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Sample records for quantum electronics conference

  1. Electron quantum optics as quantum signal processing

    OpenAIRE

    Roussel, B.; Cabart, C.; Fève, G.; Thibierge, E.; Degiovanni, P.

    2016-01-01

    The recent developments of electron quantum optics in quantum Hall edge channels have given us new ways to probe the behavior of electrons in quantum conductors. It has brought new quantities called electronic coherences under the spotlight. In this paper, we explore the relations between electron quantum optics and signal processing through a global review of the various methods for accessing single- and two-electron coherences in electron quantum optics. We interpret electron quantum optics...

  2. Quantum electronics basic theory

    CERN Document Server

    Fain, V M; Sanders, J H

    1969-01-01

    Quantum Electronics, Volume 1: Basic Theory is a condensed and generalized description of the many research and rapid progress done on the subject. It is translated from the Russian language. The volume describes the basic theory of quantum electronics, and shows how the concepts and equations followed in quantum electronics arise from the basic principles of theoretical physics. The book then briefly discusses the interaction of an electromagnetic field with matter. The text also covers the quantum theory of relaxation process when a quantum system approaches an equilibrium state, and explai

  3. International Conference on Quantum Science and Applications (ICQSA-2016)

    International Nuclear Information System (INIS)

    Algin, A.; Arik, M.; Gavrilik, A. M.

    2016-01-01

    This special volume of Journal of Physics: Conference Series is dedicated to the proceedings of “International Conference on Quantum Science and Applications (ICQSA-2016)”. The conference was organized by the Centre for Quantum Research and Applications at Eskisehir Osmangazi University, Eskisehir, Turkey. It was held in Eskisehir Osmangazi University Congress and Culture Centre during May 25-27, 2016 http://icqsa2016.ogu.edu.tr. It gathered actively 143 participants from different disciplines in natural and applied sciences coming from 16 different countries from all over the word. It was the first international conference in its content on the scientific research fields of quantum science and applications in Turkey. It also consisted of 12 plenary lectures and 119 contributed oral presentations covering interdisciplinary fields of research. The ICQSA-2016 conference focused on recent modern theoretical and experimental developments of quantum science in multi-disciplinary aspects of areas of mathematics, physics, statistics, chemistry, biology, computer science, electronics, informatics, medicine, education, etc. It served as an interaction platform for students, researchers, public, and private sector delegates for sharing new scientific and technological ideas on quantum applications in science and technology. The topics of the conference were: Quantum theory and quantum computing, quantum information theory and its applications, quantum statistics and its applications, quantum thermodynamics, quantum cryptography, classical and quantum symmetries, quantum calculus in science, engineering, medicine, education, etc., classical and quantum integrable systems, modeling and numerical methods in quantum systems, other modern mathematical methods in science and technology. Each of the submitted papers for this special volume of the proceedings of ICQSA-2016 has been reviewed by external referees. There are 36 accepted papers. Besides, it is worth pointing out

  4. Advances in quantum electronics

    CERN Document Server

    Goodwin, D W

    1974-01-01

    Advances in Quantum Electronics, Volume 2 deals with the effects of quantum mechanics on the behavior of electrons in matter. This book is divided into three chapters. Chapter 1 reviews the statistical properties of optical fields and spectral processing techniques, including the use of photon correlation techniques to measure scattering effects in a number of different media. The use of optical E.P.R. and excitation spectroscopic techniques and techniques for establishing the location of impurity ions in the chalcogenides are describe in Chapter 2. The last chapter surveys the field of mode l

  5. Network-topology-adaptive quantum conference protocols

    International Nuclear Information System (INIS)

    Zhang Sheng; Wang Jian; Tang Chao-Jing; Zhang Quan

    2011-01-01

    As an important application of the quantum network communication, quantum multiparty conference has made multiparty secret communication possible. Previous quantum multiparty conference schemes based on quantum data encryption are insensitive to network topology. However, the topology of the quantum network significantly affects the communication efficiency, e.g., parallel transmission in a channel with limited bandwidth. We have proposed two distinctive protocols, which work in two basic network topologies with efficiency higher than the existing ones. We first present a protocol which works in the reticulate network using Greeberger—Horne—Zeilinger states and entanglement swapping. Another protocol, based on quantum multicasting with quantum data compression, which can improve the efficiency of the network, works in the star-like network. The security of our protocols is guaranteed by quantum key distribution and one-time-pad encryption. In general, the two protocols can be applied to any quantum network where the topology can be equivalently transformed to one of the two structures we propose in our protocols. (general)

  6. Superconducting quantum electronics

    International Nuclear Information System (INIS)

    Kose, V.

    1989-01-01

    This book reviews recent accomplishments, presents new results and discusses possible future developments of superconducting quantum electronics and high T c superconductivity. The three main parts of the book deal with fundamentals, sensitive detectors, and precision metrology. New results reported include: correct equivalent circuits modelling superconducting electronic devices; exact solution of the Mattis-Bardeen equations describing various experiments for thin films; complete theoretical description and experimental results for a new broad band spectrum analyzer; a new Josephson junction potentiometer allowing tracing of unknown voltage ratios back to well-known frequency ratios; and fast superconducting SQUID shift registers enabling the production of calculable noise power spectra in the microwave region

  7. Quantum Hall Electron Nematics

    Science.gov (United States)

    MacDonald, Allan

    In 2D electron systems hosted by crystals with hexagonal symmetry, electron nematic phases with spontaneously broken C3 symmetry are expected to occur in the quantum Hall regime when triplets of Landau levels associated with three different Fermi surface pockets are partially filled. The broken symmetry state is driven by intravalley Coulombic exchange interactions that favor spontaneously polarized valley occupations. I will discuss three different examples of 2D electron systems in which this type of broken symmetry state is expected to occur: i) the SnTe (111) surface, ii) the Bi (111) surface. and iii) unbalanced bilayer graphene. This type of quantum Hall electron nematic state has so far been confirmed only in the Bi (111) case, in which the anisotropic quasiparticle wavefunctions of the broken symmetry state were directly imaged. In the SnTe case the nematic state phase boundary is controlled by a competition between intravalley Coulomb interactions and intervalley scattering processes that increase in relative strength with magnetic field. An in-plane Zeeman field alters the phase diagram by lifting the three-fold Landau level degeneracy, yielding a ground state energy with 2 π/3 periodicity as a function of Zeeman-field orientation angle. I will comment on the possibility of observing similar states in the absence of a magnetic field. Supported by DOE Division of Materials Sciences and Engineering Grant DE-FG03-02ER45958.

  8. Proceedings of the conference on frontiers of Quantum Monte Carlo

    International Nuclear Information System (INIS)

    Gubernatis, J.E.

    1986-01-01

    This journal of conference proceedings includes papers on topics such as: computers and science; Quantum Monte Carlo; condensed matter physics (with papers including the statistical error of Green's Function Monte Carlo, a study of Trotter-like approximations, simulations of the Hubbard model, and stochastic simulation of fermions); chemistry (including papers on quantum simulations of aqueous systems, fourier path integral methods, and a study of electron solvation in polar solvents using path integral calculations); atomic molecular and nuclear physics; high-energy physics, and advanced computer designs

  9. Silicon Quantum Electronics

    NARCIS (Netherlands)

    Zwanenburg, Floris Arnoud; Dzurak, Andrew S.; Morello, Andrea; Simmons, Michelle Y.; Hollenberg, Lloyd C.L.; Klimeck, Gerhard; Rogge, Sven; Coppersmith, Susan N.; Eriksson, Mark A.

    2013-01-01

    This review describes recent groundbreaking results in Si, Si=SiGe, and dopant-based quantum dots, and it highlights the remarkable advances in Si-based quantum physics that have occurred in the past few years. This progress has been possible thanks to materials development of Si quantum devices,

  10. Quantum Electronics for Atomic Physics

    CERN Document Server

    Nagourney, Warren

    2010-01-01

    Quantum Electronics for Atomic Physics provides a course in quantum electronics for researchers in atomic physics. The book covers the usual topics, such as Gaussian beams, cavities, lasers, nonlinear optics and modulation techniques, but also includes a number of areas not usually found in a textbook on quantum electronics. It includes such practical matters as the enhancement of nonlinear processes in a build-up cavity, impedance matching into a cavity, laser frequencystabilization (including servomechanism theory), astigmatism in ring cavities, and atomic/molecular spectroscopic techniques

  11. Quantum dots: Rethinking the electronics

    Energy Technology Data Exchange (ETDEWEB)

    Bishnoi, Dimple [Department of Physics, S. S. Jain Subodh PG College, Jaipur, Rajasthan Pin-302004 (India)

    2016-05-06

    In this paper, we demonstrate theoretically that the Quantum dots are quite interesting for the electronics industry. Semiconductor quantum dots (QDs) are nanometer-scale crystals, which have unique photo physical, quantum electrical properties, size-dependent optical properties, There small size means that electrons do not have to travel as far as with larger particles, thus electronic devices can operate faster. Cheaper than modern commercial solar cells while making use of a wider variety of photon energies, including “waste heat” from the sun’s energy. Quantum dots can be used in tandem cells, which are multi junction photovoltaic cells or in the intermediate band setup. PbSe (lead selenide) is commonly used in quantum dot solar cells.

  12. International Conference on Coherence and Quantum Optics

    CERN Document Server

    RECENT DEVELOPMENTS IN QUANTUM OPTICS

    1993-01-01

    This volume is composed of papers (invited and contributed) presented at the International Conference on Coherence and Quantum Optics held at the University of Hyderabad January 5-January 10, 1991. It has been organized by Professor Girish Agarwal and his colleagues at the School of Physics, University of Hyderabad, Hyder­ abad, India under partial support from the Department of Science and Technology, Government of India, International Center for Theoretical Physics, Trieste, Italy and the National Science Foundation, USA. Without the untiring efforts of Prof. Girish Agarwal and the members of his quantum office group, the Conference and the present volume would not have been possible. Some extraordinary circumstances resulted in a delay of the publication of the present volume. Our sincere apologies to all the authors. We deeply regret the inconvenience caused due to the delay. A debt of gratitude is due to Ms. Kim Bella for the excellent typing job of the different versions and the final version of the ma...

  13. 8th Rochester Conference on Coherence and Quantum Optics

    CERN Document Server

    2001-01-01

    The Eighth Rochester Conference on Coherence and Quantum Optics was held on the campus of the University of Rochester during the period June 13-16,2001. This volume contains the proceedings of the meeting. The meeting was preceded by an affiliated conference, the International Conference on Quantum Information, with some overlapping sessions on June 13. The proceedings of the affiliated conference will be published separately by the Optical Society of America. A few papers that were presented in common plenary sessions of the two conferences will be published in both proceedings volumes. More than 268 scientists from 28 countries participated in the week long discussions and presentations. This Conference differed from the previous seven in the CQO series in several ways, the most important of which was the absence of Leonard Mandel. Professor Mandel died a few months before the conference. A special memorial symposium in his honor was held at the end of the conference. The presentations from that sym...

  14. Quantum ratchets reroute electrons

    International Nuclear Information System (INIS)

    Haenggi, P.; Reimann, P.

    1999-01-01

    Is it possible to extract energy from random fluctuations and put it to use? This challenging question has provoked discussion ever since the early days of Brownian-motion theory. For large-scale or macroscopic fluctuations, the answer is ''yes'' - the principle is demonstrated, for example, in the self-winding wristwatch. Much subtler is the issue of whether microscopic random fluctuations, such as thermal Brownian motion or even the haphazard motion of quantum particles, acting as a random energy source can cause the particles to flow in one direction only. In recent years this field has been the scene of remarkable activity, motivated by the prospect of potentially high-profile technological and biological applications, such as molecular motors. In particular the directed transport of particles in an asymmetric potential known as a ratchet has received a lot of attention. This research, however, has focused on ''thermal ratchets'' in which the particles undergo thermal Brownian motion: the next challenge is to move from the classical world and account for quantum mechanical effects. Recently a collaboration between physicists at Lund University in Sweden and the Niels Bohr Institute in Copenhagen has taken a significant step forward and built a quantum ratchet (H Linke et al. 1998 Europhys. Lett. 44 341 and 45 406). The device is based on an aluminium-doped gallium arsenide (GaAs/AlGaAs) quantum dot with a ratchet-like, triangular-shaped cavity. In this article the authors discuss the implications of this work. (UK)

  15. Quantum Fest 2016 International Conference on Quantum Phenomena, Quantum Control and Quantum Optics

    International Nuclear Information System (INIS)

    2017-01-01

    The Quantum Fest is a periodic annual festival on Quantum Phenomena, Quantum Control and Geometry of Quantum States, organized by the Center for Research and Advanced Studies (Cinvestav by its acronym in Spanish) and Unidad Profesional Interdisciplinaria en Ingeniería y Tecnologías Avanzadas del Instituto Politécnico Nacional (UPIITA-IPN) in México City, Mexico. The aim of this meeting is to bring together students and researchers which are engaged in the subjects of the festival, from both theoretical and experimental approaches, in order to get lively discussions and to enable a closer contact between them.The Quantum Fest was celebrated for the first time in the Physics Department of Cinvestav (2010), since then it has been hosted in Cinvestav, UPIITA-IPN and the Tecnológico de Monterrey, Campus Estado de México (ITESM-CEM).The Quantum Fest 2016 is the seventh edition of the festival, it took place from October 17 to 21 in the Sala de Usos Múltiples, Edificio I of UPIITA-IPN, and was addressed to join the celebration of the first eighty years of the Instituto Politécnico Nacional as well as the first twenty years of the Unidad Profesional Interdisciplinaria en Ingeniería y Tecnologías Avanzadas del Instituto Politécnico Nacional. We would like to thank the willing of the UPIITA-IPN to offer its facilities as the venue of the festival; all its help provided to simplify the logistics and organization of the conference has been welcomed and is acknowledged.The topics addressed at the short courses of the Quantum Fest 2016 were time asymmetric quantum mechanics, quantum resonances, models of quantum field theory in metamaterials, singular potentials and self-adjoint extensions, nonclassical states of light, Hardy functions and Hilbert space operators.The Lecturers of Quantum Fest 2016 were:Manuel Gadella (Valladolid University, Spain)Maribel Loaiza (Department of Mathematics, Cinvestav, Mexico)Luis Miguel Nieto (Valladolid University, Spain)Oscar Rosas

  16. International Conference on Laser Physics and Quantum Optics

    CERN Document Server

    Xie, Shengwu; Zhu, Shi-Yao; Scully, Marlan

    2000-01-01

    Since the advent of the laser about 40 years ago, the field of laser physics and quantum optics have evolved into a major discipline. The early studies included the optical coherence theory and the semiclassical and quantum mechanical theories of the laser. More recently many new and interesting effects have been predicted. These include the role of coherent atomic effects in lasing without inversion and electromagnetically induced transparency, atom optics, laser cooling and trapping, teleportation, the single-atom micromaser and its role in quantum measurement theory, to name a few. The International Conference on Laser Physics and Quantum Optics was held in Shanghai from August 25 to August 28, 1999, to discuss these and many other exciting developments in laser physics and quantum optics. The international character of the conference was manifested by the fact that scientists from over 13 countries participated and lectured at the conference. There were four keynote lectures delivered by Nobel laureate Wi...

  17. Electron correlations in quantum dots

    International Nuclear Information System (INIS)

    Tipton, Denver Leonard John

    2001-01-01

    Quantum dot structures confine electrons in a small region of space. Some properties of semiconductor quantum dots, such as the discrete energy levels and shell filling effects visible in addition spectra, have analogies to those of atoms and indeed dots are sometimes referred to as 'artificial atoms'. However, atoms and dots show some fundamental differences due to electron correlations. For real atoms, the kinetic energy of electrons dominates over their mutual Coulomb repulsion energy and for this reason the independent electron approximation works well. For quantum dots the confining potential may be shallower than that of real atoms leading to lower electron densities and a dominance of mutual Coulomb repulsion over kinetic energy. In this strongly correlated regime the independent electron picture leads to qualitatively incorrect results. This thesis concentrates on few-electron quantum dots in the strongly correlated regime both for quasi-one-dimensional and two-dimensional dots in a square confining potential. In this so-called 'Wigner' regime the ground-state electronic charge density is localised near positions of classical electrostatic minima and the interacting electronic spectrum consists of well separated spin multiplets. In the strongly correlated regime the structure of low-energy multiplets is explained by mapping onto lattice models with extended-Hubbard and Heisenberg effective Hamiltonians. The parameters for these effective models are calculated within a Hartree approximation and are shown to reproduce well the exact results obtained by numerical diagonalisation of the full interacting Hamiltonian. Comparison is made between square dots and quantum rings with full rotational symmetry. In the very low-density regime, direct diagonalisation becomes impractical due to excessive computer time for convergence. In this regime a numerical renormalisation group method is applied to one-dimensional dots, enabling effective spin-interactions to be

  18. Quantum technology past, present, future: quantum energetics (Conference Presentation)

    Science.gov (United States)

    Choi, Sang H.

    2017-04-01

    Since the development of quantum physics in the early part of the 1900s, this field of study has made remarkable contributions to our civilization. Some of these advances include lasers, light-emitting diodes (LED), sensors, spectroscopy, quantum dots, quantum gravity and quantum entanglements. In 1998, the NASA Langley Research Center established a quantum technology committee to monitor the progress in this area and initiated research to determine the potential of quantum technology for future NASA missions. The areas of interest in quantum technology at NASA included fundamental quantum-optics materials associated with quantum dots and quantum wells, device-oriented photonic crystals, smart optics, quantum conductors, quantum information and computing, teleportation theorem, and quantum energetics. A brief review of the work performed, the progress made in advancing these technologies, and the potential NASA applications of quantum technology will be presented.

  19. 2012 Gordon Research Conference, Electron donor-acceptor interactions, August 5-10 2012

    Energy Technology Data Exchange (ETDEWEB)

    McCusker, James [Michigan State Univ., East Lansing, MI (United States)

    2012-08-10

    The upcoming incarnation of the Gordon Research Conference on Electron Donor Acceptor Interactions will feature sessions on classic topics including proton-coupled electron transfer, dye-sensitized solar cells, and biological electron transfer, as well as emerging areas such as quantum coherence effects in donor-acceptor interactions, spintronics, and the application of donor-acceptor interactions in chemical synthesis.

  20. Single-electron quantum tomography in quantum Hall edge channels

    International Nuclear Information System (INIS)

    Grenier, Ch; Degiovanni, P; Herve, R; Bocquillon, E; Parmentier, F D; Placais, B; Berroir, J M; Feve, G

    2011-01-01

    We propose a quantum tomography protocol to measure single-electron coherence in quantum Hall edge channels, and therefore access for the first time the wavefunction of single-electron excitations propagating in ballistic quantum conductors. Its implementation would open the way to quantitative studies of single-electron decoherence and would provide a quantitative tool for analyzing single- to few-electron sources. We show how this protocol could be implemented using ultrahigh-sensitivity noise measurement schemes.

  1. Quantum electronics research

    International Nuclear Information System (INIS)

    Anon.

    1976-01-01

    Efficiency measurements in the rare gas excimers show that up to 50 percent of the energy deposited in a high-pressure rare gas by an electron beam can be converted to excimer fluorescence. The production kinetics and radiative properties of rare gas oxide excimers have been explored and show that short pulse lasers near 1 percent efficiency with energy storage of 10 J/liter can be constructed. The rare gas-halogen and dihalogen systems have been explored as a class of efficient radiators to complement the rare gas excimers. A Br 2 laser at 292 nm has been demonstrated, and XeBr fluorescence efficiency of 11 percent has been measured. An XeBr excimer-pumped atomic iodine laser has been demonstrated, and the systems considerations involved in scaling atomic iodine lasers to large sizes have been identified and are discussed. Oxygen, sulfur, and selenium have been analyzed as candidates for an optically pumped, visible energy storage laser. The physical and radiative properties of gaseous rare earth compounds, which may be suitable for energy storage lasers, have been measured and are discussed. Scaling considerations have been identified for drivers for large, electron-beam-pumped lasers. Theoretical studies bearing on an understanding of the basic atomic and molecular physics which must be understood for laser development and isotope separation projects have been carried out. These include efforts to develop a theoretical understanding rare-gas halogen structure and kinetics, copper vapor laser kinetics, electron interactions such as dissociative attachment, and other areas

  2. Quantum Phase Extraction in Isospectral Electronic Nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Moon, Christopher

    2010-04-28

    Quantum phase is not a direct observable and is usually determined by interferometric methods. We present a method to map complete electron wave functions, including internal quantum phase information, from measured single-state probability densities. We harness the mathematical discovery of drum-like manifolds bearing different shapes but identical resonances, and construct quantum isospectral nanostructures possessing matching electronic structure but divergent physical structure. Quantum measurement (scanning tunneling microscopy) of these 'quantum drums' [degenerate two-dimensional electron states on the Cu(111) surface confined by individually positioned CO molecules] reveals that isospectrality provides an extra topological degree of freedom enabling robust quantum state transplantation and phase extraction.

  3. 18th International Conference on Electronic Publishing

    CERN Document Server

    Dobreva, Milena

    2014-01-01

    The ways in which research data is used and handled continue to capture public attention and are the focus of increasing interest. Electronic publishing is intrinsic to digital data management, and relevant to the fields of data mining, digital publishing and social networks, with their implications for scholarly communication, information services, e-learning, e-business and the cultural heritage sector. This book presents the proceedings of the 18th International Conference on Electronic Publishing (ELPUB), held in Thessaloniki, Greece, in June 2014. The conference brings together researchers and practitioners to discuss the many aspects of electronic publishing, and the theme this year is 'Let's put data to use: digital scholarship for the next generation'. As well as examining the role of cultural heritage and service organisations in the creation, accessibility, duration and long-term preservation of data, it provides a discussion forum for the appraisal, citation and licensing of research data and the n...

  4. Resonant tunneling of electrons in quantum wires

    International Nuclear Information System (INIS)

    Krive, I.V.; Shekhter, R.I.; Jonson, M.; Krive, I.V.

    2010-01-01

    We considered resonant electron tunneling in various nanostructures including single wall carbon nanotubes, molecular transistors and quantum wires formed in two-dimensional electron gas. The review starts with a textbook description of resonant tunneling of noninteracting electrons through a double-barrier structure. The effects of electron-electron interaction in sequential and resonant electron tunneling are studied by using Luttinger liquid model of electron transport in quantum wires. The experimental aspects of the problem (fabrication of quantum wires and transport measurements) are also considered. The influence of vibrational and electromechanical effects on resonant electron tunneling in molecular transistors is discussed.

  5. Quantum Optics 6 - Quantum Engineering of Atoms and Photons - Conference Materials

    International Nuclear Information System (INIS)

    2005-01-01

    The conference organized by Center for Theoretical Physics, Institute of Physics and Warsaw University, sponsored by European Science Foundation, was held in Krynica (120 km south-east of Cracow), Poland, June 13-18 2005. This was the sixth conference of the cycle, the previous one was held in Koscielisko, Poland in 2001. This time the main subject of the conference was: Quantum Engineering of Atoms and Photons. The meeting was focused on the physics of ultracold quantum gases, which without doubts determines the frontiers of the modern atomic, molecular and optical physics. Special attention was also be given to quantum information processing, both from theoretical and experimental point of view, including possible realizations in ultracold quantum gases. The conference consisted of invited lectures and a poster session. Competition for the best poster was held, sponsored by Journal of Optics B and Journal of Physics B - for more on this, including the results of the competition visit. (author)

  6. Quantum theory at the crossroads reconsidering the 1927 Solvay conference

    CERN Document Server

    Bacciagaluppi, Guido

    2009-01-01

    We reconsider the crucial 1927 Solvay conference in the context of current research in the foundations of quantum theory. Contrary to folklore, the interpretation question was not settled at this conference and no consensus was reached; instead, a range of sharply conflicting views were presented and extensively discussed. Today, there is no longer an established or dominant interpretation of quantum theory, so it is important to re-evaluate the historical sources and keep the interpretation debate open. In this spirit, we provide a complete English translation of the original proceedings (lectures and discussions), and give background essays on the three main interpretations presented: de Broglie's pilot-wave theory, Born and Heisenberg's quantum mechanics, and Schroedinger's wave mechanics. We provide an extensive analysis of the lectures and discussions that took place, in the light of current debates about the meaning of quantum theory. The proceedings contain much unexpected material, including extensive...

  7. Advances in quantum electronics 3

    CERN Document Server

    Goodwin, D W

    2013-01-01

    Advances in Quantum Electronics, Volume 3 covers articles on the theoretical and experimental work undertaken in the field of optical pumping and on gaseous ion lasers. The book presents an overview of the optical-pumping field and a review of the use and properties of the density matrix as applied to the statistical behavior of assemblages of atoms or ions. The text discusses the application of the density matrix approach to the theory of optical-pumping r.f. spectroscopy and spin-exchange optical pumping. Optical-pumping experiments are also considered. The book further provides a comprehens

  8. PREFACE: Proceedings of the 2nd International Conference on Quantum Simulators and Design (Tokyo, Japan, 31 May-3 June 2008) Proceedings of the 2nd International Conference on Quantum Simulators and Design (Tokyo, Japan, 31 May-3 June 2008)

    Science.gov (United States)

    Akai, Hisazumi; Tsuneyuki, Shinji

    2009-02-01

    This special issue of Journal of Physics: Condensed Matter comprises selected papers from the proceedings of the 2nd International Conference on Quantum Simulators and Design (QSD2008) held in Tokyo, Japan, between 31 May and 3 June 2008. This conference was organized under the auspices of the Development of New Quantum Simulators and Quantum Design Grant-in-Aid for Scientific Research on Priority Areas, Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT). The conference focused on the development of first principles electronic structure calculations and their applications. The aim was to provide an opportunity for discussion on the progress in computational materials design and, in particular, the development of quantum simulators and quantum design. Computational materials design is a computational approach to the development of new materials. The essential ingredient is the use of quantum simulators to design a material that meets a given specification of properties and functionalities. For this to be successful, the quantum simulator should be very reliable and be applicable to systems of realistic size. During the conference, new methods of quantum simulation and quantum design were discussed including methods beyond the local density approximation of density functional theory, order-N methods, methods dealing with excitations and reactions, and the application of these methods to the design of novel materials, devices and systems. The conference provided an international forum for experimental and theoretical researchers to exchange ideas. A total of 220 delegates from eight countries participated in the conference. There were 13 invited talks, ten oral presentations and 120 posters. The 3rd International Conference on Quantum Simulators and Design will be held in Germany in the autumn of 2011.

  9. Correlated electrons in quantum matter

    CERN Document Server

    Fulde, Peter

    2012-01-01

    An understanding of the effects of electronic correlations in quantum systems is one of the most challenging problems in physics, partly due to the relevance in modern high technology. Yet there exist hardly any books on the subject which try to give a comprehensive overview on the field covering insulators, semiconductors, as well as metals. The present book tries to fill that gap. It intends to provide graduate students and researchers a comprehensive survey of electron correlations, weak and strong, in insulators, semiconductors and metals. This topic is a central one in condensed matter and beyond that in theoretical physics. The reader will have a better understanding of the great progress which has been made in the field over the past few decades.

  10. Electron transport in quantum dots

    CERN Document Server

    2003-01-01

    When I was contacted by Kluwer Academic Publishers in the Fall of 200 I, inviting me to edit a volume of papers on the issue of electron transport in quantum dots, I was excited by what I saw as an ideal opportunity to provide an overview of a field of research that has made significant contributions in recent years, both to our understanding of fundamental physics, and to the development of novel nanoelectronic technologies. The need for such a volume seemed to be made more pressing by the fact that few comprehensive reviews of this topic have appeared in the literature, in spite of the vast activity in this area over the course of the last decade or so. With this motivation, I set out to try to compile a volume that would fairly reflect the wide range of opinions that has emerged in the study of electron transport in quantum dots. Indeed, there has been no effort on my part to ensure any consistency between the different chapters, since I would prefer that this volume instead serve as a useful forum for the...

  11. Quantum optics with nanowires (Conference Presentation)

    Science.gov (United States)

    Zwiller, Val

    2017-02-01

    Nanowires offer new opportunities for nanoscale quantum optics; the quantum dot geometry in semiconducting nanowires as well as the material composition and environment can be engineered with unprecedented freedom to improve the light extraction efficiency. Quantum dots in nanowires are shown to be efficient single photon sources, in addition because of the very small fine structure splitting, we demonstrate the generation of entangled pairs of photons from a nanowire. By doping a nanowire and making ohmic contacts on both sides, a nanowire light emitting diode can be obtained with a single quantum dot as the active region. Under forward bias, this will act as an electrically pumped source of single photons. Under reverse bias, an avalanche effect can multiply photocurrent and enables the detection of single photons. Another type of nanowire under study in our group is superconducting nanowires for single photon detection, reaching efficiencies, time resolution and dark counts beyond currently available detectors. We will discuss our first attempts at combining semiconducting nanowire based single photon emitters and superconducting nanowire single photon detectors on a chip to realize integrated quantum circuits.

  12. Novel frontier in quantum metamaterials (Conference Presentation)

    Science.gov (United States)

    Jha, Pankaj K.

    2016-09-01

    Metamaterials are artificial materials with exotic physical, chemical and optical properties not found in natural materials. In the past decade they have attracted monumental attention from the scientific community owing to their applications ranging from physics to engineering. However, the conventional solid-state metamaterial platforms suffer from inevitable optical loss, defects which severely curtain their application at few-photon level. The quest for quantum optical applications with metamaterial-based technologies has stimulated researchers to engineer novel lossless materials and construct new platforms. Recently, by integrating two important and timely realms of science - trapped atom physics and metamaterials -, we proposed and theoretically demonstrated a topologically reconfigurable and lossless quantum metamaterial. The atomic lattice quantum metamaterial is immune to aforementioned critical challenges and can be employed at a single-photon level. Moreover, in stark contrast to conventional solid-state platforms, optical lattices provide the necessary freedom to precisely localize (within few nanometer of uncertainty) a probe atom, inside the atomic lattice quantum metamaterial to harness its exotic optical properties. In addition to its aforementioned novel characteristics, our atomic lattice quantum metamaterial offers a unique degree of freedom, namely all-optical control on ultrafast time scales over the photonic topological transition of isofrequency contours using weak fields, not possible with previous solid-state platforms. In this work, we leverage the tools, techniques, scientific advances in the field of atomic, molecular and optical physics, integrated with the concepts used in metamaterials to propose and theoretically demonstrate a novel platform towards quantum metamaterial with novel functionalities by bringing together the best of two worlds.

  13. Quantum electronics maser amplifiers and oscillators

    CERN Document Server

    Fain, V M; Sanders, J H

    2013-01-01

    Quantum Electronics, Volume 2: Maser Amplifiers and Oscillators deals with the experimental and theoretical aspects of maser amplifiers and oscillators which are based on the principles of quantum electronics. It shows how the concepts and equations used in quantum electronics follow from the basic principles of theoretical physics.Comprised of three chapters, this volume begins with a discussion on the elements of the theory of quantum oscillators and amplifiers working in the microwave region, along with the practical achievements in this field. Attention is paid to two-level paramagnetic ma

  14. Electron Spins in Semiconductor Quantum Dots

    NARCIS (Netherlands)

    Hanson, R.

    2005-01-01

    This thesis describes a series of experiments aimed at understanding and controlling the behavior of the spin degree of freedom of single electrons, confined in semiconductor quantum dots. This research work is motivated by the prospects of using the electron spin as a quantum bit (qubit), the basic

  15. Stark shifting two-electron quantum dot

    International Nuclear Information System (INIS)

    Dineykhan, M.; Zhaugasheva, S.A.; Duysebaeva, K.S.

    2003-01-01

    Advances in modern technology make it possible to create semiconducting nano-structures (quantum dot) in which a finite number of electrons are 'captured' in a bounded volume. A quantum dot is associated with a quantum well formed at the interface, between two finite-size semiconductors owing to different positions of the forbidden gaps on the energy scale in these semiconductors. The possibility of monitoring and controlling the properties of quantum dots attracts considerable attention to these objects, as a new elemental basis for future generations of computers. The quantum-mechanical effects and image potential play a significant role in the description of the formation mechanism quantum dot, and determined the confinement potential in a two-electron quantum dot only for the spherical symmetric case. In the present talk, we considered the formation dynamics of two-electron quantum dot with violation of spherical symmetry. So, we have standard Stark potential. The energy spectrum two-electron quantum dot were calculated. Usually Stark interactions determined the tunneling phenomena between quantum dots

  16. Spin polarization of electrons in quantum wires

    OpenAIRE

    Vasilchenko, A. A.

    2013-01-01

    The total energy of a quasi-one-dimensional electron system is calculated using density functional theory. It is shown that spontaneous ferromagnetic state in quantum wire occurs at low one-dimensional electron density. The critical electron density below which electrons are in spin-polarized state is estimated analytically.

  17. Nuclear Electronics. Proceedings of a Conference on Nuclear Electronics

    International Nuclear Information System (INIS)

    1966-01-01

    The science of electronics, which is playing a decisive role in the modern world, is particularly important in the development of the nuclear sciences, both in fundamental research on the structure of matter and in the production of power from fission. It is impractical, however, to deal with this vast and varied subject at one time. The Agency's first conference on the subject, at Belgrade in May 1961, was restricted to just a few aspects of nuclear electronics. The second conference, organized by the Agency in co-operation with the Indian Atomic Energy Commission and held at Bombay from 22 to 26 November 1965, was limited, for all practical purposes, to the use of nuclear electronics in reactor control and safety. The importance of this subject is self-evident, for the number of power reactors throughout the world is increasing every year and the economics of their operation depends just as much on optimum functioning as on improved safety. The Bombay conference, at which 48 papers were presented, was attended by a large number of participants, representing 12 countries and two international organizations. The main topics were power and neutron-flux measurements, reactor control, safety devices, and data processing to ensure optimum operation. The Proceedings, which contain both the texts and discussions of the papers presented, are of immediate interest to specialists in these fields and should form a valuable source of information

  18. Indication for quantum Darwinism in electron billiards

    Science.gov (United States)

    Brunner, R.; Akis, R.; Meisels, R.; Kuchar, F.; Ferry, D. K.

    2010-02-01

    In this paper, we investigate the dynamics in electron billiards by using classical and quantum mechanical calculations. We report on the existence of pointer states in single-dot and double-dot electron billiards. Additionally, we show that the two types of pointer states have the propensity to create offspring, i.e. they can be observed in the individual modes propagating between the external reservoirs. This can be understood as an indication that quantum Darwinism is present in the electron billiards.

  19. Electron conductance in curved quantum structures

    DEFF Research Database (Denmark)

    Willatzen, Morten; Gravesen, Jens

    2010-01-01

    is computationally fast and provides direct (geometrical) parameter insight as regards the determination of the electron transmission coefficient. We present, as a case study, calculations of the electron conductivity of a helically shaped quantum-wire structure and discuss the influence of the quantum......A differential-geometry analysis is employed to investigate the transmission of electrons through a curved quantum-wire structure. Although the problem is a three-dimensional spatial problem, the Schrodinger equation can be separated into three general coordinates. Hence, the proposed method...

  20. Physical foundations of quantum electronics

    CERN Document Server

    Klyshko, David; Kulik, Sergey

    2011-01-01

    This concise textbook introduces a graduate student to the various fields of physics related to the interaction between radiation and matter. The scope of the book is very broad, ranging from nonlinear to quantum optics and from quantum transitions in atoms to the dispersion of polaritons in continuous media. The author, Professor David Klyshko (1929-2000), is one of the founders of modern quantum optics, renowned for his theory of Spontaneous Parametric Down-Conversion (SPDC) and its applications in quantum metrology and the optics of nonclassical light. Most parts of the book contain the lec

  1. Electron quantum interferences and universal conductance fluctuations

    International Nuclear Information System (INIS)

    Benoit, A.; Pichard, J.L.

    1988-05-01

    Quantum interferences yield corrections to the classical ohmic behaviour predicted by Boltzmann theory in electronic transport: for instance the well-known ''weak localization'' effects. Furthermore, very recently, quantum interference effects have been proved to be responsible for statistically different phenomena, associated with Universal Conductance Fluctuations and observed on very small devices [fr

  2. Quantum aspects of the free electron laser

    Energy Technology Data Exchange (ETDEWEB)

    Gaiba, R.

    2007-03-15

    We study the role of Quantum Mechanics in the physics of Free Electron Lasers. While the Free Electron Laser (FEL) is usually treated as a classical device, we review the advantages of a quantum formulation of the FEL. We then show the existence of a regime of operation of the FEL that can only be described using Quantum Mechanics: if the dimensionless quantum parameter anti {rho} is smaller than 1, then in the 1-dimensional approximation the Hamiltonian that describes the FEL becomes equivalent to the Hamiltonian of a two-level system coupled to a radiation field. We give analytical and numerical solutions for the photon statistics of a Free Electron Laser operating in the quantum regime under various approximations. Since in the quantum regime the momentum of the electrons is discrete, we give a description of the electrons in phase space by introducing the Discrete Wigner Function. We then drop the assumption of a mono-energetic electron beam and describe the general case of a initial electron energy spread G({gamma}). Numerical analysis shows that the FEL quantum regime is observed only when the width of the initial momentum distribution is smaller than the momentum of the emitted photons. Both the analytical results in the linear approximation and the numerical simulations show that only the electrons close to a certain resonant energy start to emit photons. This generates the so-called Hole-burning effect in the electrons energy distribution, as it can be seen in the simulations we provide. Finally, we present a brief discussion about a fundamental uncertainty relation that ties the electron energy spread and the electron bunching. (orig.)

  3. Quantum interference effects for the electronic fluctuations in quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, J.G.G.S. [Universidade Federal da Paraiba (UFPB), Rio Tinto, PB (Brazil). Departamento de Ciencias Exatas; Hussein, M.S. [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Fisica; Barbosa, A.L.R. [Universidade Federal Rural de Pernambuco (UAEADTec/UFRPE), Recife, PE (Brazil). Unidade Academica de Ensino a Distancia. Pos-Graduacao em Fisica Aplicada

    2014-07-01

    For the main quantum interference term of coherent electronic transport, we study the effect of temperature, perpendicular and/or parallel magnetic fields, spin-orbit coupling and tunneling rates in both metallic grains and mesoscopic heterostructures. We show that the Zeeman effects determines a crucial way to characterize the quantum interference phenomena of the noise for anisotropic systems (mesoscopic heterostructures), qualitatively distinct from those observed in isotropic structures (metallic grains). (author)

  4. Quantum interference effects for the electronic fluctuations in quantum dots

    International Nuclear Information System (INIS)

    Ramos, J.G.G.S.; Hussein, M.S.; Barbosa, A.L.R.

    2014-01-01

    For the main quantum interference term of coherent electronic transport, we study the effect of temperature, perpendicular and/or parallel magnetic fields, spin-orbit coupling and tunneling rates in both metallic grains and mesoscopic heterostructures. We show that the Zeeman effects determines a crucial way to characterize the quantum interference phenomena of the noise for anisotropic systems (mesoscopic heterostructures), qualitatively distinct from those observed in isotropic structures (metallic grains). (author)

  5. Electron billiards: einselection and quantum Darwinism

    International Nuclear Information System (INIS)

    Brunner, R.; Meisels, R.; Kuchar, F.; Akis, R.; Ferry, D.K.

    2008-01-01

    Full text: The measurement of open quantum systems has been a main topic since the advent of quantum theory. It is a basic ingredient in quantum information processing. Here, the border where the two worlds of classical and quantum mechanics meet is of significant importance due to the problem of measurement. It has been shown by Zurek that in an open system the environment imposes so-called superselection rules leading to environment-induced superselection (einselection). This means that a set of preferred states (pointer states) survive the coupling with the environment. These pointer states are characterized by their robustness and their ability to create offspring. This ability to advertise information about themselves makes it possible for different observers to measure the same information. The natural promotion of certain information in a quantum system is known as quantum Darwinism. The 'fitness' in the Darwinian sense of the selected states is essentially a measure of their classicality. That is in order to measure a quantum system objectively a system has to be designed where the transition between the classical and quantum world is observable. In this respect we show by a combination of experiment and calculation that an array of electron billiards (open quantum dots) is very well suited. We demonstrate that einselection takes place in electron billiards and a set of pointer states arises. We illustrate that beside the 'regular' (single dot) pointer states a new type of einselected states arise when two or more quantum dots are coupled together and to the environment. This new type of states can not be represented by a linear combination of pointer states of the individual dots. Finally, we discuss the propensity of the new type of einselected states to make offspring in order to see if quantum Darwinism is in action in the array of electron billiards.(author)

  6. Foreword [International conference on algebra, analysis and quantum probability

    International Nuclear Information System (INIS)

    2016-01-01

    The present volume of the Journal of Physics: Conference Series represents contributions from participants of the International Conference ’’Algebra, Analysis and Quantum Probability” (Tashkent, 10-12 September 2015) organized by the Institute of Mathematics and the Faculty of Mechanics and Mathematics of the National University of Uzbekistan (NUUz) in collaboration with University Putra Malaysia (UPM) and International Islamic University Malaysia (IIUM). The Conference is dedicated to the 100th anniversary of one of the outstanding scientists of Uzbekistan, the founder of the Tashkent scientific school of functional analysis, who has initiated the investigations on operator algebras and quantum probability theory in Uzbekistan - Professor Tashmukhamed Alievich Sarymsakov (10 Sept. 1915 - 19 Dec. 1995). Among the mathematical community Professor T. A. Sarymsakov is widely known for his research in the fields of probability theory, functional analysis, general topology and their applications. A gifted teacher and skilful organizer he had a beneficial effect on the development of many new mathematicians in Uzbekistan. Professor T.A. Sarymsakov, an outstanding organizer of science in Uzbekistan, was one of the founders of the Uzbekistan Academy of Sciences, where from 1943 he was a member and Vice President, and from 1946 to 1952 president of the Academy of Sciences. Professor Sarymsakov successfully combined his fruitful scientific research with teaching and social work. During 1943-1944, 1952-1958 and 1971-1983 he was the rector of Tashkent State University (now the National University of Uzbekistan). He has made a significant contribution to the development of higher education in Uzbekistan, serving from 1959 to 1960 as the Chairman of the State Committee, and from 1960 to 1971 as the Minister of Higher and Secondary Special Education of Uzbekistan. The main objective of the scientific conference was to facilitate communication and collaboration between

  7. Designs for a quantum electron microscope.

    Science.gov (United States)

    Kruit, P; Hobbs, R G; Kim, C-S; Yang, Y; Manfrinato, V R; Hammer, J; Thomas, S; Weber, P; Klopfer, B; Kohstall, C; Juffmann, T; Kasevich, M A; Hommelhoff, P; Berggren, K K

    2016-05-01

    One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This 'quantum weirdness' could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or "quantum electron microscope". A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  8. Electronic Conference Tracking and Approval System

    Data.gov (United States)

    US Agency for International Development — eCTAS tracks information relevant to attendance and hosting conferences of USAID's Washington offices and Missions worldwide including cost, numbers attending,...

  9. 2012 International Conference on Mechanical and Electronic Engineering

    CERN Document Server

    Lin, Sally; ICMEE2012; Advances in Mechanical and Electronic Engineering v.2

    2012-01-01

    This book includes the volume 2 of the proceedings of the 2012 International Conference on Mechanical and Electronic Engineering(ICMEE2012), held at June 23-24,2012 in Hefei, China. The conference provided a rare opportunity to bring together worldwide researchers who are working in the fields. This volume 2 is focusing on Mechatronic Engineering and Technology,  Electronic Engineering and Electronic Information Technology .

  10. Electronic Conduction through Atomic Chains, Quantum Well and Quantum Wire

    International Nuclear Information System (INIS)

    Sharma, A. C.

    2011-01-01

    Charge transport is dynamically and strongly linked with atomic structure, in nanostructures. We report our ab-initio calculations on electronic transport through atomic chains and the model calculations on electron-electron and electron-phonon scattering rates in presence of random impurity potential in a quantum well and in a quantum wire. We computed synthesis and ballistic transport through; (a) C and Si based atomic chains attached to metallic electrodes, (b) armchair (AC), zigzag (ZZ), mixed, rotated-AC and rotated-ZZ geometries of small molecules made of 2S, 6C and 4H atoms attaching to metallic electrodes, and (c) carbon atomic chain attached to graphene electrodes. Computed results show that synthesis of various atomic chains are practically possible and their transmission coefficients are nonzero for a wide energy range. The ab-initio calculations on electronic transport have been performed with the use of Landauer-type scattering formalism formulated in terms of Grben's functions in combination with ground-state DFT. The electron-electron and electron-phonon scattering rates have been calculated as function of excitation energy both at zero and finite temperatures for disordered 2D and 1D systems. Our model calculations suggest that electron scattering rates in a disordered system are mainly governed by effective dimensionality of a system, carrier concentration and dynamical screening effects.

  11. 2012 International Conference on Electrical and Electronics Engineering

    CERN Document Server

    Chen, Suting; Wei, Zhanming; Xia, Jingming

    2014-01-01

    Unifying Electrical Engineering and Electronics Engineering is based on the Proceedings of the 2012 International Conference on Electrical and Electronics Engineering (ICEE 2012). This book collects the peer reviewed papers presented at the conference. The aim of the conference is to unify the two areas of Electrical and Electronics Engineering. The book examines trends and techniques in the field as well as theories and applications. The editors have chosen to include the following topics; biotechnology, power engineering, superconductivity circuits, antennas technology, system architectures and telecommunication.

  12. Quantum frustrated and correlated electron systems

    Directory of Open Access Journals (Sweden)

    P Thalmeier

    2008-06-01

    Full Text Available  Quantum phases and fluctuations in correlated electron systems with frustration and competing interactions are reviewed. In the localized moment case the S=1/2 J1 - J2 - model on a square lattice exhibits a rich phase diagram with magnetic as well as exotic hidden order phases due to the interplay of frustration and quantum fluctuations. Their signature in magnetocaloric quantities and the high field magnetization are surveyed. The possible quantum phase transitions are discussed and applied to layered vanadium oxides. In itinerant electron systems frustration is an emergent property caused by electron correlations. It leads to enhanced spin fluctuations in a very large region of momentum space and therefore may cause heavy fermion type low temperature anomalies as in the 3d spinel compound LiV2O4 . Competing on-site and inter-site electronic interactions in Kondo compounds are responsible for the quantum phase transition between nonmagnetic Kondo singlet phase and magnetic phase such as observed in many 4f compounds. They may be described by Kondo lattice and simplified Kondo necklace type models. Their quantum phase transitions are investigated by numerical exact diagonalization and analytical bond operator methods respectively.

  13. The Quantum World Unveiled by Electron Waves

    International Nuclear Information System (INIS)

    Akira Tonomura

    1998-08-01

    This book emphasizes the experimental aspects of the author's own laboratory. Instead of merely presenting a dry collection of knowledge, the author unfolds to the readers his vivid experiences of enthusiasm, sheer pleasure, and yet frustrations in the course of his own research. In this way, the book aims to arouse the reader's curiosity in the strange behaviors of electrons in the microscopic world, which differ significantly from our common sense and daily experiences of the macroscopic world. The fields of physics explored in the book are quantum mechanics, superconductivity, electron microscopy, holography, magnetism, and unified theory - areas of the author's study using electron waves. A world-renowned expert in electron holography, the author promises the interested reader a fascinating ride through the quantum world of electron waves, accompanied by many colorful illustrations that delight the senses and captivate the imagination

  14. Quantum electronics for atomic physics and telecommunication

    CERN Document Server

    Nagourney, Warren G

    2014-01-01

    Nagourney provides a course in quantum electronics for researchers in atomic physics and other related areas (including telecommunications). The book covers the usual topics, such as Gaussian beams, optical cavities, lasers, non-linear optics, modulation techniques and fibre optics, but also includes a number of areas not usually found in a textbook on quantum electronics, such as the enhancement of non-linear processes in a build-up cavity or periodically poled waveguide, impedance matching into a cavity and astigmatism in ring cavities.

  15. 7th Rochester Conference on Coherence and Quantum Optics

    CERN Document Server

    Mandel, Leonard; Wolf, Emil

    1996-01-01

    The Seventh Rochester Conference on Coherence and Quantum Optics was held on the campus of the University of Rochester during the four-day period June 7 - 10, 1996. More than 280 scientists from 33 countries participated. This book contains the Proceedings of the meeting. This Conference differed from the previous six in the series in having only a limited number of oral presentations, in order to avoid too many parallel sessions. Another new feature was the introduction of tutorial lectures. Most contributed papers were presented in poster sessions. The Conference was sponsored by the American Physical Society, by the Optical Society of America, by the International Union of Pure and Applied Physics and by the University of Rochester. We wish to express our appreciation to these organizations for their support and we especially extend our thanks to the International Union of Pure and Applied Physics for providing financial assistance to a number of speakers from Third World countries, to enable them to take ...

  16. Designs for a quantum electron microscope

    International Nuclear Information System (INIS)

    Kruit, P.; Hobbs, R.G.; Kim, C-S.; Yang, Y.; Manfrinato, V.R.; Hammer, J.; Thomas, S.; Weber, P.; Klopfer, B.; Kohstall, C.; Juffmann, T.; Kasevich, M.A.; Hommelhoff, P.; Berggren, K.K.

    2016-01-01

    One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This ‘quantum weirdness’ could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or “quantum electron microscope”. A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. - Highlights: • Quantum electron microscopy has the potential of reducing radiation damage. • QEM requires a fraction of the electron wave to pass through the sample

  17. Designs for a quantum electron microscope

    Energy Technology Data Exchange (ETDEWEB)

    Kruit, P., E-mail: p.kruit@tudelft.nl [Department of Imaging Physics, Delft University of Technology, Lorentzweg 1, 2628CJ Delft (Netherlands); Hobbs, R.G.; Kim, C-S.; Yang, Y.; Manfrinato, V.R. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Hammer, J.; Thomas, S.; Weber, P. [Department of Physics, Friedrich Alexander University Erlangen-Nürnberg (FAU), Staudtstrasse 1, d-91058 Erlangen (Germany); Klopfer, B.; Kohstall, C.; Juffmann, T.; Kasevich, M.A. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Hommelhoff, P. [Department of Physics, Friedrich Alexander University Erlangen-Nürnberg (FAU), Staudtstrasse 1, d-91058 Erlangen (Germany); Berggren, K.K. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2016-05-15

    One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This ‘quantum weirdness’ could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or “quantum electron microscope”. A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. - Highlights: • Quantum electron microscopy has the potential of reducing radiation damage. • QEM requires a fraction of the electron wave to pass through the sample

  18. Quantum lifetime in electron storage rings

    International Nuclear Information System (INIS)

    Chao, A.W.

    1977-02-01

    One of the mechanisms which contribute to beam lifetime in electron storage rings is the quantum emission of energetic photons causing particles to be lost from the rf bucket. This quantum lifetime is among other things important in defining the required aperture in a storage ring. An approximate expression of quantum lifetime, predicted by a one-dimensional model which takes into account only the betatron motion, has been used in most storage ring designs. If the beam is aperture-limited at a position with nonzero dispersion, both the betatron and synchrotron motions have to be included and a two-dimensional model must be used. An exact expression of quantum lifetime for the one-dimensional case and an approximate expression for the two-dimensional case are given

  19. Quantum lifetime in electron storage rings

    International Nuclear Information System (INIS)

    Chao, A.W.

    1977-01-01

    One of the mechanisms which contributes to beam lifetime in electron storage rings is the quantum emission of energetic photons causing particles to be lost from the rf bucket. This quantum lifetime is among other things important in defining the required aperture in a storage ring. An approximate expression of quantum lifetime, predicted by a one-dimensional model which takes into account only the betatron motion, has been used in most storage ring designs. If the beam is aperture-limited at a position with nonzero dispersion, both the betatron and synchrotron motions have to be included, and a two-dimensional model must be used. An exact expression of quantum lifetime for the one-dimensional case and an approximate expression for the two-dimensional case are given

  20. Quantum Computing with an Electron Spin Ensemble

    DEFF Research Database (Denmark)

    Wesenberg, Janus; Ardavan, A.; Briggs, G.A.D.

    2009-01-01

    We propose to encode a register of quantum bits in different collective electron spin wave excitations in a solid medium. Coupling to spins is enabled by locating them in the vicinity of a superconducting transmission line cavity, and making use of their strong collective coupling to the quantized...

  1. International Conference on Nano-electronics, Circuits & Communication Systems

    CERN Document Server

    2017-01-01

    This volume comprises select papers from the International Conference on Nano-electronics, Circuits & Communication Systems(NCCS). The conference focused on the frontier issues and their applications in business, academia, industry, and other allied areas. This international conference aimed to bring together scientists, researchers, engineers from academia and industry. The book covers technological developments and current trends in key areas such as VLSI design, IC manufacturing, and applications such as communications, ICT, and hybrid electronics. The contents of this volume will prove useful to researchers, professionals, and students alike.

  2. Electronic states in a quantum lens

    International Nuclear Information System (INIS)

    Rodriguez, Arezky H.; Trallero-Giner, C.; Ulloa, S. E.; Marin-Antuna, J.

    2001-01-01

    We present a model to find analytically the electronic states in self-assembled quantum dots with a truncated spherical cap (''lens'') geometry. A conformal analytical image is designed to map the quantum dot boundary into a dot with semispherical shape. The Hamiltonian for a carrier confined in the quantum lens is correspondingly mapped into an equivalent operator and its eigenvalues and eigenfunctions for the corresponding Dirichlet problem are analyzed. A modified Rayleigh-Schro''dinger perturbation theory is presented to obtain analytical expressions for the energy levels and wave functions as a function of the spherical cap height b and radius a of the circular cross section. Calculations for a hard wall confinement potential are presented, and the effect of decreasing symmetry on the energy values and eigenfunctions of the lens-shape quantum dot is studied. As the degeneracies of a semicircular geometry are broken for b≠a, our perturbation approach allows tracking of the split states. Energy states and electronic wave functions with m=0 present the most pronounced influence on the reduction of the lens height. The method and expressions presented here can be straightforwardly extended to deal with more general Hamiltonians, including strains and valence-band coupling effects in Group III--V and Group II--VI self-assembled quantum dots

  3. Electron quantum optics in ballistic chiral conductors

    Energy Technology Data Exchange (ETDEWEB)

    Bocquillon, Erwann; Freulon, Vincent; Parmentier, Francois D.; Berroir, Jean-Marc; Placais, Bernard; Feve, Gwendal [Laboratoire Pierre Aigrain, Ecole Normale Superieure, CNRS (UMR 8551), Universite Pierre et Marie Curie, Universite Paris Diderot, Paris (France); Wahl, Claire; Rech, Jerome; Jonckheere, Thibaut; Martin, Thierry [Aix Marseille Universite, CNRS, CPT, UMR 7332, Marseille (France); Universite de Toulon, CNRS, CPT, UMR 7332, La Garde (France); Grenier, Charles; Ferraro, Dario; Degiovanni, Pascal [Universite de Lyon, Federation de Physique Andre Marie Ampere, CNRS - Laboratoire de Physique de l' Ecole Normale Superieure de Lyon, Lyon (France)

    2014-01-15

    The edge channels of the quantum Hall effect provide one dimensional chiral and ballistic wires along which electrons can be guided in an optics-like setup. Electronic propagation can then be analyzed using concepts and tools derived from optics. After a brief review of electron optics experiments performed using stationary current sources which continuously emit electrons in the conductor, this paper focuses on triggered sources, which can generate on-demand a single particle state. It first outlines the electron optics formalism and its analogies and differences with photon optics and then turns to the presentation of single electron emitters and their characterization through the measurements of the average electrical current and its correlations. This is followed by a discussion of electron quantum optics experiments in the Hanbury-Brown and Twiss geometry where two-particle interferences occur. Finally, Coulomb interactions effects and their influence on single electron states are considered. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Electron quantum optics in ballistic chiral conductors

    International Nuclear Information System (INIS)

    Bocquillon, Erwann; Freulon, Vincent; Parmentier, Francois D.; Berroir, Jean-Marc; Placais, Bernard; Feve, Gwendal; Wahl, Claire; Rech, Jerome; Jonckheere, Thibaut; Martin, Thierry; Grenier, Charles; Ferraro, Dario; Degiovanni, Pascal

    2014-01-01

    The edge channels of the quantum Hall effect provide one dimensional chiral and ballistic wires along which electrons can be guided in an optics-like setup. Electronic propagation can then be analyzed using concepts and tools derived from optics. After a brief review of electron optics experiments performed using stationary current sources which continuously emit electrons in the conductor, this paper focuses on triggered sources, which can generate on-demand a single particle state. It first outlines the electron optics formalism and its analogies and differences with photon optics and then turns to the presentation of single electron emitters and their characterization through the measurements of the average electrical current and its correlations. This is followed by a discussion of electron quantum optics experiments in the Hanbury-Brown and Twiss geometry where two-particle interferences occur. Finally, Coulomb interactions effects and their influence on single electron states are considered. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Electron states in semiconductor quantum dots

    International Nuclear Information System (INIS)

    Dhayal, Suman S.; Ramaniah, Lavanya M.; Ruda, Harry E.; Nair, Selvakumar V.

    2014-01-01

    In this work, the electronic structures of quantum dots (QDs) of nine direct band gap semiconductor materials belonging to the group II-VI and III-V families are investigated, within the empirical tight-binding framework, in the effective bond orbital model. This methodology is shown to accurately describe these systems, yielding, at the same time, qualitative insights into their electronic properties. Various features of the bulk band structure such as band-gaps, band curvature, and band widths around symmetry points affect the quantum confinement of electrons and holes. These effects are identified and quantified. A comparison with experimental data yields good agreement with the calculations. These theoretical results would help quantify the optical response of QDs of these materials and provide useful input for applications

  6. Electron Raman scattering in quantum well wires

    International Nuclear Information System (INIS)

    Zhao Xiangfu; Liu Cuihong

    2007-01-01

    Electron Raman scattering (ERS) is investigated in a semiconductor quantum well wire (QWW) of cylindrical geometry for T=0K and neglecting phonon-assisted transitions. The differential cross-section (DCS) involved in this process is calculated as a function of a scattering frequency and the cylindrical radius. Electron states are confined within a QWW. Single parabolic conduction and valence bands are assumed. The selection rules are studied. Singularities in the spectra are interpreted for various cylindrical radii. ERS discussed here can provide direct information about the electron band structure of the system

  7. The electronic properties of semiconductor quantum dots

    International Nuclear Information System (INIS)

    Barker, J.A.

    2000-10-01

    This work is an investigation into the electronic behaviour of semiconductor quantum dots, particularly self-assembled quantum dot arrays. Processor-efficient models are developed to describe the electronic structure of dots, deriving analytic formulae for the strain tensor, piezoelectric distribution and diffusion- induced evolution of the confinement potential, for dots of arbitrary initial shape and composition profile. These models are then applied to experimental data. Transitions due to individual quantum dots have a narrow linewidth as a result of their discrete density of states. By contrast, quantum dot arrays exhibit inhomogeneous broadening which is generally attributed to size variations between the individual dots in the ensemble. Interpreting the results of double resonance spectroscopy, it is seen that variation in the indium composition of the nominally InAs dots is also present. This result also explains the otherwise confusing relationship between the spread in the ground-state and excited-state transition energies. Careful analysis shows that, in addition to the variations in size and composition, some other as yet unidentified broadening mechanism must also be present. The influence of rapid thermal annealing on dot electronic structure is also considered, finding that the experimentally observed blue-shift and narrowing of the photoluminescence linewidth may both be explained in terms of normal In/Ga interdiffusion. InAs/GaAs self-assembled quantum dots are commonly assumed to have a pyramidal geometry, so that we would expect the energy separation of the ground-state electron and hole levels in the dot to be largest at a positive applied field. This should also be the case for any dot of uniform composition whose shape tapers inwards from base to top, counter to the results of experimental Stark-shift spectroscopy which show a peak transition energy at a negative applied field. It is demonstrated that this inversion of the ground state

  8. Proceedings of 10. Conference on Electron Microscopy of Solids

    International Nuclear Information System (INIS)

    1999-01-01

    The new technical solutions and methodical variants of electron microscopy i. e. transmission electron microscopy and scanning electron microscopy have been presented. Development of new methods and microscope constructions which became more and more sophisticated causes the progress in possible applications. The broad spectrum of such applications in metallurgy, materials science, chemical engineering, electronics, physical chemistry, solid state physics, mineralogy and other branches of science and technique have been performed and discussed at the conference

  9. XXIII International Conference on Nonlinear Dynamics of Electronic Systems

    CERN Document Server

    Stoop, Ruedi; Stramaglia, Sebastiano

    2017-01-01

    This book collects contributions to the XXIII international conference “Nonlinear dynamics of electronic systems”. Topics range from non-linearity in electronic circuits to synchronisation effects in complex networks to biological systems, neural dynamics and the complex organisation of the brain. Resting on a solid mathematical basis, these investigations address highly interdisciplinary problems in physics, engineering, biology and biochemistry.

  10. Electron-electron interaction in Multiple Quantum Wells

    Science.gov (United States)

    Zybert, M.; Marchewka, M.; Tomaka, G.; Sheregii, E. M.

    2012-07-01

    The complex investigation of the magneto-transport effects in structures containing multiple quantum well (MQWs) based on the GaAs/AlGaAs-heterostructures has been performed. The MQWs investigated have different electron densities in QWs. The parameters of 2DEG in MQWs were determined from the data of the Integer Quantum Hall Effect (IQHE) and Shubnikov-de Haas oscillations (SdH) observed at low temperatures (0.6-4.2 K). The method of calculation of the electron states energies in MQWs has been developed which is based on the splitting of these states due to the exchange interaction (SAS-splitting, see D. Płoch et al., Phys. Rev. B 79 (2009) 195434) including the screening of this interaction. The IQHE and SdH observed in these multilayer structures with the third degree of freedom for electrons are interpreted from this.

  11. Third International Electronic Conference on Medicinal Chemistry (ECMC-3

    Directory of Open Access Journals (Sweden)

    Annie Mayence

    2018-02-01

    Full Text Available The third International Electronic Conference on Medicinal Chemistry, organized and sponsored by MDPI AG, publisher, and the journal Pharmaceuticals, took place in November 2017 on the SciForum website (www.sciforum.net/conference/ecmc-3. Around 300 authors from 34 different countries participated at the event, which hosted more than 70 presentations, keynotes, videos, and posters. A short description of some works presented during that scientific meeting is disclosed in this report.

  12. Exact diagonalization library for quantum electron models

    Science.gov (United States)

    Iskakov, Sergei; Danilov, Michael

    2018-04-01

    We present an exact diagonalization C++ template library (EDLib) for solving quantum electron models, including the single-band finite Hubbard cluster and the multi-orbital impurity Anderson model. The observables that can be computed using EDLib are single particle Green's functions and spin-spin correlation functions. This code provides three different types of Hamiltonian matrix storage that can be chosen based on the model.

  13. PREFACE: International Conference on Strongly Correlated Electron Systems (SCES 2011)

    Science.gov (United States)

    Littlewood, P. B.; Lonzarich, G. G.; Saxena, S. S.; Sutherland, M. L.; Sebastian, S. E.; Artacho, E.; Grosche, F. M.; Hadzibabic, Z.

    2012-11-01

    The Strongly Correlated Electron Systems Conference (SCES) 2011, was held from 29 August-3 September 2011, in Cambridge, UK. SCES'2011 was dedicated to 100 years of superconductivity and covered a range of topics in the area of strongly correlated systems. The correlated electronic and magnetic materials featured include f-electron based heavy fermion intermetallics and d-electron based transition metal compounds. The meeting welcomed to Cambridge 657 participants from 23 countries, who presented 127 talks (including 16 plenary, 57 invited, and 54 contributed) and 736 posters in 40 sessions over five full days of meetings. This proceedings volume contains papers reporting on the science presented at the meeting. This work deepens our understanding of the rich physical phenomena that arise from correlation effects. Strongly correlated systems are known for their remarkable array of emergent phenomena: the traditional subjects of superconductivity, magnetism and metal-insulator transitions have been joined by non-Fermi liquid phenomena, topologically protected quantum states, atomic and photonic gases, and quantum phase transitions. These are some of the most challenging and interesting phenomena in science. As well as the science driver, there is underlying interest in energy-dense materials, which make use of 'small' electrons packed to the highest possible density. These are by definition 'strongly correlated'. For example: good photovoltaics must be efficient optical absorbers, which means that photons will generate tightly bound electron-hole pairs (excitons) that must then be ionised at a heterointerface and transported to contacts; efficient solid state refrigeration depends on substantial entropy changes in a unit cell, with large local electrical or magnetic moments; efficient lighting is in a real sense the inverse of photovoltaics; the limit of an efficient battery is a supercapacitor employing mixed valent ions; fuel cells and solar to fuel conversion

  14. Book of abstracts of the second Uzbekistan physical electronics conference

    International Nuclear Information System (INIS)

    1999-11-01

    The second Uzbekistan Physical Electronics Conference on was held on 3-5 November, 1999 in Tashkent, Uzbekistan. The specialists discussed both theoretical and experimental research results in the field of interaction of corpuscular beams with solid state surface: fundamental problem of adsorption; surface ionization; electron, ion, photon emission; scattering of the particles on the surface; action of ion and electron irradiation, plasma treatment of material surface and also the problems of solid state electronics and applications of fundamental problems of physical electronics to surface diagnostics, ecology, technology and agriculture. More than 300 talks were presented in the meeting on the subjects mentioned above(A.A.D.)

  15. Electron Liquids in Semiconductor Quantum Structures

    International Nuclear Information System (INIS)

    Pinczuk, Aron

    2009-01-01

    The groups led by Stormer and Pinczuk have focused this project on goals that seek the elucidation of novel many-particle effects that emerge in two-dimensional electron systems (2DES) as the result from fundamental quantum interactions. This experimental research is conducted under extreme conditions of temperature and magnetic field. From the materials point of view, the ultra-high mobility systems in GaAs/AlGaAs quantum structures continue to be at the forefront of this research. The newcomer materials are based on graphene, a single atomic layer of graphite. The graphene research is attracting enormous attention from many communities involved in condensed matter research. The investigated many-particle phenomena include the integer and fractional quantum Hall effect, composite fermions, and Dirac fermions, and a diverse group of electron solid and liquid crystal phases. The Stormer group performed magneto-transport experiments and far-infrared spectroscopy, while the Pinczuk group explores manifestations of such phases in optical spectra.

  16. 1st International Conference on Advancements of Medical Electronics

    CERN Document Server

    Bag, Sandip; Ganguly, Karabi; Sarkar, Indranath; Biswas, Papun

    2015-01-01

    The book is a collection of peer-reviewed scientific papers submitted by active researchers in the 1st International Conference on Advancements of Medical Electronics (ICAME2015). The conference is organized jointly by the Department of Biomedical Engineering and Electronics and Communication Engineering, JIS College of Engineering, West Bengal, India. The primary objective of the conference is to strengthen interdisciplinary research and its applications for the welfare of humanity. A galaxy of academicians, professionals, scientists, statesman and researchers from different parts of the country and abroad got together and shared their knowledge. The book presents research articles of medical image processing & analysis, biomedical instrumentation & measurements, DSP & clinical applications, embedded systems & its applications in healthcare. The book can be referred as a tool for further research.

  17. 2015 Applications in Electronics Pervading Industry, Environment and Society Conference

    CERN Document Server

    2017-01-01

    This book provides a thorough overview of cutting-edge research on electronics applications relevant to industry, the environment, and society at large. It covers a broad spectrum of application domains, from automotive to space and from health to security, while devoting special attention to the use of embedded devices and sensors for imaging, communication and control. The book is based on the 2015 ApplePies Conference, held in Rome, which brought together researchers and stakeholders to consider the most significant current trends in the field of applied electronics and to debate visions for the future. Areas addressed by the conference included information communication technology; biotechnology and biomedical imaging; space; secure, clean and efficient energy; the environment; and smart, green and integrated transport. As electronics technology continues to develop apace, constantly meeting previously unthinkable targets, further attention needs to be directed toward the electronics applications and the ...

  18. International Conference on Strongly Correlated Electron Systems 2017 (SCES2017)

    Science.gov (United States)

    2018-05-01

    The 2017 International Conference on Strongly Correlated Electron Systems, SCES 2017, took place at the Clarion Congress Hotel in Prague, Czech Republic from July 17 to 21, 2017. The meeting was held under the auspices of the Department of Condensed Matter Physics of the Faculty of Mathematics and Physics of the Charles University.

  19. 2nd International Conference on Electric and Electronics (EEIC 2012)

    CERN Document Server

    Advances in Electric and Electronics

    2012-01-01

    This volume contains 108 full length papers presented at the 2nd International Conference on Electric and Electronics (EEIC 2012), held on April 21-22 in Sanya, China, which brings together researchers working in many different areas of education and learning to foster international collaborations and exchange of new ideas. This volume can be divided into two sections on the basis of the classification of manuscripts considered: the first section deals with Electric and the second section with Electronics.

  20. International Conference on Power Electronics and Renewable Energy Systems

    CERN Document Server

    Suresh, L; Dash, Subhransu; Panigrahi, Bijaya

    2015-01-01

    The book is a collection of high-quality peer-reviewed research papers presented in Proceedings of International Conference on Power Electronics and Renewable Energy Systems (ICPERES 2014) held at Rajalakshmi Engineering College, Chennai, India. These research papers provide the latest developments in the broad area of Power Electronics and Renewable Energy. The book discusses wide variety of industrial, engineering and scientific applications of the emerging techniques. It presents invited papers from the inventors/originators of new applications and advanced technologies.

  1. PREFACE: 19th International Conference on Electron Dynamics in Semiconductors, Optoelectronics and Nanostructures (EDISON'19)

    Science.gov (United States)

    González, T.; Martín-Martínez, M. J.; Mateos, J.

    2015-10-01

    from Japan and USA. The two topics receiving more abstracts correspond to fields attracting a lot of attention and research activity in the last years: electron dynamics in graphene and related materials and devices, and THz phenomena in nanostructures. Other topics like coherent dynamics in ultrafast optical phenomena or quantum processing, and semiconductor-based spintronics, had also an important presence in the program. Thanks are given to the members of the International and Scientific Program Committees for their valuable and qualified assistance in the selection of invited speakers and the review of the submitted contributions; and also to those attendees who assisted us in the review process of the papers included in this volume. We would like also to thank the institutions and sponsors that contributed to support the conference. Firstly the University of Salamanca, one of the oldest in the world, commemorating within three years, in 2018, the 8th century of its foundation in 1218. EDISON'19 can be considered as one more of the events taking place to celebrate such centennial. The Salamanca City Council also contributed in the organization of the conference. We acknowledge as well the support from the Spanish Ministry of Economy and Competitiveness, and from our sponsors and exhibitors, Oxford Instruments and Rohde&Schwarz. Finally, we would like to thank all participants and authors of the proceedings for their support and contributions to the conference. We devote this volume to the memory of Prof. Daniel Pardo, our dear boss in Salamanca for many years, who passed away in 2013. He was the pioneer of our activity in the field of the conference and would have enjoyed a lot the celebration of EDISON in Salamanca.

  2. Conferences on electronic waste in Costa Rica

    International Nuclear Information System (INIS)

    Roa Gutierrez, Floria

    2006-01-01

    The management system of electronic waste is a project organized and financed by the bilateral agreement Costa Rica - Holanda, it is integrated by governmental and non-governmental enterprises. It was divided in two phases, first performed in 2003 which provided a diagnosis on the management of electronic resources, based on the diagnosis a propose of strategy for recycling was made. The second phase is given in 2005 with the implementation and realization of the project including two pilots plans located one at the Instituto Tecnologico de Costa Rica and another in the community of Escazu, at the end some recommendations were given to strengthen the system. The electronic waste were divided in white line, gray and brown line; those with pollutants such as phosphorus, chromium, cadmium, barium, lead, beryllium, mercury are toxic and have different effects on human health. The project in Costa Rica has taken as examples several recycling plants in different countries, among them one installed in Belgica. As an outstanding figure of the diagnosis made it was determined that Costa Rica has no legal support regarding the handling of such materials. It has been accumulated in 2007 more than 24 260 tonnes and is growing rapidly year after year. Within the achieved progress in the implementation of the project are: the creation of a legal support, the organization of the compliance unit of the project, the valuation of environmental costs and the increase of enterprises offering the service of primary treatment [es

  3. PREFACE: International Conference on Quantum Simulators and Design, Hiroshima, Japan, 3 6 December 2006

    Science.gov (United States)

    Akai, Hisazumi; Oguchi, Tamio

    2007-09-01

    This special issue of Journal of Physics: Condensed Matter comprises selected papers from the 1st International Conference on Quantum Simulators and Design (QSD2006) held in Hiroshima, Japan, 3-6 December 2006. This conference was organized under the auspices of the Development of New Quantum Simulators and Quantum Design Grant-in-Aid for Scientific Research on Priority Areas, Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT), and Hiroshima University Quantum design is a computational approach to the development of new materials with specified properties and functionalities. The basic ingredient is the use of quantum simulations to design a material that meets a given specification of properties and functionalities. For this to be successful, the quantum simulation should be highly reliable and be applicable to systems of realistic size. A central interest is, therefore, the development of new methods of quantum simulation and quantum design. This includes methods beyond the local density approximation of density functional theory (LDA), order-N methods, methods dealing with excitations and reactions, and so on, as well as the application of these methods to the design of new materials and devices. The field of quantum design has developed rapidly in the past few years and this conference provides an international forum for experimental and theoretical researchers to exchange ideas. A total of 183 delegates from 8 countries participated in the conference. There were 18 invited talks, 16 oral presentations and 100 posters. There were many new ideas and we foresee dramatic progress in the coming years. The 2nd International Conference on Quantum Simulators and Design will be held in Tokyo, Japan, 31 May-3 June 2008.

  4. Electronic conductance of quantum wire with serial periodic potential structures

    International Nuclear Information System (INIS)

    Fayad, Hisham M.; Shabat, Mohammed M.; Abdus Salam International Centre for Theoretical Physics, Trieste

    2000-08-01

    A theory based on the total transfer matrix is presented to investigate the electronic conductance in a quantum wire with serial periodic potentials. We apply the formalism in computation of the electronic conductance in a wire with different physical parameters of the wire structure. The numerical results could be used in designing some future quantum electronic devices. (author)

  5. Electronic properties of assemblies of zno quantum dots

    NARCIS (Netherlands)

    Roest, Aarnoud Laurens

    2003-01-01

    Electron transport in an assembly of ZnO quantum dots has been studied using an electrochemically gated transistor. The electron mobility shows a step-wise increase as a function of the electron occupation per quantum dot. When the occupation number is below two, transport occurs by tunnelling

  6. 2nd International Conference on Measurement Instrumentation and Electronics

    International Nuclear Information System (INIS)

    2017-01-01

    Preface It is our great pleasure to welcome you to 2017 2nd International Conference on Measurement Instrumentation and Electronics which has been held in Prague, Czech Republic during June 9-11, 2017. ICMIE 2017 is dedicated to issues related to measurement instrumentation and electronics. The major goal and feature of the conference is to bring academic scientists, engineers, industry researchers together to exchange and share their experiences and research results, and discuss the practical challenges encountered and the solutions adopted. Professors from Czech Republic, Germany and Italy are invited to deliver keynote speeches regarding latest information in their respective expertise areas. It is a golden opportunity for the students, researchers and engineers to interact with the experts and specialists to get their advice or consultation on technical matters, teaching methods and strategies. These proceedings present a selection from papers submitted to the conference from universities, research institutes and industries. All of the papers were subjected to peer-review by conference committee members and international reviewers. The papers selected depended on their quality and their relevancy to the conference. The volume tends to present to the readers the recent advances in the field of computer and communication system, system design and measurement and control technology, power electronics and electrical engineering, materials science and engineering, power machinery and equipment maintenance, architectural design and project management, environmental analysis and detection etc. We would like to thank all the authors who have contributed to this volume and also to the organizing committee, reviewers, speakers, chairpersons, and all the conference participants for their support to ICMIE 2017. ICMIE 2017 Organizing Committee June 20th, 2017 (paper)

  7. 8th international conference on electronic spectroscopy and structure

    Energy Technology Data Exchange (ETDEWEB)

    Robinson, Art

    2000-10-16

    Gathering from 33 countries around the world, 408 registrants and a number of local drop-in participants descended on the Clark Kerr Campus of the University of California, Berkeley, from Monday, August 7 through Saturday, August 12, 2000 for the Eighth International Conference on Electronic Structure and Spectroscopy (ICESS8). At the conference, participants benefited from an extensive scientific program comprising more than 100 oral presentations (plenary lectures and invited and contributed talks) and 330 poster presentations, as well as ample time for socializing and a tour of the Advanced Light Source (ALS) at the nearby Lawrence Berkeley National Laboratory.

  8. Quantum revivals in the motion of electron in magnetic field

    International Nuclear Information System (INIS)

    Filipowicz, P.; Mostowski, J.

    1981-01-01

    We show that the motion of a relativistic electron in constant homogeneous magnetic field exhibits quasiperiodic behaviour (quantum revivals) and discuss the possibility of their observation. (author)

  9. EPR and development of quantum electronics

    International Nuclear Information System (INIS)

    Manenkov, A A

    2011-01-01

    A role of electron paramagnetic resonance in development of quantum electronics is discussed. Basic principles and history of masers are briefly described. Spin-levels of paramagnetic ions in crystals as a very suitable object for active media of solid-state masers (called as EPR-masers) and physical processes in EPR-masers (population inversion of energy states) are analyzed. This analysis demonstrates a significant role of relaxation processes in multi-level spin-systems for efficient maser action. In this context peculiarities of spin-lattice and spin-spin cross relaxation processes in multi-level systems are analyzed. Development of EPR-masers and their application in radioastronomy and far-space communication systems are briefly described.

  10. Quantum computation in semiconductor quantum dots of electron-spin asymmetric anisotropic exchange

    International Nuclear Information System (INIS)

    Hao Xiang; Zhu Shiqun

    2007-01-01

    The universal quantum computation is obtained when there exists asymmetric anisotropic exchange between electron spins in coupled semiconductor quantum dots. The asymmetric Heisenberg model can be transformed into the isotropic model through the control of two local unitary rotations for the realization of essential quantum gates. The rotations on each qubit are symmetrical and depend on the strength and orientation of asymmetric exchange. The implementation of the axially symmetric local magnetic fields can assist the construction of quantum logic gates in anisotropic coupled quantum dots. This proposal can efficiently use each physical electron spin as a logical qubit in the universal quantum computation

  11. Proceedings of 11. Conference on Electron Microscopy of Solids

    International Nuclear Information System (INIS)

    2002-01-01

    The conference is the cyclically organised discussion forum on problems connected with application of different electron microscopy techniques for the study of solid state materials. The main topics of 11 conference on Electron Microscopy of Solids held in Krynica (PL) in 2002 was: application of TEM in materials science; analytical techniques and orientation imaging in materials science; high resolution TEM in electronic materials; TEM and SEM application in ceramic and composites; advanced TEM techniques; advanced analytical and orientation imaging techniques; application of TEM in investigations of amorphous and nanocrystalline material; Intermetallic and superalloys; TEM application in martensite alloys; TEM and SEM application in research of iron base alloys; TEM studies of deformed alloys; TEM application in thin films and surface layer studies; TEM and SEM application in materials science

  12. 5th International Conference on Electronics, Communications and Networks

    CERN Document Server

    2016-01-01

    This book comprises peer-reviewed contributions presented at the 5th International Conference on Electronics, Communications and Networks (CECNet 2015), held in Shanghai, China, 12-15 December, 2015. It includes new multi-disciplinary topics spanning a unique depth and breadth of cutting-edge research areas in Electronic Engineering, Communications and Networks, and Computer Technology. More generally, it is of interest to academics, students and professionals involved in Consumer Electronics Technology, Communication Engineering and Technology, Wireless Communication Systems and Technology, and Computer Engineering and Technology.

  13. Few electron quantum dot coupling to donor implanted electron spins

    Science.gov (United States)

    Rudolph, Martin; Harvey-Collard, Patrick; Neilson, Erik; Gamble, John; Muller, Richard; Jacobson, Toby; Ten-Eyck, Greg; Wendt, Joel; Pluym, Tammy; Lilly, Michael; Carroll, Malcolm

    2015-03-01

    Donor-based Si qubits are receiving increased interest because of recent demonstrations of high fidelity electron or nuclear spin qubits and their coupling. Quantum dot (QD) mediated interactions between donors are of interest for future coupling of two donors. We present experiment and modeling of a polysilicon/Si MOS QD, charge-sensed by a neighboring many electron QD, capable of coupling to one or two donor implanted electron spins (D) while tuned to the few electron regime. The unique design employs two neighboring gated wire FETs and self-aligned implants, which supports many configurations of implanted donors. We can access the (0,1) ⇔(1,0) transition between the D and QD, as well as the resonance condition between the few electron QD and two donors ((0,N,1) ⇔(0,N +1,0) ⇔(1,N,0)). We characterize capacitances and tunnel rate behavior combined with semi-classical and full configuration interaction simulations to study the energy landscape and kinetics of D-QD transitions. This work was performed, in part, at the Center for Integrated Nanotechnologies, a U.S. DOE, Office of Basic Energy Sciences user facility. The work was supported by the Sandia National Laboratories Directed Research and Development Program. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

  14. PREFACE: XXVIII International Conference on Photonic, Electronic and Atomic Collisions (ICPEAC 2013)

    Science.gov (United States)

    Xiao, Guoqing; Cai, Xiaohong; Ding, Dajun; Ma, Xinwen; Zhao, Yongtao

    2014-04-01

    The 28th International Conference on Photonic, Electronic and Atomic Collisions (XXVIII ICPEAC) was held by the Institute of Modern Physics, Chinese Academy of Sciences (IMP) on 24-30 July, 2013 in Lanzhou, China. The 444 conference participants came from 37 countries and/or regions. Five plenary lectures, more than 80 progress reports and special reports had been arranged according to the decision of the ICPEAC International General Committee. Meanwhile, more than 650 abstracts were selected as poster presentations. Before the conference, three highly distinguished scientists, Professor Joachim Burgdöorfer, Professor Hossein Sadeghpour and Professor Yasunori Yamazaki, presented tutorial lectures with the support of the IMP Branch of Youth Innovation Promotion Association, CAS (IMP-YIPA). During the conference, Professor Jianwei Pan from University of Sciences and Technology in China presented an enlightening public lecture on quantum communication. Furthermore, 2013 IUPAP Young Scientist Prize was awarded to Dr T Jahnke from Johann Wolfgang Goethe University of Germany. The Sheldon Datz Prize for an Outstanding Young Scientist Attending ICPEAC was awarded to Dr Diogo Almeida from University of Fribourg of Switzerland. As a biannual academic conference, ICPEAC is one of the most important international conferences on atomic and molecular physics. The topic of the conference covers the recent progresses in photonic, electronic, atomic, ionic, molecular, cluster collisions with matter. With a history back to 1958, ICPEAC came to China for the very first time. IMP has been preparing the conference six years before, ever since the ICPEAC International General Committee made the decision to hold the XXVIII ICPEAC in Lanzhou. This proceedings includes the papers of the two plenary lectures, 40 progress reports, 17 special reports and 337 posters, which were reviewed and revised according to the comments of the referees. The Local Organizing Committee would like to

  15. Electronic quantum noise and microwave photons

    International Nuclear Information System (INIS)

    Bize-Reydellet, L.H.

    2003-06-01

    This work is devoted to the experimental study of quantum electronic noise in mesoscopic conductors. In the first part of this thesis, we studied shot noise in a one-dimensional ballistic conductor: a quantum point contact (QPC). We showed experimentally that, when one of the QPC contacts is irradiated with microwave photons, we observe partition noise in the absence of net current flowing through the sample. Thus, we validate the scattering theory of photo-assisted shot noise first by measuring the Fano factor without bias voltage across the conductor, and then by measuring shot noise in the doubly non equilibrium situation, where both a bias voltage and a microwave modulation are applied. In the second part, we realized the first tests of a new experimental set-up which will be able to measure high frequency noise of a mesoscopic conductor and the photon statistics emitted by this conductor in the measurement circuit. These tests consist in realizing Hanbury-Brown and Twiss type experiments (intensity interferometry) with two kinds of microwave photon source. First, we used a thermal incoherent source (macroscopic 50 Ohms resistor). It showed super-Poissonian noise, since the power fluctuations are proportional to the square of the mean photon power. Secondly, we studied a classical monochromatic source, which shows a Poissonian statistics. The giant Fano factor measured is perfectly explained by the attenuator and amplifier noise. (author)

  16. Polarized electrons, trions, and nuclei in charged quantum dots

    Science.gov (United States)

    Bracker, A. S.; Tischler, J. G.; Korenev, V. L.; Gammon, D.

    2003-07-01

    We have investigated spin polarization in GaAs quantum dots. Excitons and trions are polarized directly by optical excitation and studied through polarization of photoluminescence. Electrons and nuclei are polarized indirectly through subsequent relaxation processes. Polarized electrons are identified by the Hanle effect for exciton and trion photoluminescence, while polarized nuclei are identified through the Overhauser effect in individual charged quantum dots.

  17. Quantum Hall Effect: proposed multi-electron tunneling experiment

    International Nuclear Information System (INIS)

    Kostadinov, I.Z.

    1985-11-01

    Here we propose a tunneling experiment for the fractional and Integral Quantum Hall Effect. It may demonstrate multi-electron tunneling and may provide information about the nature of the macroscopic quantum states of 2D electronic liquid or solid. (author)

  18. Robust Optimal Design of Quantum Electronic Devices

    Directory of Open Access Journals (Sweden)

    Ociel Morales

    2018-01-01

    Full Text Available We consider the optimal design of a sequence of quantum barriers, in order to manufacture an electronic device at the nanoscale such that the dependence of its transmission coefficient on the bias voltage is linear. The technique presented here is easily adaptable to other response characteristics. There are two distinguishing features of our approach. First, the transmission coefficient is determined using a semiclassical approximation, so we can explicitly compute the gradient of the objective function. Second, in contrast with earlier treatments, manufacturing uncertainties are incorporated in the model through random variables; the optimal design problem is formulated in a probabilistic setting and then solved using a stochastic collocation method. As a measure of robustness, a weighted sum of the expectation and the variance of a least-squares performance metric is considered. Several simulations illustrate the proposed technique, which shows an improvement in accuracy over 69% with respect to brute-force, Monte-Carlo-based methods.

  19. Electronic properties of superlattices on quantum rings.

    Science.gov (United States)

    da Costa, D R; Chaves, A; Ferreira, W P; Farias, G A; Ferreira, R

    2017-04-26

    We present a theoretical study of the one-electron states of a semiconductor-made quantum ring (QR) containing a series of piecewise-constant wells and barriers distributed along the ring circumference. The single quantum well and the superlattice cases are considered in detail. We also investigate how such confining potentials affect the Aharonov-Bohm like oscillations of the energy spectrum and current in the presence of a magnetic field. The model is simple enough so as to allow obtaining various analytical or quasi-analytical results. We show that the well-in-a-ring structure presents enhanced localization features, as well as specific geometrical resonances in its above-barrier spectrum. We stress that the superlattice-in-a-ring structure allows giving a physical meaning to the often used but usually artificial Born-von-Karman periodic conditions, and discuss in detail the formation of energy minibands and minigaps for the circumferential motion, as well as several properties of the superlattice eigenstates in the presence of the magnetic field. We obtain that the Aharonov-Bohm oscillations of below-barrier miniband states are reinforced, owing to the important tunnel coupling between neighbour wells of the superlattice, which permits the electron to move in the ring. Additionally, we analysis a superlattice-like structure made of a regular distribution of ionized impurities placed around the QR, a system that may implement the superlattice in a ring idea. Finally, we consider several random disorder models, in order to study roughness disorder and to tackle the robustness of some results against deviations from the ideally nanostructured ring system.

  20. Quantum logic gates based on coherent electron transport in quantum wires.

    Science.gov (United States)

    Bertoni, A; Bordone, P; Brunetti, R; Jacoboni, C; Reggiani, S

    2000-06-19

    It is shown that the universal set of quantum logic gates can be realized using solid-state quantum bits based on coherent electron transport in quantum wires. The elementary quantum bits are realized with a proper design of two quantum wires coupled through a potential barrier. Numerical simulations show that (a) a proper design of the coupling barrier allows one to realize any one-qbit rotation and (b) Coulomb interaction between two qbits of this kind allows the implementation of the CNOT gate. These systems are based on a mature technology and seem to be integrable with conventional electronics.

  1. 15th International Conference on Non-Hermitian Hamiltonians in Quantum Physics

    CERN Document Server

    Passante, Roberto; Trapani, Camillo

    2016-01-01

    This book presents the Proceedings of the 15th International Conference on Non-Hermitian Hamiltonians in Quantum Physics, held in Palermo, Italy, from 18 to 23 May 2015. Non-Hermitian operators, and non-Hermitian Hamiltonians in particular, have recently received considerable attention from both the mathematics and physics communities. There has been a growing interest in non-Hermitian Hamiltonians in quantum physics since the discovery that PT-symmetric Hamiltonians can have a real spectrum and thus a physical relevance. The main subjects considered in this book include: PT-symmetry in quantum physics, PT-optics, Spectral singularities and spectral techniques, Indefinite-metric theories, Open quantum systems, Krein space methods, and Biorthogonal systems and applications. The book also provides a summary of recent advances in pseudo-Hermitian Hamiltonians and PT-symmetric Hamiltonians, as well as their applications in quantum physics and in the theory of open quantum systems.

  2. International Conference on Quantum Mathematical Physics : a Bridge between Mathematics and Physics

    CERN Document Server

    Kleiner, Johannes; Röken, Christian; Tolksdorf, Jürgen

    2016-01-01

    Quantum physics has been highly successful for more than 90 years. Nevertheless, a rigorous construction of interacting quantum field theory is still missing. Moreover, it is still unclear how to combine quantum physics and general relativity in a unified physical theory. Attacking these challenging problems of contemporary physics requires highly advanced mathematical methods as well as radically new physical concepts. This book presents different physical ideas and mathematical approaches in this direction. It contains a carefully selected cross-section of lectures which took place in autumn 2014 at the sixth conference ``Quantum Mathematical Physics - A Bridge between Mathematics and Physics'' in Regensburg, Germany. In the tradition of the other proceedings covering this series of conferences, a special feature of this book is the exposition of a wide variety of approaches, with the intention to facilitate a comparison. The book is mainly addressed to mathematicians and physicists who are interested in fu...

  3. Quantum tunneling and field electron emission theories

    CERN Document Server

    Liang, Shi-Dong

    2013-01-01

    Quantum tunneling is an essential issue in quantum physics. Especially, the rapid development of nanotechnology in recent years promises a lot of applications in condensed matter physics, surface science and nanodevices, which are growing interests in fundamental issues, computational techniques and potential applications of quantum tunneling. The book involves two relevant topics. One is quantum tunneling theory in condensed matter physics, including the basic concepts and methods, especially for recent developments in mesoscopic physics and computational formulation. The second part is the f

  4. Quantum tunneling resonant electron transfer process in Lorentzian plasmas

    International Nuclear Information System (INIS)

    Hong, Woo-Pyo; Jung, Young-Dae

    2014-01-01

    The quantum tunneling resonant electron transfer process between a positive ion and a neutral atom collision is investigated in nonthermal generalized Lorentzian plasmas. The result shows that the nonthermal effect enhances the resonant electron transfer cross section in Lorentzian plasmas. It is found that the nonthermal effect on the classical resonant electron transfer cross section is more significant than that on the quantum tunneling resonant charge transfer cross section. It is shown that the nonthermal effect on the resonant electron transfer cross section decreases with an increase of the Debye length. In addition, the nonthermal effect on the quantum tunneling resonant electron transfer cross section decreases with increasing collision energy. The variation of nonthermal and plasma shielding effects on the quantum tunneling resonant electron transfer process is also discussed

  5. PREFACE: XXVIth International Conference on Photonic, Electronic and Atomic Collisions

    Science.gov (United States)

    Orel, Ann; Starace, Anthony F.; Nikolić, Dragan; Berrah, Nora; Gorczyca, Thomas W.; Kamber, Emanuel Y.; Tanis, John A.

    2009-12-01

    The XXVIth International Conference on Photonic, Electronic and Atomic Collisions was held on the campus of Western Michigan University (WMU) in Kalamazoo during 22-28 July 2009. Kalamazoo, the home of a major state university amid pleasant surroundings, was a delightful place for the conference. The 473 scientific participants, 111 of whom were students, had many fruitful discussions and exchanges that contributed to the success of the conference. Participants from 43 countries made the conference truly international in scope. The 590 abstracts that were presented on the first four days formed the heart of the conference and provided ample opportunity for discussion. This change, allowing the conference to end with invited talks, was a departure from the format used at previous ICPEAC gatherings in which the conferences ended with a poster session. The abstracts were split almost equally between the three main conference areas, i.e., photonic, electronic, and atomic collisions, and the posters were distributed across the days of the conference so that approximately equal numbers of abstracts in the different areas were scheduled for each day. Of the total number of presented abstracts, 517 of these are included in this proceedings volume, the first time that abstracts have been published by ICPEAC. There were 5 plenary lectures covering the different areas of the conference: Paul Corkum (University of Ottawa) talked on attosecond physics with atoms and molecules, Serge Haroche (Collège de France) on non-destructive photon counting, Toshiyuki Azuma (Tokyo Metropolitan University) on resonant coherent excitation of highly-charged ions in crystals, Eva Lindroth (Stockholm University) on atomic structure effects, and Alfred Müller (Justus Liebig University) on resonance phenomena in electron- and photon-ion collisions. Two speakers gave very illuminating public lectures that drew many people from the local area, as well as conference participants: Patricia Dehmer

  6. Electronic structure of semiconductor quantum films

    International Nuclear Information System (INIS)

    Zhang, S.B.; Yeh, C.; Zunger, A.

    1993-01-01

    The electronic structure of thin (≤30 A) free-standing ideal films of Si(001), Si(110), and GaAs(110) is calculated using a plane-wave pseudopotential description. Unlike the expectation based on the simple effective-mass model, we find the following. (i) The band gaps of (001) quantum films exhibit even-odd oscillation as a function of the number N of monolayers. (ii) In addition to sine-type envelope functions which vanish at the film boundaries, some states have cosine envelope functions with extrema at boundaries. (iii) Even-layer Si(001) films exhibit at the valence-band maximum a state whose energy does not vary with the film thickness. Such zero confinement states have constant envelope throughout the film. (iv) Optical transitions in films exhibit boundary-imposed selection rules. Furthermore, oscillator strengths for pseudodirect transitions in the vicinity of forbidden direct transitions can be enhanced by several orders of magnitude. These findings, obtained in direct supercell calculations, can be explained in terms of a truncated crystal (TC) analysis. In this approach the film's wave functions are expanded in terms of pairs of bulk wave functions exhibiting a destructive interference at the boundaries. This maps the eigenvalue spectra of a film onto the bulk band structure evaluated at special k points which satisfy the boundary conditions. We find that the TC representation reproduces accurately the above-mentioned results of direct diagonalization of the film's Hamiltonian. This provides a simple alternative to the effective-mass model and relates the properties of quantum structures to those of the bulk material

  7. International Conference on NextGen Electronic Technologies

    CERN Document Server

    Thalmann, Nadia; Bhaaskaran, V

    2017-01-01

    This book is a collection of keynote lectures from international experts presented at International Conference on NextGen Electronic Technologies (ICNETS2-2016). ICNETS2 encompasses six symposia covering all aspects of electronics and communications domains, including relevant nano/micro materials and devices . This volume comprises of recent research in areas like computational signal processing analysis, intelligent embedded systems, nanoelectronic materials and devices, optical and microwave technologies, VLSI design: circuits systems and application, and wireless communication networks, and the internet of things. The contents of this book will be useful to researchers, professionals, and students working in the core areas of electronics and their applications, especially to signal processing, embedded systems, and networking.

  8. Electron Raman scattering in asymmetrical multiple quantum wells

    International Nuclear Information System (INIS)

    Betancourt-Riera, R; Rosas, R; Marin-Enriquez, I; Riera, R; Marin, J L

    2005-01-01

    Optical properties of asymmetrical multiple quantum wells for the construction of quantum cascade lasers are calculated, and expressions for the electronic states of asymmetrical multiple quantum wells are presented. The gain and differential cross-section for an electron Raman scattering process are obtained. Also, the emission spectra for several scattering configurations are discussed, and the corresponding selection rules for the processes involved are studied; an interpretation of the singularities found in the spectra is given. The electron Raman scattering studied here can be used to provide direct information about the efficiency of the lasers

  9. Nonequilibrium Electron Transport Through a Quantum Dot from Kubo Formula

    International Nuclear Information System (INIS)

    Lue Rong; Zhang Guangming

    2005-01-01

    Based on the Kubo formula for an electron tunneling junction, we revisit the nonequilibrium transport properties through a quantum dot. Since the Fermi level of the quantum dot is set by the conduction electrons of the leads, we calculate the electron current from the left side by assuming the quantum dot coupled to the right lead as another side of the tunneling junction, and the other way round is used to calculate the current from the right side. By symmetrizing these two currents, an effective local density states on the dot can be obtained, and is discussed at high and low temperatures, respectively.

  10. 3. International Conference on Quantum Electrodynamics and Statistical Physics. Book of abstracts

    International Nuclear Information System (INIS)

    2011-01-01

    The conference deals with the up-to-data problems of quantum field theory and elementary particle theory, QED processes at high energy, cosmology, theory of irreversible processes, nonlinear dynamics and chaos, phase transition and diffusion processes in condensed matter and gases.

  11. In situ electron-beam polymerization stabilized quantum dot micelles.

    Science.gov (United States)

    Travert-Branger, Nathalie; Dubois, Fabien; Renault, Jean-Philippe; Pin, Serge; Mahler, Benoit; Gravel, Edmond; Dubertret, Benoit; Doris, Eric

    2011-04-19

    A polymerizable amphiphile polymer containing PEG was synthesized and used to encapsulate quantum dots in micelles. The quantum dot micelles were then polymerized using a "clean" electron beam process that did not require any post-irradiation purification. Fluorescence spectroscopy revealed that the polymerized micelles provided an organic coating that preserved the quantum dot fluorescence better than nonpolymerized micelles, even under harsh conditions. © 2011 American Chemical Society

  12. Substantially Enhancing Quantum Coherence of Electrons in Graphene via Electron-Plasmon Coupling.

    Science.gov (United States)

    Cheng, Guanghui; Qin, Wei; Lin, Meng-Hsien; Wei, Laiming; Fan, Xiaodong; Zhang, Huayang; Gwo, Shangjr; Zeng, Changgan; Hou, J G; Zhang, Zhenyu

    2017-10-13

    The interplays between different quasiparticles in solids lay the foundation for a wide spectrum of intriguing quantum effects, yet how the collective plasmon excitations affect the quantum transport of electrons remains largely unexplored. Here we provide the first demonstration that when the electron-plasmon coupling is introduced, the quantum coherence of electrons in graphene is substantially enhanced with the quantum coherence length almost tripled. We further develop a microscopic model to interpret the striking observations, emphasizing the vital role of the graphene plasmons in suppressing electron-electron dephasing. The novel and transformative concept of plasmon-enhanced quantum coherence sheds new insight into interquasiparticle interactions, and further extends a new dimension to exploit nontrivial quantum phenomena and devices in solid systems.

  13. PREFACE: ISEC 2005: The 10th International Superconductive Electronics Conference

    Science.gov (United States)

    Rogalla, Horst

    2006-05-01

    The 10th International Superconductive Electronics Conference took place in Noordwijkerhout in the Netherlands, 5-9 September 2005, not far from the birthplace of superconductivity in Leiden nearly 100 years ago. There have been many reasons to celebrate the 10th ISEC: not only was it the 20th anniversary, but also the achievements since the first conference in Tokyo in 1987 are tremendous. We have seen whole new groups of superconductive materials come into play, such as oxide superconductors with maximum Tc in excess of 100 K, carbon nanotubes, as well as the realization of new digital concepts from saturation logic to the ultra-fast RSFQ-logic. We have learned that superconductors not only show s-wave symmetries in the spatial arrangement of the order parameter, but also that d-wave dependence in oxide superconductors is now well accepted and can even be successfully applied to digital circuits. We are now used to operating SQUIDs in liquid nitrogen; fT sensitivity of SQUID magnetometers is not surprising anymore and can even be reached with oxide-superconductor based SQUIDs. Even frequency discriminating wide-band single photon detection with superconductive devices, and Josephson voltage standards with tens of thousands of junctions, nowadays belong to the daily life of advanced laboratories. ISEC has played a very important role in this development. The first conferences were held in 1987 and 1989 in Tokyo, and subsequently took place in Glasgow (UK), Boulder (USA), Nagoya (Japan), Berlin (Germany), Berkeley (USA), Osaka (Japan), Sydney (Australia), and in 2005 for the first time in the Netherlands. These conferences have provided platforms for the presentation of the research and development results of this community and for the vivid discussion of achievements and strategies for the further development of superconductive electronics. The 10th conference has played a very important role in this context. The results in laboratories show great potential and

  14. Electronic structure and lattice relaxations in quantum confined Pb films

    NARCIS (Netherlands)

    Mans, A.

    2005-01-01

    Epitaxial films that are only several atoms layers thick exhibit interesting properties associated with quantum confinement. The electrons form standing waves, just like a violin string, clamped at both ends. In ultrathin lead films, this so-called `quantum size effect' (QSE) alters the physical

  15. Electron transport and coherence in semiconductor quantum dots and rings

    NARCIS (Netherlands)

    Van der Wiel, W.G.

    2002-01-01

    A number of experiments on electron transport and coherence in semiconductor vertical and lateral quantum dots and semiconductor rings is described. Quantum dots are often referred to as "artificial atoms", because of their similarities with real atoms. Examples of such atom-like properties that

  16. Quantum Electronic Matter in Two Dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Eisenstein, James [California Inst. of Technology (CalTech), Pasadena, CA (United States)

    2015-01-27

    -layer cousins. In particular, the exotic collective (and deeply quantum mechanical) electronic phases which develop when a large magnetic field is applied have been a major focus of effort. Significant results have been obtained from both ordinary electrical measurements and from more sophisticated thermoelectric studies of such systems. Related studies of few-layer graphenes have elucidated the transition from the two- to three-dimensional electrical properties of carbon-based conductors. Investigations like these expand our understanding of electronic materials general. While there are certainly immediate fundamental scientific pay-offs, it is also true that research of this kind ultimately leads to technological breakthroughs in the long term. By way of example, superconductivity was undoubtedly regarded as a useless novelty when it was discovered in 1911. Who could have known then that it would become crucial to the medical revolution brought about by magnetic resonance imaging decades later?

  17. Influence of scattering processes on electron quantum states in nanowires

    Directory of Open Access Journals (Sweden)

    Pozdnyakov Dmitry

    2007-01-01

    Full Text Available AbstractIn the framework of quantum perturbation theory the self-consistent method of calculation of electron scattering rates in nanowires with the one-dimensional electron gas in the quantum limit is worked out. The developed method allows both the collisional broadening and the quantum correlations between scattering events to be taken into account. It is an alternativeper seto the Fock approximation for the self-energy approach based on Green’s function formalism. However this approach is free of mathematical difficulties typical to the Fock approximation. Moreover, the developed method is simpler than the Fock approximation from the computational point of view. Using the approximation of stable one-particle quantum states it is proved that the electron scattering processes determine the dependence of electron energy versus its wave vector.

  18. Gated-controlled electron pumping in connected quantum rings

    International Nuclear Information System (INIS)

    Lima, R.P.A.; Domínguez-Adame, F.

    2014-01-01

    We study the electronic transport across connected quantum rings attached to leads and subjected to time-harmonic side-gate voltages. Using the Floquet formalism, we calculate the net pumped current generated and controlled by the side-gate voltage. The control of the current is achieved by varying the phase shift between the two side-gate voltages as well as the Fermi energy. In particular, the maximum current is reached when the side-gate voltages are in quadrature. This new design based on connected quantum rings controlled without magnetic fields can be easily integrated in standard electronic devices. - Highlights: • We introduce and study a minimal setup to pump electrons through connected quantum rings. • Quantum pumping is achieved by time-harmonic side-gate voltages instead of the more conventional time-dependent magnetic fluxes. • Our new design could be easily integrated in standard electronic devices

  19. Nonequilibrium electron transport through quantum dots in the Kondo regime

    DEFF Research Database (Denmark)

    Wölfle, Peter; Paaske, Jens; Rosch, Achim

    2005-01-01

    Electron transport at large bias voltage through quantum dots in the Kondo regime is described within the perturbative renormalization group extended to nonequilibrium. The conductance, local magnetization, dynamical spin susceptibility and local spectral function are calculated. We show how...

  20. PREFACE: International Conference on Strongly Correlated Electron Systems 2014 (SCES2014)

    Science.gov (United States)

    2015-03-01

    The 2014 International Conference on Strongly Correlated Electron Systems (SCES) was held in Grenoble from the 7th to 11th of July on the campus of the University of Grenoble. It was a great privilege to have the conference in Grenoble after the series of meetings in Sendai (1992), San Diego (1993), Amsterdam (1994), Goa (1995), Zürich (1996), Paris (1998), Nagano (1999), Ann Arbor (2001), Krakow (2002), Karlsruhe (2004), Vienna (2005), Houston (2007), Buzios (2008), Santa Fe (2010), Cambridge (2011) and Tokyo (2013). Every three years, SCES joins the triennial conference on magnetism ICM. In 2015, ICM will take place in Barcelona. The meeting gathered an audience of 875 participants who actively interacted inside and outside of conference rooms. A large number of posters (530) was balanced with four parallel oral sessions which included 86 invited speakers and 141 short oral contributions. A useful arrangement was the possibility to put poster presentations on the website so participants could see them all through the conference week. Each morning two plenary sessions were held, ending on Friday with experimental and theoretical summaries delivered by Philipp Gegenwart (Augsburg) and Andrew Millis (Columbia). The plenary sessions were given by Gabriel Kotliar (Rutgers), Masashi Kawasaki (Tokyo), Jennifer Hoffman (Harvard), Mathias Vojta (Dresden), Ashvin Vishwanath (Berkeley), Andrea Cavalleri (Hamburg), Marc-Henri Julien (Grenoble), Neil Mathur (Cambridge), Giniyat Khaliullin (Stuttgart), and Toshiro Sakakibara (Tokyo). The parallel oral sessions were prepared by 40 symposium organizers selected by the chairman (Antoine Georges) and co-chairman (Kamran Behnia) of the Program Committee with the supplementary rule that speakers had not delivered an invited talk at the previous SCES conference held in 2013 in Tokyo. Special attention was given to help young researchers via grants to 40 overseas students. Perhaps due to the additional possibility of cheap

  1. First International Conference on Electrical, Electronic and Communications Engineering

    CERN Document Server

    Vyas, Nalinaksh; Sanei, Saeid; Deb, Kalyanmoy

    2017-01-01

    The book reports on advanced theories and methods in two related engineering fields: electrical and electronic engineering, and communications engineering and computing. It highlights areas of global and growing importance, such as renewable energy, power systems, mobile communications, security and the Internet of Things (IoT). The contributions cover a number of current research issues, including smart grids, photovoltaic systems, wireless power transfer, signal processing, 4G and 5G technologies, IoT applications, mobile cloud computing and many more. Based on the proceedings of the first International Conference on Emerging Trends in Electrical, Electronic and Communications Engineering (ELECOM 2016), held in Voila Bagatelle, Mauritius from November 25 to 27, 2016, the book provides graduate students, researchers and professionals with a snapshot of the state-of-the-art and a source of new ideas for future research and collaborations.

  2. Inhomogeneous effects in the quantum free electron laser

    International Nuclear Information System (INIS)

    Piovella, N.; Bonifacio, R.

    2006-01-01

    We include inhomogeneous effects in the quantum model of a free electron laser taking into account the initial energy spread of the electron beam. From a linear analysis, we obtain a generalized dispersion relation, from which the exponential gain can be explicitly calculated. We determine the maximum allowed initial energy spread in the quantum exponential regime and we discuss the limit of large energy spread

  3. Electron-electron interactions in graphene field-induced quantum dots in a high magnetic field

    DEFF Research Database (Denmark)

    Orlof, A.; Shylau, Artsem; Zozoulenko, I. V.

    2015-01-01

    We study the effect of electron-electron interaction in graphene quantum dots defined by an external electrostatic potential and a high magnetic field. To account for the electron-electron interaction, we use the Thomas-Fermi approximation and find that electron screening causes the formation...... of compressible strips in the potential profile and the electron density. We numerically solve the Dirac equations describing the electron dynamics in quantum dots, and we demonstrate that compressible strips lead to the appearance of plateaus in the electron energies as a function of the magnetic field. Finally...

  4. DISCOURSE AND PARTICIPATION IN ESL FACE-TO-FACE AND WRITTEN ELECTRONIC CONFERENCES

    Directory of Open Access Journals (Sweden)

    Michael Fitze

    2006-01-01

    Full Text Available This study was a comparative investigation of face-to-face and written electronic conferences. The participants were advanced English as a second language (hereafter: ESL students. The two types of conferences were compared in terms of textual features and participation. There was no statistically significant difference in the total number of words that students produced in an equivalent amount of time in the two types of conferences. The discourse in written electronic conferences displayed greater lexical range, and students in these conferences produced more discourse demonstrating interactive competence. The statistically significant finding of increased lexical range in written electronic conferences persisted even when the interactive discourse was eliminated from the conference transcripts and the transcripts were reanalyzed. This finding suggests that, during written electronic conferences, students were better able to use and practice a wider range of vocabulary related to the topics. For one of the groups, participation in written electronic conferences was more balanced among students, while for the other group participation was about equally balanced regardless of the conference setting. This last finding came as a surprise and points to a need for further research into variables that might mediate balanced participation in face-to-face and written electronic conferences.

  5. Electronic transient processes and optical spectra in quantum dots for quantum computing

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Zdeněk, Petr; Khás, Zdeněk

    2004-01-01

    Roč. 3, č. 1 (2004), s. 17-25 ISSN 1536-125X R&D Projects: GA AV ČR IAA1010113 Institutional research plan: CEZ:AV0Z1010914 Keywords : depopulation * electronic relaxation * optical spectra * quantum dots * self-assembled quantum dots * upconversion Subject RIV: BE - Theoretical Physics Impact factor: 3.176, year: 2004

  6. Terahertz Plasma Waves in Two Dimensional Quantum Electron Gas with Electron Scattering

    International Nuclear Information System (INIS)

    Zhang Liping

    2015-01-01

    We investigate the Terahertz (THz) plasma waves in a two-dimensional (2D) electron gas in a nanometer field effect transistor (FET) with quantum effects, the electron scattering, the thermal motion of electrons and electron exchange-correlation. We find that, while the electron scattering, the wave number along y direction and the electron exchange-correlation suppress the radiation power, but the thermal motion of electrons and the quantum effects can amplify the radiation power. The radiation frequency decreases with electron exchange-correlation contributions, but increases with quantum effects, the wave number along y direction and thermal motion of electrons. It is worth mentioning that the electron scattering has scarce influence on the radiation frequency. These properties could be of great help to the realization of practical THz plasma oscillations in nanometer FET. (paper)

  7. Electron Transport in Coupled Quantum Dots

    National Research Council Canada - National Science Library

    Antoniadis, D

    1998-01-01

    In the course of the investigation funded by this proposal we fabricated, modeled, and measured a variety of quantum dot structures in order to better understand how such nanostructures might be used for computation...

  8. 2011 Gordon Research Conference on Quantum Control of Light and Matter

    International Nuclear Information System (INIS)

    Weinacht, Thomas

    2011-01-01

    Quantum control of light and matter is the quest to steer a physical process to a desirable outcome, employing constructive and destructive interference. Three basic questions address feasibility of quantum control: (1) The problem of controllability, does a control field exist for a preset initial and target state; (2) Synthesis, constructively finding the field that leads to the target; and (3) Optimal Control Theory - optimizing the field that carries out this task. These continue to be the fundamental theoretical questions to be addressed in the conference. How to realize control fields in the laboratory is an ongoing challenge. This task is very diverse viewing the emergence of control scenarios ranging from attoseconds to microseconds. How do the experimental observations reflect on the theoretical framework? The typical arena of quantum control is an open environment where much of the control is indirect. How are control scenarios realized in dissipative open systems? Can new control opportunities emerge? Can one null decoherence effects? An ideal setting for control is ultracold matter. The initial and final state can be defined more precisely. Coherent control unifies many fields of physical science. A lesson learned in one field can reflect on another. Currently quantum information processing has emerged as a primary target of control where the key issue is controlling quantum gate operation. Modern nonlinear spectroscopy has emerged as another primary field. The challenge is to unravel the dynamics of molecular systems undergoing strong interactions with the environment. Quantum optics where non-classical fields are to be generated and employed. Finally, coherent control is the basis for quantum engineering. These issues will be under the limelight of the Gordon conference on Quantum Control of Light and Matter.

  9. Electron Raman scattering in a HgS/CdS spherical quantum dot quantum well

    International Nuclear Information System (INIS)

    Zhong Qinghu; Lai Liping

    2013-01-01

    Electron Raman scattering (ERS) is investigated in a spherical HgS/CdS quantum dot quantum well (QDQW). The differential cross section (DCS) is calculated as a function of the scattering frequency and the sizes of QDQW. Single parabolic conduction and valence bands are assumed. The selection rules for the processes are studied. Singularities in the spectra are found and interpreted. The ERS studied here can be used to provide direct information about the electron band structure of these systems. (semiconductor physics)

  10. FTL Quantum Models of the Photon and the Electron

    International Nuclear Information System (INIS)

    Gauthier, Richard F.

    2007-01-01

    A photon is modeled by an uncharged superluminal quantum moving at 1.414c along an open 45-degree helical trajectory with radius R = λ/2π (where λ is the helical pitch or wavelength). A mostly superluminal spatial model of an electron is composed of a charged pointlike quantum circulating at an extremely high frequency ( 2.5 x 1020 hz) in a closed, double-looped hehcal trajectory whose helical pitch is one Compton wavelength h/mc. The quantum has energy and momentum but not rest mass, so its speed is not limited by c. sThe quantum's speed is superluminal 57% of the time and subluminal 43% of the time, passing through c twice in each trajectory cycle. The quantum's maximum speed in the electron's rest frame is 2.515c and its minimum speed is .707c. The electron model's helical trajectory parameters are selected to produce the electron's spin (ℎ/2π)/2 and approximate (without small QED corrections) magnetic moment e(ℎ/2π)/2m (the Bohr magneton μB) as well as its Dirac equation-related 'jittery motion' angular frequency 2mc2/(ℎ/2π), amplitude (ℎ/2π)/2mc and internal speed c. The two possible helicities of the electron model correspond to the electron and the positron. With these models, an electron is like a closed circulating photon. The electron's inertia is proposed to be related to the electron model's circulating internal Compton momentum mc. The internal superluminalily of the photon model, the internal superluminahty/subluminality of the electron model, and the proposed approach to the electron's inertia as ''momentum at rest'' within the electron, could be relevant to possible mechanisms of superluminal communication and transportation

  11. Quantum phase transitions of strongly correlated electron systems

    International Nuclear Information System (INIS)

    Imada, Masatoshi

    1998-01-01

    Interacting electrons in solids undergo various quantum phase transitions driven by quantum fluctuations. The quantum transitions take place at zero temperature by changing a parameter to control quantum fluctuations rather than thermal fluctuations. In contrast to classical phase transitions driven by thermal fluctuations, the quantum transitions have many different features where quantum dynamics introduces a source of intrinsic fluctuations tightly connected with spatial correlations and they have been a subject of recent intensive studies as we see below. Interacting electron systems cannot be fully understood without deep analyses of the quantum phase transitions themselves, because they are widely seen and play essential roles in many phenomena. Typical and important examples of the quantum phase transitions include metal-insulator transitions, (2, 3, 4, 5, 6, 7, 8, 9) metal-superconductor transitions, superconductor-insulator transitions, magnetic transitions to antiferromagnetic or ferromagnetic phases in metals as well as in Mott insulators, and charge ordering transitions. Here, we focus on three different types of transitions

  12. Classical behavior of few-electron parabolic quantum dots

    International Nuclear Information System (INIS)

    Ciftja, O.

    2009-01-01

    Quantum dots are intricate and fascinating systems to study novel phenomena of great theoretical and practical interest because low dimensionality coupled with the interplay between strong correlations, quantum confinement and magnetic field creates unique conditions for emergence of fundamentally new physics. In this work we consider two-dimensional semiconductor quantum dot systems consisting of few interacting electrons confined in an isotropic parabolic potential. We study the many-electron quantum ground state properties of such systems in presence of a perpendicular magnetic field as the number of electrons is varied using exact numerical diagonalizations and other approaches. The results derived from the calculations of the quantum model are then compared to corresponding results for a classical model of parabolically confined point charges who interact with a Coulomb potential. We find that, for a wide range of parameters and magnetic fields considered in this work, the quantum ground state energy is very close to the classical energy of the most stable classical configuration under the condition that the classical energy is properly adjusted to incorporate the quantum zero point motion.

  13. EDITORIAL: Electron Microscopy and Analysis Group Conference 2011 (EMAG 2011)

    Science.gov (United States)

    Moebus, Guenter; Walther, Thomas; Brydson, Rik; Ozkaya, Dogan; MacLaren, Ian; Donnelly, Steve; Nellist, Pete; Li, Ziyou; Baker, Richard; Chiu, YuLung

    2012-07-01

    The biennial EMAG conference has established a strong reputation as a key event for the national and international electron microscopy community. In 2011 the meeting was held at The University of Birmingham, and I must first take this opportunity of thanking Birmingham for hosting the conference and for the excellent support we received from the local organisers. As a committee, we are delighted to see that enthusiasm for the EMAG conference series continues to be strong. We received more than 160 submitted abstracts, and 157 delegates attended the meeting. The scientific programme organiser, Ian MacLaren, put together an exciting programme. Plenary lectures were presented by Professor Knut Urban, Dr Frances Ross and Dr Richard Henderson. There were a further 10 invited speakers, from the UK, Continental Europe, Australia, the USA and Japan. The quality of the contributed oral and poster presentations was also very high. EMAG is keen to encourage student participation, and a winner and two runners-up were presented with prizes for the best oral and poster presentations from a student. I am always struck by the scientific quality of the oral and poster contributions and the vibrant discussions that occur both in the formal sessions and in the exhibition space at EMAG. I am convinced that a crucial part of maintaining that scientific quality is the opportunity that is offered of having a paper fully reviewed by two internationally selected referees and published in the Journal of Physics: Conference Series. For many students, this is the first fully reviewed paper they publish. I hope that you, like me, will be struck by the scientific quality of the 87 papers that follow, and that you will find them interesting and informative. Finally I must thank the platinum sponsors for their support of the meeting. These were Gatan, Zeiss, FEI, JEOL and Hitachi. I must also thank the European Microscopy Society for their generous sponsorship and support for the travel costs of

  14. Measurement of quantum noise in a single-electron transistor near the quantum limit

    Science.gov (United States)

    Xue, W. W.; Ji, Z.; Pan, Feng; Stettenheim, Joel; Blencowe, M. P.; Rimberg, A. J.

    2009-09-01

    Quantum measurement has challenged physicists for almost a century. Classically, there is no lower bound on the noise a measurement may add. Quantum mechanically, however, measuring a system necessarily perturbs it. When applied to electrical amplifiers, this means that improved sensitivity requires increased backaction that itself contributes noise. The result is a strict quantum limit on added amplifier noise. To approach this limit, a quantum-limited amplifier must possess an ideal balance between sensitivity and backaction; furthermore, its noise must dominate that of subsequent classical amplifiers. Here, we report the first complete and quantitative measurement of the quantum noise of a superconducting single-electron transistor (S-SET) near a double Cooper-pair resonance predicted to have the right combination of sensitivity and backaction. A simultaneous measurement of our S-SET's charge sensitivity indicates that it operates within a factor of 3.6 of the quantum limit, a fourfold improvement over the nearest comparable results.

  15. Electron self-trapping at quantum and classical critical points

    NARCIS (Netherlands)

    Auslender, M.I.; Katsnelson, M.I.

    2006-01-01

    Using Feynman path integral technique estimations of the ground state energy have been found for a conduction electron interacting with order parameter fluctuations near quantum critical points. In some cases only singular perturbation theory in the coupling constant emerges for the electron ground

  16. Phonon excess heating in electronic relaxation theory in quantum dots

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Lin, Ch. Y.

    2008-01-01

    Roč. 22, č. 20 (2008), s. 3439-3460 ISSN 0217-9792 R&D Projects: GA MŠk ME 866 Institutional research plan: CEZ:AV0Z10100520 Keywords : quantum dots * electron -phonon interaction * electron ic transport Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.558, year: 2008

  17. Quantum electron transfer processes induced by thermo-coherent ...

    Indian Academy of Sciences (India)

    WINTEC

    Thermo-coherent state; electron transfer; quantum rate. 1. Introduction. The study ... two surfaces,16 namely, one electron two-centered exchange problem,7–10 many ... temperature classical regime for the single and the two-mode cases have ...

  18. Quantum-mechanical treatment of an electron undergoing synchrotron radiation.

    Science.gov (United States)

    White, D.

    1972-01-01

    The problem of an electron moving perpendicular to an intense magnetic field is approached from the framework of quantum mechanics. A numerical solution to the related rate equations describing the probabilities of occupation of the electron's energy states is put forth along with the expected errors involved. The quantum-mechanical approach is found to predict a significant amount of energy broadening with time for an initially monoenergetic electron beam entering a region of an intense magnetic field as long as the product of initial energy and magnetic field is of order 50 MG BeV or larger.

  19. Quantum synchrotron spectra from semirelativistic electrons in teragauss magnetic fields

    International Nuclear Information System (INIS)

    Brainerd, J.J.

    1987-01-01

    Synchrotron spectra are calculated from quantum electrodynamic transition rates for thermal and power-law electron distributions. It is shown that quantum effects appear in thermal spectra when the photon energy is greater than the electron temperature, and in power-law spectra when the electron energy in units of the electron rest mass times the magnetic field strength in units of the critical field strength is of order unity. These spectra are compared with spectra calculated from the ultrarelativistic approximation for synchrotron emission. It is found that the approximation for the power-law spectra is good, and the approximation for thermal spectra produces the shape of the spectrum accurately but fails to give the correct normalization. Single photon pair creation masks the quantum effects for power-law distributions, so only modifications to thermal spectra are important for gamma-ray bursts. 13 references

  20. Electron-electron interaction in p-SiGe/Ge quantum wells

    International Nuclear Information System (INIS)

    Roessner, Benjamin; Kaenel, Hans von; Chrastina, Daniel; Isella, Giovanni; Batlogg, Bertram

    2005-01-01

    The temperature dependent magnetoresistance of high mobility p-SiGe/Ge quantum wells is studied with hole densities ranging from 1.7 to 5.9 x 10 11 cm -2 . At magnetic fields below the onset of quantum oscillations that reflect the high mobility values (up to 75000 cm 2 /Vs), we observe the clear signatures of electron-electron interaction. We compare our experiment with the theory of electron-electron interaction including the Zeeman band splitting. The observed magnetoresistance is well explained as a superposition of band structure induced positive magnetoresistance and the negative magntoresistance due to the electron-electron interaction effect

  1. Toward efficient fiber-based quantum interface (Conference Presentation)

    Science.gov (United States)

    Soshenko, Vladimir; Vorobyov, Vadim V.; Bolshedvorsky, Stepan; Lebedev, Nikolay; Akimov, Alexey V.; Sorokin, Vadim; Smolyaninov, Andrey

    2016-04-01

    NV center in diamond is attracting a lot of attention in quantum information processing community [1]. Been spin system in clean and well-controlled environment of diamond it shows outstanding performance as quantum memory even at room temperature, spin control with single shot optical readout and possibility to build up quantum registers even on single NV center. Moreover, NV centers could be used as high-resolution sensitive elements of detectors of magnetic or electric field, temperature, tension, force or rotation. For all of these applications collection of the light emitted by NV center is crucial point. There were number of approaches suggested to address this issue, proposing use of surface plasmoms [2], manufacturing structures in diamond [3] etc. One of the key feature of any practically important interface is compatibility with the fiber technology. Several groups attacking this problem using various approaches. One of them is placing of nanodiamonds in the holes of photonic crystal fiber [4], another is utilization of AFM to pick and place nanodiamond on the tapered fiber[5]. We have developed a novel technique of placing a nanodiamond with single NV center on the tapered fiber by controlled transfer of a nanodiamond from one "donor" tapered fiber to the "target" clean tapered fiber. We verify our ability to transfer only single color centers by means of measurement of second order correlation function. With this technique, we were able to double collection efficiency of confocal microscope. The majority of the factors limiting the collection of photons via optical fiber are technical and may be removed allowing order of magnitude improved in collection. We also discuss number of extensions of this technique to all fiber excitation and integration with nanostructures. References: [1] Marcus W. Doherty, Neil B. Manson, Paul Delaney, Fedor Jelezko, Jörg Wrachtrup, Lloyd C.L. Hollenberg , " The nitrogen-vacancy colour centre in diamond," Physics Reports

  2. Classical-quantum correspondence in electron-positron pair creation

    International Nuclear Information System (INIS)

    Chott, N. I.; Su, Q.; Grobe, R.

    2007-01-01

    We examine the creation of electron-positron pairs in a very strong force field. Using numerical solutions to quantum field theory we calculate the spatial and momentum probability distributions for the created particles. A comparison with classical mechanical phase space calculations suggests that despite the fully relativistic and quantum mechanical nature of the matter creation process, most aspects can be reproduced accurately in terms of classical mechanics

  3. Many electron effects in semiconductor quantum dots

    Indian Academy of Sciences (India)

    Semiconductor quantum dots (QDs) exhibit shell structures, very similar to atoms. Termed as 'artificial atoms' by some, they are much larger (1 100 nm) than real atoms. One can study a variety of manyelectron effects in them, which are otherwise difficult to observe in a real atom. We have treated these effects within the ...

  4. Quantum theory of the electron liquid

    National Research Council Canada - National Science Library

    Giuliani, Gabriele; Vignale, Giovanni

    2005-01-01

    ... to the Wigner crystal, from the Luttinger liquid to the quantum Hall liquid, are extensively discussed. Both static and time-dependent density functional theory are presented in detail. Although the emphasis is on the development of the basic physical ideas and on a critical discussion of the most useful approximations, the formal derivation of the r...

  5. Quantum Electron Tunneling in Respiratory Complex I1

    Science.gov (United States)

    Hayashi, Tomoyuki; Stuchebrukhov, Alexei A.

    2014-01-01

    We have simulated the atomistic details of electronic wiring of all Fe/S clusters in complex I, a key enzyme in the respiratory electron transport chain. The tunneling current theory of many-electron systems is applied to the broken-symmetry (BS) states of the protein at the ZINDO level. One-electron tunneling approximation is found to hold in electron tunneling between the anti-ferromagnetic binuclear and tetranuclear Fe/S clusters with moderate induced polarization of the core electrons. Calculated tunneling energy is about 3 eV higher than Fermi level in the band gap of the protein, which supports that the mechanism of electron transfer is quantum mechanical tunneling, as in the rest of electron transport chain. Resulting electron tunneling pathways consist of up to three key contributing protein residues between neighboring Fe/S clusters. A distinct signature of the wave properties of electrons is observed as quantum interferences when multiple tunneling pathways exist. In N6a-N6b, electron tunnels along different pathways depending on the involved BS states, suggesting possible fluctuations of the tunneling pathways driven by the local protein environment. The calculated distance dependence of the electron transfer rates with internal water molecules included are in good agreement with a reported phenomenological relation. PMID:21495666

  6. Single electron-spin memory with a semiconductor quantum dot

    International Nuclear Information System (INIS)

    Young, Robert J; Dewhurst, Samuel J; Stevenson, R Mark; Atkinson, Paola; Bennett, Anthony J; Ward, Martin B; Cooper, Ken; Ritchie, David A; Shields, Andrew J

    2007-01-01

    We show storage of the circular polarization of an optical field, transferring it to the spin-state of an individual electron confined in a single semiconductor quantum dot. The state is subsequently read out through the electronically-triggered emission of a single photon. The emitted photon shares the same polarization as the initial pulse but has a different energy, making the transfer of quantum information between different physical systems possible. With an applied magnetic field of 2 T, spin memory is preserved for at least 1000 times more than the exciton's radiative lifetime

  7. Proceedings of the international conference on selected topics in quantum field theory and mathematical physics

    Energy Technology Data Exchange (ETDEWEB)

    Niederle, J; Bednar, M; Bicak, J

    1987-01-01

    The conference, the fourth in the series of conferences on this subject, was held at the Bechyne castle (Czechoslovakia) on June 23-27, 1986, and was attended by about 100 theoreticians from 15 countries. The conference was organized by the Institute of Physics of the Czechoslovak Academy of Sciences in Prague together with the Faculties of Mathematics and Physics of the Charles University, Prague, and of the Comenius University, Bratislava, the Faculty of Nuclear Science and Physical Engineering of the Czech Techical University, Prague, with the Institute of Physics of the Electro-Physical Research Centre of the Slovak Academy of Sciences, Bratislava, and the Institute of Nuclear Physics of the Czechoslovak Academy of Sciences in Rez. It was sponsored by the International Union for Pure and Applied Physics, the International Association of Mathematical Physics and the Physical Scientific Section of the Union of Czechoslovak Mathematicians and Physicists. The main subjects discussed at the conference were: supersymmetries, supergravity and superstring theories; quantum field theory and in particular gauge theories, theories on lattices, renormalization; selected topics in non-linear equations, scattering theory and quantization. Details are given in the attached program. The proceedings include invited talks and contributions presented respectively at the morning and afternoon sessions of the conference. The main part of the proceedings will be published in the Czechoslovak Journal of Physics v. 37(1987), nos. 3,4 and 9.

  8. Proceedings of the international conference on selected topics in quantum field theory and mathematical physics

    International Nuclear Information System (INIS)

    Niederle, J.; Bednar, M.; Bicak, J.

    1987-01-01

    The conference, the fourth in the series of conferences on this subject, was held at the Bechyne castle (Czechoslovakia) on June 23-27, 1986, and was attended by about 100 theoreticians from 15 countries. The conference was organized by the Institute of Physics of the Czechoslovak Academy of Sciences in Prague together with the Faculties of Mathematics and Physics of the Charles University, Prague, and of the Comenius University, Bratislava, the Faculty of Nuclear Science and Physical Engineering of the Czech Techical University, Prague, with the Institute of Physics of the Electro-Physical Research Centre of the Slovak Academy of Sciences, Bratislava, and the Institute of Nuclear Physics of the Czechoslovak Academy of Sciences in Rez. It was sponsored by the International Union for Pure and Applied Physics, the International Association of Mathematical Physics and the Physical Scientific Section of the Union of Czechoslovak Mathematicians and Physicists. The main subjects discussed at the conference were: supersymmetries, supergravity and superstring theories; quantum field theory and in particular gauge theories, theories on lattices, renormalization; selected topics in non-linear equations, scattering theory and quantization. Details are given in the attached program. The proceedings include invited talks and contributions presented respectively at the morning and afternoon sessions of the conference. The main part of the proceedings will be published in the Czechoslovak Journal of Physics v. 37(1987), nos. 3,4 and 9. (author)

  9. Proceedings of 8. national conference on nuclear electronic and nuclear detection technology: Pt.1

    International Nuclear Information System (INIS)

    1996-01-01

    The 8th National Conference on Nuclear Electronics and Nuclear Detection Technology was held during 2-7, 12, 1996 in Zhuhai, Guangdong, China. 184 pieces of papers were collected in the conference proceedings. The contents of the conference proceedings are: nuclear electronics, nuclear detectors, nuclear instruments and its application, nuclear medical electronics, computer applications in nuclear sciences and technology, measurement of nuclear monitoring and nuclear explosion, radiation hardened electronics, liquid scintillation counting techniques and miscellaneous. Reported hereafter is the first part of the proceedings

  10. Orientation-dependent imaging of electronically excited quantum dots

    Science.gov (United States)

    Nguyen, Duc; Goings, Joshua J.; Nguyen, Huy A.; Lyding, Joseph; Li, Xiaosong; Gruebele, Martin

    2018-02-01

    We previously demonstrated that we can image electronic excitations of quantum dots by single-molecule absorption scanning tunneling microscopy (SMA-STM). With this technique, a modulated laser beam periodically saturates an electronic transition of a single nanoparticle, and the resulting tunneling current modulation ΔI(x0, y0) maps out the SMA-STM image. In this paper, we first derive the basic theory to calculate ΔI(x0, y0) in the one-electron approximation. For near-resonant tunneling through an empty orbital "i" of the nanostructure, the SMA-STM signal is approximately proportional to the electron density |φi) (x0,y0)|nudge quantum dots on the surface and roll them, thus imaging excited state electronic structure of a single quantum dot at different orientations. We use density functional theory to model ODMs at various orientations, for qualitative comparison with the SMA-STM experiment. The model demonstrates that our experimentally observed signal monitors excited states, localized by defects near the surface of an individual quantum dot. The sub-nanometer super-resolution imaging technique demonstrated here could become useful for mapping out the three-dimensional structure of excited states localized by defects within nanomaterials.

  11. Controlling electron quantum dot qubits by spin-orbit interactions

    International Nuclear Information System (INIS)

    Stano, P.

    2007-01-01

    Single electron confined in a quantum dot is studied. A special emphasis is laid on the spin properties and the influence of spin-orbit interactions on the system. The study is motivated by a perspective exploitation of the spin of the confined electron as a qubit, a basic building block of in a foreseen quantum computer. The electron is described using the single band effective mass approximation, with parameters typical for a lateral electrostatically defined quantum dot in a GaAs/AlGaAs heterostructure. The stemming data for the analysis are obtained by numerical methods of exact diagonalization, however, all important conclusions are explained analytically. The work focuses on three main areas -- electron spectrum, phonon induced relaxation and electrically and magnetically induced Rabi oscillations. It is shown, how spin-orbit interactions influence the energy spectrum, cause finite spin relaxation and allow for all-electrical manipulation of the spin qubit. Among the main results is the discovery of easy passages, where the spin relaxation is unusually slow and the qubit is protected against parasitic electrical fields connected with manipulation by resonant electromagnetic fields. The results provide direct guide for manufacturing quantum dots with much improved properties, suitable for realizing single electron spin qubits. (orig.)

  12. A quantum field theory of the extended electron

    International Nuclear Information System (INIS)

    Salesi, Giovanni; Recami, Erasmo; Universidade Estadual de Campinas, SP

    1993-12-01

    In a recent paper, the classical model of Barut and Zanghi (BZ) for the electron spin which interpreted the Zitterbewegung (zbw) motion along helical paths and its quantum version have been investigated by using the language of Clifford algebras. In also doing, a new non-linear Dirac-like equation (NDE) was derived. We want to readdress the whole subject, and complete it, by adopting - for the sake of physical clarity - the ordinary tensorial language. In particular, we re-derive here the NDE for the electron quantum field, show it to be associated with a new conserved probability current, and stress its importance for a quantum field theory of spin 1/2 fermions. Actually, we propose this equation in substitution for the Dirac equation, which comes from the former by averaging over a zbw cycle. We then derive a new equation of motion for the quantum field velocity, which will allow us to regard the electron as an extended object, with a classically intelligible internal structure (thus overcoming some known, long-standing problems). We carefully the solutions of the NDE; with special attention to those implying (at the classical limit) light-like helical motions, since these appear to be the most adequate equations for the electron description, from the kinematical and physical points of view, and do cope with the electron electromagnetic properties (such as Coulomb field and intrinsic magnetic moment). (author). 18 refs

  13. A quantum field theory of the extended electron

    Energy Technology Data Exchange (ETDEWEB)

    Salesi, Giovanni [Universita Statale di Catania (Italy). Dipt. di Fisica; Recami, Erasmo [Universita Statale di Bergamo, Dalmine, BG (Italy). Facolta di Ingegneria; [Universidade Estadual de Campinas, SP (Brazil). Dept. de Matematica Aplicada

    1993-12-01

    In a recent paper, the classical model of Barut and Zanghi (BZ) for the electron spin which interpreted the Zitterbewegung (zbw) motion along helical paths and its quantum version have been investigated by using the language of Clifford algebras. In also doing, a new non-linear Dirac-like equation (NDE) was derived. We want to readdress the whole subject, and complete it, by adopting - for the sake of physical clarity - the ordinary tensorial language. In particular, we re-derive here the NDE for the electron quantum field, show it to be associated with a new conserved probability current, and stress its importance for a quantum field theory of spin 1/2 fermions. Actually, we propose this equation in substitution for the Dirac equation, which comes from the former by averaging over a zbw cycle. We then derive a new equation of motion for the quantum field velocity, which will allow us to regard the electron as an extended object, with a classically intelligible internal structure (thus overcoming some known, long-standing problems). We carefully the solutions of the NDE; with special attention to those implying (at the classical limit) light-like helical motions, since these appear to be the most adequate equations for the electron description, from the kinematical and physical points of view, and do cope with the electron electromagnetic properties (such as Coulomb field and intrinsic magnetic moment). (author). 18 refs.

  14. Controlling electron quantum dot qubits by spin-orbit interactions

    Energy Technology Data Exchange (ETDEWEB)

    Stano, P.

    2007-01-15

    Single electron confined in a quantum dot is studied. A special emphasis is laid on the spin properties and the influence of spin-orbit interactions on the system. The study is motivated by a perspective exploitation of the spin of the confined electron as a qubit, a basic building block of in a foreseen quantum computer. The electron is described using the single band effective mass approximation, with parameters typical for a lateral electrostatically defined quantum dot in a GaAs/AlGaAs heterostructure. The stemming data for the analysis are obtained by numerical methods of exact diagonalization, however, all important conclusions are explained analytically. The work focuses on three main areas -- electron spectrum, phonon induced relaxation and electrically and magnetically induced Rabi oscillations. It is shown, how spin-orbit interactions influence the energy spectrum, cause finite spin relaxation and allow for all-electrical manipulation of the spin qubit. Among the main results is the discovery of easy passages, where the spin relaxation is unusually slow and the qubit is protected against parasitic electrical fields connected with manipulation by resonant electromagnetic fields. The results provide direct guide for manufacturing quantum dots with much improved properties, suitable for realizing single electron spin qubits. (orig.)

  15. Complex dynamics in planar two-electron quantum dots

    International Nuclear Information System (INIS)

    Schroeter, Sebastian Josef Arthur

    2013-01-01

    Quantum dots play an important role in a wide range of recent experimental and technological developments. In particular they are promising candidates for realisations of quantum bits and further applications in quantum information theory. The harmonically confined Hooke's atom model is experimentally verified and separates in centre-of-mass and relative coordinates. Findings that are contradictory to this separability call for an extension of the model, in particular changing the confinement potential. In order to study effects of an anharmonic confinement potential on spectral properties of planar two-electron quantum dots a sophisticated numerical approach is developed. Comparison between the Helium atom, Hooke's atom and an anharmonic potential model are undertaken in order to improve the description of quantum dots. Classical and quantum features of complexity and chaos are investigated and used to characterise the dynamics of the system to be mixed regular-chaotic. Influence of decoherence can be described by quantum fidelity, which measures the effect of a perturbation on the time evolution. The quantum fidelity of eigenstates of the system depends strongly on the properties of the perturbation. Several methods for solving the time-dependent Schrödinger equation are implemented and a high level of accuracy for long time evolutions is achieved. The concept of offset entanglement, the entanglement of harmonic models in the noninteracting limit, is introduced. This concept explains different questions raised in the literature for harmonic quantum dot models, recently. It shows that only in the groundstate the electrons are not entangled in the fermionic sense. The applicability, validity, and origin of Hund's first rule in general quantum dot models is further addressed. In fact Hund's first rule is only applicable, and in this case also valid, for one pair of singlet and triplet states in Hooke's atom. For more realistic models of two-electron quantum dots an

  16. Complex dynamics in planar two-electron quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Schroeter, Sebastian Josef Arthur

    2013-06-25

    Quantum dots play an important role in a wide range of recent experimental and technological developments. In particular they are promising candidates for realisations of quantum bits and further applications in quantum information theory. The harmonically confined Hooke's atom model is experimentally verified and separates in centre-of-mass and relative coordinates. Findings that are contradictory to this separability call for an extension of the model, in particular changing the confinement potential. In order to study effects of an anharmonic confinement potential on spectral properties of planar two-electron quantum dots a sophisticated numerical approach is developed. Comparison between the Helium atom, Hooke's atom and an anharmonic potential model are undertaken in order to improve the description of quantum dots. Classical and quantum features of complexity and chaos are investigated and used to characterise the dynamics of the system to be mixed regular-chaotic. Influence of decoherence can be described by quantum fidelity, which measures the effect of a perturbation on the time evolution. The quantum fidelity of eigenstates of the system depends strongly on the properties of the perturbation. Several methods for solving the time-dependent Schrödinger equation are implemented and a high level of accuracy for long time evolutions is achieved. The concept of offset entanglement, the entanglement of harmonic models in the noninteracting limit, is introduced. This concept explains different questions raised in the literature for harmonic quantum dot models, recently. It shows that only in the groundstate the electrons are not entangled in the fermionic sense. The applicability, validity, and origin of Hund's first rule in general quantum dot models is further addressed. In fact Hund's first rule is only applicable, and in this case also valid, for one pair of singlet and triplet states in Hooke's atom. For more realistic models of two-electron

  17. Electronic properties of asymmetrical quantum dots dressed by laser field

    Energy Technology Data Exchange (ETDEWEB)

    Kibis, O.V. [Department of Applied and Theoretical Physics, Novosibirsk State Technical University, Karl Marx Avenue 20, 630092 Novosibirsk (Russian Federation); Slepyan, G.Ya.; Maksimenko, S.A. [Institute for Nuclear Problems, Belarus State University, Bobruyskaya St. 11, 220050 Minsk (Belarus); Hoffmann, A. [Institut fuer Festkoerperphysik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)

    2012-05-15

    In the present paper, we demonstrate theoretically that the strong non-resonant interaction between asymmetrical quantum dots (QDs) and a laser field results in harmonic oscillations of their band gap. It is shown that such oscillations change the spectrum of elementary electron excitations in QDs: in the absence of the laser pumping there is only one resonant electron frequency, but QDs dressed by the laser field have a set of electron resonant frequencies. One expects that this modification of elementary electron excitations in QDs can be observable in optical experiments. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. From quantum transitions to electronic motions

    Science.gov (United States)

    Krausz, Ferenc

    2017-01-01

    Laser spectroscopy and chromoscopy permit precision measurement of quantum transitions and captures atomic-scale dynamics, respectively. Frequency- and time-domain metrology ranks among the supreme laser disciplines in fundamental science. For decades, these fields evolved independently, without interaction and synergy between them. This has changed profoundly with controlling the position of the equidistant frequency spikes of a mode-locked laser oscillator. By the self-referencing technique invented by Theodor Hänsch, the comb can be coherently linked to microwaves and used for precision measurements of energy differences between quantum states. The resultant optical frequency synthesis has revolutionized precision spectroscopy. Locking the comb lines to the resonator round-trip frequency by the same approach has given rise to laser pulses with controlled field oscillations. This article reviews, from a personal perspective, how the bridge between frequency- and time-resolved metrology emerged on the turn of the millennium and how synthesized several-cycle laser fields have been instrumental in establishing the basic tools and techniques for attosecond science.

  19. Electron energy spectrum in core-shell elliptic quantum wire

    Directory of Open Access Journals (Sweden)

    V.Holovatsky

    2007-01-01

    Full Text Available The electron energy spectrum in core-shell elliptic quantum wire and elliptic semiconductor nanotubes are investigated within the effective mass approximation. The solution of Schrodinger equation based on the Mathieu functions is obtained in elliptic coordinates. The dependencies of the electron size quantization spectrum on the size and shape of the core-shell nanowire and nanotube are calculated. It is shown that the ellipticity of a quantum wire leads to break of degeneration of quasiparticle energy spectrum. The dependences of the energy of odd and even electron states on the ratio between semiaxes are of a nonmonotonous character. The anticrosing effects are observed at the dependencies of electron energy spectrum on the transversal size of the core-shell nanowire.

  20. Electron Raman scattering in a cylindrical quantum dot

    International Nuclear Information System (INIS)

    Zhong Qinghu; Yi Xuehua

    2012-01-01

    Electron Raman scattering (ERS) is investigated in a CdS cylindrical quantum dot (QD). The differential cross section is calculated as a function of the scattering frequency and the size of the QD. Single parabolic conduction and valence bands are assumed, and singularities in the spectrum are found and interpreted. The selection rules for the processes are also studied. The ERS studied here can be used to provide direct information about the electron band structure of these systems. (semiconductor physics)

  1. Imaging electron wave functions inside open quantum rings.

    Science.gov (United States)

    Martins, F; Hackens, B; Pala, M G; Ouisse, T; Sellier, H; Wallart, X; Bollaert, S; Cappy, A; Chevrier, J; Bayot, V; Huant, S

    2007-09-28

    Combining scanning gate microscopy (SGM) experiments and simulations, we demonstrate low temperature imaging of the electron probability density |Psi|(2)(x,y) in embedded mesoscopic quantum rings. The tip-induced conductance modulations share the same temperature dependence as the Aharonov-Bohm effect, indicating that they originate from electron wave function interferences. Simulations of both |Psi|(2)(x,y) and SGM conductance maps reproduce the main experimental observations and link fringes in SGM images to |Psi|(2)(x,y).

  2. Exact wave functions of two-electron quantum rings.

    Science.gov (United States)

    Loos, Pierre-François; Gill, Peter M W

    2012-02-24

    We demonstrate that the Schrödinger equation for two electrons on a ring, which is the usual paradigm to model quantum rings, is solvable in closed form for particular values of the radius. We show that both polynomial and irrational solutions can be found for any value of the angular momentum and that the singlet and triplet manifolds, which are degenerate, have distinct geometric phases. We also study the nodal structure associated with these two-electron states.

  3. Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy

    Science.gov (United States)

    Priebe, Katharina E.; Rathje, Christopher; Yalunin, Sergey V.; Hohage, Thorsten; Feist, Armin; Schäfer, Sascha; Ropers, Claus

    2017-12-01

    Ultrafast electron and X-ray imaging and spectroscopy are the basis for an ongoing revolution in the understanding of dynamical atomic-scale processes in matter. The underlying technology relies heavily on laser science for the generation and characterization of ever shorter pulses. Recent findings suggest that ultrafast electron microscopy with attosecond-structured wavefunctions may be feasible. However, such future technologies call for means to both prepare and fully analyse the corresponding free-electron quantum states. Here, we introduce a framework for the preparation, coherent manipulation and characterization of free-electron quantum states, experimentally demonstrating attosecond electron pulse trains. Phase-locked optical fields coherently control the electron wavefunction along the beam direction. We establish a new variant of quantum state tomography—`SQUIRRELS'—for free-electron ensembles. The ability to tailor and quantitatively map electron quantum states will promote the nanoscale study of electron-matter entanglement and new forms of ultrafast electron microscopy down to the attosecond regime.

  4. Electron Energy Level Statistics in Graphene Quantum Dots

    NARCIS (Netherlands)

    De Raedt, H.; Katsnellson, M. I.; Katsnelson, M.I.

    2008-01-01

    Motivated by recent experimental observations of size quantization of electron energy levels in graphene quantum dots [7] we investigate the level statistics in the simplest tight-binding model for different dot shapes by computer simulation. The results are in a reasonable agreement with the

  5. Hot electrons in superlattices: quantum transport versus Boltzmann equation

    DEFF Research Database (Denmark)

    Wacker, Andreas; Jauho, Antti-Pekka; Rott, S.

    1999-01-01

    A self-consistent solution of the transport equation is presented for semiconductor superlattices within different approaches: (i) a full quantum transport model based on nonequilibrium Green functions, (ii) the semiclassical Boltzmann equation for electrons in a miniband, and (iii) Boltzmann...

  6. Quantum noise in a terahertz hot electron bolometer mixer

    NARCIS (Netherlands)

    Zhang, W.; Khosropanah, P.; Gao, J. R.; Kollberg, E. L.; Yngvesson, K. S.; Bansal, T.; Barends, R.; Klapwijk, T. M.

    2010-01-01

    We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model

  7. Stark-like electron transfer between quantum wells

    International Nuclear Information System (INIS)

    Dubovis, S.A.; Voronko, A.N.; Basharov, A.M.

    2008-01-01

    The Stark-like mechanism of electron transfer between two energy subband localized in remote quantum wells is examined theoretically. Estimations of major parameters of the problem in case of delta-function-wells model are adduced. Schematic model allowing experimental study of Stark-like transfer is proposed

  8. The quantum mechanical analysis of the free electron laser

    International Nuclear Information System (INIS)

    Dattoli, G.; Renieri, A.

    1985-01-01

    A quantum analysis of the Free Electron Laser is presented. The theory is developed both in single and longitudinal multimode regimes. Finally a self-consistent procedure to study the growth of the laser signal from the vacuum to the macroscopic level is presented

  9. Applied nonlinear optics in the journal 'Quantum Electronics'

    International Nuclear Information System (INIS)

    Grechin, Sergei G; Dmitriev, Valentin G; Chirkin, Anatolii S

    2011-01-01

    A brief historical review of the experimental and theoretical works on nonlinear optical frequency conversion (generation of harmonics, up- and down-conversion, parametric oscillation), which have been published in the journal 'Quantum Electronics' for the last 40 years, is presented.

  10. Distribution of tunnelling times for quantum electron transport

    International Nuclear Information System (INIS)

    Rudge, Samuel L.; Kosov, Daniel S.

    2016-01-01

    In electron transport, the tunnelling time is the time taken for an electron to tunnel out of a system after it has tunnelled in. We define the tunnelling time distribution for quantum processes in a dissipative environment and develop a practical approach for calculating it, where the environment is described by the general Markovian master equation. We illustrate the theory by using the rate equation to compute the tunnelling time distribution for electron transport through a molecular junction. The tunnelling time distribution is exponential, which indicates that Markovian quantum tunnelling is a Poissonian statistical process. The tunnelling time distribution is used not only to study the quantum statistics of tunnelling along the average electric current but also to analyse extreme quantum events where an electron jumps against the applied voltage bias. The average tunnelling time shows distinctly different temperature dependence for p- and n-type molecular junctions and therefore provides a sensitive tool to probe the alignment of molecular orbitals relative to the electrode Fermi energy.

  11. Quantum simulations of small electron-hole complexes

    International Nuclear Information System (INIS)

    Lee, M.A.; Kalia, R.K.; Vashishta, P.D.

    1984-09-01

    The Green's Function Monte Carlo method is applied to the calculation of the binding energies of electron-hole complexes in semiconductors. The quantum simulation method allows the unambiguous determination of the ground state energy and the effects of band anisotropy on the binding energy. 22 refs., 1 fig

  12. Electron-electron scattering and mobilities in semiconductors and quantum wells

    International Nuclear Information System (INIS)

    Lyo, S.K.

    1986-01-01

    The effect of electron-electron scattering on the mobility in semiconductors and semiconductor quantum wells is examined. A general exact formula is derived for the mobility, when the electron-electron collision rate is much faster than other scattering rates such as those by ionized impurities and phonons. In this limit, the transport relaxation rate is independent of the carrier's energy and contributions to the inverse mobility from individual scattering mechanism add up. The mobility becomes significantly reduced from its value in the absence of electron-electron scattering. When the collision rates are not necessarily dominated by electron-electron scattering, the mobility is calculated by the Kohler-Sondheimer variational method in the presence of ionized-impurity scattering and acoustic-phonon scattering in a nondegenerate two-dimensional quantum well

  13. Quantum State Transfer from a Single Photon to a Distant Quantum-Dot Electron Spin

    Science.gov (United States)

    He, Yu; He, Yu-Ming; Wei, Yu-Jia; Jiang, Xiao; Chen, Kai; Lu, Chao-Yang; Pan, Jian-Wei; Schneider, Christian; Kamp, Martin; Höfling, Sven

    2017-08-01

    Quantum state transfer from flying photons to stationary matter qubits is an important element in the realization of quantum networks. Self-assembled semiconductor quantum dots provide a promising solid-state platform hosting both single photon and spin, with an inherent light-matter interface. Here, we develop a method to coherently and actively control the single-photon frequency bins in superposition using electro-optic modulators, and measure the spin-photon entanglement with a fidelity of 0.796 ±0.020 . Further, by Greenberger-Horne-Zeilinger-type state projection on the frequency, path, and polarization degrees of freedom of a single photon, we demonstrate quantum state transfer from a single photon to a single electron spin confined in an InGaAs quantum dot, separated by 5 m. The quantum state mapping from the photon's polarization to the electron's spin is demonstrated along three different axes on the Bloch sphere, with an average fidelity of 78.5%.

  14. Correlated electron phenomena in ultra-low disorder quantum wires

    International Nuclear Information System (INIS)

    Reilly, D.J.; Facer, G.R.; Dzurak, A.S.; Kane, B.E.; Clark, R.G.; Lumpkin, N.E.

    1999-01-01

    Full text: Quantum point contacts in the lowest disorder HEMTs display structure at 0.7 x 2e 2 /h, which cannot be interpreted within a single particle Landauer model. This structure has been attributed to a spontaneous spin polarisation at zero B field. We have developed novel GaAs/AlGaAs enhancement mode FETs, which avoid the random impurity potential present in conventional MODFET devices by using epitaxially grown gates to produce ultra-low-disorder QPCs and quantum wires using electron beam lithography. The ballistic mean free path within these devices exceeds 160 μm 2 . Quantum wires of 5 μm in length show up to 15 conductance plateaux, indicating that these may be the lowest-disorder quantum wires fabricated using conventional surface patterning techniques. These structures are ideal for the study of correlation effects in QPCs and quantum wires as a function of electron density. Our data provides strong evidence that correlation effects are enhanced as the length of the 1D region is increased and also that additional structure moves close to 0.5 x 2e 2 /h, the value expected for an ideal spin-split 1D level

  15. On the applicability of one- and many-electron quantum chemistry models for hydrated electron clusters

    Science.gov (United States)

    Turi, László

    2016-04-01

    We evaluate the applicability of a hierarchy of quantum models in characterizing the binding energy of excess electrons to water clusters. In particular, we calculate the vertical detachment energy of an excess electron from water cluster anions with methods that include one-electron pseudopotential calculations, density functional theory (DFT) based calculations, and ab initio quantum chemistry using MP2 and eom-EA-CCSD levels of theory. The examined clusters range from the smallest cluster size (n = 2) up to nearly nanosize clusters with n = 1000 molecules. The examined cluster configurations are extracted from mixed quantum-classical molecular dynamics trajectories of cluster anions with n = 1000 water molecules using two different one-electron pseudopotenial models. We find that while MP2 calculations with large diffuse basis set provide a reasonable description for the hydrated electron system, DFT methods should be used with precaution and only after careful benchmarking. Strictly tested one-electron psudopotentials can still be considered as reasonable alternatives to DFT methods, especially in large systems. The results of quantum chemistry calculations performed on configurations, that represent possible excess electron binding motifs in the clusters, appear to be consistent with the results using a cavity structure preferring one-electron pseudopotential for the hydrated electron, while they are in sharp disagreement with the structural predictions of a non-cavity model.

  16. On the applicability of one- and many-electron quantum chemistry models for hydrated electron clusters

    Energy Technology Data Exchange (ETDEWEB)

    Turi, László, E-mail: turi@chem.elte.hu [Department of Physical Chemistry, Eötvös Loránd University, P.O. Box 32, H-1518 Budapest 112 (Hungary)

    2016-04-21

    We evaluate the applicability of a hierarchy of quantum models in characterizing the binding energy of excess electrons to water clusters. In particular, we calculate the vertical detachment energy of an excess electron from water cluster anions with methods that include one-electron pseudopotential calculations, density functional theory (DFT) based calculations, and ab initio quantum chemistry using MP2 and eom-EA-CCSD levels of theory. The examined clusters range from the smallest cluster size (n = 2) up to nearly nanosize clusters with n = 1000 molecules. The examined cluster configurations are extracted from mixed quantum-classical molecular dynamics trajectories of cluster anions with n = 1000 water molecules using two different one-electron pseudopotenial models. We find that while MP2 calculations with large diffuse basis set provide a reasonable description for the hydrated electron system, DFT methods should be used with precaution and only after careful benchmarking. Strictly tested one-electron psudopotentials can still be considered as reasonable alternatives to DFT methods, especially in large systems. The results of quantum chemistry calculations performed on configurations, that represent possible excess electron binding motifs in the clusters, appear to be consistent with the results using a cavity structure preferring one-electron pseudopotential for the hydrated electron, while they are in sharp disagreement with the structural predictions of a non-cavity model.

  17. Conference: Superconductivity, theory and practical challenges of a quantum phenonemon | 25 August | Uni Dufour

    CERN Multimedia

    2015-01-01

    On Tuesday, 25 August, J. Georg Bednorz (Nobel prize in physics 1987, IBM Research Zurich) and Louis Taillefer (physicist and professor at the University of Sherbrooke, Canada, and at the Canadian Institute for Advanced Research) will give a conference on the fascinating theme of superconductivity. "Superconductivity: theory and practical challenges of a quantum phenonemon" Uni Dufour Tuesday, 25 August at 7 p.m. This conference is organized by the Faculty of science of the University of Geneva, as part of the International Congress Materials and Mechanisms of Superconductivity (M2S - 2015). Discovered more than 100 years ago, superconductivity remains one of the most fascinating manifestations of the laws of physics, observable only at low temperatures. This phenomenon, which allows the transport of electricity without any loss of energy, leads to various technological applications, for example in magnetically levitated vehicles, in MRI and in ...

  18. Analysis of quantum semiconductor heterostructures by ballistic electron emission spectroscopy

    Science.gov (United States)

    Guthrie, Daniel K.

    1998-09-01

    The microelectronics industry is diligently working to achieve the goal of gigascale integration (GSI) by early in the 21st century. For the past twenty-five years, progress toward this goal has been made by continually scaling down device technology. Unfortunately, this trend cannot continue to the point of producing arbitrarily small device sizes. One possible solution to this problem that is currently under intensive study is the relatively new area of quantum devices. Quantum devices represent a new class of microelectronic devices that operate by utilizing the wave-like nature (reflection, refraction, and confinement) of electrons together with the laws of quantum mechanics to construct useful devices. One difficulty associated with these structures is the absence of measurement techniques that can fully characterize carrier transport in such devices. This thesis addresses this need by focusing on the study of carrier transport in quantum semiconductor heterostructures using a relatively new and versatile measurement technique known as ballistic electron emission spectroscopy (BEES). To achieve this goal, a systematic approach that encompasses a set of progressively more complex structures is utilized. First, the simplest BEES structure possible, the metal/semiconductor interface, is thoroughly investigated in order to provide a foundation for measurements on more the complex structures. By modifying the semiclassical model commonly used to describe the experimental BEES spectrum, a very complete and accurate description of the basic structure has been achieved. Next, a very simple semiconductor heterostructure, a Ga1-xAlxAs single-barrier structure, was measured and analyzed. Low-temperature measurements on this structure were used to investigate the band structure and electron-wave interference effects in the Ga1-xAlxAs single barrier structure. These measurements are extended to a simple quantum device by designing, measuring, and analyzing a set of

  19. Electron-longitudinal-acoustic-phonon scattering in double-quantum-dot based quantum gates

    International Nuclear Information System (INIS)

    Zhao Peiji; Woolard, Dwight L.

    2008-01-01

    We propose a nanostructure design which can significantly suppress longitudinal-acoustic-phonon-electron scattering in double-quantum-dot based quantum gates for quantum computing. The calculated relaxation rates vs. bias voltage exhibit a double-peak feature with a minimum approaching 10 5 s -1 . In this matter, the energy conservation law prohibits scattering contributions from phonons with large momenta; furthermore, increasing the barrier height between the double quantum dots reduces coupling strength between the dots. Hence, the joint action of the energy conservation law and the decoupling greatly reduces the scattering rates. The degrading effects of temperatures can be reduced simply by increasing the height of the barrier between the dots

  20. Electron-Electron and Electron-Phonon interactions effects on the tunnel electronic spectrum of PbS quantum dots

    Science.gov (United States)

    Wang, Hongyue; Lhuillier, Emmanuel; Yu, Qian; Mottaghizadeh, Alireza; Ulysse, Christian; Zimmers, Alexandre; Dubertret, Benoit; Aubin, Herve

    2015-03-01

    We present a tunnel spectroscopy study of the electronic spectrum of single PbS Quantum Dots (QDs) trapped between nanometer-spaced electrodes, measured at low temperature T=5 K. The carrier filling of the QD can be controlled either by the drain voltage in the shell filling regime or by a gate voltage. In the empty QD, the tunnel spectrum presents the expected signature of the 8x degenerated excited levels. In the drain controlled shell filling regime, the levels degeneracies are lifted by the global electrostatic Coulomb energy of the QD; in the gate controlled shell filling regime, the levels degeneracies are lifted by the intra-Coulomb interactions. In the charged quantum dot, electron-phonons interactions lead to the apparition of Franck-Condon side bands on the single excited levels and possibly Franck Condon blockade at low energy. The sharpening of excited levels at higher gate voltage suggests that the magnitude of electron-phonon interactions is decreased upon increasing the electron filling in the quantum dot. This work was supported by the French ANR Grants 10-BLAN-0409-01, 09-BLAN-0388-01, by the Region Ile-de-France in the framework of DIM Nano-K and by China Scholarship Council.

  1. 10th Biennial Conference on Classical and Quantum Relativistic Dynamics of Particles and Fields

    International Nuclear Information System (INIS)

    2017-01-01

    Preface The International Association for Relativistic Dynamics was organized in February 1998 in Houston, Texas, with John R. Fanchi as president. Although the subject of relativistic dynamics has been explored, from both classical and quantum mechanical points of view, since the work of Einstein and Dirac, its most striking development has been in the framework of quantum field theory. The very accurate calculations of spectral and scattering properties, for example, of the anomalous magnetic moment of the electron and the Lamb shift in quantum electrodynamics, and many qualitative features of the strong and electroweak interactions, demonstrate the very great power of description achieved in this framework. Yet, many fundamental questions remain to be clarified, such as the structure of classical relativistic dynamical theories on the level of Hamilton and Lagrange in Minkowski space as well as on the curved manifolds of general relativity. There, moreover, remained the important questions of the covariant classical description of systems at high energy for which particle production effects are not large, such as discussed in Synge’s book, The Relativistic Gas , and in Balescu’s book on relativistic statistical mechanics, and the development of a consistent single and many body relativistic quantum theory. In recent years, the very high accuracy of telescopes and advanced facilities for computation have brought a high level of interest in cosmological problems such as the structure of galaxies (dark matter) and the apparently anomalous expansion of the universe (dark energy). Some of the papers reported here deal with these problems, as well as other fundamental related issues. It was for this purpose, to bring together researchers from a wide variety of fields, such as particle physics, astrophysics, cosmology, foundations of relativity theory, and mathematical physics, with a common interest in relativistic dynamics, to investigate fundamental questions of

  2. Quantum effects in biological electron transfer

    Czech Academy of Sciences Publication Activity Database

    de la Lande, A.; Babcock, N. S.; Řezáč, Jan; Levy, B.; Sanders, B. C.; Salahub, D.

    2012-01-01

    Roč. 14, č. 17 (2012), s. 5902-5918 ISSN 1463-9076 Institutional research plan: CEZ:AV0Z40550506 Keywords : electron transfer * tunnelling * decoherence * semi-classical molecular dynamics * density functional theory Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.829, year: 2012

  3. Electron localization and optical absorption of polygonal quantum rings

    Science.gov (United States)

    Sitek, Anna; Serra, Llorenç; Gudmundsson, Vidar; Manolescu, Andrei

    2015-06-01

    We investigate theoretically polygonal quantum rings and focus mostly on the triangular geometry where the corner effects are maximal. Such rings can be seen as short core-shell nanowires, a generation of semiconductor heterostructures with multiple applications. We show how the geometry of the sample determines the electronic energy spectrum, and also the localization of electrons, with effects on the optical absorption. In particular, we show that irrespective of the ring shape low-energy electrons are always attracted by corners and are localized in their vicinity. The absorption spectrum in the presence of a magnetic field shows only two peaks within the corner-localized state domain, each associated with different circular polarization. This picture may be changed by an external electric field which allows previously forbidden transitions, and thus enables the number of corners to be determined. We show that polygonal quantum rings allow absorption of waves from distant ranges of the electromagnetic spectrum within one sample.

  4. Electron Spin Optical Orientation in Charged Quantum Dots

    Science.gov (United States)

    Shabaev, A.; Gershoni, D.; Korenev, V. L.

    2005-03-01

    We present a theory of nonresonant optical orientation of electron spins localized in quantum dots. This theory explains the negative circularly polarized photoluminescence of singlet trions localized in quantum dots previously observed in experiments where trion polarization changed to negative with time and where the degree of the negative polarization increased with intensity of pumping light. We have shown that this effect can be explained by the accumulation of dark excitons that occurs due to the spin blocking of the singlet trion formation - the major mechanism of dark exciton recombination. The accumulation of dark excitons results from a lack of electrons with a spin matching the exciton polarization. The electron spin lifetime is shortened by a transverse magnetic field or a temperature increase. This takes the block off the dark exciton recombination and restores the positive degree of trion polarization. The presented theory gives good agreement with experimental data.

  5. Quantum noise in a terahertz hot electron bolometer mixer

    OpenAIRE

    Zhang, W.; Khosropanah, P.; Gao, J. R.; Kollberg, E. L.; Yngvesson, K. S.; Bansal, T.; Barends, R.; Klapwijk, T. M.

    2010-01-01

    We have measured the noise temperature of a single, sensitive superconducting NbN hot electron bolometer (HEB) mixer in a frequency range from 1.6 to 5.3 THz, using a setup with all the key components in vacuum. By analyzing the measured receiver noise temperature using a quantum noise (QN) model for HEB mixers, we confirm the effect of QN. The QN is found to be responsible for about half of the receiver noise at the highest frequency in our measurements. The ?-factor (the quantum efficiency ...

  6. Solid state lasers: a major direction in quantum electronics

    International Nuclear Information System (INIS)

    Shcherbakov, I.A.

    2004-01-01

    The aim of the report is to analyze development of solid-state lasers (SSL) as one of the most important avenues of the quantum electronics. The obtained intensity of a laser radiation at the focus equal to 5x10 1 0 W/cm 2 (the field intensity equal to about 5x10 1 0 V/cm 2 ) is noted to enable to observe nonlinear quantum- electrodynamic effects. Besides, one managed to increase the SSL efficiency conventionally equal to maximum 3% up to 48-50%. Paper describes new types of SSLs, namely, the crystalline fiber lasers with the lateral gradient of the index of refraction [ru

  7. Two Electron States in a Quantum Ring on a Sphere

    International Nuclear Information System (INIS)

    Kazaryan, Eduard M.; Shahnazaryan, Vanik A.; Sarkisyan, Hayk A.

    2014-01-01

    Two electron states in a quantum ring on a spherical surface are discussed. The problem is discussed within the frameworks of Russell–Saunders coupling scheme, that is, the spin–orbit coupling is neglected. Treating Coulomb interaction as a perturbation, the energy correction for different states is calculated. The dependence of the Coulomb interaction energy on external polar boundary angle of quantum ring is obtained. In analogue with the helium atom the concept of states exchange time is introduced, and its dependence on geometrical parameters of the ring is shown. (author)

  8. Quantum algebraic representation of localization and motion of a Dirac electron

    International Nuclear Information System (INIS)

    Jaekel, Marc-Thierry; Reynaud, Serge

    2001-01-01

    Quantum algebraic observables representing localization in space-time of a Dirac electron are defined. Inertial motion of the electron is represented in the quantum algebra with electron mass acting as the generator of motion. Since transformations to uniformly accelerated frames are naturally included in this conformally invariant description, the quantum algebra is also able to deal with uniformly accelerated motion

  9. Electron transport in quantum wires: possible current instability mechanism

    International Nuclear Information System (INIS)

    Sablikov, V.A.

    2001-01-01

    The electrons nonlinear and dynamic transition in quantum wires connecting the electron reservoirs, are studies with an account of the Coulomb interaction distribution of electron density between the reservoirs and the wire. It is established that there exist two processes, leading to electrical instability in such structure. One of them is expressed in form of multistability of the charge accumulated in the wire, and negative differential conductivity. The other one is connected with origination of negative dynamic conductivity in the narrow frequency range near the resonance frequency of the charge waves on the wire length [ru

  10. Field dependence of the electron spin relaxation in quantum dots.

    Science.gov (United States)

    Calero, Carlos; Chudnovsky, E M; Garanin, D A

    2005-10-14

    The interaction of the electron spin with local elastic twists due to transverse phonons is studied. The universal dependence of the spin-relaxation rate on the strength and direction of the magnetic field is obtained in terms of the electron gyromagnetic tensor and macroscopic elastic constants of the solid. The theory contains no unknown parameters and it can be easily tested in experiment. At high magnetic field it provides a parameter-free lower bound on the electron spin relaxation in quantum dots.

  11. Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures

    Science.gov (United States)

    2018-02-19

    AFRL-AFOSR-JP-TR-2018-0012 Nano Electronics on Atomically Controlled van der Waals Quantum Heterostructures PHILIP Kim HARVARD COLLEGE PRESIDENT...21-02-2018 2.  REPORT TYPE      Final 3.  DATES COVERED (From - To)      15 Aug 2015 to 14 Feb 2017 4.  TITLE AND SUBTITLE Nano Electronics on...NOTES 14.  ABSTRACT We report molecular beam epitaxial growth and electronic transport properties of high quality topological insulator Bi2Se3 thin films

  12. Natural occupation numbers in two-electron quantum rings.

    Science.gov (United States)

    Tognetti, Vincent; Loos, Pierre-François

    2016-02-07

    Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.

  13. Natural occupation numbers in two-electron quantum rings

    Energy Technology Data Exchange (ETDEWEB)

    Tognetti, Vincent, E-mail: vincent.tognetti@univ-rouen.fr [Normandy Univ., COBRA UMR 6014 & FR 3038, Université de Rouen, INSA Rouen, CNRS, 1 rue Tesniére, 76821 Mont Saint Aignan, Cedex (France); Loos, Pierre-François [Research School of Chemistry, Australian National University, Canberra ACT 2601 (Australia)

    2016-02-07

    Natural orbitals (NOs) are central constituents for evaluating correlation energies through efficient approximations. Here, we report the closed-form expression of the NOs of two-electron quantum rings, which are prototypical finite-extension systems and new starting points for the development of exchange-correlation functionals in density functional theory. We also show that the natural occupation numbers for these two-electron paradigms are in general non-vanishing and follow the same power law decay as atomic and molecular two-electron systems.

  14. Nuclear Electronics I. Proceedings of the Conference on Nuclear Electronics. Vol. I

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1962-04-15

    Nuclear instruments are used in almost every phase of atomic energy work, from assessing health hazards and prospecting for nuclear materials to plant control and nuclear physics experiments. The demands on nucleonic instrumentation are growing steadily. High-energy particle physics need such instruments for measuring extremely short times; in various research experiments most advanced electronic systems are required; and routine applications of radioisotopes call for more reliable instruments for automated counting facilities. In order to give designers and users of nuclear instrumentation an opportunity to discuss the research results and to exchange information on recent developments and new designs, the International Atomic Energy Agency, in co-operation with the Federal Nuclear Energy Commission of Yugoslavia, organized a Conference on Nuclear Electronics which was held in Belgrade from 15-20 May 1961. It was attended by more than 300 scientists from nearly 30 countries and five international organizations. Over 150 papers were read and discussed. As the field of nuclear electronics has expanded considerably, it was impossible to discuss all aspects of nuclear electronics in one series of meetings. Included in the main topics were radiation detectors, electronic circuitry in conventional and fast-pulse techniques and advanced electronic systems used in nuclear research. The Proceedings presented in these volumes contain the full records of the Conference, including discussions. The present state of technique, together with current trends and developments, are outlined. Of particular value should be the world-wide survey on progress recently made in such fields as those connected with semiconductor detectors, spark counters, luminescence chambers and fast electronic facilities for nuclear physics research. Together with the Proceedings of the Symposium on the same subject held in Paris and also published by the International Atomic Energy Agency, these volumes

  15. Nuclear Electronics II. Proceedings of the Conference on Nuclear Electronics. V. II

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1962-04-15

    Nuclear instruments are used in almost every phase of atomic energy work, from assessing health hazards and prospecting for nuclear materials to plant control and nuclear physics experiments. The demands on nucleonic instrumentation are growing steadily. High-energy particle physics need such instruments for measuring extremely short times; in various research experiments most advanced electronic systems are required; and routine applications of radioisotopes call for more reliable instruments for automated counting facilities. In order to give designers and users of nuclear instrumentation an opportunity to discuss the research results and to exchange information on recent developments and new designs, the International Atomic Energy Agency, in co-operation with the Federal Nuclear Energy Commission of Yugoslavia, organized a Conference on Nuclear Electronics which was held in Belgrade from 15-20 May 1961. It was attended by more than 300 scientists from nearly 30 countries and five international organizations. Over 150 papers were read and discussed. As the field of nuclear electronics has expanded considerably, it was impossible to discuss all aspects of nuclear electronics in one series of meetings. Included in the main topics were radiation detectors, electronic circuitry in conventional and fast-pulse techniques and advanced electronic systems used in nuclear research. The Proceedings presented in these volumes contain the full records of the Conference, including discussions. The present state of technique, together with current trends and developments, are outlined. Of particular value should be the world-wide survey on progress recently made in such fields as those connected with semiconductor detectors, spark counters, luminescence chambers and fast electronic facilities for nuclear physics research. Together with the Proceedings of the Symposium on the same subject held in Paris and also published by the International Atomic Energy Agency, these volumes

  16. Nuclear Electronics III. Proceedings of the Conference on Nuclear Electronics. V. III

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1962-04-15

    Nuclear instruments are used in almost every phase of atomic energy work, from assessing health hazards and prospecting for nuclear materials to plant control and nuclear physics experiments. The demands on nucleonic instrumentation are growing steadily. High-energy particle physics need such instruments for measuring extremely short times; in various research experiments most advanced electronic systems are required; and routine applications of radioisotopes call for more reliable instruments for automated counting facilities. In order to give designers and users of nuclear instrumentation an opportunity to discuss the research results and to exchange information on recent developments and new designs, the International Atomic Energy Agency, in co-operation with the Federal Nuclear Energy Commission of Yugoslavia, organized a Conference on Nuclear Electronics which was held in Belgrade from 15-20 May 1961. It was attended by more than 300 scientists from nearly 30 countries and five international organizations. Over 150 papers were read and discussed. As the field of nuclear electronics has expanded considerably, it was impossible to discuss all aspects of nuclear electronics in one series of meetings. Included in the main topics were radiation detectors, electronic circuitry in conventional and fast-pulse techniques and advanced electronic systems used in nuclear research. The Proceedings presented in these volumes contain the full records of the Conference, including discussions. The present state of technique, together with current trends and developments, are outlined. Of particular value should be the world-wide survey on progress recently made in such fields as those connected with semiconductor detectors, spark counters, luminescence chambers and fast electronic facilities for nuclear physics research. Together with the Proceedings of the Symposium on the same subject held in Paris and also published by the International Atomic Energy Agency, these volumes

  17. ADVISOR Users Conference Proceedings 2000 - Final Electronic version

    Energy Technology Data Exchange (ETDEWEB)

    NREL

    2000-09-26

    This is a compilation of papers presented at the ADVISOR (ADvanced Vehicle SimulatOR) Users Conference held in Costa Mesa, California, August 24-25, 2000. Major topics of the conference included modeling and simulation; partnering with the auto industry; co-simulation: partnering with the software industry in optimization and thermal modeling and geometric and mechanical modeling; forward-looking simulations coupled with ADVISOR; new concepts from universities; validation, vehicle development and applications.

  18. 2008 Electron Donor Acceptor Interactions Gordon Research Conference-August 3-8, 2009

    Energy Technology Data Exchange (ETDEWEB)

    Forbes, Malcolm [Univ. of North Carolina, Chapel Hill, NC (United States); Gray, Nancy Ryan [Gordon Research Conferences, West Kingston, RI (United States)

    2009-09-19

    The conference presents and advances the current frontiers in experimental and theoretical studies of Electron Transfer and Transport in Molecular and Nano-scale Systems. The program includes sessions on coupled electron transfers, molecular solar energy conversion, biological and biomimetic systems, spin effects, ultrafast reactions and technical frontiers as well as electron transport in single molecules and devices.

  19. International Conference on Emerging Research in Electronics, Computer Science and Technology

    CERN Document Server

    Sheshadri, Holalu; Padma, M

    2014-01-01

    PES College of Engineering is organizing an International Conference on Emerging Research in Electronics, Computer Science and Technology (ICERECT-12) in Mandya and merging the event with Golden Jubilee of the Institute. The Proceedings of the Conference presents high quality, peer reviewed articles from the field of Electronics, Computer Science and Technology. The book is a compilation of research papers from the cutting-edge technologies and it is targeted towards the scientific community actively involved in research activities.

  20. PREFACE: Electron Microscopy and Analysis Group Conference (EMAG2015)

    Science.gov (United States)

    MacLaren, Ian

    2015-10-01

    2015 marked a new venture for the EMAG group of the Institute of Physics in that the conference was held in conjunction with the MMC2015 conference at the wonderful Manchester Central conference centre. As anyone who was there would be able to confirm, this went exceptionally well and was a really vibrant and top quality conference. The oral sessions were filled with good talks, the poster sessions were very lively, and there was a good balance between oral sessions with a specifically "EMAG" identity, and the integration into a larger conference with the ability to switch between up to six parallel sessions covering physical sciences, techniques, and life sciences. The large conference also attracted a wide range of exhibitors, and this is essential for the ongoing success of all of our work, in a field that is very dependent on continued technical innovation and on collaborations between academic researchers and commercial developers of microscopes, holders, detectors, spectrometers, sample preparation equipment, and software, among other things. As has long been the case at EMAG, all oral and poster presenters were invited to submit papers for consideration for the proceedings. As ever, these papers were independently reviewed by other conference attendees, with the aim of continuing the long tradition of the EMAG proceedings being a top quality, peer-reviewed publication, worthy of reference in future years. Whilst I recognise that not all presenters were able to submit papers to the proceedings (for instance due to the need not to prejudice publication in some other journals, or due to avoiding duplicate publication of data), we are gratified that our presenters submitted as many papers as they did. The 41 papers included provide an interesting snapshot of many of the areas covered in the conference presentations, including functional materials, coatings, 3D microscopy, FIB and SEM, nanomaterials, magnetic and structural materials, advances in EM techniques

  1. Coherent Electron Scattering Captured by an Attosecond Quantum Stroboscope

    International Nuclear Information System (INIS)

    Mauritsson, J.; Johnsson, P.; Mansten, E.; Swoboda, M.; Ruchon, T.; L'Huillier, A.; Schafer, K. J.

    2008-01-01

    We demonstrate a quantum stroboscope based on a sequence of identical attosecond pulses that are used to release electrons into a strong infrared (IR) laser field exactly once per laser cycle. The resulting electron momentum distributions are recorded as a function of time delay between the IR laser and the attosecond pulse train using a velocity map imaging spectrometer. Because our train of attosecond pulses creates a train of identical electron wave packets, a single ionization event can be studied stroboscopically. This technique has enabled us to image the coherent electron scattering that takes place when the IR field is sufficiently strong to reverse the initial direction of the electron motion causing it to rescatter from its parent ion

  2. Approximate calculation of electronic energy levels of axially symmetric quantum dot and quantum ring by using energy dependent effective mass

    International Nuclear Information System (INIS)

    Yu-Min, Liu; Zhong-Yuan, Yu; Xiao-Min, Ren

    2009-01-01

    Calculations of electronic structures about the semiconductor quantum dot and the semiconductor quantum ring are presented in this paper. To reduce the calculation costs, for the quantum dot and the quantum ring, their simplified axially symmetric shapes are utilized in our analysis. The energy dependent effective mass is taken into account in solving the Schrödinger equations in the single band effective mass approximation. The calculated results show that the energy dependent effective mass should be considered only for relatively small volume quantum dots or small quantum rings. For large size quantum materials, both the energy dependent effective mass and the parabolic effective mass can give the same results. The energy states and the effective masses of the quantum dot and the quantum ring as a function of geometric parameters are also discussed in detail. (general)

  3. Electron Acceptor Materials Engineering in Colloidal Quantum Dot Solar Cells

    KAUST Repository

    Liu, Huan

    2011-07-15

    Lead sulfide colloidal quantum dot (CQD) solar cells with a solar power conversion efficiency of 5.6% are reported. The result is achieved through careful optimization of the titanium dioxide electrode that serves as the electron acceptor. Metal-ion-doped sol-gel-derived titanium dioxide electrodes produce a tunable-bandedge, well-passivated materials platform for CQD solar cell optimization. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Pico-femtosecond image-tube photography in quantum electronics

    International Nuclear Information System (INIS)

    Schelev, M Ya

    2001-01-01

    The possibility of experimental achievement of the time resolution of image-converter tubes (ICTs) corresponding to the theoretical limit of 10 fs is considered as applied to quantum electronics problems. A new generation of ICTs with a temporal resolution of 200 - 500 fs has been developed for recording femtosecond laser radiation. The entirely new devices based on time-analysing ICTs such as femtosecond photoelectronic diffractometers, have been created for studying the dynamics of phase transitions in substances using diffrac-tion of electrons with energies ranging from 20 to 40 keV. (femtosecond technologies)

  5. Characterization of encapsulated quantum dots via electron channeling contrast imaging

    Energy Technology Data Exchange (ETDEWEB)

    Deitz, Julia I.; McComb, David W. [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Carnevale, Santino D. [Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); De Graef, Marc [Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States); Grassman, Tyler J., E-mail: grassman.5@osu.edu [Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43210 (United States); Department of Electrical and Computer Engineering, The Ohio State University, Columbus, Ohio 43210 (United States)

    2016-08-08

    A method for characterization of encapsulated epitaxial quantum dots (QD) in plan-view geometry using electron channeling contrast imaging (ECCI) is presented. The efficacy of the method, which requires minimal sample preparation, is demonstrated with proof-of-concept data from encapsulated (sub-surface) epitaxial InAs QDs within a GaAs matrix. Imaging of the QDs under multiple diffraction conditions is presented, establishing that ECCI can provide effectively identical visualization capabilities as conventional two-beam transmission electron microscopy. This method facilitates rapid, non-destructive characterization of sub-surface QDs giving immediate access to valuable nanostructural information.

  6. Quantum mechanical force field for water with explicit electronic polarization.

    Science.gov (United States)

    Han, Jaebeom; Mazack, Michael J M; Zhang, Peng; Truhlar, Donald G; Gao, Jiali

    2013-08-07

    A quantum mechanical force field (QMFF) for water is described. Unlike traditional approaches that use quantum mechanical results and experimental data to parameterize empirical potential energy functions, the present QMFF uses a quantum mechanical framework to represent intramolecular and intermolecular interactions in an entire condensed-phase system. In particular, the internal energy terms used in molecular mechanics are replaced by a quantum mechanical formalism that naturally includes electronic polarization due to intermolecular interactions and its effects on the force constants of the intramolecular force field. As a quantum mechanical force field, both intermolecular interactions and the Hamiltonian describing the individual molecular fragments can be parameterized to strive for accuracy and computational efficiency. In this work, we introduce a polarizable molecular orbital model Hamiltonian for water and for oxygen- and hydrogen-containing compounds, whereas the electrostatic potential responsible for intermolecular interactions in the liquid and in solution is modeled by a three-point charge representation that realistically reproduces the total molecular dipole moment and the local hybridization contributions. The present QMFF for water, which is called the XP3P (explicit polarization with three-point-charge potential) model, is suitable for modeling both gas-phase clusters and liquid water. The paper demonstrates the performance of the XP3P model for water and proton clusters and the properties of the pure liquid from about 900 × 10(6) self-consistent-field calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as across

  7. Study of quantum spin correlations of relativistic electron pairs - Testing nonlocality of relativistic quantum mechanics

    International Nuclear Information System (INIS)

    Bodek, K.; Rozpędzik, D.; Zejma, J.; Caban, P.; Rembieliński, J.; Włodarczyk, M.; Ciborowski, J.; Enders, J.; Köhler, A.; Kozela, A.

    2013-01-01

    The Polish-German project QUEST aims at studying relativistic quantum spin correlations of the Einstein-Rosen-Podolsky-Bohm type, through measurement of the correlation function and the corresponding probabilities for relativistic electron pairs. The results will be compared to theoretical predictions obtained by us within the framework of relativistic quantum mechanics, based on assumptions regarding the form of the relativistic spin operator. Agreement or divergence will be interpreted in the context of non-uniqueness of the relativistic spin operator in quantum mechanics as well as dependence of the correlation function on the choice of observables representing the spin. Pairs of correlated electrons will originate from the Mo/ller scattering of polarized 15 MeV electrons provided by the superconducting Darmstadt electron linear accelerator S-DALINAC, TU Darmstadt, incident on a Be target. Spin projections will be determined using the Mott polarimetry technique. Measurements (starting 2013) are planned for longitudinal and transverse beam polarizations and different orientations of the beam polarization vector w.r.t. the Mo/ller scattering plane. This is the first project to study relativistic spin correlations for particles with mass

  8. Quantum entanglement in electron optics generation, characterization, and applications

    CERN Document Server

    Chandra, Naresh

    2013-01-01

    This monograph forms an interdisciplinary study in atomic, molecular, and quantum information (QI) science. Here a reader will find that applications of the tools developed in QI provide new physical insights into electron optics as well as properties of atoms & molecules which, in turn, are useful in studying QI both at fundamental and applied levels. In particular, this book investigates entanglement properties of flying electronic qubits generated in some of the well known processes capable of taking place in an atom or a molecule following the absorption of a photon. Here, one can generate Coulombic or fine-structure entanglement of electronic qubits. The properties of these entanglements differ not only from each other, but also from those when spin of an inner-shell photoelectron is entangled with the polarization of the subsequent fluorescence. Spins of an outer-shell electron and of a residual photoion can have free or bound entanglement in a laboratory.

  9. The quantum dynamics of electronically nonadiabatic chemical reactions

    Science.gov (United States)

    Truhlar, Donald G.

    1993-01-01

    Considerable progress was achieved on the quantum mechanical treatment of electronically nonadiabatic collisions involving energy transfer and chemical reaction in the collision of an electronically excited atom with a molecule. In the first step, a new diabatic representation for the coupled potential energy surfaces was created. A two-state diabatic representation was developed which was designed to realistically reproduce the two lowest adiabatic states of the valence bond model and also to have the following three desirable features: (1) it is more economical to evaluate; (2) it is more portable; and (3) all spline fits are replaced by analytic functions. The new representation consists of a set of two coupled diabatic potential energy surfaces plus a coupling surface. It is suitable for dynamics calculations on both the electronic quenching and reaction processes in collisions of Na(3p2p) with H2. The new two-state representation was obtained by a three-step process from a modified eight-state diatomics-in-molecules (DIM) representation of Blais. The second step required the development of new dynamical methods. A formalism was developed for treating reactions with very general basis functions including electronically excited states. Our formalism is based on the generalized Newton, scattered wave, and outgoing wave variational principles that were used previously for reactive collisions on a single potential energy surface, and it incorporates three new features: (1) the basis functions include electronic degrees of freedom, as required to treat reactions involving electronic excitation and two or more coupled potential energy surfaces; (2) the primitive electronic basis is assumed to be diabatic, and it is not assumed that it diagonalizes the electronic Hamiltonian even asymptotically; and (3) contracted basis functions for vibrational-rotational-orbital degrees of freedom are included in a very general way, similar to previous prescriptions for locally

  10. Physics of lateral triple quantum-dot molecules with controlled electron numbers.

    Science.gov (United States)

    Hsieh, Chang-Yu; Shim, Yun-Pil; Korkusinski, Marek; Hawrylak, Pawel

    2012-11-01

    We review the recent progress in theory and experiments with lateral triple quantum dots with controlled electron numbers down to one electron in each dot. The theory covers electronic and spin properties as a function of topology, number of electrons, gate voltage and external magnetic field. The orbital Hund's rules and Nagaoka ferromagnetism, magnetic frustration and chirality, interplay of quantum interference and electron-electron interactions and geometrical phases are described and related to charging and transport spectroscopy. Fabrication techniques and recent experiments are covered, as well as potential applications of triple quantum-dot molecule in coherent control, spin manipulation and quantum computation.

  11. Universal quantum gates on electron-spin qubits with quantum dots inside single-side optical microcavities.

    Science.gov (United States)

    Wei, Hai-Rui; Deng, Fu-Guo

    2014-01-13

    We present some compact quantum circuits for a deterministic quantum computing on electron-spin qubits assisted by quantum dots inside single-side optical microcavities, including the CNOT, Toffoli, and Fredkin gates. They are constructed by exploiting the giant optical Faraday rotation induced by a single-electron spin in a quantum dot inside a single-side optical microcavity as a result of cavity quantum electrodynamics. Our universal quantum gates have some advantages. First, all the gates are accomplished with a success probability of 100% in principle. Second, our schemes require no additional electron-spin qubits and they are achieved by some input-output processes of a single photon. Third, our circuits for these gates are simple and economic. Moreover, our devices for these gates work in both the weak coupling and the strong coupling regimes, and they are feasible in experiment.

  12. Pseudorandom binary injection of levitons for electron quantum optics

    Science.gov (United States)

    Glattli, D. C.; Roulleau, P.

    2018-03-01

    The recent realization of single-electron sources lets us envision performing electron quantum optics experiments, where electrons can be viewed as flying qubits propagating in a ballistic conductor. To date, all electron sources operate in a periodic electron injection mode, leading to energy spectrum singularities in various physical observables which sometimes hide the bare nature of physical effects. To go beyond this, we propose a spread-spectrum approach where electron flying qubits are injected in a nonperiodic manner following a pseudorandom binary bit pattern. Extending the Floquet scattering theory approach from periodic to spread-spectrum drive, the shot noise of pseudorandom binary sequences of single-electron injection can be calculated for leviton and nonleviton sources. Our new approach allows us to disentangle the physics of the manipulated excitations from that of the injection protocol. In particular, the spread-spectrum approach is shown to provide better knowledge of electronic Hong-Ou-Mandel correlations and to clarify the nature of the pulse train coherence and the role of the dynamical orthogonality catastrophe for noninteger charge injection.

  13. Probing quantum coherence in single-atom electron spin resonance

    Science.gov (United States)

    Willke, Philip; Paul, William; Natterer, Fabian D.; Yang, Kai; Bae, Yujeong; Choi, Taeyoung; Fernández-Rossier, Joaquin; Heinrich, Andreas J.; Lutz, Christoper P.

    2018-01-01

    Spin resonance of individual spin centers allows applications ranging from quantum information technology to atomic-scale magnetometry. To protect the quantum properties of a spin, control over its local environment, including energy relaxation and decoherence processes, is crucial. However, in most existing architectures, the environment remains fixed by the crystal structure and electrical contacts. Recently, spin-polarized scanning tunneling microscopy (STM), in combination with electron spin resonance (ESR), allowed the study of single adatoms and inter-atomic coupling with an unprecedented combination of spatial and energy resolution. We elucidate and control the interplay of an Fe single spin with its atomic-scale environment by precisely tuning the phase coherence time T2 using the STM tip as a variable electrode. We find that the decoherence rate is the sum of two main contributions. The first scales linearly with tunnel current and shows that, on average, every tunneling electron causes one dephasing event. The second, effective even without current, arises from thermally activated spin-flip processes of tip spins. Understanding these interactions allows us to maximize T2 and improve the energy resolution. It also allows us to maximize the amplitude of the ESR signal, which supports measurements even at elevated temperatures as high as 4 K. Thus, ESR-STM allows control of quantum coherence in individual, electrically accessible spins. PMID:29464211

  14. European Power Electronic conference in Aalborg, Denmark - 1000 participants discussing the future energy technologies

    DEFF Research Database (Denmark)

    Blaabjerg, Frede; Munk-Nielsen, Stig

    2007-01-01

    The European Power Electronics and Adjustable Speed Drives conference with technical sponsorship of IEEE Industrial Electronic Society has been held in Aalborg, Denmark, during the first days of September 2007 with an overwhelming success and participation. It was hosted by Aalborg University's I...

  15. Resonance fluorescence and electron spin in semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yong

    2009-11-18

    The work presented in this dissertation contains the first observation of spin-resolved resonance fluorescence from a single quantum dot and its application of direct measurement of electron spin dynamics. The Mollow triplet and the Mollow quintuplet, which are the hallmarks of resonance fluorescence, are presented as the non-spin-resolved and spin-resolved resonance fluorescence spectrum, respectively. The negligible laser background contribution, the near pure radiative broadened spectrum and the anti-bunching photon statistics imply the sideband photons are background-free and near transform-limited single photons. This demonstration is a promising step towards the heralded single photon generation and electron spin readout. Instead of resolving spectrum, an alternative spin-readout scheme by counting resonance fluorescence photons under moderate laser power is demonstrated. The measurements of n-shot time-resolved resonance fluorescence readout are carried out to reveal electron spin dynamics of the measurement induced back action and the spin relaxation. Hyperfine interaction and heavy-light hole mixing are identified as the relevant mechanisms for the back action and phonon-assistant spin-orbit interaction dominates the spin relaxation. After a detailed discussion on charge-spin configurations in coupled quantum dots system, the single-shot readout on electron spin are proposed. (orig.)

  16. Resonance fluorescence and electron spin in semiconductor quantum dots

    International Nuclear Information System (INIS)

    Zhao, Yong

    2009-01-01

    The work presented in this dissertation contains the first observation of spin-resolved resonance fluorescence from a single quantum dot and its application of direct measurement of electron spin dynamics. The Mollow triplet and the Mollow quintuplet, which are the hallmarks of resonance fluorescence, are presented as the non-spin-resolved and spin-resolved resonance fluorescence spectrum, respectively. The negligible laser background contribution, the near pure radiative broadened spectrum and the anti-bunching photon statistics imply the sideband photons are background-free and near transform-limited single photons. This demonstration is a promising step towards the heralded single photon generation and electron spin readout. Instead of resolving spectrum, an alternative spin-readout scheme by counting resonance fluorescence photons under moderate laser power is demonstrated. The measurements of n-shot time-resolved resonance fluorescence readout are carried out to reveal electron spin dynamics of the measurement induced back action and the spin relaxation. Hyperfine interaction and heavy-light hole mixing are identified as the relevant mechanisms for the back action and phonon-assistant spin-orbit interaction dominates the spin relaxation. After a detailed discussion on charge-spin configurations in coupled quantum dots system, the single-shot readout on electron spin are proposed. (orig.)

  17. Quantum coherent optical phase modulation in an ultrafast transmission electron microscope.

    Science.gov (United States)

    Feist, Armin; Echternkamp, Katharina E; Schauss, Jakob; Yalunin, Sergey V; Schäfer, Sascha; Ropers, Claus

    2015-05-14

    Coherent manipulation of quantum systems with light is expected to be a cornerstone of future information and communication technology, including quantum computation and cryptography. The transfer of an optical phase onto a quantum wavefunction is a defining aspect of coherent interactions and forms the basis of quantum state preparation, synchronization and metrology. Light-phase-modulated electron states near atoms and molecules are essential for the techniques of attosecond science, including the generation of extreme-ultraviolet pulses and orbital tomography. In contrast, the quantum-coherent phase-modulation of energetic free-electron beams has not been demonstrated, although it promises direct access to ultrafast imaging and spectroscopy with tailored electron pulses on the attosecond scale. Here we demonstrate the coherent quantum state manipulation of free-electron populations in an electron microscope beam. We employ the interaction of ultrashort electron pulses with optical near-fields to induce Rabi oscillations in the populations of electron momentum states, observed as a function of the optical driving field. Excellent agreement with the scaling of an equal-Rabi multilevel quantum ladder is obtained, representing the observation of a light-driven 'quantum walk' coherently reshaping electron density in momentum space. We note that, after the interaction, the optically generated superposition of momentum states evolves into a train of attosecond electron pulses. Our results reveal the potential of quantum control for the precision structuring of electron densities, with possible applications ranging from ultrafast electron spectroscopy and microscopy to accelerator science and free-electron lasers.

  18. Two dimensional electron systems for solid state quantum computation

    Science.gov (United States)

    Mondal, Sumit

    Two dimensional electron systems based on GaAs/AlGaAs heterostructures are extremely useful in various scientific investigations of recent times including the search for quantum computational schemes. Although significant strides have been made over the past few years to realize solid state qubits on GaAs/AlGaAs 2DEGs, there are numerous factors limiting the progress. We attempt to identify factors that have material and design-specific origin and develop ways to overcome them. The thesis is divided in two broad segments. In the first segment we describe the realization of a new field-effect induced two dimensional electron system on GaAs/AlGaAs heterostructure where the novel device-design is expected to suppress the level of charge noise present in the device. Modulation-doped GaAs/AlGaAs heterostructures are utilized extensively in the study of quantum transport in nanostructures, but charge fluctuations associated with remote ionized dopants often produce deleterious effects. Electric field-induced carrier systems offer an attractive alternative if certain challenges can be overcome. We demonstrate a field-effect transistor in which the active channel is locally devoid of modulation-doping, but silicon dopant atoms are retained in the ohmic contact region to facilitate low-resistance contacts. A high quality two-dimensional electron gas is induced by a field-effect that is tunable over a density range of 6.5x10 10cm-2 to 2.6x1011cm-2 . Device design, fabrication, and low temperature (T=0.3K) characterization results are discussed. The demonstrated device-design overcomes several existing limitations in the fabrication of field-induced 2DEGs and might find utility in hosting nanostructures required for making spin qubits. The second broad segment describes our effort to correlate transport parameters measured at T=0.3K to the strength of the fractional quantum Hall state observed at nu=5/2 in the second Landau level of high-mobility GaAs/AlGaAs two dimensional

  19. Quantum-Sequencing: Fast electronic single DNA molecule sequencing

    Science.gov (United States)

    Casamada Ribot, Josep; Chatterjee, Anushree; Nagpal, Prashant

    2014-03-01

    A major goal of third-generation sequencing technologies is to develop a fast, reliable, enzyme-free, high-throughput and cost-effective, single-molecule sequencing method. Here, we present the first demonstration of unique ``electronic fingerprint'' of all nucleotides (A, G, T, C), with single-molecule DNA sequencing, using Quantum-tunneling Sequencing (Q-Seq) at room temperature. We show that the electronic state of the nucleobases shift depending on the pH, with most distinct states identified at acidic pH. We also demonstrate identification of single nucleotide modifications (methylation here). Using these unique electronic fingerprints (or tunneling data), we report a partial sequence of beta lactamase (bla) gene, which encodes resistance to beta-lactam antibiotics, with over 95% success rate. These results highlight the potential of Q-Seq as a robust technique for next-generation sequencing.

  20. Confined quantum systems: spectral properties of two-electron quantum dots

    International Nuclear Information System (INIS)

    Sako, T; Diercksen, G H F

    2003-01-01

    The spectrum, electron-density distribution and ground-state correlation energy of two electrons confined by an anisotropic harmonic oscillator potential have been studied for different confinement strengths ω by using the quantum chemical configuration interaction (CI) method employing a large Cartesian anisotropic Gaussian basis set and a full CI wavefunction. Energy level diagrams and electron-density distributions are displayed for selected electronic states and confinement parameters. The total energy and spacing between energy levels increase in all cases with increasing ω. The energy level structure cannot be matched by scaling with respect to ω. The correlation energy of the ground state is comparable in magnitude to that of the helium atom. It increases for increasing ω. The percentage of the correlation energy with respect to the total energy of the ground state is considerably larger than that of the helium atom

  1. Physics of lateral triple quantum-dot molecules with controlled electron numbers

    International Nuclear Information System (INIS)

    Hsieh, Chang-Yu; Shim, Yun-Pil; Korkusinski, Marek; Hawrylak, Pawel

    2012-01-01

    We review the recent progress in theory and experiments with lateral triple quantum dots with controlled electron numbers down to one electron in each dot. The theory covers electronic and spin properties as a function of topology, number of electrons, gate voltage and external magnetic field. The orbital Hund's rules and Nagaoka ferromagnetism, magnetic frustration and chirality, interplay of quantum interference and electron–electron interactions and geometrical phases are described and related to charging and transport spectroscopy. Fabrication techniques and recent experiments are covered, as well as potential applications of triple quantum-dot molecule in coherent control, spin manipulation and quantum computation. (review article)

  2. Fluorinated graphene films with graphene quantum dots for electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Antonova, I. V., E-mail: antonova@isp.nsc.ru [Rzhanov Institute of Semiconductor Physics, Russian Academy of Sciences, Siberian Branch, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Nebogatikova, N. A.; Prinz, V. Ya. [Rzhanov Institute of Semiconductor Physics, Russian Academy of Sciences, Siberian Branch, Novosibirsk 630090 (Russian Federation)

    2016-06-14

    This work analyzes carrier transport, the relaxation of non-equilibrium charge, and the electronic structure of fluorinated graphene (FG) films with graphene quantum dots (GQDs). The FG films with GQDs were fabricated by means of chemical functionalization in an aqueous solution of hydrofluoric acid. High fluctuations of potential relief inside the FG barriers have been detected in the range of up to 200 mV. A phenomenological expression that describes the dependence of the time of non-equilibrium charge emission from GQDs on quantum confinement levels and film thickness (potential barrier parameters between GQDs) is suggested. An increase in the degree of functionalization leads to a decrease in GQD size, the removal of the GQD effect on carrier transport, and the relaxation of non-equilibrium charge. The study of the electronic properties of FG films with GQDs has revealed a unipolar resistive switching effect in the films with a relatively high degree of fluorination and a high current modulation (up to ON/OFF ∼ 10{sup 4}–10{sup 5}) in transistor-like structures with a lower degree of fluorination. 2D films with GQDs are believed to have considerable potential for various electronic applications (nonvolatile memory, 2D connections with optical control and logic elements).

  3. Quantum-Dynamical Theory of Electron Exchange Correlation

    Directory of Open Access Journals (Sweden)

    Burke Ritchie

    2013-01-01

    aggregate, is elucidated. The relationship depends on the use of spin-dependent quantum trajectories (SDQT to evaluate Coulomb’s law between any two electrons as an instantaneous interaction in space and time rather than as a quantum-mean interaction in the form of screening and exchange potentials. Hence FDS depends in an ab initio sense on the inference of SDQT from Dirac’s equation, which provides for relativistic Lorentz invariance and a permanent magnetic moment (or spin in the electron’s equation of motion. Schroedinger’s time-dependent equation can be used to evaluate the SDQT in the nonrelativistic regime of electron velocity. Remarkably FDS is a relativistic property of an ensemble of electron, even though it is of order c0 in the nonrelativistic limit, in agreement with experimental observation. Finally it is shown that covalent versus separated-atoms limits can be characterized by the SDQT. As an example of the use of SDQT in a canonical structure problem, the energies of the 1Σg and 3Σu states of H2 are calculated and compared with the accurate variational energies of Kolos and Wolniewitz.

  4. Hybridization of electron states in a step quantum well in a magnetic field

    International Nuclear Information System (INIS)

    Barseghyan, M.G.; Kirakosyan, A.A.

    2005-01-01

    The quantum states and energy levels of an electrion in a rectangular step quantum well in a magnetic field parallel to the plane of two-dimentional electron gas are investigated. It is shown that the joint effect of the magnetic field and confining potential of the quantum well results in redical change of the electron spectrum. The dependence of the electron energy levels on the quantum well parameters, magnetic field induction and projection of the wave-vector along the magnetic field induction are calculated. Numerical calculations are carried out for a AlAs/GaAlAs/GaAs/AlAs step quantum well

  5. Interferometry of Klein tunnelling electrons in graphene quantum rings

    Science.gov (United States)

    de Sousa, D. J. P.; Chaves, Andrey; Pereira, J. M.; Farias, G. A.

    2017-01-01

    We theoretically study a current switch that exploits the phase acquired by a charge carrier as it tunnels through a potential barrier in graphene. The system acts as an interferometer based on an armchair graphene quantum ring, where the phase difference between interfering electronic wave functions for each path can be controlled by tuning either the height or the width of a potential barrier in the ring arms. By varying the parameters of the potential barriers, the interference can become completely destructive. We demonstrate how this interference effect can be used for developing a simple graphene-based logic gate with a high on/off ratio.

  6. Electronic States and Persistent Currents in Nanowire Quantum Ring

    Science.gov (United States)

    Kokurin, I. A.

    2018-04-01

    The new model of a quantum ring (QR) defined inside a nanowire (NW) is proposed. The one-particle Hamiltonian for electron in [111]-oriented NW QR is constructed taking into account both Rashba and Dresselhaus spin-orbit coupling (SOC). The energy levels as a function of magnetic field are found using the exact numerical diagonalization. The persistent currents (both charge and spin) are calculated. The specificity of SOC and arising anticrossings in energy spectrum lead to unusual features in persistent current behavior. The variation of magnetic field or carrier concentration by means of gate can lead to pure spin persistent current with the charge current being zero.

  7. Quantum theory of the optical and electronic properties of semiconductors

    CERN Document Server

    Haug, Hartmut

    1990-01-01

    The current technological revolution in the development of computing devices has created a demand for a textbook on the quantum theory of the electronic and optical properties of semiconductors and semiconductor devices. This book successfully fulfills this need. Based on lectures given by the authors, it is a comprehensive introduction for researchers or graduate-level students to the subject. Certain sections can also serve as a graduate-level textbook for use in solid state physics courses or for more specialized courses. The final chapters establish a direct link to current research in sem

  8. ICTEI-2015: International Conference on Telecommunications, Electronics and Informatics. Proceedings

    International Nuclear Information System (INIS)

    Kantser, V.; Andronic, S.

    2015-01-01

    This book includes articles which cover a vast range of subjects, such as: telecommunications networks and technologies; electronic, optoelectronic, photonic and information systems and devices; materials, components and equipment in electronics and communications; informatics and computer science; software development and testing etc.

  9. Tomonaga-Luttinger physics in electronic quantum circuits.

    Science.gov (United States)

    Jezouin, S; Albert, M; Parmentier, F D; Anthore, A; Gennser, U; Cavanna, A; Safi, I; Pierre, F

    2013-01-01

    In one-dimensional conductors, interactions result in correlated electronic systems. At low energy, a hallmark signature of the so-called Tomonaga-Luttinger liquids is the universal conductance curve predicted in presence of an impurity. A seemingly different topic is the quantum laws of electricity, when distinct quantum conductors are assembled in a circuit. In particular, the conductances are suppressed at low energy, a phenomenon called dynamical Coulomb blockade. Here we investigate the conductance of mesoscopic circuits constituted by a short single-channel quantum conductor in series with a resistance, and demonstrate a proposed link to Tomonaga-Luttinger physics. We reformulate and establish experimentally a recently derived phenomenological expression for the conductance using a wide range of circuits, including carbon nanotube data obtained elsewhere. By confronting both conductance data and phenomenological expression with the universal Tomonaga-Luttinger conductance curve, we demonstrate experimentally the predicted mapping between dynamical Coulomb blockade and the transport across a Tomonaga-Luttinger liquid with an impurity.

  10. Optical manipulation of electron spin in quantum dot systems

    Science.gov (United States)

    Villas-Boas, Jose; Ulloa, Sergio; Govorov, Alexander

    2006-03-01

    Self-assembled quantum dots (QDs) are of particular interest for fundamental physics because of their similarity with atoms. Coupling two of such dots and addressing them with polarized laser light pulses is perhaps even more interesting. In this paper we use a multi-exciton density matrix formalism to model the spin dynamics of a system with single or double layers of QDs. Our model includes the anisotropic electron-hole exchange in the dots, the presence of wetting layer states, and interdot tunneling [1]. Our results show that it is possible to switch the spin polarization of a single self-assembled quantum dot under elliptically polarized light by increasing the laser intensity. In the nonlinear mechanism described here, intense elliptically polarized light creates an effective exchange channel between the exciton spin states through biexciton states, as we demonstrate by numerical and analytical methods. We further show that the effect persists in realistic ensembles of dots, and we propose alternative ways to detect it. We also extend our study to a double layer of quantum dots, where we find a competition between Rabi frequency and tunneling oscillations. [1] J. M. Villas-Boas, S. E. Ulloa, and A. O. Govorov, Phys. Rev. Lett. 94, 057404 (2005); Phys. Rev. B 69, 125342 (2004).

  11. Photon-Electron Interactions in Dirac Quantum Materials

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Xiaodong [Univ. of Washington, Seattle, WA (United States). Dept. of Material Science and Engineering

    2017-11-10

    The objective of this proposal was to explore the fundamental light-matter interactions in a new class of Dirac quantum materials, atomically thin transition metal dichalcogenides (TMDs). Monolayer TMDs are newly discovered two-dimensional semiconductors with direct bandgap. Due to their hexagonal lattice structure, the band edge localizes at corner of Brillouin zone, i.e. “Dirac valleys”. This gives the corresponding electron states a “valley index” (or pseudospin) in addition to the real spin. Remarkably, the valley pseudospins have circularly polarized optical selection rules, providing the first solid state system for dynamic control of the valley degree of freedom. During this award, we have developed a suite of advanced nano-optical spectroscopy tools in the investigation and manipulation of charge, spin, and valley degrees of freedom in monolayer semiconductors. Emerging physical phenomena, such as quantum coherence between valley pseudospins, have been demonstrated for the first time in solids. In addition to monolayers, we have developed a framework in engineering, formulating, and understanding valley pseudospin physics in 2D heterostructures formed by different monolayer semiconductors. We demonstrated long-lived valley-polarized interlayer excitons with valley-dependent many-body interaction effects. These works push the research frontier in understanding the light-matter interactions in atomically-thin quantum materials for protentional transformative energy technologies.

  12. Indium antimonide quantum well structures for electronic device applications

    Science.gov (United States)

    Edirisooriya, Madhavie

    The electron effective mass is smaller in InSb than in any other III-V semiconductor. Since the electron mobility depends inversely on the effective mass, InSb-based devices are attractive for field effect transistors, magnetic field sensors, ballistic transport devices, and other applications where the performance depends on a high mobility or a long mean free path. In addition, electrons in InSb have a large g-factor and strong spin orbit coupling, which makes them well suited for certain spin transport devices. The first n-channel InSb high electron mobility transistor (HEMT) was produced in 2005 with a power-delay product superior to HEMTs with a channel made from any other III-V semiconductor. The high electron mobility in the InSb quantum-well channel increases the switching speed and lowers the required supply voltage. This dissertation focuses on several materials challenges that can further increase the appeal of InSb quantum wells for transistors and other electronic device applications. First, the electron mobility in InSb quantum wells, which is the highest for any semiconductor quantum well, can be further increased by reducing scattering by crystal defects. InSb-based heteroepitaxy is usually performed on semi-insulating GaAs (001) substrates due to the lack of a lattice matched semi-insulating substrate. The 14.6% mismatch between the lattice parameters of GaAs and InSb results in the formation of structural defects such as threading dislocations and microtwins which degrade the electrical and optical properties of InSb-based devices. Chapter 1 reviews the methods and procedures for growing InSb-based heterostructures by molecular beam epitaxy. Chapters 2 and 3 introduce techniques for minimizing the crystalline defects in InSb-based structures grown on GaAs substrates. Chapter 2 discusses a method of reducing threading dislocations by incorporating AlyIn1-ySb interlayers in an AlxIn1-xSb buffer layer and the reduction of microtwin defects by growth

  13. Proceedings of 2011 International Conference on Electronic Engineering, Communication and Management

    CERN Document Server

    Lin, Sally

    2012-01-01

      This volume presents the main results of 2011 International Conference on Electronic  Engineering, Communication and Management (EECM2011) held December 24-25, 2011, Beijing China. The EECM2011 is an integrated conference providing a valuable opportunity for researchers, scholars and scientists to exchange their ideas face to face together. The main focus of the EECM 2011 and the present 2 volumes “Advances in Electronic Engineering, Communication and Management” is on Power Engineering, Electrical engineering applications, Electrical machines, as well as Communication and Information Systems Engineering.

  14. Proceedings of 2011 International Conference on Electronic Engineering, Communication and Management

    CERN Document Server

    Lin, Sally

    2012-01-01

    This volume presents the main results of 2011 International Conference on Electronic  Engineering, Communication and Management (EECM2011) held December 24-25, 2011, Beijing China. The EECM2011 is an integrated conference providing a valuable opportunity for researchers, scholars and scientists to exchange their ideas face to face together. The main focus of the EECM 2011 and the present 2 volumes “Advances in Electronic Engineering, Communication and Management” is on Power Engineering, Electrical engineering applications, Electrical machines, as well as Communication and Information Systems Engineering.

  15. Demonstration of quantum entanglement between a single electron spin confined to an InAs quantum dot and a photon.

    Science.gov (United States)

    Schaibley, J R; Burgers, A P; McCracken, G A; Duan, L-M; Berman, P R; Steel, D G; Bracker, A S; Gammon, D; Sham, L J

    2013-04-19

    The electron spin state of a singly charged semiconductor quantum dot has been shown to form a suitable single qubit for quantum computing architectures with fast gate times. A key challenge in realizing a useful quantum dot quantum computing architecture lies in demonstrating the ability to scale the system to many qubits. In this Letter, we report an all optical experimental demonstration of quantum entanglement between a single electron spin confined to a single charged semiconductor quantum dot and the polarization state of a photon spontaneously emitted from the quantum dot's excited state. We obtain a lower bound on the fidelity of entanglement of 0.59±0.04, which is 84% of the maximum achievable given the timing resolution of available single photon detectors. In future applications, such as measurement-based spin-spin entanglement which does not require sub-nanosecond timing resolution, we estimate that this system would enable near ideal performance. The inferred (usable) entanglement generation rate is 3×10(3) s(-1). This spin-photon entanglement is the first step to a scalable quantum dot quantum computing architecture relying on photon (flying) qubits to mediate entanglement between distant nodes of a quantum dot network.

  16. 2012 Aspen Winter Conference New Paradigms for Low-Dimensional Electronic Materials, February 5-10, 2012

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Joel; Rabe, Karin; Nayak, Chetan; Troyer, Matthias

    2012-05-01

    Aspen Center for Physics Project Summary DOE Budget Period: 10/1/2011 to 9/30/2012 Contract # DE-SC0007479 New Paradigms for Low-Dimensional Electronic Materials The 2012 Aspen Winter Conference on Condensed Matter Physics was held at the Aspen Center for Physics from February 5 to 10, 2012. Seventy-four participants from seven countries, and several universities and national labs attended the workshop titled, New Paradigms for Low-Dimensional Electronic Materials. There were 34 formal talks, and a number of informal discussions held during the week. Talks covered a variety of topics related to DOE BES priorities, including, for example, advanced photon techniques (Hasan, Abbamonte, Orenstein, Shen, Ghosh) and predictive theoretical modeling of materials properties (Rappe, Pickett, Balents, Zhang, Vanderbilt); the full conference schedule is provided with this report. The week's events included a public lecture (Quantum Matters given by Chetan Nayak from Microsoft Research) and attended by 234 members of the public, and a physics caf© geared for high schoolers that is a discussion with physicists conducted by Kathryn Moler (Stanford University) and Andrew M. Rappe (University of Pennsylvania) and attended by 67 locals and visitors. While there were no published proceedings, some of the talks are posted online and can be Googled. The workshop was organized by Joel Moore (University of California Berkeley), Chetan Nayak (Microsoft Research), Karin Rabe (Rutgers University), and Matthias Troyer (ETH Zurich). Two organizers who did not attend the conference were Gabriel Aeppli (University College London & London Centre for Nanotechnology) and Andrea Cavalleri (Oxford University & Max Planck Hamburg).

  17. Non-quantum electronic responses of zinc oxide nanomaterials

    International Nuclear Information System (INIS)

    Kim, Hansoo; Kim, Younghyun

    2013-01-01

    The influence of the high surface-to-volume ratio of ZnO nanomaterials, whose sizes are large enough to exclude the quantum effect, on electronic properties was investigated by spatially resolved valence electron energy loss spectroscopy. ZnO nanowires, nanoplates, and nanotubes with different sizes were fabricated and characterized. Both the reduced volume and the increased surface area of the large ZnO nanomaterials were found to be able to modify electronic properties significantly. Hence, a nanoplate and a nanotube with very small volumes show unique energy loss functions and dielectric functions different from those of bulk ZnO at all the probe points. On the other hand, a nanowire with a relatively large diameter (70 nm) has electronic properties similar to those of bulk ZnO at the center. However, they are dissimilar at the edge of the nanowire due to the component of surface parallel to the electron path and the reduced interaction volume. Moreover, some interband transitions shift positions and bulk plasmons change oscillator strength depending upon the size of the volume and the geometry of the surface. These empirical results demonstrate that semiconducting nanomaterials larger than the exciton Bohr radius can still behave differently from bulk materials due to the high ratio between surface area and volume. (paper)

  18. Response of a relativistic quantum magnetized electron gas

    International Nuclear Information System (INIS)

    Melrose, Donald B; Weise, Jeanette I

    2009-01-01

    The response 4-tensor is derived for a spin-independent, relativistic magnetized quantum electron gas. The sum over spins is carried out both directly and using a procedure due to Ritus. The 4-tensor components are written in terms of a sum over the two solutions of the resonance condition for the particle 4-momentum. It is shown that the dispersive properties may be described in terms of a single plasma dispersion function, for arbitrary occupation numbers for electrons and positrons in each Landau level. The plasma dispersion function is evaluated explicitly in the completely degenerate and nondegenerate thermal limits. The perpendicular wave number appears in the arguments of J-functions, which are proportional to generalized Laguerre polynomials, but not in the plasma dispersion function. The result generalizes a known form for the response tensor for parallel propagation (in the completely degenerate case), when the J-functions are either zero or unity, to arbitrary angles of propagation.

  19. Quantum Kinetic Theory and Applications Electrons, Photons, Phonons

    CERN Document Server

    Vasko, Fedir T

    2006-01-01

    This lecture-style monograph is addressed to several categories of readers. First, it will be useful for graduate students studying theory. Second, the topics covered should be interesting for postgraduate students of various specializations. Third, the researchers who want to understand the background of modern theoretical issues in more detail can find a number of useful results here. The phenomena covered involve kinetics of electron, phonon, and photon systems in solids. The dynamical properties and interactions of electrons, phonons, and photons are briefly described in Chapter 1. Further, in Chapters 2-8, the authors present the main theoretical methods: linear response theory, various kinetic equations for the quasiparticles under consideration, and diagram technique. The presentation of the key approaches is always accompanied by solutions of concrete problems to illustrate ways to apply the theory. The remaining chapters are devoted to various manifestations of quantum transport in solids. The choice...

  20. SPAD electronics for high-speed quantum communications

    Science.gov (United States)

    Bienfang, Joshua C.; Restelli, Alessandro; Migdall, Alan

    2011-01-01

    We discuss high-speed electronics that support the use of single-photon avalanche diodes (SPADs) in gigahertz singlephoton communications systems. For InGaAs/InP SPADs, recent work has demonstrated reduced afterpulsing and count rates approaching 500 MHz can be achieved with gigahertz periodic-gating techniques designed to minimize the total avalanche charge to less than 100 fC. We investigate afterpulsing in this regime and establish a connection to observations using more conventional techniques. For Si SPADs, we report the benefits of improved timing electronics that enhance the temporal resolution of Si SPADs used in a free-space quantum key distribution (QKD) system operating in the GHz regime. We establish that the effects of count-rate fluctuations induced by daytime turbulent scintillation are significantly reduced, benefitting the performance of the QKD system.

  1. Numerical simulations of time-resolved quantum electronics

    International Nuclear Information System (INIS)

    Gaury, Benoit; Weston, Joseph; Santin, Matthieu; Houzet, Manuel; Groth, Christoph; Waintal, Xavier

    2014-01-01

    Numerical simulation has become a major tool in quantum electronics both for fundamental and applied purposes. While for a long time those simulations focused on stationary properties (e.g. DC currents), the recent experimental trend toward GHz frequencies and beyond has triggered a new interest for handling time-dependent perturbations. As the experimental frequencies get higher, it becomes possible to conceive experiments which are both time-resolved and fast enough to probe the internal quantum dynamics of the system. This paper discusses the technical aspects–mathematical and numerical–associated with the numerical simulations of such a setup in the time domain (i.e. beyond the single-frequency AC limit). After a short review of the state of the art, we develop a theoretical framework for the calculation of time-resolved observables in a general multiterminal system subject to an arbitrary time-dependent perturbation (oscillating electrostatic gates, voltage pulses, time-varying magnetic fields, etc.) The approach is mathematically equivalent to (i) the time-dependent scattering formalism, (ii) the time-resolved non-equilibrium Green’s function (NEGF) formalism and (iii) the partition-free approach. The central object of our theory is a wave function that obeys a simple Schrödinger equation with an additional source term that accounts for the electrons injected from the electrodes. The time-resolved observables (current, density, etc.) and the (inelastic) scattering matrix are simply expressed in terms of this wave function. We use our approach to develop a numerical technique for simulating time-resolved quantum transport. We find that the use of this wave function is advantageous for numerical simulations resulting in a speed up of many orders of magnitude with respect to the direct integration of NEGF equations. Our technique allows one to simulate realistic situations beyond simple models, a subject that was until now beyond the simulation

  2. 2nd Biennial Conference on Refrigeration for Cryogenic Sensors and Electronic Systems

    CERN Document Server

    1983-01-01

    This proceedings documents the output of the Second Biennial Conference on Refrigeration for Cryogenic Sensors and Electronic Systems held at the National Aeronautics and Space Administration's Goddard Space Flight Center, Greenbelt, Maryland, on December 7-8, 1982. Building on the first open meeting hosted by the National Bureau of Standards in 1980, the focus of this second meeting was again on low-temperature, closed-cycle cooler technology. However, higher temperature coolers (77 K), with technology applicable to the low temperature coolers, were considered to be within the scope of this meeting. This second conference consisted of 30 papers presented by representatives of industry, government, and academia. The conference proceedings reproduced here was published by the NASA Goddard Space Flight Center in Greenbelt Maryland as NASA Conference Publication 2287.

  3. Poly-silicon quantum-dot single-electron transistors

    International Nuclear Information System (INIS)

    Kang, Kwon-Chil; Lee, Joung-Eob; Lee, Jung-Han; Lee, Jong-Ho; Shin, Hyung-Cheol; Park, Byung-Gook

    2012-01-01

    For operation of a single-electron transistors (SETs) at room temperature, we proposed a fabrication method for a SET with a self-aligned quantum dot by using polycrystalline silicon (poly-Si). The self-aligned quantum dot is formed by the selective etching of a silicon nanowire on a planarized surface and the subsequent deposition and etch-back of poly-silicon or chemical mechanical polishing (CMP). The two tunneling barriers of the SET are fabricated by thermal oxidation. Also, to decrease the leakage current and control the gate capacitance, we deposit a hard oxide mask layer. The control gate is formed by using an electron beam and photolithography on chemical vapor deposition (CVD). Owing to the small capacitance of the narrow control gate due to the tetraethyl orthosilicate (TEOS) hard mask, we observe clear Coulomb oscillation peaks and differential trans-conductance curves at room temperature. The clear oscillation period of the fabricated SET is 2.0 V.

  4. PREFACE: IARD 2010: The 7th Biennial Conference on Classical and Quantum Relativistic Dynamics of Particles and Fields

    Science.gov (United States)

    Horwitz, Lawrence; Hu, Bei-Lok; Lee, Da-Shin; Gill, Tepper; Land, Martin

    2011-12-01

    Although the subject of relativistic dynamics has been explored from both classical and quantum mechanical points of view since the work of Einstein and Dirac, its most striking development has been in the framework of quantum field theory. The very accurate calculations of spectral and scattering properties, for example, of the anamolous magnetic moment of the electron and the Lamb shift in quantum electrodynamics, and many qualitative features of the strong and electroweak interactions, demonstrate the very great power of description achieved in this framework. Yet, many fundamental questions remain to be clarified, such as the structure of classical realtivistic dynamical theories on the level of Hamilton and Lagrange in Minkowski space as well as on the curved manifolds of general relativity. There moreover remains the important question of the covariant classical description of systems at high energy for which particle production effects are not large, such as discussed in Synge's book, The Relativistic Gas, and in Balescu's book on relativistic statistical mechanics. In recent years, the study of high energy plasmas and heavy ion collisions has emphasized the importance of developing the techniques of relativistic mechanics. The results of Linder et al (Phys. Rev. Lett. 95 0040401 (2005)) as well as the more recent work of Palacios et al (Phys. Rev. Lett. 103 253001 (2009)) and others, have shown that there must be a quantum theory with coherence in time. Such a theory, manifestly covariant under the transformations of special relativity with an invariant evolution parameter, such as that of Stueckelberg (Helv. Phys. Acta 14 322, 588 (1941); 15 23 (1942); see also R P Feynman Phys. Rev. 80 4401 and J S Schwinger Phys. Rev. 82 664 (1951)) could provide a suitable basis for the study of such questions, as well as many others for which the application of the standard methods of quantum field theory are difficult to manage, involving, in particular, local

  5. Spin boson models for quantum decoherence of electronic excitations of biomolecules and quantum dots in a solvent

    International Nuclear Information System (INIS)

    Gilmore, Joel; McKenzie, Ross H

    2005-01-01

    We give a theoretical treatment of the interaction of electronic excitations (excitons) in biomolecules and quantum dots with the surrounding polar solvent. Significant quantum decoherence occurs due to the interaction of the electric dipole moment of the solute with the fluctuating electric dipole moments of the individual molecules in the solvent. We introduce spin boson models which could be used to describe the effects of decoherence on the quantum dynamics of biomolecules which undergo light-induced conformational change and on biomolecules or quantum dots which are coupled by Foerster resonant energy transfer

  6. XI Scientific Conference Selected Issues of Electrical Engineering and Electronics (WZEE)

    CERN Document Server

    Mazur, Damian; Analysis and Simulation of Electrical and Computer Systems

    2015-01-01

    This book presents the selected results of the XI Scientific Conference Selected Issues of Electrical Engineering and Electronics (WZEE) which was held in Rzeszów and Czarna, Poland on September 27-30, 2013. The main aim of the Conference was to provide academia and industry to discuss and present the latest technological advantages and research results and to integrate the new interdisciplinary scientific circle in the field of electrical engineering, electronics and mechatronics. The Conference was organized by the Rzeszów Division of Polish Association of Theoretical and Applied Electrical Engineering (PTETiS) in cooperation with Rzeszów University of Technology, the Faculty of Electrical and Computer Engineering and Rzeszów University, the Faculty of Mathematics and Natural Sciences.  

  7. Alignment creation by elastic electron scattering. A quantum treatment

    International Nuclear Information System (INIS)

    Csanak, G.; Kilcrease, D.P.; Fursa, D.V.; Bray, I.

    2004-01-01

    Alignment creation by elastic heavy particle scattering has been studied by many authors. A formula for the alignment creation cross section by elastic scattering is obtained by quantum-mechanical methods. The formula obtained differs from the analogous formula relevant for inelastic electron scattering. In the case of a J=1 to J=1 transition according to the inelastic formula, the alignment created is proportional to the quantity σ (1) - σ (0) where σ (M) is the excitation cross section of the M magnetic sublevel and thus σ (1) = (σ 1-1 + σ 10 + σ 11 )/3 and σ (0) = (σ 0-1 +σ 00 + σ 01 )/3 where σ MM' refers to the cross section of the electron impact induced M' to M transition. In the elastic scattering alignment creation formula obtained in the case of a J=1 to J=1 elastic scattering, the alignment created is proportional to the quantity q(1) - q(0) where q(1) σ (1) - σ 11 /3 and q(0) = σ 00 /3. Thus in obtaining q(M), the elastic scattering cross section by the M magnetic sublevel, σ MM' , is subtracted. This derivation considered only direct scattering, i.e. the incident electron was considered distinguishable from the target electrons. (Y.Kazumata)

  8. Quantum dynamics and electronic spectroscopy within the framework of wavelets

    International Nuclear Information System (INIS)

    Toutounji, Mohamad

    2013-01-01

    This paper serves as a first-time report on formulating important aspects of electronic spectroscopy and quantum dynamics in condensed harmonic systems using the framework of wavelets, and a stepping stone to our future work on developing anharmonic wavelets. The Morlet wavelet is taken to be the mother wavelet for the initial state of the system of interest. This work reports daughter wavelets that may be used to study spectroscopy and dynamics of harmonic systems. These wavelets are shown to arise naturally upon optical electronic transition of the system of interest. Natural birth of basis (daughter) wavelets emerging on exciting an electronic two-level system coupled, both linearly and quadratically, to harmonic phonons is discussed. It is shown that this takes place through using the unitary dilation and translation operators, which happen to be part of the time evolution operator of the final electronic state. The corresponding optical autocorrelation function and linear absorption spectra are calculated to test the applicability and correctness of the herein results. The link between basis wavelets and the Liouville space generating function is established. An anharmonic mother wavelet is also proposed in the case of anharmonic electron–phonon coupling. A brief description of deriving anharmonic wavelets and the corresponding anharmonic Liouville space generating function is explored. In conclusion, a mother wavelet (be it harmonic or anharmonic) which accounts for Duschinsky mixing is suggested. (paper)

  9. Green development within product families, Electronics goes green 2000+ conference

    DEFF Research Database (Denmark)

    Lenau, Torben Anker; Willum, Ole; Frees, Niels

    2001-01-01

    , based on environ-mental and economical importance as well as the existence of several producers. Using this method, five families have been selected, namely mobile phones, vacuum cleaners, industrial valves with electronic controls, lighting and ventilation. Collaboration with 5 industrial companies has...

  10. Computer-automated tuning of semiconductor double quantum dots into the single-electron regime

    Energy Technology Data Exchange (ETDEWEB)

    Baart, T. A.; Vandersypen, L. M. K. [QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Eendebak, P. T. [QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Netherlands Organisation for Applied Scientific Research (TNO), P.O. Box 155, 2600 AD Delft (Netherlands); Reichl, C.; Wegscheider, W. [Solid State Physics Laboratory, ETH Zürich, 8093 Zürich (Switzerland)

    2016-05-23

    We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.

  11. High-fidelity quantum gates on quantum-dot-confined electron spins in low-Q optical microcavities

    Science.gov (United States)

    Li, Tao; Gao, Jian-Cun; Deng, Fu-Guo; Long, Gui-Lu

    2018-04-01

    We propose some high-fidelity quantum circuits for quantum computing on electron spins of quantum dots (QD) embedded in low-Q optical microcavities, including the two-qubit controlled-NOT gate and the multiple-target-qubit controlled-NOT gate. The fidelities of both quantum gates can, in principle, be robust to imperfections involved in a practical input-output process of a single photon by converting the infidelity into a heralded error. Furthermore, the influence of two different decay channels is detailed. By decreasing the quality factor of the present microcavity, we can largely increase the efficiencies of these quantum gates while their high fidelities remain unaffected. This proposal also has another advantage regarding its experimental feasibility, in that both quantum gates can work faithfully even when the QD-cavity systems are non-identical, which is of particular importance in current semiconductor QD technology.

  12. Renormalization of effective mass in self-assembled quantum dots due to electron-electron interactions

    International Nuclear Information System (INIS)

    Babinski, A; Korkusinski, M; Hawrylak, P; Wasilewski, Z R; Potemski, M

    2013-01-01

    Magnetic-field dispersion of the multiexcitons related to the p shell of a single quantum dot (QD) is analysed in this work. The reduced cyclotron effective mass of carriers is determined from the energy splitting between the p + - and p − - related multiexcitonic emission lines. The reduced mass in the occupied QD was found to be larger than the mass related to the QD's single particle structure. The apparent increase of the reduced mass with increasing excitonic occupation of the dot is related to the mass renoralization due to electron-electron interactions within a multiexcitonic droplet

  13. Single electron probes of fractional quantum hall states

    Science.gov (United States)

    Venkatachalam, Vivek

    When electrons are confined to a two dimensional layer with a perpendicular applied magnetic field, such that the ratio of electrons to flux quanta (nu) is a small integer or simple rational value, these electrons condense into remarkable new phases of matter that are strikingly different from the metallic electron gas that exists in the absence of a magnetic field. These phases, called integer or fractional quantum Hall (IQH or FQH) states, appear to be conventional insulators in their bulk, but behave as a dissipationless metal along their edge. Furthermore, electrical measurements of such a system are largely insensitive to the detailed geometry of how the system is contacted or even how large the system is... only the order in which contacts are made appears to matter. This insensitivity to local geometry has since appeared in a number of other two and three dimensional systems, earning them the classification of "topological insulators" and prompting an enormous experimental and theoretical effort to understand their properties and perhaps manipulate these properties to create robust quantum information processors. The focus of this thesis will be two experiments designed to elucidate remarkable properties of the metallic edge and insulating bulk of certain FQH systems. To study such systems, we can use mesoscopic devices known as single electron transistors (SETs). These devices operate by watching single electrons hop into and out of a confining box and into a nearby wire (for measurement). If it is initially unfavorable for an electron to leave the box, it can be made favorable by bringing another charge nearby, modifying the energy of the confined electron and pushing it out of the box and into the nearby wire. In this way, the SET can measure nearby charges. Alternatively, we can heat up the nearby wire to make it easier for electrons to enter and leave the box. In this way, the SET is a sensitive thermometer. First, by operating the SET as an

  14. Impact of Relativistic Electron Beam on Hole Acoustic Instability in Quantum Semiconductor Plasmas

    Science.gov (United States)

    Siddique, M.; Jamil, M.; Rasheed, A.; Areeb, F.; Javed, Asif; Sumera, P.

    2018-01-01

    We studied the influence of the classical relativistic beam of electrons on the hole acoustic wave (HAW) instability exciting in the semiconductor quantum plasmas. We conducted this study by using the quantum-hydrodynamic model of dense plasmas, incorporating the quantum effects of semiconductor plasma species which include degeneracy pressure, exchange-correlation potential and Bohm potential. Analysis of the quantum characteristics of semiconductor plasma species along with relativistic effect of beam electrons on the dispersion relation of the HAW is given in detail qualitatively and quantitatively by plotting them numerically. It is worth mentioning that the relativistic electron beam (REB) stabilises the HAWs exciting in semiconductor (GaAs) degenerate plasma.

  15. Electron states and electron Raman scattering in semiconductor double cylindrical quantum well wire

    International Nuclear Information System (INIS)

    Munguía-Rodríguez, M; Riera, R; Betancourt-Riera, Ri; Betancourt-Riera, Re; Nieto Jalil, J M

    2016-01-01

    The differential cross section for an electron Raman scattering process in a semiconductor GaAs/AlGaAs double quantum well wire is calculated, and expressions for the electronic states are presented. The system is modeled by considering T = 0 K and also with a single parabolic conduction band, which is split into a subband system due to the confinement. The gain and differential cross-section for an electron Raman scattering process are obtained. In addition, the emission spectra for several scattering configurations are discussed, and interpretations of the singularities found in the spectra are given. The electron Raman scattering studied here can be used to provide direct information about the efficiency of the lasers. (paper)

  16. PREFACE: First Mediterranean Conference on Classical and Quantum Gravity (MCCQG 2009)

    Science.gov (United States)

    Basilakos, Spyros; Cadoni, Mariano; Cavaglia, Marco; Christodoulakis, Theodosios; Vagenas, Elias C.

    2010-04-01

    The year 2009 signals the birth of a new conference series under the name of Mediterranean Conference on Classical and Quantum Gravity (MCCQG). The main purpose of this new series is to bring together physicists working on General Relativity, Field Theory, and related areas to discuss the present status and latest developments in the classical and quantum treatment of gravitational systems, as well as to support and strengthen the scientific communication between the physicists of the wide Mediterranean region, working in the field of Classical and Quantum Gravity. For the latter reason, we plan to organize all future conferences of this series in the Mediterranean region. The First Mediterranean Conference on Classical and Quantum Gravity took place at the Orthodox Academy of Crete (OAC) in Kolymbari (Crete, Greece) from 14-18 September 2009. Physicists from countries all around the world travelled to Kolymbari to discuss hot topics in the classical and quantum treatment of gravitational systems such as string theory and branes, classical gravity and alternative theories, gravitational waves and experiments, quantum gravity, cosmology, and black holes. The program consisted of invited plenary talks and contributed talks in parallel sessions. We were able to give full financial support for accommodation to all invited speakers and partial support to younger people at the beginning of their scientific careers. In particular, help was provided to students and scientists from non-EU countries. The financial support was provided by the Academy of Athens and the Tomalla Foundation. During the MCCQG two social events were organized. The first one was a half-day guided bus excursion to Knossos and the surrounding area which took place on 16 September. The second one was the conference dinner on 18 September at the OAC. Traditional Cretan dishes were served and dancers performing in traditional costumes entertained the participants. These events contributed to create a

  17. Correlative Light- and Electron Microscopy Using Quantum Dot Nanoparticles.

    Science.gov (United States)

    Killingsworth, Murray C; Bobryshev, Yuri V

    2016-08-07

    A method is described whereby quantum dot (QD) nanoparticles can be used for correlative immunocytochemical studies of human pathology tissue using widefield fluorescence light microscopy and transmission electron microscopy (TEM). To demonstrate the protocol we have immunolabeled ultrathin epoxy sections of human somatostatinoma tumor using a primary antibody to somatostatin, followed by a biotinylated secondary antibody and visualization with streptavidin conjugated 585 nm cadmium-selenium (CdSe) quantum dots (QDs). The sections are mounted on a TEM specimen grid then placed on a glass slide for observation by widefield fluorescence light microscopy. Light microscopy reveals 585 nm QD labeling as bright orange fluorescence forming a granular pattern within the tumor cell cytoplasm. At low to mid-range magnification by light microscopy the labeling pattern can be easily recognized and the level of non-specific or background labeling assessed. This is a critical step for subsequent interpretation of the immunolabeling pattern by TEM and evaluation of the morphological context. The same section is then blotted dry and viewed by TEM. QD probes are seen to be attached to amorphous material contained in individual secretory granules. Images are acquired from the same region of interest (ROI) seen by light microscopy for correlative analysis. Corresponding images from each modality may then be blended to overlay fluorescence data on TEM ultrastructure of the corresponding region.

  18. Quantum mechanical simulations of polymers for molecular electronics and photonics

    International Nuclear Information System (INIS)

    Dupuis, M.; Villar, H.O.; Clementi, E.

    1987-01-01

    Ab initio quantum mechanical studies can play an important role in obtaining a detailed understanding of the electronic structure of existing materials, and in predicting the properties of new ones. In this article the authors give a general outline of their research activity in two areas dealing with new materials, specifically, conducting polymers and polymers with non-linear optical properties. The authors present the strategy followed for the study of these molecular systems, and an overview of their findings concerning the structure of the prototypical conducting polymer, i.e. pure and doped polyacetylene (PA). They focused attention on vibrational spectra and infrared and Raman intensities. The results of self-consistent-field (SCF) calculations on charged soliton-like molecules are consistent with experimental observation. In particular, they show that the theoretically established accidental mutual exclusion of infrared and Raman bands invalidates the requirement formulated on the basis of the interpretation of experimental data, that defects in PA must have local C/sub 2h/ symmetry. These conclusions are derived from extensive calculations for which supercomputer performance was imperative and carried out on the parallel supercomputer assembled at IBM-Kingston as a loosely coupled array of processors (LCAP). The authors briefly describe this computer system which has proven to be ideally suited to the methods of ab initio quantum chemistry

  19. Inelastic electron and light scattering from the elementary electronic excitations in quantum wells: Zero magnetic field

    Directory of Open Access Journals (Sweden)

    Manvir S. Kushwaha

    2012-09-01

    Full Text Available The most fundamental approach to an understanding of electronic, optical, and transport phenomena which the condensed matter physics (of conventional as well as nonconventional systems offers is generally founded on two experiments: the inelastic electron scattering and the inelastic light scattering. This work embarks on providing a systematic framework for the theory of inelastic electron scattering and of inelastic light scattering from the electronic excitations in GaAs/Ga1−xAlxAs quantum wells. To this end, we start with the Kubo's correlation function to derive the generalized nonlocal, dynamic dielectric function, and the inverse dielectric function within the framework of Bohm-Pines’ random-phase approximation. This is followed by a thorough development of the theory of inelastic electron scattering and of inelastic light scattering. The methodological part is then subjected to the analytical diagnoses which allow us to sense the subtlety of the analytical results and the importance of their applications. The general analytical results, which know no bounds regarding, e.g., the subband occupancy, are then specified so as to make them applicable to practicality. After trying and testing the eigenfunctions, we compute the density of states, the Fermi energy, the full excitation spectrum made up of intrasubband and intersubband – single-particle and collective (plasmon – excitations, the loss functions for all the principal geometries envisioned for the inelastic electron scattering, and the Raman intensity, which provides a measure of the real transitions induced by the (laser probe, for the inelastic light scattering. It is found that the dominant contribution to both the loss peaks and the Raman peaks comes from the collective (plasmon excitations. As to the single-particle peaks, the analysis indicates a long-lasting lack of quantitative comparison between theory and experiments. It is inferred that the inelastic electron

  20. Coupled electron-phonon transport from molecular dynamics with quantum baths

    DEFF Research Database (Denmark)

    Lu, Jing Tao; Wang, J. S.

    2009-01-01

    Based on generalized quantum Langevin equations for the tight-binding wavefunction amplitudes and lattice displacements, electron and phonon quantum transport are obtained exactly using molecular dynamics (MD) in the ballistic regime. The electron-phonon interactions can be handled with a quasi...

  1. Towards quantum optics and entanglement with electron spin ensembles in semiconductors

    NARCIS (Netherlands)

    van der Wal, Caspar H.; Sladkov, Maksym

    We discuss a technique and a material system that enable the controlled realization of quantum entanglement between spin-wave modes of electron ensembles in two spatially separated pieces of semiconductor material. The approach uses electron ensembles in GaAs quantum wells that are located inside

  2. Direct Observation of Electron-to-Hole Energy Transfer in CdSe Quantum Dots

    NARCIS (Netherlands)

    Hendry, E.; Koeberg, M.; Wang, F.; Zhang, H.; de Mello Donega, C.; Vanmaekelbergh, D.; Bonn, M.

    2006-01-01

    We independently determine the subpicosecond cooling rates for holes and electrons in CdSe quantum dots. Time-resolved luminescence and terahertz spectroscopy reveal that the rate of hole cooling, following photoexcitation of the quantum dots, depends critically on the electron excess energy. This

  3. Fundamental length, bubble electrons and non-local quantum electrodynamics

    International Nuclear Information System (INIS)

    Hsu, J.P.; Mac, E.

    1977-06-01

    Based on the concept of a bubble electron and the approach of Pais and Uhlenbeck, one constructs a finite quantum electrodynamics which is relativistically invariant, macro-causal and unitary. In this model, fields and their interaction are local, but the action function of free fields is nonlocal. The propagators are modified so that a fundamental length L is naturally introduced to physics. The modified static potential is given by V(r) = e/r for r greater than L and V(r) = 0 for r less than L, which is produced by the bubble source r -1 ddelta(r-L)/dr rather than a point source. It is found that L less than 4 x 10 -15 cm. Experimental consequences and modifications of strict causality at short distances, vertical bars 2 vertical bar approximately L 2 , are discussed

  4. Does the Finite Size of Electrons Affect Quantum Noise in Electronic Devices?

    International Nuclear Information System (INIS)

    Colomés, E; Marian, D; Oriols, X

    2015-01-01

    Quantum transport is commonly studied with the use of quasi-particle infinite- extended states. This leads to a powerful formalism, the scattering-states theory, able to capture in compact formulas quantities of interest, such as average current, noise, etc.. However, when investigating the spatial size-dependence of quasi-particle wave packets in quantum noise with exchange and tunneling, unexpected new terms appear in the quantum noise expression. For this purpose, the two particle transmission and reflection probabilities for two initial one-particle wave packets (with opposite central momentums) spatially localized at each side of a potential barrier are studied. After the interaction, each wave packet splits into a transmitted and a reflected component. It can be shown that the probability of detecting two (identically injected) electrons at the same side of the barrier is different from zero in very common (single or double barrier) scenarios. This originates an increase of quantum noise which cannot be obtained through the scattering states formalism. (paper)

  5. Dimension-dependent stimulated radiative interaction of a single electron quantum wavepacket

    Science.gov (United States)

    Gover, Avraham; Pan, Yiming

    2018-06-01

    In the foundation of quantum mechanics, the spatial dimensions of electron wavepacket are understood only in terms of an expectation value - the probability distribution of the particle location. One can still inquire how the quantum electron wavepacket size affects a physical process. Here we address the fundamental physics problem of particle-wave duality and the measurability of a free electron quantum wavepacket. Our analysis of stimulated radiative interaction of an electron wavepacket, accompanied by numerical computations, reveals two limits. In the quantum regime of long wavepacket size relative to radiation wavelength, one obtains only quantum-recoil multiphoton sidebands in the electron energy spectrum. In the opposite regime, the wavepacket interaction approaches the limit of classical point-particle acceleration. The wavepacket features can be revealed in experiments carried out in the intermediate regime of wavepacket size commensurate with the radiation wavelength.

  6. Interacting Electrons and Holes in Quasi-2D Quantum Dots in Strong Magnetic Fields

    Science.gov (United States)

    Hawrylak, P.; Sheng, W.; Cheng, S.-J.

    2004-09-01

    Theory of optical properties of interacting electrons and holes in quasi-2D quantum dots in strong magnetic fields is discussed. In two dimensions and the lowest Landau level, hidden symmetries control the interaction of the interacting system with light. By confining electrons and holes into quantum dots hidden symmetries can be removed and the excitation spectrum of electrons and excitons can be observed. We discuss a theory electronic and of excitonic quantum Hall droplets at a filling factorν=2. For an excitonic quantum Hall droplet the characteristic emission spectra are predicted to be related to the total spin of electron and hole configurations. For the electronic droplet the excitation spectrum of the droplet can be mapped out by measuring the emission for increasing number of electrons.

  7. Interacting electrons and holes in quasi-2D quantum dots in strong magnetic fields

    International Nuclear Information System (INIS)

    Hawrylak, P.; Sheng, W.; Cheng, S.-J.

    2004-01-01

    Theory of optical properties of interacting electrons and holes in quasi-2D quantum dots in strong magnetic fields is discussed. In two dimensions and the lowest Landau level, hidden symmetries control the interaction of the interacting system with light. By confining electrons and holes into quantum dots hidden symmetries can be removed and the excitation spectrum of electrons and excitons can be observed. We discuss a theory electronic and excitonic quantum Hall droplets at a filling factor υ = 2. For an excitonic quantum Hall droplet the characteristic emission spectra are predicted to be related to the total spin of electron and hole configurations. For the electronic droplet the excitation spectrum of the droplet can be mapped out by measuring the emission for increasing number of electrons. (author)

  8. Quantum Monte Carlo for electronic structure: Recent developments and applications

    International Nuclear Information System (INIS)

    Rodriguez, M.M.S.; Lawrence Berkeley Lab., CA

    1995-04-01

    Quantum Monte Carlo (QMC) methods have been found to give excellent results when applied to chemical systems. The main goal of the present work is to use QMC to perform electronic structure calculations. In QMC, a Monte Carlo simulation is used to solve the Schroedinger equation, taking advantage of its analogy to a classical diffusion process with branching. In the present work the author focuses on how to extend the usefulness of QMC to more meaningful molecular systems. This study is aimed at questions concerning polyatomic and large atomic number systems. The accuracy of the solution obtained is determined by the accuracy of the trial wave function's nodal structure. Efforts in the group have given great emphasis to finding optimized wave functions for the QMC calculations. Little work had been done by systematically looking at a family of systems to see how the best wave functions evolve with system size. In this work the author presents a study of trial wave functions for C, CH, C 2 H and C 2 H 2 . The goal is to study how to build wave functions for larger systems by accumulating knowledge from the wave functions of its fragments as well as gaining some knowledge on the usefulness of multi-reference wave functions. In a MC calculation of a heavy atom, for reasonable time steps most moves for core electrons are rejected. For this reason true equilibration is rarely achieved. A method proposed by Batrouni and Reynolds modifies the way the simulation is performed without altering the final steady-state solution. It introduces an acceleration matrix chosen so that all coordinates (i.e., of core and valence electrons) propagate at comparable speeds. A study of the results obtained using their proposed matrix suggests that it may not be the optimum choice. In this work the author has found that the desired mixing of coordinates between core and valence electrons is not achieved when using this matrix. A bibliography of 175 references is included

  9. Nanosecond-timescale spin transfer using individual electrons in a quadruple-quantum-dot device

    Energy Technology Data Exchange (ETDEWEB)

    Baart, T. A.; Jovanovic, N.; Vandersypen, L. M. K. [QuTech and Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Reichl, C.; Wegscheider, W. [Solid State Physics Laboratory, ETH Zürich, 8093 Zürich (Switzerland)

    2016-07-25

    The ability to coherently transport electron-spin states between different sites of gate-defined semiconductor quantum dots is an essential ingredient for a quantum-dot-based quantum computer. Previous shuttles using electrostatic gating were too slow to move an electron within the spin dephasing time across an array. Here, we report a nanosecond-timescale spin transfer of individual electrons across a quadruple-quantum-dot device. Utilizing enhanced relaxation rates at a so-called hot spot, we can upper bound the shuttle time to at most 150 ns. While actual shuttle times are likely shorter, 150 ns is already fast enough to preserve spin coherence in, e.g., silicon based quantum dots. This work therefore realizes an important prerequisite for coherent spin transfer in quantum dot arrays.

  10. Bend-imitating theory and electron scattering in sharply-bent quantum nanowires

    International Nuclear Information System (INIS)

    Vakhnenko, O.O.

    2011-01-01

    The concept of bend-imitating description as applied to the one-electron quantum mechanics in sharply-bent ideal electron waveguides and its development into a self consistent theory are presented. In the framework of bend-imitating approach, the investigation of the electron scattering in a doubly-bent 2D quantum wire with S-like bend has been made, and the explicit dependences of the transmission and reflection coefficients on geometrical parameters of a structure, as well as on the electron energy, have been obtained. The total elimination of the mixing between the scattering channels of a S-like bent quantum wire is predicted.

  11. Coulomb drag: a probe of electron interactions in coupled quantum wells

    DEFF Research Database (Denmark)

    Jauho, Antti-Pekka

    1996-01-01

    As semiconductor devices shrink in size and in dimensionality, interactions between charge carriers become more and more important. There is a simple physical reason behind this behavior: fewer carriers lead to less effective screening, and hence stronger effective interactions. A point in case...... are one-dimensional systems (quantum wires): there electron-electron interactions may lead to a behavior, which is qualitatively different from the standard Fermi liquid picture (Luttinger liquids). Electron-electron interactions also play a central role in the fractional quantum Hall effect, which...... be the study of quantum wires: there the interactions may lead to even more dramatic effects...

  12. Electronic structure properties of the In(Ga)As/GaAs quantum dot–quantum well tunnel-injection system

    International Nuclear Information System (INIS)

    Sęk, Grzegorz; Andrzejewski, Janusz; Ryczko, Krzysztof; Poloczek, Przemysław; Misiewicz, Jan; Semenova, Elizaveta S; Lemaitre, Aristide; Patriarche, Gilles; Ramdane, Aberrahim

    2009-01-01

    We report on the electronic properties of GaAs-substrate-based structures designed as a tunnel-injection system composed of self-assembled InAs quantum dots and an In 0.3 Ga 0.7 As quantum well separated by a GaAs barrier. We have performed photoluminescence and photoreflectance measurements which have allowed the determination of the optical transitions in the QW–QD tunnel structure and its respective references with just quantum dots or a quantum well. The effective mass calculations of the band structure dependence on the tunnelling barrier thickness have shown that in spite of an expected significant tunnelling between both parts of the system, its strong asymmetry and the strain distribution cause that the quantum-mechanical-coupling-induced energy shift of the optical transitions is almost negligible for the lowest energy states and weakly sensitive to the width of the barrier, which finds confirmation in the existing experimental data

  13. Si quantum dots for nano electronics: From materials to applications

    International Nuclear Information System (INIS)

    Lombardo, S.; Spinella, C.; Rimini, E.

    2005-01-01

    This paper reviews the subject of Si quantum dots embedded in dielectric and its application to the realization of non volatile semiconductor memories. In the first part of the paper various approaches for the analysis of the materials through transmission electron microscopy (TEM) are critically discussed. The advantages coming from an innovative application of energy filtered TEM are put in clear evidence. The paper then focuses on the synthesis of the materials: two different methodologies for the realization of the dots, both based on chemical vapor deposition are described in detail, and physical models providing some understanding of the observed phenomenology are reported. We then discuss the application of this nano technology to the realization of the storage nodes in non volatile semiconductor memories. The following sections describe the electrical characteristics found in the test devices and some key aspects are described in terms of quantitative models. The test devices show several performance advantages, indicating that the approach is an excellent candidate for the realization of Flash memories of the nano electronic era

  14. Revealing electronic open quantum systems with subsystem TDDFT

    Science.gov (United States)

    Krishtal, Alisa; Pavanello, Michele

    2016-03-01

    Open quantum systems (OQSs) are perhaps the most realistic systems one can approach through simulations. In recent years, describing OQSs with Density Functional Theory (DFT) has been a prominent avenue of research with most approaches based on a density matrix partitioning in conjunction with an ad-hoc description of system-bath interactions. We propose a different theoretical approach to OQSs based on partitioning of the electron density. Employing the machinery of subsystem DFT (and its time-dependent extension), we provide a novel way of isolating and analyzing the various terms contributing to the coupling between the system and the surrounding bath. To illustrate the theory, we provide numerical simulations on a toy system (a molecular dimer) and on a condensed phase system (solvated excimer). The simulations show that non-Markovian dynamics in the electronic system-bath interactions are important in chemical applications. For instance, we show that the superexchange mechanism of transport in donor-bridge-acceptor systems is a non-Markovian interaction between the donor-acceptor (OQS) with the bridge (bath) which is fully characterized by real-time subsystem time-dependent DFT.

  15. Free-electron laser and related quantum beams

    International Nuclear Information System (INIS)

    Minehara, Eisuke J.

    2003-01-01

    Past, present and future development programs of the JAERI super-conducting rf linac-based FELs and light sources with and without energy recovery have been discussed and introduced briefly. The JAERI FEL group has successfully discovered, and realized the brand-new FEL lasing mode of 255 fs ultra fast pulse, 6-9% high-efficiency, one GW high peak power, a few kW average power, and wide tunability of medium and far infrared wavelength regions at the same time. Using the new lasing, we could realize a powerful and efficient free-electron laser (FEL) for industrial uses near future. In order to realize such a tunable, ultra-short-pulse, high averaged-power FEL, we have needed the efficient and powerful CW FEL driver of the JAERI compact, stand-alone and zero-boil-off super-conducting rf linac with an energy-recovery geometry. The JAERI energy-recovery and/or super-conducting rf linac driver has been developed to use as an industrial electron irradiator, and millimeter-wave, far-infrared, mid-infrared, near-infrared and shorter wavelength quantum beam sources. (author)

  16. Free-electron laser and related quantum beams

    Energy Technology Data Exchange (ETDEWEB)

    Minehara, Eisuke J [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-07-01

    Past, present and future development programs of the JAERI super-conducting rf linac-based FELs and light sources with and without energy recovery have been discussed and introduced briefly. The JAERI FEL group has successfully discovered, and realized the brand-new FEL lasing mode of 255 fs ultra fast pulse, 6-9% high-efficiency, one GW high peak power, a few kW average power, and wide tunability of medium and far infrared wavelength regions at the same time. Using the new lasing, we could realize a powerful and efficient free-electron laser (FEL) for industrial uses near future. In order to realize such a tunable, ultra-short-pulse, high averaged-power FEL, we have needed the efficient and powerful CW FEL driver of the JAERI compact, stand-alone and zero-boil-off super-conducting rf linac with an energy-recovery geometry. The JAERI energy-recovery and/or super-conducting rf linac driver has been developed to use as an industrial electron irradiator, and millimeter-wave, far-infrared, mid-infrared, near-infrared and shorter wavelength quantum beam sources. (author)

  17. Revealing electronic open quantum systems with subsystem TDDFT.

    Science.gov (United States)

    Krishtal, Alisa; Pavanello, Michele

    2016-03-28

    Open quantum systems (OQSs) are perhaps the most realistic systems one can approach through simulations. In recent years, describing OQSs with Density Functional Theory (DFT) has been a prominent avenue of research with most approaches based on a density matrix partitioning in conjunction with an ad-hoc description of system-bath interactions. We propose a different theoretical approach to OQSs based on partitioning of the electron density. Employing the machinery of subsystem DFT (and its time-dependent extension), we provide a novel way of isolating and analyzing the various terms contributing to the coupling between the system and the surrounding bath. To illustrate the theory, we provide numerical simulations on a toy system (a molecular dimer) and on a condensed phase system (solvated excimer). The simulations show that non-Markovian dynamics in the electronic system-bath interactions are important in chemical applications. For instance, we show that the superexchange mechanism of transport in donor-bridge-acceptor systems is a non-Markovian interaction between the donor-acceptor (OQS) with the bridge (bath) which is fully characterized by real-time subsystem time-dependent DFT.

  18. Electron interaction and spin effects in quantum wires, quantum dots and quantum point contacts: a first-principles mean-field approach

    International Nuclear Information System (INIS)

    Zozoulenko, I V; Ihnatsenka, S

    2008-01-01

    We have developed a mean-field first-principles approach for studying electronic and transport properties of low dimensional lateral structures in the integer quantum Hall regime. The electron interactions and spin effects are included within the spin density functional theory in the local density approximation where the conductance, the density, the effective potentials and the band structure are calculated on the basis of the Green's function technique. In this paper we present a systematic review of the major results obtained on the energetics, spin polarization, effective g factor, magnetosubband and edge state structure of split-gate and cleaved-edge overgrown quantum wires as well as on the conductance of quantum point contacts (QPCs) and open quantum dots. In particular, we discuss how the spin-resolved subband structure, the current densities, the confining potentials, as well as the spin polarization of the electron and current densities in quantum wires and antidots evolve when an applied magnetic field varies. We also discuss the role of the electron interaction and spin effects in the conductance of open systems focusing our attention on the 0.7 conductance anomaly in the QPCs. Special emphasis is given to the effect of the electron interaction on the conductance oscillations and their statistics in open quantum dots as well as to interpretation of the related experiments on the ultralow temperature saturation of the coherence time in open dots

  19. Computation of quantum electron transport with local current conservation using quantum trajectories

    International Nuclear Information System (INIS)

    Alarcón, A; Oriols, X

    2009-01-01

    A recent proposal for modeling time-dependent quantum electron transport with Coulomb and exchange correlations using quantum (Bohm) trajectories (Oriols 2007 Phys. Rev. Lett. 98 066803) is extended towards the computation of the total (particle plus displacement) current in mesoscopic devices. In particular, two different methods for the practical computation of the total current are compared. The first method computes the particle and the displacement currents from the rate of Bohm particles crossing a particular surface and the time-dependent variations of the electric field there. The second method uses the Ramo–Shockley theorem to compute the total current on that surface from the knowledge of the Bohm particle dynamics in a 3D volume and the time-dependent variations of the electric field on the boundaries of that volume. From a computational point of view, it is shown that both methods achieve local current conservation, but the second is preferred because it is free from 'spurious' peaks. A numerical example, a Bohm trajectory crossing a double-barrier tunneling structure, is presented, supporting the conclusions

  20. The equation of motion of an electron: a debate in classical and quantum physics

    International Nuclear Information System (INIS)

    Kim, K.-J.

    1999-01-01

    The current status of understanding of the equation of motion of an electron is summarized. Classically, a consistent, linearized theory exists for an electron of finite extent, as long as the size of the electron is larger than the classical electron radius. Nonrelativistic quantum mechanics seems to offer a tine theory even in the point-particle limit

  1. Transmission electron microscopy study of vertical quantum dots molecules grown by droplet epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Maldonado, D., E-mail: david.hernandez@uca.es [Departamento de Ciencia de los Materiales e I.M. y Q.I., Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, s/n, 11510 Puerto Real, Cadiz (Spain); Herrera, M.; Sales, D.L. [Departamento de Ciencia de los Materiales e I.M. y Q.I., Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, s/n, 11510 Puerto Real, Cadiz (Spain); Alonso-Gonzalez, P.; Gonzalez, Y.; Gonzalez, L. [Instituto de Microelectronica de Madrid (CNM-CSIC), Isaac Newton 8 (PTM), 28760 Tres Cantos, Madrid (Spain); Pizarro, J.; Galindo, P.L. [Departamento de Lenguajes y Sistemas Informaticos, CASEM, Universidad de Cadiz, Campus Rio San Pedro, s/n, 11510 Puerto Real, Cadiz (Spain); Molina, S.I. [Departamento de Ciencia de los Materiales e I.M. y Q.I., Facultad de Ciencias, Universidad de Cadiz, Campus Rio San Pedro, s/n, 11510 Puerto Real, Cadiz (Spain)

    2010-07-01

    The compositional distribution of InAs quantum dots grown by molecular beam epitaxy on GaAs capped InAs quantum dots has been studied in this work. Upper quantum dots are nucleated preferentially on top of the quantum dots underneath, which have been nucleated by droplet epitaxy. The growth process of these nanostructures, which are usually called as quantum dots molecules, has been explained. In order to understand this growth process, the analysis of the strain has been carried out from a 3D model of the nanostructure built from transmission electron microscopy images sensitive to the composition.

  2. Transmission electron microscopy study of vertical quantum dots molecules grown by droplet epitaxy

    International Nuclear Information System (INIS)

    Hernandez-Maldonado, D.; Herrera, M.; Sales, D.L.; Alonso-Gonzalez, P.; Gonzalez, Y.; Gonzalez, L.; Pizarro, J.; Galindo, P.L.; Molina, S.I.

    2010-01-01

    The compositional distribution of InAs quantum dots grown by molecular beam epitaxy on GaAs capped InAs quantum dots has been studied in this work. Upper quantum dots are nucleated preferentially on top of the quantum dots underneath, which have been nucleated by droplet epitaxy. The growth process of these nanostructures, which are usually called as quantum dots molecules, has been explained. In order to understand this growth process, the analysis of the strain has been carried out from a 3D model of the nanostructure built from transmission electron microscopy images sensitive to the composition.

  3. Spinor-electron wave guided modes in coupled quantum wells structures by solving the Dirac equation

    International Nuclear Information System (INIS)

    Linares, Jesus; Nistal, Maria C.

    2009-01-01

    A quantum analysis based on the Dirac equation of the propagation of spinor-electron waves in coupled quantum wells, or equivalently coupled electron waveguides, is presented. The complete optical wave equations for Spin-Up (SU) and Spin-Down (SD) spinor-electron waves in these electron guides couplers are derived from the Dirac equation. The relativistic amplitudes and dispersion equations of the spinor-electron wave-guided modes in a planar quantum coupler formed by two coupled quantum wells, or equivalently by two coupled slab electron waveguides, are exactly derived. The main outcomes related to the spinor modal structure, such as the breaking of the non-relativistic degenerate spin states, the appearance of phase shifts associated with the spin polarization and so on, are shown.

  4. Entanglement transfer from electrons to photons in quantum dots: an open quantum system approach

    International Nuclear Information System (INIS)

    Budich, Jan C; Trauzettel, Bjoern

    2010-01-01

    We investigate entanglement transfer from a system of two spin-entangled electron-hole pairs, each placed in a separate single mode cavity, to the photons emitted due to cavity leakage. Dipole selection rules and a splitting between the light hole and the heavy hole subbands are the crucial ingredients establishing a one-to-one correspondence between electron spins and circular photon polarizations. To account for the measurement of the photons as well as dephasing effects, we choose a stochastic Schroedinger equation and a conditional master equation approach, respectively. The influence of interactions with the environment as well as asymmetries in the coherent couplings on the photon entanglement is analysed for two concrete measurement schemes. The first one is designed to violate the Clauser-Horne-Shimony-Holt (CHSH) inequality, while the second one employs the visibility of interference fringes to prove the entanglement of the photons. Because of the spatial separation of the entangled electronic system over two quantum dots, a successful verification of entangled photons emitted by this system would imply the detection of nonlocal spin entanglement of massive particles in a solid state structure.

  5. 2010 Electron Donor-Acceptor Interactions Gordon Research Conference, August 8 - 13, 2010.

    Energy Technology Data Exchange (ETDEWEB)

    Gerald Meyer

    2010-08-18

    The Gordon Research Conference on Electron Donor Acceptor Interactions (GRC EDAI) presents and advances the current frontiers in experimental and theoretical studies of Electron Transfer Processes and Energy Conversion. The fundamental concepts underpinning the field of electron transfer and charge transport phenomena are understood, but fascinating experimental discoveries and novel applications based on charge transfer processes are expanding the discipline. Simultaneously, global challenges for development of viable and economical alternative energy resources, on which many researchers in the field focus their efforts, are now the subject of daily news headlines. Enduring themes of this conference relate to photosynthesis, both natural and artificial, and solar energy conversion. More recent developments include molecular electronics, optical switches, and nanoscale charge transport structures of both natural (biological) and man-made origin. The GRC EDAI is one of the major international meetings advancing this field, and is one of the few scientific meetings where fundamental research in solar energy conversion has a leading voice. The program includes sessions on coupled electron transfers, molecular solar energy conversion, biological and biomimetic systems, spin effects, ultrafast reactions and technical frontiers as well as electron transport in single molecules and devices. In addition to disseminating the latest advances in the field of electron transfer processes, the conference is an excellent forum for scientists from different disciplines to meet and initiate new directions; for scientists from different countries to make contacts; for young scientists to network and establish personal contacts with other young scientists and with established scientists who, otherwise, might not have the time to meet young people. The EDAI GRC also features an interactive atmosphere with lively poster sessions, a few of which are selected for oral presentations.

  6. Quasiparticle properties of a coupled quantum-wire electron-phonon system

    DEFF Research Database (Denmark)

    Hwang, E. H.; Hu, Ben Yu-Kuang; Sarma, S. Das

    1996-01-01

    We study leading-order many-body effects of longitudinal-optical phonons on electronic properties of one-dimensional quantum-wire systems. We calculate the quasiparticle properties of a weakly polar one-dimensional electron gas in the presence of both electron-phonon and electron-electron interac......We study leading-order many-body effects of longitudinal-optical phonons on electronic properties of one-dimensional quantum-wire systems. We calculate the quasiparticle properties of a weakly polar one-dimensional electron gas in the presence of both electron-phonon and electron......-electron interactions, The leading-order dynamical screening approximation (GW approximation) is used to obtain the electron self-energy, the quasiparticle spectral function, and the quasiparticle damping rate in our calculation by treating electrons and phonons on an equal footing. Our theory includes effects (within...... theoretical results for quasiparticle properties....

  7. PREFACE: IARD 2012: 8th Biennial Conference on Classical and Quantum Relativistic Dynamics of Particles and Fields

    Science.gov (United States)

    Horwitz, L. P.; Land, Martin C.; Gill, Tepper; Lusanna, Luca; Salucci, Paolo

    2013-04-01

    Although the subject of relativistic dynamics has been explored, from both classical and quantum mechanical points of view, since the work of Einstein and Dirac, its most striking development has been in the framework of quantum field theory. The very accurate calculations of spectral and scattering properties, for example, of the anomalous magnetic moment of the electron and the Lamb shift in quantum electrodynamics, and many qualitative features of the strong and electroweak interactions, demonstrate the very great power of description achieved in this framework. Yet, many fundamental questions remain to be clarified, such as the structure of classical relativistic dynamical theories on the level of Hamilton and Lagrange in Minkowski space as well as on the curved manifolds of general relativity. There moreover remains the important question of the covariant classical description of systems at high energy for which particle production effects are not large, such as discussed in Synge's book, The Relativistic Gas, and in Balescu's book on relativistic statistical mechanics. In recent years, the study of high energy plasmas and heavy ion collisions has emphasized the importance of developing the techniques of relativistic mechanics. The results of Lindner et al [Physical Review Letters 95 0040401 (2005)] as well as the more recent proposal of Palacios et al [Phys. Rev. Lett. 103 253001 (2009)] and others, have shown that there must be a quantum theory with coherence in time. Such a theory, manifestly covariant under the transformations of special relativity with an invariant evolution parameter, such as that of Stueckelberg [Helv. Phys. Acta 14 322, 588 (1941); 15 23 (1942); see also R P Feynman Phys. Rev. 80 4401 and J S Schwinger Phys. Rev. 82 664 (1951)] could provide a suitable basis for the study of such questions, as well as many others for which the application of the standard methods of quantum field theory are difficult to manage, involving, in particular

  8. Path integrals for electronic densities, reactivity indices, and localization functions in quantum systems.

    Science.gov (United States)

    Putz, Mihai V

    2009-11-10

    The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI) development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr's quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions - all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving) many-electronic systems.

  9. Path Integrals for Electronic Densities, Reactivity Indices, and Localization Functions in Quantum Systems

    Directory of Open Access Journals (Sweden)

    Mihai V. Putz

    2009-11-01

    Full Text Available The density matrix theory, the ancestor of density functional theory, provides the immediate framework for Path Integral (PI development, allowing the canonical density be extended for the many-electronic systems through the density functional closure relationship. Yet, the use of path integral formalism for electronic density prescription presents several advantages: assures the inner quantum mechanical description of the system by parameterized paths; averages the quantum fluctuations; behaves as the propagator for time-space evolution of quantum information; resembles Schrödinger equation; allows quantum statistical description of the system through partition function computing. In this framework, four levels of path integral formalism were presented: the Feynman quantum mechanical, the semiclassical, the Feynman-Kleinert effective classical, and the Fokker-Planck non-equilibrium ones. In each case the density matrix or/and the canonical density were rigorously defined and presented. The practical specializations for quantum free and harmonic motions, for statistical high and low temperature limits, the smearing justification for the Bohr’s quantum stability postulate with the paradigmatic Hydrogen atomic excursion, along the quantum chemical calculation of semiclassical electronegativity and hardness, of chemical action and Mulliken electronegativity, as well as by the Markovian generalizations of Becke-Edgecombe electronic focalization functions – all advocate for the reliability of assuming PI formalism of quantum mechanics as a versatile one, suited for analytically and/or computationally modeling of a variety of fundamental physical and chemical reactivity concepts characterizing the (density driving many-electronic systems.

  10. Geometric phase and quantum interference in photosynthetic reaction center: Regulation of electron transfer

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yuming, E-mail: ymsun@ytu.edu.cn; Su, Yuehua; Dai, Zhenhong; Wang, WeiTian

    2016-10-20

    Photosynthesis is driven by electron transfer in reaction centers in which the functional unit is composed of several simple molecules C{sub 2}-symmetrically arranged into two branches. In view of quantum mechanism, both branches are possible pathways traversed by the transferred electron. Due to different evolution of spin state along two pathways in transmembrane electric potential (TEP), quantum state of the transferred electron at the bridged site acquires a geometric phase difference dependent on TEP, the most efficient electron transport takes place in a specific range of TEP beyond which electron transfer is dramatically suppressed. What’s more, reaction center acts like elaborately designed quantum device preparing polarized spin dependent on TEP for the transferred electron to regulate the reduction potential at bridged site. In brief, electron transfer generates the TEP, reversely, TEP modulates the efficiency of electron transfer. This may be an important approach to maintaining an appreciable pH environment in photosynthesis.

  11. Irregular Aharonov–Bohm effect for interacting electrons in a ZnO quantum ring

    International Nuclear Information System (INIS)

    Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk

    2017-01-01

    The electronic states and optical transitions of a ZnO quantum ring containing few interacting electrons in an applied magnetic field are found to be very different from those in a conventional semiconductor system, such as a GaAs ring. The strong Zeeman interaction and the Coulomb interaction of the ZnO system, two important characteristics of the electron system in ZnO, exert a profound influence on the electron states and on the optical properties of the ring. In particular, our results indicate that the Aharonov–Bohm (AB) effect in a ZnO quantum ring strongly depends on the electron number. In fact, for two electrons in the ZnO ring, the AB oscillations become aperiodic, while for three electrons (interacting) the AB oscillations completely disappear. Therefore, unlike in conventional quantum ring topology, here the AB effect (and the resulting persistent current) can be controlled by varying the electron number. (paper)

  12. Quantum theory of the optical and electronic properties of semiconductors

    CERN Document Server

    Haug, Hartmut

    2009-01-01

    This invaluable textbook presents the basic elements needed to understand and research into semiconductor physics. It deals with elementary excitations in bulk and low-dimensional semiconductors, including quantum wells, quantum wires and quantum dots. The basic principles underlying optical nonlinearities are developed, including excitonic and many-body plasma effects. Fundamentals of optical bistability, semiconductor lasers, femtosecond excitation, the optical Stark effect, the semiconductor photon echo, magneto-optic effects, as well as bulk and quantum-confined Franz-Keldysh effects, are covered. The material is presented in sufficient detail for graduate students and researchers with a general background in quantum mechanics.This fifth edition includes an additional chapter on 'Quantum Optical Effects' where the theory of quantum optical effects in semiconductors is detailed. Besides deriving the 'semiconductor luminescence equations' and the expression for the stationary luminescence spectrum, the resu...

  13. Analytic and numerical calculations of quantum synchrotron spectra from relativistic electron distributions

    International Nuclear Information System (INIS)

    Brainerd, J.J.; Petrosian, V.

    1987-01-01

    Calculations are performed numerically and analytically of synchrotron spectra for thermal and power-law electron distributions using the single-particle synchrotron power spectrum derived from quantum electrodynamics. It is found that the photon energy at which quantum effects appear is proportional to temperature and independent of field strength for thermal spectra; quantum effects introduce an exponential roll-off away from the classical spectra. For power law spectra, the photon energy at which quantum effects appear is inversely proportional to the magnetic field strength; quantum effects produce a steeper power law than is found classically. The results are compared with spectra derived from the classical power spectrum with an energy cutoff ensuring conservation of energy. It is found that an energy cutoff is generally an inadequate approximation of quantum effects for low photon energies and for thermal spectra, but gives reasonable results for high-energy emission from power-law electron distributions. 17 references

  14. Physics colloquium: Electron counting in quantum dots in and out of equilibrium

    CERN Multimedia

    Geneva University

    2011-01-01

    GENEVA UNIVERSITY Ecole de physique Département de physique nucléaire et corspusculaire 24, quai Ernest-Ansermet 1211 Genève 4 Tél.: (022) 379 62 73 Fax: (022) 379 69 92olé   Lundi 31 octobre 2011 17h00 - Ecole de Physique, Auditoire Stueckelberg PHYSICS COLLOQUIUM « Electron counting in quantum dots in and out of equilibrium » Prof. Klaus Ensslin Solid State Physics Laboratory, ETH Zurich, 8093 Zurich, Switzerland   Electron transport through quantum dots is governed by Coulomb blockade. Using a nearby quantum point contact the time-dependent charge flow through quantum dots can be monitored on the basis of single electrons. This way electron transport has been investigated in equilibrium as well as out of equilibrium. Recently it has become possible to experimentally verify the fluctuation theorem. The talk will also address electron counting experiments in grapheme. Une verrée ...

  15. Two-electron states in double quantum dot in direct electric field

    International Nuclear Information System (INIS)

    Burdov, V.A.

    2001-01-01

    One determined analytically the wave functions of stationary states and the spectrum of two-electron system in symmetric binary quantum point. It is shown that in the normal state at the absence of external electric field the electrons due to the Coulomb blockade can not be collectively in one quantum point. In the external electric field the situation changes. When a certain critical value of field intensity is reached the probability of detection of both electrons in one quantum point by a jump increases from zero up to 1 [ru

  16. Electronic structure and correlated wave functions of a few electron quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Sako, Tokuei [Laboratory of Physics, College of Science and Technology, Nihon University, 7-24-1 Narashinodai, Funabashi, Chiba 274-8501 (Japan); Ishida, Hiroshi [College of Humanities and Sciences, Nihon University, Tokyo 156-8550 (Japan); Fujikawa, Kazuo [Institute of Quantum Science, College of Science and Technology, Nihon University, Chiyoda-ku, Tokyo 101-8308 (Japan)

    2015-01-22

    The energy spectra and wave functions of a few electrons confined by a quasi-one-dimensional harmonic and anharmonic potentials have been studied by using a full configuration interaction method employing a Cartesian anisotropic Gaussian basis set. The energy spectra are classified into three regimes of the strength of confinement, namely, large, medium and small. The polyad quantum number defined by a total number of nodes in the wave functions is shown to be a key ingredient to interpret the energy spectra for the whole range of the confinement strength. The nodal pattern of the wave functions exhibits normal modes for the harmonic confining potential, indicating collective motions of electrons. These normal modes are shown to undergo a transition to local modes for an anharmonic potential with large anharmonicity.

  17. Quantum Monte Carlo for electronic structure: Recent developments and applications

    Energy Technology Data Exchange (ETDEWEB)

    Rodriquez, Maria Milagos Soto [Lawrence Berkeley Lab. and Univ. of California, Berkeley, CA (United States). Dept. of Chemistry

    1995-04-01

    Quantum Monte Carlo (QMC) methods have been found to give excellent results when applied to chemical systems. The main goal of the present work is to use QMC to perform electronic structure calculations. In QMC, a Monte Carlo simulation is used to solve the Schroedinger equation, taking advantage of its analogy to a classical diffusion process with branching. In the present work the author focuses on how to extend the usefulness of QMC to more meaningful molecular systems. This study is aimed at questions concerning polyatomic and large atomic number systems. The accuracy of the solution obtained is determined by the accuracy of the trial wave function`s nodal structure. Efforts in the group have given great emphasis to finding optimized wave functions for the QMC calculations. Little work had been done by systematically looking at a family of systems to see how the best wave functions evolve with system size. In this work the author presents a study of trial wave functions for C, CH, C2H and C2H2. The goal is to study how to build wave functions for larger systems by accumulating knowledge from the wave functions of its fragments as well as gaining some knowledge on the usefulness of multi-reference wave functions. In a MC calculation of a heavy atom, for reasonable time steps most moves for core electrons are rejected. For this reason true equilibration is rarely achieved. A method proposed by Batrouni and Reynolds modifies the way the simulation is performed without altering the final steady-state solution. It introduces an acceleration matrix chosen so that all coordinates (i.e., of core and valence electrons) propagate at comparable speeds. A study of the results obtained using their proposed matrix suggests that it may not be the optimum choice. In this work the author has found that the desired mixing of coordinates between core and valence electrons is not achieved when using this matrix. A bibliography of 175 references is

  18. Controllable Continuous evolution of electronic states in a single quantum ring

    OpenAIRE

    Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk; Laroze, David

    2017-01-01

    Intense terahertz laser field is shown to have a profound effect on the electronic and optical properties of quantum rings, where the isotropic and anisotropic quantum rings can now be treated on equal footing. We have demonstrated that in isotropic quantum rings the laser field creates irregular AB oscillations that are usually expected in anisotropic rings. Further, we have shown for the first time that intense laser fields can restore the {\\it isotropic} physical properties in anisotropic ...

  19. Electronic properties and optical absorption of a phosphorene quantum dot

    Science.gov (United States)

    Liang, F. X.; Ren, Y. H.; Zhang, X. D.; Jiang, Z. T.

    2018-03-01

    Using the tight-binding Hamiltonian approach, we theoretically study the electronic and optical properties of a triangular phosphorene quantum dot (PQD) including one normal zigzag edge and two skewed armchair edges (ZAA-PQD). It is shown that the energy spectrum can be classified into the filled band (FB), the zero-energy band (ZB), and the unfilled band (UB). Numerical calculations of the FB, ZB, and UB probability distributions show that the FB and the UB correspond to the bulk states, while the ZB corresponds to the edge states, which appear on all of the three edges of the ZAA-PQD sharply different from the other PQDs. We also find that the strains and the electric fields can affect the energy levels inhomogeneously. Then the optical properties of the ZAA-PQD are investigated. There appear some strong low-energy optical absorption peaks indicating its sensitive low-energy optical response that is absent in other PQDs. Moreover, the strains and the electric fields can make inhomogeneous influences on the optical spectrum of the ZAA-PQD. This work may provide a useful reference for designing the electrical, mechanical, and optical PQD devices.

  20. Tuning of few-electron states and optical absorption anisotropy in GaAs quantum rings.

    Science.gov (United States)

    Wu, Zhenhua; Li, Jian; Li, Jun; Yin, Huaxiang; Liu, Yu

    2017-11-15

    The electronic and optical properties of a GaAs quantum ring (QR) with few electrons in the presence of the Rashba spin-orbit interaction (RSOI) and the Dresselhaus spin-orbit interaction (DSOI) have been investigated theoretically. The configuration interaction (CI) method is employed to calculate the eigenvalues and eigenstates of the multiple-electron QR accurately. Our numerical results demonstrate that the symmetry breaking induced by the RSOI and DSOI leads to an anisotropic distribution of multi-electron states. The Coulomb interaction offers additional modulation of the electron distribution and thus the optical absorption indices in the quantum rings. By tuning the magnetic/electric fields and/or electron numbers in a quantum ring, one can change its optical properties significantly. Our theory provides a new way to control the multi-electron states and optical properties of a QR by hybrid modulations or by electrical means only.

  1. PREFACE: XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC2015)

    Science.gov (United States)

    Díaz, C.; Rabadán, I.; García, G.; Méndez, L.; Martín, F.

    2015-09-01

    The 29th International Conference on Photonic, Electronic and Atomic Collisions (XXIX ICPEAC) was held at the Palacio de Congresos ''El Greco'', Toledo, Spain, on 22-28 July, 2015, and was organized by the Universidad Autónoma de Madrid (UAM) and the Consejo Superior de Investigaciones Científicas (CSIC). ICPEAC is held biannually and is one of the most important international conferences on atomic and molecular physics. The topic of the conference covers the recent progresses in photonic, electronic, and atomic collisions with matter. With a history back to 1958, ICPEAC came to Spain in 2015 for the very first time. UAM and CSIC had been preparing the conference for six years, ever since the ICPEAC International General Committee made the decision to hold the XXIX ICPEAC in Toledo. The conference gathered 670 participants from 52 countries and attracted 854 contributed papers for presentation in poster sessions. Among the latter, 754 are presented in issues 2-12 of this volume of the Journal of Physics Conference Series. In addition, five plenary lectures, including the opening one by the Nobel laureate Prof. Ahmed H. Zewail and the lectures by Prof. Maciej Lewenstein, Prof. Paul Scheier, Prof. Philip H. Bucksbaum, and Prof. Stephen J. Buckman, 62 progress reports and 26 special reports were presented following the decision of the ICPEAC International General Committee. Detailed write-ups of most of the latter are presented in issue 1 of this volume, constituting a comprehensive tangible record of the meeting. On the occasion of the International Year of Light (IYL2015) and with the support of the Fundación Española para la Ciencia y la Tecnología (FECYT), the program was completed with two public lectures delivered by the Nobel laureate Prof. Serge Haroche and the Príncipe de Asturias laureate Prof. Pedro M. Echenique on, respectively, ''Fifty years of laser revolutions in physics'rquot; and ''The sublime usefulness of useless science''. Also a

  2. Optical pumping of electron and nuclear spin in a negatively-charged quantum dot

    Science.gov (United States)

    Bracker, Allan; Gershoni, David; Korenev, Vladimir

    2005-03-01

    We report optical pumping of electron and nuclear spins in an individual negatively-charged quantum dot. With a bias-controlled heterostructure, we inject one electron into the quantum dot. Intense laser excitation produces negative photoluminescence polarization, which is easily erased by the Hanle effect, demonstrating optical pumping of a long-lived resident electron. The electron spin lifetime is consistent with the influence of nuclear spin fluctuations. Measuring the Overhauser effect in high magnetic fields, we observe a high degree of nuclear spin polarization, which is closely correlated to electron spin pumping.

  3. On the quantum Landau collision operator and electron collisions in dense plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Daligault, Jérôme, E-mail: daligaul@lanl.gov [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2016-03-15

    The quantum Landau collision operator, which extends the widely used Landau/Fokker-Planck collision operator to include quantum statistical effects, is discussed. The quantum extension can serve as a reference model for including electron collisions in non-equilibrium dense plasmas, in which the quantum nature of electrons cannot be neglected. In this paper, the properties of the Landau collision operator that have been useful in traditional plasma kinetic theory and plasma transport theory are extended to the quantum case. We outline basic properties in connection with the conservation laws, the H-theorem, and the global and local equilibrium distributions. We discuss the Fokker-Planck form of the operator in terms of three potentials that extend the usual two Rosenbluth potentials. We establish practical closed-form expressions for these potentials under local thermal equilibrium conditions in terms of Fermi-Dirac and Bose-Einstein integrals. We study the properties of linearized quantum Landau operator, and extend two popular approximations used in plasma physics to include collisions in kinetic simulations. We apply the quantum Landau operator to the classic test-particle problem to illustrate the physical effects embodied in the quantum extension. We present useful closed-form expressions for the electron-ion momentum and energy transfer rates. Throughout the paper, similarities and differences between the quantum and classical Landau collision operators are emphasized.

  4. On the quantum Landau collision operator and electron collisions in dense plasmas

    Science.gov (United States)

    Daligault, Jérôme

    2016-03-01

    The quantum Landau collision operator, which extends the widely used Landau/Fokker-Planck collision operator to include quantum statistical effects, is discussed. The quantum extension can serve as a reference model for including electron collisions in non-equilibrium dense plasmas, in which the quantum nature of electrons cannot be neglected. In this paper, the properties of the Landau collision operator that have been useful in traditional plasma kinetic theory and plasma transport theory are extended to the quantum case. We outline basic properties in connection with the conservation laws, the H-theorem, and the global and local equilibrium distributions. We discuss the Fokker-Planck form of the operator in terms of three potentials that extend the usual two Rosenbluth potentials. We establish practical closed-form expressions for these potentials under local thermal equilibrium conditions in terms of Fermi-Dirac and Bose-Einstein integrals. We study the properties of linearized quantum Landau operator, and extend two popular approximations used in plasma physics to include collisions in kinetic simulations. We apply the quantum Landau operator to the classic test-particle problem to illustrate the physical effects embodied in the quantum extension. We present useful closed-form expressions for the electron-ion momentum and energy transfer rates. Throughout the paper, similarities and differences between the quantum and classical Landau collision operators are emphasized.

  5. Antwerp Advanced Study Institute on Electronic Structure, Dynamics and Quantum Structural Properties of Condensed Matter

    CERN Document Server

    Camp, Piet

    1985-01-01

    The 1984 Advanced Study Institute on "Electronic Structure, Dynamics and Quantum Structural Properties of Condensed Matter" took place at the Corsendonk Conference Center, close to the City of Antwerpen, from July 16 till 27, 1984. This NATO Advanced Study Institute was motivated by the research in my Institute, where, in 1971, a project was started on "ab-initio" phonon calculations in Silicon. I~ is my pleasure to thank several instances and people who made this ASI possible. First of all, the sponsor of the Institute, the NATO Scientific Committee. Next, the co-sponsors: Agfa-Gevaert, Bell Telephone Mfg. Co. N.V., C & A, Esso Belgium·, CDC Belgium, Janssens Pharmaceutica, Kredietbank and the Scientific Office of the U.S. Army. Special thanks are due to Dr. P. Van Camp and Drs. H. Nachtegaele, who, over several months, prepared the practical aspects of the ASI with the secretarial help of Mrs. R.-M. Vandekerkhof. I also like to. thank Mrs. M. Cuyvers who prepared and organized the subject and material ...

  6. Quantum spin-glass transition in the two-dimensional electron gas

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 58; Issue 2 ... Spin glasses; quantum phase transition; ferromagnetism; electron gas. ... We argue that a quantum transition involving the destruction of the spin-glass order in an applied in-plane magnetic field offers a natural explanation of some features of recent ...

  7. Learning nitrogen-vacancy electron spin dynamics on a silicon quantum photonic simulator

    NARCIS (Netherlands)

    Wang, J.; Paesani, S.; Santagati, R.; Knauer, S.; Gentile, A. A.; Wiebe, N.; Petruzzella, M.; Laing, A.; Rarity, J. G.; O'Brien, J. L.; Thompson, M. G.

    2017-01-01

    We present the experimental demonstration of quantum Hamiltonian learning. Using an integrated silicon-photonics quantum simulator with the classical machine learning technique, we successfully learn the Hamiltonian dynamics of a diamond nitrogen-vacancy center's electron ground-state spin.

  8. Giant electron-hole transport asymmetry in ultra-short quantum transistors

    Science.gov (United States)

    McRae, A. C.; Tayari, V.; Porter, J. M.; Champagne, A. R.

    2017-01-01

    Making use of bipolar transport in single-wall carbon nanotube quantum transistors would permit a single device to operate as both a quantum dot and a ballistic conductor or as two quantum dots with different charging energies. Here we report ultra-clean 10 to 100 nm scale suspended nanotube transistors with a large electron-hole transport asymmetry. The devices consist of naked nanotube channels contacted with sections of tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers. These tunnel barriers define a single quantum dot whose charging energies to add an electron or a hole are vastly different (e−h charging energy asymmetry). We parameterize the e−h transport asymmetry by the ratio of the hole and electron charging energies ηe−h. This asymmetry is maximized for short channels and small band gap tubes. In a small band gap device, we demonstrate the fabrication of a dual functionality quantum device acting as a quantum dot for holes and a much longer quantum bus for electrons. In a 14 nm-long channel, ηe−h reaches up to 2.6 for a device with a band gap of 270 meV. The charging energies in this device exceed 100 meV. PMID:28561024

  9. Modulation transfer function and detective quantum efficiency of electron bombarded charge coupled device detector for low energy electrons

    Czech Academy of Sciences Publication Activity Database

    Horáček, Miroslav

    2005-01-01

    Roč. 76, č. 9 (2005), 093704:1-6 ISSN 0034-6748 R&D Projects: GA ČR(CZ) GA202/03/1575 Keywords : electron bombarded CCD * modulation transfer function * detective quantum efficiency Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.235, year: 2005

  10. The effect of intramolecular quantum modes on free energy relationships for electron transfer reactions

    DEFF Research Database (Denmark)

    Ulstrup, Jens; Jortner, Joshua

    1975-01-01

    A general quantum mechanical description of exothermic electron transfer reactions is formulated by treating such reactions as the nonradiative decay of a ''supermolecule'' consisting of the electron donor, the electron acceptor, and the polar solvent. In particular, the role of the high-frequenc...

  11. Quantum dynamical phenomena of independent electrons in semiconductor superlattices subject to a uniform electric field

    International Nuclear Information System (INIS)

    Bouchard, A.M.

    1994-01-01

    This report discusses the following topics: Bloch oscillations and other dynamical phenomena of electrons in semiconductor superlattices; solvable dynamical model of an electron in a one-dimensional aperiodic lattice subject to a uniform electric field; and quantum dynamical phenomena of electrons in aperiodic semiconductor superlattices

  12. Formulation of a Mesoscopic Electron Beam Splitter with Application in Semiconductor Based Quantum Computing

    OpenAIRE

    Shanker, A.; Bhowmik, D.; Bhattacharya, T. K.

    2010-01-01

    We aim to analytically arrive at a beam splitter formulation for electron waves. The electron beam splitter is an essential component of quantum logical devices. To arrive at the beam splitter structure, the electrons are treated as waves, i.e. we assume the transport to be ballistic. Ballistic electrons are electrons that travel over such short distances that their phase coherence is maintained. For mesoscopic devices with size smaller than the mean free path, the phase relaxation length and...

  13. Quantum Nuclear Extension of Electron Nuclear Dynamics on Folded Effective-Potential Surfaces

    DEFF Research Database (Denmark)

    Hall, B.; Deumens, E.; Ohrn, Y.

    2014-01-01

    A perennial problem in quantum scattering calculations is accurate theoretical treatment of low energy collisions. We propose a method of extracting a folded, nonadiabatic, effective potential energy surface from electron nuclear dynamics (END) trajectories; we then perform nuclear wave packet...

  14. The effect of quantum correction on plasma electron heating in ultraviolet laser interaction

    Energy Technology Data Exchange (ETDEWEB)

    Zare, S.; Sadighi-Bonabi, R., E-mail: Sadighi@sharif.ir; Anvari, A. [Department of Physics, Sharif University of Technology, P.O. Box 11365-9567, Tehran (Iran, Islamic Republic of); Yazdani, E. [Department of Energy Engineering and Physics, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Hora, H. [Department of Theoretical Physics, University of New South Wales, Sydney 2052 (Australia)

    2015-04-14

    The interaction of the sub-picosecond UV laser in sub-relativistic intensities with deuterium is investigated. At high plasma temperatures, based on the quantum correction in the collision frequency, the electron heating and the ion block generation in plasma are studied. It is found that due to the quantum correction, the electron heating increases considerably and the electron temperature uniformly reaches up to the maximum value of 4.91 × 10{sup 7 }K. Considering the quantum correction, the electron temperature at the laser initial coupling stage is improved more than 66.55% of the amount achieved in the classical model. As a consequence, by the modified collision frequency, the ion block is accelerated quicker with higher maximum velocity in comparison with the one by the classical collision frequency. This study proves the necessity of considering a quantum mechanical correction in the collision frequency at high plasma temperatures.

  15. The features of ballistic electron transport in a suspended quantum point contact

    International Nuclear Information System (INIS)

    Shevyrin, A. A.; Budantsev, M. V.; Bakarov, A. K.; Toropov, A. I.; Pogosov, A. G.; Ishutkin, S. V.; Shesterikov, E. V.

    2014-01-01

    A suspended quantum point contact and the effects of the suspension are investigated by performing identical electrical measurements on the same experimental sample before and after the suspension. In both cases, the sample demonstrates conductance quantization. However, the suspended quantum point contact shows certain features not observed before the suspension, namely, plateaus at the conductance values being non-integer multiples of the conductance quantum, including the “0.7-anomaly.” These features can be attributed to the strengthening of electron-electron interaction because of the electric field confinement within the suspended membrane. Thus, the suspended quantum point contact represents a one-dimensional system with strong electron-electron interaction

  16. Applications and research on nano power electronics: an adventure beyond quantum electronics

    Science.gov (United States)

    Chakraborty, Arindam; Emadi, Ali

    2005-06-01

    This paper is a roadmap to the exhaustive role of the newly emerging field of nanotechnology in various application and research areas. Some of the today's important topics are plasma, dielectric layer semiconductor, and carbon nanoparticle based technologies. Carbon nanotubes are very useful for the purpose of fabricating nano opto power devices. The basic concept behind tunneling of electrons has been utilized to define another scope of this technology, and thus came many quantum scale tunneling devices and elements. Fabrication of crystal semiconductors of high quality along with oxides of nano aspect would give rise to superior device performance and find applications such as LEDs, LASER, VLSI technology and also in highly efficient solar cells. Many nano-research based organizations are fully devoted to develop nano power cells, which would give birth to new battery cells, tunneling devises, with high power quality, longer lives, and higher activation rates. Different electronics industries as well as the military organizations would be largely benefited due to this major component and system design ideas of 'Smart Power' technologies. The contribution of nano scale power electronics would be realized in various fields like switching devices, electromechanical systems and quantum science. Such a sophisticated technology will have great impact on the modernization of robotics; space systems, automotive systems and many other fields. The highly emerging field of nanomedicine according to specialists would bring a dramatic revolution in the present century. However nanomedicine is nothing but an integration of biology, medicine and technology. Thermoelectric materials as been referred earlier also are used in case of implantable medical equipments for generation of electric power sufficient for those equipments.

  17. Electron-beam generated porous dextran gels: experimental and quantum chemical studies.

    Science.gov (United States)

    Naumov, Sergej; Knolle, Wolfgang; Becher, Jana; Schnabelrauch, Matthias; Reichelt, Senta

    2014-06-01

    The aim of this work was to investigate the reaction mechanism of electron-beam generated macroporous dextran cryogels by quantum chemical calculation and electron paramagnetic resonance measurements. Electron-beam radiation was used to initiate the cross-linking reaction of methacrylated dextran in semifrozen aqueous solutions. The pore morphology of the resulting cryogels was visualized by scanning electron microscopy. Quantum chemical calculations and electron paramagnetic resonance studies provided information on the most probable reaction pathway and the chain growth radicals. The most probable reaction pathway was a ring opening reaction and the addition of a C-atom to the double-bond of the methacrylated dextran molecule. First detailed quantum chemical calculation on the reaction mechanism of electron-beam initiated cross-linking reaction of methacrylated dextran are presented.

  18. FIRST EXPERIMENTAL RESULTS FROM DEGAS, THE QUANTUM LIMITED BRIGHTNESS ELECTRON SOURCE

    International Nuclear Information System (INIS)

    Zolotorev, Max S.; Commins, Eugene D.; Oneill, James; Sannibale, Fernando; Tremsin, Anton; Wan, Weishi

    2008-01-01

    The construction of DEGAS (DEGenerate Advanced Source), a proof of principle for a quantum limited brightness electron source, has been completed at the Lawrence Berkeley National Laboratory. The commissioning and the characterization of this source, designed to generate coherent single electron 'bunches' with brightness approaching the quantum limit at a repetition rate of few MHz, has been started. In this paper the first experimental results are described

  19. Landau damping effects on collision-induced quantum interference in electron-hole plasmas

    International Nuclear Information System (INIS)

    Hwa-Min, Kim; Young-Dae, Jung

    2007-01-01

    The Landau damping effects on the quantum interference in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Born method and the total spin states are considered to obtain the scattering cross-section by using the effective screened potential model. It is found that the Landau damping effects enhance the scattering cross-section, especially, near the scattering angle θ L = π/4. (authors)

  20. Landau damping effects on collision-induced quantum interference in electron-hole plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hwa-Min, Kim [Daegu Univ. Catholic, Dept. of Electronics Engineering (Korea, Republic of); Young-Dae, Jung [Hanyang Univ., Dept. of Applied Physics, Seoul (Korea, Republic of)

    2007-07-15

    The Landau damping effects on the quantum interference in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Born method and the total spin states are considered to obtain the scattering cross-section by using the effective screened potential model. It is found that the Landau damping effects enhance the scattering cross-section, especially, near the scattering angle {theta}{sub L} = {pi}/4. (authors)

  1. On the role of electron quantum tunneling in charging of dust grains in complex plasma

    International Nuclear Information System (INIS)

    Tyshetskiy, Yu.O.; Vladimirov, S.V.

    2011-01-01

    The aim of this work is calculate ion additional current associated with the quantum tunneling of plasma electrons, that are classically forbidden to overcome the repulsive potential barrier, onto the negatively charged grain. We compare this additional quantum tunneling current with the classical electron current from plasma onto the grain and analyze how this additional current affects the self-consistent equilibrium grain charge for different plasma parameters and grain sizes.

  2. Experimental Study of Electronic Quantum Interference, Photonic Crystal Cavity, Photonic Band Edge Effects for Optical Amplification

    Science.gov (United States)

    2016-01-26

    AFRL-RV-PS- AFRL-RV-PS- TR-2016-0003 TR-2016-0003 EXPERIMENTAL STUDY OF ELECTRONIC QUANTUM INTERFERENCE , PHOTONIC CRYSTAL CAVITY, PHOTONIC BAND...EDGE EFFECTS FOR OPTICAL AMPLIFICATION Shawn-Yu Lin Rensselaer Polytechnic Institute 110 8th Street Troy, New York 12180 26 Jan 2016 Final Report...2014 – 11 Jan 2016 4. TITLE AND SUBTITLE Experimental Study of Electronic Quantum Interference , Photonic Crystal Cavity, Photonic Band Edge Effects

  3. Quantum decoherence in electronic current flowing through carbon nanotubes induced by thermal atomic vibrations

    Science.gov (United States)

    Ishizeki, Keisuke; Sasaoka, Kenji; Konabe, Satoru; Souma, Satofumi; Yamamoto, Takahiro

    2018-06-01

    We theoretically investigate quantum decoherence in electronic currents flowing through metallic carbon nanotubes caused by thermal atomic vibrations using the time-dependent Schrödinger equation for an open system. We reveal that the quantum coherence of conduction electrons decays exponentially with tube length at a fixed temperature, and that the decay rate increases with temperature. We also find that the phase relaxation length due to the thermal atomic vibrations is inversely proportional to temperature.

  4. Correlated nuclear and electronic dynamics in photoionized systems studied by quantum and mixed quantum-classical approaches

    International Nuclear Information System (INIS)

    Li, Zheng

    2014-09-01

    The advent of free electron lasers and high harmonic sources enables the investigation of electronic and nuclear dynamics of molecules and solids with atomic spatial resolution and femtosecond/attosecond time resolution, using bright and ultrashort laser pulses of frequency from terahertz to hard x-ray range. With the help of ultrashort laser pulses, the nuclear and electronic dynamics can be initiated, monitored and actively controlled at the typical time scale in the femtosecond to attosecond realm. Meanwhile, theoretical tools are required to describe the underlying mechanism. This doctoral thesis focuses on the development of theoretical tools based on full quantum mechanical multiconfiguration time-dependent Hartree (MCTDH) and mixed quantum classical approaches, which can be applied to describe the dynamical behavior of gas phase molecules and strongly correlated solids in the presence of ultrashort laser pulses. In the first part of this thesis, the focus is on the motion of electron holes in gas phase molecular ions created by extreme ultraviolet (XUV) photoionization and watched by spectroscopic approaches. The XUV photons create electron-hole in the valence orbitals of molecules by photoionization, the electron hole, as a positively charged quasi-particle, can then interact with the nuclei and the rest of electrons, leading to coupled non-Born-Oppenheimer dynamics. I present our study on electron-hole relaxation dynamics in valence ionized molecular ions of moderate size, using quantum wave packet and mixed quantum-classical approaches, using photoionized [H + (H 2 O) n ] + molecular ion as example. We have shown that the coupled motion of the electron-hole and the nuclei can be mapped out with femtosecond resolution by core-level x-ray transient absorption spectroscopy. Furthermore, in specific cases, the XUV photon can create a coherent electron hole, that can maintain its coherence to time scales of ∝ 1 picosecond. Employing XUV pump - IR probe

  5. Simulation of electronic structure Hamiltonians in a superconducting quantum computer architecture

    Energy Technology Data Exchange (ETDEWEB)

    Kaicher, Michael; Wilhelm, Frank K. [Theoretical Physics, Saarland University, 66123 Saarbruecken (Germany); Love, Peter J. [Department of Physics, Haverford College, Haverford, Pennsylvania 19041 (United States)

    2015-07-01

    Quantum chemistry has become one of the most promising applications within the field of quantum computation. Simulating the electronic structure Hamiltonian (ESH) in the Bravyi-Kitaev (BK)-Basis to compute the ground state energies of atoms/molecules reduces the number of qubit operations needed to simulate a single fermionic operation to O(log(n)) as compared to O(n) in the Jordan-Wigner-Transformation. In this work we will present the details of the BK-Transformation, show an example of implementation in a superconducting quantum computer architecture and compare it to the most recent quantum chemistry algorithms suggesting a constant overhead.

  6. Mode locking of electron spin coherences in singly charged quantum dots.

    Science.gov (United States)

    Greilich, A; Yakovlev, D R; Shabaev, A; Efros, Al L; Yugova, I A; Oulton, R; Stavarache, V; Reuter, D; Wieck, A; Bayer, M

    2006-07-21

    The fast dephasing of electron spins in an ensemble of quantum dots is detrimental for applications in quantum information processing. We show here that dephasing can be overcome by using a periodic train of light pulses to synchronize the phases of the precessing spins, and we demonstrate this effect in an ensemble of singly charged (In,Ga)As/GaAs quantum dots. This mode locking leads to constructive interference of contributions to Faraday rotation and presents potential applications based on robust quantum coherence within an ensemble of dots.

  7. Injection of a single electron from static to moving quantum dots.

    Science.gov (United States)

    Bertrand, Benoit; Hermelin, Sylvain; Mortemousque, Pierre-André; Takada, Shintaro; Yamamoto, Michihisa; Tarucha, Seigo; Ludwig, Arne; Wieck, Andreas D; Bäuerle, Christopher; Meunier, Tristan

    2016-05-27

    We study the injection mechanism of a single electron from a static quantum dot into a moving quantum dot. The moving quantum dots are created with surface acoustic waves (SAWs) in a long depleted channel. We demonstrate that the injection process is characterized by an activation law with a threshold that depends on the SAW amplitude and on the dot-channel potential gradient. By sufficiently increasing the SAW modulation amplitude, we can reach a regime where the transfer has unity probability and is potentially adiabatic. This study points to the relevant regime to use moving dots in quantum information protocols.

  8. Cavity Exciton-Polariton mediated, Single-Shot Quantum Non-Demolition measurement of a Quantum Dot Electron Spin

    Science.gov (United States)

    Puri, Shruti; McMahon, Peter; Yamamoto, Yoshihisa

    2014-03-01

    The quantum non-demolition (QND) measurement of a single electron spin is of great importance in measurement-based quantum computing schemes. The current single-shot readout demonstrations exhibit substantial spin-flip backaction. We propose a QND readout scheme for quantum dot (QD) electron spins in Faraday geometry, which differs from previous proposals and implementations in that it relies on a novel physical mechanism: the spin-dependent Coulomb exchange interaction between a QD spin and optically-excited quantum well (QW) microcavity exciton-polaritons. The Coulomb exchange interaction causes a spin-dependent shift in the resonance energy of the polarized polaritons, thus causing the phase and intensity response of left circularly polarized light to be different to that of the right circularly polarized light. As a result the QD electron's spin can be inferred from the response to a linearly polarized probe. We show that by a careful design of the system, any spin-flip backaction can be eliminated and a QND measurement of the QD electron spin can be performed within a few 10's of nanoseconds with fidelity 99:95%. This improves upon current optical QD spin readout techniques across multiple metrics, including fidelity, speed and scalability. National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan.

  9. 1st International Conference on Opto-Electronics and Applied Optics

    CERN Document Server

    Bhattacharya, Indrani

    2015-01-01

    The Proceedings of First International Conference on Opto-Electronics and Applied Optics 2014, IEM OPTRONIX 2014 presents the research contributions presented in the conference by researchers from both India and abroad. Contributions from established scientists as well as students are included. The book is organized to enable easy access to various topics of interest.   The first part includes the Keynote addresses by Phillip Russell, Max Planck Institute of the Light Sciences, Erlangen, Germany and Lorenzo Pavesi, University of Trento, Italy.   The second part focuses on the Plenary Talks given by eminent scientists, namely, Azizur Rahman, City University London, London; Bishnu Pal, President, The Optical Society of India; Kamakhya Ghatak, National Institute of Technology, Agartala; Kehar Singh, Former Professor, India Institute of Technology Delhi; Mourad Zghal, SUPCOM, University of Carthage, Tunisia; Partha Roy Chaudhuri, IIT Kharagpur; S K. Bhadra, CSIR-Central Glass and Ceramic Research Institute, Kol...

  10. Nonplasmonic Hot-Electron Photocurrents from Mn-Doped Quantum Dots in Photoelectrochemical Cells.

    Science.gov (United States)

    Dong, Yitong; Rossi, Daniel; Parobek, David; Son, Dong Hee

    2016-03-03

    We report the measurement of the hot-electron current in a photoelectrochemical cell constructed from a glass/ITO/Al2 O3 (ITO=indium tin oxide) electrode coated with Mn-doped quantum dots, where hot electrons with a large excess kinetic energy were produced through upconversion of the excitons into hot electron hole pairs under photoexcitation at 3 eV. In our recent study (J. Am. Chem. Soc. 2015, 137, 5549), we demonstrated the generation of hot electrons in Mn-doped II-VI semiconductor quantum dots and their usefulness in photocatalytic H2 production reaction, taking advantage of the more efficient charge transfer of hot electrons compared with band-edge electrons. Here, we show that hot electrons produced in Mn-doped CdS/ZnS quantum dots possess sufficient kinetic energy to overcome the energy barrier from a 5.4-7.5 nm thick Al2 O3 layer producing a hot-electron current in photoelectrochemical cell. This work demonstrates the possibility of harvesting hot electrons not only at the interface of the doped quantum dot surface, but also far away from it, thus taking advantage of the capability of hot electrons for long-range electron transfer across a thick energy barrier. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Resonant tunneling diodes based on ZnO for quantum cascade structures (Conference Presentation)

    Science.gov (United States)

    Hinkov, Borislav; Schwarz, Benedikt; Harrer, Andreas; Ristanic, Daniela; Schrenk, Werner; Hugues, Maxime; Chauveau, Jean-Michel; Strasser, Gottfried

    2017-02-01

    The terahertz (THz) spectral range (lambda 30µm - 300µm) is also known as the "THz-gap" because of the lack of compact semiconductor devices. Various real-world applications would strongly benefit from such sources like trace-gas spectroscopy or security-screening. A crucial step is the operation of THz-emitting lasers at room temperature. But this seems out of reach with current devices, of which GaAs-based quantum cascade lasers (QCLs) seem to be the most promising ones. They are limited by the parasitic, non-optical LO-phonon transitions (36meV in GaAs), being on the same order as the thermal energy at room temperature (kT = 26meV). This can be solved by using larger LO-phonon materials like ZnO (E_LO = 72meV). But to master the fabrication of ZnO-based QC structures, a high quality epitaxial growth is crucial followed by a well-controlled fabrication process including ZnO/ZnMgO etching. We use devices grown on m-plane ZnO-substrate by molecular beam epitaxy. They are patterned by reactive ion etching in a CH4-based chemistry (CH4:H2:Ar/30:3:3 sccm) into 50μm to 150μm square mesas. Resonant tunneling diode structures are investigated in this geometry and are presented including different barrier- and well-configurations. We extract contact resistances of 8e-5 Omega cm^2 for un-annealed Ti/Au contacts and an electron mobility of above 130cm^2/Vs, both in good agreement with literature. Proving that resonant electron tunneling can be achieved in ZnO is one of the crucial building blocks of a QCL. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 665107.

  12. Enhanced carrier collection efficiency and reduced quantum state absorption by electron doping in self-assembled quantum dot solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tian, E-mail: tianlee@umd.edu, E-mail: dage@ece.umd.edu; Dagenais, Mario, E-mail: tianlee@umd.edu, E-mail: dage@ece.umd.edu [Department of Electrical Engineering, University of Maryland, College Park, Maryland 20742 (United States); Lu, Haofeng; Fu, Lan; Tan, Hark Hoe; Jagadish, Chennupati [Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia)

    2015-02-02

    Reduced quantum dot (QD) absorption due to state filling effects and enhanced electron transport in doped QDs are demonstrated to play a key role in solar energy conversion. Reduced QD state absorption with increased n-doping is observed in the self-assembled In{sub 0.5}Ga{sub 0.5}As/GaAs QDs from high resolution below-bandgap external quantum efficiency (EQE) measurement, which is a direct consequence of the Pauli exclusion principle. We also show that besides partial filling of the quantum states, electron-doping produces negatively charged QDs that exert a repulsive Coulomb force on the mobile electrons, thus altering the electron trajectory and reducing the probability of electron capture, leading to an improved collection efficiency of photo-generated carriers, as indicated by an absolute above-bandgap EQE measurement. The resulting redistribution of the mobile electron in the planar direction is further validated by the observed photoluminescence intensity dependence on doping.

  13. Repetitive readout of a single electronic spin via quantum logic with nuclear spin ancillae.

    Science.gov (United States)

    Jiang, L; Hodges, J S; Maze, J R; Maurer, P; Taylor, J M; Cory, D G; Hemmer, P R; Walsworth, R L; Yacoby, A; Zibrov, A S; Lukin, M D

    2009-10-09

    Robust measurement of single quantum bits plays a key role in the realization of quantum computation and communication as well as in quantum metrology and sensing. We have implemented a method for the improved readout of single electronic spin qubits in solid-state systems. The method makes use of quantum logic operations on a system consisting of a single electronic spin and several proximal nuclear spin ancillae in order to repetitively readout the state of the electronic spin. Using coherent manipulation of a single nitrogen vacancy center in room-temperature diamond, full quantum control of an electronic-nuclear system consisting of up to three spins was achieved. We took advantage of a single nuclear-spin memory in order to obtain a 10-fold enhancement in the signal amplitude of the electronic spin readout. We also present a two-level, concatenated procedure to improve the readout by use of a pair of nuclear spin ancillae, an important step toward the realization of robust quantum information processors using electronic- and nuclear-spin qubits. Our technique can be used to improve the sensitivity and speed of spin-based nanoscale diamond magnetometers.

  14. Quantum-classical transition in the electron dynamics of thin metal films

    Energy Technology Data Exchange (ETDEWEB)

    Jasiak, R; Manfredi, G; Hervieux, P-A [Institut de Physique et Chimie des Materiaux, CNRS and Universite de Strasbourg, BP 43, F-67034 Strasbourg (France); Haefele, M [INRIA Nancy Grand-Est and Institut de Recherche en Mathematiques Avancees, 7 rue Rene Descartes, F-67084 Strasbourg (France)], E-mail: Giovanni.Manfredi@ipcms.u-strasbg.fr

    2009-06-15

    The quantum electrons dynamics in a thin metal film is studied numerically using the self-consistent Wigner-Poisson equations. The initial equilibrium is computed from the Kohn-Sham equations at finite temperature, and then mapped into the phase-space Wigner function. The time-dependent results are compared systematically with those obtained previously with a classical approach (Vlasov-Poisson equations). It is found that, for large excitations, the quantum and classical dynamics display the same low-frequency oscillations due to ballistic electrons bouncing back and forth on the film surfaces. However, below a certain excitation energy (roughly corresponding to one quantum of plasmon energy {Dirac_h}{omega}{sub p}), the quantum and classical results diverge, and the ballistic oscillations are no longer observed. These results provide an example of a quantum-classical transition that may be observed with current pump-probe experiments on thin metal films.

  15. Quantum-classical transition in the electron dynamics of thin metal films

    International Nuclear Information System (INIS)

    Jasiak, R; Manfredi, G; Hervieux, P-A; Haefele, M

    2009-01-01

    The quantum electrons dynamics in a thin metal film is studied numerically using the self-consistent Wigner-Poisson equations. The initial equilibrium is computed from the Kohn-Sham equations at finite temperature, and then mapped into the phase-space Wigner function. The time-dependent results are compared systematically with those obtained previously with a classical approach (Vlasov-Poisson equations). It is found that, for large excitations, the quantum and classical dynamics display the same low-frequency oscillations due to ballistic electrons bouncing back and forth on the film surfaces. However, below a certain excitation energy (roughly corresponding to one quantum of plasmon energy ℎω p ), the quantum and classical results diverge, and the ballistic oscillations are no longer observed. These results provide an example of a quantum-classical transition that may be observed with current pump-probe experiments on thin metal films.

  16. Assessing the quantum physics impacts on future x-ray free-electron lasers

    Energy Technology Data Exchange (ETDEWEB)

    Schmitt, Mark J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Anisimov, Petr Mikhaylovich [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-10-06

    A new quantum mechanical theory of x-ray free electron lasers (XFELs) has been successfully developed that has placed LANL at the forefront of the understanding of quantum effects in XFELs. Our quantum theory describes the interaction of relativistic electrons with x-ray radiation in the periodic magnetic field of an undulator using the same mathematical formalism as classical XFEL theory. This places classical and quantum treatments on the same footing and allows for a continuous transition from one regime to the other eliminating the disparate analytical approaches previously used. Moreover, Dr. Anisimov, the architect of this new theory, is now considered a resource in the international FEL community for assessing quantum effects in XFELs.

  17. Time-resolved electron transport in quantum-dot systems; Zeitaufgeloester Elektronentransport in Quantendotsystemen

    Energy Technology Data Exchange (ETDEWEB)

    Croy, Alexander

    2010-06-30

    In this thesis the time-resolved electron transport in quantum dot systems was studied. For this two different formalisms were presented: The nonequilibrium Green functions and the generalized quantum master equations. For both formalisms a propagation method for the numerical calculation of time-resolved expectation values, like the occupation and the electron current, was developed. For the demonstration of the propagation method two different question formulations were considered. On the one hand the stochastically driven resonant-level model was studied. On the other hand the pulse-induced transport through a double quantum dot was considered.

  18. Relativistic quantum dynamics in strong fields: Photon emission from heavy, few-electron ions

    International Nuclear Information System (INIS)

    Fritzsche, S.; Stoehlker, T.

    2005-03-01

    Recent progress in the study of the photon emission from highly-charged heavy ions is reviewed. These investigations show that high-Z ions provide a unique tool for improving the understanding of the electron-electron and electron-photon interaction in the presence of strong fields. Apart from the bound-state transitions, which are accurately described in the framework of quantum electrodynamics, much information has been obtained also from the radiative capture of (quasi-) free electrons by high-Z ions. Many features in the observed spectra hereby confirm the inherently relativistic behavior of even the simplest compound quantum systems in nature. (orig.)

  19. Current correlations for the transport of interacting electrons through parallel quantum dots in a photon cavity

    Science.gov (United States)

    Gudmundsson, Vidar; Abdullah, Nzar Rauf; Sitek, Anna; Goan, Hsi-Sheng; Tang, Chi-Shung; Manolescu, Andrei

    2018-06-01

    We calculate the current correlations for the steady-state electron transport through multi-level parallel quantum dots embedded in a short quantum wire, that is placed in a non-perfect photon cavity. We account for the electron-electron Coulomb interaction, and the para- and diamagnetic electron-photon interactions with a stepwise scheme of configuration interactions and truncation of the many-body Fock spaces. In the spectral density of the temporal current-current correlations we identify all the transitions, radiative and non-radiative, active in the system in order to maintain the steady state. We observe strong signs of two types of Rabi oscillations.

  20. Electron-phonon thermalization in a scalable method for real-time quantum dynamics

    Science.gov (United States)

    Rizzi, Valerio; Todorov, Tchavdar N.; Kohanoff, Jorge J.; Correa, Alfredo A.

    2016-01-01

    We present a quantum simulation method that follows the dynamics of out-of-equilibrium many-body systems of electrons and oscillators in real time. Its cost is linear in the number of oscillators and it can probe time scales from attoseconds to hundreds of picoseconds. Contrary to Ehrenfest dynamics, it can thermalize starting from a variety of initial conditions, including electronic population inversion. While an electronic temperature can be defined in terms of a nonequilibrium entropy, a Fermi-Dirac distribution in general emerges only after thermalization. These results can be used to construct a kinetic model of electron-phonon equilibration based on the explicit quantum dynamics.

  1. Controlling the thermoelectric effect by mechanical manipulation of the electron's quantum phase in atomic junctions.

    Science.gov (United States)

    Aiba, Akira; Demir, Firuz; Kaneko, Satoshi; Fujii, Shintaro; Nishino, Tomoaki; Tsukagoshi, Kazuhito; Saffarzadeh, Alireza; Kirczenow, George; Kiguchi, Manabu

    2017-08-11

    The thermoelectric voltage developed across an atomic metal junction (i.e., a nanostructure in which one or a few atoms connect two metal electrodes) in response to a temperature difference between the electrodes, results from the quantum interference of electrons that pass through the junction multiple times after being scattered by the surrounding defects. Here we report successfully tuning this quantum interference and thus controlling the magnitude and sign of the thermoelectric voltage by applying a mechanical force that deforms the junction. The observed switching of the thermoelectric voltage is reversible and can be cycled many times. Our ab initio and semi-empirical calculations elucidate the detailed mechanism by which the quantum interference is tuned. We show that the applied strain alters the quantum phases of electrons passing through the narrowest part of the junction and hence modifies the electronic quantum interference in the device. Tuning the quantum interference causes the energies of electronic transport resonances to shift, which affects the thermoelectric voltage. These experimental and theoretical studies reveal that Au atomic junctions can be made to exhibit both positive and negative thermoelectric voltages on demand, and demonstrate the importance and tunability of the quantum interference effect in the atomic-scale metal nanostructures.

  2. Electroluminescence Caused by the Transport of Interacting Electrons through Parallel Quantum Dots in a Photon Cavity

    Science.gov (United States)

    Gudmundsson, Vidar; Abdulla, Nzar Rauf; Sitek, Anna; Goan, Hsi-Sheng; Tang, Chi-Shung; Manolescu, Andrei

    2018-02-01

    We show that a Rabi-splitting of the states of strongly interacting electrons in parallel quantum dots embedded in a short quantum wire placed in a photon cavity can be produced by either the para- or the dia-magnetic electron-photon interactions when the geometry of the system is properly accounted for and the photon field is tuned close to a resonance with the electron system. We use these two resonances to explore the electroluminescence caused by the transport of electrons through the one- and two-electron ground states of the system and their corresponding conventional and vacuum electroluminescense as the central system is opened up by coupling it to external leads acting as electron reservoirs. Our analysis indicates that high-order electron-photon processes are necessary to adequately construct the cavity-photon dressed electron states needed to describe both types of electroluminescence.

  3. Dynamical localization of two electrons in triple-quantum-dot shuttles

    International Nuclear Information System (INIS)

    Qu, Jinxian; Duan, Suqing; Yang, Ning

    2012-01-01

    The dynamical localization phenomena in two-electron quantum-dot shuttles driven by an ac field have been investigated and analyzed by the Floquet theory. The dynamical localization occurs near the anti-crossings in Floquet eigenenergy spectrum. The oscillation of the quantum-dot shuttles may increase the possibility of the dynamical localization. Especially, even if the two electrons are initialized in two neighbor dots, they can be localized there for appropriate intensity of the driven field. The studies may help the understanding of dynamical localization in electron shuttles and expand the application potential of nanoelectromechanical devices. -- Highlights: ► The dynamical localization in electron shuttle is studied by Floquet theory. ► There is a relation between quasi-energy anti-crossings and dynamical localization. ► The oscillation of quantum dot increases the dynamical localization. ► Even the electrons are initialized in different dots, the localization can occur.

  4. Electrical Initialization of Electron and Nuclear Spins in a Single Quantum Dot at Zero Magnetic Field.

    Science.gov (United States)

    Cadiz, Fabian; Djeffal, Abdelhak; Lagarde, Delphine; Balocchi, Andrea; Tao, Bingshan; Xu, Bo; Liang, Shiheng; Stoffel, Mathieu; Devaux, Xavier; Jaffres, Henri; George, Jean-Marie; Hehn, Michel; Mangin, Stephane; Carrere, Helene; Marie, Xavier; Amand, Thierry; Han, Xiufeng; Wang, Zhanguo; Urbaszek, Bernhard; Lu, Yuan; Renucci, Pierre

    2018-04-11

    The emission of circularly polarized light from a single quantum dot relies on the injection of carriers with well-defined spin polarization. Here we demonstrate single dot electroluminescence (EL) with a circular polarization degree up to 35% at zero applied magnetic field. The injection of spin-polarized electrons is achieved by combining ultrathin CoFeB electrodes on top of a spin-LED device with p-type InGaAs quantum dots in the active region. We measure an Overhauser shift of several microelectronvolts at zero magnetic field for the positively charged exciton (trion X + ) EL emission, which changes sign as we reverse the injected electron spin orientation. This is a signature of dynamic polarization of the nuclear spins in the quantum dot induced by the hyperfine interaction with the electrically injected electron spin. This study paves the way for electrical control of nuclear spin polarization in a single quantum dot without any external magnetic field.

  5. Two-dimensional electron gas in monolayer InN quantum wells

    International Nuclear Information System (INIS)

    Pan, W.; Wang, G. T.; Dimakis, E.; Moustakas, T. D.; Tsui, D. C.

    2014-01-01

    We report in this letter experimental results that confirm the two-dimensional nature of the electron systems in a superlattice structure of 40 InN quantum wells consisting of one monolayer of InN embedded between 10 nm GaN barriers. The electron density and mobility of the two-dimensional electron system (2DES) in these InN quantum wells are 5 × 10 15  cm −2 (or 1.25 × 10 14  cm −2 per InN quantum well, assuming all the quantum wells are connected by diffused indium contacts) and 420 cm 2 /Vs, respectively. Moreover, the diagonal resistance of the 2DES shows virtually no temperature dependence in a wide temperature range, indicating the topological nature of the 2DES

  6. Quantum theory for 1D X-ray free electron laser

    Science.gov (United States)

    Anisimov, Petr M.

    2018-06-01

    Classical 1D X-ray Free Electron Laser (X-ray FEL) theory has stood the test of time by guiding FEL design and development prior to any full-scale analysis. Future X-ray FELs and inverse-Compton sources, where photon recoil approaches an electron energy spread value, push the classical theory to its limits of applicability. After substantial efforts by the community to find what those limits are, there is no universally agreed upon quantum approach to design and development of future X-ray sources. We offer a new approach to formulate the quantum theory for 1D X-ray FELs that has an obvious connection to the classical theory, which allows for immediate transfer of knowledge between the two regimes. We exploit this connection in order to draw quantum mechanical conclusions about the quantum nature of electrons and generated radiation in terms of FEL variables.

  7. Single-shot quantum nondemolition measurement of a quantum-dot electron spin using cavity exciton-polaritons

    Science.gov (United States)

    Puri, Shruti; McMahon, Peter L.; Yamamoto, Yoshihisa

    2014-10-01

    We propose a scheme to perform single-shot quantum nondemolition (QND) readout of the spin of an electron trapped in a semiconductor quantum dot (QD). Our proposal relies on the interaction of the QD electron spin with optically excited, quantum well (QW) microcavity exciton-polaritons. The spin-dependent Coulomb exchange interaction between the QD electron and cavity polaritons causes the phase and intensity response of left circularly polarized light to be different than that of right circularly polarized light, in such a way that the QD electron's spin can be inferred from the response to a linearly polarized probe reflected or transmitted from the cavity. We show that with careful device design it is possible to essentially eliminate spin-flip Raman transitions. Thus a QND measurement of the QD electron spin can be performed within a few tens of nanoseconds with fidelity ˜99.95%. This improves upon current optical QD spin readout techniques across multiple metrics, including speed and scalability.

  8. Coupled quantum-classical method for long range charge transfer: relevance of the nuclear motion to the quantum electron dynamics

    International Nuclear Information System (INIS)

    Da Silva, Robson; Hoff, Diego A; Rego, Luis G C

    2015-01-01

    Charge and excitonic-energy transfer phenomena are fundamental for energy conversion in solar cells as well as artificial photosynthesis. Currently, much interest is being paid to light-harvesting and energy transduction processes in supramolecular structures, where nuclear dynamics has a major influence on electronic quantum dynamics. For this reason, the simulation of long range electron transfer in supramolecular structures, under environmental conditions described within an atomistic framework, has been a difficult problem to study. This work describes a coupled quantum mechanics/molecular mechanics method that aims at describing long range charge transfer processes in supramolecular systems, taking into account the atomistic details of large molecular structures, the underlying nuclear motion, and environmental effects. The method is applied to investigate the relevance of electron–nuclei interaction on the mechanisms for photo-induced electron–hole pair separation in dye-sensitized interfaces as well as electronic dynamics in molecular structures. (paper)

  9. Symposium on quantum electronics. Extended abstracts of contributed papers

    Energy Technology Data Exchange (ETDEWEB)

    1981-02-01

    Extended abstracts are provided for papers presented in these subject areas: lasers; quantum optics; nonlinear optics; laser photochemistry; laser spectroscopy; laser scattering; laser produced plasma; and laser applications. (GHT)

  10. Jahn-Teller effect in molecular electronics: quantum cellular automata

    Science.gov (United States)

    Tsukerblat, B.; Palii, A.; Clemente-Juan, J. M.; Coronado, E.

    2017-05-01

    The article summarizes the main results of application of the theory of the Jahn-Teller (JT) and pseudo JT effects to the description of molecular quantum dot cellular automata (QCA), a new paradigm of quantum computing. The following issues are discussed: 1) QCA as a new paradigm of quantum computing, principles and advantages; 2) molecular implementation of QCA; 3) role of the JT effect in charge trapping, encoding of binary information in the quantum cell and non-linear cell-cell response; 4) spin-switching in molecular QCA based on mixed-valence cell; 5) intervalence optical absorption in tetrameric molecular mixed-valence cell through the symmetry assisted approach to the multimode/multilevel JT and pseudo JT problems.

  11. International Conference on Microtechnology and Thermal Problems in Electronics (MicroTherm'2015) and International Conference on Smart Engineering of New Materials (SENM'2015)

    International Nuclear Information System (INIS)

    2016-01-01

    The issue covers selected papers presented during the Joint Event of two International Cyclic Conferences: MicroTherm – Microtechnology and Thermal Problems in Electronics and SENM – Smart Engineering of New Materials. The Duoconference was held in Lodz, Poland on 23-25 June 2015. It gathered almost 200 participants from 20 countries. MicroTherm is an International Conference on Microtechnology and Thermal Problems in Electronics that is organised every two years, since 1996. The success of the first seminar devoted to thermal management aspects, and the successive conferences have led us to the eleventh edition. Since the first meeting, the scope of the Conference has expanded, following the progress of electronics. Now, it covers subjects connected with extreme temperature, electronics, sensors and measurement techniques, modelling, simulation, wide band-gap materials, packaging and reliability, renewable energy sources and photonics with special emphasis on microelectronic technologies. The tradition of SENM dates back to 1985 when the First International Conference on Diamond Crystallization under Reduced Pressure was held in Jabłonna, Poland. Since then, the Conference is organised regularly every five years. From the early beginning the main aim of this event was the creation of an international forum of scientists for the presentation of the newest achievements and investigation results in vacuum and plasma techniques, synthesis, characterisation and application of diamond, its derivatives and other wide bandgap materials. Over time, the scope of the conference has expanded to include nanomaterials, biomaterials and new functional materials, in the range of production, design and optimisation of the synthesis and modification technologies. Traditionally, the programme of MicroTherm’2015 and SENM’2015 is comprised of invited talks and regular sessions in the form of planar discussions and poster presentations, which also include a Students’ Session

  12. Recombination kinetics of photogenerated electrons in InGaAs/InP quantum wells

    Science.gov (United States)

    Tito, M. A.; Pusep, Yu. A.; Gold, A.; Teodoro, M. D.; Marques, G. E.; LaPierre, R. R.

    2016-03-01

    The electron transport and recombination processes of photoexcited electron-hole pairs were studied in InGaAs/InP single quantum wells. Comprehensive transport data analysis reveals a asymmetric shape of the quantum well potential where the electron mobility was found to be dominated by interface-roughness scattering. The low-temperature time-resolved photoluminescence was employed to investigate recombination kinetics of photogenerated electrons. Remarkable modification of Auger recombination was observed with variation of the electron mobility. In high mobility quantum wells, the increasing pump power resulted in a new and unexpected phenomenon: a considerably enhanced Auger non-radiative recombination time. We propose that the distribution of the photoexcited electrons over different conduction band valleys might account for this effect. In low mobility quantum wells, disorder-induced relaxation of the momentum conservation rule causes inter-valley transitions to be insignificant; as a consequence, the non-radiative recombination time is reduced with the increase in pump power. Thus, interface-roughness scattering was found responsible for both transport properties and dynamic optical response in InGaAs/InP quantum wells.

  13. Physics at the FQMT'11 conference

    NARCIS (Netherlands)

    Špička, V.; Nieuwenhuizen, T.M.; Keefe, P.D.

    2012-01-01

    This paper deals with the recent state of the art of the following topics presented at the FQMT’11 conference: foundations of quantum physics, quantum measurement; nonequilibrium quantum statistical physics; quantum thermodynamics; quantum measurement, entanglement and coherence; dissipation,

  14. Two-electrons quantum dot in plasmas under the external fields

    Science.gov (United States)

    Bahar, M. K.; Soylu, A.

    2018-02-01

    In this study, for the first time, the combined effects of the external electric field, magnetic field, and confinement frequency on energies of two-electron parabolic quantum dots in Debye and quantum plasmas modeled by more general exponential cosine screened Coulomb (MGECSC) potential are investigated by numerically solving the Schrödinger equation using the asymptotic iteration method. The MGECSC potential includes four different potential forms when considering different sets of the parameters in potential. Since the plasma is an important experimental argument for quantum dots, the influence of plasmas modeled by the MGECSC potential on quantum dots is probed. The confinement frequency of quantum dots and the external fields created significant quantum restrictions on quantum dot. In this study, as well as discussion of the functionalities of the quantum restrictions for experimental applications, the parameters are also compared with each other in terms of influence and behaviour. In this manner, the motivation points of this study are summarized as follows: Which parameter can be alternative to which parameter, in terms of experimental applications? Which parameters exhibit similar behaviour? What is the role of plasmas on the corresponding behaviours? In the light of these research studies, it can be said that obtained results and performed discussions would be important in experimental and theoretical research related to plasma physics and/or quantum dots.

  15. Broadening of Plasmonic Resonance Due to Electron Collisions with Nanoparticle Boundary: а Quantum Mechanical Consideration

    DEFF Research Database (Denmark)

    Uskov, Alexander; Protsenko, Igor E.; Mortensen, N. Asger

    2014-01-01

    We present a quantum mechanical approach to calculate broadening of plasmonic resonances in metallic nanostructures due to collisions of electrons with the surface of the structure. The approach is applicable if the characteristic size of the structure is much larger than the de Broglie electron...

  16. Relaxation of the electron spin in quantum dots via one- and two-phonon processes

    International Nuclear Information System (INIS)

    Calero, C.; Chudnovsky, E.M.; Garanin, D.A.

    2007-01-01

    We have studied direct and Raman processes of the decay of electron spin states in a quantum dot via radiation of phonons corresponding to elastic twists. Universal dependence of the spin relaxation rate on the strength and direction of the magnetic field has been obtained in terms of the electron gyromagnetic tensor and macroscopic elastic constants of the solid

  17. Relaxation of the electron spin in quantum dots via one- and two-phonon processes

    Energy Technology Data Exchange (ETDEWEB)

    Calero, C. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States)]. E-mail: carlos.calero-borrallo@lehman.cuny.edu; Chudnovsky, E.M. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States); Garanin, D.A. [Department of Physics and Astronomy, Lehman College, City University of New York, 250 Bedford Park Boulevard West, Bronx, NY 10468-1589 (United States)

    2007-09-15

    We have studied direct and Raman processes of the decay of electron spin states in a quantum dot via radiation of phonons corresponding to elastic twists. Universal dependence of the spin relaxation rate on the strength and direction of the magnetic field has been obtained in terms of the electron gyromagnetic tensor and macroscopic elastic constants of the solid.

  18. Self-consistent electronic structure of spin-polarized dilute magnetic semiconductor quantum wells

    International Nuclear Information System (INIS)

    Hong, S. P.; Yi, K. S.; Quinn, J. J.

    2000-01-01

    The electronic properties of spin-symmetry-broken dilute magnetic semiconductor quantum wells are investigated self-consistently at zero temperature. The spin-split subband structure and carrier concentration of modulation-doped quantum wells are examined in the presence of a strong magnetic field. The effects of exchange and correlations of electrons are included in a local-spin-density-functional approximation. We demonstrate that exchange correlation of electrons decreases the spin-split subband energy but enhances the carrier density in a spin-polarized quantum well. We also observe that as the magnetic field increases, the concentration of spin-down (majority) electrons increases but that of spin-up (minority) electrons decreases. The effect of orbital quantization on the in-plane motion of electrons is also examined and shows a sawtoothlike variation in subband electron concentrations as the magnetic-field intensity increases. The latter variation is attributed to the presence of ionized donors acting as the electron reservoir, which is partially responsible for the formation of the integer quantum Hall plateaus. (c) 2000 The American Physical Society

  19. Quantum computers based on electron spins controlled by ultrafast off-resonant single optical pulses.

    Science.gov (United States)

    Clark, Susan M; Fu, Kai-Mei C; Ladd, Thaddeus D; Yamamoto, Yoshihisa

    2007-07-27

    We describe a fast quantum computer based on optically controlled electron spins in charged quantum dots that are coupled to microcavities. This scheme uses broadband optical pulses to rotate electron spins and provide the clock signal to the system. Nonlocal two-qubit gates are performed by phase shifts induced by electron spins on laser pulses propagating along a shared waveguide. Numerical simulations of this scheme demonstrate high-fidelity single-qubit and two-qubit gates with operation times comparable to the inverse Zeeman frequency.

  20. Hot electron and real space transfer in double-quantum-well structures

    International Nuclear Information System (INIS)

    Okuno, Eiichi; Sawaki, Nobuhiko; Akasaki, Isamu; Kano, Hiroyuki; Hashimoto, Masafumi.

    1991-01-01

    The hot electron phenomena and real space transfer (RST) effect are studied in GaAs/AlGaAs double-quantum-well (DQW) structures, in which we have two kind of quantum wells with different widths. The drift velocity and the electron temperature at liquid helium temperature are investigated as a function of the external electric field applied parallel to the heterointerface. By increasing the field, the electron temperature rises and reaches a plateau in the intermediate region, followed by further rise in the high-field region. The appearance of the plateau is attributed to the RST effect between the two quantum wells. The threshold field for the appearance of the plateau is determined by the difference energy between the quantized levels in two wells. The energy loss rate as a function of the electron temperature indicates that the RST is assisted by LO phonon scattering. (author)

  1. Stabilization of the Electron-Nuclear Spin Orientation in Quantum Dots by the Nuclear Quadrupole Interaction

    Science.gov (United States)

    Dzhioev, R. I.; Korenev, V. L.

    2007-07-01

    The nuclear quadrupole interaction eliminates the restrictions imposed by hyperfine interaction on the spin coherence of an electron and nuclei in a quantum dot. The strain-induced nuclear quadrupole interaction suppresses the nuclear spin flip and makes possible the zero-field dynamic nuclear polarization in self-organized InP/InGaP quantum dots. The direction of the effective nuclear magnetic field is fixed in space, thus quenching the magnetic depolarization of the electron spin in the quantum dot. The quadrupole interaction suppresses the zero-field electron spin decoherence also for the case of nonpolarized nuclei. These results provide a new vision of the role of the nuclear quadrupole interaction in nanostructures: it elongates the spin memory of the electron-nuclear system.

  2. Excitons formed from spatially separated electrons and holes in Ge/Si geterostructures with Ge quantum dots

    International Nuclear Information System (INIS)

    Pokutnyj, S.I.

    2016-01-01

    The effect of a significant increase in the exciton binding energy of space-separated electrons and holes (hole moves in the volume of the quantum dot, and the electron is localized on a spherical surface section quantum dot-matrix) in nanosystems containing germanium quantum dots grown in a matrix of silicon by compared with the binding energy of an exciton in a silicon single crystal. It was found that in such nanosystems in the conduction band silicon matrix is first a zone of states of electron-hole pairs, which with increasing radius of the quantum dot becomes a zone of exciton states, located in the band gap of silicon matrix. It is shown that the mechanism of light absorption in nanosystems due to transitions between quantum-electron levels of the electron-hole pairs, as well as the electron transitions between quantum-exciton levels.

  3. Quantum well electronic states in a tilted magnetic field.

    Science.gov (United States)

    Trallero-Giner, C; Padilha, J X; Lopez-Richard, V; Marques, G E; Castelano, L K

    2017-08-16

    We report the energy spectrum and the eigenstates of conduction and uncoupled valence bands of a quantum well under the influence of a tilted magnetic field. In the framework of the envelope approximation, we implement two analytical approaches to obtain the nontrivial solutions of the tilted magnetic field: (a) the Bubnov-Galerkin spectral method and b) the perturbation theory. We discuss the validity of each method for a broad range of magnetic field intensity and orientation as well as quantum well thickness. By estimating the accuracy of the perturbation method, we provide explicit analytical solutions for quantum wells in a tilted magnetic field configuration that can be employed to study several quantitative phenomena.

  4. Research Area 4.1 Nano- and Bio-Electronics: Lester Eastman Conference on High-Performance Devices

    Science.gov (United States)

    2017-06-02

    significantly lower. Moreover, wells containing MoS2 on the polyimide film had a large amount of cells growing on the material, further indicating high ...SECURITY CLASSIFICATION OF: 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND SUBTITLE 13. SUPPLEMENTARY NOTES 12. DISTRIBUTION AVAILIBILITY STATEMENT 6...Research Area 4.1 Nano- and Bio-Electronics: Lester Eastman Conference on High -Performance Devices The 2016 IEEE Lester Eastman Conference of High

  5. Controllable continuous evolution of electronic states in a single quantum ring

    Science.gov (United States)

    Chakraborty, Tapash; Manaselyan, Aram; Barseghyan, Manuk; Laroze, David

    2018-02-01

    An intense terahertz laser field is shown to have a profound effect on the electronic and optical properties of quantum rings where the isotropic and anisotropic quantum rings can now be treated on equal footing. We have demonstrated that in isotropic quantum rings the laser field creates unusual Aharonov-Bohm oscillations that are usually expected in anisotropic rings. Furthermore, we have shown that intense laser fields can restore the isotropic physical properties in anisotropic quantum rings. In principle, all types of anisotropies (structural, effective masses, defects, etc.) can evolve as in isotropic rings in our present approach. Most importantly, we have found a continuous evolution of the energy spectra and intraband optical characteristics of structurally anisotropic quantum rings to those of isotropic rings in a controlled manner with the help of a laser field.

  6. Quantum effects on the formation of negative hydrogen ion by polarization electron capture in partially ionized dense hydrogen plasmas

    International Nuclear Information System (INIS)

    Jung, Young-Dae; Kato, Daiji

    2009-05-01

    The quantum effects on the formation of the negative hydrogen ion (H - ) by the polarization electron capture process are investigated in partially ionized dense hydrogen plasmas. It is shown that the quantum effect strongly suppresses the electron capture radius as well as the cross section for the formation of the negative hydrogen ion. In addition, it has been found that the electron capture position is receded from the center of the projectile with decreasing the quantum effect of the plasma. (author)

  7. Theses of reports of International Conference 'Physics of the condensed matter state at low temperatures'

    International Nuclear Information System (INIS)

    Neklyudov, I.M.

    2006-01-01

    The main topics of this conference deal with: fundamental base of superconductivity; superconductors with high critical parameters and applied superconductivity; quantum phenomena in condensed media; physics of strength and plasticity; electronic and magnetic properties of metals

  8. Electronic structures of GaAs/AlxGa1-xAs quantum double rings

    Directory of Open Access Journals (Sweden)

    Li Shu-Shen

    2006-01-01

    Full Text Available AbstractIn the framework of effective mass envelope function theory, the electronic structures of GaAs/AlxGa1-xAs quantum double rings (QDRs are studied. Our model can be used to calculate the electronic structures of quantum wells, wires, dots, and the single ring. In calculations, the effects due to the different effective masses of electrons and holes in GaAs and AlxGa1-xAs and the valence band mixing are considered. The energy levels of electrons and holes are calculated for different shapes of QDRs. The calculated results are useful in designing and fabricating the interrelated photoelectric devices. The single electron states presented here are useful for the study of the electron correlations and the effects of magnetic fields in QDRs.

  9. Book of abstracts of 13. national conference on nuclear structure and 9. symposium on 'nuclear structure and quantum mechanics'

    International Nuclear Information System (INIS)

    2010-07-01

    13. national conference on nuclear structure and 9. symposium on 'nuclear structure and quantum mechanics' was held by China Nuclear Physics Society in Chifeng, 25 to 30 July, 2010. The proceedings collects the abstracts of 102 articles

  10. Relaxation of electron energy in the polar semiconductor double quantum dots

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Khás, Zdeněk; Zdeněk, Petr; Čerňanský, Marian; Lin, C. Y.

    2002-01-01

    Roč. 314, - (2002), s. 490-493 ISSN 0921-4526 R&D Projects: GA AV ČR IAA1010113; GA MŠk OC P5.20 Institutional research plan: CEZ:AV0Z1010914 Keywords : quantum dots * relaxation * double quantum dots * electron-photon interaction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.609, year: 2002

  11. Chaos in Dirac electron optics: Emergence of a relativistic quantum chimera

    OpenAIRE

    Xu, Hong-Ya; Wang, Guang-Lei; Huang, Liang; Lai, Ying-Cheng

    2018-01-01

    We uncover a remarkable quantum scattering phenomenon in two-dimensional Dirac material systems where the manifestations of both classically integrable and chaotic dynamics emerge simultaneously and are electrically controllable. The distinct relativistic quantum fingerprints associated with different electron spin states are due to a physical mechanism analogous to chiroptical effect in the presence of degeneracy breaking. The phenomenon mimics a chimera state in classical complex dynamical ...

  12. Deep learning the quantum phase transitions in random two-dimensional electron systems

    International Nuclear Information System (INIS)

    Ohtsuki, Tomoki; Ohtsuki, Tomi

    2016-01-01

    Random electron systems show rich phases such as Anderson insulator, diffusive metal, quantum Hall and quantum anomalous Hall insulators, Weyl semimetal, as well as strong/weak topological insulators. Eigenfunctions of each matter phase have specific features, but owing to the random nature of systems, determining the matter phase from eigenfunctions is difficult. Here, we propose the deep learning algorithm to capture the features of eigenfunctions. Localization-delocalization transition, as well as disordered Chern insulator-Anderson insulator transition, is discussed. (author)

  13. Run-away electrons in relativistic spin (1) /(2) quantum electrodynamics

    International Nuclear Information System (INIS)

    Low, F.E.

    1998-01-01

    The existence of run-away solutions in classical and non-relativistic quantum electrodynamics is reviewed. It is shown that the less singular high energy behavior of relativistic spin (1) /(2) quantum electrodynamics precludes an analogous behavior in that theory. However, a Landau-like anomalous pole in the photon propagation function or in the electron-massive photon forward scattering amplitude would generate a new run-away, characterized by an energy scale ω∼m e thinspexp(1/α). This contrasts with the energy scale ω∼m e /α associated with the classical and non-relativistic quantum run-aways. copyright 1998 Academic Press, Inc

  14. Optical Pumping of the Electronic and Nuclear Spin of Single Charge-Tunable Quantum Dots

    Science.gov (United States)

    Bracker, A. S.; Stinaff, E. A.; Gammon, D.; Ware, M. E.; Tischler, J. G.; Shabaev, A.; Efros, Al. L.; Park, D.; Gershoni, D.; Korenev, V. L.; Merkulov, I. A.

    2005-02-01

    We present a comprehensive examination of optical pumping of spins in individual GaAs quantum dots as we change the net charge from positive to neutral to negative with a charge-tunable heterostructure. Negative photoluminescence polarization memory is enhanced by optical pumping of ground state electron spins, which we prove with the first measurements of the Hanle effect on an individual quantum dot. We use the Overhauser effect in a high longitudinal magnetic field to demonstrate efficient optical pumping of nuclear spins for all three charge states of the quantum dot.

  15. Hot electron dynamics at semiconductor surfaces: Implications for quantum dot photovoltaics

    Science.gov (United States)

    Tisdale, William A., III

    Finding a viable supply of clean, renewable energy is one of the most daunting challenges facing the world today. Solar cells have had limited impact in meeting this challenge because of their high cost and low power conversion efficiencies. Semiconductor nanocrystals, or quantum dots, are promising materials for use in novel solar cells because they can be processed with potentially inexpensive solution-based techniques and because they are predicted to have novel optoelectronic properties that could enable the realization of ultra-efficient solar power converters. However, there is a lack of fundamental understanding regarding the behavior of highly-excited, or "hot," charge carriers near quantum-dot and semiconductor interfaces, which is of paramount importance to the rational design of high-efficiency devices. The elucidation of these ultrafast hot electron dynamics is the central aim of this Dissertation. I present a theoretical framework for treating the electronic interactions between quantum dots and bulk semiconductor surfaces and propose a novel experimental technique, time-resolved surface second harmonic generation (TR-SHG), for probing these interactions. I then describe a series of experimental investigations into hot electron dynamics in specific quantum-dot/semiconductor systems. A two-photon photoelectron spectroscopy (2PPE) study of the technologically-relevant ZnO(1010) surface reveals ultrafast (sub-30fs) cooling of hot electrons in the bulk conduction band, which is due to strong electron-phonon coupling in this highly polar material. The presence of a continuum of defect states near the conduction band edge results in Fermi-level pinning and upward (n-type) band-bending at the (1010) surface and provides an alternate route for electronic relaxation. In monolayer films of colloidal PbSe quantum dots, chemical treatment with either hydrazine or 1,2-ethanedithiol results in strong and tunable electronic coupling between neighboring quantum dots

  16. Plexciton quenching by resonant electron transfer from quantum emitter to metallic nanoantenna.

    Science.gov (United States)

    Marinica, D C; Lourenço-Martins, H; Aizpurua, J; Borisov, A G

    2013-01-01

    Coupling molecular excitons and localized surface plasmons in hybrid nanostructures leads to appealing, tunable optical properties. In this respect, the knowledge about the excitation dynamics of a quantum emitter close to a plasmonic nanoantenna is of importance from fundamental and practical points of view. We address here the effect of the excited electron tunneling from the emitter into a metallic nanoparticle(s) in the optical response. When close to a plasmonic nanoparticle, the excited state localized on a quantum emitter becomes short-lived because of the electronic coupling with metal conduction band states. We show that as a consequence, the characteristic features associated with the quantum emitter disappear from the optical absorption spectrum. Thus, for the hybrid nanostructure studied here and comprising quantum emitter in the narrow gap of a plasmonic dimer nanoantenna, the quantum tunneling might quench the plexcitonic states. Under certain conditions the optical response of the system approaches that of the individual plasmonic dimer. Excitation decay via resonant electron transfer can play an important role in many situations of interest such as in surface-enhanced spectroscopies, photovoltaics, catalysis, or quantum information, among others.

  17. Propagation of a TE surface mode in a relativistic electron beam–quantum plasma system

    International Nuclear Information System (INIS)

    Abdel Aziz, M.

    2012-01-01

    The dispersion properties of a transverse electric (TE) surface waves propagating along the interface between a magneto-quantum plasma–relativistic beam system and vacuum are studied by using the quantum hydrodynamic model. The general dispersion relations are derived and analyzed in some special cases of interest. Moreover, the effects of density gradients for the beam and plasma on the dispersion properties of surface waves are investigated. The kind of dispersion relations depends strongly on the ambient magnetic field B o via the gyro-frequency ω c , the quantum parameters, and the width of the plasma layer as well as the relativistic factor for the electron beam. It is found that the quantum effects play a crucial role to facilitate the propagation of TE surface waves. -- Highlights: ► Propagation of TE surface waves on bounded magneto-quantum plasma by relativistic beam is studied. ► The quantum plasma consists of transitional layer adjacent to uniform layer. ► Influence of quantum effects on the propagation of TE surface waves are taken into account. ► Effects of homogeneity and inhomogeneity for beam on TE surface waves are considered. ► It is found that quantum effects facilitate the propagation of TE surface modes.

  18. Quantum-mechanical analysis of low-gain free-electron laser oscillators

    Science.gov (United States)

    Fares, H.; Yamada, M.; Chiadroni, E.; Ferrario, M.

    2018-05-01

    In the previous classical theory of the low-gain free-electron laser (FEL) oscillators, the electron is described as a point-like particle, a delta function in the spatial space. On the other hand, in the previous quantum treatments, the electron is described as a plane wave with a single momentum state, a delta function in the momentum space. In reality, an electron must have statistical uncertainties in the position and momentum domains. Then, the electron is neither a point-like charge nor a plane wave of a single momentum. In this paper, we rephrase the theory of the low-gain FEL where the interacting electron is represented quantum mechanically by a plane wave with a finite spreading length (i.e., a wave packet). Using the concepts of the transformation of reference frames and the statistical quantum mechanics, an expression for the single-pass radiation gain is derived. The spectral broadening of the radiation is expressed in terms of the spreading length of an electron, the relaxation time characterizing the energy spread of electrons, and the interaction time. We introduce a comparison between our results and those obtained in the already known classical analyses where a good agreement between both results is shown. While the correspondence between our results and the classical results are shown, novel insights into the electron dynamics and the interaction mechanism are presented.

  19. Peculiarities of resonant tunneling of electrons through the triply degenerate state of a quantum well

    International Nuclear Information System (INIS)

    Jermakov, V.M.

    1997-01-01

    In the case of low transparency of barriers, tunneling of electrons through a double barrier system with account their Coulomb interaction in the inter barrier space (quantum well) is considered. The quantum state of the well is supposed to be triply degenerated. It was shown that the dependence of quantum well accupation on the applied bias has a step like character at low temperatures, and there is a threshold value in the region of small applied bias. These properties can be explained by splitting of states in the well due to the electron interaction. The considered system also has bistability properties. This is due to the possibility for electrons to occupy upper levels in the well while lower levels remain empty. Charge fluctuations in the well are also discussed

  20. Signatures of quantum radiation reaction in laser-electron-beam collisions

    International Nuclear Information System (INIS)

    Wang, H. Y.; Yan, X. Q.; Zepf, M.

    2015-01-01

    Electron dynamics in the collision of an electron beam with a high-intensity focused ultrashort laser pulse are investigated using three-dimensional QED particle-in-cell (PIC) simulations, and the results are compared with those calculated by classical Landau and Lifshitz PIC simulations. Significant differences are observed from the angular dependence of the electron energy distribution patterns for the two different approaches, because photon emission is no longer well approximated by a continuous process in the quantum radiation-dominated regime. The stochastic nature of photon emission results in strong signatures of quantum radiation-reaction effects under certain conditions. We show that the laser spot size and duration greatly influence these signatures due to the competition of QED effects and the ponderomotive force, which is well described in the classical approximation. The clearest signatures of quantum radiation reaction are found in the limit of large laser spots and few cycle pulse durations

  1. Nonequilibrium Green function techniques applied to hot electron quantum transport

    International Nuclear Information System (INIS)

    Jauho, A.P.

    1989-01-01

    During the last few years considerable effort has been devoted to deriving quantum transport equations for semiconductors under extreme conditions (high electric fields, spatial quantization in one or two directions). Here we review the results obtained with nonequilibrium Green function techniques as formulated by Baym and Kadanoff, or by Keldysh. In particular, the following topics will be discussed: (i) Systematic approaches to reduce the transport equation governing the correlation function to a transport equation for the Wigner function; (ii) Approximations reducing the nonmarkovian quantum transport equation to a numerically tractable form, and results for model semiconductors; (iii) Recent progress in extending the formalism to inhomogeneous systems; and (iv) Nonequilibrium screening. In all sections we try to direct the reader's attention to points where the present understanding is (at best) incomplete, and indicate possible lines for future work. (orig.)

  2. The Strength of Chaos: Accurate Simulation of Resonant Electron Scattering by Many-Electron Ions and Atoms in the Presence of Quantum Chaos

    Science.gov (United States)

    2017-01-20

    AFRL-AFOSR-JP-TR-2017-0012 The Strength of Chaos : accurate simulation of resonant electron scattering by many-electron ions and atoms in the presence...of quantum chaos Igor Bray CURTIN UNIVERSITY OF TECHNOLOGY Final Report 01/20/2017 DISTRIBUTION A: Distribution approved for public release. AF...SUBTITLE The Strength of Chaos : accurate simulation of resonant electron scattering by many- electron ions and atoms in the presence of quantum chaos

  3. Electron and hole spectrum in InAs quantum dot renormalized by InAs/GaAs heterostructure deformation

    International Nuclear Information System (INIS)

    Dan'kiv, O.O.; Peleshchak, R.M.

    2005-01-01

    Analytical expressions describing the energy spectrum of electrons and holes are obtained for a quantum dot occurring in a self-consistent strain field created by an array of coherently stressed quantum dots. A method of taking into account the lattice mismatch at the quantum dot-matrix interface is proposed that allows for the dependence of the mismatch parameter on the quantum dot size and the matrix layer thickness. It is shown that the internal elastic strain arising at the quantum dot-matrix interface influences the energy spectrum of electrons more significantly than the spectrum of holes [ru

  4. The electron-nuclear spin system in (In,Ga)As quantum dots

    International Nuclear Information System (INIS)

    Auer, Thomas

    2008-01-01

    For a long time, the nuclear spins in quantum dots were virtually ignored. It was thought that the interaction strength was so small that the interaction between the nuclei and electrons could only be observed under very specific optical pumping conditions. Then, in the pursuit of long living electron spins as a building block for quantum information storage and processing, their destructive action on the lifetime of the electron spin became apparent. The nuclear spin system increasingly gained the attention of the quantum dot community. It seemed that the randomly oriented, fluctuating nuclear spins can only be counteracted by strong magnetic fields suppressing the depolarising effect of the random nuclear spin fluctuation fields on a single electron spin. Gradually, however, the work done thirty years before on the electron-nuclear spin system in bulk semiconductors attracted the notice of scientists again. Some of the old experiments could be performed with quantum dots as well. It could be shown that the nuclear spins in quantum dots may well be polarised by optical orientation and that their action is not always destructive at all. The nuclear spins in quantum dots are increasingly used in order to create and tailor a specific environment for a single electron in a quantum dot. In this way quantum dots contain their own ''nuclear nanomagnet''. This might be the future of the studies on the electron-nuclear spin system. The aim of this work is to shed some more light on the complex interdependent system formed of an electron spin and the nuclear spin ensemble in quantum dots. The effects are manifold, often unexpected, sometimes miraculous. Nevertheless, I believe that this work is another tiny step towards the understanding of this challenging system. I have shown that the randomly polarised nuclear spin system always affects the electron spin of a single electron in quantum dots. Further we have seen, however, that the nuclear spin system can easily be

  5. Quantum tunneling of electron snake states in an inhomogeneous magnetic field

    Science.gov (United States)

    Hoodbhoy, Pervez

    2018-05-01

    In a two dimensional free electron gas subjected to a perpendicular spatially varying magnetic field, the classical paths of electrons are snake-like trajectories that weave along the line where the field crosses zero. But quantum mechanically this system is described by a symmetric double well potential which, for low excitations, leads to very different electron behavior. We compute the spectrum, as well as the wavefunctions, for states of definite parity in the limit of nearly degenerate states, i.e. for electrons sufficiently far from the B z   =  0 line. Transitions between the states are shown to give rise to a tunneling current. If the well is made asymmetrical by a time-dependent parity breaking perturbation then Rabi-like oscillations between parity states occur. Resonances can be excited and used to stimulate the transfer of electrons from one side of the potential barrier to the other through quantum tunneling.

  6. Quantum tunneling of electron snake states in an inhomogeneous magnetic field.

    Science.gov (United States)

    Hoodbhoy, Pervez

    2018-05-10

    In a two dimensional free electron gas subjected to a perpendicular spatially varying magnetic field, the classical paths of electrons are snake-like trajectories that weave along the line where the field crosses zero. But quantum mechanically this system is described by a symmetric double well potential which, for low excitations, leads to very different electron behavior. We compute the spectrum, as well as the wavefunctions, for states of definite parity in the limit of nearly degenerate states, i.e. for electrons sufficiently far from the B z   =  0 line. Transitions between the states are shown to give rise to a tunneling current. If the well is made asymmetrical by a time-dependent parity breaking perturbation then Rabi-like oscillations between parity states occur. Resonances can be excited and used to stimulate the transfer of electrons from one side of the potential barrier to the other through quantum tunneling.

  7. Electron-phonon interaction in quantum transport through quantum dots and molecular systems

    Science.gov (United States)

    Ojeda, J. H.; Duque, C. A.; Laroze, D.

    2016-12-01

    The quantum transport and effects of decoherence properties are studied in quantum dots systems and finite homogeneous chains of aromatic molecules connected to two semi-infinite leads. We study these systems based on the tight-binding approach through Green's function technique within a real space renormalization and polaron transformation schemes. In particular, we calculate the transmission probability following the Landauer-Büttiker formalism, the I - V characteristics and the noise power of current fluctuations taken into account the decoherence. Our results may explain the inelastic effects through nanoscopic systems.

  8. Quantum teleportation and entanglement swapping of electron spins in superconducting hybrid structures

    Energy Technology Data Exchange (ETDEWEB)

    Bubanja, Vladimir, E-mail: vladimir.bubanja@callaghaninnovation.govt.nz

    2015-06-15

    We present schemes for quantum teleportation and entanglement swapping of electronic spin states in hybrid superconductor–normal-metal systems. The proposed schemes employ subgap transport whereby the lowest order processes involve Cooper pair-electron and double Cooper-pair cotunneling in quantum teleportation and entanglement swapping protocols, respectively. The competition between elastic cotunneling and Cooper-pair splitting results in the success probability of 25% in both cases. Described implementations of these protocols are within reach of present-day experimental techniques.

  9. Capture dynamics of hot electrons on quantum dots in RTDs studied by noise measurement

    International Nuclear Information System (INIS)

    Hees, S S; Kardynal, B E; Shields, A J; Farrer, I; Ritchie, D A

    2008-01-01

    We investigate the noise in quantum dot resonant tunnelling diodes (QDRTDs), where the quantum dots (QDs) placed in the collector experience electric fields that vary in a wide range. The trapping/detrapping of electrons on the QDs dominated the measured electrical noise. The model that we derived for the noise explains the experimental data well. The QD capture cross-section is one to two orders of magnitude smaller than the physical size of the QDs due to the reduced probability of capturing a hot electron on the QD. The model is a powerful tool to design the noise characteristics of QDRTD single photon-detectors

  10. A comparative analysis of electronic and molecular quantum dot cellular automata

    International Nuclear Information System (INIS)

    Umamahesvari, H.; Ajitha, D.

    2015-01-01

    This paper presents a comparative analysis of electronic quantum-dot cellular automata (EQCA) and Magnetic quantum dot Cellular Automata (MQCA). QCA is a computing paradigm that encodes and processes information by the position of individual electrons. To enhance the high dense and ultra-low power devices, various researches have been actively carried out to find an alternative way to continue and follow Moore’s law, so called “beyond CMOS technology”. There have been several proposals for physically implementing QCA, EQCA and MQCA are the two important QCAs reported so far. This paper provides a comparative study on these two QCAs

  11. Opto-electronic and quantum transport properties of semiconductor nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Sabathil, M.

    2005-01-01

    In this work a novel and efficient method for the calculation of the ballistic transport properties of open semiconductor nanostructures connected to external reservoirs is presented. It is based on the Green's function formalism and reduces the effort to obtain the transmission and the carrier density to a single solution of a hermitian eigenvalue problem with dimensions proportional to the size of the decoupled device and the multiple inversion of a small matrix with dimensions proportional to the size of the contacts to the leads. Using this method, the 4-band GaAs hole transport through a 2-dimensional three-terminal T-junction device, and the resonant tunneling current through a 3-dimensional InAs quantum dot molecule embedded into an InP heterostructure have been calculated. The further extension of the method into a charge self-consistent scheme enables the efficient prediction of the IV-characteristics of highly doped nanoscale field effect transistors in the ballistic regime, including the influence of quasi bound states and the exchange-correlation interaction. Buettiker probes are used to emulate the effect of inelastic scattering on the current for simple 1D devices, systematically analyzing the dependence of the density of states and the resulting self-consistent potential on the scattering strength. The second major topic of this work is the modeling of the optical response of quantum confined neutral and charged excitons in single and coupled self-assembled InGaAs quantum dots. For this purpose the existing device simulator nextnano{sup 3} has been extended to incorporate particle-particle interactions within the means of density functional theory in local density approximation. In this way the exciton transition energies for neutral and charged excitons as a function of an externally applied electric field have been calculated, revealing a systematic reduction of the intrinsic dipole with the addition of extra holes to the exciton, a finding

  12. Semiconductor Quantum Electron Wave Transport, Diffraction, and Interference: Analysis, Device, and Measurement.

    Science.gov (United States)

    Henderson, Gregory Newell

    Semiconductor device dimensions are rapidly approaching a fundamental limit where drift-diffusion equations and the depletion approximation are no longer valid. In this regime, quantum effects can dominate device response. To increase further device density and speed, new devices must be designed that use these phenomena to positive advantage. In addition, quantum effects provide opportunities for a new class of devices which can perform functions previously unattainable with "conventional" semiconductor devices. This thesis has described research in the analysis of electron wave effects in semiconductors and the development of methods for the design, fabrication, and characterization of quantum devices based on these effects. First, an exact set of quantitative analogies are presented which allow the use of well understood optical design and analysis tools for the development of electron wave semiconductor devices. Motivated by these analogies, methods are presented for modeling electron wave grating diffraction using both an exact rigorous coupled-wave analysis and approximate analyses which are useful for grating design. Example electron wave grating switch and multiplexer designs are presented. In analogy to thin-film optics, the design and analysis of electron wave Fabry-Perot interference filters are also discussed. An innovative technique has been developed for testing these (and other) electron wave structures using Ballistic Electron Emission Microscopy (BEEM). This technique uses a liquid-helium temperature scanning tunneling microscope (STM) to perform spectroscopy of the electron transmittance as a function of electron energy. Experimental results show that BEEM can resolve even weak quantum effects, such as the reflectivity of a single interface between materials. Finally, methods are discussed for incorporating asymmetric electron wave Fabry-Perot filters into optoelectronic devices. Theoretical and experimental results show that such structures could

  13. Electronic properties in a quantum well structure of Weyl semimetal

    International Nuclear Information System (INIS)

    You, Wen-Long; Zhou, Jiao-Jiao; Wang, Xue-Feng; Oleś, Andrzej M.

    2016-01-01

    We investigate the confined states and transport of three-dimensional Weyl electrons around a one-dimensional external rectangular electrostatic potential. The confined states with finite transverse wave vector exist at energies higher than the half well depth or lower than the half barrier height. The rectangular potential appears completely transparent to the normal incident electrons but not otherwise. The tunneling transmission coefficient is sensitive to their incident angle and shows resonant peaks when their energy coincides with the confined spectra. In addition, for the electrons in the conduction (valence) band through a potential barrier (well), the transmission spectrum has a gap of width increasing with the incident angle. Interestingly, the electron linear zero-temperature conductance over the potential can approach zero when the Fermi energy is aligned to the top and bottom energies of the potential, when only electron beams normal to the potential interfaces can pass through. The considered structure can be used to collimate the Weyl electron beams.

  14. Standardization of quantum technologies and QKD activities within ETSI (Conference Presentation)

    Science.gov (United States)

    Lenhart, Gaby

    2016-04-01

    In order to establish new ICT technologies successfully on the market it is essential to build trust within any potential users. This is especially true for technologies which are based upon paradigms that are not yet familiar to these users, such as quantum technologies. Technical standards are an excellent means to offer a certain degree of legal reliability and technical interoperability that is required by industry for commercial take up. While such standards on the one hand must be clear enough to provide strict rules for implementers, on the other hand they also must remain flexible enough to not restrict progress in further research and development on the standardized technology. Hence such standards have to be produced by a wide variety of stakeholders taking into account all their different needs. The paper will provide some insight into the general mechanisms of standardization and their relation to quantum technologies. Alongside with the relevance of standardization as an enabler for certification of quantum based technologies it will explain its potential for securing intellectual property. In its first part paper will concentrate on the advantages of standardization and discuss fears some of the stakeholders share, in detail. The second part will focus on the technical work going on in ETSI in relation to quantum technologies. In 2008 ETSI created a standards work group on Quantum Key Distribution, the ETSI ISG QKD and more recently a group on Quantum-Safe Cryptography, the ETSI ISG QSC. A significant part of the technical work of these groups has already been published and will be introduced in the following. However a big share of work is still ongoing and lot more is planned for the future, as are continuous revisions and updates of the published specifications. This standardization work covers several levels: It starts of by problem statements in the form of use cases, from which technical requirements can be derived. These requirements then form

  15. I-V characteristic of electronic transport through a quantum dot chain: The role of antiresonance

    International Nuclear Information System (INIS)

    Liu Yu; Zheng Yisong; Gong Weijiang; Lue Tianquan

    2006-01-01

    The I-V spectrum of electronic transport through a quantum dot chain is calculated by means of the nonequilibrium Green function technique. In such a system, two arbitrary quantum dots are connected with two electron reservoirs through leads. When the dot-lead coupling is very weak, a series of discrete resonant peaks in electron transmission function cause staircase-like I-V characteristic. On the contrary, in the relatively strong dot-lead coupling regime, stairs in the I-V spectrum due to resonance vanish. However, when there are some dangling quantum dots in the chain outside two leads, the antiresonance which corresponds to the zero points of electron transmission function brings about novel staircase characteristic in the I-V spectrum. Moreover, two features in the I-V spectrum arising from the antiresonance are pointed out, which are significant for possible device applications. One is the multiple negative differential conductance regions, and another is regarding to create a highly spin-polarized current through the quantum dot chain by the interplay of the resonance and antiresonance. Finally, we focus on the role that the many-body effect plays on the antiresonance. Our result is that the antiresonance remains when the electron interaction is considered to the second order approximation

  16. Nature does not rely on long-lived electronic quantum coherence for photosynthetic energy transfer

    Science.gov (United States)

    Duan, Hong-Guang; Prokhorenko, Valentyn I.; Cogdell, Richard J.; Ashraf, Khuram; Stevens, Amy L.; Thorwart, Michael; Miller, R. J. Dwayne

    2017-08-01

    During the first steps of photosynthesis, the energy of impinging solar photons is transformed into electronic excitation energy of the light-harvesting biomolecular complexes. The subsequent energy transfer to the reaction center is commonly rationalized in terms of excitons moving on a grid of biomolecular chromophores on typical timescales Olson protein, in which interference oscillatory signals up to 1.5 ps were reported and interpreted as direct evidence of exceptionally long-lived electronic quantum coherence. Here, we show that the optical 2D photon echo spectra of this complex at ambient temperature in aqueous solution do not provide evidence of any long-lived electronic quantum coherence, but confirm the orthodox view of rapidly decaying electronic quantum coherence on a timescale of 60 fs. Our results can be considered as generic and give no hint that electronic quantum coherence plays any biofunctional role in real photoactive biomolecular complexes. Because in this structurally well-defined protein the distances between bacteriochlorophylls are comparable to those of other light-harvesting complexes, we anticipate that this finding is general and directly applies to even larger photoactive biomolecular complexes.

  17. Physical reason for quantum behaviour of the electron and stability of the main state of the hydrogen atom

    International Nuclear Information System (INIS)

    Rangelov, J.M.

    1986-01-01

    An electron model is proposed explaining the physical reasons for its nonrelativistic quantum-mechanical behaviour, the origin of its own mechanical and magnetic momentum and field energy. As an example the main electron state in hydrogen atom is obtained

  18. The Bravyi-Kitaev transformation for quantum computation of electronic structure

    Science.gov (United States)

    Seeley, Jacob T.; Richard, Martin J.; Love, Peter J.

    2012-12-01

    Quantum simulation is an important application of future quantum computers with applications in quantum chemistry, condensed matter, and beyond. Quantum simulation of fermionic systems presents a specific challenge. The Jordan-Wigner transformation allows for representation of a fermionic operator by O(n) qubit operations. Here, we develop an alternative method of simulating fermions with qubits, first proposed by Bravyi and Kitaev [Ann. Phys. 298, 210 (2002), 10.1006/aphy.2002.6254; e-print arXiv:quant-ph/0003137v2], that reduces the simulation cost to O(log n) qubit operations for one fermionic operation. We apply this new Bravyi-Kitaev transformation to the task of simulating quantum chemical Hamiltonians, and give a detailed example for the simplest possible case of molecular hydrogen in a minimal basis. We show that the quantum circuit for simulating a single Trotter time step of the Bravyi-Kitaev derived Hamiltonian for H2 requires fewer gate applications than the equivalent circuit derived from the Jordan-Wigner transformation. Since the scaling of the Bravyi-Kitaev method is asymptotically better than the Jordan-Wigner method, this result for molecular hydrogen in a minimal basis demonstrates the superior efficiency of the Bravyi-Kitaev method for all quantum computations of electronic structure.

  19. Quantum Calculations of Electron Tunneling in Respiratory Complex III.

    Science.gov (United States)

    Hagras, Muhammad A; Hayashi, Tomoyuki; Stuchebrukhov, Alexei A

    2015-11-19

    The most detailed and comprehensive to date study of electron transfer reactions in the respiratory complex III of aerobic cells, also known as bc1 complex, is reported. In the framework of the tunneling current theory, electron tunneling rates and atomistic tunneling pathways between different redox centers were investigated for all electron transfer reactions comprising different stages of the proton-motive Q-cycle. The calculations reveal that complex III is a smart nanomachine, which under certain conditions undergoes conformational changes gating electron transfer, or channeling electrons to specific pathways. One-electron tunneling approximation was adopted in the tunneling calculations, which were performed using hybrid Broken-Symmetry (BS) unrestricted DFT/ZINDO levels of theory. The tunneling orbitals were determined using an exact biorthogonalization scheme that uniquely separates pairs of tunneling orbitals with small overlaps out of the remaining Franck-Condon orbitals with significant overlap. Electron transfer rates in different redox pairs show exponential distance dependence, in agreement with the reported experimental data; some reactions involve coupled proton transfer. Proper treatment of a concerted two-electron bifurcated tunneling reaction at the Q(o) site is given.

  20. Chaos in Dirac Electron Optics: Emergence of a Relativistic Quantum Chimera.

    Science.gov (United States)

    Xu, Hong-Ya; Wang, Guang-Lei; Huang, Liang; Lai, Ying-Cheng

    2018-03-23

    We uncover a remarkable quantum scattering phenomenon in two-dimensional Dirac material systems where the manifestations of both classically integrable and chaotic dynamics emerge simultaneously and are electrically controllable. The distinct relativistic quantum fingerprints associated with different electron spin states are due to a physical mechanism analogous to a chiroptical effect in the presence of degeneracy breaking. The phenomenon mimics a chimera state in classical complex dynamical systems but here in a relativistic quantum setting-henceforth the term "Dirac quantum chimera," associated with which are physical phenomena with potentially significant applications such as enhancement of spin polarization, unusual coexisting quasibound states for distinct spin configurations, and spin selective caustics. Experimental observations of these phenomena are possible through, e.g., optical realizations of ballistic Dirac fermion systems.

  1. Chaos in Dirac Electron Optics: Emergence of a Relativistic Quantum Chimera

    Science.gov (United States)

    Xu, Hong-Ya; Wang, Guang-Lei; Huang, Liang; Lai, Ying-Cheng

    2018-03-01

    We uncover a remarkable quantum scattering phenomenon in two-dimensional Dirac material systems where the manifestations of both classically integrable and chaotic dynamics emerge simultaneously and are electrically controllable. The distinct relativistic quantum fingerprints associated with different electron spin states are due to a physical mechanism analogous to a chiroptical effect in the presence of degeneracy breaking. The phenomenon mimics a chimera state in classical complex dynamical systems but here in a relativistic quantum setting—henceforth the term "Dirac quantum chimera," associated with which are physical phenomena with potentially significant applications such as enhancement of spin polarization, unusual coexisting quasibound states for distinct spin configurations, and spin selective caustics. Experimental observations of these phenomena are possible through, e.g., optical realizations of ballistic Dirac fermion systems.

  2. Resonant electronic excitation energy transfer by Dexter mechanism in the quantum dot system

    Science.gov (United States)

    Samosvat, D. M.; Chikalova-Luzina, O. P.; Vyatkin, V. M.; Zegrya, G. G.

    2016-11-01

    In present work the energy transfer between quantum dots by the exchange (Dexter) mechanism is analysed. The interdot Coulomb interaction is taken into consideration. It is assumed that the quantum dot-donor and the quantum dot-acceptor are made from the same compound A3B5 and embedded in the matrix of other material creating potential barriers for electron and holes. The dependences of the energy transfer rate on the quantum-dot system parameters are found using the Kane model that provides the most adequate description spectra of semiconductors A3B5. Numerical calculations show that the rate of the energy transfer by Dexter mechanism is comparable to the rate of the energy transfer by electrostatic mechanism at the distances approaching to the contact ones.

  3. Resonant electronic excitation energy transfer by Dexter mechanism in the quantum dot system

    International Nuclear Information System (INIS)

    Samosvat, D M; Chikalova-Luzina, O P; Zegrya, G G; Vyatkin, V M

    2016-01-01

    In present work the energy transfer between quantum dots by the exchange (Dexter) mechanism is analysed. The interdot Coulomb interaction is taken into consideration. It is assumed that the quantum dot-donor and the quantum dot-acceptor are made from the same compound A3B5 and embedded in the matrix of other material creating potential barriers for electron and holes. The dependences of the energy transfer rate on the quantum-dot system parameters are found using the Kane model that provides the most adequate description spectra of semiconductors A3B5. Numerical calculations show that the rate of the energy transfer by Dexter mechanism is comparable to the rate of the energy transfer by electrostatic mechanism at the distances approaching to the contact ones. (paper)

  4. Electron confinement in quantum nanostructures: Self-consistent Poisson-Schroedinger theory

    International Nuclear Information System (INIS)

    Luscombe, J.H.; Bouchard, A.M.; Luban, M.

    1992-01-01

    We compute the self-consistent electron states and confining potential, V(r,T), for laterally confined cylindrical quantum wires at a temperature T from a numerical solution of the coupled Poisson and Schroedinger (PS) equations. Finite-temperature effects are included in the electron density function, n(r,T), via the single-particle density matrix in the grand-canonical ensemble using the self-consistent bound states. We compare our results for a GaAs quantum wire with those obtained previously [J. H. Luscombe and M. Luban, Appl. Phys. Lett. 57, 61 (1990)] from a finite-temperature Thomas-Fermi (TF) approximation. We find that the TF results agree well with those of the more realistic, but also more computationally intensive PS theory, except for low temperatures or for cases where the quantum wire is almost, but not totally, depleted due to a combination of either small geometry, surface boundary conditions, or low doping concentrations. In the latter situations, the number of subbands that are populated is relatively small, and both n(r,T) and V(r,T) exhibit Friedel-type oscillations. Otherwise the TF theory, which is based on free-particle states, is remarkably accurate. We also present results for the partial electron density functions associated with the angular momentum quantum numbers, and discuss their role in populating the quantum wire

  5. Plasmonic photocatalytic reactions enhanced by hot electrons in a one-dimensional quantum well

    Directory of Open Access Journals (Sweden)

    H. J. Huang

    2015-11-01

    Full Text Available The plasmonic endothermic oxidation of ammonium ions in a spinning disk reactor resulted in light energy transformation through quantum hot charge carriers (QHC, or quantum hot electrons, during a chemical reaction. It is demonstrated with a simple model that light of various intensities enhance the chemical oxidization of ammonium ions in water. It was further observed that light illumination, which induces the formation of plasmons on a platinum (Pt thin film, provided higher processing efficiency compared with the reaction on a bare glass disk. These induced plasmons generate quantum hot electrons with increasing momentum and energy in the one-dimensional quantum well of a Pt thin film. The energy carried by the quantum hot electrons provided the energy needed to catalyze the chemical reaction. The results indicate that one-dimensional confinement in spherical coordinates (i.e., nanoparticles is not necessary to provide an extra excited state for QHC generation; an 8 nm Pt thin film for one-dimensional confinement in Cartesian coordinates can also provide the extra excited state for the generation of QHC.

  6. Electron Spin Coherence Times in Si/SiGe Quantum Dots

    Science.gov (United States)

    Jock, R. M.; He, Jianhua; Tyryshkin, A. M.; Lyon, S. A.; Lee, C.-H.; Huang, S.-H.; Liu, C. W.

    2014-03-01

    Single electron spin states in silicon have shown a great deal of promise as qubits due to their long spin relaxation (T1) and coherence (T2) times. Recent results exhibit a T2 of 250 us for electrons confined in Si/SiGe quantum dots at 350 mK. These experiments used conventional X-band (10 GHz) pulsed Electron Spin Resonance on a large area (3.5 mm x 20 mm), dual-gated, undoped Si/SiGe heterostructure quantum dots. These dots are induced in a natural Si quantum well by e-beam defined gates having a lithographic radius of 150 nm and pitch of 700 nm. The relatively large size of these dots led to closely spaced energy levels and long T2's could only be measured at sub-Kelvin temperatures. At 2K confined electrons displayed a 3 us T2, which is comparable to that of 2D electrons at that temperature. Decreasing the quantum dot size increases the electron confinement and reduces the effects of valley-splitting and spin-orbit coupling on the electron spin coherence times. We will report results on dots with 80 nm lithographic radii and a 375 nm pitch. This device displays an extended electron coherence time of 30 us at 2K, suggesting tighter confinement of electrons. Further measurements at lower temperatures are in progress. This work was supported in part by NSF through the Materials World Network program (DMR-1107606) and the Princeton MRSEC (DMR-0819860), and in part by the U.S. Army Research Office (W911NF-13-1-0179).

  7. Electron acoustic waves and parametric instabilities in a 4-component relativistic quantum plasma with Thomas-Fermi distributed electrons

    Science.gov (United States)

    Ikramullah, Ahmad, Rashid; Sharif, Saqib; Khattak, Fida Younus

    2018-01-01

    The interaction of Circularly Polarized Electro-Magnetic (CPEM) waves with a 4-component relativistic quantum plasma is studied. The plasma constituents are: relativistic-degenerate electrons and positrons, dynamic degenerate ions, and Thomas-Fermi distributed electrons in the background. We have employed the Klein-Gordon equations for the electrons as well as for the positrons, while the ions are represented by the Schrödinger equation. The Maxwell and Poisson equations are used for electromagnetic waves. Three modes are observed: one of the modes is associated with the electron acoustic wave, a second mode at frequencies greater than the electron acoustic wave mode could be associated with the positrons, and the third one at the lowest frequencies could be associated with the ions. Furthermore, Stimulated Raman Scattering (SRS), Modulational, and Stimulated Brillouin Scattering (SBS) instabilities are studied. It is observed that the growth rates of both the SRS and SBS instabilities decrease with increase in the quantum parameter of the plasma. It is also observed that the scattering spectra in both the SRS and SBS get restricted to very small wavenumber regions. It is shown that for low amplitude CPEM wave interaction with the quantum plasma, the positron concentration has no effect on the SRS and SBS spectra. In the case of large amplitude CPEM wave interaction, however, one observes spectral changes with varying positron concentrations. An increase in the positron concentration also enhances the scattering instability growth rates. Moreover, the growth rate first increases and then decreases with increasing intensity of the CPEM wave, indicating an optimum value of the CPEM wave intensity for the growth of these scattering instabilities. The modulational instability also shows dependence on the quantum parameter as well as on the positron concentration.

  8. Photoluminescent (PL) or electroluminescent (EL) quantum dots for display, lighting, and photomedicine (Conference Presentation)

    Science.gov (United States)

    Dong, Yajie

    2017-02-01

    Quantum dots (QDs) have gone through a long journey before finding their ways into the display field. This talk will briefly touch on the history before trying to answer several key questions related to QDs applications in display: What are QDs? How are they made? What properties do they have and Why? How can these properties be used to improve color and efficiency of display, in either photoluminescence (PL) or electroluminescence (EL) mode? And what are the remaining challenges for QDs wide adoption in display industry? Lastly, some most recent progresses in our UCF lab at both PL and EL fronts will be highlighted. For PL, a cadmium-free perovskite-polymer composite films with exceptionally narrow emission green peaks (FWHM 20 nm) and good water and thermal stability will be reported. Together with red quantum dots or PFS/KSF phosphors as down-converters for blue LEDs, a white-light source with 95% Rec. 2020 color gamut was demonstrated [1]. For EL, red quantum dot light emitting devices (QLEDs) with record luminance of 165,000 Cd/m2 has been obtained at a current density of 1000 mA/cm2 with a low driving voltage of 5.8 V and CIE coordinates of (0.69, 0.31). [2] The potential of using these QLEDs for light sources for integrated sensing platform [3] or high efficiency, high color quality hybrid white OLED [4] will be discussed. [1] Y. N. Wang, J. He, H. Chen, J. S. Chen, R. D. Zhu, P. Ma, A. Towers, Y. Lin, A. J. Gesquiere, S. T. Wu, Y. J. Dong. Ultrastable, Highly Luminescent Organic-Inorganic Perovskite - Polymer Composite Films, Advanced Materials, accepted, (2016). [2] Y. J. Dong, J.M. Caruge, Z. Q. Zhou, C. Hamilton, Z. Popovic, J. Ho, M. Stevenson, G. Liu, V. Bulovic, M. Bawendi, P. T. Kazlas, S. Coe-Sullivan, and J. Steckel Ultra-bright, Highly Efficient, Low Roll-off Inverted Quantum-Dot Light Emitting Devices (QLEDs). SID Symp. Dig. Tech. Pap. 46, 270-273 (2015). [3] J. He, H. Chen, S. T. Wu, and Y. J. Dong, Integrated Sensing Platform Based on Quantum

  9. The temperature dependence of quantum spin pumping generated using electron spin resonance with three-magnon splittings

    International Nuclear Information System (INIS)

    Nakata, Kouki

    2013-01-01

    On the basis of the Schwinger–Keldysh formalism, we have closely investigated the temperature dependence of quantum spin pumping generated using electron spin resonance. We have clarified that three-magnon splittings excite non-zero modes of magnons and characterize the temperature dependence of quantum spin pumping generated using electron spin resonance. (paper)

  10. Impurity with two electrons in the spherical quantum dot with Unite confinement potential

    International Nuclear Information System (INIS)

    Baghdasaryan, D A; Ghaltaghchyan, H Ts; Kazaryan, E M; Sarkisyan, H A

    2016-01-01

    Two-electron states in a spherical QD with the hydrogenic impurity located in the center and with a finite height confinement potential barrier are investigated. The effective mass mismatch have been taken into account. The dependence of ground state energy and Coulomb electron-electron interaction energy correction on the QD size is studied. The problem of the state exchange time control in QD is discussed, taking into account the spins of the electrons in the Russell-Saunders approximation. The effect of quantum emission has been shown. (paper)

  11. On the fly quantum dynamics of electronic and nuclear wave packets

    Science.gov (United States)

    Komarova, Ksenia G.; Remacle, F.; Levine, R. D.

    2018-05-01

    Multielectronic states quantum dynamics on a grid is described in a manner motivated by on the fly classical trajectory computations. Non stationary electronic states are prepared by a few cycle laser pulse. The nuclei respond and begin moving. We solve the time dependent Schrödinger equation for the electronic and nuclear dynamics for excitation from the ground electronic state. A satisfactory accuracy is possible using a localized description on a discrete grid. This enables computing on the fly for both the nuclear and electronic dynamics including non-adiabatic couplings. Attosecond dynamics in LiH is used as an example.

  12. Electronically Active Impurities in Colloidal Quantum Dot Solids

    KAUST Repository

    Carey, Graham H.

    2014-11-25

    © 2014 American Chemical Society. Colloidal quantum dot films have seen rapid progress as active materials in photodetection, light emission, and photovoltaics. Their processing from the solution phase makes them an attractive option for these applications due to the expected cost reductions associated with liquid-phase material deposition. Colloidally stable nanoparticles capped using long, insulating aliphatic ligands are used to form semiconducting, insoluble films via a solid-state ligand exchange in which the original ligands are replaced with short bifunctional ligands. Here we show that this ligand exchange can have unintended and undesired side effects: a high molecular weight complex can form, containing both lead oleate and the shorter conductive ligand, and this poorly soluble complex can end up embedded within the colloidal quantum dot (CQD) active layer. We further show that, by adding an acidic treatment during film processing, we can break up and wash away these complexes, producing a higher quality CQD solid. The improved material leads to photovoltaic devices with reduced series resistance and enhanced fill factor relative to controls employing previously reported CQD solids. (Figure Presented).

  13. Electronically Active Impurities in Colloidal Quantum Dot Solids

    KAUST Repository

    Carey, Graham H.; Kramer, Illan J.; Kanjanaboos, Pongsakorn; Moreno-Bautista, Gabriel; Voznyy, Oleksandr; Rollny, Lisa; Tang, Joel A.; Hoogland, Sjoerd; Sargent, Edward H.

    2014-01-01

    © 2014 American Chemical Society. Colloidal quantum dot films have seen rapid progress as active materials in photodetection, light emission, and photovoltaics. Their processing from the solution phase makes them an attractive option for these applications due to the expected cost reductions associated with liquid-phase material deposition. Colloidally stable nanoparticles capped using long, insulating aliphatic ligands are used to form semiconducting, insoluble films via a solid-state ligand exchange in which the original ligands are replaced with short bifunctional ligands. Here we show that this ligand exchange can have unintended and undesired side effects: a high molecular weight complex can form, containing both lead oleate and the shorter conductive ligand, and this poorly soluble complex can end up embedded within the colloidal quantum dot (CQD) active layer. We further show that, by adding an acidic treatment during film processing, we can break up and wash away these complexes, producing a higher quality CQD solid. The improved material leads to photovoltaic devices with reduced series resistance and enhanced fill factor relative to controls employing previously reported CQD solids. (Figure Presented).

  14. Electron spin resonance and spin-valley physics in a silicon double quantum dot.

    Science.gov (United States)

    Hao, Xiaojie; Ruskov, Rusko; Xiao, Ming; Tahan, Charles; Jiang, HongWen

    2014-05-14

    Silicon quantum dots are a leading approach for solid-state quantum bits. However, developing this technology is complicated by the multi-valley nature of silicon. Here we observe transport of individual electrons in a silicon CMOS-based double quantum dot under electron spin resonance. An anticrossing of the driven dot energy levels is observed when the Zeeman and valley splittings coincide. A detected anticrossing splitting of 60 MHz is interpreted as a direct measure of spin and valley mixing, facilitated by spin-orbit interaction in the presence of non-ideal interfaces. A lower bound of spin dephasing time of 63 ns is extracted. We also describe a possible experimental evidence of an unconventional spin-valley blockade, despite the assumption of non-ideal interfaces. This understanding of silicon spin-valley physics should enable better control and read-out techniques for the spin qubits in an all CMOS silicon approach.

  15. Hybrid quantum circuit with a superconducting qubit coupled to an electron spin ensemble

    Energy Technology Data Exchange (ETDEWEB)

    Kubo, Yuimaru; Grezes, Cecile; Vion, Denis; Esteve, Daniel; Bertet, Patrice [Quantronics Group, SPEC (CNRS URA 2464), CEA-Saclay, 91191 Gif-sur-Yvette (France); Diniz, Igor; Auffeves, Alexia [Institut Neel, CNRS, BP 166, 38042 Grenoble (France); Isoya, Jun-ichi [Research Center for Knowledge Communities, University of Tsukuba, 305-8550 Tsukuba (Japan); Jacques, Vincent; Dreau, Anais; Roch, Jean-Francois [LPQM (CNRS, UMR 8537), Ecole Normale Superieure de Cachan, 94235 Cachan (France)

    2013-07-01

    We report the experimental realization of a hybrid quantum circuit combining a superconducting qubit and an ensemble of electronic spins. The qubit, of the transmon type, is coherently coupled to the spin ensemble consisting of nitrogen-vacancy (NV) centers in a diamond crystal via a frequency-tunable superconducting resonator acting as a quantum bus. Using this circuit, we prepare arbitrary superpositions of the qubit states that we store into collective excitations of the spin ensemble and retrieve back into the qubit. We also report a new method for detecting the magnetic resonance of electronic spins at low temperature with a qubit using the hybrid quantum circuit, as well as our recent progress on spin echo experiments.

  16. The ground state magnetic moment and susceptibility of a two electron Gaussian quantum dot

    Science.gov (United States)

    Boda, Aalu; Chatterjee, Ashok

    2018-04-01

    The problem of two interacting electrons moving in a two-dimensional semiconductor quantum dot with Gaussian confinement under the influence of an external magnetic field is studied by using a method of numerical diagonalization of the Hamiltonian matrix with in the effective-mass approximation. The energy spectrum is calculated as a function of the magnetic field. We find the ground state magnetic moment and the magnetic susceptibility show zero temperature diamagnetic peaks due to exchange induced singlet-triplet oscillations. The position and the number of these peaks depend on the size of the quantum dot and also strength of the electro-electron interaction. The theory is applied to a GaAs quantum dot.

  17. Electron-nuclear interaction in 13C nanotube double quantum dots

    DEFF Research Database (Denmark)

    Churchill, H O H; Bestwick, A J; Harlow, J W

    2009-01-01

    For coherent electron spins, hyperfine coupling to nuclei in the host material can either be a dominant source of unwanted spin decoherence or, if controlled effectively, a resource enabling storage and retrieval of quantum information. To investigate the effect of a controllable nuclear...... environment on the evolution of confined electron spins, we have fabricated and measured gate-defined double quantum dots with integrated charge sensors made from single-walled carbon nanotubes with a variable concentration of 13C (nuclear spin I=1/2) among the majority zero-nuclear-spin 12C atoms. We observe...... strong isotope effects in spin-blockaded transport, and from the magnetic field dependence estimate the hyperfine coupling in 13C nanotubes to be of the order of 100 ¿µeV, two orders of magnitude larger than anticipated. 13C-enhanced nanotubes are an interesting system for spin-based quantum information...

  18. High-harmonic generation in a quantum electron gas trapped in a nonparabolic and anisotropic well

    Science.gov (United States)

    Hurst, Jérôme; Lévêque-Simon, Kévin; Hervieux, Paul-Antoine; Manfredi, Giovanni; Haas, Fernando

    2016-05-01

    An effective self-consistent model is derived and used to study the dynamics of an electron gas confined in a nonparabolic and anisotropic quantum well. This approach is based on the equations of quantum hydrodynamics, which incorporate quantum and nonlinear effects in an approximate fashion. The effective model consists of a set of six coupled differential equations (dynamical system) for the electric dipole and the size of the electron gas. Using this model we show that: (i) high harmonic generation is related to the appearance of chaos in the phase space, as attested to by related Poincaré sections; (ii) higher order harmonics can be excited efficiently and with relatively weak driving fields by making use of chirped electromagnetic waves.

  19. Quantum Theory of Conducting Matter Newtonian Equations of Motion for a Bloch Electron

    CERN Document Server

    Fujita, Shigeji

    2007-01-01

    Quantum Theory of Conducting Matter: Newtonian Equations of Motion for a Bloch Electron targets scientists, researchers and graduate-level students focused on experimentation in the fields of physics, chemistry, electrical engineering, and material sciences. It is important that the reader have an understanding of dynamics, quantum mechanics, thermodynamics, statistical mechanics, electromagnetism and solid-state physics. Many worked-out problems are included in the book to aid the reader's comprehension of the subject. The Bloch electron (wave packet) moves by following the Newtonian equation of motion. Under an applied magnetic field B the electron circulates around the field B counterclockwise or clockwise depending on the curvature of the Fermi surface. The signs of the Hall coefficient and the Seebeck coefficient are known to give the sign of the major carrier charge. For alkali metals, both are negative, indicating that the carriers are "electrons." These features arise from the Fermi surface difference...

  20. Electronic structure of charge carriers in a polysilane quantum wire

    International Nuclear Information System (INIS)

    Kumagai, J.; Yoshida, H.; Ichikawa, T.

    1997-01-01

    The ESR, ESEEM and spectrophotometric studies on polysilane radical ions revealed that charge carriers, hole and conducting electrons, are not delocalized all over the Si-Si main chain but confined to a part of the chain composed of only six Si atoms, probably near the branch on the main chain. Comparison of the ESR spectra of the radical cations and anions revealed that the hole can migrate from the main chain to an adjacent polymer chain via the side chains, whereas the conducting electron can not migrate since the side chains act as good intermolecular insulators for the electron. (author)

  1. Proceedings of the first international conference on indium phosphide and related materials for advanced electronic and optical devices

    International Nuclear Information System (INIS)

    Singh, R.; Messick, L.J.

    1989-01-01

    This book contains the proceedings of the first international conference on indium phosphide and related materials for advanced electronic and optical devices. Topics covered include: Growth and characterization of bulk and epitaxial films, Passivation technology, Processing technology, High speed optoelectronic integrated circuits, and Solar cells

  2. Multidimensional Quantum Mechanical Modeling of Electron Transfer and Electronic Coherence in Plant Cryptochromes: The Role of Initial Bath Conditions.

    Science.gov (United States)

    Mendive-Tapia, David; Mangaud, Etienne; Firmino, Thiago; de la Lande, Aurélien; Desouter-Lecomte, Michèle; Meyer, Hans-Dieter; Gatti, Fabien

    2018-01-11

    A multidimensional quantum mechanical protocol is used to describe the photoinduced electron transfer and electronic coherence in plant cryptochromes without any semiempirical, e.g., experimentally obtained, parameters. Starting from a two-level spin-boson Hamiltonian we look at the effect that the initial photoinduced nuclear bath distribution has on an intermediate step of this biological electron transfer cascade for two idealized cases. The first assumes a slow equilibration of the nuclear bath with respect to the previous electron transfer step that leads to an ultrafast decay with little temperature dependence; while the second assumes a prior fast bath equilibration on the donor potential energy surface leading to a much slower decay, which contrarily displays a high temperature dependence and a better agreement with previous theoretical and experimental results. Beyond Marcus and semiclassical pictures these results unravel the strong impact that the presence or not of equilibrium initial conditions has on the electronic population and coherence dynamics at the quantum dynamics level in this and conceivably in other biological electron transfer cascades.

  3. Giant titanium electron wave function in gallium oxide: A potential electron-nuclear spin system for quantum information processing

    Science.gov (United States)

    Mentink-Vigier, Frédéric; Binet, Laurent; Vignoles, Gerard; Gourier, Didier; Vezin, Hervé

    2010-11-01

    The hyperfine interactions of the unpaired electron with eight surrounding G69a and G71a nuclei in Ti-doped β-Ga2O3 were analyzed by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopies. They are dominated by strong isotropic hyperfine couplings due to a direct Fermi contact interaction with Ga nuclei in octahedral sites of rutile-type chains oriented along b axis, revealing a large anisotropic spatial extension of the electron wave function. Titanium in β-Ga2O3 is thus best described as a diffuse (Ti4+-e-) pair rather than as a localized Ti3+ . Both electron and G69a nuclear spin Rabi oscillations could be observed by pulsed EPR and pulsed ENDOR, respectively. The electron spin decoherence time is about 1μs (at 4 K) and an upper bound of 520μs (at 8 K) is estimated for the nuclear decoherence time. Thus, β-Ga2O3:Ti appears to be a potential spin-bus system for quantum information processing with a large nuclear spin quantum register.

  4. Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve.

    Science.gov (United States)

    Ma, Jing-Min; Zhao, Jia; Zhang, Kai-Cheng; Peng, Ya-Jing; Chi, Feng

    2011-03-28

    Spin-dependent transport through a quantum-dot (QD) ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR) as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively.PACS numbers:

  5. Quantum interference effect in electron tunneling through a quantum-dot-ring spin valve

    Directory of Open Access Journals (Sweden)

    Ma Jing-Min

    2011-01-01

    Full Text Available Abstract Spin-dependent transport through a quantum-dot (QD ring coupled to ferromagnetic leads with noncollinear magnetizations is studied theoretically. Tunneling current, current spin polarization and tunnel magnetoresistance (TMR as functions of the bias voltage and the direct coupling strength between the two leads are analyzed by the nonequilibrium Green's function technique. It is shown that the magnitudes of these quantities are sensitive to the relative angle between the leads' magnetic moments and the quantum interference effect originated from the inter-lead coupling. We pay particular attention on the Coulomb blockade regime and find the relative current magnitudes of different magnetization angles can be reversed by tuning the inter-lead coupling strength, resulting in sign change of the TMR. For large enough inter-lead coupling strength, the current spin polarizations for parallel and antiparallel magnetic configurations will approach to unit and zero, respectively. PACS numbers:

  6. Experiments on melting in classical and quantum two dimensional electron systems

    International Nuclear Information System (INIS)

    Williams, F.I.B.

    1991-01-01

    ''Two dimensional electron system'' (2DES) here refers to electrons whose dynamics is free in 2 dimensions but blocked in the third. Experiments have been performed in two limiting situations: the classical, low density, limit realised by electrons deposited on a liquid helium surface and the quantum, high density, limit realised by electrons at an interface between two epitaxially matched semiconductors. In the classical system, where T Q c so that the thermodynamic state is determined by the competition between the temperature and the Coulomb interaction, melting is induced either by raising the temperature at constant density or by lowering the density at finite temperature. In the quantum system, it is not possible to lower the density below about 100n W without the Coulomb interaction losing out to the random field representing the extrinsic disorder imposed by the semiconductor host. Instead one has to induce crystallisation with the help of the Lorentz force, by applying a perpendicular magnetic field B [2] . As the quantum magnetic length l c = (Planck constant c/eB) 1/2 is reduced with respect to the interelectronic spacing a, expressed by the filling factor ν 2l c 2 /a 2 , the system exhibits the quantum Hall effect (QHE), first for integer then for fractional values of ν. The fractional quantum Hall effect (FQHE) is a result of Coulomb induced correlation in the quantum liquid, but as ν is decreased still further the correlations are expected to take on long-range crystal-like periodicity accompanied by elastic shear rigidity. Such a state can nonetheless be destroyed by the disordering effect of temperature, giving rise to a phase boundary in a (T, B) plane. The aim of experiment is first to determine the phase diagram and then to help elucidate the mechanism of the melting. (author)

  7. The Unruh effect and quantum fluctuations of electrons in storage rings

    International Nuclear Information System (INIS)

    Bell, J.S.; Leinaas, J.M.

    1987-01-01

    The quantum fluctuation of electron orbits in ideal storage rings is a sort of Fulling-Unruh effect (heating by acceleration in vacuum). To spell this out, the effect is analyzed in an appropriate comoving, and so accelerating and rotating, co-ordinate system. The depolarization of the electrons is a related effect, but is greatly complicated by spin-orbit coupling. This analysis confirms the standard result for the polarization, except in the neighbourhood of a narrow resonance. (orig.)

  8. The Unruh effect and quantum fluctuations of electrons in storage rings

    International Nuclear Information System (INIS)

    Bell, J.S.; Leinaas, J.M.

    1995-01-01

    The quantum fluctuation of electron orbits in ideal storage rings is a sort of Fulling-Unruh effect (heating by acceleration in vacuum). To spell this out, the effect is analyzed in an appropriate comoving, and so accelerating and rotating, co-ordinate system. The depolarization of the electrons is a related effect, but is greatly complicated by spin-orbit coupling. This analysis confirms the standard result for the polarization, except in the neighbourhood of a narrow resonance. (author)

  9. Green's function for electrons in a narrow quantum well in a parallel magnetic field

    International Nuclear Information System (INIS)

    Horing, Norman J. Morgenstern; Glasser, M. Lawrence; Dong Bing

    2005-01-01

    Electron dynamics in a narrow quantum well in a parallel magnetic field of arbitrary strength are examined here. We derive an explicit analytical closed-form solution for the Green's function of Landau-quantized electrons in skipping states of motion between the narrow well walls coupled with in-plane translational motion and hybridized with the zero-field lowest subband energy eigenstate. Such Landau-quantized modes are not uniformly spaced

  10. Angular distribution of electrons ejected by charged particles. IV. Combined classical and quantum-mechanical treatment

    NARCIS (Netherlands)

    Boesten, L.G.J.; Bonsen, T.F.M.

    1975-01-01

    Angular distributions of electrons ejected from helium by 100 and 300 keV protons have been calculated by a method which is a comination of the classical three-body collision theory and the quantum-mechanical Born approximation. The results of this theory have been compared with the corresponding

  11. Electron Spin Polarization and Detection in InAs Quantum Dots Through p-Shell Trions

    Science.gov (United States)

    2010-01-08

    optical control of spin states in quantum dots. II. EXPERIMENT The QD sample consists of 20 layers of InAs QDs, grown by molecular -beam epitaxy through...anisotropic 2D harmonic poten- tials. The electrons and holes are described by Fock- Darwin states harmonic oscillators with lateral sizes ax and ay in this

  12. Electronic and excitonic properties of self-assembled semiconductor quantum rings

    NARCIS (Netherlands)

    Fomin, V.M.; Gladilin, V.N.; Devreese, J.T.; Blokland, J.H.; Christianen, P.C.M.; Maan, J.C.; Taboada, A.G.; Granados, D.; Garcia, J.M.; Kleemans, N.A.J.M.; Genuchten, van H.C.M.; Bozkurt, M.; Koenraad, P.M.; Wixforth, A.; Lorke, A.

    2009-01-01

    Theoretical analysis of the electron energy spectrum and the magnetization in a strained InxGa1-xAs/GaAs selfassembled quantum ring (SAQR) is performed using realistic parameters, determined from the cross-sectional scanning-tunneling microscopy characterization. The Aharonov-Bohm oscillations in

  13. Broadband Cooling Spectra of Hot Electrons and Holes in PbSe Quantum Dots

    NARCIS (Netherlands)

    Spoor, F.C.M.; Tomić, Stanko; Houtepen, A.J.; Siebbeles, L.D.A.

    2017-01-01

    Understanding cooling of hot charge carriers in semiconductor quantum dots (QDs) is of fundamental interest and useful to enhance the performance of QDs in photovoltaics. We study electron and hole cooling dynamics in PbSe QDs up to high energies where carrier multiplication occurs. We

  14. Electronic properties of excited states in single InAs quantum dots

    International Nuclear Information System (INIS)

    Warming, Till

    2009-01-01

    The application of quantum-mechanical effects in semiconductor nanostructures enables the realization of novel opto-electronic devices. Examples are given by single-photon emitters and emitters of entangled photon pairs, both being essential for quantum cryptography, or for qubit systems as needed for quantum computing. InAs/GaAs quantum dots are one of the most promising candidates for such applications. A detailed knowledge of the electronic properties of quantum dots is a prerequisite for this development. The aim of this work is an experimental access to the detailed electronic structure of the excited states in single InAs/GaAs quantum dots including few-particle effects and in particular exchange interaction. The experimental approach is micro photoluminescence excitation spectroscopy (μPLE). One of the main difficulties using μPLE to probe single QDs is the unambiguous assignment of the observed resonances in the spectrum to specific transitions. By comparing micro photoluminescence (μPL) and μPLE spectra, the identification of the main resonances becomes possible. The key is given by the fine structure of the hot trion. Excitation spectroscopy on single charged QDs enables for the first time the complete observation of a non-trivial fine structure of an excitonic complex in a QD, the hot trion. Modelling based on eight-band k.p theory in combination with a configuration interaction scheme is in excellent agreement. Therewith the simulation also enables realistic predictions on the fine structure of the ground-state exciton which is of large importance for single quantum dot devices. Theory concludes from the observed transitions that the structural symmetry of the QDs is broken. Micro photoluminescence excitation spectroscopy combined with resonantly excited micro photoluminescence enables an optical access to the single particle states of the hole without the influence of few-particle coulomb interactions. Based on this knowledge the exciton binding

  15. Quantum Monte Carlo methods and strongly correlated electrons on honeycomb structures

    Energy Technology Data Exchange (ETDEWEB)

    Lang, Thomas C.

    2010-12-16

    In this thesis we apply recently developed, as well as sophisticated quantum Monte Carlo methods to numerically investigate models of strongly correlated electron systems on honeycomb structures. The latter are of particular interest owing to their unique properties when simulating electrons on them, like the relativistic dispersion, strong quantum fluctuations and their resistance against instabilities. This work covers several projects including the advancement of the weak-coupling continuous time quantum Monte Carlo and its application to zero temperature and phonons, quantum phase transitions of valence bond solids in spin-1/2 Heisenberg systems using projector quantum Monte Carlo in the valence bond basis, and the magnetic field induced transition to a canted antiferromagnet of the Hubbard model on the honeycomb lattice. The emphasis lies on two projects investigating the phase diagram of the SU(2) and the SU(N)-symmetric Hubbard model on the hexagonal lattice. At sufficiently low temperatures, condensed-matter systems tend to develop order. An exception are quantum spin-liquids, where fluctuations prevent a transition to an ordered state down to the lowest temperatures. Previously elusive in experimentally relevant microscopic two-dimensional models, we show by means of large-scale quantum Monte Carlo simulations of the SU(2) Hubbard model on the honeycomb lattice, that a quantum spin-liquid emerges between the state described by massless Dirac fermions and an antiferromagnetically ordered Mott insulator. This unexpected quantum-disordered state is found to be a short-range resonating valence bond liquid, akin to the one proposed for high temperature superconductors. Inspired by the rich phase diagrams of SU(N) models we study the SU(N)-symmetric Hubbard Heisenberg quantum antiferromagnet on the honeycomb lattice to investigate the reliability of 1/N corrections to large-N results by means of numerically exact QMC simulations. We study the melting of phases

  16. Quantum tunneling recombination in a system of randomly distributed trapped electrons and positive ions.

    Science.gov (United States)

    Pagonis, Vasilis; Kulp, Christopher; Chaney, Charity-Grace; Tachiya, M

    2017-09-13

    During the past 10 years, quantum tunneling has been established as one of the dominant mechanisms for recombination in random distributions of electrons and positive ions, and in many dosimetric materials. Specifically quantum tunneling has been shown to be closely associated with two important effects in luminescence materials, namely long term afterglow luminescence and anomalous fading. Two of the common assumptions of quantum tunneling models based on random distributions of electrons and positive ions are: (a) An electron tunnels from a donor to the nearest acceptor, and (b) the concentration of electrons is much lower than that of positive ions at all times during the tunneling process. This paper presents theoretical studies for arbitrary relative concentrations of electrons and positive ions in the solid. Two new differential equations are derived which describe the loss of charge in the solid by tunneling, and they are solved analytically. The analytical solution compares well with the results of Monte Carlo simulations carried out in a random distribution of electrons and positive ions. Possible experimental implications of the model are discussed for tunneling phenomena in long term afterglow signals, and also for anomalous fading studies in feldspars and apatite samples.

  17. Size-dependent electronic eigenstates of multilayer organic quantum wells

    International Nuclear Information System (INIS)

    Nguyen Ba An; Hanamura, E.

    1995-09-01

    A detailed theoretical treatment is given eigenfunctions and eigenenergies of a multilayer organic quantum well sandwiched between two different dielectric media. The abrupt change of dielectric constants at the interfaces distorts the wave function and results in possible surface states in addition to propagating states. The proper boundary conditions are accounted for by the method of image charges. Analytic criteria for existence of surface states are established using the nearest layers approximation, which depend not only on the intralayer parameters but also on the number of layers. The size dependence together with the dependence on signs and relative magnitudes of the structure parameters fully determine the energy spectrum of propagating states as well as the number and the location of surface states. (author). 28 refs, 10 figs, 2 tabs

  18. Binding of two-electron metastable states in semiconductor quantum dots under a magnetic field

    Science.gov (United States)

    Garagiola, Mariano; Pont, Federico M.; Osenda, Omar

    2018-04-01

    Applying a strong enough magnetic field results in the binding of few-electron resonant states. The mechanism was proposed many years ago but its verification in laboratory conditions is far more recent. In this work we study the binding of two-electron resonant states. The electrons are confined in a cylindrical quantum dot which is embedded in a semiconductor wire. The geometry considered is similar to the one used in actual experimental setups. The low-energy two-electron spectrum is calculated numerically from an effective-mass approximation Hamiltonian modelling the system. Methods for binding threshold calculations in systems with one and two electrons are thoroughly studied; in particular, we use quantum information quantities to assess when the strong lateral confinement approximation can be used to obtain reliable low-energy spectra. For simplicity, only cases without bound states in the absence of an external field are considered. Under these conditions, the binding threshold for the one-electron case is given by the lowest Landau energy level. Moreover, the energy of the one-electron bounded resonance can be used to obtain the two-electron binding threshold. It is shown that for realistic values of the two-electron model parameters it is feasible to bind resonances with field strengths of a few tens of tesla.

  19. Electronic properties of novel topological quantum materials studied by angle-resolved photoemission spectroscopy (ARPES)

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yun [Iowa State Univ., Ames, IA (United States)

    2016-12-17

    The discovery of quantum Hall e ect has motivated the use of topology instead of broken symmetry to classify the states of matter. Quantum spin Hall e ect has been proposed to have a separation of spin currents as an analogue of the charge currents separation in quantum Hall e ect, leading us to the era of topological insulators. Three-dimensional analogue of the Dirac state in graphene has brought us the three-dimensional Dirac states. Materials with three-dimensional Dirac states could potentially be the parent compounds for Weyl semimetals and topological insulators when time-reversal or space inversion symmetry is broken. In addition to the single Dirac point linking the two dispersion cones in the Dirac/Weyl semimetals, Dirac points can form a line in the momentum space, resulting in a topological node line semimetal. These fascinating novel topological quantum materials could provide us platforms for studying the relativistic physics in condensed matter systems and potentially lead to design of new electronic devices that run faster and consume less power than traditional, silicon based transistors. In this thesis, we present the electronic properties of novel topological quantum materials studied by angle-resolved photoemission spectroscopy (ARPES).

  20. Structural, electronic properties, and quantum capacitance of B, N and P-doped armchair carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mousavi-Khoshdel, S. Morteza, E-mail: mmousavi@iust.ac.ir [Department of Chemistry, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Jahanbakhsh-bonab, Parisa [Department of Chemistry, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Targholi, Ehsan [Young Researchers and Elite Club, Abhar Branch, Islamic Azad University, Abhar (Iran, Islamic Republic of)

    2016-10-07

    Using DFT calculations, we study the structural parameters, electronic properties and quantum capacitance of N, B, and P-doped armchair carbon nanotubes (CNTs). Fermi level shifts towards conduction band and valence band in N- and B-doped CNTs, respectively. While in the case of P atom, despite having an extra valence electron than carbon, there is no shift in Fermi level. The results revealed from a symmetric capacitance enhancement in P-doped CNT and an asymmetric capacitance enhancement in B and N-doped CNTs. The greatest amount of quantum capacitance of N-doped (6, 6) CNT could be achieved at the concentration range of 0.1–0.15. - Highlights: • Exploration of variation in quantum capacitance of CNTs through doping N, B and P atoms. • Quantum capacitance of CNTs is sensitive to impurities entered in carbon nanotubes. • Maximum quantum capacitance of N-doped CNTs is achieved at the concentration range of 0.1–0.15.

  1. Characterization of quantum well structures using a photocathode electron microscope

    Science.gov (United States)

    Spencer, Michael G.; Scott, Craig J.

    1989-01-01

    Present day integrated circuits pose a challenge to conventional electronic and mechanical test methods. Feature sizes in the submicron and nanometric regime require radical approaches in order to facilitate electrical contact to circuits and devices being tested. In addition, microwave operating frequencies require careful attention to distributed effects when considering the electrical signal paths within and external to the device under test. An alternative testing approach which combines the best of electrical and optical time domain testing is presented, namely photocathode electron microscope quantitative voltage contrast (PEMQVC).

  2. Synthesis of colloidal SnSe quantum dots by electron beam irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Li Zhen; Peng Liwei; Fang Yaoguo; Chen Zhiwen [Shanghai Applied Radiation Institute, Shanghai University, Shanghai 201800 (China); Pan Dengyu [Institute of Nanochemistry and Nanobiology, Shanghai University, Shanghai 201800 (China); Wu Minghong, E-mail: mhwu@staff.shu.edu.cn [Shanghai Applied Radiation Institute, Shanghai University, Shanghai 201800 (China)

    2011-12-15

    Water-soluble orthorhombic colloidal SnSe quantum dots with an average diameter of 4 nm were successfully prepared by a novel irradiation route using an electronic accelerator as a radiation source and hexadecyl trimethyl ammonium bromide (CTAB) as a surfactant. The quantum dots exhibit a large direct bandgap of 3.89 eV, greatly blue shifted compared with that of bulk SnSe (1.0 eV) due to the quantum confinement effect. The quantum dots show blue photoluminescence at {approx}420 nm. The influence of CTAB on the growth of the quantum dots was investigated and a possible reaction/growth mechanism was proposed. - Highlights: > A rapid, facile and green strategy is developed to synthesize SnSe QDs. > The raw materials are green and easily obtained. > The surfactant CTAB plays an important role in the formation of SnSe quantum dots. > The obtained SnSe QDs is well-dispersed with the average size of around 4 nm.

  3. Towards a Room-Temperature Spin Quantum Bus in Diamond via Electron Photoionization, Transport, and Capture

    Directory of Open Access Journals (Sweden)

    M. W. Doherty

    2016-11-01

    Full Text Available Diamond is a proven solid-state platform for spin-based quantum technology. The nitrogen-vacancy center in diamond has been used to realize small-scale quantum information processing and quantum sensing under ambient conditions. A major barrier in the development of large-scale quantum information processing in diamond is the connection of nitrogen-vacancy spin registers by a quantum bus at room temperature. Given that diamond is expected to be an ideal spin transport material, the coherent transport of spin directly between the spin registers offers a potential solution. Yet, there has been no demonstration of spin transport in diamond due to difficulties in achieving spin injection and detection via conventional methods. Here, we exploit detailed knowledge of the paramagnetic defects in diamond to identify novel mechanisms to photoionize, transport, and capture spin-polarized electrons in diamond at room temperature. Having identified these mechanisms, we explore how they may be combined to realize an on-chip spin quantum bus.

  4. Electronic transport through a quantum dot chain with strong dot-lead coupling

    International Nuclear Information System (INIS)

    Liu, Yu; Zheng, Yisong; Gong, Weijiang; Gao, Wenzhu; Lue, Tianquan

    2007-01-01

    By means of the non-equilibrium Green function technique, the electronic transport through an N-quantum-dot chain is theoretically studied. By calculating the linear conductance spectrum and the local density of states in quantum dots, we find the resonant peaks in the spectra coincides with the eigen-energies of the N-quantum-dot chain when the dot-lead coupling is relatively weak. With the increase of the dot-lead coupling, such a correspondence becomes inaccurate. When the dot-lead coupling exceeds twice the interdot coupling, such a mapping collapses completely. The linear conductance turn to reflect the eigen-energies of the (N-2)- or (N-1)-quantum dot chain instead. The two peripheral quantum dots do not manifest themselves in the linear conductance spectrum. More interestingly, with the further increase of the dot-lead coupling, the system behaves just like an (N-2)- or (N-1)-quantum dot chain in weak dot-lead coupling limit, since the resonant peaks becomes narrower with the increase of dot-lead coupling

  5. National Physics Conference. Paper Abstracts

    International Nuclear Information System (INIS)

    Marinela Dumitriu, Editorial Coordination.

    1995-01-01

    This book contains the abstracts of the proceedings of the annual Romanian Physics Conference organized by Romanian Physics Society. The conference was held on November 30 to December 2, 1995 in the city of Baia Mare. It was organized in the following nine sections: 1 - Astrophysics, Particle Physics, Nuclear Physics, Molecular and Atomic Physics; 2 - Plasma Physics; 3 - Biophysics; 4 - Technical Physics; 5 - Theoretical Physics; 6 -The Physics of Energy; 7 - The Physics of Environment 8 - Solid State Physics; 9 - Optical and Quantum Electronics. The full texts can be obtained on request from the Romanian Physical Society or directly from authors

  6. Spin-orbit interaction in quantum dots and quantum wires of correlated electrons - a way to spintronics?

    International Nuclear Information System (INIS)

    Birkholz, Jens Eiko

    2008-01-01

    We study the influence of the spin-orbit interaction on the electronic transport through quantum dots and quantum wires of correlated electrons. Starting with a one-dimensional infinite continuum model without Coulomb interaction, we analyze the interplay of the spin-orbit interaction, an external magnetic field, and an external potential leading to currents with significant spin-polarization in appropriate parameter regimes. Since lattice models are known to often be superior to continuum models in describing the experimental situation of low-dimensional mesoscopic systems, we construct a lattice model which exhibits the same low-energy physics in terms of energy dispersion and spin expectation values. Confining the lattice to finite length and connecting it to two semi-infinite noninteracting Fermi liquid leads, we calculate the zero temperature linear conductance using the Landauer-Bttiker formalism and show that spin-polarization effects also evolve for the lattice model by adding an adequate potential structure and can be controlled by tuning the overall chemical potential of the system (quantum wire and leads). Next, we allow for a finite Coulomb interaction and use the functional renormalization group (fRG) method to capture correlation effects induced by the Coulomb interaction. The interacting system is thereby transformed into a noninteracting system with renormalized system parameters. For short wires (∝100 lattice sites), we show that the energy regime in which spin polarization is found is strongly affected by the Coulomb interaction. For long wires (>1000 lattice sites), we find the power-law suppression of the total linear conductance on low energy scales typical for inhomogeneous Luttinger liquids while the degree of spin polarization stays constant. Considering quantum dots which consist of two lattice sites, we observe the well-known Kondo effect and analyze, how the Kondo temperature is affected by the spin-orbit interaction. Moreover, we show

  7. Electron - polar acoustical phonon interactions in nitride based diluted magnetic semiconductor quantum well via hot electron magnetotransport

    International Nuclear Information System (INIS)

    Pandya, Ankur; Shinde, Satyam; Jha, Prafulla K.

    2015-01-01

    In this paper the hot electron transport properties like carrier energy and momentum scattering rates and electron energy loss rates are calculated via interactions of electrons with polar acoustical phonons for Mn doped BN quantum well in BN nanosheets via piezoelectric scattering and deformation potential mechanisms at low temperatures with high electric field. Electron energy loss rate increases with the electric field. It is observed that at low temperatures and for low electric field the phonon absorption is taking place whereas, for sufficient large electric field, phonon emission takes place. Under the piezoelectric (polar acoustical phonon) scattering mechanism, the carrier scattering rate decreases with the reduction of electric field at low temperatures wherein, the scattering rate variation with electric field is limited by a specific temperature beyond which there is no any impact of electric field on such scattering

  8. Stern-Gerlach experiment, electron spin and intermediate quantum mechanics

    Energy Technology Data Exchange (ETDEWEB)

    Mackintosh, A.R. (Copenhagen Univ. (Denmark). H.C. Oersted Inst.)

    1983-01-01

    The paper deals with the theory of electron spin. The Stern-Gerlach experiment, the anticommutation relations and the properties of spin operators are discussed. The Pauli theory, Dirac transformation theory, the double Stern-Gerlach experiment, the EPR paradox and Bell's inequality are also covered.

  9. Electron Transport in Quantum Dots and Heat Transport in Molecules

    DEFF Research Database (Denmark)

    Kirsanskas, Gediminas

    Since the invention of the transistor in 1947 and the development of integrated circuits in the late 1950’s, there was a rapid progress in the development and miniaturization of the solid state devices and electronic circuit components. This miniaturization raises a question “How small do we have...

  10. Electronic Structure of ZnO Quantum Dots studied by High-frequency EPR, ESE, ENDOR and ODMR Spectroscopy

    NARCIS (Netherlands)

    Baranov, P.G.; Romanov, N.G.; Bundakova, A.P.; de Mello-Donega, Celso; Schmidt, J.

    2016-01-01

    High-frequency electron paramagnetic resonance (EPR), electron spin echo (ESE), electron-nuclear double resonance (ENDOR) and optically detected magnetic resonance (ODMR) were applied for the investigation of the electronic properties of ZnO colloidal quantum dots (QDs) which consist of a ZnO

  11. Electron-Phonon Coupling and Resonant Relaxation from 1D and 1P States in PbS Quantum Dots.

    Science.gov (United States)

    Kennehan, Eric R; Doucette, Grayson S; Marshall, Ashley R; Grieco, Christopher; Munson, Kyle T; Beard, Matthew C; Asbury, John B

    2018-05-31

    Observations of the hot-phonon bottleneck, which is predicted to slow the rate of hot carrier cooling in quantum confined nanocrystals, have been limited to date for reasons that are not fully understood. We used time-resolved infrared spectroscopy to directly measure higher energy intraband transitions in PbS colloidal quantum dots. Direct measurements of these intraband transitions permitted detailed analysis of the electronic overlap of the quantum confined states that may influence their relaxation processes. In smaller PbS nanocrystals, where the hot-phonon bottleneck is expected to be most pronounced, we found that relaxation of parity selection rules combined with stronger electron-phonon coupling led to greater spectral overlap of transitions among the quantum confined states. This created pathways for fast energy transfer and relaxation that may bypass the predicted hot-phonon bottleneck. In contrast, larger, but still quantum confined nanocrystals did not exhibit such relaxation of the parity selection rules and possessed narrower intraband states. These observations were consistent with slower relaxation dynamics that have been measured in larger quantum confined systems. These findings indicated that, at small radii, electron-phonon interactions overcome the advantageous increase in energetic separation of the electronic states for PbS quantum dots. Selection of appropriately sized quantum dots, which minimize spectral broadening due to electron-phonon interactions while maximizing electronic state separation, is necessary to observe the hot-phonon bottleneck. Such optimization may provide a framework for achieving efficient hot carrier collection and multiple exciton generation.

  12. Nuclear quantum effects on the nonadiabatic decay mechanism of an excited hydrated electron

    Science.gov (United States)

    Borgis, Daniel; Rossky, Peter J.; Turi, László

    2007-11-01

    We present a kinetic analysis of the nonadiabatic decay mechanism of an excited state hydrated electron to the ground state. The theoretical treatment is based on a quantized, gap dependent golden rule rate constant formula which describes the nonadiabatic transition rate between two quantum states. The rate formula is expressed in terms of quantum time correlation functions of the energy gap and of the nonadiabatic coupling. These gap dependent quantities are evaluated from three different sets of mixed quantum-classical molecular dynamics simulations of a hydrated electron equilibrated (a) in its ground state, (b) in its first excited state, and (c) on a hypothetical mixed potential energy surface which is the average of the ground and the first excited electronic states. The quantized, gap dependent rate results are applied in a phenomenological kinetic equation which provides the survival probability function of the excited state electron. Although the lifetime of the equilibrated excited state electron is computed to be very short (well under 100fs), the survival probability function for the nonequilibrium process in pump-probe experiments yields an effective excited state lifetime of around 300fs, a value that is consistent with the findings of several experimental groups and previous theoretical estimates.

  13. InN/GaN quantum dot superlattices: Charge-carrier states and surface electronic structure

    Science.gov (United States)

    Kanouni, F.; Brezini, A.; Djenane, M.; Zou, Q.

    2018-03-01

    We have theoretically investigated the electron energy spectra and surface states energy in the three dimensionally ordered quantum dot superlattices (QDSLs) made of InN and GaN semiconductors. The QDSL is assumed in this model to be a matrix of GaN containing cubic dots of InN of the same size and uniformly distributed. For the miniband’s structure calculation, the resolution of the effective mass Schrödinger equation is done by decoupling it in the three directions within the framework of Kronig-Penney model. We found that the electrons minibands in infinite ODSLs are clearly different from those in the conventional quantum-well superlattices. The electrons localization and charge-carrier states are very dependent on the quasicrystallographic directions, the size and the shape of the dots which play a role of the artificial atoms in such QD supracrystal. The energy spectrum of the electron states localized at the surface of InN/GaN QDSL is represented by Kronig-Penney like-model, calculated via direct matching procedure. The calculation results show that the substrate breaks symmetrical shape of QDSL on which some localized electronic surface states can be produced in minigap regions. Furthermore, we have noticed that the surface states degeneracy is achieved in like very thin bands located in the minigaps, identified by different quantum numbers nx, ny, nz. Moreover, the surface energy bands split due to the reduction of the symmetry of the QDSL in z-direction.

  14. Carrier emission from the electronic states of self-assembled indium arsenide quantum dots

    International Nuclear Information System (INIS)

    Lin, S.W.; Song, A.M.; Missous, M.; Hawkins, I.D; Hamilton, B.; Engstroem, O.; Peaker, A.R.

    2006-01-01

    We have used the new technique of high resolution (Laplace) transient spectroscopy to examine the electronic states of ensembles of self-assembled quantum dots of InAs in a GaAs matrix. These have been produced by solid source MBE. We have monitored the s and p state occupancies as a function of time under thermal excitation over a range of temperatures after electrons have been captured by the quantum dots with different Fermi level positions. This can provide more information about the interaction of the dots with the host matrix than is possible with optical techniques and gives new fundamental insights into how such dots may operate in electronic devices such as memory and sensors. The increase in resolution of Laplace transient spectroscopy over conventional experiments reveals quite specific rates of carrier loss which we attribute to tunnelling at low temperatures and a combination of thermal emission and tunnelling as the temperature is increased

  15. Temperature dependent transport of two dimensional electrons in the integral quantum Hall regime

    International Nuclear Information System (INIS)

    Wi, H.P.

    1986-01-01

    This thesis is concerned with the temperature dependent electronic transport properties of a two dimensional electron gas subject to background potential fluctuations and a perpendicular magnetic field. The author carried out an extensive temperature dependent study of the transport coefficients, in the region of an integral quantum plateau, in an In/sub x/Ga/sub 1-x/As/InP heterostructure for 4.2K 10 cm -2 meV -1 ) even at the middle between two Landau levels, which is unexpected from model calculations based on short ranged randomness. In addition, the different T dependent behavior of rho/sub xx/ between the states in the tails and those near the center of a Landau level, indicates the existence of different electron states in a Landau level. Additionally, the author reports T-dependent transport measurements in the transition region between two quantum plateaus in several different materials

  16. Theoretical modelling of electron transport in InAs/GaAs quantum dot superlattices

    International Nuclear Information System (INIS)

    Vukmirovic, Nenad; Ikonic, Zoran; Savic, Ivana; Indjin, Dragan; Harrison, Paul

    2006-01-01

    A theoretical model describing the electron transport in InAs/GaAs quantum dot infrared photodetectors, modelled as ideal quantum dot superlattices, is presented. The carrier wave functions and energy levels were evaluated using the strain dependent 8-band k.p Hamiltonian and used to calculate all intra- and inter-period transition rates due to interaction with phonons and electromagnetic radiation. The interaction with longitudinal acoustic phonons and electromagnetic radiation was treated perturbatively within the framework of Fermi's golden rule, while the interaction with longitudinal optical phonons was considered taking into account their strong coupling to electrons. The populations of energy levels were then found from a system of rate equations, and the electron current in the superlattice was subsequently extracted. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Quantum mechanics of electronic-rotational energy transfer in F(2P) + H2 collisions

    International Nuclear Information System (INIS)

    Wyatt, R.E.; Walker, R.B.

    1977-01-01

    A theoretical study is made of electronic-rotational energy transfer in F( 2 P) + H 2 three-dimensional collisions, with electronic matrix elements from DIM theory. The quantum close-coupled equations are integrated via the R-matrix propagation method. Inelastic quenching probabilities are emphasized, with and without simulated open reaction channels. Interweaving patterns in the transition probability for even and odd nuclear parity vs. J (total angular momentum quantum number) are analyzed in terms of avoided crossing structure in the electrotational energy correlation diagrams. Localized regions where electronic quenching is dominant are identified in the correlation diagrams, and are confirmed in separate calculations which neglect interchannel mixing in local regions of the atom-molecule separation. Open reaction channels are found to have little influence on the quenching probabilities in these low energy calculations

  18. Interaction of two solitary waves in quantum electron-positron-ion plasma

    International Nuclear Information System (INIS)

    Xu Yanxia; Lin Maimai; Shi Yuren; Duan Wenshan; Liu Zongming; Chen Jianmin

    2011-01-01

    The collision between two ion-acoustic solitary waves with arbitrary colliding angle θ in an unmagnetized, ultracold quantum three-component e-p-i plasma has been investigated. By using the extended Poincare-Lighthill-Kuo (PLK) perturbation method, we obtain the KdV equations and the analytical phase shifts after the collision of two solitary waves in this three-component plasma. The effects of the quantum parameter H, the ratio of Fermi positron temperature to Fermi electron temperature σ, the ratio of Fermi positron number density to Fermi electron number density μ, and the ratio of Fermi ion temperature to Fermi electron temperature ρ on the phase shifts are studied. It is found that these parameters can significantly influence the phase shifts of the solitons.

  19. Theoretical modelling of electron transport in InAs/GaAs quantum dot superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Vukmirovic, Nenad; Ikonic, Zoran; Savic, Ivana; Indjin, Dragan; Harrison, Paul [School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT (United Kingdom)

    2006-07-01

    A theoretical model describing the electron transport in InAs/GaAs quantum dot infrared photodetectors, modelled as ideal quantum dot superlattices, is presented. The carrier wave functions and energy levels were evaluated using the strain dependent 8-band k.p Hamiltonian and used to calculate all intra- and inter-period transition rates due to interaction with phonons and electromagnetic radiation. The interaction with longitudinal acoustic phonons and electromagnetic radiation was treated perturbatively within the framework of Fermi's golden rule, while the interaction with longitudinal optical phonons was considered taking into account their strong coupling to electrons. The populations of energy levels were then found from a system of rate equations, and the electron current in the superlattice was subsequently extracted. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Investigation by perturbative and analytical method of electronic properties of square quantum well under electric field

    Directory of Open Access Journals (Sweden)

    Mustafa Kemal BAHAR

    2010-06-01

    Full Text Available In this study, the effects of applied electric field on the isolated square quantum well was investigated by analytic and perturbative method. The energy eigen values and wave functions in quantum well were found by perturbative method. Later, the electric field effects were investigated by analytic method, the results of perturbative and analytic method were compared. As well as both of results fit with each other, it was observed that externally applied electric field changed importantly electronic properties of the system.

  1. Hydrodynamic theory for quantum plasmonics: Linear-response dynamics of the inhomogeneous electron gas

    DEFF Research Database (Denmark)

    Yan, Wei

    2015-01-01

    We investigate the hydrodynamic theory of metals, offering systematic studies of the linear-response dynamics for an inhomogeneous electron gas. We include the quantum functional terms of the Thomas-Fermi kinetic energy, the von Weizsa¨cker kinetic energy, and the exchange-correlation Coulomb...... energies under the local density approximation. The advantages, limitations, and possible improvements of the hydrodynamic theory are transparently demonstrated. The roles of various parameters in the theory are identified. We anticipate that the hydrodynamic theory can be applied to investigate the linear...... response of complex metallic nanostructures, including quantum effects, by adjusting theory parameters appropriately....

  2. Spin relaxation in quantum dots due to electron exchange with leads.

    Science.gov (United States)

    Vorontsov, A B; Vavilov, M G

    2008-11-28

    We calculate spin relaxation rates in lateral quantum dot systems due to electron exchange between dots and leads. Using rate equations, we develop a theoretical description of the experimentally observed electric current in the spin blockade regime of double quantum dots. A single expression fits the entire current profile and describes the structure of both the conduction peaks and the suppressed ("valley") region. Extrinsic rates calculated here have to be taken into account for accurate extraction of intrinsic relaxation rates due to the spin-orbit and hyperfine spin scattering mechanisms from spin blockade measurements.

  3. On the exact spectra of two electrons confined by two-dimensional quantum dots

    International Nuclear Information System (INIS)

    Soldatov, A.V.; Bogolubov Jr, N.N.

    2005-12-01

    Applicability of the method of intermediate problems to investigation of the energy spectrum and eigenstates of a two- electron two-dimensional quantum dot (QD) formed by a parabolic confining potential is discussed. It is argued that the method of intermediate problems, which provides convergent improvable lower bound estimates for eigenvalues of linear half-bound Hermitian operators in Hilbert space, can be fused with the classical Rayleigh-Ritz variational method and stochastic variational method thus providing an efficient tool of verification of the results obtained so far by various analytical and numerical methods being of current usage for studies of quantum dot models. (author)

  4. Intersubband spectroscopy of ZnO/ZnMgO quantum wells grown on m-plane ZnO substrates for quantum cascade device applications (Conference Presentation)

    Science.gov (United States)

    Quach, Patrick; Jollivet, Arnaud; Isac, Nathalie; Bousseksou, Adel; Ariel, Frédéric; Tchernycheva, Maria; Julien, François H.; Montes Bajo, Miguel; Tamayo-Arriola, Julen; Hierro, Adrián.; Le Biavan, Nolwenn; Hugues, Maxime; Chauveau, Jean-Michel

    2017-03-01

    Quantum cascade (QC) lasers opens new prospects for powerful sources operating at THz frequencies. Up to now the best THz QC lasers are based on intersubband emission in GaAs/AlGaAs quantum well (QW) heterostructures. The maximum operating temperature is 200 K, which is too low for wide-spread applications. This is due to the rather low LO-phonon energy (36 meV) of GaAs-based materials. Indeed, thermal activation allows non-radiative path through electron-phonon interaction which destroys the population inversion. Wide band gap materials such as ZnO have been predicted to provide much higher operating temperatures because of the high value of their LO-phonon energy. However, despite some observations of intersubband absorption in c-plane ZnO/ZnMgO quantum wells, little is known on the fundamental parameters such as the conduction band offset in such heterostructures. In addition the internal field inherent to c-plane grown heterostuctures is an handicap for the design of QC lasers and detectors. In this talk, we will review a systematic investigation of ZnO/ZnMgO QW heterostructures with various Mg content and QW thicknesses grown by plasma molecular beam epitaxy on low-defect m-plane ZnO substrates. We will show that most samples exhibit TM-polarized intersubband absorption at room temperature linked either to bound-to-quasi bound inter-miniband absorption or to bound-to bound intersubband absorption depending on the Mg content of the barrier material. This systematic study allows for the first time to estimate the conduction band offset of ZnO/ZnMgO heterostructures, opening prospects for the design of QC devices operating at THz frequencies. This was supported by the European Union's Horizon 2020 research and innovation programme under grant agreement #665107.

  5. Cavity-photon contribution to the effective interaction of electrons in parallel quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Gudmundsson, Vidar [Science Institute, University of Iceland, Reykjavik (Iceland); Sitek, Anna [Science Institute, University of Iceland, Reykjavik (Iceland); Department of Theoretical Physics, Faculty of Fundamental Problems of Technology, Wroclaw University of Technology (Poland); Abdullah, Nzar Rauf [Science Institute, University of Iceland, Reykjavik (Iceland); Physics Department, Faculty of Science and Science Education, School of Science, University of Sulaimani, Kurdistan Region (Iraq); Tang, Chi-Shung [Department of Mechanical Engineering, National United University, Miaoli (China); Manolescu, Andrei [School of Science and Engineering, Reykjavik University (Iceland)

    2016-05-15

    A single cavity photon mode is expected to modify the Coulomb interaction of an electron system in the cavity. Here we investigate this phenomena in a parallel double quantum dot system. We explore properties of the closed system and the system after it has been opened up for electron transport. We show how results for both cases support the idea that the effective electron-electron interaction becomes more repulsive in the presence of a cavity photon field. This can be understood in terms of the cavity photons dressing the polarization terms in the effective mutual electron interaction leading to nontrivial delocalization or polarization of the charge in the double parallel dot potential. In addition, we find that the effective repulsion of the electrons can be reduced by quadrupolar collective oscillations excited by an external classical dipole electric field. (copyright 2015 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. Cavity-photon contribution to the effective interaction of electrons in parallel quantum dots

    Science.gov (United States)

    Gudmundsson, Vidar; Sitek, Anna; Abdullah, Nzar Rauf; Tang, Chi-Shung; Manolescu, Andrei

    2016-05-01

    A single cavity photon mode is expected to modify the Coulomb interaction of an electron system in the cavity. Here we investigate this phenomena in a parallel double quantum dot system. We explore properties of the closed system and the system after it has been opened up for electron transport. We show how results for both cases support the idea that the effective electron-electron interaction becomes more repulsive in the presence of a cavity photon field. This can be understood in terms of the cavity photons dressing the polarization terms in the effective mutual electron interaction leading to nontrivial delocalization or polarization of the charge in the double parallel dot potential. In addition, we find that the effective repulsion of the electrons can be reduced by quadrupolar collective oscillations excited by an external classical dipole electric field.

  7. Quantum-chemical studies of quasi-one-dimensional electron systems. Part 2. Cumulenes and origin of the forbidden zone

    Directory of Open Access Journals (Sweden)

    Yuriy Kruglyak

    2015-06-01

    Full Text Available This review is devoted to the basic problem in quantum theory of quasi-one-dimensional electron systems like polyenes (Part 1 and cumulenes (Part 2 – physical origin of the forbidden zone in these and analogous 1D electron systems due to two possible effects – Peierls instability (bond alternation and Mott instability (electron correlation. Both possible contradiction and coexistence of the Mott and Peierls instabilities are summerized on the basis of the Kiev quantum chemistry team research projects.

  8. Electron Raman scattering in semiconductor quantum wire in an external magnetic field

    International Nuclear Information System (INIS)

    Betancourt-Riera, Ri; Nieto Jalil, J M; Riera, R; Betancourt-Riera, Re; Rosas, R

    2008-01-01

    The differential cross-section for an electron Raman scattering process in a semiconductor quantum wire in the presence of an external magnetic field perpendicular to the plane of confinement is calculated. We assume a single parabolic conduction band. The emission spectra for different scattering configurations and the selection rules for the processes are studied. Singularities in the spectra are found and interpreted. The electron Raman scattering studied here can be used to provide direct information about the electron band and subband structure of these confinement systems. The magnetic field distribution is considered constant with value B 0 inside the wire and zero outside

  9. Electron-energy relaxation in polar semiconductor double quantum dots

    Czech Academy of Sciences Publication Activity Database

    Král, Karel; Khás, Zdeněk; Zdeněk, Petr; Čerňanský, Marian; Lin, C. Y.

    2001-01-01

    Roč. 15, č. 27 (2001), s. 3503-3512 ISSN 0217-9792 R&D Projects: GA AV ČR IAA1010113; GA MŠk OC P5.20 Institutional research plan: CEZ:AV0Z1010914 Keywords : electron ic energy relaxation * zero-dimensional nanostructures Subject RIV: BE - The oretical Physics Impact factor: 0.523, year: 2001

  10. Modulation transfer function and detective quantum efficiency of electron bombarded charge coupled device detector for low energy electrons

    International Nuclear Information System (INIS)

    Horacek, Miroslav

    2005-01-01

    The use of a thinned back-side illuminated charge coupled device chip as two-dimensional sensor working in direct electron bombarded mode at optimum energy of the incident signal electrons is demonstrated and the measurements of the modulation transfer function (MTF) and detective quantum efficiency (DQE) are described. The MTF was measured for energy of electrons 4 keV using an edge projection method and a stripe projection method. The decrease of the MTF for a maximum spatial frequency of 20.8 cycles/mm, corresponding to the pixel size 24x24 μm, is 0.75≅-2.5 dB, and it is approximately the same for both horizontal and vertical directions. DQE was measured using an empty image and the mixing factor method. Empty images were acquired for energies of electrons from 2 to 5 keV and for various doses, ranging from nearly dark image to a nearly saturated one. DQE increases with increasing energy of bombarded electrons and reaches 0.92 for electron energy of 5 keV. For this energy the detector will be used for the angle- and energy-selective detection of signal electrons in the scanning low energy electron microscope

  11. Theory of Correlated Pairs of Electrons Oscillating in Resonant Quantum States to Reach the Critical Temperature in a Metal

    OpenAIRE

    Aroche, Raúl Riera; Rosas-Cabrera, Rodrigo Arturo; Burgos, Rodrigo Arturo Rosas; Betancourt-Riera, René; Betancourt-Riera, Ricardo

    2017-01-01

    The formation of Correlated Electron Pairs Oscillating around the Fermi level in Resonant Quantum States (CEPO-RQS), when a metal is cooled to its critical temperature T=Tc, is studied. The necessary conditions for the existence of CEPO-RQS are analyzed. The participation of electron-electron interaction screened by an electron dielectric constant of the form proposed by Thomas Fermi is considered and a physical meaning for the electron-phonon-electron interaction in the formation of the CEPO...

  12. 3rd International Conference on Opto-Electronics and Applied Optics

    CERN Document Server

    Chakrabarti, Satyajit; Reehal, Haricharan; Lakshminarayanan, Vasudevan

    2017-01-01

    The Proceedings of 3rd International Conference on Opto-Electronics and Applied Optics, OPTRONIX 2016 is an effort to promote and present the research works by scientists and researchers including students in India and abroad in the area of Green Photonics and other related areas as well as to raise awareness about the recent trends of research and development in the area of the related fields. The book has been organized in such a way that it will be easier for the readers to go through and find out the topic of their interests. The first part includes the Keynote addresses by Rajesh Gupta, Department of Energy Science and Engineering, Indian Institute of Technology, Bombay; P.T. Ajith Kumar, President and Leading Scientist Light Logics Holography and Optics, Crescent Hill, Trivandrum, Kerala; and K.K. Ghosh, Institute of Engineering & Management, Kolkata, India.  The second part focuses on the Plenary and Invited Talks given by eminent scientists namely, Vasudevan Lakshminarayanan, University of Wate...

  13. Biomolecular Structure Information from High-Speed Quantum Mechanical Electronic Spectra Calculation.

    Science.gov (United States)

    Seibert, Jakob; Bannwarth, Christoph; Grimme, Stefan

    2017-08-30

    A fully quantum mechanical (QM) treatment to calculate electronic absorption (UV-vis) and circular dichroism (CD) spectra of typical biomolecules with thousands of atoms is presented. With our highly efficient sTDA-xTB method, spectra averaged along structures from molecular dynamics (MD) simulations can be computed in a reasonable time frame on standard desktop computers. This way, nonequilibrium structure and conformational, as well as purely quantum mechanical effects like charge-transfer or exciton-coupling, are included. Different from other contemporary approaches, the entire system is treated quantum mechanically and neither fragmentation nor system-specific adjustment is necessary. Among the systems considered are a large DNA fragment, oligopeptides, and even entire proteins in an implicit solvent. We propose the method in tandem with experimental spectroscopy or X-ray studies for the elucidation of complex (bio)molecular structures including metallo-proteins like myoglobin.

  14. Modern quantum chemistry introduction to advanced electronic structure theory

    CERN Document Server

    Szabo, Attila

    1996-01-01

    The aim of this graduate-level textbook is to present and explain, at other than a superficial level, modem ab initio approaches to the calculation of the electronic structure and properties of molecules. The first three chapters contain introductory material culminating in a thorough discussion of the Hartree-Fock approximation.The remaining four chapters describe a variety of more sophisticated approaches, which improve upon this approximation.Among the highlights of the seven chapters are (1) a review of the mathematics (mostly matrix algebra) required for the rest of the book, (2) an intr

  15. Quantum oscillations and the electronic transport properties in multichain nanorings

    International Nuclear Information System (INIS)

    Racolta, D.

    2009-01-01

    We consider a system of multichain nanorings in static electric and magnetic field. The magnetic field induces characteristic phase changes. These phase shifts produce interference phenomena in the case of nanosystems for which the coherence length is larger than the sample dimension. We obtain energy solutions that are dependent on the number of sites N α characterizing a chain, of phase on the phase φ α and on the applied voltage. We found rich oscillations structures exhibited by the magnetic flux and we established the transmission probability. This proceeds by applying Landauer conductance formulae which opens the way to study electronic transport properties. (authors)

  16. Optical Biosensors: A Revolution Towards Quantum Nanoscale Electronics Device Fabrication

    Directory of Open Access Journals (Sweden)

    D. Dey

    2011-01-01

    Full Text Available The dimension of biomolecules is of few nanometers, so the biomolecular devices ought to be of that range so a better understanding about the performance of the electronic biomolecular devices can be obtained at nanoscale. Development of optical biomolecular device is a new move towards revolution of nano-bioelectronics. Optical biosensor is one of such nano-biomolecular devices that has a potential to pave a new dimension of research and device fabrication in the field of optical and biomedical fields. This paper is a very small report about optical biosensor and its development and importance in various fields.

  17. Universal Quantum Criticality in the Metal-Insulator Transition of Two-Dimensional Interacting Dirac Electrons

    Directory of Open Access Journals (Sweden)

    Yuichi Otsuka

    2016-03-01

    Full Text Available The metal-insulator transition has been a subject of intense research since Mott first proposed that the metallic behavior of interacting electrons could turn to an insulating one as electron correlations increase. Here, we consider electrons with massless Dirac-like dispersion in two spatial dimensions, described by the Hubbard models on two geometrically different lattices, and perform numerically exact calculations on unprecedentedly large systems that, combined with a careful finite-size scaling analysis, allow us to explore the quantum critical behavior in the vicinity of the interaction-driven metal-insulator transition. Thereby, we find that the transition is continuous, and we determine the quantum criticality for the corresponding universality class, which is described in the continuous limit by the Gross-Neveu model, a model extensively studied in quantum field theory. Furthermore, we discuss a fluctuation-driven scenario for the metal-insulator transition in the interacting Dirac electrons: The metal-insulator transition is triggered only by the vanishing of the quasiparticle weight, not by the Dirac Fermi velocity, which instead remains finite near the transition. This important feature cannot be captured by a simple mean-field or Gutzwiller-type approximate picture but is rather consistent with the low-energy behavior of the Gross-Neveu model.

  18. Direct Identification of Atomic-Like Electronic Levels in InAs Nano crystal Quantum Dots

    International Nuclear Information System (INIS)

    Millo, O.; Katz, D.

    1999-01-01

    The size dependent level structure of InAs nano crystals in the range 2-7 nm in diameter is investigated using both tunneling and optical spectroscopies. The tunneling measurements are performed using a cryogenic scanning tunneling microscope on individual nano crystals that, are attached to a gold substrate via dithiol molecules. The tunneling I-V characteristics manifest an interplay between single electron charging and quantum size effects. We are able to directly identify quantum confined states of isolated InAs nano crystals having s and p symmetries. These states are observed in the I-V curves as two and six-fold single electron charging multiplets. Excellent agreement is found between the strongly allowed optical transitions [1] and the spacing of levels detected in the tunneling experiment. This correlation provides new information on the quantum-dot level structure, from which we conclude that the top-most valence band state has both s and p characteristics. The interplay between level structure singles electron charging of the nano crystals obeys an atomic-like Aufbau sequential electron level occupation

  19. Helical edge states and fractional quantum Hall effect in a graphene electron-hole bilayer.

    Science.gov (United States)

    Sanchez-Yamagishi, Javier D; Luo, Jason Y; Young, Andrea F; Hunt, Benjamin M; Watanabe, Kenji; Taniguchi, Takashi; Ashoori, Raymond C; Jarillo-Herrero, Pablo

    2017-02-01

    Helical 1D electronic systems are a promising route towards realizing circuits of topological quantum states that exhibit non-Abelian statistics. Here, we demonstrate a versatile platform to realize 1D systems made by combining quantum Hall (QH) edge states of opposite chiralities in a graphene electron-hole bilayer at moderate magnetic fields. Using this approach, we engineer helical 1D edge conductors where the counterpropagating modes are localized in separate electron and hole layers by a tunable electric field. These helical conductors exhibit strong non-local transport signals and suppressed backscattering due to the opposite spin polarizations of the counterpropagating modes. Unlike other approaches used for realizing helical states, the graphene electron-hole bilayer can be used to build new 1D systems incorporating fractional edge states. Indeed, we are able to tune the bilayer devices into a regime hosting fractional and integer edge states of opposite chiralities, paving the way towards 1D helical conductors with fractional quantum statistics.

  20. Quantum ontologies

    International Nuclear Information System (INIS)

    Stapp, H.P.

    1988-12-01

    Quantum ontologies are conceptions of the constitution of the universe that are compatible with quantum theory. The ontological orientation is contrasted to the pragmatic orientation of science, and reasons are given for considering quantum ontologies both within science, and in broader contexts. The principal quantum ontologies are described and evaluated. Invited paper at conference: Bell's Theorem, Quantum Theory, and Conceptions of the Universe, George Mason University, October 20-21, 1988. 16 refs

  1. National Physics Conference

    International Nuclear Information System (INIS)

    Oancea, Margareta; Sandu, Doina; Calboreanu, Rodica

    2000-01-01

    The National Physics Conference organized annually by the Romanian Physical Society has been held in Constanta, Romania on September 21-23, 2000. It covered the following 12 sections: - 1. Astrophysics and High Energy (9 reports); - 2. Atomic and Molecular Physics (20 reports); - 3. Nuclear Physics (18 reports); - 4. Technical and Engineering Physics (34 reports); - 5. Condensed Matter Physics (67 reports); - 6. Optics and Quantum Electronics (12 reports); - 7. Plasma Physics (27 reports); - 8. Biophysics (30 reports); - 9. Physics for Energy (17 reports); - 10. Mathematical and Computational Physics (20 reports); -11. Physics and Education (8 reports); - 12. Earth and Environmental Physics (16 reports). The proceedings contains mainly short communications

  2. Enhanced Electronic Properties of SnO2 via Electron Transfer from Graphene Quantum Dots for Efficient Perovskite Solar Cells.

    Science.gov (United States)

    Xie, Jiangsheng; Huang, Kun; Yu, Xuegong; Yang, Zhengrui; Xiao, Ke; Qiang, Yaping; Zhu, Xiaodong; Xu, Lingbo; Wang, Peng; Cui, Can; Yang, Deren

    2017-09-26

    Tin dioxide (SnO 2 ) has been demonstrated as an effective electron-transporting layer (ETL) for attaining high-performance perovskite solar cells (PSCs). However, the numerous trap states in low-temperature solution processed SnO 2 will reduce the PSCs performance and result in serious hysteresis. Here, we report a strategy to improve the electronic properties in SnO 2 through a facile treatment of the films with adding a small amount of graphene quantum dots (GQDs). We demonstrate that the photogenerated electrons in GQDs can transfer to the conduction band of SnO 2 . The transferred electrons from the GQDs will effectively fill the electron traps as well as improve the conductivity of SnO 2 , which is beneficial for improving the electron extraction efficiency and reducing the recombination at the ETLs/perovskite interface. The device fabricated with SnO 2 :GQDs could reach an average power conversion efficiency (PCE) of 19.2 ± 1.0% and a highest steady-state PCE of 20.23% with very little hysteresis. Our study provides an effective way to enhance the performance of perovskite solar cells through improving the electronic properties of SnO 2 .

  3. Spin of a Multielectron Quantum Dot and Its Interaction with a Neighboring Electron

    Directory of Open Access Journals (Sweden)

    Filip K. Malinowski

    2018-03-01

    Full Text Available We investigate the spin of a multielectron GaAs quantum dot in a sequence of nine charge occupancies, by exchange coupling the multielectron dot to a neighboring two-electron double quantum dot. For all nine occupancies, we make use of a leakage spectroscopy technique to reconstruct the spectrum of spin states in the vicinity of the interdot charge transition between a single- and a multielectron quantum dot. In the same regime we also perform time-resolved measurements of coherent exchange oscillations between the single- and multielectron quantum dot. With these measurements, we identify distinct characteristics of the multielectron spin state, depending on whether the dot’s occupancy is even or odd. For three out of four even occupancies, we do not observe any exchange interaction with the single quantum dot, indicating a spin-0 ground state. For the one remaining even occupancy, we observe an exchange interaction that we associate with a spin-1 multielectron quantum dot ground state. For all five of the odd occupancies, we observe an exchange interaction associated with a spin-1/2 ground state. For three of these odd occupancies, we clearly demonstrate that the exchange interaction changes sign in the vicinity of the charge transition. For one of these, the exchange interaction is negative (i.e., triplet preferring beyond the interdot charge transition, consistent with the observed spin-1 for the next (even occupancy. Our experimental results are interpreted through the use of a Hubbard model involving two orbitals of the multielectron quantum dot. Allowing for the spin correlation energy (i.e., including a term favoring Hund’s rules and different tunnel coupling to different orbitals, we qualitatively reproduce the measured exchange profiles for all occupancies.

  4. Confinement control mechanism for two-electron Hulthen quantum dots in plasmas

    Science.gov (United States)

    Bahar, M. K.; Soylu, A.

    2018-05-01

    In this study, for the first time, the energies of two-electron Hulthen quantum dots (TEHQdots) embedded in Debye and quantum plasmas modeled by the more general exponential cosine screened Coulomb (MGECSC) potential under the combined influence of electric and magnetic fields are investigated by numerically solving the Schrödinger equation using the asymptotic iteration method. To do this, the four different forms of the MGECSC potential, which set through the different cases of the potential parameters, are taken into consideration. We propose that plasma environments form considerable quantum mechanical effects for quantum dots and other atomic systems and that plasmas are important experimental arguments. In this study, by considering the quantum dot parameters, the external field parameters, and the plasma screening parameters, a control mechanism of the confinement on energies of TEHQdots and the frequency of the radiation emitted by TEHQdots as a result of any excitation is discussed. In this mechanism, the behaviors, similarities, the functionalities of the control parameters, and the influences of plasmas on these quantities are explored.

  5. Modulation of a compressional electromagnetic wave in a magnetized electron-positron quantum plasma.

    Science.gov (United States)

    Amin, M R

    2015-09-01

    Amplitude modulation of a compressional electromagnetic wave in a strongly magnetized electron-positron pair plasma is considered in the quantum magnetohydrodynamic regime. The important ingredients of this study are the inclusion of the external strong magnetic field, Fermi quantum degeneracy pressure, particle exchange potential, quantum diffraction effects via the Bohm potential, and dissipative effect due to collision of the charged carriers. A modified-nonlinear Schödinger equation is developed for the compressional magnetic field of the electromagnetic wave by employing the standard reductive perturbation technique. The linear and nonlinear dispersions of the electromagnetic wave are discussed in detail. For some parameter ranges, relevant to dense astrophysical objects such as the outer layers of white dwarfs, neutron stars, and magnetars, etc., it is found that the compressional electromagnetic wave is modulationally unstable and propagates as a dissipated electromagnetic wave. It is also found that the quantum effects due to the particle exchange potential and the Bohm potential are negligibly small in comparison to the effects of the Fermi quantum degeneracy pressure. The numerical results on the growth rate of the modulation instability is also presented.

  6. Superconducting single electron transistor for charge sensing in Si/SiGe-based quantum dots

    Science.gov (United States)

    Yang, Zhen

    Si-based quantum devices, including Si/SiGe quantum dots (QD), are promising candidates for spin-based quantum bits (quits), which are a potential platform for quantum information processing. Meanwhile, qubit readout remains a challenging task related to semiconductor-based quantum computation. This thesis describes two readout devices for Si/SiGe QDs and the techniques for developing them from a traditional single electron transistor (SET). By embedding an SET in a tank circuit and operating it in the radio-frequency (RF) regime, a superconducting RF-SET has quick response as well as ultra high charge sensitivity and can be an excellent charge sensor for the QDs. We demonstrate such RF-SETs for QDs in a Si/SiGe heterostructure. Characterization of the SET in magnetic fields is studied for future exploration of advanced techniques such as spin detection and spin state manipulation. By replacing the tank circuit with a high-quality-factor microwave cavity, the embedded SET will be operated in the supercurrent regime as a single Cooper pair transistor (CPT) to further increase the charge sensitivity and reduce any dissipation. The operating principle and implementation of the cavity-embedded CPT (cCPT) will be introduced.

  7. Physics colloquium: Single-electron counting in quantum metrology and in statistical mechanics

    CERN Multimedia

    Geneva University

    2011-01-01

    GENEVA UNIVERSITY Ecole de physique Département de physique nucléaire et corspusculaire 24, quai Ernest-Ansermet 1211 Genève 4 Tél.: (022) 379 62 73 Fax: (022) 379 69 92olé   Lundi 17 octobre 2011 17h00 - Ecole de Physique, Auditoire Stueckelberg PHYSICS COLLOQUIUM « Single-electron counting in quantum metrology and in statistical mechanics » Prof. Jukka Pekola Low Temperature Laboratory, Aalto University Helsinki, Finland   First I discuss the basics of single-electron tunneling and its potential applications in metrology. My main focus is in developing an accurate source of single-electron current for the realization of the unit ampere. I discuss the principle and the present status of the so-called single- electron turnstile. Investigation of errors in transporting electrons one by one has revealed a wealth of observations on fundamental phenomena in mesoscopic superconductivity, including individual Andreev...

  8. 2004 Electron Donor Acceptor Interactions Gordon Conference - August 8-13, 2004

    Energy Technology Data Exchange (ETDEWEB)

    GUILFORD JONES; S ST

    2005-09-14

    The 2004 Gordon Conference on Donor/Acceptor Interactions will take place at Salve Regina University in Newport, Rhode Island on August 8-13, 2004. The conference will be devoted to the consequences of charge interaction and charge motion in molecular and materials systems.

  9. Fractional conductance oscillations in quantum rings: wave packet picture of transport in a few-electron system.

    Science.gov (United States)

    Chwiej, T; Szafran, B

    2013-04-17

    We study electron transfer across a two-terminal quantum ring using a time-dependent description of the scattering process. For the considered scattering event the quantum ring is initially charged with one or two electrons, with another electron incident to the ring from the input channel. We study the electron transfer probability (T) as a function of the external magnetic field. We determine the periodicity of T for a varied number of electrons confined within the ring. For that purpose we develop a method to describe the wave packet dynamics for a few electrons participating in the scattering process, taking into full account the electron-electron correlations. We find that electron transfer across the quantum ring initially charged by a single electron acquires a distinct periodicity of half of the magnetic flux quantum (Φ0/2), corresponding to the formation of a transient two-electron state inside the ring. In the case of a three-electron scattering problem with two electrons initially occupying the ring, a period of Φ0/3 for T is formed in the limit of thin channels. The effect of disorder present in the confinement potential of the ring is also discussed.

  10. Quantum transport through disordered 1D wires: Conductance via localized and delocalized electrons

    International Nuclear Information System (INIS)

    Gopar, Víctor A.

    2014-01-01

    Coherent electronic transport through disordered systems, like quantum wires, is a topic of fundamental and practical interest. In particular, the exponential localization of electron wave functions-Anderson localization-due to the presence of disorder has been widely studied. In fact, Anderson localization, is not an phenomenon exclusive to electrons but it has been observed in microwave and acoustic experiments, photonic materials, cold atoms, etc. Nowadays, many properties of electronic transport of quantum wires have been successfully described within a scaling approach to Anderson localization. On the other hand, anomalous localization or delocalization is, in relation to the Anderson problem, a less studied phenomenon. Although one can find signatures of anomalous localization in very different systems in nature. In the problem of electronic transport, a source of delocalization may come from symmetries present in the system and particular disorder configurations, like the so-called Lévy-type disorder. We have developed a theoretical model to describe the statistical properties of transport when electron wave functions are delocalized. In particular, we show that only two physical parameters determine the complete conductance distribution

  11. Confinement of an electron in a non-homogeneous magnetic field: Integrable vs superintegrable quantum systems

    International Nuclear Information System (INIS)

    Contreras-Astorga, A.; Negro, J.; Tristao, S.

    2016-01-01

    This paper deals with the problem of an electron in a non-homogeneous magnetic field perpendicular to a plane. From the classical point of view this is an integrable, but not superintegrable, solvable system. In the quantum framework of the Dirac equation this integrable system is solvable too; the energy levels and wavefunctions of bound states, for its reduction to the plane, are computed. The effective one-dimensional matrix Hamiltonian is shown to belong to a shape-invariant hierarchy. Through this example we will shed some light on the specific properties of a quantum integrable system with respect to those characteristic of superintegrable systems. - Highlights: • The system: an electron in a non-homogeneous magnetic field. • This is a solvable integrable but not superintegrable system. • Solutions to the discrete Dirac spectrum are found. • The shape-invariance of Dirac matrix Hamiltonians is characterized. • Specific properties of integrable, not superintegrable, systems are analyzed.

  12. Confinement of an electron in a non-homogeneous magnetic field: Integrable vs superintegrable quantum systems

    Energy Technology Data Exchange (ETDEWEB)

    Contreras-Astorga, A., E-mail: alonso.contreras.astorga@gmail.com [Department of Mathematics and Actuarial Science, Indiana University Northwest, 3400 Broadway, Gary, IN 46408 (United States); Departamento de Física, Cinvestav, A.P. 14-740, 07000 México D.F. (Mexico); Negro, J., E-mail: jnegro@fta.uva.es [Departamento de Física Teórica, Atómica y Óptica and IMUVA, Universidad de Valladolid, E-47011 Valladolid (Spain); Tristao, S., E-mail: hetsudoyaguiu@gmail.com [Departamento de Física Teórica, Atómica y Óptica and IMUVA, Universidad de Valladolid, E-47011 Valladolid (Spain)

    2016-01-08

    This paper deals with the problem of an electron in a non-homogeneous magnetic field perpendicular to a plane. From the classical point of view this is an integrable, but not superintegrable, solvable system. In the quantum framework of the Dirac equation this integrable system is solvable too; the energy levels and wavefunctions of bound states, for its reduction to the plane, are computed. The effective one-dimensional matrix Hamiltonian is shown to belong to a shape-invariant hierarchy. Through this example we will shed some light on the specific properties of a quantum integrable system with respect to those characteristic of superintegrable systems. - Highlights: • The system: an electron in a non-homogeneous magnetic field. • This is a solvable integrable but not superintegrable system. • Solutions to the discrete Dirac spectrum are found. • The shape-invariance of Dirac matrix Hamiltonians is characterized. • Specific properties of integrable, not superintegrable, systems are analyzed.

  13. Classical and quantum theories of the polarization bremsstrahlung in the local electron density model

    International Nuclear Information System (INIS)

    Astapenko, V.A.; Bureeva, L.A.; Lisitsa, V.S.

    2000-01-01

    Classical and quantum theories of polarization bremsstrahlung in a statistical (Thomas-Fermi) potential of complex atoms and ions are developed. The basic assumptions of the theories correspond to the approximations employed earlier in classical and quantum calculations of ordinary bremsstrahlung in a static potential. This makes it possible to study on a unified basis the contribution of both channels in the radiation taking account of their interference. The classical model makes it possible to obtain simple universal formulas for the spectral characteristics of the radiation. The theory is applied to electrons with moderate energies, which are characteristic for plasma applications, specifically, radiation from electrons on the argon-like ion KII at frequencies close to its ionization potential. The computational results show the importance of taking account of the polarization channel of the radiation for plasma with heavy ions

  14. Quadratic and coulomb terms for the spectrum of a three-electron quantum dot

    International Nuclear Information System (INIS)

    Hassanabadi, H.; Hamzavi, M.; Zarrinkamar, S.; Rajabi, A.A.

    2010-01-01

    We consider the Hamiltonian of a three-electron quantum dot composed of quadratic plus Coulomb terms and calculate the system's spectra. We next apply the hyperradius to reduce the three-body Schroedinger equation into a one-variable differential equation that is solvable. To avoid the complexity, the Taylor expansion of the effective potential is enters the problem and thereby a solution is found for the eigenvalues of the corresponding three-body Schroedinger equation in terms of the Wigner parameter. Using a quasi-analytical approach, we have calculated the energy eigenvalues of the Schroedinger equation corresponding to a three-electron quantum dot. In addition to the hyperspherical coordinates, much of mathematical complexity has been avoided using the idea of Taylor expansion for the potential. For the potential, we have considered quadratic plus Coulomb terms. The obtained energy eigenvalues in terms of the Wigner parameter are given in tabular form. (author)

  15. Dynamic electron-ion collisions and nuclear quantum effects in quantum simulation of warm dense matter

    Science.gov (United States)

    Kang, Dongdong; Dai, Jiayu

    2018-02-01

    The structural, thermodynamic and transport properties of warm dense matter (WDM) are crucial to the fields of astrophysics and planet science, as well as inertial confinement fusion. WDM refers to the states of matter in a regime of temperature and density between cold condensed matter and hot ideal plasmas, where the density is from near-solid up to ten times solid density, and the temperature between 0.1 and 100 eV. In the WDM regime, matter exhibits moderately or strongly coupled, partially degenerate properties. Therefore, the methods used to deal with condensed matter and isolated atoms need to be properly validated for WDM. It is therefore a big challenge to understand WDM within a unified theoretical description with reliable accuracy. Here, we review the progress in the theoretical study of WDM with state-of-the-art simulations, i.e. quantum Langevin molecular dynamics and first principles path integral molecular dynamics. The related applications for WDM are also included.

  16. From Mahan excitons to Landau levels at high magnetic fields: 2DFT spectroscopy reveals hidden quantum correlations (Conference Presentation)

    Science.gov (United States)

    Karaiskaj, Denis

    2017-02-01

    Two-dimensional electron gases have been the subject of research for decades. Modulation doped GaAs quantum wells in the absence of magnetic fields exhibit interesting many-body physics such as the Fermi edge singularity or Mahan exciton and can be regarded as a collective excitation of the system. Under high magnetic fields Landau levels form which have been studied using transport and optical measurements. Nonlinear coherent two-dimensional Fourier transform (2DFT) spectroscopy however provides new insights into these systems. We present the 2DFT spectra of Mahan Excitons associated with the heavy-hole and light-hole resonances observed in a modulation doped GaAs/AlGaAs single quantum well [1]. These resonances are observed to be strongly coupled through many-body interactions. The 2DFT spectra were measured using co-linear, cross-linear, and co-circular polarizations and reveal striking differences. Furthermore, 2DFT spectra at high magnetic fields performed at the National High Magnetic Field Lab (NHMFL) in Tallahassee, Florida will be discussed. The spectra exhibit new features and peculiar line shapes suggesting interesting underlying physics. [1] J. Paul, C. E. Stevens, C. Liu, P. Dey, C. McIntyre, V. Turkowski, J. L. Reno, D. J. Hilton, and D. Karaiskaj, Phys. Rev. Lett.116, 157401 (2016).

  17. Adaptation of quantum chemistry software for the electronic structure calculations on GPU for solid-state systems

    International Nuclear Information System (INIS)

    Gusakov, V.E.; Bel'ko, V.I.; Dorozhkin, N.N.

    2015-01-01

    We report on adaptation of quantum chemistry software - Quantum Espresso and LASTO - for the electronic structure calculations for the complex solid-state systems on the GeForce series GPUs using the nVIDIA CUDA technology. Specifically, protective covering based on transition metal nitrides are considered. (authors)

  18. A study of transport suppression in an undoped AlGaAs/GaAs quantum dot single-electron transistor

    DEFF Research Database (Denmark)

    See, A. M.; Klochan, O.; Micolich, P.

    2013-01-01

    . The temperature and magnetic field dependences of these features indicate the couplings between the leads and the quantum dot states are suppressed. We attribute this to two possible mechanisms: spin effects which determine whether a particular charge transition is allowed based on the change in total spin......, and the interference effects which arise from coherent tunnelling of electrons in the quantum dot....

  19. First-principles study of the electronic structure of CdS/ZnSe coupled quantum dots

    NARCIS (Netherlands)

    Ganguli, N.; Acharya, S.; Dasgupta, I.

    2014-01-01

    We have studied the electronic structure of CdS/ZnSe coupled quantum dots, a novel heterostructure at the nanoscale. Our calculations reveal CdS/ZnSe coupled quantum dots are type II in nature where the anion p states play an important role in deciding the band offset for the highest occupied

  20. Quantum-Chemical Electron Densities of Proteins and of Selected Protein Sites from Subsystem Density Functional Theory

    NARCIS (Netherlands)

    Kiewisch, K.; Jacob, C.R.; Visscher, L.

    2013-01-01

    The ability to calculate accurate electron densities of full proteins or of selected sites in proteins is a prerequisite for a fully quantum-mechanical calculation of protein-protein and protein-ligand interaction energies. Quantum-chemical subsystem methods capable of treating proteins and other