51 research outputs found
Multiphoton Discrete Fractional Fourier Dynamics in Waveguide Beam Splitters
We demonstrate that when a waveguide beam splitter (BS) is excited by N
indistinguishable photons, the arising multiphoton states evolve in a way as if
they were coupled to each other with coupling strengths that are identical to
the ones exhibited by a discrete fractional Fourier system. Based on the
properties of the discrete fractional Fourier transform, we then derive a
multiphoton suppression law for 50/50 BSs, thereby generalizing the
Hong-Ou-Mandel effect. Furthermore, we examine the possibility of performing
simultaneous multiphoton quantum random walks by using a single waveguide BS in
combination with photon number resolving detectors. We anticipate that the
multiphoton lattice-like structures unveiled in this work will be useful to
identify new effects and applications of high-dimensional multiphoton states.Comment: Accepted for publication in JOSA B on June 26, 201
Identification of Light Sources using Machine Learning
The identification of light sources represents a task of utmost importance
for the development of multiple photonic technologies. Over the last decades,
the identification of light sources as diverse as sunlight, laser radiation and
molecule fluorescence has relied on the collection of photon statistics or the
implementation of quantum state tomography. In general, this task requires an
extensive number of measurements to unveil the characteristic statistical
fluctuations and correlation properties of light, particularly in the
low-photon flux regime. In this article, we exploit the self-learning features
of artificial neural networks and naive Bayes classifier to dramatically reduce
the number of measurements required to discriminate thermal light from coherent
light at the single-photon level. We demonstrate robust light identification
with tens of measurements at mean photon numbers below one. Our work
demonstrates an improvement in terms of the number of measurements of several
orders of magnitude with respect to conventional schemes for characterization
of light sources. Our work has important implications for multiple photonic
technologies such as LIDAR and microscopy.Comment: 8 pages, 10 figure
Observation of the modification of quantum statistics of plasmonic systems
For almost two decades, researchers have observed the preservation of the quantum statistical properties of bosons in a large variety of plasmonic systems. In addition, the possibility of preserving nonclassical correlations in light-matter interactions mediated by scattering among photons and plasmons stimulated the idea of the conservation of quantum statistics in plasmonic systems. It has also been assumed that similar dynamics underlie the conservation of the quantum fluctuations that define the nature of light sources. So far, plasmonic experiments have been performed in nanoscale systems in which complex multiparticle interactions are restrained. Here, we demonstrate that the quantum statistics of multiparticle systems are not always preserved in plasmonic platforms and report the observation of their modification. Moreover, we show that optical near fields provide additional scattering paths that can induce complex multiparticle interactions. Remarkably, the resulting multiparticle dynamics can, in turn, lead to the modification of the excitation mode of plasmonic systems. These observations are validated through the quantum theory of optical coherence for single- and multi-mode plasmonic systems. Our findings unveil the possibility of using multiparticle scattering to perform exquisite control of quantum plasmonic systems
Multiphoton Quantum-State Engineering using Conditional Measurements
The quantum theory of electromagnetic radiation predicts characteristic
statistical fluctuations for light sources as diverse as sunlight, laser
radiation and molecule fluorescence. Indeed, these underlying statistical
fluctuations of light are associated with the fundamental physical processes
behind their generation. In this contribution, we demonstrate that the
manipulation of the quantum electromagnetic fluctuations of a pair of vacuum
states leads to a novel family of quantum-correlated multiphoton states with
tunable mean photon numbers and degree of correlation. Our technique relies on
the use of conditional measurements to engineer the excitation mode of the
field through the simultaneous subtraction of photons from two-mode squeezed
vacuum states. The experimental generation of multiphoton states with quantum
correlations by means of photon subtraction unveils novel mechanisms to control
fundamental properties of light. As a remarkable example, we demonstrate the
engineering of a quantum correlated state of light, with nearly Poissonian
photon statistics, that constitutes the first step towards the generation of
entangled lasers. Our technique enables a robust protocol to prepare quantum
states with multiple photons in high-dimensional spaces and, as such, it
constitutes a novel platform for exploring quantum phenomena in mesoscopic
systems
Hyperoxemia and excess oxygen use in early acute respiratory distress syndrome : Insights from the LUNG SAFE study
Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Concerns exist regarding the prevalence and impact of unnecessary oxygen use in patients with acute respiratory distress syndrome (ARDS). We examined this issue in patients with ARDS enrolled in the Large observational study to UNderstand the Global impact of Severe Acute respiratory FailurE (LUNG SAFE) study. Methods: In this secondary analysis of the LUNG SAFE study, we wished to determine the prevalence and the outcomes associated with hyperoxemia on day 1, sustained hyperoxemia, and excessive oxygen use in patients with early ARDS. Patients who fulfilled criteria of ARDS on day 1 and day 2 of acute hypoxemic respiratory failure were categorized based on the presence of hyperoxemia (PaO2 > 100 mmHg) on day 1, sustained (i.e., present on day 1 and day 2) hyperoxemia, or excessive oxygen use (FIO2 ≥ 0.60 during hyperoxemia). Results: Of 2005 patients that met the inclusion criteria, 131 (6.5%) were hypoxemic (PaO2 < 55 mmHg), 607 (30%) had hyperoxemia on day 1, and 250 (12%) had sustained hyperoxemia. Excess FIO2 use occurred in 400 (66%) out of 607 patients with hyperoxemia. Excess FIO2 use decreased from day 1 to day 2 of ARDS, with most hyperoxemic patients on day 2 receiving relatively low FIO2. Multivariate analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FIO2 use and adverse clinical outcomes. Mortality was 42% in patients with excess FIO2 use, compared to 39% in a propensity-matched sample of normoxemic (PaO2 55-100 mmHg) patients (P = 0.47). Conclusions: Hyperoxemia and excess oxygen use are both prevalent in early ARDS but are most often non-sustained. No relationship was found between hyperoxemia or excessive oxygen use and patient outcome in this cohort. Trial registration: LUNG-SAFE is registered with ClinicalTrials.gov, NCT02010073publishersversionPeer reviewe
Importance of excitation and trapping conditions in photosynthetic environment-assisted energy transport
It has been argued that excitonic energy transport in photosynthetic complexes is efficient because of a balance between coherent evolution and decoherence, a phenomenon called environment-assisted quantum transport (ENAQT). Studies of ENAQT have usually assumed that the excitation is initially localized on a particular chromophore, and that it is transferred to a reaction center through a similarly localized trap. However, these assumptions are not physically accurate. We show that more realistic models of excitation and trapping can lead to very different predictions about the importance of ENAQT. In particular, although ENAQT is a robust effect if one assumes a localized trap, its effect can be negligible if the trapping is more accurately modeled as Förster transfer to a reaction center. Our results call into question the suggested role of ENAQT in the photosynthetic process of green sulfur bacteria and highlight the subtleties associated with drawing lessons for designing biomimetic light-harvesting complexes
Identification of particle mixtures using machine-learning-assisted laser diffraction analysis
We demonstrate a smart laser-diffraction analysis technique for particle
mixture identification. We retrieve information about the size, geometry, and
ratio concentration of two-component heterogeneous particle mixtures with an
efficiency above 92%. In contrast to commonly-used laser diffraction schemes --
in which a large number of detectors is needed -- our machine-learning-assisted
protocol makes use of a single far-field diffraction pattern, contained within
a small angle () around the light propagation axis. Because
of its reliability and ease of implementation, our work may pave the way
towards the development of novel smart identification technologies for sample
classification and particle contamination monitoring in industrial
manufacturing processes.Comment: 7 pages, 4 figure
Multiphoton Hong-Ou-Mandel Interferometry with Entangled Photon-Subtracted States
We demonstrate generation of entangled photon-subtracted states and manipulation of their quantum fluctuations. The flexibility of our technique allows us to explore Hong-Ou-Mandel interferometry with mesoscopic states that resemble systems of entangled lasers
Immunocompromised patients with acute respiratory distress syndrome: Secondary analysis of the LUNG SAFE database
Background: The aim of this study was to describe data on epidemiology, ventilatory management, and outcome of acute respiratory distress syndrome (ARDS) in immunocompromised patients. Methods: We performed a post hoc analysis on the cohort of immunocompromised patients enrolled in the Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE) study. The LUNG SAFE study was an international, prospective study including hypoxemic patients in 459 ICUs from 50 countries across 5 continents. Results: Of 2813 patients with ARDS, 584 (20.8%) were immunocompromised, 38.9% of whom had an unspecified cause. Pneumonia, nonpulmonary sepsis, and noncardiogenic shock were their most common risk factors for ARDS. Hospital mortality was higher in immunocompromised than in immunocompetent patients (52.4% vs 36.2%; p < 0.0001), despite similar severity of ARDS. Decisions regarding limiting life-sustaining measures were significantly more frequent in immunocompromised patients (27.1% vs 18.6%; p < 0.0001). Use of noninvasive ventilation (NIV) as first-line treatment was higher in immunocompromised patients (20.9% vs 15.9%; p = 0.0048), and immunodeficiency remained independently associated with the use of NIV after adjustment for confounders. Forty-eight percent of the patients treated with NIV were intubated, and their mortality was not different from that of the patients invasively ventilated ab initio. Conclusions: Immunosuppression is frequent in patients with ARDS, and infections are the main risk factors for ARDS in these immunocompromised patients. Their management differs from that of immunocompetent patients, particularly the greater use of NIV as first-line ventilation strategy. Compared with immunocompetent subjects, they have higher mortality regardless of ARDS severity as well as a higher frequency of limitation of life-sustaining measures. Nonetheless, nearly half of these patients survive to hospital discharge. Trial registration: ClinicalTrials.gov, NCT02010073. Registered on 12 December 2013
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