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

A. Derevianko, M. Pospelov

Scarlett Gauthier, Thirupathaiah Vasantam, Gayane Vardoyan

To effectively support the execution of quantum network applications for multiple sets of user-controlled quantum nodes, a quantum network must efficiently allocate shared resources. We study traffic models for a type of quantum network hub called an entanglement generation switch (EGS), a device that allocates resources to enable entanglement generation between nodes in response to user-generated demand. We propose an on-demand resource allocation algorithm, where a demand is either blocked if no resources are available or else results in immediate resource allocation. We model the EGS as an Erlang loss system, with demands corresponding to sessions whose arrival is modeled as a Poisson process. To reflect the operation of a practical quantum switch, our model captures scenarios where a resource is allocated for batches of entanglement generation attempts, possibly interleaved with calibration periods for the quantum network nodes. Calibration periods are necessary to correct against drifts or jumps in the physical parameters of a quantum node that occur on a timescale that is long compared to the duration of an attempt. We then derive a formula for the demand blocking probability under three different traffic scenarios using analytical methods from applied probability and queueing theory. We prove an insensitivity theorem which guarantees that the probability a demand is blocked only depends upon the mean duration of each entanglement generation attempt and calibration period, and is not sensitive to the underlying distributions of attempt and calibration period duration. We provide numerical results to support our analysis. Our numerical results suggest that there exist parameter regimes where it is beneficial for nodes to relinquish control of EGS resources during their calibration periods. This benefit is quantified by the blocking probability and the total entanglement generated in a fixed period of time. Our work is the first analysis of traffic characteristics at an EGS system and provides a valuable analytic tool for devising performance driven resource allocation algorithms.

A. S. Joglekar, A. G. R. Thomas, A. L. Milder et al.

Differentiable programming, enabled by automatic differentiation (AD), provides a robust framework for gradient-based optimization in computational plasma physics. While optimization is often only used towards design, we demonstrate that it can also be used for discovery and bridging the gap towards multi-scale modeling. We discuss four applications: (1) discovering novel nonlinear plasma phenomena, including a previously unknown superadditive wavepacket interaction regime, by optimizing differentiable kinetic simulations; (2) learning hidden variables that capture spatiotemporally non-local kinetic effects in fluid simulations, enabling hydrodynamic models to reproduce large Knudsen number physics typically requiring kinetic solvers; (3) accelerating Thomson scattering analysis by over $140\times$ while enabling extraction of velocity distribution functions with $\mathcal{O}(10^3)$ parameters; and (4) inverse design of spatiotemporal laser pulses that achieve target far-field behavior where full space-time coupling improves performance by $15\times$ over spatial or temporal optimization alone. These examples illustrate that differentiable programming not only accelerates existing design and inference workflows but enables qualitatively new capabilities, from algorithmic physics discovery to high-dimensional inference and design previously considered intractable.

Kilian Dremel, Dimitri Prjamkov, Markus Firsching et al.

One of the primary difficulties in computed tomography (CT) is reconstructing cross-sectional images from measured projections of a physical object. There exist several classical methods for this task of generating a digital representation of the object, including filtered backprojection or simultaneous algebraic reconstruction technique. Our research aims to explore the potential of quantum computing in the field of industrial X-ray transmission tomography. Specifically, this work focuses on the application of a method similar to that proposed by Nau et al. (2023) on real CT data to demonstrate the feasibility of quadratic-unconstrained-binary-optimization-based tomographic reconstruction. Starting with simulated phantoms, results with simulated annealing as well as real annealing hardware are shown, leading to the application on measured cone-beam CT data. The results demonstrate that tomographic reconstruction using quantum annealing is feasible for both simulated and real-world applications. Yet, current limitations—involving the maximum processable size and bit depth of voxel values of the images, both correlated with the number of densely connected qubits within the annealing hardware—imply the need of future research to further improve the results. This approach, despite its early stage, has the potential to enable more sophisticated reconstructions, providing an alternative to traditional classical methods.

Andrew S. Greenspon, Mark Dong, Ian Christen et al.

Nanophotonic resonators are central to numerous applications, from efficient spin–photon interfaces to laser oscillators and precision sensing. A leading approach consists of photonic crystal (PhC) cavities, which have been realized in a wide range of dielectric materials. However, translating proof-of-concept devices into a functional system entails a number of additional challenges, inspiring new approaches that combine resonators with wavelength-scale confinement and high quality factors; scalable integration with integrated circuits and photonic circuits; electrical or mechanical cavity tuning; and, in many cases, a need for heterogeneous integration with functional materials such as III–V semiconductors or diamond color centers for spin–photon interfaces. Here we introduce a concept that generates a finely tunable PhC cavity at a selected wavelength between two heterogeneous optical materials whose properties satisfy the above requirements. The cavity is formed by stamping a hard-to-process material with simple waveguide geometries on top of an easy-to-process material consisting of dielectric grating mirrors and active tuning capability. We simulate our concept for the particularly challenging design problem of multiplexed quantum repeaters based on arrays of cavity-coupled diamond color centers, achieving theoretically calculated unloaded quality factors of 106, mode volumes as small as 1.2(λ/neff)3, and maintaining >60% total on-chip collection efficiency of fluorescent photons. We further introduce a method of low-power piezoelectric tuning of these hybrid diamond cavities, simulating optical resonance shifts up to ∼760 GHz and color center fluorescence tuning of 5 GHz independent of cavity tuning. These results will motivate integrated photonic cavities toward larger scale systems-compatible designs.

Yu. N. Eroshenko

Abstract Massive primordial black holes may have formed in the early universe, accounting for a small fraction of dark matter. Most of dark matter, however, may be composed of elementary particles or black holes with smaller masses. These objects could form dense spikes around the large black holes during the radiation-dominated phase of the universe’s evolution. Dark matter particles can annihilate in the spikes. In this study, we discuss the structure and properties of the spikes, considering their transformation due to annihilation. In the hybrid scenario involving black holes of various masses, small black holes can collide and merge in the central regions around larger black holes.

Anna Hallin

The rise of foundation models -- large, pretrained machine learning models that can be finetuned to a variety of tasks -- has revolutionized the fields of natural language processing and computer vision. In high-energy physics, the question of whether these models can be implemented directly in physics research, or even built from scratch, tailored for particle physics data, has generated an increasing amount of attention. This review, which is the first on the topic of foundation models in high-energy physics, summarizes and discusses the research that has been published in the field so far.

Jorge F. Urbán, José A. Pons

This study enhances the application of Physics-Informed Neural Networks (PINNs) for modeling discontinuous solutions in both hydrodynamics and relativistic hydrodynamics. Conventional PINNs, trained with partial differential equation residuals, frequently face convergence issues and lower accuracy near discontinuities. To address these issues, we build on the recently proposed locally linearized PINNs (LLPINNs), which improve shock detection by modifying the Jacobian matrix resulting from the linearization of the equations, only in regions where the velocity field exhibits strong compression. However, the original LLPINN framework required a priori knowledge of shock velocities, limiting its practical utility. We present a generalized LLPINN method that dynamically computes shock speeds using neighboring states and applies jump conditions through entropy constraints. Additionally, we introduce locally Roe PINNs (LRPINNs), which incorporate an approximate Roe Riemann solver to improve shock resolution and conservation properties across discontinuities. These methods are adapted to two-dimensional Riemann problems by using a divergence-based shock detection combined with dimensional splitting, delivering precise solutions. Compared to a high-order weighted essentially non-oscillatory solver, our method produces sharper shock transitions but smoother solutions in areas with small-scale vortex structures. Future research will aim to improve the resolution of these small-scale features without compromising the model's ability to accurately capture shocks.

Wei Chen

Abstract The momentum space of topological insulators and topological superconductors is equipped with a quantum metric defined from the overlap of neighboring valence band states or quasihole states. We investigate the quantum geometrical properties of these materials within the framework of Dirac models and differential geometry. Their momentum space is found to be always a maximally symmetric space with a constant Ricci scalar, and the vacuum Einstein equation is satisfied in 3D with a finite cosmological constant. For linear Dirac models, several geometrical properties are found to be independent of the band gap, including a peculiar straight line geodesic, constant volume of the curved momentum space, and the exponential decay form of the nonlocal topological marker, indicating the peculiar yet universal quantum geometrical properties of these models.

K. Haydukivska, V. Blavatska

We analyze the universal conformational properties of complex copolymer macromolecules, based on two topologies: the rosette structure containing fc linear branches and fr closed loops grafted to the central core, and the symmetric pom-pom structure, consisting of a backbone linear chain terminated by two branching points with functionalities f. We assume that the constituent strands (branches) of these structures can be of two different  chemical species a and b. Depending on the solvent conditions, the inter- or intrachain interactions of some links may vanish, which corresponds to Θ-state of the corresponding polymer species.  Applying both the analytical approach within the frames of direct polymer renormalization and numerical simulations based on the lattice model of polymer,   we evaluated the set of parameters characterizing the size properties of constituent parts of two complex topologies  and estimated quantitatively the impact of interactions between constituent parts on these size characteristics.

I. F. Hussein, A. A. Al-Rubaiee, A. F. Mkhaiber

This paper investigates extensive air showers by estimating the muon and electron mean arrival time distributions at ultrahigh energies for various cosmic-ray particles. The Monte Carlo package AIRES (version 19.04.00) was used to perform simulations at energies of 1019 and 1020 eV. The influence of primary particles (p, 56Fe, and 16O), energies, and zenith angles (0°, 10°, and 20°) on the mean arrival time of muonic and electromagnetic shower disks created in an extensive air shower was examined. Parameterized mean arrival time distributions were calculated for secondary particles e-, e+, and μ, created by proton, iron, and oxygen nuclei at energy 1019 eV in a vertical shower. A polynomial function for these primaries in vertical showers was established using the results of this simulation. The results were compared with the KASCADE-Grande experiment and Sciutto's simulations at energy 1020 eV and θ = 0. In this work the construction of a database that can be used to compute the arrival time of elementary particles is crucial in ultra-high energy ranges through an analytic description between the time structure and the distance distribution.

Yixian Liu, Kaichong Li, Wenjie Liu et al.

Abstract Landau levels, previously proposed and verified in condensed matter systems, are conventionally achieved by introducing an external magnetic field that interacts with electrons. In phononic systems, people have proposed the method of applying strain to structures to form artificial synthetic magnetic fields, which in turn induces the emergence of Landau levels. While most of the current implementations about Landau levels are based on three-dimensional (3D) Weyl systems, the experimental realization of chiral Landau levels in two-dimensional (2D) Dirac acoustic systems remains an open and interesting topic. In this work, we present an innovative approach to generate the chiral Landau levels within a 2D acoustic system by introducing an in-plane artificial pseudomagnetic field. Through breaking the spatial parity symmetry and opening the Dirac cones, we introduce position-dependent effective mass terms to Hamiltonian and confirm the existence of chiral Landau levels by simulations and experiments. Furthermore, We verify the strong robustness of the zeroth Landau level to different kinds of defects. This work provides a feasible way to realize chiral Landau levels in 2D acoustic systems and suggests potential applications in other 2D artificial structures.

Y. Alexanian, J. Saugnier, C. Decorse et al.

Abstract The possibilities of combining several degrees of freedom inside a unique material have recently been highlighted in their dynamics and proposed as information carriers in quantum devices where their cross-manipulation by external parameters such as electric and magnetic fields could enhance their functionalities. An emblematic example is that of electromagnons, spin-waves dressed with electric dipoles, that are fingerprints of multiferroics. Point-like objects have also been identified, which may take the form of excited quasiparticles. This is the case for magnetic monopoles, the exotic excitations of spin ices, that have been recently proposed to carry an electric dipole, although experimental evidences remain elusive. Presently, we investigate the electrical signature of a classical spin ice and a related compound that supports quantum fluctuations. Our in-depth study clearly attributes magneto-electricity to the correlated spin ice phase distinguishing it from extrinsic and single-ion effects. Our calculations show that the proposed model conferring magneto-electricity to monopoles is not sufficient, calling for higher-order contributions.

Qazi Maaz Us Salam, Ishtiaq Ahmed, Rizwan Khalid et al.

Inspired by the discrepancies observed in the $b\to s\ell^+\ell^-$ neutral current decays, we study the decay channel $B_c\to D_s^{(\ast)} \,\ell^+\ell^-$ ($\ell=μ,τ$), which is based on the same flavor changing neutral current (FCNC) transition at the quark level. The current study shows that this decay channel can provide a useful probe for physics beyond the standard model. We use the helicity formalism while employing the effective theory approach where we include the effects of vector and axial vector `new' physics (NP) operators. In this study, we have computed the branching ratio $\mathcal{B}_r$, the $D^\ast$ helicity fraction $f_L$, the lepton forward-backward asymmetry $\mathcal{A}_{FB}$, and the lepton flavor universality ratio (LFU) $R^{τμ}_{D_s^*}$. In addition, as a complementary check on the LFU, we also calculate the various other LFU observables, $R_{i}^{τμ}$ where $i=A_{FB}$, $f_L$. We assume that the NP universal coupling is present for both muons and tauons, while the non-universal coupling is only present for muons. Regarding these couplings, we employ the latest global fit to the $b\to s\ell^+\ell^-$ data, which is recently computed in arXiv:2304.07330. We give predictions of some of the mentioned observables within the SM and the various NP scenarios. We have found that not only are the considered observables sensitive to NP but are also helpful in distinguishing among the different NP scenarios. These results can be tested at the LHCb, HL-LHC, and FCC-ee, and therefore, a precise measurements of these observables not only deepens our understanding of the $b\to s\ell^+\ell^-$ process but also provides a window of opportunity to possibly study various NP scenarios.

Steven W. Tarr, Emily Alicea-Muñoz

Science communication skills are considered essential learning objectives for undergraduate physics students. However, high enrollment and limited class resources present significant barriers to providing students ample opportunities to practice their formal presentation skills. We investigate the use of integrated critical reflection and peer evaluation activities in a physics senior seminar course both to improve student learning outcomes and to supplement highly restricted presentation time. Throughout the semester, each student delivers one 8-min multimedia presentation on either their research or an upper-division course topic. Following each presentation, audience members complete one of two randomly assigned peer evaluations: a treatment form that prompts critical reflection or a control form that does not. Each class period concludes with a short quiz on concepts presented in that day's presentations. We observe minimal differences in quiz scores between students in the control and treatment groups. Instead, we find that retention and transfer of presentation content correlate with certain metrics of presentation quality described in the Cognitive Theory of Multimedia Learning and with self-identified prior exposure to presentation topics.

S. B. Chernyshenko, V. M. Dobishuk, O. Yu. Okhrimenko et al.

The upgraded Large Hadron Collider beauty (LHCb) detector will provide data taken in Run3 at the instantaneous luminosity of proton-proton collisions increased to 2⋅1033 cm-2s-1 at energies of up to 14 TeV. To ensure the safe operation of the experiment, a new beam and background Radiation Monitoring System (RMS-R3) was built. RMS-R3 is based on metal-foil detector technology developed at the Institute for Nuclear Research, National Academy of Sciences of Ukraine (Kyiv, Ukraine). The system comprises four detector modules with two sensors in each. Their frequency response is proportional to the flux of incident charged particles. The modules are located around the beam pipe at a distance of 2.2 m from the interaction point. The results measured during the Run3 in 2022 testify to the reliable operation of the system. Applying the asymmetry method, high-accuracy data were obtained on the localization of the interactions region and the beam and background contribution.

V Djurberg, S Majdi, N Suntornwipat et al.

Using the state of valley-polarization of electrons in solids is a promising new paradigm for information storage and processing. The central challenge in utilizing valley-polarization for this purpose is to develop methods for manipulating and reading out the final valley state. Here, we demonstrate optical detection of valley-polarized electrons in diamond. It is achieved by capturing images of electroluminescence from nitrogen-vacancy centers at the surface of a diamond sample that are excited by electrons drifting and diffusing through the sample. Monte Carlo simulations are performed to interpret the resulting experimental diffusion patterns. Our results give insight into the drift-diffusion of valley-polarized electrons in diamond and yield a way of analyzing the valley-polarization of ensembles of electrons.

Andreas Crivellin, Bruce Mellado

The currently accepted mathematical description of the fundamental constituents and interactions of matter is the Standard Model of particle physics. Its last missing particle, the famous Higgs boson, was observed at the Large Hadron Collider at CERN in 2012. However, it is clear that the Standard Model cannot be the ultimate theory of Nature, and e.g. cannot account for Dark Matter or non-vanishing neutrino masses (and does not include gravity). In fact, searches for physics beyond the SM have been intensified since the Higgs boson discovery. In this article, we review the hints for new physics, called ``anomalies'', obtained in particle physics experiments within the last years. We consider both direct high-energy searches for new resonances at the LHC and indirect low-energy precision experiments. These anomalies range from the nuclear scale (approximately the mass of the proton) to the electroweak scale (i.e. the mass of the Higgs boson) to the TeV scale (the highest scale directly accessible at the LHC), therefore spanning over four orders of magnitude. After discussing the experimental and theoretical status of the anomalies, we summarize possible explanations in terms of new particles and new interactions. In particular, new Higgs bosons and leptoquarks are promising candidates. Discovery prospects and implications for future colliders are discussed.

A. T. Rudchik, A. A. Rudchik, O. O. Chepurnov et al.

New experimental data of angular distributions for the 6Li(10B,9Be)7Be reaction were measured at the energy Elab(10B) = 51 MeV for the ground states of nuclei and excited 0.429 - 7.2 MeV states of 7Be. The reaction experimental data were analyzed within coupled-reaction-channels method (CRC) for many types of the nucleon and cluster transfers which spectroscopic amplitudes (factors) in the 9Be and 7Be nuclei were calculated using translation invariant shell model. The Woods - Saxon potential was used for CRC-calculations. The 6Li + 10B potential parameters were deduced before from the analysis of experimental data of 10B ions scattering by 6Li nuclei at the energy Elab(10B) = 51 MeV, and the 9Be + 7Be potential parameters for exit reaction channel were deduced from the CRC calculations fitting to the reaction experimental data. Thus, the information about the 9Be + 7Be optical potential, the basic reaction mechanisms and the 9Be and 7Be nuclei structures were deduced.

H. Miao, G. Fabbris, R. J. Koch et al.

Abstract The unconventional normal-state properties of the cuprates are often discussed in terms of emergent electronic order that onsets below a putative critical doping of x c ≈ 0.19. Charge density wave (CDW) correlations represent one such order; however, experimental evidence for such order generally spans a limited range of doping that falls short of the critical value x c, leading to questions regarding its essential relevance. Here, we use X-ray diffraction to demonstrate that CDW correlations in La2−x Sr x CuO4 persist up to a doping of at least x = 0.21. The correlations show strong changes through the superconducting transition, but no obvious discontinuity through x c ≈ 0.19, despite changes in Fermi surface topology and electronic transport at this doping. These results demonstrate the interaction between CDWs and superconductivity even in overdoped cuprates and prompt a reconsideration of the role of CDW correlations in the high-temperature cuprate phase diagram.