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Sample records for quantum chaotic scattering

  1. Universal chaotic scattering on quantum graphs.

    PubMed

    Pluhař, Z; Weidenmüller, H A

    2013-01-18

    We calculate the S-matrix correlation function for chaotic scattering on quantum graphs and show that it agrees with that of random-matrix theory. We also calculate all higher S-matrix correlation functions in the Ericson regime. These, too, agree with random-matrix theory results as far as the latter are known. We conjecture that our results give a universal description of chaotic scattering.

  2. Quantum chaotic scattering in graphene systems in the absence of invariant classical dynamics.

    PubMed

    Wang, Guang-Lei; Ying, Lei; Lai, Ying-Cheng; Grebogi, Celso

    2013-05-01

    Quantum chaotic scattering is referred to as the study of quantum behaviors of open Hamiltonian systems that exhibit transient chaos in the classical limit. Traditionally a central issue in this field is how the elements of the scattering matrix or their functions fluctuate as a system parameter, e.g., the electron Fermi energy, is changed. A tacit hypothesis underlying previous works was that the underlying classical phase-space structure remains invariant as the parameter varies, so semiclassical theory can be used to explain various phenomena in quantum chaotic scattering. There are, however, experimental situations where the corresponding classical chaotic dynamics can change characteristically with some physical parameter. Multiple-terminal quantum dots are one such example where, when a magnetic field is present, the classical chaotic-scattering dynamics can change between being nonhyperbolic and being hyperbolic as the Fermi energy is changed continuously. For such systems semiclassical theory is inadequate to account for the characteristics of conductance fluctuations with the Fermi energy. To develop a general framework for quantum chaotic scattering associated with variable classical dynamics, we use multi-terminal graphene quantum-dot systems as a prototypical model. We find that significant conductance fluctuations occur with the Fermi energy even for fixed magnetic field strength, and the characteristics of the fluctuation patterns depend on the energy. We propose and validate that the statistical behaviors of the conductance-fluctuation patterns can be understood by the complex eigenvalue spectrum of the generalized, complex Hamiltonian of the system which includes self-energies resulted from the interactions between the device and the semi-infinite leads. As the Fermi energy is increased, complex eigenvalues with extremely smaller imaginary parts emerge, leading to sharp resonances in the conductance.

  3. Correlation functions and correlation widths in quantum-chaotic scattering for mesoscopic systems and nuclei.

    PubMed

    Ramos, J G G S; Barbosa, A L R; Carlson, B V; Frederico, T; Hussein, M S

    2016-01-01

    We derive analytical expressions for the correlation functions of the electronic conductance fluctuations of an open quantum dot under several conditions. Both the variation of energy and that of an external parameter, such as an applied perpendicular or parallel magnetic fields, are considered in the general case of partial openness. These expressions are then used to obtain the ensemble-averaged density of maxima, a measure recently suggested to contain invaluable information concerning the correlation widths of chaotic systems. The correlation width is then calculated for the case of energy variation, and a significant deviation from the Weisskopf estimate is found in the case of two terminals. The results are extended to more than two terminals. All of our results are analytical. The use of these results in other fields, such as nuclei, where the system can only be studied through a variation of the energy, is then discussed.

  4. Correlation functions and correlation widths in quantum-chaotic scattering for mesoscopic systems and nuclei

    NASA Astrophysics Data System (ADS)

    Ramos, J. G. G. S.; Barbosa, A. L. R.; Carlson, B. V.; Frederico, T.; Hussein, M. S.

    2016-01-01

    We derive analytical expressions for the correlation functions of the electronic conductance fluctuations of an open quantum dot under several conditions. Both the variation of energy and that of an external parameter, such as an applied perpendicular or parallel magnetic fields, are considered in the general case of partial openness. These expressions are then used to obtain the ensemble-averaged density of maxima, a measure recently suggested to contain invaluable information concerning the correlation widths of chaotic systems. The correlation width is then calculated for the case of energy variation, and a significant deviation from the Weisskopf estimate is found in the case of two terminals. The results are extended to more than two terminals. All of our results are analytical. The use of these results in other fields, such as nuclei, where the system can only be studied through a variation of the energy, is then discussed.

  5. Resonant scattering in graphene with a gate-defined chaotic quantum dot

    NASA Astrophysics Data System (ADS)

    Schneider, Martin; Brouwer, Piet W.

    2011-09-01

    We investigate the conductance of an undoped graphene sheet with two metallic contacts and an electrostatically gated island (quantum dot) between the contacts. Our analysis is based on the matrix Green function formalism, which was recently adapted to graphene by Titov [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.076802 104, 076802 (2010)]. We find pronounced differences between the case of a stadium-shaped dot (which has chaotic classical dynamics) and a disk-shaped dot (which has integrable classical dynamics) in the limit that the dot size is small in comparison to the distance between the contacts. In particular, for the stadium-shaped dot the two-terminal conductance shows Fano resonances as a function of the gate voltage, which cross over to Breit-Wigner resonances only in the limit of completely separated resonances, whereas for a disk-shaped dot sharp Breit-Wigner resonances resulting from higher angular momentum remain present throughout.

  6. Driving trajectories in chaotic scattering.

    PubMed

    Macau, Elbert E N; Caldas, Iberê L

    2002-02-01

    In this work we introduce a general approach for targeting in chaotic scattering that can be used to find a transfer trajectory between any two points located inside the scattering region. We show that this method can be used in association with a control of chaos strategy to drive around and keep a particle inside the scattering region. As an illustration of how powerful this approach is, we use it in a case of practical interest in celestial mechanics in which it is desired to control the evolution of two satellites that evolve around a large central body.

  7. New developments in classical chaotic scattering.

    PubMed

    Seoane, Jesús M; Sanjuán, Miguel A F

    2013-01-01

    Classical chaotic scattering is a topic of fundamental interest in nonlinear physics due to the numerous existing applications in fields such as celestial mechanics, atomic and nuclear physics and fluid mechanics, among others. Many new advances in chaotic scattering have been achieved in the last few decades. This work provides a current overview of the field, where our attention has been mainly focused on the most important contributions related to the theoretical framework of chaotic scattering, the fractal dimension, the basins boundaries and new applications, among others. Numerical techniques and algorithms, as well as analytical tools used for its analysis, are also included. We also show some of the experimental setups that have been implemented to study diverse manifestations of chaotic scattering. Furthermore, new theoretical aspects such as the study of this phenomenon in time-dependent systems, different transitions and bifurcations to chaotic scattering and a classification of boundaries in different types according to symbolic dynamics are also shown. Finally, some recent progress on chaotic scattering in higher dimensions is also described.

  8. Fractal dimension in nonhyperbolic chaotic scattering

    NASA Technical Reports Server (NTRS)

    Lau, Yun-Tung; Finn, John M.; Ott, Edward

    1991-01-01

    In chaotic scattering there is a Cantor set of input-variable values of zero Lebesgue measure (i.e., zero total length) on which the scattering function is singular. For cases where the dynamics leading to chaotic scattering is nonhyperbolic (e.g., there are Kolmogorov-Arnol'd-Moser tori), the nature of this singular set is fundamentally different from that in the hyperbolic case. In particular, for the nonhyperbolic case, although the singular set has zero total length, strong evidence is presented to show that its fractal dimension is 1.

  9. Basin topology in dissipative chaotic scattering.

    PubMed

    Seoane, Jesús M; Aguirre, Jacobo; Sanjuán, Miguel A F; Lai, Ying-Cheng

    2006-06-01

    Chaotic scattering in open Hamiltonian systems under weak dissipation is not only of fundamental interest but also important for problems of current concern such as the advection and transport of inertial particles in fluid flows. Previous work using discrete maps demonstrated that nonhyperbolic chaotic scattering is structurally unstable in the sense that the algebraic decay of scattering particles immediately becomes exponential in the presence of weak dissipation. Here we extend the result to continuous-time Hamiltonian systems by using the Henon-Heiles system as a prototype model. More importantly, we go beyond to investigate the basin structure of scattering dynamics. A surprising finding is that, in the common case where multiple destinations exist for scattering trajectories, Wada basin boundaries are common and they appear to be structurally stable under weak dissipation, even when other characteristics of the nonhyperbolic scattering dynamics are not. We provide numerical evidence and a geometric theory for the structural stability of the complex basin topology.

  10. Quantum chaotic resonances from short periodic orbits.

    PubMed

    Novaes, M; Pedrosa, J M; Wisniacki, D; Carlo, G G; Keating, J P

    2009-09-01

    We present an approach to calculating the quantum resonances and resonance wave functions of chaotic scattering systems, based on the construction of states localized on classical periodic orbits and adapted to the dynamics. Typically only a few such states are necessary for constructing a resonance. Using only short orbits (with periods up to the Ehrenfest time), we obtain approximations to the longest-living states, avoiding computation of the background of short living states. This makes our approach considerably more efficient than previous ones. The number of long-lived states produced within our formulation is in agreement with the fractal Weyl law conjectured recently in this setting. We confirm the accuracy of the approximations using the open quantum baker map as an example.

  11. Exploring Classically Chaotic Potentials with a Matter Wave Quantum Probe

    SciTech Connect

    Gattobigio, G. L.; Couvert, A.; Georgeot, B.; Guery-Odelin, D.

    2011-12-16

    We study an experimental setup in which a quantum probe, provided by a quasimonomode guided atom laser, interacts with a static localized attractive potential whose characteristic parameters are tunable. In this system, classical mechanics predicts a transition from regular to chaotic behavior as a result of the coupling between the different degrees of freedom. Our experimental results display a clear signature of this transition. On the basis of extensive numerical simulations, we discuss the quantum versus classical physics predictions in this context. This system opens new possibilities for investigating quantum scattering, provides a new testing ground for classical and quantum chaos, and enables us to revisit the quantum-classical correspondence.

  12. Dynamical trapping and chaotic scattering of the harmonically driven barrier.

    PubMed

    Koch, Florian R N; Lenz, Florian; Petri, Christoph; Diakonos, Fotios K; Schmelcher, Peter

    2008-11-01

    A detailed analysis of the classical nonlinear dynamics of a single driven square potential barrier with harmonically oscillating position is performed. The system exhibits dynamical trapping which is associated with the existence of a stable island in phase space. Due to the unstable periodic orbits of the KAM structure, the driven barrier is a chaotic scatterer and shows stickiness of scattering trajectories in the vicinity of the stable island. The transmission function of a suitably prepared ensemble yields results which are very similar to tunneling resonances in the quantum mechanical regime. However, the origin of these resonances is different in the classical regime.

  13. Will Quantum Cosmology Resurrect Chaotic Inflation Model?

    NASA Astrophysics Data System (ADS)

    Kim, Sang Pyo; Kim, Won

    2016-07-01

    The single field chaotic inflation model with a monomial power greater than one seems to be ruled out by the recent Planck and WMAP CMB data while Starobinsky model with a higher curvature term seems to be a viable model. Higher curvature terms being originated from quantum fluctuations, we revisit the quantum cosmology of the Wheeler-DeWitt equation for the chaotic inflation model. The semiclassical cosmology emerges from quantum cosmology with fluctuations of spacetimes and matter when the wave function is peaked around the semiclassical trajectory with quantum corrections a la the de Broglie-Bohm pilot theory.

  14. Chaotic Scattering in Planetary Rings

    NASA Astrophysics Data System (ADS)

    Petit, Jean-Marc

    The gravitational interaction of two small satellites, on initially close circular, coplanar orbits leads to a one-parameter family of solutions. When varying the parameter h of the family, the solution changes continuously on an interval and then undergoes a sudden change. The set of discontinuities has a Cantor-like structure.Similar phenomena have been observed in other problems of scattering. Such a behavior is related to the presence of periodic orbits and homo- and heteroclinic points. It can be shown that in the vicinity of a homo- or heteroclinic point, one can define a symbolic dynamics (Moser, 1973).The large eigenvalue (600) of the satellite problem limits the possibility of numerical exploration. A model problem, the inclined billiard (Hénon, 1988), was designed with a tunable eigenvalue, for which the symbolic dynamics can be analytically defined, thus fully elucidating the structure of the family.

  15. Conductance fluctuations in chaotic bilayer graphene quantum dots.

    PubMed

    Bao, Rui; Huang, Liang; Lai, Ying-Cheng; Grebogi, Celso

    2015-07-01

    Previous studies of quantum chaotic scattering established a connection between classical dynamics and quantum transport properties: Integrable or mixed classical dynamics can lead to sharp conductance fluctuations but chaos is capable of smoothing out the conductance variations. Relativistic quantum transport through single-layer graphene systems, for which the quasiparticles are massless Dirac fermions, exhibits, due to scarring, this classical-quantum correspondence, but sharp conductance fluctuations persist to a certain extent even when the classical system is fully chaotic. There is an open issue regarding the effect of finite mass on relativistic quantum transport. To address this issue, we study quantum transport in chaotic bilayer graphene quantum dots for which the quasiparticles have a finite mass. An interesting phenomenon is that, when traveling along the classical ballistic orbit, the quasiparticle tends to hop back and forth between the two layers, exhibiting a Zitterbewegung-like effect. We find signatures of abrupt conductance variations, indicating that the mass has little effect on relativistic quantum transport. In solid-state electronic devices based on Dirac materials, sharp conductance fluctuations are thus expected, regardless of whether the quasiparticle is massless or massive and whether there is chaos in the classical limit.

  16. Fractal dynamics in chaotic quantum transport

    NASA Astrophysics Data System (ADS)

    Rasanen, Esa; Kotimaki, Ville; Hennig, Holger; Heller, Eric

    2013-03-01

    Despite several experiments on chaotic quantum transport, corresponding ab initio quantum simulations have been out of reach so far. Here we carry out quantum transport calculations in real space and real time for a two-dimensional stadium cavity that shows chaotic dynamics. Applying a large set of magnetic fields yields a complete picture of the magnetoconductance that indicates fractal scaling on intermediate time scales. Two methods that originate from different fields of physics are used to analyze the scaling exponent and the fractal dimension. They lead to consistent results that, in turn, qualitatively agree with the previous experimental data.

  17. Quantum Response of Weakly Chaotic Systems

    DTIC Science & Technology

    2010-10-01

    Quantum chaos; semiclassical methods Abstract – Chaotic systems, that have a small Lyapunov exponent , do not obey the common random matrix theory...BSF). 14. ABSTRACT Chaotic systems, that have a small Lyapunov exponent , do not obey the common random matrix theory predictions within a wide...also to system with zero Lyapunov exponent (tR =∞), e.g. the triangular billiard [20], and pseudointegrable billiards [21], and to systems with a

  18. Effects of periodic forcing in chaotic scattering.

    PubMed

    Blesa, Fernando; Seoane, Jesús M; Barrio, Roberto; Sanjuán, Miguel A F

    2014-04-01

    The effects of a periodic forcing on chaotic scattering are relevant in certain situations of physical interest. We investigate the effects of the forcing amplitude and the external frequency in both the survival probability of the particles in the scattering region and the exit basins associated to phase space. We have found an exponential decay law for the survival probability of the particles in the scattering region. A resonant-like behavior is uncovered where the critical values of the frequencies ω≃1 and ω≃2 permit the particles to escape faster than for other different values. On the other hand, the computation of the exit basins in phase space reveals the existence of Wada basins depending of the frequency values. We provide some heuristic arguments that are in good agreement with the numerical results. Our results are expected to be relevant for physical phenomena such as the effect of companion galaxies, among others.

  19. Global relativistic effects in chaotic scattering

    NASA Astrophysics Data System (ADS)

    Bernal, Juan D.; Seoane, Jesús M.; Sanjuán, Miguel A. F.

    2017-03-01

    The phenomenon of chaotic scattering is very relevant in different fields of science and engineering. It has been mainly studied in the context of Newtonian mechanics, where the velocities of the particles are low in comparison with the speed of light. Here, we analyze global properties such as the escape time distribution and the decay law of the Hénon-Heiles system in the context of special relativity. Our results show that the average escape time decreases with increasing values of the relativistic factor β . As a matter of fact, we have found a crossover point for which the KAM islands in the phase space are destroyed when β ≃0.4 . On the other hand, the study of the survival probability of particles in the scattering region shows an algebraic decay for values of β ≤0.4 , and this law becomes exponential for β >0.4 . Surprisingly, a scaling law between the exponent of the decay law and the β factor is uncovered where a quadratic fitting between them is found. The results of our numerical simulations agree faithfully with our qualitative arguments. We expect this work to be useful for a better understanding of both chaotic and relativistic systems.

  20. Association of scattering matrices in quantum networks

    SciTech Connect

    Almeida, F.A.G.; Macêdo, A.M.S.

    2013-06-15

    Algorithms based on operations that associate scattering matrices in series or in parallel (analogous to impedance association in a classical circuit) are developed here. We exemplify their application by calculating the total scattering matrix of several types of quantum networks, such as star graphs and a chain of chaotic quantum dots, obtaining results with good agreement with the literature. Through a computational-time analysis we compare the efficiency of two algorithms for the simulation of a chain of chaotic quantum dots based on series association operations of (i) two-by-two centers and (ii) three-by-three ones. Empirical results point out that the algorithm (ii) is more efficient than (i) for small number of open scattering channels. A direct counting of floating point operations justifies quantitatively the superiority of the algorithm (i) for large number of open scattering channels.

  1. Fractal dynamics in chaotic quantum transport.

    PubMed

    Kotimäki, V; Räsänen, E; Hennig, H; Heller, E J

    2013-08-01

    Despite several experiments on chaotic quantum transport in two-dimensional systems such as semiconductor quantum dots, corresponding quantum simulations within a real-space model have been out of reach so far. Here we carry out quantum transport calculations in real space and real time for a two-dimensional stadium cavity that shows chaotic dynamics. By applying a large set of magnetic fields we obtain a complete picture of magnetoconductance that indicates fractal scaling. In the calculations of the fractality we use detrended fluctuation analysis-a widely used method in time-series analysis-and show its usefulness in the interpretation of the conductance curves. Comparison with a standard method to extract the fractal dimension leads to consistent results that in turn qualitatively agree with the previous experimental data.

  2. Fractal dynamics in chaotic quantum transport

    NASA Astrophysics Data System (ADS)

    Kotimäki, V.; Räsänen, E.; Hennig, H.; Heller, E. J.

    2013-08-01

    Despite several experiments on chaotic quantum transport in two-dimensional systems such as semiconductor quantum dots, corresponding quantum simulations within a real-space model have been out of reach so far. Here we carry out quantum transport calculations in real space and real time for a two-dimensional stadium cavity that shows chaotic dynamics. By applying a large set of magnetic fields we obtain a complete picture of magnetoconductance that indicates fractal scaling. In the calculations of the fractality we use detrended fluctuation analysis—a widely used method in time-series analysis—and show its usefulness in the interpretation of the conductance curves. Comparison with a standard method to extract the fractal dimension leads to consistent results that in turn qualitatively agree with the previous experimental data.

  3. Cusp-scaling behavior in fractal dimension of chaotic scattering.

    PubMed

    Motter, Adilson E; Lai, Ying-Cheng

    2002-06-01

    A topological bifurcation in chaotic scattering is characterized by a sudden change in the topology of the infinite set of unstable periodic orbits embedded in the underlying chaotic invariant set. We uncover a scaling law for the fractal dimension of the chaotic set for such a bifurcation. Our analysis and numerical computations in both two- and three-degrees-of-freedom systems suggest a striking feature associated with these subtle bifurcations: the dimension typically exhibits a sharp, cusplike local minimum at the bifurcation.

  4. Sensing small changes in a wave chaotic scattering system

    SciTech Connect

    Taddese, Biniyam Tesfaye; Antonsen, Thomas M.; Ott, Edward; Anlage, Steven M.

    2010-12-01

    Classical analogs of the quantum mechanical concepts of the Loschmidt Echo and quantum fidelity are developed with the goal of detecting small perturbations in a closed wave chaotic region. Sensing techniques that employ a one-recording-channel time-reversal-mirror, which in turn relies on time reversal invariance and spatial reciprocity of the classical wave equation, are introduced. In analogy with quantum fidelity, we employ scattering fidelity techniques which work by comparing response signals of the scattering region, by means of cross correlation and mutual information of signals. The performance of the sensing techniques is compared for various perturbations induced experimentally in an acoustic resonant cavity. The acoustic signals are parametrically processed to mitigate the effect of dissipation and to vary the spatial diversity of the sensing schemes. In addition to static boundary condition perturbations at specified locations, perturbations to the medium of wave propagation are shown to be detectable, opening up various real world sensing applications in which a false negative cannot be tolerated.

  5. Parametric number covariance in quantum chaotic spectra.

    PubMed

    Vinayak; Kumar, Sandeep; Pandey, Akhilesh

    2016-03-01

    We study spectral parametric correlations in quantum chaotic systems and introduce the number covariance as a measure of such correlations. We derive analytic results for the classical random matrix ensembles using the binary correlation method and obtain compact expressions for the covariance. We illustrate the universality of this measure by presenting the spectral analysis of the quantum kicked rotors for the time-reversal invariant and time-reversal noninvariant cases. A local version of the parametric number variance introduced earlier is also investigated.

  6. Correlation-modulated chaotic scattering in the earth's magnetosphere

    NASA Technical Reports Server (NTRS)

    Buechner, J.

    1991-01-01

    It is shown that due to correlations between subsequent separatrix traversals the chaotic scattering of thermal ions and energetic electrons in the plasma sheet of the earth's magnetotail is modulated, oscillating in dependence on the strength of the magnetic field inhomogeneity and particle energy. Correlation-modulated chaotic scattering creates non-Maxwellian features of the magnetotail ion distribution both in the CPS and the PSBL. It also causes an oscillating latitudinal variation of the auroral ion precipitation.

  7. Chaotic Behaviour in Quantum Dynamics.

    DTIC Science & Technology

    1986-12-01

    1.6 Relevance of Classical Analisys to the Problem of Microwave Ionization The other nonconservative system discussed in this report - the H-atom in...a microwave field - had never been sublected to quantum analisys , neither theoretical nor computational, up to the start of our program. Nevertheless...m, . A2) can tie expanded in a double Fourier series in the angle variables Xi, X2: (I,, A, ,klk2 Z= > (ni, n,, n) e i(0 K C) The coefficeuts z ,i can

  8. Quantum chaotic dynamics and random polynomials

    SciTech Connect

    Bogomolny, E.; Bohigas, O.; Leboeuf, P.

    1996-12-01

    We investigate the distribution of roots of polynomials of high degree with random coefficients which, among others, appear naturally in the context of {open_quotes}quantum chaotic dynamics.{close_quotes} It is shown that under quite general conditions their roots tend to concentrate near the unit circle in the complex plane. In order to further increase this tendency, we study in detail the particular case of self-inversive random polynomials and show that for them a finite portion of all roots lies exactly on the unit circle. Correlation functions of these roots are also computed analytically, and compared to the correlations of eigenvalues of random matrices. The problem of ergodicity of chaotic wavefunctions is also considered. For that purpose we introduce a family of random polynomials whose roots spread uniformly over phase space. While these results are consistent with random matrix theory predictions, they provide a new and different insight into the problem of quantum ergodicity Special attention is devoted to the role of symmetries in the distribution of roots of random polynomials.

  9. Andreev Conductance of a Chaotic Quantum Dot

    NASA Astrophysics Data System (ADS)

    Clerk, A. A.; Brouwer, P. W.; Ambegaokar, V.

    2000-03-01

    Using random matrix theory, we study the full magnetic field (B) and voltage (V) dependence of the Andreev conductance of a chaotic quantum dot coupled via point contacts to both a normal metal and a superconductor. We recover previous results in the zero and large B,V limits, but also observe interesting non-monotonic behaviour in the crossover regime. Our results demonstrate that the induced superconductivity effect previously seen in calculations of the density of states (J.A. Melsen, P.W. Brouwer, K.M. Frahm and C.W.J. Beenakker, Europhys. Lett., 35), 7 (1996). can also have a pronounced signature in the conductance; this may explain certain anomalous features observed in recent experiments on metallic normal-superconducting point contacts (P. Chalsani, S.K. Uphadyay, R.A. Buhrman, unpublished.).

  10. Quantum backflow and scattering

    NASA Astrophysics Data System (ADS)

    Bostelmann, Henning; Cadamuro, Daniela; Lechner, Gandalf

    2017-07-01

    Backflow is the phenomenon that the probability current of a quantum particle on the line can flow in the direction opposite to its momentum. In this paper, previous investigations of backflow, pertaining to interaction-free dynamics or purely kinematical aspects, are extended to scattering situations in short-range potentials. It is shown that backflow is a universal quantum effect which exists in any such potential, and is always of bounded spatial extent in a specific sense. The effects of reflection and transmission processes on backflow are investigated, both analytically for general potentials and numerically in various concrete examples.

  11. Absorption and Direct Processes in Chaotic Wave Scattering

    SciTech Connect

    Mendez-Sanchez, R. A.; Baez, G.; Martinez-Mares, M.

    2010-12-21

    Recent results on the scattering of waves by chaotic systems with losses and direct processes are discussed. We start by showing the results without direct processes nor absorption. We then discuss systems with direct processes and lossy systems separately. Finally the discussion of systems with both direct processes and loses is given. We will see how the regimes of strong and weak absorption are modified by the presence of the direct processes.

  12. Emergence of Chaotic Scattering in Ultracold Er and Dy

    NASA Astrophysics Data System (ADS)

    Maier, T.; Kadau, H.; Schmitt, M.; Wenzel, M.; Ferrier-Barbut, I.; Pfau, T.; Frisch, A.; Baier, S.; Aikawa, K.; Chomaz, L.; Mark, M. J.; Ferlaino, F.; Makrides, C.; Tiesinga, E.; Petrov, A.; Kotochigova, S.

    2015-10-01

    We show that for ultracold magnetic lanthanide atoms chaotic scattering emerges due to a combination of anisotropic interaction potentials and Zeeman coupling under an external magnetic field. This scattering is studied in a collaborative experimental and theoretical effort for both dysprosium and erbium. We present extensive atom-loss measurements of their dense magnetic Feshbach-resonance spectra, analyze their statistical properties, and compare to predictions from a random-matrix-theory-inspired model. Furthermore, theoretical coupled-channels simulations of the anisotropic molecular Hamiltonian at zero magnetic field show that weakly bound, near threshold diatomic levels form overlapping, uncoupled chaotic series that when combined are randomly distributed. The Zeeman interaction shifts and couples these levels, leading to a Feshbach spectrum of zero-energy bound states with nearest-neighbor spacings that changes from randomly to chaotically distributed for increasing magnetic field. Finally, we show that the extreme temperature sensitivity of a small, but sizable fraction of the resonances in the Dy and Er atom-loss spectra is due to resonant nonzero partial-wave collisions. Our threshold analysis for these resonances indicates a large collision-energy dependence of the three-body recombination rate.

  13. Binary black hole shadows, chaotic scattering and the Cantor set

    NASA Astrophysics Data System (ADS)

    Shipley, Jake O.; Dolan, Sam R.

    2016-09-01

    We investigate the qualitative features of binary black hole shadows using the model of two extremally charged black holes in static equilibrium (a Majumdar-Papapetrou solution). Our perspective is that binary spacetimes are natural exemplars of chaotic scattering, because they admit more than one fundamental null orbit, and thus an uncountably infinite set of perpetual null orbits which generate scattering singularities in initial data. Inspired by the three-disc model, we develop an appropriate symbolic dynamics to describe planar null geodesics on the double black hole spacetime. We show that a one-dimensional (1D) black hole shadow may be constructed through an iterative procedure akin to the construction of the Cantor set; thus the 1D shadow is self-similar. Next, we study non-planar rays, to understand how angular momentum affects the existence and properties of the fundamental null orbits. Taking slices through 2D shadows, we observe three types of 1D shadow: regular, Cantor-like, and highly chaotic. The switch from Cantor-like to regular occurs where outer fundamental orbits are forbidden by angular momentum. The highly chaotic part is associated with an unexpected feature: stable and bounded null orbits, which exist around two black holes of equal mass M separated by {a}1\\lt a\\lt \\sqrt{2}{a}1, where {a}1=4M/\\sqrt{27}. To show how this possibility arises, we define a certain potential function and classify its stationary points. We conjecture that the highly chaotic parts of the 2D shadow possess the Wada property. Finally, we consider the possibility of following null geodesics through event horizons, and chaos in the maximally extended spacetime.

  14. Experimental Demonstration of Coherent Control in Quantum Chaotic Systems

    NASA Astrophysics Data System (ADS)

    Bitter, M.; Milner, V.

    2017-01-01

    We experimentally demonstrate coherent control of a quantum system, whose dynamics is chaotic in the classical limit. Interaction of diatomic molecules with a periodic sequence of ultrashort laser pulses leads to the dynamical localization of the molecular angular momentum, a characteristic feature of the chaotic quantum kicked rotor. By changing the phases of the rotational states in the initially prepared coherent wave packet, we control the rotational distribution of the final localized state and its total energy. We demonstrate the anticipated sensitivity of control to the exact parameters of the kicking field, as well as its disappearance in the classical regime of excitation.

  15. Anticorrelation for conductance fluctuations in chaotic quantum dots.

    PubMed

    Barbosa, A L R; Hussein, M S; Ramos, J G G S

    2013-07-01

    We investigate the correlation functions of mesoscopic electronic transport in open chaotic quantum dots with finite tunnel barriers in the crossover between Wigner-Dyson ensembles. Using an analytical stub formalism, we show the emergence of a depletion and amplification of conductance fluctuations as a function of tunnel barriers for both parametric variations of electron energy and magnetoconductance fields. Furthermore, even for pure Dyson ensembles, correlation functions of conductance fluctuations in chaotic quantum dots can exhibit anticorrelation. Experimental support to our findings is pointed out.

  16. Electric circuit networks equivalent to chaotic quantum billiards

    SciTech Connect

    Bulgakov, Evgeny N.; Maksimov, Dmitrii N.; Sadreev, Almas F.

    2005-04-01

    We consider two electric RLC resonance networks that are equivalent to quantum billiards. In a network of inductors grounded by capacitors, the eigenvalues of the quantum billiard correspond to the squared resonant frequencies. In a network of capacitors grounded by inductors, the eigenvalues of the billiard are given by the inverse of the squared resonant frequencies. In both cases, the local voltages play the role of the wave function of the quantum billiard. However, unlike for quantum billiards, there is a heat power because of the resistance of the inductors. In the equivalent chaotic billiards, we derive a distribution of the heat power which describes well the numerical statistics.

  17. Quantum localization of chaotic eigenstates and the level spacing distribution

    NASA Astrophysics Data System (ADS)

    Batistić, Benjamin; Robnik, Marko

    2013-11-01

    The phenomenon of quantum localization in classically chaotic eigenstates is one of the main issues in quantum chaos (or wave chaos), and thus plays an important role in general quantum mechanics or even in general wave mechanics. In this work we propose two different localization measures characterizing the degree of quantum localization, and study their relation to another fundamental aspect of quantum chaos, namely the (energy) spectral statistics. Our approach and method is quite general, and we apply it to billiard systems. One of the signatures of the localization of chaotic eigenstates is a fractional power-law repulsion between the nearest energy levels in the sense that the probability density to find successive levels on a distance S goes like ∝Sβ for small S, where 0≤β≤1, and β=1 corresponds to completely extended states. We show that there is a clear functional relation between the exponent β and the two different localization measures. One is based on the information entropy and the other one on the correlation properties of the Husimi functions. We show that the two definitions are surprisingly linearly equivalent. The approach is applied in the case of a mixed-type billiard system [M. Robnik, J. Phys. A: Math. Gen.JPHAC50305-447010.1088/0305-4470/16/17/014 16, 3971 (1983)], in which the separation of regular and chaotic eigenstates is performed.

  18. Spiral Structures and Chaotic Scattering of Coorbital Satellites

    NASA Astrophysics Data System (ADS)

    Henrard, Jacques; Navarro, Juan F.

    2001-04-01

    The fractal nature of the transitions between two sets of orbits separated by heteroclinic or homoclinic orbits is well known. We analyze in detail this phenomenon in Hill's problem where one set of orbits corresponds to coorbital satellites exchanging semi-major axis after close encounter (horse-shoe orbits) and the other corresponds to orbits which do not exchange semi-major axis (passing-by orbits). With the help of a normalized approximation of the vicinity of unstable periodic orbits, we show that the fractal structure is intimately tied to a special spiral structure of the Poincaré maps. We show that each basin is composed of a few ‘well behaved’ areas and of an infinity of intertwined tongues and subtongues winding around them. This behaviour is generic and is likely to be present in large classes of chaotic scattering problems.

  19. Theory of chaos regularization of tunneling in chaotic quantum dots.

    PubMed

    Lee, Ming-Jer; Antonsen, Thomas M; Ott, Edward; Pecora, Louis M

    2012-11-01

    Recent numerical experiments of Pecora et al. [Phys. Rev. E 83, 065201 (2011)] have investigated tunneling between two-dimensional symmetric double wells separated by a tunneling barrier. The wells were bounded by hard walls and by the potential barrier which was created by a step increase from the zero potential within a well to a uniform barrier potential within the barrier region, which is a situation potentially realizable in the context of quantum dots. Numerical results for the splitting of energy levels between symmetric and antisymmetric eigenstates were calculated. It was found that the splittings vary erratically from state to state, and the statistics of these variations were studied for different well shapes with the fluctuation levels being much less in chaotic wells than in comparable nonchaotic wells. Here we develop a quantitative theory for the statistics of the energy level splittings for chaotic wells. Our theory is based on the random plane wave hypothesis of Berry. While the fluctuation statistics are very different for chaotic and nonchaotic well dynamics, we show that the mean splittings of differently shaped wells, including integrable and chaotic wells, are the same if their well areas and barrier parameters are the same. We also consider the case of tunneling from a single well into a region with outgoing quantum waves.

  20. Pseudo random number generator based on quantum chaotic map

    NASA Astrophysics Data System (ADS)

    Akhshani, A.; Akhavan, A.; Mobaraki, A.; Lim, S.-C.; Hassan, Z.

    2014-01-01

    For many years dissipative quantum maps were widely used as informative models of quantum chaos. In this paper, a new scheme for generating good pseudo-random numbers (PRNG), based on quantum logistic map is proposed. Note that the PRNG merely relies on the equations used in the quantum chaotic map. The algorithm is not complex, which does not impose high requirement on computer hardware and thus computation speed is fast. In order to face the challenge of using the proposed PRNG in quantum cryptography and other practical applications, the proposed PRNG is subjected to statistical tests using well-known test suites such as NIST, DIEHARD, ENT and TestU01. The results of the statistical tests were promising, as the proposed PRNG successfully passed all these tests. Moreover, the degree of non-periodicity of the chaotic sequences of the quantum map is investigated through the Scale index technique. The obtained result shows that, the sequence is more non-periodic. From these results it can be concluded that, the new scheme can generate a high percentage of usable pseudo-random numbers for simulation and other applications in scientific computing.

  1. Synchronization between uncertain nonidentical networks with quantum chaotic behavior

    NASA Astrophysics Data System (ADS)

    Li, Wenlin; Li, Chong; Song, Heshan

    2016-11-01

    Synchronization between uncertain nonidentical networks with quantum chaotic behavior is researched. The identification laws of unknown parameters in state equations of network nodes, the adaptive laws of configuration matrix elements and outer coupling strengths are determined based on Lyapunov theorem. The conditions of realizing synchronization between uncertain nonidentical networks are discussed and obtained. Further, Jaynes-Cummings model in physics are taken as the nodes of two networks and simulation results show that the synchronization performance between networks is very stable.

  2. Microwave study of quantum n-disk scattering

    PubMed

    Lu; Viola; Pance; Rose; Sridhar

    2000-04-01

    We describe a wave-mechanical implementation of classically chaotic n-disk scattering based on thin two-dimensional microwave cavities. Two-, three-, and four-disk scatterings are investigated in detail. The experiments, which are able to probe the stationary Green's function of the system, yield both frequencies and widths of the low-lying quantum resonances. The observed spectra are found to be in good agreement with calculations based on semiclassical periodic orbit theory. Wave-vector autocorrelation functions are analyzed for various scattering geometries, the small wave-vector behavior allowing one to extract the escape rate from the quantum repeller. Quantitative agreement is found with the value predicted from classical scattering theory. For intermediate energies, nonuniversal oscillations are detected in the autocorrelation function, reflecting the presence of periodic orbits.

  3. Quantum Computing and the Onset of Quantum Chaotic Motion

    DTIC Science & Technology

    2007-11-02

    for Nuclear Theory Program on "Chaos and Interactions: from Nuclei to Quantum Dots’", University of Washington, Seattle, USA, 17 July, 2002. I...to Quantum Dots’", University of Washington, Seattle, USA, 17 July, 2002. G. Casati “Quantum computers and quantum chaos” Institute for Nuclear...Theory Program on "Chaos and Interactions: from Nuclei to Quantum Dots’", University of Washington, Seattle, USA, 17 July, 2002. 2. Scientific

  4. Scattering in Quantum Lattice Gases

    NASA Astrophysics Data System (ADS)

    O'Hara, Andrew; Love, Peter

    2009-03-01

    Quantum Lattice Gas Automata (QLGA) are of interest for their use in simulating quantum mechanics on both classical and quantum computers. QLGAs are an extension of classical Lattice Gas Automata where the constraint of unitary evolution is added. In the late 1990s, David A. Meyer as well as Bruce Boghosian and Washington Taylor produced similar models of QLGAs. We start by presenting a unified version of these models and study them from the point of view of the physics of wave-packet scattering. We show that the Meyer and Boghosian-Taylor models are actually the same basic model with slightly different parameterizations and limits. We then implement these models computationally using the Python programming language and show that QLGAs are able to replicate the analytic results of quantum mechanics (for example reflected and transmitted amplitudes for step potentials and the Klein paradox).

  5. Quantum theory of Thomson scattering

    NASA Astrophysics Data System (ADS)

    Crowley, B. J. B.; Gregori, G.

    2014-12-01

    The general theory of the scattering of electromagnetic radiation in atomic plasmas and metals, in the non-relativistic regime, in which account is taken of the Kramers-Heisenberg polarization terms in the Hamiltonian, is described from a quantum mechanical viewpoint. As well as deriving the general formula for the double differential Thomson scattering cross section in an isotropic finite temperature multi-component system, this work also considers closely related phenomena such as absorption, refraction, Raman scattering, resonant (Rayleigh) scattering and Bragg scattering, and derives many essential relationships between these quantities. In particular, the work introduces the concept of scattering strength and the strength-density field which replaces the normal particle density field in the standard treatment of scattering by a collection of similar particles and it is the decomposition of the strength-density correlation function into more familiar-looking components that leads to the final result. Comparisons are made with previous work, in particular that of Chihara [1].

  6. Wave chaotic experiments and models for complicated wave scattering systems

    NASA Astrophysics Data System (ADS)

    Yeh, Jen-Hao

    Wave scattering in a complicated environment is a common challenge in many engineering fields because the complexity makes exact solutions impractical to find, and the sensitivity to detail in the short-wavelength limit makes a numerical solution relevant only to a specific realization. On the other hand, wave chaos offers a statistical approach to understand the properties of complicated wave systems through the use of random matrix theory (RMT). A bridge between the theory and practical applications is the random coupling model (RCM) which connects the universal features predicted by RMT and the specific details of a real wave scattering system. The RCM gives a complete model for many wave properties and is beneficial for many physical and engineering fields that involve complicated wave scattering systems. One major contribution of this dissertation is that I have utilized three microwave systems to thoroughly test the RCM in complicated wave systems with varied loss, including a cryogenic system with a superconducting microwave cavity for testing the extremely-low-loss case. I have also experimentally tested an extension of the RCM that includes short-orbit corrections. Another novel result is development of a complete model based on the RCM for the fading phenomenon extensively studied in the wireless communication fields. This fading model encompasses the traditional fading models as its high-loss limit case and further predicts the fading statistics in the low-loss limit. This model provides the first physical explanation for the fitting parameters used in fading models. I have also applied the RCM to additional experimental wave properties of a complicated wave system, such as the impedance matrix, the scattering matrix, the variance ratio, and the thermopower. These predictions are significant for nuclear scattering, atomic physics, quantum transport in condensed matter systems, electromagnetics, acoustics, geophysics, etc.

  7. The Classical Scattering of Waves: Some Analogies with Quantum Scattering

    DTIC Science & Technology

    1992-01-01

    Code . Approved for public release; distribution is unlimited. 13. Abstract (Maximum 200 words). The scattering of waves in classical physics and quantum...both areas. 92-235222’ 14. Subject Terms. IS. Number of Page. Acoustic scattering , shallow water, waveguide propagation . 27 16. Price Code . 17. Security...Numbers. The Classical Scattering of Waves: Some Analogies with Quantum Scattering Contract ,~~ ~ -V ,~Pom Element NO- 0601153N 6. Author(s). t

  8. Universality in chaotic quantum transport: the concordance between random-matrix and semiclassical theories.

    PubMed

    Berkolaiko, Gregory; Kuipers, Jack

    2012-04-01

    Electronic transport through chaotic quantum dots exhibits universal, system-independent properties, consistent with random-matrix theory. The quantum transport can also be rooted, via the semiclassical approximation, in sums over the classical scattering trajectories. Correlations between such trajectories can be organized diagrammatically and have been shown to yield universal answers for some observables. Here, we develop the general combinatorial treatment of the semiclassical diagrams, through a connection to factorizations of permutations. We show agreement between the semiclassical and random matrix approaches to the moments of the transmission eigenvalues. The result is valid for all moments to all orders of the expansion in inverse channel number for all three main symmetry classes (with and without time-reversal symmetry and spin-orbit interaction) and extends to nonlinear statistics. This finally explains the applicability of random-matrix theory to chaotic quantum transport in terms of the underlying dynamics as well as providing semiclassical access to the probability density of the transmission eigenvalues.

  9. Universality in chaotic quantum transport: The concordance between random-matrix and semiclassical theories

    NASA Astrophysics Data System (ADS)

    Berkolaiko, Gregory; Kuipers, Jack

    2012-04-01

    Electronic transport through chaotic quantum dots exhibits universal, system-independent properties, consistent with random-matrix theory. The quantum transport can also be rooted, via the semiclassical approximation, in sums over the classical scattering trajectories. Correlations between such trajectories can be organized diagrammatically and have been shown to yield universal answers for some observables. Here, we develop the general combinatorial treatment of the semiclassical diagrams, through a connection to factorizations of permutations. We show agreement between the semiclassical and random matrix approaches to the moments of the transmission eigenvalues. The result is valid for all moments to all orders of the expansion in inverse channel number for all three main symmetry classes (with and without time-reversal symmetry and spin-orbit interaction) and extends to nonlinear statistics. This finally explains the applicability of random-matrix theory to chaotic quantum transport in terms of the underlying dynamics as well as providing semiclassical access to the probability density of the transmission eigenvalues.

  10. Power Spectrum of Long Eigenlevel Sequences in Quantum Chaotic Systems

    NASA Astrophysics Data System (ADS)

    Riser, Roman; Osipov, Vladimir Al.; Kanzieper, Eugene

    2017-05-01

    We present a nonperturbative analysis of the power spectrum of energy level fluctuations in fully chaotic quantum structures. Focusing on systems with broken time-reversal symmetry, we employ a finite-N random matrix theory to derive an exact multidimensional integral representation of the power spectrum. The N →∞ limit of the exact solution furnishes the main result of this study—a universal, parameter-free prediction for the power spectrum expressed in terms of a fifth Painlevé transcendent. Extensive numerics lends further support to our theory which, as discussed at length, invalidates a traditional assumption that the power spectrum is merely determined by the spectral form factor of a quantum system.

  11. Internal temperature of quantum chaotic systems at the nanoscale

    NASA Astrophysics Data System (ADS)

    Wang, Jiaozi; Wang, Wen-ge

    2017-09-01

    The extent to which a temperature can be appropriately assigned to a small quantum system, as an internal property but not as a property of any large environment, is still an open problem. In this paper, a method is proposed for solving this problem, by which a studied small system is coupled to a two-level system as a probe, the latter of which can be measured by measurement devices. A main difficulty in the determination of possible temperature of the studied system comes from the back-action of the probe-system coupling to the system. For small quantum chaotic systems, we show that a temperature can be determined, the value of which is sensitive to neither the form, location, and strength of the probe-system coupling, nor the Hamiltonian and initial state of the probe. The temperature thus obtained turns out to have the form of Boltzmann temperature.

  12. Quantum Color Image Encryption Algorithm Based on A Hyper-Chaotic System and Quantum Fourier Transform

    NASA Astrophysics Data System (ADS)

    Tan, Ru-Chao; Lei, Tong; Zhao, Qing-Min; Gong, Li-Hua; Zhou, Zhi-Hong

    2016-12-01

    To improve the slow processing speed of the classical image encryption algorithms and enhance the security of the private color images, a new quantum color image encryption algorithm based on a hyper-chaotic system is proposed, in which the sequences generated by the Chen's hyper-chaotic system are scrambled and diffused with three components of the original color image. Sequentially, the quantum Fourier transform is exploited to fulfill the encryption. Numerical simulations show that the presented quantum color image encryption algorithm possesses large key space to resist illegal attacks, sensitive dependence on initial keys, uniform distribution of gray values for the encrypted image and weak correlation between two adjacent pixels in the cipher-image.

  13. Scale invariance in chaotic time series: Classical and quantum examples

    NASA Astrophysics Data System (ADS)

    Landa, Emmanuel; Morales, Irving O.; Stránský, Pavel; Fossion, Rubén; Velázquez, Victor; López Vieyra, J. C.; Frank, Alejandro

    Important aspects of chaotic behavior appear in systems of low dimension, as illustrated by the Map Module 1. It is indeed a remarkable fact that all systems tha make a transition from order to disorder display common properties, irrespective of their exacta functional form. We discuss evidence for 1/f power spectra in the chaotic time series associated in classical and quantum examples, the one-dimensional map module 1 and the spectrum of 48Ca. A Detrended Fluctuation Analysis (DFA) method is applied to investigate the scaling properties of the energy fluctuations in the spectrum of 48Ca obtained with a large realistic shell model calculation (ANTOINE code) and with a random shell model (TBRE) calculation also in the time series obtained with the map mod 1. We compare the scale invariant properties of the 48Ca nuclear spectrum sith similar analyses applied to the RMT ensambles GOE and GDE. A comparison with the corresponding power spectra is made in both cases. The possible consequences of the results are discussed.

  14. Decoherence induced by a chaotic enviroment: A quantum walker with a complex coin

    SciTech Connect

    Ermann, Leonardo; Paz, Juan Pablo; Saraceno, Marcos

    2006-01-15

    We study the differences between the processes of decoherence induced by chaotic and regular environments. For this we analyze a family of simple models that contain both regular and chaotic environments. In all cases the system of interest is a ''quantum walker,'' i.e., a quantum particle that can move on a lattice with a finite number of sites. The walker interacts with an environment which has a D-dimensional Hilbert space. The results we obtain suggest that regular and chaotic environments are not distinguishable from each other in a (short) time scale t*, which scales with the dimensionality of the environment as t*{proportional_to}log{sub 2}(D). However, chaotic environments continue to be effective over exponentially longer time scales while regular environments tend to reach saturation much sooner. We present both numerical and analytical results supporting this conclusion. The family of chaotic evolutions we consider includes the so-called quantum multibaker map as a particular case.

  15. Classical and quantum chaotic angular-momentum pumps.

    PubMed

    Dittrich, T; Dubeibe, F L

    2015-03-06

    We study directed transport of charge and intrinsic angular momentum by periodically driven scattering in the regime of fast and strong driving. A spin-orbit coupling through a kicked magnetic field confined to a compact region in space leads to irregular scattering and triggers spin flips in a spatially asymmetric manner which allows us to generate polarized currents. The dynamical mechanisms responsible for the spin separation carry over to the quantum level and give rise to spin pumping. Our theory based on the Floquet formalism is confirmed by numerical solutions of the time-dependent inhomogeneous Schrödinger equation with a continuous source term.

  16. Parameter estimation of fractional-order chaotic systems by using quantum parallel particle swarm optimization algorithm.

    PubMed

    Huang, Yu; Guo, Feng; Li, Yongling; Liu, Yufeng

    2015-01-01

    Parameter estimation for fractional-order chaotic systems is an important issue in fractional-order chaotic control and synchronization and could be essentially formulated as a multidimensional optimization problem. A novel algorithm called quantum parallel particle swarm optimization (QPPSO) is proposed to solve the parameter estimation for fractional-order chaotic systems. The parallel characteristic of quantum computing is used in QPPSO. This characteristic increases the calculation of each generation exponentially. The behavior of particles in quantum space is restrained by the quantum evolution equation, which consists of the current rotation angle, individual optimal quantum rotation angle, and global optimal quantum rotation angle. Numerical simulation based on several typical fractional-order systems and comparisons with some typical existing algorithms show the effectiveness and efficiency of the proposed algorithm.

  17. Parameter Estimation of Fractional-Order Chaotic Systems by Using Quantum Parallel Particle Swarm Optimization Algorithm

    PubMed Central

    Huang, Yu; Guo, Feng; Li, Yongling; Liu, Yufeng

    2015-01-01

    Parameter estimation for fractional-order chaotic systems is an important issue in fractional-order chaotic control and synchronization and could be essentially formulated as a multidimensional optimization problem. A novel algorithm called quantum parallel particle swarm optimization (QPPSO) is proposed to solve the parameter estimation for fractional-order chaotic systems. The parallel characteristic of quantum computing is used in QPPSO. This characteristic increases the calculation of each generation exponentially. The behavior of particles in quantum space is restrained by the quantum evolution equation, which consists of the current rotation angle, individual optimal quantum rotation angle, and global optimal quantum rotation angle. Numerical simulation based on several typical fractional-order systems and comparisons with some typical existing algorithms show the effectiveness and efficiency of the proposed algorithm. PMID:25603158

  18. Interaction effects in a chaotic graphene quantum billiard

    NASA Astrophysics Data System (ADS)

    Hagymási, Imre; Vancsó, Péter; Pálinkás, András; Osváth, Zoltán

    2017-02-01

    We investigate the local electronic structure of a Sinai-like, quadrilateral graphene quantum billiard with zigzag and armchair edges using scanning tunneling microscopy (STM) at room temperature. It is revealed that besides the (√{3 }×√{3 }) R 30∘ superstructure, which is caused by the intervalley scattering, its overtones also appear in the STM measurements, which are attributed to the Umklapp processes. We point out that these results can be well understood by taking into account the Coulomb interaction in the quantum billiard, accounting for both the measured density of state values and the experimentally observed topography patterns. The analysis of the level-spacing distribution substantiates the experimental findings as well. We also reveal the magnetic properties of our system which should be relevant in future graphene based electronic and spintronic applications.

  19. A theory of nonequilibrium steady states in quantum chaotic systems

    NASA Astrophysics Data System (ADS)

    Wang, Pei

    2017-09-01

    Nonequilibrium steady state (NESS) is a quasistationary state, in which exist currents that continuously produce entropy, but the local observables are stationary everywhere. We propose a theory of NESS under the framework of quantum chaos. In an isolated quantum system whose density matrix follows a unitary evolution, there exist initial states for which the thermodynamic limit and the long-time limit are noncommutative. The density matrix \\hat ρ of these states displays a universal structure. Suppose that \\renewcommand{\\ket}[1]{{\\vert #1 >}} \\ketα and \\renewcommand{\\ket}[1]{{\\vert #1 >}} \\ketβ are different eigenstates of the Hamiltonian with energies E_α and E_β , respectively. \\renewcommand{\\bra}[1]{< #1 \\vert}} \\renewcommand{\\ket}[1]{{\\vert #1 >} \\braα\\hat ρ \\ketβ behaves as a random number which has zero mean. In thermodynamic limit, the variance of \\renewcommand{\\bra}[1]{< #1 \\vert}} \\renewcommand{\\ket}[1]{{\\vert #1 >} \\braα\\hat ρ \\ketβ is a smooth function of ≤ft\\vert E_α-E_β\\right\\vert , scaling as 1/≤ft\\vert E_α-E_β\\right\\vert 2 in the limit ≤ft\\vert E_α-E_β\\right\\vert \\to 0 . If and only if this scaling law is obeyed, the initial state evolves into NESS in the long time limit. We present numerical evidence of our hypothesis in a few chaotic models. Furthermore, we find that our hypothesis indicates the eigenstate thermalization hypothesis (ETH) for current operators in a bipartite system.

  20. Photodissociation in quantum chaotic systems: Random-matrix theory of cross-section fluctuations

    SciTech Connect

    Fyodorov, Y.V.; Alhassid, Y.

    1998-11-01

    Using the random matrix description of open quantum chaotic systems we calculate in closed form the universal autocorrelation function and the probability distribution of the total photodissociation cross section in the regime of quantum chaos. {copyright} {ital 1998} {ital The American Physical Society}

  1. Truncated horseshoes and formal languages in chaotic scattering.

    PubMed

    Troll, G.

    1993-10-01

    In this paper we study parameter families of truncated horseshoes as models of multiscattering systems which show a transition to chaos without losing hyperbolicity, so that the topological features of the transition are completely describable by a parametrized family of symbolic dynamics. At a fixed parameter value the corresponding horseshoe represents the set of orbits trapped in the scattering region. The bifurcations are a pure boundary effect and no other bifurcations such as saddle center bifurcations occur in this transition scenario. Truncated horseshoes actually arise in concrete potential scattering under suitable conditions. It is shown that a simple scattering model introduced earlier can realize this scenario in a certain parameter range (the "truncated sawshoe"). For this purpose, we solve the inverse scattering problem of finding the central potential associated to the sawshoe model. Furthermore, we review classification schemes for the transition to chaos of truncated horseshoes originating from symbolic dynamics and formal language theory and apply them to the truncated double horseshoe and the truncated sawshoe.

  2. Inverse scattering problem for quantum graph vertices

    SciTech Connect

    Cheon, Taksu; Turek, Ondrej; Exner, Pavel

    2011-06-15

    We demonstrate how the inverse scattering problem of a quantum star graph can be solved by means of diagonalization of the Hermitian unitary matrix when the vertex coupling is of the scale-invariant (or Fueloep-Tsutsui) form. This enables the construction of quantum graphs with desired properties in a tailor-made fashion. The procedure is illustrated on the example of quantum vertices with equal transmission probabilities.

  3. The chaotic saddle of a three degrees of freedom scattering system reconstructed from cross-section data

    NASA Astrophysics Data System (ADS)

    Drótos, G.; Jung, C.

    2016-06-01

    The topic of this paper is hyperbolic chaotic scattering in a three degrees of freedom system. We generalize how shadows in the domain of the doubly differential cross-section are found: they are traced out by the appropriately filtered unstable manifolds of the periodic trajectories in the chaotic saddle. These shadows are related to the rainbow singularities in the doubly differential cross-section. As a result of this relation, we discover a method of how to recognize in the cross section a smoothly deformed image of the chaotic saddle, allowing the reconstruction of the symbolic dynamics of the chaotic saddle, its topology and its scaling factors.

  4. Scattering resonances in the extreme quantum limit

    NASA Astrophysics Data System (ADS)

    Hersch, Jesse Shines

    This thesis addresses topics in low energy scattering in quantum mechanics, in particular, resonance phenomena. Hence the title: the phrase ``extreme quantum limit'' refers to the situation when the wavelengths of the particles in the system are larger than every other scale, so that the behavior is far into the quantum regime. A powerful tool in the problems of low energy scattering is the point scatterer model, and will be used extensively throughout the thesis. Therefore, we begin with a thorough introduction to this model in Chapter 2. As a first application of the point scatterer model, we will investigate the phenomenon of the proximity resonance, which is one example of strange quantum behavior appearing at low energy. Proximity resonances will be addressed theoretically in Chapter 3, and experimentally in Chapter 4. Threshold resonances, another type of low energy scattering resonance, are considered in Chapter 5, along with their connection to the Efimov and Thomas effects, and scattering in the presence of an external confining potential. Although the point scatterer model will serve us well in the work presented here, it does have its limitations. These limitations will be removed in Chapter 6, where we describe how to extend the model to include higher partial waves. In Chapter 7, we extend the model one step further, and illustrate how to treat vector wave scattering with the model. Finally, in Chapter 8 we will depart from the topic of low energy scattering and investigate the influence of diffraction on an open quantum mechanical system, again both experimentally and theoretically.

  5. Light-like scattering in quantum gravity

    NASA Astrophysics Data System (ADS)

    Bjerrum-Bohr, N. E. J.; Donoghue, John F.; Holstein, Barry R.; Planté, Ludovic; Vanhove, Pierre

    2016-11-01

    We consider scattering in quantum gravity and derive long-range classical and quantum contributions to the scattering of light-like bosons and fermions (spin-0, spin- 1/2 , spin-1) from an external massive scalar field, such as the Sun or a black hole. This is achieved by treating general relativity as an effective field theory and identifying the non-analytic pieces of the one-loop gravitational scattering amplitude. It is emphasized throughout the paper how modern amplitude techniques, involving spinor-helicity variables, unitarity, and squaring relations in gravity enable much simplified computations. We directly verify, as predicted by general relativity, that all classical effects in our computation are universal (in the context of matter type and statistics). Using an eikonal procedure we confirm the post-Newtonian general relativity correction for light-like bending around large stellar objects. We also comment on treating effects from quantum ℏ dependent terms using the same eikonal method.

  6. Quantum synchronization of chaotic oscillator behaviors among coupled BEC-optomechanical systems

    NASA Astrophysics Data System (ADS)

    Li, Wenlin; Li, Chong; Song, Heshan

    2017-03-01

    We consider and theoretically analyze a Bose-Einstein condensate (BEC) trapped inside an optomechanical system consisting of single-mode optical cavity with a moving end mirror. The BEC is formally analogous to a mirror driven by radiation pressure with strong nonlinear coupling. Such a nonlinear enhancement can make the oscillator display chaotic behavior. By establishing proper oscillator couplings, we find that this chaotic motion can be synchronized with other oscillators, even an oscillator network. We also discuss the scheme feasibility by analyzing recent experiment parameters. Our results provide a promising platform for the quantum signal transmission and quantum logic control, and they are of potential applications in quantum information processing and quantum networks.

  7. Quantum scattering on a cone revisited

    NASA Astrophysics Data System (ADS)

    Barroso, V. S.; Pitelli, J. P. M.

    2017-07-01

    We revisit the scattering of quantum test particles on the conical (2 +1 )-dimensional spacetime and find the scattering amplitude as a function of the boundary conditions imposed at the apex of the cone. We show that the boundary condition is responsible for a purely analytical term in the scattering amplitude, in addition to those coming from purely topological effects. Since it is possible to have nonequivalent physical evolutions for the wave packet (each one corresponding to a different boundary condition), it seems crucial to have an observable quantity specifying which evolution has been prescribed.

  8. Effective production of orbital quantum entanglement in chaotic quantum dots with nonideal contacts

    NASA Astrophysics Data System (ADS)

    Santos, E. H.; Almeida, F. A. G.

    2016-09-01

    We study orbital entanglement production in a chaotic quantum dot with two-channel leads by varying the opacity of the contacts in the unitary and orthogonal Wigner-Dyson ensembles. We computed the occurrence probability of entangled states (squared norm) and its concurrence (entanglement level). We also define an entanglement production factor to properly evaluate the entanglement behavior in the system considering effective aspects. The results are numerically obtained through (i) integrations over random matrix ensembles (exact results) for the scenario of one contact ideally fixed and (ii) random matrix simulations for arbitrary contact opacities (sampling). Those outcomes are in mutual agreement and indicate that the optimum effective production of orbital entanglement is achieved when both contacts are ideal and the time-reversal symmetry is broken.

  9. Stochastic methods for zero energy quantum scattering

    NASA Astrophysics Data System (ADS)

    Koch, Justus H.; Mall, Hubertus R.; Lenz, Stefan

    1998-02-01

    We investigate the use of stochastic methods for zero energy quantum scattering based on a path integral approach. With the application to the scattering of a projectile from a nuclear many-body target in mind, we use the potential scattering of a particle as a test for the accuracy and efficiency of several methods. To be able to deal with complex potentials, we introduce a path sampling action and a modified scattering observable. The approaches considered are the random walk, where the points of a path are sequentially generated, and the Langevin algorithm, which updates an entire path. Several improvements are investigated. A cluster algorithm for dealing with scattering problems is finally proposed, which shows the best accuracy and stability.

  10. Statistics of time delay and scattering correlation functions in chaotic systems. I. Random matrix theory

    SciTech Connect

    Novaes, Marcel

    2015-06-15

    We consider the statistics of time delay in a chaotic cavity having M open channels, in the absence of time-reversal invariance. In the random matrix theory approach, we compute the average value of polynomial functions of the time delay matrix Q = − iħS{sup †}dS/dE, where S is the scattering matrix. Our results do not assume M to be large. In a companion paper, we develop a semiclassical approximation to S-matrix correlation functions, from which the statistics of Q can also be derived. Together, these papers contribute to establishing the conjectured equivalence between the random matrix and the semiclassical approaches.

  11. Statistics of time delay and scattering correlation functions in chaotic systems. I. Random matrix theory

    NASA Astrophysics Data System (ADS)

    Novaes, Marcel

    2015-06-01

    We consider the statistics of time delay in a chaotic cavity having M open channels, in the absence of time-reversal invariance. In the random matrix theory approach, we compute the average value of polynomial functions of the time delay matrix Q = - iħS†dS/dE, where S is the scattering matrix. Our results do not assume M to be large. In a companion paper, we develop a semiclassical approximation to S-matrix correlation functions, from which the statistics of Q can also be derived. Together, these papers contribute to establishing the conjectured equivalence between the random matrix and the semiclassical approaches.

  12. Insights into the softening of chaotic statistical models by quantum considerations

    NASA Astrophysics Data System (ADS)

    Cafaro, C.; Giffin, A.; Lupo, C.; Mancini, S.

    2012-05-01

    We analyze the information geometry and the entropic dynamics of a 3D Gaussian statistical model and compare our analysis to that of a 2D Gaussian statistical model obtained from the higher-dimensional model via introduction of an additional information constraint that resembles the quantum mechanical canonical minimum uncertainty relation. We uncover that the chaoticity of the 2D Gaussian statistical model, quantified by means of the Information Geometric Entropy (IGE), is softened with respect to the chaoticity of the 3D Gaussian statistical model.

  13. Regular and chaotic quantum dynamics in atom-diatom reactive collisions

    SciTech Connect

    Gevorkyan, A. S.; Nyman, G.

    2008-05-15

    A new microirreversible 3D theory of quantum multichannel scattering in the three-body system is developed. The quantum approach is constructed on the generating trajectory tubes which allow taking into account influence of classical nonintegrability of the dynamical quantum system. When the volume of classical chaos in phase space is larger than the quantum cell in the corresponding quantum system, quantum chaos is generated. The probability of quantum transitions is constructed for this case. The collinear collision of the Li + (FH) {sup {yields}}(LiF) + H system is used for numerical illustration of a system generating quantum (wave) chaos.

  14. Statistics of quantum transport in weakly nonideal chaotic cavities.

    PubMed

    Rodríguez-Pérez, Sergio; Marino, Ricardo; Novaes, Marcel; Vivo, Pierpaolo

    2013-11-01

    We consider statistics of electronic transport in chaotic cavities where time-reversal symmetry is broken and one of the leads is weakly nonideal; that is, it contains tunnel barriers characterized by tunneling probabilities Γ(i). Using symmetric function expansions and a generalized Selberg integral, we develop a systematic perturbation theory in 1-Γ(i) valid for an arbitrary number of channels and obtain explicit formulas up to second order for the average and variance of the conductance and for the average shot noise. Higher moments of the conductance are considered to leading order.

  15. Isotropic quantum scattering and unconventional superconductivity.

    PubMed

    Park, T; Sidorov, V A; Ronning, F; Zhu, J-X; Tokiwa, Y; Lee, H; Bauer, E D; Movshovich, R; Sarrao, J L; Thompson, J D

    2008-11-20

    Superconductivity without phonons has been proposed for strongly correlated electron materials that are tuned close to a zero-temperature magnetic instability of itinerant charge carriers. Near this boundary, quantum fluctuations of magnetic degrees of freedom assume the role of phonons in conventional superconductors, creating an attractive interaction that 'glues' electrons into superconducting pairs. Here we show that superconductivity can arise from a very different spectrum of fluctuations associated with a local (or Kondo-breakdown) quantum critical point that is revealed in isotropic scattering of charge carriers and a sublinear, temperature-dependent electrical resistivity. At this critical point, accessed by applying pressure to the strongly correlated, local-moment antiferromagnet CeRhIn(5), magnetic and charge fluctuations coexist and produce electronic scattering that is maximal at the optimal pressure for superconductivity. This previously unanticipated source of pairing glue opens possibilities for understanding and discovering new unconventional forms of superconductivity.

  16. Study of possible chaotic, quasi-periodic and periodic structures in quantum dusty plasma

    SciTech Connect

    Ghosh, Uday Narayan; Chatterjee, Prasanta; Roychoudhury, Rajkumar

    2014-11-15

    Existence of chaotic, quasi-periodic, and periodic structures of dust-ion acoustic waves is studied in quantum dusty plasmas through dynamical system approach. A system of coupled differential equations is derived from the fluid model and subsequently, variational matrix is obtained. The characteristic equation is obtained at the equilibrium point, and the behavior of nonlinear waves is studied numerically using Runge-Kutta method. The behavior of the dynamical system changes significantly when any of plasma parameters, such as the dust concentration parameter, temperature ratio, or the quantum diffraction parameter, is varied. The change of the characteristic of solution of the system is extensively studied. It is found that the system changes its behavior from chaotic pattern to limit cycle behavior.

  17. Quantum smearing in hybrid inflation with chaotic potentials

    NASA Astrophysics Data System (ADS)

    Ahmed, Waqas; Ishaque, Ommair; Rehman, Mansoor Ur

    2016-01-01

    We study the impact of 1-loop radiative corrections in a nonsupersymmetric model of hybrid inflation (HI) with chaotic (polynomial-like) potential, V0 + λpϕp. These corrections can arise from the possible couplings of inflaton with other fields which can play an active role in the reheating process. The tree-level predictions of these models are shown to lie outside of the Planck’s latest bounds on the scalar spectral index ns and the tensor to scalar ratio r. However, the radiatively corrected version of these models, V0 + λpϕp + Aϕ4ln ϕ, is fully consistent with the Planck’s data. More specifically, fermionic radiative correction (A < 0) reduces the tensor to scalar ratio significantly and a red-tilted spectral index ns < 1, consistent with Planck’s data, is obtained even for sub-Planckian field-values.

  18. Semiclassical matrix model for quantum chaotic transport with time-reversal symmetry

    SciTech Connect

    Novaes, Marcel

    2015-10-15

    We show that the semiclassical approach to chaotic quantum transport in the presence of time-reversal symmetry can be described by a matrix model. In other words, we construct a matrix integral whose perturbative expansion satisfies the semiclassical diagrammatic rules for the calculation of transport statistics. One of the virtues of this approach is that it leads very naturally to the semiclassical derivation of universal predictions from random matrix theory.

  19. Considerations concerning diffraction scattering in quantum chromodynamics

    NASA Astrophysics Data System (ADS)

    Nachtmann, O.

    1991-08-01

    A model for diffractive, especially elastic hadron-hadron scattering at high c.m. energies squared s and small momentum transfer squared | t| is developed, based on quantum chromodynamics (QCD). First the scattering of hadron constituents, partons, is considered. In this paper we study mainly the scattering of quarks and antiquarks. The s-dependence of the amplitudes is treated by analytical means using a functional integral approach and an eikonal approximation. The t-dependence of the amplitudes is then shown to be governed by a certain correlation function of gluon string operators. A calculation of this function by non-perturbative methods in the framework of lattice OCD or in the stochastic vacuum field model should be feasible. The transition from the parton to the hadron level is accomplished by constructing an effective S-operator in terms of local tensor operators. In this way we avoid dealing explicitly with hadronic wave functions. In our approach the bound state nature of the hadrons enters through matrix elements of the local operators, where information from deep inelastic lepton-hadron scattering exists. The resulting expression for the elastic hadron-hadron scattering amplitude is discussed and is shown to lead to an understanding of various phenomenological findings. The physical picture emerging is one where single partons of the hadrons interact at a time, i.e., the "Pomeron" couples to single partons. This was suggested previously by phenomenological analyses of experiments and by theoretical investigations of an abelian gluon model.

  20. Persistent Currents and Addition Spectrum in Strongly Interacting Chaotic Quantum Dots

    NASA Astrophysics Data System (ADS)

    Herman, Damir; Mathur, H.; Murthy, Ganpathy

    2003-03-01

    Murthy and Shankar(Ganpathy Murthy, R. Shankar, Quantum Dots with Disorder and Interactions: A Solvable Large-g Limit), family cond-mat/0209136 have introduced a non-perturbative approach to analyzing the effects of interaction and randomness in chaotic quantum dots in the limit of large Thouless number. Using this framework we study two experimentally observable quantities in the strongly interacting regime. First we compare the Coulomb blockade peak spacing distribution in the strong coupling regime to the distribution in the weak coupling regime (described by the ``universal Hamiltonian''). Second we study persistent currents in mesoscopic rings in the regime of strong interaction.

  1. Semiclassical calculation of heavy-ion scattering in the chaotic regime

    SciTech Connect

    Dasso, C. H.; Gallardo, M. I.; Saraceno, M.

    2007-05-15

    The semiclassical approach has proven to be a most valuable tool for the construction of the scattering matrix and accurate evaluation of cross sections in a large variety of heavy-ion collision problems. In its familiar implementation, however, its use is restricted to what is now known as the 'regular regime', as it makes use of classical reaction functions that must be continuous and interpolable. In this paper we identify what version of the semiclassical formalisms may be especially suitable for extension into the chaotic regime that develops at energies close to the Coulomb barrier. We also show the crucial role of the absorptive part of the ion-ion potential to retain the usefulness of the semiclassical methods under conditions of irregularity.

  2. Effect of chiral symmetry on chaotic scattering from Majorana zero modes.

    PubMed

    Schomerus, H; Marciani, M; Beenakker, C W J

    2015-04-24

    In many of the experimental systems that may host Majorana zero modes, a so-called chiral symmetry exists that protects overlapping zero modes from splitting up. This symmetry is operative in a superconducting nanowire that is narrower than the spin-orbit scattering length, and at the Dirac point of a superconductor-topological insulator heterostructure. Here we show that chiral symmetry strongly modifies the dynamical and spectral properties of a chaotic scatterer, even if it binds only a single zero mode. These properties are quantified by the Wigner-Smith time-delay matrix Q=-iℏS^{†}dS/dE, the Hermitian energy derivative of the scattering matrix, related to the density of states by ρ=(2πℏ)^{-1}TrQ. We compute the probability distribution of Q and ρ, dependent on the number ν of Majorana zero modes, in the chiral ensembles of random-matrix theory. Chiral symmetry is essential for a significant ν dependence.

  3. Husimi-Wehrl entropy in the quantum chaotic system -An efficient calculational method-

    NASA Astrophysics Data System (ADS)

    Tsukiji, Hidekazu; Iida, Hideaki; Kunihiro, Teiji; Ohnishi, Akira

    2014-09-01

    Early thermalization in heavy ion collisions still remains a theoretical challenge. It was suggested in the hydrodynamical analyses of the relativistic heavy-ion collisions at RHIC and later at LHC. There are many proposals for pinning down the underlying mechanism for it. Quantum fluctuations on top of the classical configurations (glasma) are found to induce instabilities. It may trigger the chaotic behavior of the gauge field and eventually give rise to entropy production. In this work, we investigate thermalization of glasma by using the Husimi-Wehrl entropy. Quasi-distribution function defined in phase space should be useful to describe possible chaotic behavior of a quantum system. We adopt the Husimi distribution function to discuss entropy production of quantum systems. Husimi function is a minimally coarse-grained Wigner function and semi-positive definite. As a first stage of the study, we calculate the Husimi-Wehrl (H-W) entropy of a quantum Yang-Mills system [Tsai, Muller (2012)] with two-degrees of freedom. We propose a Monte-Carlo method to numerically calculate the time evolution of the Husimi function and the H-W entropy. We also discuss an extension of the method to quantum field theories.

  4. Random matrix theory of a chaotic Andreev quantum dot

    SciTech Connect

    Altland, A.; Zirnbauer, M.R.

    1996-04-01

    A new universality class distinct from the standard Wigner-Dyson class is identified. This class is realized by putting a metallic quantum dot in contact with a superconductor, while applying a magnetic field so as to make the pairing field effectively vanish on average. A random-matrix description of the spectral and transport properties of such a quantum dot is proposed. The weak-localization correction to the tunnel conductance is nonzero and results from the depletion of the density of states due to the coupling with the superconductor. Semiclassically, the depletion is caused by a singular mode of phase-coherent long-range propagation of particles and holes. {copyright} {ital 1996 The American Physical Society.}

  5. Scattering in PT-symmetric quantum mechanics

    SciTech Connect

    Cannata, Francesco . E-mail: Francesco.Cannata@bo.infn.it; Dedonder, Jean-Pierre . E-mail: dedonder@paris7.jussieu.fr; Ventura, Alberto . E-mail: Alberto.Ventura@bologna.enea.it

    2007-02-15

    A general formalism is worked out for the description of one-dimensional scattering in non-hermitian quantum mechanics and constraints on transmission and reflection coefficients are derived in the cases of P, T or PT invariance of the Hamiltonian. Applications to some solvable PT-symmetric potentials are shown in detail. Our main original results concern the association of reflectionless potentials with asymptotic exact PT symmetry and the peculiarities of separable kernels of non-local potentials in connection with Hermiticity, T invariance and PT invariance.

  6. Effect of Multiple Scattering in a Quantum Well

    NASA Astrophysics Data System (ADS)

    Sheng, Hanyu; Chua, Soo-Jin; Sinkkonen, Juha

    This paper gives a potentially useful application to quantum well of the theory of scattering in the Born approximation. The simple formulae for multiple scattering in a quantum well of double barrier structure are derived. The multiple scattering parameter is the complex mean free path. We show that the amplitude of the coherent wave will be exponentially attenuated and the phase of the wave will be delayed because of the scattering.

  7. Complex scattering dynamics and the quantum Hall effects

    SciTech Connect

    Trugman, S.A.

    1994-12-16

    We review both classical and quantum potential scattering in two dimensions in a magnetic field, with applications to the quantum Hall effect. Classical scattering is complex, due to the approach of scattering states to an infinite number of dynamically bound states. Quantum scattering follows the classical behavior rather closely, exhibiting sharp resonances in place of the classical bound states. Extended scatterers provide a quantitative explanation for the breakdown of the QHE at a comparatively small Hall voltage as seen by Kawaji et al., and possibly for noise effects.

  8. Why we don`t need quantum planetary dynamics, or on decoherence and the correspondence principle for chaotic systems

    SciTech Connect

    Zurek, W.H.; Pas, J.P. |

    1995-08-01

    Violation of correspondence principle may occur for very macroscopic byt isolated quantum systems on rather short timescales as illustrated by the case of Hyperion, the chaotically tumbling moon of Saturn, for which quantum and classical predictions are expected to diverge on a timescale of approximately 20 years. Motivated by Hyperion, we review salient features of ``quantum chaos`` and show that decoherence is the essential ingredient of the classical limit, as it enables one to solve the apparent paradox caused by the breakdown of the correspondence principle for classically chaotic systems.

  9. Testing the Predictions of Random Matrix Theory in Low Loss Wave Chaotic Scattering Systems

    NASA Astrophysics Data System (ADS)

    Yeh, Jen-Hao; Antonsen, Thomas; Ott, Edward; Anlage, Steven

    2013-03-01

    Wave chaos is a field where researchers apply random matrix theory (RMT) to predict the statistics of wave properties in complicated wave scattering systems. The RMT predictions have successfully demonstrated universality of the distributions of these wave properties, which only depend on the loss parameter of the system and the physical symmetry. Examination of these predictions in very low loss systems is interesting because extreme limits for the distribution functions and other predictions are encountered. Therefore, we use a wave-chaotic superconducting cavity to establish a low loss environment and test RMT predictions, including the statistics of the scattering (S) matrix and the impedance (Z) matrix, the universality (or lack thereof) of the Z- and S-variance ratios, and the statistics of the proper delay times of the Wigner-Smith time-delay matrix. We have applied an in-situ microwave calibration method (Thru-Reflection-Line method) to calibrate the cryostat system, and we also applied the random coupling model to remove the system-specific features. Our experimental results of different properties agree with the RMT predictions. This work is funded by the ONR/Maryland AppEl Center Task A2 (contract No. N000140911190), the AFOSR under grant FA95500710049, and Center for Nanophysics and Advanced Materials.

  10. Chaotic scattering of pitch angles in the current sheet of the magnetotail

    NASA Technical Reports Server (NTRS)

    Burkhart, G. R.; Chen, J.

    1992-01-01

    The modified Harris field model is used to investigate the process of pitch angle scattering by a current sheet. The relationship between the incoming asymptotic pitch angle alpha(in) and the outgoing asymptotic pitch angle alpha(out) is studied from first principles by numerically integrating the equation of motion. Evidence that charged particles undergo chaotic scattering by the current sheet is found. For fixed alpha(in), it is shown that alpha(out) exhibits sensitive dependence on the energy parameter in certain energy ranges. For a fixed energy parameter value in the same energy ranges, alpha(out) sensitively depends on alpha(in). For other energy values, alpha(out) does not show sensitive dependence on alpha(in) for most phase angles. A distribution of alpha(in) is mapped from the asymptotic region to the midplane, and it is found that the resulting particle distribution should have beam structures with well-collimated pitch angles near each resonance energy value. Implications for the particle distribution functions in the earth's magnetotail are discussed.

  11. Scattered-wave-packet formalism with applications to barrier scattering and quantum transistors.

    PubMed

    Chou, Chia-Chun; Wyatt, Robert E

    2011-11-01

    The scattered wave formalism developed for a quantum subsystem interacting with reservoirs through open boundaries is applied to one- or two-dimensional barrier scattering and quantum transistors. The total wave function is divided into incident and scattered components. Markovian outgoing wave boundary conditions are imposed on the scattered or total wave function by either the ratio or polynomial methods. For barrier scattering problems, accurate time-dependent transmission probabilities are obtained through the integration of the modified time-dependent Schrödinger equations for the scattered wave function. For quantum transistors, the time-dependent transport is studied for a quantum wave packet propagating through the conduction channel of a field effect transistor. This study shows that the scattered wave formalism significantly reduces computational effort relative to other open boundary methods and demonstrates wide applications to quantum dynamical processes.

  12. Relativistic quantum scattering yielded by Lorentz symmetry breaking effects

    NASA Astrophysics Data System (ADS)

    Mota, H. F.; Bakke, K.; Belich, H.

    2017-08-01

    We investigate the scattering of a relativistic scalar quantum particle induced by a scattering-like potential that arises from the effects of the violation of the Lorentz symmetry. We then obtain the scattering phase shift caused by the influence of such a potential and use it to calculate the exact expressions for the scattering amplitude as well as for the total scattering cross-section through the optical theorem. In addition, we estimate an upper bound for the Lorentz symmetry violation parameters.

  13. Quantum Dissipation due to the Interaction with Chaotic Degrees of Freedom and the Correspondence Principle

    NASA Astrophysics Data System (ADS)

    Cohen, Doron

    1999-06-01

    Both in atomic and in mesoscopic physics it is interesting to consider the energy time dependence of a parametrically driven chaotic system. We assume an Hamiltonian H\\(Q,P;x\\(t\\)\\) where x\\(t\\) = Vt. The velocity V is slow in the classical sense but not necessarily in the quantum-mechanical sense. The crossover (in time) from ballistic to diffusive energy spreading is studied. Dissipation is the associated irreversible growth of the average energy. It is found that a dimensionless velocity vPR determines the nature of the dynamics, and controls the route towards quantal-classical correspondence. A perturbative regime and a nonperturbative semiclassical regime are distinguished.

  14. Observation of 'scarred' wavefunctions in a quantum well with chaotic electron dynamics

    NASA Astrophysics Data System (ADS)

    Wilkinson, P. B.; Fromhold, T. M.; Eaves, L.; Sheard, F. W.; Miura, N.; Takamasu, T.

    1996-04-01

    QUALITATIVE insight into the properties of a quantum-mechanical system can be gained from the study of the relationship between the system's classical newtonian dynamics, and its quantum dynamics as described by the Schrödinger equation. The Bohr-Sommerfeld quantization scheme-which underlies the historically important Bohr model for hydrogen-like atoms-describes the relationship between the classical and quantum-mechanical regimes, but only for systems with stable, periodic or quasi-periodic orbits1. Only recently has progress been made in understanding the quantization of systems that exhibit non-periodic, chaotic motion. The spectra of quantized energy levels for such systems are irregular, and show fluctuations associated with unstable periodic orbits of the corresponding classical system1-3. These orbits appear as 'scars'-concentrations of probability amplitude-in the wavefunction of the system4. Although wavefunction scarring has been the subject of extensive theoretical investigation5-10, it has not hitherto been observed experimentally in a quantum system. Here we use tunnel-current spectroscopy to map the quantum-mechanical energy levels of an electron confined in a semiconductor quantum well in a high magnetic field10-13. We find clear experimental evidence for wavefunction scarring, in full agreement with theoretical predictions10.

  15. Scattering of Second Sound Waves by Quantum Vorticity

    NASA Astrophysics Data System (ADS)

    Lund, Fernando; Steinberg, Victor

    1995-08-01

    A new method of detection and measurement of quantum vorticity by scattering second sound off quantized vortices in superfluid helium is suggested. Theoretical calculations of the relative amplitude of the scattered second sound waves from a single quantum vortex, a vortex lattice, and bulk vorticity are presented. The relevant estimates show that an experimental verification of the method is feasible. Moreover, it can even be used for the detection of a single quantum vortex.

  16. Suppression of Quantum Scattering in Strongly Confined Systems

    SciTech Connect

    Kim, J. I.; Melezhik, V. S.; Schmelcher, P.

    2006-11-10

    We demonstrate that scattering of particles strongly interacting in three dimensions (3D) can be suppressed at low energies in a quasi-one-dimensional (1D) confinement. The underlying mechanism is the interference of the s- and p-wave scattering contributions with large s- and p-wave 3D scattering lengths being a necessary prerequisite. This low-dimensional quantum scattering effect might be useful in 'interacting' quasi-1D ultracold atomic gases, guided atom interferometry, and impurity scattering in strongly confined quantum wire-based electronic devices.

  17. Periodic orbit effects on conductance peak heights in a chaotic quantum dot

    SciTech Connect

    Kaplan, L.

    2000-09-01

    We study the effects of short-time classical dynamics on the distribution of Coulomb blockade peak heights in a chaotic quantum dot. The location of one or both leads relative to the short unstable orbits, as well as relative to the symmetry lines, can have large effects on the moments and on the head and tail of the conductance distribution. We study these effects analytically as a function of the stability exponent of the orbits involved, and also numerically using the stadium billiard as a model. The predicted behavior is robust, depending only on the short-time behavior of the many-body quantum system, and consequently insensitive to moderate-sized perturbations and interactions. (c) 2000 The American Physical Society.

  18. Deep Wavelet Scattering for Quantum Energy Regression

    NASA Astrophysics Data System (ADS)

    Hirn, Matthew

    Physical functionals are usually computed as solutions of variational problems or from solutions of partial differential equations, which may require huge computations for complex systems. Quantum chemistry calculations of ground state molecular energies is such an example. Indeed, if x is a quantum molecular state, then the ground state energy E0 (x) is the minimum eigenvalue solution of the time independent Schrödinger Equation, which is computationally intensive for large systems. Machine learning algorithms do not simulate the physical system but estimate solutions by interpolating values provided by a training set of known examples {(xi ,E0 (xi) } i <= n . However, precise interpolations may require a number of examples that is exponential in the system dimension, and are thus intractable. This curse of dimensionality may be circumvented by computing interpolations in smaller approximation spaces, which take advantage of physical invariants. Linear regressions of E0 over a dictionary Φ ={ϕk } k compute an approximation E 0 as: E 0 (x) =∑kwkϕk (x) , where the weights {wk } k are selected to minimize the error between E0 and E 0 on the training set. The key to such a regression approach then lies in the design of the dictionary Φ. It must be intricate enough to capture the essential variability of E0 (x) over the molecular states x of interest, while simple enough so that evaluation of Φ (x) is significantly less intensive than a direct quantum mechanical computation (or approximation) of E0 (x) . In this talk we present a novel dictionary Φ for the regression of quantum mechanical energies based on the scattering transform of an intermediate, approximate electron density representation ρx of the state x. The scattering transform has the architecture of a deep convolutional network, composed of an alternating sequence of linear filters and nonlinear maps. Whereas in many deep learning tasks the linear filters are learned from the training data, here

  19. Electron scattering and mobility in a quantum well heterolayer

    NASA Astrophysics Data System (ADS)

    Arora, Vijay K.; Naeem, Athar

    1984-11-01

    The theory of electron-lattice scattering is analyzed for a quantum-well heterolayer under the conditions that the de Broglie wavelength of an electron is comparable to or larger than the width of the layer, and donor impurities are removed in an adjacent nonconducting layer. The mobility due to isotropic scattering by acoustic phonons, point defects, and alloy scattering is found to increase whereas that due to polar-optic phon scattering is found to decrease with increasing thickness.

  20. Chaotic quantum ratchets and filters with cold atoms in optical lattices: Properties of Floquet states

    NASA Astrophysics Data System (ADS)

    Hur, Gwang-Ok

    The -kicked rotor is a paradigm of quantum chaos. Its realisation with clouds of cold atoms in pulsed optical lattices demonstrated the well-known quantum chaos phenomenon of 'dynamical localisation'. In those experi ments by several groups world-wide, the £-kicks were applied at equal time intervals. However, recent theoretical and experimental work by the cold atom group at UCL Monteiro et al 2002, Jonckheere et al 2003, Jones et al 2004 showed that novel quantum and classical dynamics arises if the atomic cloud is pulsed with repeating sequences of unequally spaced kicks. In Mon teiro et al 2002 it was found that the energy absorption rates depend on the momentum of the atoms relative to the optical lattice hence a type of chaotic ratchet was proposed. In Jonckheere et al and Jones et al, a possible mechanism for selecting atoms according to their momenta (velocity filter) was investigated. The aim of this thesis was to study the properties of the underlying eigen values and eigenstates. Despite the unequally-spaced kicks, these systems are still time-periodic, so we in fact investigated the Floquet states, which are eigenstates of U(T), the one-period time evolution operator. The Floquet states and corresponding eigenvalues were obtained by diagonalising a ma trix representation of the operator U(T). It was found that the form of the eigenstates enables us to analyse qual itatively the atomic momentum probability distributions, N(p) measured experimentally. In particular, the momentum width of the individual eigen states varies strongly with < p > as expected from the theoretical and ex- perimental results obtained previously. In addition, at specific < p > close to values which in the experiment yield directed motion (ratchet transport), the probability distribution of the individual Floquet states is asymmetric, mirroring the asymmetric N(p) measured in clouds of cesium atoms. In the penultimate chapter, the spectral fluctuations (eigenvalue statis tics) are

  1. A modified Lax-Phillips scattering theory for quantum mechanics

    NASA Astrophysics Data System (ADS)

    Strauss, Y.

    2015-07-01

    The Lax-Phillips scattering theory is an appealing abstract framework for the analysis of scattering resonances. Quantum mechanical adaptations of the theory have been proposed. However, since these quantum adaptations essentially retain the original structure of the theory, assuming the existence of incoming and outgoing subspaces for the evolution and requiring the spectrum of the generator of evolution to be unbounded from below, their range of applications is rather limited. In this paper, it is shown that if we replace the assumption regarding the existence of incoming and outgoing subspaces by the assumption of the existence of Lyapunov operators for the quantum evolution (the existence of which has been proved for certain classes of quantum mechanical scattering problems), then it is possible to construct a structure analogous to the Lax-Phillips structure for scattering problems for which the spectrum of the generator of evolution is bounded from below.

  2. A modified Lax-Phillips scattering theory for quantum mechanics

    SciTech Connect

    Strauss, Y.

    2015-07-15

    The Lax-Phillips scattering theory is an appealing abstract framework for the analysis of scattering resonances. Quantum mechanical adaptations of the theory have been proposed. However, since these quantum adaptations essentially retain the original structure of the theory, assuming the existence of incoming and outgoing subspaces for the evolution and requiring the spectrum of the generator of evolution to be unbounded from below, their range of applications is rather limited. In this paper, it is shown that if we replace the assumption regarding the existence of incoming and outgoing subspaces by the assumption of the existence of Lyapunov operators for the quantum evolution (the existence of which has been proved for certain classes of quantum mechanical scattering problems), then it is possible to construct a structure analogous to the Lax-Phillips structure for scattering problems for which the spectrum of the generator of evolution is bounded from below.

  3. Resonant Scattering of Surface Plasmon Polaritons by Dressed Quantum Dots

    DTIC Science & Technology

    2014-06-23

    Resonant scattering of surface plasmon polaritons by dressed quantum dots Danhong Huang,1 Michelle Easter,2 Godfrey Gumbs,3 A. A. Maradudin,4 Shawn... polariton waves (SPP) by embedded semiconductor quantum dots above the dielectric/metal interface is explored in the strong-coupling regime. In con- trast to...induced polarization field, treated as a source term9 arising from photo-excited electrons, allows for a resonant scattering of surface plasmon- polariton

  4. Ponderomotive potential and backward Raman scattering in dense quantum plasmas

    SciTech Connect

    Son, S.

    2014-03-15

    The backward Raman scattering is studied in dense quantum plasmas. The coefficients in the backward Raman scattering is found to be underestimated (overestimated) in the classical theory if the excited Langmuir wave has low-wave vector (high-wave vector). The second-order quantum perturbation theory shows that the second harmonic of the ponderomotive potential arises naturally even in a single particle motion contrary to the classical prediction.

  5. Weak localization and conductance fluctuations in a quantum dot with parallel magnetic field and spin-orbit scattering

    NASA Astrophysics Data System (ADS)

    Cremers, Jan-Hein; Brouwer, Piet W.; Fal'Ko, Vladimir I.

    2003-09-01

    In the presence of both spin-orbit scattering and a magnetic field the conductance of a chaotic GaAs quantum dot displays quite a rich behavior. Using a Hamiltonian derived by Aleiner and Fal’ko [Phys. Rev. Lett. 87, 256801 (2001)] we calculate the weak localization correction and the covariance of the conductance, as a function of parallel and perpendicular magnetic field and spin-orbit coupling strength. We also show how the combination of an in-plane magnetic field and spin-orbit scattering gives rise to a component to the magnetoconductance that is antisymmetric with respect to reversal of the perpendicular component of the magnetic field and how spin-orbit scattering leads to a “magnetic-field echo” in the conductance autocorrelation function. Our results can be used for a measurement of the Dresselhaus and Bychkov-Rashba spin-orbit scattering lengths in a GaAs/GaAlAs heterostructure.

  6. Parameter scaling in the decoherent quantum-classical transition for chaotic rf superconducting quantum interference devices.

    PubMed

    Mao, Ting; Yu, Yang

    2010-01-01

    We numerically investigated the quantum-classical transition in rf-superconducting quantum interference device (SQUID) systems coupled to a dissipative environment. It is found that chaos emerges and the degree of chaos, the maximal Lyapunov exponent lambda(m), exhibits nonmonotonic behavior as a function of the coupling strength D. By measuring the proximity of quantum and classical evolution with the uncertainty of dynamics, we show that the uncertainty is a monotonic function of lambda(m)/D. In addition, the scaling holds in SQUID systems to a relatively smaller variant Planck's over [symbol: see text], suggesting the universality for this scaling.

  7. The Loschmidt echo in classically chaotic systems: Quantum chaos, irreversibility and decoherence

    NASA Astrophysics Data System (ADS)

    Cucchietti, Fernando M.

    2004-10-01

    The Loschmidt echo (LE) is a measure of the sensitivity of quantum mechanics to perturbations in the evolution operator. It is defined as the overlap of two wave functions evolved from the same initial state but with slightly different Hamiltonians. Thus, it also serves as a quantification of irreversibility in quantum mechanics. In this thesis the LE is studied in systems that have a classical counterpart with dynamical instability, that is, classically chaotic. An analytical treatment that makes use of the semiclassical approximation is presented. It is shown that, under certain regime of the parameters, the LE decays exponentially. Furthermore, for strong enough perturbations, the decay rate is given by the Lyapunov exponent of the classical system. Some particularly interesting examples are given. The analytical results are supported by thorough numerical studies. In addition, some regimes not accessible to the theory are explored, showing that the LE and its Lyapunov regime present the same form of universality ascribed to classical chaos. In a sense, this is evidence that the LE is a robust temporal signature of chaos in the quantum realm. Finally, the relation between the LE and the quantum to classical transition is explored, in particular with the theory of decoherence. Using two different approaches, a semiclassical approximation to Wigner functions and a master equation for the LE, it is shown that the decoherence rate and the decay rate of the LE are equal. The relationship between these quantities results mutually beneficial, in terms of the broader resources of decoherence theory and of the possible experimental realization of the LE.

  8. Resonant scattering of surface plasmon polaritons by dressed quantum dots

    SciTech Connect

    Huang, Danhong; Cardimona, Dave; Easter, Michelle; Gumbs, Godfrey; Maradudin, A. A.; Lin, Shawn-Yu; Zhang, Xiang

    2014-06-23

    The resonant scattering of surface plasmon-polariton waves (SPP) by embedded semiconductor quantum dots above the dielectric/metal interface is explored in the strong-coupling regime. In contrast to non-resonant scattering by a localized dielectric surface defect, a strong resonant peak in the spectrum of the scattered field is predicted that is accompanied by two side valleys. The peak height depends nonlinearly on the amplitude of SPP waves, reflecting the feedback dynamics from a photon-dressed electron-hole plasma inside the quantum dots. This unique behavior in the scattered field peak strength is correlated with the occurrence of a resonant dip in the absorption spectrum of SPP waves due to the interband photon-dressing effect. Our result on the scattering of SPP waves may be experimentally observable and applied to spatially selective illumination and imaging of individual molecules.

  9. Optical scatter of quantum noise filter cavity optics

    NASA Astrophysics Data System (ADS)

    Vander-Hyde, Daniel; Amra, Claude; Lequime, Michel; Magaña-Sandoval, Fabian; Smith, Joshua R.; Zerrad, Myriam

    2015-07-01

    Optical cavities to filter squeezed light for quantum noise reduction require optics with very low scattering losses. We report on measured light scattering from two super-polished fused silica optics before and after applying highly-reflective ion-beam sputtered dielectric coatings. We used an imaging scatterometer that illuminates the sample with a linearly polarized 1064 nm wavelength laser at a fixed angle of incidence and records images of back scatter for azimuthal angles in the plane of the laser beam. We extract from these images the bidirectional reflectance distribution function (BRDF) of the optics with and without coating and estimate their integrated scatter. We find that application of these coatings led to a more than 50% increase of the integrated wide-angle scatter, to 5.00+/- 0.30 and 3.38+/- 0.20 ppm for the two coated samples. In addition, the BRDF function of the coated optics takes on a pattern of maxima versus azimuthal angle. We compare with a scattering model to show that this is qualitatively consistent with roughness scattering from the coating layer interfaces. These results are part of a broader study to understand and minimize optical loss in quantum noise filter cavities for interferometric gravitational-wave detectors. The scattering measured for these samples is acceptable for the 16 m long filter cavities envisioned for the Laser Interferometer Gravitational-wave Observatory (LIGO), though reducing the loss further would improve LIGO’s quantum-noise limited performance.

  10. Quantum scattering model of energy transfer in photosynthetic complexes

    NASA Astrophysics Data System (ADS)

    Ai, Bao-quan; Zhu, Shi-Liang

    2015-12-01

    We develop a quantum scattering model to describe the exciton transport through the Fenna-Matthews-Olson (FMO) complex. It is found that the exciton transport involving the optimal quantum coherence is more efficient than that involving classical behaviour alone. Furthermore, we also find that the quantum resonance condition is easier to be fulfilled in multiple pathways than that in one pathway. We then definitely demonstrate that the optimal distribution of the pigments, the multitude of energy delivery pathways and the quantum effects are combined together to contribute to the perfect energy transport in the FMO complex.

  11. Quantum Radiation Reaction Effects in Multiphoton Compton Scattering

    SciTech Connect

    Di Piazza, A.; Hatsagortsyan, K. Z.; Keitel, C. H.

    2010-11-26

    Radiation reaction effects in the interaction of an electron and a strong laser field are investigated in the realm of quantum electrodynamics. We identify the quantum radiation reaction with the multiple photon recoils experienced by the laser-driven electron due to consecutive incoherent photon emissions. After determining a quantum radiation dominated regime, we demonstrate how in this regime quantum signatures of the radiation reaction strongly affect multiphoton Compton scattering spectra and that they could be measurable in principle with presently available laser technology.

  12. Quantum theory of surface-plasmon polariton scattering

    SciTech Connect

    Ballester, D.; Tame, M. S.; Kim, M. S.

    2010-07-15

    We introduce the quantum mechanical formalism for treating surface plasmon polariton scattering at an interface. Our developed theory--which differs fundamentally from the analogous photonic scenario--is used to investigate the possibility of plasmonic beam splitters at the quantum level. Remarkably, we find that a wide range of splitting ratios can be reached. As an application, we characterize a 50:50 plasmonic beam splitter and investigate first-order quantum interference of surface plasmon polaritons. The results of this theoretical study show that surface plasmon beam splitters are able to reliably and efficiently operate in the quantum domain.

  13. Particle scattering in loop quantum gravity.

    PubMed

    Modesto, Leonardo; Rovelli, Carlo

    2005-11-04

    We devise a technique for defining and computing -point functions in the context of a background-independent gravitational quantum field theory. We construct a tentative implementation of this technique in a perturbatively finite model defined using spin foam techniques in the context of loop quantum gravity.

  14. Chaotic Expansions of Elements of the Universal Enveloping Superalgebra Associated with a Z2-graded Quantum Stochastic Calculus

    NASA Astrophysics Data System (ADS)

    Eyre, T. M. W.

    Given a polynomial function f of classical stochastic integrator processes whose differentials satisfy a closed Ito multiplication table, we can express the stochastic derivative of f as We establish an analogue of this formula in the form of a chaotic decomposition for Z2-graded theories of quantum stochastic calculus based on the natural coalgebra structure of the universal enveloping superalgebra.

  15. Classical And Quantum Rainbow Scattering From Surfaces

    SciTech Connect

    Winter, H.; Schueller, A.; Busch, M.; Seifert, J.; Wethekam, S.

    2011-06-01

    The structure of clean and adsorbate covered surfaces as well as of ultrathin films can be investigated by grazing scattering of fast atoms. We present two recent experimental techniques which allow one to study the structure of ordered arrangements of surface atoms in detail. (1) Rainbow scattering under axial surface channeling conditions, and (2) fast atom diffraction. Our examples demonstrate the attractive features of grazing fast atom scattering as a powerful analytical tool in studies on the structure of surfaces. We will concentrate our discussion on the structure of ultrathin silica films on a Mo(112) surface and of adsorbed oxygen atoms on a Fe(110) surface.

  16. Electromagnetic scattering in the open elliptic quantum billiard

    NASA Astrophysics Data System (ADS)

    Garcia-Gracia, Hipolito; Gutiérrez-Vega, Julio C.

    2012-10-01

    The study of open quantum billiards has gained popularity in the last decades, including different common and uncommon geometries such as the circular and stadium billiards. We study the electromagnetic scattering of a linearly polarized electric field in the elliptic quantum billiard with hyperbolic channels. We analyze the effect of different parameters on the scattering in a billiard configuration obtained by displacing both channels by the same angle. We observed that for the configuration proposed in this work the polarization of the electric field is conserved.

  17. Chaotic scattering in solitary wave interactions: A singular iterated-map description

    SciTech Connect

    Goodman, Roy H.

    2008-06-15

    We derive a family of singular iterated maps--closely related to Poincare maps--that describe chaotic interactions between colliding solitary waves. The chaotic behavior of such solitary-wave collisions depends on the transfer of energy to a secondary mode of oscillation, often an internal mode of the pulse. This map allows us to go beyond previous analyses and to understand the interactions in the case when this mode is excited prior to the first collision. The map is derived using Melnikov integrals and matched asymptotic expansions and generalizes a ''multipulse'' Melnikov integral. It allows one to find not only multipulse heteroclinic orbits, but exotic periodic orbits. The maps exhibit singular behavior, including regions of infinite winding. These maps are shown to be singular versions of the conservative Ikeda map from laser physics and connections are made with problems from celestial mechanics and fluid mechanics.

  18. Chaotic scattering in solitary wave interactions: a singular iterated-map description.

    PubMed

    Goodman, Roy H

    2008-06-01

    We derive a family of singular iterated maps--closely related to Poincare maps--that describe chaotic interactions between colliding solitary waves. The chaotic behavior of such solitary-wave collisions depends on the transfer of energy to a secondary mode of oscillation, often an internal mode of the pulse. This map allows us to go beyond previous analyses and to understand the interactions in the case when this mode is excited prior to the first collision. The map is derived using Melnikov integrals and matched asymptotic expansions and generalizes a "multipulse" Melnikov integral. It allows one to find not only multipulse heteroclinic orbits, but exotic periodic orbits. The maps exhibit singular behavior, including regions of infinite winding. These maps are shown to be singular versions of the conservative Ikeda map from laser physics and connections are made with problems from celestial mechanics and fluid mechanics.

  19. Crystals for neutron scattering studies of quantum magnetism

    SciTech Connect

    Yankova, Tantiana; Hüvonen, Dan; Mühlbauer, Sebastian; Schmidiger, David; Wulf, Erik; Hong, Tao; Garlea, Vasile O; Custelcean, Radu; Ehlers, Georg

    2012-01-01

    We review a strategy for targeted synthesis of large single crystal samples of prototype quantum magnets for inelastic neutron scattering experiments. Four case studies of organic copper halogenide S = 1/2 systems are presented. They are meant to illustrate that exciting experimental results pertaining to the forefront of many-body quantum physics can be obtained on samples grown using very simple techniques, standard laboratory equipment, and almost no experience in advanced crystal growth techniques.

  20. Scattering theory for the quantum envelope of a classical system

    SciTech Connect

    Sudarshan, E.C.G.

    1993-12-31

    Classical dynamics, reformulated in terms of its quantum envelope is studied for the stationary states of the interacting system. The dynamical variable of ``elapsed time`` plays a crucial role in this study. It is shown that the perturbation series for the elapsed time can be summed in various simple cases even when standard perturbation series diverge. For the special class of systems where the interactions fall off sufficiently fast at infinity one could define ``in`` and ``out`` states; and consequently the wave matrices and scattering matrices. The scattering phase shifts bear a simple relation to the time delay in scattering.

  1. Scattering through a straight quantum waveguide with combined boundary conditions

    SciTech Connect

    Briet, Ph. Soccorsi, E.; Dittrich, J.

    2014-11-15

    Scattering through a straight two-dimensional quantum waveguide R×(0,d) with Dirichlet boundary conditions on (R{sub −}{sup *}×(y=0))∪(R{sub +}{sup *}×(y=d)) and Neumann boundary condition on (R{sub −}{sup *}×(y=d))∪(R{sub +}{sup *}×(y=0)) is considered using stationary scattering theory. The existence of a matching conditions solution at x = 0 is proved. The use of stationary scattering theory is justified showing its relation to the wave packets motion. As an illustration, the matching conditions are also solved numerically and the transition probabilities are shown.

  2. Quantum-entanglement-initiated super Raman scattering

    SciTech Connect

    Agarwal, G. S.

    2011-02-15

    It has now been possible to prepare a chain of ions in an entangled state and thus the question arises: How will the optical properties of a chain of entangled ions differ from say a chain of independent particles? We investigate nonlinear optical processes in such chains. Since light scattering is quite a versatile technique to probe matter, we explicitly demonstrate the possibility of entanglement-produced super Raman scattering. Our results suggest the possibility of similar enhancement factors in other nonlinear processes like four-wave mixing.

  3. Quantum Chromodynamics and Deep Inelastic Scattering

    NASA Astrophysics Data System (ADS)

    Ellis, R. Keith

    2016-10-01

    This article first describes the parton model which was the precursor of the QCD description of hard scattering processes. After the discovery of QCD and asymptotic freedom, the first successful applications were to Deep Inelastic lepton-hadron scattering. The subsequent application of QCD to processes with two initial state hadrons required the understanding and proof of factorization. To take the fledgling theory and turn it into the robust calculational engine it has become today, required a number of technical and conceptual developments which will be described. Prospects for higher loop calculations are also reviewed.

  4. Noninertial effects on nonrelativistic topological quantum scattering

    NASA Astrophysics Data System (ADS)

    Mota, H. F.; Bakke, K.

    2017-08-01

    We investigate noninertial effects on the scattering problem of a nonrelativistic particle in the cosmic string spacetime. By considering the nonrelativistic limit of the Dirac equation we are able to show, in the regime of small rotational frequencies, that the phase shift has two contribution: one related to the noninertial reference frame, and the other, due to the cosmic string conical topology. We also show that both the incident wave and the scattering amplitude are altered as a consequence of the noninertial reference frame and depend on the rotational frequency.

  5. Chaotic spectroscopy.

    PubMed

    Doron, Eyal; Smilansky, Uzy

    1992-01-01

    The spectra of quantized chaotic billiards from the point of view of scattering theory are discussed. It is shown how the spectral and resonance density functions both fluctuate about a common mean. A semiclassical treatment explains this in terms of classical scattering trajectories and periodic orbits of the Poincare scattering map. It is shown that this formalism provides an alternative derivation and a new interpretation of Gutzwiller's periodic orbits sum for the spectral density. Moreover, it is a convenient starting point for a derivation of a Riemann-Siegel "look alike" expression for the secular equation in terms of periodic orbits of finite length.

  6. Scattering of quantum wave packets by shallow potential islands: a quantum lens.

    PubMed

    Goussev, Arseni; Richter, Klaus

    2013-05-01

    We consider the problem of quantum scattering of a localized wave packet by a weak Gaussian potential in two spatial dimensions. We show that, under certain conditions, this problem bears close analogy with that of focusing (or defocusing) of light rays by a thin optical lens: Quantum interference between straight paths yields the same lens equation as for refracted rays in classical optics.

  7. Quantum corral resonance widths: lossy scattering as acoustics.

    PubMed

    Barr, Matthew C; Zaletel, Michael P; Heller, Eric J

    2010-09-08

    We present an approach to predicting extrinsic electron resonance widths within quantum corral nanostructures based on analogies with acoustics. Established quantum mechanical methods for calculating resonance widths, such as multiple scattering theory, build up the scattering atom by atom, ignoring the structure formed by the atoms, such as walls or enclosures. Conversely, particle-in-a-box models, assuming continuous walls, have long been successful in predicting quantum corral energy levels, but not resonance widths. In acoustics, partial reflection from walls and various enclosures has long been incorporated for determining reverberation times. Pursuing an exact analogy between the local density of states of a quantum corral and the acoustic impedance of a concert hall, we show electron lifetimes in nanoscopic structures of arbitrary convex shape are well accounted for by the Sabine formula for acoustic reverberation times. This provides a particularly compact and intuitive prescription for extrinsic finite lifetimes in a particle-in-a-box with leaky walls, including quantum corral atomic walls, given single particle scattering properties.

  8. Cavity-enhanced coherent light scattering from a quantum dot

    PubMed Central

    Bennett, Anthony J.; Lee, James P.; Ellis, David J. P.; Meany, Thomas; Murray, Eoin; Floether, Frederik F.; Griffths, Jonathan P.; Farrer, Ian; Ritchie, David A.; Shields, Andrew J.

    2016-01-01

    The generation of coherent and indistinguishable single photons is a critical step for photonic quantum technologies in information processing and metrology. A promising system is the resonant optical excitation of solid-state emitters embedded in wavelength-scale three-dimensional cavities. However, the challenge here is to reject the unwanted excitation to a level below the quantum signal. We demonstrate this using coherent photon scattering from a quantum dot in a micropillar. The cavity is shown to enhance the fraction of light that is resonantly scattered toward unity, generating antibunched indistinguishable photons that are 16 times narrower than the time-bandwidth limit, even when the transition is near saturation. Finally, deterministic excitation is used to create two-photon N00N states with which we make superresolving phase measurements in a photonic circuit. PMID:27152337

  9. Cavity-enhanced coherent light scattering from a quantum dot.

    PubMed

    Bennett, Anthony J; Lee, James P; Ellis, David J P; Meany, Thomas; Murray, Eoin; Floether, Frederik F; Griffths, Jonathan P; Farrer, Ian; Ritchie, David A; Shields, Andrew J

    2016-04-01

    The generation of coherent and indistinguishable single photons is a critical step for photonic quantum technologies in information processing and metrology. A promising system is the resonant optical excitation of solid-state emitters embedded in wavelength-scale three-dimensional cavities. However, the challenge here is to reject the unwanted excitation to a level below the quantum signal. We demonstrate this using coherent photon scattering from a quantum dot in a micropillar. The cavity is shown to enhance the fraction of light that is resonantly scattered toward unity, generating antibunched indistinguishable photons that are 16 times narrower than the time-bandwidth limit, even when the transition is near saturation. Finally, deterministic excitation is used to create two-photon N00N states with which we make superresolving phase measurements in a photonic circuit.

  10. Temporal Quantum Correlations in Inelastic Light Scattering from Water

    NASA Astrophysics Data System (ADS)

    Kasperczyk, Mark; de Aguiar Júnior, Filomeno S.; Rabelo, Cassiano; Saraiva, Andre; Santos, Marcelo F.; Novotny, Lukas; Jorio, Ado

    2016-12-01

    Water is one of the most prevalent chemicals on our planet, an integral part of both our environment and our existence as a species. Yet it is also rich in anomalous behaviors. Here we reveal that water is a novel—yet ubiquitous—source for quantum correlated photon pairs at ambient conditions. The photon pairs are produced through Raman scattering, and the correlations arise from the shared quantum of a vibrational mode between the Stokes and anti-Stokes scattering events. We confirm the nonclassical nature of the produced photon pairs by showing that the cross-correlation and autocorrelations of the signals violate a Cauchy-Schwarz inequality by over 5 orders of magnitude. The unprecedented degree of violating the inequality in pure water, as well as the well-defined polarization properties of the photon pairs, points to its usefulness in quantum information.

  11. Metallic behaviour in SOI quantum wells with strong intervalley scattering

    PubMed Central

    Renard, V. T.; Duchemin, I.; Niida, Y.; Fujiwara, A.; Hirayama, Y.; Takashina, K.

    2013-01-01

    The fundamental properties of valleys are recently attracting growing attention due to electrons in new and topical materials possessing this degree-of-freedom and recent proposals for valleytronics devices. In silicon MOSFETs, the interest has a longer history since the valley degree of freedom had been identified as a key parameter in the observation of the controversial “metallic behaviour” in two dimensions. However, while it has been recently demonstrated that lifting valley degeneracy can destroy the metallic behaviour, little is known about the role of intervalley scattering. Here, we show that the metallic behaviour can be observed in the presence of strong intervalley scattering in silicon on insulator (SOI) quantum wells. Analysis of the conductivity in terms of quantum corrections reveals that interactions are much stronger in SOI than in conventional MOSFETs, leading to the metallic behaviour despite the strong intervalley scattering. PMID:23774638

  12. Study of dual-directional high rate secure communication systems using chaotic multiple-quantum-well lasers

    NASA Astrophysics Data System (ADS)

    Yan, Sen-Lin

    2007-11-01

    A scheme of synchronized injection multi-quantum-well (MQW) laser system using optical coupling-feedback is presented for performing chaotic dual-directional secure communication. The performance characterization of chaos masking is investigated theoretically, the equation of synchronization demodulation is deduced and its root is also given. Chaos masking encoding with a rate of 5Gbit/s and a modulation frequency of 1GHz, chaos modulation with a rate of 0.2Gbit/s and a modulation frequency of 0.2 GHz and chaos shifting key with a rate of 0.2Gbit/s are numerically simulated, separately. The ratio of the signal to the absolute synchronous error and the time for achieving synchronous demodulation are analysed in detail. The results illustrate that the system has stronger privacy and good performances so that it can be applied in chaotic dual-directional high rate secure communications.

  13. Quantum error correction of photon-scattering errors

    NASA Astrophysics Data System (ADS)

    Akerman, Nitzan; Glickman, Yinnon; Kotler, Shlomi; Ozeri, Roee

    2011-05-01

    Photon scattering by an atomic ground-state superposition is often considered as a source of decoherence. The same process also results in atom-photon entanglement which had been directly observed in various experiments using single atom, ion or a diamond nitrogen-vacancy center. Here we combine these two aspects to implement a quantum error correction protocol. We encode a qubit in the two Zeeman-splitted ground states of a single trapped 88 Sr+ ion. Photons are resonantly scattered on the S1 / 2 -->P1 / 2 transition. We study the process of single photon scattering i.e. the excitation of the ion to the excited manifold followed by a spontaneous emission and decay. In the absence of any knowledge on the emitted photon, the ion-qubit coherence is lost. However the joined ion-photon system still maintains coherence. We show that while scattering events where spin population is preserved (Rayleigh scattering) do not affect coherence, spin-changing (Raman) scattering events result in coherent amplitude exchange between the two qubit states. By applying a unitary spin rotation that is dependent on the detected photon polarization we retrieve the ion-qubit initial state. We characterize this quantum error correction protocol by process tomography and demonstrate an ability to preserve ion-qubit coherence with high fidelity.

  14. Superpersistent currents and whispering gallery modes in relativistic quantum chaotic systems

    PubMed Central

    Xu, Hongya; Huang, Liang; Lai, Ying-Cheng; Grebogi, Celso

    2015-01-01

    Persistent currents (PCs), one of the most intriguing manifestations of the Aharonov-Bohm (AB) effect, are known to vanish for Schrödinger particles in the presence of random scatterings, e.g., due to classical chaos. But would this still be the case for Dirac fermions? Addressing this question is of significant value due to the tremendous recent interest in two-dimensional Dirac materials. We investigate relativistic quantum AB rings threaded by a magnetic flux and find that PCs are extremely robust. Even for highly asymmetric rings that host fully developed classical chaos, the amplitudes of PCs are of the same order of magnitude as those for integrable rings, henceforth the term superpersistent currents (SPCs). A striking finding is that the SPCs can be attributed to a robust type of relativistic quantum states, i.e., Dirac whispering gallery modes (WGMs) that carry large angular momenta and travel along the boundaries. We propose an experimental scheme using topological insulators to observe and characterize Dirac WGMs and SPCs, and speculate that these features can potentially be the base for a new class of relativistic qubit systems. Our discovery of WGMs in relativistic quantum systems is remarkable because, although WGMs are common in photonic systems, they are relatively rare in electronic systems. PMID:25758591

  15. Quantum scattering theory of a single-photon Fock state in three-dimensional spaces.

    PubMed

    Liu, Jingfeng; Zhou, Ming; Yu, Zongfu

    2016-09-15

    A quantum scattering theory is developed for Fock states scattered by two-level systems in three-dimensional free space. It is built upon the one-dimensional scattering theory developed in waveguide quantum electrodynamics. The theory fully quantizes the incident light as Fock states and uses a non-perturbative method to calculate the scattering matrix.

  16. Density fluctuations due to Raman forward scattering in quantum plasma

    SciTech Connect

    Kumar, Punit Singh, Shiv; Rathore, Nisha Singh

    2016-05-06

    Density fluctuations due Raman forward scattering (RFS) is analysed in the interaction of a high intensity laser pulse with high density quantum plasma. The interaction model is developed using the quantum hydrodynamic (QHD) model which consist of a set of equations describing the transport of charge, density, momentum and energy of a charged particle system interacting through a self-consistent electrostatic potential. The nonlinear source current has been obtained incorporating the effects of quantum Bohm potential, Fermi pressure and electron spin. The laser spectrum is strongly modulated by the interaction, showing sidebands at the plasma frequency. Furthermore, as the quiver velocity of the electrons in the high electric field of the laser beam is quit large, various quantum effects are observed which can be attributed to the variation of electron mass with laser intensity.

  17. Orbital free DFT versus single density equation: a perspective through quantum domain behavior of a classically chaotic system.

    PubMed

    Chakraborty, Debdutta; Kar, Susmita; Chattaraj, Pratim Kumar

    2015-12-21

    The orbital free density functional theory and the single density equation approach are formally equivalent. An orbital free density based quantum dynamical strategy is used to study the quantum-classical correspondence in both weakly and strongly coupled van der Pol and Duffing oscillators in the presence of an external electric field in one dimension. The resulting quantum hydrodynamic equations of motion are solved through an implicit Euler type real space method involving a moving weighted least square technique. The Lagrangian framework used here allows the numerical grid points to follow the wave packet trajectory. The associated classical equations of motion are solved using a sixth order Runge-Kutta method and the Ehrenfest dynamics is followed through the solution of the time dependent Schrodinger equation using a time dependent Fourier Grid Hamiltonian technique. Various diagnostics reveal a close parallelism between classical regular as well as chaotic dynamics and that obtained from the Bohmian mechanics.

  18. Coherent scattering in two dimensions: Graphene and quantum corrals

    NASA Astrophysics Data System (ADS)

    Barr, Matthew Christopher

    Two dimensional electronic materials provide a vibrant area for applying basic quantum mechanics and scattering theory. In quantum corrals, multiple scattering leads to resonances closely approximating eigenstates of an equivalently shaped billiard. We extend the analogy using methods from acoustics to demonstrate that the billiard conception of quantum corrals is a useful one even in wavelength regimes close to corral size. Resonance widths can be described by a simple relationship proportional to the perimeter to area ratio of the enclosure and the average reflection of a classical path. In graphene, we study the unique behavior strain induces on the effective Dirac Hamiltonian by creating an effective pseudomagnetic field. These fields induce an energy splitting of degenerate eigenstates of certain graphene quantum dots which is distinct from that of an applied scalar potential and can in principle be observed in the conductance through the dot. Additionally, for strain bubbles smaller than the effective Dirac wavelength, the scattering is shown to be distinct from other impurity types. This leads to characteristic features in the conductance, as a function of the bubble position, through regions containing a strong strain bubble.

  19. Transition representations of quantum evolution with application to scattering resonances

    SciTech Connect

    Strauss, Y.

    2011-03-15

    A Lyapunov operator is a self-adjoint quantum observable whose expectation value varies monotonically as time increases and may serve as a marker for the flow of time in a quantum system. In this paper it is shown that the existence of a certain type of Lyapunov operator leads to representations of the quantum dynamics, termed transition representations, in which an evolving quantum state {psi}(t) is decomposed into a sum {psi}(t) ={psi}{sup b}(t) +{psi}{sup f}(t) of a backward asymptotic component and a forward asymptotic component such that the evolution process is represented as a transition from {psi}{sup b}(t) to {psi}{sup f}(t). When applied to the evolution of scattering resonances, such transition representations separate the process of decay of a scattering resonance from the evolution of outgoing waves corresponding to the probability 'released' by the resonance and carried away to spatial infinity. This separation property clearly exhibits the spatial probability distribution profile of a resonance. Moreover, it leads to the definition of exact resonance states as elements of the physical Hilbert space corresponding to the scattering problem. These resonance states evolve naturally according to a semigroup law of evolution.

  20. Statistics of time delay and scattering correlation functions in chaotic systems. II. Semiclassical approximation

    SciTech Connect

    Novaes, Marcel

    2015-06-15

    We consider S-matrix correlation functions for a chaotic cavity having M open channels, in the absence of time-reversal invariance. Relying on a semiclassical approximation, we compute the average over E of the quantities Tr[S{sup †}(E − ϵ) S(E + ϵ)]{sup n}, for general positive integer n. Our result is an infinite series in ϵ, whose coefficients are rational functions of M. From this, we extract moments of the time delay matrix Q = − iħS{sup †}dS/dE and check that the first 8 of them agree with the random matrix theory prediction from our previous paper [M. Novaes, J. Math. Phys. 56, 062110 (2015)].

  1. Parameter-dependent spectral statistics of chaotic quantum graphs: Neumann versus circular orthogonal ensemble boundary conditions.

    PubMed

    Hul, Oleh; Sirko, Leszek

    2011-06-01

    The parameter-dependent spectral statistics of totally connected quantum graphs with n = 4-30 vertices, such as the parametric velocities correlation functions and the distribution of curvatures, are studied. The inverse participation ratio (IPR), an important measure of localization effects, was also numerically investigated. In the calculations, we successfully used two different theoretical approaches. The first approach was based on the graphs' eigenenergies and wave functions calculations, while the second one used the eigenphases and the eigenvectors of the bond scattering matrix S(k). We considered graphs with Neumann and circular orthogonal ensemble (COE) boundary conditions. We show that in contrast to large Neumann graphs, for which the departure of many parameter-dependent spectral statistics from the random matrix theory (RMT) predictions is observed, for large COE graphs, the spectral statistics and IPR are in good agreement with the RMT predictions.

  2. Controlling a class of chaotic quantum system under disturbances and noisy measurements: Application to 1D Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Aguilar-López, Ricardo; López-Pérez, Pablo A.; Lara-Cisneros, Gerardo; Femat, Ricardo

    2016-09-01

    In this paper, a robust nonlinear feedback control scheme with adaptive gain is proposed to control the chaotic behavior in a Bose-Einstein condensate (BEC). The control goal concerns the track or regulation purposes. The BEC system is represented as stochastic ordinary differential equations with measured output perturbed by Gaussian noise, which represents the nature of the quantum systems. The convergence of the BEC control law is analyzed under the frame of the Lyapunov stability theory. Numerical experiments show an adequate performance of the proposed methodology under the required conditions. The results are applicable when the shape of the condensate is sufficiently simple.

  3. Resonances of quantum mechanical scattering systems and Lax-Phillips scattering theory

    NASA Astrophysics Data System (ADS)

    Baumgärtel, Hellmut

    2010-11-01

    For selected classes of quantum mechanical scattering systems a canonical association of a decay semigroup is presented. The spectrum of the generator of this semigroup is a pure eigenvalue spectrum and it coincides with the set of all resonances. The essential condition for the results is the meromorphic continuability of the scattering matrix onto {C}setminus (-infty,0] and the rims {R}-± i0. Further finite multiplicity is assumed. The approach is based on an adaption of the Lax-Phillips scattering theory to semibounded Hamiltonians. It is applied to trace class perturbations with analyticity conditions. A further example is the potential scattering for central-symmetric potentials with compact support and angular momentum 0.

  4. Landau retardation on the occurrence scattering time in quantum electron-hole plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Woo-Pyo; Jung, Young-Dae

    2016-03-01

    The Landau damping effects on the occurrence scattering time in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Shukla-Stenflo-Bingham effective potential model is employed to obtain the occurrence scattering time in a quantum electron-hole plasma. The result shows that the influence of Landau damping produces the imaginary term in the scattering amplitude. It is then found that the Landau damping generates the retardation effect on the occurrence scattering time. It is found that the occurrence scattering time increases in forward scattering domains and decreases in backward scattering domains with an increase of the Landau parameter. It is also found that the occurrence scattering time decreases with increasing collision energy. In addition, it is found that the quantum shielding effect enhances the occurrence scattering time in the forward scattering and, however, suppresses the occurrence scattering time in the backward scattering.

  5. Quantum random bit generation using stimulated Raman scattering.

    PubMed

    Bustard, Philip J; Moffatt, Doug; Lausten, Rune; Wu, Guorong; Walmsley, Ian A; Sussman, Benjamin J

    2011-12-05

    Random number sequences are a critical resource in a wide variety of information systems, including applications in cryptography, simulation, and data sampling. We introduce a quantum random number generator based on the phase measurement of Stokes light generated by amplification of zero-point vacuum fluctuations using stimulated Raman scattering. This is an example of quantum noise amplification using the most noise-free process possible: near unitary quantum evolution. The use of phase offers robustness to classical pump noise and the ability to generate multiple bits per measurement. The Stokes light is generated with high intensity and as a result, fast detectors with high signal-to-noise ratios can be used for measurement, eliminating the need for single-photon sensitive devices. The demonstrated implementation uses optical phonons in bulk diamond.

  6. Quantum scattering on SN2 reactions: Influence of azimuthal rotations

    NASA Astrophysics Data System (ADS)

    Schmatz, Stefan; Clary, David C.

    1998-11-01

    Time independent quantum scattering calculations have been carried out on the SN2 Walden inversion reaction Cl-+CH3Cl(v,k)→ClCH3(v',k')+Cl-. The two C-Cl stretching degrees of freedom (quantum numbers v and v') and the azimuthal angle describing the rotation of the CH3 group (quantum numbers k and k') are treated explicitly. An infinite order sudden approximation has been introduced using Radau coordinates for the stretching modes. The potential energy surface of Vande Linde and Hase is used. The scattering problem is formulated in hyperspherical coordinates. For the reaction (k=0→k'=0) substitution is observed for initial vibrational excitation with v⩾2. If the system departs from the collinear reaction pathway (initial rotational excitation) the substitution cross sections are strongly decreased. The state-to-state cross sections σvk→v'k' are large only for transitions with Δk=0. The total reaction cross sections σvk for given v vary only slightly at low values of the azimuthal quantum number k and rise for larger values of k. This is explained by multiple (avoided) crossings of the hyperspherical adiabats.

  7. Quantum Monte Carlo Calculations of Nucleon-Nucleus Scattering

    NASA Astrophysics Data System (ADS)

    Wiringa, R. B.; Nollett, Kenneth M.; Pieper, Steven C.; Brida, I.

    2009-10-01

    We report recent quantum Monte Carlo (variational and Green's function) calculations of elastic nucleon-nucleus scattering. We are adding the cases of proton-^4He, neutron-^3H and proton-^3He scattering to a previous GFMC study of neutron-^4He scattering [1]. To do this requires generalizing our methods to include long-range Coulomb forces and to treat coupled channels. The two four-body cases can be compared to other accurate four-body calculational methods such as the AGS equations and hyperspherical harmonic expansions. We will present results for the Argonne v18 interaction alone and with Urbana and Illinois three-nucleon potentials. [4pt] [1] K.M. Nollett, S. C. Pieper, R.B. Wiringa, J. Carlson, and G.M. Hale, Phys. Rev. Lett. 99, 022502 (2007)

  8. Memory of the Initial Conditions in an Incompletely Chaotic Quantum System: Universal Predictions with Application to Cold Atoms

    NASA Astrophysics Data System (ADS)

    Yurovsky, V. A.; Olshanii, M.

    2011-01-01

    Two zero-range-interacting atoms in a circular, transversely harmonic waveguide are used as a test bench for a quantitative description of the crossover between integrability and chaos in a quantum system with no selection rules. For such systems we show that the expectation value after relaxation of a generic observable is given by a linear interpolation between its initial and thermal expectation values. The variable of this interpolation is universal; it governs this simple law to cover the whole spectrum of the chaotic behavior from integrable regime through the well-developed quantum chaos. The predictions are confirmed for the waveguide system, where the mode occupations and the trapping energy were used as the observables of interest; a variety of the initial states and a full range of the interaction strengths have been tested.

  9. Entanglement and the generation of random states in the quantum chaotic dynamics of kicked coupled tops.

    PubMed

    Trail, Collin M; Madhok, Vaibhav; Deutsch, Ivan H

    2008-10-01

    We study the dynamical generation of entanglement as a signature of chaos in a system of periodically kicked coupled tops, where chaos and entanglement arise from the same physical mechanism. The long-time-averaged entanglement as a function of the position of an initially localized wave packet very closely correlates with the classical phase space surface of section--it is nearly uniform in the chaotic sea, and reproduces the detailed structure of the regular islands. The uniform value in the chaotic sea is explained by the random state conjecture. As classically chaotic dynamics take localized distributions in phase space to random distributions, quantized versions take localized coherent states to pseudorandom states in Hilbert space. Such random states are highly entangled, with an average value near that of the maximally entangled state. For a map with global chaos, we derive that value based on analytic results for the entropy of random states. For a mixed phase space, we use the Percival conjecture to identify a "chaotic subspace" of the Hilbert space. The typical entanglement, averaged over the unitarily invariant Haar measure in this subspace, agrees with the long-time-averaged entanglement for initial states in the chaotic sea. In all cases the dynamically generated entanglement is that of a random complex vector, even though the system is time-reversal invariant, and the Floquet operator is a member of the circular orthogonal ensemble.

  10. Random matrix theory of quantum transport in chaotic cavities with nonideal leads

    NASA Astrophysics Data System (ADS)

    Jarosz, Andrzej; Vidal, Pedro; Kanzieper, Eugene

    2015-05-01

    We determine the joint probability density function (JPDF) of reflection eigenvalues in three Dyson's ensembles of normal-conducting chaotic cavities coupled to the outside world through both ballistic and tunnel point contacts. Expressing the JPDF in terms of hypergeometric functions of matrix arguments (labeled by the Dyson index β ), we further show that reflection eigenvalues form a determinantal ensemble at β =2 and a new type of a Pfaffian ensemble at β =4 . As an application, we derive a simple analytic expression for the concurrence distribution describing production of orbitally entangled electrons in chaotic cavities with tunnel point contacts when time-reversal symmetry is preserved.

  11. The study of effects of small perturbations on chaotic systems

    SciTech Connect

    Grebogi, C. . Lab. for Plasma Research); Yorke, J.A. . Inst. for Physical Science and Technology)

    1990-12-01

    This report discusses the following topics on small perturbations on chaotic systems: controlling chaos; shadowing and noise reduction; chaotic scattering; random maps; magnetic dynamo; and aids transmission. (LSP)

  12. Quantum inverse scattering and the lambda deformed principal chiral model

    NASA Astrophysics Data System (ADS)

    Appadu, Calan; Hollowood, Timothy J.; Price, Dafydd

    2017-07-01

    The lambda model is a one parameter deformation of the principal chiral model that arises when regularizing the non-compactness of a non-abelian T dual in string theory. It is a current-current deformation of a WZW model that is known to be integrable at the classical and quantum level. The standard techniques of the quantum inverse scattering method cannot be applied because the Poisson bracket is non ultra-local. Inspired by an approach of Faddeev and Reshetikhin, we show that in this class of models, there is a way to deform the symplectic structure of the theory leading to a much simpler theory that is ultra-local and can be quantized on the lattice whilst preserving integrability. This lattice theory takes the form of a generalized spin chain that can be solved by standard algebraic Bethe Ansatz techniques. We then argue that the IR limit of the lattice theory lies in the universality class of the lambda model implying that the spin chain provides a way to apply the quantum inverse scattering method to this non ultra-local theory. This points to a way of applying the same ideas to other lambda models and potentially the string world-sheet theory in the gauge-gravity correspondence.

  13. Positron scattering from hydrogen atom embedded in dense quantum plasma

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Arka; Kamali, M. Z. M.; Ghoshal, Arijit; Ratnavelu, K.

    2013-08-01

    Scattering of positrons from the ground state of hydrogen atoms embedded in dense quantum plasma has been investigated by applying a formulation of the three-body collision problem in the form of coupled multi-channel two-body Lippmann-Schwinger equations. The interactions among the charged particles in dense quantum plasma have been represented by exponential cosine-screened Coulomb potentials. Variationally determined hydrogenic wave function has been employed to calculate the partial-wave scattering amplitude. Plasma screening effects on various possible mode of fragmentation of the system e++H(1s) during the collision, such as 1s →1s and 2s→2s elastic collisions, 1s→2s excitation, positronium formation, elastic proton-positronium collisions, have been reported in the energy range 13.6-350 eV. Furthermore, a comparison has been made on the plasma screening effect of a dense quantum plasma with that of a weakly coupled plasma for which the plasma screening effect has been represented by the Debye model. Our results for the unscreened case are in fair agreement with some of the most accurate results available in the literature.

  14. Positron scattering from hydrogen atom embedded in dense quantum plasma

    SciTech Connect

    Bhattacharya, Arka; Kamali, M. Z. M.; Ghoshal, Arijit; Ratnavelu, K.

    2013-08-15

    Scattering of positrons from the ground state of hydrogen atoms embedded in dense quantum plasma has been investigated by applying a formulation of the three-body collision problem in the form of coupled multi-channel two-body Lippmann-Schwinger equations. The interactions among the charged particles in dense quantum plasma have been represented by exponential cosine-screened Coulomb potentials. Variationally determined hydrogenic wave function has been employed to calculate the partial-wave scattering amplitude. Plasma screening effects on various possible mode of fragmentation of the system e{sup +}+H(1s) during the collision, such as 1s→1s and 2s→2s elastic collisions, 1s→2s excitation, positronium formation, elastic proton-positronium collisions, have been reported in the energy range 13.6-350 eV. Furthermore, a comparison has been made on the plasma screening effect of a dense quantum plasma with that of a weakly coupled plasma for which the plasma screening effect has been represented by the Debye model. Our results for the unscreened case are in fair agreement with some of the most accurate results available in the literature.

  15. Communication: Heavy atom quantum diffraction by scattering from surfaces.

    PubMed

    Moix, Jeremy M; Pollak, Eli

    2011-01-07

    Typically one expects that when a heavy particle collides with a surface, the scattered angular distribution will follow classical mechanics. The heavy mass usually assures that the coherence length of the incident particle in the direction of the propagation of the particle (the parallel direction) will be much shorter than the characteristic lattice length of the surface, thus leading to a classical description. Recent work on molecular interferometry has shown that extreme collimation of the beam creates a perpendicular coherence length which is sufficiently long so as to observe interference of very heavy species passing through a grating. Here we show, using quantum mechanical simulations, that the same effect will lead to quantum diffraction of heavy particles colliding with a surface. The effect is robust with respect to the incident energy, the angle of incidence, and the mass of the particle.

  16. Fingerprints of quantum spin ice in Raman scattering

    NASA Astrophysics Data System (ADS)

    Fu, Jianlong; Rau, Jeffrey G.; Gingras, Michel J. P.; Perkins, Natalia B.

    2017-07-01

    We develop a theory of the dynamical response of a minimal model of quantum spin ice (QSI) by means of inelastic light scattering. In particular, we are interested in the Raman response of the fractionalized U(1) spin liquid realized in the XXZ QSI. We show that the low-energy Raman intensity is dominated by spinon and gauge fluctuations. We find that the Raman response in the QSI state of that model appears only in the T2 g polarization channel. We show that the Raman intensity profile displays a broad continuum from the spinons and coupled spinon and gauge fluctuations, and a low-energy peak arising entirely from gauge fluctuations. Both features originate from the exotic interaction between photon and the fractionalized excitations of QSI. Our theoretical results suggest that inelastic Raman scattering can in principle serve as a promising experimental probe of the nature of a U(1) spin liquid in QSI.

  17. Single quantum dot controls a plasmonic cavity's scattering and anisotropy.

    PubMed

    Hartsfield, Thomas; Chang, Wei-Shun; Yang, Seung-Cheol; Ma, Tzuhsuan; Shi, Jinwei; Sun, Liuyang; Shvets, Gennady; Link, Stephan; Li, Xiaoqin

    2015-10-06

    Plasmonic cavities represent a promising platform for controlling light-matter interaction due to their exceptionally small mode volume and high density of photonic states. Using plasmonic cavities for enhancing light's coupling to individual two-level systems, such as single semiconductor quantum dots (QD), is particularly desirable for exploring cavity quantum electrodynamic (QED) effects and using them in quantum information applications. The lack of experimental progress in this area is in part due to the difficulty of precisely placing a QD within nanometers of the plasmonic cavity. Here, we study the simplest plasmonic cavity in the form of a spherical metallic nanoparticle (MNP). By controllably positioning a semiconductor QD in the close proximity of the MNP cavity via atomic force microscope (AFM) manipulation, the scattering spectrum of the MNP is dramatically modified due to Fano interference between the classical plasmonic resonance of the MNP and the quantized exciton resonance in the QD. Moreover, our experiment demonstrates that a single two-level system can render a spherical MNP strongly anisotropic. These findings represent an important step toward realizing quantum plasmonic devices.

  18. Quantum numbers of the colorless objects in diffractive scattering

    NASA Astrophysics Data System (ADS)

    Ta-chung, Meng

    1997-04-01

    It is pointed out that a considerable part of the colorless objects in lepton- and hadron-induced diffractive scattering processes can be considered as virtual quark-antiquark pairs in states characterized by the quantum-numbers JPC=0-+, IG=0+, where J stands for total angular momentum, I for isospin, P, C and G stand for parity, C-parity and G-parity respectively, and that such quark-antiquark pairs are created by interacting soft-gluons. Theoretical arguments and experimental evidences in support of the proposed picture are presented.

  19. A quantum reactive scattering perspective on electronic nonadiabaticity

    NASA Astrophysics Data System (ADS)

    Peng, Yang; Ghiringhelli, Luca M.; Appel, Heiko

    2014-07-01

    Based on quantum reactive-scattering theory, we propose a method for studying the electronic nonadiabaticity in collision processes involving electron-ion rearrangements. We investigate the state-to-state transition probability for electron-ion rearrangements with two comparable approaches. In the first approach the information of the electron is only contained in the ground-state Born-Oppenheimer potential-energy surface, which is the starting point of common reactive-scattering calculations. In the second approach, the electron is explicitly taken into account and included in the calculations at the same level as the ions. Hence, the deviation in the results between the two approaches directly reflects the electronic nonadiabaticity during the collision process. To illustrate the method, we apply it to the well-known proton-transfer model of Shin and Metiu, generalized in order to allow for reactive scattering channels. We show that our explicit electron approach is able to capture electronic nonadiabaticity and the renormalization of the reaction barrier near the classical turning points of the potential in nuclear configuration space. In contrast, system properties near the equilibrium geometry of the asymptotic scattering channels are hardly affected by electronic nonadiabatic effects. We also present an analytical expression for the transition amplitude of the asymmetric proton-transfer model based on the direct evaluation of integrals over the involved Airy functions.

  20. Chaotic dynamics and conductance measurements in microstructures

    SciTech Connect

    Marcus, C.M.

    1993-05-01

    At low temperatures (T<{approximately}1K), electronic conductance through metallic or semiconductor microstructures commonly exhibits quasirandom fluctuations-for instance as a function of an applied magnetic field-resulting from quantum interference. The random character of these fluctuations does not require disorder in the materials, as such fluctuations are also observed in the ballistic regime, i.e. in devices smaller than the electron mean free path, so that essentially all large-angle scattering occurs as specular reflection from the walls of the device rather than from impurities. In principle, such fluctuations would persist even in the absence of disorder, arising purely from quantum interference of electrons scattering chaotically from the geometrical features of the device. This talk will describe recent experiments measuring conductance fluctuations at millikelvin temperatures in submicron {open_quotes}quantum dots{close_quotes} in the shape of an open circle and stadium billiard. The structures were fabricated from GaAs/AlGaAs heterostructures using precise electron beam lithography. Spectral properties of the observed fluctuations will be discussed in the context of recent semiclassical theories based on quantum chaotic scattering. Both the circle and stadium structures exhibit strong fluctuations, raising the question: what role does chaos play in these experiments?

  1. Quantum scattering engineering of quantum well infrared photodetectors in the tunneling regime

    NASA Astrophysics Data System (ADS)

    Lhuillier, Emmanuel; Rosencher, Emmanuel; Ribet-Mohamed, Isabelle; Nedelcu, Alexandru; Doyennette, Laetitia; Berger, Vincent

    2010-12-01

    Dark current is shown to be significantly reduced in quantum well infrared photodetectors in the tunneling regime, i.e., at very low temperature, by shifting the dopant impurity layers away from the central part of the wells. This result confirms that the interwell tunneling current is dominated by charged impurity scattering in usual structures. The experimental results are in good quantitative agreement with the proposed theory. This dark current reduction is pushing further the ultimate performances of quantum well infrared photodetectors for the detection of low infrared photon fluxes. Routes to further improvements are briefly sketched.

  2. Neutron scattering measurements of low-dimensional quantum systems

    NASA Astrophysics Data System (ADS)

    Haravifard, Sara

    Low dimensional quantum magnets which display a collective singlet ground state and a gap in their magnetic excitation spectrum provide a framework for much exotic phase behavior in new materials, with high temperature superconductivity being the best appreciated example. Neutron scattering techniques can be applied to study a wide variety of problems in condensed matter physics. These techniques are particularly useful as applied to understanding the magnetic properties of quantum magnets that display exotic phases. SrCu2(BO3)2, is a rare example of a two-dimensional quantum magnet for which an exact theoretical solution describing its ground state is known to be a collective singlet. Previous high resolution neutron scattering measurements identified the most prominent features of the spin excitation spectrum in SrCu2(BO3)2, including the presence of one and two triplet excitations and weak dispersion characteristic of subleading terms in the spin Hamiltonian. The resemblance between the spin gap behavior in the Mott insulator SrCu 2(BO3)2 and that associated with high temperature superconductors motivated the consideration of the significance of doping in order to understand the properties of this quantum magnetic system. For this reason, a series of neutron scattering studies on doped SrCu2(BO 3)2 were initiated. These series of investigations began with the performance of neutron scattering measurements on a SrCu(2-x)Mgx(BO 3)2 single crystal in order to introduce magnetic vacancies to the system. These results revealed the presence of new spin excitations within the singlet-triplet gap of this system. Application of a magnetic field induces Zeeman-split states associated with un-paired spins which exist as a consequence of doping with quenched non-magnetic impurities. Additional substantial broadening of both the one and two triplet excitations is observed in the doped system as compared to the pure system. Theoretical calculations are shown to qualitatively

  3. Computational method for the quantum Hamilton-Jacobi equation: one-dimensional scattering problems.

    PubMed

    Chou, Chia-Chun; Wyatt, Robert E

    2006-12-01

    One-dimensional scattering problems are investigated in the framework of the quantum Hamilton-Jacobi formalism. First, the pole structure of the quantum momentum function for scattering wave functions is analyzed. The significant differences of the pole structure of this function between scattering wave functions and bound state wave functions are pointed out. An accurate computational method for the quantum Hamilton-Jacobi equation for general one-dimensional scattering problems is presented to obtain the scattering wave function and the reflection and transmission coefficients. The computational approach is demonstrated by analysis of scattering from a one-dimensional potential barrier. We not only present an alternative approach to the numerical solution of the wave function and the reflection and transmission coefficients but also provide a computational aspect within the quantum Hamilton-Jacobi formalism. The method proposed here should be useful for general one-dimensional scattering problems.

  4. Coverage-dependent quantum versus classical scattering of thermal neon atoms from Li/Cu(100).

    PubMed

    Maclaren, D A; Huang, C; Levi, A C; Allison, W

    2008-09-07

    We show that subtle variations in surface structure can enhance quantum scattering and quench atom-surface energy transfer. The scattering of thermal energy neon atoms from a lithium overlayer on a copper substrate switches between a classical regime, dominated by multiphonon interactions, and a quantum regime, dominated by elastic diffraction. The transition is achieved by simple tailoring of the lithium coverage and quantum scattering dominates only in the narrow coverage range of theta=0.3-0.6 ML. The results are described qualitatively using a modified Debye-Waller model that incorporates an approximate quantum treatment of the adsorbate-substrate vibration.

  5. Detecting quantum coherence of Bose gases in optical lattices by scattering light intensity in cavity.

    PubMed

    Zhou, Xiaoji; Xu, Xu; Yin, Lan; Liu, W M; Chen, Xuzong

    2010-07-19

    We propose a new method of detecting quantum coherence of a Bose gas trapped in a one-dimensional optical lattice by measuring the light intensity from Raman scattering in cavity. After pump and displacement process, the intensity or amplitude of scattering light is different for different quantum states of a Bose gas, such as superfluid and Mott-Insulator states. This method can also be useful to detect quantum states of atoms with two components in an optical lattice.

  6. Resonant Raman scattering in self-assembled quantum dots

    SciTech Connect

    Menendez-Proupin, E.; Trallero-Giner, C.; Ulloa, S. E.

    1999-12-15

    A theoretical treatment for first-order resonant Raman scattering in self-assembled quantum dots (SAQD's) of different materials is presented. The dots are modeled as cylindrical disks with elliptical cross section, to simulate shape and confinement anisotropies obtained from the SAQD growth conditions. Coulomb interaction between electron and hole is considered in an envelope function Hamiltonian approach and the eigenvalues and eigenfunctions are obtained by a matrix diagonalization technique. By including excitonic intermediate states in the Raman process, the scattering efficiency and cross section are calculated for long-range Froehlich exciton-phonon interaction. The Froehlich interaction in the SAQD is considered in an approach in which both the mechanical and electrostatic matching boundary conditions are fulfilled at the SAQD interfaces. Exciton and confined phonon selection rules are derived for Raman processes. Characteristic results for SAQD's are presented, including InAs dots in GaAs, as well as CdSe dots in ZnSe substrates. We analyze how Raman spectroscopy would give information on carrier masses, confinement anisotropy effects, and SAQD geometry. (c) 1999 The American Physical Society.

  7. Time Delay for Dispersive Systems in Quantum Scattering Theory

    NASA Astrophysics Data System (ADS)

    Tiedra de Aldecoa, Rafael

    We consider time delay and symmetrized time delay (defined in terms of sojourn times) for quantum scattering pairs {H0 = h(P), H}, where h(P) is a dispersive operator of hypoelliptic-type. For instance, h(P) can be one of the usual elliptic operators such as the Schrödinger operator h(P) = P2 or the square-root Klein-Gordon operator h(P) = √ {1 + P2}. We show under general conditions that the symmetrized time delay exists for all smooth even localization functions. It is equal to the Eisenbud-Wigner time delay plus a contribution due to the non-radial component of the localization function. If the scattering operator S commutes with some function of the velocity operator ∇h(P), then the time delay also exists and is equal to the symmetrized time delay. As an illustration of our results, we consider the case of a one-dimensional Friedrichs Hamiltonian perturbed by a finite rank potential. Our study puts into evidence an integral formula relating the operator of differentiation with respect to the kinetic energy h(P) to the time evolution of localization operators.

  8. Quantum tunneling and scattering of a composite object

    NASA Astrophysics Data System (ADS)

    Ahsan, Naureen

    Reaction physics involving composite objects with internal degrees of freedom is an important subject since it is encountered in the context of nuclear processes like fusion, fission, particle decay, as well as many other branches of science. Quantum tunneling and scattering of a composite object are explored in this work. A few model Hamiltonians are chosen as examples where a two-particle system interacts, in one dimension, with a target that poses a delta-potential or an infinite wall potential. It is assumed that only one of the two components interacts with the target. The study includes the harmonic oscillator and the infinite square well as examples of intrinsic Hamiltonians that do not allow the projectile to break up, and a finite square well and a delta-well as examples of Hamiltonians that do. The Projection Method and the Variable Phase Method are applied with the aim of an exact solution to the relevant scattering problems. These methods are discussed in the context of the pertinent convergence issues related thereto, and of their applicability. Virtual excitations of the projectile into the classically forbidden energy-domain are found to play a dominant and non-perturbative role in shaping reaction observables, giving rise to enhanced or reduced tunneling in various situations. Cusps and discontinuities are found to appear in observables as manifestations of unitarity and redistribution of flux at the thresholds. The intrinsic structure gives rise to resonancelike behavior in tunneling probabilities. It is also shown that there is charge asymmetry in the scattering of a composite object, unlike in the case of a structureless particle.

  9. Truncated Linear Statistics Associated with the Eigenvalues of Random Matrices II. Partial Sums over Proper Time Delays for Chaotic Quantum Dots

    NASA Astrophysics Data System (ADS)

    Grabsch, Aurélien; Majumdar, Satya N.; Texier, Christophe

    2017-06-01

    Invariant ensembles of random matrices are characterized by the distribution of their eigenvalues \\{λ _1,\\ldots ,λ _N\\}. We study the distribution of truncated linear statistics of the form \\tilde{L}=\\sum _{i=1}^p f(λ _i) with pchaotic quantum dots, which are characteristic times of the scattering process. Using the Coulomb gas technique, we derive the large deviation function for \\tilde{L}. Large deviations of linear statistics L=\\sum _{i=1}^N f(λ _i) are usually dominated by the energy of the Coulomb gas, which scales as ˜ N^2, implying that the relative fluctuations are of order 1 / N. For the truncated linear statistics considered here, there is a whole region (including the typical fluctuations region), where the energy of the Coulomb gas is frozen and the large deviation function is purely controlled by an entropic effect. Because the entropy scales as ˜ N, the relative fluctuations are of order 1/√{N}. Our analysis relies on the mapping on a problem of p fictitious non-interacting fermions in N energy levels, which can exhibit both positive and negative effective (absolute) temperatures. We determine the large deviation function characterizing the distribution of the truncated linear statistics, and show that, for the case considered here (f(λ )=1/λ ), the corresponding phase diagram is separated in three different phases.

  10. Coherent backscattering and forward-scattering peaks in the quantum kicked rotor

    NASA Astrophysics Data System (ADS)

    Lemarié, G.; Müller, Cord A.; Guéry-Odelin, D.; Miniatura, C.

    2017-04-01

    We propose and analyze an experimental scheme using the quantum kicked rotor to observe the newly predicted coherent forward-scattering peak together with its long-known twin brother, the coherent backscattering peak. Contrary to coherent backscattering, which arises already under weak-localization conditions, coherent forward scattering is only triggered by Anderson or strong localization. So far, coherent forward scattering has not been observed in conservative systems with elastic scattering by spatial disorder. We propose to turn to the quantum kicked rotor, which has a long and successful history as an accurate experimental platform to observe dynamical localization, i.e., Anderson localization in momentum space. We analyze the coherent forward-scattering effect for the quantum kicked rotor by extensive numerical simulations, both in the orthogonal and unitary class of disordered quantum systems, and show that an experimental realization involving phase-space rotation techniques is within reach of state-of-the-art cold-atom experiments.

  11. Subband Quantum Scattering Times for Algaas/GaAs Obtained Using Digital Filtering

    NASA Technical Reports Server (NTRS)

    Mena, R. A.; Schacham, S. E.; Haughland, E. J.; Alterovitz, S. A.; Bibyk, S. B.; Ringel, S. A.

    1995-01-01

    In this study we investigate both the transport and quantum scattering times as a function of the carrier concentration for a modulation doped Al(0.3)Ga(0.7)As/GaAs structure. Carriers in the well are generated as a result of the persistent photoconductivity effect. When more than one subband becomes populated, digital filtering is used to separate the components for each of the excited subbands. We find that the quantum scattering time for the ground subband increases initially as the carrier concentration is increased. However, once the second subband becomes populated, the ground subband scattering time begins to decrease. The quantum scattering time for the excited subband is also observed to decrease as the concentration is increased. From the ratio of the transport and quantum scattering times, it is seen that the transport in the well becomes more isotropic also as the concentration is increased.

  12. Towards a Social Theory of School Administrative Practice in a Complex, Chaotic, Quantum World.

    ERIC Educational Resources Information Center

    Beavis, Allan K.

    Educational administration, like many other social sciences, has traditionally followed the rubrics of classical science with its emphasis on prediction and control and attempts to understand the whole by understanding in ever finer detail how the parts fit together. However, the "new" science (especially quantum mechanics, complexity,…

  13. Quantum and classical study of surface characterization by three-dimensional helium atom scattering.

    PubMed

    Moix, Jeremy M; Pollak, Eli; Allison, William

    2011-01-14

    Exact time-dependent wavepacket calculations of helium atom scattering from model symmetric, chiral, and hexagonal surfaces are presented and compared with their classical counterparts. Analysis of the momentum distribution of the scattered wavepacket provides a convenient method to obtain the resulting energy and angle resolved scattering distributions. The classical distributions are characterized by standard rainbow scattering from corrugated surfaces. It is shown that the classical results are closely related to their quantum counterparts and capture the qualitative features appearing therein. Both the quantum and classical distributions are capable of distinguishing between the structures of the three surfaces.

  14. Analysis of the scatter effect on detective quantum efficiency of digital mammography

    NASA Astrophysics Data System (ADS)

    Park, Jiwoong; Yun, Seungman; Kim, Dong Woon; Baek, Cheol-Ha; Youn, Hanbean; Jeon, Hosang; Kim, Ho Kyung

    2016-03-01

    The scatter effect on detective quantum efficiency (DQE) of digital mammography is investigated using the cascaded-systems model. The cascaded-systems model includes a scatter-reduction device as a binomial selection stage. Quantum-noise-limited operation approximates the system DQE into the multiplication form of the scatter-reduction device DQE and the conventional detector DQE. The developed DQE model is validated in comparisons with the measured results using a CMOS flat-panel detector under scatter environments. For various scatter-reduction devices, the slot-scan method shows the best scatter-cleanup performance in terms of DQE, and the scatter-cleanup performance of the conventional one-dimensional grid is rather worse than the air gap. The developed model can also be applied to general radiography and will be very useful for a better design of imaging chain.

  15. Scattering theory of nonlinear thermoelectricity in quantum coherent conductors.

    PubMed

    Meair, Jonathan; Jacquod, Philippe

    2013-02-27

    We construct a scattering theory of weakly nonlinear thermoelectric transport through sub-micron scale conductors. The theory incorporates the leading nonlinear contributions in temperature and voltage biases to the charge and heat currents. Because of the finite capacitances of sub-micron scale conducting circuits, fundamental conservation laws such as gauge invariance and current conservation require special care to be preserved. We do this by extending the approach of Christen and Büttiker (1996 Europhys. Lett. 35 523) to coupled charge and heat transport. In this way we write relations connecting nonlinear transport coefficients in a manner similar to Mott's relation between the linear thermopower and the linear conductance. We derive sum rules that nonlinear transport coefficients must satisfy to preserve gauge invariance and current conservation. We illustrate our theory by calculating the efficiency of heat engines and the coefficient of performance of thermoelectric refrigerators based on quantum point contacts and resonant tunneling barriers. We identify, in particular, rectification effects that increase device performance.

  16. Scattering theory of nonlinear thermoelectricity in quantum coherent conductors

    NASA Astrophysics Data System (ADS)

    Meair, Jonathan; Jacquod, Philippe

    2013-02-01

    We construct a scattering theory of weakly nonlinear thermoelectric transport through sub-micron scale conductors. The theory incorporates the leading nonlinear contributions in temperature and voltage biases to the charge and heat currents. Because of the finite capacitances of sub-micron scale conducting circuits, fundamental conservation laws such as gauge invariance and current conservation require special care to be preserved. We do this by extending the approach of Christen and Büttiker (1996 Europhys. Lett. 35 523) to coupled charge and heat transport. In this way we write relations connecting nonlinear transport coefficients in a manner similar to Mott’s relation between the linear thermopower and the linear conductance. We derive sum rules that nonlinear transport coefficients must satisfy to preserve gauge invariance and current conservation. We illustrate our theory by calculating the efficiency of heat engines and the coefficient of performance of thermoelectric refrigerators based on quantum point contacts and resonant tunneling barriers. We identify, in particular, rectification effects that increase device performance.

  17. Forward scattering approximation and bosonization in integer quantum Hall systems

    SciTech Connect

    Rosenau da Costa, M. Westfahl, H.; Caldeira, A.O.

    2008-03-15

    In this work, we present a model and a method to study integer quantum Hall (IQH) systems. Making use of the Landau levels structure we divide these two-dimensional systems into a set of interacting one-dimensional gases, one for each guiding center. We show that the so-called strong field approximation, used by Kallin and Halperin and by MacDonald, is equivalent, in first order, to a forward scattering approximation and analyze the IQH systems within this approximation. Using an appropriate variation of the Landau level bosonization method we obtain the dispersion relations for the collective excitations and the single-particle spectral functions. For the bulk states, these results evidence a behavior typical of non-normal strongly correlated systems, including the spin-charge splitting of the single-particle spectral function. We discuss the origin of this behavior in the light of the Tomonaga-Luttinger model and the bosonization of two-dimensional electron gases.

  18. Modern integral equation techniques for quantum reactive scattering theory

    SciTech Connect

    Auerbach, Scott Michael

    1993-11-01

    Rigorous calculations of cross sections and rate constants for elementary gas phase chemical reactions are performed for comparison with experiment, to ensure that our picture of the chemical reaction is complete. We focus on the H/D+H2 → H2/DH + H reaction, and use the time independent integral equation technique in quantum reactive scattering theory. We examine the sensitivity of H+H2 state resolved integral cross sections σ{sub v'j',vj}(E) for the transitions (v = 0,j = 0) to (v'} = 1,j' = 1,3), to the difference between the Liu-Siegbahn-Truhlar-Horowitz (LSTH) and double many body expansion (DMBE) ab initio potential energy surfaces (PES). This sensitivity analysis is performed to determine the origin of a large discrepancy between experimental cross sections with sharply peaked energy dependence and theoretical ones with smooth energy dependence. We find that the LSTH and DMBE PESs give virtually identical cross sections, which lends credence to the theoretical energy dependence.

  19. Impact of quantum effects on relativistic electron motion in a chaotic regime

    NASA Astrophysics Data System (ADS)

    Bashinov, A. V.; Kim, A. V.; Sergeev, A. M.

    2015-10-01

    The impact of quantum effects on electron dynamics in a plane linearly polarized standing wave with relativistic amplitudes is considered. Using spectral analysis of Lyapunov characteristic exponents with and without radiation losses we show that the contraction effect of phase space due to the radiation reaction force in the classical form does not occur in the quantum case when the discreteness of photon emission is taken into account. It is also demonstrated that electron bunch kinetics has a diffusion solution rather than the d'Alambert type solution as in the classical description. For this case, we applied the Markov chain formalism and showed that this method gives exact characteristics of electron bunch evolution, such as motion of the center of mass and electron bunch dimensions.

  20. Impact of quantum effects on relativistic electron motion in a chaotic regime.

    PubMed

    Bashinov, A V; Kim, A V; Sergeev, A M

    2015-10-01

    The impact of quantum effects on electron dynamics in a plane linearly polarized standing wave with relativistic amplitudes is considered. Using spectral analysis of Lyapunov characteristic exponents with and without radiation losses we show that the contraction effect of phase space due to the radiation reaction force in the classical form does not occur in the quantum case when the discreteness of photon emission is taken into account. It is also demonstrated that electron bunch kinetics has a diffusion solution rather than the d'Alambert type solution as in the classical description. For this case, we applied the Markov chain formalism and showed that this method gives exact characteristics of electron bunch evolution, such as motion of the center of mass and electron bunch dimensions.

  1. Chaotic quantum ratchets and filters with cold atoms in optical lattices: Analysis using Floquet states

    SciTech Connect

    Hur, G.; Creffield, C.E.; Jones, P.H.; Monteiro, T.S.

    2005-07-15

    Recently, cesium atoms in optical lattices subjected to cycles of unequally spaced pulses have been found to show interesting behavior: they represent an experimental demonstration of a Hamiltonian ratchet mechanism, and they show strong variability of the dynamical localization lengths as a function of initial momentum. The behavior differs qualitatively from corresponding atomic systems pulsed with equal periods, which are a textbook implementation of a well-studied quantum chaos paradigm, the quantum {delta}-kicked rotor ({delta}-QKR). We investigate here the properties of the corresponding eigenstates (Floquet states) in the parameter regime of the recent experiments and compare them with those of the eigenstates of the {delta}-QKR at similar kicking strengths. We show that by studying the properties of the Floquet states we can shed light on the form of the observed ratchet current, as well as variations in the dynamical localization length.

  2. Fluctuation phenomena in chaotic Dirac quantum dots: Artificial atoms on graphene flakes

    NASA Astrophysics Data System (ADS)

    Ramos, J. G. G. S.; Hussein, M. S.; Barbosa, A. L. R.

    2016-03-01

    We develop the stub model for the Dirac quantum dot, an electron confining device on a grapheme surface. Analytical results for the average conductance and the correlation functions are obtained and found in agreement with those found previously using semiclassical calculation. Comparison with available data is presented. The results reported here demonstrate the applicability of random matrix theory in the case of Dirac electrons confined in a stadium.

  3. Perturbative Quantum Analysis and Classical Limit of the Electron Scattering by a Solenoidal Magnetic Field

    SciTech Connect

    Murguia, Gabriela; Moreno, Matias; Torres, Manuel

    2009-04-20

    A well known example in quantum electrodynamics (QED) shows that Coulomb scattering of unpolarized electrons, calculated to lowest order in perturbation theory, yields a results that exactly coincides (in the non-relativistic limit) with the Rutherford formula. We examine an analogous example, the classical and perturbative quantum scattering of an electron by a magnetic field confined in an infinite solenoid of finite radius. The results obtained for the classical and the quantum differential cross sections display marked differences. While this may not be a complete surprise, one should expect to recover the classical expression by applying the classical limit to the quantum result. This turn not to be the case. Surprisingly enough, it is shown that the classical result can not be recuperated even if higher order corrections are included. To recover the classic correspondence of the quantum scattering problem a suitable non-perturbative methodology should be applied.

  4. Review of the inverse scattering problem at fixed energy in quantum mechanics

    NASA Technical Reports Server (NTRS)

    Sabatier, P. C.

    1972-01-01

    Methods of solution of the inverse scattering problem at fixed energy in quantum mechanics are presented. Scattering experiments of a beam of particles at a nonrelativisitic energy by a target made up of particles are analyzed. The Schroedinger equation is used to develop the quantum mechanical description of the system and one of several functions depending on the relative distance of the particles. The inverse problem is the construction of the potentials from experimental measurements.

  5. Quantum Theory of (H,H{Sub 2}) Scattering: Approximate Treatments of Reactive Scattering

    DOE R&D Accomplishments Database

    Tang, K. T.; Karplus, M.

    1970-10-01

    A quantum mechanical study is made of reactive scattering in the (H, H{sub 2}) system. The problem is formulated in terms of a form of the distorted-wave Born approximation (DWBA) suitable for collisions in which all particles have finite mass. For certain incident energies, differential and total cross sections, as well as other attributes of the reactive collisions, (e.g. reaction configuration), are determined. Two limiting models in the DWBA formulation are compared; in one, the molecule is unperturbed by the incoming atom and in the other, the molecule adiabatically follows the incoming atom. For thermal incident energies and semi-empirical interaction potential employed, the adiabatic model seems to be more appropriate. Since the DWBA method is too complicated for a general study of the (H, H{sub 2}) reaction, a much simpler approximation method, the “linear model” is developed. This model is very different in concept from treatments in which the three atoms are constrained to move on a line throughout the collision. The present model includes the full three-dimensional aspect of the collision and it is only the evaluation of the transition matrix element itself that is simplified. It is found that the linear model, when appropriately normalized, gives results in good agreement with that of the DWBA method. By application of this model, the energy dependence, rotational state of dependence and other properties of the total and differential reactions cross sections are determined. These results of the quantum mechanical treatment are compared with the classical calculation for the same potential surface. The most important result is that, in agreement with the classical treatment, the differential cross sections are strongly backward peaked at low energies and shifts in the forward direction as the energy increases. Finally, the implications of the present calculations for a theory of chemical kinetics are discussed.

  6. Spectral statistics for the evolution operator of a quantum particle showing chaotic diffusion of the coordinate

    SciTech Connect

    Kolovsky, A.R.

    1997-08-01

    We study the spectral properties of the evolution operator of a quantum particle subject to a space-periodic time-dependent potential. Two qualitatively different regimes of the system dynamics are compared: case (i), when the spreading of the wave packet is asymptotically ballistic; and case (ii), when the wave packet spreads diffusively. As time increases, the spectrum is shown to approach Poisson statistics in case (i) and circular unitary ensemble statistics in case (ii). A scaling relation for the velocity and curvature distributions of the spectral bands are found. {copyright} {ital 1997} {ital The American Physical Society}

  7. Fermion-fermion scattering in quantum field theory with superconducting circuits.

    PubMed

    García-Álvarez, L; Casanova, J; Mezzacapo, A; Egusquiza, I L; Lamata, L; Romero, G; Solano, E

    2015-02-20

    We propose an analog-digital quantum simulation of fermion-fermion scattering mediated by a continuum of bosonic modes within a circuit quantum electrodynamics scenario. This quantum technology naturally provides strong coupling of superconducting qubits with a continuum of electromagnetic modes in an open transmission line. In this way, we propose qubits to efficiently simulate fermionic modes via digital techniques, while we consider the continuum complexity of an open transmission line to simulate the continuum complexity of bosonic modes in quantum field theories. Therefore, we believe that the complexity-simulating-complexity concept should become a leading paradigm in any effort towards scalable quantum simulations.

  8. Plasmon-excitonic scattering of light from a nanoparticle located near a quantum well

    NASA Astrophysics Data System (ADS)

    Kosobukin, V. A.

    2015-07-01

    A solution is presented for the problem of resonant elastic scattering of polarized light from a nanoparticle and a quantum well located near semiconductor surface. Coupling between surface plasmons of the metal particle and quasi-2D excitons of the quantum well is taken into account. The problem is solved by the Green's functions technique treating the resonant polarization response of particle and quantum well in a self-consistent approximation. The effective polarizability is found for a metal nanoparticle of ellipsoidal shape with account of dynamical effect of "image" charges caused by semiconductor surface and quantum well. Spectra are numerically calculated for a model structure "metal-semiconductor" including a silver nanoparticle and a quantum well AlGaAs/GaAs. Appearance of exciton-plasmon interaction in the resonant scattering of light is interpreted as an enhancement by surface plasmons of the optical response due to quantum-well quasi-2D excitons.

  9. Angle-resolved scattering spectroscopy of explosives using an external cavity quantum cascade laser

    SciTech Connect

    Suter, Jonathan D.; Bernacki, Bruce E.; Phillips, Mark C.

    2012-04-01

    Investigation of angle-resolved scattering from solid explosives residues on a car door for non-contact sensing geometries. Illumination with a mid-infrared external cavity quantum cascade laser tuning between 7 and 8 microns was detected both with a sensitive single point detector and a hyperspectral imaging camera. Spectral scattering phenomena were discussed and possibilities for hyperspectral imaging at large scattering angles were outlined.

  10. Wigner-function formalism applied to semiconductor quantum devices: Need for nonlocal scattering models

    NASA Astrophysics Data System (ADS)

    Iotti, Rita Claudia; Dolcini, Fabrizio; Rossi, Fausto

    2017-09-01

    In designing and optimizing new-generation nanomaterials and related quantum devices, dissipation versus decoherence phenomena are often accounted for via local scattering models, such as relaxation-time and Boltzmann-like schemes. Here we show that the use of such local scattering approaches within the Wigner-function formalism may lead to unphysical results, namely anomalous suppression of intersubband relaxation, incorrect thermalization dynamics, and violation of probability-density positivity. Furthermore, we propose a quantum-mechanical generalization of relaxation-time and Boltzmann-like models, resulting in nonlocal scattering superoperators that enable one to overcome such limitations.

  11. Accurate Calculations of Rotationally Inelastic Scattering Cross Sections Using Mixed Quantum/Classical Theory.

    PubMed

    Semenov, Alexander; Babikov, Dmitri

    2014-01-16

    For computational treatment of rotationally inelastic scattering of molecules, we propose to use the mixed quantum/classical theory, MQCT. The old idea of treating translational motion classically, while quantum mechanics is used for rotational degrees of freedom, is developed to the new level and is applied to Na + N2 collisions in a broad range of energies. Comparison with full-quantum calculations shows that MQCT accurately reproduces all, even minor, features of energy dependence of cross sections, except scattering resonances at very low energies. The remarkable success of MQCT opens up wide opportunities for computational predictions of inelastic scattering cross sections at higher temperatures and/or for polyatomic molecules and heavier quenchers, which is computationally close to impossible within the full-quantum framework.

  12. Programmable two-photon quantum interference in 103 channels in opaque scattering media

    NASA Astrophysics Data System (ADS)

    Wolterink, Tom A. W.; Uppu, Ravitej; Ctistis, Georgios; Vos, Willem L.; Boller, Klaus-J.; Pinkse, Pepijn W. H.

    2016-05-01

    We investigate two-photon quantum interference in an opaque scattering medium that intrinsically supports a large number of transmission channels. By adaptive spatial phase modulation of the incident wave fronts, the photons are directed at targeted speckle spots or output channels. From 103 experimentally available coupled channels, we select two channels and enhance their transmission to realize the equivalent of a fully programmable 2 ×2 beam splitter. By sending pairs of single photons from a parametric down-conversion source through the opaque scattering medium, we observe two-photon quantum interference. The programed beam splitter need not fulfill energy conservation over the two selected output channels and hence could be nonunitary. Consequently, we have the freedom to tune the quantum interference from bunching (Hong-Ou-Mandel-like) to antibunching. Our results establish opaque scattering media as a platform for high-dimensional quantum interference that is notably relevant for boson sampling and physical-key-based authentication.

  13. On classical and quantum effects at scattering of ultrarelativistic electrons in ultrathin crystal

    NASA Astrophysics Data System (ADS)

    Shulga, S. N.; Shul'ga, N. F.; Barsuk, S.; Chaikovska, I.; Chehab, R.

    2017-07-01

    Classical and quantum properties of scattering of ultrarelativistic electrons in ultrathin crystals are considered. A comparison is made of these two ways of study of scattering process. In classical consideration we remark the appearance of sharp peaks in angular distribution of scattered particles, that is treated as a manifestation of the rainbow scattering phenomenon, and in quantum case we show sharp peaks in the angular distribution that arise from the interference of single electrons on numerous crystal planes and can be expressed in terms of reciprocal lattice vectors. We show that for some parameters the quantum predictions substantially differ from the classical ones. The influence of beam divergence on the possibility of experimental observation of the studied effects is estimated.

  14. Error in trapped-ion quantum gates due to spontaneous photon scattering

    NASA Astrophysics Data System (ADS)

    Ozeri, R.; Langer, C.; Jost, J. D.; Blakestad, R. B.; Britton, J.; Chiaverini, J.; Hume, D.; Itano, W. M.; Knill, E.; Leibfried, D.; Reichle, R.; Seidelin, S.; Wesenberg, J. H.; Wineland, D. J.

    2006-05-01

    Quantum bits that are encoded into hyperfine states of trapped ions are a promising system for Quantum Information Processing (QIP). Quantum gates performed on trapped ions use laser induced stimulated Raman transitions. The spontaneous scattering of photons therefore sets a fundamental limit to the gate fidelity. Here we present a calculation that explores these limits. Errors are shown to arise from two sources. The first is due to spin relaxation (spontaneous Raman photon-scattering events) and the second due to the momentum-recoil that is imparted to the trapped ions in the scattering process. It is shown that the gate error due to spontaneous photon scattering can be reduced to very small values with the use of high laser power. It is further shown that error levels required for fault-tolerant QIP are within reach of experimentally realistic laser parameters.

  15. Regular and Chaotic Quantum Dynamics of Two-Level Atoms in a Selfconsistent Radiation Field

    NASA Technical Reports Server (NTRS)

    Konkov, L. E.; Prants, S. V.

    1996-01-01

    Dynamics of two-level atoms interacting with their own radiation field in a single-mode high-quality resonator is considered. The dynamical system consists of two second-order differential equations, one for the atomic SU(2) dynamical-group parameter and another for the field strength. With the help of the maximal Lyapunov exponent for this set, we numerically investigate transitions from regularity to deterministic quantum chaos in such a simple model. Increasing the collective coupling constant b is identical with 8(pi)N(sub 0)(d(exp 2))/hw, we observed for initially unexcited atoms a usual sharp transition to chaos at b(sub c) approx. equal to 1. If we take the dimensionless individual Rabi frequency a = Omega/2w as a control parameter, then a sequence of order-to-chaos transitions has been observed starting with the critical value a(sub c) approx. equal to 0.25 at the same initial conditions.

  16. Resonances in positron-hydrogen scattering in dense quantum plasmas

    SciTech Connect

    Jiang, Zishi; Zhang, Yong-Zhi; Kar, Sabyasachi

    2015-05-15

    We have investigated the S-wave resonance states in positron-hydrogen system embedded in dense quantum plasmas using Hylleraas-type wave functions within the framework of the stabilization method. The effect of quantum plasmas has been incorporated using the exponential-cosine-screened Coulomb (modified Yukawa-type) potential. Resonance parameters (both position and width) below the Ps n = 2 threshold are reported as functions of plasma screening parameters.

  17. The study of effects of small perturbations on chaotic systems

    SciTech Connect

    Grebogi, C.; Yorke, J.A.

    1991-12-01

    This report discusses the following topics: controlling chaotic dynamical systems; embedding of experimental data; effect of noise on critical exponents of crises; transition to chaotic scattering; and distribution of floaters on a fluid surface. (LSP)

  18. Exact scattering matrix of graphs in magnetic field and quantum noise

    SciTech Connect

    Caudrelier, Vincent; Mintchev, Mihail; Ragoucy, Eric

    2014-08-15

    We consider arbitrary quantum wire networks modelled by finite, noncompact, connected quantum graphs in the presence of an external magnetic field. We find a general formula for the total scattering matrix of the network in terms of its local scattering properties and its metric structure. This is applied to a quantum ring with N external edges. Connecting the external edges of the ring to heat reservoirs, we study the quantum transport on the graph in ambient magnetic field. We consider two types of dynamics on the ring: the free Schrödinger and the free massless Dirac equations. For each case, a detailed study of the thermal noise is performed analytically. Interestingly enough, in presence of a magnetic field, the standard linear Johnson-Nyquist law for the low temperature behaviour of the thermal noise becomes nonlinear. The precise regime of validity of this effect is discussed and a typical signature of the underlying dynamics is observed.

  19. Towards inclusion of excited vibrational states in ultracold molecule-molecule quantum scattering calculations

    NASA Astrophysics Data System (ADS)

    Ticknor, Christopher; Kendrick, Brian

    2016-05-01

    We report progress towards including excited vibrational states in quantum scattering calculations of NaK-NaK at ultracold temperatures. We systematically use all pair potentials to build a complete 4 body potential energy surface. We study this 4-body potential and the asymptotic ro-vibrational 2-body basis. This allows for a more complete interaction as two molecules approach each other. We study where and how vibrationally excited states influence the asymptotic 2-body ro-vibrational scattering potentials. This work is an intermediate step in performing the complete scattering calculations as we develop tools to bring together the long range, ultracold 2-body scattering problem and the short range 4-body quantum chemistry problem.

  20. Exciton-mediated Raman scattering in CdS quantum dot

    NASA Astrophysics Data System (ADS)

    Guo, Xiaotong; Liu, Cuihong

    2017-09-01

    A theoretical calculation of the differential cross section (DCS) is presented for the exciton-mediated Stokes Raman scattering in CdS quantum dot within the frame work of effective mass approximation at T = 0 K. Numerical calculations reveal that the excitonic effects cause blue shifts in Raman spectroscopy. The magnitude of the Raman shift depends on the quantum confinement, the Coulomb interaction, and the incident photon energy.

  1. Multiphonon excitation and quantum decoherence in neon scattering from solid surfaces

    NASA Astrophysics Data System (ADS)

    Al Taleb, Amjad; Anemone, Gloria; Hayes, W. W.; Manson, J. R.; Farías, Daniel

    2017-02-01

    We present angle- and energy-resolved analysis of Ne scattering from a Ni(111) surface at moderate beam energy and surface temperature. Variation of the surface temperature allows the transition from a pure quantum regime, where single-phonon events are observed, to the classical regime, where multiphonon excitations are observed. The latter can be reproduced by classical calculations. Therefore, our data lie on the border between the coherent quantum regime and the incoherent classical regime.

  2. Resonances in Coupled πK-ηK Scattering from Quantum Chromodynamics

    DOE PAGES

    Dudek, Jozef J.; Edwards, Robert G.; Thomas, Christopher E.; ...

    2014-10-01

    Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled πK, ηK scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.

  3. Simulations of light-light scattering in quantum vacuum

    NASA Astrophysics Data System (ADS)

    Carneiro, Pedro; Grismayer, Thomas; Silva, LuíS.; Fonseca, Ricardo

    2016-10-01

    Facilities such as the Extreme Light Infrastructure (ELI) or the VULCAN 20 PW project, as well as the Petta-Watt SLAC project, coupled with the x-ray LCLSII source will allow to perform the first experiments on the probing of quantum vacuum. In our work, we developed a numerical method to self-consistently solve the nonlinear system of Maxwell's equations including quantum corrections of vacuum polarization. The robustness of our algorithm allied to the ability to integrate this tool within a particle-in-cell (PIC) method, represents an important milestone in modeling future planned experiments to prove the existence of the quantum vacuum. Such experiments aim to measure the induced ellipticity on a x-ray pulse after probing a strong optical pump due to the quantum vacuum fluctuations. We present simulation results of both the ellipticity induced and polarization rotation, using realistic laser parameters of the Petta-Watt SLAC project, and the x-ray LCLSII source, whilst taking into account all finite-size multi-dimensional effects. We show how the ellipticity induced varies as a function of the distance to the axis of the beam, proving the importance of taking into account finite-size effects. This work serves as an important tool to complement existing efforts within the community to probe the effects of the quantum vacuum, in the strong field regime, for the first time.

  4. Quantum theory of (femtosecond) time-resolved stimulated Raman scattering.

    PubMed

    Sun, Zhigang; Lu, J; Zhang, Dong H; Lee, Soo-Y

    2008-04-14

    We present a complete perturbation theory of stimulated Raman scattering (SRS), which includes the new experimental technique of femtosecond stimulated Raman scattering (FSRS), where a picosecond Raman pump pulse and a femtosecond probe pulse simultaneously act on a stationary or nonstationary vibrational state. It is shown that eight terms in perturbation theory are required to account for SRS, with observation along the probe pulse direction, and they can be grouped into four nonlinear processes which are labeled as stimulated Raman scattering or inverse Raman scattering (IRS): SRS(I), SRS(II), IRS(I), and IRS(II). Previous FSRS theories have used only the SRS(I) process or only the "resonance Raman scattering" term in SRS(I). Each process can be represented by an overlap between a wave packet in the initial electronic state and a wave packet in the excited Raman electronic state. Calculations were performed with Gaussian Raman pump and probe pulses on displaced harmonic potentials to illustrate various features of FSRS, such as high time and frequency resolution; Raman gain for the Stokes line, Raman loss for the anti-Stokes line, and absence of the Rayleigh line in off-resonance FSRS from a stationary or decaying v=0 state; dispersive line shapes in resonance FSRS; and the possibility of observing vibrational wave packet motion with off-resonance FSRS.

  5. Vibrational Scattering Anisotropy Generated by Multichannel Quantum Interference

    SciTech Connect

    Miron, Catalin; Kimberg, Victor; Morin, Paul; Nicolas, Christophe; Kosugi, Nobuhiro; Gavrilyuk, Sergey; Gel'mukhanov, Faris

    2010-08-27

    Based on angularly and vibrationally resolved electron spectroscopy measurements in acetylene, we report the first observation of anomalously strong vibrational anisotropy of resonant Auger scattering through the C 1s{yields}{pi}{sup *} excited state. We provide a theoretical model explaining the new phenomenon by three coexisting interference effects: (i) interference between resonant and direct photoionization channels, (ii) interference of the scattering channels through the core-excited bending states with orthogonal orientation of the molecular orbitals, (iii) scattering through two wells of the double-well bending mode potential. The interplay of nuclear and electronic motions offers in this case a new type of nuclear wave packet interferometry sensitive to the anisotropy of nuclear dynamics: whether which-path information is available or not depends on the final vibrational state serving for path selection.

  6. Redundant information from thermal illumination: quantum Darwinism in scattered photons

    NASA Astrophysics Data System (ADS)

    Jess Riedel, C.; Zurek, Wojciech H.

    2011-07-01

    We study quantum Darwinism, the redundant recording of information about the preferred states of a decohering system by its environment, for an object illuminated by a blackbody. We calculate the quantum mutual information between the object and its photon environment for blackbodies that cover an arbitrary section of the sky. In particular, we demonstrate that more extended sources have a reduced ability to create redundant information about the system, in agreement with previous evidence that initial mixedness of an environment slows—but does not stop—the production of records. We also show that the qualitative results are robust for more general initial states of the system.

  7. Effects of interface roughness scattering on device performance of indirectly pumped terahertz quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Ghasem Razavipour, Seyed; Dupont, Emmanuel; Wasilewski, Zbig R.; Ban, Dayan

    2015-06-01

    The impacts of interface roughness (IR) scattering on device performance of indirectly-pumped (IDP) terahertz quantum cascade lasers are studied. Three different active region designs with almost the same lasing frequency at threshold and comparable oscillator strength are experimentally investigated and the measurement data are analyzed and compared with numerical simulation. The simulation results show that all structures suffer from the detrimental effect of intersubband roughness scattering in terms of threshold current density, and probably operating temperature. The intrasubband IR scattering time could also to be a limiting factor in the IDP structures due to the employed high energetic barrier.

  8. One-phonon Raman scattering in a two-dimensional quantum pseudo-dot system

    NASA Astrophysics Data System (ADS)

    Taghavi, S. Abdolvahab; Rezaei, G.; Karimi, M. J.

    2017-10-01

    We present theoretical results concerning the electron Raman scattering process related to the longitudinal optical (LO) phonon modes in a two - dimensional quantum pseudo - dot, under the influence of a uniform magnetic field. The Fröhlich electron - phonon interaction for resonance Raman scattering is considered. External magnetic field, the geometrical size of the pseudo - dot and the electron - phonon interaction effects on the differential cross - section of the Raman scattering are investigated. Our Results reveal that the geometrical parameters of the pseudo - dot as well as the external magnetic field and electron - phonon interaction have a great influence on the position and the magnitude of the peaks of the emission spectra.

  9. Intersubband carrier scattering in n - and p-Si/SiGe quantum wells with diffuse interfaces

    NASA Astrophysics Data System (ADS)

    Valavanis, A.; Ikonić, Z.; Kelsall, R. W.

    2008-02-01

    Scattering rate calculations in two-dimensional Si/Si1-xGex systems have typically been restricted to rectangular Ge profiles at interfaces between layers. Real interfaces, however, may exhibit diffuse Ge profiles either by design or as a limitation of the growth process. It is shown here that alloy disorder scattering dramatically increases with Ge interdiffusion in (100) and (111) n -type quantum wells, but remains almost constant in (100) p -type heterostructures. It is also shown that smoothing of the confining potential leads to large changes in subband energies and scattering rates, and a method is presented for calculating growth process tolerances.

  10. Multi-user quantum private comparison with scattered preparation and one-way convergent transmission of quantum states

    NASA Astrophysics Data System (ADS)

    Ye, TianYu; Ji, ZhaoXu

    2017-09-01

    Quantum private comparison (QPC) aims to accomplish the equality comparison of the secrets from different users without disclosing their genuine contents by using the principles of quantum mechanics. In this paper, we summarize eight modes of quantum state preparation and transmission existing in current QPC protocols first. Then, by using the mode of scattered preparation and one-way convergent transmission, we construct a new multi-user quantum private comparison (MQPC) protocol with two-particle maximally entangled states, which can accomplish arbitrary pair's comparison of equality among K users within one execution. Analysis turns out that its output correctness and its security against both the outside attack and the participant attack are guaranteed. The proposed MQPC protocol can be implemented with current technologies. It can be concluded that the mode of scattered preparation and one-way convergent transmission of quantum states is beneficial to designing the MQPC protocol which can accomplish arbitrary pair's comparison of equality among K users within one execution.

  11. Stimulated scattering of electromagnetic waves carrying orbital angular momentum in quantum plasmas.

    PubMed

    Shukla, P K; Eliasson, B; Stenflo, L

    2012-07-01

    We investigate stimulated scattering instabilities of coherent circularly polarized electromagnetic (CPEM) waves carrying orbital angular momentum (OAM) in dense quantum plasmas with degenerate electrons and nondegenerate ions. For this purpose, we employ the coupled equations for the CPEM wave vector potential and the driven (by the ponderomotive force of the CPEM waves) equations for the electron and ion plasma oscillations. The electrons are significantly affected by the quantum forces (viz., the quantum statistical pressure, the quantum Bohm potential, as well as the electron exchange and electron correlations due to electron spin), which are included in the framework of the quantum hydrodynamical description of the electrons. Furthermore, our investigation of the stimulated Brillouin instability of coherent CPEM waves uses the generalized ion momentum equation that includes strong ion coupling effects. The nonlinear equations for the coupled CPEM and quantum plasma waves are then analyzed to obtain nonlinear dispersion relations which exhibit stimulated Raman, stimulated Brillouin, and modulational instabilities of CPEM waves carrying OAM. The present results are useful for understanding the origin of scattered light off low-frequency density fluctuations in high-energy density plasmas where quantum effects are eminent.

  12. Rotationally Inelastic Scattering of Quantum-State-Selected ND3 with Ar.

    PubMed

    Tkáč, Ondřej; Saha, Ashim K; Loreau, Jérôme; Parker, David H; van der Avoird, Ad; Orr-Ewing, Andrew J

    2015-06-11

    Rotationally inelastic scattering of ND3 with Ar is studied at mean collision energies of 410 and 310 cm(–1). In the experimental component of the study, ND3 molecules are prepared by supersonic expansion and subsequent hexapole state selection in the ground electronic and vibrational levels and in the jk(±) = 1(1) rotational level. A beam of state-selected ND3 molecules is crossed with a beam of Ar, and scattered ND3 molecules are detected in single final j′k′(±) quantum states using resonance enhanced multiphoton ionization spectroscopy. State-to-state differential cross sections for rotational-level changing collisions are obtained by velocity map imaging. The experimental measurements are compared with close-coupling quantum-mechanical scattering calculations performed using an ab initio potential energy surface. The computed DCSs agree well with the experimental measurements, confirming the high quality of the potential energy surface. The angular distributions are dominated by forward scattering for all measured final rotational and vibrational inversion symmetry states. This outcome is in contrast to our recent results for inelastic scattering of ND3 with He, where we observed significant amount of sideways and backward scattering for some final rotational levels of ND3. The differences between He and Ar collision partners are explained by differences in the potential energy surfaces that govern the scattering dynamics.

  13. Solution of coupled integral equations for quantum scattering in the presence of complex potentials

    SciTech Connect

    Franz, Jan

    2015-01-15

    In this paper, we present a method to compute solutions of coupled integral equations for quantum scattering problems in the presence of a complex potential. We show how the elastic and absorption cross sections can be obtained from the numerical solution of these equations in the asymptotic region at large radial distances.

  14. Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

    PubMed

    Mani, Arjun; Benjamin, Colin

    2016-04-13

    On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin-orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible--the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case.

  15. Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

    NASA Astrophysics Data System (ADS)

    Mani, Arjun; Benjamin, Colin

    2016-04-01

    On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin-orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible—the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case.

  16. Grazing-incidence small-angle X-ray scattering: application to the study of quantum dot lattices.

    PubMed

    Buljan, Maja; Radić, Nikola; Bernstorff, Sigrid; Dražić, Goran; Bogdanović-Radović, Iva; Holý, Václav

    2012-01-01

    The ordering of quantum dots in three-dimensional quantum dot lattices is investigated by grazing-incidence small-angle X-ray scattering (GISAXS). Theoretical models describing GISAXS intensity distributions for three general classes of lattices of quantum dots are proposed. The classes differ in the type of disorder of the positions of the quantum dots. The models enable full structure determination, including lattice type, lattice parameters, the type and degree of disorder in the quantum dot positions and the distributions of the quantum dot sizes. Applications of the developed models are demonstrated using experimentally measured data from several types of quantum dot lattices formed by a self-assembly process.

  17. Formation of Fabry-Perot resonances in double-barrier chaotic billiards

    NASA Astrophysics Data System (ADS)

    Macêdo, A. M.; Souza, Andre M.

    2005-06-01

    We study wave transport through a chaotic quantum billiard attached to two waveguides via barriers of arbitrary transparencies in the semiclassical limit of a large number of open scattering channels. We focus attention on the ergodic regime, which is described by using a random-matrix approach to chaotic resonance scattering together with an extended version of Nazarov’s circuit theory. By varying the relative strength of the barriers’ transparencies a reorganization of the relevant resonances in the energy interval where transport takes place leads to a full suppression of high transmission modes. We provide a detailed quantitative description of the process by means of both numerical and analytical evaluations of the average density of transmission eigenvalues. We show that the density of Fabry-Perot modes can be used as a kind of order parameter for this quantum transition. A diagram is presented as a function of the transparencies of the barriers exhibiting the transport regimes and the transition lines.

  18. The spectrum and properties of the scattering cross section of electrons in open spherical quantum dots

    SciTech Connect

    Tkach, N. V. Seti, Ju.

    2009-03-15

    In the effective mass approximation in the model of rectangular potentials, the scattering cross section of electrons in an open spherical quantum dot is calculated for the first time. It is shown that, for such a nanosystem with a barrier of several monolayers, the experimental measurements of the scattering cross section allow adequate identification of the resonance energies and the widths of resonance states in the low-energy region of the quasi-stationary electron spectrum. It is also shown that, for an open spherical quantum dot with a low-strength potential barrier, the adequate spectral parameters of the quasi-stationary spectrum are the generalized resonance energies and widths determined via the probability of an electron being inside the quantum dot.

  19. Scattering of nanowire surface plasmons coupled to quantum dots with azimuthal angle difference

    NASA Astrophysics Data System (ADS)

    Kuo, Po-Chen; Chen, Guang-Yin; Chen, Yueh-Nan

    2016-11-01

    Coherent scatterings of surface plasmons coupled to quantun dots have attracted great attention in plasmonics. Recently, an experiment has shown that the quantum dots located nearby a nanowire can be separated not only in distance, but also an angle ϕ along the cylindrical direction. Here, by using the real-space Hamiltonian and the transfer matrix method, we analytically obtain the transmission/reflection spectra of nanowire surface plasmons coupled to quantum dots with an azimuthal angle difference. We find that the scattering spectra can show completely different features due to different positions and azimuthal angles of the quantum dots. When additionally coupling a cavity to the dots, we obtain the Fano-like line shape in the transmission and reflection spectra due to the interference between the localized and delocalized modes.

  20. Scattering of nanowire surface plasmons coupled to quantum dots with azimuthal angle difference

    PubMed Central

    Kuo, Po-Chen; Chen, Guang-Yin; Chen, Yueh-Nan

    2016-01-01

    Coherent scatterings of surface plasmons coupled to quantun dots have attracted great attention in plasmonics. Recently, an experiment has shown that the quantum dots located nearby a nanowire can be separated not only in distance, but also an angle ϕ along the cylindrical direction. Here, by using the real-space Hamiltonian and the transfer matrix method, we analytically obtain the transmission/reflection spectra of nanowire surface plasmons coupled to quantum dots with an azimuthal angle difference. We find that the scattering spectra can show completely different features due to different positions and azimuthal angles of the quantum dots. When additionally coupling a cavity to the dots, we obtain the Fano-like line shape in the transmission and reflection spectra due to the interference between the localized and delocalized modes. PMID:27892942

  1. Scattering of nanowire surface plasmons coupled to quantum dots with azimuthal angle difference.

    PubMed

    Kuo, Po-Chen; Chen, Guang-Yin; Chen, Yueh-Nan

    2016-11-28

    Coherent scatterings of surface plasmons coupled to quantun dots have attracted great attention in plasmonics. Recently, an experiment has shown that the quantum dots located nearby a nanowire can be separated not only in distance, but also an angle ϕ along the cylindrical direction. Here, by using the real-space Hamiltonian and the transfer matrix method, we analytically obtain the transmission/reflection spectra of nanowire surface plasmons coupled to quantum dots with an azimuthal angle difference. We find that the scattering spectra can show completely different features due to different positions and azimuthal angles of the quantum dots. When additionally coupling a cavity to the dots, we obtain the Fano-like line shape in the transmission and reflection spectra due to the interference between the localized and delocalized modes.

  2. Time-delay of classical and quantum scattering processes: a conceptual overview and a general definition

    NASA Astrophysics Data System (ADS)

    Sassoli de Bianchi, Massimiliano

    2012-04-01

    We present a step by step introduction to the notion of time-delay in classical and quantum mechanics, with the aim of clarifying its foundation at a conceptual level. In doing so, we motivate the introduction of the concepts of "fuzzy" and "free-flight" sojourn times that we use to provide the most general possible definition for the quantum time-delay, valid for simple and multichannel scattering systems, with or without conditions on the observation of the scattering particle, and for incoming wave packets whose energy can be smeared out or sharply peaked (fixed energy). We conclude our conceptual analysis by presenting what we think is the right interpretation of the concepts of sojourn and delay times in quantum mechanics, explaining why, in ultimate analysis, they should not be called "times."

  3. Implementing quantum gates through scattering between a static and a flying qubit

    NASA Astrophysics Data System (ADS)

    Cordourier-Maruri, Guillermo; Ciccarello, Francesco; Omar, Yasser; Z, Michelangelo; de Coss, Romeo; Bose, Sougato

    2011-03-01

    We investigate whether a two-qubit quantum gate can be implemented in a scattering process involving a flying and a static qubit. We focus on a paradigmatic setup made out of a mobile particle and a quantum impurity, whose respective spin degrees of freedom couple to each other during a one-dimensional scattering process. A condition for the occurrence of quantum gates is derived in terms of spin-dependent transmission coefficients. This can be fulfilled through the insertion of an additional narrow potential barrier. Under resonance conditions this procedure enables a gate only for Heisenberg interactions and fails for an XY interaction. We show the existence of parameter regimes for which gates able to establish a maximum amount of entanglement can be implemented. The gates are found to be robust to variations of the optimal parameters.

  4. Impact of Coulomb Scattering on the Ultrafast Gain Recovery in InGaAs Quantum Dots

    NASA Astrophysics Data System (ADS)

    Gomis-Bresco, J.; Dommers, S.; Temnov, V. V.; Woggon, U.; Laemmlin, M.; Bimberg, D.; Malic, E.; Richter, M.; Schöll, E.; Knorr, A.

    2008-12-01

    The application of quantum dot (QD) semiconductor optical amplifiers (SOAs) in above 100-Gbit Ethernet networks demands an ultrafast gain recovery on time scales similar to that of the input pulse ˜100GHz repetition frequency. Microscopic scattering processes have to act at shortest possible time scales and mechanisms speeding up the Coulomb scattering have to be explored, controlled, and exploited. We present a microscopic description of the gain recovery by coupled polarization- and population dynamics in a thermal nonequilibrium situation going beyond rate-equation models and discuss the limitations of Coulomb scattering between 0D and 2D-confined quantum states. An experiment is designed which demonstrates the control of gain recovery for THz pulse trains in InGaAs QD-based SOAs under powerful electrical injection.

  5. Quantum statistics of Raman scattering model with Stokes mode generation

    NASA Technical Reports Server (NTRS)

    Tanatar, Bilal; Shumovsky, Alexander S.

    1994-01-01

    The model describing three coupled quantum oscillators with decay of Rayleigh mode into the Stokes and vibration (phonon) modes is examined. Due to the Manley-Rowe relations the problem of exact eigenvalues and eigenstates is reduced to the calculation of new orthogonal polynomials defined both by the difference and differential equations. The quantum statistical properties are examined in the case when initially: the Stokes mode is in the vacuum state; the Rayleigh mode is in the number state; and the vibration mode is in the number of or squeezed states. The collapses and revivals are obtained for different initial conditions as well as the change in time the sub-Poisson distribution by the super-Poisson distribution and vice versa.

  6. Quantum chaos for point scatterers on flat tori.

    PubMed

    Ueberschär, Henrik

    2014-01-28

    This survey article deals with a delta potential--also known as a point scatterer--on flat two- and three-dimensional tori. We introduce the main conjectures regarding the spectral and wave function statistics of this model in the so-called weak and strong coupling regimes. We report on recent progress as well as a number of open problems in this field.

  7. Controlling Inelastic Light Scattering Quantum Pathways in Graphene

    DTIC Science & Technology

    2011-03-31

    dielectric21,22. Figure 1a displays a diagram of a typical device . The carrier concentration in graphene is controlled by the top gate voltage (Vg). The doping...dependence of electrical transport, optical transmis- sion and inelastic light scattering are measured on the same graphene devices . Figure 1b shows...the electrical resistance curve of a graphene device , which has a charge neutral point (CNP) at 1.2V. The resistance decreases from the CNP value on

  8. Quantum Chaos

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Chirikov, Boris

    1995-04-01

    in two-electron atoms R. Blümel and W. P. Reinhardt; Part III. Semiclassical Approximations: 20. Semiclassical theory of spectral rigidity M. V. Berry; 21. Semiclassical structure of trace formulas R. G. Littlejohn; 22. h-Expansion for quantum trace formulas P. Gaspard; 23. Pinball scattering B. Eckhardt, G. Russberg, P. Cvitanovic, P. E. Rosenqvist and P. Scherer; 24. Logarithm breaking time in quantum chaos G. P. Berman and G. M. Zaslavsky; 25. Semiclassical propagation: how long can it last? M. A. Sepulveda, S. Tomsovic and E. J. Heller; 26. The quantized Baker's transformation N. L. Balazs and A. Voros; 27. Classical structures in the quantized baker transformation M. Saraceno; 28. Quantum nodal points as fingerprints of classical chaos P. Leboeuf and A. Voros; 29. Chaology of action billiards A. M. Ozorio de Almeida and M. A. M. de Aguiar; Part IV. Level Statistics and Random Matrix Theory: 30. Characterization of chaotic quantum spectra and universality of level fluctuation laws O. Bohigas, M. J. Giannono, and C. Schmit; 31. Quantum chaos, localization and band random matrices F. M. Izrailev; 32. Structural invariance in channel space: a step toward understanding chaotic scattering in quantum mechanics T. H. Seligman; 33. Spectral properties of a Fermi accelerating disk R. Badrinarayanan and J. J. José; 34. Spectral properties of systems with dynamical localization T. Dittrich and U. Smilansky; 35. Unbound quantum diffusion and fractal spectra T. Geisel, R. Ketzmerick and G. Petschel; 36. Microwave studies in irregularly shaped billiards H.-J. Stöckmann, J. Stein and M. Kollman; Index.

  9. Quantum Chaos

    NASA Astrophysics Data System (ADS)

    Casati, Giulio; Chirikov, Boris

    2006-11-01

    in two-electron atoms R. Blümel and W. P. Reinhardt; Part III. Semiclassical Approximations: 20. Semiclassical theory of spectral rigidity M. V. Berry; 21. Semiclassical structure of trace formulas R. G. Littlejohn; 22. h-Expansion for quantum trace formulas P. Gaspard; 23. Pinball scattering B. Eckhardt, G. Russberg, P. Cvitanovic, P. E. Rosenqvist and P. Scherer; 24. Logarithm breaking time in quantum chaos G. P. Berman and G. M. Zaslavsky; 25. Semiclassical propagation: how long can it last? M. A. Sepulveda, S. Tomsovic and E. J. Heller; 26. The quantized Baker's transformation N. L. Balazs and A. Voros; 27. Classical structures in the quantized baker transformation M. Saraceno; 28. Quantum nodal points as fingerprints of classical chaos P. Leboeuf and A. Voros; 29. Chaology of action billiards A. M. Ozorio de Almeida and M. A. M. de Aguiar; Part IV. Level Statistics and Random Matrix Theory: 30. Characterization of chaotic quantum spectra and universality of level fluctuation laws O. Bohigas, M. J. Giannono, and C. Schmit; 31. Quantum chaos, localization and band random matrices F. M. Izrailev; 32. Structural invariance in channel space: a step toward understanding chaotic scattering in quantum mechanics T. H. Seligman; 33. Spectral properties of a Fermi accelerating disk R. Badrinarayanan and J. J. José; 34. Spectral properties of systems with dynamical localization T. Dittrich and U. Smilansky; 35. Unbound quantum diffusion and fractal spectra T. Geisel, R. Ketzmerick and G. Petschel; 36. Microwave studies in irregularly shaped billiards H.-J. Stöckmann, J. Stein and M. Kollman; Index.

  10. Grazing-incidence small-angle X-ray scattering: application to the study of quantum dot lattices

    SciTech Connect

    Buljan, Maja Radić, Nikola; Bernstorff, Sigrid; Dražić, Goran; Bogdanović-Radović, Iva; Holý, Václav

    2012-01-01

    The modelling of grazing-incidence small-angle X-ray scattering (GISAXS) from three-dimensional quantum dot lattices is described. The ordering of quantum dots in three-dimensional quantum dot lattices is investigated by grazing-incidence small-angle X-ray scattering (GISAXS). Theoretical models describing GISAXS intensity distributions for three general classes of lattices of quantum dots are proposed. The classes differ in the type of disorder of the positions of the quantum dots. The models enable full structure determination, including lattice type, lattice parameters, the type and degree of disorder in the quantum dot positions and the distributions of the quantum dot sizes. Applications of the developed models are demonstrated using experimentally measured data from several types of quantum dot lattices formed by a self-assembly process.

  11. Relativistic scattering of fermions in quaternionic quantum mechanics

    NASA Astrophysics Data System (ADS)

    Hassanabadi, Hassan; Sobhani, Hadi; Banerjee, Abhijit

    2017-09-01

    In this article, we propose a quaternionic version of the Dirac equation in the presence of scalar and vector potentials. It has been shown that in complex limit of such an equation, the complex version of this equation can be covered. After setting a quaternionic form for the Dirac delta potential, scattering due to the considered interaction has been studied. Wave functions and discontinuity conditions of the problem considered have been derived in detail. Using the continuity equation, we have found a constraint implying the conservation law of the probability current.

  12. Quantum mechanical limit to plasmonic enhancement as observed by surface-enhanced Raman scattering.

    PubMed

    Zhu, Wenqi; Crozier, Kenneth B

    2014-10-14

    Plasmonic nanostructures enable light to be concentrated into nanoscale 'hotspots', wherein the intensity of light can be enhanced by orders of magnitude. This plasmonic enhancement significantly boosts the efficiency of nanoscale light-matter interactions, enabling unique linear and nonlinear optical applications. Large enhancements are often observed within narrow gaps or at sharp tips, as predicted by the classical electromagnetic theory. Only recently has it become appreciated that quantum mechanical effects could emerge as the feature size approaches atomic length-scale. Here we experimentally demonstrate, through observations of surface-enhanced Raman scattering, that the emergence of electron tunnelling at optical frequencies limits the maximum achievable plasmonic enhancement. Such quantum mechanical effects are revealed for metallic nanostructures with gap-widths in the single-digit angstrom range by correlating each structure with its optical properties. This work furthers our understanding of quantum mechanical effects in plasmonic systems and could enable future applications of quantum plasmonics.

  13. Coupled force-balance and scattering equations for nonlinear transport in quantum wires

    NASA Astrophysics Data System (ADS)

    Huang, Danhong; Gumbs, Godfrey

    2009-07-01

    The coupled force-balance and scattering equations have been derived and applied to study nonlinear transport of electrons subjected to a strong dc electric field in an elastic-scattering-limited quantum wire. Numerical results have demonstrated both field-induced heating-up and cooling-down behaviors in the nonequilibrium part of the total electron-distribution function by varying the impurity density or the width of the quantum wire. The obtained asymmetric distribution function in momentum space invalidates the application of the energy-balance equation to our quantum-wire system in the center-of-mass frame. The experimentally observed suppression of mobility by a driving field for the center-of-mass motion in the quantum-wire system has been reproduced [see K. Tsubaki , Electr. Lett. 24, 1267 (1988); M. Hauser , Sci. Technol. 9, 951 (1994)]. In addition, the thermal enhancement of mobility in the elastic-scattering-limited system has been demonstrated, in accordance with a similar prediction made for graphene nanoribbons [see T. Fang , Phys. Rev. B 78, 205403 (2008)]. This thermal enhancement has been found to play a more and more significant role with higher lattice temperature and becomes stronger for a low-driving field.

  14. Spin correlation tensor for measurement of quantum entanglement in electron–electron scattering

    NASA Astrophysics Data System (ADS)

    Tsurikov, D. E.; Samarin, S. N.; Williams, J. F.; Artamonov, O. M.

    2017-04-01

    We consider the problem of correct measurement of a quantum entanglement in the two-body electron–electron scattering. An expression is derived for a spin correlation tensor of a pure two-electron state. A geometric measure of a quantum entanglement as the distance between two forms of this tensor in entangled and separable cases is presented. Due to such definition, one does not need to look for the closest separable state to the analyzed state. We prove that introduced measure satisfies properties of a valid entanglement measure: nonnegativity, discriminance, normalization, non-growth under local operations and classical communication. This measure is calculated for a problem of electron–electron scattering. We prove that it does not depend on the azimuthal rotation angle of the second electron spin relative to the first electron spin before scattering. We specify how to find a spin correlation tensor and the related measure of a quantum entanglement in an experiment with electron–electron scattering. Finally, the introduced measure is extended to the mixed states.

  15. Effects of magnetic field on electron-electron intersubband scattering rates in quantum wells.

    NASA Astrophysics Data System (ADS)

    Kempa, K.; Zhou, Y.; Engelbrecht, J.; Bakshi, P.

    2001-03-01

    Electron-electron scattering dominates the physics of carrier relaxation in quantum nano-structures used as active regions of THz radiation sources. This is the limiting mechanism in achieving population inversion, and reducing its deleterious effects could clear the way to a THz laser. We study here the inter-subband relaxation processes due to the electron-electron scattering in quantum well structures, in a magnetic field. We obtain the scattering rate from the imaginary part of the electron self-energy in the random phase approximation, extending our earlier studies [1] to nonzero magnetic fields. We find that the scattering rate is peaked at two possible sets of arrangements of the Landau levels (LL) of the two subbands of interest. The first set occurs when the LL of both subbands align, and the other when the LL misalign, so that the LL of one subband lie exactly in the middle between those of the other subband. Experiments on various quantum cascade structures show that the misaligned set of transitions is completely suppressed. >From our calculations this implies that there is no population inversion in those structures. Work supported by US Army Research Office. [1] K. Kempa, P. Bakshi, J. R. Engelbrecht, and Y. Zhou, Phys. Rev. B61, 11083 (2000).

  16. A simple method for finding the scattering coefficients of quantum graphs

    SciTech Connect

    Cottrell, Seth S.

    2015-09-15

    Quantum walks are roughly analogous to classical random walks, and similar to classical walks they have been used to find new (quantum) algorithms. When studying the behavior of large graphs or combinations of graphs, it is useful to find the response of a subgraph to signals of different frequencies. In doing so, we can replace an entire subgraph with a single vertex with variable scattering coefficients. In this paper, a simple technique for quickly finding the scattering coefficients of any discrete-time quantum graph will be presented. These scattering coefficients can be expressed entirely in terms of the characteristic polynomial of the graph’s time step operator. This is a marked improvement over previous techniques which have traditionally required finding eigenstates for a given eigenvalue, which is far more computationally costly. With the scattering coefficients we can easily derive the “impulse response” which is the key to predicting the response of a graph to any signal. This gives us a powerful set of tools for rapidly understanding the behavior of graphs or for reducing a large graph into its constituent subgraphs regardless of how they are connected.

  17. New Model of One-dimensional Completed Scattering and the Problem of Quantum Nonlocality

    NASA Astrophysics Data System (ADS)

    Chuprikov, N. L.

    2007-02-01

    The origin of nonlocality in quantum mechanics (QM) is analyzed from the viewpoint of our new model of a one-dimensional (1D) completed scattering. Our study of quantum nonlocality complements those carried out by Volovich and Khrennikov. They pointed to an unphysical character of nonlocality in Bell's theorem whose context does not contain the very structure of the space-time. However, there is another reason leading to nonlocality in QM. The existing model of a 1D completed scattering evidences that QM, as it stands, even with a proper space-time context, contradicts special relativity. By our model this scattering process represents an entanglement of two coherently evolved alternative sub-processes, transmission and reflection; whose characteristics are measured well after the scattering event. Quantum nonlocality appears in this problem due to the inconsistency of the superposition principle with the corpuscular properties of a particle. It can take part only in one of the sub-processes. However the superposition principle allows introducing observables common for them. In the fresh wording, this principle must forbid introducing observables for entangled states.

  18. Quantum interference of fast atoms scattered off crystal surfaces

    NASA Astrophysics Data System (ADS)

    Gravielle, M. S.

    2015-01-01

    The striking observation of interference structures produced by grazing impact of fast atoms on crystal surfaces reported a few years ago [1,2] has given rise to the development of a powerful surface analysis technique. This article gives a brief account of the main features of the process, using the Surface Eikonal (SE) approximation as a theoretical tool to analyze the different mechanisms responsible for the quantum interference. The SE approach is a semiclassical method based on the use of the eikonal wave function, which takes into account the coherent superposition of transition amplitudes for different axially channeled trajectories. It has proved to provide a quite good description of experimental diffraction patterns for different collision systems.

  19. Vibronic Raman Scattering at the Quantum Limit of Plasmons

    SciTech Connect

    El-Khoury, Patrick Z.; Hess, Wayne P.

    2014-07-09

    We record sequences of Raman spectra at a plasmonic junction formed by a gold AFM tip in contact with a silver surface coated with 4,4’-dimercaptostilbene (DMS). A 2D correlation analysis of the recorded trajectories reveals that the observable vibrational states can be divided into sub-sets. The first set comprises the totally symmetric vibrations of DMS (ag) that are neither correlated with each other nor to the fluctuating background, which is assigned to the signature of charge transfer plasmons tunneling through DMS. The second set consists of bu vibrations, which are correlated both with each other and with the continuum. Our findings are rationalized on the basis of the charge-transfer theory of Raman scattering, and illustrate how the tunneling plasmons modulate the vibronic coupling term from which the intensities of the bu states are derived.

  20. Directly probing anisotropy in atom-molecule collisions through quantum scattering resonances

    NASA Astrophysics Data System (ADS)

    Klein, Ayelet; Shagam, Yuval; Skomorowski, Wojciech; Żuchowski, Piotr S.; Pawlak, Mariusz; Janssen, Liesbeth M. C.; Moiseyev, Nimrod; van de Meerakker, Sebastiaan Y. T.; van der Avoird, Ad; Koch, Christiane P.; Narevicius, Edvardas

    2017-01-01

    Anisotropy is a fundamental property of particle interactions. It occupies a central role in cold and ultracold molecular processes, where orientation-dependent long-range forces have been studied in ultracold polar molecule collisions. In the cold collisions regime, quantization of the intermolecular degrees of freedom leads to quantum scattering resonances. Although these states have been shown to be sensitive to details of the interaction potential, the effect of anisotropy on quantum resonances has so far eluded experimental observation. Here, we directly measure the anisotropy in atom-molecule interactions via quantum resonances by changing the quantum state of the internal molecular rotor. We observe that a quantum scattering resonance at a collision energy of kB × 270 mK appears in the Penning ionization of molecular hydrogen with metastable helium only if the molecule is rotationally excited. We use state-of-the-art ab initio theory to show that control over the rotational state effectively switches the anisotropy on or off, disentangling the isotropic and anisotropic parts of the interaction.

  1. Scattering theory of topological phases in discrete-time quantum walks

    NASA Astrophysics Data System (ADS)

    Tarasinski, B.; Asbóth, J. K.; Dahlhaus, J. P.

    2014-04-01

    One-dimensional discrete-time quantum walks show a rich spectrum of topological phases that have so far been exclusively analyzed using the Floquet operator in momentum space. In this work, we introduce an alternative approach to topology which is based on the scattering matrix of a quantum walk, adapting concepts from time-independent systems. For quantum walks with gaps in the quasienergy spectrum at 0 and π, we find three different types of topological invariants, which apply dependent on the symmetries of the system. These determine the number of protected boundary states at an interface between two quantum-walk regions. Quantum walks with an unequal number of leftward and rightward shifts per cycle are characterized by the number of perfectly transmitting unidirectional modes they support, which is equal to their nontrivial quasienergy winding. Our classification provides a unified framework that includes all known types of topology in one-dimensional discrete-time quantum walks and is very well suited for the analysis of finite-size and disorder effects. We provide a simple scheme to directly measure the topological invariants in an optical quantum-walk experiment.

  2. Topological edge states and fractional quantum Hall effect from umklapp scattering.

    PubMed

    Klinovaja, Jelena; Loss, Daniel

    2013-11-08

    We study anisotropic lattice strips in the presence of a magnetic field in the quantum Hall effect regime. At specific magnetic fields, causing resonant umklapp scattering, the system is gapped in the bulk and supports chiral edge states in close analogy to topological insulators. In electron gases with stripes, these gaps result in plateaus for the Hall conductivity exactly at the known fillings n/m (both positive integers and m odd) for the integer and fractional quantum Hall effect. For double strips, we find topological phase transitions with phases that support midgap edge states with flat dispersion. The topological effects predicted here could be tested directly in optical lattices.

  3. Resonant raman scattering in complexes of nc-Si/SiO2 quantum dots and oligonucleotides

    NASA Astrophysics Data System (ADS)

    Bairamov, F. B.; Poloskin, E. D.; Kornev, A. A.; Chernev, A. L.; Toporov, V. V.; Dubina, M. V.; Röder, C.; Sprung, C.; Lipsanen, H.; Bairamov, B. Kh.

    2014-11-01

    We report on the functionalization of nanocrystalline nc-Si/SiO2 semiconductor quantum dots (QDs) by short d(20G, 20T) oligonucleotides. The obtained complexes have been studied by Raman spectroscopy techniques with high spectral and spatial resolution. A new phenomenon of multiband resonant light scattering on single oligonucleotide molecules has been discovered, and peculiarities of this effect related to the nonradiative transfer of photoexcitation from nc-Si/SiO2 quantum dots to d(20G, 20T) oligonucleotide molecules have been revealed.

  4. Quantum reactive scattering of ultracold NH(X (3)Σ(-)) radicals in a magnetic trap.

    PubMed

    Janssen, Liesbeth M C; van der Avoird, Ad; Groenenboom, Gerrit C

    2013-02-08

    We investigate the ultracold reaction dynamics of magnetically trapped NH(X (3)Σ(-)) radicals using rigorous quantum scattering calculations involving three coupled potential energy surfaces. We find that the reactive NH+NH cross section is driven by a short-ranged collisional mechanism, and its magnitude is only weakly dependent on magnetic field strength. Unlike most ultracold reactions observed so far, the NH+NH scattering dynamics is nonuniversal. Our results indicate that chemical reactions can cause more trap loss than spin-inelastic NH+NH collisions, making molecular evaporative cooling more difficult than previously anticipated.

  5. Quantum Mechanical Description of Raman Scattering from Molecules in Plasmonic Cavities.

    PubMed

    Schmidt, Mikolaj K; Esteban, Ruben; González-Tudela, Alejandro; Giedke, Geza; Aizpurua, Javier

    2016-06-28

    Plasmon-enhanced Raman scattering can push single-molecule vibrational spectroscopy beyond a regime addressable by classical electrodynamics. We employ a quantum electrodynamics (QED) description of the coherent interaction of plasmons and molecular vibrations that reveal the emergence of nonlinearities in the inelastic response of the system. For realistic situations, we predict the onset of phonon-stimulated Raman scattering and a counterintuitive dependence of the anti-Stokes emission on the frequency of excitation. We further show that this QED framework opens a venue to analyze the correlations of photons emitted from a plasmonic cavity.

  6. Methods for calculating X-ray diffuse scattering from a crystalline medium with spheroidal quantum dots

    NASA Astrophysics Data System (ADS)

    Punegov, V. I.; Sivkov, D. V.

    2015-03-01

    Two independent approaches to calculate the angular distribution of X-ray diffusion scattering from a crystalline medium with spheroidal quantum dots (QDs) have been proposed. The first method is based on the analytical solution involving the multipole expansion of elastic strain fields beyond QDs. The second approach is based on calculations of atomic displacements near QDs by the Green's function method. An analysis of the diffuse scattering intensity distribution in the reciprocal space within these two approaches shows that both methods yield similar results for the chosen models of QD spatial distribution.

  7. Nonequilibrium charge susceptibility and dynamical conductance: identification of scattering processes in quantum transport.

    PubMed

    Ness, H; Dash, L K

    2012-03-23

    We calculate the nonequilibrium charge transport properties of nanoscale junctions in the steady state and extend the concept of charge susceptibility to the nonequilibrium conditions. We show that the nonequilibrium charge susceptibility is related to the nonlinear dynamical conductance. In spectroscopic terms, both contain the same features versus applied bias when charge fluctuation occurs in the corresponding electronic resonances. However, we show that, while the conductance exhibits features at biases corresponding to inelastic scattering with no charge fluctuations, the nonequilibrium charge susceptibility does not. We suggest that measuring both the nonequilibrium conductance and charge susceptibility in the same experiment will permit us to differentiate between different scattering processes in quantum transport.

  8. Scattering of an attractive Bose-Einstein condensate from a barrier: Formation of quantum superposition states

    NASA Astrophysics Data System (ADS)

    Streltsov, Alexej I.; Alon, Ofir E.; Cederbaum, Lorenz S.

    2009-10-01

    Scattering in one dimension of an attractive ultracold bosonic cloud from a barrier can lead to the formation of two nonoverlapping clouds. Once formed, the clouds travel with constant velocity, in general different in magnitude from that of the incoming cloud, and do not disperse. The phenomenon and its mechanism—transformation of kinetic energy to internal energy of the scattered cloud—are obtained by solving the time-dependent many-boson Schrödinger equation. The analysis of the wave function shows that the object formed corresponds to a quantum superposition state of two distinct wave packets traveling through real space.

  9. Broadband calibrated scattering parameters characterization of a superconducting quantum interference device amplifier

    SciTech Connect

    Ranzani, Leonardo; Spietz, Lafe; Aumentado, Jose

    2013-07-08

    In this work, we characterize the 2-port scattering parameters of a superconducting quantum interference device amplifier at {approx}20 mK over several gigahertz of bandwidth. The measurement reference plane is positioned on a 6.25 {Omega} microstrip line situated directly at the input and output of the device by means of a thru-reflect-line cryogenic calibration procedure. From the scattering parameters, we derive the device available power gain, isolation, and input impedance over the 2-8 GHz range. This measurement methodology provides a path towards designing wide-band matching circuits for low impedance superconducting amplifiers operating at dilution refrigerator temperatures.

  10. Probing the Quantum State of a 1D Bose Gas Using Off-Resonant Light Scattering

    SciTech Connect

    Sykes, A. G.; Ballagh, R. J.

    2011-12-30

    We present a theoretical treatment of coherent light scattering from an interacting 1D Bose gas at finite temperatures. We show how this can provide a nondestructive measurement of the atomic system states. The equilibrium states are determined by the temperature and interaction strength, and are characterized by the spatial density-density correlation function. We show how this correlation function is encoded in the angular distribution of the fluctuations of the scattered light intensity, thus providing a sensitive, quantitative probe of the density-density correlation function and therefore the quantum state of the gas.

  11. Scattering problems in the fractional quantum mechanics governed by the 2D space-fractional Schrödinger equation

    SciTech Connect

    Dong, Jianping

    2014-03-15

    The 2D space-fractional Schrödinger equation in the time-independent and time-dependent cases for the scattering problems in the fractional quantum mechanics is studied. We define the Green's functions for the two cases and give the mathematical expression of them in infinite series form and in terms of some special functions. The asymptotic formulas of the Green's functions are also given, and applied to get the approximate wave functions for the fractional quantum scattering problems. These results contain those in the standard (integer) quantum mechanics as special cases, and can be applied to study the complex quantum systems.

  12. Scattering problems in the fractional quantum mechanics governed by the 2D space-fractional Schrödinger equation

    SciTech Connect

    Dong, Jianping

    2014-03-15

    The 2D space-fractional Schrödinger equation in the time-independent and time-dependent cases for the scattering problems in the fractional quantum mechanics is studied. We define the Green's functions for the two cases and give the mathematical expression of them in infinite series form and in terms of some special functions. The asymptotic formulas of the Green's functions are also given, and applied to get the approximate wave functions for the fractional quantum scattering problems. These results contain those in the standard (integer) quantum mechanics as special cases, and can be applied to study the complex quantum systems.

  13. A chaotic cosmology.

    PubMed

    Barrow, J D

    1977-05-12

    An anisotropic, inhomogeneous cosmological model is proposed in which the inhomogeneity is generated by shear fluctuations. This is a sufficient condition for dissipative heating by collisional neutrinos to explain the present large heat content of the universe, S(b o) approximately 10(8), together with its isotropy and comparative homogeneity on large scales when the photons were last scattered. The model does not require the chaotic motions to be arbitrarily truncated on large scales and isotropises early enough with high entropy to ensure the synthesis of light elements with the observed abundancies. A population of black holes which arises in a natural way can also provide the necessary ingredients for a theory of galaxy formation and morphology. The 10(15)-g black holes, predicted by some authors, are not necessarily expected to be a feature of chaotic cosmologies.

  14. Quantum scattering theory in light of an exactly solvable model with rearrangement collisions

    SciTech Connect

    Varma, S.; Sudarshan, E.C.

    1996-04-01

    We present an exactly solvable quantum field theory which allows rearrangement collisions. We solve the model in the relevant sectors and demonstrate the orthonormality and completeness of the solutions, and construct the {ital S}-matrix. In light of the exact solutions constructed, we discuss various issues and assumptions in quantum scattering theory, including the isometry of the M{umlt o}ller wave matrix, the normalization and completeness of asymptotic states, and the nonorthogonality of basis states. We show that these common assertions are not obtained in this model. We suggest a general formalism for scattering theory which overcomes these and other shortcomings and limitations of the existing formalisms in the literature. {copyright} {ital 1996 American Institute of Physics.}

  15. Microstrip superconducting quantum interference device radio-frequency amplifier: Scattering parameters and input coupling

    SciTech Connect

    Kinion, D; Clarke, J

    2008-01-24

    The scattering parameters of an amplifier based on a dc Superconducting QUantum Interference Device (SQUID) are directly measured at 4.2 K. The results can be described using an equivalent circuit model of the fundamental resonance of the microstrip resonator which forms the input of the amplifier. The circuit model is used to determine the series capacitance required for critical coupling of the microstrip to the input circuit.

  16. Interface roughness scattering in p-Si/SiGe asymmetric quantum wells

    NASA Astrophysics Data System (ADS)

    Califano, Marco; Vinh, N. Q.; Phillips, P. J.; Ikonic, Z.; Kelsall, R. W.; Harrison, P.; Pidgeon, C. R.; Murdin, B. N.; Paul, D. J.; Townsend, P.; Zhang, J.; Ross, I. M.; Cullis, A. G.

    2007-03-01

    Of paramount importance in the design of a quantum cascade laser is the ability to engineer carrier lifetimes. These can be strongly influenced by the quality of the interfaces: fluctuations in the well width result in local fluctuations of the carriers' confining potential, which act as a scattering potential. We report the direct determination of non-radiative lifetimes in Si/SiGe asymmetric quantum wells designed to access spatially indirect interwell transitions between heavy-hole states, at photon energies below the optical phonon energy. We show both experimentally and theoretically that, for the interface quality currently achievable experimentally interface roughness will dominate all other scattering processes up to about 200 K. By comparing our results obtained for two different structures we deduce that in this regime both barrier and well widths play an important role in the determination of the carrier lifetime. Comparison with recent data for III-V multiple quantum wells leads us to the conclusion that the dominant role of interface roughness scattering at low temperature found here is a general feature of a wide range of semiconductor heterostructures not limited to IV-IV materials.

  17. Light Scattering Induced Giant Red-Shift in Photoluminescence from CdTe Quantum Dots Encapsulated in Polyacrylamide Gel Nanospheres

    NASA Astrophysics Data System (ADS)

    Garner, Brett W.; Cai, Tong; Hu, Zhibing; Kim, Moon; Neogi, Arup

    2009-07-01

    The photoluminescence emission from CdTe quantum dots embedded in hydrogel nanospheres based on poly(N-isopropylacrylamide) (PNIPAM) polymer is observed to be modified by the random light scattering within the colloidal medium. Photoluminescence emission from CdTe quantum dots of various size has been observed making the gel fluorescent. The optical properties of the quantum dots entrapped within the gel microspheres can be modified due to change in refractive index, volume density of the surrounding hydrogel medium. A red-shift of ˜100 nm has been observed from quantum dots emitting in the green wavelength region as the cell length is increased. This shift is due to secondary scattering and energy transfer induced by the larger scattering cross-section within the medium which results in a re-excitation of larger sized quantum dots.

  18. Raman scattering from confined phonons in GaAs/AlGaAs quantum wires

    NASA Astrophysics Data System (ADS)

    Bairamov, B. H.; Aydinli, A.; Tanatar, B.; Güven, K.; Gurevich, S.; Mel'tser, B. Ya.; Ivanov, S. V.; Kop'ev, P. S.; Smirnitskii, V. B.; Timofeev, F. N.

    1998-10-01

    We report on photoluminescence and Raman scattering performed at low temperature (T = 10 K) on GaAs/Al0.3Ga0.7As quantum-well wires with effective wire widths ofL = 100.0 and 10.9 nm prepared by molecular beam epitaxial growth followed by holographic patterning, reactive ion etching, and anodic thinning. We find evidence for the existence of longitudinal optical phonon modes confined to the GaAs quantum wire. The observed frequency at οL10 = 285.6 cm-1forL = 11.0 nm is in good agreement with that calculated on the basis of the dispersive dielectric continuum theory of Enderleinas applied to the GaAs/Al0.3Ga0.7As system. Our results indicate the high crystalline quality of the quantum-well wires fabricated using these techniques.

  19. Recent Advances in Development and Applications of the Mixed Quantum/Classical Theory for Inelastic Scattering.

    PubMed

    Babikov, Dmitri; Semenov, Alexander

    2016-01-28

    A mixed quantum/classical approach to inelastic scattering (MQCT) is developed in which the relative motion of two collision partners is treated classically, and the rotational and vibrational motion of each molecule is treated quantum mechanically. The cases of molecule + atom and molecule + molecule are considered including diatomics, symmetric-top rotors, and asymmetric-top rotor molecules. Phase information is taken into consideration, permitting calculations of elastic and inelastic, total and differential cross sections for excitation and quenching. The method is numerically efficient and intrinsically parallel. The scaling law of MQCT is favorable, which enables calculations at high collision energies and for complicated molecules. Benchmark studies are carried out for several quite different molecular systems (N2 + Na, H2 + He, CO + He, CH3 + He, H2O + He, HCOOCH3 + He, and H2 + N2) in a broad range of collision energies, which demonstrates that MQCT is a viable approach to inelastic scattering. At higher collision energies it can confidently replace the computationally expensive full-quantum calculations. At low collision energies and for low-mass systems results of MQCT are less accurate but are still reasonable. A proposal is made for blending MQCT calculations at higher energies with full-quantum calculations at low energies.

  20. Quantum Critical Quasiparticle Scattering within the Superconducting State of CeCoIn5

    DOE PAGES

    Paglione, Johnpierre; Tanatar, M. A.; Reid, J.-Ph.; ...

    2016-06-27

    The thermal conductivity κ of the heavy-fermion metal CeCoIn5 was measured in the normal and superconducting states as a function of temperature T and magnetic field H, for a current and field parallel to the [100] direction. Inside the superconducting state, when the field is lower than the upper critical field Hc2, κ/T is found to increase as T→0, just as in a metal and in contrast to the behavior of all known superconductors. This is due to unpaired electrons on part of the Fermi surface, which dominate the transport above a certain field. The evolution of κ/T with fieldmore » reveals that the electron-electron scattering (or transport mass m*) of those unpaired electrons diverges as H→Hc2 from below, in the same way that it does in the normal state as H→Hc2 from above. This shows that the unpaired electrons sense the proximity of the field-tuned quantum critical point of CeCoIn5 at H*=Hc2 even from inside the superconducting state. In conclusion, the fact that the quantum critical scattering of the unpaired electrons is much weaker than the average scattering of all electrons in the normal state reveals a k-space correlation between the strength of pairing and the strength of scattering, pointing to a common mechanism, presumably antiferromagnetic fluctuations.« less

  1. Scattering-induced quantum correlation in electronic waveguides with static magnetic impurities

    NASA Astrophysics Data System (ADS)

    Ghanbari-Adivi, E.; Soltani, M.; Alami, Z.; Sheikhali, M.

    2016-10-01

    Entanglement generation due to low-energy scattering of the transporting electrons in an electronic waveguide by a quantum dot magnetic impurity is theoretically investigated. The transverse confining potential of the waveguide is considered as a two-dimensional harmonic potential, and the interaction of the electron with the impurity is described by a zero-range pseudopotential modulated by an Ising or a Heisenberg spin interaction. Our calculation shows that the scattering process leads to creation of a considerable amount of entanglement in the state of the reflected and transmitted electrons. The situation is extended to the scattering of the electrons by two well-separated magnetic impurities localized on the nanowire axis. It is shown that the scattering process causes the magnetic impurities embedded in the nanowire to share their quantum information; subsequently, they can be entangled by spin interaction with the injected electron. The created entanglement between the impurities is calculated and discussed. It is shown that the exact three-dimensional problem can be approximated as a one-dimensional problem under certain circumstances. The approximate results are compared to exact calculations and discussed.

  2. Quantum Critical Quasiparticle Scattering within the Superconducting State of CeCoIn5

    NASA Astrophysics Data System (ADS)

    Paglione, Johnpierre; Tanatar, M. A.; Reid, J.-Ph.; Shakeripour, H.; Petrovic, C.; Taillefer, Louis

    2016-07-01

    The thermal conductivity κ of the heavy-fermion metal CeCoIn5 was measured in the normal and superconducting states as a function of temperature T and magnetic field H , for a current and field parallel to the [100] direction. Inside the superconducting state, when the field is lower than the upper critical field Hc 2, κ /T is found to increase as T →0 , just as in a metal and in contrast to the behavior of all known superconductors. This is due to unpaired electrons on part of the Fermi surface, which dominate the transport above a certain field. The evolution of κ /T with field reveals that the electron-electron scattering (or transport mass m⋆) of those unpaired electrons diverges as H →Hc 2 from below, in the same way that it does in the normal state as H →Hc 2 from above. This shows that the unpaired electrons sense the proximity of the field-tuned quantum critical point of CeCoIn5 at H⋆=Hc 2 even from inside the superconducting state. The fact that the quantum critical scattering of the unpaired electrons is much weaker than the average scattering of all electrons in the normal state reveals a k -space correlation between the strength of pairing and the strength of scattering, pointing to a common mechanism, presumably antiferromagnetic fluctuations.

  3. Unified quantum theory of elastic and inelastic atomic scattering from a physisorbed monolayer solid

    NASA Astrophysics Data System (ADS)

    Bruch, L. W.; Hansen, F. Y.; Dammann, B.

    2017-06-01

    A unified quantum theory of the elastic and inelastic scattering of low energy He atoms by a physisorbed monolayer solid in the one-phonon approximation is given. It uses a time-dependent wave packet with phonon creation and annihilation components and has a self-consistent feedback between the wave functions for elastic and inelastic scattered atoms. An attenuation of diffraction scattering by inelastic processes thus is inherent in the theory. The atomic motion and monolayer vibrations in the harmonic approximation are treated quantum mechanically and unitarity is preserved. The evaluation of specific one-phonon events includes contributions from diffuse inelastic scattering in other phonon modes. Effects of thermally excited phonons are included using a mean field approximation. The theory is applied to an incommensurate Xe/Pt(111) monolayer (incident energy Ei=4 -16 meV), a commensurate Xe/graphite monolayer (Ei≃64 meV), and an incommensurate Xe/Cu(001) monolayer (Ei≃8 meV). The monolayers are very corrugated targets and there are transient closed diffraction and inelastic channels in the calculations. In many cases, the energy gain events have strengths comparable to the energy loss events.

  4. Density matrix modeling of quantum cascade lasers without an artificially localized basis: A generalized scattering approach

    NASA Astrophysics Data System (ADS)

    Pan, Andrew; Burnett, Benjamin A.; Chui, Chi On; Williams, Benjamin S.

    2017-08-01

    We derive a density matrix (DM) theory for quantum cascade lasers (QCLs) that describes the influence of scattering on coherences through a generalized scattering superoperator. The theory enables quantitative modeling of QCLs, including localization and tunneling effects, using the well-defined energy eigenstates rather than the ad hoc localized basis states required by most previous DM models. Our microscopic approach to scattering also eliminates the need for phenomenological transition or dephasing rates. We discuss the physical interpretation and numerical implementation of the theory, presenting sets of both energy-resolved and thermally averaged equations, which can be used for detailed or compact device modeling. We illustrate the theory's applications by simulating a high performance resonant-phonon terahertz (THz) QCL design, which cannot be easily or accurately modeled using conventional DM methods. We show that the theory's inclusion of coherences is crucial for describing localization and tunneling effects consistent with experiment.

  5. Neutron scattering in the proximate quantum spin liquid α-RuCl3

    NASA Astrophysics Data System (ADS)

    Banerjee, Arnab; Yan, Jiaqiang; Knolle, Johannes; Bridges, Craig A.; Stone, Matthew B.; Lumsden, Mark D.; Mandrus, David G.; Tennant, David A.; Moessner, Roderich; Nagler, Stephen E.

    2017-06-01

    The Kitaev quantum spin liquid (KQSL) is an exotic emergent state of matter exhibiting Majorana fermion and gauge flux excitations. The magnetic insulator α-RuCl3 is thought to realize a proximate KQSL. We used neutron scattering on single crystals of α-RuCl3 to reconstruct dynamical correlations in energy-momentum space. We discovered highly unusual signals, including a column of scattering over a large energy interval around the Brillouin zone center, which is very stable with temperature. This finding is consistent with scattering from the Majorana excitations of a KQSL. Other, more delicate experimental features can be transparently associated with perturbations to an ideal model. Our results encourage further study of this prototypical material and may open a window into investigating emergent magnetic Majorana fermions in correlated materials.

  6. Electron states and electron Raman scattering in a semiconductor step-quantum well wire

    NASA Astrophysics Data System (ADS)

    Betancourt-Riera, Ri.; Betancourt-Riera, Re.; Munguía-Rodríguez, M.

    2017-06-01

    The differential cross-section for an electron Raman scattering process in a semiconductor GaAs / AlGaAs step-quantum well wire is calculated and expressions for the electron states are presented. The system is modeled by considering T = 0 K and also by a single parabolic conduction band, which is split into a sub-band system due to confinement. The net Raman gain for an electron Raman scattering process is obtained. Also, the emission spectra for several scattering configurations are discussed, and the interpretation of the singularities found in the spectra is given. The results obtained in this study are compared with those obtained for other structures, and so it has been demonstrated that the wire shows greater efficiency.

  7. Dissipation in deforming chaotic billiards

    NASA Astrophysics Data System (ADS)

    Barnett, Alexander Harvey

    Chaotic billiards (hard-walled cavities) in two or more dimensions are paradigm systems in the fields of classical and quantum chaos. We study the dissipation (irreversible heating) rate in such billiard systems due to general shape deformations which are periodic in time. We are motivated by older studies of one-body nuclear dissipation and by anticipated mesoscopic applications. We review the classical and quantum linear response theories of dissipation rate and demonstrate their correspondence in the semiclassical limit. In both pictures, heating is a result of stochastic energy spreading. The heating rate can be expressed as a frequency-dependent friction coefficient μ(ω), which depends on billiard shape and deformation choice. We show that there is a special class of deformations for which μ vanishes as like a power law in the small- ω limit. Namely, for deformations which cause translations and dilations μ ~ ω4 whereas for those which cause rotations μ ~ ω2. This contrasts the generic case for which μ ~ ω4 We show how a systematic treatment of this special class leads to an improved version of the `wall formula' estimate for μ(0). We show that the special nature of dilation (a new result) is semiclassically equivalent to a quasi- orthogonality relation between the (undeformed) billiard quantum eigenstates on the boundary. This quasi- orthogonality forms the heart of a `scaling method' for the numerical calculation of quantum eigenstates, invented recently by Vergini and Saraceno. The scaling method is orders of magnitude more efficient than any other known billiard quantization method, however an adequate explanation for its success has been lacking until now. We explain the scaling method, its errors, and applications. We also present improvements to Heller's plane wave method. Two smaller projects conclude the thesis. Firstly, we give a new formalism for quantum point contact (QPC) conductance in terms of scattering cross-section in the half

  8. Heralded quantum repeater based on the scattering of photons off single emitters using parametric down-conversion source

    PubMed Central

    Song, Guo-Zhu; Wu, Fang-Zhou; Zhang, Mei; Yang, Guo-Jian

    2016-01-01

    Quantum repeater is the key element in quantum communication and quantum information processing. Here, we investigate the possibility of achieving a heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides. We design the compact quantum circuits for nonlocal entanglement generation, entanglement swapping, and entanglement purification, and discuss the feasibility of our protocols with current experimental technology. In our scheme, we use a parametric down-conversion source instead of ideal single-photon sources to realize the heralded quantum repeater. Moreover, our protocols can turn faulty events into the detection of photon polarization, and the fidelity can reach 100% in principle. Our scheme is attractive and scalable, since it can be realized with artificial solid-state quantum systems. With developed experimental technique on controlling emitter-waveguide systems, the repeater may be very useful in long-distance quantum communication. PMID:27350159

  9. h/2 e Oscillations and negative magneto-resistance in ballistic chaotic Aharonov-Bohm billiards

    NASA Astrophysics Data System (ADS)

    Kawabata, Shiro; Nakamura, Katsuhiro

    1998-07-01

    We study the quantum-interference effect for the single ballistic Aharonov-Bohm (AB) billiard. The reflection coefficient δRD is calculated by use of semi-classical scattering theory. We find: (i) h/2 e Altshuler-Aronov-Spivak (AAS) oscillation is experimentally observable in both ballistic and diffusive systems; (ii) a magnetic field in the conducting region leads to "negative magneto-resistance" and "dampening of the AAS oscillation amplitude". Chaotic and regular AB billiards have turned out to lead to qualitatively different semi-classical formulas for conductance with their behavior determined only by knowledge regarding the underlying classical scattering.

  10. Optical absorption in highly strained Ge/SiGe quantum wells: The role of Γ→ Δ scattering

    NASA Astrophysics Data System (ADS)

    Lever, L.; Ikonić, Z.; Valavanis, A.; Kelsall, R. W.; Myronov, M.; Leadley, D. R.; Hu, Y.; Owens, N.; Gardes, F. Y.; Reed, G. T.

    2012-12-01

    We report the observation of the quantum-confined Stark effect in Ge/SiGe multiple quantum well heterostructures grown on Si0.22Ge0.78 virtual substrates. The large compressive strain in the Ge quantum well layers caused by the lattice mismatch with the virtual substrate results in a blue shift of the direct absorption edge, as well as a reduction in the Γ-valley scattering lifetime because of strain-induced splittings of the conduction band valleys. We investigate theoretically the Γ-valley carrier lifetimes by evaluating the Γ →L and Γ →Δ scattering rates in strained Ge/SiGe semiconductor heterostructures. These scattering rates are used to determine the lifetime broadening of excitonic peaks and the indirect absorption in simulated absorption spectra, which are compared with measured absorption spectra for quantum well structures with systematically varied dimensions. We find that Γ →Δ scattering is significant in compressively strained Ge quantum wells and that the Γ-valley electron lifetime is less than 50 fs in the highly strained structures reported here, where Γ →Δ scattering accounted for approximately half of the total scattering rate.

  11. Fully quantum state-resolved inelastic scattering of NO(X) + Kr: Differential cross sections and product rotational alignment

    SciTech Connect

    Brouard, M. Chadwick, H.; Gordon, S. D. S.; Hornung, B.; Nichols, B.; Kłos, J.; Aoiz, F. J.; Stolte, S.

    2014-10-28

    Fully quantum state selected and resolved inelastic scattering of NO(X) by krypton has been investigated. Initial Λ-doublet state selection is achieved using an inhomogeneous hexapole electric field. Differential cross sections and even-moment polarization dependent differential cross sections have been obtained at a collision energy of 514 cm{sup −1} for both spin-orbit and parity conserving and changing collisions. Experimental results are compared with those obtained from quantum scattering calculations and are shown to be in very good agreement. Hard shell quantum scattering calculations are also performed to determine the effects of the different parts of the potential on the scattering dynamics. Comparisons are also made with the NO(X) + Ar system.

  12. Fully quantum state-resolved inelastic scattering of NO(X) + Kr: differential cross sections and product rotational alignment.

    PubMed

    Brouard, M; Chadwick, H; Gordon, S D S; Hornung, B; Nichols, B; Kłos, J; Aoiz, F J; Stolte, S

    2014-10-28

    Fully quantum state selected and resolved inelastic scattering of NO(X) by krypton has been investigated. Initial Λ-doublet state selection is achieved using an inhomogeneous hexapole electric field. Differential cross sections and even-moment polarization dependent differential cross sections have been obtained at a collision energy of 514 cm(-1) for both spin-orbit and parity conserving and changing collisions. Experimental results are compared with those obtained from quantum scattering calculations and are shown to be in very good agreement. Hard shell quantum scattering calculations are also performed to determine the effects of the different parts of the potential on the scattering dynamics. Comparisons are also made with the NO(X) + Ar system.

  13. Scattering mechanisms in shallow undoped Si/SiGe quantum wells

    NASA Astrophysics Data System (ADS)

    Laroche, D.; Huang, S.-H.; Nielsen, E.; Chuang, Y.; Li, J.-Y.; Liu, C. W.; Lu, T. M.

    2015-10-01

    We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ˜ 100 nm to ˜ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ ∝ nα, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ˜ 2.3. At the highest achievable densities in the quantum wells buried at intermediate depth, an exponent α ˜ 5 is observed. We propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.

  14. Scattering of a vortex pair by a single quantum vortex in a Bose-Einstein condensate

    NASA Astrophysics Data System (ADS)

    Smirnov, L. A.; Smirnov, A. I.; Mironov, V. A.

    2016-01-01

    We analyze the scattering of vortex pairs (the particular case of 2D dark solitons) by a single quantum vortex in a Bose-Einstein condensate with repulsive interaction between atoms. For this purpose, an asymptotic theory describing the dynamics of such 2D soliton-like formations in an arbitrary smoothly nonuniform flow of a ultracold Bose gas is developed. Disregarding the radiation loss associated with acoustic wave emission, we demonstrate that vortex-antivortex pairs can be put in correspondence with quasiparticles, and their behavior can be described by canonical Hamilton equations. For these equations, we determine the integrals of motion that can be used to classify various regimes of scattering of vortex pairs by a single quantum vortex. Theoretical constructions are confirmed by numerical calculations performed directly in terms of the Gross-Pitaevskii equation. We propose a method for estimating the radiation loss in a collision of a soliton-like formation with a phase singularity. It is shown by direct numerical simulation that under certain conditions, the interaction of vortex pairs with a core of a single quantum vortex is accompanied by quite intense acoustic wave emission; as a result, the conditions for applicability of the asymptotic theory developed here are violated. In particular, it is visually demonstrated by a specific example how radiation losses lead to a transformation of a vortex-antivortex pair into a vortex-free 2D dark soliton (i.e., to the annihilation of phase singularities).

  15. Scattering of a vortex pair by a single quantum vortex in a Bose–Einstein condensate

    SciTech Connect

    Smirnov, L. A. Smirnov, A. I. Mironov, V. A.

    2016-01-15

    We analyze the scattering of vortex pairs (the particular case of 2D dark solitons) by a single quantum vortex in a Bose–Einstein condensate with repulsive interaction between atoms. For this purpose, an asymptotic theory describing the dynamics of such 2D soliton-like formations in an arbitrary smoothly nonuniform flow of a ultracold Bose gas is developed. Disregarding the radiation loss associated with acoustic wave emission, we demonstrate that vortex–antivortex pairs can be put in correspondence with quasiparticles, and their behavior can be described by canonical Hamilton equations. For these equations, we determine the integrals of motion that can be used to classify various regimes of scattering of vortex pairs by a single quantum vortex. Theoretical constructions are confirmed by numerical calculations performed directly in terms of the Gross–Pitaevskii equation. We propose a method for estimating the radiation loss in a collision of a soliton-like formation with a phase singularity. It is shown by direct numerical simulation that under certain conditions, the interaction of vortex pairs with a core of a single quantum vortex is accompanied by quite intense acoustic wave emission; as a result, the conditions for applicability of the asymptotic theory developed here are violated. In particular, it is visually demonstrated by a specific example how radiation losses lead to a transformation of a vortex–antivortex pair into a vortex-free 2D dark soliton (i.e., to the annihilation of phase singularities).

  16. Scattering mechanisms in shallow undoped Si/SiGe quantum wells

    DOE PAGES

    Laroche, Dominique; Huang, S. -H.; Nielsen, Erik; ...

    2015-10-07

    We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ~ 100 nm to ~ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ ∝ nα, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ~ 2.3. At the highest achievable densities in the quantum wellsmore » buried at intermediate depth, an exponent α ~ 5 is observed. Lastly, we propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.« less

  17. Scattering mechanisms in shallow undoped Si/SiGe quantum wells

    SciTech Connect

    Laroche, Dominique; Huang, S. -H.; Nielsen, Erik; Chuang, Y.; Li, J. -Y.; Liu, C. W.; Lu, Tzu -Ming

    2015-10-07

    We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ~ 100 nm to ~ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ ∝ nα, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ~ 2.3. At the highest achievable densities in the quantum wells buried at intermediate depth, an exponent α ~ 5 is observed. Lastly, we propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.

  18. Scattering mechanisms in shallow undoped Si/SiGe quantum wells

    SciTech Connect

    Laroche, D.; Nielsen, E.; Lu, T. M.; Huang, S.-H.; Chuang, Y.; Li, J.-Y. Liu, C. W.

    2015-10-15

    We report the magneto-transport study and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with depth ranging from ∼ 100 nm to ∼ 10 nm away from the heterostructure surface. The peak mobility increases with depth, suggesting that charge centers near the oxide/semiconductor interface are the dominant scattering source. The power-law exponent of the electron mobility versus density curve, μ ∝ n{sup α}, is extracted as a function of the depth of the Si quantum well. At intermediate densities, the power-law dependence is characterized by α ∼ 2.3. At the highest achievable densities in the quantum wells buried at intermediate depth, an exponent α ∼ 5 is observed. We propose and show by simulations that this increase in the mobility dependence on the density can be explained by a non-equilibrium model where trapped electrons smooth out the potential landscape seen by the two-dimensional electron gas.

  19. Resonance states and beating pattern induced by quantum impurity scattering in Weyl/Dirac semimetals

    NASA Astrophysics Data System (ADS)

    Zheng, Shi-Han; Wang, Rui-Qiang; Zhong, Min; Duan, Hou-Jian

    2016-11-01

    Currently, Weyl semimetals (WSMs) are drawing great interest as a new topological nontrivial phase. When most of the studies concentrated on the clean host WSMs, it is expected that the dirty WSM system would present rich physics due to the interplay between the WSM states and the impurities embedded inside these materials. We investigate theoretically the change of local density of states in three-dimensional Dirac and Weyl bulk states scattered off a quantum impurity. It is found that the quantum impurity scattering can create nodal resonance and Kondo peak/dip in the host bulk states, remarkably modifying the pristine spectrum structure. Moreover, the joint effect of the separation of Weyl nodes and the Friedel interference oscillation causes the unique battering feature. We in detail an- alyze the different contribution from the intra- and inter-node scattering processes and present various scenarios as a consequence of competition between them. Importantly, these behaviors are sensitive significantly to the displacement of Weyl nodes in energy or momentum, from which the distinctive fingerprints can be extracted to identify various semimetal materials experimentally by employing the scanning tunneling microscope.

  20. Resonance states and beating pattern induced by quantum impurity scattering in Weyl/Dirac semimetals

    PubMed Central

    Zheng, Shi-Han; Wang, Rui-Qiang; Zhong, Min; Duan, Hou-Jian

    2016-01-01

    Currently, Weyl semimetals (WSMs) are drawing great interest as a new topological nontrivial phase. When most of the studies concentrated on the clean host WSMs, it is expected that the dirty WSM system would present rich physics due to the interplay between the WSM states and the impurities embedded inside these materials. We investigate theoretically the change of local density of states in three-dimensional Dirac and Weyl bulk states scattered off a quantum impurity. It is found that the quantum impurity scattering can create nodal resonance and Kondo peak/dip in the host bulk states, remarkably modifying the pristine spectrum structure. Moreover, the joint effect of the separation of Weyl nodes and the Friedel interference oscillation causes the unique battering feature. We in detail an- alyze the different contribution from the intra- and inter-node scattering processes and present various scenarios as a consequence of competition between them. Importantly, these behaviors are sensitive significantly to the displacement of Weyl nodes in energy or momentum, from which the distinctive fingerprints can be extracted to identify various semimetal materials experimentally by employing the scanning tunneling microscope. PMID:27808262

  1. Quantum conductance fluctuations and classical short-path dynamics

    SciTech Connect

    Ishio, H.; Burgdoerfer, J. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6377 )

    1995-01-15

    We present numerical results for ballistic-electron quantum transport through weakly open integrable circle and chaotic stadium billiards. The geometry of the pair of conducting leads is chosen in accordance with recent experiments for semiconductor microstructures [Marcus [ital et] [ital al]., Phys. Rev. Lett. [bold 69], 506 (1992)]. The conductance as a function of the Fermi wave number displays characteristic noisy fluctuations for both the integrable and the chaotic systems. We show that structures in the conductance autocorrelation function as a function of the Fermi wave number are related to short-length classical orbits. This correspondence permits incorporation of effects of phase decoherence due to incoherent scattering into the quantum calculation.

  2. Quantum random bit generation using energy fluctuations in stimulated Raman scattering.

    PubMed

    Bustard, Philip J; England, Duncan G; Nunn, Josh; Moffatt, Doug; Spanner, Michael; Lausten, Rune; Sussman, Benjamin J

    2013-12-02

    Random number sequences are a critical resource in modern information processing systems, with applications in cryptography, numerical simulation, and data sampling. We introduce a quantum random number generator based on the measurement of pulse energy quantum fluctuations in Stokes light generated by spontaneously-initiated stimulated Raman scattering. Bright Stokes pulse energy fluctuations up to five times the mean energy are measured with fast photodiodes and converted to unbiased random binary strings. Since the pulse energy is a continuous variable, multiple bits can be extracted from a single measurement. Our approach can be generalized to a wide range of Raman active materials; here we demonstrate a prototype using the optical phonon line in bulk diamond.

  3. Positron scattering from hydrogen atom in dense quantum plasmas: Positronium formation in Rydberg states

    NASA Astrophysics Data System (ADS)

    Rej, Pramit; Ghoshal, Arijit

    2017-04-01

    Effects of dense quantum plasmas on positronium (Ps) formation in an arbitrary nlm-state in the scattering of positrons from the ground state of hydrogen atoms have been investigated within the framework of a distorted wave theory that incorporates the effect of screened dipole polarization potential. The interaction of charged particles in plasmas has been modeled by a modified Debye-Huckel potential. Effects of plasma screening on the structures of differential and total cross sections have been explored for various incident positron energies in the range 20-300 eV. For the free atomic case, our results are in conformity with the existing results available in the literature. It has been found that for small screening effects, the cross section presents the oscillatory behaviour. To the best of our knowledge, this is the first attempt to estimate the screening effects on the differential and total cross sections for Ps formation in Rydberg states in dense quantum plasmas.

  4. Factorizations in special relativity and quantum scattering on the line II

    NASA Astrophysics Data System (ADS)

    Brezov, Danail S.; Mladenova, Clementina D.; Mladenov, Ivaïlo M.

    2016-12-01

    The present paper may be regarded as a continuation of both [1] and [2]: we discuss the same physical context as in the former, while applying a specific decomposition technique initially proposed in the latter. The method used in [1], however, is completely different (based on repetitive conjugation) and has more in common with the familiar Wigner decomposition [3]. Here we obtain in a dynamical manner a compact two-factor decomposition, which in the Euclidean case allows for convenient parametrizations in rigid body kinematics and quantum-mechanical angular momenta. Applied to the group Spin(2, 1) ≅ SL(2, ℝ), this technique yields numerous applications in hyperbolic geometry and 2 + 1 dimensional special relativity. However, we choose to illustrate it with a particular problem arising in quantum mechanical scattering theory. The extension to SO(3, 1) and SO(2, 2) is discussed as well and numerical examples are provided in the former case.

  5. Applications of Quantum Theory of Atomic and Molecular Scattering to Problems in Hypersonic Flow

    NASA Technical Reports Server (NTRS)

    Malik, F. Bary

    1995-01-01

    The general status of a grant to investigate the applications of quantum theory in atomic and molecular scattering problems in hypersonic flow is summarized. Abstracts of five articles and eleven full-length articles published or submitted for publication are included as attachments. The following topics are addressed in these articles: fragmentation of heavy ions (HZE particles); parameterization of absorption cross sections; light ion transport; emission of light fragments as an indicator of equilibrated populations; quantum mechanical, optical model methods for calculating cross sections for particle fragmentation by hydrogen; evaluation of NUCFRG2, the semi-empirical nuclear fragmentation database; investigation of the single- and double-ionization of He by proton and anti-proton collisions; Bose-Einstein condensation of nuclei; and a liquid drop model in HZE particle fragmentation by hydrogen.

  6. Quantum description of high-frequency Raman scattering from pairs of argon atoms

    NASA Astrophysics Data System (ADS)

    Chrysos, Michael; Gaye, Omar; LeDuff, Yves

    1996-02-01

    The quantum theory is applied for the accurate computation of high-frequency (up to 0953-4075/29/3/022/img1) spectral intensities in Ar - Ar collision-induced light scattering (CILS) processes at room temperature. Numerically, this becomes possible by means of the two-point Fox - Goodwin integrator, propagating on a grid the ratio of the wavefunction at adjacent points. Wavefunctions are normalized in a handy way which is based on the notion of the local wavenumber. Various potentials and anisotropy models are tested and compared. For frequencies exceeding 0953-4075/29/3/022/img2 our results show significant deviations as compared to the theoretical predictions of the classical theory. When the self-consistent field (SCF) anisotropy is applied, a clear tendency of the quantum calculation to approach recent experimental data is observed.

  7. Quantum interference by localized scattering waves of gapless helical modes in narrow strips of topological insulators

    NASA Astrophysics Data System (ADS)

    Takagaki, Y.

    2016-09-01

    Quantum interference in scattering from a potential offset is investigated in narrow strips of two-dimensional systems described by the Bernevig-Hughes-Zhang Hamiltonian. Attention is focused on the situations where the transmission in the scattering region takes place around the Dirac point of topological insulators when the hybridization energy gap is eliminated by utilizing transverse interference. Apart from conventional periodic transmission modulation that takes place when the length of the potential offset region is varied, resonant disappearances of reflection occur for short potential offsets. The anomalous resonance appears not only for the four-band Hamiltonian but also for the two-band Hamiltonian, manifesting the generality of the phenomenon. Evanescent-like waves excited around the potential steps are indicated to be responsible for the anomalous behavior. The interference states can couple with each other and generic reduction in the amplitude of transmission modulation occurs upon coupling with the periodic modulation.

  8. Inverse Scattering and Local Observable Algebras in Integrable Quantum Field Theories

    NASA Astrophysics Data System (ADS)

    Alazzawi, Sabina; Lechner, Gandalf

    2017-09-01

    We present a solution method for the inverse scattering problem for integrable two-dimensional relativistic quantum field theories, specified in terms of a given massive single particle spectrum and a factorizing S-matrix. An arbitrary number of massive particles transforming under an arbitrary compact global gauge group is allowed, thereby generalizing previous constructions of scalar theories. The two-particle S-matrix S is assumed to be an analytic solution of the Yang-Baxter equation with standard properties, including unitarity, TCP invariance, and crossing symmetry. Using methods from operator algebras and complex analysis, we identify sufficient criteria on S that imply the solution of the inverse scattering problem. These conditions are shown to be satisfied in particular by so-called diagonal S-matrices, but presumably also in other cases such as the O( N)-invariant nonlinear {σ}-models.

  9. Limits to coherent scattering and photon coalescence from solid-state quantum emitters

    NASA Astrophysics Data System (ADS)

    Iles-Smith, Jake; McCutcheon, Dara P. S.; Mørk, Jesper; Nazir, Ahsan

    2017-05-01

    The desire to produce high-quality single photons for applications in quantum information science has lead to renewed interest in exploring solid-state emitters in the weak excitation regime. Under these conditions it is expected that photons are coherently scattered, and so benefit from a substantial suppression of detrimental interactions between the source and its surrounding environment. Nevertheless, we demonstrate here that this reasoning is incomplete, as phonon interactions continue to play a crucial role in determining solid-state emission characteristics even for very weak excitation. We find that the sideband resulting from non-Markovian relaxation of the phonon environment is excitation strength independent. It thus leads to an intrinsic limit to the fraction of coherently scattered light and to the visibility of two-photon coalescence at weak driving, both of which are absent for atomic systems or within simpler Markovian treatments.

  10. Effects of phonon scattering on the magneto-conductance in single and double quantum wires

    NASA Astrophysics Data System (ADS)

    Huang, D.; Lyo, S. K.

    2003-03-01

    We present an exact numerical formalism for the solution of the Boltzmann equation dominated by elastic (e.g., interface-roughness) and phonon scattering in a quasi-one-dimensional system. The result is employed to study the temperature-dependent conductance of a single and tunnel-coupled double quantum wells (DQWs) as a function of a perpendicular magnetic field. According to recent studies, the zero-temperature conductance is enhanced dramatically as a function of the field when the Fermi level lies inside the anticrossing gap of the DQWs. [S. K. Lyo, J. Phys.-Condens. Matter 8, L703 (1996), D. Huang and S. K. Lyo, ibid, 12, 3383 (2000), S. V. Korepov and M. A. Liberman, Phys. Rev. B 60, 13770 (1999)] Our results show that phonon scattering modifies the conductance and its enhancement significantly at temperatures corresponding to the gap energy or the sublevel separation or higher.

  11. Barrier scattering with complex-valued quantum trajectories: Taxonomy and analysis of isochrones

    SciTech Connect

    David, Julianne K.; Wyatt, Robert E.

    2008-03-07

    To facilitate the search for isochrones when using complex-valued trajectory methods for quantum barrier scattering calculations, the structure and shape of isochrones in the complex plane were studied. Isochrone segments were categorized based on their distinguishing features, which are shared by each situation studied: High and low energy wave packets, scattering from both thick and thin Gaussian and Eckart barriers of varying height. The characteristic shape of the isochrone is a trifurcated system: Trajectories that transmit the barrier are launched from the lower branch (T), while the middle and upper branches form the segments for reflected trajectories (F and B). In addition, a model is presented for the curved section of the lower branch (from which transmitted trajectories are launched), and important features of the complex extension of the initial wave packet are identified.

  12. Imaging quantum stereodynamics through Fraunhofer scattering of NO radicals with rare-gas atoms

    NASA Astrophysics Data System (ADS)

    Onvlee, Jolijn; Gordon, Sean D. S.; Vogels, Sjoerd N.; Auth, Thomas; Karman, Tijs; Nichols, Bethan; van der Avoird, Ad; Groenenboom, Gerrit C.; Brouard, Mark; van de Meerakker, Sebastiaan Y. T.

    2016-10-01

    Stereodynamics describes how the vector properties of molecules, such as the directions in which they move and the axes about which they rotate, affect the probabilities (or cross-sections) of specific processes or transitions that occur on collision. The main aspects of stereodynamics in inelastic atom-molecule collisions can often be understood from classical considerations, in which the particles are represented by billiard-ball-like hard objects. In a quantum picture, however, the collision is described in terms of matter waves, which can also scatter into the region of the geometrical shadow of the object and reveal detailed information on the pure quantum-mechanical contribution to the stereodynamics. Here we present measurements of irregular diffraction patterns for NO radicals colliding with rare-gas atoms that can be explained by the analytical Fraunhofer model. They reveal a hitherto overlooked dependence on (or 'propensity rule' for) the magnetic quantum number m of the molecules, and a previously unrecognized type of quantum stereodynamics that has no classical analogue or interpretation.

  13. Single quantum dot controls a plasmonic cavity’s scattering and anisotropy

    PubMed Central

    Hartsfield, Thomas; Chang, Wei-Shun; Yang, Seung-Cheol; Ma, Tzuhsuan; Shi, Jinwei; Sun, Liuyang; Shvets, Gennady; Link, Stephan; Li, Xiaoqin

    2015-01-01

    Plasmonic cavities represent a promising platform for controlling light–matter interaction due to their exceptionally small mode volume and high density of photonic states. Using plasmonic cavities for enhancing light’s coupling to individual two-level systems, such as single semiconductor quantum dots (QD), is particularly desirable for exploring cavity quantum electrodynamic (QED) effects and using them in quantum information applications. The lack of experimental progress in this area is in part due to the difficulty of precisely placing a QD within nanometers of the plasmonic cavity. Here, we study the simplest plasmonic cavity in the form of a spherical metallic nanoparticle (MNP). By controllably positioning a semiconductor QD in the close proximity of the MNP cavity via atomic force microscope (AFM) manipulation, the scattering spectrum of the MNP is dramatically modified due to Fano interference between the classical plasmonic resonance of the MNP and the quantized exciton resonance in the QD. Moreover, our experiment demonstrates that a single two-level system can render a spherical MNP strongly anisotropic. These findings represent an important step toward realizing quantum plasmonic devices. PMID:26372957

  14. Quantum stochastic approach for molecule/surface scattering. I. Atom-phonon interactions

    NASA Astrophysics Data System (ADS)

    Bittner, Eric R.; Light, John C.

    1993-11-01

    We present a general, fully quantum mechanical theory for molecule surface scattering at finite temperature within the time dependent Hartree (TDH) factorization. We show the formal manipulations which reduce the total molecule-surface-bath Schrödinger equation into a form which is computationally convenient to use. Under the TDH factorization, the molecular portion of the wavefunction evolves according to a mean-field Hamiltonian which is dependent upon both time and temperature. The temporal and thermal dependence is due to stochastic and dissipative terms that appear in the Heisenberg equations of motion for the phonon operators upon averaging over the bath states. The resulting equations of motion are solved in one dimension self consistently using quantum wavepackets and the discrete variable representation. We compute energy transfer to the phonons as a function of surface temperature and initial energy and compare our results to results obtained using other mean-field models, namely an averaged mean-field model and a fully quantum model based upon a dissipative form of the quantum Liouville equation. It appears that the model presented here provides a better estimation of energy transfer between the molecule and the surface.

  15. Imaging quantum stereodynamics through Fraunhofer scattering of NO radicals with rare-gas atoms.

    PubMed

    Onvlee, Jolijn; Gordon, Sean D S; Vogels, Sjoerd N; Auth, Thomas; Karman, Tijs; Nichols, Bethan; van der Avoird, Ad; Groenenboom, Gerrit C; Brouard, Mark; van de Meerakker, Sebastiaan Y T

    2017-03-01

    Stereodynamics describes how the vector properties of molecules, such as the directions in which they move and the axes about which they rotate, affect the probabilities (or cross-sections) of specific processes or transitions that occur on collision. The main aspects of stereodynamics in inelastic atom-molecule collisions can often be understood from classical considerations, in which the particles are represented by billiard-ball-like hard objects. In a quantum picture, however, the collision is described in terms of matter waves, which can also scatter into the region of the geometrical shadow of the object and reveal detailed information on the pure quantum-mechanical contribution to the stereodynamics. Here we present measurements of irregular diffraction patterns for NO radicals colliding with rare-gas atoms that can be explained by the analytical Fraunhofer model. They reveal a hitherto overlooked dependence on (or 'propensity rule' for) the magnetic quantum number m of the molecules, and a previously unrecognized type of quantum stereodynamics that has no classical analogue or interpretation.

  16. Scattering of He Atoms from a Microstructured Grating: Quantum Reflection Probabilities and Diffraction Patterns.

    PubMed

    Miret-Artés, Salvador; Pollak, Eli

    2017-03-02

    The quantum reflection measured previously by Zhao et al. ( Phys. Rev. A 2008 , 78 , 010902(R) ) for the scattering of He atoms off of a microstructured grating is described and analyzed theoretically. Using the close-coupling formalism with a complex absorbing potential and describing the long-range interaction in terms of the Casimir-van der Waals potential, we find probabilities and diffraction patterns that are in fairly good agreement with the experimental results. The central outcomes of this study are two-fold. First is the theoretical confirmation that, indeed, the phenomenon of quantum reflection may be detected not only through the elastic peak but also in terms of a quantum reflected diffraction pattern. Second, we demonstrate that the phenomenon of quantum reflection is the result of a coherent process where all of the potential regions are involved on an equal footing. It is a nonlocal property and cannot be related only to the long-range badlands region of the potential of interaction.

  17. Topological quantum scattering under the influence of a nontrivial boundary condition

    NASA Astrophysics Data System (ADS)

    Mota, Herondy

    2016-04-01

    We consider the quantum scattering problem of a relativistic particle in (2 + 1)-dimensional cosmic string spacetime under the influence of a nontrivial boundary condition imposed on the solution of the Klein-Gordon equation. The solution is then shifted as consequence of the nontrivial boundary condition and the role of the phase shift is to produce an Aharonov-Bohm-like effect. We examine the connection between this phase shift and the electromagnetic and gravitational analogous of the Aharonov-Bohm effect and compare the present results with previous ones obtained in the literature, also considering non-relativistic cases.

  18. Effect of spin-flip scattering on the electron transport through double quantum dots

    NASA Astrophysics Data System (ADS)

    Yang, Fu-Bin; Huang, Rui; Cheng, Yan

    2015-05-01

    We systematically investigate the electron transport through double quantum dots (DQD) with particular emphasis on the spin-flip scattering of an electron in the DQD. By means of the slave-boson mean-field approximation, we calculate the linear conductance and the transmission in the Kondo regime at zero temperature. The obtained results show that both the linear conductance and transmission probability are quite sensitive to the spin-flip strength when the DQD structure is changed among the serial, parallel and T-shaped. It is suggested that such a theoretical model can be used to study the physical phenomenon related to the spin manipulation transport.

  19. Influence of screening on longitudinal-optical phonon scattering in quantum cascade lasers

    SciTech Connect

    Ezhov, Ivan; Jirauschek, Christian

    2016-01-21

    We theoretically investigate the influence of screening on electron-longitudinal optical phonon scattering in quantum cascade lasers. By employing ensemble Monte Carlo simulations, an advanced screening model based on the random-phase approximation is compared to the more elementary Thomas-Fermi and Debye models. For mid-infrared structures, and to a lesser extent also for terahertz designs, the inclusion of screening is shown to affect the simulated current and optical output power. Furthermore, it is demonstrated that by using the electron temperature rather than the lattice temperature, the Debye model can be significantly improved.

  20. Dynamical basis sets for algebraic variational calculations in quantum-mechanical scattering theory

    NASA Technical Reports Server (NTRS)

    Sun, Yan; Kouri, Donald J.; Truhlar, Donald G.; Schwenke, David W.

    1990-01-01

    New basis sets are proposed for linear algebraic variational calculations of transition amplitudes in quantum-mechanical scattering problems. These basis sets are hybrids of those that yield the Kohn variational principle (KVP) and those that yield the generalized Newton variational principle (GNVP) when substituted in Schlessinger's stationary expression for the T operator. Trial calculations show that efficiencies almost as great as that of the GNVP and much greater than the KVP can be obtained, even for basis sets with the majority of the members independent of energy.

  1. Transient energy relaxation in scattering-assisted terahertz quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Wang, F.; Guo, X. G.; Cao, J. C.

    2017-03-01

    We adopt a self-consistent Maxwell-Bloch method to investigate the energy relaxation process from unsaturated to saturated in the scattering-assisted terahertz quantum cascade laser. In the lasing-establishment process, more nonequilibrium LO phonons are accumulated and more electrons are thermalized. At the same time, more efficient energy relaxation of the saturated situation can be found compared with the unsaturated situation. These phenomena stem from the improved electron transport efficiency across the active region, due to the lasing-induced lifetime reduction of electrons in the upper lasing subband. The simulation results are qualitatively identical with previous experimental results.

  2. Roton Minimum as a Fingerprint of Magnon-Higgs Scattering in Ordered Quantum Antiferromagnets.

    PubMed

    Powalski, M; Uhrig, G S; Schmidt, K P

    2015-11-13

    A quantitative description of magnons in long-range ordered quantum antiferromagnets is presented which is consistent from low to high energies. It is illustrated for the generic S=1/2 Heisenberg model on the square lattice. The approach is based on a continuous similarity transformation in momentum space using the scaling dimension as the truncation criterion. Evidence is found for significant magnon-magnon attraction inducing a Higgs resonance. The high-energy roton minimum in the magnon dispersion appears to be induced by strong magnon-Higgs scattering.

  3. Effects of a scattering center on the ground-state energy of quantum-dot lithium

    NASA Astrophysics Data System (ADS)

    Vatansever, Z. D.; Sakiroglu, S.; Sokmen, I.

    2017-03-01

    In this paper, the effects of a repulsive scattering center on the ground-state energy and spin properties of a three-electron parabolic quantum dot are investigated theoretically by means of configuration interaction method. Phase transition from a weakly correlated regime to a strongly correlated regime is examined from several strengths and positions of Gaussian impurity. Numerical results reveal that the transition from spin-1/2 to spin-3/2 state depends strongly on the location of the impurity which accordingly states the controllability of the spin polarization. Moreover, broken circular symmetry results in more pronounced electronic charge localization.

  4. Time-dependent treatment of scattering. II - Novel integral equation approach to quantum wave packets

    NASA Technical Reports Server (NTRS)

    Sharafeddin, Omar A.; Judson, Richard S.; Kouri, Donald J.; Hoffman, David K.

    1990-01-01

    The novel wave-packet propagation scheme presented is based on the time-dependent form of the Lippman-Schwinger integral equation and does not require extensive matrix inversions, thereby facilitating application to systems in which some degrees of freedom express the potential in a basis expansion. The matrix to be inverted is a function of the kinetic energy operator, and is accordingly diagonal in a Bessel function basis set. Transition amplitudes for various orbital angular momentum quantum numbers are obtainable via either Fourier transform of the amplitude density from the time to the energy domain, or the direct analysis of the scattered wave packet.

  5. Raman scattering in InAs/AlGaAs quantum dot nanostructures

    SciTech Connect

    Giulotto, E.; Geddo, M.; Grandi, M. S.; Guizzetti, G.; Trevisi, G.; Seravalli, L.; Frigeri, P.; Franchi, S.

    2011-03-14

    We report on Raman scattering experiments on InAs/Al{sub x}Ga{sub 1-x}As quantum dot heterostructures with 0{<=}x{<=}0.6. The samples were prepared by using molecular beam epitaxy (MBE) and atomic layer MBE for the growth of different layers. For x>0, we detected several lines originating from the Al{sub x}Ga{sub 1-x}As alloy. These can be related to scattering from GaAs-like and AlAs-like phonons with q congruent with 0, and weaker scattering from disorder-activated phonons with q{ne}0. In particular, we identified a line at {approx}250 cm{sup -1} as due to disorder-activated longitudinal optical phonons in the alloy. This conclusion is different than the attribution of this line to scattering from dots and, consequently, we do not recognize the possibility of deriving any information about the actual composition of the dots from an analysis of this line as proposed by other authors.

  6. Quantum scattering in one-dimensional systems satisfying the minimal length uncertainty relation

    NASA Astrophysics Data System (ADS)

    Bernardo, Reginald Christian S.; Esguerra, Jose Perico H.

    2016-12-01

    In quantum gravity theories, when the scattering energy is comparable to the Planck energy the Heisenberg uncertainty principle breaks down and is replaced by the minimal length uncertainty relation. In this paper, the consequences of the minimal length uncertainty relation on one-dimensional quantum scattering are studied using an approach involving a recently proposed second-order differential equation. An exact analytical expression for the tunneling probability through a locally-periodic rectangular potential barrier system is obtained. Results show that the existence of a non-zero minimal length uncertainty tends to shift the resonant tunneling energies to the positive direction. Scattering through a locally-periodic potential composed of double-rectangular potential barriers shows that the first band of resonant tunneling energies widens for minimal length cases when the double-rectangular potential barrier is symmetric but narrows down when the double-rectangular potential barrier is asymmetric. A numerical solution which exploits the use of Wronskians is used to calculate the transmission probabilities through the Pöschl-Teller well, Gaussian barrier, and double-Gaussian barrier. Results show that the probability of passage through the Pöschl-Teller well and Gaussian barrier is smaller in the minimal length cases compared to the non-minimal length case. For the double-Gaussian barrier, the probability of passage for energies that are more positive than the resonant tunneling energy is larger in the minimal length cases compared to the non-minimal length case. The approach is exact and applicable to many types of scattering potential.

  7. Quantum scattering in one-dimensional systems satisfying the minimal length uncertainty relation

    SciTech Connect

    Bernardo, Reginald Christian S. Esguerra, Jose Perico H.

    2016-12-15

    In quantum gravity theories, when the scattering energy is comparable to the Planck energy the Heisenberg uncertainty principle breaks down and is replaced by the minimal length uncertainty relation. In this paper, the consequences of the minimal length uncertainty relation on one-dimensional quantum scattering are studied using an approach involving a recently proposed second-order differential equation. An exact analytical expression for the tunneling probability through a locally-periodic rectangular potential barrier system is obtained. Results show that the existence of a non-zero minimal length uncertainty tends to shift the resonant tunneling energies to the positive direction. Scattering through a locally-periodic potential composed of double-rectangular potential barriers shows that the first band of resonant tunneling energies widens for minimal length cases when the double-rectangular potential barrier is symmetric but narrows down when the double-rectangular potential barrier is asymmetric. A numerical solution which exploits the use of Wronskians is used to calculate the transmission probabilities through the Pöschl–Teller well, Gaussian barrier, and double-Gaussian barrier. Results show that the probability of passage through the Pöschl–Teller well and Gaussian barrier is smaller in the minimal length cases compared to the non-minimal length case. For the double-Gaussian barrier, the probability of passage for energies that are more positive than the resonant tunneling energy is larger in the minimal length cases compared to the non-minimal length case. The approach is exact and applicable to many types of scattering potential.

  8. Phase-dependent magnetoconductance fluctuations in a chaotic Josephson junction

    NASA Astrophysics Data System (ADS)

    Brouwer, P. W.; Beenakker, C. W. J.

    1996-11-01

    Motivated by recent experiments by Den Hartog et al., we present a random-matrix theory for the magnetoconductance fluctuations of a chaotic quantum dot that is coupled by point contacts to two superconductors and one or two normal metals. There are aperiodic conductance fluctuations as a function of the magnetic field through the quantum dot and 2π-periodic fluctuations as a function of the phase difference φ of the superconductors. If the coupling to the superconductors is weak compared to the coupling to the normal metals, the φ dependence of the conductance is harmonic, as observed in the experiment. In the opposite regime, the conductance becomes a random 2π-periodic function of φ, in agreement with the theory of Altshuler and Spivak. The theoretical method employs an extension of the circular ensemble which can describe the magnetic-field dependence of the scattering matrix.

  9. Resonance Rayleigh scattering and resonance non-linear scattering method for the determination of aminoglycoside antibiotics with water solubility CdS quantum dots as probe.

    PubMed

    Liu, Zhengwen; Liu, Shaopu; Wang, Lei; Peng, Juanjuan; He, Youqiu

    2009-09-15

    In pH 6.6 Britton-Robinson buffer medium, the CdS quantum dots capped by thioglycolic acid could react with aminoglycoside (AGs) antibiotics such as neomycin sulfate (NEO) and streptomycin sulfate (STP) to form the large aggregates by virtue of electrostatic attraction and the hydrophobic force, which resulted in a great enhancement of resonance Rayleigh scattering (RRS) and resonance non-linear scattering such as second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum scattering peak was located at 310 nm for RRS, 568 nm for SOS and 390 nm for FDS, respectively. The enhancements of scattering intensity (DeltaI) were directly proportional to the concentration of AGs in a certain ranges. A new method for the determination of trace NEO and STP using CdS quantum dots probe was developed. The detection limits (3 sigma) were 1.7 ng mL(-1) (NEO) and 4.4 ng mL(-1) (STP) by RRS method, were 5.2 ng mL(-1) (NEO) and 20.9 ng mL(-1) (STP) by SOS method and were 4.4 ng mL(-1) (NEO) and 25.7 ng mL(-1) (STP) by FDS method, respectively. The sensitivity of RRS method was the highest. The optimum conditions and influence factors were investigated. In addition, the reaction mechanism was discussed.

  10. The study of effects of small perturbations on chaotic systems. Progress report, January 1991--December 1991

    SciTech Connect

    Grebogi, C.; Yorke, J.A.

    1991-12-01

    This report discusses the following topics: controlling chaotic dynamical systems; embedding of experimental data; effect of noise on critical exponents of crises; transition to chaotic scattering; and distribution of floaters on a fluid surface. (LSP)

  11. Approximating chaotic saddles for delay differential equations

    NASA Astrophysics Data System (ADS)

    Taylor, S. Richard; Campbell, Sue Ann

    2007-04-01

    Chaotic saddles are unstable invariant sets in the phase space of dynamical systems that exhibit transient chaos. They play a key role in mediating transport processes involving scattering and chaotic transients. Here we present evidence (long chaotic transients and fractal basins of attraction) of transient chaos in a “logistic” delay differential equation. We adapt an existing method (stagger-and-step) to numerically construct the chaotic saddle for this system. This is the first such analysis of transient chaos in an infinite-dimensional dynamical system, and in delay differential equations in particular. Using Poincaré section techniques we illustrate approaches to visualizing the saddle set, and confirm that the saddle has the Cantor-like fractal structure consistent with a chaotic saddle generated by horseshoe-type dynamics.

  12. Distribution of zeros of the S-matrix of chaotic cavities with localized losses and coherent perfect absorption: non-perturbative results

    NASA Astrophysics Data System (ADS)

    Fyodorov, Yan V.; Suwunnarat, Suwun; Kottos, Tsampikos

    2017-07-01

    We employ the random matrix theory framework to calculate the density of zeroes of an M-channel scattering matrix describing a chaotic cavity with a single localized absorber embedded in it. Our approach extends beyond the weak-coupling limit of the cavity with the channels and applies for any absorption strength. Importantly it provides an insight for the optimal amount of loss needed to realize a chaotic coherent perfect absorbing trap. Our predictions are tested against simulations for two types of traps: a complex network of resonators and quantum graphs.

  13. C*-algebraic scattering theory and explicitly solvable quantum field theories

    NASA Astrophysics Data System (ADS)

    Warchall, Henry A.

    1985-06-01

    A general theoretical framework is developed for the treatment of a class of quantum field theories that are explicitly exactly solvable, but require the use of C*-algebraic techniques because time-dependent scattering theory cannot be constructed in any one natural representation of the observable algebra. The purpose is to exhibit mechanisms by which inequivalent representations of the observable algebra can arise in quantum field theory, in a setting free of other complications commonly associated with the specification of dynamics. One of two major results is the development of necessary and sufficient conditions for the concurrent unitary implementation of two automorphism groups in a class of quasifree representations of the algebra of the canonical commutation relations (CCR). The automorphism groups considered are induced by one-parameter groups of symplectic transformations on the classical phase space over which the Weyl algebra of the CCR is built; each symplectic group is conjugate by a fixed symplectic transformation to a one-parameter unitary group. The second result, an analog to the Birman-Belopol'skii theorem in two-Hilbert-space scattering theory, gives sufficient conditions for the existence of Mo/ller wave morphisms in theories with time-development automorphism groups of the above type. In a paper which follows, this framework is used to analyze a particular model system for which wave operators fail to exist in any natural representation of the observable algebra, but for which wave morphisms and an associated S matrix are easily constructed.

  14. Angle-resolved scattering spectroscopy of explosives using an external cavity quantum cascade laser

    NASA Astrophysics Data System (ADS)

    Suter, Jonathan D.; Bernacki, Bruce E.; Phillips, Mark C.

    2012-01-01

    We present a study of the spectral and angular dependence of the diffuse scatter of mid-infrared (MIR) laser light from explosives residues on surfaces. Experiments were performed using an external cavity quantum cascade laser (ECQCL) tunable between 7 and 8 μm (1270 to 1400 cm-1) for surface illumination. A mercury cadmium telluride (MCT) detector was used to detect backscattered spectra as a function of surface angle at a 2 meter standoff. A ferroelectric focal plane array was used to build hyperspectral images at a 0.5 meter standoff. Residues of RDX, tetryl, and TNT were investigated on surfaces including a painted car door for angles between zero (specular) and 50 degrees. We observe spectral signatures of the explosives in the diffuse scattering geometry which differ significantly from those observed in transmission geometries. Characterization of the scattered light spectra of explosives on surfaces will be essential for understanding the performance of standoff explosives detection instruments and developing robust spectral analysis techniques.

  15. Scattering mechanisms of highest-mobility InAs /AlxGa1 -xSb quantum wells

    NASA Astrophysics Data System (ADS)

    Tschirky, T.; Mueller, S.; Lehner, Ch. A.; Fält, S.; Ihn, T.; Ensslin, K.; Wegscheider, W.

    2017-03-01

    We study molecular beam epitaxially grown undoped AlxGa1 -xSb /InAs/AlSb quantum wells with different buffer and barrier designs and varying quantum well width. The highest mobilities were achieved with Al0.33Ga0.67Sb buffers and lower barriers and a quantum well width of 24 nm. These quasi-single-interface InAs/AlSb quantum well devices reached a gate-tuned mobility of 2.4 ×106cm2 /V s at a density of 1 ×1012cm-2 and 1.3 K. In Hall bar devices boundary scattering is found to strongly influence the mobility determination in this mobility regime. Ionized background impurity scattering at low electron densities, device boundary scattering at intermediate electron densities, and intersubband scattering at high electron densities were identified as the most likely dominant scattering processes. Ringlike structures in the Landau fan can be explained using a single-particle model of crossing Landau levels.

  16. Polarization-Dependent Interference of Coherent Scattering from Orthogonal Dipole Moments of a Resonantly Excited Quantum Dot

    NASA Astrophysics Data System (ADS)

    Chen, Disheng; Lander, Gary R.; Solomon, Glenn S.; Flagg, Edward B.

    2017-01-01

    Resonant photoluminescence excitation (RPLE) spectra of a neutral InGaAs quantum dot show unconventional line shapes that depend on the detection polarization. We characterize this phenomenon by performing polarization-dependent RPLE measurements and simulating the measured spectra with a three-level quantum model. The spectra are explained by interference between fields coherently scattered from the two fine structure split exciton states, and the measurements enable extraction of the steady-state coherence between the two exciton states.

  17. Inelastic electron and Raman scattering from the collective excitations in quantum wires: Zero magnetic field

    NASA Astrophysics Data System (ADS)

    Kushwaha, Manvir S.

    2013-04-01

    The nanofabrication technology has taught us that an m-dimensional confining potential imposed upon an n-dimensional electron gas paves the way to a quasi-(n-m)-dimensional electron gas, with m ⩽ n and 1 ⩽ n, m ⩽ 3. This is the road to the (semiconducting) quasi-n dimensional electron gas systems we have been happily traversing on now for almost two decades. Achieving quasi-one dimensional electron gas (Q-1DEG) [or quantum wire(s) for more practical purposes] led us to some mixed moments in this journey: while the reduced phase space for the scattering led us believe in the route to the faster electron devices, the proximity to the 1D systems left us in the dilemma of describing it as a Fermi liquid or as a Luttinger liquid. No one had ever suspected the potential of the former, but it took quite a while for some to convince the others on the latter. A realistic Q-1DEG system at the low temperatures is best describable as a Fermi liquid rather than as a Luttinger liquid. In the language of condensed matter physics, a critical scrutiny of Q-1DEG systems has provided us with a host of exotic (electronic, optical, and transport) phenomena unseen in their higher- or lower-dimensional counterparts. This has motivated us to undertake a systematic investigation of the inelastic electron scattering (IES) and the inelastic light scattering (ILS) from the elementary electronic excitations in quantum wires. We begin with the Kubo's correlation functions to derive the generalized dielectric function, the inverse dielectric function, and the Dyson equation for the dynamic screened potential in the framework of Bohm-Pines' random-phase approximation. These fundamental tools then lead us to develop methodically the theory of IES and ILS for the Q-1DEG systems. As an application of the general formal results, which know no bounds regarding the subband occupancy, we compute the density of states, the Fermi energy, the full excitation spectrum [comprised of intrasubband and

  18. Plasmonics for surface-enhanced Raman scattering: from classical to quantum

    NASA Astrophysics Data System (ADS)

    Zhu, Wenqi

    dimers formed above a gold film integrated with a one-dimensional array of gold stripes. For both antenna types, beamed Raman scattering is observed. In most cases, the electromagnetic enhancement mechanism of SERS can be understood by classical electromagnetic theory. Only recently has it become well-appreciated that quantum mechanical effects such as nonlocality and electron tunneling emerge as the feature sizes of metallic nanostructures approach atomic length-scales. We unambiguously demonstrate the emergence of electron tunneling at optical frequencies for metallic nanostructures with gap-widths in the single-digit angstrom range. Moreover we experimentally demonstrate, for the first time the best of our knowledge, that the emergence of electron tunneling limits the maximum achievable SERS enhancement.

  19. 3. QUANTUM DOTS AND WELLS, MESOSCOPIC NETWORKS : Spectroscopy of electron-electron scattering in a 2DEG

    NASA Astrophysics Data System (ADS)

    Buhmann, H.; Predel, H.; Molenkamp, L. W.; Gurzhi, R. N.; Kalinenko, A. N.; Kopeliovich, A. I.; Yanovsky, A. V.

    2001-10-01

    Experimentally electron-beam injection and detection via quantum point-contacts is used to investigate the scattering of a non-equilibrium electron distribution in a two-dimensional electron gas (2DEG) of a GaAs/(Ga,Al)As heterostructure. The energy dependence of electron-electron scattering processes has been studied in a weak magnetic field by investigating the detector signal. Assuming electron beams with a narrow opening angle a magnetic field B perpendicular to the 2DEG plane causes only electrons which are scattered in a point O at an angle α to reach the detector. Thus, it is possible to measure directly the energy dependence of the angular electron distribution after scattering. The experimental data give a clear evidence for the importance of small angle scattering processes in two-dimensional systems, as predicted theoretically.

  20. Electron Raman scattering in a double quantum well tuned by an external nonresonant intense laser field

    NASA Astrophysics Data System (ADS)

    Tiutiunnyk, A.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. M.; Restrepo, R. L.; Ungan, F.; Martínez-Orozco, J. C.; Kasapoglu, E.; Duque, C. A.

    2017-02-01

    In this work we shall present a study of inelastic light scattering involving inter-subband electron transitions in coupled GaAs-(Ga,Al)As quantum wells. Calculations include the electron related Raman differential cross section and Raman gain. The effects of an external nonresonant intense laser field are used in order to tune these output properties. The confined electron states will be described by means of a diagonalization procedure within the effective mass and parabolic band approximations. It is shown that the application of the intense laser field can produce values of the intersubband electron Raman gain above 400 cm-1. The system proposed here is an alternative choice for the development of AlxGa1-xAs semiconductor laser diodes that can be tuned via an external nonresonant intense laser field.

  1. Spin-flip relaxation via optical phonon scattering in quantum dots

    SciTech Connect

    Wang, Zi-Wu; Liu, Lei; Li, Shu-Shen

    2013-12-14

    Based on the spin-orbit coupling admixture mechanism, we theoretically investigate the spin-flip relaxation via optical phonon scattering in quantum dots by considering the effect of lattice relaxation due to the electron-acoustic phonon deformation potential coupling. The relaxation rate displays a cusp-like structure (or a spin hot spot) that becomes more clearly with increasing temperature. We also calculate the relaxation rate of the spin-conserving process, which follows a Gaussian form and is several orders of magnitude larger than that of spin-flip process. Moreover, we find that the relaxation rate displays the oscillatory behavior due to the interplay effects between the magnetic and spatial confinement for the spin-flip process not for the spin-conserving process. The trends of increasing and decreasing temperature dependence of the relaxation rates for two relaxation processes are obtained in the present model.

  2. Floquet Scattering Matrix Theory of Heat Fluctuations in Dynamical Quantum Conductors

    NASA Astrophysics Data System (ADS)

    Moskalets, Michael

    2014-05-01

    I present the Floquet scattering matrix theory of low-frequency heat fluctuations in driven quantum-coherent conductors in the linear response regime and beyond. The Floquet theory elucidates the use of the Callen-Welton fluctuation-dissipation theorem for a description of heat fluctuations in a multiterminal case. The intrinsic fluctuations of energy of dynamically excited electrons are identified as the fundamental source of heat noise not revealed by the electrical noise. The role of backscattering in the increase of heat noise above the level defined by the Callen-Welton theorem is highlighted. The exception is the case when a conductor is driven by a Lorentzian voltage pulse with quantized flux. The heat noise in this case falls down to the level pertaining to a linear response regime.

  3. Progesterone and testosterone studies by neutron scattering and nuclear magnetic resonance methods and quantum chemistry calculations

    NASA Astrophysics Data System (ADS)

    Szyczewski, A.; Hołderna-Natkaniec, K.; Natkaniec, I.

    2004-05-01

    Inelastic incoherent neutron scattering spectra of progesterone and testosterone measured at 20 and 290 K were compared with the IR spectra measured at 290 K. The Phonon Density of States spectra display well resolved peaks of low frequency internal vibration modes up to 1200 cm -1. The quantum chemistry calculations were performed by semiempirical PM3 method and by the density functional theory method with different basic sets for isolated molecule, as well as for the dimer system of testosterone. The proposed assignment of internal vibrations of normal modes enable us to conclude about the sequence of the onset of the torsion movements of the CH 3 groups. These conclusions were correlated with the results of proton molecular dynamics studies performed by NMR method. The GAUSSIAN program had been used for calculations.

  4. Neutron scattering signatures of the 3D hyperhoneycomb Kitaev quantum spin liquid

    NASA Astrophysics Data System (ADS)

    Smith, A.; Knolle, J.; Kovrizhin, D. L.; Chalker, J. T.; Moessner, R.

    2015-11-01

    Motivated by recent synthesis of the hyperhoneycomb material β -Li2IrO3 , we study the dynamical structure factor (DSF) of the corresponding 3D Kitaev quantum spin-liquid (QSL), whose fractionalized degrees of freedom are Majorana fermions and emergent flux loops. The properties of this 3D model are known to differ in important ways from those of its 2D counterpart—it has a finite-temperature phase transition, as well as distinct features in the Raman response. We show, however, that the qualitative behavior of the DSF is broadly dimension-independent. Characteristics of the 3D DSF include a response gap even in the gapless QSL phase and an energy dependence deriving from the Majorana fermion density of states. Since the majority of the response is from states containing a single Majorana excitation, our results suggest inelastic neutron scattering as the spectroscopy of choice to illuminate the physics of Majorana fermions in Kitaev QSLs.

  5. Electron states and electron Raman scattering in semiconductor step-quantum well: Electric field effect

    NASA Astrophysics Data System (ADS)

    Betancourt-Riera, Ri.; Betancourt-Riera, Re.; Ferrer-Moreno, L. A.; Jalil, J. M. Nieto

    2017-04-01

    In this work we determine and show the expressions of the electron states of a step-quantum well with the presence of an external electric field, developed in a GaAs / AlGaAs matrix. The electron states are obtained using the envelope function approximation. In this work it is only necessary to consider a single conduction band, which due to the confinement is divided into a subband system, with T = 0K . Expressions for the electron states and the differential cross-section for an intraband electron Raman scattering process of are presented, the net Raman gain is also calculated. In addition, the interpretation of the singularities found in the emission or excitation spectra is given, since several dispersion configurations are discussed. Furthermore, the effects of an electric field on the electron states and on the differential cross section are studied.

  6. Simulating Surface-Enhanced Hyper-Raman Scattering Using Atomistic Electrodynamics-Quantum Mechanical Models.

    PubMed

    Hu, Zhongwei; Chulhai, Dhabih V; Jensen, Lasse

    2016-12-13

    Surface-enhanced hyper-Raman scattering (SEHRS) is the two-photon analogue of surface-enhanced Raman scattering (SERS), which has proven to be a powerful tool to study molecular structures and surface enhancements. However, few theoretical approaches to SEHRS exist and most neglect the atomistic descriptions of the metal surface and molecular resonance effects. In this work, we present two atomistic electrodynamics-quantum mechanical models to simulate SEHRS. The first is the discrete interaction model/quantum mechanical (DIM/QM) model, which combines an atomistic electrodynamics model of the nanoparticle with a time-dependent density functional theory description of the molecule. The second model is a dressed-tensors method that describes the molecule as a point-dipole and point-quadrupole object interacting with the enhanced local field and field-gradients (FG) from the nanoparticle. In both of these models, the resonance effects are treated efficiently by means of damped quadratic response theory. Using these methods, we simulate SEHRS spectra for benzene and pyridine. Our results show that the FG effects in SEHRS play an important role in determining both the surface selection rules and the enhancements. We find that FG effects are more important in SEHRS than in SERS. We also show that the spectral features of small molecules can be accurately described by accounting for the interactions between the molecule and the local field and FG of the nanoparticle. However, at short distances between the metal and molecule, we find significant differences in the SEHRS enhancements predicted using the DIM/QM and the dressed-tensors methods.

  7. Resonant Raman Scattering from Bound Magnetorotons in the Fractional Quantum Hall Regime

    NASA Astrophysics Data System (ADS)

    He, Song

    1996-03-01

    We investigate excitation spectra of a fractional quantum Hall system at ν=1/3 using both theoretical and experimental techniques. Using finite-size numerical diagonalizations, we have studied systematically the excitation spectra, the nature of the low-lying excited states, and the density response function of a ν=1/3 system. Our numerical results indicate that two rotons at the roton minimum can form a weakly bound composite object, giving rise to excited states below the collective mode at long wavelengths. We argue that only these two roton composite objects contribute to the resonant Raman scattering at low momentum transfers. Using the experimental technique of resonant Raman scattering, we have identified the contributions to the Raman intensity from the internal excitations of the fractional quantum Hall system by studying their dependence on the incoming light energy, the filling factor, and the temperature. As a function of the energy shift, the Raman intensity shows a sharp peak at an energy shift of about twice of the energy gap at the roton minimum. We propose that this sharp peak is related to a two roton bound state. The sharp peak is followed by a broader peak, which we think is related to the two-roton continuum. When a grating pattern is put on the sample so that small but finite momentum transfer can be achieved, we observed another peak at about twice of the energy gap Δ_q=∞. We suspect this peak is related to the collective mode at long wavelength. Finally, we propose an excitation spectra consistent with our numerical and experimental results. * This work is a collaboration with P. M. Platzman, A. Pinczuk, B. S. Dennis, L. L. Sohn, L. N. Pfeiffer, and K. W. West.

  8. The Strength of Chaos: Accurate Simulation of Resonant Electron Scattering by Many-Electron Ions and Atoms in the Presence of Quantum Chaos

    DTIC Science & Technology

    2017-01-20

    AFRL-AFOSR-JP-TR-2017-0012 The Strength of Chaos: accurate simulation of resonant electron scattering by many-electron ions and atoms in the presence...SUBTITLE The Strength of Chaos: accurate simulation of resonant electron scattering by many- electron ions and atoms in the presence of quantum chaos...Strength of Chaos: accurate simulation of resonant electron scattering by many-electron ions and atoms in the presence of quantum chaos” Date 13

  9. Analysis of temporal evolution of quantum dot surface chemistry by surface-enhanced Raman scattering

    NASA Astrophysics Data System (ADS)

    Doğan, Ilker; Gresback, Ryan; Nozaki, Tomohiro; van de Sanden, Mauritius C. M.

    2016-07-01

    Temporal evolution of surface chemistry during oxidation of silicon quantum dot (Si-QD) surfaces were probed using surface-enhanced Raman scattering (SERS). A monolayer of hydrogen and chlorine terminated plasma-synthesized Si-QDs were spin-coated on silver oxide thin films. A clearly enhanced signal of surface modes, including Si-Clx and Si-Hx modes were observed from as-synthesized Si-QDs as a result of the plasmonic enhancement of the Raman signal at Si-QD/silver oxide interface. Upon oxidation, a gradual decrease of Si-Clx and Si-Hx modes, and an emergence of Si-Ox and Si-O-Hx modes have been observed. In addition, first, second and third transverse optical modes of Si-QDs were also observed in the SERS spectra, revealing information on the crystalline morphology of Si-QDs. An absence of any of the abovementioned spectral features, but only the first transverse optical mode of Si-QDs from thick Si-QD films validated that the spectral features observed from Si-QDs on silver oxide thin films are originated from the SERS effect. These results indicate that real-time SERS is a powerful diagnostic tool and a novel approach to probe the dynamic surface/interface chemistry of quantum dots, especially when they involve in oxidative, catalytic, and electrochemical surface/interface reactions.

  10. Neutron scattering studies of a bond-disordered S = 1 quantum spin liquid

    NASA Astrophysics Data System (ADS)

    Povarov, Kirill; Wulf, Erik; Hüvonen, Dan; Gvasaliya, Severian; Ressouche, Eric; Ollivier, Jacques; Paduan-Filho, Armando; Zheludev, Andrey

    2015-03-01

    We report the results of the neutron scattering studies of a bond-disordered modification of a well-known gapped S = 1 antiferromagnetic quantum system NiCl2 . 4SC(NH2)2 (commonly referred to as DTN). The focus of the study is a zero-field spin-liquid phase of a compound with 6% of Cl to Br substitution. Inelastic neutron time-of-flight measurements at a temperature of 60 mK were employed to map the magnetic excitation spectrum over the whole Brillouin zone with a high resolution. In addition, we have also investigated the critical properties of the field-induced phase transition in DTN specimen with various concentration of Br by means of neutron diffraction. We compare these experimental results to the bulk measurements on DTN with similar levels of Cl/Br substitution and recent theoretical predictions for disordered quantum magnets. This work was partially supported by the Swiss National Fund.

  11. Analysis of temporal evolution of quantum dot surface chemistry by surface-enhanced Raman scattering

    PubMed Central

    Doğan, İlker; Gresback, Ryan; Nozaki, Tomohiro; van de Sanden, Mauritius C. M.

    2016-01-01

    Temporal evolution of surface chemistry during oxidation of silicon quantum dot (Si-QD) surfaces were probed using surface-enhanced Raman scattering (SERS). A monolayer of hydrogen and chlorine terminated plasma-synthesized Si-QDs were spin-coated on silver oxide thin films. A clearly enhanced signal of surface modes, including Si-Clx and Si-Hx modes were observed from as-synthesized Si-QDs as a result of the plasmonic enhancement of the Raman signal at Si-QD/silver oxide interface. Upon oxidation, a gradual decrease of Si-Clx and Si-Hx modes, and an emergence of Si-Ox and Si-O-Hx modes have been observed. In addition, first, second and third transverse optical modes of Si-QDs were also observed in the SERS spectra, revealing information on the crystalline morphology of Si-QDs. An absence of any of the abovementioned spectral features, but only the first transverse optical mode of Si-QDs from thick Si-QD films validated that the spectral features observed from Si-QDs on silver oxide thin films are originated from the SERS effect. These results indicate that real-time SERS is a powerful diagnostic tool and a novel approach to probe the dynamic surface/interface chemistry of quantum dots, especially when they involve in oxidative, catalytic, and electrochemical surface/interface reactions. PMID:27389331

  12. Analytic, non-perturbative, gauge-invariant quantum chromodynamics: Nucleon scattering and binding potentials

    SciTech Connect

    Fried, H.M.; Gabellini, Y.; Grandou, T.; Sheu, Y.-M.

    2013-11-15

    Removal of the quenched approximation in the mechanism which produced an analytic estimate of quark-binding potentials, along with a reasonable conjecture of the color structure of the nucleon formed by such a binding potential, is shown to generate an effective nucleon scattering and binding potential. The mass-scale factor on the order of the pion mass, previously introduced to define the transverse imprecision of quark coordinates, is again used, while the strength of the potential is proportional to the square of a renormalized quantum chromodynamics (QCD) coupling constant. The potential so derived does not include corrections due to spin, angular momentum, nucleon structure, and electroweak interactions; rather, it is qualitative in nature, showing how Nuclear Physics can arise from fundamental QCD. -- Highlights: •Nucleon–nucleon forces are derived qualitatively from basic realistic quantum chromodynamics. •An effective nucleon binding is obtained from the simplest unquenched approximation. •A model deuteron binding energy of −2.2 MeV follows with α{sub s,R}=12.5.

  13. Carrier capture in InGaN/GaN quantum wells: Role of electron-electron scattering

    NASA Astrophysics Data System (ADS)

    Vallone, Marco; Goano, Michele; Bertazzi, Francesco; Ghione, Giovanni

    2017-03-01

    The competition of electron-electron interband scattering (ee) and longitudinal optical phonon emission (e-ph) as electron capture mechanisms is theoretically investigated in III-nitride quantum wells. The non-trivial separation of their scattering probabilities is discussed, and compact expressions for capture time are obtained in the framework of the quantum many-body formalism. At the typical operating conditions of light emitting diodes (LEDs), the model predicts an increasing importance of ee scattering as a capture mechanism with increasing carrier density. Verifications against recent experiments are presented to support this finding and confirm the need for population-dependent capture time expressions including both ee and e-ph mechanisms for an accurate description of LED carrier dynamics and efficiency.

  14. Quantum scattering calculations for ro-vibrational de-excitation of CO by hydrogen atoms

    NASA Astrophysics Data System (ADS)

    Song, Lei; Balakrishnan, N.; van der Avoird, Ad; Karman, Tijs; Groenenboom, Gerrit C.

    2015-05-01

    We present quantum-mechanical scattering calculations for ro-vibrational relaxation of carbon monoxide (CO) in collision with hydrogen atoms. Collisional cross sections of CO ro-vibrational transitions from v = 1, j = 0 - 30 to v' = 0, j' are calculated using the close coupling method for collision energies between 0.1 and 15 000 cm-1 based on the three-dimensional potential energy surface of Song et al. [J. Phys. Chem. A 117, 7571 (2013)]. Cross sections of transitions from v = 1, j ≥ 3 to v' = 0, j' are reported for the first time at this level of theory. Also calculations by the more approximate coupled states and infinite order sudden (IOS) methods are performed in order to test the applicability of these methods to H-CO ro-vibrational inelastic scattering. Vibrational de-excitation rate coefficients of CO (v = 1) are presented for the temperature range from 100 K to 3000 K and are compared with the available experimental and theoretical data. All of these results and additional rate coefficients reported in a forthcoming paper are important for including the effects of H-CO collisions in astrophysical models.

  15. Progesterone and testosterone studies by neutron-scattering methods and quantum chemistry calculations

    NASA Astrophysics Data System (ADS)

    Holderna-Natkaniec, K.; Szyczewski, A.; Natkaniec, I.; Khavryutchenko, V. D.; Pawlukojc, A.

    Inelastic incoherent neutron scattering (IINS) and neutron diffraction spectra of progesterone and testosterone were measured simultaneously on the NERA spectrometer at the IBR-2 pulsed reactor in Dubna. Both studied samples do not indicate any phase transition in the temperature range from 20 to 290K. The IINS spectra have been transformed to the phonon density of states (PDS) in the one-phonon scattering approximation. The PDS spectra display well-resolved peaks of low-frequency internal vibration modes up to 600cm-1. The assignment of these modes was proposed taking into account the results of calculations of the structure and dynamics of isolated molecules of the investigated substances. The quantum chemistry calculations were performed by the semi-empirical PM3 method and at the restricted Hartree-Fock level with the 6-31* basis set. The lower internal modes assigned to torsional vibration of the androstane skeleton mix with the lattice vibrations. The intense bands in the PDS spectra in the frequency range from 150 to 300cm-1 are related to librations of structurally inequivalent methyl groups.

  16. Z3-order theory of quantum inelastic scattering of charges by solids

    NASA Astrophysics Data System (ADS)

    Nazarov, V. U.; Nishigaki, S.

    2002-03-01

    Although the nonlinear response of solids in such phenomena as ion slowing and second harmonic generation has been studied since long ago, to our knowledge there has not existed a quantum theory of the inelastic scattering of charges by solids beyond the first Born approximation. In this paper we relate the inelastic cross section in the second Born approximation to the order Z3 to the quadratic retarded density-response function in the same (but far less trivial) fashion it has been known for the first Born approximation, deriving by this a formula applicable to describe the electron and positron energy-loss spectroscopy. The complete account of recoil is preserved. Our general formalism neither relies on a specific approximation to the dielectric response (such as the random phase approximation) nor is it restricted to scattering by a homogeneous electron gas: it is ``exact'' in the sense of inclusion of exchange and correlation and is applicable to targets of arbitrary symmetry. Based on this formalism, we perform explicit calculations of the Z3 contribution to plasmon excitation by electrons and positrons in a simple hydrodynamic model of electron gas and discuss the results, which prove to be instructive in the general case too.

  17. Quantum scattering calculations for ro-vibrational de-excitation of CO by hydrogen atoms

    SciTech Connect

    Song, Lei; Avoird, Ad van der; Karman, Tijs; Groenenboom, Gerrit C.; Balakrishnan, N.

    2015-05-28

    We present quantum-mechanical scattering calculations for ro-vibrational relaxation of carbon monoxide (CO) in collision with hydrogen atoms. Collisional cross sections of CO ro-vibrational transitions from v = 1, j = 0 − 30 to v′ = 0, j′ are calculated using the close coupling method for collision energies between 0.1 and 15 000 cm{sup −1} based on the three-dimensional potential energy surface of Song et al. [J. Phys. Chem. A 117, 7571 (2013)]. Cross sections of transitions from v = 1, j ≥ 3 to v′ = 0, j′ are reported for the first time at this level of theory. Also calculations by the more approximate coupled states and infinite order sudden (IOS) methods are performed in order to test the applicability of these methods to H–CO ro-vibrational inelastic scattering. Vibrational de-excitation rate coefficients of CO (v = 1) are presented for the temperature range from 100 K to 3000 K and are compared with the available experimental and theoretical data. All of these results and additional rate coefficients reported in a forthcoming paper are important for including the effects of H–CO collisions in astrophysical models.

  18. Optical phonon scattering in quantum cascade laser in a magnetic field

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Regnault, N.; Ferreira, R.; Zhu, B. F.; Bastard, G.

    2010-01-01

    We report on a theoretical study of the interaction between Landau quantized electrons and phonons in the presence of Landau level (LL) broadening due to alloy scattering, which are related to the period in 1/B decrease of light output of an 8.4 μm GaInAs/AlInAs quantum cascade laser subjected to strong magnetic fields. The magneto-polaron states are formed by an exact diagonalization of the Fröhlich interaction between the LL |E2, n = 0> and the |E1, p≠0>⊗|1LO> manifold. The self consistent Born approximation is used to study the polaron broadening. We show that polaron gaps of perfect material are washed out in high magnetic fields. Specific cases of p = 2 are checked with numerical calculations. Intersubband scattering rates of electrons in alloy broadened Landau level states due to the Fröhlich electron-phonon interaction are also calculated using the Fermi golden rule.

  19. Quantum State-Resolved Reactive and Inelastic Scattering at Gas-Liquid and Gas-Solid Interfaces

    NASA Astrophysics Data System (ADS)

    Grütter, Monika; Nelson, Daniel J.; Nesbitt, David J.

    2012-06-01

    Quantum state-resolved reactive and inelastic scattering at gas-liquid and gas-solid interfaces has become a research field of considerable interest in recent years. The collision and reaction dynamics of internally cold gas beams from liquid or solid surfaces is governed by two main processes, impulsive scattering (IS), where the incident particles scatter in a few-collisions environment from the surface, and trapping-desorption (TD), where full equilibration to the surface temperature (T{TD}≈ T{s}) occurs prior to the particles' return to the gas phase. Impulsive scattering events, on the other hand, result in significant rotational, and to a lesser extent vibrational, excitation of the scattered molecules, which can be well-described by a Boltzmann-distribution at a temperature (T{IS}>>T{s}). The quantum-state resolved detection used here allows the disentanglement of the rotational, vibrational, and translational degrees of freedom of the scattered molecules. The two examples discussed are (i) reactive scattering of monoatomic fluorine from room-temperature ionic liquids (RTILs) and (ii) inelastic scattering of benzene from a heated (˜500 K) gold surface. In the former experiment, rovibrational states of the nascent HF beam are detected using direct infrared absorption spectroscopy, and in the latter, a resonace-enhanced multi-photon-ionization (REMPI) scheme is employed in combination with a velocity-map imaging (VMI) device, which allows the detection of different vibrational states of benzene excited during the scattering process. M. E. Saecker, S. T. Govoni, D. V. Kowalski, M. E. King and G. M. Nathanson Science 252, 1421, 1991. A. M. Zolot, W. W. Harper, B. G. Perkins, P. J. Dagdigian and D. J. Nesbitt J. Chem. Phys 125, 021101, 2006. J. R. Roscioli and D. J. Nesbitt Faraday Disc. 150, 471, 2011.

  20. Quantum and classical dynamics of reactive scattering of H2 from metal surfaces.

    PubMed

    Kroes, Geert-Jan; Díaz, Cristina

    2016-06-27

    We review the state-of-the art in dynamics calculations on the reactive scattering of H2 from metal surfaces, which is an important model system of an elementary reaction that is relevant to heterogeneous catalysis. In many applications, quantum dynamics and classical trajectory calculations are performed within the Born-Oppenheimer static surface model. However, ab initio molecular dynamics (AIMD) is finding increased use in applications aimed at modeling the effect of surface phonons on the dynamics. Molecular dynamics with electronic friction has been used to model the effect of electron-hole pair excitation. Most applications are still based on potential energy surfaces (PESs) or forces computed with density functional theory (DFT), using a density functional within the generalized gradient approximation to the exchange-correlation energy. A new development is the use of a semi-empirical version of DFT (the specific reaction parameter (SRP) approach to DFT). We also discuss the accurate methods that have become available to represent electronic structure data for the molecule-surface interaction in global PESs. It has now become possible to describe highly activated H2 + metal surface reactions with chemical accuracy using the SRP-DFT approach, as has been shown for H2 + Cu(111) and Cu(100). However, chemical accuracy with SRP-DFT has yet to be demonstrated for weakly activated systems like H2 + Ru(0001) and non-activated systems like H2 + Pd(111), for which SRP DFs are not yet available. There is now considerable evidence that electron-hole pair (ehp) excitation does not need to be modeled to achieve the (chemically) accurate calculation of dissociative chemisorption and scattering probabilities. Dynamics calculations show that phonons can be safely neglected in the chemically accurate calculation of sticking probabilities on cold metal surfaces for activated systems, and in the calculation of a number of other observables. However, there is now sufficient

  1. Quantum non-Abelian hydrodynamics: Anyonic or spin-orbital entangled liquids, nonunitarity of scattering matrix and charge fractionalization

    NASA Astrophysics Data System (ADS)

    Pareek, Tribhuvan Prasad

    2015-09-01

    In this article, we develop an exact (nonadiabatic, nonperturbative) density matrix scattering theory for a two component quantum liquid which interacts or scatters off from a generic spin-dependent quantum potential. The generic spin dependent quantum potential [Eq. (1)] is a matrix potential, hence, adiabaticity criterion is ill-defined. Therefore the full matrix potential should be treated nonadiabatically. We succeed in doing so using the notion of vectorial matrices which allows us to obtain an exact analytical expression for the scattered density matrix (SDM), ϱsc [Eq. (30)]. We find that the number or charge density in scattered fluid, Tr(ϱsc), expressions in Eqs. (32) depends on nontrivial quantum interference coefficients, Qα β 0ijk, which arises due to quantum interference between spin-independent and spin-dependent scattering amplitudes and among spin-dependent scattering amplitudes. Further it is shown that Tr(ϱsc) can be expressed in a compact form [Eq. (39)] where the effect of quantum interference coefficients can be included using a vector Qαβ, which allows us to define a vector order parameterQ. Since the number density is obtained using an exact scattered density matrix, therefore, we do not need to prove that Q is non-zero. However, for sake of completeness, we make detailed mathematical analysis for the conditions under which the vector order parameterQ would be zero or nonzero. We find that in presence of spin-dependent interaction the vector order parameterQ is necessarily nonzero and is related to the commutator and anti-commutator of scattering matrix S with its dagger S† [Eq. (78)]. It is further shown that Q≠0, implies four physically equivalent conditions,i.e., spin-orbital entanglement is nonzero, non-Abelian scattering phase, i.e., matrices, scattering matrix is nonunitary and the broken time reversal symmetry for SDM. This also implies that quasi particle excitation are anyonic in nature, hence, charge fractionalization is a

  2. Heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides

    NASA Astrophysics Data System (ADS)

    Song, Guo-Zhu; Zhang, Mei; Ai, Qing; Yang, Guo-Jian; Alsaedi, Ahmed; Hobiny, Aatef; Deng, Fu-Guo

    2017-03-01

    We propose a heralded quantum repeater based on the scattering of photons off single emitters in one-dimensional waveguides. We show the details by implementing nonlocal entanglement generation, entanglement swapping, and entanglement purification modules with atoms in waveguides, and discuss the feasibility of the repeater with currently achievable technology. In our scheme, the faulty events can be discarded by detecting the polarization of the photons. That is, our protocols are accomplished with a fidelity of 100% in principle, which is advantageous for implementing realistic long-distance quantum communication. Moreover, additional atomic qubits are not required, but only a single-photon medium. Our scheme is scalable and attractive since it can be realized in solid-state quantum systems. With the great progress on controlling atom-waveguide systems, the repeater may be very useful in quantum information processing in the future.

  3. Casimir force between integrable and chaotic pistons

    SciTech Connect

    Alvarez, Ezequiel; Mazzitelli, Francisco D.; Wisniacki, Diego A.; Monastra, Alejandro G.

    2010-11-15

    We have computed numerically the Casimir force between two identical pistons inside a very long cylinder, considering different shapes for the pistons. The pistons can be considered quantum billiards, whose spectrum determines the vacuum force. The smooth part of the spectrum fixes the force at short distances and depends only on geometric quantities like the area or perimeter of the piston. However, correcting terms to the force, coming from the oscillating part of the spectrum which is related to the classical dynamics of the billiard, could be qualitatively different for classically integrable or chaotic systems. We have performed a detailed numerical analysis of the corresponding Casimir force for pistons with regular and chaotic classical dynamics. For a family of stadium billiards, we have found that the correcting part of the Casimir force presents a sudden change in the transition from regular to chaotic geometries. This suggests that there could be signatures of quantum chaos in the Casimir effect.

  4. Benchmark studies of the Bending Corrected Rotating Linear Model (BCRLM) reactive scattering code: Implications for accurate quantum calculations

    SciTech Connect

    Hayes, E.F.; Darakjian, Z. . Dept. of Chemistry); Walker, R.B. )

    1990-01-01

    The Bending Corrected Rotating Linear Model (BCRLM), developed by Hayes and Walker, is a simple approximation to the true multidimensional scattering problem for reaction of the type: A + BC {yields} AB + C. While the BCRLM method is simpler than methods designed to obtain accurate three dimensional quantum scattering results, this turns out to be a major advantage in terms of our benchmarking studies. The computer code used to obtain BCRLM scattering results is written for the most part in standard FORTRAN and has been reported to several scalar, vector, and parallel architecture computers including the IBM 3090-600J, the Cray XMP and YMP, the Ardent Titan, IBM RISC System/6000, Convex C-1 and the MIPS 2000. Benchmark results will be reported for each of these machines with an emphasis on comparing the scalar, vector, and parallel performance for the standard code with minimum modifications. Detailed analysis of the mapping of the BCRLM approach onto both shared and distributed memory parallel architecture machines indicates the importance of introducing several key changes in the basic strategy and algorithums used to calculate scattering results. This analysis of the BCRLM approach provides some insights into optimal strategies for mapping three dimensional quantum scattering methods, such as the Parker-Pack method, onto shared or distributed memory parallel computers.

  5. Coherent scattering of an atom in the field of a standing wave under conditions of initial quantum correlation of subsystems

    SciTech Connect

    Trubilko, A. I.

    2016-10-15

    Coherent scattering of a two-level atom in the field of a quantized standing wave of a micromaser is considered under conditions of initial quantum correlation between the atom and the field. Such a correlation can be produced by a broadband parametric source. The interaction leading to scattering of the atom from the nonuniform field occurs in the dispersion limit or in the wing of the absorption line of the atom. Apart from the quantized field, the atom simultaneously interacts with two classical counterpropagating waves with different frequencies, which are acting in the plane perpendicular to the atom’s propagation velocity and to the wavevector of the standing wave. Joint action of the quantized field and two classical waves induces effective two-photon and Raman resonance interaction on the working transition. The effective Hamiltonian of the interaction is derived using the unitary transformation method developed for a moving atom. A strong effect is detected, which makes it possible to distinguish the correlated initial state of the atom and the field in the scattering of atom from the state of independent systems. For all three waves, scattering is not observed when systems with quantum correlation are prepared using a high-intensity parametric source. Conversely, when the atom interacts only with the nonuniform field of the standing wave, scattering is not observed in the case of the initial factorized state.

  6. A hybrid atomistic electrodynamics-quantum mechanical approach for simulating surface-enhanced Raman scattering.

    PubMed

    Payton, John L; Morton, Seth M; Moore, Justin E; Jensen, Lasse

    2014-01-21

    Surface-enhanced Raman scattering (SERS) is a technique that has broad implications for biological and chemical sensing applications by providing the ability to simultaneously detect and identify a single molecule. The Raman scattering of molecules adsorbed on metal nanoparticles can be enhanced by many orders of magnitude. These enhancements stem from a twofold mechanism: an electromagnetic mechanism (EM), which is due to the enhanced local field near the metal surface, and a chemical mechanism (CM), which is due to the adsorbate specific interactions between the metal surface and the molecules. The local field near the metal surface can be significantly enhanced due to the plasmon excitation, and therefore chemists generally accept that the EM provides the majority of the enhancements. While classical electrodynamics simulations can accurately simulate the local electric field around metal nanoparticles, they offer few insights into the spectral changes that occur in SERS. First-principles simulations can directly predict the Raman spectrum but are limited to small metal clusters and therefore are often used for understanding the CM. Thus, there is a need for developing new methods that bridge the electrodynamics simulations of the metal nanoparticle and the first-principles simulations of the molecule to facilitate direct simulations of SERS spectra. In this Account, we discuss our recent work on developing a hybrid atomistic electrodynamics-quantum mechanical approach to simulate SERS. This hybrid method is called the discrete interaction model/quantum mechanics (DIM/QM) method and consists of an atomistic electrodynamics model of the metal nanoparticle and a time-dependent density functional theory (TDDFT) description of the molecule. In contrast to most previous work, the DIM/QM method enables us to retain a detailed atomistic structure of the nanoparticle and provides a natural bridge between the electronic structure methods and the macroscopic

  7. Dual quantum electrodynamics: Dyon-dyon and charge-monopole scattering in a high-energy approximation

    SciTech Connect

    Gamberg, Leonard; Milton, Kimball A.

    2000-04-01

    We develop the quantum field theory of electron-point magnetic monopole interactions and, more generally, dyon-dyon interactions, based on the original string-dependent ''nonlocal'' action of Dirac and Schwinger. We demonstrate that a viable nonperturbative quantum field theoretic formulation can be constructed that results in a string independent cross section for monopole-electron and dyon-dyon scattering. Such calculations can be done only by using nonperturbative approximations such as the eikonal approximation and not by some mutilation of lowest-order perturbation theory. (c) 2000 The American Physical Society.

  8. Resonant absorption of electromagnetic radiation in a quantum channel due to the scattering of electrons by impurities

    NASA Astrophysics Data System (ADS)

    Karpunin, V. V.; Margulis, V. A.

    2017-06-01

    We have found an analytical expression for the absorption coefficient of electromagnetic radiation in a quantum channel with a parabolic confinement potential. The calculation has been performed using the second-order perturbation theory taking into account the scattering of a quasi-one-dimensional electron gas by ionized impurities. We have analyzed the dependences of the absorption coefficient on the frequency of the electromagnetic radiation and the magnetic field. The appearance of additional resonant peaks, which are caused by scattering by impurities, has been found.

  9. Chaotic Behaviour in Quantum Dynamics

    DTIC Science & Technology

    1991-09-01

    is in some sense an approximation for the real Schrodinger equation . This is by no means obvious: the connection between the discrete time defined by...but even by the numerical solution of the Schrodinger equation (Figs.l), thus fully supporting the validity of the Kepler Map approach also for the...confirmed by extensive numerical simulations of the time-dependeut Schrodinger equation since 19842. In addition to that the Kepler map yields an

  10. Quantum Chemistry in Nanoscale Environments: Insights on Surface-Enhanced Raman Scattering and Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Olivares-Amaya, Roberto

    The understanding of molecular effects in nanoscale environments is becoming increasingly relevant for various emerging fields. These include spectroscopy for molecular identification as well as in finding molecules for energy harvesting. Theoretical quantum chemistry has been increasingly useful to address these phenomena to yield an understanding of these effects. In the first part of this dissertation, we study the chemical effect of surface-enhanced Raman scattering (SERS). We use quantum chemistry simulations to study the metal-molecule interactions present in these systems. We find that the excitations that provide a chemical enhancement contain a mixed contribution from the metal and the molecule. Moreover, using atomistic studies we propose an additional source of enhancement, where a transition metal dopant surface could provide an additional enhancement. We also develop methods to study the electrostatic effects of molecules in metallic environments. We study the importance of image-charge effects, as well as field-bias to molecules interacting with perfect conductors. The atomistic modeling and the electrostatic approximation enable us to study the effects of the metal interacting with the molecule in a complementary fashion, which provides a better understanding of the complex effects present in SERS. In the second part of this dissertation, we present the Harvard Clean Energy Project, a high-throughput approach for a large-scale computational screening and design of organic photovoltaic materials. We create molecular libraries to search for candidates structures and use quantum chemistry, machine learning and cheminformatics methods to characterize these systems and find structure-property relations. The scale of this study requires an equally large computational resource. We rely on distributed volunteer computing to obtain these properties. In the third part of this dissertation we present our work related to the acceleration of electronic structure

  11. Andreev reflection and Aharonov-Bohm oscillations through a parallel-coupled double quantum dot with spin-flip scattering.

    PubMed

    Li, Jin-Liang; Li, Yu-Xian

    2008-11-19

    Using nonequilibrium Green's function techniques, we investigate Andreev reflection and Aharonov-Bohm oscillations through a parallel-coupled double quantum dot connected with a ferromagnetic lead and a superconductor lead. The possibility of controlling Andreev reflection and Aharonov-Bohm oscillations of the system is explored by tuning the interdot coupling, the gate voltage, the magnetic flux, and the intradot spin-flip scattering. When the spin-flip scattering increases, Fano resonant peaks resulting from the asymmetrical levels of the two quantum dots begin to split, and Aharonov-Bohm oscillations are suppressed. Due to the interdot coupling, one strongly and one weakly coupled state of the system can be formed. The magnetic flux can exchange the function of the two states, which leads to a swap effect.

  12. S-matrix decomposition, natural reaction channels, and the quantum transition state approach to reactive scattering

    NASA Astrophysics Data System (ADS)

    Manthe, Uwe; Ellerbrock, Roman

    2016-05-01

    A new approach for the quantum-state resolved analysis of polyatomic reactions is introduced. Based on the singular value decomposition of the S-matrix, energy-dependent natural reaction channels and natural reaction probabilities are defined. It is shown that the natural reaction probabilities are equal to the eigenvalues of the reaction probability operator [U. Manthe and W. H. Miller, J. Chem. Phys. 99, 3411 (1993)]. Consequently, the natural reaction channels can be interpreted as uniquely defined pathways through the transition state of the reaction. The analysis can efficiently be combined with reactive scattering calculations based on the propagation of thermal flux eigenstates. In contrast to a decomposition based straightforwardly on thermal flux eigenstates, it does not depend on the choice of the dividing surface separating reactants from products. The new approach is illustrated studying a prototypical example, the H + CH4 → H2 + CH3 reaction. The natural reaction probabilities and the contributions of the different vibrational states of the methyl product to the natural reaction channels are calculated and discussed. The relation between the thermal flux eigenstates and the natural reaction channels is studied in detail.

  13. Full-dimensional quantum dynamics of rovibrationally inelastic scattering between CN and H2.

    PubMed

    Yang, Benhui; Wang, X H; Stancil, P C; Bowman, J M; Balakrishnan, N; Forrey, R C

    2016-12-14

    We report six-dimensional (6D) potential energy surface (PES) and rovibrational scattering calculations for the CN-H2 collision system. The PES was computed using the high-level ab initio spin-restricted coupled-cluster with single, double, and perturbative triple excitations-F12B method and fitted to an analytic function using an invariant polynomial method in 6D. Quantum close-coupling calculations are reported for rotational transitions in CN by H2 and D2 collisions in 6D as well as four-dimensional (4D) within a rigid rotor model for collision energies of 1.0-1500 cm(-1). Comparisons with experimental data and previous 4D calculations are presented for CN rotational levels j1 = 4 and 11. For the first time, rovibrational quenching cross sections and rate coefficients of CN (v1 = 1,j1 = 0) in collisions with para- and ortho-H2 are also reported in full-dimension. Agreement for pure rotational transitions is found to be good, but no experimental data on rovibrational collisional quenching for CN-H2 are available. Applications of the current rotational and rovibrational rate coefficients in astrophysical modeling are briefly discussed.

  14. Full-dimensional quantum dynamics of rovibrationally inelastic scattering between CN and H2

    NASA Astrophysics Data System (ADS)

    Yang, Benhui; Wang, X. H.; Stancil, P. C.; Bowman, J. M.; Balakrishnan, N.; Forrey, R. C.

    2016-12-01

    We report six-dimensional (6D) potential energy surface (PES) and rovibrational scattering calculations for the CN-H2 collision system. The PES was computed using the high-level ab initio spin-restricted coupled-cluster with single, double, and perturbative triple excitations-F12B method and fitted to an analytic function using an invariant polynomial method in 6D. Quantum close-coupling calculations are reported for rotational transitions in CN by H2 and D2 collisions in 6D as well as four-dimensional (4D) within a rigid rotor model for collision energies of 1.0-1500 cm-1. Comparisons with experimental data and previous 4D calculations are presented for CN rotational levels j1 = 4 and 11. For the first time, rovibrational quenching cross sections and rate coefficients of CN (v1 = 1,j1 = 0) in collisions with para- and ortho-H2 are also reported in full-dimension. Agreement for pure rotational transitions is found to be good, but no experimental data on rovibrational collisional quenching for CN-H2 are available. Applications of the current rotational and rovibrational rate coefficients in astrophysical modeling are briefly discussed.

  15. Scattering mechanisms in shallow undoped Si/SiGe quantum wells

    NASA Astrophysics Data System (ADS)

    Laroche, Dominique; Huang, Shih-Hsien; Nielsen, Erik; Chuang, Yen; Li, Jiun-Yun; Liu, Chih-Wen; Lu, Tzu-Ming

    We report the magneto-transport and scattering mechanism analysis of a series of increasingly shallow Si/SiGe quantum wells with the shallowest 2DEG located only ~ 10 nm away from the surface. The peak mobility increases with increasing depth, suggesting that charge centers near the oxide/semiconductor interface is the main source of disorder. The power-law exponent of the mobility versus density curve, μ ~nα , is extracted as a function of the depth. At intermediate densities, the power-law dependence is characterized by α ~ 2 . 3 while at the highest achievable densities for devices with intermediate depth, an exponent α ~ 5 is observed. We propose, and show by simulations, that this increase in α is explained by a non-equilibrium model where electrons migrating to the surface smooth out the potential landscape seen by the 2DEG. This work has been supported by the Division of Materials Sciences and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy (DOE). Sandia National Laboratories is a multi program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's National Nuclear Security Administration under contract DE-AC04-94AL

  16. Experimental inelastic neutron scattering spectrum of hydrogen hexagonal clathrate-hydrate compared with rigorous quantum simulations

    NASA Astrophysics Data System (ADS)

    Celli, Milva; Powers, Anna; Colognesi, Daniele; Xu, Minzhong; Bačić, Zlatko; Ulivi, Lorenzo

    2013-10-01

    We have performed high-resolution inelastic neutron scattering (INS) measurements on binary hydrogen clathrate hydrates exhibiting the hexagonal structure (sH). Two samples, differing only in the ortho/para fraction of hydrogen, were prepared using heavy water and methyl tert-butyl ether as the promoter in its perdeuterated form. The INS spectrum of the translation-rotation (TR) excitations of the guest H2 molecule was obtained by subtracting the very weak signal due to the D2O lattice modes. By means of a subtraction procedure, it has been possible to obtain separately the spectra of caged p-H2 and o-H2. sH clathrates are comprised of three distinct types of cages, two of which, differing in shape and size, are each occupied by one H2 molecule only. Both contribute to the measured INS spectrum which is, therefore, rather complex and challenging to assign unambiguously. To assist with the interpretation, the INS spectra are calculated accurately utilizing the quantum methodology which incorporates the coupled five-dimensional TR energy levels and wave functions of the H2 molecule confined in each type of nanocage. The computed INS spectra are highly realistic and reflect the complexity of the coupled TR dynamics of the guest H2 in the anisotropic confining environment. The simulated INS spectra of p-H2 and o-H2 in the small and medium cages are compared with the experimental data, and are indispensable for their interpretation.

  17. S-matrix decomposition, natural reaction channels, and the quantum transition state approach to reactive scattering.

    PubMed

    Manthe, Uwe; Ellerbrock, Roman

    2016-05-28

    A new approach for the quantum-state resolved analysis of polyatomic reactions is introduced. Based on the singular value decomposition of the S-matrix, energy-dependent natural reaction channels and natural reaction probabilities are defined. It is shown that the natural reaction probabilities are equal to the eigenvalues of the reaction probability operator [U. Manthe and W. H. Miller, J. Chem. Phys. 99, 3411 (1993)]. Consequently, the natural reaction channels can be interpreted as uniquely defined pathways through the transition state of the reaction. The analysis can efficiently be combined with reactive scattering calculations based on the propagation of thermal flux eigenstates. In contrast to a decomposition based straightforwardly on thermal flux eigenstates, it does not depend on the choice of the dividing surface separating reactants from products. The new approach is illustrated studying a prototypical example, the H + CH4 → H2 + CH3 reaction. The natural reaction probabilities and the contributions of the different vibrational states of the methyl product to the natural reaction channels are calculated and discussed. The relation between the thermal flux eigenstates and the natural reaction channels is studied in detail.

  18. Discrete states and carrier-phonon scattering in quantum dot population dynamics

    PubMed Central

    Man, Minh Tan; Lee, Hong Seok

    2015-01-01

    The influence of the growth conditions of multilayer CdTe/ZnTe quantum dots (QDs) on Si substrate upon their carrier dynamics is studied using intensity integration and broadening photoluminescence. The unusual temperature dependence of the line broadening is explained using a model for interband transitions that involves a lowest discrete electronic state (1Se) with different discrete hole states (1S3/2 and 2S3/2) and a 1P transition. These transitions are expected to play a critical role in both the thermally activated energy and the line broadening of the QDs. We also demonstrate that a thermally activated transition between two different states occurs with band low-temperature quenching, with values separated by 5.8–16 meV. The main nonradiative process is thermal escape assisted by carrier scattering via emission of longitudinal phonons through the hole states at high temperature, with an average energy of 19.3–20.2 meV. PMID:25652600

  19. Trajectory approach to dissipative quantum phase space dynamics: Application to barrier scattering.

    PubMed

    Hughes, Keith H; Wyatt, Robert E

    2004-03-01

    The Caldeira-Leggett master equation, expressed in Lindblad form, has been used in the numerical study of the effect of a thermal environment on the dynamics of the scattering of a wave packet from a repulsive Eckart barrier. The dynamics are studied in terms of phase space trajectories associated with the distribution function, W(q,p,t). The equations of motion for the trajectories include quantum terms that introduce nonlocality into the motion, which imply that an ensemble of correlated trajectories needs to be propagated. However, use of the derivative propagation method (DPM) allows each trajectory to be propagated individually. This is achieved by deriving equations of motion for the partial derivatives of W(q,p,t) that appear in the master equation. The effects of dissipation on the trajectories are studied and results are shown for the transmission probability. On short time scales, decoherence is demonstrated by a swelling of trajectories into momentum space. For a nondissipative system, a comparison is made of the DPM with the "exact" transmission probability calculated from a fixed grid calculation.

  20. Effect of Pure Dephasing and Phonon Scattering on the Coupling of Semiconductor Quantum Dots to Optical Cavities

    NASA Astrophysics Data System (ADS)

    Jarlov, C.; Wodey, É.; Lyasota, A.; Calic, M.; Gallo, P.; Dwir, B.; Rudra, A.; Kapon, E.

    2016-08-01

    Using site-controlled semiconductor quantum dots (QDs) free of multiexcitonic continuum states, integrated with photonic crystal membrane cavities, we clarify the effects of pure dephasing and phonon scattering on exciton-cavity coupling in the weak-coupling regime. In particular, the observed QD-cavity copolarization and cavity mode feeding versus QD-cavity detuning are explained quantitatively by a model of a two-level system embedded in a solid-state environment.

  1. Excitation energy-dependent nature of Raman scattering spectrum in GaInNAs/GaAs quantum well structures.

    PubMed

    Erol, Ayse; Akalin, Elif; Sarcan, Fahrettin; Donmez, Omer; Akyuz, Sevim; Arikan, Cetin M; Puustinen, Janne; Guina, Mircea

    2012-11-28

    The excitation energy-dependent nature of Raman scattering spectrum, vibration, electronic or both, has been studied using different excitation sources on as-grown and annealed n- and p-type modulation-doped Ga1 - xInxNyAs1 - y/GaAs quantum well structures. The samples were grown by molecular beam technique with different N concentrations (y = 0%, 0.9%, 1.2%, 1.7%) at the same In concentration of 32%. Micro-Raman measurements have been carried out using 532 and 758 nm lines of diode lasers, and the 1064 nm line of the Nd-YAG laser has been used for Fourier transform-Raman scattering measurements. Raman scattering measurements with different excitation sources have revealed that the excitation energy is the decisive mechanism on the nature of the Raman scattering spectrum. When the excitation energy is close to the electronic band gap energy of any constituent semiconductor materials in the sample, electronic transition dominates the spectrum, leading to a very broad peak. In the condition that the excitation energy is much higher than the band gap energy, only vibrational modes contribute to the Raman scattering spectrum of the samples. Line shapes of the Raman scattering spectrum with the 785 and 1064 nm lines of lasers have been observed to be very broad peaks, whose absolute peak energy values are in good agreement with the ones obtained from photoluminescence measurements. On the other hand, Raman scattering spectrum with the 532 nm line has exhibited only vibrational modes. As a complementary tool of Raman scattering measurements with the excitation source of 532 nm, which shows weak vibrational transitions, attenuated total reflectance infrared spectroscopy has been also carried out. The results exhibited that the nature of the Raman scattering spectrum is strongly excitation energy-dependent, and with suitable excitation energy, electronic and/or vibrational transitions can be investigated.

  2. Quantum dynamical simulation of the scattering of Ar from a frozen LiF(100) surface based on a first principles interaction potential.

    PubMed

    Azuri, Asaf; Pollak, Eli

    2015-07-07

    In-plane two and three dimensional diffraction patterns are computed for the vertical scattering of an Ar atom from a frozen LiF(100) surface. Suitable collimation of the incoming wavepacket serves to reveal the quantum mechanical diffraction. The interaction potential is based on a fit to an ab initio potential calculated using density functional theory with dispersion corrections. Due to the potential coupling found between the two horizontal surface directions, there are noticeable differences between the quantum angular distributions computed for two and three dimensional scattering. The quantum results are compared to analogous classical Wigner computations on the same surface and with the same conditions. The classical dynamics largely provides the envelope for the quantum diffractive scattering. The classical results also show that the corrugation along the [110] direction of the surface is smaller than along the [100] direction, in qualitative agreement with experimental observations of unimodal and bimodal scattering for the [110] and [100] directions, respectively.

  3. Quantum dynamical simulation of the scattering of Ar from a frozen LiF(100) surface based on a first principles interaction potential

    SciTech Connect

    Azuri, Asaf; Pollak, Eli

    2015-07-07

    In-plane two and three dimensional diffraction patterns are computed for the vertical scattering of an Ar atom from a frozen LiF(100) surface. Suitable collimation of the incoming wavepacket serves to reveal the quantum mechanical diffraction. The interaction potential is based on a fit to an ab initio potential calculated using density functional theory with dispersion corrections. Due to the potential coupling found between the two horizontal surface directions, there are noticeable differences between the quantum angular distributions computed for two and three dimensional scattering. The quantum results are compared to analogous classical Wigner computations on the same surface and with the same conditions. The classical dynamics largely provides the envelope for the quantum diffractive scattering. The classical results also show that the corrugation along the [110] direction of the surface is smaller than along the [100] direction, in qualitative agreement with experimental observations of unimodal and bimodal scattering for the [110] and [100] directions, respectively.

  4. Inelastic electron scattering off a quantum dot in the cotunneling regime: The signature of mesoscopic Stoner instability

    NASA Astrophysics Data System (ADS)

    Repin, E. V.; Burmistrov, I. S.

    2016-04-01

    We explore the inelastic electron-scattering cross section off a metallic quantum dot close to the Stoner instability. We focus on the regime of strong Coulomb blockade in which the scattering cross section is dominated by the cotunneling processes. For large enough exchange interaction, the quantum dot acquires a finite total spin in the ground state. In this so-called mesoscopic Stoner instability regime, we find that at low enough temperatures, the inelastic scattering cross section (including the contribution due to an elastic electron spin flip) for an electron with an energy close to the chemical potential is different from the case of a magnetic impurity with the same spin. This difference stems from (i) the presence of low-lying many-body states of a quantum dot and (ii) the correlations of the tunneling amplitudes. Our results provide a possible explanation for the absence of the dephasing rate saturation at low temperatures in a recent experiment [N. Teneh, A. Yu. Kuntsevich, V. M. Pudalov, and M. Reznikov, Phys. Rev. Lett. 109, 226403 (2012), 10.1103/PhysRevLett.109.226403] in which the existence of local spin droplets in disordered electron liquid has been unraveled.

  5. Non-resonant elastic scattering of low-energy photons by atomic sodium confined in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Ghosh, Avijit; Ray, Debasis

    2015-03-01

    The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

  6. Non-resonant elastic scattering of low-energy photons by atomic sodium confined in quantum plasmas

    SciTech Connect

    Ghosh, Avijit Ray, Debasis

    2015-03-15

    The non-resonant elastic scattering of low-energy photons by the bound valence electron in the ground state 3s of atomic sodium confined in quantum plasmas is investigated theoretically. The incident photon energy is assumed to be much smaller than the 3s-3p excitation energy. The alkali atom sodium is first formulated as an effective one-electron problem in which the attractive interaction between the valence electron and the atomic ion core is simulated by a spherically symmetric model potential. The Shukla-Eliasson oscillatory exponential cosine screened-Coulomb potential model is then used to mimic the effective two-body (valence-core) interaction within quantum plasmas. Non-relativistic calculations performed within the electric dipole approximation indicate that the non-resonant elastic photon scattering cross-section undergoes a dramatic growth by several orders of magnitude as the quantum wave number increases. A qualitative explanation of this phenomenon is presented. In the absence of the oscillatory cosine screening term, a similar growth is observed at larger values of the quantum wave number. Our computed relevant atomic data are in very good agreement with the experimental as well as the previous theoretical data for the zero-screening (free atom) case, and with the very limited, accurate theoretical results available for the case of exponential screened-Coulomb two-body interaction, without the cosine screening term.

  7. Hidden quantum phase transition in Mn1 -xFexGe evidenced by small-angle neutron scattering

    NASA Astrophysics Data System (ADS)

    Altynbaev, E.; Siegfried, S.-A.; Moskvin, E.; Menzel, D.; Dewhurst, C.; Heinemann, A.; Feoktystov, A.; Fomicheva, L.; Tsvyashchenko, A.; Grigoriev, S.

    2016-11-01

    The magnetic system of the Mn1 -xFexGe solid solution is ordered in a spiral spin structure in the whole concentration range of x ∈[0 ÷1 ] . The close inspection of the small-angle neutron-scattering data reveals the quantum phase transition from the long-range ordered to short-range ordered helical structure upon increase of Fe concentration at x ∈[0.25 ÷0.4 ] . The short-range order (SRO) of the helical structure is identified as a Lorentzian contribution, while long-range order is associated with the Gaussian contribution into the scattering profile function. The scenario of the quantum phase transition with x as a driving parameter is similar to the thermal phase transition in pure MnGe. The quantum nature of the SRO is proved by the temperature-independent correlation length of the helical structure at low- and intermediate-temperature ranges with remarkable decrease above certain temperature TQ. We suggest the x -dependent modification of the effective Ruderman-Kittel-Kasuya-Yosida exchange interaction within the Heisenberg model of magnetism to explain the quantum critical regime in Mn1 -xFexGe .

  8. Amplitude-phase coupling and chirp in quantum-dot lasers: influence of charge carrier scattering dynamics.

    PubMed

    Lingnau, Benjamin; Chow, Weng W; Lüdge, Kathy

    2014-03-10

    We investigate the dependence of the amplitude-phase coupling in quantum-dot (QD) lasers on the charge-carrier scattering timescales. The carrier scattering processes influence the relaxation oscillation parameters, as well as the frequency chirp, which are both important parameters when determining the modulation performance of the laser device and its reaction to optical perturbations. We find that the FM/AM response exhibits a strong dependence on the modulation frequency, which leads to a modified optical response of QD lasers when compared to conventional laser devices. Furthermore, the frequency response curve changes with the scattering time scales, which can allow for an optimization of the laser stability towards optical perturbations.

  9. A MATLAB-based finite-element visualization of quantum reactive scattering. I. Collinear atom-diatom reactions

    NASA Astrophysics Data System (ADS)

    Warehime, Mick; Alexander, Millard H.

    2014-07-01

    We restate the application of the finite element method to collinear triatomic reactive scattering dynamics with a novel treatment of the scattering boundary conditions. The method provides directly the reactive scattering wave function and, subsequently, the probability current density field. Visualizing these quantities provides additional insight into the quantum dynamics of simple chemical reactions beyond simplistic one-dimensional models. Application is made here to a symmetric reaction (H+H2), a heavy-light-light reaction (F+H2), and a heavy-light-heavy reaction (F+HCl). To accompany this article, we have written a MATLAB code which is fast, simple enough to be accessible to a wide audience, as well as generally applicable to any problem that can be mapped onto a collinear atom-diatom reaction. The code and user's manual are available for download from http://www2.chem.umd.edu/groups/alexander/FEM.

  10. A MATLAB-based finite-element visualization of quantum reactive scattering. I. Collinear atom-diatom reactions

    SciTech Connect

    Warehime, Mick; Alexander, Millard H.

    2014-07-14

    We restate the application of the finite element method to collinear triatomic reactive scattering dynamics with a novel treatment of the scattering boundary conditions. The method provides directly the reactive scattering wave function and, subsequently, the probability current density field. Visualizing these quantities provides additional insight into the quantum dynamics of simple chemical reactions beyond simplistic one-dimensional models. Application is made here to a symmetric reaction (H+H{sub 2}), a heavy-light-light reaction (F+H{sub 2}), and a heavy-light-heavy reaction (F+HCl). To accompany this article, we have written a MATLAB code which is fast, simple enough to be accessible to a wide audience, as well as generally applicable to any problem that can be mapped onto a collinear atom-diatom reaction. The code and user's manual are available for download from http://www2.chem.umd.edu/groups/alexander/FEM.

  11. Multiparticle Correlations in Mesoscopic Scattering: Boson Sampling, Birthday Paradox, and Hong-Ou-Mandel Profiles

    NASA Astrophysics Data System (ADS)

    Urbina, Juan-Diego; Kuipers, Jack; Matsumoto, Sho; Hummel, Quirin; Richter, Klaus

    2016-03-01

    The interplay between single-particle interference and quantum indistinguishability leads to signature correlations in many-body scattering. We uncover these with a semiclassical calculation of the transmission probabilities through mesoscopic cavities for systems of noninteracting particles. For chaotic cavities we provide the universal form of the first two moments of the transmission probabilities over ensembles of random unitary matrices, including weak localization and dephasing effects. If the incoming many-body state consists of two macroscopically occupied wave packets, their time delay drives a quantum-classical transition along a boundary determined by the bosonic birthday paradox. Mesoscopic chaotic scattering of Bose-Einstein condensates is, then, a realistic candidate to build a boson sampler and to observe the macroscopic Hong-Ou-Mandel effect.

  12. Probing microstructures of molybdenum disulfide quantum dots by resonant Raman scattering

    NASA Astrophysics Data System (ADS)

    Bai, Ruipeng; Wang, Peijie; Fang, Yan

    2017-04-01

    Research on the photoluminescence (PL) mechanism of MoS2 quantum dots (MQDs) has entered into a new age that involves analyzing the complicated microstructures of MQDs that are presumably significant for PL emission. However, microstructures of MQDs have not been clearly observed and thoroughly identified by conventional detection techniques. In this work, pure MQDs were fabricated by pulsed laser ablation along the direction parallel to basal planes of the MoS2 crystal in deionized water to enable resonant Raman measurements. Resonant Raman scattering (RRS) that corresponds to microstructures of MQDs, especially defects and disorders at the edges and surfaces of MQDs, is obtained, which is distinctly different from that of bulk and monolayer MoS2 and has not been characterized in such a direct method by RRS spectroscopy. The highest intensity of the defect-induced LA(M) peak at approximately 217 cm-1, which is similar to the D band of graphene, indicates the existence of enormous defects and disorders. Furthermore, the LA(M) peak is split into a shoulder at 212 cm-1 and a peak at 217 cm-1 which are due to double resonance processes derived from defects on the edges and disorders in the planes, respectively. More resonant two-phonon Raman processes appear because of the strong electron-phonon coupling at resonance. In addition, the typical phonon modes of MoS2 and Raman-silent phonon modes are analyzed and identified. This work indicates that the features of microstructures of MQDs can be convincingly and experimentally characterized by RRS spectroscopy.

  13. Characterization of phthalocyanine functionalized quantum dots by dynamic light scattering, laser Doppler, and capillary electrophoresis.

    PubMed

    Ramírez-García, Gonzalo; Oluwole, David O; Nxele, Siphesihle Robin; d'Orlyé, Fanny; Nyokong, Tebello; Bedioui, Fethi; Varenne, Anne

    2017-02-01

    In this work, we characterized different phtalocyanine-capped core/shell/shell quantum dots (QDs) in terms of stability, ζ-potential, and size at various pH and ionic strengths, by means of capillary electrophoresis (CE), and compared these results to the ones obtained by laser Doppler electrophoresis (LDE) and dynamic light scattering (DLS). The effect of the phthalocyanine metallic center (Zn, Al, or In), the number (one or four), and nature of substituents (carboxyphenoxy- or sulfonated-) of functionalization on the phthalocyanine physicochemical properties were evaluated. Whereas QDs capped with zinc mono-carboxyphenoxy-phtalocyanine (ZnMCPPc-QDs) remained aggregated in the whole analyzed pH range, even at low ionic strength, QDs capped with zinc tetracarboxyphenoxy phtalocyanine (ZnTPPc-QDs) were easily dispersed in buffers at pH equal to or higher than 7.4. QDs capped with aluminum tetrasulfonated phthalocyanine (AlTSPPc-QDs) and indium tetracarboxyphenoxy phthalocyanines (InTCPPc-QDs) were stable in aqueous suspension only at pH higher than 9.0 due to the presence of functional groups bound to the metallic center of the phthalocyanine. The ζ-potential values determined by CE for all the samples decreased when ionic strength increased, being well correlated with the aggregation of the nanoconjugates at elevated salt concentrations. The use of electrokinetic methodologies has provided insights into the colloidal stability of the photosensitizer-functionalized QDs in physiological relevant solutions and thereby, its usefulness for improving their design and applications for photodynamic therapy. Graphical Abstract Schematic illustration of the phthalocyanine capped QDs nanoconjugates and the capillary electrophoresis methods applied for size and ζ-potential characterization.

  14. Role of interface roughness scattering, temperature, and structural parameters on the performance characteristics of III-nitride quantum cascade detectors

    NASA Astrophysics Data System (ADS)

    Saha, S.; Kumar, J.

    2017-02-01

    A III-nitride quantum cascade detector (QCD) for the fiber optic communication wavelength (˜1.5 μm) has been designed, and the effect of intersubband scattering processes such as longitudinal-optical phonon scattering, ionized impurity scattering, and more importantly interface roughness scattering on responsivity performance has been analyzed. Carrier transport in the detector is modeled using a simplified rate equation approach. It is observed that inclusion of interface roughness scattering in the carrier transport model significantly enhances the responsivity performance of the detector. The effects of roughness conditions for instance mean roughness height and correlation length on responsivity have been examined. The responsivity of the designed detector drops by 2.16 mA/W at 400 K compared to its low temperature value at 50 K and the detection wavelength change with temperature is insignificant, which are very helpful for the stable detection of the radiation for a wide range of operating temperatures and show the thermal stability of III-nitride QCDs. The effects of active well widths, extractor barrier widths, and extractor well widths have been further investigated. A higher responsivity performance is observed for narrower barrier widths. It is noticed that change in the active well width significantly modifies the responsivity of the detector and the wavelength gets red shifted for larger active well widths.

  15. Synchronization of chaotic systems

    SciTech Connect

    Pecora, Louis M.; Carroll, Thomas L.

    2015-09-15

    We review some of the history and early work in the area of synchronization in chaotic systems. We start with our own discovery of the phenomenon, but go on to establish the historical timeline of this topic back to the earliest known paper. The topic of synchronization of chaotic systems has always been intriguing, since chaotic systems are known to resist synchronization because of their positive Lyapunov exponents. The convergence of the two systems to identical trajectories is a surprise. We show how people originally thought about this process and how the concept of synchronization changed over the years to a more geometric view using synchronization manifolds. We also show that building synchronizing systems leads naturally to engineering more complex systems whose constituents are chaotic, but which can be tuned to output various chaotic signals. We finally end up at a topic that is still in very active exploration today and that is synchronization of dynamical systems in networks of oscillators.

  16. Inelastic Scattering of Identical Molecules within Framework of the Mixed Quantum/Classical Theory: Application to Rotational Excitations in H2 + H2.

    PubMed

    Semenov, Alexander; Babikov, Dmitri

    2016-06-09

    Theoretical foundation is laid out for description of permutation symmetry in the inelastic scattering processes that involve collisions of two identical molecules, within the framework of the mixed quantum/classical theory (MQCT). In this approach, the rotational (and vibrational) states of two molecules are treated quantum-mechanically, whereas their translational motion (responsible for scattering) is treated classically. This theory is applied to H2 + H2 system, and the state-to-state transition cross sections are compared versus those obtained from the full-quantum calculations and experimental results from the literature. Good agreement is found in all cases. It is also found that results of MQCT, where the Coriolis coupling is included classically, are somewhat closer to exact full-quantum results than results of the other approximate quantum methods, where those coupling terms are neglected. These new developments allow applications of MQCT to a broad variety of molecular systems and processes.

  17. Resonant soft x-ray scattering from La1-xSrxMnO3 quantum wire arrays

    NASA Astrophysics Data System (ADS)

    Wang, Shuai; Smadici, Serban; Lee, James; Odlyzko, Michael; Zhai, Xiaofang; Eckstein, James; Shah, Amish; Zuo, Jian-Min; Abbamonte, Peter; Bhattacharya, Anand

    2009-03-01

    Any finite sized, patterned system with an energy gap is expected to have elementary excitations that are characteristic of its boundary. To test this idea we have fabricated large arrays (>60000 elements) of colossal magnetoresistance- phase La2/3 Sr1/3 MnO3 quantum wires. These wires are 80 nm in width so have properties that are dominated by edge effects. We used resonant soft x-ray scattering (RSXS) and SQUID magnetometry to study their magnetic properties. We found that patterning lowers the Curie temperature and suppresses the degree of magnetization. RSXS studies show diffraction maxima from the wire period, as well as temperature-dependent diffuse scattering. We will discuss these results in the context of combined structural and magnetic disorder. Funding #: DOE grants DE-FG02-07ER46453 and DE-FG02-06ER46285

  18. Quantum Scattering Study of Ro-Vibrational Excitations in N+N(sub 2) Collisions under Re-entry Conditions

    NASA Technical Reports Server (NTRS)

    Wang, Dunyou; Stallcop, James R.; Dateo, Christopher E.; Schwenke, David W.; Huo, Winifred M.

    2004-01-01

    A three-dimensional time-dependent quantum dynamics approach using a recently developed ab initio potential energy surface is applied to study ro-vibrational excitation in N+N2 exchange scattering for collision energies in the range 2.1- 3.2 eV. State-to-state integral exchange cross sections are examined to determine the distribution of excited rotational states of N(sub 2). The results demonstrate that highly-excited rotational states are produced by exchange scattering and furthermore, that the maximum value of (Delta)j increases rapidly with increasing collision energies. Integral exchange cross sections and exchange rate constants for excitation to the lower (upsilon = 0-3) vibrational energy levels are presented as a function of the collision energy. Excited-vibrational-state distributions for temperatures at 2,000 K and 10,000 K are included.

  19. Scattering rates due to electron-phonon interaction in CdS1-xSex quantum dots

    NASA Astrophysics Data System (ADS)

    Alcalde, Augusto M.; Weber, Gerald

    2000-11-01

    We calculate electron-LO-confined and surface phonon scattering rates in CdS1-xSex spherical quantum dots. The phonon modes are described in the frame of the two-mode dielectric continuum model, and the standard k.p formalism is used for treating the electronic band structure. We include the effects of inhomogeneous broadening due to statistical dot size distribution, which can create a wide channel of efficient relaxation. We demonstrate that changes in the concentration can generate variations of more than one order of magnitude in the relaxation rates.

  20. Donor-impurity-related optical response and electron Raman scattering in GaAs cone-like quantum dots

    NASA Astrophysics Data System (ADS)

    Gil-Corrales, A.; Morales, A. L.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.

    2017-02-01

    The donor-impurity-related optical absorption, relative refractive index changes, and Raman scattering in GaAs cone-like quantum dots are theoretically investigated. Calculations are performed within the effective mass and parabolic band approximations, using the variational procedure to include the electron-impurity correlation effects. The study involves 1 s -like, 2px-like, and 2pz-like states. The conical structure is chosen in such a way that the cone height is large enough in comparison with the base radius thus allowing the use a quasi-analytic solution of the uncorrelated Schrödinger-like electron states.

  1. Surface enhanced Raman scattering effect of CdSe/ZnS quantum dots hybridized with Au nanowire

    NASA Astrophysics Data System (ADS)

    Lee, Yong-baek; Ho Lee, Seok; Lee, Sunmi; Lee, Hyunsoo; Kim, Jeongyong; Joo, Jinsoo

    2013-01-01

    Functionalized CdSe/ZnS quantum dots (QDs) were attached to the surface of Au nanowire (NW). Analysis of optical absorption spectra disclosed surface plasmon bands of Au NWs at 562 and 627 nm and showing an overlap with the QD absorption band. Micro Raman spectra (λex = 514 nm) of the QDs/Au single NW exhibited surface enhanced Raman scattering (SERS) peaks at 180, 205, and 277 cm-1, corresponding to surface, longitudinal, and transverse optical phonon modes, respectively. From time-resolved fluorescence spectra, the exciton lifetime of QDs decreased after hybridization with Au NW due to the energy transfer, supporting the SERS effect.

  2. Time-dependent multiple scattering approach for a single finger-gate in a Rashba-type quantum channel .

    NASA Astrophysics Data System (ADS)

    Wang, Lu-Yao

    2006-03-01

    We consider a Rashba-type quantum channel (RQC) consisting of one AC-biased finger-gates (FG) that orient perpendicularly and located above the RQC. Such an AC-biased FG gives rise to a local time-modulation in the Rashba coupling parameter, and generates a dc spin current (SC). A static potential is located inside or outside the FG in the RQC and the backscattering effect is studied. We use analytical time-dependent multiple scattering approach to treat the effect of the SC suppression due to a static potential in the RQC.

  3. Classical Fractals and Quantum Chaos in Ultracold Dipolar Collisions.

    PubMed

    Yang, B C; Pérez-Ríos, Jesús; Robicheaux, F

    2017-04-14

    We examine a dipolar-gas model to address fundamental issues regarding the correspondence between classical chaos and quantum observations in ultracold dipolar collisions. The theoretical model consists of a short-range Lennard-Jones potential well with an anisotropic, long-range dipole-dipole interaction between two atoms. Both the classical and quantum dynamics are explored for the same Hamiltonian of the system. The classical chaotic scattering is revealed by the fractals developed in the scattering function (defined as the final atom separation as a function of initial conditions), while the quantum chaotic features lead to the repulsion of the eigenphases from the corresponding quantum S matrix. The nearest-eigenphase-spacing statistics have an intermediate behavior between the Poisson and the Wigner-Dyson distributions. The character of the distribution can be controlled by changing an effective Planck constant or the dipole moment. The degree of quantum chaos shows a good correspondence with the overall average of the classical scattering function. The results presented here also provide helpful insights for understanding the role of the inherent dipole-dipole interaction in the currently ongoing experiments on ultracold collisions of highly magnetic atoms.

  4. Electron scattering from gas phase cis-diamminedichloroplatinum(II): quantum analysis of resonance dynamics.

    PubMed

    Carey, Ralph; Lucchese, Robert R; Gianturco, F A

    2013-05-28

    We present scattering calculations of electron collisions with the platinum-containing compound cis-diamminedichloroplatinum (CDDP), commonly known as cisplatin, between 0.5 eV and 6 eV, and the corresponding isolated Pt atom from 0.1 eV to 10 eV. We find evidence of resonances in e(-)-CDDP scattering, using an ab initio description of the target. We computed scattering matrix elements from equations incorporating exchange and polarization effects through the use of the static-exchange plus density functional correlation potential. Additionally, we made use of a purely local adiabatic model potential that allows Siegert eigenstates to be calculated, thereby allowing inspection of the possible resonant scattering wave functions. The total cross section for electron scattering from (5d(10)) (1)S Pt displays a large magnitude, monotonic decay from the initial collision energies, with no apparent resonance scattering features in any scattering symmetry. By contrast, the e(-)-CDDP scattering cross section shows a small feature near 3.8 eV, which results from a narrow, well localized resonance of b2 symmetry. These findings are then related to the possible electron-mediated mechanism of the action of CDDP on DNA replication as suggested by recent experiments.

  5. Electron scattering from gas phase cis-diamminedichloroplatinum(II): Quantum analysis of resonance dynamics

    NASA Astrophysics Data System (ADS)

    Carey, Ralph; Lucchese, Robert R.; Gianturco, F. A.

    2013-05-01

    We present scattering calculations of electron collisions with the platinum-containing compound cis-diamminedichloroplatinum (CDDP), commonly known as cisplatin, between 0.5 eV and 6 eV, and the corresponding isolated Pt atom from 0.1 eV to 10 eV. We find evidence of resonances in e--CDDP scattering, using an ab initio description of the target. We computed scattering matrix elements from equations incorporating exchange and polarization effects through the use of the static-exchange plus density functional correlation potential. Additionally, we made use of a purely local adiabatic model potential that allows Siegert eigenstates to be calculated, thereby allowing inspection of the possible resonant scattering wave functions. The total cross section for electron scattering from (5d10) 1S Pt displays a large magnitude, monotonic decay from the initial collision energies, with no apparent resonance scattering features in any scattering symmetry. By contrast, the e--CDDP scattering cross section shows a small feature near 3.8 eV, which results from a narrow, well localized resonance of b2 symmetry. These findings are then related to the possible electron-mediated mechanism of the action of CDDP on DNA replication as suggested by recent experiments.

  6. Chaotic Neural Networks and Beyond

    NASA Astrophysics Data System (ADS)

    Aihara, Kazuyuki; Yamada, Taiji; Oku, Makito

    2013-01-01

    A chaotic neuron model which is closely related to deterministic chaos observed experimentally with squid giant axons is explained, and used to construct a chaotic neural network model. Further, such a chaotic neural network is extended to different chaotic models such as a largescale memory relation network, a locally connected network, a vector-valued network, and a quaternionic-valued neuron.

  7. Chaotic Boltzmann machines

    PubMed Central

    Suzuki, Hideyuki; Imura, Jun-ichi; Horio, Yoshihiko; Aihara, Kazuyuki

    2013-01-01

    The chaotic Boltzmann machine proposed in this paper is a chaotic pseudo-billiard system that works as a Boltzmann machine. Chaotic Boltzmann machines are shown numerically to have computing abilities comparable to conventional (stochastic) Boltzmann machines. Since no randomness is required, efficient hardware implementation is expected. Moreover, the ferromagnetic phase transition of the Ising model is shown to be characterised by the largest Lyapunov exponent of the proposed system. In general, a method to relate probabilistic models to nonlinear dynamics by derandomising Gibbs sampling is presented. PMID:23558425

  8. Chaotic Boltzmann machines

    NASA Astrophysics Data System (ADS)

    Suzuki, Hideyuki; Imura, Jun-Ichi; Horio, Yoshihiko; Aihara, Kazuyuki

    2013-04-01

    The chaotic Boltzmann machine proposed in this paper is a chaotic pseudo-billiard system that works as a Boltzmann machine. Chaotic Boltzmann machines are shown numerically to have computing abilities comparable to conventional (stochastic) Boltzmann machines. Since no randomness is required, efficient hardware implementation is expected. Moreover, the ferromagnetic phase transition of the Ising model is shown to be characterised by the largest Lyapunov exponent of the proposed system. In general, a method to relate probabilistic models to nonlinear dynamics by derandomising Gibbs sampling is presented.

  9. Chaotic Boltzmann machines.

    PubMed

    Suzuki, Hideyuki; Imura, Jun-ichi; Horio, Yoshihiko; Aihara, Kazuyuki

    2013-01-01

    The chaotic Boltzmann machine proposed in this paper is a chaotic pseudo-billiard system that works as a Boltzmann machine. Chaotic Boltzmann machines are shown numerically to have computing abilities comparable to conventional (stochastic) Boltzmann machines. Since no randomness is required, efficient hardware implementation is expected. Moreover, the ferromagnetic phase transition of the Ising model is shown to be characterised by the largest Lyapunov exponent of the proposed system. In general, a method to relate probabilistic models to nonlinear dynamics by derandomising Gibbs sampling is presented.

  10. Coherent scattering of a multiphoton quantum superposition by a mirror BEC.

    PubMed

    De Martini, Francesco; Sciarrino, Fabio; Vitelli, Chiara; Cataliotti, Francesco S

    2010-02-05

    We present the proposition of an experiment in which the multiphoton quantum superposition consisting of N approximately 10{5} particles generated by a quantum-injected optical parametric amplifier, seeded by a single-photon belonging to an Einstein-Podolsky-Rosen entangled pair, is made to interact with a mirror-Bose-Einstein condensate (BEC) shaped as a Bragg interference structure. The overall process will realize a macroscopic quantum superposition involving a microscopic single-photon state of polarization entangled with the coherent macroscopic transfer of momentum to the BEC structure, acting in spacelike separated distant places.

  11. Raman scattering as a tool for the evaluation of strain in GaN/AlN quantum dots: The effect of capping

    NASA Astrophysics Data System (ADS)

    Cros, A.; Garro, N.; Cantarero, A.; Coraux, J.; Renevier, H.; Daudin, B.

    2007-10-01

    The strain state of GaN/AlN quantum dots grown on 6H-SiC has been investigated as a function of AlN capping thickness by three different techniques. On the one hand, resonant Raman scattering allowed the detection of the A1(LO) quasiconfined mode. It was found that its frequency increases with AlN deposition, while its linewidth did not evolve significantly. Available experiments of multiwavelength anomalous diffraction and diffraction anomalous fine structure on the same samples provided the determination of the wurtzite lattice parameters a and c of the quantum dots. A very good agreement is found between resonant Raman scattering and x-ray measurements, especially concerning the in-plane strain state. The results demonstrate the adequacy of Raman scattering, in combination with the deformation potential and biaxial approximations, to determine quantitatively values of strain in GaN quantum dot layers.

  12. Quantum spin correlations in Møller scattering of relativistic electron beams

    NASA Astrophysics Data System (ADS)

    Włodarczyk, Marta; Caban, Paweł; Ciborowski, Jacek; DrÄ gowski, Michał; Rembieliński, Jakub

    2017-02-01

    The relativistic spin correlation function was calculated for a pair of electrons originating from Møller scattering of two polarized electron beams. The results were discussed in view of a possible measurement of the correlation function and the corresponding probabilities. The special case of scattering off a stationary target (both polarized and unpolarized) was also analyzed. It was shown that the Clauser-Horne-Shimony-Holt (CHSH) inequality may be violated in the relativistic energy range when both scattering electrons are highly polarized.

  13. Chaotic frequency modulation

    NASA Astrophysics Data System (ADS)

    Bernhardt, Paul A.

    1993-11-01

    Chaotic Frequency Modulation (CFM) provides the basis for a nonlinear communications system with (1) good noise suppression and (2) analogue signal encryption for secure communication links. A practical realization for a CFM transmitter employs an autonomous chaotic relaxation oscillator (ACRO) circuit for use as a chaotic voltage controlled oscillator (CVCO). The ACRO is simple to construct, consisting of only two capacitors, one inductor, a bistable nonlinear element, and a modulated current source. The CVCO period (Pk) is a nonlinear function of the current (mk) and the two previous pulse periods. Demodulation requires the use of at least three successive waveform-periods. Experimental and theoretical studies of the CVCO circuit have shown that (1) the ACRO return maps of pulse periods are embedded in three dimensions, (2) chaotic outputs are difficult to decode without prior knowledge of the circuit parameters, and (3) demodulation may be accomplished with a digital signal processor.

  14. Temperature effects on multi-particle scattering in a gapped quantum magnet

    NASA Astrophysics Data System (ADS)

    Notbohm, S.; Tennant, D. A.; Lake, B.; Canfield, P. C.; Fielden, J.; Kögerler, P.; Mikeska, H.-J.; Luckmann, C.; Telling, M. T. F.

    2007-03-01

    We report measurements of the temperature effects on the dimerized antiferromagnetic chain material, copper nitrate Cu(NO3)2·2.5D2O. Using inelastic neutron scattering we have measured the temperature dependence of the one- and two-magnon excitation spectra as well as the temperature induced one-magnon intra-band scattering in a single crystal. Comparison is made with numerical evaluations of thermal averages based on the calculation for a chain of 16 spins.

  15. Wave operator in few-body quantum scattering with Coulomb-like interactions

    SciTech Connect

    Kroeger, H.

    1985-01-01

    Functional analytical methods like strong approximation of operator-valued functions and Dunfords' calculus are applied to yield a contour integral representation with a finite contour of wave operators for nonrelativistic potential scattering with Coulomb and short-range interactions, which avoids high singularities of Coulomb-like Green's functions of stationary scattering theory. The Green's function is the unique solution of the resolvent equation, which has an A-proper kernel allowing projector methods for its solution.

  16. Quantum Image Encryption Algorithm Based on Quantum Image XOR Operations

    NASA Astrophysics Data System (ADS)

    Gong, Li-Hua; He, Xiang-Tao; Cheng, Shan; Hua, Tian-Xiang; Zhou, Nan-Run

    2016-07-01

    A novel encryption algorithm for quantum images based on quantum image XOR operations is designed. The quantum image XOR operations are designed by using the hyper-chaotic sequences generated with the Chen's hyper-chaotic system to control the control-NOT operation, which is used to encode gray-level information. The initial conditions of the Chen's hyper-chaotic system are the keys, which guarantee the security of the proposed quantum image encryption algorithm. Numerical simulations and theoretical analyses demonstrate that the proposed quantum image encryption algorithm has larger key space, higher key sensitivity, stronger resistance of statistical analysis and lower computational complexity than its classical counterparts.

  17. Effective cross section for scattering from a quasi-stationary state and Einstein relations in the quantum theory of radiation

    SciTech Connect

    Shekhtman, V.L.

    1995-12-01

    A theoretical investigation of the correlation between the resonance scattering from a quasi-stationary state and the Einstein relations in the quantum theory of radiation was carried out. On the basis of the Einstein relations, the mode-averaged value of the total scattering cross section at the frequency of the resonance maximum was obtained in the general form. With allowance for radiative, vibronic, transverse, and inhomogeneous widths of a zero-phonon line, relations were obtained that permit the oscillator strength of a resonance electronic transition to be found from measurements of the absorption cross section at the resonance frequency and the half-width of the absorption spectral line. The relations depend on the shape of the absorption spectrum. The cases of the Lorentzian, Gaussian, and Voigt line shapes were considered. Using the E-2A transitions in an optically excited ruby as an example, the cross section of the phonon resonance scattering from impurity centers in crystals with a sufficiently large value of the Debye-Waller factor, e{sup {minus}2M}{ge} 0.5, was considered. The results can be applied in phonon spectroscopy. The main results are interpreted in detail in terms of the Bohr spectroscopic correspondence principle. A new derivation is given of the Ladenburg formula relating the transition probabilities and the dispersion constants. 23 refs., 1 fig.

  18. Electron and donor-impurity-related Raman scattering and Raman gain in triangular quantum dots under an applied electric field

    NASA Astrophysics Data System (ADS)

    Tiutiunnyk, Anton; Akimov, Volodymyr; Tulupenko, Viktor; Mora-Ramos, Miguel E.; Kasapoglu, Esin; Morales, Alvaro L.; Duque, Carlos Alberto

    2016-04-01

    The differential cross-section of electron Raman scattering and the Raman gain are calculated and analysed in the case of prismatic quantum dots with equilateral triangle base shape. The study takes into account their dependencies on the size of the triangle, the influence of externally applied electric field as well as the presence of an ionized donor center located at the triangle's orthocenter. The calculations are made within the effective mass and parabolic band approximations, with a diagonalization scheme being applied to obtain the eigenfunctions and eigenvalues of the x- y Hamiltonian. The incident and secondary (scattered) radiation have been considered linearly-polarized along the y-direction, coinciding with the direction of the applied electric field. For the case with an impurity center, Raman scattering with the intermediate state energy below the initial state one has been found to show maximum differential cross-section more than by an order of magnitude bigger than that resulting from the scheme with lower intermediate state energy. The Raman gain has maximum magnitude around 35 nm dot size and electric field of 40 kV/cm for the case without impurity and at maximum considered values of the input parameters for the case with impurity. Values of Raman gain of the order of up to 104cm-1 are predicted in both cases.

  19. Partial wave analysis of scattering with the nonlocal Aharonov-Bohm effect and the anomalous cross section induced by quantum interference

    SciTech Connect

    Lin, D.-H.

    2004-05-01

    Partial wave theory of a three dimensional scattering problem for an arbitrary short range potential and a nonlocal Aharonov-Bohm magnetic flux is established. The scattering process of a 'hard sphere'-like potential and the magnetic flux is examined. An anomalous total cross section is revealed at the specific quantized magnetic flux at low energy which helps explain the composite fermion and boson model in the fractional quantum Hall effect. Since the nonlocal quantum interference of magnetic flux on the charged particles is universal, the nonlocal effect is expected to appear in a quite general potential system and will be useful in understanding some other phenomena in mesoscopic physics.

  20. Resonances in Coupled πK-ηK Scattering from Quantum Chromodynamics

    SciTech Connect

    Dudek, Jozef J.; Edwards, Robert G.; Thomas, Christopher E.; Wilson, David J.

    2014-10-01

    Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled πK, ηK scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.

  1. Cascade Chaotic System With Applications.

    PubMed

    Zhou, Yicong; Hua, Zhongyun; Pun, Chi-Man; Chen, C L Philip

    2015-09-01

    Chaotic maps are widely used in different applications. Motivated by the cascade structure in electronic circuits, this paper introduces a general chaotic framework called the cascade chaotic system (CCS). Using two 1-D chaotic maps as seed maps, CCS is able to generate a huge number of new chaotic maps. Examples and evaluations show the CCS's robustness. Compared with corresponding seed maps, newly generated chaotic maps are more unpredictable and have better chaotic performance, more parameters, and complex chaotic properties. To investigate applications of CCS, we introduce a pseudo-random number generator (PRNG) and a data encryption system using a chaotic map generated by CCS. Simulation and analysis demonstrate that the proposed PRNG has high quality of randomness and that the data encryption system is able to protect different types of data with a high-security level.

  2. Mixed Quantum/Classical Theory for Molecule-Molecule Inelastic Scattering: Derivations of Equations and Application to N2 + H2 System.

    PubMed

    Semenov, Alexander; Babikov, Dmitri

    2015-12-17

    The mixed quantum classical theory, MQCT, for inelastic scattering of two molecules is developed, in which the internal (rotational, vibrational) motion of both collision partners is treated with quantum mechanics, and the molecule-molecule scattering (translational motion) is described by classical trajectories. The resultant MQCT formalism includes a system of coupled differential equations for quantum probability amplitudes, and the classical equations of motion in the mean-field potential. Numerical tests of this theory are carried out for several most important rotational state-to-state transitions in the N2 + H2 system, in a broad range of collision energies. Besides scattering resonances (at low collision energies) excellent agreement with full-quantum results is obtained, including the excitation thresholds, the maxima of cross sections, and even some smaller features, such as slight oscillations of energy dependencies. Most importantly, at higher energies the results of MQCT are nearly identical to the full quantum results, which makes this approach a good alternative to the full-quantum calculations that become computationally expensive at higher collision energies and for heavier collision partners. Extensions of this theory to include vibrational transitions or general asymmetric-top rotor (polyatomic) molecules are relatively straightforward.

  3. Enhancing chaoticity of spatiotemporal chaos.

    PubMed

    Li, Xiaowen; Zhang, Heqiao; Xue, Yu; Hu, Gang

    2005-01-01

    In some practical situations strong chaos is needed. This introduces the task of chaos control with enhancing chaoticity rather than suppressing chaoticity. In this paper a simple method of linear amplifications incorporating modulo operations is suggested to make spatiotemporal systems, which may be originally chaotic or nonchaotic, strongly chaotic. Specifically, this control can eliminate periodic windows, increase the values and the number of positive Lyapunov exponents, make the probability distributions of the output chaotic sequences more homogeneous, and reduce the correlations of chaotic outputs for different times and different space units. The applicability of the method to practical tasks, in particular to random number generators and secure communications, is briefly discussed.

  4. Quantum state resolved inelastic and reactive scattering dynamics in molecular systems via high resolution IR laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Chapman, William Brewster

    This thesis describes a series of experiments undertaken to investigate inelastic and reactive molecular collision dynamics at the quantum-state resolved level of detail. First, time- and frequency-resolved infrared laser absorption is used to probe state-resolved collisional energy transfer in scattering of fast C1(2P3/2) radicals with room temperature HCl molecules. Final state distributions of HCl are monitored via transient infrared laser absorption yielding absolute integral collisional cross sections for energy transfer into final rotational states. Analysis of translational distributions inferred from high-resolution infrared Dopplerimetry leads to state-resolved differential scattering cross sections, which exhibit forward scattering into all observed levels. Results are compared with quasiclassical trajectory calculations on a recently proposed potential surface. Second, absolute state-to-state cross sections are reported for rotationally inelastic scattering of HF, CH4, and H2O with rare gases in crossed supersonic jets. Column-integrated densities of HF, CH4, and H2O in initial and final scattering states are probed in the jet intersection region via direct infrared laser absorption. Total inelastic cross sections for loss out of rotational ground states and excitation into higher states are determined in absolute units from the dependence of infrared absorption signals on collider gas concentration. Comparison is made with close coupling calculations performed on best available potential energy surfaces for each of the scattering systems. Finally, fluorine radicals from a pulsed discharge source are crossed with supersonically cooled hydrogen molecules to study the F + H2 /to HF(v,J) + H reaction under single collision conditions. HF(v,J) product states are probed with complete rovibrational state resolution via direct infrared laser absorption. The nascent HF(v,J) state distribution is measured for all populated vibrational manifolds at a collision

  5. Quantum Darwinism in an Everyday Environment: Huge Redundancy in Scattered Photons

    NASA Astrophysics Data System (ADS)

    Riedel, C. Jess; Zurek, Wojciech H.

    2010-07-01

    We study quantum Darwinism—the redundant recording of information about the preferred states of a decohering system by its environment—for an object illuminated by a blackbody. In the cases of point-source and isotropic illumination, we calculate the quantum mutual information between the object and its photon environment. We demonstrate that this realistic model exhibits fast and extensive proliferation of information about the object into the environment and results in redundancies orders of magnitude larger than the exactly soluble models considered to date.

  6. Quantum Darwinism in an everyday environment: huge redundancy in scattered photons.

    PubMed

    Riedel, C Jess; Zurek, Wojciech H

    2010-07-09

    We study quantum Darwinism--the redundant recording of information about the preferred states of a decohering system by its environment--for an object illuminated by a blackbody. In the cases of point-source and isotropic illumination, we calculate the quantum mutual information between the object and its photon environment. We demonstrate that this realistic model exhibits fast and extensive proliferation of information about the object into the environment and results in redundancies orders of magnitude larger than the exactly soluble models considered to date.

  7. Quantum scattering calculation for reaction Br + H2 on two potential energy surfaces

    NASA Astrophysics Data System (ADS)

    Quan, Wei-Long; Tang, Ping-Ying; Tang, Bi-Yu

    Three-dimensional time-dependent quantum wave packet calculations have been carried out for Br + H2 on a new global ab initio and a semi-empirical extended London-Eyring-Polanyi-Sato potential energy surface. It is shown that on the ab initio surface, the threshold energy is much lower, and the reaction probabilities, cross sections, and rate constants are much larger. The effects of the initial rovibrational excitation have also been studied. Comparison of rate constants with experimental measurement implies that the ab initio surface is more suitable for quantum dynamic calculation. The possible reasons and mechanism for the dynamical difference on the two PES are analyzed and discussed.

  8. Persistent currents for interacting electrons in ballistic/chaotic billiards

    NASA Astrophysics Data System (ADS)

    Zelyak, Oleksandr; Murthy, Ganpathy

    2005-03-01

    We study persistent currents in a quantum billiard enclosing a magnetic flux φ by analytical and numerical methods. We concentrate on the family of Robnik-Berry billiards generated by conformal maps of the unit disk. We study the persistent current as a function of magnetic flux and parameters of the billiard in the chaotic regime. We include Fermi-liquid interactions in a mean-field approach, justified by the recent large-N approach[1] for ballistic/chaotic quantum dots. [1] G. Murthy, R. Shankar, D. Herman, and H. Mathur, Phys. Rev. B 69, 075321 (2004); G. Murthy, R. Shankar, and H. Mathur, cond-mat/0411280.

  9. Phenomenological scattering-rate model for the simulation of the current density and emission power in mid-infrared quantum cascade lasers

    SciTech Connect

    Kurlov, S. S.; Flores, Y. V.; Elagin, M.; Semtsiv, M. P.; Masselink, W. T.; Schrottke, L.; Grahn, H. T.; Tarasov, G. G.

    2016-04-07

    A phenomenological scattering-rate model introduced for terahertz quantum cascade lasers (QCLs) [Schrottke et al., Semicond. Sci. Technol. 25, 045025 (2010)] is extended to mid-infrared (MIR) QCLs by including the energy dependence of the intersubband scattering rates for energies higher than the longitudinal optical phonon energy. This energy dependence is obtained from a phenomenological fit of the intersubband scattering rates based on published lifetimes of a number of MIR QCLs. In our approach, the total intersubband scattering rate is written as the product of the exchange integral for the squared moduli of the envelope functions and a phenomenological factor that depends only on the transition energy. Using the model to calculate scattering rates and imposing periodical boundary conditions on the current density, we find a good agreement with low-temperature data for current-voltage, power-current, and energy-photon flux characteristics for a QCL emitting at 5.2 μm.

  10. Equivalence of a tip bremsstrahlung quantum and an elastically scattered electron at ultrahigh energies

    NASA Astrophysics Data System (ADS)

    Jakubassa-Amundsen, D. H.

    2012-04-01

    In the scattering of relativistic spin-polarized electrons from point nuclei, two types of polarization correlations are compared: those of a left- or right-circular bremsstrahlung photon at the short-wavelength limit (when the outgoing electron is not observed) and those of an elastically scattered, left- or right-handed electron. Bremsstrahlung is calculated from the Dirac-Sommerfeld-Maue model, and elastic electron scattering is obtained from a partial-wave analysis. By considering a gold target and electron energies Ei up to 20 MeV, a striking similarity of the respective polarization correlations is found to develop when the collision energy is increased beyond 5 MeV. From analytical Born results for light targets it is shown that only for a longitudinally spin-polarized electron do the respective polarization correlations agree in the limit Ei→∞. In the general case, a very high nuclear charge is needed in addition, leading to a sum rule for bremsstrahlung well known from elastic electron scattering.

  11. Robert R. Wilson Prize II: A Quantum Field Theory Approach to Intrabeam Scattering

    NASA Astrophysics Data System (ADS)

    Bjorken, James

    2017-01-01

    My involvement in the intrabeam scattering problem was very brief, from the autumn of 1981 to the summer of 1982. It occurred during my tenure at Fermilab. I entered the subject as an amateur in accelerator theory. But my experience in elementary-particle theory turned out to be of help in advancing the subject.

  12. Three-dimensional analysis of free-space light propagation based on quantum mechanical scattering theory of light

    NASA Astrophysics Data System (ADS)

    Son, Hyeonho; Choi, Honggu; Oh, Kyunghwan

    2017-01-01

    In this paper, a free-space light propagation analysis between 3-dimensional (3-D) volumetric spaces is proposed. In contrast to conventional scalar diffraction, the proposed theory is based on quantum mechanical scattering providing a general volumetric analysis for the free-space light propagation. Assuming a plane wave light incidence, we obtained a new analytic formula for 3-D volumetric convolution, which provided a transfer function in a closed form used for caculating the electric fields at the observation points. The proposed method was consistent with the conventional numerical methods for a 2-dimensional aperture and can be further applied to exact calculation of diffraction fields from 3-D surfaces, providing a compact reconstruction algorithm for 3-D images in a computer generated hologram.

  13. The HD molecule in small and medium cages of clathrate hydrates: Quantum dynamics studied by neutron scattering measurements and computation

    NASA Astrophysics Data System (ADS)

    Colognesi, Daniele; Powers, Anna; Celli, Milva; Xu, Minzhong; Bačić, Zlatko; Ulivi, Lorenzo

    2014-10-01

    We report inelastic neutron scattering (INS) measurements on molecular hydrogen deuteride (HD) trapped in binary cubic (sII) and hexagonal (sH) clathrate hydrates, performed at low temperature using two different neutron spectrometers in order to probe both energy and momentum transfer. The INS spectra of binary clathrate samples exhibit a rich structure containing sharp bands arising from both the rotational transitions and the rattling modes of the guest molecule. For the clathrates with sII structure, there is a very good agreement with the rigorous fully quantum simulations which account for the subtle effects of the anisotropy, angular and radial, of the host cage on the HD microscopic dynamics. The sH clathrate sample presents a much greater challenge, due to the uncertainties regarding the crystal structure, which is known only for similar crystals with different promoter, but nor for HD (or H2) plus methyl tert-butyl ether (MTBE-d12).

  14. Exact quantum scattering calculations of transport properties for the H{sub 2}O–H system

    SciTech Connect

    Dagdigian, Paul J.; Alexander, Millard H.

    2013-11-21

    Transport properties for collisions of water with hydrogen atoms are computed by means of exact quantum scattering calculations. For this purpose, a potential energy surface (PES) was computed for the interaction of rigid H{sub 2}O, frozen at its equilibrium geometry, with a hydrogen atom, using a coupled-cluster method that includes all singles and doubles excitations, as well as perturbative contributions of connected triple excitations. To investigate the importance of the anisotropy of the PES on transport properties, calculations were performed with the full potential and with the spherical average of the PES. We also explored the determination of the spherical average of the PES from radial cuts in six directions parallel and perpendicular to the C{sub 2} axis of the molecule. Finally, the computed transport properties were compared with those computed with a Lennard-Jones 12-6 potential.

  15. The HD molecule in small and medium cages of clathrate hydrates: Quantum dynamics studied by neutron scattering measurements and computation

    SciTech Connect

    Colognesi, Daniele; Celli, Milva; Ulivi, Lorenzo; Powers, Anna; Xu, Minzhong; Bačić, Zlatko

    2014-10-07

    We report inelastic neutron scattering (INS) measurements on molecular hydrogen deuteride (HD) trapped in binary cubic (sII) and hexagonal (sH) clathrate hydrates, performed at low temperature using two different neutron spectrometers in order to probe both energy and momentum transfer. The INS spectra of binary clathrate samples exhibit a rich structure containing sharp bands arising from both the rotational transitions and the rattling modes of the guest molecule. For the clathrates with sII structure, there is a very good agreement with the rigorous fully quantum simulations which account for the subtle effects of the anisotropy, angular and radial, of the host cage on the HD microscopic dynamics. The sH clathrate sample presents a much greater challenge, due to the uncertainties regarding the crystal structure, which is known only for similar crystals with different promoter, but nor for HD (or H{sub 2}) plus methyl tert-butyl ether (MTBE-d12)

  16. On-Resonance Fluorescence, Resonance Rayleigh Scattering, and Ratiometric Resonance Synchronous Spectroscopy of Molecular- and Quantum Dot-Fluorophores.

    PubMed

    Siriwardana, Kumudu; Nettles, Charles B; Vithanage, Buddhini C N; Zhou, Yadong; Zou, Shengli; Zhang, Dongmao

    2016-09-20

    Existing studies on molecular fluorescence have almost exclusively been focused on Stokes-shifted fluorescence spectroscopy (SSF) in which the emitted photon is detected at the wavelengths longer than that for the excitation photons. Information on fluorophore on-resonance fluorescence (ORF) and resonance Rayleigh scattering (RRS) is limited and often problematic due to the complex interplay of the fluorophore photon absorption, ORF emission, RRS, and solvent Rayleigh scattering. Reported herein is a relatively large-scale systematic study on fluorophore ORF and RRS using the conventional UV-vis extinction and SSF measurements in combination with the recently reported ratiometric resonance synchronous spectroscopic (R2S2, pronounced as "R-Two-S-Two") method. A series of fundamental parameters including fluorophore ORF cross sections and quantum yields have been quantified for the first time for a total of 12 molecular and 6 semiconductor quantum dot (QD) fluorophores. All fluorophore spectra comprise a well-defined Gaussian peak with a full width at half-maximum ranging from 4 to 30 nm. However, the RRS features of fluorophores differ drastically. The effect of fluorophore aggregation on its RRS, UV-vis, R2S2, and SSF spectra was also discussed. This work highlights the critical importance of the combined UV-vis extinction, SSF, and R2S2 spectroscopic measurements for material characterizations. The method and insights described in this work can be directly used for improving the reliability of RRS spectroscopic methods in chemical analysis. In addition, it should pave the way for developing novel R2S2-based analytical applications.

  17. Raman scattering of InAs/AlAs quantum dot superlattices grown on (001) and (311)B GaAs surfaces

    PubMed Central

    2012-01-01

    We present a comparative analysis of Raman scattering by acoustic and optical phonons in InAs/AlAs quantum dot superlattices grown on (001) and (311)B GaAs surfaces. Doublets of folded longitudinal acoustic phonons up to the fifth order were observed in the Raman spectra of (001)- and (311)B-oriented quantum dot superlattices measured in polarized scattering geometries. The energy positions of the folded acoustic phonons are well described by the elastic continuum model. Besides the acoustic phonons, the spectra display features related to confined transverse and longitudinal optical as well as interface phonons in quantum dots and spacer layers. Their frequency positions are discussed in terms of phonon confinement, elastic stress, and atomic intermixing. PMID:22916827

  18. Raman scattering of InAs/AlAs quantum dot superlattices grown on (001) and (311)B GaAs surfaces.

    PubMed

    Milekhin, Alexander; Yeryukov, Nikolay; Toropov, Alexander; Dmitriev, Dmitry; Sheremet, Evgeniya; Zahn, Dietrich Rt

    2012-08-23

    We present a comparative analysis of Raman scattering by acoustic and optical phonons in InAs/AlAs quantum dot superlattices grown on (001) and (311)B GaAs surfaces. Doublets of folded longitudinal acoustic phonons up to the fifth order were observed in the Raman spectra of (001)- and (311)B-oriented quantum dot superlattices measured in polarized scattering geometries. The energy positions of the folded acoustic phonons are well described by the elastic continuum model. Besides the acoustic phonons, the spectra display features related to confined transverse and longitudinal optical as well as interface phonons in quantum dots and spacer layers. Their frequency positions are discussed in terms of phonon confinement, elastic stress, and atomic intermixing.

  19. 21 THz quantum-cascade laser operating up to 144 K based on a scattering-assisted injection design

    SciTech Connect

    Khanal, Sudeep; Reno, John L.; Kumar, Sushil

    2015-07-22

    A 2.1 THz quantum cascade laser (QCL) based on a scattering-assisted injection and resonant-phonon depopulation design scheme is demonstrated. The QCL is based on a four-well period implemented in the GaAs/Al0.15Ga0.85As material system. The QCL operates up to a heat-sink temperature of 144 K in pulsed-mode, which is considerably higher than that achieved for previously reported THz QCLs operating around the frequency of 2 THz. At 46 K, the threshold current-density was measured as ~745 A/cm2 with a peak-power output of ~10 mW. Electrically stable operation in a positive differential-resistance regime is achieved by a careful choice of design parameters. The results validate the robustness of scattering-assisted injection schemes for development of low-frequency (ν < 2.5 THz) QCLs.

  20. 21 THz quantum-cascade laser operating up to 144 K based on a scattering-assisted injection design

    DOE PAGES

    Khanal, Sudeep; Reno, John L.; Kumar, Sushil

    2015-07-22

    A 2.1 THz quantum cascade laser (QCL) based on a scattering-assisted injection and resonant-phonon depopulation design scheme is demonstrated. The QCL is based on a four-well period implemented in the GaAs/Al0.15Ga0.85As material system. The QCL operates up to a heat-sink temperature of 144 K in pulsed-mode, which is considerably higher than that achieved for previously reported THz QCLs operating around the frequency of 2 THz. At 46 K, the threshold current-density was measured as ~745 A/cm2 with a peak-power output of ~10 mW. Electrically stable operation in a positive differential-resistance regime is achieved by a careful choice of design parameters.more » The results validate the robustness of scattering-assisted injection schemes for development of low-frequency (ν < 2.5 THz) QCLs.« less

  1. External quantum efficiency response of thin silicon solar cell based on plasmonic scattering of indium and silver nanoparticles.

    PubMed

    Ho, Wen-Jeng; Lee, Yi-Yu; Su, Shih-Ya

    2014-01-01

    This study characterized the plasmonic scattering effects of indium nanoparticles (In NPs) on the front surface and silver nanoparticles (Ag NPs) on the rear surface of a thin silicon solar cell according to external quantum efficiency (EQE) and photovoltaic current-voltage. The EQE response indicates that, at wavelengths of 300 to 800 nm, the ratio of the number of photo-carriers collected to the number of incident photons shining on a thin Si solar cell was enhanced by the In NPs, and at wavelengths of 1,000 to 1,200 nm, by the Ag NPs. These results demonstrate the effectiveness of combining the broadband plasmonic scattering of two metals in enhancing the overall photovoltaic performance of a thin silicon solar cell. Short-circuit current was increased by 31.88% (from 2.98 to 3.93 mA) and conversion efficiency was increased by 32.72% (from 9.81% to 13.02%), compared to bare thin Si solar cells.

  2. External quantum efficiency response of thin silicon solar cell based on plasmonic scattering of indium and silver nanoparticles

    PubMed Central

    2014-01-01

    This study characterized the plasmonic scattering effects of indium nanoparticles (In NPs) on the front surface and silver nanoparticles (Ag NPs) on the rear surface of a thin silicon solar cell according to external quantum efficiency (EQE) and photovoltaic current–voltage. The EQE response indicates that, at wavelengths of 300 to 800 nm, the ratio of the number of photo-carriers collected to the number of incident photons shining on a thin Si solar cell was enhanced by the In NPs, and at wavelengths of 1,000 to 1,200 nm, by the Ag NPs. These results demonstrate the effectiveness of combining the broadband plasmonic scattering of two metals in enhancing the overall photovoltaic performance of a thin silicon solar cell. Short-circuit current was increased by 31.88% (from 2.98 to 3.93 mA) and conversion efficiency was increased by 32.72% (from 9.81% to 13.02%), compared to bare thin Si solar cells. PMID:25258606

  3. Quantum Darwinism in an Everyday Environment: Huge Redundancy in Scattered Photons

    NASA Astrophysics Data System (ADS)

    Riedel, Charles; Zurek, Wojciech

    2011-03-01

    We study quantum Darwinism---the redundant recording of information about the preferred states of a decohering system by its environment---for an object illuminated by a blackbody. In the cases of point-source, small disk, and isotropic illumination, we calculate the quantum mutual information between the object and its photon environment. We demonstrate that this realistic model exhibits fast and extensive proliferation of information about the object into the environment and results in redundancies orders of magnitude larger than the exactly soluble models considered to date. We also demonstrate a reduced ability to create records as initial environmental mixedness increases, in agreement with previous studies. This research is supported by the U.S. Department of Energy through the LANL/LDRD program and, in part, by the Foundational Questions Institute (FQXi).

  4. Fully quantum state-resolved inelastic scattering between He and NO(X 2Π)

    NASA Astrophysics Data System (ADS)

    Kłos, J.; Aoiz, F. J.; Verdasco, J. E.; Brouard, M.; Marinakis, S.; Stolte, S.

    2007-07-01

    Quantum mechanical close-coupling calculations have been used to obtain fully quantum state-resolved differential cross sections and opacity functions for the rotationally inelastic collisions of NO(XΠ2) with He at collision energies of 63 and 147meV using the most recent ab initio potential energy surfaces of Kłos et al. [J. Chem. Phys. 112, 2195 (2000)]. Double peaks observed in the Λ-doublet resolved differential cross sections are shown to be related to the presence of analogous peaks in the corresponding opacity functions. These structures can be linked directly to a specific expansion term in the potential, and reflect the fact that NO is not quite homonuclear.

  5. Fully quantum state-resolved inelastic scattering between He and NO(X (2)Pi).

    PubMed

    Kłos, J; Aoiz, F J; Verdasco, J E; Brouard, M; Marinakis, S; Stolte, S

    2007-07-21

    Quantum mechanical close-coupling calculations have been used to obtain fully quantum state-resolved differential cross sections and opacity functions for the rotationally inelastic collisions of NO(X (2)Pi) with He at collision energies of 63 and 147 meV using the most recent ab initio potential energy surfaces of Kłos et al. [J. Chem. Phys. 112, 2195 (2000)]. Double peaks observed in the Lambda-doublet resolved differential cross sections are shown to be related to the presence of analogous peaks in the corresponding opacity functions. These structures can be linked directly to a specific expansion term in the potential, and reflect the fact that NO is not quite homonuclear.

  6. Scattering States of HULTHÉN Interaction in Minimal Length Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Hassanabadi, H.; Zarrinkamar, S.; Maghsoodi, E.

    2013-05-01

    We first revisit the nonrelativistic minimal length quantum mechanics and reveal an interesting symmetry of the problem. In fact, we will show that the cumbersome problem can be cast into the ordinary Schrödinger equation with a new effective potential. Next, as a typical example, we show the minimal length Schrödinger equation in the presence of a nonminimal Hulthén vector interaction. The transmission and reflection coefficients are reported as well.

  7. Reprint of : Effect of incoherent scattering on three-terminal quantum Hall thermoelectrics

    NASA Astrophysics Data System (ADS)

    Sánchez, Rafael; Sothmann, Björn; Jordan, Andrew N.

    2016-08-01

    A three-terminal conductor presents peculiar thermoelectric and thermal properties in the quantum Hall regime: it can behave as a symmetric rectifier and as an ideal thermal diode. These properties rely on the coherent propagation along chiral edge channels. We investigate the effect of breaking the coherent propagation by the introduction of a probe terminal. It is shown that chiral effects not only survive the presence of incoherence but they can even improve the thermoelectric performance in the totally incoherent regime.

  8. Semi-phenomenological analysis of neutron scattering results for quasi-two dimensional quantum anti-ferromagnet

    NASA Astrophysics Data System (ADS)

    Sarkar, Subhajit; Chaudhury, Ranjan; Paul, Samir K.

    2017-01-01

    The available results from the inelastic neutron scattering experiment performed on the quasi-two dimensional spin 1/2 anti-ferromagnetic material La2CuO4 have been analysed theoretically. The formalism of ours is based on a semi-classical like treatment involving a model of an ideal gas of mobile vortices and anti-vortices built on the background of the Néel state, using the bipartite classical spin configuration corresponding to an XY-anisotropic Heisenberg anti-ferromagnet on a square lattice. The results for the integrated intensities for our spin 1/2 model corresponding to different temperatures, show occurrence of vigorous unphysical oscillations, when convoluted with a realistic spectral window function. These results indicate failure of the conventional semi-classical theoretical model of ideal vortex/anti-vortex gas arising in the Berezinskii-Kosterlitz-Thouless theory for the low spin magnetic systems. A full fledged quantum mechanical formalism and calculations seem crucial for the understanding of topological excitations in such low spin systems. Furthermore, a severe disagreement is found to occur at finite values of energy transfer between the integrated intensities obtained theoretically from the conventional formalism and those obtained experimentally. This further suggests strongly that the full quantum treatment should also incorporate the interaction between the fragile-magnons and the topological excitations. This is quite plausible in view of the recent work establishing such a process in XXZ quantum ferromagnet on 2D lattice. The high spin XXZ quasi-two dimensional antiferromagnet like MnPS3 however follows the conventional theory quite well.

  9. Simple Chaotic Hyperjerk System

    NASA Astrophysics Data System (ADS)

    Dalkiran, Fatma Yildirim; Sprott, J. C.

    In literature many chaotic systems, based on third-order jerk equations with different nonlinear functions, are available. A jerk system is taken to be a part of dynamical systems that can exhibit regular and chaotic behavior. By extension, a hyperjerk system can be described as a dynamical system with nth-order ordinary differential equations where n is 4 or up to. Hyperjerk systems have been investigated in literature in the last decade. This paper consists of numerical studies and experimental realization on FPAA for fourth-order hyperjerk system with exponential nonlinear function.

  10. Nonlocal chaotic phase synchronization

    NASA Astrophysics Data System (ADS)

    Zhan, Meng; Zheng, Zhi-Gang; Hu, Gang; Peng, Xi-Hong

    2000-09-01

    A novel synchronization behavior, nonlocal chaotic phase synchronization, is investigated. For two coupled Rossler oscillators with only one forced by an injected periodic signal, the phase of the unforced oscillator can be locked to the phase of the periodic signal while the forced one is well unlocked by the signal; in a chain of coupled chaotic oscillators with nearest coupling, the phase of an oscillator (or a cluster) can be locked to another nonneighbor one. Moreover, the mechanism underlying the transition to nonlocal synchronization is discussed in detail.

  11. Experiments in chaotic dynamics

    NASA Astrophysics Data System (ADS)

    Moon, F. C.

    Mathematical tools for the description of chaotic phenomena in physical systems are described and demonstrated, summarizing in part the principles presented in the author's book-length treatise on chaotic vibrations (Moon, 1987). Consideration is given to phase-plane and pseudo-phase-plane techniques, bifurcation diagrams, FFTs, autocorrelation functions, single and double Poincare maps, reduction to one-dimensional maps, Liapunov exponents, fractal dimensions, invariant distributions, chaos diagrams, and basin-boundary diagrams. The results obtained by application of these methods to data from typical mechanical and electronic oscillation experiments are presented graphically and discussed in detail.

  12. Inelastic light scattering studies of quantum phase transitions in copper titanium diselenium and multiferroic terbium manganese trioxygen

    NASA Astrophysics Data System (ADS)

    Barath, Harini

    In this dissertation, inelastic (Raman) light scattering techniques are used to probe the temperature- and magnetic-field-induced phase transitions of two strongly correlated systems---the magnetoelectric multiferroic TbMnO3 and the layered dichalcogenide TiSe2. In general, strongly correlated materials have a strong coupling between charge, spin, lattice and orbital degrees of freedom. Because of the interplay between various competing orders, these systems have highly complex phase diagrams and exhibit interesting phenomena such as colossal magnetoresistance (CMR), high temperature superconductivity and charge/orbital ordering (COO). Magnetoelectric multiferroics are an important and interesting sub-class of strongly correlated systems. These are systems whose magnetic and electric orders are strongly coupled, thereby showing exquisite tunability of the electric polarization via applied magnetic fields, and vice-versa. One such system is the perovskite manganite, TbMnO3, which shows magnetic-field-tuned rearrangement of the electric polarization vector in the ferroelectric phase below a critical temperature, Tc ˜ 28 K. This ferroelectric phase transition is accompanied, and in fact caused, by a magnetic phase transition from an incommensurate spiral magnetic arrangement of the Mn3+ ions to a commensurate magnetic phase as a function of applied field. We use Raman scattering to carefully probe this magnetic-field-tuned phase transition in microscopic detail. Our measurements indicate that field-induced quantum fluctuations of commensurate domains, which likely drive the field-induced polarization flop in this material, are found near the field-tuned incommensurate-commensurate phase transition. The second focus of this dissertation is the study of quantum phase transitions in TiSe2 as a function of temperature and Cu-intercalation, and the comparison of the effects of intercalation and pressure on the charge-density-wave (CDW) order in this system. All these

  13. Quantum dwell-correlation times in the scattering of two nonrelativistic particles

    SciTech Connect

    Hahne, G. E.

    2009-12-15

    In a previous paper [G. E. Hahne, J. Phys. A 36, 7149 (2003)] the author studied a nontraditional boundary value problem associated with Schroedinger's partial differential equation for the wave function of a structureless particle moving in four-dimensional spacetime: in this boundary value problem, instead of the conventional specification of initial wave-function values on a time=constant surface, suitable time-dependent boundary and normal-derivative values are given on a three-dimensional space-time surface surrounding a slablike region of interaction in four-dimensional spacetime. The particle's time coordinate plays a natural role as an operator and observable in the modified formalism. In the present paper, the formalism is extended to describe a system of two nonrelativistic particles--each with its own time coordinate--scattering from background potentials and from one another in four-dimensional spacetime. The two-body interaction is taken as a generic noninstantaneous action-at-a-distance, which depends independently on the space-time positions of the two particles. The dynamics is expressed in terms of an integral equation for the wave function, that is, a nonrelativistic version of the Bethe-Salpeter equation. An optical theorem is derived for the transition operator associated with scattering processes; when the theorem holds, the pointwise probability current density derivable from the wave function is conserved globally, that is, in a region covering the space-time domain of significant interparticle interaction. A general formula for the expected dwell-correlation time for the two particles in the space-time region in terms of the scattering matrices is worked out.

  14. Probing strong correlations with light scattering: Example of the quantum Ising model

    SciTech Connect

    Babujian, H. M.; Karowski, M.; Tsvelik, A. M.

    2016-10-01

    In this article we calculate the nonlinear susceptibility and the resonant Raman cross section for the paramagnetic phase of the ferromagnetic quantum Ising model in one dimension. In this region the spectrum of the Ising model has a gap m. The Raman cross section has a strong singularity when the energy of the outgoing photon is at the spectral gap ωf ≈ m and a square root threshold when the frequency difference between the incident and outgoing photons ωi₋ωf≈2m. Finally, the latter feature reflects the fermionic nature of the Ising model excitations.

  15. Probing strong correlations with light scattering: Example of the quantum Ising model

    DOE PAGES

    Babujian, H. M.; Karowski, M.; Tsvelik, A. M.

    2016-10-01

    In this article we calculate the nonlinear susceptibility and the resonant Raman cross section for the paramagnetic phase of the ferromagnetic quantum Ising model in one dimension. In this region the spectrum of the Ising model has a gap m. The Raman cross section has a strong singularity when the energy of the outgoing photon is at the spectral gap ωf ≈ m and a square root threshold when the frequency difference between the incident and outgoing photons ωi₋ωf≈2m. Finally, the latter feature reflects the fermionic nature of the Ising model excitations.

  16. Probing strong correlations with light scattering: Example of the quantum Ising model

    SciTech Connect

    Babujian, H. M.; Karowski, M.; Tsvelik, A. M.

    2016-10-01

    In this article we calculate the nonlinear susceptibility and the resonant Raman cross section for the paramagnetic phase of the ferromagnetic quantum Ising model in one dimension. In this region the spectrum of the Ising model has a gap m. The Raman cross section has a strong singularity when the energy of the outgoing photon is at the spectral gap ωf ≈ m and a square root threshold when the frequency difference between the incident and outgoing photons ωi₋ωf≈2m. Finally, the latter feature reflects the fermionic nature of the Ising model excitations.

  17. New- vs. chaotic- inflations

    SciTech Connect

    Barenboim, Gabriela; Park, Wan-Il E-mail: Wanil.Park@uv.es

    2016-02-01

    We show that ''spiralized' models of new-inflation can be experimentally identified mostly by their positive spectral running in direct contrast with most chaotic-inflation models which have negative runnings typically in the range of O(10{sup −4}–10{sup −3})

  18. Slowly changing potential problems in Quantum Mechanics: Adiabatic theorems, ergodic theorems, and scattering

    SciTech Connect

    Fishman, S.; Soffer, A.

    2016-07-15

    We employ the recently developed multi-time scale averaging method to study the large time behavior of slowly changing (in time) Hamiltonians. We treat some known cases in a new way, such as the Zener problem, and we give another proof of the adiabatic theorem in the gapless case. We prove a new uniform ergodic theorem for slowly changing unitary operators. This theorem is then used to derive the adiabatic theorem, do the scattering theory for such Hamiltonians, and prove some classical propagation estimates and asymptotic completeness.

  19. Enhancement of the thermoelectric figure of merit in a ferromagnet-quantum dot-superconductor device due to intradot spin-flip scattering and ac field

    NASA Astrophysics Data System (ADS)

    Xu, Wei-Ping; Zhang, Yu-Ying; Li, Zhi-Jian; Nie, Yi-Hang

    2017-08-01

    We investigate the thermoelectric properties of a ferromagnet-quantum dot-superconductor hybrid system with the intradot spin-flip scattering and the external microwave field. The results indicate that the increase of figure of merit in the gap is very slight when the spin-flip scattering strength increases, but outside the gap it significantly increases with enhancing spin-flip scattering strength. The presence of microwave field results in photon-assisted Andreev reflection and induces the satellite peaks in conductance spectrum. The appropriate match of spin-flip scattering strength, microwave field strength and frequency can significantly enhances the figure of merit of thermoelectric conversion of the device, which can be used as a scheme improving thermoelectric efficiency using microwave frequency.

  20. Chiral Scars in Chaotic Dirac Fermion Systems

    NASA Astrophysics Data System (ADS)

    Xu, Hongya; Huang, Liang; Lai, Ying-Cheng; Grebogi, Celso

    2013-02-01

    Do relativistic quantum scars in classically chaotic systems possess unique features that are not shared by nonrelativistic quantum scars? We report a class of relativistic quantum scars in massless Dirac fermion systems whose phases return to the original values or acquire a 2π change only after circulating twice about some classical unstable periodic orbits. We name such scars chiral scars, the successful identification of which has been facilitated tremendously by our development of an analytic, conformal-mapping-based method to calculate an unprecedentedly large number of eigenstates with high accuracy. Our semiclassical theory indicates that the physical origin of chiral scars can be attributed to a combined effect of chirality intrinsic to massless Dirac fermions and the geometry of the underlying classical orbit.

  1. Chaotic sequences for noisy environments

    NASA Astrophysics Data System (ADS)

    Carroll, T. L.; Rachford, F. J.

    2016-10-01

    There have been many attempts to apply chaotic signals to communications or radar, but one obstacle has been that there is no effective way to recover chaotic signals from noise larger than the signal. In this work, we create "pseudo-chaotic" signals by concatenating dictionary sequences generated from a chaotic attractor. Because the number of dictionary sequences is finite, these pseudo-chaotic signals are not actually chaotic, but they can still contain some of the desirable properties of chaos. Using dictionary sequences allows the pseudo-chaotic signal to be recovered from noise using a correlation detector and a Viterbi decoder, so the signal can be recovered from noise or interference that is larger than the signal itself.

  2. Quantum interferences induced by multiple scattering paths of the electron prior to emission in large molecules

    NASA Astrophysics Data System (ADS)

    Agueny, H.; Makhoute, A.; Tökési, K.; Dubois, A.; Hansen, J. P.

    2017-09-01

    We theoretically investigate electron emission process from a dimer generated by swift highly charged ions. The process under consideration is dealt with a non-perturbative approach by solving the time-dependent Schrödinger equation on a two-dimensional spatial grid. Numerical calculations show rich structures related to the multiple scattering paths of the electron prior to emission. This manifests by the emergence of additional oscillations with high-frequency superimposed on the Young-type oscillatory structure in the observed electron-ejected spectrum. This is not the case when calculations are performed based on the superposition principle, in which the final wave function is just a coherent sum of component wave functions described the electron emission from two-independent atoms. Within this assumption, only a direct electron emission process is taken into account. We find that contributions arising from these multiple scattering paths modify the dynamic electron emission process, and therefore, show the incorrect applicability of the above-mentioned principle, in concordance with the recent findings based on a simple three-slit interference experiment, reported in Sawant et al. (2014).

  3. Surface defects characterization in a quantum wire by coherent phonons scattering

    SciTech Connect

    Rabia, M. S.

    2015-03-30

    The influence of surface defects on the scattering properties of elastic waves in a quasi-planar crystallographic waveguide is studied in the harmonic approximation using the matching method formalism. The structural model is based on three infinite atomic chains forming a perfect lattice surmounted by an atomic surface defect. Following the Landauer approach, we solve directly the Newton dynamical equation with scattering boundary conditions and taking into account the next nearest neighbour’s interaction. A detailed study of the defect-induced fluctuations in the transmission spectra is presented for different adatom masses. As in the electronic case, the presence of localized defect-induced states leads to Fano-like resonances. In the language of mechanical vibrations, these are called continuum resonances. Numerical results reveal the intimate relation between transmission spectra and localized defect states and provide a basis for the understanding of conductance spectroscopy experiments in disordered mesoscopic systems. The results could be useful for the design of phononic devices.

  4. Methods for modeling non-equilibrium degenerate statistics and quantum-confined scattering in 3D ensemble Monte Carlo transport simulations

    NASA Astrophysics Data System (ADS)

    Crum, Dax M.; Valsaraj, Amithraj; David, John K.; Register, Leonard F.; Banerjee, Sanjay K.

    2016-12-01

    Particle-based ensemble semi-classical Monte Carlo (MC) methods employ quantum corrections (QCs) to address quantum confinement and degenerate carrier populations to model tomorrow's ultra-scaled metal-oxide-semiconductor-field-effect-transistors. Here, we present the most complete treatment of quantum confinement and carrier degeneracy effects in a three-dimensional (3D) MC device simulator to date, and illustrate their significance through simulation of n-channel Si and III-V FinFETs. Original contributions include our treatment of far-from-equilibrium degenerate statistics and QC-based modeling of surface-roughness scattering, as well as considering quantum-confined phonon and ionized-impurity scattering in 3D. Typical MC simulations approximate degenerate carrier populations as Fermi distributions to model the Pauli-blocking (PB) of scattering to occupied final states. To allow for increasingly far-from-equilibrium non-Fermi carrier distributions in ultra-scaled and III-V devices, we instead generate the final-state occupation probabilities used for PB by sampling the local carrier populations as function of energy and energy valley. This process is aided by the use of fractional carriers or sub-carriers, which minimizes classical carrier-carrier scattering intrinsically incompatible with degenerate statistics. Quantum-confinement effects are addressed through quantum-correction potentials (QCPs) generated from coupled Schrödinger-Poisson solvers, as commonly done. However, we use these valley- and orientation-dependent QCPs not just to redistribute carriers in real space, or even among energy valleys, but also to calculate confinement-dependent phonon, ionized-impurity, and surface-roughness scattering rates. FinFET simulations are used to illustrate the contributions of each of these QCs. Collectively, these quantum effects can substantially reduce and even eliminate otherwise expected benefits of considered In0.53Ga0.47 As FinFETs over otherwise identical

  5. Relationship between the field local quadrature and the quantum discord of a photon-added correlated channel under the influence of scattering and phase fluctuation noise

    NASA Astrophysics Data System (ADS)

    Domínguez-Serna, Francisco A.; Mendieta-Jimenez, Francisco J.; Rojas, Fernando

    2017-10-01

    We study quantum correlations and discord in a bipartite continuous variable hybrid system formed by linear combinations of coherent states {|{α }\\rangle } and single photon-added coherent states of the form {|{ψ }\\rangle }_{ {dp(pa)}}= N/√{2} (\\hat{a}^\\dagger {|{α }\\rangle }_a{|{α }\\rangle }_b ± \\hat{b}^\\dagger {|{α }\\rangle }_a{|{α }\\rangle }_b). We stablish a relationship between the quantum discord with a local observable (the quadrature variance for one subsystem) under the influence of scattering and phase fluctuation noise. For the pure states the quantum correlations are characterized by means of measurement induced disturbance (MID) with simultaneous quadrature measurements. In a scenario where homodyne conditional measurements are available we show that the MID provides an easy way to select optimal phases to obtain information of the maximal correlations in the channels. The quantum correlations of these entangled states with channel losses are quantitatively characterized with the quantum discord (QD) with a displaced qubit projector. We observe that as scattering increases, QD decreases monotonically. At the same time for the state {|{ψ }\\rangle }_{ {dp}}, QD is more resistant to high phase fluctuations when the average photon number n_0 is bigger than zero, but if phase fluctuations are low, QD is more resistant if n_0=0. For the dp model with scattering, we obtain an analytical expression of the QD as a function of the observable quadrature variance in a local subsystem. This relation allows us to have a way to obtain the degree of QD in the channel by just measuring a local property observable such as the quadrature variance. For the other model this relation still exists but is explored numerically. This relation is an important result that allows to identify quantum processing capabilities in terms of just local observables.

  6. Neutron scattering, solid state NMR and quantum chemistry studies of 11-keto-progesterone

    NASA Astrophysics Data System (ADS)

    Szyczewski, A.; Hołderna-Natkaniec, K.; Natkaniec, I.

    2004-07-01

    The molecule geometry, frequency and intensity of the IINS and IR vibrational bands of 11-ketoprogesterone have been obtained by the HF, PM3 and density functional theory (DFT) with the B3LYP functionals and 6-31G(d,p) basis set. The optimised bond lengths and bond angles of the steroid skeleton are in good agreement with the X-ray data. The IR and IINS spectra of ketoprogesterone, computed at the DFT level, well reproduce the vibrational wavenumbers and intensities to an accuracy allowing reliable vibrational assignments. The molecular dynamic study by 1H NMR has confirmed the sequence of onset of reorientations of subsequent methyl groups indicated by the results of quantum chemistry calculations and INS spectra.

  7. Quantum preequilibrium multistep direct calculations for nucleon scattering on deformed nuclei: a microscopic approach

    NASA Astrophysics Data System (ADS)

    Dupuis, Marc; Bonneau, Ludovic; Kawano, Toshihiko

    2008-04-01

    An introduction of the different quantum mechanics models is given for the calculation of pre-equilibrium multistep direct process for nucleon induced reaction. A practical application is presented for 238U neutron induced reaction at medium energy (10-20 MeV). The double differential cross-sections are calculated with no adjustable parameter and reproduced the data very well. The cross-sections are expressed as a sum of DWBA transition amplitudes computed with a microscopic two-body interaction. The exited states of the target are expressed as particle-hole excitations built from single particle states obtained with the HF+BCS calculation with a Skyrme force. We also perform a sensitivity study our calculations with respect to the ingredients of the model, namely the two-body interaction which generates the transitions and the target states description.

  8. Quantum interference on electron scattering in graphene by carbon impurities in underlying h -BN

    NASA Astrophysics Data System (ADS)

    Kaneko, Tomoaki; Koshino, Mikito; Saito, Riichiro

    2017-03-01

    Electronic structures and transport properties of graphene on h -BN with carbon impurities are investigated by first-principles calculation and the tight-binding model. We show that the coupling between the impurity level and the graphene's Dirac cone sensitively depends on the impurity position, and in particular, it nearly vanishes when the impurity is located right below the center of the six membered ring of graphene. The Bloch phase factor at the Brillouin zone edge plays a decisive role in the cancellation of the hopping integrals. The impurity position dependence on the electronic structures of graphene on h -BN is investigated by the first-principles calculation, and its qualitative feature is well explained by a tight-binding model with graphene and a single impurity site. We also propose a simple one-dimensional chain-impurity model to analytically describe the role of the quantum interference in the position-dependent coupling.

  9. Quantum preequilibrium multistep direct calculations for nucleon scattering on deformed nuclei: a microscopic approach

    SciTech Connect

    Dupuis, Marc; Kawano, Toshihiko; Bonneau, Ludovic

    2008-04-17

    An introduction of the different quantum mechanics models is given for the calculation of pre-equilibrium multistep direct process for nucleon induced reaction. A practical application is presented for {sup 238}U neutron induced reaction at medium energy (10-20 MeV). The double differential cross-sections are calculated with no adjustable parameter and reproduced the data very well. The cross-sections are expressed as a sum of DWBA transition amplitudes computed with a microscopic two-body interaction. The exited states of the target are expressed as particle-hole excitations built from single particle states obtained with the HF+BCS calculation with a Skyrme force. We also perform a sensitivity study our calculations with respect to the ingredients of the model, namely the two-body interaction which generates the transitions and the target states description.

  10. Experimental validation of superconducting quantum interference device sensors for electromagnetic scattering in geologic structures

    SciTech Connect

    Krauss, R.H. Jr.; Flynn, E.; Ruminer, P.

    1997-10-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This project has supported the collaborative development with Sandia National Laboratories (SNL) and the University of New Mexico (UNM) of two critical components for a hand-held low-field magnetic sensor based on superconducting quantum interference device (SQUID) sensor technology. The two components are a digital signal processing (DSP) algorithm for background noise rejection and a small hand-held dewar cooled by a cryocooler. A hand-held sensor has been designed and fabricated for detection of extremely weak magnetic fields in unshielded environments. The sensor is capable of measuring weak magnetic fields in unshielded environments and has multiple applications. We have chosen to pursue battlefield medicine as the highest probability near-term application because of stated needs of several agencies.

  11. Quantum transport through a molecular level: a scattering states numerical renormalization group study

    NASA Astrophysics Data System (ADS)

    Jovchev, Andre; Anders, Frithjof B.

    2015-10-01

    We use the scattering states numerical renormalization group (SNRG) approach to calculate the current I(V) through a single molecular level coupled to a local molecular phonon. The suppression of I for asymmetric junctions with increasing electron-phonon coupling, the hallmark of the Franck-Condon blockade, is discussed. We compare the SNRG currents with recently published data obtained by an iterative summation of path integrals approach (ISPI). Our results excellently agree with the ISPI currents for small and intermediate voltages. In the linear response regime I(V) approaches the current calculated from the equilibrium spectral function. We also present the temperature and voltage evolution of the non-equilibrium spectral functions for a particle-hole asymmetric junction with symmetric coupling to the lead.

  12. A cryogenic high pressure cell for inelastic neutron scattering measurements of quantum fluids and solids

    SciTech Connect

    Carmichael, Justin R; Omar Diallo, Souleymane

    2013-01-01

    We present our new development of a high pressure cell for inelastic neutron scattering measurements of helium at ultra-low temperatures. The cell has a large sample volume of ~140 cm3, and a working pressure of ~70 bar, with a relatively thin wall-thickness (1.1 mm) - thanks to the high yield strength aluminum used in the design. Two variants of this cell have been developed; one with permanently joined components using electron-beam welding and explosion welding, methods that have little or no impact on the global heat treatment of the cell, and another with modular and interchangeable components, which include a capacitance pressure gauge, that can be sealed using traditional indium wire technique. The performance of the cell has been tested in recent measurements on superfluid liquid helium near the solidification line.

  13. Hybrid theory and calculation of e-N2 scattering. [quantum mechanics - nuclei (nuclear physics)

    NASA Technical Reports Server (NTRS)

    Chandra, N.; Temkin, A.

    1975-01-01

    A theory of electron-molecule scattering was developed which was a synthesis of close coupling and adiabatic-nuclei theories. The theory is shown to be a close coupling theory with respect to vibrational degrees of freedom but is a adiabatic-nuclei theory with respect to rotation. It can be applied to any number of partial waves required, and the remaining ones can be calculated purely in one or the other approximation. A theoretical criterion based on fixed-nuclei calculations and not on experiment can be given as to which partial waves and energy domains require the various approximations. The theory allows all cross sections (i.e., pure rotational, vibrational, simultaneous vibration-rotation, differential and total) to be calculated. Explicit formulae for all the cross sections are presented.

  14. Complex generalized minimal residual algorithm for iterative solution of quantum-mechanical reactive scattering equations

    NASA Technical Reports Server (NTRS)

    Chatfield, David C.; Reeves, Melissa S.; Truhlar, Donald G.; Duneczky, Csilla; Schwenke, David W.

    1992-01-01

    Complex dense matrices corresponding to the D + H2 and O + HD reactions were solved using a complex generalized minimal residual (GMRes) algorithm described by Saad and Schultz (1986) and Saad (1990). To provide a test case with a different structure, the H + H2 system was also considered. It is shown that the computational effort for solutions with the GMRes algorithm depends on the dimension of the linear system, the total energy of the scattering problem, and the accuracy criterion. In several cases with dimensions in the range 1110-5632, the GMRes algorithm outperformed the LAPACK direct solver, with speedups for the linear equation solution as large as a factor of 23.

  15. The quantum nature of the OH stretching mode in ice and water probed by neutron scattering experiments

    SciTech Connect

    Senesi, Roberto; Flammini, Davide; Kolesnikov, Alexander I; Murray, Eamonn D.; Galli, Giulia; Andreani, Carla

    2013-01-01

    The OH stretching vibrational spectrum of water was measured in a wide range of temperatures across the triple point, 269 K < T < 296 K, using Inelastic Neutron Scattering (INS). The hydrogen projected density of states and the proton mean kinetic energy, _OH, were determined for the first time within the framework of a harmonic description of the proton dynamics. We found that in the liquid the value of _OH is nearly constant as a function of T, indicating that quantum effects on the OH stretching frequency are weakly dependent on temperature. In the case of ice, ab initio electronic structure calculations, using non-local van der Waals functionals, provided _OH values in agreement with INS experiments. We also found that the ratio of the stretching (_OH) to the total (_exp) kinetic energy, obtained from the present measurements, increases in going from ice, where hydrogen bonding is the strongest, to the liquid at ambient conditions and then to the vapour phase, where hydrogen bonding is the weakest. The same ratio was also derived from the combination of previous deep inelastic neutron scattering data, which does not rely upon the harmonic approximation, and the present measurements. We found that the ratio of stretching to the total kinetic energy shows a minimum in the metastable liquid phase. This finding suggests that the strength of intermolecular interactions increases in the supercooled phase, with respect to that in ice, contrary to the accepted view that supercooled water exhibits weaker hydrogen bonding than ice.

  16. Chaotic Hamiltonian Dynamics.

    NASA Astrophysics Data System (ADS)

    Bialek, James Mark

    Chaotic behavior may be observed in deterministic Hamiltonian Systems with as few as three dimensions, i.e., X, P, and t. The amount of chaotic behavior depends on the relative influence of the integrable and non-integrable parts of the Hamiltonian. The Standard Map is such a system and the amount of chaotic behavior may be varied by adjusting a single parameter. The global phase space portrait is a complicated mixture of quiescent and chaotic regions. First a new calculational method, characterized by a Fractal Diagram, is presented. This allows the quantitative prediction of the boundaries between regular and chaotic regions in phase space. Where these barriers are located gives qualitative insight into diffusion in phase space. The method is illustrated with the Standard Map but may be applied to any Hamiltonian System. The second phenomenon is the Universal Behavior predicted to occur for all area preserving maps. As a parameter is varied causing the mapping to become more chaotic a pattern is observed in the location and stability of the fixed points of the maps. The fixed points undergo an infinite sequence of period doubling bifurcations in a finite range of the parameter. The relative locations of the fixed point bifurcation and the parameter intervals between bifurcations both asymptotically approach constants which are Universal in that the same constants keep appearing in different problems. Predictions of Universal Behavior have been based on the study of algebraic mappings. The problem we examine has a Hamiltonian given by H = p^2 over {2} - lambda over{2pi}sin(2pi x)sin(2pit). This Hamiltonian describes the motion of a compass needle in a sinusoidally varying magnetic field or, equally well, the one dimensional motion of a particle in a standing wave potential. By treating the magnitude(lambda ) of the time dependent potential as a parameter and by examining the trajectories of the system in a Poincare surface of section, the resulting differential

  17. Spectral and angular dependence of mid-infrared diffuse scattering from explosives residues for standoff detection using external cavity quantum cascade lasers

    SciTech Connect

    Suter, Jonathan D.; Bernacki, Bruce E.; Phillips, Mark C.

    2012-09-01

    We present a study of the spectral and angular dependence of scattered mid-infrared light from surfaces coated with explosives residues (TNT, RDX, and tetryl) detected at a 2 meter standoff distance. An external cavity quantum cascade laser provided tunable illumination between 7 and 8 µm. Important differences were identified in the spectral features between specular reflection and diffuse scattering which will impact most practical testing scenarios and complicate material identification. We discuss some of the factors influencing the dependence of observed spectra on the experimental geometry.

  18. Spectral and angular dependence of mid-infrared diffuse scattering from explosives residues for standoff detection using external cavity quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Suter, Jonathan D.; Bernacki, Bruce; Phillips, Mark C.

    2012-09-01

    We present a study of the spectral and angular dependence of scattered mid-infrared light from surfaces coated with explosives residues (TNT, RDX, and tetryl) detected at a 2 m standoff distance. An external cavity quantum cascade laser provided tunable illumination between 7 and 8 μm. Important differences were identified in the spectral features between specular reflection and diffuse scattering which will impact most practical testing scenarios and complicate material identification. We discuss some of the factors influencing the dependence of observed spectra on the experimental geometry.

  19. Random-matrix theory of quantum transport

    SciTech Connect

    Beenakker, C.W.

    1997-07-01

    This is a review of the statistical properties of the scattering matrix of a mesoscopic system. Two geometries are contrasted: A quantum dot and a disordered wire. The quantum dot is a confined region with a chaotic classical dynamics, which is coupled to two electron reservoirs via point contacts. The disordered wire also connects two reservoirs, either directly or via a point contact or tunnel barrier. One of the two reservoirs may be in the superconducting state, in which case conduction involves Andreev reflection at the interface with the superconductor. In the case of the quantum dot, the distribution of the scattering matrix is given by either Dyson{close_quote}s circular ensemble for ballistic point contacts or the Poisson kernel for point contacts containing a tunnel barrier. In the case of the disordered wire, the distribution of the scattering matrix is obtained from the Dorokhov-Mello-Pereyra-Kumar equation, which is a one-dimensional scaling equation. The equivalence is discussed with the nonlinear {sigma} model, which is a supersymmetric field theory of localization. The distribution of scattering matrices is applied to a variety of physical phenomena, including universal conductance fluctuations, weak localization, Coulomb blockade, sub-Poissonian shot noise, reflectionless tunneling into a superconductor, and giant conductance oscillations in a Josephson junction. {copyright} {ital 1997} {ital The American Physical Society}

  20. Chaotic spectra: How to extract dynamic information

    SciTech Connect

    Taylor, H.S.; Gomez Llorente, J.M.; Zakrzewski, J.; Kulander, K.C.

    1988-10-01

    Nonlinear dynamics is applied to chaotic unassignable atomic and molecular spectra with the aim of extracting detailed information about regular dynamic motions that exist over short intervals of time. It is shown how this motion can be extracted from high resolution spectra by doing low resolution studies or by Fourier transforming limited regions of the spectrum. These motions mimic those of periodic orbits (PO) and are inserts into the dominant chaotic motion. Considering these inserts and the PO as a dynamically decoupled region of space, resonant scattering theory and stabilization methods enable us to compute ladders of resonant states which interact with the chaotic quasi-continuum computed in principle from basis sets placed off the PO. The interaction of the resonances with the quasicontinuum explains the low resolution spectra seen in such experiments. It also allows one to associate low resolution features with a particular PO. The motion on the PO thereby supplies the molecular movements whose quantization causes the low resolution spectra. Characteristic properties of the periodic orbit based resonances are discussed. The method is illustrated on the photoabsorption spectrum of the hydrogen atom in a strong magnetic field and on the photodissociation spectrum of H/sub 3//sup +/. Other molecular systems which are currently under investigation using this formalism are also mentioned. 53 refs., 10 figs., 2 tabs.

  1. Nuclear spin polarization in the electron spin-flip Raman scattering of singly charged (In,Ga)As/GaAs quantum dots

    NASA Astrophysics Data System (ADS)

    Debus, J.; Kudlacik, D.; Sapega, V. F.; Dunker, D.; Bohn, P.; Paßmann, F.; Braukmann, D.; Rautert, J.; Yakovlev, D. R.; Reuter, D.; Wieck, A. D.; Bayer, M.

    2015-11-01

    We study the interplay between the dynamic nuclear spin polarization and resonant spin-flip Raman scattering of the resident electron in an ensemble of singly charged (In,Ga)As/GaAs quantum dots by using a two-color laser excitation scheme. The shift of the electron spin-flip Raman line gives a direct measure of the optically induced Overhauser shift, while the linewidth indicates nuclear spin fluctuations. The dynamic nuclear spin polarization leads only to a reduction in the electron spin splitting induced by wetting-layer excitation that is copolarized with the resonant quantum dot excitation. The respective mechanism of the two-color spin-flip Raman scattering is discussed together with the electron-nuclear hyperfine interaction and Pauli exclusion principle. The temporal evolution of the Overhauser shift further demonstrates a nuclear spin depolarization within several seconds depending strongly on the temperature.

  2. Low-energy positron scattering from gas-phase tetrahydrofuran: A quantum treatment of the dynamics and a comparison with experiments

    SciTech Connect

    Franz, J.; Gianturco, F. A.

    2013-11-28

    In this paper we report new quantum calculations of the dynamics for low-energy positrons interacting with gaseous molecules of tetrahydrofuran. The new quantum scattering cross sections are differential and integral cross sections at collision energies between 1.0 and 25.0 eV and include a careful treatment of the additional effects on the scattering process brought about by the permanent dipole moment of the target molecule. The present results are compared with an extensive range of measured data, both for the angular distributions and for the elastic integral cross sections and agree remarkably well with all findings. The new calculated quantities reported here also show the importance of correcting the experimental integral cross sections for the angular discrimination in the forward direction.

  3. Correlation between Photooxidation and the Appearance of Raman Scattering Bands in Lead Chalcogenide Quantum Dots

    SciTech Connect

    Blackburn, Jeffrey L.; Chappell, Helen; Luther, Joseph M.; Nozik, Arthur J.; Johnson, Justin C.

    2011-02-28

    In this report, we carefully study the effects of photooxidation on the Raman spectra of lead chalcogenide (PbX) quantum dots (QDs). Photoexcitation of PbS, PbSe, and PbTe QD films at 488 nm with power densities as low as 30 W/cm2 gives rise to several peaks related to both lead(II) oxide and the group VI chalcogenates (PbXO4). The amplitudes of these peaks are shown to increase with continuous laser illumination in air, but are completely absent for samples illuminated under rigorously air-free conditions. These results suggest that the ~135 cm-1 Raman peak often assigned to an intrinsic PbX LO phonon is more likely an artifact arising from photooxidation. The myriad of potential photooxidation products formed quickly in laser-illuminated, air-exposed PbX QDs suggest that caution should be used in the assignment and interpretation of phonon spectra and phonon-mediated exciton relaxation pathways of these materials, unless the processing and experiments are conducted under air-free conditions.

  4. Quantum state resolved scattering dynamics of F+HCl-->HF(v,J)+Cl.

    PubMed

    Zolot, A M; Nesbitt, D J

    2007-09-21

    State-to-state reaction dynamics of the reaction F+HCl-->HF(v,J)+Cl have been studied under single-collision conditions using an intense discharge F atom source in crossed supersonic molecular beams at Ecom=4.3(1.3) kcal/mol. Nascent HF product is monitored by shot-noise limited direct infrared laser absorption, providing quantum state distributions as well as additional information on kinetic energy release from high resolution Dopplerimetry. The vibrational distributions are highly inverted, with 34(4)%, 44(2)%, and 8(1)% of the total population in vHF=1, 2, and 3, respectively, consistent with predominant energy release into the newly formed bond. However, there is a small [14(1)%] but significant formation channel into the vHF=0 ground state, which is directly detectable for the first time via direct absorption methods. Of particular dynamical interest, both the HF(v=2,J) and HF(v=1,J) populations exhibit strongly bimodal J distributions. These results differ significantly from previous flow and arrested-relaxation studies and may signal the presence of microscopic branching in the reaction dynamics.

  5. Frontiers of chaotic advection

    NASA Astrophysics Data System (ADS)

    Aref, Hassan; Blake, John R.; Budišić, Marko; Cardoso, Silvana S. S.; Cartwright, Julyan H. E.; Clercx, Herman J. H.; El Omari, Kamal; Feudel, Ulrike; Golestanian, Ramin; Gouillart, Emmanuelle; van Heijst, GertJan F.; Krasnopolskaya, Tatyana S.; Le Guer, Yves; MacKay, Robert S.; Meleshko, Vyacheslav V.; Metcalfe, Guy; Mezić, Igor; de Moura, Alessandro P. S.; Piro, Oreste; Speetjens, Michel F. M.; Sturman, Rob; Thiffeault, Jean-Luc; Tuval, Idan

    2017-04-01

    This work reviews the present position of and surveys future perspectives in the physics of chaotic advection: the field that emerged three decades ago at the intersection of fluid mechanics and nonlinear dynamics, which encompasses a range of applications with length scales ranging from micrometers to hundreds of kilometers, including systems as diverse as mixing and thermal processing of viscous fluids, microfluidics, biological flows, and oceanographic and atmospheric flows.

  6. Hypogenetic chaotic jerk flows

    NASA Astrophysics Data System (ADS)

    Li, Chunbiao; Sprott, Julien Clinton; Xing, Hongyan

    2016-03-01

    Removing the amplitude or polarity information in the feedback loop of a jerk structure shows that special nonlinearities with partial information in the variable can also lead to chaos. Some striking properties are found for this kind of hypogenetic chaotic jerk flow, including multistability of symmetric coexisting attractors from an asymmetric structure, hidden attractors with respect to equilibria but with global attraction, easy amplitude control, and phase reversal which is convenient for chaos applications.

  7. Taming Chaotic Circuits

    DTIC Science & Technology

    1992-09-01

    lead to lock and capture range limits. •Desigl techni~41teq., that are equipped to exploit the real nonlinear and chaotic n tWe-of the deyicl, I can...linearization. This approximation hides the global dynamics that lead to lock and capture range limits. Design techniques that are equipped to exploit...7.23 Inverted pendulum stabilized via parametric resonance ......... 1:35 7.24 True dynamics for fl = 15 ...... ....................... 137 7.25

  8. Quantum treatment of phonon scattering for modeling of three-dimensional atomistic transport

    NASA Astrophysics Data System (ADS)

    Lee, Y.; Bescond, M.; Cavassilas, N.; Logoteta, D.; Raymond, L.; Lannoo, M.; Luisier, M.

    2017-05-01

    Based on the nonequilibrium Green's function formalism, we show a numerically efficient method to treat inelastic scattering in multidimensional atomistic codes. Using a simple rescaling approach, we detail the calculations of the lowest-order approximation (LOA) [Y. Lee et al., Phys. Rev. B 93, 205411 (2016), 10.1103/PhysRevB.93.205411] series to the usual, computationally intensive, self-consistent Born approximation (SCBA). This, combined with the analytic continuation technique of Padé approximants, is applied to an atomistic code based on a tight-binding s p3d5s* model for electrons and holes, and a modified valence-force-field method for phonons. Currents in Si and Ge gate-all-around nanowire transistors are then computed considering the main crystallographic transport directions (<100 > , <110 > , <111 > ) for both n -type and p -type devices. Our results show that in most configurations, third-order LOA currents are enough to achieve a high agreement with SCBA results, while reducing the calculation time by about one order. In addition, we propose a criterion to determine the validity of such expansion techniques.

  9. Exact quantum scattering calculation of transport properties for free radicals: OH(X2Π)-helium.

    PubMed

    Dagdigian, Paul J; Alexander, Millard H

    2012-09-07

    Transport properties for OH-He are computed through quantum scattering calculations using the ab initio potential energy surfaces determined by Lee et al. [J. Chem. Phys. 113, 5736 (2000)]. To gauge the importance of the open-shell character of OH and the anisotropy of the potential on the transport properties, including the collision integrals Ω((1,1)) and Ω((2,2)), as well as the diffusion coefficient, calculations were performed with the full potential, with the difference potential V(dif) set to zero, and with only the spherical average of the potential. Slight differences (3%-5%) in the computed diffusion coefficient were found between the values obtained using the full potential and the truncated potentials. The computed diffusion coefficients were compared to recent experimental measurements and those computed with a Lennard-Jones (LJ) 12-6 potential. The values obtained with the full potential were slightly higher than the experimental values. The LJ 12-6 potential was found to underestimate the variation in temperature as compared to that obtained using the full OH-He ab initio potential.

  10. Inelastic neutron scattering, Raman, vibrational analysis with anharmonic corrections, and scaled quantum mechanical force field for polycrystalline L-alanine

    NASA Astrophysics Data System (ADS)

    Williams, Robert W.; Schlücker, Sebastian; Hudson, Bruce S.

    2008-01-01

    A scaled quantum mechanical harmonic force field (SQMFF) corrected for anharmonicity is obtained for the 23 K L-alanine crystal structure using van der Waals corrected periodic boundary condition density functional theory (DFT) calculations with the PBE functional. Scale factors are obtained with comparisons to inelastic neutron scattering (INS), Raman, and FT-IR spectra of polycrystalline L-alanine at 15-23 K. Calculated frequencies for all 153 normal modes differ from observed frequencies with a standard deviation of 6 wavenumbers. Non-bonded external k = 0 lattice modes are included, but assignments to these modes are presently ambiguous. The extension of SQMFF methodology to lattice modes is new, as are the procedures used here for providing corrections for anharmonicity and van der Waals interactions in DFT calculations on crystals. First principles Born-Oppenheimer molecular dynamics (BOMD) calculations are performed on the L-alanine crystal structure at a series of classical temperatures ranging from 23 K to 600 K. Corrections for zero-point energy (ZPE) are estimated by finding the classical temperature that reproduces the mean square displacements (MSDs) measured from the diffraction data at 23 K. External k = 0 lattice motions are weakly coupled to bonded internal modes.

  11. Effects of an elastic scatterer on the DC spin current generation in a Rashba-type quantum channel

    NASA Astrophysics Data System (ADS)

    Wang, L. Y.; Tang, C. S.; Chu, C. S.

    2006-05-01

    In this work, we consider a Rashba-type quantum channel (RQC) consisting of one AC-biased finger-gates (FG) that orient perpendicularly and located above the RQC. Such an AC-biased FG gives rise to a local time-modulation in the Rashba coupling parameter, and is shown recently to generate a DC spin current [L.Y. Wang, C.S. Tang, C.S. Chu, Cond-mat/0409291, 2004]. No charge current, however, is generated in this configuration. We explore the robustness of such DC spin current generation against elastic scattering in the RQC. The effect of backscattering is studied by introducing a static barrier that is uniform in the transverse dimension. The effects of both backscattering and subband mixing is studied by introducing a static partial-barrier that is spatially localized and non-uniform in the transverse dimension. In addition, we compare the cases of attractive and repulsive partial-barriers. It is found that attractive partial-barrier gives rise to additional DC spin current structures due to resonant inter-subband and inter-sideband transition to quasi-bound states formed just beneath subband thresholds.

  12. Search for a reliable nucleic acid force field using neutron inelastic scattering and quantum mechanical calculations: Bases, nucleosides and nucleotides

    SciTech Connect

    Leulliot, Nicolas; Ghomi, Mahmoud; Jobic, Herve

    1999-06-15

    Neutron inelastic scattering (NIS), IR and Raman spectra of the RNA constituents: bases, nucleosides and nucleotides have been analyzed. The complementary aspects of these different experimental techniques makes them especially powerful for assigning the vibrational modes of the molecules of interest. Geometry optimization and harmonic force field calculations of these molecules have been undertaken by quantum mechanical calculations at several theoretical levels: Hartree-Fock (HF), Moller-plesset second-order perturbation (MP2) and Density Functional Theory (DFT). In all cases, it has been shown that HF calculations lead to insufficient results for assigning accurately the intramolecular vibrational modes. In the case of the nucleic bases, these discrepancies could be satisfactorily removed by introducing the correlation effects at MP2 level. However, the application of the MP2 procedure to the large size molecules such as nucleosides and nucleotides is absolutely impossible, taking into account the prohibitive computational time needed. On the basis of our results, the calculations at DFT levels using B3LYP exchange and correlation functional appear to be a cost-effective alternative in obtaining a reliable force field for the whole set of nucleic acid constituents.

  13. Making baryons dark: the quantum prediction of the variation of photon-particle scattering cross section with the approach to equilibrium in deep gravity wells

    NASA Astrophysics Data System (ADS)

    Ernest, Alllan David; Collins, Matthew P.

    2015-08-01

    Analysis of astrophysical phenomena relies on knowledge of cross sections. These cross sections are measured in scattering experiments, or calculated using theoretical techniques such as partial wave analysis. It has been recently shown [1,2,3] however that photon scattering cross sections depend also on the degree of localization of the target particle, and that particles in large-scale, deep-gravity wells can exhibit lower cross sections than those measured in lab-based experiments where particles are implicitly localized. This purely quantum effect arises as a consequence of differences in the gravitational eigenspectral distribution of a particle’s wavefunction in different situations, and is in addition to the obvious notion that delocalized particle scattering is less likely simply because the target particles are ‘in a bigger box’.In this presentation we consider the quantum equilibrium statistics of particles in gravitational potentials corresponding to dark matter density profiles. We show that as galactic halos approach equilibrium, the dark eigenstates of the eigenspectral ensemble are favoured and baryons exhibit lower photon scattering cross sections, rendering halos less visible than expected from currently accepted cross sections. Traditional quantum theory thus predicts that baryons that have not coalesced into self-bound macroscopic structures such as stars, can essentially behave as dark matter simply by equilibrating within a deep gravity well. We will discuss this effect and the consequences for microwave anisotropy analysis and primordial nucleosynthesis.[1] Ernest, A. D., and Collins, M. P., 2014, Australian Institute of Physics, AIP Congress, Canberra, December, 2014.[2] Ernest, A. D., 2009, J. Phys. A: Math. Theor., 42, 115207, 115208.[3] Ernest, A. D., 2012, In Prof. Ion Cotaescu (Ed) Advances in Quantum Theory (pp 221-248). Rijeka: InTech. ISBN 978-953-51-0087-4

  14. Random Matrix Theory Approach to Chaotic Coherent Perfect Absorbers.

    PubMed

    Li, Huanan; Suwunnarat, Suwun; Fleischmann, Ragnar; Schanz, Holger; Kottos, Tsampikos

    2017-01-27

    We employ random matrix theory in order to investigate coherent perfect absorption (CPA) in lossy systems with complex internal dynamics. The loss strength γ_{CPA} and energy E_{CPA}, for which a CPA occurs, are expressed in terms of the eigenmodes of the isolated cavity-thus carrying over the information about the chaotic nature of the target-and their coupling to a finite number of scattering channels. Our results are tested against numerical calculations using complex networks of resonators and chaotic graphs as CPA cavities.

  15. Random Matrix Theory Approach to Chaotic Coherent Perfect Absorbers

    NASA Astrophysics Data System (ADS)

    Li, Huanan; Suwunnarat, Suwun; Fleischmann, Ragnar; Schanz, Holger; Kottos, Tsampikos

    2017-01-01

    We employ random matrix theory in order to investigate coherent perfect absorption (CPA) in lossy systems with complex internal dynamics. The loss strength γCPA and energy ECPA, for which a CPA occurs, are expressed in terms of the eigenmodes of the isolated cavity—thus carrying over the information about the chaotic nature of the target—and their coupling to a finite number of scattering channels. Our results are tested against numerical calculations using complex networks of resonators and chaotic graphs as CPA cavities.

  16. The chaotic obliquity of Mars

    NASA Technical Reports Server (NTRS)

    Touma, Jihad; Wisdom, Jack

    1993-01-01

    The discovery (by Laskar, 1989, 1990) that the evolution of the solar system is chaotic, made in a numerical integration of the averaged secular approximation of the equations of motions for the planets, was confirmed by Sussman and Wisdom (1992) by direct numerical integration of the whole solar system. This paper presents results of direct integrations of the rotation of Mars in the chaotically evolved planetary system, made using the same model as that used by Sussman and Wisdom. The numerical integration shows that the obliquity of Mars undergoes large chaotic variations, which occur as the system evolves in the chaotic zone associated with a secular spin-orbit resonance.

  17. A semiempirical surface scattering model for quantum corrected full-band Monte-Carlo simulation of biaxially strained Si/SiGe NMOSFETs

    NASA Astrophysics Data System (ADS)

    Pham, A. T.; Nguyen, C. D.; Jungemann, C.; Meinerzhagen, B.

    2006-04-01

    A new semiempirical surface scattering model for electrons in strained Si devices including a quantum correction has been developed and implemented into our FBMC simulator. The strain is assumed to be consistent with pseudomorphic growth on a relaxed SiGe buffer. By introducing a few additional terms into the physical scattering rates which depend on the Ge-content in the SiGe buffer, the new surface scattering model can excellently reproduce low-field inversion layer mobility measurements for a wide range of Ge-content (0-30%) and substrate doping levels (10 16-5.5 × 10 18 cm -3). As a device example, an NMOSFET with 23 nm gate length with and without a strained Si channel has been simulated by the new FBMC model.

  18. Investigation of Coulomb scattering on sSi/Si0.5Ge0.5/sSOI quantum-well p-MOSFETs

    NASA Astrophysics Data System (ADS)

    Jiao, Wen; Qiang, Liu; Chang, Liu; Yize, Wang; Bo, Zhang; Zhongying, Xue; Zengfeng, Di; Wenjie, Yu; Qingtai, Zhao

    2016-09-01

    sSi/Si0.5Ge0.5/sSOI quantum-well (QW) p-MOSFETs with HfO2/TiN gate stack were fabricated and characterized. According to the low temperature experimental results, carrier mobility of the strained Si0.5Ge0.5 QW p-MOSFET was mainly governed by phonon scattering from 300 to 150 K and Coulomb scattering below 150 K, respectively. Coulomb scattering was intensified by the accumulated inversion charges in the Si cap layer of this Si/SiGe heterostructure, which led to a degradation of carrier mobility in the SiGe channel, especially at low temperature. Project supported by the National Natural Science Foundation of China (Nos. 61306126, 61306127, 61106015) and the CAS International Collaboration and Innovation Program on High Mobility Materials Engineering.

  19. Color encryption scheme based on adapted quantum logistic map

    NASA Astrophysics Data System (ADS)

    Zaghloul, Alaa; Zhang, Tiejun; Amin, Mohamed; Abd El-Latif, Ahmed A.

    2014-04-01

    This paper presents a new color image encryption scheme based on quantum chaotic system. In this scheme, a new encryption scheme is accomplished by generating an intermediate chaotic key stream with the help of quantum chaotic logistic map. Then, each pixel is encrypted by the cipher value of the previous pixel and the adapted quantum logistic map. The results show that the proposed scheme has adequate security for the confidentiality of color images.

  20. Quantum

    NASA Astrophysics Data System (ADS)

    Elbaz, Edgard

    This book gives a new insight into the interpretation of quantum mechanics (stochastic, integral paths, decoherence), a completely new treatment of angular momentum (graphical spin algebra) and an introduction to Fermion fields (Dirac equation) and Boson fields (e.m. and Higgs) as well as an introduction to QED (quantum electrodynamics), supersymmetry and quantum cosmology.

  1. Coagulation in chaotic flows

    SciTech Connect

    Muzzio, F.J.; Ottino, J.M.

    1988-09-01

    We study coagulation in the flow field of a time-periodic deterministic chaotic flow and focus on the simplest case: point particles convected without diffusion and allowed to coagulate with probability 1 when the distance is less than d. An analysis of the underlying physics is presented. Under ''well-mixed'' conditions the system behaves as if the particles were moved by Brownian motion, and a simple kinetic model describes the main results. The poorly mixed case is considerably more complex. Spatial inhomogeneities result from competition between the rate of coagulation and mixing, and trapping and leaking of clusters due to Kolmogorov-Arnold-Moser surfaces.

  2. Nearly discontinuous chaotic mixing

    SciTech Connect

    Sharp, David Howland; Lim, Hyun K; Yu, Yan; Glimm, James G

    2009-01-01

    A new scientific approach is presented for a broad class of chaotic problems involving a high degree of mixing over rapid time scales. Rayleigh-Taylor and Richtmyer-Meshkov unstable flows are typical of such problems. Microscopic mixing properties such as chemical reaction rates for turbulent mixtures can be obtained with feasible grid resolution. The essential dependence of (some) fluid mixing observables on transport phenomena is observed. This dependence includes numerical as well as physical transport and it includes laminar as well as turbulent transport. A new approach to the mathematical theory for the underlying equations is suggested.

  3. Chaotic rotation of Hyperion?

    NASA Technical Reports Server (NTRS)

    Binzel, R. P.; Green, J. R.; Opal, C. B.

    1986-01-01

    Thomas et al. (1984) analyzed 14 Voyager 2 images of Saturn's satellite Hyperion and interpreted them to be consistent with a coherent (nonchaotic) rotation period of 13.1 days. This interpretation was criticized by Peale and Wisdom (1984), who argued that the low sampling frequency of Voyager data does not allow chaotic or nonchaotic rotation to be distinguished. New observations obtained with a higher sampling frequency are reported here which conclusively show that the 13.1 day period found by Thomas et al. was not due to coherent rotation.

  4. Chaotic systems in optical communications

    NASA Astrophysics Data System (ADS)

    Siuzdak, J.

    2016-09-01

    Communications application of chaotic oscillations of lasers with optoelectronic feedback was discussed. The possibility of eavesdropping of the transmission was analyzed. It was proved that if the rogue party precisely knows parameters of the chaotic system it may recreate the entire signals solely by observation of the optical signal power causing security breach.

  5. High resolution Dopplerimetry of correlated angular and quantum state-resolved CO(2) scattering dynamics at the gas-liquid interface.

    PubMed

    Perkins, Bradford G; Nesbitt, David J

    2010-11-14

    Full three dimensional (3D) translational distributions for quantum state-resolved scattering dynamics at the gas-liquid interface are presented for experimental and theoretical studies of CO(2) + perfluorinated surfaces. Experimentally, high resolution absorption profiles are measured as a function of incident (θ(inc)) and scattering (θ(scat)) angles for CO(2) that has been scattered from a 300 K perfluorinated polyether surface (PFPE) with an incident energy of E(inc) = 10.6(8) kcal mol(-1). Line shape analysis of the absorption profiles reveals non-equilibrium dynamics that are characterized by trapping-desorption (TD) and impulsive scattering (IS) components, with each channel simply characterized by an effective "temperature" that compares very well with previous results from rotational state analysis [Perkins and Nesbitt, J. Phys. Chem. A, 2008, 112, 9324]. From a theoretical perspective, molecular dynamics (MD) simulations of CO(2) + fluorinated self-assembled monolayer surface (F-SAMs) yield translational probability distributions that are also compared with experimental results. Trajectories are parsed by θ(scat) and J, with the results rigorously corrected by flux-to-density transformation and providing comparisons in near quantitative agreement with experiment. 3D flux and velocity distributions obtained from MD simulations are also presented to illustrate the role of in- and out-of-plane scattering.

  6. The chaotic rotation of Hyperion

    NASA Technical Reports Server (NTRS)

    Wisdom, J.; Peale, S. J.; Mignard, F.

    1984-01-01

    Under the assumption that the satellite is rotating about a principal axis that is normal to its orbit plane, a plot of spin rate-versus-orientation for Hyperion at the pericenter of its orbit has revealed a large, chaotic zone surrounding Hyperion's synchronous spin-orbit state. The chaotic zone is so large that it surrounds the 1/2 and 2 states, and libration in the 3/2 state is not possible. Rotation in the chaotic zone is also attitude-unstable. As tidal dissipation drives Hyperion's spin toward a nearly synchronous value, Hyperion necessarily enters the large chaotic zone, becoming attitude-unstable and tumbling. It is therefore predicted that Hyperion will be found to be tumbling chaotically.

  7. Fundamental concepts of quantum chaos

    NASA Astrophysics Data System (ADS)

    Robnik, M.

    2016-09-01

    We review the fundamental concepts of quantum chaos in Hamiltonian systems. The quantum evolution of bound systems does not possess the sensitive dependence on initial conditions, and thus no chaotic behaviour occurs, whereas the study of the stationary solutions of the Schrödinger equation in the quantum phase space (Wigner functions) reveals precise analogy of the structure of the classical phase portrait. We analyze the regular eigenstates associated with invariant tori in the classical phase space, and the chaotic eigenstates associated with the classically chaotic regions, and the corresponding energy spectra. The effects of quantum localization of the chaotic eigenstates are treated phenomenologically, resulting in Brody-like level statistics, which can be found also at very high-lying levels, while the coupling between the regular and the irregular eigenstates due to tunneling, and of the corresponding levels, manifests itself only in low-lying levels.

  8. Quantum mechanical generalized phase-shift approach to atom-surface scattering: A Feshbach projection approach to dealing with closed channel effects

    SciTech Connect

    Maji, Kaushik; Kouri, Donald J.

    2011-03-28

    We have developed a new method for solving quantum dynamical scattering problems, using the time-independent Schroedinger equation (TISE), based on a novel method to generalize a ''one-way'' quantum mechanical wave equation, impose correct boundary conditions, and eliminate exponentially growing closed channel solutions. The approach is readily parallelized to achieve approximate N{sup 2} scaling, where N is the number of coupled equations. The full two-way nature of the TISE is included while propagating the wave function in the scattering variable and the full S-matrix is obtained. The new algorithm is based on a ''Modified Cayley'' operator splitting approach, generalizing earlier work where the method was applied to the time-dependent Schroedinger equation. All scattering variable propagation approaches to solving the TISE involve solving a Helmholtz-type equation, and for more than one degree of freedom, these are notoriously ill-behaved, due to the unavoidable presence of exponentially growing contributions to the numerical solution. Traditionally, the method used to eliminate exponential growth has posed a major obstacle to the full parallelization of such propagation algorithms. We stabilize by using the Feshbach projection operator technique to remove all the nonphysical exponentially growing closed channels, while retaining all of the propagating open channel components, as well as exponentially decaying closed channel components.

  9. PLANETARY CHAOTIC ZONE CLEARING: DESTINATIONS AND TIMESCALES

    SciTech Connect

    Morrison, Sarah; Malhotra, Renu

    2015-01-20

    We investigate the orbital evolution of particles in a planet's chaotic zone to determine their final destinations and their timescales of clearing. There are four possible final states of chaotic particles: collision with the planet, collision with the star, escape, or bounded but non-collision orbits. In our investigations, within the framework of the planar circular restricted three body problem for planet-star mass ratio μ in the range 10{sup –9} to 10{sup –1.5}, we find no particles hitting the star. The relative frequencies of escape and collision with the planet are not scale-free, as they depend upon the size of the planet. For planet radius R{sub p} ≥ 0.001 R{sub H} where R{sub H} is the planet's Hill radius, we find that most chaotic zone particles collide with the planet for μ ≲ 10{sup –5}; particle scattering to large distances is significant only for higher mass planets. For fixed ratio R{sub p} /R{sub H} , the particle clearing timescale, T {sub cl}, has a broken power-law dependence on μ. A shallower power law, T {sub cl} ∼ μ{sup –1/3}, prevails at small μ where particles are cleared primarily by collisions with the planet; a steeper power law, T {sub cl} ∼ μ{sup –3/2}, prevails at larger μ where scattering dominates the particle loss. In the limit of vanishing planet radius, we find T {sub cl} ≈ 0.024 μ{sup –3/2}. The interior and exterior boundaries of the annular zone in which chaotic particles are cleared are increasingly asymmetric about the planet's orbit for larger planet masses; the inner boundary coincides well with the classical first order resonance overlap zone, Δa {sub cl,} {sub int} ≅ 1.2 μ{sup 0.28} a{sub p} ; the outer boundary is better described by Δa {sub cl,} {sub ext} ≅ 1.7 μ{sup 0.31} a{sub p} , where a{sub p} is the planet-star separation.

  10. A Novel Numerical Approach for Determining Chaotic Levels in Stadium Billiards

    NASA Astrophysics Data System (ADS)

    Heidari, Alireza; Ghorbani, Mohammadali

    Nowadays, study on chaos in quantum billiards has attracted a great deal of interest thanks to its nanotechnology relations and applications. In this work, the distribution of the intersection points of wave-function zeros with the boundary of circular and stadium billiards is investigated. Then, through quantitatively calculating the gyration radius for these points, the chaotic and non-chaotic states are distinguished in terms of energy levels.

  11. Wavelet phase synchronization and chaoticity.

    PubMed

    Postnikov, E B

    2009-11-01

    It has been shown that the so-called "wavelet phase" (or "time-scale") synchronization of chaotic signals is actually synchronization of smoothed functions with reduced chaotic fluctuations. This fact is based on the representation of the wavelet transform with the Morlet wavelet as a solution of the Cauchy problem for a simple diffusion equation with initial condition in a form of harmonic function modulated by a given signal. The topological background of the resulting effect is discussed. It is argued that the wavelet phase synchronization provides information about the synchronization of an averaged motion described by bounding tori instead of the fine-level classical chaotic phase synchronization.

  12. 2.1 THz quantum-cascade laser operating up to 144 K based on a scattering-assisted injection design.

    PubMed

    Khanal, Sudeep; Reno, John L; Kumar, Sushil

    2015-07-27

    A 2.1 THz quantum cascade laser (QCL) based on a scattering-assisted injection and resonant-phonon depopulation design scheme is demonstrated. The QCL is based on a four-well period implemented in the GaAs/Al0.15Ga0.85As material system. The QCL operates up to a heat-sink temperature of 144 K in pulsed-mode, which is considerably higher than that achieved for previously reported THz QCLs operating around the frequency of 2 THz. At 46 K, the threshold current-density was measured as ∼ 745 A/cm2 with a peak-power output of ∼10 mW. Electrically stable operation in a positive differential-resistance regime is achieved by a careful choice of design parameters. The results validate the robustness of scattering-assisted injection schemes for development of low-frequency (ν < 2.5 THz) QCLs.

  13. Quantum scattering approach for investigation of two interacting atoms trapped in a one-dimensional Morse potential via Lippmann-Schwinger equation

    NASA Astrophysics Data System (ADS)

    Mansoori Kermani, Maryam; Maghari, Ali

    2017-06-01

    In this work, a system including two neutral atoms confined to an external one-dimensional Morse potential was modelled. The problem can be relevant to cold atom physics, where neutral atoms may be effectively confined in radially tight tubes formed by optical lattices. The atom-atom interaction was considered as a nonlocal separable potential. Analytical expressions for wave-function as well as transition matrix were derived. The contributions of bound states and resonances in the complex energy plane were calculated. For numerical computations, the bound states in a system of argon gas confined in graphite were considered. Since the most important quantity in the low energy quantum scattering problems is "scattering length," considering various values of Morse parameters, the behavior of this parameter was described versus the reduced energy.

  14. Determination of the transport lifetime limiting scattering rate in InSb/AlxIn1-x Sb quantum wells using optical surface microscopy

    NASA Astrophysics Data System (ADS)

    McIndo, Christopher J.; Hayes, David G.; Papageorgiou, Andreas; Hanks, Laura A.; Smith, George V.; Allford, Craig P.; Zhang, Shiyong; Clarke, Edmund M.; Buckle, Philip D.

    2017-07-01

    We report magnetotransport measurements of InSb/Al1-xInxSb quantum well structures at low temperature (3 K), with evidence for 3 characteristic regimes of electron carrier density and mobility. We observe characteristic surface structure using differential interference contrast DIC (Nomarski) optical imaging, and through use of image analysis techniques, we are able to extract a representative average grain feature size for this surface structure. From this we deduce a limiting low temperature scattering mechanism not previously incorporated in transport lifetime modelling of this system, with this improved model giving strong agreement with standard low temperature Hall measurements. We have demonstrated that the mobility in such a material is critically limited by quality from the buffer layer growth, as opposed to fundamental material scattering mechanisms. This suggests that the material has immense potential for mobility improvement over that reported to date.

  15. Quantum size effect as evidenced by small-angle X-ray scattering of In{sub 2}O{sub 3} nanoparticles

    SciTech Connect

    Souza, E. C. C.; Rey, J. F. Q.; Muccillo, E. N. S.

    2009-01-29

    Indium oxide nanoparticles were synthesized by a surfactant-free room-temperature soft chemistry route. The medium particle size of the thermally treated gel was evaluated by X-ray diffraction experiments, nitrogen adsorption measurements, transmission electron microscopy observations and small-angle X-ray scattering using synchrotron radiation. The main results show the single-crystalline nature of the prepared nanoparticles with 8 nm in diameter. The photoluminescence emission spectrum at room-temperature shows a broad peak with onset at, approximately, 315 nm as a result of quantum size effect produced by a small population of nanoparticles with average size of about 2.8 nm as revealed by small-angle X-ray scattering.

  16. Ro-vibrational quenching of CO (v = 1) by He impact in a broad range of temperatures: A benchmark study using mixed quantum/classical inelastic scattering theory.

    PubMed

    Semenov, Alexander; Ivanov, Mikhail; Babikov, Dmitri

    2013-08-21

    The mixed quantum/classical approach is applied to the problem of ro-vibrational energy transfer in the inelastic collisions of CO(v = 1) with He atom, in order to predict the quenching rate coefficient in a broad range of temperatures 5 < T < 2500 K. Scattering calculations are done in two different ways: direct calculations of quenching cross sections and, alternatively, calculations of the excitation cross sections plus microscopic reversibility. In addition, a symmetrized average-velocity method of Billing is tried. Combination of these methods allows reproducing experiment in a broad range of temperatures. Excellent agreement with experiment is obtained at 400 < T < 2500 K (within 10%), good agreement in the range 100 < T < 400 K (within 25%), and semi-quantitative agreement at 40 < T < 100 K(within a factor of 2). This study provides a stringent test of the mixed quantum/classical theory, because the vibrational quantum in CO molecule is rather large and the quencher is very light (He atom). For heavier quenchers and closer to dissociation limit of the molecule, the mixed quantum/classical theory is expected to work even better.

  17. Reactive scattering of F+HD -> HF(v,J)+D: HF(v,J) nascent product state distributions and evidence for quantum transition state resonances

    SciTech Connect

    Harper, Warren W. ); Nizkorodov, Sergey A.; Nesbitt, David

    2001-12-01

    Single collision reactive scattering dynamics of F+ HDHF(v,J)+ D have been investigated exploiting high-resolution (0.0001 cm?1) infrared laser absorption for quantum state resolved detection of nascent HF(v,J) product states. State resolved Doppler profiles are recorded for a series of HF rovibrational transitions and converted into state resolved fluxes via density-to-flux analysis, yielding cross-section data for relative formation of HF(v,J) at Ecom0.6(2), 1.0(3), 1.5(3), and 1.9(4) kcal/mol. State resolved HF(v,J) products at all but the lowest collision energy exhibit Boltzmann-type populations, characteristic of direct reactive scattering dynamics. At the lowest collision energy[Ecom0.6(2) kcal/mol], however, the HF(v= 2,J) populations behave quite anomalously, exhibiting a nearly''flat'' distribution out to J11 before dropping rapidly to zero at the energetic limit. These results provide strong experimental support for quantum transition state resonance dynamics near Ecom0.6 kcal /mol corresponding classically to H atom chattering between the F and D atoms, and prove to be in remarkably quantitative agreement with theoretical wave packet predictions by Skodje et al.[J. Chem. Phys. 112, 4536 (2000)]. These fully quantum state resolved studies therefore nicely complement the recent crossed beam studies of Dong et al.[J. Chem. Phys. 113, 3633 (2000)], which confirm the presence of this resonance via angle resolved differential cross-section measurements. The observed quantum state distributions near threshold also indicate several rotational states in the HF(v= 3) vibrational manifold energetically inaccessible to F(2P3/2) reagent, but which are consistent with a minor (5%) nonadiabatic contribution from spin?orbit excited F*(2P1/2).?2002 American Institute of Physics.

  18. Fermi resonance in dynamical tunneling in a chaotic billiard.

    PubMed

    Yi, Chang-Hwan; Kim, Ji-Hwan; Yu, Hyeon-Hye; Lee, Ji-Won; Kim, Chil-Min

    2015-08-01

    We elucidate that Fermi resonance ever plays a decisive role in dynamical tunneling in a chaotic billiard. Interacting with each other through an avoided crossing, a pair of eigenfunctions are coupled through tunneling channels for dynamical tunneling. In this case, the tunneling channels are an islands chain and its pair unstable periodic orbit, which equals the quantum number difference of the eigenfunctions. This phenomenon of dynamical tunneling is confirmed in a quadrupole billiard in relation with Fermi resonance.

  19. Size effects and charge transport in metals: Quantum theory of the resistivity of nanometric metallic structures arising from electron scattering by grain boundaries and by rough surfaces

    NASA Astrophysics Data System (ADS)

    Munoz, Raul C.; Arenas, Claudio

    2017-03-01

    We discuss recent progress regarding size effects and their incidence upon the coefficients describing charge transport (resistivity, magnetoresistance, and Hall effect) induced by electron scattering from disordered grain boundaries and from rough surfaces on metallic nanostructures; we review recent measurements of the magneto transport coefficients that elucidate the electron scattering mechanisms at work. We review as well theoretical developments regarding quantum transport theories that allow calculating the increase in resistivity induced by electron-rough surface scattering (in the absence of grain boundaries) from first principles—from the parameters that describe the surface roughness that can be measured with a Scanning Tunnelling Microscope (STM). We evaluate the predicting power of the quantum version of the Fuchs-Sondheimer theory and of the model proposed by Calecki, abandoning the method of parameter fitting used for decades, but comparing instead theoretical predictions with resistivity measured in thin films where surface roughness has also been measured with a STM, and where electron-grain boundary scattering can be neglected. We also review the theory of Mayadas and Shatzkes (MS) [Phys. Rev. B 1, 1382 (1970)] used for decades, and discuss its severe conceptual difficulties that arise out of the fact that: (i) MS employed plane waves to describe the electronic states within the metal sample having periodic grain boundaries, rather than the Bloch states known since the thirties to be the solutions of the Schrödinger equation describing electrons propagating through a Krönig-Penney [Proc. R. Soc. London Ser. A 130, 499 (1931)] periodic potential; (ii) MS ignored the fact that the wave functions describing electrons propagating through a 1-D disordered potential are expected to decay exponentially with increasing distance, a fact known since the work of Anderson [Phys. Rev. 109, 1492 (1958)] in 1958 for which he was awarded the Nobel Prize in

  20. Chaotic LIDAR for Naval Applications

    DTIC Science & Technology

    2014-09-30

    Chaotic LI PAR for Naval Applications Principal Investigator William D. Jemison Organization Clarkson University Technical Section Technical...novel ultralong cavity (~100m) ring resonator was implemented for its noise-like chaotic intensity modulation. This laser generated wideband intensity...with sub-inch accuracy was demonstrated and target movements as small as 1/8* inch were accurately detected using cross correlation signal