7,786 research outputs found
Optimization of photon correlations by frequency filtering
Photon correlations are a cornerstone of Quantum Optics. Recent works [NJP 15
025019, 033036 (2013), PRA 90 052111 (2014)] have shown that by keeping track
of the frequency of the photons, rich landscapes of correlations are revealed.
Stronger correlations are usually found where the system emission is weak.
Here, we characterize both the strength and signal of such correlations,
through the introduction of the 'frequency resolved Mandel parameter'. We study
a plethora of nonlinear quantum systems, showing how one can substantially
optimize correlations by combining parameters such as pumping, filtering
windows and time delay.Comment: Small updates to take into account the recent experimental
observation of the physics here analyze
Linear and nonlinear coupling of quantum dots in microcavities
We discuss the topical and fundamental problem of strong-coupling between a
quantum dot an the single mode of a microcavity. We report seminal quantitative
descriptions of experimental data, both in the linear and in the nonlinear
regimes, based on a theoretical model that includes pumping and quantum
statistics.Comment: Proceedings of the symposium Nanostructures: Physics and Technology
2010 (http://www.ioffe.ru/NANO2010), 2 pages in proceedings styl
Open-beauty production in Pb collisions at =5 TeV: effect of the gluon nuclear densities
We present our results on open beauty production in proton-nucleus collisions
for the recent LHC Pb run at =5 TeV. We have analysed the
effect of the modification of the gluon PDFs in nucleus at the level of the
nuclear modification factor. Because of the absence of measurement in
collisions at the same energy, we also propose the study of the
forward-to-backward yield ratio in which the unknown proton-proton yield
cancel. Our results are compared with the data obtained by LHCb collaboration
and show a good agreement.Comment: 6 pages, 3 figures, Proceedings IS2013 submitted to Nuclear Physics
Effective penetration length and interstitial vortex pinning in superconducting films with regular arrays of defects
In order to compare magnetic and non-magnetic pinning we have nanostructured
two superconducting films with regular arrays of pinning centers: Cu
(non-magnetic) dots in one case, and Py (magnetic) dots in the other. For low
applied magnetic fields, when all the vortices are pinned in the artificial
inclusions, magnetic dots prove to be better pinning centers, as has been
generally accepted. Unexpectedly, when the magnetic field is increased and
interstitial vortices appear, the results are very different: we show how the
stray field generated by the magnetic dots can produce an effective reduction
of the penetration length. This results in strong consequences in the transport
properties, which, depending on the dot separation, can lead to an enhancement
or worsening of the transport characteristics. Therefore, the election of the
magnetic or non-magnetic character of the pinning sites for an effective
reduction of dissipation will depend on the range of the applied magnetic
field.Comment: 10 pages, 3 figure
On the spectroscopy of quantum dots in microcavities
At the occasion of the OECS conference in Madrid, we give a succinct account
of some recent predictions in the spectroscopy of a quantum dot in a
microcavity that remain to be observed experimentally, sometimes within the
reach of the current state of the art.Comment: OECS11 Conference proceedings, in editor style. 4 pages, 1 figure.
Animations provided separatel
Two-photon spectra of quantum emitters
We apply our recently developed theory of frequency-filtered and
time-resolved N-photon correlations to study the two-photon spectra of a
variety of systems of increasing complexity: single mode emitters with two
limiting statistics (one harmonic oscillator or a two-level system) and the
various combinations that arise from their coupling. We consider both the
linear and nonlinear regimes under incoherent excitation. We find that even the
simplest systems display a rich dynamics of emission, not accessible by simple
single photon spectroscopy. In the strong coupling regime, novel two-photon
emission processes involving virtual states are revealed. Furthermore, two
general results are unraveled by two-photon correlations with narrow linewidth
detectors: i) filtering induced bunching and ii) breakdown of the
semi-classical theory. We show how to overcome this shortcoming in a
fully-quantized picture.Comment: 27 pages, 8 figure
Superconducting/magnetic three state nanodevice for memory and reading applications
We present a simple nanodevice that can operate in two modes: i) three-state
memory and ii) reading device. The nanodevice is fabricated with an array of
ordered triangular-shaped nanomagnets embedded in a superconducting thin film.
The input signal is ac current and the output signal is dc voltage. Vortex
ratchet effect in combination with out of plane magnetic anisotropy of the
nanomagnets is the background physics which governs the nanodevice performance.Comment: 10 pages, 4 figure
Dynamics of formation and decay of coherence in a polariton condensate
We study the dynamics of formation and decay of a condensate of microcavity
polaritons. We investigate the relationship between the number of particles,
the emission's linewidth and its degree of linear polarization which serves as
the order parameter. Tracking the condensate's formation, we show that, even
when interactions are negligible, coherence is not determined only by
occupation of the ground state. As a result of the competition between the
coherent and thermal fractions of the condensate, the highest coherence is
obtained some time after the particle number has reached its maximum
Scaling of the conductance in gold nanotubes
A new form of gold nanobridges has been recently observed in ultrahigh-vacuum
experiments, where the gold atoms rearrange to build helical nanotubes, akin in
some respects to carbon nanotubes. The good reproducibility of these wires and
their unexpected stability will allow for conductance measurements and make
them promising candidates for future applications . We present here a study of
the transport properties of these nanotubes in order to understand the role of
chirality and of the different orbitals in quantum transport observables. The
conductance per atomic row shows a light decreasing trend as the diameter
grows, which is also shown through an analytical formula based on a one-orbital
model.Comment: 5 pages, 6 figure
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