156 research outputs found
Continuous-Variable Entangled States of Light carrying Orbital Angular Momentum
The orbital angular momentum of light, unlike spin, is an
infinite-dimensional discrete variable and may hence offer enhanced
performances for encoding, transmitting, and processing information in the
quantum regime. Hitherto, this degree of freedom of light has been studied
mainly in the context of quantum states with definite number of photons. On the
other hand, field-quadrature continuous-variable quantum states of light allow
implementing many important quantum protocols not accessible with photon-number
states. Here, we present the first generation and complete experimental
characterization of a bipartite continuous-variable Gaussian entangled state
endowed with non-zero orbital angular momentum. A q-plate is used to transfer
the continuous-variable entanglement initially generated in polarization into
orbital angular momentum. We then apply a reconfigurable homodyne detector to
various combinations of orbital angular momentum modes in order to reconstruct
the entire quantum-state covariance matrix, by directly measuring the
fluctuations of quadrature operators. Our work is a step towards generating
multipartite continuous-variable entanglement in a single optical beam.Comment: To appear in Phys. Rev.
Detection of Zak phases and topological invariants in a chiral quantum walk of twisted photons
Topological insulators are fascinating states of matter exhibiting protected
edge states and robust quantized features in their bulk. Here, we propose and
validate experimentally a method to detect topological properties in the bulk
of one-dimensional chiral systems. We first introduce the mean chiral
displacement, and we show that it rapidly approaches a multiple of the Zak
phase in the long time limit. Then we measure the Zak phase in a photonic
quantum walk, by direct observation of the mean chiral displacement in its
bulk. Next, we measure the Zak phase in an alternative, inequivalent timeframe,
and combine the two windings to characterize the full phase diagram of this
Floquet system. Finally, we prove the robustness of the measure by introducing
dynamical disorder in the system. This detection method is extremely general,
as it can be applied to all one-dimensional platforms simulating static or
Floquet chiral systems.Comment: 10 pages, 7 color figures (incl. appendices) Close to the published
versio
Red light-emitting Carborane-BODIPY dyes: Synthesis and properties of visible-light tuned fluorophores with enhanced boron content
A small library of 2,6- and 3,5-distyrenyl-substituted carborane-BODIPY dyes was efficiently synthesized by
means of a Pd-catalyzed Heck coupling reaction. Styrenyl-carborane derivatives were exploited as molecular
tools to insert two carborane clusters into the fluorophore core and to extend the π-conjugation of the final
molecule in a single synthetic step. The synthetic approach allows to increase the molecular diversity of this class
of fluorescent dyes by the synthesis of symmetric or asymmetric units with enhanced boron content. The
structural characterization and the photoluminescence (PL) properties of synthesized dyes were evaluated, and
the structure/properties relationships have been investigated by theoretical calculations. The developed compounds
exhibit a significant bathochromic shift compared to their parent fluorophore scaffolds, and absorption
and emission patterns were practically unaffected by the different substituents (Me or Ph) on the Ccluster atom
(Cc) of the carborane cage or the cluster isomer (ortho- or meta-carborane). Remarkably, the presence of carborane
units at 2,6-positions of the fluorophore produced a significant increase of the emission fluorescent
quantum yields, which could be slightly tuned by changing the Cc-substituent and the carborane isomer, as well
as introducing ethylene glycol groups at the meso-position of the BODIPY
Simple method for the characterization of intense Laguerre-Gauss vector vortex beams
We report on a method for the characterization of intense, structured optical fields through the analysis of the size and surface structures formed inside the annular ablation crater created on the target surface. In particular, we apply the technique to laser ablation of crystalline silicon induced by femtosecond vector vortex beams. We show that a rapid direct estimate of the beam waist parameter is obtained through a measure of the crater radii. The variation of the internal and external radii of the annular crater as a function of the laser pulse energy, at fixed number of pulses, provides another way to evaluate the beam spot size through numerical fitting of the obtained experimental data points. A reliable estimate of the spot size is of paramount importance to investigate pulsed laser-induced effects on the target material. Our experimental findings offer a facile way to characterize focused, high intensity complex optical vector beams which are more and more applied in laser-matter interaction experiments
Dose–Volume Constraints fOr oRganS At risk In Radiotherapy (CORSAIR): An “All-in-One” Multicenter–Multidisciplinary Practical Summary
BACKGROUND: The safe use of radiotherapy (RT) requires compliance with dose/volume constraints (DVCs) for organs at risk (OaRs). However, the available recommendations are sometimes conflicting and scattered across a number of different documents. Therefore, the aim of this work is to provide, in a single document, practical indications on DVCs for OaRs in external beam RT available in the literature.MATERIAL AND METHODS: A multidisciplinary team collected bibliographic information on the anatomical definition of OaRs, on the imaging methods needed for their definition, and on DVCs in general and in specific settings (curative RT of Hodgkin's lymphomas, postoperative RT of breast tumors, curative RT of pediatric cancers, stereotactic ablative RT of ventricular arrythmia). The information provided in terms of DVCs was graded based on levels of evidence.RESULTS: Over 650 papers/documents/websites were examined. The search results, together with the levels of evidence, are presented in tabular form.CONCLUSIONS: A working tool, based on collected guidelines on DVCs in different settings, is provided to help in daily clinical practice of RT departments. This could be a first step for further optimizations
Roadmap on structured waves
Structured waves are ubiquitous for all areas of wave physics, both classical
and quantum, where the wavefields are inhomogeneous and cannot be approximated
by a single plane wave. Even the interference of two plane waves, or a single
inhomogeneous (evanescent) wave, provides a number of nontrivial phenomena and
additional functionalities as compared to a single plane wave. Complex
wavefields with inhomogeneities in the amplitude, phase, and polarization,
including topological structures and singularities, underpin modern nanooptics
and photonics, yet they are equally important, e.g., for quantum matter waves,
acoustics, water waves, etc. Structured waves are crucial in optical and
electron microscopy, wave propagation and scattering, imaging, communications,
quantum optics, topological and non-Hermitian wave systems, quantum
condensed-matter systems, optomechanics, plasmonics and metamaterials, optical
and acoustic manipulation, and so forth. This Roadmap is written collectively
by prominent researchers and aims to survey the role of structured waves in
various areas of wave physics. Providing background, current research, and
anticipating future developments, it will be of interest to a wide
cross-disciplinary audience.Comment: 110 pages, many figure
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