Generating indistinguishable photons from a quantum dot in a noisy environment

Single photons from semiconductor quantum dots are promising resources for linear optical quantum computing, or, when coupled to spin states, quantum repeaters. To realize such schemes, the photons must exhibit a high degree of indistinguishability. However, the solid-state environment presents inherent obstacles for this requirement as intrinsic semiconductor fluctuations can destroy the photon indistinguishability. Here, we demonstrate that resonant excitation of a quantum dot with a narrow-band laser generates near transform limited power spectra and indistinguishable photons from a single quantum dot in an environment with many charge-fluctuating traps. The specificity of the resonant excitation suppresses the excited state population in the quantum dot when it is detuned due to spectral fluctuations. The dynamics of this process lead to flickering of the emission over long time scales (>5 μs) and reduces the time-averaged count rates. Nevertheless, in spite of significant spectral fluctuations, high visibility two-photon interference can be achieved. This approach is useful for quantum dots with nearby surface states in processed photonic structures and quantum emitters in emerging platforms, such as two-dimensional semiconductors

Discriminative capacity and construct validity of the Clock Drawing Test in Mild Cognitive Impairment and Alzheimer's disease

OBJECTIVES: The aim of this study was to analyze the psychometric and diagnostic properties of the Clock Drawing Test (CDT), scored according to the Babins, Rouleau, and Cahn scoring systems, for Mild Cognitive Impairment (MCI) and Alzheimer's disease (AD) screening, and develop corresponding cutoff scores. Additionally, we assessed the construct validity of the CDT through exploratory and confirmatory factor analysis. METHODS: We developed a cross-sectional study of ambulatory MCI and AD patients, divided in two clinical groups (450 MCI and 250 mild AD patients) and a normal control group (N = 400). All participants were assessed with the CDT, Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) for convergent validity. RESULTS: The selected scoring systems presented adequate validity and reliability values. The proposed cutoff scores showed 60 to 65% sensitivity and 58 to 62% specificity to identify MCI patients. The corresponding values for AD were 84 to 90% sensitivity and 76 to 78% specificity. Exploratory and confirmatory factor analysis revealed that the Babins scoring system had good construct validity and allowed us to propose a three-factor model for this system. CONCLUSIONS: Our results confirmed the complexity of the CDT and support it as a cognitive screening instrument particularly sensitive to AD. The use of the CDT with MCI patients should be interpreted with more caution due to the lower sensitivity and specificity for milder forms of cognitive impairment.info:eu-repo/semantics/publishedVersio

Exciton-Phonon Interaction Model for Singlet Fission in Prototypical Molecular Crystals

In singlet fission (SF), a spin-conserving splitting of one singlet exciton into two triplet excitation states, the transition between localized electronic states can be controlled and modulated by delocalized lattice phonons. In this work, we built an exciton–phonon (ex–ph) interaction model accounting local electronic states coupled with both local molecular vibrations and low frequency intermolecular phonon modes for SF in crystalline tetracene and rubrene. On the basis of the calculated electronic couplings at the equilibrium structure of the molecular dimer, a superexchange path for SF was found for tetracene while couplings between the triplet pair (TT) state and other diabatic states are zero for rubrene due to the high symmetry. Our further ex–ph spectral density analysis and quantum dynamics simulation based on our ex–ph interaction model suggested a thermal-activated mechanism for SF in rubrene crystal via symmetry breaking by nuclear vibration, which is in agreement with recent experiments. It is also shown that thermal fluctuations of electronic couplings in both tetracene and rubrene are mostly in the same order of magnitude at room temperature, and this could be one of the reasons for both tetracene and rubrene to exhibit SF time scales within a close range (hundreds to thousands of femtoseconds) in experiments

Commission des Communautes Europeennes: Groupe du Porte-Parole. Reunion de la Commission du 27/6/79 = Commission of European Communities: Spokesman Group. Meeting of the Commission on 27/6/79. Spokesman Service Note to National Offices Bio No. (79) 210, 27 June 1979

Rabi oscillations of a two-level atom appear as a quantum interference effect between the amplitudes associated to atomic superpositions, in analogy with the classic double-slit experiment which manifests a sinusoidal interference pattern. By extension, through direct detection of time-resolved resonance fluorescence from a quantum-dot neutral exciton driven in the Rabi regime, we experimentally demonstrate triple-slit-type quantum interference via quantum erasure in a V-type three-level artificial atom. This result is of fundamental interest in the experimental studies of the properties of V-type 3-level systems and may pave the way for further insight into their coherence properties as well as applications for quantum information schemes. It also suggests quantum dots as candidates for multi-path-interference experiments for probing foundational concepts in quantum physics.Comment: 5 pages, 4 figures. Accepted versio

The Noncommutative Harmonic Oscillator based in Simplectic Representation of Galilei Group

In this work we study symplectic unitary representations for the Galilei group. As a consequence the Schr\"odinger equation is derived in phase space. The formalism is based on the non-commutative structure of the star-product, and using the group theory approach as a guide a physical consistent theory in phase space is constructed. The state is described by a quasi-probability amplitude that is in association with the Wigner function. The 3D harmonic oscillator and the noncommutative oscillator are studied in phase space as an application, and the Wigner function associated to both cases are determined.Comment: 7 pages,no figure

Optical and physicochemical characterizations of a cellulosic/CdSe-QDs@S-DAB5 film

CdSe quantum dots nanoparticles were coated with the thiolated (DiAminoButane based dendrimer) DAB dendrimer of fifth generation (S-DAB(5)) and embedded in a highly hydrophilic regenerated cellulose (RC) film by simple dip-coating method (immersion in QD-dendrimer aqueous solution) as a way to get a flexible nano-engineered film (RC-4/CdSe-QDs@S-DAB(5)) with high transparency and photoluminescence properties for different applications. Optical changes in the RC film associated with QDs inclusion were determined by spectroscopic ellipsometry (SE) measurements, which provide information on changes caused in the refraction index and the extinction coefficients of the film, as well as by light transmittance/reflectance curves and photoluminescence (PL) spectra. Impedance spectroscopy (IS) and other typical physicochemical techniques for material characterization (TEM, SEM and XPS) have also been used in order to have more complete information on film characteristics. A comparison of RC-4/CdSe-QDs@S-DAB(5) film optical characteristics with those exhibited by other RC-modified films depending on the type of dendrimer was also carried out

A secreted serine protease of Paracoccidioides brasiliensis and its interactions with fungal proteins

<p>Abstract</p> <p>Background</p> <p><it>Paracoccidioides brasiliensis </it>is a thermodimorphic fungus, the causative agent of paracoccidioidomycosis (PCM). Serine proteases are widely distributed and this class of peptidase has been related to pathogenesis and nitrogen starvation in pathogenic fungi.</p> <p>Results</p> <p>A cDNA (<it>Pb</it>sp) encoding a secreted serine protease (<it>Pb</it>SP), was isolated from a cDNA library constructed with RNAs of fungal yeast cells recovered from liver of infected mice. Recombinant <it>Pb</it>SP was produced in <it>Escherichia coli</it>, and used to develop polyclonal antibodies that were able to detect a 66 kDa protein in the <it>P. brasiliensis </it>proteome. <it>In vitro </it>deglycosylation assays with endoglycosidase H demonstrated that <it>Pb</it>SP is a <it>N</it>-glycosylated molecule. The <it>Pb</it>sp transcript and the protein were induced during nitrogen starvation. The <it>Pb</it>sp transcript was also induced in yeast cells infecting murine macrophages. Interactions of <it>Pb</it>SP with <it>P. brasiliensis </it>proteins were evaluated by two-hybrid assay in the yeast <it>Saccharomyces cerevisiae</it>. <it>Pb</it>SP interacts with a peptidyl prolyl cis-trans isomerase, calnexin, HSP70 and a cell wall protein PWP2.</p> <p>Conclusions</p> <p>A secreted subtilisin induced during nitrogen starvation was characterized indicating the possible role of this protein in the nitrogen acquisition. <it>Pb</it>SP interactions with other <it>P. brasiliensis </it>proteins were reported. Proteins interacting with <it>Pb</it>SP are related to folding process, protein trafficking and cytoskeleton reorganization.</p

College Within A College (CwiC) – Population Health

Seminar presentation (55 PowerPoint Slides) The development of programmatic tracks providing students with academic opportunities outside of the traditional medical curriculum represents a national trend in medical education. With HRSA Interdisciplinary and Interprofessional Joint Graduate Degree five-year funding, the Department of Family and Community Medicine at ThomasJeffersonUniversitycreated an Inter-professional Primary Care Dual Degree Program (IPCDDP), which builds on JeffersonMedicalCollege’s College within a College (CwiC) Scholarly Concentrations Program in Population Health. The mission of the IPCDDP is to provide outstanding training in primary care and innovative education in chronic care management and population and public health in order to prepare primary care leaders to serve as future change agents working to improve the health of Americans, especially its most vulnerable and underserved populations. Key CwiC-PH components include: Year 1 – enhanced population health components of Introduction to Clinical Medicine (ICM) I, participation in community health initiatives, journal club, and twice monthly seminars Summer – population health related programs Year 2 – case studies in Fundamentals of Clinical Medicine, twice monthly seminars emphasizing application of the social and behavioral foundations of Public Health Year 3 – On going advising, enhanced clerkship experiences, Capstone planning Year 4 – Two community electives and completion of a Capstone Project Benefits to students include a certificate upon completion of the program, and 15 credits applied to the MPH program at Jefferson. The development, institutional collaboration, and a detailed description of the CwiC – PH program will be presented along with implementation, evaluation, and sustainability plans. Learning Objectives: Participants attending this session will be able to: 1. Organize an approach to integrating population health into health professional’s curriculum 2. Apply a methodology to recruit students into an area of concentration in population health 3. Identify the challenges in curricular reform and innovatio

A review of estimation of distribution algorithms in bioinformatics

Evolutionary search algorithms have become an essential asset in the algorithmic toolbox for solving high-dimensional optimization problems in across a broad range of bioinformatics problems. Genetic algorithms, the most well-known and representative evolutionary search technique, have been the subject of the major part of such applications. Estimation of distribution algorithms (EDAs) offer a novel evolutionary paradigm that constitutes a natural and attractive alternative to genetic algorithms. They make use of a probabilistic model, learnt from the promising solutions, to guide the search process. In this paper, we set out a basic taxonomy of EDA techniques, underlining the nature and complexity of the probabilistic model of each EDA variant. We review a set of innovative works that make use of EDA techniques to solve challenging bioinformatics problems, emphasizing the EDA paradigm's potential for further research in this domain