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Изучаются аппроксимации Эрмита-Паде второго типа для функции Вейля, соответствующей ортогональным многочленам Мейкснера, и ее производной. Найдено предельное распределение нулей общих знаменателей этих аппроксимаций - многочленов совместной ортогональности с дискретной мерой. Доказано, что предельная мера является единственным решением задачи равновесия с матрицей Анжелеско теории логарифмического потенциала. Обнаружен эффект выталкивания части нулей с вещественной оси на некоторую кривую в комплексной плоскости. Получен явный вид предельной меры в терминах алгебраических функций. Библиография: 10 названий.

—Articulatory event detectors, i.e., detectors of transitions from one articulatory state to another, are formed on based on analysis of spectral–temporal inhomogeneities in a speech signal. A triad such as /pause–fricative–vowel/ is segmented and recognized in the space of the principal components of the response spectrum of the detector of the pause–fricative transition, the spectrum of the fricative at its peak energy, and the response spectrum of the detector of the fricative–vowel transition at this detector’s peak. The root-mean-square error with respect to manual marking for the onset of fricatives is, on average, about 12 ms, and for the moment of the fricative–vowel transition, about 5 ms. Triad recognition errors with the same fricative and different subsequent vowels, as well as triad recognition errors differing only in the presence or absence of vocal excitement, constituted a few percent.

Introduction. The most urgent tasks of road construction is to improve the sustainability of the roadway, on which the durability of the road surface largely depends and vibration processes are widely used. Moreover, the mechanization of production processes in construction, the growth of power and speed of technological equipment lead to increasing in dynamic loads on its parts and assemblies. To reduce the dynamic loads in the parts and assemblies of construction machines and equipment, as well as to reduce the negative impact of vibration on the staff, it is necessary to isolate the vibration-generating units and assemblies from the base part of the machine.Materials and methods. The vibro-supports of various designs are used to isolate the vibro-active elements of machines. The authors propose the vibration support design with a quasi-zero stiffness effect, in which the rubber-cord shell of the I-09 type is used as a supporting elastic element, and also the toroid-shaped rubber shell that relies on four identical support segments. In addition, each segment represents the fourth part of the annular tube and cut into two parts by a vertical cylindrical plane. The outer parts of each segment are connected with hinges to the posts and fixed on the support base, and the inner parts of each segment are also connected to a supporting elastic element and a vibration-proof mass is connected by means of hinges. The authors describe the working procedure of the proposed construction and compile the mathematical model of vibration support with a quasi-zero stiffness effect.Results. As a result, the equations of the mathematical model are performed in Matlab with the Simulink extension. The values of the equations are used to plot the strain variation of the toroidal shell of the corrector, which depends on the mass displacement, as well as on the motion patterns of a vibrationproof object of 100 kg for variants of the carrier spring without additional volume and with additional volume of the 1 - 10 Hz pneumatic spring carrier.Discussion and conclusions. The authors determine the pressure in the corrector shell, depending on the isolated object mass. Therefore, the deformation of the corrector shell could be provided with a support structure due to the elasticity of the shell material. The usage of additional volume together with the stiffness corrector allows to obtain a wider area of the load characteristics with quasi-zero stiffness and to improve the vibration-protective properties of the support.

On a comprehensive speech database, speaker recognition characteristics are compared under the usage of various voice-source models. Inverse problems to find a source via vowel speech segments are solved on the base of a special speech-production model and voice-source models (A-source, piecewise-linear source, nonparametric source, and source found by means of the spectral relation method). In the first stage, we find the pulses such that the relative residuals of their segmented and their theoretical analogs computed by means of the speech-production model are less than 0.25. For the selected pulses, a posteriori estimates of the error of their determining are computed and the final selection of the source pulses is performed: for the recognition procedure, we leave only pulses with a posteriori estimates of the error less than the accepted level 0.3. In the space of parameters found for each source model, a statistical model is created for each speaker and the recognition is performed. For the speaker recognition with respect to one vowel, the mean error is approximately equal to 66% for the piecewise-linear source, 61% for the spectral relation method, and 33% for the A-source.

Because of the low sensitivity of a thulium optical clock to black-body radiation and good accuracy and stability estimations, it is considered as a promising transportable optical clock. One of the leading systematic effects for Tm clock transition, i.e., the second-order Zeeman effect, can be canceled by probing two clock transitions between different hyperfine levels of ground and metastable states during clock operation. Herein, we demonstrate efficient optical pumping into the ${m}_{F}=0$ state of both ground hyperfine levels using single-frequency radiation at 418.8 nm. We prepared the atoms in both target states simultaneously and excited two clock transitions alternately. The resulting population of ${m}_{F}=0$ states of ground hyperfine levels was 36% and 3.8% of the initial number of atoms with less than 4% and 0.4% on nonzero magnetic sublevels, respectively. We performed numerical simulations of the optical pumping process, which is able to explain experimental results well.

Properties of silicon-vacancy (SiV) colour centres in ultra-nanosize diamonds are studied. Nanodiamonds are obtained at a high temperature and pressure, which induced transformations in mixtures of organic and hetero-organic compounds without metal-catalysts. The size distribution of grown nanodiamonds is determined by the methods of transmission electron microscopy and atomic-force microscopy, as well as by using the model of phonon spatial localisation. In addition, Raman spectra of various nanodiamonds and luminescence properties of SiV-centres are investigated.

The vocal source and the pulse shape of the glottal flow are determined through the regularized ratio of the speech signal spectra at the intervals of the open and closed vocal slit within each period of the fundamental tone. Three databases were used: Russian numerals for 216 men and 177 women, the base obtained by converting the Russian database by the codec on 9.2 kbps, and the TIMIT database. The pitch period and 7 coefficients for the principal components of the glottal flow provide an average error of recognizing males below 8% for a sequence of 6 vowels. The minimum average recognition error for the initial base of Russian numerals for females makes about 15%, for males in the codec database makes about 15%, and for males in the TIMIT makes about 44%. The minimum average error of males’ recognition in the space of 7 coefficients for the principal components in the Russian database makes about 26%, but about 27% of the speakers have an average error of less than 10%.

The paper considers the inverse problem of finding the shape of a voice-source pulse from a specified segment of a speech signal using a special mathematical model that relates these quantities. A variational method for solving the formulated inverse problem for two new parametric classes of sources is proposed: a piecewise-linear source and an A-source. The error in the obtained approximate solutions of the inverse problem is considered, and a technique to numerically estimate this error is proposed, which is based on the theory of a posteriori estimates of the accuracy in solving ill-posed problems. A computer study of the adequacy of the proposed models of sources, and a study of the a posteriori estimates of the accuracy in solving inverse problems for such sources were performed using various types of voice signals. Numerical experiments for speech signals showed satisfactory properties of such a posteriori estimates, which represent the upper bounds of possible errors in solving the inverse problem. The estimate of the most probable error in determining the source-pulse shapes for the investigated speech material is on average ~7%. It is noted that the a posteriori accuracy estimates can be used as a criterion for the quality of determining the voice-source pulse shape in the speaker-identification problem.

The asymptotic behavior of the Hermite–Pade approximants of the first type for two beta functions are studied. The results are expressed in terms of equilibrium problems of logarithmic potential theory and in terms of meromorphic functions on Riemann surfaces.

The inverse problem with respect to functions proportional to a voice source and volume velocity of the air flow through the glottis is solved as follows: we compute the inverse Fourier transform of the regularized fraction of short-term speech-signal spectra at intervals with an opened (closed) glottis, minimizing the optimality criterion with respect to the regularization parameter and the glottis opening (closing) time. The optimality criterion for solutions includes the values of the volume velocity and its time derivative at the ends of the interval with an opened glottis and the total value of the negative volume velocity. To obtain an empirical error estimate for the solution, experiments using synthesized signals with various parameters, direct measurements of the glottis, and signals synchronously recorded through pairs of microphones of different types are performed. The most probable determination error for the volume velocity is less than 5% for synthetic sources; if the area of the glottis of the source is measured experimentally, then the said error is about 10%. The discrepancy of solutions for the same signal synchronously recorded through a pair of microphones of different types is less than 10%.

The extrema of the logarithmic derivative of the mean energy of a voice signal in the frequency range of 1000–3000 Hz are used to determine the instants of opening and closure of the glottis. The inaccuracy of analysis is estimated with the Arctic CMU database, which contains synchronous recordings of speech signals and electro-glottograms. The estimates of the instants of opening and closure of the glottis, found by the developed algorithm, are compared with the instants of the maximum and minimum of the derivative from electro-glottogram signals, which are taken as the “true” instants. The mean square deviation of the glottal opening instant from the extrema of the derivative from the electro-glottogram signals for different speakers is in the range of 1.03–1.64 ms. The error rate of a false estimate of the glottal opening instant is from 0.01 to 0.14%, and the error rate of omission is from 0.42 to 2.38%. An error-detection algorithm is developed. The mean square deviation with an relative—to the period of the fundamental tone—error in detecting the glottal opening instant is in the range of 13–18% for the most probable error from 0 to +5%.

In this paper, we realize growth of the delta doped layer (3 nm thick) with high concentration of nitrogen atoms (about 1.4 × 1019 cm−3) during CVD diamond growth process. We experimentally investigate the distribution of the nitrogen inside the grown layer and formation of the NV centers during such growth. Using confocal microscopy, we analyze the spatial distribution of the NV centers and investigate the formation efficiency of the NV centers in delta doped layers. The spatial distribution is measured by two methods, using second-order correlation function and emission volume analysis, and NV center concentration is found to be 3.9 ± 0.6 and 2.7 ± 0.2 μm-2 consequently. The divergence between the methods is discussed. As-grown NV centers formation efficiency was found to be 30 times lower than in the case of uniform doped diamond growth. Nevertheless, coherence time of an electron spin for a single NV center inside the delta layer was found to be around 1 μs which is quite reasonable given the concentration of the nitrogen in the sample.

Ensembles of nitrogen-vacancy color centers in diamond hold promise for ultra-precise magnetometery, competing with superconducting quantum interference device detectors. Sensor and metrology applications for situations involving high sensitivity require efficient manipulation of the nitrogen-vacancy color centers electronic spins within large volume. Thus, the design of microwave antennas providing a uniform and strong microwave magnetic field over a relatively large volume is on a high demand. In this paper we report different antenna designs based on low loss high permittivity dielectric materials for coherent manipulation of a large ensemble of nitrogen-vacancy color centers in diamond. The operational principle of the proposed antennas is based on excitation of transverse electric (TE) or hybrid electromagnetic (HEM) modes of dielectric resonators. The first antenna design is based on TE01 mode excited inside the resonator made on a ceramic with permittivity of 80. The uniformity of the microwave magnetic field generated by the antenna was verified by measurement of the optically detected magnetic resonance and Rabi frequency in a high-density ensemble of nitrogen-vacancy color centers placed in the center bore of the antenna. Rabi frequency of 10 MHz in a volume of 7 cubic millimeters with a standard deviation of less than 1% at 5 W pump power has been measured at the room temperature. This is enough to coherently excite all color centers in commercially available diamond plates at room temperature. The second antenna design is based on HEM11δ mode excited in the ceramic resonator characterized by the permittivity of 235. The numerical simulations predict the Rabi frequency value of 34.85 MHz in a volume of 6 cubic millimeters with a standard deviation of less than 5% at 5 W pump power. The obtained result paves the way to improve the sensitivity of cutting-edge nitrogen-vacancy color centers based magnetometers by several orders of magnitude, practically reaching superconducting quantum interference device detectors level of sensitivity.

Minimization of internal degrees of freedom is an important step in the cooling of atomic species to degeneracy temperature. Here, we report on the loading of 6*10^5 thulium atoms optically polarized at maximum possible magnetic quantum number mf=-4 state into dipole trap operating at 532 nm. The purity of polarizations of the atoms was experimentally verified using a Stern-Gerlach-type experiment. Experimental measured polarization of the state is 3.91(26).

Ensembles of nitrogen-vacancy color centers in diamond hold promise for ultra-precise magnetometry, competing with superconducting quantum interference device detectors. By utilizing the advantages of dielectric materials, such as very low losses for electromagnetic field, with the potential for creating high Q-factor resonators with strong concentration of the field within it, we implemented a dielectric resonator antenna for coherent manipulation of a large ensemble of nitrogen-vacancy centers in diamond. We reached average Rabi frequency of 10 MHz in a volume of 7 mm3 with a standard deviation of less than 1% at a moderate pump power. The obtained result enables use of large volume low nitrogen-vacancy concentration diamond plates in modern nitrogen-vacancy magnetometers thus improving sensitivity via larger coherence time and higher optical detected magnetic resonance contrast.

NV centers ensemble have proven to be sensitive and versatile sensor platform for many applications such as magnetometry [1, 2], electric field sensing [3], thermometry [4] and rotation sensing [5]. The tradeoff between concentration of NVs and coherence lifetime of the electronic spin limits the maximum sensitivity of such devices. Recently usage of quantum memory associated with nuclear spins nearby NV center was shown to dramatically increase the sensitivity via accumulation of the sensed signal in memory [6]. This way sensing on single NV center can benefit a lot from nearby environment, but extension of this technique on atomic ensemble is still quite challenging. Here we present a versatile platform for quantum manipulation with a highly dense NV ensemble in HPHT diamond plates. In our work, we demonstrate several approaches to initialize quantum memory in regular magnetic fields, manipulation of quantum memory, and reading the quantum information from it. Also, we carefully study decoherence rate in our sample using “Echo” and “FID” techniques. We believe the key sources of decoherence in our samples are natural abundance of 13C isotopes and P1 centers. To better understand and clarify contribution of each component we studied number of samples with different defect concentrations. Besides, multifrequency resonances were investigated in NV ensembles both experimentally and theoretically. Previously multifrequency resonances were studied in single NV center system at various combinations of transverse and longitudinal MW and RF field allowing to detect many-photon transitions in electron spin subshell[7]. Here we provide study of additional series of resonances achieved in NV ensemble configuration with a close look to the many-photon transitions both in electron and nuclear eigen states. This resonances could be utilized to hyperpolarize the nuclear spin environment in diamond.

Second-stage laser cooling of thulium atoms at the 530.7 nm transition with a natural linewidth of 350 kHz offers an interesting possibility to study different regimes of a magneto-optical trap (MOT). The intermediate value of the spectral linewidth of the cooling transition allows the observation of three distinct regimes depending on intensity and detuning of the cooling beams. Namely, the "bowl-shaped" regime when light pressure force competes with gravity, the "double structure" regime with interplay between Doppler and polarization-gradient (sub-Doppler) cooling, and the "symmetric" regime when Doppler cooling dominates over sub-Doppler cooling and gravity. The polarization-gradient cooling manifests itself by a two-temperature momentum distribution of atoms resulting in a double-structure of the spatial MOT profile consisting of a cold central fraction surrounded by a hot halo. We studied the "double structure" regime at different saturation parameters and compared observations with calculations based on semiclassical and quantum approaches. The quantum treatment adequately reproduces experimental results if the MOT magnetic field is properly taken into account., Comment: 7 pages, 6 figures

Integration of solid-state quantum emitters such as NV center in diamond with tapered optical fiber is demanded by number of applications ranging from sensing and imaging to quantum communications and computations. Nevertheless, utilization of a single NV center coupled with an optical fiber meets significant challenge of fiber fluorescence that can considerably mask emission of the quantum object. In this paper, we analyze main sources of such fluorescence for the case of NV center coupled to tapered single mode optical fiber and discuss possible ways of improving signal to noise ratio in this case.

NV center in diamond is attracting a lot of attention in quantum information processing community [1]. Been spin system in clean and well-controlled environment of diamond it shows outstanding performance as quantum memory even at room temperature, spin control with single shot optical readout and possibility to build up quantum registers even on single NV center. Moreover, NV centers could be used as high-resolution sensitive elements of detectors of magnetic or electric field, temperature, tension, force or rotation. For all of these applications collection of the light emitted by NV center is crucial point. There were number of approaches suggested to address this issue, proposing use of surface plasmoms [2], manufacturing structures in diamond [3] etc. One of the key feature of any practically important interface is compatibility with the fiber technology. Several groups attacking this problem using various approaches. One of them is placing of nanodiamonds in the holes of photonic crystal fiber [4], another is utilization of AFM to pick and place nanodiamond on the tapered fiber[5]. We have developed a novel technique of placing a nanodiamond with single NV center on the tapered fiber by controlled transfer of a nanodiamond from one “donor” tapered fiber to the “target” clean tapered fiber. We verify our ability to transfer only single color centers by means of measurement of second order correlation function. With this technique, we were able to double collection efficiency of confocal microscope. The majority of the factors limiting the collection of photons via optical fiber are technical and may be removed allowing order of magnitude improved in collection. We also discuss number of extensions of this technique to all fiber excitation and integration with nanostructures. References: [1] Marcus W. Doherty, Neil B. Manson, Paul Delaney, Fedor Jelezko, Jorg Wrachtrup, Lloyd C.L. Hollenberg , " The nitrogen-vacancy colour centre in diamond," Physics Reports, vol. 528, no. 1, p. 1–45, 2013. [2] A.V. Akimov, A. Mukherjee, C.L. Yu, D.E. Chang, A.S. Zibrov, P.R. Hemmer, H. Park and M.D. Lukin, "Generation of single optical plasmons in metallic nanowires coupled to quantum dots," Nature, vol. 450, p. 402–406, 2007. [3] Michael J. Burek , Yiwen Chu, Madelaine S.Z. Liddy, Parth Patel, Jake Rochman , Srujan Meesala, Wooyoung Hong, Qimin Quan, Mikhail D. Lukin and Marko Loncar High quality-factor optical nanocavities in bulk single-crystal diamond, Nature communications 6718 (2014) [4] Tim Schroder, Andreas W. Schell, Gunter Kewes, Thomas Aichele, and Oliver Benson Fiber-Integrated Diamond-Based Single Photon Source, Nano Lett. 2011, 11, 198-202 [5]Lars Liebermeister, et. al. “Tapered fiber coupling of single photons emitted by a deterministically positioned single nitrogen vacancy center”, Appl. Phys. Lett. 104, 031101 (2014)

Further development of quantum emitter based communication and sensing applications intrinsically depends on the availability of robust single-photon detectors. Here, we demonstrate a new generation of superconducting single-photon detectors specifically optimized for the 500–1100 nm wavelength range, which overlaps with the emission spectrum of many interesting solid-state atom-like systems, such as nitrogen-vacancy and silicon-vacancy centers in diamond. The fabricated detectors have a wide dynamic range (up to 350 million counts per second), low dark count rate (down to 0.1 counts per second), excellent jitter (62 ps), and the possibility of on-chip integration with a quantum emitter. In addition to performance characterization, we tested the detectors in real experimental conditions involving nanodiamond nitrogen-vacancy emitters enhanced by a hyperbolic metamaterial.

We studied light-assisted collisions of Tm atoms in a magneto-optical trap (MOT), working on a weak cooling transition at 530.7 nm [$4{f}^{13}(^{2}F^{o})6{s}^{2},\phantom{\rule{0.16em}{0ex}}J=7/2,\phantom{\rule{0.16em}{0ex}}F=4$ to $4{f}^{12}(^{3}H_{6})5{d}_{5/2}6{s}^{2},\phantom{\rule{0.16em}{0ex}}J=9/2,\phantom{\rule{0.16em}{0ex}}F=5$]. We observed a strong influence from radiation trapping and light-assisted collisions on the dynamics of this trap. We carefully separated these two contributions and measured the binary loss rate constant at different laser powers and detuning frequencies near the cooling transition. Analyzing losses from the MOT, we found the light-assisted inelastic binary loss rate constant to reach values of up to $\ensuremath{\beta}={10}^{\ensuremath{-}9}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{3}/\mathrm{s}$ and gave the upper bound on a branching ratio $kl0.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ for the 530.7 nm transition.

We consider a narrow magneto-dipole transition in the $^{169}\text{Tm}$ atom at the wavelength of $1.14 \ensuremath{\mu}\mathrm{m}$ as a candidate for a two-dimensional-optical lattice clock. Calculating dynamic polarizabilities of the two clock levels $[\text{Xe}]4{f}^{13}6{s}^{2}(J=7/2)$ and $[\text{Xe}]4{f}^{13}6{s}^{2}(J=5/2)$ in the spectral range from 250 to 1200 nm, we find a ``magic'' wavelength for the optical lattice at 807 nm. Frequency shifts due to black-body radiation (BBR), the van der Waals interaction, the magnetic dipole-dipole interaction, and other effects which can perturb the transition frequency are calculated. The transition at $1.14 \ensuremath{\mu}\mathrm{m}$ demonstrates low sensitivity to the BBR shift corresponding to $8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$ in fractional units at room temperature which makes it an interesting candidate for high-performance optical clocks. The total estimated frequency uncertainty is less than $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}$ in fractional units. By direct excitation of the $1.14 \ensuremath{\mu}\mathrm{m}$ transition in Tm atoms loaded into an optical dipole trap, we set the lower limit for the lifetime of the upper clock level $[\text{Xe}]4{f}^{13}6{s}^{2}(J=5/2)$ of 112 ms which corresponds to a natural spectral linewidth narrower than 1.4 Hz. The polarizability of the Tm ground state was measured by the excitation of parametric resonances in the optical dipole trap at 532 nm.

In this paper, we experimentally investigate optical and spin properties of NV centers in aggregates of detonation nanodiamonds. We show that despite the small size of nanodiamonds forming the aggregate, the NV centers in these aggregates exhibit spin properties comparable to similar size nanodiamonds grown by other methods, but with brightness enhanced by a factor of 2.