8,323 research outputs found
Conditional generation of sub-Poissonian light from two-mode squeezed vacuum via balanced homodyne detection on idler mode
A simple scheme for conditional generation of nonclassical light with
sub-Poissonian photon-number statistics is proposed. The method utilizes
entanglement of signal and idler modes in two-mode squeezed vacuum state
generated in optical parametric amplifier. A quadrature component of the idler
mode is measured in balanced homodyne detector and only those experimental runs
where the absolute value of the measured quadrature is higher than certain
threshold are accepted. If the threshold is large enough then the conditional
output state of signal mode exhibits reduction of photon-number fluctuations
below the coherent-state level.Comment: 7 pages, 6 figures, REVTe
Unified Treatment of Heterodyne Detection: the Shapiro-Wagner and Caves Frameworks
A comparative study is performed on two heterodyne systems of photon
detectors expressed in terms of a signal annihilation operator and an image
band creation operator called Shapiro-Wagner and Caves' frame, respectively.
This approach is based on the introduction of a convenient operator
which allows a unified formulation of both cases. For the Shapiro-Wagner
scheme, where , quantum phase and amplitude
are exactly defined in the context of relative number state (RNS)
representation, while a procedure is devised to handle suitably and in a
consistent way Caves' framework, characterized by , within the approximate simultaneous measurements of
noncommuting variables. In such a case RNS phase and amplitude make sense only
approximately.Comment: 25 pages. Just very minor editorial cosmetic change
Coherence Resonance in Optical Feedback Chaos: Hiding Frequency in Chaos Communication
In this chapter, an experimentally and numerically conducted investigation of the existence of high chaotic spiking in the dynamics of semiconductor lasers with AC-coupled optical feedback, the bifurcation diagram by feedback strength attenuation and the bias current as a control parameter was done. A semiconductor laser subjected to an external optical feedback can present a big change of dynamic behaviors, such as periodic and quasi-periodic oscillations, chaos, coherence collapse, and low-frequency fluctuations (LFF’s) that degrade the laser characteristics. The chaotic instability is experimentally investigated on feedback strength as a control parameter, and the resulted dynamic is monostability. Finally, we indicated that the observed chaotic dynamic is a good candidate to hide information in order to investigate the resonance phenomena, which is important for chaos to encrypt data in optical communication, where data disappear when modulated in a chaos carrier. The aim of this chapter is to investigate the encryption area in the chaotic system when the applied frequency is 1–500 MHz, for satisfying the secure communication
Apparatus and Method for Triboelectrostatic Separation
A triboelectrostatic separation apparatus includes a separator with an inlet, a separation chamber, first and second electrodes, a variable voltage source for applying respective positive and negative voltage potentials to the electrodes, a pair of separated particle outlets and a curtain gas flow generation system. The curtain gas flow generation system includes a source of curtain gas at positive pressure, a metering valve for matching curtain gas flow velocity to particle flow velocity and flow straighteners for eliminating eddy currents. A method for separating electrostatically charged particles is also described
Generation of arbitrary quantum states of traveling fields
We show that any single-mode quantum state can be generated from the vacuum
by alternate application of the coherent displacement operator and the creation
operator. We propose an experimental implementation of the scheme for traveling
optical fields, which is based on field mixings and conditional measurements in
a beam splitter array, and calculate the probability of state generation.Comment: 1 Table and 2 Postscript figures, using Latex; modifications and
changes in Figure 2, Table 1 and Eqs. 11-13,17,18,2
Remote state preparation and teleportation in phase space
Continuous variable remote state preparation and teleportation are analyzed
using Wigner functions in phase space. We suggest a remote squeezed state
preparation scheme between two parties sharing an entangled twin beam, where
homodyne detection on one beam is used as a conditional source of squeezing for
the other beam. The scheme works also with noisy measurements, and provide
squeezing if the homodyne quantum efficiency is larger than 50%. Phase space
approach is shown to provide a convenient framework to describe teleportation
as a generalized conditional measurement, and to evaluate relevant degrading
effects, such the finite amount of entanglement, the losses along the line, and
the nonunit quantum efficiency at the sender location.Comment: 2 figures, revised version to appear in J.Opt.
Conceptualizing throughput legitimacy: procedural mechanisms of accountability, transparency, inclusiveness and openness in EU governance
This symposium demonstrates the potential for throughput legitimacy as a concept for shedding empirical light on the strengths and weaknesses of multi-level governance, as well as challenging the concept theoretically. This article introduces the symposium by conceptualizing throughput legitimacy as an ‘umbrella concept’, encompassing a constellation
of normative criteria not necessarily empirically interrelated. It argues that in order to interrogate multi-level governance processes in all their complexity, it makes sense for us to develop normative standards that are not naïve about the empirical realities of how power is exercised within multilevel governance, or how it may interact with legitimacy. We argue that while throughput legitimacy has its normative limits, it can be substantively useful for these purposes. While being no replacement for input and output legitimacy, throughput legitimacy offers distinctive normative criteria— accountability, transparency, inclusiveness and openness— and points towards substantive institutional reforms.Published versio
Stoner gap in the superconducting ferromagnet UGe2
We report the temperature () dependence of ferromagnetic Bragg peak
intensities and dc magnetization of the superconducting ferromagnet UGe2 under
pressure (). We have found that the low- behavior of the uniform
magnetization can be explained by a conventional Stoner model. A functional
analysis of the data produces the following results: The ferromagnetic state
below a critical pressure can be understood as the perfectly polarized state,
in which heavy quasiparticles occupy only majority spin bands. A Stoner gap
decreases monotonically with increasing pressure and increases
linearly with magnetic field. We show that the present analysis based on the
Stoner model is justified by a consistency check, i.e., comparison of density
of states at the Fermi energy deduced from the analysis with observed
electronic specific heat coeffieients. We also argue the influence of the
ferromagnetism on the superconductivity.Comment: 5 pages, 4 figures. to be published in Phys. Rev.
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