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Search Results: 1 - 10 of 5926 matches for " Markus Arndt "
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Quantum interferometry with complex molecules
Markus Arndt,Klaus Hornberger
Physics , 2009,
Abstract: This chapter reviews recent experiments on matter wave interferometry with large molecules. Starting from an elementary introduction to matter wave physics we discuss far-field diffraction and near-field interferometry with thermally excited many-body systems. We describe the constraints imposed by decoherence and dephasing effects, and present an outlook to the future challenges in macromolecule and cluster interferometry.
Interferometry with large molecules: exploration of coherence, decoherence and novel beam methods
Arndt, Markus;Hackermüller, Lucia;Reiger, Elisabeth;
Brazilian Journal of Physics , 2005, DOI: 10.1590/S0103-97332005000200004
Abstract: quantum experiments with complex objects are of fundamental interest as they allow to quantitatively trace the quantum-to-classical transition under the influence of various interactions between the quantum object and its environment. we briefly review the present status of matter wave interferometry and decoherence studies with large molecules and focus in particular on the challenges for novel beam methods for molecular quantum optics with clusters, macromolecules or nanocrystals.
Quantum physics meets biology
Markus Arndt,Thomas Juffmann,Vlatko Vedral
Physics , 2009,
Abstract: Quantum physics and biology have long been regarded as unrelated disciplines, describing nature at the inanimate microlevel on the one hand and living species on the other hand. Over the last decades the life sciences have succeeded in providing ever more and refined explanations of macroscopic phenomena that were based on an improved understanding of molecular structures and mechanisms. Simultaneously, quantum physics, originally rooted in a world view of quantum coherences, entanglement and other non-classical effects, has been heading towards systems of increasing complexity. The present perspective article shall serve as a pedestrian guide to the growing interconnections between the two fields. We recapitulate the generic and sometimes unintuitive characteristics of quantum physics and point to a number of applications in the life sciences. We discuss our criteria for a future quantum biology, its current status, recent experimental progress and also the restrictions that nature imposes on bold extrapolations of quantum theory to macroscopic phenomena.
Experimental verification of the Heisenberg uncertainty principle for hot fullerene molecules
Olaf Nairz,Markus Arndt,Anton Zeilinger
Physics , 2001, DOI: 10.1103/PhysRevA.65.032109
Abstract: The Heisenberg uncertainty principle for material objects is an essential corner stone of quantum mechanics and clearly visualizes the wave nature of matter. Here we report a demonstration of the Heisenberg uncertainty principle for the most massive, complex and hottest single object so far, the fullerene molecule C70 at a temperature of 900 K. We find a good quantitative agreement with the theoretical expectation: dx * dp = h, where dx is the width of the restricting slit, dp is the momentum transfer required to deflect the fullerene to the first interference minimum and h is Planck's quantum of action.
Theory of decoherence in a matter wave Talbot-Lau interferometer
Klaus Hornberger,John E. Sipe,Markus Arndt
Physics , 2004, DOI: 10.1103/PhysRevA.70.053608
Abstract: We present a theoretical framework to describe the effects of decoherence on matter waves in Talbot-Lau interferometry. Using a Wigner description of the stationary beam the loss of interference contrast can be calculated in closed form. The formulation includes both the decohering coupling to the environment and the coherent interaction with the grating walls. It facilitates the quantitative distinction of genuine quantum interference from the expectations of classical mechanics. We provide realistic microscopic descriptions of the experimentally relevant interactions in terms of the bulk properties of the particles and show that the treatment is equivalent to solving the corresponding master equation in paraxial approximation.
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.
Master Equation for the Motion of a Polarizable Particle in a Multimode Cavity
Stefan Nimmrichter,Klemens Hammerer,Peter Asenbaum,Helmut Ritsch,Markus Arndt
Physics , 2010, DOI: 10.1088/1367-2630/12/8/083003
Abstract: We derive a master equation for the motion of a polarizable particle weakly interacting with one or several strongly pumped cavity modes. We focus here on massive particles with complex internal structure such as large molecules and clusters, for which we assume a linear scalar polarizability mediating the particle-light interaction. The predicted friction and diffusion coefficients are in good agreement with former semiclassical calculations for atoms and small molecules in weakly pumped cavities, while the current rigorous quantum treatment and numerical assessment sheds a light on the feasibility of experiments that aim at optically manipulating beams of massive molecules with multimode cavities.
Polarizability measurements in a molecule near-field interferometer
Martin Berninger,André Stefanov,Sarayut Deachapunya,Markus Arndt
Physics , 2007, DOI: 10.1103/PhysRevA.76.013607
Abstract: We apply near-field matter-wave interferometry to determine the absolute scalar polarizability of the fullerenes C$_{60}$ and C$_{70}$. A key feature of our experiment is the combination of good transmission and high spatial resolution, gained by wide molecular beams passing through sub-micron gratings. This allows to significantly facilitate the observation of field-dependent beam shifts. We thus measure the polarizability to be $\alpha=88.9 \pm 0.9 \pm 5.1 \rm \AA^{3}$ for C$_{60}$ and to $\alpha = 108.5 \pm 2.0 \pm 6.2 \rm \AA^{3}$ for C$_{70}$.
Gas phase sorting of nanoparticles
Hendrik Ulbricht,Martin Berninger,Sarayut Deachapunya,Andre Stefanov,Markus Arndt
Physics , 2007,
Abstract: We discuss Stark deflectometry of micro-modulated molecular beams for the enrichment of biomolecular isomers as well as single-wall carbon nanotubes and we demonstrate the working principle of this idea with fullerenes. The sorting is based on the species-dependent polarizability-to-mass ratio $\alpha/m$. The device is compatible with a high molecular throughput, and the spatial micro-modulation of the beam permits to obtain a fine spatial resolution and a high sorting sensitivity.
Absolute absorption spectroscopy based on molecule interferometry
Stefan Nimmrichter,Klaus Hornberger,Hendrik Ulbricht,Markus Arndt
Physics , 2008, DOI: 10.1103/PhysRevA.78.063607
Abstract: We propose a new method to measure the absolute photon absorption cross section of neutral molecules in a molecular beam. It is independent of our knowledge of the particle beam density, nor does it rely on photo-induced fragmentation or ionization. The method is based on resolving the recoil resulting from photon absorption by means of near-field matter-wave interference, and it thus applies even to very dilute beams with low optical densities. Our discussion includes the possibility of internal state conversion as well as fluorescence. We assess the influence of various experimental uncertainties and show that the measurement of absolute absorption cross sections is conceivable with high precision and using existing technologies.
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