Quantum theory of a polarization phase-gate in an atomic tripod configuration

We present the quantum theory of a polarization phase-gate that can be realized in a sample of ultracold rubidium atoms driven into a tripod configuration. The main advantages of this scheme are in its relative simplicity and inherent symmetry. It is shown that the conditional phase shifts of order $\pi$ can be attained.Comment: X International Conference on Quantum Optics, Minsk, Belaru

Prospects for photon blockade in four level systems in the N configuration with more than one atom

We show that for appropriate choices of parameters it is possible to achieve photon blockade in idealised one, two and three atom systems. We also include realistic parameter ranges for rubidium as the atomic species. Our results circumvent the doubts cast by recent discussion in the literature (Grangier et al Phys. Rev Lett. 81, 2833 (1998), Imamoglu et al Phys. Rev. Lett. 81, 2836 (1998)) on the possibility of photon blockade in multi-atom systems.Comment: 8 page, revtex, 7 figures, gif. Submitted to Journal of Optics B: Quantum and Semiclassical Optic

Clinical analysis of etiology, risk factors and outcome in patients with acute kidney injury.

Acute kidney injury is characterized by a rapid loss of renal excretory function with the increase of nitrogen compounds in the blood and with different outcome. Objective: Since descriptions of the risk factors and sequelae of acute kidney injury (AKI) remain relatively limited, the objective of this study was to determine etiology and clinical characteristics of AKI, as well as risk factors for adverse outcome of renal function and death in AKI patients. Methods: We retrospectively studied a cohort of 84 adult AKI patients admitted to Nephrology Clinic in University Clinical Centre Sarajevo during period 2012-2014. Demographic, laboratory and clinical parameters were retrieved. The in-hospital and 6 months mortality were recorded. Renal function outcome was defined 3 months following discharge. Results: Majority of patients were older (median age 73.5 years) with great severity of AKI (Stage III in 78.5% of cases) and high burden of comorbidities (mean Charlson comorbidity index, CCI score 6.4±3.05). The most common causes of AKI were acute interstitial nephritis (16.7%), heart failure (15.5%), gastroenterocolitis (13.1%), and sepsis (12%). Renal function recovery was recorded in 48.8% of patients, with prevalence of 10.7% of intrahospital mortality and 37.3% of 6 months mortality. Risk factors for poor outcome of renal function and mortality in AKI patients were increasing age and higher CCI score, while protective factor was higher diuresis. Sepsis proved to be risk factor for deat

Optimized phase switching using a single atom nonlinearity

We show that a nonlinear phase shift of pi can be obtained by using a single two level atom in a one sided cavity with negligible losses. This result implies that the use of a one sided cavity can significantly improve the pi/18 phase shift previously observed by Turchette et al. [Phys. Rev. Lett. 75, 4710 (1995)].Comment: 6 pages, 3 figures, added comments on derivation and assumption

Strongly interacting polaritons in coupled arrays of cavities

Observing quantum phenomena in strongly correlated many-particle systems is difficult because of the short length- and timescales involved. Exerting control over the state of individual elements within such a system is even more so, and represents a hurdle in the realization of quantum computing devices. Substantial progress has been achieved with arrays of Josephson junctions and cold atoms in optical lattices, where detailed control over collective properties is feasible, but addressing individual sites remains a challenge. Here we show that a system of polaritons held in an array of resonant optical cavities—which could be realized using photonic crystals or toroidal microresonators—can form a strongly interacting many-body system showing quantum phase transitions, where individual particles can be controlled and measured. The system also offers the possibility to generate attractive on-site potentials yielding highly entangled states and a phase with particles much more delocalized than in superfluids

Continuous-variable entanglement purification with atomic systems

We present a proposal for entanglement purification of the continuous-variable quantum state of two propagating optical fields. The scheme is based on letting each field interact with a local node, an atomic ensemble, whose internal collective excitation plays the role of an ancillary continuous variable resource. Entanglement purification is achieved by a dichotomic measurement, representing the required non-Gaussian element, and which consists in detecting the presence or absence of collective excitations in the atomic ensemble. This scheme can be extended to networks, where the nodes are single trapped atoms, and constitutes an important building block for the implementation of a continuous-variable quantum repeater.Comment: Published in Feature Issue "Quantum Optical Information Technologies

Entanglement Purification with Hybrid Systems

We propose a scheme for continuous variable entanglement purification using the interaction of two-mode squeezed beams with cold trapped atomic ensembles. In the limit of very large number of atoms, a collective atomic ensemble excitation becomes a continuous quantity. Measurement of populations in the two lower levels is of non-Gaussian nature that is necessary for the entanglement purification.We foresee the use of this scheme for implementation of a continuous variable quantum repeater.11 page(s

CFD analysis of VVT/VVA on the gas exchange and fuel-air mixing in a diesel engine

A three-dimensional simulation was carried out for investigating effects of negative valve overlap (NVO) on gas exchange and fuel-air mixing processes in a diesel homogeneous charge compression ignition (HCCI) engine with early fuel injection. It was found that the case with longer NVO produced a stronger swirl motion and a more significant vortex below the intake valve due to the high annular jet flow through the valve curtain area during the intake stroke. However, there was not much difference in the values of swirl ratio, tumble ratio and turbulence intensity between different NVOs at the end of compression stroke. It was also seen that enlarged NVO not just increased in-cylinder temperature but also improved the temperature homogeneity. With increased NVO, there is a bigger spray shape and more droplets exist in gaps of sprays. This demonstrates that stronger turbulence intensity and higher temperature homogeneity with higher NVO improve fuel vaporization and air-fuel mixing.Peer reviewe