Coherent states in quantum mechanics

International Nuclear Information System (INIS)

Rodrigues, R. de Lima; Fernandes Junior, Damasio; Batista, Sheyla Marques

2001-12-01

We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out. (author)

Coherent states and rational surfaces

International Nuclear Information System (INIS)

Brody, Dorje C; Graefe, Eva-Maria

2010-01-01

The state spaces of generalized coherent states associated with special unitary groups are shown to form rational curves and surfaces in the space of pure states. These curves and surfaces are generated by the various Veronese embeddings of the underlying state space into higher dimensional state spaces. This construction is applied to the parameterization of generalized coherent states, which is useful for practical calculations, and provides an elementary combinatorial approach to the geometry of the coherent state space. The results are extended to Hilbert spaces with indefinite inner products, leading to the introduction of a new kind of generalized coherent states.

Fuzzy spheres from inequivalent coherent states quantizations

International Nuclear Information System (INIS)

Gazeau, Jean Pierre; Huguet, Eric; Lachieze-Rey, Marc; Renaud, Jacques

2007-01-01

The existence of a family of coherent states (CS) solving the identity in a Hilbert space allows, under certain conditions, to quantize functions defined on the measure space of CS parameters. The application of this procedure to the 2-sphere provides a family of inequivalent CS quantizations based on the spin spherical harmonics (the CS quantization from usual spherical harmonics appears to give a trivial issue for the Cartesian coordinates). We compare these CS quantizations to the usual (Madore) construction of the fuzzy sphere. Due to these differences, our procedure yields new types of fuzzy spheres. Moreover, the general applicability of CS quantization suggests similar constructions of fuzzy versions of a large variety of sets

Ordering states with various coherence measures

Science.gov (United States)

Yang, Long-Mei; Chen, Bin; Fei, Shao-Ming; Wang, Zhi-Xi

2018-04-01

Quantum coherence is one of the most significant theories in quantum physics. Ordering states with various coherence measures is an intriguing task in quantification theory of coherence. In this paper, we study this problem by use of four important coherence measures—the l_1 norm of coherence, the relative entropy of coherence, the geometric measure of coherence and the modified trace distance measure of coherence. We show that each pair of these measures give a different ordering of qudit states when d≥3. However, for single-qubit states, the l_1 norm of coherence and the geometric coherence provide the same ordering. We also show that the relative entropy of coherence and the geometric coherence give a different ordering for single-qubit states. Then we partially answer the open question proposed in Liu et al. (Quantum Inf Process 15:4189, 2016) whether all the coherence measures give a different ordering of states.

Quantum learning of coherent states

Energy Technology Data Exchange (ETDEWEB)

Sentis, Gael [Universitat Autonoma de Barcelona, Fisica Teorica: Informacio i Fenomens Quantics, Barcelona (Spain); Guta, Madalin; Adesso, Gerardo [University of Nottingham, School of Mathematical Sciences, Nottingham (United Kingdom)

2015-12-15

We develop a quantum learning scheme for binary discrimination of coherent states of light. This is a problem of technological relevance for the reading of information stored in a digital memory. In our setting, a coherent light source is used to illuminate a memory cell and retrieve its encoded bit by determining the quantum state of the reflected signal. We consider a situation where the amplitude of the states produced by the source is not fully known, but instead this information is encoded in a large training set comprising many copies of the same coherent state. We show that an optimal global measurement, performed jointly over the signal and the training set, provides higher successful identification rates than any learning strategy based on first estimating the unknown amplitude by means of Gaussian measurements on the training set, followed by an adaptive discrimination procedure on the signal. By considering a simplified variant of the problem, we argue that this is the case even for non-Gaussian estimation measurements. Our results show that, even in absence of entanglement, collective quantum measurements yield an enhancement in the readout of classical information, which is particularly relevant in the operating regime of low-energy signals. (orig.)

Quantum learning of coherent states

International Nuclear Information System (INIS)

Sentis, Gael; Guta, Madalin; Adesso, Gerardo

2015-01-01

We develop a quantum learning scheme for binary discrimination of coherent states of light. This is a problem of technological relevance for the reading of information stored in a digital memory. In our setting, a coherent light source is used to illuminate a memory cell and retrieve its encoded bit by determining the quantum state of the reflected signal. We consider a situation where the amplitude of the states produced by the source is not fully known, but instead this information is encoded in a large training set comprising many copies of the same coherent state. We show that an optimal global measurement, performed jointly over the signal and the training set, provides higher successful identification rates than any learning strategy based on first estimating the unknown amplitude by means of Gaussian measurements on the training set, followed by an adaptive discrimination procedure on the signal. By considering a simplified variant of the problem, we argue that this is the case even for non-Gaussian estimation measurements. Our results show that, even in absence of entanglement, collective quantum measurements yield an enhancement in the readout of classical information, which is particularly relevant in the operating regime of low-energy signals. (orig.)

The coherent state variational algorithm and the QCD deconfinement phase transition

International Nuclear Information System (INIS)

Somsky, W.R.

1989-01-01

This thesis describes the coherent state variational algorithm, its implementation in a recently completed set of computer programs, and its application to the study of the QCD deconfinement phase transition. The coherent state variational algorithm is a computational method for studying the large-N limit of non-abelian gauge theories by direct exploitation of the classical nature of this limit. Unlike Monte Carlo methods, this technique is applicable to both euclidean and hamiltonian formulations of lattice gauge theories and is deterministic, rather than statistical, in nature. The first part of this thesis presents the theoretical basis of the coherent state algorithm and describes the application of the algorithm, to non-abelian lattice gauge theories. The second part describes the symbolic methods involved in the computer implementation of the coherent state algorithm and gives an overview of the programs which form the full coherent state implementation. The final part of this thesis discusses the application of the coherent state algorithm to the study of the QCD deconfinement phase transition at large N. The results obtained are indicative of a second-order transition for lattices of temporal extent N ν = 1 and N τ = 2 in both three and four space-time dimensions

Femtosecond time-resolved studies of coherent vibrational Raman scattering in large gas-phase molecules

International Nuclear Information System (INIS)

Hayden, C.C.; Chandler, D.W.

1995-01-01

Results are presented from femtosecond time-resolved coherent Raman experiments in which we excite and monitor vibrational coherence in gas-phase samples of benzene and 1,3,5-hexatriene. Different physical mechanisms for coherence decay are seen in these two molecules. In benzene, where the Raman polarizability is largely isotropic, the Q branch of the vibrational Raman spectrum is the primary feature excited. Molecules in different rotational states have different Q-branch transition frequencies due to vibration--rotation interaction. Thus, the macroscopic polarization that is observed in these experiments decays because it has many frequency components from molecules in different rotational states, and these frequency components go out of phase with each other. In 1,3,5-hexatriene, the Raman excitation produces molecules in a coherent superposition of rotational states, through (O, P, R, and S branch) transitions that are strong due to the large anisotropy of the Raman polarizability. The coherent superposition of rotational states corresponds to initially spatially oriented, vibrationally excited, molecules that are freely rotating. The rotation of molecules away from the initial orientation is primarily responsible for the coherence decay in this case. These experiments produce large (∼10% efficiency) Raman shifted signals with modest excitation pulse energies (10 μJ) demonstrating the feasibility of this approach for a variety of gas phase studies. copyright 1995 American Institute of Physics

Mixed coherent states in coupled chaotic systems: Design of secure wireless communication

Science.gov (United States)

Vigneshwaran, M.; Dana, S. K.; Padmanaban, E.

2016-12-01

A general coupling design is proposed to realize a mixed coherent (MC) state: coexistence of complete synchronization, antisynchronization, and amplitude death in different pairs of similar state variables of the coupled chaotic system. The stability of coupled system is ensured by the Lyapunov function and a scaling of each variable is also separately taken care of. When heterogeneity as a parameter mismatch is introduced in the coupled system, the coupling function facilitates to retain its coherence and displays the global stability with renewed scaling factor. Robust synchronization features facilitated by a MC state enable to design a dual modulation scheme: binary phase shift key (BPSK) and parameter mismatch shift key (PMSK), for secure data transmission. Two classes of decoders (coherent and noncoherent) are discussed, the noncoherent decoder shows better performance over the coherent decoder, mostly a noncoherent demodulator is preferred in biological implant applications. Both the modulation schemes are demonstrated numerically by using the Lorenz oscillator and the BPSK scheme is demonstrated experimentally using radio signals.

Error Free Quantum Reading by Quasi Bell State of Entangled Coherent States

Science.gov (United States)

Hirota, Osamu

2017-12-01

Nonclassical states of light field have been exploited to provide marvellous results in quantum information science. Usefulness of nonclassical states in quantum information science depends on whether a physical parameter as a signal is continuous or discrete. Here we present an investigation of the potential of quasi Bell states of entangled coherent states in quantum reading of the classical digital memory which was pioneered by Pirandola (Phys.Rev.Lett.,106,090504,2011). This is a typical example of discrimination for discrete quantum parameters. We show that the quasi Bell state gives the error free performance in the quantum reading that cannot be obtained by any classical state.

Painlevé IV coherent states

Energy Technology Data Exchange (ETDEWEB)

Bermudez, David, E-mail: david.bermudez@weizmann.ac.il [Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100 (Israel); Departamento de Física, Cinvestav, A.P. 14-740, 07000 México D.F. (Mexico); Contreras-Astorga, Alonso, E-mail: aloncont@iun.edu [Department of Mathematics and Actuarial Science, Indiana University Northwest, 3400 Broadway, Gary IN 46408 (United States); Departamento de Física, Cinvestav, A.P. 14-740, 07000 México D.F. (Mexico); Fernández C, David J., E-mail: david@fis.cinvestav.mx [Departamento de Física, Cinvestav, A.P. 14-740, 07000 México D.F. (Mexico)

2014-11-15

A simple way to find solutions of the Painlevé IV equation is by identifying Hamiltonian systems with third-order differential ladder operators. Some of these systems can be obtained by applying supersymmetric quantum mechanics (SUSY QM) to the harmonic oscillator. In this work, we will construct families of coherent states for such subset of SUSY partner Hamiltonians which are connected with the Painlevé IV equation. First, these coherent states are built up as eigenstates of the annihilation operator, then as displaced versions of the extremal states, both involving the related third-order ladder operators, and finally as extremal states which are also displaced but now using the so called linearized ladder operators. To each SUSY partner Hamiltonian corresponds two families of coherent states: one inside the infinite subspace associated with the isospectral part of the spectrum and another one in the finite subspace generated by the states created through the SUSY technique. - Highlights: • We use SUSY QM to obtain Hamiltonians with third-order differential ladder operators. • We show that these systems are related with the Painlevé IV equation. • We apply different definitions of coherent states to these Hamiltonians using the third-order ladder operators and some linearized ones. • We construct families of coherent states for such systems, which we called Painlevé IV coherent states.

Painlevé IV coherent states

International Nuclear Information System (INIS)

Bermudez, David; Contreras-Astorga, Alonso; Fernández C, David J.

2014-01-01

A simple way to find solutions of the Painlevé IV equation is by identifying Hamiltonian systems with third-order differential ladder operators. Some of these systems can be obtained by applying supersymmetric quantum mechanics (SUSY QM) to the harmonic oscillator. In this work, we will construct families of coherent states for such subset of SUSY partner Hamiltonians which are connected with the Painlevé IV equation. First, these coherent states are built up as eigenstates of the annihilation operator, then as displaced versions of the extremal states, both involving the related third-order ladder operators, and finally as extremal states which are also displaced but now using the so called linearized ladder operators. To each SUSY partner Hamiltonian corresponds two families of coherent states: one inside the infinite subspace associated with the isospectral part of the spectrum and another one in the finite subspace generated by the states created through the SUSY technique. - Highlights: • We use SUSY QM to obtain Hamiltonians with third-order differential ladder operators. • We show that these systems are related with the Painlevé IV equation. • We apply different definitions of coherent states to these Hamiltonians using the third-order ladder operators and some linearized ones. • We construct families of coherent states for such systems, which we called Painlevé IV coherent states

Coherent states on Hilbert modules

International Nuclear Information System (INIS)

Ali, S Twareque; Bhattacharyya, T; Roy, S S

2011-01-01

We generalize the concept of coherent states, traditionally defined as special families of vectors on Hilbert spaces, to Hilbert modules. We show that Hilbert modules over C*-algebras are the natural settings for a generalization of coherent states defined on Hilbert spaces. We consider those Hilbert C*-modules which have a natural left action from another C*-algebra, say A. The coherent states are well defined in this case and they behave well with respect to the left action by A. Certain classical objects like the Cuntz algebra are related to specific examples of coherent states. Finally we show that coherent states on modules give rise to a completely positive definite kernel between two C*-algebras, in complete analogy to the Hilbert space situation. Related to this, there is a dilation result for positive operator-valued measures, in the sense of Naimark. A number of examples are worked out to illustrate the theory. Some possible physical applications are also mentioned.

Coherent states in quantum physics

CERN Document Server

Gazeau, Jean-Pierre

2009-01-01

This self-contained introduction discusses the evolution of the notion of coherent states, from the early works of Schrödinger to the most recent advances, including signal analysis. An integrated and modern approach to the utility of coherent states in many different branches of physics, it strikes a balance between mathematical and physical descriptions.Split into two parts, the first introduces readers to the most familiar coherent states, their origin, their construction, and their application and relevance to various selected domains of physics. Part II, mostly based on recent original results, is devoted to the question of quantization of various sets through coherent states, and shows the link to procedures in signal analysis. Title: Coherent States in Quantum Physics Print ISBN: 9783527407095 Author(s): Gazeau, Jean-Pierre eISBN: 9783527628292 Publisher: Wiley-VCH Dewey: 530.12 Publication Date: 23 Sep, 2009 Pages: 360 Category: Science, Science: Physics LCCN: Language: English Edition: N/A LCSH:

Coherent states versus De Broglie-Wavelets

International Nuclear Information System (INIS)

Barut, A.O.

1993-08-01

There are two types of nonspreading localized wave forms representing a stable, individual, indivisible, single quantum particle with interference properties endowed with classical (hidden) parameters, i.e. initial positions and velocity: coherent states and wavelets. The first is exactly known for oscillator, the second for free particles. Their relation and their construction is discussed from a new unified point of view. We then extend this contraction to the Coulomb problem, where with the introduction of a new time variable T, nonspreading states are obtained. (author). 10 refs

Optimally cloned binary coherent states

Science.gov (United States)

Müller, C. R.; Leuchs, G.; Marquardt, Ch.; Andersen, U. L.

2017-10-01

Binary coherent state alphabets can be represented in a two-dimensional Hilbert space. We capitalize this formal connection between the otherwise distinct domains of qubits and continuous variable states to map binary phase-shift keyed coherent states onto the Bloch sphere and to derive their quantum-optimal clones. We analyze the Wigner function and the cumulants of the clones, and we conclude that optimal cloning of binary coherent states requires a nonlinearity above second order. We propose several practical and near-optimal cloning schemes and compare their cloning fidelity to the optimal cloner.

Geometry of spin coherent states

Science.gov (United States)

Chryssomalakos, C.; Guzmán-González, E.; Serrano-Ensástiga, E.

2018-04-01

Spin states of maximal projection along some direction in space are called (spin) coherent, and are, in many respects, the ‘most classical’ available. For any spin s, the spin coherent states form a 2-sphere in the projective Hilbert space \

Generalized Spin Coherent States: Construction and Some Physical Properties

International Nuclear Information System (INIS)

Berrada, K.; El Baz, M.; Hassouni, Y.

2009-12-01

A generalized deformation of the su(2) algebra and a scheme for constructing associated spin coherent states is developed. The problem of resolving the unity operator in terms of these states is addressed and solved for some particular cases. The construction is carried using a deformation of Holstein-Primakoff realization of the su(2) algebra. The physical properties of these states is studied through the calculation of Mandel's parameter. (author)

Coherent states and covariant semi-spectral measures

International Nuclear Information System (INIS)

Scutaru, H.

1976-01-01

The close connection between Mackey's theory of imprimitivity systems and the so called generalized coherent states introduced by Perelomov is established. Coherent states give a covariant description of the ''localization'' of a quantum system in the phase space in a similar way as the imprimitivity systems give a covariant description of the localization of a quantum system in the configuration space. The observation that for any system of coherent states one can define a covariant semi-spectral measure made possible a rigurous formulation of this idea. A generalization of the notion of coherent states is given. Covariant semi-spectral measures associated with systems of coherent states are defined and characterized. Necessary and sufficient conditions for a unitary representation of a Lie group to be i) a subrepresentation of an induced one and ii) a representation with coherent states are given (author)

Coherent states for polynomial su(2) algebra

International Nuclear Information System (INIS)

Sadiq, Muhammad; Inomata, Akira

2007-01-01

A class of generalized coherent states is constructed for a polynomial su(2) algebra in a group-free manner. As a special case, the coherent states for the cubic su(2) algebra are discussed. The states so constructed reduce to the usual SU(2) coherent states in the linear limit

Quantum oscillators in the canonical coherent states

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, R. de Lima [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Lima, A.F. de; Ferreira, K. de Araujo [Paraiba Univ., Campina Grande, PB (Brazil). Dept. de Fisica; Vaidya, A.N. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Fisica

2001-11-01

The main characteristics of the quantum oscillator coherent states including the two-particle Calogero interaction are investigated. We show that these Calogero coherent states are the eigenstates of the second-order differential annihilation operator which is deduced via Wigner-Heisenberg algebraic technique and correspond exactly to the pure uncharged-bosonic states. They posses the important properties of non-orthogonality and completeness. The minimum uncertainty relation for the Wigner oscillator coherent states are investigated. New sets of even and odd coherent states are point out. (author)

Coherent State Quantization and Moment Problem

Directory of Open Access Journals (Sweden)

J. P. Gazeau

2010-01-01

Full Text Available Berezin-Klauder-Toeplitz (“anti-Wick” or “coherent state” quantization of the complex plane, viewed as the phase space of a particle moving on the line, is derived from the resolution of the unity provided by the standard (or gaussian coherent states. The construction of these states and their attractive properties are essentially based on the energy spectrum of the harmonic oscillator, that is on natural numbers. We follow in this work the same path by considering sequences of non-negative numbers and their associated “non-linear” coherent states. We illustrate our approach with the 2-d motion of a charged particle in a uniform magnetic field. By solving the involved Stieltjes moment problem we construct a family of coherent states for this model. We then proceed with the corresponding coherent state quantization and we show that this procedure takes into account the circle topology of the classical motion.

Quantum communication with coherent states of light

Science.gov (United States)

Khan, Imran; Elser, Dominique; Dirmeier, Thomas; Marquardt, Christoph; Leuchs, Gerd

2017-06-01

Quantum communication offers long-term security especially, but not only, relevant to government and industrial users. It is worth noting that, for the first time in the history of cryptographic encoding, we are currently in the situation that secure communication can be based on the fundamental laws of physics (information theoretical security) rather than on algorithmic security relying on the complexity of algorithms, which is periodically endangered as standard computer technology advances. On a fundamental level, the security of quantum key distribution (QKD) relies on the non-orthogonality of the quantum states used. So even coherent states are well suited for this task, the quantum states that largely describe the light generated by laser systems. Depending on whether one uses detectors resolving single or multiple photon states or detectors measuring the field quadratures, one speaks of, respectively, a discrete- or a continuous-variable description. Continuous-variable QKD with coherent states uses a technology that is very similar to the one employed in classical coherent communication systems, the backbone of today's Internet connections. Here, we review recent developments in this field in two connected regimes: (i) improving QKD equipment by implementing front-end telecom devices and (ii) research into satellite QKD for bridging long distances by building upon existing optical satellite links. This article is part of the themed issue 'Quantum technology for the 21st century'.

Teleportation of a Coherent Superposition State Via a nonmaximally Entangled Coherent Xhannel

Institute of Scientific and Technical Information of China (English)

无

2002-01-01

@@ We investigate the problemm of teleportation of a superposition coherent state with nonmaximally entangled coherent channel. Two strategies are considered to complete the task. The first one uses entanglement concentration to purify the channel to a maximally entangled one. The second one teleports the state through the nonmaximally entangled coherent channel directly. We find that the probabilities of successful teleportations for the two strategies are depend on the amplitudes of the coherent states and the mean fidelity of teleportation using the first strategy is always less than that of the second strategy.

Coherent states in quaternionic quantum mechanics

Science.gov (United States)

Adler, Stephen L.; Millard, Andrew C.

1997-05-01

We develop Perelomov's coherent states formalism to include the case of a quaternionic Hilbert space. We find that, because of the closure requirement, an attempted quaternionic generalization of the special nilpotent or Weyl group reduces to the normal complex case. For the case of the compact group SU(2), however, coherent states can be formulated using the quaternionic half-integer spin matrices of Finkelstein, Jauch, and Speiser, giving a nontrivial quaternionic analog of coherent states.

Coherent states of the real symplectic group in a complex analytic parametrization. I. Unitary-operator coherent states

International Nuclear Information System (INIS)

Quesne, C.

1986-01-01

In the present series of papers, the coherent states of Sp(2d,R), corresponding to the positive discrete series irreducible representations 1 +n/2> encountered in physical applications, are analyzed in detail with special emphasis on those of Sp(4,R) and Sp(6,R). The present paper discusses the unitary-operator coherent states, as defined by Klauder, Perelomov, and Gilmore. These states are parametrized by the points of the coset space Sp(2d,R)/H, where H is the stability group of the Sp(2d,R) irreducible representation lowest weight state, chosen as the reference state, and depends upon the relative values of lambda 1 ,...,lambda/sub d/, subject to the conditions lambda 1 > or =lambda 2 > or = x x x > or =lambda/sub d/> or =0. A parametrization of Sp(2d,R)/H corresponding to a factorization of the latter into a product of coset spaces Sp(2d,R)/U(d) and U(d)/H is chosen. The overlap of two coherent states is calculated, the action of the Sp(2d,R) generators on the coherent states is determined, and the explicit form of the unity resolution relation satisfied by the coherent states in the representation space of the irreducible representation is obtained. The Hilbert space of analytic functions arising from the coherent state representation is studied in detail. Finally, some applications of the formalism developed in the present paper are outlined

Electron-impact coherence parameters for 41 P 1 excitation of zinc

Science.gov (United States)

Piwiński, Mariusz; Kłosowski, Łukasz; Chwirot, Stanisław; Fursa, Dmitry V.; Bray, Igor; Das, Tapasi; Srivastava, Rajesh

2018-04-01

We present electron-impact coherence parameters (EICP) for electron-impact excitation of 41 P 1 state of zinc atoms for collision energies 40 eV and 60 eV. The experimental results are presented together with convergent close-coupling and relativistic distorted-wave approximation theoretical predictions. The results are compared and discussed with EICP data for collision energies 80 eV and 100 eV.

Symmetric discrete coherent states for n-qubits

International Nuclear Information System (INIS)

Muñoz, C; Klimov, A B; Sánchez-Soto, L L

2012-01-01

We put forward a method of constructing discrete coherent states for n qubits. After establishing appropriate displacement operators, the coherent states appear as displaced versions of a fiducial vector that is fixed by imposing a number of natural symmetry requirements on its Q-function. Using these coherent states, we establish a partial order in the discrete phase space, which allows us to picture some n-qubit states as apparent distributions. We also analyze correlations in terms of sums of squared Q-functions. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

Coherent states in quaternionic quantum mechanics

International Nuclear Information System (INIS)

Adler, S.L.; Millard, A.C.

1997-01-01

We develop Perelomov close-quote s coherent states formalism to include the case of a quaternionic Hilbert space. We find that, because of the closure requirement, an attempted quaternionic generalization of the special nilpotent or Weyl group reduces to the normal complex case. For the case of the compact group SU(2), however, coherent states can be formulated using the quaternionic half-integer spin matrices of Finkelstein, Jauch, and Speiser, giving a nontrivial quaternionic analog of coherent states. copyright 1997 American Institute of Physics

Quantum key distribution with a single photon from a squeezed coherent state

International Nuclear Information System (INIS)

Matsuoka, Masahiro; Hirano, Takuya

2003-01-01

Squeezing of the coherent state by optical parametric amplifier is shown to efficiently produce single-photon states with reduced multiphoton probabilities compared with the weak coherent light. It can be a better source for a longer-distance quantum key distribution and also for other quantum optical experiments. The necessary condition for a secure quantum key distribution given by Brassard et al. is analyzed as functions of the coherent-state amplitude and squeeze parameter. Similarly, the rate of the gained secure bits G after error correction and privacy amplification given by Luetkenhaus is calculated. Compared with the weak coherent light, it is found that G is about ten times larger and its high level continues on about two times longer distance. By improvement of the detector efficiency it is shown that the distance extends further. Measurement of the intensity correlation function and the relation to photon antibunching are discussed for the experimental verification of the single-photon generation

From Coherent States in Adjacent Graphene Layers toward Low-Power Logic Circuits

International Nuclear Information System (INIS)

Register, L.F.; Basu, D.; Reddy, D.

2011-01-01

Colleagues and we recently proposed a new type of transistor, a Bilayer Pseudo Spin Field Effect Transistor (BiSFET), based on many-body coherent states in coupled electron and hole layers in graphene. Here we review the basic BiSFET device concept and ongoing efforts to determine how such a device, which would be far from a drop-in replacement for MOSFETs in CMOS logic, could be used for low-power logic operation, and to model the effects of engineer able device parameters on the formation and gating of interlayer coherent state.

Asymmetry and coherence weight of quantum states

Science.gov (United States)

Bu, Kaifeng; Anand, Namit; Singh, Uttam

2018-03-01

The asymmetry of quantum states is an important resource in quantum information processing tasks such as quantum metrology and quantum communication. In this paper, we introduce the notion of asymmetry weight—an operationally motivated asymmetry quantifier in the resource theory of asymmetry. We study the convexity and monotonicity properties of asymmetry weight and focus on its interplay with the corresponding semidefinite programming (SDP) forms along with its connection to other asymmetry measures. Since the SDP form of asymmetry weight is closely related to asymmetry witnesses, we find that the asymmetry weight can be regarded as a (state-dependent) asymmetry witness. Moreover, some specific entanglement witnesses can be viewed as a special case of an asymmetry witness—which indicates a potential connection between asymmetry and entanglement. We also provide an operationally meaningful coherence measure, which we term coherence weight, and investigate its relationship to other coherence measures like the robustness of coherence and the l1 norm of coherence. In particular, we show that for Werner states in any dimension d all three coherence quantifiers, namely, the coherence weight, the robustness of coherence, and the l1 norm of coherence, are equal and are given by a single letter formula.

Gaussian cloning of coherent states with known phases

International Nuclear Information System (INIS)

Alexanian, Moorad

2006-01-01

The fidelity for cloning coherent states is improved over that provided by optimal Gaussian and non-Gaussian cloners for the subset of coherent states that are prepared with known phases. Gaussian quantum cloning duplicates all coherent states with an optimal fidelity of 2/3. Non-Gaussian cloners give optimal single-clone fidelity for a symmetric 1-to-2 cloner of 0.6826. Coherent states that have known phases can be cloned with a fidelity of 4/5. The latter is realized by a combination of two beam splitters and a four-wave mixer operated in the nonlinear regime, all of which are realized by interaction Hamiltonians that are quadratic in the photon operators. Therefore, the known Gaussian devices for cloning coherent states are extended when cloning coherent states with known phases by considering a nonbalanced beam splitter at the input side of the amplifier

The coherent state on SUq(2) homogeneous space

International Nuclear Information System (INIS)

Aizawa, N; Chakrabarti, R

2009-01-01

The generalized coherent states for quantum groups introduced by Jurco and StovIcek are studied for the simplest example SU q (2) in full detail. It is shown that the normalized SU q (2) coherent states enjoy the property of completeness, and allow a resolution of the unity. This feature is expected to play a key role in the application of these coherent states in physical models. The homogeneous space of SU q (2), i.e. the q-sphere of Podles, is reproduced in complex coordinates by using the coherent states. Differential calculus in the complex form on the homogeneous space is developed. The high spin limit of the SU q (2) coherent states is also discussed.

Coherent states approach to Penning trap

International Nuclear Information System (INIS)

Fernandez, David J; Velazquez, Mercedes

2009-01-01

By using a matrix technique, which allows us to identify directly the ladder operators, the Penning trap coherent states are derived as eigenstates of the appropriate annihilation operators. These states are compared with those obtained through the displacement operator. The associated wavefunctions and mean values for some relevant operators in these states are also evaluated. It turns out that the Penning trap coherent states minimize the Heisenberg uncertainty relation

Coherent and squeezed states in phase space

International Nuclear Information System (INIS)

Jannussis, A.; Bartzis, V.; Vlahos, E.

1990-01-01

In the present paper, the coherent and the squeezed states in phase space have been studied. From the wave functions of the coherent and the squeezed state, their corresponding Wigner distribution functions are calculated. Especially the calculation of the corresponding Wigner functions for the above states permits the determination of the mean values of position and momentum and thus the Heisenberg uncertainty relation. In fact, from the related results, it is concluded that the uncertainty relation of the coherent and associated squeezed states is the same

Construction of classical and non-classical coherent photon states

International Nuclear Information System (INIS)

Honegger, Reinhard; Rieckers, Alfred

2001-01-01

It is well known that the diagonal matrix elements of all-order coherent states for the quantized electromagnetic field have to constitute a Poisson distribution with respect to the photon number. The present work gives first the summary of a constructive scheme, developed previously, which determines in terms of an auxiliary Hilbert space all possible off-diagonal elements for the all-order coherent density operators in Fock space and which identifies all extremal coherent states. In terms of this formalism it is then demonstrated that each pure classical coherent state is a uniformly phase locked (quantum) coherent superposition of number states. In a mixed classical coherent state the exponential of the locked phase is shown to be replaced by a rather arbitrary unitary operator in the auxiliary Hilbert space. On the other hand classes for density operators--and for their normally ordered characteristic functions--of non-classical coherent states are obtained, especially by rather weak perturbations of classical coherent states. These illustrate various forms of breaking the classical uniform phase locking and exhibit rather peculiar properties, such as asymmetric fluctuations for the quadrature phase operators. Several criteria for non-classicality are put forward and applied to the elaborated non-classical coherent states, providing counterexamples against too simple arguments for classicality. It is concluded that classicality is only a stable concept for coherent states with macroscopic intensity

von Neumann's hypothesis concerning coherent states

International Nuclear Information System (INIS)

Zak, J

2003-01-01

An orthonormal basis of modified coherent states is constructed. Each member of the basis is an infinite sum of coherent states on a von Neumann lattice. A single state is assigned to each unit cell of area h (Planck constant) in the phase plane. The uncertainties of the coordinate x and the square of the momentum p 2 for these states are shown to be similar to those for the usual coherent states. Expansions in the newly established set are discussed and it is shown that any function in the kq-representation can be written as a sum of two fixed kq-functions. Approximate commuting operators for x and p 2 are defined on a lattice in phase plane according to von Neumann's prescription. (leeter to the editor)

Coherent states for quadratic Hamiltonians

International Nuclear Information System (INIS)

Contreras-Astorga, Alonso; Fernandez C, David J; Velazquez, Mercedes

2011-01-01

The coherent states for a set of quadratic Hamiltonians in the trap regime are constructed. A matrix technique which allows us to directly identify the creation and annihilation operators will be presented. Then, the coherent states as simultaneous eigenstates of the annihilation operators will be derived, and will be compared with those attained through the displacement operator method. The corresponding wavefunction will be found, and a general procedure for obtaining several mean values involving the canonical operators in these states will be described. The results will be illustrated through the asymmetric Penning trap.

Analytic coherent states for generalized potentials

International Nuclear Information System (INIS)

Nieto, M.M.; Simmons, L.M. Jr.

1978-01-01

A prescription is given for finding coherent states in generalized potentials. By coherent states is meant states which in time follow the motion that a classical particle would. This prescription is based upon finding those natural classical variables which vary as the sine and the cosine of the classical ω/sub c/t. As an example, the symmetric Rosen--Morse potential is discussed in detail

Fault-tolerant linear optical quantum computing with small-amplitude coherent States.

Science.gov (United States)

Lund, A P; Ralph, T C; Haselgrove, H L

2008-01-25

Quantum computing using two coherent states as a qubit basis is a proposed alternative architecture with lower overheads but has been questioned as a practical way of performing quantum computing due to the fragility of diagonal states with large coherent amplitudes. We show that using error correction only small amplitudes (alpha>1.2) are required for fault-tolerant quantum computing. We study fault tolerance under the effects of small amplitudes and loss using a Monte Carlo simulation. The first encoding level resources are orders of magnitude lower than the best single photon scheme.

Signatures of discrete breathers in coherent state quantum dynamics

International Nuclear Information System (INIS)

Igumenshchev, Kirill; Ovchinnikov, Misha; Prezhdo, Oleg; Maniadis, Panagiotis

2013-01-01

In classical mechanics, discrete breathers (DBs) – a spatial time-periodic localization of energy – are predicted in a large variety of nonlinear systems. Motivated by a conceptual bridging of the DB phenomena in classical and quantum mechanical representations, we study their signatures in the dynamics of a quantum equivalent of a classical mechanical point in phase space – a coherent state. In contrast to the classical point that exhibits either delocalized or localized motion, the coherent state shows signatures of both localized and delocalized behavior. The transition from normal to local modes have different characteristics in quantum and classical perspectives. Here, we get an insight into the connection between classical and quantum perspectives by analyzing the decomposition of the coherent state into system's eigenstates, and analyzing the spacial distribution of the wave-function density within these eigenstates. We find that the delocalized and localized eigenvalue components of the coherent state are separated by a mixed region, where both kinds of behavior can be observed. Further analysis leads to the following observations. Considered as a function of coupling, energy eigenstates go through avoided crossings between tunneling and non-tunneling modes. The dominance of tunneling modes in the high nonlinearity region is compromised by the appearance of new types of modes – high order tunneling modes – that are similar to the tunneling modes but have attributes of non-tunneling modes. Certain types of excitations preferentially excite higher order tunneling modes, allowing one to study their properties. Since auto-correlation functions decrease quickly in highly nonlinear systems, short-time dynamics are sufficient for modeling quantum DBs. This work provides a foundation for implementing modern semi-classical methods to model quantum DBs, bridging classical and quantum mechanical signatures of DBs, and understanding spectroscopic experiments

Coherent electron - hole state and femtosecond cooperative emission in bulk GaAs

International Nuclear Information System (INIS)

Vasil'ev, Petr P; Kan, H; Ohta, H; Hiruma, T

2002-01-01

The conditions for obtaining a collective coherent electron - hole state in semiconductors are discussed. The results of the experimental study of the regime of cooperative recombination of high-density electrons and holes (more than 3 x 10 18 cm -3 ) in bulk GaAs at room temperature are presented. It is shown that the collective pairing of electrons and holes and their condensation cause the formation of a short-living coherent electron - hole BCS-like state, which exhibits radiative recombination in the form of high-power femtosecond optical pulses. It is experimentally demonstrated that almost all of the electrons and holes available are condensed at the very bottoms of the bands and are at the cooperative state. The average lifetime of this state is measured to be of about 300 fs. The dependences of the order parameter (the energy gap of the spectrum of electrons and holes) and the Fermi energy of the coherent BCS state on the electron - hole concentration are obtained. (special issue devoted to the 80th anniversary of academician n g basov's birth)

Communication: Fully coherent quantum state hopping

Energy Technology Data Exchange (ETDEWEB)

Martens, Craig C., E-mail: cmartens@uci.edu [University of California, Irvine, California 92697-2025 (United States)

2015-10-14

In this paper, we describe a new and fully coherent stochastic surface hopping method for simulating mixed quantum-classical systems. We illustrate the approach on the simple but unforgiving problem of quantum evolution of a two-state quantum system in the limit of unperturbed pure state dynamics and for dissipative evolution in the presence of both stationary and nonstationary random environments. We formulate our approach in the Liouville representation and describe the density matrix elements by ensembles of trajectories. Population dynamics are represented by stochastic surface hops for trajectories representing diagonal density matrix elements. These are combined with an unconventional coherent stochastic hopping algorithm for trajectories representing off-diagonal quantum coherences. The latter generalizes the binary (0,1) “probability” of a trajectory to be associated with a given state to allow integers that can be negative or greater than unity in magnitude. Unlike existing surface hopping methods, the dynamics of the ensembles are fully entangled, correctly capturing the coherent and nonlocal structure of quantum mechanics.

Anisotropic superconducting state parameters of Tl-2212 superconductors

International Nuclear Information System (INIS)

Khaskalam, Amit K.; Singh, R.K.; Varshney, Dinesh

2001-01-01

We have estimated the superconducting state parameters and their anisotropy in thallium based superconductors (Tl-2212), in the frame work of Fermi liquid approach. Determination of the effective mass of the charge carriers from the Fermi velocity and estimated anisotropic superconducting state parameters, particularly, the magnetic penetration depth along and perpendicular to the conducting plane. The coherence length along and perpendicular to the ab plane is evaluated and appears to be higher. The temperature dependence of penetration depth, their anisotropy and Ginsburg Landau parameter for optimised doped Tl based cuprates shows the power law. The technique permits a consistency with the reported data. (author)

Coherent control of long-distance steady-state entanglement in lossy resonator arrays

Science.gov (United States)

Angelakis, D. G.; Dai, L.; Kwek, L. C.

2010-07-01

We show that coherent control of the steady-state long-distance entanglement between pairs of cavity-atom systems in an array of lossy and driven coupled resonators is possible. The cavities are doped with atoms and are connected through waveguides, other cavities or fibers depending on the implementation. We find that the steady-state entanglement can be coherently controlled through the tuning of the phase difference between the driving fields. It can also be surprisingly high in spite of the pumps being classical fields. For some implementations where the connecting element can be a fiber, long-distance steady-state quantum correlations can be established. Furthermore, the maximal of entanglement for any pair is achieved when their corresponding direct coupling is much smaller than their individual couplings to the third party. This effect is reminiscent of the establishment of coherence between otherwise uncoupled atomic levels using classical coherent fields. We suggest a method to measure this entanglement by analyzing the correlations of the emitted photons from the array and also analyze the above results for a range of values of the system parameters, different network geometries and possible implementation technologies.

Coherent states: a contemporary panorama Coherent states: a contemporary panorama

Science.gov (United States)

Twareque Ali, S.; Antoine, Jean-Pierre; Bagarello, Fabio; Gazeau, Jean-Pierre

2012-06-01

Coherent states (CS) of the harmonic oscillator (also called canonical CS) were introduced in 1926 by Schrödinger in answer to a remark by Lorentz on the classical interpretation of the wave function. They were rediscovered in the early 1960s, first (somewhat implicitly) by Klauder in the context of a novel representation of quantum states, then by Glauber and Sudarshan for the description of coherence in lasers. Since then, CS have grown into an extremely rich domain that pervades almost every corner of physics and have also led to the development of several flourishing topics in mathematics. Along the way, a number of review articles have appeared in the literature, devoted to CS, notably the 1985 reprint volume of Klauder and Skagerstam [1], the 1990 review paper by Zhang et al [2], the 1993 Oak Ridge Conference [3] and the 1995 review paper by Ali et al [4]. Textbooks also have been published, among which one might mention the ground breaking text of Perelomov [5] focusing on the group-theoretical aspects, that of Ali et al [6]1 analyzing systematically the mathematical structure beyond the group-theoretical approach and also the relation to wavelet analysis, that of Dodonov and Man'ko [7] mostly devoted to quantum optics, that of Gazeau [8] more oriented towards the physical, probabilistic and quantization aspects, and finally the very recent one by Combescure and Robert [9]. In retrospect, one can see that the development of CS has gone through a two-phase transition. First, the (simultaneous) discovery in 1972 by Gilmore and Perelomov that CS were rooted in group theory, then the realization that CS can be defined in a purely algebraic way, as an eigenvalue problem or by a series expansion (Malkin and Man'ko 1969, Barut and Girardello 1971, Gazeau and Klauder 1999; references to the original articles may be found in the textbooks quoted above). Both facts resulted in an explosive expansion of the CS literature. We thought, therefore, that the time was ripe

A coherent structure approach for parameter estimation in Lagrangian Data Assimilation

Science.gov (United States)

Maclean, John; Santitissadeekorn, Naratip; Jones, Christopher K. R. T.

2017-12-01

We introduce a data assimilation method to estimate model parameters with observations of passive tracers by directly assimilating Lagrangian Coherent Structures. Our approach differs from the usual Lagrangian Data Assimilation approach, where parameters are estimated based on tracer trajectories. We employ the Approximate Bayesian Computation (ABC) framework to avoid computing the likelihood function of the coherent structure, which is usually unavailable. We solve the ABC by a Sequential Monte Carlo (SMC) method, and use Principal Component Analysis (PCA) to identify the coherent patterns from tracer trajectory data. Our new method shows remarkably improved results compared to the bootstrap particle filter when the physical model exhibits chaotic advection.

Wigner function for the generalized excited pair coherent state

International Nuclear Information System (INIS)

Meng Xiangguo; Wang Jisuo; Liang Baolong; Li Hongqi

2008-01-01

This paper introduces the generalized excited pair coherent state (GEPCS). Using the entangled state |η> representation of Wigner operator, it obtains the Wigner function for the GEPCS. In the ρ-γ phase space, the variations of the Wigner function distributions with the parameters q, α, k and l are discussed. The tomogram of the GEPCS is calculated with the help of the Radon transform between the Wigner operator and the projection operator of the entangled state |η 1 , η 2 , τ 1 , τ 2 >. The entangled states |η> and η 1 , η 2 , τ 1 , τ 2 > provide two good representative space for studying the Wigner functions and tomograms of various two-mode correlated quantum states

Preparation of freezing quantum state for quantum coherence

Science.gov (United States)

Yang, Lian-Wu; Man, Zhong-Xiao; Zhang, Ying-Jie; Han, Feng; Du, Shao-jiang; Xia, Yun-Jie

2018-06-01

We provide a method to prepare the freezing quantum state for quantum coherence via unitary operations. The initial product state consists of the control qubit and target qubit; when it satisfies certain conditions, the initial product state converts into the particular Bell diagonal state under the unitary operations, which have the property of freezing of quantum coherence under quantum channels. We calculate the frozen quantum coherence and corresponding quantum correlations, and find that the quantities are determined by the control qubit only when the freezing phenomena occur.

Wigner Function of Thermo-Invariant Coherent State

International Nuclear Information System (INIS)

Xue-Fen, Xu; Shi-Qun, Zhu

2008-01-01

By using the thermal Winger operator of thermo-field dynamics in the coherent thermal state |ξ) representation and the technique of integration within an ordered product of operators, the Wigner function of the thermo-invariant coherent state |z,ℵ> is derived. The nonclassical properties of state |z,ℵ> is discussed based on the negativity of the Wigner function. (general)

Nuclear structure with coherent states

CERN Document Server

Raduta, Apolodor Aristotel

2015-01-01

This book covers the essential features of a large variety of nuclear structure properties, both collective and microscopic in nature. Most of results are given in an analytical form thus giving deep insight into the relevant phenomena. Using coherent states as variational states, which allows a description in the classical phase space, or provides the generating function for a boson basis, is an efficient tool to account, in a realistic fashion, for many complex properties. A detailed comparison with all existing nuclear structure models provides readers with a proper framework and, at the same time, demonstrates the prospects for new developments. The topics addressed are very much of current concern in the field. The book will appeal to practicing researchers and, due to its self-contained account, can also be successfully read and used by new graduate students.

A heating mechanism of ions due to large amplitude coherent ion acoustic wave

International Nuclear Information System (INIS)

Yajima, Nobuo; Kawai, Yoshinobu; Kogiso, Ken.

1978-05-01

Ion heating mechanism in a plasma with a coherent ion acoustic wave is studied experimentally and numerically. Ions are accelerated periodically in the electrostatic potential of the coherent wave and their oscillation energy is converted into the thermal energy of ions through the collision with the neutral atoms in plasma. The Monte Carlo calculation is applied to obtain the ion temperature. The amplitude of the electrostatic potential, the mean number of collisions and the mean life time of ions are treated as parameters in the calculation. The numerical results are compared with the experiments and both of them agree well. It is found that the ion temperature increases as the amplitude of the coherent wave increases and the high energy tail in the distribution function of ions are observed for the case of large wave-amplitude. (author)

Special Properties of Coherence Scanning Interferometers for large Measurement Volumes

International Nuclear Information System (INIS)

Bauer, W

2011-01-01

In contrast to many other optical methods the uncertainty of Coherence Scanning Interferometer (CSI) in vertical direction is independent from the field of view. Therefore CSIs are ideal instruments for measuring 3D-profiles of larger areas (36x28mm 2 , e.g.) with high precision. This is of advantage for the determination of form parameters like flatness, parallelism and steps heights within a short time. In addition, using a telecentric beam path allows measurements of deep lying surfaces (<70mm) and the determination of form parameters with large step-heights. The lateral and spatial resolution, however, are reduced. In this presentation different metrological characteristics together with their potential errors are analyzed for large-scale measuring CSIs. Therefore these instruments are ideal tools in quality control for good/bad selections, e.g. The consequences for the practical use in industry and for standardization are discussed by examples of workpieces of automotive suppliers or from the steel industry.

Completeness for coherent states in a magnetic–solenoid field

International Nuclear Information System (INIS)

Bagrov, V G; Gavrilov, S P; Gitman, D M; Górska, K

2012-01-01

This paper completes our study of coherent states in the so-called magnetic–solenoid field (a collinear combination of a constant uniform magnetic field and Aharonov–Bohm solenoid field) presented in Bagrov et al (2010 J. Phys. A: Math. Theor. 43 354016, 2011 J. Phys. A: Math. Theor. 44 055301). Here, we succeeded in proving nontrivial completeness relations for non-relativistic and relativistic coherent states in such a field. In addition, we solve here the relevant Stieltjes moment problem and present a comparative analysis of our coherent states and the well-known, in the case of pure uniform magnetic field, Malkin–Man’ko coherent states. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

Coherent states in quantum mechanics; Estados coerentes em mecanica quantica

Energy Technology Data Exchange (ETDEWEB)

Rodrigues, R. de Lima [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)]. E-mail: rafaelr@cbpf.br; Fernandes Junior, Damasio; Batista, Sheyla Marques [Paraiba Univ., Campina Grande, PB (Brazil). Dept. de Engenharia Eletrica

2001-12-01

We present a review work on the coherent states is non-relativistic quantum mechanics analysing the quantum oscillators in the coherent states. The coherent states obtained via a displacement operator that act on the wave function of ground state of the oscillator and the connection with Quantum Optics which were implemented by Glauber have also been considered. A possible generalization to the construction of new coherent states it is point out. (author)

Coherent states for quantum compact groups

CERN Document Server

Jurco, B

1996-01-01

Coherent states are introduced and their properties are discussed for all simple quantum compact groups. The multiplicative form of the canonical element for the quantum double is used to introduce the holomorphic coordinates on a general quantum dressing orbit and interpret the coherent state as a holomorphic function on this orbit with values in the carrier Hilbert space of an irreducible representation of the corresponding quantized enveloping algebra. Using Gauss decomposition, the commutation relations for the holomorphic coordinates on the dressing orbit are derived explicitly and given in a compact R--matrix formulation (generalizing this way the q--deformed Grassmann and flag manifolds). The antiholomorphic realization of the irreducible representations of a compact quantum group (the analogue of the Borel--Weil construction) are described using the concept of coherent state. The relation between representation theory and non--commutative differential geometry is suggested.}

Affine coherent states and Toeplitz operators

Science.gov (United States)

Hutníková, Mária; Hutník, Ondrej

2012-06-01

We study a parameterized family of Toeplitz operators in the context of affine coherent states based on the Calderón reproducing formula (= resolution of unity on L_2( {R})) and the specific admissible wavelets (= affine coherent states in L_2( {R})) related to Laguerre functions. Symbols of such Calderón-Toeplitz operators as individual coordinates of the affine group (= upper half-plane with the hyperbolic geometry) are considered. In this case, a certain class of pseudo-differential operators, their properties and their operator algebras are investigated. As a result of this study, the Fredholm symbol algebras of the Calderón-Toeplitz operator algebras for these particular cases of symbols are described. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.

Coherent states, pseudodifferential analysis and arithmetic

Science.gov (United States)

Unterberger, André

2012-06-01

Basic questions regarding families of coherent states include describing some constructions of such and the way they can be applied to operator theory or partial differential equations. In both questions, pseudodifferential analysis is important. Recent developments indicate that they can contribute to methods in arithmetic, especially modular form theory. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.

Coherent states on horospheric three-dimensional Lobachevsky space

Energy Technology Data Exchange (ETDEWEB)

Kurochkin, Yu., E-mail: y.kurochkin@ifanbel.bas-net.by; Shoukavy, Dz., E-mail: shoukavy@ifanbel.bas-net.by [Institute of Physics, National Academy of Sciences of Belarus, 68 Nezalezhnasci Ave., Minsk 220072 (Belarus); Rybak, I., E-mail: Ivan.Rybak@astro.up.pt [Institute of Physics, National Academy of Sciences of Belarus, 68 Nezalezhnasci Ave., Minsk 220072 (Belarus); Instituto de Astrofísica e Ciências do Espaço, CAUP, Rua das Estrelas, 4150-762 Porto (Portugal); Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre 687, 4169-007 Porto (Portugal)

2016-08-15

In the paper it is shown that due to separation of variables in the Laplace-Beltrami operator (Hamiltonian of a free quantum particle) in horospheric and quasi-Cartesian coordinates of three dimensional Lobachevsky space, it is possible to introduce standard (“conventional” according to Perelomov [Generalized Coherent States and Their Applications (Springer-Verlag, 1986), p. 320]) coherent states. Some problems (oscillator on horosphere, charged particle in analogy of constant uniform magnetic field) where coherent states are suitable for treating were considered.

“Stringy” coherent states inspired by generalized uncertainty principle

Science.gov (United States)

Ghosh, Subir; Roy, Pinaki

2012-05-01

Coherent States with Fractional Revival property, that explicitly satisfy the Generalized Uncertainty Principle (GUP), have been constructed in the context of Generalized Harmonic Oscillator. The existence of such states is essential in motivating the GUP based phenomenological results present in the literature which otherwise would be of purely academic interest. The effective phase space is Non-Canonical (or Non-Commutative in popular terminology). Our results have a smooth commutative limit, equivalent to Heisenberg Uncertainty Principle. The Fractional Revival time analysis yields an independent bound on the GUP parameter. Using this and similar bounds obtained here, we derive the largest possible value of the (GUP induced) minimum length scale. Mandel parameter analysis shows that the statistics is Sub-Poissonian. Correspondence Principle is deformed in an interesting way. Our computational scheme is very simple as it requires only first order corrected energy values and undeformed basis states.

“Stringy” coherent states inspired by generalized uncertainty principle

International Nuclear Information System (INIS)

Ghosh, Subir; Roy, Pinaki

2012-01-01

Coherent States with Fractional Revival property, that explicitly satisfy the Generalized Uncertainty Principle (GUP), have been constructed in the context of Generalized Harmonic Oscillator. The existence of such states is essential in motivating the GUP based phenomenological results present in the literature which otherwise would be of purely academic interest. The effective phase space is Non-Canonical (or Non-Commutative in popular terminology). Our results have a smooth commutative limit, equivalent to Heisenberg Uncertainty Principle. The Fractional Revival time analysis yields an independent bound on the GUP parameter. Using this and similar bounds obtained here, we derive the largest possible value of the (GUP induced) minimum length scale. Mandel parameter analysis shows that the statistics is Sub-Poissonian. Correspondence Principle is deformed in an interesting way. Our computational scheme is very simple as it requires only first order corrected energy values and undeformed basis states.

Quantitative measures of entanglement in pair-coherent states

International Nuclear Information System (INIS)

Agarwal, G S; Biswas, Asoka

2005-01-01

The pair-coherent states for a two-mode radiation field are known to belong to a family of states with non-Gaussian wavefunction. The nature of quantum entanglement between the two modes and some features of non-classicality are studied for such states. The existing criterion for inseparability are examined in the context of pair-coherent states

Coherent states for quantum compact groups

International Nuclear Information System (INIS)

Jurco, B.; Stovicek, P.; CTU, Prague

1996-01-01

Coherent states are introduced and their properties are discussed for simple quantum compact groups A l , B l , C l and D l . The multiplicative form of the canonical element for the quantum double is used to introduce the holomorphic coordinates on a general quantum dressing orbit. The coherent state is interpreted as a holomorphic function on this orbit with values in the carrier Hilbert space of an irreducible representation of the corresponding quantized enveloping algebra. Using Gauss decomposition, the commutation relations for the holomorphic coordinates on the dressing orbit are derived explicitly and given in a compact R-matrix formulation (generalizing this way the q-deformed Grassmann and flag manifolds). The antiholomorphic realization of the irreducible representations of a compact quantum group (the analogue of the Borel-Weil construction) is described using the concept of coherent state. The relation between representation theory and non-commutative differential geometry is suggested. (orig.)

Information cloning of harmonic oscillator coherent states

Indian Academy of Sciences (India)

We show that in the case of unknown harmonic oscillator coherent statesit is possible to achieve what we call perfect information cloning. By this we mean that it is still possible to make arbitrary number of copies of a state which has exactly the same information content as the original unknown coherent state. By making use ...

Wigner functions and tomograms of the photon-depleted even and odd coherent states

International Nuclear Information System (INIS)

Wang Jisuo; Meng Xiangguo

2008-01-01

Using the coherent state representation of Wigner operator and the technique of integration within an ordered product (IWOP) of operators, this paper derives the Wigner functions for the photon-depleted even and odd coherent states (PDEOCSs). Moreover, in terms of the Wigner functions with respect to the complex parameter α the nonclassical properties of the PDEOCSs are discussed. The results show that the nonclassicality for the state |β, m) o (or |β, m) e ) is more pronounced when m is even (or odd). According to the marginal distributions of the Wigner functions, the physical meaning of the Wigner functions is given. Further, the tomograms of the PDEOCSs are calculated with the aid of newly introduced intermediate coordinate-momentum representation in quantum optics

Complexified coherent states and quantum evolution with non-Hermitian Hamiltonians

International Nuclear Information System (INIS)

Graefe, Eva-Maria; Schubert, Roman

2012-01-01

The complex geometry underlying the Schrödinger dynamics of coherent states for non-Hermitian Hamiltonians is investigated. In particular, two seemingly contradictory approaches are compared: (i) a complex WKB formalism, for which the centres of coherent states naturally evolve along complex trajectories, which leads to a class of complexified coherent states; (ii) the investigation of the dynamical equations for the real expectation values of position and momentum, for which an Ehrenfest theorem has been derived in a previous paper, yielding real but non-Hamiltonian classical dynamics on phase space for the real centres of coherent states. Both approaches become exact for quadratic Hamiltonians. The apparent contradiction is resolved building on an observation by Huber, Heller and Littlejohn, that complexified coherent states are equivalent if their centres lie on a specific complex Lagrangian manifold. A rich underlying complex symplectic geometry is unravelled. In particular, a natural complex structure is identified that defines a projection from complex to real phase space, mapping complexified coherent states to their real equivalents. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

Coherent states for quantum compact groups

Energy Technology Data Exchange (ETDEWEB)

Jurco, B. [European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.; Stovicek, P. [Ceske Vysoke Uceni Technicke, Prague (Czech Republic). Dept. of Mathematics]|[CTU, Prague (Czech Republic). Doppler Inst.

1996-12-01

Coherent states are introduced and their properties are discussed for simple quantum compact groups A{sub l}, B{sub l}, C{sub l} and D{sub l}. The multiplicative form of the canonical element for the quantum double is used to introduce the holomorphic coordinates on a general quantum dressing orbit. The coherent state is interpreted as a holomorphic function on this orbit with values in the carrier Hilbert space of an irreducible representation of the corresponding quantized enveloping algebra. Using Gauss decomposition, the commutation relations for the holomorphic coordinates on the dressing orbit are derived explicitly and given in a compact R-matrix formulation (generalizing this way the q-deformed Grassmann and flag manifolds). The antiholomorphic realization of the irreducible representations of a compact quantum group (the analogue of the Borel-Weil construction) is described using the concept of coherent state. The relation between representation theory and non-commutative differential geometry is suggested. (orig.)

Quantum Properties of the Superposition of Two Nearly Identical Coherent States

Science.gov (United States)

Othman, Anas; Yevick, David

2018-04-01

In this paper, we examine the properties of the state obtained when two nearly identical coherent states are superimposed. We found that this state exhibits many nonclassical properties such as sub-Poissonian statistics, squeezing and a partially negative Wigner function. These and other properties indicate that such states, here termed near coherent states, are significantly closer to coherent states more than the generalized Schrördinger cat states. We finally provide an experimental procedure for generating the near coherent states.

Hilbert W*-modules and coherent states

International Nuclear Information System (INIS)

Bhattacharyya, T; Roy, S Shyam

2012-01-01

Hilbert C*-module valued coherent states was introduced earlier by Ali, Bhattacharyya and Shyam Roy. We consider the case when the underlying C*-algebra is a W*-algebra. The construction is similar with a substantial gain. The associated reproducing kernel is now algebra valued, rather than taking values in the space of bounded linear operators between two C*-algebras. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

A fast BDD algorithm for large coherent fault trees analysis

International Nuclear Information System (INIS)

Jung, Woo Sik; Han, Sang Hoon; Ha, Jaejoo

2004-01-01

Although a binary decision diagram (BDD) algorithm has been tried to solve large fault trees until quite recently, they are not efficiently solved in a short time since the size of a BDD structure exponentially increases according to the number of variables. Furthermore, the truncation of If-Then-Else (ITE) connectives by the probability or size limit and the subsuming to delete subsets could not be directly applied to the intermediate BDD structure under construction. This is the motivation for this work. This paper presents an efficient BDD algorithm for large coherent systems (coherent BDD algorithm) by which the truncation and subsuming could be performed in the progress of the construction of the BDD structure. A set of new formulae developed in this study for AND or OR operation between two ITE connectives of a coherent system makes it possible to delete subsets and truncate ITE connectives with a probability or size limit in the intermediate BDD structure under construction. By means of the truncation and subsuming in every step of the calculation, large fault trees for coherent systems (coherent fault trees) are efficiently solved in a short time using less memory. Furthermore, the coherent BDD algorithm from the aspect of the size of a BDD structure is much less sensitive to variable ordering than the conventional BDD algorithm

Action–angle variables, ladder operators and coherent states

International Nuclear Information System (INIS)

Campoamor-Stursberg, R.; Gadella, M.; Kuru, Ş.; Negro, J.

2012-01-01

This Letter is devoted to the building of coherent states from arguments based on classical action–angle variables. First, we show how these classical variables are associated to an algebraic structure in terms of Poisson brackets. In the quantum context these considerations are implemented by ladder type operators and a structure known as spectrum generating algebra. All this allows to generate coherent states and thereby the correspondence of classical–quantum properties by means of the aforementioned underlying structure. This approach is illustrated with the example of the one-dimensional Pöschl–Teller potential system. -- Highlights: ► We study the building of coherent states from classical action–angle variables arguments. ► The classical variables are associated to an algebraic structure in terms of Poisson brackets. ► In the quantum context these considerations are implemented by ladder type operators. ► All this allows to formulate coherent states and the correspondence of classical–quantum properties.

Manipulating Quantum Coherence in Solid State Systems

CERN Document Server

Flatté, Michael E; The NATO Advanced Study Institute "Manipulating Quantum Coherence in Solid State Systems"

2007-01-01

The NATO Advanced Study Institute "Manipulating Quantum Coherence in Solid State Systems", in Cluj-Napoca, Romania, August 29-September 9, 2005, presented a fundamental introduction to solid-state approaches to achieving quantum computation. This proceedings volume describes the properties of quantum coherence in semiconductor spin-based systems and the behavior of quantum coherence in superconducting systems. Semiconductor spin-based approaches to quantum computation have made tremendous advances in the past several years. Coherent populations of spins can be oriented, manipulated and detected experimentally. Rapid progress has been made towards performing the same tasks on individual spins (nuclear, ionic, or electronic) with all-electrical means. Superconducting approaches to quantum computation have demonstrated single qubits based on charge eigenstates as well as flux eigenstates. These topics have been presented in a pedagogical fashion by leading researchers in the fields of semiconductor-spin-based qu...

Symmetric structures of coherent states in superfluid helium-4

International Nuclear Information System (INIS)

Ahmad, M.

1981-02-01

Coherent States in superfluid helium-4 are discussed and symmetric structures are assigned to these states. Discrete and continuous series functions are exhibited for such states. Coherent State structure has been assigned to oscillating condensed bosons and their inter-relations and their effects on the superfluid system are analysed. (author)

Long-distance measurement-device-independent quantum key distribution with coherent-state superpositions.

Science.gov (United States)

Yin, H-L; Cao, W-F; Fu, Y; Tang, Y-L; Liu, Y; Chen, T-Y; Chen, Z-B

2014-09-15

Measurement-device-independent quantum key distribution (MDI-QKD) with decoy-state method is believed to be securely applied to defeat various hacking attacks in practical quantum key distribution systems. Recently, the coherent-state superpositions (CSS) have emerged as an alternative to single-photon qubits for quantum information processing and metrology. Here, in this Letter, CSS are exploited as the source in MDI-QKD. We present an analytical method that gives two tight formulas to estimate the lower bound of yield and the upper bound of bit error rate. We exploit the standard statistical analysis and Chernoff bound to perform the parameter estimation. Chernoff bound can provide good bounds in the long-distance MDI-QKD. Our results show that with CSS, both the security transmission distance and secure key rate are significantly improved compared with those of the weak coherent states in the finite-data case.

Even and odd combinations of nonlinear coherent states

International Nuclear Information System (INIS)

De los Santos-Sanchez, O; Recamier, J

2011-01-01

In this work we present some statistical properties of even and odd combinations of nonlinear coherent states associated with two nonlinear potentials; one supporting a finite number of bound states and the other supporting an infinite number of bound states, within the framework of an f-deformed algebra. We calculate their normalized variance and the temporal evolution of their dispersion relations using nonlinear coherent states defined as (a) eigensates of the deformed annihilation operator and (b) those states created by the application of a deformed displacement operator upon the ground state of the oscillator.

Coherent Control of Ground State NaK Molecules

Science.gov (United States)

Yan, Zoe; Park, Jee Woo; Loh, Huanqian; Will, Sebastian; Zwierlein, Martin

2016-05-01

Ultracold dipolar molecules exhibit anisotropic, tunable, long-range interactions, making them attractive for the study of novel states of matter and quantum information processing. We demonstrate the creation and control of 23 Na40 K molecules in their rovibronic and hyperfine ground state. By applying microwaves, we drive coherent Rabi oscillations of spin-polarized molecules between the rotational ground state (J=0) and J=1. The control afforded by microwave manipulation allows us to pursue engineered dipolar interactions via microwave dressing. By driving a two-photon transition, we are also able to observe Ramsey fringes between different J=0 hyperfine states, with coherence times as long as 0.5s. The realization of long coherence times between different molecular states is crucial for applications in quantum information processing. NSF, AFOSR- MURI, Alfred P. Sloan Foundation, DARPA-OLE

Coherent states of general time-dependent harmonic oscillator

Indian Academy of Sciences (India)

Abstract. By introducing an invariant operator, we obtain exact wave functions for a general time-dependent quadratic harmonic oscillator. The coherent states, both in x- and p-spaces, are calculated. We confirm that the uncertainty product in coherent state is always larger than Η/2 and is equal to the minimum of the ...

Coherent states of quantum systems. [Hamiltonians, variable magnetic field, adiabatic approximation

Energy Technology Data Exchange (ETDEWEB)

Trifonov, D A

1975-01-01

Time-evolution of coherent states and uncertainty relations for quantum systems are considered as well as the relation between the various types of coherent states. The most general form of the Hamiltonians that keep the uncertainty products at a minimum is found using the coherent states. The minimum uncertainty packets are shown to be coherent states of the type nonstationary-system coherent states. Two specific systems, namely that of a generalized N-dimensional oscillator and that of a charged particle moving in a variable magnetic field, are treated as examples. The adiabatic approximation to the uncertainty products for these systems is also discussed and the minimality is found to be retained with an exponential accuracy.

Characterising the large coherence length at diamond’s beamline I13L

Energy Technology Data Exchange (ETDEWEB)

Wagner, U. H., E-mail: ulrich.wagner@diamond.ac.uk; Parsons, A. [Diamond Light Source Ltd, Didcot, UK, OX11 0DE (United Kingdom); Rahomaki, J.; Vogt, U. [KTH Royal Institute of Technology, Stockholm, Sweden, SE-100 44 (Sweden); Rau, C. [Diamond Light Source Ltd, Didcot, UK, OX11 0DE (United Kingdom); Northwestern University, Chicago, IL 60611-3008 (United States)

2016-07-27

I13 is a 250 m long hard x-ray beamline (6 keV to 35 keV) at the Diamond Light Source. The beamline comprises of two independent experimental endstations: one for imaging in direct space using x-ray microscopy and one for imaging in reciprocal space using coherent diffraction based imaging techniques [1]. An outstanding feature of the coherence branch, due to its length and a new generation of ultra-stable beamline instrumentation [2], is its capability of delivering a very large coherence length well beyond 200 μm, providing opportunities for unique x-ray optical experiments. In this paper we discuss the challenges of measuring a large coherence length and present quantitative measurement based on analyzing diffraction patterns from a boron fiber [3]. We also discuss the limitations of this classical method in respect to detector performance, very short and long coherence lengths. Furthermore we demonstrate how a Ronchi grating setup [4] can be used to quickly establish if the beam is coherent over a large area.

Characterising the large coherence length at diamond’s beamline I13L

International Nuclear Information System (INIS)

Wagner, U. H.; Parsons, A.; Rahomaki, J.; Vogt, U.; Rau, C.

2016-01-01

I13 is a 250 m long hard x-ray beamline (6 keV to 35 keV) at the Diamond Light Source. The beamline comprises of two independent experimental endstations: one for imaging in direct space using x-ray microscopy and one for imaging in reciprocal space using coherent diffraction based imaging techniques [1]. An outstanding feature of the coherence branch, due to its length and a new generation of ultra-stable beamline instrumentation [2], is its capability of delivering a very large coherence length well beyond 200 μm, providing opportunities for unique x-ray optical experiments. In this paper we discuss the challenges of measuring a large coherence length and present quantitative measurement based on analyzing diffraction patterns from a boron fiber [3]. We also discuss the limitations of this classical method in respect to detector performance, very short and long coherence lengths. Furthermore we demonstrate how a Ronchi grating setup [4] can be used to quickly establish if the beam is coherent over a large area.

Non-linear wave packet dynamics of coherent states

Indian Academy of Sciences (India)

In recent years, the non-linear quantum dynamics of these states have revealed some striking features. It was found that under the action of a Hamil- tonian which is a non-linear function of the photon operator(s) only, an initial coherent state loses its coherent structure quickly due to quantum dephasing induced by the non-.

On coherent states

International Nuclear Information System (INIS)

Polubarinov, I.V.

1975-01-01

A definition of the coherent state representation is given in this paper. In the representation quantum theory equations take the form of classical field theory equations (with causality inherent to the latter) not only in simple cases (free field and interactions with an external current or field), but also in the general case of closed systems of interacting fields. And, conversely, a classical field theory can be transformed into a form of a quantum one

Practical somewhat-secure quantum somewhat-homomorphic encryption with coherent states

Science.gov (United States)

Tan, Si-Hui; Ouyang, Yingkai; Rohde, Peter P.

2018-04-01

We present a scheme for implementing homomorphic encryption on coherent states encoded using phase-shift keys. The encryption operations require only rotations in phase space, which commute with computations in the code space performed via passive linear optics, and with generalized nonlinear phase operations that are polynomials of the photon-number operator in the code space. This encoding scheme can thus be applied to any computation with coherent-state inputs, and the computation proceeds via a combination of passive linear optics and generalized nonlinear phase operations. An example of such a computation is matrix multiplication, whereby a vector representing coherent-state amplitudes is multiplied by a matrix representing a linear optics network, yielding a new vector of coherent-state amplitudes. By finding an orthogonal partitioning of the support of our encoded states, we quantify the security of our scheme via the indistinguishability of the encrypted code words. While we focus on coherent-state encodings, we expect that this phase-key encoding technique could apply to any continuous-variable computation scheme where the phase-shift operator commutes with the computation.

Experimental demonstration of macroscopic quantum coherence in Gaussian states

DEFF Research Database (Denmark)

Marquardt, C.; Andersen, Ulrik Lund; Leuchs, G.

2007-01-01

We witness experimentally the presence of macroscopic coherence in Gaussian quantum states using a recently proposed criterion [E. G. Cavalcanti and M. D. Reid, Phys. Rev. Lett. 97 170405 (2006)]. The macroscopic coherence stems from interference between macroscopically distinct states in phase...

Average subentropy, coherence and entanglement of random mixed quantum states

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lin, E-mail: godyalin@163.com [Institute of Mathematics, Hangzhou Dianzi University, Hangzhou 310018 (China); Singh, Uttam, E-mail: uttamsingh@hri.res.in [Harish-Chandra Research Institute, Allahabad, 211019 (India); Pati, Arun K., E-mail: akpati@hri.res.in [Harish-Chandra Research Institute, Allahabad, 211019 (India)

2017-02-15

Compact expressions for the average subentropy and coherence are obtained for random mixed states that are generated via various probability measures. Surprisingly, our results show that the average subentropy of random mixed states approaches the maximum value of the subentropy which is attained for the maximally mixed state as we increase the dimension. In the special case of the random mixed states sampled from the induced measure via partial tracing of random bipartite pure states, we establish the typicality of the relative entropy of coherence for random mixed states invoking the concentration of measure phenomenon. Our results also indicate that mixed quantum states are less useful compared to pure quantum states in higher dimension when we extract quantum coherence as a resource. This is because of the fact that average coherence of random mixed states is bounded uniformly, however, the average coherence of random pure states increases with the increasing dimension. As an important application, we establish the typicality of relative entropy of entanglement and distillable entanglement for a specific class of random bipartite mixed states. In particular, most of the random states in this specific class have relative entropy of entanglement and distillable entanglement equal to some fixed number (to within an arbitrary small error), thereby hugely reducing the complexity of computation of these entanglement measures for this specific class of mixed states.

Vector coherent state representations and their inner products

International Nuclear Information System (INIS)

Rowe, D J

2012-01-01

Several advances have extended the power and versatility of coherent state theory to the extent that it has become a vital tool in the representation theory of Lie groups and their Lie algebras. Representative applications are reviewed and some new developments are introduced. The examples given are chosen to illustrate special features of the scalar and vector coherent state constructions and how they work in practical situations. Comparisons are made with Mackey's theory of induced representations. For simplicity, we focus on square integrable (discrete series) unitary representations although many of the techniques apply more generally, with minor adjustment. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (review)

Negativity of Two-Qubit System Through Spin Coherent States

International Nuclear Information System (INIS)

Berrada, K.; El Baz, M.; Hassouni, Y.; Eleuch, H.

2009-12-01

Using the negativity, we express and analyze the entanglement of two-qubit nonorthogonal pure states through the spin coherent states. We formulate this measure in terms of the amplitudes of coherent states and we give the conditions for the minimal and the maximal entanglement. We generalize this formalism to the case of a class of mixed states and show that the negativity is also a function of probabilities. (author)

Coherent inflation for large quantum superpositions of levitated microspheres

Science.gov (United States)

Romero-Isart, Oriol

2017-12-01

We show that coherent inflation (CI), namely quantum dynamics generated by inverted conservative potentials acting on the center of mass of a massive object, is an enabling tool to prepare large spatial quantum superpositions in a double-slit experiment. Combined with cryogenic, extreme high vacuum, and low-vibration environments, we argue that it is experimentally feasible to exploit CI to prepare the center of mass of a micrometer-sized object in a spatial quantum superposition comparable to its size. In such a hitherto unexplored parameter regime gravitationally-induced decoherence could be unambiguously falsified. We present a protocol to implement CI in a double-slit experiment by letting a levitated microsphere traverse a static potential landscape. Such a protocol could be experimentally implemented with an all-magnetic scheme using superconducting microspheres.

Coherent states for certain time-dependent systems

International Nuclear Information System (INIS)

Pedrosa, I.A.

1989-01-01

Hartley and Ray have constructed and studied coherent states for the time-dependent oscillator. Here we show how to construct states for more general time-dependent systems. We also show that these states are equivalent to the well-known squeezed states. (author) [pt

Coherent states of non-relativistic electron in the magnetic-solenoid field

International Nuclear Information System (INIS)

Bagrov, V G; Gavrilov, S P; Filho, D P Meira; Gitman, D M

2010-01-01

In the present work we construct coherent states in the magnetic-solenoid field, which is a superposition of the Aharonov-Bohm field and a collinear uniform magnetic field. In the problem under consideration there are two kinds of coherent states, those which correspond to classical trajectories which embrace the solenoid and those which do not. The constructed coherent states reproduce exactly classical trajectories, maintain their form under the time evolution and form a complete set of functions, which can be useful in semiclassical calculations. In the absence of the solenoid field these states are reduced to the well known in the case of uniform magnetic field Malkin-Man'ko coherent states.

A study of quadrupole dynamics: quantification of classical motion chaos, and new features of the coherent states model

International Nuclear Information System (INIS)

Baran, V.

1995-01-01

The thesis has three main parts. In the first part a fourth order quadrupole boson Hamiltonian is semi classically treated through a time-dependent variational principle (TDVP), the variational states being of coherent type for the boson operators b 20 + and 1/√2 (b 22 + + b 2-2 + ). The static ground state is studied as a function of the parameters involved in the model Hamiltonian. Linearizing the classical equations of motion one obtains the RPA approach for the many boson correlations. There are two RPA roots which describe the beta and gamma vibrations, respectively. Several quantization procedures for both small and large amplitude regimes are discussed. The quantized Hamiltonians are compared with some others which were previously obtained by using different methods. A special attention is paid to the quantal states associated to some of the peaks appearing in the Fourier spectrum of the classical action density. Some of the quantal states exhibit a pronounced anharmonic structure. Therefore the procedure may be used for a unified description of small and large amplitude regimes. In the next part the semiclassical foundations of the Coherent State Model are established using the formalism elaborated in the previous section. In the third part the semiclassical treatment through a time-dependent variational principle (TDVP) of the fourth order quadrupole boson Hamiltonian H is continued. In the parameter space of H there are regions, conventionally called as 'nuclear phases', determining specific static properties. Several ground states corresponding to different equilibrium shapes are found as static solutions of classical equations of motion. The non-integrable system may follow a chaotic trajectory. The mechanism of destroying the tori bearing regular orbits and the onset of chaos may depend on nuclear phase. The regular and chaotic motions are analyzed in terms of Poincare sections and Lyapunov largest exponent. Specific features of various phases are

Security improvement by using a modified coherent state for quantum cryptography

International Nuclear Information System (INIS)

Lu, Y.J.; Zhu, Luobei; Ou, Z.Y.

2005-01-01

Weak coherent states as a photon source for quantum cryptography have a limit in secure data rate and transmission distance because of the presence of multiphoton events and loss in transmission line. Two-photon events in a coherent state can be taken out by a two-photon interference scheme. We investigate the security issue of utilizing this modified coherent state in quantum cryptography. A 4-dB improvement in the secure data rate or a nearly twofold increase in transmission distance over the coherent state are found. With a recently proposed and improved encoding strategy, further improvement is possible

Asymmetric Penning trap coherent states

International Nuclear Information System (INIS)

Contreras-Astorga, Alonso; Fernandez, David J.

2010-01-01

By using a matrix technique, which allows to identify directly the ladder operators, the coherent states of the asymmetric Penning trap are derived as eigenstates of the appropriate annihilation operators. They are compared with those obtained through the displacement operator method.

Hybrid entanglement concentration assisted with single coherent state

International Nuclear Information System (INIS)

Guo Rui; Zhou Lan; Sheng Yu-Bo; Gu Shi-Pu; Wang Xing-Fu

2016-01-01

Hybrid entangled state (HES) is a new type of entanglement, which combines the advantages of an entangled polarization state and an entangled coherent state. HES is widely discussed in the applications of quantum communication and computation. In this paper, we propose three entanglement concentration protocols (ECPs) for Bell-type HES, W-type HES, and cluster-type HES, respectively. After performing these ECPs, we can obtain the maximally entangled HES with some success probability. All the ECPs exploit the single coherent state to complete the concentration. These protocols are based on the linear optics, which are feasible in future experiments. (paper)

Coherent states of non-relativistic electron in the magnetic-solenoid field

Energy Technology Data Exchange (ETDEWEB)

Bagrov, V G [Department of Physics, Tomsk State University, 634050, Tomsk (Russian Federation); Gavrilov, S P; Filho, D P Meira [Institute of Physics, University of Sao Paulo (Brazil); Gitman, D M, E-mail: bagrov@phys.tsu.r, E-mail: gavrilovsergeyp@yahoo.co, E-mail: gitman@dfn.if.usp.b, E-mail: dmeira@dfn.if.usp.b [Institute of Physics, University of Sao Paulo, CP 66318, CEP 05315-970 Sao Paulo (Brazil)

2010-09-03

In the present work we construct coherent states in the magnetic-solenoid field, which is a superposition of the Aharonov-Bohm field and a collinear uniform magnetic field. In the problem under consideration there are two kinds of coherent states, those which correspond to classical trajectories which embrace the solenoid and those which do not. The constructed coherent states reproduce exactly classical trajectories, maintain their form under the time evolution and form a complete set of functions, which can be useful in semiclassical calculations. In the absence of the solenoid field these states are reduced to the well known in the case of uniform magnetic field Malkin-Man'ko coherent states.

The Generalized Coherent State ansatz: Application to quantum electron-vibrational dynamics

Energy Technology Data Exchange (ETDEWEB)

Borrelli, Raffaele, E-mail: raffaele.borrelli@unito.it [DISAFA, Università di Torino, I-10095 Grugliasco (Italy); Gelin, Maxim F. [Departement of Chemistry, Technische Universität München, D-85747 Garching (Germany)

2016-12-20

A new ansatz for molecular vibronic wave functions based on a superposition of time-dependent Generalized Coherent States is developed and analysed. The methodology is specifically tailored to describe the time evolution of the wave function of a system in which several interacting electronic states are coupled to a bath of harmonic oscillators. The equations of motion for the wave packet parameters are obtained by using the Dirac–Frenkel time-dependent variational principle. The methodology is used to describe the quantum dynamical behavior of a model polaron system and its scaling and convergence properties are discussed and compared with numerically exact results.

Generalized coherent states for the Coulomb problem in one dimension

International Nuclear Information System (INIS)

Nouri, S.

2002-01-01

A set of generalized coherent states for the one-dimensional Coulomb problem in coordinate representation is constructed. At first, we obtain a mapping for proper transformation of the one-dimensional Coulomb problem into a nonrotating four-dimensional isotropic harmonic oscillator in the hyperspherical space, and the generalized coherent states for the one-dimensional Coulomb problem is then obtained in exact closed form. This exactly soluble model can provide an adequate means for a quantum coherency description of the Coulomb problem in one dimension, sample for coherent aspects of the exciton model in one-dimension example in high-temperature superconductivity, semiconductors, and polymers. Also, it can be useful for investigating the coherent scattering of the Coulomb particles in one dimension

Maths-type q-deformed coherent states for q>1

International Nuclear Information System (INIS)

Quesne, C.; Penson, K.A.; Tkachuk, V.M.

2003-01-01

Maths-type q-deformed coherent states with q>1 allow a resolution of unity in the form of an ordinary integral. They are sub-Poissonian and squeezed. They may be associated with a harmonic oscillator with minimal uncertainties in both position and momentum and are intelligent coherent states for the corresponding deformed Heisenberg algebra

Role of initial coherence on entanglement dynamics of two qubit X states

Science.gov (United States)

V, Namitha C.; Satyanarayana, S. V. M.

2018-02-01

Bipartite entanglement is a necessary resource in most processes in quantum information science. Decoherence resulting from the interaction of the bipartite system with environment not only degrades the entanglement, but can result in abrupt disentanglement, known as entanglement sudden death (ESD). In some cases, a subsequent revival of entanglement is also possible. ESD is an undesirable feature for the state to be used as a resource in applications. In order to delay or avoid ESD, it is necessary to understand its origin. In this work we investigate the role of initial coherence on entanglement dynamics of a spatially separated two qubit system in a common vacuum reservoir with dipolar interaction. We construct two classes of X states, namely, states with one photon coherence (X 1) and states with two photon coherence (X 2). Considering them as initial states, we study entanglement dynamics under Markov approximation. We find for states in X 1, ESD time, revival time and time over which the state remains disentangled increase with increase in coherence. On the other hand for states in X 2, with increase in coherence ESD time increases, revival time remains same and time of disentanglement decreases. Thus, states with two photon coherence are better resources for applications since their entanglement is robust against decoherence compared to states with one photon coherence.

Quantum coherence generated by interference-induced state selectiveness

OpenAIRE

Garreau, Jean Claude

2001-01-01

The relations between quantum coherence and quantum interference are discussed. A general method for generation of quantum coherence through interference-induced state selection is introduced and then applied to `simple' atomic systems under two-photon transitions, with applications in quantum optics and laser cooling.

Coherent light squeezing states within a modified microring system

Directory of Open Access Journals (Sweden)

J. Ali

2018-06-01

Full Text Available We have proposed the simple method of the squeezed light generation in the modified microring resonator, which is known as the microring conjugate mirror (MCM. When the monochromatic light is input into the MCM, the general form of the squeezed coherent states for a quantum harmonic oscillator can be generated by controlling the additional two side rings, which are the phase modulators. By using the graphical method called the Optiwave program, the coherent squeezed states of coherent light within an MCM can be obtained and interpreted as the amplitude, phase, quadrature and photon number-squeezed states. This method has shown potentials for microring related device design, which can be used before practical applications.

Coherent light squeezing states within a modified microring system

Science.gov (United States)

Ali, J.; Pornsuwancharoen, N.; Youplao, P.; Aziz, M. S.; Amiri, I. S.; Chaiwong, K.; Chiangga, S.; Singh, G.; Yupapin, P.

2018-06-01

We have proposed the simple method of the squeezed light generation in the modified microring resonator, which is known as the microring conjugate mirror (MCM). When the monochromatic light is input into the MCM, the general form of the squeezed coherent states for a quantum harmonic oscillator can be generated by controlling the additional two side rings, which are the phase modulators. By using the graphical method called the Optiwave program, the coherent squeezed states of coherent light within an MCM can be obtained and interpreted as the amplitude, phase, quadrature and photon number-squeezed states. This method has shown potentials for microring related device design, which can be used before practical applications.

Quantum coherence: Reciprocity and distribution

Energy Technology Data Exchange (ETDEWEB)

Kumar, Asutosh, E-mail: asukumar@hri.res.in [Harish-Chandra Research Institute, Allahabad-211019 (India); Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094 (India)

2017-03-18

Quantum coherence is the outcome of the superposition principle. Recently, it has been theorized as a quantum resource, and is the premise of quantum correlations in multipartite systems. It is therefore interesting to study the coherence content and its distribution in a multipartite quantum system. In this work, we show analytically as well as numerically the reciprocity between coherence and mixedness of a quantum state. We find that this trade-off is a general feature in the sense that it is true for large spectra of measures of coherence and of mixedness. We also study the distribution of coherence in multipartite systems by looking at monogamy-type relation–which we refer to as additivity relation–between coherences of different parts of the system. We show that for the Dicke states, while the normalized measures of coherence violate the additivity relation, the unnormalized ones satisfy the same. - Highlights: • Quantum coherence. • Reciprocity between quantum coherence and mixedness. • Distribution of quantum coherence in multipartite quantum systems. • Additivity relation for distribution of quantum coherence in Dicke and “X” states.

Painlevé IV Hamiltonian systems and coherent states

International Nuclear Information System (INIS)

Bermudez, D; Contreras-Astorga, A; Fernández C, D J

2015-01-01

Schrödinger Hamiltonians with third-order differential ladder operators are linked to the Painlevé IV equation. Some of these appear from applying SUSY QM to the harmonic oscillator. Departing from them, we will build coherent states as eigenstates of the annihilation operator, then as displaced versions of the extremal states, both involving the third-order ladder operators, and finally as displaced extremal states using linearized ladder operators. To each Hamiltonian corresponds two families of coherent states for fixed ladder operators: one in the infinite dimension subspace associated with the oscillator spectrum and another in the finite dimension one generated by the eigenstates created by SUSY QM. (paper)

Deformed exterior algebra, quons and their coherent states

International Nuclear Information System (INIS)

El Baz, M.; Hassouni, Y.

2002-08-01

We review the notion of the deformation of the exterior wedge product. This allows us to construct the deformation of the algebra of exterior forms over a vector space and also over an arbitrary manifold. We relate this approach to the generalized statistics and we study quons, as a particular case of these generalized statistics. We also give their statistical properties. A large part of the work is devoted to the problem of constructing coherent states for the deformed oscillators. We give a review of all the approaches existing in the literature concerning this point and enforce it with many examples. (author)

First-Order Polynomial Heisenberg Algebras and Coherent States

International Nuclear Information System (INIS)

Castillo-Celeita, M; Fernández C, D J

2016-01-01

The polynomial Heisenberg algebras (PHA) are deformations of the Heisenberg- Weyl algebra characterizing the underlying symmetry of the supersymmetric partners of the Harmonic oscillator. When looking for the simplest system ruled by PHA, however, we end up with the harmonic oscillator. In this paper we are going to realize the first-order PHA through the harmonic oscillator. The associated coherent states will be also constructed, which turn out to be the well known even and odd coherent states. (paper)

Generation of picosecond pulsed coherent state superpositions

DEFF Research Database (Denmark)

Dong, Ruifang; Tipsmark, Anders; Laghaout, Amine

2014-01-01

We present the generation of approximated coherent state superpositions-referred to as Schrodinger cat states-by the process of subtracting single photons from picosecond pulsed squeezed states of light. The squeezed vacuum states are produced by spontaneous parametric down-conversion (SPDC...... which exhibit non-Gaussian behavior. (C) 2014 Optical Society of America...

Generalized coherent states related to the associated Bessel functions and Morse potential

International Nuclear Information System (INIS)

Mojaveri, B; Amiri Faseghandis, S

2014-01-01

Using the associated Bessel functions, a shape-invariant Lie algebra spanned by ladder operators plus the identity operator, is realized. The Hilbert space of the associated Bessel functions, representing the Lie algebra, are established and two kinds of generalized coherent states as an appropriate superposition of these functions are constructed. By implying appropriate similarity transformation on the constructed coherent states, the generalized coherent states for the Morse potential are obtained. By considering some statistical characteristics, it is revealed that the constructed coherent states indeed possess nonclassical features, such as squeezing and sub-Poissonian statistics. (paper)

Optimally cloned binary coherent states

DEFF Research Database (Denmark)

Mueller, C. R.; Leuchs, G.; Marquardt, Ch

2017-01-01

their quantum-optimal clones. We analyze the Wigner function and the cumulants of the clones, and we conclude that optimal cloning of binary coherent states requires a nonlinearity above second order. We propose several practical and near-optimal cloning schemes and compare their cloning fidelity to the optimal...

K-dimensional trio coherent states

International Nuclear Information System (INIS)

Yi, Hyo Seok; Nguyen, Ba An; Kim, Jaewan

2004-01-01

We introduce a novel class of higher-order, three-mode states called K-dimensional trio coherent states. We study their mathematical properties and prove that they form a complete set in a truncated Fock space. We also study their physical content by explicitly showing that they exhibit nonclassical features such as oscillatory number distribution, sub-Poissonian statistics, Cauchy-Schwarz inequality violation and phase-space quantum interferences. Finally, we propose an experimental scheme to realize the state with K = 2 in the quantized vibronic motion of a trapped ion

Two-way QKD with single-photon-added coherent states

Science.gov (United States)

Miranda, Mario; Mundarain, Douglas

2017-12-01

In this work we present a two-way quantum key distribution (QKD) scheme that uses single-photon-added coherent states and displacement operations. The first party randomly sends coherent states (CS) or single-photon-added coherent states (SPACS) to the second party. The latter sends back the same state it received. Both parties decide which kind of states they are receiving by detecting or not a photon on the received signal after displacement operations. The first party must determine whether its sent and received states are equal; otherwise, the case must be discarded. We are going to show that an eavesdropper provided with a beam splitter gets the same information in any of the non-discarded cases. The key can be obtained by assigning 0 to CS and 1 to SPACS in the non-discarded cases. This protocol guarantees keys' security in the presence of a beam splitter attack even for states with a high number of photons in the sent signal. It also works in a lossy quantum channel, becoming a good bet for improving long-distance QKD.

Scalable posterior approximations for large-scale Bayesian inverse problems via likelihood-informed parameter and state reduction

Science.gov (United States)

Cui, Tiangang; Marzouk, Youssef; Willcox, Karen

2016-06-01

Two major bottlenecks to the solution of large-scale Bayesian inverse problems are the scaling of posterior sampling algorithms to high-dimensional parameter spaces and the computational cost of forward model evaluations. Yet incomplete or noisy data, the state variation and parameter dependence of the forward model, and correlations in the prior collectively provide useful structure that can be exploited for dimension reduction in this setting-both in the parameter space of the inverse problem and in the state space of the forward model. To this end, we show how to jointly construct low-dimensional subspaces of the parameter space and the state space in order to accelerate the Bayesian solution of the inverse problem. As a byproduct of state dimension reduction, we also show how to identify low-dimensional subspaces of the data in problems with high-dimensional observations. These subspaces enable approximation of the posterior as a product of two factors: (i) a projection of the posterior onto a low-dimensional parameter subspace, wherein the original likelihood is replaced by an approximation involving a reduced model; and (ii) the marginal prior distribution on the high-dimensional complement of the parameter subspace. We present and compare several strategies for constructing these subspaces using only a limited number of forward and adjoint model simulations. The resulting posterior approximations can rapidly be characterized using standard sampling techniques, e.g., Markov chain Monte Carlo. Two numerical examples demonstrate the accuracy and efficiency of our approach: inversion of an integral equation in atmospheric remote sensing, where the data dimension is very high; and the inference of a heterogeneous transmissivity field in a groundwater system, which involves a partial differential equation forward model with high dimensional state and parameters.

Coherent-state representation for the QCD ground state

International Nuclear Information System (INIS)

Celenza, L.S.; Ji, C.; Shakin, C.M.

1987-01-01

We make use of the temporal gauge to construct a coherent state which is meant to describe the gluon condensate in the QCD vacuum under the assumption that the condensate is in a zero-momentum mode. The state so constructed is a color singlet and will yield finite, nonperturbative vacuum expectation values such as . (This matrix element is found to have a value of about 0.012 GeV 4 in QCD sum-rule studies.)

Quantum mechanical noise in coherent-state and squeezed-state Michelson interferometers

International Nuclear Information System (INIS)

Assaf, Ohad; Ben-Aryeh, Yacob

2002-01-01

In the present study we extend and generalize previous results for coherent-state and squeezed-state Michelson interferometer quantum mechanical uncertainties (or fluctuations), which are commonly referred to as 'quantum noise'. The calculation of photon counting (PC) fluctuations in the squeezed-state interferometer is extended to fourth-order correlation functions used as the measured signal. We also generalize a 'unified model' for treating both PC and radiation pressure fluctuations in the coherent-state interferometer, by using mathematical methods which apply to Kerr-type interactions. The results are more general than those reported previously in two ways. First, we obtain exact expressions, which lead to previous results under certain approximations. Second, we deal with cases in which the responses of the two mirrors to radiation pressure are not equal

Proof of an entropy conjecture for Bloch coherent spin states and its generalizations

DEFF Research Database (Denmark)

H. Lieb, Elliott; Solovej, Jan Philip

2014-01-01

Wehrl used Glauber coherent states to define a map from quantum density matrices to classical phase space densities and conjectured that for Glauber coherent states the mininimum classical entropy would occur for density matrices equal to projectors onto coherent states. This was proved by Lieb...

Heisenberg-limited interferometry with pair coherent states and parity measurements

International Nuclear Information System (INIS)

Gerry, Christopher C.; Mimih, Jihane

2010-01-01

After reviewing parity-measurement-based interferometry with twin Fock states, which allows for supersensitivity (Heisenberg limited) and super-resolution, we consider interferometry with two different superpositions of twin Fock states, namely, two-mode squeezed vacuum states and pair coherent states. This study is motivated by the experimental challenge of producing twin Fock states on opposite sides of a beam splitter. We find that input two-mode squeezed states, while allowing for Heisenberg-limited sensitivity, do not yield super-resolutions, whereas both are possible with input pair coherent states.

Direct, coherent and incoherent intermediate state tunneling and scanning tunnel microscopy (STM)

International Nuclear Information System (INIS)

Halbritter, J.

1997-01-01

Theory and experiment in tunneling are still qualitative in nature, which hold true also for the latest developments in direct-, resonant-, coherent- and incoherent-tunneling. Those tunnel processes have recently branched out of the field of ''solid state tunnel junctions'' into the fields of scanning tunnel microscopy (STM), single electron tunneling (SET) and semiconducting resonant tunnel structures (RTS). All these fields have promoted the understanding of tunneling in different ways reaching from the effect of coherence, of incoherence and of charging in tunneling, to spin flip or inelastic effects. STM allows not only the accurate measurements of the tunnel current and its voltage dependence but, more importantly, the easy quantification via the (quantum) tunnel channel conductance and the distance dependence. This new degree of freedom entering exponentially the tunnel current allows an unique identification of individual tunnel channels and their quantification. In STM measurements large tunnel currents are observed for large distances d > 1 nm explainable by intermediate state tunneling. Direct tunneling with its reduced tunnel time and reduced off-site Coulomb charging bridges distances below 1 nm, only. The effective charge transfer process with its larger off-site and on-site charging at intermediate states dominates tunnel transfer in STM, biology and chemistry over distances in the nm-range. Intermediates state tunneling becomes variable range hopping conduction for distances larger than d > 2 nm, for larger densities of intermediate states n 1 (ε) and for larger temperatures T or voltages U, still allowing high resolution imaging

Special deformed exponential functions leading to more consistent Klauder's coherent states

International Nuclear Information System (INIS)

El Baz, M.; Hassouni, Y.

2001-08-01

We give a general approach for the construction of deformed oscillators. These ones could be seen as describing deformed bosons. Basing on new definitions of certain quantum series, we demonstrate that they are nothing but the ordinary exponential functions in the limit when the deformation parameters goes to one. We also prove that these series converge to a complex function, in a given convergence radius that we calculate. Klauder's Coherent States are explicitly found through these functions that we design by deformed exponential functions. (author)

Coherent states in the quantum multiverse

International Nuclear Information System (INIS)

Robles-Perez, S.; Hassouni, Y.; Gonzalez-Diaz, P.F.

2010-01-01

In this Letter, we study the role of coherent states in the realm of quantum cosmology, both in a second-quantized single universe and in a third-quantized quantum multiverse. In particular, most emphasis will be paid to the quantum description of multiverses made of accelerated universes. We have shown that the quantum states involved at a quantum mechanical multiverse whose single universes are accelerated are given by squeezed states having no classical analogs.

Coherent states in the quantum multiverse

Energy Technology Data Exchange (ETDEWEB)

Robles-Perez, S., E-mail: salvarp@imaff.cfmac.csic.e [Colina de los Chopos, Centro de Fisica ' Miguel Catalan' , Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Estacion Ecologica de Biocosmologia, Medellin (Spain); Hassouni, Y. [Laboratoire de Physique Theorique, Faculte des Sciences-Universite Sidi Med Ben Abdellah, Avenue Ibn Batouta B.P: 1014, Agdal Rabat (Morocco); Gonzalez-Diaz, P.F. [Colina de los Chopos, Centro de Fisica ' Miguel Catalan' , Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 121, 28006 Madrid (Spain); Estacion Ecologica de Biocosmologia, Medellin (Spain)

2010-01-11

In this Letter, we study the role of coherent states in the realm of quantum cosmology, both in a second-quantized single universe and in a third-quantized quantum multiverse. In particular, most emphasis will be paid to the quantum description of multiverses made of accelerated universes. We have shown that the quantum states involved at a quantum mechanical multiverse whose single universes are accelerated are given by squeezed states having no classical analogs.

The study of entanglement and teleportation of the harmonic oscillator bipartite coherent states

Directory of Open Access Journals (Sweden)

A Rabeie and

2015-01-01

Full Text Available In this paper, we reproduce the harmonic oscillator bipartite coherent states with imperfect cloning of coherent states. We show that if these entangled coherent states are embedded in a vacuum environment, their entanglement is degraded but not totally lost . Also, the optimal fidelity of these states is worked out for investigating their teleportation

Geometric measure of pairwise quantum discord for superpositions of multipartite generalized coherent states

International Nuclear Information System (INIS)

Daoud, M.; Ahl Laamara, R.

2012-01-01

We give the explicit expressions of the pairwise quantum correlations present in superpositions of multipartite coherent states. A special attention is devoted to the evaluation of the geometric quantum discord. The dynamics of quantum correlations under a dephasing channel is analyzed. A comparison of geometric measure of quantum discord with that of concurrence shows that quantum discord in multipartite coherent states is more resilient to dissipative environments than is quantum entanglement. To illustrate our results, we consider some special superpositions of Weyl–Heisenberg, SU(2) and SU(1,1) coherent states which interpolate between Werner and Greenberger–Horne–Zeilinger states. -- Highlights: ► Pairwise quantum correlations multipartite coherent states. ► Explicit expression of geometric quantum discord. ► Entanglement sudden death and quantum discord robustness. ► Generalized coherent states interpolating between Werner and Greenberger–Horne–Zeilinger states

Geometric measure of pairwise quantum discord for superpositions of multipartite generalized coherent states

Energy Technology Data Exchange (ETDEWEB)

Daoud, M., E-mail: m_daoud@hotmail.com [Department of Physics, Faculty of Sciences, University Ibnou Zohr, Agadir (Morocco); Ahl Laamara, R., E-mail: ahllaamara@gmail.com [LPHE-Modeling and Simulation, Faculty of Sciences, University Mohammed V, Rabat (Morocco); Centre of Physics and Mathematics, CPM, CNESTEN, Rabat (Morocco)

2012-07-16

We give the explicit expressions of the pairwise quantum correlations present in superpositions of multipartite coherent states. A special attention is devoted to the evaluation of the geometric quantum discord. The dynamics of quantum correlations under a dephasing channel is analyzed. A comparison of geometric measure of quantum discord with that of concurrence shows that quantum discord in multipartite coherent states is more resilient to dissipative environments than is quantum entanglement. To illustrate our results, we consider some special superpositions of Weyl–Heisenberg, SU(2) and SU(1,1) coherent states which interpolate between Werner and Greenberger–Horne–Zeilinger states. -- Highlights: ► Pairwise quantum correlations multipartite coherent states. ► Explicit expression of geometric quantum discord. ► Entanglement sudden death and quantum discord robustness. ► Generalized coherent states interpolating between Werner and Greenberger–Horne–Zeilinger states.

Entangled Coherent States Generation in two Superconducting LC Circuits

International Nuclear Information System (INIS)

Chen Meiyu; Zhang Weimin

2008-01-01

We proposed a novel pure electronic (solid state) device consisting of two superconducting LC circuits coupled to a superconducting flux qubit. The entangled coherent states of the two LC modes is generated through the measurement of the flux qubit states. The interaction of the flux qubit and two LC circuits is controlled by the external microwave control lines. The geometrical structure of the LC circuits is adjustable and makes a strong coupling between them achievable. This entangled coherent state generator can be realized by using the conventional microelectronic fabrication techniques which increases the feasibility of the experiment.

Noncommutative Geometry of the Moyal Plane: Translation Isometries, Connes' Distance on Coherent States, Pythagoras Equality

Science.gov (United States)

Martinetti, Pierre; Tomassini, Luca

2013-10-01

We study the metric aspect of the Moyal plane from Connes' noncommutative geometry point of view. First, we compute Connes' spectral distance associated with the natural isometric action of on the algebra of the Moyal plane . We show that the distance between any state of and any of its translated states is precisely the amplitude of the translation. As a consequence, we obtain the spectral distance between coherent states of the quantum harmonic oscillator as the Euclidean distance on the plane. We investigate the classical limit, showing that the set of coherent states equipped with Connes' spectral distance tends towards the Euclidean plane as the parameter of deformation goes to zero. The extension of these results to the action of the symplectic group is also discussed, with particular emphasis on the orbits of coherent states under rotations. Second, we compute the spectral distance in the double Moyal plane, intended as the product of (the minimal unitization of) by . We show that on the set of states obtained by translation of an arbitrary state of , this distance is given by the Pythagoras theorem. On the way, we prove some Pythagoras inequalities for the product of arbitrary unital and non-degenerate spectral triples. Applied to the Doplicher- Fredenhagen-Roberts model of quantum spacetime [DFR], these two theorems show that Connes' spectral distance and the DFR quantum length coincide on the set of states of optimal localization.

Coherent state methods for semi-classical heavy-ion physics

International Nuclear Information System (INIS)

Remaud, B.; Sebille, F.; Raffray, Y.

1985-01-01

A semi-classical model of many fermion systems is developed in view of solving the Vlasov equation; it provides an unified description of both static and dynamic properties of the system. The phase space distribution functions are written as convolution products of generalized coherent state distributions with semi-probabilistic weight functions. The generalized coherent states are defined from the local constants of motion of the dynamical system; they may reduce to the usuel ones (eigen states of the annihilation operator) only at the harmonic limit. Solving the Vlasov equation consists in two steps: (i) search for weight functions which properly describe the initial density distributions (ii) calculation of the evolutions of the coherent state set which acts as a moving basis for the Vlasov equation solutions. Sample applications to statics are analyzed: fermions in a harmonic field, self-consistent nuclear slabs. Outlooks of dynamical applications are discussed with a special attention to the fast nucleon emission in heavy-ion reactions

Multiclustered chimeras in large semiconductor laser arrays with nonlocal interactions

Science.gov (United States)

Shena, J.; Hizanidis, J.; Hövel, P.; Tsironis, G. P.

2017-09-01

The dynamics of a large array of coupled semiconductor lasers is studied numerically for a nonlocal coupling scheme. Our focus is on chimera states, a self-organized spatiotemporal pattern of coexisting coherence and incoherence. In laser systems, such states have been previously found for global and nearest-neighbor coupling, mainly in small networks. The technological advantage of large arrays has motivated us to study a system of 200 nonlocally coupled lasers with respect to the emerging collective dynamics. Moreover, the nonlocal nature of the coupling allows us to obtain robust chimera states with multiple (in)coherent domains. The crucial parameters are the coupling strength, the coupling phase and the range of the nonlocal interaction. We find that multiclustered chimera states exist in a wide region of the parameter space and we provide quantitative characterization for the obtained spatiotemporal patterns. By proposing two different experimental setups for the realization of the nonlocal coupling scheme, we are confident that our results can be confirmed in the laboratory.

Coherent states associated to the Jacobi group

International Nuclear Information System (INIS)

Berceanu, S.

2007-01-01

.The coherent states (CS) offer a useful connection between classical and quantum mechanics. In several previous works we have constructed CS attached to the Jacobi group. It is well known that the Jacobi group appears in Quantum Mechanics, Geometric Quantization, Optics. The mathematicians have given the name 'Jacobi group' to the semidirect product of the Heisenberg-Weyl group and the symplectic group. The same group is known to physicists under other names, as the Schroedinger group. Also the name 'Weyl-symplectic' group is used for the same semi-direct product of the Heisenberg-Weyl group and the symplectic group. In this paper we review and discuss some properties of the coherent states associated to the Jacobi group. (author)

A group property for the coherent state representation of fermionic squeezing operators

Science.gov (United States)

Fan, Hong-yi; Li, Chao

2004-06-01

For the two-mode fermionic squeezing operators we find that their coherent state projection operator representation make up a loyal representation, which is homomorphic to an SO(4) group, though the fermionic coherent states are not mutual orthogonal. Thus the result of successively operating with many fermionic squeezing operators on a state can be equivalent to a single operation. The fermionic squeezing operators are mappings of orthogonal transformations in Grassmann number pseudo-classical space in the fermionic coherent state representation.

A group property for the coherent state representation of fermionic squeezing operators

International Nuclear Information System (INIS)

Fan Hongyi; Li Chao

2004-01-01

For the two-mode fermionic squeezing operators we find that their coherent state projection operator representation make up a loyal representation, which is homomorphic to an SO(4) group, though the fermionic coherent states are not mutual orthogonal. Thus the result of successively operating with many fermionic squeezing operators on a state can be equivalent to a single operation. The fermionic squeezing operators are mappings of orthogonal transformations in Grassmann number pseudo-classical space in the fermionic coherent state representation

Practical purification scheme for decohered coherent-state superpositions via partial homodyne detection

International Nuclear Information System (INIS)

Suzuki, Shigenari; Takeoka, Masahiro; Sasaki, Masahide; Andersen, Ulrik L.; Kannari, Fumihiko

2006-01-01

We present a simple protocol to purify a coherent-state superposition that has undergone a linear lossy channel. The scheme constitutes only a single beam splitter and a homodyne detector, and thus is experimentally feasible. In practice, a superposition of coherent states is transformed into a classical mixture of coherent states by linear loss, which is usually the dominant decoherence mechanism in optical systems. We also address the possibility of producing a larger amplitude superposition state from decohered states, and show that in most cases the decoherence of the states are amplified along with the amplitude

Entanglement diversion and quantum teleportation of entangled coherent states

Institute of Scientific and Technical Information of China (English)

Cai Xin-Hua; Guo Jie-Rong; Nie Jian-Jun; Jia Jin-Ping

2006-01-01

The proposals on entanglement diversion and quantum teleportation of entangled coherent states are presented.In these proposals,the entanglement between two coherent states,|α〉and |-α〉,with the same amplitude but a phase difference of π is utilized as a quantum channel.The processes of the entanglement diversion and the teleportation are achieved by using the 5050 symmetric beam splitters,the phase shifters and the photodetectors with the help of classical information.

Coherence Evolution and Transfer Supplemented by Sender's Initial-State Restoring

Science.gov (United States)

Fel'dman, E. B.; Zenchuk, A. I.

2017-12-01

The evolution of quantum coherences comes with a set of conservation laws provided that the Hamiltonian governing this evolution conserves the spin-excitation number. At that, coherences do not intertwist during the evolution. Using the transmission line and the receiver in the initial ground state we can transfer the coherences to the receiver without interaction between them, although the matrix elements contributing to each particular coherence intertwist in the receiver's state. Therefore we propose a tool based on the unitary transformation at the receiver side to untwist these elements and thus restore (at least partially) the structure of the sender's initial density matrix. A communication line with two-qubit sender and receiver is considered as an example of implementation of this technique.

General sets of coherent states and the Jaynes-Cummings model

International Nuclear Information System (INIS)

Daoud, M.; Hussin, V.

2002-01-01

General sets of coherent states are constructed for quantum systems admitting a nondegenerate infinite discrete energy spectrum. They are eigenstates of an annihilation operator and satisfy the usual properties of standard coherent states. The application of such a construction to the quantum optics Jaynes-Cummings model leads to a new understanding of the properties of this model. (author)

Impact parameter analysis of coherent and incoherent pion production on nuclei by 11.7GeV/c π+

International Nuclear Information System (INIS)

Arnold, R.; Barshay, S.; Riester, J.L.

1976-01-01

Using the complete momentum measurements for 2, 3, 4 and 5 pion final states. The impact parameter structure, with the following principal results has been studied. Evidence is presented for an empirical method that can help in the separation of coherent events on nuclei. Incoherent nuclear production exhibits lower-bound impact parameters which decrease systematically with an increasing number of produced pions. The experimental b-distributions can be very well fitted by a single simple scaled functional form, dsigmasub(N)(b)/d 2 bvector proportional to F(N/f(b)), this N-distribution yields a ratio (dispersion/average dispersion) of about 0.35 at any impact parameter [fr

Entanglement of Grassmannian Coherent States for Multi-Partite n-Level Systems

Directory of Open Access Journals (Sweden)

Ghader Najarbashi

2011-01-01

Full Text Available In this paper, we investigate the entanglement of multi-partite Grassmannian coherent states (GCSs described by Grassmann numbers for n>2 degree of nilpotency. Choosing an appropriate weight function, we show that it is possible to construct some well-known entangled pure states, consisting of GHZ, W, Bell, cluster type and bi-separable states, which are obtained by integrating over tensor product of GCSs. It is shown that for three level systems, the Grassmann creation and annihilation operators b and b^† together with bz form a closed deformed algebra, i.e., SU_q(2 with q=e^{2πi/3}, which is useful to construct entangled qutrit-states. The same argument holds for three level squeezed states. Moreover combining the Grassmann and bosonic coherent states we construct maximal entangled super coherent states.

Coherent states for FLRW space-times in loop quantum gravity

International Nuclear Information System (INIS)

Magliaro, Elena; Perini, Claudio; Marciano, Antonino

2011-01-01

We construct a class of coherent spin-network states that capture properties of curved space-times of the Friedmann-Lamaitre-Robertson-Walker type on which they are peaked. The data coded by a coherent state are associated to a cellular decomposition of a spatial (t=const) section with a dual graph given by the complete five-vertex graph, though the construction can be easily generalized to other graphs. The labels of coherent states are complex SL(2,C) variables, one for each link of the graph, and are computed through a smearing process starting from a continuum extrinsic and intrinsic geometry of the canonical surface. The construction covers both Euclidean and Lorentzian signatures; in the Euclidean case and in the limit of flat space we reproduce the simplicial 4-simplex semiclassical states used in spin foams.

Discrete coherent and squeezed states of many-qudit systems

International Nuclear Information System (INIS)

Klimov, Andrei B.; Munoz, Carlos; Sanchez-Soto, Luis L.

2009-01-01

We consider the phase space for n identical qudits (each one of dimension d, with d a primer number) as a grid of d n xd n points and use the finite Galois field GF(d n ) to label the corresponding axes. The associated displacement operators permit to define s-parametrized quasidistributions on this grid, with properties analogous to their continuous counterparts. These displacements allow also for the construction of finite coherent states, once a fiducial state is fixed. We take this reference as one eigenstate of the discrete Fourier transform and study the factorization properties of the resulting coherent states. We extend these ideas to include discrete squeezed states, and show their intriguing relation with entangled states of different qudits.

Generating single-photon catalyzed coherent states with quantum-optical catalysis

Energy Technology Data Exchange (ETDEWEB)

Xu, Xue-xiang, E-mail: xuxuexiang@jxnu.edu.cn [Center for Quantum Science and Technology, Jiangxi Normal University, Nanchang 330022 (China); Yuan, Hong-chun [College of Electrical and Optoelectronic Engineering, Changzhou Institute of Technology, Changzhou 213002 (China)

2016-07-15

We theoretically generate single-photon catalyzed coherent states (SPCCSs) by means of quantum-optical catalysis based on the beam splitter (BS) or the parametric amplifier (PA). These states are obtained in one of the BS (or PA) output channels if a coherent state and a single-photon Fock state are present in two input ports and a single photon is registered in the other output port. The success probabilities of the detection (also the normalization factors) are discussed, which is different for BS and PA catalysis. In addition, we prove that the generated states catalyzed by BS and PA devices are actually the same quantum states after analyzing photon number distribution of the SPCCSs. The quantum properties of the SPCCSs, such as sub-Poissonian distribution, anti-bunching effect, quadrature squeezing effect, and the negativity of the Wigner function are investigated in detail. The results show that the SPCCSs are non-Gaussian states with an abundance of nonclassicality. - Highlights: • We generate single-photon catalyzed coherent states with quantum-optical catalysis. • We prove the equivalent effects of the lossless beam splitter and the non-degenerate parametric amplifier. • Some nonclassical properties of the generated states are investigated in detail.

Biometric parameters in different stages of primary angle closure using low-coherence interferometry.

Science.gov (United States)

Yazdani, Shahin; Akbarian, Shadi; Pakravan, Mohammad; Doozandeh, Azadeh; Afrouzifar, Mohsen

2015-03-01

To compare ocular biometric parameters using low-coherence interferometry among siblings affected with different degrees of primary angle closure (PAC). In this cross-sectional comparative study, a total of 170 eyes of 86 siblings from 47 families underwent low-coherence interferometry (LenStar 900; Haag-Streit, Koeniz, Switzerland) to determine central corneal thickness, anterior chamber depth (ACD), aqueous depth (AD), lens thickness (LT), vitreous depth, and axial length (AL). Regression coefficients were applied to show the trend of the measured variables in different stages of angle closure. To evaluate the discriminative power of the parameters, receiver operating characteristic curves were used. Best cutoff points were selected based on the Youden index. Sensitivity, specificity, positive and negative predicative values, positive and negative likelihood ratios, and diagnostic accuracy were determined for each variable. All biometric parameters changed significantly from normal eyes to PAC suspects, PAC, and PAC glaucoma; there was a significant stepwise decrease in central corneal thickness, ACD, AD, vitreous depth, and AL, and an increase in LT and LT/AL. Anterior chamber depth and AD had the best diagnostic power for detecting angle closure; best levels of sensitivity and specificity were obtained with cutoff values of 3.11 mm for ACD and 2.57 mm for AD. Biometric parameters measured by low-coherence interferometry demonstrated a significant and stepwise change among eyes affected with various degrees of angle closure. Although the current classification scheme for angle closure is based on anatomical features, it has excellent correlation with biometric parameters.

Coherent states, 6j symbols and properties of the next to leading order asymptotic expansions

Energy Technology Data Exchange (ETDEWEB)

Kamiński, Wojciech, E-mail: wkaminsk@fuw.edu.pl [Wydział Fizyki, Uniwersytet Warszawski, Hoża 69, 00-681, Warsaw (Poland); Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada); Max Planck Institute for Gravitational Physics, Am Mühlenberg 1, D-14476 Potsdam (Germany); Steinhaus, Sebastian, E-mail: steinhaus.sebastian@gmail.com [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Waterloo, Ontario N2L 2Y5 (Canada); Max Planck Institute for Gravitational Physics, Am Mühlenberg 1, D-14476 Potsdam (Germany)

2013-12-15

We present the first complete derivation of the well-known asymptotic expansion of the SU(2) 6j symbol using a coherent state approach, in particular we succeed in computing the determinant of the Hessian matrix. To do so, we smear the coherent states and perform a partial stationary point analysis with respect to the smearing parameters. This allows us to transform the variables from group elements to dihedral angles of a tetrahedron resulting in an effective action, which coincides with the action of first order Regge calculus associated to a tetrahedron. To perform the remaining stationary point analysis, we compute its Hessian matrix and obtain the correct measure factor. Furthermore, we expand the discussion of the asymptotic formula to next to leading order terms, prove some of their properties and derive a recursion relation for the full 6j symbol.

Coherent states, 6j symbols and properties of the next to leading order asymptotic expansions

International Nuclear Information System (INIS)

Kamiński, Wojciech; Steinhaus, Sebastian

2013-01-01

We present the first complete derivation of the well-known asymptotic expansion of the SU(2) 6j symbol using a coherent state approach, in particular we succeed in computing the determinant of the Hessian matrix. To do so, we smear the coherent states and perform a partial stationary point analysis with respect to the smearing parameters. This allows us to transform the variables from group elements to dihedral angles of a tetrahedron resulting in an effective action, which coincides with the action of first order Regge calculus associated to a tetrahedron. To perform the remaining stationary point analysis, we compute its Hessian matrix and obtain the correct measure factor. Furthermore, we expand the discussion of the asymptotic formula to next to leading order terms, prove some of their properties and derive a recursion relation for the full 6j symbol

Coherent states, 6j symbols and properties of the next to leading order asymptotic expansions

Science.gov (United States)

Kamiński, Wojciech; Steinhaus, Sebastian

2013-12-01

We present the first complete derivation of the well-known asymptotic expansion of the SU(2) 6j symbol using a coherent state approach, in particular we succeed in computing the determinant of the Hessian matrix. To do so, we smear the coherent states and perform a partial stationary point analysis with respect to the smearing parameters. This allows us to transform the variables from group elements to dihedral angles of a tetrahedron resulting in an effective action, which coincides with the action of first order Regge calculus associated to a tetrahedron. To perform the remaining stationary point analysis, we compute its Hessian matrix and obtain the correct measure factor. Furthermore, we expand the discussion of the asymptotic formula to next to leading order terms, prove some of their properties and derive a recursion relation for the full 6j symbol.

State and parameter estimation in biotechnical batch reactors

NARCIS (Netherlands)

Keesman, K.J.

2000-01-01

In this paper the problem of state and parameter estimation in biotechnical batch reactors is considered. Models describing the biotechnical process behaviour are usually nonlinear with time-varying parameters. Hence, the resulting large dimensions of the augmented state vector, roughly > 7, in

Coherent states and parasupersymmetric quantum mechanics

Science.gov (United States)

Debergh, Nathalie

1992-01-01

It is well known that Parafermi and Parabose statistics are natural extensions of the usual Fermi and Bose ones, enhancing trilinear (anti)commutation relations instead of bilinear ones. Due to this generalization, positive parameters appear: the so-called orders of paraquantization p (= 1, 2, 3, ...) and h sub 0 (= 1/2, 1, 3/2, ...), respectively, the first value leading in each case to the usual statistics. The superpostion of the parabosonic and parafermionic operators gives rise to parasupermultiplets for which mixed trilinear relations have already been studied leading to two (nonequivalent) sets: the relative Parabose and the relative Parafermi ones. For the specific values p = 1 = 2h sub 0, these sets reduce to the well known supersymmetry. Coherent states associated with this last model have been recently put in evidence through the annihilation operator point of view and the group theoretical approach or displacement operator context. We propose to realize the corresponding studies within the new context p = 2 = 2h sub 0, being then directly extended to any order of paraquantization.

Theory and practice of dressed coherent states in circuit QED

Energy Technology Data Exchange (ETDEWEB)

Wilhelm, Frank [Theoretical Physics, Saarland University, Campus E 2.6, 66123 Saarbruecken (Germany); Govia, Luke C.G. [Theoretical Physics, Saarland University, Campus E 2.6, 66123 Saarbruecken (Germany); Department of Physics, McGill University, Montreal (Canada)

2016-07-01

In the dispersive regime of qubit-cavity coupling, classical cavity drive populates the cavity, but leaves the qubit state unaffected. However, the dispersive Hamiltonian is derived after both a frame transformation and an approximation. Therefore, to connect to external experimental devices, the inverse frame transformation from the dispersive frame back to the lab frame is necessary. We show that in the lab frame the system is best described by an entangled state known as the dressed coherent state, and thus even in the dispersive regime, entanglement is generated between the qubit and the cavity. Also, we show that further qubit evolution depends on both the amplitude and phase of the dressed coherent state. This provides a limitation to readout in the dispersive regime. We show that only in the limit of infinite measurement time is this protocol QND, as the formation of a dressed coherent state in the qubit-cavity system applies an effective rotation to the qubit state. We show how this rotation can be corrected by a unitary operation, leading to improved qubit initialization by measurement and unitary feedback.

The coordinate coherent states approach revisited

International Nuclear Information System (INIS)

Miao, Yan-Gang; Zhang, Shao-Jun

2013-01-01

We revisit the coordinate coherent states approach through two different quantization procedures in the quantum field theory on the noncommutative Minkowski plane. The first procedure, which is based on the normal commutation relation between an annihilation and creation operators, deduces that a point mass can be described by a Gaussian function instead of the usual Dirac delta function. However, we argue this specific quantization by adopting the canonical one (based on the canonical commutation relation between a field and its conjugate momentum) and show that a point mass should still be described by the Dirac delta function, which implies that the concept of point particles is still valid when we deal with the noncommutativity by following the coordinate coherent states approach. In order to investigate the dependence on quantization procedures, we apply the two quantization procedures to the Unruh effect and Hawking radiation and find that they give rise to significantly different results. Under the first quantization procedure, the Unruh temperature and Unruh spectrum are not deformed by noncommutativity, but the Hawking temperature is deformed by noncommutativity while the radiation specturm is untack. However, under the second quantization procedure, the Unruh temperature and Hawking temperature are untack but the both spectra are modified by an effective greybody (deformed) factor. - Highlights: ► Suggest a canonical quantization in the coordinate coherent states approach. ► Prove the validity of the concept of point particles. ► Apply the canonical quantization to the Unruh effect and Hawking radiation. ► Find no deformations in the Unruh temperature and Hawking temperature. ► Provide the modified spectra of the Unruh effect and Hawking radiation.

Coherent semiclassical states for loop quantum cosmology

International Nuclear Information System (INIS)

Corichi, Alejandro; Montoya, Edison

2011-01-01

The spatially flat Friedmann-Robertson-Walker cosmological model with a massless scalar field in loop quantum cosmology admits a description in terms of a completely solvable model. This has been used to prove that: (i) the quantum bounce that replaces the big bang singularity is generic; (ii) there is an upper bound on the energy density for all states, and (iii) semiclassical states at late times had to be semiclassical before the bounce. Here we consider a family of exact solutions to the theory, corresponding to generalized coherent Gaussian and squeezed states. We analyze the behavior of basic physical observables and impose restrictions on the states based on physical considerations. These turn out to be enough to select, from all the generalized coherent states, those that behave semiclassical at late times. We study then the properties of such states near the bounce where the most 'quantum behavior' is expected. As it turns out, the states remain sharply peaked and semiclassical at the bounce and the dynamics is very well approximated by the ''effective theory'' throughout the time evolution. We compare the semiclassicality properties of squeezed states to those of the Gaussian semiclassical states and conclude that the Gaussians are better behaved. In particular, the asymmetry in the relative fluctuations before and after the bounce are negligible, thus ruling out claims of so-called 'cosmic forgetfulness'.

Manipulating quantum coherence of charge states in interacting double-dot Aharonov–Bohm interferometers

Science.gov (United States)

Jin, Jinshuang; Wang, Shikuan; Zhou, Jiahuan; Zhang, Wei-Min; Yan, YiJing

2018-04-01

We investigate the dynamics of charge-state coherence in a degenerate double-dot Aharonov–Bohm interferometer with finite inter-dot Coulomb interactions. The quantum coherence of the charge states is found to be sensitive to the transport setup configurations, involving both the single-electron impurity channels and the Coulomb-assisted ones. We numerically demonstrate the emergence of a complete coherence between the two charge states, with the relative phase being continuously controllable through the magnetic flux. Interestingly, a fully coherent charge qubit arises at the double-dots electron pair tunneling resonance condition, where the chemical potential of one electrode is tuned at the center between a single-electron impurity channel and the related Coulomb-assisted channel. This pure quantum state of charge qubit could be experimentally realized at the current–voltage characteristic turnover position, where differential conductance sign changes. We further elaborate the underlying mechanism for both the real-time and the stationary charge-states coherence in the double-dot systems of study.

Structure Transformation and Coherent Interface in Large Lattice-Mismatched Nanoscale Multilayers

Directory of Open Access Journals (Sweden)

J. Y. Xie

2013-01-01

Full Text Available Nanoscale Al/W multilayers were fabricated by DC magnetron sputtering and characterized by transmission electron microscopy and high-resolution electron microscopy. Despite the large lattice mismatch and significantly different lattice structures between Al and W, a structural transition from face-centered cubic to body-centered cubic in Al layers was observed when the individual layer thickness was reduced from 5 nm to 1 nm, forming coherent Al/W interfaces. For potential mechanisms underlying the observed structure transition and forming of coherent interfaces, it was suggested that the reduction of interfacial energy and high stresses induced by large lattice-mismatch play a crucial role.

On the spectra and coherence of some surface meteorological parameters in the Arabian Sea

Digital Repository Service at National Institute of Oceanography (India)

RameshKumar, M.R.; Fernandes, A.A.

. In addition to peaks in the annual, semiannual and four-month periodicities, the various surface parameters exhibited some energy at 2, 3 and 4 year cycles. It was also found that most of the surface meteorological parameters were coherent (at 95% confidence...

A probabilistic CNOT gate for coherent state qubits

International Nuclear Information System (INIS)

Oliveira, M.S.R.; Vasconcelos, H.M.; Silva, J.B.R.

2013-01-01

We propose a scheme for implementing a probabilistic controlled-NOT (CNOT) gate for coherent state qubits using only linear optics and a particular four-mode state. The proposed optical setup works, as a CNOT gate, near-faithful when |α| 2 ⩾25 and independent of the input state. The key element for realizing the proposed CNOT scheme is the entangled four-mode state.

Reconsidering harmonic and anharmonic coherent states: Partial differential equations approach

Energy Technology Data Exchange (ETDEWEB)

Toutounji, Mohamad, E-mail: Mtoutounji@uaeu.ac.ae

2015-02-15

This article presents a new approach to dealing with time dependent quantities such as autocorrelation function of harmonic and anharmonic systems using coherent states and partial differential equations. The approach that is normally used to evaluate dynamical quantities involves formidable operator algebra. That operator algebra becomes insurmountable when employing Morse oscillator coherent states. This problem becomes even more complicated in case of Morse oscillator as it tends to exhibit divergent dynamics. This approach employs linear partial differential equations, some of which may be solved exactly and analytically, thereby avoiding the cumbersome noncommutative algebra required to manipulate coherent states of Morse oscillator. Additionally, the arising integrals while using the herein presented method feature stability and high numerical efficiency. The correctness, applicability, and utility of the above approach are tested by reproducing the partition and optical autocorrelation function of the harmonic oscillator. A closed-form expression for the equilibrium canonical partition function of the Morse oscillator is derived using its coherent states and partial differential equations. Also, a nonequilibrium autocorrelation function expression for weak electron–phonon coupling in condensed systems is derived for displaced Morse oscillator in electronic state. Finally, the utility of the method is demonstrated through further simplifying the Morse oscillator partition function or autocorrelation function expressions reported by other researchers in unevaluated form of second-order derivative exponential. Comparison with exact dynamics shows identical results.

Unconditional quantum cloning of coherent states with linear optics

International Nuclear Information System (INIS)

Leuchs, G.; Andersen, U.L.; Josse, V.

2005-01-01

Intense light pulses with non-classical properties are used to implement protocols for quantum communication. Most of the elements in the tool box needed to assemble the experimental set-ups for these protocols are readily described by Bogoliubov transformations corresponding to Gaussian transformations that map Gaussian states onto Gaussian states. One particularly interesting application is quantum cloning of a coherent state. A scheme for optimal Gaussian cloning of optical coherent states is proposed and experimentally demonstrated. Its optical realization is based entirely on simple linear optical elements and homodyne detection. The optimality of the presented scheme is only limited by detection inefficiencies. Experimentally we achieved a cloning fidelity of about 65%, which almost touches the optimal value of 2/3. (author)

Fractals as macroscopic manifestation of squeezed coherent states and brain dynamics

International Nuclear Information System (INIS)

Vitiello, Giuseppe

2012-01-01

Recent results on the relation between self-similarity and squeezed coherent states are presented. I consider fractals which are generated iteratively according to a prescribed recipe, the so-called deterministic fractals. Fractal properties are incorporated in the framework of the theory of the entire analytical functions and deformed coherent states. Conversely, fractal properties of squeezed coherent states are recognized. This sheds some light on the understanding of the dynamical origin of fractals and their global nature emerging from local deformation processes. The self-similarity in brain background activity suggested by laboratory observations of power-law distributions of power spectral densities of electrocorticograms is also discussed and accounted in the frame of the dissipative many-body model of brain.

CANCER-PAthological breakdown of coherent energy states

Czech Academy of Sciences Publication Activity Database

Pokorný, Jiří; Pokorný, Jan; Kobilková, J.; Jandová, Anna; Vrba, J.; Vrba, J. jr.

2014-01-01

Roč. 9, č. 1 (2014), s. 115-133 ISSN 1793-0480 Institutional support: RVO:67985882 ; RVO:68378271 Keywords : breakdown of coherent states * Cancer electrodynamics * Warburg effect Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering; BO - Biophysics (FZU-D)

Coherent states for a polynomial su(1, 1) algebra and a conditionally solvable system

International Nuclear Information System (INIS)

Sadiq, Muhammad; Inomata, Akira; Junker, Georg

2009-01-01

In a previous paper (2007 J. Phys. A: Math. Theor. 40 11105), we constructed a class of coherent states for a polynomially deformed su(2) algebra. In this paper, we first prepare the discrete representations of the nonlinearly deformed su(1, 1) algebra. Then we extend the previous procedure to construct a discrete class of coherent states for a polynomial su(1, 1) algebra which contains the Barut-Girardello set and the Perelomov set of the SU(1, 1) coherent states as special cases. We also construct coherent states for the cubic algebra related to the conditionally solvable radial oscillator problem.

Determination of the depth-resolved Stokes parameters of light backscattered from turbid media by use of polarization-sensitive optical coherence tomography

International Nuclear Information System (INIS)

Boer, J.F. de; Milner, T.E.; Nelson, J.S.

1999-01-01

Polarization-sensitive optical coherence tomography (PS-OCT) was used to characterize completely the polarization state of light backscattered from turbid media. Using a low-coherence light source, one can determine the Stokes parameters of backscattered light as a function of optical path in turbid media. To demonstrate the application of this technique we determined the birefringence and the optical axis in fibrous tissue (rodent muscle) and in vivo rodent skin. PS-OCT has potentially useful applications in biomedical optics by imaging simultaneously the structural properties of turbid biological materials and their effects on the polarization state of backscattered light. This method may also find applications in material science for investigation of polarization properties (e.g., birefringence) in opaque media such as ceramics and crystals. copyright 1999 Optical Society of America

A probabilistic CNOT gate for coherent state qubits

Energy Technology Data Exchange (ETDEWEB)

Oliveira, M.S.R.; Vasconcelos, H.M.; Silva, J.B.R., E-mail: joaobrs@ufc.br

2013-11-22

We propose a scheme for implementing a probabilistic controlled-NOT (CNOT) gate for coherent state qubits using only linear optics and a particular four-mode state. The proposed optical setup works, as a CNOT gate, near-faithful when |α|{sup 2}⩾25 and independent of the input state. The key element for realizing the proposed CNOT scheme is the entangled four-mode state.

The utility of affine variables and affine coherent states

International Nuclear Information System (INIS)

Klauder, John R

2012-01-01

Affine coherent states are generated by affine kinematical variables much like canonical coherent states are generated by canonical kinematical variables. Although all classical and quantum formalisms normally entail canonical variables, it is shown that affine variables can serve equally well for many classical and quantum studies. This general purpose analysis provides tools to discuss two major applications: (1) the completely successful quantization of a nonrenormalizable scalar quantum field theory by affine techniques, in complete contrast to canonical techniques which only offer triviality; and (2) a formulation of the kinematical portion of quantum gravity that favors affine kinematical variables over canonical kinematical variables, and which generates a framework in which a favorable analysis of the constrained dynamical issues can take place. All this is possible because of the close connection between the affine and the canonical stories, while the few distinctions can be used to advantage when appropriate. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (review)

Generation of entangled coherent states for distant Bose-Einstein condensates via electromagnetically induced transparency

International Nuclear Information System (INIS)

Kuang, L.-M.; Chen Zengbing; Pan Jianwei

2007-01-01

We propose a method to generate entangled coherent states between two spatially separated atomic Bose-Einstein condensates (BECs) via the technique of electromagnetically induced transparency (EIT). Two strong coupling laser beams and two entangled probe laser beams are used to cause two distant BECs to be in EIT states and to generate an atom-photon entangled state between probe lasers and distant BECs. The two BECs are initially in unentangled product coherent states while the probe lasers are initially in an entangled state. Entangled states of two distant BECs can be created through the performance of projective measurements upon the two outgoing probe lasers under certain conditions. Concretely, we propose two protocols to show how to generate entangled coherent states of the two distant BECs. One is a single-photon scheme in which an entangled single-photon state is used as the quantum channel to generate entangled distant BECs. The other is a multiphoton scheme where an entangled coherent state of the probe lasers is used as the quantum channel. Additionally, we also obtain some atom-photon entangled states of particular interest such as entangled states between a pair of optical Bell states (or quasi-Bell-states) and a pair of atomic entangled coherent states (or quasi-Bell-states)

Discrimination of optical coherent states using a photon number resolving detector

DEFF Research Database (Denmark)

Wittmann, C.; Andersen, Ulrik Lund; Leuchs, G.

2010-01-01

The discrimination of non-orthogonal quantum states with reduced or without errors is a fundamental task in quantum measurement theory. In this work, we investigate a quantum measurement strategy capable of discriminating two coherent states probabilistically with significantly smaller error...... probabilities than can be obtained using non-probabilistic state discrimination. We find that appropriate postselection of the measurement data of a photon number resolving detector can be used to discriminate two coherent states with small error probability. We compare our new receiver to an optimal...

Bound states in quantum field theory and coherent states: A fresh look

International Nuclear Information System (INIS)

Misra, S.P.

1986-09-01

We consider here bound state equations in quantum field theory where the state explicitly includes radiation quanta as constituents with the number of such quanta not fixed. The fully interacting system is dealt with through equal time commutators/anticommutators of field operators. The multiparticle channel for the radiation field is approximated through coherent state representations. (author)

A study of quadrupole dynamics: quantification of classical motion chaos, and new features of the coherent states model. Resume of Ph.D thesis

International Nuclear Information System (INIS)

Baran, V.

1995-01-01

This resume of the Ph.D. thesis has three main parts. In the first part a fourth order quadrupole boson Hamiltonian is semi classically treated through a time-dependent variational principle (TDVP), the variational states being of coherent type for the boson operators b 20 + and 1/√2 (b 22 + + b 2-2 + ). The static ground state is studied as a function of the parameters involved in the model Hamiltonian. Linearizing the classical equations of motion one obtains the RPA approach for the many boson correlations. There are two RPA roots which describe the beta and gamma vibrations, respectively. Several quantization procedures for both small and large amplitude regimes are discussed. The quantized Hamiltonians are compared with some others which were previously obtained by using different methods. A special attention is paid to the quantal states associated to some of the peaks appearing in the Fourier spectrum of the classical action density. Some of the quantal states exhibit a pronounced anharmonic structure. Therefore the procedure may be used for a unified description of small and large amplitude regimes. In the next part the semiclassical foundations of the Coherent State Model are established using the formalism elaborated in the previous section. In the third part the semiclassical treatment through a time-dependent variational principle (TDVP) of the fourth order quadrupole boson Hamiltonian H is continued. In the parameter space of H there are regions, conventionally called as 'nuclear phases', determining specific static properties. Several ground states corresponding to different equilibrium shapes are found as static solutions of classical equations of motion. The non-integrable system may follow a chaotic trajectory. The mechanism of destroying the tori bearing regular orbits and the onset of chaos may depend on nuclear phase. The regular and chaotic motions are analyzed in terms of Poincare sections and Lyapunov largest exponent. Specific features of

Insufficiency of avoided crossings for witnessing large-scale quantum coherence in flux qubits

Science.gov (United States)

Fröwis, Florian; Yadin, Benjamin; Gisin, Nicolas

2018-04-01

Do experiments based on superconducting loops segmented with Josephson junctions (e.g., flux qubits) show macroscopic quantum behavior in the sense of Schrödinger's cat example? Various arguments based on microscopic and phenomenological models were recently adduced in this debate. We approach this problem by adapting (to flux qubits) the framework of large-scale quantum coherence, which was already successfully applied to spin ensembles and photonic systems. We show that contemporary experiments might show quantum coherence more than 100 times larger than experiments in the classical regime. However, we argue that the often-used demonstration of an avoided crossing in the energy spectrum is not sufficient to make a conclusion about the presence of large-scale quantum coherence. Alternative, rigorous witnesses are proposed.

Coherent correlated states of interacting particles - the possible key to paradoxes and features of LENR

International Nuclear Information System (INIS)

Vysotskii, Vladimir I.; Vysotskyy, Mykhaylo V.

2015-01-01

In this article, the universal mechanism of optimization of low energy nuclear reactions (LENR) on the basis of coherent correlated states (CCS) of interacting particles is discussed. Formation of these states is the result of special nonstationary low energy action to parameters of potential well containing interacting particles. It was shown that in real nuclear-physical systems usage of CCS leads to sharp growth (up to 10 30 -10 100 and more) of Coulomb barrier penetrability at very low energy of interacting particles. Several successful LENR experiments based on CCS are discussed. (author)

Coherent excitation of a single atom to a Rydberg state

DEFF Research Database (Denmark)

Miroshnychenko, Yevhen; Gaëtan, Alpha; Evellin, Charles

2010-01-01

We present the coherent excitation of a single Rubidium atom to the Rydberg state 58d3/2 using a two-photon transition. The experimental setup is described in detail, as are experimental techniques and procedures. The coherence of the excitation is revealed by observing Rabi oscillations between...

Increasing Entanglement between Gaussian States by Coherent Photon Subtraction

DEFF Research Database (Denmark)

Ourjoumtsev, Alexei; Dantan, Aurelien Romain; Tualle Brouri, Rosa

2007-01-01

We experimentally demonstrate that the entanglement between Gaussian entangled states can be increased by non-Gaussian operations. Coherent subtraction of single photons from Gaussian quadrature-entangled light pulses, created by a nondegenerate parametric amplifier, produces delocalized states...

Spectral coherent-state quantum cryptography.

Science.gov (United States)

Cincotti, Gabriella; Spiekman, Leo; Wada, Naoya; Kitayama, Ken-ichi

2008-11-01

A novel implementation of quantum-noise optical cryptography is proposed, which is based on a simplified architecture that allows long-haul, high-speed transmission in a fiber optical network. By using a single multiport encoder/decoder and 16 phase shifters, this new approach can provide the same confidentiality as other implementations of Yuen's encryption protocol, which use a larger number of phase or polarization coherent states. Data confidentiality and error probability for authorized and unauthorized receivers are carefully analyzed.

Generalized Weyl–Heisenberg Algebra, Qudit Systems and Entanglement Measure of Symmetric States via Spin Coherent States

Directory of Open Access Journals (Sweden)

Mohammed Daoud

2018-04-01

Full Text Available A relation is established in the present paper between Dicke states in a d-dimensional space and vectors in the representation space of a generalized Weyl–Heisenberg algebra of finite dimension d. This provides a natural way to deal with the separable and entangled states of a system of N = d − 1 symmetric qubit states. Using the decomposition property of Dicke states, it is shown that the separable states coincide with the Perelomov coherent states associated with the generalized Weyl–Heisenberg algebra considered in this paper. In the so-called Majorana scheme, the qudit (d-level states are represented by N points on the Bloch sphere; roughly speaking, it can be said that a qudit (in a d-dimensional space is describable by a N-qubit vector (in a N-dimensional space. In such a scheme, the permanent of the matrix describing the overlap between the N qubits makes it possible to measure the entanglement between the N qubits forming the qudit. This is confirmed by a Fubini–Study metric analysis. A new parameter, proportional to the permanent and called perma-concurrence, is introduced for characterizing the entanglement of a symmetric qudit arising from N qubits. For d = 3 ( ⇔ N = 2 , this parameter constitutes an alternative to the concurrence for two qubits. Other examples are given for d = 4 and 5. A connection between Majorana stars and zeros of a Bargmmann function for qudits closes this article.

Nonlinear coherent loss for generating non-classical states

International Nuclear Information System (INIS)

Mikhalychev, A; Mogilevtsev, D; Kilin, S

2011-01-01

Here, we discuss a generation of non-classical states of bosonic mode with the help of artificially designed loss, namely the nonlinear coherent loss. We show how to generate superpositions of Fock states, and how it is possible to 'comb' the initial states leaving only states with certain properties in the resulting superposition (for example, a generation of a superposition of Fock states with odd number of particles). We discuss purity of generated states and estimate maximal achievable generation fidelity.

Coherence properties and quantum state transportation in an optical conveyor belt.

Science.gov (United States)

Kuhr, S; Alt, W; Schrader, D; Dotsenko, I; Miroshnychenko, Y; Rosenfeld, W; Khudaverdyan, M; Gomer, V; Rauschenbeutel, A; Meschede, D

2003-11-21

We have prepared and detected quantum coherences of trapped cesium atoms with long dephasing times. Controlled transport by an "optical conveyor belt" over macroscopic distances preserves the atomic coherence with slight reduction of coherence time. The limiting dephasing effects are experimentally identified, and we present an analytical model of the reversible and irreversible dephasing mechanisms. Our experimental methods are applicable at the single-atom level. Coherent quantum bit operations along with quantum state transport open the route towards a "quantum shift register" of individual neutral atoms.

Clifford coherent state transforms on spheres

Science.gov (United States)

Dang, Pei; Mourão, José; Nunes, João P.; Qian, Tao

2018-01-01

We introduce a one-parameter family of transforms, U(m)t,t > 0, from the Hilbert space of Clifford algebra valued square integrable functions on the m-dimensional sphere, L2(Sm , dσm) ⊗Cm+1, to the Hilbert spaces, ML2(R m + 1 ∖ { 0 } , dμt) , of solutions of the Euclidean Dirac equation on R m + 1 ∖ { 0 } which are square integrable with respect to appropriate measures, dμt. We prove that these transforms are unitary isomorphisms of the Hilbert spaces and are extensions of the Segal-Bargman coherent state transform, U(1) :L2(S1 , dσ1) ⟶ HL2(C ∖ { 0 } , dμ) , to higher dimensional spheres in the context of Clifford analysis. In Clifford analysis it is natural to replace the analytic continuation from Sm to SCm as in (Hall, 1994; Stenzel, 1999; Hall and Mitchell, 2002) by the Cauchy-Kowalewski extension from Sm to R m + 1 ∖ { 0 } . One then obtains a unitary isomorphism from an L2-Hilbert space to a Hilbert space of solutions of the Dirac equation, that is to a Hilbert space of monogenic functions.

Coherent states in the fermionic Fock space

International Nuclear Information System (INIS)

Oeckl, Robert

2015-01-01

We construct the coherent states in the sense of Gilmore and Perelomov for the fermionic Fock space. Our treatment is from the outset adapted to the infinite-dimensional case. The fermionic Fock space becomes in this way a reproducing kernel Hilbert space of continuous holomorphic functions. (paper)

Pseudo-Hermitian coherent states under the generalized quantum condition with position-dependent mass

International Nuclear Information System (INIS)

Yahiaoui, S A; Bentaiba, M

2012-01-01

In the context of the factorization method, we investigate the pseudo-Hermitian coherent states and their Hermitian counterpart coherent states under the generalized quantum condition in the framework of a position-dependent mass. By considering a specific modification in the superpotential, suitable annihilation and creation operators are constructed in order to reproduce the Hermitian counterpart Hamiltonian in the factorized form. We show that by means of these ladder operators, we can construct a wide range of exactly solvable potentials as well as their accompanying coherent states. Alternatively, we explore the relationship between the pseudo-Hermitian Hamiltonian and its Hermitian counterparts, obtained from a similarity transformation, to construct the associated pseudo-Hermitian coherent states. These latter preserve the structure of Perelomov’s states and minimize the generalized position–momentum uncertainty principle. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Quantum physics with non-Hermitian operators’. (paper)

Teleportation of Unknown Superpositions of Collective Atomic Coherent States

Institute of Scientific and Technical Information of China (English)

ZHENG ShiBiao

2001-01-01

We propose a scheme to teleport an unknown superposition of two atomic coherent states with different phases. Our scheme is based on resonant and dispersive atom-field interaction. Our scheme provides a possibility of teleporting macroscopic superposition states of many atoms first time.``

Instantaneous coherent destruction of tunneling and fast quantum state preparation for strongly pulsed spin qubits in diamond

DEFF Research Database (Denmark)

Wubs, Martijn

2010-01-01

Qubits driven by resonant strong pulses are studied and a parameter regime is explored in which the dynamics can be solved in closed form. Instantaneous coherent destruction of tunneling can be seen for longer pulses, whereas shorter pulses allow a fast preparation of the qubit state. Results...... are compared with recent experiments of pulsed nitrogen-vacancy center spin qubits in diamond....

Electromagnetically induced transparency and absorption due to optical and ground-state coherences in 6Li

International Nuclear Information System (INIS)

Fuchs, J; Duffy, G J; Rowlands, W J; Lezama, A; Hannaford, P; Akulshin, A M

2007-01-01

We present an experimental study of sub-natural width resonances in fluorescence from a collimated beam of 6 Li atoms excited on the D 1 and D 2 lines by a bichromatic laser field. We show that in addition to ground-state Zeeman coherence, coherent population oscillations between ground and excited states contribute to the sub-natural resonances. High-contrast resonances of electromagnetically induced transparency and electromagnetically induced absorption due to both effects, i.e., ground-state Zeeman coherence and coherent population oscillations, are observed

The SU(1, 1) Perelomov number coherent states and the non-degenerate parametric amplifier

Energy Technology Data Exchange (ETDEWEB)

Ojeda-Guillén, D., E-mail: dojedag@ipn.mx; Granados, V. D. [Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ed. 9, Unidad Profesional Adolfo López Mateos, C.P. 07738 México D. F. (Mexico); Mota, R. D. [Escuela Superior de Ingeniería Mecánica y Eléctrica, Unidad Culhuacán, Instituto Politécnico Nacional, Av. Santa Ana No. 1000, Col. San Francisco Culhuacán, Delegación Coyoacán, C.P. 04430, México D. F. (Mexico)

2014-04-15

We construct the Perelomov number coherent states for an arbitrary su(1, 1) group operation and study some of their properties. We introduce three operators which act on Perelomov number coherent states and close the su(1, 1) Lie algebra. By using the tilting transformation we apply our results to obtain the energy spectrum and eigenfunctions of the non-degenerate parametric amplifier. We show that these eigenfunctions are the Perelomov number coherent states of the two-dimensional harmonic oscillator.

Projective measurement onto arbitrary superposition of weak coherent state bases

DEFF Research Database (Denmark)

Izumi, Shuro; Takeoka, Masahiro; Wakui, Kentaro

2018-01-01

One of the peculiar features in quantum mechanics is that a superposition of macroscopically distinct states can exist. In optical system, this is highlighted by a superposition of coherent states (SCS), i.e. a superposition of classical states. Recently this highly nontrivial quantum state and i...

Testing nonlocal realism with entangled coherent states

International Nuclear Information System (INIS)

Paternostro, Mauro; Jeong, Hyunseok

2010-01-01

We investigate the violation of nonlocal realism using entangled coherent states (ECSs) under nonlinear operations and homodyne measurements. We address recently proposed Leggett-type inequalities, including a class of optimized incompatibility inequalities proposed by Branciard et al. [Nature Phys. 4, 681 (2008)], and thoroughly assess the effects of detection inefficiency.

2D-Zernike Polynomials and Coherent State Quantization of the Unit Disc

Energy Technology Data Exchange (ETDEWEB)

Thirulogasanthar, K., E-mail: santhar@gmail.com [Concordia University, Department of Comuter Science and Software Engineering (Canada); Saad, Nasser, E-mail: nsaad@upei.ca [University of Prince Edward Island, Department of mathematics and Statistics (Canada); Honnouvo, G., E-mail: g-honnouvo@yahoo.fr [McGill University, Department of Mathematics and Statistics (Canada)

2015-12-15

Using the orthonormality of the 2D-Zernike polynomials, reproducing kernels, reproducing kernel Hilbert spaces, and ensuring coherent states attained. With the aid of the so-obtained coherent states, the complex unit disc is quantized. Associated upper symbols, lower symbols and related generalized Berezin transforms also obtained. A number of necessary summation formulas for the 2D-Zernike polynomials proved.

Security proof of continuous-variable quantum key distribution using three coherent states

Science.gov (United States)

Brádler, Kamil; Weedbrook, Christian

2018-02-01

We introduce a ternary quantum key distribution (QKD) protocol and asymptotic security proof based on three coherent states and homodyne detection. Previous work had considered the binary case of two coherent states and here we nontrivially extend this to three. Our motivation is to leverage the practical benefits of both discrete and continuous (Gaussian) encoding schemes creating a best-of-both-worlds approach; namely, the postprocessing of discrete encodings and the hardware benefits of continuous ones. We present a thorough and detailed security proof in the limit of infinite signal states which allows us to lower bound the secret key rate. We calculate this is in the context of collective eavesdropping attacks and reverse reconciliation postprocessing. Finally, we compare the ternary coherent state protocol to other well-known QKD schemes (and fundamental repeaterless limits) in terms of secret key rates and loss.

Decoherence and Fidelity in Teleportation of Coherent Photon-Added Two-Mode Squeezed Thermal States

Science.gov (United States)

Li, Heng-Mei; Yuan, Hong-Chun; Wan, Zhi-Long; Wang, Zhen

2018-04-01

We theoretically introduce a kind of non-Gaussian entangled resources, i.e., coherent photon-added two-mode squeezed thermal states (CPA-TMSTS), by successively performing coherent photon addition operation to the two-mode squeezed thermal states. The normalization factor related to bivariate Hermite polynomials is obtained. Based upon it, the nonclassicality and decoherence process are analyzed by virtue of the Wigner function. It is shown that the coherent photon addition operation is an effective way in generating partial negative values of Wigner function, which clearly manifests the nonclassicality and non-Gaussianity of the target states. Additionally, the fidelity in teleporting coherent states using CPA-TMSTS as entangled resource is quantified both analytically and numerically. It is found that the CPA-TMSTS is an entangled resource of high-efficiency and high-fidelity in quantum teleportation.

Special issue on coherent states: mathematical and physical aspects Special issue on coherent states: mathematical and physical aspects

Science.gov (United States)

Twareque Ali, Syed; Antoine, Jean-Pierre; Bagarello, Fabio; Gazeau, Jean-Pierre

2011-07-01

This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to coherent states. The motivation behind this special issue is to gather in a single comprehensive volume the main aspects (past and present), latest developments, different viewpoints and directions being followed in this multidisciplinary field. Given the impressive development of the field in the past two decades, the topicality of such a volume can hardly be overemphasized. We strongly believe that such a special issue could become a particularly valuable reference for the broad scientific community working in mathematical and theoretical physics, as well as in signal processing and mathematics. Editorial policy The Guest Editors for this issue will be Syed Twareque Ali, Jean-Pierre Antoine, Fabio Bagarello and Jean-Pierre Gazeau. Potential topics include, but are not limited to, developments in the theory and applications of coherent states in: quantum optics, optomechanics, Bose-Einstein condensates quantum information, quantum measurement signal processing quantum gravity pseudo-Hermitian quantum mechanics supersymmetric quantum mechanics non-commutative quantum mechanics quantization theory harmonic and functional analysis operator theory Berezin-Toeplitz operators, PT-symmetric operators holomorphic representation theory, reproducing kernel spaces generalization of coherent states All contributions will be refereed and processed according to the usual procedure of the journal. Papers should report original and significant research that has not already been published. Guidelines for preparation of contributions The deadline for contributed papers will be 31 October 2011. This deadline will allow the special issue to appear before the end of May 2012 There is a nominal page limit of 15 printed pages per contribution (invited review papers can be longer). For papers exceeding this limit, the Guest Editors reserve the right to request a

Teleportation of a two-mode entangled coherent state encoded with two-qubit information

Energy Technology Data Exchange (ETDEWEB)

Mishra, Manoj K; Prakash, Hari, E-mail: manoj.qit@gmail.co, E-mail: prakash_hari123@rediffmail.co [Department of physics, University of Allahabad, Allahabad (India)

2010-09-28

We propose a scheme to teleport a two-mode entangled coherent state encoded with two-qubit information, which is better than the two schemes recently proposed by Liao and Kuang (2007 J. Phys. B: At. Mol. Opt. Phys. 40 1183) and by Phien and Nguyen (2008 Phys. Lett. A 372 2825) in that our scheme gives higher value of minimum assured fidelity and minimum average fidelity without using any nonlinear interactions. For involved coherent states | {+-} {alpha}), minimum average fidelity in our case is {>=}0.99 for |{alpha}| {>=} 1.6 (i.e. |{alpha}|{sup 2} {>=} 2.6), while previously proposed schemes referred above report the same for |{alpha}| {>=} 5 (i.e. |{alpha}|{sup 2} {>=} 25). Since it is very challenging to produce superposed coherent states of high coherent amplitude (|{alpha}|), our teleportation scheme is at the reach of modern technology.

The separation of vibrational coherence from ground- and excited-electronic states in P3HT film

KAUST Repository

Song, Yin

2015-06-07

© 2015 AIP Publishing LLC. Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S (λ 1, T∼ 2, λ 3)) along the population time (T∼ 2) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S (λ 1, ν∼ 2, λ 3)). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ ν∼ 2) in the rephasing beating map and at negative frequency (- ν∼ 2) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems.

The separation of vibrational coherence from ground- and excited-electronic states in P3HT film

International Nuclear Information System (INIS)

Song, Yin; Hellmann, Christoph; Stingelin, Natalie; Scholes, Gregory D.

2015-01-01

Concurrence of the vibrational coherence and ultrafast electron transfer has been observed in polymer/fullerene blends. However, it is difficult to experimentally investigate the role that the excited-state vibrational coherence plays during the electron transfer process since vibrational coherence from the ground- and excited-electronic states is usually temporally and spectrally overlapped. Here, we performed 2-dimensional electronic spectroscopy (2D ES) measurements on poly(3-hexylthiophene) (P3HT) films. By Fourier transforming the whole 2D ES datasets (S(λ 1 ,T ~ 2 ,λ 3 )) along the population time (T ~ 2 ) axis, we develop and propose a protocol capable of separating vibrational coherence from the ground- and excited-electronic states in 3D rephasing and nonrephasing beating maps (S(λ 1 ,ν ~ 2 ,λ 3 )). We found that the vibrational coherence from pure excited electronic states appears at positive frequency (+ν ~ 2 ) in the rephasing beating map and at negative frequency (−ν ~ 2 ) in the nonrephasing beating map. Furthermore, we also found that vibrational coherence from excited electronic state had a long dephasing time of 244 fs. The long-lived excited-state vibrational coherence indicates that coherence may be involved in the electron transfer process. Our findings not only shed light on the mechanism of ultrafast electron transfer in organic photovoltaics but also are beneficial for the study of the coherence effect on photoexcited dynamics in other systems

Quantum beats from the coherent interaction of hole states with surface state in near-surface quantum well

Energy Technology Data Exchange (ETDEWEB)

Khan, Salahuddin; Jayabalan, J., E-mail: jjaya@rrcat.gov.in; Chari, Rama; Pal, Suparna [Laser Physics Applications Section, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Porwal, Sanjay; Sharma, Tarun Kumar; Oak, S. M. [Semiconductor Physics and Devices Lab., Solid State Laser Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India)

2014-08-18

We report tunneling assisted beating of carriers in a near-surface single GaAsP/AlGaAs quantum well using transient reflectivity measurement. The observed damped oscillating signal has a period of 120 ± 6 fs which corresponds to the energy difference between lh1 and hh2 hole states in the quantum well. Comparing the transient reflectivity signal at different photon energies and with a buried quantum well sample, we show that the beating is caused by the coherent coupling between surface state and the hole states (lh1 and hh2) in the near-surface quantum well. The dependence of decay of coherence of these tunneling carriers on the excitation fluence is also reported. This observation on the coherent tunneling of carrier is important for future quantum device applications.

Quantum beats from the coherent interaction of hole states with surface state in near-surface quantum well

International Nuclear Information System (INIS)

Khan, Salahuddin; Jayabalan, J.; Chari, Rama; Pal, Suparna; Porwal, Sanjay; Sharma, Tarun Kumar; Oak, S. M.

2014-01-01

We report tunneling assisted beating of carriers in a near-surface single GaAsP/AlGaAs quantum well using transient reflectivity measurement. The observed damped oscillating signal has a period of 120 ± 6 fs which corresponds to the energy difference between lh1 and hh2 hole states in the quantum well. Comparing the transient reflectivity signal at different photon energies and with a buried quantum well sample, we show that the beating is caused by the coherent coupling between surface state and the hole states (lh1 and hh2) in the near-surface quantum well. The dependence of decay of coherence of these tunneling carriers on the excitation fluence is also reported. This observation on the coherent tunneling of carrier is important for future quantum device applications.

Study of coherent structures of turbulence with large wall-normal gradients in thermophysical properties using direct numerical simulation

International Nuclear Information System (INIS)

Reinink, Shawn K.; Yaras, Metin I.

2015-01-01

Forced-convection heat transfer in a heated working fluid at a thermodynamic state near its pseudocritical point is poorly predicted by correlations calibrated with data at subcritical temperatures and pressures. This is suggested to be primarily due to the influence of large wall-normal thermophysical property gradients that develop in proximity of the pseudocritical point on the concentration of coherent turbulence structures near the wall. The physical mechanisms dominating this influence remain poorly understood. In the present study, direct numerical simulation is used to study the development of coherent vortical structures within a turbulent spot under the influence of large wall-normal property gradients. A turbulent spot rather than a fully turbulent boundary layer is used for the study, for the coherent structures of turbulence in a spot tend to be in a more organized state which may allow for more effective identification of cause-and-effect relationships. Large wall-normal gradients in thermophysical properties are created by heating the working fluid which is near the pseudocritical thermodynamic state. It is found that during improved heat transfer, wall-normal gradients in density accelerate the growth of the Kelvin-Helmholtz instability mechanism in the shear layer enveloping low-speed streaks, causing it to roll up into hairpin vortices at a faster rate. It is suggested that this occurs by the baroclinic vorticity generation mechanism which accelerates the streamwise grouping of vorticity during shear layer roll-up. The increased roll-up frequency leads to reduced streamwise spacing between hairpin vortices in wave packets. The density gradients also promote the sinuous instability mode in low-speed streaks. The resulting oscillations in the streaks in the streamwise-spanwise plane lead to locally reduced spanwise spacing between hairpin vortices forming over adjacent low-speed streaks. The reduction in streamwise and spanwise spacing between

[Dextrals and sinistrals (right-handers and left-handers): specificity of interhemispheric brain asymmetry and EEG coherence parameters].

Science.gov (United States)

Zhavoronkova, L A

2007-01-01

Data of literature about morphological, functional and biochemical specificity of the brain interhemispheric asymmetry of healthy right-handers and left-handers and about peculiarity of dynamics of cerebral pathology in patients with different individual asymmetry profiles are presented at the present article. Results of our investigation by using coherence parameters of electroencephalogram (EEG) in healthy right-handers and left-handers in state of rest, during functional tests and sleeping and in patients with different forms of the brain organic damage were analyzed too. EEG coherence analysis revealed the reciprocal changing of alpha-beta and theta-delta spectral bands in right-handers whilein left-handers synchronous changing of all EEG spectral bands were observed. Data about regional-frequent specificity of EEG coherence, peculiarity of EEG asymmetry in right-handers and left-handers, aslo about specificity of EEG spectral band genesis and point of view about a role of the brain regulator systems in forming of interhemispheric asymmetry in different functional states allowed to propose the conception about principle of interhermispheric brain asymmetry formation in left-handers and left-handers. Following this conception in dextrals elements of concurrent (summary-reciprocal) cooperation are predominant at the character of interhemispheric and cortical-subcortical interaction while in sinistrals a principle of concordance (supplementary) is preferable. These peculiarities the brain organization determine, from the first side, the quicker revovery of functions damaged after cranio-cerebral trauma in left-handers in comparison right-handers and from the other side - they determine the forming of the more expressed pathology in the remote terms after exposure the low dose of radiation.

Controlled ultrafast transfer and stability degree of generalized coherent states of a kicked two-level ion

Science.gov (United States)

Chen, Hao; Kong, Chao; Hai, Wenhua

2018-06-01

We investigate quantum dynamics of a two-level ion trapped in the Lamb-Dicke regime of a δ -kicked optical lattice, based on the exact generalized coherent states rotated by a π / 2 pulse of Ramsey type experiment. The spatiotemporal evolutions of the spin-motion entangled states in different parameter regions are illustrated, and the parameter regions of different degrees of quantum stability described by the quantum fidelity are found. Time evolutions of the probability for the ion being in different pseudospin states reveal that the ultrafast entanglement generation and population transfers of the system can be analytically controlled by managing the laser pulses. The probability in an initially disentangled state shows periodic collapses (entanglement) and revivals (de-entanglement). Reduction of the stability degree results in enlarging the period of de-entanglement, while the instability and potential chaos will cause the sustained entanglement. The results could be justified experimentally in the existing setups and may be useful in engineering quantum dynamics for quantum information processing.

Parameter optimization in biased decoy-state quantum key distribution with both source errors and statistical fluctuations

Science.gov (United States)

Zhu, Jian-Rong; Li, Jian; Zhang, Chun-Mei; Wang, Qin

2017-10-01

The decoy-state method has been widely used in commercial quantum key distribution (QKD) systems. In view of the practical decoy-state QKD with both source errors and statistical fluctuations, we propose a universal model of full parameter optimization in biased decoy-state QKD with phase-randomized sources. Besides, we adopt this model to carry out simulations of two widely used sources: weak coherent source (WCS) and heralded single-photon source (HSPS). Results show that full parameter optimization can significantly improve not only the secure transmission distance but also the final key generation rate. And when taking source errors and statistical fluctuations into account, the performance of decoy-state QKD using HSPS suffered less than that of decoy-state QKD using WCS.

Nonlinear dynamics of semiclassical coherent states in periodic potentials

International Nuclear Information System (INIS)

Carles, Rémi; Sparber, Christof

2012-01-01

We consider nonlinear Schrödinger equations with either local or nonlocal nonlinearities. In addition, we include periodic potentials as used, for example, in matter wave experiments in optical lattices. By considering the corresponding semiclassical scaling regime, we construct asymptotic solutions, which are concentrated both in space and in frequency around the effective semiclassical phase-space flow induced by Bloch’s spectral problem. The dynamics of these generalized coherent states is governed by a nonlinear Schrödinger model with effective mass. In the case of nonlocal nonlinearities, we establish a novel averaging-type result in the critical case. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

A coherent modified Redfield theory for excitation energy transfer in molecular aggregates

Energy Technology Data Exchange (ETDEWEB)

Hwang-Fu, Yu-Hsien; Chen, Wei; Cheng, Yuan-Chung, E-mail: yuanchung@ntu.edu.tw

2015-02-02

Highlights: • A CMRT method for coherent energy transfer in molecular aggregates was developed. • Applicability of the method was verified in two-site systems with various parameters. • CMRT accurately describes population dynamics in the FMO-complex. • The method is accurate in a large parameter space and computationally efficient. - Abstract: Excitation energy transfer (EET) is crucial in photosynthetic light harvesting, and quantum coherence has been recently proven to be a ubiquitous phenomenon in photosynthetic EET. In this work, we derive a coherent modified Redfield theory (CMRT) that generalizes the modified Redfield theory to treat coherence dynamics. We apply the CMRT method to simulate the EET in a dimer system and compare the results with those obtained from numerically exact path integral calculations. The comparison shows that CMRT provides excellent computational efficiency and accuracy within a large EET parameter space. Furthermore, we simulate the EET dynamics in the FMO complex at 77 K using CMRT. The results show pronounced non-Markovian effects and long-lasting coherences in the ultrafast EET, in excellent agreement with calculations using the hierarchy equation of motion approach. In summary, we have successfully developed a simple yet powerful framework for coherent EET dynamics in photosynthetic systems and organic materials.

Entanglement between total intensity and polarization for pairs of coherent states

Science.gov (United States)

Sanchidrián-Vaca, Carlos; Luis, Alfredo

2018-04-01

We examine entanglement between number and polarization, or number and relative phase, in pair coherent states and two-mode squeezed vacuum via linear entropy and covariance criteria. We consider the embedding of the two-mode Hilbert space in a larger space to get a well-defined factorization of the number-phase variables. This can be regarded as a kind of protoentanglement that can be extracted and converted into real particle entanglement via feasible experimental procedures. In particular this reveals interesting entanglement properties of pairs of coherent states.

On irreversible evolutions of two-level systems approaching coherent and squeezed states

International Nuclear Information System (INIS)

Jurco, B.; Tolar, J.

1988-01-01

The concepts of completely positive quantum dynamical semigroups and SU(2)-related generalized coherence and squeezing are used to investigate conditions for Markovian evolutions leading to coherent, intelligent, minimum-uncertainty and squeezed asymptotic stationary states in a 2-level system. (author). 10 refs

Coherent and generalized intelligent states for infinite square well potential and nonlinear oscillators

International Nuclear Information System (INIS)

El Kinani, A.H; Daoud, M.

2001-10-01

This article is an illustration of the construction of coherent and generalized intelligent states which has been recently proposed by us for an arbitrary quantum system. We treat the quantum system submitted to the infinite square well potential and the nonlinear oscillators. By means of the analytical representation of the coherent states a la Gazeau-Klauder and those a la Klauder-Perelomov, we derive the generalized intelligent states in analytical ways. (author)

New SUSYQM coherent states for Pöschl-Teller potentials: a detailed mathematical analysis

Science.gov (United States)

Bergeron, H.; Siegl, P.; Youssef, A.

2012-06-01

In a recent short note (Bergeron et al 2010 Europhys. Lett. 92 60003), we have presented the good properties of a new family of semi-classical states for Pöschl-Teller potentials. These states are built from a supersymmetric quantum mechanics (SUSYQM) approach and the parameters of these ‘coherent’ states are points in the classical phase space. In this paper, we develop all the mathematical aspects that have been left out of the previous paper (proof of the resolution of unity, detailed calculations of the quantized version of classical observables and mathematical study of the resulting operators: problems of domains, self-adjointness or self-adjoint extensions). Some additional questions such as asymptotic behavior are also studied. Moreover, the framework is extended to a larger class of Pöschl-Teller potentials. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’.

New SUSYQM coherent states for Pöschl–Teller potentials: a detailed mathematical analysis

International Nuclear Information System (INIS)

Bergeron, H; Siegl, P; Youssef, A

2012-01-01

In a recent short note (Bergeron et al 2010 Europhys. Lett. 92 60003), we have presented the good properties of a new family of semi-classical states for Pöschl–Teller potentials. These states are built from a supersymmetric quantum mechanics (SUSYQM) approach and the parameters of these ‘coherent’ states are points in the classical phase space. In this paper, we develop all the mathematical aspects that have been left out of the previous paper (proof of the resolution of unity, detailed calculations of the quantized version of classical observables and mathematical study of the resulting operators: problems of domains, self-adjointness or self-adjoint extensions). Some additional questions such as asymptotic behavior are also studied. Moreover, the framework is extended to a larger class of Pöschl–Teller potentials. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Coherent states: mathematical and physical aspects’. (paper)

Coherence properties of the radiation from X-ray free electron laser

Energy Technology Data Exchange (ETDEWEB)

Saldin, E L; Schneidmiller, E A; Yurkov, M V

2006-08-15

We present a comprehensive analysis of coherence properties of the radiation from X-ray free electron laser (XFEL). We consider practically important case when XFEL is optimized for maximum gain. Such an optimization allows to reduce significantly parameter space. Application of similarity techniques to the results of numerical simulations allows to present all output characteristics of the optimized XFEL as functions of the only parameter, ratio of the emittance to the radiation wavelength, {epsilon}=2{pi} {epsilon}/{lambda}. Our studies show that optimum performance of the XFEL in terms of transverse coherence is achieved at the value of the parameter {epsilon} of about unity. At smaller values of {epsilon} the degree of transverse coherence is reduced due to strong influence of poor longitudinal coherence on a transverse one. At large values of the emittance the degree of transverse coherence degrades due to poor mode selection. Comparative analysis of existing XFEL projects, European XFEL, LCLS, and SCSS is presented as well. (orig.)

The semiclassical coherent state propagator in the Weyl representation

International Nuclear Information System (INIS)

Braun, Carol; Li, Feifei; Garg, Anupam; Stone, Michael

2015-01-01

It is shown that the semiclassical coherent state propagator takes its simplest form when the quantum mechanical Hamiltonian is replaced by its Weyl symbol in defining the classical action, in that there is then no need for a Solari-Kochetov correction. It is also shown that such a correction exists if a symbol other than the Weyl symbol is chosen and that its form is different depending on the symbol chosen. The various forms of the propagator based on different symbols are shown to be equivalent provided the correspondingly correct Solari-Kochetov correction is included. All these results are shown for both particle and spin coherent state propagators. The global anomaly in the fluctuation determinant is further elucidated by a study of the connection between the discrete fluctuation determinant and the discrete Jacobi equation

Dynamics of coherent states in regular and chaotic regimes of the non-integrable Dicke model

Science.gov (United States)

Lerma-Hernández, S.; Chávez-Carlos, J.; Bastarrachea-Magnani, M. A.; López-del-Carpio, B.; Hirsch, J. G.

2018-04-01

The quantum dynamics of initial coherent states is studied in the Dicke model and correlated with the dynamics, regular or chaotic, of their classical limit. Analytical expressions for the survival probability, i.e. the probability of finding the system in its initial state at time t, are provided in the regular regions of the model. The results for regular regimes are compared with those of the chaotic ones. It is found that initial coherent states in regular regions have a much longer equilibration time than those located in chaotic regions. The properties of the distributions for the initial coherent states in the Hamiltonian eigenbasis are also studied. It is found that for regular states the components with no negligible contribution are organized in sequences of energy levels distributed according to Gaussian functions. In the case of chaotic coherent states, the energy components do not have a simple structure and the number of participating energy levels is larger than in the regular cases.

Chimera states in three dimensions

International Nuclear Information System (INIS)

Maistrenko, Yuri; Sudakov, Oleksandr; Osiv, Oleksiy; Maistrenko, Volodymyr

2015-01-01

The chimera state is a recently discovered dynamical phenomenon in arrays of nonlocally coupled oscillators, that displays a self-organized spatial pattern of coexisting coherence and incoherence. In this paper, the first evidence of three-dimensional chimera states is reported for the Kuramoto model of phase oscillators in 3D grid topology with periodic boundary conditions. Systematic analysis of the dependence of the spatiotemporal dynamics on the range and strength of coupling shows that there are two principal classes of the chimera patterns which exist in large domains of the parameter space: (I) oscillating and (II) spirally rotating. Characteristic examples from the first class include coherent as well as incoherent balls, tubes, crosses, and layers in incoherent or coherent surrounding; the second class includes scroll waves with incoherent, randomized rolls of different modality and dynamics. Numerical simulations started from various initial conditions indicate that the states are stable over the integration time. Videos of the dynamics of the chimera states are presented in supplementary material. It is concluded that three-dimensional chimera states, which are novel spatiotemporal patterns involving the coexistence of coherent and incoherent domains, can represent one of the inherent features of nature. (paper)

Time-delayed feedback control of coherence resonance chimeras

Science.gov (United States)

Zakharova, Anna; Semenova, Nadezhda; Anishchenko, Vadim; Schöll, Eckehard

2017-11-01

Using the model of a FitzHugh-Nagumo system in the excitable regime, we investigate the influence of time-delayed feedback on noise-induced chimera states in a network with nonlocal coupling, i.e., coherence resonance chimeras. It is shown that time-delayed feedback allows for the control of the range of parameter values where these chimera states occur. Moreover, for the feedback delay close to the intrinsic period of the system, we find a novel regime which we call period-two coherence resonance chimera.

Chromatic Dispersion Estimation in Digital Coherent Receivers

DEFF Research Database (Denmark)

Soriano, Ruben Andres; Hauske, Fabian N.; Guerrero Gonzalez, Neil

2011-01-01

Polarization-diverse coherent demodulation allows to compensate large values of accumulated linear distortion by digital signal processing. In particular, in uncompensated links without optical dispersion compensation, the parameter of the residual chromatic dispersion (CD) is vital to set...

Greenberger-Horne-Zeilinger-type and W-type entangled coherent states: Generation and Bell-type inequality tests without photon counting

International Nuclear Information System (INIS)

Jeong, Hyunseok; Nguyen Ba An

2006-01-01

We study Greenberger-Horne-Zeilinger-type (GHZ-type) and W-type three-mode entangled coherent states. Both types of entangled coherent states violate Mermin's version of the Bell inequality with threshold photon detection (i.e., without photon counting). Such an experiment can be performed using linear optics elements and threshold detectors with significant Bell violations for GHZ-type entangled coherent states. However, to demonstrate Bell-type inequality violations for W-type entangled coherent states, additional nonlinear interactions are needed. We also propose an optical scheme to generate W-type entangled coherent states in free-traveling optical fields. The required resources for the generation are a single-photon source, a coherent state source, beam splitters, phase shifters, photodetectors, and Kerr nonlinearities. Our scheme does not necessarily require strong Kerr nonlinear interactions; i.e., weak nonlinearities can be used for the generation of the W-type entangled coherent states. Furthermore, it is also robust against inefficiencies of the single-photon source and the photon detectors

Semi-classical behavior of Poschl-Teller coherent states

Czech Academy of Sciences Publication Activity Database

Bergeron, H.; Gazeau, J.P.; Siegl, Petr; Youssef, A.

2010-01-01

Roč. 92, č. 6 (2010), s. 60003 ISSN 0295-5075 R&D Projects: GA MŠk LC06002 Institutional research plan: CEZ:AV0Z10480505 Institutional support: RVO:61389005 Keywords : coherent states * Pöschl-Teller potential * quantization Subject RIV: BE - Theoretical Physics Impact factor: 2.753, year: 2010

Bursting and critical layer frequencies in minimal turbulent dynamics and connections to exact coherent states

Science.gov (United States)

Park, Jae Sung; Shekar, Ashwin; Graham, Michael D.

2018-01-01

The dynamics of the turbulent near-wall region is known to be dominated by coherent structures. These near-wall coherent structures are observed to burst in a very intermittent fashion, exporting turbulent kinetic energy to the rest of the flow. In addition, they are closely related to invariant solutions known as exact coherent states (ECS), some of which display nonlinear critical layer dynamics (motions that are highly localized around the surface on which the streamwise velocity matches the wave speed of ECS). The present work aims to investigate temporal coherence in minimal channel flow relevant to turbulent bursting and critical layer dynamics and its connection to the instability of ECS. It is seen that the minimal channel turbulence displays frequencies very close to those displayed by an ECS family recently identified in the channel flow geometry. The frequencies of these ECS are determined by critical layer structures and thus might be described as "critical layer frequencies." While the bursting frequency is predominant near the wall, the ECS frequencies (critical layer frequencies) become predominant over the bursting frequency at larger distances from the wall, and increasingly so as Reynolds number increases. Turbulent bursts are classified into strong and relatively weak classes with respect to an intermittent approach to a lower branch ECS. This temporally intermittent approach is closely related to an intermittent low drag event, called hibernating turbulence, found in minimal and large domains. The relationship between the strong burst and the instability of the lower branch ECS is further discussed in state space. The state-space dynamics of strong bursts is very similar to that of the unstable manifolds of the lower branch ECS. In particular, strong bursting processes are always preceded by hibernation events. This precursor dynamics to strong turbulence may aid in development of more effective control schemes by a way of anticipating dynamics

Geometry of generalized coherent states

International Nuclear Information System (INIS)

Bacry, H.; Centre National de la Recherche Scientifique, 13 - Marseille; Grossmann, A.; Zak, J.

1975-09-01

Various attempts have been made to generalize the concept of coherent states (c.s.). One of them, due to Perelomov, seems to be very promising but no restrictive enough. The Perelomov c.s. are briefly reviewed. One shows how his definition gives rise to Radcliffe's c.s. Relationship between the usual and Radcliffe's c.s. can be investigated either from group contraction point of view (Arecchi et al.) or from a physical point of view (with the aid of the Poincare sphere of elliptic polarizations of electromagnetic plane waves). The question of finding complete subsets of c.s. is revisited and an attempt is made to restrict the Perelomov definition [fr

Collapse and Revival of an Atomic Beam Interacting with a Coherent State Light Field

International Nuclear Information System (INIS)

Ben, Li; Jing-Biao, Chen

2009-01-01

We report on the phenomena of the periodic spontaneous collapse and revival in the dynamics of an atomic beam interacting with a single-mode and coherent-state light field. Conventional collapse and revival by Eberly et al. [Phys. Rev. Lett. 44 (1980) 1323] are presented in the case of the evolution with time of the population inversion. Here, we study the evolution with coupling strength of population inversion. We define the collapse and revival coupling strengths as characteristic parameters to describe the above collapse and revival. Furthermore, we present the analytic formulas for the population inversion, the collapse and revival coupling strengths

Parameter Diversity Induced Multiple Spatial Coherence Resonances and Spiral Waves in Neuronal Network with and Without Noise

International Nuclear Information System (INIS)

Li Yuye; Jia Bing; Gu Huaguang; An Shucheng

2012-01-01

Diversity in the neurons and noise are inevitable in the real neuronal network. In this paper, parameter diversity induced spiral waves and multiple spatial coherence resonances in a two-dimensional neuronal network without or with noise are simulated. The relationship between the multiple resonances and the multiple transitions between patterns of spiral waves are identified. The coherence degrees induced by the diversity are suppressed when noise is introduced and noise density is increased. The results suggest that natural nervous system might profit from both parameter diversity and noise, provided a possible approach to control formation and transition of spiral wave by the cooperation between the diversity and noise. (general)

On the dynamics of generalized coherent states

International Nuclear Information System (INIS)

Nikolov, B.A.; Trifonov, D.A.

1981-01-01

The exact and stable evolutions of generalized coherent states (GCS) for quantum system are considered by making use of the time- dependent integrals of motion method and of the Klauder approach to the relationship between quantum and classical mechanics. It is shown that one can construct for any quantum system overcomplete family of states, related to the unitary representations of the Lie group G by means of integral of motion generators, and the possibility of using this group as a dynamic symmetry group is pointed out. The relation of the GCS with quantum measurement theory is also established [ru

Pisot q-coherent states quantization of the harmonic oscillator

Energy Technology Data Exchange (ETDEWEB)

Gazeau, J.P., E-mail: gazeau@apc.univ-paris7.fr [Laboratoire APC, Univ. Paris Diderot, Sorbonne Paris Cite, 75205 Paris (France); Olmo, M.A. del, E-mail: olmo@fta.uva.es [Departamento de Fisica Teorica and IMEVA, Universidad de Valladolid, E-47005, Valladolid (Spain)

2013-03-15

We revisit the quantized version of the harmonic oscillator obtained through a q-dependent family of coherent states. For each q, 0states form an overcomplete set that resolves the unity with respect to an explicit measure. We restrict our study to the case in which q{sup -1} is a quadratic unit Pisot number, since then the q-deformed integers form Fibonacci-like sequences of integers. We then examine the main characteristics of the corresponding quantum oscillator: localization in the configuration and in the phase spaces, angle operator, probability distributions and related statistical features, time evolution and semi-classical phase space trajectories. - Highlights: Black-Right-Pointing-Pointer Quantized version of the harmonic oscillator (HO) through a q-family of coherent states. Black-Right-Pointing-Pointer For q,0states form an overcomplete set that resolves the unity with respect to an explicit measure. Black-Right-Pointing-Pointer q-Deformed numbers are Fibonacci-like integer sequences (1/q a quadratic unit Pisot number). Black-Right-Pointing-Pointer We examine the main physical characteristics of the corresponding quantum oscillator.

Continuous-variable quantum teleportation of even and odd coherent states through varied gain channels

Institute of Scientific and Technical Information of China (English)

Li Ying; Zhang Jing; Zhang Jun-Xiang; Zhang Tian-Cai

2006-01-01

This paper has investigated quantum teleportation of even and odd coherent states in terms of the EPR entanglement states for continuous variables. It discusses the relationship between the fidelity and the entanglement of EPR states, which is characterized by the degree of squeezing and the gain of classical channels. It shows that the quality of teleporting quantum states also depends on the characteristics of the states themselves. The properties of teleporting even and odd coherent states at different intensities are investigated. The difference of teleporting two such kinds of quantum states are analysed based on the quantum distance function.

On coherent states for the simplest quantum groups

International Nuclear Information System (INIS)

Jurco, B.

1991-01-01

The coherent states for the simplest quantum groups (q-Heisenberg-Weyl, SU q (2) and the discrete series of representations of SU q (1, 1)) are introduced and their properties investigated. The corresponding analytic representations, path integrals, and q-deformation of Berezin's quantization on C, a sphere, and the Lobatchevsky plane are discussed. (orig.)

Coherence in quantum estimation

Science.gov (United States)

Giorda, Paolo; Allegra, Michele

2018-01-01

The geometry of quantum states provides a unifying framework for estimation processes based on quantum probes, and it establishes the ultimate bounds of the achievable precision. We show a relation between the statistical distance between infinitesimally close quantum states and the second order variation of the coherence of the optimal measurement basis with respect to the state of the probe. In quantum phase estimation protocols, this leads to propose coherence as the relevant resource that one has to engineer and control to optimize the estimation precision. Furthermore, the main object of the theory i.e. the symmetric logarithmic derivative, in many cases allows one to identify a proper factorization of the whole Hilbert space in two subsystems. The factorization allows one to discuss the role of coherence versus correlations in estimation protocols; to show how certain estimation processes can be completely or effectively described within a single-qubit subsystem; and to derive lower bounds for the scaling of the estimation precision with the number of probes used. We illustrate how the framework works for both noiseless and noisy estimation procedures, in particular those based on multi-qubit GHZ-states. Finally we succinctly analyze estimation protocols based on zero-temperature critical behavior. We identify the coherence that is at the heart of their efficiency, and we show how it exhibits the non-analyticities and scaling behavior proper of a large class of quantum phase transitions.

Efficient one-out-of-two quantum oblivious transfer based on four-coherent-state postselection protocol

International Nuclear Information System (INIS)

Chen, I-C; Hwang Tzonelih; Li C-M

2008-01-01

On the basis of the modified four-coherent-state post-selection quantum key distribution protocol (Namiki and Hirano 2006 Preprint quant-ph/0608144v1), two 1-out-of-2 quantum oblivious transfer (QOT 2 1 ) protocols are proposed. The first proposed protocol (called the receiver-based QOT 2 1 protocol) requires the coherent states to be prepared by the receiver, whereas the second protocol (called the sender-based QOT 2 1 protocol) allows the coherent states to be generated by the sender. The main advantages of the proposed protocols are that (i) no quantum bit commitment schemes and the assumption of quantum memory are needed; (ii) less communication cost between participants is required, i.e. the receiver-based QOT 2 1 protocol requires only one quantum communication and one classical communication and the sender-based QOT 2 1 protocol requires only one quantum communication between participants during protocol execution; and (iii) the utilization of quantum states is very efficient, wherein the receiver-based and the sender-based QOT 2 1 protocols use only two coherent pulses and one coherent pulse respectively for sending the sender's two messages

Thermal Wigner Operator in Coherent Thermal State Representation and Its Application

Institute of Scientific and Technical Information of China (English)

FAN HongYi

2002-01-01

In the coherent thermal state representation we introduce thermal Wigner operator and find that it is"squeezed" under the thermal transformation. The thermal Wigner operator provides us with a new direct and neatapproach for deriving Wigner functions of thermal states.

Towards a coherent picture of excitonic coherence in the Fenna–Matthews–Olson complex

International Nuclear Information System (INIS)

Fidler, Andrew F; Caram, Justin R; Hayes, Dugan; Engel, Gregory S

2012-01-01

Observations of long-lived coherence between excited states in several photosynthetic antenna complexes has motivated interest in developing a more detailed understanding of the role of the protein matrix in guiding the underlying dynamics of the system. These experiments suggest that classical rate laws may not provide an adequate description of the energy transfer process and that quantum effects must be taken into account to describe the near unity transfer efficiency in these systems. Recently, it has been shown that coherences between different pairs of excitons dephase at different rates. These details should provide some insight about the underlying electronic structure of the complex and its coupling to the protein bath. Here we show that a simple model can account for the different dephasing rates as well as the most current available experimental evidence of excitonic coherences in the Fenna–Matthews–Olson complex. The differences in dephasing rates can be understood as arising largely from differences in the delocalization and shared character between the underlying electronic states. We also suggest that the anomalously low dephasing rate of the exciton 1–2 coherence is enhanced by non-secular effects. (paper)

On coherent states for the simplest quantum groups

Energy Technology Data Exchange (ETDEWEB)

Jurco, B. (Palackeho Univ., Olomouc (Czechoslovakia). Dept. of Optics)

1991-01-01

The coherent states for the simplest quantum groups (q-Heisenberg-Weyl, SU{sub q}(2) and the discrete series of representations of SU{sub q}(1, 1)) are introduced and their properties investigated. The corresponding analytic representations, path integrals, and q-deformation of Berezin's quantization on C, a sphere, and the Lobatchevsky plane are discussed. (orig.).

Coherent states for oscillators of non-conventional statistics

International Nuclear Information System (INIS)

Dao Vong Duc; Nguyen Ba An

1998-12-01

In this work we consider systematically the concept of coherent states for oscillators of non-conventional statistics - parabose oscillator, infinite statistics oscillator and generalised q-deformed oscillator. The expressions for the quadrature variances and particle number distribution are derived and displayed graphically. The obtained results show drastic changes when going from one statistics to another. (author)

Quantum nonlinear lattices and coherent state vectors

DEFF Research Database (Denmark)

Ellinas, Demosthenes; Johansson, M.; Christiansen, Peter Leth

1999-01-01

for the state vectors invokes the study of the Riemannian and symplectic geometry of the CSV manifolds as generalized phase spaces. Next, we investigate analytically and numerically the behavior of mean values and uncertainties of some physically interesting observables as well as the modifications...... (FP) model. Based on the respective dynamical symmetries of the models, a method is put forward which by use of the associated boson and spin coherent state vectors (CSV) and a factorization ansatz for the solution of the Schrodinger equation, leads to quasiclassical Hamiltonian equations of motion...... state vectors, and accounts for the quantum correlations of the lattice sites that develop during the time evolution of the systems. (C) 1999 Elsevier Science B.V. All rights reserved....

Sequence memory based on coherent spin-interaction neural networks.

Science.gov (United States)

Xia, Min; Wong, W K; Wang, Zhijie

2014-12-01

Sequence information processing, for instance, the sequence memory, plays an important role on many functions of brain. In the workings of the human brain, the steady-state period is alterable. However, in the existing sequence memory models using heteroassociations, the steady-state period cannot be changed in the sequence recall. In this work, a novel neural network model for sequence memory with controllable steady-state period based on coherent spininteraction is proposed. In the proposed model, neurons fire collectively in a phase-coherent manner, which lets a neuron group respond differently to different patterns and also lets different neuron groups respond differently to one pattern. The simulation results demonstrating the performance of the sequence memory are presented. By introducing a new coherent spin-interaction sequence memory model, the steady-state period can be controlled by dimension parameters and the overlap between the input pattern and the stored patterns. The sequence storage capacity is enlarged by coherent spin interaction compared with the existing sequence memory models. Furthermore, the sequence storage capacity has an exponential relationship to the dimension of the neural network.

Coherent x-rays from PEP

International Nuclear Information System (INIS)

Baird, S.; Nuhn, H.-D.; Tatchyn, R.; Winick, H.; Fisher, A.S.; Gallardo, J.C.; Pellegrini, C.

1991-01-01

This paper explores the use of a large-circumference, high-energy, electron-positron collider such as PEP to drive a free-electron laser (FEL), producing high levels of coherent power at short wavelengths. The author consider Self-Amplified Spontaneous Emission (SASE), in which electron bunches with low emittance, high peak current and small energy spread radiate coherently in a single passthrough a long undulator. As the electron beam passes down the undulator, its interaction with the increasingly intense spontaneous radiation causes a bunch density modulation at the optical wavelength, resulting in stimulated emissional growth of coherent power in a single pass. The need for optical-cavity mirrors, which place a lower limit on the wavelength of a conventional FEL oscillator, is avoided. The authors explore various combinations of electron-beam and undulator parameters, as well as special undulator designs and optical klystrons (OK), to reach high average or peak coherent power at wavelengths around 40 angstrom by achieving significant exponential gain or full saturation. Examples are presented for devices that achieve high peak coherent power (up to about 400 MW) with lower average coherent power (about 20 mW) and other devices which produce a few watts of average coherent power

Coherent quantum phase slip in two-component bosonic atomtronic circuits

International Nuclear Information System (INIS)

Gallemí, A; Mateo, A Muñoz; Mayol, R; Guilleumas, M

2016-01-01

Coherent quantum phase slip consists in the coherent transfer of vortices in superfluids. We investigate this phenomenon in two miscible coherently coupled components of a spinor Bose gas confined in a toroidal trap. After imprinting different vortex states, i.e. states with quantized circulation, on each component, we demonstrate that during the whole dynamics the system remains in a linear superposition of two current states in spite of the nonlinearity, and can be mapped onto a linear Josephson problem. We propose this system as a good candidate for the realization of a Mooij–Harmans qubit and remark its feasibility for implementation in current experiments with 87 Rb, since we have used values for the physical parameters currently available in laboratories. (paper)

Change of State of a Dynamical Unit in the Transition of Coherence

International Nuclear Information System (INIS)

Yang Yan-Jin; Du Ru-Hai; Wang Sheng-Jun; Jin Tao; Qu Shi-Xian

2015-01-01

The change of state of one map in the network of nonlocal coupled logistic maps at the transition of coherence is studied. With the increase of coupling strength, the network dynamics transits from the incoherent state into the coherent state. In the process, the iteration of the map first changes from chaos to period state, then from periodic to chaotic state again. For the periodic doubling bifurcations, similar to an isolated map, the largest Lyapunov exponent tends to zero from a negative value. However, the states of coupled maps exhibit complex behavior rather than converge to a few fixed values. The behavior brings a new chimera state of coupled logistic maps. The bifurcation diagram is identical to the phase order of maps iterations. For the bifurcation between 1-band and multi-band chaos, the symmetry of chaotic bands emerges and the transition of the order of iteration direction occurs

Coherent secondary emission from resonantly excited two-exciton states

DEFF Research Database (Denmark)

Birkedal, Dan

2000-01-01

The coherent interaction of light and the electronic states of semiconductors near the fundamental bandgap has been a very active topic of research since the advent of ultrafast lasers. While many of the ultrafast nonlinear properties of semiconductors have been well explained within mean field...

Entanglement between atomic thermal states and coherent or squeezed photons in a damping cavity

Science.gov (United States)

Yadollahi, F.; Safaiee, R.; Golshan, M. M.

2018-02-01

In the present study, the standard Jaynes-Cummings model, in a lossy cavity, is employed to characterize the entanglement between atoms and photons when the former is initially in a thermal state (mixed ensemble) while the latter is described by either coherent or squeezed distributions. The whole system is thus assumed to be in equilibrium with a heat reservoir at a finite temperature T, and the measure of negativity is used to determine the time evolution of atom-photon entanglement. To this end, the master equation for the density matrix, in the secular approximation, is solved and a partial transposition of the result is made. The degree of atom-photon entanglement is then numerically computed, through the negativity, as a function of time and temperature. To justify the behavior of atom-photon entanglement, moreover, we employ the so obtained total density matrix to compute and analyze the time evolution of the initial photonic coherent or squeezed probability distributions and the squeezing parameters. On more practical points, our results demonstrate that as the initial photon mean number increases, the atom-photon entanglement decays at a faster pace for the coherent distribution compared to the squeezed one. Moreover, it is shown that the degree of atom-photon entanglement is much higher and more stable for the squeezed distribution than that for the coherent one. Consequently, we conclude that the time intervals during which the atom-photon entanglement is distillable is longer for the squeezed distribution. It is also illustrated that as the temperature increases the rate of approaching separability is faster for the coherent initial distribution. The novel point of the present report is the calculation of dynamical density matrix (containing all physical information) for the combined system of atom-photon in a lossy cavity, as well as the corresponding negativity, at a finite temperature.

Delayed coherent quantum feedback from a scattering theory and a matrix product state perspective

Science.gov (United States)

Guimond, P.-O.; Pletyukhov, M.; Pichler, H.; Zoller, P.

2017-12-01

We study the scattering of photons propagating in a semi-infinite waveguide terminated by a mirror and interacting with a quantum emitter. This paradigm constitutes an example of coherent quantum feedback, where light emitted towards the mirror gets redirected back to the emitter. We derive an analytical solution for the scattering of two-photon states, which is based on an exact resummation of the perturbative expansion of the scattering matrix, in a regime where the time delay of the coherent feedback is comparable to the timescale of the quantum emitter’s dynamics. We compare the results with numerical simulations based on matrix product state techniques simulating the full dynamics of the system, and extend the study to the scattering of coherent states beyond the low-power limit.

Semiclassical description of quantum rotator in terms of SU(2) coherent states

International Nuclear Information System (INIS)

Gitman, D M; Petrusevich, D A; Shelepin, A L

2013-01-01

We introduce coordinates of the rigid body (rotator) using mutual positions between body-fixed and space-fixed reference frames. Wave functions that depend on such coordinates can be treated as scalar functions of the group SU(2). Irreducible representations of the group SU(2) × SU(2) in the space of such functions describe their possible transformations under independent rotations of the both reference frames. We construct sets of the corresponding group SU(2) × SU(2) Perelomov coherent states (CS) with a fixed angular momentum j of the rotator as special orbits of the latter group. Minimization of different uncertainty relations is discussed. The classical limit corresponds to the limit j → ∞. Considering Hamiltonians of rotators with different characteristics, we study the time evolution of the constructed CS. In some cases, the CS time evolution is completely or partially reduced to their parameter time evolution. If these parameters are chosen as Euler angles, then they obey the Euler equations in the classical limit. Quantum corrections to the motion of the quantum rotator can be found from exact equations on the CS parameters. (paper)

Thermal Wigner Operator in Coherent Thermal State Representation and Its Application

Institute of Scientific and Technical Information of China (English)

FANHong－Yi

2002-01-01

In the coherent thermal state representation we introduce thermal Wigner operator and find that it is “squeezed” under the thermal transformation.The thermal Wigner operator provides us with a new direct and neat approach for deriving Wigner functions of thermal states.

Coherent states of a particle in a magnetic field and the Stieltjes moment problem

International Nuclear Information System (INIS)

Gazeau, J.P.; Baldiotti, M.C.; Gitman, D.M.

2009-01-01

A solution to a version of the Stieltjes moment problem is presented. Using this solution, we construct a family of coherent states of a charged particle in a uniform magnetic field. We prove that these states form an overcomplete set that is normalized and resolves the unity. By the help of these coherent states we construct the Fock-Bergmann representation related to the particle quantization. This quantization procedure takes into account a circle topology of the classical motion.

Coherent states of a particle in a magnetic field and the Stieltjes moment problem

Energy Technology Data Exchange (ETDEWEB)

Gazeau, J.P. [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318-CEP, 05315-970 Sao Paulo, S.P. (Brazil)], E-mail: gazeau@apc.univ-paris7.fr; Baldiotti, M.C. [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318-CEP, 05315-970 Sao Paulo, S.P. (Brazil)], E-mail: baldiott@fma.if.usp.br; Gitman, D.M. [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318-CEP, 05315-970 Sao Paulo, S.P. (Brazil)], E-mail: gitman@dfn.if.usp.br

2009-05-11

A solution to a version of the Stieltjes moment problem is presented. Using this solution, we construct a family of coherent states of a charged particle in a uniform magnetic field. We prove that these states form an overcomplete set that is normalized and resolves the unity. By the help of these coherent states we construct the Fock-Bergmann representation related to the particle quantization. This quantization procedure takes into account a circle topology of the classical motion.

Coherence and entanglement in the ground state of a bosonic Josephson junction: From macroscopic Schroedinger cat states to separable Fock states

International Nuclear Information System (INIS)

Mazzarella, G.; Toigo, F.; Salasnich, L.; Parola, A.

2011-01-01

We consider a bosonic Josephson junction made of N ultracold and dilute atoms confined by a quasi-one-dimensional double-well potential within the two-site Bose-Hubbard model framework. The behavior of the system is investigated at zero temperature by varying the interatomic interaction from the strongly attractive regime to the repulsive one. We show that the ground state exhibits a crossover from a macroscopic Schroedinger-cat state to a separable Fock state through an atomic coherent regime. By diagonalizing the Bose-Hubbard Hamiltonian we characterize the emergence of the macroscopic cat states by calculating the Fisher information F, the coherence by means of the visibility α of the interference fringes in the momentum distribution, and the quantum correlations by using the entanglement entropy S. Both Fisher information and visibility are shown to be related to the ground-state energy by employing the Hellmann-Feynman theorem. This result, together with a perturbative calculation of the ground-state energy, allows simple analytical formulas for F and α to be obtained over a range of interactions, in excellent agreement with the exact diagonalization of the Bose-Hubbard Hamiltonian. In the attractive regime the entanglement entropy attains values very close to its upper limit for a specific interaction strength lying in the region where coherence is lost and self-trapping sets in.

Reproducing Kernels and Coherent States on Julia Sets

Energy Technology Data Exchange (ETDEWEB)

Thirulogasanthar, K., E-mail: santhar@cs.concordia.ca; Krzyzak, A. [Concordia University, Department of Computer Science and Software Engineering (Canada)], E-mail: krzyzak@cs.concordia.ca; Honnouvo, G. [Concordia University, Department of Mathematics and Statistics (Canada)], E-mail: g_honnouvo@yahoo.fr

2007-11-15

We construct classes of coherent states on domains arising from dynamical systems. An orthonormal family of vectors associated to the generating transformation of a Julia set is found as a family of square integrable vectors, and, thereby, reproducing kernels and reproducing kernel Hilbert spaces are associated to Julia sets. We also present analogous results on domains arising from iterated function systems.

Reproducing Kernels and Coherent States on Julia Sets

International Nuclear Information System (INIS)

Thirulogasanthar, K.; Krzyzak, A.; Honnouvo, G.

2007-01-01

We construct classes of coherent states on domains arising from dynamical systems. An orthonormal family of vectors associated to the generating transformation of a Julia set is found as a family of square integrable vectors, and, thereby, reproducing kernels and reproducing kernel Hilbert spaces are associated to Julia sets. We also present analogous results on domains arising from iterated function systems

Coherent states of an electron in a quantized electromagnetic wave

International Nuclear Information System (INIS)

Bagrov, V.G.; Bukhbinder, I.L.; Gitman, D.M.; Lavrov, P.M.

1977-01-01

Coherent states for interacting electrons and photons in a plane elecmagnetic wave are found. Trajectories of the electron and the characteristics of the electromagnetic field are investigated. Limiting transition to the given external field is studied

Coherent Waves in Seismic Researches

Science.gov (United States)

Emanov, A.; Seleznev, V. S.

2013-05-01

Development of digital processing algorithms of seismic wave fields for the purpose of useful event picking to study environment and other objects is the basis for the establishment of new seismic techniques. In the submitted paper a fundamental property of seismic wave field coherence is used. The authors extended conception of coherence types of observed wave fields and devised a technique of coherent component selection from observed wave field. Time coherence and space coherence are widely known. In this paper conception "parameter coherence" has been added. The parameter by which wave field is coherent can be the most manifold. The reason is that the wave field is a multivariate process described by a set of parameters. Coherence in the first place means independence of linear connection in wave field of parameter. In seismic wave fields, recorded in confined space, in building-blocks and stratified mediums time coherent standing waves are formed. In prospecting seismology at observation systems with multiple overlapping head waves are coherent by parallel correlation course or, in other words, by one measurement on generalized plane of observation system. For detail prospecting seismology at observation systems with multiple overlapping on basis of coherence property by one measurement of area algorithms have been developed, permitting seismic records to be converted to head wave time sections which have neither reflected nor other types of waves. Conversion in time section is executed on any specified observation base. Energy storage of head waves relative to noise on basis of multiplicity of observation system is realized within area of head wave recording. Conversion on base below the area of wave tracking is performed with lack of signal/noise ratio relative to maximum of this ratio, fit to observation system. Construction of head wave time section and dynamic plots a basis of automatic processing have been developed, similar to CDP procedure in method of

Glaucoma Diagnostic Ability of the Optical Coherence Tomography Angiography Vessel Density Parameters.

Science.gov (United States)

Chung, Jae Keun; Hwang, Young Hoon; Wi, Jae Min; Kim, Mijin; Jung, Jong Jin

2017-11-01

To investigate the glaucoma diagnostic abilities of vessel density parameters as determined by optical coherence tomography (OCT) angiography in different stages of glaucoma. A total of 113 healthy eyes and 140 glaucomatous eyes were enrolled. Diagnostic abilities of the OCT vessel density parameters in the optic nerve head (ONH), peripapillary, and macular regions were evaluated by calculating the area under the receiver operation characteristic curves (AUCs). AUCs of the peripapillary vessel density parameters and circumpapillary retinal nerve fiber layer (RNFL) thickness were compared. OCT angiography vessel densities in the ONH, peripapillary, and macular regions in the glaucomatous eyes were significantly lower than those in the healthy eyes (P glaucoma detection. The peripapillary vessel density parameters showed similar AUCs with the corresponding sectoral RNFL thickness (P > 0.05). However, in the early stage of glaucoma, the AUCs of the inferotemporal and temporal peripapillary vessel densities were significantly lower than that of the RNFL thickness (P glaucoma diagnostic ability with circumpapillary RNFL thickness, in the early stage, the vessel density parameters showed limited clinical value.

Search and Coherence-Building in Intuition and Insight Problem Solving

Directory of Open Access Journals (Sweden)

Michael Öllinger

2017-05-01

Full Text Available Coherence-building is a key concept for a better understanding of the underlying mechanisms of intuition and insight problem solving. There are several accounts that address certain aspects of coherence-building. However, there is still no proper framework defining the general principles of coherence-building. We propose a four-stage model of coherence-building. The first stage starts with spreading activation restricted by constraints. This dynamic is a well-defined rule based process. The second stage is characterized by detecting a coherent state. We adopted a fluency account assuming that the ease of information processing indicates the realization of a coherent state. The third stage is designated to evaluate the result of the coherence-building process and assess whether the given problem is solved or not. If the coherent state does not fit the requirements of the task, the process re-enters at stage 1. These three stages characterize intuition. For insight problem solving a fourth stage is necessary, which restructures the given representation after repeated failure, so that a new search space results. The new search space enables new coherent states. We provide a review of the most important findings, outline our model, present a large number of examples, deduce potential new paradigms and measures that might help to decipher the underlying cognitive processes.

Physical properties of a new coherent state of the almost-degenerate infinite-U lattice Anderson model

International Nuclear Information System (INIS)

Tolpin, A.E.

1992-01-01

A new approach toward understanding the heavy-fermion systems (HFS) within a framework of the almost-degenerate lattice Anderson Hamiltonian in the Kondo regime is proposed. In the coherent low-temperature regime, operators in the effective Hamiltonian are found to belong to an SU(2J + 3) dynamical algebra. A canonical transformation is employed to decouple the quasiparticle branches, thereby setting up the decoupling equation. It is found that this decoupling equation has a solution of the symmetry-altering type. The thermodynamic response functions and other quantities are calculated for this new state. This solution is a consequence of the degeneracy of the uncoupled f-orbitals. It is characterized by the interatomic hopping of f-electrons, which produces the spin-delocalization regime and with the renormalized f-level pinned close to the Fermi level. This is also found to be the source of the apparent spin-compensation regime, which is accompanied by large enhancement of the thermodynamic response functions. In addition, the calculated phase coherence length is found to be much greater than a lattice constant, thereby showing a many-body character of this new state. It is believed that this new state provides an accurate description of the heavy-fermion state at low temperatures. The stability conditions for the new regime are also discussed

Dephasing in coherent communication with weak signal states

International Nuclear Information System (INIS)

Jarzyna, Marcin; Banaszek, Konrad; Demkowicz-Dobrzański, Rafał

2014-01-01

We analyse the ultimate quantum limit on the accessible information for an optical communication scheme when time bins carry coherent light pulses prepared in one of several orthogonal modes and the phase undergoes diffusion after each channel use. This scheme, an example of a quantum memory channel, can be viewed as noisy pulse position modulation (PPM) keying with phase fluctuations occurring between consecutive PPM symbols. We derive a general expression for the output states in the Fock basis and implement a numerical procedure to calculate the Holevo quantity. Using asymptotic properties of Toeplitz matrices, we also present an analytic expression for the Holevo quantity valid for very weak signals and sufficiently strong dephasing when the dominant contribution comes from the single-photon sector in the Hilbert space of signal states. Based on numerical results we conjecture an inequality for contributions to the Holevo quantity from multiphoton sectors which implies that in the asymptotic limit of weak signals, for arbitrarily small dephasing the accessible information scales linearly with the average number of photons contained in the pulse. Such behaviour presents a qualitative departure from the fully coherent case. (paper)

A phenomenological model for collisional coherence transfer in an optically pumped atomic system

Energy Technology Data Exchange (ETDEWEB)

Khanbekyan, K; Bevilaqua, G; Mariotti, E; Moi, L [Universita degli Studi di Siena, Siena, 53100 (Italy); Khanbekyan, A; Papoyan, A, E-mail: karen.khanbekyan@gmail.com [Institute for Physical Research, National Academy of Sciences, Ashtarak 2 (Armenia)

2011-03-14

We consider a dual {Lambda}-system under double laser excitation to investigate the possibility of indirect coherence transfer between atomic ground states through an excited state. The atomic system is excited by a frequency modulated pump laser and probed by a low-power cw laser. All the decoherence mechanisms are discussed and taken into account. Adjustment of parameters of the two radiations aimed at maximization of coherence transfer is addressed. The study can help to understand the phenomena as collisional transfer of coherence and can find application in the experimental realization of atomic sensors.

Spectrum structure and coherent state of the two-particle Calogero-Sutherland model: an application of the pseudo-angular-momentum operator method

International Nuclear Information System (INIS)

Li Wenbo; Li Mishan; Li Yaling; Wen Xiaoyang; Yuan Guangjun; Zhang Chi; Yang Tao

2005-01-01

The generality of the Calogero-Sutherland model (CSM) is studied with the aid of its several variations. The CSM is then solved by a new approach, the pseudo-angular-momentum operator method. The symmetry in spectrum space and valid region of the parameter are discussed. Analytic expressions of the eigenstate are obtained. The coherent states of the CSM are also discussed

Parameter and State Estimator for State Space Models

Directory of Open Access Journals (Sweden)

Ruifeng Ding

2014-01-01

Full Text Available This paper proposes a parameter and state estimator for canonical state space systems from measured input-output data. The key is to solve the system state from the state equation and to substitute it into the output equation, eliminating the state variables, and the resulting equation contains only the system inputs and outputs, and to derive a least squares parameter identification algorithm. Furthermore, the system states are computed from the estimated parameters and the input-output data. Convergence analysis using the martingale convergence theorem indicates that the parameter estimates converge to their true values. Finally, an illustrative example is provided to show that the proposed algorithm is effective.

Extended SUSY quantum mechanics, intertwining operators and coherent states

International Nuclear Information System (INIS)

Bagarello, F.

2008-01-01

We propose an extension of supersymmetric quantum mechanics which produces a family of isospectral Hamiltonians. Our procedure slightly extends the idea of intertwining operators. Several examples of the construction are given. Further, we show how to build up vector coherent states of the Gazeau-Klauder type associated to our Hamiltonians

Quantum entropy and uncertainty for two-mode squeezed, coherent and intelligent spin states

Science.gov (United States)

Aragone, C.; Mundarain, D.

1993-01-01

We compute the quantum entropy for monomode and two-mode systems set in squeezed states. Thereafter, the quantum entropy is also calculated for angular momentum algebra when the system is either in a coherent or in an intelligent spin state. These values are compared with the corresponding values of the respective uncertainties. In general, quantum entropies and uncertainties have the same minimum and maximum points. However, for coherent and intelligent spin states, it is found that some minima for the quantum entropy turn out to be uncertainty maxima. We feel that the quantum entropy we use provides the right answer, since it is given in an essentially unique way.

Coherent spin-rotational dynamics of oxygen superrotors

Science.gov (United States)

Milner, Alexander A.; Korobenko, Aleksey; Milner, Valery

2014-09-01

We use state- and time-resolved coherent Raman spectroscopy to study the rotational dynamics of oxygen molecules in ultra-high rotational states. While it is possible to reach rotational quantum numbers up to N≈ 50 by increasing the gas temperature to 1500 K, low population levels and gas densities result in correspondingly weak optical response. By spinning {{O}2} molecules with an optical centrifuge, we efficiently excite extreme rotational states with N≤slant 109 in high-density room temperature ensembles. Fast molecular rotation results in the enhanced robustness of the created rotational wave packets against collisions, enabling us to observe the effects of weak spin-rotation coupling in the coherent rotational dynamics of oxygen. The decay rate of spin-rotational coherence due to collisions is measured as a function of the molecular angular momentum and its dependence on the collisional adiabaticity parameter is discussed. We find that at high values of N, the rotational decoherence of oxygen is much faster than that of the previously studied non-magnetic nitrogen molecules, pointing at the effects of spin relaxation in paramagnetic gases.

New construction of coherent states for generalized harmonic oscillators

International Nuclear Information System (INIS)

El Baz, M.; Hassouni, Y.; Madouri, F.

2001-08-01

A dynamical algebra A q , englobing many of the deformed harmonic oscillator algebras is introduced. One of its special cases is extensively developed. A general method for constructing coherent states related to any algebra of the type A q is discussed. The construction following this method is carried out for the special case. (author)

Probabilistic cloning of coherent states without a phase reference

DEFF Research Database (Denmark)

Müller, Christian R.; Wittmann, Christoffer; Marek, Petr

2012-01-01

We present a probabilistic cloning scheme operating independently of any phase reference. The scheme is based solely on a phase-randomized displacement and photon counting, omitting the need for nonclassical resources and nonlinear materials. In an experimental implementation, we employ the scheme...... to clone coherent states from a phase covariant alphabet and demonstrate that the cloner is capable of outperforming the hitherto best-performing deterministic scheme. An analysis of the covariances between the output states shows that uncorrelated clones can be approached asymptotically...

Adaptive estimation of a time-varying phase with coherent states: Smoothing can give an unbounded improvement over filtering

Science.gov (United States)

Laverick, Kiarn T.; Wiseman, Howard M.; Dinani, Hossein T.; Berry, Dominic W.

2018-04-01

The problem of measuring a time-varying phase, even when the statistics of the variation is known, is considerably harder than that of measuring a constant phase. In particular, the usual bounds on accuracy, such as the 1 /(4 n ¯) standard quantum limit with coherent states, do not apply. Here, by restricting to coherent states, we are able to analytically obtain the achievable accuracy, the equivalent of the standard quantum limit, for a wide class of phase variation. In particular, we consider the case where the phase has Gaussian statistics and a power-law spectrum equal to κp -1/|ω| p for large ω , for some p >1 . For coherent states with mean photon flux N , we give the quantum Cramér-Rao bound on the mean-square phase error as [psin(π /p ) ] -1(4N /κ ) -(p -1 )/p . Next, we consider whether the bound can be achieved by an adaptive homodyne measurement in the limit N /κ ≫1 , which allows the photocurrent to be linearized. Applying the optimal filtering for the resultant linear Gaussian system, we find the same scaling with N , but with a prefactor larger by a factor of p . By contrast, if we employ optimal smoothing we can exactly obtain the quantum Cramér-Rao bound. That is, contrary to previously considered (p =2 ) cases of phase estimation, here the improvement offered by smoothing over filtering is not limited to a factor of 2 but rather can be unbounded by a factor of p . We also study numerically the performance of these estimators for an adaptive measurement in the limit where N /κ is not large and find a more complicated picture.

Coherent defects in superconducting circuits

International Nuclear Information System (INIS)

Mueller, Clemens

2011-01-01

The interaction of superconducting circuits with additional quantum systems is a topic that has found extensive study in the recent past. In the limit where the added system are incoherent, this is the standard field of decoherence and the system dynamics can be described by a simple master equation. In the other limit however, when the additional parts are coherent, the resulting time-evolution can become more complicated. In this thesis we have investigated the interaction of superconducting circuits with coherent and incoherent two-level defects. We have shown theoretical calculations characterizing this interaction for all relevant parameter regimes. In the weak coupling limit, the interaction can be described in an effective bath picture, where the TLS act as parts of a large, decohering environment. For strong coupling, however, the coherent dynamics of the full coupled system has to be considered. We show the calculations of the coupled time-evolution and again characterize the interaction by an effective decoherence rate. We also used experimental data to characterize the microscopic origin of the defects and the details of their interaction with the circuits. The results obtained by analyzing spectroscopic data allow us to place strong constraint on several microscopic models for the observed TLS. However, these calculations are not yet fully conclusive as to the physical nature of the TLS. We propose additional experiments to fully characterize the interaction part of the Hamiltonian, thus providing the answer to the question of the physical origin of the coupling. Additionally we have developed a method to directly drive individual defect states via virtual excitation of the qubit. This method allows one to directly probe the properties of single TLS and possibly make use of their superior coherence times for quantum information purposes. The last part of this thesis provided a way for a possible implementation of geometric quantum computation in

Quantum bit string commitment protocol using polarization of mesoscopic coherent states

International Nuclear Information System (INIS)

Mendonca, Fabio Alencar; Ramos, Rubens Viana

2008-01-01

In this work, we propose a quantum bit string commitment protocol using polarization of mesoscopic coherent states. The protocol is described and its security against brute force and quantum cloning machine attack is analyzed

Quantum bit string commitment protocol using polarization of mesoscopic coherent states

Science.gov (United States)

Mendonça, Fábio Alencar; Ramos, Rubens Viana

2008-02-01

In this work, we propose a quantum bit string commitment protocol using polarization of mesoscopic coherent states. The protocol is described and its security against brute force and quantum cloning machine attack is analyzed.

Quantifying Neural Oscillatory Synchronization: A Comparison between Spectral Coherence and Phase-Locking Value Approaches

Science.gov (United States)

Lowet, Eric; Roberts, Mark J.; Bonizzi, Pietro; Karel, Joël; De Weerd, Peter

2016-01-01

Synchronization or phase-locking between oscillating neuronal groups is considered to be important for coordination of information among cortical networks. Spectral coherence is a commonly used approach to quantify phase locking between neural signals. We systematically explored the validity of spectral coherence measures for quantifying synchronization among neural oscillators. To that aim, we simulated coupled oscillatory signals that exhibited synchronization dynamics using an abstract phase-oscillator model as well as interacting gamma-generating spiking neural networks. We found that, within a large parameter range, the spectral coherence measure deviated substantially from the expected phase-locking. Moreover, spectral coherence did not converge to the expected value with increasing signal-to-noise ratio. We found that spectral coherence particularly failed when oscillators were in the partially (intermittent) synchronized state, which we expect to be the most likely state for neural synchronization. The failure was due to the fast frequency and amplitude changes induced by synchronization forces. We then investigated whether spectral coherence reflected the information flow among networks measured by transfer entropy (TE) of spike trains. We found that spectral coherence failed to robustly reflect changes in synchrony-mediated information flow between neural networks in many instances. As an alternative approach we explored a phase-locking value (PLV) method based on the reconstruction of the instantaneous phase. As one approach for reconstructing instantaneous phase, we used the Hilbert Transform (HT) preceded by Singular Spectrum Decomposition (SSD) of the signal. PLV estimates have broad applicability as they do not rely on stationarity, and, unlike spectral coherence, they enable more accurate estimations of oscillatory synchronization across a wide range of different synchronization regimes, and better tracking of synchronization-mediated information

Quantifying Neural Oscillatory Synchronization: A Comparison between Spectral Coherence and Phase-Locking Value Approaches.

Directory of Open Access Journals (Sweden)

Eric Lowet

Full Text Available Synchronization or phase-locking between oscillating neuronal groups is considered to be important for coordination of information among cortical networks. Spectral coherence is a commonly used approach to quantify phase locking between neural signals. We systematically explored the validity of spectral coherence measures for quantifying synchronization among neural oscillators. To that aim, we simulated coupled oscillatory signals that exhibited synchronization dynamics using an abstract phase-oscillator model as well as interacting gamma-generating spiking neural networks. We found that, within a large parameter range, the spectral coherence measure deviated substantially from the expected phase-locking. Moreover, spectral coherence did not converge to the expected value with increasing signal-to-noise ratio. We found that spectral coherence particularly failed when oscillators were in the partially (intermittent synchronized state, which we expect to be the most likely state for neural synchronization. The failure was due to the fast frequency and amplitude changes induced by synchronization forces. We then investigated whether spectral coherence reflected the information flow among networks measured by transfer entropy (TE of spike trains. We found that spectral coherence failed to robustly reflect changes in synchrony-mediated information flow between neural networks in many instances. As an alternative approach we explored a phase-locking value (PLV method based on the reconstruction of the instantaneous phase. As one approach for reconstructing instantaneous phase, we used the Hilbert Transform (HT preceded by Singular Spectrum Decomposition (SSD of the signal. PLV estimates have broad applicability as they do not rely on stationarity, and, unlike spectral coherence, they enable more accurate estimations of oscillatory synchronization across a wide range of different synchronization regimes, and better tracking of synchronization

Generation of optical coherent state superpositions for quantum information processing

DEFF Research Database (Denmark)

Tipsmark, Anders

2012-01-01

I dette projektarbejde med titlen “Generation of optical coherent state superpositions for quantum information processing” har målet været at generere optiske kat-tilstande. Dette er en kvantemekanisk superpositions tilstand af to koherente tilstande med stor amplitude. Sådan en tilstand er...

Coherent and semiclassical states in a magnetic field in the presence of the Aharonov-Bohm solenoid

Energy Technology Data Exchange (ETDEWEB)

Bagrov, V G [Department of Physics, Tomsk State University, 634050 Tomsk (Russian Federation); Gavrilov, S P; Gitman, D M; Filho, D P Meira, E-mail: bagrov@phys.tsu.ru, E-mail: gavrilovsergeyp@yahoo.com, E-mail: gitman@dfn.if.usp.br, E-mail: dmeira@dfn.if.usp.br [Institute of Physics, University of Sao Paulo, CP 66318, CEP 05315-970 Sao Paulo, SP (Brazil)

2011-02-04

A new approach to constructing coherent states (CS) and semiclassical states (SS) in a magnetic-solenoid field is proposed. The main idea is based on the fact that the AB solenoid breaks the translational symmetry in the xy-plane; this has a topological effect such that there appear two types of trajectories which embrace and do not embrace the solenoid. Due to this fact, one has to construct two different kinds of CS/SS which correspond to such trajectories in the semiclassical limit. Following this idea, we construct CS in two steps, first the instantaneous CS (ICS) and then the time-dependent CS/SS as an evolution of the ICS. The construction is realized for nonrelativistic and relativistic spinning particles both in (2 + 1) and (3 + 1) dimensions and gives a non-trivial example of SS/CS for systems with a nonquadratic Hamiltonian. It is stressed that CS depending on their parameters (quantum numbers) describe both pure quantum and semiclassical states. An analysis is represented that classifies parameters of the CS in such respect. Such a classification is used for the semiclassical decompositions of various physical quantities.

Coherent and semiclassical states in a magnetic field in the presence of the Aharonov-Bohm solenoid

International Nuclear Information System (INIS)

Bagrov, V G; Gavrilov, S P; Gitman, D M; Filho, D P Meira

2011-01-01

A new approach to constructing coherent states (CS) and semiclassical states (SS) in a magnetic-solenoid field is proposed. The main idea is based on the fact that the AB solenoid breaks the translational symmetry in the xy-plane; this has a topological effect such that there appear two types of trajectories which embrace and do not embrace the solenoid. Due to this fact, one has to construct two different kinds of CS/SS which correspond to such trajectories in the semiclassical limit. Following this idea, we construct CS in two steps, first the instantaneous CS (ICS) and then the time-dependent CS/SS as an evolution of the ICS. The construction is realized for nonrelativistic and relativistic spinning particles both in (2 + 1) and (3 + 1) dimensions and gives a non-trivial example of SS/CS for systems with a nonquadratic Hamiltonian. It is stressed that CS depending on their parameters (quantum numbers) describe both pure quantum and semiclassical states. An analysis is represented that classifies parameters of the CS in such respect. Such a classification is used for the semiclassical decompositions of various physical quantities.

Generalization of fewest-switches surface hopping for coherences

Science.gov (United States)

Tempelaar, Roel; Reichman, David R.

2018-03-01

Fewest-switches surface hopping (FSSH) is perhaps the most widely used mixed quantum-classical approach for the modeling of non-adiabatic processes, but its original formulation is restricted to (adiabatic) population terms of the quantum density matrix, leaving its implementations with an inconsistency in the treatment of populations and coherences. In this article, we propose a generalization of FSSH that treats both coherence and population terms on equal footing and which formally reduces to the conventional FSSH algorithm for the case of populations. This approach, coherent fewest-switches surface hopping (C-FSSH), employs a decoupling of population relaxation and pure dephasing and involves two replicas of the classical trajectories interacting with two active surfaces. Through extensive benchmark calculations of a spin-boson model involving a Debye spectral density, we demonstrate the potential of C-FSSH to deliver highly accurate results for a large region of parameter space. Its uniform description of populations and coherences is found to resolve incorrect behavior observed for conventional FSSH in various cases, in particular at low temperature, while the parameter space regions where it breaks down are shown to be quite limited. Its computational expenses are virtually identical to conventional FSSH.

Apparent Dependence of Rate- and State-Dependent Friction Parameters on Loading Velocity and Cumulative Displacement Inferred from Large-Scale Biaxial Friction Experiments

Science.gov (United States)

Urata, Yumi; Yamashita, Futoshi; Fukuyama, Eiichi; Noda, Hiroyuki; Mizoguchi, Kazuo

2017-06-01

We investigated the constitutive parameters in the rate- and state-dependent friction (RSF) law by conducting numerical simulations, using the friction data from large-scale biaxial rock friction experiments for Indian metagabbro. The sliding surface area was 1.5 m long and 0.5 m wide, slid for 400 s under a normal stress of 1.33 MPa at a loading velocity of either 0.1 or 1.0 mm/s. During the experiments, many stick-slips were observed and those features were as follows. (1) The friction drop and recurrence time of the stick-slip events increased with cumulative slip displacement in an experiment before which the gouges on the surface were removed, but they became almost constant throughout an experiment conducted after several experiments without gouge removal. (2) The friction drop was larger and the recurrence time was shorter in the experiments with faster loading velocity. We applied a one-degree-of-freedom spring-slider model with mass to estimate the RSF parameters by fitting the stick-slip intervals and slip-weakening curves measured based on spring force and acceleration of the specimens. We developed an efficient algorithm for the numerical time integration, and we conducted forward modeling for evolution parameters ( b) and the state-evolution distances (L_{{c}}), keeping the direct effect parameter ( a) constant. We then identified the confident range of b and L_{{c}} values. Comparison between the results of the experiments and our simulations suggests that both b and L_{{c}} increase as the cumulative slip displacement increases, and b increases and L_{{c}} decreases as the loading velocity increases. Conventional RSF laws could not explain the large-scale friction data, and more complex state evolution laws are needed.

On coherent-state representations of quantum mechanics: Wave mechanics in phase space

DEFF Research Database (Denmark)

Møller, Klaus Braagaard; Jørgensen, Thomas Godsk; Torres-Vega, Gabino

1997-01-01

In this article we argue that the state-vector phase-space representation recently proposed by Torres-Vega and co-workers [introduced in J. Chem. Phys. 98, 3103 (1993)] coincides with the totality of coherent-state representations for the Heisenberg-Weyl group. This fact leads to ambiguities when...

Generation of new spatial and temporal coherent states using VECSEL technology: VORTEX, high order Laguerre-Gauss mode, continuum source

Science.gov (United States)

Sellahi, Mohamed; Seghilani, Mohamed Seghir; Sagnes, Isabelle; Beaudoin, Gregoire; Lafosse, Xavier; Legratiet, Luc; Lalanne, Philippe; Myara, Mikhal; Garnache, Arnaud

2017-11-01

Since years, the VeCSEL concept is pointed out as a technology of choice for beyond-state-of-the-art laser light sources. The targeted coherent state in CW is typically the common gaussian TEM00, single frequency, linearly polarized lightstate. In this work, we take advantage of the VeCSEL technology for the generation of other kinds of coherent states, thanks to the insertion of intracavity functions, such as low-loss intensity and phase filters integrated on a semiconductor chip. This technological development permitted to demonstrate very pure high-order Laguerre-Gauss mode, both degenerate and non-degenerate(vortex)modes, preserving the coherence properties of usual TEM00 VeCSELs. This technology paves the way for the generation of other coherences (Bessel beams) or new functionnalities (wavelength filtering, etc.). We also explore new time domain coherence : owing to a high gain semiconductor chip design and the insertion of intracavity AOM, we demonstrated the first Frequecy-Shifted-Feedback VeCSEL, with a broadband coherence state as wide as 300 GHz.

Classical motion and coherent states for Poeschl-Teller potentials

International Nuclear Information System (INIS)

Cruz y Cruz, S.; Kuru, S.; Negro, J.

2008-01-01

The trigonometric and hyperbolic Poeschl-Teller potentials are dealt with from the point of view of classical and quantum mechanics. We show that there is a natural correspondence between the algebraic structure of these two approaches for both kind of potentials. Then, the coherent states are constructed and the appropriate classical variables are compared with the expected values of their corresponding quantum operators

Coherent captivity of population in gas of excited atoms

International Nuclear Information System (INIS)

Anisimov, P.M.; Akhmedzhanov, R.A.; Zelenskij, I.V.; Kolesov, R.L.; Kuznetsova, E.A.

2003-01-01

The coherent captivity of the population in the gaseous discharge on the transitions between the neon atoms excited levels is studied. The resonances, corresponding to the origination of the population coherent captivity in the Λ- and V-schemes on the Zeeman sublevels of the low and upper working states, were observed in the presence of the longitudinal magnetic field. The effect of the nonlinear rotation of the polarization plane under the conditions of the population coherent captivity was studied. The possibility of applying the results of the work for the diagnostics of the local magnetic fields and other plasma parameters in the gaseous discharges is considered [ru

Symplectic Group Representation of the Two-Mode Squeezing Operator in the Coherent State Basis

Science.gov (United States)

Fan, Hong-Yi; Chen, Jun-Hua

2003-11-01

We find that the coherent state projection operator representation of the two-mode squeezing operator constitutes a loyal group representation of symplectic group, which is a remarkable property of the coherent state. As a consequence, the resultant effect of successively applying two-mode squeezing operators are equivalent to a single squeezing in the two-mode Fock space. Generalization of this property to the 2n-mode case is also discussed. The project supported by National Natural Science Foundation of China under Grant No. 10575057

Security bound of continuous-variable quantum key distribution with noisy coherent states and channel

International Nuclear Information System (INIS)

Shen Yong; Yang Jian; Guo Hong

2009-01-01

Security of a continuous-variable quantum key distribution protocol based on noisy coherent states and channel is analysed. Assuming that the noise of coherent states is induced by Fred, a neutral party relative to others, we prove that the prepare-and-measurement scheme (P and M) and entanglement-based scheme (E-B) are equivalent. Then, we show that this protocol is secure against Gaussian collective attacks even if the channel is lossy and noisy, and, further, a lower bound to the secure key rate is derived.

Security bound of continuous-variable quantum key distribution with noisy coherent states and channel

Energy Technology Data Exchange (ETDEWEB)

Shen Yong; Yang Jian; Guo Hong, E-mail: hongguo@pku.edu.c [CREAM Group, State Key Laboratory of Advanced Optical Communication Systems and Networks (Peking University) and Institute of Quantum Electronics, School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)

2009-12-14

Security of a continuous-variable quantum key distribution protocol based on noisy coherent states and channel is analysed. Assuming that the noise of coherent states is induced by Fred, a neutral party relative to others, we prove that the prepare-and-measurement scheme (P and M) and entanglement-based scheme (E-B) are equivalent. Then, we show that this protocol is secure against Gaussian collective attacks even if the channel is lossy and noisy, and, further, a lower bound to the secure key rate is derived.

Absence of coherent peaks in a Z2 fractionalized BCS superconducting state

Science.gov (United States)

Zhong, Yin; Lu, Han-Tao; Luo, Hong-Gang

2015-01-01

We explore a Z2 fractionalized Bardeen-Cooper-Schrieffer (BCS) superconducting state, which is a minimal extension of usual BCS framework. It is found that this state has similar thermal and transport properties, but its single-particle feature strongly deviates from the coherent quasiparticle behavior of the classic/conventional BCS superconducting state. The fingerprint of such Z2 BCS state is the absence of the BCS coherent peaks and instead a kink in the local density of state occurs, which in principle could be probed by scanning tunneling microscopy or point-contact spectroscopy experiments. The corresponding exactly soluble models that realize the desirable Z2 fractionalized BCS state are presented. In addition, we also study the extended t-U-J model by using Z2 slave-spin representation and find that the Z2 BCS state may exist when the paring structure is fully gapped or has nodes. The prototypical wave-function of such a Z2 BCS state is also proposed, which could be taken as trial wave-function in current numerical techniques. Furthermore, the pairing mechanism of Z2 BCS state is argued from both weak and strong coupling perspective. The present work may be helpful to further study the unconventional superconductivity and its relation to non-Fermi liquids.

Coherent states related with SU(N) and SU(N,1) groups

International Nuclear Information System (INIS)

Gitman, D.M.; Shelepin, A.L.

1990-01-01

The basis of coherent state (CS) for symmetric presentations of groups SU(N) and SU(N,1) is plotted, its properties being investigated. Evolution of CS is considered. Relation between CS of groups SU(N) and Glauber is ascertained

Extremely large nonsaturating magnetoresistance and ultrahigh mobility due to topological surface states in the metallic Bi2Te3 topological insulator

Science.gov (United States)

Shrestha, K.; Chou, M.; Graf, D.; Yang, H. D.; Lorenz, B.; Chu, C. W.

2017-05-01

Weak antilocalization (WAL) effects in Bi2Te3 single crystals have been investigated at high and low bulk charge-carrier concentrations. At low charge-carrier density the WAL curves scale with the normal component of the magnetic field, demonstrating the dominance of topological surface states in magnetoconductivity. At high charge-carrier density the WAL curves scale with neither the applied field nor its normal component, implying a mixture of bulk and surface conduction. WAL due to topological surface states shows no dependence on the nature (electrons or holes) of the bulk charge carriers. The observations of an extremely large nonsaturating magnetoresistance and ultrahigh mobility in the samples with lower carrier density further support the presence of surface states. The physical parameters characterizing the WAL effects are calculated using the Hikami-Larkin-Nagaoka formula. At high charge-carrier concentrations, there is a greater number of conduction channels and a decrease in the phase coherence length compared to low charge-carrier concentrations. The extremely large magnetoresistance and high mobility of topological insulators have great technological value and can be exploited in magnetoelectric sensors and memory devices.

Population coherent control of Rydberg potassium atom via adiabatic passage

International Nuclear Information System (INIS)

Jiang Li-Juan; Zhang Xian-Zhou; Jia Guang-Rui; Zhang Yong-Hui; Xia Li-Hua

2013-01-01

The time-dependent multilevel approach (TDMA) and B-spline expansion technique are used to study the coherent population transfer between the quantum states of a potassium atom by a single frequency-chirped microwave pulse. The Rydberg potassium atom energy levels of n = 6–15, l = 0–5 states in zero field are calculated and the results are in good agreement with other theoretical values. The time evolutions of the population transfer of the six states from n = 70 to n = 75 in different microwave fields are obtained. The results show that the coherent control of the population transfer from the lower states to the higher ones can be accomplished by optimizing the microwave pulse parameters. (atomic and molecular physics)

Vacuum-induced coherence in quantum dot systems

Science.gov (United States)

Sitek, Anna; Machnikowski, Paweł

2012-11-01

We present a theoretical study of vacuum-induced coherence in a pair of vertically stacked semiconductor quantum dots. The process consists in a coherent excitation transfer from a single-exciton state localized in one dot to a delocalized state in which the exciton occupation gets trapped. We study the influence of the factors characteristic of quantum dot systems (as opposed to natural atoms): energy mismatch, coupling between the single-exciton states localized in different dots, and different and nonparallel dipoles due to sub-band mixing, as well as coupling to phonons. We show that the destructive effect of the energy mismatch can be overcome by an appropriate interplay of the dipole moments and coupling between the dots which allows one to observe the trapping effect even in a structure with technologically realistic energy splitting of the order of milli-electron volts. We also analyze the impact of phonon dynamics on the occupation trapping and show that phonon effects are suppressed in a certain range of system parameters. This analysis shows that the vacuum-induced coherence effect and the associated long-living trapped excitonic population can be achieved in quantum dots.

Optically controlled locking of the nuclear field via coherent dark-state spectroscopy.

Science.gov (United States)

Xu, Xiaodong; Yao, Wang; Sun, Bo; Steel, Duncan G; Bracker, Allan S; Gammon, Daniel; Sham, L J

2009-06-25

A single electron or hole spin trapped inside a semiconductor quantum dot forms the foundation for many proposed quantum logic devices. In group III-V materials, the resonance and coherence between two ground states of the single spin are inevitably affected by the lattice nuclear spins through the hyperfine interaction, while the dynamics of the single spin also influence the nuclear environment. Recent efforts have been made to protect the coherence of spins in quantum dots by suppressing the nuclear spin fluctuations. However, coherent control of a single spin in a single dot with simultaneous suppression of the nuclear fluctuations has yet to be achieved. Here we report the suppression of nuclear field fluctuations in a singly charged quantum dot to well below the thermal value, as shown by an enhancement of the single electron spin dephasing time T(2)*, which we measure using coherent dark-state spectroscopy. The suppression of nuclear fluctuations is found to result from a hole-spin assisted dynamic nuclear spin polarization feedback process, where the stable value of the nuclear field is determined only by the laser frequencies at fixed laser powers. This nuclear field locking is further demonstrated in a three-laser measurement, indicating a possible enhancement of the electron spin T(2)* by a factor of several hundred. This is a simple and powerful method of enhancing the electron spin coherence time without use of 'spin echo'-type techniques. We expect that our results will enable the reproducible preparation of the nuclear spin environment for repetitive control and measurement of a single spin with minimal statistical broadening.

A Coherent vorticity preserving eddy-viscosity correction for Large-Eddy Simulation

Science.gov (United States)

Chapelier, J.-B.; Wasistho, B.; Scalo, C.

2018-04-01

This paper introduces a new approach to Large-Eddy Simulation (LES) where subgrid-scale (SGS) dissipation is applied proportionally to the degree of local spectral broadening, hence mitigated or deactivated in regions dominated by large-scale and/or laminar vortical motion. The proposed coherent-vorticity preserving (CvP) LES methodology is based on the evaluation of the ratio of the test-filtered to resolved (or grid-filtered) enstrophy, σ. Values of σ close to 1 indicate low sub-test-filter turbulent activity, justifying local deactivation of the SGS dissipation. The intensity of the SGS dissipation is progressively increased for σ activated in developed turbulence characterized by σ ≤σeq, where the value σeq is derived assuming a Kolmogorov spectrum. The proposed approach can be applied to any eddy-viscosity model, is algorithmically simple and computationally inexpensive. LES of Taylor-Green vortex breakdown demonstrates that the CvP methodology improves the performance of traditional, non-dynamic dissipative SGS models, capturing the peak of total turbulent kinetic energy dissipation during transition. Similar accuracy is obtained by adopting Germano's dynamic procedure albeit at more than twice the computational overhead. A CvP-LES of a pair of unstable periodic helical vortices is shown to predict accurately the experimentally observed growth rate using coarse resolutions. The ability of the CvP methodology to dynamically sort the coherent, large-scale motion from the smaller, broadband scales during transition is demonstrated via flow visualizations. LES of compressible channel are carried out and show a good match with a reference DNS.

Tunnel splitting in biaxial spin models investigated with spin-coherent-state path integrals

International Nuclear Information System (INIS)

Chen Zhide; Liang, J.-Q.; Pu, F.-C.

2003-01-01

Tunnel splitting in biaxial spin models is investigated with a full evaluation of the fluctuation functional integrals of the Euclidean kernel in the framework of spin-coherent-state path integrals which leads to a magnitude of tunnel splitting quantitatively comparable with the numerical results in terms of diagonalization of the Hamilton operator. An additional factor resulted from a global time transformation converting the position-dependent mass to a constant one seems to be equivalent to the semiclassical correction of the Lagrangian proposed by Enz and Schilling. A long standing question whether the spin-coherent-state representation of path integrals can result in an accurate tunnel splitting is therefore resolved

QCD jets from coherent states

Energy Technology Data Exchange (ETDEWEB)

Curci, G [European Organization for Nuclear Research, Geneva (Switzerland); Greco, M; Srivastava, Y [Istituto Nazionale di Fisica Nucleare, Frascati (Italy). Lab. Nazionale di Frascati

1979-11-19

A recently proposed approach to the problem of infrared and mass singularities in QCD based on the formalism of coherent states, is extended to discuss massless quark and gluon jets. The present results include all leading (ln delta) terms as well as finite terms in the energy loss epsilon, in addition to the usual ln epsilon associated with ln delta. The formulae agree with explicit perturbative calculations, whenever available. Explicit expressions for the total Ksub(T) distributions are given which take into account transverse-momentum conservation. Predictions are also made for the Q/sup 2/ dependence of the mean Ksub(T)/sup 2/ for quark and gluon jets. The jet ksub(T) distributions are extrapolated for low ksub(T) and shown to describe with good accuracy the data for eanti e..-->..qanti q..-->.. hadrons. Numerical predictions are also presented for the forthcoming PETRA, PEP and LEP machines.

Inequivalent coherent state representations in group field theory

Science.gov (United States)

Kegeles, Alexander; Oriti, Daniele; Tomlin, Casey

2018-06-01

In this paper we propose an algebraic formulation of group field theory and consider non-Fock representations based on coherent states. We show that we can construct representations with an infinite number of degrees of freedom on compact manifolds. We also show that these representations break translation symmetry. Since such representations can be regarded as quantum gravitational systems with an infinite number of fundamental pre-geometric building blocks, they may be more suitable for the description of effective geometrical phases of the theory.

Revisiting the simplicity constraints and coherent intertwiners

International Nuclear Information System (INIS)

Dupuis, Maite; Livine, Etera R

2011-01-01

In the context of loop quantum gravity and spinfoam models, the simplicity constraints are essential in that they allow one to write general relativity as a constrained topological BF theory. In this work, we apply the recently developed U(N) framework for SU(2) intertwiners to the issue of imposing the simplicity constraints to spin network states. More particularly, we focus on solving on individual intertwiners in the 4D Euclidean theory. We review the standard way of solving the simplicity constraints using coherent intertwiners and we explain how these fit within the U(N) framework. Then we show how these constraints can be written as a closed u(N) algebra and we propose a set of U(N) coherent states that solves all the simplicity constraints weakly for an arbitrary Immirzi parameter.

Coherently combining data between detectors for all-sky semi-coherent continuous gravitational wave searches

International Nuclear Information System (INIS)

Goetz, E; Riles, K

2016-01-01

We present a method for coherently combining short data segments from gravitational-wave detectors to improve the sensitivity of semi-coherent searches for continuous gravitational waves. All-sky searches for continuous gravitational waves from unknown sources are computationally limited. The semi-coherent approach reduces the computational cost by dividing the entire observation timespan into short segments to be analyzed coherently, then combined together incoherently. Semi-coherent analyses that attempt to improve sensitivity by coherently combining data from multiple detectors face a computational challenge in accounting for uncertainties in signal parameters. In this article, we lay out a technique to meet this challenge using summed Fourier transform coefficients. Applying this technique to one all-sky search algorithm called TwoSpect, we confirm that the sensitivity of all-sky, semi-coherent searches can be improved by coherently combining the short data segments, e.g., by up to 42% over a single detector for an all-sky search. For misaligned detectors, however, this improvement requires careful attention when marginalizing over unknown polarization parameters. In addition, care must be taken in correcting for differential detector velocity due to the Earth’s rotation for high signal frequencies and widely separated detectors. (paper)

Coherent quantum states of a relativistic particle in an electromagnetic plane wave and a parallel magnetic field

International Nuclear Information System (INIS)

Colavita, E.; Hacyan, S.

2014-01-01

We analyze the solutions of the Klein–Gordon and Dirac equations describing a charged particle in an electromagnetic plane wave combined with a magnetic field parallel to the direction of propagation of the wave. It is shown that the Klein–Gordon equation admits coherent states as solutions, while the corresponding solutions of the Dirac equation are superpositions of coherent and displaced-number states. Particular attention is paid to the resonant case in which the motion of the particle is unbounded. -- Highlights: •We study a relativistic electron in a particular electromagnetic field configuration. •New exact solutions of the Klein–Gordon and Dirac equations are obtained. •Coherent and displaced number states can describe a relativistic particle

Phase Coherence of Large Amplitude MHD Waves in the Earth's Foreshock: Geotail Observations

International Nuclear Information System (INIS)

Hada, Tohru; Koga, Daiki; Yamamoto, Eiko

2003-01-01

Large amplitude MHD turbulence is commonly found in the earth's foreshock region. It can be represented as a superposition of Fourier modes with characteristic frequency, amplitude, and phase. Nonlinear interactions between the Fourier modes are likely to produce finite correlation among the wave phases. For discussions of various transport processes of energetic particles, it is fundamentally important to determine whether the wave phases are randomly distributed (as assumed in quasi-linear theories) or they have a finite coherence. However, naive inspection of wave phases does not reveal anything, as the wave phase is sensitively related to the choice of origin of the coordinate, which should be arbitrary. Using a method based on a surrogate data technique and a fractal analysis, we analyzed Geotail magnetic field data to evaluate the phase coherence among the MHD waves in the earth's foreshock region. We show that the correlation of wave phases does exist, indicating that the nonlinear interactions between the waves is in progress. Furthermore, by introducing an index to represent the degree of the phase coherence, we discuss that the wave phases become more coherent as the turbulence amplitude increases, and also as the propagation angle of the most dominant wave mode becomes oblique. Details of the analysis as well as implications of the present results to transport processes of energetic particles will be discussed

Quantum cryptography using coherent states: Randomized encryption and key generation

Science.gov (United States)

Corndorf, Eric

With the advent of the global optical-telecommunications infrastructure, an increasing number of individuals, companies, and agencies communicate information with one another over public networks or physically-insecure private networks. While the majority of the traffic flowing through these networks requires little or no assurance of secrecy, the same cannot be said for certain communications between banks, between government agencies, within the military, and between corporations. In these arenas, the need to specify some level of secrecy in communications is a high priority. While the current approaches to securing sensitive information (namely the public-key-cryptography infrastructure and deterministic private-key ciphers like AES and 3DES) seem to be cryptographically strong based on empirical evidence, there exist no mathematical proofs of secrecy for any widely deployed cryptosystem. As an example, the ubiquitous public-key cryptosystems infer all of their secrecy from the assumption that factoring of the product of two large primes is necessarily time consuming---something which has not, and perhaps cannot, be proven. Since the 1980s, the possibility of using quantum-mechanical features of light as a physical mechanism for satisfying particular cryptographic objectives has been explored. This research has been fueled by the hopes that cryptosystems based on quantum systems may provide provable levels of secrecy which are at least as valid as quantum mechanics itself. Unfortunately, the most widely considered quantum-cryptographic protocols (BB84 and the Ekert protocol) have serious implementation problems. Specifically, they require quantum-mechanical states which are not readily available, and they rely on unproven relations between intrusion-level detection and the information available to an attacker. As a result, the secrecy level provided by these experimental implementations is entirely unspecified. In an effort to provably satisfy the cryptographic

Evaluation of the product ratio coherent model in forecasting mortality rates and life expectancy at births by States

Science.gov (United States)

Shair, Syazreen Niza; Yusof, Aida Yuzi; Asmuni, Nurin Haniah

2017-05-01

Coherent mortality forecasting models have recently received increasing attention particularly in their application to sub-populations. The advantage of coherent models over independent models is the ability to forecast a non-divergent mortality for two or more sub-populations. One of the coherent models was recently developed by [1] known as the product-ratio model. This model is an extension version of the functional independent model from [2]. The product-ratio model has been applied in a developed country, Australia [1] and has been extended in a developing nation, Malaysia [3]. While [3] accounted for coherency of mortality rates between gender and ethnic group, the coherency between states in Malaysia has never been explored. This paper will forecast the mortality rates of Malaysian sub-populations according to states using the product ratio coherent model and its independent version— the functional independent model. The forecast accuracies of two different models are evaluated using the out-of-sample error measurements— the mean absolute forecast error (MAFE) for age-specific death rates and the mean forecast error (MFE) for the life expectancy at birth. We employ Malaysian mortality time series data from 1991 to 2014, segregated by age, gender and states.

Optical Coherence Tomography Parameters in Morbidly Obese Patients Who Underwent Laparoscopic Sleeve Gastrectomy

Directory of Open Access Journals (Sweden)

Berna Dogan

2016-01-01

Full Text Available Purpose. To investigate changes in optical coherence tomography parameters in morbidly obese patients who had undergone laparoscopic sleeve gastrectomy (LSG. Methods. A total of 41 eyes of 41 morbidly obese patients (BMI ≥ 40 who had undergone LSG were included in study. The topographic optic disc parameters, central macular thickness (CMT, total macular volume (TMV, and retinal ganglion cell layer (RGCL were measured by spectral-domain optical coherence tomography (SD-OCT. Subfoveal choroidal thickness (SFCT was measured by enhanced deep imaging-optical coherence tomography (EDI-OCT. Results. The mean CMT was 237.4±24.5 μm, 239.3±24.1 μm, and 240.4±24.5 μm preoperatively, 3 months postoperatively, and 6 months postoperatively, respectively (p<0.01. The mean TMV was 9.88±0.52 mm3, 9.96±0.56 mm3, and 9.99±0.56 mm3 preoperatively, 3 months postoperatively, and 6 months postoperatively, respectively (p<0.01. The mean RGCL was 81.2±6.5 μm, 82.7±6.6 μm, and 82.9±6.5 μm preoperatively, 3 months postoperatively, and 6 months postoperatively, respectively (p<0.01. The mean SFCT was 309.8±71.8 μm, 331.0±81.4 μm, and 352.7±81.4 μm preoperatively, 3 months postoperatively, and 6 months postoperatively, respectively (p<0.01. No statistically significant differences were found between the preoperative values and 3- and 6-month postoperative values in rim area (p=0.34, disc area (p=0.64, vertical cup/disc ratio (p=0.39, cup volume (p=0.08, or retinal nerve fiber layer (p=0.90. Conclusions. Morbidly obese patients who undergo LSG experience a statistically significant increase in CMT, TMV, SFCT, and RGCL at 3 months and 6 months after surgery.

Path integrals and coherent states of SU(2) and SU(1,1)

CERN Document Server

Inomata, Akira; Kuratsuji, Hiroshi

1992-01-01

The authors examine several topical subjects, commencing with a general introduction to path integrals in quantum mechanics and the group theoretical backgrounds for path integrals. Applications of harmonic analysis, polar coordinate formulation, various techniques and path integrals on SU(2) and SU(1, 1) are discussed. Soluble examples presented include particle-flux system, a pulsed oscillator, magnetic monopole, the Coulomb problem in curved space and others.The second part deals with the SU(2) coherent states and their applications. Construction and generalization of the SU(2) coherent sta

On the construction of coherent states of position dependent mass Schroedinger equation endowed with effective potential

International Nuclear Information System (INIS)

Chithiika Ruby, V.; Senthilvelan, M.

2010-01-01

In this paper, we propose an algorithm to construct coherent states for an exactly solvable position dependent mass Schroedinger equation. We use point canonical transformation method and obtain ground state eigenfunction of the position dependent mass Schroedinger equation. We fix the ladder operators in the deformed form and obtain explicit expression of the deformed superpotential in terms of mass distribution and its derivative. We also prove that these deformed operators lead to minimum uncertainty relations. Further, we illustrate our algorithm with two examples, in which the coherent states given for the second example are new.

Coherent states field theory in supramolecular polymer physics

Science.gov (United States)

Fredrickson, Glenn H.; Delaney, Kris T.

2018-05-01

In 1970, Edwards and Freed presented an elegant representation of interacting branched polymers that resembles the coherent states (CS) formulation of second-quantized field theory. This CS polymer field theory has been largely overlooked during the intervening period in favor of more conventional "auxiliary field" (AF) interacting polymer representations that form the basis of modern self-consistent field theory (SCFT) and field-theoretic simulation approaches. Here we argue that the CS representation provides a simpler and computationally more efficient framework than the AF approach for broad classes of reversibly bonding polymers encountered in supramolecular polymer science. The CS formalism is reviewed, initially for a simple homopolymer solution, and then extended to supramolecular polymers capable of forming reversible linkages and networks. In the context of the Edwards model of a non-reacting homopolymer solution and one and two-component models of telechelic reacting polymers, we discuss the structure of CS mean-field theory, including the equivalence to SCFT, and show how weak-amplitude expansions (random phase approximations) can be readily developed without explicit enumeration of all reaction products in a mixture. We further illustrate how to analyze CS field theories beyond SCFT at the level of Gaussian field fluctuations and provide a perspective on direct numerical simulations using a recently developed complex Langevin technique.

SU(1,1) coherent states for Dirac–Kepler–Coulomb problem in D+1 dimensions with scalar and vector potentials

Energy Technology Data Exchange (ETDEWEB)

Ojeda-Guillén, D., E-mail: dogphysics@gmail.com [Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ed. 9, Unidad Profesional Adolfo López Mateos, C.P. 07738, México D.F. (Mexico); Mota, R.D. [Escuela Superior de Ingeniería Mecánica y Eléctrica, Unidad Culhuacán, Instituto Politécnico Nacional, Av. Santa Ana No. 1000, Col. San Francisco Culhuacán, Delegación Coyoacán, C.P. 04430, México D.F. (Mexico); Granados, V.D. [Escuela Superior de Física y Matemáticas, Instituto Politécnico Nacional, Ed. 9, Unidad Profesional Adolfo López Mateos, C.P. 07738, México D.F. (Mexico)

2014-08-14

We decouple the Dirac's radial equations in D+1 dimensions with Coulomb-type scalar and vector potentials through appropriate transformations. We study each of these uncoupled second-order equations in an algebraic way by using an su(1,1) algebra realization. Based on the theory of irreducible representations, we find the energy spectrum and the radial eigenfunctions. We construct the Perelomov coherent states for the Sturmian basis, which is the basis for the unitary irreducible representation of the su(1,1) Lie algebra. The physical radial coherent states for our problem are obtained by applying the inverse original transformations to the Sturmian coherent states. - Highlights: • We solve the most general Dirac–Kepler–Coulomb problem. • The eigenfunctions and energy spectrum are obtained in a purely algebraic way. • We construct the radial SU(1,1) coherent states for the Kepler–Coulomb problem.

SU(1,1) coherent states for Dirac–Kepler–Coulomb problem in D+1 dimensions with scalar and vector potentials

International Nuclear Information System (INIS)

Ojeda-Guillén, D.; Mota, R.D.; Granados, V.D.

2014-01-01

We decouple the Dirac's radial equations in D+1 dimensions with Coulomb-type scalar and vector potentials through appropriate transformations. We study each of these uncoupled second-order equations in an algebraic way by using an su(1,1) algebra realization. Based on the theory of irreducible representations, we find the energy spectrum and the radial eigenfunctions. We construct the Perelomov coherent states for the Sturmian basis, which is the basis for the unitary irreducible representation of the su(1,1) Lie algebra. The physical radial coherent states for our problem are obtained by applying the inverse original transformations to the Sturmian coherent states. - Highlights: • We solve the most general Dirac–Kepler–Coulomb problem. • The eigenfunctions and energy spectrum are obtained in a purely algebraic way. • We construct the radial SU(1,1) coherent states for the Kepler–Coulomb problem

General displaced SU(1, 1) number states: Revisited

Energy Technology Data Exchange (ETDEWEB)

Dehghani, A., E-mail: alireza.dehghani@gmail.com, E-mail: a-dehghani@tabrizu.ac.ir [Physics Department, Payame Noor University, P.O. Box 19395-3697 Tehran (Iran, Islamic Republic of)

2014-04-15

The most general displaced number states, based on the bosonic and an irreducible representation of the Lie algebra symmetry of su(1, 1) and associated with the Calogero-Sutherland model are introduced. Here, we utilize the Barut-Girardello displacement operator instead of the Klauder-Perelomov counterpart, to construct new kind of the displaced number states which can be classified in nonlinear coherent states regime, too, with special nonlinearity functions. They depend on two parameters, and can be converted into the well-known Barut-Girardello coherent and number states, respectively, depending on which of the parameters equal to zero. A discussion of the statistical properties of these states is included. Significant are their squeezing properties and anti-bunching effects which can be raised by increasing the energy quantum number. Depending on the particular choice of the parameters of the above scenario, we are able to determine the status of compliance with flexible statistics. Major parts of the issue is spent on something that these states, in fact, should be considered as new kind of photon-added coherent states, too. Which can be reproduced through an iterated action of a creation operator on new nonlinear Barut-Girardello coherent states. Where the latter carry, also, outstanding statistical features.

Faithful test of nonlocal realism with entangled coherent states

International Nuclear Information System (INIS)

Lee, Chang-Woo; Jeong, Hyunseok; Paternostro, Mauro

2011-01-01

We investigate the violation of Leggett's inequality for nonlocal realism using entangled coherent states and various types of local measurements. We prove mathematically the relation between the violation of the Clauser-Horne-Shimony-Holt form of Bell's inequality and Leggett's one when tested by the same resources. For Leggett inequalities, we generalize the nonlocal realistic bound to systems in Hilbert spaces larger than bidimensional ones and introduce an optimization technique that allows one to achieve larger degrees of violation by adjusting the local measurement settings. Our work describes the steps that should be performed to produce a self-consistent generalization of Leggett's original arguments to continuous-variable states.

Teleportation of atomic states with a weak coherent cavity field

Institute of Scientific and Technical Information of China (English)

Zheng Shi-Biao

2005-01-01

A scheme is proposed for the teleportation of an unknown atomic state. The scheme is based on the resonant interaction of atoms with a coherent cavity field. The mean photon-number of the cavity field is much smaller than one and thus the cavity decay can be effectively suppressed. Another adwntage of the scheme is that only one cavity is required.

Cross coherence independent component analysis in resting and action states EEG discrimination

International Nuclear Information System (INIS)

Almurshedi, A; Ismail, A K

2014-01-01

Cross Coherence time frequency transform and independent component analysis (ICA) method were used to analyse the electroencephalogram (EEG) signals in resting and action states during open and close eyes conditions. From the topographical scalp distributions of delta, theta, alpha, and beta power spectrum can clearly discriminate between the signal when the eyes were open or closed, but it was difficult to distinguish between resting and action states when the eyes were closed. In open eyes condition, the frontal area (Fp1, Fp2) was activated (higher power) in delta and theta bands whilst occipital (O1, O2) and partial (P3, P4, Pz) area of brain was activated alpha band in closed eyes condition. The cross coherence method of time frequency analysis is capable of discrimination between rest and action brain signals in closed eyes condition

Large-scale coherent structures of suspended dust concentration in the neutral atmospheric surface layer: A large-eddy simulation study

Science.gov (United States)

Zhang, Yangyue; Hu, Ruifeng; Zheng, Xiaojing

2018-04-01

Dust particles can remain suspended in the atmospheric boundary layer, motions of which are primarily determined by turbulent diffusion and gravitational settling. Little is known about the spatial organizations of suspended dust concentration and how turbulent coherent motions contribute to the vertical transport of dust particles. Numerous studies in recent years have revealed that large- and very-large-scale motions in the logarithmic region of laboratory-scale turbulent boundary layers also exist in the high Reynolds number atmospheric boundary layer, but their influence on dust transport is still unclear. In this study, numerical simulations of dust transport in a neutral atmospheric boundary layer based on an Eulerian modeling approach and large-eddy simulation technique are performed to investigate the coherent structures of dust concentration. The instantaneous fields confirm the existence of very long meandering streaks of dust concentration, with alternating high- and low-concentration regions. A strong negative correlation between the streamwise velocity and concentration and a mild positive correlation between the vertical velocity and concentration are observed. The spatial length scales and inclination angles of concentration structures are determined, compared with their flow counterparts. The conditionally averaged fields vividly depict that high- and low-concentration events are accompanied by a pair of counter-rotating quasi-streamwise vortices, with a downwash inside the low-concentration region and an upwash inside the high-concentration region. Through the quadrant analysis, it is indicated that the vertical dust transport is closely related to the large-scale roll modes, and ejections in high-concentration regions are the major mechanisms for the upward motions of dust particles.

On the dynamics of generalized coherent states

International Nuclear Information System (INIS)

Nikolov, B.A.; Trifonov, D.A.

1981-01-01

Using the Klauder approach the stable evolution of generalized coherent states (GCS) for some groups (SU(2), SU(1.1) and U(N)) is considered and it is shown that one and the same classical solution z(t) can correctly characterize the quantum evolution for many different (in general nonequivalent) systems. As examples some concrete systems are treated in greater detail: it is obtained that the nonstationary systems of the singular oscillator, of the particle motion in a magnetic field and of the oscillator with a friction all have stable SU(1.1) GCS whose quantum evolution is determined by one and the same classical function z(t). The physical properties of the constructed SU(1.1)GCS are discussed and it is shown particularly that in the case of discrete series Dsub(k)sup((+)) they are those states for which the quantum mean value coincides with the statistical one for an oscillator in a thermostat [ru

Visual coherence for large-scale line-plot visualizations

KAUST Repository

Muigg, Philipp

2011-06-01

Displaying a large number of lines within a limited amount of screen space is a task that is common to many different classes of visualization techniques such as time-series visualizations, parallel coordinates, link-node diagrams, and phase-space diagrams. This paper addresses the challenging problems of cluttering and overdraw inherent to such visualizations. We generate a 2x2 tensor field during line rasterization that encodes the distribution of line orientations through each image pixel. Anisotropic diffusion of a noise texture is then used to generate a dense, coherent visualization of line orientation. In order to represent features of different scales, we employ a multi-resolution representation of the tensor field. The resulting technique can easily be applied to a wide variety of line-based visualizations. We demonstrate this for parallel coordinates, a time-series visualization, and a phase-space diagram. Furthermore, we demonstrate how to integrate a focus+context approach by incorporating a second tensor field. Our approach achieves interactive rendering performance for large data sets containing millions of data items, due to its image-based nature and ease of implementation on GPUs. Simulation results from computational fluid dynamics are used to evaluate the performance and usefulness of the proposed method. © 2011 The Author(s).

Visual coherence for large-scale line-plot visualizations

KAUST Repository

Muigg, Philipp; Hadwiger, Markus; Doleisch, Helmut; Grö ller, Eduard M.

2011-01-01

Displaying a large number of lines within a limited amount of screen space is a task that is common to many different classes of visualization techniques such as time-series visualizations, parallel coordinates, link-node diagrams, and phase-space diagrams. This paper addresses the challenging problems of cluttering and overdraw inherent to such visualizations. We generate a 2x2 tensor field during line rasterization that encodes the distribution of line orientations through each image pixel. Anisotropic diffusion of a noise texture is then used to generate a dense, coherent visualization of line orientation. In order to represent features of different scales, we employ a multi-resolution representation of the tensor field. The resulting technique can easily be applied to a wide variety of line-based visualizations. We demonstrate this for parallel coordinates, a time-series visualization, and a phase-space diagram. Furthermore, we demonstrate how to integrate a focus+context approach by incorporating a second tensor field. Our approach achieves interactive rendering performance for large data sets containing millions of data items, due to its image-based nature and ease of implementation on GPUs. Simulation results from computational fluid dynamics are used to evaluate the performance and usefulness of the proposed method. © 2011 The Author(s).

Towards phase-coherent caloritronics in superconducting circuits

Science.gov (United States)

Fornieri, Antonio; Giazotto, Francesco

2017-10-01

The emerging field of phase-coherent caloritronics (from the Latin word calor, heat) is based on the possibility of controlling heat currents by using the phase difference of the superconducting order parameter. The goal is to design and implement thermal devices that can control energy transfer with a degree of accuracy approaching that reached for charge transport by contemporary electronic components. This can be done by making use of the macroscopic quantum coherence intrinsic to superconducting condensates, which manifests itself through the Josephson effect and the proximity effect. Here, we review recent experimental results obtained in the realization of heat interferometers and thermal rectifiers, and discuss a few proposals for exotic nonlinear phase-coherent caloritronic devices, such as thermal transistors, solid-state memories, phase-coherent heat splitters, microwave refrigerators, thermal engines and heat valves. Besides being attractive from the fundamental physics point of view, these systems are expected to have a vast impact on many cryogenic microcircuits requiring energy management, and possibly lay the first stone for the foundation of electronic thermal logic.

Metaphor Coherence in the Book of Job

Science.gov (United States)

Hawley, Lance R.

2016-01-01

Within the book of Job, the interlocutors (Job, the friends, and Yahweh) seem to largely ignore one another's arguments within their dialogical discourse. This observation leads some to propose that the dialogue lacks conceptual coherence. I argue that the interlocutors tangentially attend to previously stated points-of-view and attempt to…

Emergence of a super-synchronized mobbing state in a large population of coupled chemical oscillators

Science.gov (United States)

Ghoshal, Gourab; Muñuzuri, Alberto P.; Pérez-Mercader, Juan

2016-01-01

Oscillatory phenomena are ubiquitous in Nature. The ability of a large population of coupled oscillators to synchronize constitutes an important mechanism to express information and establish communication among members. To understand such phenomena, models and experimental realizations of globally coupled oscillators have proven to be invaluable in settings as varied as chemical, biological and physical systems. A variety of rich dynamical behavior has been uncovered, although usually in the context of a single state of synchronization or lack thereof. Through the experimental and numerical study of a large population of discrete chemical oscillators, here we report on the unexpected discovery of a new phenomenon revealing the existence of dynamically distinct synchronized states reflecting different degrees of communication. Specifically, we discover a novel large-amplitude super-synchronized state separated from the conventionally reported synchronized and quiescent states through an unusual sharp jump transition when sampling the strong coupling limit. Our results assume significance for further elucidating globally coherent phenomena, such as in neuropathologies, bacterial cell colonies, social systems and semiconductor lasers.

Exploiting large-scale correlations to detect continuous gravitational waves.

Science.gov (United States)

Pletsch, Holger J; Allen, Bruce

2009-10-30

Fully coherent searches (over realistic ranges of parameter space and year-long observation times) for unknown sources of continuous gravitational waves are computationally prohibitive. Less expensive hierarchical searches divide the data into shorter segments which are analyzed coherently, then detection statistics from different segments are combined incoherently. The novel method presented here solves the long-standing problem of how best to do the incoherent combination. The optimal solution exploits large-scale parameter-space correlations in the coherent detection statistic. Application to simulated data shows dramatic sensitivity improvements compared with previously available (ad hoc) methods, increasing the spatial volume probed by more than 2 orders of magnitude at lower computational cost.

Mismatch removal via coherent spatial relations

Science.gov (United States)

Chen, Jun; Ma, Jiayi; Yang, Changcai; Tian, Jinwen

2014-07-01

We propose a method for removing mismatches from the given putative point correspondences in image pairs based on "coherent spatial relations." Under the Bayesian framework, we formulate our approach as a maximum likelihood problem and solve a coherent spatial relation between the putative point correspondences using an expectation-maximization (EM) algorithm. Our approach associates each point correspondence with a latent variable indicating it as being either an inlier or an outlier, and alternatively estimates the inlier set and recovers the coherent spatial relation. It can handle not only the case of image pairs with rigid motions but also the case of image pairs with nonrigid motions. To parameterize the coherent spatial relation, we choose two-view geometry and thin-plate spline as models for rigid and nonrigid cases, respectively. The mismatches could be successfully removed via the coherent spatial relations after the EM algorithm converges. The quantitative results on various experimental data demonstrate that our method outperforms many state-of-the-art methods, it is not affected by low initial correct match percentages, and is robust to most geometric transformations including a large viewing angle, image rotation, and affine transformation.

ALOS PALSAR Winter Coherence and Summer Intensities for Large Scale Forest Monitoring in Siberia

Science.gov (United States)

Thiel, Christian; Thiel, Carolin; Santoro, Maurizio; Schmullius, Christiane

2008-11-01

In this paper summer intensity and winter coherence images are used for large scale forest monitoring. The intensities (FBD HH/HV) have been acquired during summer 2007 and feature the K&C intensity stripes [1]. The processing consisted of radiometric calibration, orthorectification, and topographic normalisation. The coherence has been estimated from interferometric pairs with 46-days repeat-pass intervals. The pairs have been acquired during the winters 2006/2007 and 2007/2008. During both winters suited weather conditions have been reported. Interferometric processing consisted of SLC co-registration at sub-pixel level, common-band filtering in range and azimuth and generation of a differential interferogram, which was used in the coherence estimation procedure based on adaptive estimation. All images were geocoded using SRTM data. The pixel size of the final SAR products is 50 m x 50 m. It could already be demonstrated, that by using PALSAR intensities and winter coherence forest and non-forest can be clearly separated [2]. By combining both data types hardly any overlap of the class signatures was detected, even though the analysis was conducted on pixel level and no speckle filter has been applied. Thus, the delineation of a forest cover mask could be executed operationally. The major hitch is the definition of a biomass threshold for regrowing forest to be distinguished as forest.

Infinite coherence time of edge spins in finite-length chains

Science.gov (United States)

Maceira, Ivo A.; Mila, Frédéric

2018-02-01

Motivated by the recent observation that exponentially long coherence times can be achieved for edge spins in models with strong zero modes, we study the impact of level crossings in finite-length spin chains on the dynamics of the edge spins. Focusing on the X Y spin-1 /2 chain with a transverse or longitudinal magnetic field, two models relevant to understanding recent experimental results on cobalt adatoms, we show that the edge spins can remain coherent for an infinite time even for a finite-length chain if the magnetic field is tuned to a value at which there is a level crossing. Furthermore, we show that the edge spins remain coherent for any initial state for the integrable case of a transverse field because all states have level crossings at the same value of the field, while the coherence time is increasingly large for lower temperatures in the case of a longitudinal field, which is nonintegrable.

Partially coherent twisted states in arrays of coupled phase oscillators

Energy Technology Data Exchange (ETDEWEB)

Omel' chenko, Oleh E.; Wolfrum, Matthias [Weierstrass Institute, Mohrenstrasse 39, 10117 Berlin (Germany); Laing, Carlo R. [INMS, Massey University, Private Bag 102-904 NSMC, Auckland (New Zealand)

2014-06-15

We consider a one-dimensional array of phase oscillators with non-local coupling and a Lorentzian distribution of natural frequencies. The primary objects of interest are partially coherent states that are uniformly “twisted” in space. To analyze these, we take the continuum limit, perform an Ott/Antonsen reduction, integrate over the natural frequencies, and study the resulting spatio-temporal system on an unbounded domain. We show that these twisted states and their stability can be calculated explicitly. We find that stable twisted states with different wave numbers appear for increasing coupling strength in the well-known Eckhaus scenario. Simulations of finite arrays of oscillators show good agreement with results of the analysis of the infinite system.

Partially coherent twisted states in arrays of coupled phase oscillators

International Nuclear Information System (INIS)

Omel'chenko, Oleh E.; Wolfrum, Matthias; Laing, Carlo R.

2014-01-01

We consider a one-dimensional array of phase oscillators with non-local coupling and a Lorentzian distribution of natural frequencies. The primary objects of interest are partially coherent states that are uniformly “twisted” in space. To analyze these, we take the continuum limit, perform an Ott/Antonsen reduction, integrate over the natural frequencies, and study the resulting spatio-temporal system on an unbounded domain. We show that these twisted states and their stability can be calculated explicitly. We find that stable twisted states with different wave numbers appear for increasing coupling strength in the well-known Eckhaus scenario. Simulations of finite arrays of oscillators show good agreement with results of the analysis of the infinite system

Security of quantum key distribution with a laser reference coherent state, resistant to loss in the communication channel

International Nuclear Information System (INIS)

Molotkov, S N; Potapova, T A

2015-01-01

The problem of quantum key distribution security in channels with large losses is still open. Quasi-single-photon sources of quantum states with losses in the quantum communication channel open up the possibility of attacking with unambiguous state discrimination (USD) measurements, resulting in a loss of privacy. In this letter, the problem is solved by counting the classic reference pulses. Conservation of the number of counts of intense coherent pulses makes it impossible to conduct USD measurements. Moreover, the losses in the communication channel are considered to be unknown in advance and are subject to change throughout the series parcels. Unlike other protocols, differential phase shift (Inoue et al 2002 Phys. Rev. Lett. 89 037902, Inoue et al 2003 Phys. Rev. A 68 022317, Takesue et al 2007 Nat. Photon. 1 343, Wen et al 2009 Phys. Rev. Lett. 103 170503) and coherent one way (Stucki et al 2005 Appl. Phys. Lett. 87 194108, Branciard et al 2005 Appl. Phys. Lett. 87 194108, Branciard et al 2008 New J. Phys. 10 013031, Stucki et al 2008 Opt. Express 17 13326), the simplicity of the protocol makes it possible to carry out a complete analysis of its security. (letter)

Non-equilibrium coherent vortex states and subharmonic giant Shapiro steps in Josephson junction arrays

International Nuclear Information System (INIS)

Dominguez, D.; Jose, J.V.; Northeastern Univ., Boston, MA

1994-01-01

This is a review of recent work on the dynamic response of Josephson junction arrays driven by dc and ac currents. The arrays are modeled by the resistively shunted Josephson junction model, appropriate for proximity effect junctions, including self-induced magnetic fields as well as disorder. The relevance of the self-induced fields is measured as a function of a parameter κ = λ L /a, with λ L the London penetration depth of the arrays, and a the lattice spacing. The transition from Type II (κ > 1) to Type I (κ < 1) behavior is studied in detail. The authors compare the results for models with self, self + nearest-neighbor, and full inductance matrices. In the κ = ∞ limit, they find that when the initial state has at least one vortex-antivortex pair, after a characteristic transient time these vortices unbind and radiate other vortices. These radiated vortices settle into a parity-broken, time-periodic, axisymmetric coherent vortex state (ACVS), characterized by alternate rows of positive and negative vortices lying along a tilted axis. The ACVS produces subharmonic steps in the current voltage (IV) characteristics, typical of giant Shapiro steps. For finite κ they find that the IV's show subharmonic giant Shapiro steps, even at zero external magnetic field. They find that these subharmonic steps are produced by a whole family of coherent vortex oscillating patterns, with their structure changing as a function of κ. In general, they find that these patterns are due to a breakdown of translational invariance produced, for example, by disorder of antisymmetric edge-fields. The zero field case results are in good qualitative agreement with experiments in Nb-Au-Nb arrays

The quantum potential and ''causal'' trajectories for stationary states and for coherent states

International Nuclear Information System (INIS)

Barut, A.O.; Bozic, M.

1988-07-01

We show for stationary states in a central potential that the quantum action S is only a part of the classical action W and derive an expression for the ''quantum potential'' U Q in terms of the other part. The association of momenta of some ''particles'' in the causal interpretation of quantum mechanics by p-vector=∇S and by dp-vector'/dt=-∇(V+U Q ) gives for stationary states very different orbits which have no relation to classical orbits but express some flow properties of the quantum mechanical current. For coherent states, on the other hand, p-vector and p-vector' as well as the quantum mechanical average p-vector and classical momenta, all four, lead to essentially the same trajectories except for different integration constants. The spinning particle is also considered. (author). 27 refs, 2 figs

High-dimensional quantum key distribution with the entangled single-photon-added coherent state

Energy Technology Data Exchange (ETDEWEB)

Wang, Yang [Zhengzhou Information Science and Technology Institute, Zhengzhou, 450001 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Bao, Wan-Su, E-mail: 2010thzz@sina.com [Zhengzhou Information Science and Technology Institute, Zhengzhou, 450001 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Bao, Hai-Ze; Zhou, Chun; Jiang, Mu-Sheng; Li, Hong-Wei [Zhengzhou Information Science and Technology Institute, Zhengzhou, 450001 (China); Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2017-04-25

High-dimensional quantum key distribution (HD-QKD) can generate more secure bits for one detection event so that it can achieve long distance key distribution with a high secret key capacity. In this Letter, we present a decoy state HD-QKD scheme with the entangled single-photon-added coherent state (ESPACS) source. We present two tight formulas to estimate the single-photon fraction of postselected events and Eve's Holevo information and derive lower bounds on the secret key capacity and the secret key rate of our protocol. We also present finite-key analysis for our protocol by using the Chernoff bound. Our numerical results show that our protocol using one decoy state can perform better than that of previous HD-QKD protocol with the spontaneous parametric down conversion (SPDC) using two decoy states. Moreover, when considering finite resources, the advantage is more obvious. - Highlights: • Implement the single-photon-added coherent state source into the high-dimensional quantum key distribution. • Enhance both the secret key capacity and the secret key rate compared with previous schemes. • Show an excellent performance in view of statistical fluctuations.

High-dimensional quantum key distribution with the entangled single-photon-added coherent state

International Nuclear Information System (INIS)

Wang, Yang; Bao, Wan-Su; Bao, Hai-Ze; Zhou, Chun; Jiang, Mu-Sheng; Li, Hong-Wei

2017-01-01

High-dimensional quantum key distribution (HD-QKD) can generate more secure bits for one detection event so that it can achieve long distance key distribution with a high secret key capacity. In this Letter, we present a decoy state HD-QKD scheme with the entangled single-photon-added coherent state (ESPACS) source. We present two tight formulas to estimate the single-photon fraction of postselected events and Eve's Holevo information and derive lower bounds on the secret key capacity and the secret key rate of our protocol. We also present finite-key analysis for our protocol by using the Chernoff bound. Our numerical results show that our protocol using one decoy state can perform better than that of previous HD-QKD protocol with the spontaneous parametric down conversion (SPDC) using two decoy states. Moreover, when considering finite resources, the advantage is more obvious. - Highlights: • Implement the single-photon-added coherent state source into the high-dimensional quantum key distribution. • Enhance both the secret key capacity and the secret key rate compared with previous schemes. • Show an excellent performance in view of statistical fluctuations.

Coherent and Semiclassical States of a Charged Particle in a Constant Electric Field

Science.gov (United States)

Adorno, T. C.; Pereira, A. S.

2018-05-01

The method of integrals of motion is used to construct families of generalized coherent states of a nonrelativistic spinless charged particle in a constant electric field. Families of states, differing in the values of their standard deviations at the initial time, are obtained. Depending on the initial values of the standard deviations, and also on the electric field, it turns out to be possible to identify some families with semiclassical states.

Electromagnetic spatial coherence wavelets

International Nuclear Information System (INIS)

Castaneda, R.; Garcia-Sucerquia, J.

2005-10-01

The recently introduced concept of spatial coherence wavelets is generalized for describing the propagation of electromagnetic fields in the free space. For this aim, the spatial coherence wavelet tensor is introduced as an elementary amount, in terms of which the formerly known quantities for this domain can be expressed. It allows analyzing the relationship between the spatial coherence properties and the polarization state of the electromagnetic wave. This approach is completely consistent with the recently introduced unified theory of coherence and polarization for random electromagnetic beams, but it provides a further insight about the causal relationship between the polarization states at different planes along the propagation path. (author)

A coherent polarimeter array for the Large Scale Polarization Explorer balloon experiment

OpenAIRE

Bersanelli, M.; Mennella, A.; Morgante, G.; Zannoni, M.; Addamo, G.; Baschirotto, A.; Battaglia, P.; Baù, A.; Cappellini, B.; Cavaliere, F.; Cuttaia, F.; Del Torto, F.; Donzelli, S.; Farooqui, Z.; Frailis, M.

2012-01-01

We discuss the design and expected performance of STRIP (STRatospheric Italian Polarimeter), an array of coherent receivers designed to fly on board the LSPE (Large Scale Polarization Explorer) balloon experiment. The STRIP focal plane array comprises 49 elements in Q band and 7 elements in W-band using cryogenic HEMT low noise amplifiers and high performance waveguide components. In operation, the array will be cooled to 20 K and placed in the focal plane of a $\\sim 0.6$ meter telescope prov...

Optic disc size and other parameters from optical coherence tomography in Vietnamese-Americans.

Science.gov (United States)

Peng, Pai-Huei; Fu, Sheena; Nguyen, Ngoc; Porco, Travis; Lin, Shan C

2011-08-01

To investigate the optic disc parameters by optical coherence tomography (OCT) in Vietnamese with various types of glaucoma. Medical charts of Vietnamese and White patients within a single practice were reviewed. Disc and rim areas by OCT were compared among nonglaucoma controls, different types of glaucoma, and glaucoma suspect. The association of these parameters with demographic and ocular features was evaluated. Data from 1416 Vietnamese and 57 White patients were included. A larger mean disc area was observed in eyes with primary angle-closure glaucoma than in eyes with primary angle-closure and primary angle-closure suspect (both PVietnamese patients with glaucoma and glaucoma suspicion had larger discs than diagnosis-matched Whites (P=0.043 and 0.021, respectively). Vietnamese patients with glaucoma seem to have larger optic discs than White patients. Central corneal thickness had no association with disc area in this study population.

From quantum coherence to quantum correlations

Science.gov (United States)

Sun, Yuan; Mao, Yuanyuan; Luo, Shunlong

2017-06-01

In quantum mechanics, quantum coherence of a state relative to a quantum measurement can be identified with the quantumness that has to be destroyed by the measurement. In particular, quantum coherence of a bipartite state relative to a local quantum measurement encodes quantum correlations in the state. If one takes minimization with respect to the local measurements, then one is led to quantifiers which capture quantum correlations from the perspective of coherence. In this vein, quantum discord, which quantifies the minimal correlations that have to be destroyed by quantum measurements, can be identified as the minimal coherence, with the coherence measured by the relative entropy of coherence. To advocate and formulate this idea in a general context, we first review coherence relative to Lüders measurements which extends the notion of coherence relative to von Neumann measurements (or equivalently, orthonomal bases), and highlight the observation that quantum discord arises as minimal coherence through two prototypical examples. Then, we introduce some novel measures of quantum correlations in terms of coherence, illustrate them through examples, investigate their fundamental properties and implications, and indicate their applications to quantum metrology.

Spiral wave chimera states in large populations of coupled chemical oscillators

Science.gov (United States)

Totz, Jan Frederik; Rode, Julian; Tinsley, Mark R.; Showalter, Kenneth; Engel, Harald

2018-03-01

The coexistence of coherent and incoherent dynamics in a population of identically coupled oscillators is known as a chimera state1,2. Discovered in 20023, this counterintuitive dynamical behaviour has inspired extensive theoretical and experimental activity4-15. The spiral wave chimera is a particularly remarkable chimera state, in which an ordered spiral wave rotates around a core consisting of asynchronous oscillators. Spiral wave chimeras were theoretically predicted in 200416 and numerically studied in a variety of systems17-23. Here, we report their experimental verification using large populations of nonlocally coupled Belousov-Zhabotinsky chemical oscillators10,18 in a two-dimensional array. We characterize previously unreported spatiotemporal dynamics, including erratic motion of the asynchronous spiral core, growth and splitting of the cores, as well as the transition from the chimera state to disordered behaviour. Spiral wave chimeras are likely to occur in other systems with long-range interactions, such as cortical tissues24, cilia carpets25, SQUID metamaterials26 and arrays of optomechanical oscillators9.

Characterization of collective Gaussian attacks and security of coherent-state quantum cryptography.

Science.gov (United States)

Pirandola, Stefano; Braunstein, Samuel L; Lloyd, Seth

2008-11-14

We provide a simple description of the most general collective Gaussian attack in continuous-variable quantum cryptography. In the scenario of such general attacks, we analyze the asymptotic secret-key rates which are achievable with coherent states, joint measurements of the quadratures and one-way classical communication.

Infrared frequency-tunable coherent thermal sources

International Nuclear Information System (INIS)

Wang, Hao; Yang, Yue; Wang, Liping

2015-01-01

In this work, we numerically demonstrate an infrared (IR) frequency-tunable selective thermal emitter made of graphene-covered silicon carbide (SiC) gratings. Rigorous coupled-wave analysis shows temporally-coherent emission peaks associated with magnetic polariton (MP), whose resonance frequency can be dynamically tuned within the phonon absorption band of SiC by varying graphene chemical potential. An analytical inductor–capacitor circuit model is introduced to quantitatively predict the resonance frequency and further elucidate the mechanism for the tunable emission peak. The effects of grating geometric parameters, such as grating height, groove width and grating period, on the selective emission peak are explored. The direction-independent behavior of MP and associated coherent emission are also demonstrated. Moreover, by depositing four layers of graphene sheets onto the SiC gratings, a large tunability of 8.5% in peak frequency can be obtained to yield the coherent emission covering a broad frequency range from 820 to 890 cm −1 . The novel tunable metamaterial could pave the way to a new class of tunable thermal sources in the IR region. (paper)

Operational resource theory of total quantum coherence

Science.gov (United States)

Yang, Si-ren; Yu, Chang-shui

2018-01-01

Quantum coherence is an essential feature of quantum mechanics and is an important physical resource in quantum information. Recently, the resource theory of quantum coherence has been established parallel with that of entanglement. In the resource theory, a resource can be well defined if given three ingredients: the free states, the resource, the (restricted) free operations. In this paper, we study the resource theory of coherence in a different light, that is, we consider the total coherence defined by the basis-free coherence maximized among all potential basis. We define the distillable total coherence and the total coherence cost and in both the asymptotic regime and the single-copy regime show the reversible transformation between a state with certain total coherence and the state with the unit reference total coherence. Extensively, we demonstrate that the total coherence can also be completely converted to the total correlation with the equal amount by the free operations. We also provide the alternative understanding of the total coherence, respectively, based on the entanglement and the total correlation in a different way.

Long-lived coherence in carotenoids

Energy Technology Data Exchange (ETDEWEB)

Davis, J A; Cannon, E; Van Dao, L; Hannaford, P [ARC Centre of Excellence for Coherent X-ray Science, Centre for Atom Optics and Ultrafast Spectroscopy, Swinburne University of Technology, Victoria 3122 (Australia); Quiney, H M; Nugent, K A, E-mail: jdavis@swin.edu.a [ARC Centre of Excellence for Coherent X-ray Science, School of Physics, University of Melbourne, Victoria 3010 (Australia)

2010-08-15

We use two-colour vibronic coherence spectroscopy to observe long-lived vibrational coherences in the ground electronic state of carotenoid molecules, with decoherence times in excess of 1 ps. Lycopene and spheroidene were studied isolated in solution, and within the LH2 light-harvesting complex extracted from purple bacteria. The vibrational coherence time is shown to increase significantly for the carotenoid in the complex, providing further support to previous assertions that long-lived electronic coherences in light-harvesting complexes are facilitated by in-phase motion of the chromophores and surrounding proteins. Using this technique, we are also able to follow the evolution of excited state coherences and find that for carotenoids in the light-harvesting complex the (S{sub 2}|S{sub 0}) superposition remains coherent for more than 70 fs. In addition to the implications of this long electronic decoherence time, the extended coherence allows us to observe the evolution of the excited state wavepacket. These experiments reveal an enhancement of the vibronic coupling to the first vibrational level of the C-C stretching mode and/or methyl-rocking mode in the ground electronic state 70 fs after the initial excitation. These observations open the door to future experiments and modelling that may be able to resolve the relaxation dynamics of carotenoids in solution and in natural light-harvesting systems.

Long-lived coherence in carotenoids

International Nuclear Information System (INIS)

Davis, J A; Cannon, E; Van Dao, L; Hannaford, P; Quiney, H M; Nugent, K A

2010-01-01

We use two-colour vibronic coherence spectroscopy to observe long-lived vibrational coherences in the ground electronic state of carotenoid molecules, with decoherence times in excess of 1 ps. Lycopene and spheroidene were studied isolated in solution, and within the LH2 light-harvesting complex extracted from purple bacteria. The vibrational coherence time is shown to increase significantly for the carotenoid in the complex, providing further support to previous assertions that long-lived electronic coherences in light-harvesting complexes are facilitated by in-phase motion of the chromophores and surrounding proteins. Using this technique, we are also able to follow the evolution of excited state coherences and find that for carotenoids in the light-harvesting complex the (S 2 |S 0 ) superposition remains coherent for more than 70 fs. In addition to the implications of this long electronic decoherence time, the extended coherence allows us to observe the evolution of the excited state wavepacket. These experiments reveal an enhancement of the vibronic coupling to the first vibrational level of the C-C stretching mode and/or methyl-rocking mode in the ground electronic state 70 fs after the initial excitation. These observations open the door to future experiments and modelling that may be able to resolve the relaxation dynamics of carotenoids in solution and in natural light-harvesting systems.

Conditional sampling technique to test the applicability of the Taylor hypothesis for the large-scale coherent structures

Science.gov (United States)

Hussain, A. K. M. F.

1980-01-01

Comparisons of the distributions of large scale structures in turbulent flow with distributions based on time dependent signals from stationary probes and the Taylor hypothesis are presented. The study investigated an area in the near field of a 7.62 cm circular air jet at a Re of 32,000, specifically having coherent structures through small-amplitude controlled excitation and stable vortex pairing in the jet column mode. Hot-wire and X-wire anemometry were employed to establish phase averaged spatial distributions of longitudinal and lateral velocities, coherent Reynolds stress and vorticity, background turbulent intensities, streamlines and pseudo-stream functions. The Taylor hypothesis was used to calculate spatial distributions of the phase-averaged properties, with results indicating that the usage of the local time-average velocity or streamwise velocity produces large distortions.

Average intensity and coherence properties of a partially coherent Lorentz-Gauss beam propagating through oceanic turbulence

Science.gov (United States)

Liu, Dajun; Wang, Guiqiu; Wang, Yaochuan

2018-01-01

Based on the Huygens-Fresnel integral and the relationship of Lorentz distribution and Hermite-Gauss function, the average intensity and coherence properties of a partially coherent Lorentz-Gauss beam propagating through oceanic turbulence have been investigated by using numerical examples. The influences of beam parameters and oceanic turbulence on the propagation properties are also discussed in details. It is shown that the partially coherent Lorentz-Gauss beam with smaller coherence length will spread faster in oceanic turbulence, and the stronger oceanic turbulence will accelerate the spreading of partially coherent Lorentz-Gauss beam in oceanic turbulence.

Coherent states and related quantizations for unbounded motions

International Nuclear Information System (INIS)

Bagrov, V G; Gazeau, J-P; Gitman, D M; Levin, A D

2012-01-01

We discuss the construction of coherent states (CS) for systems with continuous spectra. First, we propose to adopt the Malkin–Manko approach, developed for systems with discrete spectra, to the case under consideration. Following this approach, we consider two examples, a free particle and a particle in a linear potential. Second, we generalize the approach of action-angle CS to systems with continuous spectra. In the first approach we start with a well-defined quantum formulation (canonical quantization) of a physical system and the construction of CS follows from such a quantization. In the second approach, the quantization procedure is inherent to the CS construction itself. (paper)

Coherent states with classical motion: from an analytic method complementary to group theory

International Nuclear Information System (INIS)

Nieto, M.M.

1982-01-01

From the motivation of Schroedinger, that of finding states which follow the motion which a classical particle would have in a given potential, we discuss generalizations of the coherent states of the harmonic oscillator. We focus on a method which is the analytic complement to the group theory point of view. It uses a minimum uncertainty formalism as its basis. We discuss the properties and time evolution of these states, always keeping in mind the desire to find quantum states which follow the classical motion

Coherent and conventional gravidynamic quantum 1/f noise

Science.gov (United States)

Handel, Peter H.; George, Thomas F.

2008-04-01

Quantum 1/f noise is a fundamental fluctuation of currents, physical cross sections or process rates, caused by infrared coupling of the current carriers to very low frequency (soft) quanta, also known as infraquanta. The latter are soft gravitons in the gravidynamic case with the coupling constant g= pGM2/Nch considered here -- soft photons in the electrodynamic case and soft transversal piezo-phonons in the lattice-dynamical case. Here p=3.14 and F=psi. Quantum 1/f noise is a new aspect of quantum mechanics expressed mainly through the coherent quantum 1/f effect 2g/pf derived here for large systems, and mainly through the conventional quantum 1/f effect for small systems or individual particles. Both effects are present in general, and their effects are superposed in a first approximation with the help of a coherence (weight) parameter s" that will be derived elsewhere for the gravitational case. The spectral density of fractional fluctuations S(dj/j,f) for j=e(hk/2pm)|F|2 is S(F2,f)/ = S(j,f)/2 = [4ps"/(1+s")]GM2/pfNch = 4.4 10E9 M2/(pfNgram2). Here s" = 2N'GM/c2=N'rs, where N' is the number of particles of mass M per unit length of the current, rs their Schwarzschild radius, and s" is our coherence (weight) parameter giving the ratio of coherent to conventional quantum 1/f contributions.

Quantum dual signature scheme based on coherent states with entanglement swapping

International Nuclear Information System (INIS)

Liu Jia-Li; Shi Rong-Hua; Shi Jin-Jing; Lv Ge-Li; Guo Ying

2016-01-01

A novel quantum dual signature scheme, which combines two signed messages expected to be sent to two diverse receivers Bob and Charlie, is designed by applying entanglement swapping with coherent states. The signatory Alice signs two different messages with unitary operations (corresponding to the secret keys) and applies entanglement swapping to generate a quantum dual signature. The dual signature is firstly sent to the verifier Bob who extracts and verifies the signature of one message and transmits the rest of the dual signature to the verifier Charlie who verifies the signature of the other message. The transmission of the dual signature is realized with quantum teleportation of coherent states. The analysis shows that the security of secret keys and the security criteria of the signature protocol can be greatly guaranteed. An extensional multi-party quantum dual signature scheme which considers the case with more than three participants is also proposed in this paper and this scheme can remain secure. The proposed schemes are completely suited for the quantum communication network including multiple participants and can be applied to the e-commerce system which requires a secure payment among the customer, business and bank. (paper)

On-chip generation of high-dimensional entangled quantum states and their coherent control.

Science.gov (United States)

Kues, Michael; Reimer, Christian; Roztocki, Piotr; Cortés, Luis Romero; Sciara, Stefania; Wetzel, Benjamin; Zhang, Yanbing; Cino, Alfonso; Chu, Sai T; Little, Brent E; Moss, David J; Caspani, Lucia; Azaña, José; Morandotti, Roberto

2017-06-28

Optical quantum states based on entangled photons are essential for solving questions in fundamental physics and are at the heart of quantum information science. Specifically, the realization of high-dimensional states (D-level quantum systems, that is, qudits, with D > 2) and their control are necessary for fundamental investigations of quantum mechanics, for increasing the sensitivity of quantum imaging schemes, for improving the robustness and key rate of quantum communication protocols, for enabling a richer variety of quantum simulations, and for achieving more efficient and error-tolerant quantum computation. Integrated photonics has recently become a leading platform for the compact, cost-efficient, and stable generation and processing of non-classical optical states. However, so far, integrated entangled quantum sources have been limited to qubits (D = 2). Here we demonstrate on-chip generation of entangled qudit states, where the photons are created in a coherent superposition of multiple high-purity frequency modes. In particular, we confirm the realization of a quantum system with at least one hundred dimensions, formed by two entangled qudits with D = 10. Furthermore, using state-of-the-art, yet off-the-shelf telecommunications components, we introduce a coherent manipulation platform with which to control frequency-entangled states, capable of performing deterministic high-dimensional gate operations. We validate this platform by measuring Bell inequality violations and performing quantum state tomography. Our work enables the generation and processing of high-dimensional quantum states in a single spatial mode.

Generation of concatenated Greenberger-Horne-Zeilinger-type entangled coherent state based on linear optics

Science.gov (United States)

Guo, Rui; Zhou, Lan; Gu, Shi-Pu; Wang, Xing-Fu; Sheng, Yu-Bo

2017-03-01

The concatenated Greenberger-Horne-Zeilinger (C-GHZ) state is a new type of multipartite entangled state, which has potential application in future quantum information. In this paper, we propose a protocol of constructing arbitrary C-GHZ entangled state approximatively. Different from previous protocols, each logic qubit is encoded in the coherent state. This protocol is based on the linear optics, which is feasible in experimental technology. This protocol may be useful in quantum information based on the C-GHZ state.

Unification of the Two-Parameter Equation of State and the Principle of Corresponding States

DEFF Research Database (Denmark)

Mollerup, Jørgen

1998-01-01

A two-parameter equation of state is a two-parameter corresponding states model. A two-parameter corresponding states model is composed of two scale factor correlations and a reference fluid equation of state. In a two-parameter equation of state the reference equation of state is the two-paramet...

A Modified Differential Coherent Bit Synchronization Algorithm for BeiDou Weak Signals with Large Frequency Deviation.

Science.gov (United States)

Han, Zhifeng; Liu, Jianye; Li, Rongbing; Zeng, Qinghua; Wang, Yi

2017-07-04

BeiDou system navigation messages are modulated with a secondary NH (Neumann-Hoffman) code of 1 kbps, where frequent bit transitions limit the coherent integration time to 1 millisecond. Therefore, a bit synchronization algorithm is necessary to obtain bit edges and NH code phases. In order to realize bit synchronization for BeiDou weak signals with large frequency deviation, a bit synchronization algorithm based on differential coherent and maximum likelihood is proposed. Firstly, a differential coherent approach is used to remove the effect of frequency deviation, and the differential delay time is set to be a multiple of bit cycle to remove the influence of NH code. Secondly, the maximum likelihood function detection is used to improve the detection probability of weak signals. Finally, Monte Carlo simulations are conducted to analyze the detection performance of the proposed algorithm compared with a traditional algorithm under the CN0s of 20~40 dB-Hz and different frequency deviations. The results show that the proposed algorithm outperforms the traditional method with a frequency deviation of 50 Hz. This algorithm can remove the effect of BeiDou NH code effectively and weaken the influence of frequency deviation. To confirm the feasibility of the proposed algorithm, real data tests are conducted. The proposed algorithm is suitable for BeiDou weak signal bit synchronization with large frequency deviation.

Continuous-variable quantum cloning of coherent states with phase-conjugate input modes using linear optics

International Nuclear Information System (INIS)

Chen, Haixia; Zhang, Jing

2007-01-01

We propose a scheme for continuous-variable quantum cloning of coherent states with phase-conjugate input modes using linear optics. The quantum cloning machine yields M identical optimal clones from N replicas of a coherent state and N replicas of its phase conjugate. This scheme can be straightforwardly implemented with the setups accessible at present since its optical implementation only employs simple linear optical elements and homodyne detection. Compared with the original scheme for continuous-variable quantum cloning with phase-conjugate input modes proposed by Cerf and Iblisdir [Phys. Rev. Lett. 87, 247903 (2001)], which utilized a nondegenerate optical parametric amplifier, our scheme loses the output of phase-conjugate clones and is regarded as irreversible quantum cloning

Multiscale coherent structures in tokamak plasma turbulence

International Nuclear Information System (INIS)

Xu, G. S.; Wan, B. N.; Zhang, W.; Yang, Q. W.; Wang, L.; Wen, Y. Z.

2006-01-01

A 12-tip poloidal probe array is used on the HT-7 superconducting tokamak [Li, Wan, and Mao, Plasma Phys. Controlled Fusion 42, 135 (2000)] to measure plasma turbulence in the edge region. Some statistical analysis techniques are used to characterize the turbulence structures. It is found that the plasma turbulence is composed of multiscale coherent structures, i.e., turbulent eddies and there is self-similarity in a relative short scale range. The presence of the self-similarity is found due to the structural similarity of these eddies between different scales. These turbulent eddies constitute the basic convection cells, so the self-similar range is just the dominant scale range relevant to transport. The experimental results also indicate that the plasma turbulence is dominated by low-frequency and long-wavelength fluctuation components and its dispersion relation shows typical electron-drift-wave characteristics. Some large-scale coherent structures intermittently burst out and exhibit a very long poloidal extent, even longer than 6 cm. It is found that these large-scale coherent structures are mainly contributed by the low-frequency and long-wavelength fluctuating components and their presence is responsible for the observations of long-range correlations, i.e., the correlation in the scale range much longer than the turbulence decorrelation scale. These experimental observations suggest that the coexistence of multiscale coherent structures results in the self-similar turbulent state

Optimal multicopy asymmetric Gaussian cloning of coherent states

International Nuclear Information System (INIS)

Fiurasek, Jaromir; Cerf, Nicolas J.

2007-01-01

We investigate the asymmetric Gaussian cloning of coherent states which produces M copies from N input replicas in such a way that the fidelity of each copy may be different. We show that the optimal asymmetric Gaussian cloning can be performed with a single phase-insensitive amplifier and an array of beam splitters. We obtain a simple analytical expression characterizing the set of optimal asymmetric Gaussian cloning machines and prove the optimality of these cloners using the formalism of Gaussian completely positive maps and semidefinite programming techniques. We also present an alternative implementation of the asymmetric cloning machine where the phase-insensitive amplifier is replaced with a beam splitter, heterodyne detector, and feedforward

Optimal multicopy asymmetric Gaussian cloning of coherent states

Science.gov (United States)

Fiurášek, Jaromír; Cerf, Nicolas J.

2007-05-01

We investigate the asymmetric Gaussian cloning of coherent states which produces M copies from N input replicas in such a way that the fidelity of each copy may be different. We show that the optimal asymmetric Gaussian cloning can be performed with a single phase-insensitive amplifier and an array of beam splitters. We obtain a simple analytical expression characterizing the set of optimal asymmetric Gaussian cloning machines and prove the optimality of these cloners using the formalism of Gaussian completely positive maps and semidefinite programming techniques. We also present an alternative implementation of the asymmetric cloning machine where the phase-insensitive amplifier is replaced with a beam splitter, heterodyne detector, and feedforward.

Representation of coherent states in many-boson theory

International Nuclear Information System (INIS)

Vakarchuk, I.A.

1978-01-01

Solution of the Bloch equation for the density matrix of the system of interacting Bose particles in the coherent states representation is obtained. The matrix of the thermodynamical potential functional is represented in the form of the functional series over the eigen-values of the annihilation operator and the coefficient functions are the matrix elements of cluster operators. A simple functional integration in the partition sum leads to the well-known quantum virial expansions and the standard perturbation theory series. Possibilities of application of the expressions obtained to the investigation of the lambda-transition in the liquid He 4 and the generalization to the case of the many-fermion system is discussed

Correlation characteristics of optical coherence tomography images of turbid media with statistically inhomogeneous optical parameters

International Nuclear Information System (INIS)

Dolin, Lev S.; Sergeeva, Ekaterina A.; Turchin, Ilya V.

2012-01-01

Noisy structure of optical coherence tomography (OCT) images of turbid medium contains information about spatial variations of its optical parameters. We propose analytical model of statistical characteristics of OCT signal fluctuations from turbid medium with spatially inhomogeneous coefficients of absorption and backscattering. Analytically predicted correlation characteristics of OCT signal from spatially inhomogeneous medium are in good agreement with the results of correlation analysis of OCT images of different biological tissues. The proposed model can be efficiently applied for quantitative evaluation of statistical properties of absorption and backscattering fluctuations basing on correlation characteristics of OCT images.

Importance sampling large deviations in nonequilibrium steady states. I

Science.gov (United States)

Ray, Ushnish; Chan, Garnet Kin-Lic; Limmer, David T.

2018-03-01

Large deviation functions contain information on the stability and response of systems driven into nonequilibrium steady states and in such a way are similar to free energies for systems at equilibrium. As with equilibrium free energies, evaluating large deviation functions numerically for all but the simplest systems is difficult because by construction they depend on exponentially rare events. In this first paper of a series, we evaluate different trajectory-based sampling methods capable of computing large deviation functions of time integrated observables within nonequilibrium steady states. We illustrate some convergence criteria and best practices using a number of different models, including a biased Brownian walker, a driven lattice gas, and a model of self-assembly. We show how two popular methods for sampling trajectory ensembles, transition path sampling and diffusion Monte Carlo, suffer from exponentially diverging correlations in trajectory space as a function of the bias parameter when estimating large deviation functions. Improving the efficiencies of these algorithms requires introducing guiding functions for the trajectories.

Importance sampling large deviations in nonequilibrium steady states. I.

Science.gov (United States)

Ray, Ushnish; Chan, Garnet Kin-Lic; Limmer, David T

2018-03-28

Large deviation functions contain information on the stability and response of systems driven into nonequilibrium steady states and in such a way are similar to free energies for systems at equilibrium. As with equilibrium free energies, evaluating large deviation functions numerically for all but the simplest systems is difficult because by construction they depend on exponentially rare events. In this first paper of a series, we evaluate different trajectory-based sampling methods capable of computing large deviation functions of time integrated observables within nonequilibrium steady states. We illustrate some convergence criteria and best practices using a number of different models, including a biased Brownian walker, a driven lattice gas, and a model of self-assembly. We show how two popular methods for sampling trajectory ensembles, transition path sampling and diffusion Monte Carlo, suffer from exponentially diverging correlations in trajectory space as a function of the bias parameter when estimating large deviation functions. Improving the efficiencies of these algorithms requires introducing guiding functions for the trajectories.

Coherence and entanglement measures based on Rényi relative entropies

International Nuclear Information System (INIS)

Zhu, Huangjun; Hayashi, Masahito; Chen, Lin

2017-01-01

We study systematically resource measures of coherence and entanglement based on Rényi relative entropies, which include the logarithmic robustness of coherence, geometric coherence, and conventional relative entropy of coherence together with their entanglement analogues. First, we show that each Rényi relative entropy of coherence is equal to the corresponding Rényi relative entropy of entanglement for any maximally correlated state. By virtue of this observation, we establish a simple operational connection between entanglement measures and coherence measures based on Rényi relative entropies. We then prove that all these coherence measures, including the logarithmic robustness of coherence, are additive. Accordingly, all these entanglement measures are additive for maximally correlated states. In addition, we derive analytical formulas for Rényi relative entropies of entanglement of maximally correlated states and bipartite pure states, which reproduce a number of classic results on the relative entropy of entanglement and logarithmic robustness of entanglement in a unified framework. Several nontrivial bounds for Rényi relative entropies of coherence (entanglement) are further derived, which improve over results known previously. Moreover, we determine all states whose relative entropy of coherence is equal to the logarithmic robustness of coherence. As an application, we provide an upper bound for the exact coherence distillation rate, which is saturated for pure states. (paper)

Coherence of light. 2. ed.

International Nuclear Information System (INIS)

Perina, J.

1985-01-01

This book puts the theory of coherence of light on a rigorous mathematical footing. It deals with the classical and quantum theories and with their inter-relationships, including many results from the author's own research. Particular attention is paid to the detection of optical fields, using the correlation functions, photocount statistics and coherent state. Radiometry with light fields of arbitrary states of coherence is discussed and the coherent state methods are demonstrated by photon statistics of radiation in random and nonlinear media, using the Heisenberg-Langevin and Fokker-Planck approaches to the interaction of radiation with matter. Many experimental and theoretical results are compared. A full list of references to theoretical and experimental literature is provided. The book is intended for researchers and postgraduate students in the fields of quantum optics, quantum electronics, statistical optics, nonlinear optics, optical communication and optoelectronics. (Auth.)

Nonclassical features of trimodal excited coherent Greenberger - Horne - Zeilinger(GHZ) - type state

Science.gov (United States)

Merlin, J.; Ahmed, A. B. M.; Mohammed, S. Naina

2017-06-01

We examine the influence of photon excitation on each mode of the Glauber coherent GHZ type tripartite state. Concurrence is adopted as entanglement measure between bipartite entangled state. The pairwise concurrence is calculated and used as a quantifier of intermodal entanglement. The entanglement distribution among three modes is investigated using tangle as a measure and the residual entanglement is also calculated. The effect of the photon addition process on the quadrature squeezing is investigated. The higher order squeezing capacity of the photon addition process is also shown.

Momentum projection and relativistic boost of solitons: Coherent states and projection

International Nuclear Information System (INIS)

Luebeck, E.G.; Birse, M.C.; Henley, E.M.; Wilets, L.

1986-01-01

We present a method for calculating center-of-mass corrections to hadron properties in soliton models and we apply the method to the soliton bag model. A coherent state is used to provide a quantum wave function corresponding to the mean-field approximation. This state is projected onto a zero-momentum eigenstate. States of nonzero momentum can be constructed from this with a Lorentz boost operator. Hence center-of-mass corrections can be made in a properly relativistic way. The energy of the projected zero-momentum state is the hadron mass with spurious center-of-mass energy removed. We apply a variational principle to our projected state and use three ''virial theorems'' to test our approximate solution. We also study projection of general one-mode states. Projection reduces the nucleon energy by up to 25%. Variation after projection gives a further reduction of less than 20%. Somewhat larger reductions in the energy are found for meson states

Effect of decoherence on fidelity in teleportation using entangled coherent states

International Nuclear Information System (INIS)

Prakash, H; Chandra, N; Prakash, R; Shivani

2007-01-01

A scheme of teleporting a superposition of coherent states (α) and ( - α) using a beam splitter and two phase shifters was proposed by van Enk and Hirota (2001 Phys. Rev. A 64 022313). The authors concluded that the probability for successful teleportation is 1/2. In this paper, it is shown that the authors' scheme can be altered slightly so as to obtain an almost perfect teleportation for an appreciable value of (α) 2 . For (α) 2 = 5, the minimum of average fidelity, which is the minimum of the sum of the product of probability of occurrence of any case, and the corresponding fidelity is less than 1 by a quantity ∼10 -4 . We also discuss the effect of decoherence on teleportation fidelity. We find that if no photons are counted in both final outputs, the minimum assured fidelity is still non-zero except when there is no decoherence and the information is an even coherent state. For non-zero photon counts, minimum assured fidelity decreases with an increase in (α) 2 for low noise. For high noise, however, it increases, attains a maximum value and then decreases with (α) 2 . The average fidelity depends appreciably on the information for low values of (α) 2 only

Generation of coherent states of photon-added type via pathway of eigenfunctions

International Nuclear Information System (INIS)

Gorska, K; Penson, K A; Duchamp, G H E

2010-01-01

We obtain and investigate the regular eigenfunctions of simple differential operators x r d r+1 /dx r+1 , r = 1, 2, ..., with the eigenvalues equal to 1. With the help of these eigenfunctions, we construct a non-unitary analogue of a boson displacement operator which will be acting on the vacuum. In this way, we generate collective quantum states of the Fock space which are normalized and equipped with the resolution of unity with the positive weight functions that we obtain explicitly. These states are thus coherent states in the sense of Klauder. They span the truncated Fock space without first r lowest-lying basis states: |0), |1), ..., |r - 1). These states are squeezed, sub-Poissonian in nature and reminiscent of photon-added states in Agarwal and Tara (1991 Phys. Rev. A 43 492).

Quantum Coherence, Time-Translation Symmetry, and Thermodynamics

Directory of Open Access Journals (Sweden)

Matteo Lostaglio

2015-04-01

Full Text Available The first law of thermodynamics imposes not just a constraint on the energy content of systems in extreme quantum regimes but also symmetry constraints related to the thermodynamic processing of quantum coherence. We show that this thermodynamic symmetry decomposes any quantum state into mode operators that quantify the coherence present in the state. We then establish general upper and lower bounds for the evolution of quantum coherence under arbitrary thermal operations, valid for any temperature. We identify primitive coherence manipulations and show that the transfer of coherence between energy levels manifests irreversibility not captured by free energy. Moreover, the recently developed thermomajorization relations on block-diagonal quantum states are observed to be special cases of this symmetry analysis.

Using co-occurrence to evaluate belief coherence in a large non clinical sample.

Directory of Open Access Journals (Sweden)

Rachel Pechey

Full Text Available Much of the recent neuropsychological literature on false beliefs (delusions has tended to focus on individual or single beliefs, with few studies actually investigating the relationship or co-occurrence between different types of co-existing beliefs. Quine and Ullian proposed the hypothesis that our beliefs form an interconnected web in which the beliefs that make up that system must somehow "cohere" with one another and avoid cognitive dissonance. As such beliefs are unlikely to be encapsulated (i.e., exist in isolation from other beliefs. The aim of this preliminary study was to empirically evaluate the probability of belief co-occurrence as one indicator of coherence in a large sample of subjects involving three different thematic sets of beliefs (delusion-like, paranormal & religious, and societal/cultural. Results showed that the degree of belief co-endorsement between beliefs within thematic groupings was greater than random occurrence, lending support to Quine and Ullian's coherentist account. Some associations, however, were relatively weak, providing for well-established examples of cognitive dissonance.

A large scale GIS geodatabase of soil parameters supporting the modeling of conservation practice alternatives in the United States

Science.gov (United States)

Water quality modeling requires across-scale support of combined digital soil elements and simulation parameters. This paper presents the unprecedented development of a large spatial scale (1:250,000) ArcGIS geodatabase coverage designed as a functional repository of soil-parameters for modeling an...

Extraction of optical scattering parameters and attenuation compensation in optical coherence tomography images of multi-layered tissue structures

DEFF Research Database (Denmark)

Thrane, Lars; Frosz, Michael Henoch; Tycho, Andreas

2004-01-01

A recently developed analytical optical coherence tomography (OCT) model [Thrane et al., J. Opt. Soc. Am. A 17, 484 (2000)] allows the extraction of optical scattering parameters from OCT images, thereby permitting attenuation compensation in those images. By expanding this theoretical model, we...... have developed a new method for extracting optical scattering parameters from multilayered tissue structures in vivo. To verify this, we used a Monte Carlo (MC) OCT model as a numerical phantom to simulate the OCT signal for het-erogeneous multilayered tissue. Excellent agreement between the extracted......, and the results hold promise for expanding the functional imaging capabilities of OCT....

New applications of Boson's coherent states of double modes at regular product

International Nuclear Information System (INIS)

Zhang Yongde; Ren Yong

1987-05-01

This paper presents a series of new applications of boson's coherent states of double modes by means of the technique of regular products. They include non-coupled double oscillator solutions at two time dependent extra-sources; coupled double oscillator solutions at two time dependent extra-sources; some applications to regular momentum theory; an explicit expression for time-reversal operator. (author). 7 refs

Low frequency steady-state brain responses modulate large scale functional networks in a frequency-specific means.

Science.gov (United States)

Wang, Yi-Feng; Long, Zhiliang; Cui, Qian; Liu, Feng; Jing, Xiu-Juan; Chen, Heng; Guo, Xiao-Nan; Yan, Jin H; Chen, Hua-Fu

2016-01-01

Neural oscillations are essential for brain functions. Research has suggested that the frequency of neural oscillations is lower for more integrative and remote communications. In this vein, some resting-state studies have suggested that large scale networks function in the very low frequency range (frequency characteristics of brain networks because both resting-state studies and conventional frequency tagging approaches cannot simultaneously capture multiple large scale networks in controllable cognitive activities. In this preliminary study, we aimed to examine whether large scale networks can be modulated by task-induced low frequency steady-state brain responses (lfSSBRs) in a frequency-specific pattern. In a revised attention network test, the lfSSBRs were evoked in the triple network system and sensory-motor system, indicating that large scale networks can be modulated in a frequency tagging way. Furthermore, the inter- and intranetwork synchronizations as well as coherence were increased at the fundamental frequency and the first harmonic rather than at other frequency bands, indicating a frequency-specific modulation of information communication. However, there was no difference among attention conditions, indicating that lfSSBRs modulate the general attention state much stronger than distinguishing attention conditions. This study provides insights into the advantage and mechanism of lfSSBRs. More importantly, it paves a new way to investigate frequency-specific large scale brain activities. © 2015 Wiley Periodicals, Inc.

Communication: Coherences observed in vivo in photosynthetic bacteria using two-dimensional electronic spectroscopy

International Nuclear Information System (INIS)

Dahlberg, Peter D.; Norris, Graham J.; Wang, Cheng; Viswanathan, Subha; Singh, Ved P.; Engel, Gregory S.

2015-01-01

Energy transfer through large disordered antenna networks in photosynthetic organisms can occur with a quantum efficiency of nearly 100%. This energy transfer is facilitated by the electronic structure of the photosynthetic antennae as well as interactions between electronic states and the surrounding environment. Coherences in time-domain spectroscopy provide a fine probe of how a system interacts with its surroundings. In two-dimensional electronic spectroscopy, coherences can appear on both the ground and excited state surfaces revealing detailed information regarding electronic structure, system-bath coupling, energy transfer, and energetic coupling in complex chemical systems. Numerous studies have revealed coherences in isolated photosynthetic pigment-protein complexes, but these coherences have not been observed in vivo due to the small amplitude of these signals and the intense scatter from whole cells. Here, we present data acquired using ultrafast video-acquisition gradient-assisted photon echo spectroscopy to observe quantum beating signals from coherences in vivo. Experiments were conducted on isolated light harvesting complex II (LH2) from Rhodobacter sphaeroides, whole cells of R. sphaeroides, and whole cells of R. sphaeroides grown in 30% deuterated media. A vibronic coherence was observed following laser excitation at ambient temperature between the B850 and the B850 ∗ states of LH2 in each of the 3 samples with a lifetime of ∼40-60 fs

Communication: Coherences observed in vivo in photosynthetic bacteria using two-dimensional electronic spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Dahlberg, Peter D. [Graduate Program in the Biophysical Sciences, Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States); Norris, Graham J.; Wang, Cheng; Viswanathan, Subha; Singh, Ved P.; Engel, Gregory S., E-mail: gsengel@uchicago.edu [Department of Chemistry, Institute for Biophysical Dynamics, and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637 (United States)

2015-09-14

Energy transfer through large disordered antenna networks in photosynthetic organisms can occur with a quantum efficiency of nearly 100%. This energy transfer is facilitated by the electronic structure of the photosynthetic antennae as well as interactions between electronic states and the surrounding environment. Coherences in time-domain spectroscopy provide a fine probe of how a system interacts with its surroundings. In two-dimensional electronic spectroscopy, coherences can appear on both the ground and excited state surfaces revealing detailed information regarding electronic structure, system-bath coupling, energy transfer, and energetic coupling in complex chemical systems. Numerous studies have revealed coherences in isolated photosynthetic pigment-protein complexes, but these coherences have not been observed in vivo due to the small amplitude of these signals and the intense scatter from whole cells. Here, we present data acquired using ultrafast video-acquisition gradient-assisted photon echo spectroscopy to observe quantum beating signals from coherences in vivo. Experiments were conducted on isolated light harvesting complex II (LH2) from Rhodobacter sphaeroides, whole cells of R. sphaeroides, and whole cells of R. sphaeroides grown in 30% deuterated media. A vibronic coherence was observed following laser excitation at ambient temperature between the B850 and the B850{sup ∗} states of LH2 in each of the 3 samples with a lifetime of ∼40-60 fs.

Quantum teleportation of an arbitrary two-mode coherent state using only linear optics elements

International Nuclear Information System (INIS)

Ho Ngoc Phien; Nguyen Ba An

2008-01-01

We propose a linear optics scheme to teleport an arbitrary two-mode coherent state. The devices used are beam-splitters, phase-shifters and ideal photo-detectors capable of distinguishing between even and odd photon numbers. The scheme achieves faithful teleportation with a probability of 1/4. However, with additional use of an appropriate displacement operator, the teleported state can always be made near-faithful

Models of coherent exciton condensation

International Nuclear Information System (INIS)

Littlewood, P B; Eastham, P R; Keeling, J M J; Marchetti, F M; Simons, B D; Szymanska, M H

2004-01-01

That excitons in solids might condense into a phase-coherent ground state was proposed about 40 years ago, and has been attracting experimental and theoretical attention ever since. Although experimental confirmation has been hard to come by, the concepts released by this phenomenon have been widely influential. This tutorial review discusses general aspects of the theory of exciton and polariton condensates, focusing on the reasons for coherence in the ground state wavefunction, the BCS to Bose crossover(s) for excitons and for polaritons, and the relationship of the coherent condensates to standard lasers

Models of coherent exciton condensation

Energy Technology Data Exchange (ETDEWEB)

Littlewood, P B [Theory of Condensed Matter, Cavendish Laboratory, Cambridge CB3 0HE (United Kingdom); Eastham, P R [Theory of Condensed Matter, Cavendish Laboratory, Cambridge CB3 0HE (United Kingdom); Keeling, J M J [Theory of Condensed Matter, Cavendish Laboratory, Cambridge CB3 0HE (United Kingdom); Marchetti, F M [Theory of Condensed Matter, Cavendish Laboratory, Cambridge CB3 0HE (United Kingdom); Simons, B D [Theory of Condensed Matter, Cavendish Laboratory, Cambridge CB3 0HE (United Kingdom); Szymanska, M H [Theory of Condensed Matter, Cavendish Laboratory, Cambridge CB3 0HE (United Kingdom)

2004-09-08

That excitons in solids might condense into a phase-coherent ground state was proposed about 40 years ago, and has been attracting experimental and theoretical attention ever since. Although experimental confirmation has been hard to come by, the concepts released by this phenomenon have been widely influential. This tutorial review discusses general aspects of the theory of exciton and polariton condensates, focusing on the reasons for coherence in the ground state wavefunction, the BCS to Bose crossover(s) for excitons and for polaritons, and the relationship of the coherent condensates to standard lasers.

Laser diode technology for coherent communications

Science.gov (United States)

Channin, D. J.; Palfrey, S. L.; Toda, M.

1989-01-01

The effect of diode laser characteristics on the overall performance capabilities of coherent communication systems is discussed. In particular, attention is given to optical performance issues for diode lasers in coherent systems, measurements of key performance parameters, and optical requirements for coherent single-channel and multichannel communication systems. The discussion also covers limitations imposed by diode laser optical performance on multichannel system capabilities and implications for future developments.

Analysis on the steady-state coherent synchrotron radiation with strong shielding

International Nuclear Information System (INIS)

Li, R.; Bohn, C.L.; Bisognano, J.J.

1997-01-01

There are several papers concerning shielding of coherent synchrotron radiation (CSR) emitted by a Gaussian line charge on a circular orbit centered between two parallel conducting plates. Previous asymptotic analyses in the frequency domain show that shielded steady-state CSR mainly arises from harmonics in the bunch frequency exceeding the threshold harmonic for satisfying the boundary conditions at the plates. In this paper the authors extend the frequency-domain analysis into the regime of strong shielding, in which the threshold harmonic exceeds the characteristic frequency of the bunch. The result is then compared to the shielded steady-state CSR power obtained using image charges

Enhancing quantum entanglement for continuous variables by a coherent superposition of photon subtraction and addition

Energy Technology Data Exchange (ETDEWEB)

Lee, Su-Yong; Kim, Ho-Joon [Department of Physics, Texas A and M University at Qatar, P.O. Box 23874, Doha (Qatar); Ji, Se-Wan [School of Computational Sciences, Korea Institute for Advanced Study, Seoul 130-012 (Korea, Republic of); Nha, Hyunchul [Department of Physics, Texas A and M University at Qatar, P.O. Box 23874, Doha (Qatar); Institute fuer Quantenphysik, Universitaet Ulm, D-89069 Ulm (Germany)

2011-07-15

We investigate how the entanglement properties of a two-mode state can be improved by performing a coherent superposition operation ta+ra{sup {dagger}} of photon subtraction and addition, proposed by Lee and Nha [Phys. Rev. A 82, 053812 (2010)], on each mode. We show that the degree of entanglement, the Einstein-Podolsky-Rosen-type correlation, and the performance of quantum teleportation can be all enhanced for the output state when the coherent operation is applied to a two-mode squeezed state. The effects of the coherent operation are more prominent than those of the mere photon subtraction a and the addition a{sup {dagger}} particularly in the small-squeezing regime, whereas the optimal operation becomes the photon subtraction (case of r=0) in the large-squeezing regime.

Coherent states of systems with quadratic Hamiltonians

Energy Technology Data Exchange (ETDEWEB)

Bagrov, V.G., E-mail: bagrov@phys.tsu.ru [Department of Physics, Tomsk State University, Tomsk (Russian Federation); Gitman, D.M., E-mail: gitman@if.usp.br [Tomsk State University, Tomsk (Russian Federation); Pereira, A.S., E-mail: albertoufcg@hotmail.com [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Fisica

2015-06-15

Different families of generalized coherent states (CS) for one-dimensional systems with general time-dependent quadratic Hamiltonian are constructed. In principle, all known CS of systems with quadratic Hamiltonian are members of these families. Some of the constructed generalized CS are close enough to the well-known due to Schroedinger and Glauber CS of a harmonic oscillator; we call them simply CS. However, even among these CS, there exist different families of complete sets of CS. These families differ by values of standard deviations at the initial time instant. According to the values of these initial standard deviations, one can identify some of the families with semiclassical CS. We discuss properties of the constructed CS, in particular, completeness relations, minimization of uncertainty relations and so on. As a unknown application of the general construction, we consider different CS of an oscillator with a time dependent frequency. (author)

Coherent states of systems with quadratic Hamiltonians

International Nuclear Information System (INIS)

Bagrov, V.G.; Gitman, D.M.; Pereira, A.S.

2015-01-01

Different families of generalized coherent states (CS) for one-dimensional systems with general time-dependent quadratic Hamiltonian are constructed. In principle, all known CS of systems with quadratic Hamiltonian are members of these families. Some of the constructed generalized CS are close enough to the well-known due to Schroedinger and Glauber CS of a harmonic oscillator; we call them simply CS. However, even among these CS, there exist different families of complete sets of CS. These families differ by values of standard deviations at the initial time instant. According to the values of these initial standard deviations, one can identify some of the families with semiclassical CS. We discuss properties of the constructed CS, in particular, completeness relations, minimization of uncertainty relations and so on. As a unknown application of the general construction, we consider different CS of an oscillator with a time dependent frequency. (author)

Optical Coherence and Quantum Optics

CERN Document Server

Mandel, Leonard

1995-01-01

This book presents a systematic account of optical coherence theory within the framework of classical optics, as applied to such topics as radiation from sources of different states of coherence, foundations of radiometry, effects of source coherence on the spectra of radiated fields, coherence theory of laser modes, and scattering of partially coherent light by random media. The book starts with a full mathematical introduction to the subject area and each chapter concludes with a set of exercises. The authors are renowned scientists and have made substantial contributions to many of the topi

Coherent State Projection Operator Representation of Symplectic Transformations as a Loyal Representation of Symplectic Group

Science.gov (United States)

Fan, Hong-Yi; Chen, Jun-Hua

2002-08-01

We find that the coherent state projection operator representation of symplectic transformation constitutes a loyal group representation of symplectic group. The result of successively applying squeezing operators on number state can be easily derived. The project supported by National Natural Science Foundation of China under Grant No. 10575057 and the President Foundation of the Chinese Academy of Sciences

Phase Properties of Photon-Added Coherent States for Nonharmonic Oscillators in a Nonlinear Kerr Medium

Science.gov (United States)

Jahanbakhsh, F.; Honarasa, G.

2018-04-01

The potential of nonharmonic systems has several applications in the field of quantum physics. The photon-added coherent states for annharmonic oscillators in a nonlinear Kerr medium can be used to describe some quantum systems. In this paper, the phase properties of these states including number-phase Wigner distribution function, Pegg-Barnett phase distribution function, number-phase squeezing and number-phase entropic uncertainty relations are investigated. It is found that these states can be considered as the nonclassical states.

Misalignment sensitivity in an intra-cavity coherently combined crossed-Porro resonator configuration

Science.gov (United States)

Alperovich, Z.; Buchinsky, O.; Greenstein, S.; Ishaaya, A. A.

2017-08-01

We investigate the misalignment sensitivity in a crossed-Porro resonator configuration when coherently combining two pulsed multimode Nd:YAG laser channels. To the best of our knowledge, this is the first reported study of this configuration. The configuration is based on a passive intra-cavity interferometric combiner that promotes self-phase locking and coherent combining. Detailed misalignment sensitivity measurements are presented, examining both translation and angular deviations of the end prisms and combiner, and are compared to the results for standard flat end-mirror configurations. The results show that the most sensitive parameter in the crossed-Porro resonator configuration is the angular tuning of the intra-cavity interferometric combiner, which is ~±54 µrad. In comparison, with the flat end mirror configuration, the most sensitive parameter in the resonator is the angular tuning of the output coupler, which is ~±11 µrad. Thus, with the crossed-Porro configuration, we obtain significantly reduced sensitivity. This ability to reduce the misalignment sensitivity in coherently combined solid-state configurations may be beneficial in paving their way into practical use in a variety of demanding applications.

Coherent state approach for the Φ6-lattice model and phase transitions

International Nuclear Information System (INIS)

Aguero-Granados, M.A.; Makhan'kov, V.G.

1991-01-01

Phase transitions in the lattice version of the Φ 6 -field theory are studied. The generalized coherent states approach to is used. In such a way the roles of kinks and bubbles in phase transitions have been reexamined. It is shown via a numerical analysis that first and second order phase transitions appear due to the behaviour of kinks and bubbles excitations. 12 refs.; 10 figs

Evaluating of Tear Meniscus Parameters with Optical Coherent Tomography in Dry-Eye Patients

Directory of Open Access Journals (Sweden)

Gülizar Soyugelen Demirok

2013-08-01

Full Text Available Purpose: To evaluate the changes in meniscus parameters with optical coherence tomography (OCT after treatment and consider the correlation between the OCT parameters and dry-eye tests. Material and Method: Thirty-two dry-eye patients and 30 healthy individuals were included. Visual acuities, biomicroscopic evaluation, Schirmer-I test, tear-break-up time (T-BUT, and lower-tear meniscus parameters measured with OCT were evaluated. Ocular surface disease index (OSDI was performed. The measurements were repeated on the 10th day and 1st month of the treatment. Lower tear meniscus height (LTMH, depth (LTMD, area (LTMA and α-angle were measured. The tear meniscus parameters of the dry-eye group were compared with the control group before treatment, and the correlation between the dry-eye tests and OCT measurements were evaluated. The change in the results of the dry-eye tests and OCT measurements with treatment were assessed. Results: There was statistically no significant difference between the age and gender of the patients in groups. Before treatment the mean Schirmer-I test, TBUT and OSDI scores were different. The LTMH and LTMA were higher in the control group. In the dry-eye group before treatment, there was a negative correlation between the OSDI score and OCT parameters, however, no meaningful correlation was observed between any other test and OCT parameters. Although there were no change in LTMD and α-angle with treatment, the 1st month values of LTMH and LTMA were significantly higher from the pre-treatment and 10th day values. Discussion: When diagnosing dry-eye, TBUT and OSDI scores were found to be more effective compared to Schirmer-I test for the diagnosis of dry eye. Although not adequate by itself, tear meniscus parameters measured with OCT, LTMH and LTMA, may be helpful for evaluating the efficacy of treatment, and the correlation of these two parameters with the OSDI score may increase the objectivity while questioning the

Customized Steady-State Constraints for Parameter Estimation in Non-Linear Ordinary Differential Equation Models.

Science.gov (United States)

Rosenblatt, Marcus; Timmer, Jens; Kaschek, Daniel

2016-01-01

Ordinary differential equation models have become a wide-spread approach to analyze dynamical systems and understand underlying mechanisms. Model parameters are often unknown and have to be estimated from experimental data, e.g., by maximum-likelihood estimation. In particular, models of biological systems contain a large number of parameters. To reduce the dimensionality of the parameter space, steady-state information is incorporated in the parameter estimation process. For non-linear models, analytical steady-state calculation typically leads to higher-order polynomial equations for which no closed-form solutions can be obtained. This can be circumvented by solving the steady-state equations for kinetic parameters, which results in a linear equation system with comparatively simple solutions. At the same time multiplicity of steady-state solutions is avoided, which otherwise is problematic for optimization. When solved for kinetic parameters, however, steady-state constraints tend to become negative for particular model specifications, thus, generating new types of optimization problems. Here, we present an algorithm based on graph theory that derives non-negative, analytical steady-state expressions by stepwise removal of cyclic dependencies between dynamical variables. The algorithm avoids multiple steady-state solutions by construction. We show that our method is applicable to most common classes of biochemical reaction networks containing inhibition terms, mass-action and Hill-type kinetic equations. Comparing the performance of parameter estimation for different analytical and numerical methods of incorporating steady-state information, we show that our approach is especially well-tailored to guarantee a high success rate of optimization.

Theory of coherent c-axis Josephson tunneling between layered superconductors

International Nuclear Information System (INIS)

Arnold, G. B.; Klemm, R. A.

2000-01-01

We calculate exactly the Josephson current for c-axis coherent tunneling between two layered superconductors, each with internal coherent tight-binding intra- and interlayer quasiparticle dispersions. Our results also apply when one or both of the superconductors is a bulk material, and include the usually neglected effects of surface states. For weak tunneling, our results reduce to our previous results derived using the tunneling Hamiltonian. Our results are also correct for strong tunneling. However, the c-axis tunneling expressions of Tanaka and Kashiwaya are shown to be incorrect in any limit. In addition, we consider the c-axis coherent critical current between two identical layered superconductors twisted an angle φ 0 about the c axis with respect to each other. Regardless of the order-parameter symmetry, our coherent tunneling results using a tight-binding intralayer quasiparticle dispersion are inconsistent with the recent c-axis twist bicrystal Bi 2 Sr 2 CaCu 2 O 8+δ twist junction experiments of Li et al. [Li et al., Phys. Rev. Lett. 83, 4160 (1999)]. (c) 2000 The American Physical Society

Infinite-mode squeezed coherent states and non-equilibrium statistical mechanics (phase-space-picture approach)

International Nuclear Information System (INIS)

Yeh, L.

1992-01-01

The phase-space-picture approach to quantum non-equilibrium statistical mechanics via the characteristic function of infinite- mode squeezed coherent states is introduced. We use quantum Brownian motion as an example to show how this approach provides an interesting geometrical interpretation of quantum non-equilibrium phenomena

Quantum dual signature scheme based on coherent states with entanglement swapping

Science.gov (United States)

Liu, Jia-Li; Shi, Rong-Hua; Shi, Jin-Jing; Lv, Ge-Li; Guo, Ying

2016-08-01

A novel quantum dual signature scheme, which combines two signed messages expected to be sent to two diverse receivers Bob and Charlie, is designed by applying entanglement swapping with coherent states. The signatory Alice signs two different messages with unitary operations (corresponding to the secret keys) and applies entanglement swapping to generate a quantum dual signature. The dual signature is firstly sent to the verifier Bob who extracts and verifies the signature of one message and transmits the rest of the dual signature to the verifier Charlie who verifies the signature of the other message. The transmission of the dual signature is realized with quantum teleportation of coherent states. The analysis shows that the security of secret keys and the security criteria of the signature protocol can be greatly guaranteed. An extensional multi-party quantum dual signature scheme which considers the case with more than three participants is also proposed in this paper and this scheme can remain secure. The proposed schemes are completely suited for the quantum communication network including multiple participants and can be applied to the e-commerce system which requires a secure payment among the customer, business and bank. Project supported by the National Natural Science Foundation of China (Grant Nos. 61272495, 61379153, and 61401519) and the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20130162110012).

Evidence of Large Fluctuations of Stock Return and Financial Crises from Turkey: Using Wavelet Coherency and Varma Modeling to Forecast Stock Return

Science.gov (United States)

Oygur, Tunc; Unal, Gazanfer

Shocks, jumps, booms and busts are typical large fluctuation markers which appear in crisis. Models and leading indicators vary according to crisis type in spite of the fact that there are a lot of different models and leading indicators in literature to determine structure of crisis. In this paper, we investigate structure of dynamic correlation of stock return, interest rate, exchange rate and trade balance differences in crisis periods in Turkey over the period between October 1990 and March 2015 by applying wavelet coherency methodologies to determine nature of crises. The time period includes the Turkeys currency and banking crises; US sub-prime mortgage crisis and the European sovereign debt crisis occurred in 1994, 2001, 2008 and 2009, respectively. Empirical results showed that stock return, interest rate, exchange rate and trade balance differences are significantly linked during the financial crises in Turkey. The cross wavelet power, the wavelet coherency, the multiple wavelet coherency and the quadruple wavelet coherency methodologies have been used to examine structure of dynamic correlation. Moreover, in consequence of quadruple and multiple wavelet coherence, strongly correlated large scales indicate linear behavior and, hence VARMA (vector autoregressive moving average) gives better fitting and forecasting performance. In addition, increasing the dimensions of the model for strongly correlated scales leads to more accurate results compared to scalar counterparts.

Coherence properties in superconducting flux qubits

Energy Technology Data Exchange (ETDEWEB)

Spilla, Samuele

2015-02-16

The research work discussed in this thesis deals with the study of superconducting Josephson qubits. Superconducting qubits are solid-state artificial atoms which are based on lithographically defined Josephson tunnel junctions properties. When sufficiently cooled, these superconducting devices exhibit quantized states of charge, flux or junction phase depending on their design parameters. This allows to observe coherent evolutions of their states. The results presented can be divided into two parts. In a first part we investigate operations of superconducting qubits based on the quantum coherence in superconducting quantum interference devices (SQUID). We explain experimental data which has been observed in a SQUID subjected to fast, large-amplitude modifications of its effective potential shape. The motivations for this work come from the fact that in the past few years there have been attempts to interpret the supposed quantum behavior of physical systems, such as Josephson devices, within a classical framework. Moreover, we analyze the possibility of generating GHZ states, namely maximally entangled states, in a quantum system made out of three Josephson qubits. In particular, we investigate the possible limitations of the GHZ state generation due to coupling to bosonic baths. In the second part of the thesis we address a particular cause of decoherence of flux qubits which has been disregarded until now: thermal gradients, which can arise due to accidental non equilibrium quasiparticle distributions. The reason for these detrimental effects is that heat currents flowing through Josephson tunnel junctions in response to a temperature gradient are periodic functions of the phase difference between the electrodes. The phase dependence of the heat current comes from Andreev reflection, namely an interplay between the quasiparticles which carry heat and the superconducting condensate which is sensitive to the superconducting phase difference. Generally speaking

Glauber theory and the quantum coherence of curvature inhomogeneities

CERN Document Server

Giovannini, Massimo

2017-01-12

The curvature inhomogeneities are systematically scrutinized in the framework of the Glauber approach. The amplified quantum fluctuations of the scalar and tensor modes of the geometry are shown to be first-order coherent while the interference of the corresponding intensities is larger than in the case of Bose-Einstein correlations. After showing that the degree of second-order coherence does not suffice to characterize unambiguously the curvature inhomogeneities, we argue that direct analyses of the degrees of third and fourth-order coherence are necessary to discriminate between different correlated states and to infer more reliably the statistical properties of the large-scale fluctuations. We speculate that the moments of the multiplicity distributions of the relic phonons might be observationally accessible thanks to new generations of instruments able to count the single photons of the Cosmic Microwave Background in the THz region.

Can Excited State Electronic Coherence Be Tuned via Molecular Structural Modification? A First-Principles Quantum Electronic Dynamics Study of Pyrazolate-Bridged Pt(II) Dimers

Energy Technology Data Exchange (ETDEWEB)

Lingerfelt, David B.; Lestrange, Patrick J.; Radler, Joseph J.; Brown-Xu, Samantha E.; Kim, Pyosang; Castellano, Felix N.; Chen, Lin X.; Li, Xiaosong

2017-02-24

Materials and molecular systems exhibiting long-lived electronic coherence can facilitate coherent transport, opening the door to efficient charge and energy transport beyond traditional methods. Recently, signatures of a possible coherent, recurrent electronic motion were identified in femtosecond pump-probe spectroscopy experiments on a binuclear platinum complex, where a persistent periodic beating in the transient absorption signal’s anisotropy was observed. In this study, we investigate the excitonic dynamics that underlie the suspected electronic coherence for a series of binuclear platinum complexes exhibiting a range of interplatinum distances. Results suggest that the long-lived coherence can only result when competitive electronic couplings are in balance. At longer Pt-Pt distances, the electronic couplings between the two halves of the binuclear system weaken, and exciton localization and recombination is favored on short time scales. For short Pt-Pt distances, electronic couplings between the states in the coherent superposition are stronger than the coupling with other excitonic states, leading to long-lived coherence.

Criterion of transverse coherence of self-amplified spontaneous emission in high gain free electron laser amplifiers

International Nuclear Information System (INIS)

Xie, M.; Kim, K.J.

1995-01-01

In a high gain free electron laser amplifier based on Self-Amplified Spontaneous Emission (SASE) the spontaneous radiation generated by an electron beam near the undulator entrance is amplified many orders of magnitude along the undulator. The transverse coherence properties of the amplified radiation depends on both the amplification process and the coherence of the seed radiation (the undulator radiation generated in the first gain length or so). The evolution of the transverse coherence in the amplification process is studied based on the solution of the coupled Maxwell-Vlasov equations including higher order transverse modes. The coherence of the seed radiation is determined by the number of coherent modes in the phase space area of the undulator radiation. We discuss the criterion of transverse coherence and identify governing parameters over a broad range of parameters. In particular we re-examine the well known emittance criterion for the undulator radiation, which states that full transverse coherence is guaranteed if the rms emittance is smaller than the wavelength divided by 4π. It is found that this criterion is modified for SASE because of the different optimization conditions required for the electron beam. Our analysis is a generalization of the previous study by Yu and Krinsky for the case of vanishing emittance with parallel electron beam. Understanding the transverse coherence of SASE is important for the X-ray free electron laser projects now under consideration at SLAC and DESY

Coherence in electron energy loss spectrometry

International Nuclear Information System (INIS)

Schattschneider, P.; Werner, W.S.M.

2005-01-01

Coherence effects in electron energy loss spectrometry (EELS) and in energy filtering are largely neglected although they occur frequently due to Bragg scattering in crystals. We discuss how coherence in the inelastically scattered wave field can be described by the mixed dynamic form factor (MDFF), and how it relates to the density matrix of the scattered electrons. Among the many aspects of 'inelastic coherence' are filtered high-resolution images, dipole-forbidden transitions, coherence in plasma excitations, errors in chemical microanalysis, coherent double plasmons, and circular dichroism

Coherent Behavior and the Bound State of Water and K(+) Imply Another Model of Bioenergetics: Negative Entropy Instead of High-energy Bonds.

Science.gov (United States)

Jaeken, Laurent; Vasilievich Matveev, Vladimir

2012-01-01

Observations of coherent cellular behavior cannot be integrated into widely accepted membrane (pump) theory (MT) and its steady state energetics because of the thermal noise of assumed ordinary cell water and freely soluble cytoplasmic K(+). However, Ling disproved MT and proposed an alternative based on coherence, showing that rest (R) and action (A) are two different phases of protoplasm with different energy levels. The R-state is a coherent metastable low-entropy state as water and K(+) are bound to unfolded proteins. The A-state is the higher-entropy state because water and K(+) are free. The R-to-A phase transition is regarded as a mechanism to release energy for biological work, replacing the classical concept of high-energy bonds. Subsequent inactivation during the endergonic A-to-R phase transition needs an input of metabolic energy to restore the low entropy R-state. Matveev's native aggregation hypothesis allows to integrate the energetic details of globular proteins into this view.

The SUSY oscillator from local geometry: Dynamics and coherent states

International Nuclear Information System (INIS)

Thienel, H.P.

1994-01-01

The choice of a coordinate chart on an analytical R n (R a n ) provides a representation of the n-dimensional SUSY oscillator. The corresponding Hilbert space is Cartan's exterior algebra endowed with a suitable scalar product. The exterior derivative gives rise to the algebra of the n-dimensional SUSY oscillator. Its euclidean dynamics is an inherent consequence of the geometry imposed by the Lie derivative generating the dilations, i.e. evolution of the quantum system corresponds to parametrization of a sequence of charts by euclidean time. Coherent states emerge as a natural structure related to the Lie derivative generating the translations. (orig.)

Large-Scale Curriculum Reform in Finland--Exploring the Interrelation between Implementation Strategy, the Function of the Reform, and Curriculum Coherence

Science.gov (United States)

Pietarinen, Janne; Pyhältö, Kirsi; Soini, Tiina

2017-01-01

The study aims to gain a better understanding of the national large-scale curriculum process in terms of the used implementation strategies, the function of the reform, and the curriculum coherence perceived by the stakeholders accountable in constructing the national core curriculum in Finland. A large body of school reform literature has shown…

Coherent vector-meson photoproduction with nuclear breakup in relativistic heavy-ion collisions

International Nuclear Information System (INIS)

Baltz, Anthony J.; Klein, Spencer R.; Nystrand, Joakim

2002-01-01

Relativistic heavy ions are copious sources of virtual photons. The large photon flux gives rise to a substantial photonuclear interaction probability at impact parameters where no hadronic interactions can occur. Multiple photonuclear interactions in a single collision are possible. In this Letter, we use mutual Coulomb excitation of both nuclei as a tag for moderate-impact-parameter collisions. We calculate the cross section for coherent vector-meson production accompanied by mutual excitation and show that the median impact parameter is much smaller than for untagged production. The vector-meson rapidity and transverse-momentum distribution are very different from untagged exclusive vector-meson production

Coherence matrix of plasmonic beams

DEFF Research Database (Denmark)

Novitsky, Andrey; Lavrinenko, Andrei

2013-01-01

We consider monochromatic electromagnetic beams of surface plasmon-polaritons created at interfaces between dielectric media and metals. We theoretically study non-coherent superpositions of elementary surface waves and discuss their spectral degree of polarization, Stokes parameters, and the for...... of the spectral coherence matrix. We compare the polarization properties of the surface plasmonspolaritons as three-dimensional and two-dimensional fields concluding that the latter is superior....

Calculation of the Coherent Synchrotron Radiation Impedance from a Wiggler

International Nuclear Information System (INIS)

Wu, Juhao

2003-01-01

Most studies of Coherent Synchrotron Radiation (CSR) have only considered the radiation from independent dipole magnets. However, in the damping rings of future linear colliders, a large fraction of the radiation power will be emitted in damping wigglers. In this paper, the longitudinal wakefield and impedance due to CSR in a wiggler are derived in the limit of a large wiggler parameter K. After an appropriate scaling, the results can be expressed in terms of universal functions, which are independent of K. Analytical asymptotic results are obtained for the wakefield in the limit of large and small distances, and for the impedance in the limit of small and high frequencies

CALCULATION OF THE COHERENT RADIATION IMPDENACE FROM A WIGGLER

International Nuclear Information System (INIS)

Wu, J

2004-01-01

Most studies of coherent synchrotron radiation (CSR) have considered only the radiation from independent dipole magnets. However, in the damping rings of future linear colliders and many high luminosity factories, a large fraction of the radiation power will be emitted in damping wigglers. In this paper, the longitudinal wakefield and impedance due to CSR in a wiggler are derived in the limit of a large wiggler parameter K. After an appropriate scaling, the results can be expressed in terms of universal functions, which are independent of K. Analytical asymptotic results are obtained for the wakefield in the limit of large and small distances, and for the impedance in the limit of small and high frequencies

Coherent structures in the Es layer and neutral middle atmosphere

Science.gov (United States)

Mošna, Zbyšek; Knížová, Petra Koucká; Potužníková, Kateřina

2015-12-01

The present paper shows results from the summer campaign performed during geomagnetically quiet period from June 1 to August 31, 2009. Within time-series of stratospheric and mesospheric temperatures at pressure levels 10-0.1 hPa, mesospheric winds measured in Collm, Germany, and the sporadic E-layer parameters foEs and hEs measured at the Pruhonice station we detected specific coherent wave-bursts in planetary wave domain. Permanent wave-like activity is observed in all analyzed data sets. However, the number of wave-like structures persistent in large range of height from the stratosphere to lower ionosphere is limited. The only coherent modes that are detected on consequent levels of the atmosphere are those corresponding to eigenmodes of planetary waves.

The separation of vibrational coherence from ground- and excited-electronic states in P3HT film

KAUST Repository

Song, Yin; Hellmann, Christoph; Stingelin, Natalie; Scholes, Gregory D.