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

A Picone, A Brambilla

Abstract Heterostructures consisting of graphene (Gr) and metal-oxides are gaining increasing attention due to their exceptional structural, electronic, and chemical properties. Understanding the characteristics of the Gr/metal-oxide interface is crucial for designing advanced materials with tailored properties for a wide range of technological applications. Gr is often employed as a substrate for the stabilisation of metal-oxides nanoclusters, enhancing their performance in heterogeneous catalysis. Conversely, the integration of atomically flat, ultra-thin metal-oxides with Gr enables precise modulation of its electronic properties, thereby unlocking novel possibilities for advancements in nano-electronics. This review explores the atomic-scale details of interfaces formed between Gr and metal-oxide films, analysed from a surface science perspective. Special attention is directed toward the role of Gr in shaping the morphology of metal-oxides, as well as in addressing the challenges of stabilising a Gr layer on an oxide surface. The electronic coupling between Gr and metal oxides is examined, with a focus on the implications for both catalytic and electronic applications of these heterostructures.

Dongkwon Lee, Seonho Lee, Jaebum Park et al.

Strain mediated by mechanical motion provides a powerful resource for controlling solid-state qubits in hybrid quantum systems. Leveraging more than one mechanical mode enables extended control capabilities that are inaccessible with a single mode. In this work, we experimentally demonstrate multimode strain engineering in hybrid systems comprising nitrogen-vacancy (NV) centers in diamond coupled to the mechanical motion of diamond oscillators via strain. By simultaneously driving flexural and torsional modes in T- and U-shaped oscillators and tuning their relative phases and amplitudes, we selectively enhance or suppress longitudinal strain coupling. Numerical simulations further suggest the possibility of independently controlling both longitudinal and transverse strains using membrane-like oscillators that support nearly degenerate mechanical modes. This approach paves the way for advanced mechanical control in hybrid quantum systems through multimode engineering.

Chunxiang Song, Yanan Liu, Daoyi Dong et al.

The stabilization of quantum states is a fundamental problem for realizing various quantum technologies. Measurement-based-feedback strategies have demonstrated powerful performance, and the construction of quantum control signals using measurement information has attracted great interest. However, the interaction between quantum systems and the environment is inevitable, especially when measurements are introduced, which leads to decoherence. To mitigate decoherence, it is desirable to stabilize quantum systems faster, thereby reducing the time of interaction with the environment. In this article, we utilize information obtained from measurement and apply deep reinforcement learning (DRL) algorithms, without explicitly constructing specific complex measurement-control mappings, to rapidly drive random initial quantum state to the target state. The proposed DRL algorithm has the ability to speed up the convergence to a target state, which shortens the interaction between quantum systems and their environments to protect coherence. Simulations are performed on two- and three-qubit systems, and the results show that our algorithm can successfully stabilize a random initial quantum system to the target entangled state, with a convergence time faster than traditional methods such as Lyapunov feedback control and several DRL algorithms with different reward functions. Moreover, it exhibits robustness against imperfect measurements and delays in system evolution.

D. A. Yelisieiev, O. V. Yelisieieva, Yu. О. Нurkalenko et al.

Fluorinederivatives of 4'-phenyl-3-hydroxyflavone have been synthesized and used as activators for radiation-resistant plastic scintillators based on polystyrene. Plastic scintillators containing 1.0 wt. % of the corresponding activators were created. The spectral-luminescent and scintillation properties of the obtained materials were studied, and their radiation resistance was determined. It was shown that the use of fluorinederivatives of 4'-phenyl-3-hydroxyflavone enables the production of plastic scintillators with radiation resistance at the level of 490 kGy.

Ali Övgün, Reggie C. Pantig, Bobomurat Ahmedov et al.

Motivated by the work of Scully \textit{et al.} [ \textcolor{blue}{Proc. Nat. Acad. Sci. 115, 8131 (2018)}] and Camblong \textit{et al.}[ \textcolor{blue}{Phys. Rev. D 102, 085010 (2020)}], we investigate horizon-brightened acceleration radiation (HBAR) for freely falling two-level atoms in the geometry of a Bardeen regular black hole. Building on the quantum-optics approach to acceleration radiation and its near-horizon conformal quantum mechanics (CQM) structure, we show that the dominant physics is again governed by an inverse-square potential in the radial Klein-Gordon equation, with an effective coupling fixed by the Bardeen surface gravity. Using geodesic expansions and a near-horizon CQM reduction of the scalar field, we derive the excitation probability for atoms falling through a Boulware-like vacuum in the presence of a stretched-horizon mirror. The resulting spectrum is Planckian in the mode frequency, with a temperature determined by the Bardeen Hawking temperature. We analyze how the regular core parameter controls the strength of the radiation and demonstrate that the excitation probability is strongly suppressed as the geometry approaches the extremal (cold remnant) limit. Numerical results illustrate the dependence of the spectrum on the Bardeen parameter and on the atomic transition frequency.

Katsunori Wakabayashi

D. M. Nasef, E. T. Ellafi, S. M. El-Kadi

This theoretical study investigates the properties of even-even 162-17870Yb isotopes using the interacting vector boson model (IVBM). Our study focuses on the ground state band and negative parity band energy-level patterns, which provide insights into the shapes and symmetries of these nuclei. Furthermore, we investigate the collective properties of these isotopes, such as rotational and vibrational motion, as well as their interplay. The results of our theoretical analysis shed light on the structural evolution of ytterbium isotopes with increasing neutron numbers. The comparison of our theoretical predictions with experimental data will provide valuable insights into the nuclear structure of these isotopes and help validate the IVBM model's effectiveness in describing collective phenomena. This theoretical study employs the IVBM to investigate the dynamic symmetry of even-even 162-17870Yb isotopes. By conducting tests such as the ratio, backbending, and staggering analyses, we aim to determine the underlying symmetries governing the behavior of these isotopes. These results indicate that 16270Yb possess O(6) symmetry, 164-16670Yb have transition O(6) - SU(3) symmetry, and 168-17870Yb possess SU(3) symmetry. The study's outcomes show that the IVBM is dependable and useful for nuclear physics research because it aligns well with the corresponding experimental data.

Avior Almoalem, Roni Gofman, Yuval Nitzav et al.

Abstract 4Hb-TaS2 is a superconductor that exhibits unique characteristics such as time-reversal symmetry breaking, hidden magnetic memory, and topological edge modes. It is a naturally occurring heterostructure comprising of alternating layers of 1H-TaS2 and 1T-TaS2. The former is a well-known superconductor, while the latter is a correlated insulator with a possible non- trivial magnetic ground state. In this study, we use angle resolved photoemission spectroscopy to investigate the normal state electronic structure of this unconventional superconductor. Our findings reveal that the band structure of 4Hb-TaS2 fundamentally differs from that of its constituent materials. Specifically, we observe a significant charge transfer from the 1T layers to the 1H layers that drives the 1T layers away from half-filling. In addition, we find a substantial reduction in inter-layer coupling in 4Hb-TaS2 compared to the coupling in 2H-TaS2 that results in a pronounced spin-valley locking within 4Hb-TaS2.

Gines Carrascal, Paula Hernamperez, Guillermo Botella et al.

In portfolio theory, the investment portfolio optimization problem is one of those problems whose complexity grows exponentially with the number of assets. By backtesting classical and quantum computing algorithms, we can get a sense of how these algorithms might perform in the real world. This work establishes a methodology for backtesting classical and quantum algorithms in equivalent conditions, and uses it to explore four quantum and three classical computing algorithms for portfolio optimization and compares the results. Running 10 000 experiments on equivalent conditions we find that quantum can match or slightly outperform classical results, showing a better escalability trend. To the best of our knowledge, this is the first work that performs a systematic backtesting comparison of classical and quantum portfolio optimization algorithms. In this work, we also analyze in more detail the variational quantum eigensolver algorithm, applied to solve the portfolio optimization problem, running on simulators and real quantum computers from IBM. The benefits and drawbacks of backtesting are discussed, as well as some of the challenges involved in using real quantum computers of more than 100 qubits. Results show quantum algorithms can be competitive with classical ones, with the advantage of being able to handle a large number of assets in a reasonable time on a future larger quantum computer.

Patrick Müller, Wilfried Nörtershäuser

The analysis of experimental results with Python often requires writing many code scripts which all need access to the same set of functions. In a common field of research, this set will be nearly the same for many users. The qspec Python package was developed to provide functions for physical formulas, simulations and data analysis routines widely used in laser spectroscopy and related fields. Most functions are compatible with numpy arrays, enabling fast calculations with large samples of data. A multidimensional linear regression algorithm enables a King plot analyses over multiple atomic transitions. A modular framework for constructing lineshape models can be used to fit large sets of spectroscopy data. A simulation module within the package provides user-friendly methods to simulate the coherent time-evolution of atoms in electro-magnetic fields without the need to explicitly derive a Hamiltonian.

Jun Ye, Peter Zoller

Atomic, molecular, and optical (AMO) physics has been at the forefront of the development of quantum science while laying the foundation for modern technology. With the growing capabilities of quantum control of many atoms for engineered many-body states and quantum entanglement, a key question emerges: what critical impact will the second quantum revolution with ubiquitous applications of entanglement bring to bear on fundamental physics? In this Essay, we argue that a compelling long-term vision for fundamental physics and novel applications is to harness the rapid development of quantum information science to define and advance the frontiers of measurement physics, with strong potential for fundamental discoveries. As quantum technologies, such as fault-tolerant quantum computing and entangled quantum sensor networks, become much more advanced than today's realization, we wonder what doors of basic science can these tools unlock? We anticipate that some of the most intriguing and challenging problems, such as quantum aspects of gravity, fundamental symmetries, or new physics beyond the minimal standard model, will be tackled at the emerging quantum measurement frontier.

Emilian Marius Nica, Muhammad Akram, Aayush Vijayvargia et al.

Abstract We determine the phase diagram of a bilayer, Yao-Lee spin-orbital model with inter-layer interactions (J), for several stackings and moiré superlattices. For AA stacking, a gapped $${{\mathbb{Z}}}_{2}$$ Z 2 quantum spin liquid phase emerges at a finite J c. We show that this phase survives in the well-controlled large-J limit, where an isotropic honeycomb toric code emerges. For moiré superlattices, a finite-q inter-layer hybridization is stabilized. This connects inequivalent Dirac points, effectively ‘untwisting’ the system. Our study thus provides insight into the spin-liquid phases of bilayer spin-orbital Kitaev materials.

Aikaterini Flessa Savvidou, Andrzej Ptok, G. Sharma et al.

Abstract We report a transport study on Pd3In7 which displays multiple Dirac type-II nodes in its electronic dispersion. Pd3In7 is characterized by low residual resistivities and high mobilities, which are consistent with Dirac-like quasiparticles. For an applied magnetic field (μ 0 H) having a non-zero component along the electrical current, we find a large, positive, and linear in μ 0 H longitudinal magnetoresistivity (LMR). The sign of the LMR and its linear dependence deviate from the behavior reported for the chiral-anomaly-driven LMR in Weyl semimetals. Interestingly, such anomalous LMR is consistent with predictions for the role of the anomaly in type-II Weyl semimetals. In contrast, the transverse or conventional magnetoresistivity (CMR for electric fields E⊥μ 0 H) is large and positive, increasing by 103−104 % as a function of μ 0 H while following an anomalous, angle-dependent power law $${\rho }_{{{{\rm{xx}}}}}\propto {({\mu }_{0}H)}^{n}$$ ρ xx ∝ ( μ 0 H ) n with n(θ) ≤ 1. The order of magnitude of the CMR, and its anomalous power-law, is explained in terms of uncompensated electron and hole-like Fermi surfaces characterized by anisotropic carrier scattering likely due to the lack of Lorentz invariance.

Qiang Zou, Silu Huang, Wonhee Ko et al.

Abstract Single crystalline BaMnSb2 is considered as a 3D Weyl semimetal with the 2D electronic structure containing Dirac cones from the Sb sheet. We report experimental investigation of low-temperature cleaved BaMnSb2 surfaces using scanning tunneling microscopy/spectroscopy and low energy electron diffraction. By natural cleavage, we find two terminations: one is Ba (above the orthorhombically distorted Sb sheet) and another Sb2 (at the surface of the Sb/Mn/Sb sandwich layer). Both terminations show the 2 × 1 surface reconstructions, with drastically different morphologies and electronic properties, however. The reconstructed structures, defect types and nature of the electronic structures of the two terminations are extensively studied. The quasiparticle interference (QPI) analysis is conducted at the energy range between −2 V and 2 V, although no interesting states are observed near the Fermi level, the surface-projected electronic band structures strongly depend on the surface termination above 1.6 V. The existence of defects can greatly modify the local density of states to create electronic phase separations on the surface in the order of tens of nm scale. Our observation on the atomic structures of the terminations and the corresponding electronic structures provides critical information towards an understanding of topological properties of BaMnSb2.

A. Chronister, M. Zingl, A. Pustogow et al.

Abstract We perform nuclear magnetic resonance (NMR) measurements of the oxygen-17 Knight shifts for Sr2RuO4, while subjected to uniaxial stress applied along [100] direction. The resulting strain is associated with a strong variation of the temperature and magnetic field dependence of the inferred magnetic response. A quasiparticle description based on density-functional theory calculations, supplemented by many-body renormalizations, is found to reproduce our experimental results, and highlights the key role of a van-Hove singularity. The Fermi-liquid coherence scale is shown to be tunable by strain, and driven to low values as the associated Lifshitz transition is approached.

Anu Kumari, Satyabrata Adhikari

Quantification of entanglement is one of the most important problem in quantum information theory. In this work, we will study this problem by defining a physically realizable measure of entanglement for any arbitrary dimensional bipartite system $ρ$, which we named as structured negativity $(N_S(ρ))$. We have shown that the introduced measure satisfies the properties of a valid entanglement monotone. We also have established an inequality that relate negativity and the structured negativity. For $d\otimes d$ dimensional state, we conjecture from the result obtained in this work that negativity coincide with the structured negativity when the number of negative eigenvalues of the partially transposed matrix is equal to $\frac{d(d-1)}{2}$. Moreover, we proved that the structured negativity not only implementable in the laboratory but also a better measure of entanglement in comparison to negativity. In few cases, we obtain that structure negativity gives better result than the lower bound of the concurrence obtained by Albeverio [Phys. Rev. Lett. \textbf{95}, 040504 (2005)].

V. M. Samsonov

William Steinhardt, P. A. Maksimov, Sachith Dissanayake et al.

Abstract Recently, Yb-based triangular-lattice antiferromagnets have garnered significant interest as possible quantum spin-liquid candidates. One example is YbMgGaO4, which showed many promising spin-liquid features, but also possesses a high degree of disorder owing to site-mixing between the non-magnetic cations. To further elucidate the role of chemical disorder and to explore the phase diagram of these materials in applied field, we present neutron scattering and sensitive magnetometry measurements of the closely related compound, YbZnGaO4. Our results suggest a difference in magnetic anisotropy between the two compounds, and we use key observations of the magnetic phase crossover to motivate an exploration of the field- and exchange parameter-dependent phase diagram, providing an expanded view of the available magnetic states in applied field. This enriched map of the phase space serves as a basis to restrict the values of parameters describing the magnetic Hamiltonian with broad application to recently discovered related materials.

Nicola Manini

Yvonne Leifels