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

Yaniv Kurman, Lior Ella, Ramon Szmuk et al.

Reaching fault-tolerant quantum computation relies on the successful implementation of non-Clifford circuits with quantum error correction (QEC). In QEC, quantum gates and measurements encode quantum information into an error-protected Hilbert space, while classical processing decodes the measurements into logical errors. QEC non-Clifford gates pose the greatest computation challenge from the classical controller's perspective, as they require mid-circuit decoding-dependent feed-forward—modifying the physical gate sequence based on the decoding outcome of previous measurements within the same circuit. In this work, we introduce the first benchmarks to holistically evaluate the capability of a combined controller–decoder system to run non-Clifford QEC circuits. We show that executing an error-corrected non-Clifford circuit, comprised of numerous non-Clifford gates, strictly hinges upon the classical controller–decoder system. Particularly, its ability to perform decoding-based feed-forward with low latency, defined as the time between the last measurement required for decoding and the dependent mid-circuit quantum operation. We analyze how the system's latency dictates the circuit's operational regime: latency divergence, classical-controller-limited runtime, or quantum-operation-limited runtime. Based on this understanding, we introduce latency-based benchmarks to set a standard for developing QEC control systems as the essential components of fault-tolerant quantum computation.

Institute for Nuclear Research

Brief biography and scientific achievements of Leonid Anatoliyovych Bulavin in relation with his 80-th anniversary.

Satoshi Okamoto, Naoto Nagaosa

Abstract The spin Hall (SH) effect, the conversion of the electric current to the spin current along the transverse direction, relies on the relativistic spin-orbit coupling (SOC). Here, we develop a microscopic theory on the mechanisms of the SH effect in magnetic metals, where itinerant electrons are coupled with localized magnetic moments via the Hund exchange interaction and the SOC. Both antiferromagnetic metals and ferromagnetic metals are considered. It is shown that the SH conductivity can be significantly enhanced by the spin fluctuation when approaching the magnetic transition temperature of both cases. For antiferromagnetic metals, the pure SH effect appears in the entire temperature range, while for ferromagnetic metals, the pure SH effect is expected to be replaced by the anomalous Hall effect below the transition temperature. We discuss possible experimental realizations and the effect of the quantum criticality when the antiferromagnetic transition temperature is tuned to zero temperature.

Nafis Irtija, Jim Plusquellic, Eirini Eleni Tsiropoulou et al.

Electronic control systems used for quantum computing have become increasingly complex as multiple qubit technologies employ larger numbers of qubits with higher fidelity target. Whereas the control systems for different technologies share some similarities, parameters, such as pulse duration, throughput, real-time feedback, and latency requirements, vary widely depending on the qubit type. In this article, we evaluate the performance of modern system-on-chip (SoC) architectures in meeting the control demands associated with performing quantum gates on trapped-ion qubits, particularly focusing on communication within the SoC. A principal focus of this article is the data transfer latency and throughput of several high-speed on-chip mechanisms on Xilinx multiprocessor SoCs, including those that utilize direct memory access (DMA). They are measured and evaluated to determine an upper bound on the time required to reconfigure a gate parameter. Worst-case and average-case bandwidth requirements for a custom gate sequencer core are compared with the experimental results. The lowest variability, highest throughput data-transfer mechanism is DMA between the real-time processing unit (RPU) and the programmable logic, where bandwidths up to 19.2 GB/s are possible. For context, this enables the reconfiguration of qubit gates in less than 2 <inline-formula><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>s, comparable to the fastest gate time. Though this article focuses on trapped-ion control systems, the gate abstraction scheme and measured communication rates are applicable to a broad range of quantum computing technologies.

Wei-Chen Chien, Yu-Han Chang, Cheng Xin Lu et al.

Ultra-thin superconducting aluminum films of 3-nm grown on sapphire by molecule-beam epitaxy show excellent superconductivity and large kinetic inductance. This results in a record high Kerr non-linearity of 33 kHz and 3.62 MHz per photon in notch-type and transmission-type resonators, respectively. 4-wave mixing leverages this non-linearity to achieve 12 dB parametric amplification in transmission type resonator, making the ultra-thin film ideal for photon detection and amplification applications.

F. Mazzola, C. -M. Yim, V. Sunko et al.

Abstract Controlling spin wave excitations in magnetic materials underpins the burgeoning field of magnonics. Yet, little is known about how magnons interact with the conduction electrons of itinerant magnets, or how this interplay can be controlled. Via a surface-sensitive spectroscopic approach, we demonstrate a strong electron–magnon coupling at the Pd-terminated surface of the delafossite oxide PdCoO2, where a polar surface charge mediates a Stoner transition to itinerant surface ferromagnetism. We show how the coupling is enhanced sevenfold with increasing surface disorder, and concomitant charge carrier doping, becoming sufficiently strong to drive the system into a polaronic regime, accompanied by a significant quasiparticle mass enhancement. Our study thus sheds light on electron–magnon interactions in solid-state materials, and the ways in which these can be controlled.

Ádám Butykai, Korbinian Geirhos, Dávid Szaller et al.

Abstract In polar magnets, such as GaV4S8, GaV4Se8 and VOSe2O5, modulated magnetic phases namely the cycloidal and the Néel-type skyrmion lattice states were identified over extended temperature ranges, even down to zero Kelvin. Our combined small-angle neutron scattering and magnetization study shows the robustness of the Néel-type magnetic modulations also against magnetic fields up to 2 T in the polar GaMo4S8. In addition to the large upper critical field, enhanced spin-orbit coupling stabilize cycloidal, Néel skyrmion lattice phases with sub-10 nm periodicity and a peculiar distribution of the magnetic modulation vectors. Moreover, we detected an additional single-q state not observed in any other polar magnets. Thus, our work demonstrates that non-centrosymmetric magnets with 4d and 5d electron systems may give rise to various highly compressed modulated states.

Je-Ho Lee, Youngsu Choi, Seung-Hwan Do et al.

Abstract The van der Waals Kitaev magnet α-RuCl3 has recently garnered considerable attention due to its possible realization of topological spin liquids. Combining Raman spectroscopy with numerical calculations, we report here the thickness dependence of electronic structure and ensuing low-energy excitations for exfoliated α-RuCl3. We observe two pronounced peaks at A1 = 249 meV and A2 = 454 meV, which are assigned to single and double spin-orbit (SO) excitons, respectively. Our numerical calculations support this interpretation by reproducing their spectral energy and shape with the electronic parameters: SO coupling λ = 140 meV, Hund’s coupling J H = 350 meV, and on-site Coulomb interaction U = 2.35 eV. The multiple SO excitons persist down to a single layer, whereas their peaks shift slightly to lower energy. For frequencies below 350 cm−1, both a magnetic continuum and phonons show noticeable thickness dependence. These results demonstrate that a SO entangled j eff = 1/2 picture remains valid in a monolayer limit despite the presence of lattice distortions.

M. Horio, Q. Wang, V. Granata et al.

Abstract Electronic band structures in solids stem from a periodic potential reflecting the structure of either the crystal lattice or electronic order. In the stoichiometric ruthenate Ca3Ru2O7, numerous Fermi surface-sensitive probes indicate a low-temperature electronic reconstruction. Yet, the causality and the reconstructed band structure remain unsolved. Here, we show by angle-resolved photoemission spectroscopy, how in Ca3Ru2O7 a C 2-symmetric massive Dirac semimetal is realized through a Brillouin-zone preserving electronic reconstruction. This Dirac semimetal emerges in a two-stage transition upon cooling. The Dirac point and band velocities are consistent with constraints set by quantum oscillation, thermodynamic, and transport experiments, suggesting that the complete Fermi surface is resolved. The reconstructed structure—incompatible with translational-symmetry-breaking density waves—serves as an important test for band structure calculations of correlated electron systems.

I. M. Maloshtan, S. V. Polishchuk, Yu. V. Khomutinin

Results of the small-field experimental study of the dynamics of biological availability of freshly added standard radioactive solution of 137Cs in peat-bog soil are presented. The initial values of the 137Cs concentration ratios CR(t) and transfer factors TF(t), in the aboveground phytomass of natural meadow grass vegetation in peat-bog soils in the real soil-climatic conditions of Western Polissya were determined. Based on the results of the field and laboratory studies, the values of fast and slow periods of the ecological half-reduction (Tfe and Tse, respectively) of CR and TF of radioactive cesium in the studied soils were estimated. The model for prediction of the dynamics of CR and TF of radioactive cesium into natural meadow grass vegetation from peat-bog soils with its abnormal high biological availability was proposed.

Luca Amendola, Stephen Appleby, Anastasios Avgoustidis et al.

Abstract Euclid is a European Space Agency medium-class mission selected for launch in 2020 within the cosmic vision 2015–2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. Euclid will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and red-shifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky. Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis. This review has been planned and carried out within Euclid’s Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission.

D. M. Holiaka, S. E. Levchuk, V. P. Protsak et al.

Using the calculated values for wood samples (relative diameter, height and relative activity concentration of 137Cs) selected in different parts of the profile tree stems, statistical and graphical interpretation of the regularity of the distribution of 137Cs in the wood of model trees of Scots pine were performed. In the research, detected observation uniformity of samples in the studied profiles stems for the relative activity concentration of 137Cs, calculated on the base of the ratio of the activity concentration of tree rings for certain years to their median at height of 1.3 m. Three intervals of the relative diameters for stem wood of model trees at height of 1.3 m of the study stand were obtained, that is characterized by significant difference on the activity concentration of 137Cs: d(ω)1.3m ≤ 0.55 (Am(ω) = 0.63 ± 0.08); 0.55 < d(ω)1.3m ≤ 0.95 (Am(ω) = 1.01 ± 0.04); 0.95 < d(ω)1.3m ≤ 1.0 (Am(ω) = 2.1 ± 0.5).

M. V. Zheltonozhska, N. V. Kulich, A. I. Lypska et al.

Nonradiochemical method of measurement of 90Sr and137Cs activity in environmental samples is proposed. This method is based on spectrometrical investigation of electrons accompanied the decay of the 90Sr and137Cs. Accounting for the contribution to the total activity of the samples from the zones with the density of the contamination 1 - 5 Кu/km2 the 40K electrons allowed to improve the accuracy of the measurements for the samples of small rodents up to 15 - 20 % (the ratio of A (137Cs)/A (90Sr) was from 2 to 100), for samples of soil up to 10 - 15 % (the change of activity in these samples was ten thousand times). The results of the spectrometric measurements were confirmed by the traditional radiochemical research.

L. S. Pirnach

The second part of complex research of the Chernobyl cooling pond bottom sediments are presented Data about vertical distribution of radioactive pollution 137Cs, 241Am, 90Sr in a solid phase of sediments are received. Distribution coefficients 137Cs and 90Sr, selectivity coefficients of their exchange with similar cations and physical-chemical forms are defined. Results of research of radionuclide chemical recovery from the sediment samples are analyzed.

O. M. Volkova, V. V. Belyaev, O. L. Zarubin et al.

Formation of absorbed dose for different species of fishes Kanev reservoir from incorporated radionuclides, water and sediment was studied. The distinct migratory behavior of fish and the spatial distribution of radionuclides in bottom area were considered. The absorbed radiation dose per year of fish ranged from 170 to 1300 mGy/year.

A. I. Levon, G. Graw, Y. Eisermann et al.

The excitation spectra in the deformed nucleus 230Th were studied by means of the (p, t) reaction, using the Q3D spectrograph facility at the Munich Tandem accelerator. The angular distributions of tritons are measured for about 200 excitations seen in the triton spectra up to 3.3 MeV. Firm 0+ assignments are made for 16 excited states by comparison of experimental angular distributions with the calculated ones using the CHUCK3 code and relatively firm - for 4 states. Assignments up to spin 6+ are made for other states. Analysis of the obtained data will be presented in forthcoming paper.

I. E. Anokhin, O. S. Zinets

The possibility of using the silicon strip-detector coated with a polyethylene film for the coordinate determination of fast neutrons has been discussed. The accuracy of the fast neutron coordinate determination is dependent on peculiarities of the interaction of neutrons with polyethylene and the accuracy of the registration of the recoil protons produced by fast neutrons in a polyethylene film, i.e. energies and angular distributions of the recoil protons and characteristics of tracks produced in the detector. The average charge collected on strips as a function of coordinates of incident neutrons has been calculated. It is shown that the most important for the best charge collection and accuracy of the coordinate determination is the choice of the interstrip distance. The other factors influencing on the coordinate determination (the distribution of the electrical field in the detector, the ratio of the track length to the interstrip distance) have been discussed.

A. T. Rudchik, Yu. O. Shyrma, E. I. Koshchy et al.

Angular distributions of the 12C + 18O elastic and inelastic scattering were measured at the energy Elab(18O) = 105 MeV (Ec.m. = 42 MeV). These data and data known from the literature at the energies Ec.m. = 12.9 - 56 МеV were analysed within the optical model and coupled-reactionchannels method. The sets of the Woods-Saxon (12С + 18O)-potential parameters were deduced and their energy dependence was studied. It was found the isotopic differences in the (12С + 16O)- and (12С + 18O)-potentials parameters and in their surface forms. The mechanisms of elastic and inelastic (12С + 18O)-scattering and role of transfer reactions were studied.

V. V. Levenets, O. P. Omelnyk, A. O. Shchur et al.

Results of examination of spectrometer performances CdTe (CdZnTe) detectors are submitted at recording gamma radiations in a range of 15 - 500 keV, and alpha radiations in a range of 4 - 8 MeV. It was shown, that such detectors may be used for the solution of analytical problems with definition of elements from lanthanum up to plutonium with recording X-ray of K-series and a spectrometry of particles in the method of NRA and at identification of isotopes.

Loll Renate

The construction of a consistent theory of quantum gravity is a problem in theoretical physics that has so far defied all attempts at resolution. One ansatz to try to obtain a non-trivial quantum theory proceeds via a discretization of space-time and the Einstein action. I review here three major areas of research: gauge-theoretic approaches, both in a path-integral and a Hamiltonian formulation; quantum Regge calculus; and the method of dynamical triangulations, confining attention to work that is strictly four-dimensional, strictly discrete, and strictly quantum in nature.