Download or read book Silicon and Silicon germanium Epitaxy for Quantum Dot Device Fabrications Towards an Electron Spin based Quantum Computer written by Kun Yao and published by . This book was released on 2009 with total page 354 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigating Valley States and Their Interactions in Silicon Silicon Germanium Quantum Dots written by Nicholas Penthorn and published by . This book was released on 2020 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum computing in nanoscale silicon heterostructures has received much attention, both from the scientific community and private industry, largely due to compatibility with highly-developed silicon-based device fabrication and design present in essentially all aspects of modern life. Breakthroughs in quantum control and coupled qubit systems in silicon in the last five years have accelerated scientific research in this area, with gate-defined quantum dots at the forefront of this effort. As techniques for quantum control become more sophisticated, subtle details of the silicon band structure are now of vital importance for the ultimate success of silicon quantum computing. Chief among these band features are the valley states, regions of the conduction band that form the ground state and a nearly degenerate excited state in quantum dot heterostructures. These valley states and their effects on electron dynamics can lead to quantum information loss and qubit decoherence, and so detailed characterization of the valleys is of great importance. In this work, I first describe a spectroscopic technique utilizing fast voltage pulses on one or two gates in a double quantum dot device to precisely measure the relevant valley state energies in both quantum dots as well as the coupling between valley states and electron orbital states. With this information, the valley states are leveraged to form a novel qubit basis with innate protection against decoherence from charge noise. Sub-nanosecond operations on this "valley qubit" are used to demonstrate complete quantum control. Finally, using real-time read-out of energy-selective tunneling in a single quantum dot, pure valley state coherence in the form of intervalley relaxation is directly probed. This relaxation is subsequently linked to spin-valley electron dynamics and the observance of a valley-dependent tunneling process is discussed theoretically using tight-binding formalism.

Download or read book Semiconductor Spintronics and Quantum Computation written by D.D. Awschalom and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: The past few decades of research and development in solid-state semicon ductor physics and electronics have witnessed a rapid growth in the drive to exploit quantum mechanics in the design and function of semiconductor devices. This has been fueled for instance by the remarkable advances in our ability to fabricate nanostructures such as quantum wells, quantum wires and quantum dots. Despite this contemporary focus on semiconductor "quantum devices," a principal quantum mechanical aspect of the electron - its spin has it accounts for an added quan largely been ignored (except in as much as tum mechanical degeneracy). In recent years, however, a new paradigm of electronics based on the spin degree of freedom of the electron has begun to emerge. This field of semiconductor "spintronics" (spin transport electron ics or spin-based electronics) places electron spin rather than charge at the very center of interest. The underlying basis for this new electronics is the intimate connection between the charge and spin degrees of freedom of the electron via the Pauli principle. A crucial implication of this relationship is that spin effects can often be accessed through the orbital properties of the electron in the solid state. Examples for this are optical measurements of the spin state based on the Faraday effect and spin-dependent transport measure ments such as giant magneto-resistance (GMR). In this manner, information can be encoded in not only the electron's charge but also in its spin state, i. e.

Download or read book Development of Silicon Germanium based Quantum Dots for Nanoelectronic Device Applications written by Sandro John Di Giacomo and published by . This book was released on 2005 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: As CMOS dimensions decrease each year, the International Technology Roadmap for Semiconductors (ITRS) encourages development of "emerging research devices" to eventually replace CMOS. SiGe-based quantum dots, the focus of this study, are attractive because they can be integrated with existing Si -based devices and fabricated using existing processes. This process exploits self-limiting effects in Si nanopillar oxidation and Ge segregation during SiGe oxidation to fabricate uniformly sized Ge quantum dots suitable for room temperature operation. In this study, four fabrication processes were investigated: electron-beam lithography (EBL), inductively-coupled plasma (ICP) etching, thermal oxidation, and transmission electron microscopy (TEM). The samples consisted of rows of closely spaced Si nanopillars, with diameters of 25-100 nm and heights of 80-600 nm.

Download or read book Quantum Semiconductor Devices and Technologies written by Tom Pearsall and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: stacked QD structure and is useful for examining the possibility of all optical measurement of stacked QD layers. Optical absorption spectra of self-assembled QDs has been little reported, and further investigation in necessary to study hole-burning memory. 2.5 Summary This chapter describes recent advances in quantum dot fabrication tech nologies, focusing on our self-formed quantum dot technologies including TSR quantum dots and SK-mode self-assembled quantum dots. As is described in this chapter, there are many possible device applications such as quantum dot tunneling memory devices, quantum dot fioating-dot gate FETs, quantum dot lasers, and quantum dot hole-burning memory devices. The quantum dot laser applications seem to be the most practicable among these applications. However, many problems remain to be solved before even this application becomes practical. The most important issue is to of self-assembled quantum dots more pre control the size and position cisely, with an accuracy on an atomic scale. The confinement must be enough to keep the separation energy between quantized energy levels high enough to get high-temperature characteristics. The lasing oscillation frequency should be fixed at 1.3 f.lITl or 1.5 f.lITl for optical communication. Phonon bottleneck problems should be solved by the optimization of device structures. Fortunately, there is much activity in the area of quantum dot lasers and, therefore, many breakthroughs will be made, along with the exploration of other new application areas.

Download or read book Heterostructure Modifications Fabrication Improvements and Measurement Automation of Si SiGe Quantum Dots for Quantum Computation written by Thomas Walter McJunkin and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum computing - leveraging quantum phenomena to perform complex and otherwise intractable computational problems - has rapidly progressed from a theoretical aspiration to a potential reality. Currently, there are many competing approaches to the way the physical qubits (quantum bits) are built, from trapped ions, to superconducting circuits, to semiconductor quantum dots, and beyond. Here, we focus on quantum dots, where electrons or holes are confined within a semiconductor and the quantized nature of charge and spin are utilized for computation. Within the field of quantum dots, heterostructures made of silicon and silicon-germanium are especially enticing due to their low density of defects and nuclear spin. Although quantum dots are a promising avenue for quantum computation because of their intrinsically small size and similarity to classical transistors, nearly every aspect of their design, realization, and control has yet to be fully optimized.This thesis explores modifications to the heterostructure, fabrication, and measurement of Si/SiGe quantum dots in the pursuit of improved quantum dot qubits. The valley splitting in silicon quantum dots, a near degeneracy of the lowest lying energy states, is critical to the formation and performance of silicon qubits. In this work, we present several modifications to the Si/SiGe heterostructure in an effort to enhance this splitting. In particular, we investigate the effects of introducing germanium to the silicon quantum well by the inclusion of a single spike in germanium concentration or an oscillatory concentration throughout the well. We present experimental measurements of the energy spectrum arising from both modifications and, coupled with theoretical support, demonstrate enhancements to the valley splitting. Next, we present several fabrication techniques with the goal of improved quantum dot functionality and lowered charge noise, a major barrier to higher quality devices. We report a new strategy for etched-palladium fabrication and discuss the current progress. Finally, we present work towards the automation of quantum dot tuning. As quantum dot devices increase in the number of qubits, so do the number of electrostatic gates which control the device. We discuss the development of automated tuning procedures and present a procedure for the formation of well-controlled quantum dots from initial voltage settings.

Download or read book Scalable and High sensitivity Readout of Silicon Quantum Devices written by Simon Schaal and published by . This book was released on 2020 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quantum computing is predicted to provide unprecedented enhancements in computational power. A quantum computer requires implementation of a well-defined and controlled quantum system of many interconnected qubits, each defined using fragile quantum states. The interest in a spin-based quantum computer in silicon stems from demonstrations of very long spin-coherence times, high-fidelity single spin control and compatibility with industrial mass-fabrication. Industrial scale fabrication of the silicon platform offers a clear route towards a large-scale quantum computer, however, some of the processes and techniques employed in qubit demonstrators are incompatible with a dense and foundry-fabricated architecture. In particular, spin-readout utilises external sensors that require nearly the same footprint as qubit devices. In this thesis, improved readout techniques for silicon quantum devices are presented and routes towards implementation of a scalable and high-sensitivity readout architecture are investigated. Firstly, readout sensitivity of compact gate-based sensors is improved using a high-quality factor resonator and Josephson parametric amplifier that are fabricated separately from quantum dots. Secondly, an integrated transistor-based control circuit is presented using which sequential readout of two quantum dot devices using the same gate-based sensor is achieved. Finally, a large-scale readout architecture based on random-access and frequency multiplexing is introduced. The impact of readout circuit footprint on readout sensitivity is determined, showing routes towards integration of conventional circuits with quantum devices in a dense architecture, and a fault-tolerant architecture based on mediated exchange is introduced, capable of relaxing the limitations on available control circuit footprint per qubit. Demonstrations are based on foundry-fabricated transistors and few-electron quantum dots, showing that industry fabrication is a viable route towards quantum computation at a scale large enough to begin addressing the most challenging computational problems.

Download or read book Technology of Quantum Devices written by Manijeh Razeghi and published by Springer Science & Business Media. This book was released on 2009-12-11 with total page 570 pages. Available in PDF, EPUB and Kindle. Book excerpt: Technology of Quantum Devices offers a multi-disciplinary overview of solid state physics, photonics and semiconductor growth and fabrication. Readers will find up-to-date coverage of compound semiconductors, crystal growth techniques, silicon and compound semiconductor device technology, in addition to intersubband and semiconductor lasers. Recent findings in quantum tunneling transport, quantum well intersubband photodetectors (QWIP) and quantum dot photodetectors (QWDIP) are described, along with a thorough set of sample problems.

Download or read book Experimental Investigation of Silicon Metal oxide semiconductor Based Triple Quantum Dot written by Hong Pan and published by . This book was released on 2013 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the rapid progress in nanofabrication, scientists and researchers are now able to make lateral quantum dots in semiconductor materials. The few electrons confined in these quantum dots provide the possibility of realizing a qubit, the building block of a quantum computer. Tremendous effort has been put in the solid state quantum information field in the last ten years of making single electron spin qubit or singlet triplet qubit based on two electron spin. However, the operation of these types of qubit requires additional engineering by either integrating a microwave loop or an external magnet to creat field difference. This thesis project was inspired by DiVincenzo's proposal of developing qubit based on three electrons controlled by Heisenberg exchange interactions only, which is called "exchange-only" qubit. All the qubit operation can be done in principle via electrical pulses only. We proposed to make the triple quantum device in silicon system. This type of device will have small qubit decoherence, easy integration to industry infrustructure and great chance of scaling up to a real quantum computer. We developed and fabricated the electrostatically defined triple quantum dot (TQD) device in a silicon metal-oxide-oxide structure. We characterized its electrostatic properties using a quantum point contact charge sensing channel nearby. We are be able to obtain the charge stability diagram in the last few elelctron regime that provides the experimental basis of forming a exchange only qubit. We demonstrated the tunability of the TQD by acheiving the quadruple points where all three dots are on resonance. This is the first experimental demonstration of well controlled triple quantum dot device in silicon system. The constant interaction model and the hubbard model for triple quantum dot system are developed to help understand the electrostatic dynamics. Tunnel couplings between quantum dots, which determines the exchange interactions, are extracted using various fitting methods. We implemented the qubit manipulation with three quantum dots in both a linearly and a triangularly arranged geometry. For the first time, we observed coherent oscillation in the Si MOS based triple quantum dot device with oscillation frequency of 2MHz and 7MHz. We suspect the these oscillations are related with spin dynamics in our system. These experimental investigations demonstrate that we have the ability to develop triple quantum dot device for exchange ony qubit and the potential to perform qubit operation in the future.

Download or read book Semiconductor Quantum Bits written by Oliver Benson and published by Pan Stanford Publishing. This book was released on 2009 with total page 515 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights state-of-the-art qubit implementations in semiconductors and provides an extensive overview of this newly emerging field. Semiconductor nanostructures have huge potential as future quantum information devices as they provide various ways of qubit implementation (electron spin, electronic excitation) as well as a way to transfer quantum information from stationary qubits to flying qubits (photons). Therefore, this book unites contributions from leading experts in the field, reporting cutting-edge results on spin qubit preparation, read-out and transfer. The latest theoretical as well as experimental studies of decoherence in these quantum information systems are also provided. Novel demonstrations of complex flying qubit states and first applications of semiconductor-based quantum information devices are given, too.

Download or read book Advancement of Silicon based Spin Qubits written by Elliot Connors and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Electron spins in gate-defined quantum dots have emerged as a leading candidate for quantum-information-processing applications, including quantum computation. Long coherence times and compatibility with conventional semiconductor-manufacturing techniques contribute to the appeal of implementing these devices as quantum bits, or qubits. Recent research efforts have demonstrated many of the fundamental requirements for their utilization in a future quantum processor. Despite this, further development in the performance of these devices is necessary if the goal is truly to realize a universal quantum computer. Improvements will likely come in the form of both device-engineering advancements as well as novel qubit-operation and qubit-measurement schemes. This thesis describes a number of experiments carried out in gate-defined quantum dots in Si/SiGe, including demonstrations of high-fidelity spin-measurement, multiple studies of environmental noise, and coherent control of electron-spin qubits. This work represents the first realization of such devices in the Nichol Group at the University of Rochester. Together, the results represent the advancement of our understanding of silicon-based quantum dots and spin qubits"--Page xii.

Download or read book Silicon in the Quantum Limit written by Charles George Tahan and published by . This book was released on 2005 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Germanium Based Technologies written by Cor Claeys and published by Elsevier. This book was released on 2011-07-28 with total page 476 pages. Available in PDF, EPUB and Kindle. Book excerpt: Germanium is a semiconductor material that formed the basis for the development of transistor technology. Although the breakthrough of planar technology and integrated circuits put silicon in the foreground, in recent years there has been a renewed interest in germanium, which has been triggered by its strong potential for deep submicron (sub 45 nm) technologies. Germanium-Based technologies: From Materials to Devices is the first book to provide a broad, in-depth coverage of the field, including recent advances in Ge-technology and the fundamentals in material science, device physics and semiconductor processing. The contributing authors are international experts with a world-wide recognition and involved in the leading research in the field. The book also covers applications and the use of Ge for optoelectronics, detectors and solar cells. An ideal reference work for students and scientists working in the field of physics of semiconductor devices and materials, as well as for engineers in research centres and industry. Both the newcomer and the expert should benefit from this unique book. State-of-the-art information available for the first time as an all-in-source Extensive reference list making it an indispensable reference book Broad coverage from fundamental aspects up to industrial applications

Download or read book Silicon silicon germanium Quantum Dots with Single electron Transistor Charge Sensors written by Mingyun Yuan and published by . This book was released on 2013 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: Si/SiGe quantum dots (QDs) are promising candidates for spin-based quantum bits (qubits) as a result of the reduced spin-orbit coupling as well as the Si isotopes with zero nuclear spin. Meanwhile qubit readout is a challenge related to semiconductor-based quantum computation. A superconducting single-electron transistor (SET), when operating in the radio-frequency (rf) regime, has a combination of high charge sensitivity and low back-action and can potentially become an ideal charge sensor for the QDs. This thesis describes the development of superconducting SET charge sensors for Si/SiGe QDs. Using rf-SETs we have detected real-time electron tunneling events on the order of 10 microseconds in a single QD and mapped out the stability diagram of a double QD, showing spin blockade and bias triangles due to excited-state transitions. In addition Kondo effects that are significantly different from the standard spin 1/2 model have been observed and investigated in both perpendicular and in-plane magnetic fields, indicating the interplay between the spin and valley degrees of freedom in Si.

Download or read book Photonics and Electronics with Germanium written by Kazumi Wada and published by John Wiley & Sons. This book was released on 2015-05-06 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: Representing a further step towards enabling the convergence of computing and communication, this handbook and reference treats germanium electronics and optics on an equal footing. Renowned experts paint the big picture, combining both introductory material and the latest results. The first part of the book introduces readers to the fundamental properties of germanium, such as band offsets, impurities, defects and surface structures, which determine the performance of germanium-based devices in conjunction with conventional silicon technology. The second part covers methods of preparing and processing germanium structures, including chemical and physical vapor deposition, condensation approaches and chemical etching. The third and largest part gives a broad overview of the applications of integrated germanium technology: waveguides, photodetectors, modulators, ring resonators, transistors and, prominently, light-emitting devices. An invaluable one-stop resource for both researchers and developers.

Download or read book Progress Towards Two qubit Devices in Si sige Heterostructures written by Ryan Howard Foote and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since being proposed almost 40 years ago, scientists across many disciplines have made great progress in the fields of quantum computation and quantum information. Instead of a classical bit (0 or 1), a quantum computer uses a two-level quantum system as a quantum bit or qubit. By controllably manipulating the quantum-mechanical properties of these qubits, a quantum computer could, for example, be used to simulate other, less well understood quantum systems, or to run certain classes of quantum algorithms that cannot be run on classical hardware. In order to build a quantum computer, certain basic requirements must be met. As with a classical computer, logic gates are necessary to controllably manipulate qubits to perform calculations. One such requirement for a universal quantum computer is a two-qubit logic gate. This is an inherently quantum mechanical gate, which has no classical analog. For example, the controlled-not two-qubit gate will perform a not operation on the target qubit if and only if the control qubit is in the one state, else it does nothing to the target qubit. In either case, the control qubit is left unchanged and unmeasured. Being able to perform this gate with high fidelity is critical to creating a quantum computer. In this dissertation, I present progress towards fabricating, characterizing, and manipulating two-qubit devices in Si/SiGe heterostructures. First, I motivate the use of quantum dot qubits hosted in Si/SiGe as a suitable platform for quantum computing. Then, I present characterization of Si/SiGe substrates and discuss fabrication of a quantum dot device. Next, I outline the electronics set up for measuring a quantum dot device in a dilution refrigerator. I then present results of two, published experiments which explore multi-qubit systems: one which demonstrates controllable tunnel coupling between a quantum dot an a nearby localized impurity, and the other which demonstrates state-conditional Landau-Zener-Stückelberg oscillations between capacitively coupled double quantum dots in a quadruple quantum dot device. Next I discuss fabrication and characterization of micromagnets for spin qubit applications. I finally conclude by discussing future research avenues towards realizing a robust, multi-qubit device in silicon.

Download or read book Chemical Abstracts written by and published by . This book was released on 2002 with total page 2540 pages. Available in PDF, EPUB and Kindle. Book excerpt: