Publications (24)0 Total impact
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Article: State reconstruction of a multimode twin beam using photodetection
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ABSTRACT: Robust and reliable method for reconstructing quasi-distributions of integrated intensities of twin beams generated in spontaneous parametric down-conversion and entangled in photon numbers is suggested. It utilizes the first and second photocount moments and minimizes the declination from experimental photocount histograms. Qualitatively different forms of quasi-distributions for quantum and classical states are suggested in the method. The transition from quantum to classical states caused by an increased detection noise is discussed. Momentum criterion for non-classicality of twin beams is suggested.02/2013; -
Article: Photon-number distributions of twin beams generated in spontaneous parametric down-conversion and measured by an intensified CCD camera
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ABSTRACT: The measurement of photon-number statistics of fields composed of photon pairs, generated in spontaneous parametric down-conversion and detected by an intensified CCD camera is described. Final quantum detection efficiencies, electronic noises, finite numbers of detector pixels, transverse intensity spatial profiles of the detected beams as well as losses of single photons from a pair are taken into account in a developed general theory of photon-number detection. The measured data provided by an iCCD camera with single-photon detection sensitivity are analyzed along the developed theory. Joint signal-idler photon-number distributions are recovered using the reconstruction method based on the principle of maximum likelihood. The range of applicability of the method is discussed. The reconstructed joint signal-idler photon-number distribution is compared with that obtained by a method that uses superposition of signal and noise and minimizes photoelectron entropy. Statistics of the reconstructed fields are identified to be multi-mode Gaussian. Elements of the measured as well as the reconstructed joint signal-idler photon-number distributions violate classical inequalities. Sub-shot-noise correlations in the difference of the signal and idler photon numbers as well as partial suppression of odd elements in the distribution of the sum of signal and idler photon numbers are observed.02/2012; -
Article: Entanglement between an auto-ionization system and a neighbor atom
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ABSTRACT: Entanglement between two electrons belonging to an auto-ionization system and a neighbor two-level atom produced by the dipole-dipole interaction is studied. The entanglement is quantified using the quadratic negativity of a bipartite system including the continuum of states. Suitable conditions for the generation of highly entangled states of two electrons are revealed. Internal structure of the entanglement is elucidated using the spectral density of quadratic negativity.01/2012; -
Article: Spatial properties of entangled photon pairs generated in nonlinear layered structures
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ABSTRACT: A spatial quantum model of spontaneous parametric down-conversion in nonlinear layered structures is developed expanding the interacting vectorial fields into monochromatic plane waves. A two-photon spectral amplitude depending on the signal- and idler-field frequencies and propagation directions is used to derive transverse profiles of the emitted fields as well as their spatial correlations. Intensity spatial profiles and their spatial correlations are mainly determined by the positions of transmission peaks formed in these structures with photonic bands. A method for geometry optimization of the structures with respect to efficiency of the nonlinear process is suggested. Several structures composed of GaN/AlN layers are analyzed as typical examples. They allow the generation of photon pairs correlated in several emission directions. Photon-pair generation rates increasing better than the second power of the number of layers can be reached. Also structures efficiently generated photon pairs showing anti-bunching and anti-coalescence can be obtained. Three reasons for splitting the correlated area in photonic-band-gap structures are revealed: zig-zag movement of photons inside the structure, spatial symmetry and polarization-dependent properties. Also spectral splitting can be observed in these structures.11/2011; -
Article: Photoelectron spectra in an autoionization system interacting with a neighboring atom
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ABSTRACT: Photoelectron ionization spectra of an autoionization system with one discrete level interacting with a neighbor two-level atom are discussed. The formula for long-time ionization spectra is derived. According to this formula, the spectra can be composed of up to eight peaks. Moreover, the Fano-like zeros for weak optical pumping are identified in these spectra. The conditional ionization spectra depending on the state of the neighbor atom exhibit oscillations at the Rabi frequency. Dynamical spectral zeros occurring once per the Rabi period are revealed in these spectra.PHYSICAL REVIEW A. 04/2011; 83(5). -
Article: Photoelectron ionization spectra in a system interacting with a neighbor atom
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ABSTRACT: Photoelectron ionization spectra of a system interacting with a neighbor two-level atom are investigated using the Laplace-transform method. These spectra are typically composed of several peaks. Photoelectron ionization spectra conditioned by the measurement on the two-level atom show oscillations at the Rabi frequency. The presence of spectral zeros occurring periodically with the Rabi period is predicted. This phenomenon is analyzed in detail.03/2011; -
Article: Randomly poled crystals as a source of photon pairs
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ABSTRACT: Generation of photon pairs from randomly poled nonlinear crystals is investigated using analytically soluble model and numerical calculations. Randomly poled crystals are discovered as sources of entangled ultra broad-band signal and idler fields. Their photon-pair generation rates scale linearly with the number of domains. Entanglement times as short as several fs can be reached. Comparison with chirped periodically-poled structures is given and reveals close similarity.01/2011; -
Article: Transverse coherence of photon pairs generated in spontaneous parametric down-conversion
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ABSTRACT: Coherence properties of the down-converted beams generated in spontaneous parametric down-conversion are investigated in detail using an iCCD camera. Experimental results are compared with those from a theoretical model developed for pulsed pumping with a Gaussian transverse profile. The results allow to tailor the shape of correlation area of the signal and idler photons using pump-field and crystal parameters. As an example, splitting of a correlation area caused by a two-peak pump-field spectrum is experimentally studied.03/2010; -
Article: Angular uncertainty of momentum correlations in parametric fluorescence
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ABSTRACT: Uncertainty in the determination of emission angles of signal and idler photons is investigated. The role of divergence of the pump beam, width of the pump spectrum, and size of the crystal is elucidated. Experimental data obtained by an iCCD camera are in a good agreement with a numerical model that provides angular and spectral characteristics of the signal and idler fields. Comment: 7 pages, 4 figures12/2009; -
Article: Emission of photon pairs at discontinuities of nonlinearity in spontaneous parametric down-conversion
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ABSTRACT: In order to fulfil the continuity requirements for electric- and magnetic-field amplitudes at discontinuities of chi2 nonlinearity additional photon pairs have to be emitted in the area of discontinuity. Generalized two-photon spectral amplitudes can be used to describe properties of photon pairs generated in this process that we call surface spontaneous parametric down-conversion. The spectral structure of such photon pairs is similar to that derived for photon pairs generated in the volume. Surface and volume contributions to spontaneous down-conversion can be comparable as an example of nonlinear layered structures shows. Comment: 11 pages, 8 figures10/2009; -
Article: Photon-pair generation in random nonlinear layered structures
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ABSTRACT: Nonlinearity and sharp transmission spectra of random 1D nonlinear layered structures are combined together to produce photon pairs with extremely narrow spectral bandwidths. Indistinguishable photons in a pair are nearly unentangled. Also two-photon states with coincident frequencies can be conveniently generated in these structures if photon pairs generated into a certain range of emission angles are superposed. If two photons are emitted into two different resonant peaks, the ratio of their spectral bandwidths may differ considerably from one and two photons remain nearly unentangled. Comment: 10 pages, 16 figures08/2009; -
Article: Random nonlinear layered structures as sources of photon pairs for quantum-information processing
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ABSTRACT: Random nonlinear layered structures have been found to be a useful source of photon pairs with perfectly indistinguishable un-entangled photons emitted into a very narrow spectral range. Localization of the interacting optical fields typical for random structures gives relatively high photon-pair fluxes. Superposing photon-pair emission quantum paths at different emission angles, several kinds of two-photon states (including states with coincident frequencies) useful in quantum-information processing can easily be generated. Comment: 4 pages, 5 figures07/2009; -
Article: Properties of entangled photon pairs generated in periodically poled nonlinear crystals
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ABSTRACT: Using a rigorous quantum model a comprehensive study of physical properties of entangled photon pairs generated in spontaneous parametric down-conversion in chirped periodically-poled crystals is presented. Spectral, temporal, as well as spatial characteristics of photon pairs are analyzed. Spectral bandwidths, photon-pair flux, and entanglement area can be effectively controlled by chirping. Quantification of entanglement between photons in a pair is given. Splitting of entanglement area in the transverse plane accompanied by spectral splitting has been revealed. Using the model temperature dependencies of the experimental intensity profiles reported in literature have been explained.02/2009; -
Article: Correlations in photon-numbers and integrated intensities in parametric processes involving three optical fields
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ABSTRACT: Two strongly-pumped parametric interactions are simultaneously realized in a single nonlinear crystal in order to generate three strongly correlated optical fields. By combining together the outputs of two of the three detectors measuring intensities of the generated fields, we obtain the joint photocount statistics between the single field and the sum of the other two. Moreover, we develop a microscopic quantum theory to determine the joint photon-number distribution and the joint quasi-distributions of integrated intensities and prove nonclassical nature of the three-mode state. Finally, by performing a conditional measurement on the single field, we obtain a state endowed with a sub-Poissonian statistics, as testified by the analysis of the conditional Fano factor. The role of quantum detection efficiencies in this conditional state-preparation method is discussed in detail. Comment: 9 pages, 14 figures01/2009; -
Article: Simple direct measurement of nonclassical joint signal-idler photon-number statistics and correlation area of twin photon beams
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ABSTRACT: The measurement of joint signal-idler photon-number distribution of a field obtained from spontaneous parametric downconversion using an intensified CCD camera is presented. It is shown that a classicality criterion is violated directly by the measured data. Characteristic dimensions of the area of correlation are determined in the same experimental setup.09/2007; -
Article: Antisymmetric entangled two-photon states generated in nonlinear GaN/AlN photonic-band-gap structures
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ABSTRACT: The properties of an entangled two-photon state antisymmetric in frequencies are studied. At a beam-splitter, two entangled photons are perfectly anti-correlated. In addition, they cannot be detected at the same time instant despite the fact that their detection times are confined to a narrow time window, i.e. they are temporally anti-bunched. Using nonlinear photonic-band-gap structures made of GaN/AlN, two schemes for generating such states are described. Comment: 5 pages, 7 PostScript figures08/2007; -
Article: Squeezed-light generation in a nonlinear planar waveguide with a periodic corrugation
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ABSTRACT: Two-mode nonlinear interaction (second-harmonic and second-subharmonic generation) in a planar waveguide with a small periodic corrugation at the surface is studied. Scattering of the interacting fields on the corrugation leads to constructive interference that enhances the nonlinear process provided that all the interactions are phase matched. Conditions for the overall phase matching are found. Compared with a perfectly quasi-phase-matched waveguide, better values of squeezing as well as higher intensities are reached under these conditions. Procedure for finding optimum values of parameters for squeezed-light generation is described. Comment: 14 pages, 14 figures08/2007; -
Article: Experimental joint signal-idler quasi-distributions and photon-number statistics for mesoscopic twin beams
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ABSTRACT: Joint signal-idler photoelectron distributions of twin beams containing several tens of photons per mode have been measured recently. Exploiting a microscopic quantum theory for joint quasi-distributions in parametric down-conversion developed earlier we characterize properties of twin beams in terms of quasi-distributions using experimental data. Negative values as well as oscillating behaviour in quantum region are characteristic for the subsequently determined joint signal-idler quasi-distributions of integrated intensities. Also the conditional and difference photon-number distributions are shown to be sub-Poissonian and sub-shot-noise, respectively. Comment: 7 pages, 6 figures08/2007; -
Article: Properties of entangled photon pairs generated in one-dimensional nonlinear photonic-band-gap structures
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ABSTRACT: We have developed a rigorous quantum model of spontaneous parametric down-conversion in a nonlinear 1D photonic-band-gap structure based upon expansion of the field into monochromatic plane waves. The model provides a two-photon amplitude of a created photon pair. The spectra of the signal and idler fields, their intensity profiles in the time domain, as well as the coincidence-count interference pattern in a Hong-Ou-Mandel interferometer are determined both for cw and pulsed pumping regimes in terms of the two-photon amplitude. A broad range of parameters characterizing the emitted down-converted fields can be used. As an example, a structure composed of 49 layers of GaN/AlN is analyzed as a suitable source of photon pairs having high efficiency. Comment: 14 pages, 23 figures04/2006; -
Article: Influence of pump-field scattering to nonclassical-light generation in a photonic band-gap nonlinear planar waveguide
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ABSTRACT: Optical parametric process occurring in a nonlinear planar waveguide can serve as a source of light with nonclassical properties. Properties of the generated fields are substantially modified by scattering of the nonlinearly interacting fields in a photonic band-gap structure inside the waveguide. A quantum model of linear operator amplitude corrections to amplitude mean-values provides conditions for an efficient squeezed-light generation as well as generation of light with sub-Poissonian photon-number statistics. Destructive influence of phase mismatch of the nonlinear interaction can fully be compensated using a suitable photonic-band gap structure inside the waveguide. Also an increase of signal-to-noise ratio of an incident optical field can be reached in the waveguide.01/2005;
Top co-authors
Institutions
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2011
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Palacký University of Olomouc
Olomouc, Olomoucky kraj, Czech Republic
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2009
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Academy of Sciences of the Czech Republic
- Fyzikální ústav
Praha, Hlavni mesto Praha, Czech Republic
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