105,069 research outputs found
Measurement of high-order polarization mode dispersion
We demonstrate a new method to measure high-order polarization mode dispersion (PMD) using the Jones matrix exponential expansion. High-order PMD is characterized by measuring a series of characteristic matrices, which are convenient quantities for analyzing PMD effects in the time-domain. An experimental method is developed to estimate the validity range of the exponential expansion
Calibration and High Fidelity Measurement of a Quantum Photonic Chip
Integrated quantum photonic circuits are becoming increasingly complex.
Accurate calibration of device parameters and detailed characterization of the
prepared quantum states are critically important for future progress. Here we
report on an effective experimental calibration method based on Bayesian
updating and Markov chain Monte Carlo integration. We use this calibration
technique to characterize a two qubit chip and extract the reflectivities of
its directional couplers. An average quantum state tomography fidelity of
93.79+/-1.05% against the four Bell states is achieved. Furthermore, comparing
the measured density matrices against a model using the non-ideal device
parameters derived from the calibration we achieve an average fidelity of
97.57+/-0.96%. This pinpoints non-ideality of chip parameters as a major factor
in the decrease of Bell state fidelity. We also perform quantum state
tomography for Bell states while continuously varying photon distinguishability
and find excellent agreement with theory
Connection between the Largest Lyapunov Exponent, Density Fluctuation and Multifragmentation in Excited Nuclear Systems
Within a quantum molecular dynamics model we calculate the largest Lyapunov
exponent (LLE), density fluctuation and mass distribution of fragments for a
series of nuclear systems at different initial temperatures. It is found that
the peaks at the temperature ("critical temperature") where the density
fluctuation reaches a maximal value and the mass distribution of fragments is
best fitted by the Fisher's power law from which the critical exponents for
mass and charge distribution are obtained. The time-dependent behavior of the
LLE and density fluctuation is studied. We find that the time scale of the
density fluctuation is much longer than the inverse LLE, which indicates that
the chaotic motion can be well developed during the process of fragment
formation. The finite-size effect on "critical temperature" for nuclear systems
ranging from Calcium to superheavy nuclei is also studied.Comment: 18 pages, 8 figures Submited to Phys. Rev.
Strange mass dependence of the tricritical point in the U(3)_L x U(3)_R chiral sigma model
We study the strange quark mass dependence of the tricritical point of the
U(3)_L x U(3)_R linear sigma model in the chiral limit. Assuming that the
tricritical point is at a large strange mass value, the strange sector as well
as the \eta-a_0 sector decouples from the light degrees of freedom which
determines the thermodynamics. By tracing this decoupling we arrive from the
original U(3)_L x U(3)_R symmetric model, going through the U(2)_L x U(2)_R
symmetric one, at the SU(2)_L x SU(2)_R linear sigma model. One-loop level beta
functions for the running of the parameters in each of these models and
tree-level matching of the coupling of these models performed at intermediate
scales are used to determine the influence of the heavy sector on the
parameters of the SU(2)_L x SU(2)_R linear sigma model. By investigating the
thermodynamics of this latter model we identified the tricritical surface of
the U(3)_L x U(3)_R linear sigma model in the chiral limit. To apply the
results for QCD we used different scenarios for the m_s and \mu_q dependence of
the effective model parameters, then the \mu_q^TCP(m_s) function can be
determined. Depending on the details, a curve bending upwards or downwards near
\mu_q=0 can be obtained, while with explicit chemical potential dependence of
the parameters the direction of the curve can change with m_s, too.Comment: 17 pages, 6 figures, uses revtex4-
On the improvement of the low energy neutrino factory
The low energy neutrino factory has been proposed as a very sensitive setup
for future searches for CP violation and matter effects. Here we study how its
performance is affected when the experimental specifications of the setup are
varied. Most notably, we have considered the addition of the 'platinum' nu_{mu}
-> nu_{e} channel. We find that, whilst theoretically the extra channel
provides very useful complementary information and helps to lift degeneracies,
its practical usefulness is lost when considering realistic background levels.
Conversely, an increase in statistics in the 'golden' nu_{e} -> nu_{mu} channel
and, to some extent, an improvement in the energy resolution, lead to an
important increase in the performance of the facility, given the rich energy
dependence of the 'golden' channel at these energies. We show that a low energy
neutrino factory with a baseline of 1300 km, muon energy of 4.5 GeV, and either
a 20 kton totally active scintillating detector or 100 kton liquid argon
detector, can have outstanding sensitivity to the neutrino oscillation
parameters theta13, delta and the mass hierarchy. For our estimated exposure of
2.8 x 10^{23} kton x decays per muon polarity, the low energy neutrino factory
has sensitivity to theta13 and delta for sin^{2}(2theta13) > 10^{-4} and to the
mass hierarchy for sin^{2}(2theta13) > 10^{-3}.Comment: 13 pages, 8 eps figures. Version published in PRD - experimental
section with preliminary results removed, abstract and conclusions re-written
accordingly, title changed, author list amended
Segregation and precipitation of Er in Ge
Although Er-doped Genanomaterials are attractive for photonic applications, very little is known about the basic properties of Er in Ge. Here, the authors study the annealing behavior of Geimplanted with keV Er ions to doses resulting in âČ1at.% of Er. Large redistribution of Er, with segregation at the amorphous/crystalline interface, starts at âł500°C, while lower temperatures are required for material recrystallization. However, even at 400°C, Er forms precipitates. The concentration of Er trapped in the bulk after recrystallization decreases with increasing temperature but is independent of the initial bulk Er concentration for the range of ion doses studied here.Work at the ANU was supported
by the ARC
Hour-glass magnetic excitations induced by nanoscopic phase separation in cobalt oxides LaSrCoO
The magnetic excitations in the cuprate superconductors might be essential
for an understanding of high-temperature superconductivity. In these cuprate
superconductors the magnetic excitation spectrum resembles an hour-glass and
certain resonant magnetic excitations within are believed to be connected to
the pairing mechanism which is corroborated by the observation of a universal
linear scaling of superconducting gap and magnetic resonance energy. So far,
charge stripes are widely believed to be involved in the physics of hour-glass
spectra. Here we study an isostructural cobaltate that also exhibits an
hour-glass magnetic spectrum. Instead of the expected charge stripe order we
observe nano phase separation and unravel a microscopically split origin of
hour-glass spectra on the nano scale pointing to a connection between the
magnetic resonance peak and the spin gap originating in islands of the
antiferromagnetic parent insulator. Our findings open new ways to theories of
magnetic excitations and superconductivity in cuprate superconductors.Comment: Nature Communications 5, 5731 (2014
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