Results for "Robert W. Boyd"

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Quantum Imaging TechnologiesJun 06 2014Over the past three decades, quantum mechanics has allowed the development of technologies that provide unconditionally secure communication. In parallel, the quantum nature of the transverse electromagnetic field has spawned the field of quantum imaging ... More
Custom-tailored spatial mode sorting by controlled random scatteringJan 20 2017The need to increase data transfer rates constitutes a key challenge in modern information-driven societies. Taking advantage of the transverse spatial modes of light to encode more information is a promising avenue for both classical and quantum photonics. ... More
Influence of radiative damping on the optical-frequency susceptibilityAug 29 2003Motivated by recent discussions concerning the manner in which damping appears in the electric polarizability, we show that (a) there is a dependence of the nonresonant contribution on the damping and that (b) the damping enters according to the "opposite ... More
Influence of damping on the vanishing of the electro-optic effect in chiral isotropic mediaDec 16 2002Using first principles, it is demonstrated that radiative damping alone cannot lead to a nonvanishing electro-optic effect in a chiral isotropic medium. This conclusion is in contrast with that obtained by a calculation in which damping effects are included ... More
Reply to comment on "Observation of subluminal twisted light in vacuum"Dec 06 2016Recently, we showed experimentally that light carrying orbital angular momentum experiences a slight subluminality under free-space propagation [1]. We thank Saari [2] for pointing out an apparent discrepancy between our theoretical results and the well-known ... More
High-dimensional quantum cloning and applications to quantum hackingAug 15 2016Attempts at cloning a quantum system result in the introduction of imperfections in the state of the copies. This is a consequence of the no-cloning theorem, which is a fundamental law of quantum physics and the backbone of security for quantum communications. ... More
Generation of Caustics and Spatial Rogue Waves from Nonlinear InstabilityJun 06 2017Caustics are natural phenomena in which nature concentrates the energy of waves. Although, they are known mostly in optics, caustics are intrinsic to all wave phenomena. For example, studies show that fluctuations in the profile of an ocean floor can ... More
Recovering full coherence in a qubit by measuring half of its environmentFeb 25 2015Mar 19 2015When quantum systems interact with the environment they lose their quantum properties, such as coherence. Quantum erasure makes it possible to restore coherence in a system by measuring its environment, but accessing the whole of it may be prohibitive: ... More
Generation of a spin-polarized electron beam by multipoles magnetic fieldsJun 10 2013The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin--magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical ... More
Exploring Energy-Time Entanglement Using Geometric PhaseNov 14 2017Using the signal and idler photons produced by parametric downconversion, we report an experimental observation of a violation of the Bell inequality for energy and time based purely on the geometric phases of the signal and idler photons. We thus show ... More
Entanglement verification via nonlinear witnessesOct 03 2012The controlled generation of entangled states and their subsequent detection are integral aspects of quantum information science. In this work, we analyse the application of nonlinear witnesses to the verification of entanglement, and we demonstrate experimentally ... More
Quantum-secured imagingDec 11 2012We have built an imaging system that uses a photon's position or time-of-flight information to image an object, while using the photon's polarization for security. This ability allows us to obtain an image which is secure against an attack in which the ... More
Theory of multiplexed photon number discriminationJan 21 2016Although some non-trivial photon number resolving detectors exist, it may still be convenient to discriminate photon number states with the method of multiplexed detection. Multiplexing can be performed with paths in real space, with paths in time, and ... More
Using surface lattice resonances to engineer nonlinear optical processes in metal nanoparticle arraysFeb 28 2018Collective responses of localized surface plasmon resonances, known as surface lattice resonances (SLRs) in metal nanoparticle arrays, can lead to high quality factors (~100), large local-field enhancements and strong light-matter interactions. SLRs have ... More
The optimal bound of quantum erasure with limited meansOct 08 2014In practical applications of quantum information science, quantum systems can have non-negligible interactions with the environment, and this generally degrades the power of quantum protocols as it introduces noise. Counteracting this by appropriately ... More
Free-space communication through turbulence: a comparison of plane-wave and orbital-angular-momentum encodingsApr 02 2013Free-space communication allows one to use spatial mode encoding, which is susceptible to the effects of diffraction and turbulence. Here, we discuss the optimum communication modes of a system while taking such effects into account. We construct a free-space ... More
Measurement of the Orbital Angular Momentum Spectrum of Partially Coherent Fields using Double Angular Slit InterferenceAug 15 2012Nov 16 2012We implement an interferometric method using two angular slits to measure the orbital angular momentum (OAM) mode spectrum of a partially coherent field. As the angular separation of the slits changes, an interference pattern for a particular OAM mode ... More
Supersensitive measurement of angular displacements using entangled photonsNov 12 2010We show that the use of entangled photons having non-zero orbital angular momentum (OAM) increases the resolution and sensitivity of angular-displacement measurements performed using an interferometer. By employing a 4$\times$4 matrix formulation to study ... More
Sub-fidelity as a measure of irreversibility of decoherenceJan 21 2016Quantum correlations between two systems can be impaired by the presence of an environment, as it can make systems decohere. We wish to evaluate how much coherence has been irreversibly lost. To do so, we study two qubits which leak correlations into ... More
Weak Value Amplification Can Outperform Conventional Measurement in the Presence of Detector SaturationDec 13 2016Weak value amplification (WVA) is a technique in which one can magnify the apparent strength of a measurement signal. Some have claimed that WVA can outperform more conventional measurement schemes in parameter estimation. Nonetheless, a significant body ... More
Efficient separation of the orbital angular momentum eigenstates of lightJun 04 2013Nov 15 2013Orbital angular momentum (OAM) of light is an attractive degree of freedom for funda- mentals studies in quantum mechanics. In addition, the discrete unbounded state-space of OAM has been used to enhance classical and quantum communications. Unambiguous ... More
Integrated multi vector vortex beam generatorMar 19 2013Jun 28 2013A novel method to generate and manipulate vector vortex beams in an integrated, ring resonator based geometry is proposed. We show numerically that a ring resonator, with an appropriate grating, addressed by a vertically displaced access waveguide emits ... More
Nonlinear optomechanical pressureMar 08 2014Mar 15 2014A transparent material exhibits ultra-fast optical nonlinearity and is subject to optical pressure if irradiated by a laser beam. However, the effect of nonlinearity on optical pressure is often overlooked, even if a nonlinear optical pressure may be ... More
A Primary Radiation Standard Based on Quantum Nonlinear OpticsAug 15 2018The spectrum of vacuum fluctuations of the electromagnetic field is determined solely from first physical principles and can be seen as a fundamental property that qualifies as a primary radiation standard. We demonstrate that the amplitude of these quantum ... More
Measurement of the Photon-Plasmon Coupling PhaseApr 23 2019Scattering processes have played a crucial role in the development of quantum theory. In the field of optics, scattering phase shifts have been utilized to unveil interesting forms of light-matter interactions. Here, we investigate the mode-coupling phase ... More
Controlling induced coherence for quantum imagingFeb 24 2017Induced coherence in parametric down-conversion between two coherently pumped nonlinear crystals that share a common idler mode can be used as an imaging technique. Based on the interference between the two signal modes of the crystals, an image can be ... More
Influence of pump coherence on the quantum properties of spontaneous parametric down-conversionJul 12 2018The correlation properties of the pump field in spontaneous parametric down-conversion are crucial in determining the degree of entanglement of generated signal and idler photons. We find theoretically that continuous-variable entanglement of the transverse ... More
Hanbury Brown and Twiss Interferometry with Twisted LightFeb 07 2015Apr 08 2016The rich physics exhibited by random optical wave fields permitted Hanbury Brown and Twiss to unveil fundamental aspects of light. Furthermore, it has been recognized that optical vortices are ubiquitous in random light and that the phase distribution ... More
The influence of pump coherence on the generation of position-momentum entanglement in down-conversionDec 22 2018Strong correlations in two conjugate variables are the signature of quantum entanglement and have played a key role in the development of modern physics. Entangled photons have become a standard tool in quantum information and foundations. An impressive ... More
Arbitrary optical wavefront shaping via spin-to-orbit couplingAug 23 2016Converting spin angular momentum to orbital angular momentum has been shown to be a practical and efficient method for generating optical beams carrying orbital angular momentum and possessing a space-varying polarized field. Here, we present novel liquid ... More
Electromagnetic Momentum in Dispersive Dielectric MediaOct 05 2009When the effects of dispersion are included, neither the Abraham nor the Minkowski expression for electromagnetic momentum in a dielectric medium gives the correct recoil momentum for absorbers or emitters of radiation. The total momentum density associated ... More
Single-shot measurement of the orbital-angular-momentum spectrum of partially coherent fieldsDec 01 2016Dec 02 2016We propose an image inversion-based interferometric technique for measuring the orbital-angular-momentum (OAM) spectrum of a field that is a symmetric incoherent distribution of OAM eigenstates. The technique directly encodes the angular correlation function ... More
Real-time imaging of spin-to-orbital angular momentum quantum state teleportationApr 30 2014Quantum teleportation is a process in which an unknown quantum state is transferred between two spatially separated subspaces of a bipartite quantum system which share an entangled state and communicate classically. In the case of photonic states, this ... More
Chiral optical response of planar and symmetric nanotrimers enabled by heteromaterial selectionJan 08 2016Chirality is an intriguing property of certain molecules, materials or artificial nanostructures, which allows them to interact with the spin angular momentum of the impinging light field. Due to their chiral geometry, they can distinguish between left- ... More
Observation of subluminal twisted light in vacuumDec 08 2015Einstein's theory of relativity establishes the speed of light in vacuum, c, as a fundamental constant. However, the speed of light pulses can be altered significantly in dispersive materials. While significant control can be exerted over the speed of ... More
Near-Perfect Sorting of Orbital Angular Momentum and Angular Position States of LightAug 14 2012Nov 29 2012We present a novel method for efficient sorting of photons prepared in states of orbital angular momentum (OAM) and angular position (ANG). A log-polar optical transform is used in combination with a holographic beam-splitting method to achieve better ... More
Wigner distribution of twisted photonsDec 04 2015We present the first experimental characterization of the azimuthal Wigner distribution of a photon. Our protocol fully characterizes the transverse structure of a photon in conjugate bases of orbital angular momentum (OAM) and azimuthal angle (ANG). ... More
Quantum, Nonlocal Aberration CancellationJun 11 2019Phase distortions, or aberrations, can negatively influence the performance of an optical imaging system. Through the use of position-momentum entangled photons, we nonlocally correct for aberrations in one photon's optical path by intentionally introducing ... More
Experimental investigation of Popper's proposed ghost-diffraction experimentDec 20 2016In an effort to challenge the Copenhagen interpretation of quantum mechanics, Karl Popper proposed an experiment involving spatially separated entangled particles. In this experiment, one of the particles passes through a very narrow slit, and thereby ... More
A "fair sampling" perspective on an apparent violation of dualityFeb 26 2014In the event in which a quantum mechanical particle can pass from an initial state to a final state along two possible paths, the duality principle states that "the simultaneous observation of wave and particle behavior is prohibited". [M. O. Scully, ... More
Colloquium: Understanding Quantum Weak Values: Basics and ApplicationsMay 30 2013Apr 01 2014Since its introduction 25 years ago, the quantum weak value has gradually transitioned from a theoretical curiosity to a practical laboratory tool. While its utility is apparent in the recent explosion of weak value experiments, its interpretation has ... More
Optical spin-to-orbital angular momentum conversion in ultra-thin metasurfaces with arbitrary topological chargesJul 21 2014Orbital angular momentum associated with the helical phase-front of optical beams provides an unbounded \qo{space} for both classical and quantum communications. Among the different approaches to generate and manipulate orbital angular momentum states ... More
Beyond the perturbative description of the nonlinear optical response of low-index materialsFeb 14 2017Jul 15 2017We show that standard approximations in nonlinear optics are violated for situations involving a small value of the linear refractive index. Consequently, the conventional equation for the intensity-dependent refractive index, $n(I) = n_0 + n_2 I$, becomes ... More
Bichromatic Local Oscillator for Detection of Two-Mode Squeezed States of LightMay 26 2006We present a new technique for the detection of two-mode squeezed states of light that allows for a simple characterization of these quantum states. The usual detection scheme, based on heterodyne measurements, requires the use of a local oscillator with ... More
Nonlinear optics with full three-dimensional illuminationSep 28 2018Feb 27 2019We investigate the nonlinear optical process of third-harmonic generation in the thus far unexplored regime of focusing the pump light from a full solid angle, where the nonlinear process is dominantly driven by a standing dipole-wave. We elucidate the ... More
State transfer based on classical nonseparabilityMar 12 2015Aug 20 2015We present a state transfer protocol that is mathematically equivalent to quantum teleportation, but uses classical nonseparability instead of quantum entanglement. In our implementation we take advantage of nonseparability among three parties: orbital ... More
Compressive Direct Measurement of the Quantum Wave FunctionApr 10 2014Nov 29 2014The direct measurement of a complex wavefunction has been recently realized by using weak-values. In this paper, we introduce a method that exploits sparsity for compressive measurement of the transverse spatial wavefunction of photons. The procedure ... More
Amplification of Angular Rotations Using Weak MeasurementsDec 10 2013Apr 28 2014We present a weak measurement protocol that permits a sensitive estimation of angular rotations based on the concept of weak-value amplification. The shift in the state of a pointer, in both angular position and the conjugate orbital angular momentum ... More
Nonlinear optics with full three-dimensional illuminationSep 28 2018We investigate the nonlinear optical process of third-harmonic generation in argon gas in a thus-far-unexplored regime of focusing the pump light from a full solid angle. We reason that the observed generation of frequency-tripled photons is due to six-wave ... More
Limitations to the determination of a Laguerre-Gauss spectrum via projective, phase-flattening measurementJan 15 2014Apr 22 2014One of the most widely used techniques for measuring the orbital angular momentum components of a light beam is to flatten the spiral phase front of a mode, in order to couple it to a single-mode optical fiber. This method, however, suffers from an efficiency ... More
The phase sensitivity of a fully quantum three-mode nonlinear interferometerAug 18 2018We study a nonlinear interferometer consisting of two consecutive parametric amplifiers, where all three optical fields (pump, signal and idler) are treated quantum mechanically, allowing for pump depletion and other quantum phenomena. The interaction ... More
Imaging with a small number of photonsAug 27 2014Low-light-level imaging techniques have application in many diverse fields, ranging from biological sciences to security. We demonstrate a single-photon imaging system based on a time-gated inten- sified CCD (ICCD) camera in which the image of an object ... More
Direct Measurement of a 27-Dimensional Orbital-Angular-Momentum State VectorJun 03 2013Jan 18 2014The measurement of a quantum state poses a unique challenge for experimentalists. Recently, the technique of "direct measurement" was proposed for characterizing a quantum state in-situ through sequential weak and strong measurements. While this method ... More
Tighter spots of light with superposed orbital angular momentum beamsJun 01 2016The possibility of focusing light to an ever tighter spot has important implications for many applications and fields of optics research, such as nano-optics and plasmonics, laser-scanning microscopy, optical data storage and many more. The size of lateral ... More
Quantum States of Light Produced by a High-Gain Optical Parametric Amplifier for Use in Quantum LithographyAug 22 2006We present a theoretical analysis of the properties of an unseeded optical parametic amplifier (OPA) used as the source of entangled photons for applications in quantum lithography. We first study the dependence of the excitation rate of a two-photon ... More
Single-shot measurement of the orbital-angular-momentum spectrum of lightDec 01 2016Oct 21 2017The existing methods for measuring the orbital-angular-momentum (OAM) spectrum suffer from issues such as poor efficiency, strict interferometric stability requirements, and too much loss. Furthermore, most techniques inevitably discard part of the field ... More
Single-shot measurement of the orbital-angular-momentum spectrum of partially coherent fieldsDec 01 2016We propose an image inversion-based interferometric technique for measuring the orbital-angular- momentum (OAM) spectrum of a field that is an incoherent mixture of OAM eigenstates. The tech- nique directly encodes the angular correlation function of ... More
EPR-based ghost imaging using a single-photon-sensitive cameraDec 20 2012Aug 05 2013Correlated-photon imaging, popularly known as ghost imaging, is a technique whereby an image is formed from light that has never interacted with the object. In ghost imaging experiments two correlated light fields are produced. One of these fields illuminates ... More
Achromatic orbital angular momentum generatorJun 30 2014Nov 06 2014We describe a novel approach for generating light beams that carry orbital angular momentum (OAM) by means of total internal reflection in an isotropic medium. A continuous space-varying cylindrically symmetric reflector, in the form of \textit{two glued ... More
Divergence of an orbital-angular-momentum-carrying beam upon propagationOct 31 2014There is recent interest in the use of light beams carrying orbital angular momentum (OAM) for creating multiple channels within free-space optical communication systems. One limiting issue is that, for a given beam size at the transmitter, the beam divergence ... More
Wide-bandwidth, tunable, multiple-pulse-width optical delays using slow light in cesium vaporApr 10 2007We demonstrate an all-optical delay line in hot cesium vapor that tunably delays 275 ps input pulses up to 6.8 ns and 740 input ps pulses up to 59 ns (group index of approximately 200) with little pulse distortion. The delay is made tunable with a fast ... More
Quantum probabilities from quantum entanglement: Experimentally unpacking the Born ruleApr 06 2016The Born rule, a foundational axiom used to deduce probabilities of events from wavefunctions, is indispensable in the everyday practice of quantum physics. It is also key in the quest to reconcile the ostensibly inconsistent laws of the quantum and classical ... More
Multiplexing Free-Space Channels using Twisted LightDec 28 2015We experimentally demonstrate an interferometric protocol for multiplexing optical states of light, with potential to become a standard element in free-space communication schemes that utilize light endowed with orbital angular momentum (OAM). We demonstrate ... More
Direct measurement of a one-million-dimensional photonic stateMar 16 2015Retrieving the vast amount of information carried by a photon is an enduring challenge in quantum metrology science and quantum photonics research. The transverse spatial state of a photon is a convenient high-dimensional quantum system for study, as ... More
Full characterisation of polarisation states of light via direct measurementJun 12 2012Oct 31 2013Ascertaining the physical state of a system is vital in order to understand and predict its behaviour. Tomography is a standard approach used to determine the form of an unknown state. Here we show that an alternative approach, based on sequential weak ... More
On-chip spectroscopy with thermally-tuned high-Q photonic crystal cavitiesNov 03 2015Spectroscopic methods are a sensitive way to determine the chemical composition of potentially hazardous materials. Here, we demonstrate that thermally-tuned high-Q photonic crystal cavities can be used as a compact high-resolution on-chip spectrometer. ... More
The duality principle in the presence of postselectionJun 17 2014Jun 19 2014The duality principle, a cornerstone of quantum mechanics, limits the coexistence of wave and particle behaviours of quantum systems. This limitation takes a quantitative form when applied to the visibility $\mathcal V$ and predictability $\mathcal P$ ... More
Super-critical phasematching for photon pair generation in structured light modesOct 05 2016We propose a method for directly producing radially and azimuthally polarized photon pairs through spontaneous parametric downconversion (SPDC). This method constitutes a novel geometry for SPDC, in which a radially polarized Bessel-Gauss pump beam is ... More
Hardy's paradox tested in the spin-orbit Hilbert space of single photonsMar 22 2014We test experimentally the quantum ``paradox'' proposed by Lucien Hardy in 1993 [Phys. Rev. Lett. 71, 1665 (1993)] by using single photons instead of photon pairs. This is achieved by addressing two compatible degrees of freedom of the same particle, ... More
Holographic generation of highly twisted electron beamsDec 11 2014Free electrons can possess an intrinsic orbital angular momentum, similar to those in an electron cloud, upon free-space propagation. The wavefront corresponding to the electron's wavefunction forms a helical structure with a number of twists given by ... More
Temporal Coherence and Indistinguishability in Two-Photon Interference EffectsDec 17 2007Feb 11 2008We show that temporal two-photon interference effects involving the signal and idler photons created by parametric down-conversion can be fully characterized in terms of the variations of two length parameters--called the biphoton path-length difference ... More
Conditional preparation of states containing a definite number of photonsSep 28 2007Nov 01 2007A technique for conditionally creating single- or multimode photon-number states is analyzed using Bayesian theory. We consider the heralded N-photon states created from the photons produced by an unseeded optical parametric amplifier when the heralding ... More
Quantum spatial superresolution by optical centroid measurementsMay 11 2011Quantum lithography (QL) has been suggested as a means of achieving enhanced spatial resolution for optical imaging, but its realization has been held back by the low multi-photon detection rates of recording materials. Recently, an optical centroid measurement ... More
Towards Polarization-based Excitation Tailoring for Extended Raman SpectroscopyMay 29 2019Undoubtedly, Raman spectroscopy is one of the most elaborated spectroscopy tools in materials science, chemistry, medicine and optics. However, when it comes to the analysis of nanostructured specimens, accessing the Raman spectra resulting from an exciting ... More
Comment on "Nonreciprocal cavities and the time-bandwidth limit"Jun 13 2019In their paper in Optica 6, 104 (2019), Mann et al. claim that time-invariant nonreciprocal cavities cannot overcome the time-bandwidth limit, based on their numerical analysis and temporal coupled-mode theory of an example structure. In this comment, ... More
Compressive Object Tracking using Entangled PhotonsJun 10 2013We present a compressive sensing protocol that tracks a moving object by removing static components from a scene. The implementation is carried out on a ghost imaging scheme to minimize both the number of photons and the number of measurements required ... More
Experimental generation of an optical field with arbitrary spatial coherence propertiesDec 24 2013Apr 28 2014We describe an experimental technique to generate a quasi-monochromatic field with any arbitrary spatial coherence properties that can be described by the cross-spectral density function, $W(\mathbf{r_1,r_2})$. This is done by using a dynamic binary amplitude ... More
Weak-value amplification of the fast-light effect in rubidium vaporDec 09 2014We use weak-value amplification to enhance the polarization-sensitive fast-light effect from induced Raman absorption in hot rubidium vapor. We experimentally demonstrate that projecting the output signal into an appropriate polarization state enables ... More
Rapid Generation of Light Beams Carrying Orbital Angular MomentumNov 19 2013We report a technique for encoding both amplitude and phase variations onto a laser beam using a single digital micro-mirror device (DMD). Using this technique, we generate Laguerre-Gaussian and vortex orbital-angular-momentum (OAM) modes, along with ... More
Experimental investigation of high-dimensional quantum key distribution protocols with twisted photonsFeb 15 2018Nov 29 2018Quantum key distribution is on the verge of real world applications, where perfectly secure information can be distributed among multiple parties. Several quantum cryptographic protocols have been theoretically proposed and independently realized in different ... More
Single-parameter scaling in the magnetoresistance of optimally doped La$_{2-x}$Sr$_{x}$CuO$_4$May 07 2019We show that the recent magnetoresistance data on thin-film La$_{2-x}$Sr$_{x}$CuO$_4$ (LSCO) in strong magnetic fields ($B$) obeys a single-parameter scaling of the form MR$(B,T)=f(\mu_H(T)B)$, where $\mu_H^{-1}(T)\sim T^{\alpha}$ ($1\le\alpha\le2$), ... More
Measurement of the radial mode spectrum of photons through a phase-retrieval methodSep 21 2018We propose and demonstrate a simple and easy-to-implement projective-measurement protocol to determine the radial index 'p' of a Laguerre-Gaussian (LGlp) mode. Our method entails converting any specified high-order LG0p mode into a near-Gaussian distribution ... More
Sorting photons by radial quantum numberNov 22 2017The Laguerre-Gaussian (LG) modes constitute a complete basis set for representing the transverse structure of a {paraxial} photon field in free space. Earlier workers have shown how to construct a device for sorting a photon according to its azimuthal ... More
Enhanced spectral sensitivity of a chip-scale photonic-crystal slow-light interferometerJan 28 2016We experimentally demonstrate that the spectral sensitivity of a Mach-Zehnder (MZ) interferometer can be enhanced through structural slow light. We observe a 20 times enhancement by placing a dispersion-engineered-slow-light photonic-crystal waveguide ... More
Ultra-wide-band slow light in photonic crystal coupled-cavity waveguidesJun 29 2017Slow light propagation in structured materials is a highly promising approach for realizing on-chip integrated photonic devices based on enhanced optical nonlinearities. One of the most successful research avenues consists in engineering the band dispersion ... More
Multi-twist polarization ribbon topologies in highly-confined optical fieldsJan 31 2019Electromagnetic plane waves, solutions to Maxwell's equations, are said to be `transverse' in vacuum. Namely, the waves' oscillatory electric and magnetic fields are confined within a plane transverse to the waves' propagation direction. Under tight-focusing ... More
Engineering the Frequency Spectrum of Bright Squeezed Vacuum via Group Velocity Dispersion in an SU(1,1) InterferometerOct 07 2016Bright squeezed vacuum, a promising tool for quantum information, can be generated by high-gain parametric down-conversion. However, its frequency and angular spectra are typically quite broad, which is undesirable for applications requiring single-mode ... More
Superhump periods in the UGSU-type dwarf nova SDSSp J082409.73+493124.4Jul 12 2007We present observations and analysis of the first reported superoutburst of the dwarf nova SDSSp J082409.73+493124.4 during February/March 2007. From a maximum observed magnitude of 15.4C it declined at 0.09 mag/d for 7 days, flattened out around magnitude ... More
Hermite-Gaussian mode sorterSep 29 2018The Hermite-Gaussian (HG) modes, sometimes also referred to as transverse electromagnetic modes in free space, form a complete and orthonormal basis that have been extensively used to describe optical fields. In addition, these modes have been shown to ... More
The Taylor-Frank method cannot be applied to some biologically important, continuous fitness functionsSep 06 2012The Taylor-Frank method for making kin selection models when fitness is a nonlinear function of a continuous phenotype requires this function to be differentiable. This assumption sometimes fails for biologically important fitness functions, for instance ... More
New measurements and analysis of the \b{eta} Cephei star V909 CassiopeiaeMar 31 2018V909 Cas is a little-studied example of a \b{eta} Cep pulsating variable located in the OB association Cas OB8 in the Perseus spiral arm of the Milky Way. Photometric observations in 2016-7 provided 30 new times of pulsation extrema and enabled its mean ... More
Invasion, polymorphic equilibria and fixation of a mutant social allele in group structured populationsNov 14 2012Stable mixtures of cooperators and defectors are often seen in nature. This fact is at odds with predictions based on linear public goods games under weak selection. That model implies fixation either of cooperators or of defectors, and the former scenario ... More
Exotic Looped Trajectories of Photons in Three-Slit InterferenceOct 27 2016The validity of the superposition principle and of Born's rule are well-accepted tenants of quantum mechanics. Surprisingly, it has recently been predicted that the intensity pattern formed in a three-slit experiment is seemingly in contradiction with ... More
Underwater Quantum Key Distribution in Outdoor Conditions with Twisted PhotonsJan 31 2018Quantum communication has been successfully implemented in optical fibres and through free-space [1-3]. Fibre systems, though capable of fast key rates and low quantum bit error rates (QBERs), are impractical in communicating with destinations without ... More
Orbital angular momentum modes of high-gain parametric down-conversionDec 21 2016Light beams with orbital angular momentum (OAM) are convenient carriers of quantum information. They can be also used for imparting rotational motion to particles and provide high resolution in imaging. Due to the conservation of OAM in parametric down-conversion ... More
Finite-key security analysis for multilevel quantum key distributionDec 17 2015Jul 20 2016We present a detailed security analysis of a d-dimensional quantum key distribution protocol based on two and three mutually unbiased bases (MUBs) both in an asymptotic and finite key length scenario. The finite secret key rates are calculated as a function ... More
Squarefree values of trinomial discriminantsFeb 20 2014Aug 08 2014The discriminant of a trinomial of the form $x^n \pm x^m \pm 1$ has the form $\pm n^n \pm (n-m)^{n-m} m^m$ if $n$ and $m$ are relatively prime. We investigate when these discriminants have nontrivial square factors. We explain various unlikely-seeming ... More
Solution Refinement at Regular Points of Conic ProblemsNov 06 2018Most numerical methods for conic problems use the homogenous primal-dual embedding, which yields a primal-dual solution or a certificate establishing primal or dual infeasibility. Following Patrinos (and others, 2018), we express the embedding as the ... More
Quantum-limited estimation of the axial separation of two incoherent point sourcesOct 02 2018Spatial mode demultiplexing has recently been proposed as a method to overcome the diffraction limits and can be used to precisely measure the transverse separation between two point sources. Here we show that superresolution can also be achieved along ... More
Influence of Atmospheric Turbulence on Optical Communications using Orbital Angular Momentum for EncodingApr 25 2012Jun 04 2012We describe an experimental implementation of a free-space 11-dimensional communication system using orbital angular momentum (OAM) modes. This system has a maximum measured OAM channel capacity of 2.12 bits/photon. The effects of Kolmogorov thin-phase ... More