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  • We demonstrate the experimental realization of a two-qubit Mølmer–Sørensen gate on a magnetic field-insensitive hyperfine transition in 9Be+ ions using microwave near-fields emitted by a single microwave conductor embedded in a surface-electrode ion trap. The design of the conductor was optimized to produce a high oscillating magnetic field gradient at the ion position. The measured gate fidelity is determined to be 98.2 ± 1.2% and is limited by technical imperfections, as is confirmed by a comprehensive numerical error analysis. The conductor design can potentially simplify the implementation of multi-qubit gates and represents a self-contained, scalable module for entangling gates within the quantum CCD architecture for an ion-trap quantum computer. © 2019, The Author(s).
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  • Frequencies... Pressure oscillations... Pressure oscillation... Oscillations
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    • Collection
  • After the publication of this work [1], we became aware of the fact that the frequency of the ultrasound transmitter that we used for determining the elastic moduli of the trabecular bone specimens was not correctly specified. The oscillation frequency of the ultrasound transmitter was 2 MHz (and not 100 MHz as stated in our work) while we used a sampling rate of 100 MHz. In our publication, the oscillation frequency and sampling rate were confounded. Therefore also the statement in the discussion that we might have determined elastic moduli of trabecular bone tissue rather than the elastic properties of whole specimens because we used an ultrasound frequency > 2 MHz is wrong and has to be omitted.
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  • Frequency fluctuation... Frequency standards... Local oscillator frequencies... Local oscillators... Local oscillator noise
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  • Since January 2004 the High Resolution Stereo Camera (HRSC) is mapping planet Mars. The multi-line sensor on board the ESA Mission Mars Express images the Martian surface with a resolution of up to 1 2 m per pixel in three dimensions and in color. As part of the Photogrammetric/Cartographic Working Group of the HRSC Science Team the Institute of Photogrammetry and GeoInformation (IPI) of the Leibniz Universitat Hannover is involved in photogrammetrically processing the HRSC image data. To derive high quality 3D surface models, color orthoimages or other products, the accuracy of the observed position and attitude information in many cases should be improved. This is carried out via a bundle adjustment. In a considerable number of orbits the results of the bundle adjustment are disturbed by high frequency oscillations. This paper describes the impact of the high frequency angular spacecraft movement to the processing results of the last seven years of image acquisition and how the quality of the HRSC data products is significantly improved by modeling these oscillations.
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  • Zwei-Qubit Gatter... two-qubit gates
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  • frequency standard
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    • Collection
  • The velocity distribution of the electrons within a plasma shock front is investigated by methods of the kinetic theory arranged in a manner to account for heavy deviations from thermodynamic equilibrium. The distribution function exhibits two peaks and becomes unstable with respect to electron oscillations if the shock wave is sufficiently strong (MACH number M ≳ 6.5). The second peak is formed by run-away-electrons, i. e. those fast electrons which transgress the shock front from the hot region. The frequencies, wave numbers, growing rates, phase and group velocities of the excited oscillations, and the influence of the OHMIC damping are calculated approximatively. The results are applied to the non-thermal radiofrequency radiation of the sun.
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  • oscillator
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  • Spin noise (SN) spectroscopy measurements on delicate semiconductor spin systems, like single (In,Ga) As quantum dots, are currently not limited by optical shot noise but rather by the electronic noise of the detection system. We report on a realization of homodyne SN spectroscopy enabling shot-noise-limited SN measurements. The proof-of-principle measurements on impurities in an isotopically enriched rubidium atom vapor show that homodyne SN spectroscopy can be utilized even in the low-frequency spectrum, which facilitates advanced semiconductor spin research like higher order SN measurements on spin qubits.
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