Results for "J. Whittaker"

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Automated Analysis, Reporting, and Archiving for Robotic Nondestructive Assay of Holdup DepositsJan 29 2019To decommission deactivated gaseous diffusion enrichment facilities, miles of contaminated pipe must be measured. The current method requires thousands of manual measurements, repeated manual data transcription, and months of manual analysis. The Pipe ... More
Steady states of a chi-three parametric oscillator with coupled polarisationsJun 11 2003Polarisation effects in the microcavity parametric oscillator are studied using a simple model in which two chi-three optical parametric oscillators are coupled together. It is found that there are, in general, a number of steady states of the model under ... More
3D visualizations of nano-scale phase separation and ultrafast dynamic correlation between phases in (Na0.32K0.68)0.95Fe1.75Se2Mar 14 2019Phase separation of metallic and antiferromagnetic (AFM) insulating phases in alkaline iron selenides (AxFe2-ySe2) continues to attract intense interest because the relationship between two peculiar features probably is a key to clarifying the pairing ... More
Improvising Linguistic Style: Social and Affective Bases for Agent PersonalityFeb 26 1997This paper introduces Linguistic Style Improvisation, a theory and set of algorithms for improvisation of spoken utterances by artificial agents, with applications to interactive story and dialogue systems. We argue that linguistic style is a key aspect ... More
Functorial properties of Putnam's homology theory for Smale spacesJul 11 2014Jun 30 2016We investigate functorial properties of Putnam's homology theory for Smale spaces. Our analysis shows that the addition of a conjugacy condition is necessary to ensure functoriality. Several examples are discussed that elucidate the need for our additional ... More
Wieler solenoids, Cuntz-Pimsner algebras and K-theoryJun 17 2016We study irreducible Smale spaces with totally disconnected stable sets and their associated $K$-theoretic invariants. Such Smale spaces arise as Wieler solenoids, and we restrict to those arising from open surjections. The paper follows three converging ... More
Dynamical correspondences for Smale spacesMay 20 2015Aug 09 2015We initiate the study of correspondences for Smale spaces. Correspondences are shown to provide a notion of a generalized morphism between Smale spaces and are a special case of finite equivalences. Furthermore, for shifts of finite type, a correspondence ... More
A Robot for Nondestructive Assay of Holdup Deposits in Gaseous Diffusion PipingJan 29 2019Miles of contaminated pipe must be measured, foot by foot, as part of the decommissioning effort at deactivated gaseous diffusion enrichment facilities. The current method requires cutting away asbestos-lined thermal enclosures and performing repeated, ... More
A frequency and sensitivity tunable microresonator array for high-speed quantum processor readoutSep 18 2015Apr 22 2016Superconducting microresonators have been successfully utilized as detection elements for a wide variety of applications. With multiplexing factors exceeding 1,000 detectors per transmission line, they are the most scalable low-temperature detector technology ... More
The Hilbert transform: Applications to atomic spectraNov 24 2014Feb 05 2015In many areas of physics, the Kramers-Kronig (KK) relations are used to extract information about the real part of the optical response of a medium from its imaginary counterpart. In this paper we discuss an alternative but mathematically equivalent approach ... More
Optical response of gas-phase atoms at less than $λ/80$ from a dielectric surfaceMar 12 2014We present experimental observations of atom-light interactions within tens of nanometers (down to 11~nm) of a sapphire surface. Using photon counting we detect the fluorescence from of order one thousand Rb or Cs atoms, confined in a vapor with thickness ... More
Spectroscopic detection of atom-surface interactions in an atomic vapour layer with nanoscale thicknessMay 26 2015We measure the resonance line shape of atomic vapor layers with nanoscale thickness confined between two sapphire windows. The measurement is performed by scanning a probe laser through resonance and collecting the scattered light. The line shape is dominated ... More
Mixed Initiative in Dialogue: An Investigation into Discourse SegmentationApr 05 1995Conversation between two people is usually of mixed-initiative, with control over the conversation being transferred from one person to another. We apply a set of rules for the transfer of control to 4 sets of dialogues consisting of a total of 1862 turns. ... More
Circuit cavity electromechanics in the strong coupling regimeNov 12 2010Demonstrating and exploiting the quantum nature of larger, more macroscopic mechanical objects would help us to directly investigate the limitations of quantum-based measurements and quantum information protocols, as well as test long standing questions ... More
C*-algebras of tilings with infinite rotational symmetryOct 11 2010A tiling with infinite rotational symmetry, such as the Conway-Radin Pinwheel Tiling, gives rise to a topological dynamical system to which an \'etale equivalence relation is associated. A groupoid C*-algebra for a tiling is produced and a separating ... More
Molecular dynamics of open systems: construction of a mean-field particle reservoirFeb 19 2019The simulation of open molecular systems requires explicit or implicit reservoirs of energy and particles. Whereas full atomistic resolution is desired in the region of interest, there is some freedom in the implementation of the reservoirs. Here, we ... More
Cues and control in Expert-Client DialoguesApr 05 1995We conducted an empirical analysis into the relation between control and discourse structure. We applied control criteria to four dialogues and identified 3 levels of discourse structure. We investigated the mechanism for changing control between these ... More
Spectral triples for hyperbolic dynamical systemsNov 15 2010Aug 31 2013Spectral triples are defined for C*-algebras associated with hyperbolic dynamical systems known as Smale spaces. The spectral dimension of one of these spectral triples is shown to recover the topological entropy of the Smale space.
Sideband Cooling Micromechanical Motion to the Quantum Ground StateMar 10 2011The advent of laser cooling techniques revolutionized the study of many atomic-scale systems. This has fueled progress towards quantum computers by preparing trapped ions in their motional ground state, and generating new states of matter by achieving ... More
Architectural considerations in the design of a superconducting quantum annealing processorJan 21 2014We have developed a quantum annealing processor, based on an array of tunably coupled rf-SQUID flux qubits, fabricated in a superconducting integrated circuit process [1]. Implementing this type of processor at a scale of 512 qubits and 1472 programmable ... More
Tunable-Cavity QED with Phase QubitsAug 08 2014We describe a tunable-cavity QED architecture with an rf SQUID phase qubit inductively coupled to a single-mode, resonant cavity with a tunable frequency that allows for both microwave readout of tunneling and dispersive measurements of the qubit. Dispersive ... More
An aperiodic monotile that forces nonperiodicity through a local dendritic growth ruleMar 04 2019We introduce a new type of aperiodic hexagonal monotile; a prototile that admits infinitely many tilings of the plane, but any such tiling lacks any translational symmetry. Adding a copy of our monotile to a patch of tiles must satisfy two rules that ... More
Dipolar broadening of nuclear spin resonance under dynamical pumpingMay 10 2012We study the polarisation dependence of the homogeneously broadened nuclear spin resonance in a crystal. We employ a combinatorial method to restrict the nuclear states to a fixed polarisation and show that the centre of the resonance is shifted linearly ... More
Photon blockade and nonlinear effects for a quantum dot strongly coupled to a semiconductor microcavityAug 24 2008Jul 01 2011Our model comprehensively simulates modern nanoscale semiconductor microcavities incorporating cavity quantum electrodynamics within both the weak and strong coupling regimes, using on-resonant laser excitation and nonresonant excitation due to a wetting ... More
RFSQUID-Mediated Coherent Tunable Coupling Between a Superconducting Phase Qubit and a Lumped Element ResonatorJan 06 2010We demonstrate coherent tunable coupling between a superconducting phase qubit and a lumped element resonator. The coupling strength is mediated by a flux-biased RF SQUID operated in the non-hysteretic regime. By tuning the applied flux bias to the RF ... More
Demonstration of nonstoquastic Hamiltonian in coupled superconducting flux qubitsMar 14 2019Mar 15 2019Quantum annealing (QA) is a heuristic algorithm for finding low-energy configurations of a system, with applications in optimization, machine learning, and quantum simulation. Up to now, all implementations of QA have been limited to qubits coupled via ... More
Efficient pooling designs for library screeningDec 04 1994We describe efficient methods for screening clone libraries, based on pooling schemes which we call ``random $k$-sets designs''. In these designs, the pools in which any clone occurs are equally likely to be any possible selection of $k$ from the $v$ ... More
Ultrafast reflectivity modulation in AlGaAs/InAlGaAs multiple quantum well photonic crystal waveguidesFeb 11 2014We report an ultrafast optical tuning of the reflectivity of AlGaAs/InAlGaAs multiple quantum well photonic crystal waveguides using a reflection geometry, pump-probe technique.
Fractal spectral triples on Kellendonk's $C^*$-algebra of a substitution tilingApr 21 2015We introduce a new class of noncommutative spectral triples on Kellendonk's $C^*$-algebra associated with a nonperiodic substitution tiling. These spectral triples are constructed from fractal trees on tilings, which define a geodesic distance between ... More
Tripartite interactions between two phase qubits and a resonant cavityMar 31 2010The creation and manipulation of multipartite entangled states is important for advancements in quantum computation and communication, and for testing our fundamental understanding of quantum mechanics and precision measurements. Multipartite entanglement ... More
Spatial Coherence of a polariton condensate in 1D acoustic latticeMay 08 2012Several mechanisms are discussed which could determine the spatial coherence of a polariton condensate confined to a one dimensional wire. The mechanisms considered are polariton-polariton interactions, disorder scattering and non-equilibrium occupation ... More
Fractal spectral triples on Kellendonk's $C^*$-algebra of a substitution tilingApr 21 2015Dec 09 2016We introduce a new class of noncommutative spectral triples on Kellendonk's $C^*$-algebra associated with a nonperiodic substitution tiling. These spectral triples are constructed from fractal trees on tilings, which define a geodesic distance between ... More
Time-Domain Detection of Weakly Coupled TLS Fluctuators in Phase QubitsApr 16 2010We report on a method for detecting weakly coupled spurious two-level system fluctuators (TLSs) in superconducting qubits. This method is more sensitive that standard spectroscopic techniques for locating TLSs with a reduced data acquisition time.
Tuning effective hyperfine fields in PEDOT:PSS thin films by dopingApr 14 2018Using electrically detected magnetic resonance spectroscopy, we demonstrate that doping the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) with ethylene glycol allows for the control of effective local charge carrier ... More
Cohomology of the Pinwheel TilingDec 18 2012We provide a computation of the cohomology of the Pinwheel tiling using the Anderson-Putnam complex. A border forcing version of the Pinwheel tiling is constructed that allows an explicit construction of the complex for the quotient of the continuous ... More
Deploying SDN in GÉANT production networkSep 18 2017Since the demand for more bandwidth, agile infrastructures and services grows, it becomes challenging for Service Providers like G\'EANT to manage the proprietary underlay, while keeping costs low. In such a scenario, Software Defined Networking (SDN), ... More
Low-loss superconducting resonant circuits using vacuum-gap-based microwave componentsOct 27 2009Jun 25 2010We have produced high-quality complex microwave circuits, such as multiplexed resonators and superconducting phase qubits, using a "vacuum-gap" technology that eliminates lossy dielectric materials. We have improved our design and fabrication strategy ... More
Coherence properties of the microcavity polariton condensateNov 26 2008A theoretical model is presented which explains the dominant decoherence process in a microcavity polariton condensate. The mechanism which is invoked is the effect of self-phase modulation, whereby interactions transform polariton number fluctuations ... More
Role of incoherent substrate reflections in photonic crystal spectroscopyDec 16 2010A method is presented for modelling the optical properties of a photonic crystal structure mounted on a substrate which is thick enough that the light reflected from the back is incoherent with reflections from the front. Transmission and reflection spectra ... More
Weak lensing using only galaxy position anglesNov 15 2013Sep 25 2014We develop a method for performing a weak lensing analysis using only measurements of galaxy position angles. By analysing the statistical properties of the galaxy orientations given a known intrinsic ellipticity distribution, we show that it is possible ... More
Position-momentum entangled photon pairs in non-linear wave-guides and transmission linesNov 11 2015Apr 26 2016We analyse the correlation properties of light in non-linear wave-guides and transmission lines, predict the position-momentum realization of EPR paradox for photon pairs in Kerr-type non-linear photonic circuits, and we show how two-photon entangled ... More
Rabi oscillations of two-photon states in nonlinear optical resonatorsFeb 29 2016We demonstrate that four-wave mixing processes in high-quality non-linear resonators can lead to Rabi-like oscillations in photon occupation numbers and second-order correlation functions, being a characteristic feature of the presence of entangled photon ... More
Synergy, suppression and immorality: forward differences of the entropy functionJan 18 2015Conditional mutual information is important in the selection and interpretation of graphical models. Its empirical version is well known as a generalised likelihood ratio test and that it may be represented as a difference in entropy. We consider the ... More
Twisted C*-algebras associated to finitely aligned higher-rank graphsOct 29 2013Aug 06 2014We introduce twisted relative Cuntz-Krieger algebras associated to finitely aligned higher-rank graphs and give a comprehensive treatment of their fundamental structural properties. We establish versions of the usual uniqueness theorems and the classification ... More
Conservation of Quantum Correlations in Multimode Systems with $U(1)$ SymmetryNov 02 2017Feb 22 2019We present a theoretical investigation of the properties of quantum correlation functions in a dissipative multimode system. We define a total mth order equal-time correlation function, summed over all modes, which is shown to be conserved if the Hamiltonian ... More
A fractal version of the pinwheel tilingJan 13 2010Jan 25 2011We introduce a fractal version of the pinwheel substitution tiling. There are thirteen basic prototiles, all of which have fractal boundaries. These tiles, along with their reflections and rotations, create a tiling space which is mutually locally derivable ... More
Equilibrium Conditions for the Floating of Multiple Interfacial ObjectsSep 01 2005Feb 09 2006We study the effect of interactions between objects floating at fluid interfaces, for the case in which the objects are primarily supported by surface tension. We give conditions on the density and size of these objects for equilibrium to be possible ... More
Optical source of individual pairs of color-conjugated photonsAug 25 2016We demonstrate that Kerr nonlinearity in optical circuits can lead to both resonant four-wave mixing and photon blockade, which can be used for high-yield generation of high-fidelity individual photon pairs with conjugated frequencies. We propose an optical ... More
Quantum optics of nonlinear systems in cascadeMay 23 2018In this letter, we investigate the quantum optical properties of driven-dissipative nonlinear systems in a cascade configuration. We show that pumping a nonlinear system with a state having a noncoherent statistics, can improve the antibunching of the ... More
Sub-shot-noise transmission measurement using optically gated single photonsNov 23 2016Harnessing the unique properties of quantum mechanics offers the possibility to deliver new technologies that can fundamentally outperform their classical counterparts. These technologies only deliver advantages when components operate with performance ... More
Spin Textures of Polariton Condensates in a Tunable Microcavity with Strong Spin-Orbit InteractionApr 09 2015We report an extended family of spin textures in coexisting modes of zero-dimensional polariton condensates spatially confined in tunable open microcavity structures. The coupling between photon spin and angular momentum, which is enhanced in the open ... More
Short-term variability and mass loss in Be stars I. BRITE satellite photometry of $η$ and $μ$ CentauriFeb 04 2016Empirical evidence for the involvement of nonradial pulsations (NRP's) in the mass loss from Be stars ranges from (i) a singular case (\object{$\mu$ Cen}) of repetitive mass ejections triggered by multi-mode beating to (ii) several photometric reports ... More
Combining BRITE and ground-based photometry for the Beta Cephei star Nu Eridani: impact on photometric pulsation mode identification and detection of several g modesSep 29 2016We report a simultaneous ground and space-based photometric study of the Beta Cephei star Nu Eridani. Half a year of observations have been obtained by four of the five satellites constituting BRITE-Constellation, supplemented with ground-based photoelectric ... More
Measurement crosstalk between two phase qubits coupled by a coplanar waveguideFeb 03 2010We analyze the measurement crosstalk between two flux-biased phase qubits coupled by a resonant coplanar waveguide cavity. After the first qubit is measured, the superconducting phase can undergo damped oscillations resulting in an a.c. voltage that produces ... More
Temperature and Voltage Driven Tunable Metal-Insulator Transition in Individual $W_{x}V_{1-x}O_{2}$ nanowiresDec 12 2010Results from transport measurements in individual $W_{x}V_{1-x}O_{2}$ nanowires with varying extents of $W$ doping are presented. An abrupt thermally driven metal-insulator transition (MIT) is observed in these wires and the transition temperature decreases ... More
Quantum statistics of four-wave mixing by a non-linear resonant microcavityAug 04 2014We analyse the correlation and spectral properties of two-photon states resonantly transmitted by a non-linear optical microcavity. We trace the correlation properties of transmitted two-photon states to the decay spectrum of multi-photon resonances in ... More
Ensuring Data Integrity in Electronic Health Records: A Quality Health Care ImplicationFeb 02 2018An Electronic Health Record (EHR) system must enable efficient availability of meaningful, accurate and complete data to assist improved clinical administration through the development, implementation and optimisation of clinical pathways. Therefore data ... More
Estimating the weak-lensing rotation signal in radio cosmic shear surveysDec 05 2016Weak lensing has become an increasingly important tool in cosmology and the use of galaxy shapes to measure cosmic shear has become routine. The weak-lensing distortion tensor contains two other effects in addition to the two components of shear: the ... More
A demonstration of position angle-only weak lensing shear estimators on the GREAT3 simulationsMay 29 2015We develop and apply the position angle-only shear estimator of Whittaker et al. (2014) to realistic galaxy images. This is done by demonstrating the method on the simulations of the GREAT3 challenge (Mandelbaum et al. 2014b), which include contributions ... More
Fractal dual substitution tilingsOct 17 2014Starting with a substitution tiling, we demonstrate a method for constructing infinitely many new substitution tilings. Each of these new tilings is derived from a graph iterated function system and the tiles have fractal boundary. We show that each of ... More
STEREO observations of HD 90386 (RX Sex): a Delta Scuti or a hybrid star?Jan 31 2017HD 90386 is a rarely studied bright A2V type Delta Scuti star (V = 6.66 mag). It displays short-term light curve variations which are originated due to either a beating phenomenon or a non-periodic variation. In this paper, we presented high-precision ... More
K-Theoretic Duality for Hyperbolic Dynamical SystemsSep 25 2010The K-theoretic analog of Spanier-Whitehead duality for noncommutative C*-algebras is shown to hold for the Ruelle algebras associated to irreducible Smale spaces. This had previously been proved only for shifts of finite type. Implications of this result ... More
Graph algebras and orbit equivalenceOct 08 2014We introduce the notion of orbit equivalence of directed graphs, following Matsumoto's notion of continuous orbit equivalence for topological Markov shifts. We show that two graphs in which every cycle has an exit are orbit equivalent if and only if there ... More
Equilibrium states on the Cuntz-Pimsner algebras of self-similar actionsJan 21 2013May 17 2014We consider a family of Cuntz-Pimsner algebras associated to self-similar group actions, and their Toeplitz analogues. Both families carry natural dynamics implemented by automorphic actions of the real line, and we investigate the equilibrium states ... More
Zappa-Szép products of semigroups and their C*-algebrasSep 02 2013Jan 20 2014Zappa-Sz\'ep products of semigroups encompass both the self-similar group actions of Nekrashevych and the quasi-lattice-ordered groups of Nica. We use Li's construction of semigroup $C^*$-algebras to associate a $C^*$-algebra to Zappa-Sz\'ep products ... More
Topological spaces associated to higher-rank graphsOct 23 2013Jun 08 2016We investigate which topological spaces can be constructed as topological realisations of higher-rank graphs. We describe equivalence relations on higher-rank graphs for which the quotient is again a higher-rank graph, and show that identifying isomorphic ... More
Separating weak lensing and intrinsic alignments using radio observationsFeb 28 2015We discuss methods for performing weak lensing using radio observations to recover information about the intrinsic structural properties of the source galaxies. Radio surveys provide unique information that can benefit weak lensing studies, such as HI ... More
Equilibrium states on operator algebras associated to self-similar actions of groupoids on graphsOct 02 2016We consider self-similar actions of groupoids on the path spaces of finite directed graphs, and construct examples of such self-similar actions using a suitable notion of graph automaton. Self-similar groupoid actions have a Cuntz-Pimsner algebra and ... More
Linguistic Reflexes of Well-Being and Happiness in EchoAug 31 2017Different theories posit different sources for feelings of well-being and happiness. Appraisal theory grounds our emotional responses in our goals and desires and their fulfillment, or lack of fulfillment. Self Determination theory posits that the basis ... More
Effect of photonic spin-orbit coupling on the topological edge modes of a Su-Schrieffer-Heeger chainDec 05 2018We study the effect of photonic spin-orbit coupling (SOC) in micropillar lattices on the topological edge states of a one-dimensional chain with a zigzag geometry, corresponding to the Su-Schrieffer-Heeger model equipped with an additional internal degree ... More
Massive pulsating stars observed by BRITE-Constellation. I. The triple system Beta Centauri (Agena)Feb 08 2016This paper aims to precisely determine the masses and detect pulsation modes in the two massive components of Beta Cen with BRITE-Constellation photometry. In addition, seismic models for the components are considered and the effects of fast rotation ... More
Studying the photometric and spectroscopic variability of the magnetic hot supergiant $ζ$ Orionis AaApr 03 2017Massive stars play a significant role in the chemical and dynamical evolution of galaxies. However, much of their variability, particularly during their evolved supergiant stage, is poorly understood. To understand the variability of evolved massive stars ... More
Testing randomness with photonsDec 06 2013Generating and characterising randomness is fundamentally important in both classical and quantum information science. Here we report the experimental demonstration of ensembles of pseudorandom optical processes comprising what are known as t-designs. ... More
Full Stark Control of Polariton States on a Spin-Orbit HypersphereJun 07 2016Nov 21 2016The orbital angular momentum and the polarisation of light are physical quantities widely investigated for classical and quantum information processing. In this work we propose to take advantage of strong light-matter coupling, circular-symmetric confinement, ... More
Statistics of excitons in quantum dots and the resulting microcavity emission spectraMay 30 2005Nov 24 2005A theoretical investigation is presented of the statistics of excitons in quantum dots (QDs) of different sizes. A formalism is developed to build the exciton creation operator in a dot from the single exciton wavefunction and it is shown how this operator ... More
Logic Gates with Bright Dissipative Polariton Solitons in Bragg-Cavity SystemsNov 12 2015Optical solitons are an ideal platform for the implementation of communication lines, since they can be packed extremely close one to another without risking partial loss of the encoded information due to their interaction. On the other hand, soliton-soliton ... More
The roAp star $α$ Circini as seen by BRITE-ConstellationJan 19 2016We report on an analysis of high-precision, multi-colour photometric observations of the rapidly-oscillating Ap (roAp) star $\alpha$ Cir. These observations were obtained with the BRITE-Constellation, which is a coordinated mission of five nanosatellites ... More
The BRITE Constellation nanosatellite mission: Testing, commissioning and operationsJul 31 2016BRITE (BRIght Target Explorer) Constellation, the first nanosatellite mission applied to astrophysical research, is a collaboration among Austria, Canada and Poland. The fleet of satellites (6 launched, 5 functioning) performs precise optical photometry ... More
Zappa-Szép product groupoids and C*-blendsJul 14 2015We study the external and internal Zappa-Sz\'ep product of topological groupoids. We show that under natural continuity assumptions the Zappa-Sz\'ep product groupoid is \'etale if and only if the individual groupoids are \'etale. In our main result we ... More
Feline coronaviruses associated with feline infectious peritonitis have modifications to spike protein activation sites at two discrete positionsDec 12 2014Feline infectious peritonitis (FIP) is associated with mutations in the feline coronavirus (FCoV) genome that are thought to convert the subclinical feline enteric coronavirus (FECV) into the lethal feline infectious peritonitis virus (FIPV). A key feature ... More
Zappa-Szép product groupoids and C*-blendsJul 14 2015Jun 14 2017We study the external and internal Zappa-Sz\'ep product of topological groupoids. We show that under natural continuity assumptions the Zappa-Sz\'ep product groupoid is \'etale if and only if the individual groupoids are \'etale. In our main result we ... More
3-D Volumetric Gamma-ray Imaging and Source Localization with a Mobile RobotFeb 15 2018Mar 31 2018Radiation detection has largely been a manual inspection process with point sensors such as Geiger-Muller counters and scintillation spectrometers to date. While their observations of source proximity prove useful, they lack the directional information ... More
Separating electric field and thermal effects across the metal-insulator transition in vanadium oxide nanobeamsJan 16 2014We present results from an experimental study of the equilibrium and non-equilibrium transport properties of vanadium oxide nanobeams near the metal-insulator transition (MIT). Application of a large electric field in the insulating phase across the nanobeams ... More
Observation of topological phenomena in a programmable lattice of 1,800 qubitsMar 06 2018The celebrated work of Berezinskii, Kosterlitz and Thouless in the 1970s revealed exotic phases of matter governed by topological properties of low-dimensional materials such as thin films of superfluids and superconductors. Key to this phenomenon is ... More
People born in the Middle East but residing in the Netherlands: Invariant population size estimates and the role of active and passive covariatesSep 27 2012Including covariates in loglinear models of population registers improves population size estimates for two reasons. First, it is possible to take heterogeneity of inclusion probabilities over the levels of a covariate into account; and second, it allows ... More
Propagating Disturbances in Coronal Loops: A Detailed Analysis of Propagation SpeedsMay 04 2012May 16 2012Quasi-periodic disturbances have been observed in the outer solar atmosphere for many years now. Although first interpreted as upflows (Schrijver et al. (1999)), they have been widely regarded as slow magnetoacoustic waves, due to observed velocities ... More
Full Stark Control of Polariton States on a Spin-Orbit HypersphereJun 07 2016The orbital angular momentum and the polarisation of light are among the physical quantities most widely investigated for the implementation of classical and quantum information processing. In this work we propose to exploit states where these two degrees ... More
Spontaneous and triggered vortices in polariton OPO superfluidsMar 26 2010We study non-equilibrium polariton superfluids in the optical parametric oscillator (OPO) regime using a two-component Gross-Pitaevskii equation with pumping and decay. We identify a regime above OPO threshold, where the system undergoes spontaneous symmetry ... More
CruzAffect at AffCon 2019 Shared Task: A feature-rich approach to characterize happinessFeb 16 2019We present our system, CruzAffect, for the CL-Aff Shared Task 2019. CruzAffect consists of several types of robust and efficient models for affective classification tasks. We utilize both traditional classifiers, such as XGBoosted Forest, as well as a ... More
Synthesis, Characterization, and Finite Size Effects on Electrical Transport of Nanoribbons of the Charge-Density Wave Conductor NbSe3Nov 30 2011NbSe3 exhibits remarkable anisotropy in most of its physical properties and has been a model system for studies of quasi-one-dimensional charge-density-wave (CDW) phenomena. Herein, we report the synthesis, characterization, and electrical transport of ... More
Transient Structures and Stream Interaction Regions in the Solar Wind: Results from EISCAT Interplanetary Scintillation, STEREO HI and Venus Express ASPERA-4 MeasurementsJul 17 2012We discuss the detection and evolution of a complex series of transient and quasi-static solar wind structures in the days following the well-known comet 2P / Encke tail disconnection event in April 2007. The evolution of transient solar wind structures ... More
Demonstration of nonstoquastic Hamiltonian in coupled superconducting flux qubitsMar 14 2019Quantum annealing (QA) is a heuristic algorithm for finding low-energy configurations of a system, with applications in optimization, machine learning, and quantum simulation. Up to now, all implementations of QA have been limited to qubits coupled via ... More
Quantum-enhanced absorption spectroscopyAug 04 2015Absorption spectroscopy is routinely used to characterise chemical and biological samples. For the state-of-the-art in absorption spectroscopy, precision is theoretically limited by shot-noise due to the fundamental Poisson-distribution of photon number ... More
Injection of orbital angular momentum and storage of quantized vortices in polariton superfluidsSep 09 2015Apr 18 2016We report the experimental investigation and theoretical modeling of a rotating polariton superfluid relying on an innovative method for the injection of angular momentum. This novel, multi-pump injection method uses four coherent lasers arranged in a ... More
Quantum-enhanced tomography of unitary processesFeb 12 2014A fundamental task in photonics is to characterise an unknown optical process, defined by properties such as birefringence, spectral response, thickness and flatness. Amongst many ways to achieve this, single-photon probes can be used in a method called ... More
Probing the accelerating Universe with radio weak lensing in the JVLA Sky SurveyDec 19 2013Dec 30 2013We outline the prospects for performing pioneering radio weak gravitational lensing analyses using observations from a potential forthcoming JVLA Sky Survey program. A large-scale survey with the JVLA can offer interesting and unique opportunities for ... More
First science with SALT: peering at the accreting polar caps of the eclipsing polar SDSS J015543.40+002807.2Jul 12 2006We describe briefly the properties of the recently completed Southern African Large Telescope (SALT), along with its first light imager SALTICAM. Using this instrument, we present 4.3 hr of high speed unfiltered photometric observations of the eclipsing ... More
Single-photon nonlinearity of a semiconductor quantum dot in a cavityDec 01 2006A single atom in a cavity is the model system of cavity quantum electrodynamics (CQED). The strong coupling regime between the atom and cavity-confined photon corresponds to the reversible exchange of energy between the two modes, and underpins a wide ... More
Demonstrating an absolute quantum advantage in direct absorption measurementNov 23 2016Engineering apparatus that harness quantum theory offers practical advantages over current technology. A fundamentally more powerful prospect is the long-standing prediction that such quantum technologies could out-perform any future iteration of their ... More
Effect of Interactions on Vortices in a Non-equilibrium Polariton CondensateSep 27 2013We demonstrate the creation of vortices in a macroscopically occupied polariton state formed in a semiconductor microcavity. A weak external laser beam carrying orbital angular momentum (OAM) is used to imprint a vortex on the condensate arising from ... More