Vol 38, No 2 (2017)

We describe the main features of resonances in scattering, determining the resonances in view of the theory of collisions in a two-body system, as well as the resonances emerging as a result of collisions in a few-body system. We analyze regularities in the emergence of such resonances and their characteristics. We discuss the results of calculations of the resonant processes occurring during collisions of electrons with diatomic molecules, in view of the quantum theory of scattering in a few-body system based on the Faddeev–Yakubovsky equations.

We consider a four-level atom (FLA) interacting with a field mode that is initially in a coherent state associated with a generalized Heisenberg algebra (CSGHA). The dynamical behavior of quantum entropy, the Pancharatnam phase, and the Mandel parameter are investigated. The statistical and nonclassical properties of the field in regard to its CSGHA are discussed through the evolution of the Mandel parameter, and the effects of the initial atomic state position and time-dependent coupling given in terms of atomic speed and acceleration are examined. The results show that the CSGHA strength and time-dependent coupling based on the atomic speed and acceleration have the potential to affect the time evolution of the entanglement, the Pancharatnam phase, and the Mandel parameter.

We describe the ambiguous discrimination of two quantum states using the receiver operation characteristics (ROC) analysis, an approach prevalent in classical statistics. We obtain a new comprehensive picture of this otherwise well-studied problem, in which various important quantities such as the fidelity and the trace distance of two quantum states obtain an operational meaning in a very intuitive way. In addition, we introduce a new quantity which is a generalization of the classical Bhattacharyya coefficient to the quantum scenario different from the one prevalently used in the literature. This derives logically from the ROC representation and provides an alternative characterization of the similarity of two quantum states. We describe some its properties, including the monotony under completely positive maps.

We present the results of theoretical and numerical research on the burning of spherical thermonuclear targets under conditions where the peripheral part of the deuterium–tritium plasma is mixed with the surrounding inert substance of the target ablator; this takes place as a result of the development of hydrodynamic instabilities during the process of compression under the laser-pulse action. We investigate targets with parameters corresponding to the irradiation conditions given by the Russian Project on Megajoule Facility with an energy of about 2 MJ. For the investigated class of targets conforming to a large part of the evaporated ablator substance (no less than 75% of its initial mass), we show that the mixing does not spread to the region of strongly compressed fuel, which introduces a determining contribution to the propagation of the burning wave, not to speak of the central part of hot plasma responsible for the initiation of the burning wave. For this reason, the negative effect of the mixing on the burning efficiency of such targets is insignificant, and, as compared with the target burn in the absence of mixing, the released fusion energy decreased by no more than 20%.

Precision drilling can improve the microhole quality by yielding a reduced recast layer thickness and no heat-affected zone. We evaluate the quality of the helical drilled holes, e.g., the recast layer, microcracks, and circularity by scanning electron microscopy. We investigate the overlap rate of the laser beam and find its influence on the efficiency of through-hole machining. The microhole entrance, exit, and side walls are smooth, without an accumulation of spattering material and the formation of a recast layer and microcracks. Optimum parameters for drilling through holes on alloy material GH2132 are a thickness of 500 μm, a laser fluence of 3.06 · 10⁻² J/mm², a pulse repetition rate of 100 kHz, and a helical speed of 60 rev/s. The tapering phenomenon can be avoided by using a helical system with a rotating stage, and the hole circularity is fairly good. Picosecond laser helical drilling can be effective for manufacturing microholes with a high quality. The development of high-power picosecond laser would promote picosecond laser drilling with future industrial relevance.

We demonstrate experimentally all-optical wavelength conversion based on four-wave mixing in dispersion-engineered silicon nanowaveguides with a picosecond pulse pump. We find that the conversion efficiency is significantly limited by nonlinear losses induced by the two-photon absorption and freecarrier absorption. Using a picosecond pulse pump centered at 1,550 nm, we show that the input continuous-wave signals can efficiently be converted into a broadband idler pulse in silicon waveguides with various dimensions. Conversion efficiencies versus signal wavelengths are different for silicon waveguides with different dimensions due to the variation in the phase mismatch; we obtain a conversion efficiency of – 32 dB in silicon nanowaveguides with a length of 5.8 mm. Such on-chip optical wavelength converters can find important potential applications in highly-integrated optical circuits for all-optical ultrafast signal processing.