Motional heating of spatially extended ion crystals

We study heating of motional modes of a single ion and of extended ion crystals trapped in a linear radio frequency (rf) Paul trap with a precision of Δ ṅ ≈ 0.1 phonons s-1. Single-ion axial and radial heating rates are consistent and electric field noise has been stable over the course of four years. At a secular frequency of ω sec = 2π × 620 kHz, we measure ṅ = 0.56 (6) phonons s-1 per ion for the center-of-mass (com) mode of linear chains of up to 11 ions and observe no significant heating of the out-of-phase (oop) modes. By displacing the ions away from the nodal line, inducing excess micromotion, rf noise heats the com mode quadratically as a function of radial displacement r by phonons s-1 μm-2 per ion, while the oop modes are protected from rf-noise induced heating in linear chains. By changing the quality factor of the resonant rf circuit from Q = 542 to Q = 204, we observe an increase of rf noise by a factor of up to 3. We show that the rf-noise induced heating of motional modes of extended crystals also depends on the symmetry of the crystal and of the mode itself. As an example, we consider several 2D and 3D crystal configurations. Heating rates of up to 500 ph s-1 are observed for individual modes, giving rise to a total kinetic energy increase and thus a fractional time dilation shift of up to -0.3 × 10-18 s-1 of the total system. In addition, we detail how the excitation probability of the individual ions is reduced and decoherence is increased due to the Debye-Waller effect

Application of harmonic wavelets to processing oscillating hydroacoustic signals

The paper is devoted to the application of specific functions called harmonic wavelets, which are aimed at processing a wide range of oscillating hydroacoustic signals including multiharmonic and transient signals. We provide basics of the harmonic wavelet transform and a two-stage algorithm for computing wavelet coefficients based on the discrete Fourier transform. We introduce a special efficiency factor of applying these wavelets to oscillating hydroacoustic signals. Application of harmonic wavelets is efficient for processing oscillating hydroacoustic signals since harmonic wavelets have similarities with these types of signals. In many cases the best basis is the basis that has high correlation with the investigated signals since signal representation in such a basis will require a small number of components. We devote special attention to a very important practical task - denoising of oscillating signals using special statistical criteria and wavelet-based thresholding

Coherent Excitation of the Highly Forbidden Electric Octupole Transition in Yb+ 172

We report on the first coherent excitation of the highly forbidden S21/2?F27/2 electric octupole (E3) transition in a single trapped Yb+172 ion, an isotope without nuclear spin. Using the transition in Yb+171 as a reference, we determine the transition frequency to be 642 116 784 950 887.6(2.4) Hz. We map out the magnetic field environment using the forbidden S21/2?D25/2 electric quadrupole (E2) transition and determine its frequency to be 729 476 867 027 206.8(4.4) Hz. Our results are a factor of 1×105 (3×105) more accurate for the E2 (E3) transition compared to previous measurements. The results open up the way to search for new physics via precise isotope shift measurements and improved tests of local Lorentz invariance using the metastable F27/2 state of Yb+. © 2020 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI

Finite-temperature spectrum at the symmetry-breaking linear to zigzag transition

International audienceWe investigate the normal-mode spectrum of a trapped ion chain at the symmetry-breaking linear to zigzag transition and at finite temperatures. For this purpose, we modulate the amplitude of the Doppler cooling laser to excite and measure mode oscillations. The expected mode softening at the critical point, a signature of the second-order transition, is not observed. Numerical simulations show that this is mainly due to the finite temperature of the chain. Inspection of the trajectories suggest that the thermal shifts of the normal-mode spectrum can be understood by the ions collectively jumping between the two ground-state configurations of the symmetry-broken phase. We develop an effective analytical model, which allows us to reproduce the low-frequency spectrum as a function of the temperature and close to the transition point. In this model, the frequency shift of the soft mode is due to the anharmonic coupling with the high-frequency modes of the spectrum, acting as an averaged effective thermal environment. Our study could prove important for implementing ground-state laser cooling close to the critical point

Efficient formation of excitons in a dense electron-hole plasma at room temperature

Hangleiter A, Jin Z, Gerhard M, et al. Efficient formation of excitons in a dense electron-hole plasma at room temperature. Physical Review B. 2015;92(24): 241305

Impedance boundary conditions for the environment above the hydrocarbon deposits in the amplitude-modulated signal mode

Представлены результаты теоретического анализа взаимодействия амплитудно-модулированных сигналов с углеводородной залежью. Даны рекомендации по разработке методов поиска углеводородных залежей. The article presents the results of theoretical analysis of interaction of amplitude-modulated signals with hydrocarbon deposits. There are recommendations for the development of the methods of search of hydrocarbon deposits