1,154 research outputs found

    A Study of the Trends in the Level of Preparation and Placement of New Teachers in the White Public Schools of Tennessee From 1938-1939 through 1947-1948

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    (From the Introduction) Equalization of educational opportunity was an ideal expressed by the founders of our nation. It is a principle that is fundamental in American education--a principle based upon the assumption that our democracy is best served by extending to all children an equal minimum opportunity to attend schools staffed with the best qualified teachers available. A denial of this principle is to defeat the basic purposes of American education as they were expressed by its founders and a they have been developed to meet the needs of our modern society

    Frequency up- and down-conversions in two-mode cavity quantum electrodynamics

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    In this letter we present a scheme for the implementation of frequency up- and down-conversion operations in two-mode cavity quantum electrodynamics (QED). This protocol for engineering bilinear two-mode interactions could enlarge perspectives for quantum information manipulation and also be employed for fundamental tests of quantum theory in cavity QED. As an application we show how to generate a two-mode squeezed state in cavity QED (the original entangled state of Einstein-Podolsky-Rosen)

    Quantum Connectivity of Space-Time and Gravitationally Induced Decorrelation of Entanglement

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    We discuss an alternative formulation of the problem of quantum optical fields in a curved space-time using localized operators. We contrast the new formulation with the standard approach and find observable differences for entangled states. We propose an experiment in which an entangled pair of optical pulses are propagated through non-uniform gravitational fields and find that the new formulation predicts de-correlation of the optical entanglement under experimentally realistic conditions

    Single-photon optomechanics in the strong coupling regime

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    We give a theoretical description of a coherently driven opto-mechanical system with a single added photon. The photon source is modeled as a cavity which initially contains one photon and which is irreversibly coupled to the opto-mechanical system. We show that the probability for the additional photon to be emitted by the opto-mechanical cavity will exhibit oscillations under a Lorentzian envelope, when the driven interaction with the mechanical resonator is strong enough. Our scheme provides a feasible route towards quantum state transfer between optical photons and micromechanical resonators.Comment: 14 pages, 6 figure

    Quantum nondemolition measurements in optical cavities

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    We analyze schemes for performing quantum nondemolition (QND) measurements in optical cavities. We consider three schemes: (1) measurement of a quadrature phase amplitude using a parametric process, (2) measurement of a quadrature phase amplitude using the optical Kerr effect in a nonlinear fiber, and (3) measurement of the photon number also using the Kerr effect in a fiber. We show that in the second scheme an enhancement of the QND effect may be obtained by making the cavity finesse for the signal larger than that for the probe

    Quantum limits to all-optical phase shifts in a Kerr nonlinear medium

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    We consider two copropagating fields in a nonlinear Kerr medium, each with a particular phase and intensity. The Kerr medium possesses an intensity-dependent refractive index and the phase shift of each field thus depends on the intensities of the fields. Classically it is possible to induce an arbitrary phase shift of one field (the signal field) by either increasing the intensity of the other field (the control field) or by increasing the interaction legnth. We show that if the intensity of the control field is low, the phase shift on the signal is limited by the discrete nature of the photon-number distribution in the control field and cannot be increased simply by increasing the interaction length. In general the maximum phase shift of the signal field is φ if the control field possesses φ photons. This limit arises as a consequence of quantum recurrence effects

    Quantum Entanglement and Teleportation in Higher Dimensional Black Hole Spacetimes

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    We study the properties of quantum entanglement and teleportation in the background of stationary and rotating curved space-times with extra dimensions. We show that a maximally entangled Bell state in an inertial frame becomes less entangled in curved space due to the well-known Hawking-Unruh effect. The degree of entanglement is found to be degraded with increasing the extra dimensions. For a finite black hole surface gravity, the observer may choose higher frequency mode to keep high level entanglement. The fidelity of quantum teleporation is also reduced because of the Hawking-Unruh effect. We discuss the fidelity as a function of extra dimensions, mode frequency, black hole mass and black hole angular momentum parameter for both bosonic and fermionic resources.Comment: 15 pages, 10 figures,contents expande

    HIV-associated Cryptococcal Meningitis: a Review of Novel Short-Course and Oral Therapies

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    Abstract Purpose of review HIV-associated cryptococcal meningitis remains a significant public health problem in parts of Africa and Asia and a major cause of AIDS-related mortality, accounting for 15% of all AIDS-related deaths worldwide. Cryptococcal meningitis is uniformly fatal if untreated, and access to antifungal therapy in regions with the highest burden is often limited. Outcomes with fluconazole monotherapy are poor, and induction treatment with amphotericin B and high-dose fluconazole for 2 weeks is associated with significant drug-related toxicities and prolonged hospital admissions. This review focuses on the potential of novel short-course and oral combination therapies for cryptococcal meningitis. Recent findings Recent clinical trials have shown that shorter courses of amphotericin, if paired with oral flucytosine, rather than fluconazole, can achieve non-inferior mortality outcomes. In addition, an oral combination of fluconazole and flucytosine is a potential alternative. Liposomal amphotericin B may further simplify treatment; it is associated with fewer drug-related toxicities, and a recent phase II randomised controlled trial demonstrated that a single, high dose of liposomal amphotericin is non-inferior to 14 standard daily doses at clearing Cryptococcus from cerebrospinal fluid. This has been taken forward to an ongoing phase III, clinical endpoint study. Summary The incidence and mortality associated with cryptococcal meningitis is still unacceptably high. There is evidence supporting the use of short-course amphotericin B and oral combination antifungal treatment regimens for cryptococcal meningitis (CM). Ongoing research into short-course, high-dose treatment with liposomal amphotericin may also help reduce the impact of this devastating disease. </jats:sec

    Wigner Function Evolution of Quantum States in Presence of Self-Kerr Interaction

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    A Fokker-Planck equation for the Wigner function evolution in a noisy Kerr medium (χ(3)\chi^{(3)} non-linearity) is presented. We numerically solved this equation taking a coherent state as an initial condition. The dissipation effects are discussed. We provide examples of quantum interference, sub-Planck phase space structures, and Gaussian versus non-Gaussian dynamical evolution of the state. The results also apply to the description of a nanomechanical resonator with an intrinsic Duffing nonlinearity.Comment: 10 pages, 11 figure

    Chaos and coherence in an optical system subject to photon nondemolition measurement

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    We consider the effect of quantum-nondemolition monitoring of the photon number on the quantum suppression of classical chaos in a recently proposed quantum optical model, the parametrically kicked nonlinear oscillator [G. J. Milburn, Phys. Rev. A 41, 6567 (1990)]. Classically the effect of the quantum-nondemolition measurement is equivalent to a phase diffusion in the phase plane of the oscillator. A similar result holds in the quantum description, but in addition the measurement rapidly diagonalizes the system density operator in the photon-number basis. This has the effect of causing the evolution of the quantum moments to approach the corresponding classical moments and thus restores the classical dynamics for practical purposes
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