Quantum correlations of two optical fields close to electromagnetically induced transparency

We show that three-level atoms excited by two cavity modes in a $\Lambda$ configuration close to electromagnetically induced transparency can produce strongly squeezed bright beams or correlated beams which can be used for quantum non demolition measurements. The input intensity is the experimental "knob" for tuning the system into a squeezer or a quantum non demolition device. The quantum correlations become ideal at a critical point characterized by the appearance of a switching behavior in the mean fields intensities. Our predictions, based on a realistic fully quantum 3-level model including cavity losses and spontaneous emission, allow direct comparison with future experiments.Comment: 4 pages, 5 figure

Maximal-entropy random walks in complex networks with limited information

J.G.-G. was supported by MICINN through the Ramon y Cajal program and by grants FIS2008-01240 and MTM2009-13848

Advancing the Vincentian Tradition through Strategic Service and Research

This article reveals how St. John’s University implemented mission-focused programs to advance its unique Catholic perspective, that of the Vincentian tradition to serve the poor and remedy social inequities. Heeding the 1986 call of Pope John Paul II to Vincentian institutions, all levels of the university from incoming freshmen to the board of trustees have embraced the Pope’s message to serve the poor and needy. Major program initiatives have included an expanded and enriched academic service-learning (ASL) program with a Discover New York service component for all incoming freshmen; the creation of a Vincentian Institute for Social Action to coordinate student and faculty service and research efforts with community partners; the establishment of a 4-year undergraduate Ozanam Scholar Program to engage students in extensive service and research under faculty mentorship; sustainable collaborations with community partners whose mission focus is compatible with the Vincentian perspective; and a dedicated effort to measure program impact through outcomes-based quantitative and qualitative research methodologies. Religiously affiliated institutions may find program components and organizational strategies to be beneficial in their own work in serving the poor, needy, and disenfranchised

Entanglement properties of degenerate four-wave mixing of matter-waves in a periodic potential

In a recent experiment Campbell et al. [Phys. Rev. Lett. 96, 020406 (2006)] observed degenerate four-wave mixing of matter-waves in a one-dimensional optical lattice, a process with potential for generating entanglement among atoms. We analyse the essential quantum features of the experiment to show that entanglement is created between the quadratures of the two scattered atomic clouds and is a true many-body (rather than two-body) effect. We demonstrate a significant violation of entanglement inequalities that is robust to a moderate level of coherent seeding. The system is thus a promising candididate for generating macroscopically entangled atomic samples.Comment: 4 pages, 3 figure

Defective phagocytic corpse processing results in neurodegeneration and can be rescued by TORC1 activation

This work was supported by NIH Grants R01 GM094452 (K.M.) and F31 GM099425 (J.I.E.), BU Alzheimer's Disease Core Center NIH Grant P30 AG13846, Boston University Undergraduate Research Opportunities Program grants (J.A.T., V.S.), and NIH Grant R01 AG044113 to M.B.F. We thank the Bloomington Stock Center, TRiP at Harvard Medical School, the Kyoto Drosophila Genetic Resource Center, Estee Kurant, Eric Baehrecke, Marc Freeman, and Mary Logan for fly strains. We thank Todd Blute for assistance with electron microscopy and the Developmental Studies Hybridoma Bank for antibodies. (R01 GM094452 - NIH; F31 GM099425 - NIH; R01 AG044113 - NIH; P30 AG13846 - BU Alzheimer's Disease Core Center NIH Grant; Boston University Undergraduate Research Opportunities Program)https://www.jneurosci.org/content/36/11/3170.longPublished versionPublished versio

Long-lived quantum memory with nuclear atomic spins

We propose to store non-classical states of light into the macroscopic collective nuclear spin ($10^{18}$ atoms) of a $^3$He vapor, using metastability exchange collisions. These collisions, commonly used to transfer orientation from the metastable state $2^{3}S\_1$ to the ground state state of $^3$He, can also transfer quantum correlations. This gives a possible experimental scheme to map a squeezed vacuum field state onto a nuclear spin state with very long storage times (hours).Comment: 4 page

Bogoliubov dynamics of condensate collisions using the positive-P representation

We formulate the time-dependent Bogoliubov dynamics of colliding Bose-Einstein condensates in terms of a positive-P representation of the Bogoliubov field. We obtain stochastic evolution equations for the field which converge to the full Bogoliubov description as the number of realisations grows. The numerical effort grows linearly with the size of the computational lattice. We benchmark the efficiency and accuracy of our description against Wigner distribution and exact positive-P methods. We consider its regime of applicability, and show that it is the most efficient method in the common situation - when the total particle number in the system is insufficient for a truncated Wigner treatment.Comment: 9 pages. 5 figure

Fragmentation, domain formation and atom number fluctuations of a two-species Bose-Einstein condensate in an optical lattice

We theoretically study the loading of a two-species Bose-Einstein condensate to an optical lattice in a tightly-confined one-dimensional trap. Due to quantum fluctuations the relative inter and intra species phase coherence between the atoms and the on-site atom number fluctuations are reduced in the miscible regime. For the immiscible case the fluctuations are enhanced and the atoms form metastable interleaved spatially separated domains where the domain length and its fluctuations are affected by quantum fluctuations.Comment: 32 page

Flow graphs: interweaving dynamics and structure

The behavior of complex systems is determined not only by the topological organization of their interconnections but also by the dynamical processes taking place among their constituents. A faithful modeling of the dynamics is essential because different dynamical processes may be affected very differently by network topology. A full characterization of such systems thus requires a formalization that encompasses both aspects simultaneously, rather than relying only on the topological adjacency matrix. To achieve this, we introduce the concept of flow graphs, namely weighted networks where dynamical flows are embedded into the link weights. Flow graphs provide an integrated representation of the structure and dynamics of the system, which can then be analyzed with standard tools from network theory. Conversely, a structural network feature of our choice can also be used as the basis for the construction of a flow graph that will then encompass a dynamics biased by such a feature. We illustrate the ideas by focusing on the mathematical properties of generic linear processes on complex networks that can be represented as biased random walks and also explore their dual consensus dynamics.Comment: 4 pages, 1 figur

Historical comparison of gender inequality in scientific careers across countries and disciplines

There is extensive, yet fragmented, evidence of gender differences in academia suggesting that women are under-represented in most scientific disciplines, publish fewer articles throughout a career, and their work acquires fewer citations. Here, we offer a comprehensive picture of longitudinal gender discrepancies in performance through a bibliometric analysis of academic careers by reconstructing the complete publication history of over 1.5 million gender-identified authors whose publishing career ended between 1955 and 2010, covering 83 countries and 13 disciplines. We find that, paradoxically, the increase of participation of women in science over the past 60 years was accompanied by an increase of gender differences in both productivity and impact. Most surprisingly though, we uncover two gender invariants, finding that men and women publish at a comparable annual rate and have equivalent career-wise impact for the same size body of work. Finally, we demonstrate that differences in dropout rates and career length explain a large portion of the reported career-wise differences in productivity and impact. This comprehensive picture of gender inequality in academia can help rephrase the conversation around the sustainability of women's careers in academia, with important consequences for institutions and policy makers.Comment: 23 pages, 4 figures, and S