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Search Results: 1 - 10 of 669115 matches for " J. L. S?rensen "
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A Major Change in the Stratigraphy of the Santorini Volcano in Greece  [PDF]
Walter L. Friedrich, Annette H?jen Srensen, J. Richard Wilson, Michael Fytikas, Spyridon Pavlides, Samson Katsipis
International Journal of Geosciences (IJG) , 2017, DOI: 10.4236/ijg.2017.86043
Abstract: Two prominent and similar pumice series were described on Thera in 1879— the Upper and Lower Pumice Series (UPS and LPS). Since then, geologists have treated the two series separately because they seemingly occurred at distinct levels and had different ages. Here we show that these two pumice series are identical; there is no LPS on Santorini. All stratigraphic conclusions based on the LPS from Santorini should therefore be discarded. The water-filled Santorini caldera with its steep inner slopes existed before the eruption. Volcano-tectonic effects in connection with caldera formation created concentric terraces that were mantled by the products of the Late Bronze Age (LBA) eruption. Subsequent erosion only left remnants of the mantle behind. Topographic effects followed by slumping during sedimentation caused confusion of the stratigraphy on the caldera wall. Our results are supported by geological, paleontological and archaeological evidence. Furthermore, the caldera with its minerals, pigments, harbours and hot springs was accessible for the Thereans. This reinterpretation opens new perspectives for archaeological research. The catastrophic LBA eruption (previously called the Minoan eruption) destroyed a flourishing culture on Santorini and impacted neighbouring cultures around 1613 BC.
Heater self-calibration technique for shape prediction of fiber tapers
Heidi L. Srensen,Eugene S. Polzik,Jürgen Appel
Physics , 2013, DOI: 10.1109/JLT.2014.2314319
Abstract: In the production of tapered optical fibers, it is important to control the fiber shape according to application-dependent requirements and to ensure adiabatic tapers. Especially in the transition regions, the fiber shape depends on the heater properties. The axial viscosity profile of the fiber within the heater can, however, be hard to access and is therefore often approximated by assuming a uniform temperature distribution. We present a method for easy experimental calibration of the viscosity profile within the heater. This allows the determination of the resultant fiber shape for arbitrary pulling procedures, using only an additional camera and the fiber drawing setup itself. We find very good agreement between the modeled and measured fiber shape.
Ground-State Energy and Spin Gap of Spin-1/2 Kagome Heisenberg Antiferromagnetic Clusters: Large Scale Exact Diagonalization Results
A. M. L?uchli,J. Sudan,E. S. Srensen
Physics , 2011, DOI: 10.1103/PhysRevB.83.212401
Abstract: We present a comprehensive list of ground state energies and spin gaps of finite kagome clusters with up to 42 spins obtained using large-scale exact diagonalization techniques. This represents the current limit of this exact approach. For a fixed number of spins N we study several cluster shapes under periodic boundary conditions in both directions resulting in a toroidal geometry. The clusters are characterized by their side length and diagonal as well as the shortest "Manhattan" diameter of the torii. A finite-size scaling analysis of the ground state energy as well as the spin gap is then performed in terms of the shortest toroidal diameter as well as the shortest "Manhattan" diameter. The structure of the spin-spin correlations further supports the importance of short loops wrapping around the torii.
Doppler cooling of calcium ions using a dipole-forbidden transition
R. J. Hendricks,J. L. Srensen,C. Champenois,M. Knoop,M. Drewsen
Physics , 2007, DOI: 10.1103/PhysRevA.77.021401
Abstract: Doppler cooling of calcium ions has been experimentally demonstrated using the S1/2 to D5/2 dipole-forbidden transition. Scattering forces and fluorescence levels a factor of 5 smaller than for usual Doppler cooling on the dipole allowed S1/2 to P1/2 transition have been achieved. Since the light scattered from the ions can be monitored at (violet) wavelengths that are very different from the excitation wavelengths, single ions can be detected with an essentially zero background level. This, as well as other features of the cooling scheme, can be extremely valuable for ion trap based quantum information processing.
Scalable Quantum Networks based on Few-Qubit Registers
L. Jiang,J. M. Taylor,A. S. Srensen,M. D. Lukin
Physics , 2007, DOI: 10.1142/S0219749910006058
Abstract: We describe and analyze a hybrid approach to scalable quantum computation based on an optically connected network of few-qubit quantum registers. We show that probabilistically connected five-qubit quantum registers suffice for deterministic, fault-tolerant quantum computation even when state preparation, measurement, and entanglement generation all have substantial errors. We discuss requirements for achieving fault-tolerant operation for two specific implementations of our approach.
Spatial and vertical extent of nucleation events in the Midwestern USA: insights from the Nucleation In ForesTs (NIFTy) experiment
S. C. Pryor, R. J. Barthelmie, L. L. S rensen, J. G. McGrath, P. Hopke,T. Pet j
Atmospheric Chemistry and Physics (ACP) & Discussions (ACPD) , 2011,
Abstract: Measurements of aerosol particle physical and chemical properties, gas phase concentrations and meteorological parameters were made along a transect in southern Indiana during the Nucleation In ForesTs (NIFTy) experiment conducted in May 2008. These measurements indicate nucleation was observed at all three measurement sites on almost half of all sampling days. The intensity of the nucleation events, as measured by the increase in ≥10 nm aerosol particle number concentrations of approximately 2×104 cm 3 over a layer of at least 300 m depth, is in good agreement with recent model results for the Midwestern USA derived using PMCAMx-UF. During the hour after termination of nucleation approximately half of the number concentration reduction is due to coagulation, while the remainder is due in equal parts to dry deposition and entrainment of relatively ultra-fine aerosol particle free troposphere air. Clear nucleation with continuous subsequent growth is only observed on days when the morning fractional cloud cover was less than 30%. It is associated with a clear transition from a strongly stratified atmosphere with low turbulence intensity and weak vertical velocities, to much a weaker vertical gradient of wind speed, increased turbulence intensity and stronger downwards vertical velocities, consistent with growth of the mixed layer and entrainment of air from the residual layer. Nucleation intensity is not very strongly determined by the prevailing condensational sink. However, there is a strong correlation between both a modified version of the Nucleation Parameter from Boy and Kulmala (2002) and ultrafine aerosol particle number concentrations, and mean morning H2SO4 concentrations and ultrafine aerosol particle number concentrations. Five A-class event days during NIFTy were characterized by values of the dimensionless nucleation parameter of Kuang et al. (2010) that are below 0.3, further indicating the applicability of their postulate that nucleation is favored by LΓ values below 0.7. Based on aerosol particle composition measurements it appears that aerosol particle formation and initial growth to approximately 30 nm diameter is dominated by ammonium and sulfate. Conservative estimates of the percent contribution of H2SO4 to aerosol particle growth (for sub-30 nm aerosol particles) on five A-class event days ranged from 23 to 85%.
Coulomb corrections to the three-body correlation function in high-energy heavy ion reactions
E. O. Alt,T. Cs?rg?,B. L?rstad,and J. Schmidt-Srensen
Physics , 1998, DOI: 10.1016/S0370-2693(99)00588-2
Abstract: Starting from an asymptotically correct three-body Coulomb wave-function, we determine the effect of Coulomb final state interaction on the three-particle Bose-Einstein correlation function of similarly charged particles. We numerically estimate that the Riverside approximation is not precise enough to determine the three-body Coulomb correction factor in the correlation function, if the characteristic HBT radius parameter is 5 - 10 fm, which is the range of interest in high-energy heavy ion physics.
Non-Destructive Identification of Cold and Extremely Localized Single Molecular Ions
M. Drewsen,A. Mortensen,R. Martinussen,P. Staanum,J. L. Srensen
Physics , 2004, DOI: 10.1103/PhysRevLett.93.243201
Abstract: A simple and non-destructive method for identification of a single molecular ion sympathetically cooled by a single laser cooled atomic ion in a linear Paul trap is demonstrated. The technique is based on a precise determination of the molecular ion mass through a measurement of the eigenfrequency of a common motional mode of the two ions. The demonstrated mass resolution is sufficiently high that a particular molecular ion species can be distinguished from other equally charged atomic or molecular ions having the same total number of nucleons.
Squeezing and entanglement of atomic beams
L. -M. Duan,A. Srensen,J. I. Cirac,P. Zoller
Physics , 2000, DOI: 10.1103/PhysRevLett.85.3991
Abstract: We propose and analyze a scheme for generating entangled atomic beams out of a Bose-Einstein condensate using spin-exchanging collisions. In particular, we show how to create both atomic squeezed states and entangled states of pairs of atoms.
Environment Assisted Precision Measurement
G. Goldstein,P. Cappellaro,J. R. Maze,J. S. Hodges,L. Jiang,A. S. Srensen,M. D. Lukin
Physics , 2009, DOI: 10.1103/PhysRevLett.106.140502
Abstract: We describe a method to enhance the sensitivity of precision measurements that takes advantage of a quantum sensor's environment to amplify its response to weak external perturbations. An individual qubit is used to sense the dynamics of surrounding ancillary qubits, which are in turn affected by the external field to be measured. The resulting sensitivity enhancement is determined by the number of ancillas that are coupled strongly to the sensor qubit; it does not depend on the exact values of the coupling strengths and is resilient to many forms of decoherence. The method achieves nearly Heisenberg-limited precision measurement, using a novel class of entangled states. We discuss specific applications to improve clock sensitivity using trapped ions and magnetic sensing based on electronic spins in diamond.
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