15,419 research outputs found
Experimental investigation of linear-optics-based quantum target detection
The development of new techniques to improve measurements is crucial for all
sciences. By employing quantum systems as sensors to probe some physical
property of interest allows the application of quantum resources, such as
coherent superpositions and quantum correlations, to increase measurement
precision. Here we experimentally investigate a scheme for quantum target
detection based on linear optical measurment devices, when the object is
immersed in unpolarized background light. By comparing the quantum
(polarization-entangled photon pairs) and the classical (separable polarization
states), we found that the quantum strategy provides us an improvement over the
classical one in our experiment when the signal to noise ratio is greater than
1/40, or about 16dB of noise. This is in constrast to quantum target detection
considering non-linear optical detection schemes, which have shown resilience
to extreme amounts of noise. A theoretical model is developed which shows that,
in this linear-optics context, the quantum strategy suffers from the
contribution of multiple background photons. This effect does not appear in our
classical scheme. By improving the two-photon detection electronics, it should
be possible to achieve a polarization-based quantum advantage for a signal to
noise ratio that is close to 1/400 for current technology.Comment: comments are welcome, submitted to PR
Gluon mass generation without seagull divergences
Dynamical gluon mass generation has been traditionally plagued with seagull
divergences, and all regularization procedures proposed over the years yield
finite but scheme-dependent gluon masses. In this work we show how such
divergences can be eliminated completely by virtue of a characteristic
identity, valid in dimensional regularization. The ability to trigger the
aforementioned identity hinges crucially on the particular Ansatz employed for
the three-gluon vertex entering into the Schwinger-Dyson equation governing the
gluon propagator. The use of the appropriate three-gluon vertex brings about an
additional advantage: one obtains two separate (but coupled) integral
equations, one for the effective charge and one for the gluon mass. This system
of integral equations has a unique solution, which unambiguously determines
these two quantities. Most notably, the effective charge freezes in the
infrared, and the gluon mass displays power-law running in the ultraviolet, in
agreement with earlier considerations.Comment: 37 pages, 9 figures; minor typos corrected and a few brief
explanatory remarks adde
Hierarchy plus anarchy in quark masses and mixings
We introduce a new parameterisation of the effect of unknown corrections from
new physics on quark and lepton mass matrices. This parameterisation is used in
order to study how the hierarchies of quark masses and mixing angles are
modified by random perturbations of the Yukawa matrices. We discuss several
examples of flavour relations predicted by different textures, analysing how
these relations are influenced by the random perturbations. We also comment on
the unlikely possibility that unknown corrections contribute significantly to
the hierarchy of masses and mixings.Comment: LaTeX, 18 pages, 16 PS figure
A Possible Detection of Occultation by a Proto-planetary Clump in GM Cephei
GM Cep in the young (~4 Myr) open cluster Trumpler 37 has been known to be an
abrupt variable and to have a circumstellar disk with very active accretion.
Our monitoring observations in 2009-2011 revealed the star to show sporadic
flare events, each with brightening of < 0.5 mag lasting for days. These
brightening events, associated with a color change toward the blue, should
originate from an increased accretion activity. Moreover, the star also
underwent a brightness drop of ~1 mag lasting for about a month, during which
the star became bluer when fainter. Such brightness drops seem to have a
recurrence time scale of a year, as evidenced in our data and the photometric
behavior of GM Cep over a century. Between consecutive drops, the star
brightened gradually by about 1 mag and became blue at peak luminosity. We
propose that the drop is caused by obscuration of the central star by an
orbiting dust concentration. The UX Orionis type of activity in GM Cep
therefore exemplifies the disk inhomogeneity process in transition between
grain coagulation and planetesimal formation in a young circumstellar disk.Comment: In submission to the Astrophysical Journal, 4 figure
Colossal magnon-phonon coupling in multiferroic EuYMnO
We report the spectra of magnetically induced electric dipole absorption in
EuYMnO from temperature dependent far infrared
spectroscopy (10-250 cm). These spectra, which occur only in the
polarization, consist of two relatively narrow electromagnon features that
onset at K and a broad absorption band that persists to
temperatures well above K. The observed excitations account for the
step up of the static dielectric constant in the ferroelectric phase. The
electromagnon at 80 cm is observed to be strongly coupled to the nearby
lowest optical phonon which transfers more than 1/2 of its spectral weight to
the magnon. We attribute the origin of the broad background absorption to the
two magnon emission decay process of the phonon.Comment: 4 pages, 3 figure
Synchrotron x-ray study of lattice vibrations in CdCr2O4
Using inelastic x-ray scattering we have investigated lattice vibrations in a
geometric frustrated system CdCr2O4 that upon cooling undergoes a spin-Peierls
phase transition at TN = 7.8 K from a cubic and paramagnetic to a tetragonal
and Neel state. Phonon modes measured around Brillouin zone boundaries show
energy shifts when the transition occurs. Our analysis shows that the shifting
can be understood as the ordinary effects of the lowering of the crystal
symmetry
Dynamics of gravity driven three-dimensional thin films on hydrophilic-hydrophobic patterned substrates
We investigate numerically the dynamics of unstable gravity driven
three-dimensional thin liquid films on hydrophilic-hydrophobic patterned
substrates of longitudinal stripes and checkerboard arrangements. The thin film
can be guided preferentially on hydrophilic longitudinal stripes, while fingers
develop on adjacent hydrophobic stripes if their width is large enough. On
checkerboard patterns, the film fingering occurs on hydrophobic domains, while
lateral spreading is favoured on hydrophilic domains, providing a mechanism to
tune the growth rate of the film. By means of kinematical arguments, we
quantitatively predict the growth rate of the contact line on checkerboard
arrangements, providing a first step towards potential techniques that control
thin film growth in experimental setups.Comment: 30 pages, 12 figure
K*(892)0 Production in Relativistic Heavy Ion Collisions at sqrt(s_NN) = 130 GeV
Preliminary results on the K*(892)0 -> pi + K production using the
mixed-event technique are presented. The measurements are performed at
mid-rapidity by the STAR detector in sqrt(s_NN) = 130 GeV Au-Au collisions at
RHIC. The K*0 to negative hadron, kaon and phi ratios are obtained and compared
to the measurements in e+e-, pp and pbarp at various energies.Comment: 8 pages, 3 figures, proceedings of Strange Quarks in Matter
(SQM2001), Frankfurt am Main, Germany, to be published in J. Phys.
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