### 33 results for qubit oscillator frequency

Contributors: Levy, Y., Pismenny, J., Reissner, A., Riess, W.

Date: 2002-01-01

**Frequencies**...Pressure **oscillations**...Pressure **oscillation**...The correlation between the **frequencies** of pressure **oscillation** ωosc and the rotor speed (**frequencies** of rotor rotation ωRR) under established rotating stall were determined by three methods: directly from the time diagram of the **oscillation** process, from the behavior diagram of parameters in space and time and from **frequency** characteristics. In total accordance with the Theory of Nonlinear **Oscillation**, by all methods of analysis, the links are in the form of integer ratios: ωosc / ωRR = 1:2 (for n/ nd= 0.6, where n - rotor speed in the experiment and nd- rotor speed from data-sheet) and ωosc / ωRR = 3:7 (for n/ nd = 0.8 and 0.95). The phases of parameter **oscillations** in the transverse cross-section are equal to the sensor angles in compressor stator. This is in agreement with the theoretical concept of single-cell configurations of rotating stall.,publishedVersion,...**Oscillations** ... The correlation between the **frequencies** of pressure **oscillation** ωosc and the rotor speed (**frequencies** of rotor rotation ωRR) under established rotating stall were determined by three methods: directly from the time diagram of the **oscillation** process, from the behavior diagram of parameters in space and time and from **frequency** characteristics. In total accordance with the Theory of Nonlinear **Oscillation**, by all methods of analysis, the links are in the form of integer ratios: ωosc / ωRR = 1:2 (for n/ nd= 0.6, where n - rotor speed in the experiment and nd- rotor speed from data-sheet) and ωosc / ωRR = 3:7 (for n/ nd = 0.8 and 0.95). The phases of parameter **oscillations** in the transverse cross-section are equal to the sensor angles in compressor stator. This is in agreement with the theoretical concept of single-cell configurations of rotating stall.,publishedVersion,

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Contributors: Pressel, Thomas, Bouguecha, Anas, Vogt, Ute, Meyer-Lindenberg, Andrea, Behrens, Bernd-Arno, Nolte, Ingo, Windhagen, Henning

Date: 2005-01-01

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. ... 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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Contributors: Bostelmann, Jonas, Heipke, Christian

Date: 2011-01-01

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**. ... 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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Contributors: Leroux, Ian D., Scharnhorst, Nils, Hannig, Stephan, Kramer, Johannes, Pelzer, Lennart, Stepanova, Mariia, Schmidt, Piet O.

Date: 2017-01-01

**Frequency** fluctuation...**Frequency** standards...For atomic **frequency** standards in which fluctuations of the local **oscillator** (LO) **frequency** are the dominant noise source, we examine the role of the the servo algorithm that predicts and corrects these **frequency** fluctuations. We derive the optimal linear prediction algorithm, showing how to measure the relevant spectral properties of the noise and optimise servo parameters while the standard is running, using only the atomic error signal. We find that, for realistic LO noise spectra, a conventional integrating servo with a properly chosen gain performs nearly as well as the optimal linear predictor. Using simple analytical models and numerical simulations, we establish optimum probe times as a function of clock atom number and of the dominant noise type in the local **oscillator**. We calculate the resulting LO-dependent scaling of achievable clock stability with atom number for product states as well as for maximally-correlated states.,Alexander von Humboldt foundation,EMPIR,EU/HORIZON 2020,DFG/CRC/1128,DFG/CRC/1227,publishedVersion,...Local **oscillator** **frequencies**...Local **oscillators**...Local **oscillator** noise ... For atomic **frequency** standards in which fluctuations of the local **oscillator** (LO) **frequency** are the dominant noise source, we examine the role of the the servo algorithm that predicts and corrects these **frequency** fluctuations. We derive the optimal linear prediction algorithm, showing how to measure the relevant spectral properties of the noise and optimise servo parameters while the standard is running, using only the atomic error signal. We find that, for realistic LO noise spectra, a conventional integrating servo with a properly chosen gain performs nearly as well as the optimal linear predictor. Using simple analytical models and numerical simulations, we establish optimum probe times as a function of clock atom number and of the dominant noise type in the local **oscillator**. We calculate the resulting LO-dependent scaling of achievable clock stability with atom number for product states as well as for maximally-correlated states.,Alexander von Humboldt foundation,EMPIR,EU/HORIZON 2020,DFG/CRC/1128,DFG/CRC/1227,publishedVersion,

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Contributors: Welly, J.D.

Date: 1963-01-01

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. ... 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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Contributors: Sterin, Pavel, Wiegand, Julia, Hübner, Jens, Oestreich, Michael

Date: 2018-01-01

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**. ... 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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Contributors: Schilling, Manuel, Timmen, Ludger

Date: 2016-01-01

The absolute measurement of g is currently realized through the laser interferometric measurement of a free falling retro-reflector. The Micro-g LaCoste FG5X is a free-fall gravimeter with a laser interferometer in Mach-Zehnder configuration which uses simultaneous time and distance measurements to calculate the absolute value of g. Because the instrument itself contains the necessary working standards for precise time and length measurements, it is considered independent of external references. The timing is kept with a 10MHz rubidium **oscillator** with a stability of 5x10e-10. The length unit is realized by the laser interferometer. The **frequency** calibrated and iodine stabilized helium-neon laser has a wavelength of 633 nm and an accuracy of 2.5x10e-11. In 2012 the FG5-220 of the Institut für Erdmessung (IfE) was upgraded to the FG5X-220. The upgrade included a new dropping chamber with a longer free fall and new electronics including a new rubidium **oscillator**. The metrological traceability to measurement units of the Système International d’unités (SI unit) is ensured by two complementary and successive approaches: the comparison of **frequencies** with standards of higher order and the comparison of the measured g to a reference measured by absolute gravimeters defined as primary standards within the SI. A number of experiments to test the rubidium **oscillator** were performed. The **oscillator** showed a linear drift of 0.2x10e-3 Hz per month (= 0.3 nm/s² per month) in the first 18 months of use. A jump in the **frequency** of 0.01 Hz (=20 nm/s²) was revealed recently and the drift rate changed to 0.4x10e-3 Hz/month.,acceptedVersion,...**frequency** standard ... The absolute measurement of g is currently realized through the laser interferometric measurement of a free falling retro-reflector. The Micro-g LaCoste FG5X is a free-fall gravimeter with a laser interferometer in Mach-Zehnder configuration which uses simultaneous time and distance measurements to calculate the absolute value of g. Because the instrument itself contains the necessary working standards for precise time and length measurements, it is considered independent of external references. The timing is kept with a 10MHz rubidium **oscillator** with a stability of 5x10e-10. The length unit is realized by the laser interferometer. The **frequency** calibrated and iodine stabilized helium-neon laser has a wavelength of 633 nm and an accuracy of 2.5x10e-11. In 2012 the FG5-220 of the Institut für Erdmessung (IfE) was upgraded to the FG5X-220. The upgrade included a new dropping chamber with a longer free fall and new electronics including a new rubidium **oscillator**. The metrological traceability to measurement units of the Système International d’unités (SI unit) is ensured by two complementary and successive approaches: the comparison of **frequencies** with standards of higher order and the comparison of the measured g to a reference measured by absolute gravimeters defined as primary standards within the SI. A number of experiments to test the rubidium **oscillator** were performed. The **oscillator** showed a linear drift of 0.2x10e-3 Hz per month (= 0.3 nm/s² per month) in the first 18 months of use. A jump in the **frequency** of 0.01 Hz (=20 nm/s²) was revealed recently and the drift rate changed to 0.4x10e-3 Hz/month.,acceptedVersion,

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Contributors: Schilling, Manuel, Timmen, Ludger

Date: 2015-01-01

The absolute measurement of g is currently realized through the laser interferometric measurement of a free falling retro-reflector. The Micro-g LaCoste FG5X is a free-fall gravimeter with a laser interferometer in Mach-Zehnder configuration which uses simultaneous time and distance measurements to calculate the absolute value of g. Because the instrument itself contains the necessary working standards for precise time and length measurements, it is considered independent of external references. The timing is kept with a 10 MHz rubidium **oscillator** with a stability of 5×10e−10 . The length unit is realized by the laser interferometer. The **frequency** calibrated and iodine stabilized helium-neon laser has a wavelength of 633 nm and an accuracy of 2.5×10e−11. In 2012 the FG5-220 of the Institut für Erdmessung (IfE) was upgraded to the FG5X-220. The upgrade included a new dropping chamber with a longer free fall and new electronics including a new rubidium **oscillator**. The metrological traceability to measurement units of the Système International d’unités (SI unit) is ensured by two complementary and successive approaches: the comparison of **frequencies** with standards of higher order and the comparison of the measured g to a reference measured by absolute gravimeters defined as primary standards within the SI. A number of experiments to test the rubidium **oscillator** were performed. The **oscillator** showed a linear drift of 0.2×10e−3 Hz per month (=0.3 nm/s² per month) in the first 18 months of use. A jump in the **frequency** of 0.01 Hz (=20 nm/s² ) was revealed recently and the drift rate changed to −0.5×10e−3 Hz /month.,publishedVersion,...**frequency** standard ... The absolute measurement of g is currently realized through the laser interferometric measurement of a free falling retro-reflector. The Micro-g LaCoste FG5X is a free-fall gravimeter with a laser interferometer in Mach-Zehnder configuration which uses simultaneous time and distance measurements to calculate the absolute value of g. Because the instrument itself contains the necessary working standards for precise time and length measurements, it is considered independent of external references. The timing is kept with a 10 MHz rubidium **oscillator** with a stability of 5×10e−10 . The length unit is realized by the laser interferometer. The **frequency** calibrated and iodine stabilized helium-neon laser has a wavelength of 633 nm and an accuracy of 2.5×10e−11. In 2012 the FG5-220 of the Institut für Erdmessung (IfE) was upgraded to the FG5X-220. The upgrade included a new dropping chamber with a longer free fall and new electronics including a new rubidium **oscillator**. The metrological traceability to measurement units of the Système International d’unités (SI unit) is ensured by two complementary and successive approaches: the comparison of **frequencies** with standards of higher order and the comparison of the measured g to a reference measured by absolute gravimeters defined as primary standards within the SI. A number of experiments to test the rubidium **oscillator** were performed. The **oscillator** showed a linear drift of 0.2×10e−3 Hz per month (=0.3 nm/s² per month) in the first 18 months of use. A jump in the **frequency** of 0.01 Hz (=20 nm/s² ) was revealed recently and the drift rate changed to −0.5×10e−3 Hz /month.,publishedVersion,

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Contributors: Pakhomov, A.V., Arkhipov, R.M., Arkhipov, M.V., Demircan, A., Morgner, U., Rosanov, N.N., Babushkin, Ihar

Date: 2019-01-01

Up to now, full tunability of waveforms was possible only in electronics, up to radio-**frequencies**. Here we propose a new concept of producing few-cycle terahertz (THz) pulses with widely tunable waveforms. It is based on control of the phase delay between different parts of the THz wavefront using linear diffractive optical elements. Suitable subcycle THz wavefronts can be generated via coherent excitation of nonlinear low-**frequency** **oscillators** by few-cycle optical pulses. Using this approach it is possible to shape the electric field rather than the slow pulse envelope, obtaining, for instance, rectangular or triangular waveforms in the THz range. The method is upscalable to the optical range if the attosecond pump pulses are used. ... Up to now, full tunability of waveforms was possible only in electronics, up to radio-**frequencies**. Here we propose a new concept of producing few-cycle terahertz (THz) pulses with widely tunable waveforms. It is based on control of the phase delay between different parts of the THz wavefront using linear diffractive optical elements. Suitable subcycle THz wavefronts can be generated via coherent excitation of nonlinear low-**frequency** **oscillators** by few-cycle optical pulses. Using this approach it is possible to shape the electric field rather than the slow pulse envelope, obtaining, for instance, rectangular or triangular waveforms in the THz range. The method is upscalable to the optical range if the attosecond pump pulses are used.

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Contributors: Hahn, Henning

Date: 2019-01-01

Zwei-**Qubit** Gatter...two-**qubit** gates...Towards the goal of a large-scale quantum computer based on trapped ions, near-ﬁeld microwaves represent a promising approach to perform the techni- cally challenging key operation of a two-**qubit** entangling gate. In this thesis we present the ﬁrst microwave-driven two-**qubit** gate in 9Be+ ions employing a ﬁrst-order ﬁeld-independent **qubit** transition and a scalable surface-electrode ion trap at room temperature. We test the quality of the gate operation by producing a maximally entangled state and measuring the resulting state preparation ﬁdelity in a reduced tomography procedure. For the best two- **qubit** gate achieved in the system we ﬁnd this ﬁdelity to be F = 98.2 ± 1.2 %. Following a comprehensive error analysis based on numerical simulations and experimentally determined input parameters, we identify current inﬁdelity con- tributions of the apparatus. Here, the natural error source of the microwave near-ﬁeld approach, namely ﬂuctuating AC Zeeman shifts, could be reduced to the 10^−4 level due to the optimized design of the employed microwave con- ductor. As we ﬁnd that the three largest errors can all be reduced upon purely technical improvements, higher ﬁdelities are feasible in the future. Besides the gate realization, the thesis also comprises the initial characterization of the employed ion trap as well as the design and construction of a Raman laser at ∼ 313 nm which is utilized to perform near ground state cooling of radial modes of a single- and two-ion crystal. Here, ensuing heating rate measure- ments on a single-ion’s radial modes show good agreement with the electric- ﬁeld noise spectral density expected from literature given the chosen mode **frequency** and nearest ion-to-electrode distance of 70 µm. Finally, we present the operation of a ﬁrst multi-layer ion trap whose electrode layout features a 3-dimensional microwave conductor intended for performing microwave-driven two-**qubit** gates. Following a characterization of the resulting near-ﬁeld pat- tern using a single ion as a local ﬁeld probe, we ﬁnd the multi-layer conductor to have signiﬁcantly better ﬁeld properties when compared to an equivalent single-layer design. Given these promising results, future work will focus on the integration of similar microwave circuitry in a multi-zone trap array as envisioned by the QCCD architecture. ... Towards the goal of a large-scale quantum computer based on trapped ions, near-ﬁeld microwaves represent a promising approach to perform the techni- cally challenging key operation of a two-**qubit** entangling gate. In this thesis we present the ﬁrst microwave-driven two-**qubit** gate in 9Be+ ions employing a ﬁrst-order ﬁeld-independent **qubit** transition and a scalable surface-electrode ion trap at room temperature. We test the quality of the gate operation by producing a maximally entangled state and measuring the resulting state preparation ﬁdelity in a reduced tomography procedure. For the best two- **qubit** gate achieved in the system we ﬁnd this ﬁdelity to be F = 98.2 ± 1.2 %. Following a comprehensive error analysis based on numerical simulations and experimentally determined input parameters, we identify current inﬁdelity con- tributions of the apparatus. Here, the natural error source of the microwave near-ﬁeld approach, namely ﬂuctuating AC Zeeman shifts, could be reduced to the 10^−4 level due to the optimized design of the employed microwave con- ductor. As we ﬁnd that the three largest errors can all be reduced upon purely technical improvements, higher ﬁdelities are feasible in the future. Besides the gate realization, the thesis also comprises the initial characterization of the employed ion trap as well as the design and construction of a Raman laser at ∼ 313 nm which is utilized to perform near ground state cooling of radial modes of a single- and two-ion crystal. Here, ensuing heating rate measure- ments on a single-ion’s radial modes show good agreement with the electric- ﬁeld noise spectral density expected from literature given the chosen mode **frequency** and nearest ion-to-electrode distance of 70 µm. Finally, we present the operation of a ﬁrst multi-layer ion trap whose electrode layout features a 3-dimensional microwave conductor intended for performing microwave-driven two-**qubit** gates. Following a characterization of the resulting near-ﬁeld pat- tern using a single ion as a local ﬁeld probe, we ﬁnd the multi-layer conductor to have signiﬁcantly better ﬁeld properties when compared to an equivalent single-layer design. Given these promising results, future work will focus on the integration of similar microwave circuitry in a multi-zone trap array as envisioned by the QCCD architecture.

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