Search results for "Metro"

Latvijas Universitātes prezidiju konvents

1929

Prezidiju konventa sastāvs

1937

Quantum sensor networks as exotic field telescopes for multi-messenger astronomy

2020

Multi-messenger astronomy, the coordinated observation of different classes of signals originating from the same astrophysical event, provides a wealth of information about astrophysical processes with far-reaching implications. So far, the focus of multi-messenger astronomy has been the search for conventional signals from known fundamental forces and standard model particles, like gravitational waves (GW). In addition to these known effects, quantum sensor networks could be used to search for astrophysical signals predicted by beyond-standard-model (BSM) theories. Exotic bosonic fields are ubiquitous features of BSM theories and appear while seeking to understand the nature of dark matter…

Comprehensive formulation of the temperature dependent dispersion of optical materials; illustration with the case of temperature tuning of a mid-IR …

2009

International audience; The temperature dependence of refractive indices of optical materials is characterized in this work by what we call their normalized thermo-optic coefficients. These ones are determined experimentally through interferometric measurements of thermal expansion, and changes in optical thickness at a few laser wavelengths as function of temperature. A suitable vectorial formalism applied to these data allows predicting the thermal evolution of the refractive index all over the useful range of transparency. The validity and reliability of our methodology is demonstrated through temperature tuning of a mid-IR HgGa2S4 OPO, pumped at 1.0642 μm by a Nd:YAG laser. Measured the…

Stability of laser cavity-solitons for metrological applications

2023

Laser cavity-solitons can appear in systems comprised of a nonlinear microcavity nested within an amplifying fiber loop. These states are robust and self-emergent and constitute an attractive class of solitons that are highly suitable for microcomb generation. Here, we present a detailed study of the free-running stability properties of the carrier frequency and repetition rate of single solitons, which are the most suitable states for developing robust ultrafast and high repetition rate comb sources. We achieve free-running fractional stability on both optical carrier and repetition rate (i.e., 48.9 GHz) frequencies on the order of [Formula: see text] for a 1 s gate time. The repetition r…

Continuous-Variable Quantum Teleportation of Discrete-Variable Entanglement

2013

We experimentally demonstrate continuous-variable quantum teleportation of discrete-variable entanglement in the form of a split single photon. Entanglement is optimally transferred for finite resource squeezing by tuning the teleporter's feedforward gain.

Observation of coherent quench dynamics in a metallic many-body state of fermionic atoms

2014

Quantum simulation with ultracold atoms has become a powerful technique to gain insight into interacting many-body systems. In particular, the possibility to study nonequilibrium dynamics offers a unique pathway to understand correlations and excitations in strongly interacting quantum matter. So far, coherent nonequilibrium dynamics has exclusively been observed in ultracold many-body systems of bosonic atoms. Here we report on the observation of coherent quench dynamics of fermionic atoms. A metallic state of ultracold spin-polarised fermions is prepared along with a Bose-Einstein condensate in a shallow three-dimensional optical lattice. After a quench that suppresses tunnelling between …

Feasibility of Coulomb blockade thermometry in metrology

2000

Abstract Coulomb blockade thermometer (CBT) is a simple, magnetic-field-independent primary thermometer for everyday use at cryogenic temperatures. Its properties are well understood by now. The absolute accuracy at present is about ±0.5%. Recently, we have started studying the possibility of using CBT in metrological applications. We have especially in mind the future extension of the international temperature scale below 0.65 K, which is the lower end of ITS-90. Experiments with arrays containing more than 100 tunnel junctions in series are in progress in order to decrease the effects of electromagnetic environment and of co-tunnelling even below the present level.

Close packing of clusters:  Application toAl100

2003

The lowest energy configurations of close-packed clusters up to N=110 atoms with stacking faults are studied using the Monte Carlo method with Metropolis algorithm. Two types of contact interactions, a pair-potential and a many-atom interaction, are used. Enhanced stability is shown for N=12, 26, 38, 50, 59, 61, 68, 75, 79, 86, 100 and 102, of which only the sizes 38, 75, 79, 86, and 102 are pure FCC clusters, the others having stacking faults. A connection between the model potential and density functional calculations is studied in the case of Al_100. The density functional calculations are consistent with the experimental fact that there exist epitaxially grown FCC clusters starting from…

Monte Carlo simulation of correlated electrons in disordered systems

1992

Abstract The properties of many-electron states in disordered systems with long-range electron-eletron interaction are investigated by means of a Monte Carlo simulation. Using the Metropolis algorithm, three-dimensional systems up to 512 sites are systematically analysed. The low-lying excitations are investigated in order to distinguish between one-particle and many-particle hopping. In the interesting regime in which disorder and correlation effects are equally important we find that variable-range hopping is insignificant for electron transfer when compared with the contribution from nearest-neighbour one-electron hopping processes as well as variable-number hopping.