High-precision group-delay dispersion measurements of optical fibers via fingerprint-spectral wavelength-to-time mapping

The group-delay dispersion of an optical fiber was measured with the time-of-flight method, using fingerprint-like characteristic spectra from a mode-locked fiber laser source. To determine the group-delay dispersion up to the fourth order, least-squares fitting was applied to the overall time waveform mapped on the time axis for the fingerprint-spectral broadband pulses through a long optical fiber. The analysis of all 4003 data points reduced statistical uncertainty, and provided second-, third-, and fourth-order dispersion with uncertainties of 0.02%, 0.4%, and 4%,respectively.

Wideband dispersion removal and mode separation of Lamb waves based on two-component laser interferometer measurement

Ultrasonic Lamb waves are considered as a sensitive and effective tool for nondestructive testing and evaluation of plate-like or pipe-like structures. The nature of multimode and dispersion causes the wave packets to spread, and the modes overlap in both time and frequency domains as they propagate through the structures. By using a two-component laser interferometer technique, in combination with a priori knowledge of the dispersion characteristics and wave structure information of Lamb wave modes, a two-component signal processing technique is presented for implementing dispersion removal and mode separation simultaneously for two modes mixture signals of Lamb waves. The proposed algorithm is first processed and verified using synthetic Lamb wave signals. Then, the two-component displacements test experiment is conducted using different aluminum plate samples. Moreover, we confirm the effectiveness and robustness of this method.

Best Bounds on Measures of Risk and Probability of Ruin for Alpha Unimodal Random Variables When There Is Limited Moment Information

This paper presents explicit formulae giving tight upper and lower bounds on the expectations of alpha-unimodal random variables having a known range and given set of moments. Such bounds can be useful in ordering of random variables in terms of risk and in PERT analysis where there is only incomplete stochastic information concerning the variables under investigation. Explicit closed form solutions are also given involving alpha-unimodal random variables having a known mean for two particularly important measures of risk—the squared distance or variance, and the absolute deviation. In addition, optimal tight bounds are given for the probability of ruin in the collective risk model when the severity distribution has an alpha-unimodal distribution with known moments.

Pulsar B0531 + 21 in the Crab Nebula

The Crab Nebula and its pulsar PSR B0531 + 21 is the space laboratory for the study of fundamental physical processes. From the beginning of the current century up to date, the giant pulses of the pulsar in the Crab Nebula are regularly observed on the Large Phased Array of the Pushchino Radio Astronomy Observatory of the Lebedev Physical Institute at a frequency 111 MHz. The connection between the scattering time scale of radio pulses and the dispersion measure of the pulsar, which was established earlier together with Jodrell Bank, is confirmed. The observed variations in the scattering of radio pulses and their partial correlation with the dispersion measure are explained by the eclipse of the pulsar by dense plasma clouds with fluctuations in the electron density significantly exceeding the corresponding fluctuations in the interstellar medium. The question of a possible connection between period failers (glitches), dispersion measure variations, radio pulses scattering and gamma-ray flares is discussed.

Spatially resolved measurement of plasmon dispersion using Fourier-plane spectral imaging

We show that Fourier-plane imaging in conjunction with the Kretschmann–Raether configuration can be used for measuring polariton dispersion with spatial discrimination of the sample, over the whole visible spectral range.We demonstrate the functionality of our design on several architectures, including plasmonic waveguides, and show that our new design enables the measurement of plasmonic dispersion curves of spatially inhomogeneous structures with features as small as 3 μm, in a single shot.

Optimal readout of superconducting qubits exploiting high-level states

High-fidelity initialization,manipulation,and measurement of qubits are important in quantum computing.For the Google’s Sycamore processor,the gate fidelity of single-and two-qubit logic operations has improved to>99.6%,whereas single-shot measurement fidelity remains at the level of 97%,which severely limits the ap-plication of the superconducting approach to large-scale quantum computing.The current measurement scheme relies on the dispersive interaction between the qubit and the readout resonator,which was proposed back in 2004.However,the measurement fidelity is limited by the trade-offbetween the state separation and relax-ation time of the two-level system.Recently,an exciting phenomenon was observed experimentally,wherein the separation-decay limit could be alleviated by exploiting the cascade decay nature of the higher levels;however,the mechanism and effectiveness of this phenomenon are still unclear.Herein,we present a theoretical tool to extract different types of errors in high-level states encoding dispersive measurement.For the realistic parame-ters of Google’s Sycamore processor,the use of state|2>is sufficient to suppress 92%of the decay readout error on average,where the total readout error is dominated by the background thermal excitation.We also show counter-intuitively that,the assistance of high-level states is effective in the measurement of logic 0,where there is no decay process.

Mass transfer mechanisms in fixed-bed adsorption of erythromycin

The equilibrium and kinetic characteristics of the adsorption of erythromycin to Sepabeads SP825 were determined.The equilibrium data in a batch system was well described by a Langmuir isotherm.The separation performance was investigated in a fixed-bed system with respect to the adsorption superficial velocity,ionic strength and pH.A mathematical model was used to simulate the mass transfer mechanism,taking film mass transfer,pore diffusion and axial dispersion into account.The model predictions were consistent with the experi-mental data and were consequently used to determine the mass transfer coefficients.