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Ivette Schuller

Technical University of Berlin

Abstract: The insight that the world is fundamentally quantum mechanical inspired the development of quantum information theory. However, the world is not only quantum but also relativistic, and indeed many implementations of quantum information tasks involve truly relativistic systems. In this talk I consider relativistic effects on entanglement in flat and curved spacetimes. I will emphasize the qualitative differences to a non-relativistic treatment, and demonstrate that a thorough understanding of quantum information theory requires taking relativity into account. The exploitation of such relativistic effects will likely play an increasing role in the future development of quantum information theory. The relevance of these results extends beyond pure quantum information theory, and applications to foundational questions in cosmology and black hole physics will be presented.

Hendrik Ulbricht

University of Southampton

Abstract: Matter wave interferometry experiments with very massive molecules has the potential to test fundamental physics as the quantum to classical transition. But the very same experimental setup can also be used to investigate molecular porperties as for instance static and dynamic polarizabilities, electric dipole moments, absoprtion cross sections and van der Waals interaction parameter from collision cross sections to an high degree of precision - as well as for molecular and nanoparticle beam sorting. I will report on the recent status of molecule interfernce with Talbot-Lau and Kapitz-Dirac-Talbot-Lau interferometers [Gerlich et al., Nature Physics 3, 711 - 715 (2007)] with organic molecules of masses of up to 2500 amu and then extend on the various metrology opportunities [Gerlich et al., Angw. Chem. 47, 6195-6198 (2008)]. Particle beam manipulation techniques as for the slowing and cooling of massive molecules are central to both probing quantum limits and molecule metrology and I will also discuss those.

Tobias Osborne

Royal Holloway

Abstract: In 1972 Lieb and Robinson proved a bound on the velocity of propagation of correlations through an interacting spin system. This bound, when phrased in slightly more modern terms, says that all information, both classical and quantum, is exponentially attenuated outside of a light cone with an effective speed of light determined by the lattice structure. In this talk I will discuss the state of the art of Lieb-Robinson type bounds, including systems with static and dynamical disorder. It turns out that, when disorder is present, the Lieb-Robinson bound can be replaced by a stronger bound. The bounds that arise depend on the nature and strength of the disorder and at least three types of behaviour can be identified: information propagates either ballistically, diffusively, or is  strongly localised. Implications for fault tolerance in quantum computers will be sketched.

Physics Colloquium:  Léon Sanche

Groupe en Sciences des Radiations, Faculté de médecine, Université de Sherbrooke, Sherbrooke (Québec)

Abstract: 

Electrons with energies in the range 0-30 eV can induce at interfaces and within condensed matter specific reactions which are of relevance to applied fields such as nanolithography, dielectric aging, radiation waste management, radiation processing, astrobiology, planetary and atmospheric chemistry, surface photochemistry, radiobiology, radiotherapy and ballistic electronics. The action of low energy electrons (LEEs) in materials of relevance to five of these fields has been investigated with model systems consisting of pure or doped thin molecular films. The target film is deposited on a metal or semi-conductor substrate and bombarded by a LEE beam (0-30 eV) under ultra high vacuum (UHV) conditions. Neutral fragments and ions emanating from these films are analysed by mass spectrometry. The products remaining in the films are analyzed in situ by X-ray photoelectron and electron energy loss spectroscopies; they can also be removed from the UHV system and analyzed by HPLC and LC/MS. By comparing the results of the theory and different experiments, it is possible to determine fundamental mechanisms that are involved in the chemical reactions induced by LEEs. Such mechanisms involve (1) the formation of transient anions which play a dominant role in the fragmentation of all molecules investigated; (2) dipolar dissociation which produces an anion and a cation and (3) reactive scattering, which induces non-thermal reactions. The transient anions fragment the parent molecules by decaying into dissociative electronically excited states or by dissociating into a stable anion and a neutral radical. These fragments usually initiate other reactions with nearby molecules, causing further chemical damage. The damage caused by transient anions is dependent on the molecular environment

Andrew Ho

Royal Holloway

Abstract: We study the conditions under which, using a canonical transformation, the phases sought after for the repulsive Hubbard model, namely a Mott insulator in the paramagnetic and anti- ferromagnetic phases, and a putative d-wave superfluid can be deduced from observations in an optical lattice loaded with a spin-imbalanced ultra-cold Fermi gas with attractive interactions, thus realizing the attractive Hubbard model. We argue that the Mott insulator and antiferromagnetic phase of the repulsive Hubbard model are easier to observe in the attractive Hubbard mode as a band insulator of Cooper pairs and superfluid phase, respectively. The putative d-wave superfluid phase of the repulsive Hubbard model doped away from half-filling is related to a d-wave antiferromagnetic phase for the attractive Hubbard model. We discuss the advantages of this approach to 'quantum simulate' the Hubbard model in an optical lattice over the simulation of the doped Hubbard model in the repulsive regime.

Florian Marquardt

University of Munich

Abstract: In this talk I will review recent progress in the physics of the interaction between radiation and mechanical motion. The paradigmatic system in this field of 'optomechanics' consists of an optical cavity with a movable mirror attached to a cantilever. I will discuss how the coupled dynamics of the light field inside the cavity and the cantilever motion gives rise to a series of interesting effects. On the level of classical dynamics, I will present the theory of nonlinear oscillations and the corresponding attractor diagram. Furthermore, it is possible to cool the cantilever by irradiating the cavity with a red-detuned laser beam. I will present the quantum theory of optomechanical cooling and discuss the prospects for reaching the ground state of the cantilever's center-of-mass motion. Among the interesting opportunities that open up in the quantum regime, I discuss the quantum nonlinear dynamics of an optomechanical system and the detection of quantum jumps.

Susan Perkin

University College London

Abstract: Over recent years significant progress has been made in understanding the molecular basis of lubrication by hydrocarbon liquids, aqueous liquids, and soft materials. I will begin by introducing this field and the apparatus we use to study shear forces with molecular resolution in film thickness: the 'surface force balance' (SFB), which is currently being constructed in UCL. I will then present high-resolution measurements of the friction force between two atomically smooth mica plates separated by films of water and of ionic liquids, for film thickness down to a single molecular diameter. Our recent experiments using ionic liquids, in particular, are helping us to understand the role of molecular characteristics such as charge and hydrophobicity on friction and lubrication. We are working towards a molecular-level understanding of the mechanisms of lubrication, which will lead to custom design of molecular lubricants for individual applications in nanotechnology, mechanics and micro-mechanics.

Maurizio Musso

Division of Physics and Biophysics, Department of Materials Engineering and Physics,  University of Salzburg

Abstract:  Raman spectroscopy is a spectroscopic technique capable to deliver information similar, but in some aspects complementary, to that obtained from infrared absorption spectroscopy on the molecular structure and dynamics in molecular systems. The Raman scattering signal is the result of the interaction between the electric field of the monochromatic electromagnetic wave incident on the sample under study and the polarizability of the electron shell of the bonded atoms, which gets modulated by their nuclear motion (vibrations and rotations). The thermodynamic state of the sample (temperature, pressure, concentration) influences the intra- and intermolecular vibrational couplings, and so the spectral details observed.

Raman spectroscopy has been since the invention of the laser a well-established research tool concerning molecular structure and dynamics in many fields of condensed matter physics and chemistry, and in the last two decades it has found increasing relevance in the chemical analysis of macroscopic and microscopic samples in the field of materials and life sciences. I will present some of my research activity related on the one hand to intermolecular interactions and molecular liquid structure, and on the other hand on the carotenoids content of selected biomaterials.

Ken Taylor

Queen's University Belfast

Abstract: Over the past 15 years we have developed methods in Belfast for solving accurately the time-dependent Schroedinger equation (TDSE) for few electron atoms and molecules in intense laser fields (Comp Phys Commun 114 1 (1998)). Application of these methods has led to significant discoveries in advance of laboratory experiment (e.g.  Phys Rev Lett 96 133001 (2006)). Very recently (Phys Rev A 78 063420 (2008)) these methods have been extended and combined with R-matrix concepts allowing their application to the TDSE of a general multi-electron atom or molecule.  The talk will review the methods and present results for intense light ranging from x-ray wavelengths right through to the infra-red.

Alan Aspuru-Guzik

Harvard University

Abstract: In this talk, I will discuss the one-to-one correspondence between vector potentials and particle and current densities in the context of master equations with arbitrary memory kernels, therefore extending Time-Dependent Current-Density Functional Theory (TD-CDFT) to the domain of generalized many-body open quantum systems. I will describe  numerical tests of our proposed scheme with a model system, and several considerations for the future development of functionals are indicated. Our results formalize the possibility of practicing TD-CDFT in OQS, hence expanding the applicability of the theory to non-Hamiltonian evolutions. I will briefly discuss the relevance of such theories for application domains such as excitonic energy transfer.

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