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

Yue Qin, Chester Shu, Hon Ki Tsang

Quantum frequency combs (QFCs) are essential to quantum photonic systems, enabling high dimensional entanglement in both temporal and frequency domains. Silicon photonics offers a promising platform for scalable and monolithic quantum photonic integrated circuits. However, its performance in QFC generation has been hindered by nonlinear losses and restricted phase-matching bandwidth. To overcome these challenges, we introduce a novel design strategy that combines high-order spatial mode engineering with an optimized free-carrier loss suppression structure in a silicon micro-ring resonator. This approach enables a broadband QFC spanning 150 nm, along with a high single pair photon brightness of 6.43 × 109 Hz/mW2/GHz and photon efficiency of 19.9 GHz/mW2 with the collection of 11 frequency bins. The generated QFCs produce heralded single photons with low heralded second-order correlation gh20=0.0024 and energy-time entangled photon pairs with high visibility of 98.19%. Consistent performance across wafer-scale multiple dies confirms the robustness and manufacturability of the designed device. This work establishes a scalable and high-yield pathway toward monolithic quantum photonic integrated circuits.

Yosuke Ueno, Satoshi Imamura, Yuna Tomida et al.

Cryogenic quantum computers play a leading role in demonstrating quantum advantage. Given the severe constraints on the cooling capacity in cryogenic environments, thermal design is crucial for the scalability of these computers. The sources of heat dissipation include passive inflow via intertemperature wires and the power consumption of components located in the cryostat, such as wire amplifiers and quantum–classical interfaces. Thus, a critical challenge is to reduce the number of wires by reducing the required intertemperature bandwidth while maintaining minimal additional power consumption in the cryostat. One solution to address this challenge is near-data processing using ultralow-power computational logic within the cryostat. Based on the workload analysis and domain-specific system design focused on variational quantum algorithms (VQAs), we propose the cryogenic counter-based coprocessor for VQAs (C3-VQA) to enhance the design scalability of cryogenic quantum computers under the thermal constraint. The C3-VQA utilizes single-flux-quantum logic, which is an ultralow-power superconducting digital circuit that operates at the 4 K environment. The C3-VQA precomputes a part of the expectation value calculations for VQAs and buffers intermediate values using simple bit operation units and counters in the cryostat, thereby reducing the required intertemperature bandwidth with small additional power consumption. Consequently, the C3-VQA reduces the number of wires, leading to a reduction in the total heat dissipation in the cryostat. Our evaluation shows that the C3-VQA reduces the total heat dissipation at the 4 K stage by 30% and 81% under sequential-shot and parallel-shot execution scenarios, respectively. Furthermore, a case study in quantum chemistry shows that the C3-VQA reduces total heat dissipation by 87% with a 10 000-qubit system.

Alexander Hampel, Peitao Liu, Cesare Franchini et al.

Daiji Kato, Masaomi Tanaka, Gediminas Gaigalas et al.

Lanthanides play most important roles in the opacities for kilonova, ultraviolet-optical-infrared emission from neutron star mergers. Although several efforts have been made to construct atomic data, the accuracy in the opacity is not fully assessed and understood. In this paper, we perform atomic calculations for singly ionized lanthanides with improved strategies, aiming at understanding the physics of the lanthanide opacities in kilonova ejecta and necessary accuracy in atomic data. Our results show systematically lower energy level distributions as compared with our previous study (Paper I). As a result, the opacities evaluated with our new results are higher by a factor of up to 3 - 10, depending on the element and wavelength range. For a lanthanide-rich element mixture, our results give a higher opacity than that in Paper I by a factor of about 1.5. We also present opacities by using the results of ab-initio atomic calculations by using Grasp2K code. In general, our new opacities show good agreements with those with ab-initio calculations. We identify that structure of the lanthanide opacities are controlled by transition arrays among several configurations, for which derivation of accurate energy level distribution is important to obtain reliable opacities.

Benjamin Elder, Giorgio Mentasti, Elizabeth Pasatembou et al.

Wide classes of new fundamental physics theories cause apparent variations in particle mass ratios in space and time. In theories that violate the weak equivalence principle (EP), those variations are not uniform across all particles and may be detected with atomic and molecular clock frequency comparisons. In this work we explore the potential to detect those variations with near-future clock comparisons. We begin by searching published clock data for variations in the electron-proton mass ratio. We then undertake a statistical analysis to model the noise in a variety of clock pairs that can be built in the near future according to the current state of the art, determining their sensitivity to various fundamental physics signals. Those signals are then connected to constraints on fundamental physics theories that lead directly or indirectly to an effective EP-violating, including those motivated by dark matter, dark energy, the vacuum energy problem, unification or other open questions of fundamental physics. This work results in projections for tight new bounds on fundamental physics that could be achieved with atomic and molecular clocks within the next few years. Our code for this work is packaged into a forecast tool that translates clock characteristics into bounds on fundamental physics.

Ramesh Dhakal, Samuel Griffith, Stephen M. Winter

Abstract FePS3 is a layered van der Waals (vdW) Ising antiferromagnet that has recently been studied in the context of true 2D magnetism and emerged as an ideal material platform for investigating strong spin-phonon coupling, and non-linear magneto-optical phenomena. In this work, we demonstrate an important unresolved role of spin-orbit coupling (SOC) in the ground state and excitations of this compound. Combining first-principles calculations with linear flavor wave theory (LFWT), we find strong mixing and spectral overlap of different spin-orbital single-ion states. Low-lying excitations form hybrid spin-orbit exciton/magnon modes. Complete parameterization of the low-energy model requires nearly half a million coupling constants. Despite this complexity, such a model can be inexpensively derived using local many-body-based approaches, which yield quantitative agreement with recent experiments. The results highlight the importance of SOC even in first-row transition metals and provide essential insight into the properties of 2D magnets with unquenched orbital moments.

Max Hirschberger, Bertalan G. Szigeti, Mamoun Hemmida et al.

Abstract Skyrmion lattices (SkL) in centrosymmetric materials typically have a magnetic period on the nanometer-scale, so that the coupling between magnetic superstructures and the underlying crystal lattice cannot be neglected. We reveal the commensurate locking of a SkL to the atomic lattice in Gd3Ru4Al12 via high-resolution resonant elastic x-ray scattering (REXS). Weak easy-plane magnetic anisotropy, demonstrated here by a combination of ferromagnetic resonance and REXS, penalizes placing a skyrmion core on a site of the atomic lattice. Under these conditions, a commensurate SkL, locked to the crystal lattice, is stable at finite temperatures – but gives way to a competing incommensurate ground state upon cooling. We discuss the role of Umklapp-terms in the Hamiltonian for the formation of this lattice-locked state, its magnetic space group, and the role of slight discommensurations, or (line) defects in the magnetic texture. We also contrast our findings with the case of SkLs in noncentrosymmetric material platforms.

Marco Antonio Barroca, Rodrigo Neumann Barros Ferreira, Mathias Steiner

Direct air capture (DAC) of carbon dioxide is a promising method for mitigating climate change. Solid sorbents, such as metal–organic frameworks, are currently being tested for DAC application. However, their potential for deployment at scale has not been fully realized. The computational discovery of solid sorbents is challenging, given the vast chemical search space and the DAC requirements for molecular selectivity. Quantum computing can potentially accelerate the discovery of solid sorbents for DAC by predicting molecular binding energies. In this work, we explore algorithms for predicting gas adsorption in metal–organic frameworks using a quantum computer. In particular, we simulate the potential energy surfaces of CO2, N2, and H2O molecules at the Mg+2 metal center that represents the binding sites of typical metal–organic frameworks. We apply the qubit-ADAPT-VQE technique to run simulations on both classical and quantum computing hardware and achieve reasonable accuracy while maintaining hardware efficiency.

J. L. Figueiredo, J. T. Mendonça, H. Terças

A rigorous treatment of light-matter interactions typically requires an interacting quantum field theory. However, most applications of interest are handled using classical or semiclassical models, which are valid only when quantum-field fluctuations can be neglected. This approximation breaks down in scenarios involving large light intensities or degenerate matter, where additional quantum effects become significant. In this work, we address these limitations by developing a quantum kinetic framework that treats both light and matter fields on equal footing, naturally incorporating both linear and nonlinear interactions. To accurately account for light fluctuations, we introduce a photon distribution function that, together with the classical electromagnetic fields, provides a better description of the photon fluid. From this formalism, we derive kinetic equations from first principles that recover classical electrodynamical results while revealing couplings that are absent in the corresponding classical theory. Furthermore, by addressing the Coulomb interaction in the Hartree-Fock approximation, we include the role of fermionic exchange exactly in both kinetic and fluid regimes through a generalized Fock potential. The latter provides corrections not only to the electrostatic forces but also to the plasma velocity fields, which become significant in degenerate conditions.

Ping Wang, Zheng Feng, Yuhe Yang et al.

Abstract The Orbital Hall effect, which originates from materials with weak spin-orbit coupling, has attracted considerable interest for spin-orbitronic applications. Here, we demonstrate the inverse effect of the orbital Hall effect and observe orbitronic terahertz emission in the Ti and Mn materials. Through spin-orbit transition in the ferromagnetic layer, the generated orbital current can be converted to charge current in the Ti and Mn layers via the inverse orbital Hall effect. Furthermore, the inserted W layer provides an additional conversion of the orbital-charge current in the Ti and Mn layers, significantly enhancing the orbitronic terahertz emission. Moreover, the orbitronic terahertz emission can be manipulated by cooperating with the inverse orbital Hall effect and the inverse spin Hall effect in the different sample configurations. Our results not only discover the physical mechanism of condensed matter physics but also pave the way for designing promising spin-orbitronic devices and terahertz emitters.

Florian Beißer, Dennis Haag, Rafael Ballabriga et al.

Eye lens dosimetry has been an important field of research in the last decade. Dose measurements with a prototype of an active personal eye lens dosemeter based on the Dosepix detector are presented. The personal dose equivalent at $3\,$mm depth of soft tissue, $H_\text{p}(3)$, was measured in the center front of a water-filled cylinder phantom with a height and diameter of $20\,$cm. The energy dependence of the normalized response is investigated for mean photon energies between $12.4\,$keV and $248\,$keV for continuous reference radiation fields (N-series) according to ISO 4037. The response normalized to N-60 ($\overline{E}=47.9\,\text{keV}$) at $0^\circ$ angle of irradiation stays within the approval limits of IEC 61526 for angles of incidence between $-75^\circ$ and $+75^\circ$. Performance in pulsed photon fields was tested for varying dose rates from $0.1\,\frac{\text{Sv}}{\text{h}}$ up to $1000\,\frac{\text{Sv}}{\text{h}}$ and pulse durations from $1\,\text{ms}$ up to $10\,\text{s}$. The dose measurement works well within the approval limits (acc. to IEC 61526) up to $1\,\frac{\text{Sv}}{\text{h}}$. No significant influence of the pulse duration on the measured dose is found. Reproducibility measurements yield a coefficient of variation which does not exceed $1\,\%$ for two tested eye lens dosemeter prototypes.

Michele Grossi, Noelle Ibrahim, Voica Radescu et al.

This article presents a first end-to-end application of a quantum support vector machine (QSVM) algorithm for a classification problem in the financial payment industry using the IBM Safer Payments and IBM Quantum Computers via the Qiskit software stack. Based on real card payment data, a thorough comparison is performed to assess the complementary impact brought in by the current state-of-the-art quantum machine-learning algorithms with respect to the classical approach. A new method to search for best features is explored using the QSVM's feature map characteristics. The results are compared using fraud-specific key performance indicators, i.e., accuracy, recall, and false positive rate, extracted from analyses based on human expertise (such as rule decisions), classical machine-learning algorithms (such as random forest and XGBoost), and quantum-based machine-learning algorithms using QSVM. In addition, a hybrid classical–quantum approach is explored by using an ensemble model that combines classical and quantum algorithms to better improve the fraud prevention decision. We found, as expected, that the results highly depend on feature selections and algorithms that are used to select them. The QSVM provides a complementary exploration of the feature space that led to an improved accuracy of the mixed quantum-classical method for fraud detection, on a drastically reduced dataset to fit current state of quantum hardware.

Dante M. Kennes, Martin Claassen, Lede Xian et al.

Twisted van der Waals heterostructures have latterly received prominent attention for their many remarkable experimental properties, and the promise that they hold for realising elusive states of matter in the laboratory. We propose that these systems can, in fact, be used as a robust quantum simulation platform that enables the study of strongly correlated physics and topology in quantum materials. Among the features that make these materials a versatile toolbox are the tunability of their properties through readily accessible external parameters such as gating, straining, packing and twist angle; the feasibility to realize and control a large number of fundamental many-body quantum models relevant in the field of condensed-matter physics; and finally, the availability of experimental readout protocols that directly map their rich phase diagrams in and out of equilibrium. This general framework makes it possible to robustly realize and functionalize new phases of matter in a modular fashion, thus broadening the landscape of accessible physics and holding promise for future technological applications.

V. P. Krasnov, V. V. Melnik, T. V. Kurbet et al.

Results of many years of the research on 137Cs accumulation of Lily of the valley (Convallaria majalis L.) in the above-ground phytomass in wet sugrudy of the mixed forests of Zhytomyr Polissia are presented. The radionuclide specific activity in Lily of the valley decreased by 11.1 - 17.3 times during the observation period (1991 - 2018). The increase of this indicator was revealed in certain years and periods, which is possibly due to weather conditions of particular year and cyclic migration of 137Cs in forest biogeocoenosis. The dependence between the density of 137Cs radioactive contamination of soil and the content of radionuclide in grass as well as in common inflorescences of Lily of the valley is revealed.

А. Т. Rudchik, А. А. Rudchik, О. E. Kutsyk et al.

The 12С(15N, 14С)13N reaction at the energy Еlab(15N) = 81 MeV for ground and excited states of 14С and 13N nuclei was investigated. New experimental data of the reaction cross-sections were obtained. The data were analyzed within the coupled reaction channels method (CRC). The 15N + 12С elastic scattering as well as the more important reactions of nucleon and cluster transfers were included in the channels-coupling scheme. In the CRC-calculations, the Woods - Saxon potentials (WS) were used for the interactions of 15N + 12С and 14С + 13N nuclei in the entrance and exit reaction channels. WS potential parameters for the reaction entrance channel were deduced previously from CRC-analysis of the 15N + 12С elastic and inelastic scattering data, then the WS potential parameters for the reaction exit channel were deduced from the fitting of 12С(15N, 14С)13N reaction data. The spectroscopic amplitudes of nucleons and clusters, used in the CRC-calculations, were computed within translational invariant shell model. As the results of the reaction CRC-analysis, the information about WS potential of 14С + 13N nuclei interaction as well as about mechanisms of nucleons and clusters transfer was deduced. It was found, that transfers of protons and 2n-clusters dominate in this reaction. It was also studied the differences of the reaction CRC cross-sections calculated using the 14С + 13N і 14С + 14N potentials in the reaction exit channel (isotopic effects).

Per Hyldgaard, Yang Jiao, Vivekanand Shukla

We review the screening nature and many-body physics foundation of the van der Waals density functional (vdW-DF) method, a systematic approach to construct truly nonlocal exchange-correlation energy density functionals. To that end we define and focus on a class of consistent vdW-DF versions that adhere to the Lindhard screening logic of the full method formulation. The consistent-exchange vdW-DF-cx version and its spin extension represent the first examples of this class; In general, consistent vdW-DFs reflect a concerted expansion of a formal recast of the adiabatic-connection formula, an exponential summation of contributions to the local-field response, and the Dyson equation. We argue that the screening emphasis is essential because the exchange-correlation energy reflects an effective electrodynamics set by a long-range interaction. Two consequences are that 1) there are, in principle, no wiggle room in how one balances exchange and correlation, for example, in vdW-DF-cx, and that 2) consistent vdW-DFs have a formal structure that allows them to incorporate vertex-correction effects, at least in the case of levels that experience recoil-less interactions (for example, near the Fermi surface). We explore the extent to which the strictly nonempirical vdW-DF-cx formulation can serve as a systematic extension of the constraint-based semilocal functionals. For validation, we provide a complete survey of vdW-DF-cx performance for broad molecular processes and comparing to the quantum-chemistry calculations that are summarized in that paper. We also provide new vdW-DF-cx results for metal surface energies and work functions that we compare to experiment. Finally, we use the screening insight to separate the vdW-DF nonlocal-correlation term and present tools to compute and map the binding signatures.

Fa Peng Huang

Motivated by the absence of dark matter signal in dark matter direct detection experiments and new physics signal at LHC, we study how to hear the echoes of the new physics, especially the dark matter and baryogenesis by new approaches, such as the gravitational wave experiments.

Daniel Mayer, Felix Schmidt, Daniel Adam et al.

We report on the experimental doping of a $^{87}$Rubidium (Rb) Bose-Einstein condensate (BEC) with individual neutral $^{133}$Cesium (Cs) atoms. We discuss the experimental tools and procedures to facilitate Cs-Rb interaction. First, we use degenerate Raman side-band cooling of the impurities to enhance the immersion efficiency for the impurity in the quantum gas. We identify the immersed fraction of Cs impurities from the thermalization of Cs atoms upon impinging on a BEC, where elastic collisions lead to a localization of Cs atoms in the Rb cloud. Second, further enhancement of the immersion probability is obtained by localizing the Cs atoms in a species-selective optical lattice and subsequent transport into the Rb cloud. Here, impurity-BEC interaction is monitored by position and time resolved three-body loss of Cs impurities immersed into the BEC. This combination of experimental methods allows for the controlled doping of a BEC with neutral impurity atoms, paving the way to impurity aided probing and coherent impurity-quantum bath interaction.

O. V. Mikhailov

Version of the origin of material metallic impurities in silicate matrix of lava-like fuel-containing masses (LFCM), which were formed during the Chernobyl Unit 4 accident, is presented. Based on comparative quantitative characteristics of observable mass ratios of iron, chromium and nickel in different LFCM clusters and potential sources of their appearance - metal structures, the degree of impact of various factors on the formation of metal components in Chernobyl corium (MCC) was given. It was concluded that initial MCC composition was formed on the basis of 08X18H10T stainless steel melt, from which the elements of fuel channel structure and lower water pipelines were manufactured.

Hongli Guo, Shruba Gangopadhyay, Okan Köksal et al.

Condensed Matter Physics: quantised Hall transport in two dimensional magnetic insulators Simulations predict a Chern insulating state with quantized anomalous Hall transport in insulators without an applied magnetic field. These strongly correlated systems are designed based on transition metal oxides, unlike existing weakly correlated electron-based examples whose bulk conduction masks surface currents. An international team led by Warren Pickett at the University of California Davis designed the materials based on a buckled honeycomb lattice. By tuning spin, orbital, charge, and lattice degrees of freedom as well as strain, they predict robust ruthenium and osmium bilayers with conducting boundary states, while retaining a bulk bandgap of up to 130 meV. These properties, topologically protected by electronic entanglement, provide promise of applications in next generation electronics and possibly quantum computing. These systems offer more robust platforms than previously suggested and guide experimental synthesis to exploit these emergent phenomena.