1,508 research outputs found
Cross-Phase Modulation Enhancement Via a Resonating Cavity: Semiclassical Description
We evaluate the advantages of performing cross-phase modulation (XPM) on a
very-far-off-resonance atomic system. We consider a ladder system with a weak
(few-photon level) control coherent field imparting a conditional nonlinear
phase shift on a probe beam. We find that by coupling to an optical resonator
the optimal XPM is enhanced proportional to the finesse of the resonator by a
factor of . We present a semi-classical description of the system and
show that the phenomenon is optimal in the self-defined condition of
off-resonance-effective-cooperativity equal to one
Practical Advantages of Almost-Balanced-Weak-Values Metrological Techniques
Precision measurements of ultra-small linear velocities of one of the mirrors
in a Michelson interferometer are performed using two different weak-values
techniques. We show that the technique of Almost-Balanced Weak Values (ABWV)
offers practical advantages over the technique of Weak-Value Amplification
(WVA), resulting in larger signal-to-noise ratios and the possibility of longer
integration times due to robustness to slow drifts. As an example of the
performance of the ABWV protocol we report a velocity sensitivity of 60 fm/s
after 40 hours of integration time. The sensitivity of the Doppler shift due to
the moving mirror is of 150 nHz
Technical advantages for weak value amplification: When less is more
The technical merits of weak value amplification techniques are analyzed. We
consider models of several different types of technical noise in an optical
context and show that weak value amplification techniques (which only use a
small fraction of the photons) compare favorably with standard techniques
(which uses all of them). Using the Fisher information metric, we demonstrate
that weak value techniques can put all of the Fisher information about the
detected parameter into a small portion of the events and show how this fact
alone gives technical advantages. We go on to consider a time correlated noise
model, and find that a Fisher information analysis indicates that while the
standard method can have much larger information about the detected parameter
than the postselected technique. However, the estimator needed to gather the
information is technically difficult to implement, showing that the inefficient
(but practical) signal-to-noise estimation of the parameter is usually
superior. We also describe other technical advantages unique to imaginary weak
value amplification techniques, focusing on beam deflection measurements. In
this case, we discuss combined noise types (such as detector transverse jitter,
angular beam jitter before the interferometer and turbulence) for which the
interferometric weak value technique gives higher Fisher information over
conventional methods. We go on to calculate the Fisher information of the
recently proposed photon recycling scheme for beam deflection measurements, and
show it further boosts the Fisher information by the inverse postselection
probability relative to the standard measurement case
Complementary weak-value amplification with concatenated postselections
We measure a transverse momentum kick in a Sagnac interferometer using
weak-value amplification with two postselections. The first postselection is
controlled by a polarization dependent phase mismatch between both paths of a
Sagnac interferometer and the second postselection is controlled by a polarizer
at the exit port. By monitoring the darkport of the interferometer, we study
the complementary amplification of the concatenated postselections, where the
polarization extinction ratio is greater than the contrast of the spatial
interference. In this case, we find an improvement in the amplification of the
signal of interest by introducing a second postselection to the system
Can Anomalous Amplification be Attained Without Postselection?
We present a parameter estimation technique based on performing joint
measurements of a weak interaction away from the weak-value-amplification
approximation. Two detectors are used to collect full statistics of the
correlations between two weakly entangled degrees of freedom. Without the need
of postselection, the protocol resembles the anomalous amplification of an
imaginary-weak-value-like response. The amplification is induced in the
difference signal of both detectors allowing robustness to different sources of
technical noise, and offering in addition the advantages of balanced signals
for precision metrology. All of the Fisher information about the parameter of
interest is collected, and a phase controls the amplification response. We
experimentally demonstrate the proposed technique by measuring polarization
rotations in a linearly polarized laser pulse. The effective sensitivity and
precision of a split detector is increased when compared to a conventional
continuous-wave balanced detection technique
Catalizadores heterogéneos utilizados para la obtención de biodiesel
El ahorro energético y el cuidado medioambiental son de gran importancia en todos los países, debido a estos aspectos se ha desarrollado la búsqueda de combustibles alternos para sustituir los provenientes defuentes fósiles. En este artículo se presenta información relacionada con los diferentes catalizadores utilizados para la producción de biodiesel, mencionando su clasificación química y física, también se citan las propiedades químicas y las características morfológicas que los hacen ser una opción apropiada para utilizarlos en la reacción de transesterificación, la cual está implicada en la producción de biodiesel. Además, se resalta la importancia de los catalizadores heterogéneos por sus características de baja contaminación al medio ambiente, su capacidad de ser reutilizados y porque pueden separarse fácilmente del producto
Cross-Phase Modulation Enhancement via a Resonating Cavity: Semiclassical Description
We evaluate the advantages of performing cross-phase modulation (XPM) on a very-far-off-resonance atomic system. We consider a ladder system with a weak (few-photon level) control coherent field imparting a conditional nonlinear phase shift on a probe beam. We find that by coupling to an optical resonator, the optimal XPM is enhanced proportional to the finesse of the resonator by a factor of ��/4��. We present a semiclassical description of the system and show that the phenomenon is optimal in the self-defined condition of off-resonance effective cooperativity equal to one
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