Hasil untuk "Atomic physics. Constitution and properties of matter"

Taj Kumar, Aviral Kumar Pandey, Anand Kumar et al.

We propose a novel method for enhancing phase estimation in the displacement-assisted SU(1,1) [DSU(1,1)] interferometer by incorporating the photon recycling technique, evaluated under both single-intensity detection (SID) and homodyne detection (HD) schemes. Our analysis shows that utilizing the photon recycling technique, the photon-recycled DSU(1,1) interferometer performs better than the conventional DSU(1,1) interferometer under certain conditions. We also demonstrate that this improvement is achievable in both SID and HD schemes. In addition, to discuss the maximum sensitivity achieved by our proposed model, we have calculated the quantum Cramér–Rao bound (QCRB) within the framework and found that our proposed model approaches the QCRB. Therefore, we believe that our findings offer a promising new approach to improving phase sensitivity through photon recycling.

Zhaobo Liu, Xiaoming Shi, Jing Wang et al.

Abstract Ferroelectricity in crystalline hafnium oxide has attracted considerable attention because of its potential application for memory devices. A recent breakthrough involves electric-field-induced crystallization, allowing HfO2-based materials to avoid high-temperature crystallization, which is unexpected in the back-end-of-line process. However, due to the lack of clarity in understanding the mechanisms during the crystallization process, we aim to employ theoretical methods for simulation, to guide experimental endeavors. In this work, we extended our phase-field model by coupling the crystallization model and time-dependent Ginzburg-Landau equation to analyze the crystalline properties and the polarization evolution of Hf0.5Zr0.5O2 thin film under applying an electric field periodic pulse. Through this approach, we found a wake-up effect during the process of crystallization and a transformation from orthorhombic nano-domains to the stripe domain. Furthermore, we have proposed an innovative artificial neural synapse concept based on the continuous polarization variation under applied electric field pulses. Our research lays the theoretical groundwork for the advancement of electric-field-induced crystallization in the hafnium oxide system.

Aymeric Delteil

High-dimensional quantum units of information, or qudits, can carry more than one quantum bit of information in a single degree of freedom and can, therefore, be used to boost the performance of quantum communication and quantum computation protocols. A photon in a superposition of 2N time bins—a time-bin qudit—contains as much information as N qubits. Here, we show that N-qubit states encoded in a single time-bin qudit can be arbitrarily and deterministically generated, manipulated, and measured using a number of linear optics elements that scale linearly with N, as opposed to prior proposals of single-qudit implementation of N-qubit logic, which typically requires O(2N) elements. The simple and cost-effective implementation we propose can be used as a small-scale quantum processor. We then demonstrate a path toward scalability by interfacing distinct qudit processors to a matter qubit (atom or quantum dot spin) in an optical resonator. Such a cavity quantum electrodynamics system allows for more advanced functionalities, such as single-qubit nondemolition measurement and two-qubit gates between distinct qudits. It could also enable quantum interfaces with other matter quantum nodes in the context of quantum networks and distributed quantum computing.

Fabian Hader, Sarah Fleitmann, Jan Vogelbruch et al.

Quantum dots (QDs) must be tuned precisely to provide a suitable basis for quantum computation. A scalable platform for quantum computing can only be achieved by fully automating the tuning process. One crucial step is to trap the appropriate number of electrons in the QDs, typically accomplished by analyzing charge stability diagrams (CSDs). Training and testing automation algorithms require large amounts of data, which can be either measured and manually labeled in an experiment or simulated. This article introduces a new approach to the realistic simulation of such measurements. Our flexible framework enables the simulation of ideal CSD data complemented with appropriate sensor responses and distortions. We suggest using this simulation to benchmark published algorithms. Also, we encourage the extension by custom models and parameter sets to drive the development of robust technology-independent algorithms.

Wenjie Zhou, Jingfeng Liu, Juanfeng Zhu et al.

Single-photon sources based on plexcitonic systems are notable for their fast fluorescence rates, typically >100 GHz. Our investigations reveal that exceptional points (EPs) may unveil the quantum limit of fluorescence rates in plexcitonic single-photon sources. By employing a non-Hermitian Hamiltonian framework and field quantization model, we demonstrate how the fluorescence rate can be ingeniously designed in an exemplified plexcitonic system consisting of a nanocube-on-mirror cavity and a single quantum emitter. We predict the highest fluorescence rates of 11.0, 13.9, and 14.7 THz at the EPs with typical dipole moments of 25, 30, and 35 D, respectively.

Yu. M. Sinyukov, V. M. Shapoval, M. D. Adzhymambetov

In the present work, we combine and systemize the results of our recent research activity aiming to reveal the spatiotemporal structure of those extremely hot, dense, and rapidly expanding systems, which form in ultrarelativistic heavy ion collisions, as well as to reproduce in computer simulations the experimentally measured bulk observables. The latter include hadronic yields, particle number ratios, transverse momentum spectra, νn coefficients, and the femtoscopy scales, calculated for different collision energies within the integrated hydrokinetic model. We investigate how our simulation results depend on the model tuning, in particular, the utilized equation of state for quark-gluon matter and discuss the effect of the post-hydrodynamic stage of the system's evolution on the observables formation.

Rui Tang, Filippo Boi, Yi-Han Cheng

Abstract The recent observations of exotic quantum phenomena in AV3Sb5 (A = K, Rb, Cs) kagome superconductors have attracted significant attention in materials physics. Here, we propose an innovative two-frequencies laser model for ultrafast control of transient structural distortions. Using first-principles density functional theory in conjunction with the perturbative regime of nonlinear phononics, we investigate the nonharmonic potential energy, the crystal lattice dynamics and the topological properties of CsV3Sb5. We find that driving two infrared-active phonons of different frequencies promotes the desired Raman phonon vibrations, in which the displacement of Sb atoms is closely related to superconductivity. We demonstrate that the dimensional crossover and the topological nontrivial to trivial state transition of superconductor CsV3Sb5 can be triggered by ultrafast optical control. This work can be applied to other layered quantum materials and provide guidance for experiments related to photoinduced topology and superconductivity.

Si Jiang, Sirui Lu, Dong-Ling Deng

Abstract We study the robustness of machine learning approaches to adversarial perturbations, with a focus on supervised learning scenarios. We find that typical phase classifiers based on deep neural networks are extremely vulnerable to adversarial perturbations: adding a tiny amount of carefully crafted noises into the original legitimate examples will cause the classifiers to make incorrect predictions at a notably high confidence level. Through the lens of activation maps, we find that some important underlying physical principles and symmetries remain to be adequately captured for classifiers with even near-perfect performance. This explains why adversarial perturbations exist for fooling these classifiers. In addition, we find that, after adversarial training the classifiers will become more consistent with physical laws and consequently more robust to certain kinds of adversarial perturbations. Our results provide valuable guidance for both theoretical and experimental future studies on applying machine learning techniques to condensed matter physics.

S.-K. Bac, K. Koller, F. Lux et al.

Abstract Three-dimensional (3D) compensated MnBi2Te4 is antiferromagnetic, but undergoes a spin-flop transition at intermediate fields, resulting in a canted phase before saturation. In this work, we experimentally show that the anomalous Hall effect (AHE) in MnBi2Te4 originates from a topological response that is sensitive to the perpendicular magnetic moment and to its canting angle. Synthesis by molecular beam epitaxy allows us to obtain a large-area quasi-3D 24-layer MnBi2Te4 with near-perfect compensation that hosts the phase diagram observed in bulk which we utilize to probe the AHE. This AHE is seen to exhibit an antiferromagnetic response at low magnetic fields, and a clear evolution at intermediate fields through surface and bulk spin-flop transitions into saturation. Throughout this evolution, the AHE is super-linear versus magnetization rather than the expected linear relationship. We reveal that this discrepancy is related to the canting angle, consistent with the symmetry of the crystal. Our findings bring to light a topological anomalous Hall response that can be found in non-collinear ferromagnetic, and antiferromagnetic phases.

Jon Nelson, Marc Vuffray, Andrey Y. Lokhov et al.

As a wide variety of quantum computing platforms become available, methods for assessing and comparing the performance of these devices are of increasing interest and importance. Inspired by the success of single-qubit error rate computations for tracking the progress of gate-based quantum computers, this work proposes a quantum annealing single-qubit assessment (QASA) protocol for quantifying the performance of individual qubits in quantum annealing computers. The proposed protocol scales to large quantum annealers with thousands of qubits and provides unique insights into the distribution of qubit properties within a particular hardware device. The efficacy of the QASA protocol is demonstrated by analyzing the properties of a D-Wave 2000Q system, revealing unanticipated correlations in the qubit performance of that device. A study repeating the QASA protocol at different annealing times highlights how the method can be utilized to understand the impact of annealing parameters on qubit performance. Overall, the proposed QASA protocol provides a useful tool for assessing the performance of current and emerging quantum annealing devices.

L. A. Bulavin, T. V. Nagorna, D. Chudoba et al.

Results of studies of the cluster state of fullerenes C60 and C70 in a solution of toluene with acetonitrile, performed by small-angle neutron scattering are presented. The experiment has been carried out using the small-angle scattering spectrometer YuMO, located at the IBR-2 reactor of the Joint Institute for Nuclear Research (Dubna). It has shown that a content of acetonitrile in the solution is increased, the agglomerated fraction was increasing. Sharp tendency to aggregation was observed after the certain threshold value of acetonitrile concentration was exceeded. The processes of C60 and C70 fullerenes’ cluster formation were analyzed in comparison.

A. E. Borzakovskiy, T. V. Kovalinska, V. I. Sakhno et al.

Irradiation technology of big size polymer pellicles on the cyclotron U-120 of INR of NAS of Ukraine with α particles is described. Irradiation with α-particles and photons of high energies allows to produce nano-porous filter materials from new domestic polymers. The last ones have higher physical and mechanical indices and pro-vide obtaining nuclear membranes of enhanced strength. Technology is also improved on the stage of material sensitization.

Heung-Sik Kim, Hae-Young Kee

Condensed-matter physics: materials for Haldane model The topological Haldane model (FHM) on a honeycomb lattice describes a mechanism through which a quantum Hall effect can emerge as an intrinsic property from the band structure in the absence of an external magnetic field. Despite its simplicity, this model has proved to be challenging in the physical implementation. A team led by Hae-Young Kee at Canada’s University of Toronto proposed a way to search for realistic materials to experimentally realize the THM showing that effectively spinless fermion with complex next nearest neighbour hopping integrals can be found in ferromagnetic insulators with strong Hund’s coupling and finite spin orbital coupling. The authors suggest that a series of iron based honeycomb ferromagnetic insulators in the form of AFe2(PO4)2 (A=Ba, Cs, K and La) possess Chern bands featured by the THM. This work provides a playground for the identification of new correlated topological materials.

Institute for Nuclear Research

Brief biography and scientific achievements of Oleksandr Grygorovych Magner in relation with his 70-th anniversary

V. V. Talko, A. I. Lypska, I. P. Drozd et al.

Remote radiobiological effects in male rats prenatally exposed by 131I in different periods of gestation were studied. It was established that the negative effects of irradiation of 131I in utero in the distant period are manifested by disorders of the functioning of the pituitary-thyroid link of endocrine regulation, pro-antioxidant equilibrium, changes in the lipid-lipoprotein spectrum of blood serum. As a result of irradiation of 131I in utero throughout the period of gestation, discoordination in the functioning of the pituitary-thyroid link of endocrine regulation, a violation of the pro-antioxidant balance by increasing the intensity of lipoperoxidation processes and the activity reducing of enzymes of antioxidant defense, the atherogenic orientation of changes in the lipid-lipoprotein spectrum was established. As a result of irradiation by 131I in utero during the third trimester of gestation, the development of hypothyroidism, changes in pro-antioxidant balance due to the activation of antioxidant defense, and the reduction of the concentration of the main classes of lipids have been established.

Anonymous

V. F. Chekhun, E. A. Dyomina, M. O. Druzhyna et al.

New data on cytogenetic approximation of the experimental cytogenetic dependence "dose - effect" based on the spline regression model that improves biological dosimetry of human radiological exposure were received. This is achieved by reducing the error of the determination of absorbed dose as compared to the traditional use of linear and linear-quadratic models and makes it possible to predict the effect of dose curves on plateau.

E. S. Konobeevski, M. V. Mordovskoy, I. M. Sharapov et al.

We report preliminary results of a kinematically complete experiment on measurement of nd breakup reaction yield at neutron beam RADEX of Institute for Nuclear Research (Moscow, Russia). In the experiment two secondary neutrons are detected in geometry of neutron-neutron final-state interaction. Data are obtained at energy of incident neutrons En = 40 - 60 MeV for various divergence angles of two neutrons ΔΘ = 4, 6, 8º. 1S0 neutron-neutron scattering length ann were determined by comparison of the experimental dependence of reaction yield on the relative energy of two secondary neutrons with results of simulation depending on ann. For En = 40 MeV and ΔΘ = 6º (the highest statistics in the experiment) the value ann = -17.9 ± 1.0 fm is obtained. The further improving of accuracy of the experiment and more rigorous theoretical analysis will allow one to remove the existing difference in ann values obtained in different experiments.

S. N. Pelykh

Main features of a fuel element cladding state change mathematical model for a WWER-1000 reactor plant operated in the mode of varying loading are listed. The integrated model is based on the energy creep theory, uses the finite element method for imultaneous solution of the fuel element heat conduction and mechanical deformation equa-tions. Proposed mathematical model allows us to determine the influence of the WWER-1000 regime parameters and fuel assembly design characteristics on the change of cladding properties under different loading conditions of normal operation, as well as the cladding limiting state at variable loading depending on the length, depth and number of cycles.

Institute of Nuclear Research

Brief biography and scientific achievements of Georgii Dmytrovych Latyshev's 100 anniversary.