Literatura científica selecionada sobre o tema "Single-Photon wavepackets"

This paper demonstrates how a classical detector that collects non-interacting individual classical massive free particles can generate a quantum interference pattern. The proposed classical picture requires that particles carry the information of a phase equal to an action integral along their trajectory. At the point of their detection, a special type of detector collects the phases from all individual particles reaching it, adds them up over time as complex numbers, and divides them by the square root of their number. The detector announces a number of detections equal to the square of the amplitude of the resulting complex number. An interference pattern is gradually built from the collection of particle phases in the detection bins of the detector after several repetitions of the experiment. We obtain perfect agreement with three solutions of the Schrödinger equation for free particles: a Gaussian wavepacket, two Gaussian wavepackets approaching each other, and a Gaussian wavepacket reflecting off a wall. The main conclusion of the present work is that the interference of quantum mechanics is basically due to the detectors that collect the particles when there are macroscopic detectors operating as proposed. Finally, a simple physical experiment with a single-photon detector is proposed that will be able to test our theory.

We propose a passively self-error-rejecting single-qubit transmission scheme for an arbitrary polarization state of a single qubit over a collective-noise channel, without resorting to additional qubits and entanglement. By splitting a single qubit into some wavepackets with some Mach-Zehnder interferometers, we can obtain an uncorrupted state with a success probability approaching 100% via postselection in different time bins, independent of the parameters of collective noise. It is simpler and more flexible than the schemes utilizing decoherence-free subspace and those with additional qubits. One can directly apply this scheme to almost all quantum communication protocols based on single photons or entangled photon systems against a collective noise.

A lossless beamsplitter has certain (complex-valued) probability amplitudes for sending an incoming photon into one of two possible directions. We use elementary laws of classical and quantum optics to obtain general relations among the magnitudes and phases of these probability amplitudes. Proceeding to examine a pair of (nearly) single-mode wavepackets in the number-states [Formula: see text] and [Formula: see text] that simultaneously arrive at the splitter's input ports, we find the distribution of photon-number states at the output ports using an argument inspired by Feynman's scattering analysis of indistinguishable Bose particles. The result thus obtained coincides with that of the standard quantum-optical treatment of beamsplitters via annihilation and creation operators [Formula: see text] and [Formula: see text]. A simple application of the Feynman method provides a form of justification for the Bose enhancement implicit in the well-known formulas [Formula: see text] and [Formula: see text].

The “quantum walk” has emerged recently as a paradigmatic process for the dynamic simulation of complex quantum systems, entanglement production and quantum computation. Hitherto, photonic implementations of quantum walks have mainly been based on multipath interferometric schemes in real space. We report the experimental realization of a discrete quantum walk taking place in the orbital angular momentum space of light, both for a single photon and for two simultaneous photons. In contrast to previous implementations, the whole process develops in a single light beam, with no need of interferometers; it requires optical resources scaling linearly with the number of steps; and it allows flexible control of input and output superposition states. Exploiting the latter property, we explored the system band structure in momentum space and the associated spin-orbit topological features by simulating the quantum dynamics of Gaussian wavepackets. Our demonstration introduces a novel versatile photonic platform for quantum simulations.

A multicenter (LCAO) B-spline basis is described in detail, and its capabilities concerning affording convergent solutions for electronic continuum states and wavepacket propagation are presented. It forms the core of the Tiresia code, which implements static-DFT and TDDFT hamiltonians, as well as single channel Dyson-DFT and Dyson-TDDFT descriptions to include correlation in the bound states. Together they afford accurate and computationally efficient descriptions of photoionization properties of complex systems, both in the single photon and strong field environments. A number of examples are provided.

Abstract We present an exact solution for the propagation of quantized massless scalar particles in a two-dimensional variation of the Alcubierre metric. Classical localized wavepacket solutions are derived using closed expressions for light-ray coordinates, and corresponding annihilation operators are constructed using the concept of locally positive and negative frequencies. The theory is used to describe the loss of fringe visibility in a single-photon interferometer, and the reduction of entanglement between two 2D photons, if one photon travels through a region with spacetime curvature. We derive an expansion of the field operator in terms of localized modes by means of an over-completeness relation. The quantization procedure also applies to massive and charged scalar fields in an n-dimensional globally hyperbolic spacetime.

Au cours des dernières décennies, l’optique quantique a évolué des cavités à facteur de qualité élevé des premières expériences vers de nouvelles conceptions de cavités impliquant des modes à fuite. Bien que les modèles utilisés dans des expériences standard soient efficaces pour reproduire ces expériences, les fuites de photons sont la plupart du temps traitées de manière phénoménologique ce qui limite l'interprétation des résultats et ne permet pas une étude systématique. Dans ce manuscrit, nous adoptons une approche différente et, à partir des premiers principes, nous dérivons des modèles effectifs qui permettent la caractérisation complète d'un photon unique produit dans la cavité et se propageant dans l'espace libre. Nous proposons un schéma atome-cavité pour la génération de photons uniques et analysons rigoureusement le photon unique sortant dans les domaines temporel et fréquentiel pour différents régimes de couplage. Nous étendons l'analyse en étudiant des modèles de cavités plus réalistes, prenant notamment en compte la structure diélectrique multicouche des miroirs de la cavité. Nous évaluons la force du couplage dipolaire entre un seul émetteur et le champ de rayonnement dans une telle cavité optique. Notre modèle permet de faire varier librement la fréquence de résonance de la cavité, la fréquence de la transition lumineuse ou atomique, ainsi que la longueur d'onde associée à la mise en forme du miroir diélectrique. En particulier, nous montrons qu'en raison des effets induits par la nature multicouche du miroir de la cavité, même dans le régime de cavité haute finesse tel que défini habituellement, la description du système cavité-réservoir peut différer de celle où la structure du miroir est négligée. Pour les cavités très courtes, la longueur effective utilisée pour déterminer le volume du mode de la cavité et les longueurs définissant les résonances sont différentes, et diffèrent notablement de la longueur géométrique de la cavité. Ce n'est que pour des cavités beaucoup plus longues que leur longueur d'onde de résonance que le volume du mode se rapproche asymptotiquement de celui normalement supposé à partir de leur longueur géométrique. Sur la base de ces résultats, nous définissons une fonction de réponse généralisée de la cavité et une fonction de couplage cavité-réservoir, qui tiennent compte de la structure géométrique du miroir de la cavité. Cela nous permet de définir une réflectivité effective pour la cavité avec un miroir multicouche comme si elle avait une structure négligeable. Nous estimons l'erreur d'une telle définition en considérant des cavités de différentes longueurs et structures de miroir. Enfin, nous appliquons ce modèle pour caractériser un photon unique produit dans une telle cavité et se propageant à l'extérieur dans l'espace libre
Over the last decades, quantum optics has evolved from high-quality-factor cavities in the early experiments toward new cavity designs involving leaky modes. Despite efficient models to describe standard experiments, photon leakage is most of the time treated phenomenologically, which restricts the interpretation of the results and does not allow systematic studies. In this manuscript, we take a different approach, and starting from first principles, we derive effective models that allow complete characterization of a leaking single photon produced in the cavity and propagating in free space. We propose an atom-cavity scheme for single-photon generation, and we rigorously analyze the outgoing single photon in time and frequency domains for different coupling regimes. We extend the analysis by studying more realistic cavity models, namely taking into account the multilayer dielectric structure of cavity mirrors. We evaluate the dipole coupling strength between a single emitter and the radiation field within such an optical cavity. Our model allows one to freely vary the resonance frequency of the cavity, the frequency of light or atomic transition addressing it, and the design wavelength of the dielectric mirror. In particular, we show that due to the effects induced by the multilayer nature of the cavity mirror, even in the standardly defined high-finesse cavity regime, the cavity-reservoir system description might differ from the one where the structure of the mirror is neglected. For very short cavities, the effective length used to determine the cavity mode volume and the lengths defining the resonances are different, and also found to diverge appreciably from the geometric length of the cavity. Only for cavities much longer than their resonant wavelength does the mode volume asymptotically approach that normally assumed from their geometric length. Based on these results, we define a generalized cavity response function and cavity-reservoir coupling function, which account for the geometric structure of the cavity mirror. This allows us to define an effective reflectivity for the cavity with a multilayer mirror as if it had a negligible structure. We estimate the error of such a definition by considering cavities of different lengths and mirror structures. Finally, we apply this model to characterize a single photon produced in such a cavity and propagating outside in free space

We have demonstrated for the first time spatiotemporal nonspreading quantum Airy photons with long coherence times by merging quantum optics in cold atomic ensembles and nondiffracting spatial photonics.

We consider photons experiencing reflection, tunneling or trapping by refractive index fronts moving at the speed of light. We show that evolution equations in such situations are determined uniquely via the quantum-classical correspondence principle.

We experimentally demonstrate the efficient, broadband (4.7 THz), and controllable all-optical manipulation of single photons in a nonlinear photonic crystal fiber, in agreement with performed simulations of nonlinear pulse propagation, based on the quantum-classical correspondence principle.