Search

Some of the most sensitive and precise measurements--for example, of inertia.sup.1, gravity.sup.2 and rotation.sup.3--are based on matter-wave interferometry with free-falling atomic clouds. To achieve very high sensitivities, the interrogation time has to be very long, and consequently the experimental apparatus needs to be very tall (in some cases reaching ten or even one hundred metres) or the experiments must be performed in microgravity in space.sup.4-7. Cancelling gravitational acceleration (for example, in atomtronic circuits.sup.8,9 and matter-wave guides.sup.10) is expected to result in compact devices with extended interrogation times and therefore increased sensitivity. Here we demonstrate smooth and controllable matter-wave guides by transporting Bose-Einstein condensates (BECs) over macroscopic distances. We use a neutral-atom accelerator ring to bring BECs to very high speeds (16 times their sound velocity) and transport them in a magnetic matter-wave guide for 15 centimetres while fully preserving their internal coherence. The resulting high angular momentum of more than 40,000h per atom (where h is the reduced Planck constant) gives access to the higher Landau levels of quantum Hall states, and the hypersonic velocities achieved, combined with our ability to control potentials with picokelvin precision, will facilitate the study of superfluidity and give rise to tunnelling and a large range of transport regimes of ultracold atoms.sup.11-13. Coherent matter-wave guides are expected to enable interaction times of several seconds in highly compact devices and lead to portable guided-atom interferometers for applications such as inertial navigation and gravity mapping. Bose-Einstein condensates are transported at hypersonic speeds over a distance of 15 cm in a neutral-atom accelerator ring while preserving their internal coherence., Author(s): Saurabh Pandey [sup.1] [sup.2] , Hector Mas [sup.1] [sup.3] , Giannis Drougakis [sup.1] [sup.2] , Premjith Thekkeppatt [sup.1] , Vasiliki Bolpasi [sup.1] , Georgios Vasilakis [sup.1] , Konstantinos Poulios [...]

Protecting the dynamics of coupled quantum systems from decoherence by the environment is a key challenge for solid-state quantum information processing (1,2). An idle quantum bit (qubit) can be efficiently [...]

Three's the limit for multiple excitons Long-range correlations between charge particles (electrons and 'holes') in semiconductors lead to many-body effects, which are of fundamental interest and also of importance in optoelectronic applications. The exciton state, in which an electron and hole are paired, has been extensively studied, but the properties of multiple exciton states involving three or more charge particles are largely unknown as they are challenging to observe experimentally. Daniel Turner and Keith Nelson have extended a spectroscopy technique called multidimensional Fourier transform optical spectroscopy, and demonstrate its ability to generate and characterize bi-excitons, tri-excitons and other unbound correlations in a gallium arsenide nanostructure. This experiment involves controlling the geometry, temporal delays and optical phases of up to seven light fields simultaneously. The findings are of particular interest as it was previously not known whether tri-excitons -- involving correlations between six particles -- could exist at all. The authors also present clear evidence that four-exciton states do not exist, indicating an upper limit for many-body correlations in this type of semiconductor system. The exciton state in semiconductors, where an electron and hole are paired, has been studied extensively, but the properties of exciton states involving three or more charged particles are largely unknown. These authors use a challenging spectroscopy technique to generate and characterize biexcitons, triexcitons and other, unbound, correlations in a gallium arsenide nanostructure. It was previously unknown whether triexcitons, which involve correlations between six particles, can exist at all. Strong, long-range Coulomb interactions can lead to correlated motions of multiple charged particles, which can induce important many-body effects in semiconductors. The exciton states formed from correlated electron-hole pairs have been studied extensively.sup.1,2, but basic properties of multiple-exciton correlations--such as coherence times, population lifetimes, binding energies and the number of particles that can be correlated--are largely unknown because they are not spectroscopically accessible from the ground state. Here we present direct observations of high-order coherences in gallium arsenide quantum wells, achieved using two-dimensional multiple-quantum spectroscopy methods in which up to seven successive light fields were used. The measurements were made possible by the combination of a reconfigurable spatial beam-shaper that formed multiple beams in specified geometries and a spatiotemporal pulse-shaper that controlled the relative optical phases and temporal delays among pulses in all the beams. The results reveal triexciton coherences (correlations of three excitons or six particles), whose existence was not obvious because the third exciton spin is unpaired, and the values of their coherence times and binding energies. Rephasing of biexcitons, triexcitons and unbound two-exciton coherences was demonstrated. We also determined that there are no significant unbound correlations of three excitons and no bound or unbound four-exciton (eight-particle) correlations. Thus, the limits, as well as the properties, of many-body correlations in this system were revealed. The measurement methods open a new window into high-order many-body interactions in materials and molecules.sup.3, and the present results should guide ongoing work on first-principles calculations of electronic interactions in semiconductor nanostructures.sup.4., Author(s): Daniel B. Turner [sup.1] , Keith A. Nelson [sup.1] Author Affiliations: (1) Department of Chemistry, Massachusetts Institute of Technology, Cambridge, USA Main A primary focus of condensed-matter research is [...]

The coherent polarization scattering matrix decomposition presented in Cameron et al. brought attention to the importance of Symmetric Scatterer Space, the space of scattering matrices corresponding to symmetric scatterers. Each symmetric scatterer scattering matrix can be associated with a complex number z, the scatterer-type parameter, where [absolute value of z] [less than or equal to] 1. A distance measure, d([z.sub.1], [z.sub.2]), was defined on Symmetric Scatterer Space providing a means of comparing scattering matrices. It will be demonstrated that Symmetric Scatterer Space is a metric space with metric d([z.sub.1], [z.sub.2]). A new mapping of the Unit Disc representation of Symmetric Scatterer Space to a sphere is also presented along with a metric on the sphere, [d.sub.s]([[theta].sub.1], [[phi].sub.1]; [[theta].sub.2], [[phi].sub.2]), that is equivalent to the metric d([z.sub.1], [z.sub.2]) on the Unit Disc. Index Terms--Coherent decomposition, conservative, polarimetry, polarization, radar polarimetry, radar scattering, radar target classification, symmetric scatterer, synthetic aperture radar (SAR).

The dual-tree quaternion wavelet transform (QWT) is a novel two-dimensional (2-D) multiscale wavelet representation for coherent processing of relative location information in images. Findings reveal an efficient analysis of the phase behavior around edge regions.

A consistent estimation procedure for the evolutionary coherence via a linear filtering approach is discussed. Findings reveal the ability of the proposed procedure in automatically selecting the optimal window width for estimating local coherence.

The coherence function is used as a tool for identifying and/or compensating the nonlinear block in a Hammerstein system. Findings reveal low computational complexity of the system.

Selective fluorescence excitation of specific molecular species is demonstrated by using coherent control of two-photon excitation with supercontinuum pulses generated with a microstructure fiber. Pulse shaping prior to pulse propagation through the fiber is controlled by a self-learning optimization loop so that the highest fluorescence signal contrast between two fluorescent proteins is obtainable. The self-learning optimization loop successfully controls both the optical nonlinarity of the microstructure fiber and the two-photon excitation of the fluorescent proteins. OCIS codes: 320.2250, 320.550, 320.7110.

Major challenges to low speed microflight are the transient and time-averaged velocities arising from the atmospheric boundary layer, particularly turbulence a few meters above the ground. In this paper, prior work on the temporal and spatial characteristics of the atmospheric boundary layer close to the ground, and the relative turbulence as perceived by a moving craft, are considered. New measurements are described that document the time-averaged and transient velocities at a height of 4 m above the ground. These were made using a bank of four multihole pressure probes laterally separated by 150 and 50 mm on a mast above a test car. Transient flow pitch angles were investigated and it was found, that the overall variation with lateral separation decreased relatively slowly with reducing separation, but that both this and the pitch angle coherence may be described nondimensionally. As the slow decrease in pitch variation with lateral spacing implies that the roll inputs arising from vertical fluctuations would increase with reducing span, it is speculated that increasingly active and authoritative control systems are required. DOI: 10.2514/1.22670

Closed-form solutions for the bit-error rate of a free-space, heterodyne optical communication system is derived when the optical beam is subjected to K-distributed optical turbulence. It is assumed that the scintillation index is confined to the range (2,3) or that the number of scatterers in the propagation path is a random variable. Index Terms--Coherent, free space, optical, turbulence.

The law of coherence helps us understand the physical force behind the increasing complexity of the evolutionary process, from quanta, to cells, to self-awareness and collective consciousness. The coherent electromagnetic field is the inner glue of every system, the 'intelligent' energy--information communication that assures a cooperative and synergic behavior to all the components of the system, as a whole, allowing harmonious evolution and unity of consciousness. Neuropsychological experiments show that the different brain areas communicate with more or less coherence according to different states of consciousness: high values are correlated with states of psychophysical integrity and well-being, whereas low values with states of conflict and depression. If we expand isomorphically these brain discoveries, we will have four main general states of coherence: from disgregation to unity, which represents an important element, in the General System Theory, to differentiate between inanimate and animate system, and to understand how billions cells become a single living organism, and then how billions of human beings could eventually generate planetary consciousness. In this light the resolution of the global ecosystem crisis implicates human transformation from a low to a highly coherent state of consciousness. The key to the entire process seems to be the coherent nature of consciousness. KEYWORDS: Brain synchronization, coherence, evolution of consciousness, self-awareness, unity of consciousness.

Ervin Laszlo's Science and the Akashic Field claims that there is a shift in Zeitgeist that allows us to view a field that entails coherence among residents of the universe, residents that hitherto have seemed far apart both in space and time. 1 agree with this claim but suggest that we need to clear up several ambiguities that have hindered understanding and therefore acceptance. Basic to clarification are an understanding of waves, spectra, and the formulations of quantum physics. KEYWORDS: Akashic Field, holism, quantum physics, waves, wholism.

People recall taboo words better than neutral words in many experimental contexts. The present rapid serial visual presentation (RSVP) experiments demonstrated this taboo-superiority effect for immediate recall of mixed lists containing taboo and neutral words matched for familiarity, length, and category coherence. Under binding theory (MacKay et al., 2004), taboo superiority reflects an interference effect: Because the emotional reaction system prioritizes binding mechanisms for linking the source of an emotion to its context, taboo words capture the mechanisms for encoding list context in mixed lists, impairing the encoding of adjacent neutral words when RSVP rates are sufficiently rapid. However, for pure or unmixed lists, binding theory predicted no better recall of taboo-only than of neutral-only lists at fast or slow rates. Present results supported this prediction, suggesting that taboo superiority in immediate recall reflects context-specific binding processes, rather than context-free arousal effects, or emotion-linked differences in rehearsal, processing time, output interference, time-based decay, or guessing biases. Keywords: emotion, short-term memory, arousal, binding

The interface-specific fourth-order x(super 4) coherent Raman spectroscopy in the frequency domain is demonstrated. The fingerprint vibrational spectrum of R800 at the air/water interface for the wide spectral region from 100 cm (sup -1) to 3600 cm(sup -1) is observed with spectroscopy to indicate that the interface of a few molecular diameter thickness was successfully probed by the frequency-domain x(super 4) spectroscopy.

A compression algorithm for signals measured during power disturbances that obtain good compression ratios while preserving important features for signal analysis is proposed. Methods to obtain a representation of a signal based on damped sinusoids together with procedures to eliminate post-echo and pre-echo errors that often appear on greedy decomposition algorithms are presented.

The Charlier polynomials are used for constructing oscillator-like systems. We introduce coherent states of the system are defined and study the main properties (in particular, the (over)completeness property). We show [...]

A new coherent array imaging method, phased subarray (PSA) imaging that performs partial transmit and receive beam-forming using a subset of adjacent elements at each firing step is proposed. The low-resolution subarray images are laterally upsampled, interpolated, weighted, and coherently summed to form the final high-resolution PSA image.

Theoretical analysis of nonadiabatic electron-transfer reactions in molecules usually assumes that electron amplitude propogates coherently from the reductant to the oxidant via covalent and noncovalent coupling pathways. An attempt is made to show that when the tunneling electron excites local bridge vibrations (inelastic tunneling), the excitation 'labels' the physical pathway traversed.

The making of an inference-based decision may be accompanied by an increase in the coherence of assessments of the individual arguments related to the alternatives at hand. Two approaches for studying emergence coherence are developed.

Coherent optical beams are used to communicate, store, and process information in a growing number of applications. The availability of coherent laser sources is of critical importance for the realization of such optical information systems. An incoherent source randomly populates the available temporal and spatial channels of the optical system, making it difficult to represent information. Coherent laser sources provide a stable carrier on which to encode information, making it possible to realize powerful information-processing techniques such as wavelength division multiplexing in fiber networks, gated holographic imaging, and three-dimensional optical data storage., Introduction In computers, communication networks, sensors, and other information systems, information is encoded in the various properties of electromagnetic fields. The optical portion of the electromagnetic spectrum has been used [...]

Coherent reception depends upon matching of phase between the transmitted and received signal. Fast convolution techniques based on fast Fourier tansform (FFT) are widely used for extracting time delay information from such matching. The latency in processing a large data window of the received signal is a serious overhead for mission critical real time applications. The implementation of a parallel algorithm for correlation of long data sequences in multiprocessor environment is demonstrated here. The algorithm does processing while acquiring the received signal and reduces the computation overhead considerably because of inherent parallelism. Index Terms--Block correlator, coherent, multiprocessor, parallel algorithm.

A comprehensive, quantitative analysis that combines a hierarchical theoretical approach with experimental measurements is presented of the deformation behavior of coherently strained InAs/GaAs(111)A heteroepitaxial systems. The experimental measurements are found to be in excellent agreement with the calculated lattice interplanar distances and the corresponding strain fields in the thin mechanically unconstrained substrates considered in the theoretical analysis.

The utility of a semiclassical initial value representation to simulate coherent control is explored. It is observed that the coherent control over ICN photodissociation is extensive.

The observation of a resonant, coherent nuclear motion is reported in the elimination reaction of 1,3-dibromopropane (a system with 27 internal degrees of freedom) using femtosecond time-resolved mass spectrometry. The C-Br bond clevage occurs with a reaction time of 2.5 ps and yields the 3-bromopropyl radical, which subsequently reacts to give cyclopropane in 7.5 ps.

The generalized coherence estimate was analyzed.

Byline: Shukla Basu (1), R.K. Roychoudhury (2) Keywords: anharmonic oscillator; coherent states; nonlinear oscillation Abstract: A perturbation solution of the nonlinear oscillation of the form x + [omega] .sup.2 x + bx.sup.2 + ax.sup.3 = 0 is obtained, using the coherent states constructed out of quantum oscillator states. The equation of the spine obtained here is compared with that obtained by using an averaging procedure. It is found that the equation obtained in the present case is simpler and different from the other. Also the method used here has the distinct advantage that it is suitable for any nonlinear oscillator containing both even and odd higher order terms. Author Affiliation: (1) School of Mathematical and Information Sciences, Coventry University, Priory St., Coventry, CV1 5FB, UK (2) Physics and Applied Mathematics Unit, Indian Statistical Institute, Calcutta, India Article History: Registration Date: 08/10/2004

The reason why atomic physicists are interested in celestial mechanics is simple: the gravitational and Coulombic potentials are mathematically identical and a one-electron atom is, therefore, governed by the same Hamiltonian as is the Kepler problem. However, once one goes beyond the two-body Kepler problem the connections between atomic physics and celestial mechanics become less direct. For example, the three-body problem, arguably the raison d'etre of celestial mechanics for several centuries, has received relatively little attention from atomic physicists because it does not have a direct quantum counterpart: three quantum particles cannot mutually attract one another and at the same time interact through a purely Coulombic force law. Nevertheless, in the last five years several research groups have discovered that quantum analogues of a particular limit of the three-body problem, the restricted three-body problem, not only exist but contain dramatically new physics. This article will describe this work and in particular will demonstrate the possibility of producing localized electronic states in atoms that are direct analogs of the coherent states of the harmonic oscillator. These coherent wavepackets behave in a similar way to the coherent states of the harmonic oscillator and the resulting atom mimics a 'classical' or Bohr atom although external fields must be used to maintain their integrity. Such wavepacket states are of as much fundamental interest in laser chemistry as they are in atomic, molecular, optical, and solid state physics. The potential applications of time-evolving quantum wavepackets seem limitless; some examples of their uses include: the exploration of the boundary between classical and quantum mechanics, the investigation of the interpretation of quantum mechanics by creating experimental realizations of such classic experiments as Schrodinger's Cat, the control of chemical reaction dynamics to achieve laser isotope separation, the storage of coherence for quantum computational or communications purposes, and the construction of optical switches and modulators.

Anthropogenic features show up as highly coherent objects even in heavily decorrelated interferograms. In order to assess whether the information from such features is still usable, the stability of their phase and coherence is analyzed through a series of interferograms. The results indicate that these features can remain interferometrically stable over several years. Index Terms - Coherence, differential SAR interferometry, man-made features.

Nonoverlapping probe and pump pulses are used in studying the extreme asymmetry of four-wave mixing (FWM) excitation spectrum when steady-state excitation is replaced with pulsed excitation. In this condition, only the Rabi sideband near the resonance frequency persists while there is no FWM spectrum if the probe follows the pump. However, the FWM signal becomes more intense when the probe precedes the pump. This phenomenon is caused by free-induction decay (FID) in which coherence survives the FID pulse.

Temperature dependencies of magnetic properties were measured in barium-ferrite thin films with grains having in-plane aligned as well as randomly oriented easy axes. The temperature dependence of [H.sub.c] was shown to be similar to that of the effective anisotropy field, which is determined by the crystalline and shape anisotropies. The measured [H.sub.c] values in the easy-axis aligned and randomly oriented films are significantly smaller than those predicted by the Stoner-Wohlfarth (SW) coherent rotation model. Such discrepancies are believed to be caused by incoherent rotation. Deviations from the SW model were also found within a wide temperature range in the angular dependence of coercivity and remanent coercivity, the field dependence of torque and rotational hysteresis. These led to the conclusion that temperature has only weak affects on the rotation mode of the magnetization. The discrepancies between the thermal activation volume and the grain size which were found previously at room temperature, and were believed to be yet another signature of incoherent rotation, were shown to also exist at a low temperature of 173 K. Index Terms - Barium ferrite, incoherent rotation, magnetic recording media, thermal activation, thin film.

Byline: F.P. Temme (1) Abstract: For automorphic spin symmetries over isotopomer networks defining both NMR coherence transfer and cage-cluster ro-vibrational (RV) weighting phenomena, the role of Schur functions (SF) and their SF products (SFP) (restricted to S.sub.n) is re-evaluated, beyond that typical of atomic physics. It is seen now as being equally applicable to molecular physics. Our special focus here is on the SU2 x S.sub.n dual group for its importance in replacing (Jucys) recoupling schemata by generalised S.sub.n democracy invariants, which ensure the retention of simple reducibility (SR) of carrier spaces for superboson mappings, under U x P(I) actions over Liouville space, i.e., as in Physica A 198 (1993) 245. SFP mapping onto S.sub.n and simple Young rule SF mappings onto {[[lambda]]}(S.sub.n) sets are developed in the high n-index, weak-branching limit and utilise known similarities in the algorithms for the Young and Littlewood--Richardson rules. Over discrete k rank, from k=n (down), the [summation over (term)].sub.I1/2{/T .sup.k(I1/2)/x007D k-set orders are related to the au ordered bipartite [chi] .sub.12n .sup.[[lambda]] (S 2n.sub.characters. Author Affiliation: (1) Department of Chemistry, Queen's University, Kingston, Canada, K7L 3N6 Article History: Registration Date: 20/10/2004

A natural definition that associate two vector random processes with arbitrary dimensions was formed using the algebraic associativity of the matrices and vectors. The coherence matrix for the two vector random processes was found to be the Hermitian matrix. Using real eigenvalues, the matrix can be transformed to a diagonal form. The larger eigenvalue corresponds to the coherence of the vectors examined with respect to the direction of minimum noise variance, while the lesser value characterizes the direction of maximum noise variance for two-dimensional processes.