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

Sigurd Huber, Michael Epping

Phase-only pattern synthesis is a long-standing and hard to solve problem in antenna engineering. Due to its nonlinear nature, this kind of optimization problem is classically approached with iterative algorithms, where the convergence time depends on the problem topology. Often these heuristic solution routines get stuck in local optima and yield suboptimal results. This article addresses phase-only pattern synthesis by using a variational quantum algorithm, the quantum approximate optimization algorithm. In this context, a mathematical approach is presented, which discretizes the optimization variables and allows representing the original nonlinear functional as a higher order polynomial. In contrast to other series expansion techniques it turns out that this polynomial has finite length without introducing any approximations. This makes phase-only patterns synthesis problems suitable to be solved on quantum computers with standard gate sets. The mathematical treatment of this optimization problem is complemented by a complexity analysis and a performance analysis. Finally, the challenges regarding future deployment of quantum approximate optimization for phase-only pattern synthesis are discussed.

Gemma Rius

Radiation effects in electronic systems have been extensively studied within the context of classical micro- and nano-electronics, enabling reliable operation in space, nuclear, and other harsh environments through well-established concepts such as total ionizing dose, displacement damage, and single-event effects. Superconducting quantum technologies, however, operate in a fundamentally different regime, relying on macroscopic quantum coherence at millikelvin temperatures and energy scales many orders of magnitude smaller than those associated with ionizing radiation. Recent experiments have revealed that even rare radiation events, originating from cosmic rays or natural radioactivity, can generate quasiparticle bursts and non-equilibrium phonons, leading to decoherence and spatially correlated errors across multiple qubits. These phenomena challenge classical notions of radiation hardness and locality that underpin conventional mitigation strategies. This perspective bridges decades of radiation-effects knowledge from classical electronics with emerging insights from superconducting quantum devices, circuits, and qubits. The limitations of directly translating classical radiation-hardness concepts to quantum hardware and examining radiation interactions with superconducting materials and Josephson junctions are highlighted, and the distinct implications for quantum computing vs quantum sensing are discussed. Finally, critical gaps in testing, modeling, and multiscale simulation methodologies are identified, outlining directions toward radiation-aware quantum engineering that integrate materials science, device physics, and system-level design to enable robust, deployable quantum technologies.

Kai Zhang, Sen Kuang

Traditional many-body teleportation relies on the strong interaction property of a quantum many-body system, which usually requires numerous qubits and entanglement resources, making it difficult to realize experimentally. A natural scheme is to use a 1-D spin chain with simple structure to realize many-body teleportation. In this article, we analyze the conditions for general quantum many-body teleportation and construct an effective control Hamiltonian, realizing quantum many-body teleportation on the controlled 1-D spin chain. Our scheme, which only requires forward evolution and local measurements, can be used to perform quantum state transfer without the special presetting and modulation of coupling parameters of the chain and without strict control over the evolution time, thereby enhancing the experimental realizability. Furthermore, we improve the efficiency and accuracy of quantum state transfer by introducing quantum optimal control technique to optimize the control pulse sequences.

Alessio Di Santo, Walter Tiberti, Dajana Cassioli

Quantum secret sharing (QSS) is a cryptographic protocol that leverages quantum mechanics to distribute a secret among multiple parties. With respect to the classical counterpart, in QSS, the secret is encoded into quantum states and shared by a dealer such that only an authorized subsets of participants, i.e., the players, can reconstruct it. Several state-of-the-art studies aim to transpose classical secret sharing into the quantum realm, while maintaining their reliance on traditional network topologies (e.g., star, ring, and fully connected), and require that all the <inline-formula><tex-math notation="LaTeX">$n$</tex-math></inline-formula> players calculate the secret. These studies exploit the Greenberger&#x2013;Horne&#x2013;Zeilinger state, which is a type of maximally entangled quantum state involving three or more qubits. However, none of these works account for redundancy, enhanced security/privacy features, or authentication mechanisms able to fingerprint players. To address these gaps, in this article, we introduce a new concept of QSS, which leans on a generic distributed quantum network, based on a threshold scheme, where all the players collaborate also to the routing of quantum information among them. The dealer, by exploiting a custom flexible weighting system, takes advantage of a newly defined quantum Dijkstra algorithm to select the most suitable subset of <inline-formula><tex-math notation="LaTeX">$t$</tex-math></inline-formula> players, out of the entire set on <inline-formula><tex-math notation="LaTeX">$n$</tex-math></inline-formula> players, to involve in the computation. To fingerprint and authenticate users, CRYSTAL-Kyber primitives are adopted, while also protecting each player&#x2019;s privacy by hiding their identities. We show the effectiveness and performance of the proposed protocol by testing it against the main classical and quantum attacks, thereby improving the state-of-the-art security measures.

Alexia Salavrakos, Nicolas Maring, Pierre-Emmanuel Emeriau et al.

Photonic platforms occupy a central place in quantum technologies. They appear in quantum networks and communication, in near-term quantum advantage schemes, as well as in fault-tolerant quantum computing proposals. In this perspective article, we review the advances and challenges of this technology, and we focus on algorithms and protocols that we call photon-native, i.e. which closely follow the specificities of the hardware.

C. Shang, M. De Gregorio, Q. Buchinger et al.

We report the development of high quality InAs quantum dots with an ultra-low density of 2 × 107 cm−2 on (001) GaAs substrates. A significant reduction in the emission wavelength inhomogeneity has been observed. A representative dot has been characterized under cryogenic temperatures, demonstrating a close-to-ideal antibunching of both the exciton and biexciton emissions with a fitted g(2)(0) = 0.008 and 0.059, respectively.

Alon Kukliansky, Marko Orescanin, Chad Bollmann et al.

The escalating threat and impact of network-based attacks necessitate innovative intrusion detection systems. Machine learning has shown promise, with recent strides in quantum machine learning offering new avenues. However, the potential of quantum computing is tempered by challenges in current noisy intermediate-scale quantum era machines. In this article, we explore quantum neural networks (QNNs) for intrusion detection, optimizing their performance within current quantum computing limitations. Our approach includes efficient classical feature encoding, QNN classifier selection, and performance tuning leveraging current quantum computational power. This study culminates in an optimized multilayered QNN architecture for network intrusion detection. A small version of the proposed architecture was implemented on IonQ&#x0027;s Aria-1 quantum computer, achieving a notable 0.86 F1 score using the NF-UNSW-NB15 dataset. In addition, we introduce a novel metric, certainty factor, laying the foundation for future integration of uncertainty measures in quantum classification outputs. Moreover, this factor is used to predict the noise susceptibility of our quantum binary classification system.

Feng Tang, Xiangang Wan

Abstract Topological materials usually possess protected gapless states in either the boundary or bulk, exhibiting various properties such as spin-momentum locking, Klein tunneling, Fermi arcs and so on. Database searches using symmetry data at high-symmetry points have catalogued thousands of topological materials revealing a magnitude of band nodes (BNs) at high-symmetry points or lying within high-symmetry lines/planes. A complete mapping from symmetry data (namely, representation of little group) in any BN to the k ⋅ p $k\cdot p$ model characterizing low-energy Hamiltonian around the BN (and from the k ⋅ p $k\cdot p$ model to concrete BN, inversely), is expected to complete the characterization of all BNs and gapless states. Here we first review recent progress on classifying BNs by systematically and automatically constructing k ⋅ p $k\cdot p$ models based on recently completed tabulation of all irreducible (co-)representation matrices of little groups of the 1651 magnetic space groups. As one indispensable input in constructing a symmetry-allowed and generic k ⋅ p $k\cdot p$ model, the expansion order, has been carefully and systematically truncated for any BN to a reasonable nonzero integer, by comparing the emanating nodal structure (ENS, including nodal point, nodal line and nodal surface) near the BN obtained by the explicitly constructed k ⋅ p $k\cdot p$ model and that by pure symmetry analysis using compatibility relations (CRs). Owing to the progress, we are able to summarize all 25 different configurations of ENS near BN required by CRs, provide a complete mapping from k ⋅ p $k\cdot p$ model to its realization around BN, and the corresponding ENS by CRs in an accessible file, and also reveal the protection mechanism of additional nodal lines that escape conventional analysis by CRs and is only predictable by constructing k ⋅ p $k\cdot p$ model. The symmetry-based classification results on all BNs could facilitate large-scale materials prediction and hold promise for realizing topological semimetals suitable for device applications.

Agnès Fienga, Olivier Minazzoli

Abstract We describe here how planetary ephemerides are built in the framework of General Relativity and how they can be used to test alternative theories. We focus on the definition of the reference frame (space and time) in which the planetary ephemeris is described, the equations of motion that govern the orbits of solar system bodies and electromagnetic waves. After a review on the existing planetary and lunar ephemerides, we summarize the results obtained considering full modifications of the ephemeris framework with direct comparisons with the observations of planetary systems, with a specific attention for the PPN formalism. We then discuss other formalisms such as Einstein-dilaton theories, the massless graviton and MOND. The paper finally concludes on some comments and recommendations regarding misinterpreted measurements of the advance of perihelia.

Sang-Wook Cheong, Fei-Ting Huang

Abstract Altermagnetism is introduced as a category of magnetic states with ‘collinear’ antiferromagnetic spins and alternating variations of local structures around spins in such a way that the symmetry allows typical ferromagnetic behaviors. Altermagnets exhibiting ferromagnetic behaviors without any external perturbations (type-I) turn out to belong to the ferromagnetic point group. Other altermagnets (type-II and type-III) can have ferromagnetic behaviors only with external perturbations such as electric current or stress, which conserve parity-time-reversal (PT) symmetry. All types of altermagnets themselves have broken PT symmetry. The concept of altermagnetism can be extended to accommodate non-collinear spins and multiple local-structure variations.

Akio Kawasaki

Technologies for manipulating single atoms have advanced drastically in the past decades. Due to their excellent controllability of internal states, atoms serve as one of the ideal platforms as quantum systems. One major research direction in atomic systems is the precise determination of physical quantities using atoms, which is included in the field of precision measurements. One of such precisely measured physical quantities is energy differences between two energy levels in atoms, which is symbolized by the remarkable fractional uncertainty of $10^{-18}$ or lower achieved in the state-of-the-art atomic clocks. Two-level systems in atoms are sensitive to various external fields and can, therefore, function as quantum sensors. The effect of these fields manifests as energy shifts in the two-level system. Traditionally, such shifts are induced by electric or magnetic fields, as recognized even before the advent of precision spectroscopy with lasers. With high-precision measurements, tiny energy shifts caused by hypothetical fields weakly coupled to ordinary matter or by small effects mediated by massive particles can be potentially detectable, which are conventionally dealt with in the field of nuclear and particle physics. In most cases, the atomic systems as quantum sensors have not been sensitive enough to detect such effects. Instead, experiments searching for these interactions have placed constraints on coupling constants, except in a few cases where effects are predicted by the Standard Model of particle physics. Nonetheless, measurements and searches for these effects in atomic systems have led to the emergence of a new field of physics.

Yu Ji, Zehao Dong, Hao Wang et al.

Abstract Layered superconductors exhibit strong anisotropic responses to magnetic fields in out-of-plane and in-plane orientations, due to their distinct vortex structures and upper critical field values. Here, we utilize the planar tunnel junction technique to perform continuous magnetic field-dependent dI/dV spectroscopy measurements on 2H-NbSe2 under different field orientations. We observe characteristic kink features for weak in-plane magnetic fields, but the overall behaviors are quite similar for different field orientations despite the distinct vortex generation processes and widely different upper critical field values. Especially, the generic square root dependence of the Fermi level density of state on magnetic field indicates that the Doppler shift plays a central role in the low energy excitations of 2H-NbSe2 in the presence of magnetic field.

V. V. Levenets, O. Yu. Lonin, O. P. Omelnik et al.

The decontamination properties of shampoos for cesium, strontium, and cobalt were determined. The method has been developed for determining the decontaminating properties of shampoos. The chemical part of the study includes the preparation of hair, which consists of forced pollution and subsequent washing. Stable isotopes were used in the work. This has increased the safety of staff during chemical hair research. The analytical part includes the quantitative determination of the cesium, strontium, and cobalt in the hair, which was carried out by the Particle-Induced X-ray Emission (PIXE) method using the analytical nuclear-physical complex "Sokol". Various shampoos were analyzed, and their decontamination properties were determined. During the research, various samples of shampoos, which are presented on the market of Ukraine, were considered. It has been established that TM "Ringo" shampoo has the best deactivating properties for cesium (Kd - 574.0) and insignificant deactivating properties for strontium (Kd - 3.1) and cobalt (Kd - 3.6). It was determined that with multi-isotope contamination (a mixture of cesium, strontium, and cobalt isotopes) decrease in the deactivation coefficient for all isotopes was observed, which is due to the competition factor of the isotopes in the complexation process with shampoo. Reduction of decontaminating properties was observed on all samples of shampoos.

M. Ceccardi, A. Zeugner, L. C. Folkers et al.

Abstract The recently discovered magnetic topological insulators (MnBi2Te4)(Bi2Te3) n , n = 0–4, are an ideal playground to study the influence of magnetic properties on band topology, giving access to diverse quantum states in a single compound. In the low temperature-antiferromagnetic state and vanishing magnetic field, the n = 1 system is a topological insulator protected by a combination of time reversal and a translation symmetries. It has been argued that, when the antiferromagnetic phase is forced to a the fully spin polarized state by the application of an external magnetic field, this system develops Weyl cones in the conduction band, which become accessible in presence of an intrinsic electronic doping. In this work, we experimentally prove the raising of field-induced Weyl state through the detection of an intrinsic anomalous Nernst effect in a bulk single crystal of MnBi4Te7.

Yue Yu, Harold Y. Hwang, S. Raghu et al.

Abstract Recent experiments on Nb-doped SrTiO3 have shown that the superconducting energy gap to the transition temperature ratio maintains the Bardeen–Cooper–Schrieffer (BCS) value throughout its superconducting dome. Motivated by these and related studies, we show that the Cooper pairing mediated by a single soft transverse-optical phonon is the most natural mechanism for such a superconducting dome given experimental constraints, and present the microscopic theory for this pairing mechanism. Furthermore, we show that this mechanism is consistent with the T 2 resistivity in the normal state. Lastly, we discuss what physical insights SrTiO3 provides for superconductivity in other quantum paraelectrics such as KTaO3.

Chandralekha Singh

This article describes reflections on the Fifth International Conference on Women in Physics which was a conference attended by 215 female physicists and a few male physicists from 49 different countries. The article focuses on the barriers that women face in their professional advancement in physics and the extent to which the situation is different in various countries.

Yilun Xu, Gang Huang, Jan Balewski et al.

As quantum information processors grow in quantum bit (qubit) count and functionality, the control and measurement system becomes a limiting factor to large-scale extensibility. To tackle this challenge and keep pace with rapidly evolving classical control requirements, full control stack access is essential to system-level optimization. We design a modular field-programmable gate array (FPGA)-based system called QubiC to control and measure a superconducting quantum processing unit. The system includes room temperature electronics hardware, FPGA gateware, and engineering software. A prototype hardware module is assembled from several commercial off-the-shelf evaluation boards and in-house-developed circuit boards. Gateware and software are designed to implement basic qubit control and measurement protocols. System functionality and performance are demonstrated by performing qubit chip characterization, gate optimization, and randomized benchmarking sequences on a superconducting quantum processor operating at the Advanced Quantum Testbed at the Lawrence Berkeley National Laboratory. The single-qubit and two-qubit process fidelities are measured to be 0.9980 <inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.0001 and 0.948 <inline-formula><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 0.004, respectively, by randomized benchmarking. With fast circuit sequence loading capability, the QubiC performs randomized compiling experiments efficiently and improves the feasibility of executing more complex algorithms.

Sa'ad R. Yousif, Ali Abid Abojassim, Anes Hayder

The study focuses on measuring the values of 238U, 232Th and 40K natural radionuclides in soil samples in Badra oil field area (Iraq). Also, the radiological risk data were calculated for all samples in this study. The technique used in this study was gamma-ray spectrometry with NaI(Tl) detector. The averages of specific activity are: 24.7 Bq/kg for 238U, 13.6 Bq/kg for 232Th, and 538.9 Bq/kg for 40K. Besides, the estimations of radiological effects like the radium equivalent (Raeq), the absorbed dose rate (Dr), external hazard index (Hex), internal hazard index (Hin), representative gamma hazard index (Iγ) and the total annual effective dose equivalent (AEDE) are 85.5 Bq/kg, 42.1 nGy/h, 0.23, 0.30, 0.66 and 0.26 mSv/y, respectively. When comparing the results in the study area with the world mean values specified by the UNSCEAR, OCDE and ICRP, the study terminates that the limits of health risk are safe and may not menace the workers at these locations due to these radionuclide limits. The values were subjected to GIS environment under the WGS1984 coordinate system for the sake of results' coordination, and processed in Inverse Distance Weighted interpolation as the best processing.

Rie Y Umetsu, Masato Tsujikawa, Kotaro Saito et al.

Abstract The magnetic properties and atomic arrangement of Mn 2 CoGa Heusler alloy were investigated experimentally and by theoretical calculations. The magnetic moment derived from spontaneous magnetization at 5 K was 2.06 μ B /f.u. and was close to the integer number of the expected value from theoretical calculation and the Slater–Pauling rule predicted by Galanakis et al . The Curie temperature and L 2 1 - B 2 order–disorder phase transition temperature were 741 and 1047 K, respectively. Powder neutron diffraction experiment results suggested that the atomic arrangement prefers an L 2 1b -type structure rather than that of Hg 2 CuTi, being consistent with our previous results of high-angle annular dark-field-scanning transmission electron microscopic observations. The magnetic moments obtained were in good agreement with the theoretical values in the model of the L 2 1b -type structure. The density of states obtained by the first-principles calculation combined with the coherent potential approximation in Mn 2 CoGa with the L 2 1b -type crystal structure maintained the half-metallic character, even though disordering by Mn and Co atoms was introduced.

О. I. Davydovska, V. Yu. Denisov, V. O. Nesterov

Effective nucleus-nucleus potential is studied within the framework of the double folding approach, where the contribution of the kinetic energy of the nucleons is taken into account additionally. The potentials of nucleus-nucleus interaction for the system 40Сa + 40Сa with and without the internal kinetic energy of the nucleons are obtained. It is shown that the accounting of the contribution of kinetic energy to the potential allows to simultaneously describe the experimental cross sections of the subbarrier fusion and elastic scattering.