333 research outputs found
Dual and anti-dual modes in dielectric spheres
We present how the angular momentum of light can play an important role to
induce a dual or anti-dual behaviour on a dielectric particle. Although the
material the particle is made of is not dual, i.e. a dielectric does not
interact with an electrical field in the same way as it does with a magnetic
one, a spherical particle can behave as a dual system when the correct
excitation beam is chosen. We study the conditions under which this induced
dual or anti-dual behaviour can be induced.Comment: 13 pages, 5 figure
Measurement and shaping of biphoton spectral wavefunctions
In this work we present a simple method to reconstruct the complex spectral
wavefunction of a biphoton, and hence gain complete information about the
spectral and temporal properties of a photon pair. The technique, which relies
on quantum interference, is applicable to biphoton states produced with a
monochromatic pump when a shift of the pump frequency produces a shift in the
relative frequencies contributing to the biphoton. We demonstrate an example of
such a situation in type-II parametric down-conversion (SPDC) allowing
arbitrary paraxial spatial pump and detection modes. Moreover, our test cases
demonstrate the possibility to shape the spectral wavefunction. This is
achieved by choosing the spatial mode of the pump and of the detection modes,
and takes advantage of spatiotemporal correlations.Comment: Supplementary information also available. Comments and feedback
appreciated. Compared to the previous version, here we have made the
following changes: -corrected a typo in the text between Eq. (11) and (12)
-corrected a typo in the references -added reference
Visualizing the emission of a single photon with frequency and time resolved spectroscopy
At the dawn of Quantum Physics, Wigner and Weisskopf obtained a full
analytical description (a \textit{photon portrait}) of the emission of a single
photon by a two-level system, using the basis of frequency modes (Weisskopf and
Wigner, "Zeitschrift f\"ur Physik", 63, 1930). A direct experimental
reconstruction of this portrait demands an accurate measurement of a time
resolved fluorescence spectrum, with high sensitivity to the off-resonant
frequencies and ultrafast dynamics describing the photon creation. In this work
we demonstrate such an experimental technique in a superconducting waveguide
Quantum Electrodynamics (wQED) platform, using single transmon qubit and two
coupled transmon qubits as quantum emitters. In both scenarios, the photon
portraits agree quantitatively with the predictions of the input-output theory
and qualitatively with Wigner-Weisskopf theory. We believe that our technique
allows not only for interesting visualization of fundamental principles, but
may serve as a tool, e.g. to realize multi-dimensional spectroscopy in
waveguide Quantum Electrodynamics.Comment: 18 pages, 10 figures including appendice
Toward Quantum Superposition of Living Organisms
The most striking feature of quantum mechanics is the existence of
superposition states, where an object appears to be in different situations at
the same time. The existence of such states has been tested with small objects,
like atoms, ions, electrons and photons, and even with molecules. More
recently, it has been possible to create superpositions of collections of
photons, atoms, or Cooper pairs. Current progress in optomechanical systems may
soon allow us to create superpositions of even larger objects, like micro-sized
mirrors or cantilevers, and thus to test quantum mechanical phenomena at larger
scales. Here we propose a method to cool down and create quantum superpositions
of the motion of sub-wavelength, arbitrarily shaped dielectric objects trapped
inside a high--finesse cavity at a very low pressure. Our method is ideally
suited for the smallest living organisms, such as viruses, which survive under
low vacuum pressures, and optically behave as dielectric objects. This opens up
the possibility of testing the quantum nature of living organisms by creating
quantum superposition states in very much the same spirit as the original
Schr\"odinger's cat "gedanken" paradigm. We anticipate our essay to be a
starting point to experimentally address fundamental questions, such as the
role of life and consciousness in quantum mechanics.Comment: 9 pages, 4 figures, published versio
Symmetry Protection of Photonic Entanglement in the Interaction with a Single Nanoaperture
In this work, we experimentally show that quantum entanglement can be symmetry protected in the interaction with a single subwavelength plasmonic nanoaperture, with a total volume of V ∼ 0.2λ^3. In particular, we experimentally demonstrate that two-photon entanglement can be either completely preserved or completely lost after the interaction with the nanoaperture, solely depending on the relative phase between the quantum states. We achieve this effect by using specially engineered two-photon states to match the properties of the nanoaperture. In this way we can access a symmetry protected state, i.e., a state constrained by the geometry of the interaction to retain its entanglement. In spite of the small volume of interaction, we show that the symmetry protected entangled state retains its main properties. This connection between nanophotonics and quantum optics probes the fundamental limits of the phenomenon of quantum interference
Electromagnetic duality symmetry and helicity conservation for the macroscopic Maxwell's equations (previously "Experimental demonstration of electromagnetic duality symmetry breaking")
Modern physics is largely devoted to study conservation laws, such as charge,
energy, linear momentum or angular momentum, because they give us information
about the symmetries of our universe. Here, we propose to add the relationship
between electromagnetic duality and helicity to the toolkit. Generalized
electromagnetic duality symmetry, broken in the microscopic Maxwell's equations
by the empirical absence of magnetic charges, can be restored for the
macroscopic Maxwell's equations. The restoration of this symmetry is shown to
be independent of the geometry of the problem. These results provide a simple
and powerful tool for the study of light-matter interactions within the
framework of symmetries and conservation laws. We apply such framework to the
experimental investigation of helicity transformations in cylindrical
nanoapertures, and we find that the transformation is significantly enhanced by
the coupling to surface modes, where electromagnetic duality is strongly
broken.Comment: 26 pages, 4 figure
Tissue Localization and Extracellular Matrix Degradation by PI, PII and PIII Snake Venom Metalloproteinases: Clues on the Mechanisms of Venom-Induced Hemorrhage
20 páginas, 4 figuras, 3 tablas y 7 tablas en material suplementario.Snake venom hemorrhagic metalloproteinases (SVMPs) of the PI, PII and PIII classes were compared in terms of tissue localization and their ability to hydrolyze basement membrane components in vivo, as well as by a proteomics analysis of exudates collected in tissue injected with these enzymes. Immunohistochemical analyses of co-localization of these SVMPs with type IV collagen revealed that PII and PIII enzymes co-localized with type IV collagen in capillaries, arterioles and post-capillary venules to a higher extent than PI SVMP, which showed a more widespread distribution in the tissue. The patterns of hydrolysis by these three SVMPs of laminin, type VI collagen and nidogen in vivo greatly differ, whereas the three enzymes showed a similar pattern of degradation of type IV collagen, supporting the concept that hydrolysis of this component is critical for the destabilization of microvessel structure leading to hemorrhage. Proteomic analysis of wound exudate revealed similarities and differences between the action of the three SVMPs. Higher extent of proteolysis was observed for the PI enzyme regarding several extracellular matrix components and fibrinogen, whereas exudates from mice injected with PII and PIII SVMPs had higher amounts of some intracellular proteins. Our results provide novel clues for understanding the mechanisms by which SVMPs induce damage to the microvasculature and generate hemorrhage.This work was performed in partial fulfillment of the requirements for the PhD degree for Cristina Herrera at Universidad de Costa Rica.Peer reviewe
Rehabilitation and outcomes after complicated vs uncomplicated mild TBI:results from the CENTER-TBI study
Background: Despite existing guidelines for managing mild traumatic brain injury (mTBI), evidence-based treatments are still scarce and large-scale studies on the provision and impact of specific rehabilitation services are needed. This study aimed to describe the provision of rehabilitation to patients after complicated and uncomplicated mTBI and investigate factors associated with functional outcome, symptom burden, and TBI-specific health-related quality of life (HRQOL) up to six months after injury. Methods: Patients (n = 1379) with mTBI from the Collaborative European NeuroTrauma Effectiveness Research in TBI (CENTER-TBI) study who reported whether they received rehabilitation services during the first six months post-injury and who participated in outcome assessments were included. Functional outcome was measured with the Glasgow Outcome Scale – Extended (GOSE), symptom burden with the Rivermead Post Concussion Symptoms Questionnaire (RPQ), and HRQOL with the Quality of Life after Brain Injury – Overall Scale (QOLIBRI-OS). We examined whether transition of care (TOC) pathways, receiving rehabilitation services, sociodemographic (incl. geographic), premorbid, and injury-related factors were associated with outcomes using regression models. For easy comparison, we estimated ordinal regression models for all outcomes where the scores were classified based on quantiles. Results: Overall, 43% of patients with complicated and 20% with uncomplicated mTBI reported receiving rehabilitation services, primarily in physical and cognitive domains. Patients with complicated mTBI had lower functional level, higher symptom burden, and lower HRQOL compared to uncomplicated mTBI. Rehabilitation services at three or six months and a higher number of TOC were associated with unfavorable outcomes in all models, in addition to pre-morbid psychiatric problems. Being male and having more than 13 years of education was associated with more favorable outcomes. Sustaining major trauma was associated with unfavorable GOSE outcome, whereas living in Southern and Eastern European regions was associated with lower HRQOL. Conclusions: Patients with complicated mTBI reported more unfavorable outcomes and received rehabilitation services more frequently. Receiving rehabilitation services and higher number of care transitions were indicators of injury severity and associated with unfavorable outcomes. The findings should be interpreted carefully and validated in future studies as we applied a novel analytic approach. Trial registration: ClinicalTrials.gov NCT02210221.</p
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