Transverse Field Research Articles

Impact of quantum information encoding and metallic leads on dynamical multipartite correlation formation in semiconductor quantum dot arrays

Abstract This study investigates quantum information scrambling (QIS) in a semiconductor quantum dot array. Starting with the 1D Transverse Field Ising model, we expand to more relevant quasi-2D frameworks such as the Heisenberg chain, super-extended Fermi-Hubbard and hardcore Fermi-Hubbard models. Assessing their relevance to semiconductor spin-qubit quantum computers, simulations of multipartite entanglement formation examine qubit encoding strategies’ fidelity, stability, and robustness, revealing trade-offs among these aspects. Furthermore, we investigate the weakly coupled metallic injector/detector (I/D) leads’ significant impact on QIS behavior by employing Ω lead N-single orbital impurities weakly coupled Anderson models. We observe sign flips in spatiotemporal tripartite mutual information I3 which result in significant effects on dynamical quantum entanglement structures and their formation. Exploring carrier number effects, we identify optimal regions for QIS enhancement. Our findings emphasize the necessity of proper qubit encoding and I/D lead influence on quantum devices amidst noise and impurities.

Multipartite Entanglement in Crossing the Quantum Critical Point

Abstract We investigate the multipartite entanglement for a slow quantum quench crossing a critical point. We consider the quantum Ising model and the Lipkin-Meshkov-Glick model, which are local and full-connected quantum systems, respectively. The multipartite entanglement is quantified by quantum Fisher information with the generator defined as the operator of the ferromagnetic order parameter. The quench dynamics begins with a ground state in a paramagnetic phase, and then the transverse field is driven slowly to cross a quantum critical point, and ends with a zero transverse field. For the quantum Ising model, based on methods of matrix product states, we calculate the quantum Fisher information density of the final state. Numerical results of both linear and nonlinear quenches show that the quantum Fisher information density of the final state scales as a power law of the quench rate, which overall conforms to the prediction of the Kibble-Zurek mechanism with a small correction. We show that this correction results from the long-range behaviors. We also calculate the quantum Fisher information density in the Lipkin-Meshkov-Glick model. The results show that the scaling of quantum Fisher information in this full-connected system conforms to the Kibble-Zurek mechanism better, since the long-range physics cannot be defined in this nonlocal system. Our results reveal that the multipartite entanglement provides an alternative viewpoint to understand the dynamics of quantum phase transitions, specifically, the nontrivial long-range physics.

The Nature of the Elongated Granulations and Stretched Dark Lanes in a Newly Emerging Flux Region

In this study, we explore the elongated granulations and stretched dark lanes within the emerging anti-Hale active region NOAA AR 12720. Utilizing high-resolution observations from the New Vacuum Solar Telescope, we discern a prevalence of elongated granules and stretched dark lanes associated with the emergence of new magnetic flux positioned between two primary opposing magnetic polarities. These elongated granulations and stretched dark lanes exhibit an alignment of strong transverse fields and a significant inclination angle. The endpoints of these features separate from each other, with their midpoints predominantly characterized by blueshifted signals in the photosphere. This suggests a close association between elongated granules and stretched dark lanes with the newly emerging flux. Additionally, we find that the stretched dark lanes display a more pronounced correlation with strong blueshifts and photospheric transverse magnetic fields compared to the elongated granulations. The transverse magnetic field within these stretched dark lanes reaches magnitudes of approximately 300–400 G, and the inclination angle demonstrates an “arch-like” pattern along the trajectory of the stretched dark lane. Based on these observed characteristics, we infer the presence of an emerging flux tube with an “arch-like” shape situated along the stretched dark lane. Consequently, we conclude that the stretched dark lanes likely represent manifestations of the emerging flux tube, while the elongated granulations may correspond to the gaps between the emerging flux tubes.

Electrotunable superlubricity of two-dimensional ZIF-8

Electric field control can actively, dynamically, and repeatably influence the interface friction behavior. The unique properties of two-dimensional (2D) ZIF-8 make it a promising lubricating material for electromechanical devices. The study on the electrotunable superlubricity of 2D ZIF-8 is carried out under longitudinal and transverse electric fields respectively, resulting in an order of magnitude variation in friction coefficient (μ: 0.0037∼0.0124). Through the experiments and simulation, the regulation mechanism of electric fields on the lubricating properties of 2D ZIF-8 is attributed to the coupling effect of adhesion regulation and out-of-plane deformation regulation: The weakening of anchoring effect reduces the adhesion between probe and 2D ZIF-8; the tight binding of interfacial charge under longitudinal electric field as well as the increase in surface stiffness caused by lattice tension under transverse electric field, both restrain the out-of-plane deformation during friction. The electrotunable superlubricity of 2D ZIF-8 helps achieve rapid and flexible adjustment of the friction interface in electro-mechanical systems under charged conditions, illuminating the future development prospects for intelligent control.

Confinement in the Transverse Field Ising Model on the Heavy Hex Lattice

Inspired by a recent quantum computing experiment [Y. Kim , ], we study the emergence of confinement in the transverse field Ising model on a decorated hexagonal lattice. Using an infinite tensor network state optimized with belief propagation we show how a quench from a broken symmetry state leads to striking nonthermal behavior underpinned by persistent oscillations and saturation of the entanglement entropy. We explain this phenomenon by constructing a minimal model based on the confinement of elementary excitations. Our model is in excellent agreement with our numerical results. For quenches to larger values of the transverse field and/or from nonsymmetry broken states, our numerical results display the expected signatures of thermalization: a linear growth of entanglement entropy in time, propagation of correlations, and the saturation of observables to their thermal averages. These results provide a physical explanation for the unexpected classical simulability of the quantum dynamics. Published by the American Physical Society 2024

Impact of valley degeneracy on the thermoelectric properties of zig-zag graphene nanoribbons with staggered sublattice potentials and transverse electric fields.

This study investigates the band inversion of flat bands in zig-zag graphene nanoribbons (ZGNRs) using a tight-binding model. The band inversion results from symmetry breaking in the transverse direction, achievable through deposition on specific substrates such as separated silicon carbide or hexagonal boron nitride sheets. Upon band inversion, ZGNRs exhibit electronic structures characterized by valley degeneracy and band gap properties, which can be modulated by transverse electric fields. To explore the impact of this level degeneracy on thermoelectric properties, we employ Green's function techniques to calculate thermoelectric quantities in ZGNR segments with staggered sublattice potentials and transverse electric fields. Two carrier transport scenarios are considered: the chemical potential is positioned above and below the highest occupied molecular orbital. We analyze thermionic-assisted transport (TAT) and direct ballistic transport (DBT). Level degeneracy enhances the electric power factors of ZGNRs by increasing electrical conductance, while the Seebeck coefficient remains robust in the TAT scenario. Conversely, in DBT, the enhancement of the power factor primarily stems from improvements in the Seebeck coefficient at elevated temperatures.

Meshfree method for bending and free vibration analysis of laminated plates using the Reissner’s mixed variational theorem

Free vibration and bending behavior of laminated plates are investigated using a combination of Reissner’s mixed variational theorem and the meshless radial point interpolation method. By introducing Reissner’s mixed variational theorem, a refined transverse shear stress field is derived based on three-dimensional (3D) elasticity equations. The efficiency and accuracy of this model are demonstrated through numerical examples. It is found that accurate prediction of shear stresses significantly improves the prediction of natural frequency for composite laminated plates. The difference between shear stresses derived from 3D equilibrium equations and that from constitutive equations is significant.

Quantum-coherence-assisted dynamical phase transition in the one-dimensional transverse-field Ising model

Quantum coherence will undoubtedly play a fundamental role in understanding the dynamics of quantum many-body systems; therefore, to be able to reveal its genuine contribution is of great importance. In this paper, we focus our discussions on the one-dimensional transverse field quantum Ising model initialized in the coherent Gibbs state, and investigate the effects of quantum coherence on dynamical quantum phase transition (DQPT). After quenching the strength of the transverse field, the effects of quantum coherence are studied using Fisher zeros and the rate function of the Loschmidt echo. We find that quantum coherence not only recovers DQPT destroyed by thermal fluctuations, but also generates some entirely new DQPTs, which are independent of the equilibrium quantum critical point. We also find that the Fisher zero cutting the imaginary axis is not sufficient to generate DQPT because it also requires the Fisher zeros to be tightly bound close enough to the neighborhood of the imaginary axis. It can be manifested that DQPTs are rooted in quantum fluctuations. This work reveals new information on the fundamental connection between quantum critical phenomena and quantum coherence.

First in-vivo magic angle directional imaging using dedicated low-field MRI.

To report the first in-vivo results from exploiting the magic angle effect, using a dedicated low-field MRI scanner that can be rotated about two axes. The magic angle directional imaging (MADI) method is used to depict collagen microstructures with 3D collagen tractography of knee ligaments and the meniscus. A novel low-field MRI system was developed, based on a transverse field open magnet, where the magnet can be rotated about two orthogonal axes. Sets of volume scans at various orientations were obtained in healthy volunteers. The experiments focused on the anterior cruciate ligament (ACL) and the meniscus of the knee. The images were co-registered, anatomical regions of interest (ROIs) were selected and the collagen fiber orientations in each voxel were estimated from the observed image intensity variations. The 3D collagen tractography was superimposed on conventional volume images. The MADI method was successfully employed for the first time producing in-vivo results comparable to those previously reported for excised animal specimens using conventional MRI. Tractography plots were generated for the ACL and the menisci. These results are consistent with the known microstructure of collagen fibers in these tissues. Images obtained using low-field MRI with 1 mm3 resolution were of sufficient quality for the MADI method, which was shown to produce high quality in-vivo information of collagen microstructures. This was achieved using a cost effective and sustainable low-field magnet making the technique potentially accessible and scalable, potentially changing the way we image injuries or disease in joints.

Canonical coordinates for Yang-Mills-Chern-Simons theory

We consider the classical field theory of 2+1-dimensional Yang-Mills-Chern-Simons theory on an arbitrary spatial manifold. We first define a gauge covariant transverse electric field strength, which together with the gauge covariant scalar magnetic field strength can be taken as coordinates on the classical phase space. We then determine the Poisson-Dirac bracket and find that these coordinates are canonically conjugate to each other. The Hamiltonian is non-polynomial when expressed in terms of these coordinates, but can be expanded in a power series in the coupling constant with polynomial coefficients.

First Principles Variational Formulation and Analytical Solutions for Third Order Shear Deformable Beams with Simple Supports using Fourier Series Method

The Fourier series method for solving bending problems of third-order shear deformable beams (TSBD) is presented in this paper. The theory accounts for transverse shear deformation and is suitable for moderately thick beams. Transverse shear stress-free conditions are valid at the beam surfaces for TSDB. The field equations are two coupled ordinary differential equations in terms of two unknown displacement functions – transverse deflection w(x) and warping function For simply supported ends considered, the loading and unknown functions w(x) and are represented in Fourier series that satisfies the boundary conditions. The problem is reduced to a system of algebraic equations in terms of the Fourier coefficients wn and which is solved to obtain wn and Axial and transverse displacements fields, axial bending stress and transverse shear stress are then determined for the cases of point load at midspan, uniformly and linearly distributed loads over the span. The results are identical with previous results obtained by other scholars who used Ritz variational methods and other mathematical tools. For moderately thick beams under uniform load with l/h = 4, the results obtained for is 0.516% greater than the exact result by Timoshenko and Goodier while for thick beams under uniform load with l/h = 2, the result for is 1.96% greater than the exact result by Timoshenko and Goodier. Similar acceptable variation was obtained for for beams under linearly distributed load with the variations being less than 2% for l/h = 2. However, unacceptable variations of 68.37% were found for in thick beams under point load, for l/h = 2.0. The variation for however reduced to 12.513% for moderately thick beams under point load for l/h =4.

Transverse magnetic supermodes in plasmonic optical fibers excited by radially polarized light

The overlap integrals method, with a fully vectorial formulation, is used to model the selective excitation of the TM01 mode in a few-mode optical fiber with a radially polarized donut beam, and its coupling to guided modes having a plasmonic character (supermodes). The analyses were performed on a waveguide formed as a step-index few-mode optical fiber coated with a thin gold film, at an operating wavelength of 1310 nm. The waveguide was found to support modes having optical fiber, circular metallic waveguide, and surface plasmon characteristics, depending on geometrical and material parameters. Three purely bound transverse magnetic (radially polarized) supermodes were identified: Two symmetric, labeled sTM01 and sTM02 modes, and one asymmetric, labeled ab mode, where symmetry pertains to the transverse electric field distribution over the gold film. The effective mode indices of the supermodes were studied as a function of the thickness of the gold film and its proximity to the fiber core. Considerations for the selective excitation of the sTM01 mode are discussed along with its possible applications. The transmittance of the supermodes is found to be robust even at sharp waveguide transitions. The results predict that effective excitation of TM supermodes with strong plasmonic character, without significant coupling losses, can be achieved by exciting the fiber with a radially polarized donut beam.

Vectorial spatial differentiation of optical beams with metal–dielectric multilayers enabled by spin Hall effect of light and resonant reflection zero

We theoretically describe and numerically investigate the operation of “vectorial” optical differentiation of a three-dimensional light beam, which consists in simultaneous computation of two partial derivatives of the incident beam profile with respect to two spatial coordinates in different transverse electric field components. It is implemented upon reflection of the beam from a layered structure by simultaneously utilizing the effect of optical resonance and the spin Hall effect of light. As an example of a layered structure performing this operation, we propose a three-layer metal–dielectric–metal (MDM) structure. We show that by choosing the parameters of the MDM structure, it is possible to achieve the so-called isotropic vectorial differentiation, for which the intensity of the reflected optical beam (squared electric field magnitude) is proportional to the squared absolute value of the gradient of the incident linearly polarized beam. The presented numerical simulation results demonstrate high-quality vectorial differentiation and confirm the developed theoretical description.

Analytical derivation and extension of the anti-Kibble-Zurek scaling in the transverse field Ising model

Analytical derivation and extension of the anti-Kibble-Zurek scaling in the transverse field Ising model

Thermoelectric properties of MoS2-MoTe2 and MoS2-MoSe2lateral hetero-structures: The effects of external magnetic, transverse electric fields and nanoribbon width

Extensive research is underway to improve the thermoelectric properties of materials by enhancing the figure of merit (ZT). In this study, we are investigating the thermoelectric properties of MoS2/MoTe2 and MoS2/MoSe2 lateral heterostructures (LH-S) under the influence of external magnetic fields (EMF) and transverse electric fields (TEF). We employ the non-equilibrium Green's function (N-EGF) and tight-binding (TB) methods for our analysis. The results obtained indicate that the ZT for MoS2-MoTe2 and MoS2-MoSe2 LH-S enhanced with an increase in the TEF. The ZT of MoS2-MoSe2 LH-S increases near room temperature, while the ZT of MoS2-MoTe2 LH-S increases with an increase in EMF across the entire temperature range. Additionally, the ZT for MoS2-MoSe2 LH-S increases with an increase in the nanoribbon width, whereas for MoS2-MoTe2 LH-S, it decreases. The results reveal that the semiconductor type of MoS2-MoSe2 and MoS2-MoTe2 LH-S changes from n-type to p-type when subjected to EMF and transverse TEF. The examination of the temperature dependence of ZT in the presence of TEF and EMF for MoS2-MoTe2 and MoS2-MoSe2 LH-S indicates that these structures are highly promising candidates for use in electrical devices.

Modulation of electronic and thermal properties of boron phosphide nanotubes under electric and magnetic fields

This work theoretically investigates the thermoelectric properties of boron phosphide nanotubes (BPNTs) using the tight-binding model, Green function method, and Kubo formalism, focusing on a zigzag BPNT with indices (20, 0). The tight binding parameters obtained by matching its band structure with calculated density functional theory band structure. The study examines the effects of transverse electric fields and axial magnetic fields on various physical properties, such as band structure, density of states (DOS), heat capacity, magnetic susceptibility, and other thermoelectric properties. BPNTs consistently show semiconducting properties with a nearly 1 eV direct band gap. The electronic properties of BPNTs are significantly affected by applied electric field, which at very strong strengths can induce a semiconducting to metallic phase transition. In contrast, the magnetic field leads to the splitting of energy bands, especially around the Fermi level. The DOS also changes with the electric field, including variations in the position, intensity, and number of DOS peaks. The thermal properties and thermoelectric performance of BPNTs are temperature-dependent. Increasing of excited electrons thermal energy cause more occupation of high energy levels in the conduction bands. The electric field further enhances the thermal properties of BPNTs by modifying their electronic properties and reducing the band gap. Stronger electric fields cause a noticeable enhancement in the BPNTs thermal properties because it is increasing the concentration of excited charge carriers. This aspect is crucial for improving the thermoelectric efficiency of BPNTs, making them more competitive for practical applications.

Dynamical phase transitions, caustics, and quantum dark bands

Abstract We provide a new perspective on quantum dynamical phase transitions (DPTs) by explaining their origin in terms of caustics that form in the Fock space representation of the many-body state over time, using the fully connected transverse field Ising model as an example. In this way we establish a connection between DPTs in a quantum spin system and an everyday natural phenomenon: The dark band between the primary and secondary bows (caustics) in rainbows known as Alexander’s dark band. The DPT occurs when the Loschmidt echo crosses the switching line between the evanescent tails of two back-to-back Airy functions that dress neighbouring fold caustics in Fock space and is the time-dependent analogue of what is seen as a function of angle in the sky. The structural stability and universal properties of caustics, as described mathematically by catastrophe theory, explains the generic occurrence of DPTs in the model and suggests that our analysis has wide applicability. Based on our thorough analytical understanding we propose a protocol which can be used to verify the existence of a DPT in a finite system experiment.

Chromoelectric flux tubes within non-Abelian Proca theory

Flux tube solutions within non-Abelian SU(3) Proca theory with external sources are obtained. It is shown that such tubes have a longitudinal chromoelectric field possessing two components (nonlinear and gradient), as well as a transverse chromomagnetic field whose force lines create concentric circles with the center on the axis of the tube. The scenario of a possible relationship between non-Abelian Proca theory and quantum chromodynamics is considered. In such scenario: (a) the components of color fields have different behavior: those which are almost classical, and those which are purely quantum; (b) the second components create a gluon condensate that is a source of the field for the almost classical components of the Proca field; (c) Proca masses may appear as a result of an approximate description of the gluon condensate; (d) the question of gauge invariance is considered. It is shown that the results obtained are in good agreement with the results of lattice calculations. We make an assumption that an approximate description of a flux tube in quantum chromodynamics can be carried out using classical Proca equations but with a mandatory account of a gluon condensate.

Effective spin models and magnetic phases of an insulating bosonic ladder with unconventional synthetic flux

We investigate the Mott insulating phases of a two-component bosonic lattice gas in the presence of gauge field. Such a system is described by a two-leg ladder model with an unconventional flux. The synthetic flux is generated by the spin-dependent tunneling and the site-dependent spin-flip. In the Mott regime, these two effects lead to Dzyaloshinskii-Moriya (DM) interaction and an external field that is rotating in the xy-plane. We obtain a very general XYZ model with the DM interaction, the spiral field, and the transverse field. Various interesting magnetic Hamiltonians can be covered by adjusting lattice parameters. The DM interaction or the spiral field can lead to spiral order when they appear alone. The interplay of DM coupling and spiral field leads to the emergence of a new multi-frequency spiral order between the paramagnetic phase and the spiral ferromagnetic phase. Ground state phases are investigated by focusing on order parameters, spin-spin correlation functions, and structure factors. Calculations are performed by using time evolution block decimation (TEBD) based on matrix product state (MPS).

Quasiprobabilities in Quantum Thermodynamics and Many-Body Systems

In this tutorial, we present the definition, interpretation, and properties of some of the main quasiprobabilities that can describe the statistics of measurement outcomes evaluated at two or more times. Such statistics incorporate the incompatibility of the measurement observables and the state of the measured quantum system. We particularly focus on Kirkwood-Dirac quasiprobabilities and related distributions. We also discuss techniques to experimentally access a quasiprobability distribution, ranging from the weak two-point measurement scheme, to a Ramsey-like interferometric scheme and procedures assisted by an external detector. Once defined the fundamental concepts following the standpoint of joint measurability in quantum mechanics, we illustrate the use of quasiprobabilities in quantum thermodynamics to describe the quantum statistics of work and heat, and to explain anomalies in the energy exchanges entailed by a given thermodynamic transformation. On the one hand, in work protocols, we show how absorbed energy can be converted to extractable work and vice versa due to Hamiltonian incompatibility at distinct times. On the other hand, in exchange processes between two quantum systems initially at different temperatures, we explain how quantum correlations in their initial state may induce cold-to-hot energy exchanges, which are unnatural between any pair of equilibrium nondriven systems. We conclude the tutorial by giving simple examples where quasiprobabilities are applied to many-body systems: scrambling of quantum information, sensitivity to local perturbations, and quantum work statistics in the quenched dynamics of models that can be mapped onto systems of free fermions, for instance, the Ising model with a transverse field. Throughout the tutorial, we meticulously present derivations of essential concepts alongside straightforward examples, aiming to enhance comprehension and facilitate learning. Published by the American Physical Society 2024