Minimal resonator loss for circuit quantum electrodynamics
Barends, R.; Vercruyssen, N.; Endo, A.; De Visser, P.J.; Zijlstra, T.; Klapwijk, T.M.; Diener, P.; Yates, S.J.C.; Baselmans, J.J.A.
2010-01-01
We report quality factors of up to 500x10³ in superconducting resonators at the single photon levels needed for circuit quantum electrodynamics. This result is achieved by using NbTiN and removing the dielectric from regions with high electric fields. As demonstrated by a comparison with Ta, the
Parametric resonance in quantum electrodynamics vacuum birefringence
Arza, Ariel; Elias, Ricardo Gabriel
2018-05-01
Vacuum magnetic birefringence is one of the most interesting nonlinear phenomena in quantum electrodynamics because it is a pure photon-photon result of the theory and it directly signalizes the violation of the classical superposition principle of electromagnetic fields in the full quantum theory. We perform analytical and numerical calculations when an electromagnetic wave interacts with an oscillating external magnetic field. We find that in an ideal cavity, when the external field frequency is around the electromagnetic wave frequency, the normal and parallel components of the wave suffer parametric resonance at different rates, producing a vacuum birefringence effect growing in time. We also study the case where there is no cavity and the oscillating magnetic field is spatially localized in a region of length L . In both cases we find also a rotation of the elliptical axis.
Resonator quantum electrodynamics on a microtrap chip
International Nuclear Information System (INIS)
Steinmetz, Tilo
2008-01-01
In the present dissertation experiments on resonator quantum electrodynamics on a microtrap chip are described. Thereby for the first time single atoms catched in a chip trap could be detected. For this in the framework of this thesis a novel optical microresonator was developed, which can because of its miniaturization be combined with the microtrap technique introduced in our working group for the manipulation of ultracold atoms. For this resonator glass-fiber ends are used as mirror substrates, between which a standing light wave is formed. With such a fiber Fabry-Perot resonator we obtain a finess of up to ∼37,000. Because of the small mode volumina in spite of moderate resonator quality the coherent interaction between an atom and a photon can be made so large that the regime of the strong atom-resonator coupling is reached. For the one-atom-one-photon coupling rate and the one-atom-one-photon cooperativity thereby record values of g 0 =2π.300 MHz respectively C 0 =210 are reached. Just so for the first time the strong coupling regime between a Bose-Einstein condensate (BEC) and the field of a high-quality resonator could be reached. The BEC was thereby by means of the magnetic microtrap potentials deterministically brought to a position within the resonator and totally transformed in a well defined antinode of an additionally optical standing-wave trap. The spectrum of the coupled atom-resonator system was measured for different atomic numbers and atom-resonator detunings, whereby a collective vacuum Rabi splitting of more than 20 GHz could be reached. [de
Entangling distant resonant exchange qubits via circuit quantum electrodynamics
Srinivasa, V.; Taylor, J. M.; Tahan, Charles
2016-11-01
We investigate a hybrid quantum system consisting of spatially separated resonant exchange qubits, defined in three-electron semiconductor triple quantum dots, that are coupled via a superconducting transmission line resonator. Drawing on methods from circuit quantum electrodynamics and Hartmann-Hahn double resonance techniques, we analyze three specific approaches for implementing resonator-mediated two-qubit entangling gates in both dispersive and resonant regimes of interaction. We calculate entangling gate fidelities as well as the rate of relaxation via phonons for resonant exchange qubits in silicon triple dots and show that such an implementation is particularly well suited to achieving the strong coupling regime. Our approach combines the favorable coherence properties of encoded spin qubits in silicon with the rapid and robust long-range entanglement provided by circuit QED systems.
International Nuclear Information System (INIS)
Akhiezer, A.I.
1983-01-01
Basic ideas of quantum electrodynamics history of its origination and its importance are outlined. It is shown low the notion of the field for each kind of particles and the notion of vacuum for such field had originated and been affirmed how a new language of the Feynman diagrams had appeared without which it is quite impossible to described complex processes of particle scattering and mutual transformation. The main problem of the quantum electrodynamics is to find a scattering matrix, which solution comes to the determination of the Green electrodynamic functions. A review is given of papers on clarifying the asymptotic behaviour of the Green electrodynamic functions in the range of high pulses, on studying the Compton effect, bremsstrahlung irradiation Raman light scattering elastic scattering during channeling of charged particles in a crystal
Greiner, Walter
2009-01-01
This textbook on Quantum Electrodynamics is a thorough introductory text providing all necessary mathematical tools together with many examples and worked problems. In their presentation of the subject the authors adopt a heuristic approach based on the propagator formalism. The latter is introduced in the first two chapters in both its nonrelativistic and relativistic versions. Subsequently, a large number of scattering and radiation processes involving electrons, positrons, and photons are introduced and their theoretical treatment is presented in great detail. Higher order processes and renormalization are also included. The book concludes with a discussion of two-particle states and the interaction of spinless bosons. This completely revised and corrected new edition provides several additions to enable deeper insight in formalism and application of quantum electrodynamics.
1990-01-01
Quantum electrodynamics is an essential building block and an integral part of the gauge theory of unified electromagnetic, weak, and strong interactions, the so-called standard model. Its failure or breakdown at some level would have a most profound impact on the theoretical foundations of elementary particle physics as a whole. Thus the validity of QED has been the subject of intense experimental tests over more than 40 years of its history. This volume presents an up-to-date review of high precision experimental tests of QED together with comprehensive discussion of required theoretical wor
Experiments on two-resonator circuit quantum electrodynamics. A superconducting quantum switch
Energy Technology Data Exchange (ETDEWEB)
Hoffmann, Elisabeth Christiane Maria
2013-05-29
The field of cavity quantum electrodynamics (QED) studies the interaction between light and matter on a fundamental level. In typical experiments individual natural atoms are interacting with individual photons trapped in three-dimensional cavities. Within the last decade the prospering new field of circuit QED has been developed. Here, the natural atoms are replaced by artificial solid state quantum circuits offering large dipole moments which are coupled to quasi-onedimensional cavities providing a small mode volume and hence a large vacuum field strength. In our experiments Josephson junction based superconducting quantum bits are coupled to superconducting microwave resonators. In circuit QED the number of parameters that can be varied is increased and regimes that are not accessible using natural atoms can be entered and investigated. Apart from design flexibility and tunability of system parameters a particular advantage of circuit QED is the scalability to larger system size enabled by well developed micro- and nanofabrication tools. When scaling up the resonator-qubit systems beyond a few coupled circuits, the rapidly increasing number of interacting subsystems requires an active control and directed transmission of quantum signals. This can, for example, be achieved by implementing switchable coupling between two microwave resonators. To this end, a superconducting flux qubit is used to realize a suitable coupling between two microwave resonators, all working in the Gigahertz regime. The resulting device is called quantum switch. The flux qubit mediates a second order tunable and switchable coupling between the resonators. Depending on the qubit state, this coupling can compensate for the direct geometric coupling of the two resonators. As the qubit may also be in a quantum superposition state, the switch itself can be ''quantum'': it can be a superposition of ''on'' and ''off''. This work
Experiments on two-resonator circuit quantum electrodynamics. A superconducting quantum switch
International Nuclear Information System (INIS)
Hoffmann, Elisabeth Christiane Maria
2013-01-01
The field of cavity quantum electrodynamics (QED) studies the interaction between light and matter on a fundamental level. In typical experiments individual natural atoms are interacting with individual photons trapped in three-dimensional cavities. Within the last decade the prospering new field of circuit QED has been developed. Here, the natural atoms are replaced by artificial solid state quantum circuits offering large dipole moments which are coupled to quasi-onedimensional cavities providing a small mode volume and hence a large vacuum field strength. In our experiments Josephson junction based superconducting quantum bits are coupled to superconducting microwave resonators. In circuit QED the number of parameters that can be varied is increased and regimes that are not accessible using natural atoms can be entered and investigated. Apart from design flexibility and tunability of system parameters a particular advantage of circuit QED is the scalability to larger system size enabled by well developed micro- and nanofabrication tools. When scaling up the resonator-qubit systems beyond a few coupled circuits, the rapidly increasing number of interacting subsystems requires an active control and directed transmission of quantum signals. This can, for example, be achieved by implementing switchable coupling between two microwave resonators. To this end, a superconducting flux qubit is used to realize a suitable coupling between two microwave resonators, all working in the Gigahertz regime. The resulting device is called quantum switch. The flux qubit mediates a second order tunable and switchable coupling between the resonators. Depending on the qubit state, this coupling can compensate for the direct geometric coupling of the two resonators. As the qubit may also be in a quantum superposition state, the switch itself can be ''quantum'': it can be a superposition of ''on'' and ''off''. This work presents the theoretical background, the fabrication techniques and
Impact of quantum electrodynamics
International Nuclear Information System (INIS)
Brodsky, S.J.
1975-12-01
A review is given of recent developments in quantum electrodynamics, particularly those involving tests of muon dynamics as well as quantum electrodynamics tests. A new limit on possible muon composite structure is also given. The impact of quantum electrodynamics and its generalizations, the gauge theories, to other areas of physics, including the weak and strong interactions and the atomic spectrum of new particles. The consequences of scale invariance in hadron, atomic, and nuclear physics are reviewed. 119 references
Energy Technology Data Exchange (ETDEWEB)
Steinmetz, Tilo
2008-04-29
In the present dissertation experiments on resonator quantum electrodynamics on a microtrap chip are described. Thereby for the first time single atoms catched in a chip trap could be detected. For this in the framework of this thesis a novel optical microresonator was developed, which can because of its miniaturization be combined with the microtrap technique introduced in our working group for the manipulation of ultracold atoms. For this resonator glass-fiber ends are used as mirror substrates, between which a standing light wave is formed. With such a fiber Fabry-Perot resonator we obtain a finess of up to {approx}37,000. Because of the small mode volumina in spite of moderate resonator quality the coherent interaction between an atom and a photon can be made so large that the regime of the strong atom-resonator coupling is reached. For the one-atom-one-photon coupling rate and the one-atom-one-photon cooperativity thereby record values of g{sub 0}=2{pi}.300 MHz respectively C{sub 0}=210 are reached. Just so for the first time the strong coupling regime between a Bose-Einstein condensate (BEC) and the field of a high-quality resonator could be reached. The BEC was thereby by means of the magnetic microtrap potentials deterministically brought to a position within the resonator and totally transformed in a well defined antinode of an additionally optical standing-wave trap. The spectrum of the coupled atom-resonator system was measured for different atomic numbers and atom-resonator detunings, whereby a collective vacuum Rabi splitting of more than 20 GHz could be reached. [German] In der vorliegenden Dissertation werden Experimente zur Resonator-Quantenelektrodynamik auf einem Mikrofallenchip beschrieben. Dabei konnte u. a. erstmals einzelne, in einer Chipfalle gefangene Atome detektiert werden. Hier fuer wurde im Rahmen dieser Arbeit ein neuartiger optischer Mikroresonator entwickelt, der sich dank seiner Miniaturisierung mit der in unserer Arbeitsgruppe
Raby chaotic vacuum oscillations in resonator quantum electrodynamics
International Nuclear Information System (INIS)
Kon'kov, L.E.; Prants, S.V.
1997-01-01
It is shown in numerical experiments with two-level atoms, moving through a single-mode high-quality resonator, that a new type of spontaneous radiation - the Raby chaotic vacuum oscillation - originates in the mode of strong atom-field bonds
Quantum electrodynamics of resonant energy transfer in condensed matter
International Nuclear Information System (INIS)
Juzeliunas, G.; Andrews, D.L.
1994-01-01
A microscopic many-body QED theory for dipole-dipole resonance energy transfer has been developed from first principles. A distinctive feature of the theory is full incorporation of the dielectric effects of the supporting medium. The approach employs the concept of bath polaritons mediating the energy transfer. The transfer rate is derived in terms of the Green's operator corresponding to the polariton matrix Hamiltonian. In contrast to the more common lossless polariton models, the present theory accommodates an arbitrary number of energy levels for each molecule of the medium. This includes, a case of special interest, where the excitation energy spectrum of the bath molecules is sufficiently dense that it can be treated as a quasicontinuum in the energy region in question, as in the condensed phase normally results from homogeneous and inhomogeneous line broadening. In such a situation, the photon ''dressed'' by the medium polarization (the polariton) acquires a finite lifetime, the role of the dissipative subsystem being played by bath molecules. It is this which leads to the appearance of the exponential decay factor in the microscopically derived pair transfer rates. Accordingly, the problem associated with potentially infinite total ensemble rates, due to the divergent R -2 contribution, is solved from first principles. In addition, the medium modifies the distance dependence of the energy transfer function A(R) and also produces extra modifications due to screening contributions and local field effects. The formalism addresses cases where the surrounding medium is either absorbing or lossless over the range of energies transferred. In the latter case the exponential factor does not appear and the dielectric medium effect in the near zone reduces to that which is familiar from the theory of radiationless (Foerster) energy transfer
Teleportation of two-atom entangled state in resonant cavity quantum electrodynamics
Institute of Scientific and Technical Information of China (English)
Yang Zhen-Biao
2007-01-01
An alternative scheme is presented for teleportation of a two-atom entangled state in cavity quantum electrodynamics (QED). It is based on the resonant atom-cavity field interaction. In the scheme, only one cavity is involved, and the number of the atoms needed to be detected is decreased compared with the previous scheme. Since the resonant atom-cavity field interaction greatly reduces the interaction time, the decoherence effect can be effectively suppressed during the teleportation process. The experimental feasibility of the scheme is discussed. The scheme can easily be generalized to the teleportation of N-atom Greeninger-Horne-Zeilinger (GHZ) entangled states. The number of atoms needed to be detected does not increase as the number of the atoms in the GHZ state increases.
Molecular quantum electrodynamics
Craig, D P
1998-01-01
This systematic introduction to quantum electrodynamics focuses on the interaction of radiation with outer electrons and nuclei of atoms and molecules, answering the long-standing need of chemists and physicists for a comprehensive text on this highly specialized subject.Geared toward postgraduate students in the chemical sciences who require an understanding of quantum electrodynamics as applied to the interpretation of optical experiments on atoms and molecules, the text offers a detailed explanation of the quantum theory of electromagnetic radiation and its interaction with matter. It feat
No drama quantum electrodynamics?
International Nuclear Information System (INIS)
Akhmeteli, Andrey
2013-01-01
This article builds on recent work (Akhmeteli in Int. J. Quantum Inf. 9(Supp01):17, 2011; J. Math. Phys. 52:082303, 2011), providing a theory that is based on spinor electrodynamics, is described by a system of partial differential equations in 3+1 dimensions, but reproduces unitary evolution of a quantum field theory in the Fock space. To this end, after introduction of a complex four-potential of electromagnetic field, which generates the same electromagnetic fields as the initial real four-potential, the spinor field is algebraically eliminated from the equations of spinor electrodynamics. It is proven that the resulting equations for electromagnetic field describe independent evolution of the latter and can be embedded into a quantum field theory using a generalized Carleman linearization procedure. The theory provides a simple and at least reasonably realistic model, valuable for interpretation of quantum theory. The issues related to the Bell theorem are discussed. (orig.)
Quantum mechanics and electrodynamics
Zamastil, Jaroslav
2017-01-01
This book highlights the power and elegance of algebraic methods of solving problems in quantum mechanics. It shows that symmetries not only provide elegant solutions to problems that can be solved exactly, but also substantially simplify problems that must be solved approximately. Furthermore, the book provides an elementary exposition of quantum electrodynamics and its application to low-energy physics, along with a thorough analysis of the role of relativistic, magnetic, and quantum electrodynamic effects in atomic spectroscopy. Included are essential derivations made clear through detailed, transparent calculations. The book’s commitment to deriving advanced results with elementary techniques, as well as its inclusion of exercises will enamor it to advanced undergraduate and graduate students.
Cavity quantum electrodynamics
International Nuclear Information System (INIS)
Walther, Herbert; Varcoe, Benjamin T H; Englert, Berthold-Georg; Becker, Thomas
2006-01-01
This paper reviews the work on cavity quantum electrodynamics of free atoms. In recent years, cavity experiments have also been conducted on a variety of solid-state systems resulting in many interesting applications, of which microlasers, photon bandgap structures and quantum dot structures in cavities are outstanding examples. Although these phenomena and systems are very interesting, discussion is limited here to free atoms and mostly single atoms because these systems exhibit clean quantum phenomena and are not disturbed by a variety of other effects. At the centre of our review is the work on the one-atom maser, but we also give a survey of the entire field, using free atoms in order to show the large variety of problems dealt with. The cavity interaction can be separated into two main regimes: the weak coupling in cavity or cavity-like structures with low quality factors Q and the strong coupling when high-Q cavities are involved. The weak coupling leads to modification of spontaneous transitions and level shifts, whereas the strong coupling enables one to observe a periodic exchange of photons between atoms and the radiation field. In this case, atoms and photons are entangled, this being the basis for a variety of phenomena observed, some of them leading to interesting applications in quantum information processing. The cavity experiments with free atoms reached a new domain with the advent of experiments in the visible spectral region. A review on recent achievements in this area is also given
Experimental status of quantum electrodynamics
International Nuclear Information System (INIS)
Drell, S.D.
1978-10-01
This review of the experimental status of quantum electrodynamics covers the fine structure constant, the muon g-2 value, the Lamb shift in hydrogen, the finite proton radius, progress in muonium, and positronium. 37 references
Reassessment of Bohm's quantum electrodynamics
International Nuclear Information System (INIS)
Baumann, K.
1986-01-01
Bohm's interpretation of quantum theory is reexamined, with emphasis on quantum electrodynamics. Subjects of the discussion are the observability of 'hidden' variables, the applicability of Bohm's theory to spinor QED, the violation of Lorentz invariance, and variants of Bohm's theory. A formulation of causal quantum field theory in terms of distributions is also presented. (Author)
Quantum Hall effect in quantum electrodynamics
International Nuclear Information System (INIS)
Penin, Alexander A.
2009-01-01
We consider the quantum Hall effect in quantum electrodynamics and find a deviation from the quantum-mechanical prediction for the Hall conductivity due to radiative antiscreening of electric charge in an external magnetic field. A weak dependence of the universal von Klitzing constant on the magnetic field strength, which can possibly be observed in a dedicated experiment, is predicted
Scalar formalism for quantum electrodynamics
International Nuclear Information System (INIS)
Hostler, L.C.
1985-01-01
A set of Feynman rules, similar to the rules of scalar electrodynamics, is derived for a full quantum electrodynamics based on the relativistic Klein--Gordon--type wave equation ]Pi/sub μ/Pi/sub μ/+m 2 +ie sigma x (E +iB)]phi = 0, Pi/sub μ/ equivalent-i partial/sub μ/-eA/sub μ/, for spin- 1/2 particles [J. Math. Phys. 23, 1179 (1982); J. Math. Phys. 24, 2366 (1983)]. In this equation, phi is a 2 x 1 Pauli spinor and sigma/sub a/, a = 1,2,3, are the usual 2 x 2 Pauli spin matrices. The irreducible self-energy parts are compared to those of conventional quantum electrodynamics
The Relation between Classical and Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Mario Bacelar Valente
2011-01-01
Full Text Available Quantum electrodynamics presents intrinsic limitations in the description of physical processes that make it impossible to recover from it the type of description we have in classical electrodynamics. Hence one cannot consider classical electrodynamics as reducing to quantum electrodynamics and being recovered from it by some sort of limiting procedure. Quantum electrodynamics has to be seen not as an more fundamental theory, but as an upgrade of classical electrodynamics, which permits an extension of classical theory to the description of phenomena that, while being related to the conceptual framework of the classical theory, cannot be addressed from the classical theory.
Spectral ansatz in quantum electrodynamics
International Nuclear Information System (INIS)
Atkinson, D.; Slim, H.A.
1979-01-01
An ansatz of Delbourgo and Salam for the spectral representation of the vertex function in quantum electrodynamics. The Ward-Takahashi identity is respected, and the electron propagator does not have a ghost. The infra-red and ultraviolet behaviours of the electron propagator in this theory are considered, and a rigorous existence theorem for the propagator in the Yennie gauge is presented
Quantum electrodynamics of strong fields
International Nuclear Information System (INIS)
Greiner, W.
1983-01-01
Quantum Electrodynamics of Strong Fields provides a broad survey of the theoretical and experimental work accomplished, presenting papers by a group of international researchers who have made significant contributions to this developing area. Exploring the quantum theory of strong fields, the volume focuses on the phase transition to a charged vacuum in strong electric fields. The contributors also discuss such related topics as QED at short distances, precision tests of QED, nonperturbative QCD and confinement, pion condensation, and strong gravitational fields In addition, the volume features a historical paper on the roots of quantum field theory in the history of quantum physics by noted researcher Friedrich Hund
Bogolyubov axiomatic method in quantum electrodynamics
International Nuclear Information System (INIS)
Bazhanov, V.V.; Pron'ko, G.P.; Solov'ev, L.D.
1979-01-01
A number of problems of quantum electrodynamics are reviewed which permit an exact solution for both strong and electromagnetic interactions. The solutions have been obtained in the framework of the S-matrix method based on the Bogolyubov axiomatic approach supplemented with some axioms which make it possible to extended the field of application of the Bogolyubov approach for quantum electrodynamics. Infrared ''renormalization'' of axioms and fundamental equations of the S-matrix electrodynamics is discussed. Low-energy theorems for matrix elements of radiative operators have been obtained as solutions of fundamental equations. The low-energy theorems are used for describing the electrodynamic phenomena of soft photons. The bremsstrahlung amplitude is found. A generalized threshold theorem is formulated for the Compton scattering amplitude. The results of examining the infrared asymptotics of the charged particle Green functions, the small-angle scattering of charged particles and electromagnetic effects on heavy narrow resonance production are presented. The problems discussed show that the consequences of general principles of the relativistic quantum theory supplemented with requirements on gauge invariance are essentially nontrivial
Quantum electrodynamics with compensating current
Energy Technology Data Exchange (ETDEWEB)
Bechler, A [Warsaw Univ. (Poland). Instytut Fizyki Teoretycznej
1974-01-01
A formulation of quantum electrodynamics is proposed in which all the propagators and field operators are gauge invariant. It is based on an old idea of Heisenberg and Euler which consists in the introduction of the linear integrals of potentials as arguments of the exponential functions. This method is generalized by an introduction of the so-called ''compensating currents'', which ensure local, i.e. in every point of space-time, charge conservation. The linear integral method is a particular case of that proposed in this paper. As the starting point we use quantum electrodynamics with a non-zero, small photon mass (Proca theory). It is shown that, due to the presence of the compensating current, the theory is fully renormalizable in Hilbert space with positive definite scalar product. The problem of the definition of the current operator is also briefly discussed.
Compton Operator in Quantum Electrodynamics
International Nuclear Information System (INIS)
Garcia, Hector Luna; Garcia, Luz Maria
2015-01-01
In the frame in the quantum electrodynamics exist four basic operators; the electron self-energy, vacuum polarization, vertex correction, and the Compton operator. The first three operators are very important by its relation with renormalized and Ward identity. However, the Compton operator has equal importance, but without divergence, and little attention has been given it. We have calculated the Compton operator and obtained the closed expression for it in the frame of dimensionally continuous integration and hypergeometric functions
Quantum electrodynamics and light rays
International Nuclear Information System (INIS)
Sudarshan, E.C.G.
1978-11-01
Light is a quantum electrodynamic entity and hence bundles of rays must be describable in this framework. The duality in the description of elementary optical phenomena is demonstrated in terms of two-point correlation functions and in terms of collections of light rays. The generalizations necessary to deal with two-slit interference and diffraction by a rectangular slit are worked out and the usefulness of the notion of rays of darkness illustrated. 10 references
Quantum electrodynamics with unstable vacuum
Energy Technology Data Exchange (ETDEWEB)
Fradkin, E.S. (P.N. Lebedev Physical Inst., USSR Academy of Sciences, Moscow (USSR)); Gitman, D.M. (Moscow Inst. of Radio Engineering Electronics and Automation (USSR)); Shvartsman, Sh.M. (Tomsk State Pedagogical Inst. (USSR))
1991-01-01
Intense external fields destabilize vacuum inducing the creation of particle pairs. In this book the formalism of quantum electrodynamics (QED), using a special perturbation theory with matrix propagators, is systematically analyzed for such systems. The developed approach is, however, general for any quantum field with unstable vacuum. The authors propose solutions for real pair-creating fields. They discuss the general form for the causal function and many other Green's functions, as well as methods for finding them. Analogies to the optical theorem and rules for computing total probabilities are given, as are solutions for non-Abelian theories. (orig.).
Energy Technology Data Exchange (ETDEWEB)
Sarabi, B.; Ramanayaka, A. N. [Laboratory for Physical Sciences, College Park, Maryland 20740 (United States); Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Burin, A. L. [Department of Chemistry, Tulane University, New Orleans, Louisiana 70118 (United States); Wellstood, F. C. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Joint Quantum Institute, University of Maryland, College Park, Maryland 20742 (United States); Osborn, K. D. [Laboratory for Physical Sciences, College Park, Maryland 20740 (United States); Joint Quantum Institute, University of Maryland, College Park, Maryland 20742 (United States)
2015-04-27
Random tunneling two-level systems (TLSs) in dielectrics have been of interest recently because they adversely affect the performance of superconducting qubits. The coupling of TLSs to qubits has allowed individual TLS characterization, which has previously been limited to TLSs within (thin) Josephson tunneling barriers made from aluminum oxide. Here, we report on the measurement of an individual TLS within the capacitor of a lumped-element LC microwave resonator, which forms a cavity quantum electrodynamics (CQED) system and allows for individual TLS characterization in a different structure and material than demonstrated with qubits. Due to the reduced volume of the dielectric (80 μm{sup 3}), even with a moderate dielectric thickness (250 nm), we achieve the strong coupling regime as evidenced by the vacuum Rabi splitting observed in the cavity spectrum. A TLS with a coherence time of 3.2 μs was observed in a film of silicon nitride as analyzed with a Jaynes-Cummings spectral model, which is larger than seen from superconducting qubits. As the drive power is increased, we observe an unusual but explicable set of continuous and discrete crossovers from the vacuum Rabi split transitions to the Glauber (coherent) state.
Electrodynamics of quantum spin liquids
Dressel, Martin; Pustogow, Andrej
2018-05-01
Quantum spin liquids attract great interest due to their exceptional magnetic properties characterized by the absence of long-range order down to low temperatures despite the strong magnetic interaction. Commonly, these compounds are strongly correlated electron systems, and their electrodynamic response is governed by the Mott gap in the excitation spectrum. Here we summarize and discuss the optical properties of several two-dimensional quantum spin liquid candidates. First we consider the inorganic material herbertsmithite ZnCu3(OH)6Cl2 and related compounds, which crystallize in a kagome lattice. Then we turn to the organic compounds -EtMe3Sb[Pd(dmit)2]2, κ-(BEDT-TTF)2Ag2(CN)3 and κ-(BEDT-TTF)2Cu2(CN)3, where the spins are arranged in an almost perfect triangular lattice, leading to strong frustration. Due to differences in bandwidth, the effective correlation strength varies over a wide range, leading to a rather distinct behavior as far as the electrodynamic properties are concerned. We discuss the spinon contributions to the optical conductivity in comparison to metallic quantum fluctuations in the vicinity of the Mott transition.
Minimal theory of quantum electrodynamics
International Nuclear Information System (INIS)
Berrondo, M.; Jauregui, R.
1986-01-01
Within the general framework of the Lehmann-Symanzik-Zimmermann axiomatic field theory, we obtain a simple and coherent formulation of quantum electrodynamics. The definitions of the current densities fulfill the one-particle stability condition, and the commutation relations for the interacting fields are obtained rather than being postulated a priori, thus avoiding the inconsistencies which appear in the canonical formalism. This is possible due to the fact that we use the integral form of the equations of motion in order to compute the propagators and the S matrix. The resulting spectral representations automatically fulfill the correct boundary conditions thus fixing the ubiquitous quasilocal operators in a unique fashion
Quantum quincunx in cavity quantum electrodynamics
International Nuclear Information System (INIS)
Sanders, Barry C.; Bartlett, Stephen D.; Tregenna, Ben; Knight, Peter L.
2003-01-01
We introduce the quantum quincunx, which physically demonstrates the quantum walk and is analogous to Galton's quincunx for demonstrating the random walk by employing gravity to draw pellets through pegs on a board, thereby yielding a binomial distribution of final peg locations. In contradistinction to the theoretical studies of quantum walks over orthogonal lattice states, we introduce quantum walks over nonorthogonal lattice states (specifically, coherent states on a circle) to demonstrate that the key features of a quantum walk are observable albeit for strict parameter ranges. A quantum quincunx may be realized with current cavity quantum electrodynamics capabilities, and precise control over decoherence in such experiments allows a remarkable decrease in the position noise, or spread, with increasing decoherence
Experimental status of quantum electrodynamics
International Nuclear Information System (INIS)
Drell, S.D.
1980-01-01
The speech of Drell S. on the symposium dedicated to 60th anniversary of Schwinger J. is presented. The fundamental status of the hero of the day in quantum field theory, which turned into quantum electrodynamics, are stated. The theory has been perfectly experimentally confirmed and now is the main model permitting to explain weak and strong interactions. The attention is paid on the difference between theoretical and experimental values of the electron anomalous magnetic moment (asub(e)) obtained in the sixth order of perturbation theory. It is necessary to carry out calculations in the octic order of the perturbation theory in order to obtain more precise value of asub(e). The theory and the experimental difference is demonstrated on the example of estimation of fine and hyperfine structure of hydrogen, muonium, and positronium
Potentialities of Revised Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Lehnert B.
2013-10-01
Full Text Available The potentialities of a revised quantum electrodynamic theory (RQED earlier established by the author are reconsidered, also in respect to other fundamental theories such as those by Dirac and Higgs. The RQED theory is characterized by intrinsic linear symmetry breaking due to a nonzero divergence of the electric field strength in the vacuum state, as supported by the Zero Point Energy and the experimentally confirmed Casimir force. It includes the results of electron spin and antimatter by Dirac, as well as the rest mass of elementary particles predicted by Higgs in terms of spontaneous nonlinear symmetry breaking. It will here be put into doubt whether the approach by Higgs is the only theory which becomes necessary for explaining the particle rest masses. In addition, RQED theory leads to new results beyond those being available from the theories by Dirac, Higgs and the Standard Model, such as in applications to leptons and the photon.
Triumphs and failures of quantum electrodynamics
International Nuclear Information System (INIS)
Bialynicki-Birula, I.
1996-01-01
Quantum electrodynamics, after more than sixty years since its discovery, still presents challenges and offers rewards to inquiring minds. This presentation describes some theoretical intricacies of this beautiful theory. (author)
REDUCE in elementary particle physics. Quantum electrodynamics
International Nuclear Information System (INIS)
Grozin, A.G.
1990-01-01
This preprint is the second part of the problem book on using REDUCE for calculations of cross sections and decay probabilities in elementary particle physics. It contains examples of calculations in quantum electrodynamics. 5 refs
Mathematical aspects of field quantization. Quantum electrodynamics
International Nuclear Information System (INIS)
Bongaarts, P.J.M.
1983-01-01
Fundamental mathematical aspects of quantum field theory are discussed. A brief review of various approaches to mathematical problems of quantum electrodynamics is given, preceded by a more extensive account of the development of ideas on the mathematical nature of quantum fields in general, providing an appropriate historical context. (author)
Free-space quantum electrodynamics with a single Rydberg superatom
DEFF Research Database (Denmark)
Paris-Mandoki, Asaf; Braun, Christoph; Kumlin, Jan
2017-01-01
The interaction of a single photon with an individual two-level system is the textbook example of quantum electrodynamics. Achieving strong coupling in this system has so far required confinement of the light field inside resonators or waveguides. Here, we demonstrate strong coherent coupling...
Engineering squeezed states of microwave radiation with circuit quantum electrodynamics
International Nuclear Information System (INIS)
Li Pengbo; Li Fuli
2011-01-01
We introduce a squeezed state source for microwave radiation with tunable parameters in circuit quantum electrodynamics. We show that when a superconducting artificial multilevel atom interacting with a transmission line resonator is suitably driven by external classical fields, two-mode squeezed states of the cavity modes can be engineered in a controllable fashion from the vacuum state via adiabatic following of the ground state of the system. This scheme appears to be robust against decoherence and is realizable with present techniques in circuit quantum electrodynamics.
Thermodynamic potential in quantum electrodynamics
International Nuclear Information System (INIS)
Morley, P.D.
1978-01-01
The thermodynamic potential, Ω, in quantum electrodynamics (QED) is derived using the path-integral formalism. Renormalization of Ω is shown by proving the following theorem: Ω/sub B/(e/sub B/,m/sub B/,T,μ) - Ω/sub B/(e/sub B/,m/sub B/,T = 0,μ = 0) = Ω/sub R/(e/sub R/,m/sub R/,T,μ,S), where B and R refer to bare and renormalized quantities, respectively, and S is the Euclidean subtraction momentum squared. This theorem is proved explicitly to e/sub R/ 4 order and could be analogously extended to any higher order. Renormalization-group equations are derived for Ω/sub R/, and it is shown that perturbation theory in a medium is governed by effective coupling constants which are functions of the density. The behavior of the theory at high densities is governed by the Euclidean ultraviolet behavior of the theory in the vacuum
Quantum classical correspondence in nonrelativistic electrodynamics
International Nuclear Information System (INIS)
Ritchie, B.; Weatherford, C.A.
1999-01-01
A form of classical electrodynamic field exists which gives exact agreement with the operator field of quantum electrodynamics (QED) for the Lamb shift of a harmonically bound point electron. Here it is pointed out that this form of classical theory, with its physically acceptable interpretation, is the result of an unconventional resolution of a mathematically ambiguous term in classical field theory. Finally, a quantum classical correspondence principle is shown to exist in the sense that the classical field and expectation value of the QED operator field are identical, if retardation is neglected in the latter
Dyson-Schwinger equations in quantum electrodynamics
International Nuclear Information System (INIS)
Slim, H.A.
1981-01-01
A quantum field theory is completely determined by the knowledge of its Green functions and this thesis is concerned with the Salam and Delbourgo approximation method for the determination of the Green functions. In chapter 2 a Lorentz covariant, canonical formulation for quantum electrodynamics is described. In chapter 3 the definition of the Green functions in quantum electrodynamics is given with a derivation of the Dyson-Schwinger equations. The Ward-Takahashi identities, which are a consequence of current conservation, are derived and finally renormalization is briefly mentioned and the equations for the renormalized quantities are given. The gauge transformations, changing the gauge-parameter, a, discussed in Chapter 2 for the field operators, also have implications for the Green functions, and these are worked out in Chapter 4 for the electron propagator, which is not gauge-invariant. Before developing the main approximation, a simple, non-relativistic model is studied in Chapter 5. It has the feature of being exactly solvable in a way which closely resembles the approximation method of Chapter 6 for relativistic quantum electrodynamics. There the Dyson-Schwinger equations for the electron and photon propagator are studied. In chapter 7, the Johnson-Baker-Willey program of finite quantum electrodynamics is considered, in connection with the Ansatz of Salam and Delbourgo, and the question of a possible fixed point of the coupling constant is considered. In the last chapter, some remarks are made about how the results of the approximation scheme can be improved. (Auth.)
Massless quantum electrodynamics: a variational study
International Nuclear Information System (INIS)
Piquini, P.C.
1990-01-01
The variational method was used to study the probable existence of a compound vacuum in quantum electrodynamics. An Ansatz containing a condensate of electron-positron pairs was investigated and an optimization equation for the condensate wave function found. (L.C.J.A.)
Quantum-electrodynamics corrections in pionic hydrogen
Schlesser, S.; Le Bigot, E. -O.; Indelicato, P.; Pachucki, K.
2011-01-01
We investigate all pure quantum-electrodynamics corrections to the np --> 1s, n = 2-4 transition energies of pionic hydrogen larger than 1 meV, which requires an accurate evaluation of all relevant contributions up to order alpha 5. These values are needed to extract an accurate strong interaction
Lamb Shift in Nonrelativistic Quantum Electrodynamics.
Grotch, Howard
1981-01-01
The bound electron self-energy or Lamb shift is calculated in nonrelativistic quantum electrodynamics. Retardation is retained and also an interaction previously dropped in other nonrelativistic approaches is kept. Results are finite without introducing a cutoff and lead to a Lamb shift in hydrogen of 1030.9 MHz. (Author/JN)
Atomic physics tests of quantum electrodynamics
International Nuclear Information System (INIS)
Mohr, P.J.
1976-08-01
The tests of quantum electrodynamics derived from bound systems and the free electron and muon magnetic moments are reviewed. The emphasis is on the areas in which recent developments in theory or experiment have taken place. Also determinations of the fine structure constant from the Josephson effect and the fine structure of helium are discussed
Quantum electrodynamics with the spear magnetic detector
International Nuclear Information System (INIS)
Zipse, J.E.
1975-09-01
One makes a study of quantum electrodynamic processes which are present at the SPEAR colliding beam magnetic detector. We begin by describing the experiment performed by the SLAC-LBL collaboration and the results concerning the strong interaction. Then the interactions e + e - → e + e - and e + e - → μ + μ - are considered along with their third-order radiative corrections. These events, previously used to determine new limits for cutoff parameters in QED breakdown models, are further studied to show that the full distribution in coplanarity angle fits the theoretical prediction well. The major focus is on the fourth order two-photon process, e + e - → e + e - A + A - , which only recently has been realized to be significant in such experiments. Cross sections are derived and calculated exactly for this process and the results compared to a Weizacker-Williams equivalent photon calculation. The two-photon data are then isolated and fit to the calculation. A special experiment was done where the small-angle scattered electron or positron is ''tagged'' along with particles in the main detector. Cross sections and coplanarity distributions are measured and compared to calculation. Through these studies, one feels confident that one understand the nature of the two-photon process in the detector. One further explores the hadronic physics of the two-photon process, e + e - → e + e - hadrons, measuring pion cross sections, searching for resonances, and discussing future experiments
Cavity quantum electrodynamics with Anderson-localized modes
DEFF Research Database (Denmark)
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren
2010-01-01
by a factor of 15 on resonance with the Anderson-localized mode, and 94% of the emitted single photons coupled to the mode. Disordered photonic media thus provide an efficient platform for quantum electrodynamics, offering an approach to inherently disorder-robust quantum information devices.......A major challenge in quantum optics and quantum information technology is to enhance the interaction between single photons and single quantum emitters. This requires highly engineered optical cavities that are inherently sensitive to fabrication imperfections. We have demonstrated a fundamentally...... different approach in which disorder is used as a resource rather than a nuisance. We generated strongly confined Anderson-localized cavity modes by deliberately adding disorder to photonic crystal waveguides. The emission rate of a semiconductor quantum dot embedded in the waveguide was enhanced...
Foundations of classical and quantum electrodynamics
Toptygin, Igor N
2014-01-01
This advanced textbook covers many fundamental, traditional and new branches of electrodynamics, as well as the related fields of special relativity, quantum mechanics and quantum electrodynamics. The book introduces the material at different levels, oriented towards 3rd–4th year bachelor, master, and PhD students. This is so as to describe the whole complexity of physical phenomena. The required mathematical background is collated in Chapter 1, while the necessary physical background is included in the main text of the corresponding chapters and also given in appendices. It contains approximately 800 examples and problems, many of which are described in detail. Some of these problems are designed for students to work on their own with only the answers and descriptions of results, and may be solved selectively. Equally suitable as a reference for researchers specialized in science and engineering.
Recent advances in bound state quantum electrodynamics
International Nuclear Information System (INIS)
Brodsky, S.J.; Lepage, G.P.
1977-06-01
Recent developments are reviewed in four areas of computational quantum electrodynamics: a new relativistic two-body formalism equal in rigor to the Bethe-Salpeter formalism but with strong calculational advantages is discussed; recent work on the computation of the decay rate of bound systems (positronium in particular) is presented; limits on possible composite structure of leptons are discussed; a new multidimensional integration program ('VEGAS') suitable for higher order calculations is presented
Ward-Takahashi identities in quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Nishijima, K; Sasaki, R [Tokyo Univ. (Japan). Dept. of Physics
1975-03-01
The Ward-Takahashi identities are derived for connected Green's functions in quantum electrodynamics without recourse to equal-time commutation relations, field equations and the Feynman-Dyson perturbation expansions. The argument is based on the dispersion formulation of field theories and only finite expressions are used throughout this derivation. These identities are shown to be consequences of the subtraction conditions imposed upon the 2-, 3- and 4-point Green's functions.
Some basic problems of quantum electrodynamics
International Nuclear Information System (INIS)
Steinmann, O.
1981-01-01
QED (= quantum electrodynamics) is often said to be one of the most successful theories, if not 'the' most successful one, that we possess in physics. That it is a theory is, however, not yet established beyond possible doubt. In this talk I report on the present state of this problem. The question is whether the computational rules of QED, which stand up so well to all practical tests, can be founded logically in a consistent, exactly formulizable, theory. (orig./HSI)
Self-energy quantum electrodynamics: Multipole radiation
International Nuclear Information System (INIS)
Salamin, Y.I.
1993-01-01
Within the context of Barut's self-field approach to quantum electrodynamics, it is shown that the exact relativistic expression for the Einstein A-coefficient of atomic spontaneous emission reduces, in the long wavelength approximation, to a form containing electric- and magnetic-like multipole contributions related to the transition charge and current distributions of the relativistic electron. A number of interesting features of the expressions involved are discussed, and their generalization to interacting composite systems is also pointed out. 10 refs
Quantum Electrodynamics in Photonic Crystal Waveguides
DEFF Research Database (Denmark)
Nielsen, Henri Thyrrestrup
In this thesis we have performed quantum electrodynamics (QED) experiments in photonic crystal (PhC) waveguides and cavity QED in the Anderson localized regime in disordered PhC waveguides. Decay rate measurements of quantum dots embedded in PhC waveguides has been used to map out the variations...... in the local density of states (LDOS) in PhC waveguides. From decay rate measurements on quantum dot lines temperature tuned in the vicinity of the waveguide band edge, a β-factor for a single quantum dot of more then 85% has been extracted. Finite difference time domain simulations (FDTD) for disordered Ph...... is shown to increase from 3 − 7 um for no intentional disorder to 25 um for 6% disorder. A distribution of losses is seen to be necessary to explain the measured Q-factor distributions. Finally we have performed a cavity QED experiment between single quantum dots and an Anderson localized mode, where a β...
Solid-state cavity quantum electrodynamics using quantum dots
International Nuclear Information System (INIS)
Gerard, J.M.; Gayral, B.; Moreau, E.; Robert, I.; Abram, I.
2001-01-01
We review the recent development of solid-state cavity quantum electrodynamics using single self-assembled InAs quantum dots and three-dimensional semiconductor microcavities. We discuss first prospects for observing a strong coupling regime for single quantum dots. We then demonstrate that the strong Purcell effect observed for single quantum dots in the weak coupling regime allows us to prepare emitted photons in a given state (the same spatial mode, the same polarization). We present finally the first single-mode solid-state source of single photons, based on an isolated quantum dot in a pillar microcavity. This optoelectronic device, the first ever to rely on a cavity quantum electrodynamics effect, exploits both Coulomb interaction between trapped carriers in a single quantum dot and single mode photon tunneling in the microcavity. (author)
Quantum electrodynamics in strong external fields
International Nuclear Information System (INIS)
Mueller, B.; Rafelski, J.; Kirsch, J.
1981-05-01
We review the theoretical description of quantum electrodynamics in the presence of strong and supercritical fields. In particular, the process of the spontaneous vacuum decay accompanied by the observable positron emission in heavy ion collisions is described. Emphasis is put on the proper formulation of many-body aspects in the framework of quantum field theory. The extension of the theory to the description of Bose fields and many-body effects is presented, and the Klein paradox is resolved. Some implications of the theoretical methods developed here are presented concerning non-abelian gauge theories and the quark confinement puzzle. (orig.)
Nonrelativistic quantum electrodynamic approach to photoemission theory
International Nuclear Information System (INIS)
Fujikawa, Takashi; Arai, Hiroko
2005-01-01
A new nonrelativistic many-body theory to analyze X-ray photoelectron spectroscopy (XPS) spectra has been developed on the basis of quantum electrodynamic (QED) Keldysh Green's function approach. To obtain XPS current density we calculate electron Green's function g which partly includes electron-photon interactions. We first separate longitudinal and transverse parts of these Green's functions in the Coulomb gauge. The transverse electron selfenergy describes the electron-photon interaction, whereas the longitudinal electron selfenergy describes the electron-electron interaction. We derive the QED Hedin's equation from which we obtain systematic skeleton expansion in the power series of the screened Coulomb interaction W and the photon Green's function D kl . We show the present theory provides a sound theoretical tool to study complicated many-body processes such as the electron propagation damping, intrinsic, extrinsic losses and their interference, and furthermore, resonant photoemission processes. We have also found the importance of the mixed photon Green's functions D 0k and D k0 which have been supposed to be unimportant for the XPS analyses. They, however, directly describe the radiation field screening. In this work, photon field screening effects are discussed in one-step theory, where the electron-photon interaction operator Δ is proved to be replaced by ε -1 Δ beyond linear approximation. Beyond free photon Green's function approximation, photon scatterings from the electron density are incorporated within the present QED theory. These photon field effects can directly describe the microscopic photon field spatial variation specific to near the surface region and nanoparticle systems
Investigation on regulators in quantum electrodynamics
Stora, Raymond Félix
We present in this work three models which are able to suppress the divergences of approximate versions of Quantum Electrodynamics.It is indeed argued that, in view of the smallness of the fine structure constant, not only the first terms of a perturbation expansion, or of an expansion according to the number of particles involved in intermediate states, gives a fair approximattonbut furthermore, that it is in these terms that a breakdown of electrodynamics should be sought. Our goal is to connect the high energy behaviour of relevant physical processes with the suppression of the divergences. Our goal is to connect the high energy behaviour of relevant physical processes with the suppression of the divergences. The first model assumes the existence of a photon cut off, whose observable consequences are clearly stated, and of a fermion out off which, although unable to give a satisfactory ...
Quantum electrodynamics of particles with arbitrary spin
International Nuclear Information System (INIS)
Green, H.S.
1978-01-01
A generalization of quantum electrodynamics is developed for particles of higher spin, with careful attention to the requirements of consistency, causality, unitarity and renormalizability. It is shown that field equations studied previously by the author are expressible in arbitrarily many different forms, which are equivalent in the absence of electromagnetic interactions, but not when electromagnetic coupling is introduced in a gauge-invariant way. A form is chosen which satisfies the requirements of casuality. It is shown how to define a particle density, which is positive-definite in the subspace spanned by solutions of the field equation, and satisifies a Lorentz-invariant conservation law. The quantization and renormalization of the resulting electrodynamics is studied, and is found to require only minor modifications of the existing theory for particles of spin 1/2
Clothed Particles in Quantum Electrodynamics and Quantum Chromodynamics
Directory of Open Access Journals (Sweden)
Shebeko Alexander
2016-01-01
Full Text Available The notion of clothing in quantum field theory (QFT, put forward by Greenberg and Schweber and developed by M. Shirokov, is applied in quantum electrodynamics (QED and quantum chromodynamics (QCD. Along the guideline we have derived a novel analytic expression for the QED Hamiltonian in the clothed particle representation (CPR. In addition, we are trying to realize this notion in QCD (to be definite for the gauge group SU(3 when drawing parallels between QCD and QED.
Circuit quantum electrodynamics with a spin qubit.
Petersson, K D; McFaul, L W; Schroer, M D; Jung, M; Taylor, J M; Houck, A A; Petta, J R
2012-10-18
Electron spins trapped in quantum dots have been proposed as basic building blocks of a future quantum processor. Although fast, 180-picosecond, two-quantum-bit (two-qubit) operations can be realized using nearest-neighbour exchange coupling, a scalable, spin-based quantum computing architecture will almost certainly require long-range qubit interactions. Circuit quantum electrodynamics (cQED) allows spatially separated superconducting qubits to interact via a superconducting microwave cavity that acts as a 'quantum bus', making possible two-qubit entanglement and the implementation of simple quantum algorithms. Here we combine the cQED architecture with spin qubits by coupling an indium arsenide nanowire double quantum dot to a superconducting cavity. The architecture allows us to achieve a charge-cavity coupling rate of about 30 megahertz, consistent with coupling rates obtained in gallium arsenide quantum dots. Furthermore, the strong spin-orbit interaction of indium arsenide allows us to drive spin rotations electrically with a local gate electrode, and the charge-cavity interaction provides a measurement of the resulting spin dynamics. Our results demonstrate how the cQED architecture can be used as a sensitive probe of single-spin physics and that a spin-cavity coupling rate of about one megahertz is feasible, presenting the possibility of long-range spin coupling via superconducting microwave cavities.
Maxwell electrodynamics subjected to quantum vacuum fluctuations
International Nuclear Information System (INIS)
Gevorkyan, A. S.; Gevorkyan, A. A.
2011-01-01
The propagation of electromagnetic waves in the vacuum is considered taking into account quantum fluctuations in the limits of Maxwell-Langevin (ML) equations. For a model of “white noise” fluctuations, using ML equations, a second order partial differential equation is found which describes the quantum distribution of virtual particles in vacuum. It is proved that in order to satisfy observed facts, the Lamb Shift etc, the virtual particles should be quantized in unperturbed vacuum. It is shown that the quantized virtual particles in toto (approximately 86 percent) are condensed on the “ground state” energy level. It is proved that the extension of Maxwell electrodynamics with inclusion of the vacuum quantum field fluctuations may be constructed on a 6D space-time continuum with a 2D compactified subspace. Their influence on the refraction indexes of vacuum is studied.
Quantum electrodynamics in curved space-time
International Nuclear Information System (INIS)
Buchbinder, I.L.; Gitman, D.M.; Fradkin, E.S.
1981-01-01
The lagrangian of quantum electrodynamics in curved space-time is constructed and the interaction picture taking into account the external gravitational field exactly is introduced. The transform from the Heisenberg picture to the interaction picture is carried out in a manifestly covariant way. The properties of free spinor and electromagnetic quantum fields are discussed and conditions under which initial and final creation and annihilation operators are connected by unitarity transformation are indicated. The derivation of Feynman's rules for quantum processes are calculated on the base of generalized normal product of operators. The way of reduction formula derivations is indicated and the suitable Green's functions are introduced. A generating functional for this Green's function is defined and the system of functional equations for them is obtained. The representation of different generating funcationals by means of functional integrals is introduced. Some consequences of S-matrix unitary condition are considered which leads to the generalization of the optic theorem
A Process Algebra Approach to Quantum Electrodynamics
Sulis, William
2017-12-01
The process algebra program is directed towards developing a realist model of quantum mechanics free of paradoxes, divergences and conceptual confusions. From this perspective, fundamental phenomena are viewed as emerging from primitive informational elements generated by processes. The process algebra has been shown to successfully reproduce scalar non-relativistic quantum mechanics (NRQM) without the usual paradoxes and dualities. NRQM appears as an effective theory which emerges under specific asymptotic limits. Space-time, scalar particle wave functions and the Born rule are all emergent in this framework. In this paper, the process algebra model is reviewed, extended to the relativistic setting, and then applied to the problem of electrodynamics. A semiclassical version is presented in which a Minkowski-like space-time emerges as well as a vector potential that is discrete and photon-like at small scales and near-continuous and wave-like at large scales. QED is viewed as an effective theory at small scales while Maxwell theory becomes an effective theory at large scales. The process algebra version of quantum electrodynamics is intuitive and realist, free from divergences and eliminates the distinction between particle, field and wave. Computations are carried out using the configuration space process covering map, although the connection to second quantization has not been fully explored.
Quantum Electrodynamical Shifts in Multivalent Heavy Ions.
Tupitsyn, I I; Kozlov, M G; Safronova, M S; Shabaev, V M; Dzuba, V A
2016-12-16
The quantum electrodynamics (QED) corrections are directly incorporated into the most accurate treatment of the correlation corrections for ions with complex electronic structure of interest to metrology and tests of fundamental physics. We compared the performance of four different QED potentials for various systems to access the accuracy of QED calculations and to make a prediction of highly charged ion properties urgently needed for planning future experiments. We find that all four potentials give consistent and reliable results for ions of interest. For the strongly bound electrons, the nonlocal potentials are more accurate than the local potential.
Quantum electrodynamics with arbitrary charge on a noncommutative space
International Nuclear Information System (INIS)
Zhou Wanping; Long Zhengwen; Cai Shaohong
2009-01-01
Using the Seiberg-Witten map, we obtain a quantum electrodynamics on a noncommutative space, which has arbitrary charge and keep the gauge invariance to at the leading order in theta. The one-loop divergence and Compton scattering are reinvestigated. The noncommutative effects are larger than those in ordinary noncommutative quantum electrodynamics. (authors)
Fundamental tests in Cavity Quantum Electrodynamics
CERN. Geneva
2010-01-01
At the dawn of quantum physics, Einstein and Bohr had the dream to confine a photon in a box and to use this contraption in order to illustrate the strange laws of the quantum world. Cavity Quantum Electrodynamics has now made this dream real, allowing us to actually achieve in the laboratory variants of the thought experiments of the founding fathers of quantum theory. In our work at Ecole Normale Supérieure, we use a beam of Rydberg atoms to manipulate and probe non-destructively microwave photons trapped in a very high Q superconducting cavity. We realize ideal quantum non-demolition (QND) measurements of photon numbers, observe the radiation quantum jumps due to cavity relaxation and prepare non-classical fields such as Fock and Schrödinger cat states. Combining QND photon counting with a homodyne mixing method, we reconstruct the Wigner functions of these non-classical states and, by taking snapshots of these functions at increasing times, obtain movies of the decoherence process. These experiments ope...
Radiation damping and decoherence in quantum electrodynamics
International Nuclear Information System (INIS)
Breuer, H.P.
2000-01-01
The processes of radiation damping and decoherence in quantum electrodynamics are studied from an open system's point of view. Employing functional techniques of field theory, the degrees of freedom of the radiation field are eliminated to obtain the influence phase functional which describes the reduced dynamics of the matter variables. The general theory is applied to the dynamics of a single electron in the radiation field. From a study of the wave packet dynamics a quantitative measure for the degree of decoherence, the decoherence function, is deduced. The latter is shown to describe the emergence of decoherence through the emission of bremsstrahlung caused by the relative motion of interfering wave packets. It is argued that this mechanism is the most fundamental process in quantum electrodynamics leading to the destruction of coherence, since it dominates for short times and because it is at work even in the electromagnetic field vacuum at zero temperature. It turns out that decoherence trough bremsstrahlung is very small for single electrons but extremely large for superpositions of many-particle states. (orig.)
Pole-factorization theorem in quantum electrodynamics
International Nuclear Information System (INIS)
Stapp, H.P.
1996-01-01
In quantum electrodynamics a classical part of the S-matrix is normally factored out in order to obtain a quantum remainder that can be treated perturbatively without the occurrence of infrared divergences. However, this separation, as usually performed, introduces spurious large-distance effects that produce an apparent breakdown of the important correspondence between stable particles and poles of the S-matrix, and, consequently, lead to apparent violations of the correspondence principle and to incorrect results for computations in the mesoscopic domain lying between the atomic and classical regimes. An improved computational technique is described that allows valid results to be obtained in this domain, and that leads, for the quantum remainder, in the cases studied, to a physical-region singularity structure that, as regards the most singular parts, is the same as the normal physical-region analytic structure in theories in which all particles have non-zero mass. The key innovations here are to define the classical part in coordinate space, rather than in momentum space, and to define there a separation of the photon-electron coupling into its classical and quantum parts that has the following properties: (1) The contributions from the terms containing only classical couplings can be summed to all orders to give a unitary operator that generates the coherent state that corresponds to the appropriate classical process, and (2) The quantum remainder can be rigorously shown to exhibit, as regards its most singular parts, the normal analytic structure. 22 refs
Cavity quantum electrodynamics in application to plasmonics and metamaterials
Directory of Open Access Journals (Sweden)
Pavel Ginzburg
2016-11-01
Full Text Available Frontier quantum engineering tasks require reliable control over light-matter interaction dynamics, which could be obtained by introducing electromagnetic structuring. Initiated by the Purcell's discovery of spontaneous emission acceleration in a cavity, the concept of electromagnetic modes' design have gained a considerable amount of attention due to development of photonic crystals, micro-resonators, plasmonic nanostructures and metamaterials. Those approaches, however, offer qualitatively different strategies for tailoring light-matter interactions and are based on either high quality factor modes shaping, near field control, or both. Remarkably, rigorous quantum mechanical description might address those processes in a different fashion. While traditional cavity quantum electrodynamics tools are commonly based on mode decomposition approach, few challenges rise once dispersive and lossy nanostructures, such as noble metals (plasmonic antennas or metamaterials, are involved. The primary objective of this review is to introduce key methods and techniques while aiming to obtain comprehensive quantum mechanical description of spontaneous, stimulated and higher order emission and interaction processes, tailored by nanostructured material environment. The main challenge and the complexity here are set by the level of rigorousity, up to which materials should be treated. While relatively big nanostructured features (10nm and larger could be addressed by applying fluctuation–dissipation theorem and corresponding Green functions' analysis, smaller objects will require individual approach. Effects of material granularity, spatial dispersion, tunneling over small gaps, material memory and others will be reviewed. Quantum phenomena, inspired and tailored by nanostructured environment, plays a key role in development of quantum information devices and related technologies. Rigorous analysis is required for both examination of experimental observations
δ expansion applied to quantum electrodynamics
International Nuclear Information System (INIS)
Bender, C.M.; Boettcher, S.; Milton, K.A.
1992-01-01
A recently proposed technique known as the δ expansion provides a nonperturbative treatment of a quantum field theory. The δ-expansion approach can be applied to electrodynamics in such a way that local gauge invariance is preserved. In this paper it is shown that for electrodynamic processes involving only external photon lines and no external electron lines the δ expansion is equivalent to a fermion loop expansion. That is, the coefficient of δ n in the δ expansion is precisely the sum of all n-electron-loop Feynman diagrams in a conventional weak-coupling approximation. This equivalence does not extend to processes having external electron lines. When external electron lines are present, the δ expansion is truly nonperturbative and does not have a simple interpretation as a resummation of conventional Feynman diagrams. To illustrate the nonperturbative character of the δ expansion we perform a speculative calculation of the fermion condensate in the massive Schwinger model in the limit of large coupling constant
Higher order corrections in quantum electrodynamics
International Nuclear Information System (INIS)
Rafael, E.
1977-01-01
Theoretical contributions to high-order corrections in purely leptonic systems, such as electrons and muons, muonium (μ + e - ) and positronium (e + e - ), are reviewed to establish the validity of quantum electrodynamics (QED). Two types of QED contributions to the anomalous magnetic moments are considered, from diagrams with one fermion type lines and those witn two fermion type lines. The contributions up to eighth order are compared to the data available with a different accuracy. Good agreement is stated within the experimental errors. The experimental accuracy of the muonium hyperfine structure and of the radiative corrections to the decay of positronium are compared to the one attainable in theoretical calculations. The need for a higher precision in both experimental data and theoretical calculations is stated
Digital Quantum Simulation of Spin Models with Circuit Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Y. Salathé
2015-06-01
Full Text Available Systems of interacting quantum spins show a rich spectrum of quantum phases and display interesting many-body dynamics. Computing characteristics of even small systems on conventional computers poses significant challenges. A quantum simulator has the potential to outperform standard computers in calculating the evolution of complex quantum systems. Here, we perform a digital quantum simulation of the paradigmatic Heisenberg and Ising interacting spin models using a two transmon-qubit circuit quantum electrodynamics setup. We make use of the exchange interaction naturally present in the simulator to construct a digital decomposition of the model-specific evolution and extract its full dynamics. This approach is universal and efficient, employing only resources that are polynomial in the number of spins, and indicates a path towards the controlled simulation of general spin dynamics in superconducting qubit platforms.
Does quantum electrodynamics have an arrow of time?
Atkinson, David
Quantum electrodynamics is a time-symmetric theory that is part of the electroweak interaction, which is invariant under a generalized form of this symmetry, the PCT transformation. The thesis is defended that the arrow of time in electrodynamics is a consequence of the assumption of an initial
Structure an dynamics in cavity quantum electrodynamics
International Nuclear Information System (INIS)
Kimble, H.J.
1994-01-01
Much of the theoretical background related to the radiative processes for atoms in the presence of boundaries comes from two often disjoint areas, namely cavity quantum electrodynamics and optical bistability with two-state atoms. While the former of these areas has been associated to a large degree with studies in a perturbative domain of altered associated to a large degree with studies in a perturbative domain of altered emission processes in the presence of boundaries other than those of free space, the latter is often viewed from the perspective of hysteresis cycles and device applications. With the exception of the laser, however, perhaps the most extensive investigations of quantum statistical processes in quantum optics are to be found in the literature on bistability with two-state atoms and on cavity QED. Unfortunately, the degree of overlap of these two areas has not always been fully appreciated. This circumstance is perhaps due in part to the fact that the investigation of dynamical processes in cavity QED has had as its cornerstone the Jaynes-Cummings problem, with extensions to include, for example, small amounts of dissipation. On the other hand, a principle aspect of the bistability literature has been the study of quantum fluctuations in open systems for which dissipation plays a central role, but for which the coherent quantum dynamics of the Haynes-Cummings model are to a large measure lost due to the usual assumption of large system size and weak coupling (as in the standard theory of the laser). 132 refs., 26 figs., 1 tab
Mixed fermion-photon condensate in strongly coupled quantum electrodynamics
International Nuclear Information System (INIS)
Gusynin, V.P.; Kushnir, V.A.
1989-01-01
The existence of a new mixed fermion-photon condensate breaking chiral symmetry in strongly coupled phase of quantum electrodynamics is shown. An analytical expression for the renormalized condensate is obtained. 20 refs.; 2 figs
Quantum electrodynamic effects for light and heavy nuclei
International Nuclear Information System (INIS)
Anon.
1973-01-01
The autoionization of positrons and the problem of vacuum polarization are discussed within the framework of quantum field theory. Various possible heavy ion experiments to check on the nonlinearity of electrodynamics are described. (8 figures) (U.S.)
Dimensional renormalization and comparison of renormalization schemes in quantum electrodynamics
International Nuclear Information System (INIS)
Coquereaux, R.
1979-02-01
The method of dimensional renormalization as applied to quantum electrodynamics is discussed. A general method is given which allows one to compare the various quantities like coupling constants and masses that appear in different renormalization schemes
Three-dimensional quantum electrodynamics as an effective interaction
International Nuclear Information System (INIS)
Abdalla, E.; Carvalho Filho, F.M. de
1995-10-01
We obtain a Quantum Electrodynamics in 2 + 1 dimensions by applying a Kaluza-Klein type method of dimensional reduction to Quantum Electrodynamics in 3 + 1 dimensions rendering the model more realistic to application in solid-state systems, invariant under translations in one direction. We show that the model obtained leads to an effective action exhibiting an interesting phase structure and that the generated Chern-Simons term survives only in the broken phase. (author). 20 refs
A Way to Revised Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Lehnert B.
2012-04-01
Full Text Available In conventional theoretical physics and its Standard Model the guiding principle is that the equations are symmetrical. This limitation leads to a number of difficulties, because it does not permit masses for leptons and quarks, the electron tends to “explode” un- der the action of its self-charge, a corresponding photon model has no spin, and such a model cannot account for the “needle radiation” proposed by Einstein and observed in the photoelectric e ff ect and in two-slit experiments. This paper summarizes a revised Lorentz and gauge invariant quantum electrodynamic theory based on a nonzero electric field divergence in the vacuum and characterized by linear intrinsic broken symmetry. It thus provides an alternative to the Higgs concept of nonlinear spontaneous broken sym- metry, for solving the difficulties of the Standard Model. New results are obtained, such as nonzero and finite lepton rest masses, a point-charge-like behavior of the electron due to a revised renormalization procedure, a magnetic volume force which counteracts the electrostatic eigen-force of the electron, a nonzero spin of the photon and of light beams, needle radiation, and an improved understanding of the photoelectric effect, two-slit ex- periments, electron-positron pair formation, and cork-screw-shaped light beams.
Macroscopic quantum electrodynamics of high-Q cavities
International Nuclear Information System (INIS)
Khanbekyan, Mikayel
2009-01-01
In this thesis macroscopic quantum electrodynamics in linear media was applied in order to develop an universally valid quantum theory for the description of the interaction of the electromagnetic field with atomic sources in high-Q cavities. In this theory a complete description of the characteristics of the emitted radiation is given. The theory allows to show the limits of the applicability of the usually applied theory. In order to establish an as possible generally valid theory first the atom-field interaction was studied in the framework of macroscopic quantum electrodynamics in dispersive and absorptive media. In order to describe the electromagnetic field from Maxwell's equations was started, whereby the noise-current densities, which are connected with the absorption of the medium, were included. The solution of these equations expresses the electromagnetic field variables by the noise-current densities by means of Green's tensor of the macroscopic Maxwell equations. The explicit quantization is performed by means of the noise-current densities, whereby a diagonal Hamiltonian is introduced, which then guarantees the time development according to Maxwell's equation and the fulfillment of the fundamental simultaneous commutation relations of the field variables. In the case of the interaction of the medium-supported field with atoms the Hamiltonian must be extended by atom-field interactions energies, whereby the canonical coupling schemes of the minimal or multipolar coupling can be used. The dieelectric properties of the material bodies as well as their shape are coded in the Green tensor of the macroscopic Maxwell equations. As preparing step first the Green tensor was specified in order to derive three-dimensional input-output relations for the electromagnetic field operators on a plane multilayer structure. Such a general dewscription of the electromagnetic field allows the inclusion both of dispersion and absorption of the media and the possible
Quantum electrodynamics with 1D arti cial atoms
DEFF Research Database (Denmark)
Javadi, Alisa
A 1D atom, a single quantum emitter coupled to a single optical mode, exhibits rich quantum electrodynamic (QED) e_ects and is thought to be the key ingredient for many applications in quantuminformation processing. Single quantum dots (QD) in photonic-crystal waveguides (PCW) constitute a robust...... as expected from the theory. The value of g(2)(0) is around 1.08. The results con_rm the observation of an on-chip giant optical nonlinearity and the 1D atom behavior. Another direction in this thesis has been to investigate the e_ect of Anderson localization on the electrodynamics of QDs in PCWs. A large...
Causal approach to (2+1)-dimensional Quantum Electrodynamics
International Nuclear Information System (INIS)
Scharf, G.; Wreszinski, W.F.; Pimentel, B.M.; Tomazelli, J.L.
1993-05-01
It is shown that the causal approach to (2+1)-dimensional quantum electrodynamics yields a well-defined perturbative theory. In particular, and in contrast to renormalized perturbative quantum field theory, it is free of any ambiguities and ascribes a nonzero value to the dynamically generated, nonperturbative photon mass. (author). 12 refs
Relativization of phases in quantum electrodynamics
International Nuclear Information System (INIS)
Lesche, B.
1981-01-01
The idea of relativism is applied to gauge theories in order to eliminate nonphysical degrees of freedom. Spinor electrodynamics is taken as an example to show how this program might be put into practice. (author)
On foundational and geometric critical aspects of quantum electrodynamics
International Nuclear Information System (INIS)
Prugovecki, E.
1994-01-01
The foundational difficulties encountered by the conventional formulation of quantum electrodynamics, and the criticism by Dirac Schwinger, Rohrlich, and others, aimed at some of the physical and mathematical premises underlying that formulation, are reviewed and discussed. The basic failings of the conventional methods of quantization of the electromagnetic field are pointed out, especially with regard to the issue of local (anti) commutativity of quantum fields as an embodiment of relativistic microcausality. A brief description is given of a recently advanced new type of approach to quantum electrodynamics, and to quantum field theory in general, which is epistemically based on intrinsically quantum ideas about the physical nature of spacetime, and is mathematically based on a fiber theoretical formulation of quantum geometries, aimed in part at removing the aforementioned difficulties and inconsistencies. It is shown that these ideas can be traced to a conceptualization of spacetime outlined by Einstein in the last edition of his well-known semipopular exposition of relativity theory. 57 refs
On the Emergence of the Coulomb Forces in Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Jan Naudts
2017-01-01
Full Text Available A simple transformation of field variables eliminates Coulomb forces from the theory of quantum electrodynamics. This suggests that Coulomb forces may be an emergent phenomenon rather than being fundamental. This possibility is investigated in the context of reducible quantum electrodynamics. It is shown that states exist which bind free photon and free electron fields. The binding energy peaks in the long-wavelength limit. This makes it plausible that Coulomb forces result from the interaction of the electron/positron field with long-wavelength transversely polarized photons.
Optical-lattice Hamiltonians for relativistic quantum electrodynamics
International Nuclear Information System (INIS)
Kapit, Eliot; Mueller, Erich
2011-01-01
We show how interpenetrating optical lattices containing Bose-Fermi mixtures can be constructed to emulate the thermodynamics of quantum electrodynamics (QED). We present models of neutral atoms on lattices in 1+1, 2+1, and 3+1 dimensions whose low-energy effective action reduces to that of photons coupled to Dirac fermions of the corresponding dimensionality. We give special attention to (2+1)-dimensional quantum electrodynamics (QED3) and discuss how two of its most interesting features, chiral symmetry breaking and Chern-Simons physics, could be observed experimentally.
Time-dependent Kohn-Sham approach to quantum electrodynamics
International Nuclear Information System (INIS)
Ruggenthaler, M.; Mackenroth, F.; Bauer, D.
2011-01-01
We prove a generalization of the van Leeuwen theorem toward quantum electrodynamics, providing the formal foundations of a time-dependent Kohn-Sham construction for coupled quantized matter and electromagnetic fields. We circumvent the symmetry-causality problems associated with the action-functional approach to Kohn-Sham systems. We show that the effective external four-potential and four-current of the Kohn-Sham system are uniquely defined and that the effective four-current takes a very simple form. Further we rederive the Runge-Gross theorem for quantum electrodynamics.
Implementing phase-covariant cloning in circuit quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Zhu, Meng-Zheng [School of Physics and Material Science, Anhui University, Hefei 230039 (China); School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000 (China); Ye, Liu, E-mail: yeliu@ahu.edu.cn [School of Physics and Material Science, Anhui University, Hefei 230039 (China)
2016-10-15
An efficient scheme is proposed to implement phase-covariant quantum cloning by using a superconducting transmon qubit coupled to a microwave cavity resonator in the strong dispersive limit of circuit quantum electrodynamics (QED). By solving the master equation numerically, we plot the Wigner function and Poisson distribution of the cavity mode after each operation in the cloning transformation sequence according to two logic circuits proposed. The visualizations of the quasi-probability distribution in phase-space for the cavity mode and the occupation probability distribution in the Fock basis enable us to penetrate the evolution process of cavity mode during the phase-covariant cloning (PCC) transformation. With the help of numerical simulation method, we find out that the present cloning machine is not the isotropic model because its output fidelity depends on the polar angle and the azimuthal angle of the initial input state on the Bloch sphere. The fidelity for the actual output clone of the present scheme is slightly smaller than one in the theoretical case. The simulation results are consistent with the theoretical ones. This further corroborates our scheme based on circuit QED can implement efficiently PCC transformation.
Infrared phenomena in quantum electrodynamics : II. Bremsstrahlung and compton scattering
Haeringen, W. van
The infrared aspects of quantum electrodynamics are discussed by treating two examples of scattering processes, bremsstrahlung and Compton scattering. As in the previous paper one uses a non-covariant diagram technique which gives very clear insight in the cancelling of infrared divergences between
Dimensional regularization and infrared divergences in quantum electrodynamics
International Nuclear Information System (INIS)
Marculescu, S.
1979-01-01
Dimensional continuation was devised as a powerful regularization method for ultraviolet divergences in quantum field theories. Recently it was clear, at least for quantum electrodynamics, that such a method could be employed for factorizing out infrared divergences from the on-shell S-matrix elements. This provides a renormalization scheme on the electron mass-shell without using a gauge violating ''photon mass''. (author)
Charge-field formulation of quantum electrodynamics (QEMED)
International Nuclear Information System (INIS)
Leiter, D.
1980-01-01
By expressing classical electron theory in terms of 'charge-field' functional structures, it is shown that a finite formulation of the classical electrodynamics of point charges emerges in a simple and elegant fashion. This is used to construct a 'charge-field' quantum electrodynamic theory. It is found that interacting photon states are generated as a secondary manifestation of electron-positron quantization, and do not require the usual 'free' canonical quantization scheme. The possibility is discussed that this approach may lead to a better formulation of quantum electrodynamics in the Heisenberg picture and suggests a crucial experimental test to distinguish this new 'charge-field' quantum electrodynamics 'QEMED' from the standard QED formulation. Specifically QEMED predicts that the 'Einstein principle of separability' should be found to be valid for correlated photon polarization measurements, in which the polarizers are changed more rapidly than a characteristic photon travel time. Such an experiment (Aspect 1976) can distinguish between QEMED and QED in a complete and clear-cut fashion. (U.K.)
Higher order energy transfer. Quantum electrodynamical calculations and graphical representation
International Nuclear Information System (INIS)
Jenkins, R.D.
2000-01-01
In Chapter 1, a novel method of calculating quantum electrodynamic amplitudes is formulated using combinatorial theory. This technique is used throughout instead of conventional time-ordered methods. A variety of hyperspaces are discussed to highlight isomorphism between a number of A generalisation of Pascal's triangle is shown to be beneficial in determining the form of hyperspace graphs. Chapter 2 describes laser assisted resonance energy transfer (LARET), a higher order perturbative contribution to the well-known process resonance energy transfer, accommodating an off resonance auxiliary laser field to stimulate the migration. Interest focuses on energy exchanges between two uncorrelated molecular species, as in a system where molecules are randomly oriented. Both phase-weighted and standard isotropic averaging are required for the calculations. Results are discussed in terms of a laser intensity-dependent mechanism. Identifying the applied field regime where LARET should prove experimentally significant, transfer rate increases of up to 30% are predicted. General results for three-center energy transfer are elucidated in chapter 3. Cooperative and accretive mechanistic pathways are identified with theory formulated to elicit their role in a variety of energy transfer phenomena and their relative dominance. In multichromophoric the interplay of such factors is analysed with regard to molecular architectures. The alignments and magnitudes of donor and acceptor transition moments and polarisabilities prove to have profound effects on achievable pooling efficiency for linear configurations. Also optimum configurations are offered. In ionic lattices, although both mechanisms play significant roles in pooling and cutting processes, only the accretive is responsible for sensitisation. The local, microscopic level results are used to gauge the lattice response, encompassing concentration and structural effects. (author)
Massive lepton pair production in massive quantum electrodynamics
International Nuclear Information System (INIS)
Raychaudhuri, P.
1976-01-01
The pp → l + +l - +x inclusive interaction has been studied at high energies in terms of the massive quantum electrodynamics. The differential cross-section (dsigma/dQ 2 ) is derived and proves to be proportional to Q -4 , where Q-mass of the lepton pair. Basic features of the cross-section are demonstrated to be consistent with the Drell-Yan model
Logarithmic of mass singularities theorem in non massive quantum electrodynamics
International Nuclear Information System (INIS)
Mares G, R.; Luna, H.
1997-01-01
We give an explicit example of the use of dimensional regularization to calculate in a unified approach, all the ultraviolet, infrared and mass singularities, by considering the LMS (logarithms of mass singularities) theorem in the frame of massless QED (Quantum electrodynamics). In the calculation of the divergent part of the cross section, all singularities are found to cancel provided soft and hard photon emission are both taken into account. (Author)
Quantum electrodynamics and light rays. [Two-point correlation functions
Energy Technology Data Exchange (ETDEWEB)
Sudarshan, E.C.G.
1978-11-01
Light is a quantum electrodynamic entity and hence bundles of rays must be describable in this framework. The duality in the description of elementary optical phenomena is demonstrated in terms of two-point correlation functions and in terms of collections of light rays. The generalizations necessary to deal with two-slit interference and diffraction by a rectangular slit are worked out and the usefulness of the notion of rays of darkness illustrated. 10 references.
Fixed point structure of quenched, planar quantum electrodynamics
International Nuclear Information System (INIS)
Love, S.T.
1986-07-01
Gauge theories exhibiting a hierarchy of fermion mass scales may contain a pseudo-Nambu-Boldstone boson of spontaneously broken scale invariance. The relation between scale and chiral symmetry breaking is studied analytically in quenched, planar quantum electrodynamics in four dimensions. The model possesses a novel nonperturbative ultraviolet fixed point governing its strong coupling phase which requires the mixing of four fermion operators. 12 refs
Progress in quantum electrodynamics theory of highly charged ions
Volotka, A. V.; Glazov, D. A.; Plunien, G.; Shabaev, V. M.
2013-01-01
Recent progress in quantum electrodynamics (QED) calculations of highly charged ions is reviewed. The theoretical predictions for the binding energies, the hyperfine splittings, and the g factors are presented and compared with available experimental data. Special attention is paid to tests of bound-state QED at strong field regime. Future prospects for tests of QED at the strongest electric and magnetic fields as well as for determination of the fine structure constant and the nuclear magnet...
On the renormalization group equations of quantum electrodynamics
International Nuclear Information System (INIS)
Hirayama, Minoru
1980-01-01
The renormalization group equations of quantum electrodynamics are discussed. The solution of the Gell-Mann-Low equation is presented in a convenient form. The interrelation between the Nishijima-Tomozawa equation and the Gell-Mann-Low equation is clarified. The reciprocal effective charge, so to speak, turns out to play an important role to discuss renormalization group equations. Arguments are given that the reciprocal effective charge vanishes as the renormalization momentum tends to infinity. (author)
Macroscopic quantum electrodynamics of high-Q cavities
Energy Technology Data Exchange (ETDEWEB)
Khanbekyan, Mikayel
2009-10-27
In this thesis macroscopic quantum electrodynamics in linear media was applied in order to develop an universally valid quantum theory for the description of the interaction of the electromagnetic field with atomic sources in high-Q cavities. In this theory a complete description of the characteristics of the emitted radiation is given. The theory allows to show the limits of the applicability of the usually applied theory. In order to establish an as possible generally valid theory first the atom-field interaction was studied in the framework of macroscopic quantum electrodynamics in dispersive and absorptive media. In order to describe the electromagnetic field from Maxwell's equations was started, whereby the noise-current densities, which are connected with the absorption of the medium, were included. The solution of these equations expresses the electromagnetic field variables by the noise-current densities by means of Green's tensor of the macroscopic Maxwell equations. The explicit quantization is performed by means of the noise-current densities, whereby a diagonal Hamiltonian is introduced, which then guarantees the time development according to Maxwell's equation and the fulfillment of the fundamental simultaneous commutation relations of the field variables. In the case of the interaction of the medium-supported field with atoms the Hamiltonian must be extended by atom-field interactions energies, whereby the canonical coupling schemes of the minimal or multipolar coupling can be used. The dieelectric properties of the material bodies as well as their shape are coded in the Green tensor of the macroscopic Maxwell equations. As preparing step first the Green tensor was specified in order to derive three-dimensional input-output relations for the electromagnetic field operators on a plane multilayer structure. Such a general dewscription of the electromagnetic field allows the inclusion both of dispersion and absorption of the media and the
Problems of quantum electrodynamics with external field creating pairs
International Nuclear Information System (INIS)
Fradkin, E.S.; Gitman, D.M.
1979-11-01
This paper is a preliminary version of a review of the results obtained by the authors and their collaborators which mainly concern problems of quantum electrodynamics with the pair-creating external field. In this paper the Furry picture is constructed for quantum electrodynamics with the pair-creating external field. It is shown, that various Green functions in the external field arise in the theory in a natural way. Special features of usage of the unitarity conditions for calculating the total probabilities of transitions are discussed. Perturbation theory for determining the mean electromagnetic field is constructed. Effective Lagrangians for pair-creating fields are built. One of the possible ways to introduce external field in quantum electrodynamics is considered. All the Green functions arising in the theory suggested are calculated for a constant field and a plane wave field. For the case of the electric field the total probability of creation of pairs from the vacuum accompanied by the photon irradiation and the total probability of transition from a single-electron state accompanied by the photon irradiation and creation of pairs are obtained by using the formulated rules for calculating the total probabilities of transitions. (author)
The quantum Hall's effect: A quantum electrodynamic phenomenon
International Nuclear Information System (INIS)
Arbab, A. I.
2012-01-01
We have applied Maxwell's equations to study the physics of quantum Hall's effect. The electromagnetic properties of this system are obtained. The Hall's voltage, V H = 2πħ 2 n s /em, where n s is the electron number density, for a 2-dimensional system, and h = 2πħ is the Planck's constant, is found to coincide with the voltage drop across the quantum capacitor. Consideration of the cyclotronic motion of electrons is found to give rise to Hall's resistance. Ohmic resistances in the horizontal and vertical directions have been found to exist before equilibrium state is reached. At a fundamental level, the Hall's effect is found to be equivalent to a resonant LCR circuit with L H = 2π m/e 2 n s and C H = me 2 /2πħ 2 n s satisfying the resonance condition with resonant frequency equal to the inverse of the scattering (relaxation) time, τ s . The Hall's resistance is found to be R H = √L H /C H . The Hall's resistance may be connected with the impedance that the electron wave experiences when it propagates in the 2-dimensional gas. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Multi-qubit circuit quantum electrodynamics
International Nuclear Information System (INIS)
Viehmann, Oliver
2013-01-01
Circuit QED systems are macroscopic, man-made quantum systems in which superconducting artificial atoms, also called Josephson qubits, interact with a quantized electromagnetic field. These systems have been devised to mimic the physics of elementary quantum optical systems with real atoms in a scalable and more flexible framework. This opens up a variety of possible applications of circuit QED systems. For instance, they provide a promising platform for processing quantum information. Recent years have seen rapid experimental progress on these systems, and experiments with multi-component circuit QED architectures are currently starting to come within reach. In this thesis, circuit QED systems with multiple Josephson qubits are studied theoretically. We focus on simple and experimentally realistic extensions of the currently operated circuit QED setups and pursue investigations in two main directions. First, we consider the equilibrium behavior of circuit QED systems containing a large number of mutually noninteracting Josephson charge qubits. The currently accepted standard description of circuit QED predicts the possibility of superradiant phase transitions in such systems. However, a full microscopic treatment shows that a no-go theorem for superradiant phase transitions known from atomic physics applies to circuit QED systems as well. This reveals previously unknown limitations of the applicability of the standard theory of circuit QED to multi-qubit systems. Second, we explore the potential of circuit QED for quantum simulations of interacting quantum many-body systems. We propose and analyze a circuit QED architecture that implements the quantum Ising chain in a time-dependent transverse magnetic field. Our setup can be used to study quench dynamics, the propagation of localized excitations, and other non-equilibrium features in this paradigmatic model in the theory of non-equilibrium thermodynamics and quantumcritical phenomena. The setup is based on a
Multi-qubit circuit quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Viehmann, Oliver
2013-09-03
Circuit QED systems are macroscopic, man-made quantum systems in which superconducting artificial atoms, also called Josephson qubits, interact with a quantized electromagnetic field. These systems have been devised to mimic the physics of elementary quantum optical systems with real atoms in a scalable and more flexible framework. This opens up a variety of possible applications of circuit QED systems. For instance, they provide a promising platform for processing quantum information. Recent years have seen rapid experimental progress on these systems, and experiments with multi-component circuit QED architectures are currently starting to come within reach. In this thesis, circuit QED systems with multiple Josephson qubits are studied theoretically. We focus on simple and experimentally realistic extensions of the currently operated circuit QED setups and pursue investigations in two main directions. First, we consider the equilibrium behavior of circuit QED systems containing a large number of mutually noninteracting Josephson charge qubits. The currently accepted standard description of circuit QED predicts the possibility of superradiant phase transitions in such systems. However, a full microscopic treatment shows that a no-go theorem for superradiant phase transitions known from atomic physics applies to circuit QED systems as well. This reveals previously unknown limitations of the applicability of the standard theory of circuit QED to multi-qubit systems. Second, we explore the potential of circuit QED for quantum simulations of interacting quantum many-body systems. We propose and analyze a circuit QED architecture that implements the quantum Ising chain in a time-dependent transverse magnetic field. Our setup can be used to study quench dynamics, the propagation of localized excitations, and other non-equilibrium features in this paradigmatic model in the theory of non-equilibrium thermodynamics and quantumcritical phenomena. The setup is based on a
Methods for accurate calculations in high-energy quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Ericsson, K. E. [Institute of Theoretical Physics, Uppsala (Sweden)
1963-01-15
In this paper ''quantum electrodynamics'' (QED) will be used in the sense of a closed theory of point-like photons and electrons. Muons could then easily be included. We make the usual assumption that the perturbation expansion of renormalized QED gives at least an asymptotic expression of the exact theory, i.e. that the sum over a few terms in the beginning of the perturbation series is a good approximation of the exact theory. We expect QED in this sense to break down at small distances, i. e. at large momentum transfers, because of structure effects resulting from other kinds of interaction, primarily the interactions of the electromagnetic field with the current of strongly interacting particles. This will first show up as vacuum polarization through mesons. On the other hand we have no reason to believe that the fundamental theory of electrodynamics, i.e. the theory of a massless vector field interacting with a.conserved current, will break down.
Efficient Multiphoton Generation in Waveguide Quantum Electrodynamics
González-Tudela, A.; Paulisch, V.; Kimble, H. J.; Cirac, J. I.
2017-05-01
Engineering quantum states of light is at the basis of many quantum technologies such as quantum cryptography, teleportation, or metrology among others. Though, single photons can be generated in many scenarios, the efficient and reliable generation of complex single-mode multiphoton states is still a long-standing goal in the field, as current methods either suffer from low fidelities or small probabilities. Here we discuss several protocols which harness the strong and long-range atomic interactions induced by waveguide QED to efficiently load excitations in a collection of atoms, which can then be triggered to produce the desired multiphoton state. In order to boost the success probability and fidelity of each excitation process, atoms are used to both generate the excitations in the rest, as well as to herald the successful generation. Furthermore, to overcome the exponential scaling of the probability of success with the number of excitations, we design a protocol to merge excitations that are present in different internal atomic levels with a polynomial scaling.
Modified Maxwell equations in quantum electrodynamics
Harmuth, Henning F; Meffert, Beate
2001-01-01
Divergencies in quantum field theory referred to as "infinite zero-point energy" have been a problem for 70 years. Renormalization has always been considered an unsatisfactory remedy. In 1985 it was found that Maxwell's equations generally do not have solutions that satisfy the causality law. An additional term for magnetic dipole currents corrected this shortcoming. Rotating magnetic dipoles produce magnetic dipole currents, just as rotating electric dipoles in a material like barium titanate produce electric dipole currents. Electric dipole currents were always part of Maxwell's equations. T
Tunable coupling and ultrastrong interaction in circuit quantum electrodynamics
International Nuclear Information System (INIS)
Baust, Alexander Theodor
2015-01-01
For future quantum information and quantum simulation architectures with superconducting circuits, a profound understanding of the coupling mechanisms between the individual building blocks is essential. In our work, we investigate galvanically coupled qubit-resonator systems, demonstrate the phenomenon of ultrastrong coupling and realize qubit mediated tunable and switchable coupling between two frequency-degenerate coplanar microwave resonators.
On conformal invariance in gauge theories. Quantum electrodynamics
International Nuclear Information System (INIS)
Zaikov, R.P.
1983-01-01
In the present paper another nontrivial model of the conformal quantum electrodynamics is proposed. The main hypothesis is that the electromagnetic potential together with an additional zero scale, dimensional scalar field is transformed by a nonbasic and, consequently, nondecomposable representation of the conformal group. There are found nontrivial conformal covariant two-point functions and an invariant action from which equations of motion are derived. There is considered the covariant procedure of quantization and it is shown that the norm of one-particle physical states is positive definite
On a gauge invariant subtraction scheme for massive quantum electrodynamics
International Nuclear Information System (INIS)
Abdalla, E.; Gomes, M.; Koeberle, R.
A momentum-space subtraction scheme for massive quantum electrodynamics is proposed which respects gauge invariance, in contrast to ordinary normal product techniques. As a consequence the dependence of Green functions on the ghost mass becomes very simple and formally gauge invariant normal products of degree up to four, when subtracted according to the proposed scheme, are automatically gauge invariant. As an aplication we discuss the proof of the Adler-Bardeen theorem. Zero mass limits can be taken for Green function after the integration over intermediate states has been carried out [pt
Dimensional regularization and renormalization of Coulomb gauge quantum electrodynamics
International Nuclear Information System (INIS)
Heckathorn, D.
1979-01-01
Quantum electrodynamics is renormalized in the Coulomb gauge with covariant counter terms and without momentum-dependent wave-function renormalization constants. It is shown how to dimensionally regularize non-covariant integrals occurring in this guage, and prove that the 'minimal' subtraction prescription excludes non-covariant counter terms. Motivated by the need for a renormalized Coulomb gauge formalism in certain practical calculations, the author introduces a convenient prescription with physical parameters. The renormalization group equations for the Coulomb gauge are derived. (Auth.)
Lamb shift in quantum electrodynamics (semiclassical theory)
International Nuclear Information System (INIS)
Blaive, B.; Boudet, R.
1989-01-01
This paper aims to bring some arguments to the proof of the Barut and Van Huele formula, which gives the Lamb shift in the semi-classical theory model: by shortening the calculation owing to the use of a decomposition of the self-potential of the electron; by eliminating the appeal to a divergent series; by bringing justifications and clarifications on some important points of the proof. The effective calculation of the coefficients of the formula is achieved for some of them, and the general analytical form of these coefficients is explicited. It is also proved that the B. and V.H. formula must give results at least as close to the experiment as those of the Bethe formula, which is obtained in Quantum Theory of Fields. Finally one shows that the B. and V.H. formula provides a justification de facto for the cut-off which is used for associating finite numbers to the divergent integrals of the Bethe formula [fr
Waveguide quantum electrodynamics in squeezed vacuum
You, Jieyu; Liao, Zeyang; Li, Sheng-Wen; Zubairy, M. Suhail
2018-02-01
We study the dynamics of a general multiemitter system coupled to the squeezed vacuum reservoir and derive a master equation for this system based on the Weisskopf-Wigner approximation. In this theory, we include the effect of positions of the squeezing sources which is usually neglected in the previous studies. We apply this theory to a quasi-one-dimensional waveguide case where the squeezing in one dimension is experimentally achievable. We show that while dipole-dipole interaction induced by ordinary vacuum depends on the emitter separation, the two-photon process due to the squeezed vacuum depends on the positions of the emitters with respect to the squeezing sources. The dephasing rate, decay rate, and the resonance fluorescence of the waveguide-QED in the squeezed vacuum are controllable by changing the positions of emitters. Furthermore, we demonstrate that the stationary maximum entangled NOON state for identical emitters can be reached with arbitrary initial state when the center-of-mass position of the emitters satisfies certain conditions.
Phenomenology of the vacuum in quantum electrodynamics and beyond
Energy Technology Data Exchange (ETDEWEB)
Doebrich, Babette
2011-09-30
Determining forces that arise by the restriction of the fluctuation modes of the vacuum by the insertion of boundaries or the observation of altered light propagation in external fields is a versatile means to investigate the vacuum structure of quantum electrodynamics. For these quantum vacuum probes, the vacuum can be understood and effectively modeled as a medium. Investigating the properties of this medium cannot only test and broaden our understanding of known interactions but can also be a valuable tool in the search for particles at low energy scales which arise in extensions of the standard model. In this thesis, we first study the geometry dependence of fluctuation modes in the Dirichlet-scalar analog of Casimir-Polder forces between an atom and a surface with arbitrary uniaxial corrugations. To this end we employ a technique which is fully nonperturbative in the height profile. We parameterize the differences to the distance dependencies in the planar limit in terms of an anomalous dimension quantifying the power-law deviation from the planar case. In numerical studies of experimentally relevant corrugations, we identify a universal regime of the anomalous dimension at larger distances. We argue that this universality arises as the relevant fluctuations average over corrugation structures smaller than the atom-wall distance. Turning to modified light propagation as a probe of the quantum vacuum, we show that a combination of strong, pulsed magnets and gravitational-wave interferometers can not only facilitate the detection of strong-field QED phenomena, but also significantly enlarges the accessible parameter space of hypothetical hidden-sector particles. We identify pulsed magnets as a suitable strong-field source to induce quantum nonlinearities, since their pulse frequency can be perfectly matched with the domain of highest sensitivity of modern gravitational-wave interferometers. Pushing current laboratory field-strengths to their limits, we suggest a
Phenomenology of the vacuum in quantum electrodynamics and beyond
International Nuclear Information System (INIS)
Doebrich, Babette
2011-01-01
Determining forces that arise by the restriction of the fluctuation modes of the vacuum by the insertion of boundaries or the observation of altered light propagation in external fields is a versatile means to investigate the vacuum structure of quantum electrodynamics. For these quantum vacuum probes, the vacuum can be understood and effectively modeled as a medium. Investigating the properties of this medium cannot only test and broaden our understanding of known interactions but can also be a valuable tool in the search for particles at low energy scales which arise in extensions of the standard model. In this thesis, we first study the geometry dependence of fluctuation modes in the Dirichlet-scalar analog of Casimir-Polder forces between an atom and a surface with arbitrary uniaxial corrugations. To this end we employ a technique which is fully nonperturbative in the height profile. We parameterize the differences to the distance dependencies in the planar limit in terms of an anomalous dimension quantifying the power-law deviation from the planar case. In numerical studies of experimentally relevant corrugations, we identify a universal regime of the anomalous dimension at larger distances. We argue that this universality arises as the relevant fluctuations average over corrugation structures smaller than the atom-wall distance. Turning to modified light propagation as a probe of the quantum vacuum, we show that a combination of strong, pulsed magnets and gravitational-wave interferometers can not only facilitate the detection of strong-field QED phenomena, but also significantly enlarges the accessible parameter space of hypothetical hidden-sector particles. We identify pulsed magnets as a suitable strong-field source to induce quantum nonlinearities, since their pulse frequency can be perfectly matched with the domain of highest sensitivity of modern gravitational-wave interferometers. Pushing current laboratory field-strengths to their limits, we suggest a
Structure of the vertex function in finite quantum electrodynamics
International Nuclear Information System (INIS)
Mannheim, P.D.
1975-01-01
We study the structure of the renormalized electromagnetic current vertes, GAMMA-tilde/sub μ/(p,p+q,q), in finite quantum electrodynamics. Using conformal invariance we find that GAMMA-tilde/sub μ/(p,p,0) takes the simple form of Z 1 γ/sub μ/ when the external fermions are far off the mass shell. We interpret this result as an old theorem on the structure of the vertex function due to Gell--Mann and Zachariasen. We give the general structure of the vertex for arbitrary momentum transfer parametrically, and discuss how the Bethe--Salpeter equation and the Federbush--Johnson theorem are satisfied. We contrast the meaning of pointlike in a finite field theory with the meaning understood in the parton model. We discuss to what extent the condition Z 1 = 0, which may hold in conformal theories other than finite quantum electrodynamics, may be interpreted as a bootstrap condition. We show that the vanishing of Z 1 prevents their being bound states in the Migdal--Polyakov bootstrap
Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space
Energy Technology Data Exchange (ETDEWEB)
Zahn, J.W.
2006-12-15
We study field theories on the noncommutative Minkowski space with noncommuting time. The focus lies on dispersion relations in quantized interacting models in the Yang-Feldman formalism. In particular, we compute the two-point correlation function of the field strength in noncommutative quantum electrodynamics to second order. At this, we take into account the covariant coordinates that allow the construction of local gauge invariant quantities (observables). It turns out that this does not remove the well-known severe infrared problem, as one might have hoped. Instead, things become worse, since nonlocal divergences appear. We also show that these cancel in a supersymmetric version of the theory if the covariant coordinates are adjusted accordingly. Furthermore, we study the {phi}{sup 3} and the Wess-Zumino model and show that the distortion of the dispersion relations is moderate for parameters typical for the Higgs field. We also discuss the formulation of gauge theories on noncommutative spaces and study classical electrodynamics on the noncommutative Minkowski space using covariant coordinates. In particular, we compute the change of the speed of light due to nonlinear effects in the presence of a background field. Finally, we examine the so-called twist approach to quantum field theory on the noncommutative Minkowski space and point out some conceptual problems of this approach. (orig.)
Dispersion relations in quantum electrodynamics on the noncommutative Minkowski space
International Nuclear Information System (INIS)
Zahn, J.W.
2006-12-01
We study field theories on the noncommutative Minkowski space with noncommuting time. The focus lies on dispersion relations in quantized interacting models in the Yang-Feldman formalism. In particular, we compute the two-point correlation function of the field strength in noncommutative quantum electrodynamics to second order. At this, we take into account the covariant coordinates that allow the construction of local gauge invariant quantities (observables). It turns out that this does not remove the well-known severe infrared problem, as one might have hoped. Instead, things become worse, since nonlocal divergences appear. We also show that these cancel in a supersymmetric version of the theory if the covariant coordinates are adjusted accordingly. Furthermore, we study the Φ 3 and the Wess-Zumino model and show that the distortion of the dispersion relations is moderate for parameters typical for the Higgs field. We also discuss the formulation of gauge theories on noncommutative spaces and study classical electrodynamics on the noncommutative Minkowski space using covariant coordinates. In particular, we compute the change of the speed of light due to nonlinear effects in the presence of a background field. Finally, we examine the so-called twist approach to quantum field theory on the noncommutative Minkowski space and point out some conceptual problems of this approach. (orig.)
Two-dimensional Yukawa interactions from nonlocal Proca quantum electrodynamics
Alves, Van Sérgio; Macrı, Tommaso; Magalhães, Gabriel C.; Marino, E. C.; Nascimento, Leandro O.
2018-05-01
We derive two versions of an effective model to describe dynamical effects of the Yukawa interaction among Dirac electrons in the plane. Such short-range interaction is obtained by introducing a mass term for the intermediate particle, which may be either scalar or an abelian gauge field, both of them in (3 +1 ) dimensions. Thereafter, we consider that the fermionic matter field propagates only in (2 +1 ) dimensions, whereas the bosonic field is free to propagate out of the plane. Within these assumptions, we apply a mechanism for dimensional reduction, which yields an effective model in (2 +1 ) dimensions. In particular, for the gauge-field case, we use the Stueckelberg mechanism in order to preserve gauge invariance. We refer to this version as nonlocal-Proca quantum electrodynamics (NPQED). For both scalar and gauge cases, the effective models reproduce the usual Yukawa interaction in the static limit. By means of perturbation theory at one loop, we calculate the mass renormalization of the Dirac field. Our model is a generalization of Pseudo quantum electrodynamics (PQED), which is a gauge-field model that provides a Coulomb interaction for two-dimensional electrons. Possibilities of application to Fermi-Bose mixtures in mixed dimensions, using cold atoms, are briefly discussed.
Towards measuring quantum electrodynamic torque with a levitated nanorod
Xu, Zhujing; Bang, Jaehoon; Ahn, Jonghoon; Hoang, Thai M.; Li, Tongcang
2017-04-01
According to quantum electrodynamics, quantum fluctuations of electromagnetic fields give rise to a zero-point energy that never vanishes, even in the absence of electromagnetic sources. The interaction energy will not only lead to the well-known Casimir force but will also contribute to the Casimir torque for anisotropic materials. We propose to use an optically levitated nanorod in vacuum and a birefringent substrate to experimentally investigate the QED torque. We have previously observed the libration of an optically levitated non-spherical nanoparticle in vacuum and found it to be an ultrasensitive torque sensor. A nanorod with a long axis of 300nm and a diameter of 60nm levitated in vacuum at 10 (- 8) torr will have a remarkable torque detection sensitivity on the order of 10 (- 28) Nm/ √Hz, which will be sufficient to detect the Casimir torque. This work is partially supported by the National Science Foundation under Grant No.1555035-PHY.
Infra-red finiteness in quantum electro-dynamics
International Nuclear Information System (INIS)
Kawai, Takahiro
1984-01-01
The authors report some mathematical aspects of a recent solution of the infra-red catastrophe in quantum electro-dynamics. A principal result is that the coordinate space Feynman function can be separated into two factors the first of which is a unitary operator in photon space representing the classical electro-magnetic contribution to the amplitude, and the second of which is a residual factor representing the quantum fluctuation about the classical contribution. The main objectives were to verify: (i) the residual factor is free of infra-red divergences, and (ii) the dominant part of the singularity of the residual factor on the positive-α Landau surface has the same analytic form as it would have if the photons were massive. (Auth.)
Digital Quantum Simulation of Spin Models with Circuit Quantum Electrodynamics
Salathé, Y.; Mondal, M.; Oppliger, M.; Heinsoo, J.; Kurpiers, P.; Potočnik, A.; Mezzacapo, Antonio; Las Heras García, Urtzi; Lamata Manuel, Lucas; Solano Villanueva, Enrique Leónidas; Filipp, S.; Wallraff, A.
2015-01-01
Systems of interacting quantum spins show a rich spectrum of quantum phases and display interesting many-body dynamics. Computing characteristics of even small systems on conventional computers poses significant challenges. A quantum simulator has the potential to outperform standard computers in calculating the evolution of complex quantum systems. Here, we perform a digital quantum simulation of the paradigmatic Heisenberg and Ising interacting spin models using a two transmon-qubit circuit...
Two-dimensional quantum electrodynamics as a model in the constructive quantum field theory
International Nuclear Information System (INIS)
Ito, K.R.
1976-01-01
We investigate two-dimensional quantum electrodynamics((QED) 2 ) type models on the basis of the Hamiltonian formalism of a vector field. The transformation into a sine-Gordon equation is clarified as a generalized mass-shift transformation through canonical linear transformations. (auth.)
The new topological sectors associated with quantum electrodynamics
International Nuclear Information System (INIS)
Marino, E.C.
1994-01-01
A formulation of Quantum Electrodynamics in terms of an antisymmetric-tensor gauge field is presented. In this formulation the topological current of this field appears as a source for the electromagnetic field and the topological charge therefore acts physically as an electric charge. These nontrivial, electrically charged, sectors contain massless states orthogonal to the vacuum which are created by a gauge invariant operator can be interpreted as coherent states of photons. The new states do interact with the charged states of QCD in the usual way. It is argued that if these new sectors are in fact realized in nature then a very intense background electromagnetic field is necessary for the experimental observation of them. The order of magnitude of the intensity threshold is presented. (author). 2 refs
Axiomatic field theory and quantum electrodynamics: the massive case
International Nuclear Information System (INIS)
Steinmann, O.
1975-01-01
Massive quantum electrodynamics of the electron is formulated as an LSZ theory of the electromagnetic field F(μν) and the electron-positron fields PSI. The interaction is introduced with the help of mathematically well defined subsidiary conditions. These are: 1) gauge invariance of the first kind, assumed to be generated by a conserved current j(μ); 2) the homogeneous Maxwell equations and a massive version of the inhomogeneous Maxwell equations; 3) a minimality condition concerning the high momentum behaviour of the theory. The inhomogeneous Maxwell equation is a linear differential equation connecting Fsub(μν) with the current Jsub(μ). No Lagrangian, no non-linear field equations, and no explicit expression of Jsub(μ) in terms of PSI, anti-PSI are needed. It is shown in perturbation theory that the proposed conditions fix the physically relevant (i.e. observable) quantities of the theory uniquely
Higgs-Like Particle due to Revised Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
Lehnert B.
2013-07-01
Full Text Available A Higgs-like particle having zero net electric charge, zero spin, and a nonzero rest mass can be deduced from an earlier elaborated revised quantum electrodynamical theory which is based on linear symmetry breaking through a nonzero electric ﬁeld divergence in the vacuum state. This special particle is obtained from a composite longitudinal solution based on a zero magnetic ﬁeld strength and on a nonzero divergence but a vanishing curl of the electric ﬁeld strength. The present theory further diﬀers from that of the nonlinear spontaneously broken symmetry by Higgs, in which elementary particles obtain their masses through an interaction with the Higgs ﬁeld. An experimental proof of the basic features of a Higgs-like particle thus supports the present theory, but does not for certain conﬁrm the process which would generate massive particles through a Higgs ﬁeld
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
Directory of Open Access Journals (Sweden)
Guilherme Tosi
2014-08-01
Full Text Available Recent advances in silicon nanofabrication have allowed the manipulation of spin qubits that are extremely isolated from noise sources, being therefore the semiconductor equivalent of single atoms in vacuum. We investigate the possibility of directly coupling an electron spin qubit to a superconducting resonator magnetic vacuum field. By using resonators modified to increase the vacuum magnetic field at the qubit location, and isotopically purified 28Si substrates, it is possible to achieve coupling rates faster than the single spin dephasing. This opens up new avenues for circuit-quantum electrodynamics with spins, and provides a pathway for dispersive read-out of spin qubits via superconducting resonators.
Resonant quantum transitions in trapped antihydrogen atoms
Amole, C; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Capra, A; Cesar, C L; Charlton, M; Deller, A; Donnan, P H; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Shields, C R; Silveira, D M; Stracka, S; So, C; Thompson, R I; van der Werf, D P; Wurtele, J S
2012-01-01
The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom’s stature lies in its simplicity and in the accuracy with which its spectrum can be measured1 and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and—by comparison with measurements on its antimatter counterpart, antihydrogen—the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state2, 3 of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave...
Applications of the infinite momentum method to quantum electrodynamics and bound state problem
International Nuclear Information System (INIS)
Brodsky, S.J.
1973-01-01
It is shown that the infinite momentum method is a valid and useful calculational alternative to standard perturbation theory methods. The most exciting future applications may be in bound state problems in quantum electrodynamics
DEFF Research Database (Denmark)
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren
2011-01-01
of the spontaneous emission decay rate by up to a factor 15 and an efficiency of channeling single photons into Anderson-localized modes reaching values as high as 94%. These results prove that disordered photonic media provide an efficient platform for quantum electrodynamics, offering a novel route to quantum......We demonstrate that the spontaneous emission decay rate of semiconductor quantum dots can be strongly modified by the coupling to disorder-induced Anderson-localized photonic modes. We experimentally measure, by means of time-resolved photoluminescence spectroscopy, the enhancement...
Measuring the effective phonon density of states of a quantum dot in cavity quantum electrodynamics
DEFF Research Database (Denmark)
Madsen, Kristian Høeg; Nielsen, Per Kær; Kreiner-Møller, Asger
2013-01-01
We employ detuning-dependent decay-rate measurements of a quantum dot in a photonic-crystal cavity to study the influence of phonon dephasing in a solid-state quantum-electrodynamics experiment. The experimental data agree with a microscopic non-Markovian model accounting for dephasing from...... longitudinal acoustic phonons, and the analysis explains the difference between nonresonant cavity feeding in different nanocavities. From the comparison between experiment and theory we extract the effective phonon density of states experienced by the quantum dot in the nanocavity. This quantity determines...
Use of the classical approximation in quantum electrodynamics
International Nuclear Information System (INIS)
Brezin, Edouard
1970-01-01
Approximations commonly used in the study of the classical limit of quantum mechanics are applied, with justification, to quantum electrodynamics. First, the infrared divergence in the scattering of two charged particles is examined with the help of a remarkable series of Feynman diagrams, which in particular preserves gauge invariance and a correct static limit. Looking for the poles in energy of the scattering amplitude, a formula for the binding energies of two charged particles, which generalizes the Balmer formula and takes into account the correct relativistic kinematics, has been derived. A second type of applications concerns phenomena due to the interaction of the electromagnetic field with the vacuum current and charge fluctuations. For instance, when the intensities become very high, the theory predicts the creation of electron-positron pairs by the field. The creation rate is known in the limit of static fields, and the aim of these calculations was to demonstrate the role of frequency in the domain starting from the lowest frequencies up to X-rays. The pair production rate was found to be entirely negligible, even for the most intense laser beams. An increase in frequency, even up to several tens of keV, did not have any effect on the pair production. (author) [fr
Scale covariant physics: a 'quantum deformation' of classical electrodynamics
International Nuclear Information System (INIS)
Knoll, Yehonatan; Yavneh, Irad
2010-01-01
We present a deformation of classical electrodynamics, continuously depending on a 'quantum parameter', featuring manifest gauge, Poincare and scale covariance. The theory, dubbed extended charge dynamics (ECD), associates a certain length scale with each charge which, due to scale covariance, is an attribute of a solution, not a parameter of the theory. When the EM field experienced by an ECD charge is slowly varying over that length scale, the dynamics of the charge reduces to classical dynamics, its emitted radiation reduces to the familiar Lienard-Wiechert potential and the above length scale is identified as the charge's Compton length. It is conjectured that quantum mechanics describes statistical aspects of ensembles of ECD solutions, much like classical thermodynamics describes statistical aspects of ensembles of classical solutions. A unique 'remote sensing' feature of ECD, supporting that conjecture, is presented, along with an explanation for the illusion of a photon within a classical treatment of the EM field. Finally, a novel conservation law associated with the scale covariance of ECD is derived, indicating that the scale of a solution may 'drift' with time at a constant rate, much like translation covariance implies a uniform drift of the (average) position.
Coherent perfect absorption in a quantum nonlinear regime of cavity quantum electrodynamics
Wei, Yang-hua; Gu, Wen-ju; Yang, Guoqing; Zhu, Yifu; Li, Gao-xiang
2018-05-01
Coherent perfect absorption (CPA) is investigated in the quantum nonlinear regime of cavity quantum electrodynamics (CQED), in which a single two-level atom couples to a single-mode cavity weakly driven by two identical laser fields. In the strong-coupling regime and due to the photon blockade effect, the weakly driven CQED system can be described as a quantum system with three polariton states. CPA is achieved at a critical input field strength when the frequency of the input fields matches the polariton transition frequency. In the quantum nonlinear regime, the incoherent dissipation processes such as atomic and photon decays place a lower bound for the purity of the intracavity quantum field. Our results show that under the CPA condition, the intracavity field always exhibits the quadrature squeezing property manifested by the quantum nonlinearity, and the outgoing photon flux displays the super-Poissonian distribution.
Quantum gravitational contributions to the beta function of quantum electrodynamics
International Nuclear Information System (INIS)
Felipe, Jean Carlos Coelho; Brito, Luis Cleber Tavares de; Nemes, Maria Carolina; Sampaio, Marcos
2011-01-01
Full text: Because of the negative mass dimension of the coupling constant perturbative Einstein quantum gravity (EQG) is nonrenormalizable. However, one can still make sense of EQG if it's interpreted as an effective field theory within a low energy expansion of a more fundamental theory. In an effective field theory all interactions compatible with its essential symmetry content are in principle allowed into the Lagrangian and thus it establishes a systematic framework to calculate quantum gravitational effects. This approach has been used to study the asymptotic behavior at high energies of quantum field theories that incorporate the gravitational field. Some studies analyze the asymptotic freedom for the coupling constants of some theories including gravitation near the Planck scale. For example, Robinson and Wilczek suggest that the gravitational field improve the asymptotic freedom of pure Yang-Mills near the Planck scale. Already , a similar calculation in the Maxwell-Einstein theory suggest that such conclusion is gauge dependence. This result was obtained by Pietrykowski. D. Toms say what the effective action is calculated in a gauge-condition independent version of the background field method using dimensional regularization it's argued that the gravitational field plays no role in the beta function of the Yang-Mills coupling. Another calculation done by Ebert, Plefka and Rodigast using conventional diagrammatic methods confirms the result obtained by Toms. In a recent publication, again published by Toms in 2010, claimed that quadratic divergent contributions were responsible to improve asymptotic freedom of fine structure constant by quantum gravity effects by using proper time cutoff regularization and effective action methods. However, the physical reality of the result in Tom's was questioned in recent work. This purpose of this work is to shed light on the origin of such controversies using only a diagrammatic analysis. As an effective model EQG is
Nonlinear quantum electrodynamic and electroweak processes in strong laser fields
Energy Technology Data Exchange (ETDEWEB)
Meuren, Sebastian
2015-06-24
Various nonlinear electrodynamic and electroweak processes in strong plane-wave laser fields are considered with an emphasis on short-pulse effects. In particular, the momentum distribution of photoproduced electron-positron pairs is calculated numerically and a semiclassical interpretation of its characteristic features is established. By proving the optical theorem, compact double-integral expressions for the total pair-creation probability are obtained and numerically evaluated. The exponential decay of the photon wave function in a plane wave is included by solving the Schwinger-Dyson equations to leading-order in the quasistatic approximation. In this respect, the polarization operator in a plane wave is investigated and its Ward-Takahashi identity verified. A classical analysis indicates that a photoproduced electron-positron pair recollides for certain initial conditions. The contributions of such recollision processes to the polarization operator are identified and calculated both analytically and numerically. Furthermore, the existence of nontrivial electron-spin dynamics induced by quantum fluctuations is verified for ultra-short laser pulses. Finally, the exchange of weak gauge bosons is considered, which is essential for neutrino-photon interactions. In particular, the axial-vector-vector coupling tensor is calculated and the so-called Adler-Bell-Jackiw (ABJ) anomaly investigated.
Hu, Zhongwei; Chulhai, Dhabih V; Jensen, Lasse
2016-12-13
Surface-enhanced hyper-Raman scattering (SEHRS) is the two-photon analogue of surface-enhanced Raman scattering (SERS), which has proven to be a powerful tool to study molecular structures and surface enhancements. However, few theoretical approaches to SEHRS exist and most neglect the atomistic descriptions of the metal surface and molecular resonance effects. In this work, we present two atomistic electrodynamics-quantum mechanical models to simulate SEHRS. The first is the discrete interaction model/quantum mechanical (DIM/QM) model, which combines an atomistic electrodynamics model of the nanoparticle with a time-dependent density functional theory description of the molecule. The second model is a dressed-tensors method that describes the molecule as a point-dipole and point-quadrupole object interacting with the enhanced local field and field-gradients (FG) from the nanoparticle. In both of these models, the resonance effects are treated efficiently by means of damped quadratic response theory. Using these methods, we simulate SEHRS spectra for benzene and pyridine. Our results show that the FG effects in SEHRS play an important role in determining both the surface selection rules and the enhancements. We find that FG effects are more important in SEHRS than in SERS. We also show that the spectral features of small molecules can be accurately described by accounting for the interactions between the molecule and the local field and FG of the nanoparticle. However, at short distances between the metal and molecule, we find significant differences in the SEHRS enhancements predicted using the DIM/QM and the dressed-tensors methods.
International Nuclear Information System (INIS)
Cisneros S, A.; McIntosh, H.V.
1982-01-01
A discussion of the nature of quantum mechanical resonances is presented from the point of view of the spectral theory of operators. In the case of Bohr-Feshbach resonances, graphs are presented to illustrate the theory showing the decay of a doubly excited metastable state and the excitation of the resonance by an incident particle with proper energy. A characterization of resonances is given as well as a procedure to determine widths using the spectral density function. A sufficient condition is given for the validity of the Breit-Wigner formula for Bohr-Feshbach resonances. (author)
Multi-qubit parity measurement in circuit quantum electrodynamics
International Nuclear Information System (INIS)
DiVincenzo, David P; Solgun, Firat
2013-01-01
We present a concept for performing direct parity measurements on three or more qubits in microwave structures with superconducting resonators coupled to Josephson-junction qubits. We write the quantum-eraser conditions that must be fulfilled for the parity measurements as requirements for the scattering phase shift of our microwave structure. We show that these conditions can be fulfilled with present-day devices. We present one particular scheme, implemented with two-dimensional cavity techniques, in which each qubit should be coupled equally to two different microwave cavities. The magnitudes of the couplings that are needed are in the range that has been achieved in current experiments. A quantum calculation indicates that the measurement is optimal if the scattering signal can be measured with near single-photon sensitivity. A comparison with an extension of a related proposal from cavity optics is presented. We present a second scheme, for which a scalable implementation of the four-qubit parities of the surface quantum error correction code can be envisioned. It uses three-dimensional cavity structures, using cavity symmetries to achieve the necessary multiple resonant modes within a single resonant structure. (paper)
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
Generating functional of the mean field in quantum electrodynamics with non-stable vacuum
International Nuclear Information System (INIS)
Gitman, D.M.; Kuchin, V.A.
1981-01-01
Generating functional for calculating a mean field, in the case of unstable vacuum, in quantum field theory has been suggested. Continual representation for the generating functional of the mean field has been found in the case of quantum electrodynamics with an external field. Generating electron-positron pairs from vacuum [ru
Quantum-electrodynamic influences on the lifetime of metastable states
International Nuclear Information System (INIS)
Brenner, G.
2007-01-01
High-precision lifetime measurements of the metastable 1s 2 2s 2 2p 2 P 0 3/2 level in boronlike Ar XIV and the 3s 2 2p 2 P 0 3/2 level in aluminumlike Fe XIV were performed at the Heidelberg electron beam ion trap (HD-EBIT). The lifetimes were inferred by monitoring their optical decay curves resulting from the magnetic dipole (M1) transition 1s 2 2s 2 2p 2 P 0 3/2 - 2 P 0 1/2 and 3s 2 3p 2 P 0 3/2 - 2 P 0 1/2 to the ground state configuration with transition wavelengths of 441.256 nm and 530.29 nm, respectively. Possible systematic error sources were investigated by studying the dependence of the decay times of the curves on various trapping conditions with high statistical significance. A new trapping scheme for lifetime measurements at an EBIT has been applied and allowed to reach an unprecedented precision in the realm of lifetime determinations on highly charged ions. The results of 9.573(4)( +12 -5 ) ms (stat)(syst) for Ar XIV and 16.726(10)(+17) ms (stat)(syst) for Fe XIV with a relative accuracy of 0.14% and 0.13%, respectively, make these measurements for the first time sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM). The results, improving the accuracy of previous measurements by factors of 10 and 6, respectively, show a clear discrepancy of about 3σ and 4σ to the trend of existing theoretical models, which in almost all cases predict a shorter lifetime, when adjusted for the EAMM. The obvious disagreement between experimental results and the predictions points at the incompleteness of the theoretical models used. (orig.)
Quantum electrodynamic theory of recombination of an electron with a highly charged ion
International Nuclear Information System (INIS)
Shabaev, V.M.
1994-01-01
The consequent quantum electrodynamic theory of the process of the recombination of an electron with a multicharged ion is considered. The reduction technique for the calculation of this process by perturbation theory is formulated. The process of the recombination of an electron with a very highly charged one-electron ion for the case of resonance with the doubly excited (2s,2s) 0 , (2p 1/2 ,2p 1/2 ) 0 , (2s,2p 1/2 ) 0,1 states is studied. The formulas for the cross section of the process are derived for two possible versions of the experiment. The interference between the radiative-recombination process and the dielectronic-recombination (DR) process, and the interference between the DR amplitudes for the levels with the identical quantum numbers [(2s,2s) 0 , (2p 1/2 ) 0 ] are taken into account. The deviation of the shape of the resonances from the Lorentz one, due to the interference terms, is discussed
Optimization of three-dimensional micropost microcavities for cavity quantum electrodynamics
International Nuclear Information System (INIS)
Vuckovic, Jelena; Pelton, Matthew; Scherer, Axel; Yamamoto, Yoshihisa
2002-01-01
This paper presents a detailed analysis, based on the first-principles finite-difference time-domain method, of the resonant frequency, quality factor (Q), mode volume (V), and radiation pattern of the fundamental (HE 11 ) mode in a three-dimensional distributed-Bragg-reflector (DBR) micropost microcavity. By treating this structure as a one-dimensional cylindrical photonic crystal containing a single defect, we are able to push the limits of Q/V beyond those achievable by standard micropost designs, based on the simple rules established for planar DBR microcavities. We show that some of the rules that work well for designing large-diameter microposts (e.g., high-refractive-index contrast) fail to provide high-quality cavities with small diameters. By tuning the thicknesses of mirror layers and the spacer, the number of mirror pairs, the refractive indices of high- and low-refractive index regions, and the cavity diameter, we are able to achieve Q as high as 10 4 , together with a mode volume of 1.6 cubic wavelengths of light in the high-refractive-index material. The combination of high Q and small V makes these structures promising candidates for the observation of such cavity-quantum-electrodynamics phenomena as strong coupling between a quantum dot and the cavity field, and single-quantum-dot lasing
A derivation of the classical limit of quantum mechanics and quantum electrodynamics
International Nuclear Information System (INIS)
Ajanapon, P.
1985-01-01
Instead of regarding the classical limit as the h → 0, an alternative view based on the physical interpretation of the elements of the density matrix is proposed. According to this alternative view, taking the classical limit corresponds to taking the diagonal elements and ignoring the off-diagonal elements of the density matrix. As illustrations of this alternative approach, the classical limits of quantum mechanics and quantum electrodynamics are derived. The derivation is carried out in two stages. First, the statistical classical limit is derived. Then with an appropriate initial condition, the deterministic classical limit is obtained. In the case of quantum mechanics, it is found that the classical limit of Schroedinger's wave mechanics is at best statistical, i.e., Schroedinger's wave mechanics does not reduce to deterministic (Hamilton's or Newton's) classical mechanics. In order to obtain the latter, it is necessary to start out initially with a mixture at the level of statistical quantum mechanics. The derivation hinges on the use of the Feynman path integral rigorously defined with the aid of nonstandard analysis. Nonstandard analysis is also applied to extend the method to the case of quantum electrodynamics. The fundamental decoupling problem arising form the use of Grassmann variables is circumvented by the use of c-number electron fields, but antisymmetrically tagged. The basic classical (deterministic) field equations are obtained in the classical limit with appropriate initial conditions. The result raises the question as to what the corresponding classical field equations obtained in the classical limit from the renormalized Lagrangian containing infinite counterterms really mean
Free field theories of spin-mass trajectories and quantum electrodynamics in the null plane
Energy Technology Data Exchange (ETDEWEB)
Bart, G.R.; Fenster, S.
1976-06-01
The ten generators of the Poincare algebra for quantum electrodynamics and other gauge theories are given in the null plane. The explicit correspondence of their field-theoretic form to the Bacry-Chang group-theoretic form in the free case is pointed out. It is then noticed that the forms are independent of the spin and allow inclusion of charge quantum numbers at will, which indicates that they represent an advantageous free-particle starting point for a hadron theory with positive spin-mass trajectories (SMT) and with interaction. The internal oscillator content is extracted for both gauge theories and dual resonance models. Interactions are cubic and quartic in the fields. In the dual model they encompass the SMT, whereas no straightforward extension to SMT is possible for the manifestly covariant theories. The requirements of a field-theoretic SMT interaction are spelled out in an algebraic form which guarantees Poincare invariance; however no such interaction is yet known. The approach indicates how a realistic spectrum might be achieved without composite hadrons and incorporating full Poincare invariance.
Free field theories of spin-mass trajectories and quantum electrodynamics in the null plane
International Nuclear Information System (INIS)
Bart, G.R.; Fenster, S.
1976-06-01
The ten generators of the Poincare algebra for quantum electrodynamics and other gauge theories are given in the null plane. The explicit correspondence of their field-theoretic form to the Bacry-Chang group-theoretic form in the free case is pointed out. It is then noticed that the forms are independent of the spin and allow inclusion of charge quantum numbers at will, which indicates that they represent an advantageous free-particle starting point for a hadron theory with positive spin-mass trajectories (SMT) and with interaction. The internal oscillator content is extracted for both gauge theories and dual resonance models. Interactions are cubic and quartic in the fields. In the dual model they encompass the SMT, whereas no straightforward extension to SMT is possible for the manifestly covariant theories. The requirements of a field-theoretic SMT interaction are spelled out in an algebraic form which guarantees Poincare invariance; however no such interaction is yet known. The approach indicates how a realistic spectrum might be achieved without composite hadrons and incorporating full Poincare invariance
On the New Symmetries in Electrodynamics and Quantum Theory
Kotel'nikov, G. A.
2004-01-01
The generalized definition of symmetry is formulated. Application of this definition for symmetric analysis of theoretical physics equations is considered. The version of electrodynamics is constructed permitting the faster-than-light motions of particles with real masses. Some elements of physical interpretation of the proposed theory are presented.
Permanent dipole moments and damping in nonlinear optics. A quantum electrodynamic description
International Nuclear Information System (INIS)
Davila-Smith, L.C.
1999-01-01
Based on the well-known transformation of the electric-dipole interaction, different nonlinear optical processes are analysed. The transformation provides a convenient means for ascertaining the effects of permanent dipoles on the optical behaviour of systems with a response dominated by two energy levels. By establishing the general validity of the procedure for parametric and non-parametric processes, it is shown how the detailed structure of the optical nonlinearity can be ascertained, based on a novel interpretation of the relevant quantum electrodynamical Feynman diagrams. This transformation is used to analysed a novel five-wave mixing process, which is also developed in this thesis. This process is of considerable interest for its involvement in the generation of even harmonics in isotropic media. Also, the flexibility in the beam geometry affords considerable scope for the study of the polarisation and angular dependence. Finally, a general study of the effects of resonance in matter-radiation interactions is given, justifying the phenomenological incorporation of the damping addenda. The two alternative convention used when the damping is introduced are discussed, showing that both conventions lead to different physical results. Based on these studies the resonance effects are considered in relation to different multiphoton processes. (author)
Theory and simulation of cavity quantum electro-dynamics in multi-partite quantum complex systems
Energy Technology Data Exchange (ETDEWEB)
Alidoosty Shahraki, Moslem; Khorasani, Sina; Aram, Mohammad Hasan [Sharif University of Technology, School of Electrical Engineering, Tehran (Iran, Islamic Republic of)
2014-05-15
The cavity quantum electrodynamics of various complex systems is here analyzed using a general versatile code developed in this research. Such quantum multi-partite systems normally consist of an arbitrary number of quantum dots in interaction with an arbitrary number of cavity modes. As an example, a nine-partition system is simulated under different coupling regimes, consisting of eight emitters interacting with one cavity mode. Two-level emitters (e.g. quantum dots) are assumed to have an arrangement in the form of a linear chain, defining the mutual dipole-dipole interactions. It was observed that plotting the system trajectory in the phase space reveals a chaotic behavior in the so-called ultrastrong-coupling regime. This result is mathematically confirmed by detailed calculation of the Kolmogorov entropy, as a measure of chaotic behavior. In order to study the computational complexity of our code, various multi-partite systems consisting of one to eight quantum dots in interaction with one cavity mode were solved individually. Computation run times and the allocated memory for each system were measured. (orig.)
Yang--Mills gauge theories and Baker--Johnson quantum electrodynamics
International Nuclear Information System (INIS)
Lemmon, J.; Mahanthappa, K.T.
1976-01-01
We show that the physical mass of a fermion in a symmetric asymptotically free non-Abelian vector gauge theory is dynamical in origin. We comment on the close analogy that exists between such a theory and the Baker--Johnson finite quantum electrodynamics. Comments are also made when there is spontaneous symmetry breaking
The positronium and the dipositronium in a Hartree-Fock approximation of quantum electrodynamics
DEFF Research Database (Denmark)
Sok, Jérémy Vithya
2016-01-01
The Bogoliubov-Dirac-Fock (BDF) model is a no-photon approximation of quantum electrodynamics. It allows to study relativistic electrons in interaction with the Dirac sea. A state is fully characterized by its one-body density matrix, an infinite rank non-negative projector. We prove the existence...
Quasi-potential approach to the problem of bound states in quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Rizov, V A; Todorov, I T [Bylgarska Akademiya na Naukite, Sofia. Inst. za Yadrena Izsledvaniya i Yadrena Energetika
1975-07-01
The paper reviews two types of quasipotential equations. An equation with a non-local potential is derived from the equations of motion of quantum electrodynamics. It is also related to a Bethe-Salpeter type of equation for the retarded Green function. Most of the paper is devoted to a systematic study of a local version of the Logunov-Tavkhelidze quasipotential approach.
Haeringen, W. van
In view of remaining obscurities and difficulties in existing treatments of the infrared divergences in quantum electrodynamics this problem has been considered anew. The approximate model introduced in 1937 by Bloch and Nordsieck is rediscussed. It is explicitly shown to be a good substitute for
International Nuclear Information System (INIS)
Gorskij, A.S.; Ioffe, B.L.; Khodzhamiryan, A.Yu.
1989-01-01
It is shown that in massless electrodynamics (when the electron mass is strictly zero) the cross section of longitudinal photon interaction on mass shell is nonvanishing. The reasons of appearance of this effects and its possible consequences as well as analogous effects in other quantum field theories (especially non-Abelian gauge theories) are discussed. 7 refs.; 2 figs
International Nuclear Information System (INIS)
Galvao, C.A.P.; Mignaco, J.A.
1994-01-01
The classical electromagnetic theory is analysed which corresponds to the two-dimensional quantum electrodynamics with massless spinor fields (Schwinger model). The chiral anomaly is introduced as a currents property, which in the two-dimensional spinor fields are duality related. It is also shown that the resulting classical theory is consistent. (author). 5 refs
Processes of arbitrary order in quantum electrodynamics with a pair-creating external field
International Nuclear Information System (INIS)
Gitman, D.M.
1977-01-01
Dyson's perturbation theory analogue for quantum electrodynamical processes with arbitrary initial and final states in an external field creating pairs is discussed. The interaction with the field is taken into account exactly. The possibility of using Feynman diagrams, together with modified correspondence rules, for the representation of the above mentioned processes is demonstrated. (author)
Mode expansions in the quantum electrodynamics of photonic media with disorder
DEFF Research Database (Denmark)
Wubs, Martijn; Mortensen, N. Asger
2012-01-01
We address two issues in the quantum electrodynamical description of photonic media with some disorder, neglecting material dispersion. When choosing a gauge in which the static potential vanishes, the normal modes of the medium with disorder satisfy another transversality condition than the modes......, we find the gauge transformation that makes the static potential zero, thereby generalizing work by Glauber and Lewenstein [Phys. Rev. A 43, 467 (1991)]. Our results are relevant for the quantum optics of disordered photonic crystals....
Resonant quantum transitions in trapped antihydrogen atoms.
Amole, C; Ashkezari, M D; Baquero-Ruiz, M; Bertsche, W; Bowe, P D; Butler, E; Capra, A; Cesar, C L; Charlton, M; Deller, A; Donnan, P H; Eriksson, S; Fajans, J; Friesen, T; Fujiwara, M C; Gill, D R; Gutierrez, A; Hangst, J S; Hardy, W N; Hayden, M E; Humphries, A J; Isaac, C A; Jonsell, S; Kurchaninov, L; Little, A; Madsen, N; McKenna, J T K; Menary, S; Napoli, S C; Nolan, P; Olchanski, K; Olin, A; Pusa, P; Rasmussen, C Ø; Robicheaux, F; Sarid, E; Shields, C R; Silveira, D M; Stracka, S; So, C; Thompson, R I; van der Werf, D P; Wurtele, J S
2012-03-07
The hydrogen atom is one of the most important and influential model systems in modern physics. Attempts to understand its spectrum are inextricably linked to the early history and development of quantum mechanics. The hydrogen atom's stature lies in its simplicity and in the accuracy with which its spectrum can be measured and compared to theory. Today its spectrum remains a valuable tool for determining the values of fundamental constants and for challenging the limits of modern physics, including the validity of quantum electrodynamics and--by comparison with measurements on its antimatter counterpart, antihydrogen--the validity of CPT (charge conjugation, parity and time reversal) symmetry. Here we report spectroscopy of a pure antimatter atom, demonstrating resonant quantum transitions in antihydrogen. We have manipulated the internal spin state of antihydrogen atoms so as to induce magnetic resonance transitions between hyperfine levels of the positronic ground state. We used resonant microwave radiation to flip the spin of the positron in antihydrogen atoms that were magnetically trapped in the ALPHA apparatus. The spin flip causes trapped anti-atoms to be ejected from the trap. We look for evidence of resonant interaction by comparing the survival rate of trapped atoms irradiated with microwaves on-resonance to that of atoms subjected to microwaves that are off-resonance. In one variant of the experiment, we detect 23 atoms that survive in 110 trapping attempts with microwaves off-resonance (0.21 per attempt), and only two atoms that survive in 103 attempts with microwaves on-resonance (0.02 per attempt). We also describe the direct detection of the annihilation of antihydrogen atoms ejected by the microwaves.
Inflationary universe from higher derivative quantum gravity coupled with scalar electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Myrzakulov, R. [Department of General & Theoretical Physics and Eurasian Center for Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan); Odintsov, S.D. [Consejo Superior de Investigaciones Científicas, ICE/CSIC-IEEC, Campus UAB, Facultat de Ciències, Torre C5-Parell-2a pl, E-08193 Bellaterra, Barcelona (Spain); Institut de Ciencies de l' Espai (IEEC-CSIC), Campus UAB, Carrer de Can Magrans, s/n 08193 Cerdanyola del Valles, Barcelona (Spain); Tomsk State Pedagogical University, 634050 Tomsk (Russian Federation); Tomsk State University of Control Systems and Radioelectronics (TUSUR) 634050 Tomsk (Russian Federation); Sebastiani, L., E-mail: lorenzo.sebastiani@unitn.it [Department of General & Theoretical Physics and Eurasian Center for Theoretical Physics, Eurasian National University, Astana 010008 (Kazakhstan)
2016-06-15
We study inflation for a quantum scalar electrodynamics model in curved space–time and for higher-derivative quantum gravity (QG) coupled with scalar electrodynamics. The corresponding renormalization-group (RG) improved potential is evaluated for both theories in Jordan frame where non-minimal scalar-gravitational coupling sector is explicitly kept. The role of one-loop quantum corrections is investigated by showing how these corrections enter in the expressions for the slow-roll parameters, the spectral index and the tensor-to-scalar ratio and how they influence the bound of the Hubble parameter at the beginning of the primordial acceleration. We demonstrate that the viable inflation maybe successfully realized, so that it turns out to be consistent with last Planck and BICEP2/Keck Array data.
Classical and quantum electrodynamics and the B(3) field
Evans, Myron W
2001-01-01
It is well known that classical electrodynamics is riddled with internal inconsistencies springing from the fact that it is a linear, Abelian theory in which the potentials are unphysical. This volume offers a self-consistent hypothesis which removes some of these problems, as well as builds a framework on which linear and nonlinear optics are treated as a non-Abelian gauge field theory based on the emergence of the fundamental magnetizing field of radiation, the B(3) field. Contents: Interaction of Electromagnetic Radiation with One Fermion; The Field Equations of Classical O (3) b Electrodyn
Quantum electrodynamics tests and X-rays standards using pionic atoms and highly charged ions
International Nuclear Information System (INIS)
Martino, Trassinelli
2005-12-01
The object of this thesis is to present a new measurement of the pion mass using pionic nitrogen X-ray spectroscopy and results on helium-like argon and sulphur spectroscopy. The new pion mass has been measured with an accuracy of 1.7 ppm, 30% better that the present world average value, and it is obtained from Bragg spectroscopy of 5 ->4 pionic nitrogen transitions using the theoretical predictions provided by quantum electrodynamics. We have got: m(π - ) = (139.571042 ± 0.000210 ± 0.000110) where the first error is due to the statistics and the second is the systematic error. I present the calculation of the hyperfine structure and recoil corrections for pionic atoms using a new perturbation method for the Klein-Gordon equation. The spectrometer used for this measurement has been characterized with the relativistic M1 transitions from helium-like ions produced with a new device, the Electron-Cyclotron-Resonance Ion Trap. High statistics spectra from these ions have enabled us to measure transition energies with an accuracy of some ppm which has allowed us to compare theoretical predictions with experiment data. X-ray emission from pionic atoms and multicharged ions can be used to define new types of X-ray standards for energies of a few keV
Baumann, Gerd
2005-01-01
Mathematica for Theoretical Physics: Electrodynamics, Quantum Mechanics, General Relativity, and Fractals This second edition of Baumann's Mathematica® in Theoretical Physics shows readers how to solve physical problems and deal with their underlying theoretical concepts while using Mathematica® to derive numeric and symbolic solutions. Each example and calculation can be evaluated by the reader, and the reader can change the example calculations and adopt the given code to related or similar problems. The second edition has been completely revised and expanded into two volumes: The first volume covers classical mechanics and nonlinear dynamics. Both topics are the basis of a regular mechanics course. The second volume covers electrodynamics, quantum mechanics, relativity, and fractals and fractional calculus. New examples have been added and the representation has been reworked to provide a more interactive problem-solving presentation. This book can be used as a textbook or as a reference work, by student...
Energy Technology Data Exchange (ETDEWEB)
Dosch, H G [Heidelberg Univ. (F.R. Germany). Inst. fuer Theoretische Physik; Mueller, V F [Trier-Kaiserslautern Univ., Kaiserslautern (F.R. Germany). Fachbereich Physik
1975-01-01
Extending the inductive renormalization procedure of Epstein and Glaser which is essentially based on locality, we show that quantum electrodynamics in an external time independent electromagnetic field has a renormalizable formal perturbation expansion. The interaction involving the quantized radiation field but not the action of the external field is treated by perturbation theory. It turns out that vacuum polarization is undetermined in the framework of such a theory.
Bound states in the two-dimension massive quantum electrodynamics (Qed2)
International Nuclear Information System (INIS)
Alves, V.S.; Gomes, M.
1994-01-01
This work studies the fermion-antifermion bound states in the (1+1)D two-dimension massive quantum electrodynamic in the 1/N expansion. The scattering matrices in the non-relativistic approximation have been calculated through TQC, and compared with the cross section in the Born approximation, and therefore the potential responsible by the interactions in the scattering processes have been obtained. Using Schroedinger equation, the existence of possible bound states have been investigated
Dynamical Mass Generation and Confinement in Maxwell-Chern-Simons Planar Quantum Electrodynamics
International Nuclear Information System (INIS)
Sanchez Madrigal, S; Raya, A; Hofmann, C P
2011-01-01
We study the non-perturbative phenomena of Dynamical Mass Generation and Confinement by truncating at the non-perturbative level the Schwinger-Dyson equations in Maxwell-Chern-Simons planar quantum electrodynamics. We obtain numerical solutions for the fermion propagator in Landau gauge within the so-called rainbow approximation. A comparison with the ordinary theory without the Chern-Simons term is presented.
Quantum electrodynamics within the framework of a new 4-dimensional symmetry
International Nuclear Information System (INIS)
Hsu, J.P.
1977-06-01
Quantum electrodynamics is discussed within the framework of a new 4-dimensional symmetry in which the concept of time, the propagation of light and the transformation property of many physical quantities are drastically different from those in special relativity. However, they are consistent with experiments. The new framework allows for natural developments of additional concepts. A possible and crucial experimental test of the new 4-dimensional symmetry is discussed
Cavity quantum electrodynamics in the Anderson-localized regime
DEFF Research Database (Denmark)
Sapienza, Luca; Nielsen, Henri Thyrrestrup; Stobbe, Søren
2010-01-01
We experimentally measure, by means of time-resolved photoluminescence spectroscopy, a 15-fold enhancement of the spontaneous emission decay rate of single semiconductor quantum dots coupled to disorder-induced Anderson-localized modes with efficiencies reaching 94%.......We experimentally measure, by means of time-resolved photoluminescence spectroscopy, a 15-fold enhancement of the spontaneous emission decay rate of single semiconductor quantum dots coupled to disorder-induced Anderson-localized modes with efficiencies reaching 94%....
FDTD method using for electrodynamic simulation of resonator accelerating structures
International Nuclear Information System (INIS)
Vorogushin, M.F.; Svistunov, Yu.A.; Chetverikov, I.O.; Malyshev, V.N.; Malyukhov, M.V.
2000-01-01
The finite difference method in the time area (FDTD) makes it possible to model both stationary and nonstationary processes, originating by the beam and field interaction. Possibilities of the method by modeling the fields in the resonant accelerating structures are demonstrated. The possibility of considering the transition processes is important besides the solution of the problem on determination of frequencies and distribution in the space of the resonators oscillations proper types. The program presented makes it possible to obtain practical results for modeling accelerating structures on personal computers [ru
International Nuclear Information System (INIS)
Krasnikov, N.V.
1991-01-01
Study of the ultraviolet behavior of asymptotically nonfree theories is one of the most important problems of quantum field theory. Unfortunately, not too much is known about the ultraviolet properties in asymptotically nonfree theories; the main obstacle is the growth of the effective coupling constant in the ultraviolet region, which renders perturbation theory inapplicable. It is shown that in quantum electrodynamics in n = 4 + 2 var-epsilon space-time (var-epsilon > 0) the photon propagator has the ultraviolet asymptotic behavior D(k 2 ) ∼ (k 2 ) -1-var-epsilon . In the case var-epsilon R ≤ -3π var-epsilon + O(var-epsilon 2 )
Instantaneous action-at-a-distance formulation of quantum electrodynamics
International Nuclear Information System (INIS)
Vora-Singha, P.
1977-01-01
Classical conserved quantities, namely energy, linear momentum, angular momentum and the center of mass constant, which are computed from Kerner's symmetric joint Lagrangian, are interpreted quantum mechanically in Heisenberg representation. The energy, when expanded and truncated after the 1/c 2 term, has interaction terms with the sign opposite to the interaction term in the Darwin Hamiltonian. When interpreted quantum mechanically, the energy (up to the 1/c 2 term) and the Darwin Hamiltonian are called the Modified-Breit ad Breit operators, respectively. The total energy, when interpreted quantum mechanically, is called the energy operator. The three operators, namely, the Breit, Modified-Breit, and energy operators are applied to plane wave scattering, He2P fine structure splitting and positronium. In He2P fine structure splitting, when the calculation is compared to available experimental results, the Modified-Breit and the energy operators seem to give wrong predictions
Random electrodynamics : a classical foundation for key quantum concepts
International Nuclear Information System (INIS)
Sachidanandam, S.
1981-01-01
The model of random electrodynamics, in which electromagnetic particles are subjected, in a classical manner, to the forces of radiation damping and the fluctuating zero-point fields provides the framework in which the following results are obtained: (1) The precession dynamics of a long-lived, non-relativistic particle with a magnetic moment proportional to its spin, leads to a self-consistent determination of the spin value as one-half. (2) The internal dynamic underlying the intrinsic magnetic moment of a Dirac particle yields a classically visualizable picture of the spin-magnetic moment. (3) The Bose correlation among indistinguishable, non-interacting, spin-zero Particles arises from the coupling through the common- zero point fields and the radiation reaction fields when the particles are close together in both the r vector and the energy spaces. (4) The (exclusion principle-induced) correlation among identical, non-interacting magnetic particles with spin 1/2 is brought about by the coupling, (through the common fields of radiation reaction and the vacuum fluctuations), of the spins as well as the translational motions when the particles are close together in r vector and the energy spaces. (5) A dilute gas of free electrons has a Maxwellian distribution of velocities and the correct value of the djamagnetic moment in the presence of a magnetic field. Considerations on the centre of mass motion of a composite neutral particle lead to a simple resolution of the foundational paradoxes of statistical mechanics. (6) An approximate treatment of the hydrogen atom leads to a description of the evolution to the ground state at absolute zero and an estimation of the mass frequency and the line-width of the radiation emitted when an excited atom decays. (author)
Quantum electrodynamical torques in the presence of Brownian motion
Munday, J. N.; Iannuzzi, D.; Capasso, F.
2006-01-01
Quantum fluctuations of the electromagnetic field give rise to a zero-point energy that persists even in the absence of electromagnetic sources. One striking consequence of the zero-point energy is manifested in the Casimir force, which causes two electrically neutral metallic plates to attract in
Epitaxial lift-off for solid-state cavity quantum electrodynamics
International Nuclear Information System (INIS)
Greuter, Lukas; Najer, Daniel; Kuhlmann, Andreas V.; Starosielec, Sebastian; Warburton, Richard J.; Valentin, Sascha R.; Ludwig, Arne; Wieck, Andreas D.
2015-01-01
We demonstrate an approach to incorporate self-assembled quantum dots into a Fabry-Pérot-like microcavity. Thereby, a 3λ/4 GaAs layer containing quantum dots is epitaxially removed and attached by van der Waals bonding to one of the microcavity mirrors. We reach a finesse as high as 4100 with this configuration limited by the reflectivity of the dielectric mirrors and not by scattering at the semiconductor-mirror interface, demonstrating that the epitaxial lift-off procedure is a promising procedure for cavity quantum electrodynamics in the solid state. As a first step in this direction, we demonstrate a clear cavity-quantum dot interaction in the weak coupling regime with a Purcell factor in the order of 3. Estimations of the coupling strength via the Purcell factor suggest that we are close to the strong coupling regime
Many-body physics with circuit quantum electrodynamics
International Nuclear Information System (INIS)
Leib, Martin H.
2015-01-01
We present proposals to simulate many-body physics with superconducting circuits. The ''body'' to work with for superconducting circuits is the microwave photon and interaction is induced by the nonlinearity of the Josephson effect. We present two different approaches to simulate Bose-Hubbard physics, one based on a polariton scheme and another with nonlinear resonators. We also present a Dicke-model like simulator for ultrastrongly coupled Josephson junctions to a resonator and show a scheme for implementing long range interactions.
Quantum electrodynamics in the light-front Weyl gauge
International Nuclear Information System (INIS)
Przeszowski, J.; Naus, H.W.; Kalloniatis, A.C.
1996-01-01
We examine (3+1)-dimensional QED quantized in the open-quote open-quote front form close-quote close-quote with finite open-quote open-quote volume close-quote close-quote regularization, namely, in discretized light-cone quantization. Instead of the light-cone or Coulomb gauges, we impose the light-front Weyl gauge A - =0. The Dirac method is used to arrive at the quantum commutation relations for the independent variables. We apply open-quote open-quote quantum-mechanical gauge fixing close-quote close-quote to implement Gauss close-quote law, and derive the physical Hamiltonian in terms of unconstrained variables. As in the instant form, this Hamiltonian is invariant under global residual gauge transformations, namely, displacements. On the light cone the symmetry manifests itself quite differently. copyright 1996 The American Physical Society
Electrodynamically trapped Yb+ ions for quantum information processing
International Nuclear Information System (INIS)
Balzer, Chr.; Braun, A.; Hannemann, T.; Wunderlich, Chr.; Paape, Chr.; Ettler, M.; Neuhauser, W.
2006-01-01
Highly efficient, nearly deterministic, and isotope selective generation of Yb + ions by one- and two-color photoionization is demonstrated. State preparation and state selective detection of hyperfine states in 171 Yb + is investigated in order to optimize the purity of the prepared state and to time-optimize the detection process. Linear laser-cooled Yb + ion crystals confined in a Paul trap are demonstrated. Advantageous features of different previous ion trap experiments are combined, while at the same time the number of possible error sources is reduced by using a comparatively simple experimental apparatus. This opens a new path toward quantum state manipulation of individual trapped ions, and in particular, to scalable quantum computing
Cavity quantum electrodynamics with a Rydberg-blocked atomic ensemble
DEFF Research Database (Denmark)
Guerlin, Christine; Brion, Etienne; Esslinger, Tilman
2010-01-01
The realization of a Jaynes-Cummings model in the optical domain is proposed for an atomic ensemble. The scheme exploits the collective coupling of the atoms to a quantized cavity mode and the nonlinearity introduced by coupling to high-lying Rydberg states. A two-photon transition resonantly cou...
DEFF Research Database (Denmark)
Reitzenstein, S.; Schneider, C.; Albert, F.
2011-01-01
Semiconductor quantum dots (QDs) are fascinating nanoscopic structures for photonics and future quantum information technology. However, the random position of self-organized QDs inhibits a deterministic coupling in devices relying on cavity quantum electrodynamics (cQED) effects which complicates......, e.g., the large scale fabrication of quantum light sources. As a result, large efforts focus on the growth and the device integration of site-controlled QDs. We present the growth of low density arrays of site-controlled In(Ga)As QDs where shallow etched nanoholes act as nucleation sites...... linewidth, the oscillator strength and the quantum efficiency. A stacked growth of strain coupled SCQDs forming on wet chemically etched nanoholes provide the smallest linewidth with an average value of 210 μeV. Using time resolved photoluminescence studies on samples with a varying thickness of the capping...
International Nuclear Information System (INIS)
Becher, P.; Joos, H.
1977-07-01
It is the aim of the main part of these lectures to show how most of the expected dynamical properties of quantum chromodynamics are realised in 1+1 dimensional quantum electrodynamics. Asymptotic freedom, the infrared limit, quark confinement and bag approximation are discussed in detail. (BJ) [de
International Nuclear Information System (INIS)
Brevik, I.
1983-01-01
The canonical quantum theory for an electromagnetic field within an isotropic nondispersive medium, whose permittivity, epsilon, and permeability μ satisfy the condition epsilonμ=1, is developed. This condition is found to simplify the electromagnetic formalism considerably and is of interest not only to quantum electrodynamics (QED) but also to quantum chromodynamics (QDC) in view of the formal analogy existing between these two theories to the zero-order in the gauge coupling constant. After giving a survey of the general formalism, this paper discusses appropriate modifications of known experiments in optics: the Ashkin-Dziedzic pressure experiment (1973), the Barlow experiment (1912), and the levitation experiment of Ashkin (1970) and others. Finally, a calculation is given of Casimir (i.e., zero-point) surface force acting on one of two spherical interfaces separating three media from each other, under certain simplifying conditions
Energy Technology Data Exchange (ETDEWEB)
Nakanishi, N [Kyoto Univ. (Japan). Research Inst. for Mathematical Sciences
1974-12-01
The Lehmann--Symanzik--Zimmermann formalism is presented for manifestly covariant quantum electrodynamics involving a gauge parameter ..cap alpha... Contrary to Kaellen's assertion, it is shown that one can consistently formulate the asymptotic condition for the electromagnetic field and construct the Fock space of asymptotic states. Except for the case of Feynman gauge (..cap alpha..=1), the formalism is somewhat complicated because of the presence of dipole ghosts, but emphasis is laid on the very existence of a consistent formalism. The completeness relation for the asymptotic states is presented so that the generalized unitarity relation can be written down. Indefinite-metric theory of a massive vector field is briefly discussed.
International Nuclear Information System (INIS)
Zhukovskii, K.V.; Eminov, P.A.
1995-01-01
The one-loop approximation is used to calculate the effects of finite temperature and nonzero chemical potential on the electron energy shift in a (2 + 1)-quantum electrodynamic system containing a Churn-Simon term. The induced electron mass is derived with a massless (2 + 1)-quantum electrodynamic system together with the exchange correction to the thermodynamic potential for a completely degenerate electron gas. It is shown that in the last case, incorporating the Churn-Simon term leads to loss of the gap in the direction law
Krupka, Jerzy; Aleshkevych, Pavlo; Salski, Bartlomiej; Kopyt, Pawel
2018-02-01
The mode of uniform precession, or Kittel mode, in a magnetized ferromagnetic sphere, has recently been proven to be the magnetic plasmon resonance. In this paper we show how to apply the electrodynamic model of the magnetic plasmon resonance for accurate measurements of the ferromagnetic resonance linewidth ΔH. Two measurement methods are presented. The first one employs Q-factor measurements of the magnetic plasmon resonance coupled to the resonance of an empty metallic cavity. Such coupled modes are known as magnon-polariton modes, i.e. hybridized modes between the collective spin excitation and the cavity excitation. The second one employs direct Q-factor measurements of the magnetic plasmon resonance in a filter setup with two orthogonal semi-loops used for coupling. Q-factor measurements are performed employing a vector network analyser. The methods presented in this paper allow one to extend the measurement range of the ferromagnetic resonance linewidth ΔH well beyond the limits of the commonly used measurement standards in terms of the size of the samples and the lowest measurable linewidths. Samples that can be measured with the newly proposed methods may have larger size as compared to the size of samples that were used in the standard methods restricted by the limits of perturbation theory.
Precision spectroscopy on hydrogen and deuterium. Test of the bound-state quantum electrodynamics
International Nuclear Information System (INIS)
Fendel, P.
2005-06-01
An optical measurement of the hyperfine splitting of the 2s state in deuterium performed for the first time and the description of the arrangement for the measurement of the 1s-3s frequency in hydrogen by excitation with a frequency combexpect the reader of this thesis. Both experiments have the goal to test the bound-state quantum electrodynamics (QED) with high precision. The measurement of the hyperfine splitting serves thereby for the improvement of the accuracy of the so called D 21 =8E HFS (2s)-E HFS (1s) difference. Because D 21 is far-reachingly independent on the nuclear structure in spite of not accurately known proton charge radii QED can be tested on a level of 10 -7 . In the framework of the thesis present here the error of this quantity was reduced by a factor of three. The result for the 2s hyperfine splitting is: f D HFS =40924454(7) Hz. By a new kind of the data acquisition furthermore many systematic errors, especially the nonlinear drift of the reference resonator, could be reduced in comparison to a similar measurement on hydrogen. The second part of the thesis describes the efforts which were and will be taken in order to test QED by means of their perdiction of the 1s Lamb shift. For this the frequency of the 1s-3s transition in hydrogen shall be measured absolutely for the first time. A further novum is that for this a frequency-quadrupled mode-coupled laser shall be come into operation. Especially the construction and the stabilization of a ps laser, the construction of two frequency-doubling stages, the arrangement for the measurement of the absolute frequency of the spectroscopy laser, the alteration of the existing 1s-2s vacuum system, and the development of the measurement software is described. Additionally in this thesis the theory of the two-photon frequency-comb spectroscopy is further developed. Concrete expressions for the expected line shape and the influence of the chirp on the excitation rate are presented
Stopping single photons in one-dimensional circuit quantum electrodynamics systems
International Nuclear Information System (INIS)
Shen, J.-T.; Povinelli, M. L.; Sandhu, Sunil; Fan Shanhui
2007-01-01
We propose a mechanism to stop and time reverse single photons in one-dimensional circuit quantum electrodynamics systems. As a concrete example, we exploit the large tunability of the superconducting charge quantum bit (charge qubit) to predict one-photon transport properties in multiple-qubit systems with dynamically controlled transition frequencies. In particular, two qubits coupled to a waveguide give rise to a single-photon transmission line shape that is analogous to electromagnetically induced transparency in atomic systems. Furthermore, by cascading double-qubit structures to form an array and dynamically controlling the qubit transition frequencies, a single photon can be stopped, stored, and time reversed. With a properly designed array, two photons can be stopped and stored in the system at the same time. Moreover, the unit cell of the array can be designed to be of deep subwavelength scale, miniaturizing the circuit
Classical resonances and quantum scarring
International Nuclear Information System (INIS)
Manderfeld, Christopher
2003-01-01
We study the correspondence between phase-space localization of quantum (quasi-)energy eigenstates and classical correlation decay, given by Ruelle-Pollicott resonances of the Frobenius-Perron operator. It will be shown that scarred (quasi-)energy eigenstates are correlated: pairs of eigenstates strongly overlap in phase space (scar in same phase-space regions) if the difference of their eigenenergies is close to the phase of a leading classical resonance. Phase-space localization of quantum states will be measured by L 2 norms of their Husimi functions
Berestetskii, Vladimir B; Pitaevskii, L P
1982-01-01
Several significant additions have been made to the second edition, including the operator method of calculating the bremsstrahlung cross-section, the calcualtion of the probabilities of photon-induced pair production and photon decay in a magneticfield, the asymptotic form of the scattering amplitudes at high energies, inelastic scattering of electrons by hadrons, and the transformation of electron-positron pairs into hadrons.
International Nuclear Information System (INIS)
Heller, E.J.
1996-01-01
It is well known that at long wavelengths λ an s-wave scatterer can have a scattering cross section σ on the order of λ 2 , much larger than its physical size, as measured by the range of its potential. Very interesting phenomena can arise when two or more identical scatterers are placed close together, well within one wavelength. We show that, for a pair of identical scatterers, an extremely narrow p-wave open-quote open-quote proximity close-quote close-quote resonance develops from a broader s-wave resonance of the individual scatterers. A new s-wave resonance of the pair also appears. The relation of these proximity resonances (so called because they appear when the scatterers are close together) to the Thomas and Efimov effects is discussed. copyright 1996 The American Physical Society
Bookshelf (Early Quantum Electrodynamics - A Source Book, by Arthur I. Miller)
International Nuclear Information System (INIS)
Anon.
1994-01-01
Many people these days would say that quantum electrodynamics, the quantum picture of electromagnetic radiation, dates from 1947-8 with the work of Sin-itoro Tomonaga, Julian Schwinger and Richard Feynman. However this was the modern reformulation of a theory whose genesis was Paul Dirac's 1927 work on the quantization of radiation and was subsequently, and painfully, pieced together in the 1930s. Until the Second World War, the science of quantum electrodynamics advanced steadily, driven for the most part by the intellects which had produced modern quantum mechanics - notably Dirac, Heisenberg and Pauli. After Dirac's 1928 relativistic theory of the electron, Heisenberg and Pauli went on to cast an initial quantum formalism for the interaction between radiation and electrons. During this time many intellectual hurdles had to be crossed - the negative energy states predicted by Dirac's equation and their final identification as antimatter electrons (positrons), the whole problem of explaining quantum force mechanisms as particle exchanges, Fermi's explanation of beta decay, and Yukawa's explanation of the nuclear force. Heisenberg's invention of the S-matrix and his ideas on the transmission of nuclear forces through exchange mechanisms revolutionized both our picture of the quantum world. These problems were not easy - several times during the 1920s even these intellects almost despaired. A shadow across the subject was the continual problem of troublesome infinities in mass terms and elsewhere. It was not until the ordered renormalization recipes of the immediate post-war period that these infinities were finally hidden from sight. Science historian Arthur Miller traces these developments in the first half of the book, and signals how these early developments were eventually to dovetail with the exciting new developments of the late 1940s. Supplementing the survey are eleven fascinating landmark papers by Heisenberg, Dirac, Weisskopf
International Nuclear Information System (INIS)
Zalialiutdinov, T; Baukina, Yu; Solovyev, D; Labzowsky, L
2014-01-01
The theory of multiphoton cascade transitions with two-photon links is considered within two different approaches: quantum electrodynamical (QED) and phenomenological quantum mechanical (QM). A problem of regularization of the cascade contributions is investigated in detail. It is argued that the correct regularization should include both initial and intermediate level widths in the singular energy denominators. This result follows both from the QED and from the QM approach. Particular transitions nl → 1s + 2γ with nl = 3s, 4s, 3d, 4d and nl → 1s + 3γ with nl = 3p, 4p are considered as examples. The importance of the proper cascade regularization is also demonstrated. (paper)
Superconducting resonators as beam splitters for linear-optics quantum computation.
Chirolli, Luca; Burkard, Guido; Kumar, Shwetank; Divincenzo, David P
2010-06-11
We propose and analyze a technique for producing a beam-splitting quantum gate between two modes of a ring-resonator superconducting cavity. The cavity has two integrated superconducting quantum interference devices (SQUIDs) that are modulated by applying an external magnetic field. The gate is accomplished by applying a radio frequency pulse to one of the SQUIDs at the difference of the two mode frequencies. Departures from perfect beam splitting only arise from corrections to the rotating wave approximation; an exact calculation gives a fidelity of >0.9992. Our construction completes the toolkit for linear-optics quantum computing in circuit quantum electrodynamics.
Non-relativistic Limit of a Dirac Polaron in Relativistic Quantum Electrodynamics
Arai, A
2006-01-01
A quantum system of a Dirac particle interacting with the quantum radiation field is considered in the case where no external potentials exist. Then the total momentum of the system is conserved and the total Hamiltonian is unitarily equivalent to the direct integral $\\int_{{\\bf R}^3}^\\oplus\\overline{H({\\bf p})}d{\\bf p}$ of a family of self-adjoint operators $\\overline{H({\\bf p})}$ acting in the Hilbert space $\\oplus^4{\\cal F}_{\\rm rad}$, where ${\\cal F}_{\\rm rad}$ is the Hilbert space of the quantum radiation field. The fibre operator $\\overline{H({\\bf p})}$ is called the Hamiltonian of the Dirac polaron with total momentum ${\\bf p} \\in {\\bf R}^3$. The main result of this paper is concerned with the non-relativistic (scaling) limit of $\\overline{H({\\bf p})}$. It is proven that the non-relativistic limit of $\\overline{H({\\bf p})}$ yields a self-adjoint extension of a Hamiltonian of a polaron with spin $1/2$ in non-relativistic quantum electrodynamics.
Correlation of Dirac potentials and atomic inversion in cavity quantum electrodynamics
International Nuclear Information System (INIS)
Trisetyarso, Agung
2010-01-01
Controlling the time evolution of the population of two states in cavity quantum electrodynamics is necessary by tuning the modified Rabi frequency in which the extra classical effect of electromagnetic field is taken into account. The theoretical explanation underlying the perturbation of potential on spatial regime of bloch sphere is by the use of Bagrov-Baldiotti-Gitman-Shamshutdinova-Darboux transformations [Bagrov et al., 'Darboux transformation for two-level system', Ann. Phys. 14, 390 (2005)] on the electromagnetic field potential in one-dimensional stationary Dirac model in which the Pauli matrices are the central parameters for controlling the collapse and revival of the Rabi oscillations. It is shown that by choosing σ 1 in the transformation generates the parabolic potential causing the total collapse of oscillations, while (σ 2 ,σ 3 ) yield the harmonic oscillator potentials ensuring the coherence of qubits.
The positronium and the dipositronium in a Hartree-Fock approximation of quantum electrodynamics
Sok, Jérémy
2016-02-01
The Bogoliubov-Dirac-Fock (BDF) model is a no-photon approximation of quantum electrodynamics. It allows to study relativistic electrons in interaction with the Dirac sea. A state is fully characterized by its one-body density matrix, an infinite rank non-negative projector. We prove the existence of the para-positronium, the bound state of an electron and a positron with antiparallel spins, in the BDF model represented by a critical point of the energy functional in the absence of an external field. We also prove the existence of the dipositronium, a molecule made of two electrons and two positrons that also appears as a critical point. More generally, for any half integer j ∈ 1/2 + Z + , we prove the existence of a critical point of the energy functional made of 2j + 1 electrons and 2j + 1 positrons.
Energy Technology Data Exchange (ETDEWEB)
Steinmann, O [Bielefeld Univ. (F.R. Germany). Fakultaet fuer Physik
1975-01-01
Massive quantum electrodynamics of the electron is formulated as an LSZ theory of the electromagnetic field F(..mu nu..) and the electron-positron fields PSI. The interaction is introduced with the help of mathematically well defined subsidiary conditions. These are: 1) gauge invariance of the first kind, assumed to be generated by a conserved current j(..mu..); 2) the homogeneous Maxwell equations and a massive version of the inhomogeneous Maxwell equations; 3) a minimality condition concerning the high momentum behaviour of the theory. The inhomogeneous Maxwell equation is a linear differential equation connecting Fsub(..mu nu..) with the current Jsub(..mu..). No Lagrangian, no non-linear field equations, and no explicit expression of Jsub(..mu..) in terms of PSI, anti-PSI are needed. It is shown in perturbation theory that the proposed conditions fix the physically relevant (i.e. observable) quantities of the theory uniquely.
A comprehensive coordinate space renormalization of quantum electrodynamics to two-loop order
International Nuclear Information System (INIS)
Haagensen, P.E.; Latorre, J.I.
1993-01-01
We develop a coordinate space renormalization of massless quantum electrodynamics using the powerful method of differential renormalization. Bare one-loop amplitudes are finite at non-coincident external points, but do not accept a Fourier transform into momentum space. The method provides a systematic procedure to obtain one-loop renormalized amplitudes with finite Fourier transforms in strictly four dimensions without the appearance of integrals or the use of a regulator. Higher loops are solved similarly by renormalizing from the inner singularities outwards to the global one. We compute all one- and two-loop 1PI diagrams, run renormalization group equations on them. and check Ward identities. The method furthermore allows us to discern a particular pattern of renormalization under which certain amplitudes are seen not to contain higher-loop leading logarithms. We finally present the computation of the chiral triangle showing that differential renormalization emerges as a natural scheme to tackle γ 5 problems
Confinement in Maxwell-Chern-Simons planar quantum electrodynamics and the 1/N approximation
International Nuclear Information System (INIS)
Hofmann, Christoph P.; Raya, Alfredo; Madrigal, Saul Sanchez
2010-01-01
We study the analytical structure of the fermion propagator in planar quantum electrodynamics coupled to a Chern-Simons term within a four-component spinor formalism. The dynamical generation of parity-preserving and parity-violating fermion mass terms is considered, through the solution of the corresponding Schwinger-Dyson equation for the fermion propagator at leading order of the 1/N approximation in Landau gauge. The theory undergoes a first-order phase transition toward chiral symmetry restoration when the Chern-Simons coefficient θ reaches a critical value which depends upon the number of fermion families considered. Parity-violating masses, however, are generated for arbitrarily large values of the said coefficient. On the confinement scenario, complete charge screening - characteristic of the 1/N approximation - is observed in the entire (N,θ)-plane through the local and global properties of the vector part of the fermion propagator.
Reduced Dirac equation and Lamb shift as off-mass-shell effect in quantum electrodynamics
International Nuclear Information System (INIS)
Ni Guang-Jiong; Xu Jian-Jun; Lou Sen-Yue
2011-01-01
Based on the accurate experimental data of energy-level differences in hydrogen-like atoms, especially the 1S—2S transitions of hydrogen and deuterium, the necessity of introducing a reduced Dirac equation with reduced mass as the substitution of original electron mass is stressed. Based on new cognition about the essence of special relativity, we provide a reasonable argument for the reduced Dirac equation to have two symmetries, the invariance under the (newly defined) space-time inversion and that under the pure space inversion, in a noninertial frame. By using the reduced Dirac equation and within the framework of quantum electrodynamics in covariant form, the Lamb shift can be evaluated (at one-loop level) as the radiative correction on a bound electron staying in an off-mass-shell state—-a new approach eliminating the infrared divergence. Hence the whole calculation, though with limited accuracy, is simplified, getting rid of all divergences and free of ambiguity. (general)
International Nuclear Information System (INIS)
Ito, K.R.
1975-01-01
The Schwinger model is considered in the Landau-gauge formalism of quantum electrodynamics. This model can be solved exactly on the assumption of no radiative corrections to the anomaly. It is found that the photon obtains a non-zero mass through the Higgs mechanism. In this case, the would-be Nambu-Goldstone boson is an associated boson which is constructed from a pair of two-component massless fermions. This would-be Nambu-Goldstone boson appears as a result of the spontaneous breaking of the gauge invariance of the first kind, and it becomes unphysical through the Higgs mechanism. However, as all the fermions themselves decouple from photons, they cannot appear as real particles in our world. (author)
Quantum electrodynamic corrections for the valence shell in heavy many-electron atoms
International Nuclear Information System (INIS)
Thierfelder, C.; Schwerdtfeger, P.
2010-01-01
We present quantum electrodynamic (QED) calculations within the picture of bound-state QED for the frequency-dependent Breit interaction between electrons, the vacuum polarization, and the electron self-energy correction starting from the Dirac-Coulomb Hamiltonian for the ionization potentials of the group 1, 2, 11, 12, 13, and 18 elements of the periodic table, and down to the superheavy elements up to nuclear charge Z=120. The results for the s-block elements are in very good agreement with earlier studies by Labzowsky et al. [Phys. Rev. A 59, 2707 (1999)]. We discuss the influence of the variational versus perturbative treatment of the Breit interaction for valence-space ionization potentials. We argue that the lowest-order QED contributions become as important as the Breit interaction for ionization potentials out of the valence s shell.
The eigenfunction method and the mass operator in intense-field quantum electrodynamics
International Nuclear Information System (INIS)
Ritus, V.I.
1987-01-01
A method is given for calculating radiation effects in constant intense-field quantum electrodynamics; this method is based on the use of the eigenfunctions of the mass operator and diagonalization of the latter. A compact expression is found for the eigenvalue of the mass operator of the electron in a random constant field together with the corresponding elastic scattering amplitude. The anomalous electric moment that arises in the field with a pseudoscalar EH not equal to O is found and investigated in detail together with the anomalous magnetic moment in the electrical field that approaches the double Schwinger value with an increase in the field together with the mass shift and the rate of decay of the ground state of the electron in the electrical field
Oscillating dipole with fractional quantum source in Aharonov-Bohm electrodynamics
Directory of Open Access Journals (Sweden)
Giovanni Modanese
Full Text Available We show, in the case of a special dipolar source, that electromagnetic fields in fractional quantum mechanics have an unexpected space dependence: propagating fields may have non-transverse components, and the distinction between near-field zone and wave zone is blurred. We employ an extension of Maxwell theory, Aharonov-Bohm electrodynamics, which is compatible with currents jν conserved globally but not locally; we have derived in another work the field equation ∂μFμν=jν+iν, where iν is a non-local function of jν, called “secondary current”. Y. Wei has recently proved that the probability current in fractional quantum mechanics is in general not locally conserved. We compute this current for a Gaussian wave packet with fractional parameter a=3/2 and find that in a suitable limit it can be approximated by our simplified dipolar source. Currents which are not locally conserved may be present also in other quantum systems whose wave functions satisfy non-local equations. The combined electromagnetic effects of such sources and their secondary currents are very interesting both theoretically and for potential applications. Keywords: Generalized Maxwell theory, Fractional Schrödinger equation, Local current conservation
Cohen, Ian J.; Lessard, Marc; Lund, Eric J.; Bounds, Scott R.; Kletzing, Craig; Kaeppler, Stephen R.; Sigsbee, Kristine M.; Streltsov, Anatoly V.; Labelle, James W.; Dombrowski, Micah P.;
2011-01-01
In 2009, the Auroral Current and Electrodynamics Structure (ACES) High and Low sounding rockets were launched from the Poker Flat Rocket Range (PFRR) in Alaska, with the science objective of gathering in-situ data to quantify current closure in a discrete auroral arc. As ACES High crossed through the return current of an arc (that was monitored using an all sky camera from the ground at Fort Yukon), its instruments recorded clear Alfv nic signatures both poleward and equatorward of the return current region, but not within the main region of the return current itself. These data provide an excellent opportunity to study ionospheric feedback and how it interacts with the Alfv n resonator. We compare the observations with predictions and new results from a model of ionospheric feedback in the ionospheric Alfv n resonator (IAR) and report the significance and impact of these new data for the Magnetosphere-Ionosphere Coupling in the Alfv n Resonator (MICA) rocket mission to launch from PFRR this winter. MICA s primary science objectives specifically focus on better understanding the small-scale structure that the model predicts should exist within the return current region.
Quantum heat engine with coupled superconducting resonators
DEFF Research Database (Denmark)
Hardal, Ali Ümit Cemal; Aslan, Nur; Wilson, C. M.
2017-01-01
We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one...... the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures....
Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics
DEFF Research Database (Denmark)
Madsen, Kristian Høeg; Lodahl, Peter
2013-01-01
-resolved measurements reveal that the actual coupling strength is significantly smaller than anticipated from the spectral measurements and that the quantum dot is rather weakly coupled to the cavity. We suggest that the observed Rabi splitting is due to cavity feeding by other quantum dots and/or multi...
Broadband filters for abatement of spontaneous emission in circuit quantum electrodynamics
Energy Technology Data Exchange (ETDEWEB)
Bronn, Nicholas T., E-mail: ntbronn@us.ibm.com; Hertzberg, Jared B.; Córcoles, Antonio D.; Gambetta, Jay M.; Chow, Jerry M. [IBM T.J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States); Liu, Yanbing; Houck, Andrew A. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States)
2015-10-26
The ability to perform fast, high-fidelity readout of quantum bits (qubits) is essential to the goal of building a quantum computer. However, coupling a fast measurement channel to a superconducting qubit typically also speeds up its relaxation via spontaneous emission. Here, we use impedance engineering to design a filter by which photons may easily leave the resonator at the cavity frequency but not at the qubit frequency. We implement this broadband filter in both an on-chip and off-chip configuration.
International Nuclear Information System (INIS)
Ding, X.; Sun, R.; Dong, C.; Koike, F.; Kato, D.; Murakami, I.; Sakaue, H.A.
2017-01-01
The electron correlation effects and Breit interaction as well as Quantum Electro-Dynamics (QED) effects were expected to have important contribution to the energy level and transition properties of heavy highly charged ions. The study of W 54+ ion provide necessary reference data for the fusion plasma physics as tungsten was chosen to be used as the armour material of the divertor of the ITER project. The ground states [Ne]3s 2 3p 6 3d 2 and first excited states [Ne]3s 2 3p 5 3d 3 of W 54+ ion have been studied by using Multi-Configuration Dirac-Fock method with the implementation of Grasp2K package. A restricted active space method was employed to investigate the correlation contribution from different models. The Breit interaction and QED effects were taken into account in the relativistic configuration interaction calculation with the converged wavefunction. It is found that the correlation contribution from 3s and 3p orbital have important contribution to the energy level, transition wavelength and probability of the ground and the first excited state of W 54+ ion. (authors)
Self-Localized Quasi-Particle Excitation in Quantum Electrodynamics and Its Physical Interpretation
Directory of Open Access Journals (Sweden)
Ilya D. Feranchuk
2007-12-01
Full Text Available The self-localized quasi-particle excitation of the electron-positron field (EPF is found for the first time in the framework of a standard form of the quantum electrodynamics. This state is interpreted as the ''physical'' electron (positron and it allows one to solve the following problems: i to express the ''primary'' charge $e_0$ and the mass $m_0$ of the ''bare'' electron in terms of the observed values of $e$ and $m$ of the ''physical'' electron without any infinite parameters and by essentially nonperturbative way; ii to consider $mu$-meson as another self-localized EPF state and to estimate the ratio $m_mu/m$; iii to prove that the self-localized state is Lorentz-invariant and its energy spectrum corresponds to the relativistic free particle with the observed mass $m$; iv to show that the expansion in a power of the observed charge $e ll 1$ corresponds to the strong coupling expansion in a power of the ''primary'' charge $e^{-1}_0 sim e$ when the interaction between the ''physical'' electron and the transverse electromagnetic field is considered by means of the perturbation theory and all terms of this series are free from the ultraviolet divergence.
Eigenfunction method and mass operator in the quantum electrodynamics of a constant field
International Nuclear Information System (INIS)
Ritus, V.I.
1978-01-01
A method is presented for the calculation of radiative effects in the quantum electrodynamics of an intense constant field. It is based on the application of the mass operator eigenfunctions and on diagonalization of the operator. A compact expression for the proper value of the electron mass operator in an arbitrary constant field and the corresponding elastic scattering amplitude are found. The imaginary part of the amplitude determines the decay rate of various states of the electron in the field; the real part contains the mass shift and the anomalous magnetic and electric moments as functions of the field and electron momentum. THe anomalous electric moment which arises in a field with a pseudoscalar EH not equal to 0 and the anomalous magnetic moment in an electric field which tends to the double Schwinger value with increase of the field strength are found and investigated in detail as are the mass shift and decay rate of the ground state of an electron in an electric field. In a weak field the mass shift contains the linear with respect to the field modulus classical term which characterizes the effect of acceleration on the structure of electron
Magnetic monopole plasma phase in (2+1)d compact quantum electrodynamics with fermionic matter
International Nuclear Information System (INIS)
Armour, Wesley; Hands, Simon; Lucini, Biagio; Kogut, John B.; Strouthos, Costas; Vranas, Pavlos
2011-01-01
We present the first evidence from lattice simulations that the magnetic monopoles in three-dimensional compact quantum electrodynamics (cQED 3 ) with N f =2 and N f =4 four-component fermion flavors are in a plasma phase. The evidence is based mainly on the divergence of the monopole susceptibility (polarizability) with the lattice size at weak gauge couplings. A weak four-Fermi term added to the cQED 3 action enabled simulations with massless fermions. The exact chiral symmetry of the interaction terms forbids symmetry breaking lattice discretization counterterms to appear in the theory's effective action. It is also shown that the scenario of a monopole plasma does not depend on the strength of the four-Fermi coupling. Other observables such as the densities of isolated dipoles and monopoles and the so-called specific heat show that a crossover from a dense monopole plasma to a dilute monopole gas occurs at strong couplings. The implications of our results on the stability of U(1) spin liquids in two spatial dimensions are also discussed.
Energy Technology Data Exchange (ETDEWEB)
Gumberidze, A.; Stoehlker, T. [Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany)]|[Frankfurt Univ. (Germany). Inst. fuer Kernphysik; Banas, D. [Pedagogical Univ., Kielce (PL). Inst. of Phys.] [and others
2005-05-01
X-ray spectra following radiative recombination of free electrons with bare uranium ions (U{sup 92+}) were measured at the electron cooler of the ESR storage ring. The most intense lines observed in the spectra can be attributed to the characteristic Lyman ground-state transitions and to the recombination of free electrons into the K-shell of the ions. Our experiment was carried out by utilizing the deceleration technique which leads to a considerable reduction of the uncertainties associated with Doppler corrections. This, in combination with the 0 observation geometry, allowed us to determine the ground-state Lamb shift in hydrogen-like uranium (U{sup 91+}) from the observed X-ray lines with an accuracy of 1%. The present result is about 3 times more precise than the most accurate value available up to now and provides the most stringent test of bound-state quantum electrodynamics for one-electron systems in the strong-field regime. (orig.)
Quantum Graphs And Their Resonance Properties
International Nuclear Information System (INIS)
Lipovsky, J.
2016-01-01
In the current review, we study the model of quantum graphs. We focus mainly on the resonance properties of quantum graphs. We define resolvent and scattering resonances and show their equivalence. We present various results on the asymptotics of the number of resolvent resonances in both non-magnetic and magnetic quantum graphs and find bounds on the coefficient by the leading term of the asymptotics. We explain methods how to find the spectral and resonance condition. Most of the notions and theorems are illustrated in examples. We show how to find resonances numerically and, in a simple example, we find trajectories of resonances in the complex plane. We discuss Fermi’s golden rule for quantum graphs and distribution of the mean intensity for the topological resonances. (author)
Quantum Simulation of the Ultrastrong-Coupling Dynamics in Circuit Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
D. Ballester
2012-05-01
Full Text Available We propose a method to get experimental access to the physics of the ultrastrong- and deep-strong-coupling regimes of light-matter interaction through the quantum simulation of their dynamics in standard circuit QED. The method makes use of a two-tone driving scheme, using state-of-the-art circuit-QED technology, and can be easily extended to general cavity-QED setups. We provide examples of ultrastrong- and deep-strong-coupling quantum effects that would be otherwise inaccessible.
Quantum field theory II: quantum electrodynamics. A bridge between mathematicians and physicists
International Nuclear Information System (INIS)
Zeidler, Eberhard
2009-01-01
This is the second volume of a modern introduction to quantum field theory which addresses both mathematicians and physicists ranging from advanced undergraduate students to professional scientists. This book seeks to bridge the existing gap between the different languages used by mathematicians and physicists. For students of mathematics it is shown that detailed knowledge of the physical background helps to discover interesting interrelationships between quite diverse mathematical topics. For students of physics fairly advanced mathematics, beyond that included in the usual curriculum in physics, is presented. The present volume concerns a detailed study of the mathematical and physical aspects of the quantum theory of light. (orig.)
Quantum field theory II: quantum electrodynamics. A bridge between mathematicians and physicists
Energy Technology Data Exchange (ETDEWEB)
Zeidler, Eberhard [Max Planck Institute for Mathematics in the Sciences, Leipzig (Germany)
2009-07-01
This is the second volume of a modern introduction to quantum field theory which addresses both mathematicians and physicists ranging from advanced undergraduate students to professional scientists. This book seeks to bridge the existing gap between the different languages used by mathematicians and physicists. For students of mathematics it is shown that detailed knowledge of the physical background helps to discover interesting interrelationships between quite diverse mathematical topics. For students of physics fairly advanced mathematics, beyond that included in the usual curriculum in physics, is presented. The present volume concerns a detailed study of the mathematical and physical aspects of the quantum theory of light. (orig.)
Resonant transfer of excitons and quantum computation
International Nuclear Information System (INIS)
Lovett, Brendon W.; Reina, John H.; Nazir, Ahsan; Kothari, Beeneet; Briggs, G. Andrew D.
2003-01-01
Resonant energy transfer mechanisms have been observed in the sensitized luminescence of solids, and in quantum dots, molecular nanostructures, and photosynthetic organisms. We demonstrate that such mechanisms, together with the exciton-exciton binding energy shift typical of these nanostructures, can be used to perform universal quantum logic and generate quantum entanglement
DEFF Research Database (Denmark)
Madsen, Kristian Høeg; Ates, Serkan; Reitzenstein, S.
2010-01-01
The coupling between a quantum dot (QD) and a micropillar cavity is experimentally investigated by performing time-resolved, correlation, and two-photon interference measurements. The Jaynes-Cummings model including dissipative Lindblad terms and dephasing is analyzed, and all the parameters...
Bloch-wave engineering of quantum dot-micropillars for cavity quantum electrodynamics experiments
DEFF Research Database (Denmark)
Lermer, Matthias; Gregersen, Niels; Dunzer, Florian
2012-01-01
scattering loss leads to record-high visibility of the strong coupling in MPs with modest oscillator strength quantum dots. A quality factor of 13,600 and a Rabi splitting of 85 \\mueV with an estimated visibility v of 0.38 are observed for a small mode volume MP with a diameter dc of 850 nm....
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.
Exploiting Quantum Resonance to Solve Combinatorial Problems
Zak, Michail; Fijany, Amir
2006-01-01
Quantum resonance would be exploited in a proposed quantum-computing approach to the solution of combinatorial optimization problems. In quantum computing in general, one takes advantage of the fact that an algorithm cannot be decoupled from the physical effects available to implement it. Prior approaches to quantum computing have involved exploitation of only a subset of known quantum physical effects, notably including parallelism and entanglement, but not including resonance. In the proposed approach, one would utilize the combinatorial properties of tensor-product decomposability of unitary evolution of many-particle quantum systems for physically simulating solutions to NP-complete problems (a class of problems that are intractable with respect to classical methods of computation). In this approach, reinforcement and selection of a desired solution would be executed by means of quantum resonance. Classes of NP-complete problems that are important in practice and could be solved by the proposed approach include planning, scheduling, search, and optimal design.
Long, Junling; Ku, H. S.; Wu, Xian; Gu, Xiu; Lake, Russell E.; Bal, Mustafa; Liu, Yu-xi; Pappas, David P.
2018-02-01
Quantum networks will enable extraordinary capabilities for communicating and processing quantum information. These networks require a reliable means of storage, retrieval, and manipulation of quantum states at the network nodes. A node receives one or more coherent inputs and sends a conditional output to the next cascaded node in the network through a quantum channel. Here, we demonstrate this basic functionality by using the quantum interference mechanism of electromagnetically induced transparency in a transmon qubit coupled to a superconducting resonator. First, we apply a microwave bias, i.e., drive, to the qubit-cavity system to prepare a Λ -type three-level system of polariton states. Second, we input two interchangeable microwave signals, i.e., a probe tone and a control tone, and observe that transmission of the probe tone is conditional upon the presence of the control tone that switches the state of the device with up to 99.73% transmission extinction. Importantly, our electromagnetically induced transparency scheme uses all dipole allowed transitions. We infer high dark state preparation fidelities of >99.39 % and negative group velocities of up to -0.52 ±0.09 km /s based on our data.
Pakniat, R.; Soltani, M.; Tavassoly, M. K.
2018-03-01
Recently we studied the effect of photon addition in the initial coherent field on the entanglement swapping which causes some improvements in the process [Soltani et al., Int. J. Mod. Phys. B 31, 1750198 (2017)]. In this paper, we investigate the influence of multiphoton transitions in the atom-field interaction based on the cavity quantum electrodynamics on the entanglement swapping and show its considerable constructive effect on this process. The presented model consists of two two-level atoms namely A1 and A2 and two distinct cavity fields F1 and F2. Initially, the atoms are prepared in a maximally entangled state and the fields in the cavities are prepared in hybrid entangled state of number and coherent states, separately. Making the atom A2 to interact with the field F1 (via the generalized Jaynes-Cummings model which allows m-photon transitions between atomic levels in the emission and absorption processes) followed by their detection allows us to arrive at the entanglement swapping from the two atoms A1, A2 and the two fields F1, F2 to the atom-field A1-F2 system. Then, we pay our attention to the time evolution of success probability of detecting processes and fidelity. Also, to determine the amount of entanglement of the generated entangled state in the swapping process, the linear entropy is evaluated and the effect of parameter m concerning the multiphoton transitions on these quantities is investigated, numerically. It is observed that, by increasing the number of photons in the transition process, one may obtain considerable improvement in the relevant quantities of the entanglement swapping. In detail, the satisfactorily acceptable values 1 and 0.5 corresponding to success probability and fidelity are obtained for most of the times during observing of the above-mentioned procedure. We concluded that the presented formalism in this paper is much more advantageous than our presentation model in our earlier work mentioned above.
International Nuclear Information System (INIS)
Hiroshima, Fumio
2002-01-01
Scaling limits of the Hamiltonian H of a system of N charged particles coupled to a quantized radiation field are considered. Ultraviolet cutoffs, λ 1 ,...,λ N , are imposed on the radiation field and the Coulomb gauge is taken. It is the so-called Pauli-Fierz model in nonrelativistic quantum electrodynamics. We mainly consider two cases: (i) all the ultraviolet cutoffs are identical, λ 1 =···=λ N , (ii) supports of ultraviolet cutoffs have no intersection, supp λ i intersection supp λ j = null-set , i≠j. The Hamiltonian acts on L 2 (R dN )(multiply-in-circle sign)F, where F is a symmetric Fock space, and has the form H=H el (multiply-in-circle sign)1+B+1(multiply-in-circle sign)H quad . Here H el denotes a particle Hamiltonian, H quad a quadratic field operator, and B an interaction term. The scaling is introduced as H(κ)=H el (multiply-in-circle sign)1+κ l B+κ 2 1(multiply-in-circle sign)H quad , where κ is a scaling parameter and l≤2 a parameter of the scaling. Performing a mass renormalization we consider the scaling limit of H(κ) as κ→∞ in the strong resolvent sense. Then effective Hamiltonians H eff in L 2 (R dN ) infected with reaction of effect of the radiation field is derived. In particular (1) effective Hamiltonians with an effective potential for l=2, and (2) effective Hamiltonians with an observed mass for l=1, are obtained
International Nuclear Information System (INIS)
Heusler, Stefan
2006-01-01
The main focus of the second, enlarged edition of the book Mathematica for Theoretical Physics is on computational examples using the computer program Mathematica in various areas in physics. It is a notebook rather than a textbook. Indeed, the book is just a printout of the Mathematica notebooks included on the CD. The second edition is divided into two volumes, the first covering classical mechanics and nonlinear dynamics, the second dealing with examples in electrodynamics, quantum mechanics, general relativity and fractal geometry. The second volume is not suited for newcomers because basic and simple physical ideas which lead to complex formulas are not explained in detail. Instead, the computer technology makes it possible to write down and manipulate formulas of practically any length. For researchers with experience in computing, the book contains a lot of interesting and non-trivial examples. Most of the examples discussed are standard textbook problems, but the power of Mathematica opens the path to more sophisticated solutions. For example, the exact solution for the perihelion shift of Mercury within general relativity is worked out in detail using elliptic functions. The virial equation of state for molecules' interaction with Lennard-Jones-like potentials is discussed, including both classical and quantum corrections to the second virial coefficient. Interestingly, closed solutions become available using sophisticated computing methods within Mathematica. In my opinion, the textbook should not show formulas in detail which cover three or more pages-these technical data should just be contained on the CD. Instead, the textbook should focus on more detailed explanation of the physical concepts behind the technicalities. The discussion of the virial equation would benefit much from replacing 15 pages of Mathematica output with 15 pages of further explanation and motivation. In this combination, the power of computing merged with physical intuition would
Propagator of stochastic electrodynamics
International Nuclear Information System (INIS)
Cavalleri, G.
1981-01-01
The ''elementary propagator'' for the position of a free charged particle subject to the zero-point electromagnetic field with Lorentz-invariant spectral density proportionalω 3 is obtained. The nonstationary process for the position is solved by the stationary process for the acceleration. The dispersion of the position elementary propagator is compared with that of quantum electrodynamics. Finally, the evolution of the probability density is obtained starting from an initial distribution confined in a small volume and with a Gaussian distribution in the velocities. The resulting probability density for the position turns out to be equal, to within radiative corrections, to psipsi* where psi is the Kennard wave packet. If the radiative corrections are retained, the present result is new since the corresponding expression in quantum electrodynamics has not yet been found. Besides preceding quantum electrodynamics for this problem, no renormalization is required in stochastic electrodynamics
Quantum heat engine with coupled superconducting resonators
DEFF Research Database (Denmark)
Hardal, Ali Ümit Cemal; Aslan, Nur; Wilson, C. M.
2017-01-01
the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal......We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one...... the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures....
Microwave-Controlled Generation of Shaped Single Photons in Circuit Quantum Electrodynamics
Directory of Open Access Journals (Sweden)
M. Pechal
2014-10-01
Full Text Available Large-scale quantum information processors or quantum communication networks will require reliable exchange of information between spatially separated nodes. The links connecting these nodes can be established using traveling photons that need to be absorbed at the receiving node with high efficiency. This is achievable by shaping the temporal profile of the photons and absorbing them at the receiver by time reversing the emission process. Here, we demonstrate a scheme for creating shaped microwave photons using a superconducting transmon-type three-level system coupled to a transmission line resonator. In a second-order process induced by a modulated microwave drive, we controllably transfer a single excitation from the third level of the transmon to the resonator and shape the emitted photon. We reconstruct the density matrices of the created single-photon states and show that the photons are antibunched. We also create multipeaked photons with a controlled amplitude and phase. In contrast to similar existing schemes, the one we present here is based solely on microwave drives, enabling operation with fixed frequency transmons.
Joint quantum state tomography of an entangled qubit–resonator hybrid
International Nuclear Information System (INIS)
LinPeng, X Y; Zhang, H Z; Xu, K; Li, C Y; Zhong, Y P; Wang, Z L; Wang, H; Xie, Q W
2013-01-01
The integration of superconducting qubits and resonators in one circuit offers a promising solution for quantum information processing (QIP), which also realizes the on-chip analogue of cavity quantum electrodynamics (QED), known as circuit QED. In most prototype circuit designs, qubits are active processing elements and resonators are peripherals. As resonators typically have better coherence performance and more accessible energy levels, it is proposed that the entangled qubit–resonator hybrid can be used as a processing element. To achieve such a goal, an accurate measurement of the hybrid is first necessary. Here we demonstrate a joint quantum state tomography (QST) technique to fully characterize an entangled qubit–resonator hybrid. We benchmarked our QST technique by generating and accurately characterizing multiple states, e.g. |gN〉 + |e(N − 1)〉 where (|g〉 and |e〉) are the ground and excited states of the qubit and (|0〉,…,|N〉) are Fock states of the resonator. We further provided a numerical method to improve the QST efficiency and measured the decoherence dynamics of the bipartite hybrid, witnessing dissipation coming from both the qubit and the N-photon Fock state. As such, the joint QST presents an important step toward actively using the qubit–resonator element for QIP in hybrid quantum devices and for studying circuit QED. (paper)
Generalized noise terms for the quantized fluctuational electrodynamics
DEFF Research Database (Denmark)
Partanen, Mikko; Hayrynen, Teppo; Tulkki, Jukka
2017-01-01
position-dependent quantum models for the photon number in resonant structures have only been formulated very recently and only for dielectric media. Here we present a general position-dependent quantized fluctuational electrodynamics (QFED) formalism that extends the consistent field quantization...
International Nuclear Information System (INIS)
Lalanne, D.
1970-01-01
The experiment we have performed on the ACO (Orsay Collider Ring) is one of the most accurate tests of quantum electrodynamics over very short interaction distances (10 -14 cm). We have studied the electron-positron elastic scattering at very wide angle. This work is divided into 4 parts. The first part reviews recent tests of quantum electrodynamics and presents the electron-positron elastic scattering. The second part describes the measurement of brightness: the experimental device, data analysis and accuracy. The measurement of brightness has been performed by detecting the photons emitted in the double Bremsstrahlung reaction: e + e - → e + e - γγ. The third part deals with the measurement of the number of Bhabha events. The last part compares the experimental value of the Bhabha scattering with the theoretically expected value. We have got the following results: the number of Bhabha events: 757 events, the experimental value for Bhabha scattering cross-section: [1.97 ± 0.09 (stat.) ± 0.10 (syst.)]*10 -31 cm 2 . The comparison of this experimental value with the expected value has allowed us to set the lower limit of the cutting parameter Λ: Λ > 2 GeV
Quantum resonances and regularity islands in quantum maps
Sokolov; Zhirov; Alonso; Casati
2000-05-01
We study analytically as well as numerically the dynamics of a quantum map near a quantum resonance of an order q. The map is embedded into a continuous unitary transformation generated by a time-independent quasi-Hamiltonian. Such a Hamiltonian generates at the very point of the resonance a local gauge transformation described by the unitary unimodular group SU(q). The resonant energy growth is attributed to the zero Liouville eigenmodes of the generator in the adjoint representation of the group while the nonzero modes yield saturating with time contribution. In a vicinity of a given resonance, the quasi-Hamiltonian is then found in the form of power expansion with respect to the detuning from the resonance. The problem is related in this way to the motion along a circle in a (q2 - 1)-component inhomogeneous "magnetic" field of a quantum particle with q intrinsic degrees of freedom described by the SU(q) group. This motion is in parallel with the classical phase oscillations near a nonlinear resonance. The most important role is played by the resonances with the orders much smaller than the typical localization length q < l. Such resonances master for exponentially long though finite times the motion in some domains around them. Explicit analytical solution is possible for a few lowest and strongest resonances.
Quantum manifestations of classical resonance zones
International Nuclear Information System (INIS)
De Leon, N.; Davis, M.J.; Heller, E.J.
1984-01-01
We examine the concept of nodal breakup of wave functions as a criterion for quantum mechanical ergodicity. We find that complex nodal structure of wave functions is not sufficient to determine quantum mechanical ergodicity. The influence of classical resonances [which manifest themselves as classical resonance zones (CRZ)] may also be responsible for the seeming complexity of nodal structure. We quantify this by reexamining one of the two systems studied by Stratt, Handy, and Miller [J. Chem. Phys. 71, 3311 (1974)] from both a quantum mechanical and classical point of view. We conclude that quasiperiodic classical motion can account for highly distorted quantum eigenstates. One should always keep this in mind when addressing questions regarding quantum mechanical ergodicity
Blencowe, M. P.; Armour, A. D.
2008-09-01
We describe a possible implementation of the nanomechanical quantum superposition generation and detection scheme described in the preceding, companion paper (Armour A D and Blencowe M P 2008 New. J. Phys. 10 095004). The implementation is based on the circuit quantum electrodynamics (QED) set-up, with the addition of a mechanical degree of freedom formed out of a suspended, doubly-clamped segment of the superconducting loop of a dc SQUID located directly opposite the centre conductor of a coplanar waveguide (CPW). The relative merits of two SQUID based qubit realizations are addressed, in particular a capacitively coupled charge qubit and inductively coupled flux qubit. It is found that both realizations are equally promising, with comparable qubit-mechanical resonator mode as well as qubit-microwave resonator mode coupling strengths.
International Nuclear Information System (INIS)
Blencowe, M P; Armour, A D
2008-01-01
We describe a possible implementation of the nanomechanical quantum superposition generation and detection scheme described in the preceding, companion paper (Armour A D and Blencowe M P 2008 New. J. Phys. 10 095004). The implementation is based on the circuit quantum electrodynamics (QED) set-up, with the addition of a mechanical degree of freedom formed out of a suspended, doubly-clamped segment of the superconducting loop of a dc SQUID located directly opposite the centre conductor of a coplanar waveguide (CPW). The relative merits of two SQUID based qubit realizations are addressed, in particular a capacitively coupled charge qubit and inductively coupled flux qubit. It is found that both realizations are equally promising, with comparable qubit-mechanical resonator mode as well as qubit-microwave resonator mode coupling strengths.
Paston, S A; Prokhvatilov, E V
2002-01-01
The Hamiltonian, reproducing the results of the two-dimensional quantum electrodynamics in the Lorentz coordinates, is constructed on the light front. The procedure of bosonization and analysis of the boson perturbation theory in all the orders by the fermions mass are applied for this purpose. Besides the common terms, originating by the naive quantization on the light front, the obtained Hamiltonian contains an additional counterterm. It is proportional to the linear combination of the fermion zero modes (multiplied by a certain factor compensating the charge and fermion number). The coefficient before this counterterm has no ultraviolet divergence, depends on the value of the fermion condensate in the theta-vacuum and by the small fermion mass is linear by it
Energy Technology Data Exchange (ETDEWEB)
Ito, K R [Kyoto Univ. (Japan). Research Inst. for Mathematical Sciences
1975-03-01
The Schwinger model is considered in the Landau-gauge formalism of quantum electrodynamics. This model can be solved exactly on the assumption of no radiative corrections to the anomaly. It is found that the photon obtains a non-zero mass through the Higgs mechanism. In this case, the would-be Nambu-Goldstone boson is an associated boson which is constructed from a pair of two-component massless fermions. This would-be Nambu-Goldstone boson appears as a result of the spontaneous breaking of the gauge invariance of the first kind, and it becomes unphysical through the Higgs mechanism. However, as all the fermions themselves decouple from photons, they cannot appear as real particles in our world.
International Nuclear Information System (INIS)
Miller, G.A.; Sorensen, L.B.
1997-01-01
Quantum electrodynamics (QED) is used to derive the differential cross sections measured in the three new experimental internal source ensemble x-ray holographies: bremsstrahlung (BXH), fluorescence (XFH), and multiple-energy (MEXH) x-ray holography. The polarization dependence of the BXH cross section is also obtained. For BXH, we study analytically and numerically the possible effects of the virtual photons and electrons which enter QED calculations in summing over the intermediate states. For the low photon and electron energies used in the current experiments, we show that the virtual intermediate states produce only very small effects. This is because the uncertainty principle limits the distance that the virtual particles can propagate to be much shorter than the separation between the regions of high electron density in the adjacent atoms. We also find that using the asymptotic form of the scattering wave function causes about a 5 10% error for near forward scattering. copyright 1997 The American Physical Society
Quantum resonance for simulating combinatorial problems
International Nuclear Information System (INIS)
Zak, Michail; Fijany, Amir
2005-01-01
Quantum computing by simulations is based upon similarity between mathematical formalism of a quantum phenomenon and phenomena to be analyzed. In this Letter, the mathematical formalism of quantum resonance combined with tensor product decomposability of unitary evolutions is mapped onto a class of NP-complete combinatorial problems. It has been demonstrated that nature has polynomial resources for solving NP-complete problems and that will help to develop a new strategy for artificial intelligence, as well as to re-evaluate the role of natural selection in biological evolution
Quantum heat engine with coupled superconducting resonators
Hardal, Ali Ü. C.; Aslan, Nur; Wilson, C. M.; Müstecaplıoǧlu, Özgür E.
2017-12-01
We propose a quantum heat engine composed of two superconducting transmission line resonators interacting with each other via an optomechanical-like coupling. One resonator is periodically excited by a thermal pump. The incoherently driven resonator induces coherent oscillations in the other one due to the coupling. A limit cycle, indicating finite power output, emerges in the thermodynamical phase space. The system implements an all-electrical analog of a photonic piston. Instead of mechanical motion, the power output is obtained as a coherent electrical charging in our case. We explore the differences between the quantum and classical descriptions of our system by solving the quantum master equation and classical Langevin equations. Specifically, we calculate the mean number of excitations, second-order coherence, as well as the entropy, temperature, power, and mean energy to reveal the signatures of quantum behavior in the statistical and thermodynamic properties of the system. We find evidence of a quantum enhancement in the power output of the engine at low temperatures.
Cold quantum gases with resonant interactions
Marcelis, B.
2008-01-01
We study ultracold gases of alkali-metal atoms in the quantum degenerate regime. The interatomic interactions in these type of systems can be tuned using resonances induced by magnetic or electric fields. The tunability of the interactions, together with the possibility of confining the atoms with
Quantum Resonance Approach to Combinatorial Optimization
Zak, Michail
1997-01-01
It is shown that quantum resonance can be used for combinatorial optimization. The advantage of the approach is in independence of the computing time upon the dimensionality of the problem. As an example, the solution to a constraint satisfaction problem of exponential complexity is demonstrated.
Quantum resonances in physical tunneling
International Nuclear Information System (INIS)
Nieto, M.M.; Truax, D.R.
1985-01-01
It has recently been emphasized that the probability of quantum tunneling is a critical function of the shape of the potential. Applying this observation to physical systems, we point out that in principal information on potential surfaces can be obtained by studying tunneling rates. This is especially true in cases where only spectral data is known, since many potentials yield the same spectrum. 13 refs., 10 figs., 1 tab
Quantum information processing and nuclear magnetic resonance
International Nuclear Information System (INIS)
Cummins, H.K.
2001-01-01
Quantum computers are information processing devices which operate by and exploit the laws of quantum mechanics, potentially allowing them to solve problems which are intractable using classical computers. This dissertation considers the practical issues involved in one of the more successful implementations to date, nuclear magnetic resonance (NMR). Techniques for dealing with systematic errors are presented, and a quantum protocol is implemented. Chapter 1 is a brief introduction to quantum computation. The physical basis of its efficiency and issues involved in its implementation are discussed. NMR quantum information processing is reviewed in more detail in Chapter 2. Chapter 3 considers some of the errors that may be introduced in the process of implementing an algorithm, and high-level ways of reducing the impact of these errors by using composite rotations. Novel general expressions for stabilising composite rotations are presented in Chapter 4 and a new class of composite rotations, tailored composite rotations, presented in Chapter 5. Chapter 6 describes some of the advantages and pitfalls of combining composite rotations. Experimental evaluations of the composite rotations are given in each case. An actual implementation of a quantum information protocol, approximate quantum cloning, is presented in Chapter 7. The dissertation ends with appendices which contain expansions of some equations and detailed calculations of certain composite rotation results, as well as spectrometer pulse sequence programs. (author)
Teber, S.; Kotikov, A. V.
2018-04-01
The field theoretic renormalization study of reduced quantum electrodynamics (QED) is performed up to two loops. In the condensed matter context, reduced QED constitutes a very natural effective relativistic field theory describing (planar) Dirac liquids, e.g., graphene and graphenelike materials, the surface states of some topological insulators, and possibly half-filled fractional quantum Hall systems. From the field theory point of view, the model involves an effective (reduced) gauge field propagating with a fractional power of the d'Alembertian in marked contrast with usual QEDs. The use of the Bogoliubov-Parasiuk-Hepp-Zimmermann prescription allows for a simple and clear understanding of the structure of the model. In particular, in relation with the ultrarelativistic limit of graphene, we straightforwardly recover the results for both the interaction correction to the optical conductivity C*=(92 -9 π2)/(18 π ) and the anomalous dimension of the fermion field γψ(α ¯ ,ξ )=2 α ¯ (1 -3 ξ )/3 -16 (ζ2NF+4 /27 ) α¯ 2+O (α¯ 3) , where α ¯=e2/(4 π )2 and ξ is the gauge-fixing parameter.
Problem of summing up ladder diagrams in quantum electrodynamics. [Cross sections
Energy Technology Data Exchange (ETDEWEB)
Gadzhiev, S A; Livashvili, A I [Azerbajdzhanskij Gosudarstvennyj Univ., Baku (USSR)
1975-03-01
A class of ladder diagrams in an asymptotic mode is considered, and a series of the perturbation theory for the given class of diagrams reduces to an integral equation obtained without approximations whatsoever. As applications of the method proposed, two electrodynamic processes are considered: the two-photon annihilation of an e/sup +/e/sup -/-pair and scattering of electons in Coulomb field. Matrix elements are provided. To derive the equations, Dirac equations and commutation relations are used. A conclusion is drawn that for the process, the log-log asymptotics and polar approximation lead to the fact that as the energy grows the cross-section of the process drops and the solution obtained indicates that such a drop occurs up to an energy of 10/sup 5/ GeV. For the second process, the region of large pulses transmitted by an electron to the external field does not lead to an increase in amplitude and cross-section.
Scale magnetic effect in quantum electrodynamics and the Wigner-Weyl formalism
Chernodub, M. N.; Zubkov, M. A.
2017-09-01
The scale magnetic effect (SME) is the generation of electric current due to a conformal anomaly in an external magnetic field in curved spacetime. The effect appears in a vacuum with electrically charged massless particles. Similarly to the Hall effect, the direction of the induced anomalous current is perpendicular to the direction of the external magnetic field B and to the gradient of the conformal factor τ , while the strength of the current is proportional to the beta function of the theory. In massive electrodynamics the SME remains valid, but the value of the induced current differs from the current generated in the system of massless fermions. In the present paper we use the Wigner-Weyl formalism to demonstrate that in accordance with the decoupling property of heavy fermions the corresponding anomalous conductivity vanishes in the large-mass limit with m2≫|e B | and m ≫|∇τ | .
Macroscopic Quantum Resonators (MAQRO): 2015 update
International Nuclear Information System (INIS)
Kaltenbaek, Rainer; Aspelmeyer, Markus; Kiesel, Nikolai; Barker, Peter F.; Bose, Sougato; Bassi, Angelo; Bateman, James; Bongs, Kai; Cruise, Adrian Michael; Braxmaier, Claus; Brukner, Caslav; Christophe, Bruno; Rodrigues, Manuel; Chwalla, Michael; Johann, Ulrich; Cohadon, Pierre-Francois; Heidmann, Antoine; Lambrecht, Astrid; Reynaud, Serge; Curceanu, Catalina; Dholakia, Kishan; Mazilu, Michael; Diosi, Lajos; Doeringshoff, Klaus; Peters, Achim; Ertmer, Wolfgang; Rasel, Ernst M.; Gieseler, Jan; Novotny, Lukas; Rondin, Loic; Guerlebeck, Norman; Herrmann, Sven; Laemmerzahl, Claus; Hechenblaikner, Gerald; Hossenfelder, Sabine; Kim, Myungshik; Milburn, Gerard J.; Mueller, Holger; Paternostro, Mauro; Pikovski, Igor; Pilan Zanoni, Andre; Riedel, Charles Jess; Roura, Albert; Schleich, Wolfgang P.; Schmiedmayer, Joerg; Schuldt, Thilo; Schwab, Keith C.; Tajmar, Martin; Tino, Guglielmo M.; Ulbricht, Hendrik; Ursin, Rupert; Vedral, Vlatko
2016-01-01
Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schroedinger's cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum and microgravity. The proposed mission Macroscopic Quantum Resonators (MAQRO) may overcome these limitations and allow addressing such fundamental questions. MAQRO harnesses recent developments in quantum optomechanics, high-mass matter-wave interferometry as well as state-of-the-art space technology to push macroscopic quantum experiments towards their ultimate performance limits and to open new horizons for applying quantum technology in space. The main scientific goal is to probe the vastly unexplored 'quantum-classical' transition for increasingly massive objects, testing the predictions of quantum theory for objects in a size and mass regime unachievable in ground-based experiments. The hardware will largely be based on available space technology. Here, we present the MAQRO proposal submitted in response to the 4th Cosmic Vision call for a medium-sized mission (M4) in 2014 of the European Space Agency (ESA) with a possible launch in 2025, and we review the progress with respect to the original MAQRO proposal for the 3rd Cosmic Vision call for a medium-sized mission (M3) in 2010. In particular, the updated proposal overcomes several critical issues of the original proposal by relying on established experimental techniques from high-mass matter-wave interferometry and by introducing novel ideas for particle loading and manipulation. Moreover, the mission design was improved to better fulfill the stringent environmental requirements for macroscopic quantum experiments. (orig.)
Macroscopic Quantum Resonators (MAQRO): 2015 update
Energy Technology Data Exchange (ETDEWEB)
Kaltenbaek, Rainer [University of Vienna, Vienna Center for Quantum Science and Technology, Vienna (Austria); Aspelmeyer, Markus; Kiesel, Nikolai [University of Vienna, Vienna Center for Quantum Science and Technology, Vienna (Austria); Barker, Peter F.; Bose, Sougato [University College London, Department of Physics and Astronomy, London (United Kingdom); Bassi, Angelo [University of Trieste, Department of Physics, Trieste (Italy); INFN - Trieste Section, Trieste (Italy); Bateman, James [University of Swansea, Department of Physics, College of Science, Swansea (United Kingdom); Bongs, Kai; Cruise, Adrian Michael [University of Birmingham, School of Physics and Astronomy, Birmingham (United Kingdom); Braxmaier, Claus [University of Bremen, Center of Applied Space Technology and Micro Gravity (ZARM), Bremen (Germany); Institute of Space Systems, German Aerospace Center (DLR), Bremen (Germany); Brukner, Caslav [University of Vienna, Vienna Center for Quantum Science and Technology, Vienna (Austria); Austrian Academy of Sciences, Institute of Quantum Optics and Quantum Information (IQOQI), Vienna (Austria); Christophe, Bruno; Rodrigues, Manuel [The French Aerospace Lab, ONERA, Chatillon (France); Chwalla, Michael; Johann, Ulrich [Airbus Defence and Space GmbH, Immenstaad (Germany); Cohadon, Pierre-Francois; Heidmann, Antoine; Lambrecht, Astrid; Reynaud, Serge [ENS-PSL Research University, Laboratoire Kastler Brossel, UPMC-Sorbonne Universites, CNRS, College de France, Paris (France); Curceanu, Catalina [Laboratori Nazionali di Frascati dell' INFN, Frascati (Italy); Dholakia, Kishan; Mazilu, Michael [University of St. Andrews, School of Physics and Astronomy, St. Andrews (United Kingdom); Diosi, Lajos [Wigner Research Center for Physics, P.O. Box 49, Budapest (Hungary); Doeringshoff, Klaus; Peters, Achim [Humboldt-Universitaet zu Berlin, Institut fuer Physik, Berlin (Germany); Ertmer, Wolfgang; Rasel, Ernst M. [Leibniz Universitaet Hannover, Institut fuer Quantenoptik, Hannover (Germany); Gieseler, Jan; Novotny, Lukas; Rondin, Loic [ETH Zuerich, Photonics Laboratory, Zuerich (Switzerland); Guerlebeck, Norman; Herrmann, Sven; Laemmerzahl, Claus [University of Bremen, Center of Applied Space Technology and Micro Gravity (ZARM), Bremen (Germany); Hechenblaikner, Gerald [Airbus Defence and Space GmbH, Immenstaad (Germany); European Southern Observatory (ESO), Garching bei Muenchen (Germany); Hossenfelder, Sabine [KTH Royal Institute of Technology and Stockholm University, Nordita, Stockholm (Sweden); Kim, Myungshik [Imperial College London, QOLS, Blackett Laboratory, London (United Kingdom); Milburn, Gerard J. [University of Queensland, ARC Centre for Engineered Quantum Systems, Brisbane (Australia); Mueller, Holger [University of California, Department of Physics, Berkeley, CA (United States); Paternostro, Mauro [Queen' s University, Centre for Theoretical Atomic, Molecular and Optical Physics, School of Mathematics and Physics, Belfast (United Kingdom); Pikovski, Igor [Harvard-Smithsonian Center for Astrophysics, ITAMP, Cambridge, MA (United States); Pilan Zanoni, Andre [Airbus Defence and Space GmbH, Immenstaad (Germany); CERN - European Organization for Nuclear Research, EN-STI-TCD, Geneva (Switzerland); Riedel, Charles Jess [Perimeter Institute for Theoretical Physics, Waterloo, ON (Canada); Roura, Albert [Universitaet Ulm, Institut fuer Quantenphysik, Ulm (Germany); Schleich, Wolfgang P. [Universitaet Ulm, Institut fuer Quantenphysik, Ulm (Germany); Texas A and M University Institute for Advanced Study (TIAS), Institute for Quantum Science and Engineering (IQSE), and Department of Physics and Astronomy, College Station, TX (United States); Schmiedmayer, Joerg [Vienna University of Technology, Vienna Center for Quantum Science and Technology, Institute of Atomic and Subatomic Physics, Vienna (Austria); Schuldt, Thilo [Institute of Space Systems, German Aerospace Center (DLR), Bremen (Germany); Schwab, Keith C. [California Institute of Technology, Applied Physics, Pasadena, CA (United States); Tajmar, Martin [Technische Universitaet Dresden, Institut fuer Luft- und Raumfahrttechnik, Dresden (Germany); Tino, Guglielmo M. [Universita di Firenze, Dipartimento di Fisica e Astronomia and LENS, INFN, Sesto Fiorentino, Firenze (Italy); Ulbricht, Hendrik [University of Southampton, Physics and Astronomy, Southampton (United Kingdom); Ursin, Rupert [Austrian Academy of Sciences, Institute of Quantum Optics and Quantum Information (IQOQI), Vienna (Austria); Vedral, Vlatko [University of Oxford, Atomic and Laser Physics, Clarendon Laboratory, Oxford (United Kingdom); National University of Singapore, Center for Quantum Technologies, Singapore (SG)
2016-12-15
Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schroedinger's cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum and microgravity. The proposed mission Macroscopic Quantum Resonators (MAQRO) may overcome these limitations and allow addressing such fundamental questions. MAQRO harnesses recent developments in quantum optomechanics, high-mass matter-wave interferometry as well as state-of-the-art space technology to push macroscopic quantum experiments towards their ultimate performance limits and to open new horizons for applying quantum technology in space. The main scientific goal is to probe the vastly unexplored 'quantum-classical' transition for increasingly massive objects, testing the predictions of quantum theory for objects in a size and mass regime unachievable in ground-based experiments. The hardware will largely be based on available space technology. Here, we present the MAQRO proposal submitted in response to the 4th Cosmic Vision call for a medium-sized mission (M4) in 2014 of the European Space Agency (ESA) with a possible launch in 2025, and we review the progress with respect to the original MAQRO proposal for the 3rd Cosmic Vision call for a medium-sized mission (M3) in 2010. In particular, the updated proposal overcomes several critical issues of the original proposal by relying on established experimental techniques from high-mass matter-wave interferometry and by introducing novel ideas for particle loading and manipulation. Moreover, the mission design was improved to better fulfill the stringent environmental requirements for macroscopic quantum experiments. (orig.)
International Nuclear Information System (INIS)
Whittingham, I.B.
1977-12-01
The bound electron propagator in quantum electrodynamics is reviewed and the Brown and Schaefer angular momentum representation of the propagator discussed. Regular and irregular solutions of the radial Dirac equations for both /E/ 2 and /E/ >or= mc 2 are required for the computation of the propagator. Analytical expressions for these solutions, and their corresponding Wronskians, are obtained for a point Coulomb potential. Some computational aspects are discussed in an appendix
QUANTUM MECHANICS. Quantum squeezing of motion in a mechanical resonator.
Wollman, E E; Lei, C U; Weinstein, A J; Suh, J; Kronwald, A; Marquardt, F; Clerk, A A; Schwab, K C
2015-08-28
According to quantum mechanics, a harmonic oscillator can never be completely at rest. Even in the ground state, its position will always have fluctuations, called the zero-point motion. Although the zero-point fluctuations are unavoidable, they can be manipulated. Using microwave frequency radiation pressure, we have manipulated the thermal fluctuations of a micrometer-scale mechanical resonator to produce a stationary quadrature-squeezed state with a minimum variance of 0.80 times that of the ground state. We also performed phase-sensitive, back-action evading measurements of a thermal state squeezed to 1.09 times the zero-point level. Our results are relevant to the quantum engineering of states of matter at large length scales, the study of decoherence of large quantum systems, and for the realization of ultrasensitive sensing of force and motion. Copyright © 2015, American Association for the Advancement of Science.
Optimization of electrodynamic characteristics of the buncher-resonator for a free electron laser
International Nuclear Information System (INIS)
Sobenin, N.P.; Kalyuzhnyj, V.E.; Kostin, D.V.; Yarygin, S.N.; Zavadtsev, A.A.
1994-01-01
Selection of geometric sizes of a resonator buncher comprising 1.5 accelerating cells and linking cell is performed. When selecting the inner resonator dimensions the attention is first of all paid to minimization of E r /E z (z, γ) function in the axial region. At the same time the value of the field overstrain coefficient under a high value of effective shunt resistance is also minimized at the expense of changing the drift tube profile. 2 refs.; 2 figs.; 4 tabs
Environment-Assisted Speed-up of the Field Evolution in Cavity Quantum Electrodynamics.
Cimmarusti, A D; Yan, Z; Patterson, B D; Corcos, L P; Orozco, L A; Deffner, S
2015-06-12
We measure the quantum speed of the state evolution of the field in a weakly driven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a preferential coupling to a tunable environment: the atoms. By controlling the environment, i.e., changing the number of atoms coupled to the optical cavity mode, an environment-assisted speed-up is realized: the quantum speed of the state repopulation in the optical cavity increases with the coupling strength between the optical cavity mode and this non-Markovian environment (the number of atoms).
Environment-Assisted Speed-up of the Field Evolution in Cavity Quantum Electrodynamics
International Nuclear Information System (INIS)
Cimmarusti, A. D.; Yan, Z.; Patterson, B. D.; Corcos, L. P.; Orozco, L. A.; Deffner, S.
2015-01-01
We measure the quantum speed of the state evolution of the field in a weakly-driven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a preferential coupling to a tunable environment: the atoms. By controlling the environment, i.e., changing the number of atoms coupled to the optical cavity mode, an environment assisted speed-up is realized: the quantum speed of the state re-population in the optical cavity increases with the coupling strength between the optical cavity mode and this non-Markovian environment (the number of atoms)
Quantum damped oscillator I: Dissipation and resonances
International Nuclear Information System (INIS)
Chruscinski, Dariusz; Jurkowski, Jacek
2006-01-01
Quantization of a damped harmonic oscillator leads to so called Bateman's dual system. The corresponding Bateman's Hamiltonian, being a self-adjoint operator, displays the discrete family of complex eigenvalues. We show that they correspond to the poles of energy eigenvectors and the corresponding resolvent operator when continued to the complex energy plane. Therefore, the corresponding generalized eigenvectors may be interpreted as resonant states which are responsible for the irreversible quantum dynamics of a damped harmonic oscillator
Selectivity in multiple quantum nuclear magnetic resonance
International Nuclear Information System (INIS)
Warren, W.S.
1980-11-01
The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible
Selectivity in multiple quantum nuclear magnetic resonance
Energy Technology Data Exchange (ETDEWEB)
Warren, Warren Sloan [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
1980-11-01
The observation of multiple-quantum nuclear magnetic resonance transitions in isotropic or anisotropic liquids is shown to give readily interpretable information on molecular configurations, rates of motional processes, and intramolecular interactions. However, the observed intensity of high multiple-quantum transitions falls off dramatically as the number of coupled spins increases. The theory of multiple-quantum NMR is developed through the density matrix formalism, and exact intensities are derived for several cases (isotropic first-order systems and anisotropic systems with high symmetry) to shown that this intensity decrease is expected if standard multiple-quantum pulse sequences are used. New pulse sequences are developed which excite coherences and produce population inversions only between selected states, even though other transitions are simultaneously resonant. One type of selective excitation presented only allows molecules to absorb and emit photons in groups of n. Coherent averaging theory is extended to describe these selective sequences, and to design sequences which are selective to arbitrarily high order in the Magnus expansion. This theory and computer calculations both show that extremely good selectivity and large signal enhancements are possible.
The propagator of stochastic electrodynamics
Cavalleri, G.
1981-01-01
The "elementary propagator" for the position of a free charged particle subject to the zero-point electromagnetic field with Lorentz-invariant spectral density ~ω3 is obtained. The nonstationary process for the position is solved by the stationary process for the acceleration. The dispersion of the position elementary propagator is compared with that of quantum electrodynamics. Finally, the evolution of the probability density is obtained starting from an initial distribution confined in a small volume and with a Gaussian distribution in the velocities. The resulting probability density for the position turns out to be equal, to within radiative corrections, to ψψ* where ψ is the Kennard wave packet. If the radiative corrections are retained, the present result is new since the corresponding expression in quantum electrodynamics has not yet been found. Besides preceding quantum electrodynamics for this problem, no renormalization is required in stochastic electrodynamics.
International Nuclear Information System (INIS)
Barut, A.O.; Dowling, J.P.
1986-12-01
Using a previously formulated theory of quantum electrodynamics based on self-energy, we give a general method for computing the Lamb shift and related Casimir-Polder energies for a quantum system in the vicinity of perfectly conducting boundaries. Our results are exact and easily extendable to a full covariant relativistic form. As a particular example we apply the method to an atom near an infinite conducting plane, and we recover the standard QED results (which are known only in the dipole approximation) in a simple and straightforward manner. This is accomplished in the context of the new theory which is not second quantized and contains no vacuum fluctuations. (author)
International Nuclear Information System (INIS)
Power, E.A.; Thirunamachandran, T.
1993-01-01
Spatial correlations between electromagnetic fields arising from neutral sources with electric-dipole transition moments are calculated using nonrelativistic quantum electrodynamics in the multipolar formalism. Expressions for electric-electric, magnetic-magnetic, and electric-magnetic correlation functions at two points r and r' are given for a source molecule in either a ground or an excited state. In contrast to the electric-electric and magnetic-magnetic cases there are no electric-magnetic correlations for a ground-state molecule. For an excited molecule the downward transitions contribute additional terms which have modulating factors depending on (r-r')/λ. From these correlation functions electric and magnetic energy densities are found by setting r=r'. These energy densities are then used in a response formalism to calculate intermolecular energy shifts. In the case of two ground-state molecules this leads to the Casimir-Polder potential. However, for a pair of molecules, one or both excited, there are additional terms arising from downward transitions. An important feature of these energies is that they exhibit an R -2 dependence for large intermolecular separations R. This dependence is interpreted in terms of the Poynting vector, which itself can be obtained by setting r=r' in the electric-magnetic correlation function
International Nuclear Information System (INIS)
Bencivinni, Daniele
2011-01-01
The chapters about the propagation of the electromagnetic field, its properties in view of the propagation in space, the accompanying momentum, its kinetic energy and its mass-equivalent distribution of the total energy coupled to the relativistic mass represent today known and scientifically for a long time acknowledged as well as proved description of each phenomena. They are successively in a mathematically simple way formally listed and explained. The fundamental results of quantum mechanics, the quantum-mechanical momentum, Planck's action quantum etc. are also presented in a simplified way. Also the essential forms of special relativity theory concerning the propagation of energy and momentum are presented. In a last setpit is checked, whether a possible common entity between the listed scientific experiences can be established. Possible explanation approaches on the described connections and the subsequent results are presented. If the gravitational waves are interpreted as quantized electromagnetic quantum waves, as matter waves, which can be assigned to a mass in the sense of Louis de Broglie and are for instance detectable as electron waves, by means of the relativistic quantum-mechanical spatial radiation gravitation could be described. So the ''quantum-mechanical wave'' could be responsible for the generation of mass via the interaction of elementary quantum fields. The propagation of one of these as mass appearing interaction of bound quantum fields can carry a conventional momentum because of its kinetic energy. The interaction in the Bose-Einstein condensate shows that the cooled rest mass exhibits the picture of a standing wave, the wave front of which propagates into the space. Because of the massive superposition of interference pattern warns the gravitational respectively matter wave can no more be isolated. A spatial radiation is however possible. Matter can generate a radiation in front of the inertial mass (quantum waves). If it succeeds to
International Nuclear Information System (INIS)
Xiao, Y-F; Gao, J; McMillan, J F; Yang, X; Wong, C W; Zou, X-B; Chen, Y-L; Han, Z-F; Guo, G-C
2008-01-01
In this paper, a scalable photonic crystal cavity array, in which single embedded quantum dots (QDs) are coherently interacting, is studied theoretically. Firstly, we examine the spectral character and optical delay brought about by the coupled cavities interacting with single QDs, in an optical analogue to electromagnetically induced transparency. Secondly, we then examine the usability of this coupled QD-cavity system for quantum phase gate operation and our numerical examples suggest that a two-qubit system with fidelity above 0.99 and photon loss below 0.04 is possible.
Directory of Open Access Journals (Sweden)
A. Stockklauser
2017-03-01
Full Text Available The strong coupling limit of cavity quantum electrodynamics (QED implies the capability of a matterlike quantum system to coherently transform an individual excitation into a single photon within a resonant structure. This not only enables essential processes required for quantum information processing but also allows for fundamental studies of matter-light interaction. In this work, we demonstrate strong coupling between the charge degree of freedom in a gate-defined GaAs double quantum dot (DQD and a frequency-tunable high impedance resonator realized using an array of superconducting quantum interference devices. In the resonant regime, we resolve the vacuum Rabi mode splitting of size 2g/2π=238 MHz at a resonator linewidth κ/2π=12 MHz and a DQD charge qubit decoherence rate of γ_{2}/2π=40 MHz extracted independently from microwave spectroscopy in the dispersive regime. Our measurements indicate a viable path towards using circuit-based cavity QED for quantum information processing in semiconductor nanostructures.
Energy Technology Data Exchange (ETDEWEB)
Chen, Hanning; McMahon, J. M.; Ratner, Mark A.; Schatz, George C.
2010-09-02
A new multiscale computational methodology was developed to effectively incorporate the scattered electric field of a plasmonic nanoparticle into a quantum mechanical (QM) optical property calculation for a nearby dye molecule. For a given location of the dye molecule with respect to the nanoparticle, a frequency-dependent scattering response function was first determined by the classical electrodynamics (ED) finite-difference time-domain (FDTD) approach. Subsequently, the time-dependent scattered electric field at the dye molecule was calculated using the FDTD scattering response function through a multidimensional Fourier transform to reflect the effect of polarization of the nanoparticle on the local field at the molecule. Finally, a real-time time-dependent density function theory (RT-TDDFT) approach was employed to obtain a desired optical property (such as absorption cross section) of the dye molecule in the presence of the nanoparticle’s scattered electric field. Our hybrid QM/ED methodology was demonstrated by investigating the absorption spectrum of the N3 dye molecule and the Raman spectrum of pyridine, both of which were shown to be significantly enhanced by a 20 nm diameter silver sphere. In contrast to traditional quantum mechanical optical calculations in which the field at the molecule is entirely determined by intensity and polarization direction of the incident light, in this work we show that the light propagation direction as well as polarization and intensity are important to nanoparticle-bound dye molecule response. At no additional computation cost compared to conventional ED and QM calculations, this method provides a reliable way to couple the response of the dye molecule’s individual electrons to the collective dielectric response of the nanoparticle.
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.
Quantum RLC circuits: Charge discreteness and resonance
Energy Technology Data Exchange (ETDEWEB)
Utreras-Diaz, Constantino A. [Instituto de Fisica, Facultad de Ciencias, Universidad Austral de Chile, Campus Isla Teja s/n, Casilla 567, Valdivia (Chile)], E-mail: cutreras@uach.cl
2008-10-20
In a recent article [C.A. Utreras-Diaz, Phys. Lett. A 372 (2008) 5059], we have advanced a semiclassical theory of quantum circuits with discrete charge and electrical resistance. In this work, we present a few elementary applications of this theory. For the zero resistance inductive circuit, we obtain the Stark ladder energies in yet another way; for the circuit driven by a combination d.c. plus a.c. electromotive force (emf) we generalize earlier results by Chandia et al. [K. Chandia, J.C. Flores, E. Lazo, Phys. Lett. A 359 (2006) 693]. As a second application, we investigate the effect of electrical resistance and charge discreteness, in the resonance conditions of a series RLC quantum circuit.
Quantum RLC circuits: Charge discreteness and resonance
International Nuclear Information System (INIS)
Utreras-Diaz, Constantino A.
2008-01-01
In a recent article [C.A. Utreras-Diaz, Phys. Lett. A 372 (2008) 5059], we have advanced a semiclassical theory of quantum circuits with discrete charge and electrical resistance. In this work, we present a few elementary applications of this theory. For the zero resistance inductive circuit, we obtain the Stark ladder energies in yet another way; for the circuit driven by a combination d.c. plus a.c. electromotive force (emf) we generalize earlier results by Chandia et al. [K. Chandia, J.C. Flores, E. Lazo, Phys. Lett. A 359 (2006) 693]. As a second application, we investigate the effect of electrical resistance and charge discreteness, in the resonance conditions of a series RLC quantum circuit
Decoherence-Free Interaction between Giant Atoms in Waveguide Quantum Electrodynamics.
Kockum, Anton Frisk; Johansson, Göran; Nori, Franco
2018-04-06
In quantum-optics experiments with both natural and artificial atoms, the atoms are usually small enough that they can be approximated as pointlike compared to the wavelength of the electromagnetic radiation with which they interact. However, superconducting qubits coupled to a meandering transmission line, or to surface acoustic waves, can realize "giant artificial atoms" that couple to a bosonic field at several points which are wavelengths apart. Here, we study setups with multiple giant atoms coupled at multiple points to a one-dimensional (1D) waveguide. We show that the giant atoms can be protected from decohering through the waveguide, but still have exchange interactions mediated by the waveguide. Unlike in decoherence-free subspaces, here the entire multiatom Hilbert space (2^{N} states for N atoms) is protected from decoherence. This is not possible with "small" atoms. We further show how this decoherence-free interaction can be designed in setups with multiple atoms to implement, e.g., a 1D chain of atoms with nearest-neighbor couplings or a collection of atoms with all-to-all connectivity. This may have important applications in quantum simulation and quantum computing.
Decoherence-Free Interaction between Giant Atoms in Waveguide Quantum Electrodynamics
Kockum, Anton Frisk; Johansson, Göran; Nori, Franco
2018-04-01
In quantum-optics experiments with both natural and artificial atoms, the atoms are usually small enough that they can be approximated as pointlike compared to the wavelength of the electromagnetic radiation with which they interact. However, superconducting qubits coupled to a meandering transmission line, or to surface acoustic waves, can realize "giant artificial atoms" that couple to a bosonic field at several points which are wavelengths apart. Here, we study setups with multiple giant atoms coupled at multiple points to a one-dimensional (1D) waveguide. We show that the giant atoms can be protected from decohering through the waveguide, but still have exchange interactions mediated by the waveguide. Unlike in decoherence-free subspaces, here the entire multiatom Hilbert space (2N states for N atoms) is protected from decoherence. This is not possible with "small" atoms. We further show how this decoherence-free interaction can be designed in setups with multiple atoms to implement, e.g., a 1D chain of atoms with nearest-neighbor couplings or a collection of atoms with all-to-all connectivity. This may have important applications in quantum simulation and quantum computing.
Hybrid Circuit Quantum Electrodynamics: Coupling a Single Silicon Spin Qubit to a Photon
2015-01-01
776 (2008). 14. M. Pioro-Ladriere, Y. Tokura, T. Obata, T. Kubo , S. Tarucha, Micromagnets for coherent control of spin-charge qubit in lateral...slanting Zeeman field. Phys. Rev. Lett. 96, 047202 (2006). 16. Y. Kubo et al., Strong coupling of a spin ensemble to a superconducting resonator. Phys
Understanding the Double Quantum Muonium RF Resonance
Kreitzman, S. R.; Cottrell, S. P.; Fleming, D. G.; Sun-Mack, S.
A physically intuitive analytical solution to the Mu + RF Hamiltonian and lineshape is developed. The method is based on reformulating the problem in a basis set that explicitly accounts for the 1q RF transitions and identifying an isolated upper 1q quasi-eigenstate within that basis. Subsequently the double quantum resonance explicitly manifests itself via the non-zero interaction term between the pair of lower ortho-normalized 1q basis states, which in this field region are substantially the | \\uparrow \\uparrow > and | \\downarrow \\downarrow > Mu states.
International Nuclear Information System (INIS)
Abyaneh, Morteza; Fleischmann, Martin; Del Giudice, Emilio; Vitiello, Giuseppe
2006-01-01
A question we are asked repeatedly is: 'what are the causes of the opposition to your belief in the reality of 'Cold Fusion?'. This question is normally asked in the context of the statement that Quantum Mechanics shows that this phenomenon is impossible (a view that we share). Our answer is always based on the statement 'but what about the modelling of such systems in terms of QED?' which is always met by the insistence that Quantum Mechanics shows that Cold Fusion is impossible. We conclude that scientists do not understand QED or, if they have some understanding of this subject, then this must be subject to some major misconceptions. This pointless dialogue (perhaps more correctly described as two monologues conducted in parallel) and the insistence on the primacy of Quantum Mechanics in the modelling of systems in the Natural Sciences is unfortunate because it obscures the outcome of the investigations in the more normal fields of the Natural Sciences (more normal than Cold Fusion). A brief outline of the work which has led to the formulation of the concept of coherence will therefore be given under the aegis of the revolutions in our understanding of the Natural Sciences which has taken place since the latter part of the 19. Century. The main illustration of the way we can demonstrate the applicability of these concepts will be based on the study of nucleation and phase growth. The development of micro-electrode substrates allows us to study the statistics of the formation of the first nucleus; it will be shown that these statistics are strictly in line with concepts developed from QED coherence. We conclude that QED coherence is not just a concept to be confined to sub-atomic physics, cosmology etc. but that it pervades the modelling of the whole of the Natural Sciences including that of 'Cold Fusion'. Some of the major steps which have taken place in the development of this subject area will be illustrated
Mirza, Imran M.; Schotland, John C.
2018-05-01
We study single photon transport in a one-dimensional disordered lattice of three-level atoms coupled to an optical waveguide. In particular, we study atoms of \\Lambda-type that are capable of exhibiting electromagnetically induced transparency (EIT) and separately consider disorder in the atomic positions and transition frequencies. We mainly address the question of how preferential emission into waveguide modes (chirality) can influence the formation of spatially localized states. Our work has relevance to experimental studies of cold atoms coupled to nanoscale waveguides and has possible applications to quantum communications.
BRST Quantisation of Histories Electrodynamics
Noltingk, D.
2001-01-01
This paper is a continuation of earlier work where a classical history theory of pure electrodynamics was developed in which the the history fields have \\emph{five} components. The extra component is associated with an extra constraint, thus enlarging the gauge group of histories electrodynamics. In this paper we quantise the classical theory developed previously by two methods. Firstly we quantise the reduced classical history space, to obtain a reduced quantum history theory. Secondly we qu...
Local effects of the quantum vacuum in Lorentz-violating electrodynamics
Martín-Ruiz, A.; Escobar, C. A.
2017-02-01
The Casimir effect is one of the most remarkable consequences of the nonzero vacuum energy predicted by quantum field theory. In this paper we use a local approach to study the Lorentz violation effects of the minimal standard model extension on the Casimir force between two parallel conducting plates in the vacuum. Using a perturbative method similar to that used for obtaining the Born series for the scattering amplitudes in quantum mechanics, we compute, at leading order in the Lorentz-violating coefficients, the relevant Green's function which satisfies given boundary conditions. The standard point-splitting technique allow us to express the vacuum expectation value of the stress-energy tensor in terms of the Green's function. We discuss its structure in the region between the plates. We compute the renormalized vacuum stress, which is obtained as the difference between the vacuum stress in the presence of the plates and that of the vacuum. The Casimir force is evaluated in an analytical fashion by two methods: by differentiating the renormalized global energy density and by computing the normal-normal component of the renormalized vacuum stress. We compute the local Casimir energy, which is found to diverge as approaching the plates, and we demonstrate that it does not contribute to the observable force.
International Nuclear Information System (INIS)
Horton-Smith, G.A.
1998-07-01
An experiment is described which studied quantum electrodynamic interactions under conditions of extremely high fields, along with a review of the relevant theory. The high fields were created by an intense, tightly-focused pulse of laser light at green or infrared wavelengths, into which was sent an ultra-relativistic electron beam of 46.6-GeV energy. The relevant theory is that of an electron in an electromagnetic wave so intense that the electron's mass is effectively shifted by the transverse momentum imparted to it by the wave, and the electron encounters field strengths comparable to the Schwinger critical field strength of 511 kV per Compton wavelength. An electron in the intense wave may radiate a photon and balance 4-momentum by absorbing multiple photons from the laser, which can lead to real photons with energies above the kinematic limit for conventional Compton scattering. All particles have significant probability of scattering multiple times while in the focus of the laser, including the photons radiated by the electrons, which may convert into electron-positron pairs, again with absorption of multiple photons from the laser. This experiment was able to measure the rates and spectra of positrons, electrons, and photons emerging from the interaction region. Results from both experiment and theoretical simulations are presented and compared. The results from the electron and positron measurements are compatible with the accepted theory, within experimental uncertainties due mainly to the laser intensity measurement. The photon spectrum shows the correct shape, but the ratio of rates in the linear and two-absorbed-photon portions of the spectrum does not vary as expected with the laser intensity, suggesting a disagreement with the accepted theory, with a significance of roughly two standard deviations. A follow-up experiment would be in order
Energy Technology Data Exchange (ETDEWEB)
Horton-Smith, G.A.
1998-07-01
An experiment is described which studied quantum electrodynamic interactions under conditions of extremely high fields, along with a review of the relevant theory. The high fields were created by an intense, tightly-focused pulse of laser light at green or infrared wavelengths, into which was sent an ultra-relativistic electron beam of 46.6-GeV energy. The relevant theory is that of an electron in an electromagnetic wave so intense that the electron's mass is effectively shifted by the transverse momentum imparted to it by the wave, and the electron encounters field strengths comparable to the Schwinger critical field strength of 511 kV per Compton wavelength. An electron in the intense wave may radiate a photon and balance 4-momentum by absorbing multiple photons from the laser, which can lead to real photons with energies above the kinematic limit for conventional Compton scattering. All particles have significant probability of scattering multiple times while in the focus of the laser, including the photons radiated by the electrons, which may convert into electron-positron pairs, again with absorption of multiple photons from the laser. This experiment was able to measure the rates and spectra of positrons, electrons, and photons emerging from the interaction region. Results from both experiment and theoretical simulations are presented and compared. The results from the electron and positron measurements are compatible with the accepted theory, within experimental uncertainties due mainly to the laser intensity measurement. The photon spectrum shows the correct shape, but the ratio of rates in the linear and two-absorbed-photon portions of the spectrum does not vary as expected with the laser intensity, suggesting a disagreement with the accepted theory, with a significance of roughly two standard deviations. A follow-up experiment would be in order.
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
Rueda, A.
1985-01-01
That particles may be accelerated by vacuum effects in quantum field theory has been repeatedly proposed in the last few years. A natural upshot of this is a mechanism for cosmic rays (CR) primaries acceleration. A mechanism for acceleration by the zero-point field (ZPE) when the ZPE is taken in a realistic sense (in opposition to a virtual field) was considered. Originally the idea was developed within a semiclassical context. The classical Einstein-Hopf model (EHM) was used to show that free isolated electromagnrtically interacting particles performed a random walk in phase space and more importantly in momentum space when submitted to the perennial action of the so called classical electromagnrtic ZPE.
International Nuclear Information System (INIS)
Rueda, A.
1985-01-01
That particles may be accelerated by vacuum effects in quantum field theory has been repeatedly proposed in the last few years. A natural upshot of this is a mechanism for cosmic rays (CR) primaries acceleration. A mechanism for acceleration by the zero-point field (ZPE) when the ZPE is taken in a realistic sense (in opposition to a virtual field) was considered. Originally the idea was developed within a semiclassical context. The calssical Einstein-Hopf model (EHM) was used to show that free isolated electromagnrtically interacting particles performed a random walk in phase space and more importantly in momentum space when submitted to the perennial action of the so called classical electromagnetic ZPE
Scaling of quantum and classical resonance peaks for the quantum kicked rotor
International Nuclear Information System (INIS)
Sadgrove, M.; Wimberger, S.; Parkings, S.; Leonhardt, R.
2005-01-01
Full text: We present results which demonstrate the relationship between the quantum resonance peaks of the classical kicked rotor and a classical resonance phenomenon. Both types of behaviour may be described using the same formalism (known as the ε - classical standard map). Furthermore, a scaling law exists for classical and quantum resonances which reduces the dynamics to a stationary function of one parameter. (author)
Energy Technology Data Exchange (ETDEWEB)
Brezin, Edouard
1970-06-22
Approximations commonly used in the study of the classical limit of quantum mechanics are applied, with justification, to quantum electrodynamics. First, the infrared divergence in the scattering of two charged particles is examined with the help of a remarkable series of Feynman diagrams, which in particular preserves gauge invariance and a correct static limit. Looking for the poles in energy of the scattering amplitude, a formula for the binding energies of two charged particles, which generalizes the Balmer formula and takes into account the correct relativistic kinematics, has been derived. A second type of applications concerns phenomena due to the interaction of the electromagnetic field with the vacuum current and charge fluctuations. For instance, when the intensities become very high, the theory predicts the creation of electron-positron pairs by the field. The creation rate is known in the limit of static fields, and the aim of these calculations was to demonstrate the role of frequency in the domain starting from the lowest frequencies up to X-rays. The pair production rate was found to be entirely negligible, even for the most intense laser beams. An increase in frequency, even up to several tens of keV, did not have any effect on the pair production. (author) [French] Des approximations habituellement reservees a l'etude de la limite classique de la mecanique quantique sont ici appliquees, apres justification, a l'electrodynamique quantique. En premier, l'etude de la divergence infrarouge dans la diffusion de deux particules chargees est conduite a l'aide d'une serie de diagrammes de Feynman possedant des proprietes remarquables, en particulier l'invariance de jauge et une limite statique correcte. De la est obtenue, en recherchant les poles dans la variable d'energie de l'amplitude de diffusion, une expression des energies de liaison de deux particules chargees tenant compte exactement de la cinematique relativiste et generalisant la formule de
Qin, Wei; Wang, Xin; Miranowicz, Adam; Zhong, Zhirong; Nori, Franco
2017-07-01
Heralded near-deterministic multiqubit controlled-phase gates with integrated error detection have recently been proposed by Borregaard et al. [Phys. Rev. Lett. 114, 110502 (2015), 10.1103/PhysRevLett.114.110502]. This protocol is based on a single four-level atom (a heralding quartit) and N three-level atoms (operational qutrits) coupled to a single-resonator mode acting as a cavity bus. Here we generalize this method for two distant resonators without the cavity bus between the heralding and operational atoms. Specifically, we analyze the two-qubit controlled-Z gate and its multiqubit-controlled generalization (i.e., a Toffoli-like gate) acting on the two-lowest levels of N qutrits inside one resonator, with their successful actions being heralded by an auxiliary microwave-driven quartit inside the other resonator. Moreover, we propose a circuit-quantum-electrodynamics realization of the protocol with flux and phase qudits in linearly coupled transmission-line resonators with dissipation. These methods offer a quadratic fidelity improvement compared to cavity-assisted deterministic gates.
Selective adsorption resonances: Quantum and stochastic approaches
International Nuclear Information System (INIS)
Sanz, A.S.; Miret-Artes, S.
2007-01-01
In this review we cover recent advances in the theory of the selective adsorption phenomenon that appears in light atom/molecule scattering off solid surfaces. Due to the universal van der Waals attractive interaction incoming gas particles can get trapped by the surface, this giving rise to the formation of quasi-bound states or resonances. The knowledge of the position and width of these resonances provides relevant direct information about the nature of the gas-surface interaction as well as about the evaporation and desorption mechanisms. This information can be obtained by means of a plethora of theoretical methods developed in both the energy and time domains, which we analyze and discuss here in detail. In particular, special emphasis is given to close-coupling, wave-packet, and trajectory-based formalisms. Furthermore, a novel description of selective adsorption resonances from a stochastic quantum perspective within the density matrix and Langevin formalisms, when correlations and fluctuations of the surface (considered as a thermal bath) are taken into account, is also proposed and discussed
Farzanehpour, Mehdi; Tokatly, Ilya; Nano-Bio Spectroscopy Group; ETSF Scientific Development Centre Team
2015-03-01
We present a rigorous formulation of the time-dependent density functional theory for interacting lattice electrons strongly coupled to cavity photons. We start with an example of one particle on a Hubbard dimer coupled to a single photonic mode, which is equivalent to the single mode spin-boson model or the quantum Rabi model. For this system we prove that the electron-photon wave function is a unique functional of the electronic density and the expectation value of the photonic coordinate, provided the initial state and the density satisfy a set of well defined conditions. Then we generalize the formalism to many interacting electrons on a lattice coupled to multiple photonic modes and prove the general mapping theorem. We also show that for a system evolving from the ground state of a lattice Hamiltonian any density with a continuous second time derivative is locally v-representable. Spanish Ministry of Economy and Competitiveness (Grant No. FIS2013-46159-C3-1-P), Grupos Consolidados UPV/EHU del Gobierno Vasco (Grant No. IT578-13), COST Actions CM1204 (XLIC) and MP1306 (EUSpec).
Mixed quantum-classical electrodynamics: Understanding spontaneous decay and zero-point energy
Li, Tao E.; Nitzan, Abraham; Sukharev, Maxim; Martinez, Todd; Chen, Hsing-Ta; Subotnik, Joseph E.
2018-03-01
The dynamics of an electronic two-level system coupled to an electromagnetic field are simulated explicitly for one- and three-dimensional systems through semiclassical propagation of the Maxwell-Liouville equations. We consider three flavors of mixed quantum-classical dynamics: (i) the classical path approximation (CPA), (ii) Ehrenfest dynamics, and (iii) symmetrical quasiclassical (SQC) dynamics. Our findings are as follows: (i) The CPA fails to recover a consistent description of spontaneous emission, (ii) a consistent "spontaneous" emission can be obtained from Ehrenfest dynamics, provided that one starts in an electronic superposition state, and (iii) spontaneous emission is always obtained using SQC dynamics. Using the SQC and Ehrenfest frameworks, we further calculate the dynamics following an incoming pulse, but here we find very different responses: SQC and Ehrenfest dynamics deviate sometimes strongly in the calculated rate of decay of the transient excited state. Nevertheless, our work confirms the earlier observations by Miller [J. Chem. Phys. 69, 2188 (1978), 10.1063/1.436793] that Ehrenfest dynamics can effectively describe some aspects of spontaneous emission and highlights interesting possibilities for studying light-matter interactions with semiclassical mechanics.
International Nuclear Information System (INIS)
Volland, H.
1984-01-01
The book Atmospheric Electrodynamics, by Hans Voland is reviewed. The book describes a wide variety of electrical phenomena occurring in the upper and lower atmosphere and develops the mathematical models which simulate these processes. The reviewer finds that the book is of interest to researchers with a background in electromagnetic theory but is of only limited use as a reference work
International Nuclear Information System (INIS)
Hawkins, C.A.
1989-02-01
Tests of Quantum Electrodynamics to order /alpha//sup 4/ in e/sup +/e/sup /minus// collisions using the ASP detector at PEP (/radical/s = 29 GeV) are presented. Measurements are made of e/sup +/e/sup /minus// /yields/ /gamma//gamma//gamma//gamma/, e/sup +/e/sup /minus// /yields/ e/sup +/e/sup /minus///gamma//gamma/ and e/sup +/e/sup /minus// /yields/ e/sup +/e/sup /minus//e/sup +/e/sup /minus// where all four final state particles are separated from the beam line and each other. These are the most precise and highest statistics measurements yet reported for these processes. The ratios of measured to predicted cross sections are /gamma//gamma//gamma//gamma/: 0.97 /plus minus/ 0.04 /plus minus/ 0.14 e/sup /+/e/sup /minus///gamma/gamma/: 0.94 /plus minus/ 0.03 /plus minus/ 0.03 e/sup +/e/sup /minus//e/sup +/e/sup /minus//: 1.01 /plus minus/ 0.02 /plus minus/ 0.04 where the first uncertainty is the systematic uncertainty, and the second is the statistical uncertainty. All measurements show good agreement with theoretical predictions. A Monte Carlo method for simulating multi-pole processes is also presented, along with applications to the e/sup +/e/sup /minus// /yields/ e/sup +/e/sup /minus///gamma//gamma/ and e/sup +/e/sup /minus// /yields/ /gamma//gamma//gamma//gamma/ processes. The first measurements of five-body /alpha//sup 5/ events (/sup 5//gamma/, e/sup +/e/sup /minus///gamma//gamma//gamma/ and e/sup +/e/sup /minus//e/sup +/ e/sup /minus///gamma/) and one candidate six-body /alpha//sup 6/event (e/sup +/e/sup /minus//4/gamma/) are reported. Both the /alpha//sup 5/ and /alpha//sup 6/ measurements agree with estimates of their cross sections. 20 refs., 34 figs., 14 tabs
Energy Technology Data Exchange (ETDEWEB)
Brenner, G.
2007-07-17
High-precision lifetime measurements of the metastable 1s{sup 2}2s{sup 2}2p{sup 2}P{sup 0}{sub 3/2} level in boronlike Ar XIV and the 3s{sup 2}2p {sup 2}P{sup 0}{sub 3/2} level in aluminumlike Fe XIV were performed at the Heidelberg electron beam ion trap (HD-EBIT). The lifetimes were inferred by monitoring their optical decay curves resulting from the magnetic dipole (M1) transition 1s{sup 2}2s{sup 2}2p{sup 2}P{sup 0}{sub 3/2}-{sup 2}P{sup 0}{sub 1/2} and 3s{sup 2}3p {sup 2}P{sup 0}{sub 3/2}-{sup 2}P{sup 0}{sub 1/2} to the ground state configuration with transition wavelengths of 441.256 nm and 530.29 nm, respectively. Possible systematic error sources were investigated by studying the dependence of the decay times of the curves on various trapping conditions with high statistical significance. A new trapping scheme for lifetime measurements at an EBIT has been applied and allowed to reach an unprecedented precision in the realm of lifetime determinations on highly charged ions. The results of 9.573(4)({sup +12}{sub -5}) ms (stat)(syst) for Ar XIV and 16.726(10)(+17) ms (stat)(syst) for Fe XIV with a relative accuracy of 0.14% and 0.13%, respectively, make these measurements for the first time sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM). The results, improving the accuracy of previous measurements by factors of 10 and 6, respectively, show a clear discrepancy of about 3{sigma} and 4{sigma} to the trend of existing theoretical models, which in almost all cases predict a shorter lifetime, when adjusted for the EAMM. The obvious disagreement between experimental results and the predictions points at the incompleteness of the theoretical models used. (orig.)
Cencek, Wojciech; Przybytek, Michał; Komasa, Jacek; Mehl, James B; Jeziorski, Bogumił; Szalewicz, Krzysztof
2012-06-14
The adiabatic, relativistic, and quantum electrodynamics (QED) contributions to the pair potential of helium were computed, fitted separately, and applied, together with the nonrelativistic Born-Oppenheimer (BO) potential, in calculations of thermophysical properties of helium and of the properties of the helium dimer. An analysis of the convergence patterns of the calculations with increasing basis set sizes allowed us to estimate the uncertainties of the total interaction energy to be below 50 ppm for interatomic separations R smaller than 4 bohrs and for the distance R = 5.6 bohrs. For other separations, the relative uncertainties are up to an order of magnitude larger (and obviously still larger near R = 4.8 bohrs where the potential crosses zero) and are dominated by the uncertainties of the nonrelativistic BO component. These estimates also include the contributions from the neglected relativistic and QED terms proportional to the fourth and higher powers of the fine-structure constant α. To obtain such high accuracy, it was necessary to employ explicitly correlated Gaussian expansions containing up to 2400 terms for smaller R (all R in the case of a QED component) and optimized orbital bases up to the cardinal number X = 7 for larger R. Near-exact asymptotic constants were used to describe the large-R behavior of all components. The fitted potential, exhibiting the minimum of -10.996 ± 0.004 K at R = 5.608 0 ± 0.000 1 bohr, was used to determine properties of the very weakly bound (4)He(2) dimer and thermophysical properties of gaseous helium. It is shown that the Casimir-Polder retardation effect, increasing the dimer size by about 2 Å relative to the nonrelativistic BO value, is almost completely accounted for by the inclusion of the Breit-interaction and the Araki-Sucher contributions to the potential, of the order α(2) and α(3), respectively. The remaining retardation effect, of the order of α(4) and higher, is practically negligible for the bound
DEFF Research Database (Denmark)
Birkedal, Dan; Shah, Jagdeep; Shchegrov, Andrei V.
2000-01-01
Resonant Rayleigh scattering from quantum well excitons is investigated using ultrafast spectral interferometry. We isolate the coherent Rayleigh scattering from incoherent luminescence in a single speckle. Averaging the resonant Rayleigh intensity over several speckles allows us to identify...... features in support of quantum corrections to the classical description of the underlying scattering process....
Zangwill, Andrew
2013-01-01
An engaging writing style and a strong focus on the physics make this comprehensive, graduate-level textbook unique among existing classical electromagnetism textbooks. Charged particles in vacuum and the electrodynamics of continuous media are given equal attention in discussions of electrostatics, magnetostatics, quasistatics, conservation laws, wave propagation, radiation, scattering, special relativity and field theory. Extensive use of qualitative arguments similar to those used by working physicists makes Modern Electrodynamics a must-have for every student of this subject. In 24 chapters, the textbook covers many more topics than can be presented in a typical two-semester course, making it easy for instructors to tailor courses to their specific needs. Close to 120 worked examples and 80 applications boxes help the reader build physical intuition and develop technical skill. Nearly 600 end-of-chapter homework problems encourage students to engage actively with the material. A solutions manual is availa...
Quasi-Resonant Absorption for Quantum Efficiency Improvement in Detectors
National Aeronautics and Space Administration — Quasi-resonant absorption has been demonstrated to enhance the quantum efficiency of devices across the spectrum, but specifically it is a challenge in the UV...
Magnetophonon resonance in double quantum wells
Ploch, D.; Sheregii, E. M.; Marchewka, M.; Wozny, M.; Tomaka, G.
2009-05-01
The experimental results obtained for the magnetotransport in pulsed magnetic fields in the InGaAs/InAlAs double quantum well (DQW) structures of two different shapes of wells and different values of the electron density are reported. The magnetophonon resonance (MPR) was observed for both types of structures within the temperature range 77-125 K. Four kinds of LO phonons are taken into account to interpret the MPR oscillations in the DQW and a method of the Landau level calculation in the DQW is elaborated for this aim. The peculiarity of the MPR in the DQW is the large number of the Landau levels caused by SAS splitting of the electron states (splitting on the symmetric and anti-symmetric states) and the large number of the phonon assistance electron transitions between Landau levels. The significant role of the carrier statistics is shown too. The behavior of the electron states in the DQWs at comparably high temperatures has been studied using the MPR. It is shown that the Huang and Manasreh [Manasreh [Phys. Rev. B 54, 2044 (1996)] model involving screening of exchange interaction is confirmed.
Quantum transport in coupled resonators enclosed synthetic magnetic flux
International Nuclear Information System (INIS)
Jin, L.
2016-01-01
Quantum transport properties are instrumental to understanding quantum coherent transport processes. Potential applications of quantum transport are widespread, in areas ranging from quantum information science to quantum engineering, and not restricted to quantum state transfer, control and manipulation. Here, we study light transport in a ring array of coupled resonators enclosed synthetic magnetic flux. The ring configuration, with an arbitrary number of resonators embedded, forms a two-arm Aharonov–Bohm interferometer. The influence of magnetic flux on light transport is investigated. Tuning the magnetic flux can lead to resonant transmission, while half-integer magnetic flux quantum leads to completely destructive interference and transmission zeros in an interferometer with two equal arms. -- Highlights: •The light transport is investigated through ring array of coupled resonators enclosed synthetic magnetic field. •Aharonov–Bohm ring interferometer of arbitrary configuration is investigated. •The half-integer magnetic flux quantum leads to destructive interference and transmission zeros for two-arm at equal length. •Complete transmission is available via tuning synthetic magnetic flux.
International Nuclear Information System (INIS)
Bouchendira, Rym; Clade, Pierre; Nez, Francois; Biraben, Francois; Guellati-Khelifa, Saida
2013-01-01
The fine structure constant α has a particular status in physics. Its precise determination is required to test the quantum electrodynamics (QED) theory. The constant α is also a keystone for the determination of other fundamental physical constants, especially the ones involved in the framework of the future International System of units. This paper presents Paris experiment, where the fine structure constant is determined by measuring the recoil velocity of a rubidium atom when it absorbs a photon. The impact of the recent improvement of QED calculations of the electron moment anomaly and the recent measurement of the cesium atom recoil at Berkeley will be discussed. The opportunity to provide a precise value of the ratio h/m u between the Planck constant and the atomic mass constant will be investigated. (copyright 2013 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
On the convergence of quantum resonant-state expansion
International Nuclear Information System (INIS)
Brown, J. M.; Bahl, A.; Jakobsen, P.; Moloney, J. V.; Kolesik, M.
2016-01-01
Completeness of the system of Stark resonant states is investigated for a one-dimensional quantum particle with the Dirac-delta potential exposed to an external homogeneous field. It is shown that the resonant series representation of a given wavefunction converges on the negative real axis while the series diverges on the positive axis. Despite the divergent nature of the resonant expansion, good approximations can be obtained in a compact spatial domain.
On the convergence of quantum resonant-state expansion
Energy Technology Data Exchange (ETDEWEB)
Brown, J. M.; Bahl, A. [College of Optical Sciences, University of Arizona, 1630 East University Boulevard, Tucson, Arizona 85721 (United States); Jakobsen, P. [Department of Mathematics and Statistics, University of Tromsø, Tromsø (Norway); Moloney, J. V.; Kolesik, M. [College of Optical Sciences, University of Arizona, 1630 East University Boulevard, Tucson, Arizona 85721 (United States); Arizona Center for Mathematical Sciences, University of Arizona, Tucson, Arizona 85721 (United States)
2016-03-15
Completeness of the system of Stark resonant states is investigated for a one-dimensional quantum particle with the Dirac-delta potential exposed to an external homogeneous field. It is shown that the resonant series representation of a given wavefunction converges on the negative real axis while the series diverges on the positive axis. Despite the divergent nature of the resonant expansion, good approximations can be obtained in a compact spatial domain.
Non-blinking quantum dot with a plasmonic nanoshell resonator
Ji, Botao; Giovanelli, Emerson; Habert, Benjamin; Spinicelli, Piernicola; Nasilowski, Michel; Xu, Xiangzhen; Lequeux, Nicolas; Hugonin, Jean-Paul; Marquier, Francois; Greffet, Jean-Jacques; Dubertret, Benoit
2015-02-01
Colloidal semiconductor quantum dots are fluorescent nanocrystals exhibiting exceptional optical properties, but their emission intensity strongly depends on their charging state and local environment. This leads to blinking at the single-particle level or even complete fluorescence quenching, and limits the applications of quantum dots as fluorescent particles. Here, we show that a single quantum dot encapsulated in a silica shell coated with a continuous gold nanoshell provides a system with a stable and Poissonian emission at room temperature that is preserved regardless of drastic changes in the local environment. This novel hybrid quantum dot/silica/gold structure behaves as a plasmonic resonator with a strong Purcell factor, in very good agreement with simulations. The gold nanoshell also acts as a shield that protects the quantum dot fluorescence and enhances its resistance to high-power photoexcitation or high-energy electron beams. This plasmonic fluorescent resonator opens the way to a new family of plasmonic nanoemitters with robust optical properties.
Energy Technology Data Exchange (ETDEWEB)
Martino, Trassinelli
2005-12-15
The object of this thesis is to present a new measurement of the pion mass using pionic nitrogen X-ray spectroscopy and results on helium-like argon and sulphur spectroscopy. The new pion mass has been measured with an accuracy of 1.7 ppm, 30% better that the present world average value, and it is obtained from Bragg spectroscopy of 5 ->4 pionic nitrogen transitions using the theoretical predictions provided by quantum electrodynamics. We have got: m({pi}{sup -}) = (139.571042 {+-} 0.000210 {+-} 0.000110) where the first error is due to the statistics and the second is the systematic error. I present the calculation of the hyperfine structure and recoil corrections for pionic atoms using a new perturbation method for the Klein-Gordon equation. The spectrometer used for this measurement has been characterized with the relativistic M1 transitions from helium-like ions produced with a new device, the Electron-Cyclotron-Resonance Ion Trap. High statistics spectra from these ions have enabled us to measure transition energies with an accuracy of some ppm which has allowed us to compare theoretical predictions with experiment data. X-ray emission from pionic atoms and multicharged ions can be used to define new types of X-ray standards for energies of a few keV.
Mechanical Resonators for Quantum Optomechanics Experiments at Room Temperature.
Norte, R A; Moura, J P; Gröblacher, S
2016-04-08
All quantum optomechanics experiments to date operate at cryogenic temperatures, imposing severe technical challenges and fundamental constraints. Here, we present a novel design of on-chip mechanical resonators which exhibit fundamental modes with frequencies f and mechanical quality factors Q_{m} sufficient to enter the optomechanical quantum regime at room temperature. We overcome previous limitations by designing ultrathin, high-stress silicon nitride (Si_{3}N_{4}) membranes, with tensile stress in the resonators' clamps close to the ultimate yield strength of the material. By patterning a photonic crystal on the SiN membranes, we observe reflectivities greater than 99%. These on-chip resonators have remarkably low mechanical dissipation, with Q_{m}∼10^{8}, while at the same time exhibiting large reflectivities. This makes them a unique platform for experiments towards the observation of massive quantum behavior at room temperature.
Quantum nondemolition squeezing of a nanomechanical resonator
Ruskov, Rusko; Schwab, Keith; Korotkov, Alexander
2005-03-01
We discuss squeezing of the nanoresonator state produced by periodic measurement of position by a quantum point contact or a single-electron transistor. The mechanism of squeezing is the stroboscopic quantum nondemolition measurement generalized to the case of continuous measurement by a weakly coupled detector. The magnitude of squeezing is calculated for the harmonic and stroboscopic modulations of measurement, taking into account detector efficiency and nanoresonator quality factor. We also analyze the operation of the quantum feedback, which prevents fluctuations of the wavepacket center due to measurement back-action. Verification of the squeezed state can be performed in almost the same way as its preparation; similar procedure can also be used for the force detection with sensitivity beyond the standard quantum limit.
International Nuclear Information System (INIS)
Tomimatsu, Toru; Shirai, Shota; Hashimoto, Katsushi; Sato, Ken; Hirayama, Yoshiro
2015-01-01
Electric-field-induced nuclear resonance (NER: nuclear electric resonance) involving quantum Hall states (QHSs) was studied at various filling factors by exploiting changes in nuclear spins polarized at quantum Hall breakdown. Distinct from the magnetic dipole interaction in nuclear magnetic resonance, the interaction of the electric-field gradient with the electric quadrupole moment plays the dominant role in the NER mechanism. The magnitude of the NER signal strongly depends on whether electronic states are localized or extended. This indicates that NER is sensitive to the screening capability of the electric field associated with QHSs
Resonant scattering of surface plasmon polaritons by dressed quantum dots
Energy Technology Data Exchange (ETDEWEB)
Huang, Danhong; Cardimona, Dave [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117 (United States); Easter, Michelle [Department of Mechanical Engineering, Stevens Institute of Technology, 1 Castle Point Terrace, Hoboken, New Jersey 07030 (United States); Gumbs, Godfrey [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065 (United States); Maradudin, A. A. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Lin, Shawn-Yu [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States); Zhang, Xiang [Department of Mechanical Engineering, 3112 Etcheverry Hall, University of California at Berkeley, Berkeley, California 94720 (United States)
2014-06-23
The resonant scattering of surface plasmon-polariton waves (SPP) by embedded semiconductor quantum dots above the dielectric/metal interface is explored in the strong-coupling regime. In contrast to non-resonant scattering by a localized dielectric surface defect, a strong resonant peak in the spectrum of the scattered field is predicted that is accompanied by two side valleys. The peak height depends nonlinearly on the amplitude of SPP waves, reflecting the feedback dynamics from a photon-dressed electron-hole plasma inside the quantum dots. This unique behavior in the scattered field peak strength is correlated with the occurrence of a resonant dip in the absorption spectrum of SPP waves due to the interband photon-dressing effect. Our result on the scattering of SPP waves may be experimentally observable and applied to spatially selective illumination and imaging of individual molecules.
Electrically protected resonant exchange qubits in triple quantum dots.
Taylor, J M; Srinivasa, V; Medford, J
2013-08-02
We present a modulated microwave approach for quantum computing with qubits comprising three spins in a triple quantum dot. This approach includes single- and two-qubit gates that are protected against low-frequency electrical noise, due to an operating point with a narrowband response to high frequency electric fields. Furthermore, existing double quantum dot advances, including robust preparation and measurement via spin-to-charge conversion, are immediately applicable to the new qubit. Finally, the electric dipole terms implicit in the high frequency coupling enable strong coupling with superconducting microwave resonators, leading to more robust two-qubit gates.
Multi-quantum spin resonances of intrinsic defects in silicon carbide
International Nuclear Information System (INIS)
Georgy Astakhov
2014-01-01
We report the observation of multi-quantum microwave absorption and emission, induced by the optical excitation of silicon vacancy related defects in silicon carbide (SiC). In particular, we observed two-quantum transitions from +3/2 to -1/2 and from -3/2 to +1/2 spin sublevels, unambiguously indicating the spin S = 3/2 ground state. Our findings may have implications for a broad range of quantum applications. On one hand, a single silicon vacancy defect is a potential source of indistinguishable microwave photon pairs due to the two-quantum emission process. On the other hand, the two-quantum absorption can be used generate a population inversion, which is a prerequisite to fabricate solid-state maser and quantum microwave amplifier. This opens a new platform cavity quantum electrodynamics experiments and quantum information processing on a single chip. (author)
Quantum mechanical coherence, resonance, and mind
International Nuclear Information System (INIS)
Stapp, H.P.
1995-01-01
Norbert Wiener and J.B.S. Haldane suggested during the early thirties that the profound changes in our conception of matter entailed by quantum theory opens the way for our thoughts, and other experiential or mind-like qualities, to play a role in nature that is causally interactive and effective, rather than purely epiphenomenal, as required by classical mechanics. The mathematical basis of this suggestion is described here, and it is then shown how, by giving mind this efficacious role in natural process, the classical character of our perceptions of the quantum universe can be seen to be a consequence of evolutionary pressures for the survival of the species
Quantum mechanical coherence, resonance, and mind
Energy Technology Data Exchange (ETDEWEB)
Stapp, H.P.
1995-03-26
Norbert Wiener and J.B.S. Haldane suggested during the early thirties that the profound changes in our conception of matter entailed by quantum theory opens the way for our thoughts, and other experiential or mind-like qualities, to play a role in nature that is causally interactive and effective, rather than purely epiphenomenal, as required by classical mechanics. The mathematical basis of this suggestion is described here, and it is then shown how, by giving mind this efficacious role in natural process, the classical character of our perceptions of the quantum universe can be seen to be a consequence of evolutionary pressures for the survival of the species.
Feshbach shape resonance for high Tc pairing in superlattices of quantum stripes and quantum wells
Directory of Open Access Journals (Sweden)
A Bianconi
2006-09-01
Full Text Available The Feshbach shape resonances in the interband pairing in superconducting superlattices of quantum wells or quantum stripes is shown to provide the mechanism for high Tc superconductivity. This mechanism provides the Tc amplification driven by the architecture of material: superlattices of quantum wells (intercalated graphite or diborides and superlattices of quantum stripes (doped high Tc cuprate perovskites where the chemical potential is tuned to a Van Hove-Lifshitz singularity (vHs in the electronic energy spectrum of the superlattice associated with the change of the Fermi surface dimensionality in one of the subbands.
Realization of quantum state privacy amplification in a nuclear magnetic resonance quantum system
International Nuclear Information System (INIS)
Hao, Liang; Wang, Chuan; Long, Gui Lu
2010-01-01
Quantum state privacy amplification (QSPA) is the quantum analogue of classical privacy amplification. If the state information of a series of single-particle states has some leakage, QSPA reduces this leakage by condensing the state information of two particles into the state of one particle. Recursive applications of the operations will eliminate the quantum state information leakage to a required minimum level. In this paper, we report the experimental implementation of a quantum state privacy amplification protocol in a nuclear magnetic resonance system. The density matrices of the states are constructed in the experiment, and the experimental results agree well with theory.
DEFF Research Database (Denmark)
Unsleber, Sebastian; McCutcheon, Dara; Dambach, Michael
2015-01-01
We demonstrate the emission of highly indistinguishable photons from a quasi-resonantly pumped coupledquantum dot–microcavity system operating in the regime of cavity quantum electrodynamics. Changing thesample temperature allows us to vary the quantum dot–cavity detuning and, on spectral resonance...
Intrinsic resonance representation of quantum mechanics
DEFF Research Database (Denmark)
Carioli, M.; Heller, E.J.; Møller, Klaus Braagaard
1997-01-01
an optimal representation, based purely on classical mechanics. ''Hidden'' constants of the motion and good actions already known to the classical mechanics are thus incorporated into the basis, leaving the quantum effects to be isolated and included by small matrix diagonalizations. This simplifies...
Quantum recurrence and integer ratios in neutron resonances
Energy Technology Data Exchange (ETDEWEB)
Ohkubo, Makio
1998-03-01
Quantum recurrence of the compound nucleus in neutron resonance reactions are described for normal modes which are excited on the compound nucleus simultaneously. In the structure of the recurrence time, integer relations among dominant level spacings are derived. The `base modes` are assumed as stable combinations of the normal modes, preferably excited in many nuclei. (author)
Existence of the Stark-Wannier quantum resonances
Energy Technology Data Exchange (ETDEWEB)
Sacchetti, Andrea, E-mail: andrea.sacchetti@unimore.it [Department of Physics, Computer Sciences and Mathematics, University of Modena e Reggio Emilia, Modena (Italy)
2014-12-15
In this paper, we prove the existence of the Stark-Wannier quantum resonances for one-dimensional Schrödinger operators with smooth periodic potential and small external homogeneous electric field. Such a result extends the existence result previously obtained in the case of periodic potentials with a finite number of open gaps.
Resonances from perturbations of quantum graphs with rationally related edges
Czech Academy of Sciences Publication Activity Database
Exner, Pavel; Lipovský, Jiří
2010-01-01
Roč. 43, č. 10 (2010), 105301/1-105301/21 ISSN 1751-8113 R&D Projects: GA MŠk LC06002 Institutional research plan: CEZ:AV0Z10480505 Keywords : quantum graphs * resonances * analyze Subject RIV: BE - Theoretical Physics Impact factor: 1.641, year: 2010
Effective Hamiltonians in quantum physics: resonances and geometric phase
International Nuclear Information System (INIS)
Rau, A R P; Uskov, D
2006-01-01
Effective Hamiltonians are often used in quantum physics, both in time-dependent and time-independent contexts. Analogies are drawn between the two usages, the discussion framed particularly for the geometric phase of a time-dependent Hamiltonian and for resonances as stationary states of a time-independent Hamiltonian
Fidelity for kicked atoms with gravity near a quantum resonance.
Dubertrand, Rémy; Guarneri, Italo; Wimberger, Sandro
2012-03-01
Kicked atoms under a constant Stark or gravity field are investigated for experimental setups with cold and ultracold atoms. The parametric stability of the quantum dynamics is studied using the fidelity. In the case of a quantum resonance, it is shown that the behavior of the fidelity depends on arithmetic properties of the gravity parameter. Close to a quantum resonance, the long-time asymptotics of the fidelity is studied by means of a pseudoclassical approximation introduced by Fishman et al. [J. Stat. Phys. 110, 911 (2003)]. The long-time decay of fidelity arises from the tunneling out of pseudoclassical stable islands, and a simple ansatz is proposed which satisfactorily reproduces the main features observed in numerical simulations.
Fano resonance and persistent current of a quantum ring
International Nuclear Information System (INIS)
Xiong Yongjian; Liang Xianting
2004-01-01
We investigate electron transport and persistent current of a quantum ring weakly attached to current leads. Assuming there is direct coupling (weakly or strongly) between two leads, electrons can transmit by the inter-lead coupling or tunneling through the quantum ring. The interference between the two paths yields asymmetric Fano line shape for conductance. In presence of interior magnetic flux, there is persistent current along the ring with narrow resonance peaks. The positions of the conductance resonances and the persistent current peaks correspond to the quasibound levels of the closed ring. This feature is helpful to determine the energy spectrum of the quantum ring. Our results show that the proposed setup provides a tunable Fano system
International Nuclear Information System (INIS)
Tiwary, S.N.
1995-01-01
The present review briefly presents the growing experimental as well as theoretical interests in recent years in the effects of (1) correlation, (2) relativity, (3) quantum electrodynamic (QED), (4) finite nuclear size (FNS) and (5) parity non-conservation (PNC) on the high precision electronic structure of alkali atoms and alkali-like ions. Many high precision experiments have been performed which need very high accurate theoretical prediction for correct interpretation and identification of different physical effects involved. Some experiments separate these effects and some do not. Several sophisticated theoretical techniques have been developed for corrections of these effects which play an extremely important role in order to obtain results of high accuracy to well below 1% level and to understand experimental observations of high precision. Correlation, relativity and finite nuclear size effects have been treated on an equal footing in some theoretical methods but QED and PNC have been calculated separately. At present, there is no theory which accounts all five effects in a coherent and unified manner. Future challenges and directions, in reliable structure calculations in atoms and ions, have been discussed and suggested. (author). 83 refs, 3 figs, 9 tabs
Implementation of Quantum Private Queries Using Nuclear Magnetic Resonance
International Nuclear Information System (INIS)
Wang Chuan; Hao Liang; Zhao Lian-Jie
2011-01-01
We present a modified protocol for the realization of a quantum private query process on a classical database. Using one-qubit query and CNOT operation, the query process can be realized in a two-mode database. In the query process, the data privacy is preserved as the sender would not reveal any information about the database besides her query information, and the database provider cannot retain any information about the query. We implement the quantum private query protocol in a nuclear magnetic resonance system. The density matrix of the memory registers are constructed. (general)
Ruelle resonances in quantum many-body dynamics
International Nuclear Information System (INIS)
Prosen, Tomaz
2002-01-01
We define a quantum Perron-Frobenius master operator over a suitable normed space of translationally invariant states adjoint to the quasi-local C* algebra of quantum lattice gasses (e.g. spin chains), whose spectrum determines the exponents of decay of time correlation functions. The theoretical ideas are applied to a generic example of kicked Ising spin 1/2 chains. We show that the 'chaotic eigenmodes' corresponding to leading eigenvalue resonances have fractal structure in the basis of local operators. (letter to the editor)
Resonances in A=6 nuclei: use of supersymmetric quantum mechanics
International Nuclear Information System (INIS)
Dutta, S.K.; Das, T.K.; Khan, M.A.; Chakrabarti, B.
2004-01-01
We propose a novel theoretical technique for the calculation of resonances at low excitation energies in weakly bound systems. Starting from an effective potential, supersymmetric quantum mechanics can be successfully used to generate families of isospectral potentials having desirable and adjustable properties. For resonance states, for which there is no bound ground state of the same spin-parity, one can construct an isospectral potential with a bound state in the continuum (BIC). The potential looks quite different but is strictly isospectral with the original one. The quasi-bound state in the original shallow potential will be effectively trapped in the deep well of the isospectral family facilitating an easier and more accurate calculation of the resonance energy. Application to 6 He, 6 Be, and 6 Li systems yields quite accurate results. The beauty of our technique: We get both the bound ground state and the resonances by a single technique and using the same potential. (author)
New Approaches to Quantum Computing using Nuclear Magnetic Resonance Spectroscopy
International Nuclear Information System (INIS)
Colvin, M; Krishnan, V V
2003-01-01
The power of a quantum computer (QC) relies on the fundamental concept of the superposition in quantum mechanics and thus allowing an inherent large-scale parallelization of computation. In a QC, binary information embodied in a quantum system, such as spin degrees of freedom of a spin-1/2 particle forms the qubits (quantum mechanical bits), over which appropriate logical gates perform the computation. In classical computers, the basic unit of information is the bit, which can take a value of either 0 or 1. Bits are connected together by logic gates to form logic circuits to implement complex logical operations. The expansion of modern computers has been driven by the developments of faster, smaller and cheaper logic gates. As the size of the logic gates become smaller toward the level of atomic dimensions, the performance of such a system is no longer considered classical but is rather governed by quantum mechanics. Quantum computers offer the potentially superior prospect of solving computational problems that are intractable to classical computers such as efficient database searches and cryptography. A variety of algorithms have been developed recently, most notably Shor's algorithm for factorizing long numbers into prime factors in polynomial time and Grover's quantum search algorithm. The algorithms that were of only theoretical interest as recently, until several methods were proposed to build an experimental QC. These methods include, trapped ions, cavity-QED, coupled quantum dots, Josephson junctions, spin resonance transistors, linear optics and nuclear magnetic resonance. Nuclear magnetic resonance (NMR) is uniquely capable of constructing small QCs and several algorithms have been implemented successfully. NMR-QC differs from other implementations in one important way that it is not a single QC, but a statistical ensemble of them. Thus, quantum computing based on NMR is considered as ensemble quantum computing. In NMR quantum computing, the spins with
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.)
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.)
Resonant photoionization absorption spectra of spherical quantum dots
Bondarenko, V
2003-01-01
We study theoretically the mid-infrared photon absorption spectra due to bound-free transitions of electrons in individual spherical quantum dots. It is established that change of the dot size in one or two atomic layers or/and number of electrons by one or two can change the peak value of the absorption spectra in orders of magnitude and energy of absorbed photons by tens of millielectronvolts. The reason for this is the formation of specific free states, called resonance states. Numerical calculations are performed for quantum dots (QDs) with radius varying up to 200 A, and one to eight electrons occupying the two lowest bound states. It is supposed that realistic QD systems with resonance states would be of much advantage to design novel infrared QD photo-detectors.
The Landauer-Büttiker formula and resonant quantum transport
DEFF Research Database (Denmark)
Cornean, Horia; Jensen, Arne; Moldoveanu, Valeriu
2006-01-01
We give a short presentation of two recent results. The first one is a rigorous proof of the Landauer-Büttiker formula, and the second one concerns resonant quantum transport. The detailed results are in [2]. In the last section we present the results of som numerical computations on a model system....... Concerning the literature, then see the starting point of our work [6]. In [4] a related, but different, problem is studied. See also [5] and the recent work [1]....
The Landauer-Büttiker formula and resonant quantum transport
DEFF Research Database (Denmark)
Cornean, Horia Decebal; Jensen, Arne; Moldoveanu, Valeriu
We give a short presentation of two recent results. The firrst one is a rigorous proof of the Landauer-Büttiker formula, and the second one concerns resonant quantum transport. The detailed results are in [2]. In the last section we present the results of some numerical computations on a model...... system.Concerning the literature, then see the starting point of our work, [6]. In [4] a related, but different, problem is studied. See also [5] and the recentwork [1]....
Resonance fluorescence and quantum interference of a single NV center
Ma, Yong-Hong; Zhang, Xue-Feng; Wu, E.
2017-11-01
The detection of a single nitrogen-vacancy center in diamond has attracted much interest, since it is expected to lead to innovative applications in various domains of quantum information, including quantum metrology, information processing and communications, as well as in various nanotechnologies, such as biological and subdiffraction limit imaging, and tests of entanglement in quantum mechanics. We propose a novel scheme of a single NV center coupled with a multi-mode superconducting microwave cavity driven by coherent fields in squeezed vacuum. We numerically investigate the spectra in-phase quadrature and out-of-phase quadrature for different driving regimes with or without detunings. It shows that the maximum squeezing can be obtained for optimal Rabi fields. Moreover, with the same parameters, the maximum squeezing is greatly increased when the detunings are nonzero compared to the resonance case.
Resonant Tunneling in Photonic Double Quantum Well Heterostructures
Directory of Open Access Journals (Sweden)
Cox Joel
2010-01-01
Full Text Available Abstract Here, we study the resonant photonic states of photonic double quantum well (PDQW heterostructures composed of two different photonic crystals. The heterostructure is denoted as B/A/B/A/B, where photonic crystals A and B act as photonic wells and barriers, respectively. The resulting band structure causes photons to become confined within the wells, where they occupy discrete quantized states. We have obtained an expression for the transmission coefficient of the PDQW heterostructure using the transfer matrix method and have found that resonant states exist within the photonic wells. These resonant states occur in split pairs, due to a coupling between degenerate states shared by each of the photonic wells. It is observed that when the resonance energy lies at a bound photonic state and the two photonic quantum wells are far away from each other, resonant states appear in the transmission spectrum of the PDQW as single peaks. However, when the wells are brought closer together, coupling between bound photonic states causes an energy-splitting effect, and the transmitted states each have two peaks. Essentially, this means that the system can be switched between single and double transparent states. We have also observed that the total number of resonant states can be controlled by varying the width of the photonic wells, and the quality factor of transmitted peaks can be drastically improved by increasing the thickness of the outer photonic barriers. It is anticipated that the resonant states described here can be used to develop new types of photonic-switching devices, optical filters, and other optoelectronic devices.
International Nuclear Information System (INIS)
Shu Chang-Gan; Xin Xia; Liu Yu-Min; Yu Zhong-Yuan; Yao Wen-Jie; Wang Dong-Lin; Cao Gui
2012-01-01
We investigate theoretically two photon entanglement processes in a photonic-crystal cavity embedding a quantum dot in the strong-coupling regime. The model proposed by Johne et al. (Johne R, Gippius N A, Pavlovic G, Solnyshkov D D, Shelykh I A and Malpuech G 2008 Phys. Rev. Lett. 100 240404), and by Robert et al. (Robert J, Gippius N A and Malpuech G 2009 Phys. Rev. B 79 155317) is modified by considering irreversible dissipation and incoherent continuous pumping for the quantum dot, which is necessary to connect the realistic experiment. The dynamics of the system is analysed by employing the Born—Markov master equation, through which the spectra for the system are computed as a function of various parameters. By means of this analysis the photon-reabsorption process in the strong-coupling regime is first observed and analysed from the perspective of radiation spectrum and the optimal parameters for observing energy-entangled photon pairs are identified. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)
International Nuclear Information System (INIS)
Gabadadze, Gregory; Rosen, Rachel A.
2008-01-01
A relativistic system of electrically charged fermions and oppositely charged massive scalars with no self-interactions, is argued to have a long-lived collective state with a net charge. The charge is residing near the surface of the spherically-symmetric state, while the interior consists of the condensed scalars, that are neutralized by the fermions. The metastability is achieved by competition of the negative pressure of the scalar condensate, against the positive pressure, mainly due to the fermions. We consider such metanuclei made of helium-4 nuclei and electrons, below nuclear but above atomic densities. Typical metanuclei represent charged balls of the atomic size, colossal mass, electric charge and excess energy. Unlike an ordinary nucleus, the charge of a metanucleus scales proportionately to its radius. The quantum mechanical decay through tunneling, and vacuum instability via pair-creation, are both suppressed for large values of the electric charge. Similar states could also be composed of other charged (pseudo)scalars, such as the pions, scalar supersymmetric partners, or in general, spin-0 states of new physics
Meystre, Pierre
2007-01-01
Elements of Quantum Optics gives a self-contained and broad coverage of the basic elements necessary to understand and carry out research in laser physics and quantum optics, including a review of basic quantum mechanics and pedagogical introductions to system-reservoir interactions and to second quantization. The text reveals the close connection between many seemingly unrelated topics, such as probe absorption, four-wave mixing, optical instabilities, resonance fluorescence and squeezing. It also comprises discussions of cavity quantum electrodynamics and atom optics. The 4th edition includes a new chapter on quantum entanglement and quantum information, as well as added discussions of the quantum beam splitter, electromagnetically induced transparency, slow light, and the input-output formalism needed to understand many problems in quantum optics. It also provides an expanded treatment of the minimum-coupling Hamiltonian and a simple derivation of the Gross-Pitaevskii equation, an important gateway to rese...
Energy Technology Data Exchange (ETDEWEB)
Waseem, Muhammad; Irfan, Muhammad [Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad 45650 (Pakistan); Qamar, Shahid, E-mail: shahid_qamar@pieas.edu.pk [Department of Physics and Applied Mathematics, Pakistan Institute of Engineering and Applied Sciences, Nilore, Islamabad 45650 (Pakistan)
2012-07-15
In this paper, we propose a scheme to realize three-qubit quantum phase gate of one qubit simultaneously controlling two target qubits using four-level superconducting quantum interference devices (SQUIDs) coupled to a superconducting resonator. The two lowest levels Divides 0 Right-Pointing-Angle-Bracket and Divides 1 Right-Pointing-Angle-Bracket of each SQUID are used to represent logical states while the higher energy levels Divides 2 Right-Pointing-Angle-Bracket and Divides 3 Right-Pointing-Angle-Bracket are utilized for gate realization. Our scheme does not require adiabatic passage, second order detuning, and the adjustment of the level spacing during gate operation which reduce the gate time significantly. The scheme is generalized for an arbitrary n-qubit quantum phase gate. We also apply the scheme to implement three-qubit quantum Fourier transform.
International Nuclear Information System (INIS)
Kist, Tarso B.L.; Orszag, M.; Davidovich, L.
1997-01-01
The dynamics of open system is frequently modeled in terms of a small system S coupled to a reservoir R, the last having an infinitely larger number of degree of freedom than S. Usually the dynamics of the S variables may be of interest, which can be studied using either Langevin equations, or master equations, or yet the path integral formulation. Useful alternatives for the master equation method are the Monte Carlo Wave-function method (MCWF), and Stochastic Schroedinger Equations (SSE's). The methods MCWF and SSE's recently experienced a fast development both in their theoretical background and applications to the study of the dissipative quantum systems dynamics in quantum optics. Even though these alternatives can be shown to be formally equivalent to the master equation approach, they are often regarded as mathematical tricks, with no relation to a concrete physical evolution of the system. The advantage of using them is that one has to deal with state vectors, instead of density matrices, thus reducing the total amount of matrix elements to be calculated. In this work, we consider the possibility of giving a physical interpretation to these methods, in terms of continuous measurements made on the evolving system. We show that physical realizations of the two methods are indeed possible, for a mode of the electromagnetic field in a cavity interacting with a continuum of modes corresponding to the field outside the cavity. Two schemes are proposed, consisting of a mode of the electromagnetic field interacting with a beam of Rydberg two-level atoms. In these schemes, the field mode plays the role of a small system and the atomic beam plays the role of a reservoir (infinitely larger number of degrees of freedom at finite temperature, the interaction between them being given by the Jaynes-Cummings model
Probing quantum coherence in single-atom electron spin resonance
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
Quantum speed limit time in a magnetic resonance
Ivanchenko, E. A.
2017-12-01
A visualization for dynamics of a qudit spin vector in a time-dependent magnetic field is realized by means of mapping a solution for a spin vector on the three-dimensional spherical curve (vector hodograph). The obtained results obviously display the quantum interference of precessional and nutational effects on the spin vector in the magnetic resonance. For any spin the bottom bounds of the quantum speed limit time (QSL) are found. It is shown that the bottom bound goes down when using multilevel spin systems. Under certain conditions the non-nil minimal time, which is necessary to achieve the orthogonal state from the initial one, is attained at spin S = 2. An estimation of the product of two and three standard deviations of the spin components are presented. We discuss the dynamics of the mutual uncertainty, conditional uncertainty and conditional variance in terms of spin standard deviations. The study can find practical applications in the magnetic resonance, 3D visualization of computational data and in designing of optimized information processing devices for quantum computation and communication.
A Magnetic Resonance Force Microscopy Quantum Computer with Tellurium Donors in Silicon
Berman, G. P.; Doolen, G. D.; Tsifrinovich, V. I.
2000-01-01
We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines the well-developed silicon technology with expected advances in MRFM.
International Nuclear Information System (INIS)
Shen Jianqi; Zeng Ruixi
2017-01-01
Quantum-dot-molecular phase coherence (and the relevant quantum-interference-switchable optical response) can be utilized to control electromagnetic wave propagation via a gate voltage, since quantum-dot molecules can exhibit an effect of quantum coherence (phase coherence) when quantum-dot-molecular discrete multilevel transitions are driven by an electromagnetic wave. Interdot tunneling of carriers (electrons and holes) controlled by the gate voltage can lead to destructive quantum interference in a quantum-dot molecule that is coupled to an incident electromagnetic wave, and gives rise to a quantum coherence effect (e.g., electromagnetically induced transparency, EIT) in a quantum-dot-molecule dielectric film. The tunable on- and off-resonance tunneling effect of an incident electromagnetic wave (probe field) through such a quantum-coherent quantum-dot-molecule dielectric film is investigated. It is found that a high gate voltage can lead to the EIT phenomenon of the quantum-dot-molecular systems. Under the condition of on-resonance light tunneling through the present quantum-dot-molecule dielectric film, the probe field should propagate without loss if the probe frequency detuning is zero. Such an effect caused by both EIT and resonant tunneling, which is sensitive to the gate voltage, can be utilized for designing devices such as photonic switching, transistors, and logic gates. (author)
International Nuclear Information System (INIS)
Phillips, S.
1985-01-01
An alternative formulation of path-integral quantization for gauge theories is proposed in which the gauge-fixing condition, normally imposed on just the gauge field itself, is imposed on the gauge-transformed gauge field, a continuous sum now being included over all configurations of the transformation field, Λ(x) that satisfy the gauge condition. It is shown, by explicit calculation, that when bilinear counterterms in the Lagrangian field density are included so as to render the two-point gauge- and fermion-field Green's functions finite, the fermion-fermion-gauge-field Green's function is divergence free. Unlike the more conventional approaches, there is no divergent vertex counterterm needed. Furthermore, the form of the fermion counterterm is a simple mass insertion only. There is no need for a divergent fermion wave-function renormalization. The cancellation of the divergences that are normally present is accomplished by the effect of, heretofor uncommon in perturbative quantum-field theory, infrared-divergent integrals. It is argued heuristically how these may be regulated by the same parameter, Λ, that is used for ultraviolet-divergent integrals, where now the cutoff is towards the lower limit of integration
International Nuclear Information System (INIS)
Horing, Norman J Morgenstern; Popov, Vyacheslav V
2006-01-01
Recent experimental observations by X.G. Peralta and S.J. Allen, et al. of dc photoconductivity resonances in steady source-drain current subject to terahertz radiation in a grid-gated double-quantum well FET suggested an association with plasmon resonances. This association was definitively confirmed for some parameter ranges in our detailed electrodynamic absorbance calculations. In this paper we propose that the reason that the dc photoconductance resonances match the plasmon resonances in semiconductors is based on a nonlinear dynamic screening mechanism. In this, we employ a shielded potential approximation that is nonlinear in the terahertz field to determine the nonequilibrium Green's function and associated density perturbation that govern the nonequilibrium dielectric polarization of the medium. This 'conditioning' of the system by the incident THz radiation results in resonant polarization response at the plasmon frequencies which, in turn, causes a sharp drop of the resistive shielded impurity scattering potentials and attendant increase of the dc source-drain current. This amounts to disabling the impurity scattering mechanism by plasmon resonant behavior in nonlinear screening
Controlling chaos-assisted directed transport via quantum resonance.
Tan, Jintao; Zou, Mingliang; Luo, Yunrong; Hai, Wenhua
2016-06-01
We report on the first demonstration of chaos-assisted directed transport of a quantum particle held in an amplitude-modulated and tilted optical lattice, through a resonance-induced double-mean displacement relating to the true classically chaotic orbits. The transport velocity is controlled by the driving amplitude and the sign of tilt, and also depends on the phase of the initial state. The chaos-assisted transport feature can be verified experimentally by using a source of single atoms to detect the double-mean displacement one by one, and can be extended to different scientific fields.
Controlling chaos-assisted directed transport via quantum resonance
Energy Technology Data Exchange (ETDEWEB)
Tan, Jintao; Zou, Mingliang; Luo, Yunrong; Hai, Wenhua, E-mail: whhai2005@aliyun.com [Department of Physics and Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha 410081, China and Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha 410081 (China)
2016-06-15
We report on the first demonstration of chaos-assisted directed transport of a quantum particle held in an amplitude-modulated and tilted optical lattice, through a resonance-induced double-mean displacement relating to the true classically chaotic orbits. The transport velocity is controlled by the driving amplitude and the sign of tilt, and also depends on the phase of the initial state. The chaos-assisted transport feature can be verified experimentally by using a source of single atoms to detect the double-mean displacement one by one, and can be extended to different scientific fields.
Energy Technology Data Exchange (ETDEWEB)
Li, Jiahua [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Key Laboratory of Fundamental Physical Quantities Measurement of Ministry of Education, Wuhan 430074 (China); Yu, Rong, E-mail: yurong321@126.com [School of Science, Hubei Province Key Laboratory of Intelligent Robot, Wuhan Institute of Technology, Wuhan 430073 (China); Ma, Jinyong; Wu, Ying, E-mail: yingwu2@163.com [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)
2014-10-28
The ability to engineer and convert photons between different modes in a solid-state approach has extensive technological implications not only for classical communication systems but also for future quantum networks. In this paper, we put forward a scheme for coherent mode conversion of optical photons by utilizing the intermediate coupling between a single quantum dot and a bimodal photonic crystal microcavity via a waveguide. Here, one mode of the photonic crystal microcavity is coherently driven by an external single-frequency continuous-wave laser field and the two cavity modes are not coupled to each other due to their orthogonal polarizations. The undriven cavity mode is thus not directly coupled to the input driving laser and the only way it can get light is via the quantum dot. The influences of the system parameters on the photon-conversion efficiency are analyzed in detail in the limit of weak probe field and it is found that high photon-conversion efficiency can be achieved under appropriate conditions. It is shown that the cavity dark mode, which is a superposition of the two optical modes and is decoupled from the quantum dot, can appear in such a hybrid optical system. We discuss the properties of the dark mode and indicate that the formation of the dark mode enables the efficient transfer of optical fields between the two cavity modes.
Inner products of resonance solutions in 1D quantum barriers
Energy Technology Data Exchange (ETDEWEB)
Julve, J [IFF, Consejo Superior de Investigaciones CientIficas, Serrano 113 bis, Madrid 28006 (Spain); De Urries, F J, E-mail: julve@imaff.cfmac.csic.e, E-mail: fernando.urries@uah.e [Departamento de Fisica, Universidad de Alcala de Henares, Alcala de Henares, Madrid (Spain)
2010-04-30
The properties of a prescription for the inner products of resonance (Gamow states), scattering (Dirac kets) and bound states for one-dimensional quantum barriers are worked out. The divergent asypmtotic behaviour of the Gamow states is regularized using a Gaussian convergence factor first introduced by Zel'dovich. With this prescription, most of these states (with discrete complex energies) are found to be orthogonal to each other and to the Dirac kets, except when they are neighbours, in which case the inner product is divergent. Therefore, as it happens for the continuum scattering states, the norm of the resonant ones remains non-calculable. Thus, they exhibit properties halfway between the (continuum real) Dirac-{delta} orthogonality and the (discrete real) Kronecker-{delta} orthogonality of the bound states.
Introduction to Electrodynamics
Griffiths, David J.
2017-06-01
1. Vector analysis; 2. Electrostatics; 3. Potentials; 4. Electric fields in matter; 5. Magnetostatics; 6. Magnetic fields in matter; 7. Electrodynamics; 8. Conservation laws; 9. Electromagnetic waves; 10. Potentials and fields; 11. Radiation; 12. Electrodynamics and relativity; Appendix A. Vector calculus in curvilinear coordinates; Appendix B. The Helmholtz theorem; Appendix C. Units; Index.
Quantum ground state and single-phonon control of a mechanical resonator.
O'Connell, A D; Hofheinz, M; Ansmann, M; Bialczak, Radoslaw C; Lenander, M; Lucero, Erik; Neeley, M; Sank, D; Wang, H; Weides, M; Wenner, J; Martinis, John M; Cleland, A N
2010-04-01
Quantum mechanics provides a highly accurate description of a wide variety of physical systems. However, a demonstration that quantum mechanics applies equally to macroscopic mechanical systems has been a long-standing challenge, hindered by the difficulty of cooling a mechanical mode to its quantum ground state. The temperatures required are typically far below those attainable with standard cryogenic methods, so significant effort has been devoted to developing alternative cooling techniques. Once in the ground state, quantum-limited measurements must then be demonstrated. Here, using conventional cryogenic refrigeration, we show that we can cool a mechanical mode to its quantum ground state by using a microwave-frequency mechanical oscillator-a 'quantum drum'-coupled to a quantum bit, which is used to measure the quantum state of the resonator. We further show that we can controllably create single quantum excitations (phonons) in the resonator, thus taking the first steps to complete quantum control of a mechanical system.
International Nuclear Information System (INIS)
Erber, T.; Hammerling, P.; Hockney, G.; Porrati, M.; Putterman, S.; La Jolla Institute, La Jolla, California 92037; Department of Physics, University of California, Los Angeles, California 90024)
1989-01-01
When a single trapped 198 Hg + ion is illuminated by two lasers, each tuned to an approximate transition, the resulting fluorescence switches on and off in a series of pulses resembling a bistable telegraph. This intermittent fluorescence can also be obtained by optical pumping with a single laser. Quantum jumps between successive atomic levels may be traced directly with multiple-resonance fluorescence. Atomic transition rates and photon antibunching distributions can be inferred from the pulse statistics and compared with quantum theory. Stochastic tests also indicate that the quantum telegraphs are good random number generators. During periods when the fluorescence is switched off, the radiationless atomic currents that generate the telegraph signals can be adjusted by varying the laser illumination: if this coherent evolution of the wave functions is sustained over sufficiently long time intervals, novel interactive precision measurements, near the limits of the time-energy uncertainty relations, are possible. Copyright 1989 Academic Press, Inc
Some double resonance and multiple quantum NMR studies in solids
Energy Technology Data Exchange (ETDEWEB)
Wemmer, D.E.
1978-08-01
The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of /sup 13/C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D/sub 2/O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, ..delta..sigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO/sub 3/.D/sub 2/O, ..cap alpha..,..beta.. d-2 HMB and ..cap alpha..,..beta..,..gamma.. d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules ..delta..m = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made.
Some double resonance and multiple quantum NMR studies in solids
International Nuclear Information System (INIS)
Wemmer, D.E.
1978-08-01
The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of 13 C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D 2 O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, Δsigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO 3 .D 2 O, α,β d-2 HMB and α,β,γ d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules Δm = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made
Baskin, Lev; Plamenevskii, Boris; Sarafanov, Oleg
2015-01-01
This volume studies electron resonant tunneling in two- and three-dimensional quantum waveguides of variable cross-sections in the time-independent approach. Mathematical models are suggested for the resonant tunneling and develop asymptotic and numerical approaches for investigating the models. Also, schemes are presented for several electronics devices based on the phenomenon of resonant tunneling. Devices based on the phenomenon of electron resonant tunneling are widely used in electronics. Efforts are directed towards refining properties of resonance structures. There are prospects for building new nanosize electronics elements based on quantum dot systems. However, the role of resonance structure can also be given to a quantum wire of variable cross-section. Instead of an "electrode - quantum dot - electrode" system, one can use a quantum wire with two narrows. A waveguide narrow is an effective potential barrier for longitudinal electron motion along a waveguide. The part of the waveguide between ...
Energy Technology Data Exchange (ETDEWEB)
Lalanne, D.
1970-07-17
The experiment we have performed on the ACO (Orsay Collider Ring) is one of the most accurate tests of quantum electrodynamics over very short interaction distances (10{sup -14} cm). We have studied the electron-positron elastic scattering at very wide angle. This work is divided into 4 parts. The first part reviews recent tests of quantum electrodynamics and presents the electron-positron elastic scattering. The second part describes the measurement of brightness: the experimental device, data analysis and accuracy. The measurement of brightness has been performed by detecting the photons emitted in the double Bremsstrahlung reaction: e{sup +}e{sup -} → e{sup +}e{sup -}γγ. The third part deals with the measurement of the number of Bhabha events. The last part compares the experimental value of the Bhabha scattering with the theoretically expected value. We have got the following results: the number of Bhabha events: 757 events, the experimental value for Bhabha scattering cross-section: [1.97 ± 0.09 (stat.) ± 0.10 (syst.)]*10{sup -31} cm{sup 2}. The comparison of this experimental value with the expected value has allowed us to set the lower limit of the cutting parameter Λ: Λ > 2 GeV.
Excited states in stochastic electrodynamics
International Nuclear Information System (INIS)
Franca, H.M.; Marshall, T.W.
1987-12-01
It is shown that the set of Wigner functions associated with the excited states of the harmonic oscillator constitute a complete set of functions over the phase space. An arbitraty distribution can be expanded in terms of these Wigner functions. By studying the time evolution, according to Stochastic Electrodynamics, of the expansion coefficients, becomes feasible to separate explicity the contributionsof the radiative reaction and the vaccuum field to the Einsten. A coefficients for this system. A simple semiclassical explanation of the Weisskopf-Heitler phenomenon in resonance fluorescence is also supplied. (author) [pt
Quantum interference in the system of Lorentzian and Fano magnetoexciton resonances in GaAs
International Nuclear Information System (INIS)
Siegner, U.; Mycek, M.; Glutsch, S.; Chemla, D.S.
1995-01-01
Using femtosecond four-wave mixing (FWM), we study the coherent dynamics of Lorentzian and Fano magnetoexciton resonances in GaAs. For unperturbed Lorentzian magnetoexcitons, we find that the time-integrated FWM signal decays due to dephasing processes as expected for Lorentzian resonances. The time-integrated FWM signal from a single Fano magnetoexciton resonance, however, decays quasi-instantaneously although the dephasing time of the Fano resonance is much longer than the time resolution of the experiment. This fast decay is the manifestation of destructive quantum interference. Although destructive quantum interference in our system is closely related to the dynamics of Fano resonances, for the simultaneous excitation of Lorentzian and Fano magnetoexciton resonances destructive quantum interference also strongly affects the dynamics of Lorentzian magnetoexcitons due to quantum-mechanical coupling between the two types of resonances
Kumar, Vinay
2016-01-01
The present book entitled Concepts of Electrodynamics meets the demand of students of all engineering, graduate, honours and postgraduate courses in a single volume. This book covers all the topics on electrodynamics as per the new syllabus prescribed by UGC and AICTE and we do hope that this book will revive interest in the study of various topics on electrodynamics which will carries the reader to a high level of understanding. The text is enriched with a large number of solved examples apart from appropriate illustrations and examples in each chapter.
Nanoscale constrictions in superconducting coplanar waveguide resonators
Energy Technology Data Exchange (ETDEWEB)
Jenkins, Mark David; Naether, Uta; Ciria, Miguel; Zueco, David; Luis, Fernando, E-mail: fluis@unizar.es [Instituto de Ciencia de Materiales de Aragón, CSIC—Universidad de Zaragoza, 50009 Zaragoza (Spain); Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Sesé, Javier [Instituto de Nanociencia de Aragón, Universidad de Zaragoza, E-50009 Zaragoza (Spain); Departamento de Física de la Materia Condensada, Universidad de Zaragoza, 50009 Zaragoza (Spain); Atkinson, James; Barco, Enrique del [Department of Physics, University of Central Florida, Orlando, Florida 32816 (United States); Sánchez-Azqueta, Carlos [Dpto. de Ingeniería Electrónica y Telecomunicaciones, Universidad de Zaragoza, 50009 Zaragoza (Spain); Majer, Johannes [Vienna Center for Quantum Science and Technology, Atominstitut, TU Wien, 1020 Vienna (Austria)
2014-10-20
We report on the design, fabrication, and characterization of superconducting coplanar waveguide resonators with nanoscopic constrictions. By reducing the size of the center line down to 50 nm, the radio frequency currents are concentrated and the magnetic field in its vicinity is increased. The device characteristics are only slightly modified by the constrictions, with changes in resonance frequency lower than 1% and internal quality factors of the same order of magnitude as the original ones. These devices could enable the achievement of higher couplings to small magnetic samples or even to single molecular spins and have applications in circuit quantum electrodynamics, quantum computing, and electron paramagnetic resonance.
Magnetic resonance force microscopy quantum computer with tellurium donors in silicon.
Berman, G P; Doolen, G D; Hammel, P C; Tsifrinovich, V I
2001-03-26
We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines well-developed silicon technology and expected advances in MRFM. Our proposal does not use electrostatic gates to realize quantum logic operations.
Magnetic Resonance Force Microscopy Quantum Computer with Tellurium Donors in Silicon
International Nuclear Information System (INIS)
Berman, G. P.; Doolen, G. D.; Hammel, P. C.; Tsifrinovich, V. I.
2001-01-01
We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines well-developed silicon technology and expected advances in MRFM. Our proposal does not use electrostatic gates to realize quantum logic operations
Foundations of electrodynamics
Moon, Parry
2013-01-01
Advanced undergraduate text presupposes some knowledge of electricity and magnetism, making substantial use of vector analysis. A serious development of electrodynamics on a postulational basis that clearly defines each concept. 1960 edition.
Quantum resonances in a single plaquette of Josephson junctions: excitations of Rabi oscillations
Fistul, M. V.
2001-01-01
We present a theoretical study of a quantum regime of the resistive (whirling) state of dc driven anisotropic single plaquette containing three small Josephson junctions. The current-voltage characteristics of such a system display resonant steps that are due to the resonant interaction between the time dependent Josephson current and the excited electromagnetic oscillations (EOs). The voltage positions of the resonances are determined by the quantum interband transitions of EOs. We show that...
International Nuclear Information System (INIS)
Boyer, T.H.
1975-01-01
The theory of classical electrodynamics with classical electromagnetic zero-point radiation is outlined here under the title random electrodynamics. The work represents a reanalysis of the bounds of validity of classical electron theory which should sharpen the understanding of the connections and distinctions between classical and quantum theories. The new theory of random electrodynamics is a classical electron theory involving Newton's equations for particle motion due to the Lorentz force, and Maxwell's equations for the electromagnetic fields with point particles as sources. However, the theory departs from the classical electron theory of Lorentz in that it adopts a new boundary condition on Maxwell's equations. It is assumed that the homogeneous boundary condition involves random classical electromagnetic radiation with a Lorentz-invariant spectrum, classical electromagnetic zero-point radiation. The implications of random electrodynamics for atomic structure, atomic spectra, and particle-interference effects are discussed on an order-of-magnitude or heuristic level. Some detailed mathematical connections and some merely heuristic connections are noted between random electrodynamics and quantum theory. (U.S.)
Programmable quantum-state discriminator by nuclear magnetic resonance
International Nuclear Information System (INIS)
Gopinath, T.; Das, Ranabir; Kumar, Anil
2005-01-01
A programmable quantum-state discriminator is implemented by using nuclear magnetic resonance. We use a two-qubit spin-1/2 system, one for the data qubit and one for the ancilla (program) qubit. This device does the unambiguous (error-free) discrimination of a pair of states of the data qubit that are symmetrically located about a fixed state. The device is used to discriminate both linearly polarized states and elliptically polarized states. The maximum probability of successful discrimination is achieved by suitably preparing the ancilla qubit. It is also shown that the probability of discrimination depends on the angle of the unitary operator of the protocol and ellipticity of the data qubit state
Nuclear-magnetic-resonance quantum calculations of the Jones polynomial
International Nuclear Information System (INIS)
Marx, Raimund; Spoerl, Andreas; Pomplun, Nikolas; Schulte-Herbrueggen, Thomas; Glaser, Steffen J.; Fahmy, Amr; Kauffman, Louis; Lomonaco, Samuel; Myers, John M.
2010-01-01
The repertoire of problems theoretically solvable by a quantum computer recently expanded to include the approximate evaluation of knot invariants, specifically the Jones polynomial. The experimental implementation of this evaluation, however, involves many known experimental challenges. Here we present experimental results for a small-scale approximate evaluation of the Jones polynomial by nuclear magnetic resonance (NMR); in addition, we show how to escape from the limitations of NMR approaches that employ pseudopure states. Specifically, we use two spin-1/2 nuclei of natural abundance chloroform and apply a sequence of unitary transforms representing the trefoil knot, the figure-eight knot, and the Borromean rings. After measuring the nuclear spin state of the molecule in each case, we are able to estimate the value of the Jones polynomial for each of the knots.
Solid-state nuclear-spin quantum computer based on magnetic resonance force microscopy
International Nuclear Information System (INIS)
Berman, G. P.; Doolen, G. D.; Hammel, P. C.; Tsifrinovich, V. I.
2000-01-01
We propose a nuclear-spin quantum computer based on magnetic resonance force microscopy (MRFM). It is shown that an MRFM single-electron spin measurement provides three essential requirements for quantum computation in solids: (a) preparation of the ground state, (b) one- and two-qubit quantum logic gates, and (c) a measurement of the final state. The proposed quantum computer can operate at temperatures up to 1 K. (c) 2000 The American Physical Society
Quantum resonances in a single plaquette of Josephson junctions: excitations of Rabi oscillations
Fistul, M. V.
2002-03-01
We present a theoretical study of a quantum regime of the resistive (whirling) state of dc driven anisotropic single plaquette containing small Josephson junctions. The current-voltage characteristics of such systems display resonant steps that are due to the resonant interaction between the time dependent Josephson current and the excited electromagnetic oscillations (EOs). The voltage positions of the resonances are determined by the quantum interband transitions of EOs. We show that in the quantum regime as the system is driven on the resonance, coherent Rabi oscillations between the quantum levels of EOs occur. At variance with the classical regime the magnitude and the width of resonances are determined by the frequency of Rabi oscillations that in turn, depends in a peculiar manner on an externally applied magnetic field and the parameters of the system.
Axiomatic electrodynamics and microscopic mechanics
International Nuclear Information System (INIS)
Yussouff, M.
1981-04-01
A new approach to theoretical physics, along with the basic formulation of a new MICROSCOPIC MECHANICS for the motion of small charged particles is described in this set of lecture notes. Starting with the classical (Newtonian) mechanics and classical fields, the important but well known properties of Classical Electromagnetic field are discussed up to section 4. The next nection describes the usual radiation damping theory and its difficulties. It is argued that the usual treatment of radiation damping is not valid for small space and time intervals and the true description of motion requires a new type of mechanics - the MICROSCOPIC MECHANICS: Section 6 and 7 are devoted to showing that not only the new microscopic mechanics goes over to Newtonian mechanics in the proper limit, but also it is closely connected with Quantum Mechanics. All the known results of the Schroedinger theory can be reproduced by microscopic mechanics which also gives a clear physical picture. It removes Einstein's famous objections against Quantum Theory and provides a clear distinction between classical and Quantum behavior. Seven Axioms (three on Classical Mechanics, two for Maxwell's theory, one for Relativity and a new Axiom on Radiation damping) are shown to combine Classical Mechanics, Maxwellian Electrodynamics, Relativity and Schroedinger's Quantum Theory within a single theoretical framework under Microscopic Mechanics which awaits further development at the present time. (orig.)
Scalable quantum memory in the ultrastrong coupling regime.
Kyaw, T H; Felicetti, S; Romero, G; Solano, E; Kwek, L-C
2015-03-02
Circuit quantum electrodynamics, consisting of superconducting artificial atoms coupled to on-chip resonators, represents a prime candidate to implement the scalable quantum computing architecture because of the presence of good tunability and controllability. Furthermore, recent advances have pushed the technology towards the ultrastrong coupling regime of light-matter interaction, where the qubit-resonator coupling strength reaches a considerable fraction of the resonator frequency. Here, we propose a qubit-resonator system operating in that regime, as a quantum memory device and study the storage and retrieval of quantum information in and from the Z2 parity-protected quantum memory, within experimentally feasible schemes. We are also convinced that our proposal might pave a way to realize a scalable quantum random-access memory due to its fast storage and readout performances.
Radiative corrections in bumblebee electrodynamics
Directory of Open Access Journals (Sweden)
R.V. Maluf
2015-10-01
Full Text Available We investigate some quantum features of the bumblebee electrodynamics in flat spacetimes. The bumblebee field is a vector field that leads to a spontaneous Lorentz symmetry breaking. For a smooth quadratic potential, the massless excitation (Nambu–Goldstone boson can be identified as the photon, transversal to the vacuum expectation value of the bumblebee field. Besides, there is a massive excitation associated with the longitudinal mode and whose presence leads to instability in the spectrum of the theory. By using the principal-value prescription, we show that no one-loop radiative corrections to the mass term is generated. Moreover, the bumblebee self-energy is not transverse, showing that the propagation of the longitudinal mode cannot be excluded from the effective theory.
Electrodynamic thermogravimetric analyzer
International Nuclear Information System (INIS)
Spjut, R.E.; Bar-Ziv, E.; Sarofim, A.F.; Longwell, J.P.
1986-01-01
The design and operation of a new device for studying single-aerosol-particle kinetics at elevated temperatures, the electrodynamic thermogravimetric analyzer (EDTGA), was examined theoretically and experimentally. The completed device consists of an electrodynamic balance modified to permit particle heating by a CO 2 laser, temperature measurement by a three-color infrared-pyrometry system, and continuous weighing by a position-control system. In this paper, the position-control, particle-weight-measurement, heating, and temperature-measurement systems are described and their limitations examined
Gate-controlled quantum collimation in nanocolumn resonant tunnelling transistors
International Nuclear Information System (INIS)
Wensorra, J; Lepsa, M I; Trellenkamp, S; Moers, J; Lueth, H; Indlekofer, K M
2009-01-01
Nanoscaled resonant tunneling transistors (RTT) based on MBE-grown GaAs/AlAs double-barrier quantum well (DBQW) structures have been fabricated by a top-down approach using electron-beam lithographic definition of the vertical nanocolumns. In the preparation process, a reproducible mask alignment accuracy of below 10 nm has been achieved and the all-around metal gate at the level of the DBQW structure has been positioned at a distance of about 20 nm relative to the semiconductor nanocolumn. Due to the specific doping profile n ++ /i/n ++ along the transistor nanocolumn, a particular confining potential is established for devices with diameters smaller than 70 nm, which causes a collimation effect of the propagating electrons. Under these conditions, room temperature optimum performance of the nano-RTTs is achieved with peak-to-valley current ratios above 2 and a peak current swing factor of about 6 for gate voltages between -6 and +6 V. These values indicate that our nano-RTTs can be successfully used in low power fast nanoelectronic circuits.
Quantum and classical control of single photon states via a mechanical resonator
International Nuclear Information System (INIS)
Basiri-Esfahani, Sahar; Myers, Casey R; Combes, Joshua; Milburn, G J
2016-01-01
Optomechanical systems typically use light to control the quantum state of a mechanical resonator. In this paper, we propose a scheme for controlling the quantum state of light using the mechanical degree of freedom as a controlled beam splitter. Preparing the mechanical resonator in non-classical states enables an optomechanical Stern–Gerlach interferometer. When the mechanical resonator has a small coherent amplitude it acts as a quantum control, entangling the optical and mechanical degrees of freedom. As the coherent amplitude of the resonator increases, we recover single photon and two-photon interference via a classically controlled beam splitter. The visibility of the two-photon interference is particularly sensitive to coherent excitations in the mechanical resonator and this could form the basis of an optically transduced weak-force sensor. (paper)
International Nuclear Information System (INIS)
Reynaud, S.; Giacobino, S.; Zinn-Justin, J.
1997-01-01
This course is dedicated to present in a pedagogical manner the recent developments in peculiar fields concerned by quantum fluctuations: quantum noise in optics, light propagation through dielectric media, sub-Poissonian light generated by lasers and masers, quantum non-demolition measurements, quantum electrodynamics applied to cavities and electrical circuits involving superconducting tunnel junctions. (A.C.)
Efficient Computation of Transition State Resonances and Reaction Rates from a Quantum Normal Form
Schubert, Roman; Waalkens, Holger; Wiggins, Stephen
2006-01-01
A quantum version of a recent formulation of transition state theory in phase space is presented. The theory developed provides an algorithm to compute quantum reaction rates and the associated Gamov-Siegert resonances with very high accuracy. The algorithm is especially efficient for
Resonant coherent quantum tunneling of the magnetization of spin-systems: Spin-parity effects
Garcia-Pablos, D; Garcia, N; de Raedt, H.A.
1997-01-01
We perform quantum dynamical calculations to study the reversal of the magnetization for systems of a few the presence of an external magnetic field at T=0 and with no dissipation. Collective quantum tunneling of the magnetization is demonstrated to occur only for some specific resonant values of
Quantum delta-kicked rotor: the effect of amplitude noise on the quantum resonances
Brouard, S
2003-01-01
We study analytically the effect of amplitude noise on the quantum resonances of an atom optics realization of the delta-kicked rotor. Noise is shown to add a time growth to the 'deterministic' energy and to induce a time increasing spreading in the momentum distribution; exact results are given for both effects. The ballistic peaks characteristic of the noiseless distribution for particular initial conditions broaden and eventually vanish, whereas the associated quadratic growth of energy persists; at large times, the survival probability decays as t sup - sup 1. Moreover, the nonexponential 'localization' linked to different initial conditions is gradually destroyed. Features specific to Gaussian noise, white and coloured, are analysed. The feasibility of experimental tests of these effects is discussed.
Förster Resonance Energy Transfer between Quantum Dot Donors and Quantum Dot Acceptors
Directory of Open Access Journals (Sweden)
Kenny F. Chou
2015-06-01
Full Text Available Förster (or fluorescence resonance energy transfer amongst semiconductor quantum dots (QDs is reviewed, with particular interest in biosensing applications. The unique optical properties of QDs provide certain advantages and also specific challenges with regards to sensor design, compared to other FRET systems. The brightness and photostability of QDs make them attractive for highly sensitive sensing and long-term, repetitive imaging applications, respectively, but the overlapping donor and acceptor excitation signals that arise when QDs serve as both the donor and acceptor lead to high background signals from direct excitation of the acceptor. The fundamentals of FRET within a nominally homogeneous QD population as well as energy transfer between two distinct colors of QDs are discussed. Examples of successful sensors are highlighted, as is cascading FRET, which can be used for solar harvesting.
Förster Resonance Energy Transfer between Quantum Dot Donors and Quantum Dot Acceptors
Chou, Kenny F.; Dennis, Allison M.
2015-01-01
Förster (or fluorescence) resonance energy transfer amongst semiconductor quantum dots (QDs) is reviewed, with particular interest in biosensing applications. The unique optical properties of QDs provide certain advantages and also specific challenges with regards to sensor design, compared to other FRET systems. The brightness and photostability of QDs make them attractive for highly sensitive sensing and long-term, repetitive imaging applications, respectively, but the overlapping donor and acceptor excitation signals that arise when QDs serve as both the donor and acceptor lead to high background signals from direct excitation of the acceptor. The fundamentals of FRET within a nominally homogeneous QD population as well as energy transfer between two distinct colors of QDs are discussed. Examples of successful sensors are highlighted, as is cascading FRET, which can be used for solar harvesting. PMID:26057041
Limits of electrodynamics: paraphotons
International Nuclear Information System (INIS)
Okun, L.B.
1982-01-01
The paper discusses the accuracy with which electromagnetic interaction is studied at large distances. Possible deviations from standard electrodynamics are investigated. The consideration is carried out the framework of a model which contains two (para) photons, the mass of one of them being non-negligible
Problems of hadron electrodynamics
International Nuclear Information System (INIS)
Rekalo, M.P.
1989-01-01
Certain directions of hadron electrodynamics referring to testing symmetry properties relatively to C-, P- and T-transformations; determination of fundamental electromagnetic characteristics of hadrons as well as to clarifying the dynamics of electromagnetic processes in which hadrons participate are analyzed briefly. 52 refs
Causality in Classical Electrodynamics
Savage, Craig
2012-01-01
Causality in electrodynamics is a subject of some confusion, especially regarding the application of Faraday's law and the Ampere-Maxwell law. This has led to the suggestion that we should not teach students that electric and magnetic fields can cause each other, but rather focus on charges and currents as the causal agents. In this paper I argue…
Gauge equivalence of the electrodynamics of charged bosons
International Nuclear Information System (INIS)
Sohn, R.; Haller, K.
1977-01-01
The quantum electrodynamics of charged scalar and vector bosons is formulated in the Lorentz gauge, and the effect of the charged particle--photon interaction on the subsidiary condition is explicitly taken into account. The results are extensions of earlier work on spinor quantum electrodynamics, but the presence of seagull vertices and anomalous current commutators in the case of the charged bosons make the extensions nontrivial. An operator gauge transformation that encompasses equations of motion as well as the commutator algebra of the field operators is developed; it is used to transform the theory from the Lorentz gauge to the Coulomb gauge
Quantum logic gates generated by SC-charge qubits coupled to a resonator
International Nuclear Information System (INIS)
Obada, A-S F; Hessian, H A; Mohamed, A-B A; Homid, Ali H
2012-01-01
We propose some quantum logic gates by using SC-charge qubits coupled to a resonator to study two types of quantum operation. By applying a classical magnetic field with the flux, a simple rotation on the target qubit is generated. Single and two-qubit gates of quantum logic gates are realized. Two-qubit joint operations are firstly generated by applying a classical magnetic field with the flux, and secondly by applying a classical magnetic field with the flux when qubits are placed a quarter of the distance along the resonator. A short discussion of fidelity is given to prove the success of the operations in implementing these gates. (paper)
Quantum erasers and probing classifications of entanglement via nuclear magnetic resonance
International Nuclear Information System (INIS)
Teklemariam, G.; Fortunato, E.M.; Pravia, M.A.; Sharf, Y.; Havel, T.F.; Cory, D.G.; Bhattaharyya, A.; Hou, J.
2002-01-01
We report the implementation of two- and three-spin quantum erasers using nuclear magnetic resonance (NMR). Quantum erasers provide a means of manipulating quantum entanglement, an important resource for quantum information processing. Here, we first use a two-spin system to illustrate the essential features of quantum erasers. The extension to a three-spin 'disentanglement eraser' shows that entanglement in a subensemble can be recovered if a proper measurement of the ancillary system is carried out. Finally, we use the same pair of orthogonal decoherent operations used in quantum erasers to probe the two classes of entanglement in tripartite quantum systems: the Greenberger-Horne-Zeilinger state and the W state. A detailed presentation is given of the experimental decoherent control methods that emulate the loss of phase information in strong measurements, and the use of NMR decoupling techniques to implement partial trace operations
International Nuclear Information System (INIS)
Tian, Si-Cong; Tong, Cun-Zhu; Ning, Yong-Qiang; Qin, Li; Liu, Yun; Wan, Ren-Gang
2014-01-01
Optical spectroscopy, a powerful tool for probing and manipulating quantum dots (QDs), has been used to investigate the resonance fluorescence spectrum from linear triple quantum dot molecules controlled by tunneling, using atomic physics methods. Interesting features such as quenching and narrowing of the fluorescence are observed. In such molecules the tunneling between the quantum dots can also induce a dark state. The results are explained by the transition properties of the dressed states generated by the coupling of the laser and the tunneling. Unlike the atomic system, in such quantum dot molecules quantum coherence can be induced using tunneling, requiring no coupling lasers, which will allow tunneling controllable quantum dot molecules to be applied to quantum optics and photonics. (paper)
Resonance fluorescence revival in a voltage-controlled semiconductor quantum dot
Reigue, Antoine; Lemaître, Aristide; Gomez Carbonell, Carmen; Ulysse, Christian; Merghem, Kamel; Guilet, Stéphane; Hostein, Richard; Voliotis, Valia
2018-02-01
We demonstrate systematic resonance fluorescence recovery with near-unity emission efficiency in single quantum dots embedded in a charge-tunable device in a wave-guiding geometry. The quantum dot charge state is controlled by a gate voltage, through carrier tunneling from a close-lying Fermi sea, stabilizing the resonantly photocreated electron-hole pair. The electric field cancels out the charging/discharging mechanisms from nearby traps toward the quantum dots, responsible for the usually observed inhibition of the resonant fluorescence. Fourier transform spectroscopy as a function of the applied voltage shows a strong increase in the coherence time though not reaching the radiative limit. These charge controlled quantum dots can act as quasi-perfect deterministic single-photon emitters, with one laser pulse converted into one emitted single photon.
Sanz, A S; Miret-Artés, S
2005-01-01
The elastic resonant scattering of He atoms off the Cu(117) surface is fully described with the formalism of quantum trajectories provided by Bohmian mechanics. Within this theory of quantum motion, the concept of trapping is widely studied and discussed. Classically, atoms undergo impulsive collisions with the surface, and then the trapped motion takes place covering at least two consecutive unit cells. However, from a Bohmian viewpoint, atom trajectories can smoothly adjust to the equipotential energy surface profile in a sort of sliding motion; thus the trapping process could eventually occur within one single unit cell. In particular, both threshold and selective adsorption resonances are explained by means of this quantum trapping considering different space and time scales. Furthermore, a mapping between each region of the (initial) incoming plane wave and the different parts of the diffraction and resonance patterns can be easily established, an important issue only provided by a quantum trajectory formalism. (c) 2005 American Institute of Physics.
Time-dependent resonant tunnelling for parallel-coupled double quantum dots
International Nuclear Information System (INIS)
Dong Bing; Djuric, Ivana; Cui, H L; Lei, X L
2004-01-01
We derive the quantum rate equations for an Aharonov-Bohm interferometer with two vertically coupled quantum dots embedded in each of two arms by means of the nonequilibrium Green function in the sequential tunnelling regime. Based on these equations, we investigate time-dependent resonant tunnelling under a small amplitude irradiation and find that the resonant photon-assisted tunnelling peaks in photocurrent demonstrate a combination behaviour of Fano and Lorentzian resonances due to the interference effect between the two pathways in this parallel configuration, which is controllable by threading the magnetic flux inside this device
Quantum resonances of Landau damping in the electromagnetic response of metallic nanoslabs.
Castillo-López, S G; Makarov, N M; Pérez-Rodríguez, F
2018-05-15
The resonant quantization of Landau damping in far-infrared absorption spectra of metal nano-thin films is predicted within the Kubo formalism. Specifically, it is found that the discretization of the electromagnetic and electron wave numbers inside a metal nanoslab produces quantum nonlocal resonances well-resolved at slab thicknesses smaller than the electromagnetic skin depth. Landau damping manifests itself precisely as such resonances, tracing the spectral curve obtained within the semiclassical Boltzmann approach. For slab thicknesses much greater than the skin depth, the classical regime emerges. Here the results of the quantum model and the Boltzmann approach coincide. Our analytical study is in perfect agreement with corresponding numerical simulations.
Maxwell equations in conformal invariant electrodynamics
International Nuclear Information System (INIS)
Fradkin, E.S.; AN SSSR, Novosibirsk. Inst. Avtomatiki i Ehlektrometrii); Kozhevnikov, A.A.; Palchik, M.Ya.; Pomeransky, A.A.
1983-01-01
We consider a conformal invariant formulation of quantum electrodynamics. Conformal invariance is achieved with a specific mathematical construction based on the indecomposable representations of the conformal group associated with the electromagnetic potential and current. As a corolary of this construction modified expressions for the 3-point Green functions are obtained which both contain transverse parts. They make it possible to formulate a conformal invariant skeleton perturbation theory. It is also shown that the Euclidean Maxwell equations in conformal electrodynamics are manifestations of its kinematical structure: in the case of the 3-point Green functions these equations follow (up to constants) from the conformal invariance while in the case of higher Green functions they are equivalent to the equality of the kernels of the partial wave expansions. This is the manifestation of the mathematical fast of a (partial) equivalence of the representations associated with the potential, current and the field tensor. (orig.)
Nuclear magnetic resonance. Advanced concepts and applications to quantum materials
International Nuclear Information System (INIS)
Kohlrautz, Jonas
2017-01-01
In this thesis, three separate topics were presented. These include the development of novel experimental NMR methods and data analysis, as well as their application to current topics of condensed matter research. The first part concerns NMR at the highest magnetic fields, i.e., in time-dependent pulsed high-field magnets. After a discussion of consequences for NMR, a method to acquire broad spectra was presented. Here, an intensity-correction for off-resonance effects was applied and the Fourier transform was modified to use time-dependent base functions. Subsequently, the method was tested with a Knight shift measurement of metallic aluminum using a second compound as a shift reference. It could be shown that signal averaging of a weak signal is possible, even across multiple field pulses. Thus, in principle, the signal-to-noise ratio can always be increased at the cost of measurement time, despite the inherently limited reproducibility of subsequent field high-field pulses. In another set of experiments, the feasibility of T 1 measurements was shown. Here, a weak radio frequency field was used to perform an adiabatic inversion of the spin system in the time-dependent field. Ensuing small-angle RF pulses monitored the relaxation process. Using a mathematical model, T 1 was then determined. Finally, this method was applied for the investigation of the spin-dimer antiferromagnet SrCu 2 (BO 3 ) 2 . Evidence for a field-induced change in the ground state of the material was found. This appears to be the first convincing observation of a field-induced phenomenon with pulsed field NMR. It proves that nuclear magnetic resonance spectroscopy at the highest fields is able to produce unique insights into quantum materials. The second part of the thesis concerns NMR investigations and analysis of cuprate high-temperature superconductors in conventional static field measurements. Results on HgBa 2 CuO 4+δ for underdoped, optimally doped, and overdoped materials revealed
Nuclear magnetic resonance. Advanced concepts and applications to quantum materials
Energy Technology Data Exchange (ETDEWEB)
Kohlrautz, Jonas
2017-05-22
In this thesis, three separate topics were presented. These include the development of novel experimental NMR methods and data analysis, as well as their application to current topics of condensed matter research. The first part concerns NMR at the highest magnetic fields, i.e., in time-dependent pulsed high-field magnets. After a discussion of consequences for NMR, a method to acquire broad spectra was presented. Here, an intensity-correction for off-resonance effects was applied and the Fourier transform was modified to use time-dependent base functions. Subsequently, the method was tested with a Knight shift measurement of metallic aluminum using a second compound as a shift reference. It could be shown that signal averaging of a weak signal is possible, even across multiple field pulses. Thus, in principle, the signal-to-noise ratio can always be increased at the cost of measurement time, despite the inherently limited reproducibility of subsequent field high-field pulses. In another set of experiments, the feasibility of T{sub 1} measurements was shown. Here, a weak radio frequency field was used to perform an adiabatic inversion of the spin system in the time-dependent field. Ensuing small-angle RF pulses monitored the relaxation process. Using a mathematical model, T{sub 1} was then determined. Finally, this method was applied for the investigation of the spin-dimer antiferromagnet SrCu{sub 2}(BO{sub 3}){sub 2}. Evidence for a field-induced change in the ground state of the material was found. This appears to be the first convincing observation of a field-induced phenomenon with pulsed field NMR. It proves that nuclear magnetic resonance spectroscopy at the highest fields is able to produce unique insights into quantum materials. The second part of the thesis concerns NMR investigations and analysis of cuprate high-temperature superconductors in conventional static field measurements. Results on HgBa{sub 2}CuO{sub 4+δ} for underdoped, optimally doped, and
Plasmon resonance-induced photoluminescence enhancement of CdTe/Cds quantum dots thin films
Energy Technology Data Exchange (ETDEWEB)
Wang, Hongyu [Nanjing University of Posts and Telecommunications, Nanjing 210003 (China); National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Xu, Ling, E-mail: xuling@nju.edu.cn [National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Wu, Yangqing; Xu, Jun; Ma, Zhongyuan; Chen, Kunji [National Laboratory of Solid State Microstructure and School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China)
2016-11-30
Highlights: • CdTe/CdS quantum dots/Au nano-rods nano-composite films were fabricated. • PL intensity of the quantum dots films was enhanced due to Au nanorods. • Internal quantum efficiency increased due to localized surface plasmon resonance. • The lifetimes of quantum dots films decreased after interaction with Au nano-rods. - Abstract: CdTe/CdS quantum dots/Au nano-rods nano-composite films were fabricated on planar Si substrates. The optical properties of all samples were investigated and the corresponding simulations were studied. It was found that the photoluminescence intensity of the CdTe/CdS quantum dots films was enhanced about 9-fold after the incorporation of Au nano-rods, the internal quantum efficiency increased from 24.3% to 35.2% due to the localized surface plasmon resonance. The time-resolved luminescence decay curves showed that the lifetimes of CdTe/CdS quantum dots films decreased to 2.8 ns after interaction with Au nano-rods. The results of finite-difference time-domain simulation indicated that Au nano-rods induced the localization of electric field, which enhanced the PL intensity of quantum dots films in the vicinity of Au nano-rods.
Theoretical physics 3 electrodynamics
Nolting, Wolfgang
2016-01-01
This textbook offers a clear and comprehensive introduction to electrodynamics, one of the core components of undergraduate physics courses. It follows on naturally from the previous volumes in this series. The first part of the book describes the interaction of electric charges and magnetic moments by introducing electro- and magnetostatics. The second part of the book establishes deeper understanding of electrodynamics with the Maxwell equations, quasistationary fields and electromagnetic fields. All sections are accompanied by a detailed introduction to the math needed. Ideally suited to undergraduate students with some grounding in classical and analytical mechanics, the book is enhanced throughout with learning features such as boxed inserts and chapter summaries, with key mathematical derivations highlighted to aid understanding. The text is supported by numerous worked examples and end of chapter problem sets. About the Theoretical Physics series Translated from the renowned and highly successful Germa...
Electrodynamics an intensive course
Chaichian, Masud; Radu, Daniel; Tureanu, Anca
2016-01-01
This book is devoted to the fundamentals of classical electrodynamics, one of the most beautiful and productive theories in physics. A general survey on the applicability of physical theories shows that only few theories can be compared to electrodynamics. Essentially, all electric and electronic devices used around the world are based on the theory of electromagnetism. It was Maxwell who created, for the first time, a unified description of the electric and magnetic phenomena in his electromagnetic field theory. Remarkably, Maxwell’s theory contained in itself also the relativistic invariance of the special relativity, a fact which was discovered only a few decades later. The present book is an outcome of the authors’ teaching experience over many years in different countries and for different students studying diverse fields of physics. The book is intended for students at the level of undergraduate and graduate studies in physics, astronomy, engineering, applied mathematics and for researchers working ...
Nonlinear electrodynamics and cosmology
International Nuclear Information System (INIS)
Breton, Nora
2010-01-01
Nonlinear electrodynamics (NLED) generalizes Maxwell's theory for strong fields. When coupled to general relativity NLED presents interesting features like the non-vanishing of the trace of the energy-momentum tensor that leads to the possibility of violation of some energy conditions and of acting as a repulsive contribution in the Raychaudhuri equation. This theory is worth to study in cosmological and astrophysical situations characterized by strong electromagnetic and gravitational fields.
The Over-Barrier Resonant States and Multi-Channel Scattering in Multiple Quantum Wells
Directory of Open Access Journals (Sweden)
A Polupanov
2016-09-01
Full Text Available We demonstrate an explicit numerical method for accurate calculation of the scattering matrix and its poles, and apply this method to describe the multi-channel scattering in the multiple quantum-wells structures. The S-matrix is continued analytically to the unphysical region of complex energy values. Results of calculations show that there exist one or more S-matrix poles, corresponding to the over-barrier resonant states critical for the effect of the absolute reflection of holes in the energy range where only the heavy ones may propagate over barriers in a structure. Light- and heavy-hole states are described by the Luttinger Hamiltonian matrix. In contrast to the single quantum-well case, at some parameters of a multiple quantum-wells structure the number of S-matrix poles may exceed that of the absolute reflection peaks, and at different values of parameters the absolute reflection peak corresponds to different resonant states. The imaginary parts of the S-matrix poles and hence the lifetimes of resonant states as well as the widths of resonant peaks of absolute reflection depend drastically on the quantum-well potential depth. In the case of shallow quantum wells there is in fact a long-living over-barrier resonant hole state.
About many-quantum transitions in nuclear magnetic resonance
International Nuclear Information System (INIS)
Saganowski, S.
1982-01-01
A new method of NMR, in which the many-quantum transitions are observed is described. In the method some theoretical aspects of impulsed methods and two-dimensional NMR spectroscopy are taken into account what allows to observe indirectly many-quantum effects. (L.I.)
Energy Technology Data Exchange (ETDEWEB)
Matsuoka, Leo, E-mail: leo-matsuoka@hiroshima-u.ac.jp [Graduate School of Engineering, Hiroshima University, Kagamiyama, Higashi-Hiroshima, 739-8527 (Japan); Segawa, Etsuo [Graduate School of Information Sciences, Tohoku University, Aoba, Sendai 980-8579 (Japan); Yuki, Kenta [Graduate School of Engineering, Hiroshima University, Kagamiyama, Higashi-Hiroshima, 739-8527 (Japan); Konno, Norio [Department of Applied Mathematics, Faculty of Engineering, Yokohama National University, Hodogaya, Yokohama 240-8501 (Japan); Obata, Nobuaki [Graduate School of Information Sciences, Tohoku University, Aoba, Sendai 980-8579 (Japan)
2017-06-09
We performed a mathematical analysis of the time-dependent dynamics of a quantum-kicked rotor implemented in a diatomic molecule under the condition of ideal quantum resonance. We examined a model system featuring a diatomic molecule in a periodic train of terahertz pulses, regarding the molecule as a rigid rotor with the state-dependent transition moment and including the effect of the magnetic quantum number M. We derived the explicit expression for the asymptotic distribution of a rotational population by making the transition matrix correspondent with a sequence of ultraspherical polynomials. The mathematical results obtained were validated by numerical simulations. - Highlights: • The behavior of the molecular quantum-kicked rotor was mathematically investigated. • The matrix elements were made correspondent with the ultraspherical polynomials. • The explicit formula for asymptotic distribution was obtained. • Complete agreement with the numerical simulation was verified.
International Nuclear Information System (INIS)
Zhen-Gang, Shi; Xiong-Wen, Chen; Xi-Xiang, Zhu; Ke-Hui, Song
2009-01-01
This paper proposes a simple scheme for realizing one-qubit and two-qubit quantum gates as well as multiqubit entanglement based on dc-SQUID charge qubits through the control of their coupling to a 1D transmission line resonator (TLR). The TLR behaves effectively as a quantum data-bus mode of a harmonic oscillator, which has several practical advantages including strong coupling strength, reproducibility, immunity to 1/f noise, and suppressed spontaneous emission. In this protocol, the data-bus does not need to stay adiabatically in its ground state, which results in not only fast quantum operation, but also high-fidelity quantum information processing. Also, it elaborates the transfer process with the 1D transmission line. (general)
Electrodynamics in Arbitrary Reference Frames and in Arbitrary Material Media
International Nuclear Information System (INIS)
Horzela, A.; Kapuscik, E.; Widomski, M.
1999-01-01
Full text: The investigation of electromagnetic phenomena in material media still belongs to the most difficult tasks of electrodynamics. Complexity and variability of material media practically exclude effective applications of methods and computational techniques elaborated in the framework of standard microscopic electrodynamics with classical vacuum as a ground state. In order to obtain satisfactorily exact descriptions of electromagnetic properties of complex material media one is enforced to use methods and approximations which are difficult to control. Moreover, they usually break covariance properties and the results obtained are valid in one reference frame which choice remains subjective and model dependent. Some time ago we have proposed a reformulation of Maxwell electrodynamics which opens new ways in study of electromagnetic processes in material media. The formalism gets rid of assumptions characteristic for vacuum electrodynamics only and it avoids the usage of constitutive relations as primary relations put on quantities needed for a complete description of an electromagnetic system. Fundamental properties of all electromagnetic quantities are their uniquely defined transformation rules and their analysis allows to determine the possible relations between them. Within such a scheme it is possible to introduce constitutive relations which do not have analogies in macroscopic classical electrodynamics. They may be used in description of microscopic electromagnetic processes in a different way than it is done in the framework of quantum electrodynamics. (author)
Weng, Qianchun; An, Zhenghua; Zhang, Bo; Chen, Pingping; Chen, Xiaoshuang; Zhu, Ziqiang; Lu, Wei
2015-03-23
Low-noise single-photon detectors that can resolve photon numbers are used to monitor the operation of quantum gates in linear-optical quantum computation. Exactly 0, 1 or 2 photons registered in a detector should be distinguished especially in long-distance quantum communication and quantum computation. Here we demonstrate a photon-number-resolving detector based on quantum dot coupled resonant tunneling diodes (QD-cRTD). Individual quantum-dots (QDs) coupled closely with adjacent quantum well (QW) of resonant tunneling diode operate as photon-gated switches- which turn on (off) the RTD tunneling current when they trap photon-generated holes (recombine with injected electrons). Proposed electron-injecting operation fills electrons into coupled QDs which turn "photon-switches" to "OFF" state and make the detector ready for multiple-photons detection. With proper decision regions defined, 1-photon and 2-photon states are resolved in 4.2 K with excellent propabilities of accuracy of 90% and 98% respectively. Further, by identifying step-like photon responses, the photon-number-resolving capability is sustained to 77 K, making the detector a promising candidate for advanced quantum information applications where photon-number-states should be accurately distinguished.
Plasmonic resonances of nanoparticles from large-scale quantum mechanical simulations
Zhang, Xu; Xiang, Hongping; Zhang, Mingliang; Lu, Gang
2017-09-01
Plasmonic resonance of metallic nanoparticles results from coherent motion of its conduction electrons, driven by incident light. For the nanoparticles less than 10 nm in diameter, localized surface plasmonic resonances become sensitive to the quantum nature of the conduction electrons. Unfortunately, quantum mechanical simulations based on time-dependent Kohn-Sham density functional theory are computationally too expensive to tackle metal particles larger than 2 nm. Herein, we introduce the recently developed time-dependent orbital-free density functional theory (TD-OFDFT) approach which enables large-scale quantum mechanical simulations of plasmonic responses of metallic nanostructures. Using TD-OFDFT, we have performed quantum mechanical simulations to understand size-dependent plasmonic response of Na nanoparticles and plasmonic responses in Na nanoparticle dimers and trimers. An outlook of future development of the TD-OFDFT method is also presented.
Phase locking and quantum statistics in a parametrically driven nonlinear resonator
Hovsepyan, G. H.; Shahinyan, A. R.; Chew, Lock Yue; Kryuchkyan, G. Yu.
2016-01-01
We discuss phase-locking phenomena at low-level of quanta for parametrically driven nonlinear Kerr resonator (PDNR) in strong quantum regime. Oscillatory mode of PDNR is created in the process of a degenerate down-conversion of photons under interaction with a train of external Gaussian pulses. We calculate the Wigner functions of cavity mode showing two-fold symmetry in phase space and analyse formation of phase-locked states in the regular as well as the quantum chaotic regime.
Measurements of diffusion resonances for the atom optics quantum kicked rotor
International Nuclear Information System (INIS)
Williams, M E K; Sadgrove, M P; Daley, A J; Gray, R N C; Tan, S M; Parkins, A S; Christensen, N; Leonhardt, R
2004-01-01
We present experimental observations of diffusion resonances for the quantum kicked rotor with weak decoherence. Cold caesium atoms are subject to a pulsed standing wave of near-resonant light, with spontaneous emission providing environmental coupling. The mean energy as a function of the pulse period is determined during the late-time diffusion period for a constant probability of spontaneous emission. Structure in the late-time energy is seen to increase with physical kicking strength. The observed structure is related to Shepelyansky's predictions for the initial quantum diffusion rates
Indefinite metric and regularization of electrodynamics
International Nuclear Information System (INIS)
Gaudin, M.
1984-06-01
The invariant regularization of Pauli and Villars in quantum electrodynamics can be considered as deriving from a local and causal lagrangian theory for spin 1/2 bosons, by introducing an indefinite metric and a condition on the allowed states similar to the Lorentz condition. The consequences are the asymptotic freedom of the photon's propagator. We present a calcultion of the effective charge to the fourth order in the coupling as a function of the auxiliary masses, the theory avoiding all mass divergencies to this order [fr
Implications of rail electrodynamics
International Nuclear Information System (INIS)
Rolader, G.E.; Jamison, K.A.
1990-01-01
A model is developed to investigate possible effects of rail electrodynamics on the performance of railguns. This model describes the oscillatory nature of the rail motion in response to the Lorentz force and the compressive restoration force of material which is behind the rails. In this simple model the rails are found to oscillate with a frequency of β. The rail dynamic behavior induces local electric fields. The authors investigate the significance of these electric fields on stationary particles (lab frame) and on particles moving at the velocity of the plasma/projectile system (projectile frame)
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)
The Ups and Downs of Classical and Quantum Formulations of Magnetic Resonance
DEFF Research Database (Denmark)
Hanson, Lars G.
2015-01-01
in the connection between the seemingly very different classical and quantum descriptions. Such understanding is needed by students, authors, and lecturers, in particular. With limited complexity, the text introduces probabilistic classical and quantum mechanics with emphasis on similarities and differences......), which gives insight into the resonance phenomenon itself as well as spectral features resulting from intramolecular J-coupling of atomic nuclei. It is discussed how classical and quantum mechanics give rise to similar expectations for basic NMR and why a classical understanding is central....
Relaxation dynamics of a quantum emitter resonantly coupled to a metal nanoparticle
DEFF Research Database (Denmark)
Nerkararyan, K. V.; Bozhevolnyi, S. I.
2014-01-01
consequence of this relaxation process is that the emission, being largely determined by the MNP, comes out with a substantial delay. A large number of system parameters in our analytical description opens new possibilities for controlling quantum emitter dynamics. (C) 2014 Optical Society of America......The presence of a metal nanoparticle (MNP) near a quantum dipole emitter, when a localized surface plasmon mode is excited via the resonant coupling with an excited quantum dipole, dramatically changes the relaxation dynamics: an exponential decay changes to step-like behavior. The main physical...
Ultrafast spectral interferometry of resonant secondary emmission from semiconductor quantum wells
DEFF Research Database (Denmark)
Birkedal, Dan; Shah, Jagdeep
1999-01-01
Recent investigations of secondary emission from quantum well excitons follwing resonant excitation have demonstrated an intricate interplay of coherent Rayleigh scattering and incoherent luminescence. We have very recently demonstrated that it is possible to isolate and time resolve the coherent...... field associated with the Rayleigh component using ultrafast spectral interferometry, thus, obtaining substantial and new information of the nature of resonant secondary emission. Our findings demonstrate that Rayleigh scattering from static disorder is inherently a non-ergodic process invalidating...
The over-barrier resonant states and multi-channel scattering by a quantum well
Directory of Open Access Journals (Sweden)
Alexander F. Polupanov
2008-06-01
Full Text Available We demonstrate an explicit numerical method for accurate calculation ofthe analytic continuation of the scattering matrix, describing the multichannelscattering by a quantum well, to the unphysical region of complexvalues of the energy. Results of calculations show that one or severalpoles of the S-matrix exist, corresponding to the over-barrier resonantstates that are critical for the effect of the absolute reflection at scatteringof the heavy hole by a quantum well in the energy range where only theheavy hole may propagate over barriers in a quantum-well structure.Light- and heavy-hole states are described by the Luttinger Hamiltonianmatrix. The qualitative behaviour of the over-barrier scattering andresonant states is the same at variation of the shape of the quantum-wellpotential, however lifetimes of resonant states depend drastically on theshape and depth of a quantum well.
Resonant tunneling spectroscopy of valley eigenstates on a donor-quantum dot coupled system
Energy Technology Data Exchange (ETDEWEB)
Kobayashi, T., E-mail: t.kobayashi@unsw.edu.au; Heijden, J. van der; House, M. G.; Hile, S. J.; Asshoff, P.; Simmons, M. Y.; Rogge, S. [Centre for Quantum Computation and Communication Technology, University of New South Wales, Sydney 2052 New South Wales (Australia); Gonzalez-Zalba, M. F. [Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Vinet, M. [Université Grenoble-Alpes and CEA, LETI, MINATEC, 38000 Grenoble (France)
2016-04-11
We report on electronic transport measurements through a silicon double quantum dot consisting of a donor and a quantum dot. Transport spectra show resonant tunneling peaks involving different valley states, which illustrate the valley splitting in a quantum dot on a Si/SiO{sub 2} interface. The detailed gate bias dependence of double dot transport allows a first direct observation of the valley splitting in the quantum dot, which is controllable between 160 and 240 μeV with an electric field dependence 1.2 ± 0.2 meV/(MV/m). A large valley splitting is an essential requirement for implementing a physical electron spin qubit in a silicon quantum dot.
Photon echo quantum random access memory integration in a quantum computer
International Nuclear Information System (INIS)
Moiseev, Sergey A; Andrianov, Sergey N
2012-01-01
We have analysed an efficient integration of multi-qubit echo quantum memory (QM) into the quantum computer scheme based on squids, quantum dots or atomic resonant ensembles in a quantum electrodynamics cavity. Here, one atomic ensemble with controllable inhomogeneous broadening is used for the QM node and other nodes characterized by the homogeneously broadened resonant line are used for processing. We have found the optimal conditions for the efficient integration of the multi-qubit QM modified for the analysed scheme, and we have determined the self-temporal modes providing a perfect reversible transfer of the photon qubits between the QM node and arbitrary processing nodes. The obtained results open the way for realization of a full-scale solid state quantum computing based on the efficient multi-qubit QM. (paper)
Wilson Fermions and Axion Electrodynamics in Optical Lattices
International Nuclear Information System (INIS)
Bermudez, A.; Martin-Delgado, M. A.; Mazza, L.; Rizzi, M.; Goldman, N.; Lewenstein, M.
2010-01-01
We show that ultracold Fermi gases in optical superlattices can be used as quantum simulators of relativistic lattice fermions in 3+1 dimensions. By exploiting laser-assisted tunneling, we find an analogue of the so-called naive Dirac fermions, and thus provide a realization of the fermion doubling problem. Moreover, we show how to implement Wilson fermions, and discuss how their mass can be inverted by tuning the laser intensities. In this regime, our atomic gas corresponds to a phase of matter where Maxwell electrodynamics is replaced by axion electrodynamics: a 3D topological insulator.
Quantum Measurement Backaction and Upconverting Microwave Signals with Mechanical Resonators
Peterson, R. W.
The limits of optical measurement and control of mechanical motion are set by the quantum nature of light. The familiar shot noise limit can be avoided by increasing the optical power, but at high enough powers, the backaction of the randomly-arriving photons' radiation pressure can grow to become the dominant force on the system. This thesis will describe an experiment showing how backaction limits the laser cooling of macroscopic drumhead membranes, as well as work on how these membranes can be used to upconvert microwave signals to optical frequencies, potentially preserving the fragile quantum state of the upconverted signal.
Resonant Scattering of Surface Plasmon Polaritons by Dressed Quantum Dots
2014-06-23
t rel d‘ jð Þ;1 Rsp ne1 nh1 ; (5) where Rsp is the spontaneous emission rate, which should be calculated by using the Kubo -Martin-Schwinger...and should be calculated by including carrier-carrier and carrier-(optical) phonon interac- tions. Moreover, we know from Eq. (5) that the total...inside a quantum dot. In our numerical calculations , we chose the quantum dot dimensions as 210 Å and 100 Å along the x and y direc- tions
Mathematical concepts of quantum mechanics. 2. ed.
International Nuclear Information System (INIS)
Gustafson, Stephen J.; Sigal, Israel Michael
2011-01-01
The book gives a streamlined introduction to quantum mechanics while describing the basic mathematical structures underpinning this discipline. Starting with an overview of key physical experiments illustrating the origin of the physical foundations, the book proceeds with a description of the basic notions of quantum mechanics and their mathematical content. It then makes its way to topics of current interest, specifically those in which mathematics plays an important role. The more advanced topics presented include many-body systems, modern perturbation theory, path integrals, the theory of resonances, quantum statistics, mean-field theory, second quantization, the theory of radiation (non-relativistic quantum electrodynamics), and the renormalization group. With different selections of chapters, the book can serve as a text for an introductory, intermediate, or advanced course in quantum mechanics. The last four chapters could also serve as an introductory course in quantum field theory. (orig.)
Resonant amplification of quantum fluctuations in a spinor gas
DEFF Research Database (Denmark)
Topic, O.; Scherer, M.; Gebreyesus, G.
2010-01-01
Bose-Einstein condensates of atoms with non-zero spin are known to constitute an ideal system to investigate fundamental properties of magnetic superfluids. More recently it was realized that they also provide the fascinating opportunity to investigate the macroscopic amplification of quantum...
Quantum averaging and resonances: two-level atom in a one-mode classical laser field
Directory of Open Access Journals (Sweden)
M. Amniat-Talab
2007-06-01
Full Text Available We use a nonperturbative method based on quantum averaging and an adapted from of resonant transformations to treat the resonances of the Hamiltonian of a two-level atom interacting with a one-mode classical field in Floquet formalism. We illustrate this method by extraction of effective Hamiltonians of the system in two regimes of weak and strong coupling. The results obtained in the strong-coupling regime, are valid in the whole range of the coupling constant for the one-photon zero-field resonance.
Quantum limits on the time-bandwidth product of an optical resonator.
Tsang, Mankei
2018-01-01
A thought-provoking proposal by Tsakmakidis et al. [Science356, 1260 (2017)SCIEAS0036-807510.1126/science.aam6662] suggests that nonreciprocal optics can break a time-bandwidth limit to passive resonators. Here I quantize their resonator model and show that quantum mechanics does impose a limit, or requires extra noise to be added in the same fashion as amplified spontaneous emission in an active resonator. I also use thermodynamics to argue that extra dissipation or noise must be present in their proposed device.
Directory of Open Access Journals (Sweden)
Chien-Hao Lin
2015-09-01
Full Text Available In the present work, we report an investigation on quantum entanglement in the doubly excited 2s2 1Se resonance state of the positronium negative ion by using highly correlated Hylleraas type wave functions, determined by calculation of the density of resonance states with the stabilization method. Once the resonance wave function is obtained, the spatial (electron-electron orbital entanglement entropies (von Neumann and linear can be quantified using the Schmidt decomposition method. Furthermore, Shannon entropy in position space, a measure for localization (or delocalization for such a doubly excited state, is also calculated.
Rouxinol, Francisco; Hao, Hugo; Lahaye, Matt
2015-03-01
Quantum electromechanical systems incorporating superconducting qubits have received extensive interest in recent years due to their promising prospects for studying fundamental topics of quantum mechanics such as quantum measurement, entanglement and decoherence in new macroscopic limits, also for their potential as elements in technological applications in quantum information network and weak force detector, to name a few. In this presentation we will discuss ours efforts toward to devise an electromechanical circuit to strongly couple a nanomechanical resonator to a superconductor qubit, where a high voltage dc-bias is required, to study quantum behavior of a mechanical resonator. Preliminary results of our latest generation of devices integrating a superconductor qubit into a high-Q voltage biased microwave cavities are presented. Developments in the circuit design to couple a mechanical resonator to a qubit in the high-Q voltage bias CPW cavity is discussed as well prospects of achieving single-phonon measurement resolution. National Science Foundation under Grant No. DMR-1056423 and Grant No. DMR-1312421.
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...
Ultrafast interfeometric investigation of resonant secondary emission from quantum well excitons
DEFF Research Database (Denmark)
Birkedal, Dan; Shah, Jagdeep; Pfeiffer, L. N.
1999-01-01
Coherent Rayleigh scattering and incoherent luminescence comprise the secondary emission from quantum well exciton following ultrafast resonant excitation. We show that coherent Rayleigh scattering forms a time-dependent speckle pattern and isolate in a single speckle the Rayleigh component from...
Monolithic integration of a resonant tunneling diode and a quantum well semiconductor laser
Grave, I.; Kan, S. C.; Griffel, G.; Wu, S. W.; Sa'Ar, A.
1991-01-01
A monolithic integration of a double barrier AlAs/GaAs resonant tunneling diode and a GaAs/AlGaAs quantum well laser is reported. Negative differential resistance and negative differential optical response are observed at room temperature. The device displays bistable electrical and optical characteristics which are voltage controlled. Operation as a two-state optical memory is demonstrated.
DEFF Research Database (Denmark)
Li, H.W.; Kardynal, Beata; Ellis, D.J.P.
2008-01-01
Quantum dot resonant tunneling diode single photon detector with independently defined absorption and sensing areas is demonstrated. The device, in which the tunneling is constricted to an aperture in an insulating layer in the emitter, shows electrical characteristics typical of high quality res...
Resonance effects in Raman scattering of quantum dots formed by the Langmuir-Blodgett method
Energy Technology Data Exchange (ETDEWEB)
Milekhin, A G; Sveshnikova, L L; Duda, T A [Institute of Semiconductor Physics, Lavrentjev av.13, 630090, Novosibirsk (Russian Federation); Surovtsev, N V; Adichtchev, S V [Institute of Automation and Electrometry, Koptyug av.1, 630090, Novosibirsk (Russian Federation); Azhniuk, Yu M [Institute of Electron Physics, Universytetska Str. 21, 88017, Uzhhorod (Ukraine); Himcinschi, C [Institut fuer Theoretische Physik, TU Bergakademie Freiberg, Leipziger Str. 23, 09596, Freiberg (Germany); Kehr, M; Zahn, D R T, E-mail: milekhin@thermo.isp.nsc.r [Semiconductor Physics, Chemnitz University of Technology, Chemnitz (Germany)
2010-09-01
The enhancement of Raman scattering by optical phonon modes in quantum dots was achieved in resonant and surface-enhanced Raman scattering experiments by approaching the laser energy to the energy of either the interband transitions or the localized surface plasmons in silver nanoclusters deposited onto the nanostructures. Resonant Raman scattering by TO, LO, and SO phonons as well as their overtones was observed for PbS, ZnS, and ZnO quantum dots while enhancement for LO and SO modes in CdS quantum dots with a factor of about 700 was measured in surface enhanced Raman scattering experiments. Multiple phonon Raman scattering observed up to 5th and 7th order for CdS and ZnO, respectively, confirms the high crystalline quality of the grown QDs.
Electric dipole spin resonance in a quantum spin dimer system driven by magnetoelectric coupling
Kimura, Shojiro; Matsumoto, Masashige; Akaki, Mitsuru; Hagiwara, Masayuki; Kindo, Koichi; Tanaka, Hidekazu
2018-04-01
In this Rapid Communication, we propose a mechanism for electric dipole active spin resonance caused by spin-dependent electric polarization in a quantum spin gapped system. This proposal was successfully confirmed by high-frequency electron spin resonance (ESR) measurements of the quantum spin dimer system KCuCl3. ESR measurements by an illuminating linearly polarized electromagnetic wave reveal that the optical transition between the singlet and triplet states in KCuCl3 is driven by an ac electric field. The selection rule of the observed transition agrees with the calculation by taking into account spin-dependent electric polarization. We suggest that spin-dependent electric polarization is effective in achieving fast control of quantum spins by an ac electric field.
Enhancement of optical Kerr effect in quantum-cascade lasers with multiple resonance levels.
Bai, Jing; Citrin, D S
2008-08-18
In this paper, we investigated the optical Kerr lensing effect in quantum-cascade lasers with multiple resonance levels. The Kerr refractive index n2 is obtained through the third-order susceptibility at the fundamental frequency chi(3)( omega; omega, omega,-omega). Resonant two-photon processes are found to have almost equal contributions to chi(3)( omega; omega, omega,-omega) as the single-photon processes, which result in the predicted enhancement of the positive nonlinear (Kerr) refractive index, and thus may enhance mode-locking of quantum-cascade lasers. Moreover, we also demonstrate an isospectral optimization strategy for further improving n2 through the band-structure design, in order to boost the multimode performance of quantum-cascade lasers. Simulation results show that the optimized stepwise multiple-quantum-well structure has n2 approximately 10-8 cm2/W, a twofold enhancement over the original flat quantum-well structure. This leads to a refractive-index change (delta)n of about 0.01, which is at the upper bound of those reported for typical Kerr medium. This stronger Kerr refractive index may be important for quantum-cascade lasers ultimately to demonstrate self-mode-locking.
Cheng, Jian-Yih; Fisher, Brandon L.; Guisinger, Nathan P.; Lilley, Carmen M.
2017-12-01
Providing a spin-free host material in the development of quantum information technology has made silicon a very interesting and desirable material for qubit design. Much of the work and experimental progress has focused on isolated phosphorous atoms. In this article, we report on the exploration of Ni-Si clusters that are atomically manufactured via self-assembly from the bottom-up and behave as isolated quantum dots. These small quantum dot structures are probed at the atomic-scale with scanning tunneling microscopy and spectroscopy, revealing robust resonance through discrete quantized energy levels within the Ni-Si clusters. The resonance energy is reproducible and the peak spacing of the quantum dot structures increases as the number of atoms in the cluster decrease. Probing these quantum dot structures on degenerately doped silicon results in the observation of negative differential resistance in both I-V and dI/dV spectra. At higher surface coverage of nickel, a well-known √19 surface modification is observed and is essentially a tightly packed array of the clusters. Spatial conductance maps reveal variations in the local density of states that suggest the clusters are influencing the electronic properties of their neighbors. All of these results are extremely encouraging towards the utilization of metal modified silicon surfaces to advance or complement existing quantum information technology.
Characterization of superconducting transmission line resonators
Energy Technology Data Exchange (ETDEWEB)
Goetz, Jan; Summer, Philipp; Meier, Sebastian; Haeberlein, Max; Wulschner, Karl Friedrich; Eder, Peter; Fischer, Michael; Schwarz, Manuel; Deppe, Frank; Fedorov, Kirill; Huebl, Hans; Menzel, Edwin [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Krawczyk, Marta; Marx, Achim [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Baust, Alexander; Xie, Edwar; Zhong, Ling; Gross, Rudolf [Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, Garching (Germany); Physik-Department, TU Muenchen, Garching (Germany); Nanosystems Initiative Munich (NIM), Muenchen (Germany)
2015-07-01
Superconducting transmission line resonators are widely used in circuit quantum electrodynamics experiments as quantum bus or storage devices. For these applications, long coherence times, which can be linked to the internal quality factor of the resonators, are crucial. Here, we show a systematic study of the internal quality factor of niobium thin film resonators. We analyze different cleaning methods and substrate parameters for coplanar waveguide as well as microstrip geometries. In addition, we investigate the impact of a niobium-aluminum interface which is necessary for galvanically coupled flux qubits made from aluminum. This interface can be avoided by fabricating the complete resonator-qubit structure using Al/AlO{sub x}/Al technology during fabrication.
Krasnoshchekov, Sergey V; Stepanov, Nikolay F
2013-11-14
In the theory of anharmonic vibrations of a polyatomic molecule, mixing the zero-order vibrational states due to cubic, quartic and higher-order terms in the potential energy expansion leads to the appearance of more-or-less isolated blocks of states (also called polyads), connected through multiple resonances. Such polyads of states can be characterized by a common secondary integer quantum number. This polyad quantum number is defined as a linear combination of the zero-order vibrational quantum numbers, attributed to normal modes, multiplied by non-negative integer polyad coefficients, which are subject to definition for any particular molecule. According to Kellman's method [J. Chem. Phys. 93, 6630 (1990)], the corresponding formalism can be conveniently described using vector algebra. In the present work, a systematic consideration of polyad quantum numbers is given in the framework of the canonical Van Vleck perturbation theory (CVPT) and its numerical-analytic operator implementation for reducing the Hamiltonian to the quasi-diagonal form, earlier developed by the authors. It is shown that CVPT provides a convenient method for the systematic identification of essential resonances and the definition of a polyad quantum number. The method presented is generally suitable for molecules of significant size and complexity, as illustrated by several examples of molecules up to six atoms. The polyad quantum number technique is very useful for assembling comprehensive basis sets for the matrix representation of the Hamiltonian after removal of all non-resonance terms by CVPT. In addition, the classification of anharmonic energy levels according to their polyad quantum numbers provides an additional means for the interpretation of observed vibrational spectra.
Quantum dynamics of crystals of molecular magnets inside microwave resonators
Energy Technology Data Exchange (ETDEWEB)
Amigo, R.; Tejada, J.; Chudnovsky, E.M.; Hernandez, J.M.; Garcia-Santiago, A. E-mail: antonio@ubxlab.comtoni@ubxlab.com
2004-05-01
It is shown that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. Strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing evidence of the coherent microwave radiation by the crystals. These observations open the possibility of building a nanomagnetic microwave laser pumped by the magnetic field.
Quantum dynamics of crystals of molecular magnets inside microwave resonators
International Nuclear Information System (INIS)
Amigo, R.; Tejada, J.; Chudnovsky, E.M.; Hernandez, J.M.; Garcia-Santiago, A.
2004-01-01
It is shown that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. Strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing evidence of the coherent microwave radiation by the crystals. These observations open the possibility of building a nanomagnetic microwave laser pumped by the magnetic field
Resonance superfluidity in a quantum degenerate Fermi gas
Kokkelmans, S.J.J.M.F.; Holland, M.; Walser, R.; Chiofalo, M.L.; Chu, S.; Vuletic, V.; Kerman, A.J.; Chin, C.
2002-01-01
We consider the superfluid phase transition that arises when a Feshbach resonance pairing occurs in a dilute Fermi gas. This is related to the phenomenon of superconductivity described by the seminal Bardeen-Cooper-Schrieffer (BCS) theory. In superconductivity, the phase transition is caused by a
Resonant scattering on impurities in the quantum Hall effect
International Nuclear Information System (INIS)
Gurvitz, A.
1994-06-01
We developed a new approach to carrier transport between the edge states via resonant scattering on impurities, which is applicable both for short and long range impurities. A detailed analysis of resonant scattering on a single impurity is performed. The results used for study of the inter-edge transport by multiple resonant hopping via different impurities' site. We found the total conductance can be obtained from an effective Schroedinger equation with constant diagonal matrix elements in the Hamiltonian, where the complex non-diagonal matrix elements are the amplitudes of a carrier hopping between different impurities. It is explicitly shown how the complex phase leads to Aharonov-Bohm oscillations in the total conductance. Neglecting the contribution of self-crossing resonant-percolation trajectories, we found that the inter-edge carrier transport is similar to propagation in one-dimensional system with off-diagonal disorder. Then we demonstrated that each Landau band has an extended state Ε Ν , while all other states are localized, and the localization length behaves as L - 1 Ν (Ε) ∼ (Ε - Ε Ν ) 2 . (author)
Eringen, A C
1990-01-01
The electrodynamics of continua is a branch ofthe physical sciences concerned with the interaction of electromagnetic fields with deformable bodies. De formable bodies are considered to be continua endowed with continuous distributions of mass and charge. The theory of electromagnetic continua is concerned with the determination of deformations, motions, stress, and elec tromagnetic fields developed in bodies upon the applications of external loads. External loads may be of mechanical origin (e.g., forces, couples, constraints placed on the surface of the body, and initial and boundary conditions arising from thermal and other changes) and/or electromagnetic origin (e.g., electric, magnetic, and current fields). Because bodies of different constitutions respond to external stimuli in a different way, it is imperative to characterize properly the response functions relevant to a given class of continua. This is done by means of the constitutive theory. For example, an elastic dielectric responds to electro...
International Nuclear Information System (INIS)
Waldron, R.A.
1979-01-01
An account is given of Ritz's electrodynamics. Ritz's paper is divided into two parts. In the first he criticises the Lorentz-Maxwell theory based on fields, and comments on alternative theories based on particle interactions. In the second he develops his own theory, also based on particle interactions. He starts from a force law which is analogous to a force law derived by Schwarzschild from the Lorentz theory. While the approach is interesting, it leads to results which do not agree with experimental results obtained several decades later, after Ritz's death. A similar approach is applied to gravitation and is shown to be capable of explaining the anomalous precession of the planet Mercury. (Auth.)
Experimental benchmarking of quantum control in zero-field nuclear magnetic resonance.
Jiang, Min; Wu, Teng; Blanchard, John W; Feng, Guanru; Peng, Xinhua; Budker, Dmitry
2018-06-01
Demonstration of coherent control and characterization of the control fidelity is important for the development of quantum architectures such as nuclear magnetic resonance (NMR). We introduce an experimental approach to realize universal quantum control, and benchmarking thereof, in zero-field NMR, an analog of conventional high-field NMR that features less-constrained spin dynamics. We design a composite pulse technique for both arbitrary one-spin rotations and a two-spin controlled-not (CNOT) gate in a heteronuclear two-spin system at zero field, which experimentally demonstrates universal quantum control in such a system. Moreover, using quantum information-inspired randomized benchmarking and partial quantum process tomography, we evaluate the quality of the control, achieving single-spin control for 13 C with an average fidelity of 0.9960(2) and two-spin control via a CNOT gate with a fidelity of 0.9877(2). Our method can also be extended to more general multispin heteronuclear systems at zero field. The realization of universal quantum control in zero-field NMR is important for quantum state/coherence preparation, pulse sequence design, and is an essential step toward applications to materials science, chemical analysis, and fundamental physics.
Experimental realization of Shor's quantum factoring algorithm using nuclear magnetic resonance.
Vandersypen, L M; Steffen, M; Breyta, G; Yannoni, C S; Sherwood, M H; Chuang, I L
The number of steps any classical computer requires in order to find the prime factors of an l-digit integer N increases exponentially with l, at least using algorithms known at present. Factoring large integers is therefore conjectured to be intractable classically, an observation underlying the security of widely used cryptographic codes. Quantum computers, however, could factor integers in only polynomial time, using Shor's quantum factoring algorithm. Although important for the study of quantum computers, experimental demonstration of this algorithm has proved elusive. Here we report an implementation of the simplest instance of Shor's algorithm: factorization of N = 15 (whose prime factors are 3 and 5). We use seven spin-1/2 nuclei in a molecule as quantum bits, which can be manipulated with room temperature liquid-state nuclear magnetic resonance techniques. This method of using nuclei to store quantum information is in principle scalable to systems containing many quantum bits, but such scalability is not implied by the present work. The significance of our work lies in the demonstration of experimental and theoretical techniques for precise control and modelling of complex quantum computers. In particular, we present a simple, parameter-free but predictive model of decoherence effects in our system.
Jahromi, Hamed Dehdashti; Mahmoodi, Ali; Sheikhi, Mohammad Hossein; Zarifkar, Abbas
2016-10-20
Reduction of dark current at high-temperature operation is a great challenge in conventional quantum dot infrared photodetectors, as the rate of thermal excitations resulting in the dark current increases exponentially with temperature. A resonant tunneling barrier is the best candidate for suppression of dark current, enhancement in signal-to-noise ratio, and selective extraction of different wavelength response. In this paper, we use a physical model developed by the authors recently to design a proper resonant tunneling barrier for quantum infrared photodetectors and to study and analyze the spectral response of these devices. The calculated transmission coefficient of electrons by this model and its dependency on bias voltage are in agreement with experimental results. Furthermore, based on the calculated transmission coefficient, the dark current of a quantum dot infrared photodetector with a resonant tunneling barrier is calculated and compared with the experimental data. The validity of our model is proven through this comparison. Theoretical dark current by our model shows better agreement with the experimental data and is more accurate than the previously developed model. Moreover, noise in the device is calculated. Finally, the effect of different parameters, such as temperature, size of quantum dots, and bias voltage, on the performance of the device is simulated and studied.
Quantum revivals in periodically driven systems close to nonlinear resonances
International Nuclear Information System (INIS)
Saif, Farhan; Fortunato, Mauro
2002-01-01
We calculate the quantum revival time for a wave packet initially well localized in a one-dimensional potential in the presence of an external periodic modulating field. The dependence of the revival time on various parameters of the driven system is shown analytically. As an example of an application of our approach, we compare the analytically obtained values of the revival time for various modulation strengths with the numerically computed ones in the case of a driven gravitational cavity. We show that they are in very good agreement
Born-Infeld Nonlinear Electrodynamics
International Nuclear Information System (INIS)
Bialynicki-Birula, I.
1999-01-01
This is only a summary of a lecture delivered at the Infeld Centennial Meeting. In the lecture the history of the Born-Infeld nonlinear electrodynamics was presented and some general features of the theory were discussed. (author)
From Pauli's birthday to 'Confinement Resonances' – a potted history of Quantum Confinement
International Nuclear Information System (INIS)
Connerade, J P
2013-01-01
Quantum Confinement is in some sense a new subject. International meetings dedicated to Quantum Confinement have occurred only recently in Mexico City (the first in 2010 and the second, in September 2011). However, at least in principle, the subject has existed since a very long time. Surprisingly perhaps, it lay dormant for many years, for want of suitable experimental examples. However, when one looks carefully at its origin, it turns out to have a long and distinguished history. In fact, the problem of quantum confinement raises a number of very interesting issues concerning boundary conditions in elementary quantum mechanics and how they should be applied to real problems. Some of these issues were missed in the earliest papers, but are implicit in the structure of quantum mechanics, and lead to the notion of Confinement Resonances, the existence of which was predicted theoretically more than ten years ago. Although, for several reasons, these resonances remained elusive for a very long time, they have now been observed experimentally, which puts the whole subject in much better shape and, together with the advent of metallofullerenes, has contributed to its revival.
Advanced action in classical electrodynamics
Boozer, A. D.
2008-01-01
The time evolution of a charged point particle is governed by a second-order integro-differential equation that exhibits advanced effects, in which the particle responds to an external force before the force is applied. In this paper we give a simple physical argument that clarifies the origin and physical meaning of these advanced effects, and we compare ordinary electrodynamics with a toy model of electrodynamics in which advanced effects do not occur.
One phonon resonant Raman scattering in free-standing quantum wires
International Nuclear Information System (INIS)
Zhao, Xiang-Fu; Liu, Cui-Hong
2007-01-01
The scattering intensity (SI) of a free-standing cylindrical semiconductor quantum wire for an electron resonant Raman scattering (ERRS) process associated with bulk longitudinal optical (LO) phonon modes and surface optical (SO) phonon modes is calculated separately for T=0 K. The Frohlich interaction is considered to illustrate the theory for GaAs and CdS systems. Electron states are confined within a free-standing quantum wire (FSW). Single parabolic conduction and valence bands are assumed. The selection rules are studied. Numerical results and a discussion are also presented for various radii of the cylindrical
A space-time lattice version of scalar electrodynamics
International Nuclear Information System (INIS)
Kijowski, J.; Thielmann, A.
1993-10-01
A Minkowski-lattice version of quantum scalar electrodynamics is constructed. Quantum field is consequently described in a gauge-independent way, i.e. the algebra of quantum observables of the theory is generated by gauge-invariant operators assigned to zero-, one-, and two-dimensional elements of the lattice. The operators satisfy canonical commutation relations. Field dynamics is formulated in terms of difference equations imposed on the field operators. The dynamics is obtained from a discrete version of the path-integral. (author). 19 refs
An eigenvalue approach to quantum plasmonics based on a self-consistent hydrodynamics method.
Ding, Kun; Chan, C T
2018-02-28
Plasmonics has attracted much attention not only because it has useful properties such as strong field enhancement, but also because it reveals the quantum nature of matter. To handle quantum plasmonics effects, ab initio packages or empirical Feibelman d-parameters have been used to explore the quantum correction of plasmonic resonances. However, most of these methods are formulated within the quasi-static framework. The self-consistent hydrodynamics model offers a reliable approach to study quantum plasmonics because it can incorporate the quantum effect of the electron gas into classical electrodynamics in a consistent manner. Instead of the standard scattering method, we formulate the self-consistent hydrodynamics method as an eigenvalue problem to study quantum plasmonics with electrons and photons treated on the same footing. We find that the eigenvalue approach must involve a global operator, which originates from the energy functional of the electron gas. This manifests the intrinsic nonlocality of the response of quantum plasmonic resonances. Our model gives the analytical forms of quantum corrections to plasmonic modes, incorporating quantum electron spill-out effects and electrodynamical retardation. We apply our method to study the quantum surface plasmon polariton for a single flat interface.
Subgap resonant quasiparticle transport in normal-superconductor quantum dot devices
Energy Technology Data Exchange (ETDEWEB)
Gramich, J., E-mail: joerg.gramich@unibas.ch; Baumgartner, A.; Schönenberger, C. [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)
2016-04-25
We report thermally activated transport resonances for biases below the superconducting energy gap in a carbon nanotube quantum dot (QD) device with a superconducting Pb and a normal metal contact. These resonances are due to the superconductor's finite quasi-particle population at elevated temperatures and can only be observed when the QD life-time broadening is considerably smaller than the gap. This condition is fulfilled in our QD devices with optimized Pd/Pb/In multi-layer contacts, which result in reproducibly large and “clean” superconducting transport gaps with a strong conductance suppression for subgap biases. We show that these gaps close monotonically with increasing magnetic field and temperature. The accurate description of the subgap resonances by a simple resonant tunneling model illustrates the ideal characteristics of the reported Pb contacts and gives an alternative access to the tunnel coupling strengths in a QD.
Electrodynamics of Magnetoactive Media
International Nuclear Information System (INIS)
Browning, P K
2004-01-01
'Electrodynamics of Magnetoactive Media' is an unusual book in that it cuts across conventional physics discipline boundaries. The unifying theme allowing this is, quite simply, the physics of magnetic fields in various media. I believe the authors are correct in stating that the book is unique in specifically covering electrodynamic phenomena associated with magnetic fields, though of course some of the more elementary aspects are covered in the classical textbooks on electromagnetism, which are duly acknowledged. This interdisciplinarity makes the book very interesting to people with a range of backgrounds. For example, as a plasma physicist, I was familiar with most of the material on plasmas, but liquid crystals and superconductors were entirely new territory for me. These chapters were indeed both accessible and interesting, and it was surprising for me to see how much commonality there is in the physics of these various media. The first part of the book covers some fundamentals of electrodynamics and magnetostatics, and of electromagnetic waves. Most of this material is covered in textbooks on electromagnetism, and some of it is very basic (for example, LRC circuit theory, surely covered in most first year physics courses, is included) but it is perhaps a useful prelude for what is to come. The generic topic of charged particle motion in electromagnetic fields is well covered. Three main magnetoactive media are then discussed: plasmas (focusing on waves), liquid crystals and superconductors. It is all too easy to criticise a book on the grounds of omitted material, but I do feel that a chapter on magnetostatics in plasmas would have been very helpful, covering force-free fields and so on. Some interesting analogies could then have been exploited. For example, I was intrigued to discover an equation for magnetic fields in superconductors (equation (9.36)) which, apart from a change of sign, is identical to the Helmholtz equation used to model linear force
Transmission resonances in a semiconductor-superconductor junction quantum interference structure
International Nuclear Information System (INIS)
Takagaki, Y.; Tokura, Y.
1996-01-01
Transport properties in a quantum resonator structure of a normal-conductor endash superconductor (NS) junction are calculated. Quasiparticles in a cavity region undergo multiple reflections due to an abrupt change in the width of the wire and the NS interface. Quantum interference of the reflections modulates the nominal normal reflection probability at the NS boundary. We show that various NS structures can be regarded as the quantum resonator because of the absence of propagation along the NS interface. When the incident energy coincides with the quasibound state energy levels, the zero-voltage conductance exhibits peaks for small voltages applied to the NS junction. The transmission peaks change to dips of nearly perfect reflection when the applied voltage exceeds a critical value. Two branches of the resonance, which are roughly characterized by electron and hole wavelengths, emerge from the individual dip, and the energy difference between them increases with increasing voltage. The electronlike and holelike resonance dips originating from different quasibound states at zero-voltage cross one after another when the voltage approaches the superconducting gap. We find that both crossing and anticrossing can be produced. It is shown that the individual resonance state in the NS system is associated with two zeros and two poles in the complex energy plane. The behavior of the resonance is explained in terms of splitting and merging of the zero-pole pairs. We examine the Green close-quote s function of a one-dimensional NS system in order to find out how the transmission properties are influenced by the scattering from the NS interface. copyright 1996 The American Physical Society
Spin resonance with trapped ions
Energy Technology Data Exchange (ETDEWEB)
Wunderlich, Ch; Balzer, Ch; Hannemann, T; Mintert, F; Neuhauser, W; Reiss, D; Toschek, P E [Institut fuer Laser-Physik, Universitaet Hamburg, Jungiusstrasse 9, 20355 Hamburg (Germany)
2003-03-14
A modified ion trap is described where experiments (in particular related to quantum information processing) that usually require optical radiation can be carried out using microwave or radio frequency electromagnetic fields. Instead of applying the usual methods for coherent manipulation of trapped ions, a string of ions in such a modified trap can be treated like a molecule in nuclear magnetic resonance experiments taking advantage of spin-spin coupling. The collection of trapped ions can be viewed as an N-qubit molecule with adjustable spin-spin coupling constants. Given N identically prepared quantum mechanical two-level systems (qubits), the optimal strategy to estimate their quantum state requires collective measurements. Using the ground state hyperfine levels of electrodynamically trapped {sup 171}Yb{sup +}, we have implemented an adaptive algorithm for state estimation involving sequential measurements on arbitrary qubit states.
Spin resonance with trapped ions
International Nuclear Information System (INIS)
Wunderlich, Ch; Balzer, Ch; Hannemann, T; Mintert, F; Neuhauser, W; Reiss, D; Toschek, P E
2003-01-01
A modified ion trap is described where experiments (in particular related to quantum information processing) that usually require optical radiation can be carried out using microwave or radio frequency electromagnetic fields. Instead of applying the usual methods for coherent manipulation of trapped ions, a string of ions in such a modified trap can be treated like a molecule in nuclear magnetic resonance experiments taking advantage of spin-spin coupling. The collection of trapped ions can be viewed as an N-qubit molecule with adjustable spin-spin coupling constants. Given N identically prepared quantum mechanical two-level systems (qubits), the optimal strategy to estimate their quantum state requires collective measurements. Using the ground state hyperfine levels of electrodynamically trapped 171 Yb + , we have implemented an adaptive algorithm for state estimation involving sequential measurements on arbitrary qubit states
Optical Resonance of A Three-Level System in Semiconductor Quantum Dots
Directory of Open Access Journals (Sweden)
Nguyen Van Hieu
2017-11-01
Full Text Available The optical resonance of a three-level system of the strongly correlated electrons in the twolevel semiconductor quantum dot interacting with the linearly polarized monochromatic electromagnetic radiation is studied. With the application of the Green function method the expressions of the state vectors and the energies of the stationary states of the system in the regime of the optical resonance are derived. The Rabi oscillations of the electron populations at different levels as well as the Rabi splitting of the peaks in the photon emission spectra are investigated. PACS numbers: 71.35.-y, 78.55.-m, 78.67.Hc
Resonance Raman and quantum chemical studies of short polyene radical cations
DEFF Research Database (Denmark)
Keszthelyi, T.; Wilbrandt, R.; Bally, T.
1997-01-01
,3,5-hexatriene have been studied. The radical cations were generated radiolytically in a glassy Freon matrix and investigated by optical absorption and resonance Raman spectroscopy. Ab initio and density functional molecular-orbital calculations have been carried out to predict equilibrium structures...... and to assist assignment of the resonance Raman spectra. A new and improved scaled quantum mechanical force field for the butadiene radical cation was also determined. The presence of more than one rotamer was observed in all the polyene radical cations we investigated. (C) 1997 Elsevier Science B.V....
A Comparison of Resonant Tunneling Based on Schrödinger's Equation and Quantum Hydrodynamics
Directory of Open Access Journals (Sweden)
Naoufel Ben Abdallah
2002-01-01
Full Text Available Smooth quantum hydrodynamic (QHD model simulations of the current–voltage curve of a resonant tunneling diode at 300K are compared with that predicted by the mixed-state Schrödinger equation approach. Although the resonant peak for the QHD simulation occurs at 0.15V instead of the Schrödinger equation value of 0.2V, there is good qualitative agreement between the current–voltage curves for the two models, including the predicted peak current values.
Optimized coplanar waveguide resonators for a superconductor–atom interface
Energy Technology Data Exchange (ETDEWEB)
Beck, M. A., E-mail: mabeck2@wisc.edu; Isaacs, J. A.; Booth, D.; Pritchard, J. D.; Saffman, M.; McDermott, R. [Department of Physics, University Of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706 (United States)
2016-08-29
We describe the design and characterization of superconducting coplanar waveguide cavities tailored to facilitate strong coupling between superconducting quantum circuits and single trapped Rydberg atoms. For initial superconductor–atom experiments at 4.2 K, we show that resonator quality factors above 10{sup 4} can be readily achieved. Furthermore, we demonstrate that the incorporation of thick-film copper electrodes at a voltage antinode of the resonator provides a route to enhance the zero-point electric fields of the resonator in a trapping region that is 40 μm above the chip surface, thereby minimizing chip heating from scattered trap light. The combination of high resonator quality factor and strong electric dipole coupling between the resonator and the atom should make it possible to achieve the strong coupling limit of cavity quantum electrodynamics with this system.
On the study of quantum properties of space-time with interferometers and resonant bars
International Nuclear Information System (INIS)
Amelino-Camelia, G.
2001-01-01
The expectation that it should not be possible to gain experimental insight on the structure of space-time at Planckian distance scales has been recently challenged by several studies which have shown that there are a few classes of experiments with sensitivity sufficient for setting significant limits on certain candidate Planckian pictures of space-time. With respect to quantum space-time fluctuations, one of the most popular predictions of various Quantum-Gravity approaches, the experiments that have the best sensitivity are the same experiments which are used in searches of the classical-physics phenomenon of gravity waves. In experiments searching for classical gravity waves the presence of quantum space-time fluctuations would introduce a source of noise just like the ordinary (non-gravitational) quantum properties of the photons composing the laser beam used in interferometry introduce a source of noise. The sensitivity to distance fluctuations achieved (or being achieved) by modern interferometers and resonant-bar detectors is here described in terms of the Planck length, hoping that this characterization may prove useful for theorists attempting to gain some intuition for these sensitivity levels. While theory work on Quantum Gravity is not yet ready to provide definite noise models, there are some general characteristics of Quantum-Gravity-induced noise that could be used in experimental studies. (author)
Plexciton quenching by resonant electron transfer from quantum emitter to metallic nanoantenna.
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.
Particles, fields and quantum theory
International Nuclear Information System (INIS)
Bongaarts, P.J.M.
1982-01-01
The author gives an introduction to the development of gauge theories of the fundamental interactions. Starting from classical mechanics and quantum mechanics the development of quantum electrodynamics and non-abelian gauge theories is described. (HSI)
Energy Technology Data Exchange (ETDEWEB)
Munehiro, H
1980-05-29
When driving the carriage of a printer through a rotating motor, there are problems regarding the limited accuracy of the carriage position due to rotation or contraction and ageing of the cable. In order to solve the problem, a direct drive system was proposed, in which the printer carriage is driven by a linear motor. If one wants to keep the motor circuit of such a motor compact, then the magnetic flux density in the air gap must be reduced or the motor travel must be reduced. It is the purpose of this invention to create an electrodynamic linear motor, which on the one hand is compact and light and on the other hand has a relatively high constant force over a large travel. The invention is characterised by the fact that magnetic fields of alternating polarity are generated at equal intervals in the magnetic field, and that the coil arrangement has 2 adjacent coils, whose size corresponds to half the length of each magnetic pole. A logic circuit is provided to select one of the two coils and to determine the direction of the current depending on the signals of a magnetic field sensor on the coil arrangement.
Eringen, A C
1990-01-01
This is the second volume of a two-volume set presenting a unified approach to the electrodynamics of continua, based on the principles of contemporary continuum of physics. The first volume was devoted mainly to the development of the theory and applications to deformable solid media. This volume extends the developments of the first volume to richer and newer grounds. It contains discussions on fluid media, magnetohydrodynamics, eletrohydrodynamics and media with more complicated structures. With the discussion, in the last two chapters, of memory-dependent materials and non-local E-M theory, the authors account for the nonlocal effects arising from motions and fields of material points at past times and at spatially distant points. This discussion is included here to stimulate further research in these important fields, which are presently in development stages. The second volume is self-contained and can be studied without the help of volume I. A section summarizing the constitutive equations and the unde...
Nuclear magnetic resonance detection and spectroscopy of single proteins using quantum logic.
Lovchinsky, I; Sushkov, A O; Urbach, E; de Leon, N P; Choi, S; De Greve, K; Evans, R; Gertner, R; Bersin, E; Müller, C; McGuinness, L; Jelezko, F; Walsworth, R L; Park, H; Lukin, M D
2016-02-19
Nuclear magnetic resonance spectroscopy is a powerful tool for the structural analysis of organic compounds and biomolecules but typically requires macroscopic sample quantities. We use a sensor, which consists of two quantum bits corresponding to an electronic spin and an ancillary nuclear spin, to demonstrate room temperature magnetic resonance detection and spectroscopy of multiple nuclear species within individual ubiquitin proteins attached to the diamond surface. Using quantum logic to improve readout fidelity and a surface-treatment technique to extend the spin coherence time of shallow nitrogen-vacancy centers, we demonstrate magnetic field sensitivity sufficient to detect individual proton spins within 1 second of integration. This gain in sensitivity enables high-confidence detection of individual proteins and allows us to observe spectral features that reveal information about their chemical composition. Copyright © 2016, American Association for the Advancement of Science.
Non-existence of rest-frame spin-eigenstate spinors in their own electrodynamics
Fabbri, Luca; da Rocha, Roldão
2018-05-01
We assume a physical situation where gravity with torsion is neglected for an electrodynamically self-interacting spinor that will be taken in its rest-frame and spin-eigenstate: we demonstrate that under this circumstance no solution exists for the system of field equations. Despite such a situation might look artificial nevertheless it represents the instance that is commonly taken as the basis for all computations of quantum electrodynamics.
Explanation of the quantum phenomenon of off-resonant cavity-mode emission
Echeverri-Arteaga, Santiago; Vinck-Posada, Herbert; Gómez, Edgar A.
2018-04-01
We theoretically investigate the unexpected occurrence of an extra emission peak that has been experimentally observed in off-resonant studies of cavity QED systems. Our results within the Markovian master equation approach successfully explain why the central peak arises, and how it reveals that the system is suffering a dynamical phase transition induced by the phonon-mediated coupling. Our findings are in qualitative agreement with previous reported experimental results, and the fundamental physics behind this quantum phenomenon is understood.
Quantum Entanglement of a Tunneling Spin with Mechanical Modes of a Torsional Resonator
Directory of Open Access Journals (Sweden)
D. A. Garanin
2011-08-01
Full Text Available We solve the Schrödinger equation for various quantum regimes describing a tunneling macrospin coupled to a torsional oscillator. The energy spectrum and freezing of spin tunneling are studied. Magnetic susceptibility, noise spectrum, and decoherence due to entanglement of spin and mechanical modes are computed. We show that the presence of a tunneling spin can be detected via splitting of the mechanical mode at the resonance. Our results apply to experiments with magnetic molecules coupled to nanoresonators.
Zero Quantum Nuclear Magnetic Resonance experiments utilizing a toroid cell and coil
Bebout, William Roach
1989-01-01
Over the past ten to fifteen years the area of Nuclear Magnetic Resonance (NMR) Spectroscopy has seen tremendous growth. For example, in conjunction with multiple quantum NMR, molecular structural mapping of a compound can be easily performed in a two dimensional (2D) experiment. However, only two kinds of detector coils have been typically used in NMR studies. These are the solenoid coil and the Helmholtz coil. The solenoid coil was very popular with the permanent and e...
Non-Weyl resonance asymptotics for quantum graphs in a magnetic field
Czech Academy of Sciences Publication Activity Database
Exner, Pavel; Lipovský, J.
2011-01-01
Roč. 375, č. 4 (2011), s. 805-807 ISSN 0375-9601 R&D Projects: GA MŠk LC06002; GA ČR GAP203/11/0701 Institutional research plan: CEZ:AV0Z10480505 Keywords : Quantum graphs * Magnetic field * Resonances Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 1.632, year: 2011
Gambarota, Giulio
2017-07-15
Magnetic resonance spectroscopy (MRS) is a well established modality for investigating tissue metabolism in vivo. In recent years, many efforts by the scientific community have been directed towards the improvement of metabolite detection and quantitation. Quantum mechanics simulations allow for investigations of the MR signal behaviour of metabolites; thus, they provide an essential tool in the optimization of metabolite detection. In this review, we will examine quantum mechanics simulations based on the density matrix formalism. The density matrix was introduced by von Neumann in 1927 to take into account statistical effects within the theory of quantum mechanics. We will discuss the main steps of the density matrix simulation of an arbitrary spin system and show some examples for the strongly coupled two spin system. Copyright © 2016 Elsevier Inc. All rights reserved.
Electron spin resonance and spin-valley physics in a silicon double quantum dot.
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.
Demonstration of quantum logic gates in liquid crystal nuclear magnetic resonance
International Nuclear Information System (INIS)
Marjanska, Malgorzata; Chuang, Isaac L.; Kubinec, Mark G.
2000-01-01
1 H- 13 C heteronuclear dipolar couplings are used to produce the NMR (nuclear magnetic resonance) version of a two bit controlled-NOT quantum logic gate. This gate is coupled with the Hadamard gate to complete a circuit which generates the Einstein-Podolsky-Rosen (EPR) state which is the maximally entangled state of a pair of spins. The EPR state is crucial for the potential exponential speed advantage of quantum computers over their classical counterparts. We sample the deviation density matrix of the two spin system to verify the presence of the EPR state. EPR state lifetimes are also measured with this technique, thereby demonstrating the viability of liquid crystals as a platform for quantum computing. (c) 2000 American Institute of Physics
On the electrodynamics of spinning particles
International Nuclear Information System (INIS)
Holten, J.W. van
1990-01-01
The electrodynamics of spinning point particles is considered. A modification of the Lorentz force law is introduced which can be interpreted as a classical limit of the Dirac-Klein-Gordon equation. An improved version of the inhomogeneous Maxwell equations is constructed to describe the classical fields of spinning particles. Both classical and quantum electrodynamics are shown to predict relativistic time-dilatation effects for spinning particles in an electromagnetic field, even in the limit of zero velocity. The life-time of unstable charged particles moving in a Coulomb field is computed for both spin-zero and spin-half particles. Comparison shows spin effects to be present but relatively small. The magnitude of further spin-dependent correction from hyperfine interactions is computed. A measurement of the life-time of muons in atomic bound states separated by such spin-dependent hyperfine interactions would provide a clean test for the effect predicted. Similar effects are shown to arise in non-abelian gauge theories such as QCD. (author). 18 refs
Becchi-Rouet-Stora-Tyutin quantization of histories electrodynamics
International Nuclear Information System (INIS)
Noltingk, Duncan
2002-01-01
This article is a continuation of earlier work where a classical history theory of pure electrodynamics was developed in which the history fields have five components. The extra component is associated with an extra constraint, thus enlarging the gauge group of histories electrodynamics. In this article we quantize the classical theory developed previously by two methods. First we quantize the reduced classical history space to obtain a reduced quantum history theory. Second we quantize the classical BRST-extended history space, and use the Becchi-Rouet-Stora-Tyutin charge to define a 'cohomological' quantum history theory. Finally, we show that the reduced history theory is isomorphic (as a history theory) to the cohomological history theory
Quantized fluctuational electrodynamics for three-dimensional plasmonic structures
DEFF Research Database (Denmark)
Partanen, Mikko; Häyrynen, Teppo; Tulkki, Jukka
2017-01-01
We recently introduced a quantized fluctuational electrodynamics (QFED) formalism that provides a physically insightful definition of an effective position-dependent photon-number operator and the associated ladder operators. However, this far the formalism has been applicable only for the normal...... formalism, we apply it to study the local steady-state photon numbers and field temperatures in a light-emitting near-surface InGaN quantum-well structure with a metallic coating supporting surface plasmons....
Sun, Jason; Choi, Kwong-Kit; DeCuir, Eric; Olver, Kimberley; Fu, Richard
2017-07-01
The infrared absorption of SF6 gas is narrowband and peaks at 10.6 μm. This narrowband absorption posts a stringent requirement on the corresponding sensors as they need to collect enough signal from this limited spectral bandwidth to maintain a high sensitivity. Resonator-quantum well infrared photodetectors (R-QWIPs) are the next generation of QWIP detectors that use resonances to increase the quantum efficiency for more efficient signal collection. Since the resonant approach is applicable to narrowband as well as broadband, it is particularly suitable for this application. We designed and fabricated R-QWIPs for SF6 gas detection. To achieve the expected performance, the detector geometry must be produced according to precise specifications. In particular, the height of the diffractive elements and the thickness of the active resonator must be uniform, and accurately realized to within 0.05 μm. Additionally, the substrates of the detectors must be completely removed to prevent the escape of unabsorbed light in the detectors. To achieve these specifications, two optimized inductively coupled plasma etching processes were developed. Due to submicron detector feature sizes and overlay tolerance, we used an advanced semiconductor material lithography stepper instead of a contact mask aligner to pattern wafers. Using these etching techniques and tool, we have fabricated focal plane arrays with 30-μm pixel pitch and 320×256 format. The initial test revealed promising results.
Magnetic forces and localized resonances in electron transfer through quantum rings.
Poniedziałek, M R; Szafran, B
2010-11-24
We study the current flow through semiconductor quantum rings. In high magnetic fields the current is usually injected into the arm of the ring preferred by classical magnetic forces. However, for narrow magnetic field intervals that appear periodically on the magnetic field scale the current is injected into the other arm of the ring. We indicate that the appearance of the anomalous-non-classical-current circulation results from Fano interference involving localized resonant states. The identification of the Fano interference is based on the comparison of the solution of the scattering problem with the results of the stabilization method. The latter employs the bound-state type calculations and allows us to extract both the energy of metastable states localized within the ring and the width of resonances by analysis of the energy spectrum of a finite size system as a function of its length. The Fano resonances involving states of anomalous current circulation become extremely narrow on both the magnetic field and energy scales. This is consistent with the orientation of the Lorentz force that tends to keep the electron within the ring and thus increases the lifetime of the electron localization within the ring. Absence of periodic Fano resonances in electron transfer probability through a quantum ring containing an elastic scatterer is also explained.
Zheng, Yuanliao; Chen, Pingping; Ding, Jiayi; Yang, Heming; Nie, Xiaofei; Zhou, Xiaohao; Chen, Xiaoshuang; Lu, Wei
2018-06-01
A hybrid structure consisting of periodic gold stripes and an overlaying gold film has been proposed as the optical coupler of a long-wave quantum well infrared photodetector. Absorption spectra and field distributions of the structure at back-side normal incidence are calculated by the finite difference time-domain method. The results indicate that the intersubband absorption can be greatly enhanced based on the waveguide resonance as well as the surface plasmon polariton (SPP) mode. With the optimized structural parameters of the periodic gold stripes, the maximal intersubband absorption can exceed 80%, which is much higher than the SPP-enhanced intersubband absorption (the one of the standard device. The relationship between the structural parameters and the waveguide resonant wavelength is derived. Other advantages of the efficient optical coupling based on waveguide resonance are also discussed.
Some properties of the resonant state in quantum mechanics and its computation
International Nuclear Information System (INIS)
Hatano, Naomichi; Sasada, Keita; Nakamura, Hiroaki; Petrosky, Tomio
2007-08-01
The resonant state of the open quantum system is studied from the viewpoint of the outgoing momentum flux. We show that the number of particles is conserved for a resonant state, it we use an expanding volume of integration in order to take account of the outgoing momentum flux; the number of particles would decay exponentially in a fixed volume of integration. Moreover, we introduce new numerical methods of treating the resonant state with the use of the effective potential. We first give a numerical method of finding a resonance pole in the complex energy plane. The method seeks an energy eigenvalue iteratively. We found that our method leads to a super-convergence, the convergence exponential with respect to the iteration step. The present method is completely independent of commonly used complex scaling. We also give a numerical trick for computing the time evolution of the resonant state in limited spatial area. Since the wave function of the resonant state is diverging away from the scattering potential, it has been previously difficult to follow its time evolution numerically in a finite area. (author)
In-Depth Development of Classical Electrodynamics
Directory of Open Access Journals (Sweden)
Keilman Y. N.
2008-01-01
Full Text Available There is hope that a properly developed Classical Electrodynamics (CED will be able to play a role in a unified field theory explaining electromagnetism, quantum phenomena, and gravitation. There is much work that has to be done in this direction. In this article we propose a move towards this aim by refining the basic principles of an improved CED. Attention is focused on the reinterpretation of the E-M potential. We use these basic principles to obtain solutions that explain the interactions between a constant electromagnetic field and a thin layer of material continuum; between a constant electromagnetic field and a spherical configuration of material continuum (for a charged elementary particle; between a transverse electromagnetic wave and a material continuum; between a longitudinal aether wave (dummy wave and a material continuum.
Resonant shallow donor magnetopolaron effect in a GaAs/AlGaAs quantum dot in high magnetic fields
International Nuclear Information System (INIS)
Zhu Kadi.
1993-11-01
Resonant shallow donor magnetopolaron effect in a GaAs/AlGaAs quantum dot in high magnetic fields is investigated by the variational treatment. It is shown that both the cyclotron resonant frequency ω * c+ due to the 1s-p+ hydrogenic transition and the cyclotron resonant frequency ω * c- due to the 1s-p - hydrogenic transition increase with the decrease of the dot size. The cyclotron resonant frequency ω * c+ is always larger than the bulk LO-phonon frequency ω LO , while the cyclotron resonant frequency ω * c- is lower than ω LO for larger quantum dots (l 0 > 2.0.r 0 , r 0 is the polaron radius). The results also show that the Coulomb interaction effect on the resonant frequencies is significant. (author). 26 refs, 3 figs
Rabi model as a quantum coherent heat engine: From quantum biology to superconducting circuits
Altintas, Ferdi; Hardal, Ali Ü. C.; Müstecaplıoǧlu, Özgür E.
2015-02-01
We propose a multilevel quantum heat engine with a working medium described by a generalized Rabi model which consists of a two-level system coupled to a single-mode bosonic field. The model is constructed to be a continuum limit of a quantum biological description of light-harvesting complexes so that it can amplify quantum coherence by a mechanism which is a quantum analog of classical Huygens clocks. The engine operates in a quantum Otto cycle where the working medium is coupled to classical heat baths in the isochoric processes of the four-stroke cycle, while either the coupling strength or the resonance frequency is changed in the adiabatic stages. We found that such an engine can produce work with an efficiency close to the Carnot bound when it operates at low temperatures and in the ultrastrong-coupling regime. The interplay of the effects of quantum coherence and quantum correlations on the engine performance is discussed in terms of second-order coherence, quantum mutual information, and the logarithmic negativity of entanglement. We point out that the proposed quantum Otto engine can be implemented experimentally with modern circuit quantum electrodynamic systems where flux qubits can be coupled ultrastrongly to superconducting transmission-line resonators.
Electrodynamic Dust Shield Demonstrator
Stankie, Charles G.
2013-01-01
The objective of the project was to design and manufacture a device to demonstrate a new technology developed by NASA's Electrostatics and Surface Physics Laboratory. The technology itself is a system which uses magnetic principles to remove regolith dust from its surface. This project was to create an enclosure that will be used to demonstrate the effectiveness of the invention to The Office of the Chief Technologist. ONE of the most important challenges of space exploration is actually caused by something very small and seemingly insignificant. Dust in space, most notably on the moon and Mars, has caused many unforeseen issues. Dirt and dust on Earth, while a nuisance, can be easily cleaned and kept at bay. However, there is considerably less weathering and erosion in space. As a result, the microscopic particles are extremely rough and abrasive. They are also electrostatically charged, so they cling to everything they make contact with. This was first noted to be a major problem during the Apollo missions. Dust would stick to the spacesuits, and could not be wiped off as predicted. Dust was brought back into the spacecraft, and was even inhaled by astronauts. This is a major health hazard. Atmospheric storms and other events can also cause dust to coat surfaces of spacecraft. This can cause abrasive damage to the craft. The coating can also reduce the effectiveness of thermal insulation and solar panels.' A group of engineers at Kennedy Space Center's Electrostatics and Surface Physics Laboratory have developed a new technology, called the Electrodynamic Dust Shield, to help alleviate these problems. It is based off of the electric curtain concept developed at NASA in 1967. "The EDS is an active dust mitigation technology that uses traveling electric fields to transport electrostatically charged dust particles along surfaces. To generate the traveling electric fields, the EDS consists of a multilayer dielectric coating with an embedded thin electrode grid
Few Issues Related to an Electrodynamic Exciter Control
Čala, M.
2015-01-01
There are multiple problems to solve when controlling an electromagnetic exciter for vibrations generation. Main challenge is to straighten a frequency response of an exciter which is normally not uniform due to resonances resulting from the mechanical construction of an exciter, specimen to test, or mounting fixture. This paper describes number of aspects to consider, which arose during implementation of the control system for small electrodynamic exciter on the Department of Control and Ins...
Gravitational waves and electrodynamics: new perspectives.
Cabral, Francisco; Lobo, Francisco S N
2017-01-01
Given the recent direct measurement of gravitational waves (GWs) by the LIGO-VIRGO collaboration, the coupling between electromagnetic fields and gravity have a special relevance since it opens new perspectives for future GW detectors and also potentially provides information on the physics of highly energetic GW sources. We explore such couplings using the field equations of electrodynamics on (pseudo) Riemann manifolds and apply it to the background of a GW, seen as a linear perturbation of Minkowski geometry. Electric and magnetic oscillations are induced that propagate as electromagnetic waves and contain information as regards the GW which generates them. The most relevant results are the presence of longitudinal modes and dynamical polarization patterns of electromagnetic radiation induced by GWs. These effects might be amplified using appropriate resonators, effectively improving the signal to noise ratio around a specific frequency. We also briefly address the generation of charge density fluctuations induced by GWs and the implications for astrophysics.
Gravitational waves and electrodynamics: new perspectives
Energy Technology Data Exchange (ETDEWEB)
Cabral, Francisco; Lobo, Francisco S.N. [Faculdade de Ciencias da Universidade de Lisboa, Instituto de Astrofisica e Ciencias do Espaco, Lisbon (Portugal)
2017-04-15
Given the recent direct measurement of gravitational waves (GWs) by the LIGO-VIRGO collaboration, the coupling between electromagnetic fields and gravity have a special relevance since it opens new perspectives for future GW detectors and also potentially provides information on the physics of highly energetic GW sources. We explore such couplings using the field equations of electrodynamics on (pseudo) Riemann manifolds and apply it to the background of a GW, seen as a linear perturbation of Minkowski geometry. Electric and magnetic oscillations are induced that propagate as electromagnetic waves and contain information as regards the GW which generates them. The most relevant results are the presence of longitudinal modes and dynamical polarization patterns of electromagnetic radiation induced by GWs. These effects might be amplified using appropriate resonators, effectively improving the signal to noise ratio around a specific frequency. We also briefly address the generation of charge density fluctuations induced by GWs and the implications for astrophysics. (orig.)
Cosmological effects of nonlinear electrodynamics
International Nuclear Information System (INIS)
Novello, M; Goulart, E; Salim, J M; Bergliaffa, S E Perez
2007-01-01
It will be shown that a given realization of nonlinear electrodynamics, used as a source of Einstein's equations, generates a cosmological model with interesting features, namely a phase of current cosmic acceleration, and the absence of an initial singularity, thus pointing to a way of solving two important problems in cosmology
Temperature dependence of the fundamental excitonic resonance in lead-salt quantum dots
International Nuclear Information System (INIS)
Yue, Fangyu; Tomm, Jens W.; Kruschke, Detlef; Ullrich, Bruno; Chu, Junhao
2015-01-01
The temperature dependences of the fundamental excitonic resonance in PbS and PbSe quantum dots fabricated by various technologies are experimentally determined. Above ∼150 K, sub-linearities of the temperature shifts and halfwidths are observed. This behavior is analyzed within the existing standard models. Concordant modeling, however, becomes possible only within the frame of a three-level system that takes into account both bright and dark excitonic states as well as phonon-assisted carrier redistribution between these states. Our results show that luminescence characterization of lead-salt quantum dots necessarily requires both low temperatures and excitation densities in order to provide reliable ensemble parameters
Yamasaki, Tomoaki; Ueda, Miki; Maegawa, Satoru
2003-05-01
A molecular nanomagnet Fe8 with a total spin S=10 in the ground state attracts much attention as a substance which exhibits the quantum tunneling of magnetization below 300 mK. We performed 1H NMR measurements for a single crystal of Fe8 in temperature range between 20 and 800 mK. The spectra below 300 mK strongly depend on the sequence of the applied field and those in the positive and negative fields are not symmetric about zero field, while they are symmetric above 300 mK. We discuss the origin of this hysteresis phenomenon, relating to the initial spin state of molecules, the resonant quantum tunneling and the nuclear spin relaxation process.
International Nuclear Information System (INIS)
Yamasaki, Tomoaki; Ueda, Miki; Maegawa, Satoru
2003-01-01
A molecular nanomagnet Fe8 with a total spin S=10 in the ground state attracts much attention as a substance which exhibits the quantum tunneling of magnetization below 300 mK. We performed 1 H NMR measurements for a single crystal of Fe8 in temperature range between 20 and 800 mK. The spectra below 300 mK strongly depend on the sequence of the applied field and those in the positive and negative fields are not symmetric about zero field, while they are symmetric above 300 mK. We discuss the origin of this hysteresis phenomenon, relating to the initial spin state of molecules, the resonant quantum tunneling and the nuclear spin relaxation process
Resonant Pump-dump Quantum Control of Solvated Dye Molecules with Phase Jumps
Konar, Arkaprabha; Lozovoy, Vadim; Dantus, Marcos
2014-03-01
Quantum coherent control of two photon and multiphoton excitation processes in atomic and condensed phase systems employing phase jumps has been well studied and understood. Here we demonstrate coherent quantum control of a two photon resonant pump-dump process in a complex solvated dye molecule. Phase jump in the frequency domain via a pulse shaper is employed to coherently enhance the stimulated emission by an order of magnitude when compared to transform limited pulses. Red shifted stimulated emission from successive low energy Stokes shifted excited states leading to narrowband emission are observed upon scanning the pi step across the excitation spectrum. A binary search space routine was also employed to investigate the effects of other types of phase jumps on stimulated emission and to determine the optimum phase that maximizes the emission. Understanding the underlying mechanism of this kind of enhancement will guide us in designing pulse shapes for enhancing stimulated emission, which can be further applied in the field of imaging.
Resonator reset in circuit QED by optimal control for large open quantum systems
Boutin, Samuel; Andersen, Christian Kraglund; Venkatraman, Jayameenakshi; Ferris, Andrew J.; Blais, Alexandre
2017-10-01
We study an implementation of the open GRAPE (gradient ascent pulse engineering) algorithm well suited for large open quantum systems. While typical implementations of optimal control algorithms for open quantum systems rely on explicit matrix exponential calculations, our implementation avoids these operations, leading to a polynomial speedup of the open GRAPE algorithm in cases of interest. This speedup, as well as the reduced memory requirements of our implementation, are illustrated by comparison to a standard implementation of open GRAPE. As a practical example, we apply this open-system optimization method to active reset of a readout resonator in circuit QED. In this problem, the shape of a microwave pulse is optimized such as to empty the cavity from measurement photons as fast as possible. Using our open GRAPE implementation, we obtain pulse shapes, leading to a reset time over 4 times faster than passive reset.
Noncommutative quantum electrodynamics in path integral framework
Energy Technology Data Exchange (ETDEWEB)
Bourouaine, S; Benslama, A [Departement de Physique, Faculte des Sciences, Universite Mentouri, Constantine (Algeria)
2005-08-19
In this paper, the dynamics of a relativistic particle of spin 1/2, interacting with an external electromagnetic field in noncommutative space, is studied in the path integral framework. By adopting the Fradkin-Gitman formulation, the exact Green's function in noncommutative space (NCGF) for the quadratic case of a constant electromagnetic field is computed, and it is shown that its form is similar to its counterpart given in commutative space. In addition, it is deduced that the effect of noncommutativity has the same effect as an additional constant field depending on a noncommutative {theta} matrix.
Noncommutative quantum electrodynamics in path integral framework
International Nuclear Information System (INIS)
Bourouaine, S; Benslama, A
2005-01-01
In this paper, the dynamics of a relativistic particle of spin 1/2, interacting with an external electromagnetic field in noncommutative space, is studied in the path integral framework. By adopting the Fradkin-Gitman formulation, the exact Green's function in noncommutative space (NCGF) for the quadratic case of a constant electromagnetic field is computed, and it is shown that its form is similar to its counterpart given in commutative space. In addition, it is deduced that the effect of noncommutativity has the same effect as an additional constant field depending on a noncommutative θ matrix
Nonperturbative quantum electrodynamics at T≠0
International Nuclear Information System (INIS)
Pevzner, M.Sh.
1990-01-01
On the base of Schwinger-Dyson equation for the electron temperature Green's function in the nonperturbative QED in the ladder approximation the ordinary differential equation for the function, connected with temperature one has been obtained. The relation, to which the temperature depending electron mass m(T) satisfies, has been found; its low-temperature behaviour has been studied. The phase transition has been shown to take place in the model, that is accompanied by the chiral symmetry restoration. 34 refs
Results in finite temperature quantum electrodynamics
International Nuclear Information System (INIS)
Down, D.M.
1985-01-01
First, three quantities of physical interest are calculated. The first two quantities are the self energy of the electron at order α and the self mass of the electron at order α 2 due to its interaction with a thermal bath of photons. The third quantity of physical interest is the thermal contribution to the self mass of the axion. Second, some formal developments are presented. First among these is the proof of an extension to the familiar optical theorem to cover processes taking place at finite temperature. Then an example of the application of the theorem is given for a simple field theory involving two types of scalar particles. The example illustrates that the relationship between the forward scattering amplitude and the total cross section is more complex at finite temperature than at zero temperature. Third, a method for calculating the wave function renormalization constant at finite temperature for an electron in a thermal bath of photons is presented. This method is compared with methods invented by other authors
Quantum electrodynamics at high temperature. 2
International Nuclear Information System (INIS)
Alvarez-Estrada, R.F.
1988-01-01
The photon sector of QED in d = 3 spatial dimensions is analyzed at high temperature thereby generalizing nontrivially a previous study for d = 1. The imaginary time formalism and an improved renormalized perturbation theory which incorporates second order Debye screening are used. General results are presented for the leading high temperature contributions to all renormalized connected photon Green's functions for fixed external momenta (much smaller than the temperature) to all orders in the improved perturbation theory. Those leading contributions are ultraviolet finite, infrared convergent and gauge invariant, and display an interesting form of dimensional reduction at high temperature. A new path integral representations is given for the high temperature partition function with an external photon source, which is shown to generate all leading high temperature Green's functions mentioned above, and, so, it displays neatly the kind of dimensional reduction which makes QED to become simpler at high temperature. This limiting partition function corresponds to an imaginary time dependent electron positron field interacting with an electromagnetic field at zero imaginary time, and it depends on the renormalized electron mass and electric charge, the second order contribution to the usual renormalization constant Z 3 and a new mass term, which is associated to the photon field with vanishing Lorentz index. The new mass term corresponds to a finite number of diagrams in the high temperature improved perturbation theory and carriers ultraviolet divergences which are compensated for by other contributions (so that the leading high temperature Green's functions referred to above are ultraviolet finite). The dominant high temperature contributions to the renormalized thermodynamic potential to all perturbative orders: i) are given in terms of the above leading high-temperature contributions to the photon Green's functions (except for a few diagrams of low order in the improved perturbation theory), ii) are both ultraviolet and infrared finite. (author)
Scalar Quantum Electrodynamics: Perturbation Theory and Beyond
International Nuclear Information System (INIS)
Bashir, A.; Gutierrez-Guerrero, L. X.; Concha-Sanchez, Y.
2006-01-01
In this article, we calculate scalar propagator in arbitrary dimensions and gauge and the three-point scalar-photon vertex in arbitrary dimensions and Feynman gauge, both at the one loop level. We also discuss constraints on their non perturbative structure imposed by requirements of gauge invariance and perturbation theory