Browsing by Author "Voskoboynikov, Oleksandr"

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Ballistic Aharonov-Bohm quantum bits and quantum gates
(2008-03-01)
Yu, Leo
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Voskoboynikov, Oleksandr
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交大名義發表
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National Chiao Tung University
We propose an architecture to perform quantum computation, using ballistic electrons as qubits and coupled quantum rings as quantum gates. In the proposed architecture two adjacent one-dimensional wires, creating a single qubit, are connected to two coupled quantum rings, where the required magnetic flux is provided by enclosed nano-sized magnets. The phase modulation of the wave function of the ballistic electrons under the Aharonov-Bohm effect is carefully designed to facilitate reprogrammable and dynamically controllable quantum gates. Arbitrary single-qubit quantum gates with high fidelity can be constructed on the basis of this architecture. (C) 2007 Elsevier Ltd. All rights reserved.
Exciton wave function localization and exciton diamagnetic coefficient in semiconductor quantum rings without reflection symmetry
(2013-08-12)
Voskoboynikov, Oleksandr
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Chiu, W. T.
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Thu, L. M.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
We theoretically study how reflection asymmetry affects the neutral exciton diamagnetic coefficient in self-assembled InGaAs/GaAs semiconductor wobbled quantum rings. The previously proposed mapping method is used to simulate the exciton wave function and energy in the rings. The description is suited to clarify the important question of the exciton diamagnetic coefficient stability in the rings with broken reflection symmetry. Our simulation results confirm that the exciton wave function of the reflection symmetrical (balanced) wobbled ring is distributed equally over two potential valleys corresponding to the hills in the ring's shape. At the same time, even a very small reflectional imbalance in the geometry and (or) material content of the wobbled rings destroys the ringlike shape of the exciton wave function and causes the localization of the function in one of the potential valleys of the ring (dotlike shape of the exciton wave function). This leads to a rapid decrease of the exciton diamagnetic coefficient. Our calculation results are in good agreement with recent experimental observations.
GaAs Polariton Interference in Magnetic Field: Oblique Incident Ellipsometry Measurement
(2014-11-15)
Su, Sheng-Kai
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Voskoboynikov, Oleksandr
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Li, Liang-Chen
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Suen, Yuen-Wuu
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Lee, Chien-Ping
The properties of GaAs polaritons propagating in a magnetic field have been investigated using a self-designed ellipsometry system with an oblique incident angle. Interesting fine structures, which have not been reported, have been observed and their magneto-optical behavior cannot be explained by the known properties of excitonic states. Treating the surface and the growth interface as boundaries, we attribute the fine structures to the interference among various polariton modes. A model considering the polariton spatial dispersion and exciton effective mass increase induced by its center of mass and relative motion coupling is proposed to explain the magnetic response of interference ellipsometry spectra.
HYBRID MODEL FOR SIMULATION OF MAGNETO-OPTICAL RESPONSE OF LAYERS OF SEMICONDUCTOR NANO-OBJECTS
(2010)
Voskoboynikov, Oleksandr
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交大名義發表
;
National Chiao Tung University
In this paper a multiscale hybrid model for evaluation of the collective magnetooptical response of semiconductor nano-object systems is presented. The model is based on a modification of the discrete dipole approximation and can efficiently describe the response from systems of arbitrary-shaped nano-objects embedded into a host semiconductor. The approach requires a simultaneous multiscale electrodynamic and quantum mechanical description. As an example of the model implementation, simulation of the magneto-ellipsometry of a layer of embedded semiconductor triple quantum dot molecules was performed. It was demonstrated that the model can be used to reproduce from conventional ellipsometric data important information on the quantum mechanics of the semiconductor nano-objects.
Low temperature and high magnetic field spectroscopic ellipsometry system
(2014-05-01)
Su, Sheng-Kai
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Li, Liang-Chen
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Suen, Yuen-Wuu
;
Wu, Jau-Yang
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Kuo, Hong-Rong
We report on the design and implementation of a spectral ellipsometer at near-infrared wavelength (700-1000 nm) for samples placed in high magnetic fields (up to 14 T) at low temperatures (similar to 4.2 K). The main optical components are integrated in a probe, which can be inserted into a conventional long-neck He dewar and has a very long free-space optical path (similar to 1.8 mx2). A polarizer-sample-(quarter-wave plate)-rotating analyzer configuration was employed. Two dielectric mirrors, one before and one after the sample in the optical path, helped to reflect the light back to the analyzer and a two-axis piezo-driven goniometer under the sample holder was used to control the direction of the reflected light. Functional test results performed on an intrinsic GaAs wafer and analysis on the random error of the system are shown. We obtained both amplitude and phase ellipsometric spectra simultaneously and observed helicity transformation at energies near the GaAs exciton transitions in the phase spectra. Significant shifts of them induced by magnetic fields were observed and fitted with a simple model. This system will allow us to study the collective magneto-optical response of materials and spatial dispersive exciton-polariton related problems in high external magnetic fields at low temperatures. (C) 2014 AIP Publishing LLC.
Low temperature and high magnetic field spectroscopic ellipsometry system
(2014-05-01)
Su, Sheng-Kai
;
Li, Liang-Chen
;
Suen, Yuen-Wuu
;
Wu, Jau-Yang
;
Kuo, Hong-Rong
We report on the design and implementation of a spectral ellipsometer at near-infrared wavelength (700-1000 nm) for samples placed in high magnetic fields (up to 14 T) at low temperatures (similar to 4.2 K). The main optical components are integrated in a probe, which can be inserted into a conventional long-neck He dewar and has a very long free-space optical path (similar to 1.8 mx2). A polarizer-sample-(quarter-wave plate)-rotating analyzer configuration was employed. Two dielectric mirrors, one before and one after the sample in the optical path, helped to reflect the light back to the analyzer and a two-axis piezo-driven goniometer under the sample holder was used to control the direction of the reflected light. Functional test results performed on an intrinsic GaAs wafer and analysis on the random error of the system are shown. We obtained both amplitude and phase ellipsometric spectra simultaneously and observed helicity transformation at energies near the GaAs exciton transitions in the phase spectra. Significant shifts of them induced by magnetic fields were observed and fitted with a simple model. This system will allow us to study the collective magneto-optical response of materials and spatial dispersive exciton-polariton related problems in high external magnetic fields at low temperatures. (C) 2014 AIP Publishing LLC.
Magneto-optics of layers of triple quantum dot molecules
(2009-04-01)
Le Minh, Thu
;
Voskoboynikov, Oleksandr
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We consider theoretically the impact of the coherent manipulation of electronic states in the triple vertical lens-shaped circular InAs/GaAs quantum dot molecules on the collective magneto-optical reflection from layers of those nano-objects. The quantum dots have substantially different diameters in contrast to most of the known simulations. We demonstrate a possibility to drive molecular electronic ground states (to redistribute electronic wave functions within the molecule) by applying an external magnetic field along the system's growth direction. The change in the states leads to the redistribution of the intensity of the reflectance and absorbance peaks in the collective magneto-optical response of a layer of the triple quantum dot molecules. Varying the distance between quantum dots within the layer one can study optically the transition from "molecular" to "atomic" configuration. We show that the changes in the quantum mechanical behaviour of the molecules can be made observable by monitoring changes of the ellipsometric parameters Psi and Delta in the magneto-optical response of layers of such nano-objects. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim