Photons as quasi-charged particles

The Schrodinger motion of a charged quantum particle in an electromagnetic potential can be simulated by the paraxial dynamics of photons propagating through a spatially inhomogeneous medium. The inhomogeneity induces geometric effects that generate an artificial vector potential to which signal photons are coupled. This phenomenon can be implemented with slow light propagating through an a gas of double-Lambda atoms in an electromagnetically-induced transparency setting with spatially varied control fields. It can lead to a reduced dispersion of signal photons and a topological phase shift of Aharonov-Bohm type

Continuous loading of 1^{1}S0_{0} calcium atoms into an optical dipole trap

We demonstrate an efficient scheme for continuous trap loading based upon spatially selective optical pumping. We discuss the case of $^{1}$S$_{0}$ calcium atoms in an optical dipole trap (ODT), however, similar strategies should be applicable to a wide range of atomic species. Our starting point is a reservoir of moderately cold ($\approx 300 \mu$K) metastable $^{3}$P$_{2}$-atoms prepared by means of a magneto-optic trap (triplet-MOT). A focused 532 nm laser beam produces a strongly elongated optical potential for $^{1}$S$_{0}$-atoms with up to 350 $\mu$K well depth. A weak focused laser beam at 430 nm, carefully superimposed upon the ODT beam, selectively pumps the $^{3}$P$_{2}$-atoms inside the capture volume to the singlet state, where they are confined by the ODT. The triplet-MOT perpetually refills the capture volume with $^{3}$P$_{2}$-atoms thus providing a continuous stream of cold atoms into the ODT at a rate of $10^7$s$^{-1}$. Limited by evaporation loss, in 200 ms we typically load $5 \times 10^5$ atoms with an initial radial temperature of 85 $\mu$K. After terminating the loading we observe evaporation during 50 ms leaving us with $10^5$ atoms at radial temperatures close to 40 $\mu$K and a peak phase space density of $6.8 \times 10^{-5}$. We point out that a comparable scheme could be employed to load a dipole trap with $^{3}$P$_{0}$-atoms.Comment: 4 pages, 4 figure

Raman Adiabatic Transfer of Optical States

We analyze electromagnetically induced transparency and light storage in an ensemble of atoms with multiple excited levels (multi-Lambda configuration) which are coupled to one of the ground states by quantized signal fields and to the other one via classical control fields. We present a basis transformation of atomic and optical states which reduces the analysis of the system to that of EIT in a regular 3-level configuration. We demonstrate the existence of dark state polaritons and propose a protocol to transfer quantum information from one optical mode to another by an adiabatic control of the control fields

Energy transfer in porphyrin-functionalized graphene

We present a theoretical study on the molecule–substrate interaction within the porphyrin-functionalized graphene. Recent experiments on porphyrin-functionalized carbon nanotubes have revealed an extremely efficient energy transfer from the adsorbed molecules to the carbon substrate. To investigate the energy transfer mechanism, we have characterized the hybrid structure within the density functional theory including the calculation of the molecular transition dipole moment, which allows us to determine the Förster coupling rate. We find a strongly pronounced Förster-induced energy transfer in the range of fs−1 inline image confirming the experimental observations

Many-body Green's function theory for electron-phonon interactions: the Kadanoff-Baym approach to spectral properties of the Holstein dimer

We present a Kadanoff-Baym formalism to study time-dependent phenomena for systems of interacting electrons and phonons in the framework of many-body perturbation theory. The formalism takes correctly into account effects of the initial preparation of an equilibrium state, and allows for an explicit time-dependence of both the electronic and phononic degrees of freedom. The method is applied to investigate the charge neutral and non-neutral excitation spectra of a homogeneous, two-site, two-electron Holstein model. This is an extension of a previous study of the ground state properties in the Hartree (H), partially self-consistent Born (Gd) and fully self-consistent Born (GD) approximations published in Ref. [arXiv:1403.2968]. We show that choosing a homogeneous ground state solution leads to unstable dynamics for a sufficiently strong interaction, and that allowing a symmetry-broken state prevents this. The instability is caused by the bifurcation of the ground state and understood physically to be connected with the bipolaronic crossover of the exact system. This mean-field instability persists in the partially self-consistent Born approximation but is not found for the fully self-consistent Born approximation. By understanding the stability properties, we are able to study the linear response regime by calculating the density-density response function by time-propagation. This functions amounts to a solution of the Bethe-Salpeter equation with a sophisticated kernel. The results indicate that none of the approximations is able to describe the response function during or beyond the bipolaronic crossover for the parameters investigated. Overall, we provide an extensive discussion on when the approximations are valid, and how they fail to describe the studied exact properties of the chosen model system.Comment: 12 figure

Quality of life of elderly persons with newly diagnosed cancer.

The aim was to investigate quality of life (QoL) in elderly persons newly diagnosed with cancer (65+ years) in relation to age, contact with the health-care system, ability to perform activities of daily living (ADL), hope, social network and support, and to identify which factors were associated with low QoL. The sample consisted of 101 patients (75 women and 26 men) newly diagnosed with cancer. EORTC QLQ-C30, Nowotny's Hope Scale, Katz ADL and the Interview Schedule for Social Interaction (ISSI) were used. The analysis was carried out in four age groups and revealed no significant differences in QoL. Compared with the other age groups, those of a high age (80+ years) more often lived alone, used more home-help service and had a smaller social network. Factors associated with low QoL were 'no other incomes than retirement pension', 'low level of hope' and 'lung cancer'. In addition, 'being told that the cancer disease has not come to an end', 'needing more help in activities of daily living', 'getting help from grown-up children' and 'needing help with PADL' were associated with low QoL. Those at risk of inferior QoL, that is, having poor economy, low level of hope and lung cancer need special attendance and specific interventions to improve QoL

Practical and effective higher-order optimizations

Inlining is an optimization that replaces a call to a function with that function’s body. This optimization not only reduces the overhead of a function call, but can expose additional optimization oppor-tunities to the compiler, such as removing redundant operations or unused conditional branches. Another optimization, copy propaga-tion, replaces a redundant copy of a still-live variable with the origi-nal. Copy propagation can reduce the total number of live variables, reducing register pressure and memory usage, and possibly elimi-nating redundant memory-to-memory copies. In practice, both of these optimizations are implemented in nearly every modern com-piler. These two optimizations are practical to implement and effec-tive in first-order languages, but in languages with lexically-scoped first-class functions (aka, closures), these optimizations are no

Reprint of: CAA Broadband Noise Prediction for Aeroacoustic Design

AbstractThe current status of a hybrid RANS/CAA approach for the simulation of broadband sound generation is presented. The method rests on the use of steady Reynolds Averaged Navier-Stokes (RANS) simulation to prescribe the time-averaged motion of turbulent flow. By means of synthetic turbulence the steady one-point statistics (e.g. turbulent kinetic energy) and turbulent length- and time-scales of RANS are translated into fluctuations of turbulent velocity (or vorticity), whose statistics very accurately reproduce the spatial target distributions of RANS. The synthetic fluctuations are used to prescribe sound sources which drive linear acoustic perturbation equations. The whole approach represents a methodology to solve statistical noise theories with state-of-the-art Computational Aeroacoustics (CAA) tools in the time-domain. A brief overview of the synthetic turbulence model and its numerical discretization in terms of the Random Particle-Mesh (RPM) and Fast Random Particle-Mesh (FRPM) method is given. Results are presented for trailing edge, slat, jet, and combustion noise. Some problems related to the formulation of vortex sound sources are discussed

Multimode electromagnetically-induced transparency on a single atomic line

We experimentally investigate electromagnetically-induced transparency (EIT) created on an inhomogeneously broadened 5S_1/2-5P_1/2 transition in rubidium vapor using a control field of a complex temporal shape. A comb-shaped transparency spectrum enhances the delay-bandwidth product and the light storage capacity for a matched probe pulse by a factor of about 50 compared to a single EIT line [D. D. Yavuz, Phys. Rev. A 75, 031801 (2007)]. If the temporal mode of the control field is slowly changed while the probe is propagating through the EIT medium, the probe will adiabatically follow, providing a means to perform frequency conversion and optical routing

Effect of spin orbit scattering on the magnetic and superconducting properties of nearly ferromagnetic metals: application to granular Pt

We calculate the effect of scattering on the static, exchange enhanced, spin susceptibility and show that in particular spin orbit scattering leads to a reduction of the giant moments and spin glass freezing temperature due to dilute magnetic impurities. The harmful spin fluctuation contribution to the intra-grain pairing interaction is strongly reduced opening the way for BCS superconductivity. We are thus able to explain the superconducting and magnetic properties recently observed in granular Pt as due to scattering effects in single small grains.Comment: 9 pages 3 figures, accepted for publication in Phys. Rev. Letter