Polarization phase gate with a tripod atomic system

We analyze the nonlinear optical response of a four-level atomic system driven into a tripod configuration. The large cross-Kerr nonlinearities that occurr in such a system are shown to produce nonlinear phase shift of order $\pi$. Such a substantial shift may be observed in a cold atomic gas in a magneto-optical trap where it coupl be fasibly exploited towards the realization of a polarization quantum phase gate. The experimental feasibility of such a gate is here examined in detail.Comment: Corrected versio

Optical pattern recognition based on color vision models

A channel transformation based on opponent-color theory of the color vision models is applied to optical pattern recognition so that the conventional red, green, and blue (RGB) channels are transformed into bright-dark, red-green, and yellow-blue (ATD) channels. Matched filtering and correlation are performed over the new components of the target and the scene in the ATD system. The proposed transformation allows us to reduce the number of channels commonly used in color pattern recognition, passing from the three RGB channels to the two red-green and yellow-blue opponent-color channels

Cavity QED quantum phase gates for a single longitudinal mode of the intracavity field

A single three-level atom driven by a longitudinal mode of a high-Q cavity is used to implement two-qubit quantum phase gates for the intracavity field. The two qubits are associated with the zero- and one-photon Fock states of each of the two opposite circular polarization states of the field. The three-level atom mediates the conditional phase gate provided the two polarization states and the atom interact in a V-type configuration and the two-photon resonance condition is satisfied. Microwave and optical implementations are discussed with gate fidelities being evaluated against several decoherence mechanisms such as atomic velocity fluctuations or the presence of a weak magnetic field. The use of coherent states for both polarization states is investigated to assess the entanglement capability of the proposed quantum gates

Endocardial Approach for Substrate Ablation in Brugada Syndrome

Radiofrequency ablation (RFA) in Brugada syndrome (BrS) has been performed by both endocardial and epicardial. The substrate in BrS is not completely understood. We investigate the functional endocardial substrate and its correlation with clinical, electrophysiological and ECG findings in order to guide an endocardial ablation. Two patients agreed to undergo an endocardial biopsy and the samples were examined with transmission electron microscopy (TEM) to investigate the correlation between functional and ultrastructural alterations. About 13 patients (38.7 ± 12.3 years old) with spontaneous type 1 ECG BrS pattern, inducible VF with programmed ventricular stimulation (PVS) and syncope without prodromes were enrolled. Before endocardial mapping, the patients underwent flecainide testing with the purpose of measuring the greatest ST-segment elevation for to be correlated with the size and location of substrate in the electro-anatomic map. Patients underwent endocardial bipolar and electro-anatomic mapping with the purpose of identify areas of abnormal electrograms (EGMs) as target for RFA and determine the location and size of the substrate. When the greatest ST-segment elevation was in the third intercostal space (ICS), the substrate was located upper in the longitudinal plane of the right ventricular outflow tract (RVOT) and a greatest ST-segment elevation in fourth ICS correspond with a location of substrate in lower region of longitudinal plane of RVOT. A QRS complex widening on its initial and final part, with prolonged transmural and regional depolarization time of RVOT corresponded to the substrate located in the anterior-lateral region of RVOT. A QRS complex widening rightwards and only prolonged transmural depolarization time corresponded with a substrate located in the anterior, anterior-septal or septal region of RVOT. RFA of endocardial substrate suppressed the inducibility and ECG BrS pattern during 34.7 ± 15.5 months. After RFA, flecainide testing confirmed elimination of the ECG BrS pattern. Endocardial biopsy showed a correlation between functional and ultrastructural alterations. Endocardial RFA can eliminate the BrS phenotype and inducibility during programmed ventricular stimulation (PVS)

Electromagnetically induced transparency with a standing-wave drive in the frequency up-conversion regime

We study electromagnetically induced transparency for a probe traveling-wave (TW) laser field in closed Doppler-broadened three-level systems driven by a standing-wave (SW) laser field of moderate intensity (its Rabi frequencies are smaller than the Doppler width of the driven transition). We show that probe windows of transparency occur for values of the probe to drive field frequency ratio R close to half-integer values. For optical transitions and typical values of Doppler broadening for atoms in a vapor cell, we show that for R>1 a SW drive field is appreciably more efficient than a TW drive in inducing probe transparency. As examples, we consider parameters for real cascade schemes in barium atoms with R≈1.5 and in beryllium atoms with R≈3.5 showing that probe transmission values well above 50% are possible for conditions in which it is almost negligible either without driving field or with only one of the TW components of the drive. We show that a strongly asymmetric drive having two TW components with unequal intensities is even more eficient than a symmetric SW drive in inducing probe transparency. The case of arbitrary probe intensity is also considered

Lasing without inversion in three-level systems without external coherent driving

We have studied an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity. This system generates two laser fields, one of them without population inversion. Both ladder and V-type three-level schemes are considered with a ratio R=ωα/ωβ of inversionless laser frequency ωα to ordinary laser frequency ωβ of R=0.67 and R=1.88, respectively. Dual-wavelength lasing extends up to Doppler-broadening values for optical transitions of atoms in a vapor cell. Some considerations for the practical realization of this dual-wavelength laser are discussed

Photoswitchable diacylglycerols enable optical control of protein kinase C.

Increased levels of the second messenger lipid diacylglycerol (DAG) induce downstream signaling events including the translocation of C1-domain-containing proteins toward the plasma membrane. Here, we introduce three light-sensitive DAGs, termed PhoDAGs, which feature a photoswitchable acyl chain. The PhoDAGs are inactive in the dark and promote the translocation of proteins that feature C1 domains toward the plasma membrane upon a flash of UV-A light. This effect is quickly reversed after the termination of photostimulation or by irradiation with blue light, permitting the generation of oscillation patterns. Both protein kinase C and Munc13 can thus be put under optical control. PhoDAGs control vesicle release in excitable cells, such as mouse pancreatic islets and hippocampal neurons, and modulate synaptic transmission in Caenorhabditis elegans. As such, the PhoDAGs afford an unprecedented degree of spatiotemporal control and are broadly applicable tools to study DAG signaling

Dynamics of coherently pumped lasers with linearly polarized pump and generated fields

The influence of light polarization on the dynamics of an optically pumped single-mode laser with a homogeneously broadened four-level medium is theoretically investigated in detail. Pump and laser fields with either parallel or crossed linear polarizations are considered, as are typical in far-infrared-laser experiments. Numerical simulations reveal dramatically different dynamic behaviors for these two polarization configurations. The analysis of the model equations allows us to find the physical origin of both behaviors. In particular, the crossed-polarization configuration is shown to be effective in decoupling the pump and laser fields, thus allowing for the appearance of Lorenz-type dynamics

Ghrelin, Sleep Reduction and Evening Preference: Relationships to CLOCK 3111 T/C SNP and Weight Loss

Circadian Locomotor Output Cycles Kaput (CLOCK), an essential element of the positive regulatory arm in the human biological clock, is involved in metabolic regulation. The aim was to investigate the behavioral (sleep duration, eating patterns and chronobiological characteristics) and hormonal (plasma ghrelin and leptin concentrations) factors which could explain the previously reported association between the CLOCK 3111T/C SNP and weight loss.We recruited 1495 overweight/obese subjects (BMI: 25-40 kg/m(2)) of 20-65 y. who attended outpatient obesity clinics in Murcia, in southeastern Spain. We detected an association between the CLOCK 3111T/C SNP and weight loss, which was particularly evident after 12-14 weeks of treatment (P = 0.038). Specifically, carriers of the minor C allele were more resistant to weight loss than TT individuals (Mean±SEM) (8.71±0.59 kg vs 10.4±0.57 kg) C and TT respectively. In addition, our data show that minor C allele carriers had: 1. shorter sleep duration Mean ± SEM (7.0±0.05 vs 7.3±0.05) C and TT respectively (P = 0.039), 2. higher plasma ghrelin concentrations Mean ± SEM (pg/ml) (1108±49 vs 976±47)(P = 0.034); 3. delayed breakfast time; 4. evening preference and 5. less compliance with a Mediterranean Diet pattern, as compared with TT homozygotes.Sleep reduction, changes in ghrelin values, alterations of eating behaviors and evening preference that characterized CLOCK 3111C carriers could be affecting weight loss. Our results support the hypothesis that the influence of the CLOCK gene may extend to a broad range of variables linked with human behaviors