Measurement of the biphoton second-order correlation function with analog detectors.

An experimental scheme and data processing approaches are proposed for measuring by analog photo detectors the normalized second-order correlation function of the biphoton field generated under spontaneous parametric down-conversion. Obtained results are especially important for quantum SPDC-based technologies in the long-wave spectral ranges, where it is difficult to use the single-photon detector at least in one of the two biphoton channels. The methods of discrimination of analog detection samples are developed to eliminate the negative influence of the detection noises and get quantitatively true values of both the correlation function and the detector quantum efficiency. The methods are demonstrated depending on whether two single-photon avalanche photo detectors are used in both SPDC channels, or at least one single-photon detector is replaced by a photo-multiplier tube which cannot operate in the photon counting mode.

Direct test of the "quantum vampire's" shadow absence with use of thermal light.

The counterintuitive nature of quantum physics leads to a number of paradoxes. One of them is a "quantum vampire" effect [Fedorov et al., Optica2, 112 (2015)OPTIC82334-253610.1364/OPTICA.2.000112], which means that the photon annihilation in a part of a large beam does not change the shape of the beam profile (i.e., does not cast a shadow), but it may change the total beam intensity. Previously, this effect was demonstrated just in a simplified double-mode regime [Fedorov et al., Optica2, 112 (2015), OPTIC82334-253610.1364/OPTICA.2.000112 Katamadze et al., Optica5, 723 (2018)OPTIC82334-253610.1364/OPTICA.5.000723]. In this Letter, a direct test of shadow absence after the photon annihilation was performed using the thermal state of light at the input.

Luminescence in germania-silica fibers in a 1-2 µm region.

We analyze the origins of the luminescence in germania-silica fibers with high germanium concentration (about 30 mol.% GeO2) in the region of 1-2 µm with a laser pump at the wavelength 532 nm. We show that such fibers demonstrate the high level of luminescence which unlikely allows the observation of photon triplets, generated in a third-order spontaneous parametric downconversion process in such fibers. The only efficient approach to the luminescence reduction is the hydrogen saturation of fiber samples; however, even in this case, the level of residual luminescence is still too high for three-photon registration.

Beating the Abbe diffraction limit in confocal microscopy via nonclassical photon statistics.

We experimentally demonstrate quantum enhanced resolution in confocal fluorescence microscopy exploiting the nonclassical photon statistics of single nitrogen-vacancy color centers in diamond. By developing a general model of superresolution based on the direct sampling of the kth-order autocorrelation function of the photoluminescence signal, we show the possibility to resolve, in principle, arbitrarily close emitting centers.

[Acetylsalicylic acid and kurantil in the prevention of pregnancy complications in glomerulonephritis and hypertension]. / Atsetilsalitsilovaia kislota i kurantil v profilaktike oslozhnenii beremennosti pri glomerulonefrite i gipertonicheskoi bolezni.

A controlled clinical trial included 64 pregnant females suffering from chronic glomerulonephritis (CGN) and hypertension: 31 patients received acetylsalicylic acid (ASA) in a dose 125 mg/day and curantyl (150-225 mg/day) from gestation week 12-19 till delivery, 33 control females were not given the drugs. Prenatal care and labour management were similar. Total number of the complications (fetal and natal deaths, preterm labour, intrauterine fetal retardation, late toxicosis, premature detachment of normally located placenta) as well as the number of pregnancies with complications were less in the test group. The same was true for the second pregnancies versus the first ones when ASA and curantyl were not given. It is suggested that low-dose ASA plus curantyl improve placental circulation eventually resulting in less frequent occurrence of pregnancy complications and in better pregnancy outcomes in CGN and hypertensive women.