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Results for "S. V. Jeffers"

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The effect of M dwarf starspot activity on low-mass planet detection thresholdsNov 04 2010In light of the growing interest in searching for low mass, rocky planets, we investigate the impact of starspots on radial velocity searches for earth-mass planets in orbit about M dwarf stars. Since new surveys targeting M dwarfs will likely be carried ... More
Magnetic activity on AB Doradus: Temporal evolution of starspots and differential rotation from 1988 to 1994Oct 09 2006Surface brightness maps for the young K0 dwarf AB Doradus are reconstructed from archival data sets for epochs spanning 1988 to 1994. By using the signal-to-noise enhancement technique of Least-Squares Deconvolution, our results show a greatly increased ... More
Variable magnetic field geometry of the young sun HN Peg (HD 206860)Oct 30 2014The large-scale magnetic field of solar-type stars reconstructed from their spectropolarimetric observations provide important insight into their underlying dynamo processes.We aim to investigate the temporal variability of the large-scale surface magnetic ... More
Fidelity for imperfect postselectionNov 26 2007We describe a simple measure of fidelity for mixed state postselecting devices. The measure is most appropriate for postselection where the task performed by the output is only effected by a specific state.
Hubble Space Telescope Observations of SV Cam: II. First Derivative Lightcurve Modelling using PHOENIX and ATLAS Model AtmospheresFeb 02 2006The variation of the specific intensity across the stellar disc is essential input parameter in surface brightness reconstruction techniques such as Doppler imaging, where the relative intensity contributions of different surface elements are important ... More
Direct Evidence for a Polar Spot on SV CamJan 31 2005We have used spectrophotometric data from the Hubble Space Telescope to eclipse-map the primary component of the RS CVn binary SV Cam over 9 HST orbits. We find from these observations and the HIPPARCOS parallax that the surface flux in the eclipsed low-latitude ... More
Imaging the circumstellar environment of the young T Tauri star SU AurigaeNov 19 2013The circumstellar environments of classical T Tauri stars are challenging to directly image because of their high star-to-disk contrast ratio. One method to overcome this is by using imaging polarimetry where scattered and consequently polarised starlight ... More
Data Reduction Techniques for High Contrast Imaging Polarimetry. Applications to ExPoMay 15 2011Imaging polarimetry is a powerful tool for detecting and characterizing exoplanets and circumstellar environments. Polarimetry allows a separation of the light coming from an unpolarized source such as a star and the polarized source such as a planet ... More
Constraining the Circumbinary Envelope of Z CMa via imaging polarimetryMay 16 2012Z CMa is a complex binary system, composed of a Herbig Be and an FU Ori star. The Herbig star is surrounded by a dust cocoon of variable geometry, and the whole system is surrounded by an infalling envelope. Previous spectropolarimetric observations have ... More
Hubble Space Telescope Observations of SV Cam: I. The Importance of Unresolved Starspot Distributions in Lightcurve FittingFeb 02 2006We have used maximum entropy eclipse mapping to recover images of the visual surface brightness distribution of the primary component of the RS CVn eclipsing binary SV Cam, using high-precision photometry data obtained during three primary eclipses with ... More
PolarBase: a data base of high resolution spectropolarimetric stellar observationsJan 06 2014Apr 22 2014PolarBase is an evolving data base that contains all stellar data collected with the ESPaDOnS and NARVAL high-resolution spectropolarimeters, in their reduced form, as soon as they become public. As of early 2014, observations of 2,000 stellar objects ... More
Substellar companions and isolated planetary mass objects from protostellar disc fragmentationOct 23 2003Self-gravitating protostellar discs are unstable to fragmentation if the gas can cool on a time scale that is short compared to the orbital period. We use a combination of hydrodynamic simulations and N-body orbit integrations to study the long term evolution ... More
Is it possible to detect planets around young active G and K dwarfs?Nov 14 2013Theoretical predictions suggest that the distribution of planets in very young stars could be very different to that typically observed in Gyr old systems that are the current focus of radial velocity surveys. However, the detection of planets around ... More
The color dependent morphology of the post-AGB star HD161796Mar 07 2013Context. Many protoplanetary nebulae show strong asymmetries in their surrounding shell, pointing to asymmetries during the mass loss phase. Questions concerning the origin and the onset of deviations from spherical symmetry are important for our understanding ... More
The Extreme Polarimeter: Design, Performance, First Results & UpgradesNov 27 2012Well over 700 exoplanets have been detected to date. Only a handful of these have been observed directly. Direct observation is extremely challenging due to the small separation and very large contrast involved. Imaging polarimetry offers a way to decrease ... More
Could a change in magnetic field geometry cause the break in the wind-activity relation?Sep 29 2015Wood et al suggested that mass-loss rate is a function of X-ray flux ($\dot{M} \propto F_x^{1.34}$) for dwarf stars with $F_x \lesssim F_{x,6} \equiv 10^6$ erg cm$^{-2}$ s$^{-1}$. However, more active stars do not obey this relation. These authors suggested ... More
Starspot distributions on fully convective M dwarfs: implications for radial velocity planet searchesSep 17 2015Since M4.5 - M9 dwarfs exhibit equatorial rotation velocities of order 10 km/s on average, radial velocity surveys targeting this stellar population will likely need to find methods to effectively remove starspot jitter. We present the first high resolution ... More
The evolution of surface magnetic fields in young solar-type stars I: the first 250 MyrJan 04 2016The surface rotation rates of young solar-type stars vary rapidly with age from the end of the pre-main sequence through the early main sequence. Important changes in the dynamos operating in these stars may result from this evolution, which should be ... More
Temporal variability of the wind from the star τ BoötisMar 30 2016We present new wind models for {\tau} Bo\"otis ({\tau} Boo), a hot-Jupiter-host-star whose observable magnetic cycles makes it a uniquely useful target for our goal of monitoring the temporal variability of stellar winds and their exoplanetary impacts. ... More
Recovering planet radial velocity signals in the presence of starspot activity in fully convective starsDec 03 2016Accounting for stellar activity is a crucial component of the search for ever-smaller planets orbiting stars of all spectral types. We use Doppler imaging methods to demonstrate that starspot induced radial velocity variability can be effectively reduced ... More
Chemical spots in the absence of magnetic field in the binary HgMn star 66 EridaniFeb 23 2011According to our current understanding, a subclass of the upper main sequence chemically peculiar stars, called mercury-manganese (HgMn), is non-magnetic. Nevertheless, chemical inhomogeneities were recently discovered on their surfaces. At the same time, ... More
The search for magnetic fields in mercury-manganese starsOct 19 2010We performed a highly sensitive search for magnetic fields on a large set of HgMn stars. With the aid of a new polarimeter attached to the HARPS spectrometer at the ESO 3.6m-telescope, we obtained high-quality circular polarization spectra of 41 single ... More
The Evolving Magnetic Topology of $τ$ BoötisApr 08 2016We present six epochs of spectropolarimetric observations of the hot-Jupiter-hosting star $\tau$ Bo\"otis that extend the exceptional previous multi-year data set of its large-scale magnetic field. Our results confirm that the large-scale magnetic field ... More
Are there tangled magnetic fields on HgMn stars?Apr 24 2013Several recent spectrophotometric studies failed to detect significant global magnetic fields in late-B HgMn chemically peculiar stars, but some investigations have suggested the presence of strong unstructured or tangled fields in these objects. We used ... More
Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712 I. Spectropolarimetric observations in all four Stokes parametersJun 05 2013High-resolution spectropolarimetric observations provide simultaneous information about stellar magnetic field topologies and three-dimensional distributions of chemical elements. Here we present analysis of a unique full Stokes vector spectropolarimetric ... More
Magnetically Controlled Accretion on the Classical T Tauri Stars GQ Lupi and TW HydraeJan 14 2013Jan 29 2013We present high spectral resolution ($R\approx108,000$) Stokes $V$ polarimetry of the Classical T Tauri stars (CTTSs) GQ Lup and TW Hya obtained with the polarimetric upgrade to the HARPS spectrometer on the ESO 3.6 m telescope. We present data on both ... More
Magnetism, chemical spots, and stratification in the HgMn star phi PhoenicisNov 25 2011Jan 27 2012Mercury-manganese (HgMn) stars have been considered as non-magnetic and non-variable chemically peculiar (CP) stars for a long time. However, recent discoveries of the variability in spectral line profiles have suggested an inhomogeneous surface distribution ... More
No magnetic field in the spotted HgMn star mu LeporisOct 04 2011Chemically peculiar stars of the mercury-manganese (HgMn) type represent a new class of spotted late-B stars, in which evolving surface chemical inhomogeneities are apparently unrelated to the presence of strong magnetic fields but are produced by some ... More
First detection of linear polarization in the line profiles of active cool starsMar 30 2011The application of high-resolution spectropolarimetry has led to major progress in understanding the magnetism and activity of late-type stars. During the last decade, magnetic fields have been discovered and mapped for many types of active cool stars ... More
ROPS: A New Search for Habitable Earths in the Southern SkyApr 27 2012May 04 2012We present the first results from our Red Optical Planet Survey (ROPS) to search for low mass planets orbiting late type dwarfs (M5.5V - M9V) in their habitable zones (HZ). Our observations, with the red arm of the MIKE spectrograph (0.5 - 0.9 microns) ... More
Precision radial velocities of 15 M5 - M9 dwarfsJan 21 2014Jan 23 2014We present radial velocity measurements of a sample of M5V-M9V stars from our Red-Optical Planet Survey, ROPS, operating at 0.65-1.025 micron. Radial velocities for 15 stars, with r.m.s. precision down to 2.5 m/s over a week long time scale are achieved ... More
A BCool survey of the magnetic fields of planet-hosting solar-type starsNov 23 2016We present a spectropolarimetric snapshot survey of solar-type planet hosting stars. In addition to 14 planet-hosting stars observed as part of the BCool magnetic snapshot survey, we obtained magnetic observations of a further 19 planet-hosting solar-type ... More
Multiple views of magnetism in cool starsAug 16 2012Magnetic fields are regarded as a crucial element for our understanding of stellar physics. They can be studied with a variety of methods which provide complementary - and sometimes contradictory - information about the structure, strength and dynamics ... More
Direct imaging of a massive dust cloud around R Coronae BorealisMar 06 2012We present recent polarimetric images of the highly variable star R CrB using ExPo and archival WFPC2 images from the HST. We observed R CrB during its current dramatic minimum where it decreased more than 9 mag due to the formation of an obscuring dust ... More
Surprising detection of an equatorial dust lane on the AGB star IRC+10216Dec 16 2014Understanding the formation of planetary nebulae remains elusive because in the preceding asymtotic giant branch (AGB) phase these stars are heavily enshrouded in an optically thick dusty envelope. To further understand the morphology of the circumstellar ... More
BP Piscium: its flaring disk imaged with SPHERE/ZIMPOLOct 20 2016Whether BP Piscium (BP Psc) is either a pre-main sequence T Tauri star at d ~ 80 pc, or a post-main sequence G giant at d ~ 300 pc is still not clear. As a first-ascent giant, it is the first to be observed with a molecular and dust disk. Alternatively, ... More
A solar-like magnetic cycle on the mature K-dwarf 61 Cyg A (HD 201091)Jun 03 2016The long-term monitoring of magnetic cycles in cool stars is a key diagnostic in understanding how dynamo generation and amplification of magnetic fields occur in stars similar in structure to the Sun. We investigate the temporal evolution of a possible ... More
J band Variability of M Dwarfs in the WFCAM Transit SurveyNov 22 2012Dec 07 2012We present an analysis of the photometric variability of M dwarfs in the WFCAM Transit Survey. Although periodic lightcurve variability in low mass stars is generally dominated by photospheric star spot activity, M dwarf variability in the J band has ... More
CARMENES input catalogue of M dwarfs II. High-resolution imaging with FastCamAug 29 2016Aims: We search for low-mass companions of M dwarfs and characterize their multiplicity fraction with the purpose of helping in the selection of the most appropriate targets for the CARMENES exoplanet survey. Methods: We obtained high-resolution images ... More
Spectroscopic characterisation of CARMENES target candidates from FEROS, CAFE and HRS high-resolution spectraJul 29 2016CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs) started a new planet survey on M-dwarfs in January this year. The new high-resolution spectrographs are operating in the visible ... More
The energy budget of stellar magnetic fields: comparing non-potential simulations and observationsOct 26 2016The magnetic geometry of the surface magnetic fields of more than 55 cool stars have now been mapped using spectropolarimetry. In order to better understand these observations, we compare the magnetic field topology at different surface scale sizes of ... More
A maximum entropy approach to detect close-in giant planets around active starsFeb 28 2015Oct 09 2015(shortened for arXiv) We aim to progress towards more efficient exoplanet detection around active stars by optimizing the use of Doppler Imaging in radial velocity measurements. We propose a simple method to simultaneously extract a brightness map and ... More
Magnetic field and wind of Kappa Ceti: towards the planetary habitability of the young Sun when life arose on EarthMar 12 2016We report magnetic field measurements for Kappa1~Cet, a proxy of the young Sun when life arose on Earth. We carry out an analysis of the magnetic properties determined from spectropolarimetric observations and reconstruct its large-scale surface magnetic ... More
CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOSFeb 26 2015Context. CARMENES is a stabilised, high-resolution, double-channel spectrograph at the 3.5 m Calar Alto telescope. It is optimally designed for radial-velocity surveys of M dwarfs with potentially habitable Earth-mass planets. Aims. We prepare a list ... More
Modelling the Hidden Magnetic Field of Low-Mass StarsJan 18 2014Zeeman-Doppler imaging is a spectropolarimetric technique that is used to map the large-scale surface magnetic fields of stars. These maps in turn are used to study the structure of the stars' coronae and winds. This method, however, misses any small-scale ... More
Experimental demonstration of quantum digital signatures using phase-encoded coherent states of lightJun 04 2013Digital signatures are frequently used in data transfer to prevent impersonation, repudiation and message tampering. Currently used classical digital signature schemes rely on public key encryption techniques, where the complexity of so-called "one-way" ... More
Experimental Implementation of a Quantum Optical State Comparison AmplifierApr 16 2014Quantum optical amplification that beats the noise addition limit for deterministic amplifiers has been realized experimentally using several different nondeterministic protocols. These schemes either require single-photon sources, or operate by noise ... More
The CARMENES search for exoplanets around M dwarfs - Photospheric parameters of target stars from high-resolution spectroscopyFeb 08 2018The new CARMENES instrument comprises two high-resolution and high-stability spectrographs that are used to search for habitable planets around M dwarfs in the visible and near-infrared regime via the Doppler technique. Characterising our target sample ... More
The energy budget of stellar magnetic fieldsAug 06 2015Spectropolarimetric observations have been used to map stellar magnetic fields, many of which display strong bands of azimuthal fields that are toroidal. A number of explanations have been proposed to explain how such fields might be generated though ... More
The connection between stellar activity cycles and magnetic field topologyOct 12 2016Zeeman Doppler imaging has successfully mapped the large-scale magnetic fields of stars over a large range of spectral types, rotation periods and ages. When observed over multiple epochs, some stars show polarity reversals in their global magnetic fields. ... More
Security against jamming and noise exclusion in imagingSep 09 2016We describe a protocol by which an imaging system could be protected against jamming by a malevolent party. Our protocol not only allows recognition of the jamming, but also allows for the recovery of the true image from the jammed one. We apply the method ... More
A Bcool magnetic snapshot survey of solar-type starsNov 14 2013Stellar magnetic field measurements obtained from spectropolarimetry offer key data for activity and dynamo studies, and we present the results of a major high-resolution spectropolarimetric Bcool project magnetic snapshot survey of 170 solar-type stars ... More
The CARMENES search for exoplanets around M dwarfs: Wing asymmetries of H$α$, Na I D, and He I linesJan 31 2018Stellar activity is ubiquitously encountered in M dwarfs and often characterised by the H$\alpha$ line. In the most active M dwarfs, H$\alpha$ is found in emission, sometimes with a complex line profile. Previous studies have reported extended wings and ... More
Radial velocity signatures of Zeeman broadeningJan 14 2013Stellar activity signatures such as spots and plage can significantly limit the search for extrasolar planets. Current models of activity-induced radial velocity (RV) signals focused on the impact of temperature contrast in spots predicting the signal ... More
Analysis of combined radial velocities and activity of BD+20 1790: evidence supporting the existence of a planetary companionFeb 18 2015This paper presents the simultaneous Bayesian analysis of the radial velocity and activity indices for the K5Ve active star BD+20 1790, that was proposed to host a close-in massive planet by Hern\'an-Obispo et al. (2010). The Bayesian analysis supports ... More
The effects of stellar winds on the magnetospheres and potential habitability of exoplanetsSep 03 2014Context: The principle definition of habitability for exoplanets is whether they can sustain liquid water on their surfaces, i.e. that they orbit within the habitable zone. However, the planet's magnetosphere should also be considered, since without it, ... More
Two planets around Kapteyn's star : a cold and a temperate super-Earth orbiting the nearest halo red-dwarfJun 03 2014Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this paper, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object ... More
CARMENES input catalogue of M dwarfs: III. Rotation and activity from high-resolution spectroscopic observationsFeb 06 2018CARMENES is a spectrograph for radial velocity surveys of M dwarfs with the aim of detecting Earth-mass planets orbiting in the habitable zones of their host stars. To ensure an optimal use of the CARMENES Guaranteed Time Observations, in this paper we ... More
Realization of Quantum Digital Signatures without the requirement of quantum memoryNov 22 2013May 14 2014Digital signatures are widely used to provide security for electronic communications, for example in financial transactions and electronic mail. Currently used classical digital signature schemes, however, only offer security relying on unproven computational ... More
No evidence for activity correlations in the radial velocities of Kapteyn's starJun 30 2015Stellar activity may induce Doppler variability at the level of a few m/s which can then be confused by the Doppler signal of an exoplanet orbiting the star. To first order, linear correlations between radial velocity measurements and activity indices ... More
Quantum nature of laser lightSep 15 2005All compositions of a mixed-state density operator are equivalent for the prediction of the probabilities of future outcomes of measurements. For retrodiction, however, this is not the case. The retrodictive formalism of quantum mechanics provides a criterion ... More
High-resolution spectropolarimetric of k Cet: A proxy for the young SunOct 28 2013Among the solar proxies studied in the Sun in Time k Cet (HD 20630) stands out as potentially having a mass very close to solar and a young age. On this study, we monitored the magnetic field and the chromospheric activity from the Ca II H & K lines of ... More
The Quantum Hilbert HotelJun 01 2015In 1924 David Hilbert conceived a paradoxical tale involving a hotel with an infinite number of rooms to illustrate some aspects of the mathematical notion of "infinity". In continuous-variable quantum mechanics we routinely make use of infinite state ... More
A terrestrial planet candidate in a temperate orbit around Proxima CentauriSep 12 2016At a distance of 1.295 parsecs, the red-dwarf Proxima Centauri ($\alpha$ Centauri C, GL 551, HIP 70890, or simply Proxima) is the Sun's closest stellar neighbor and one of the best studied low-mass stars. It has an effective temperature of only $\sim$ ... More
Quantum Optical State Comparison AmplifierNov 22 2013It is a fundamental principle of quantum theory that an unknown state cannot be copied or, as a consequence, an unknown optical signal cannot be amplified deterministically and perfectly. Here we describe a protocol that provides nondeterministic quantum ... More
Frictional quantum decoherenceJul 19 2007The dynamics associated with a measurement-based master equation for quantum Brownian motion are investigated. A scheme for obtaining time evolution from general initial conditions is derived. This is applied to analyze dissipation and decoherence in ... More
Stellar magnetism: empirical trends with age and rotationApr 10 2014We investigate how the observed large-scale surface magnetic fields of low-mass stars (~0.1 -- 2 Msun), reconstructed through Zeeman-Doppler imaging (ZDI), vary with age t, rotation and X-ray emission. Our sample consists of 104 magnetic maps of 73 stars, ... More
Atomic RetrodictionJul 04 2001Measurement of a quantum system provides information concerning the state in which it was prepared. In this paper we show how the retrodictive formalism can be used to evaluate the probability associated with any one of a given set of preparation events. ... More
Quantum retrodiction in open systemsAug 13 2002Quantum retrodiction involves finding the probabilities for various preparation events given a measurement event. This theory has been studied for some time but mainly as an interesting concept associated with time asymmetry in quantum mechanics. Recent ... More
On the mechanical properties of matter wavesJul 05 2004Electromagnetic waves and fluids have locally conserved mechanical properties associated with them and we may expect these to exist for matter waves. We present a semiclassical description of the continuity equations relating to these conserved properties ... More
Bayes' theorem and quantum retrodictionJun 25 2001We derive on the basis of Bayes' theorem a simple but general expression for the retrodicted premeasurement state associated with the result of any measurement. The retrodictive density operator is the normalised probability operator measure element associated ... More
Semiclassical theory of matter-wave detectionJun 11 2003We derive a semiclassical theory for the detection of matter-waves. This theory draws on the theories of semiclassical optical detection and fluid mechanics. We observe that the intrinsically dispersive nature of matter-waves is important in deriving ... More
Grassmann Phase Space Methods for Fermions. II. Field TheoryApr 12 2016Apr 19 2016In both quantum optics and cold atom physics, the behaviour of bosonic photons and atoms is often treated using phase space methods, where mode annihilation and creation operators are represented by c-number phase space variables, with the density operator ... More
Retrodiction as a tool for micromaser field measurementsJul 16 2002We use retrodictive quantum theory to describe cavity field measurements by successive atomic detections in the micromaser. We calculate the state of the micromaser cavity field prior to detection of sequences of atoms in either the excited or ground ... More
Retrodiction with two-level atoms: atomic previvalsJul 30 2002In the Jaynes-Cummings model a two-level atom interacts with a single-mode electromagnetic field. Quantum mechanics predicts collapses and revivals in the probability that a measurement will show the atom to be excited at various times after the initial ... More
Quantum theory of preparation and measurementJul 30 2002The conventional postulate for the probabilistic interpretation of quantum mechanics is asymmetric in preparation and measurement, making retrodiction reliant on inference by use of Bayes' theorem. Here, a more fundamental symmetric postulate is presented, ... More
Master Equation for Retrodiction of Quantum Communication SignalsJul 27 2001We derive the master equation that governs the evolution of the measured state backwards in time in an open system. This allows us to determine probabilities for a given set of preparation events from the results of subsequent measurements, which has ... More
Measuring NothingJul 12 2012Measurement is integral to quantum information processing and communication; it is how information encoded in the state of a system is transformed into classical signals for further use. In quantum optics, measurements are typically destructive, so that ... More
Gaia17biu/SN 2017egm in NGC 3191: The closest hydrogen-poor superluminous supernova to date is in a "normal", massive, metal-rich spiral galaxyAug 02 2017Dec 25 2017Hydrogen-poor superluminous supernovae (SLSNe-I) have been predominantly found in low-metallicity, star-forming dwarf galaxies. Here we identify Gaia17biu/SN 2017egm as an SLSN-I occurring in a "normal" spiral galaxy (NGC 3191) in terms of stellar mass ... More
Weak magnetic fields in Ap/Bp stars: Evidence for a dipole field lower limit and a tentative interpretation of the magnetic dichotomyOct 08 2007We have investigated a sample of 28 well-known spectroscopically-identified magnetic Ap/Bp stars, with weak, poorly-determined or previously undetected magnetic fields, with the aim of exploring the weak part of the magnetic field distribution of Ap/Bp ... More
Why are some A stars magnetic, while most are not?Dec 21 2007A small fraction of intermediate-mass main sequence (A and B type) stars have strong, organised magnetic fields. The large majority of such stars, however, show no evidence for magnetic fields, even when observed with very high precision. In this paper ... More
Grassmann Variables and the Jaynes-Cummings ModelMar 22 2012This paper shows that phase space methods using a positive P type distribution function involving both c-number variables (for the cavity mode) and Grassmann variables (for the two level atom) can be used to treat the Jaynes-Cummings model. Although it ... More
Quantum probability rule: a generalisation of the theorems of Gleason and BuschAug 05 2013Apr 16 2014Busch's theorem deriving the standard quantum probability rule can be regarded as a more general form of Gleason's theorem. Here we show that a further generalisation is possible by reducing the number of quantum postulates used by Busch. We do not assume ... More
Maximum Confidence Quantum MeasurementsApr 05 2006We consider the problem of discriminating between states of a specified set with maximum confidence. For a set of linearly independent states unambiguous discrimination is possible if we allow for the possibility of an inconclusive result. For linearly ... More
Measurement master equationFeb 17 2006We derive a master equation describing the evolution of a quantum system subjected to a sequence of observations. These measurements occur randomly at a given rate and can be of a very general form. As an example, we analyse the effects of these measurements ... More
Magnetic fields on young, moderately rotating Sun-like stars - I: HD~35296 and HD~29615Feb 20 2015Observations of the magnetic fields of young solar-type stars provide a way to investigate the signatures of their magnetic activity and dynamos. Spectropolarimetry enables the study of these stellar magnetic fields and was thus employed at the T\'{e}lescope ... More
A Bcool spectropolarimetric survey of over 150 solar-type starsOct 24 2013As part of the Bcool project, over 150 solar-type stars chosen mainly from planet search databases have been observed between 2006 and 2013 using the NARVAL and ESPaDOnS spectropolarimeters on the Telescope Bernard Lyot (Pic du Midi, France) and the Canada ... More
On role of symmetries in Kelvin wave turbulenceJul 19 2010E.V. Kozik and B.V. Svistunov (KS) paper "Symmetries and Interaction Coefficients of Kelvin waves", arXiv:1006.1789v1, [cond-mat.other] 9 Jun 2010, contains a comment on paper "Symmetries and Interaction coefficients of Kelvin waves", V. V. Lebedev and ... More
Retrodictive states and two-photon quantum imagingMar 17 2003We use retrodictive quantum theory to analyse two-photon quantum imaging systems. The formalism is particularly suitable for calculating conditional probability distributions.
Coherent absorption of N00N statesMar 14 2016Recent results in deeply subwavelength thickness films demonstrated coherent control and logical gate operations with both classical and single photon light sources. However, quantum processing and devices typically involve more than one photon and non-trivial ... More
Empirical Emission Functions for LPM Suppression of Photon Emission from Quark-Gluon PlasmaNov 06 2002The LPM suppression of photon emission rates from the quark gluon plasma have been studied at different physical conditions of the plasma given by temperature and chemical potentials.The integral equation for the transverse vector function (f(p_t)) consisting ... More
On the Variational method for LPM Suppression of Photon Emission from Quark-Gluon PlasmaAug 12 2002The photon emission rates from the quark gluon plasma have been studied considering LPM suppression effects. The integral equation for the transverse vector function (f(p)) that consists of multiple scattering effects has been solved using self-consistent ... More
Active and sterile neutrino oscillations inside the Sun in a phenomenological (3+1+2)-modelOct 22 2013Feb 13 2015A generalized model with three active and three sterile neutrinos is considered on the basis of the experimental data, which allow existence of anomalies beyond the minimally extended Standard Model with three active neutrinos with different masses. One ... More
Nonlinear tunneling of BEC in an optical lattice: signatures of quantum collapse and revivalJan 19 2008Quantum theory of the intraband resonant tunneling of a Bose-Einstein condensate loaded in a twodimensional optical lattice is considered. It is shown that the phenomena of quantum collapse and revival can be observed in the fully quantum problem. The ... More
Understanding fusion and its suppression for the $^{9}$Be projectile with different targetsFeb 28 2014The role of the breakup process and one neutron stripping on the near barrier fusion are investigated for the weakly bound projectile $^{9}$Be on $^{28}$Si, $^{89}$Y, $^{124}$Sn, $^{144}$Sm and $^{208}$Pb targets. Continuum-discretized coupled channels ... More
Anomalous Scaling in Kolmogorov--1941 TurbulenceNov 24 1994We show that the Kolmogorov-1941 picture of fully developed hydrodynamic turbulence (with the scaling of the structure functions $S_n(R) \propto R^{n/3}$) necessarily leads to an anomalous scaling for correlation functions which include the rate of energy ... More
Quantum switching at a mean-field instability of a Bose-Einstein condensate in an optical latticeOct 01 2008Jan 10 2009It is shown that bifurcations of the mean-field dynamics of a Bose-Einstein condensate can be related with the quantum phase transitions of the original many-body system. As an example we explore the intra-band tunneling in the two-dimensional optical ... More
Nonlinear intraband tunneling of BEC in a cubic three-dimensional latticeJan 19 2008The intra-band tunneling of a Bose-Einstein condensate between three degenerate high-symmetry X-points of the Brillouin zone of a cubic optical lattice is studied in the quantum regime by reduction to a three-mode model. The mean-field approximation of ... More
On quantization of weakly nonlinear lattices. Envelope solitonsMar 23 2001A way of quantizing weakly nonlinear lattices is proposed. It is based on introducing "pseudo-field" operators. In the new formalism quantum envelope solitons together with phonons are regarded as elementary quasi-particles making up boson gas. In the ... More
An Extended Approximation for the Lowest-lying States in Odd-mass NucleiDec 06 2010An enhanced model, based on the Extended Boson Approximation, for the lowest-lying states in odd-mass nuclei is presented. Our approach is built on the Quasiparticle Phonon Model, extending it to take into account the ground state correlations due to ... More