Showing papers in "European Physical Journal D in 2019"

SAGE: A proposal for a space atomic gravity explorer

Abstract: The proposed mission “Space Atomic Gravity Explorer” (SAGE) has the scientific objective to investigate gravitational waves, dark matter, and other fundamental aspects of gravity as well as the connection between gravitational physics and quantum physics using new quantum sensors, namely, optical atomic clocks and atom interferometers based on ultracold strontium atoms.

Soliton propagation of electromagnetic field vectors of polarized light ray traveling in a coiled optical fiber in Minkowski space with Bishop equations

Abstract: In this paper, we firstly obtain the evolution equations of the magnetic field and electric field vectors of polarized light ray propagating along a coiled optical fiber in Minkowski space. Then we define new kinds of binormal motions and new kinds of Hasimoto transformations to relate these evolution equations into the nonlinear Schrodinger’s equation. During this procedure, we use a parallel adapted frame or more commonly known as Bishop frame to characterize the coiled optical fiber geometrically. We also propose perturbed solutions of the nonlinear Schrodinger’s evolution equation that governs the propagation of solitons through the electric field (E) and magnetic field (M) vectors. Finally, we provide some numerical simulations to supplement the analytical outcomes.

Determination of electron inelastic mean free path of three transition metals from reflection electron energy loss spectroscopy spectrum measurement data

Abstract: The energy loss functions (ELFs) of three transition metals (Cr, Co and Pd) have been derived from reflection electron energy loss spectroscopy spectrum with a theoretical analysis of the measured data [Xu et al., J. Appl. Phys. 123, 043306 (2018)]. In this work, we update our previous ELFs in a wider photon energy region (0–200 eV) with a better accuracy, which is verified by sum rules and a root-mean-square deviation. The electron inelastic mean free paths (IMFPs) of Cr, Co and Pd have been calculated with the obtained ELFs by adopting a dielectric response theory. We employ both the single-pole approximation and full Penn algorithm for the calculation of IMFPs, and the calculated results are compared with other references.

The effect of non-Markovianity on the measurement-based uncertainty

Abstract: The uncertainty principle is one of fundamental traits in quantum mechanics, which essentially lies at the heart of quantum theory. The principle manifests that the measurement outcomes with respect to two incompatible observables cannot be predicted accurately. In fact, it can be expressed in terms of entropic measurement in the quantum information theory, since Berta et al. have indicated that uncertainty’s bound can be reduced when considering a particle as a quantum memory correlated with the particle to be measured. In this paper, we investigate the dynamical features of the entropic uncertainty within the non-Markovian regimes, and also compare several proposed bounds in such a scenario. We find that the uncertainty exhibits a non-monotonic behavior, and certify that the lower bound proposed by Adabi et al. is optimized. Besides, Stimulatingly, it turns out that the lower bound is not fully anti-correlated with the quantum correlation of the system, and associated with the A’s minimal conditional entropy $ {S}_{\mathrm{min}}^{A|B}$ . Besides, we offer a possible physical explanation for this behavior. Noteworthily, we propose a simple and working approach to manipulate the magnitude of the measurement uncertainty via a type of non-unitary operations.

Effect of Dzyaloshinskii-Moriya interaction on quantum entanglement in superconductors models of high T c

Abstract: The modified spin-wave (MSW) theory and SU(N) Schwinger boson theory (SBW) are employed to study the quantum entanglement in one- (1D) and two-dimensional (2D) Heisenberg antiferromagnets with Dzyaloshinskii–Moriya (DM) interaction which are models to superconducting materials of high critical temperature Tc such as La2CuO4. For the 1D case, we consider integer spin and for 2D case, since the behavior is independent on the spin value, we consider the one-half-spin and square lattice. We get the entanglement entropy in function of the temperature T where we have not gotten large variation of the quantum entanglement with the changing of the anisotropy Δ and DM interaction constant D.

Energy transfer from intense laser pulse to dielectrics in time-dependent density functional theory

Abstract: Energy transfer processes from a high-intensity ultrashort laser pulse to electrons in simple dielectrics, silicon, diamond, and α-quartz are theoretically investigated by first-principles calculations based on time-dependent density functional theory (TDDFT). Dependences on frequency as well as intensity of the laser pulse are examined in detail, making a comparison with the Keldysh theory. Although the Keldysh theory reliably reproduces the main features of the TDDFT calculation, we find some deviations between results by the two theories. The origin of the differences is examined in detail.

Correlations in a system of classical-like coins simulating spin-1/2 states in the probability representation of quantum mechanics

Abstract: An analog of classical “hidden variables” for qubit states is presented. The states of qubit (two-level atom, spin-1/2 particle) are mapped onto the states of three classical-like coins. The bijective map of the states corresponds to the presence of correlations of random classical-like variables associated with the coin positions “up” or “down” and the observables are mapped onto quantum observables described by Hermitian matrices. The connection of the classical-coin statistics with the statistical properties of qubits is found.

Laser Solitons in 1D, 2D and 3D

Abstract: We review research of spatial and spatiotemporal dissipative solitons and their complexes in laser with saturable absorption, beginning from geometrically one-dimensional (1D) and turning to two-dimensional (2D) and then to three-dimensional (3D) ones. We demonstrate evolution of features, including topological ones, with their enrichment, of the laser localized structures with increase of the scheme’s geometrical dimensionality.

Light drag via electron tunneling and incoherent pumping in semiconductor three-level InAs/GaAs double quantum dot molecules

Abstract: We theoretically investigate the lateral and rotary light-drag in semiconductor three-level InAs/GaAs double quantum dot molecules. No coherent laser fields are used and the coherence is created by interdot electron tunneling. The effect of interdot electron tunneling on lateral and rotary light-drag is discussed. Moreover, it is shown that applying an incoherent pumping field to the probe transition changes the subluminal to superluminal condition. It is observed that the light polarization state drags opposite and along with the medium motion in superluminal and subluminal propagating regions, respectively.

Effect of initial system–environment correlations with spin environments

Abstract: Understanding the dynamics of open quantum systems is a highly important task for the implementation of emerging quantum technologies. To make the problem tractable theoretically, it is common to neglect initial system–environment correlations. However, this assumption is questionable in situations where the system is interacting strongly with the environment. In particular, the system state preparation can then influence the dynamics of the system via the system–environment correlations. To gain insight into the effect of these correlations, we solve an exactly solvable model of a quantum spin interacting with a spin environment both with and without initial correlations for arbitrary system–environment coupling strengths. We show that the effect of the system state preparation may or may not be significant in the strong system–environment coupling regime at low temperatures. We also study the dynamics of the entanglement between two spins interacting with a common spin environment with and without initial system–environment correlations to demonstrate that the correlations can play a significant role in the dynamics of two-qubit systems as well.

Bose-condensed optomechanical-like system and a Fabry–Perot cavity with one movable mirror: quantum correlations from the perspectives of quantum optics

Abstract: From the perspective of quantum optics, various lower- and higher-order nonclassical features of correlations have been studied for two physical systems- (i) an optomechanical system composed of a Fabry–Perot cavity with one nonlinearly oscillating mirror and (ii) an optomechanical-like system formed using a Bose–Einstein condensate (BEC) trapped inside an optical cavity. The investigation is performed using a perturbation method that leads to closed form analytic expressions for the time evolution of the relevant bosonic operators. In the first system, it is observed that the radiation pressure coupling leads to the emergence of lower- and higher-order single-mode and two-mode quantum correlations. The effects of the coherent interaction of a nonlinear oscillating mirror with the cavity mode are also studied, and it is observed that the optomechanical system studied here becomes more correlated when the coupling strength is increased. It is also observed that the possibility of observing entanglement depends on the phase of the movable mirror. The Hamiltonian of the trapped BEC system is obtained as a special case of the Hamiltonian of the first system, and the existence of quantum correlations in the trapped BEC system has been established, and variations of those with various physical parameters have been reported with an aim to understand the underlying physical process that leads to and controls the correlations. Finally, the possibility of observing these correlations under the effect of environment has also been performed.

Resonant excitations of a Bose Einstein condensate in an optical lattice

Abstract: We investigate experimentally a Bose Einstein condensate placed in a 1D optical lattice whose phase or amplitude is modulated in a frequency range resonant with the first bands of the band structure. More precisely, we study the effect of the strength of a weak extra external confinement superimposed to the lattice on the 1 and 2-phonon transitions. We identify lines immune or very sensitive to the external confinement despite many orders of magnitude of difference in strength compared to the lattice. We interpret those features and present 1D numerical simulations including atom-atom interactions consistent with the experimental observations. Using the band mapping technique, we also get a direct access to the populations that have undergone n-phonon transitions for each modulation frequency including for non-zero quasi-momentum.

Acousto-optic interaction in Raman–Nath acousto-optic diffraction

Abstract: In this article, acousto-optic interaction in Raman–Nath acousto-optic diffraction has been discussed. By studying the relations between the power of the diffracted light and its origin in the ultrasonic field, we found that the phase of the diffracted light is modulated temporally and spatially by the ultrasonic wave. Finally, we present a method to obtain the Raman–Nath acousto-optic diffraction without the optical phase modulations.

New symmetric and planar designs of reversible full-adders/subtractors in quantum-dot cellular automata

Abstract: Quantum-dot Cellular Automata (QCA) is one of the emerging nanotechnologies, promising an alternative to CMOS technology due to a faster speed, smaller size, lower power consumption, higher scale integration, and higher switching frequency. In addition, power dissipation is the main limitation of all the nanoelectronics design techniques including the QCA. Researchers have proposed various mechanisms to solve this problem. Among them, reversible computing is considered as a reliable solution to reduce the power dissipation. On the other hand, adders are fundamental circuits for most digital systems. So, in this paper, the focus is on designing of reversible full-adders in logical and layout levels. For this aim, the first, a method for converting irreversible functions to reversible ones is investigated. Based on it, two novel designs of reversible full-adders/subtractors are presented. In another section, a new five-input majority gate is introduced. By using of this gate, a new reversible full-adder is designed. Finally, the proposed structures are extended to design three new 8-bit reversible full-adder/subtractors. The results are indicative of the outperformance of the proposed designs in comparison with the best available ones in terms of area, complexity, delay, reversible/irreversible layout, and also in logic level in terms of garbage outputs, control inputs, number of majority and NOT gates.

Plasma potential probes for hot plasmas - A review and some news

Abstract: Plasma probes are well established diagnostic tools. They are not complicated, relatively easy to construct and to handle. The easiest and fastest accessible parameter is their floating potential. However, the floating potential of a cold probe is not very significant. Much more important and relevant is the plasma potential. But in most types of plasmas, consisting mainly of electrons and only positive ions, the floating potential is more negative than the plasma potential by a factor proportional to the electron temperature. Obviously this is due to the much higher mobility of the electrons. We present a review on probes whose floating potential is close to or ideally equal to the plasma potential. Such probes we name Plasma Potential Probes (PPP) and they can either be Electron Emissive Probes (EEP) or so-called Electron Screening Probes (EPS). These probes make it possible to measure the plasma potential directly and thus with high temporal resolution. An EEP compensates the plasma electron current by an electron emission current from the probe into the plasma, thereby rendering the current-voltage characteristic symmetric with respect to the plasma potential and shifting the floating potential towards the plasma potential. Only the simplest case of an EEP floating exactly on the plasma potential is discussed here in which case no sheath is present around the probe. An ESP, principally operable only in strong magnetic fields, screens off most of the plasma electron current from the probe collector, taking advantage of the fact that the gyro radius of electrons is usually much smaller than that of the ions. Also in this case we obtain a symmetric current-voltage characteristic and a shift of the probe’s floating potential towards the plasma potential. We have developed strong and robust EEPs and two types of ESPs, called BUnker Probes (BUP), for the use in the Scrape-Off Layer (SOL) of Medium-Size Tokamaks (MST), and other types of strongly magnetized hot plasmas. These probes are presented in detail.

Higher dimensional entanglement without correlations

Abstract: It has been demonstrated both theoretically and experimentally that genuine multipartite entanglement between qubits can exist even in the absence of multipartite correlations. Here, we provide first examples of this effect in higher dimensional systems – qudits. We construct states in which genuine N-partite entanglement between qudits is supported only by correlations involving strictly less than N particles. The construction differs in several aspects from the ones for qubits. The states introduced here are a natural test-bed for candidate quantifiers of genuinely multipartite quantum correlations.

Scattering theory of the screened Casimir interaction in electrolytes

Abstract: We apply the scattering approach to the Casimir interaction between two dielectric half-spaces separated by an electrolyte solution. We take the nonlocal electromagnetic response of the intervening medium into account, which results from the presence of movable ions in solution. In addition to the usual transverse modes, we consider longitudinal channels and their coupling by reflection at the surface of the local dielectric. The Casimir interaction energy is calculated from the matrix describing a round-trip of coupled transverse and longitudinal waves between the interacting surfaces. The nonzero-frequency contributions are approximately unaffected by the presence of ions. We find, at zero frequency, a contribution from longitudinal channels, which is screened over a distance of the order of the Debye length, alongside an unscreened term arising from transverse-magnetic modes. The latter defines the long-distance asymptotic limit for the interaction.

Influence of Dzyaloshinskii-Moriya interaction and external fields on quantum entanglement in half-integer spin one-dimensional antiferromagnets

Abstract: The effect of uniform Dzyaloshinskii-Moriya interaction (antisymmetric spin coupling) and arbitrary oriented external magnetic fields in the x and z directions hx, hy, on quantum entanglement is investigated in the quantum spin-1/2 one-dimensional Heisenberg antiferromagnetic model. The Von Neumann entropy of quantum entanglement is calculated employing Abelian bosonization and density matrix renormalization group. We investigate the influence of quantum phase transition of three competing phases (Neel phase, dimerized phase and gapless Luttinger liquid phase) on quantum entanglement at zero-temperature.

Contribution of higher order corrections to the dust acoustic soliton energy in non-Maxwellian dusty plasma

Abstract: The contribution of higher order corrections to the DA soliton energy in the presence of nonthermal ions is investigated Our plasma model is inspired from the experimental study of Bandyopadhyay et al [P Bandypadhyay, G Prasad, A Sen, PK Kaw, Phys Rev Lett 101, 065006 (2008)] Using the approach based on the expansion of Sagdeev potential up to the fourth-order, a second order inhomogeneous differential equation termed dressed soliton is obtained The latter is divided into two contributions, the usual K-dV solution and the higher order correction structure Our results reveal that the main quantities of these localized structures are significantly modified by the nonthermality effects In particular, an increase of ion’s nonthermal character leads to an increase of the amplitude and width of all the structures The role the higher order corrections and nonthermal ions may play on the energy carried by the DA soliton is then examined For a given value of nonthermal parameter α, it is shown that due to the higher order correction contribution, the departure between the K-dV soliton energy and the dressed one becomes more important as soliton velocity λ increases For the sake of comparison, the presented model is reduced to a Maxwellian plasma and the results are compared to their experimental counterparts

Reactive molecular dynamics simulations of organometallic compound W(CO)6 fragmentation

Abstract: Irradiation- and collision-induced fragmentation studies provide information about geometry, electronic properties and interactions between structural units of various molecular systems. Such knowledge brings insights into irradiation-driven chemistry of molecular systems which is exploited in different technological applications. An accurate atomistic-level simulation of irradiation-driven chemistry requires reliable models of molecular fragmentation which can be verified against mass spectrometry experiments. In this work fragmentation of a tungsten hexacarbonyl, W(CO)6, molecule is studied by means of reactive molecular dynamics simulations. The quantitatively correct fragmentation picture including different fragmentation channels is reproduced. We show that distribution of the deposited energy over all degrees of freedom of the parent molecule leads to thermal evaporation of CO groups and the formation of W(CO)n+ (n = 0 – 5) fragments. Another type of fragments, WC(CO)n+ (n = 0 – 4), is produced due to cleavage of a C–O bond as a result of localized energy deposition. Calculated fragment appearance energies are in good agreement with experimental data. These fragmentation mechanisms have a general physical nature and should take place in radiation-induced fragmentation of different molecular and biomolecular systems.

Positron binding to hydrocarbon molecules: calculation using the positron–electron correlation polarization potential

Abstract: Positron binding energies of naphthalene and alkanes (CnH2n+2 with n = 3 − 16) are calculated using the correlation polarization potential approach, where the short-range positron–electron correlation potential is modeled by the density-functional expression taken from a homogenous electron gas model. In the case of naphthalene, the calculated positron binding energy is found to reasonably agree with the experimental measurement. In the case of CnH2n+2 with the linear all-trans conformation we found positive positron binding energies for n ≥ 8 while the positron is not bound for n ≤ 7. This result cannot reproduce the previous experimental study, where the positron was bound for all alkanes with 3 ≤n ≤ 16. In addition, our calculated positron binding energies for n ≥ 9 are much larger than the experimental values although the generalized gradient approximation could improve the calculated values. We also investigated the conformer dependence of the positron binding energy for C16H34 and found that the positron binding energies significantly depend on the conformational structure; hairpin-like and crown-like structures generally have large positron binding energies, while single and multiple gauche structures have smaller binding energies.

Low- and high-order nonlinear optical studies of ZnO nanocrystals, nanoparticles, and nanorods

Abstract: Variable shapes and sizes of the zinc oxide nanostructures attract the attention due to the peculiarities of their nonlinear optical properties. We report the second-, third-, and high-order nonlinear optical studies of ZnO nanostructures using 800 nm, 40 fs pulses. We analyze the second harmonic generation as a function of the energy of the 800 nm laser pulses irradiating ZnO nanostructures. The studied samples possess the quadratic dependence of the second harmonic yield at the variable intensity of laser radiation. The Z-scan studies of ZnO nanoparticles suspension using 400 nm probe pulses allow determining their nonlinear refractive index (4 × 10−11 cm2 W−1) and nonlinear absorption coefficient (8 × 10−7 cm W−1). We also analyze the optical limiting properties of ZnO nanoparticles suspension. The propagation of femtosecond pulses through the plasmas containing ZnO nanoparticles allowed generation of high harmonics up to the 29th order.

New generalized binomial theorems involving two-variable Hermite polynomials via quantum optics approach and their applications

Abstract: We extend the ordinary binomial theorem to the case which involves two-variable Hermite polynomials in the context of quantum optics, and analytically obtain several new generalized binomial theorems whose results exactly equal the single- or two-mode Hermite polynomials. As their applications in the field of quantum optics, we analytically prove that the multiple-photon-subtracted squeezed state ambnesa†b†+ra†+tb† |00⟩ is equivalent to the Hermite-polynomial-weighted quantum state serving as an easily produced non-Gaussian entangled information resource, and the Wigner functions of spin coherent states and their marginal distributions are respectively the Laguerre polynomials and the Hermite polynomials.

Study of electron collision from bioalcohols from 10 to 5000 eV

Abstract: The electron-impact cross sections are obtained for alkyl bioalcohols in the energy range from ionization threshold to 5000 eV. The molecular wavefunction of targets are obtained from the multi-centre expansion of the Gaussian-type orbitals within a single determinant Hartree–Fock self consistent field scheme. The three dimensional molecular quantities like wavefunction, density and potentials are expanded at the centre of mass of molecule using the Single Centre Expansion formalism. The interaction potential is assumed to be local in nature and is approximated by static, correlation-polarization and exchange effects. The elastic cross sections are obtained after solving the coupled integro-radial differential equations using Volterra integral form. The inelastic ionization cross sections are computed by Binary-Encounter-Bethe method. The total cross sections are obtained after summing the elastic and inelastic cross sections incoherently. The scattering calculations were also performed for glycerol and phenol. The cross sections obtained from present methodology are in good agreement with available results. The study of e− scattering from different targets has helped in expressing a relationship between the total cross section of two different targets in a most simple but effective way.

The interaction of guanine nucleobase with B 40 borospherene

Abstract: The adsorption of guanine nucleobase on borospherene (B40) is investigated with density functional theory (DFT). We obtained that guanine is adsorbed on the surface of B40 cluster in five different stable configurations. The considerable adsorption energies (−1.023 ~ −1.586 eV) and charge transfers (0.292 ~ 0.345|e|) indicate that the guanine can be adsorbed on the surface of B40 in chemisorption state. The direct orbital overlaps between B40 and guanine account for the chemisorption. Depending on the significant variation of electrical conductivity, it is discovered that B40 cluster is feasible as a promising sensor for guanine nucleobase.

Thermal study of the atomic ratio effect on a cylindrical and an ellipsoidal shaped HgTlI discharge lamps

Abstract: The purpose of this paper is to study the thermal behavior of a high-intensity HgTlI lamp in a cylindrical shape, compared to an ellipsoidal lamp during variations of the mercury to thallium atomic ratio. For this, we developed a chemical model under Local Thermodynamic Equilibrium conditions. Then, it was coupled with a three-dimensional code, time-dependent that solves the systems of equations for the mass, energy and momentum, as well as the equation of Laplace for the plasma using Comsol Multiphysics coupled with Matlab. Based on the variations of the mercury to thallium ratio, we analyzed the temperature fields, the heat conduction flow, the convective flow and the accumulation of mercury behind the electrodes for both of the shapes in different mercury to thallium ratios.

Schemes to avoid entanglement sudden death of decohering two qubit system

Abstract: We investigate the entanglement dynamics of two interacting qubits in a common vacuum environment. The inevitable environment interaction leads to entanglement sudden death (ESD) in a two qubit entangled system. The entanglement dynamics can be modified by the use of local unitary operations (quantum gates), applied on the system during its evolution. We show that these operations not only delays or avoids the ESD but also advances the entanglement revival with an enhanced entanglement depending on the time of operation. We have analytically found out different time windows for switching with different quantum gates so that the ESD can be completely avoided in the subsequent evolution of the system. Our result offers practical applications in the field of quantum information processing where the entanglement is a necessary resource.

Scattering of e∓ from ytterbium atoms

Abstract: The differential, total, momentum transfer and viscosity cross sections for the elastic scattering of electrons and positrons by ytterbium atoms have been calculated. We have also calculated the total inelastic and ionization cross sections. In addition, the Sherman function S(θ) and the inelastic mean free paths have been determined for the scattering of both projectiles. The critical minima in the elastic differential cross sections (DCS) were determined from the analysis of the DCS and S(θ). These investigations have been carried out within the framework of two different theoretical approaches at the impact energies 1 eV–0.5 GeV for both projectiles. In the atomic domain the solution involves a complex projectile-atom optical potential while in the nuclear domain only the nuclear potential has been employed. Both approaches employ the Dirac partial wave analysis. Our results are in reasonable agreement with available experimental data and other theoretical findings. To the best of our knowledge, for positron scattering, there are no experimental data available in the literature.

Ionization of guanine, adenine and thymine molecules by electron impact

Abstract: The method and results of the study of positive ions yield in the mass-spectrometric investigations by electron impact ionization of molecules of guanine, adenine and thymine are described. Mass spectrum obtained by electron impact has been measured in a crossed electron–molecule beam experiment ionization at the electron energy 70 eV. The ionization energy of the molecule and the appearance potential of some fragment ions were obtained. The mass spectra and fragmentation schemes of adenine and thymine molecules by electron impact were analyzed. The analysis of measured mass spectra is carried out, schemes of fragmentation of guanine, adenine and thymine molecules are proposed, which illustrate the most probable channels for the formation of ionic fragments in an electron impact, when the energy of the incident electrons is much higher than the ionization potential of the molecule. An explanation of the behaviours of the obtained temperature dependences of ions can be due to the difference in the character of the formation and fragmentation of the guanine, thymine and adenine molecules by electron impact.

Ab initio molecular dynamics studies of Au38(SR)24 isomers under heating

Abstract: Despite the great success in achieving monodispersity for a great number of monolayer-protected clusters, to date little is known about the dynamics of these ultra-small metal systems, their decomposition mechanisms, and the energy that separates their structural isomers. In this work, we use density functional theory (DFT) to calculate and compare the ground state energy and the Born-Oppenheimer molecular dynamics of two well-known Au38(SCH2CH2Ph)24 nanocluster isomers. The aim is to shed light on the energy difference between the two clusters isomers and analyze their decomposition mechanisms triggered by high temperatures. The results demonstrate that the energy that separates the two isomers is of the same order of magnitude as the energy difference between the fcc and hcp phases of bulk gold reported earlier. Moreover, the MD simulations show disordering and eventual fragmentation of the cluster structures at high temperature which seem to proceed via spontaneous formation of Aux(SR)y polymeric chains. Hence, these results greatly contribute to understanding the possible decomposition mechanism, stability and robustness of existing and new monolayer-protected clusters.