Optimization of two-photon wave function in parametric down conversion by adaptive optics control of the pump radiation.

We present an efficient method for optimizing the spatial profile of entangled-photon wave function produced in a spontaneous parametric down conversion process. A deformable mirror that modifies a wavefront of a 404 nm CW diode laser pump interacting with a nonlinear ß-barium borate type-I crystal effectively controls the profile of the joint biphoton function. The use of a feedback signal extracted from the biphoton coincidence rate is used to achieve the optimal wavefront shape. The optimization of the two-photon coupling into two, single spatial modes for correlated detection is used for a practical demonstration of this physical principle.

High-speed and high-efficiency travelling wave single-photon detectors embedded in nanophotonic circuits.

Ultrafast, high-efficiency single-photon detectors are among the most sought-after elements in modern quantum optics and quantum communication. However, imperfect modal matching and finite photon absorption rates have usually limited their maximum attainable detection efficiency. Here we demonstrate superconducting nanowire detectors atop nanophotonic waveguides, which enable a drastic increase of the absorption length for incoming photons. This allows us to achieve high on-chip single-photon detection efficiency up to 91% at telecom wavelengths, repeatable across several fabricated chips. We also observe remarkably low dark count rates without significant compromise of the on-chip detection efficiency. The detectors are fully embedded in scalable silicon photonic circuits and provide ultrashort timing jitter of 18 ps. Exploiting this high temporal resolution, we demonstrate ballistic photon transport in silicon ring resonators. Our direct implementation of a high-performance single-photon detector on chip overcomes a major barrier in integrated quantum photonics.

Broadband source of polarization entangled photons.

A broadband source of polarization entangled photons based on type-II spontaneous parametric down conversion from a chirped PPKTP crystal is presented. With numerical simulation and experimental evaluation, we report a source of broadband polarization entangled states with a bandwidth of approximately 125 nm for use in quantum interferometry. The technique has the potential to become a basis for the development of flexible broadband sources with designed spectral properties.

Evaluation of polarization mode dispersion in a telecommunication wavelength selective switch using quantum interferometry.

A polarization mode dispersion (PMD) measurement of a commercial telecommunication wavelength selective switch (WSS) using a quantum interferometric technique with polarization-entangled states is presented. Polarization-entangled photons with a broad spectral width covering the telecom band are produced using a chirped periodically poled nonlinear crystal. The first demonstration of a quantum metrology application using an industrial commercial device shows a promising future for practical high-resolution quantum interference.

Precise evaluation of polarization mode dispersion by separation of even- and odd-order effects in quantum interferometry.

The use of quantum correlations between photons to separate measure even- and odd-order components of polarization mode dispersion (PMD) and chromatic dispersion in discrete optical elements is investigated. Two types of apparatus are discussed which use coincidence counting of entangled photon pairs to allow sub-femtosecond resolution for measurement of both PMD and chromatic dispersion. Group delays can be measured with a resolution of order 0.1 fs, whereas attosecond resolution can be achieved for phase delays.

Twin-photon confocal microscopy.

A recently introduced two-channel confocal microscope with correlated detection promises up to 50% improvement in transverse spatial resolution [Simon, Sergienko, Optics Express 18, 9765 (2010)] via the use of photon correlations. Here we achieve similar results in a different manner, introducing a triple-confocal correlated microscope which exploits the correlations present in optical parametric amplifiers. It is based on tight focusing of pump radiation onto a thin sample positioned in front of a nonlinear crystal, followed by coincidence detection of signal and idler photons, each focused onto a pinhole. This approach offers further resolution enhancement in confocal microscopy.

The correlation confocal microscope.

A new type of confocal microscope is described which makes use of intensity correlations between spatially correlated beams of light. It is shown that this apparatus leads to significantly improved transverse resolution.

[Studying the anti-ulcer activity of gastrobiol].

Gastrobiol--a new preparation comprising a mixture of lyophilized sea-buckthorn oil, vitamin U, and magnesium oxide, produces a pronounced antiulcerous action on the mucous membrane of the stomach and duodenum. The regenerative effect of gastrobiol is more pronounced than that of pure sea-buckthorn oil and methyluracil.

[Imaging of inflammatory foci with 99m technecium labeled antimicrobial oligopeptide].

A direct method using 99mtechnecium to label the synthetic antimicrobial oligopeptide ubiquicidine with a molecular mass of 1.7 kDa has been developed. The radiochemical purity of the resultant labeled compound was more than 98%. A combination of ubiquicidine and 99mtechnecium showed stability in blood plasma. The biological study indicated that the complex was renally excreted from blood flow rapidly (the half-life is 30 min). It accumulated in the experimental inflammatory focus of laboratory animals, peaking 1-2 hours after intravenous injection when the inflammatory focus/intact tissue ratio amounted up to 2.6-3.4, which could yield satisfactory abscess scintigrams. The findings make it possible to consider ubiquicidine as a promising compound for the design of radiopharmaceutical to image inflammatory foci.

Role of entanglement in two-photon imaging.

The use of entangled photons in an imaging system can exhibit effects that cannot be mimicked by any other two-photon source, whatever the strength of the correlations between the two photons. We consider a two-photon imaging system in which one photon is used to probe a remote (transmissive or scattering) object, while the other serves as a reference. We discuss the role of entanglement versus correlation in such a setting, and demonstrate that entanglement is a prerequisite for achieving distributed quantum imaging.

[Some aspects of cerebral autonomic vascular dystonia in patients with mitral valve prolapse]. / Osobennosti tserebral'noi vegetativno-sosudistoi distonii u bol'nykh s prolapsom mitral'nogo klapana.

Some aspects of origination of vegetovascular dystonia (VVD) in patients with mitral valve prolapse are considered. Forms of VVD manifestation are presented. Possible causes of VVD development accompanying mitral valve prolapse are analyzed. Original investigations have been carried out designed to study the condition of cerebral bloodflow in those patients suffering from VVD as a manifestation of mitral valve with the aid of the transcranial dopplerography technique. The authors have come to the conclusion that it is necessary for us to use a differentiated approach toward choosing a corresponding policy of managing patients.

Entanglement in cascaded-crystal parametric down-conversion.

We use spontaneous parametric down-conversion in a cascade of crystals, driven by a single monochromatic cw pump laser, to study the interference of entangled photon pairs. By changing the distance between the crystals, the observed quantum interference pattern varies continuously from that associated with a longer single crystal to that associated with independent emissions from two distinct crystals. Postselection via spectral filtering suppresses this phenomenon. These findings are expected to advance the field of quantum-state engineering.

Ellipsometric measurements by use of photon pairs generated by spontaneous parametric downconversion.

We present a novel interferometric technique for performing ellipsometric measurements. This technique relies on the use of a nonclassical optical source, namely, polarization-entangled twin photons generated by spontaneous parametric downconversion from a nonlinear crystal, in conjunction with a coincidence-detection scheme. Ellipsometric measurements acquired with this scheme are absolute; i.e., they do not require source and detector calibration.

Influence of hot-carrier luminescence from avalanche photodiodes on time-correlated photon detection.

We present the results of our time-resolved measurements of hot-carrier luminescence from passively quenched Geiger-mode avalanche photodiodes. In time-correlated photon-counting (TCPC) experiments, hot-carrier luminescence interferes overwhelmingly with the coincidence spectrum, which results in artifacts. This potential problem should be taken into account in setting up TCPC experiments.

Absolute standardless calibration of photodetectors based on quantum two-photon fields.

A new method of absolute calibration of photodetectors based on a nonclassical effect in nonlinear optics is discussed. The combined influence of a monochromatic flux of pump photons and quantum vacuum noise on a nonlinear crystal with no center of symmetry results in the appearance of rigorously correlated pairs of photons with continuous spectral distribution in the spontaneous parametric scattering of light (spontaneous parametric downconversion) process. The presence of an optical field in a broad spectral range created by the two-photon states (biphotons) makes it possible to develop a new method of measuring the spectral distribution of the absolute value of the quantum efficiency of photodetectors, both in photon counting and in analog regimes, that does not use any calibrated standard light sources (étalons). The feasibility of the method is demonstrated on different types of photomultiplier tube.

[Effect of sealed chamber conditions on the functional state of the human adrenal cortex (based on data from a study of the 11-hydroxycortico-steroid content in the blood plasma)]. / Vliianie uslovii germokamery na funktsional'noe sostoianie kory nadpochechnikov cheloveka (po dannym issledovaniia soderzhaniia 11-oksikortikosteroidov v plazme krovi.

The effect of a changed atmosphere, hypoxia, hypercapnia, their combinations and different motor activities on the adrenocortical function was studied in 36 test subjects kept in an 8 m3 altitude chamber. Human adaptation to the environmental changes developed with an active involvement of the adrenal cortex. The level and direction of the changes depended on both the force of the influences and on the initial state of the test subjects.