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Search Results: 1 - 10 of 1847 matches for " Leonid Krivitsky "
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Measurement of photon correlations with multipixel photon counters
Dmitry Kalashnikov,Leonid A. Krivitsky
Physics , 2014, DOI: 10.1364/JOSAB.31.000B25
Abstract: Development of reliable photon number resolving detectors (PNRD), devices which are capable to distinguish 1,2,3.. photons, is of a great importance for quantum optics and its applications. A new class of affordable PNRD is based on multipixel photon counters (MPPC). Here we review results of experiments on using MPPCs for direct characterization of squeezed vacuum (SV) states, generated via parametric downconversion (PDC). We use MPPCs to measure the second order normalized intensity correlation function (g^(2)) and directly detect the two-mode squeezing of SV states. We also present a method of calibration of crosstalk probability in MPPCs based on g^(2) measurements of coherent states.
Spectrally Resolved Quantum Tomography of Polarization Entangled States
Dmitry A. Kalashnikov,Leonid A. Krivitsky
Physics , 2010, DOI: 10.1088/1367-2630/12/9/093040
Abstract: We study broadband polarization entangled states generated within the line width of type-II Spontaneous Parametric Down Conversion (SPDC). Applying a complete quantum polarization tomography protocol at arbitrary combination of frequency and angular sideband modes we reveal a complex structure of non-degenerate non-collinear polarization entangled states generated within the SPDC line width. It is demonstrated that simultaneous compensation of longitudinal and transverse walk off leads to homogenizing the structure of polarization entanglement.
Tailoring polarization entanglement in anisotropy-compensated SPDC
Giorgio Brida,Marco Genovese,Maria V. Chekhova,Leonid A. Krivitsky
Physics , 2007, DOI: 10.1103/PhysRevA.77.015805
Abstract: We show that the angular spectrum of type-II SPDC contains a continuum of maximally entangled states. For the realization of a bright source of entangled two-photon states, a standard technique is to compensate for the transverse walk-off in the production crystal. We demonstrate that polarization entangled states can be effectively engineered by generalizing this approach. Our method allows to considerably enrich the set of generated entangled states with a controlled tailoring them.
Imaging of Spatial Correlations of Two-Photon States
Ivan B. Bobrov,Dmitry A. Kalashnikov,Leonid A. Krivitsky
Physics , 2014, DOI: 10.1103/PhysRevA.89.043814
Abstract: We use a fiber based double slit Young interferometer for studying the far-field spatial distribution of the two-photon coincidence rate (coincidence pattern) for various quantum states with different degree of spatial entanglement. The realized experimental approach allows to characterize coincidence patterns for different states without any modifications of the setup. Measurements were carried out with path-entangled and separable states. The dependence of the coincidence pattern on the phase of the interferometer for superposition and separable states was studied. The results have implications for using of nonclassical light in multiphoton imaging, quantum lithography, and studies of phase decoherence.
Crosstalk calibration of multi-pixel photon counters using coherent states
Dmitry A. Kalashnikov,Si-Hui Tan,Leonid A. Krivitsky
Physics , 2012, DOI: 10.1364/OE.20.005044
Abstract: We present a novel method of calibration of crosstalk probability for multi-pixel photon counters (MPPCs) based on the measurement of the normalized second-order intensity correlation function of coherent light. The method was tested for several MPPCs, and was shown to be advantageous over the traditional calibration method based on the measurements of the dark noise statistics. The method can be applied without the need of modification for different kinds of spatially resolved single photon detectors.
Experimental observation of double-peak structure of coincidence spectra in ultra-fast Spontaneous Parametric Down Conversion
Dmitry A. Kalashnikov,Mikhail V. Fedorov,Leonid A. Krivitsky
Physics , 2012, DOI: 10.1103/PhysRevA.87.013803
Abstract: The requirement on the symmetry of the biphoton wave function results in a double peak structure of the coincidence spectra of Spontaneous Parametric Down Conversion (SPDC) [1]. In this work we report the experimental observation of this effect by careful tailoring parameters of the SPDC crystal, the ultra-fast pump laser, and the measurement setup. The results are shown to be relevant to quantum state engineering of ultra-fast polarization-, or frequency-entangled mixed states.
Method of targeted delivery of laser beam to isolated retinal rods by fiber optics
Nigel Sim,Dmitri Bessarab,C. Michael Jones,Leonid A. Krivitsky
Physics , 2013,
Abstract: A method of controllable light delivery to retinal rod cells using an optical fiber is described. Photo-induced current of the living rod cells was measured with the suction electrode technique. The approach was tested with measurements relating the spatial distribution of the light intensity to photo-induced current. In addition, the ion current responses of rod cells to polarized light at two different orientation geometries of the cells were studied.
Locomotion of microspheres for super-resolution imaging
Leonid A. Krivitsky,Jia Jun Wang,Zengbo Wang,Boris Lukiyanchuk
Physics , 2013, DOI: 10.1038/srep03501
Abstract: Super-resolution imaging using sub-diffraction field localization by micron sized transparent beads (microspheres) was recently demonstrated [1]. Practical applications in microscopy require control over the positioning of the microspheres. We present a simple method of positioning and controllable movement of a microsphere by using a glass micropipette. This allows sub-diffraction imaging at arbitrary points in three dimensions, as well as the ability to track moving objects. The results are relevant to a broad scope of applications, including sample inspection, and bio-imaging.
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.
Two-Photon Polarization Interference for Pulsed SPDC in a PPKTP Waveguide
Malte Avenhaus,Maria V. Chekhova,Leonid A. Krivitsky,Gerd Leuchs,Christine Silberhorn
Physics , 2008, DOI: 10.1103/PhysRevA.79.043836
Abstract: We study the spectral properties of Spontaneous Parametric Down Conversion in a periodically poled waveguided structure of KTP crystal pumped by ultra-short pulses. Our theoretical analysis reveals a strongly multimode and asymmetric structure of the two-photon spectral amplitude for type-II SPDC. Experimental evidence, based on Hong-Ou-Mandel polarization interference with narrowband filtering, confirms this result.
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