Results for "S. P. Walborn"

total 236988took 0.16s
Quantum communication without alignment using multiple-qubit single-photon statesMar 07 2007Mar 07 2007We propose a scheme for encoding logical qubits in a subspace protected against collective rotations around the propagation axis using the polarization and transverse spatial degrees of freedom of single photons. This encoding allows for quantum key distribution ... More
Generalized Hermite-Gauss decomposition of the two-photon state produced by spontaneous parametric down-conversionAug 21 2012We provide a general decomposition of the two-photon state produced by spontaneous parametric down-conversion in Hermite-Gaussian modes, in the case that the pump beam is described by a Hermite-Gaussian beam of any order. We show that the spatial correlations ... More
A Family of Continuous Variable Entanglement Criteria using General Entropy FunctionsMay 06 2010We derive a family of entanglement criteria for continuous variable systems based on the R\'enyi entropy of complementary distributions. We show that these entanglement witnesses can be more sensitive than those based on second-order moments, as well ... More
Four-dimensional Quantum Key Distribution using Position-Momentum and Polarization CorrelationsOct 12 2005We demonstrate experimentally that it is possible to prepare and detect photon pairs created by spontaneous parametric down-conversion which exhibit simultaneous position-momentum and polarization correlations that are adequate to implement a four-dimensional ... More
Experimental investigation of quantum key distribution with position and momentum of photon pairsNov 25 2004Jan 12 2005We investigate the utility of Einstein-Podolsky-Rosen correlations of the position and momentum of photon pairs from parametric down-conversion in the implementation of a secure quantum key distribution protocol. We show that security is guaranteed by ... More
Hyperentanglement-assisted Bell-state analysisJul 29 2003We propose a simple scheme for complete Bell-state measurement of photons using hyperentangled states - entangled in multiple degrees of freedom. In addition to hyperentanglement, our scheme requires only linear optics and single photon detectors, and ... More
Conservation and entanglement of Hermite-Gaussian modes in parametric down-conversionJul 27 2004Feb 22 2005We show that the transfer of the angular spectrum of the pump beam to the two-photon state in spontaneous parametric down-conversion enables the generation of entangled Hermite-Gaussian modes. We derive an analytical expression for the two-photon state ... More
Systematic Construction of Genuine Multipartite Entanglement Criteria using Uncertainty RelationsJul 27 2014Dec 04 2015A general procedure to construct criteria for identifying genuine multipartite continuous variable entanglement is presented. It relies on the proper definition of adequate global operators describing the multipartite system, the positive partial transpose ... More
Uncertainty relations for characteristic functionsMay 18 2015Oct 14 2015We present the uncertainty relation for the characteristic functions (ChUR) of the quantum mechanical position and momentum probability distributions. This inequality is more general than the Heisenberg Uncertainty Relation, and is saturated in two extremal ... More
Propagation of transverse intensity correlations of a two-photon stateFeb 10 2009The propagation of transverse spatial correlations of photon pairs through arbitrary first-order linear optical systems is studied experimentally and theoretically using the fractional Fourier transform. Highly-correlated photon pairs in an EPR-like state ... More
Quantum key distribution with higher-order alphabets using spatially-encoded quditsOct 12 2005Mar 10 2006We propose and demonstrate a quantum key distribution scheme in higher-order $d$-dimensional alphabets using spatial degrees of freedom of photons. Our implementation allows for the transmission of 4.56 bits per sifted photon, while providing improved ... More
Continuous variable quantum computation with spatial degrees of freedom of photonsJun 15 2011We discuss the use of the transverse spatial degrees of freedom of photons propagating in the paraxial approximation for continuous variable information processing. Given the wide variety of linear optical devices available, a diverse range of operations ... More
Spatial correlations in parametric down-conversionOct 06 2010The transverse spatial effects observed in photon pairs produced by parametric down-conversion provide a robust and fertile testing ground for studies of quantum mechanics, non-classical states of light, correlated imaging and quantum information. Over ... More
Observation of tunable Popescu-Rohrlich correlations through post-selection of a gaussian stateSep 16 2009We show that non-local Popescu-Rohrlich correlations can be observed in the post-selected results of binned position measurements on a two-party gaussian state. Our experiment is based on the spatial correlations of entangled photons and lens systems. ... More
Detection of transverse entanglement in phase spaceJun 18 2008Transverse entanglement between pairs of photons can be detected through intensity correlation measurements in the near and far fields. We show theoretically and experimentally that at intermediate zones, it is also possible to detect transverse entanglement ... More
Continuous discretization of infinite dimensional Hilbert spacesOct 16 2013In quantum theory, observables with a continuous spectrum are known to be fundamentally different from those with a discrete and finite spectrum. While some fundamental tests and applications of quantum mechanics originally formulated for discrete variables ... More
Experimental determination of multipartite entanglement with incomplete informationDec 07 2014Sep 25 2015Multipartite entanglement is very poorly understood despite all the theoretical and experimental advances of the last decades. Preparation, manipulation and identification of this resource is crucial for both practical and fundamental reasons. However, ... More
Quantum information processing in phase space: A modular variables approachDec 09 2015Sep 12 2016Binary quantum information can be fault tolerantly encoded in states defined in infinite dimensional Hilbert spaces. Such states define a computational basis, and permit a perfect equivalence between continuous and discrete universal operations. The drawback ... More
Distillation of quantum steeringJun 03 2019We show -- both theoretically and experimentally -- that Einstein-Podolsky-Rosen steering can be distilled. We present a distillation protocol that -- in the asymptotic infinite-copy limit -- outputs a perfect singlet assemblage even for inputs that are ... More
Experimental observation of spatial antibunching of photonsJun 06 2002We report an interference experiment that shows transverse spatial antibunching of photons. Using collinear parametric down-conversion in a Young-type fourth-order interference setup we show interference patterns that violate the classical Schwarz inequality ... More
Multimode Hong-Ou-Mandel interferenceDec 03 2002We consider multimode two-photon interference at a beam splitter by photons created by spontaneous parametric down-conversion. The resulting interference pattern is shown to depend upon the transverse spatial symmetry of the pump beam. In an experiment, ... More
Experimental Observation of Quantum Chaos in a Beam of LightJul 23 2012Mar 06 2014The manner in which unpredictable chaotic dynamics manifests itself in quantum mechanics is a key question in the field of quantum chaos. Indeed, very distinct quantum features can appear due to underlying classical nonlinear dynamics. Here we observe ... More
Production of optical phase space vortices with non-locally distributed mode convertersJan 14 2011Optical vortices have been observed in a wide variety of optical systems. They can be observed directly in the wavefront of optical beams, or in the correlations between pairs of entangled photons. We present a novel optical vortex which appears in a ... More
Optical Bell-state analysis in the coincidence basisDec 10 2002Many quantum information protocols require a Bell-state measurement of entangled systems. Most optical Bell-state measurements utilize two-photon interference at a beam splitter. By creating polarization-entangled photons with spontaneous parametric down-conversion ... More
Reliable Entanglement Detection Under Coarse--Grained MeasurementsOct 22 2012Jun 17 2013We derive reliable entanglement witnesses for coarse--grained measurements on continuous variable systems. These witnesses never return a "false positive" for identification of entanglement, under any degree of coarse graining. We show that, even in the ... More
Mutually Unbiased Coarse-Grained Measurements of Two or More Phase-Space VariablesApr 12 2018Mutual unbiasedness of the eigenstates of phase-space operators-such as position and momentum, or their standard coarse grained versions-exists only in the limiting case of infinite squeezing. In [Phys. Rev. Lett. 120, 040403 (2018)] it was shown that ... More
Observation of a Non-local Optical VortexFeb 10 2009Jul 24 2009We report the observation of an optical vortex in the correlations of photons produced from spontaneous parametric down-conversion. The singularity appears in a non-local coordinate plane consisting of one degree of freedom of each photon.
Experimental entanglement redistribution under decoherence channelsJul 15 2014When an initially entangled pair of qubits undergoes local decoherence processes, there are a number of ways in which the original entanglement can spread throughout the multipartite system consisting of the two qubits and their environments. Here we ... More
Quantum information with modular variablesJun 24 2014We introduce a novel strategy, based on the use of modular variables, to encode and deterministically process quantum information using states described by continuous variables. Our formalism leads to a general recipe to adapt existing quantum information ... More
An Entropic Einstein-Podolsky-Rosen CriterionJul 24 2009We propose an EPR inequality based on an entropic uncertainty relation for complementary continuous variable observables. This inequality is more sensitive than the previously established EPR inequality based on inferred variances, and opens up the possibility ... More
Multimode Hong-Ou-Mandel InterferometryDec 03 2004We review some recent experiments based upon multimode two-photon interference of photon pairs created by spontaneous parametric down-conversion. The new element provided by these experiments is the inclusion of the transverse spatial profiles of the ... More
Detecting entanglement of continuous variables with three mutually unbiased basesApr 25 2016An uncertainty relation is introduced for a symmetric arrangement of three mutually unbiased bases in continuous variable phase space, and then used to derive a bipartite entanglement criterion based on the variance of global operators composed of these ... More
Generation of a two-photon singlet beamMar 12 2005Controlling the pump beam transverse profile in multimode Hong-Ou-Mandel interference, we generate a ''localized" two-photon singlet state, in which both photons propagate in the same beam. This type of multi-photon singlet beam may useful in quantum ... More
Spatial antibunching of photons with parametric down-conversionJun 06 2002Sep 09 2002The theoretical framework behind a recent experiment by Nogueira et. al. [Phys. Rev. Lett. 86}, 4009 (2001)] of spatial antibunching in a two-photon state generated by collinear type II parametric down-conversion and a birefringent double-slit is presented. ... More
A double-slit quantum eraserJun 13 2001We report a quantum eraser experiment which actually uses a Young double-slit to create interference. The experiment can be considered an optical analogy of an experiment proposed by Scully, Englert and Walther. One photon of an entangled pair is incident ... More
Entanglement and conservation of orbital angular momentum in spontaneous parametric down-conversionMar 02 2005We show that the transfer of the plane wave spectrum of the pump beam to the fourth-order transverse spatial correlation function of the two-photon field generated by spontaneous parametric down-conversion leads to the conservation and entanglement of ... More
Quantum Non-Demolition Test of Bipartite ComplementarityFeb 08 2007We present a quantum circuit that implements a non-demolition measurement of complementary single- and bi-partite properties of a two-qubit system: entanglement and single-partite visibility and predictability. The system must be in a pure state with ... More
Transverse spatial and frequency properties of two-photon states generated by spontaneous parametric down-conversionJun 27 2008We present a detailed account of the two-photon states generated by SPDC in both type I and type II phase matching, including the effects of anisotropy of the nonlinear medium and the frequency spread of the down-converted fields. Accurate as well as ... More
Pismis 24-1: The Stellar Upper Mass Limit PreservedDec 01 2006Jan 22 2007Is there a stellar upper mass limit? Recent statistical work seems to indicate that there is and that it is in the vicinity of 150 solar masses. In this paper we use HST and ground-based data to investigate the brightest members of the cluster Pismis ... More
Entropic Entanglement Criteria for Continuous VariablesSep 01 2009We derive several entanglement criteria for bipartite continuous variable quantum systems based on the Shannon entropy. These criteria are more sensitive than those involving only second-order moments, and are equivalent to well-known variance product ... More
Quantum-Enhanced Sensing from Hyper-EntanglementSep 13 2017Hyperentanglement --- simultaneous entanglement between multiple degrees of freedom of two or more systems --- has been used to enhance quantum information tasks such as quantum communication and photonic quantum computing. Here we show that hyperentanglement ... More
Experimental Observation of Environment-induced Sudden Death of EntanglementJan 25 2007We demonstrate the difference between local, single-particle dynamics and global dynamics of entangled quantum systems coupled to independent environments. Using an all-optical experimental setup, we show that, while the environment-induced decay of each ... More
Experimental Observation of Quantum Correlations in Modular VariablesAug 30 2012We experimentally detect entanglement in modular position and momentum variables of photon pairs which have passed through $D$-slit apertures. We first employ an entanglement criteria recently proposed in [Phys. Rev. Lett. {\bf 106}, 210501 (2011)], using ... More
Detection of entanglement in asymmetric quantum networks and multipartite quantum steeringDec 24 2014Feb 14 2016The future of quantum communication relies on quantum networks composed by observers sharing multipartite quantum states. The certification of multipartite entanglement will be crucial to the usefulness of these networks. In many real situations it is ... More
Optimal Uncertainty Relations for Extremely Coarse-grained MeasurementsApr 21 2012We derive two quantum uncertainty relations for position and momentum coarse-grained measurements. Building on previous results, we first improve the lower bound for uncertainty relations using the Renyi entropy, particularly in the case of coarse-grained ... More
Heisenberg Uncertainty Relation for Coarse-grained ObservablesOct 06 2011We ask which is the best strategy to reveal uncertainty relations between comple- mentary observables of a continuous variable system for coarse-grained measurements. This leads to the derivation of new uncertainty relations for coarse-grained measurements ... More
Experimental multipartite entanglement and randomness certification of the W state in the quantum steering scenarioSep 01 2016Recently [Cavalcanti et al. Nat Commun 6, 7941 (2015)] proposed a method to certify the presence of entanglement in asymmetric networks, where some users do not have control over the measurements they are performing. Such asymmetry naturally emerges in ... More
Experimental investigation of the dynamics of entanglement: Sudden death, complementarity, and continuous monitoring of the environmentApr 29 2008Apr 30 2008We report on an experimental investigation of the dynamics of entanglement between a single qubit and its environment, as well as for pairs of qubits interacting independently with individual environments, using photons obtained from parametric down-conversion. ... More
Deterministic Quantum Computation With One Photonic QubitAug 05 2015We show that deterministic quantum computing with one qubit (DQC1) can be experimentally implemented with a spatial light modulator, using the polarization and the transverse spatial degrees of freedom of light. The scheme allows the computation of the ... More
Ancilla-assisted measurement of photonic spatial correlations and entanglementFeb 12 2014We report an experiment in which the moments of spatial coordinates of down-converted photons are measured directly, without having to reconstruct any marginal probability distributions. We use a spatial light modulator to couple the spatial degrees of ... More
Testing for entanglement with periodic imagesJun 03 2015For more than twenty years, the spatial entanglement of photon pairs have been used to uncover interesting aspects of quantum physics. A key advantage of spatial variables of single photons relates to the intrinsic high dimensionality of its state space, ... More
Testing for entanglement with periodic coarse-grainingJun 03 2015Feb 06 2018Continuous variables systems find valuable applications in quantum information processing. To deal with an infinite-dimensional Hilbert space, one in general has to handle large numbers of discretized measurements in tasks such as entanglement detection. ... More
Linear-optical simulation of the cooling of a cluster-state Hamiltonian systemJan 16 2014Mar 26 2014A measurement-based quantum computer could consist of a local-gapped Hamiltonian system, whose thermal states --at sufficiently low temperature-- are universal resources for the computation. Initialization of the computer would correspond to cooling the ... More
Characterization of a spatial light modulator as a polarization quantum channelMay 02 2014Spatial light modulators are versatile devices employed in a vast range of applications to modify the transverse phase or amplitude profile of an incident light beam. Most experiments are designed to use a specific polarization which renders optimal sensitivity ... More
General conditions for maximal violation of non-contextuality in discrete and continuous variablesDec 10 2015May 31 2016The contextuality of quantum mechanics, \textit{i.e.} the measurement outcome dependence upon previously made measurements, can be shown by the violation of inequalities based on measurements of well chosen observables. An important property of such observables ... More
The stellar upper mass limit in the solar neighborhoodFeb 20 2007We are using HST GO programs 10205, 10602, and 10898 to test the stellar upper mass limit in the solar vicinity by attempting to detect optical close companions, thus lowering the calculated evolutionary masses. We have observed with ACS/HRC all the known ... More
Flow of Quantum Correlations from a Two-Qubit System to its EnvironmentSep 25 2013The open-system dynamics of entanglement plays an important role in the assessment of the robustness of quantum information processes and also in the investigation of the classical limit of quantum mechanics. Here we show that, subjacent to this dynamics, ... More
General conditions for maximal violation of non-contextuality in discrete and continuous variablesDec 10 2015Mar 15 2017The contextuality of quantum mechanics, i.e. the measurement outcome dependence upon previously made measurements, can be shown by the violation of inequalities based on measurements of well chosen observables. An important property of such observables ... More
Experimental investigation of linear-optics-based quantum target detectionApr 12 2019The development of new techniques to improve measurements is crucial for all sciences. By employing quantum systems as sensors to probe some physical property of interest allows the application of quantum resources, such as coherent superpositions and ... More
Achieving metrological precision limits through post-selectionJun 10 2016Post-selection strategies have been proposed with the aim of amplifying weak signals, which may help to overcome detection thresholds associated with technical noise in high-precision measurements. Here we use an optical setup to experimentally explore ... More
Non-Markovianity through flow of information between a system and an environmentOct 09 2014Nov 24 2014Exchange of information between a quantum system and its surrounding environment plays a fundamental role in the study of the dynamics of open quantum systems. Here we discuss the role of the information exchange in the non-Markovian behavior of dynamical ... More
Klyshko's Advanced-Wave Picture in Stimulated Parametric Down-Conversion with a Spatially Structured Pump BeamMay 16 2018Aug 12 2018The advanced-wave picture is "... an intuitive treatment of two-photon correlation with the help of the concept of an effective field acting upon one of the two detectors and formed by parametric conversion of the advanced wave emitted by the second detector ... More
Photonic polarization gears for ultra-sensitive angular measurementsJun 07 2013Sep 26 2013Quantum metrology bears a great promise in enhancing measurement precision, but is unlikely to become practical in the near future. Its concepts can nevertheless inspire classical or hybrid methods of immediate value. Here, we demonstrate NOON-like photonic ... More
Non-Markovianity through accessible informationFeb 21 2014Jun 04 2014The degree of non-Markovianity of quantum processes has been characterized in several different ways in the recent literature. However, the relationship between the non-Markovian behavior and the flow of information between the system and the environment ... More
Compact star clusters of the LMC HII region N11CJul 27 2000Based on imaging and spectroscopy obtained at the ESO NTT telescope and using an efficient image analysis algorithm, we study the core of the LMC OB association LH13, particularly the two compact stellar clusters Sk-6641 and HNT in the HII, region N11C. ... More
Experimental investigation of dynamical invariants in bipartite entanglementMar 09 2011The non-conservation of entanglement, when two or more particles interact, sets it apart from other dynamical quantities like energy and momentum. It does not allow the interpretation of the subtle dynamics of entanglement as a flow of this quantity between ... More
The Correlation between X-Ray Line Ionization and Optical Spectral Types of the OB StarsJul 27 2009Marked correlations are reported between the ionization of the X-ray line spectra of normal OB stars, as observed by the Chandra X-Ray Observatory, and their optical spectral types. These correlations include the progressive weakening of the higher ionization ... More
High-resolution X-ray spectroscopy of the magnetic Of?p star HD148937Nov 30 2011High-resolution data of the peculiar magnetic massive star HD148937 were obtained with Chandra-HETGS, and are presented here in combination with a re-analysis of the older XMM-RGS data. The lines of the high-Z elements (Mg, Si, S) were found to be unshifted ... More
The VLT-FLAMES Tarantula Survey XVI. The optical+NIR extinction laws in 30 Doradus and the photometric determination of the effective temperatures of OB starsFeb 13 2014Mar 01 2014Context: The commonly used extinction laws of Cardelli et al. (1989) have limitations that, among other issues, hamper the determination of the effective temperatures of O and early B stars from optical+NIR photometry. Aims: We aim to develop a new family ... More
Emergence of the pointer basis through the dynamics of correlationsMar 22 2012Oct 04 2012We use the classical correlation between a quantum system being measured and its measurement apparatus to analyze the amount of information being retrieved in a quantum measurement process. Accounting for decoherence of the apparatus, we show that these ... More
The spectral variability and magnetic field characteristics of the Of?p star HD 148937Aug 24 2011Sep 24 2011We report magnetic and spectroscopic observations and modeling of the Of?p star HD 148937 within the context of the MiMeS LP at the CFHT. Thirty-two high signal-to-noise ratio circularly polarised (Stokes V) spectra and 13 unpolarised (Stokes I) spectra ... More
IMF biases and how to correct themJun 13 2005We discuss possible sources of biases in the determination of the initial mass function (IMF) introduced by the binning of the data, the uncertainty in the determinations of masses, and the existence of unresolved multiple systems. Those three effects ... More
Global X-ray properties of the O and B stars in CarinaMar 01 2011The key empirical property of the X-ray emission from O stars is a strong correlation between the bolometric and X-ray luminosities. In the framework of the Chandra Carina Complex Project, 129 O and B stars have been detected as X-ray sources; 78 of those, ... More
Extreme resonance line profile variations in the ultraviolet spectra of NGC 1624-2: probing the giant magnetosphere of the most strongly magnetized known O-type starNov 25 2018In this paper, we present high-resolution HST/COS observations of the extreme magnetic O star NGC 1624-2. These represent the first ultraviolet spectra of this archetypal object. We examine the variability of its wind-sensitive resonance lines, comparing ... More
Quantum Erasure: Quantum Interference RevisitedMar 07 2005Recent experiments in quantum optics have shed light on the foundations of quantum physics. Quantum erasers - modified quantum interference experiments - show that quantum entanglement is responsible for the complementarity principle.
Quantum Information Processing by Weaving Quantum Talbot CarpetsDec 08 2014Single photon interference due to passage through a periodic grating is considered in a novel proposal for processing D-dimensional quantum systems (quDits) encoded in the spatial degrees of freedom of light. We show that free space propagation naturally ... More
Complete experimental toolbox for alignment-free quantum communicationMar 29 2012Quantum communication employs the counter-intuitive features of quantum physics to perform tasks that are im- possible in the classical world. It is crucial for testing the foundations of quantum theory and promises to rev- olutionize our information ... More
EPR Steering Inequalities from Entropic Uncertainty RelationsMar 29 2013We use entropic uncertainty relations to formulate inequalities that witness Einstein-Podolsky-Rosen (EPR) steering correlations in diverse quantum systems. We then use these inequalities to formulate symmetric EPR-steering inequalities using the mutual ... More
Entanglement breaking channels and entanglement sudden deathFeb 23 2016The occurrence of entanglement sudden death in the evolution of a bipartite system depends on both the initial state and the channel responsible for the evolution. An extreme case is that of entanglement braking channels, which are channels that acting ... More
On the presence and absence of disks around O-type starsSep 04 2009(abridged) As the favoured progenitors of long-duration gamma-ray bursts, massive stars may represent our best signposts of individual objects in the early Universe, but special conditions seem required to make these bursters, which might originate from ... More
One-sided Device-Independent Quantum Key Distribution: Security, feasibility, and the connection with steeringSep 07 2011Jan 23 2012We analyze the security and feasibility of a protocol for Quantum Key Distribution (QKD), in a context where only one of the two parties trusts his measurement apparatus. This scenario lies naturally between standard QKD, where both parties trust their ... More
Free-Space Entangled Quantum CarpetsFeb 23 2017The Talbot effect in quantum physics is known to produce intricate patterns in the probability distribution of a particle, known as "quantum carpets", corresponding to the revival and replication of the initial wave function. Recently, it was shown that ... More
Properties of Galactic B supergiantsJun 29 2006Physical and wind properties of Galactic B supergiants are presented based upon non-LTE line blanketed model atmospheres, including Sher 25 toward the NGC 3603 cluster. We compare Halpha derived wind densities with recent results for SMC B supergiants ... More
The ultraviolet and optical spectra of luminous B-type stars in the Small Magellanic CloudSep 16 2004We present ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) of 12 early B-type stars in the Small Magellanic Cloud (SMC), comprising 9 supergiants and 3 giants. A morphological comparison with Galactic analogues is made using archival ... More
The VLT-FLAMES Tarantula survey XX. The nature of the X-ray bright emission line star VFTS 399Mar 03 2015The stellar population of the 30 Doradus star-forming region in the Large Magellanic Cloud contains a subset of apparently single, rapidly rotating O-type stars. The physical processes leading to the formation of this cohort are currently uncertain. One ... More
The VLT-FLAMES Tarantula Survey XVIII. Classifications and radial velocities of the B-type starsJan 16 2015We present spectral classifications for 438 B-type stars observed as part of the VLT-FLAMES Tarantula Survey (VFTS) in the 30 Doradus region of the Large Magellanic Cloud. Radial velocities are provided for 307 apparently single stars, and for 99 targets ... More
The VLT-FLAMES Tarantula Survey XIX. B-type Supergiants - Atmospheric parameters and nitrogen abundances to investigate the role of binarity and the width of the main sequenceDec 08 2014Jan 12 2015TLUSTY non-LTE model atmosphere calculations have been used to determine atmospheric parameters and nitrogen (N) abundances for 34 single and 18 binary B-type supergiants (BSGs). The effects of flux contribution from an unseen secondary were considered ... More
The VLT-FLAMES Tarantula Survey VIII. Multiplicity properties of the O-type star populationSep 20 2012Aims. We analyze the multiplicity properties of the massive O-type star population. With 360 O-type stars, this is the largest homogeneous sample of massive stars analyzed to date. Methods. We use multi-epoch spectroscopy and variability analysis to identify ... More
Multiwavelength Systematics of OB SpectraOct 27 2006The systematics of OB spectra are reviewed in the optical domain, dominated by photospheric lines, and in the far ultraviolet (both IUE and FUSE ranges), in which the stellar-wind profiles dominate. First, the two-dimensional (temperature, luminosity) ... More
HST astrometry in the 30 Doradus region: II. Runaway stars from new proper motions in the Large Magellanic CloudApr 23 2018We present a catalog of relative proper motions for 368,787 stars in the 30 Doradus region of the Large Magellanic Cloud (LMC), based on a dedicated two-epoch survey with the Hubble Space Telescope (HST) and supplemented with proper motions from our pilot ... More
The VLT-FLAMES Tarantula Survey XXV. Surface nitrogen abundances of O-type giants and supergiantsSep 01 2016Theoretically, rotation-induced chemical mixing in massive stars has far reaching evolutionary consequences, affecting the sequence of morphological phases, lifetimes, nucleosynthesis, and supernova characteristics. Using a sample of 72 presumably single ... More
Morphogical Characteristics of OB Spectra and EnvironmentsDec 02 2010Following a brief exposition of the morphological process, two examples of its application in contemporary astronomy are presented. The first comprises a major digital, blue-violet spectral classification program on Galactic O stars, that has already ... More
Optically observable zero-age main-sequence O starsJan 19 2007Feb 15 2007A list of 50 optically observable O stars that are likely on or very near the ZAMS is presented. They have been selected on the basis of five distinct criteria, although some of them exhibit more than one. Three of the criteria are spectroscopic (He II ... More
Direct measurement of the biphoton Wigner function through two-photon interferenceApr 26 2013Sep 26 2013The Hong-Ou-Mandel (HOM) experiment was a benchmark in quantum optics, evidencing the quantum nature of the photon. In order to go deeper, and obtain the complete information about the quantum state of a system, for instance, composed by photons, the ... More
Spectroscopic Classification of 42 LMC OB Stars: Selection of Probes for the Hot Gaseous Halo of the LMCMay 31 2001Interstellar C IV absorption line studies of the hot gaseous halo of the Large Magellanic Cloud (LMC) have been hindered by non-ideal selections of early-type probe stars in regions where C+3 can be produced locally via photoionization, fast stellar winds, ... More
Optical simulation of the free Dirac equationFeb 11 2019We present a classical optics simulation of the one-dimensional Dirac equation for a free particle. Positive and negative energy components are represented by orthogonal polarizations of a free propagating beam, while the spatial profile represents the ... More
Surface abundances of ON starsApr 23 2015Massive stars burn hydrogen through the CNO cycle during most of their evolution. When mixing is efficient, or when mass transfer in binary systems happens, chemically processed material is observed at the surface of O and B stars. ON stars show stronger ... More
Spectral Classification of O2-3.5If*/WN5-7 starsMay 24 2011An updated classification scheme for transition O2-3.5If*/WN5-7 stars is presented, following recent revisions to the spectral classifications for O and WN stars. We propose that O2-3.5If*, O2-3.5If*/WN5-7 and WN5-7 stars may be discriminated using the ... More