The low-temperature physics of structurally amorphous materials is governed by low-energy two-level system (TLS) defects. Being impervious to most traditional condensed matter probes, the exact origin and nature of TLS remain elusive. Recent advances toward realizing stable high-coherence quantum computing platforms have increased the importance of studying TLS in solid-state quantum circuits, as they are a persistent source of decoherence and instability. Here, performing scanning gate microscopy on a live superconducting NbN resonator at millikelvin temperatures, we locate individual TLS, directly revealing their microscopic nature. Mapping and visualizing the most detrimental TLS in the bath pinpoints the dominant sources of ubiquitous 1/f dielectric noise and energy relaxation. We also deduce the three-dimensional orientation of individual TLS electric dipole moments. Combining these insights with structural information of the underlying materials can help unravel the detailed microscopic nature and chemical origin of TLS, directing targeted strategies for their eventual mitigation.

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.

Abstract Synchronisation of the Bloch oscillations in a small Josephson junction (JJ) under the microwave radiation leading to the current quantisation at a current equal to Cooper-pair charge × frequency × integer has been proposed as the effect dual to the Shapiro steps. Experimental confirmation of this phenomenon was delayed for a long time until last year's breakthrough when the current quantisation was demonstrated in the superconducting nanowires. The compact high impedance environment of the nanowires played a key role in the experiment. Direct observation of the current quantization in the JJs would answer the fundamental question of the Bloch oscillations and open a more feasible road for the metrological application. Here we place JJs in the high impedance environment and demonstrate dual Shapiro steps for frequencies up to 24 GHz (I=7.7 nA). The current quantisation exists, however, only in a narrow range of JJ parameters, the critical current and capacitance. We carry out a systematic study to explain this by invoking the model of the JJ in presence of the thermal noise. The findings are important for the fundamental physics and application to quantum metrology.

Synchronization of Bloch oscillations in small Josephson junctions (JJs) under microwave radiation, which leads to current quantization, has been proposed as an effect that is dual to the appearance of Shapiro steps. This current quantization was recently demonstrated in superconducting nanowires in a compact high-impedance environment. Direct observation of current quantization in JJs would confirm the synchronization of Bloch oscillations with microwaves and help with the realisation of the metrological current standard. Here, we place JJs in a high-impedance environment and demonstrate dual Shapiro steps for frequencies up to 24 GHz (I = 7.7 nA). Current quantization exists, however, only in a narrow range of JJ parameters. We carry out a systematic study to explain this by invoking the model of a JJ in the presence of thermal noise. The findings are important for fundamental physics and application in quantum metrology. Josephson junctions are used for SQUIDs, voltage standards, and superconducting qubits. These applications are located at one corner of the device parameter space. Here, the authors shed light on the other corner and show the quantized current of Josephson junctions - dual to the quantized voltage.

The quantum Josephson voltage standard is well established across the metrology community for many years. It relies on the synchronisation of the flux tunneling in the S/I/S Josepson junctions (JJ) with the microwave radiation (MW). The phenomenon is called the Shapiro steps. Together with the Quantum Hall resistance standard, the voltage standard forms the foundation of electrostatic metrology. The current is then defined as the ratio of the voltage and resistance. Realisation of the quantum current standard, would close the electrostatic metrological triangle of voltage-resistance-current. The current quantisation, the inverse Shapiro steps, was recently shown using the superconducting nanowires and small JJ. The effect is a synchronization of the MW with the Cooper pair tunnelling. This paves the way to combine the JJ voltage and current standards on the same chip and demonstrate feasibility of the multi-standard operation. We show the voltage and current quantization on the same chip up to frequency of 10 GHz, corresponding to the amplitudes 0.021 mV and 3.23 nA respectively. The accuracy of the voltage and current quantisation, however, is relatively low, 35 ppk and 100 ppk respectively. We discuss measures to optimise the JJs, circuit and environment to boost the amplitude and accuracy of the standards.

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.

Grating couplers are widely used to couple waveguide modes with the far field. Their usefulness is determined not only by energy efficiency but also by additional supported functionality. In this paper, we demonstrate a plasmonic grating on a silicon nitride slab waveguide that couples both TE and TM waveguide modes with circularly polarized light in the far field. Specifically, we experimentally confirmed that circularly polarized light excites TE and TM modes propagating in opposite directions, and the direction is controlled by the handedness. The routing efficiency for normally incident light reaches up to 95%. The same structure operates in the outcoupling regime as well, demonstrating up to 97% degree of circular polarization, where the handedness is determined by the polarization and propagation direction of outcoupled modes. Our results pave the way for the realization of polarization-division multiplexers and demultiplexers, integrated circular polarization emitters, as well as detectors of the polarization state of the incident optical field.

We study operation of a superconducting quantum interference devices (SQUIDs) based on a new bilayer material. They can be used for the ultra-sensitive detection of magnetic momentum at temperatures down to milliKelvin range. Typically, thermal origin hysteresis of the symmetric SQUID current-voltage curves limits operating temperatures to T>0.6Tc. We used a new bilayer material for SQUID fabrication, namely proximity-coupled superconductor/normal-metal (S/N) bilayers (aluminum 25 nm/platinum 5 nm). Because of the 5 nm Pt-layer, Al/Pt devices show nonhysteretic behavior in a broad temperature range from 20 mK to 0.8 K. Furthermore, the Al/Pt bilayer devices demonstrate an order of magnitude lower critical current compared to the Al devices, which decreases the screening parameter (βL) and improves the modulation depth of the critical current by magnetic flux. Operation at lower temperatures reduces thermal noise and increases the SQUID magnetic field resolution. Moreover, we expect strong decrease of two-level fluctuators on the surface of aluminum due to Pt-layer oxidation protection and hence significant reduction of the 1/f noise. Optimized geometry of Al/Pt symmetric SQUIDs is promising for the detection of single-electron spin flip.

This work is devoted to the distribution of tasks in groups of unmanned aerial vehicles (UAVs) under conditions of a significant excess of the number of tasks over the number of agents. The main tasks solved by UAVs: survey and reconnaissance of territories, detection of dangerous objects or places of emergencies, search for victims, etc. The efficiency of solving the problems listed above achieved by the simultaneous use of a group of UAVs, the ele-ments (agents) of which can carry out the tasks of inspecting and scanning various areas of space in parallel. The article proposes an iterative method for distributing tasks in a group of UAVs with a significant excess of the num-ber of tasks over the number of agents (5-20 times). The proposed method for heterogeneous groups of UAVs based on a two-stage procedure for distributing agents of different specializations among task clusters, taking into account the agent's value function. At the first stage, the base part of the agents is distributed, the remaining agents at the second stage distributed in order to average the distance traveled by each agent. Execution of tasks within a cluster implemented by simulating annealing. To evaluate the effectiveness of the method variants, a comparison made with the greedy task distribution algorithm and the collective goal distribution algorithm. The analogs under consideration are widespread, universal and have a high convergence of the solution. Experimental studies car-ried out by computer simulation, where 2000 experiments carried out with various changes in the number of group agents and generation of a task map. The results showed the high efficiency of the task distribution method in terms of reducing the distance traveled by the agents of the UAV group when performing tasks in comparison with analogues. The efficiency of the path traveled by agents is up to 28% depending on the number of agents and tasks in the cluster, which is a scientific increment of the result of the study.

We demonstrate capacitive coupling of coherent quantum phase slip (CQPS) flux qubits to a resonator patterned on a highly disordered TiN film. We are able to detect and characterise CQPS flux qubits with linewidths down to Δ ω = 12 ± 1 MHz on several resonator modes, and show that, unlike inductive coupling, here the coupling strength does not depend on the qubit’s energy. Since the qubit is galvanically decoupled from the resonator, our approach provides flexibility in material, design and fabrication choices for CQPS-based devices. Our results are two-fold: we report CQPS in TiN and demonstrate, to our knowledge for the first time, capacitive coupling of a CQPS flux qubit.

The article presents a method for distributing tasks to agents of a heterogeneous UAV group in a cluster field of tasks, when the number of tasks exceeds the number of agents by 5–20 times. The proposed task distribution method based on a three-stage procedure for distributing agents of different specializations among task clusters, taking into account the agent value function. To evaluate the effectiveness, the method compared with the greedy task distribution algorithm, the collective plan improvement algorithm, and the consensus-based linking algorithm with local rescheduling. 2400 experiments were carried out with different group sizes and randomly generated task maps, the results of which revealed the high efficiency of the proposed method. According to the results of the study, a relationship found between the efficiency of the method depending on the concentration of the number of tasks per agent. With an increase in the specific number of tasks per agent, the task execution time improves and the indicator of the path traveled by agents worsens. With a ratio of 5–10 agents per 100 tasks, the method shows the best results in terms of the parameters of the path traveled by agents and task execution time.

Memristors are expected to form a major cornerstone in the upcoming renaissance of analog computing, owing to their very small spatial footprint and low power consumption. Due to the nature of their structure and operation, the response of a memristor is intrinsically tied to local variabilities in the device. This characteristic is amplified by currently employed semiconductor fabrication processes, which introduce spatial inhomogeneities into the structural fabric that makes up the layers of memristors. In this work, we propose a novel q-deformed current–voltage model for memristors based on the superstatistics framework, which allows the description of system-level responses while taking local variabilities into account. Applied on a Ag–Cu based synaptic memory cell, we demonstrate that our model has a 4%–14% lower error than currently used models. Additionally, we show how the resulting q-parameter can be used to make statements about the internal makeup of the memristor, giving insights to spatial inhomogeneities and quality control.

Twisted bilayer graphene (TBLG) has emerged as an exciting new material with tunable electronic properties ranging from superconductivity to correlated insulating phases. But current methods of fabrication and identification of TBLG are painstaking and laborious. In this work, we combine Raman spectroscopy with the Gaussian mixture model (GMM) data clustering algorithm to identify areas with particular twist angles, from a TBLG sample with a mixture of orientations. We present two approaches to this cluster analysis: training the GMM on Raman parameters returned by peak fits, and on full Raman spectra with dimensionality reduced by principal component analysis. In both cases we demonstrate that GMM can identify regions of distinct twist angle from within Raman datacubes. We also show that once a model has been trained, and the identified clusters labelled, the model can be reapplied to new Raman scans to assess the similarity between the materials in the new region and the testing region. This could enable high-throughput fabrication of TBLG, by allowing computerised detection of particular twist angles from automated large-area scans.

The purpose of this article is to evaluate the performance of the developed iterative method for distributing tasks in a swarm of UAVs in a clustered target field. This article presents an iterative method for distributing tasks among agents of a swarm of unmanned aerial vehicles (UAVs) in a clustered target field, when the number of tasks significantly exceeds the number of agents. The main tasks solved by UAVs are surveillance and reconnaissance, detection of dangerous objects or places of emergency, search for victims, etc. The efficiency of solving the problems listed above is achieved by the simultaneous use of a group of UAVs, the elements (agents) of which can carry out the tasks of inspecting and scanning various areas in parallel. At the same time, the number of tasks can significantly exceed the number of UAV swarm agents. To organize the work of a swarm of UAVs in this case, it is necessary to solve the problem of labor division, considering the conditions of the problem. The results showed the high efficiency of the proposed task distribution method according to the criterion of minimizing the travel distance of agents.

The operating principle of traveling-wave parametric amplifiers is typically understood in terms of the standard coupled mode theory, which describes the evolution of forward propagating waves without any reflections, i.e. for perfect impedance matching. However, in practice, superconducting microwave amplifiers are unmatched nonlinear finite-length devices, where the reflecting waves undergo complex parametric processes, not described by the standard coupled mode theory. Here, we present an analytical solution for the TWPA gain, which includes the interaction of reflected waves. These reflections result in corrections to the well-known results of the standard coupled mode theory, which are obtained for both 3-wave and 4-wave mixing processes. Due to these reflections, gain is enhanced and unwanted nonlinear phase modulations are suppressed. Predictions of the model are experimentally demonstrated on two types of unmatched TWPA, based on coplanar waveguides with a central wire consisting of i) a high kinetic inductance superconductor, and ii) an array of 2000 Josephson junctions.

Plasmonic metasurfaces form a convenient platform for light manipulation at the nanoscale due to their specific localized surface plasmons. Even despite high intrinsic Joule losses, plasmonic nanoparticles are very effective for light manipulation. Here, we show the lattice of plasmonic nanoparticles onto a dielectric waveguide that efficiently couples oppositely propagating guided modes to circularly polarized light beams of different handedness. We demonstrate 80% degree of circular polarization for the out-coupled emission of GaAs-waveguide-embedded quantum dots. The results allow us to consider the lattice as a circular-polarization-controlled grating coupler and make this structure prospective for further implementation as an efficient coupling interface for integrated devices.

Labor division in multi-robotic systems allows distributing tasks between agents in order to increase the efficiency of performing the global task.Collective decision-making methods allow agents to form the "agent-task" pairs.In this paper, we consider the case when the number of tasks significantly exceeds the number of agents.We propose an iterative method of labor division in multi-robotic systems.It uses collective decision-making to assign a cluster of subtasks to an agent.The paper examines different ratios between cluster size, number of clusters, and number of agents in order to find ratios that provide minimal average global task execution time and minimal average energy consumption.

The development of new types of technology actualizes the issues of ensuring their information security. The aim of the work is to increase the security of the collective decision-making process in swarm robotic systems from negative impacts by identifying malicious robots. It is proposed to use confidence in choosing an alternative when reaching a consensus as a criterion for identifying malicious robots - a malicious robot, having a special behavior strategy, does not fully take into account the signs of the external environment and information from other robots, which means that such a robot will change its mind with characteristic features for each malicious strategy, and its degree of confidence will be different from the usual voting robot. The modeling performed and the obtained experimental data on three types of malicious behavioral strategies demonstrate the possibility of using the degree of confidence to identify malicious robots. The advantages of the approach are taking into account a large number of alternatives and universality, which lies in the fact that the method is based on the mechanisms of collective decision-making, which proceed in the same way on various hardware platforms of swarm robotic systems. The proposed method can serve as a basis for the development of more complex security mechanisms in swarm robotic systems.

We report on development of an array of spectral sensitive detectors cooled down to 70 K by the compact cryocooler. The spectral sensitive operation of the detectors, explored between 0.16 THz and 0.22 THz, is due to the resonant excitation of the plasma waves in the two-dimensional electron gas of GaAs/AlGaAs heterostructure. A typical responsivity of the detectors is 0.01 A/W at 70 K while it increases by two orders of magnitude when the detector array is cooled down to 0.5 K. The photo-response has surprisingly a narrow peak of spectral sensitivity, $$\sim$$ 2–5%, which are highly likely due to the dimensional resonances of the plasma waves. As a demonstration of the spectral sensitive operation we detect a spectral feature of LiNbO $$_{3}$$ crystal at 0.174 THz.