Semiconductor Spintronics and Quantum Computation


Book Description

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.




Optical Generation and Control of Quantum Coherence in Semiconductor Nanostructures


Book Description

The fundamental concept of quantum coherence plays a central role in quantum physics, cutting across disciplines of quantum optics, atomic and condensed matter physics. Quantum coherence represents a universal property of the quantum s- tems that applies both to light and matter thereby tying together materials and p- nomena. Moreover, the optical coherence can be transferred to the medium through the light-matter interactions. Since the early days of quantum mechanics there has been a desire to control dynamics of quantum systems. The generation and c- trol of quantum coherence in matter by optical means, in particular, represents a viable way to achieve this longstanding goal and semiconductor nanostructures are the most promising candidates for controllable quantum systems. Optical generation and control of coherent light-matter states in semiconductor quantum nanostructures is precisely the scope of the present book. Recently, there has been a great deal of interest in the subject of quantum coh- ence. We are currently witnessing parallel growth of activities in different physical systems that are all built around the central concept of manipulation of quantum coherence. The burgeoning activities in solid-state systems, and semiconductors in particular, have been strongly driven by the unprecedented control of coherence that previously has been demonstrated in quantum optics of atoms and molecules, and is now taking advantage of the remarkable advances in semiconductor fabrication technologies. A recent impetus to exploit the coherent quantum phenomena comes from the emergence of the quantum information paradigm.




Manipulating Quantum Coherence in Solid State Systems


Book Description

This book features the proceedings of the NATO Advanced Study Institute "Manipulating Quantum Coherence in Solid State Systems", held in Cluj-Napoca, Romania, August 2005, which presented a fundamental introduction to solid-state approaches to achieving quantum computation. This proceedings volume describes the properties of quantum coherence in semiconductor spin-based systems and the behavior of quantum coherence in superconducting systems.




Spin-orbit Coupling Effects in Two-Dimensional Electron and Hole Systems


Book Description

The first part provides a general introduction to the electronic structure of quasi-two-dimensional systems with a particular focus on group-theoretical methods. The main part of the monograph is devoted to spin-orbit coupling phenomena at zero and nonzero magnetic fields. Throughout the book, the main focus is on a thorough discussion of the physical ideas and a detailed interpretation of the results. Accurate numerical calculations are complemented by simple and transparent analytical models that capture the important physics.




Spins in Optically Active Quantum Dots


Book Description

Filling a gap in the literature, this up-to-date introduction to the field provides an overview of current experimental techniques, basic theoretical concepts, and sample fabrication methods. Following an introduction, this monograph deals with optically active quantum dots and their integration into electro-optical devices, before looking at the theory of quantum confined states and quantum dots interacting with the radiation field. Final chapters cover spin-spin interaction in quantum dots as well as spin and charge states, showing how to use single spins for break-through quantum computation. A conclusion and outlook round off the volume. The result is a primer providing the essential basic knowledge necessary for young researchers entering the field, as well as semiconductor and theoretical physicists, PhD students in physics and material sciences, electrical engineers and materials scientists.




Read-Out and Coherent Manipulation of an Isolated Nuclear Spin


Book Description

This thesis sheds new light on the worldwide first electrical manipulation of a single nuclear spin. Over the last four decades, the size of a bit, the smallest logical unit in a computer, has decreased by more than two orders of magnitude and will soon reach a limit where quantum phenomena become important. Inspired by the power of quantum mechanics, researchers have already identified pure quantum systems, having, analog to a classical bit, two controllable and readable states. In this regard, the inherent spin of electrons or nuclei with its two eigenstates, spin up and spin down, is a promising candidate. Using expertise in the field of single-molecule magnets, the author developed a molecular transistor, which allows quantum information to be written onto a single nuclear spin by means of an electric field only, and, in addition, enables the electronic read-out of this quantum state. This novel approach opens a path to addressing and manipulating individual nuclear spins within a very confined space (a single molecule), at high speed. Thus, the author was able to show that single molecule magnets are promising candidates for quantum information processing, which is triggering a new field of research towards molecular quantum electronics.




Spintronics


Book Description

This new volume focuses on a new, exciting field of research: Spintronics, the area also known as spin-based electronics. The ultimate aim of researchers in this area is to develop new devices that exploit the spin of an electron instead of, or in addition to, its electronic charge. In recent years many groups worldwide have devoted huge efforts to research of spintronic materials, from their technology through characterization to modeling. The resultant explosion of papers in this field and the solid scientific results achieved justify the publication of this volume. Its goal is to summarize the current level of understanding and to highlight some key results and milestones that have been achieved to date. Semiconductor spintronics is expected to lead to a new generation of transistors, lasers and integrated magnetic sensors that can be used to create ultra-low power, high-speed memory, logic and photonic devices. In addition, development of novel devices such as spin-polarized light emitters, spin field effect transistors, integrated sensors and high-temperature electronics is anticipated. - Spintronics has emerged as one of the fastest growing areas of research - This text presents an in-depth examination of the most recent technological spintronic developments - Includes contributions from leading scholars and industry experts




Towards Solid-State Quantum Repeaters


Book Description

Towards Solid-State Quantum Repeaters: Ultrafast, Coherent Optical Control and Spin-Photon Entanglement in Charged InAs Quantum Dots summarizes several state-of-the-art coherent spin manipulation experiments in III-V quantum dots. Both high-fidelity optical manipulation, decoherence due to nuclear spins and the spin coherence extraction are discussed, as is the generation of entanglement between a single spin qubit and a photonic qubit. The experimental results are analyzed and discussed in the context of future quantum technologies, such as quantum repeaters. Single spins in optically active semiconductor host materials have emerged as leading candidates for quantum information processing (QIP). The quantum nature of the spin allows for encoding of stationary, memory quantum bits (qubits), and the relatively weak interaction with the host material preserves the spin coherence. On the other hand, optically active host materials permit direct interfacing with light, which can be used for all-optical qubit manipulation, and for efficiently mapping matter qubits into photonic qubits that are suited for long-distance quantum communication.




Detection and Interaction of Single Quantum States


Book Description

This book highlights the findings and achievements in the major research plan “Detection and Interaction of Single Quantum States” funded by the National Natural Science Foundation of China (NSFC). The 8-year plan started in 2011 and consisted of 107 projects conducted by Chinese universities and research institutes. The book covers the plan's research background, achievements, and follow-up prospects. The plan aimed to tackle one of the major challenges for researchers worldwide—to establish precise detection and control of single quantum states in time, space, energy, and momentum. The plan integrated precise detection means with the ultrahigh resolution of time, space, and energy, under extreme conditions such as ultrahigh vacuum, ultralow temperature, high magnetic field, and ultrahigh pressure, using interdisciplinary research methods in physics, chemistry, informatics, and materials science. The book focuses on the exploration of new phenomena, theories, and concepts of single quantum states, describes new techniques and methods of single quantum states, and presents the purification and construction of single-quantum-state systems. It is a concise and valuable source of information for researchers in quantum science and graduate students interested in the research field.