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

Chaebin Kim, Olivia Vilella, Youjin Lee et al.

Abstract Topological spin textures are a spectacular manifestation of the chirality of the magnetic nanostructures protected by topology. Most known skyrmion systems are restricted to a topological charge of one, require an external magnetic field for stabilization, and are only reported in a few materials. Here, we investigate the possibility that the Kitaev anisotropic-exchange interaction stabilizes a higher-order skyrmion crystal in the insulating van der Waals magnet NiI2. We unveil and explain the incommensurate static and dynamic magnetic correlations across three temperature-driven magnetic phases of this compound using neutron scattering measurements, simulations, and modeling. Our parameter optimisation yields a minimal Kitaev-Heisenberg Hamiltonian for NiI2 which reproduces the experimentally observed magnetic excitations. Monte Carlo simulations for this model predict the emergence of the higher-order skyrmion crystal but neutron diffraction and optical experiments in the candidate intermediate temperature regime are inconclusive. We discuss possible deviations from the Kitaev-Heisenberg model that explains our results and conclude that NiI2, in addition to multiferroic properties in the bulk and few-layer limits, is a Kitaev bulk material proximate to the finite temperature higher-order skyrmion crystal phase.

S. Stengel, J. I. Choi, A. B. Solanki et al.

Quantum emitters operating at telecom wavelengths are essential for the advancement of quantum technologies, particularly for the development of integrated on-chip devices for quantum computing, communication, and sensing. Coupling resonant structures to an epsilon-near-zero (ENZ) environment has been shown to enhance their optical performance by both increasing spontaneous emission rates and improving emission directionality. In this work, we comparatively study the emission characteristics of colloidal PbS/CdS (core/shell) quantum dots at telecom wavelengths on different substrates. Two different sets of quantum dots, emitting within and outside the epsilon-near-zero region, are deposited on both glass and indium tin oxide (ITO) substrates. Our results demonstrate that coupling quantum dots to the ENZ spectral region results in a reduction in photoluminescence lifetime of 54 times, a 7.5-fold increase in saturation intensity, and a relative emission cone narrowing from 17.6° to 10.3°. These results underline the strong dependence of quantum dot emission properties on the spectral overlap with the epsilon-near-zero condition, highlighting the potential of transparent conducting oxides, such as ITO, for integration into next-generation quantum photonic devices. Owing to their CMOS compatibility, fabrication tunability, and high thermal and optical damage thresholds, these ENZ materials offer a robust platform for scalable and high-performance quantum optical systems operating within the telecom bandwidth.

Soumya Das, Goutam Paul, Anindya Banerji

Quantum teleportation efficiently transfers quantum information between distant locations by utilizing a pre-established composite system. Assessing the effectiveness of teleportation hinges on its fidelity, representing the similarity between input and output states. This fidelity, in turn, relies on a singlet fraction, quantifying the resemblance of the composite system to maximally entangled states. The relation between teleportation fidelity and singlet fraction given by Horodecki et al. [Phys. Rev. A 60, 1888 (1999)] does not hold for distinguishable particles with multiple degrees of freedom or indistinguishable particles with single or multiple degrees of freedom. In this paper, we propose generalized expressions for teleportation fidelity and singlet fraction and derive their relations, applicable to both distinguishable and indistinguishable particles with single or multiple degrees of freedom. We derive an upper bound for the generalized singlet fraction for distinguishable particles using the monogamy of singlet fraction by Kay et al. [Phys. Rev. Lett. 103, 050501 (2009)]. We also show how our relation helps characterize different types of composite states in terms of their distinguishability, separability, the presence of maximally entangled structure, and the number of degrees of freedom. We complement our theory with two practical illustrations. First, we demonstrate two counter-intuitive values of generalized singlet fraction using our optical circuit and the circuit of Li et al. [Phys. Rev. Lett. 120, 050404 (2018)]. Finally, we show that using an additional degree of freedom as an ancilla instead of a particle can be advantageous in quantum cryptographic protocols.

Wenbo Shi, Neel Kanth Kundu, Robert Malaney

Quantum routers direct a quantum signal from one input path to a quantum superposition of multiple output paths and are considered important elements of future quantum networks. To extend the scalability of quantum networks, multi-layer quantum routers, which allow for further superposition of paths, were proposed. Due to the numerous limitations of current quantum devices, quantum error mitigation methods become potential solutions for realizing practical quantum routers in the near term. Zero-Noise Extrapolation (ZNE) and Clifford Data Regression (CDR) are two promising quantum error mitigation methods. Based on the characteristics of these two methods, we propose a new method, named extrapolated CDR (eCDR). We benchmark the performance of multi-layer quantum routers implemented on current superconducting quantum devices instantiated with the ZNE, CDR, and eCDR methods. Our experimental results show that the new eCDR method improves the fidelity result of the two-layer quantum router. Our work highlights how new mitigation methods built from different components of pre-existing methods, and designed with a core application in mind, can lead to significant performance enhancements.

Laura Di Marino, Luigi Di Palma, Michele Riccio et al.

Quantum computation requires high-fidelity qubit readout, preserving the quantum state. In the case of superconductings qubits, readout is typically performed using a complex analog experimental setup operating at room temperature, which poses significant technological and economic barriers to large system scalability. An alternative approach is to perform a cryogenic on-chip qubit readout based on a Josephson digital phase detector (JDPD): a flux switchable device capable of digitizing the phase sign of a coherent input. The readout operation includes the flux excitation of the JDPD to evolve from a single- to a double-minima potential. In this work, the effect of the flux bias characteristics on the JDPD performances is studied numerically. To meet the identified requirements that maximize detection fidelity and tackle the engineering challenges, a cryogenic on-chip single flux quantum-based flux bias driver is proposed and discussed.

E. M. Anderson, C. R. Allemang, A. J. Leenheer et al.

Atomic precision advanced manufacturing (APAM) dopes silicon with enough carriers to change its electronic structure and can be used to create novel devices by defining metallic regions whose boundaries have single-atom abruptness. Incompatibility with the thermal and lithography process requirements for gated silicon transistor manufacturing have inhibited exploration of both how APAM can enhance CMOS performance and how transistor manufacturing steps can accelerate the discovery of new APAM device concepts. In this work, we introduce an APAM process that enables direct integration into the middle of a transistor manufacturing workflow. We show that a process that combines sputtering and annealing with a hardmask preserves a defining characteristic of APAM, a doping density far in excess of the solid solubility limit, while trading another, the atomic precision, for compatibility with manufacturing. The electrical characteristics of a chip combining a transistor with an APAM resistor show that the APAM module has only affected the transistor through the addition of a resistance and not by altering the transistor. This proof-of-concept demonstration also outlines the requirements and limitations of a unified APAM tool, which could be introduced into manufacturing environments, greatly expanding access to this technology and inspiring a new generation of devices with it.

Xiangyi Zhou, Rongzhi Gao, Ziyang Hu et al.

In rechargeable batteries, electron transport properties of inorganics in the solid-electrolyte interphase (SEI) critically determine the safety, lifespan and capacity loss of batteries. However, the electron transport properties of heterogeneous interfaces among different solid inorganics in SEI have not been studied experimentally or theoretically yet, although such heterogeneous interfaces exist inevitably. Here, by employing non-equilibrium Green's function (NEGF) method, we theoretically evaluated the atomic-scale electron transport properties under bias voltage for LiF/Li2O interfaces and single-component layers of them, since LiF and Li2O are common stable inorganics in the SEI. We reveal that heterogeneous interfaces orthogonal to the external electric-field direction greatly impede electron transport in SEI, whereas heterogeneous parallel-orientated interfaces enhance it. Structural disorders induced by densely distributed interfaces can severely interfere with electron transport. For each component, single-crystal LiF is highly effective to block electron transport, with a critical thickness of 2.9 nm, much smaller than that of Li2O (19.0 nm). This study sheds a new light into direct and quantitative understanding of the electron transport properties of heterogeneous interfaces in SEI, which holds promise for the advancement of a new generation of high-performance batteries.

Samudra Dasgupta, Travis S. Humble

In this article, we investigate the stability of probabilistic error cancellation (PEC) outcomes in the presence of nonstationary noise, which is an obstacle to achieving accurate observable estimates. Leveraging Bayesian methods, we design a strategy to enhance PEC stability and accuracy. Our experiments using a five-qubit implementation of the Bernstein–Vazirani algorithm and conducted on the ibm_kolkata device reveal a 42% improvement in accuracy and a 60% enhancement in stability compared to nonadaptive PEC. These results underscore the importance of adaptive estimation processes to effectively address nonstationary noise, vital for advancing PEC utility.

Yi-Ming Wu, Yuxuan Wang

Abstract We present a theory for charge-4e superconductivity as a leading low-temperature instability with a nontrivial d-wave symmetry. We show that in several microscopic models for the pair-density-wave (PDW) state, when the PDW wave vectors connect special parts of the Fermi surface, the predominant interaction is in the bosonic pairing channel mediated by exchanging low-energy fermions. This bosonic pairing interaction is repulsive in the s-wave channel but attractive in the d-wave one, leading to a d-wave charge-4e superconductor. By analyzing the Ginzburg-Landau free energy including higher-order fluctuation effects of PDW, we find that the charge-4e superconductivity emerges as a vestigial order of PDW, and sets in via a first-order transition. Both the gap amplitude and the transition temperature decay monotonically with increasing superfluid stiffness of the PDW order. Our work provides a microscopic mechanism of higher-charge condensates with unconventional ordering symmetry in strongly-correlated materials.

Sang Hyun Choi, Zhi-Feng Huang, Nigel Goldenfeld

Chiral active matter is predicted to exhibit odd elasticity, with nontraditional elastic response arising from a combination of chirality, being out of equilibrium, and the presence of nonreciprocal interactions. One of the resulting phenomena is the possible occurrence of odd elastic waves in overdamped systems, although its experimental realization still remains elusive. Here we show that in overdamped active systems, noise is required to generate persistent elastic waves. In the chiral crystalline phase of active matter, such as that found recently in populations of swimming starfish embryos, the noise arises from the self-driving of active particles and their mutual collisions, a key factor that has been missing in previous studies. We identify the criterion for the occurrence of noise-driven odd elastic waves and construct the corresponding phase diagram, which is also applicable to general chiral active crystals. Our results can be used to predict the experimental conditions for achieving a transition to self-sustained elastic waves in overdamped active systems.

X. Y. Feng, Z. Zhao, J. Luo et al.

Abstract Clarifying the interplay between charge-density waves (CDWs) and superconductivity is important in the kagome metal CsV3Sb5, and pressure (P) can play a crucial role. Here, we present 121/123Sb nuclear quadrupole resonance (NQR) measurements under hydrostatic pressures up to 2.43 GPa in CsV3Sb5 single crystals. We demonstrate that the CDW gradually changes from a commensurate modulation with a star-of-David (SoD) pattern to an incommensurate one with a superimposed SoD and Tri-hexagonal (TrH) pattern stacking along the c-axis. Moreover, the linewidth δ ν of 121/123Sb-NQR spectra increases with cooling down to T CDW, indicating the appearance of a short-range CDW order due to CDW fluctuations pinned by quenched disorders. The δ ν shows a Curie–Weiss temperature dependence and tends to diverge at P c ~ 1.9 GPa, suggesting that a CDW quantum critical point (QCP) exists at P c where T c shows the maximum. For P > P c, spin fluctuations are enhanced when the CDW is suppressed. Our results suggest that the maximal T c at P c ~ 1.9 GPa is related to the CDW QCP, and the presence of spin fluctuations prevents the T c from a rapid decrease otherwise, after the CDW is completely suppressed.

Brian Doolittle, R. Thomas Bromley, Nathan Killoran et al.

The noise and complexity inherent to quantum communication networks leads to technical challenges in designing quantum network protocols using classical methods. We address this issue with a hybrid variational quantum optimization (VQO) framework that simulates quantum networks on quantum hardware and optimizes the simulation using differential programming. We maximize nonlocality in noisy quantum networks to showcase our VQO framework. Using a classical simulator, we investigate the noise robustness of quantum nonlocality. Our VQO methods reproduce known results and uncover novel phenomena. We find that maximally entangled states maximize nonlocality in the presence of unital qubit channels, while nonmaximally entangled states can maximize nonlocality in the presence of nonunital qubit channels. Thus, we show VQO to be a practical design tool for quantum networks even when run on a classical simulator. Finally, using IBM quantum computers, we demonstrate that our VQO framework can maximize nonlocality on noisy quantum hardware. In the long term, our VQO techniques show promise of scaling beyond classical approaches and can be deployed on quantum network hardware to optimize network protocols against their inherent noise.

Artur Pambukhchyan, Sizhe Weng, Indu Aravind et al.

Nitrogen-vacancy (NV) and silicon-vacancy (SiV) color defects in diamond are promising systems for applications in quantum technology. The NV and SiV centers have multiple charge states, and their charge states have different electronic, optical and spin properties. For the NV centers, most investigations for quantum sensing applications are targeted on the negatively charged NV (NV ^− ), and it is important for the NV centers to be in the NV ^− state. However, it is known that the NV centers are converted to the neutrally charged state (NV ^0 ) under laser excitation. An energetically favorable charge state for the NV and SiV centers depends on their local environments. It is essential to understand and control the charge state dynamics for their quantum applications. In this work, we discuss the charge state dynamics of NV and SiV centers under high-voltage nanosecond pulse discharges. The NV and SiV centers coexist in the diamond crystal. The high-voltage pulses enable manipulating the charge states efficiently. These voltage-induced changes in charge states are probed by their photoluminescence spectral analysis. The analysis result from the present experiment shows that the high-voltage nanosecond pulses cause shifts of the chemical potential and can convert the charge states of NV and SiV centers with the transition rates of ∼MHz. This result also indicates that the major population of the SiV centers in the sample is the doubly negatively charged state (SiV ^2− ), which is often overlooked because of its non-fluorescent and non-magnetic nature. This demonstration paves a path for a method of rapid manipulation of the NV and SiV charge states in the future.

Eddy Keming Chen

Despite its apparent complexity, our world seems to be governed by simple laws of physics. This volume provides a philosophical introduction to such laws. I explain how they are connected to some of the central issues in philosophy, such as ontology, possibility, explanation, induction, counterfactuals, time, determinism, and fundamentality. I suggest that laws are fundamental facts that govern the world by constraining its physical possibilities. I examine three hallmarks of laws--simplicity, exactness, and objectivity--and discuss whether and how they may be associated with laws of physics.

Guannan Chen, Anuva Aishwarya, Mark R. Hirsbrunner et al.

Abstract The Fe-based superconductor Fe (Se,Te) combines non-trivial topology with unconventional superconductivity and may be an ideal platform to realize exotic states such as high-order topological corner modes and Majorana modes. Thin films of Fe (Se,Te) are particularly important for device fabrication and phase sensitive transport measurements. While bulk Fe (Se,Te) has been extensively studied, the nature of the superconducting order parameter in the monolayer limit has not yet been explored. In this work, we study monolayer films of Fe (Se,Te) on Bi2Te3 with scanning tunneling spectroscopy. Monolayer Fe (Se,Te)/Bi2Te3 heterostructures host a multigap superconducting state that strongly resembles the bulk. Analysis of the phase-referenced quasiparticle interference signal reveals a sign-changing s-wave order parameter similar to the bulk as well as a unique pattern of sign changes which have not been observed in the bulk. Our work establishes monolayer Fe (Se,Te)/Bi2Te3 as a robust multi-band unconventional superconductor and sets the stage for explorations of non-trivial topology in this highly-tunable system.

L. Jadoual, A. Afkir, A. El Boujlaidi et al.

Ion photon emission in the wavelength range of 280 - 420 nm resulting from 5 Kr+ ion beam sputtering from titanium in the presence and the absence of oxygen was studied experimentally. The observed spectra consist of a series of discrete lines superimposed with a broadband continuum. Discrete lines are attributed to excited neutral Ti I and excited ions Ti II. The differences in the observed intensities of spectral lines are discussed in terms of the electron-transfer processes between the excited sputtered atom and electronic levels of the solid. The radiative dissociation process and breaking of chemical bonds seem to contribute to the enhancement of emitted photons intensity. Continuum radiation was observed and is very probably related to the electronic structure of titanium. The collective deactivation of 3d-shell electrons appears to play a role in the emission of this radiation.

R. Kh. Gainutdinov, A. I. Garifullin, M. A. Khamadeev et al.

The periodic changes in the physical and chemical properties of the chemical elements are caused by the periodic change of the ionization energies, which are constant for each element that manifested in the Periodic Table. However, as has been recently shown the modification of the electromagnetic field in the photonic crystals gives rise to the modification of the electron electromagnetic mass. We show that the effect can significantly change the ionization energy of atoms placed in voids of photonic crystals consisting of metamaterials with a highly tunable refractive index and voids. The controllability of these materials gives rise to the controllability of the ionization energies over a wide range.

Luca Salasnich

Luca Salasnich

V. M. Antropov, O. V. Marinich, O. G. Tretyak et al.

The paper provides an overview of radioactive waste temporary storage sites (RWTSS) located at the Chornobyl exclusion zone. The screening, investigation, and other activities currently undertaken at RWTSS in order to ensure their safety, as well as associated obstacles, are outlined. Possible ways of the management of radioactive waste stored in RWTSS are determined, and the necessity of taking the relevant decisions is highlighted.