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

Maryia Zinouyeva, Rolf Heid, Giacomo Merzoni et al.

Abstract The experimental determination of the magnitude and momentum dependence of electron-phonon coupling (EPC) is an outstanding problem in condensed matter physics. The intensity of phonon peaks in Resonant Inelastic X-ray Scattering (RIXS) spectra can be related to the underlying EPC strength under significant approximations whose validity deserves careful verification. We measured the Cu L3 RIXS phonon intensity as a function of incident photon energy and momentum transfer in several layered cuprates. For CaCuO2, La2−x Sr x CuO4+δ , and YBa2Cu3O6, using a generally accepted theoretical model, we quantitatively estimate the EPC for the bond-stretching mode along the high-symmetry directions (ζ,0) and (ζ,ζ), and as a function of the azimuthal angle φ at fixed q ∥. We compare our results with theoretical predictions and find that the q ∥-dependence of the phonon RIXS intensity can be largely ascribed to the phonon symmetry. However, a more satisfactory prediction of the experimental results requires an accurate description of the electronic structure close to the Fermi level. Our extensive investigation indicates that Cu L3 RIXS can reliably determine the momentum dependence of EPC for the bond-stretching modes of cuprates. Moreover, the large experimental basis provided here constitutes a stringent test for advanced theoretical predictions on the EPC.

Alto Osada, Koichiro Miyanishi

Recent advances in quantum technologies rely on precise control and integration of quantum objects, and technological breakthroughs are anticipated for further scaling up to realize practical applications. Trapped-ion quantum technology is a promising candidate to realize them, while its scalability depends on the development of intra-node scaling up, reproducibility of quantum nodes, and photonic interconnection among them. Utilization of integrated photonics instead of free-space optics is a crucial step toward mass production of trapped-ion quantum nodes and manifests itself as useful for laser delivery for various quantum operations and photon detection. However, the whole architecture of the scalable photonic circuits for them is left unexplored. In this work, we discuss photonic routing architectures for trapped-ion quantum devices, in which lasers of multiple wavelengths are delivered to multiple trapping zones within a single chip. We analyze two methods of configuring nanophotonic waveguides and compare them in terms of loss of total laser power. This work opens up a new landscape of photonic architecture for trapped-ion quantum technologies, which broadens the scope of integrated photonics for quantum technologies.

Koichiro Takahashi, Hong-Fei Huang, Jie-Xiang Yu et al.

Abstract α-MnTe, an A-type collinear antiferromagnet, has recently attracted significant attention due to its pronounced spin splitting despite having net zero magnetization, a phenomenon unique for a new class of magnetism dubbed altermagnetism. In this work, we develop a minimal effective Hamiltonian for MnTe based on realistic orbitals near the Fermi level at both the Γ and A points based on group representation theory, first-principles calculations, and tight-binding modeling. The Hamiltonian exhibits qualitatively distinct electron transport characteristics between these high-symmetry points and for different in-plane Néel vector orientations along the $$[11\bar{2}0]$$ [ 11 2 ¯ 0 ] and $$[1\bar{1}00]$$ [ 1 1 ¯ 00 ] directions. Although the spin–orbit coupling (SOC) is believed to be not important in altermagnets, we show the dominant role of SOC in the spin splitting and valence electrons of MnTe. These findings provide critical insights into altermagnetic electron transport in MnTe and establish a model playground for future theoretical and experimental studies.

Wen Ning, Ri-Hua Zheng, Jia-Hao Lü et al.

The quantum Rabi model (QRM), composed of a qubit interacting with a quantized photonic field, is a cornerstone of quantum optics. The QRM with dominant unitary dynamics has been demonstrated in circuit quantum electrodynamics (QED) systems, but an open QRM with a strong photonic dissipation has not been experimentally explored. We here present the first experimental demonstration of such an open system in circuit QED, featuring a controlled competition between the coherent qubit-field interaction and the photonic dissipation. We map out the photon number distributions of the dissipative resonator for different coupling strengths in the steady state. We further observe the variation of the photon number during the system’s evolution toward the steady state with fixed control parameters. The results demonstrate that the system’s behavior is significantly modified by photonic dissipation.

Klavs Hansen

A.A. Burkov

Sara Ayman Metwalli, Rodney Van Meter

This article introduces a process framework for debugging quantum circuits, focusing on three distinct types of circuit blocks: amplitude–permutation, phase-modulation, and amplitude–redistribution circuit blocks. Our research addresses the critical need for specialized debugging approaches tailored to the unique properties of each circuit type. For amplitude–permutation circuits, we propose techniques to correct amplitude–permutations mimicking classical operations. In phase-modulation circuits, our proposed strategy targets the precise calibration of phase alterations essential for quantum computations. The most complex amplitude–redistribution circuits demand advanced methods to adjust probability amplitudes. This research bridges a vital gap in current methodologies and lays the groundwork for future advancements in quantum circuit debugging. Our contributions are twofold: we present a comprehensive unit testing tool (Cirquo) and debugging approaches tailored to the unique demands of quantum computing, and we provide empirical evidence of its effectiveness in optimizing quantum circuit performance. This work is a crucial step toward realizing robust quantum computing systems and their applications in various domains.

Nishikanta Mohanty, Bikash K. Behera, Christopher Ferrie

The vehicle routing problem (VRP) is an NP-hard optimization problem that has been an interest of research for decades in science and industry. The objective is to plan routes of vehicles to deliver goods to a fixed number of customers with optimal efficiency. Classical tools and methods provide good approximations to reach the optimal global solution. Quantum computing and quantum machine learning provide a new approach to solving combinatorial optimization of problems faster due to inherent speedups of quantum effects. Many solutions of VRP are offered across different quantum computing platforms using hybrid algorithms, such as quantum approximate optimization algorithm and quadratic unconstrained binary optimization. In this work, we build a basic VRP solver for three and four cities using the variational quantum eigensolver on a fixed ansatz. The work is further extended to evaluate the robustness of the solution in several examples of noisy quantum channels. We find that the performance of the quantum algorithm depends heavily on what noise model is used. In general, noise is detrimental, but not equally so among different noise sources.

Hiroshi C. Watanabe, Rudy Raymond, Yu-Ya Ohnishi et al.

Variational quantum algorithms, which utilize parameterized quantum circuits (PQCs), are promising tools to achieve quantum advantage for optimization problems on near-term quantum devices. Their PQCs have been conventionally constructed from parameterized rotational angles of single-qubit gates around a predetermined set of axes and two-qubit entangling gates, such as <sc>cnot</sc> gates. We propose a method to construct a PQC by continuous parameterization of both the angles and the axes of its single-qubit rotation gates. The method is based on the observation that when rotational angles are fixed, optimal axes of rotations can be computed by solving a system of linear equations whose coefficients can be determined from the PQC with small computational overhead. The method can be further simplified to select axes freely from continuous parameters with rotational angles fixed to <inline-formula><tex-math notation="LaTeX">$\pi$</tex-math></inline-formula>. We show the simplified free-axis selection method has better expressibility against other structural optimization methods when measured with Kullback&#x2013;Leibler divergence. We also demonstrate PQCs with free-axis selection are more effective to search the ground states of Hamiltonians for condensed matter physics, quantum chemistry, and combinatorial optimization. Because free-axis selection allows designing PQCs without specifying their single-qubit rotational axes, it may significantly improve the handiness of PQCs.

Hai-Sheng Li

The well-known 3-bit Hermitian gate (a Toffoli gate) has been implemented using Clifford+T circuits. Compared with the Peres gate, its implementation circuit requires more controlled-<sc>not</sc> <sc>(cnot)</sc> gates. However, the Peres gate is not Hermitian. This article reports four 3-bit Hermitian gates named LI gates, whose realized circuits have the same T-count, T-depth, and <sc>cnot</sc>-count as the Peres gate. Furthermore, two decomposition methods of a multiple-control Toffoli (MCT) gate are proposed for different primary optimization goals. Then, we design the equality, less-than, and full comparators with the minimum circuit width using proposed Hermitian gates and optimized MCT gates. A fault-tolerant circuit is required for robust quantum computing. Clifford+T circuits are accepted solutions for fault-tolerant implementation. Considering T-count, T-depth, <sc>cnot</sc>-count, and circuit width as the primary optimization goals, we design the optimized Clifford+T circuits of three comparators using LI gates and optimized MCT gates. Comparison and analysis show that the proposed comparators have better overall performances for T-count, T-depth, <sc>cnot</sc>-count, and circuit width than the best-known comparators without quantum measurements.

V. О. Zheltonozhskyi, D. E. Myznikov, A. M. Savrasov et al.

The γ-spectra were measured of the structural materials of the 2nd unit of the Chornobyl NPP which were irradiated by bremsstrahlung with end-point energy 37 MeV. Using the ratio of the 57Co and 58Co activities, the nickel and cobalt masses ratio was determined. Using the obtained data and the measured 60Co activity in the studied samples, a method for determining of the 63Ni activity was developed. Radiochemical validation of the created method was performed and good quantitative agreement of 63Ni activities obtained by spectroscopic and radiochemical methods was obtained.

Janusz Kusyk, Samah M. Saeed, Muharrem Umit Uyar

Computationally expensive applications, including machine learning, chemical simulations, and financial modeling, are promising candidates for noisy intermediate scale quantum (NISQ) computers. In these problems, one important challenge is mapping a quantum circuit onto NISQ hardware while satisfying physical constraints of an underlying quantum architecture. Quantum circuit compilation (QCC) aims to generate feasible mappings such that a quantum circuit can be executed in a given hardware platform with acceptable confidence in outcomes. Physical constraints of a NISQ computer change frequently, requiring QCC process to be repeated often. When a circuit cannot directly be executed on a quantum hardware due to its physical limitations, it is necessary to modify the circuit by adding new quantum gates and auxiliary qubits, increasing its space and time complexity. An inefficient QCC may significantly increase error rate and circuit latency for even the simplest algorithms. In this article, we present artificial intelligence (AI)-based and heuristic-based methods recently reported in the literature that attempt to address these QCC challenges. We group them based on underlying techniques that they implement, such as AI algorithms including genetic algorithms, genetic programming, ant colony optimization and AI planning, and heuristics methods employing greedy algorithms, satisfiability problem solvers, dynamic, and graph optimization techniques. We discuss performance of each QCC technique and evaluate its potential limitations.

R. Ramazashvili, P. D. Grigoriev, T. Helm et al.

Abstract Most of solid-state spin physics arising from spin–orbit coupling, from fundamental phenomena to industrial applications, relies on symmetry-protected degeneracies. So does the Zeeman spin–orbit coupling, expected to manifest itself in a wide range of antiferromagnetic conductors. Yet, experimental proof of this phenomenon has been lacking. Here we demonstrate that the Néel state of the layered organic superconductor κ-(BETS)2FeBr4 shows no spin modulation of the Shubnikov–de Haas oscillations, contrary to its paramagnetic state. This is unambiguous evidence for the spin degeneracy of Landau levels, a direct manifestation of the Zeeman spin–orbit coupling. Likewise, we show that spin modulation is absent in electron-doped Nd1.85Ce0.15CuO4, which evidences the presence of Néel order in this cuprate superconductor even at optimal doping. Obtained on two very different materials, our results demonstrate the generic character of the Zeeman spin–orbit coupling.

Hasan Bircan

Luca Salasnich

R. Bernabei, P. Belli, F. Cappella et al.

Several of the many proposed Dark Matter candidate particles, already investigated with lower exposure and a higher software energy threshold, are further analyzed including the first DAMA/LIBRA-phase2 data release, with an exposure of 1.13 tyr and a lower software energy threshold (1 keV). The cumulative exposure above 2 keV considering also DAMA/NaI and DAMA/LIBRA-phase1 results is now 2.46 tyr. The analysis permits to constrain the parameters’ space of the considered candidates restricting their values – with respect to previous analyses – thanks to the increase of the exposure and to the lower energy threshold.

A. P. Lashko, T. N. Lashko

Some sections of the 177mLu conversion electron spectra were measured by means of π 2 magnetic β-spectrometer. Relative intensities of internal-conversion electron lines and absolute values of internal conversion coefficients on L-subshells of 177Lu for γ116 keV transition were determined with high precision. The experimental data were compared with theoretical values.

V. A. Babenko, N. M. Petrov

Simple relations between the masses of the two lightest up and down quarks were obtained on the basis of the simple physically based model compatible with the present-day theory of strong interactions, i.e. with quantum chromodynamics. Relations between the u and d quark masses, on one hand, and nucleon and pion masses, on the other hand, are also established. Thus, the obtained in such a way elementary formula mu/md = 1/(1+√2), relating u and d quark masses, appears to be in excellent agreement with a number of theoretical calculations of the ratio mu/md of the lightest quark masses. The u and d quark masses mu = 1.903 MeV, md = 4.594 MeV, calculated with the help of the obtained relations, are also in very good agreement with the modern evaluations and calculations of these quantities. The average of the u and d quark masses m̅ud = ΔMπ/√2 ≅ 3.248 MeV, obtained in the proposed approach, is in good agreement with previous calculations too.

V. I. Gulik

Investigations aimed for the optimization of fuel compositions for two-zone subcritical reactor are considered. The study of inner fast zone for two-zone subcritical reactor with homogeneous fuel concerning the geometrical, material and economical characteristics was carried out within the scope of this paper. The possibility of dividing of the inner zone into subzones with different fuel for two-zone subcritical systems was shown. It is possible to find the optimal ratio for volume of outer subzone to volume of inner subzone depending on the purpose of using such a subcritical systems.

V. V. Galchenko, V. I. Gulik, I. I. Shlapak

The description of calculation scheme of fuel assembly for preparation of few-group characteristics is considered with help of Serpent code. This code uses the Monte-Carlo method and energy continuous microscopic data libraries. Serpent code is devoted for calculation of fuel assembly characteristics, burnup calculations and preparation of few-group homogenized macroscopic cross-sections. The results of verification simulations in comparison with other codes (WIMS, HELIOS, NESSEL etc.), which are used for neutron-physical analysis of VVER type fuel, are presented.