Stimulated Raman adiabatic passage into continuum

We propose a technique which produces nearly complete ionization of the population of a discrete state coupled to a continuum by a two-photon transition via a lossy intermediate state whose lifetime is much shorter than the interaction duration. We show that using counterintuitively ordered pulses, as in stimulated Raman adiabatic passage (STIRAP), wherein the pulse coupling the intermediate state to the continuum precedes and partly overlaps the pulse coupling the initial and intermediate states, greatly increases the ionization signal and strongly reduces the population loss due to spontaneous emission through the lossy state. For strong spontaneous emission from that state, however, the ionization is never complete because the dark state required for STIRAP does not exist. We demonstrate that this drawback can be eliminated almost completely by creating a laser-induced continuum structure (LICS) by embedding a third discrete state into the continuum with a third control laser. This LICS introduces some coherence into the continuum, which enables a STIRAP-like population transfer into the continuum. A highly accurate analytic description is developed and numerical results are presented for Gaussian pulse shapes

Incoherent matter-wave solitons

The dynamics of matter-wave solitons in Bose-Einstein condensates (BEC) is considerably affected by the presence of a surrounding thermal cloud and by condensate depletion during its evolution. We analyze these aspects of BEC soliton dynamics, using time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory. The condensate is initially prepared within a harmonic trap at finite temperature, and solitonic behavior is studied by subsequently propagating the TDHFB equations without confinement. Numerical results demonstrate the collapse of the BEC via collisional emission of atom pairs into the thermal cloud, resulting in splitting of the initial density into two solitonic structures with opposite momentum. Each one of these solitary matter waves is a mixture of condensed and noncondensed particles, constituting an analog of optical random-phase solitons.Comment: 4 pages, 2 figures, new TDHFB result

Neuro-protective effects of Crocin on brain and cerebellum tissues in diabetic rats

Background: Increase in free oxygen radicals and the disruption of defense system make the neurons and astrocytes more sensitive against oxidative damage.Materials and Methods: Rats were divided into three groups containing 10, rats in each group namely: control (C) group, Diabetes Mellitus (DM) group, and Diabetes Mellitus + crocin (DM+crocin) group. Tissue samples were processed by routine histological and biochemical procedures. The sections were stained with Hematoxylen-eosin. Malondialdehyde (MDA), glutathione (GSH), blood glucose, HbA1c levels and xanthine oxidase (XO) activities were assayed.Results: The histological appearence of the cerebrum and cerebellum were normal in the control group. DM group showed some histopathological changes including congestion, perivascular and perineuronal edema in cerebrum. In DM + crocin group, histopathological changes in cerebrum and cerebellum markedly reduced. MDA level and XO activities increased significantly in DM group (P<0.01), but decreased significantly in DM + crocin group when compared to DM group (P<0.01). Blood glucose concentrations increased significantly (p<0.01) in DM group), but decreased significantly in DM + crocin group when compared with DM group (p<0.05). Blood HbA1c levels were normal in control group. But there were significant differences between control and DM groups (p<0.01). On the other hand, blood HbA1c levels decreased in DM+crocin group when compared with the DM group, but it was not statistically significant (p > 0.05).Conclusion: Due to the fact that crocin has an antioxidant and anti-hyperglycemic effects, it can protect the brain and cerebellum tissue  against the complications of oxidative stress.Key words: Diabetes mellitus, oxidative stress, crocin, brain, cerebellum

Coherently Controlled Nanoscale Molecular Deposition

Quantum interference effects are shown to provide a means of controlling and enhancing the focusing a collimated neutral molecular beam onto a surface. The nature of the aperiodic pattern formed can be altered by varying laser field characteristics and the system geometry.Comment: 13 pages (inculding 4 figures), LaTeX (Phys. Rev. Lett., 2000, in Press

ADDMC: Weighted Model Counting with Algebraic Decision Diagrams

We present an algorithm to compute exact literal-weighted model counts of Boolean formulas in Conjunctive Normal Form. Our algorithm employs dynamic programming and uses Algebraic Decision Diagrams as the primary data structure. We implement this technique in ADDMC, a new model counter. We empirically evaluate various heuristics that can be used with ADDMC. We then compare ADDMC to state-of-the-art exact weighted model counters (Cachet, c2d, d4, and miniC2D) on 1914 standard model counting benchmarks and show that ADDMC significantly improves the virtual best solver.Comment: Presented at AAAI 202

Formation of Two Component Bose Condensate During the Chemical Potential Curve Crossing

In this article we study the formation of the two modes Bose-Einstein condensate and the correlation between them. We show that beyond the mean field approximation the dissociation of a molecular condensate due to the chemical potential curve crossing leads to the formation of two modes condensate. We also show that these two modes are correlated in a two mode squeezed state.Comment: 10 page

Spatial methods for event reconstruction in CLEAN

In CLEAN (Cryogenic Low Energy Astrophysics with Noble gases), a proposed neutrino and dark matter detector, background discrimination is possible if one can determine the location of an ionizing radiation event with high accuracy. We simulate ionizing radiation events that produce multiple scintillation photons within a spherical detection volume filled with liquid neon. We estimate the radial location of a particular ionizing radiation event based on the observed count data corresponding to that event. The count data are collected by detectors mounted at the spherical boundary of the detection volume. We neglect absorption, but account for Rayleigh scattering. To account for wavelength-shifting of the scintillation light, we assume that photons are absorbed and re-emitted at the detectors. Here, we develop spatial Maximum Likelihood methods for event reconstruction, and study their performance in computer simulation experiments. We also study a method based on the centroid of the observed count data. We calibrate our estimates based on training data

Collisional shifts in optical-lattice atom clocks

We theoretically study the effects of elastic collisions on the determination of frequency standards via Ramsey fringe spectroscopy in optical-lattice atom clocks. Interparticle interactions of bosonic atoms in multiply-occupied lattice sites can cause a linear frequency shift, as well as generate asymmetric Ramsey fringe patterns and reduce fringe visibility due to interparticle entanglement. We propose a method of reducing these collisional effects in an optical lattice by introducing a phase difference of $\pi$ between the Ramsey driving fields in adjacent sites. This configuration suppresses site to site hopping due to interference of two tunneling pathways, without degrading fringe visibility. Consequently, the probability of double occupancy is reduced, leading to cancellation of collisional shifts.Comment: 15 pages, 11 figure

Qualitative Analysis of Partially-observable Markov Decision Processes

We study observation-based strategies for partially-observable Markov decision processes (POMDPs) with omega-regular objectives. An observation-based strategy relies on partial information about the history of a play, namely, on the past sequence of observations. We consider the qualitative analysis problem: given a POMDP with an omega-regular objective, whether there is an observation-based strategy to achieve the objective with probability~1 (almost-sure winning), or with positive probability (positive winning). Our main results are twofold. First, we present a complete picture of the computational complexity of the qualitative analysis of POMDP s with parity objectives (a canonical form to express omega-regular objectives) and its subclasses. Our contribution consists in establishing several upper and lower bounds that were not known in literature. Second, we present optimal bounds (matching upper and lower bounds) on the memory required by pure and randomized observation-based strategies for the qualitative analysis of POMDP s with parity objectives and its subclasses