by varying the thickness of the intermediate s-layer. The proposed structure is a promising scalable control element for the use in superconducting electronics.

The extensive development of the field of spiking neural networks has led to many areas of research that have a direct impact on people's lives. As the most bio-similar of all neural networks, spiking neural networks not only allow the solution of recognition and clustering problems (including dynamics), but also contribute to the growing knowledge of the human nervous system. Our analysis has shown that the hardware implementation is of great importance, since the specifics of the physical processes in the network cells affect their ability to simulate the neural activity of living neural tissue, the efficiency of certain stages of information processing, storage and transmission. This survey reviews existing hardware neuromorphic implementations of bio-inspired spiking networks in the "semiconductor", "superconductor" and "optical" domains. Special attention is given to the possibility of effective "hybrids" of different approaches

A basic element of a quantum network based on two single‐mode waveguides is proposed with different frequencies connected by a solid‐state qubit. Using a simple example of a possible superconducting implementation, the usefulness of the simplifications used in the general theoretical consideration has been justified. The non‐classical field in a single‐mode with a frequency of is fed to the input of a qubit controller and transformed into a non‐classical field in an output single‐mode with a frequency of . The interface can establish a quantum connection between solid‐state and photonic flying qubits with adjustable pulse shapes and carrier frequencies. This allows quantum information to be transferred to other superconducting or atomic‐based quantum registers or chips. The peculiarities of the wave‐qubit interactions are described, showing how they help to control the quantum state of the non‐classical field. On this basis, the operating principles of solid‐state and flying qubits for the future quantum information platforms are considered.

We study the effect of electrode width on superconducting current transport in Nb-Au-Nb Josephson bridges. The critical current as well as the normal bridge resistance drop with decreasing electrode width on scales of a few mu m, which are orders of magnitude larger than the estimated coherence length of the Au strip. We consider several physical reasons for such an anomalous influence of the width W of the superconducting electrode on the critical current I-c (AIWIc) and provide model fits for the resistive and superconducting properties of the bridges. The smooth dependence of the Nb-Au-Nb bridge parameters on the electrode width can be used to optimize the design of superconducting devices for specific applications.

We have studied the Thouless energy in Josephson superconductor-normal metal-superconductor (SN-N-NS) bridges analytically and numerically, taking into account the influence of the sub-electrode regions. We have found a significant suppression of the Thouless energy with increasing interfacial resistance, in agreement with experimental results. The analysis of the temperature dependence of the critical current in Josephson junctions in comparison with the expressions for the Thouless energy may allow the determination of the interface parameters of S and N-layers.

It is known that the dielectric layer (resonator) located behind the conducting plate of the bolometer system can significantly increase its sensitivity near the resonance frequencies. In this paper, the possibility of receiving broadband electromagnetic signals in a multilayer bolometric meta-material made of alternating conducting (e.g., silicon semiconductor) and dielectric layers is demonstrated both experimentally and numerically. It is shown that such a multilayer structure acts as a lattice of resonators and can significantly increase the width of the frequency band of efficient electromagnetic energy absorption. The parameters of the dielectric and semiconductor layers determine the frequency bands. Numerical modeling of the effect has been carried out under the conditions of our experiment. The numerical results show acceptable qualitative agreement with the experimental data. This study develops the previously proposed technique of resonant absorption of electromagnetic signals in bolometric structures.

An analytical solution has been found to describe dynamic processes in a superconducting nanointerferometer with negligibly low inductances that is included in a high-Q factor resonator. The effect of nonlinearity in the system, as well as the effect of external parametric pumping, has been analyzed. The screening of detected dynamic modes in the studied nanostructure in the resonator is performed in a wide range and their positions on the plane of the parameters have been determined. A significant influence of phase effects on the evolution of the system has been demonstrated and phase relations allowing one to control the output signal intensity have been evaluated. The detected effects open new possibilities for developing and testing basic elements of modern quantum computing systems.

We have studied the proximity effect in an SF1S1F2s superconducting spin valve consisting of a massive superconducting electrode (S) and a multilayer structure formed by thin ferromagnetic (F1,2) and superconducting (S1, s) layers. Within the framework of the Usadel equations, we have shown that changing the mutual orientation of the magnetization vectors of the F1,2 layers from parallel to antiparallel serves to trigger superconductivity in the outer thin s-film. We studied the changes in the pair potential in the outer s-film and found the regions of parameters with a significant spin-valve effect. The strongest effect occurs in the region of parameters where the pair-potential sign is changed in the parallel state. This feature reveals new ways to design devices with highly tunable inductance and critical current.

In this article, we consider designs of simple analog artificial neural networks based on adiabatic Josephson cells with a sigmoid activation function. A new approach based on the gradient descent method is developed to adjust the circuit parameters, allowing efficient signal transmission between the network layers. The proposed solution is demonstrated on the example of a system that implements XOR and OR logical operations.

Despite its insensitivity to charge noise, the transmon's anharmonicity and control pulse length are limited. Transmon state control traditionally involves a quadrature mixer that mixes microwave signals from a room-temperature oscillator and an arbitrary waveform generator to control the single qubit states. Scaling upquan tum processors faces challenges in hardware, management of qubit operations, and read-out procedure due to the large amount of expensive room-temperature equipment required for each qubit. Operating at millikelvin temperatures, these devices introduce thermal noise, reducing qubit lifetime and distorting control signals. An alternative promising control method is based on superconducting digital electronics. In these digital circuits, a bit of information is represented by a short unipolar voltage pulse generated when a single flux quantum (SFQ) pulse passes through a Josephson junction. The qubit states are controlled by the action of a sequence of SFQ pulses, with the pulse-to-pulse timing adjusted to induce a coherent rotation of the state vector in the computational subspace and to minimize leakage to the outside. The paper discusses a method for controlling the states of a transmon qubit using digital superconducting electronics. In this approach, the sequences of picosecond voltage pulses are used to control the state of a quantum computing system. We have considered a control scheme based on a bipolar pulse generator and proposed an algorithm for finding the optimal implementation of a bipolar short pulse control sequence for performing high-precision single-bit operations (with fidelity equal to 99,99 %) using deep learning algorithms with rein forcement: AlphaGo Zero, AlphaZero and Proximal Policy.

Different regimes of electromagnetic signal transmission through heterostructures formed by a sequence of conducting and non-conducting layers are discussed for various ratios between the frequency of radiation and the transport frequency of electron scattering in the conducting layers. Possibility to increase the efficiency of detecting or filtering electromagnetic radiation in a wide range of frequency range (from subTHz to far IR) in such structures is analyzed. Keywords: propagation of electromagnetic waves in heterostructures, resonant tunneling, THz-IR detectors, bolometers.

We examine the effect of resonant absorption of electromagnetic signals in a silicon semiconductor plasma layer when the dielectric plate is placed behind it both experimentally and numerically. It is shown that such plate acts as a dielectric resonator and can significantly increase the electromagnetic energy absorption in the semiconductor for certain frequencies determined by the dielectric plate parameters. Numerical modelling of the effect is performed under the conditions of conducted experiment. The numerical results are found to be in qualitative agreement with experimental ones. This study confirms the proposed earlier method of increasing the efficiency of bolometric-type detectors of electromagnetic radiation.

The imitative modelling of processes in the brain of living beings is an ambitious task. However, advances in the complexity of existing hardware brain models are limited by their low speed and high energy consumption. A superconducting circuit with Josephson junctions closely mimics the neuronal membrane with channels involved in the operation of the sodium-potassium pump. The dynamic processes in such a system are characterised by a duration of picoseconds and an energy level of attojoules. In this work, two superconducting models of a biological neuron are studied. New modes of their operation are identified, including the so-called bursting mode, which plays an important role in biological neural networks. The possibility of switching between different modes in situ is shown, providing the possibility of dynamic control of the system. A synaptic connection that mimics the short-term potentiation of a biological synapse is developed and demonstrated. Finally, the simplest two-neuron chain comprising the proposed bio-inspired components is simulated, and the prospects of superconducting hardware biosimilars are briefly discussed.

A radical reduction in power consumption is becoming an important task in the development of supercomputers. Artificial neural networks (ANNs) based on superconducting elements of spintronics seem to be the most promising solution. A superconducting ANN needs to develop two basic elements - a nonlinear (neuron) and a linear connecting element (synapse). The theoretical and experimental results of this complex and interdisciplinary problem are presented in this paper. The results of our theoretical and experimental study of the proximity effect in a stacked superconductor/ferromagnet (S/F) superlattice with Co-ferromagnetic layers of various thicknesses and coercive fields and Nb-superconducting layers of constant thickness equal to the coherence length of niobium and some studies using computer simulation of the formation of such multilayer nanostructures and their magnetic properties are presented in this article.

Adiabatic superconducting logic circuits can ensure the practical implementation of operations with the energy dissipation below the Landauer limit. However, applications of the existing solutions are limited because of two contradictory requirements of a high energy efficiency and a sufficiently fast response of devices. Josephson junctions with a negative critical current (π junctions) allow one to obtain a certain form of the potential energy of superconducting circuits and, as a result, a practically required degree of control of dynamic processes in the proposed reversible logic cells. The features of the current transport and balance of Josephson phases in circuits with π junctions make it possible to improve the coupling between the parts of a reversible computer by a factor more than 2. At the same time, the continuous evolution of the state is ensured at higher critical currents and higher characteristic voltages of the main Josephson junctions of adiabatic superconducting logic cells, which allows an increase in the response rate.

In this paper, we present a theoretical study of electronic transport in planar Josephson Superconductor–Normal Metal–Superconductor (SN-N-NS) bridges with arbitrary transparency of the SN interfaces. We formulate and solve the two-dimensional problem of finding the spatial distribution of the supercurrent in the SN electrodes. This allows us to determine the scale of the weak coupling region in the SN-N-NS bridges, i.e., to describe this structure as a serial connection between the Josephson contact and the linear inductance of the current-carrying electrodes. We show that the presence of a two-dimensional spatial current distribution in the SN electrodes leads to a modification of the current–phase relation and the critical current magnitude of the bridges. In particular, the critical current decreases as the overlap area of the SN parts of the electrodes decreases. We show that this is accompanied by a transformation of the SN-N-NS structure from an SNS-type weak link to a double-barrier SINIS contact. In addition, we find the range of interface transparency in order to optimise device performance. The features we have discovered should have a significant impact on the operation of small-scale superconducting electronic devices, and should be taken into account in their design.