Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

We revisited the quantum Zeno paradox, which claims that a generic quantum system prepared in a state which is not an eigenstate of the Hamiltonian operator and is continuously observed never decays. Since any perfectly isolated quantum system always interact with a vacuum field, we analyze the possibility of using this fact to solve the above mentioned conceptual problem. Therefore we discuss a two-level system or qubit-Bose field interaction Hamiltonians. We consider the quantum dynamics of this two-level system, prepared in the excited state interacting with a Bose field prepared in the Poincare invariant vacuum state. Using a first-order approximation in time-dependent perturbation theory, we evaluate the probability of spontaneous decay of the two-level system driven by the ...

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Science.gov (United States)

A quantum secure direct communication scheme using dense coding is proposed. At first, the sender (Alice) prepares four-particle genuine entangled states and shares them with the receiver (Bob) by sending two particles in each entangled state to him. Secondly, Alice encodes secret information by performing the unitary transformations on her particles and transmits them to Bob. Finally, Bob performs the joint measurements on his particles to decode the secret information. The two-step security test guarantees the security of communication.

Energy Technology Data Exchange (ETDEWEB)

Since information has been regarded os a physical entity, the field of quantum information theory has blossomed. This brings novel applications, such as quantum computation. This field has attracted the attention of numerous researchers with backgrounds ranging from computer science, mathematics and engineering, to the physical sciences. Thus, we now have an interdisciplinary field where great efforts are being made in order to build devices that should allow for the processing of information at a quantum level, and also in the understanding of the complex structure of some physical processes at a more basic level. This thesis is devoted to the theoretical study of structures at the nanometer-scale, 'nanostructures', through physical processes that mainly involve the solid-state and quantum optics, in order to propose reliable schemes for the processing of ...

International Nuclear Information System (INIS)

The authors present a summary of the present state of the quantum field theory of tachyons. (W.D.L.).

Energy Technology Data Exchange (ETDEWEB)

Recently, the public has become aware of keywords like ''Quantum computer'' or ''Quantum cryptography''. Regarding their potential application in solid state based quantum information processing and their overall benefit in fundamental research quantum dots have gained more and more public interest. In this context, quantum dots are often referred to as ''artificial atoms'', a term subsuming their physical properties quite nicely and emphasizing the huge potential for further investigations. The basic mechanism to be considered is the theoretical model of a two-level system. A quantum dot itself represents this kind of system quite nicely, provided that only the presence or absence of a single exciton in the ground ...

International Nuclear Information System (INIS)

Quantum key distribution (QKD) can, in principle, provide unconditional security based on the fundamental laws of physics. Unfortunately, a practical QKD system may contain overlooked imperfections and may thus violate some of the assumptions in the security proofs of QKD. It is important to explore these assumptions. One key assumption is that the sender (Alice) can prepare the required quantum states without errors. However, such an assumption may be violated in a practical QKD system. In this paper, we perform a proof-of-principle experiment to demonstrate a technically feasible 'intercept- and-resend' attack that exploits such a security loophole in a commercial 'plug and play' QKD system. The resulting quantum bit error rate is 19.7%, which is substantially lower than the well-known 25% error rate for an intercept-and-resend attack in BB84. The attack we utilize is the ...

Energy Technology Data Exchange (ETDEWEB)

At the occasion of the OECS conference in Madrid, we give a succinct account of some recent predictions in the spectroscopy of a quantum dot in a microcavity that remain to be observed experimentally, sometimes within the reach of the current state of the art.

CERN Document Server

When quantum gravity is used to discuss the big bang singularity, the most important, though rarely addressed, question is what role genuine quantum degrees of freedom play. Here, complete effective equations are derived for isotropic models with an interacting scalar to all orders in the expansions involved. The resulting coupling terms show that quantum fluctuations do not affect the bounce much. Quantum correlations, however, do have an important role and could even eliminate the bounce. How quantum gravity regularizes the big bang depends crucially on properties of the quantum state.

CERN Document Server

By using a laser and maser in tandem, it is possible to obtain laser action in the hot exhaust gases involved in heat engine operation. Such a "quantum afterburner" involves the internal quantum states of working gas atoms or molecules as well as the techniques of cavity quantum electrodynamics and is therefore in the domain of quantum thermodynamics. As an example, it is shown that Otto cycle engine performance can be improved beyond that of the "ideal" Otto heat engine.

CERN Document Server

We study quantum Darwinism -- the redundant recording of information about a decohering system by its environment -- in zero-temperature quantum Brownian motion. An initially nonlocal quantum state leaves a record whose redundancy increases rapidly with its spatial extent. Significant delocalization (e.g., a Schroedinger's Cat state) causes high redundancy: many observers can measure the system's position without perturbing it. This explains the objective (i.e. classical) existence of einselected, decoherence-resistant pointer states of macroscopic objects.

Science.gov (United States)

A controlled bidirectional quantum secret direct communication scheme is proposed by using a Greenberger-Horne-Zeilinger (GHZ) state. In the scheme, two users can exchange their secret messages simultaneously with a set of devices under the control of a third party. The security of the scheme is analysed and confirmed.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

The diamond norm measures the distance between two quantum channels. From an operational viewpoint, this norm measures how well we can distinguish between two channels by applying them to the input states of arbitrarily large dimensions. In this paper, we show that the diamond norm can be conveniently, and in a physically transparent way, computed by means of a Monte Carlo algorithm based on the Fano representation of quantum states and quantum operations. The effectiveness of this algorithm is illustrated for several single-qubit quantum channels.

Energy Technology Data Exchange (ETDEWEB)

A theoretical study of an exciton confined in a quantum ring is presented. The quantum ring is described as a two-dimensional circular quantum dot with a repulsive core, which is modelled with the help of two Gaussian functions. We have applied the variational method and investigated the evolution of the low-energy exciton spectrum with the change of the confinement potential. The calculations have been performed for the recently produced self-assembled ring-shaped InGaAs quantum dots. We have shown that the repulsive core strongly increases the radiative transition probability from the exciton ground state at the expense of the decreasing probability of the transitions from the excited states. This effect results from the orthogonality properties of the exciton wavefunctions, which are specific to the quantum-ring confinement potential. We ...

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Science.gov (United States)

This is the homepage of "an Australian multi-university collaboration undertaking research on the fundamental physics and technology of building, at the atomic level, a solid state quantum computer in silicon together with other high potential implementations." Although attempts to develop a quantum computer have met with limited success, the centre has substantial resources invested in advancing toward practical uses of quantum computing technology. The site provides a very good introduction to the principles and implications of quantum computing, as well as details about various research projects underway at the Australian universities. Links to conference and journal papers produced by members of the centre, many from 2003, are also provided.

Energy Technology Data Exchange (ETDEWEB)

In this talk, we explore the feasibility of quantum computation using continuous-variable systems by means of local measurements only. In the first part of the talk, we will identify crucial limitations that arise when starting from Gaussian cluster states. This is done by resorting to a Gaussian projected entangled pair picture as well as to notions of continuous-variable quantum repeater networks. In the second part, we look at instances in which these limitations can be overcome, and how suitable encodings of qubits in oscillators and feasible non-Gaussian resource states give rise to universal schemes for quantum computing.

International Nuclear Information System (INIS)

A measuring-basis encrypted quantum key distribution scheme is proposed by using twelve nonorthogonal states in a four-state system and the measuring-basis encryption technique. In this scheme, two bits of classical information can be encoded on one four-state particle and the transmitted particles can be fully used.

Energy Technology Data Exchange (ETDEWEB)

The difference between the two nonclassical lights, i.e., the squeezed state and number-phase minimum uncertainty state (NUS) is discussed. The four different generation principles for NUS are described. They are: unitary evolution using self-phase modulation; nonunitary state reduction by the first kind measurement; controlled state reduction by quantum correlation measurement-feedback, and high saturated laser oscillation with suppressed-pump-noise. The constant current-driven semiconductor laser based on the last principle generated the NUS with photon number noise reduced below the standard quantum limit by 40 percent in the entire frequency region from dc to 1.1 GHz. Several applications of NUS including quantum communication, quantum mechanical computers and interferometric gravitational detection are discussed ...

Energy Technology Data Exchange (ETDEWEB)

We propose a novel scheme for scalable solid state quantum computing, where superconducting microwave transmission line resonators (cavities) are arranged in a two-dimensional grid on the surface of a chip, coupling to superconducting qubits (charge or flux) at the intersections. We analyze how tasks of quantum information processing can be implemented in such a topology, including efficient two-qubit gates between any two qubits on the grid and elements of fault-tolerant computation.

Energy Technology Data Exchange (ETDEWEB)

The construction of networks consisting of optically interconnected processing units is a promising way to scale up quantum information processing systems. To store quantum information, single trapped atoms are among the most proven candidates. By placing them in high finesse optical resonators, a bidirectional information exchange between the atoms and photons becomes possible with, in principle, unit efficiency. Such an interface between stationary and ying qubits constitutes a possible node of a future quantum network. The results presented in this thesis demonstrate the prospects of a quantum interface consisting of a single atom trapped within the mode of a high-finesse optical cavity. In a two-step process, we distribute entanglement between the stored atom and two subsequently emitted single photons. The long atom trapping times achieved in the system together with the high photon collection ...

Science.gov (United States)

Two avowable quantum communication schemes are proposed. One is an avowable teleportation protocol based on the quantum cryptography. In this protocol one teleports a set of one-particle states based on the availability of an honest arbitrator, the keys and the Einstein Podolsky Rosen pairs shared by the communication parties and the arbitrator. The key point is that the fact of the teleportation can neither be disavowed by the sender nor be denied by the receiver. Another is an avowable quantum secure direct communication scheme. A one-way Hash function chosen by the communication parties helps the receiver to validate the truth of the information and to avoid disavowing for the sender.

DEFF Research Database (Denmark)

We suggest and study designed defects in an otherwise periodic potential modulation of a two-dimensional electron gas as an alternative approach to electron spin based quantum information processing in the solid-state using conventional gate-defined quantum dots. We calculate the band structure and density of states for a periodic potential modulation, referred to as an antidot lattice, and find that localized states appear, when designed defects are introduced in the lattice. Such defect states may form the building blocks for quantum computing in a large antidot lattice, allowing for coherent electron transport between distant defect states in the lattice, and for a tunnel coupling of neighboring defect states with corresponding electrostatically controllable exchange coupling between different ...

International Nuclear Information System (INIS)

The theory of spontaneous decay is studied using both quantum electrodynamics (QED) and semiclassical theories of radiation. There are qualitative differences between the theories in the prediction of interference phenomena. In QED, systems which were excited with pulsed laser light do not exhibit quantum interference effects associated with lower state splittings. On the other hand, semiclassical treatments of spontaneous decay do indicate the existence of interference effects not present in QED. In addition to this, differences are found between the predictions of fluorescence intensity in the presence of lower-state level crossings under continuous excitation. (U.S.).

CERN Document Server

Classical control theory has played a major role in the development of present-day technologies. Likewise, recently developed quantum optimal control methods can be applied to emerging quantum technologies, e.g. quantum information processing -- until now, at the level of a few qubits. However, such methods encounter severe limits when applied to many-body quantum systems: due to the complexity of simulating the latter, existing quantum control algorithms (requiring many iterations to converge) usually fail to yield a desired final state within an acceptable computational time. In contrast, we present here a strategy for controlling a vast range of non-integrable one-dimensional systems that is efficiently applicable to quantum many-body systems, as it can be merged with state-of-the-art tensor network simulation methods ...

Energy Technology Data Exchange (ETDEWEB)

The supersymmetry in quantum mechanics and shape invariance condition are applied as an algebraic method to solving the Dirac-Coulomb problem. The ground state and the excited states are investigated via new generalized ladder operators. (author)

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

CERN Document Server

The unavoidable irreversible losses of power in a heat engine are found to be of quantum origin. Following thermodynamic tradition a model quantum heat engine operating by the Otto cycle is analyzed. The working medium of the model is composed of an ensemble of harmonic oscillators. A link is established between the quantum observables and thermodynamical variables based on the concept of canonical invariance. These quantum variables are sufficient to determine the state of the system and with it all thermodynamical variables. Conditions for optimal work, power and entropy production show that maximum power is a compromise between the quasistatic limit of adiabatic following on the compression and expansion branches and a sudden limit of very short time allocation to these branches. At high temperatures and quasistatic operating conditions the efficiency at maximum power coincides ...

CERN Document Server

Bargmann's superselection rule, which forbids the existence of superpositions of states with different mass and, therefore, implies the impossibility of describing unstable particles in non-relativistic quantum mechanics, arises as a consequence of demanding Galilean covariance of Schr\\"odinger's equation. However, the usual Galilean transformations inadequately describe the symmetries of non-relativistic quantum mechanics since they fail to take into account relativistic time contraction effects which can produce non-relativistic phases in the wavefunction. In this paper we describe the incompatibility between Bargmann's rule and Lorentz transformations in the low-velocities limit, we analyze its classical origin and we show that the Extended Galilei group characterizes better the symmetries of the theory. Furthermore, we claim that a proper description of non-relativistic quantum mechanics requires a ...

CERN Document Server

We consider the role of quantum effects in the transfer of hyrogen-like species in enzyme-catalysed reactions. This study is stimulated by claims that the observed magnitude and temperature dependence of kinetic isotope effects imply that quantum tunneling below the energy barrier associated with the transition state significantly enhances the reaction rate in many enzymes. We use a path integral approach which provides a general framework to understand tunneling in a quantum system which interacts with an environment at non-zero temperature. Here the quantum system is the active site of the enzyme and the environment is the surrounding protein and water. Tunneling well below the barrier only occurs for temperatures less than a temperature $T_0$ which is determined by the curvature of potential energy surface near the top of the barrier. We argue that for most enzymes this ...

Energy Technology Data Exchange (ETDEWEB)

We introduce a novel scheme for one-way quantum computing (QC) based on the use of information encoded qubits in an effective cluster state resource. With the correct encoding structure, we show that it is possible to protect the entangled resource from phase damping decoherence, where the effective cluster state can be described as residing in a decoherence-free subspace (DFS) of its supporting quantum system. One-way QC then requires either single or two-qubit adaptive measurements. As an example where this proposal can be realized, we describe an optical lattice set-up where the scheme provides robust quantum information processing. We also outline how one can adapt the model to provide protection from other types of decoherence.

Energy Technology Data Exchange (ETDEWEB)

Hamiltonian light-front dynamics of quantum fields may provide a useful approach to systematic nonperturbative approximations to quantum field theories. The authors investigate inequivalent Hilbert-space representations of the light-front field algebra in which the stability group of the light front is implemented by unitary transformations. The Hilbert space representation of states is generated by the operator algebra from the vacuum state. There is a large class of vacuum states besides the Fock vacuum which meets all the invariance requirements. The light-front Hamiltonian must annihilate the vacuum and have a positive spectrum. Relations are exhibited of the Hamiltonian to the nontrivial vacuum structure. 30 refs.

International Nuclear Information System (INIS)

We propose a scheme of quantum computation with nonlinear quantum optics. Polarization states of photons are used for qubits. Photons with different frequencies represent different qubits. Single qubit rotation operation is implemented through optical elements like the Faraday polarization rotator. Photons are separated into different optical paths, or merged into a single optical path using dichromatic mirrors. The controlled-NOT gate between two qubits is implemented by the proper combination of parametric up and down conversions. This scheme has the following features: (1) No auxiliary qubits are required in the controlled-NOT gate operation; (2) No measurement is required in the course of the computation; (3) It is resource efficient and conceptually simple.

CERN Document Server

The quantum $N$-body problem is studied in the context of nonrelativistic quantum mechanics with a one-dimensional deformed Heisenberg algebra of the form $[\\hat x,\\hat p]=i(1+\\beta \\hat p^2)$, leading to the existence of a minimal observable length $\\sqrt\\beta$. For a generic pairwise interaction potential, analytical formulas are obtained that allow to estimate the ground-state energy of the $N$-body system by finding the ground-state energy of a corresponding two-body problem. It is first shown that, in the harmonic oscillator case, the $\\beta$-dependent term grows faster with $N$ than the $\\beta$-independent one. Then, it is argued that such a behavior should be observed also with generic potentials and for $D$-dimensional systems. In consequence, quantum $N$-body bound states might be interesting places to look at nontrivial manifestations of a ...

CERN Document Server

The problem of a spin 1 charged particle with electromagnetic polarizability, obeying a generalized 15-component quantum mechanical equation, is investigated in presence of the external Coulomb potential. With the use of the Wigner's functions techniques, separation of variables in the spherical tetrad basis is done and the 15-component radial system is given. It is shown that there exists a class of quantum states for which the additional characteristics, polarizability, does not manifest itself anyhow; at this the energy spectrum of the system coincides with the known spectrum of the scalar particle. For j=0 states, a 2-order differential equation is derived, it contains an additional potential term 1/r^{4}. In analogous approach wave functions the generalized particle are examined in presence of external Dirac monopole field. It is shown that there exists one special state with ...

Energy Technology Data Exchange (ETDEWEB)

We propose an extension of Gaussian mixture models in the statistical-mechanical point of view. The conventional Gaussian mixture models are formulated to divide all points in given data to some kinds of classes. We introduce some quantum states constructed by superposing conventional classes in linear combinations. Our extension can provide a new algorithm in classifications of data by means of linear response formulas in the statistical mechanics.

CERN Document Server

The Arnowitt-Deser-Misner canonical formulation of general relativity is extended to the covariant brane-world theory in arbitrary dimensions. The exclusive probing of the extra dimensions makes a substantial difference, allowing for the construction of a non-constrained canonical theory. The quantum states of the brane-world geometry are defined by the Tomonaga-Schwinger equation, whose integrability conditions are determined by the classical perturbations of submanifolds contained in the Nash's differentiable embedding theorem. In principle, quantum brane-world theory can be tested by current experiments in astrophysics and by near future laboratory experiments at Tev energy. The implications to the black-hole information loss problem, to the accelerating cosmology, and to a quantum mathematical theory of four-sub manifolds are briefly commented.

CERN Document Server

The quantum nature of the electromagnetic field imposes a fundamental limit on the sensitivity of optical precision measurements such as spectroscopy, microscopy, and interferometry. The so-called quantum limit is set by the zero-point fluctuations of the electromagnetic field, which constrain the precision with which optical signals can be measured. In the world of precision measurement, laser-interferometric gravitational wave (GW) detectors are the most sensitive position meters ever operated, capable of measuring distance changes on the order of 10^-18 m RMS over kilometer separations caused by GWs from astronomical sources. The sensitivity of currently operational and future GW detectors is limited by quantum optical noise. Here we demonstrate a 44% improvement in displacement sensitivity of a prototype GW detector with suspended quasi-free mirrors at frequencies where the sensitivity is shot-noise-limited, by ...

International Nuclear Information System (INIS)

The canonical quantum theory of gravity-quantum geometrodynamics (QG)-is applied to the homogeneous Bianchi type IX cosmological model. As a result, a framework for the quantum theory of homogeneous cosmologies is developed. We show that the theory is internally consistent and prove that it possesses the correct classical limit (the theory of general relativity). To emphasize the special role that the constraints play in this new theory, we compare it to the traditional ADM square-root and Wheeler-DeWitt quantization schemes. We show that, unlike traditional approaches, QG leads to a well-defined Schroedinger equation for the wavefunction of the universe that is inherently coupled to the expectation value of the constraint equations. This coupling to the constraints is responsible for the appearance of a coherent spacetime picture. Thus, the physical meaning of the constraints of the theory is quite different from Dirac's ...

Energy Technology Data Exchange (ETDEWEB)

Semiconductor nanocrystals smaller than the bulk exciton show substantial quantum confinement effects. Recent experiments including Stark effect, resonance Raman, valence band photoemission, and near edge X-ray adsorption will be used to put together a picture of the nanocrystal electronic states.

International Nuclear Information System (INIS)

We present a deterministic secure direct communication scheme via entanglement swapping, where a set of ordered maximally entangled three-particle states (GHZ states), initially shared by three spatially separated parties, Alice, Bob and Charlie, functions as a quantum information channel. After ensuring the safety of the quantum channel, Alice and Bob apply a series of local operations on their respective particles according to the tripartite stipulation and the secret message they both want to send to Charlie. By three of Alice, Bob and Charlie's Bell measurement results, Charlie is able to infer the secret messages directly. The secret messages are faithfully transmitted from Alice and Bob to Charlie via initially shared pairs of GHZ states without revealing any information to a potential eavesdropper. Since there is no transmission of the qubits carrying the secret message ...

CERN Document Server

Quantum man

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

Many-particle confinement (localization) is studied for a 1D system of spinless fermions with nearest-neighbour hopping and interaction, or equivalently, for an anisotropic Heisenberg spin-1/2 chain. This system is frequently used to model quantum computers with perpetually coupled qubits. We construct a bounded sequence of site energies that leads to strong single-particle confinement of all states on individual sites. We show that this sequence also leads to a confinement of all many-particle states in an infinite system for a time that scales as a high power of the reciprocal hopping integral. The confinement is achieved for strong interaction between the particles while keeping the overall bandwidth of site energies comparatively small. The results show the viability of quantum computing with time-independent qubit coupling.

CERN Document Server

Solid-state single-photon sources have many desirable features that make them attractive for applications in quantum information processing. However, the phase coherence of such devices can be severely compromised by coupling to the solid-state environment. Here, we study the effects of realistic dephasing environments on a pair of solid-state single photon sources in the context of quantum interference effects such as the Hong-Ou-Mandel dip. By means of exact solutions for the non-Markovian dynamics of the sources, we show that the resulting loss of visibility depends crucially on the timing of photon detection events. Our results demonstrate that the effective visibility can be improved via temporal post-selection, and also that time-resolved interference can be a useful probe of the interaction between the emitter and its host environment.

International Nuclear Information System (INIS)

In this paper, molecular quantum computation is numerically studied with the quantum search algorithm (Grover's algorithm) by means of optimal control simulation. Qubits are implemented in the vibronic states of I_2, while gate operations are realized by optimally designed laser pulses. The methodological aspects of the simulation are discussed in detail. We show that the algorithm for solving a gate pulse-design problem has the same mathematical form as a state-to-state control problem in the density matrix formalism, which provides monotonically convergent algorithms as an alternative to the Krotov method. The sequential irradiation of separately designed gate pulses leads to the population distribution predicted by Grover's algorithm. The computational accuracy is reduced by the imperfect quality of the pulse design and by the electronic decoherence processes that are modeled by the non-Markovian ...

UK PubMed Central (United Kingdom)

Quantum computing is a quickly growing research field. This article introduces the basic concepts of quantum computing, recent developments in quantum searching, and decoherence in a possible quantum...Full Text Available

CERN Document Server

The most striking feature of quantum mechanics is the existence of superposition states, where an object appears to be in different situations at the same time. Up to now, the existence of such states has been tested with small objects, like atoms, ions, electrons and photons, and even with molecules. Recently, it has been even possible to create superpositions of collections of photons, atoms, or Cooper pairs. Current progress in optomechanical systems may soon allow us to create superpositions of even larger objects, like micro-sized mirrors or cantilevers, and thus to test quantum mechanical phenomena at larger scales. Here we propose a method to cool down and create quantum superpositions of the motion of sub-wavelength, arbitrarily shaped dielectric objects trapped inside a high--finesse cavity at a very low pressure. Our method is ideally suited for the smallest living ...

Science.gov (United States)

We propose a simultaneous quantum secure direct communication scheme between one party and other three parties via four-particle GHZ states and swapping quantum entanglement. In the scheme, three spatially separated senders, Alice, Bob and Charlie, transmit their secret messages to a remote receiver Diana by performing a series of local operations on their respective particles according to the quadripartite stipulation. From Alice, Bob, Charlie and Diana's Bell measurement results, Diana can infer the secret messages. If a perfect quantum channel is used, the secret messages are faithfully transmitted from Alice, Bob and Charlie to Diana via initially shared pairs of four-particle GHZ states without revealing any information to a potential eavesdropper. As there is no transmission of the qubits carrying the secret message in the public channel, it is completely secure for the direct ...

CERN Document Server

We use the semi-classical approximation in perturbative scalar quantum electrodynamics to calculate the quantum correction to the Larmor radiation formula to first order in Planck's constant in the non-relativistic approximation, choosing the initial state of the charged particle to be a momentum eigenstate. We calculate this correction in two cases: in the first case the charged particle is accelerated by a time-dependent but space-independent vector potential whereas in the second case it is accelerated by a time-independent vector potential which is a function of one spatial coordinate. We find that the corrections in these two cases are different even for a charged particle with the same classical motion. The correction in each case turns out to be non-local in time in contrast to the classical approximation.

CERN Document Server

The structure of irreducible representations of (restricted) U_q(sl(3)) at roots of unity is understood within the Gelfand--Zetlin basis. The latter needs a weakened definition, where the quadratic Casimir operator of the quantum subalgebra U_q(sl(2)) of U_q(sl(3)) is not completely diagonalized. This is necessary in order to take in account the indecomposable U_q(sl(2))-modules that appear. The set of redefined (mixed) states has a teepee shape inside the pyramid made with the whole representation.

International Nuclear Information System (INIS)

Recent work on N=2 supersymmetric Bianchi type IX cosmologies coupled to a scalar field is extended to a general treatment of homogeneous quantum cosmologies with explicitly solvable momentum constraints, i.e., Bianchi types I, II, VII, VIII in addition to the Bianchi type IX, and special cases, namely, the Freidmann universes, the Kantowski-Sachs space, and Taub-NUT space. In addition to the earlier explicit solution of the Wheeler-DeWitt equation for Bianchi type IX, describing a virtual wormhole fluctuation, an additional explicit solution is given and identified with the ''no-boundary state.''.

CERN Document Server

We consider non-relativistic systems in quantum mechanics interacting through the Coulomb potential, and discuss the existence of bound states which are stable against spontaneous dissociation into smaller atoms or ions. We review the studies that have been made of specific mass configurations and also the properties of the domain of stability in the space of masses or inverse masses. These rigorous results are supplemented by numerical investigations using accurate variational methods. A section is devoted to systems of three arbitrary charges and another to molecules in a world with two space-dimensions.

CERN Document Server

We describe a scheme for quantum error correction that employs feedback and weak measurement rather than the standard tools of projective measurement and fast controlled unitary gates. The advantage of this scheme over previous protocols (for example Ahn et. al, PRA, 65, 042301 (2001)), is that it requires little side processing while remaining robust to measurement inefficiency, and is therefore considerably more practical. We evaluate the performance of our scheme by simulating the correction of bit-flips. We also consider implementation in a solid-state quantum computation architecture and estimate the maximal error rate which could be corrected with current technology.

Energy Technology Data Exchange (ETDEWEB)

An algebraic formulation of the electromagnetic field in which various quantization procedures can be described was chosen to discuss perturbation calculations. It is shown that the Feynman rules and the second order calculation of the self-energy of the electron can be developed on the basis of the Fermi method of quantization. The algebraic approach clarifies the problems in defining the vacuum and other states which are associated with calculations in terms of field algebra operators. It is demonstrated that the vacuum state defined on the field algebra by Schwinger leads to incorrect results in the self-energy calculation.

UK PubMed Central (United Kingdom)

The synthesis of a new kind of magnetic, fluorescent multifunctional nanoparticles (~30 nm in diameter) was demonstrated, where multiple fluorescent CdTe quantum dots (QDs) are covalently linked...Full Text Available

CERN Document Server

We propose genuine ($k$, $m$)-threshold controlling schemes for controlled teleportation via multi-particle entangled states, where the teleportation of a quantum state from a sender (Alice) to a receiver (Bob) is under the control of $m$ supervisors such that $k$ ($k\\leq m$) or more of these supervisors can help Bob recover the transferred state. By construction, anyone of our quantum channels is a genuine multipartite entangled state of which any two parts are inseparable. Their properties are compared and contrasted with those of the well-known Greenberger-Horne-Zeilinger, W, and linear cluster states, and also several other genuine multipartite entangled states recently introduced in literature. We show that our schemes are secure against both Bob's dishonesty and supervisors' treacheries. For the latter case, the ...

Energy Technology Data Exchange (ETDEWEB)

Langmuir-Blodgett (LB) preparations containing stacked monolayers of phospholipids or stearic acid were irradiated with UV light and the electric conductance perpendicular to the planes of the monolayers was measured. There was no observable change of conductance when LB preparations of stearic acid were irradiated. For LB preparations of phospholipids, a rise of conductance, dependent on dose rate, was observed, reaching an equilibrium level after a few hours. After irradiation the conductance fell with a temperature-dependent time constant, and eventually reached a final level a little above the initial value. A three-state model is proposed for the LB phospholipid preparations. This suggests that the absorption of one photon raises a molecule from the ground to an excited state; and the absorption of a second photon carries it into a damaged but repairable or ...

Science.gov (United States)

We study a two-level atom in interaction with a real massless scalar quantum field in a spacetime with a reflecting boundary. The presence of the boundary modifies the quantum fluctuations of the scalar field, which in turn modifies the radiative properties of atoms. We calculate the rate of change of the mean atomic energy of the atom for both inertial motion and uniform acceleration. It is found that the modifications induced by the presence of a boundary make the spontaneous radiation rate of an excited inertial atom oscillate near the boundary and this oscillatory behavior may offer a possible opportunity for experimental tests for geometrical (boundary) effects in flat spacetime. While for accelerated atoms, the transitions from ground states to excited states are found to be possible even in a vacuum due to changes in the vacuum fluctuations induced by both the presence of the boundary and the ...

Science.gov (United States)

Recent proposals have shown that a quantum degenerate gas of alkaline earth atoms can be used for a number of novel quantum computing and quantum simulation experiments. Strontium is a good candidate for such experiments because it can be controlled with high precision, as demonstrated in recent atomic clock experiments. Unfortunately, the small scattering length of strontium is not amenable to evaporative cooling techniques that are used to reach quantum degeneracy. Furthermore, increasing the scattering length of alkaline earths with a magnetic Feshbach resonance is not possible due to their spinless electronic ground state configuration. However, recent theoretical and experimental work suggests the possibility of changing scattering lengths in alkaline earths with laser light. Using this optical Feshbach resonance near strontium's narrow ^1S0->^3P1 intercombination transition ...

Science.gov (United States)

... of Packaging Requirements. MIL-STD-2073-1 DoD Packaging Data Forms Instruction for Preparation and Use. I DATA ...

International Nuclear Information System (INIS)

(Jun 1972). United States Woolson, WA Las Vegas, Nev. 18 Jun 1972.

Energy Technology Data Exchange (ETDEWEB)

The synthesis, characterization, and photophysical properties of several Pt(II) complexes of quinoxaline-2,3-dithiolate (qdt) and 6,7-dimethylquinoxaline-2,3-dithiolate (dmqdt) are described. Specifically, (TBA){sub 2}[Pt(qdt){sub 2}], where TBA = tetra-n-butylammonium, Pt(COD)(qdt), where COD = 1,5-cyclooctadiene, and Pt(phen)(qdt), where phen = 1,10-phenanthroline, and their dmqdt analogs have been prepared and examined with respect to their photophysical properties. Highly structured emission from Pt(COD)(qdt) in frozen glass solution at 77 K has been detected, having a major vibrational progression of 1370 cm{sup {minus}1} corresponding to a C=C stretching frequency of the quinoxalinedithiolate backbone. Solution luminescence from (TBA){sub 2}[Pt(qdt){sub 2}] and Pt(phen)(qdt) has been detected with quantum yields, {Phi}{sub em}, of 10{sup {minus}5} and 10{sup {minus}3}, respectively, although the latter is highly sensitive to solvent ...

Energy Technology Data Exchange (ETDEWEB)

We numerically constructed elementary phase-correct global quantum gates by using molecular electronic and vibrational states to encode two qubits and implement the Deutsch-Jozsa algorithm. The calculations were based on optimal control theory (OCT). The molecular species we chose were Na{sub 2} and Li{sub 2}. The electronic X{sup 1}{sigma}{sub g}{sup +} and A{sup 1}{sigma}{sub u}{sup +} states were taken as two orthonormalized energy levels of the electronic qubit. The vibrational qubits were those involved in these electronic states. The time duration of the optimized pulses with high fidelity was typically 500-900 fs, which reflects the wavepacket dynamics in electronically ground and excited states. When implementing the Deutsch-Jozsa algorithm by combining these elementary gates, we obtained a maximum probability 83.12% for Li{sub 2} molecule, which indicates that the ...

CERN Document Server

A simple and efficient method for characterization of multidimensional Gaussian states is suggested and experimentally demonstrated. Our scheme shows analogies with tomography of finite dimensional quantum states, with the covariance matrix playing the role of the density matrix and homodyne detection providing Stern-Gerlach-like projections. The major difference stems from a different character of relevant noises: while the statistics of Stern-Gerlach-like measurements is governed by binomial statistics, the detection of quadrature variances correspond to chi-square statistics. For Gaussian and near Gaussian states the suggested method provides, compared to standard tomography techniques, more stable and reliable reconstructions. In addition, by putting together reconstruction methods for Gaussian and arbitrary states, we obtain a tool to detect the non-Gaussian character of ...

International Nuclear Information System (INIS)

The details and principles of an apparatus built for measurements of fluorescence quantum yields and cascade-free lifetimes of open-shell cations are reported. These rely on the detection of coincidences between energy selected photo-electrons and undispersed photons. The results of such measurements for CO"+_2,COS"+,CS"+_2 and N_2O"+ in selected vibrational levels of their excited states are presented. Non-unity fluorescence quantum yields are found for some vibronic levels of CO"+_2(B), COS"+(A), N_2O"+(A) and a non-exponential decay is observed for CS"+_2(B). The data yield the following values for the radiative lifetimes: CO"+_2(A) 124 +- 6 ns,CO"+_2(B) 140 +- 7 ns, COS"+(A) 550 +- 50 ns and N_2O"+(A) 240 +- 12 ns. (orig.).

International Nuclear Information System (INIS)

The development of our understanding of the quantum states of nuclei is viewed from a historical perspective. The characteristics of nuclear energy levels are presented, and interpretations of these excitations in terms of simple vibrational and rotational modes are presented. The application of energy level schemes in a variety of fields is briefly summarized. (author). 18 refs., 7 figs.

Energy Technology Data Exchange (ETDEWEB)

We propose triplet superconductors, such as ruthenates, as prospective materials for qubit construction. The vectorial nature of the order parameter in triplet superconductors makes it conceptually easy to estimate the performance of the qubits. The Cooper condensate of pairs in triplet superconductors has all the attributes of Bose-Einstein condensates and should facilitate long decoherence times for these qubits, relative to other vectorial schemes for qubits, such as small ferromagnets. There are other benefits, which the superconducting state provides for requirements such as entanglement between qubits via the proximity effect, etc. We consider these benefits in detail, although our consideration is only preliminary and further experimental and theoretical research will undoubtedly introduce correctives.

Energy Technology Data Exchange (ETDEWEB)

Neutron deficient nuclei with mass numbers A {approx} 90 and 40 {<=} Z {<=} 44 have been studied making use of the Osiris and Nordball spectrometers. The high spin states of these nuclei and their electromagnetic decay properties are compared to shell model calculations based on the core {sup 88}Sr and using different parametrizations of the residual interaction. The dependence of the mean square deviations of experimental and theoretical level energies, branching ratios, and transition probabilities on the neutron numbers N = 46-50 and the validity of seniority as a good quantum number are discussed. (orig.).

CERN Document Server

We study dipolar bosons in a 1D optical lattice and identify a region in parameter space---strong coupling but relatively weak on-site repulsion---hosting a series of stable CDW states whose low-energy excitations, built from "fractional domain walls", are remarkably similar to those of non-abelian fractional quantum Hall states. Here, a conventional domain wall between translated CDW's may split by inserting strings of degenerate, but inequivalent, CDW states. Outside these insulating regions, we find numerous supersolids as well as a superfluid regime. The mentioned phases should be accessible experimentally, and in particular, the fractional domain walls can be created in the ground state using single-site addressing, i.e. by locally changing the chemical potential.

International Nuclear Information System (INIS)

The next relativistic correction to #alpha# to for bound state mass of two charged scalar particles is calculated in the quantum scalar electrodynamics by the functional integral method. Contribution of the ''nonphysical'' time variable turned out to be important and leads to nonanalytic dependence of the bound state mass on #alpha#. In conclusion, one can say that the functional approach is the best mathematical representation to preserve the gauge invariance. The lowest approximation of this functional representation is the pure nonrelativistic Feynman path integral representation of the nonrelativistic Schroedinger equation. The functional integral representation shows that any regular series for next corrections to #alpha# does not exist and these corrections cannot be reduced to some terms of the nonrelativistic potential in the Schroedinger picture. In other words, the ''nonphysical'' time coordinate is important and ...

Energy Technology Data Exchange (ETDEWEB)

Our investigation concerns the class of Josephson-like systems, sharing the same nonlinear Hamiltonian. Among the latter a Josephson junction with an external biasing circuit is considered. We diagonalize the fully nonlinear Hamiltonian (in the superconductive regime of the junction) in the Fock space of the TBHA (two-boson Heisenberg algebra) and prove that such algebra leads quite naturally to the theoretical realization of codewords and logical operators: the codewords are defined as the even and odd coherent states of the TBHA, while the logical operators are expressed in terms of operators in the same algebra. Our theoretical construction corresponds to a continuous variable quantum computation scheme; the continuous variables are identified in terms of the physical operators of the junction. The link between this scheme and the technique of fermionization of bosonic systems is also discussed.

CERN Document Server

We investigate decoherence in quantum systems coupled via dephasing-type interactions to an arbitrary environment with chaotic underlying classical dynamics. The coherences of the reduced state of the central system written in the preferential energy eigenbasis are quantum Loschmidt echoes, which in the strong coupling regime are characterized at long times scales by fluctuations around a constant mean value. We show that due to the chaotic dynamics of the environment, the mean value and the width of the Loschmidt echo fluctuations are inversely proportional to the quantity we define as the effective Hilbert space dimension of the environment, which in general is smaller than the dimension of the entire available Hilbert space. Nevertheless, in the semiclassical regime this effective Hilbert space dimension is in general large, in which case even a chaotic environment with few degrees of freedom produces decoherence without ...

Energy Technology Data Exchange (ETDEWEB)

The choice of vacuum state for a quantum scalar field propagating in a de Sitter spacetime (massive and arbitrarily coupled to the gravitational field) is discussed. The problem of finite-time initial conditions for the mode functions is analyzed, as well as how these determine the vacuum state of the quantum system. The principle guiding the choice of vacuum state is the following: one wants the vacuum contribution to the energy-momentum tensor to contain all the ultraviolet divergent terms, so that the particle creation terms are finite, and covariantly conserved. There is a suitable set of modes (instantaneous adiabatic basis) in which this splitting of the expectation value of the energy-momentum tensor can be carried out. Numerical results are presented for different finite-time initial conditions (m = 0.6, {zeta} = 1/6). The nature of the particle creation effect is described ...

International Nuclear Information System (INIS)

The antisymmetric many-body trial state which describes a system of interacting fermions is parametrized in terms of localized wave packets. The equations of motion are derived from the time-dependent quantum variational principle. The resulting fermionic molecular dynamics (FMD) equations include a wide range of semi-quantal to classical physics extending from deformed Hartree-Fock theory to newtonian molecular dynamics. Conservation laws are discussed in connection with the choice of the trial state. The model is applied to heavy-ion collisions with which its basic features are illustrated. The results show a great variety of phenomena including deeply inelastic collisions, fusion, incomplete fusion, fragmentation, neck emission, promptly emitted nucleons and evaporation. ((orig.)).

Energy Technology Data Exchange (ETDEWEB)

We provide an example in which the Heisenberg and the Schroedinger pictures of quantum mechanics give different results, thus confirming the statement of P.A.M. Dirac that the two pictures may lead to inequivalent results. We consider a one-dimensional nonrelativistic charged harmonic oscillator (frequency {omega}{sub 0} and mass m), and take into account the action of the radiation reaction and the vacuum electromagnetic forces on the charged oscillator. We show that the Heisenberg picture gives the correct value, {Dirac_h}{omega}{sub 0}/2, for the ground state energy of the harmonic oscillator in both cases of classical and quantized vacuum fields. In the case of the Schroedinger picture, considering classical vacuum fields, and using a simple calculation for the classical radiation reaction force that is valid in the limit of large mass (mc{sup 2} >> {Dirac_h}{omega}{sub 0}), we obtain the value {Dirac_h}{omega}{sub 0} for the ...

International Science & Technology Center (ISTC)

Realization of Pharmacological Tests, Development of the Specifications and Technical Documentation and Registration in the Russian Federation of Medical Products as Soluble Tablets of Acetylsalicylic Acid/Calcium Carbonate in Two Dosages Intended for use as Medical Products Smoothing, Febrifugal and Antiaggregation Action and Development of Technology of Tableting the Above-Stated Preparations

Energy Technology Data Exchange (ETDEWEB)

We study the static potential of open bosonic membranes in the 1/d approximation, where d is the space-time dimensionality. For a fixed square boundary of side length R we find, in contrast to the string potential, no critical distance below which tachyons appear. Instead, we find a correction factor to the classical potential, V/sub cl/=kR/sup 2/, which for small distances shifts the perturbative ground state energy by a positive constant. We interpret the shift as the mass gap of this quantum membrane.

Science.gov (United States)

The electronic transitions and photodissociation of the bromine molecule were studied in the visible-near UV continuum using dynamic simulation. The molar extinction coefficients in this study were obtained in numerical calculations. The quantum yields of the spin-orbit Br*(2 P 1/2) product at different photon frequencies were determined. Time-dependent density functional theory was used to analyze the highest five occupied and lowest five unoccupied Br2 orbitals. The transition to the 1? u state was found to be most probable in the visible-near UV absorption range.

International Nuclear Information System (INIS)

This paper describes the observation and partial wave analysis of 1203 (22 GeV) #pi#"-p #-># phi phi n events. This is an OZI suppressed channel in which the OZI suppression is found to be absent. Assuming QCD and the OZI rule as Ansatzen, it is concluded that the breakdown of the OZI suppression is due to glueballs. The g/sub T/(2160) and the g/sub T/(2320) with I/sup G/J/sup PC/ = 0"+2"+"+ are two resonances determined from the partial wave analysis. It is concluded that one or two primary glueballs with the above quantum numbers are responsible for the observed two states. A brief discussion of other glueball candidates and some relevant phenomenology is also included.

Energy Technology Data Exchange (ETDEWEB)

A simplified relativistic configuration interaction method is used to study the dielectronic satellite transition processes. In this method, the infinite resonant doubly excited states can be calculated, and furthermore, the whole high-n dielectronic satellite transition processes can be treated conveniently by interpolation (rather than extrapolation) in the frame of quantum defect theory. As an example, we calculate the contributions from high-n dielectronic satellites to the K{alpha} resonance line in helium-like iron, and the results are in good agreement with the experimental measurements. (orig.) 39 refs.

Energy Technology Data Exchange (ETDEWEB)

Effect of ultrasonic-wave irradiation on the Mn-Zn ferrite powder suspension prepared by solid-state reaction and alcoholic dehydration methods was investigated. Size, distribution, and morphology of the powders prepared at different temperatures were examined, as a function of irradiation time. It was observed that the powders were reduced in size by ultrasonic energy through distinct routes. 8 refs., 7 figs., 1 tab.

CERN Document Server

We discuss models of computing that are beyond classical. The primary motivation is to unearth the cause of nonclassical advantages in computation. Completeness results from computational complexity theory lead to the identification of very disparate problems, and offer a kaleidoscopic view into the realm of quantum enhancements in computation. Emphasis is placed on the `power of one qubit' model, and the boundary between quantum and classical correlations as delineated by quantum discord. A recent result by Eastin on the role of this boundary in the efficient classical simulation of quantum computation is discussed. Perceived drawbacks in the interpretation of quantum discord as a relevant certificate of quantum enhancements are addressed.

Energy Technology Data Exchange (ETDEWEB)

We study fluctuation properties of strength function phenomena by employing a quantum mechanical model where a single parent state couples with a large number of background states. The background system is devised in such a way that the classical dynamics of the system may show a regular, an irregular, or a chaotic character as a function of a single parameter. The coupling of the parent state to the background states produces a fragmentation of the parent state, giving rise to a strength function phenomenon. We study various measures of the strength function that characterize its bulk structure or fluctuation properties. They include energy moments, strength distribution, fractal dimensions of the strength function, and Fourier transform of the autocorrelation function. Some of these measures, such as strength distribution or Fourier transform of the ...

International Nuclear Information System (INIS)

A dense silica glass was prepared by consolidating a highly dispersed silicic acid powder (particle size 1H magic-angle spinning (MAS) NMR confirmed an increase in hydroxyl groups in the sample prepared by SPS relative to that of the conventional SiO2 reference glass. Aside from the comparably high water content, we conclude from the similarity of the IR-reflectance and the 29Si MAS NMR spectra of the SPS sample and the corresponding spectra of the conventionally prepared silica glass, that the short- and medium-range order is virtually the same in both materials. Raman spectroscopy, however, suggests that the number of three- and four-membered rings is significantly smaller in the SPS sample compared to the conventionally prepared sample. Based on these results we conclude that it is possible to prepare glasses by compacting amorphous powders by the SPS process. The SPS process may ...

CERN Document Server

General relativity postulates the Minkowski space-time to be the standard flat geometry against which we compare all curved space-times and the gravitational ground state where particles, quantum fields and their vacuum states are primarily conceived. On the other hand, experimental evidences show that there exists a non-zero cosmological constant, which implies in a deSitter space-time, not compatible with the assumed Minkowski structure. Such inconsistency is shown to be a consequence of the lack of a application independent curvature standard in Riemann's geometry, leading eventually to the cosmological constant problem in general relativity. We show how the curvature standard in Riemann's geometry can be fixed by Nash's theorem on locally embedded Riemannian geometries, which imply in the existence of extra dimensions. The resulting gravitational theory is more general than general relativity, similar to brane-world ...

Energy Technology Data Exchange (ETDEWEB)

The electronic structure of small niobium clusters Nb/sub n/ (n = 2, 4, 6, 9) has been calculated applying two different quantum-chemical approximation methods (Extended Hueckel (EH) method; SW-X/sub alpha/ method). It was found that both the methods led to the same results concerning equilibrium structures, energy level schemes, Fermi energies and band widths as well as the densities of states of the clusters. In solving solid state problems of transition metals with the aid of the cluster model a better adaptation of the EH method should be expected by adjusting the EH parameters to the SW-X/sub alpha/ results.

International Nuclear Information System (INIS)

A very simple theoretical scheme is proposed to implement two- and three-qubit controlled-phase gates firstly only using a single resonant interaction between ladder-type three-level atoms and the single-mode cavity. In the presented protocol, the quantum information is encoded on the stable ground states of the atoms (as the controlling qubits) and the zero- and one-photon Fock states of cavity-field (as the target qubit). Under the influence of the atomic spontaneous emission, the decay of the cavity-mode, and deviation of the coupling strength, the three-qubit controlled-phase gate may have a comparatively high fidelity. The experimental feasibility of controlled-phase gate and the case that is extended to realize N-qubit controlled-phase gate are also discussed. (general)

Energy Technology Data Exchange (ETDEWEB)

One chemical reagent, hydrazine hydrate, was discovered to accelerate the growth of semiconductor nanocrystals (cadmium telluride) instead of additional energy, which was applied to the synthesis of high-quality CdTe nanocrystals at room temperature and ambient conditions within several hours. Under this mild condition the mercapto stabilizers were not destroyed, and they guaranteed CdTe nanocrystal particle sizes with narrow and uniform distribution over the largest possible range. The CdTe nanocrystals (photoluminescence emission range of 530-660 nm) synthesized in this way had very good spectral properties; for instance, they showed high photoluminescence quantum yield of up to 60%. Furthermore, we have succeeded in detecting the living Borrelia burgdorferi of Lyme disease by its photoluminescence image using CdTe nanocrystals.

International Nuclear Information System (INIS)

We investigate the dynamics of an 11-dimensional homogeneous cosmological model. We assume that the t = const hypersurfaces are products of a 3-dimensional Bianchi type-IX space and a 7-dimensional torus. Most results of our investigation hold when the 7-dimensional torus is replaced by an m-dimensional torus T/sup m/. We show that for a large class of vacuum solutions the physical space expands while the microspace contracts providing a natural mechanism of dimensional reduction. Matter satisfying a simple barotropic equation of state always breaks the process of dynamical dimensional reduction. With special attention we study the behavior of our model close to the initial singularity. In contrast with the 4-dimensional Bianchi type-IX cosmological model the Kasner solution always describes an approach to the initial singularity. We study the transition from the Kasner regime to the oscillatory regime. We show that matter does not significantly change this ...

International Nuclear Information System (INIS)

An outline is given of time-dependent wavepacket methods as applied to calculations of molecular collisions with solid surfaces. The methods reviewed include numerical integration algorithms for the time-dependent Schroedinger equation, semiclassical wavepacket treatments, and approximations that treat some of the degrees-of-freedom quantum-mechanically and others classically. The computational and numerical characteristics of these methods are discussed, with emphasis on their particular advantages and relevance in the context of certain molecule/surface scattering problems. For the semiclassical and mixed quantal-classical treatments, the approximation errors and their physical origins are discussed. For the quantum wavepacket techniques a numerical error analysis is presented. The computational efficiency of the various algorithms is considered and examined in the context of several applications. The main focus is on diffractive scattering ...

Energy Technology Data Exchange (ETDEWEB)

The new frustrated square-lattice system, Pb{sub 2}VO(PO{sub 4}){sub 2}, has been investigated using polarised neutron scattering. From these studies, made on powdered samples, we have determined the nature of the exchange interactions and the magnetic ordering for this novel quantum magnet. Quantum order from disorder occurs at low temperature, and the ground state observed below the Neel temperature T {sub N}{approx}3.7 K is a collinear antiferromagnet. At room temperature there are no magnetic correlations and it is possible to model the scattering with the V{sup 4+} magnetic form factor. However, at T{approx}20 K, a temperature well into the paramagnetic phase, magnetic correlations are observed, and these spin correlations have been modelled using a high-temperature series expansion. Ferromagnetic nearest-neighbour exchange J {sub 1}{approx}-2 K and antiferromagnetic next-nearest-neighbour exchange J {sub 2}{approx}6.5 ...

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

International Nuclear Information System (INIS)

Apart from conventional phase transitions driven by the thermal effects, quantum phase transitions generated by quantum fluctuations have their own mechanisms that are reflected in critical phenomena. Quantum phase transitions have an origin from spontaneous symmetry breaking commonly to thermal phase transitions. Even in this case, inherent quantum fluctuations substantially modify and yield new aspects. Quantum phase transitions have, however, another mechanism caused by topology changes, which gives completely new characters. Recently, a mechanism which connects these two has been found. Proimities from first-order transitions and phase separatins as well as from multiphase coexistence also generate characteristic and unconventional quantum criticalities. Understanding novel quantum criticalities offers a firm basis of recent active ...

Energy Technology Data Exchange (ETDEWEB)

Over the past two decades, quantum computing has become a popular and promising approach to trying to solve computationally difficult problems. Missing in many descriptions of quantum computing is just how probability enters into the process. Here, we discuss some simple examples of how uncertainty and probability enter, and how this and the ideas of quantum computing challenge our interpretations of quantum mechanics. It is found that this uncertainty can lead to intrinsic decoherence, and this raises challenges for error correction. (viewpoint)

Energy Technology Data Exchange (ETDEWEB)

Visual excitation is initiated by the absorption of a photon by the 11-cis retinal chromophore bound within the pigment called rhodopsin. We have used a variety of vibrational spectroscopies to obtain information about the vibrational nuclear dynamics that lead to this efficient photochemical isomerization. The cis-trans isomerization in rhodopsin is complete in only 200 fs. The extreme speed of this process, which is consistent with the {approximately}50 fs lifetime indicated by the spontaneous emission yield, suggests that the photochemistry involves non-stationary states or vibrational coherence. Recent studies have in fact observed vibrationally coherent oscillations of the ground state photoproduct called bathorhodopsin following impulsive excitation of the rhodopsin reactant. This conclusively demonstrates that the isomerization process in rhodopsin is vibrationally coherent. These observations further suggest that the isomerization ...

Energy Technology Data Exchange (ETDEWEB)

In this study, the state-of-the art for estimating LERF is considered for the regulatory risk-informed decisions. The consideration is mainly focused on (1) the relationship between Level 2 PSA and LERF evaluation methodology, (2) the standard requirements in terms of modeling preparation and the acceptance criteria based on the application capability II of ASME PRA standard, and (3) some pending issues for developing and proposing a simplified LERF model. This study is preliminarily presented and will be updated for establishing detailed evaluation scheme of extended MPAS (multi-purpose probabilistic analysis of safety) model and preparing the technical basis.

Energy Technology Data Exchange (ETDEWEB)

This lectures aim at giving graduate students an introduction to a working knowledge of path integral methods in a wide variety of fields in physics. Consequently, the the lecture notes are organized in three main parts dealing with non-relativistic quantum mechanics, many-body physics and field theory. In the first part the basic concepts of path integrals are developed in the usual heuristic, non-mathematical way followed by the standard examples of quadratic Lagrangians for which the path integrals can be solved exactly. Applications include semi-classical expansions, scattering problems and the representation of Green functions as path integrals. In the last chapter of this part it is shown how (euclidean) path integrals can be treated numerically by Monte-Carlo methods with a program for the anharmonic oscillator as an explicit example. The second part deals with the application of path integrals in statistical mechanics and many-body problems. Various ...

Energy Technology Data Exchange (ETDEWEB)

This contribution is intended to introduce the principles of quantum computing to those who always wanted to know about quantum computing but never dared to ask. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

International Nuclear Information System (INIS)

The introduction of oxygen in the vicinity of a metallic target surface, bombarded with positive argon ions of twenty kiloelectron-volts, increases the number of sputtered atoms in the excited state. This phenomenon of exaltation, very sensitive in the case of nickel and aluminium, is much less marked in the case of molybdenum. Moreover, the emission of excited particles coming from the beam's ions is not modified. A quantum-mechanical model of a kinetic emission process, which permits the interpretation of the clean metallic target's emission phenomena, seems insufficient to explain all of the results obtained in the presence of oxygen. In this last case one can therfore use a thermodynamic model in which excited metallic particles can be formed directly by chemical surface reactions of neutralization or reduction. (orig.).

International Nuclear Information System (INIS)

The magnetic ordering temperature of some rare-earth-based heavy-fermion compounds is strongly pressure dependent and can be completely suppressed at a critical pressure, p_c, making way for novel correlated electron states close to this quantum critical point. We have studied the clean heavy-fermion antiferromagnets CePd_2Si_2 and CeIn_3 in a series of resistivity measurements at high pressures up to 3.2 GPa and down to temperatures in the mK region. In both materials, superconductivity appears in a small window of a few tenths of a GPa on either side of p_c. We present detailed measurements of the superconducting and magnetic temperature-pressure phase diagram, which indicate that superconductivity in these materials is enhanced, rather than suppressed, by the closeness to magnetic order. (author)

International Nuclear Information System (INIS)

The metallo-organic chemical vapor deposition (MOCVD) process has been used with great success to grow AlGaAs-GaAs and InGaAsP-InGaAs-InP heterostructure materials for electronic and optoelectronic applications. Devices fabricated from Al/sub x/Ga/sub 1-x/As-GaAs heterostructures grown by MOCVD include bipolar transistors, field-effect transistors (FETs), high-mobility (or modulation-doped) FETs, large-area high-efficiency solar cells, low-threshold lasers, high-power lasers, quantum-well lasers, and visible lasers. The state of the art for the MOCFD growth of optoelectronic devices is reviewed in this paper, and some comments are made regarding future trends in the growth of these materials by MOCVD.

Energy Technology Data Exchange (ETDEWEB)

We present a systematic study of the magnetization, Hall effect and specific heat on single crystals of Mn{sub 4}Si{sub 7}. Curie-Weiss law is observed above 43 K. At low-temperature moments order in an anisotropic helical state and are aligned above 1 T. We observe an anomalous Hall effect in both {rho}{sub H} vs. B and in R{sub H} vs. T curves and a field dependence of the low T specific heat due to spin fluctuations. The magnetic moments (p{sub eff} and p{sub sat}) are the lowest reported for similar itinerant magnetic systems, this suggests that Mn{sub 4}Si{sub 7} is a good candidate to observe critical quantum fluctuations expected for a marginal Fermi liquid.

British Library Electronic Table of Contents (United Kingdom)

In this Letter, we present Quantum Mechanics/Molecular Mechanics (QM/MM) calculations on molecules containing a 2-deoxycytidine-3prime-monophosphate moiety (3prime-dCMPH). In particular, we examine the effect that including neighbouring nucleotides at the Molecular Mechanic (MM) level has on the calculated electron affinities and on the energetic barriers of the C3prime-O3prime bond cleavage. Our results demonstrate that the surrounding nucleotides relocate the excess electron from the p* orbital of the base to a diffuse phosphate-centred orbital, leading to the formation of a dipole-bound anion state. Both the electron affinities and the activation energy of C3prime-O3prime bond cleavage are strongly increased.

CERN Document Server

The controlled growth of nanowires (NWs) with dimensions comparable to the Fermi wavelengths of the charge carriers allows fundamental investigations of quantum confinement phenomena. Here, we present studies of proximity-induced superconductivity in undoped Ge/Si core/shell NW heterostructures contacted by superconducting leads. By using a top gate electrode to modulate the carrier density in the NW, the critical supercurrent can be tuned from zero to greater than 100 nA. Furthermore, discrete sub-bands form in the NW due to confinement in the radial direction, which results in stepwise increases in the critical current as a function of gate voltage. Transport measurements on these superconductor-NW-superconductor devices reveal high-order (n = 25) resonant multiple Andreev reflections, indicating that the NW channel is smooth and the charge transport is highly coherent. The ability to create and control coherent superconducting ordered states ...

International Nuclear Information System (INIS)

Nowadays, diamond and the nitrogen-vacancy (NV) colour centres constitute the best solid-state system in view of quantum-computing applications. It has also been shown recently that single NV centres could be used as nanoscale magnetic sensors. Such applications require the creation of single NV centres with very high resolution and with a high efficiency. The nano-implanter at the university of Bochum provides low energy nitrogen ions which can be implanted through a hole pierced in the tip of an atomic force microscope. Ultrapure diamond samples have been implanted with spot sizes of 50nm and less. Stimulated Emission Depletion (STED) microscopy has been used to characterise and resolve the implanted spots.

Energy Technology Data Exchange (ETDEWEB)

Gamma-aminobutyric acid type A receptor-associated protein (GABARAP) belongs to a family of small ubiquitin-like adaptor proteins implicated in intracellular vesicle trafficking and autophagy. We have used diffusion-ordered nuclear magnetic resonance spectroscopy to study the temperature and concentration dependence of the diffusion properties of GABARAP. Our data suggest the presence of distinct conformational states and provide support for self-association of GABARAP molecules. Assuming a monomer-dimer equilibrium, a temperature-dependent dissociation constant could be derived. Based on a temperature series of {sup 1}H{sup 15}N heteronuclear single quantum coherence nuclear magnetic resonance spectra, we propose residues potentially involved in GABARAP self-interaction. The possible biological significance of these observations is discussed with respect to alternative scenarios of oligomerization.

International Nuclear Information System (INIS)

As part of the general QC/QA management of the k_0-standardization, three types of 'SMELS' (synthetic multi-element standards) are being developed to check the performance of k_0-NAA when implemented in a laboratory. Phenol-formaldehyde resin is proposed in this paper as the matrix of choice. Based on previous work, this material could be prepared with sufficient purity so as to make interferences with the spiking elements negligible. The matrix was found to be adequately resistant towards high neutron flux irradiation. A selection was made of compounds, soluble in ethyl alcohol, for spiking the prepolymer ethanolic solution with the elements of interest. Finally, some prototypes were prepared and a satisfactory homogeneity of the spiked elements was found for 50 mg sample intake.

International Nuclear Information System (INIS)

A series of sputtered tungsten-carbon multilayer structures with periods ranging from 2 to 12 nm in the as-prepared state and after annealing at 500 degrees C for 4 hours has been studied with high resolution transmission electron microscopy. The evolution with annealing of the microstructure of these multilayers depends on their period.As-prepared structures appear predominantly amorphous from TEM imaging and diffraction. Annealing results in crystallization of the W-rich layers into WC in the larger period samples, and less complete or no crystallization in the smaller period samples. X-ray scattering reveals that annealing expands the period in a systematic way. The layers remain remarkably well-defined after annealing under these conditions.

CERN Document Server

Theory of quantum games is relatively new to the literature and its applications to various areas of research are being explored. It is a novel interpretation of strategies and decisions in quantum domain. In the earlier work on quantum games considerable attention was given to the resolution of dilemmas present in corresponding classical games. Two separate quantum schemes were presented by Eisert et al. and Marinatto and Weber to resolve dilemmas in Prisoners' Dilemma and Battle of Sexes games respectively. However for the latter scheme it was argued that dilemma was not resolved. We have modified the quantization scheme of Marinatto and Weber to resolve the dilemma. We have developed a generalized quantization scheme for two person non-zero sum games which reduces to the existing schemes under certain conditions. Applications of this generalized quantization scheme to quantum ...

Energy Technology Data Exchange (ETDEWEB)

We survey results in lattice quantum chromodynamics from groups in the USQCD Collaboration. The main focus is on physics, but many aspects of the discussion are aimed at an audience of computational physicists.

Energy Technology Data Exchange (ETDEWEB)

There is considerable interest in the use of silicon devices as qubits for quantum computing. The existence of nuclear spin in a silicon isotope and the complex band structure of silicon are unfavourable for this application of silicon devices. (viewpoint)

CERN Document Server

A process has been proposed to increase the efficiency of an ideal Otto cycle via a quantum heat engine that has no cooler reservoir. We show that such a process is not feasible.

International Nuclear Information System (INIS)

We describe a new apparatus that combines pulsed laser excitation in a molecular beam with surface-science methods for preparation of clean single-crystal surfaces and detection of adsorbates to enable state-selected studies of gas-surface reaction dynamics. Reactant molecules are prepared in specific vibrationally excited states via overtone pumping using tunable, narrow-band laser radiation. The collision-free environment of the molecular beam prevents relaxation of the prepared molecules before impact on the target surface and enables complete control over the collision energy and incidence angle. Chemisorption products are detected after a given deposition time by Auger electron spectroscopy. To achieve sufficient beam flux of state-selected reactant molecules for product detection by standard surface-science techniques, we use a high-intensity, short-pulse ...

CERN Document Server

We summarize results of recent studies of heavy quarkonia correlators and spectral functions at finite temperatures from lattice QCD and systematic T-matrix studies using QCD motivated finite-temperature potentials. We argue that heavy quarkonia dissociation shall occur in the temperature range $1.2 \\le T_d/T_c \\le 1.5$ by the interplay of both screening and absorption in the strongly correlated plasma medium. We discuss these effects on the quantum mechanical evolution of quarkonia states within a time-dependent harmonic oscillator model with complex oscillator strength and compare the results with data for $R_{\\rm AA}/R_{\\rm AA}^{\\rm CNM}$ from RHIC and SPS experiments. We speculate whether the suppression pattern of the rather precise NA60 data from In-In collisions may be related to the recently discovered X(3872) state. Theoretical support for this hypothesis comes from the cluster expansion of the plasma ...

International Nuclear Information System (INIS)

A merged-beams electron-energy-loss technique is described, by which absolute cross sections can be measured for near-threshold electron-impact excitation of multipy charged ions. Results are reported here for absolute total electron-impact excitation cross sections for the O"5"+(2s#->#2p) transition from below threshold to 1.6 eV above threshold. The experimental data are in good agremeent with a seven-state close-coupling calculation throughout the energy range of the experiment. Results agree with calculations showing that more than 90% of the electrons causing excitation are ejected in the backward direction in the center-of-mass frame. This backscattering is shown in both quantum-mechanical and semiclassical calculations. Evidence is observed for high-lying metastable autoionizing states with a lifetime of approximately 0.9 #mu#s which are made to ionize by electron impact.

CERN Document Server

How much information is stored in the ground-state of a system without \\emph{any symmetry} and how can we extract it? This question is investigated by analyzing the behavior of a topological Chern Insulator (CI) in the presence of disorder, with a focus on its entanglement spectrum (EtS) constructed from the ground state. For systems with symmetries, the EtS was shown to contain explicit information revealed by sorting the EtS against the conserved quantum numbers. In the absence of any symmetry, we demonstrate that statistical methods such as the level statistics of the EtS can be equally insightful, allowing us to distinguish when an insulator is in a topological or trivial phase and to map the boundary between the two phases, where EtS becomes entirely delocalized. The phase diagram of a CI is explicitly computed as function of Fermi level ($E_F$) and disorder strength using the level statistics of the EtS and energy ...

CERN Document Server

Preparing the works for the St-Genis roundabout.

Energy Technology Data Exchange (ETDEWEB)

Neutral beam systems for the next generation of magnetic fusion devices will be based on negative ions. Developments are progressing steadily, and large negative ion-based systems are under preparation for JT60-U and LHD, and are being considered for ITER. An overview of the physics of the production, acceleration and neutralization of large negative ion beams is given. The present state of the art in R and D is also surveyed. (Author).

International Nuclear Information System (INIS)

In the present study the Pb content in Bi(2223) phase by regression or curve fitting method are optimized. The best fitting curve can be obtained by the method of least square. To study the effect of Pb content in Pb substituted Bi (2223) superconductors, prepared by solid state reaction method data is obtained. The deviation of T_c from the target value for different Pb content is summarized

Energy Technology Data Exchange (ETDEWEB)

The Battery Life Estimator (BLE) Manual has been prepared to assist developers in their efforts to estimate the calendar life of advanced batteries for automotive applications. Testing requirements and procedures are defined by the various manuals previously published under the United States Advanced Battery Consortium (USABC). The purpose of this manual is to describe and standardize a method for estimating calendar life based on statistical models and degradation data acquired from typical USABC battery testing.

CERN Document Server

We define the Bloch spectrum of a quantum graph to be the collection of the spectra of a family of Schr\\"odinger operators parametrized by the cohomology of the quantum graph. We show that the Bloch spectrum determines the Albanese torus, the block structure and the planarity of the graph. It determines a geometric dual of a planar graph. This enables us to show that the Bloch spectrum completely determines planar 3-connected quantum graphs.

International Nuclear Information System (INIS)

We discuss the use of active control to reduce mirror position fluctuations at the quantum level. We have shown in a recent experiment that it is possible to reduce the thermal noise of a mirror by measuring and controlling its motion with an optomechanical sensor based on a high-finesse optical cavity. This approach can be extended to lock the mirror motion at the quantum level, and to suppress the quantum effects of radiation pressure in interferometric measurements such as gravitational-wave detectors. The sensitivity improvement is furthermore independent of losses in the interferometer.

Science.gov (United States)

DC Field, Value, Language.

International Nuclear Information System (INIS)

... Abstract only 1063-7869 v. 44(10) CLASSICAL AND QUANTUM MECHANICS,

British Library Electronic Table of Contents (United Kingdom)

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CERN Document Server

Here we show that self-propulsion in quantum vacuum may be achieved by rotating or aggregating magneto-electric nano-particles. The back-action follows from changes in momentum of electro-magnetic zero-point fluctuations, generated in magneto-electric materials. This effect may provide new tools for investigation of the quantum nature of our world. It might also serve in the future as a "quantum wheel" to correct satellite orientation in space.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

International Nuclear Information System (INIS)

Oxyfluoride aluminosilicate glasses in the composition of 50SiO2-20Al2O3-20LiF-10GdF3-0.5TmF3-xYbF3 (x = 0, 1.0, 2.5, 5, 7.5, 10, 15, 20, 25 and 30 mol%) have been prepared to study their thermal and optical properties. From the differential thermal analysis measurements, glass transition temperatures and onset crystallization temperatures have been evaluated and from them glass stability factors were calculated. Glass stabilities decreased gradually with fluoride content increment in all the studied glasses. The photoluminescence and decay measurements have also been carried out for all these glasses. In these glasses, an efficient near infrared quantum cutting with optimal quantum efficiency approaching 187% has been demonstrated, by exploring the co-operative downconversion mechanism from Tm3+ to Yb3+, with 467 nm (Tm3+ : 3H6 ? 1G4) excitation wavelength. These glasses are promising materials to achieve high efficiency ...

Energy Technology Data Exchange (ETDEWEB)

The high temperature solid-state reaction between LiNiO{sub 2} and V{sub 2}O{sub 3} (or V{sub 2}O{sub 5}) in air used to prepare LiNiVO{sub 4} has been further studied. This quaternary Li-Ni-V-O reaction is strongly dependent on reaction temperature and lithium stoichiometry in Li{sub x}Ni{sub 2-x}O{sub 2} and has produced a highly crystalline LiNiVO{sub 4} material whose structure has been confirmed to be an inverse spinel by Rietveld analysis with a Bragg R-factor of 1.18 in the absence of crystal orientation preference. The cell performance of LiNiVO{sub 4} prepared at various temperatures or by varying x-values in Li{sub x}Ni{sub 2-x}O{sub 2} has been examined in lithium coin cells and indicated that preparation at low temperatures or when x=0.89 provided an electrode material with higher cell capacity. (orig.)

Energy Technology Data Exchange (ETDEWEB)

This paper reports progress in the fabrication and characterization of an array of 1nm-scale colloidal particles (i.e., quantum-dot array) that can be operated to execute nontrivial and innovative computations, possibly including quantum logic. We discuss the actual fabrication of 2-nm metal clusters as an example of possible quantum dot implementation. Innovative and unconventional paradigms underlie the different stages of this work. For example, regular array geometry is achieved by directing appropriately derivatized metal clusters to preselected locations along a stretched strand of an engineered DNA sequence.

Energy Technology Data Exchange (ETDEWEB)

Ultraviolet photoelectron spectra were measured for vanadyl phthalocyanine (VOPc) ultrathin films prepared on graphite to study effects of the molecular orientation and the electric dipole layer on the organic electronic states. VOPc has a permanent electric dipole perpendicular to the molecular plane, hence a well-defined electric dipole layer could be intentionally prepared by using the oriented monolayer. The observed binding-energy difference of the highest occupied molecular orbital (HOMO) bands between the oriented monolayer and the double layer was found to agree with the vacuum level shift, leading to a conclusion that the molecular energy level with respect to the substrate Fermi level is changed when the molecule is in the electric dipole layer.

British Library Electronic Table of Contents (United Kingdom)

Some of the most important problems facing the United States and China, indeed facing our entire planet, require approaches that are fundamentally multidisciplinary in nature. Many of those require skills in computer science (CS), basic understanding of another discipline, and the ability to apply the skills in one discipline to the problems of another. Modern training in computer science needs to prepare students to work in other disciplines or to work on multidisciplinary problems. What do we do to prepare them for a multidisciplinary world when there are already too many things we want to teach them about computer science? This paper describes successful examples of multidisciplinary education at the interface between CS and the biological sciences, as well as other examples involving C...

Science.gov (United States)

An inclusion complex between imazalil (IMZ), a selected fungicide, and cyclomaltoheptaose (beta-cyclodextrin, betaCD) was obtained using supercritical fluid carbon dioxide. The best preparation conditions were determined, and the inclusion complex was investigated by means of 1H NMR spectroscopy in aqueous solution and 13C CPMAS NMR spectroscopy in the solid state. Information on the geometry of the betaCD/IMZ complex was obtained from ROESY spectroscopy, while the dynamics of the inclusion complex in the kilohertz range was obtained from the proton spin-lattice relaxation times in the rotating frame, T(1rho) (1H). PMID:14553984

Energy Technology Data Exchange (ETDEWEB)

Positron annihilation experiments on Fe-Cu model dilute alloys of nuclear reactor pressure vessel (RPV) steels have been performed after neutron irradiation in JMTR. Nanovoids whose inner surfaces were covered by Cu atoms were clearly observed. The nanovoids transformed to ultrafine Cu precipitates by dissociating their vacancies after annealing at around 400degC. The nanovoids and the ultrafine Cu precipitates are strongly suggested to be responsible for irradiation-induced embrittlement of RPV steels. Effects of Ni, Mn and P addition on the nanovoid and Cu precipitate formations were also studied. The nanovoid formation was enhanced by Ni and P, but suppressed by Mn. The Cu precipitates after annealing around 400degC were almost free from these doping elements and hence were pure Cu in the chemical composition. Furthermore the Fermi surface of the 'embedded' Cu precipitates with a body centered cubic crystal structure was obtained from two dimensional angular ...

CERN Document Server

A new mathematical framework is formulated to derive the effective equations of motion for the constrained quantum system which possesses an internal clock. In the realm close to classical behavior, the quantum evolution is approximated by a finite system of coupled but ordinary differential equations adhered to the weakly imposed Hamiltonian constraint. For the simplified version of loop quantum cosmology in the Bianchi I model with a free massless scalar filed, the resulting effective equations of motion affirm the bouncing scenario predicted by the previous studies: The big bang singularity is resolved and replaced by the big bounces, which take place up to three times, once in each diagonal direction, whenever the directional density approaches the critical value in the regime of Planckian density. It is also revealed that back-reaction arises from the quantum corrections and modifies the precise ...

CERN Document Server

The study of quantum walk process has been widely divided into the two standard variants, the discrete-time quantum walk (DTQW) and the continuous-time quantum walk (CTQW). The connection between the two variants has been established by considering limiting value of the coin operation parameter in the DTQW and the coin degree of freedom is show to be unnecessary [26]. But the coin degree of freedom is an additional resource which can be exploited to control the dynamics of the QW process. In this paper we present a generic quantum walk (QW) model using a quantum coin-embedded unitary shift operation U_{C}. The standard version of the DTQW and the CTQW can be conveniently retrieved from this generic model retaining the features of the coin degree of freedom in both the variants.

Energy Technology Data Exchange (ETDEWEB)

We study free and self-interacting scalar quantum field theories in a flat Robertson-Walker metric in the functional Schroedinger picture. We discuss Schroedinger picture quantization, relating it to conventional Heisenberg picture quantization. For the interacting theory, we introduce the time-dependent Gaussian approximation to study time evolution of pure and mixed states and we establish renormalizability of the approximation. We also study the question of computing a finite, renormalized energy-momentum tensor for both the free and the interacting theory in the Gaussian appproximation. Using the adiabatic expansion, we show that the entire subtration necessary to make the the energy-momentum tensor finite in the free theory can be written in terms of covariantly conserved tensors. We further show that the same subtraction is sufficient to make the energy-momentum tensor finite in the Gaussian approximation for the interacting theory ...

Energy Technology Data Exchange (ETDEWEB)

We discuss recent results obtained for the heavy-fermion metals UPd{sub 2}Al{sub 3} and YbRh{sub 2}Si{sub 2}. UPd{sub 2}Al{sub 3} is the first among all superconductors for which tunneling and inelastic neutron-scattering data highlight a non-phononic, i.e., magnetic-exciton mediated, pair state. YbRh{sub 2}Si{sub 2} represents a model system exhibiting pronounced non-Fermi liquid effects above a weak antiferromagnetic phase transition at T{sub N}=70 mK. Upon approaching the quantum critical point (T{sub N}{yields}0), by low doping with Ge, one observes for T<0.3 K disparate behavior in the temperature dependences of both the electrical resistivity and the electronic specific heat as well as a Curie-Weiss law in the uniform magnetic susceptibility, implying uncompensated large 4f moments. These observations indicate a break up of the composite quasiparticles into their local f-spin and itinerant conduction-electron parts.

International Nuclear Information System (INIS)

Due to the increased computer power and advanced algorithms, quantum mechanical calculations based on Density Functional Theory are more and more widely used to solve real materials science problems. In this context large nonlinear generalized eigenvalue problems must be solved repeatedly to calculate the electronic ground state of a solid or molecule. Due to the nonlinear nature of this problem, an iterative solution of the eigenvalue problem can be more efficient provided it does not disturb the convergence of the self-consistent-field problem. The blocked Davidson method is one of the widely used and efficient schemes for that purpose, but its performance depends critically on the preconditioning, i.e. the procedure to improve the search space for an accurate solution. For more diagonally dominated problems, which appear typically for plane wave based pseudopotential calculations, the inverse of the diagonal of (H - ES) is used. However, for ...

Science.gov (United States)

Efficient, low-temperature conversion of infrared light into visible light (red, orange, green) is reported at single heterojunctions and undoped quantum wells of GaAs and ordered Al{sub {ital x}}Ga{sub 1{minus}{ital x}}InP{sub 2}; an increase in photon energy of 700 meV is obtained. The signal originates from the high-band-gap layers and disappears only if the excitation energy is tuned below the GaAs band gap. The intensity of the up-converted photoluminescence (PL) is found to decrease significantly slower with increasing temperature than that of the regular PL and it remains observable up to 200 K. Interface-induced cold Auger processes along with the presence of trapped states for both electrons and holes in these ordered alloys account for this nonlinear mechanism. A colinear double-beam experiment confirms this. {copyright} {ital 1996 The American Physical Society.}

Energy Technology Data Exchange (ETDEWEB)

We measured ESR of phosphorous-doped silicon with a low concentration of P, n, at high magnetic fields and low temperatures to investigate the states of nuclear spin. A sample with n = 6.52 x 10{sup 16} /cm{sup 3} was studied at 2.85 T (80 GHz) from 30 K to 2.3 K by field-modulating cw-ESR for a fixed 0 dB power. As the temperature was lowered, the out-of-phase signal appeared around 18 K, reached at a maximum intensity at 13 K, and disappeared around 6 K. The out-of-phase signal is referred to the field modulation. The in-phase signal started to change from the derivative of absorption spectrum at high temperatures to absorption-like shape around 15 K and asymmetry of intensity for two peaks of hyperfine-separated signals increased as temperatures was lowered. Below 10 K, the saturation of the in-phase signal started to appear. We speculate that the asymmetry is caused by saturation effect and dynamic nuclear polarization of {sup 31}P nuclear spin due to drastic ...

Energy Technology Data Exchange (ETDEWEB)

The University of Georgia, in collaboration with GE Global Research, has investigated the relevant quenching mechanism of phosphor coatings used in white light devices based on UV LEDs. The final goal of the project was the design and fabrication of a high-efficacy white light UV-LED device through improved geometry and optimized phosphor coatings. At the end of the research period, which was extended to seamlessly carry over the research to a follow-up program, we have demonstrated a two-fold improvement in the conversion efficiency of a white light LED device, where the increase efficacy is due to both improved phosphor quantum efficiency and lamp geometry. Working prototypes have been displayed at DOE sponsored meetings and during the final presentation at the DOE Headquarters in Washington, DC. During the first phase of the project, a fundamental understanding of quenching processes in UV-LEDs was obtained, and the relationships that describe the performance of ...

Energy Technology Data Exchange (ETDEWEB)

In the present dissertation, a hierarchical multiscale approach for modeling FePt nanoparticles by atomistic computer simulations is developed. By describing the interatomic interactions on different levels of sophistication, various time and length scales can be accessed. Methods range from static quantum-mechanic total-energy calculations of small periodic systems to simulations of whole particles over an extended time by using simple lattice Hamiltonians. By employing these methods, the energetic and thermodynamic stability of non-crystalline multiply twinned FePt nanoparticles is investigated. Subsequently, the thermodynamics of the order-disorder transition in FePt nanoparticles is analyzed, including the influence of particle size, composition and modified surface energies by different chemical surroundings. In order to identify processes that reduce or enhance the rate of transformation from the disordered to the ordered state, the ...

International Nuclear Information System (INIS)

With the preeminence of A-15 superconducting multifilamentary wires in magnet technology, it has become important to understand the thermodynamic factors influencing the formation of these compounds under solid-state reaction conditions. The six systems Nb--Sn, Nb--Ga, Nb--Ge, Nb--Al, V--Si, and V--Ga were prepared as single filament bronze wires and heat treated in an attempt to precipitate the appropriate A-15 compound. The compounds observed to form were categorized using a formation temperature ratio (stability index) based on the melting temperatures of the constituents which make up the single filament composites. This study has led to several predictions regarding the formation of A-15 compounds using a solid-state bronze diffusion technique. The results of experimentation based on these predictions are presented.

International Nuclear Information System (INIS)

At atmospheric pressure and room temperature, dielectric barrier discharge induced plasma oxidation for achieving supported TiO2 photocatalysts derived from TiCl4 adsorbed onto ?-Al2O3 pellets was studied. The supported TiO2/?-Al2O3photocatalysts prepared by a cyclic 'adsorption-discharge' approach, without requirement of heat treatment, exhibit high activity in the photocatalytic degradation reaction of formaldehyde. The mass spectra and optical emission spectra during O2/Ar discharge for oxidizing the adsorbed-state TiCl4 were measured. The mechanism for the TiO2 formation from adsorbed-state TiCl4 by plasma oxidation was discussed.

Energy Technology Data Exchange (ETDEWEB)

This report discusses the UTR-10 reactor at Iowa State University which went critical on low enriched uranium (LEU) fuel on August 14, 1991. However, subsequent to the criticality experiments the fuel plates started to discolor. In addition, roll pins used to lift the fuel assemblies were discovered to be cracked. It was determined that these problems were due to chemical agents in the primary coolant water. The roll pins were replaced by solid stainless steel pins. The primary coolant was replaced and the reactor is currently in operation. Surveillance specimens will be used to monitor any possible future discoloration. The high enriched fuel (HEU) is being prepared for eventual shipment to a high enriched fuel receiving facility.

Energy Technology Data Exchange (ETDEWEB)

Chars prepared from potassium-exchanged carboxy methyl cellulose at several heat treatment temperatures (HTTs) were gasified in air isothermally at selected gasification temperatures (GTs) in the range 633-893 K to investigate the catalytic effectiveness of potassium species. The chars displayed a noticeable jump in gasification rate at a particular gasification temperature (called jump temperature, T{sub j}). The magnitude of jump was much less than that reported for copper and nickel catalysis, but comparable with that for calcium catalysis. Increase in HTT caused a decrease in the jump temperature of chars in contrast with the increase observed in copper, nickel and calcium catalysis; also the magnitude of jump did not decrease, but remained unaltered, on increasing HTT. The different behavior of potassium catalysis is correlated to a change in the chemical state of potassium at higher HTT. The results reveal the dependence of jump ...

International Nuclear Information System (INIS)

This paper aimed to the evaluation of different kinds of sorbent material preparation and to the evaluation of their characteristics at different pH conditions by X-ray fluorescence analysis. This method is suitable for identification and determination of elements in samples of different character, state and origin because it is a polycomponent, non-destructive, fast and simple analytical method. Moreover, it allows timeadvantageous and reliable measurements. This paper studies problems concerning the determination of some selected elements (Mn, Fe, Ni, Cu, Zn, Pb) in pharmaceutical samples of sodium chloride in the solid state as well as in its solution by sorption on chelating extraction membrane 3M Empore"T"M and on the strongly acidic ion-exchanger Dowex 50Wx8. Conditions for the most effective sorption of determined elements are also interpreted. (author)

Energy Technology Data Exchange (ETDEWEB)

Monodisperse noble metal nanoparticles are of tremendous interest for numerous applications, such as surface-enhanced Raman spectroscopy, catalysis or biosensing. However, preparation of monodisperse metal nanoparticles is still a challenging task, because typical preparation methods yield nanoparticle ensembles with broad shape and/or size distributions. To overcome this drawback, tailoring of metal nanoparticles with laser light has been developed, which is based on the pronounced shape- and size-dependent optical properties of metal nanoparticles. I will demonstrate that nanoparticle tailoring with ns-pulsed laser light is a suitable method to prepare nanoparticle ensembles with a narrow shape and/or size distribution. While irradiation with ns-pulsed laser light during nanoparticle growth permits a precise shape tailoring, post-grown irradiation allows a size tailoring. For example, the initial broad Gaussian size ...

International Nuclear Information System (INIS)

Using a new approach to quaternion mechanics based on De Broglie waves, it is shown that such a theory describes tachyons and that the quantum theory of tachyons should be a quaternionic one. (U.K.).

International Nuclear Information System (INIS)

We obtain a symmetry algebra for any unitary minimal model by using the representation of conformal field theories. This symmetry algebra can be interpreted as a quantum group. The generalization to non-unitary minimal models is direct. (orig.).

UK PubMed Central (United Kingdom)

A technique is described for displaying distinct tissue layers of large blood vessel walls as well as measuring their mechanical strain. The technique is based on deuterium double-quantum-filtered (DQF)...Full Text Available

Energy Technology Data Exchange (ETDEWEB)

This course is based upon lectures in physics given by Professor Feynman at the California institute of technology during 1961 and 1962. This volume is dedicated to quantum physics, semiconductors, symmetry and advanced principles of physics.

International Nuclear Information System (INIS)

Considered is a new type of generalized asymptotic functions, which are not functionals on some space of test functions as the Schwartz distributions. The definition of the generalized asymptotic functions is given. It is pointed out that in future the particular asymptotic functions will be used for solving some topics of quantum mechanics and quantum theory.

CERN Document Server

The Large Hadron Collider (LHC) project, approved by the CERN Council in December 1994, has now fully entered its construction phase, with the detailed technical definition of the major systems, and the adjudication of a number of large procurement contracts. We first recall the main features and characteristics of the LHC, report on the advances in definition of the layout and optics as well as on preparation of the injector complex, and review recent progress in the key technical systems of the main ring: magnets, cryogenics and vacuum, as well as civil construction, which has started following acceptance by authorities in the Host States.

International Nuclear Information System (INIS)

The procedure of charge-coupled devices (CCD) are investigated by using MOS capacitors for enhancing their ionizing radiation tolerance. Authors have found that the gate oxidation temperature, thickness of SiO_2 gate insulator and high temperature processes after gate oxidation are crucial for determining the radiation tolerance of the devices, and proposed to decrease the thickness of gate insulator, perform gate oxidation at 1000 deg C by means of dry oxidation and minimize the number of high temperature procedure steps after gate oxidation. All stated above is a necessary preparation for priducing radiation hardened charge-coupled devices.

Energy Technology Data Exchange (ETDEWEB)

The ElectroScan environmental scanning electron microscope (ESEM) is one of the most exciting new developments in the field of Electron Microscopy. The ESEM differs from conventional Scanning Electron Microscopes (SEM) by being able to examine materials including liquids and oils in their natural state with no prior sample preparation. Accessory equipment, cooling, heating and manipulating devices allow the manipulation of samples thus making it possible for the first time to image dynamic processes such as wetting, drying, absorption, corrosion, melting, crystallisation, curing and fracturing at high magnification. Papers concerning the historical development of the ESEM are given in a bibliography at the end of this paper. 24 refs., 18 figs.

International Nuclear Information System (INIS)

The conventional treatment of quantum field theories including tachyons is presented, in particular the phi"4 theory. (W.D.L.).

Energy Technology Data Exchange (ETDEWEB)

Trapped ions are a near ideal system to study quantum information processing due to the high degree of control over the ion's external confinement and internal degrees of freedom. We demonstrate the key steps necessary for trapped ion quantum computing and focus on phonon-mediated entangling gates. We highlight several key algorithms implemented over the last decade with these gates and give a detailed description of Grover's quantum database search implemented with two trapped ion qubits.

International Nuclear Information System (INIS)

We study a quantum computing system using microwave photons in transmission line resonators on a superconducting chip as qubits. We show that linear optics and other controls necessary for quantum computing can be implemented by coupling to Josephson devices on the same chip. By taking advantage of the strong nonlinearities in Josephson junctions, photonic qubit interactions can be realized. We analyze the gate error rate to demonstrate that our scheme is realistic even for Josephson devices with limited decoherence times. As a conceptually innovative solution based on existing technologies, our scheme provides an integrated and scalable approach to the next key milestone for photonic qubit quantum computing.

Science.gov (United States)

In this paper, we proposed a novel quantum secure direct communication scheme with one-time pad in stabilizer formalism. Based on the reuse of qubit sequence, an efficient secure communication of secret messages without first producing a shared secret key can be achieved. One hence may find that the amount of private key needed for quantum communication is smaller than that in the general case. Therefore, the present protocol which is feasible with the present-day techniques may be applied to quantum communication with short-length encoding.

Energy Technology Data Exchange (ETDEWEB)

The propriety of the cosmic no-hair conjecture to the Bianchi-type-IX spacetime is discussed from a quantum cosmological point of view. It is shown that most, but not all, classical universes which are created quantum cosmologically are inflationary. The probability of inflation among such universes is also discussed.

International Nuclear Information System (INIS)

We propose two schemes for the implementation of quantum discrete Fourier transform in the ion trap system. In each scheme we design a tunable two-qubit phase gate as the main ingredient. The experimental implementation of the schemes would be an important step toward complex quantum computation in the ion trap system.

CERN Document Server

Two-dimensional generalization of the original peak finding algorithm suggested earlier is given. The ideology of the algorithm emerged from the well known quantum mechanical tunneling property which enables small bodies to penetrate through narrow potential barriers. We further merge this ``quantum'' ideology with the philosophy of Particle Swarm Optimization to get the global optimization algorithm which can be called Quantum Swarm Optimization. The functionality of the newborn algorithm is tested on some benchmark optimization problems.

Energy Technology Data Exchange (ETDEWEB)

An extremely simple and convenient method is presented for computing eigenvalues in quantum mechanics by representing position and momentum operators in matrix form. The simplicity and success of the method is illustrated by numerical results concerning eigenvalues of bound systems and resonances for Hermitian and non-Hermitian Hamiltonians as well as driven quantum systems. Various MATLAB program codes are listed. (author)

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.

Energy Technology Data Exchange (ETDEWEB)

No abstract prepared.