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Sample records for processes euclidean quantum

  1. Scattering in the Euclidean formulation of relativistic quantum mechanics

    NASA Astrophysics Data System (ADS)

    Polyzou, Wayne

    2013-10-01

    Euclidean relativistic quantum mechanics is a formulation of relativistic quantum mechanics based on the Osterwalder-Schrader reconstruction theorem that exploits the logical independence of locality from the rest of the axioms of Euclidean field theory. I discuss the properties of Euclidean Green functions necessary for the existence of Møller wave operators and the construction of these wave operators in this formalism. Supported by the US Department of Energy, Grant - DE-AC02-81ER40038.

  2. Rate of quantum ergodicity in Euclidean billiards

    NASA Astrophysics Data System (ADS)

    Bäcker, A.; Schubert, R.; Stifter, P.

    1998-05-01

    For a large class of quantized ergodic flows the quantum ergodicity theorem states that almost all eigenfunctions become equidistributed in the semiclassical limit. In this work we give a short introduction to the formulation of the quantum ergodicity theorem for general observables in terms of pseudodifferential operators and show that it is equivalent to the semiclassical eigenfunction hypothesis for the Wigner function in the case of ergodic systems. Of great importance is the rate by which the quantum-mechanical expectation values of an observable tend to their mean value. This is studied numerically for three Euclidean billiards (stadium, cosine, and cardioid billiard) using up to 6000 eigenfunctions. We find that in configuration space the rate of quantum ergodicity is strongly influenced by localized eigenfunctions such as bouncing-ball modes or scarred eigenfunctions. We give a detailed discussion and explanation of these effects using a simple but powerful model. For the rate of quantum ergodicity in momentum space we observe a slower decay. We also study the suitably normalized fluctuations of the expectation values around their mean and find good agreement with a Gaussian distribution.

  3. Scattering asymptotic conditions in Euclidean relativistic quantum theory

    NASA Astrophysics Data System (ADS)

    Aiello, Gordon J.; Polyzou, W. N.

    2016-03-01

    We discuss the formulation of the scattering asymptotic condition as a strong limit in Euclidean quantum theories satisfying the Osterwalder-Schrader axioms. When used with the invariance principle this provides a constructive method to compute scattering observables directly in the Euclidean formulation of the theory, without an explicit analytic continuation.

  4. Fake Instability in the Euclidean Formalism of Quantum Tunneling

    SciTech Connect

    Aoyama, H.; Harano, T.; Sato, M.; Kikuchi, H.; Wada, S.

    1997-11-01

    The Euclidean path-integral formalism is studied for the system without any unstable state. While the usual bounce calculation yields a fake complex energy spectrum, proper account of the global structure of the functional space is shown to lead to the real eigenvalues. For this purpose, the valley instanton is constructed by the proper valley method and the dilute-gas approximation is carried out. This establishes a general imaginary-time formalism, unifying the instanton and the bounce method. {copyright} {ital 1997} {ital The American Physical Society}

  5. Entropic Force and its Fluctuation in Euclidean Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Zhao, Yue

    In this paper, we study the idea about gravity as entropic force proposed by Verlinde. By interpreting Euclidean gravity in the language of thermodynamic quantities on holographic screen, we find the gravitational force can be calculated from the change of entropy on the screen. We show that normal gravity calculation can be reinterpreted in the language of thermodynamic variables. We also study the fluctuation of the force and find the fluctuation acting on the point-like particle can never be larger than the expectation value of the force. For a black hole in AdS space, by gauge/gravity duality, the fluctuation may be interpreted as arising from thermal fluctuation in the boundary description. And for a black hole in flat space, the ratio between fluctuation and force goes to a constant (T)/(m) at infinity.

  6. Quantum Anomalies for Generalized Euclidean Taub-Newman Metrics

    NASA Astrophysics Data System (ADS)

    Visinescu, Mihai; Visinescu, Anca

    2008-09-01

    We investigate the gravitational and axial anomalies with regard to quadratic constants of motion for the Euclidean Taub-Newman-Unti-Tamburino (Taub-NUT) space and its generalizations as was done by Iwai and Katayama. The generalized Taub-NUT metrics exhibit in general gravitational anomalies. This is in contrast with the fact that the standard Taub-NUT metric does not exhibit gravitational anomalies, which is a consequence of the fact that it admits Killing-Yano tensors forming Stäckel-Killing tensors as products. For the axial anomaly, interpreted as the index of the Dirac operator, the role of Killing-Yano tensors is irrelevant. We compute the index of the Dirac operator for the generalized Taub-NUT metrics with the APS boundary conditions and find these metrics do not contribute to the axial anomaly for not too large deformations of the standard Taub-NUT metric.

  7. Towards spectral geometric methods for Euclidean quantum gravity

    NASA Astrophysics Data System (ADS)

    Panine, Mikhail; Kempf, Achim

    2016-04-01

    The unification of general relativity with quantum theory will also require a coming together of the two quite different mathematical languages of general relativity and quantum theory, i.e., of differential geometry and functional analysis, respectively. Of particular interest in this regard is the field of spectral geometry, which studies to which extent the shape of a Riemannian manifold is describable in terms of the spectra of differential operators defined on the manifold. Spectral geometry is hard because it is highly nonlinear, but linearized spectral geometry, i.e., the task to determine small shape changes from small spectral changes, is much more tractable and may be iterated to approximate the full problem. Here, we generalize this approach, allowing, in particular, nonequal finite numbers of shape and spectral degrees of freedom. This allows us to study how well the shape degrees of freedom are encoded in the eigenvalues. We apply this strategy numerically to a class of planar domains and find that the reconstruction of small shape changes from small spectral changes is possible if enough eigenvalues are used. While isospectral nonisometric shapes are known to exist, we find evidence that generically shaped isospectral nonisometric shapes, if existing, are exceedingly rare.

  8. Clear evidence of a continuum theory of 4D Euclidean simplicial quantum gravity

    NASA Astrophysics Data System (ADS)

    Egawa, H. S.; Horata, S.; Yukawa, T.

    2002-03-01

    Four-dimensional (4D) simplicial quantum gravity coupled to both scalar fields ( NX) and gauge fields ( NA) has been studied using Monte-Carlo simulations. The matter dependence of the string susceptibility exponent γ (4) is estimated. Furthermore, we compare our numerical results with Background-Metric-Indepenent (BMI) formulation conjectured to describe the quantum field theory of gravity in 4D. The numerical results suggest that the 4D simplicial quantum gravity is related to the conformal gravity in 4D. Therefore, we propose a phase structure in detail with adding both scalar and gauge fields and discuss the possibility and the property of a continuum theory of 4D Euclidean simplicial quantum gravity.

  9. Clear evidence of a continuum theory of 4D Euclidean simplicial quantum gravity

    NASA Astrophysics Data System (ADS)

    Egawa, H. S.; Horata, S.; Yukawa, T.

    Four-dimensional (4D) simplicial quantum gravity coupled to both scalar fields (NX) and gauge fields (NA) has been studied using Monte-Carlo simulations. The matter dependence of the string susceptibility exponent γ(4) is estimated. Furthermore, we compare our numerical results with Background-Metric-Indepenent (BMI) formulation conjectured to describe the quantum field theory of gravity in 4D. The numerical results suggest that the 4D simplicial quantum gravity is related to the conformal gravity in 4D. Therefore, we propose a phase structure in detail with adding both scalar and gauge fields and discuss the possibility and the property of a continuum theory of 4D Euclidean simplicial quantum gravity.

  10. Bayesian Approach to Spectral Function Reconstruction for Euclidean Quantum Field Theories

    NASA Astrophysics Data System (ADS)

    Burnier, Yannis; Rothkopf, Alexander

    2013-11-01

    We present a novel approach to the inference of spectral functions from Euclidean time correlator data that makes close contact with modern Bayesian concepts. Our method differs significantly from the maximum entropy method (MEM). A new set of axioms is postulated for the prior probability, leading to an improved expression, which is devoid of the asymptotically flat directions present in the Shanon-Jaynes entropy. Hyperparameters are integrated out explicitly, liberating us from the Gaussian approximations underlying the evidence approach of the maximum entropy method. We present a realistic test of our method in the context of the nonperturbative extraction of the heavy quark potential. Based on hard-thermal-loop correlator mock data, we establish firm requirements in the number of data points and their accuracy for a successful extraction of the potential from lattice QCD. Finally we reinvestigate quenched lattice QCD correlators from a previous study and provide an improved potential estimation at T=2.33TC.

  11. Bayesian approach to spectral function reconstruction for Euclidean quantum field theories.

    PubMed

    Burnier, Yannis; Rothkopf, Alexander

    2013-11-01

    We present a novel approach to the inference of spectral functions from Euclidean time correlator data that makes close contact with modern Bayesian concepts. Our method differs significantly from the maximum entropy method (MEM). A new set of axioms is postulated for the prior probability, leading to an improved expression, which is devoid of the asymptotically flat directions present in the Shanon-Jaynes entropy. Hyperparameters are integrated out explicitly, liberating us from the Gaussian approximations underlying the evidence approach of the maximum entropy method. We present a realistic test of our method in the context of the nonperturbative extraction of the heavy quark potential. Based on hard-thermal-loop correlator mock data, we establish firm requirements in the number of data points and their accuracy for a successful extraction of the potential from lattice QCD. Finally we reinvestigate quenched lattice QCD correlators from a previous study and provide an improved potential estimation at T=2.33T(C). PMID:24237510

  12. Perceptual or Analytical Processing? Evidence from Children's and Adult's Performance on the Euclidean Traveling Salesperson Problem

    ERIC Educational Resources Information Center

    van Rooij, Iris; Schactman, Alissa; Kadlec, Helena; Stege, Ulrike

    2006-01-01

    The Euclidean Traveling Salesperson Problem (E-TSP) is a useful task to study how humans optimize when faced with computational intractability. It has been found that humans are capable of finding high-quality solutions for E-TSP in a relatively short time and with seemingly little cognitive effort. This observation has led to two general…

  13. Quantum Stochastic Processes

    SciTech Connect

    Spring, William Joseph

    2009-04-13

    We consider quantum analogues of n-parameter stochastic processes, associated integrals and martingale properties extending classical results obtained in [1, 2, 3], and quantum results in [4, 5, 6, 7, 8, 9, 10].

  14. Euclidean Epstein-Glaser renormalization

    SciTech Connect

    Keller, Kai J.

    2009-10-15

    In the framework of perturbative algebraic quantum field theory recently developed by Brunetti, Duetsch, and Fredenhagen (http://arxiv.org/abs/0901.2038) I give a general construction of so-called Euclidean time-ordered products, i.e., algebraic versions of the Schwinger functions, for scalar quantum field theories on spaces of Euclidean signature. This is done by generalizing the recursive construction of time-ordered products by Epstein and Glaser, originally formulated for quantum field theories on Minkowski space [Epstein and Glaser, Ann. Inst. Henri Poincare 19, 211 (1973)]. An essential input of Epstein-Glaser renormalization is the causal structure of Minkowski space. The absence of this causal structure in the Euclidean framework makes it necessary to modify the original construction of Epstein and Glaser at two points. First, the whole construction has to be performed with an only partially defined product on (interaction) functionals. This is due to the fact that the fundamental solutions of the Helmholtz operator (-{delta}+m{sup 2}) of Euclidean quantum field theory have a unique singularity structure, i.e., they are unique up to a smooth part. Second, one needs to (re)introduce a (rather natural) 'Euclidean causality' condition for the recursion of Epstein and Glaser to be applicable.

  15. Euclidean Epstein-Glaser renormalization

    NASA Astrophysics Data System (ADS)

    Keller, Kai J.

    2009-10-01

    In the framework of perturbative algebraic quantum field theory recently developed by Brunetti, Dütsch, and Fredenhagen (http://arxiv.org/abs/0901.2038) I give a general construction of so-called Euclidean time-ordered products, i.e., algebraic versions of the Schwinger functions, for scalar quantum field theories on spaces of Euclidean signature. This is done by generalizing the recursive construction of time-ordered products by Epstein and Glaser, originally formulated for quantum field theories on Minkowski space [Epstein and Glaser, Ann. Inst. Henri Poincare 19, 211 (1973)]. An essential input of Epstein-Glaser renormalization is the causal structure of Minkowski space. The absence of this causal structure in the Euclidean framework makes it necessary to modify the original construction of Epstein and Glaser at two points. First, the whole construction has to be performed with an only partially defined product on (interaction) functionals. This is due to the fact that the fundamental solutions of the Helmholtz operator (-Δ+m2) of Euclidean quantum field theory have a unique singularity structure, i.e., they are unique up to a smooth part. Second, one needs to (re)introduce a (rather natural) "Euclidean causality" condition for the recursion of Epstein and Glaser to be applicable.

  16. Quantum deformations of D = 4 Euclidean, Lorentz, Kleinian and quaternionic o⋆ (4) symmetries in unified o (4 ; C) setting

    NASA Astrophysics Data System (ADS)

    Borowiec, A.; Lukierski, J.; Tolstoy, V. N.

    2016-03-01

    We employ new calculational technique and present complete list of classical r-matrices for D = 4 complex homogeneous orthogonal Lie algebra o (4 ; C), the rotational symmetry of four-dimensional complex space-time. Further applying reality conditions we obtain the classical r-matrices for all possible real forms of o (4 ; C): Euclidean o (4), Lorentz o (3 , 1), Kleinian o (2 , 2) and quaternionic o⋆ (4) Lie algebras. For o (3 , 1) we get known four classical D = 4 Lorentz r-matrices, but for other real Lie algebras (Euclidean, Kleinian, quaternionic) we provide new results and mention some applications.

  17. Hybrid quantum information processing

    SciTech Connect

    Furusawa, Akira

    2014-12-04

    I will briefly explain the definition and advantage of hybrid quantum information processing, which is hybridization of qubit and continuous-variable technologies. The final goal would be realization of universal gate sets both for qubit and continuous-variable quantum information processing with the hybrid technologies. For that purpose, qubit teleportation with a continuousvariable teleporter is one of the most important ingredients.

  18. PREFACE: Quantum information processing

    NASA Astrophysics Data System (ADS)

    Briggs, Andrew; Ferry, David; Stoneham, Marshall

    2006-05-01

    Microelectronics and the classical information technologies transformed the physics of semiconductors. Photonics has given optical materials a new direction. Quantum information technologies, we believe, will have immense impact on condensed matter physics. The novel systems of quantum information processing need to be designed and made. Their behaviours must be manipulated in ways that are intrinsically quantal and generally nanoscale. Both in this special issue and in previous issues (see e.g., Spiller T P and Munro W J 2006 J. Phys.: Condens. Matter 18 V1-10) we see the emergence of new ideas that link the fundamentals of science to the pragmatism of market-led industry. We hope these papers will be followed by many others on quantum information processing in the Journal of Physics: Condensed Matter.

  19. Quantum thermodynamics of general quantum processes

    NASA Astrophysics Data System (ADS)

    Binder, Felix; Vinjanampathy, Sai; Modi, Kavan; Goold, John

    2015-03-01

    Accurately describing work extraction from a quantum system is a central objective for the extension of thermodynamics to individual quantum systems. The concepts of work and heat are surprisingly subtle when generalizations are made to arbitrary quantum states. We formulate an operational thermodynamics suitable for application to an open quantum system undergoing quantum evolution under a general quantum process by which we mean a completely positive and trace-preserving map. We derive an operational first law of thermodynamics for such processes and show consistency with the second law. We show that heat, from the first law, is positive when the input state of the map majorizes the output state. Moreover, the change in entropy is also positive for the same majorization condition. This makes a strong connection between the two operational laws of thermodynamics.

  20. Quantum thermodynamics of general quantum processes.

    PubMed

    Binder, Felix; Vinjanampathy, Sai; Modi, Kavan; Goold, John

    2015-03-01

    Accurately describing work extraction from a quantum system is a central objective for the extension of thermodynamics to individual quantum systems. The concepts of work and heat are surprisingly subtle when generalizations are made to arbitrary quantum states. We formulate an operational thermodynamics suitable for application to an open quantum system undergoing quantum evolution under a general quantum process by which we mean a completely positive and trace-preserving map. We derive an operational first law of thermodynamics for such processes and show consistency with the second law. We show that heat, from the first law, is positive when the input state of the map majorizes the output state. Moreover, the change in entropy is also positive for the same majorization condition. This makes a strong connection between the two operational laws of thermodynamics. PMID:25871066

  1. The Development of Euclidean and Non-Euclidean Cosmologies

    ERIC Educational Resources Information Center

    Norman, P. D.

    1975-01-01

    Discusses early Euclidean cosmologies, inadequacies in classical Euclidean cosmology, and the development of non-Euclidean cosmologies. Explains the present state of the theory of cosmology including the work of Dirac, Sandage, and Gott. (CP)

  2. Chiral Anomaly in Euclidean (2+1)-DIMENSIONAL Space and AN Application to the Quantum Hall Effect

    NASA Astrophysics Data System (ADS)

    Bracken, Paul

    The chiral anomaly in (2+1)-dimensions and its relationship to the zero mode of the Dirac equation in the massless case is studied. Solutions are obtained for the Dirac equation under a vector potential which generates a constant magnetic field. It is shown that there is an anomaly term associated with the corresponding chiral transformation. It can be calculated by using the regularization procedure of Fujikawa. The results are applied to the quantum Hall effect.

  3. Information metric and Euclidean Janus correspondence

    NASA Astrophysics Data System (ADS)

    Bak, Dongsu

    2016-05-01

    We consider the quantum information metric of a family of CFTs perturbed by an exactly marginal operator, which has the dual description of the Euclidean Janus geometries. We first clarify its two dimensional case dual to the three dimensional Janus geometry, which recently appeared in arxiv:arXiv:1507.07555[2]. We generalize this correspondence to higher dimensions and get a precise agreement between the both sides. We also show that the mixed-state information metric of the same family of CFTs has a dual description in the Euclidean version of the Janus time-dependent black hole geometry.

  4. Optical Hybrid Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Takeda, Shuntaro; Furusawa, Akira

    Historically, two complementary approaches to optical quantum information processing have been pursued: qubits and continuous-variables, each exploiting either particle or wave nature of light. However, both approaches have pros and cons. In recent years, there has been a significant progress in combining both approaches with a view to realizing hybrid protocols that overcome the current limitations. In this chapter, we first review the development of the two approaches with a special focus on quantum teleportation and its applications. We then introduce our recent research progress in realizing quantum teleportation by a hybrid scheme, and mention its future applications to universal and fault-tolerant quantum information processing.

  5. Euclidean black hole vortices

    NASA Technical Reports Server (NTRS)

    Dowker, Fay; Gregory, Ruth; Traschen, Jennie

    1991-01-01

    We argue the existence of solutions of the Euclidean Einstein equations that correspond to a vortex sitting at the horizon of a black hole. We find the asymptotic behaviors, at the horizon and at infinity, of vortex solutions for the gauge and scalar fields in an abelian Higgs model on a Euclidean Schwarzschild background and interpolate between them by integrating the equations numerically. Calculating the backreaction shows that the effect of the vortex is to cut a slice out of the Schwarzschild geometry. Consequences of these solutions for black hole thermodynamics are discussed.

  6. Hybrid quantum information processing

    NASA Astrophysics Data System (ADS)

    Furusawa, Akira

    2013-03-01

    There are two types of schemes for quantum information processing (QIP). One is based on qubits, and the other is based on continuous variables (CVs), where the computational basis for qubit QIP is { | 0 > , | 1 > } and that for CV QIP is { | x > } (- ∞ < x < ∞). A universal gate set for qubit QIP is {`bit flip'σx, `phase flip'σz, `Hadamard gate'H, ` π / 8 gate', `controlled NOT (CNOT) gate'}. Similarly, a universal gate set for CV QIP is {` x-displacement' D& circ; (x) , ` p-displacement' D& circ; (ip) , `Fourier gate' F& circ;, `cubic phase gate'e ikxcirc;3, `quantum non-demolition (QND) gate'}. There is one-to-one correspondence between them. CV version of `bit flip'σx is ` x-displacement' D& circ; (x) , which changes the value of the computational basis. Similarly, CV version of `phase flip'σz is ` p-displacement' D& circ; (ip) , where `phase flip'σz switches the ``value'' of `conjugate basis' of qubit { | + > , | - > } (| +/- > = (| 0 > +/- | 1 >) / √{ 2}) and ` p-displacement' D& circ; (ip) changes the value of CV conjugate basis { | p > }. `Hadamard' and `Fourier' gates transform computational bases to respective conjugate bases. CV version of ` π / 8 gate' is a `cubic phase gate'e ikxcirc;3, and CV version of CNOT gate is a QND gate. However, the origin of nonlinearity for QIP is totally different, here the very basic nonlinear operation is calculation of multiplication and of course it is the heart of information processing. The nonlinearity of qubit QIP comes from a CNOT gate, while that of CV QIP comes from a cubic phase gate. Since nonlinear operations are harder to realize compared to linear operations, the most difficult operation for qubit is a CNOT gate, while the counter part, a QND gate, is not so difficult. CNOT and QND gates are both entangling gates, it follows that creating entanglement is easier for CV QIP compared to qubit QIP. Here, creating entanglement is the heart of QIP. So, it is a big advantage of CV QIP. On

  7. Observables of Euclidean Supergravity

    NASA Astrophysics Data System (ADS)

    Vancea, Ion V.

    1997-10-01

    The set of constraints under which the eigenvalues of the Dirac operator can play the role of the dynamical variables for Euclidean supergravity is derived. These constraints arise when the gauge invariance of the eigenvalues of the Dirac operator is imposed. They impose conditions which restrict the eigenspinors of the Dirac operator.

  8. Euclidean supergravity in five dimensions

    NASA Astrophysics Data System (ADS)

    Sabra, Wafic A.; Vaughan, Owen

    2016-09-01

    We construct a 5D, N = 2 Euclidean theory of supergravity coupled to vector multiplets. Upon reducing this theory over a circle we recover the action of 4D, N = 2 Euclidean supergravity coupled to vector multiplets.

  9. Enjoyment of Euclidean Planar Triangles

    ERIC Educational Resources Information Center

    Srinivasan, V. K.

    2013-01-01

    This article adopts the following classification for a Euclidean planar [triangle]ABC, purely based on angles alone. A Euclidean planar triangle is said to be acute angled if all the three angles of the Euclidean planar [triangle]ABC are acute angles. It is said to be right angled at a specific vertex, say B, if the angle ?ABC is a right angle…

  10. Quantum information processing : science & technology.

    SciTech Connect

    Horton, Rebecca; Carroll, Malcolm S.; Tarman, Thomas David

    2010-09-01

    Qubits demonstrated using GaAs double quantum dots (DQD). The qubit basis states are the (1) singlet and (2) triplet stationary states. Long spin decoherence times in silicon spurs translation of GaAs qubit in to silicon. In the near term the goals are: (1) Develop surface gate enhancement mode double quantum dots (MOS & strained-Si/SiGe) to demonstrate few electrons and spin read-out and to examine impurity doped quantum-dots as an alternative architecture; (2) Use mobility, C-V, ESR, quantum dot performance & modeling to feedback and improve upon processing, this includes development of atomic precision fabrication at SNL; (3) Examine integrated electronics approaches to RF-SET; (4) Use combinations of numerical packages for multi-scale simulation of quantum dot systems (NEMO3D, EMT, TCAD, SPICE); and (5) Continue micro-architecture evaluation for different device and transport architectures.

  11. Eigenforms, Discrete Processes and Quantum Processes

    NASA Astrophysics Data System (ADS)

    Kauffman, Louis H.

    2012-05-01

    This essay is a discussion of the concept of eigenform, due to Heinz von Foerster, and its relationship with discrete physics and quantum mechanics. We interpret the square root of minus one as a simple oscillatory process - a clock, and as an eigenform. By taking a generalization of this identification of i as a clock and eigenform, we show how quantum mechanics emerges from discrete physics.

  12. Efficient Quantum Information Processing via Quantum Compressions

    NASA Astrophysics Data System (ADS)

    Deng, Y.; Luo, M. X.; Ma, S. Y.

    2016-01-01

    Our purpose is to improve the quantum transmission efficiency and reduce the resource cost by quantum compressions. The lossless quantum compression is accomplished using invertible quantum transformations and applied to the quantum teleportation and the simultaneous transmission over quantum butterfly networks. New schemes can greatly reduce the entanglement cost, and partially solve transmission conflictions over common links. Moreover, the local compression scheme is useful for approximate entanglement creations from pre-shared entanglements. This special task has not been addressed because of the quantum no-cloning theorem. Our scheme depends on the local quantum compression and the bipartite entanglement transfer. Simulations show the success probability is greatly dependent of the minimal entanglement coefficient. These results may be useful in general quantum network communication.

  13. Action with Acceleration i: Euclidean Hamiltonian and Path Integral

    NASA Astrophysics Data System (ADS)

    Baaquie, Belal E.

    2013-10-01

    An action having an acceleration term in addition to the usual velocity term is analyzed. The quantum mechanical system is directly defined for Euclidean time using the path integral. The Euclidean Hamiltonian is shown to yield the acceleration Lagrangian and the path integral with the correct boundary conditions. Due to the acceleration term, the state space depends on both position and velocity — and hence the Euclidean Hamiltonian depends on two degrees of freedom. The Hamiltonian for the acceleration system is non-Hermitian and can be mapped to a Hermitian Hamiltonian using a similarity transformation; the matrix elements of the similarity transformation are explicitly evaluated.

  14. Practicality of quantum information processing

    NASA Astrophysics Data System (ADS)

    Lau, Hoi-Kwan

    Quantum Information Processing (QIP) is expected to bring revolutionary enhancement to various technological areas. However, today's QIP applications are far from being practical. The problem involves both hardware issues, i.e., quantum devices are imperfect, and software issues, i.e., the functionality of some QIP applications is not fully understood. Aiming to improve the practicality of QIP, in my PhD research I have studied various topics in quantum cryptography and ion trap quantum computation. In quantum cryptography, I first studied the security of position-based quantum cryptography (PBQC). I discovered a wrong assumption in the previous literature that the cheaters are not allowed to share entangled resources. I proposed entanglement attacks that could cheat all known PBQC protocols. I also studied the practicality of continuous-variable (CV) quantum secret sharing (QSS). While the security of CV QSS was considered by the literature only in the limit of infinite squeezing, I found that finitely squeezed CV resources could also provide finite secret sharing rate. Our work relaxes the stringent resources requirement of implementing QSS. In ion trap quantum computation, I studied the phase error of quantum information induced by dc Stark effect during ion transportation. I found an optimized ion trajectory for which the phase error is the minimum. I also defined a threshold speed, above which ion transportation would induce significant error. In addition, I proposed a new application for ion trap systems as universal bosonic simulators (UBS). I introduced two architectures, and discussed their respective strength and weakness. I illustrated the implementations of bosonic state initialization, transformation, and measurement by applying radiation fields or by varying the trap potential. When comparing with conducting optical experiments, the ion trap UBS is advantageous in higher state initialization efficiency and higher measurement accuracy. Finally, I

  15. Euclideanization of Maxwell-Chern-Simons theory

    NASA Astrophysics Data System (ADS)

    Bowman, Daniel Alan

    We quantize the theory of electromagnetism in 2 + 1-spacetime dimensions with the addition of the topological Chern-Simons term using an indefinite metric formalism. In the process, we also quantize the Proca and pure Maxwell theories, which are shown to be related to the Maxwell-Chern-Simons theory. Next, we Euclideanize these three theories, obtaining path space formulae and investigating Osterwalder-Schrader positivity in each case. Finally, we obtain a characterization of those Euclidean states that correspond to physical states in the relativistic theories.

  16. Quantum optics with quantum dots. Towards semiconductor sources of quantum light for quantum information processing

    NASA Astrophysics Data System (ADS)

    Beveratos, Alexios; Abram, Izo; Gérard, Jean-Michel; Robert-Philip, Isabelle

    2014-12-01

    For the past fifteen years, single semiconductor quantum dots, often referred to as solid-state artificial atoms, have been at the forefront of various research direction lines for experimental quantum information science, in particular in the development of practical sources of quantum states of light. Here we review the research to date, on the tailoring of the emission properties from single quantum dots producing single photons, indistinguishable single photons and entangled photon pairs. Finally, the progress and future prospects for applications of single dots in quantum information processing is considered.

  17. Experimental Quantum Randomness Processing Using Superconducting Qubits.

    PubMed

    Yuan, Xiao; Liu, Ke; Xu, Yuan; Wang, Weiting; Ma, Yuwei; Zhang, Fang; Yan, Zhaopeng; Vijay, R; Sun, Luyan; Ma, Xiongfeng

    2016-07-01

    Coherently manipulating multipartite quantum correlations leads to remarkable advantages in quantum information processing. A fundamental question is whether such quantum advantages persist only by exploiting multipartite correlations, such as entanglement. Recently, Dale, Jennings, and Rudolph negated the question by showing that a randomness processing, quantum Bernoulli factory, using quantum coherence, is strictly more powerful than the one with classical mechanics. In this Letter, focusing on the same scenario, we propose a theoretical protocol that is classically impossible but can be implemented solely using quantum coherence without entanglement. We demonstrate the protocol by exploiting the high-fidelity quantum state preparation and measurement with a superconducting qubit in the circuit quantum electrodynamics architecture and a nearly quantum-limited parametric amplifier. Our experiment shows the advantage of using quantum coherence of a single qubit for information processing even when multipartite correlation is not present. PMID:27419550

  18. Experimental Quantum Randomness Processing Using Superconducting Qubits

    NASA Astrophysics Data System (ADS)

    Yuan, Xiao; Liu, Ke; Xu, Yuan; Wang, Weiting; Ma, Yuwei; Zhang, Fang; Yan, Zhaopeng; Vijay, R.; Sun, Luyan; Ma, Xiongfeng

    2016-07-01

    Coherently manipulating multipartite quantum correlations leads to remarkable advantages in quantum information processing. A fundamental question is whether such quantum advantages persist only by exploiting multipartite correlations, such as entanglement. Recently, Dale, Jennings, and Rudolph negated the question by showing that a randomness processing, quantum Bernoulli factory, using quantum coherence, is strictly more powerful than the one with classical mechanics. In this Letter, focusing on the same scenario, we propose a theoretical protocol that is classically impossible but can be implemented solely using quantum coherence without entanglement. We demonstrate the protocol by exploiting the high-fidelity quantum state preparation and measurement with a superconducting qubit in the circuit quantum electrodynamics architecture and a nearly quantum-limited parametric amplifier. Our experiment shows the advantage of using quantum coherence of a single qubit for information processing even when multipartite correlation is not present.

  19. Lateral Quantum Dots for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    House, Matthew Gregory

    The possibility of building a computer that takes advantage of the most subtle nature of quantum physics has been driving a lot of research in atomic and solid state physics for some time. It is still not clear what physical system or systems can be used for this purpose. One possibility that has been attracting significant attention from researchers is to use the spin state of an electron confined in a semiconductor quantum dot. The electron spin is magnetic in nature, so it naturally is well isolated from electrical fluctuations that can a loss of quantum coherence. It can also be manipulated electrically, by taking advantage of the exchange interaction. In this work we describe several experiments we have done to study the electron spin properties of lateral quantum dots. We have developed lateral quantum dot devices based on the silicon metal-oxide-semiconductor transistor, and studied the physics of electrons confined in these quantum dots. We measured the electron spin excited state lifetime, which was found to be as long as 30 ms at the lowest magnetic fields that we could measure. We fabricated and characterized a silicon double quantum dot. Using this double quantum dot design, we fabricated devices which combined a silicon double quantum dot with a superconducting microwave resonator. The microwave resonator was found to be sensitive to two-dimensional electrons in the transistor channel, which we measured and characterized. We developed a new method for extracting information from random telegraph signals, which are produced when we observe thermal fluctuations of electrons in quantum dots. The new statistical method, based on the hidden Markov model, allows us to detect spin-dependent effects in such fluctuations even though we are not able to directly observe the electron spin. We use this analysis technique on data from two experiments involving gallium arsenide quantum dots and use it to measure spin-dependent tunneling rates. Our results advance the

  20. Quantum Information Processing with Trapped Ions

    SciTech Connect

    Barrett, M.D.; Schaetz, T.; Chiaverini, J.; Leibfried, D.; Britton, J.; Itano, W.M.; Jost, J.D.; Langer, C.; Ozeri, R.; Wineland, D.J.; Knill, E.

    2005-05-05

    We summarize two experiments on the creation and manipulation of multi-particle entangled states of trapped atomic ions - quantum dense coding and quantum teleportation. The techniques used in these experiments constitute an important step toward performing large-scale quantum information processing. The techniques also have application in other areas of physics, providing improvement in quantum-limited measurement and fundamental tests of quantum mechanical principles, for example.

  1. Whiteheadian process and quantum theory

    SciTech Connect

    Stapp, H.

    1998-08-01

    There are deep similarities between Whitehead's idea of the process by which nature unfolds and the ideas of quantum theory. Whitehead says that the world is made of ''actual occasions'', each of which arises from potentialities created by prior actual occasions. These actual occasions are happenings modeled on experiential events, each of which comes into being and then perishes, only to be replaced by a successor. It is these experience-like happenings that are the basic realities of nature, according to Whitehead, not the persisting physical particles that Newtonian physics took be the basic entities. Similarly, Heisenberg says that what is really happening in a quantum process is the emergence of an actual from potentialities created by prior actualities. In the orthodox Copenhagen interpretation of quantum theory the actual things to which the theory refer are increments in ''our knowledge''. These increments are experiential events. The particles of classical physics lose their fundamental status: they dissolve into diffuse clouds of possibilities. At each stage of the unfolding of nature the complete cloud of possibilities acts like the potentiality for the occurrence of a next increment in knowledge, whose occurrence can radically change the cloud of possibilities/potentialities for the still-later increments in knowledge. The fundamental difference between these ideas about nature and the classical ideas that reigned from the time of Newton until this century concerns the status of the experiential aspects of nature. These are things such as thoughts, ideas, feelings, and sensations. They are distinguished from the physical aspects of nature, which are described in terms of quantities explicitly located in tiny regions of space and time. According to the ideas of classical physics the physical world is made up exclusively of things of this latter type, and the unfolding of the physical world is determined by causal connections involving only these things

  2. Debugging quantum processes using monitoring measurements

    NASA Astrophysics Data System (ADS)

    Li, Yangjia; Ying, Mingsheng

    2014-04-01

    Since observation on a quantum system may cause the system state collapse, it is usually hard to find a way to monitor a quantum process, which is a quantum system that continuously evolves. We propose a protocol that can debug a quantum process by monitoring, but not disturb the evolution of the system. This protocol consists of an error detector and a debugging strategy. The detector is a projection operator that is orthogonal to the anticipated system state at a sequence of time points, and the strategy is used to specify these time points. As an example, we show how to debug the computational process of quantum search using this protocol. By applying the Skolem-Mahler-Lech theorem in algebraic number theory, we find an algorithm to construct all of the debugging protocols for quantum processes of time-independent Hamiltonians.

  3. Photonic qubits for remote quantum information processing

    NASA Astrophysics Data System (ADS)

    Maunz, P.; Olmschenk, S.; Hayes, D.; Matsukevich, D. N.; Duan, L.-M.; Monroe, C.

    2009-05-01

    Quantum information processing between remote quantum memories relies on a fast and faithful quantum channel. Recent experiments employed both, the photonic polarization and frequency qubits, in order to entangle remote atoms [1, 2], to teleport quantum information [3] and to operate a quantum gate between distant atoms. Here, we compare the dierent schemes used in these experiments and analyze the advantages of the dierent choices of atomic and photonic qubits and their coherence properties. [4pt] [1] D. L. Moehring et al. Nature 449, 68 (2007).[0pt] [2] D. N. Matsukevich et al. Phys. Rev. Lett. 100, 150404 2008).[0pt] [3] S. Olmschenk et al. Science, 323, 486 (2009).

  4. Generalized Hofmann quantum process fidelity bounds for quantum filters

    NASA Astrophysics Data System (ADS)

    Sedlák, Michal; Fiurášek, Jaromír

    2016-04-01

    We propose and investigate bounds on the quantum process fidelity of quantum filters, i.e., probabilistic quantum operations represented by a single Kraus operator K . These bounds generalize the Hofmann bounds on the quantum process fidelity of unitary operations [H. F. Hofmann, Phys. Rev. Lett. 94, 160504 (2005), 10.1103/PhysRevLett.94.160504] and are based on probing the quantum filter with pure states forming two mutually unbiased bases. Determination of these bounds therefore requires far fewer measurements than full quantum process tomography. We find that it is particularly suitable to construct one of the probe bases from the right eigenstates of K , because in this case the bounds are tight in the sense that if the actual filter coincides with the ideal one, then both the lower and the upper bounds are equal to 1. We theoretically investigate the application of these bounds to a two-qubit optical quantum filter formed by the interference of two photons on a partially polarizing beam splitter. For an experimentally convenient choice of factorized input states and measurements we study the tightness of the bounds. We show that more stringent bounds can be obtained by more sophisticated processing of the data using convex optimization and we compare our methods for different choices of the input probe states.

  5. Euclidean, Spherical, and Hyperbolic Shadows

    ERIC Educational Resources Information Center

    Hoban, Ryan

    2013-01-01

    Many classical problems in elementary calculus use Euclidean geometry. This article takes such a problem and solves it in hyperbolic and in spherical geometry instead. The solution requires only the ability to compute distances and intersections of points in these geometries. The dramatically different results we obtain illustrate the effect…

  6. Enjoyment of Euclidean planar triangles

    NASA Astrophysics Data System (ADS)

    Srinivasan, V. K.

    2013-09-01

    This article adopts the following classification for a Euclidean planar ?, purely based on angles alone. A Euclidean planar triangle is said to be acute angled if all the three angles of the Euclidean planar ? are acute angles. It is said to be right angled at a specific vertex, say B, if the angle ? is a right angle with the two remaining angles as acute angles. It is said to be obtuse angled at the vertex B if ? is an obtuse angle, with the two remaining angles as acute angles. In spite of the availability of numerous text books that contain our human knowledge of Euclidean plane geometry, softwares can offer newer insights about the characterizations of planar geometrical objects. The author's characterizations of triangles involve points like the centroid G, the orthocentre H of the ?, the circumcentre S of the ?, the centre N of the nine-point circle of the ?. Also the radical centre rc of three involved diameter circles of the sides BC, AC and AB of the ? provides a reformulation of the orthocentre, resulting in an interesting theorem, dubbed by the author as 'Three Circles Theorem'. This provides a special result for a right-angled ?, again dubbed by the author as 'The Four Circles Theorem'. Apart from providing various inter connections between the geometrical points, the relationships between shapes of the triangle and the behaviour of the points are reasonably explored in this article. Most of these results will be useful to students that take courses in Euclidean Geometry at the college level and the high school level. This article will be useful to teachers in mathematics at the high school level and the college level.

  7. Virtual Processes and Quantum Tunnelling as Fictions

    ERIC Educational Resources Information Center

    Arthur, Richard T. W.

    2012-01-01

    In this paper it is argued that virtual processes are dispensable fictions. The argument proceeds by a comparison with the phenomenon of quantum tunnelling. Building on an analysis of Levy-Leblond and Balibar, it is argued that, although the phenomenon known as quantum tunnelling certainly occurs and is at the basis of many paradigmatic quantum…

  8. Provable quantum advantage in randomness processing.

    PubMed

    Dale, Howard; Jennings, David; Rudolph, Terry

    2015-01-01

    Quantum advantage is notoriously hard to find and even harder to prove. For example the class of functions computable with classical physics exactly coincides with the class computable quantum mechanically. It is strongly believed, but not proven, that quantum computing provides exponential speed-up for a range of problems, such as factoring. Here we address a computational scenario of randomness processing in which quantum theory provably yields, not only resource reduction over classical stochastic physics, but a strictly larger class of problems which can be solved. Beyond new foundational insights into the nature and malleability of randomness, and the distinction between quantum and classical information, these results also offer the potential of developing classically intractable simulations with currently accessible quantum technologies. PMID:26381816

  9. Compressed Sensing Quantum Process Tomography for Superconducting Quantum Gates

    NASA Astrophysics Data System (ADS)

    Rodionov, Andrey

    An important challenge in quantum information science and quantum computing is the experimental realization of high-fidelity quantum operations on multi-qubit systems. Quantum process tomography (QPT) is a procedure devised to fully characterize a quantum operation. We first present the results of the estimation of the process matrix for superconducting multi-qubit quantum gates using the full data set employing various methods: linear inversion, maximum likelihood, and least-squares. To alleviate the problem of exponential resource scaling needed to characterize a multi-qubit system, we next investigate a compressed sensing (CS) method for QPT of two-qubit and three-qubit quantum gates. Using experimental data for two-qubit controlled-Z gates, taken with both Xmon and superconducting phase qubits, we obtain estimates for the process matrices with reasonably high fidelities compared to full QPT, despite using significantly reduced sets of initial states and measurement configurations. We show that the CS method still works when the amount of data is so small that the standard QPT would have an underdetermined system of equations. We also apply the CS method to the analysis of the three-qubit Toffoli gate with simulated noise, and similarly show that the method works well for a substantially reduced set of data. For the CS calculations we use two different bases in which the process matrix is approximately sparse (the Pauli-error basis and the singular value decomposition basis), and show that the resulting estimates of the process matrices match with reasonably high fidelity. For both two-qubit and three-qubit gates, we characterize the quantum process by its process matrix and average state fidelity, as well as by the corresponding standard deviation defined via the variation of the state fidelity for different initial states. We calculate the standard deviation of the average state fidelity both analytically and numerically, using a Monte Carlo method. Overall

  10. Euclidean Geometry via Programming.

    ERIC Educational Resources Information Center

    Filimonov, Rossen; Kreith, Kurt

    1992-01-01

    Describes the Plane Geometry System computer software developed at the Educational Computer Systems laboratory in Sofia, Bulgaria. The system enables students to use the concept of "algorithm" to correspond to the process of "deductive proof" in the development of plane geometry. Provides an example of the software's capability and compares it to…

  11. Trapped Atomic Ions and Quantum Information Processing

    SciTech Connect

    Wineland, D. J.; Leibfried, D.; Bergquist, J. C.; Blakestad, R. B.; Bollinger, J. J.; Britton, J.; Chiaverini, J.; Epstein, R. J.; Hume, D. B.; Itano, W. M.; Jost, J. D.; Koelemeij, J. C. J.; Langer, C.; Ozeri, R.; Reichle, R.; Rosenband, T.; Schaetz, T.; Schmidt, P. O.; Seidelin, S.; Shiga, N.

    2006-11-07

    The basic requirements for quantum computing and quantum simulation (single- and multi-qubit gates, long memory times, etc.) have been demonstrated in separate experiments on trapped ions. Construction of a large-scale information processor will require synthesis of these elements and implementation of high-fidelity operations on a very large number of qubits. This is still well in the future. NIST and other groups are addressing part of the scaling issue by trying to fabricate multi-zone arrays of traps that would allow highly-parallel and scalable processing. In the near term, some simple quantum processing protocols are being used to aid in quantum metrology, such as in atomic clocks. As the number of qubits increases, Schroedinger's cat paradox and the measurement problem in quantum mechanics become more apparent; with luck, trapped ion systems might be able to shed light on these fundamental issues.

  12. Quantum processes: A Whiteheadian interpretation of quantum field theory

    NASA Astrophysics Data System (ADS)

    Bain, Jonathan

    Quantum processes: A Whiteheadian interpretation of quantum field theory is an ambitious and thought-provoking exercise in physics and metaphysics, combining an erudite study of the very complex metaphysics of A.N. Whitehead with a well-informed discussion of contemporary issues in the philosophy of algebraic quantum field theory. Hättich's overall goal is to construct an interpretation of quantum field theory. He does this by translating key concepts in Whitehead's metaphysics into the language of algebraic quantum field theory. In brief, this Hättich-Whitehead (H-W, hereafter) interpretation takes "actual occasions" as the fundamental ontological entities of quantum field theory. An actual occasion is the result of two types of processes: a "transition process" in which a set of initial possibly-possessed properties for the occasion (in the form of "eternal objects") is localized to a space-time region; and a "concrescence process" in which a subset of these initial possibly-possessed properties is selected and actualized to produce the occasion. Essential to these processes is the "underlying activity", which conditions the way in which properties are initially selected and subsequently actualized. In short, under the H-W interpretation of quantum field theory, an initial set of possibly-possessed eternal objects is represented by a Boolean sublattice of the lattice of projection operators determined by a von Neumann algebra R (O) associated with a region O of Minkowski space-time, and the underlying activity is represented by a state on R (O) obtained by conditionalizing off of the vacuum state. The details associated with the H-W interpretation involve imposing constraints on these representations motivated by principles found in Whitehead's metaphysics. These details are spelled out in the three sections of the book. The first section is a summary and critique of Whitehead's metaphysics, the second section introduces the formalism of algebraic quantum field

  13. General Nth order integrals of motion in the Euclidean plane

    NASA Astrophysics Data System (ADS)

    Post, S.; Winternitz, P.

    2015-10-01

    The general form of an integral of motion that is a polynomial of order N in the momenta is presented for a Hamiltonian system in two-dimensional Euclidean space. The classical and the quantum cases are treated separately, emphasizing both the similarities and the differences between the two. The main application will be to study Nth order superintegrable systems that allow separation of variables in the Hamilton-Jacobi and Schrödinger equations, respectively.

  14. Quantum metrology with unitary parametrization processes

    PubMed Central

    Liu, Jing; Jing, Xiao-Xing; Wang, Xiaoguang

    2015-01-01

    Quantum Fisher information is a central quantity in quantum metrology. We discuss an alternative representation of quantum Fisher information for unitary parametrization processes. In this representation, all information of parametrization transformation, i.e., the entire dynamical information, is totally involved in a Hermitian operator . Utilizing this representation, quantum Fisher information is only determined by and the initial state. Furthermore, can be expressed in an expanded form. The highlights of this form is that it can bring great convenience during the calculation for the Hamiltonians owning recursive commutations with their partial derivative. We apply this representation in a collective spin system and show the specific expression of . For a simple case, a spin-half system, the quantum Fisher information is given and the optimal states to access maximum quantum Fisher information are found. Moreover, for an exponential form initial state, an analytical expression of quantum Fisher information by operator is provided. The multiparameter quantum metrology is also considered and discussed utilizing this representation. PMID:25708678

  15. Experimental demonstration of simplified quantum process tomography.

    PubMed

    Wu, Z; Li, S; Zheng, W; Peng, X; Feng, M

    2013-01-14

    The essential tool to characterize dynamics of an open quantum system is quantum process tomography (QPT). Although standard QPT methods are hard to be scalable, simplified QPT approach is available if we have the prior knowledge that the system Hamiltonian commutes with the system-environment interaction Hamiltonian. Using a nuclear magnetic resonance (NMR) quantum simulator, we experimentally simulate dephasing channels to demonstrate the simplified QPT as well as the standard QPT method as a comparison. The experimental results agree well with our predictions which confirm the validity and better efficiency of the simplified QPT. PMID:23320694

  16. Self-duality in Euclidean supergravity

    NASA Astrophysics Data System (ADS)

    Obrien, G. M.; Tchrakian, D. H.

    1985-01-01

    The compatibility conditions for curvatures satisfying self-duality (Hawking, 1978) and double-duality (Hehl et al., 1978) ansaetze in the theory of vacuum (Euclidean) supergravity and for the double-duality ansatz in Minkowski theory are investigated theoretically. It is found that the equations of motion of Euclidean supergravity admit solutions with self-dual curvature which correspond to nontrivial field configurations, and that the double-duality ansatz leads to nontrival configurations in both Euclidean and Minkowski cases.

  17. Quantum information processing with trapped ion chains

    NASA Astrophysics Data System (ADS)

    Manning, Timothy Andrew

    Trapped atomic ion systems are currently the most advanced platform for quantum information processing. Their long coherence times, pristine state initialization and detection, and precisely controllable and versatile interactions make them excellent quantum systems for experiments in quantum computation and quantum simulation. One of the more promising schemes for quantum computing consists of performing single and multi-qubit quantum gates on qubits in a linear ion crystal. Some of the key challenges of scaling such a system are the individual addressing of arbitrary subsets of ions and controlling the growing complexity of motional mode interactions as the number of qubits increases or when the gates are performed faster. Traditional entangling quantum gates between ion qubits use laser pulses to couple the qubit states to the collective motion of the crystal, thereby generating a spin-spin interaction that can produce entanglement between selected qubits. The intrinsic limitations on the performance of gates using this method can be alleviated by applying optimally shaped pulses instead of pulses with constant amplitude. This thesis explains the theory behind this pulse shaping scheme and how it is implemented on a chain of Yb ions held in a linear radiofrequency 'Paul' trap. Several experiments demonstrate the technique in chains of two, three, and five ions using various types of pulse shapes. A tightly focused individual addressing beam allows us to apply the entangling gates to a target pair of ions, and technical issues related to such tight focusing are discussed. Other advantages to the pulse shaping scheme include a robustness against detuning errors and the possibility of suppressing undesirable coupling due to optical spillover on neighboring ions. Combined with ion shuttling, we harness these features to perform sequential gates to different qubit pairs in order to create genuine tripartite entangled states and demonstrate the programmable quantum

  18. Exclusive processes in quantum chromodynamics

    SciTech Connect

    Brodsky, S.J.; Lepage, G.P.

    1981-06-01

    Large momentum transfer exclusive processes and the short distance structure of hadronic wave functions can be systematically analyzed within the context of perturbative QCD. Predictions for meson form factors, two-photon processes ..gamma gamma.. ..-->.. M anti M, hadronic decays of heavy quark systems, and a number of other related QCD phenomena are reviewed.

  19. Sub-Poissonian processes in quantum optics

    NASA Astrophysics Data System (ADS)

    Davidovich, Luiz

    1996-01-01

    The author reviews methods for generating sub-Poissonian light and related concepts. This light has energy fluctuations reduced below the level which corresponds to a classical Poissonian process (shot-noise level). After an introduction to the concept of nonclassical light, an overview is given of the main methods of quantum-noise reduction. Sub-Poissonian processes are exemplified in different areas of optics, ranging from single-atom resonance fluorescence to nonlinear optics, laser physics, and cavity quantum electrodynamics. Emphasis is placed on the conceptual foundations, and on developments in laser theory that lead to the possibility, already demonstrated experimentally, of linewidth narrowing and sub-Poissonian light generation in lasers and masers. The sources of quantum noise in these devices are analyzed, and four noise-suppression methods are discussed in detail: regularization of the pumping, suppression of spontaneous-emission noise, nonadiabatic evolution of the atomic variables, and twin-beam generation.

  20. From geometry to algebra: the Euclidean way with technology

    NASA Astrophysics Data System (ADS)

    Ferrarello, Daniela; Flavia Mammana, Maria; Pennisi, Mario

    2016-05-01

    In this paper, we present the results of an experimental classroom activity, history-based with a phylogenetic approach, to achieve algebra properties through geometry. In particular, we used Euclidean propositions, processed them by a dynamic geometry system and translate them into algebraic special products.

  1. Reversibility in Quantum Models of Stochastic Processes

    NASA Astrophysics Data System (ADS)

    Gier, David; Crutchfield, James; Mahoney, John; James, Ryan

    Natural phenomena such as time series of neural firing, orientation of layers in crystal stacking and successive measurements in spin-systems are inherently probabilistic. The provably minimal classical models of such stochastic processes are ɛ-machines, which consist of internal states, transition probabilities between states and output values. The topological properties of the ɛ-machine for a given process characterize the structure, memory and patterns of that process. However ɛ-machines are often not ideal because their statistical complexity (Cμ) is demonstrably greater than the excess entropy (E) of the processes they represent. Quantum models (q-machines) of the same processes can do better in that their statistical complexity (Cq) obeys the relation Cμ >= Cq >= E. q-machines can be constructed to consider longer lengths of strings, resulting in greater compression. With code-words of sufficiently long length, the statistical complexity becomes time-symmetric - a feature apparently novel to this quantum representation. This result has ramifications for compression of classical information in quantum computing and quantum communication technology.

  2. Primordial scalar power spectrum from the Euclidean big bounce

    NASA Astrophysics Data System (ADS)

    Schander, Susanne; Barrau, Aurélien; Bolliet, Boris; Linsefors, Linda; Mielczarek, Jakub; Grain, Julien

    2016-01-01

    In effective models of loop quantum cosmology, the holonomy corrections are associated with deformations of space-time symmetries. The most evident manifestation of the deformations is the emergence of a Euclidean phase accompanying the nonsingular bouncing dynamics of the scale factor. In this article, we compute the power spectrum of scalar perturbations generated in this model, with a massive scalar field as the matter content. Instantaneous and adiabatic vacuum-type initial conditions for scalar perturbations are imposed in the contracting phase. The evolution through the Euclidean region is calculated based on the extrapolation of the time direction pointed by the vectors normal to the Cauchy hypersurface in the Lorentzian domains. The obtained power spectrum is characterized by a suppression in the IR regime and oscillations in the intermediate energy range. Furthermore, the speculative extension of the analysis in the UV reveals a specific rise of the power leading to results incompatible with the data.

  3. Measurement and Fundamental Processes in Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Jaeger, Gregg

    2015-07-01

    In the standard mathematical formulation of quantum mechanics, measurement is an additional, exceptional fundamental process rather than an often complex, but ordinary process which happens also to serve a particular epistemic function: during a measurement of one of its properties which is not already determined by a preceding measurement, a measured system, even if closed, is taken to change its state discontinuously rather than continuously as is usual. Many, including Bell, have been concerned about the fundamental role thus given to measurement in the foundation of the theory. Others, including the early Bohr and Schwinger, have suggested that quantum mechanics naturally incorporates the unavoidable uncontrollable disturbance of physical state that accompanies any local measurement without the need for an exceptional fundamental process or a special measurement theory. Disturbance is unanalyzable for Bohr, but for Schwinger it is due to physical interactions' being borne by fundamental particles having discrete properties and behavior which is beyond physical control. Here, Schwinger's approach is distinguished from more well known treatments of measurement, with the conclusion that, unlike most, it does not suffer under Bell's critique of quantum measurement. Finally, Schwinger's critique of measurement theory is explicated as a call for a deeper investigation of measurement processes that requires the use of a theory of quantum fields.

  4. Basing quantum theory on information processing

    NASA Astrophysics Data System (ADS)

    Barnum, Howard

    2008-03-01

    I consider information-based derivations of the quantum formalism, in a framework encompassing quantum and classical theory and a broad spectrum of theories serving as foils to them. The most ambitious hope for such a derivation is a role analogous to Einstein's development of the dynamics and kinetics of macroscopic bodies, and later of their gravitational interactions, on the basis of simple principles with clear operational meanings and experimental consequences. Short of this, it could still provide a principled understanding of the features of quantum mechanics that account for its greater-than-classical information-processing power, helping guide the search for new quantum algorithms and protocols. I summarize the convex operational framework for theories, and discuss information-processing in theories therein. Results include the fact that information that can be obtained without disturbance is inherently classical, generalized no-cloning and no-broadcasting theorems, exponentially secure bit commitment in all non-classical theories without entanglement, properties of theories that allow teleportation, and properties of theories that allow ``remote steering'' of ensembles using entanglement. Joint work with collaborators including Jonathan Barrett, Matthew Leifer, Alexander Wilce, Oscar Dahlsten, and Ben Toner.

  5. Zero energy scattering calculation in Euclidean space

    NASA Astrophysics Data System (ADS)

    Carbonell, J.; Karmanov, V. A.

    2016-03-01

    We show that the Bethe-Salpeter equation for the scattering amplitude in the limit of zero incident energy can be transformed into a purely Euclidean form, as it is the case for the bound states. The decoupling between Euclidean and Minkowski amplitudes is only possible for zero energy scattering observables and allows determining the scattering length from the Euclidean Bethe-Salpeter amplitude. Such a possibility strongly simplifies the numerical solution of the Bethe-Salpeter equation and suggests an alternative way to compute the scattering length in Lattice Euclidean calculations without using the Luscher formalism. The derivations contained in this work were performed for scalar particles and one-boson exchange kernel. They can be generalized to the fermion case and more involved interactions.

  6. Virtual Processes and Quantum Tunnelling as Fictions

    NASA Astrophysics Data System (ADS)

    Arthur, Richard T. W.

    2012-10-01

    In this paper it is argued that virtual processes are dispensable fictions. The argument proceeds by a comparison with the phenomenon of quantum tunnelling. Building on an analysis of Lévy-Leblond and Balibar, it is argued that, although the phenomenon known as quantum tunnelling certainly occurs and is at the basis of many paradigmatic quantum effects, the implied conceptualization of it as a free particle burrowing through a potential barrier is flawed. An alpha particle, for example, does not exist as a free particle inside a uranium nucleus and then "burrow through" the massive potential barrier of the repulsive Coulomb potential: rather, it can be interpreted as existing in a bound state which gives it a corresponding (absolutely tiny, but) finite probability of appearing on the other side of the barrier. If the part of the state function representing the transmission through the barrier is conceived as representing a particle trajectory, the particle will have imaginary momentum and negative kinetic energy. A similar analysis then applies to virtual processes. For example, if (as in Hawking's conception of black hole radiation) one imagines a pair of particles created at the Schwarzschild radius, one of which drops into the black hole, at its creation that particle will have imaginary momentum and negative kinetic energy; so will the pion that is imagined as mediating the nuclear exchange force on the standard model. In each case, it is argued, the phenomenon can be understood in terms of a finite probability of transmission predicted by quantum theory, without appealing to particle trajectories. The idea that a particle "penetrates" a barrier that it does not have the energy to surmount, or that a pair of particles is "virtually" produced one on either side of the Schwarzschild radius, in defiance of energy conservation, should be discarded as unphysical.

  7. Fast Encoding Method for Image Vector Quantization Based on Multiple Appropriate Features to Estimate Euclidean Distance

    NASA Astrophysics Data System (ADS)

    Pan, Zhibin; Kotani, Koji; Ohmi, Tadahiro

    The encoding process of finding the best-matched codeword (winner) for a certain input vector in image vector quantization (VQ) is computationally very expensive due to a lot of k-dimensional Euclidean distance computations. In order to speed up the VQ encoding process, it is beneficial to firstly estimate how large the Euclidean distance is between the input vector and a candidate codeword by using appropriate low dimensional features of a vector instead of an immediate Euclidean distance computation. If the estimated Euclidean distance is large enough, it implies that the current candidate codeword could not be a winner so that it can be rejected safely and thus avoid actual Euclidean distance computation. Sum (1-D), L2 norm (1-D) and partial sums (2-D) of a vector are used together as the appropriate features in this paper because they are the first three simplest features. Then, four estimations of Euclidean distance between the input vector and a codeword are connected to each other by the Cauchy-Schwarz inequality to realize codeword rejection. For typical standard images with very different details (Lena, F-16, Pepper and Baboon), the final remaining must-do actual Euclidean distance computations can be eliminated obviously and the total computational cost including all overhead can also be reduced obviously compared to the state-of-the-art EEENNS method meanwhile keeping a full search (FS) equivalent PSNR.

  8. Non-Euclidean-normed Statistical Mechanics

    NASA Astrophysics Data System (ADS)

    Livadiotis, George

    2016-03-01

    This analysis introduces a possible generalization of Statistical Mechanics within the framework of non-Euclidean metrics induced by the Lp norms. The internal energy is interpreted by the non-Euclidean Lp-normed expectation value of a given energy spectrum. The presented non-Euclidean adaptation of Statistical Mechanics involves finding the stationary probability distribution in the Canonical Ensemble by maximizing the Boltzmann-Gibbs and Tsallis entropy under the constraint of internal energy. The derived non-Euclidean Canonical probability distributions are respectively given by an exponential, and by a q-deformed exponential, of a power-law dependence on energy states. The case of the continuous energy spectrum is thoroughly examined. The Canonical probability distribution is analytically calculated for a power-law density of energy. The relevant non-Euclidean-normed kappa distribution is also derived. This analysis exposes the possible values of the q- or κ-indices, which are strictly limited to certain ranges, depending on the given Lp-norm. The equipartition of energy in each degree of freedom and the extensivity of the internal energy, are also shown. Surprisingly, the physical temperature coincides with the kinetically defined temperature, similar to the Euclidean case. Finally, the connection with thermodynamics arises through the well-known standard classical formalisms.

  9. Quantum process reconstruction based on mutually unbiased basis

    NASA Astrophysics Data System (ADS)

    Fernández-Pérez, A.; Klimov, A. B.; Saavedra, C.

    2011-05-01

    We study a quantum process reconstruction based on the use of mutually unbiased projectors (MUB projectors) as input states for a D-dimensional quantum system, with D being a power of a prime number. This approach connects the results of quantum-state tomography using mutually unbiased bases with the coefficients of a quantum process, expanded in terms of MUB projectors. We also study the performance of the reconstruction scheme against random errors when measuring probabilities at the MUB projectors.

  10. Cold atom quantum emulation of ultrafast processes

    NASA Astrophysics Data System (ADS)

    Rajagopal, Shankari; Geiger, Zachary; Fujiwara, Kurt; Singh, Kevin; Senaratne, Ruwan; Weld, David

    2016-05-01

    Pulsed lasers are an invaluable probe of fast electron dynamics in condensed matter systems. However, despite tremendous progress, physical limitations on lasers and a lack of exact theoretical models still limit the exploration of ultrafast processes in solids. We discuss a possible complementary approach, in which lattice-trapped cold neutral atoms driven far from equilibrium are used as a quantum emulator of ultrafast physics at sub-cycle timescales. The cold atom context is in many ways a natural choice for such experiments: equilibration timescales are more than ten orders of magnitude slower than those in solids, and strong driving forces are easily produced and manipulated. Our experimental approach uses ultracold strontium in optical traps. Multiple stable isotopes and a long-lived metastable state provide control over interaction strengths, while a narrow-linewidth transition expands the typical cold-atom toolbox of readout techniques. We discuss initial efforts in quantum emulation of tunnel ionization and development of a platform for more complicated endeavors, including the study of multiple-pulse sequences and recollision processes. We acknowledge support from the NSF GRFP, the AFOSR, the ARO and DURIP program, the Alfred P. Sloan Foundation, and the University of California Office of the President.

  11. Anomalously soft non-Euclidean spring

    NASA Astrophysics Data System (ADS)

    Levin, Ido; Sharon, Eran

    In this work we study the mechanical properties of a frustrated elastic ribbon spring - the non-Euclidean minimal spring. This spring belongs to the family of non-Euclidean plates: it has no spontaneous curvature, but its lateral intrinsic geometry is described by a non-Euclidean reference metric. The reference metric of the minimal spring is hyperbolic, and can be embedded as a minimal surface. We argue that the existence of a continuous set of such isometric minimal surfaces with different extensions leads to a complete degeneracy of the bulk elastic energy of the minimal spring under elongation. This degeneracy is removed only by boundary layer effects. As a result, the mechanical properties of the minimal spring are unusual: the spring is ultra-soft with rigidity that depends on the thickness, t , as t raise 0 . 7 ex 7 7 2 lower 0 . 7 ex 2, and does not explicitly depend on the ribbon's width. These predictions are confirmed by a numerical study of a constrained spring. This work is the first to address the unusual mechanical properties of constrained non-Euclidean elastic objects. We also present a novel experimental system that is capable of constructing such objects, along with many other non-Euclidean plates.

  12. Compact component for integrated quantum optic processing

    PubMed Central

    Sahu, Partha Pratim

    2015-01-01

    Quantum interference is indispensable to derive integrated quantum optic technologies (1–2). For further progress in large scale integration of quantum optic circuit, we have introduced first time two mode interference (TMI) coupler as an ultra compact component. The quantum interference varying with coupling length corresponding to the coupling ratio is studied and the larger HOM dip with peak visibility ~0.963 ± 0.009 is found at half coupling length of TMI coupler. Our results also demonstrate complex quantum interference with high fabrication tolerance and quantum visibility in TMI coupler. PMID:26584759

  13. Quantum Information Processing using Scalable Techniques

    NASA Astrophysics Data System (ADS)

    Hanneke, D.; Bowler, R.; Jost, J. D.; Home, J. P.; Lin, Y.; Tan, T.-R.; Leibfried, D.; Wineland, D. J.

    2011-05-01

    We report progress towards improving our previous demonstrations that combined all the fundamental building blocks required for scalable quantum information processing using trapped atomic ions. Included elements are long-lived qubits; a laser-induced universal gate set; state initialization and readout; and information transport, including co-trapping a second ion species to reinitialize motion without qubit decoherence. Recent efforts have focused on reducing experimental overhead and increasing gate fidelity. Most of the experimental duty cycle was previously used for transport, separation, and recombination of ion chains as well as re-cooling of motional excitation. We have addressed these issues by developing and implementing an arbitrary waveform generator with an update rate far above the ions' motional frequencies. To reduce gate errors, we actively stabilize the position of several UV (313 nm) laser beams. We have also switched the two-qubit entangling gate to one that acts directly on 9Be+ hyperfine qubit states whose energy separation is magnetic-fluctuation insensitive. This work is supported by DARPA, NSA, ONR, IARPA, Sandia, and the NIST Quantum Information Program.

  14. Entropy Transfer of Quantum Gravity Information Processing

    NASA Astrophysics Data System (ADS)

    Gyongyosi, Laszlo; Imre, Sandor

    2015-05-01

    We introduce the term smooth entanglement entropy transfer, a phenomenon that is a consequence of the causality-cancellation property of the quantum gravity environment. The causality-cancellation of the quantum gravity space removes the causal dependencies of the local systems. We study the physical effects of the causality-cancellation and show that it stimulates entropy transfer between the quantum gravity environment and the independent local systems of the quantum gravity space. The entropy transfer reduces the entropies of the contributing local systems and increases the entropy of the quantum gravity environment. We discuss the space-time geometry structure of the quantum gravity environment and the local quantum systems. We propose the space-time geometry model of the smooth entropy transfer. We reveal on a smooth Cauchy slice that the space-time geometry of the quantum gravity environment dynamically adapts to the vanishing causality. We prove that the Cauchy area expansion, along with the dilation of the Rindler horizon area of the quantum gravity environment, is a corollary of the causality-cancellation of the quantum gravity environment. This work was partially supported by the GOP-1.1.1-11-2012-0092 (Secure quantum key distribution between two units on optical fiber network) project sponsored by the EU and European Structural Fund, and by the COST Action MP1006.

  15. Quantum information processing with narrow band two-photon state

    NASA Astrophysics Data System (ADS)

    Lu, Yajun

    Application of quantum sources in communication and information processing are believed to bring a new revolution to the on-going information age. The generation of applicable quantum sources such as single photon state and two-photon state, appears to be one of the most difficult in experimental quantum optics. Spontaneous Parametric Down-Conversion (PDC) is known to generate two-photon state, but bandwidth problem makes it less applicable in quantum information processing. The aim of this work is to generate a narrow band two-photon state and apply it to quantum information processing. We start by developing a cavity enhanced PDC device to narrow the bandwidth of the two-photon state. Direct measurement of the bandwidth of the generated state has been made and the quantum theory of such a device has been investigated. An application of this narrow band two-photon state is to generate anti-bunched photons for quantum cryptography, based on the quantum interference between the two-photon state and a coherent state. The feasibility of this scheme for pulsed pump is also investigated. When applying the concept of mode locking in lasers to a two-photon state, we have mode-locked two-photon state which exhibits a comb-like correlation function and may be used for engineering of quantum states in time domain. Other applications such as demonstration of single photon nonlocality, nonlinear sign gate in quantum computation, and direct measurement of quantum beating, will also be addressed.

  16. Simulated quantum process tomography of quantum gates with Rydberg superatoms

    NASA Astrophysics Data System (ADS)

    Beterov, I. I.; Saffman, M.; Yakshina, E. A.; Tretyakov, D. B.; Entin, V. M.; Hamzina, G. N.; Ryabtsev, I. I.

    2016-06-01

    We have numerically simulated quantum tomography of single-qubit and two-qubit quantum gates with qubits represented by mesoscopic ensembles containing random numbers of atoms. Such ensembles of strongly interacting atoms in the regime of Rydberg blockade are known as Rydberg superatoms. The stimulated Raman adiabatic passage (STIRAP) in the regime of Rydberg blockade is used for determining Rydberg excitation in the ensemble, required for the storage of quantum information in the collective state of the atomic ensemble and implementation of two-qubit gates. The optimized shapes of the STIRAP pulses are used to achieve high fidelity of the population transfer. Our simulations confirm the validity and high fidelity of single-qubit and two-qubit gates with Rydberg superatoms.

  17. Anomalously Soft Non-Euclidean Springs

    NASA Astrophysics Data System (ADS)

    Levin, Ido; Sharon, Eran

    2016-01-01

    In this work we study the mechanical properties of a frustrated elastic ribbon spring—the non-Euclidean minimal spring. This spring belongs to the family of non-Euclidean plates: it has no spontaneous curvature, but its lateral intrinsic geometry is described by a non-Euclidean reference metric. The reference metric of the minimal spring is hyperbolic, and can be embedded as a minimal surface. We argue that the existence of a continuous set of such isometric minimal surfaces with different extensions leads to a complete degeneracy of the bulk elastic energy of the minimal spring under elongation. This degeneracy is removed only by boundary layer effects. As a result, the mechanical properties of the minimal spring are unusual: the spring is ultrasoft with a rigidity that depends on the thickness t as t7 /2 and does not explicitly depend on the ribbon's width. Moreover, we show that as the ribbon is widened, the rigidity may even decrease. These predictions are confirmed by a numerical study of a constrained spring. This work is the first to address the unusual mechanical properties of constrained non-Euclidean elastic objects.

  18. Making Euclidean Geometry Compulsory: Are We Prepared?

    ERIC Educational Resources Information Center

    Van Putten, Sonja; Howie, Sarah; Stols, Gerrit

    2010-01-01

    This study investigated the attitude towards, as well as the level of understanding of Euclidean geometry in pre-service mathematics education (PME) students. In order to do so, a case study was undertaken within which a one group pre-post-test procedure was conducted around a geometry module, and a representative group of students was interviewed…

  19. Gate fidelity fluctuations and quantum process invariants

    SciTech Connect

    Magesan, Easwar; Emerson, Joseph; Blume-Kohout, Robin

    2011-07-15

    We characterize the quantum gate fidelity in a state-independent manner by giving an explicit expression for its variance. The method we provide can be extended to calculate all higher order moments of the gate fidelity. Using these results, we obtain a simple expression for the variance of a single-qubit system and deduce the asymptotic behavior for large-dimensional quantum systems. Applications of these results to quantum chaos and randomized benchmarking are discussed.

  20. Photonic crystal chips for optical communications and quantum information processing

    NASA Astrophysics Data System (ADS)

    Englund, Dirk; Fushman, Ilya; Faraon, Andrei; Ellis, Bryan; Vučković, Jelena

    2008-08-01

    We discuss recent our recent progress on functional photonic crystals devices and circuits for classical and quantum information processing. For classical applications, we have demonstrated a room-temperature-operated, low threshold, nanocavity laser with pulse width in the picosecond regime; and an all-optical switch controlled with 60 fJ pulses that shows switching time on the order of tens of picoseconds. For quantum information processing, we discuss the promise of quantum networks on multifunctional photonic crystals chips. We also discuss a new coherent probing technique of quantum dots coupled to photonic crystal nanocavities and demonstrate amplitude and phase nonlinearities realized with control beams at the single photon level.

  1. Processing quantum information with relativistic motion of atoms.

    PubMed

    Martín-Martínez, Eduardo; Aasen, David; Kempf, Achim

    2013-04-19

    We show that particle detectors, such as two-level atoms, in noninertial motion (or in gravitational fields) could be used to build quantum gates for the processing of quantum information. Concretely, we show that through suitably chosen noninertial trajectories of the detectors the interaction Hamiltonian's time dependence can be modulated to yield arbitrary rotations in the Bloch sphere due to relativistic quantum effects. PMID:23679587

  2. Photoactivated biological processes as quantum measurements

    NASA Astrophysics Data System (ADS)

    Imamoglu, A.; Whaley, K. B.

    2015-02-01

    We outline a framework for describing photoactivated biological reactions as generalized quantum measurements of external fields, for which the biological system takes on the role of a quantum meter. By using general arguments regarding the Hamiltonian that describes the measurement interaction, we identify the cases where it is essential for a complex chemical or biological system to exhibit nonequilibrium quantum coherent dynamics in order to achieve the requisite functionality. We illustrate the analysis by considering measurement of the solar radiation field in photosynthesis and measurement of the earth's magnetic field in avian magnetoreception.

  3. Quantum coherence, wormholes, and the cosmological constant

    SciTech Connect

    Unruh, W.G. )

    1989-08-15

    Coleman has argued that if wormhole solutions to the Euclidean action coupled to matter dominate the Euclidean path integral for quantum gravity, they do not lead to a loss of quantum coherence for wave functions in our Universe. Furthermore, they also lead to the prediction that the ultimate'' cosmological constant is zero. I analyze the assumptions that go into this result and argue that the presence of wormhole solutions does lead to a loss of quantum coherence and, furthermore, completely destroys the Euclidean quantum theory by producing a highly nonlocal effective Euclidean action which is violently unbounded from below.

  4. Minimized state complexity of quantum-encoded cryptic processes

    NASA Astrophysics Data System (ADS)

    Riechers, Paul M.; Mahoney, John R.; Aghamohammadi, Cina; Crutchfield, James P.

    2016-05-01

    The predictive information required for proper trajectory sampling of a stochastic process can be more efficiently transmitted via a quantum channel than a classical one. This recent discovery allows quantum information processing to drastically reduce the memory necessary to simulate complex classical stochastic processes. It also points to a new perspective on the intrinsic complexity that nature must employ in generating the processes we observe. The quantum advantage increases with codeword length: the length of process sequences used in constructing the quantum communication scheme. In analogy with the classical complexity measure, statistical complexity, we use this reduced communication cost as an entropic measure of state complexity in the quantum representation. Previously difficult to compute, the quantum advantage is expressed here in closed form using spectral decomposition. This allows for efficient numerical computation of the quantum-reduced state complexity at all encoding lengths, including infinite. Additionally, it makes clear how finite-codeword reduction in state complexity is controlled by the classical process's cryptic order, and it allows asymptotic analysis of infinite-cryptic-order processes.

  5. Quantum Information Processing with Modular Networks

    NASA Astrophysics Data System (ADS)

    Crocker, Clayton; Inlek, Ismail V.; Hucul, David; Sosnova, Ksenia; Vittorini, Grahame; Monroe, Chris

    2015-05-01

    Trapped atomic ions are qubit standards for the production of entangled states in quantum information science and metrology applications. Trapped ions can exhibit very long coherence times, external fields can drive strong local interactions via phonons, and remote qubits can be entangled via photons. Transferring quantum information across spatially separated ion trap modules for a scalable quantum network architecture relies on the juxtaposition of both phononic and photonic buses. We report the successful combination of these protocols within and between two ion trap modules on a unit structure of this architecture where the remote entanglement generation rate exceeds the experimentally measured decoherence rate. Additionally, we report an experimental implementation of a technique to maintain phase coherence between spatially and temporally distributed quantum gate operations, a crucial prerequisite for scalability. Finally, we discuss our progress towards addressing the issue of uncontrolled cross-talk between photonic qubits and memory qubits by implementing a second ion species, Barium, to generate the photonic link. This work is supported by the ARO with funding from the IARPA MQCO program, the DARPA Quiness Program, the ARO MURI on Hybrid Quantum Circuits, the AFOSR MURI on Quantum Transduction, and the NSF Physics Frontier Center at JQI.

  6. Controlled Hawking process by quantum energy teleportation

    SciTech Connect

    Hotta, Masahiro

    2010-02-15

    In this paper, a new quantum mechanical method to extract energy from black holes with contracting horizons is proposed. The method is based on a gedanken experiment on quantum energy teleportation, which has been recently proposed in quantum information theory. We consider this quantum energy teleportation protocol for N massless fields in near-horizon regions of large-mass black holes with near-horizon geometry described by the Minkowski metric. For each field, a two-level spin is strongly coupled with the local quantum fluctuation outside the horizon during a short time period. After the measurement of N fields, N-bit information is obtained. During the measurement, positive-energy wave packets of the fields form and then fall into the black hole. The amount of excitation energy is independent of the measurement result. After absorption of the wave packets and increase of the black-hole mass, a measurement-result-dependent local operation of the N fields is performed outside the horizon. Then, accompanying the extraction of positive energy from the quantum fluctuation by the operation, negative-energy wave packets of the fields form and then fall into the black hole, decreasing the black-hole mass. This implies that a part of the absorbed positive energy emitted from the measurement devices is effectively retrieved from the black hole via the measurement results.

  7. The Euclidean distribution of fast radio bursts

    NASA Astrophysics Data System (ADS)

    Oppermann, Niels; Connor, Liam D.; Pen, Ue-Li

    2016-09-01

    We investigate whether current data on the distribution of observed flux densities of fast radio bursts (FRBs) are consistent with a constant source density in Euclidean space. We use the number of FRBs detected in two surveys with different characteristics along with the observed signal-to-noise ratios of the detected FRBs in a formalism similar to a V/Vmax-test to constrain the distribution of flux densities. We find consistency between the data and a Euclidean distribution. Any extension of this model is therefore not data-driven and needs to be motivated separately. As a byproduct we also obtain new improved limits for the FRB rate at 1.4 GHz, which had not been constrained in this way before.

  8. Using quantum filters to process images of diffuse axonal injury

    NASA Astrophysics Data System (ADS)

    Pineda Osorio, Mateo

    2014-06-01

    Some images corresponding to a diffuse axonal injury (DAI) are processed using several quantum filters such as Hermite Weibull and Morse. Diffuse axonal injury is a particular, common and severe case of traumatic brain injury (TBI). DAI involves global damage on microscopic scale of brain tissue and causes serious neurologic abnormalities. New imaging techniques provide excellent images showing cellular damages related to DAI. Said images can be processed with quantum filters, which accomplish high resolutions of dendritic and axonal structures both in normal and pathological state. Using the Laplacian operators from the new quantum filters, excellent edge detectors for neurofiber resolution are obtained. Image quantum processing of DAI images is made using computer algebra, specifically Maple. Quantum filter plugins construction is proposed as a future research line, which can incorporated to the ImageJ software package, making its use simpler for medical personnel.

  9. Orientation Maps in V1 and Non-Euclidean Geometry.

    PubMed

    Afgoustidis, Alexandre

    2015-12-01

    In the primary visual cortex, the processing of information uses the distribution of orientations in the visual input: neurons react to some orientations in the stimulus more than to others. In many species, orientation preference is mapped in a remarkable way on the cortical surface, and this organization of the neural population seems to be important for visual processing. Now, existing models for the geometry and development of orientation preference maps in higher mammals make a crucial use of symmetry considerations. In this paper, we consider probabilistic models for V1 maps from the point of view of group theory; we focus on Gaussian random fields with symmetry properties and review the probabilistic arguments that allow one to estimate pinwheel densities and predict the observed value of π. Then, in order to test the relevance of general symmetry arguments and to introduce methods which could be of use in modeling curved regions, we reconsider this model in the light of group representation theory, the canonical mathematics of symmetry. We show that through the Plancherel decomposition of the space of complex-valued maps on the Euclidean plane, each infinite-dimensional irreducible unitary representation of the special Euclidean group yields a unique V1-like map, and we use representation theory as a symmetry-based toolbox to build orientation maps adapted to the most famous non-Euclidean geometries, viz. spherical and hyperbolic geometry. We find that most of the dominant traits of V1 maps are preserved in these; we also study the link between symmetry and the statistics of singularities in orientation maps, and show what the striking quantitative characteristics observed in animals become in our curved models. PMID:26082007

  10. Parton physics on a Euclidean lattice.

    PubMed

    Ji, Xiangdong

    2013-06-28

    I show that the parton physics related to correlations of quarks and gluons on the light cone can be studied through the matrix elements of frame-dependent, equal-time correlators in the large momentum limit. This observation allows practical calculations of parton properties on a Euclidean lattice. As an example, I demonstrate how to recover the leading-twist quark distribution by boosting an equal-time correlator to a large momentum. PMID:23848864

  11. Understanding Entanglement as a Resource for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Cohen, Scott M.

    2008-05-01

    Ever since Erwin Schrodinger shocked the physics world by killing (and not killing) his cat, entanglement has played a critical role in attempts to understand quantum mechanics. More recently, entanglement has been shown to be a valuable resource, of central importance for quantum computation and the processing of quantum information. In this talk, I will describe a new diagrammatic approach to understanding why entanglement is so valuable, the key idea being that entanglement between two systems ``creates'' multiple images of the state of a third. By way of example, I will show how to ``visualize'' teleportation of unknown quantum states, and how to use entanglement to implement an interaction between spatially separated (and therefore non-interacting!) systems. These ideas have also proven useful in quantum state discrimination, where the state of a quantum system is unknown and is to be determined.

  12. Manipulation of Entangled States for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Bose, S.; Huelga, S. F.; Jonathan, D.; Knight, P. L.; Murao, M.; Plenio, M. B.; Vedral, V.

    Entanglement manipulation, and especially Entanglement Swapping is at the heart of current work on quantum information processing, purification and quantum teleportation. We will discuss how it may be generalized to multiparticle systems and how this enables multi-user quantum cryptographic protocols to be developed. Our scheme allows us to establish multiparticle entanglement between particles which belong to distant users in a communication network through a prior distribution of Bell state singlets followed by local measurements. We compare our method for generating entanglement with existing schemes using simple quantum networks, and highlight the advantages and applications in cryptographic conferencing and in reading messages from more than one source through a single quantum measurement. We also discuss how entanglement leads to the idea of `telecloning', in which a teleportation-like protocol can be found which reproduces the output of an optimal quantum cloning machine.

  13. Experimental quantum process tomography of non-trace-preserving maps

    SciTech Connect

    Bongioanni, Irene; Sansoni, Linda; Sciarrino, Fabio; Mataloni, Paolo; Vallone, Giuseppe

    2010-10-15

    The ability of fully reconstructing quantum maps is a fundamental task of quantum information, in particular when coupling with the environment and experimental imperfections of devices are taken into account. In this context, we carry out a quantum process tomography approach for a set of non-trace-preserving maps. We introduce an operator P to characterize the state-dependent probability of success for the process under investigation. We also evaluate the result of approximating the process with a trace-preserving one.

  14. Log-Euclidean metrics for fast and simple calculus on diffusion tensors.

    PubMed

    Arsigny, Vincent; Fillard, Pierre; Pennec, Xavier; Ayache, Nicholas

    2006-08-01

    Diffusion tensor imaging (DT-MRI or DTI) is an emerging imaging modality whose importance has been growing considerably. However, the processing of this type of data (i.e., symmetric positive-definite matrices), called "tensors" here, has proved difficult in recent years. Usual Euclidean operations on matrices suffer from many defects on tensors, which have led to the use of many ad hoc methods. Recently, affine-invariant Riemannian metrics have been proposed as a rigorous and general framework in which these defects are corrected. These metrics have excellent theoretical properties and provide powerful processing tools, but also lead in practice to complex and slow algorithms. To remedy this limitation, a new family of Riemannian metrics called Log-Euclidean is proposed in this article. They also have excellent theoretical properties and yield similar results in practice, but with much simpler and faster computations. This new approach is based on a novel vector space structure for tensors. In this framework, Riemannian computations can be converted into Euclidean ones once tensors have been transformed into their matrix logarithms. Theoretical aspects are presented and the Euclidean, affine-invariant, and Log-Euclidean frameworks are compared experimentally. The comparison is carried out on interpolation and regularization tasks on synthetic and clinical 3D DTI data. PMID:16788917

  15. Scalable quantum information processing with photons and atoms

    NASA Astrophysics Data System (ADS)

    Pan, Jian-Wei

    Over the past three decades, the promises of super-fast quantum computing and secure quantum cryptography have spurred a world-wide interest in quantum information, generating fascinating quantum technologies for coherent manipulation of individual quantum systems. However, the distance of fiber-based quantum communications is limited due to intrinsic fiber loss and decreasing of entanglement quality. Moreover, probabilistic single-photon source and entanglement source demand exponentially increased overheads for scalable quantum information processing. To overcome these problems, we are taking two paths in parallel: quantum repeaters and through satellite. We used the decoy-state QKD protocol to close the loophole of imperfect photon source, and used the measurement-device-independent QKD protocol to close the loophole of imperfect photon detectors--two main loopholes in quantum cryptograph. Based on these techniques, we are now building world's biggest quantum secure communication backbone, from Beijing to Shanghai, with a distance exceeding 2000 km. Meanwhile, we are developing practically useful quantum repeaters that combine entanglement swapping, entanglement purification, and quantum memory for the ultra-long distance quantum communication. The second line is satellite-based global quantum communication, taking advantage of the negligible photon loss and decoherence in the atmosphere. We realized teleportation and entanglement distribution over 100 km, and later on a rapidly moving platform. We are also making efforts toward the generation of multiphoton entanglement and its use in teleportation of multiple properties of a single quantum particle, topological error correction, quantum algorithms for solving systems of linear equations and machine learning. Finally, I will talk about our recent experiments on quantum simulations on ultracold atoms. On the one hand, by applying an optical Raman lattice technique, we realized a two-dimensional spin-obit (SO

  16. Quantum process tomography by 2D fluorescence spectroscopy

    SciTech Connect

    Pachón, Leonardo A.; Marcus, Andrew H.; Aspuru-Guzik, Alán

    2015-06-07

    Reconstruction of the dynamics (quantum process tomography) of the single-exciton manifold in energy transfer systems is proposed here on the basis of two-dimensional fluorescence spectroscopy (2D-FS) with phase-modulation. The quantum-process-tomography protocol introduced here benefits from, e.g., the sensitivity enhancement ascribed to 2D-FS. Although the isotropically averaged spectroscopic signals depend on the quantum yield parameter Γ of the doubly excited-exciton manifold, it is shown that the reconstruction of the dynamics is insensitive to this parameter. Applications to foundational and applied problems, as well as further extensions, are discussed.

  17. Heralded processes on continuous-variable spaces as quantum maps

    SciTech Connect

    Ferreyrol, Franck; Spagnolo, Nicolò; Blandino, Rémi; Barbieri, Marco; Tualle-Brouri, Rosa

    2014-12-04

    Heralding processes, which only work when a measurement on a part of the system give the good result, are particularly interesting for continuous-variables. They permit non-Gaussian transformations that are necessary for several continuous-variable quantum information tasks. However if maps and quantum process tomography are commonly used to describe quantum transformations in discrete-variable space, they are much rarer in the continuous-variable domain. Also, no convenient tool for representing maps in a way more adapted to the particularities of continuous variables have yet been explored. In this paper we try to fill this gap by presenting such a tool.

  18. Quantum information processing with electronic and nuclear spins in semiconductors

    NASA Astrophysics Data System (ADS)

    Klimov, Paul Victor

    Traditional electronic and communication devices operate by processing binary information encoded as bits. Such digital devices have led to the most advanced technologies that we encounter in our everyday lives and they influence virtually every aspect of our society. Nonetheless, there exists a much richer way to encode and process information. By encoding information in quantum mechanical states as qubits, phenomena such as coherence and entanglement can be harnessed to execute tasks that are intractable to digital devices. Under this paradigm, it should be possible to realize quantum computers, quantum communication networks and quantum sensors that outperform their classical counterparts. The electronic spin states of color-center defects in the semiconductor silicon carbide have recently emerged as promising qubit candidates. They have long-lived quantum coherence up to room temperature, they can be controlled with mature magnetic resonance techniques, and they have a built-in optical interface operating near the telecommunication bands. In this thesis I will present two of our contributions to this field. The first is the electric-field control of electron spin qubits. This development lays foundation for quantum electronics that operate via electrical gating, much like traditional electronics. The second is the universal control and entanglement of electron and nuclear spin qubits in an ensemble under ambient conditions. This development lays foundation for quantum devices that have a built-in redundancy and can operate in real-world conditions. Both developments represent important steps towards practical quantum devices in an electronic grade material.

  19. Towards Quantum Information Processing with Superconducting Circuits

    NASA Astrophysics Data System (ADS)

    Schoelkopf, Robert

    2011-03-01

    In the dozen years since the initial demonstrations that superconducting circuits based on Josephson junctions could be considered as qubits, there has been remarkable progress in the field. Several different ``species'' of these artificial atoms have been designed and tested, and coherence times have increased by more than 1,000, or a factor of 10 every three years. While real devices are still far from satisfying all the DiVincenzo criteria with fidelities that would meet the error correction threshold, one can nonetheless perform preparation, control, quantum logic, and measurement on multiple superconducting qubits, all with surprisingly high purity and precision given that these are man-made, solid-state systems. In recent years we have seen the preparation of highly-entangled multi-qubit states that violate the Bell and Mermin inequalities, as well as the demonstration of single quantum algorithms, which all benefit from the strong coupling, addressability, and all-electronic control that is possible with these systems. Many experiments employ the concept of a ``quantum bus,'' where qubits couple via superconducting transmission lines that form high-quality resonant cavities. A spinoff of this work is the advent of quantum optics on a chip: microwaves are photons too! The combination of qubits coupled to cavities has allowed the preparation and detection of single gigahertz photons, as well as other highly non-classical states of microwave light. Great progress has also been made in quantum measurement, and other Josephson circuits are now delivering amplifiers that operate at or beyond the Heisenberg limit. In this talk I will attempt to give an overview of some of the key concepts, some experimental highlights from recent years, and point out some possible directions for the future in this field. I would like to acknowledge all my collaborators at Yale, and funding from ARO, NSA/LPS, NSF, and IARPA.

  20. Process tomography via sequential measurements on a single quantum system

    NASA Astrophysics Data System (ADS)

    Bassa, Humairah; Goyal, Sandeep K.; Choudhary, Sujit K.; Uys, Hermann; Diósi, Lajos; Konrad, Thomas

    2015-09-01

    We utilize a discrete (sequential) measurement protocol to investigate quantum process tomography of a single two-level quantum system, with an unknown initial state, undergoing Rabi oscillations. The ignorance of the dynamical parameters is encoded into a continuous-variable classical system which is coupled to the two-level quantum system via a generalized Hamiltonian. This combined estimate of the quantum state and dynamical parameters is updated by using the information obtained from sequential measurements on the quantum system and, after a sufficient waiting period, faithful state monitoring and parameter determination is obtained. Numerical evidence is used to demonstrate the convergence of the state estimate to the true state of the hybrid system.

  1. Occam’s Quantum Strop: Synchronizing and Compressing Classical Cryptic Processes via a Quantum Channel

    NASA Astrophysics Data System (ADS)

    Mahoney, John R.; Aghamohammadi, Cina; Crutchfield, James P.

    2016-02-01

    A stochastic process’ statistical complexity stands out as a fundamental property: the minimum information required to synchronize one process generator to another. How much information is required, though, when synchronizing over a quantum channel? Recent work demonstrated that representing causal similarity as quantum state-indistinguishability provides a quantum advantage. We generalize this to synchronization and offer a sequence of constructions that exploit extended causal structures, finding substantial increase of the quantum advantage. We demonstrate that maximum compression is determined by the process’ cryptic order-a classical, topological property closely allied to Markov order, itself a measure of historical dependence. We introduce an efficient algorithm that computes the quantum advantage and close noting that the advantage comes at a cost-one trades off prediction for generation complexity.

  2. Occam’s Quantum Strop: Synchronizing and Compressing Classical Cryptic Processes via a Quantum Channel

    PubMed Central

    Mahoney, John R.; Aghamohammadi, Cina; Crutchfield, James P.

    2016-01-01

    A stochastic process’ statistical complexity stands out as a fundamental property: the minimum information required to synchronize one process generator to another. How much information is required, though, when synchronizing over a quantum channel? Recent work demonstrated that representing causal similarity as quantum state-indistinguishability provides a quantum advantage. We generalize this to synchronization and offer a sequence of constructions that exploit extended causal structures, finding substantial increase of the quantum advantage. We demonstrate that maximum compression is determined by the process’ cryptic order–a classical, topological property closely allied to Markov order, itself a measure of historical dependence. We introduce an efficient algorithm that computes the quantum advantage and close noting that the advantage comes at a cost–one trades off prediction for generation complexity. PMID:26876796

  3. Robin conditions on the Euclidean ball

    NASA Astrophysics Data System (ADS)

    Dowker, J. S.

    1996-04-01

    Techniques are presented for calculating directly the scalar functional determinant on the Euclidean d-ball. General formulae are given for Dirichlet and Robin boundary conditions when d is even and the field is massless. The method involves a large mass asymptotic limit which is carried out in detail for d = 2 as an exercise, incidentally producing some specific summations and identities. Extensive use is made of the Watson - Kober summation formula. The calculation of the finite-mass determinant is also briefly considered.

  4. Broadband invisibility by non-Euclidean cloaking.

    PubMed

    Leonhardt, Ulf; Tyc, Tomás

    2009-01-01

    Invisibility and negative refraction are both applications of transformation optics where the material of a device performs a coordinate transformation for electromagnetic fields. The device creates the illusion that light propagates through empty flat space, whereas in physical space, light is bent around a hidden interior or seems to run backward in space or time. All of the previous proposals for invisibility require materials with extreme properties. Here we show that transformation optics of a curved, non-Euclidean space (such as the surface of a virtual sphere) relax these requirements and can lead to invisibility in a broad band of the spectrum. PMID:19023043

  5. Quantum correlation dynamics in photosynthetic processes assisted by molecular vibrations

    SciTech Connect

    Giorgi, G.L.; Roncaglia, M.; Raffa, F.A.; Genovese, M.

    2015-10-15

    During the long course of evolution, nature has learnt how to exploit quantum effects. In fact, recent experiments reveal the existence of quantum processes whose coherence extends over unexpectedly long time and space ranges. In particular, photosynthetic processes in light-harvesting complexes display a typical oscillatory dynamics ascribed to quantum coherence. Here, we consider the simple model where a dimer made of two chromophores is strongly coupled with a quasi-resonant vibrational mode. We observe the occurrence of wide oscillations of genuine quantum correlations, between electronic excitations and the environment, represented by vibrational bosonic modes. Such a quantum dynamics has been unveiled through the calculation of the negativity of entanglement and the discord, indicators widely used in quantum information for quantifying the resources needed to realize quantum technologies. We also discuss the possibility of approximating additional weakly-coupled off-resonant vibrational modes, simulating the disturbances induced by the rest of the environment, by a single vibrational mode. Within this approximation, one can show that the off-resonant bath behaves like a classical source of noise.

  6. Statistical mechanical studies on the information processing with quantum fluctuation

    NASA Astrophysics Data System (ADS)

    Otsubo, Yosuke; Inoue, Jun-Ichi; Nagata, Kenji; Okada, Masato

    2014-03-01

    Quantum fluctuation induces the tunneling between states in a system and then can be used in combinatorial optimization problems. Such an algorithm is called quantum adiabatic computing. In this work, we investigate the quality of an information processing based on Bayes inference with the quantum fluctuation through the statistical mechanical approach. We then focus on the error correcting codes and CDMA multiuser demodulation which are described by conventional solvable spin glass models and can be analyzed by replica method in the thermodynamic limit. Introducing the quantum fluctuation into the decoding process of each problem, which is called quantum maximizer of the posteriori probability (QMPM) estimate, we analyze the decoding quality and then compare the results with those by the conventional MPM estimate which corresponds to finite temperature decoding From our limited results, the MPM based on the quantum fluctuation seems to achieve the same decoding quality as the thermal MPM does. We clarify the relationship between the optimal amplitude of transverse field and temperature for the mixture of quantum and classical MPMs. This work is supported by JSPS KAKENHI Grant Numbers 12J06501, 25330283, 25120009.

  7. Survey of control performance in quantum information processing

    NASA Astrophysics Data System (ADS)

    Hocker, David; Zheng, Yicong; Kosut, Robert; Brun, Todd; Rabitz, Herschel

    2016-08-01

    There is a rich variety of physics underlying the fundamental gating operations for quantum information processing (QIP). A key aspect of a QIP system is how noise may enter during quantum operations and how suppressing or correcting its effects can best be addressed. Quantum control techniques have been developed to specifically address this effort, although a detailed classification of the compatibility of controls schemes with noise sources found in common quantum systems has not yet been performed. This work numerically examines the performance of modern control methods for suppressing decoherence in the presence of noise forms found in viable quantum systems. The noise-averaged process matrix for controlled one-qubit and two-qubit operations are calculated across noise found in systems driven by Markovian open quantum dynamics. Rather than aiming to describe the absolute best control scheme for a given physical circumstance, this work serves instead to classify quantum control behavior across a large class of noise forms so that opportunities for improving QIP performance may be identified.

  8. Quantum tunneling resonant electron transfer process in Lorentzian plasmas

    SciTech Connect

    Hong, Woo-Pyo; Jung, Young-Dae

    2014-08-15

    The quantum tunneling resonant electron transfer process between a positive ion and a neutral atom collision is investigated in nonthermal generalized Lorentzian plasmas. The result shows that the nonthermal effect enhances the resonant electron transfer cross section in Lorentzian plasmas. It is found that the nonthermal effect on the classical resonant electron transfer cross section is more significant than that on the quantum tunneling resonant charge transfer cross section. It is shown that the nonthermal effect on the resonant electron transfer cross section decreases with an increase of the Debye length. In addition, the nonthermal effect on the quantum tunneling resonant electron transfer cross section decreases with increasing collision energy. The variation of nonthermal and plasma shielding effects on the quantum tunneling resonant electron transfer process is also discussed.

  9. Log-Euclidean free-form deformation

    NASA Astrophysics Data System (ADS)

    Modat, Marc; Ridgway, Gerard R.; Daga, Pankaj; Cardoso, M. J.; Hawkes, David J.; Ashburner, John; Ourselin, Sébastien

    2011-03-01

    The Free-Form Deformation (FFD) algorithm is a widely used method for non-rigid registration. Modifications have previously been proposed to ensure topology preservation and invertibility within this framework. However, in practice, none of these yield the inverse transformation itself, and one loses the parsimonious B-spline parametrisation. We present a novel log-Euclidean FFD approach in which a spline model of a stationary velocity field is exponentiated to yield a diffeomorphism, using an efficient scaling-and-squaring algorithm. The log-Euclidean framework allows easy computation of a consistent inverse transformation, and offers advantages in group-wise atlas building and statistical analysis. We optimise the Normalised Mutual Information plus a regularisation term based on the Jacobian determinant of the transformation, and we present a novel analytical gradient of the latter. The proposed method has been assessed against a fast FFD implementation (F3D) using simulated T1- and T2-weighted magnetic resonance brain images. The overlap measures between propagated grey matter tissue probability maps used in the simulations show similar results for both approaches; however, our new method obtains more reasonable Jacobian values, and yields inverse transformations.

  10. Duality in physiological time: Euclidean and fractal.

    PubMed

    Günther, B; Morgado, E

    1996-01-01

    The aim of the present study was to differentiate two modalities of intrinsic time scales: i- the geometric or Euclidean modality, which is based on the constant speed of mass transport or of wave transmission in cylindrical structures (arteries, veins, nerves), whose allometric exponent (TE = aMb) is b = 0.33, where M is body mass (kg) and a the mass coefficient; ii- the fractal time scale (TF), which is characteristic of organs with self-similar branching structures and with volume-specific flows, whose allometric exponent is b = 0.25. The proposed dichotomy could be confirmed by means of the statistical analysis of empirical allometric exponents (b). Our findings demonstrate the need to separate the chronology of bulk transport at long distances (inter-organic) which follows an Euclidean geometry (cylinders), from the fractal time scale, which operates at short distances (intra-organic) and is represented by a self-similar branching system which determines both the morphometric and physiometric characteristics within each organ. PMID:9278701

  11. Founding Gravitation in 4D Euclidean Space-Time Geometry

    SciTech Connect

    Winkler, Franz-Guenter

    2010-11-24

    The Euclidean interpretation of special relativity which has been suggested by the author is a formulation of special relativity in ordinary 4D Euclidean space-time geometry. The natural and geometrically intuitive generalization of this view involves variations of the speed of light (depending on location and direction) and a Euclidean principle of general covariance. In this article, a gravitation model by Jan Broekaert, which implements a view of relativity theory in the spirit of Lorentz and Poincare, is reconstructed and shown to fulfill the principles of the Euclidean approach after an appropriate reinterpretation.

  12. MEDOF - MINIMUM EUCLIDEAN DISTANCE OPTIMAL FILTER

    NASA Technical Reports Server (NTRS)

    Barton, R. S.

    1994-01-01

    The Minimum Euclidean Distance Optimal Filter program, MEDOF, generates filters for use in optical correlators. The algorithm implemented in MEDOF follows theory put forth by Richard D. Juday of NASA/JSC. This program analytically optimizes filters on arbitrary spatial light modulators such as coupled, binary, full complex, and fractional 2pi phase. MEDOF optimizes these modulators on a number of metrics including: correlation peak intensity at the origin for the centered appearance of the reference image in the input plane, signal to noise ratio including the correlation detector noise as well as the colored additive input noise, peak to correlation energy defined as the fraction of the signal energy passed by the filter that shows up in the correlation spot, and the peak to total energy which is a generalization of PCE that adds the passed colored input noise to the input image's passed energy. The user of MEDOF supplies the functions that describe the following quantities: 1) the reference signal, 2) the realizable complex encodings of both the input and filter SLM, 3) the noise model, possibly colored, as it adds at the reference image and at the correlation detection plane, and 4) the metric to analyze, here taken to be one of the analytical ones like SNR (signal to noise ratio) or PCE (peak to correlation energy) rather than peak to secondary ratio. MEDOF calculates filters for arbitrary modulators and a wide range of metrics as described above. MEDOF examines the statistics of the encoded input image's noise (if SNR or PCE is selected) and the filter SLM's (Spatial Light Modulator) available values. These statistics are used as the basis of a range for searching for the magnitude and phase of k, a pragmatically based complex constant for computing the filter transmittance from the electric field. The filter is produced for the mesh points in those ranges and the value of the metric that results from these points is computed. When the search is concluded, the

  13. Quantum stochastic processes for maps on Hilbert C*-modules

    SciTech Connect

    Heo, Jaeseong; Ji, Un Cig

    2011-05-15

    We discuss pairs ({phi}, {Phi}) of maps, where {phi} is a map between C*-algebras and {Phi} is a {phi}-module map between Hilbert C*-modules, which are generalization of representations of Hilbert C*-modules. A covariant version of Stinespring's theorem for such a pair ({phi}, {Phi}) is established, and quantum stochastic processes constructed from pairs ({l_brace}{phi}{sub t{r_brace}}, {l_brace}{Phi}{sub t{r_brace}}) of families of such maps are studied. We prove that the quantum stochastic process J={l_brace}J{sub t{r_brace}} constructed from a {phi}-quantum dynamical semigroup {Phi}={l_brace}{Phi}{sub t{r_brace}} is a j-map for the quantum stochastic process j={l_brace}j{sub t{r_brace}} constructed from the given quantum dynamical semigroup {phi}={l_brace}{phi}{sub t{r_brace}}, and that J is covariant if the {phi}-quantum dynamical semigroup {Phi} is covariant.

  14. Pure sources and efficient detectors for optical quantum information processing

    NASA Astrophysics Data System (ADS)

    Zielnicki, Kevin

    Over the last sixty years, classical information theory has revolutionized the understanding of the nature of information, and how it can be quantified and manipulated. Quantum information processing extends these lessons to quantum systems, where the properties of intrinsic uncertainty and entanglement fundamentally defy classical explanation. This growing field has many potential applications, including computing, cryptography, communication, and metrology. As inherently mobile quantum particles, photons are likely to play an important role in any mature large-scale quantum information processing system. However, the available methods for producing and detecting complex multi-photon states place practical limits on the feasibility of sophisticated optical quantum information processing experiments. In a typical quantum information protocol, a source first produces an interesting or useful quantum state (or set of states), perhaps involving superposition or entanglement. Then, some manipulations are performed on this state, perhaps involving quantum logic gates which further manipulate or entangle the intial state. Finally, the state must be detected, obtaining some desired measurement result, e.g., for secure communication or computationally efficient factoring. The work presented here concerns the first and last stages of this process as they relate to photons: sources and detectors. Our work on sources is based on the need for optimized non-classical states of light delivered at high rates, particularly of single photons in a pure quantum state. We seek to better understand the properties of spontaneous parameteric downconversion (SPDC) sources of photon pairs, and in doing so, produce such an optimized source. We report an SPDC source which produces pure heralded single photons with little or no spectral filtering, allowing a significant rate enhancement. Our work on detectors is based on the need to reliably measure single-photon states. We have focused on

  15. Human face recognition by Euclidean distance and neural network

    NASA Astrophysics Data System (ADS)

    Pornpanomchai, Chomtip; Inkuna, Chittrapol

    2010-02-01

    The idea of this project development is to improve the concept of human face recognition that has been studied in order to apply it for a more precise and effective recognition of human faces, and offered an alternative to agencies with respect to their access-departure control system. To accomplish this, a technique of calculation of distances between face features, including efficient face recognition though a neural network, is used. The system uses a technique of image processing consisting of 3 major processes: 1) preprocessing or preparation of images, 2) feature extraction from images of eyes, ears, nose and mouth, used for a calculation of Euclidean distances between each organ; and 3) face recognition using a neural network method. Based on the experimental results from reading image of a total of 200 images from 100 human faces, the system can correctly recognize 96 % with average access time of 3.304 sec per image.

  16. Quantum-Classical Hybrid for Information Processing

    NASA Technical Reports Server (NTRS)

    Zak, Michail

    2011-01-01

    Based upon quantum-inspired entanglement in quantum-classical hybrids, a simple algorithm for instantaneous transmissions of non-intentional messages (chosen at random) to remote distances is proposed. The idea is to implement instantaneous transmission of conditional information on remote distances via a quantum-classical hybrid that preserves superposition of random solutions, while allowing one to measure its state variables using classical methods. Such a hybrid system reinforces the advantages, and minimizes the limitations, of both quantum and classical characteristics. Consider n observers, and assume that each of them gets a copy of the system and runs it separately. Although they run identical systems, the outcomes of even synchronized runs may be different because the solutions of these systems are random. However, the global constrain must be satisfied. Therefore, if the observer #1 (the sender) made a measurement of the acceleration v(sub 1) at t =T, then the receiver, by measuring the corresponding acceleration v(sub 1) at t =T, may get a wrong value because the accelerations are random, and only their ratios are deterministic. Obviously, the transmission of this knowledge is instantaneous as soon as the measurements have been performed. In addition to that, the distance between the observers is irrelevant because the x-coordinate does not enter the governing equations. However, the Shannon information transmitted is zero. None of the senders can control the outcomes of their measurements because they are random. The senders cannot transmit intentional messages. Nevertheless, based on the transmitted knowledge, they can coordinate their actions based on conditional information. If the observer #1 knows his own measurements, the measurements of the others can be fully determined. It is important to emphasize that the origin of entanglement of all the observers is the joint probability density that couples their actions. There is no centralized source

  17. Differential topology of adiabatically controlled quantum processes

    NASA Astrophysics Data System (ADS)

    Jonckheere, Edmond A.; Rezakhani, Ali T.; Ahmad, Farooq

    2013-03-01

    It is shown that in a controlled adiabatic homotopy between two Hamiltonians, H 0 and H 1, the gap or "anti-crossing" phenomenon can be viewed as the development of cusps and swallow tails in the region of the complex plane where two critical value curves of the quadratic map associated with the numerical range of H 0 + i H 1 come close. The "near crossing" in the energy level plots happens to be a generic situation, in the sense that a crossing is a manifestation of the quadratic numerical range map being unstable in the sense of differential topology. The stable singularities that can develop are identified and it is shown that they could occur near the gap, making those singularities of paramount importance. Various applications, including the quantum random walk, are provided to illustrate this theory.

  18. Entanglement and Quantum Information Processing with Trapped Ions*

    NASA Astrophysics Data System (ADS)

    Chiaverini, John

    2004-05-01

    Atomic ions confined in radio frequency traps, cooled and addressed with laser pulses, constitute a scalable system for bringing about and exploring quantum entanglement and information processing. Along with relatively high entangling-gate and single-qubit-rotation fidelities, long coherence times enable the execution of some basic quantum algorithms and communication protocols. At NIST we use a multi-zone trap in which entanglement can be distributed over the zones through the spatial separation and combination of several entangled ion qubits, each of which can be separately measured. Current experiments include superdense coding, quantum teleportation, entanglement-enhanced quantum state detection, and entangled state spectroscopy. These experiments and those from other groups will be summarized. *This work was supported by ARDA/NSA and NIST, and done in collaboration with T. Schaetz, M. Barrett, D. Leibfried, J. Britton, W. Itano, J. Jost, C. Langer, R. Ozeri, T. Rosenband, and D. J. Wineland.

  19. On the general constraints in single qubit quantum process tomography

    DOE PAGESBeta

    Bhandari, Ramesh; Peters, Nicholas A.

    2016-05-18

    In this study, we briefly review single-qubit quantum process tomography for trace-preserving and nontrace-preserving processes, and derive explicit forms of the general constraints for fitting experimental data. These forms provide additional insight into the structure of the process matrix. We illustrate this with several examples, including a discussion of qubit leakage error models and the intuition which can be gained from their process matrices.

  20. On the general constraints in single qubit quantum process tomography

    NASA Astrophysics Data System (ADS)

    Bhandari, Ramesh; Peters, Nicholas A.

    2016-05-01

    We briefly review single-qubit quantum process tomography for trace-preserving and nontrace-preserving processes, and derive explicit forms of the general constraints for fitting experimental data. These forms provide additional insight into the structure of the process matrix. We illustrate this with several examples, including a discussion of qubit leakage error models and the intuition which can be gained from their process matrices.

  1. On the general constraints in single qubit quantum process tomography

    PubMed Central

    Bhandari, Ramesh; Peters, Nicholas A.

    2016-01-01

    We briefly review single-qubit quantum process tomography for trace-preserving and nontrace-preserving processes, and derive explicit forms of the general constraints for fitting experimental data. These forms provide additional insight into the structure of the process matrix. We illustrate this with several examples, including a discussion of qubit leakage error models and the intuition which can be gained from their process matrices. PMID:27188691

  2. Colloidal quantum dot solids for solution-processed solar cells

    NASA Astrophysics Data System (ADS)

    Yuan, Mingjian; Liu, Mengxia; Sargent, Edward H.

    2016-03-01

    Solution-processed photovoltaic technologies represent a promising way to reduce the cost and increase the efficiency of solar energy harvesting. Among these, colloidal semiconductor quantum dot photovoltaics have the advantage of a spectrally tuneable infrared bandgap, which enables use in multi-junction cells, as well as the benefit of generating and harvesting multiple charge carrier pairs per absorbed photon. Here we review recent progress in colloidal quantum dot photovoltaics, focusing on three fronts. First, we examine strategies to manage the abundant surfaces of quantum dots, strategies that have led to progress in the removal of electronic trap states. Second, we consider new device architectures that have improved device performance to certified efficiencies of 10.6%. Third, we focus on progress in solution-phase chemical processing, such as spray-coating and centrifugal casting, which has led to the demonstration of manufacturing-ready process technologies.

  3. Electron-exchange and quantum screening effects on the Thomson scattering process in quantum Fermi plasmas

    SciTech Connect

    Lee, Gyeong Won; Jung, Young-Dae; Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, New York 12180-3590

    2013-06-15

    The influence of the electron-exchange and quantum screening on the Thomson scattering process is investigated in degenerate quantum Fermi plasmas. The Thomson scattering cross section in quantum plasmas is obtained by the plasma dielectric function and fluctuation-dissipation theorem as a function of the electron-exchange parameter, Fermi energy, plasmon energy, and wave number. It is shown that the electron-exchange effect enhances the Thomson scattering cross section in quantum plasmas. It is also shown that the differential Thomson scattering cross section has a minimum at the scattering angle Θ=π/2. It is also found that the Thomson scattering cross section increases with an increase of the Fermi energy. In addition, the Thomson scattering cross section is found to be decreased with increasing plasmon energy.

  4. Supersymmetric solutions to Euclidean Romans supergravity

    NASA Astrophysics Data System (ADS)

    Alday, Luis F.; Fluder, Martin; Gregory, Carolina Matte; Richmond, Paul; Sparks, James

    2016-02-01

    We study Euclidean Romans supergravity in six dimensions with a non-trivial Abelian R-symmetry gauge field. We show that supersymmetric solutions are in one-to-one correspondence with solutions to a set of differential constraints on an SU(2) structure. As an application of our results we (i) show that this structure reduces at a conformal boundary to the five-dimensional rigid supersymmetric geometry previously studied by the authors, (ii) find a general expression for the holographic dual of the VEV of a BPS Wilson loop, matching an exact field theory computation, (iii) construct holographic duals to squashed Sasaki-Einstein backgrounds, again matching to a field theory computation, and (iv) find new analytic solutions.

  5. Euclidean supergravity in terms of Dirac eigenvalues

    NASA Astrophysics Data System (ADS)

    Vancea, Ion V.

    1998-08-01

    It has been recently shown that the eigenvalues of the Dirac operator can be considered as dynamical variables of Euclidean gravity. The purpose of this paper is to explore the possibility that the eigenvalues of the Dirac operator might play the same role in the case of supergravity. It is shown that for this purpose some primary constraints on covariant phase space as well as secondary constraints on the eigenspinors must be imposed. The validity of primary constraints under covariant transport is further analyzed. It is shown that in this case restrictions on the tangent bundle and on the spinor bundle of spacetime arise. The form of these restrictions is determined under some simplifying assumptions. It is also shown that manifolds with flat curvature of tangent bundle and spinor bundle satisfy these restrictions and thus they support the Dirac eigenvalues as global observables.

  6. Shape Selection in Non-Euclidean Plates

    NASA Astrophysics Data System (ADS)

    Gemmer, John; Venkataramani, Shankar

    2010-03-01

    We present a theoretical study of free non-Euclidean plates with a disc geometry and a prescribed metric that corresponds to a constant negative Gaussian curvature. We take the equilibrium configuration taken by the these sheets to be a minimum of a F"oppel Von-Kàrmàn type functional in which configurations free of any in plane stretching correspond to isometric embeddings of the metric. We show for all radii there exists low bending energy configurations free of any in plane stretching that obtain a periodic profile. The number of periods in these configurations is set by the condition that the principle curvatures of the surface remain finite and grows approximately exponentially with the radius of the disc.

  7. Experimental reversion of the optimal quantum cloning and flipping processes

    SciTech Connect

    Sciarrino, Fabio; Secondi, Veronica; De Martini, Francesco

    2006-04-15

    The quantum cloner machine maps an unknown arbitrary input qubit into two optimal clones and one optimal flipped qubit. By combining linear and nonlinear optical methods we experimentally implement a scheme that, after the cloning transformation, restores the original input qubit in one of the output channels, by using local measurements, classical communication, and feedforward. This nonlocal method demonstrates how the information on the input qubit can be restored after the cloning process. The realization of the reversion process is expected to find useful applications in the field of modern multipartite quantum cryptography.

  8. Straight monotonic embedding of data sets in Euclidean spaces.

    PubMed

    Courrieu, Pierre

    2002-12-01

    This paper presents a fast incremental algorithm for embedding data sets belonging to various topological spaces in Euclidean spaces. This is useful for networks whose input consists of non-Euclidean (possibly non-numerical) data, for the on-line computation of spatial maps in autonomous agent navigation problems, and for building internal representations from empirical similarity data. PMID:12425437

  9. Semi-Euclidean quasi-elliptic planar motion

    NASA Astrophysics Data System (ADS)

    Bekar, Murat; Yayli, Yusuf

    2016-06-01

    The aim of this paper is to study the algebra of split semi-quaternions with their basic properties. Also, the results of the Euclidean planar motion given by Blaschke and Grünwald is generalized to semi-Euclidean planar motion by using the algebra of split semi-quaternions.

  10. Deductive Systems: Finite and Non-Euclidean Geometries.

    ERIC Educational Resources Information Center

    Runion, Garth E.; Lockwood, James R.

    The study of the non-Euclidean geometries resulting from changes in the Euclidean parallel postulate often strengthens an individual's awareness and understanding of the deductive systems of mathematics in general. Students at both the high school and college levels are frequently fascinated by the study of deductive systems such as the two…

  11. Structure preserving transformations in hyperkähler Euclidean spaces

    NASA Astrophysics Data System (ADS)

    Gaeta, G.; Rodríguez, M. A.

    2016-02-01

    The definition and structure of hyperkähler structure preserving transformations (invariance group) for quaternionic structures have been recently studied and some preliminary results on the Euclidean case discussed. In this work we present the whole structure of the invariance Lie algebra in the Euclidean case for any dimension.

  12. The FEYNMAN tools for quantum information processing: Design and implementation

    NASA Astrophysics Data System (ADS)

    Fritzsche, S.

    2014-06-01

    The FEYNMAN tools have been re-designed with the goal to establish and implement a high-level (computer) language that is capable to deal with the physics of finite, n-qubit systems, from frequently required computations to mathematically advanced tasks in quantum information processing. In particular, emphasis has been placed to introduce a small but powerful set of keystring-driven commands in order to support both, symbolic and numerical computations. Though the current design is implemented again within the framework of MAPLE, it is general and flexible enough to be utilized and combined with other languages and computational environments. The present implementation facilitates a large number of computational tasks, including the definition, manipulation and parametrization of quantum states, the evaluation of quantum measures and quantum operations, the evolution of quantum noise in discrete models, quantum measurements and state estimation, and several others. The design is based on a few high-level commands, with a syntax close to the mathematical notation and its use in the literature, and which can be generalized quite readily in order to solve computational tasks at even higher degree of complexity. In this work, I present and discuss the (re-design of the) FEYNMAN tools and make major parts of the code available for public use. Moreover, a few selected examples are shown and demonstrate possible application of this toolbox. The FEYNMAN tools are provided as MAPLE library and can hence be used on all platforms on which this computer-algebra system is accessible.

  13. Synchronization of optical photons for quantum information processing

    PubMed Central

    Makino, Kenzo; Hashimoto, Yosuke; Yoshikawa, Jun-ichi; Ohdan, Hideaki; Toyama, Takeshi; van Loock, Peter; Furusawa, Akira

    2016-01-01

    A fundamental element of quantum information processing with photonic qubits is the nonclassical quantum interference between two photons when they bunch together via the Hong-Ou-Mandel (HOM) effect. Ultimately, many such photons must be processed in complex interferometric networks. For this purpose, it is essential to synchronize the arrival times of the flying photons and to keep their purities high. On the basis of the recent experimental success of single-photon storage with high purity, we demonstrate for the first time the HOM interference of two heralded, nearly pure optical photons synchronized through two independent quantum memories. Controlled storage times of up to 1.8 μs for about 90 events per second were achieved with purities that were sufficiently high for a negative Wigner function confirmed with homodyne measurements. PMID:27386536

  14. Synchronization of optical photons for quantum information processing.

    PubMed

    Makino, Kenzo; Hashimoto, Yosuke; Yoshikawa, Jun-Ichi; Ohdan, Hideaki; Toyama, Takeshi; van Loock, Peter; Furusawa, Akira

    2016-05-01

    A fundamental element of quantum information processing with photonic qubits is the nonclassical quantum interference between two photons when they bunch together via the Hong-Ou-Mandel (HOM) effect. Ultimately, many such photons must be processed in complex interferometric networks. For this purpose, it is essential to synchronize the arrival times of the flying photons and to keep their purities high. On the basis of the recent experimental success of single-photon storage with high purity, we demonstrate for the first time the HOM interference of two heralded, nearly pure optical photons synchronized through two independent quantum memories. Controlled storage times of up to 1.8 μs for about 90 events per second were achieved with purities that were sufficiently high for a negative Wigner function confirmed with homodyne measurements. PMID:27386536

  15. Quantum control and process tomography of a semiconductor quantum dot hybrid qubit

    NASA Astrophysics Data System (ADS)

    Kim, Dohun; Shi, Zhan; Simmons, C. B.; Ward, D. R.; Prance, J. R.; Koh, Teck Seng; Gamble, John King; Savage, D. E.; Lagally, M. G.; Friesen, Mark; Coppersmith, S. N.; Eriksson, Mark A.

    2014-07-01

    The similarities between gated quantum dots and the transistors in modern microelectronics--in fabrication methods, physical structure and voltage scales for manipulation--have led to great interest in the development of quantum bits (qubits) in semiconductor quantum dots. Although quantum dot spin qubits have demonstrated long coherence times, their manipulation is often slower than desired for important future applications, such as factoring. Furthermore, scalability and manufacturability are enhanced when qubits are as simple as possible. Previous work has increased the speed of spin qubit rotations by making use of integrated micromagnets, dynamic pumping of nuclear spins or the addition of a third quantum dot. Here we demonstrate a qubit that is a hybrid of spin and charge. It is simple, requiring neither nuclear-state preparation nor micromagnets. Unlike previous double-dot qubits, the hybrid qubit enables fast rotations about two axes of the Bloch sphere. We demonstrate full control on the Bloch sphere with π-rotation times of less than 100 picoseconds in two orthogonal directions, which is more than an order of magnitude faster than any other double-dot qubit. The speed arises from the qubit's charge-like characteristics, and its spin-like features result in resistance to decoherence over a wide range of gate voltages. We achieve full process tomography in our electrically controlled semiconductor quantum dot qubit, extracting high fidelities of 85 per cent for X rotations (transitions between qubit states) and 94 per cent for Z rotations (phase accumulation between qubit states).

  16. Quantum information processing by nuclear magnetic resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Havel, T. F.; Cory, D. G.; Lloyd, S.; Boulant, N.; Fortunato, E. M.; Pravia, M. A.; Teklemariam, G.; Weinstein, Y. S.; Bhattacharyya, A.; Hou, J.

    2002-03-01

    Nuclear magnetic resonance (NMR) is a direct macroscopic manifestation of the quantum mechanics of the intrinsic angular momentum of atomic nuclei. It is best known for its extraordinary range of applications, which include molecular structure determination, medical imaging, and measurements of flow and diffusion rates. Most recently, liquid-state NMR spectroscopy has been found to provide a powerful experimental tool for the development and evaluation of the coherent control techniques needed for quantum information processing. This burgeoning new interdisciplinary field has the potential to achieve cryptographic, communications, and computational feats far beyond what is possible with known classical physics. Indeed, NMR has made the demonstration of many of these feats sufficiently simple to be carried out by high school summer interns working in our laboratory (see the last two authors). In this paper the basic principles of quantum information processing by NMR spectroscopy are described, along with several illustrative experiments suitable for incorporation into the undergraduate physics curriculum. These experiments are spin-spin interferometry, an implementation of the quantum Fourier transform, and the quantum simulation of a harmonic oscillator.

  17. Quantum dots in photonic crystals: from quantum information processing to single photon nonlinear optics

    NASA Astrophysics Data System (ADS)

    Vuckovic, Jelena

    2009-05-01

    Quantum dots in photonic crystals are interesting both as a testbed for fundamental cavity quantum electrodynamics (QED) experiments, as well as a platform for quantum and classical information processing. Quantum dot-photonic crystal cavity QED has been probed both in photoluminescence and coherently, by resonant light scattering from such a system [1]. In the latter case, both intensity and photon statistics of the reflected beam have been analyzed as a function of wavelength, leading to observation of effects such as photon blockade and photon induced tunneling - for the first time in solid state [2]. The system has also been employed to achieve a controlled phase and amplitude modulation between two modes of light at the single photon level [3] - nonlinearity observed so far only in atomic physics systems. These demonstrations lie at the core of a number of proposals for quantum information processing, and could also be employed to build novel devices, such as optical switches controlled at a single photon level. [4pt] [1] Dirk Englund, Andrei Faraon, Ilya Fushman, Nick Stoltz, Pierre Petroff, and Jelena Vuckovic, ``Controlling cavity reflectivity with a single quantum dot," Nature ,ol. 450, No. 7171, pp. 857-861, December 2007[0pt] [2] Andrei Faraon, Ilya Fushman, Dirk Englund, Nick Stoltz, Pierre Petroff, and Jelena Vuckovic, ``Coherent generation of nonclassical light on a chip via photon-induced tunneling and blockade," Nature Physics ,ol. 4, pp. 859 - 863 (2008)[0pt] [3] Ilya Fushman, Dirk Englund, Andrei Faraon, Nick Stoltz, Pierre Petroff, and Jelena Vuckovic, ``Controlled phase shift with a single quantum dot," Science ,ol. 320, number 5877, pp. 769-772 ( 2008)

  18. Fast Quantum Algorithms for Numerical Integrals and Stochastic Processes

    NASA Technical Reports Server (NTRS)

    Abrams, D.; Williams, C.

    1999-01-01

    We discuss quantum algorithms that calculate numerical integrals and descriptive statistics of stochastic processes. With either of two distinct approaches, one obtains an exponential speed increase in comparison to the fastest known classical deterministic algotithms and a quadratic speed increase incomparison to classical Monte Carlo methods.

  19. Locality and time irreversibility in quantum processes

    NASA Astrophysics Data System (ADS)

    Slavnov, D. A.

    2014-06-01

    We discuss problems arising in three very different physical processes: an electron scattering on a nucleus, an experiment with delayed choice, and the cosmological Big Bang. We describe the role of soft and supersoft photons in solutions of the arising problems.

  20. Quantum states for quantum processes: A toy model for ammonia inversion spectra

    SciTech Connect

    Arteca, Gustavo A.; Tapia, O.

    2011-07-15

    Chemical transformations are viewed here as quantum processes modulated by external fields, that is, as shifts in reactant to product amplitudes within a quantum state represented by a linear (coherent) superposition of electronuclear basis functions; their electronic quantum numbers identify the ''chemical species.'' This basis set can be mapped from attractors built from a unique electronic configurational space that is invariant with respect to the nuclear geometry. In turn, the quantum numbers that label these basis functions and the semiclassical potentials for the electronic attractors may be used to derive reaction coordinates to monitor progress as a function of the applied field. A generalization of Feynman's three-state model for the ammonia inversion process illustrates the scheme; to enforce symmetry for the entire inversion process model and ensure invariance with respect to nuclear configurations, the three attractors and their basis functions are computed with a grid of fixed floating Gaussian functions. The external-field modulation of the effective inversion barrier is discussed within this conceptual approach. This analysis brings the descriptions of chemical processes near modern technologies that employ molecules to encode information by means of confinement and external fields.

  1. Fast Quantum Algorithm for Predicting Descriptive Statistics of Stochastic Processes

    NASA Technical Reports Server (NTRS)

    Williams Colin P.

    1999-01-01

    Stochastic processes are used as a modeling tool in several sub-fields of physics, biology, and finance. Analytic understanding of the long term behavior of such processes is only tractable for very simple types of stochastic processes such as Markovian processes. However, in real world applications more complex stochastic processes often arise. In physics, the complicating factor might be nonlinearities; in biology it might be memory effects; and in finance is might be the non-random intentional behavior of participants in a market. In the absence of analytic insight, one is forced to understand these more complex stochastic processes via numerical simulation techniques. In this paper we present a quantum algorithm for performing such simulations. In particular, we show how a quantum algorithm can predict arbitrary descriptive statistics (moments) of N-step stochastic processes in just O(square root of N) time. That is, the quantum complexity is the square root of the classical complexity for performing such simulations. This is a significant speedup in comparison to the current state of the art.

  2. A model of the measurement process in quantum theory

    NASA Astrophysics Data System (ADS)

    Diel, H. H.

    2015-07-01

    The so-called measurement problem of quantum theory (QT) is still lacking a satisfactory, or at least widely agreed upon, solution. A number of theories, known as interpretations of quantum theory, have been proposed and found differing acceptance among physicists. Most of the proposed theories try to explain what happens during a QT measurement using a modification of the declarative equations that define the possible results of a measurement of QT observables or by making assumptions outside the scope of falsifiable physics. This paper proposes a solution to the QT measurement problem in terms of a model of the process for the evolution of two QT systems that interact in a way that represents a measurement. The model assumes that the interactions between the measured QT object and the measurement apparatus are ’’normal” interactions which adhere to the laws of quantum field theory.

  3. Evolution of quantum-like modeling in decision making processes

    NASA Astrophysics Data System (ADS)

    Khrennikova, Polina

    2012-12-01

    The application of the mathematical formalism of quantum mechanics to model behavioral patterns in social science and economics is a novel and constantly emerging field. The aim of the so called 'quantum like' models is to model the decision making processes in a macroscopic setting, capturing the particular 'context' in which the decisions are taken. Several subsequent empirical findings proved that when making a decision people tend to violate the axioms of expected utility theory and Savage's Sure Thing principle, thus violating the law of total probability. A quantum probability formula was devised to describe more accurately the decision making processes. A next step in the development of QL-modeling in decision making was the application of Schrödinger equation to describe the evolution of people's mental states. A shortcoming of Schrödinger equation is its inability to capture dynamics of an open system; the brain of the decision maker can be regarded as such, actively interacting with the external environment. Recently the master equation, by which quantum physics describes the process of decoherence as the result of interaction of the mental state with the environmental 'bath', was introduced for modeling the human decision making. The external environment and memory can be referred to as a complex 'context' influencing the final decision outcomes. The master equation can be considered as a pioneering and promising apparatus for modeling the dynamics of decision making in different contexts.

  4. Nonparametric estimation of quantum states, processes and measurements

    NASA Astrophysics Data System (ADS)

    Lougovski, Pavel; Bennink, Ryan

    Quantum state, process, and measurement estimation methods traditionally use parametric models, in which the number and role of relevant parameters is assumed to be known. When such an assumption cannot be justified, a common approach in many disciplines is to fit the experimental data to multiple models with different sets of parameters and utilize an information criterion to select the best fitting model. However, it is not always possible to assume a model with a finite (countable) number of parameters. This typically happens when there are unobserved variables that stem from hidden correlations that can only be unveiled after collecting experimental data. How does one perform quantum characterization in this situation? We present a novel nonparametric method of experimental quantum system characterization based on the Dirichlet Process (DP) that addresses this problem. Using DP as a prior in conjunction with Bayesian estimation methods allows us to increase model complexity (number of parameters) adaptively as the number of experimental observations grows. We illustrate our approach for the one-qubit case and show how a probability density function for an unknown quantum process can be estimated.

  5. Evolution of quantum-like modeling in decision making processes

    SciTech Connect

    Khrennikova, Polina

    2012-12-18

    The application of the mathematical formalism of quantum mechanics to model behavioral patterns in social science and economics is a novel and constantly emerging field. The aim of the so called 'quantum like' models is to model the decision making processes in a macroscopic setting, capturing the particular 'context' in which the decisions are taken. Several subsequent empirical findings proved that when making a decision people tend to violate the axioms of expected utility theory and Savage's Sure Thing principle, thus violating the law of total probability. A quantum probability formula was devised to describe more accurately the decision making processes. A next step in the development of QL-modeling in decision making was the application of Schroedinger equation to describe the evolution of people's mental states. A shortcoming of Schroedinger equation is its inability to capture dynamics of an open system; the brain of the decision maker can be regarded as such, actively interacting with the external environment. Recently the master equation, by which quantum physics describes the process of decoherence as the result of interaction of the mental state with the environmental 'bath', was introduced for modeling the human decision making. The external environment and memory can be referred to as a complex 'context' influencing the final decision outcomes. The master equation can be considered as a pioneering and promising apparatus for modeling the dynamics of decision making in different contexts.

  6. Novel classical post-processing for quantum key distribution-based quantum private query

    NASA Astrophysics Data System (ADS)

    Yang, Yu-Guang; Liu, Zhi-Chao; Chen, Xiu-Bo; Cao, Wei-Feng; Zhou, Yi-Hua; Shi, Wei-Min

    2016-06-01

    Existing classical post-processing (CPP) schemes for quantum key distribution (QKD)-based quantum private queries (QPQs) including the kN→ N , N→ N , and rM→ N ones have been found imperfect in terms of communication efficiency and security. In this paper, we propose a novel CPP scheme for QKD-based QPQs. The proposed CPP scheme reduces the communication complexity and improves the security of QKD-based QPQ protocols largely. Furthermore, the proposed CPP scheme can provide a multi-bit query efficiently.

  7. Understanding Entanglement as a Resource for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Cohen, Scott M.

    2009-03-01

    Ever since Erwin Schrodinger shocked the physics world by killing (and not killing) his cat, entanglement has played a critical role in attempts to understand quantum mechanics. More recently, entanglement has been shown to be a valuable resource, of central importance for quantum computation and the processing of quantum information. In this talk, I will describe a new diagrammatic approach to understanding why entanglement is so valuable, the key idea being that entanglement between two systems ``creates'' multiple images of the state of a third. By way of example, I will show how to ``visualize'' teleportation of unknown quantum states, and how to use entanglement to determine the (unknown) state of a spatially distributed, multipartite quantum system. Illustrative examples of this entanglement-assisted local state discrimination are sets of orthogonal product states exhibiting what is known as ``non-locality without entanglement'', including unextendible product bases. These ideas have also proven useful in using entanglement to implement a unitary interaction between spatially separated (and therefore non-interacting!) systems.

  8. Measuring the heat exchange of a quantum process.

    PubMed

    Goold, John; Poschinger, Ulrich; Modi, Kavan

    2014-08-01

    Very recently, interferometric methods have been proposed to measure the full statistics of work performed on a driven quantum system [Dorner et al., Phys. Rev. Lett. 110, 230601 (2013) and Mazzola et al., Phys. Rev. Lett. 110, 230602 (2013)]. The advantage of such schemes is that they replace the necessity to make projective measurements by performing phase estimation on an appropriately coupled ancilla qubit. These proposals are one possible route to the tangible experimental exploration of quantum thermodynamics, a subject which is the center of much current attention due to the current control of mesoscopic quantum systems. In this Rapid Communication we demonstrate that a modification of the phase estimation protocols can be used in order to measure the heat distribution of a quantum process. In addition, we demonstrate how our scheme maybe implemented using ion trap technology. Our scheme should pave the way for experimental explorations of the Landauer principle and hence the intricate energy to information conversion in mesoscopic quantum systems. PMID:25215667

  9. Surface processes during purification of InP quantum dots

    PubMed Central

    Emelin, Pavel; Vinokurov, Alexander; Dorofeev, Sergey; Abakumov, Artem; Kuznetsova, Tatiana

    2014-01-01

    Summary Recently, a new simple and fast method for the synthesis of InP quantum dots by using phosphine as phosphorous precursor and myristic acid as surface stabilizer was reported. Purification after synthesis is necessary to obtain samples with good optical properties. Two methods of purification were compared and the surface processes which occur during purification were studied. Traditional precipitation with acetone is accompanied by a small increase in photoluminescence. It occurs that during the purification the hydrolysis of the indium precursor takes place, which leads to a better surface passivation. The electrophoretic purification technique does not increase luminescence efficiency but yields very pure quantum dots in only a few minutes. Additionally, the formation of In(OH)3 during the low temperature synthesis was explained. Purification of quantum dots is a very significant part of postsynthetical treatment that determines the properties of the material. But this subject is not sufficiently discussed in the literature. The paper is devoted to the processes that occur at the surface of quantum dots during purification. A new method of purification, electrophoresis, is investigated and described in particular. PMID:25161857

  10. METHODOLOGICAL NOTES: Permutation asymmetry of the relativistic velocity addition law and non-Euclidean geometry

    NASA Astrophysics Data System (ADS)

    Ritus, V. I.

    2008-07-01

    The asymmetry of the relativistic addition law for noncollinear velocities under the velocity permutation leads to two modified triangles on a Euclidean plane depicting the addition of unpermuted and permuted velocities and the appearance of a nonzero angle ω between two resulting velocities. A particle spin rotates through the same angle ω under a Lorentz boost with a velocity noncollinear to the particle velocity. Three mutually connected three-parameter representations of the angle ω, obtained by the author earlier, express the three-parameter symmetry of the sides and angles of two Euclidean triangles identical to the sine and cosine theorems for the sides and angles of a single geodesic triangle on the surface of a pseudosphere. Namely, all three representations of the angle ω, after a transformation of one of them, coincide with the representations of the area of a pseudospherical triangle expressed in terms of any two of its sides and the angle between them. The angle ω is also symmetrically expressed in terms of three angles or three sides of a geodesic triangle, and therefore it is an invariant of the group of triangle motions over the pseudo-sphere surface, the group that includes the Lorentz group. Although the pseudospheres in Euclidean and pseudo-Euclidean spaces are locally isometric, only the latter is isometric to the entire Lobachevsky plane and forms a homogeneous isotropic curved 4-velocity space in the flat Minkowski space. In this connection, relativistic physical processes that may be related to the pseudosphere in Euclidean space are especially interesting.

  11. Towards Hybrid Quantum Information Processing with Polar Molecules

    NASA Astrophysics Data System (ADS)

    Rabl, Peter

    2008-05-01

    With the ongoing miniaturization of on-chip traps for atoms and ions it is timely to think about coherent interfaces between AMO and solid state systems with potential applications for new hybrid implementations for quantum computers. In this talk I will discuss a potential scenario, where ensembles of polar molecules serve as long-lived quantum memories for superconducting qubits and quantum information is transmitted via a high-Q microwave cavity. Polar molecules combine the exceptional features of a large electric dipole moment and long-lived rotational states with level splittings in the GHz regime. When trapped close to the surface of a chip this combination allows strong interactions with coherent solid state devices, e.g., superconducting microwave cavities or Josephson qubits. I will first introduce the system consisting of a single polar molecule coupled to a stripline cavity which realizes a cavity QED system in the microwave regime and discuss applications for quantum information processing, state detection and new cavity-assisted cooling schemes for polar molecules. I will then switch to molecular ensemble qubits where quantum information is encoded in collective spin or rotational excitations of an ensemble of N molecules. Ensemble qubits benefit from a collectively enhanced coupling ˜√N which allows quantum state transfer between the molecules and, e.g., a charge qubit on a timescale that is compatible with typical coherence times in a solid state environment. With the goal to protect ensemble qubits from collisions, I will finally discuss a scenario, where molecules are prepared in a crystalline phase under 1D trapping conditions and dipole moments aligned by an external field.

  12. Quantum measurement in coherence-vector representation

    NASA Astrophysics Data System (ADS)

    Zhou, Tao

    2016-04-01

    We consider the quantum measurements on a finite quantum system in coherence-vector representation. In this representation, all the density operators of an N-level ( N ⩾ 2) quantum system constitute a convex set M (N) embedded in an ( N 2 - 1)-dimensional Euclidean space R^{N^2 - 1}, and we find that an orthogonal measurement is an ( N - 1)-dimensional projector operator on R^{N^2 - 1}. The states unchanged by an orthogonal measurement form an ( N - 1)-dimensional simplex, and in the case when N is prime or power of prime, the space of the density operator is a direct sum of ( N + 1) such simplices. The mathematical description of quantum measurement is plain in this representation, and this may have further applications in quantum information processing.

  13. A versatile source of single photons for quantum information processing

    NASA Astrophysics Data System (ADS)

    Förtsch, Michael; Fürst, Josef U.; Wittmann, Christoffer; Strekalov, Dmitry; Aiello, Andrea; Chekhova, Maria V.; Silberhorn, Christine; Leuchs, Gerd; Marquardt, Christoph

    2013-05-01

    The generation of high-quality single-photon states with controllable narrow spectral bandwidths and central frequencies is key to facilitate efficient coupling of any atomic system to non-classical light fields. Such an interaction is essential in numerous experiments for fundamental science and applications in quantum communication and information processing, as well as in quantum metrology. Here we implement a fully tunable, narrow-band and efficient single-photon source based on a whispering gallery mode resonator. Our disk-shaped, monolithic and intrinsically stable resonator is made of lithium niobate and supports a cavity-assisted spontaneous parametric down-conversion process. The generated photon pairs are emitted into two highly tunable resonator modes. We verify wavelength tuning over 100 nm of both modes with controllable bandwidth between 7.2 and 13 MHz. Heralding of single photons yields anti-bunching with g(2)(0)<0.2.

  14. Quantum tomography of near-unitary processes in high-dimensional quantum systems

    NASA Astrophysics Data System (ADS)

    Lysne, Nathan; Sosa Martinez, Hector; Jessen, Poul; Baldwin, Charles; Kalev, Amir; Deutsch, Ivan

    2016-05-01

    Quantum Tomography (QT) is often considered the ideal tool for experimental debugging of quantum devices, capable of delivering complete information about quantum states (QST) or processes (QPT). In practice, the protocols used for QT are resource intensive and scale poorly with system size. In this situation, a well behaved model system with access to large state spaces (qudits) can serve as a useful platform for examining the tradeoffs between resource cost and accuracy inherent in QT. In past years we have developed one such experimental testbed, consisting of the electron-nuclear spins in the electronic ground state of individual Cs atoms. Our available toolkit includes high fidelity state preparation, complete unitary control, arbitrary orthogonal measurements, and accurate and efficient QST in Hilbert space dimensions up to d = 16. Using these tools, we have recently completed a comprehensive study of QPT in 4, 7 and 16 dimensions. Our results show that QPT of near-unitary processes is quite feasible if one chooses optimal input states and efficient QST on the outputs. We further show that for unitary processes in high dimensional spaces, one can use informationally incomplete QPT to achieve high-fidelity process reconstruction (90% in d = 16) with greatly reduced resource requirements.

  15. Classical Wave Model of Quantum-Like Processing in Brain

    NASA Astrophysics Data System (ADS)

    Khrennikov, A.

    2011-01-01

    We discuss the conjecture on quantum-like (QL) processing of information in the brain. It is not based on the physical quantum brain (e.g., Penrose) - quantum physical carriers of information. In our approach the brain created the QL representation (QLR) of information in Hilbert space. It uses quantum information rules in decision making. The existence of such QLR was (at least preliminary) confirmed by experimental data from cognitive psychology. The violation of the law of total probability in these experiments is an important sign of nonclassicality of data. In so called "constructive wave function approach" such data can be represented by complex amplitudes. We presented 1,2 the QL model of decision making. In this paper we speculate on a possible physical realization of QLR in the brain: a classical wave model producing QLR . It is based on variety of time scales in the brain. Each pair of scales (fine - the background fluctuations of electromagnetic field and rough - the cognitive image scale) induces the QL representation. The background field plays the crucial role in creation of "superstrong QL correlations" in the brain.

  16. Arbitrary waveform generator for quantum information processing with trapped ions

    NASA Astrophysics Data System (ADS)

    Bowler, R.; Warring, U.; Britton, J. W.; Sawyer, B. C.; Amini, J.

    2013-03-01

    Atomic ions confined in multi-electrode traps have been proposed as a basis for scalable quantum information processing. This scheme involves transporting ions between spatially distinct locations by use of time-varying electric potentials combined with laser or microwave pulses for quantum logic in specific locations. We report the development of a fast multi-channel arbitrary waveform generator for applying the time-varying electric potentials used for transport and for shaping quantum logic pulses. The generator is based on a field-programmable gate array controlled ensemble of 16-bit digital-to-analog converters with an update frequency of 50 MHz and an output range of ±10 V. The update rate of the waveform generator is much faster than relevant motional frequencies of the confined ions in our experiments, allowing diabatic control of the ion motion. Numerous pre-loaded sets of time-varying voltages can be selected with 40 ns latency conditioned on real-time signals. Here we describe the device and demonstrate some of its uses in ion-based quantum information experiments, including speed-up of ion transport and the shaping of laser and microwave pulses.

  17. Quantum information processing and quantum-limited metrology using trapped ions at NIST.

    NASA Astrophysics Data System (ADS)

    Wineland, David

    2007-03-01

    With the use of atomic ions confined in a multi-zone array, we implement simple quantum algorithms and study the problems in scaling such a device to tens of qubits [1]. Current work is devoted to better control of classical parameters such as laser intensity, suppression of heating from ambient fluctuating electric fields, and studying limitations caused by more fundamental sources of decoherence, such as spontaneous emission. Along with other groups, we are studying ways to increase the number of trap zones; in particular, we concentrate on a surface-electrode multi-zone geometry. Although a general purpose quantum computer appears to be a distant goal, simple applications of quantum information processing methods enable new techniques for spectroscopy and efficient quantum detection. [1] Current research in collaboration with D. Leibfried, J. Amini, J. C. Bergquist, R. B. Blakestad, J. J. Bollinger, J. Britton, K. Brown, R. J. Epstein, D. B. Hume, W. M. Itano, J. D. Jost, E. Knill, C. Langer, R. Ozeri, T. Rosenband, S. Seidelin, N. Shiga, and J. H. Wesenberg.

  18. Limits Of Quantum Information In Weak Interaction Processes Of Hyperons

    PubMed Central

    Hiesmayr, B. C.

    2015-01-01

    We analyze the achievable limits of the quantum information processing of the weak interaction revealed by hyperons with spin. We find that the weak decay process corresponds to an interferometric device with a fixed visibility and fixed phase difference for each hyperon. Nature chooses rather low visibilities expressing a preference to parity conserving or violating processes (except for the decay Σ+→ pπ0). The decay process can be considered as an open quantum channel that carries the information of the hyperon spin to the angular distribution of the momentum of the daughter particles. We find a simple geometrical information theoretic interpretation of this process: two quantization axes are chosen spontaneously with probabilities where α is proportional to the visibility times the real part of the phase shift. Differently stated, the weak interaction process corresponds to spin measurements with an imperfect Stern-Gerlach apparatus. Equipped with this information theoretic insight we show how entanglement can be measured in these systems and why Bell’s nonlocality (in contradiction to common misconception in literature) cannot be revealed in hyperon decays. Last but not least we study under which circumstances contextuality can be revealed. PMID:26144247

  19. Quantum processes as a mechanism in olfaction for smell recognition?

    NASA Astrophysics Data System (ADS)

    Brookes, Jennifer

    2011-03-01

    The physics of smell is not well understood. The biological processes that occur following a signalling event are well understood (Buck 1991). However, the reasons how and why a signalling event occurs when a particular smell molecule and receptor combination is made, remains un-established. Luca Turin proposes a signalling mechanism which determines smell molecules by quantum mechanics (Turin 1996). Investigation of this mechanism shows it to be physically robust (Brookes,et al, 2007), and consequences of the theory provides quantitative measurements of smell and interesting potential experiments that may determine whether the recognition of smell is a quantum event. Brookes, J.C, Hartoutsiou, F, Horsfield, A.P and Stoneham, A.M. (2007). Physical Review Letters 98, no. 3 038101 Buck, L. (1991) Cell, 65, no.1 (4): 175-187. Turin, L. (1996) Chemical Sences 21, no 6. 773-791 With many thanks to the Wellcome Trust.

  20. Being qua becoming: Aristotle's "Metaphysics", quantum physics, and Process Philosophy

    NASA Astrophysics Data System (ADS)

    Johnson, David Kelley

    In Aristotle's First Philosophy, science and philosophy were partners, but with the rise of empiricism, went their separate ways. Metaphysics combined the rational and irrational (i.e. final cause/unmoved mover) elements of existence to equate being with substance, postulating prime matter as pure potential that was actuated by form to create everything. Modern science reveres pure reason and postulates its theory of being by a rigorous scientific methodology. The Standard Model defines matter as energy formed into fundamental particles via forces contained in fields. Science has proved Aristotle's universe wrong in many ways, but as physics delves deeper into the quantum world, empiricism is reaching its limits concerning fundamental questions of existence. To achieve its avowed mission of explaining existence completely, physics must reunite with philosophy in a metascience modeled on the First Philosophy of Aristotle. One theory of being that integrates quantum physics and metaphysics is Process Philosophy.

  1. Review of solar fuel-producing quantum conversion processes

    NASA Astrophysics Data System (ADS)

    Peterson, D. B.; Biddle, J. R.; Fujita, T.

    1984-05-01

    The status and potential of fuel-producing solar photochemical processes are discussed. Research focused on splitting water to produce dihydrogen and is at a relatively early stage of development. Current emphasis is primarily directed toward understanding the basic chemistry underlying such quantum conversion processes. Theoretical analyses by various investigators predict a limiting thermodynamic efficiency of 31% for devices with a single photosystem operating with unfocused sunlight at 300 K. When non-idealities are included, it appears unlikely that actual devices will have efficiencies greater than 12 to 15%. Observed efficiencies are well below theoretical limits. Cyclic homogeneous photochemical processes for splitting water have efficiencies considerably less than 1%. Efficiency can be significantly increased by addition of a sacrificial reagent; however, such systems are no longer cyclic and it is doubtful that they would be economical on a commercial scale. The observed efficiencies for photoelectrochemical processes are also low but such systems appear more promising than homogeneous photochemical systems. Operating and systems options, including operation at elevated temperature and hybrid and coupled quantum-thermal conversion processes, are also considered.

  2. Review of solar fuel-producing quantum conversion processes

    NASA Technical Reports Server (NTRS)

    Peterson, D. B.; Biddle, J. R.; Fujita, T.

    1984-01-01

    The status and potential of fuel-producing solar photochemical processes are discussed. Research focused on splitting water to produce dihydrogen and is at a relatively early stage of development. Current emphasis is primarily directed toward understanding the basic chemistry underlying such quantum conversion processes. Theoretical analyses by various investigators predict a limiting thermodynamic efficiency of 31% for devices with a single photosystem operating with unfocused sunlight at 300 K. When non-idealities are included, it appears unlikely that actual devices will have efficiencies greater than 12 to 15%. Observed efficiencies are well below theoretical limits. Cyclic homogeneous photochemical processes for splitting water have efficiencies considerably less than 1%. Efficiency can be significantly increased by addition of a sacrificial reagent; however, such systems are no longer cyclic and it is doubtful that they would be economical on a commercial scale. The observed efficiencies for photoelectrochemical processes are also low but such systems appear more promising than homogeneous photochemical systems. Operating and systems options, including operation at elevated temperature and hybrid and coupled quantum-thermal conversion processes, are also considered.

  3. Wick rotation for quantum field theories on degenerate Moyal space(-time)

    SciTech Connect

    Grosse, Harald; Lechner, Gandalf; Ludwig, Thomas; Verch, Rainer

    2013-02-15

    In this paper the connection between quantum field theories on flat noncommutative space(-times) in Euclidean and Lorentzian signature is studied for the case that time is still commutative. By making use of the algebraic framework of quantum field theory and an analytic continuation of the symmetry groups which are compatible with the structure of Moyal space, a general correspondence between field theories on Euclidean space satisfying a time zero condition and quantum field theories on Moyal Minkowski space is presented ('Wick rotation'). It is then shown that field theories transferred to Moyal space(-time) by Rieffel deformation and warped convolution fit into this framework, and that the processes of Wick rotation and deformation commute.

  4. A quantum theoretical approach to information processing in neural networks

    NASA Astrophysics Data System (ADS)

    Barahona da Fonseca, José; Barahona da Fonseca, Isabel; Suarez Araujo, Carmen Paz; Simões da Fonseca, José

    2000-05-01

    A reinterpretation of experimental data on learning was used to formulate a law on data acquisition similar to the Hamiltonian of a mechanical system. A matrix of costs in decision making specifies values attributable to a barrier that opposed to hypothesis formation about decision making. The interpretation of the encoding costs as frequencies of oscillatory phenomena leads to a quantum paradigm based in the models of photoelectric effect as well as of a particle against a potential barrier. Cognitive processes are envisaged as complex phenomena represented by structures linked by valence bounds. This metaphor is used to find some prerequisites to certain types of conscious experience as well as to find an explanation for some pathological distortions of cognitive operations as they are represented in the context of the isolobal model. Those quantum phenomena are understood as representing an analogue programming for specific special purpose computations. The formation of complex chemical structures within the context of isolobal theory is understood as an analog quantum paradigm for complex cognitive computations.

  5. Flexible intuitions of Euclidean geometry in an Amazonian indigene group.

    PubMed

    Izard, Véronique; Pica, Pierre; Spelke, Elizabeth S; Dehaene, Stanislas

    2011-06-14

    Kant argued that Euclidean geometry is synthesized on the basis of an a priori intuition of space. This proposal inspired much behavioral research probing whether spatial navigation in humans and animals conforms to the predictions of Euclidean geometry. However, Euclidean geometry also includes concepts that transcend the perceptible, such as objects that are infinitely small or infinitely large, or statements of necessity and impossibility. We tested the hypothesis that certain aspects of nonperceptible Euclidian geometry map onto intuitions of space that are present in all humans, even in the absence of formal mathematical education. Our tests probed intuitions of points, lines, and surfaces in participants from an indigene group in the Amazon, the Mundurucu, as well as adults and age-matched children controls from the United States and France and younger US children without education in geometry. The responses of Mundurucu adults and children converged with that of mathematically educated adults and children and revealed an intuitive understanding of essential properties of Euclidean geometry. For instance, on a surface described to them as perfectly planar, the Mundurucu's estimations of the internal angles of triangles added up to ~180 degrees, and when asked explicitly, they stated that there exists one single parallel line to any given line through a given point. These intuitions were also partially in place in the group of younger US participants. We conclude that, during childhood, humans develop geometrical intuitions that spontaneously accord with the principles of Euclidean geometry, even in the absence of training in mathematics. PMID:21606377

  6. The Hippocampus and Entorhinal Cortex Encode the Path and Euclidean Distances to Goals during Navigation

    PubMed Central

    Howard, Lorelei R.; Javadi, Amir Homayoun; Yu, Yichao; Mill, Ravi D.; Morrison, Laura C.; Knight, Rebecca; Loftus, Michelle M.; Staskute, Laura; Spiers, Hugo J.

    2014-01-01

    Summary Background Despite decades of research on spatial memory, we know surprisingly little about how the brain guides navigation to goals. While some models argue that vectors are represented for navigational guidance, other models postulate that the future path is computed. Although the hippocampal formation has been implicated in processing spatial goal information, it remains unclear whether this region processes path- or vector-related information. Results We report neuroimaging data collected from subjects navigating London’s Soho district; these data reveal that both the path distance and the Euclidean distance to the goal are encoded by the medial temporal lobe during navigation. While activity in the posterior hippocampus was sensitive to the distance along the path, activity in the entorhinal cortex was correlated with the Euclidean distance component of a vector to the goal. During travel periods, posterior hippocampal activity increased as the path to the goal became longer, but at decision points, activity in this region increased as the path to the goal became closer and more direct. Importantly, sensitivity to the distance was abolished in these brain areas when travel was guided by external cues. Conclusions The results indicate that the hippocampal formation contains representations of both the Euclidean distance and the path distance to goals during navigation. These findings argue that the hippocampal formation houses a flexible guidance system that changes how it represents distance to the goal depending on the fluctuating demands of navigation. PMID:24909328

  7. Quantum Mechanics and Perceptive Processes: A Reply to Elio Conte

    NASA Astrophysics Data System (ADS)

    Ghirardi, GianCarlo

    2015-07-01

    Recently, Elio Conte has commented a paper by the present author devoted to analyze the possibility of checking experimentally whether the perceptual process can lead to the collapse of the wavefunction. Here we answer to the comments by Conte and we show that he has missed to grasp the crucial elements of our proposal. Morever, we discuss some ideas put forward by Conte concerning the occurrence of quantum superpositions of different states of consciousness and we show that they are rather vague and not cogent.

  8. Quantum processes in short and intensive electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Titov, A. I.; Kämpfer, Burkhard; Hosaka, Atsushi; Takabe, Hideaki

    2016-05-01

    This work provides an overview of our recent results in studying two most important and widely discussed quantum processes: electron-positron pairs production off a probe photon propagating through a polarized short-pulsed electromagnetic (e.g. laser) wave field or generalized Breit-Wheeler process, and a single a photon emission off an electron interacting with the laser pules, so-called non-linear Compton scattering. We show that the probabilities of particle production in both processes are determined by interplay of two dynamical effects, where the first one is related to the shape and duration of the pulse and the second one is non-linear dynamics of the interaction of charged fermions with a strong electromagnetic field. We elaborate suitable expressions for the production probabilities and cross sections, convenient for studying evolution of the plasma in presence of strong electromagnetic fields.

  9. Discontinuous automorphisms of the proper Galilei and Euclidean groups

    SciTech Connect

    Adeleke, S.A. )

    1989-04-01

    The author shows that there are numerous discontinuous automorphisms of the three-dimensional Euclidean group and thus of the Galilei group, as numerous as the subsets of the real numbers, 2{sup aleph-null}, to be exact. These automorphisms arise from the derivations of the field of real numbers. Tits gave an example of a discontinuous automorphism for the semidirect product of the general linear group GL{sub n}(K) in n dimensions with the additive group of n {times} n matrices. He observes that if one uses the quaternion representation of the rotations and the form of Tits example, one obtains discontinuous automorphisms of the Euclidean group in three dimensions. He shows that all automorphisms of the Euclidean group in higher dimensions are continuous.

  10. Cold atoms in cavity QED for quantum information processing

    NASA Astrophysics Data System (ADS)

    Vernooy, David William

    2000-11-01

    The new field of quantum information science has exploded into virtually every area of modern physics because of the promise it holds for understanding physical limits to communication, computation and more generally the processing of information. Remarkably, this has come concomitantly with stunning successes at integrating laser cooling and trapping techniques with high finesse microresonators. A regime where some of the new theoretical ideas may be experimentally tested in the particular setting of cavity quantum electrodynamics (QED) has now been reached. This thesis contains three inter-related parts. First, work with microspheres as a possible next generation microcavity is presented, including both successful attempts to push the limits of their quality factors in the near infrared and first experimental results at atomic interaction with the mode of the sphere at the one-photon level. The unique properties of these resonators led to some theoretical investigations of the atom-field interaction emphasizing the quantization of the atomic center of mass degrees of freedom. This has been largely unexplored both theoretically and experimentally to this point, yet remains an extremely important aspect of most serious implementations of quantum information processing in the setting of optical cavity QED. Finally, the emphasis of the last part of this thesis is on an attempt at intracavity atomic localization in the laboratory. Results to date include the first ever trapping of single atoms inside a high finesse microresonator. The techniques and capabilities developed en route to this achievement should form the experimental backbone for future work in optical cavity QED.

  11. Black hole thermodynamics from Euclidean horizon constraints.

    PubMed

    Carlip, S

    2007-07-13

    To explain black hole thermodynamics in quantum gravity, one must introduce constraints to ensure that a black hole is actually present. I show that for a large class of black holes, such "horizon constraints" allow the use of conformal field theory techniques to compute the density of states, reproducing the Bekenstein-Hawking entropy in a nearly model-independent manner. One standard string theory approach to black hole entropy arises as a special case, lending support to the claim that the mechanism may be "universal." I argue that the relevant degrees of freedom are Goldstone-boson-like excitations arising from the weak breaking of symmetry by the constraints. PMID:17678209

  12. Modeling of Euclidean braided fiber architectures to optimize composite properties

    NASA Technical Reports Server (NTRS)

    Armstrong-Carroll, E.; Pastore, C.; Ko, F. K.

    1992-01-01

    Three-dimensional braided fiber reinforcements are a very effective toughening mechanism for composite materials. The integral yarn path inherent to this fiber architecture allows for effective multidirectional dispersion of strain energy and negates delamination problems. In this paper a geometric model of Euclidean braid fiber architectures is presented. This information is used to determine the degree of geometric isotropy in the braids. This information, when combined with candidate material properties, can be used to quickly generate an estimate of the available load-carrying capacity of Euclidean braids at any arbitrary angle.

  13. A candidate for a classical lump in four euclidean dimensions

    NASA Astrophysics Data System (ADS)

    Tchrakian, D. H.

    1985-05-01

    A generalisation of the Yang-Mills-Maxwell-Higgs (YMMH) system is proposed. This system is the residual theory obtained from the dimensional reduction characterized by M8 = E4 × S2 × S2, of a gauge theory which has finite action field configurations in eight euclidean dimensions. The resulting system reduces to YMMH for a small radius of compactification (η-1 and η2- and is put forward as a possible classical lump in four euclidean dimensions. Mailing address during 1984-1985: School of Theoretical Physics, Dublin Institute for Advanced Studies, 10 Burlington Road, Dublin 4, Ireland.

  14. Experimental characterization of quantum correlated triple beams generated by cascaded four-wave mixing processes

    SciTech Connect

    Qin, Zhongzhong; Cao, Leiming; Jing, Jietai

    2015-05-25

    Quantum correlations and entanglement shared among multiple modes are fundamental ingredients of most continuous-variable quantum technologies. Recently, a method used to generate multiple quantum correlated beams using cascaded four-wave mixing (FWM) processes was theoretically proposed and experimentally realized by our group [Z. Qin et al., Phys. Rev. Lett. 113, 023602 (2014)]. Our study of triple-beam quantum correlation paves the way to showing the tripartite entanglement in our system. Our system also promises to find applications in quantum information and precision measurement such as the controlled quantum communications, the generation of multiple quantum correlated images, and the realization of a multiport nonlinear interferometer. For its applications, the degree of quantum correlation is a crucial figure of merit. In this letter, we experimentally study how various parameters, such as the cell temperatures, one-photon, and two-photon detunings, influence the degree of quantum correlation between the triple beams generated from the cascaded two-FWM configuration.

  15. Irreversible Work and Inner Friction in Quantum Thermodynamic Processes

    NASA Astrophysics Data System (ADS)

    Plastina, F.; Alecce, A.; Apollaro, T. J. G.; Falcone, G.; Francica, G.; Galve, F.; Lo Gullo, N.; Zambrini, R.

    2014-12-01

    We discuss the thermodynamics of closed quantum systems driven out of equilibrium by a change in a control parameter and undergoing a unitary process. We compare the work actually done on the system with the one that would be performed along ideal adiabatic and isothermal transformations. The comparison with the latter leads to the introduction of irreversible work, while that with the former leads to the introduction of inner friction. We show that these two quantities can be treated on an equal footing, as both can be linked with the heat exchanged in thermalization processes and both can be expressed as relative entropies. Furthermore, we show that a specific fluctuation relation for the entropy production associated with the inner friction exists, which allows the inner friction to be written in terms of its cumulants.

  16. Irreversible work and inner friction in quantum thermodynamic processes.

    PubMed

    Plastina, F; Alecce, A; Apollaro, T J G; Falcone, G; Francica, G; Galve, F; Lo Gullo, N; Zambrini, R

    2014-12-31

    We discuss the thermodynamics of closed quantum systems driven out of equilibrium by a change in a control parameter and undergoing a unitary process. We compare the work actually done on the system with the one that would be performed along ideal adiabatic and isothermal transformations. The comparison with the latter leads to the introduction of irreversible work, while that with the former leads to the introduction of inner friction. We show that these two quantities can be treated on an equal footing, as both can be linked with the heat exchanged in thermalization processes and both can be expressed as relative entropies. Furthermore, we show that a specific fluctuation relation for the entropy production associated with the inner friction exists, which allows the inner friction to be written in terms of its cumulants. PMID:25615295

  17. Myoelectric control of artificial limb inspired by quantum information processing

    NASA Astrophysics Data System (ADS)

    Siomau, Michael; Jiang, Ning

    2015-03-01

    Precise and elegant coordination of a prosthesis across many degrees of freedom represents a significant challenge to efficient rehabilitation of people with limb deficiency. Processing the electrical neural signals collected from the surface of the remnant muscles of the stump is a common way to initiate and control the different movements available to the artificial limb. Based on the assumption that there are distinguishable and repeatable signal patterns among different types of muscular activation, the problem of prosthesis control reduces to one of pattern recognition. Widely accepted classical methods for pattern recognition, however, cannot provide simultaneous and proportional control of the artificial limb. Here we show that, in principle, quantum information processing of the neural signals allows us to overcome the above-mentioned difficulties, suggesting a very simple scheme for myoelectric control of artificial limb with advanced functionalities.

  18. Two photon processes in ZnO quantum dots

    NASA Astrophysics Data System (ADS)

    Maikhuri, Deepti; Purohit, S. P.; Mathur, K. C.

    2016-01-01

    The two-photon bound-bound (TPBB) and the two-photon bound-free (TPBF) processes are studied for the electron in the initial 1S state in the conduction band of the ZnO quantum dot (QD) embedded in the HfO2 and the AlN matrices. The energy and the wave functions of the QD are obtained by using the effective mass approximation with a finite barrier height at the dot-matrix interface. Using the second order perturbation theory results are obtained for the two-photon absorption coefficient and the photoelectric cross section. The photoelectric cross section ratio for the circularly to the linearly polarized photons is also obtained. It is observed that the two-photon processes depend significantly on the polarization of the incident beam, the dot size, and the surrounding matrix. It is found that the electric quadrupole interaction enhance the TPBF photoelectric cross section.

  19. Trion-based Optical Processes in Semiconductor Quantum Wells

    NASA Astrophysics Data System (ADS)

    Baldwin, Thomas Kendrick

    In a semiconductor, negative charge is carried by conduction-band electrons and positive charge is carried by valence-band holes. While charge transport properties can be understood by considering the motion of these carriers individually, the optical properties are largely determined by their mutual interaction. The hydrogen-like bound state of an electron with a hole, or exciton, is the fundamental optical excitation in direct-gap materials such as gallium arsenide and cadmium telluride. In this dissertation, we consider charged excitons, or trions. A bound state of an exciton with a resident electron or hole, trions are a relatively pure manifestation of the three-body problem which can be studied experimentally. This is a subject of practical as well as academic interest: Since the trion is the elementary optical excitation of a resident free carrier, the related optical processes can open pathways for manipulating carrier spin and carrier transport. We present three experimental investigations of trion-based optical processes in semiconductor quantum wells. In the first, we demonstrate electromagnetically induced transparency via the electron spin coherence made possible by the trion transition. We explore the practical limits of this technique in high magnetic fields. In the second, we present a direct measurement of trion and exciton oscillator strength at high magnetic fields. These data reveal insights about the structure of the trion's three-body wavefunction relative to that of its next excited state, the triplet trion. In the last, we investigate the mechanism underlying exciton-correlated tunneling, an optically-controllable transport process in mixed-type quantum wells. Extensive experimental studies indicate that it is due to a local, indirect interaction between an exciton and a hole, forming one more example of a trion-mediated optical process. This dissertation includes previously published co-authored material.

  20. A universal quantum frequency converter via four-wave-mixing processes

    NASA Astrophysics Data System (ADS)

    Cheng, Mingfei; Fang, Jinghuai

    2016-06-01

    We present a convenient and flexible way to realize a universal quantum frequency converter by using nondegenerate four-wave-mixing processes in the ladder-type three-level atomic system. It is shown that quantum state exchange between two fields with large frequency difference can be readily achieved, where one corresponds to the atomic resonant transition in the visible spectral region for quantum memory and the other to the telecommunication range wavelength (1550 nm) for long-distance transmission over optical fiber. This method would bring great facility in realistic quantum information processing protocols with atomic ensembles as quantum memory and low-loss optical fiber as transmission channel.

  1. A Scalable Microfabricated Ion Trap for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Maunz, Peter; Haltli, Raymond; Hollowell, Andrew; Lobser, Daniel; Mizrahi, Jonathan; Rembetski, John; Resnick, Paul; Sterk, Jonathan D.; Stick, Daniel L.; Blain, Matthew G.

    2016-05-01

    Trapped Ion Quantum Information Processing (QIP) relies on complex microfabricated trap structures to enable scaling of the number of quantum bits. Building on previous demonstrations of surface-electrode ion traps, we have designed and characterized the Sandia high-optical-access (HOA-2) microfabricated ion trap. This trap features high optical access, high trap frequencies, low heating rates, and negligible charging of dielectric trap components. We have observed trap lifetimes of more than 100h, measured trap heating rates for ytterbium of less than 40quanta/s, and demonstrated shuttling of ions from a slotted to an above surface region and through a Y-junction. Furthermore, we summarize demonstrations of high-fidelity single and two-qubit gates realized in this trap. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000. This work was supported by the Intelligence Advanced Research Projects Activity (IARPA).

  2. On refractive processes in strong laser field quantum electrodynamics

    SciTech Connect

    Di Piazza, A.

    2013-11-15

    Refractive processes in strong-field QED are pure quantum processes, which involve only external photons and the background electromagnetic field. We show analytically that such processes occurring in a plane-wave field and involving external real photons are all characterized by a surprisingly modest net exchange of energy and momentum with the laser field, corresponding to a few laser photons, even in the limit of ultra-relativistic laser intensities. We obtain this result by a direct calculation of the transition matrix element of an arbitrary refractive QED process and accounting exactly for the background plane-wave field. A simple physical explanation of this modest net exchange of laser photons is provided, based on the fact that the laser field couples with the external photons only indirectly through virtual electron–positron pairs. For stronger and stronger laser fields, the pairs cover a shorter and shorter distance before they annihilate again, such that the laser can transfer to them an energy corresponding to only a few photons. These results can be relevant for the future experiments aiming to test strong-field QED at present and next-generation facilities. -- Highlights: •Investigation of the one-loop amplitude of refractive QED processes in a laser field. •The amplitude is suppressed for a large number of net-exchanged laser photons. •Suggestion for first observation of high-nonlinear vacuum effects in a laser field.

  3. The quantum formulation derived from assumptions of epistemic processes

    NASA Astrophysics Data System (ADS)

    Helland, Inge S.

    2015-04-01

    Motivated by Quantum Bayesianism I give background for a general epistemic approach to quantum mechanics, where complementarity and symmetry are the only essential features. A general definition of a symmetric epistemic setting is introduced, and for this setting the basic Hilbert space formalism is arrived at under certain technical assumptions. Other aspects of ordinary quantum mechanics will be developed from the same basis elsewhere.

  4. A Gilbert-Varshamov type bound for Euclidean packings

    NASA Astrophysics Data System (ADS)

    Nebe, Gabriele; Xing, Chaoping

    2008-12-01

    This paper develops a method to obtain a Gilbert-Varshamov type bound for dense packings in the Euclidean spaces using suitable lattices. For the Leech lattice the obtained bounds are quite reasonable for large dimensions, better than the Minkowski-Hlawka bound, but not as good as the lower bound given by Keith Ball in 1992.

  5. The Role of Structure in Learning Non-Euclidean Geometry

    ERIC Educational Resources Information Center

    Asmuth, Jennifer A.

    2009-01-01

    How do people learn novel mathematical information that contradicts prior knowledge? The focus of this thesis is the role of structure in the acquisition of knowledge about hyperbolic geometry, a non-Euclidean geometry. In a series of three experiments, I contrast a more holistic structure--training based on closed figures--with a mathematically…

  6. Equivalence between Euclidean and in-in formalisms in de Sitter QFT

    SciTech Connect

    Higuchi, Atsushi; Marolf, Donald; Morrison, Ian A.

    2011-04-15

    We study the relation between two sets of correlators in interacting quantum field theory on de Sitter space. The first are correlators computed using in-in perturbation theory in the expanding cosmological patch of de Sitter space (also known as the conformal patch, or the Poincare patch), and for which the free propagators are taken to be those of the free Euclidean vacuum. The second are correlators obtained by analytic continuation from Euclidean de Sitter; i.e., they are correlators in the fully interacting Hartle-Hawking state. We give an analytic argument that these correlators coincide for interacting massive scalar fields with any m{sup 2}>0. We also verify this result via direct calculation in simple examples. The correspondence holds diagram by diagram, and at any finite value of an appropriate Pauli-Villars regulator mass M. Along the way, we note interesting connections between various prescriptions for perturbation theory in general static spacetimes with bifurcate Killing horizons.

  7. Capture process in nuclear reactions with a quantum master equation

    SciTech Connect

    Sargsyan, V. V.; Kanokov, Z.; Adamian, G. G.; Antonenko, N. V.; Scheid, W.

    2009-09-15

    Projectile-nucleus capture by a target nucleus at bombarding energies in the vicinity of the Coulomb barrier is treated with the reduced-density-matrix formalism. The effects of dissipation and fluctuations on the capture process are taken self-consistently into account within the quantum model suggested. The excitation functions for the capture in the reactions {sup 16}O, {sup 19}F, {sup 26}Mg, {sup 28}Si, {sup 32,34,36,38}S, {sup 40,48}Ca, {sup 50}Ti, {sup 52}Cr+{sup 208}Pb with spherical nuclei are calculated and compared with the experimental data. At bombarding energies about (15-25) MeV above the Coulomb barrier the maximum of capture cross section is revealed for the {sup 58}Ni+{sup 208}Pb reaction.

  8. Effects of image processing on the detective quantum efficiency

    NASA Astrophysics Data System (ADS)

    Park, Hye-Suk; Kim, Hee-Joung; Cho, Hyo-Min; Lee, Chang-Lae; Lee, Seung-Wan; Choi, Yu-Na

    2010-04-01

    Digital radiography has gained popularity in many areas of clinical practice. This transition brings interest in advancing the methodologies for image quality characterization. However, as the methodologies for such characterizations have not been standardized, the results of these studies cannot be directly compared. The primary objective of this study was to standardize methodologies for image quality characterization. The secondary objective was to evaluate affected factors to Modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) according to image processing algorithm. Image performance parameters such as MTF, NPS, and DQE were evaluated using the international electro-technical commission (IEC 62220-1)-defined RQA5 radiographic techniques. Computed radiography (CR) images of hand posterior-anterior (PA) for measuring signal to noise ratio (SNR), slit image for measuring MTF, white image for measuring NPS were obtained and various Multi-Scale Image Contrast Amplification (MUSICA) parameters were applied to each of acquired images. In results, all of modified images were considerably influence on evaluating SNR, MTF, NPS, and DQE. Modified images by the post-processing had higher DQE than the MUSICA=0 image. This suggests that MUSICA values, as a post-processing, have an affect on the image when it is evaluating for image quality. In conclusion, the control parameters of image processing could be accounted for evaluating characterization of image quality in same way. The results of this study could be guided as a baseline to evaluate imaging systems and their imaging characteristics by measuring MTF, NPS, and DQE.

  9. Quantum superpositions and entanglement of thermal states at high temperatures and their applications to quantum-information processing

    SciTech Connect

    Jeong, Hyunseok; Ralph, Timothy C.

    2007-10-15

    We study characteristics of superpositions and entanglement of thermal states at high temperatures and discuss their applications to quantum-information processing. We introduce thermal-state qubits and thermal-Bell states, which are a generalization of pure-state qubits and Bell states to thermal mixtures. A scheme is then presented to discriminate between the four thermal-Bell states without photon number resolving detection but with Kerr nonlinear interactions and two single-photon detectors. This enables one to perform quantum teleportation and gate operations for quantum computation with thermal-state qubits.

  10. A Vector Approach to Euclidean Geometry: Inner Product Spaces, Euclidean Geometry and Trigonometry, Volume 2. Teacher's Edition.

    ERIC Educational Resources Information Center

    Vaughan, Herbert E.; Szabo, Steven

    This is the teacher's edition of a text for the second year of a two-year high school geometry course. The course bases plane and solid geometry and trigonometry on the fact that the translations of a Euclidean space constitute a vector space which has an inner product. Congruence is a geometric topic reserved for Volume 2. Volume 2 opens with an…

  11. Korn's inequality and Donati's theorem for the conformal Killing operator on pseudo-Euclidean space

    NASA Astrophysics Data System (ADS)

    Wang, Wei

    2008-09-01

    We prove the Korn's inequality for the conformal Killing operator on pseudo-Euclidean space , and an existence theorem for solutions to the non-homogeneous conformal Killing equation, which is a pseudo-Euclidean conformal generalization of Donati's theorem for Euclidean Killing operator.

  12. Biharmonic Submanifolds with Parallel Mean Curvature Vector in Pseudo-Euclidean Spaces

    NASA Astrophysics Data System (ADS)

    Fu, Yu

    2013-12-01

    In this paper, we investigate biharmonic submanifolds in pseudo-Euclidean spaces with arbitrary index and dimension. We give a complete classification of biharmonic spacelike submanifolds with parallel mean curvature vector in pseudo-Euclidean spaces. We also determine all biharmonic Lorentzian surfaces with parallel mean curvature vector field in pseudo-Euclidean spaces.

  13. Fabrication of silica integrated waveguide circuits for quantum enhanced sensing, quantum information processing and number resolving detection

    NASA Astrophysics Data System (ADS)

    Smith, Peter G. R.; Gates, James C.; Holmes, Christopher; Gawith, Corin B. E.; Carpenter, Lewis G.; Mennea, Paolo L.; Posner, Matthew T.; Cooper, Peter A.; Lynch, Stephen G.

    2015-01-01

    Integrated optics is becoming increasingly important for applications in quantum information processing, quantum sensing and for advanced measurement. Intrinsically stable and low-loss it provides essential routing and coupling for quantum optical experiments offering functions such as interconnects, couplers, phase delays and routing. Silica-onsilicon has particular attractions, and in this work the fabrication approaches and advantages of the technique will be explored. In particular, UV direct writing of waveguides and Bragg gratings proves useful for its rapid-prototyping capability and its ability to provide grating for characterization of components for loss, birefringence and coupling ratio. This review concentrates on the fabrication of planar waveguide devices, and ways in which direct UV writing provides important functionality. Examples of applications of silica-on-silicon waveguides include quantum enhanced interferometry, teleportation, boson sampling as well as hybrid operation for single photon detection with transition edge sensors directly placed onto waveguide devices.

  14. Percolation threshold on planar Euclidean Gabriel graphs

    NASA Astrophysics Data System (ADS)

    Norrenbrock, Christoph

    2016-04-01

    In the present article, numerical simulations have been performed to find the bond and site percolation thresholds on two-dimensional Gabriel graphs (GG) for Poisson point processes. GGs belong to the family of "proximity graphs" and are discussed, e.g., in context of the construction of backbones for wireless ad-hoc networks. Finite-size scaling analyses have been performed to find the critical points and critical exponents ν, β and γ. The critical exponents obtained this way verify that the associated universality class is that of standard 2D percolation.

  15. Percolation threshold on planar Euclidean Gabriel graphs

    NASA Astrophysics Data System (ADS)

    Norrenbrock, Christoph

    2016-05-01

    In the present article, numerical simulations have been performed to find the bond and site percolation thresholds on two-dimensional Gabriel graphs (GG) for Poisson point processes. GGs belong to the family of "proximity graphs" and are discussed, e.g., in context of the construction of backbones for wireless ad-hoc networks. Finite-size scaling analyses have been performed to find the critical points and critical exponents ν, β and γ. The critical exponents obtained this way verify that the associated universality class is that of standard 2D percolation.

  16. Certifying single-system steering for quantum-information processing

    NASA Astrophysics Data System (ADS)

    Li, Che-Ming; Chen, Yueh-Nan; Lambert, Neill; Chiu, Ching-Yi; Nori, Franco

    2015-12-01

    Einstein-Podolsky-Rosen (EPR) steering describes how different ensembles of quantum states can be remotely prepared by measuring one particle of an entangled pair. Here, we investigate quantum steering for single quantum d -dimensional systems (qudits) and devise efficient conditions to certify the steerability therein, which we find are applicable both to single-system steering and EPR steering. In the single-system case our steering conditions enable the unambiguous ruling out of generic classical means of mimicking steering. Ruling out "false-steering" scenarios has implications for securing channels against both cloning-based individual attack and coherent attacks when implementing quantum key distribution using qudits. We also show that these steering conditions also have applications in quantum computation, in that they can serve as an efficient criterion for the evaluation of quantum logic gates of arbitrary size. Finally, we describe how the nonlocal EPR variant of these conditions also function as tools for identifying faithful one-way quantum computation, secure entanglement-based quantum communication, and genuine multipartite EPR steering.

  17. Tackling higher derivative ghosts with the Euclidean path integral

    SciTech Connect

    Fontanini, Michele; Trodden, Mark

    2011-05-15

    An alternative to the effective field theory approach to treat ghosts in higher derivative theories is to attempt to integrate them out via the Euclidean path integral formalism. It has been suggested that this method could provide a consistent framework within which we might tolerate the ghost degrees of freedom that plague, among other theories, the higher derivative gravity models that have been proposed to explain cosmic acceleration. We consider the extension of this idea to treating a class of terms with order six derivatives, and find that for a general term the Euclidean path integral approach works in the most trivial background, Minkowski. Moreover we see that even in de Sitter background, despite some difficulties, it is possible to define a probability distribution for tensorial perturbations of the metric.

  18. Euclidean space-time diffeomorphisms and their Fueter subgroups

    SciTech Connect

    Guersey, F.; Jiang, W. )

    1992-02-01

    Holomorphic Fueter functions of the position quaternion form a subgroup of Euclidean space-time diffeomorphisms. An {ital O}(4) covariant treatment of such mappings is presented with the quaternionic argument {ital x} being replaced by either {ital {bar p}x} or {ital x{bar p}} involving self-dual and anti-self-dual structures and {ital p} denoting an arbitrary Euclidean time direction. An infinite group (the quasiconformal group) is exhibited that admits the conformal group SO(5,1) as a subgroup, in analogy to the two-dimensional case in which the Moebius group SO(3,1) is a subgroup of the infinite Virasoro group. The ensuing (3+1) covariant decomposition of diffeomorphisms suggests covariant gauges that throw the metric and the stress tensors in standard forms suitable for canonical quantization, leading to improved'' energy-momentum tensors. Other possible applications to current algebra and gravity will be mentioned.

  19. Optimal recovery of linear operators in non-Euclidean metrics

    SciTech Connect

    Osipenko, K Yu

    2014-10-31

    The paper looks at problems concerning the recovery of operators from noisy information in non-Euclidean metrics. A number of general theorems are proved and applied to recovery problems for functions and their derivatives from the noisy Fourier transform. In some cases, a family of optimal methods is found, from which the methods requiring the least amount of original information are singled out. Bibliography: 25 titles.

  20. Controlling Atomic, Solid-State and Hybrid Systems for Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Gullans, Michael John

    Quantum information science involves the use of precise control over quantum systems to explore new technologies. However, as quantum systems are scaled up they require an ever deeper understanding of many-body physics to achieve the required degree of control. Current experiments are entering a regime which requires active control of a mesoscopic number of coupled quantum systems or quantum bits (qubits). This thesis describes several approaches to this goal and shows how mesoscopic quantum systems can be controlled and utilized for quantum information tasks. The first system we consider is the nuclear spin environment of GaAs double quantum dots containing two electrons. We show that the through appropriate control of dynamic nuclear polarization one can prepare the nuclear spin environment in three distinct collective quantum states which are useful for quantum information processing with electron spin qubits. We then investigate a hybrid system in which an optical lattice is formed in the near field scattering off an array of metallic nanoparticles by utilizing the plasmonic resonance of the nanoparticles. We show that such a system would realize new regimes of dense, ultra-cold quantum matter and can be used to create a quantum network of atoms and plasmons. Finally we investigate quantum nonlinear optical systems. We show that the intrinsic nonlinearity for plasmons in graphene can be large enough to make a quantum gate for single photons. We also consider two nonlinear optical systems based on ultracold gases of atoms. In one case, we demonstrate an all-optical single photon switch using cavity quantum electrodynamics (QED) and slow light. In the second case, we study few photon physics in strongly interacting Rydberg polariton systems, where we demonstrate the existence of two and three photon bound states and study their properties.

  1. Quantum cognition: The possibility of processing with nuclear spins in the brain

    NASA Astrophysics Data System (ADS)

    Fisher, Matthew P. A.

    2015-11-01

    The possibility that quantum processing with nuclear spins might be operative in the brain is explored. Phosphorus is identified as the unique biological element with a nuclear spin that can serve as a qubit for such putative quantum processing-a neural qubit-while the phosphate ion is the only possible qubit-transporter. We identify the "Posner molecule", Ca9(PO4)6, as the unique molecule that can protect the neural qubits on very long times and thereby serve as a (working) quantum-memory. A central requirement for quantum-processing is quantum entanglement. It is argued that the enzyme catalyzed chemical reaction which breaks a pyrophosphate ion into two phosphate ions can quantum entangle pairs of qubits. Posner molecules, formed by binding such phosphate pairs with extracellular calcium ions, will inherit the nuclear spin entanglement. A mechanism for transporting Posner molecules into presynaptic neurons during vesicle endocytosis is proposed. Quantum measurements can occur when a pair of Posner molecules chemically bind and subsequently melt, releasing a shower of intra-cellular calcium ions that can trigger further neurotransmitter release and enhance the probability of post-synaptic neuron firing. Multiple entangled Posner molecules, triggering non-local quantum correlations of neuron firing rates, would provide the key mechanism for neural quantum processing. Implications, both in vitro and in vivo, are briefly mentioned.

  2. Euclidean Complex Relativistic Mechanics: A New Special Relativity Theory

    NASA Astrophysics Data System (ADS)

    Vossos, Spyridon; Vossos, Elias

    2015-09-01

    Relativity Theory (RT) was fundamental for the development of Quantum Mechanics (QMs). Special Relativity (SR), as is applied until now, cancels the transitive attribute in parallelism, when three observers are related, because Lorentz Boost (LB) is not closed transformation. In this presentation, considering Linear Spacetime Transformation (LSTT), we demand the maintenance of Minkowski Spacetime Interval (S2). In addition, we demand this LSTT to be closed, so there is no need for axes rotation. The solution is the Vossos Matrix (ΛB) containing real and imaginary numbers. As a result, space becomes complex, but time remains real. Thus, the transitive attribute in parallelism, which is equivalent to the Euclidean Request (ER), is also valid for moving observers. Choosing real spacetime for the unmoved observer (O), all the natural sizes are real, too. Using Vossos Transformation (VT) for moving observers, the four-vectors’ zeroth component (such as energy) is real, in contrast with spatial components that are complex, but their norm is real. It is proved that moving (relative to O) human O' meter length, according to Lorentz Boost (LB). In addition, we find Rotation Matrix Vossos-Lorentz (RBL) that turns natural sizes’ complex components to real. We also prove that Speed of Light in Vacuum (c) is invariant, when complex components are used and VT is closed for three sequential observers. After, we find out the connection between two moving (relative to O) observers: X"= ΛLO"(o) ΛLO(O') X', using Lorentz Matrix (ΛL). We applied this theory, finding relations between natural sizes, that are the same as these extracted by Classic Relativity (CR), when two observers are related (i.e. relativistic Doppler shift is the same). But, the results are different, when more than two observers are related. VT of Electromagnetic Tensor (Fμv), leads to Complex Electromagnetic Fields (CEMFs) for a moving observer. When the unmoved observer O and a moving observer O' are

  3. Fractal and Euclidean descriptors of platelet shape.

    PubMed

    Kraus, Max-Joseph; Neeb, Heiko; Strasser, Erwin F

    2014-01-01

    Platelet shape change is a dynamic membrane surface process that exhibits remarkable morphological heterogeneity. Once the outline of an irregular shape is identified and segmented from a digital image, several mathematical descriptors can be applied to numerical characterize the irregularity of the shapes surface. 13072 platelet outlines (PLO) were segmented automatically from 1928 microscopic images using a newly developed algorithm for the software product Matlab R2012b. The fractal dimension (FD), circularity, eccentricity, area and perimeter of each PLO were determined. 972 PLO were randomly assigned for computer-assisted manual measurement of platelet diameter as well as number, width and length of filopodia per platelet. FD can be used as a surrogate parameter for determining the roughness of the PLO and circularity can be used as a surrogate to estimate the number and length of filopodia. The relationship between FD and perimeter of the PLO reveals the existence of distinct groups of platelets with significant structural differences which may be caused by platelet activation. This new method allows for the standardized continuous numerical classification of platelet shape and its dynamic change, which is useful for the analysis of altered platelet activity (e.g. inflammatory diseases, contact activation, drug testing). PMID:24224894

  4. [Effects of quantum nonlocality in the water activation process].

    PubMed

    Zatsepina, O V; Stekhin, A A; Yakovleva, G V

    2014-01-01

    The dynamic alterations of the magnetic flux density of the water volume, activated with structurally stressed calcium carbonate in micellar form have been investigated. The phase of the associated water was established to exhibit electrical and magnetic properties, recorded by in B&E meter in the frequency range of 5Hz - 2kHz. Alterations in water Eh (redox) potential and the magnetic flux density B testify to synchronous auto-oscillatory changes. This gives evidence of non-linearity of the relationship between auto-oscillatory processes excited in the water; and reflects the nonlocal in time the relationship between the states of water, manifesting in a change of water activity on the 1st and 2nd day in negative time. The mechanism of action of associated water phase is shown to be described by de Broglie concept of matter waves with taking into account delocalized in time states of phase of electron wave packet in accordance with the transactional interpretation of quantum physics. PMID:24749297

  5. Energy transfer processes in semiconductor quantum dots: bacteriorhodopsin hybrid system

    NASA Astrophysics Data System (ADS)

    Rakovich, Aliaksandra; Sukhanova, Alyona; Bouchonville, Nicolas; Molinari, Michael; Troyon, Michel; Cohen, Jacques H. M.; Rakovich, Yury; Donegan, John F.; Nabiev, Igor

    2009-05-01

    The potential impact of nanoscience on energy transfer processes in biomolecules was investigated on the example of a complex between fluorescent semiconductor nanocrystals and photochromic membrane protein. The interactions between colloidal CdTe quantum dots (QDs) and bacteriorhodopsin (bR) protein were studied by a variety of spectroscopic techniques, including integrated and time-resolved fluorescence spectroscopies, zeta potential and size measurement, and fluorescence correlation spectroscopy. QDs' luminescence was found to be strongly modulated by bacteriorhodopsin, but in a controllable way. Decreasing emission lifetimes and blue shifts in QDs' emission at increasing protein concentrations suggest that quenching occurs via Förster resonance energy transfer. On the other hand, concave Stern-Volmer plots and sigmoidal photoluminescence quenching curves imply that the self-assembling of NCs and bR exists, and the number of nanocrystals (NCs) per bacteriorhodopsin contributing to energy transfer can be determined from the inflection points of sigmoidal curves. This number was found to be highly dependent not only on the spectral overlap between NC emission and bR absorption bands, but also on nanocrystal surface charge. These results demonstrate the potential of how inorganic nanoscale materials can be employed to improve the generic molecular functions of biomolecules. The observed interactions between CdTe nanocrystals and bacteriorhodopsin can provide the basis for the development of novel functional materials with unique photonic properties and applications in areas such as all-optical switching, photovoltaics and data storage.

  6. (e,3e) process on a quantum dot

    SciTech Connect

    Srivastava, M.K.

    2004-12-01

    The exact initial state wave function of an interacting electron pair in a quantum dot under parabolic confinement and neutralization of the dot by the substrate after ejection of electrons is exploited to obtain the fivefold differential cross section (X) of the (e,3e) process on the dot. The reflections of the center-of-mass (c.m.) motion and relative motion on X are decoupled if the incident and scattered electrons are energetic and the ejected electrons are slow. The results are studied in fixed mutual angle (with zero c.m. momentum K) and Bethe ridge modes which allow the 'cleanest' analysis of the contribution of the relative motion. The Coulomb interaction between the emitted electrons is found to qualitatively change the angular distribution of X. In the mode in which the magnitude of K is equal to the momentum transfer q, the angular distribution of X with respect to {theta}{sub Kq}=cos{sup -1}(K{center_dot}q) leads to a mapping of the initial c.m. wave function of the ejected pair. However, the c.m. motion is found to be best studied in the kinematics where the relative momentum k-vector of the ejected pair is equal to q-vector.

  7. Physical Meaning of the Optimum Measurement Process in Quantum Detection Theory

    NASA Technical Reports Server (NTRS)

    Osaki, Masao; Kozuka, Haruhisa; Hirota, Osamu

    1996-01-01

    The optimum measurement processes are represented as the optimum detection operators in the quantum detection theory. The error probability by the optimum detection operators goes beyond the standard quantum limit automatically. However the optimum detection operators are given by pure mathematical descriptions. In order to realize a communication system overcoming the standard quantum limit, we try to give the physical meaning of the optimum detection operators.

  8. Quantum Simulation of Dissipative Processes without Reservoir Engineering

    PubMed Central

    Di Candia, R.; Pedernales, J. S.; del Campo, A.; Solano, E.; Casanova, J.

    2015-01-01

    We present a quantum algorithm to simulate general finite dimensional Lindblad master equations without the requirement of engineering the system-environment interactions. The proposed method is able to simulate both Markovian and non-Markovian quantum dynamics. It consists in the quantum computation of the dissipative corrections to the unitary evolution of the system of interest, via the reconstruction of the response functions associated with the Lindblad operators. Our approach is equally applicable to dynamics generated by effectively non-Hermitian Hamiltonians. We confirm the quality of our method providing specific error bounds that quantify its accuracy. PMID:26024437

  9. Quantum simulation of dissipative processes without reservoir engineering

    SciTech Connect

    Di Candia, R.; Pedernales, J. S.; del Campo, A.; Solano, E.; Casanova, J.

    2015-05-29

    We present a quantum algorithm to simulate general finite dimensional Lindblad master equations without the requirement of engineering the system-environment interactions. The proposed method is able to simulate both Markovian and non-Markovian quantum dynamics. It consists in the quantum computation of the dissipative corrections to the unitary evolution of the system of interest, via the reconstruction of the response functions associated with the Lindblad operators. Our approach is equally applicable to dynamics generated by effectively non-Hermitian Hamiltonians. We confirm the quality of our method providing specific error bounds that quantify its accuracy.

  10. Path integration and perturbation theory with complex Euclidean actions

    NASA Astrophysics Data System (ADS)

    Alexanian, Garnik; MacKenzie, R.; Paranjape, M. B.; Ruel, Jonathan

    2008-05-01

    The Euclidean path integral quite often involves an action that is not completely real, i.e. a complex action. This occurs when the Minkowski action contains t-odd CP-violating terms. This usually consists of topological terms, such as the Chern-Simons term in odd dimensions, the Wess-Zumino term, the θ term or Chern character in 4-dimensional gauge theories, or other topological densities. Analytic continuation to Euclidean time yields an imaginary term in the Euclidean action. It also occurs when the action contains fermions, the fermion path integral being in general a sum over positive and negative real numbers. Negative numbers correspond to the exponential of iπ and hence indicate the presence of an imaginary term in the action. In the presence of imaginary terms in the Euclidean action, the usual method of perturbative quantization can fail. Here the action is expanded about its critical points, the quadratic part serving to define the Gaussian free theory and the higher order terms defining the perturbative interactions. For a complex action, the critical points are generically obtained at complex field configurations. Hence the contour of path integration does not pass through the critical points and the perturbative paradigm cannot be directly implemented. The contour of path integration has to be deformed to pass through the complex critical point using a generalized method of steepest descent, in order to do so. Typically, this procedure is not followed. Rather, only the real part of the Euclidean action is considered, and its critical points are used to define the perturbation theory, a procedure that can lead to incorrect results. In this article we present a simple example to illustrate this point. The example consists of N scalar fields in 0+1 dimensions interacting with a U(1) gauge field in the presence of a Chern-Simons term. In this example the path integral can be done exactly, the procedure of deformation of the contour of path integration

  11. Macroscopic non-classical states and terahertz quantum processing in room-temperature diamond

    NASA Astrophysics Data System (ADS)

    Lee, K. C.; Sussman, B. J.; Sprague, M. R.; Michelberger, P.; Reim, K. F.; Nunn, J.; Langford, N. K.; Bustard, P. J.; Jaksch, D.; Walmsley, I. A.

    2012-01-01

    The nature of the transition between the familiar classical, macroscopic world and the quantum, microscopic one continues to be poorly understood. Expanding the regime of observable quantum behaviour to large-scale objects is therefore an exciting open problem. In macroscopic systems of interacting particles, rapid thermalization usually destroys any quantum coherence before it can be measured or used at room temperature. Here, we demonstrate quantum processing in the vibrational modes of a macroscopic diamond sample under ambient conditions. Using ultrafast Raman scattering, we create an extended, highly non-classical state in the optical phonon modes of bulk diamond. Direct measurement of phonon coherence and correlations establishes the non-classical nature of the crystal dynamics. These results show that optical phonons in diamond provide a unique opportunity for the study of large-scale quantum behaviour, and highlight the potential for diamond as a micro-photonic quantum processor capable of operating at terahertz rates.

  12. Quantum information processing with long-wavelength radiation

    NASA Astrophysics Data System (ADS)

    Murgia, David; Weidt, Sebastian; Randall, Joseph; Lekitsch, Bjoern; Webster, Simon; Navickas, Tomas; Grounds, Anton; Rodriguez, Andrea; Webb, Anna; Standing, Eamon; Pearce, Stuart; Sari, Ibrahim; Kiang, Kian; Rattanasonti, Hwanjit; Kraft, Michael; Hensinger, Winfried

    To this point, the entanglement of ions has predominantly been performed using lasers. Using long wavelength radiation with static magnetic field gradients provides an architecture to simplify construction of a large scale quantum computer. The use of microwave-dressed states protects against decoherence from fluctuating magnetic fields, with radio-frequency fields used for qubit manipulation. I will report the realisation of spin-motion entanglement using long-wavelength radiation, and a new method to efficiently prepare dressed-state qubits and qutrits, reducing experimental complexity of gate operations. I will also report demonstration of ground state cooling using long wavelength radiation, which may increase two-qubit entanglement fidelity. I will then report demonstration of a high-fidelity long-wavelength two-ion quantum gate using dressed states. Combining these results with microfabricated ion traps allows for scaling towards a large scale ion trap quantum computer, and provides a platform for quantum simulations of fundamental physics. I will report progress towards the operation of microchip ion traps with extremely high magnetic field gradients for multi-ion quantum gates.

  13. Pose Estimation using 1D Fourier Transform and Euclidean Distance Matching of CAD Model and Inspected Model Part

    NASA Astrophysics Data System (ADS)

    Zulkoffli, Zuliani; Abu Bakar, Elmi

    2016-02-01

    This paper present pose estimation relation of CAD model object and Projection Real Object (PRI). Image sequence of PRI and CAD model rotate on z axis at 10 degree interval in simulation and real scene used in this experiment. All this image is go through preprocessing stage to rescale object size and image size and transform all the image into silhouette. Correlation of CAD and PRI image is going through in this stage. Magnitude spectrum shows a reliable value in range 0.99 to 1.00 and Phase spectrum correlation shows a fluctuate graph in range 0.56 - 0.97. Euclidean distance correlation graph for CAD and PRI shows 2 zone of similar value due to almost symmetrical object shape. Processing stage of retrieval inspected PRI image in CAD database was carried out using range phase spectrum and maximum magnitude spectrum value within ±10% tolerance. Additional processing stage of retrieval inspected PRI image using Euclidean distance within ±5% tolerance also carried out. Euclidean matching shows a reliable result compared to range phase spectrum and maximum magnitude spectrum value by sacrificing more than 5 times processing time.

  14. Stable hypersurfaces with zero scalar curvature in Euclidean space

    NASA Astrophysics Data System (ADS)

    Alencar, Hilário; do Carmo, Manfredo; Neto, Gregório Silva

    2016-04-01

    In this paper we prove some results concerning stability of hypersurfaces in the four dimensional Euclidean space with zero scalar curvature. First we prove there is no complete stable hypersurface with zero scalar curvature, polynomial growth of integral of the mean curvature, and with the Gauss-Kronecker curvature bounded away from zero. We conclude this paper giving a sufficient condition for a regular domain to be stable in terms of the mean and the Gauss-Kronecker curvatures of the hypersurface and the radius of the smallest extrinsic ball which contains the domain.

  15. Multi-stability in folded shells: non-Euclidean origami

    NASA Astrophysics Data System (ADS)

    Evans, Arthur

    2015-03-01

    Both natural and man-made structures benefit from having multiple mechanically stable states, from the quick snapping motion of hummingbird beaks to micro-textured surfaces with tunable roughness. Rather than discuss special fabrication techniques for creating bi-stability through material anisotropy, in this talk I will present several examples of how folding a structure can modify the energy landscape and thus lead to multiple stable states. Using ideas from origami and differential geometry, I will discuss how deforming a non-Euclidean surface can be done either continuously or discontinuously, and explore the effects that global constraints have on the ultimate stability of the surface.

  16. On cohomogeneity one biharmonic hypersurfaces into the Euclidean space

    NASA Astrophysics Data System (ADS)

    Montaldo, S.; Oniciuc, C.; Ratto, A.

    2016-08-01

    The aim of this paper is to prove that there exists no cohomogeneity one G-invariant proper biharmonic hypersurface into the Euclidean space Rn, where G denotes a transformation group which acts on Rn by isometries, with codimension two principal orbits. This result may be considered in the context of the Chen conjecture, since this family of hypersurfaces includes examples with up to seven distinct principal curvatures. The paper uses the methods of equivariant differential geometry. In particular, the technique of proof provides a unified treatment for all these G-actions.

  17. Reply to ``Comment on `Why quantum mechanics cannot be formulated as a Markov process' ''

    NASA Astrophysics Data System (ADS)

    Gillespie, Daniel T.

    1997-10-01

    It is argued that the stochastic model of a quantum-mechanical two-state oscillator discussed in the preceding Comment by Hardy et al. [Phys. Rev. A 56, 3301 (1997)] does not constitute a valid classical stochastic process.

  18. Multipartite entanglement arising from dense Euclidean lattices in dimensions 4-24

    NASA Astrophysics Data System (ADS)

    Planat, Michel

    2012-02-01

    The group of automorphisms of Euclidean (embedded in {R}^n ) dense lattices such as the root lattices D4 and E8, the Barnes-Wall lattice BW16, the unimodular lattice D12+ and the Leech lattice Λ24 may be generated by entangled quantum gates of the corresponding dimension. These (real) gates/lattices are useful for quantum error correction: for instance, the two- and four-qubit real Clifford groups are the automorphism groups of the lattices D4 and BW16, respectively, and the three-qubit real Clifford group is maximal in the Weyl group W(E8). Technically, the automorphism group Aut(Λ) of the lattice Λ is the set of orthogonal matrices B such that, following the conjugation action by the generating matrix of the lattice, the output matrix is unimodular (of determinant ±1, with integer entries). When the degree n is equal to the number of basis elements of Λ, Aut(Λ) also acts on basis vectors and is generated with matrices B such that the sum of squared entries in a row is 1, i.e. B may be seen as a quantum gate. For the dense lattices listed above, maximal multipartite entanglement arises. In particular, one finds a balanced tripartite entanglement in E8 (the two- and three-tangles have the same magnitude 1/4) and a Greenberger-Horne-Zeilinger-type entanglement in BW16. In this paper, we also investigate the entangled gates from D12+ and Λ24, by seeing them as systems coupling a qutrit to two- and three-qubits, respectively. In addition to quantum computing, the work may be related to particle physics in the spirit of Planat et al (2011 Rep. Math. Phys. 66 39-51).

  19. Pattern-recalling processes in quantum Hopfield networks far from saturation

    NASA Astrophysics Data System (ADS)

    Inoue, Jun-ichi

    2011-05-01

    As a mathematical model of associative memories, the Hopfield model was now well-established and a lot of studies to reveal the pattern-recalling process have been done from various different approaches. As well-known, a single neuron is itself an uncertain, noisy unit with a finite unnegligible error in the input-output relation. To model the situation artificially, a kind of 'heat bath' that surrounds neurons is introduced. The heat bath, which is a source of noise, is specified by the 'temperature'. Several studies concerning the pattern-recalling processes of the Hopfield model governed by the Glauber-dynamics at finite temperature were already reported. However, we might extend the 'thermal noise' to the quantum-mechanical variant. In this paper, in terms of the stochastic process of quantum-mechanical Markov chain Monte Carlo method (the quantum MCMC), we analytically derive macroscopically deterministic equations of order parameters such as 'overlap' in a quantum-mechanical variant of the Hopfield neural networks (let us call quantum Hopfield model or quantum Hopfield networks). For the case in which non-extensive number p of patterns are embedded via asymmetric Hebbian connections, namely, p/N → 0 for the number of neuron N → ∞ ('far from saturation'), we evaluate the recalling processes for one of the built-in patterns under the influence of quantum-mechanical noise.

  20. Scheme for Quantum Cloning and Quantum Information Processing with Trapped Ions

    NASA Astrophysics Data System (ADS)

    Zhan, Zhi-Ming

    In this paper, a scheme is presented to implement the 1→2 universal quantum cloning machine (UQCM) with trapped ions. In this way, we also show that quantum information can be directly transferred from one ion to another. The distinct advantage of the scheme lies in the fact that it does not use the vibrational mode as the data bus. The vibrational mode is only virtually excited, which makes our scheme insensitive to heating, provided the system remains in the Lamb-Dicke regime.

  1. A High-Speed Pipelined Degree-Computationless Modified Euclidean Algorithm Architecture for Reed-Solomon Decoders

    NASA Astrophysics Data System (ADS)

    Lee, Seungbeom; Lee, Hanho

    This paper presents a novel high-speed low-complexity pipelined degree-computationless modified Euclidean (pDCME) algorithm architecture for high-speed RS decoders. The pDCME algorithm allows elimination of the degree-computation so as to reduce hardware complexity and obtain high-speed processing. A high-speed RS decoder based on the pDCME algorithm has been designed and implemented with 0.13-μm CMOS standard cell technology in a supply voltage of 1.1V. The proposed RS decoder operates at a clock frequency of 660MHz and has a throughput of 5.3Gb/s. The proposed architecture requires approximately 15% fewer gate counts and a simpler control logic than architectures based on the popular modified Euclidean algorithm.

  2. Energy transfer processes in ZnSe/(Zn,Mn)Se double quantum wells

    NASA Astrophysics Data System (ADS)

    Jankowski, Stephanie; Horst, Swantje; Chernikov, Alexej; Chatterjee, Sangam; Heimbrodt, Wolfram

    2009-10-01

    The complex interplay of energy transfer and tunneling processes in a series of asymmetric ZnSe/(Zn,Mn)Se double quantum-well (DQW) structures is investigated. Steady-state and time-resolved photoluminescence at low temperatures and external magnetic fields up to 7 T in this system show remarkable differences to earlier studies on CdTe/(Cd,Mn)Te DQWs. The pure quantum-mechanical tunneling process is only a minor contribution to the magnetic field dependence of the emission even in case of small barriers and strong QW coupling. The experimental results are supported by quantum-well calculations.

  3. Toward quantum-like modeling of financial processes

    NASA Astrophysics Data System (ADS)

    Choustova, Olga

    2007-05-01

    We apply methods of quantum mechanics for mathematical modeling of price dynamics at the financial market. We propose to describe behavioral financial factors (e.g., expectations of traders) by using the pilot wave (Bohmian) model of quantum mechanics. Trajectories of prices are determined by two financial potentials: classical-like V(q) ("hard" market conditions, e.g., natural resources) and quantum-like U(q) (behavioral market conditions). On the one hand, our Bohmian model is a quantum-like model for the financial market, cf. with works of W. Segal, I. E. Segal, E. Haven, E. W. Piotrowski, J. Sladkowski. On the other hand, (since Bohmian mechanics provides the possibility to describe individual price trajectories) it belongs to the domain of extended research on deterministic dynamics for financial assets (C.W.J. Granger, W.A. Barnett, A. J. Benhabib, W.A. Brock, C. Sayers, J. Y. Campbell, A. W. Lo, A. C. MacKinlay, A. Serletis, S. Kuchta, M. Frank, R. Gencay, T. Stengos, M. J. Hinich, D. Patterson, D. A. Hsieh, D. T. Caplan, J.A. Scheinkman, B. LeBaron and many others).

  4. Elementary Quantum Mechanics in a High-Energy Process

    ERIC Educational Resources Information Center

    Denville, A.; And Others

    1978-01-01

    Compares two approaches to strong absorption in elementary quantum mechanics; the black sphere and a model based on the continuum theory of nuclear reactions. Examines the application to proton-antiproton interactions at low momenta and concludes that the second model is the appropriate and simplest to use. (Author/GA)

  5. Non-Euclidean classification of medically imaged objects via s-reps.

    PubMed

    Hong, Junpyo; Vicory, Jared; Schulz, Jörn; Styner, Martin; Marron, J S; Pizer, Stephen M

    2016-07-01

    Classifying medically imaged objects, e.g., into diseased and normal classes, has been one of the important goals in medical imaging. We propose a novel classification scheme that uses a skeletal representation to provide rich non-Euclidean geometric object properties. Our statistical method combines distance weighted discrimination (DWD) with a carefully chosen Euclideanization which takes full advantage of the geometry of the manifold on which these non-Euclidean geometric object properties (GOPs) live. Our method is evaluated via the task of classifying 3D hippocampi between schizophrenics and healthy controls. We address three central questions. 1) Does adding shape features increase discriminative power over the more standard classification based only on global volume? 2) If so, does our skeletal representation provide greater discriminative power than a conventional boundary point distribution model (PDM)? 3) Especially, is Euclideanization of non-Euclidean shape properties important in achieving high discriminative power? Measuring the capability of a method in terms of area under the receiver operator characteristic (ROC) curve, we show that our proposed method achieves strongly better classification than both the classification method based on global volume alone and the s-rep-based classification method without proper Euclideanization of non-Euclidean GOPs. We show classification using Euclideanized s-reps is also superior to classification using PDMs, whether the PDMs are first Euclideanized or not. We also show improved performance with Euclideanized boundary PDMs over non-linear boundary PDMs. This demonstrates the benefit that proper Euclideanization of non-Euclidean GOPs brings not only to s-rep-based classification but also to PDM-based classification. PMID:26963609

  6. Optimizing the choice of spin-squeezed states for detecting and characterizing quantum processes

    DOE PAGESBeta

    Rozema, Lee A.; Mahler, Dylan H.; Blume-Kohout, Robin; Steinberg, Aephraim M.

    2014-11-07

    Quantum metrology uses quantum states with no classical counterpart to measure a physical quantity with extraordinary sensitivity or precision. Most such schemes characterize a dynamical process by probing it with a specially designed quantum state. The success of such a scheme usually relies on the process belonging to a particular one-parameter family. If this assumption is violated, or if the goal is to measure more than one parameter, a different quantum state may perform better. In the most extreme case, we know nothing about the process and wish to learn everything. This requires quantum process tomography, which demands an informationallymore » complete set of probe states. It is very convenient if this set is group covariant—i.e., each element is generated by applying an element of the quantum system’s natural symmetry group to a single fixed fiducial state. In this paper, we consider metrology with 2-photon (“biphoton”) states and report experimental studies of different states’ sensitivity to small, unknown collective SU(2) rotations [“SU(2) jitter”]. Maximally entangled N00N states are the most sensitive detectors of such a rotation, yet they are also among the worst at fully characterizing an a priori unknown process. We identify (and confirm experimentally) the best SU(2)-covariant set for process tomography; these states are all less entangled than the N00N state, and are characterized by the fact that they form a 2-design.« less

  7. Non-Euclidean geometry of twisted filament bundle packing

    PubMed Central

    Bruss, Isaac R.; Grason, Gregory M.

    2012-01-01

    Densely packed and twisted assemblies of filaments are crucial structural motifs in macroscopic materials (cables, ropes, and textiles) as well as synthetic and biological nanomaterials (fibrous proteins). We study the unique and nontrivial packing geometry of this universal material design from two perspectives. First, we show that the problem of twisted bundle packing can be mapped exactly onto the problem of disc packing on a curved surface, the geometry of which has a positive, spherical curvature close to the center of rotation and approaches the intrinsically flat geometry of a cylinder far from the bundle center. From this mapping, we find the packing of any twisted bundle is geometrically frustrated, as it makes the sixfold geometry of filament close packing impossible at the core of the fiber. This geometrical equivalence leads to a spectrum of close-packed fiber geometries, whose low symmetry (five-, four-, three-, and twofold) reflect non-Euclidean packing constraints at the bundle core. Second, we explore the ground-state structure of twisted filament assemblies formed under the influence of adhesive interactions by a computational model. Here, we find that the underlying non-Euclidean geometry of twisted fiber packing disrupts the regular lattice packing of filaments above a critical radius, proportional to the helical pitch. Above this critical radius, the ground-state packing includes the presence of between one and six excess fivefold disclinations in the cross-sectional order. PMID:22711799

  8. Subvoxel accurate graph search using non-Euclidean graph space.

    PubMed

    Abràmoff, Michael D; Wu, Xiaodong; Lee, Kyungmoo; Tang, Li

    2014-01-01

    Graph search is attractive for the quantitative analysis of volumetric medical images, and especially for layered tissues, because it allows globally optimal solutions in low-order polynomial time. However, because nodes of graphs typically encode evenly distributed voxels of the volume with arcs connecting orthogonally sampled voxels in Euclidean space, segmentation cannot achieve greater precision than a single unit, i.e. the distance between two adjoining nodes, and partial volume effects are ignored. We generalize the graph to non-Euclidean space by allowing non-equidistant spacing between nodes, so that subvoxel accurate segmentation is achievable. Because the number of nodes and edges in the graph remains the same, running time and memory use are similar, while all the advantages of graph search, including global optimality and computational efficiency, are retained. A deformation field calculated from the volume data adaptively changes regional node density so that node density varies with the inverse of the expected cost. We validated our approach using optical coherence tomography (OCT) images of the retina and 3-D MR of the arterial wall, and achieved statistically significant increased accuracy. Our approach allows improved accuracy in volume data acquired with the same hardware, and also, preserved accuracy with lower resolution, more cost-effective, image acquisition equipment. The method is not limited to any specific imaging modality and readily extensible to higher dimensions. PMID:25314272

  9. Scaled norm-based Euclidean projection for sparse speaker adaptation

    NASA Astrophysics Data System (ADS)

    Kim, Younggwan; Kim, Myung Jong; Kim, Hoirin

    2015-12-01

    To reduce data storage for speaker adaptive (SA) models, in our previous work, we proposed a sparse speaker adaptation method which can efficiently reduce the number of adapted parameters by using Euclidean projection onto the L 1-ball (EPL1) while maintaining recognition performance comparable to maximum a posteriori (MAP) adaptation. In the EPL1-based sparse speaker adaptation framework, however, the adapted Gaussian mean vectors are mostly concentrated on dimensions having large variances because of assuming unit variance for all dimensions. To make EPL1 more flexible, in this paper, we propose scaled norm-based Euclidean projection (SNEP) which can consider dimension-specific variances. By using SNEP, we also propose a new sparse speaker adaptation method which can consider the variances of a speaker-independent model. Our experiments show that the adapted components of mean vectors are evenly distributed in all dimensions, and we can obtain sparsely adapted models with no loss of phone recognition performance from the proposed method compared with MAP adaptation.

  10. Integrated System Technologies for Modular Trapped Ion Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Crain, Stephen G.

    Although trapped ion technology is well-suited for quantum information science, scalability of the system remains one of the main challenges. One of the challenges associated with scaling the ion trap quantum computer is the ability to individually manipulate the increasing number of qubits. Using micro-mirrors fabricated with micro-electromechanical systems (MEMS) technology, laser beams are focused on individual ions in a linear chain and steer the focal point in two dimensions. Multiple single qubit gates are demonstrated on trapped 171Yb+ qubits and the gate performance is characterized using quantum state tomography. The system features negligible crosstalk to neighboring ions (< 3e-4), and switching speeds comparable to typical single qubit gate times (< 2 mus). In a separate experiment, photons scattered from the 171Yb+ ion are coupled into an optical fiber with 63% efficiency using a high numerical aperture lens (0.6 NA). The coupled photons are directed to superconducting nanowire single photon detectors (SNSPD), which provide a higher detector efficiency (69%) compared to traditional photomultiplier tubes (35%). The total system photon collection efficiency is increased from 2.2% to 3.4%, which allows for fast state detection of the qubit. For a detection beam intensity of 11 mW/cm 2, the average detection time is 23.7 mus with 99.885(7)% detection fidelity. The technologies demonstrated in this thesis can be integrated to form a single quantum register with all of the necessary resources to perform local gates as well as high fidelity readout and provide a photon link to other systems.

  11. A Model of the Creative Process Based on Quantum Physics and Vedic Science.

    ERIC Educational Resources Information Center

    Rose, Laura Hall

    1988-01-01

    Using tenets from Vedic science and quantum physics, this model of the creative process suggests that the unified field of creation is pure consciousness, and that the development of the creative process within individuals mirrors the creative process within the universe. Rational and supra-rational creative thinking techniques are also described.…

  12. All-optical measurement-based quantum-information processing in quantum dots.

    PubMed

    Kolli, Avinash; Lovett, Brendon W; Benjamin, Simon C; Stace, Thomas M

    2006-12-22

    Parity measurements on qubits can generate the entanglement resource necessary for scalable quantum computation. Here we describe a method for fast optical parity measurements on electron spin qubits within coupled quantum dots. The measurement scheme, which can be realized with existing technology, consists of the optical excitation of excitonic states followed by monitored relaxation. Conditional on the observation of a photon, the system is projected into the odd/even-parity subspaces. Our model incorporates all the primary sources of error, including detector inefficiency, effects of spatial separation and nonresonance of the dots, and also unwanted excitations. Through an analytical treatment we establish that the scheme is robust to such effects. Two applications are presented: a realization of a controlled-NOT gate, and a technique for growing large scale graph states. PMID:17280337

  13. Towards quantum information processing with impurity spins insilicon

    SciTech Connect

    Schenkel, T.; Liddle, J.A.; Bokor, J.; Rangelow, I.W.; Park,S.J.; Persaud, A.

    2004-03-01

    The finding of algorithms for factoring and data base search that promise substantially increased computational power, as well as the expectation for efficient simulation of quantum systems have spawned an intense interest in the realization of quantum information processors [1]. Solid state implementations of quantum computers scaled to >1000 quantum bits ('qubits') promise to revolutionize information technology, but requirements with regard to sources of decoherence in solid state environments are sobering. Here, we briefly review basic approaches to impurity spin based qubits and present progress in our effort to form prototype qubit test structures. Since Kane's bold silicon based spin qubit proposal was first published in 1998 [2], several groups have taken up the challenge of fabricating elementary building blocks [3-5], and several exciting variations of single donor qubit schemes have emerged [6]. Single donor atoms, e. g. {sup 31}P, are 'natural quantum dots' in a silicon matrix, and the spins of electrons and nuclei of individual donor atoms are attractive two level systems for encoding of quantum information. The coupling to the solid state environment is weak, so that decoherence times are long (hours for nuclear spins, and {approx}60 ms for electron spins of isolated P atoms in silicon [7]), while control over individual spins for one qubit operations becomes possible when individual qubits are aligned to electrodes that allow shifting of electron spin resonances in global magnetic fields by application of control voltages. Two qubit operations require an interaction that couples, and entangles qubits. The exchange interaction, J, is a prime candidate for mediation of two qubit operations, since it can be turned on and off by variation of the wave function overlap between neighboring qubits, and coherent manipulation of quantum information with the exchange interaction alone has been shown to be universal [8]. However, detailed band structure

  14. Interacting Photons in Waveguide-QED and Applications in Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Zheng, Huaixiu

    Strong coupling between light and matter has been demonstrated both in classical cavity quantum electrodynamics (QED) systems and in more recent circuit-QED experiments. This enables the generation of strong nonlinear photon-photon interactions at the single-photon level, which is of great interest for the observation of quantum nonlinear optical phenomena, the control of light quanta in quantum information protocols such as quantum networking, as well as the study of strongly correlated quantum many-body systems using light. Recently, strong coupling has also been realized in a variety of one-dimensional (1D) waveguide- QED experimental systems, which in turn makes them promising candidates for quantum information processing. Compared to cavity-QED systems, there are two new features in waveguide-QED: the existence of a continuum of states and the restricted 1D phase space, which together bring in new physical effects, such as the bound-state effects. This thesis consists of two parts: 1) understanding the fundamental interaction between local quantum objects, such as two-level systems and four-level systems, and photons confined in the waveguide; 2) exploring its implications in quantum information processing, in particular photonic quantum computation and quantum key distribution. First, we demonstrate that by coupling a two-level system (TLS) or three/four-level system to a 1D continuum, strongly-correlated photons can be generated inside the waveguide. Photon-photon bound states, which decay exponentially as a function of the relative coordinates of photons, appear in multiphoton scattering processes. As a result, photon bunching and antibunching can be observed in the photon-photon correlation function, and nonclassical light source can be generated on demand. In the case of an N-type four-level system, we show that the effective photon-photon interaction mediated by the four-level system, gives rise to a variety of nonlinear optical phenomena, including

  15. A three-process quantum engine cycle consisting of a two-level system

    NASA Astrophysics Data System (ADS)

    Ou, CongJie; Huang, ZhiFu; Lin, BiHong; Chen, JinCan

    2014-07-01

    Based on the thermodynamic properties of isoenergetic, adiabatic and isothermal quantum processes, it is shown that it is possible to combine the three processes into a quantum engine cycle. The efficiency of the three-process cycle can be derived and is dependent on the highest and lowest temperatures. The efficiency in some operation regions does not demonstrate a monotonically increasing function of the temperature difference. When the highest temperature of the cycle is larger than the critical temperature, which can be determined by the characteristics of the three-process cycle, a unique region where the efficiency decreased with the increase of the temperature difference exists.

  16. Theoretical analysis of on-chip linear quantum optical information processing networks

    NASA Astrophysics Data System (ADS)

    Hach, Edwin E.; Preble, Stefan F.; Steidle, Jeffrey A.

    2015-05-01

    We present a quantum optical analysis of waveguides directionally coupled to ring resonators, an architecture realizable using silicon nanophotonics. The innate scalability of the silicon platform allows for the possibility of "on-chip" quantum computation and information processing. In this paper, we briefly review a comprehensive method for analyzing the quantum mechanical output of such a network for an arbitrary input state of the quantized, traveling electromagnetic field in the continuous wave (cw) limit. Specifically, we briefly review a recent theoretical result identifying a particular device topology that yields, via Passive Quantum Optical Feedback (PQOF), dramatic and unexpected enhancements of the Hong-Ou-Mandel Effect, an effect central to the operation of many quantum information processing systems. Next, we extend the analysis to our proposal for a scalable, on-chip realization of the Nonlinear Sign (NS) shifter essential for implementation of the Knill-Laflamme-Milburn (KLM) protocol for Linear Optical Quantum Computing (LOQC). Finally, we discuss generalizations to arbitrary networks of directionally coupled ring resonators along with possible applications is the areas of quantum metrology and sensitive photon detection.

  17. Quantum learning of classical stochastic processes: The completely positive realization problem

    NASA Astrophysics Data System (ADS)

    Monràs, Alex; Winter, Andreas

    2016-01-01

    Among several tasks in Machine Learning, a specially important one is the problem of inferring the latent variables of a system and their causal relations with the observed behavior. A paradigmatic instance of this is the task of inferring the hidden Markov model underlying a given stochastic process. This is known as the positive realization problem (PRP), [L. Benvenuti and L. Farina, IEEE Trans. Autom. Control 49(5), 651-664 (2004)] and constitutes a central problem in machine learning. The PRP and its solutions have far-reaching consequences in many areas of systems and control theory, and is nowadays an important piece in the broad field of positive systems theory. We consider the scenario where the latent variables are quantum (i.e., quantum states of a finite-dimensional system) and the system dynamics is constrained only by physical transformations on the quantum system. The observable dynamics is then described by a quantum instrument, and the task is to determine which quantum instrument — if any — yields the process at hand by iterative application. We take as a starting point the theory of quasi-realizations, whence a description of the dynamics of the process is given in terms of linear maps on state vectors and probabilities are given by linear functionals on the state vectors. This description, despite its remarkable resemblance with the hidden Markov model, or the iterated quantum instrument, is however devoid of any stochastic or quantum mechanical interpretation, as said maps fail to satisfy any positivity conditions. The completely positive realization problem then consists in determining whether an equivalent quantum mechanical description of the same process exists. We generalize some key results of stochastic realization theory, and show that the problem has deep connections with operator systems theory, giving possible insight to the lifting problem in quotient operator systems. Our results have potential applications in quantum machine

  18. Long-lasting hybrid quantum information processing in a cavity-protection regime

    NASA Astrophysics Data System (ADS)

    Chiesa, A.; Santini, P.; Gerace, D.; Carretta, S.

    2016-03-01

    Implementing complex sequences of gates is crucial for any quantum computing architecture to become practical. This requires long-lived qubits which can be manipulated many times without errors. Here we propose a scheme to process hybrid qubits consisting of spin ensembles coupled to superconducting resonators in a cavity-protection regime, which enhances their coherence time by orders of magnitude. We perform numerical experiments for the quantum simulation of the X Y model and the quantum Fourier transform, by including all the main decoherence mechanisms and assuming system parameters that are guaranteed by present technology.

  19. On quantum mechanical transport coefficients in nonequilibrium nuclear processes with application to heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Hamdouni, Yamen

    2010-12-01

    The elements of the quantum mechanical Markovian diffusion matrix leading to a Gibbs equilibrium state for a set of N coupled quantum harmonic oscillators are derived within Lindblad's axiomatic approach. Consequences of the fundamental constraints on the quantum friction coefficients are discussed. We derive the equations of motion for the expectation values and variances, and we solve them analytically. We apply our results to the description of the charge and mass asymmetry coordinates in heavy-ion collisions, and we investigate the effect of dissipation on tunneling in sub-barrier processes.

  20. Space–time-bounded quantum fields for detection processes

    PubMed Central

    Aguayo, Fernando J.; Jaroszkiewicz, George

    2014-01-01

    We discuss a quantum field detection model comprising two types of detection procedures: maximal detection, where the initial state of the system and detectors undergoes an irreversible evolution, and minimal detection, where the system–detector interaction consists of a small, reversible coupling and posterior maximal detection performed over the detector system. Combined, these detection procedures allow for a time-dependent description of signalling experiments involving yes/no type of questions. A particular minimal detection model, stable in the presence of the vacuum, is presented and studied, successfully reproducing the localization of the state after a detection. PMID:24711717

  1. Quantum Trajectories for Squeezed Input Processes: Explicit Solutions

    NASA Astrophysics Data System (ADS)

    Dabrowska, Anita; Gough, John

    2016-03-01

    We consider the quantum (trajectories) filtering equation for the case when the system is driven by Bose field inputs prepared in an arbitrary non-zero mean Gaussian state. The a posteriori evolution of the system is conditioned by the results of a single or double homodyne measurements. The system interacting with the Bose field is a single cavity mode taken initially in a Gaussian state. We show explicit solutions using the method of characteristic functions to the filtering equations exploiting the linear Gaussian nature of the problem.

  2. Solution-processed, high-performance light-emitting diodes based on quantum dots.

    PubMed

    Dai, Xingliang; Zhang, Zhenxing; Jin, Yizheng; Niu, Yuan; Cao, Hujia; Liang, Xiaoyong; Chen, Liwei; Wang, Jianpu; Peng, Xiaogang

    2014-11-01

    Solution-processed optoelectronic and electronic devices are attractive owing to the potential for low-cost fabrication of large-area devices and the compatibility with lightweight, flexible plastic substrates. Solution-processed light-emitting diodes (LEDs) using conjugated polymers or quantum dots as emitters have attracted great interest over the past two decades. However, the overall performance of solution-processed LEDs--including their efficiency, efficiency roll-off at high current densities, turn-on voltage and lifetime under operational conditions-remains inferior to that of the best vacuum-deposited organic LEDs. Here we report a solution-processed, multilayer quantum-dot-based LED with excellent performance and reproducibility. It exhibits colour-saturated deep-red emission, sub-bandgap turn-on at 1.7 volts, high external quantum efficiencies of up to 20.5 per cent, low efficiency roll-off (up to 15.1 per cent of the external quantum efficiency at 100 mA cm(-2)), and a long operational lifetime of more than 100,000 hours at 100 cd m(-2), making this device the best-performing solution-processed red LED so far, comparable to state-of-the-art vacuum-deposited organic LEDs. This optoelectronic performance is achieved by inserting an insulating layer between the quantum dot layer and the oxide electron-transport layer to optimize charge balance in the device and preserve the superior emissive properties of the quantum dots. We anticipate that our results will be a starting point for further research, leading to high-performance, all-solution-processed quantum-dot-based LEDs ideal for next-generation display and solid-state lighting technologies. PMID:25363773

  3. BPS Wilson loops in Minkowski spacetime and Euclidean space

    NASA Astrophysics Data System (ADS)

    Ouyang, Hao; Wu, Jun-Bao; Zhang, Jia-ju

    2015-12-01

    We give evidence that spacelike BPS Wilson loops do not exist in Minkowski spacetime. We show that spacelike Wilson loops in Minkowski spacetime cannot preserve any supersymmetries, in d = 4 N = 4 super Yang-Mills theory, d = 3 N = 2 super Chern-Simons-matter theory, and d = 3 N = 6 Aharony-Bergman-Jafferis-Maldacena theory. We not only show this using infinite straight lines and circles as examples, but also we give proofs for general curves. We attribute this to the conflicts of the reality conditions of the spinors. However, spacelike Wilson loops do exist in Euclidean space. There are both BPS Wilson loops along infinite straight lines and circular BPS Wilson loops. This is because the reality conditions of the spinors are lost after Wick rotation. The result is reasonable in view of the AdS/CFT correspondence.

  4. On the Euclidean version of the photon number integral

    SciTech Connect

    Ruijsenaars, S.; Stodolsky, L.

    2008-02-15

    We reconsider the Euclidean version of the photon number integral introduced by Stodolsky [Acta Phys. Pol. B 33, 2659 (2002), e-print hep-th/02053131].This integral is well defined for any smooth non-self-intersecting curve in R{sup N}. Besides studying general features of this integral (including its conformal invariance), we evaluate it explicitly for the ellipse. The result is n{sub ellipse}=({xi}{sup -1}+{xi}){pi}{sup 2}, where {xi} is the ratio of the minor and major axes. This is in agreement with the previous result n{sub circle}=2{pi}{sup 2} and also with the conjecture that the minimum value of n for any plane curve occurs for the circle.

  5. On the high-density expansion for Euclidean random matrices

    NASA Astrophysics Data System (ADS)

    Grigera, T. S.; Martin-Mayor, V.; Parisi, G.; Urbani, P.; Verrocchio, P.

    2011-02-01

    Diagrammatic techniques to compute perturbatively the spectral properties of Euclidean random matrices (ERM) in the high-density regime are introduced and discussed in detail. Such techniques are developed in two alternative and very different formulations of the mathematical problem and are shown to give identical results up to second order in the perturbative expansion. One method, based on writing the so-called resolvent function as a Taylor series, allows us to group the diagrams into a small number of topological classes, providing a simple way to determine the infrared (small momenta) behaviour of the theory up to third order, which is of interest for the comparison with experiments. The other method, which reformulates the problem as a field theory, can instead be used to study the infrared behaviour at any perturbative order.

  6. Defects and boundary layers in non-Euclidean plates

    NASA Astrophysics Data System (ADS)

    Gemmer, J. A.; Venkataramani, S. C.

    2012-12-01

    We investigate the behaviour of non-Euclidean plates with constant negative Gaussian curvature using the Föppl-von Kármán reduced theory of elasticity. Motivated by recent experimental results, we focus on annuli with a periodic profile. We prove rigorous upper and lower bounds for the elastic energy that scales like the thickness squared. In particular we show that are only two types of global minimizers—deformations that remain flat and saddle shaped deformations with isolated regions of stretching near the edge of the annulus. We also show that there exist local minimizers with a periodic profile that have additional boundary layers near their lines of inflection. These additional boundary layers are a new phenomenon in thin elastic sheets and are necessary to regularize jump discontinuities in the azimuthal curvature across lines of inflection. We rigorously derive scaling laws for the width of these boundary layers as a function of the thickness of the sheet.

  7. Action with Acceleration II: Euclidean Hamiltonian and Jordan Blocks

    NASA Astrophysics Data System (ADS)

    Baaquie, Belal E.

    2013-10-01

    The Euclidean action with acceleration has been analyzed in Ref. 1, and referred to henceforth as Paper I, for its Hamiltonian and path integral. In this paper, the state space of the Hamiltonian is analyzed for the case when it is pseudo-Hermitian (equivalent to a Hermitian Hamiltonian), as well as the case when it is inequivalent. The propagator is computed using both creation and destruction operators as well as the path integral. A state space calculation of the propagator shows the crucial role played by the dual state vectors that yields a result impossible to obtain from a Hermitian Hamiltonian. When it is not pseudo-Hermitian, the Hamiltonian is shown to be a direct sum of Jordan blocks.

  8. Self-dual solutions of Yang-Mills theory on Euclidean AdS space

    SciTech Connect

    Sarioglu, Oezguer; Tekin, Bayram

    2009-05-15

    We find nontrivial, time-dependent solutions of the (anti) self-dual Yang-Mills equations in the four-dimensional Euclidean anti-de Sitter space. In contrast to the Euclidean flat space, the action depends on the moduli parameters and the charge can take any noninteger value.

  9. Shape Selection in the non-Euclidean Model of Elasticity

    NASA Astrophysics Data System (ADS)

    Gemmer, John

    In this dissertation we investigate the behavior of radially symmetric non-Euclidean plates of thickness t with constant negative Gaussian curvature. We present a complete study of these plates using the Foppl-von Karman and Kirchhoff reduced theories of elasticity. Motivated by experimental results, we focus on deformations with a periodic profile. For the Foppl-von Karman model, we prove rigorously that minimizers of the elastic energy converge to saddle shaped isometric immersions. In studying this convergence, we prove rigorous upper and lower bounds for the energy that scale like the thickness t squared. Furthermore, for deformation with n-waves we prove that the lower bound scales like nt2 while the upper bound scales like n2t2. We also investigate the scaling with thickness of boundary layers where the stretching energy is concentrated with decreasing thickness. For the Kichhoff model, we investigate isometric immersions of disks with constant negative curvature into R2, and the minimizers for the bending energy, i.e. the L2 norm of the principal curvatures over the class of W2,2 isometric immersions. We show the existence of smooth immersions of arbitrarily large geodesic balls in the hyperbolic plane into Euclidean space. In elucidating the connection between these immersions and the non-existence/singularity results of Hilbert and Amsler, we obtain a lower bound for the L infinity norm of the principal curvatures for such smooth isometric immersions. We also construct piecewise smooth isometric immersions that have a periodic profile, are globally W2,2, and numerically have lower bending energy than their smooth counterparts. The number of periods in these configurations is set by the condition that the principal curvatures of the surface remain finite and grow approximately exponentially with the radius of the disc.

  10. On the phase diagram of 2d Lorentzian Quantum Gravity

    NASA Astrophysics Data System (ADS)

    Ambjørn, Jan; Anagnostopoulos, K. N.; Loll, R.

    The phase diagram of 2d Lorentzian quantum gravity (LQG) coupled to conformal matter is studied. A phase transition is observed at c = c crit ( {1}/{2} < c crit < 4) which can be thought of as the analogue of the c = 1 barrier of Euclidean quantum gravity (EQG). The non-trivial properties of the quantum geometry are discussed.

  11. Application of Euclidean distance measurement and principal component analysis for gene identification.

    PubMed

    Ghosh, Antara; Barman, Soma

    2016-06-01

    Gene systems are extremely complex, heterogeneous, and noisy in nature. Many statistical tools which are used to extract relevant feature from genes provide fuzzy and ambiguous information. High-dimensional gene expression database available in public domain usually contains thousands of genes. Efficient prediction method is demanding nowadays for accurate identification of such database. Euclidean distance measurement and principal component analysis methods are applied on such databases to identify the genes. In both methods, prediction algorithm is based on homology search approach. Digital Signal Processing technique along with statistical method is used for analysis of genes in both cases. A two-level decision logic is used for gene classification as healthy or cancerous. This binary logic minimizes the prediction error and improves prediction accuracy. Superiority of the method is judged by receiver operating characteristic curve. PMID:26877227

  12. Unstable spiral waves and local Euclidean symmetry in a model of cardiac tissue

    SciTech Connect

    Marcotte, Christopher D.; Grigoriev, Roman O.

    2015-06-15

    This paper investigates the properties of unstable single-spiral wave solutions arising in the Karma model of two-dimensional cardiac tissue. In particular, we discuss how such solutions can be computed numerically on domains of arbitrary shape and study how their stability, rotational frequency, and spatial drift depend on the size of the domain as well as the position of the spiral core with respect to the boundaries. We also discuss how the breaking of local Euclidean symmetry due to finite size effects as well as the spatial discretization of the model is reflected in the structure and dynamics of spiral waves. This analysis allows identification of a self-sustaining process responsible for maintaining the state of spiral chaos featuring multiple interacting spirals.

  13. Artificial immune system via Euclidean Distance Minimization for anomaly detection in bearings

    NASA Astrophysics Data System (ADS)

    Montechiesi, L.; Cocconcelli, M.; Rubini, R.

    2016-08-01

    In recent years new diagnostics methodologies have emerged, with particular interest into machinery operating in non-stationary conditions. In fact continuous speed changes and variable loads make non-trivial the spectrum analysis. A variable speed means a variable characteristic fault frequency related to the damage that is no more recognizable in the spectrum. To overcome this problem the scientific community proposed different approaches listed in two main categories: model-based approaches and expert systems. In this context the paper aims to present a simple expert system derived from the mechanisms of the immune system called Euclidean Distance Minimization, and its application in a real case of bearing faults recognition. The proposed method is a simplification of the original process, adapted by the class of Artificial Immune Systems, which proved to be useful and promising in different application fields. Comparative results are provided, with a complete explanation of the algorithm and its functioning aspects.

  14. 3D Lorentzian loop quantum gravity and the spinor approach

    NASA Astrophysics Data System (ADS)

    Girelli, Florian; Sellaroli, Giuseppe

    2015-12-01

    We consider the generalization of the "spinor approach" to the Lorentzian case, in the context of three-dimensional loop quantum gravity with cosmological constant Λ =0 . The key technical tool that allows this generalization is the recoupling theory between unitary infinite-dimensional representations and nonunitary finite-dimensional ones, obtained in the process of generalizing the Wigner-Eckart theorem to SU(1,1). We use SU(1,1) tensor operators to build observables and a solvable quantum Hamiltonian constraint, analogous to the one introduced by V. Bonzom and his collaborators in the Euclidean case (with both Λ =0 and Λ ≠0 ). We show that the Lorentzian Ponzano-Regge amplitude is the solution of the quantum Hamiltonian constraint by recovering the Biedenharn-Elliott relation [generalized to the case where unitary and nonunitary SU(1,1) representations are coupled to each other]. Our formalism is sufficiently general that both the Lorentzian and the Euclidean case can be recovered (with Λ =0 ).

  15. Multiple particle production processes in the light'' of quantum optics

    SciTech Connect

    Friedlander, E.M.

    1990-09-01

    Ever since the observation that high-energy nuclear active'' cosmic-ray particles create bunches of penetrating particles upon hitting targets, a controversy has raged about whether these secondaries are created in a single act'' or whether many hadrons are just the result of an intra-nuclear cascade, yielding one meson in every step. I cannot escape the impression that: the latter kind of model appeals naturally as a consequence of an innate bio-morphism in our way of thinking and that in one guise or another it has tenaciously survived to this day, also for hadron-hadron collisions, via multi-peripheral models to the modern parton shower approach. Indeed, from the very beginning of theoretical consideration of multiparticle production, the possibility of many particles arising from a single hot'' system has been explored, with many fruitful results, not the least of which are the s{sup 1/4} dependence of the mean produced particle multiplicity and the thermal'' shape of the P{sub T} spectra. An important consequence of the thermodynamical-hydrodynamical models is that particle emission is treated in analogy to black-body radiation, implying for the secondaries a set of specific Quantum-Statistical properties, very similar to those observed in quantum optics. From here on I shall try to review a number of implications and applications of this QS analogy in the study of multiplicity distributions of the produced secondaries. I will touch only in passing another very important topic of this class, the Bose-Einstein two-particle correlations.

  16. Random Coulomb antiferromagnets: From diluted spin liquids to Euclidean random matrices

    NASA Astrophysics Data System (ADS)

    Rehn, J.; Sen, Arnab; Andreanov, A.; Damle, Kedar; Moessner, R.; Scardicchio, A.

    2015-08-01

    We study a disordered classical Heisenberg magnet with uniformly antiferromagnetic interactions which are frustrated on account of their long-range Coulomb form, i.e., J (r )˜-A lnr in d =2 and J (r )˜A /r in d =3 . This arises naturally as the T →0 limit of the emergent interactions between vacancy-induced degrees of freedom in a class of diluted Coulomb spin liquids (including the classical Heisenberg antiferromagnets in checkerboard, SCGO, and pyrochlore lattices) and presents a novel variant of a disordered long-range spin Hamiltonian. Using detailed analytical and numerical studies we establish that this model exhibits a very broad paramagnetic regime that extends to very large values of A in both d =2 and d =3 . In d =2 , using the lattice-Green-function-based finite-size regularization of the Coulomb potential (which corresponds naturally to the underlying low-temperature limit of the emergent interactions between orphans), we find evidence that freezing into a glassy state occurs only in the limit of strong coupling, A =∞ , while no such transition seems to exist in d =3 . We also demonstrate the presence and importance of screening for such a magnet. We analyze the spectrum of the Euclidean random matrices describing a Gaussian version of this problem and identify a corresponding quantum mechanical scattering problem.

  17. Geostatistical analysis of groundwater level using Euclidean and non-Euclidean distance metrics and variable variogram fitting criteria

    NASA Astrophysics Data System (ADS)

    Theodoridou, Panagiota G.; Karatzas, George P.; Varouchakis, Emmanouil A.; Corzo Perez, Gerald A.

    2015-04-01

    Groundwater level is an important information in hydrological modelling. Geostatistical methods are often employed to map the free surface of an aquifer. In geostatistical analysis using Kriging techniques the selection of the optimal variogram model is very important for the optimal method performance. This work compares three different criteria, the least squares sum method, the Akaike Information Criterion and the Cressie's Indicator, to assess the theoretical variogram that fits to the experimental one and investigates the impact on the prediction results. Moreover, five different distance functions (Euclidean, Minkowski, Manhattan, Canberra, and Bray-Curtis) are applied to calculate the distance between observations that affects both the variogram calculation and the Kriging estimator. Cross validation analysis in terms of Ordinary Kriging is applied by using sequentially a different distance metric and the above three variogram fitting criteria. The spatial dependence of the observations in the tested dataset is studied by fitting classical variogram models and the Matérn model. The proposed comparison analysis performed for a data set of two hundred fifty hydraulic head measurements distributed over an alluvial aquifer that covers an area of 210 km2. The study area is located in the Prefecture of Drama, which belongs to the Water District of East Macedonia (Greece). This area was selected in terms of hydro-geological data availability and geological homogeneity. The analysis showed that a combination of the Akaike information Criterion for the variogram fitting assessment and the Brays-Curtis distance metric provided the most accurate cross-validation results. The Power-law variogram model provided the best fit to the experimental data. The aforementioned approach for the specific dataset in terms of the Ordinary Kriging method improves the prediction efficiency in comparison to the classical Euclidean distance metric. Therefore, maps of the spatial

  18. Quantum chemical methods for the investigation of photoinitiated processes in biological systems: theory and applications.

    PubMed

    Dreuw, Andreas

    2006-11-13

    With the advent of modern computers and advances in the development of efficient quantum chemical computer codes, the meaningful computation of large molecular systems at a quantum mechanical level became feasible. Recent experimental effort to understand photoinitiated processes in biological systems, for instance photosynthesis or vision, at a molecular level also triggered theoretical investigations in this field. In this Minireview, standard quantum chemical methods are presented that are applicable and recently used for the calculation of excited states of photoinitiated processes in biological molecular systems. These methods comprise configuration interaction singles, the complete active space self-consistent field method, and time-dependent density functional theory and its variants. Semiempirical approaches are also covered. Their basic theoretical concepts and mathematical equations are briefly outlined, and their properties and limitations are discussed. Recent successful applications of the methods to photoinitiated processes in biological systems are described and theoretical tools for the analysis of excited states are presented. PMID:17009357

  19. Optimizing the choice of spin-squeezed states for detecting and characterizing quantum processes

    SciTech Connect

    Rozema, Lee A.; Mahler, Dylan H.; Blume-Kohout, Robin; Steinberg, Aephraim M.

    2014-11-07

    Quantum metrology uses quantum states with no classical counterpart to measure a physical quantity with extraordinary sensitivity or precision. Most such schemes characterize a dynamical process by probing it with a specially designed quantum state. The success of such a scheme usually relies on the process belonging to a particular one-parameter family. If this assumption is violated, or if the goal is to measure more than one parameter, a different quantum state may perform better. In the most extreme case, we know nothing about the process and wish to learn everything. This requires quantum process tomography, which demands an informationally complete set of probe states. It is very convenient if this set is group covariant—i.e., each element is generated by applying an element of the quantum system’s natural symmetry group to a single fixed fiducial state. In this paper, we consider metrology with 2-photon (“biphoton”) states and report experimental studies of different states’ sensitivity to small, unknown collective SU(2) rotations [“SU(2) jitter”]. Maximally entangled N00N states are the most sensitive detectors of such a rotation, yet they are also among the worst at fully characterizing an a priori unknown process. We identify (and confirm experimentally) the best SU(2)-covariant set for process tomography; these states are all less entangled than the N00N state, and are characterized by the fact that they form a 2-design.

  20. Effect of Multiphoton Processes on Geometric Quantum Computation in Superconducting Circuit QED

    NASA Astrophysics Data System (ADS)

    Chen, Chang-Yong

    2012-11-01

    We study the influence of multi-photon processes on the geometric quantum computation in the systems of superconducting qubits based on the displacement-like and the general squeezed operator methods. As an example, we focus on the question about how to implement a two-qubit geometric phase gate using superconducting circuit quantum electrodynamics with both single- and two-photon interaction between the qubits and the cavity modes. We find that the multiphoton processes are not only controllable but also improve the gating speed. The comparison with other physical systems and experimental feasibility are discussed in detail.

  1. Phonon induced pure dephasing process of excitonic state in colloidal semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Huang, Tongyun; Han, Peng; Wang, Xinke; Feng, Shengfei; Sun, Wenfeng; Ye, Jiasheng; Zhang, Yan

    2016-04-01

    We present a theoretical study on the pure dephasing process of colloidal semiconductor quantum dots induced by lattice vibrations using continuum model calculations. By solving the time dependent Liouville-von Neumann equation, we present the ultrafast Rabi oscillations between excitonic state and virtual state via exciton-phonon interaction and obtain the pure dephasing time from the fast decayed envelope of the Rabi oscillations. The interaction between exciton and longitudinal optical phonon vibration is found to dominate the pure dephasing process and the dephasing time increases nonlinearly with the reduction of exciton-phonon coupling strength. We further find that the pure dephasing time of large quantum dots is more sensitive to temperature than small quantum dots.

  2. Inclusive and Exclusive Compton Processes in Quantum Chromodynamics

    SciTech Connect

    Ales Psaker

    2005-12-31

    In our work, we describe two types of Compton processes. As an example of an inclusive process, we consider the high-energy photoproduction of massive muon pairs off the nucleon. We analyze the process in the framework of the QCD parton model, in which the usual parton distributions emerge as a tool to describe the nucleon in terms of quark and gluonic degrees of freedom. To study its exclusive version, a new class of phenomenological functions is required, namely, generalized parton distributions. They can be considered as a generalization of the usual parton distributions measured in deeply inelastic lepton-nucleon scattering. Generalized parton distributions (GPDs) may be observed in hard exclusive reactions such as deeply virtual Compton scattering. We develop an extension of this particular process into the weak interaction sector. We also investigate a possible application of the GPD formalism to wide-angle real Compton scattering.

  3. Fisher informations and local asymptotic normality for continuous-time quantum Markov processes

    NASA Astrophysics Data System (ADS)

    Catana, Catalin; Bouten, Luc; Guţă, Mădălin

    2015-09-01

    We consider the problem of estimating an arbitrary dynamical parameter of an open quantum system in the input-output formalism. For irreducible Markov processes, we show that in the limit of large times the system-output state can be approximated by a quantum Gaussian state whose mean is proportional to the unknown parameter. This approximation holds locally in a neighbourhood of size {t}-1/2 in the parameter space, and provides an explicit expression of the asymptotic quantum Fisher information in terms of the Markov generator. Furthermore we show that additive statistics of the counting and homodyne measurements also satisfy local asymptotic normality and we compute the corresponding classical Fisher informations. The general theory is illustrated with the examples of a two-level system and the atom maser. Our results contribute towards a better understanding of the statistical and probabilistic properties of the output process, with relevance for quantum control engineering, and the theory of non-equilibrium quantum open systems.

  4. Quantum Process Tomography of an Optically-Controlled Kerr Non-linearity

    PubMed Central

    Kupchak, Connor; Rind, Samuel; Jordaan, Bertus; Figueroa, Eden

    2015-01-01

    Any optical quantum information processing machine would be comprised of fully-characterized constituent devices for both single state manipulations and tasks involving the interaction between multiple quantum optical states. Ideally for the latter, would be an apparatus capable of deterministic optical phase shifts that operate on input quantum states with the action mediated solely by auxiliary signal fields. Here we present the complete experimental characterization of a system designed for optically controlled phase shifts acting on single-photon level probe coherent states. Our setup is based on a warm vapor of rubidium atoms under the conditions of electromagnetically induced transparency with its dispersion properties modified through the use of an optically triggered N-type Kerr non-linearity. We fully characterize the performance of our device by sending in a set of input probe states and measuring the corresponding output via time-domain homodyne tomography and subsequently performing the technique of coherent state quantum process tomography. This method provides us with the precise knowledge of how our optical phase shift will modify any arbitrary input quantum state engineered in the mode of the reconstruction. PMID:26585904

  5. Quantum Process Tomography of an Optically-Controlled Kerr Non-linearity.

    PubMed

    Kupchak, Connor; Rind, Samuel; Jordaan, Bertus; Figueroa, Eden

    2015-01-01

    Any optical quantum information processing machine would be comprised of fully-characterized constituent devices for both single state manipulations and tasks involving the interaction between multiple quantum optical states. Ideally for the latter, would be an apparatus capable of deterministic optical phase shifts that operate on input quantum states with the action mediated solely by auxiliary signal fields. Here we present the complete experimental characterization of a system designed for optically controlled phase shifts acting on single-photon level probe coherent states. Our setup is based on a warm vapor of rubidium atoms under the conditions of electromagnetically induced transparency with its dispersion properties modified through the use of an optically triggered N-type Kerr non-linearity. We fully characterize the performance of our device by sending in a set of input probe states and measuring the corresponding output via time-domain homodyne tomography and subsequently performing the technique of coherent state quantum process tomography. This method provides us with the precise knowledge of how our optical phase shift will modify any arbitrary input quantum state engineered in the mode of the reconstruction. PMID:26585904

  6. Quantum Process Tomography of an Optically-Controlled Kerr Non-linearity

    NASA Astrophysics Data System (ADS)

    Kupchak, Connor; Rind, Samuel; Jordaan, Bertus; Figueroa, Eden

    2015-11-01

    Any optical quantum information processing machine would be comprised of fully-characterized constituent devices for both single state manipulations and tasks involving the interaction between multiple quantum optical states. Ideally for the latter, would be an apparatus capable of deterministic optical phase shifts that operate on input quantum states with the action mediated solely by auxiliary signal fields. Here we present the complete experimental characterization of a system designed for optically controlled phase shifts acting on single-photon level probe coherent states. Our setup is based on a warm vapor of rubidium atoms under the conditions of electromagnetically induced transparency with its dispersion properties modified through the use of an optically triggered N-type Kerr non-linearity. We fully characterize the performance of our device by sending in a set of input probe states and measuring the corresponding output via time-domain homodyne tomography and subsequently performing the technique of coherent state quantum process tomography. This method provides us with the precise knowledge of how our optical phase shift will modify any arbitrary input quantum state engineered in the mode of the reconstruction.

  7. On the complexity of some quadratic Euclidean 2-clustering problems

    NASA Astrophysics Data System (ADS)

    Kel'manov, A. V.; Pyatkin, A. V.

    2016-03-01

    Some problems of partitioning a finite set of points of Euclidean space into two clusters are considered. In these problems, the following criteria are minimized: (1) the sum over both clusters of the sums of squared pairwise distances between the elements of the cluster and (2) the sum of the (multiplied by the cardinalities of the clusters) sums of squared distances from the elements of the cluster to its geometric center, where the geometric center (or centroid) of a cluster is defined as the mean value of the elements in that cluster. Additionally, another problem close to (2) is considered, where the desired center of one of the clusters is given as input, while the center of the other cluster is unknown (is the variable to be optimized) as in problem (2). Two variants of the problems are analyzed, in which the cardinalities of the clusters are (1) parts of the input or (2) optimization variables. It is proved that all the considered problems are strongly NP-hard and that, in general, there is no fully polynomial-time approximation scheme for them (unless P = NP).

  8. Percolation thresholds on planar Euclidean relative-neighborhood graphs

    NASA Astrophysics Data System (ADS)

    Melchert, O.

    2013-04-01

    In the present article, statistical properties regarding the topology and standard percolation on relative neighborhood graphs (RNGs) for planar sets of points, considering the Euclidean metric, are put under scrutiny. RNGs belong to the family of “proximity graphs”; i.e., their edgeset encodes proximity information regarding the close neighbors for the terminal nodes of a given edge. Therefore they are, e.g., discussed in the context of the construction of backbones for wireless ad hoc networks that guarantee connectedness of all underlying nodes. Here, by means of numerical simulations, we determine the asymptotic degree and diameter of RNGs and we estimate their bond and site percolation thresholds, which were previously conjectured to be nontrivial. We compare the results to regular 2D graphs for which the degree is close to that of the RNG. Finally, we deduce the common percolation critical exponents from the RNG data to verify that the associated universality class is that of standard 2D percolation.

  9. Generating Triangulated Macromolecular Surfaces by Euclidean Distance Transform

    PubMed Central

    Xu, Dong; Zhang, Yang

    2009-01-01

    Macromolecular surfaces are fundamental representations of their three-dimensional geometric shape. Accurate calculation of protein surfaces is of critical importance in the protein structural and functional studies including ligand-protein docking and virtual screening. In contrast to analytical or parametric representation of macromolecular surfaces, triangulated mesh surfaces have been proved to be easy to describe, visualize and manipulate by computer programs. Here, we develop a new algorithm of EDTSurf for generating three major macromolecular surfaces of van der Waals surface, solvent-accessible surface and molecular surface, using the technique of fast Euclidean Distance Transform (EDT). The triangulated surfaces are constructed directly from volumetric solids by a Vertex-Connected Marching Cube algorithm that forms triangles from grid points. Compared to the analytical result, the relative error of the surface calculations by EDTSurf is <2–4% depending on the grid resolution, which is 1.5–4 times lower than the methods in the literature; and yet, the algorithm is faster and costs less computer memory than the comparative methods. The improvements in both accuracy and speed of the macromolecular surface determination should make EDTSurf a useful tool for the detailed study of protein docking and structure predictions. Both source code and the executable program of EDTSurf are freely available at http://zhang.bioinformatics.ku.edu/EDTSurf. PMID:19956577

  10. Quantum Process Tomography of a Room Temperature Optically-Controlled Phase Shift

    NASA Astrophysics Data System (ADS)

    Kupchak, Connor; Rind, Samuel; Figueroa, Eden; Stony Brook University Team

    2015-05-01

    We have developed a room temperature setup capable of optically controlled phase shifts on a weak probe field. Our system is realized in a vapor of 87Rb atoms under the conditions of electromagnetically induced transparency utilizing a N-type energy level scheme coupled by three optical fields. By varying the power of the signal field, we can control the size of an optical phase shift experienced by weak coherent state pulses of < n > ~ 1 , propagating through the vapor. We quantify the optical phase shift by measuring the process output via balanced homodyne tomography which provides us with the complete quadrature and phase information of the output states. Furthermore, we measure the output for a set of states over a subspace of the coherent state basis and gain the information to completely reconstruct our phase shift procedure by coherent state quantum process tomography. The reconstruction yields a rank-4 process superoperator which grants the ability to predict how our phase shift process will behave on an arbitrary quantum optical state in the mode of the reconstruction. Our results demonstrate progress towards room temperature systems for possible quantum gates; a key component of a future quantum processor designed to operate at room temperature. US-Navy Office of Naval Research N00141410801, National Science Foundation PHY-1404398, Natural Sciences and Engineering Research Council of Canada.

  11. Shortcuts to adiabaticity in classical and quantum processes for scale-invariant driving

    NASA Astrophysics Data System (ADS)

    Deffner, Sebastian; Jarzynski, Christopher; Del Campo, Adolfo

    2014-03-01

    All real physical processes in classical as well as in quantum devices operate in finite-time. For most applications, however, adiabatic, i.e. infinitely-slow processes, are more favorable, as these do not cause unwanted, parasitic excitations. A shortcut to adiabaticity is a driving protocol which reproduces in a short time the same final state that would result from an adiabatic process. A particular powerful technique to engineer such shortcuts is transitionless quantum driving by means of counterdiabatic fields. However, determining closed form expressions for the counterdiabatic field has generally proven to be a daunting task. In this paper, we introduce a novel approach, with which we find the explicit form of the counterdiabatic driving field in arbitrary scale-invariant dynamical processes, encompassing expansions and transport. Our approach originates in the formalism of generating functions, and unifies previous approaches independently developed for classical and quantum systems. We show how this new approach allows to design shortcuts to adiabaticity for a large class of classical and quantum, single-particle, non-linear, and many-body systems. SD and CJ acknowledge support from the National Science Foundation (USA) under grant DMR-1206971. This research is further supported by the U.S Department of Energy through the LANL/LDRD Program and a LANL J. Robert Oppenheimer fellowship (AdC).

  12. Overspinning a nearly extreme charged black hole via a quantum tunneling process.

    PubMed

    Matsas, George E A; da Silva, André R R

    2007-11-01

    We examine a nearly extreme macroscopic Reissner-Nördstrom black hole in the context of semiclassical gravity. The absorption rate associated with the quantum tunneling process of scalar particles whereby this black hole can acquire enough angular momentum to violate the weak cosmic-censorship conjecture is shown to be nonzero. PMID:17995395

  13. Study of the self-organization processes in lead sulfide quantum dots

    SciTech Connect

    Tarasov, S. A. Aleksandrova, O. A.; Maksimov, A. I.; Maraeva, E. V.; Matyushkin, L. B.; Men’kovich, E. A.; Moshnikov, V. A.; Musikhin, S. F.

    2014-12-15

    A procedure is described for the synthesis of nanoparticles based on lead chalcogenides. The procedure combines the synthesis of colloidal quantum dots (QDs) in aqueous solutions with simultaneous organization of the QDs into ordered arrays. The processes of the self-organization of QDs are analyzed at the nano- and microscopic levels by the photoluminescence method, atomic-force microscopy, and optical microscopy.

  14. Mixmaster revisited: wormhole solutions to the Bianchi IX Wheeler-DeWitt equation using the Euclidean-signature semi-classical method

    NASA Astrophysics Data System (ADS)

    Bae, Joseph H.

    2015-04-01

    A modified semi-classical method is used to construct both ground and excited state solutions to the canonically quantized vacuum Bianchi IX (Mixmaster) cosmological models. Employing a modified form of the semi-classical Ansatz we solve the relevant Wheeler-DeWitt equation asymptotically by integrating a set of linear transport equations along the flow of a suitably chosen solution to the corresponding Euclidean-signature Hamilton-Jacobi equation. For the Moncrief-Ryan (or ‘wormhole’) Hamilton-Jacobi solution, we compute the ground state quantum correction term associated with operator ordering ambiguities and show how higher order correction terms can be computed. We also determine the explicit, leading order forms of a family of excited states and show how to compute their quantum corrections as smooth, globally defined functions on the Bianchi IX minisuperspace. These excited state solutions are peaked away from the minisuperspace origin and are labeled by a pair of positive integers that can be plausibly interpreted as graviton excitation numbers for the two independent anisotropy degrees of freedom. The Euclidean-signature semi-classical method used here is applicable to more general models, representing a significant progress in the Wheeler-DeWitt approach to quantum gravity.

  15. Fluctuations and Stochastic Processes in One-Dimensional Many-Body Quantum Systems

    SciTech Connect

    Stimming, H.-P.; Mauser, N. J.; Mazets, I. E.

    2010-07-02

    We study the fluctuation properties of a one-dimensional many-body quantum system composed of interacting bosons and investigate the regimes where quantum noise or, respectively, thermal excitations are dominant. For the latter, we develop a semiclassical description of the fluctuation properties based on the Ornstein-Uhlenbeck stochastic process. As an illustration, we analyze the phase correlation functions and the full statistical distributions of the interference between two one-dimensional systems, either independent or tunnel-coupled, and compare with the Luttinger-liquid theory.

  16. Description of quantum coherence in thermodynamic processes requires constraints beyond free energy

    PubMed Central

    Lostaglio, Matteo; Jennings, David; Rudolph, Terry

    2015-01-01

    Recent studies have developed fundamental limitations on nanoscale thermodynamics, in terms of a set of independent free energy relations. Here we show that free energy relations cannot properly describe quantum coherence in thermodynamic processes. By casting time-asymmetry as a quantifiable, fundamental resource of a quantum state, we arrive at an additional, independent set of thermodynamic constraints that naturally extend the existing ones. These asymmetry relations reveal that the traditional Szilárd engine argument does not extend automatically to quantum coherences, but instead only relational coherences in a multipartite scenario can contribute to thermodynamic work. We find that coherence transformations are always irreversible. Our results also reveal additional structural parallels between thermodynamics and the theory of entanglement. PMID:25754774

  17. Confined optical-phonon-assisted cyclotron resonance in quantum wells via two-photon absorption process

    NASA Astrophysics Data System (ADS)

    Phuc, Huynh Vinh; Hien, Nguyen Dinh; Dinh, Le; Phong, Tran Cong

    2016-06-01

    The effect of confined phonons on the phonon-assisted cyclotron resonance (PACR) via both one and two photon absorption processes in a quantum well is theoretically studied. We consider cases when electrons are scattered by confined optical phonons described by the Fuchs-Kliewer slab, Ridley's guided, and Huang-Zhu models. The analytical expression of the magneto-optical absorption coefficient (MOAC) is obtained by relating it to the transition probability for the absorption of photons. It predicts resonant peaks caused by transitions between Landau levels and electric subband accompanied by confined phonons emission in the absorption spectrum. The MOAC and the full-width at half-maximum (FWHM) for the intra- and inter-subband transitions are given as functions of the magnetic field, temperature, and quantum well width. In narrow quantum wells, the phonon confinement becomes more important and should be taken into account in studying FWHM.

  18. Scattering Solutions of Bethe-Salpeter Equation in Minkowski and Euclidean Spaces

    NASA Astrophysics Data System (ADS)

    Carbonell, J.; Karmanov, V. A.

    2016-07-01

    We shortly review different methods to obtain the scattering solutions of the Bethe-Salpeter equation in Minkowski space. We emphasize the possibility to obtain the zero energy observables in terms of the Euclidean scattering amplitude.

  19. Scattering Solutions of Bethe-Salpeter Equation in Minkowski and Euclidean Spaces

    NASA Astrophysics Data System (ADS)

    Carbonell, J.; Karmanov, V. A.

    2016-06-01

    We shortly review different methods to obtain the scattering solutions of the Bethe-Salpeter equation in Minkowski space. We emphasize the possibility to obtain the zero energy observables in terms of the Euclidean scattering amplitude.

  20. The Euclidean quantisation of Kerr-Newman-de Sitter black holes

    NASA Astrophysics Data System (ADS)

    Chrusciel, Piotr T.; Hörzinger, Michael

    2016-04-01

    We study the family of Einstein-Maxwell instantons associated with the Kerr-Newman metrics with a positive cosmological constant. This leads to a quantisation condition on the masses, charges, and angular momentum parameters of the resulting Euclidean solutions.

  1. Certifying quantumness: Benchmarks for the optimal processing of generalized coherent and squeezed states

    NASA Astrophysics Data System (ADS)

    Yang, Yuxiang; Chiribella, Giulio; Adesso, Gerardo

    2014-10-01

    Quantum technology promises revolutionary advantages in information processing and transmission compared to classical technology; however, determining which specific resources are needed to surpass the capabilities of classical machines often remains a nontrivial problem. To address such a problem, one first needs to establish the best classical solutions, which set benchmarks that must be beaten by any implementation claiming to harness quantum features for an enhanced performance. Here we introduce and develop a self-contained formalism to obtain the ultimate, generally probabilistic benchmarks for quantum information protocols including teleportation and approximate cloning, with arbitrary ensembles of input states generated by a group action, so-called Gilmore-Perelomov coherent states. This allows us to construct explicit fidelity thresholds for the transmission of multimode Gaussian and non-Gaussian states of continuous-variable systems, as well as qubit and qudit pure states drawn according to nonuniform distributions on the Bloch hypersphere, which accurately model the current laboratory facilities. The performance of deterministic classical procedures such as square-root measurement strategies is further compared with the optimal probabilistic benchmarks, and the state-of-the-art performance of experimental quantum implementations against our newly derived thresholds is discussed. This work provides a comprehensive collection of directly useful criteria for the reliable certification of quantum communication technologies.

  2. Euclidean wormhole solutions of Einstein-Yang-Mills theory in diverse dimensions

    SciTech Connect

    Yoshida, K.; Hirenzaki, S. ); Shiraishi, K. )

    1990-09-15

    We solve the Euclidean Einstein equations with non-Abelian gauge fields of sufficiently large symmetry in various dimensions. In higher-dimensional spaces, we find the solutions which are similar to so-called scalar wormholes. In four-dimensional space-time, we find singular wormhole solutions with infinite Euclidean action. Wormhole solutions in the three-dimensional Einstein-Yang-Mills theory with a Chern-Simons term are also constructed.

  3. Simple algorithm for computing the communication complexity of quantum communication processes

    NASA Astrophysics Data System (ADS)

    Hansen, A.; Montina, A.; Wolf, S.

    2016-04-01

    A two-party quantum communication process with classical inputs and outcomes can be simulated by replacing the quantum channel with a classical one. The minimal amount of classical communication required to reproduce the statistics of the quantum process is called its communication complexity. In the case of many instances simulated in parallel, the minimal communication cost per instance is called the asymptotic communication complexity. Previously, we reduced the computation of the asymptotic communication complexity to a convex minimization problem. In most cases, the objective function does not have an explicit analytic form, as the function is defined as the maximum over an infinite set of convex functions. Therefore, the overall problem takes the form of a minimax problem and cannot directly be solved by standard optimization methods. In this paper, we introduce a simple algorithm to compute the asymptotic communication complexity. For some special cases with an analytic objective function one can employ available convex-optimization libraries. In the tested cases our method turned out to be notably faster. Finally, using our method we obtain 1.238 bits as a lower bound on the asymptotic communication complexity of a noiseless quantum channel with the capacity of 1 qubit. This improves the previous bound of 1.208 bits.

  4. Failure mode and effects analysis using intuitionistic fuzzy hybrid weighted Euclidean distance operator

    NASA Astrophysics Data System (ADS)

    Liu, Hu-Chen; Liu, Long; Li, Ping

    2014-10-01

    Failure mode and effects analysis (FMEA) has shown its effectiveness in examining potential failures in products, process, designs or services and has been extensively used for safety and reliability analysis in a wide range of industries. However, its approach to prioritise failure modes through a crisp risk priority number (RPN) has been criticised as having several shortcomings. The aim of this paper is to develop an efficient and comprehensive risk assessment methodology using intuitionistic fuzzy hybrid weighted Euclidean distance (IFHWED) operator to overcome the limitations and improve the effectiveness of the traditional FMEA. The diversified and uncertain assessments given by FMEA team members are treated as linguistic terms expressed in intuitionistic fuzzy numbers (IFNs). Intuitionistic fuzzy weighted averaging (IFWA) operator is used to aggregate the FMEA team members' individual assessments into a group assessment. IFHWED operator is applied thereafter to the prioritisation and selection of failure modes. Particularly, both subjective and objective weights of risk factors are considered during the risk evaluation process. A numerical example for risk assessment is given to illustrate the proposed method finally.

  5. Implications of the general constraints for single-qubit quantum process tomography

    NASA Astrophysics Data System (ADS)

    Bhandari, Ramesh; Peters, Nicholas

    We revisit the general constraints of single qubit quantum process tomography and derive simplified forms in the Pauli basis. These forms give insight into the structure of the process matrix, which we examine in light of several examples. Specifically, we study some qubit leakage error models and show how different error models are manifest in the process matrix. NAP's research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

  6. Lasing process in a closed bipartite quantum system: A thermodynamical analysis

    NASA Astrophysics Data System (ADS)

    Waldherr, G.; Mahler, G.

    2010-06-01

    Closed weakly bound bipartite quantum systems typically exhibit relaxation behavior with respect to the smaller subsystem. Here, we investigate a model composed of a finite spin network with one interfacing spin being coupled to a single electromagnetic field mode via the Jaynes-Cummings interaction. The initial pure state of the system can be chosen such that the resulting thermodynamical relaxation process is lasing/nonlasing relaxation or energy back flow from the field mode. We examine the properties of the field mode with quantum optical methods. During the lasing process, the field mode is in a phase-diffused Glauber state with no optical coherence. The thermodynamical analysis of our system is consistent with this finding: The total energy exchanged between both subsystems is found to be heat only. Yet the mapping of this function onto a thermodynamic heat engine appears to be of limited value.

  7. Quantum process tomography of a Mølmer-Sørensen interaction

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    We present a simple tomographic protocol, for two-qubit systems, that relies on a single discriminatory transition and no direct spatially selective imaging. This scheme exploits excess micromotion in the trap to realize all operations required to prepare all input states and analyze all output states. We demonstrate a two-qubit entangling gate with a Bell state production fidelity of 0.981(6), and apply the above protocol to perform the first quantum process tomography of a Mølmer-Sørensen entangling gate. We characterize its χ-process matrix, the simplest for an entanglement gate on a separable-states basis, and observe that our dominant source of error is accurately modeled by a quantum depolarization channel.

  8. Microscopic Model Calculations for the Magnetization Process of Layered Triangular-Lattice Quantum Antiferromagnets

    NASA Astrophysics Data System (ADS)

    Yamamoto, Daisuke; Marmorini, Giacomo; Danshita, Ippei

    2015-01-01

    Magnetization processes of spin-1 /2 layered triangular-lattice antiferromagnets (TLAFs) under a magnetic field H are studied by means of a numerical cluster mean-field method with a scaling scheme. We find that small antiferromagnetic couplings between the layers give rise to several types of extra quantum phase transitions among different high-field coplanar phases. Especially, a field-induced first-order transition is found to occur at H ≈0.7 Hs, where Hs is the saturation field, as another common quantum effect of ideal TLAFs in addition to the well-established one-third plateau. Our microscopic model calculation with appropriate parameters shows excellent agreement with experiments on Ba3CoSb2O9 [T. Susuki et al., Phys. Rev. Lett. 110, 267201 (2013)]. Given this fact, we suggest that the Co2 + -based compounds may allow for quantum simulations of intriguing properties of this simple frustrated model, such as quantum criticality and supersolid states.

  9. PEET: a Matlab tool for estimating physical gate errors in quantum information processing systems

    NASA Astrophysics Data System (ADS)

    Hocker, David; Kosut, Robert; Rabitz, Herschel

    2016-06-01

    A Physical Error Estimation Tool (PEET) is introduced in Matlab for predicting physical gate errors of quantum information processing (QIP) operations by constructing and then simulating gate sequences for a wide variety of user-defined, Hamiltonian-based physical systems. PEET is designed to accommodate the interdisciplinary needs of quantum computing design by assessing gate performance for users familiar with the underlying physics of QIP, as well as those interested in higher-level computing operations. The structure of PEET separates the bulk of the physical details of a system into Gate objects, while the construction of quantum computing gate operations are contained in GateSequence objects. Gate errors are estimated by Monte Carlo sampling of noisy gate operations. The main utility of PEET, though, is the implementation of QuantumControl methods that act to generate and then test gate sequence and pulse-shaping techniques for QIP performance. This work details the structure of PEET and gives instructive examples for its operation.

  10. Circuit-QED-based scalable architectures for quantum information processing with superconducting qubits

    NASA Astrophysics Data System (ADS)

    Billangeon, P.-M.; Tsai, J. S.; Nakamura, Y.

    2015-03-01

    We discuss different ways of generating entanglement in the original picture of circuit QED (XcQED) and several restrictions that arise in the context of a large-scale quantum architecture. To alleviate some of the issues posed by the presence of the nonlinearities inherent to these systems, we introduce a layout for circuit QED, wherein an artificial atom is coupled to a quantized radiation field via its longitudinal degree of freedom (ZcQED). This system is akin to ion traps used in atomic physics, but it relies on fixed coupling between the atom and the resonator. We describe a scalable architecture for processing quantum information with superconducting qubits, which is free from any type of residual interaction between the atomic and photonic degrees of freedom. Tunable interactions can be realized based on sideband transitions, and the system can be operated out of the Lamb-Dicke regime, allowing it to benefit from the possibility of achieving large coupling strengths between atoms and resonators. We also discuss a readout scheme that does not require any extra circuits and allows a qubit-specific measurement of the state of the quantum register inspired by the electron shelving technique. This scheme is quantum nondemolition (QND)-like, and allows for single-shot determination of the qubit states.

  11. Microscopic model calculations for the magnetization process of layered triangular-lattice quantum antiferromagnets.

    PubMed

    Yamamoto, Daisuke; Marmorini, Giacomo; Danshita, Ippei

    2015-01-16

    Magnetization processes of spin-1/2 layered triangular-lattice antiferromagnets (TLAFs) under a magnetic field H are studied by means of a numerical cluster mean-field method with a scaling scheme. We find that small antiferromagnetic couplings between the layers give rise to several types of extra quantum phase transitions among different high-field coplanar phases. Especially, a field-induced first-order transition is found to occur at H≈0.7H_{s}, where H_{s} is the saturation field, as another common quantum effect of ideal TLAFs in addition to the well-established one-third plateau. Our microscopic model calculation with appropriate parameters shows excellent agreement with experiments on Ba_{3}CoSb_{2}O_{9} [T. Susuki et al., Phys. Rev. Lett. 110, 267201 (2013)]. Given this fact, we suggest that the Co^{2+}-based compounds may allow for quantum simulations of intriguing properties of this simple frustrated model, such as quantum criticality and supersolid states. PMID:25635561

  12. Dynamics of the fully stripped ion-hydrogen atom charge exchange process in dense quantum plasmas

    SciTech Connect

    Zhang, Ling-yu; Wan, Jiang-feng; Zhao, Xiao-ying; Xiao, Guo-qing; Duan, Wen-shan; Qi, Xin; Yang, Lei

    2014-09-15

    The plasma screening effects of dense quantum plasmas on charge exchange processes of a fully stripped ion colliding with a hydrogen atom are studied by the classical trajectory Monte Carlo method. The inter-particle interactions are described by the exponential cosine-screened Coulomb potentials. It is found that in weak screening conditions, cross sections increase with the increase of the ionic charge Z. However, in strong screening conditions, the dependence of cross sections on the ionic charge is related to the incident particle energy. At high energies, cross sections show a linear increase with the increase of Z, whereas at low energies, cross sections for Z≥4 become approximately the same. The He{sup 2+} and C{sup 6+} impacting charge exchange cross sections in dense quantum plasmas are also compared with those in weakly coupled plasmas. The interactions are described by the static screened Coulomb potential. It is found that for both He{sup 2+} and C{sup 6+}, the oscillatory screening effects of dense quantum plasmas are almost negligible in weak screening conditions. However, in strong screening conditions, the oscillatory screening effects enhance the screening effects of dense quantum plasmas, and the enhancement becomes more and more significant with the increase of the screening parameter and the ionic charge.

  13. Transfer of entangled state, entanglement swapping and quantum information processing via the Rydberg blockade

    NASA Astrophysics Data System (ADS)

    Deng, Li; Chen, Ai-Xi; Zhang, Jian-Song

    2011-11-01

    We provide a scheme with which the transfer of the entangled state and the entanglement swapping can be realized in a system of neutral atoms via the Rydberg blockade. Our idea can be extended to teleport an unknown atomic state. According to the latest theoretical research of the Rydberg excitation and experimental reports of the Rydberg blockade effect in quantum information processing, we discuss the experimental feasibility of our scheme.

  14. Optimization of the Multi-Spectral Euclidean Distance Calculation for FPGA-based Spaceborne Systems

    NASA Technical Reports Server (NTRS)

    Cristo, Alejandro; Fisher, Kevin; Perez, Rosa M.; Martinez, Pablo; Gualtieri, Anthony J.

    2012-01-01

    Due to the high quantity of operations that spaceborne processing systems must carry out in space, new methodologies and techniques are being presented as good alternatives in order to free the main processor from work and improve the overall performance. These include the development of ancillary dedicated hardware circuits that carry out the more redundant and computationally expensive operations in a faster way, leaving the main processor free to carry out other tasks while waiting for the result. One of these devices is SpaceCube, a FPGA-based system designed by NASA. The opportunity to use FPGA reconfigurable architectures in space allows not only the optimization of the mission operations with hardware-level solutions, but also the ability to create new and improved versions of the circuits, including error corrections, once the satellite is already in orbit. In this work, we propose the optimization of a common operation in remote sensing: the Multi-Spectral Euclidean Distance calculation. For that, two different hardware architectures have been designed and implemented in a Xilinx Virtex-5 FPGA, the same model of FPGAs used by SpaceCube. Previous results have shown that the communications between the embedded processor and the circuit create a bottleneck that affects the overall performance in a negative way. In order to avoid this, advanced methods including memory sharing, Native Port Interface (NPI) connections and Data Burst Transfers have been used.

  15. Robust Automatic Pectoral Muscle Segmentation from Mammograms Using Texture Gradient and Euclidean Distance Regression.

    PubMed

    Bora, Vibha Bafna; Kothari, Ashwin G; Keskar, Avinash G

    2016-02-01

    In computer-aided diagnosis (CAD) of mediolateral oblique (MLO) view of mammogram, the accuracy of tissue segmentation highly depends on the exclusion of pectoral muscle. Robust methods for such exclusions are essential as the normal presence of pectoral muscle can bias the decision of CAD. In this paper, a novel texture gradient-based approach for automatic segmentation of pectoral muscle is proposed. The pectoral edge is initially approximated to a straight line by applying Hough transform on Probable Texture Gradient (PTG) map of the mammogram followed by block averaging with the aid of approximated line. Furthermore, a smooth pectoral muscle curve is achieved with proposed Euclidean Distance Regression (EDR) technique and polynomial modeling. The algorithm is robust to texture and overlapping fibro glandular tissues. The method is validated with 340 MLO views from three databases-including 200 randomly selected scanned film images from miniMIAS, 100 computed radiography images and 40 full-field digital mammogram images. Qualitatively, 96.75 % of the pectoral muscles are segmented with an acceptable pectoral score index. The proposed method not only outperforms state-of-the-art approaches but also accurately quantifies the pectoral edge. Thus, its high accuracy and relatively quick processing time clearly justify its suitability for CAD. PMID:26259521

  16. Epileptic Seizure Detection with Log-Euclidean Gaussian Kernel-Based Sparse Representation.

    PubMed

    Yuan, Shasha; Zhou, Weidong; Wu, Qi; Zhang, Yanli

    2016-05-01

    Epileptic seizure detection plays an important role in the diagnosis of epilepsy and reducing the massive workload of reviewing electroencephalography (EEG) recordings. In this work, a novel algorithm is developed to detect seizures employing log-Euclidean Gaussian kernel-based sparse representation (SR) in long-term EEG recordings. Unlike the traditional SR for vector data in Euclidean space, the log-Euclidean Gaussian kernel-based SR framework is proposed for seizure detection in the space of the symmetric positive definite (SPD) matrices, which form a Riemannian manifold. Since the Riemannian manifold is nonlinear, the log-Euclidean Gaussian kernel function is applied to embed it into a reproducing kernel Hilbert space (RKHS) for performing SR. The EEG signals of all channels are divided into epochs and the SPD matrices representing EEG epochs are generated by covariance descriptors. Then, the testing samples are sparsely coded over the dictionary composed by training samples utilizing log-Euclidean Gaussian kernel-based SR. The classification of testing samples is achieved by computing the minimal reconstructed residuals. The proposed method is evaluated on the Freiburg EEG dataset of 21 patients and shows its notable performance on both epoch-based and event-based assessments. Moreover, this method handles multiple channels of EEG recordings synchronously which is more speedy and efficient than traditional seizure detection methods. PMID:26906674

  17. Process output nonclassicality and nonclassicality depth of quantum-optical channels

    NASA Astrophysics Data System (ADS)

    Sabapathy, Krishna Kumar

    2016-04-01

    We introduce a quantum-optical notion of nonclassicality that we call the process output nonclassicality for multimode quantum channels. The motivation comes from an information-theoretic point of view and the emphasis is on the output states of a channel. We deem a channel to be "classical" if its outputs are always classical irrespective of the input, i.e., if the channel is nonclassicality breaking, and nonclassical otherwise. Our condition is stronger than the one considered by Rahimi-Keshari et al., [Phys. Rev. Lett. 110, 160401 (2013)], 10.1103/PhysRevLett.110.160401 and we compare the two approaches. Using our framework we then quantify the nonclassicality of a quantum process by introducing a noise-robustness type of measure that we call the nonclassicality depth of a channel. It characterizes a certain threshold noise beyond which a given channel outputs only classical states. We achieve this by generalizing a prescription by Lee [Phys. Rev. A 44, R2775 (1991), 10.1103/PhysRevA.44.R2775] to multimode states and then by extension to multimode channels.

  18. Surface ion trap structures with excellent optical access for quantum information processing

    NASA Astrophysics Data System (ADS)

    Maunz, P.; Blain, M.; Benito, F.; Chou, C.; Clark, C.; Descour, M.; Ellis, R.; Haltli, R.; Heller, E.; Kemme, S.; Sterk, J.; Tabakov, B.; Tigges, C.; Stick, D.

    2013-05-01

    Microfabricated surface electrode ion traps are necessary for the advancement of trapped ion quantum information processing as it offers a scalable way for realizing complex trap structures capable of storing and controlling many ions. The most promising way of performing two-qubit quantum gates in a chain of trapped ions is to focus laser beams on individual ions of the chain to drive gates. However, in surface ion traps the close proximity of the ions to the surface and the size of the chips usually cannot accommodate the tightly focused laser beams necessary to address individual ions parallel to the chip surface. Here we present a surface electrode ion trap monolithically fabricated in standard silicon technology that implements a linear quadrupole trap on a bowtie shaped chip with a narrow section that is only 1.2 mm wide. Laser beams parallel to the surface can be focused down to a waist of 4 μm with enough separation from the trap chip to prevent light scattering. The trap structure incorporates two Y-junctions for reordering ions and is optimized for quantum information processing. This work was supported by the Intelligence Advanced Research Projects Activity (IARPA). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  19. Entanglement and the process of measuring the position of a quantum particle

    NASA Astrophysics Data System (ADS)

    Apel, V. M.; Curilef, S.; Plastino, A. R.

    2015-03-01

    We explore the entanglement-related features exhibited by the dynamics of a composite quantum system consisting of a particle and an apparatus (here referred to as the "pointer") that measures the position of the particle. We consider measurements of finite duration, and also the limit case of instantaneous measurements. We investigate the time evolution of the quantum entanglement between the particle and the pointer, with special emphasis on the final entanglement associated with the limit case of an impulsive interaction. We consider entanglement indicators based on the expectation values of an appropriate family of observables, and also an entanglement measure computed on particular exact analytical solutions of the particle-pointer Schrödinger equation. The general behavior exhibited by the entanglement indicators is consistent with that shown by the entanglement measure evaluated on particular analytical solutions of the Schrödinger equation. In the limit of instantaneous measurements the system's entanglement dynamics corresponds to that of an ideal quantum measurement process. On the contrary, we show that the entanglement evolution corresponding to measurements of finite duration departs in important ways from the behavior associated with ideal measurements. In particular, highly localized initial states of the particle lead to highly entangled final states of the particle-pointer system. This indicates that the above mentioned initial states, in spite of having an arbitrarily small position uncertainty, are not left unchanged by a finite-duration position measurement process.

  20. Modified surface loading process for achieving improved performance of the quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Jin, Zhongxiu; Zhu, Jun; Xu, Yafeng; Zhou, Li; Dai, Songyuan

    2016-06-01

    Achieving high surface coverage of the colloidal quantum dots (QDs) on TiO2 films has been challenging for quantum dot-sensitized solar cells (QDSCs). Herein, a general surface engineering approach was proposed to increase the loading of these QDs. It was found that S2- treatment/QD re-uptake process can significantly improve the attachment of the QDs on TiO2 films. Surface concentration of the QDs was improved by ∼60%, which in turn greatly enhances light absorption and decreases carrier recombination in QDSCs. Ensuing QDSCs with optimized QD loading exhibit a power conversion efficiency of 3.66%, 83% higher than those fabricated with standard procedures.

  1. Entangled coherent states versus entangled photon pairs for practical quantum-information processing

    SciTech Connect

    Park, Kimin; Jeong, Hyunseok

    2010-12-15

    We compare effects of decoherence and detection inefficiency on entangled coherent states (ECSs) and entangled photon pairs (EPPs), both of which are known to be particularly useful for quantum-information processing (QIP). When decoherence effects caused by photon losses are heavy, the ECSs outperform the EPPs as quantum channels for teleportation both in fidelities and in success probabilities. On the other hand, when inefficient detectors are used, the teleportation scheme using the ECSs suffers undetected errors that result in the degradation of fidelity, while this is not the case for the teleportation scheme using the EPPs. Our study reveals the merits and demerits of the two types of entangled states in realizing practical QIP under realistic conditions.

  2. Distribution of chirality in the quantum walk: Markov process and entanglement

    SciTech Connect

    Romanelli, Alejandro

    2010-06-15

    The asymptotic behavior of the quantum walk on the line is investigated, focusing on the probability distribution of chirality independently of position. It is shown analytically that this distribution has a longtime limit that is stationary and depends on the initial conditions. This result is unexpected in the context of the unitary evolution of the quantum walk as it is usually linked to a Markovian process. The asymptotic value of the entanglement between the coin and the position is determined by the chirality distribution. For given asymptotic values of both the entanglement and the chirality distribution, it is possible to find the corresponding initial conditions within a particular class of spatially extended Gaussian distributions.

  3. Entanglement and the process of measuring the position of a quantum particle

    SciTech Connect

    Apel, V.M.; Curilef, S.; Plastino, A.R.

    2015-03-15

    We explore the entanglement-related features exhibited by the dynamics of a composite quantum system consisting of a particle and an apparatus (here referred to as the “pointer”) that measures the position of the particle. We consider measurements of finite duration, and also the limit case of instantaneous measurements. We investigate the time evolution of the quantum entanglement between the particle and the pointer, with special emphasis on the final entanglement associated with the limit case of an impulsive interaction. We consider entanglement indicators based on the expectation values of an appropriate family of observables, and also an entanglement measure computed on particular exact analytical solutions of the particle–pointer Schrödinger equation. The general behavior exhibited by the entanglement indicators is consistent with that shown by the entanglement measure evaluated on particular analytical solutions of the Schrödinger equation. In the limit of instantaneous measurements the system’s entanglement dynamics corresponds to that of an ideal quantum measurement process. On the contrary, we show that the entanglement evolution corresponding to measurements of finite duration departs in important ways from the behavior associated with ideal measurements. In particular, highly localized initial states of the particle lead to highly entangled final states of the particle–pointer system. This indicates that the above mentioned initial states, in spite of having an arbitrarily small position uncertainty, are not left unchanged by a finite-duration position measurement process. - Highlights: • We explore entanglement features of a quantum position measurement. • We consider instantaneous and finite-duration measurements. • We evaluate the entanglement of exact time-dependent particle–pointer states.

  4. Ab initio quantum mechanical/molecular mechanical simulation of electron transfer process: Fractional electron approach

    NASA Astrophysics Data System (ADS)

    Zeng, Xiancheng; Hu, Hao; Hu, Xiangqian; Cohen, Aron J.; Yang, Weitao

    2008-03-01

    Electron transfer (ET) reactions are one of the most important processes in chemistry and biology. Because of the quantum nature of the processes and the complicated roles of the solvent, theoretical study of ET processes is challenging. To simulate ET processes at the electronic level, we have developed an efficient density functional theory (DFT) quantum mechanical (QM)/molecular mechanical (MM) approach that uses the fractional number of electrons as the order parameter to calculate the redox free energy of ET reactions in solution. We applied this method to study the ET reactions of the aqueous metal complexes Fe(H2O)62+/3+ and Ru(H2O)62+/3+. The calculated oxidation potentials, 5.82 eV for Fe(II/III) and 5.14 eV for Ru(II/III), agree well with the experimental data, 5.50 and 4.96 eV, for iron and ruthenium, respectively. Furthermore, we have constructed the diabatic free energy surfaces from histogram analysis based on the molecular dynamics trajectories. The resulting reorganization energy and the diabatic activation energy also show good agreement with experimental data. Our calculations show that using the fractional number of electrons (FNE) as the order parameter in the thermodynamic integration process leads to efficient sampling and validate the ab initio QM/MM approach in the calculation of redox free energies.

  5. Initial conditions and quantum cosmology

    NASA Technical Reports Server (NTRS)

    Hartle, James B.

    1987-01-01

    A theory of initial conditions is necessary for a complete explanation of the presently observed large scale structural features of the universe, and a quantum theory of cosmology is probably needed for its formulation. The kinematics of quantum cosmology are reviewed, and some candidates for a law of initial conditions are discussed. The proposal that the quantum state of a closed universe is the natural analog of the ground state for closed cosmologies and is specified by a Euclidean sum over histories is sketched. When implemented in simple models, this proposal is consistent with the most important large-scale observations.

  6. Spatial Implications Associated with Using Euclidean Distance Measurements and Geographic Centroid Imputation in Health Care Research

    PubMed Central

    Jones, Stephen G; Ashby, Avery J; Momin, Soyal R; Naidoo, Allen

    2010-01-01

    Objective To determine the effect of using Euclidean measurements and zip-code centroid geo-imputation versus more precise spatial analytical techniques in health care research. Data Sources Commercially insured members from a southeastern managed care organization. Study Design Distance from admitting inpatient facility to member's home and zip-code centroid (geographic placement) was compared using Euclidean straight-line and shortest-path drive distances (measurement technique). Data Collection Administrative claims from October 2005 to September 2006. Principal Findings Measurement technique had a greater impact on distance values compared with geographic placement. Drive distance from the geocoded address was highly correlated (r=0.99) with the Euclidean distance from the zip-code centroid. Conclusions Actual differences were relatively small. Researchers without capabilities to produce drive distance measurements and/or address geocoding techniques could rely on simple linear regressions to estimate correction factors with a high degree of confidence. PMID:19780852

  7. Study on very high speed Reed-Solomon decoders using modified euclidean algorithm for volume holographic storage

    NASA Astrophysics Data System (ADS)

    Wu, Fei; Xie, Changsheng; Liu, ZhaoBin

    2003-04-01

    Volume holography is currently the subject of widespread interest as a fast-readout-rate, high-capacity digital data-storage technology. However, due to the effect of cross-talk noise, scattering noise, noise gratings formed during a multiple exposure schedule, it brings a lot of burst errors and random errors in the system. Reed-Solomon error-correction codes have been widely used to protect digital data against errors. This paper presents VLSI implementations of an 16 errors correcting (255,223) Reed-Solomon decoder architecture for volume holographic storage. We describe the Reed-Solomon decoders using modified Euclidean algorithms which are regular and simple, and naturally suitable for VLSI implementations. We design the speedily multiplication for GF(28) and pipeline structure to solve hardware complexity and high data processing rate for the Reed-Solomon decoders. We adopt high speed FPGA and have a data processing rate of 200 Mbit/s.

  8. Quantum networks reveal quantum nonlocality.

    PubMed

    Cavalcanti, Daniel; Almeida, Mafalda L; Scarani, Valerio; Acín, Antonio

    2011-01-01

    The results of local measurements on some composite quantum systems cannot be reproduced classically. This impossibility, known as quantum nonlocality, represents a milestone in the foundations of quantum theory. Quantum nonlocality is also a valuable resource for information-processing tasks, for example, quantum communication, quantum key distribution, quantum state estimation or randomness extraction. Still, deciding whether a quantum state is nonlocal remains a challenging problem. Here, we introduce a novel approach to this question: we study the nonlocal properties of quantum states when distributed and measured in networks. We show, using our framework, how any one-way entanglement distillable state leads to nonlocal correlations and prove that quantum nonlocality is a non-additive resource, which can be activated. There exist states, local at the single-copy level, that become nonlocal when taking several copies of them. Our results imply that the nonlocality of quantum states strongly depends on the measurement context. PMID:21304513

  9. Generalized Thomson problem in arbitrary dimensions and non-euclidean geometries

    NASA Astrophysics Data System (ADS)

    Batle, J.; Bagdasaryan, Armen; Abdel-Aty, M.; Abdalla, S.

    2016-06-01

    Systems of identical particles with equal charge are studied under a special type of confinement. These classical particles are free to move inside some convex region S and on the boundary of it Ω (the S d - 1 -sphere, in our case). We shall show how particles arrange themselves under the sole action of the Coulomb repulsion in many dimensions in the usual Euclidean space, therefore generalizing the so called Thomson problem to many dimensions. Also, we explore how the problem varies when non-Euclidean geometries are considered. We shall see that optimal configurations in all cases possess a high degree of symmetry, regardless of the concomitant dimension or geometry.

  10. 10D to 4D Euclidean supergravity over a Calabi-Yau three-fold

    NASA Astrophysics Data System (ADS)

    Sabra, Wafic A.; Vaughan, Owen

    2016-01-01

    We dimensionally reduce the bosonic sector of 10D Euclidean type IIA supergravity over a Calabi-Yau three-fold. The resulting theory describes the bosonic sector of 4D, {N}=2 Euclidean supergravity coupled to vector- and hyper-multiplets. We show that the scalar target manifold of the vector-multiplets is projective special para-Kähler, and is therefore of split signature, whereas the target manifold of the hyper-multiplets is (positive-definite) quaternionic Kähler.

  11. UV laser beam switching system for Yb trapped ion quantum information processing

    NASA Astrophysics Data System (ADS)

    Scherer, David R.; Hensley, Joel M.; Parameswaran, Krishnan R.; Bamford, Douglas J.; Mount, Emily; Crain, Stephen; Kim, Jungsang

    2012-02-01

    Qubits based on trapped ions are being investigated as a promising platform for scalable quantum information processing. One challenge associated with the scalability of such a multi-qubit trapped ion system is the need for an ultraviolet (UV) laser beam switching and control system to independently modulate and address large qubit arrays. In this work, we propose and experimentally demonstrate a novel architecture for a laser beam control system for trapped ion quantum computing based on fast electro-optic amplitude switching and high-fidelity electromechanical beam shuttering using a microelectromechanical systems (MEMS) deflector coupled into a single-mode optical fiber. We achieve a rise/fall time of 5 ns, power extinction of -31 dB, and pulse width repeatability of > 99.95% using an electrooptic switch based on a β-BaB2O4 (BBO) Pockels cell. A tilting MEMS mirror fabricated using a commercial foundry was used to steer UV light into a single-mode optical fiber, resulting in an electromechanical beam shutter that demonstrated a power extinction of -52 dB and a switching time of 2 μs. The combination of these two technologies allows for high-fidelity power extinction using a platform that does not suffer from temperature-induced beam steering due to changes in modulation duty cycle. The overall system is capable of UV laser beam switching to create the resolved sideband Raman cooling pulses, algorithm pulses, and read-out pulses required for quantum computing applications.

  12. Combining Dynamical Decoupling with Robust Optimal Control for Improved Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Grace, Matthew D.; Witzel, Wayne M.; Carroll, Malcolm S.

    2010-03-01

    Constructing high-fidelity control pulses that are robust to control and system/environment fluctuations is a crucial objective for quantum information processing (QIP). We combine dynamical decoupling (DD) with optimal control (OC) to identify control pulses that achieve this objective numerically. Previous DD work has shown that general errors up to (but not including) third order can be removed from π- and π/2-pulses without concatenation. By systematically integrating DD and OC, we are able to increase pulse fidelity beyond this limit. Our hybrid method of quantum control incorporates a newly-developed algorithm for robust OC, providing a nested DD-OC approach to generate robust controls. Motivated by solid-state QIP, we also incorporate relevant experimental constraints into this DD-OC formalism. To demonstrate the advantage of our approach, the resulting quantum controls are compared to previous DD results in open and uncertain model systems. This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  13. Improved performance of quantum cascade lasers through a scalable, manufacturable epitaxial-side-down mounting process

    PubMed Central

    Tsekoun, Alexei; Go, Rowel; Pushkarsky, Michael; Razeghi, Manijeh; Patel, C. Kumar N.

    2006-01-01

    We report substantially improved performance of high-power quantum cascade lasers (QCLs) by using epitaxial-side-down mounting that provides superior heat dissipation properties. We used aluminum nitride as the heatsink material and gold–tin eutectic solder. We have obtained continuous wave power output of 450 mW at 20°C from mid-IR QCLs. The improved thermal management achieved with epitaxial-side-down mounting combined with a highly manufacturable and scalable assembly process should permit incorporation of mid-IR QCLs in reliable instrumentation. PMID:16547130

  14. The free energy in a class of quantum spin systems and interchange processes

    NASA Astrophysics Data System (ADS)

    Björnberg, J. E.

    2016-07-01

    We study a class of quantum spin systems in the mean-field setting of the complete graph. For spin S = 1/2, the model is the Heisenberg ferromagnet, and for general spin S ∈ 1/2 N, it has a probabilistic representation as a cycle-weighted interchange process. We determine the free energy and the critical temperature (recovering results by Tóth and by Penrose when S = 1/2). The critical temperature is shown to coincide (as a function of S) with that of the q = 2S + 1 state classical Potts model, and the phase transition is discontinuous when S ≥ 1.

  15. Microfabricated Surface-Electrode Ion Trap for Scalable Quantum Information Processing

    SciTech Connect

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

    2006-06-30

    Individual laser-cooled {sup 24}Mg{sup +} ions are confined in a linear Paul trap with a novel geometry where gold electrodes are located in a single plane and the ions are trapped 40 {mu}m above this plane. The relatively simple trap design and fabrication procedure are important for large-scale quantum information processing (QIP) using ions. Measured ion motional frequencies are compared to simulations. Measurements of ion recooling after cooling is temporarily suspended yield a heating rate of approximately 5 motional quanta per millisecond for a trap frequency of 2.83 MHz, sufficiently low to be useful for QIP.

  16. Solution of relativistic quantum optics problems using clusters of graphical processing units

    SciTech Connect

    Gordon, D.F. Hafizi, B.; Helle, M.H.

    2014-06-15

    Numerical solution of relativistic quantum optics problems requires high performance computing due to the rapid oscillations in a relativistic wavefunction. Clusters of graphical processing units are used to accelerate the computation of a time dependent relativistic wavefunction in an arbitrary external potential. The stationary states in a Coulomb potential and uniform magnetic field are determined analytically and numerically, so that they can used as initial conditions in fully time dependent calculations. Relativistic energy levels in extreme magnetic fields are recovered as a means of validation. The relativistic ionization rate is computed for an ion illuminated by a laser field near the usual barrier suppression threshold, and the ionizing wavefunction is displayed.

  17. Experimental quantum key distribution with simulated ground-to-satellite photon losses and processing limitations

    NASA Astrophysics Data System (ADS)

    Bourgoin, Jean-Philippe; Gigov, Nikolay; Higgins, Brendon L.; Yan, Zhizhong; Meyer-Scott, Evan; Khandani, Amir K.; Lütkenhaus, Norbert; Jennewein, Thomas

    2015-11-01

    Quantum key distribution (QKD) has the potential to improve communications security by offering cryptographic keys whose security relies on the fundamental properties of quantum physics. The use of a trusted quantum receiver on an orbiting satellite is the most practical near-term solution to the challenge of achieving long-distance (global-scale) QKD, currently limited to a few hundred kilometers on the ground. This scenario presents unique challenges, such as high photon losses and restricted classical data transmission and processing power due to the limitations of a typical satellite platform. Here we demonstrate the feasibility of such a system by implementing a QKD protocol, with optical transmission and full post-processing, in the high-loss regime using minimized computing hardware at the receiver. Employing weak coherent pulses with decoy states, we demonstrate the production of secure key bits at up to 56.5 dB of photon loss. We further illustrate the feasibility of a satellite uplink by generating a secure key while experimentally emulating the varying losses predicted for realistic low-Earth-orbit satellite passes at 600 km altitude. With a 76 MHz source and including finite-size analysis, we extract 3374 bits of a secure key from the best pass. We also illustrate the potential benefit of combining multiple passes together: while one suboptimal "upper-quartile" pass produces no finite-sized key with our source, the combination of three such passes allows us to extract 165 bits of a secure key. Alternatively, we find that by increasing the signal rate to 300 MHz it would be possible to extract 21 570 bits of a secure finite-sized key in just a single upper-quartile pass.

  18. Process-Dependent Properties in Colloidally Synthesized “Giant” Core/Shell Nanocrystal Quantum Dots

    SciTech Connect

    Hollingsworth, Jennifer A.; Ghosh, Yagnaseni; Dennis, Allison M.; Mangum, Benjamin D.; Park, Young-Shin; Kundu, Janardan; Htoon, Han

    2012-06-07

    Due to their characteristic bright and stable photoluminescence, semiconductor nanocrystal quantum dots (NQDs) have attracted much interest as efficient light emitters for applications from single-particle tracking to solid-state lighting. Despite their numerous enabling traits, however, NQD optical properties are frustratingly sensitive to their chemical environment, exhibit fluorescence intermittency ('blinking'), and are susceptible to Auger recombination, an efficient nonradiative decay process. Previously, we showed for the first time that colloidal CdSe/CdS core/shell nanocrystal quantum dots (NQDs) comprising ultrathick shells (number of shell monolayers, n, > 10) grown by protracted successive ionic layer adsorption and reaction (SILAR) leads to remarkable photostability and significantly suppressed blinking behavior as a function of increasing shell thickness. We have also shown that these so-called 'giant' NQDs (g-NQDs) afford nearly complete suppression of non-radiative Auger recombination, revealed in our studies as long biexciton lifetimes and efficient multiexciton emission. The unique behavior of this core/shell system prompted us to assess correlations between specific physicochemical properties - beyond shell thickness - and functionality. Here, we demonstrate the ability of particle shape/faceting, crystalline phase, and core size to determine ensemble and single-particle optical properties (quantum yield/brightness, blinking, radiative lifetimes). Significantly, we show how reaction process parameters (surface-stabilizing ligands, ligand:NQD ratio, choice of 'inert' solvent, and modifications to the SILAR method itself) can be tuned to modify these function-dictating NQD physical properties, ultimately leading to an optimized synthetic approach that results in the complete suppression of blinking. We find that the resulting 'guiding principles' can be applied to other NQD compositions, allowing us to achieve non-blinking behavior in the near

  19. Constraints on Space-Time Manifold in Euclidean Supergravity in Terms of Dirac Eigenvalues

    NASA Astrophysics Data System (ADS)

    Ciuhu, C.; Vancea, Ion V.

    We generalize a previous work on Dirac eigenvalues as dynamical variables of Euclidean supergravity. The most general set of constraints on the curvatures of the tangent bundle and on the spinor bundle of the space-time manifold, under which space-time admits Dirac eigenvalues as observables, are derived.

  20. Thinking Outside the Euclidean Box: Riemannian Geometry and Inter-Temporal Decision-Making.

    PubMed

    Mishra, Himanshu; Mishra, Arul

    2016-01-01

    Inter-temporal decisions involves assigning values to various payoffs occurring at different temporal distances. Past research has used different approaches to study these decisions made by humans and animals. For instance, considering that people discount future payoffs at a constant rate (e.g., exponential discounting) or at variable rate (e.g., hyperbolic discounting). In this research, we question the widely assumed, but seldom questioned, notion across many of the existing approaches that the decision space, where the decision-maker perceives time and monetary payoffs, is a Euclidean space. By relaxing the rigid assumption of Euclidean space, we propose that the decision space is a more flexible Riemannian space of Constant Negative Curvature. We test our proposal by deriving a discount function, which uses the distance in the Negative Curvature space instead of Euclidean temporal distance. The distance function includes both perceived values of time as well as money, unlike past work which has considered just time. By doing so we are able to explain many of the empirical findings in inter-temporal decision-making literature. We provide converging evidence for our proposal by estimating the curvature of the decision space utilizing manifold learning algorithm and showing that the characteristics (i.e., metric properties) of the decision space resembles those of the Negative Curvature space rather than the Euclidean space. We conclude by presenting new theoretical predictions derived from our proposal and implications for how non-normative behavior is defined. PMID:27018787

  1. Thinking Outside the Euclidean Box: Riemannian Geometry and Inter-Temporal Decision-Making

    PubMed Central

    2016-01-01

    Inter-temporal decisions involves assigning values to various payoffs occurring at different temporal distances. Past research has used different approaches to study these decisions made by humans and animals. For instance, considering that people discount future payoffs at a constant rate (e.g., exponential discounting) or at variable rate (e.g., hyperbolic discounting). In this research, we question the widely assumed, but seldom questioned, notion across many of the existing approaches that the decision space, where the decision-maker perceives time and monetary payoffs, is a Euclidean space. By relaxing the rigid assumption of Euclidean space, we propose that the decision space is a more flexible Riemannian space of Constant Negative Curvature. We test our proposal by deriving a discount function, which uses the distance in the Negative Curvature space instead of Euclidean temporal distance. The distance function includes both perceived values of time as well as money, unlike past work which has considered just time. By doing so we are able to explain many of the empirical findings in inter-temporal decision-making literature. We provide converging evidence for our proposal by estimating the curvature of the decision space utilizing manifold learning algorithm and showing that the characteristics (i.e., metric properties) of the decision space resembles those of the Negative Curvature space rather than the Euclidean space. We conclude by presenting new theoretical predictions derived from our proposal and implications for how non-normative behavior is defined. PMID:27018787

  2. A Vector Approach to Euclidean Geometry: Vector Spaces and Affine Geometry, Volume 1. Teacher's Edition.

    ERIC Educational Resources Information Center

    Vaughan, Herbert E.; Szabo, Steven

    This is the teacher's edition of a text for the first year of a two-year high school geometry course. The course bases plane and solid geometry and trigonometry on the fact that the translations of a Euclidean space constitute a vector space which has an inner product. Volume 1 deals largely with affine geometry, and the notion of dimension is…

  3. The Twisted Euclidean GREEN’S Function in the Spacetime of a Cosmic String

    NASA Astrophysics Data System (ADS)

    Linet, B.

    In a conical spacetime, we determine the twisted Euclidean Green’s function for a massive scalar field. In particular, we give a convenient form for studying the vacuum averages. We then derive an integral expression of the vacuum expectation value <Φ2(x)>. In the Minkowski spacetime, we express <Φ2(x)> in terms of elementary functions.

  4. Studies in Mathematics, Volume II. Euclidean Geometry Based on Ruler and Protractor Axioms. Second Revised Edition.

    ERIC Educational Resources Information Center

    Curtis, Charles W.; And Others

    These materials were developed to help high school teachers to become familiar with the approach to tenth-grade Euclidean geometry which was adopted by the School Mathematics Study Group (SMSG). It is emphasized that the materials are unsuitable as a high school textbook. Each document contains material too difficult for most high school students.…

  5. Ab-initio reconstruction of complex Euclidean networks in two dimensions

    NASA Astrophysics Data System (ADS)

    Gujarathi, S. R.; Farrow, C. L.; Glosser, C.; Granlund, L.; Duxbury, P. M.

    2014-05-01

    Reconstruction of complex structures is an inverse problem arising in virtually all areas of science and technology, from protein structure determination to bulk heterostructure solar cells and the structure of nanoparticles. We cast this problem as a complex network problem where the edges in a network have weights equal to the Euclidean distance between their endpoints. We present a method for reconstruction of the locations of the nodes of the network given only the edge weights of the Euclidean network. The theoretical foundations of the method are based on rigidity theory, which enables derivation of a polynomial bound on its efficiency. An efficient implementation of the method is discussed and timing results indicate that the run time of the algorithm is polynomial in the number of nodes in the network. We have reconstructed Euclidean networks of about 1000 nodes in approximately 24 h on a desktop computer using this implementation. We also reconstruct Euclidean networks corresponding to polymer chains in two dimensions and planar graphene nanoparticles. We have also modified our base algorithm so that it can successfully solve random point sets when the input data are less precise.

  6. Ab-initio reconstruction of complex Euclidean networks in two dimensions.

    PubMed

    Gujarathi, S R; Farrow, C L; Glosser, C; Granlund, L; Duxbury, P M

    2014-05-01

    Reconstruction of complex structures is an inverse problem arising in virtually all areas of science and technology, from protein structure determination to bulk heterostructure solar cells and the structure of nanoparticles. We cast this problem as a complex network problem where the edges in a network have weights equal to the Euclidean distance between their endpoints. We present a method for reconstruction of the locations of the nodes of the network given only the edge weights of the Euclidean network. The theoretical foundations of the method are based on rigidity theory, which enables derivation of a polynomial bound on its efficiency. An efficient implementation of the method is discussed and timing results indicate that the run time of the algorithm is polynomial in the number of nodes in the network. We have reconstructed Euclidean networks of about 1000 nodes in approximately 24 h on a desktop computer using this implementation. We also reconstruct Euclidean networks corresponding to polymer chains in two dimensions and planar graphene nanoparticles. We have also modified our base algorithm so that it can successfully solve random point sets when the input data are less precise. PMID:25353918

  7. An orbit analysis approach to the study of superintegrable systems in the Euclidean plane

    SciTech Connect

    Adlam, C. M. McLenaghan, R. G. Smirnov, R. G.

    2007-03-15

    We classify the superintegrable potentials in the Euclidean plane by means of an orbit analysis of the space of valence two Killing tensors under the action of the group of rigid motions. Our approach generalizes the classical approach of Winternitz and collaborators by considering pairs of Killing tensors that are not both in canonical form.

  8. On the sequences ri, si, ti ∈ ℤ related to extended Euclidean algorithm and continued fractions

    NASA Astrophysics Data System (ADS)

    Muhammad, Khairun Nisak; Kamarulhaili, Hailiza

    2016-06-01

    The extended Euclidean Algorithm is a practical technique used in many cryptographic applications, where it computes the sequences ri, si, ti ∈ ℤ that always satisfy ri = si a+ tib. The integer ri is the remainder in the ith sequences. The sequences si and ti arising from the extended Euclidean algorithm are equal, up to sign, to the convergents of the continued fraction expansion of a/b. The values of (ri, si, ti) satisfy various properties which are used to solve the shortest vector problem in representing point multiplications in elliptic curves cryptography, namely the GLV (Gallant, Lambert & Vanstone) integer decomposition method and the ISD (integer sub decomposition) method. This paper is to extend the proof for each of the existing properties on (ri, si, ti). We also generate new properties which are relevant to the sequences ri, si, ti ∈ ℤ. The concepts of Euclidean algorithm, extended Euclidean algorithm and continued fractions are intertwined and the properties related to these concepts are proved. These properties together with the existing properties of the sequence (ri, si, ti) are regarded as part and parcel of the building blocks of a new generation of an efficient cryptographic protocol.

  9. k-Regular maps into Euclidean spaces and the Borsuk-Boltyanskii problem

    SciTech Connect

    Bogatyi, S A

    2002-02-28

    The Borsuk-Boltyanskii problem is solved for odd k, that is, the minimum dimension of a Euclidean space is determined into which any n-dimensional polyhedron (compactum) can be k-regularly embedded. A new lower bound is obtained for even k.

  10. System of Schwinger-Dyson equations and asymptotic behavior in the Euclidean region

    SciTech Connect

    Rochev, V. E.

    2015-05-15

    A system of Schwinger-Dyson equations for the model of scalar-field interaction is studied in a deep Euclidean region. It is shown that there exists a critical coupling constant that separates the weak-coupling region characterized by the asymptotically free behavior and the strong-coupling region, where the asymptotic behavior of field propagators becomes ultralocal.

  11. Exploring the charge/energy transfer process at the graphene/giant nanocrystal quantum dots interfaces

    NASA Astrophysics Data System (ADS)

    Gao, Yongqian; Dervishi, Enkeleda; Karan, Niladri; Ghosh, Yagnaseni; Hollingsworth, Jennifer; Doorn, Stevphen; Htoon, Han

    2014-03-01

    Due to its transparency in wide spectral range and high charge mobilities, graphene has been considered to utilize as transparent electrode for nanocrystal based photo-voltaic and light emitting diodes. A detail understanding on charge/energy transfer (CT/ET) processes between zero dimensional quantum dots and 2D graphene layer hold the key in optimizing the performance of these devices. To attain this understanding, we conduct a systematic study on CT and ET processes between a graphene layer and CdSe/CdS giant nanocrystal quantum dots (g-NQD) as the function of CdS shell thickness. In addition to analyzing PL quenching and change of PL decay dynamic, we also perform 2nd order photon correlation spectroscopy studies to investigate the effect of graphene layer on dynamic and emission efficiency of g-NQDs' multi-exciton states. In case of g-NQDs over coated with a thick 16 ML CdS shell, we observed a surprising increase of multi-exciton emission efficiency.

  12. A Closer Look into the Traditional Purification Process of CdSe Semiconductor Quantum Dots.

    PubMed

    Shakeri, Behtash; Meulenberg, Robert W

    2015-12-15

    This paper describes how the postprocessing procedure for wurtzite CdSe quantum dots (QDs) 4.8 and 6.7 nm in diameter is affected by both the choice of nonsolvent and the number of processing steps. Using a host of analytical techniques (ultraviolet-visible, photoluminescence, nuclear magnetic, X-ray photoelectron, and infrared spectroscopy, as well as thermogravimetric analysis), we find that control over the ligand type and surface density can be achieved simply by the number of washing steps used during the postprocessing procedure. Using multiple washing steps we can achieve colloidally stable solutions of QDs with organic mass fractions as low as 13% by mass. For CdSe QDs passivated with trioctylphosphine oxide (TOPO) and stearic acid (SA), essentially no TOPO is bound to the particle surface after three or four washing steps, with a plateau in the amount of SA being removed. The results can be explained using the L- and X-type ligand classification system for QDs, with L-type ligands (TOPO) removed in the early processing steps but the removal of X-type (SA) ligand stalling at a large number of washing steps due to charging of the QDs. Importantly, very little change is observed in the photoluminescence (PL) properties, suggesting that the choice of nonsolvent during postprocessing will allow the production of QD materials with very low organic content by mass but with good PL quantum yields. PMID:26625188

  13. Solution-processed colloidal quantum dot photodiodes for low-cost SWIR imaging

    NASA Astrophysics Data System (ADS)

    Klem, Ethan J. D.; Lewis, Jay; Gregory, Christopher; Cunningham, Garry; Temple, Dorota

    2012-06-01

    While InGaAs-based focal plane arrays (FPAs) provide excellent detectivity and low noise for SWIR imaging applications, wider scale adoption of systems capable of working in this spectral range is limited by high costs, limited spectral response, and costly integration with Si ROIC devices. RTI has demonstrated a novel photodiode technology based on IR-absorbing solution-processed PbS colloidal quantum dots (CQD) that can overcome these limitations of InGaAs FPAs. We have fabricated devices with quantum efficiencies exceeding 50%, and detectivities that are competitive with that of InGaAs. Dark currents of ~2 nA/cm2 were measured at temperatures compatible with solid state coolers. Additionally, by processing these devices entirely at room temperature we find them to be compatible with monolithic integration onto readout ICs, thereby removing any limitation on device size. We will show early efforts towards demonstrating a direct integration of this sensor technology onto a Si ROIC IC and describe a path towards fabricating sensors sensitive from the visible to 2200 nm at a cost comparable to that of CMOS based devices. This combination of high performance, dramatic cost reduction, and multispectral sensitivity is ideally suited to expand the use of SWIR imaging in current applications, as well as to address applications which require a multispectral sensitivity not met by existing technologies.

  14. Quantum Information Processing with Ytterbium Ions and a Frequency Comb in a Surface Trap

    NASA Astrophysics Data System (ADS)

    Mount, Emily; Baek, So-Young; Gaultney, Daniel; Crain, Stephen; Noek, Rachel; Maunz, Peter; Kim, Jungsang

    2012-06-01

    Microfabricated surface ion traps are one of the key components for building a trapped ion quantum information processor.These multi-segmented traps are fabricated using existing silicon processing technology and can provide the fields to store a chain of ions and shuttle ions within the trap structure. Using a surface trap microfabricated by Sandia National Laboratories [1] we trap individual Yb-171 ions and demonstrate fundamental quantum information processing primitives. Low light scatter from the trap and the use of photon arrival times during fluorescence state detection enables a state detection fidelity of 98%. High fidelity rotations of the hyperfine clock state qubit have been performed using a resonant microwave field. Furthermore, we have realized single qubit rotations using Raman transitions driven by a repetition-rate stabilized frequency comb, a prerequisite for realizing motional gates with frequency combs [2]. Microelectromechanical systems (MEMS) mirrors will be used to focus Raman laser beams on individual ions in a chain to perform single qubit gates. MEMS beam steering systems can easily be scaled to multiple beams to realize two-ion gates between arbitrary ions in the chain.[4pt] [1] D Stick et al., arXiv:1008.0990v2 2010[0pt] [2] D Hayes et al., PRL 104(14)2010

  15. Versatile microwave-driven trapped ion spin system for quantum information processing

    PubMed Central

    Piltz, Christian; Sriarunothai, Theeraphot; Ivanov, Svetoslav S.; Wölk, Sabine; Wunderlich, Christof

    2016-01-01

    Using trapped atomic ions, we demonstrate a tailored and versatile effective spin system suitable for quantum simulations and universal quantum computation. By simply applying microwave pulses, selected spins can be decoupled from the remaining system and, thus, can serve as a quantum memory, while simultaneously, other coupled spins perform conditional quantum dynamics. Also, microwave pulses can change the sign of spin-spin couplings, as well as their effective strength, even during the course of a quantum algorithm. Taking advantage of the simultaneous long-range coupling between three spins, a coherent quantum Fourier transform—an essential building block for many quantum algorithms—is efficiently realized. This approach, which is based on microwave-driven trapped ions and is complementary to laser-based methods, opens a new route to overcoming technical and physical challenges in the quest for a quantum simulator and a quantum computer. PMID:27419233

  16. Versatile microwave-driven trapped ion spin system for quantum information processing.

    PubMed

    Piltz, Christian; Sriarunothai, Theeraphot; Ivanov, Svetoslav S; Wölk, Sabine; Wunderlich, Christof

    2016-07-01

    Using trapped atomic ions, we demonstrate a tailored and versatile effective spin system suitable for quantum simulations and universal quantum computation. By simply applying microwave pulses, selected spins can be decoupled from the remaining system and, thus, can serve as a quantum memory, while simultaneously, other coupled spins perform conditional quantum dynamics. Also, microwave pulses can change the sign of spin-spin couplings, as well as their effective strength, even during the course of a quantum algorithm. Taking advantage of the simultaneous long-range coupling between three spins, a coherent quantum Fourier transform-an essential building block for many quantum algorithms-is efficiently realized. This approach, which is based on microwave-driven trapped ions and is complementary to laser-based methods, opens a new route to overcoming technical and physical challenges in the quest for a quantum simulator and a quantum computer. PMID:27419233

  17. Aspects of nonlocality in quantum field theory, quantum gravity and cosmology

    NASA Astrophysics Data System (ADS)

    Barvinsky, A. O.

    2015-01-01

    This paper contains a collection of essays on nonlocal phenomena in quantum field theory, gravity and cosmology. Mechanisms of nonlocal contributions to the quantum effective action are discussed within the covariant perturbation expansion in field strengths and spacetime curvatures. Euclidean version of the Schwinger-Keldysh technique for quantum expectation values is presented as a special rule of obtaining the nonlocal effective equations of motion for the mean quantum field from the Euclidean effective action. This rule is applied to a new model of ghost free nonlocal cosmology which can generate the de Sitter (dS) cosmological evolution at an arbitrary value of Λ — a model of dark energy with the dynamical scale selected by a kind of a scaling symmetry breaking mechanism. This model is shown to interpolate between the superhorizon phase of a scalar mediated gravity and the short distance general relativistic limit in a special metric frame related by a nonlocal conformal transformation to the original metric.

  18. Generalized quantum Fokker-Planck equation for photoinduced nonequilibrium processes with positive definiteness condition

    NASA Astrophysics Data System (ADS)

    Jang, Seogjoo

    2016-06-01

    This work provides a detailed derivation of a generalized quantum Fokker-Planck equation (GQFPE) appropriate for photo-induced quantum dynamical processes. The path integral method pioneered by Caldeira and Leggett (CL) [Physica A 121, 587 (1983)] is extended by utilizing a nonequilibrium influence functional applicable to different baths for the ground and the excited electronic states. Both nonequilibrium and non-Markovian effects are accounted for consistently by expanding the paths in the exponents of the influence functional up to the second order with respect to time. This procedure results in approximations involving only single time integrations for the exponents of the influence functional but with additional time dependent boundary terms that have been ignored in previous works. The boundary terms complicate the derivation of a time evolution equation but do not affect position dependent physical observables or the dynamics in the steady state limit. For an effective density operator with the boundary terms factored out, a time evolution equation is derived, through short time expansion of the effective action and Gaussian integration in analytically continued complex domain of space. This leads to a compact form of the GQFPE with time dependent kernels and additional terms, which renders the resulting equation to be in the Dekker form [Phys. Rep. 80, 1 (1981)]. Major terms of the equation are analyzed for the case of Ohmic spectral density with Drude cutoff, which shows that the new GQFPE satisfies the positive definiteness condition in medium to high temperature limit. Steady state limit of the GQFPE is shown to approach the well-known expression derived by CL in the high temperature and Markovian bath limit and also provides additional corrections due to quantum and non-Markovian effects of the bath.

  19. Generalized quantum Fokker-Planck equation for photoinduced nonequilibrium processes with positive definiteness condition.

    PubMed

    Jang, Seogjoo

    2016-06-01

    This work provides a detailed derivation of a generalized quantum Fokker-Planck equation (GQFPE) appropriate for photo-induced quantum dynamical processes. The path integral method pioneered by Caldeira and Leggett (CL) [Physica A 121, 587 (1983)] is extended by utilizing a nonequilibrium influence functional applicable to different baths for the ground and the excited electronic states. Both nonequilibrium and non-Markovian effects are accounted for consistently by expanding the paths in the exponents of the influence functional up to the second order with respect to time. This procedure results in approximations involving only single time integrations for the exponents of the influence functional but with additional time dependent boundary terms that have been ignored in previous works. The boundary terms complicate the derivation of a time evolution equation but do not affect position dependent physical observables or the dynamics in the steady state limit. For an effective density operator with the boundary terms factored out, a time evolution equation is derived, through short time expansion of the effective action and Gaussian integration in analytically continued complex domain of space. This leads to a compact form of the GQFPE with time dependent kernels and additional terms, which renders the resulting equation to be in the Dekker form [Phys. Rep. 80, 1 (1981)]. Major terms of the equation are analyzed for the case of Ohmic spectral density with Drude cutoff, which shows that the new GQFPE satisfies the positive definiteness condition in medium to high temperature limit. Steady state limit of the GQFPE is shown to approach the well-known expression derived by CL in the high temperature and Markovian bath limit and also provides additional corrections due to quantum and non-Markovian effects of the bath. PMID:27276940

  20. Effect of frequency-mismatched photons in quantum-information processing

    NASA Astrophysics Data System (ADS)

    Metz, J.; Barrett, S. D.

    2008-04-01

    Many promising schemes for quantum information processing (QIP) rely on few-photon interference effects. In these proposals, the photons are treated as being indistinguishable particles. However, single photon sources are typically subject to variation from device to device. Thus the photons emitted from different sources will not be perfectly identical, and there will be some variation in their frequencies. Here, we analyze the effect of this frequency mismatch on QIP schemes. As examples, we consider the distributed QIP protocol proposed by Barrett and Kok [Phys. Rev. A 71, 060310 (2005)], and Hong-Ou-Mandel interference which lies at the heart of many linear optical schemes for quantum computing [E. Knill, R. Laflamme, and G. J. Milburn, Nature (London) 409, 46 (2001); P. Kok, W. J. Munro, K. Nemoto, T. C. Ralph, J. P. Dowling, and G. J. Milburn, Rev. Mod. Phys. 79, 135 (2007)]. In the distributed QIP protocol, we find that the fidelity of entangled qubit states depends crucially on the time resolution of single photon detectors. In particular, There is no reduction in the fidelity when an ideal detector model is assumed, while reduced fidelities may be encountered when using realistic detectors with a finite response time. We obtain similar results in the case of Hong-Ou-Mandel interference—with perfect detectors, a modified version of quantum interference is seen, and the visibility of the interference pattern is reduced as the detector time resolution is reduced. Our findings indicate that problems due to frequency mismatch can be overcome, provided sufficiently fast detectors are available.

  1. Application of Non-Kolmogorovian Probability and Quantum Adaptive Dynamics to Unconscious Inference in Visual Perception Process

    NASA Astrophysics Data System (ADS)

    Accardi, Luigi; Khrennikov, Andrei; Ohya, Masanori; Tanaka, Yoshiharu; Yamato, Ichiro

    2016-07-01

    Recently a novel quantum information formalism — quantum adaptive dynamics — was developed and applied to modelling of information processing by bio-systems including cognitive phenomena: from molecular biology (glucose-lactose metabolism for E.coli bacteria, epigenetic evolution) to cognition, psychology. From the foundational point of view quantum adaptive dynamics describes mutual adapting of the information states of two interacting systems (physical or biological) as well as adapting of co-observations performed by the systems. In this paper we apply this formalism to model unconscious inference: the process of transition from sensation to perception. The paper combines theory and experiment. Statistical data collected in an experimental study on recognition of a particular ambiguous figure, the Schröder stairs, support the viability of the quantum(-like) model of unconscious inference including modelling of biases generated by rotation-contexts. From the probabilistic point of view, we study (for concrete experimental data) the problem of contextuality of probability, its dependence on experimental contexts. Mathematically contextuality leads to non-Komogorovness: probability distributions generated by various rotation contexts cannot be treated in the Kolmogorovian framework. At the same time they can be embedded in a “big Kolmogorov space” as conditional probabilities. However, such a Kolmogorov space has too complex structure and the operational quantum formalism in the form of quantum adaptive dynamics simplifies the modelling essentially.

  2. Ultra-low-loss optical fiber cavities for applications in quantum information processing

    NASA Astrophysics Data System (ADS)

    Uphoff, Manuel; Brekenfeld, Manuel; Niemietz, Dominik; Ritter, Stephan; Rempe, Gerhard

    2016-05-01

    Single atoms strongly coupled to optical cavities are well suited as light-matter interfaces at the single photon level. The strength of the coupling is inversely proportional to the square root of the mode volume of the cavity, which depends on the radius of curvature of the mirrors. We report on the fabrication of near-spherical surfaces with small radii of curvature on the end facets of optical fibers using a CO2 laser at 9.3 μm wavelength. The surfaces are coated with a commercial, highly reflective, dielectric coating. Cavities built from two of these fibers show a finesse of up to 190000. Due to the small radii of curvature and the high finesse of these cavities, deviations from the paraxial approximation become relevant. This results in a frequency splitting of polarization eigenmodes depending on the eccentricity of the mirrors. Our analytic model that explains this effect is in excellent agreement with our measurements. This allows for the control of the frequency splitting by the geometry of the mirror surfaces. Our results confirm the great prospects of laser-machined cavities for experiments in quantum information processing. The possibility of implementing a quantum repeater node based on our cavity technologies will also be discussed.

  3. Applications of rigged Hilbert spaces in quantum mechanics and signal processing

    NASA Astrophysics Data System (ADS)

    Celeghini, E.; Gadella, M.; del Olmo, M. A.

    2016-07-01

    Simultaneous use of discrete and continuous bases in quantum systems is not possible in the context of Hilbert spaces, but only in the more general structure of rigged Hilbert spaces (RHS). In addition, the relevant operators in RHS (but not in Hilbert space) are a realization of elements of a Lie enveloping algebra and support representations of semigroups. We explicitly construct here basis dependent RHS of the line and half-line and relate them to the universal enveloping algebras of the Weyl-Heisenberg algebra and su(1, 1), respectively. The complete sub-structure of both RHS and of the operators acting on them is obtained from their algebraic structures or from the related fractional Fourier transforms. This allows us to describe both quantum and signal processing states and their dynamics. Two relevant improvements are introduced: (i) new kinds of filters related to restrictions to subspaces and/or the elimination of high frequency fluctuations and (ii) an operatorial structure that, starting from fix objects, describes their time evolution.

  4. Quantum Fluctuations and Thermodynamic Processes in the Presence of Closed Timelike Curves

    NASA Astrophysics Data System (ADS)

    Tanaka, Tsunefumi

    1997-10-01

    A closed timelike curve (CTC) is a closed loop in spacetime whose tangent vector is everywhere timelike. A spacetime which contains CTC's will allow time travel. One of these spacetimes is Grant space. It can be constructed from Minkowski space by imposing periodic boundary conditions in spatial directions and making the boundaries move toward each other. If Hawking's chronology protection conjecture is correct, there must be a physical mechanism preventing the formation of CTC's. Currently the most promising candidate for the chronology protection mechanism is the back reaction of the metric to quantum vacuum fluctuations. In this thesis the quantum fluctuations for a massive scalar field, a self-interacting field, and for a field at nonzero temperature are calculated in Grant space. The stress-energy tensor is found to remain finite everywhere in Grant space for the massive scalar field with sufficiently large field mass. Otherwise it diverges on chronology horizons like the stress-energy tensor for a massless scalar field. If CTC's exist they will have profound effects on physical processes. Causality can be protected even in the presence of CTC's if the self-consistency condition is imposed on all processes. Simple classical thermodynamic processes of a box filled with ideal gas in the presence of CTC's are studied. If a system of boxes is closed, its state does not change as it travels through a region of spacetime with CTC's. But if the system is open, the final state will depend on the interaction with the environment. The second law of thermodynamics is shown to hold for both closed and open systems. A similar problem is investigated at a statistical level for a gas consisting of multiple selves of a single particle in a spacetime with CTC's.

  5. Quantum circuit for the proof of the security of quantum key distribution without encryption of error syndrome and noisy processing

    SciTech Connect

    Tamaki, Kiyoshi; Kato, Go

    2010-02-15

    One of the simplest security proofs of quantum key distribution is based on the so-called complementarity scenario, which involves the complementarity control of an actual protocol and a virtual protocol [M. Koashi, e-print arXiv:0704.3661 (2007)]. The existing virtual protocol has a limitation in classical postprocessing, i.e., the syndrome for the error-correction step has to be encrypted. In this paper, we remove this limitation by constructing a quantum circuit for the virtual protocol. Moreover, our circuit with a shield system gives an intuitive proof of why adding noise to the sifted key increases the bit error rate threshold in the general case in which one of the parties does not possess a qubit. Thus, our circuit bridges the simple proof and the use of wider classes of classical postprocessing.

  6. Quantum cosmology with nontrivial topologies

    SciTech Connect

    Vargas, T.

    2008-10-10

    Quantum creation of a universe with a nontrivial spatial topology is considered. Using the Euclidean functional integral prescription, we calculate the wave function of such a universe with cosmological constant and without matter. The minisuperspace path integral is calculated in the semiclassical approximation, and it is shown that in order to include the nontrivial topologies in the path integral approach to quantum cosmology, it is necessary to generalize the sum over compact and smooth 4-manifolds to sum over finite-volume compact 4-orbifolds.

  7. Chemiresistive gas sensors employing solution-processed metal oxide quantum dot films

    SciTech Connect

    Liu, Huan Xu, Songman; Li, Min; Shao, Gang; Zhang, Wenkai; Wei, Wendian; He, Mingze; Song, Huaibing; Gao, Liang; Song, Haisheng; Tang, Jiang

    2014-10-20

    We report low-temperature chemiresistive gas sensors based on tin oxide colloidal quantum dots (CQDs), in which the benefits of CQDs such as extremely small crystal size, solution-processability, and tunable surface activity are exploited to enhance the gas-sensing effect. The sensor fabrication is simply employing spin-coating followed by a solid-state ligand exchange treatment at room temperature in air ambient. The optimal gas sensor exhibited rapid and significant decrease in resistance upon H{sub 2}S gas exposure when operated at 70 °C, and it was fully recoverable upon gas release. We observed a power law correlation between the sensor response and H{sub 2}S gas concentration, and the sensing mechanism was discussed using the completely depletion model with a flat band diagram.

  8. Geometrical control of the interatomic coulombic decay process in quantum dots for infrared photodetectors.

    PubMed

    Dolbundalchok, Praphasiri; Peláez, Daniel; Aziz, Emad F; Bande, Annika

    2016-09-30

    In electron dynamics calculations the interatomic Coulombic decay (ICD) process has recently been shown to take place in two vertically-aligned quantum dots (QDs). Energy emitted during the relaxation of one electron in one QD is converted into kinetic energy of another electron ejected from a neighboring QD. As the electronic structure of QDs can be controlled by their geometries, we prove here in thorough scans of the transversal and vertical QD confinement potentials' widths that geometries are likewise control parameters for ICD. Such a comprehensive investigation has been enabled by a significant development of the calculations in terms of speed achieved among others by optimization of the grid and Coulomb interaction operator representations. As key result of this study we propose two cigar-shaped singly-charged GaAs QDs vertically aligned in the direction of their long side for a most efficient QD ICD realization useful for an infrared photodetector. © 2016 Wiley Periodicals, Inc. PMID:27452332

  9. Solution-processed high-performance colloidal quantum dot tandem photodetectors on flexible substrates

    SciTech Connect

    Jiang, Zhenyu; You, Guanjun; Wang, Li; Liu, Jie; Xu, Jian; Hu, Wenjia; Zhang, Yu

    2014-08-28

    We report a high-performance colloidal quantum dot (CQD)-based near-infrared tandem photodetector fabricated on flexible substrates via solution-processed method. The tandem photodetector on poly(ethylene terephthalate) substrates exhibited low dark current and high detectivities over ∼8.8 × 10{sup 11} Jones at near infrared range at −0.5 V bias and over ∼10{sup 13} Jones near 0 bias. The critical bend radii of ∼8 mm and ∼3 mm have been demonstrated for tensile and compressive bending, respectively. The performance of photodetectors remains stable under mechanical stress, making PbSe CQD material a promise candidate for flexible infrared sensing applications.

  10. Integrated Technologies for Large-Scale Trapped-Ion Quantum Information Processing

    NASA Astrophysics Data System (ADS)

    Sorace-Agaskar, C.; Bramhavar, S.; Kharas, D.; Mehta, K. K.; Loh, W.; Panock, R.; Bruzewicz, C. D.; McConnell, R.; Ram, R. J.; Sage, J. M.; Chiaverini, J.

    2016-05-01

    Atomic ions trapped and controlled using electromagnetic fields hold great promise for practical quantum information processing due to their inherent coherence properties and controllability. However, to realize this promise, the ability to maintain and manipulate large-scale systems is required. We present progress toward the development of, and proof-of-principle demonstrations and characterization of, several technologies that can be integrated with ion-trap arrays on-chip to enable such scaling to practically useful sizes. Of particular use are integrated photonic elements for routing and focusing light throughout a chip without the need for free-space optics. The integration of CMOS electronics and photo-detectors for on-chip control and readout, and methods for monolithic fabrication and wafer-scale integration to incorporate these capabilities into tile-able 2D ion-trap array cells, are also explored.

  11. Nearly deterministic bell measurement for multiphoton qubits and its application to quantum information processing.

    PubMed

    Lee, Seung-Woo; Park, Kimin; Ralph, Timothy C; Jeong, Hyunseok

    2015-03-20

    We propose a Bell-measurement scheme by employing a logical qubit in Greenberger-Horne-Zeilinger entanglement with an arbitrary number of photons. Remarkably, the success probability of the Bell measurement as well as teleportation of the Greenberger-Horne-Zeilinger entanglement can be made arbitrarily high using only linear optics elements and photon on-off measurements as the number of photons increases. Our scheme outperforms previous proposals using single-photon qubits when comparing the success probabilities in terms of the average photon usages. It has another important advantage for experimental feasibility in that it does not require photon-number-resolving measurements. Our proposal provides an alternative candidate for all-optical quantum information processing. PMID:25839269

  12. Rare-earth doped transparent ceramics for spectral filtering and quantum information processing

    NASA Astrophysics Data System (ADS)

    Kunkel, Nathalie; Ferrier, Alban; Thiel, Charles W.; Ramírez, Mariola O.; Bausá, Luisa E.; Cone, Rufus L.; Ikesue, Akio; Goldner, Philippe

    2015-09-01

    Homogeneous linewidths below 10 kHz are reported for the first time in high-quality Eu3+ doped Y 2O3 transparent ceramics. This result is obtained on the 7F0→5D0 transition in Eu3+ doped Y 2O3 ceramics and corresponds to an improvement of nearly one order of magnitude compared to previously reported values in transparent ceramics. Furthermore, we observed spectral hole lifetimes of ˜15 min that are long enough to enable efficient optical pumping of the nuclear hyperfine levels. Additionally, different Eu3+ concentrations (up to 1.0%) were studied, resulting in an increase of up to a factor of three in the peak absorption coefficient. These results suggest that transparent ceramics can be useful in applications where narrow and deep spectral holes can be burned into highly absorbing lines, such as quantum information processing and spectral filtering.

  13. Quantum memory Quantum memory

    NASA Astrophysics Data System (ADS)

    Le Gouët, Jean-Louis; Moiseev, Sergey

    2012-06-01

    Interaction of quantum radiation with multi-particle ensembles has sparked off intense research efforts during the past decade. Emblematic of this field is the quantum memory scheme, where a quantum state of light is mapped onto an ensemble of atoms and then recovered in its original shape. While opening new access to the basics of light-atom interaction, quantum memory also appears as a key element for information processing applications, such as linear optics quantum computation and long-distance quantum communication via quantum repeaters. Not surprisingly, it is far from trivial to practically recover a stored quantum state of light and, although impressive progress has already been accomplished, researchers are still struggling to reach this ambitious objective. This special issue provides an account of the state-of-the-art in a fast-moving research area that makes physicists, engineers and chemists work together at the forefront of their discipline, involving quantum fields and atoms in different media, magnetic resonance techniques and material science. Various strategies have been considered to store and retrieve quantum light. The explored designs belong to three main—while still overlapping—classes. In architectures derived from photon echo, information is mapped over the spectral components of inhomogeneously broadened absorption bands, such as those encountered in rare earth ion doped crystals and atomic gases in external gradient magnetic field. Protocols based on electromagnetic induced transparency also rely on resonant excitation and are ideally suited to the homogeneous absorption lines offered by laser cooled atomic clouds or ion Coulomb crystals. Finally off-resonance approaches are illustrated by Faraday and Raman processes. Coupling with an optical cavity may enhance the storage process, even for negligibly small atom number. Multiple scattering is also proposed as a way to enlarge the quantum interaction distance of light with matter. The

  14. The rigorous stochastic matrix multiplication scheme for the calculations of reduced equilibrium density matrices of open multilevel quantum systems

    NASA Astrophysics Data System (ADS)

    Chen, Xin

    2014-04-01

    Understanding the roles of the temporary and spatial structures of quantum functional noise in open multilevel quantum molecular systems attracts a lot of theoretical interests. I want to establish a rigorous and general framework for functional quantum noises from the constructive and computational perspectives, i.e., how to generate the random trajectories to reproduce the kernel and path ordering of the influence functional with effective Monte Carlo methods for arbitrary spectral densities. This construction approach aims to unify the existing stochastic models to rigorously describe the temporary and spatial structure of Gaussian quantum noises. In this paper, I review the Euclidean imaginary time influence functional and propose the stochastic matrix multiplication scheme to calculate reduced equilibrium density matrices (REDM). In addition, I review and discuss the Feynman-Vernon influence functional according to the Gaussian quadratic integral, particularly its imaginary part which is critical to the rigorous description of the quantum detailed balance. As a result, I establish the conditions under which the influence functional can be interpreted as the average of exponential functional operator over real-valued Gaussian processes for open multilevel quantum systems. I also show the difference between the local and nonlocal phonons within this framework. With the stochastic matrix multiplication scheme, I compare the normalized REDM with the Boltzmann equilibrium distribution for open multilevel quantum systems.

  15. The rigorous stochastic matrix multiplication scheme for the calculations of reduced equilibrium density matrices of open multilevel quantum systems

    SciTech Connect

    Chen, Xin

    2014-04-21

    Understanding the roles of the temporary and spatial structures of quantum functional noise in open multilevel quantum molecular systems attracts a lot of theoretical interests. I want to establish a rigorous and general framework for functional quantum noises from the constructive and computational perspectives, i.e., how to generate the random trajectories to reproduce the kernel and path ordering of the influence functional with effective Monte Carlo methods for arbitrary spectral densities. This construction approach aims to unify the existing stochastic models to rigorously describe the temporary and spatial structure of Gaussian quantum noises. In this paper, I review the Euclidean imaginary time influence functional and propose the stochastic matrix multiplication scheme to calculate reduced equilibrium density matrices (REDM). In addition, I review and discuss the Feynman-Vernon influence functional according to the Gaussian quadratic integral, particularly its imaginary part which is critical to the rigorous description of the quantum detailed balance. As a result, I establish the conditions under which the influence functional can be interpreted as the average of exponential functional operator over real-valued Gaussian processes for open multilevel quantum systems. I also show the difference between the local and nonlocal phonons within this framework. With the stochastic matrix multiplication scheme, I compare the normalized REDM with the Boltzmann equilibrium distribution for open multilevel quantum systems.

  16. Spin-vibronic quantum dynamics for ultrafast excited-state processes.

    PubMed

    Eng, Julien; Gourlaouen, Christophe; Gindensperger, Etienne; Daniel, Chantal

    2015-03-17

    Ultrafast intersystem crossing (ISC) processes coupled to nuclear relaxation and solvation dynamics play a central role in the photophysics and photochemistry of a wide range of transition metal complexes. These phenomena occurring within a few hundred femtoseconds are investigated experimentally by ultrafast picosecond and femtosecond transient absorption or luminescence spectroscopies, and optical laser pump-X-ray probe techniques using picosecond and femtosecond X-ray pulses. The interpretation of ultrafast structural changes, time-resolved spectra, quantum yields, and time scales of elementary processes or transient lifetimes needs robust theoretical tools combining state-of-the-art quantum chemistry and developments in quantum dynamics for solving the electronic and nuclear problems. Multimode molecular dynamics beyond the Born-Oppenheimer approximation has been successfully applied to many small polyatomic systems. Its application to large molecules containing a transition metal atom is still a challenge because of the nuclear dimensionality of the problem, the high density of electronic excited states, and the spin-orbit coupling effects. Rhenium(I) α-diimine carbonyl complexes, [Re(L)(CO)3(N,N)](n+) are thermally and photochemically robust and highly flexible synthetically. Structural variations of the N,N and L ligands affect the spectroscopy, the photophysics, and the photochemistry of these chromophores easily incorporated into a complex environment. Visible light absorption opens the route to a wide range of applications such as sensors, probes, or emissive labels for imaging biomolecules. Halide complexes [Re(X)(CO)3(bpy)] (X = Cl, Br, or I; bpy = 2,2'-bipyridine) exhibit complex electronic structure and large spin-orbit effects that do not correlate with the heavy atom effects. Indeed, the (1)MLCT → (3)MLCT intersystem crossing (ISC) kinetics is slower than in [Ru(bpy)3](2+) or [Fe(bpy)3](2+) despite the presence of a third-row transition metal

  17. Inverting the Nakanishi Integral Relation for a Bound State Euclidean Bethe-Salpeter Amplitude

    NASA Astrophysics Data System (ADS)

    Frederico, T.; Carbonell, J.; Gigante, V.; Karmanov, V. A.

    2016-07-01

    The extraction of the weight function g of the Nakanishi integral representation of the Bethe-Salpeter amplitude is investigated. We studied the numerical inversion of the discretized Nakanishi kernel in the case of an Euclidean bound state. The discretized kernel is regularized by adding the identity operator times a small regularisation parameter {\\varepsilon} to avoid numerically unstabilities. We have found that the weight function g as well as the associated light-front valence wave function are unstable against variation of {\\varepsilon}. These results suggest that the extraction of the Nakanishi weight function from an Euclidean amplitude, is an ill-defined problem. Without further assumptions on the solution or/and without developing more elaborate methods, the Nakanishi weight function, as well as the corresponding light-front valence wave function, cannot be safely determined.

  18. A Low-Complexity Euclidean Orthogonal LDPC Architecture for Low Power Applications.

    PubMed

    Revathy, M; Saravanan, R

    2015-01-01

    Low-density parity-check (LDPC) codes have been implemented in latest digital video broadcasting, broadband wireless access (WiMax), and fourth generation of wireless standards. In this paper, we have proposed a high efficient low-density parity-check code (LDPC) decoder architecture for low power applications. This study also considers the design and analysis of check node and variable node units and Euclidean orthogonal generator in LDPC decoder architecture. The Euclidean orthogonal generator is used to reduce the error rate of the proposed LDPC architecture, which can be incorporated between check and variable node architecture. This proposed decoder design is synthesized on Xilinx 9.2i platform and simulated using Modelsim, which is targeted to 45 nm devices. Synthesis report proves that the proposed architecture greatly reduces the power consumption and hardware utilizations on comparing with different conventional architectures. PMID:26065017

  19. A Low-Complexity Euclidean Orthogonal LDPC Architecture for Low Power Applications

    PubMed Central

    Revathy, M.; Saravanan, R.

    2015-01-01

    Low-density parity-check (LDPC) codes have been implemented in latest digital video broadcasting, broadband wireless access (WiMax), and fourth generation of wireless standards. In this paper, we have proposed a high efficient low-density parity-check code (LDPC) decoder architecture for low power applications. This study also considers the design and analysis of check node and variable node units and Euclidean orthogonal generator in LDPC decoder architecture. The Euclidean orthogonal generator is used to reduce the error rate of the proposed LDPC architecture, which can be incorporated between check and variable node architecture. This proposed decoder design is synthesized on Xilinx 9.2i platform and simulated using Modelsim, which is targeted to 45 nm devices. Synthesis report proves that the proposed architecture greatly reduces the power consumption and hardware utilizations on comparing with different conventional architectures. PMID:26065017

  20. Inverting the Nakanishi Integral Relation for a Bound State Euclidean Bethe-Salpeter Amplitude

    NASA Astrophysics Data System (ADS)

    Frederico, T.; Carbonell, J.; Gigante, V.; Karmanov, V. A.

    2016-03-01

    The extraction of the weight function g of the Nakanishi integral representation of the Bethe-Salpeter amplitude is investigated. We studied the numerical inversion of the discretized Nakanishi kernel in the case of an Euclidean bound state. The discretized kernel is regularized by adding the identity operator times a small regularisation parameter {\\varepsilon} to avoid numerically unstabilities. We have found that the weight function g as well as the associated light-front valence wave function are unstable against variation of {\\varepsilon} . These results suggest that the extraction of the Nakanishi weight function from an Euclidean amplitude, is an ill-defined problem. Without further assumptions on the solution or/and without developing more elaborate methods, the Nakanishi weight function, as well as the corresponding light-front valence wave function, cannot be safely determined.

  1. Mimicking within Euclidean space a cosmological time dilation of gamma-ray burst durations

    NASA Technical Reports Server (NTRS)

    Brainerd, J. J.

    1994-01-01

    If gamma-ray burst sources are cosmological in origin, then the time dilation at large z can correlate a burst's duration with its peak flux. Detection of this effect is thought by many to be strong evidence for a cosmological burst origin. In this Letter I show that an apparent time distortion--either a dilation or contraction--is generally expected for an ensemble of bursts that is spatially limited within Euclidean space. The appearance of this effect is correlated with the falling away of the log N-log P curve from a -3/2 slope line. An example of this effect is provided by the relativistic bulk motion model, which produces a strong time dilation when spatially limited in Euclidean space. As a consequence, envidence that weak bursts have longer durations than strong bursts is not evidence of a cosmological burst origin.

  2. Recursive Double-Size Modular Multiplications from Euclidean and Montgomery Multipliers

    NASA Astrophysics Data System (ADS)

    Yoshino, Masayuki; Okeya, Katsuyuki; Vuillaume, Camille

    A technique for computing the quotient (⌊ ab/n ⌋) of Euclidean divisions from the difference of two remainders (ab (mod n) - ab (mod n+1)) was proposed by Fischer and Seifert. The technique allows a 2l-bit modular multiplication to work on most l-bit modular multipliers. However, the cost of the quotient computation rises sharply when computing modular multiplications larger than 2l bits with a recursive approach. This paper addresses the computation cost and improves on previous 2l-bit modular multiplication algorithms to return not only the remainder but also the quotient, resulting in an higher performance in the recursive approach, which becomes twice faster in the quadrupling case and four times faster in the octupling case. In addition to Euclidean multiplication, this paper proposes a new 2l-bit Montgomery multiplication algorithm to return both of the remainder and the quotient.

  3. Geometric properties of the magnetic Laplacian on the Euclidean 4-space

    SciTech Connect

    Kazmierowski, Dominique; Zinoun, Azzouz; Intissar, Ahmed

    2010-12-15

    When the four-dimensional Euclidean space is endowed with a covariant derivative that is either self-dual or antiself-dual and of constant curvature, the corresponding magnetic Laplacian is closely related to the sub-Laplacian of the quaternionic Heisenberg group. Some geometric properties of this operator are studied. In particular, it is proved that there exists a canonical orthogonal complex structure which provides a factorization in the sense of Schroedinger.

  4. A functional technique based on the Euclidean algorithm with applications to 2-D acoustic diffractal diffusers

    NASA Astrophysics Data System (ADS)

    Cortés-Vega, Luis

    2015-09-01

    We built, based on the Euclidean algorithm, a functional technique, which allows to discover a direct proof of Chinese Remainder Theorem. Afterwards, by using this functional approach, we present some applications to 2-D acoustic diffractal diffusers. The novelty of the method is their functional algorithmic character, which improves ideas, as well as, other results of the author and his collaborators in a previous work.

  5. The generalized Weierstrass system inducing surfaces of constant and nonconstant mean curvature in Euclidean three space

    NASA Astrophysics Data System (ADS)

    Bracken, Paul

    2007-05-01

    The generalized Weierstrass (GW) system is introduced and its correspondence with the associated two-dimensional nonlinear sigma model is reviewed. The method of symmetry reduction is systematically applied to derive several classes of invariant solutions for the GW system. The solutions can be used to induce constant mean curvature surfaces in Euclidean three space. Some properties of the system for the case of nonconstant mean curvature are introduced as well.

  6. Dynamics of Intraband and Interband Auger Processes in Colloidal Core-Shell Quantum Dots.

    PubMed

    Rabouw, Freddy T; Vaxenburg, Roman; Bakulin, Artem A; van Dijk-Moes, Relinde J A; Bakker, Huib J; Rodina, Anna; Lifshitz, Efrat; L Efros, Alexander; Koenderink, A Femius; Vanmaekelbergh, Daniël

    2015-10-27

    Conventional colloidal quantum dots (QDs) suffer from rapid energy losses by nonradiative (Auger) processes, leading to sub-ns lifetimes in all excited states but the lowest-energy single exciton. Suppression of interband Auger decay, such as biexciton Auger recombination, has been achieved with the design of heterostructured core-shell QDs. Auger-like processes are also believed to be responsible for rapid intraband hot-electron cooling in QDs. However, the simultaneous effect of shell growth on interband Auger recombination and intraband hot-electron cooling has not been addressed. Here we investigate how the growth of a CdS shell affects these two relaxation processes in CdSe/CdS core-shell QDs. Using a combination of ultrafast pump-push-probe spectroscopy on the QD ensemble and analysis of the photon statistics from single QDs, we find that Auger losses in the biexciton state are suppressed with increasing shell thickness, while hot-electron cooling remains unaffected. Calculations conducted within an eight-band k·p model confirm the experimental dependence of the biexciton Auger decay on the shell thickness, and provide insights into the factors determining the cooling rate of hot carriers. PMID:26389562

  7. Density-induced processes in quantum gas mixtures in optical lattices

    NASA Astrophysics Data System (ADS)

    Jürgensen, Ole; Sengstock, Klaus; Lühmann, Dirk-Sören

    2012-10-01

    We show that off-site processes and multiorbital physics have a crucial impact on the phase diagram of quantum gas mixtures in optical lattices. In particular, we discuss Bose-Fermi mixtures where the intra- and interspecies interactions induce competing density-induced hopping processes, the so-called bond-charge interactions. Furthermore, higher bands strongly influence tunneling and on-site interactions. We apply a multiorbital interaction-induced dressing of the lowest band, which leads to renormalized hopping processes. These corrections give rise to an extended Hubbard model with intrinsically occupation-dependent parameters. The resulting decrease of the tunneling competes with a decrease of the total on-site interaction energy, both affecting the critical lattice depth of the superfluid to Mott-insulator transition. In contrast to the standard Bose-Fermi Hubbard model, we predict a large shift of the transition to shallower lattice depths with increasing Bose-Fermi attraction. The applied theoretical model allows an accurate prediction of the modified tunneling amplitudes and the critical lattice depth, both being recently observed experimentally.

  8. All-solution-processed PbS quantum dot solar modules

    NASA Astrophysics Data System (ADS)

    Jang, Jihoon; Shim, Hyung Cheoul; Ju, Yeonkyeong; Song, Jung Hoon; An, Hyejin; Yu, Jong-Su; Kwak, Sun-Woo; Lee, Taik-Min; Kim, Inyoung; Jeong, Sohee

    2015-05-01

    A rapid increase in power conversion efficiencies in colloidal quantum dot (QD) solar cells has been achieved recently with lead sulphide (PbS) QDs by adapting a heterojunction architecture, which consists of small-area devices associated with a vacuum-deposited buffer layer with metal electrodes. The preparation of QD solar modules by low-cost solution processes is required to further increase the power-to-cost ratio. Herein we demonstrate all-solution-processed flexible PbS QD solar modules with a layer-by-layer architecture comprising polyethylene terephthalate (PET) substrate/indium tin oxide (ITO)/titanium oxide (TiO2)/PbS QD/poly(3-hexylthiophene) (P3HT)/poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS)/Ag, with an active area of up to 30 cm2, exhibiting a power conversion efficiency (PCE) of 1.3% under AM 1.5 conditions (PCE of 2.2% for a 1 cm2 unit cell). Our approach affords trade-offs between power and the active area of the photovoltaic devices, which results in a low-cost power source, and which is scalable to larger areas.A rapid increase in power conversion efficiencies in colloidal quantum dot (QD) solar cells has been achieved recently with lead sulphide (PbS) QDs by adapting a heterojunction architecture, which consists of small-area devices associated with a vacuum-deposited buffer layer with metal electrodes. The preparation of QD solar modules by low-cost solution processes is required to further increase the power-to-cost ratio. Herein we demonstrate all-solution-processed flexible PbS QD solar modules with a layer-by-layer architecture comprising polyethylene terephthalate (PET) substrate/indium tin oxide (ITO)/titanium oxide (TiO2)/PbS QD/poly(3-hexylthiophene) (P3HT)/poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS)/Ag, with an active area of up to 30 cm2, exhibiting a power conversion efficiency (PCE) of 1.3% under AM 1.5 conditions (PCE of 2.2% for a 1 cm2 unit cell). Our approach affords trade

  9. Time and dark matter from the conformal symmetries of Euclidean space

    NASA Astrophysics Data System (ADS)

    Hazboun, Jeffrey S.; Wheeler, James T.

    2014-11-01

    Starting with the conformal symmetries of Euclidean space, we construct a manifold where time manifests as a part of the geometry. Though there is no matter present in the geometry studied here, geometric terms analogous to dark energy and dark matter appear when we write down the Einstein tensor. Specifically, the quotient of the conformal group of Euclidean four-space by its Weyl subgroup results in a geometry possessing many of the properties of relativistic phase space, including both a natural symplectic form and non-degenerate Killing metric. We show that the general solution posesses orthogonal Lagrangian submanifolds, with the induced metric and the spin connection on the submanifolds necessarily Lorentzian, despite the Euclidean starting point. Using an orthonormal frame adapted to the phase space properties, we also find two new tensor fields not present in Riemannian geometry. The first is a combination of the Weyl vector with the scale factor on the metric, and determines the timelike directions on the submanifolds. The second comes from the components of the spin connection, symmetric with respect to the new metric. Though this field comes from the spin connection, it transforms homogeneously. Finally, we show that in the absence of Cartan curvature and sources, the configuration space has geometric terms equivalent to a perfect fluid and a cosmological constant.

  10. Euclidean Wilson loops and minimal area surfaces in lorentzian AdS 3

    NASA Astrophysics Data System (ADS)

    Irrgang, Andrew; Kruczenski, Martin

    2015-12-01

    The AdS/CFT correspondence relates Wilson loops in N=4 SYM theory to minimal area surfaces in AdS 5 × S 5 space. If the Wilson loop is Euclidean and confined to a plane ( t, x) then the dual surface is Euclidean and lives in Lorentzian AdS 3 ⊂ AdS 5. In this paper we study such minimal area surfaces generalizing previous results obtained in the Euclidean case. Since the surfaces we consider have the topology of a disk, the holonomy of the flat current vanishes which is equivalent to the condition that a certain boundary Schrödinger equation has all its solutions anti-periodic. If the potential for that Schrödinger equation is found then reconstructing the surface and finding the area become simpler. In particular we write a formula for the Area in terms of the Schwarzian derivative of the contour. Finally an infinite parameter family of analytical solutions using Riemann Theta functions is described. In this case, both the area and the shape of the surface are given analytically and used to check the previous results.

  11. Cadmium sulfide and lead sulfide quantum dots in glass: Processing, growth, and optical absorption

    NASA Astrophysics Data System (ADS)

    Rao, Pratima Gattu Naga

    Glasses containing cadmium sulfide and lead sulfide particles were prepared, and their properties were studied. These particles exhibit quantum confinement behavior when they are smaller than their Bohr exciton radii. Quantum confinement leads to size dependence in the optical absorption of particles. This size dependence can tune the optical absorption of the material to a particular wavelength or energy and possibly enhances the nonlinear optical absorption of the particles. These properties have potential applications in photonic devices. To control the growth of these semiconductor particles in glass, the glass processing conditions were studied. CdS-doped glasses were initially prepared with CdO and ZnS. The sublimation temperature for ZnS is at 1185°C; whereas, CdO sublimes at 1559°C, and CdS at 980°C. Loss of both cadmium and sulfur was observed in open crucible melts, even when CdO and ZnS were used. Improvements in glass processing were made by use of preheat and a cover during the glass melting, resulting in better retention of both dopants. Direct CdS addition to the glasses was possible with these improvements, thus eliminating complications of zinc incorporation during the growth of the semiconductor particles. These methods were successfully applied to the synthesis of PbS-doped glasses. CdS and PbS particles were grown in alkali borosilicate glasses, and their optical absorption spectra were measured as a function of heat treatment temperature and time. The position of the absorption peak and edge shifted to longer wave-lengths, or lower energies, with longer heat treatments at a constant temperature. Both CdS and PbS particles exhibited quantum confinement. These measurements were used to calculate particle sizes from quantum confinement models. Comparisons with transmission electron microscopy (TEM) demonstrated that the 1-term effective-mass approximation was appropriate for estimating CdS particle sizes. A sophisticated four-band envelope

  12. Quantum wormholes and harmonic oscillators

    NASA Technical Reports Server (NTRS)

    Garay, Luis J.

    1993-01-01

    The quantum state of a wormhole can be represented by a path integral over all asymptotically Euclidean four-geometries and all matter fields which have prescribed values, the arguments of the wave function, on a three-surface which divides the space time manifold into two disconnected parts. Minisuperspace models which consist of a homogeneous massless scalar field coupled to a Friedmann-Robertson-Walker space time are considered. Once the path integral over the lapse function is performed, the requirement that the space time be asymptotically Euclidean can be accomplished by fixing the asymptotic gravitational momentum in the remaining path integral. It is argued that there does not exist any wave function which corresponds to asymptotic field configurations such that the effective gravitational constant is negative in the asymptotic region. Then, the wormhole wave functions can be written as linear combinations of harmonic oscillator wave functions.

  13. Quantum tunneling with global charge

    SciTech Connect

    Lee, K. )

    1994-10-15

    We investigate quantum tunneling in the theory of a complex scalar field with a global U(1) symmetry when the charge density of the initial configuration does not vanish. We discuss the possible final configurations and set up the Euclidean path integral formalism to find the bubble nucleation and to study the bubble evolution. For the stationary path, or the bounce solution, in the Euclidean time, the phase variable becomes pure imaginary so that the charge density remains real. We apply this formalism to examples when the initial charge density is small. While the phase transition considered here occurs in zero temperature, the bubble dynamics is richly complicated, involving conserved charge, the sound wave, and the supersonic bubble wall.

  14. The perception of minimal structures: performance on open and closed versions of visually presented Euclidean travelling salesperson problems.

    PubMed

    Vickers, Douglas; Bovet, Pierre; Lee, Michael D; Hughes, Peter

    2003-01-01

    The planar Euclidean version of the travelling salesperson problem (TSP) requires finding a tour of minimal length through a two-dimensional set of nodes. Despite the computational intractability of the TSP, people can produce rapid, near-optimal solutions to visually presented versions of such problems. To explain this, MacGregor et al (1999, Perception 28 1417-1428) have suggested that people use a global-to-local process, based on a perceptual tendency to organise stimuli into convex figures. We review the evidence for this idea and propose an alternative, local-to-global hypothesis, based on the detection of least distances between the nodes in an array. We present the results of an experiment in which we examined the relationships between three objective measures and performance measures of optimality and response uncertainty in tasks requiring participants to construct a closed tour or an open path. The data are not well accounted for by a process based on the convex hull. In contrast, results are generally consistent with a locally focused process based initially on the detection of nearest-neighbour clusters. Individual differences are interpreted in terms of a hierarchical process of constructing solutions, and the findings are related to a more general analysis of the role of nearest neighbours in the perception of structure and motion. PMID:12974572

  15. On the Dirac eigenvalues as observables of the on-shell N = 2 D = 4 Euclidean supergravity

    NASA Astrophysics Data System (ADS)

    Vancea, Ion Vasile

    2008-12-01

    We generalize previous works on the Dirac eigenvalues as dynamical variables of Euclidean gravity and N =1 D = 4 supergravity to on-shell N = 2 D = 4 Euclidean supergravity. The covariant phase space of the theory is defined as the space of the solutions of the equations of motion modulo the on-shell gauge transformations. In this space we define the Poisson brackets and compute their value for the Dirac eigenvalues.

  16. On the Dirac eigenvalues as observables of the on-shell N = 2D = 4 Euclidean supergravity

    NASA Astrophysics Data System (ADS)

    Vancea, Ion

    2008-12-01

    We generalize previous works on the Dirac eigenvalues as dynamical variables of Euclidean gravity and N =1 D = 4 supergravity to on-shell N = 2 D = 4 Euclidean supergravity. The covariant phase space of the theory is defined as the space of the solutions of the equations of motion modulo the on-shell gauge transformations. In this space we define the Poisson brackets and compute their value for the Dirac eigenvalues.

  17. General route for the decomposition of InAs quantum dots during the capping process

    NASA Astrophysics Data System (ADS)

    González, D.; Reyes, D. F.; Utrilla, A. D.; Ben, T.; Braza, V.; Guzman, A.; Hierro, A.; Ulloa, J. M.

    2016-03-01

    The effect of the capping process on the morphology of InAs/GaAs quantum dots (QDs) by using different GaAs-based capping layers (CLs), ranging from strain reduction layers to strain compensating layers, has been studied by transmission microscopic techniques. For this, we have measured simultaneously the height and diameter in buried and uncapped QDs covering populations of hundreds of QDs that are statistically reliable. First, the uncapped QD population evolves in all cases from a pyramidal shape into a more homogenous distribution of buried QDs with a spherical-dome shape, despite the different mechanisms implicated in the QD capping. Second, the shape of the buried QDs depends only on the final QD size, where the radius of curvature is function of the base diameter independently of the CL composition and growth conditions. An asymmetric evolution of the QDs’ morphology takes place, in which the QD height and base diameter are modified in the amount required to adopt a similar stable shape characterized by a averaged aspect ratio of 0.21. Our results contradict the traditional model of QD material redistribution from the apex to the base and point to a different universal behavior of the overgrowth processes in self-organized InAs QDs.

  18. All-solution-processed PbS quantum dot solar modules.

    PubMed

    Jang, Jihoon; Shim, Hyung Cheoul; Ju, Yeonkyeong; Song, Jung Hoon; An, Hyejin; Yu, Jong-Su; Kwak, Sun-Woo; Lee, Taik-Min; Kim, Inyoung; Jeong, Sohee

    2015-05-21

    A rapid increase in power conversion efficiencies in colloidal quantum dot (QD) solar cells has been achieved recently with lead sulphide (PbS) QDs by adapting a heterojunction architecture, which consists of small-area devices associated with a vacuum-deposited buffer layer with metal electrodes. The preparation of QD solar modules by low-cost solution processes is required to further increase the power-to-cost ratio. Herein we demonstrate all-solution-processed flexible PbS QD solar modules with a layer-by-layer architecture comprising polyethylene terephthalate (PET) substrate/indium tin oxide (ITO)/titanium oxide (TiO2)/PbS QD/poly(3-hexylthiophene) (P3HT)/poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS)/Ag, with an active area of up to 30 cm(2), exhibiting a power conversion efficiency (PCE) of 1.3% under AM 1.5 conditions (PCE of 2.2% for a 1 cm(2) unit cell). Our approach affords trade-offs between power and the active area of the photovoltaic devices, which results in a low-cost power source, and which is scalable to larger areas. PMID:25907847

  19. General route for the decomposition of InAs quantum dots during the capping process.

    PubMed

    González, D; Reyes, D F; Utrilla, A D; Ben, T; Braza, V; Guzman, A; Hierro, A; Ulloa, J M

    2016-03-29

    The effect of the capping process on the morphology of InAs/GaAs quantum dots (QDs) by using different GaAs-based capping layers (CLs), ranging from strain reduction layers to strain compensating layers, has been studied by transmission microscopic techniques. For this, we have measured simultaneously the height and diameter in buried and uncapped QDs covering populations of hundreds of QDs that are statistically reliable. First, the uncapped QD population evolves in all cases from a pyramidal shape into a more homogenous distribution of buried QDs with a spherical-dome shape, despite the different mechanisms implicated in the QD capping. Second, the shape of the buried QDs depends only on the final QD size, where the radius of curvature is function of the base diameter independently of the CL composition and growth conditions. An asymmetric evolution of the QDs' morphology takes place, in which the QD height and base diameter are modified in the amount required to adopt a similar stable shape characterized by a averaged aspect ratio of 0.21. Our results contradict the traditional model of QD material redistribution from the apex to the base and point to a different universal behavior of the overgrowth processes in self-organized InAs QDs. PMID:26891164

  20. Dynamical Processes in Open Quantum Systems from a TDDFT Perspective: Resonances and Electron Photoemission.

    PubMed

    Larsen, Ask Hjorth; De Giovannini, Umberto; Rubio, Angel

    2016-01-01

    We present a review of different computational methods to describe time-dependent phenomena in open quantum systems and their extension to a density-functional framework. We focus the discussion on electron emission processes in atoms and molecules addressing excited-state lifetimes and dissipative processes. Initially we analyze the concept of an electronic resonance, a central concept in spectroscopy associated with a metastable state from which an electron eventually escapes (electronic lifetime). Resonances play a fundamental role in many time-dependent molecular phenomena but can be rationalized from a time-independent context in terms of scattering states. We introduce the method of complex scaling, which is used to capture resonant states as localized states in the spirit of usual bound-state methods, and work on its extension to static and time-dependent density-functional theory. In a time-dependent setting, complex scaling can be used to describe excitations in the continuum as well as wave packet dynamics leading to electron emission. This process can also be treated by using open boundary conditions which allow time-dependent simulations of emission processes without artificial reflections at the boundaries (i.e., borders of the simulation box). We compare in detail different schemes to implement open boundaries, namely transparent boundaries using Green functions, and absorbing boundaries in the form of complex absorbing potentials and mask functions. The last two are regularly used together with time-dependent density-functional theory to describe the electron emission dynamics of atoms and molecules. Finally, we discuss approaches to the calculation of energy and angle-resolved time-dependent pump-probe photoelectron spectroscopy of molecular systems. PMID:25860253

  1. Impacts of Post-metallisation Processes on the Electrical and Photovoltaic Properties of Si Quantum Dot Solar Cells

    PubMed Central

    2010-01-01

    As an important step towards the realisation of silicon-based tandem solar cells using silicon quantum dots embedded in a silicon dioxide (SiO2) matrix, single-junction silicon quantum dot (Si QD) solar cells on quartz substrates have been fabricated. The total thickness of the solar cell material is 420 nm. The cells contain 4 nm diameter Si quantum dots. The impacts of post-metallisation treatments such as phosphoric acid (H3PO4) etching, nitrogen (N2) gas anneal and forming gas (Ar: H2) anneal on the cells’ electrical and photovoltaic properties are investigated. The Si QD solar cells studied in this work have achieved an open circuit voltage of 410 mV after various processes. Parameters extracted from dark I–V, light I–V and circular transfer length measurement (CTLM) suggest limiting mechanism in the Si QD solar cell operation and possible approaches for further improvement. PMID:21124642

  2. Post-processing Free Quantum Random Number Generator Based on Avalanche Photodiode Array

    NASA Astrophysics Data System (ADS)

    Yang, Li; Sheng-Kai, Liao; Fu-Tian, Liang; Qi, Shen; Hao, Liang; Cheng-Zhi, Peng

    2016-03-01

    Not Available Supported by the Chinese Academy of Sciences Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, Shanghai Branch, University of Science and Technology of China, and the National Natural Science Foundation of China under Grant No 11405172.

  3. Adiabatically implementing quantum gates

    SciTech Connect

    Sun, Jie; Lu, Songfeng Liu, Fang

    2014-06-14

    We show that, through the approach of quantum adiabatic evolution, all of the usual quantum gates can be implemented efficiently, yielding running time of order O(1). This may be considered as a useful alternative to the standard quantum computing approach, which involves quantum gates transforming quantum states during the computing process.

  4. Degradation processes in high power multi-mode InGaAs strained quantum well lasers

    NASA Astrophysics Data System (ADS)

    Sin, Yongkun; Presser, Nathan; Foran, Brendan; Moss, Steven C.

    2009-02-01

    Recently, broad-area InGaAs-AlGaAs strained quantum well (QW) lasers have attracted much attention because of their unparalleled high optical output power characteristics that narrow stripe lasers or tapered lasers can not achieve. However, broad-area lasers suffer from poor beam quality and their high reliability operation has not been proven for communications applications. This paper concerns reliability and degradation aspects of broad-area lasers. Good facet passivation techniques along with optimized structural designs have led to successful demonstration of reliable 980nm single-mode lasers, and the dominant failure mode of both single-mode and broadarea lasers is catastrophic optical mirror damage (COMD), which limits maximum output powers and also determines operating output powers. Although broad-area lasers have shown characteristics unseen from singlemode lasers including filamentation, their effects on long-term reliability and degradation processes have not been fully investigated. Filamentation can lead to instantaneous increase in optical power density and thus temperature rise at localized areas through spatial-hole burning and thermal lensing which significantly reduces filament sizes under high power operation, enhancing the COMD process. We investigated degradation processes in commercial MOCVD-grown broad-area InGaAs-AlGaAs strained QW lasers at ~975nm with and without passivation layers by performing accelerated lifetests of these devices followed by failure mode analyses with various micro-analytical techniques. Since instantaneous fluctuations of filaments can lead to faster wear-out of passivation layer thus leading to facet degradation, both passivated and unpassivated broad-area lasers were studied that yielded catastrophic failures at the front facet and also in the bulk. Electron beam induced current technique was employed to study dark line defects (DLDs) generated in degraded lasers stressed under different test conditions and focused

  5. Quantum mechanical investigation on bimolecular hydrogen abstractions in butyl acrylate-based free radical polymerization processes.

    PubMed

    Mavroudakis, Evangelos; Cuccato, Danilo; Moscatelli, Davide

    2014-03-13

    The present computational study focuses on the investigation of bimolecular hydrogen abstractions that can occur during free radical polymerization (FRP) processes. In particular, several hydrogen abstractions from four monomers (butyl acrylate, BA; styrene, ST; butyl methacrylate, BMA; vinyl acetate, VA) and three different backbone chains (poly-BA, poly-BA-co-VA, and poly-BA-co-ST) have been studied. The aim is to provide an overview of the kinetics for all possible intermolecular hydrogen abstraction reactions from all chemical species present in a bulk FRP as well as to support the understanding of the influence of chemical environment on hydrogen abstractions. All simulations were performed using density functional theory (DFT) with quantum tunneling factors estimated using the Eckart model. This study provides proof that the presence of an electron donating group in the chemical environment of the abstracted hydrogen atoms can lead to lower activation energies and higher rate coefficients for abstraction whereas the presence of an electron withdrawing group leads to opposite effects. PMID:24555565

  6. Experimental progress with novel surface electrode ion trap structures for quantum information processing

    NASA Astrophysics Data System (ADS)

    Clark, Craig; Blain, Matthew; Benito, Francisco; Chou, Chin-Wen; Descour, Mike; Ellis, Rob; Haltli, Ray; Heller, Edwin; Kemme, Shanalyn; Sterk, Jon; Tabakov, Boyan; Tigges, Chris; Maunz, Peter; Stick, Daniel

    2013-05-01

    Segmented surface electrode ion traps are one of the most mature platforms among candidates for scalable quantum information processing. In this poster, an overview of current results from four specific projects will be presented. Two projects involve increased light collection from trapped ion for state detection and/or remote entangling of distant ions. The first involves cavity integration into a linear surface trap, and the second, involves integration of diffractive optical elements into a linear surface trap for increased light collection. Another project involves a trap with a ring geometry which could be used to trap long chains of equally spaced ions. Finally, we report on initial testing of a trap structure with vastly improved in-plane optical access. In this structure in-plane beams can be focused to less than 8 microns while keeping a distance of at least 5 beam radii to the trap structure. Along with these projects other relevant progress from Sandia National Laboratory's ion trap group will be presented. This work was supported by Sandia's Laboratory Directed Research and Development (LDRD) and the Intelligence Advanced Research Projects Activity (IARPA). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  7. Rare-earth doped transparent ceramics for spectral filtering and quantum information processing

    SciTech Connect

    Kunkel, Nathalie Goldner, Philippe; Ferrier, Alban; Thiel, Charles W.; Cone, Rufus L.; Ramírez, Mariola O.; Bausá, Luisa E.; Ikesue, Akio

    2015-09-01

    Homogeneous linewidths below 10 kHz are reported for the first time in high-quality Eu{sup 3+} doped Y {sub 2}O{sub 3} transparent ceramics. This result is obtained on the {sup 7}F{sub 0}→{sup 5}D{sub 0} transition in Eu{sup 3+} doped Y {sub 2}O{sub 3} ceramics and corresponds to an improvement of nearly one order of magnitude compared to previously reported values in transparent ceramics. Furthermore, we observed spectral hole lifetimes of ∼15 min that are long enough to enable efficient optical pumping of the nuclear hyperfine levels. Additionally, different Eu{sup 3+} concentrations (up to 1.0%) were studied, resulting in an increase of up to a factor of three in the peak absorption coefficient. These results suggest that transparent ceramics can be useful in applications where narrow and deep spectral holes can be burned into highly absorbing lines, such as quantum information processing and spectral filtering.

  8. Quantum processes in 8-Oxo-Guanine-Ru(bipyridine)32+ photosynthetic systems of artificial minimal cells

    NASA Astrophysics Data System (ADS)

    Tamulis, Arvydas; Grigalavicius, Mantas; Krisciukaitis, Sarunas; Medzevicius, Giedrius

    2011-06-01

    Density functional theory methods were used to investigate various self-assembled photoactive bioorganic systems of interest for artificial minimal cells. The cell systems studied are based on nucleotides or their compounds and consisted of up to 123 atoms (not including the associated water or methanol solvent shells) and are up to 2.5 nm in diameter. The electron correlation interactions responsible for the weak hydrogen and Van derWaals chemical bonds increase due to the addition of a polar solvent (water or methanol). The precursor fatty acid molecules of the system also play a critical role in the quantum mechanical interaction based self-assembly of the photosynthetic center and the functioning of the photosynthetic processes of the artificial minimal cells. The distances between the separated sensitizer, fatty acid precursor, and methanol molecules are comparable to Van derWaals and hydrogen bonding radii. As a result the associated electron correlation interactions compress the overall system, resulting in an even smaller gap between the highest occupied molecular orbital (HOMO), and lowest unoccupied molecular orbital (LUMO) electron energy levels and photoexcited electron tunnelling occurs from the sensitizer (either Ru(bpy)32+ or [Ru(bpy)2(4-Bu-4'-Me-2,2'-bpy)]2++ derivatives) to the precursor fatty acid molecules (notation used: Me = methyl; Bu = butyl; bpy = bipyridine). The shift of the absorption spectrum to the red for the artificial protocell photosynthetic centers might be considered as the measure of the complexity of these systems.

  9. Coupled-channels quantum theory of electronic flux density in electronically adiabatic processes: fundamentals.

    PubMed

    Diestler, D J

    2012-03-22

    The Born-Oppenheimer (BO) description of electronically adiabatic molecular processes predicts a vanishing electronic flux density (j(e)), =1/2∫dR[Δ(b) (x;R) - Δ(a) (x;R)] even though the electrons certainly move in response to the movement of the nuclei. This article, the first of a pair, proposes a quantum-mechanical "coupled-channels" (CC) theory that allows the approximate extraction of j(e) from the electronically adiabatic BO wave function . The CC theory is detailed for H(2)(+), in which case j(e) can be resolved into components associated with two channels α (=a,b), each of which corresponds to the "collision" of an "internal" atom α (proton a or b plus electron) with the other nucleus β (proton b or a). The dynamical role of the electron, which accommodates itself instantaneously to the motion of the nuclei, is submerged in effective electronic probability (population) densities, Δ(α), associated with each channel (α). The Δ(α) densities are determined by the (time-independent) BO electronic energy eigenfunction, which depends parametrically on the configuration of the nuclei, the motion of which is governed by the usual BO nuclear Schrödinger equation. Intuitively appealing formal expressions for the electronic flux density are derived for H(2)(+). PMID:22103768

  10. Measurement-driven reconstruction of many-particle quantum processes by semidefinite programming with application to photosynthetic light harvesting

    NASA Astrophysics Data System (ADS)

    Foley, Jonathan J., IV; Mazziotti, David A.

    2012-07-01

    Quantum measurements provide a trove of information about a quantum system or process without solution of the Schrödnger equation, and in principle, the associated density matrix is a function of these measurements. Inversion of the measurements can produce an estimate of the density matrix, but this estimate may be unphysical, especially when the measurements are noisy or incomplete. We develop a general approach based on semidefinite programming [D. A. Mazziotti, Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.106.083001 106, 083001 (2011)] for reconstructing the density matrix from quantum measurements which leads naturally to nonnegative solutions, a critical attribute of physically realistic solutions. We discuss the use of this methodology for reconstructing p-particle reduced density matrices (p-RDMs) of N-particle systems where additional semidefinite constraints, known as N-representability conditions, are essential because they ensure that the p-RDM represents an N-particle system. Special attention is given to the N-representability conditions for the experimentally important cases where p=1 or 2. We apply the methodology to reconstructing the time-dependent quantum process of exciton transfer in a photosynthetic light-harvesting complex.

  11. The Colloidal Stabilization of Quantum Dots: Towards Manufacturable, Efficient Solution-Processed Solar Cells

    NASA Astrophysics Data System (ADS)

    Rollny, Lisa

    Understanding colloidal stabilization can influence the design of optoelectronic devices and enable improvements to their performance and stability. For photovoltaics, important characteristics of the active layer material are high conductivity along with a minimum of recombination centers. In order to capitalize on the benefits of solution-processed materials, it is important to minimize the number of processing steps: ideally, to achieve a low-cost solution, materials would be deposited using a single process step compatible with roll-to-roll manufacturing. Prior to this work, the highest-performing colloidal quantum dots (CQD) solar cells have relied on several deposition steps that are repeated in a layer-by-layer (LBL) fashion. The purpose of these process steps has been to remove the long insulating ligands used in synthesis and replace them with short ligands that allow electrical conduction. The large number of steps combined, typically implemented via spin coating, leads to inefficient materials utilization and fails to show a path to a manufacturable solution. In this work, the first CQD solar cells were designed, built, and characterized combining state-of-art performance with scalable manufacture. Firstly, I report the first automated CQD synthesis to result in CQDs that form high-performance CQD solar cells. I analyze the CQD synthesis and by separating it into two phases---nucleation and growth phase---my insights are used to create higher-quality CQDs exhibiting enhanced monodispersity. I then proceed to develop a CQD ink: a CQD solution ready for direct deposition to form a semiconducting film exhibiting low trap state density. In early trials the CQD ink showed only limited power conversion efficiencies of 2%. I designed a new ink strategy, which I term cleavable hemiketal ligands. This novel two-component ligand strategy enables the combination of colloidal stabilization (via this longer two-component ligand) and cleavability (enabling excellent

  12. Relation between Darboux and type-2 Bishop frames in Euclidean space

    NASA Astrophysics Data System (ADS)

    Yilmaz, Amine; Özyilmaz, Emin

    2016-06-01

    In this work, we investigate relationships between Darboux and type-2 Bishop frames in Euclidean space. Then, we obtain the geodesic curvature of the spherical image curve of the Darboux vector of the type-2 Bishop frame. Also, we give transition matrix between the Darboux and type-2 Bishop frames of the type-2 Bishop frames of the spherical images of the edges N→1,N→2 and b→. Finally, we express some interesting relations and illustrate of the examples by the aid Maple programe.

  13. On Local Constraints of D=4 Euclidean Supergravity in Terms of Dirac Eigenvalues

    NASA Astrophysics Data System (ADS)

    Pauna, N.; Vancea, Ion V.

    It has recently been shown that in order to have Dirac eigenvalues as observables of Euclidean supergravity, certain constraints should be imposed on the covariant phase space as well as on Dirac eigenspinors. We investigate the relationships among the constraints in the first set and argue that these relationships are not linear. We also derive a set of equations that should be satisfied by some arbitrary functions that enter as coefficients in the equation expressing the linear dependency of the constraints in order that the second set of constraints be linearly independent.

  14. Dynamics of Euclideanized Einstein-Yang-Mills systems with arbitrary gauge groups

    SciTech Connect

    Bertolami, O.; Picken, R.F. ); Maurao, J.M. ); Volobujev, I.P. )

    1991-09-30

    This paper describes the dynamics of euclideanized SO(4)-symmetric Einstein-Yang-Mills (EYM) systems with arbitrary compact gauge groups K. For the case of SO(n) and SU(n) gauge groups and simple embeddings of the isotropy group in K, the authors show that in the resulting dynamical system, the Friedmann equation decouples from the Yang-Mills equations. Furthermore, the latter can be reduced to a system of two second-order differential equations. This allows the authors to find a broad class of instanton (wormhole) solutions of the EYM equations. These solutions are not afflicted by the giant-wormhole catastrophe.

  15. Emergence of Euclidean dynamical symmetry as a consequence of shape phase mixing

    NASA Astrophysics Data System (ADS)

    Budaca, R.; Budaca, A. I.

    2016-08-01

    A hybrid model which combines γ-stable and γ-rigid collective conditions through a rigidity parameter, is used to study the critical point of the phase transition between spherical and axially symmetric shapes. The model in the equally mixed case, called X (4), exhibits properties of the Euclidean symmetry in four dimensions. The spectral properties of the new model are investigated in connection to the exact symmetry. Experimental realisation of the X (4) model is found in two N = 90 nuclei and two Pt isotopes in vicinity of experimentally observed critical point.

  16. Euclidean Dynamical Triangulation revisited: is the phase transition really 1st order?

    NASA Astrophysics Data System (ADS)

    Rindlisbacher, Tobias; de Forcrand, Philippe

    2015-05-01

    The transition between the two phases of 4D Euclidean Dynamical Triangulation [1] was long believed to be of second order until in 1996 first order behavior was found for sufficiently large systems [5, 9]. However, one may wonder if this finding was affected by the numerical methods used: to control volume fluctuations, in both studies [5, 9] an artificial harmonic potential was added to the action and in [9] measurements were taken after a fixed number of accepted instead of attempted moves which introduces an additional error. Finally the simulations suffer from strong critical slowing down which may have been underestimated.

  17. On the measure of conformal difference between Euclidean and Lobachevsky spaces

    NASA Astrophysics Data System (ADS)

    Zorich, Vladimir A.

    2011-12-01

    Euclidean space R^n and Lobachevsky space H^n are known to be not equivalent either conformally or quasiconformally. In this work we give exact asymptotics of the critical order of growth at infinity for the quasiconformality coefficient of a diffeomorphism f\\colon R^n\\to H^n for which such a mapping f is possible. We also consider the general case of immersions f\\colon M^n\\to N^n of conformally parabolic Riemannian manifolds. Bibliography: 17 titles.

  18. Spontaneous PT-Symmetry Breaking for Systems of Noncommutative Euclidean Lie Algebraic Type

    NASA Astrophysics Data System (ADS)

    Dey, Sanjib; Fring, Andreas; Mathanaranjan, Thilagarajah

    2015-11-01

    We propose a noncommutative version of the Euclidean Lie algebra E 2. Several types of non-Hermitian Hamiltonian systems expressed in terms of generic combinations of the generators of this algebra are investigated. Using the breakdown of the explicitly constructed Dyson maps as a criterium, we identify the domains in the parameter space in which the Hamiltonians have real energy spectra and determine the exceptional points signifying the crossover into the different types of spontaneously broken PT-symmetric regions with pairs of complex conjugate eigenvalues. We find exceptional points which remain invariant under the deformation as well as exceptional points becoming dependent on the deformation parameter of the algebra.

  19. Beat note stabilization of mode-locked lasers for quantum information processing.

    PubMed

    Islam, R; Campbell, W C; Choi, T; Clark, S M; Conover, C W S; Debnath, S; Edwards, E E; Fields, B; Hayes, D; Hucul, D; Inlek, I V; Johnson, K G; Korenblit, S; Lee, A; Lee, K W; Manning, T A; Matsukevich, D N; Mizrahi, J; Quraishi, Q; Senko, C; Smith, J; Monroe, C

    2014-06-01

    We stabilize a chosen radio frequency beat note between two optical fields derived from the same mode-locked laser pulse train in order to coherently manipulate quantum information. This scheme does not require access or active stabilization of the laser repetition rate. We implement and characterize this external lock, in the context of two-photon stimulated Raman transitions between the hyperfine ground states of trapped 171Yb(+) quantum bits. PMID:24876022

  20. Quantum Correlations and the Measurement Problem

    NASA Astrophysics Data System (ADS)

    Bub, Jeffrey

    2014-10-01

    The transition from classical to quantum mechanics rests on the recognition that the structure of information is not what we thought it was: there are operational, i.e., phenomenal, probabilistic correlations that lie outside the polytope of local correlations. Such correlations cannot be simulated with classical resources, which generate classical correlations represented by the points in a simplex, where the vertices of the simplex represent joint deterministic states that are the common causes of the correlations. The `no go' hidden variable theorems tell us that we can't shoe-horn phenomenal correlations outside the local polytope into a classical simplex by supposing that something has been left out of the story. The replacement of the classical simplex by the quantum convex set as the structure representing probabilistic correlations is the analogue for quantum mechanics of the replacement of Newton's Euclidean space and time by Minkowski spacetime in special relativity. The nonclassical features of quantum mechanics, including the irreducible information loss on measurement, are generic features of correlations that lie outside the classical simplex. This paper is an elaboration of these ideas, which have their source in work by Pitowsky (J. Math. Phys. 27:1556, 1986; Math. Program. 50:395, 1991; Phys. Rev. A 77:062109, 2008), Garg and Mermin (Found. Phys. 14:1-39, 1984), Barrett (Phys. Rev. A 75:032304, 2007; Phys. Rev. A 7:022101, 2005) and others, e.g., Brunner et al. (arXiv:1303.2849, 2013), but the literature goes back to Boole (An Investigation of the Laws of Thought, Dover, New York, 1951). The final section looks at the measurement problem of quantum mechanics in this context. A large part of the problem is removed by seeing that the inconsistency in reconciling the entangled state at the end of a quantum measurement process with the definiteness of the macroscopic pointer reading and the definiteness of the correlated value of the measured micro

  1. Classical and Quantum Wormholes in a Flat Λ-Decaying Cosmology

    NASA Astrophysics Data System (ADS)

    Darabi, F.

    2009-04-01

    We study the classical and quantum wormholes for a flat Euclidean Friedmann-Robertson-Walker metric with a perfect fluid including an ordinary matter source plus a source playing the role of dark energy (decaying cosmological term). It is shown that classical wormholes exist for this model and the quantum version of such wormholes are consistent with the Hawking-Page conjecture for quantum wormholes as solutions of the Wheeler-DeWitt equation.

  2. Relaxation times of the two-phonon processes with spin-flip and spin-conserving in quantum dots

    SciTech Connect

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

    2014-04-07

    We perform a theoretical investigation on the two-phonon processes of the spin-flip and spin-conserving relaxation in quantum dots in the frame of the Huang-Rhys' lattice relaxation model. We find that the relaxation time of the spin-flip is two orders of magnitude longer than that of the spin-conserving, which is in agreement with previous experimental measurements. Moreover, the opposite variational trends of the relaxation time as a function of the energy separation for two-phonon processes are obtained in different temperature regime. The relaxation times display the oscillatory behaviors at the demarcation point with increasing magnetic field, where the energy separation matches the optical phonon energy and results in the optical phonon resonance. These results are useful in understanding the intraband levels' relaxation in quantum dots and could be helpful in designing photoelectric and spin-memory devices.

  3. Quantum Discord as a Resource in Quantum Communication

    NASA Astrophysics Data System (ADS)

    Madhok, Vaibhav; Datta, Animesh

    2013-01-01

    As quantum technologies move from the issues of principle to those of practice, it is important to understand the limitations on attaining tangible quantum advantages. In the realm of quantum communication, quantum discord captures the damaging effects of a decoherent environment. This is a consequence of quantum discord quantifying the advantage of quantum coherence in quantum communication. This establishes quantum discord as a resource for quantum communication processes. We discuss this progress, which derives a quantitative relation between the yield of the fully quantum Slepian-Wolf (FQSW) protocol in the presence of noise and the quantum discord of the state involved. The significance of quantum discord in noisy versions of teleportation, super-dense coding, entanglement distillation and quantum state merging are discussed. These results lead to open questions regarding the tradeoff between quantum entanglement and discord in choosing the optimal quantum states for attaining palpable quantum advantages in noisy quantum protocols.

  4. Quantum Discord as a Resource in Quantum Communication

    NASA Astrophysics Data System (ADS)

    Madhok, Vaibhav; Datta, Animesh

    2012-06-01

    As quantum technologies move from the issues of principle to those of practice, it is important to understand the limitations on attaining tangible quantum advantages. In the realm of quantum communication, quantum discord captures the damaging effects of a decoherent environment. This is a consequence of quantum discord quantifying the advantage of quantum coherence in quantum communication. This establishes quantum discord as a resource for quantum communication processes. We discuss this progress, which derives a quantitative relation between the yield of the fully quantum Slepian-Wolf (FQSW) protocol in the presence of noise and the quantum discord of the state involved. The significance of quantum discord in noisy versions of teleportation, super-dense coding, entanglement distillation and quantum state merging are discussed. These results lead to open questions regarding the tradeoff between quantum entanglement and discord in choosing the optimal quantum states for attaining palpable quantum advantages in noisy quantum protocols.

  5. Quantum Chemistry for Solvated Molecules on Graphical Processing Units Using Polarizable Continuum Models.

    PubMed

    Liu, Fang; Luehr, Nathan; Kulik, Heather J; Martínez, Todd J

    2015-07-14

    The conductor-like polarization model (C-PCM) with switching/Gaussian smooth discretization is a widely used implicit solvation model in chemical simulations. However, its application in quantum mechanical calculations of large-scale biomolecular systems can be limited by computational expense of both the gas phase electronic structure and the solvation interaction. We have previously used graphical processing units (GPUs) to accelerate the first of these steps. Here, we extend the use of GPUs to accelerate electronic structure calculations including C-PCM solvation. Implementation on the GPU leads to significant acceleration of the generation of the required integrals for C-PCM. We further propose two strategies to improve the solution of the required linear equations: a dynamic convergence threshold and a randomized block-Jacobi preconditioner. These strategies are not specific to GPUs and are expected to be beneficial for both CPU and GPU implementations. We benchmark the performance of the new implementation using over 20 small proteins in solvent environment. Using a single GPU, our method evaluates the C-PCM related integrals and their derivatives more than 10× faster than that with a conventional CPU-based implementation. Our improvements to the linear solver provide a further 3× acceleration. The overall calculations including C-PCM solvation require, typically, 20-40% more effort than that for their gas phase counterparts for a moderate basis set and molecule surface discretization level. The relative cost of the C-PCM solvation correction decreases as the basis sets and/or cavity radii increase. Therefore, description of solvation with this model should be routine. We also discuss applications to the study of the conformational landscape of an amyloid fibril. PMID:26575750

  6. Facial expression recognition based on image Euclidean distance-supervised neighborhood preserving embedding

    NASA Astrophysics Data System (ADS)

    Chen, Li; Li, Yingjie; Li, Haibin

    2014-11-01

    High-dimensional data often lie on relatively low-dimensional manifold, while the nonlinear geometry of that manifold is often embedded in the similarities between the data points. These similar structures are captured by Neighborhood Preserving Embedding (NPE) effectively. But NPE as an unsupervised method can't utilize class information to guide the procedure of nonlinear dimensionality reduction. They ignore the geometrical structure information of local data points and the spatial information of pixels, which leads to the failure of classification. For this problem, a feature extraction method based on Image Euclidean Distance-Supervised NPE (IED-SNPE) is proposed, and is applied to facial expression recognition. Firstly, it employs Image Euclidean Distance (IED) to characterize the dissimilarity of data points. And then the neighborhood graph of the input data is constructed according to a certain kind of dissimilarity between data points. Finally, it fuses prior nonlinear facial expression manifold of facial expression images and class-label information to extract discriminative features for expression recognition. In the classification experiments on JAFFE facial expression database, IED-SNPE is used for feature extraction and compared with NPE, SNPE, and IED-NPE. The results reveal that IED-SNPE not only the local structure of expression manifold preserves well but also explicitly considers the spatial relationships among pixels in the images. So it excels NPE in feature extraction and is highly competitive with those well-known feature extraction methods.

  7. A model of quantum communication device for quantum hashing

    NASA Astrophysics Data System (ADS)

    Vasiliev, A.

    2016-02-01

    In this paper we consider a model of quantum communications between classical computers aided with quantum processors, connected by a classical and a quantum channel. This type of communications implying both classical and quantum messages with moderate use of quantum processing is implicitly used in many quantum protocols, such as quantum key distribution or quantum digital signature. We show that using the model of a quantum processor on multiatomic ensembles in the common QED cavity we can speed up quantum hashing, which can be the basis of quantum digital signature and other communication protocols.

  8. Surface processing with sulfonic acid for quantum dot and its characteristics

    NASA Astrophysics Data System (ADS)

    Shiohara, Amane; Manabe, Noriyoshi; Yamamoto, Kenji

    2006-02-01

    We developed the smaller sized quantum dots covered with sodium 2-mercaptoethanesulfonate which has a sulfonyl group (QDs-SO 3-), and compared its stability in acid, salt and buffer solutions with that of the quantum dots covered with the mercaptoundecanoic acid (QDs-MUA) and covered with the NH II group (QDs-NH II). We found that the QD-SO 3- well disperses in these solutions without quenching and this stability holds on 24 hours. Next, we observed the cell damage caused by the quantum dots. In the evaluation of cell damage, QD-SO 3- did not show noticeable cell damage in the 0.2mg/mL by the comet assay as well as QD-MUA and QD-NH II in the same concentration. All these results could suggest that SO 3- might be useful for the biomedical engineering.

  9. Simulation of the Burgers equation by NMR quantum-information processing

    SciTech Connect

    Chen Zhiying; Cory, David G.; Yepez, Jeffrey

    2006-10-15

    We report on the implementation of Burgers equation as a type-II quantum computation on a NMR quantum-information processor. Since the flow field evolving under the Burgers equation develops sharp features over time, this is a better test of liquid-state NMR implementations of type-II quantum computers than the previous examples using the diffusion equation. In particular, we show that Fourier approximations used in the encoding step are not the dominant error. Small systematic errors in the collision operator accumulate and swamp all other errors. We propose, and demonstrate, that the accumulation of this error can be avoided to a large extent by replacing the single collision operator with a set of operators with random errors and similar fidelities. Experiments have been implemented on 16 two-qubit sites for eight successive time steps for the Burgers equation.

  10. 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."

  11. Microscopic Modeling of Intersubband Optical Processes in Type II Semiconductor Quantum Wells: Linear Absorption

    NASA Technical Reports Server (NTRS)

    Li, Jian-Zhong; Kolokolov, Kanstantin I.; Ning, Cun-Zheng

    2003-01-01

    Linear absorption spectra arising from intersubband transitions in semiconductor quantum well heterostructures are analyzed using quantum kinetic theory by treating correlations to the first order within Hartree-Fock approximation. The resulting intersubband semiconductor Bloch equations take into account extrinsic dephasing contributions, carrier-longitudinal optical phonon interaction and carrier-interface roughness interaction which is considered with Ando s theory. As input for resonance lineshape calculation, a spurious-states-free 8-band kp Hamiltonian is used, in conjunction with the envelop function approximation, to compute self-consistently the energy subband structure of electrons in type II InAs/AlSb single quantum well structures. We demonstrate the interplay of nonparabolicity and many-body effects in the mid-infrared frequency range for such heterostructures.

  12. Coupled-Trajectory Quantum-Classical Approach to Electronic Decoherence in Nonadiabatic Processes

    NASA Astrophysics Data System (ADS)

    Min, Seung Kyu; Agostini, Federica; Gross, E. K. U.

    2015-08-01

    We present a novel quantum-classical approach to nonadiabatic dynamics, deduced from the coupled electronic and nuclear equations in the framework of the exact factorization of the electron-nuclear wave function. The method is based on the quasiclassical interpretation of the nuclear wave function, whose phase is related to the classical momentum and whose density is represented in terms of classical trajectories. In this approximation, electronic decoherence is naturally induced as an effect of the coupling to the nuclei and correctly reproduces the expected quantum behavior. Moreover, the splitting of the nuclear wave packet is captured as a consequence of the correct approximation of the time-dependent potential of the theory. This new approach offers a clear improvement over Ehrenfest-like dynamics. The theoretical derivation presented in this Letter is supported by numerical results that are compared to quantum mechanical calculations.

  13. A Quantum-BDI Model for Information Processing and Decision Making

    NASA Astrophysics Data System (ADS)

    Bisconti, Cristian; Corallo, Angelo; Fortunato, Laura; Gentile, Antonio A.

    2015-02-01

    This work aims to develop a novel BDI agent programming framework, which embeds the reasoning under uncertainty (probabilistic logic) and is capable of a realistic simulation of human reasoning. We claim that such a development can be addressed through the adoption of the mathematical and logical formalism derived from Quantum Mechanics: a scheme fulfilling the necessary requirements is described, useful for both the interpretation of some peculiarities in human behavior, and eventually the adoption of `quantum computing' formalism for the agent programming. This last possibility could exploit the power of quantum parallelism in practical reasoning applications. Integration with the BDI paradigm enables the straightforward adoption of efficient learning algorithms and procedures, enhancing the behavior and adaptation of the agent to the environment.

  14. Isotropic loop quantum cosmology with matter. II. The Lorentzian constraint

    NASA Astrophysics Data System (ADS)

    Hinterleitner, Franz; Major, Seth

    2003-12-01

    The Lorentzian Hamiltonian constraint is solved for isotropic loop quantum cosmology coupled to a massless scalar field. As in the Euclidean case, the discreteness of quantum geometry removes the classical singularity from the quantum Friedmann models. In spite of the absence of the classical singularity, a modified DeWitt initial condition is incompatible with a late-time smooth behavior. Further, the smooth behavior is recovered only for positive or negatives times but not both. An important feature, which is shared with the Euclidean case, is a minimal initial energy of the order of the Planck energy required for the system to evolve dynamically. By forming wave packets of the matter field, an explicit evolution in terms of an internal time is obtained.

  15. A simplified procedure for correcting both errors and erasures of a Reed-Solomon code using the Euclidean algorithm

    NASA Technical Reports Server (NTRS)

    Truong, T. K.; Hsu, I. S.; Eastman, W. L.; Reed, I. S.

    1987-01-01

    It is well known that the Euclidean algorithm or its equivalent, continued fractions, can be used to find the error locator polynomial and the error evaluator polynomial in Berlekamp's key equation needed to decode a Reed-Solomon (RS) code. A simplified procedure is developed and proved to correct erasures as well as errors by replacing the initial condition of the Euclidean algorithm by the erasure locator polynomial and the Forney syndrome polynomial. By this means, the errata locator polynomial and the errata evaluator polynomial can be obtained, simultaneously and simply, by the Euclidean algorithm only. With this improved technique the complexity of time domain RS decoders for correcting both errors and erasures is reduced substantially from previous approaches. As a consequence, decoders for correcting both errors and erasures of RS codes can be made more modular, regular, simple, and naturally suitable for both VLSI and software implementation. An example illustrating this modified decoding procedure is given for a (15, 9) RS code.

  16. Quantum information processing with defect spins in diamond and silicon carbide

    NASA Astrophysics Data System (ADS)

    Koehl, William

    2012-02-01

    Many proposals for quantum information technologies require quantum systems that can be easily manipulated by an outside observer, while remaining largely unaffected by destructive interactions with the surrounding environment. One system that matches this description is a defect in the crystal lattice of diamond known as the nitrogen-vacancy (NV) center. Electrons trapped at this defect form an atomic scale spin state that can be used as an individually addressable, solid state quantum bit (qubit) even at room temperature. The exceptional quantum properties of the diamond NV have motivated recent efforts to search for similar defects in other semiconductors, as these would expand the technological opportunities available to defect-based quantum systems [1]. We discuss these efforts, which make use of techniques from both computational materials science and experimental quantum physics, focusing on explorations of the 4H polytype of silicon carbide (4H-SiC). In particular, we present recent experimental results that identify several defect spin states in 4H-SiC that function as analogs to the diamond NV. Using optical and microwave techniques similar to those used with diamond NV qubits, the spins of these defects can be optically addressed and coherently controlled in the time domain at temperatures ranging from 20 -- 300 K. Additionally, these defects are optically active near telecom wavelengths, inhabit a host material for which there already exist industrial scale crystal growth and advanced microfabrication techniques, and possess desirable spin coherence properties comparable to those of the diamond NV. This makes them promising candidates for various photonic, spintronic, and quantum information applications that merge quantum degrees of freedom with classical electronic and optical technologies [2]. [1] J. R. Weber*, W. F. Koehl*, J. B. Varley*, A. Janotti, B. B. Buckley, C. G. Van de Walle, and D. D. Awschalom, Proc. Natl Acad. Sci. USA 107, 8513 (2010

  17. Toward Quantum Processing in Molecules: A THz-Bandwidth Coherent Memory for Light

    NASA Astrophysics Data System (ADS)

    Bustard, Philip J.; Lausten, Rune; England, Duncan G.; Sussman, Benjamin J.

    2013-08-01

    The unusual features of quantum mechanics are enabling the development of technologies not possible with classical physics. These devices utilize nonclassical phenomena in the states of atoms, ions, and solid-state media as the basis for many prototypes. Here we investigate molecular states as a distinct alternative. We demonstrate a memory for light based on storing photons in the vibrations of hydrogen molecules. The THz-bandwidth molecular memory is used to store 100-fs pulses for durations up to ˜1ns, enabling ˜104 operational time bins. The results demonstrate the promise of molecules for constructing compact ultrafast quantum photonic technologies.

  18. Simplified optical quantum-information processing via weak cross-Kerr nonlinearities

    SciTech Connect

    Guo Qi; Bai Juan; Cheng Liuyong; Wang Hongfu; Zhang Shou; Shao Xiaoqiang

    2011-05-15

    We propose a simplified parity meter for photonic qubits with cross-Kerr nonlinearities, homodyne measurement, and some optical elements. Our scheme has lower error probability than the protocol proposed in Nemoto and Munro [Phys. Rev. Lett. 93, 250502 (2004)]. Based on the present parity meter, we achieve cluster-state preparation, a complete Bell-state analyzer, and quantum teleportation. All of these schemes are nearly deterministic in the regime with little noise and include less optical elements, which makes our schemes more meaningful for large-scale quantum computing.

  19. Generating superposition of up-to three photons for continuous variable quantum information processing.

    PubMed

    Yukawa, Mitsuyoshi; Miyata, Kazunori; Mizuta, Takahiro; Yonezawa, Hidehiro; Marek, Petr; Filip, Radim; Furusawa, Akira

    2013-03-11

    We develop an experimental scheme based on a continuous-wave (cw) laser for generating arbitrary superpositions of photon number states. In this experiment, we successfully generate superposition states of zero to three photons, namely advanced versions of superpositions of two and three coherent states. They are fully compatible with developed quantum teleportation and measurement-based quantum operations with cw lasers. Due to achieved high detection efficiency, we observe, without any loss correction, multiple areas of negativity of Wigner function, which confirm strongly nonclassical nature of the generated states. PMID:23482124

  20. Converting Coherence to Quantum Correlations

    NASA Astrophysics Data System (ADS)

    Ma, Jiajun; Yadin, Benjamin; Girolami, Davide; Vedral, Vlatko; Gu, Mile

    2016-04-01

    Recent results in quantum information theory characterize quantum coherence in the context of resource theories. Here, we study the relation between quantum coherence and quantum discord, a kind of quantum correlation which appears even in nonentangled states. We prove that the creation of quantum discord with multipartite incoherent operations is bounded by the amount of quantum coherence consumed in its subsystems during the process. We show how the interplay between quantum coherence consumption and creation of quantum discord works in the preparation of multipartite quantum correlated states and in the model of deterministic quantum computation with one qubit.

  1. Quantum-state storage and processing for polarization qubits in an inhomogeneously broadened Λ-type three-level medium

    NASA Astrophysics Data System (ADS)

    Viscor, D.; Ferraro, A.; Loiko, Yu.; Mompart, J.; Ahufinger, V.

    2011-10-01

    We address the propagation of a single-photon pulse with two polarization components, i.e., a polarization qubit, in an inhomogeneously broadened “phaseonium” Λ-type three-level medium. We combine some of the nontrivial propagation effects characteristic for this kind of coherently prepared systems and the controlled reversible inhomogeneous broadening technique to propose several quantum information-processing applications, such as a protocol for polarization qubit filtering and sieving as well as a tunable polarization beam splitter. Moreover, we show that by imposing a spatial variation of the atomic coherence phase, an efficient quantum memory for the incident polarization qubit can be also implemented in Λ-type three-level systems.

  2. Kinetic-quantum chemical model for catalytic cycles: the Haber-Bosch process and the effect of reagent concentration.

    PubMed

    Kozuch, Sebastian; Shaik, Sason

    2008-07-01

    A combined kinetic-quantum chemical model is developed with the goal of estimating in a straightforward way the turnover frequency (TOF) of catalytic cycles, based on the state energies obtained by quantum chemical calculations. We describe how the apparent activation energy of the whole cycle, so-called energetic span (delta E), is influenced by the energy levels of two species: the TOF determining transition state (TDTS) and the TOF determining intermediate (TDI). Because these key species need not be adjoining states, we conclude that for catalysis there are no rate-determining steps, only rate determining states. In addition, we add here the influence of reactants concentrations. And, finally, the model is applied to the Haber-Bosch process of ammonia synthesis, for which we show how to calculate which catalyst will be the most effective under specific reagents conditions. PMID:18537227

  3. Expected number of quantum channels in quantum networks

    PubMed Central

    Chen, Xi; Wang, He-Ming; Ji, Dan-Tong; Mu, Liang-Zhu; Fan, Heng

    2015-01-01

    Quantum communication between nodes in quantum networks plays an important role in quantum information processing. Here, we proposed the use of the expected number of quantum channels as a measure of the efficiency of quantum communication for quantum networks. This measure quantified the amount of quantum information that can be teleported between nodes in a quantum network, which differs from classical case in that the quantum channels will be consumed if teleportation is performed. We further demonstrated that the expected number of quantum channels represents local correlations depicted by effective circles. Significantly, capacity of quantum communication of quantum networks quantified by ENQC is independent of distance for the communicating nodes, if the effective circles of communication nodes are not overlapped. The expected number of quantum channels can be enhanced through transformations of the lattice configurations of quantum networks via entanglement swapping. Our results can shed lights on the study of quantum communication in quantum networks. PMID:26173556

  4. Expected number of quantum channels in quantum networks.

    PubMed

    Chen, Xi; Wang, He-Ming; Ji, Dan-Tong; Mu, Liang-Zhu; Fan, Heng

    2015-01-01

    Quantum communication between nodes in quantum networks plays an important role in quantum information processing. Here, we proposed the use of the expected number of quantum channels as a measure of the efficiency of quantum communication for quantum networks. This measure quantified the amount of quantum information that can be teleported between nodes in a quantum network, which differs from classical case in that the quantum channels will be consumed if teleportation is performed. We further demonstrated that the expected number of quantum channels represents local correlations depicted by effective circles. Significantly, capacity of quantum communication of quantum networks quantified by ENQC is independent of distance for the communicating nodes, if the effective circles of communication nodes are not overlapped. The expected number of quantum channels can be enhanced through transformations of the lattice configurations of quantum networks via entanglement swapping. Our results can shed lights on the study of quantum communication in quantum networks. PMID:26173556

  5. Self-assembly and photoluminescence evolution of hydrophilic and hydrophobic quantum dots in sol–gel processes

    SciTech Connect

    Yang, Ping; Matras-Postolek, Katarzyna; Song, Xueling; Zheng, Yan; Liu, Yumeng; Ding, Kun; Nie, Shijie

    2015-10-15

    Graphical abstract: Highly luminescent quantum dots (QDs) with tunable photoluminescence (PL) wavelength were assembled into various morphologies including chain, hollow spheres, fibers, and ring structures through sol–gel processes. The PL properties during assembly as investigated. - Highlights: • Highly luminescent quantum dots (QDs) were synthesized from several ligands. • The evolution of PL in self-assembly via sol–gel processes was investigated. • CdTe QDs were assembled into a chain by controlling hydrolysis and condensation reactions. • Hollow spheres, fibers, and ring structures were created via CdSe/ZnS QDs in sol–gel processes. - Abstract: Highly luminescent quantum dots (QDs) with tunable photoluminescence (PL) wavelength were synthesized from several ligands to investigate the PL evolution in QD self-assembly via sol–gel processes. After ligand exchange, CdTe QDs were assembled into a chain by controlling the hydrolysis and condensation reaction of 3-mercaptopropyl-trimethoxysilane. The chain was then coated with a SiO{sub 2} shell from tetraethyl orthosilicate (TEOS). Hollow spheres, fibers, and ring structures were created from CdSe/ZnS QDs via various sol–gel processes. CdTe QDs revealed red-shifted and narrowed PL spectrum after assembly compared with their initial one. In contrast, the red-shift of PL spectra of CdSe/ZnS QDs is small. By optimizing experimental conditions, SiO{sub 2} spheres with multiple CdSe/ZnS QDs were fabricated using TEOS and MPS. The QDs in these SiO{sub 2} spheres retained their initial PL properties. This result is useful for application because of their high stability and high PL efficiency of 33%.

  6. Quantum microbiology.

    PubMed

    Trevors, J T; Masson, L

    2011-01-01

    During his famous 1943 lecture series at Trinity College Dublin, the reknown physicist Erwin Schrodinger discussed the failure and challenges of interpreting life by classical physics alone and that a new approach, rooted in Quantum principles, must be involved. Quantum events are simply a level of organization below the molecular level. This includes the atomic and subatomic makeup of matter in microbial metabolism and structures, as well as the organic, genetic information code of DNA and RNA. Quantum events at this time do not elucidate, for example, how specific genetic instructions were first encoded in an organic genetic code in microbial cells capable of growth and division, and its subsequent evolution over 3.6 to 4 billion years. However, due to recent technological advances, biologists and physicists are starting to demonstrate linkages between various quantum principles like quantum tunneling, entanglement and coherence in biological processes illustrating that nature has exerted some level quantum control to optimize various processes in living organisms. In this article we explore the role of quantum events in microbial processes and endeavor to show that after nearly 67 years, Schrödinger was prophetic and visionary in his view of quantum theory and its connection with some of the fundamental mechanisms of life. PMID:21368338

  7. Better Solar Cells and Manufacturing Processes Using NREL's Ultrafast Quantum Efficiency Method (Fact Sheet)

    SciTech Connect

    Not Available

    2011-08-01

    Fact sheet on the FlashQE system, a 2011 R&D 100 Award winner. A solid-state optical system by NREL and Tau Science measures solar cell quantum efficiency in less than a second, enabling a suite of new capabilities for solar cell manufacturers.

  8. Process, System, Causality, and Quantum Mechanics: A Psychoanalysis of Animal Faith

    NASA Astrophysics Data System (ADS)

    Etter, Tom; Noyes, H. Pierre

    We shall argue in this paper that a central piece of modern physics does not really belong to physics at all but to elementary probability theory. Given a joint probability distribution J on a set of random variables containing x and y, define a link between x and y to be the condition x=y on J. Define the {\\it state} D of a link x=y as the joint probability distribution matrix on x and y without the link. The two core laws of quantum mechanics are the Born probability rule, and the unitary dynamical law whose best known form is the Schrodinger's equation. Von Neumann formulated these two laws in the language of Hilbert space as prob(P) = trace(PD) and D'T = TD respectively, where P is a projection, D and D' are (von Neumann) density matrices, and T is a unitary transformation. We'll see that if we regard link states as density matrices, the algebraic forms of these two core laws occur as completely general theorems about links. When we extend probability theory by allowing cases to count negatively, we find that the Hilbert space framework of quantum mechanics proper emerges from the assumption that all D's are symmetrical in rows and columns. On the other hand, Markovian systems emerge when we assume that one of every linked variable pair has a uniform probability distribution. By representing quantum and Markovian structure in this way, we see clearly both how they differ, and also how they can coexist in natural harmony with each other, as they must in quantum measurement, which we'll examine in some detail. Looking beyond quantum mechanics, we see how both structures have their special places in a much larger continuum of formal systems that we have yet to look for in nature.

  9. Electronic and excitonic processes in light-emitting devices based on organic materials and colloidal quantum dots

    NASA Astrophysics Data System (ADS)

    Anikeeva, P. O.; Madigan, C. F.; Halpert, J. E.; Bawendi, M. G.; Bulović, V.

    2008-08-01

    We investigate the mechanism of operation of hybrid organic/colloidal quantum dot light emitting devices (QD-LEDs). Novel quantum dot (QD) deposition methods allow us to change the location of an emissive QD monolayer within a QD-LED multilayer structure. We find that the quantum efficiency of devices improves by >50% upon imbedding QD monolayers into the hole transporting layer <10nm away from the interface between hole and electron transporting layers. We consider two possible mechanisms responsible for this improvement: one based on a charge injection model of the device operation and the other based on an exciton energy-transfer model. In order to differentiate between the two suggested mechanisms, we fabricate a set of structures that enable control over charge injection into colloidal QDs. We find that the dominant process limiting QD-LED efficiency is charging of the QDs by trapped electrons. We demonstrate that with the set of organic materials implemented in this study, device efficiency is increased by maximizing energy transfer from organics to QDs and by limiting direct charge injection that contributes to QD charging.

  10. Three-frame generalized phase-shifting interferometry by a Euclidean matrix norm algorithm

    NASA Astrophysics Data System (ADS)

    Xu, Yuanyuan; Wang, Yawei; Ji, Ying; Han, Hao; Jin, Weifeng

    2016-09-01

    Generalized phase-shifting interferometry (GPSI) is one of the most effective techniques in imaging of a phase object, in which phase retrieval is an essential and important procedure. In this paper, a simple and rapid algorithm for retrieval of the unknown phase shifts in three-frame GPSI is proposed. Using this algorithm, the value of phase shift can be calculated by a determinate formula consisting of three different Euclidean matrix norms of the intensity difference between two phase shifted interferograms, and then the phase can be retrieved easily. The algorithm has the advantages of freeing from the background elimination and less computation, since it only needs three phase-shifted interferograms without no extra measurements, the iterative procedure or the integral transformation. The reliability and accuracy of this algorithm were demonstrated by simulation and experimental results.

  11. A Log-Euclidean polyaffine registration for articulated structures in medical images.

    PubMed

    Martín-Fernández, Miguel Angel; Martín-Fernández, Marcos; Alberola-López, Carlos

    2009-01-01

    In this paper we generalize the Log-Euclidean polyaffine registration framework of Arsigny et al. to deal with articulated structures. This framework has very useful properties as it guarantees the invertibility of smooth geometric transformations. In articulated registration a skeleton model is defined for rigid structures such as bones. The final transformation is affine for the bones and elastic for other tissues in the image. We extend the Arsigny el al.'s method to deal with locally-affine registration of pairs of wires. This enables the possibility of using this registration framework to deal with articulated structures. In this context, the design of the weighting functions, which merge the affine transformations defined for each pair of wires, has a great impact not only on the final result of the registration algorithm, but also on the invertibility of the global elastic transformation. Several experiments, using both synthetic images and hand radiographs, are also presented. PMID:20425983

  12. Finite Size and Dimensional Dependence in the Euclidean Traveling Salesman Problem

    NASA Astrophysics Data System (ADS)

    Percus, Allon G.; Martin, Olivier C.

    1996-02-01

    We consider the Euclidean traveling salesman problem for N cities randomly distributed in the unit d-dimensional hypercube, and investigate the finite size scaling of the mean optimal tour length LE. With toroidal boundary conditions we find, motivated by a remarkable universality in the kth nearest neighbor distribution, that LE\\(d = 2\\) = \\(0.7120+/-0.0002\\) N1/2 [1+O\\(1/N\\)] and LE\\(d = 3\\) = \\(0.6979+/-0.0002\\) N2/3[1+O\\(1/N\\)]. We then consider a mean-field approach in the limit N-->∞ which we find to be a good approximation (the error being less than 2.1% at d = 1,2, and 3), and which suggests that LE\\(d\\) = N1-1/dd/2πe \\(πd\\)1/2d[1+O\\(1/d\\)] at large d.

  13. Isospectral drums in {\\bb R}^2 , involution graphs and Euclidean TI-domains

    NASA Astrophysics Data System (ADS)

    Thas, Koen

    2007-06-01

    The widely investigated question 'Can one hear the shape of a drum?' which Kac posed in his published lecture (Kac 1966 Am. Math. Mon. 73 1-23) was eventually answered negatively in Gordon et al (1992 Invent. Math. 110 1-22) by construction of isospectral pairs in {\\bb R}^2 . Up to present, all known planar counter examples are constructed by a certain tiling method, and in this communication, we call such examples isospectral Euclidean TI-domains. From counter examples of this type, one can construct a pair of (finite) involution graphs. In this communication, we address the question as to how the isospectrality of the domains for the Laplacian influences the cospectrality of the involution graphs.

  14. ILP, the Blind, and the Elephant: Euclidean Embedding of Co-proven Queries

    NASA Astrophysics Data System (ADS)

    Schulz, Hannes; Kersting, Kristian; Karwath, Andreas

    Relational data is complex. This complexity makes one of the basic steps of ILP difficult: understanding the data and results. If the user cannot easily understand it, he draws incomplete conclusions. The situation is very much as in the parable of the blind men and the elephant that appears in many cultures. In this tale the blind work independently and with quite different pieces of information, thereby drawing very different conclusions about the nature of the beast. In contrast, visual representations make it easy to shift from one perspective to another while exploring and analyzing data. This paper describes a method for embedding interpretations and queries into a single, common Euclidean space based on their co-proven statistics. We demonstrate our method on real-world datasets showing that ILP results can indeed be captured at a glance.

  15. Estimating the chromatic numbers of Euclidean space by convex minimization methods

    SciTech Connect

    Gorskaya, Elena S; Mitricheva, Irina M; Protasov, Vladimir Yu; Raigorodskii, Andrei M

    2009-06-30

    The chromatic numbers of the Euclidean space R{sup n} with k forbidden distances are investigated (that is, the minimum numbers of colours necessary to colour all points in R{sup n} so that no two points of the same colour lie at a forbidden distance from each other). Estimates for the growth exponents of the chromatic numbers as n{yields}{infinity} are obtained. The so-called linear algebra method which has been developed is used for this. It reduces the problem of estimating the chromatic numbers to an extremal problem. To solve this latter problem a fundamentally new approach is used, which is based on the theory of convex extremal problems and convex analysis. This allows the required estimates to be found for any k. For k{<=}20 these estimates are found explicitly; they are the best possible ones in the framework of the method mentioned above. Bibliography: 18 titles.

  16. Preservice Mathematics Teachers' Perceptions of Using a Web 2.0 Technology as a Supportive Teaching-Learning Tool in a College Euclidean Geometry Course

    ERIC Educational Resources Information Center

    Hossain, Md. Mokter

    2012-01-01

    This mixed methods study examined preservice secondary mathematics teachers' perceptions of a blogging activity used as a supportive teaching-learning tool in a college Euclidean Geometry course. The effect of a 12-week blogging activity that was a standard component of a college Euclidean Geometry course offered for preservice secondary…

  17. Quantum diffusion description of the subbarrier-capture process in heavy-ion reactions

    SciTech Connect

    Kuzyakin, R. A. Sargsyan, V. V.; Adamian, G. G.; Antonenko, N. V.

    2012-04-15

    The capture of a projectile nucleus by a target nucleus at bombarding energies below the Coulomb barrier is studied on the basis of the quantum diffusion approach. The results obtained in this way for reactions involving spherical nuclei are in good agreement with available experimental data. It is shown that, beyond the range of nuclear forces, the decrease in the capture cross section as the bombarding energy decreases becomes slower.

  18. Quasi-minimal Lorentz surfaces with pointwise 1-type Gauss map in pseudo-Euclidean 4-space

    NASA Astrophysics Data System (ADS)

    Milousheva, Velichka; Turgay, Nurettin Cenk

    2016-08-01

    A Lorentz surface in the four-dimensional pseudo-Euclidean space with neutral metric is called quasi-minimal if its mean curvature vector is lightlike at each point. In the present paper we obtain the complete classification of quasi-minimal Lorentz surfaces with pointwise 1-type Gauss map.

  19. Impact of the localized wetting layer states on carrier relaxation processes in GaAs-based quantum dash structures

    SciTech Connect

    Syperek, M.; Musial, A.; Seek, G.; Podemski, P.; Misiewicz, J.; Loeffler, A.; Hoefling, S.; Worschech, L.; Forchel, A.

    2011-12-23

    The exciton kinetics in the low strain InGaAs/GaAs structures with quantum dashes on a wetting layer has been examined by means of time-resolved photoluminescence and micro-photoluminescence. There has been proven a multistage relaxation process with a key role of the exciton localization within the wetting layer revealing also short radiative lifetime of excitons in the dashes as a consequence of a weak carrier confinement. The peculiar properties of the system can be responsible for the observation of pronounced biexciton sideband, which can be related to QDash biexciton interaction with excitons confined in the wetting layer potential fluctuations.

  20. Suppression of dark current through barrier engineer for solution-processed colloidal quantum-dots infrared photodetectors

    SciTech Connect

    Jiang, Zhenyu E-mail: jianxu@engr.psu.edu; Liu, Yan; Mo, Chen; Wang, Li; Atalla, Mahmoud R. M.; Liu, Jie; Kurhade, Kandhar K.; Xu, Jian E-mail: jianxu@engr.psu.edu; Hu, Wenjia; Zhang, Wenjun; You, Guanjun; Zhang, Yu

    2015-08-31

    In an attempt to suppress the dark current, the barrier layer engineer for solution-processed PbSe colloidal quantum-dot (CQD) photodetectors has been investigated in the present study. It was found that the dark current can be significantly suppressed by implementing two types of carrier blocking layers, namely, hole blocking layer and electron blocking layer, sandwiched in between two active PbSe CQD layers. Meanwhile no adverse impact has been observed for the photo current. Our study suggests that this improvement resides on the transport pathway created via carrier recombination at intermediate layer, which provides wide implications for the suppression of dark current for infrared photodetectors.

  1. Mixed Quantum-Classical Dynamics Methods for Strong-Field Processes: Multiple-trajectory Ehrenfest dynamics + decoherence terms

    NASA Astrophysics Data System (ADS)

    Suzuki, Yasumitsu; Watanabe, Kazuyuki; Abedi, Ali; Agostini, Federica; Min, Seung Kyu; Maitra, Neepa; Gross, E. K. U.

    The exact factorization of the electron-nuclear wave function allows to define the time-dependent potential energy surfaces (TDPESs) responsible for the nuclear dynamics and electron dynamics. Recently a novel coupled-trajectory mixed quantum-classical (CT-MQC) approach based on this TDPES has been developed, which accurately reproduces both nuclear and electron dynamics. Here we study the TDPES for laser-induced electron localization with a view to developing a MQC method for strong-field processes. We show our recent progress in applying the CT-MQC approach to the systems with many degrees of freedom.

  2. Vanishing current hysteresis under competing nuclear spin pumping processes in a quadruplet spin-blockaded double quantum dot

    SciTech Connect

    Amaha, S.; Hatano, T.; Tarucha, S.; Gupta, J. A.; Austing, D. G.

    2015-04-27

    We investigate nuclear spin pumping with five-electron quadruplet spin states in a spin-blockaded weakly coupled vertical double quantum dot device. Two types of hysteretic steps in the leakage current are observed on sweeping the magnetic field and are associated with bidirectional polarization of nuclear spin. Properties of the steps are understood in terms of bias-voltage-dependent conditions for the mixing of quadruplet and doublet spin states by the hyperfine interaction. The hysteretic steps vanish when up- and down-nuclear spin pumping processes are in close competition.

  3. Quantum state of wormholes and path integral

    SciTech Connect

    Garay, L.J. )

    1991-08-15

    The quantum state of a wormhole can be represented by a path integral over all asymptotically Euclidean four-geometries and all matter fields which have prescribed values, the arguments of the wave function, on a three-surface {ital S} which divides the spacetime manifold into two disconnected parts. The ground-state wave function is picked out by requiring that there be no matter excitations in the asymptotic region. Once the path integrals over the lapse and shift functions are evaluated, the requirement that the spacetime be asymptotically Euclidean can be accomplished by fixing the asymptotic gravitational momentum in the remaining path integral. It is claimed that no wave function exists which corresponds to asymptotic field configurations such that the effective gravitational constant is negative in the asymptotic region. The wormhole wave functions are worked out in minisuperspace models with massless minimal and conformal scalar fields.

  4. Interpreting quantum discord through quantum state merging

    SciTech Connect

    Madhok, Vaibhav; Datta, Animesh

    2011-03-15

    We present an operational interpretation of quantum discord based on the quantum state merging protocol. Quantum discord is the markup in the cost of quantum communication in the process of quantum state merging, if one discards relevant prior information. Our interpretation has an intuitive explanation based on the strong subadditivity of von Neumann entropy. We use our result to provide operational interpretations of other quantities like the local purity and quantum deficit. Finally, we discuss in brief some instances where our interpretation is valid in the single-copy scenario.

  5. Decoherence processes during optical manipulation of excitonic qubits in semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Wang, Q. Q.; Muller, A.; Bianucci, P.; Rossi, E.; Xue, Q. K.; Takagahara, T.; Piermarocchi, C.; MacDonald, A. H.; Shih, C. K.

    2005-07-01

    Using photoluminescence spectroscopy, we have investigated the nature of Rabi oscillation damping during optical manipulation of excitonic qubits in self-assembled quantum dots. Rabi oscillations were recorded by varying the pulse amplitude for fixed pulse durations between 4ps and 10ps . Up to five periods are visible, making it possible to quantify the excitation dependent damping. We find that this damping is more pronounced for shorter pulse widths and show that its origin is the nonresonant excitation of carriers in the wetting layer, most likely involving bound-to-continuum and continuum-to-bound transitions.

  6. Process-chain approach to high-order perturbation calculus for quantum lattice models

    SciTech Connect

    Eckardt, Andre

    2009-05-15

    A method based on Rayleigh-Schroedinger perturbation theory is developed that allows to obtain high-order series expansions for ground-state properties of quantum lattice models. The approach is capable of treating both lattice geometries of large spatial dimensionalities d and on-site degrees of freedom with large state space dimensionalities. It has recently been used to accurately compute the zero-temperature phase diagram of the Bose-Hubbard model on a hypercubic lattice, up to arbitrary large filling and for d=2, 3, and greater [Teichmann et al., Phys. Rev. B 79, 100503(R) (2009)].0.

  7. Diagrammatic quantum mechanics

    NASA Astrophysics Data System (ADS)

    Kauffman, Louis H.; Lomonaco, Samuel J.

    2015-05-01

    This paper explores how diagrams of quantum processes can be used for modeling and for quantum epistemology. The paper is a continuation of the discussion where we began this formulation. Here we give examples of quantum networks that represent unitary transformations by dint of coherence conditions that constitute a new form of non-locality. Local quantum devices interconnected in space can form a global quantum system when appropriate coherence conditions are maintained.

  8. Enhancement of recombination process using silver and graphene quantum dot embedded intermediate layer for efficient organic tandem cells.

    PubMed

    Ho, Nhu Thuy; Tien, Huynh Ngoc; Jang, Se-Joeng; Senthilkumar, Velusamy; Park, Yun Chang; Cho, Shinuk; Kim, Yong Soo

    2016-01-01

    High performance of organic tandem solar cell is largely dependent on transparent and conductive intermediate layer (IML). The current work reports the design and fabrication of an IML using a simple solution process. The efficiency of a homo-tandem device with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester as an active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylenimine) as an IML was initially found to be 3.40%. Further enhancement of the cell efficiency was achieved using silver nanoparticles (Ag-NPs) of different sizes and graphene quantum dot embedded IML. A maximum efficiency of 4.03% was achieved using 7 nm Ag-NPs that contribute to a better recombination process. Also, the performance of the tandem cell was solely based on the electrical improvements indicated by the current - voltage measurements, external quantum efficiency and impedance analysis. The use of Ag-NPs in the IML has been shown to lengthen the life time of electron-hole pairs in the device. This study thus paves way to develop such efficient IMLs for more efficient tandem solar cells. PMID:27453530

  9. Preparation of surface-modified ZnO quantum dots through an ultrasound assisted sol-gel process

    NASA Astrophysics Data System (ADS)

    Moghaddam, E.; Youzbashi, AA; Kazemzadeh, A.; Eshraghi, MJ

    2015-08-01

    A synthetic process of zinc oxide quantum dots (QDs) is presented. It is based on a sol-gel process, carried out in an ultrasonic bath. It allows the formation of the stable colloids, containing surface-modified ZnO QDs with the aid of 3-aminopropyltriethoxysilane (APTES) as a capping agent. For this purpose, alcoholic solutions of zinc acetate dihydrate and potassium hydroxide were used as the reactants. Effect of KOH concentration, ultrasonic irradiation, and also the presence of capping agent on the characteristics of the final product were investigated. The synthesized samples were characterized by various analytical techniques such as XRD, TEM, FT-IR, UV-vis and PL spectroscopy. XRD analysis revealed the direct formation of hexagonal wurtzite nanocrystals with average size of ∼3 nm confirmed by TEM and UV-vis spectroscopy. The PL spectroscopy indicated the influence of the capping agent on reducing the defects formation during the growth of the QDs. The present synthesis method was found to be a cost-effective and simple solution route for producing pure semiconductor ZnO QDs, exhibiting the quantum confinement effects, suitable for optical and optoelectronic applications.

  10. Enhancement of recombination process using silver and graphene quantum dot embedded intermediate layer for efficient organic tandem cells

    PubMed Central

    Ho, Nhu Thuy; Tien, Huynh Ngoc; Jang, Se-Joeng; Senthilkumar, Velusamy; Park, Yun Chang; Cho, Shinuk; Kim, Yong Soo

    2016-01-01

    High performance of organic tandem solar cell is largely dependent on transparent and conductive intermediate layer (IML). The current work reports the design and fabrication of an IML using a simple solution process. The efficiency of a homo-tandem device with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester as an active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylenimine) as an IML was initially found to be 3.40%. Further enhancement of the cell efficiency was achieved using silver nanoparticles (Ag-NPs) of different sizes and graphene quantum dot embedded IML. A maximum efficiency of 4.03% was achieved using 7 nm Ag-NPs that contribute to a better recombination process. Also, the performance of the tandem cell was solely based on the electrical improvements indicated by the current - voltage measurements, external quantum efficiency and impedance analysis. The use of Ag-NPs in the IML has been shown to lengthen the life time of electron-hole pairs in the device. This study thus paves way to develop such efficient IMLs for more efficient tandem solar cells. PMID:27453530

  11. Enhancement of recombination process using silver and graphene quantum dot embedded intermediate layer for efficient organic tandem cells

    NASA Astrophysics Data System (ADS)

    Ho, Nhu Thuy; Tien, Huynh Ngoc; Jang, Se-Joeng; Senthilkumar, Velusamy; Park, Yun Chang; Cho, Shinuk; Kim, Yong Soo

    2016-07-01

    High performance of organic tandem solar cell is largely dependent on transparent and conductive intermediate layer (IML). The current work reports the design and fabrication of an IML using a simple solution process. The efficiency of a homo-tandem device with poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester as an active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(ethylenimine) as an IML was initially found to be 3.40%. Further enhancement of the cell efficiency was achieved using silver nanoparticles (Ag-NPs) of different sizes and graphene quantum dot embedded IML. A maximum efficiency of 4.03% was achieved using 7 nm Ag-NPs that contribute to a better recombination process. Also, the performance of the tandem cell was solely based on the electrical improvements indicated by the current - voltage measurements, external quantum efficiency and impedance analysis. The use of Ag-NPs in the IML has been shown to lengthen the life time of electron-hole pairs in the device. This study thus paves way to develop such efficient IMLs for more efficient tandem solar cells.

  12. High quantum-efficiency photon-number-resolving detector for photonic on-chip information processing.

    PubMed

    Calkins, Brice; Mennea, Paolo L; Lita, Adriana E; Metcalf, Benjamin J; Kolthammer, W Steven; Lamas-Linares, Antia; Spring, Justin B; Humphreys, Peter C; Mirin, Richard P; Gates, James C; Smith, Peter G R; Walmsley, Ian A; Gerrits, Thomas; Nam, Sae Woo

    2013-09-23

    The integrated optical circuit is a promising architecture for the realization of complex quantum optical states and information networks. One element that is required for many of these applications is a high-efficiency photon detector capable of photon-number discrimination. We present an integrated photonic system in the telecom band at 1550 nm based on UV-written silica-on-silicon waveguides and modified transition-edge sensors capable of number resolution and over 40 % efficiency. Exploiting the mode transmission failure of these devices, we multiplex three detectors in series to demonstrate a combined 79 % ± 2 % detection efficiency with a single pass, and 88 % ± 3 % at the operating wavelength of an on-chip terminal reflection grating. Furthermore, our optical measurements clearly demonstrate no significant unexplained loss in this system due to scattering or reflections. This waveguide and detector design therefore allows the placement of number-resolving single-photon detectors of predictable efficiency at arbitrary locations within a photonic circuit - a capability that offers great potential for many quantum optical applications. PMID:24104153

  13. Nonequilibrium entropic temperature and its lower bound for quantum stochastic processes

    NASA Astrophysics Data System (ADS)

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2014-03-01

    In this paper, we have studied the Shannon "entropic" nonequilibrium temperature (NET) of quantum Brownian systems. The Brownian particle is attached to either a bosonic or fermionic bath. Based on the Fokker-Planck description of the c-number quantum Langevin equation, we have calculated entropy production, NET, and their bounds. Entropy production (EP), the upper bound of entropy production (UBEP), and the deviation of the UBEP from EP monotonically decrease as functions of time to equilibrium value for both of the thermal baths. The deviation decreases with increase of temperature of the bosonic thermal bath, but it becomes larger as the temperature of the fermionic bath grows. We also observe that nonequilibrium temperature and its lower bound monotonically increase to equilibrium value with the progression of time. But their difference as a function of time shows an optimum behavior in most cases. Finally, we have observed that at long time, the entropic temperature (for a bosonic thermal bath) first increases nonlinearly as a function of thermodynamic temperature (TT) and, if the TT is appreciably large, then it grows linearly. But for the fermionic thermal bath, the entropic temperature decreases monotonically as a nonlinear function of thermodynamic temperature to zero value.

  14. Water-soluble CdTe quantum dots as an anode interlayer for solution-processed near infrared polymer photodetectors

    NASA Astrophysics Data System (ADS)

    Liu, Xilan; Zhou, Jinjun; Zheng, Jie; Becker, Matthew L.; Gong, Xiong

    2013-11-01

    Water-soluble cadmium telluride (CdTe) quantum dots (QDs) used as an anode interlayer in solution-processed near infrared (NIR) polymer photodetectors (PDs) were demonstrated. Polymer PDs incorporated with CdTe QDs as an anode interlayer exhibited 10-fold suppressed dark current density and analogous photocurrent density relative to poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which resulted in enhanced detectivities over 1011 Jones in the spectral range from 350 nm to 900 nm. Moreover, with the substitution of PEDOT:PSS by CdTe QDs, the stability of unencapsulated NIR polymer PDs was extended up to 650 hours, which is more than 3 times longer than those with PEDOT:PSS as an anode interlayer. These results indicated that CdTe QDs can be utilized as a solution-processable alternative to PEDOT:PSS as an anode interlayer for high performance NIR polymer PDs.

  15. Capping process of InAs/GaAs quantum dots studied by cross-sectional scanning tunneling microscopy

    SciTech Connect

    Gong, Q.; Offermans, P.; Noetzel, R.; Koenraad, P.M.; Wolter, J.H.

    2004-12-06

    The capping process of self-assembled InAs quantum dots (QDs) grown on GaAs(100) substrates by molecular-beam epitaxy is studied by cross-sectional scanning tunneling microscopy. GaAs capping at 500 deg. C causes leveling of the QDs which is completely suppressed by decreasing the growth temperature to 300 deg. C. At elevated temperature the QD leveling is driven in the initial stage of the GaAs capping process while it is quenched during continued overgrowth when the QDs become buried. For common GaAs growth rates, both phenomena take place on a similar time scale. Therefore, the size and shape of buried InAs QDs are determined by a delicate interplay between driving and quenching of the QD leveling during capping which is controlled by the GaAs growth rate and growth temperature.

  16. Determination of lung segments in computed tomography images using the Euclidean distance to the pulmonary artery

    SciTech Connect

    Stoecker, Christina; Moltz, Jan H.; Lassen, Bianca; Kuhnigk, Jan-Martin; Krass, Stefan; Welter, Stefan; Peitgen, Heinz-Otto

    2013-09-15

    Purpose: Computed tomography (CT) imaging is the modality of choice for lung cancer diagnostics. With the increasing number of lung interventions on sublobar level in recent years, determining and visualizing pulmonary segments in CT images and, in oncological cases, reliable segment-related information about the location of tumors has become increasingly desirable. Computer-assisted identification of lung segments in CT images is subject of this work.Methods: The authors present a new interactive approach for the segmentation of lung segments that uses the Euclidean distance of each point in the lung to the segmental branches of the pulmonary artery. The aim is to analyze the potential of the method. Detailed manual pulmonary artery segmentations are used to achieve the best possible segment approximation results. A detailed description of the method and its evaluation on 11 CT scans from clinical routine are given.Results: An accuracy of 2–3 mm is measured for the segment boundaries computed by the pulmonary artery-based method. On average, maximum deviations of 8 mm are observed. 135 intersegmental pulmonary veins detected in the 11 test CT scans serve as reference data. Furthermore, a comparison of the presented pulmonary artery-based approach to a similar approach that uses the Euclidean distance to the segmental branches of the bronchial tree is presented. It shows a significantly higher accuracy for the pulmonary artery-based approach in lung regions at least 30 mm distal to the lung hilum.Conclusions: A pulmonary artery-based determination of lung segments in CT images is promising. In the tests, the pulmonary artery-based determination has been shown to be superior to the bronchial tree-based determination. The suitability of the segment approximation method for application in the planning of segment resections in clinical practice has already been verified in experimental cases. However, automation of the method accompanied by an evaluation on a larger

  17. Controlling atomistic processes on Pb films via quantum size effects and lattice rotation

    SciTech Connect

    Binz, Steven

    2012-01-01

    The two main techniques used to record the data in this dissertation were Spot Profile Analysis - Low Energy Electron Diffraction (SPA-LEED) and Scanning Tunneling Microscopy (STM). A specific data analysis technique for LEED data called G(S) curves is described in depth. G(S) curves can provide a great deal of structural information about the surface; including step heights, island size, and island separation. The effects of quantum size effects (QSE) on the diffusion and critical island sizes of Pb and In on Pb films are reported. Pb depositions on the 2D In phases {radical}3 and {radical}31 to see how the phases affect the Pb growth and its strong QSE are reported.

  18. Quantum information and computation

    SciTech Connect

    Bennett, C.H.

    1995-10-01

    A new quantum theory of communication and computation is emerging, in which the stuff transmitted or processed is not classical information, but arbitrary superpositions of quantum states. {copyright} 1995 {ital American} {ital Institute} {ital of} {ital Physics}.

  19. Giant titanium electron wave function in gallium oxide: A potential electron-nuclear spin system for quantum information processing

    NASA Astrophysics Data System (ADS)

    Mentink-Vigier, Frédéric; Binet, Laurent; Vignoles, Gerard; Gourier, Didier; Vezin, Hervé

    2010-11-01

    The hyperfine interactions of the unpaired electron with eight surrounding G69a and G71a nuclei in Ti-doped β-Ga2O3 were analyzed by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopies. They are dominated by strong isotropic hyperfine couplings due to a direct Fermi contact interaction with Ga nuclei in octahedral sites of rutile-type chains oriented along b axis, revealing a large anisotropic spatial extension of the electron wave function. Titanium in β-Ga2O3 is thus best described as a diffuse (Ti4+-e-) pair rather than as a localized Ti3+ . Both electron and G69a nuclear spin Rabi oscillations could be observed by pulsed EPR and pulsed ENDOR, respectively. The electron spin decoherence time is about 1μs (at 4 K) and an upper bound of 520μs (at 8 K) is estimated for the nuclear decoherence time. Thus, β-Ga2O3:Ti appears to be a potential spin-bus system for quantum information processing with a large nuclear spin quantum register.

  20. Quantum cascade laser based monitoring of CF2 radical concentration as a diagnostic tool of dielectric etching plasma processes

    NASA Astrophysics Data System (ADS)

    Hübner, M.; Lang, N.; Zimmermann, S.; Schulz, S. E.; Buchholtz, W.; Röpcke, J.; van Helden, J. H.

    2015-01-01

    Dielectric etching plasma processes for modern interlevel dielectrics become more and more complex by the introduction of new ultra low-k dielectrics. One challenge is the minimization of sidewall damage, while etching ultra low-k porous SiCOH by fluorocarbon plasmas. The optimization of this process requires a deeper understanding of the concentration of the CF2 radical, which acts as precursor in the polymerization of the etch sample surfaces. In an industrial dielectric etching plasma reactor, the CF2 radical was measured in situ using a continuous wave quantum cascade laser (cw-QCL) around 1106.2 cm-1. We measured Doppler-resolved ro-vibrational absorption lines and determined absolute densities using transitions in the ν3 fundamental band of CF2 with the aid of an improved simulation of the line strengths. We found that the CF2 radical concentration during the etching plasma process directly correlates to the layer structure of the etched wafer. Hence, this correlation can serve as a diagnostic tool of dielectric etching plasma processes. Applying QCL based absorption spectroscopy opens up the way for advanced process monitoring and etching controlling in semiconductor manufacturing.

  1. Multi-resolutional brain network filtering and analysis via wavelets on non-Euclidean space.

    PubMed

    Kim, Won Hwa; Adluru, Nagesh; Chung, Moo K; Charchut, Sylvia; GadElkarim, Johnson J; Altshuler, Lori; Moody, Teena; Kumar, Anand; Singh, Vikas; Leow, Alex D

    2013-01-01

    Advances in resting state fMRI and diffusion weighted imaging (DWI) have led to much interest in studies that evaluate hypotheses focused on how brain connectivity networks show variations across clinically disparate groups. However, various sources of error (e.g., tractography errors, magnetic field distortion, and motion artifacts) leak into the data, and make downstream statistical analysis problematic. In small sample size studies, such noise have an unfortunate effect that the differential signal may not be identifiable and so the null hypothesis cannot be rejected. Traditionally, smoothing is often used to filter out noise. But the construction of convolving with a Gaussian kernel is not well understood on arbitrarily connected graphs. Furthermore, there are no direct analogues of scale-space theory for graphs--ones which allow to view the signal at multiple resolutions. We provide rigorous frameworks for performing 'multi-resolutional' analysis on brain connectivity graphs. These are based on the recent theory of non-Euclidean wavelets. We provide strong evidence, on brain connectivity data from a network analysis study (structural connectivity differences in adult euthymic bipolar subjects), that the proposed algorithm allows identifying statistically significant network variations, which are clinically meaningful, where classical statistical tests, if applied directly, fail. PMID:24505816

  2. Confidence analysis of standard deviational ellipse and its extension into higher dimensional euclidean space.

    PubMed

    Wang, Bin; Shi, Wenzhong; Miao, Zelang

    2015-01-01

    Standard deviational ellipse (SDE) has long served as a versatile GIS tool for delineating the geographic distribution of concerned features. This paper firstly summarizes two existing models of calculating SDE, and then proposes a novel approach to constructing the same SDE based on spectral decomposition of the sample covariance, by which the SDE concept is naturally generalized into higher dimensional Euclidean space, named standard deviational hyper-ellipsoid (SDHE). Then, rigorous recursion formulas are derived for calculating the confidence levels of scaled SDHE with arbitrary magnification ratios in any dimensional space. Besides, an inexact-newton method based iterative algorithm is also proposed for solving the corresponding magnification ratio of a scaled SDHE when the confidence probability and space dimensionality are pre-specified. These results provide an efficient manner to supersede the traditional table lookup of tabulated chi-square distribution. Finally, synthetic data is employed to generate the 1-3 multiple SDEs and SDHEs. And exploratory analysis by means of SDEs and SDHEs are also conducted for measuring the spread concentrations of Hong Kong's H1N1 in 2009. PMID:25769048

  3. a Euclidean Formulation of Interior Orientation Costraints Imposed by the Fundamental Matrix

    NASA Astrophysics Data System (ADS)

    Kalisperakis, I.; Karras, G.; Petsa, E.

    2016-06-01

    Epipolar geometry of a stereopair can be expressed either in 3D, as the relative orientation (i.e. translation and rotation) of two bundles of optical rays in case of calibrated cameras or, in case of unclalibrated cameras, in 2D as the position of the epipoles on the image planes and a projective transformation that maps points in one image to corresponding epipolar lines on the other. The typical coplanarity equation describes the first case; the Fundamental matrix describes the second. It has also been proven in the Computer Vision literature that 2D epipolar geometry imposes two independent constraints on the parameters of camera interior orientation. In this contribution these constraints are expressed directly in 3D Euclidean space by imposing the equality of the dihedral angle of epipolar planes defined by the optical axes of the two cameras or by suitably chosen corresponding epipolar lines. By means of these constraints, new closed form algorithms are proposed for the estimation of a variable or common camera constant value given the fundamental matrix and the principal point position of a stereopair.

  4. Programs for kriging and sequential Gaussian simulation with locally varying anisotropy using non-Euclidean distances

    NASA Astrophysics Data System (ADS)

    Boisvert, Jeff B.; Deutsch, Clayton V.

    2011-04-01

    Geological deposits display nonlinear features such as veins, channels or folds that result in complex spatial anisotropies that are difficult to model with currently available geostatistical techniques. The methodology presented in this paper for incorporating locally varying anisotropy in kriging or sequential Gaussian simulation is based on modifying how locations in space are related. Normally, the straight line path is used; however, when nonlinear features exist the appropriate path between locations follows along the features. The Dijkstra algorithm is used to determine the shortest path/distance between locations and a conventional covariance or variogram function is used. This nonlinear path is a non-Euclidean distance metric and positive definiteness of the resulting kriging system of equations is not guaranteed. Multidimensional scaling (landmark isometric mapping) is used to ensure positive definiteness. In addition to the variogram, the only parameters required for the implementation of kriging or sequential Gaussian simulation with locally varying anisotropy are (1) the local orientation and magnitude of anisotropy and (2) the number of dimensions required for multidimensional scaling. This paper presents a suite of programs that can be used to krige or simulate practically sized geostatistical models with locally varying anisotropy. The programs kt3d_LVA, SGS_LVA and gamv_LVA are provided.

  5. Limit theorems for minimum-weight triangulations, other euclidean functionals, and probabilistic recurrence relations

    SciTech Connect

    Golin, M.J.

    1996-12-31

    Let MWT(n) be the weight of a minimum-weight triangulation of n points chosen independently from the uniform distribution over [0, 1]{sup 2}. Previous work has shown that E(MWT(n)) = {Theta} ({radical}n). In this paper we develop techniques for proving that MWT(n)/{radical}n actually converges to a constant in both expectation and in probability. An immediate consequence is the development of an O(n{sup 2}) time algorithm that finds a triangulation whose competive ratio with the MWT is, in a probabilistic sense, exactly one. The techniques developed to prove the above results are quite general and can also prove the convergence of certain types of probabilistic recurrence equations and other Euclidean Functionals. This is illustrated by using them to prove the convergence of the weight of MWTs of random points in higher dimensions and a sketch of how to use them to prove the convergence of the degree probabilities for Delaunay triangulations in {Re}{sup 2}.

  6. Introduction to Quantum Computation

    NASA Astrophysics Data System (ADS)

    Ekert, A.

    A computation is a physical process. It may be performed by a piece of electronics or on an abacus, or in your brain, but it is a process that takes place in nature and as such it is subject to the laws of physics. Quantum computers are machines that rely on characteristically quantum phenomena, such as quantum interference and quantum entanglement in order to perform computation. In this series of lectures I want to elaborate on the computational power of such machines.

  7. Quantum Computation and Quantum Information

    NASA Astrophysics Data System (ADS)

    Nielsen, Michael A.; Chuang, Isaac L.

    2010-12-01

    Part I. Fundamental Concepts: 1. Introduction and overview; 2. Introduction to quantum mechanics; 3. Introduction to computer science; Part II. Quantum Computation: 4. Quantum circuits; 5. The quantum Fourier transform and its application; 6. Quantum search algorithms; 7. Quantum computers: physical realization; Part III. Quantum Information: 8. Quantum noise and quantum operations; 9. Distance measures for quantum information; 10. Quantum error-correction; 11. Entropy and information; 12. Quantum information theory; Appendices; References; Index.

  8. Euclidean distance and Kolmogorov-Smirnov analyses of multi-day auditory event-related potentials: a longitudinal stability study

    NASA Astrophysics Data System (ADS)

    Durato, M. V.; Albano, A. M.; Rapp, P. E.; Nawang, S. A.

    2015-06-01

    The validity of ERPs as indices of stable neurophysiological traits is partially dependent on their stability over time. Previous studies on ERP stability, however, have reported diverse stability estimates despite using the same component scoring methods. This present study explores a novel approach in investigating the longitudinal stability of average ERPs—that is, by treating the ERP waveform as a time series and then applying Euclidean Distance and Kolmogorov-Smirnov analyses to evaluate the similarity or dissimilarity between the ERP time series of different sessions or run pairs. Nonlinear dynamical analysis show that in the absence of a change in medical condition, the average ERPs of healthy human adults are highly longitudinally stable—as evaluated by both the Euclidean distance and the Kolmogorov-Smirnov test.

  9. Two-slit experiment: quantum and classical probabilities

    NASA Astrophysics Data System (ADS)

    Khrennikov, Andrei

    2015-06-01

    Inter-relation between quantum and classical probability models is one of the most fundamental problems of quantum foundations. Nowadays this problem also plays an important role in quantum technologies, in quantum cryptography and the theory of quantum random generators. In this letter, we compare the viewpoint of Richard Feynman that the behavior of quantum particles cannot be described by classical probability theory with the viewpoint that quantum-classical inter-relation is more complicated (cf, in particular, with the tomographic model of quantum mechanics developed in detail by Vladimir Man'ko). As a basic example, we consider the two-slit experiment, which played a crucial role in quantum foundational debates at the beginning of quantum mechanics (QM). In particular, its analysis led Niels Bohr to the formulation of the principle of complementarity. First, we demonstrate that in complete accordance with Feynman's viewpoint, the probabilities for the two-slit experiment have the non-Kolmogorovian structure, since they violate one of basic laws of classical probability theory, the law of total probability (the heart of the Bayesian analysis). However, then we show that these probabilities can be embedded in a natural way into the classical (Kolmogorov, 1933) probability model. To do this, one has to take into account the randomness of selection of different experimental contexts, the joint consideration of which led Feynman to a conclusion about the non-classicality of quantum probability. We compare this embedding of non-Kolmogorovian quantum probabilities into the Kolmogorov model with well-known embeddings of non-Euclidean geometries into Euclidean space (e.g., the Poincaré disk model for the Lobachvesky plane).

  10. Planarized process for resonant leaky-wave coupled phase-locked arrays of mid-IR quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Chang, C.-C.; Kirch, J. D.; Boyle, C.; Sigler, C.; Mawst, L. J.; Botez, D.; Zutter, B.; Buelow, P.; Schulte, K.; Kuech, T.; Earles, T.

    2015-03-01

    On-chip resonant leaky-wave coupling of quantum cascade lasers (QCLs) emitting at 8.36 μm has been realized by selective regrowth of interelement layers in curved trenches, defined by dry and wet etching. The fabricated structure provides large index steps (Δn = 0.10) between antiguided-array element and interelement regions. In-phase-mode operation to 5.5 W front-facet emitted power in a near-diffraction-limited far-field beam pattern, with 4.5 W in the main lobe, is demonstrated. A refined fabrication process has been developed to produce phased-locked antiguided arrays of QCLs with planar geometry. The main fabrication steps in this process include non-selective regrowth of Fe:InP in interelement trenches, defined by inductive-coupled plasma (ICP) etching, a chemical polishing (CP) step to planarize the surface, non-selective regrowth of interelement layers, ICP selective etching of interelement layers, and non-selective regrowth of InP cladding layer followed by another CP step to form the element regions. This new process results in planar InGaAs/InP interelement regions, which allows for significantly improved control over the array geometry and the dimensions of element and interelement regions. Such a planar process is highly desirable to realize shorter emitting wavelength (4.6 μm) arrays, where fabrication tolerance for single-mode operation are tighter compared to 8 μm-emitting devices.

  11. Majorana fermion realization and relevant transport processes in a triple-quantum dot system

    NASA Astrophysics Data System (ADS)

    Ming-Xun, Deng; Shi-Han, Zheng; Mou, Yang; Liang-Bin, Hu; Rui-Qiang, Wang

    2015-03-01

    Nonequilibrium electronic transports through a system hosting three quantum dots hybridized with superconductors are investigated. By tuning the relative positions of the dot levels, we illustrate the existence of Majorana fermions and show that the Majorana feimions will either survive separately on single dots or distribute themselves among different dots with tunable probabilities. As a result, different physical mechanisms appear, including local Andreev reflection (LAR), cross Andreev reflection (CAR), and cross resonant tunneling (CRT). The resulting characteristics may be used to reveal the unique properties of Majorana fermions. In addition, we discuss the spin-polarized transports and find a pure spin current and a spin filter effect due to the joint effect of CRT and CAR, which is important for designing spintronic devices. Project supported by the New Century Excellent Talents in University of China (Grant No. NCET-10-0090), the National Natural Science Foundation of China (Grant Nos. 11474106, 11174088, and 11274124), the Program for Changjiang Scholars and Innovative Research Team in University of China (Grant No. IRT1243), and the Natural Science Foundation of Guangdong Province, China (Grant No. S2012010010681).

  12. Euclidean geometry explains why lengths allow precise body mass estimates in terrestrial invertebrates: the case of oribatid mites.

    PubMed

    Caruso, T; Migliorini, M

    2009-02-01

    Indirect measures of soil invertebrate body mass M based on equations relating the latter to body length (l) are becoming increasingly used due to the required painstaking laboratory work and the technical difficulties involved in obtaining some thousands of reliable weight estimates for animals that can be very small. The implicit assumption of such equations is that dM/dV=delta, where V is body volume and delta is a constant density value. Classical Euclidean scaling implies that V is proportional to l(3) proportional to M. One may thus derive M from l when the latter can provide a good estimate of V and the assumption of a constant delta is respected. In invertebrates, equations relating weight to length indicate that the power model always provides the best fit. However, authors only focused on the empirical estimation of slopes linking the body mass to the length measure variables, sometimes fitting exponential and linear models that are not theoretically grounded. This paper explicates how power laws derive from fundamental Euclidean scaling and describes the expected allometric exponents under the above assumptions. Based on the classical Euclidean scaling theory, an equivalent sphere is defined as a theoretical sphere with a volume equal to that of the organism whose body mass must be estimated. The illustrated application to a data set on soil oribatid mites helps clarify all these issues. Lastly, a general procedure for more precise estimation of M from V and delta is suggested. PMID:18977363

  13. Quantum junction solar cells.

    PubMed

    Tang, Jiang; Liu, Huan; Zhitomirsky, David; Hoogland, Sjoerd; Wang, Xihua; Furukawa, Melissa; Levina, Larissa; Sargent, Edward H

    2012-09-12

    Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics. PMID:22881834

  14. An analysis of the probability distribution of spectral angle and Euclidean distance in hyperspectral remote sensing using microspectroscopy

    NASA Astrophysics Data System (ADS)

    Resmini, Ronald G.; Deloye, Christopher J.; Allen, David W.

    2013-05-01

    Determining the probability distribution of hyperspectral imagery (HSI) data and of the results of algorithms applied to those data, is critical to understanding algorithm performance and for establishing performance metrics such as probability of detection, false alarm rate, and minimum detectable and identifiable quantities. The results of analyses of visible/near-infrared (VNIR; 400 nm to 900 nm) HSI microscopy data of small fragments (~1.25 cm in size) of minerals are presented. HSI microscopy, also known as microspectroscopy, is the acquisition of HSI data cubes of fields of view ranging from centimeters to millimeters in size. It is imaging spectrometry but at a small spatial scale. With HSI microspectroscopy, several thousand spectral signatures may be easily acquired of individual target materials—samples of which may be quite small. With such data, probability distributions may be very precisely determined. For faceted/irregularly shaped samples and mixtures (checkerboard, intimate, or microscopic), HSI microscopy data readily facilitate a detailed assessment of the contribution of the materials, their morphology, spectral mixing interactions, radiative transfer processes, view/illumination geometry contributions, etc., to the observed probability distribution(s) of the HSI data and of algorithm output. Here, spectral angle, the individual components of spectral angle (e.g., the inner product or numerator of the spectral angle equation), Euclidean distance, and L1 norm values are calculated. Regions of interest (ROI) on the fragments are easily defined that contain thousands of spectra far from the fragments' edges though translucency sometimes remains a factor impacting spectral signatures. The aforementioned metrics are derived for the spectra in an ROI of individual mineral fragments; across ROIs of different minerals; and with an ROI of an inert background. The resulting probability distributions of the various populations of the metrics are

  15. Graphene quantum dots as a highly efficient solution-processed charge trapping medium for organic nano-floating gate memory.

    PubMed

    Ji, Yongsung; Kim, Juhan; Cha, An-Na; Lee, Sang-A; Lee, Myung Woo; Suh, Jung Sang; Bae, Sukang; Moon, Byung Joon; Lee, Sang Hyun; Lee, Dong Su; Wang, Gunuk; Kim, Tae-Wook

    2016-04-01

    A highly efficient solution-processible charge trapping medium is a prerequisite to developing high-performance organic nano-floating gate memory (NFGM) devices. Although several candidates for the charge trapping layer have been proposed for organic memory, a method for significantly increasing the density of stored charges in nanoscale layers remains a considerable challenge. Here, solution-processible graphene quantum dots (GQDs) were prepared by a modified thermal plasma jet method; the GQDs were mostly composed of carbon without any serious oxidation, which was confirmed by x-ray photoelectron spectroscopy. These GQDs have multiple energy levels because of their size distribution, and they can be effectively utilized as charge trapping media for organic NFGM applications. The NFGM device exhibited excellent reversible switching characteristics, with an on/off current ratio greater than 10(6), a stable retention time of 10(4) s and reliable cycling endurance over 100 cycles. In particular, we estimated that the GQDs layer trapped ∼7.2 × 10(12) cm(-2) charges per unit area, which is a much higher density than those of other solution-processible nanomaterials, suggesting that the GQDs layer holds promise as a highly efficient nanoscale charge trapping material. PMID:26905768

  16. Application of CdS quantum dots modified carbon paste electrode for monitoring the process of acetaminophen preparation.

    PubMed

    Pasandideh-Nadamani, M; Omrani, A; Sadeghi-Maleki, M R; Samadi-Maybodi, A

    2016-06-01

    In this research article, a novel, selective, and sensitive modified carbon paste electrode (CPE) using CdS quantum dots (QDs) is presented. The highly stable CdS QDs were successfully synthesized in an in situ process using Na2S2O3 as a precursor and thioglycolic acid as a catalyst and capping agent. The synthesis of CdS QDs was studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The synthesized CdS QDs were used for preparation of a modified carbon paste electrode (CdS/CPE). The electrochemical behavior of the electrode toward p-aminophenol (PAP) and acetaminophen (Ac) was studied, and the results demonstrated that the CdS/CPE exhibited good electrocatalytic performance toward PAP and Ac oxidation. The oxidation peak potential of each analyte in the mixture was well separated. As a result, a selective and reliable method was developed for the determination of PAP and Ac simultaneously without any chemical separations. Application of the fabricated electrode for monitoring the process of Ac preparation from PAP was investigated. The obtained results show that CdS/CPE has satisfactory analytical performance; it could be a kind of attractive and promising nanomaterial-based sensor for process monitoring via the electrochemical approach. PMID:26945834

  17. A multiplexed quantum memory.

    PubMed

    Lan, S-Y; Radnaev, A G; Collins, O A; Matsukevich, D N; Kennedy, T A; Kuzmich, A

    2009-08-01

    A quantum repeater is a system for long-distance quantum communication that employs quantum memory elements to mitigate optical fiber transmission losses. The multiplexed quantum memory (O. A. Collins, S. D. Jenkins, A. Kuzmich, and T. A. B. Kennedy, Phys. Rev. Lett. 98, 060502 (2007)) has been shown theoretically to reduce quantum memory time requirements. We present an initial implementation of a multiplexed quantum memory element in a cold rubidium gas. We show that it is possible to create atomic excitations in arbitrary memory element pairs and demonstrate the violation of Bell's inequality for light fields generated during the write and read processes. PMID:19654771

  18. New family of tilings of three-dimensional Euclidean space by tetrahedra and octahedra.

    PubMed

    Conway, John H; Jiao, Yang; Torquato, Salvatore

    2011-07-01

    It is well known that two regular tetrahedra can be combined with a single regular octahedron to tile (complete fill) three-dimensional Euclidean space . This structure was called the "octet truss" by Buckminster Fuller. It was believed that such a tiling, which is the Delaunay tessellation of the face-centered cubic (fcc) lattice, and its closely related stacking variants, are the only tessellations of that involve two different regular polyhedra. Here we identify and analyze a unique family comprised of a noncountably infinite number of periodic tilings of whose smallest repeat tiling unit consists of one regular octahedron and six smaller regular tetrahedra. We first derive an extreme member of this unique tiling family by showing that the "holes" in the optimal lattice packing of octahedra, obtained by Minkowski over a century ago, are congruent tetrahedra. This tiling has 694 distinct concave (i.e., nonconvex) repeat units, 24 of which possess central symmetry, and hence is distinctly different and combinatorically richer than the fcc tetrahedra-octahedra tiling, which only has two distinct tiling units. Then we construct a one-parameter family of octahedron packings that continuously spans from the fcc to the optimal lattice packing of octahedra. We show that the "holes" in these packings, except for the two extreme cases, are tetrahedra of two sizes, leading to a family of periodic tilings with units composed four small tetrahedra and two large tetrahedra that contact an octahedron. These tilings generally possess 2,068 distinct concave tiling units, 62 of which are centrally symmetric. PMID:21690370

  19. New family of tilings of three-dimensional Euclidean space by tetrahedra and octahedra

    PubMed Central

    Conway, John H.; Jiao, Yang; Torquato, Salvatore

    2011-01-01

    It is well known that two regular tetrahedra can be combined with a single regular octahedron to tile (complete fill) three-dimensional Euclidean space . This structure was called the “octet truss” by Buckminster Fuller. It was believed that such a tiling, which is the Delaunay tessellation of the face-centered cubic (fcc) lattice, and its closely related stacking variants, are the only tessellations of that involve two different regular polyhedra. Here we identify and analyze a unique family comprised of a noncountably infinite number of periodic tilings of whose smallest repeat tiling unit consists of one regular octahedron and six smaller regular tetrahedra. We first derive an extreme member of this unique tiling family by showing that the “holes” in the optimal lattice packing of octahedra, obtained by Minkowski over a century ago, are congruent tetrahedra. This tiling has 694 distinct concave (i.e., nonconvex) repeat units, 24 of which possess central symmetry, and hence is distinctly different and combinatorically richer than the fcc tetrahedra-octahedra tiling, which only has two distinct tiling units. Then we construct a one-parameter family of octahedron packings that continuously spans from the fcc to the optimal lattice packing of octahedra. We show that the “holes” in these packings, except for the two extreme cases, are tetrahedra of two sizes, leading to a family of periodic tilings with units composed four small tetrahedra and two large tetrahedra that contact an octahedron. These tilings generally possess 2,068 distinct concave tiling units, 62 of which are centrally symmetric. PMID:21690370

  20. Parallel algorithms for arbitrary dimensional Euclidean distance transforms with applications on arrays with reconfigurable optical buses.

    PubMed

    Wang, Yuh-Rau; Horng, Shi-Jinn

    2004-02-01

    In this paper, we present algorithms for computing the Euclidean distance transform (EDT) of a binary image on the array with reconfigurable optical buses (AROB). First, we develop a parallel algorithm termed as Algorithm Expander which can be implemented in O(1) time on an AROB with N x Ndelta processors, where delta = 1/k, k is a constant and a positive integer. Algorithm Expander is designed to compute a higher dimensional EDT based on the computed lower dimensional EDT. It functions as a general EDT expander for us to expand EDT from a lower dimension to a higher dimension. We then develop parallel algorithms for the two-dimensional (2-D)_EDT of a binary image array of size N x N in O(1) time on an AROB with N x N x Ndelta processors and for the three-dimensional (3-D)_EDT of a binary image of size N x N x N in O(1) time on an AROB with N x N x N x Ndelta processors. To the best of our knowledge, all results derived above are the best O(1) time algorithms known. We then extend it to compute the nD_EDT of a binary image of size Nn in O(n) time on an AROB with Nn+delta processors. We also apply our parallel EDT algorithms to build Voronoi diagram and Voronoi polyhetra (polygons), to find all maximal empty spheres and the largest empty sphere, and to compute the medial axis transform. All of these applications can be solved in the same time complexity on an AROB with the same number of processors as needed for solving the EDT problems in the same dimensions. PMID:15369089

  1. Tests of quantum chromodynamics in exclusive e sup + e sup minus and. gamma. gamma. processes

    SciTech Connect

    Brodsky, S.J.

    1989-09-01

    This paper discusses the following topics: Factorization theorem for exclusive processes; Electromagnetic form factors of baryons; Suppression of final state interactions; The {gamma}{pi}{sub 0} Transition form factor; Exclusive charmonium decays; The {pi}-{rho} puzzle; Time-like compton processes; Multi-hadron production; Heavy Quark exclusive states and form factor zeros in QCD; Exclusive {gamma}{gamma} reactions; Higher twist effects; and Tauonium and threshold {tau}{sup +}{tau}{sup {minus}} production. 41 refs., 15 figs. (LSP)

  2. Full analysis of multi-photon pair effects in spontaneous parametric down conversion based photonic quantum information processing

    NASA Astrophysics Data System (ADS)

    Takeoka, Masahiro; Jin, Rui-Bo; Sasaki, Masahide

    2015-04-01

    In spontaneous parametric down conversion (SPDC) based quantum information processing (QIP) experiments, there is a tradeoff between the coincidence count rates (i.e. the pumping power of the SPDC), which limits the rate of the protocol, and the visibility of the quantum interference, which limits the quality of the protocol. This tradeoff is mainly caused by the multi-photon pair emissions from the SPDCs. In theory, the problem is how to model the experiments without truncating these multi-photon emissions while including practical imperfections. In this paper, we establish a method to theoretically simulate SPDC-based QIPs which fully incorporates the effect of multi-photon emissions and various practical imperfections. The key ingredient in our method is the application of the characteristic function formalism which has been used in continuous variable QIPs. We apply our method to three examples, the Hong-Ou-Mandel interference and the Einstein-Podolsky-Rosen interference experiments, and the concatenated entanglement swapping protocol. For the first two examples, we show that our theoretical results quantitatively agree with the recent experimental results. Also we provide the closed expressions for these interference visibilities with the full multi-photon components and various imperfections. For the last example, we provide the general theoretical form of the concatenated entanglement swapping protocol in our method and show the numerical results up to five concatenations. Our method requires only a small computational resource (a few minutes by a commercially available computer), which was not possible in the previous theoretical approach. Our method will have applications in a wide range of SPDC-based QIP protocols with high accuracy and a reasonable computational resource.

  3. Modeling the quantum yields of herbicide 2,4-D decay in UV/H2O2 process.

    PubMed

    Chu, W

    2001-08-01

    The photodecay of herbicide 2,4-D in a hydrogen peroxide-aided photolysis process was studied and modeled. The decay rate of 2,4-D was known to be low in the natural environment, but rate improvement was achieved in an H2O2/UV system. The 2,4-D decay quantum yields under ultraviolet (UV) light at 253.7 nm increased from 4.86 x 10(-6) to 1.30 x 10(-4) as the ratio of [H2O2]/[2,4-D] increased from 0.05 to 12.5. Apparently, in the presence of UV light, the decay rate of 2,4-D could be greatly improved as the concentration of hydrogen peroxide increased. However, the efficiency of 2,4-D photodecay was retarded if the concentration of H2O2 was overdosed, because the excess hydrogen peroxide consumes the hydroxyl radicals (HO*) in the solution, resulting in a much weaker oxidant HO2*. The decay of 2,4-D was also pH dependent. A ranking of acid (highest), base (middle) and neutral (lowest) was observed owing to the property change of reactants and the shifting of dominant mechanisms among photolysis, photohydrolysis and chemical oxidation. Two mathematical models were proposed to predict the quantum yield for various [H2O2]/[2,4-D] ratios and initial pH levels, in which very good correlation was found for the ranges of regular application. PMID:11513426

  4. Quantum probabilities for inflation from holography

    NASA Astrophysics Data System (ADS)

    Hartle, James B.; Hawking, S. W.; Hertog, Thomas

    2014-01-01

    The evolution of the universe is determined by its quantum state. The wave function of the universe obeys the constraints of general relativity and in particular the Wheeler-DeWitt equation (WDWE). For non-zero Λ, we show that solutions of the WDWE at large volume have two domains in which geometries and fields are asymptotically real. In one the histories are Euclidean asymptotically anti-de Sitter, in the other they are Lorentzian asymptotically classical de Sitter. Further, the universal complex semiclassical asymptotic structure of solutions of the WDWE implies that the leading order in hbar quantum probabilities for classical, asymptotically de Sitter histories can be obtained from the action of asymptotically anti-de Sitter configurations. This leads to a promising, universal connection between quantum cosmology and holography.

  5. Quantum probabilities for inflation from holography

    SciTech Connect

    Hartle, James B.; Hawking, S.W.; Hertog, Thomas E-mail: S.W.Hawking@damtp.cam.ac.uk

    2014-01-01

    The evolution of the universe is determined by its quantum state. The wave function of the universe obeys the constraints of general relativity and in particular the Wheeler-DeWitt equation (WDWE). For non-zero Λ, we show that solutions of the WDWE at large volume have two domains in which geometries and fields are asymptotically real. In one the histories are Euclidean asymptotically anti-de Sitter, in the other they are Lorentzian asymptotically classical de Sitter. Further, the universal complex semiclassical asymptotic structure of solutions of the WDWE implies that the leading order in h-bar quantum probabilities for classical, asymptotically de Sitter histories can be obtained from the action of asymptotically anti-de Sitter configurations. This leads to a promising, universal connection between quantum cosmology and holography.

  6. Non-standard symmetries and quantum anomalies

    SciTech Connect

    Visinescu, Anca; Visinescu, Mihai

    2008-08-31

    Quantum anomalies are investigated on curved spacetimes. The intimate relation between Killing-Yano tensors and non-standard symmetries is pointed out. The gravitational anomalies are absent if the hidden symmetry is associated to a Killing-Yano tensor. The axial anomaly in a background gravitational field is directly related with the index of the Dirac operator. In the Dirac theory on curved spaces, Killing-Yano tensors generate Dirac-type operators involved in interesting algebraic structures. The general results are applied to the 4-dimensional Euclidean Taub-NUT space.

  7. Realism vs. Constructivism in Contemporary Physics: The Impact of the Debate on the Understanding of Quantum Theory and Its Instructional Process

    ERIC Educational Resources Information Center

    Karakostas, Vassilios; Hadzidaki, Pandora

    2005-01-01

    In the present study we attempt to incorporate the philosophical dialogue about physical reality into the instructional process of quantum mechanics. Taking into account that both scientific realism and constructivism represent, on the basis of a rather broad spectrum, prevalent philosophical currents in the domain of science education, the…

  8. The effects of post-processing on the surface and the optical properties of copper indium sulfide quantum dots.

    PubMed

    Akdas, Tugce; Distaso, Monica; Kuhri, Susanne; Winter, Benjamin; Birajdar, Balaji; Spiecker, Erdmann; Guldi, Dirk M; Peukert, Wolfgang

    2015-05-01

    In the current contribution we report on investigations regarding the surface of CuInS2 quantum dots and on different strategies to control the amount of surface ligands in a post-processing step. In particular, the reactivity of the organic components, that is, 1-dodecanthiol and 1-octadecene as ligand and solvent, respectively, during nanocrystal formation was studied. A new method to remove residuals from the reaction mixture and to detach excess organics from the surface of the nanocrystals is reported. Our new method, which is based on the utilization of acids, is compared with standard purification procedures by means of thermogravimetric analysis (TGA) with particular focus on its efficiency to remove organics. As a complement, the surface chemistry is analyzed by nuclear magnetic resonance spectroscopy (NMR) to shed light on the nature of the organic components still present after purification. Further analysis of the product by inductively coupled plasma optical emission spectroscopy (ICP-OES) is performed to verify the influence of the new purification method on surface composition and properties. Moreover, steady state and time resolved spectroscopies give insights into excitonic behavior as well as recombination processes. Finally, the new method is optimized for the purification of CuInS2-ZnS nanocrystals, which show enhanced optical properties. PMID:25643961

  9. Constructions of new families of nonbinary quantum codes

    SciTech Connect

    La Guardia, Giuliano G.

    2009-10-15

    Three code constructions generating new families of good nonbinary quantum codes are presented in this paper. The first two ones are derived from Hermitian self-orthogonal non-narrow-sense Bose-Chaudhuri-Hocquenghem (BCH) codes. The third one is derived from q-ary (q{ne}2 is a prime power) Steane's enlargement of Calderbank-Shor-Steane codes applied to Euclidean self-orthogonal non-narrow-sense BCH codes. The quantum nonbinary BCH codes presented here have parameters better than the ones available in the literature.

  10. Optimizing multi-resolution segmentation scale using empirical methods: Exploring the sensitivity of the supervised discrepancy measure Euclidean distance 2 (ED2)

    NASA Astrophysics Data System (ADS)

    Witharana, Chandi; Civco, Daniel L.

    2014-01-01

    Multiresolution segmentation (MRS) has proven to be one of the most successful image segmentation algorithms in the geographic object-based image analysis (GEOBIA) framework. This algorithm is relatively complex and user-dependent; scale, shape, and compactness are the main parameters available to users for controlling the algorithm. Plurality of segmentation results is common because each parameter may take a range of values within its parameter space or different combinations of values among parameters. Finding optimal parameter values through a trial-and-error process is commonly practiced at the expense of time and labor, thus, several alternative supervised and unsupervised methods for supervised automatic parameter setting have been proposed and tested. In the case of supervised empirical assessments, discrepancy measures are employed for computing measures of dissimilarity between a reference polygon and an image object candidate. Evidently the reliability of the optimal-parameter prediction heavily relies on the sensitivity of the segmentation quality metric. The idea behind pursuing optimal parameter setting is that, for instance, a given scale setting provides image object candidates different from the other scale setting; thus, by design the supervised quality metric should capture this difference. In this exploratory study, we selected the Euclidean distance 2 (ED2) metric, a recently proposed supervised metric, whose main design goal is to optimize the geometrical discrepancy (potential segmentation error (PSE)) and arithmetic discrepancy between image objects and reference polygons (number-of segmentation ratio (NSR)) in two dimensional Euclidean space, as a candidate to investigate the validity and efficacy of empirical discrepancy measures for finding the optimal scale parameter setting of the MRS algorithm. We chose test image scenes from four different space-borne sensors with varying spatial resolutions and scene contents and systematically

  11. Quantum abacus

    NASA Astrophysics Data System (ADS)

    Cheon, Taksu; Tsutsui, Izumi; Fülöp, Tamás

    2004-09-01

    We show that the point interactions on a line can be utilized to provide U(2) family of qubit operations for quantum information processing. Qubits are realized as states localized in either side of the point interaction which represents a controllable gate. The qubit manipulation proceeds in a manner analogous to the operation of an abacus.

  12. Pictures of Processes: Automated Graph Rewriting for Monoidal Categories and Applications to Quantum Computing

    NASA Astrophysics Data System (ADS)

    Kumar, Bhupendra

    nanowire morphology of the p-Si photocathode on the homogeneous catalytic reduction of CO2 by using p-Si/Re-catalyst junction are also described in this dissertation. For phenyl ethyl modified p-Si photocathode, the rate of homogeneous catalysis for CO2 reduction by Re-catalyst is three times greater than glassy carbon electrode and six times greater than the hexyl modified and the hydrogen terminated p-Si photocathodes. When hexyl modified p-Si nanowires are used as photocathode, the homogeneous catalytic current density increased by a factor of two compared to planar p-Si (both freshly etched and hexyl modified) photocathode. A successful light assisted generation of syngas (H2:CO = 2:1) from CO2 and water is achieved by using p-Si/Re-catalyst. In this system, water is reduced heterogeneously on p-Si surface and CO2 is reduced homogeneously by Re-catalyst. The same principle is extended to the homogeneous proton reduction by using p-Si/[FeFe] complex junction where [FeFe] complex [Fe2(micro-bdt)(CO) 6] (bdt = benzene-1,2-dithiolate)] is a proton reduction molecular catalyst. A short circuit quantum efficiency of 79 % with 100 % Faradaic efficiency and 600 mV open circuit are achieved by using p-Si/[FeFe] complex for proton reduction with 300 mM perchloric acid as a proton source. Cobalt difluororyl-diglyoximate (Co-catalyst) is a proton reduction catalyst with only 200 mV of overpotential for the hydrogen evolution reaction (HRE). The Co-catalyst is photoelectrochemically reduced with a photovoltage of 470 mV on illuminated p-Si photocathode. For p-Si photocathodes, the overpotential for proton reduction is over 1 V. In principle, p-Si/Co-catalyst junction can reduce proton to hydrogen homogeneously at underpotential. In a concluding effort, a wireless monolithic dual face single photoelectrode (multi junction photovoltaic cell which can generate a voltage higher 1.7 V) based photochemical cell is proposed for direct conversion of solar energy into liquid fuel. In this

  13. Dynamic virtual fixture on the Euclidean group for admittance-type manipulator in deforming environments

    PubMed Central

    2014-01-01

    Background In a deforming anatomic environment, the motion of an instrument suffers from complex geometrical and dynamic constraints, robot assisted minimally invasive surgery therefore requires more sophisticated skills for surgeons. This paper proposes a novel dynamic virtual fixture (DVF) to enhance the surgical operation accuracy of admittance-type medical robotics in the deforming environment. Methods A framework for DVF on the Euclidean Group SE(3) is presented, which unites rotation and translation in a compact form. First, we constructed the holonomic/non-holonomic constraints, and then searched for the corresponded reference to make a distinction between preferred and non-preferred directions. Second, different control strategies are employed to deal with the tasks along the distinguished directions. The desired spatial compliance matrix is synthesized from an allowable motion screw set to filter out the task unrelated components from manual input, the operator has complete control over the preferred directions; while the relative motion between the surgical instrument and the anatomy structures is actively tracked and cancelled, the deviation relative to the reference is compensated jointly by the operator and DVF controllers. The operator, haptic device, admittance-type proxy and virtual deforming environment are involved in a hardware-in-the-loop experiment, human-robot cooperation with the assistance of DVF controller is carried out on a deforming sphere to simulate beating heart surgery, performance of the proposed DVF on admittance-type proxy is evaluated, and both human factors and control parameters are analyzed. Results The DVF can improve the dynamic properties of human-robot cooperation in a low-frequency (0 ~ 40 rad/sec) deforming environment, and maintain synergy of orientation and translation during the operation. Statistical analysis reveals that the operator has intuitive control over the preferred directions, human and the DVF

  14. Evaluation of superconducting quantum interference devices interfaced with digital signal processing electronics for biomagnetic applications

    SciTech Connect

    Kung, Pang-Jen, Flynn, E.R.; Bracht, R.R.; Lewis, P.S.

    1994-08-01

    The performance of a dc-SQUID magnetometer driven by both analog electronics and digital signal processors are investigated and compared for biomagnetic applications. Low-noise ( < 5 {mu} {Phi} {sub 0}/{radical}Hz at 1 Hz) dc-SQUIDs were fabricated by Conductus, Inc. using the all-refractory Nb/Al/Al{sub 2}O{sub 3}/Nb process on silicon substrates with on-chip modulation coils and integral washer damping resistors. A second-order gradiometer was magnetically coupled to the input coil of the SQUID to maximize the detected signal strength. The readout of this SQUID gradiometer was achieved using a conventional flux-locked loop (FLL) circuit to provide a linearized voltage output that was proportional to the flux applied to the SQUID. A shielded cylinder was constructed to house the magnetometer to reduce ambient field noise. To realize the digital feedback loop, the analog FLL is replaced except for the preamplifier by a digital signal processing board with dual 16-bit A/D and D/A converters. This approach shows several advantages over the analog scheme including operational flexibility, cost reduction, and possibly, the enhancement of dynamic ranges and slew rates.

  15. Structure of multiphoton quantum optics. II. Bipartite systems, physical processes, and heterodyne squeezed states

    SciTech Connect

    Dell'Anno, Fabio; De Siena, Silvio; Illuminati, Fabrizio

    2004-03-01

    Extending the scheme developed for a single mode of the electromagnetic field in the preceding paper [F. Dell'Anno, S. De Siena, and F. Illuminati, Phys. Rev. A 69, 033812 (2004)], we introduce two-mode nonlinear canonical transformations depending on two heterodyne mixing angles. They are defined in terms of Hermitian nonlinear functions that realize heterodyne superpositions of conjugate quadratures of bipartite systems. The canonical transformations diagonalize a class of Hamiltonians describing nondegenerate and degenerate multiphoton processes. We determine the coherent states associated with the canonical transformations, which generalize the nondegenerate two-photon squeezed states. Such heterodyne multiphoton squeezed states are defined as the simultaneous eigenstates of the transformed, coupled annihilation operators. They are generated by nonlinear unitary evolutions acting on two-mode squeezed states. They are non-Gaussian, highly nonclassical, entangled states. For a quadratic nonlinearity the heterodyne multiphoton squeezed states define two-mode cubic phase states. The statistical properties of these states can be widely adjusted by tuning the heterodyne mixing angles, the phases of the nonlinear couplings, as well as the strength of the nonlinearity. For quadratic nonlinearity, we study the higher-order contributions to the susceptibility in nonlinear media and we suggest possible experimental realizations of multiphoton conversion processes generating the cubic-phase heterodyne squeezed states.

  16. Structure of multiphoton quantum optics. II. Bipartite systems, physical processes, and heterodyne squeezed states

    NASA Astrophysics Data System (ADS)

    dell'Anno, Fabio; de Siena, Silvio; Illuminati, Fabrizio

    2004-03-01

    Extending the scheme developed for a single mode of the electromagnetic field in the preceding paper [

    F. Dell’Anno, S. De Siena, and F. Illuminati, Phys. Rev. A 69, 033812 (2004)
    ], we introduce two-mode nonlinear canonical transformations depending on two heterodyne mixing angles. They are defined in terms of Hermitian nonlinear functions that realize heterodyne superpositions of conjugate quadratures of bipartite systems. The canonical transformations diagonalize a class of Hamiltonians describing nondegenerate and degenerate multiphoton processes. We determine the coherent states associated with the canonical transformations, which generalize the nondegenerate two-photon squeezed states. Such heterodyne multiphoton squeezed states are defined as the simultaneous eigenstates of the transformed, coupled annihilation operators. They are generated by nonlinear unitary evolutions acting on two-mode squeezed states. They are non-Gaussian, highly nonclassical, entangled states. For a quadratic nonlinearity the heterodyne multiphoton squeezed states define two-mode cubic phase states. The statistical properties of these states can be widely adjusted by tuning the heterodyne mixing angles, the phases of the nonlinear couplings, as well as the strength of the nonlinearity. For quadratic nonlinearity, we study the higher-order contributions to the susceptibility in nonlinear media and we suggest possible experimental realizations of multiphoton conversion processes generating the cubic-phase heterodyne squeezed states.

  17. Quantum Computation

    NASA Astrophysics Data System (ADS)

    Ekert, Artur

    1994-08-01

    As computers become faster they must become smaller because of the finiteness of the speed of light. The history of computer technology has involved a sequence of changes from one type of physical realisation to another - from gears to relays to valves to transistors to integrated circuits and so on. Quantum mechanics is already important in the design of microelectronic components. Soon it will be necessary to harness quantum mechanics rather than simply take it into account, and at that point it will be possible to give data processing devices new functionality.

  18. Quantum algorithms

    NASA Astrophysics Data System (ADS)

    Abrams, Daniel S.

    This thesis describes several new quantum algorithms. These include a polynomial time algorithm that uses a quantum fast Fourier transform to find eigenvalues and eigenvectors of a Hamiltonian operator, and that can be applied in cases (commonly found in ab initio physics and chemistry problems) for which all known classical algorithms require exponential time. Fast algorithms for simulating many body Fermi systems are also provided in both first and second quantized descriptions. An efficient quantum algorithm for anti-symmetrization is given as well as a detailed discussion of a simulation of the Hubbard model. In addition, quantum algorithms that calculate numerical integrals and various characteristics of stochastic processes are described. Two techniques are given, both of which obtain an exponential speed increase in comparison to the fastest known classical deterministic algorithms and a quadratic speed increase in comparison to classical Monte Carlo (probabilistic) methods. I derive a simpler and slightly faster version of Grover's mean algorithm, show how to apply quantum counting to the problem, develop some variations of these algorithms, and show how both (apparently distinct) approaches can be understood from the same unified framework. Finally, the relationship between physics and computation is explored in some more depth, and it is shown that computational complexity theory depends very sensitively on physical laws. In particular, it is shown that nonlinear quantum mechanics allows for the polynomial time solution of NP-complete and #P oracle problems. Using the Weinberg model as a simple example, the explicit construction of the necessary gates is derived from the underlying physics. Nonlinear quantum algorithms are also presented using Polchinski type nonlinearities which do not allow for superluminal communication. (Copies available exclusively from MIT Libraries, Rm. 14- 0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)

  19. Efficient Quantum Pseudorandomness

    NASA Astrophysics Data System (ADS)

    Brandão, Fernando G. S. L.; Harrow, Aram W.; Horodecki, Michał

    2016-04-01

    Randomness is both a useful way to model natural systems and a useful tool for engineered systems, e.g., in computation, communication, and control. Fully random transformations require exponential time for either classical or quantum systems, but in many cases pseudorandom operations can emulate certain properties of truly random ones. Indeed, in the classical realm there is by now a well-developed theory regarding such pseudorandom operations. However, the construction of such objects turns out to be much harder in the quantum case. Here, we show that random quantum unitary time evolutions ("circuits") are a powerful source of quantum pseudorandomness. This gives for the first time a polynomial-time construction of quantum unitary designs, which can replace fully random operations in most applications, and shows that generic quantum dynamics cannot be distinguished from truly random processes. We discuss applications of our result to quantum information science, cryptography, and understanding the self-equilibration of closed quantum dynamics.

  20. Efficient Quantum Pseudorandomness.

    PubMed

    Brandão, Fernando G S L; Harrow, Aram W; Horodecki, Michał

    2016-04-29

    Randomness is both a useful way to model natural systems and a useful tool for engineered systems, e.g., in computation, communication, and control. Fully random transformations require exponential time for either classical or quantum systems, but in many cases pseudorandom operations can emulate certain properties of truly random ones. Indeed, in the classical realm there is by now a well-developed theory regarding such pseudorandom operations. However, the construction of such objects turns out to be much harder in the quantum case. Here, we show that random quantum unitary time evolutions ("circuits") are a powerful source of quantum pseudorandomness. This gives for the first time a polynomial-time construction of quantum unitary designs, which can replace fully random operations in most applications, and shows that generic quantum dynamics cannot be distinguished from truly random processes. We discuss applications of our result to quantum information science, cryptography, and understanding the self-equilibration of closed quantum dynamics. PMID:27176509