290 research outputs found
Generation of microwave radiation by nonlinear interaction of a high-power, high-repetition rate, 1064-nm laser in KTP crystals
We report measurements of microwave (RF) generation in the centimeter band
accomplished by irradiating a nonlinear KTiOPO (KTP) crystal with a
home-made, infrared laser at nm as a result of optical rectification
(OR). The laser delivers pulse trains of duration up to s. Each train
consists of several high-intensity pulses at an adjustable repetition rate of
approximately GHz. The duration of the generated RF pulses is
determined by that of the pulse trains. We have investigated both microwave-
and second harmonic (SHG) generation as a function of the laser intensity and
of the orientation of the laser polarization with respect to the
crystallographic axes of KTP.Comment: 5 pages, 5 figures, to appear in Optics Letters, vol. 38 (2013
Cathodo- and radioluminescence of Tm:YAG and Nd:YAG in an extended wavelength range
We have studied the cathodo- and radioluminescence of Nd:YAG and of Tm:YAG
single crystals in an extended wavelength range up to m in view
of developing a new kind of detector for low-energy, low-rate energy deposition
events. Whereas the light yield in the visible range is as large as photons/MeV, in good agreement with literature results, in the
infrared range we have found a light yield photons/MeV, thereby proving that ionizing radiation is particularly
efficient in populating the low lying levels of rare earth doped crystals.Comment: submitted for publication in Journal of Luminescenc
Generation of microwave fields in cavities with laser-excited nonlinear media: competition between the second- and third-order optical nonlinearities
We discuss a scheme for the parametric amplification of the quantum fluctuations of the
electromagnetic vacuum in a three-dimensional microwave resonator, and report the preliminary
measurements to test its feasibility. In the present experimental scheme, the fundamental mode of
a microwave cavity is nonadiabatically perturbed by modulating the index of refraction of the
nonlinear optical crystal enclosed therein. Intense, multi-GHz laser pulses, such as those
delivered by a mode-locked laser source, impinge on the crystal to accomplish the n-index
modulation. We theoretically analyze the process of parametric generation, which is related to
the third-order nonlinear coefficient \u3c7(3) of the nonlinear crystal, and assess the suitable
experimental conditions for generating real photons from the vacuum. Second-order nonlinear
processes are first analyzed as a possible source of spurious photons in quantum vacuum
experiments when an ideal, mode-locked laser source is considered. The combination of a crystal
non-null \u3c7(2) coefficient and a real mode-locked laser system\u2014i.e. one featuring offset-fromcarrier
noise and unwanted secondary oscillations\u2014is also experimentally investigated, paving
the way for future experiments in three-dimensional cavities
A new technique for infrared scintillation measurements
We propose a new technique to measure the infrared scintillation light yield
of rare earth (RE) doped crystals by comparing it to near UV-visible
scintillation of a calibrated Pr:(LuY)AlO
sample. As an example, we apply this technique to provide the light yield in
visible and infrared range up to \SI{1700}{nm} of this crystal.Comment: submitted to NIM
Circulating Epigenetic Biomarkers in Malignant Pleural Mesothelioma: State of the Art and critical Evaluation
Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer, which originates from the mesothelial cells of the pleura and is associated with asbestos exposure. In light of its aggressive nature, late diagnosis and dismal prognosis, there is an urgent need for identification of biomarkers in easily accessible samples (such as blood) for early diagnosis of MPM. In the last 10 years, epigenetic markers, such as DNA methylation and microRNAs (miRNAs), have gained popularity as possible early diagnostic and prognostic biomarkers in cancer research. The aim of this review is to provide a critical analysis of the current evidences on circulating epigenetic biomarkers for MPM and on their translational potential to the clinical practice for early diagnosis and for prognosis
The QUAX proposal: a search of galactic axion with magnetic materials
Aim of the QUAX (QUaerere AXion) proposal is to exploit the interaction of
cosmological axions with the spin of electrons in a magnetized sample. Their
effect is equivalent to the application of an oscillating rf field with
frequency and amplitude which are fixed by axion mass and coupling constant,
respectively. The rf receiver module of the QUAX detector consists of
magnetized samples with the Larmor resonance frequency tuned to the axion mass
by a polarizing static magnetic field. The interaction of electrons with the
axion-equivalent rf field produces oscillations in the total magnetization of
the samples. To amplify such a tiny field, a pump field at the same frequency
is applied in a direction orthogonal to the polarizing field. The induced
oscillatory magnetization along the polarizing field is measured by a SQUID
amplifier operated at its quantum noise level.Comment: 5 pages, Contribution for the proceedings of the TAUP2015,
International Conference on Topics in Astroparticle and Underground Physics,
7-11 September 2015, Torino, Ital
Towards Recommender Systems with Community Detection and Quantum Computing
After decades of being mainly confined to theoretical research, Quantum Computing is now becoming a useful tool for solving realistic problems. This work aims to experimentally explore the feasibility of using currently available quantum computers, based on the Quantum Annealing paradigm, to build a recommender system exploiting community detection. Community detection, by partitioning users and items into densely connected clusters, can boost the accuracy of non-personalized recommendation by assuming that users within each community share similar tastes. However, community detection is a computationally expensive process. The recent availability of Quantum Annealers as cloud-based devices, constitutes a new and promising direction to explore community detection, although effectively leveraging this new technology is a long-term path that still requires advancements in both hardware and algorithms. This work aims to begin this path by assessing the quality of community detection formulated as a Quadratic Unconstrained Binary Optimization problem on a real recommendation scenario. Results on several datasets show that the quantum solver is able to detect communities of comparable quality with respect to classical solvers, but with better speedup, and the non-personalized recommendation models built on top of these communities exhibit improved recommendation quality. The takeaway is that quantum computing, although in its early stages of maturity and applicability, shows promise in its ability to support new recommendation models and to bring improved scalability as technology evolves
Laser induced fluorescence for axion dark matter detection: a feasibility study in YLiF:Er
We present a detection scheme to search for QCD axion dark matter, that is
based on a direct interaction between axions and electrons explicitly predicted
by DFSZ axion models. The local axion dark matter field shall drive transitions
between Zeeman-split atomic levels separated by the axion rest mass energy . Axion-related excitations are then detected with an upconversion scheme
involving a pump laser that converts the absorbed axion energy (
hundreds of eV) to visible or infrared photons, where single photon
detection is an established technique. The proposed scheme involves rare-earth
ions doped into solid-state crystalline materials, and the optical transitions
take place between energy levels of electron configuration. Beyond
discussing theoretical aspects and requirements to achieve a cosmologically
relevant sensitivity, especially in terms of spectroscopic material properties,
we experimentally investigate backgrounds due to the pump laser at temperatures
in the range K. Our results rule out excitation of the upper Zeeman
component of the ground state by laser-related heating effects, and are of some
help in optimizing activated material parameters to suppress the
multiphonon-assisted Stokes fluorescence.Comment: 8 pages, 5 figure
- …