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Search Results: 1 - 10 of 4449 matches for " Lucia Hackermueller "
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Influence of molecular temperature on the coherence of fullerenes in a near-field interferometer
Klaus Hornberger,Lucia Hackermueller,Markus Arndt
Physics , 2004, DOI: 10.1103/PhysRevA.71.023601
Abstract: We study C70 fullerene matter waves in a Talbot-Lau interferometer as a function of their temperature. While the ideal fringe visibility is observed at moderate molecular temperatures, we find a gradual degradation of the interference contrast if the molecules are heated before entering the interferometer. A method is developed to assess the distribution of the micro-canonical temperatures of the molecules in free flight. This way the heating-dependent reduction of interference contrast can be compared with the predictions of quantum theory. We find that the observed loss of coherence agrees quantitatively with the expected decoherence rate due to the thermal radiation emitted by the hot molecules.
Decoherence in a Talbot Lau interferometer: the influence of molecular scattering
Lucia Hackermueller,Klaus Hornberger,Bjoern Brezger,Anton Zeilinger,Markus Arndt
Physics , 2003, DOI: 10.1007/s00340-003-1312-6
Abstract: We study the interference of C70 fullerenes in a Talbot-Lau interferometer with a large separation between the diffraction gratings. This permits the observation of recurrences of the interference contrast both as a function of the de Broglie wavelength and in dependence of the interaction with background gases. We observe an exponential decrease of the fringe visibility with increasing background pressure and find good quantitative agreement with the predictions of decoherence theory. From this we extrapolate the limits of matter wave interferometry and conclude that the influence of collisional decoherence may be well under control in future experiments with proteins and even larger objects.
Decoherence of matter waves by thermal emission of radiation
Lucia Hackermueller,Klaus Hornberger,Bjoern Brezger,Anton Zeilinger,Markus Arndt
Physics , 2004, DOI: 10.1038/nature02276
Abstract: Emergent quantum technologies have led to increasing interest in decoherence - the processes that limit the appearance of quantum effects and turn them into classical phenomena. One important cause of decoherence is the interaction of a quantum system with its environment, which 'entangles' the two and distributes the quantum coherence over so many degrees of freedom as to render it unobservable. Decoherence theory has been complemented by experiments using matter waves coupled to external photons or molecules, and by investigations using coherent photon states, trapped ions and electron interferometers. Large molecules are particularly suitable for the investigation of the quantum-classical transition because they can store much energy in numerous internal degrees of freedom; the internal energy can be converted into thermal radiation and thus induce decoherence. Here we report matter wave interferometer experiments in which C70 molecules lose their quantum behaviour by thermal emission of radiation. We find good quantitative agreement between our experimental observations and microscopic decoherence theory. Decoherence by emission of thermal radiation is a general mechanism that should be relevant to all macroscopic bodies.
Optical polarizabilities of large molecules measured in near-field interferometry
Lucia Hackermueller,Klaus Hornberger,Stefan Gerlich,Michael Gring,Hendrik Ulbricht,Markus Arndt
Physics , 2007, DOI: 10.1007/s00340-007-2873-6
Abstract: We discuss a novel application of matter wave interferometry to characterize the scalar optical polarizability of molecules at 532 nm. The interferometer presented here consists of two material absorptive gratings and one central optical phase grating. The interaction of the molecules with the standing light wave is determined by the optical dipole force and is therefore directly dependent on the molecular polarizability at the wavelength of the diffracting laser light. By comparing the observed matter-wave interference contrast with a theoretical model for several intensities of the standing light wave and molecular velocities we can infer the polarizability in this first proof-of-principle experiment for the fullerenes C60 and C70 and we find a good agreement with literature values.
The wave nature of biomolecules and fluorofullerenes
Lucia Hackermueller,Stefan Uttenthaler,Klaus Hornberger,Elisabeth Reiger,Bjoern Brezger,Anton Zeilinger,Markus Arndt
Physics , 2003, DOI: 10.1103/PhysRevLett.91.090408
Abstract: We demonstrate quantum interference for tetraphenylporphyrin, the first biomolecule exhibiting wave nature, and for the fluorofullerene C60F48 using a near-field Talbot-Lau interferometer. For the porphyrins, which are distinguished by their low symmetry and their abundant occurence in organic systems, we find the theoretically expected maximal interference contrast and its expected dependence on the de Broglie wavelength. For C60F48 the observed fringe visibility is below the expected value, but the high contrast still provides good evidence for the quantum character of the observed fringe pattern. The fluorofullerenes therefore set the new mark in complexity and mass (1632 amu) for de Broglie wave experiments, exceeding the previous mass record by a factor of two.
Collisional decoherence observed in matter wave interferometry
Klaus Hornberger,Stefan Uttenthaler,Bjoern Brezger,Lucia Hackermueller,Markus Arndt,Anton Zeilinger
Physics , 2003, DOI: 10.1103/PhysRevLett.90.160401
Abstract: We study the loss of spatial coherence in the extended wave function of fullerenes due to collisions with background gases. From the gradual suppression of quantum interference with increasing gas pressure we are able to support quantitatively both the predictions of decoherence theory and our picture of the interaction process. We thus explore the practical limits of matter wave interferometry at finite gas pressures and estimate the required experimental vacuum conditions for interferometry with even larger objects.
A Kapitza-Dirac-Talbot-Lau interferometer for highly polarizable molecules
Stefan Gerlich,Lucia Hackermueller,Klaus Hornberger,Alexander Stibor,Hendrik Ulbricht,Michael Gring,Fabienne Goldfarb,Tim Savas,Marcel Mueri,Marcel Mayor,Markus Arndt
Physics , 2008, DOI: 10.1038/nphys701
Abstract: Research on matter waves is a thriving field of quantum physics and has recently stimulated many investigations with electrons, neutrons, atoms, Bose-condensed ensembles, cold clusters and hot molecules. Coherence experiments with complex objects are of interest for exploring the transition to classical physics, for measuring molecular properties and they have even been proposed for testing new models of space-time. For matter-wave experiments with complex molecules, the strongly dispersive effect of the interaction between the diffracted molecule and the grating wall is a major challenge because it imposes enormous constraints on the velocity selection of the molecular beam. We here describe the first experimental realization of a new interferometer that solves this problem by combining the advantages of a Talbot-Lau setup with the benefits of an optical phase grating and we show quantum interference with new large molecules.
Talbot-Lau interferometry with fullerenes: Sensitivity to inertial forces and vibrational dephasing
A. Stibor,K. Hornberger,L. Hackermueller,A. Zeilinger,M. Arndt
Physics , 2004,
Abstract: We discuss matter wave experiments in a near-field interferometer and focus on dephasing phenomena due to inertial forces. Their presence may result in a significant reduction of the observed interference contrast, even though they do not lead to genuine decoherence. We provide quantitative estimates for the most important effects and demonstrate experimentally the strong influence of acoustic vibrations. Since the effects of inertial forces get increasingly important for the interferometry with more massive particles they have to be identified and compensated in future experiments.
BRICS, a Multi-Centre “Legal Network”?  [PDF]
Lucia Scaffardi
Beijing Law Review (BLR) , 2014, DOI: 10.4236/blr.2014.52013
Abstract:

The paper analyzes the phenomenon of the BRICS group and its transformation into BRICs. From the first Summit, whose final declarations were mainly centered on economic, financial and commercial themes, the group attention has broadened its horizons, as to encompass health, agriculture, environment, international relations. The BRICS working method seems to suggest a new pattern of inter-state relations, based on peer-to-peer cooperation, experiences sharing and “soft” policy transfer. Given the difficult classification of this new “entity”, the author suggests considering it more as a network, where there is not a singular hegemony power, but where the relevance of the different countries varies according to the issue discussed in the Summit.

Role of interactions in 87Rb-40K Bose-Fermi mixtures in a 3d optical lattice
Th. Best,S. Will,U. Schneider,L. Hackermueller,D. -S. Luehmann,D. van Oosten,I. Bloch
Physics , 2008, DOI: 10.1103/PhysRevLett.102.030408
Abstract: We investigate the effect of interspecies interaction on a degenerate mixture of bosonic 87Rb and fermionic 40K atoms in a three-dimensional optical lattice potential. Using a Feshbach resonance, the 87Rb-40K interaction is tuned over a wide range. Through an analysis of the 87Rb momentum distribution, we find a pronounced asymmetry between strong repulsion and strong attraction. In the latter case, the Bose-Hubbard parameters are renormalized due to self-trapping, leading to a marked shift in the superfluid to Mott insulator transition with increasing Bose-Fermi interaction.
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