393 research outputs found
Infinite average lifetime of an unstable bright state in the green fluorescent protein
The time evolution of the fluorescence intensity emitted by well-defined
ensembles of Green Fluorescent Proteins has been studied by using a standard
confocal microscope. In contrast with previous results obtained in single
molecule experiments, the photo-bleaching of the ensemble is well described by
a model based on Levy statistics. Moreover, this simple theoretical model
allows us to obtain information about the energy-scales involved in the aging
process.Comment: 4 pages, 4 figure
Large 2D Coulomb crystals in a radio frequency surface ion trap
We designed and operated a surface ion trap, with an ion-substrate distance
of 500\mum, realized with standard printed-circuit-board techniques. The trap
has been loaded with up to a few thousand Sr+ ions in the Coulomb-crystal
regime. An analytical model of the pseudo-potential allowed us to determine the
parameters that drive the trap into anisotropic regimes in which we obtain
large (N>150) purely 2D ion Coulomb crystals. These crystals may open a simple
and reliable way to experiments on quantum simulations of large 2D systems.Comment: 4 pages, 4 figure
Qualidade da água de chuva armazenada em cisterna utilizada na dessedentação de suínos e bovinos de corte.
Na região do Meio Oeste Catarinense tem-se incentivado a utilização de cisternas como tecnologia capaz de ofertar água aos rebanhos. A região é caracterizada por secas severas nos meses de verão. Os objetivos da pesquisa foram: monitorar variáveis físicas, químicas e microbiológicas de qualidade da água de chuva de uma cisterna; avaliar se a água armazenada possuía qualidade para dessedentação de suínos e bovinos de corte. As concentrações de nitrato, nitrito e amônia mantiveram-se de acordo com os padrões para o consumo animal. A E. coli esteve presente em algumas amostras. A quantidade de chuva e velocidade do vento influenciaram as concentrações dos elementos nitrogenados. Investigações a fim de aprofundar esse conhecimento devem ser conduzidas para que as fontes emissoras agrícolas e pecuárias não representam alto impacto negativo para a qualidade da água. A água armazenada na cisterna apresentou qualidade satisfatória para o uso na dessedentação de suínos e bovinos de corte o que corrobora a utilização da tecnologia, visando o uso eficiente da água pelas produções pecuárias
Topologically decoherence-protected qubits with trapped ions
We show that trapped ions can be used to simulate a highly symmetrical
Hamiltonian with eingenstates naturally protected against local sources of
decoherence. This Hamiltonian involves long range coupling between particles
and provides a more efficient protection than nearest neighbor models discussed
in previous works. Our results open the perspective of experimentally realizing
in controlled atomic systems, complex entangled states with decoherence times
up to nine orders of magnitude longer than isolated quantum systems.Comment: 4 page
Photoexcitation in thin films deposited on silicon substrates by reactive pulsed laser ablation
Reactive pulsed laser ablation is a very interesting method to deposit thin films of several materials and compounds such as oxides, nitrides, semiconductors and superconductors. This technique relies on photoablation of pure elements, or a mixture of materials, with simultaneous exposure to a reactive atmosphere. In the case of oxides, reactions between the laser vaporized metals and oxygen lead to the formation of intermediate complexes and finally to oxide thin films. The reactivity of the plume has been already studied by our group in other oxides and nitrides productions and ascertained by Time of Flight Mass Spectrometry measurements [1].Thin films of semiconducting oxides such asIn2O3,SnO2, and multilayers of these two compounds have been deposited by Reactive Pulsed Laser Ablation, with the aim to evaluate the behaviour of such films under variable halogen lamp illumination.Deposition of these thin films has been carried out by a frequency doubled Nd-YAG laser (wavelength = 532 nm) on Silicon (100) substrates. A comparison, among indium oxide, tin oxide, and multilayers of indium and tin oxides, has been performed. The influence of physical parameters, such as substrate temperature and oxygen pressure in the deposition chamber, has been investigated. The deposited films have been characterized by Electric Resistance measurements
The TSS-1 mission: Results on satellite charging
In the present paper we first give a short account of the mission TSS-1 flown on the Shuttle sts-46 in August 1992 and its basic electrical configurations. We then show some results obtained from the experiment RETE on board the satellite which are relevant for the issue of satellite charging
High-fidelity preparation, gates, memory and readout of a trapped-ion quantum bit
We implement all single-qubit operations with fidelities significantly above
the minimum threshold required for fault-tolerant quantum computing, using a
trapped-ion qubit stored in hyperfine "atomic clock" states of Ca.
We measure a combined qubit state preparation and single-shot readout fidelity
of 99.93%, a memory coherence time of seconds, and an average
single-qubit gate fidelity of 99.9999%. These results are achieved in a
room-temperature microfabricated surface trap, without the use of magnetic
field shielding or dynamic decoupling techniques to overcome technical noise.Comment: Supplementary Information included. 6 nines, 7 figures, 8 page
Double-lambda microscopic model for entangled light generation by four-wave-mixing
Motivated by recent experiments, we study four-wave-mixing in an atomic
double-{\Lambda} system driven by a far-detuned pump. Using the
Heisenberg-Langevin formalism, and based on the microscopic properties of the
medium, we calculate the classical and quantum properties of seed and conju-
gate beams beyond the linear amplifier approximation. A continuous variable
approach gives us access to relative-intensity noise spectra that can be
directly compared to experiments. Restricting ourselves to the cold-atom
regime, we predict the generation of quantum-correlated beams with a
relative-intensity noise spectrum well below the standard quantum limit (down
to -6 dB). Moreover entanglement between seed and conjugate beams measured by
an inseparability down to 0.25 is expected. This work opens the way to the
generation of entangled beams by four-wave mixing in a cold atomic sample.Comment: 11 pages, 6 figures, submitted to PR
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