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Search Results: 1 - 10 of 208486 matches for " L. Krivitsky "
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Decreased Door to Balloon Time: Better Outcome for the Patient?  [PDF]
Steven B. Deutsch, Eric L. Krivitsky
World Journal of Cardiovascular Diseases (WJCD) , 2015, DOI: 10.4236/wjcd.2015.53007
Abstract: Recently the American College of Cardiology and the American Heart Association instituted DTB of 90 minutes or less as a class I recommendation. Since 2006 the percentage of patient meeting this metric has substantially increased, although research has demonstrated discrepancies in whether or not this objective is associated with better patient outcome. Here, we reviewed seven studies in effort to investigate the validity of the 90 minute or less door to balloon time. Our findings suggest that patient outcome in the setting of acute myocardial infarction is multifactorial, and while the door to balloon time metric likely has played a role in better patient outcomes it is not the sole factor in improving mortality rates.
Entanglement generation via phase-matched processes: different Bell states within the linewidth
G. Brida,M. V. Chekhova,M. Genovese,L. A. Krivitsky
Physics , 2007,
Abstract: It is shown, theoretically and experimentally, that at any type-II spontaneous parametric down-conversion (SPDC) phase matching, the decoherence-free singlet Bell state is always present within the natural bandwidth and can be filtered out by a proper spectral selection. Instead of the frequency selection, one can perform time selection of the two-photon time amplitude at the output of a dispersive fibre. Applications to quantum communication are outlined.
Dispersion spreading of polarization-entangled states of light and two-photon interference
G. Brida,M. V. Chekhova,M. Genovese,L. A. Krivitsky
Physics , 2006, DOI: 10.1134/S1054660X0704041X
Abstract: We study the interference structure of the second-order intensity correlation function for polarization-entangled two-photon light obtained from type-II collinear frequency-degenerate spontaneous parametric down-conversion (SPDC). The structure is visualised due to the spreading of the two-photon amplitude as two-photon light propagates through optical fibre with group-velocity dispersion (GVD). Because of the spreading, polarization-entangled Bell states can be obtained without any birefringence compensation at the output of the nonlinear crystal; instead, proper time selection of the intensity correlation function is required. A birefringent material inserted at the output of the nonlinear crystal (either reducing the initial o-e delay between the oppositely polarized twin photons or increasing this delay) leads to a more complicated interference structure of the correlation function.
Generation of different Bell states within the SPDC phase-matching bandwidth
G. Brida,M. V. Chekhova,M. Genovese,L. A. Krivitsky
Physics , 2007, DOI: 10.1103/PhysRevA.76.053807
Abstract: We study the frequency-angular lineshape for a phase-matched nonlinear process producing entangled states and show that there is a continuous variety of maximally-entangled states generated for different mismatch values within the natural bandwidth. Detailed considerations are made for two specific methods of polarization entanglement preparation, based on type-II spontaneous parametric down-conversion (SPDC) and on SPDC in two subsequent type-I crystals producing orthogonally polarized photon pairs. It turns out that different Bell states are produced at the center of the SPDC line and on its slopes, corresponding to about half-maximum intensity level. These Bell states can be filtered out by either frequency selection or angular selection, or both. Our theoretical calculations are confirmed by a series of experiments, performed for the two above-mentioned schemes of producing polarization-entangled photon pairs and with two kinds of measurements: frequency-selective and angular-selective.
Experimental realization of a measurement conditional unitary operation at single photon level and application to detector characterization
M. Genovese,G. Brida,M. Chekhova,M. Gramegna,L. Krivitsky,S. Kulik,M. L. Rastello
Physics , 2004, DOI: 10.1117/12.561416
Abstract: Our last experimental results on the realization of a measurement-conditional unitary operation at single photon level are presented. This gate operates by rotating by $90^o$ the polarization of a photon produced by means of Type-II Parametric Down Conversion conditional to a polarization measurement on the correlated photon. We then propose a new scheme for measuring the quantum efficiency of a single photon detection apparatus by using this set-up. We present experimental results obtained with this scheme compared with {\it traditional} biphoton calibration. Our results show the interesting potentiality of the suggested scheme.
Electronic noise-free measurements of squeezed light
Leonid A. Krivitsky,Ulrik L. Andersen,Ruifang Dong,Alexander Huck,Christoffer Wittmann,Gerd Leuchs
Physics , 2008, DOI: 10.1364/OL.33.002395
Abstract: We study the implementation of a correlation measurement technique for the characterization of squeezed light. We show that the sign of the covariance coefficient revealed from the time resolved correlation data allow us to distinguish between squeezed, coherent and thermal states. In contrast to the traditional method of characterizing squeezed light, involving measurement of the variation of the difference photocurrent, the correlation measurement method allows to eliminate the contribution of the electronic noise, which becomes a crucial issue in experiments with dim sources of squeezed light.
Conditioned Unitary Transformation on biphotons
G. Brida,M. Chekhova,M. Genovese,M. Gramegna,L. Krivitsky,S. Kulik
Physics , 2003, DOI: 10.1103/PhysRevA.70.032332
Abstract: A conditioned unitary transformation ($90^o$ polarization rotation) is performed at single-photon level. The transformation is realized by rotating polarization for one of the photons of a polarization-entangled biphoton state (signal photon) by means of a Pockel's cell triggered by the detection of the other (idler) photon after polarization selection. As a result, polarization degree for the signal beam changes from zero to the value given by the idler detector quantum efficiency. This result is relevant to practical realization of various quantum information schemes and can be used for developing a new method of absolute quantum efficiency calibration.
Orthogonality of Biphoton Polarization States
M. V. Chekhova,L. A. Krivitsky,S. P. Kulik,G. A. Maslennikov
Physics , 2003, DOI: 10.1103/PhysRevA.70.053801
Abstract: Orthogonality of two-photon polarization states belonging to a single frequency and spatial mode is demonstrated experimentally, in a generalization of the well-known anti-correlation 'dip' experiment.
Correlation Measurement of Squeezed Light
Leonid A. Krivitsky,Ulrik L. Andersen,Ruifang Dong,Alexander Huck,Christoffer Wittmann,Gerd Leuchs
Physics , 2009, DOI: 10.1103/PhysRevA.79.033828
Abstract: We study the implementation of a correlation measurement technique for the characterization of squeezed light which is nearly free of electronic noise. With two different sources of squeezed light, we show that the sign of the covariance coefficient, revealed from the time resolved correlation data, is witnessing the presence of squeezing in the system. Furthermore, we estimate the degree of squeezing using the correlation method and compare it to the standard homodyne measurement scheme. We show that the role of electronic detector noise is minimized using the correlation approach as opposed to homodyning where it often becomes a crucial issue.
Go and return propagation of biphotons in fiber and polarization entanglement
G. Brida,M. V. Chekhova,M. Genovese,L. A. Krivitsky,E. Predazzi
Physics , 2006,
Abstract: Propagation of entangled photons in optical fiber is one of the fundamental issues for realizing quantum communication protocols. When entanglement in polarization is considered, arises the problem of compensating for the fiber effect on photons polarization. In this paper we demonstrate an effective solution where a Faraday mirror allows to cancel undesired effects of polarization drift in fiber. This technique is applied to a protocol for generating Bell states by a narrow temporal selection of the second-order intensity correlation function.
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