Quantum Erasure: Quantum Interference Revisited
Walborn, Stephen P.; Cunha, Marcelo O Terra; Pádua, Sebastião; Monken, Carlos H.
2005-01-01
Recent experiments in quantum optics have shed light on the foundations of quantum physics. Quantum erasers - modified quantum interference experiments - show that quantum entanglement is responsible for the complementarity principle.
DEFF Research Database (Denmark)
Jørgensen, Jacob Lykkebo; Gagliardi, Alessio; Pecchia, Alessandro;
2014-01-01
Destructive quantum interference in single molecule electronics is an intriguing phenomenon; however, distinguishing quantum interference effects from generically low transmission is not trivial. In this paper, we discuss how quantum interference effects in the transmission lead to either low...... suppressed when quantum interference effects dominate. That is, we expand the understanding of propensity rules in inelastic electron tunneling spectroscopy to molecules with destructive quantum interference....
The quantum anomalous Hall effect
LIU, CHAO-XING; Zhang, Shou-Cheng; Qi, Xiao-Liang
2015-01-01
The quantum anomalous Hall effect is defined as a quantized Hall effect realized in a system without external magnetic field. Quantum anomalous Hall effect is a novel manifestation of topological structure in many-electron systems, and may have potential applications in future electronic devices. In recent years, quantum anomalous Hall effect has been proposed theoretically and realized experimentally. In this review article, we provide a systematic overview of the theoretical and experimenta...
Interference of Quantum Market Strategies
Piotrowski, Edward W.; Jan Sladkowski; Jacek Syska
2002-01-01
Recent development in quantum computation and quantum information theory allows to extend the scope of game theory for the quantum world. The paper is devoted to the analysis of interference of quantum strategies in quantum market games.
Entanglement and quantum interference
O'Hara, Paul
2006-01-01
In the history of quantum mechanics, much has been written about the double-slit experiment, and much debate as to its interpretation has ensued. Indeed, to explain the interference patterns for sub-atomic particles, explanations have been given not only in terms of the principle of complementarity and wave-particle duality but also in terms of quantum consciousness and parallel universes. In this paper, the topic will be discussed from the perspective of spin-coupling in the hope of further ...
Quantum Confined Fano Interference
International Nuclear Information System (INIS)
We study the transition from a dense continuum to a sparse quasicontinuum in the Fano problem. Transmission measurements on epitaxial layers of GaAs in a high magnetic field and calculations of the optical absorption show how the Fano interference disappears as quantum confinement discretizes the continuum states. The transition between quasi-one-dimensional and quasi-zero-dimensional systems occurs at length scales which are unusually large for optical experiments. copyright 1997 The American Physical Society
Quantum interference in polyenes
Energy Technology Data Exchange (ETDEWEB)
Tsuji, Yuta; Hoffmann, Roald, E-mail: rh34@cornell.edu [Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, New York 14853 (United States); Movassagh, Ramis [Department of Mathematics, Northeastern University, Boston, Massachusetts 02115, USA and Department of Mathematics, Massachusetts Institute of Technology, Building E18, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139-4307 (United States); Datta, Supriyo [School of Electrical and Computer Engineering, Purdue University, Electrical Engineering Building, 465 Northwestern Ave., West Lafayette, Indiana 47907-2035 (United States)
2014-12-14
The explicit form of the zeroth Green's function in the Hückel model, approximated by the negative of the inverse of the Hückel matrix, has direct quantum interference consequences for molecular conductance. We derive a set of rules for transmission between two electrodes attached to a polyene, when the molecule is extended by an even number of carbons at either end (transmission unchanged) or by an odd number of carbons at both ends (transmission turned on or annihilated). These prescriptions for the occurrence of quantum interference lead to an unexpected consequence for switches which realize such extension through electrocyclic reactions: for some specific attachment modes the chemically closed ring will be the ON position of the switch. Normally the signs of the entries of the Green's function matrix are assumed to have no physical significance; however, we show that the signs may have observable consequences. In particular, in the case of multiple probe attachments – if coherence in probe connections can be arranged – in some cases new destructive interference results, while in others one may have constructive interference. One such case may already exist in the literature.
Graphene quantum interference photodetector
Directory of Open Access Journals (Sweden)
Mahbub Alam
2015-03-01
Full Text Available In this work, a graphene quantum interference (QI photodetector was simulated in two regimes of operation. The structure consists of a graphene nanoribbon, Mach–Zehnder interferometer (MZI, which exhibits a strongly resonant transmission of electrons of specific energies. In the first regime of operation (that of a linear photodetector, low intensity light couples two resonant energy levels, resulting in scattering and differential transmission of current with an external quantum efficiency of up to 5.2%. In the second regime of operation, full current switching is caused by the phase decoherence of the current due to a strong photon flux in one or both of the interferometer arms in the same MZI structure. Graphene QI photodetectors have several distinct advantages: they are of very small size, they do not require p- and n-doped regions, and they exhibit a high external quantum efficiency.
Ghost Interference and Quantum Erasure
Chingangbam, Pravabati; Qureshi, Tabish
2005-01-01
The two-photon ghost interference experiment, generalized to the case of massive particles, is theoretically analyzed. It is argued that the experiment is intimately connected to a double-slit interference experiment where, the which-path information exists. The reason for not observing first order interference behind the double-slit, is clarified.It is shown that the underlying mechanism for the appearance of ghost interference is, the more familiar, quantum erasure.
Modeling double slit interference via anomalous diffusion: independently variable slit widths
Pascasio, Johannes Mesa; Fussy, Siegfried; Schwabl, Herbert; Groessing, Gerhard
2013-01-01
Based on a re-formulation of the classical explanation of quantum mechanical Gaussian dispersion (Groessing et al. 2010) as well as interference of two Gaussians (Groessing et al. 2012), we present a new and more practical way of their simulation. The quantum mechanical "decay of the wave packet" can be described by anomalous sub-quantum diffusion with a specific diffusivity varying in time due to a particle's changing thermal environment. In a simulation of the double-slit experiment with di...
Quantum Interference in Graphene Nanoconstrictions.
Gehring, Pascal; Sadeghi, Hatef; Sangtarash, Sara; Lau, Chit Siong; Liu, Junjie; Ardavan, Arzhang; Warner, Jamie H; Lambert, Colin J; Briggs, G Andrew D; Mol, Jan A
2016-07-13
We report quantum interference effects in the electrical conductance of chemical vapor deposited graphene nanoconstrictions fabricated using feedback controlled electroburning. The observed multimode Fabry-Pérot interferences can be attributed to reflections at potential steps inside the channel. Sharp antiresonance features with a Fano line shape are observed. Theoretical modeling reveals that these Fano resonances are due to localized states inside the constriction, which couple to the delocalized states that also give rise to the Fabry-Pérot interference patterns. This study provides new insight into the interplay between two fundamental forms of quantum interference in graphene nanoconstrictions. PMID:27295198
"Quantum Interference with Slits" Revisited
Rothman, Tony
2010-01-01
Marcella [arXiv:quant-ph/0703126] has presented a straightforward technique employing the Dirac formalism to calculate single- and double-slit interference patterns. He claims that no reference is made to classical optics or scattering theory and that his method therefore provides a purely quantum mechanical description of these experiments. He also presents his calculation as if no approximations are employed. We show that he implicitly makes the same approximations found in classical treatments of interference and that no new physics has been introduced. At the same time, some of the quantum mechanical arguments Marcella gives are, at best, misleading.
"Quantum Interference with Slits" Revisited
Rothman, Tony; Boughn, Stephen
2011-01-01
Marcella has presented a straightforward technique employing the Dirac formalism to calculate single- and double-slit interference patterns. He claims that no reference is made to classical optics or scattering theory and that his method therefore provides a purely quantum mechanical description of these experiments. He also presents his…
Graphene Superconducting Quantum Interference Device
Girit, Çaǧlar; Bouchiat, Vincent; Naaman, Ofer; Zhang, Yuanbo; Crommie, Michael; Zettl, Alex; Siddiqi, Irfan
2010-03-01
Graphene can support Cooper pair transport when contacted with two superconducting electrodes, resulting in the well-known Josephson effect. By depositing aluminum/palladium electrodes in the geometry of a loop onto a single graphene sheet, we fabricate a two junction dc superconducting quantum interference device (SQUID). Not only an the supercurrent in this device be increased by moving the electrostatic gate away from the Dirac point, but it can also be modulated periodically by an applied magnetic field---a potentially powerful probe of electronic transport in graphene. We analyze the magnetic field modulation of the critical current with the asymmetric/inductive SQUID model of Fulton and Dynes and discuss the variation of the fitting parameters with gate voltage.
General Quantum Interference Principle and Duality Computer
Institute of Scientific and Technical Information of China (English)
LONG Gui-Lu
2006-01-01
In this article, we propose a general principle of quantum interference for quantum system, and based on this we propose a new type of computing machine, the duality computer, that may outperform in principle both classical computer and the quantum computer. According to the general principle of quantum interference, the very essence of quantum interference is the interference of thesub-waves of the quantum system itself. A quantum system considered here can be any quantum system: a single microscopic particle, a composite quantum system such as an atom or a molecule, or a loose collection of a few quantum objects such as two independent photons. In the duality computer,the wave of the duality computer is split into several sub-waves and they pass through different routes, where different computing gate operations are performed. These sub-waves are then re-combined to interfere to give the computational results. The quantum computer, however, has only used the particle nature of quantum object. In a duality computer,it may be possible to find a marked item from an unsorted database using only a single query, and all NP-complete problems may have polynomial algorithms. Two proof-of-the-principle designs of the duality computer are presented:the giant molecule scheme and the nonlinear quantum optics scheme. We also propose thought experiment to check the related fundamental issues, the measurement efficiency of a partial wave function.
Collision-induced constructive quantum interference
International Nuclear Information System (INIS)
We theoretically study the collision-induced constructive quantum interference in an open four-level system with the density-matrix approach based on the experimental observation of constructive quantum interference between two transition pathways 3P1/2-5S (or 4D) and 3P3/2-5S (or 4D) via equal-frequency hybrid excitation in the Na2-Na system. The effects of the collision-induced coherent and incoherent decay rates and the ratio of the two transition dipole moments on the interference are analyzed. It is shown that through the incoherent process (collision), the coherence between a widely separated doublet and subsequent constructive quantum interference can be realized. The physical origin of the constructive interference can be seen clearly in the dressed-atom picture. The theoretical results can also be used to qualitatively explain the dependence of quantum interference on the experimental buffer gas pressure and sample temperature
Scaling theory for anomalous semiclassical quantum transport
International Nuclear Information System (INIS)
Quantum transport through devices coupled to electron reservoirs can be described in terms of the full counting statistics (FCS) of charge transfer. Transport observables, such as conductance and shot-noise power are just cumulants of FCS and can be obtained from the sample’s average density of transmission eigenvalues, which in turn can be obtained from a finite element representation of the saddle-point equation of the Keldysh (or supersymmetric) nonlinear sigma model, known as quantum circuit theory. Normal universal metallic behavior in the semiclassical regime is controlled by the presence of a Fabry–Pérot singularity in the average density of transmission eigenvalues. We present general conditions for the suppression of Fabry–Pérot modes in the semiclassical regime in a sample of arbitrary shape, a disordered conductor or a network of ballistic quantum dots, which leads to an anomalous metallic phase. Through a double-scaling limit, we derive a scaling equation for anomalous metallic transport, in the form of a nonlinear differential equation, which generalizes the ballistic-diffusive scaling equation of a normal metal. The two-parameter stationary solution of our scaling equation generalizes Dorokhov’s universal single-parameter distribution of transmission eigenvalues. We provide a simple interpretation of the stationary solution using a thermodynamic analogy with a spin-glass system. As an application, we consider a system formed by a diffusive wire coupled via a barrier to normal-superconductor reservoirs. We observe anomalous reflectionless tunneling, when all perfectly transmitting channels are suppressed, which cannot be explained by the usual mechanism of disorder-induced opening of tunneling channels. (paper)
Scaling theory for anomalous semiclassical quantum transport
Sena-Junior, M. I.; Macêdo, A. M. S.
2016-01-01
Quantum transport through devices coupled to electron reservoirs can be described in terms of the full counting statistics (FCS) of charge transfer. Transport observables, such as conductance and shot-noise power are just cumulants of FCS and can be obtained from the sample's average density of transmission eigenvalues, which in turn can be obtained from a finite element representation of the saddle-point equation of the Keldysh (or supersymmetric) nonlinear sigma model, known as quantum circuit theory. Normal universal metallic behavior in the semiclassical regime is controlled by the presence of a Fabry-Pérot singularity in the average density of transmission eigenvalues. We present general conditions for the suppression of Fabry-Pérot modes in the semiclassical regime in a sample of arbitrary shape, a disordered conductor or a network of ballistic quantum dots, which leads to an anomalous metallic phase. Through a double-scaling limit, we derive a scaling equation for anomalous metallic transport, in the form of a nonlinear differential equation, which generalizes the ballistic-diffusive scaling equation of a normal metal. The two-parameter stationary solution of our scaling equation generalizes Dorokhov's universal single-parameter distribution of transmission eigenvalues. We provide a simple interpretation of the stationary solution using a thermodynamic analogy with a spin-glass system. As an application, we consider a system formed by a diffusive wire coupled via a barrier to normal-superconductor reservoirs. We observe anomalous reflectionless tunneling, when all perfectly transmitting channels are suppressed, which cannot be explained by the usual mechanism of disorder-induced opening of tunneling channels.
Measurement-Based Interference in Quantum Computation
International Nuclear Information System (INIS)
The interference has been measured by the visibility in two-level systems, which, however, does not work for multi-level systems. We generalize a measure of the interference based on decoherence process, consistent with the visibility in qubit systems. By taking cluster states as examples, we show in the one-way quantum computation that the gate fidelity is proportional to the interference of the measured qubit and is inversely proportional to the interference of all register qubits. We also find that the interference increases with the number of the computing steps. So we conjecture that the interference may be the source of the speedup of the one-way quantum computation. (general)
Measurement-Based Interference in Quantum Computation
Xu, You-Yang
2013-09-01
The interference has been measured by the visibility in two-level systems, which, however, does not work for multi-level systems. We generalize a measure of the interference based on decoherence process, consistent with the visibility in qubit systems. By taking cluster states as examples, we show in the one-way quantum computation that the gate fidelity is proportional to the interference of the measured qubit and is inversely proportional to the interference of all register qubits. We also find that the interference increases with the number of the computing steps. So we conjecture that the interference may be the source of the speedup of the one-way quantum computation.
Quantum theory of two-photon interference
Wu, Xiang-Yao; Zhang, Bo-Jun; Liu, Xiao-Jing; LI Hong; Zhang, Si-Qi; Jing WANG; Wu, Yi-Heng; Li, Jing-Wu
2012-01-01
In this paper, we study two-photon interference with the approach of photon quantum theory, with specific attention to the two-photon interference experiment carried out by Milena D'Angelo et al. (Phys. Rev. Lett 87:013602, 2001). We find the theoretical result is accordance with experiment data.
Scattering Induced Quantum Interference of Multiple Quantum Optical States
DEFF Research Database (Denmark)
Ott, Johan Raunkjær; Wubs, Martijn; Mortensen, N. Asger;
2011-01-01
Using a discrete mode theory for propagation of quantum optical states, we investigate the consequences of multiple scattering on the degree of quadrature entanglement and quantum interference. We report that entangled states can be created by multiple-scattering. We furthermore show that quantum...
Quantum radiation reaction: from interference to incoherence
Dinu, Victor; Ilderton, Anton; Marklund, Mattias; Torgrimsson, Greger
2015-01-01
We investigate quantum radiation reaction in laser-electron interactions across different energy and intensity regimes. Using a fully quantum approach which also accounts exactly for the effect of the strong laser pulse on the electron motion, we identify in particular a regime in which radiation reaction is dominated by quantum interference. We find signatures of quantum radiation reaction in the electron spectra which have no classical analogue and which cannot be captured by the incoherent approximations typically used in the high-intensity regime. These signatures are measurable with presently available laser and accelerator technology.
Metasurface-Enabled Remote Quantum Interference.
Jha, Pankaj K; Ni, Xingjie; Wu, Chihhui; Wang, Yuan; Zhang, Xiang
2015-07-10
An anisotropic quantum vacuum (AQV) opens novel pathways for controlling light-matter interaction in quantum optics, condensed matter physics, etc. Here, we theoretically demonstrate a strong AQV over macroscopic distances enabled by a judiciously designed array of subwavelength-scale nanoantennas-a metasurface. We harness the phase-control ability and the polarization-dependent response of the metasurface to achieve strong anisotropy in the decay rate of a quantum emitter located over distances of hundreds of wavelengths. Such an AQV induces quantum interference among radiative decay channels in an atom with orthogonal transitions. Quantum vacuum engineering with metasurfaces holds promise for exploring new paradigms of long-range light-matter interaction for atom optics, solid-state quantum optics, quantum information processing, etc. PMID:26207477
IETS and quantum interference: propensity rules in the presence of an interference feature.
Lykkebo, Jacob; Gagliardi, Alessio; Pecchia, Alessandro; Solomon, Gemma C
2014-09-28
Destructive quantum interference in single molecule electronics is an intriguing phenomenon; however, distinguishing quantum interference effects from generically low transmission is not trivial. In this paper, we discuss how quantum interference effects in the transmission lead to either low current or a particular line shape in current-voltage curves, depending on the position of the interference feature. Second, we consider how inelastic electron tunneling spectroscopy can be used to probe the presence of an interference feature by identifying vibrational modes that are selectively suppressed when quantum interference effects dominate. That is, we expand the understanding of propensity rules in inelastic electron tunneling spectroscopy to molecules with destructive quantum interference. PMID:25273424
IETS and quantum interference: Propensity rules in the presence of an interference feature
Energy Technology Data Exchange (ETDEWEB)
Lykkebo, Jacob; Solomon, Gemma C., E-mail: gsolomon@nano.ku.dk [Nano-Science Center and Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø (Denmark); Gagliardi, Alessio [Technische Universität München, Electrical Engineering and Information Tech., Arcisstr. 21, 80333 München (Germany); Pecchia, Alessandro [Consiglio Nazionale delle Ricerche, ISMN, Via Salaria km 29.6, 00017 Monterotondo (Rome) (Italy)
2014-09-28
Destructive quantum interference in single molecule electronics is an intriguing phenomenon; however, distinguishing quantum interference effects from generically low transmission is not trivial. In this paper, we discuss how quantum interference effects in the transmission lead to either low current or a particular line shape in current-voltage curves, depending on the position of the interference feature. Second, we consider how inelastic electron tunneling spectroscopy can be used to probe the presence of an interference feature by identifying vibrational modes that are selectively suppressed when quantum interference effects dominate. That is, we expand the understanding of propensity rules in inelastic electron tunneling spectroscopy to molecules with destructive quantum interference.
IETS and quantum interference: Propensity rules in the presence of an interference feature
International Nuclear Information System (INIS)
Destructive quantum interference in single molecule electronics is an intriguing phenomenon; however, distinguishing quantum interference effects from generically low transmission is not trivial. In this paper, we discuss how quantum interference effects in the transmission lead to either low current or a particular line shape in current-voltage curves, depending on the position of the interference feature. Second, we consider how inelastic electron tunneling spectroscopy can be used to probe the presence of an interference feature by identifying vibrational modes that are selectively suppressed when quantum interference effects dominate. That is, we expand the understanding of propensity rules in inelastic electron tunneling spectroscopy to molecules with destructive quantum interference
Control of exciton transport using quantum interference
Lusk, Mark T.; Stafford, Charles A.; Zimmerman, Jeramy D.; Carr, Lincoln D.
2015-12-01
It is shown that quantum interference can be employed to create an exciton transistor. An applied potential gates the quasiparticle motion and also discriminates between quasiparticles of differing binding energy. When implemented within nanoscale assemblies, such control elements could mediate the flow of energy and information. Quantum interference can also be used to dissociate excitons as an alternative to using heterojunctions. A finite molecular setting is employed to exhibit the underlying discrete, two-particle, mesoscopic analog to Fano antiresonance. Selected entanglement measures are shown to distinguish regimes of behavior which cannot be resolved from population dynamics alone.
Quantum interference vs. quantum chaos in the nuclear shell model
International Nuclear Information System (INIS)
In this paper we study the complexity of the nuclear states in terms of a two body quadupole-quadrupole interaction. Energy distributions and eigenvectors composition exhibit a visible interference pattern which is dependent on the intensity of the interaction. In analogy with optics, the visibility of the interference is related to the purity of the states, therefore, we show that the fluctuations associated with quantum chaos have as their origin the remaining quantum coherence with a visibility magnitude close to 5%
Quantum interference effects for the electronic fluctuations in quantum dots
International Nuclear Information System (INIS)
For the main quantum interference term of coherent electronic transport, we study the effect of temperature, perpendicular and/or parallel magnetic fields, spin-orbit coupling and tunneling rates in both metallic grains and mesoscopic heterostructures. We show that the Zeeman effects determines a crucial way to characterize the quantum interference phenomena of the noise for anisotropic systems (mesoscopic heterostructures), qualitatively distinct from those observed in isotropic structures (metallic grains). (author)
Understanding quantum interference in General Nonlocality
Wanng, Hai-Jhun
2010-01-01
In this paper we attempt to give an understanding of quantum double-slit interference of fermions in the framework of General Nonlocality (GN) [J. Math. Phys. 49, 033513 (2008)] by studying the self-interaction of matter wave. From the metric of the GN, we derive a special formalism to interpret the interference contrast when the self-interaction is perturbative. According to the formalism, the characteristic of interference pattern is in agreement with experiment qualitatively. As examples, we apply the formalism to the cases governed by Schr\\"odinger current and Dirac current respectively, both of which are relevant to topology. The gap between these two cases corresponds to a spin-current effect, which is possible to test in the near future. In addition, a general interference formalism for both perturbative and non-perturbative self-interactions is presented. By analyzing the general formalism we predict that in the nonperturbative limit there is no interference at all.
Neutron Interference Experiments and Quantum Measurement Theory
Namiko, M.; Otake, Y.; Soshi, H.
1987-03-01
Physical and epistemological implications of recent experiments on the neutron interference are discussed from the viewpoint of the Machida-Namiki theory of measurement in quantum mechanics, without resort to discussion on the number-phase uncertainty relation. The same idea is also applied to the neutrino oscillation problem.
Nonclassical Paths in Quantum Interference Experiments
Sawant, Rahul; Samuel, Joseph; Sinha, Aninda; Sinha, Supurna; Sinha, Urbasi
2014-09-01
In a double slit interference experiment, the wave function at the screen with both slits open is not exactly equal to the sum of the wave functions with the slits individually open one at a time. The three scenarios represent three different boundary conditions and as such, the superposition principle should not be applicable. However, most well-known text books in quantum mechanics implicitly and/or explicitly use this assumption that is only approximately true. In our present study, we have used the Feynman path integral formalism to quantify contributions from nonclassical paths in quantum interference experiments that provide a measurable deviation from a naive application of the superposition principle. A direct experimental demonstration for the existence of these nonclassical paths is difficult to present. We find that contributions from such paths can be significant and we propose simple three-slit interference experiments to directly confirm their existence.
Radio VLBI and the quantum interference paradox
Singal, Ashok K
2016-01-01
We address here the question of interference of radio signals from astronomical sources like distant quasars, in a very long baseline interferometer (VLBI), where two (or more) distantly located radio telescopes (apertures), receive simultaneous signal from the sky. In an equivalent optical two-slit experiment, it is generally argued that for the photons involved in the interference pattern on the screen, it is not possible, even in principle, to ascertain which of the two slits a particular photon went through. It is argued that any procedure to ascertain this destroys the interference pattern. But in the case of the modern radio VLBI, it is a routine matter to record the phase and amplitude of the voltage outputs from the two radio antennas on a recording media separately and then do the correlation between the two recorded signals later in an offline manner. Does this not violate the quantum interference principle? We provide a resolution of this problem here.
Quantum Interference of Multiple Beams Induced by Multiple Scattering
DEFF Research Database (Denmark)
Ott, Johan Raunkjær; Mortensen, N. Asger; Lodahl, Peter
2011-01-01
We report on quantum interference induced by the transmission of quantized light through a multiple-scattering medium. We show that entangled states can be created by multiple-scattering and that quantum interference survives disorder averaging.......We report on quantum interference induced by the transmission of quantized light through a multiple-scattering medium. We show that entangled states can be created by multiple-scattering and that quantum interference survives disorder averaging....
Quantum coherence generated by interference-induced state selectiveness
Garreau, Jean Claude
2001-01-01
The relations between quantum coherence and quantum interference are discussed. A general method for generation of quantum coherence through interference-induced state selection is introduced and then applied to `simple' atomic systems under two-photon transitions, with applications in quantum optics and laser cooling.
IETS and quantum interference: propensity rules in the presence of an interference feature
Lykkebo, Jacob; Gagliardi, Alessio; Pecchia, Alessandro; Gemma C. Solomon
2014-01-01
Destructive quantum interference in single molecule electronics is an intriguing phe- nomenon; however, distinguishing quantum interference effects from generically low transmission is not trivial. In this paper, we discuss how quantum interference ef- fects in the transmission lead to either low current or a particular line shape in current-voltage curves, depending on the position of the interference feature. Sec- ondly, we consider how inelastic electron tunneling spectroscopy can be used ...
Strong Correlation of Fluorescence Photons without Quantum Interference
Institute of Scientific and Technical Information of China (English)
HU Xiang-Ming; WANG Fei
2007-01-01
It has been predicted that a driven three-level V atom can emit strongly correlated fluorescence photons in the presence of quantum interference. Here we examine the effects of quantum interference on the intensity correlation of fluorescence photons emitted from a driven three-level A atom. Unexpectedly, strong correlation occurs without quantum interference. The quantum interference tends to reduce the correlation function to a normal level. The essential difference between these two cases is traced to the different effects of quantum interference on coherent population trapping (CPT). For the V atom, quantum interference and coherent excitation combine to lead to CPT. For the A atom, however, the quantum interference tends to spoil CPT while the coherent excitation induces the effect.
Quantum interference in an electron-hole graphene ring system
Energy Technology Data Exchange (ETDEWEB)
Smirnov, D.; Schmidt, H.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2 30167 Hannover (Germany)
2013-12-04
Quantum interference is observed in a graphene ring system via the Aharonov Bohm effect. As graphene is a gapless semiconductor, this geometry allows to study the unique situation of quantum interference between electrons and holes in addition to the unipolar quantum interference. The period and amplitude of the observed Aharonov-Bohm oscillations are independent of the sign of the applied gate voltage showing the equivalence between unipolar and dipolar interference.
Quantum non-demolition (QND) modulation of quantum interference
Genovese, M.; Novero, C.
1999-01-01
We propose an experiment where quantum interference between two different paths is modulated by means of a QND measurement on one or both the arm of the interferometer. The QND measurement is achieved in a Kerr cell. We illustrate a scheme for the realisation of this experiment and some further developments.
Colloquium: Quantum interference of clusters and molecules
Hornberger, Klaus; Haslinger, Philipp; Nimmrichter, Stefan; Arndt, Markus
2011-01-01
We review recent progress and future prospects of matter wave interferometry with complex organic molecules and inorganic clusters. Three variants of a near-field interference effect, based on diffraction by material nanostructures, at optical phase gratings, and at ionizing laser fields are considered. We discuss the theoretical concepts underlying these experiments and the experimental challenges. This includes optimizing interferometer designs as well as understanding the role of decoherence. The high sensitivity of matter wave interference experiments to external perturbations is demonstrated to be useful for accurately measuring internal properties of delocalized nanoparticles. We conclude by investigating the prospects for probing the quantum superposition principle in the limit of high particle mass and complexity.
Quantum Anomalous Hall Effect in Magnetic Insulator Heterostructure
Xu, Gang; Jing WANG; FELSER, CLAUDIA; Qi, Xiao-Liang; Zhang, Shou-Cheng
2014-01-01
Based on ab initio calculations, we predict that a monolayer of Cr-doped (Bi,Sb)2Te3 and GdI2 heterostructure is a quantum anomalous Hall insulator with a non-trivial band gap up to 38 meV. The principle behind our prediction is that the band inversion between two topologically trivial ferromagnetic insulators can result in a non-zero Chern number, which offers a better way to realize the quantum anomalous Hall state without random magnetic doping. In addition, a simple effective model is pre...
Tunable graphene dc superconducting quantum interference device.
Girit, Caglar; Bouchiat, V; Naaman, O; Zhang, Y; Crommie, M F; Zettl, A; Siddiqi, I
2009-01-01
Graphene exhibits unique electrical properties on account of its reduced dimensionality and "relativistic" band structure. When contacted with two superconducting electrodes, graphene can support Cooper pair transport, resulting in the well-known Josephson effect. We report here the fabrication and operation of a two junction dc superconducting quantum interference device (SQUID) formed by a single graphene sheet contacted with aluminum/palladium electrodes in the geometry of a loop. The supercurrent in this device can be modulated not only via an electrostatic gate but also by an applied magnetic fielda potentially powerful probe of electronic transport in graphene and an ultrasensitive platform for nanomagnetometry. PMID:19090696
Quantum Interference and Entanglement Induced by Multiple Scattering of Light
DEFF Research Database (Denmark)
Ott, Johan Raunkjær; Mortensen, Asger; Lodahl, Peter
2010-01-01
We report on the effects of quantum interference induced by the transmission of an arbitrary number of optical quantum states through a multiple-scattering medium. We identify the role of quantum interference on the photon correlations and the degree of continuous variable entanglement between two...... output modes. It is shown that quantum interference survives averaging over all ensembles of disorder and manifests itself as increased photon correlations due to photon antibunching. Furthermore, the existence of continuous variable entanglement correlations in a volume speckle pattern is predicted. Our...... results suggest that multiple scattering provides a promising way of coherently interfering many independent quantum states of light of potential use in quantum information processing....
Phase control of light propagation via Fano interference in asymmetric double quantum wells
Energy Technology Data Exchange (ETDEWEB)
Yang, Wen-Xing, E-mail: wenxingyang2@126.com [Department of Physics, Southeast University, Nanjing 210096 (China); Institute of Photonics Technologies, National Tsing-Hua University, Hsinchu 300, Taiwan (China); Lu, Jia-Wei; Zhou, Zhi-Kang; Yang, Long [Department of Physics, Southeast University, Nanjing 210096 (China); Lee, Ray-Kuang [Institute of Photonics Technologies, National Tsing-Hua University, Hsinchu 300, Taiwan (China)
2014-05-28
We investigate the light propagation and dynamical control of a weak pulsed probe field in asymmetric double quantum wells via Fano interference, which is caused by tunneling from the excited subbands to the same continuum. Our results show that the system can produce anomalous and normal dispersion regions with negligible absorption by choosing appropriate coupling strength of the tunneling and the Fano interference. Interesting enough, the dispersion can be switched between normal and anomalous by adjusting the relative phase between the pulsed probe and coherent control fields owing to the existence of the perfectly Fano interference. Thus, the relative phase can be regarded as a switch to manipulate light propagation with subluminal or superluminal. The temporal and spatial dynamics of the pulsed probe field with hyperbolic secant envelope are analyzed.
Phase control of light propagation via Fano interference in asymmetric double quantum wells
International Nuclear Information System (INIS)
We investigate the light propagation and dynamical control of a weak pulsed probe field in asymmetric double quantum wells via Fano interference, which is caused by tunneling from the excited subbands to the same continuum. Our results show that the system can produce anomalous and normal dispersion regions with negligible absorption by choosing appropriate coupling strength of the tunneling and the Fano interference. Interesting enough, the dispersion can be switched between normal and anomalous by adjusting the relative phase between the pulsed probe and coherent control fields owing to the existence of the perfectly Fano interference. Thus, the relative phase can be regarded as a switch to manipulate light propagation with subluminal or superluminal. The temporal and spatial dynamics of the pulsed probe field with hyperbolic secant envelope are analyzed.
Anomalous conductances in an ultracold quantum wire
Kanász-Nagy, Márton; Esslinger, Tilman; Demler, Eugene A
2016-01-01
We analyze the recently measured anomalous transport properties of an ultracold gas through a ballistic constriction [S. Krinner et al., PNAS 201601812 (2016)]. The quantized conductance observed at weak interactions increases several-fold as the gas is made strongly interacting, which cannot be explained by the Landauer theory of single-channel transport. We show that this phenomenon is due to the multichannel Andreev reflections at the edges of the constriction, where the interaction and confinement result in a superconducting state. Andreev processes convert atoms of otherwise reflecting channels into the condensate propagating through the constriction, leading to a significant excess conductance. Furthermore, we find the spin conductance being suppressed by superconductivity; the agreement with experiment provides an additional support for our model.
Fraunhofer regime of operation for superconducting quantum interference filters
DEFF Research Database (Denmark)
Shadrin, A.V.; Constantinian, K.Y.; Ovsyannikov, G.A.;
2008-01-01
Series arrays of superconducting quantum interference devices (SQUIDs) with incommensurate loop areas, so-called superconducting quantum interference filters (SQIFs), are investigated in the kilohertz and the gigahertz frequency range. In SQIFs made of high-T-c bicrystal junctions the flux...
Interference of probabilities and number field structure of quantum models
Khrennikov, Andrei
2001-01-01
We study the probabilistic consequences of the choice of the basic number field in quantum formalism. We demonstrate that by choosing a number field for a linear space representation of quantum model it is possible to describe various interference phenomena. We analyse interference of probabilistic alternatives induced by real, complex, hyperbolic (Clifford) and p-adic representations.
Ruling Out Multi-Order Interference in Quantum Mechanics
Sinha, Urbasi; Jennewein, Thomas; Laflamme, Raymond; Weihs, Gregor
2010-01-01
Quantum mechanics and gravitation are two pillars of modern physics. Despite their success in describing the physical world around us, they seem to be incompatible theories. There are suggestions that one of these theories must be generalized to achieve unification. For example, Born's rule, one of the axioms of quantum mechanics could be violated. Born's rule predicts that quantum interference, as shown by a double slit diffraction experiment, occurs from pairs of paths. A generalized version of quantum mechanics might allow multi-path, i.e. higher order interferences thus leading to a deviation from the theory. We performed a three slit experiment with photons and bounded the magnitude of three path interference to less than 10-2 of the expected two-path interference, thus ruling out third and higher order interference and providing a bound on the accuracy of Born's rule. Our experiment is consistent with the postulate both in semi-classical and quantum regimes.
Anomalous Thermal Transport in Quantum Wires
Fazio, Rosario; Hekking, F. W. J.; Khmelnitskii, D. E.
1997-01-01
We study thermal transport in a one-dimensional quantum wire, connected to reservoirs. Despite of the absence of electron backscattering, interactions in the wire strongly influence thermal transport. Electrons propagate with unitary transmission through the wire and electric conductance is not affected. Energy, however, is carried by bosonic excitations (plasmons) which suffer from scattering even on scales much larger than the Fermi wavelength. If the electron density varies randomly, plasm...
Interference Visibility as a Witness of Entanglement and Quantum Correlation
Zhang, Lin; Pati, Arun Kumar; Wu, Junde
2014-01-01
In quantum information and communication one looks for the non-classical features like interference and quantum correlations to harness the true power of composite systems. We show how the concept akin to interference is, in fact, intertwined in a quantitative manner to entanglement and quantum correlation. In particular, we prove that the difference in the squared visibility for a density operator before and after a complete measurement, averaged over all unitary evolutions, is directly rela...
General relativistic effects in quantum interference of "clocks"
Zych, Magdalena; Costa, Fabio; Brukner, Časlav
2016-01-01
Quantum mechanics and general relativity have been each successfully tested in numerous experiments. However, the regime where both theories are jointly required to explain physical phenomena remains untested by laboratory experiments, and is also not fully understood by theory. This contribution reviews recent ideas for a new type of experiments: quantum interference of "clocks", which aim to test novel quantum effects that arise from time dilation. "Clock" interference experiments could be realised with atoms or photons in near future laboratory experiments.
Quantum anomalous Hall effect in magnetic topological insulators
Jing WANG; Lian, Biao; Zhang, Shou-Cheng
2014-01-01
The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimension (2D) and three-dimension (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magn...
General relativistic effects in quantum interference of ''clocks''
International Nuclear Information System (INIS)
Quantum mechanics and general relativity have been extensively and independently confirmed in many experiments. However, all experiments that measured the influence of gravity on quantum systems are still fully consistent with non-relativistic, Newtonian gravity. Here we discuss a novel effect in quantum interference experiments that can probe the interplay between quantum mechanics and general relativity. We consider interference of a ''clock'' - a particle with some evolving degrees of freedom - placed in a superposition of two different gravitational potentials. According to general relativity each amplitude of the superposition will experience a different gravitational time dilation. Due to quantum complementarity the visibility of quantum interference will thus drop to the extent to which the information about the location becomes available from the ''clock''. The clock can be implemented in an internal degree of freedom of a massive particle or in the position of a photon. The proposed experiment would thus provide the first test of quantum mechanics in curved background.
Anomalous spectral lines and relic quantum nonequilibrium
Underwood, Nicolas G
2016-01-01
We describe general features that might be observed in the line spectra of relic cosmological particles should quantum nonequilibrium be preserved in their statistics. According to our arguments, these features would represent a significant departure from those of a conventional origin. Among other features, we find a possible spectral broadening (for incident photons) that is proportional to the energy resolution of the recording telescope (and so could be orders of magnitude larger than any intrinsic broadening). Notably, for a range of possible initial conditions we find the possibility of spectral line `narrowing' whereby a telescope could observe a spectral line which is narrower than it should conventionally be able to resolve. We briefly discuss implications for the indirect search for dark matter.
Quantum interference shifts in laser spectroscopy with elliptical polarization
Amaro, Pedro; Safari, Laleh; Antognini, Aldo; Indelicato, Paul; Pohl, Randolf; Santos, José Paulo
2015-01-01
We investigate the quantum interference shifts between energetically close states, where the state structure is observed by laser spectroscopy. We report a compact and analytical expression that models the quantum interference induced shift for any admixture of circular polarization of the incident laser and angle of observation. An experimental scenario free of quantum interference can thus be predicted with this formula. Although, this study is exemplified here for muonic deuterium, it can be applied to any other laser spectroscopy measurement of $ns-n'p$ frequencies of a nonrelativistic atomic system, via a $ns\\rightarrow n'p \\rightarrow n"s $ scheme.
Quantum interference and manipulation of entanglement in silicon wire waveguide quantum circuits
International Nuclear Information System (INIS)
Integrated quantum photonic waveguide circuits are a promising approach to realizing future photonic quantum technologies. Here, we present an integrated photonic quantum technology platform utilizing the silicon-on-insulator material system, where quantum interference and the manipulation of quantum states of light are demonstrated in components orders of magnitude smaller than previous implementations. Two-photon quantum interference is presented in a multi-mode interference coupler, and the manipulation of entanglement is demonstrated in a Mach-Zehnder interferometer, opening the way to an all-silicon photonic quantum technology platform. (paper)
Photon wave functions and quantum interference experiments
Lapaire, G. G.; Sipe, J. E.
2006-01-01
We present a general theory to describe two-photon interference, including a formal description of few photon intereference in terms of single-photon amplitudes. With this formalism, it is possible to describe both frequency entangled and separable two-photon interference in terms of single-photon wave functions. Using this description, we address issues related to the physical interpretation of two-photon interference experiments. We include a discussion on how few-photon interference can be...
Quantum Dualities and Quantum Anomalous Hall Phases with Arbitrary Large Chern Numbers
Chern, Tong
2016-01-01
Quantum duality is a far reaching concept in contemporary theoretical physics. In the present paper, we reveal the quantum dualities in quantum anomalous Hall (QAH) phases through concrete two bands Hamiltonian models. Our models can realize QAH phases with arbitrary large Chern numbers. In real materials these models may be realized by stacked $n$ layer systems of $c_1=1$ QAH insulators. The topological phase transitions that can change the Chern numbers are studied. And we investigate the g...
Daniel Guterding; Jeschke, Harald O.; Roser Valentí
2015-01-01
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice M...
Asymptotic neutron scattering laws for anomalously diffusing quantum particles.
Kneller, Gerald R
2016-07-28
The paper deals with a model-free approach to the analysis of quasielastic neutron scattering intensities from anomalously diffusing quantum particles. All quantities are inferred from the asymptotic form of their time-dependent mean square displacements which grow ∝t(α), with 0 ≤ α diffusion (α = 0) is here explicitly included. We discuss in particular the intermediate scattering function for long times and the Fourier spectrum of the velocity autocorrelation function for small frequencies. Quantum effects enter in both cases through the general symmetry properties of quantum time correlation functions. It is shown that the fractional diffusion constant can be expressed by a Green-Kubo type relation involving the real part of the velocity autocorrelation function. The theory is exact in the diffusive regime and at moderate momentum transfers. PMID:27475344
Metal-to-insulator switching in quantum anomalous Hall states
Pan, Lei; Kou, Xufeng; Wang, Jing; Fan, Yabin; Choi, Eun Sang; Shao, Qiming; Zhang, Shou Cheng; Wang, Kang Lung
Quantum anomalous Hall effect (QAHE) was recently achieved in magnetic topological insulator films as a form of dissipationless transport without external magnetic field. However, the universal phase diagram of QAHE and its relation with quantum Hall effect (QHE) remain to be investigated. Here, we report the experimental observation of the giant longitudinal resistance peak and zero Hall conductance plateau at the coercive field in the six quintuple-layer (Cr0.12Bi0.26Sb0.62)2 Te3 film, and demonstrate the metal-to-insulator switching between two opposite QAHE plateau states up to 0.3 K. The universal QAHE phase diagram is further confirmed through the angle-dependent measurements. Our results address that the quantum phase transitions in both QAHE and QHE regimes are in the same universality class, yet the microscopic details are different.
Asymptotic neutron scattering laws for anomalously diffusing quantum particles
Kneller, Gerald R.
2016-07-01
The paper deals with a model-free approach to the analysis of quasielastic neutron scattering intensities from anomalously diffusing quantum particles. All quantities are inferred from the asymptotic form of their time-dependent mean square displacements which grow ∝tα, with 0 ≤ α scattering function for long times and the Fourier spectrum of the velocity autocorrelation function for small frequencies. Quantum effects enter in both cases through the general symmetry properties of quantum time correlation functions. It is shown that the fractional diffusion constant can be expressed by a Green-Kubo type relation involving the real part of the velocity autocorrelation function. The theory is exact in the diffusive regime and at moderate momentum transfers.
Interference and inequality in quantum decision theory
International Nuclear Information System (INIS)
The quantum decision theory is examined in its simplest form of two-condition two-choice setting. A set of inequalities to be satisfied by any quantum conditional probability describing the decision process is derived. Experimental data indicating the breakdown of classical explanations are critically examined with quantum theory using the full set of quantum phases.
Interference and inequality in quantum decision theory
Energy Technology Data Exchange (ETDEWEB)
Cheon, Taksu, E-mail: taksu.cheon@kochi-tech.ac.j [Laboratory of Physics, Kochi University of Technology, Tosa Yamada, Kochi 782-8502 (Japan); Takahashi, Taiki, E-mail: ttakahashi@lynx.let.hokudai.ac.j [Laboratory of Social Psychology, Department of Behavioral Science, Faculty of Letters, Hokkaido University, N.10, W.7, Kita-ku, Sapporo 060-0810 (Japan)
2010-12-01
The quantum decision theory is examined in its simplest form of two-condition two-choice setting. A set of inequalities to be satisfied by any quantum conditional probability describing the decision process is derived. Experimental data indicating the breakdown of classical explanations are critically examined with quantum theory using the full set of quantum phases.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
We propose a method of controlling the dc-SQUID(superconductiong quantum interference device)system by changing the gate voltages,which controls the amplitude of the fictitious magnetic fields Bz,and the externally applied current that produces the piercing magnetic flux Φx for the dc-SQUID system,we have also introduced a physical model for the dc-SQUID system.Using this physical model,one can obtain the non-adiabatic geometric phase gate for the single qubit and the non-adiabatic conditional geometric phase gate (controlled NOT gate) for the two qubits.It is shown that when the gate voltage and the externally applied current of the dc-SQUID system satisfies an appropriate constraint condition,the charge state evolution can be controlled exactly on a dynamic phase free path.The non-adiabatic evolution of the charge states is given as well.
Quantum Anomalous Hall Effect in Hg_1-yMn_yTe Quantum Wells
Energy Technology Data Exchange (ETDEWEB)
Liu, Chao-Xing; /Tsinghua U., Beijing /Stanford U., Phys. Dept.; Qi, Xiao-Liang; /Stanford U., Phys. Dept.; Dai, Xi; Fang, Zhong; /Beijing, Inst. Phys.; Zhang, Shou-Cheng; /Stanford U., Phys. Dept.
2010-03-19
The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg{sub 1-y}Mn{sub y}Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the Mn atoms, and the quantized Hall conductance is predicted for a range of quantum well thickness and the concentration of the Mn atoms. This effect enables dissipationless charge current in spintronics devices.
Quantum Interference between Transverse Spatial Waveguide Modes
Mohanty, Aseema; Dutt, Avik; Ramelow, Sven; Nussenzveig, Paulo; Lipson, Michal
2016-01-01
Integrated quantum optics has drastically reduced the size of table-top optical experiments to the chip-scale, allowing for demonstrations of large-scale quantum information processing and quantum simulation. However, despite these advances, practical implementations of quantum photonic circuits remain limited because they consist of large networks of waveguide interferometers that path encode information which do not easily scale. Increasing the dimensionality of current quantum systems using higher degrees of freedom such as transverse spatial field distribution, polarization, time, and frequency to encode more information per carrier will enable scalability by simplifying quantum computational architectures, increasing security and noise tolerance in quantum communication channels, and simulating richer quantum phenomena. Here we demonstrate a scalable platform for photonic quantum information processing using waveguide quantum circuit building blocks based on the transverse spatial mode degree of freedom:...
Guterding, Daniel; Jeschke, Harald O; Valentí, Roser
2016-01-01
Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions. PMID:27185665
Quantum anomalous Hall effect in topological insulator memory
Energy Technology Data Exchange (ETDEWEB)
Jalil, Mansoor B. A., E-mail: elembaj@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); Tan, S. G. [Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, Singapore 117576 (Singapore); Siu, Z. B. [Data Storage Institute, Agency for Science, Technology and Research A*STAR, DSI Building, 5 Engineering Drive 1, Singapore, Singapore 117608 (Singapore); NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore (Singapore)
2015-05-07
We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σ{sup xy} of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σ{sup xy} and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σ{sup xy} as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs.
Quantum anomalous Hall effect in topological insulator memory
International Nuclear Information System (INIS)
We theoretically investigate the quantum anomalous Hall effect (QAHE) in a magnetically coupled three-dimensional-topological insulator (3D-TI) system. We apply the generalized spin-orbit coupling Hamiltonian to obtain the Hall conductivity σxy of the system. The underlying topology of the QAHE phenomenon is then analyzed to show the quantization of σxy and its relation to the Berry phase of the system. Finally, we analyze the feasibility of utilizing σxy as a memory read-out in a 3D-TI based memory at finite temperatures, with comparison to known magnetically doped 3D-TIs
Quantum interference of independently generated telecom-band single photons
International Nuclear Information System (INIS)
We report on high-visibility quantum interference of independently generated telecom O-band (1310 nm) single photons using standard single-mode fibers. The experimental data are shown to agree well with the results of simulations using a comprehensive quantum multimode theory without the need for any fitting parameter
Quantum interference of independently generated telecom-band single photons
Energy Technology Data Exchange (ETDEWEB)
Patel, Monika [Center for Photonic Communication and Computing, Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3112 (United States); Altepeter, Joseph B.; Huang, Yu-Ping; Oza, Neal N. [Center for Photonic Communication and Computing, Department of Electrical Engineering and Computer Science, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3118 (United States); Kumar, Prem [Center for Photonic Communication and Computing, Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3112, USA and Center for Photonic Communication and Computing, Department of Electrical Engineering (United States)
2014-12-04
We report on high-visibility quantum interference of independently generated telecom O-band (1310 nm) single photons using standard single-mode fibers. The experimental data are shown to agree well with the results of simulations using a comprehensive quantum multimode theory without the need for any fitting parameter.
Two-particle interference in standard and Bohmian quantum mechanics
Energy Technology Data Exchange (ETDEWEB)
Guay, E; Marchildon, L [Departement de physique, Universite du Quebec, Trois-Rivieres, Qc, G9A 5H7 (Canada)
2003-05-23
The compatibility of standard and Bohmian quantum mechanics has recently been challenged in the context of two-particle interference, both from a theoretical and an experimental point of view. We analyse different setups proposed and derive corresponding exact forms for Bohmian equations of motion. The equations are then solved numerically, and shown to reproduce standard quantum-mechanical results.
An Exact Factorization Perspective on Quantum Interferences in Nonadiabatic Dynamics
Curchod, Basile F E; Gross, E K U
2016-01-01
Nonadiabatic quantum interferences emerge whenever nuclear wavefunctions in different electronic states meet and interact in a nonadiabatic region. In this work, we analyze how nonadiabatic quantum interferences translate in the context of the exact factorization of the molecular wavefunction. In particular, we focus our attention on the shape of the time-dependent potential energy surface - the exact surface on which the nuclear dynamics takes place - using an exactly-solvable model to reproduce different conditions for quantum interferences. The time-dependent potential energy surface develops complex features when strong interferences are present, in clear contrast to the observed behavior in simple nonadiabatic crossing cases. Nevertheless, independent classical trajectories propagated on the exact time-dependent potential energy surface reasonably conserve a distribution in configuration space that mimics the one of the exact nuclear probability density.
An exact factorization perspective on quantum interferences in nonadiabatic dynamics.
Curchod, Basile F E; Agostini, Federica; Gross, E K U
2016-07-21
Nonadiabatic quantum interferences emerge whenever nuclear wavefunctions in different electronic states meet and interact in a nonadiabatic region. In this work, we analyze how nonadiabatic quantum interferences translate in the context of the exact factorization of the molecular wavefunction. In particular, we focus our attention on the shape of the time-dependent potential energy surface-the exact surface on which the nuclear dynamics takes place. We use a one-dimensional exactly solvable model to reproduce different conditions for quantum interferences, whose characteristic features already appear in one-dimension. The time-dependent potential energy surface develops complex features when strong interferences are present, in clear contrast to the observed behavior in simple nonadiabatic crossing cases. Nevertheless, independent classical trajectories propagated on the exact time-dependent potential energy surface reasonably conserve a distribution in configuration space that mimics one of the exact nuclear probability densities. PMID:27448870
Anomalous capacitance of quantum well double-barrier diodes
Boric, Olga; Tolmunen, Timo J.; Kollberg, Erik; Frerking, Margaret A.
1992-01-01
The S-parameters of several different quantum well double barrier diodes have been measured. A technique has been developed for measuring whisker contacted diodes with an HP 8510B automatic network analyzer. Special coaxial mounts using K-connectors were designed to enable measurements up to 20 GHz. The voltage-dependent conductance and capacitance were derived from the measured reflection coefficient of each device. The C/V characteristics were observed to exhibit an anomalous increase at voltages corresponding to the negative differential resistance region (NDR). These are the first reported S-parameter measurements in the negative differential resistance region of quantum well double barrier diodes. A theory is presented that explains, in part, the observed results.
Quantum Anomalous Hall Effect in Hg$_{1-y}$Mn$_{y}$Te Quantum Wells
Liu, Chao-Xing; Qi, Xiao-Liang; Dai, Xi; Fang, Zhong; Zhang, Shou-Cheng
2008-01-01
The quantum Hall effect is usually observed when the two-dimensional electron gas is subjected to an external magnetic field, so that their quantum states form Landau levels. In this work we predict that a new phenomenon, the quantum anomalous Hall effect, can be realized in Hg$_{1-y}$Mn$_{y}$Te quantum wells, without the external magnetic field and the associated Landau levels. This effect arises purely from the spin polarization of the $Mn$ atoms, and the quantized Hall conductance is predi...
Complementarity in temporal ghost interference and temporal quantum eraser
Cho, Kiyoung; Noh, Jaewoo
2015-06-01
We present a theory for the complementarity in temporal interference and quantum erasure. We consider the case of entangled biphoton where we can get the information of single photon's arrival time without making a disturbing measurement. We find a mathematical equation for the complementary relation for a temporal double slit experiment. We also propose a quantum eraser scheme that will elucidate that the complementarity is originated from the quantum entanglement.
Hydrodynamic view of wave-packet interference: quantum caves.
Chou, Chia-Chun; Sanz, Angel S; Miret-Artés, Salvador; Wyatt, Robert E
2009-06-26
Wave-packet interference is investigated within the complex quantum Hamilton-Jacobi formalism using a hydrodynamic description. Quantum interference leads to the formation of the topological structure of quantum caves in space-time Argand plots. These caves consist of the vortical and stagnation tubes originating from the isosurfaces of the amplitude of the wave function and its first derivative. Complex quantum trajectories display counterclockwise helical wrapping around the stagnation tubes and hyperbolic deflection near the vortical tubes. The string of alternating stagnation and vortical tubes is sufficient to generate divergent trajectories. Moreover, the average wrapping time for trajectories and the rotational rate of the nodal line in the complex plane can be used to define the lifetime for interference features. PMID:19659057
Correlations, quantum entanglement and interference in nanoscopic systems
International Nuclear Information System (INIS)
Several of the most interesting quantum effects can or could be observed in nanoscopic systems. For example, the effect of strong correlations between electrons and of quantum interference can be measured in transport experiments through quantum dots, wires, individual molecules and rings formed by large molecules or arrays of quantum dots. In addition, quantum coherence and entanglement can be clearly observed in quantum corrals. In this paper we present calculations of transport properties through Aharonov–Bohm strongly correlated rings where the characteristic phenomenon of charge–spin separation is clearly observed. Additionally quantum interference effects show up in transport through π-conjugated annulene molecules producing important effects on the conductance for different source–drain configurations, leading to the possibility of an interesting switching effect. Finally, elliptic quantum corrals offer an ideal system to study quantum entanglement due to their focalizing properties. Because of an enhanced interaction between impurities localized at the foci, these systems also show interesting quantum dynamical behaviour and offer a challenging scenario for quantum information experiments
Ruling out multi-order interference in quantum mechanics.
Sinha, Urbasi; Couteau, Christophe; Jennewein, Thomas; Laflamme, Raymond; Weihs, Gregor
2010-07-23
Quantum mechanics and gravitation are two pillars of modern physics. Despite their success in describing the physical world around us, they seem to be incompatible theories. There are suggestions that one of these theories must be generalized to achieve unification. For example, Born's rule--one of the axioms of quantum mechanics--could be violated. Born's rule predicts that quantum interference, as shown by a double-slit diffraction experiment, occurs from pairs of paths. A generalized version of quantum mechanics might allow multipath (i.e., higher-order) interference, thus leading to a deviation from the theory. We performed a three-slit experiment with photons and bounded the magnitude of three-path interference to less than 10(-2) of the expected two-path interference, thus ruling out third- and higher-order interference and providing a bound on the accuracy of Born's rule. Our experiment is consistent with the postulate both in semiclassical and quantum regimes. PMID:20651147
Quantum interference of molecules -- probing the wave nature of matter
Venugopalan, Anu
2012-01-01
The double slit interference experiment has been famously described by Richard Feynman as containing the "only mystery of quantum mechanics". The history of quantum mechanics is intimately linked with the discovery of the dual nature of matter and radiation. While the double slit experiment for light is easily undertsood in terms of its wave nature, the very same experiment for particles like the electron is somewhat more difficult to comprehend. By the 1920s it was firmly established that electrons have a wave nature. However, for a very long time, most discussions pertaining to interference experiments for particles were merely gedanken experiments. It took almost six decades after the establishment of its wave nature to carry out a 'double slit interference' experiment for electrons. This set the stage for interference experiments with larger particles. In the last decade there has been spectacular progress in matter-wave interefernce experiments. Today, molecules with over a hundred atoms can be made to i...
Spying on photons with photons: quantum interference and information
Ataman, Stefan
2016-01-01
The quest to have both which-path knowledge and interference fringes in a double-slit experiment dates back to the inception of quantum mechanics (QM) and to the famous Einstein-Bohr debates. In this paper we propose and discuss an experiment able to spy on one photon's path with another photon. We modify the quantum state inside the interferometer as opposed to the traditional physical modification of the "wave-like" or "particle-like" experimental setup. We are able to show that it is the ability to harvest or not which-path information that finally limits the visibility of the interference pattern and not the "wave-like" or "particle-like" experimental setups. Remarkably, a full "particle-like" experimental setup is able to show interference fringes with 100 % visibility if the quantum state is carefully engineered.
Spying on photons with photons: quantum interference and information
Ataman, Stefan
2016-07-01
The quest to have both which-path knowledge and interference fringes in a double-slit experiment dates back to the inception of quantum mechanics (QM) and to the famous Einstein-Bohr debates. In this paper we propose and discuss an experiment able to spy on one photon's path with another photon. We modify the quantum state inside the interferometer as opposed to the traditional physical modification of the "wave-like" or "particle-like" experimental setup. We are able to show that it is the ability to harvest or not which-path information that finally limits the visibility of the interference pattern and not the "wave-like" or "particle-like" experimental setups. Remarkably, a full "particle-like" experimental setup is able to show interference fringes with 100% visibility if the quantum state is carefully engineered.
Institute of Scientific and Technical Information of China (English)
Li Yong-Qing; Li Jian; Ma Feng-Cai
2006-01-01
Collisional quantum interference (CQI) on the intramolecular rotational energy transfer is observed in an experiment with a static cell, and the integral interference angles are measured. To obtain more accurate information, an experiment with a molecular beam is carried out, and thereby the relationship between the differential interference angle and the scattering angle is obtained. Based on the first-Born approximation of time-dependent perturbation theory,the theoretical model of CQI is developed in an atom-diatom system in the condition of the molecular beam, with the long-range interaction potential taken into account. The method of measuring correctly the differential interference angle is presented. The tendencies of the differential interference angle changing with the impact parameter and relative velocity are discussed. The theoretical model presented here is important for understanding or performing the experiment in the molecular beam.
Cavity quantum interferences with three-level atoms
Ceban, Victor; Macovei, Mihai A.
2016-05-01
We discuss quantum interference phenomena in a system consisting from a laser driven three-level ladder-type emitter possessing orthogonal transition dipoles and embedded in a leaking optical resonator. The cavity mean-photon number vanishes due to the destructive nature of the interference phenomena. The effect occurs for some particular parameter regimes which were identified. Furthermore, upper bare-state population inversion occurs as well.
Quantum Interference Effects in Electronic Transport through Nanotube Contacts
Buia, Calin; Buldum, Alper; Lu, Jian Ping
2002-01-01
Quantum interference has dramatic effects on electronic transport through nanotube contacts. In optimal configuration the intertube conductance can approach that of a perfect nanotube ($4e^2/h$). The maximum conductance increases rapidly with the contact length up to 10 nm, beyond which it exhibits long wavelength oscillations. This is attributed to the resonant cavity-like interference phenomena in the contact region. For two concentric nanotubes symmetry breaking reduces the maximum intertu...
Nonmonotonic quantum-to-classical transition in multiparticle interference.
Ra, Young-Sik; Tichy, Malte C; Lim, Hyang-Tag; Kwon, Osung; Mintert, Florian; Buchleitner, Andreas; Kim, Yoon-Ho
2013-01-22
Quantum-mechanical wave-particle duality implies that probability distributions for granular detection events exhibit wave-like interference. On the single-particle level, this leads to self-interference--e.g., on transit across a double slit--for photons as well as for large, massive particles, provided that no which-way information is available to any observer, even in principle. When more than one particle enters the game, their specific many-particle quantum features are manifested in correlation functions, provided the particles cannot be distinguished. We are used to believe that interference fades away monotonically with increasing distinguishability--in accord with available experimental evidence on the single- and on the many-particle level. Here, we demonstrate experimentally and theoretically that such monotonicity of the quantum-to-classical transition is the exception rather than the rule whenever more than two particles interfere. As the distinguishability of the particles is continuously increased, different numbers of particles effectively interfere, which leads to interference signals that are, in general, nonmonotonic functions of the distinguishability of the particles. This observation opens perspectives for the experimental characterization of many-particle coherence and sheds light on decoherence processes in many-particle systems. PMID:23297196
Observation of quantum interference in molecular charge transport
DEFF Research Database (Denmark)
Guedon, Constant M.; Valkenier, Hennie; Markussen, Troels;
2012-01-01
, phenomena such as giant magnetoresistance(5), Kondo effects(6) and conductance switching(7-11) have been observed in single molecules, and theorists have predicted that it should also be possible to observe quantum interference in molecular conductors(12-18), but until now all the evidence for such...... behaviour has been indirect. Here, we report the observation of destructive quantum interference in charge transport through two-terminal molecular junctions at room temperature. We studied five different rigid p-conjugated molecular wires, all of which form self-assembled monolayers on a gold surface, and...
Anomalous vacuum energy and stability of a quantum liquid.
Trachenko, K; Brazhkin, V V
2016-03-31
We show that the vacuum (zero-point) energy of a low-temperature quantum liquid is a variable property which changes with the state of the system, in notable contrast to the static vacuum energy in solids commonly considered. We further show that this energy is inherently anomalous: it decreases with temperature and gives a negative contribution to a system's heat capacity. This effect operates in an equilibrium and macroscopic system, in marked contrast to small or out-of-equilibrium configurations discussed previously. We find that the negative contribution is over-compensated by the positive term from the excitation of longitudinal fluctuations and demonstrate how the overall positive heat capacity is related to the stability of a condensed phase at the microscopic level. PMID:26909505
Anomalous vacuum energy and stability of a quantum liquid
International Nuclear Information System (INIS)
We show that the vacuum (zero-point) energy of a low-temperature quantum liquid is a variable property which changes with the state of the system, in notable contrast to the static vacuum energy in solids commonly considered. We further show that this energy is inherently anomalous: it decreases with temperature and gives a negative contribution to a system’s heat capacity. This effect operates in an equilibrium and macroscopic system, in marked contrast to small or out-of-equilibrium configurations discussed previously. We find that the negative contribution is over-compensated by the positive term from the excitation of longitudinal fluctuations and demonstrate how the overall positive heat capacity is related to the stability of a condensed phase at the microscopic level. (letter)
Anomalous vacuum energy and stability of a quantum liquid
Trachenko, K
2016-01-01
We show that the vacuum (zero-point) energy of a low-temperature quantum liquid is a variable property which changes with the state of the system, in notable contrast to the static vacuum energy in solids commonly considered. We further show that this energy is inherently anomalous: it decreases with temperature and gives negative contribution to system's heat capacity. This effect operates in an equilibrium and macroscopic system, in marked contrast to small or out-of-equilibrium configurations discussed previously. We find that the negative contribution is over-compensated by the positive term from the excitation of longitudinal fluctuations and demonstrate how the overall positive heat capacity is related to the stability of a condensed phase at the microscopic level.
Unruh effect and macroscopic quantum interference
Steane, Andrew
2015-01-01
We investigate the influence of Unruh radiation on matter-wave interferometry experiments using neutral objects modeled as dielectric spheres. The Unruh effect leads to a loss of coherence through momentum diffusion. This is a fundamental source of decoherence that affects all objects having electromagnetic interactions. However, the effect is not large enough to prevent the observation of interference for objects of any size, even when the path separation is larger than the size of the object. When the acceleration in the interferometer arms is large, inertial tidal forces will disrupt the material integrity of the interfering objects before the Unruh decoherence of the centre of mass motion is sufficient to prevent observable interference.
Quantum interference between resonant and nonresonant photorecombination
Tu, B.; Xiao, J.; Yao, K.; Shen, Y.; Yang, Y.; Lu, D.; Li, W. X.; Qiu, M. L.; Wang, X.; Chen, C. Y.; Fu, Y.; Wei, B.; Zheng, C.; Huang, L. Y.; Zhang, B. H.; Tang, Y. J.; Hutton, R.; Zou, Y.
2016-03-01
In this paper, we present experimental and theoretical studies on the interference between resonant and nonresonant photorecombinations for the main resonances of ground-state He-, Be-, B-, C-, N-, and O-like W ions. Experiments were done using a fast electron energy scanning technique at the upgraded Shanghai electron-beam ion trap. Asymmetric resonances were observed, and their Fano factors, which measure the interference degree, were determined. The calculations were done under the framework of Fano's theory by using the flexible atomic code, in which the relativistic configuration interaction method was employed. Among the nine resonances studied in this work, eight experimental results agree with the calculation within experimental uncertainties. But the experimental result for the resonance of Be-like W ions, through the intermediate state of [(1s2s22p 1 /2) 12 p3 /2] 5 /2, deviates from its corresponding theoretical result by 1.3 times experimental uncertainty.
Interference of quantum states in electronic waveguides with impurities
International Nuclear Information System (INIS)
One investigated into effects of interference of propagating and localized states in quasi-dimensional electric waveguides containing attracting impurities (quantum points) of finite sizes. Matrix of electron scattering is calculated in terms of the Feshbach theory. It is shown that attracting impurities with finite sizes may initiate a series of the Fano asymmetric resonances in waveguide transparency. In this case, due to interference of electronic states, characteristics of resonances may oscillate at variation of impurity parameters. One determined conditions under which the effects of interference of electron waves results in collapse and swing of the Fano resonances
Observation of Quantum Interference between Separated Mechanical Oscillator Wave Packets
Kienzler, D.; Flühmann, C.; Negnevitsky, V.; Lo, H.-Y.; Marinelli, M.; Nadlinger, D.; Home, J. P.
2016-04-01
We directly observe the quantum interference between two well-separated trapped-ion mechanical oscillator wave packets. The superposed state is created from a spin-motion entangled state using a heralded measurement. Wave packet interference is observed through the energy eigenstate populations. We reconstruct the Wigner function of these states by introducing probe Hamiltonians which measure Fock state populations in displaced and squeezed bases. Squeezed-basis measurements with 8 dB squeezing allow the measurement of interference for Δ α =15.6 , corresponding to a distance of 240 nm between the two superposed wave packets.
Colloquium: Quantum interference of clusters and molecules
Hornberger, Klaus; Gerlich, Stefan; Haslinger, Philipp; Nimmrichter, Stefan; Arndt, Markus
2011-01-01
We review recent progress and future prospects of matter wave interferometry with complex organic molecules and inorganic clusters. Three variants of a near-field interference effect, based on diffraction by material nanostructures, at optical phase gratings, and at ionizing laser fields are considered. We discuss the theoretical concepts underlying these experiments and the experimental challenges. This includes optimizing interferometer designs as well as understanding the role of decoheren...
Quantum Interference in Cognition: Structural Aspects of the Brain
Aerts, Diederik
2012-01-01
We identify the presence of typically quantum effects, namely 'superposition' and 'interference', in what happens when human concepts are combined, and provide a quantum model in complex Hilbert space that represents faithfully experimental data measuring the situation of combining concepts. Our model shows how 'interference of concepts' explains the effects of underextension and overextension when two concepts combine to the disjunction of these two concepts. This result supports our earlier hypothesis that human thought has a superposed two-layered structure, one layer consisting of 'classical logical thought' and a superposed layer consisting of 'quantum conceptual thought'. Possible connections with recent findings of a 'grid-structure' for the brain are analyzed, and influences on the mind/brain relation, and consequences on applied disciplines, such as artificial intelligence and quantum computation, are considered.
Quantum Physics A First Encounter Interference, Entanglement, and Reality
Scarani, Valerio
2006-01-01
The essential features of quantum physics, largely debated since its discovery, are presented in this book, through the description (without mathematics) of recent experiments. Putting the accent on physical phenomena, this book clarifies the historical issues (delocalisation, interferences) and reaches out to modern topics (quantum cryptography, non-locality and teleportation); the debate on interpretations is serenely reviewed. - ;Quantum physics is often perceived as a weird and abstract theory, which physicists must use in order to make correct predictions. But many recent experiments have shown that the weirdness of the theory simply mirrors the weirdness of phenomena: it is Nature itself, and not only our description of it, that behaves in an astonishing way. This book selects those, among these typical quantum phenomena, whose rigorous description requires neither the formalism, nor an important. background in physics. The first part of the book deals with the phenomenon of single-particle interference...
Observation of quantum interference between separated mechanical oscillator wavepackets
Kienzler, D; Negnevitsky, V; Lo, H -Y; Marinelli, M; Nadlinger, D; Home, J P
2015-01-01
The ability of matter to be superposed at two different locations while being intrinsically connected by a quantum phase is among the most counterintuitive predictions of quantum physics. While such superpositions have been created for a variety of systems, the in-situ observation of the phase coherence has remained out of reach. Using a heralding measurement on a spin-oscillator entangled state, we project a mechanical trapped-ion oscillator into a superposition of two spatially separated states, a situation analogous to Schr\\"odinger's cat. Quantum interference is clearly observed by extracting the occupations of the energy levels. For larger states, we encounter problems in measuring the energy distribution, which we overcome by performing the analogous measurement in a squeezed Fock basis with each basis element stretched along the separation axis. Using 8 dB of squeezing we observe quantum interference for cat states with phase space separations of $\\Delta \\alpha = 15.6$, corresponding to wavepackets wit...
Quantum interference of molecules -- probing the wave nature of matter
Venugopalan, Anu
2012-01-01
The double slit interference experiment has been famously described by Richard Feynman as containing the "only mystery of quantum mechanics". The history of quantum mechanics is intimately linked with the discovery of the dual nature of matter and radiation. While the double slit experiment for light is easily undertsood in terms of its wave nature, the very same experiment for particles like the electron is somewhat more difficult to comprehend. By the 1920s it was firmly established that el...
Quantum interferences reconstruction with low homodyne detection efficiency
Energy Technology Data Exchange (ETDEWEB)
Esposito, Martina; Randi, Francesco [Universita degli studi di Trieste, Dipartimento di Fisica, Trieste (Italy); Titimbo, Kelvin; Zimmermann, Klaus; Benatti, Fabio [Universita degli studi di Trieste, Dipartimento di Fisica, Trieste (Italy); Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Trieste (Italy); Kourousias, Georgios; Curri, Alessio [Sincrotrone Trieste S.C.p.A., Trieste (Italy); Floreanini, Roberto [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Trieste (Italy); Parmigiani, Fulvio [Universita degli studi di Trieste, Dipartimento di Fisica, Trieste (Italy); Sincrotrone Trieste S.C.p.A., Trieste (Italy); University of Cologne, Institute of Physics II, Cologne (Germany); Fausti, Daniele [Universita degli studi di Trieste, Dipartimento di Fisica, Trieste (Italy); Sincrotrone Trieste S.C.p.A., Trieste (Italy)
2016-12-15
Optical homodyne tomography consists in reconstructing the quantum state of an optical field from repeated measurements of its amplitude at different field phases (homodyne data). The experimental noise, which unavoidably affects the homodyne data, leads to a detection efficiency η<1. The problem of reconstructing quantum states from noisy homodyne data sets prompted an intense scientific debate about the presence or absence of a lower homodyne efficiency bound (η>0.5) below which quantum features, like quantum interferences, cannot be retrieved. Here, by numerical experiments, we demonstrate that quantum interferences can be effectively reconstructed also for low homodyne detection efficiency. In particular, we address the challenging case of a Schroedinger cat state and test the minimax and adaptive Wigner function reconstruction technique by processing homodyne data distributed according to the chosen state but with an efficiency η>0.5. By numerically reproducing the Schroedinger's cat interference pattern, we give evidence that quantum state reconstruction is actually possible in these conditions, and provide a guideline for handling optical tomography based on homodyne data collected by low efficiency detectors. (orig.)
Quantum interferences reconstruction with low homodyne detection efficiency
International Nuclear Information System (INIS)
Optical homodyne tomography consists in reconstructing the quantum state of an optical field from repeated measurements of its amplitude at different field phases (homodyne data). The experimental noise, which unavoidably affects the homodyne data, leads to a detection efficiency η<1. The problem of reconstructing quantum states from noisy homodyne data sets prompted an intense scientific debate about the presence or absence of a lower homodyne efficiency bound (η>0.5) below which quantum features, like quantum interferences, cannot be retrieved. Here, by numerical experiments, we demonstrate that quantum interferences can be effectively reconstructed also for low homodyne detection efficiency. In particular, we address the challenging case of a Schroedinger cat state and test the minimax and adaptive Wigner function reconstruction technique by processing homodyne data distributed according to the chosen state but with an efficiency η>0.5. By numerically reproducing the Schroedinger's cat interference pattern, we give evidence that quantum state reconstruction is actually possible in these conditions, and provide a guideline for handling optical tomography based on homodyne data collected by low efficiency detectors. (orig.)
Quantum anomalous Hall effect in magnetic topological insulators
Wang, Jing; Lian, Biao; Zhang, Shou-Cheng
2015-12-01
The search for topologically non-trivial states of matter has become an important goal for condensed matter physics. Here, we give a theoretical introduction to the quantum anomalous Hall (QAH) effect based on magnetic topological insulators in two-dimensions (2D) and three-dimensions (3D). In 2D topological insulators, magnetic order breaks the symmetry between the counter-propagating helical edge states, and as a result, the quantum spin Hall effect can evolve into the QAH effect. In 3D, magnetic order opens up a gap for the topological surface states, and chiral edge state has been predicted to exist on the magnetic domain walls. We present the phase diagram in thin films of a magnetic topological insulator and review the basic mechanism of ferromagnetic order in magnetically doped topological insulators. We also review the recent experimental observation of the QAH effect. We discuss more recent theoretical work on the coexistence of the helical and chiral edge states, multi-channel chiral edge states, the theory of the plateau transition, and the thickness dependence in the QAH effect.
Institute of Scientific and Technical Information of China (English)
Wang Wei-Li; Miao Gang; Chen Yue-Hui; Tang Dan; Ma Feng-Cai
2008-01-01
Collisional quantum interference (CQI) in the intramolecular rotational energy transfer was observed in experiment by Sha and co-workers.[1] The interference angle, which measuring the degree of the coherence, were measured in the experiment of the static cell. Based on the first Born approximation of time dependent perturbation theory, taking into accounts the anisotropic Lennard-Jones interaction potentials, this paper describes the theoretical model of CQI in intramolecular rotational energy transfer in an atom-diatom collision system. In the model, the differential interference angle for the experiment of the molecular beam is calculated, the changing tendencies of the differential interference angle with the impact parameter and collision partners are obtained. This theoretical model is important for understanding or performing this kind of experiments.
Temperature effects on quantum interference in molecular junctions
DEFF Research Database (Denmark)
Markussen, Troels; Thygesen, Kristian Sommer
2014-01-01
A number of experiments have demonstrated that destructive quantum interference (QI) effects in molecular junctions lead to very low conductances even at room temperature. On the other hand, another recent experiment showed increasing conductance with temperature which was attributed to decoherence...
Quantum versus simulated annealing in wireless interference network optimization
Wang, Chi; Chen, Huo; Jonckheere, Edmond
2016-01-01
Quantum annealing (QA) serves as a specialized optimizer that is able to solve many NP-hard problems and that is believed to have a theoretical advantage over simulated annealing (SA) via quantum tunneling. With the introduction of the D-Wave programmable quantum annealer, a considerable amount of effort has been devoted to detect and quantify quantum speedup. While the debate over speedup remains inconclusive as of now, instead of attempting to show general quantum advantage, here, we focus on a novel real-world application of D-Wave in wireless networking—more specifically, the scheduling of the activation of the air-links for maximum throughput subject to interference avoidance near network nodes. In addition, D-Wave implementation is made error insensitive by a novel Hamiltonian extra penalty weight adjustment that enlarges the gap and substantially reduces the occurrence of interference violations resulting from inevitable spin bias and coupling errors. The major result of this paper is that quantum annealing benefits more than simulated annealing from this gap expansion process, both in terms of ST99 speedup and network queue occupancy. It is the hope that this could become a real-word application niche where potential benefits of quantum annealing could be objectively assessed. PMID:27181056
Quantum versus simulated annealing in wireless interference network optimization
Wang, Chi; Chen, Huo; Jonckheere, Edmond
2016-05-01
Quantum annealing (QA) serves as a specialized optimizer that is able to solve many NP-hard problems and that is believed to have a theoretical advantage over simulated annealing (SA) via quantum tunneling. With the introduction of the D-Wave programmable quantum annealer, a considerable amount of effort has been devoted to detect and quantify quantum speedup. While the debate over speedup remains inconclusive as of now, instead of attempting to show general quantum advantage, here, we focus on a novel real-world application of D-Wave in wireless networking—more specifically, the scheduling of the activation of the air-links for maximum throughput subject to interference avoidance near network nodes. In addition, D-Wave implementation is made error insensitive by a novel Hamiltonian extra penalty weight adjustment that enlarges the gap and substantially reduces the occurrence of interference violations resulting from inevitable spin bias and coupling errors. The major result of this paper is that quantum annealing benefits more than simulated annealing from this gap expansion process, both in terms of ST99 speedup and network queue occupancy. It is the hope that this could become a real-word application niche where potential benefits of quantum annealing could be objectively assessed.
Nonmonotonic quantum-to-classical transition in multiparticle interference
DEFF Research Database (Denmark)
Ra, Young-Sik; Tichy, Malte; Lim, Hyang-Tag;
2013-01-01
Quantum-mechanical wave–particle duality implies that probability distributions for granular detection events exhibit wave-like interference. On the single-particle level, this leads to self-interference—e.g., on transit across a double slit—for photons as well as for large, massive particles......, provided that no which-way information is available to any observer, even in principle. When more than one particle enters the game, their specific many-particle quantum features are manifested in correlation functions, provided the particles cannot be distinguished. We are used to believe that...... interference fades away monotonically with increasing distinguishability—in accord with available experimental evidence on the single- and on the many-particle level. Here, we demonstrate experimentally and theoretically that such monotonicity of the quantum-to-classical transition is the exception rather than...
Quantum private query based on single-photon interference
Xu, Sheng-Wei; Sun, Ying; Lin, Song
2016-08-01
Quantum private query (QPQ) has become a research hotspot recently. Specially, the quantum key distribution (QKD)-based QPQ attracts lots of attention because of its practicality. Various such kind of QPQ protocols have been proposed based on different technologies of quantum communications. Single-photon interference is one of such technologies, on which the famous QKD protocol GV95 is just based. In this paper, we propose two QPQ protocols based on single-photon interference. The first one is simpler and easier to realize, and the second one is loss tolerant and flexible, and more practical than the first one. Furthermore, we analyze both the user privacy and the database privacy in the proposed protocols.
Quantum private query based on single-photon interference
Xu, Sheng-Wei; Sun, Ying; Lin, Song
2016-05-01
Quantum private query (QPQ) has become a research hotspot recently. Specially, the quantum key distribution (QKD)-based QPQ attracts lots of attention because of its practicality. Various such kind of QPQ protocols have been proposed based on different technologies of quantum communications. Single-photon interference is one of such technologies, on which the famous QKD protocol GV95 is just based. In this paper, we propose two QPQ protocols based on single-photon interference. The first one is simpler and easier to realize, and the second one is loss tolerant and flexible, and more practical than the first one. Furthermore, we analyze both the user privacy and the database privacy in the proposed protocols.
Perspectives for quantum interference with biomolecules and biomolecular clusters
Geyer, P.; Sezer, U.; Rodewald, J.; Mairhofer, L.; Dörre, N.; Haslinger, P.; Eibenberger, S.; Brand, C.; Arndt, M.
2016-06-01
Modern quantum optics encompasses a wide field of phenomena that are either related to the discrete quantum nature of light, the quantum wave nature of matter or light–matter interactions. We here discuss new perspectives for quantum optics with biological nanoparticles. We focus in particular on the prospects of matter-wave interferometry with amino acids, nucleotides, polypeptides or DNA strands. We motivate the challenge of preparing these objects in a ‘biomimetic’ environment and argue that hydrated molecular beam sources are promising tools for quantum-assisted metrology. The method exploits the high sensitivity of matter-wave interference fringes to dephasing and shifts in the presence of external perturbations to access and determine molecular properties.
Real-time single-molecule imaging of quantum interference.
Juffmann, Thomas; Milic, Adriana; Müllneritsch, Michael; Asenbaum, Peter; Tsukernik, Alexander; Tüxen, Jens; Mayor, Marcel; Cheshnovsky, Ori; Arndt, Markus
2012-05-01
The observation of interference patterns in double-slit experiments with massive particles is generally regarded as the ultimate demonstration of the quantum nature of these objects. Such matter-wave interference has been observed for electrons, neutrons, atoms and molecules and, in contrast to classical physics, quantum interference can be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the "most beautiful experiment in physics". Here, we show how a combination of nanofabrication and nano-imaging allows us to record the full two-dimensional build-up of quantum interference patterns in real time for phthalocyanine molecules and for derivatives of phthalocyanine molecules, which have masses of 514 AMU and 1,298 AMU respectively. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence, and the gratings were machined in 10-nm-thick silicon nitride membranes to reduce the effect of van der Waals forces. Wide-field fluorescence microscopy detected the position of each molecule with an accuracy of 10 nm and revealed the build-up of a deterministic ensemble interference pattern from single molecules that arrived stochastically at the detector. In addition to providing this particularly clear demonstration of wave-particle duality, our approach could also be used to study larger molecules and explore the boundary between quantum and classical physics. PMID:22447163
Electrically tunable spin polarization of chiral edge modes in a quantum anomalous Hall insulator
Zhang, Rui-Xing; Hsu, Hsiu-Chuan; Liu, Chao-Xing
2016-06-01
In the quantum anomalous Hall effect, chiral edge modes are expected to conduct spin polarized current without dissipation and thus hold great promise for future electronics and spintronics with low energy consumption. However, spin polarization of chiral edge modes has never been established in experiments. In this work, we theoretically study spin polarization of chiral edge modes in the quantum anomalous Hall effect, based on both the effective model and more realistic tight-binding model constructed from first-principles calculations. We find that spin polarization can be manipulated by tuning either a local gate voltage or the Fermi energy. We also propose to extract spin information of chiral edge modes by contacting the quantum anomalous Hall insulator to a ferromagnetic lead. The establishment of spin polarization of chiral edge modes, as well as the manipulation and detection in a fully electrical manner, will pave the way to the applications of the quantum anomalous Hall effect in spintronics.
Quantum interference effects in a cavity QED system
International Nuclear Information System (INIS)
We consider the effect of quantum interference on population distribution and photon statistics of a cavity field interacting with dressed states of a strongly driven three-level atom. We analyse three coupling configurations of the cavity field to the driven atom, with the cavity frequency tuned to the outer Rabi sideband, the inner Rabi sideband and the central frequency of the 'singly dressed' three-level atom. The quantum doubly dressed states for each configuration are identified and the population distribution and photon statistics are interpreted in terms of transitions among these dressed states and their populations. We find that the population distribution depends strongly on quantum interference and the cavity damping. For the cavity field tuned to the outer or inner Rabi sidebands the cavity damping induces transitions between the dressed states which are forbidden for the ordinary spontaneous emission. Moreover, we find that in the case of the cavity field coupled to the inner Rabi sideband the population distribution is almost Poissonian with a large average number of photons that can be controlled by quantum interference. This system can be considered as a one-atom dressed-state laser with controlled intensity
Electromagnetically induced grating in asymmetric quantum wells via Fano interference.
Zhou, Fengxue; Qi, Yihong; Sun, Hui; Chen, Dijun; Yang, Jie; Niu, Yueping; Gong, Shangqing
2013-05-20
We propose a scheme for obtaining an electromagnetically induced grating in an asymmetric semiconductor quantum well (QW) structure via Fano interference. In our structure, owing to Fano interference, the diffraction intensity of the grating, especially the first-order diffraction, can be significantly enhanced. The diffraction efficiency of the grating can be controlled efficiently by tuning the control field intensity, the interaction length, the coupling strength of tunneling, etc. This investigation may be used to develop novel photonic devices in semiconductor QW systems. PMID:23736445
Controlling Below-Threshold Nonsequential Double Ionization via Quantum Interference
Maxwell, A S
2015-01-01
We show through simulation that quantum interference in non-sequential double ionization can be used to control the recollision with subsequent ionization (RESI) mechanism. This includes the shape, localization and symmetry of RESI electron-momentum distributions, which may be shifted from a correlated to an anti-correlated distribution or vice versa, far below the direct ionization threshold intensity. As a testing ground, we reproduce recent experimental results by employing specific coherent superpositions of excitation channels. We examine two types of interference, from electron indistinguishability and intra-cycle events, and from different excitation channels.
High-Tc superconductor quantum interference devices
International Nuclear Information System (INIS)
This patent describes a superconductive quantum interferometric device for sensing a characteristic of a magnetic field. It comprises a substrate having a surface, the substrate being selected from the group which consists of strontium titanate, aluminum oxide, sapphire, ZrO2 and mixtures thereof; a coating of MgO on the surface of the substrate; two identical thin-strip films of a high-critical temperature superconductor on the coating, each of the films having a pair of mutually parallel arms in the form of superconductor strips extending toward and aligned with super conductor strips forming corresponding arms of the other thin-strip film, and a crossbar strip connecting the arms of each thin-strip film at right angles to the arms, the high-critical-temperature superconductor being selected from the group which consists of yttrium-barium-calcium-copper-oxides, bismuth-strontium-calcium-copper-oxides, thallium-barium-copper-oxides, thallium-barium-calcium-copper-oxides, barium oxide: potassium oxide: bismuth oxides, and calcium oxide: zinc oxide: iron oxides; and insulating films on the coating between corresponding free ends of the arms thin-strip films, the insulating films being composed of a material selected from the group which consists of silicon dioxide, silicon nitride, magnesium oxide and mixture thereof
Prediction of a quantum anomalous Hall state in Co-decorated silicene
Kaloni, Thaneshwor P.
2014-01-09
Based on first-principles calculations, we demonstrate that Co-decorated silicene can host a quantum anomalous Hall state. The exchange field induced by the Co atoms combined with the strong spin-orbit coupling of the silicene opens a nontrivial band gap at the K point. As compared to other transition metals, Co-decorated silicene is unique in this respect, since usually hybridization and spin-polarization induced in the silicene suppress a quantum anomalous Hall state.
Thickness Dependence of the Quantum Anomalous Hall Effect in Magnetic Topological Insulator Films.
Feng, Xiao; Feng, Yang; Wang, Jing; Ou, Yunbo; Hao, Zhenqi; Liu, Chang; Zhang, Zuocheng; Zhang, Liguo; Lin, Chaojing; Liao, Jian; Li, Yongqing; Wang, Li-Li; Ji, Shuai-Hua; Chen, Xi; Ma, Xucun; Zhang, Shou-Cheng; Wang, Yayu; He, Ke; Xue, Qi-Kun
2016-08-01
The evolution of the quantum anomalous Hall effect with the thickness of Cr-doped (Bi,Sb)2 Te3 magnetic topological insulator films is studied, revealing how the effect is caused by the interplay of the surface states, band-bending, and ferromagnetic exchange energy. Homogeneity in ferromagnetism is found to be the key to high-temperature quantum anomalous Hall material. PMID:27166762
Particle statistics affects quantum decay and Fano interference.
Crespi, Andrea; Sansoni, Linda; Della Valle, Giuseppe; Ciamei, Alessio; Ramponi, Roberta; Sciarrino, Fabio; Mataloni, Paolo; Longhi, Stefano; Osellame, Roberto
2015-03-01
Quantum mechanical decay, Fano interference, and bound states with energy in the continuum are ubiquitous phenomena in different areas of physics. Here we experimentally demonstrate that particle statistics strongly affects quantum mechanical decay in a multiparticle system. By considering propagation of two-photon states in engineered photonic lattices, we simulate quantum decay of two noninteracting particles in a multilevel Fano-Anderson model. Remarkably, when the system sustains a bound state in the continuum, fractional decay is observed for bosonic particles, but not for fermionic ones. Complete decay in the fermionic case arises because of the Pauli exclusion principle, which forbids the bound state to be occupied by the two fermions. Our experiment indicates that particle statistics can tune many-body quantum decay from fractional to complete. PMID:25793783
Multipartite cluster entangled states for continuous variables via quantum interference
International Nuclear Information System (INIS)
Continuous variable cluster entangled states are a potential resource for universal quantum computation. Here we propose a scalable scheme to prepare a class of multimode cluster entangled states. In terms of graph states, all modes are denoted by the nodes, and the lines connecting the nodes represent the interactions between the connected nodes. Our cluster entangled states correspond to two-colourable graphs, in which the nodes belong to two different families, and the lines connect only the nodes of different families. The physical mechanism is attributed to quantum interference between multiple pathways for wave-mixing parametric interactions in near-resonant systems.
Conductance of quantum interference transistors in parallel and in series
Nikolić, K.; Nikolić, P.; Šordan, R.
1999-07-01
We theoretically study the electronic conductance G and the current-voltage characteristics of two quantum interference transistors in parallel and in series. We use two different definitions of conductance, G ˜ T and G ˜ T / R. Neither can reproduce the classical additivity law in the case of coherent transport due to quantum interference for the elements in series and quasibound states when elements are in parallel. In the case of two transistors in series, we find that the quantity T / R only qualitatively better represents the additivity law, which is probably expected because this model avoids counting the contact resistance twice. However, for the parallel configuration of transistors, the conductance is almost additive for the majority of energies when G ˜ T, except for the single-mode regime. Possible use of these configurations in digital electronics for basic logic functions is discussed.
Quantum Interference Mechanism of Cooperative Optical Phenomena in Extended Media
Valery I Rupasov
2000-01-01
In the quantum process of stimulated Raman scattering (SRS), a laser photon propagating in a resonance medium undergoes multifold conversions into a Stokes photon and back. The nontrivial ``cooperative'' behavior of the Stokes component of light transmitted through the medium is proven to be completely determined by the interference of scattering amplitudes in different sub-channels of the Stokes channel, which obviously combines all the sub-channels with an odd number of photon conversions. ...
Huang, Pu; Shi, Jun-Jie; Zhang, Min; Jiang, Xin-He; Zhong, Hong-Xia; Ding, Yi-Min; Cao, Xiong; Wu, Meng; Lu, Jing
2016-08-01
The physical origin of the observed anomalous photoluminescence (PL) behavior, that is, the large-size graphene quantum dots (GQDs) exhibiting higher PL energy than the small ones and the broadening PL spectra from deep ultraviolet to near-infrared, has been debated for many years. Obviously, it is in conflict with the well-accepted quantum confinement. Here we shed new light on these two notable debates by state-of-the-art first-principles calculations based on many-body perturbation theory. We find that quantum confinement is significant in GQDs with remarkable size-dependent exciton absorption/emission. The edge environment from alkaline to acidic conditions causes a blue shift of the PL peak. Furthermore, carbon vacancies are inclined to assemble at the GQD edge and form the tiny edge microstructures. The bound excitons, localized inside these edge microstructures, determine the anomalous PL behavior (blue and UV emission) of large-size GQDs. The bound excitons confined in the whole GQD lead to the low-energy transition. PMID:27409980
Dressed excitonic states and quantum interference in a three-level quantum dot ladder system
Energy Technology Data Exchange (ETDEWEB)
Gerardot, B D; Brunner, D; Dalgarno, P A; Warburton, R J [School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Karrai, K [Center for NanoScience and Department fuer Physik der LMU, Geschwister-Scholl-Platz 1, 80539 Munich (Germany); Badolato, A [Institute of Quantum Electronics, ETH Zurich, 8093 Zurich (Switzerland); Petroff, P M [Materials Department, University of California, Santa Barbara, CA 93106 (United States)], E-mail: b.d.gerardot@hw.ac.uk
2009-01-15
We observe dressed states and quantum interference effects in a strongly driven three-level quantum dot ladder system. The effect of a strong coupling field on one dipole transition is measured by a weak probe field on the second dipole transition using differential reflection. When the coupling energy is much larger than both the homogeneous and inhomogeneous linewidths an Autler-Townes splitting is observed. Significant differences are observed when the transitions resonant with the strong and weak fields are swapped, particularly when the coupling energy is nearly equal to the measured linewidth. This result is attributed to quantum interference: destructive or constructive interference with modest visibility is observed depending on the pump/probe geometry. The data demonstrate that coherence of both the bi-exciton and the exciton is maintained in this solid-state system, even under intense illumination, which is crucial for prospects in quantum information processing and nonlinear optical devices.
Spatially resolving valley quantum interference of a donor in silicon
Salfi, J.; Mol, J. A.; Rahman, R.; Klimeck, G.; Simmons, M. Y.; Hollenberg, L. C. L.; Rogge, S.
2014-06-01
Electron and nuclear spins of donor ensembles in isotopically pure silicon experience a vacuum-like environment, giving them extraordinary coherence. However, in contrast to a real vacuum, electrons in silicon occupy quantum superpositions of valleys in momentum space. Addressable single-qubit and two-qubit operations in silicon require that qubits are placed near interfaces, modifying the valley degrees of freedom associated with these quantum superpositions and strongly influencing qubit relaxation and exchange processes. Yet to date, spectroscopic measurements have only probed wavefunctions indirectly, preventing direct experimental access to valley population, donor position and environment. Here we directly probe the probability density of single quantum states of individual subsurface donors, in real space and reciprocal space, using scanning tunnelling spectroscopy. We directly observe quantum mechanical valley interference patterns associated with linear superpositions of valleys in the donor ground state. The valley population is found to be within 5% of a bulk donor when 2.85 ± 0.45 nm from the interface, indicating that valley-perturbation-induced enhancement of spin relaxation will be negligible for depths greater than 3 nm. The observed valley interference will render two-qubit exchange gates sensitive to atomic-scale variations in positions of subsurface donors. Moreover, these results will also be of interest for emerging schemes proposing to encode information directly in valley polarization.
Magnetic Topological Insulators and Quantum Anomalous Hall Effect
Kou, Xufeng
The engineering of topological surface states is a key to realize applicable devices based on topological insulators (TIs). Among various proposals, introducing magnetic impurities into TIs has been proven to be an effective way to open a surface gap and integrate additional ferromagnetism with the original topological order. In this Dissertation, we study both the intrinsic electrical and magnetic properties of the magnetic TI thin films grown by molecular beam epitaxy. By doping transition element Cr into the host tetradymite-type V-VI semiconductors, we achieve robust ferromagnetic order with a strong perpendicular magnetic anisotropy. With additional top-gating capability, we realize the electric-field-controlled ferromagnetism in the magnetic TI systems, and demonstrate such magneto-electric effects can be effectively manipulated, depending on the interplays between the band topology, magnetic exchange coupling, and structural engineering. Most significantly, we report the observation of quantum anomalous Hall effect (QAHE) in the Cr-doped (BiSb)2Te3 samples where dissipationless chiral edge conduction is realized in the macroscopic millimeter-size devices without the presence of any external magnetic field, and the stability of the quantized Hall conductance of e2/h is well-maintained as the film thickness varies across the 2D hybridization limit. With additional quantum confinement, we discover the metal-to-insulator switching between two opposite QAHE states, and reveal the universal QAHE phase diagram in the thin magnetic TI samples. In addition to the uniform magnetic TIs, we further investigate the TI/Cr-doped TI bilayer structures prepared by the modulation-doped growth method. By controlling the magnetic interaction profile, we observe the Dirac hole-mediated ferromagnetism and develop an effective way to manipulate its strength. Besides, the giant spin-orbit torque in such magnetic TI-based heterostructures enables us to demonstrate the current
Quantum Walks With Neutral Atoms: Quantum Interference Effects of One and Two Particles
Robens, Carsten; Meschede, Dieter; Alberti, Andrea
2015-01-01
We report on the state of the art of quantum walk experiments with neutral atoms in state-dependent optical lattices. We demonstrate a novel state-dependent transport technique enabling the control of two spin-selective sublattices in a fully independent fashion. This transport technique allowed us to carry out a test of single-particle quantum interference based on the violation of the Leggett-Garg inequality and, more recently, to probe two-particle quantum interference effects with neutral atoms cooled into the motional ground state. These experiments lay the groundwork for the study of discrete-time quantum walks of strongly interacting, indistinguishable particles to demonstrate quantum cellular automata of neutral atoms.
Controlling light pulse in triangular quantum well nanostructure via quantum interference
International Nuclear Information System (INIS)
We study numerically the optical properties of the intersubband transitions in AlGaAs/GaAs triangular quantum well nanostructure. The Schrödinger equation is being solved numerically for this structure using homemade codes. Afterward the refractive index and the absorption coefficient are calculated for general triangular quantum well using the density matrix formalism. The density matrix equations are being solved numerically for calculation of linear susceptibility. The effect of quantum interference between spontaneous emission decays on the refractive index, absorption coefficient and group velocity is studied for purposed triangular quantum well nanostructure. The result shows the linear optical properties and group index can be controlled via quantum interference between spontaneous emission decays
Unconventional superconducting quantum interference in a suspended graphene resonator
Allen, Monica; Nurgaliev, Daniyar; Akhmerov, Anton; Yacoby, Amir
2014-03-01
In a coherent electron cavity, quantum interference of electron waves replaces classical diffusion as a key feature of electronic transport. Here we report novel behavior that emerges by coupling superconducting reservoirs to a Fabry-Perot resonator in bilayer graphene. In this device, a pair of superconducting electrodes is coupled to a suspended graphene membrane and defines a ballistic cavity between the two graphene-electrode interfaces. Tuning the Fermi wavelength in the cavity with a gate electrode moves the system on and off resonance, thus inducing an oscillatory critical current whose period satisfies the Fabry-Perot interference conditions. By varying the magnetic flux through the junction, we explore the rich interplay between superconducting quantum interference and resonant cavity states and demonstrate a non-trivial correspondence between the supercurrent and normal state resistance. To describe our findings, we use a numerical model based on the tight-binding approach and Landauer-Buttiker scattering formalism. These results constitute a departure from the conventional Josephson effect in graphene and motivate exploration of new effects at the intersection of superconductivity and optics-like phenomena.
Giant fifth-order nonlinearity via tunneling induced quantum interference in triple quantum dots
International Nuclear Information System (INIS)
Schemes for giant fifth-order nonlinearity via tunneling in both linear and triangular triple quantum dots are proposed. In both configurations, the real part of the fifth-order nonlinearity can be greatly enhanced, and simultaneously the absorption is suppressed. The analytical expression and the dressed states of the system show that the two tunnelings between the neighboring quantum dots can induce quantum interference, resulting in the giant higher-order nonlinearity. The scheme proposed here may have important applications in quantum information processing at low light level
Quantum interference in an asymmetric Mach-Zehnder interferometer
Trenti, A.; Borghi, M.; Mancinelli, M.; Price, H. M.; Fontana, G.; Pavesi, L.
2016-08-01
A re-visitation of the well known free space Mach-Zehnder interferometer is reported here. The coexistence between one-photon and two-photons interference from collinear color entangled photon pairs is investigated. Thisarises from an arbitrarily small unbalance in the arm transmittance. The tuning of such asymmetry is reflected in dramatic changes in the coincidence detection, revealing beatings between one particle and two particle interference patterns. In particular, the role of the losses and of the intrinsic phase imperfectness of the lossy beamsplitter are explored in a single-port excited Mach-Zehnder interferometer. This configuration is especially useful for quantum optics on a chip, where the guiding geometry forces photons to travel in the same spatial mode.
Quantum Interference and Ballistic Transmission in Nanotube Electron Waveguides
International Nuclear Information System (INIS)
The electron transport properties of well-contacted individual single-walled carbon nanotubes are investigated in the ballistic regime. Phase coherent transport and electron interference manifest as conductance fluctuations as a function of Fermi energy. Resonance with standing waves in finite-length tubes and localized states due to imperfections are observed for various Fermi energies. Two units of quantum conductance 2G0=4e2/h are measured for the first time, corresponding to the maximum conductance limit for ballistic transport in two channels of a nanotube
Quantum interference in DNA bases probed by graphene nanoribbons
Jeong, Heejeong; Seul Kim, Han; Lee, Sung-Hoon; Lee, Dongho; Hoon Kim, Yong; Huh, Nam
2013-07-01
Based on first-principles nonequilibrium Green's function calculations, we demonstrate quantum interference (QI) effects on the tunneling conductance of deoxyribonucleic acid bases placed between zigzag graphene nanoribbon electrodes. With the analogy of QI in hydrocarbon ring structures, we hypothesize that QI can be well preserved in the π-π coupling between the carbon-based electrode and a single DNA base. We demonstrate indications of QI, such as destructively interfered anti-resonance or Fano-resonance, that affect the variation of tunneling conductance depending on the orientation of a base. We find that guanine, with a 10-fold higher transverse conductance, can be singled out from the other bases.
Quantum interference on graphs controlled by an external electric field
International Nuclear Information System (INIS)
We consider motion of a charged quantum particle on a loop with two external leads which is placed into an electrostatic field. The loop Hamiltonian is chosen in the simplest possible way; in order to join it to the free Hamiltonians describing the leads, we employ a method based on self-adjoint extensions. Under a symmetry requirement, the resulting full Hamiltonian contains four free parameters; each junction is characterized by a pair of them. The system under consideration representes a model of metallic or semiconductor structures tha can be fabricated by presently available technologies. Assuming the ballistic regime for electrons in such a structure, we calculate the resitance dependence on intensity of the external field. The results suggest the possibility of constructing quantum interference transistors whose size and switching voltage would be much smaller than in the presently used microchips
Two-photon quantum interference for an undergraduate lab
Ourjoumtsev, A.; Dheur, M.-C.; Avignon, T.; Jacubowiez, L.
2015-11-01
We present a simple setup allowing undergraduate students to reproduce the Hong-Ou-Mandel experiment during a half-day labwork session and observe the coalescence of two indistinguishable photons merging on a balanced beamsplitter. This two-photon interference effect, fundamentally related to the bosonic character of the photons, is commonly used in the fields of quantum communication and computing to test the indistinguishability of two single-photon wavepackets. The setup makes use of very few optical elements and requires little alignement that can be performed by students themselves. It allows them to gather essential experimental skills related to parametric crystals, fibre optics and single-photon detection, and to transpose abstract concepts of quantum physics to a hands-on experiment in the lab.
Real-time single-molecule imaging of quantum interference
Juffmann, Thomas; Müllneritsch, Michael; Asenbaum, Peter; Tsukernik, Alexander; Tüxen, Jens; Mayor, Marcel; Cheshnovsky, Ori; Arndt, Markus
2014-01-01
The observation of interference patterns in double-slit experiments with massive particles is generally regarded as the ultimate demonstration of the quantum nature of these objects. Such matter-wave interference has been observed for electrons, neutrons, atoms and molecules and it differs from classical wave-physics in that it can even be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the "most beautiful experiment in physics". Here we show how a combination of nanofabrication and nanoimaging methods allows us to record the full two-dimensional build-up of quantum diffraction patterns in real-time for phthalocyanine molecules PcH2 and their tailored derivatives F24PcH2 with a mass of 1298 amu. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence and the gratings were machined in 10 nm thick silicon nitride membranes to reduce the effect ...
Quantum interference in thermoelectric molecular junctions: A toy model perspective
Nozaki, Daijiro; Avdoshenko, Stas M.; Sevinçli, Hâldun; Cuniberti, Gianaurelio
2014-08-01
Quantum interference (QI) phenomena between electronic states in molecular circuits offer a new opportunity to design new types of molecular devices such as molecular sensors, interferometers, and thermoelectric devices. Controlling the QI effect is a key challenge for such applications. For the development of single molecular devices employing QI effects, a systematic study of the relationship between electronic structure and the quantum interference is needed. In order to uncover the essential topological requirements for the appearance of QI effects and the relationship between the QI-affected line shape of the transmission spectra and the electronic structures, we consider a homogeneous toy model where all on-site energies are identical and model four types of molecular junctions due to their topological connectivities. We systematically analyze their transmission spectra, density of states, and thermoelectric properties. Even without the degree of freedom for on-site energies an asymmetric Fano peak could be realized in the homogeneous systems with the cyclic configuration. We also calculate the thermoelectric properties of the model systems with and without fluctuation of on-site energies. Even under the fluctuation of the on-site energies, the finite thermoelectrics are preserved for the Fano resonance, thus cyclic configuration is promising for thermoelectric applications. This result also suggests the possibility to detect the cyclic configuration in the homogeneous systems and the presence of the QI features from thermoelectric measurements.
Cross-conjugation and quantum interference: a general correlation?
DEFF Research Database (Denmark)
Valkenier, Hennie; Guedon, Constant M.; Markussen, Troels; Thygesen, Kristian Sommer; van der Molen, Sense J.; Hummelen, Jan C.
2014-01-01
We discuss the relationship between the pi-conjugation pattern, molecular length, and charge transport properties of molecular wires, both from an experimental and a theoretical viewpoint. Specifically, we focus on the role of quantum interference in the conductance properties of cross-conjugated......We discuss the relationship between the pi-conjugation pattern, molecular length, and charge transport properties of molecular wires, both from an experimental and a theoretical viewpoint. Specifically, we focus on the role of quantum interference in the conductance properties of cross......-conjugated molecules. For this, we compare experiments on two series of dithiolated wires. The first set we synthesized consists of three dithiolated oligo(phenylene ethynylene) (OPE) benchmark compounds with increasing length. The second series synthesized comprises three molecules with different pi......-conjugation patterns, but identical lengths, i.e. an anthracene (linear conjugation), an anthraquinone (cross-conjugation), and a dihydroanthracene (broken conjugation) derivative. To benchmark reliable trends, conductance experiments on these series have been performed by various techniques. Here, we compare data...
Quantum interference in thermoelectric molecular junctions: A toy model perspective
Energy Technology Data Exchange (ETDEWEB)
Nozaki, Daijiro, E-mail: daijiro.nozaki@gmail.com, E-mail: research@nano.tu-dresden.de [Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062 Dresden (Germany); Avdoshenko, Stas M. [Department of Chemistry and Institute for Computational Engineering and Sciences, University of Texas at Austin, 100 E. 24th St. A1590, Austin, Texas 78712 (United States); Sevinçli, Hâldun [Department of Materials Science and Engineering, Izmir Institute of Technology, Gulbahce Kampusu 35430 Urla, Izmir (Turkey); Cuniberti, Gianaurelio [Institute for Materials Science and Max Bergmann Center of Biomaterials, TU Dresden, 01062 Dresden (Germany); Dresden Center for Computational Materials Science (DCCMS), TU Dresden, 01062 Dresden (Germany); Center for Advancing Electronics Dresden (cfAED), TU Dresden, 01062 Dresden (Germany)
2014-08-21
Quantum interference (QI) phenomena between electronic states in molecular circuits offer a new opportunity to design new types of molecular devices such as molecular sensors, interferometers, and thermoelectric devices. Controlling the QI effect is a key challenge for such applications. For the development of single molecular devices employing QI effects, a systematic study of the relationship between electronic structure and the quantum interference is needed. In order to uncover the essential topological requirements for the appearance of QI effects and the relationship between the QI-affected line shape of the transmission spectra and the electronic structures, we consider a homogeneous toy model where all on-site energies are identical and model four types of molecular junctions due to their topological connectivities. We systematically analyze their transmission spectra, density of states, and thermoelectric properties. Even without the degree of freedom for on-site energies an asymmetric Fano peak could be realized in the homogeneous systems with the cyclic configuration. We also calculate the thermoelectric properties of the model systems with and without fluctuation of on-site energies. Even under the fluctuation of the on-site energies, the finite thermoelectrics are preserved for the Fano resonance, thus cyclic configuration is promising for thermoelectric applications. This result also suggests the possibility to detect the cyclic configuration in the homogeneous systems and the presence of the QI features from thermoelectric measurements.
Quantum interference in thermoelectric molecular junctions: A toy model perspective
International Nuclear Information System (INIS)
Quantum interference (QI) phenomena between electronic states in molecular circuits offer a new opportunity to design new types of molecular devices such as molecular sensors, interferometers, and thermoelectric devices. Controlling the QI effect is a key challenge for such applications. For the development of single molecular devices employing QI effects, a systematic study of the relationship between electronic structure and the quantum interference is needed. In order to uncover the essential topological requirements for the appearance of QI effects and the relationship between the QI-affected line shape of the transmission spectra and the electronic structures, we consider a homogeneous toy model where all on-site energies are identical and model four types of molecular junctions due to their topological connectivities. We systematically analyze their transmission spectra, density of states, and thermoelectric properties. Even without the degree of freedom for on-site energies an asymmetric Fano peak could be realized in the homogeneous systems with the cyclic configuration. We also calculate the thermoelectric properties of the model systems with and without fluctuation of on-site energies. Even under the fluctuation of the on-site energies, the finite thermoelectrics are preserved for the Fano resonance, thus cyclic configuration is promising for thermoelectric applications. This result also suggests the possibility to detect the cyclic configuration in the homogeneous systems and the presence of the QI features from thermoelectric measurements
Trajectory description of the quantum-classical transition for wave packet interference
Chou, Chia-Chun
2016-08-01
The quantum-classical transition for wave packet interference is investigated using a hydrodynamic description. A nonlinear quantum-classical transition equation is obtained by introducing a degree of quantumness ranging from zero to one into the classical time-dependent Schrödinger equation. This equation provides a continuous description for the transition process of physical systems from purely quantum to purely classical regimes. In this study, the transition trajectory formalism is developed to provide a hydrodynamic description for the quantum-classical transition. The flow momentum of transition trajectories is defined by the gradient of the action function in the transition wave function and these trajectories follow the main features of the evolving probability density. Then, the transition trajectory formalism is employed to analyze the quantum-classical transition of wave packet interference. For the collision-like wave packet interference where the propagation velocity is faster than the spreading speed of the wave packet, the interference process remains collision-like for all the degree of quantumness. However, the interference features demonstrated by transition trajectories gradually disappear when the degree of quantumness approaches zero. For the diffraction-like wave packet interference, the interference process changes continuously from a diffraction-like to collision-like case when the degree of quantumness gradually decreases. This study provides an insightful trajectory interpretation for the quantum-classical transition of wave packet interference.
Quantum interference in a Cooper pair splitter device
Csonka, Szabolcs; Fulop, G.; Dominguez, F.; Levy Yeyati, A.; D'Hollosy, S.; Baumgartner, A.; Makk, P.; Schonenberger, C.; Guzenko, V. A.; Madsen, M. H.; Nygard, J.
Cooper pair splitting (CPS) is a process in which the electrons of naturally occurring spin singlet pairs in a superconductor are spatially separated using two quantum dots. In the present work we investigate the evolution of the conductance correlations in an InAs nanowire based CPS device in the presence of an external magnetic field. In our experiments the gate dependence of the signal that depends on both quantum dots continuously evolves from a slightly asymmetric Lorentzian to a strongly asymmetric Fano-type resonance with increasing B field. Our experiments can be understood in a simple 3 site model, which shows that the nonlocal CPS leads to symmetric line shapes, while the local transport processes can exhibit an asymmetric shape due to quantum interference. These findings demonstrate that the electrons from a Cooper pair splitter can propagate coherently after their emission from the superconductor and how a magnetic field can be used to optimize the performance of a CPS device. In addition CPS devices were developed where the nanowire segments between the two dots were removed, nonlocal measurement on such CPS devices will also be presented.
Gu, Yingfei; Wen, Xueda; Cho, Gil Young; Ryu, Shinsei; Qi, Xiao-Liang
2016-01-01
In this paper, we study $(2+1)$-dimensional quantum anomalous Hall states, i.e. band insulators with quantized Hall conductance, using the exact holographic mapping. The exact holographic mapping is an approach to holographic duality which maps the quantum anomalous Hall state to a different state living in $(3+1)$-dimensional hyperbolic space. By studying topological response properties and the entanglement spectrum, we demonstrate that the holographic dual theory of a quantum anomalous Hall state is a $(3+1)$-dimensional topological insulator. The dual description enables a new characterization of topological properties of a system by the quantum entanglement between degrees of freedom at different length scales.
An electro-optic waveform interconnect based on quantum interference
Qin, Li-Guo; Gong, Shang-Qing
2016-01-01
The ability to modulate an optical field via an electric field is regarded as a key function of electro-optic interconnects, which are used in optical communications and information processing systems. One of the main required devices for such interconnects is the electro-optic modulator (EOM). Current EOM based on the electro-optic effect and the electro-absorption effect often is bulky and power inefficient due to the weak electro-optic properties of its constituent materials. Here we propose a new mechanism to produce an arbitrary-waveform EOM based on the quantum interference, in which both the real and imaginary parts of the susceptibility are engineered coherently with the superhigh efficiency. Based on this EOM, a waveform interconnect from the voltage to the modulated optical absorption is realised. We expect that such a new type of electro-optic interconnect will have a broad range of applications including the optical communications and network.
Quantum interference induced by initial system–environment correlations
International Nuclear Information System (INIS)
We investigate the quantum interference induced by a relative phase in the correlated initial state of a system which consists in a two-level atom interacting with a damped mode of the radiation field. We show that the initial relative phase has significant effects on both the evolution of the atomic excited-state population and the information flow between the atom and the reservoir, as quantified by the trace distance. Furthermore, by considering two two-level atoms interacting with a common damped mode of the radiation field, we highlight how initial relative phases can affect the subsequent entanglement dynamics. -- Highlights: ► We study the effect of initial correlations in system–bath excitation transfer. ► We study the information flow from the bath to the system via the trace distance. ► We show how entanglement dynamics can be controlled via initial relative phases.
Josephson phase diffusion in the superconducting quantum interference device ratchet
Energy Technology Data Exchange (ETDEWEB)
Spiechowicz, Jakub [Institute of Physics, University of Silesia, 40-007 Katowice (Poland); Łuczka, Jerzy, E-mail: jerzy.luczka@us.edu.pl [Institute of Physics, University of Silesia, 40-007 Katowice (Poland); Silesian Center for Education and Interdisciplinary Research, University of Silesia, 41-500 Chorzów (Poland)
2015-05-15
We study diffusion of the Josephson phase in the asymmetric superconducting quantum interference device (SQUID) subjected to a time-periodic current and pierced by an external magnetic flux. We analyze a relation between phase diffusion and quality of transport characterized by the dc voltage across the SQUID and efficiency of the device. In doing so, we concentrate on the previously reported regime [J. Spiechowicz and J. Łuczka, New J. Phys. 17, 023054 (2015)] for which efficiency of the SQUID attains a global maximum. For long times, the mean-square displacement of the phase is a linear function of time, meaning that diffusion is normal. Its coefficient is small indicating rather regular phase evolution. However, it can be magnified several times by tailoring experimentally accessible parameters like amplitudes of the ac current or external magnetic flux. Finally, we prove that in the deterministic limit this regime is essentially non-chaotic and possesses an unexpected simplicity of attractors.
Miniaturized superconducting quantum interference magnetometers for high sensitivity applications
Granata, C.; Vettoliere, A.; Russo, M.
2007-09-01
A miniaturized niobium based dc superconducting quantum interference device (SQUID) magnetometer for high magnetic field sensitivity applications has been developed. The sensing coil consists of an integrated square superconducting coil with a length of 3mm, involving a device area much smaller with respect to the standard SQUID magnetometers with a comparable magnetic field sensitivity; so it allows increasing the spatial resolution keeping the magnetic field sensitivity unaltered. Furthermore, a small pickup coil minimizes its antenna gain, reducing the radio frequency interference. At T =4.2K, the sensors have shown smooth and resonance free V-Φ characteristics and an intrinsic white magnetic field noise spectral density as low as 5.8fT /Hz1/2, measured in flux locked loop configuration. The good agreement with the theoretical predictions guarantees the reliability and the controllability of the sensors. Due to their compactness and good characteristic parameters, such sensors are suitable for large multichannel systems used in biomagnetic imaging.
Symmetry-induced quantum interference effects in metalloporphyrin wires.
Ferradás, R; García-Suárez, V M; Ferrer, J
2013-08-14
We calculate the electronic and transport properties of a series of metalloporphyrin molecules sandwiched between gold electrodes using a combination of density functional theory and scattering theory. The impact of strong correlations at the central metallic atom is gauged by comparing our results obtained using conventional DFT and DFT + U approaches. The zero- and finite-bias transport properties may or may not show spin-filtering behavior, depending on the nature of the d state closest to the Fermi energy. The type of d state depends on the metallic atom and gives rise to interference effects that produce different Fano features. The inclusion of the U term opens a gap between the d states and changes the conductance and spin-filtering behavior qualitatively in some of the molecules. We explain the origin of the quantum interference effects found as due to the symmetry-dependent coupling between the d states and other molecular orbitals and propose the use of these systems as nanoscale chemical sensors. We also demonstrate that an adequate treatment of strong correlations is really necessary to correctly describe the transport properties of metalloporphyrins and similar molecular magnets. PMID:23838608
Quantum interference and Aharonov-Bohm oscillations in topological insulators.
Bardarson, Jens H; Moore, Joel E
2013-05-01
Topological insulators (TIs) have an insulating bulk but a metallic surface. In the simplest case, the surface electronic structure of a three-dimensional (3D) TI is described by a single two-dimensional (2D) Dirac cone. A single 2D Dirac fermion cannot be realized in an isolated 2D system with time-reversal symmetry, but rather owes its existence to the topological properties of the 3D bulk wavefunctions. The transport properties of such a surface state are of considerable current interest; they have some similarities with graphene, which also realizes Dirac fermions, but have several unique features in their response to magnetic fields. In this review we give an overview of some of the main quantum transport properties of TI surfaces. We focus on the efforts to use quantum interference phenomena, such as weak anti-localization and the Aharonov-Bohm effect, to verify in a transport experiment the Dirac nature of the surface state and its defining properties. In addition to explaining the basic ideas and predictions of the theory, we provide a survey of recent experimental work. PMID:23552181
Quantum interference and Aharonov–Bohm oscillations in topological insulators
International Nuclear Information System (INIS)
Topological insulators (TIs) have an insulating bulk but a metallic surface. In the simplest case, the surface electronic structure of a three-dimensional (3D) TI is described by a single two-dimensional (2D) Dirac cone. A single 2D Dirac fermion cannot be realized in an isolated 2D system with time-reversal symmetry, but rather owes its existence to the topological properties of the 3D bulk wavefunctions. The transport properties of such a surface state are of considerable current interest; they have some similarities with graphene, which also realizes Dirac fermions, but have several unique features in their response to magnetic fields. In this review we give an overview of some of the main quantum transport properties of TI surfaces. We focus on the efforts to use quantum interference phenomena, such as weak anti-localization and the Aharonov–Bohm effect, to verify in a transport experiment the Dirac nature of the surface state and its defining properties. In addition to explaining the basic ideas and predictions of the theory, we provide a survey of recent experimental work. (review article)
Anomalous Curie response of an impurity in a quantum critical spin-1/2 Heisenberg antiferromagnet
Höglund, Kaj; Sandvik, Anders
2007-03-01
There is a disagreement concerning the low-temperature (T) magnetic susceptibility χ^zimp˜C/T of a spin-S impurity in a nearly quantum critical antiferromagnetic host. Field-theoretical work [1] predicted an anomalous Curie constant S^2/30 quantum Monte Carlo simulations in order to resolve the controversy. Our main result is for a vacancy in a quantum critical spin-1/2 Heisenberg antiferromagnet on a bilayer lattice. In our susceptibility data for the S=1/2 impurity we observe a Curie constant C=0.262(2). Although the value falls outside the predicted range, it should correspond to an anomalous impurity response, as proposed in Ref. [1]. [1] S. Sachdev, C. Buragohain, and M. Vojta, Science 286, 2479 (1999); M. Vojta, C. Buragohain, and S. Sachdev, Phys. Rev. B 61, 15152 (2000). [2] O. P. Sushkov, Phys. Rev. B 62, 12135 (2000). [3] M. Troyer, Prog. Theor. Phys. Supp. 145, 326 (2002).
Phase Interference in a Multi-level Quantum-Dot System
Institute of Scientific and Technical Information of China (English)
ZHANG Xu-Ming; CHEN Xiao-Shuang; LU Wei
2009-01-01
@@ Considering phase interference, we investigate coherent transport in a quantum dot by using a thermopower. In the single process of the electronic transport through the quantum dot, it is shown that the phase interference between the levels of a quantum dot is like the Aharonov-Bohm effect. The result indicates that the thermopower is very sensitive to phase interference. It is also found that the phase-difference change of the different levels of the quantum dot can determine the shape of the thermopower.
International Nuclear Information System (INIS)
Microscopic particle exhibit wave properties because of wave-particle duality of quantum mechanics, numerous examples of quantum interference effect within matter-wave had been discovered. For the singlet-triplet mixed states in diatom molecule, quantum interference present in two transfer roads. The theoretical model of Quantum Interference is described in an atom-diatom system, based on the first-Born approximation of time dependent perturbation theory, taking into account the anisotropic Len- nard-Jones interaction potentials and 'straight-line' trajectory approximation, the approximation conditions of the CQI model is discussed. (authors)
Dynamic control of coherent pulses via Fano-type interference in asymmetric double quantum wells
International Nuclear Information System (INIS)
We study the temporal and spatial dynamics of two light pulses, a probe and a switch, propagating through an asymmetric double quantum well where tunneling-induced quantum interference may be observed. When such an interference takes place, in the absence of the switch, the quantum well is transparent to the probe which propagates over sufficiently long distances at very small group velocities. In the presence of a relatively strong switch, however, the probe pulse is absorbed due to the quenching of tunneling-induced quantum interference. The probe may be made to vanish even when switch and probe are somewhat delayed with respect to one another. Conversely, our asymmetric double quantum well may be rendered either opaque or transparent to the switch pulse. Such a probe-switch 'reciprocity' can be used to devise a versatile all-optical quantum interference-based solid-state switch for optical communication devices
Anomalous phase shift in a twisted quantum loop
Energy Technology Data Exchange (ETDEWEB)
Taira, Hisao [Division of Applied Physics, Graduate School of Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628 (Japan); Shima, Hiroyuki, E-mail: taira@eng.hokudai.ac.j [Department of Applied Mathematics 3, LaCaN, Universitat Politecnica de Catalunya (UPC), Barcelona 08034 (Spain)
2010-09-03
The coherent motion of electrons in a twisted quantum ring is considered to explore the effect of torsion inherent to the ring. Internal torsion of the ring composed of helical atomic configuration yields a non-trivial quantum phase shift in the electrons' eigenstates. This torsion-induced phase shift causes novel kinds of persistent current flow and an Aharonov-Bohm-like conductance oscillation. The two phenomena can occur even when no magnetic flux penetrates inside the twisted ring, thus being in complete contrast with the counterparts observed in untwisted rings.
Anomalous phase shift in a twisted quantum loop
International Nuclear Information System (INIS)
The coherent motion of electrons in a twisted quantum ring is considered to explore the effect of torsion inherent to the ring. Internal torsion of the ring composed of helical atomic configuration yields a non-trivial quantum phase shift in the electrons' eigenstates. This torsion-induced phase shift causes novel kinds of persistent current flow and an Aharonov-Bohm-like conductance oscillation. The two phenomena can occur even when no magnetic flux penetrates inside the twisted ring, thus being in complete contrast with the counterparts observed in untwisted rings.
Anomalous temperature dependence of excitation transfer between quantum dots
Czech Academy of Sciences Publication Activity Database
Král, Karel; Menšík, Miroslav
2015-01-01
Roč. 7, č. 4 (2015), 325-330. ISSN 2164-6627 R&D Projects: GA MŠk(CZ) LD14011; GA MŠk LH12236; GA MŠk LH12186 Institutional support: RVO:68378271 ; RVO:61389013 Keywords : excitation transfer * quantum dots * temperature dependence * electron-phonon interaction Subject RIV: BM - Solid Matter Physics ; Magnetism
Scaling of anomalous hall effect in amorphous CoFeB Films with accompanying quantum correction
Zhang, Yan
2015-05-08
Scaling of anomalous Hall effect in amorphous CoFeB films with thickness ranging from 2 to 160 nm have been investigated. We have found that the scaling relationship between longitudinal (ρxx) and anomalous Hall (ρAH) resistivity is distinctly different in the Bloch and localization regions. For ultrathin CoFeB films, the sheet resistance (Rxx) and anomalous Hall conductance (GAH) received quantum correction from electron localization showing two different scaling relationships at different temperature regions. In contrast, the thicker films show a metallic conductance, which have only one scaling relationship in the entire temperature range. Furthermore, in the dirty regime of localization regions, an unconventional scaling relationship View the MathML sourceσAH∝σxxα with α=1.99 is found, rather than α=1.60 predicted by the unified theory.
The Study of Quantum Interference in Metallic Photonic Crystals Doped with Four-Level Quantum Dots
Directory of Open Access Journals (Sweden)
Hatef Ali
2010-01-01
Full Text Available Abstract In this work, the absorption coefficient of a metallic photonic crystal doped with nanoparticles has been obtained using numerical simulation techniques. The effects of quantum interference and the concentration of doped particles on the absorption coefficient of the system have been investigated. The nanoparticles have been considered as semiconductor quantum dots which behave as a four-level quantum system and are driven by a single coherent laser field. The results show that changing the position of the photonic band gap about the resonant energy of the two lower levels directly affects the decay rate, and the system can be switched between transparent and opaque states if the probe laser field is tuned to the resonance frequency. These results provide an application for metallic nanostructures in the fabrication of new optical switches and photonic devices.
Quantum Interference Induced Photon Blockade in a Coupled Single Quantum Dot-Cavity System
Tang, Jing; Xu, Xiulai
2015-01-01
We propose an experimental scheme to implement a strong photon blockade with a single quantum dot coupled to a nanocavity. The photon blockade effect can be tremendously enhanced by driving the cavity and the quantum dot simultaneously with two classical laser fields. This enhancement of photon blockade is ascribed to the quantum interference effect to avoid two-photon excitation of the cavity field. Comparing with Jaynes-Cummings model, the second-order correlation function at zero time delay $g^{(2)}(0)$ in our scheme can be reduced by two orders of magnitude and the system sustains a large intracavity photon number. A red (blue) cavity-light detuning asymmetry for photon quantum statistics with bunching or antibunching characteristics is also observed. The photon blockade effect has a controllable flexibility by tuning the relative phase between the two pumping laser fields and the Rabi coupling strength between the quantum dot and the pumping field. Moreover, the photon blockade scheme based on quantum in...
Chaotic dynamics of periodically driven rf superconducting quantum interference devices
International Nuclear Information System (INIS)
We present numerical investigations of the intrinsic noise in periodically driven, high-frequency, rf superconducting quantum interference devices (SQUID's) due to the chaotic time evolution of the flux trapped in the superconducting ring. The amplitude and the frequency of the external sinusoidal magnetic flux are the control parameters of the SQUID dynamics. The present work shows in detail how the well-known quasistationary behavior evolves into chaos at high frequencies. A rich structure of subharmonic and chaotic bands is observed in the parameter space. Both intermittent and period-doubling routes to chaos are found; the latter is always preceded by a broken symmetry, and thus the former is the governing one for small amplitudes. We also discuss the experimental observability and manifestations of multiply periodic and chaotic SQUID response. In particular, the usual staircase dependence of the absorbed hysteresis power on the amplitude of the external flux is shown to be broken in a characteristic way for each main subharmonic. Thus we propose that simple dc measurements can detect important properties of the nonlinear SQUID dynamics
Quantized topological magnetoelectric effect of the zero-plateau quantum anomalous Hall state
Jing WANG; Lian, Biao; Qi, Xiao-Liang; Zhang, Shou-Cheng
2015-01-01
Topological magnetoelectric effect in a three-dimensional topological insulator is a novel phenomenon, where an electric field induces a magnetic field in the same direction, with a universal coefficient of proportionality quantized in units of $e^2/2h$. Here we propose that the topological magnetoelectric effect can be realized in the zero-plateau quantum anomalous Hall state of magnetic topological insulators or ferromagnet-topological insulator heterostructure. The finite-size effect is al...
Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2
Das, P. K.; Di Sante, D.; Vobornik, I.; Fujii, J.; Okuda, T; Bruyer, E.; Gyenis, A.; Feldman, B; Tao, J.; Ciancio, R.; Rossi, G.; Ali, M.(National Centre for Particle Physics, Universiti Malaya, Kuala Lumpur, Malaysia); Picozzi, S.; Yazdani, A.; G. Panaccione
2016-01-01
The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phenomenon, accounting for a rich variety of material properties. Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators, transition metal dichalcogenides have recently received renewed attention. In this context, the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest. Here we report angle- and spin-r...
Interference of mesoscopic particles: quantum--classical transition
Facchi, P.; Pascazio, S.; Yoneda, T
2005-01-01
We analyze the double slit interference of a mesoscopic particle. We calculate the visibility of the interference pattern, introduce a characteristic temperature that defines the onset to decoherence and scrutinize the conditions that must be satisfied for an interference experiment to be possible.
On the quantum mechanics of consciousness, with application to anomalous phenomena
International Nuclear Information System (INIS)
Theoretical explication of a growing body of empirical data on consciousness-related anomalous phenomena is unlikely to be achieved in terms of known physical processes. Rather, it will first be necessary to formulate the basic role of consciousness in the definition of reality before such anomalous experience can adequately be represented. This paper takes the position that reality is constituted only in the interaction of consciousness with its environment, and therefore that any scheme of conceptual organization developed to represent that reality must reflect the processes of consciousness as well as those of its environment. In this spirit, the concepts and formalisms of elementary quantum mechanics, as originally proposed to explain anomalous atomic-scale physical phenomena, are appropriated via metaphor to represent the general characteristics of consciousness interacting with any environment. More specifically, if consciousness is represented by a quantum mechanical wave function, and its environment by an appropriate potential profile, Schrodinger wave mechanics defines eigenfunctions and eigenvalues that can be associated with the cognitive and emotional experiences of that consciousness in that environment. To articulate this metaphor it is necessary to associate certain aspects of the formalism, such as the coordinate system, the quantum numbers, and even the metric itself, with various impressionistic descriptors of consciousness, such as its intensity, perspective, approach/avoidance attitude, balance between cognitive and emotional activity, and receptive/assertive disposition
From magnetically doped topological insulator to the quantum anomalous Hall effect
Institute of Scientific and Technical Information of China (English)
He Ke; Ma Xu-Cun; Chen Xi; Lü Li; Wang Ya-Yu; Xue Qi-Kun
2013-01-01
Quantum Hall effect (QHE),as a class of quantum phenomena that occur in macroscopic scale,is one of the most important topics in condensed matter physics.It has long been expected that QHE may occur without Landau levels so that neither extemal magnetic field nor high sample mobility is required for its study and application.Such a QHE free of Landau levels,can appear in topological insulators (TIs) with ferromagnetism as the quantized version of the anomalous Hall effect,i.e.,quantum anomalous Hall (QAH) effect.Here we review our recent work on experimental realization of the QAH effect in magnetically doped TIs.With molecular beam epitaxy,we prepare thin films of Cr-doped (Bi,Sb)2Te3 TIs with wellcontrolled chemical potential and long-range ferromagnetic order that can survive the insulating phase.In such thin films,we eventually observed the quantization of the Hall resistance at h/e2 at zero field,accompanied by a considerable drop in the longitudinal resistance.Under a strong magnetic field,the longitudinal resistance vanishes,whereas the Hall resistance remains at the quantized value.The realization of the QAH effect provides a foundation for many other novel quantum phenomena predicted in TIs,and opens a route to practical applications of quantum Hall physics in low-power-consumption electronics.
Quantum-ring spin interference device tuned by quantum point contacts
Energy Technology Data Exchange (ETDEWEB)
Diago-Cisneros, Leo [Facultad de Física, Universidad de La Habana, C.P.10400, La Habana (Cuba); Mireles, Francisco [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, C.P. 22800 Ensenada, Baja California, México (Mexico)
2013-11-21
We introduce a spin-interference device that comprises a quantum ring (QR) with three embedded quantum point contacts (QPCs) and study theoretically its spin transport properties in the presence of Rashba spin-orbit interaction. Two of the QPCs conform the lead-to-ring junctions while a third one is placed symmetrically in the upper arm of the QR. Using an appropriate scattering model for the QPCs and the S-matrix scattering approach, we analyze the role of the QPCs on the Aharonov-Bohm (AB) and Aharonov-Casher (AC) conductance oscillations of the QR-device. Exact formulas are obtained for the spin-resolved conductances of the QR-device as a function of the confinement of the QPCs and the AB/AC phases. Conditions for the appearance of resonances and anti-resonances in the spin-conductance are derived and discussed. We predict very distinctive variations of the QR-conductance oscillations not seen in previous QR proposals. In particular, we find that the interference pattern in the QR can be manipulated to a large extend by varying electrically the lead-to-ring topological parameters. The latter can be used to modulate the AB and AC phases by applying gate voltage only. We have shown also that the conductance oscillations exhibits a crossover to well-defined resonances as the lateral QPC confinement strength is increased, mapping the eigenenergies of the QR. In addition, unique features of the conductance arise by varying the aperture of the upper-arm QPC and the Rashba spin-orbit coupling. Our results may be of relevance for promising spin-orbitronics devices based on quantum interference mechanisms.
Interference with a quantum dot single-photon source and a laser at telecom wavelength
Energy Technology Data Exchange (ETDEWEB)
Felle, M. [Toshiba Research Europe Limited, Cambridge Research Laboratory, 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Centre for Advanced Photonics and Electronics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0FA (United Kingdom); Huwer, J., E-mail: jan.huwer@crl.toshiba.co.uk; Stevenson, R. M.; Skiba-Szymanska, J.; Ward, M. B.; Shields, A. J. [Toshiba Research Europe Limited, Cambridge Research Laboratory, 208 Cambridge Science Park, Milton Road, Cambridge CB4 0GZ (United Kingdom); Farrer, I.; Ritchie, D. A. [Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Penty, R. V. [Centre for Advanced Photonics and Electronics, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0FA (United Kingdom)
2015-09-28
The interference of photons emitted by dissimilar sources is an essential requirement for a wide range of photonic quantum information applications. Many of these applications are in quantum communications and need to operate at standard telecommunication wavelengths to minimize the impact of photon losses and be compatible with existing infrastructure. Here, we demonstrate for the first time the quantum interference of telecom-wavelength photons from an InAs/GaAs quantum dot single-photon source and a laser; an important step towards such applications. The results are in good agreement with a theoretical model, indicating a high degree of indistinguishability for the interfering photons.
Interference with a quantum dot single-photon source and a laser at telecom wavelength
International Nuclear Information System (INIS)
The interference of photons emitted by dissimilar sources is an essential requirement for a wide range of photonic quantum information applications. Many of these applications are in quantum communications and need to operate at standard telecommunication wavelengths to minimize the impact of photon losses and be compatible with existing infrastructure. Here, we demonstrate for the first time the quantum interference of telecom-wavelength photons from an InAs/GaAs quantum dot single-photon source and a laser; an important step towards such applications. The results are in good agreement with a theoretical model, indicating a high degree of indistinguishability for the interfering photons
Energy Technology Data Exchange (ETDEWEB)
Zhao, Dongxing; Wu, Jiarui [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Gu, Ying, E-mail: ygu@pku.edu.cn; Gong, Qihuang [State Key Laboratory for Mesoscopic Physics, Department of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)
2014-09-15
We propose tailoring of the double Fano profiles via plasmon-assisted quantum interference in a hybrid exciton-plasmon system. Tailoring is performed by the interference between two exciton channels interacting with a common localized surface plasmon. Using an applied field of low intensity, the absorption spectrum of the hybrid system reveals a double Fano lineshape with four peaks. For relatively large field intensity, a broad flat window in the absorption spectrum appears which results from the destructive interference between excitons. Because of strong constructive interference, this window vanishes as intensity is further increased. We have designed a nanometer bandpass optical filter for visible light based on tailoring of the optical spectrum. This study provides a platform for quantum interference that may have potential applications in ultracompact tunable quantum devices.
International Nuclear Information System (INIS)
We propose tailoring of the double Fano profiles via plasmon-assisted quantum interference in a hybrid exciton-plasmon system. Tailoring is performed by the interference between two exciton channels interacting with a common localized surface plasmon. Using an applied field of low intensity, the absorption spectrum of the hybrid system reveals a double Fano lineshape with four peaks. For relatively large field intensity, a broad flat window in the absorption spectrum appears which results from the destructive interference between excitons. Because of strong constructive interference, this window vanishes as intensity is further increased. We have designed a nanometer bandpass optical filter for visible light based on tailoring of the optical spectrum. This study provides a platform for quantum interference that may have potential applications in ultracompact tunable quantum devices.
SQUID detected NMR and NQR. Superconducting Quantum Interference Device.
Augustine, M P; TonThat, D M; Clarke, J
1998-03-01
The dc Superconducting QUantum Interference Device (SQUID) is a sensitive detector of magnetic flux, with a typical flux noise of the order 1 muphi0 Hz(-1/2) at liquid helium temperatures. Here phi0 = h/2e is the flux quantum. In our NMR or NQR spectrometer, a niobium wire coil wrapped around the sample is coupled to a thin film superconducting coil deposited on the SQUID to form a flux transformer. With this untuned input circuit the SQUID measures the flux, rather than the rate of change of flux, and thus retains its high sensitivity down to arbitrarily low frequencies. This feature is exploited in a cw spectrometer that monitors the change in the static magnetization of a sample induced by radio frequency irradiation. Examples of this technique are the detection of NQR in 27Al in sapphire and 11B in boron nitride, and a level crossing technique to enhance the signal of 14N in peptides. Research is now focused on a SQUID-based spectrometer for pulsed NQR and NMR, which has a bandwidth of 0-5 MHz. This spectrometer is used with spin-echo techniques to measure the NQR longitudinal and transverse relaxation times of 14N in NH4ClO4, 63+/-6 ms and 22+/-2 ms, respectively. With the aid of two-frequency pulses to excite the 359 kHz and 714 kHz resonances in ruby simultaneously, it is possible to obtain a two-dimensional NQR spectrum. As a third example, the pulsed spectrometer is used to study NMR spectrum of 129Xe after polariza-tion with optically pumped Rb. The NMR line can be detected at frequencies as low as 200 Hz. At fields below about 2 mT the longitudinal relaxation time saturates at about 2000 s. Two recent experiments in other laboratories have extended these pulsed NMR techniques to higher temperatures and smaller samples. In the first, images were obtained of mineral oil floating on water at room temperature. In the second, a SQUID configured as a thin film gradiometer was used to detect NMR in a 50 microm particle of 195Pt at 6 mT and 4.2 K. PMID:9650797
Programmable two-photon quantum interference in $10^3$ channels in opaque scattering media
Wolterink, Tom A W; Ctistis, Georgios; Vos, Willem L; Boller, Klaus -J; Pinkse, Pepijn W H
2015-01-01
We investigate two-photon quantum interference in an opaque scattering medium that intrinsically supports $10^6$ transmission channels. By adaptive spatial phase-modulation of the incident wavefronts, the photons are directed at targeted speckle spots or output channels. From $10^3$ experimentally available coupled channels, we select two channels and enhance their transmission, to realize the equivalent of a fully programmable $2\\times2$ beam splitter. By sending pairs of single photons from a parametric down-conversion source through the opaque scattering medium, we observe two-photon quantum interference. The programmed beam splitter need not fulfill energy conservation over the two selected output channels and hence could be non-unitary. Consequently, we have the freedom to tune the quantum interference from bunching (Hong-Ou-Mandel-like) to antibunching. Our results establish opaque scattering media as a platform for high-dimensional quantum interference that is notably relevant for boson sampling and ph...
Programmable two-photon quantum interference in 103 channels in opaque scattering media
Wolterink, Tom A. W.; Uppu, Ravitej; Ctistis, Georgios; Vos, Willem L.; Boller, Klaus-J.; Pinkse, Pepijn W. H.
2016-05-01
We investigate two-photon quantum interference in an opaque scattering medium that intrinsically supports a large number of transmission channels. By adaptive spatial phase modulation of the incident wave fronts, the photons are directed at targeted speckle spots or output channels. From 103 experimentally available coupled channels, we select two channels and enhance their transmission to realize the equivalent of a fully programmable 2 ×2 beam splitter. By sending pairs of single photons from a parametric down-conversion source through the opaque scattering medium, we observe two-photon quantum interference. The programed beam splitter need not fulfill energy conservation over the two selected output channels and hence could be nonunitary. Consequently, we have the freedom to tune the quantum interference from bunching (Hong-Ou-Mandel-like) to antibunching. Our results establish opaque scattering media as a platform for high-dimensional quantum interference that is notably relevant for boson sampling and physical-key-based authentication.
Microtesla magnetic resonance imaging with a superconducting quantum interference device
Energy Technology Data Exchange (ETDEWEB)
McDermott, Robert; Lee, SeungKyun; ten Haken, Bennie; Trabesinger, Andreas H.; Pines, Alexander; Clarke, John
2004-03-15
We have constructed a magnetic resonance imaging (MRI) scanner based on a dc Superconducting QUantum Interference Device (SQUID) configured as a second-derivative gradiometer. The magnetic field sensitivity of the detector is independent of frequency; it is therefore possible to obtain high-resolution images by prepolarizing the nuclear spins in a field of 300 mT and detecting the signal at 132 fYT, corresponding to a proton Larmor frequency of 5.6 kHz. The reduction in the measurement field by a factor of 10,000 compared with conventional scanners eliminates inhomogeneous broadening of the nuclear magnetic resonance lines, even in fields with relatively poor homogeneity. The narrow linewidths result in enhanced signal-to-noise ratio and spatial resolution for a fixed strength of the magnetic field gradients used to encode the image. We present two-dimensional images of phantoms and pepper slices, obtained in typical magnetic field gradients of 100 fYT/m, with a spatial resolution of about 1mm. We further demonstrate a slice-selected image of an intact pepper. By varying the time delay between removal of the polarizing field and initiation of the spin echo sequence we acquire T1-weighted contrast images of water phantoms, some of which are doped with a paramagnetic salt; here, T1 is the nuclear spin-lattice relaxation time. The techniques presented here could readily be adapted to existing multichannel SQUID systems used for magnetic source imaging of brain signals. Further potential applications include low-cost systems for tumor screening and imaging peripheral regions of the body.
Molecular internal dynamics studied by quantum path interferences in high order harmonic generation
International Nuclear Information System (INIS)
Highlights: ► Electronic trajectories in high order harmonic generation encodes attosecond and femtosecond molecular dynamical information. ► The observation of these quantum paths allows us to follow nuclear motion after ionization. ► Quantum paths interference encodes a signature of superposition of ionization channels. ► Quantum paths interference encodes a signature of transfer of population between channels due to laser coupling. ► Quantum paths interference is a promising technique to resolve ultra-fast dynamical processes after ionization. - Abstract: We investigate how short and long electron trajectory contributions to high harmonic emission and their interferences give access to information about intra-molecular dynamics. In the case of unaligned molecules, we show experimental evidence that the long trajectory contribution is more dependent upon the molecular species than the short one, providing a high sensitivity to cation nuclear dynamics from 100’s of as to a few fs after ionisation. Using theoretical approaches based on the strong field approximation and numerical integration of the time dependent Schrödinger equation, we examine how quantum path interferences encode electronic motion when the molecules are aligned. We show that the interferences are dependent upon which ionisation channels are involved and any superposition between them. In particular, quantum path interferences can encode signatures of electron dynamics if the laser field drives a coupling between the channels. Hence, molecular quantum path interferences are a promising method for attosecond spectroscopy, allowing the resolution of ultra-fast charge migration in molecules after ionisation in a self-referenced manner
Quantum interference and diffraction of parametric down-converted biphotons
Indian Academy of Sciences (India)
Ryosuke Shimizu; Keiichi Edamatsu; Tadashi Itoh
2002-08-01
We present two-photon diffraction and interference experiments utilizing parametric down-converted photon pairs (biphotons) and a transmission grating. The biphoton exhibits a diffraction-interference pattern equivalent to an effective single particle with half wavelength of the constituent photons.
Hwang, Kyusung; Kim, Yong Baek
2016-01-01
We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293
Hwang, Kyusung; Kim, Yong Baek
2016-01-01
We theoretically investigate emergent quantum phases in the thin film geometries of the pyrochore iridates, where a number of exotic quantum ground states are proposed to occur in bulk materials as a result of the interplay between electron correlation and strong spin-orbit coupling. The fate of these bulk phases as well as novel quantum states that may arise only in the thin film platforms, are studied via a theoretical model that allows layer-dependent magnetic structures. It is found that the magnetic order develop in inhomogeneous fashions in the thin film geometries. This leads to a variety of magnetic metal phases with modulated magnetic ordering patterns across different layers. Both the bulk and boundary electronic states in these phases conspire to promote unusual electronic properties. In particular, such phases are akin to the Weyl semimetal phase in the bulk system and they would exhibit an unusually large anomalous Hall effect. PMID:27418293
Quantum Anatomy of the Classical Interference of n-Photon States in a Mach-Zehnder Interferometer
Ramírez-Cruz, N.; Bastarrachea-Magnani, M. A.; Velázquez, V.
2016-03-01
In this work we present the theory for the quantum interference of states with an arbitrary number of photons in a Mach-Zehnder interferometer. We express the mathematical description of the interference in an algebraic way. We show the interference pattern of an average of a n photons input state corresponds to the classical interference pattern, which tells us the last comes from a quantum interference statistical average. Then, we propose to use this scheme to study the statistical transition from quantum to classical interference.
Probabilistic Quantum Gates between Remote Atoms through Interference of Optical Frequency Qubits
Duan, L.-M.; Madsen, M. J.; Moehring, D. L.; Maunz, P.; Kohn Jr, R N; Monroe, C.
2006-01-01
We propose a scheme to perform probabilistic quantum gates on remote trapped atom qubits through interference of optical frequency qubits. The method does not require localization of the atoms to the Lamb-Dicke limit, and is not sensitive to interferometer phase instabilities. Such probabilistic gates can be used for scalable quantum computation.
Quantum interference at direct current in ceramics YBa2Cu3O7-x
International Nuclear Information System (INIS)
The Josephson effects and quantum dc interference in superconducting ceramics YBa2Cu3O7-x having the superconducting transition temperature of 93 K are investigated experimentally. It is shown that along with the known quantum interference, observed in multilink samples of high-Tc superconducting ceramics and ac interference, in the superconducting ceramics there exists quantum interference which also occurs in one-coupled samples at direct current, the induction-voltage conversion steepness and the signal-noise ratio in the high-Tc superconducting ceramics at 77 K being commensurate with similar charateristics of classical dc squids operating at 4.2 K. It is found from the temperature dependence of the Josephson current in samples whose sizes are much greater than coherence lengths, that links in the ceramics with percolation paths of current flow refer to the SNS type percolation paths of current flow refer to the SNS type
Quantum interference in heterogeneous superconducting-photonic circuits on a silicon chip.
Schuck, C; Guo, X; Fan, L; Ma, X; Poot, M; Tang, H X
2016-01-01
Quantum information processing holds great promise for communicating and computing data efficiently. However, scaling current photonic implementation approaches to larger system size remains an outstanding challenge for realizing disruptive quantum technology. Two main ingredients of quantum information processors are quantum interference and single-photon detectors. Here we develop a hybrid superconducting-photonic circuit system to show how these elements can be combined in a scalable fashion on a silicon chip. We demonstrate the suitability of this approach for integrated quantum optics by interfering and detecting photon pairs directly on the chip with waveguide-coupled single-photon detectors. Using a directional coupler implemented with silicon nitride nanophotonic waveguides, we observe 97% interference visibility when measuring photon statistics with two monolithically integrated superconducting single-photon detectors. The photonic circuit and detector fabrication processes are compatible with standard semiconductor thin-film technology, making it possible to implement more complex and larger scale quantum photonic circuits on silicon chips. PMID:26792424
Quantum interference in heterogeneous superconducting-photonic circuits on a silicon chip
Schuck, C.; Guo, X.; Fan, L.; Ma, X.; Poot, M.; Tang, H. X.
2016-01-01
Quantum information processing holds great promise for communicating and computing data efficiently. However, scaling current photonic implementation approaches to larger system size remains an outstanding challenge for realizing disruptive quantum technology. Two main ingredients of quantum information processors are quantum interference and single-photon detectors. Here we develop a hybrid superconducting-photonic circuit system to show how these elements can be combined in a scalable fashion on a silicon chip. We demonstrate the suitability of this approach for integrated quantum optics by interfering and detecting photon pairs directly on the chip with waveguide-coupled single-photon detectors. Using a directional coupler implemented with silicon nitride nanophotonic waveguides, we observe 97% interference visibility when measuring photon statistics with two monolithically integrated superconducting single-photon detectors. The photonic circuit and detector fabrication processes are compatible with standard semiconductor thin-film technology, making it possible to implement more complex and larger scale quantum photonic circuits on silicon chips.
Multi-photon quantum interference in a multi-port integrated photonic device
Metcalf, Benjamin J; Spring, Justin B; Kundys, Dmytro; Broome, Matthew A; Humphreys, Peter; Jin, Xian-Min; Barbieri, Marco; Kolthammer, W Steven; Gates, James C; Smith, Brian J; Langford, Nathan K; Smith, Peter G R; Walmsley, Ian A
2012-01-01
Increasing the complexity of quantum photonic devices is essential for many optical information processing applications to reach a regime beyond what can be classically simulated, and integrated photonics has emerged as a leading platform for achieving this. Here, we demonstrate three-photon quantum operation of an integrated device containing three coupled interferometers, eight spatial modes and many classical and nonclassical interferences. This represents a critical advance over previous complexities and the first on-chip nonclassical interference with more than two photonic inputs. We introduce a new scheme to verify quantum behaviour, using classically characterised device elements and hierarchies of photon correlation functions. We accurately predict the device's quantum behaviour and show operation inconsistent with both classical and bi-separable quantum models. Such methods for verifying multiphoton quantum behaviour are vital for achieving increased circuit complexity. Our experiment paves the way ...
Quantum interference-enhanced deep sub-Doppler cooling of 39 K atoms beyond gray molasses
Nath, Dipankar; Rajalakshmi, G; Unnikrishnan, C S
2013-01-01
We report enhanced sub-Doppler cooling of the bosonic atoms of 39 K facilitated by formation of dark states due to the quantum interference of excitation amplitudes in the Raman configuration for the cooling and repumping lasers tuned around the D1 resonance. The temperature of about 12 {\\mu}K achieved in the two stage D2-D1 molasses is the lowest ever reported for 39 K and spans a very large parameter region where quantum interference persists robustly. We also present results on enhanced radiation heating with sub-natural linewidth (0.1{\\Gamma}) and Fano like profile, following the quantum features of 3-level coherently driven atomic system with complexities associated with optical pumping to dark states and Sisyphus effect in standing wave light fields, over and above the Raman quantum interference.
Quantum interference in the system of Lorentzian and Fano magnetoexciton resonances in GaAs
International Nuclear Information System (INIS)
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
Prediction of Quantum Anomalous Hall Insulator in half-fluorinated GaBi Honeycomb
Chen, Sung-Ping; Huang, Zhi-Quan; Crisostomo, Christian P.; Hsu, Chia-Hsiu; Chuang, Feng-Chuan; Lin, Hsin; Bansil, Arun
2016-08-01
Using first-principles electronic structure calculations, we predict half-fluorinated GaBi honeycomb under tensile strain to harbor a quantum anomalous Hall (QAH) insulator phase. We show that this QAH phase is driven by a single inversion in the band structure at the Γ point. Moreover, we have computed the electronic spectrum of a half-fluorinated GaBi nanoribbon with zigzag edges, which shows that only one edge band crosses the Fermi level within the band gap. Our results suggest that half-fluorination of the GaBi honeycomb under tensile strain could provide a new platform for developing novel spintronics devices based on the QAH effect.
Anomalous Hall effect of heavy holes in Ⅲ-Ⅴ semiconductor quantum wells
Institute of Scientific and Technical Information of China (English)
Wang Zhi-Gang; Zhang Ping
2007-01-01
The anomalous Hall effect of heavy holes in semiconductor quantum wells is studied in the intrinsic transport regime, where the Berry curvature governs the Hall current properties. Based on the first-order perturbation of wave function the expression of the Hall conductivity the same as that from the semiclassical equation of motion of the Bloch particles is derived. The dependence of Hall conductivity on the system parameters is shown. The amplitude of Hall conductivity is found to be balanced by a competition between the Zeeman splitting and the spin-orbit splitting.
Quantum interference in heterogeneous superconducting-photonic circuits on a silicon chip
Schuck, Carsten; Fan, Linran; Ma, Xiao-Song; Poot, Menno; Tang, Hong X
2015-01-01
Quantum information processing holds great promise for communicating and computing data efficiently. However, scaling current photonic implementation approaches to larger system size remains an outstanding challenge for realizing disruptive quantum technology. Two main ingredients of quantum information processors are quantum interference and single-photon detectors. Here we develop a hybrid superconducting-photonic circuit system to show how these elements can be combined in a scalable fashion on a silicon chip. We demonstrate the suitability of this approach for integrated quantum optics by interfering and detecting photon pairs directly on the chip with waveguide-coupled single-photon detectors. Using a directional coupler implemented with silicon nitride nanophotonic waveguides, we observe 97% interference visibility when measuring photon statistics with two monolithically integrated superconducting single photon detectors. The photonic circuit and detector fabrication processes are compatible with standa...
Stochastic limit method and interference in quantum many-particle systems
Aref'eva, I. Ya.; Volovich, I. V.; Kozyrev, S. V.
2015-06-01
We consider the problem of excitation energy transfer in quantum many-particle systems with a dipole interaction. The considered exciton transfer mechanism is based on quantum interference. We show that by a special choice of interaction parameters, an enhancement of the exciton transfer to a sink and suppression of the transfer to alternative sinks can be achieved. The enhancement is proportional to the number of particles in the system. We use the quantum stochastic limit method to describe the dynamics. We indicate possible applications of the proposed mechanism to quantum processes in photosynthesis.
Direct observation of large quantum interference effect in anthraquinone solid-state junctions.
Rabache, Vincent; Chaste, Julien; Petit, Philippe; Della Rocca, Maria Luisa; Martin, Pascal; Lacroix, Jean-Christophe; McCreery, Richard L; Lafarge, Philippe
2013-07-17
Quantum interference in cross-conjugated molecules embedded in solid-state devices was investigated by direct current-voltage and differential conductance transport measurements of anthraquinone (AQ)-based large area planar junctions. A thin film of AQ was grafted covalently on the junction base electrode by diazonium electroreduction, while the counter electrode was directly evaporated on top of the molecular layer. Our technique provides direct evidence of a large quantum interference effect in multiple CMOS compatible planar junctions. The quantum interference is manifested by a pronounced dip in the differential conductance close to zero voltage bias. The experimental signature is well developed at low temperature (4 K), showing a large amplitude dip with a minimum >2 orders of magnitude lower than the conductance at higher bias and is still clearly evident at room temperature. A temperature analysis of the conductance curves revealed that electron-phonon coupling is the principal decoherence mechanism causing large conductance oscillations at low temperature. PMID:23805821
Radio-Frequency Field-Induced Quantum Interference Effects in Cold Atoms
Institute of Scientific and Technical Information of China (English)
龙全; 周蜀渝; 周善钰; 王育竹
2001-01-01
We propose constructing a quantum interference configuration for cold atoms in a magneto-optical trap by applying a radio frequency field, which coherently couples adjacent Zeeman sublevels, in combination with a repumping laser field. One effect of this interference is that a dip exists in the absorption of the repumping light when the radio frequency is scanned. Our prediction has been indirectly detected through the fluorescence of cold atoms in a preliminary experiment.
Hanbury-Brown and Twiss effect without quantum interference in photon counting regime
Bai, Bin; Chen, Hui; Zheng, Huai bin; Liu, Jian bin; Liu, Rui feng; Wang, Yun long; Xu, Zhuo; Li, Fuli
2016-01-01
Usually HBT effect can be interpreted by classical (intensity fluctuation correlation) and quantum (interference of two-photon probability amplitudes) theories properly at the same time. In this manuscript, we report a deliberately designed experiment in which two chaotic light beams has the same intensity fluctuation but mutual-orthogonal polarizations to each other so there will be no interference of two-photon probability amplitudes. Classical and quantum theory give different predictions on if there should be HBT (photon bunching) effect or not in the experiment. The experiment results are used to test the two different predictions. At the end, both the temporal and spatial HBT effects are observed.
Quantum interference between nuclear excitation by electron capture and radiative recombination
P'alffy, A; Scheid, W; P\\'alffy, Adriana; Harman, Zolt\\'an; Scheid, Werner
2007-01-01
We investigate the quantum interference between the resonant process of nuclear excitation by electron capture (NEEC) followed by the radiative decay of the excited nucleus, and radiative recombination (RR). In order to derive the interference cross section, a Feshbach projection operator formalism is used. The electromagnetic field is considered by means of multipole fields. The nucleus is described by a phenomenological collective model and by making use of experimental data. The Fano profile parameters as well as the interference cross section for electric and magnetic multipole transitions in various heavy ions are presented. We discuss the experimental possibility of discerning NEEC from the RR background.
A parabolic model to control quantum interference in T-shaped molecular junctions.
Nozaki, Daijiro; Sevinçli, Hâldun; Avdoshenko, Stanislav M; Gutierrez, Rafael; Cuniberti, Gianaurelio
2013-09-01
Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical interest to develop simple methods controlling the emergence and the positions of QI effects like anti-resonances or Fano line shapes in conductance spectra. In this work, starting from a well-known generic molecular junction with a side group (T-shaped molecule), we propose a simple graphical method to visualize the conditions for the appearance of quantum interference, Fano resonances or anti-resonances, in the conductance spectrum. By introducing a simple graphical representation (parabolic diagram), we can easily visualize the relation between the electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. This parabolic model not only can predict the emergence and energetic position of quantum interference from a few electronic parameters but also can enable one to know the coupling between the side group and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions. PMID:23558406
Transport through a Strongly Correlated Quantum-Dot with Fano Interference
Wu, B. H.; J. C. Cao; Ahn, Kang-Hun
2005-01-01
We present the transport properties of a strongly correlated quantum dot attached to two leads with a side coupled non-interacting quantum dot. Transport properties are analyzed using the slave boson mean field theory which is reliable in the zero temperature and low bias regime. It is found that the transport properties are determined by the interplay of two fundamental physical phenomena,i.e. the Kondo effects and the Fano interference. The linear conductance will depart from the unitary li...
Anisotropic expansion of the Universe and generation of quantum interference in light propagation
Fanizza, G.; Tedesco, L.
2015-01-01
We investigate the electrodynamic in a Bianchi type I cosmological model. This scenario reveals the possibility that photons, during their traveling, can make quantum interference. This effect is only due to the presence of two different axes of expansion in the cosmic evolution. In other word, it is possible to conclude that a purely metrical - or, equivalently, gravitational - phenomenon gives rise up to a quantum effect that manifests itself in the light propagation.
AlO x /LiF composite protection layer for Cr-doped (Bi,Sb)2Te3 quantum anomalous Hall films
Ou, Yunbo; Feng, Yang; Feng, Xiao; Hao, Zhenqi; Zhang, Liguo; Liu, Chang; Wang, Yayu; He, Ke; Ma, Xucun; Xue, Qikun
2016-08-01
We have realized robust quantum anomalous Hall samples by protecting Cr-doped (Bi,Sb)2Te3 topological insulator films with a combination of LiF and AlO x capping layers. The AlO x /LiF composite capping layer well keeps the quantum anomalous Hall states of Cr-doped (Bi,Sb)2Te3 films and effectively prevent them from degradation induced by ambient conditions. The progress is a key step towards the realization of the quantum phenomena in heterostructures and devices based on quantum anomalous Hall system. Project supported by the National Natural Science Foundation of China (Grant No. 11325421).
Non-linear conductivity and quantum interference in disordered metals
Leadbeater, M.; Raimondi, R.; Schwab, P.; Castellani, C.
1999-01-01
We report on a novel non-linear electric field effect in the conductivity of disordered conductors. We find that an electric field gives rise to dephasing in the particle-hole channel, which depresses the interference effects due to disorder and interaction and leads to a non-linear conductivity. This non-linear effect introduces a field dependent temperature scale $T_E$ and provides a microscopic mechanism for electric field scaling at the metal-insulator transition. We also study the magnet...
Exploiting quantum interference in dye sensitized solar cells
DEFF Research Database (Denmark)
Maggio, Emanuele; Solomon, Gemma C.; Troisi, Alessandro
2014-01-01
subunits. A theory for nonadiabatic electron transfer is employed in order to take explicitly into account the contribution from the bridge states mediating the process. If a cross-conjugated fragment is present in the bridge, it is possible to suppress the charge recombination by negative interference of......A strategy to hinder the charge recombination process in dye sensitized solar cells is developed in analogy with similar approaches to modulate charge transport across nanostructures. The system studied is a TiO2 (anatase)-chromophore interface, with an unsaturated carbon bridge connecting the two...
Deterministic event-based simulation of quantum interference
De Raedt, K.; De Raedt, H.; Michielsen, K.
2004-01-01
We propose and analyse simple deterministic algorithms that can be used to construct machines that have primitive learning capabilities. We demonstrate that locally connected networks of these machines can be used to perform blind classification on an event-by-event basis, without storing the information of the individual events. We also demonstrate that properly designed networks of these machines exhibit behavior that is usually only attributed to quantum systems. We present networks that s...
The Relation between Structure and Quantum Interference in Single Molecule Junctions
DEFF Research Database (Denmark)
Markussen, Troels; Stadler, Robert; Thygesen, Kristian Sommer
2010-01-01
Quantum interference (QI) of electron pathways has recently attracted increased interest as an enabling tool for single-molecule electronic devices. Although various molecular systems have been shown to exhibit QI effects and a number of methods have been proposed for its analysis, simple guideli...... wires....
International Nuclear Information System (INIS)
We examine the absorption of a weak probe beam for a V-type atom with a closely spaced doublet and demonstrate that quantum interference between the two excitation pathways can result in very narrow resonances, transparency, and even gain without population inversion. The origin of these effects is discussed. copyright 1997 The American Physical Society
Quantum interference with photon pairs using two micro-structured fibres
International Nuclear Information System (INIS)
We demonstrate a quantum interference experiment between two photons coming from non-degenerate pairs created by four-wave mixing in two separated micro-structured fibres. When the two heralded photons are made indistinguishable a 95% visibility is demonstrated
Terahertz spectroscopy on Faraday and Kerr rotations in a quantum anomalous Hall state.
Okada, Ken N; Takahashi, Youtarou; Mogi, Masataka; Yoshimi, Ryutaro; Tsukazaki, Atsushi; Takahashi, Kei S; Ogawa, Naoki; Kawasaki, Masashi; Tokura, Yoshinori
2016-01-01
Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of the Lagrangian formalism. The quantized magnetoelectric coupling, which is generally referred to as topological magnetoelectric effect, has been predicted to induce exotic phenomena including the universal low-energy magneto-optical effects. Here we report the experimental indication of the topological magnetoelectric effect, which is exemplified by magneto-optical Faraday and Kerr rotations in the quantum anomalous Hall states of magnetic topological insulator surfaces by terahertz magneto-optics. The universal relation composed of the observed Faraday and Kerr rotation angles but not of any material parameters (for example, dielectric constant and magnetic susceptibility) well exhibits the trajectory towards the fine structure constant in the quantized limit. PMID:27436710
A new method to calculate Berry phase in one-dimensional quantum anomalous Hall insulator
Liao, Yi
2016-08-01
Based on the residue theorem and degenerate perturbation theory, we derive a new, simple and general formula for Berry phase calculation in a two-level system for which the Hamiltonian is a real symmetric matrix. The special torus topology possessed by the first Brillouin zone (1 BZ) of this kind of systems ensures the existence of a nonzero Berry phase. We verify the correctness of our formula on the Su-Schrieffer-Heeger (SSH) model. Then the Berry phase of one-dimensional quantum anomalous Hall insulator (1DQAHI) is calculated analytically by applying our method, the result being -π/2 -π/4 sgn (B) [ sgn (Δ - 4 B) + sgn (Δ) ]. Finally, illuminated by this idea, we investigate the Chern number in the two-dimensional case, and find a very simple way to determine the parameter range of the non-trivial Chern number in the phase diagram.
Quantum anomalous Hall effect in atomic crystal layers from in-plane magnetization
Ren, Yafei; Zeng, Junjie; Deng, Xinzhou; Yang, Fei; Pan, Hui; Qiao, Zhenhua
2016-08-01
We theoretically demonstrate that with in-plane magnetization, the quantum anomalous Hall effect (QAHE) can be realized in two-dimensional atomic crystal layers with preserved inversion symmetry but broken out-of-plane mirror reflection symmetry. By taking the honeycomb lattice system as an example, we find that the low-buckled structure satisfying the symmetry criteria is crucial to induce QAHE. The topologically nontrivial bulk gap carrying a Chern number of C =±1 opens in the vicinity of the saddle points M , where the band dispersion exhibits strong anisotropy. We further show that the QAHE with electrically tunable Chern number can be achieved in Bernal-stacked multilayer systems, and the applied interlayer potential differences can dramatically decrease the critical magnetization to make the QAHE experimentally feasible.
Zhang, Gu-Feng; Li, Yi; Wu, Congjun
2015-03-01
We construct a minimal four-band model for the two-dimensional topological insulators and quantum anomalous Hall insulators based on the px- and py-orbital bands in the honeycomb lattice. The multiorbital structure allows the atomic spin-orbit coupling which lifts the degeneracy between two sets of on-site Kramers doublets jz = +/-3/2 and jz = +/-1/2 . Because of the orbital angular momentum structure of Bloch-wave states at Γ and K (K') points, topological gaps are equal to the atomic spin-orbit coupling strengths, which are much larger than those based on the mechanism of the s - p band inversion.The energy spectra and eigen wave functions are solved analytically based on Clifford algebra. The competition among spin-orbit coupling λ, sublattice asymmetry m, and the Néel exchange field n results in band crossings at Γ and K (K') points, which leads to various topological band structure transitions. The quantum anomalous Hall state is reached under the condition that three gap parameters λ, m, and n satisfy the triangle inequality. Flat bands also naturally arise which allow a local construction of eigenstates. The above mechanism is related to several classes of solid state semiconductor. G.F.Z. and C.W. are supported by the NSF DMR-1410375 and AFOSR FA9550-11-1-0067(YIP). Y.L. thanks the Inamori Fellowship and the support at the Princeton Center for Theoretical Science. C.W. acknowledges financial support from the National Natural Science.
Higher-order interference and single-system postulates characterizing quantum theory
International Nuclear Information System (INIS)
We present a new characterization of quantum theory in terms of simple physical principles that is different from previous ones in two important respects: first, it only refers to properties of single systems without any assumptions on the composition of many systems; and second, it is closer to experiment by having absence of higher-order interference as a postulate, which is currently the subject of experimental investigation. We give three postulates—no higher-order interference, classical decomposability of states, and strong symmetry—and prove that the only non-classical operational probabilistic theories satisfying them are real, complex, and quaternionic quantum theory, together with three-level octonionic quantum theory and ball state spaces of arbitrary dimension. Then we show that adding observability of energy as a fourth postulate yields complex quantum theory as the unique solution, relating the emergence of the complex numbers to the possibility of Hamiltonian dynamics. We also show that there may be interesting non-quantum theories satisfying only the first two of our postulates, which would allow for higher-order interference in experiments while still respecting the contextuality analogue of the local orthogonality principle. (paper)
Anomalous Integer Quantum Hall Effect in the Ballistic Regime with Quantum Point Contacts
Wees, B.J. van; Willems, E.M.M.; Harmans, C.J.P.M.; Beenakker, C.W.J.; Houten, H. van; Williamson, J.G.; Foxon, C.T.; Harris, J.J.
1989-01-01
The Hall conductance of a wide two-dimensional electron gas has been measured in a geometry in which two quantum point contacts form controllable current and voltage probes, separated by less than the transport mean free path. Adjustable barriers in the point contacts allow selective population and
Quantum interference between H + D2 quasiclassical reaction mechanisms
Jambrina, Pablo G.; Herráez-Aguilar, Diego; Aoiz, F. Javier; Sneha, Mahima; Jankunas, Justinas; Zare, Richard N.
2015-08-01
Interferences are genuine quantum phenomena that appear whenever two seemingly distinct classical trajectories lead to the same outcome. They are common in elastic scattering but are seldom observable in chemical reactions. Here we report experimental measurements of the state-to-state angular distribution for the H + D2 reaction using the ‘photoloc’ technique. For products in low rotational and vibrational states, a characteristic oscillation pattern governs backward scattering. The comparison between the experiments, rigorous quantum calculations and classical trajectories on an accurate potential energy surface allows us to trace the origin of that structure to the quantum interference between different quasiclassical mechanisms, a phenomenon analogous to that observed in the double-slit experiment.
Entanglement via tunable Fano-type interference in asymmetric semiconductor quantum wells
International Nuclear Information System (INIS)
Entanglement is realized in asymmetric coupled double quantum wells (DQWs) trapped in a doubly resonant cavity by means of Fano-type interference through a tunneling barrier, which is different from the previous studies on entanglement induced by strong external driven fields in atomic media. We investigate the generation and evolution of entanglement and show that the strength of Fano interference can influence effectively the degree of the entanglement between two cavity modes and the enhanced entanglement can be generated in this DQW system. The present investigation may provide research opportunities in quantum entangled experiments in the DQW solid-state nanostructures and may result in a substantial impact on the technology for entanglement engineering in quantum information processing.
Influence of the quantum interference on the bosonic and fermionic ion-ion collisions
Hong, Woo-Pyo; Jung, Young-Dae
2014-03-01
The quantum interference effects on the bosonic-bosonic (He-4)-(He-4), fermionic-fermionic (He-3)-(He-3), and bosonic-fermionic (He-4)-(He-3) ion-ion collisions are investigated by using the isotope of the He nucleus in dense semiclassical Coulomb systems with the Faxen-Holtzmark method. It is found that the scattering cross section for the fermionic-fermionic ion-ion collision is greater than the bosonic-bosonic and bosonic-fermionic ion collision cross sections. It is also found that the collisional induced quantum interference effect enhances the ion-ion collision cross section in semiclassical Coulomb systems. The variation of the quantum-mechanical effect on the bosonic and fermionic ion-ion collisions is also discussed. This paper is dedicated to the late Prof. P. K. Shukla in memory of exciting and stimulating collaborations on physical processes in semiclassical Coulomb systems.
Entanglement via tunable Fano-type interference in asymmetric semiconductor quantum wells
Energy Technology Data Exchange (ETDEWEB)
Hao Xiangying, E-mail: xyhao.321@163.co [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Li Jiahua, E-mail: ai_li@126.co [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Lv Xinyou; Si Liugang; Yang Xiaoxue [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)
2009-10-12
Entanglement is realized in asymmetric coupled double quantum wells (DQWs) trapped in a doubly resonant cavity by means of Fano-type interference through a tunneling barrier, which is different from the previous studies on entanglement induced by strong external driven fields in atomic media. We investigate the generation and evolution of entanglement and show that the strength of Fano interference can influence effectively the degree of the entanglement between two cavity modes and the enhanced entanglement can be generated in this DQW system. The present investigation may provide research opportunities in quantum entangled experiments in the DQW solid-state nanostructures and may result in a substantial impact on the technology for entanglement engineering in quantum information processing.
Entanglement via tunable Fano-type interference in asymmetric semiconductor quantum wells
Hao, Xiangying; Li, Jiahua; Lv, Xin-You; Si, Liu-Gang; Yang, Xiaoxue
2009-10-01
Entanglement is realized in asymmetric coupled double quantum wells (DQWs) trapped in a doubly resonant cavity by means of Fano-type interference through a tunneling barrier, which is different from the previous studies on entanglement induced by strong external driven fields in atomic media. We investigate the generation and evolution of entanglement and show that the strength of Fano interference can influence effectively the degree of the entanglement between two cavity modes and the enhanced entanglement can be generated in this DQW system. The present investigation may provide research opportunities in quantum entangled experiments in the DQW solid-state nanostructures and may result in a substantial impact on the technology for entanglement engineering in quantum information processing.
Multiple-path Quantum Interference Effects in a Double-Aharonov-Bohm Interferometer
Directory of Open Access Journals (Sweden)
Yang XF
2010-01-01
Full Text Available Abstract We investigate quantum interference effects in a double-Aharonov-Bohm (AB interferometer consisting of five quantum dots sandwiched between two metallic electrodes in the case of symmetric dot-electrode couplings by the use of the Green’s function equation of motion method. The analytical expression for the linear conductance at zero temperature is derived to interpret numerical results. A three-peak structure in the linear conductance spectrum may evolve into a double-peak structure, and two Fano dips (zero conductance points may appear in the quantum system when the energy levels of quantum dots in arms are not aligned with one another. The AB oscillation for the magnetic flux threading the double-AB interferometer is also investigated in this paper. Our results show the period of AB oscillation can be converted from 2π to π by controlling the difference of the magnetic fluxes threading the two quantum rings.
Ji, Wei-xiao; Zhang, Chang-wen; Ding, Meng; Zhang, Bao-min; Li, Ping; Li, Feng; Ren, Miao-juan; Wang, Pei-ji; Zhang, Run-wu; Hu, Shu-jun; Yan, Shi-shen
2016-08-01
Bismuth (Bi) has attracted a great deal of attention for its strongest spin–orbit coupling (SOC) strength among main group elements. Although quantum anomalous Hall (QAH) state is predicted in half-hydrogenated Bi honeycomb monolayers Bi2H, the experimental results are still missing. Halogen atoms (X = F, Cl and Br) were also frequently used as modifications, but Bi2X films show a frustrating metallic character that masks the QAH effects. Here, first-principle calculations are performed to predict the full-cyanided bismuthene (Bi2(CN)2) as 2D topological insulator supporting quantum spin Hall state with a record large gap up to 1.10 eV, and more importantly, half-cyanogen saturated bismuthene (Bi2(CN)) as a Chern insulator supporting a valley-polarized QAH state, with a Curie temperature to be 164 K, as well as a large gap reaching 0.348 eV which could be further tuned by bi-axial strain and SOC strength. Our findings provide an appropriate and flexible material family candidate for spintronic and valleytronic devices.
Quantum backaction and noise interference in asymmetric two-cavity optomechanical systems
Yanay, Yariv; Sankey, Jack C.; Clerk, Aashish A.
2016-06-01
We study the effect of cavity damping asymmetries on backaction in a "membrane-in-the-middle" optomechanical system, where a mechanical mode modulates the coupling between two photonic modes. We show that when the energy difference between the optical modes dominates (i.e., in the adiabatic limit) this system generically realizes a dissipative optomechanical coupling, with an effective position-dependent photonic damping rate. The resulting quantum noise interference can be used to ground-state cool a mechanical resonator in the unresolved sideband regime. We explicitly demonstrate how quantum noise interference controls linear backaction effects and show that this interference persists even outside the adiabatic limit. For a one-port cavity in the extreme bad cavity limit, the interference allows one to cancel all linear backaction effects. This allows continuous measurements of position-squared, with no stringent constraints on the single-photon optomechanical coupling strength. In contrast, such a complete cancellation is not possible in the good cavity limit. This places strict bounds on the optomechanical coupling required for quantum nondemolition measurements of mechanical energy, even in a one-port device.
Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators
Chang, Cui-Zu; Li, Mingda
2016-03-01
The quantum anomalous Hall effect (QAHE), the last member of Hall family, was predicted to exhibit quantized Hall conductivity {σyx}=\\frac{{{e}2}}{h} without any external magnetic field. The QAHE shares a similar physical phenomenon with the integer quantum Hall effect (QHE), whereas its physical origin relies on the intrinsic topological inverted band structure and ferromagnetism. Since the QAHE does not require external energy input in the form of magnetic field, it is believed that this effect has unique potential for applications in future electronic devices with low-power consumption. More recently, the QAHE has been experimentally observed in thin films of the time-reversal symmetry breaking ferromagnetic (FM) topological insulators (TI), Cr- and V- doped (Bi,Sb)2Te3. In this topical review, we review the history of TI based QAHE, the route to the experimental observation of the QAHE in the above two systems, the current status of the research of the QAHE, and finally the prospects for future studies.
Anomalous behavior of the energy gap in the one-dimensional quantum XY model.
Okuyama, Manaka; Yamanaka, Yuuki; Nishimori, Hidetoshi; Rams, Marek M
2015-11-01
We reexamine the well-studied one-dimensional spin-1/2 XY model to reveal its nontrivial energy spectrum, in particular the energy gap between the ground state and the first excited state. In the case of the isotropic XY model, the XX model, the gap behaves very irregularly as a function of the system size at a second order transition point. This is in stark contrast to the usual power-law decay of the gap and is reminiscent of the similar behavior at the first order phase transition in the infinite-range quantum XY model. The gap also shows nontrivial oscillatory behavior for the phase transitions in the anisotropic model in the incommensurate phase. We observe a close relation between this anomalous behavior of the gap and the correlation functions. These results, those for the isotropic case in particular, are important from the viewpoint of quantum annealing where the efficiency of computation is strongly affected by the size dependence of the energy gap. PMID:26651656
Energy Technology Data Exchange (ETDEWEB)
Mogi, M., E-mail: mogi@cmr.t.u-tokyo.ac.jp; Yoshimi, R.; Yasuda, K.; Kozuka, Y. [Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); Tsukazaki, A. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); PRESTO, Japan Science and Technology Agency (JST), Chiyoda-ku, Tokyo 102-0075 (Japan); Takahashi, K. S. [RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan); Kawasaki, M.; Tokura, Y. [Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656 (Japan); RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198 (Japan)
2015-11-02
Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs) such as Cr- and V-doped (Bi,Sb){sub 2}Te{sub 3}. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr modulation doping into topological insulator (Bi,Sb){sub 2}Te{sub 3} films to increase the observable temperature of QAHE. By introducing the rich-Cr-doped thin (1 nm) layers at the vicinity of both the surfaces based on non-Cr-doped (Bi,Sb){sub 2}Te{sub 3} films, we have succeeded in observing the QAHE up to 2 K. The improvement in the observable temperature achieved by this modulation-doping appears to be originating from the suppression of the disorder in the surface state interacting with the rich magnetic moments. Such a superlattice designing of the stabilized QAHE may pave a way to dissipation-less electronics based on the higher-temperature and zero magnetic-field quantum conduction.
International Nuclear Information System (INIS)
Quantum anomalous Hall effect (QAHE), which generates dissipation-less edge current without external magnetic field, is observed in magnetic-ion doped topological insulators (TIs) such as Cr- and V-doped (Bi,Sb)2Te3. The QAHE emerges when the Fermi level is inside the magnetically induced gap around the original Dirac point of the TI surface state. Although the size of gap is reported to be about 50 meV, the observable temperature of QAHE has been limited below 300 mK. We attempt magnetic-Cr modulation doping into topological insulator (Bi,Sb)2Te3 films to increase the observable temperature of QAHE. By introducing the rich-Cr-doped thin (1 nm) layers at the vicinity of both the surfaces based on non-Cr-doped (Bi,Sb)2Te3 films, we have succeeded in observing the QAHE up to 2 K. The improvement in the observable temperature achieved by this modulation-doping appears to be originating from the suppression of the disorder in the surface state interacting with the rich magnetic moments. Such a superlattice designing of the stabilized QAHE may pave a way to dissipation-less electronics based on the higher-temperature and zero magnetic-field quantum conduction
Lee, H C
1998-01-01
First, we have investigated chiral edges of a quantum Hall liquids at filling factor nu=2. The separation of spin and charge degrees of freedom becomes manifest in the presence of long- range Coulomb interaction. Due to the spin-charge separation the tunneling density of states takes the form D(omega) approx ( -lnl omega l) sup 1 sup / sup 2. Experimentally, the spin-charge separation can be revealed in the temperature and voltage dependence of the tunneling current into Fermi liquid reservoir. Second, the charge and spin correlation functions of partially spin-polarized edge electrons of a quantum Hall bar are studied using effective Hamiltonian and bosonization techniques. In the presence of the Coulomb interaction between the edges with opposite chirality we find a different crossover behavior in spin and charge correlation functions. The crossover of the spin correlation function in the Coulomb dominated regime is characterized by an anomalous exponent, which originates from the finite value of the effect...
International Nuclear Information System (INIS)
We study the energetics and dispersion of anomalous dimers that are induced by the Pauli blocking effect in a quantum Fermi gas of majority atoms near interspecies resonances. Unlike in vacuum, we find that both the sign and magnitude of the dimer masses are tunable via Feshbach resonances. We also investigate the effects of particle-hole fluctuations on the dispersion of dimers and demonstrate that the particle-hole fluctuations near a Fermi surface (with Fermi momentum (ℎ/2π)kF) generally reduce the effective two-body interactions and the binding energy of dimers. Furthermore, in the limit of light minority atoms the particle-hole fluctuations disfavor the formation of dimers with a total momentum (ℎ/2π)kF, because near (ℎ/2π)kF the modes where the dominating particle-hole fluctuations appear are the softest. Our calculation suggests that near broad interspecies resonances when the minority-majority mass ratio mB/mF is smaller than a critical value (estimated to be 0.136), dimers in a finite-momentum channel are energetically favored over dimers in the zero-momentum channel. We apply our theory to quantum gases of 6Li40K, 6Li87Rb, 40K87Rb, and 6Li23Na near broad interspecies resonances, and discuss the limitations of our calculations and implications.
Quantum anomalous Hall effect in time-reversal-symmetry breaking topological insulators.
Chang, Cui-Zu; Li, Mingda
2016-03-31
The quantum anomalous Hall effect (QAHE), the last member of Hall family, was predicted to exhibit quantized Hall conductivity σ(yx) = e2/h without any external magnetic field. The QAHE shares a similar physical phenomenon with the integer quantum Hall effect (QHE), whereas its physical origin relies on the intrinsic topological inverted band structure and ferromagnetism. Since the QAHE does not require external energy input in the form of magnetic field, it is believed that this effect has unique potential for applications in future electronic devices with low-power consumption. More recently, the QAHE has been experimentally observed in thin films of the time-reversal symmetry breaking ferromagnetic (FM) topological insulators (TI), Cr- and V- doped (Bi,Sb)2Te3. In this topical review, we review the history of TI based QAHE, the route to the experimental observation of the QAHE in the above two systems, the current status of the research of the QAHE, and finally the prospects for future studies. PMID:26934535
Conte, Elio; Todarello, Orlando; Federici, Antonio; Zbilut, Joseph P
2008-01-01
We introduce the quantum theoretical formulation to determine a posteriori, if existing, the quantum wave functions and to estimate the quantum interference effects of mental states. Such quantum features are actually found in the case of an experiment involving the perception and the cognition in humans. Also some specific psychological variables are introduced and it is obtained that they characterize in a stringent manner the quantum behaviour of mind during such performed experiment.
International Nuclear Information System (INIS)
The optical bistability of a triangular quantum dot molecules embedded inside a unidirectional ring cavity is studied. The type, the threshold and the hysteresis loop of the optical bistability curves can be modified by the tunneling parameters, as well as the probe laser field. The linear and nonlinear susceptibilities of the medium are also studied to interpret the corresponding results. The physical interpretation is that the tunneling can induce the quantum interference, which modifies the linear and the nonlinear response of the medium. As a consequence, the characteristics of the optical bistability are changed. The scheme proposed here can be utilized for optimizing and controlling the optical switching process
Moodera, Jagadeesh
Breaking time reversal symmetry (TRS) in a topological insulator (TI) with ferromagnetic perturbation can lead to many exotic quantum phenomena exhibited by Dirac surface states including the quantum anomalous Hall (QAH) effect and dissipationless quantized Hall transport. The realization of the QAH effect in realistic materials requires ferromagnetic insulating materials and topologically non-trivial electronic band structures. In a TI, the ferromagnetic order and TRS breaking is achievable by conventional way, through doping with a magnetic element, or by ferromagnetic proximity coupling. Our experimental studies by both approaches will be discussed. In doped TI van Vleck ferromagnetism was observed. The proximity induced magnetism at the interface was stable, beyond the expected temperature range. We shall describe in a hard ferromagnetic TI system a robust QAH state and dissipationless edge current flow is achieved,1,2 a major step towards dissipationless electronic applications with no external fields, making such devices more amenable for metrology and spintronics applications. Our study of the gate and temperature dependences of local and nonlocal magnetoresistance, may elucidate the causes of the dissipative edge channels and the need for very low temperature to observe QAH. In close collaboration with: CuiZu Chang,2,3 Ferhat Katmis, 1 . 2 , 3 Peng Wei. 1 , 2 , 3 ; From Nuclear Eng. Dept. MIT, M. Li, J. Li; From Penn State U, W-W. Zhao, D. Y. Kim, C-x. Liu, J. K. Jain, M. H. W. Chan; From Oakridge National Lab, V. Lauter; From Northeastern U., B. A. Assaf, M. E. Jamer, D. Heiman; From Argonne Lab, J. W. Freeland; From Ruhr-Universitaet Bochum (Germany), F. S. Nogueira, I. Eremin; From Saha Institute of Nuclear Physics (India), B. Satpati. Work supported by NSF Grant DMR-1207469, the ONR Grant N00014-13-1-0301, and the STC Center for Integrated Quantum Materials under NSF Grant DMR-1231319.
Engineering two-photon high-dimensional states through quantum interference.
Zhang, Yingwen; Roux, Filippus S; Konrad, Thomas; Agnew, Megan; Leach, Jonathan; Forbes, Andrew
2016-02-01
Many protocols in quantum science, for example, linear optical quantum computing, require access to large-scale entangled quantum states. Such systems can be realized through many-particle qubits, but this approach often suffers from scalability problems. An alternative strategy is to consider a lesser number of particles that exist in high-dimensional states. The spatial modes of light are one such candidate that provides access to high-dimensional quantum states, and thus they increase the storage and processing potential of quantum information systems. We demonstrate the controlled engineering of two-photon high-dimensional states entangled in their orbital angular momentum through Hong-Ou-Mandel interference. We prepare a large range of high-dimensional entangled states and implement precise quantum state filtering. We characterize the full quantum state before and after the filter, and are thus able to determine that only the antisymmetric component of the initial state remains. This work paves the way for high-dimensional processing and communication of multiphoton quantum states, for example, in teleportation beyond qubits. PMID:26933685
Engineering two-photon high-dimensional states through quantum interference
Zhang, Yingwen; Roux, Filippus S.; Konrad, Thomas; Agnew, Megan; Leach, Jonathan; Forbes, Andrew
2016-01-01
Many protocols in quantum science, for example, linear optical quantum computing, require access to large-scale entangled quantum states. Such systems can be realized through many-particle qubits, but this approach often suffers from scalability problems. An alternative strategy is to consider a lesser number of particles that exist in high-dimensional states. The spatial modes of light are one such candidate that provides access to high-dimensional quantum states, and thus they increase the storage and processing potential of quantum information systems. We demonstrate the controlled engineering of two-photon high-dimensional states entangled in their orbital angular momentum through Hong-Ou-Mandel interference. We prepare a large range of high-dimensional entangled states and implement precise quantum state filtering. We characterize the full quantum state before and after the filter, and are thus able to determine that only the antisymmetric component of the initial state remains. This work paves the way for high-dimensional processing and communication of multiphoton quantum states, for example, in teleportation beyond qubits. PMID:26933685
Quantum Interference of Stored Coherent Spin-wave Excitations in a Two-channel Memory
Wang, Hai; Xu, Zhongxiao; Zhao, Xingbo; Zhang, Lijun; Li, Jiahua; Wu, Yuelong; Xie, Changde; Peng, Kunchi; Xiao, Min
2010-01-01
Quantum memories are essential elements in long-distance quantum networks and quantum computation. Significant advances have been achieved in demonstrating relative long-lived single-channel memory at single-photon level in cold atomic media. However, the qubit memory corresponding to store two-channel spin-wave excitations (SWEs) still faces challenges, including the limitations resulting from Larmor procession, fluctuating ambient magnetic field, and manipulation/measurement of the relative phase between the two channels. Here, we demonstrate a two-channel memory scheme in an ideal tripod atomic system, in which the total readout signal exhibits either constructive or destructive interference when the two-channel SWEs are retrieved by two reading beams with a controllable relative phase. Experimental result indicates quantum coherence between the stored SWEs. Based on such phase-sensitive storage/retrieval scheme, measurements of the relative phase between the two SWEs and Rabi oscillation, as well as elimi...
Generation of Mechanical Interference Fringes by Multi-Photon Quantum Measurement
Ringbauer, M; White, A G; Vanner, M R
2016-01-01
The exploration of wave phenomena and quantum properties of massive systems offers an intriguing pathway to study the foundations of physics and to develop a suite of quantum enhanced technologies. Here we propose and experimentally demonstrate an optomechanical scheme for the preparation of non-Gaussian states of motion of a mechanical resonator using photonic quantum measurements. Our scheme is capable of generating non-classical mechanical states without the need for strong single-photon coupling and independent of initial thermal occupation. We experimentally observe interference fringes in the mechanical position distribution, which for a two-photon measurement show phase super-resolution. Our approach can be readily generalized to generate larger mechanical superposition states using multi-port interferometry. This opens a feasible avenue to explore and exploit quantum phenomena at a macroscopic scale.
International Nuclear Information System (INIS)
The fermion in the gauge invariant formulation of the chiral Schwinger model and its relation to the fermion in the anomalous formulation is studied. A gauge invariant fermion operator is constructed that does not give rise to an asymptotic fermion field. It fits in the scheme prepared by generalized Schwinger models. Singularities in the short-distance limit of the chiral Schwinger model in the anomalous formulation lead to the conclusion that it is not a promising starting point for investigations towards realistic (3+1)-dimensional gauge theories with chiral fermion content. A new anomalous (1+1)-dimensional model is studied, the chiral quantum gravity. It is proven to be consistent if only a limited number of chiral fermions couple. The fermion propagator behaves analogously to the one in the massless Thirring model. A general rule is derived for the change of the fermion operator, which is induced by the breakdown of a gauge symmetry. (orig.)
International Nuclear Information System (INIS)
We propose a simple scheme to realize 1→M economical phase-covariant quantum cloning machine (EPQCM) with superconducting quantum interference device (SQUID) qubits. In our scheme, multi-SQUIDs are fixed into a microwave cavity by adiabatic passage for their manipulation. Based on this model, we can realize the EPQCM with high fidelity via adiabatic quantum computation
International Nuclear Information System (INIS)
Superconducting quantum interference devices (SQUIDs) incorporating thin film nanobridges as weak links have sensitivities approaching that required for single spin detection at 4.2 K. However, due to thermal hysteresis they are difficult to operate at much lower temperatures which hinder their application to many quantum measurements. To overcome this, we have developed nanoscale SQUIDs made from titanium-gold proximity bilayers. We show that their electrical properties are consistent with a theoretical model developed for heat flow in bilayers and demonstrate that they enable magnetic measurements to be made on a sample at system temperatures down to 60 mK
Review of low-noise radio-frequency amplifiers based on superconducting quantum interference device
International Nuclear Information System (INIS)
Superconducting quantum interference device (SQUID) is a sensitive detector of magnetic flux signals. Up to now, the main application of SQUIDs has been measurements of magnetic flux signals in the frequency range from near DC to several MHz. Recently, cryogenic low-noise radio-frequency (RF) amplifiers based on DC SQUID are under development aiming to detect RF signals with sensitivity approaching quantum limit. In this paper, we review the recent progress of cryogenic low-noise RF amplifiers based on SQUID technology.
Beyond Quantum interference and Optical pumping: invoking a Closed-loop phase
Kani, A
2016-01-01
Atomic coherence effects arising from coherent light-atom interaction are conventionally known to be governed by quantum interference and optical pumping mechanisms. However, anisotropic nonlinear response driven by optical field involves another fundamental effect arising from closed-loop multiphoton transitions. This closed-loop phase dictates the tensorial structure of the nonlinear susceptibility as it governs the principal coordinate system in determining, whether the light field will either compete or cooperate with the external magnetic field stimulus. Such a treatment provides deeper understanding of all magneto-optical anisotropic response. The magneto-optical response in all atomic systems is classified using closed-loop phase. The role of quantum interference in obtaining electromagnetically induced transparency or electromagnetically induced absorption in multi-level systems is identified.
Probing electron-phonon excitations in molecular junctions by quantum interference.
Bessis, C; Della Rocca, M L; Barraud, C; Martin, P; Lacroix, J C; Markussen, T; Lafarge, P
2016-01-01
Electron-phonon coupling is a fundamental inelastic interaction in condensed matter and in molecules. Here we probe phonon excitations using quantum interference in electron transport occurring in short chains of anthraquinone based molecular junctions. By studying the dependence of molecular junction's conductance as a function of bias voltage and temperature, we show that inelastic scattering of electrons by phonons can be detected as features in conductance resulting from quenching of quantum interference. Our results are in agreement with density functional theory calculations and are well described by a generic two-site model in the framework of non-equilibrium Green's functions formalism. The importance of the observed inelastic contribution to the current opens up new ways for exploring coherent electron transport through molecular devices. PMID:26864735
Vacuum-Induced Quantum Interference in a Trapped ∧-Configuration Three-Level System
Institute of Scientific and Technical Information of China (English)
WANG Zheng-Ling; YIN Jian-Ping
2005-01-01
@@ In consideration of quantization of centre-of-mass motion, we derive the second-order solution of the dynamic equation of a ∧-configuration three-level atom confined in an approximately harmonic trap by using the timedependent perturbation theory. It is found that there are a series of dark lines in the second-order probability spectrum with multi-peak structures, which is the result of the quantum interference from the same vacuum mode in the spontaneous decay process of the trapped atom from the upper level to the two nearby lower levels. Our study shows that the second-order spectrum may be modified by the oscillation frequency Ω of the trap and the frequency difference △ between two lower levels of the three-level atom, and the depth of the dark lines from the vacuum-induced quantum interference effect is strongly dependent on the above two parameters (Ω and △).
Institute of Scientific and Technical Information of China (English)
WANG Wei-Li; SONG Peng; LI Yong-Qing; MIAO Gang; MA Feng-Cai
2006-01-01
Collisional quantum interference (CQI) on rotational energy transfer was observed in Na2 (A1∑u+, v = 8～b3∏ou, v = 14) system in collision with Na [Chem. Phys. Lett. 318 (2000) 107], and the degree of the interference was measured. The integral interference angle was obtained through theoretical calculation. We will research the factors that have effect on collisional quantum interference on rotational energy transfer in Na2(A 1∑u+, v = 8 ～ b3∏0u, v = 14) -Na system. Basing on the time-dependent first order Born approximation, and taking into account the anisotropic Lennard-Jones interaction potentials and "straight-line" trajectory approximation, we obtain the factors that have effect on CQI in Na2-Na system, and obtain the relation between the integral interference angle and rotational quantum number.
Suppression of the critical current of a balanced superconducting quantum interference device
Kemppinen, Antti; Manninen, Antti J.; Möttönen, Mikko; Vartiainen, Juha J.; Peltonen, Joonas T.; Pekola, Jukka P.
2008-01-01
We present an experimental study of the magnetic flux dependence of the critical current of a balanced superconducting quantum interference device (SQUID) with three Josephson junctions in parallel. Unlike for ordinary direct current (dc) SQUIDs, the suppression of the critical current does not depend on the exact parameters of the Josephson junctions. The suppression is essentially limited only by the inductances of the SQUID loops. We demonstrate a critical current suppression ratio of high...
DeFeo, M. P.; Bhupathi, P.; K. Yu; Heitmann, T. W.; Song, C.; McDermott, R; Plourde, B. L. T.
2010-01-01
We present measurements of an amplifier based on a dc superconducting quantum interference device (SQUID) with submicron Al-AlOx-Al Josephson junctions. The small junction size reduces their self-capacitance and allows for the use of relatively large resistive shunts while maintaining nonhysteretic operation. This leads to an enhancement of the SQUID transfer function compared to SQUIDs with micron-scale junctions. The device layout is modified from that of a conventional SQUID to allow for c...
Amado, M.; Fornieri, A.; Carillo, F.; Biasiol, G; Sorba, L.; Pellegrini, V.; F. Giazotto
2013-01-01
The magneto-electrostatic tailoring of the supercurrent in quantum point contact ballistic Josephson junctions is demonstrated. An etched InAs-based heterostructure is laterally contacted to superconducting niobium leads and the existence of two etched side gates permits, in combination with the application of a perpendicular magnetic field, to modify continuously the magnetic interference pattern by depleting the weak link. For wider junctions the supercurrent presents a Fraunhofer-like inte...
Suppression of interference in quantum Hall Mach-Zehnder geometry by upstream neutral modes
Goldstein, Moshe; Gefen, Yuval
2016-01-01
Mach-Zehnder interferometry has been proposed as a probe for detecting the statistics of anyonic quasiparticles in fractional quantum Hall (FQH) states. Here we focus on interferometers made of multimode edge states with upstream modes. We find that the interference visibility is suppressed due to downstream-upstream mode entanglement; the latter serves as a "which path" detector to the downstream interfering trajectories. Our analysis tackles a concrete realization of filling factor 2/3, but...
Institute of Scientific and Technical Information of China (English)
刘当婷; 田野; 赵士平; 任育峰; 陈赓华
2015-01-01
We discuss a simple relation between the input and output signals of a superconducting quantum interference device magnetometer operating in flux locked mode in a cosine curve approximation. According to this relation, an original fast input signal can be easily retrieved from its distorted output response. This technique can be used in some areas such as sensitive and fast detection of magnetic or metallic grains in medicine and food security checking.
Perfect state transfers by selective quantum interferences within complex spin networks
Alvarez, Gonzalo A.; Mishkovsky, Mor; Danieli, Ernesto P.; Levstein, Patricia R.; Pastawski, Horacio M.; Frydman, Lucio
2010-01-01
We present a method that implement directional, perfect state transfers within a branched spin network by exploiting quantum interferences in the time-domain. That provides a tool to isolate subsystems from a large and complex one. Directionality is achieved by interrupting the spin-spin coupled evolution with periods of free Zeeman evolutions, whose timing is tuned to be commensurate with the relative phases accrued by specific spin pairs. This leads to a resonant transfer between the chosen...
International Nuclear Information System (INIS)
In this paper we analyse the effect of the anomalous magnetic moment on the non-relativistic quantum motion of a neutral particle in magnetic and electric fields produced by linear sources of constant current and charge density, respectively. (author)
Anomalous X-ray diffraction from self-assembled PbSe/PbEuTe quantum dots
International Nuclear Information System (INIS)
Anomalous X-ray scattering from self-assembled PbSe quantum dots embedded in Pb1-xEu xTe was used for the study of their structure. The measured reciprocal-space distributions of diffracted intensity were compared with simulations based on kinematical scattering theory and continuum elasticity. From the comparison, the mean chemical composition of the dots and their aspect ratio (height/width) were estimated
International Nuclear Information System (INIS)
In chapter 3, a detailed analysis is made of the lineshapes of ultrasonic quantum oscillations. In theory (1.1.1 and 1.1.2), the temperature dependences of both sub(αs) tilde and sub(vs) tilde are well described by the same formalism as the De Haas-Van Alphen (DHVA) oscillations (3.1). The field dependence of sub(αs) tilde, however, is quite abnormal: the 'Dingle' temperature measured from the field dependence of sub(αs) tilde is much lower than the Tsub(D) from vsub(s) tilde under exactly the same conditions (3.2), and the second harmonic distortion of αsub(s) tilde turns out to be 1.5 times higher than in vsub(s) tilde oscillations and DHVA effect (3.3). The anomalous behaviour of αsub(s) tilde can be understood in terms of phase smearing of the DHVA-phase rather than of Landau level broadening (3.4). The consequence of this phase-smearing concept for the width of giant quantum oscillations is shown in section 3.5. The harmonic content of the vsub(s) tilde at high magnetic field is used to determine the g-factor of the electrons in the third band of indium (3.3.1) while the deviatio n of this g-factor from the free-electron value is compared with the influence of the spin-orbit interaction and the many-body effects (3.3.2)
The Occurrence of Anomalous Conductance Plateaus and Spin Textures in Quantum Point Contacts
Wan, J.; Cahay, M.; Debray, P.; Newrock, R.
2010-03-01
Recently, we used a NEGF formalism [1] to provide a theoretical explanation for the experimentally observed 0.5G0 (G0=2e^2/h) plateau in the conductance of side-gated quantum point contacts (QPCs) in the presence of lateral spin-orbit coupling (LSOC) [2]. We showed that the 0.5G0 plateau appears in the QPCs without any external magnetic field as a result of three ingredients: an asymmetric lateral confinement, a LSOC, and a strong electron-electron (e-e) interaction. In this report, we present the results of simulations for a wide range of QPC dimensions and biasing parameters showing that the same physics predicts the appearance of other anomalous plateaus at non-integer values of G0, including the well-known 0.7G0 anomaly. These features are related to a plethora of spin textures in the QPC that depend sensitively on material, device, biasing parameters, temperature, and the strength of the e-e interaction. [1] J. Wan, M. Cahay, P. Debray, and R.S. Newrock, Phys. Rev. B 80, 155440 (2009). [2] P. Debray, S.M. Rahman, J. Wan, R.S. Newrock, M. Cahay, A.T. Ngo, S.E. Ulloa, S.T. Herbert, M. Muhammad, and M. Johnson, Nature Nanotech. 4, 759 (2009).
Route towards Localization for Quantum Anomalous Hall Systems with Chern Number 2.
Song, Zhi-Gang; Zhang, Yan-Yang; Song, Jun-Tao; Li, Shu-Shen
2016-01-01
The quantum anomalous Hall system with Chern number 2 can be destroyed by sufficiently strong disorder. During its process towards localization, it was found that the electronic states will be directly localized to an Anderson insulator (with Chern number 0), without an intermediate Hall plateau with Chern number 1. Here we investigate the topological origin of this phenomenon, by calculating the band structures and Chern numbers for disordered supercells. We find that on the route towards localization, there exists a hidden state with Chern number 1, but it is too short and too fluctuating to be practically observable. This intermediate state cannot be stabilized even after some "smart design" of the model and this should be a universal phenomena for insulators with high Chern numbers. By performing numerical scaling of conductances, we also plot the renormalization group flows for this transition, with Chern number 1 state as an unstable fixed point. This is distinct from known results, and can be tested by experiments and further theoretical analysis. PMID:26743996
Dong, Liang; Kim, Youngkuk; Er, Dequan; Rappe, Andrew M; Shenoy, Vivek B
2016-03-01
The quantum anomalous Hall (QAH) insulator is a novel topological state of matter characterized by a nonzero quantized Hall conductivity without an external magnetic field. Using first-principles calculations, we predict the QAH state in monolayers of covalent-organic frameworks based on the newly synthesized X_{3}(C_{18}H_{12}N_{6})_{2} structure where X represents 5d transition metal elements Ta, Re, and Ir. The π conjugation between X d_{xz} and d_{yz} orbitals, mediated by N p_{z} and C p_{z} orbitals, gives rise to a massive Dirac spectrum in momentum space with a band gap of up to 24 meV due to strong spin-orbit coupling. We show that the QAH state can appear by chemically engineering the exchange field and the Fermi level in the monolayer structure, resulting in nonzero Chern numbers. Our results suggest a reliable pathway toward the realization of a QAH phase at temperatures between 100 K and room temperature in covalent-organic frameworks. PMID:26991189
Dong, Liang; Kim, Youngkuk; Er, Dequan; Rappe, Andrew M.; Shenoy, Vivek B.
2016-03-01
The quantum anomalous Hall (QAH) insulator is a novel topological state of matter characterized by a nonzero quantized Hall conductivity without an external magnetic field. Using first-principles calculations, we predict the QAH state in monolayers of covalent-organic frameworks based on the newly synthesized X3(C18H12N6) 2 structure where X represents 5 d transition metal elements Ta, Re, and Ir. The π conjugation between X dx z and dy z orbitals, mediated by N pz and C pz orbitals, gives rise to a massive Dirac spectrum in momentum space with a band gap of up to 24 meV due to strong spin-orbit coupling. We show that the QAH state can appear by chemically engineering the exchange field and the Fermi level in the monolayer structure, resulting in nonzero Chern numbers. Our results suggest a reliable pathway toward the realization of a QAH phase at temperatures between 100 K and room temperature in covalent-organic frameworks.
Anomalous disorder-related phenomena in InGaN/GaN multiple quantum well heterosystems
Energy Technology Data Exchange (ETDEWEB)
Hu, Y.-J. [Department of Electrical Engineering, Technology and Science Institute of Northern Taiwan, Taipei 112, Taiwan (China); Huang, Y.-W.; Fang, C.-H.; Wang, J.-C.; Chen, Y.-F. [Group of Abel and Lie Operations In Sciences and Quantum Electro-optical Science and Technology Laboratory (GALOIS-Quest-Lab), Department of Electronic Engineering, Chang Gung University, Kwei-Shan, Tao-Yuan 333, Taiwan (China); Nee, T.-E., E-mail: neete@mail.cgu.edu.t [Group of Abel and Lie Operations In Sciences and Quantum Electro-optical Science and Technology Laboratory (GALOIS-Quest-Lab), Department of Electronic Engineering, Chang Gung University, Kwei-Shan, Tao-Yuan 333, Taiwan (China)
2010-06-15
The influences of InGaN/GaN multiple quantum well (MQW) heterostructures with InGaN/GaN and GaN barriers on carrier confinement were investigated. The degree of disordering over a broad range of temperatures from 20 to 300 K was considered. The optical and electrical properties were strongly influenced by structural and compositional disordering of the InGaN/GaN MQW heterostructures. To compare the degree of disordering we examined the temperature dependence of the luminescence spectra and electrical conductance contingent on the Berthelot-type mechanisms in the InGaN/GaN MQW heterostructures. We further considered carrier transport in the InGaN/GaN disordered systems, probability of carrier tunneling, and activation energy of the transport mechanism for devices with InGaN/GaN and GaN barriers. The optical properties of InGaN/GaN disordered heterosystems can be interpreted from the features of the absorption spectra. The anomalous temperature-dependent characteristics of the disordered InGaN/GaN MQW structures were attributable to the enhancement of the exciton confinement.
Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2
Das, Pranab Kumar; di Sante, D.; Vobornik, I.; Fujii, J.; Okuda, T.; Bruyer, E.; Gyenis, A.; Feldman, B. E.; Tao, J.; Ciancio, R.; Rossi, G.; Ali, M. N.; Picozzi, S.; Yadzani, A.; Panaccione, G.; Cava, R. J.
2016-02-01
The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phenomenon, accounting for a rich variety of material properties. Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators, transition metal dichalcogenides have recently received renewed attention. In this context, the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest. Here we report angle- and spin-resolved photoemission spectroscopy of WTe2 single crystals, through which we disentangle the role of W and Te atoms in the formation of the band structure and identify the interplay of charge, spin and orbital degrees of freedom. Supported by first-principles calculations and high-resolution surface topography, we reveal the existence of a layer-dependent behaviour. The balance of electron and hole states is found only when considering at least three Te-W-Te layers, showing that the behaviour of WTe2 is not strictly two dimensional.
Route towards Localization for Quantum Anomalous Hall Systems with Chern Number 2
Song, Zhi-Gang; Zhang, Yan-Yang; Song, Jun-Tao; Li, Shu-Shen
2016-01-01
The quantum anomalous Hall system with Chern number 2 can be destroyed by sufficiently strong disorder. During its process towards localization, it was found that the electronic states will be directly localized to an Anderson insulator (with Chern number 0), without an intermediate Hall plateau with Chern number 1. Here we investigate the topological origin of this phenomenon, by calculating the band structures and Chern numbers for disordered supercells. We find that on the route towards localization, there exists a hidden state with Chern number 1, but it is too short and too fluctuating to be practically observable. This intermediate state cannot be stabilized even after some “smart design” of the model and this should be a universal phenomena for insulators with high Chern numbers. By performing numerical scaling of conductances, we also plot the renormalization group flows for this transition, with Chern number 1 state as an unstable fixed point. This is distinct from known results, and can be tested by experiments and further theoretical analysis.
Layer-dependent quantum cooperation of electron and hole states in the anomalous semimetal WTe2.
Das, Pranab Kumar; Di Sante, D; Vobornik, I; Fujii, J; Okuda, T; Bruyer, E; Gyenis, A; Feldman, B E; Tao, J; Ciancio, R; Rossi, G; Ali, M N; Picozzi, S; Yadzani, A; Panaccione, G; Cava, R J
2016-01-01
The behaviour of electrons and holes in a crystal lattice is a fundamental quantum phenomenon, accounting for a rich variety of material properties. Boosted by the remarkable electronic and physical properties of two-dimensional materials such as graphene and topological insulators, transition metal dichalcogenides have recently received renewed attention. In this context, the anomalous bulk properties of semimetallic WTe2 have attracted considerable interest. Here we report angle- and spin-resolved photoemission spectroscopy of WTe2 single crystals, through which we disentangle the role of W and Te atoms in the formation of the band structure and identify the interplay of charge, spin and orbital degrees of freedom. Supported by first-principles calculations and high-resolution surface topography, we reveal the existence of a layer-dependent behaviour. The balance of electron and hole states is found only when considering at least three Te-W-Te layers, showing that the behaviour of WTe2 is not strictly two dimensional. PMID:26924386
International Nuclear Information System (INIS)
We present the experimental observation of the effects of macroscopic quantum tunnelling in a SQUID device, consisting of a rf SQUID coupled to a readout system based on a dc SQUID sensor. Data on the decay rate from the metastable flux states of a rf SQUID are reported, both in the classical and quantum regimes. The low dissipation level and the good insulation of the probe from external noise are encouraging in view of building a macroscopic quantum coherent system
Understanding destruction of nth-order quantum coherence in terms of multi-path interference
Zhou, D L; Sun, C P
2002-01-01
The classic example of the destruction of interference fringes in a ``which-way'' experiment, caused by an environmental interaction, may be viewed as the destruction of first-order coherence as defined by Glauber many years ago (Glauber). However, the influence of an environment can also destroy the $n$th-order quantum coherence in a quantum system, where this high order coherence is captured. We refer to this phenomenon as the $n$% th-order decoherence. In this paper we show that, just as the first-order coherence can be understood as the interference of the amplitudes for two distinct paths, the higher order coherence may be understood as the interference of multiple amplitudes corresponding to multiple paths. To see this, we introduce the concept of $n$th-order ``multi-particle wave amplitude''. It turns out that the $n$th-order correlation function can be expressed as the square norm of some ``multi-particle wave amplitude'' for the closed system or as the sum of such square norms for the open system. We...
Zhang, Ying-Tao; Deng, Xinzhou; Sun, Qing-Feng; Qiao, Zhenhua
2015-01-01
The quantum entanglement between two qubits is crucial for applications in the quantum communication. After the entanglement of photons was experimentally realized, much effort has been taken to exploit the entangled electrons in solid-state systems. Here, we propose a Cooper-pair splitter, which can generate spatially-separated but entangled electrons, in a quantum anomalous Hall insulator proximity-coupled with a superconductor. After coupling with a superconductor, the chiral edge states of the quantum anomalous Hall insulator can still survive, making the backscattering impossible. Thus, the local Andreev reflection becomes vanishing, while the crossed Andreev reflection becomes dominant in the scattering process. This indicates that our device can serve as an extremely high-efficiency Cooper-pair splitter. Furthermore, because of the chiral characteristic, our Cooper-pair splitter is robust against disorders and can work in a wide range of system parameters. Particularly, it can still function even if the system length exceeds the superconducting coherence length. PMID:26450824
International Nuclear Information System (INIS)
By means of cavity-assisted photon interference, a simple scheme is proposed to implement a symmetric economical phase-covariant quantum cloning machine of two remote qubits, with each in a separate cavity. With our present scheme, a high-fidelity cloning machine is realized. Our scheme may be quite useful in terms of distributed quantum information processing. (general)
Interference effects of choice on confidence: Quantum characteristics of evidence accumulation.
Kvam, Peter D; Pleskac, Timothy J; Yu, Shuli; Busemeyer, Jerome R
2015-08-25
Decision-making relies on a process of evidence accumulation which generates support for possible hypotheses. Models of this process derived from classical stochastic theories assume that information accumulates by moving across definite levels of evidence, carving out a single trajectory across these levels over time. In contrast, quantum decision models assume that evidence develops over time in a superposition state analogous to a wavelike pattern and that judgments and decisions are constructed by a measurement process by which a definite state of evidence is created from this indefinite state. This constructive process implies that interference effects should arise when multiple responses (measurements) are elicited over time. We report such an interference effect during a motion direction discrimination task. Decisions during the task interfered with subsequent confidence judgments, resulting in less extreme and more accurate judgments than when no decision was elicited. These results provide qualitative and quantitative support for a quantum random walk model of evidence accumulation over the popular Markov random walk model. We discuss the cognitive and neural implications of modeling evidence accumulation as a quantum dynamic system. PMID:26261322
Energy Technology Data Exchange (ETDEWEB)
Hamedi, H.R., E-mail: Hamid.r.Hamedi@gmail.com
2014-10-01
This letter explores the one dimensional (1D) and two-dimensional (2D) position dependent probe absorption spectrum in a four-subband semiconductor quantum-well (QW) system in presence of Fano-type interference. Compared with obtained results for the maximal detecting probability of electron in Hamedi (2014. Physica B 440, 83) which was 50%, in this paper, we show that the detecting probability and precision of electron localization in one period can be significantly improved and reaches to 100% at the origin of coordinates, through proper tuning the strength of Fano-type interference. Also, the influence of other controlling parameters on the localization behavior of the QW system is discussed. The obtained results may provide some new possibilities for technological applications in laser cooling or nanolithography via high-precision and high-resolution electron localization.
Fano interference in a parallel double quantum dot interferometer modified by the decoherence effect
International Nuclear Information System (INIS)
By introducing floating leads to mimic the decoherence mechanism, we study the influence of the decoherence effect on the Fano interference in electron transport through a parallel double quantum dot (QD) structure. We find that when the decoherence effect is incorporated in the resonant channel, the Fano interference can apparently be suppressed, especially in the case of φ = π (φ is the phase due to the presence of a local magnetic flux). On the other hand, if the decoherence effect is introduced into the nonresonant channel, the Fano antiresonance is independent of the strengthening of the decoherence effect. If the magnetic flux is absent, the Fano antiresonance valley will be widened by the decoherence. When φ = π, the Fano lineshape in the conductance spectrum is robust. By analyzing the electron motion is this system, we clarified all the results. We hope that these results will be helpful for relevant experiments.
International Nuclear Information System (INIS)
This letter explores the one dimensional (1D) and two-dimensional (2D) position dependent probe absorption spectrum in a four-subband semiconductor quantum-well (QW) system in presence of Fano-type interference. Compared with obtained results for the maximal detecting probability of electron in Hamedi (2014. Physica B 440, 83) which was 50%, in this paper, we show that the detecting probability and precision of electron localization in one period can be significantly improved and reaches to 100% at the origin of coordinates, through proper tuning the strength of Fano-type interference. Also, the influence of other controlling parameters on the localization behavior of the QW system is discussed. The obtained results may provide some new possibilities for technological applications in laser cooling or nanolithography via high-precision and high-resolution electron localization
Fano interference in a parallel double quantum dot interferometer modified by the decoherence effect
Energy Technology Data Exchange (ETDEWEB)
Yang, Chuan-Jing; Ren, Feng-Zhang [Henan University of Science and Technology, Luoyang (China); Gong, Wei-Jiang [Northeastern university, Shenyang (China)
2014-03-15
By introducing floating leads to mimic the decoherence mechanism, we study the influence of the decoherence effect on the Fano interference in electron transport through a parallel double quantum dot (QD) structure. We find that when the decoherence effect is incorporated in the resonant channel, the Fano interference can apparently be suppressed, especially in the case of φ = π (φ is the phase due to the presence of a local magnetic flux). On the other hand, if the decoherence effect is introduced into the nonresonant channel, the Fano antiresonance is independent of the strengthening of the decoherence effect. If the magnetic flux is absent, the Fano antiresonance valley will be widened by the decoherence. When φ = π, the Fano lineshape in the conductance spectrum is robust. By analyzing the electron motion is this system, we clarified all the results. We hope that these results will be helpful for relevant experiments.
Inelastic Fano interference induced by interdot-phonon exchange in a T-shaped double quantum dot
International Nuclear Information System (INIS)
We study the phonon-assisted Fano interference of the linear conductance spectrum by taking into account the interdot-phonon exchange in a T-shaped double quantum dot (QD), where a central QD is coupled to a side QD and two nonmagnetic or ferromagnetic electrodes. Unlike the usual Fano interference between different elastic channels, this new-type Fano interference is shown to arise from electron waves tunneling coherently through phonon-assisted bonding and antibonding states. The inelastic Fano effect, characterized by a significant resonance and a zero-value antiresonance of conductances due to destructive quantum interference, is strongly dependent on the interdot coupling and interdot electron-phonon interactions (EPI) strength. We also examine that the introduction of ferromagnetic leads does not destroy either the elastic Fano interference or the inelastic one but richens their lineshapes.
Seyyed, Hossein Asadpour; G, Solookinejad; M, Panahi; E Ahmadi, Sangachin
2016-03-01
Role of Fano interference and incoherent pumping field on optical bistability in a four-level designed InGaN/GaN quantum dot nanostructure embedded in a unidirectional ring cavity are analyzed. It is found that intensity threshold of optical bistability can be manipulated by Fano interference. It is shown that incoherent pumping fields make the threshold of optical bistability behave differently by Fano interference. Moreover, in the presence of Fano interference the medium becomes phase-dependent. Therefore, the relative phase of applied fields can affect the behaviors of optical bistability and intensity threshold can be controlled easily.
Weiß, Philipp S.; Narozhny, Boris N.; Schmalian, Jörg; Wölfle, Peter
2016-01-01
We study the temperature-dependent quantum correction to conductivity due to the interplay of spin density fluctuations and weak disorder for a two-dimensional metal near an antiferromagnetic (AFM) quantum critical point. AFM spin density fluctuations carry large momenta around the ordering vector Q and, at lowest order of the spin-fermion coupling, only scatter electrons between "hot spots" of the Fermi surface which are connected by Q . Earlier, it was seen that the quantum interference between AFM spin density fluctuations and soft diffusive modes of the disordered metal is suppressed, a consequence of the large-momentum scattering. The suppression of this interference results in a nonsingular temperature dependence of the corresponding interaction correction to conductivity. However, at higher order of the spin-fermion coupling, electrons on the entire Fermi surface can be scattered successively by two spin density fluctuations and, in total, suffer a small momentum transfer. This higher-order process can be described by composite modes which carry small momenta. We show that the interference between formally subleading composite modes and diffusive modes generates singular interaction corrections which ultimately dominate over the nonsingular first-order correction at low temperatures. We derive an effective low-energy theory from the spin-fermion model which includes the above-mentioned higher-order process implicitly and show that for weak spin-fermion coupling the small-momentum transfer is mediated by a composite propagator. Employing the conventional diagrammatic approach to impurity scattering, we find the correction δ σ ∝+ln2T for temperatures above an exponentially small crossover scale.
Energy Technology Data Exchange (ETDEWEB)
Belluzzi, Luca; Bueno, Javier Trujillo [Instituto de Astrofisica de Canarias, E-38205 La Laguna, Tenerife (Spain)
2011-12-10
The spectral line polarization produced by optically pumped atoms contains a wealth of information on the thermal and magnetic structure of a variety of astrophysical plasmas, including that of the solar atmosphere. A correct decoding of such information from the observed Stokes profiles requires a clear understanding of the effects that radiatively induced quantum interference (or coherence) between pairs of magnetic sublevels produces on these observables, in the absence of and in the presence of magnetic fields of arbitrary strength. Here we present a detailed theoretical investigation of the role of coherence between pairs of sublevels pertaining to different fine-structure J-levels, clarifying when it can be neglected for facilitating the modeling of the linear polarization produced by scattering processes in spectral lines. To this end, we apply the quantum theory of spectral line polarization and calculate the linear polarization patterns of the radiation scattered at 90 Degree-Sign by a slab of stellar atmospheric plasma, both taking into account and neglecting the above-mentioned quantum interference. Particular attention is given to the {sup 2}S - {sup 2}P, {sup 5}S - {sup 5}P, and {sup 3}P - {sup 3}S multiplets. We point out the observational signatures of this kind of interference and analyze its sensitivity to the energy separation between the interfering levels, to the amount of emissivity in the background continuum radiation, to lower-level polarization, and to the presence of a magnetic field. Some interesting applications to the following spectral lines are also presented: Ca II H and K, Mg II h and k, Na I D{sub 1} and D{sub 2}, the Ba II 4554 #Angstrom# and 4934 #Angstrom# resonance lines, the Cr I triplet at 5207 #Angstrom#, the O I triplet at 7773 #Angstrom#, the Mg I b-lines, and the H{alpha} and Ly{alpha} lines of H I.
Okano, Masayuki; Okamoto, Ryo; Nishizawa, Norihiko; Kurimura, Sunao; Takeuchi, Shigeki
2016-01-01
Quantum information technologies harness the intrinsic nature of quantum theory to beat the limitations of the classical methods for information processing and communication. Recently, the application of quantum features to metrology has attracted much attention. Quantum optical coherence tomography (QOCT), which utilizes two-photon interference between entangled photon pairs, is a promising approach to overcome the problem with optical coherence tomography (OCT): As the resolution of OCT becomes higher, degradation of the resolution due to dispersion within the medium becomes more critical. Here we report on the realization of 0.54 $\\mu$m resolution two-photon interference, which surpasses the current record resolution 0.75 $\\mu$m of low-coherence interference for OCT. In addition, the resolution for QOCT showed almost no change against the dispersion of a 1 mm thickness of water inserted in the optical path, whereas the resolution for OCT dramatically degrades. For this experiment, a highly-efficient chirpe...
Zhou, Y.; Yu, T.; Wu, M. W.
2013-06-01
We report an anomalous scaling of the D’yakonov-Perel’ spin relaxation with the momentum relaxation in semiconductor quantum wells under a strong magnetic field in the Voigt configuration. We focus on the case in which the external magnetic field is perpendicular to the spin-orbit-coupling-induced effective magnetic field and its magnitude is much larger than the latter one. It is found that the longitudinal spin relaxation time is proportional to the momentum relaxation time even in the strong-scattering limit, indicating that the D’yakonov-Perel’ spin relaxation demonstrates Elliott-Yafet-like behavior. Moreover, the transverse spin relaxation time is proportional (inversely proportional) to the momentum relaxation time in the strong- (weak-) scattering limit, both in the opposite trends against the well-established conventional D’yakonov-Perel’ spin relaxation behaviors. We further demonstrate that all the above anomalous scaling relations come from the unique form of the effective inhomogeneous broadening.
Quantum interference effects on the noise power in the CNT/aGNR/CNT junction
Fouladi, A. Ahmadi; Vahedi, Javad
2014-01-01
Based on tight-binding model and a generalized Green's function method in Landauer-B\\"uttiker formalism, the effects of quantum interference (QI) on the noise power and Fano factor of an armchair graphene nanoribbon (aGNR) sandwiched between infinite single wall carbon nanotube (SWCNT) as a CNT/aGNR/CNT system are numerically investigated. In this work, changing the aGNR to CNT electrodes contact positions and applying the magnetic field as two sources of QI are considered. We have found diff...
Quantum interference of stored dual-channel spin-wave excitations in a single tripod system
International Nuclear Information System (INIS)
We present an experimental demonstration of dual-channel memory in a single tripod atomic system. The total readout signal exhibits either constructive or destructive interference when the dual-channel spin-wave excitations (SWEs) are retrieved by two reading beams with a controllable relative phase. When the two reading beams have opposite phases, the SWEs will remain in the medium, which can be retrieved later with two in-phase reading beams. Such a phase-sensitive storage and retrieval scheme can be used to measure and control the relative phase between the two SWEs in the memory medium, which may find applications in quantum-information processing.
International Nuclear Information System (INIS)
We analyze quantum charge pumping in an open ring with a dot embedded in one of its arms. We show that cyclic driving of the dot levels by a single parameter leads to a pumped current when a static magnetic flux is simultaneously applied to the ring. Based on the computation of the Floquet-Green's functions, we show that for low driving frequencies ω0, the interplay between the spatial interference through the ring plus photon-assisted tunneling gives an average direct current (dc) which is proportional to ω02. (author)
Quantum Entanglement of Many Distant Bose—Einstein Condensates in an Optical Lattice by Interference
International Nuclear Information System (INIS)
We propose a scheme to generate maximally entangled states of two distant Bose—Einstein condensates, which are trapped in different potential wells of a one-dimensional optical lattice. We show how such maximally entangled state can be used to test the Bell inequality and realize quantum teleportation of a Bose—Einstein condensate state. The scheme proposed here is based on the interference of Bose—Einstein condensates leaking out from different potential wells of optical lattice. It is briefly pointed out that this scheme can be extended to generate maximally entangled Greenberger—Horne—Zeilinger (GHZ) states of 2m (m > 1) distant Bose—Einstein condensates. (general)
International Nuclear Information System (INIS)
The equations of motion of the symmetrical dc superconducting quantum interference device (SQUID) are numerically investigated with a 16-term Taylor-expansion routine. The coherent phase or single-junction state is found to be unstable in large regions of the phase space including areas of interest in magnetometer design. The stability problem is discussed analytically in terms of the Hill equation. Feigenbaum sequences to chaos are found at borders of stability of various types of solution. Some of these, at finite external fluxes, occur at quite physical values of SQUID parameters
High-T{sub c} superconducting quantum interference devices and biomagnetic applications
Energy Technology Data Exchange (ETDEWEB)
Yang, H. C.; Wu, C. H.; Chen, J. C.; Chen, K. L.; Chen, M. J.; Yang, S. Y. [National Taiwan University, Taipei (China); Liao, S. H.; Horng, H. E. [National Taiwan Normal University, Taipei (China)
2006-05-15
The superconducting quantum interference device (SQUID) is the most sensitive detector of the magnetic flux in the range of frequencies from dc to MHz and has widely been used in biomagnetic applications. In this paper, we highlight a few aspects of High-T{sub c} SQUIDs, novel biomagnetic applications, and perspective. We give an overview of the current status and the principle techniques used to fabricate High-T{sub c} SQUIDs. SQUID applications in magnetocardiography, biological immunoassay, and nuclear magnetic resonance are addressed. The results are discussed.
DEFF Research Database (Denmark)
Jørgensen, Jacob Lykkebo
, which is characterised by destructive quantum interference. The molecules are cross-conjugated, which means that the two parts of the molecules are conjugated to a third part, but not to each other. This gives rise to an anti-resonance in the trans- mission. In the low bias and low temperature regime......, the electrons can tunnel in- elastically from the left to the right electrode. This is the process behind inelastic electron tunnelling spectroscopy (IETS), which is a single-molecule spectroscopic method, where the vibrational ngerprint of a molecule is di- rectly observed by the tunnelling current...
Perfect state transfers by selective quantum interferences within complex spin networks
Alvarez, Gonzalo A; Danieli, Ernesto P; Levstein, Patricia R; Pastawski, Horacio M; Frydman, Lucio
2010-01-01
We present a method that implement directional, perfect state transfers within a branched spin network by exploiting quantum interferences in the time-domain. That provides a tool to isolate subsystems from a large and complex one. Directionality is achieved by interrupting the spin-spin coupled evolution with periods of free Zeeman evolutions, whose timing is tuned to be commensurate with the relative phases accrued by specific spin pairs. This leads to a resonant transfer between the chosen qubits, and to a detuning of all remaining pathways in the network, using only global manipulations. As the transfer is perfect when the selected pathway is mediated by 2 or 3 spins, distant state transfers over complex networks can be achieved by successive recouplings among specific pairs/triads of spins. These effects are illustrated with a quantum simulator involving 13C NMR on Leucine's backbone; a six-spin network.
Perfect state transfers by selective quantum interferences within complex spin networks
International Nuclear Information System (INIS)
We present a method that implements directional, perfect state transfers within a branched spin network by exploiting quantum interferences in the time domain. This method provides a tool for isolating subsystems from a large and complex one. Directionality is achieved by interrupting the spin-spin coupled evolution with periods of free Zeeman evolutions, whose timing is tuned to be commensurate with the relative phases accrued by specific spin pairs. This leads to a resonant transfer between the chosen qubits and to a detuning of all remaining pathways in the network, using only global manipulations. Since the transfer is perfect when the selected pathway is mediated by two or three spins, distant state transfers over complex networks can be achieved by successive recouplings among specific pairs or triads of spins. These effects are illustrated with a quantum simulator involving 13C NMR on leucine's backbone; a six-spin network.
A parabolic model to control quantum interference in T-shaped molecular junctions
DEFF Research Database (Denmark)
Nozaki, Daijiro; Sevincli, Haldun; Avdoshenko, Stanislav M.;
2013-01-01
interest to develop simple methods controlling the emergence and the positions of QI effects like anti-resonances or Fano line shapes in conductance spectra. In this work, starting from a well-known generic molecular junction with a side group (T-shaped molecule), we propose a simple graphical method...... and the main conduction channel from measurements in the case of orthogonal basis. The results obtained within the parabolic model are validated using density-functional based quantum transport calculations in realistic T-shaped molecular junctions.......Quantum interference (QI) effects in molecular devices have drawn increasing attention over the past years due to their unique features observed in the conductance spectrum. For the further development of single molecular devices exploiting QI effects, it is of great theoretical and practical...
Perfect state transfers by selective quantum interferences within complex spin networks
Álvarez, Gonzalo A.; Mishkovsky, Mor; Danieli, Ernesto P.; Levstein, Patricia R.; Pastawski, Horacio M.; Frydman, Lucio
2010-06-01
We present a method that implements directional, perfect state transfers within a branched spin network by exploiting quantum interferences in the time domain. This method provides a tool for isolating subsystems from a large and complex one. Directionality is achieved by interrupting the spin-spin coupled evolution with periods of free Zeeman evolutions, whose timing is tuned to be commensurate with the relative phases accrued by specific spin pairs. This leads to a resonant transfer between the chosen qubits and to a detuning of all remaining pathways in the network, using only global manipulations. Since the transfer is perfect when the selected pathway is mediated by two or three spins, distant state transfers over complex networks can be achieved by successive recouplings among specific pairs or triads of spins. These effects are illustrated with a quantum simulator involving C13 NMR on leucine’s backbone; a six-spin network.
Quantum phase slip interference device based on a shaped superconducting nanowire
International Nuclear Information System (INIS)
As was predicted by Mooij and Nazarov, the superconducting nanowires may exhibit, depending on the impedance of external electromagnetic environment, not only quantum slips of phase, but also the quantum-mechanically dual effect of coherent transfer of single Cooper pairs. We propose and realize a transistor-like superconducting circuit including two serially connected segments of a narrow (10 nm by 18 nm) nanowire joint by a wider segment with a capacitively coupled gate in between. This circuit is made of amorphous NbSi film and embedded in a network of on-chip Cr microresistors ensuring a high external impedance (>>h/e2∼25.8 kΩ) and, eventually, a charge bias regime. Virtual quantum phase slips in two narrow segments of the wire lead in this case to quantum interference of voltages on these segments making this circuit dual to the dc SQUID. Our samples demonstrated appreciable Coulomb blockade voltage (analog of critical current of the SQUID) and remarkable periodic modulation of this blockade by an electrostatic gate (analog of flux modulation in the SQUID). The obtained experimental results and the model of this QPS transistor will be presented.
The Two-Dimensional MnO2/Graphene Interface: Half-metallicity and Quantum Anomalous Hall State
Gan, Li-Yong
2015-10-07
We explore the electronic properties of the MnO2/graphene interface by first-principles calculations, showing that MnO2 becomes half-metallic. MnO2 in the MnO2/graphene/MnO2 system provides time-reversal and inversion symmetry breaking. Spin splitting by proximity occurs at the Dirac points and a topologically nontrivial band gap is opened, enabling a quantum anomalous Hall state. The half-metallicity, spin splitting, and size of the band gap depend on the interfacial interaction, which can be tuned by strain engineering.
Tripathy, Srijeet; Bhattacharyya, Tarun Kanti
2016-09-01
Due to excellent transport properties, Carbon nanotubes (CNTs) show a lot of promise in sensor and interconnect technology. However, recent studies indicate that the conductance in CNT/CNT junctions are strongly affected by the morphology and orientation between the tubes. For proper utilization of such junctions in the development of CNT based technology, it is essential to study the electronic properties of such junctions. This work presents a theoretical study of the electrical transport properties of metallic Carbon nanotube homo-junctions. The study focuses on discerning the role of inter-tube interactions, quantum interference and scattering on the transport properties on junctions between identical tubes. The electronic structure and transport calculations are conducted with an Extended Hückel Theory-Non Equilibrium Green's Function based model. The calculations indicate conductance to be varying with a changing crossing angle, with maximum conductance corresponding to lattice registry, i.e. parallel configuration between the two tubes. Further calculations for such parallel configurations indicate onset of short and long range oscillations in conductance with respect to changing overlap length. These oscillations are attributed to inter-tube coupling effects owing to changing π orbital overlap, carrier scattering and quantum interference of the incident, transmitted and reflected waves at the inter-tube junction.
Quantum interference during high-order harmonic generation from aligned molecules
Kanai, Tsuneto; Minemoto, Shinichirou; Sakai, Hirofumi
2005-05-01
High-order harmonic generation (HHG) from atoms and molecules offers potential application as a coherent ultrashort radiation source in the extreme ultraviolet and soft X-ray regions. In the three-step model of HHG, an electron tunnels out from the atom and may recombine with the parent ion (emitting a high-energy photon) after undergoing laser-driven motion in the continuum. Aligned molecules can be used to study quantum phenomena in HHG associated with molecular symmetries; in particular, simultaneous observations of both ion yields and harmonic signals under the same conditions serve to disentangle the contributions from the ionization and recombination processes. Here we report evidence for quantum interference of electron de Broglie waves in the recombination process of HHG from aligned CO2 molecules. The interference takes place within a single molecule and within one optical cycle. Characteristic modulation patterns of the harmonic signals measured as a function of the pump-probe delay are explained with simple formulae determined by the valence orbital of the molecules. We propose that simultaneous observations of both ion yields and harmonic signals can serve as a new route to probe the instantaneous structure of molecular systems.
Quantum interference during high-order harmonic generation from aligned molecules.
Kanai, Tsuneto; Minemoto, Shinichirou; Sakai, Hirofumi
2005-05-26
High-order harmonic generation (HHG) from atoms and molecules offers potential application as a coherent ultrashort radiation source in the extreme ultraviolet and soft X-ray regions. In the three-step model of HHG, an electron tunnels out from the atom and may recombine with the parent ion (emitting a high-energy photon) after undergoing laser-driven motion in the continuum. Aligned molecules can be used to study quantum phenomena in HHG associated with molecular symmetries; in particular, simultaneous observations of both ion yields and harmonic signals under the same conditions serve to disentangle the contributions from the ionization and recombination processes. Here we report evidence for quantum interference of electron de Broglie waves in the recombination process of HHG from aligned CO2 molecules. The interference takes place within a single molecule and within one optical cycle. Characteristic modulation patterns of the harmonic signals measured as a function of the pump-probe delay are explained with simple formulae determined by the valence orbital of the molecules. We propose that simultaneous observations of both ion yields and harmonic signals can serve as a new route to probe the instantaneous structure of molecular systems. PMID:15917803
The quantum interference effects in the SC II 4247 Å line of the second solar spectrum
International Nuclear Information System (INIS)
The Sc II 4247 Å line formed in the chromosphere is one of the lines well known, like the Na I D2 and Ba II D2, for its prominent triple-peak structure in Q/I and the underlying quantum interference effects governing it. In this paper, we try to study the nature of this triple-peak structure using the theory of F-state interference including the effects of partial frequency redistribution (PRD) and radiative transfer (RT). We compare our results with the observations taken in a quiet region near the solar limb. In spite of accounting for PRD and RT effects, it has not been possible to reproduce the observed triple-peak structure in Q/I. While the two wing PRD peaks (on either side of central peak) and the near wing continuum can be reproduced, the central peak is completely suppressed by the enhanced depolarization resulting from the hyperfine structure splitting. This suppression remains for all the tested widely different one-dimensional model atmospheres or for any multi-component combinations of them. While multidimensional RT effects may improve the fit to the intensity profiles, they do not appear capable of explaining the enigmatic central Q/I peak. This leads us to suspect that some aspect of quantum physics is missing.
Frequency dependence of quantum path interference in non-collinear high-order harmonic generation
Shi-Yang, Zhong; Xin-Kui, He; Hao, Teng; Peng, Ye; Li-Feng, Wang; Peng, He; Zhi-Yi, Wei
2016-02-01
High-order harmonic generation (HHG) driven by two non-collinear beams including a fundamental and its weak second harmonic is numerically studied. The interference of harmonics from adjacent electron quantum paths is found to be dependent on the relative delay of the driving pulse, and the dependences are different for different harmonic orders. This frequency dependence of the interference is attributed to the spatial frequency chirp in the HHG beam resulting from the harmonic dipole phase, which in turn provides a potential way to gain an insight into the generation of high-order harmonics. As an example, the intensity dependent dipole phase coefficient α is retrieved from the interference fringe. Project supported by the National Key Basic Research Program of China (Grant Nos. 2013CB922401 and 2013CB922402), the National Key Scientific Instrument and Equipment Development Projects, China (Grant No. 2012YQ12004704), the National Natural Science Foundation of China (Grant No. 11374356), and the International Joint Research Program of National Natural Science Foundation of China (Grant No. 61210017).
Test of some Fundamental Principles in Physics via Quantum Interference with Neutrons and Photons
Camacho, Abel
2008-01-01
The limitations and possibilities that the concept of quantum interference offers as a tool for testing fundamental physics are explored here. The use of neutron interference as an instrument to confront against measurement readouts some of the principles behind metric theories of gravity will be analyzed, as well as some discrepancies between theory and experiment. The main restrictions that this model embodies for the study of some of the features of the structure of space--time will be explicitly pointed out. For instance, the conditions imposed by the necessary use of the semiclassical approximation. Additionally, the role that photon interference could play as an element in this context is also considered. In this realm we explore the differences between first-order and second-order coherence experiments, and underline the fact that the Hanbury--Brown--Twiss effect could open up some interesting experimental possibilities in the analysis of the structure of space--time. The void, in connection with the d...
Macroscopic Quantum Phenomena and Topological Phase Interference Effects in Single-Domain Magnets
Institute of Scientific and Technical Information of China (English)
L(U) Rong; ZHU Jialin
2001-01-01
The tunneling of macroscopic object is one of the most fascinating phenomena in condensed matter physics.During the last decade,the problem of quantum tunneling of magnetization in nanometer-scale magnets has attracted a great deal of theoretical and experimental interest.A review of recent theoretical research of the macroscopic quantum phenomena in nanometer-scale single-domain magnets is presented in this paper.It includes macroscopic quantum tunneling (MQT) and coherence (MQC) in single-domain magnetic particles,the topological phase interference or spin-parity effects,and tunneling of magnetization in an arbitrarily directed magnetic field.The general formulas are shown to evaluate the tunneling rate and the tunneling level splitting for single-domain AFM particles.A nontrivial generalization of Kramers degeneracy for double-well system is provided to coherently spin tunneling for spin systems with m-fold rotational symmetry.The effects induced by the external magnetic field have been studied,where the field is along the easy,medium,hard axis,or arbitrary direction.
Magnetic Field Tuning and Quantum Interference in a Cooper Pair Splitter
Fülöp, G.; Domínguez, F.; d'Hollosy, S.; Baumgartner, A.; Makk, P.; Madsen, M. H.; Guzenko, V. A.; Nygârd, J.; Schönenberger, C.; Levy Yeyati, A.; Csonka, S.
2015-11-01
Cooper pair splitting (CPS) is a process in which the electrons of the naturally occurring spin-singlet pairs in a superconductor are spatially separated using two quantum dots. Here, we investigate the evolution of the conductance correlations in an InAs CPS device in the presence of an external magnetic field. In our experiments the gate dependence of the signal that depends on both quantum dots continuously evolves from a slightly asymmetric Lorentzian to a strongly asymmetric Fano-type resonance with increasing field. These experiments can be understood in a simple three-site model, which shows that the nonlocal CPS leads to symmetric line shapes, while the local transport processes can exhibit an asymmetric shape due to quantum interference. These findings demonstrate that the electrons from a Cooper pair splitter can propagate coherently after their emission from the superconductor and how a magnetic field can be used to optimize the performance of a CPS device. In addition, the model calculations suggest that the estimate of the CPS efficiency in the experiments is a lower bound for the actual efficiency.
Asano, M; Bliokh, Y P; Kofman, A G; Zhao, G; Ikuta, R; Yamamoto, T; Kivshar, Y S; Yang, L; Imoto, N; Ozdemir, S K; Nori, F
2016-01-01
We study inelastic resonant scattering of a Gaussian pulse with the parameters close to a zero of the complex scattering coefficient. We demonstrate, both theoretically and experimentally, that such near-zero scattering can result in anomalously-large time delays and frequency shifts of the scattered pulse. Furthermore, we reveal a close analogy of these anomalous shifts with the spatial and angular Goos-Hanchen optical beam shifts, which are amplified via quantum weak measurements. However, in contrast to other beam-shift and weak-measurement systems, we deal with a one-dimensional scalar wave without any intrinsic degrees of freedom. It is the non-Hermitian nature of the system that produces its rich and non-trivial behaviour. Our results are generic for any scattering problem, either quantum or classical. As an example, we consider the transmission of an optical pulse through a nano-fiber with a side-coupled toroidal micro-resonator. The zero of the transmission coefficient corresponds to the critical coup...
Institute of Scientific and Technical Information of China (English)
H.R.Hamedi; Ali Sari; M.Sahrai; S.H.Asadpour
2013-01-01
Optical bistability (OB) and optical multi-stability (OM) of a four-level A-type atomic system with two fold lower levels inside a unidirectional ring cavity is investigated.The effect of quantum interference arising from spontaneous emission and incoherent pumping on OB and OM is discussed.It is found that the threshold of OB and OM can be controlled by quantum interference mechanisms.In addition intensity of coupling field and the rate of an incoherent pumping field on behavior of OB and OM are then discussed.
Wang, Rui; Jacobs, Paul; Zhao, Hui; Smirl, Arthur L.
2013-06-01
The Dynamic Franz Keldysh Effect (DFKE) is produced and controlled in bulk gallium arsenide by quantum interference without the aid of externally applied fields and is spatially and temporally resolved using ellipsometric pump-probe techniques. The ˜3 THz internal driving field for the DFKE is a transient space-charge field that is associated with a critically damped coherent plasma oscillation produced by oppositely traveling ballistic electron and hole currents that are injected by two-color quantum interference techniques. The relative phase and polarization of the two pump pulses can be used to control the DFKE.
Michielsen, Kristel; Lippert, Thomas; Richter, Marcus; Barbara, Bernard; Miyashita, Seiji; De Raedt, Hans
2010-01-01
We analyze a single-particle Mach-Zehnder interferometer experiment in which the path length of one arm may change (randomly or systematically) according to the value of an external two-valued variable $x$, for each passage of a particle through the interferometer. Quantum theory predicts an interference pattern that is independent of the sequence of the values of $x$. On the other hand, corpuscular models that reproduce the results of quantum optics experiments carried out up to this date sh...
Phase-dependent quantum interference between different pathways in bichromatic harmonic generation
Institute of Scientific and Technical Information of China (English)
Cai Jun; Wang Li-Ming; Qiao Hao-Xue
2009-01-01
This paper studies the harmonic generation of the hydrogen atom subjected to a collinear bichromatic laser field by numerically solving the time-dependent Schr(o)dinger equation using the split-operator pseudo-spectral method.By adding a frequency variation to the additional field,the contributions of different pathways to particular order harmonic generation can be isolated.The quantum interference pattern between harmonic pathways,which influences the harmonic intensity,is found to be either constructive or destructive with respect to different relative phase of the two field components.Detailed description of up to the 35th-order harmonics and the harmonic pathways for a wide range of field parameters is presented.
Magnetoconductivity due to quantum interference in strongly underdoped YBa2Cu3Ox
International Nuclear Information System (INIS)
We report magnetoconductivity measurements on YBa2Cu3Ox (x=6.25 and 6.36) single crystals. Our main result is that both the in-plane Δσab and out-of-plane Δσc magnetoconductivities exhibit the field dependence characteristic of ''two-dimensional'' quantum interference in applied magnetic fields H||c. Namely, Δσc,ab∝lnH/H0>0, with Δσc/σc substantially greater than Δσab/σab. We interpret this result as an evidence of interlayer incoherence in these crystals, so that the phase-coherent trajectories are mostly confined to one bilayer
Quantum-interference-enhanced deep sub-Doppler cooling of 39K atoms in gray molasses
Nath, Dipankar; Easwaran, R. Kollengode; Rajalakshmi, G.; Unnikrishnan, C. S.
2013-11-01
We report enhanced sub-Doppler cooling of the bosonic atoms of 39K facilitated by formation of dark states with the cooling and repumping lasers tuned to the Raman resonance in Λ configuration near the D1 transition. A temperature of about 12 μK and phase-space density >2×10-5 is achieved in the two-stage D2-D1 molasses and spans a very large parameter region where quantum interference persists robustly. We also present results on enhanced radiation heating with a subnatural linewidth (0.07Γ) and a signature Fano-like profile of a coherently driven three-level atomic system. The optical Bloch equations relevant for the three-level atom in a bichromatic light field are solved with the method of continued fractions to show that cooling occurs only for a small velocity class of atoms, emphasizing the need for precooling in the D2 molasses stage.
Alignment-stabilized interference filter-tuned external-cavity quantum cascade laser.
Kischkat, Jan; Semtsiv, Mykhaylo P; Elagin, Mikaela; Monastyrskyi, Grygorii; Flores, Yuri; Kurlov, Sergii; Peters, Sven; Masselink, W Ted
2014-12-01
A passively alignment-stabilized external cavity quantum cascade laser (EC-QCL) employing a "cat's eye"-type retroreflector and an ultra-narrowband transmissive interference filter for wavelength selection is demonstrated and experimentally investigated. Compared with conventional grating-tuned ECQCLs, the setup is nearly two orders of magnitude more stable against misalignment of the components, and spectral fluctuation is reduced by one order of magnitude, allowing for a simultaneously lightweight and fail-safe construction, suitable for applications outdoors and in space. It also allows for a substantially greater level of miniaturization and cost reduction. These advantages fit in well with the general properties of modern QCLs in the promise to deliver useful and affordable mid-infrared-light sources for a variety of spectroscopic and imaging applications. PMID:25490621
Improved superconducting quantum interference device magnetometer for low cross talk operation
Granata, C.; Vettoliere, A.; Russo, M.
2006-05-01
A fully integrated dc-SQUID (superconducting quantum interference device) magnetometer based on niobium technology including a new feedback coil design is presented. With respect to a standard SQUID design, the new feedback coil design was optimized in order to reduce the mutual inductance between neighbors and to increase the coupling with the pickup coil of the SQUID itself. In such a way, it is possible to reduce cross talk due to both the feedback coil and wires. Experimental results for the characterization of the device and the cross talk measurements are reported. The measurements have been performed in liquid helium using a low noise readout electronics specifically designed for large multichannel SQUID-based instruments. The experimental data show a substantial reduction of cross talk between neighboring sensors with respect to a traditional feedback coil. Furthermore, the new feedback coil system does not introduce any noise degradation.
Exploring quantum interference in heteroatom-substituted graphene-like molecules
Sangtarash, Sara; Sadeghi, Hatef; Lambert, Colin J.
2016-07-01
If design principles for controlling quantum interference in single molecules could be elucidated and verified, then this will lay the foundations for exploiting such effects in nanoscale devices and thin-film materials. When the core of a graphene-like polyaromatic hydrocarbon (PAH) is weakly coupled to external electrodes by atoms i and j, the single-molecule electrical conductance σij depends on the choice of connecting atoms i,j. Furthermore, provided the Fermi energy is located between the HOMO and LUMO, conductance ratios σij/σlm corresponding to different connectivities i,j and l,m are determined by quantum interference within the PAH core. In this paper, we examine how such conductance ratios change when one of the carbon atoms within the `parent' PAH core is replaced by a heteroatom to yield a `daughter' molecule. For bipartite parental cores, in which odd-numbered sites are connected to even-numbered sites only, the effect of heteroatom substitution onto an odd-numbered site is summarized by the following qualitative rules: (a) when i and j are odd, both parent and daughter have low conductances, (b) when i is odd and j is even, or vice versa both parent and daughter have high conductances and (c) when i,j are both even, the parent has a low conductance and the daughter a high conductance. These rules are verified by comparison with density-functional calculations on naphthalene, anthracene, pyrene and anthanthrene cores connected via two different anchor groups to gold electrodes.If design principles for controlling quantum interference in single molecules could be elucidated and verified, then this will lay the foundations for exploiting such effects in nanoscale devices and thin-film materials. When the core of a graphene-like polyaromatic hydrocarbon (PAH) is weakly coupled to external electrodes by atoms i and j, the single-molecule electrical conductance σij depends on the choice of connecting atoms i,j. Furthermore, provided the Fermi energy is
Optical transmission modules for multi-channel superconducting quantum interference device readouts
International Nuclear Information System (INIS)
We developed an optical transmission module consisting of 16-channel analog-to-digital converter (ADC), digital-noise filter, and one-line serial transmitter, which transferred Superconducting Quantum Interference Device (SQUID) readout data to a computer by a single optical cable. A 16-channel ADC sent out SQUID readouts data with 32-bit serial data of 8-bit channel and 24-bit voltage data at a sample rate of 1.5 kSample/s. A digital-noise filter suppressed digital noises generated by digital clocks to obtain SQUID modulation as large as possible. One-line serial transmitter reformed 32-bit serial data to the modulated data that contained data and clock, and sent them through a single optical cable. When the optical transmission modules were applied to 152-channel SQUID magnetoencephalography system, this system maintained a field noise level of 3 fT/√Hz @ 100 Hz
Quantum-mechanical interference in charge exchange between hydrogen and graphene-like surfaces
International Nuclear Information System (INIS)
The neutral to negative charge fluctuation of a hydrogen atom in front of a graphene surface is calculated by using the Anderson model within an infinite intra atomic Coulomb repulsion approximation. We perform an ab initio calculation of the Anderson hybridization function that allows investigation of the effect of quantum-mechanical interference related to the Berry phase inherent to the graphene band structure. We find that consideration of the interaction of hydrogen on top of many C atoms leads to a marked asymmetry of the imaginary part of the hybridization function with respect to the Fermi level. Consequently, Fano factors larger than one and strongly dependent on the energy around the Fermi level are predicted. Moreover, the suppression of the hybridization for energies above the Fermi level can explain the unexpected large negative ion formation measured in the scattering of protons by graphite-like surfaces. (paper)
Basic concepts of quantum interference and electron transport in single-molecule electronics.
Lambert, C J
2015-02-21
This tutorial outlines the basic theoretical concepts and tools which underpin the fundamentals of phase-coherent electron transport through single molecules. The key quantity of interest is the transmission coefficient T(E), which yields the electrical conductance, current-voltage relations, the thermopower S and the thermoelectric figure of merit ZT of single-molecule devices. Since T(E) is strongly affected by quantum interference (QI), three manifestations of QI in single-molecules are discussed, namely Mach-Zehnder interferometry, Breit-Wigner resonances and Fano resonances. A simple MATLAB code is provided, which allows the novice reader to explore QI in multi-branched structures described by a tight-binding (Hückel) Hamiltonian. More generally, the strengths and limitations of materials-specific transport modelling based on density functional theory are discussed. PMID:25255961
Normal metal tunnel junction-based superconducting quantum interference proximity transistor
Energy Technology Data Exchange (ETDEWEB)
D' Ambrosio, Sophie, E-mail: sophie.dambrosio@nano.cnr.it; Meissner, Martin; Blanc, Christophe; Ronzani, Alberto; Giazotto, Francesco, E-mail: francesco.giazotto@sns.it [NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore, I-56127 Pisa (Italy)
2015-09-14
We report the fabrication and characterization of an alternative design for a superconducting quantum interference proximity transistor (SQUIPT) based on a normal metal (N) probe. The absence of direct Josephson coupling between the proximized metal nanowire and the N probe allows us to observe the full modulation of the wire density of states around zero voltage and current via the application of an external magnetic field. This results into a drastic suppression of power dissipation which can be as low as a few ∼10{sup −17} W. In this context, the interferometer allows an improvement of up to four orders of magnitude with respect to earlier SQUIPT designs and makes it ideal for extra-low power cryogenic applications. In addition, the N-SQUIPT has been recently predicted to be the enabling candidate for the implementation of coherent caloritronic devices based on proximity effect.
Cosmic Structure as the Quantum Interference of a Coherent Dark Wave
Schive, Hsi-Yu; Broadhurst, Tom
2014-01-01
The conventional cold, particle interpretation of dark matter (CDM) still lacks laboratory support and struggles with the basic properties of common dwarf galaxies, which have surprisingly uniform central masses and shallow density profiles. In contrast, galaxies predicted by CDM extend to much lower masses, with steeper, singular profiles. This tension motivates cold, wavelike dark matter ($\\psi$DM) composed of a non-relativistic Bose-Einstein condensate, so the uncertainty principle counters gravity below a Jeans scale. Here we achieve the first cosmological simulations of this quantum state at unprecedentedly high resolution capable of resolving dwarf galaxies, with only one free parameter, $\\bf{m_B}$, the boson mass. We demonstrate the large scale structure of this $\\psi$DM simulation is indistinguishable from CDM, as desired, but differs radically inside galaxies. Connected filaments and collapsed haloes form a large interference network, with gravitationally self-bound solitonic cores inside every galax...
Okano, Masayuki; Lim, Hwan Hong; Okamoto, Ryo; Nishizawa, Norihiko; Kurimura, Sunao; Takeuchi, Shigeki
2015-12-01
Quantum information technologies harness the intrinsic nature of quantum theory to beat the limitations of the classical methods for information processing and communication. Recently, the application of quantum features to metrology has attracted much attention. Quantum optical coherence tomography (QOCT), which utilizes two-photon interference between entangled photon pairs, is a promising approach to overcome the problem with optical coherence tomography (OCT): As the resolution of OCT becomes higher, degradation of the resolution due to dispersion within the medium becomes more critical. Here we report on the realization of 0.54 μm resolution two-photon interference, which surpasses the current record resolution 0.75 μm of low-coherence interference for OCT. In addition, the resolution for QOCT showed almost no change against the dispersion of a 1 mm thickness of water inserted in the optical path, whereas the resolution for OCT dramatically degrades. For this experiment, a highly-efficient chirped quasi-phase-matched lithium tantalate device was developed using a novel ‘nano-electrode-poling’ technique. The results presented here represent a breakthrough for the realization of quantum protocols, including QOCT, quantum clock synchronization, and more. Our work will open up possibilities for medical and biological applications
International Nuclear Information System (INIS)
This paper presents new theoretical results for rotational population patterns in the nuclear SQUID effect. (The term nuclear SQUID is in analogy to the solid-state Superconducting Quantum Interference Devices.) The SQUID effect is an interesting new twist to an old quest to understand Coriolis anti-pairing (CAP) effects in nuclear rotational bands. Two-neutron transfer reaction cross sections among high-spin states have long been touted as more specific CAP probes than other nuclear properties. Heavy projectiles like Sn or Pb generally are recommended to pump the deformed nucleus to as high spin as possible for transfer. The interference and sign reversal of 2n transfer amplitudes at high spin, as predicted in the early SQUID work imposes the difficult requirement of Coulomb pumping to near back-bending spins at closest approach. For Pb on rare earths we find a dramatic departure from sudden-approximation, so that the population depression occurs as low as final spin 10h. 14 refs., 8 figs
The quantum interference effects in the Sc II 4247 $\\AA$ line of the Second Solar Spectrum
Smitha, H N; Stenflo, J O; Bianda, M; Ramelli, R
2014-01-01
The Sc II 4247 $\\AA$ line formed in the chromosphere is one of the lines well known, like the Na I D$_2$ and Ba II D$_2$, for its prominent triple peak structure in $Q/I$ and the underlying quantum interference effects governing it. In this paper, we try to study the nature of this triple peak structure using the theory of $F$-state interference including the effects of partial frequency redistribution (PRD) and radiative transfer (RT). We compare our results with the observations taken in a quiet region near the solar limb. In spite of accounting for PRD and RT effects it has not been possible to reproduce the observed triple peak structure in $Q/I$. While the two wing PRD peaks (on either side of central peak) and the near wing continuum can be reproduced, the central peak is completely suppressed by the enhanced depolarization resulting from the hyperfine structure splitting. This suppression remains for all the tested widely different 1D model atmospheres or for any multi-component combinations of them. W...
Michielsen, Kristel; Lippert, Thomas; Richter, Marcus; Barbara, Bernard; Miyashita, Seiji; De Raedt, Hans
2012-01-01
We analyze a single-particle Mach-Zehnder interferometer experiment in which the path length of one arm may change (randomly or systematically) according to the value of an external two-valued variable x, for each passage of a particle through the interferometer. Quantum theory predicts an interfere
DEFF Research Database (Denmark)
Nozaki, Daijiro; Avdoshenko, Stanislav M.; Sevincli, Haldun;
2013-01-01
Recently the interest in quantum interference (QI) phenomena in molecular devices (molecular junctions) has been growing due to the unique features observed in the transmission spectra. In order to design single molecular devices exploiting QI effects as desired, it is necessary to provide simple...
Kimura, Tadamasa; Nambu, Yoshihiro; Hatanaka, Takaaki; Tomita, Akihisa; Kosaka, Hideo; Nakamura, Kazuo
2004-01-01
We have demonstrated single-photon interference over 150 km using time-division interferometers for quantum cryptography, which were composed of two integrated-optic asymmetric Mach-Zehnder interferometers, and balanced gated-mode photon detectors. The observed fringe visibility was more than 80% after 150-km transmission.
DEFF Research Database (Denmark)
García-Vela, Alberto; Henriksen, Niels Engholm
2016-01-01
The role played by quantum interference in the laser phase modulation coherent control of photofragment distributions in the weak-field regime is investigated in detail in this work. The specific application involves realistic wave packet calculations of the transient vibrational populations of t...
Institute of Scientific and Technical Information of China (English)
LI Yong-Qing; SONG Peng; CHEN Yue-Hui; WANG Wei-Li; MA Feng-Cai
2005-01-01
In our previous theoretical studies [Meng-Tao Sun, Yong-Qing Lee, and Feng-Cai Ma, Chem. Phys.Lett. 371 (2003) 342], we have reported the quantum interference on collision-induced rotational energy transfer on CO (A1П, v = 3) with inert gases, which originates from the difference between the two A-related collision potential energy surfaces. The interference angle, which measures the degree of coherence, is presented in this paper. Based on the time-dependent first order Born approximation, taking into account the anisotropic Lennard-Jones interaction potentials, the relation of the interference angle with the factors, including experimental temperature, partner, and rotational quantum number, are obtained. The changing tendencies with them are discussed. This theoretical model is important to understanding and performing this kind of experiment.
Transmission resonances in a semiconductor-superconductor junction quantum interference structure
International Nuclear Information System (INIS)
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
International Nuclear Information System (INIS)
The excitation wavelength dependence of the anomalous circular photogalvanic effect (ACPGE) current arising from the reciprocal spin Hall effect (RSHE) in undoped InGaAs/AlGaAs quantum wells is measured under normal incidence of circularly polarized light at room temperature. We found that the spot location with the maximum ACPGE current is wavelength independent. And the normalized ACPGE current decreases at smaller wavelengths, which can be attributed to the sharp decrease of the spin relaxation time (τs) and the hot electron relaxation time (τ1) at smaller wavelengths. The study of the excitation wavelength dependence of ACPGE current is a good supplement to the in-depth investigation of RSHE
Chelkowski, Szczepan; Bredtmann, Timm; Bandrauk, André D.
2013-09-01
Laser pump-probe schemes are explored numerically from a molecular time-dependent Schrödinger equation for monitoring attosecond electron motion by high-order-harmonic generation (HHG) from a coherent superposition of electronic states. Varying the time delay between the probe and pump pulse on an attosecond time scale alters the HHG signal, leading to universal interference patterns. By using an extended three-step recollision model, we show that various regular interference patterns in the HHG spectra, including continuous harmonic frequency redshifts as a function of pump-probe delay, are related to interference between specific pairs of short or long quantum orbits. For small excited-state population (regime A), interferences are controlled by electron-tunneling times, whereas for equal populations (regime B), recollision time control dominates thus allowing for control of the HHG process by the pump-probe delay time and by electron-state populations. We show that each specific pattern is closely related to the interference between pairs of specific (short or long) quantum orbits originating from a specific electron bound state. One can generate a specific pattern by varying the populations in the coherent superposition, the laser intensity, wavelength, and ionization potential of the electronic states.
Shi, Y L; Wu, J X; Zhu, C J; Xu, J P; Yang, Y P
2015-01-01
We examine a Kerr phase gate in a semiconductor quantum well structure based on the tunnelling interference effect. We show that there exist a specific signal field detuning, at which the absorption/amplification of the probe field will be eliminated with the increase of the tunnelling interference. Simultaneously, the probe field will acquire a -\\pi phase shift at the exit of the medium. We demonstrate with numerical simulations that a complete 180^\\circ phase rotation for the probe field at the exit of the medium is achieved, which may result in many applications in information science and telecommunication.
International Nuclear Information System (INIS)
We develop magnetic metallic contaminant detectors using high-temperature superconducting quantum interference devices (HTS-SQUIDs) for industrial products. Finding ultra-small metallic contaminants is an important issue for manufacturers producing commercial products such as lithium ion batteries. If such contaminants cause damages, the manufacturer of the product suffers a big financial loss due to having to recall the faulty products. Previously, we described a system for finding such ultra-small particles in food. In this study, we describe further developments of the system, for the reduction of the effect of the remnant field of the products, and we test the parallel magnetization of the products to generate the remnant field only at both ends of the products. In addition, we use an SQUID gradiometer in place of the magnetometer to reduce the edge effect by measuring the magnetic field gradient. We test the performances of the system and find that tiny iron particles as small as 50 × 50 μm2 on the electrode of a lithium ion battery could be clearly detected. This detection level is difficult to achieve when using other methods. (cross-disciplinary physics and related areas of science and technology)
Quantum interference effects on the noise power in the CNT/aGNR/CNT junction
International Nuclear Information System (INIS)
Based on the tight-binding model and a generalized Green's function method in Landauer–Büttiker formalism, the effects of quantum interference (QI) on the noise power and Fano factor of an armchair graphene nanoribbon (aGNR) sandwiched between an infinite single-walled carbon nanotube (SWCNT) as a CNT/aGNR/CNT system are numerically investigated. Changing electrode contact positions and applying magnetic field are considered as two sources of QI. We have found different Fano-resonance and anti-resonance peaks on the transmission probability in the presence of QI sources that show profound effects on the current–voltage characteristics and noise power. Our results also show that the shot noise characteristic, either in the Poisson limit (F = 1) or sub-Poisson limit (F<1), and also maximum value of the Fano factor, strongly depend on the aGNR to CNT electrodes contact positions and the magnetic field strength. These results can be useful for designing future nano-electronic devices. (paper)
Close relation between quantum interference in molecular conductance and diradical existence.
Tsuji, Yuta; Hoffmann, Roald; Strange, Mikkel; Solomon, Gemma C
2016-01-26
An empirical observation of a relationship between a striking feature of electronic transmission through a π-system, destructive quantum interference (QI), on one hand, and the stability of diradicals on the other, leads to the proof of a general theorem that relates the two. Subject to a number of simplifying assumptions, in a π-electron system, QI occurs when electrodes are attached to those positions of an N-carbon atom N-electron closed-shell hydrocarbon where the matrix elements of the Green's function vanish. These zeros come in two types, which are called easy and hard. Suppose an N+2 atom, N+2 electron hydrocarbon is formed by substituting 2 CH2 groups at two atoms, where the electrodes were. Then, if a QI feature is associated with electrode attachment to the two atoms of the original N atom system, the resulting augmented N+2 molecule will be a diradical. If there is no QI feature, i.e., transmission of current is normal if electrodes are attached to the two atoms, the resulting hydrocarbon will not be a diradical but will have a classical closed-shell electronic structure. Moreover, where a diradical exists, the easy zero is associated with a nondisjoint diradical, and the hard zero is associated with a disjoint one. A related theorem is proven for deletion of two sites from a hydrocarbon. PMID:26755578
Detection of bacteria in suspension using a superconducting Quantum interference device
International Nuclear Information System (INIS)
We demonstrate a technique for detecting magnetically-labeled Listeria monocytogenes and for measuring the binding rate between antibody-linked magnetic particles and bacteria. This assay, which is both sensitive and straightforward to perform, can quantify specific bacteria in a sample without the need to immobilize the bacteria or wash away unbound magnetic particles. In the measurement, we add 50 nm diameter superparamagnetic particles, coated with antibodies, to a liquid sample containing L. monocytogenes. We apply a pulsed magnetic field to align the magnetic dipole moments and use a high transition temperature Superconducting Quantum Interference Device (SQUID), an extremely sensitive detector of magnetic flux, to measure the magnetic relaxation signal when the field is turned off. Unbound particles randomize direction by Brownian rotation too quickly to be detected. In contrast, particles bound to L. monocytogenes are effectively immobilized and relax in about 1 s by rotation of the internal dipole moment. This Neel relaxation process is detected by the SQUID. The measurements indicate a detection limit of (5.6 ± 1.1) x 106 L. monocytogenes for a 20 (micro)L sample volume. If the sample volume were reduced to 1 nL, we estimate that the detection limit could be improved to 230 ± 40 L. monocytogenes cells. Time-resolved measurements yield the binding rate between the particles and bacteria
Development of a Cryostat to Characterize Nano-scale Superconducting Quantum Interference Devices
Longo, Mathew; Matheny, Matthew; Knudsen, Jasmine
2016-03-01
We have designed and constructed a low-noise vacuum cryostat to be used for the characterization of nano-scale superconducting quantum interference devices (SQUIDs). Such devices are very sensitive to magnetic fields and can measure changes in flux on the order of a single electron magnetic moment. As a part of the design process, we calculated the separation required between the cryogenic preamplifier and superconducting magnet, including a high-permeability magnetic shield, using a finite-element model of the apparatus. The cryostat comprises a vacuum cross at room temperature for filtered DC and shielded RF electrical connections, a thin-wall stainless steel support tube, a taper-sealed cryogenic vacuum can, and internal mechanical support and wiring for the nanoSQUID. The Dewar is modified with a room-temperature flange with a sliding seal for the cryostat. The flange supports the superconducting 3 Tesla magnet and thermometry wiring. Upon completion of the cryostat fabrication and Dewar modifications, operation of the nanoSQUIDs as transported from our collaborator's laboratory in Israel will be confirmed, as the lead forming the SQUID is sensitive to oxidation and the SQUIDs must be shipped in a vacuum container. After operation of the nanoSQUIDs is confirmed, the primary work of characterizing their high-speed properties will begin. This will include looking at the measurement of relaxation oscillations at high bandwidth in comparison to the theoretical predictions of the current model.
Parasitic effects in superconducting quantum interference device-based radiation comb generators
Bosisio, R.; Giazotto, F.; Solinas, P.
2015-12-01
We study several parasitic effects on the implementation of a Josephson radiation comb generator based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. This system can be used as a radiation generator similarly to what is done in optics and metrology, and allows one to generate up to several hundreds of harmonics of the driving frequency. First we take into account how the assumption of a finite loop geometrical inductance and junction capacitance in each SQUID may alter the operation of the devices. Then, we estimate the effect of imperfections in the fabrication of an array of SQUIDs, which is an unavoidable source of errors in practical situations. We show that the role of the junction capacitance is, in general, negligible, whereas the geometrical inductance has a beneficial effect on the performance of the device. The errors on the areas and junction resistance asymmetries may deteriorate the performance, but their effect can be limited to a large extent by a suitable choice of fabrication parameters.
Individual Mammalian Cell Magnetic Measurements with a Superconducting Quantum Interference Device
Palmstrom, Johanna C.; Brewer, Kimberly; Tee, Sui Seng; Theis, Eric; Rutt, Brian; Moler, Kathryn A.
2015-03-01
Magnetism can be introduced into otherwise nonmagnetic cells by the uptake of superparamagnetic iron oxide (SPIO) nanoparticles. SPIO nanoparticles are used in numerous biomedical applications including cellular therapies and targeted drug delivery. Currently there are few tools capable of characterizing individual magnetic nanoparticles and the magnetic properties of individual mammalian cells loaded with SPIO. Our scanning superconducting quantum interference devices (SQUIDs) are good candidates for these measurements due to their high sensitivity to magnetic dipole moments (approx. 200 μb/ √Hz) In this study, we use a scanning SQUID to image the magnetic flux from SPIO loaded H1299 lung cancer cells. We find that the magnetic moment spatially varies inside the cell with each cell having a unique distribution of moments. We also correlate these magnetic images with optical and scanning electron microscope images. These results show that the SQUID is a useful tool for imaging biological magnetism. The visualization of single cell magnetism and the quantification of magnetic dipole moments in magnetically labeled cells can be used to optimize conventional biological magnetic imaging techniques, such as MRI.
High-Tc superconducting quantum interference filters (SQIFs) made by ion irradiation
Ouanani, S.; Kermorvant, J.; Ulysse, C.; Malnou, M.; Lemaître, Y.; Marcilhac, B.; Feuillet-Palma, C.; Bergeal, N.; Crété, D.; Lesueur, J.
2016-09-01
Superconducting quantum interference filters (SQIFs) are arrays of superconducting loops of different sizes including Josephson junctions (JJ). For a random distribution of sizes, they present a non-periodic response to an applied magnetic field, with a large transfer function and a magnetic field sensitivity potentially improved with respect to that of a single SQUID. Such properties make SQIFs interesting devices to detect the magnetic component of electromagnetic waves at microwave frequencies. We have used the highly scalable technique of ion irradiation to make SQUIDs and SQIFs based on commercial YBa2Cu3O7 films, and studied their properties. Both display optimal performance as a function of temperature and bias current, that can be understood in the frame of numerical simulations that we developed. The role of asymmetries and dispersion in JJ characteristics (routinely found in high Tc superconductors technologies) is also studied. We have found that none of them impede the existence of a SQIF effect but both play a role on the emergence of the optimal point. We finally present results on SQIF made with 2000 SQUIDs in series, showing a transfer function {{d}}V/{{d}}B∼ 1000V/T.
International Nuclear Information System (INIS)
The ultra high sensitivity exhibited by Superconducting Quantum Interference Device (SQUIDs) could be the key to explore new field of nanoscience such as the investigation of small cluster of elementary magnetic moments. In this paper, an ultra high sensitive niobium nanoSQUID based on submicron Josephson tunnel junction is presented. It has been fabricated in a vertical configuration by using a three-dimensional focused ion beam sculpting technique. In such a configuration, the nanosensor loop (area of 0.25 μm2) is perpendicular to the substrate plane allowing to drastically reduce the spurious effects of the external magnetic field employed to excite the nano-objects under investigation. Main device characteristics have been measured at T=4.2 K by using a low noise readout electronics. Due to high voltage responsivity, the nanosensor has exhibited a spectral density of the magnetic flux noise as low as 1.6 μΦ0/Hz1/2. - Highlights: • Magnetic nano-sensor including sub-micrometric Josephson tunnel junctions. • Vertical design that reduces the parasitic effect of exciting magnetic field. • Non-hysteretic behavior allowing the use as magnetic flux-to-voltage transducer. • High intrinsic responsivity due to high current modulation depth. • Low intrinsic magnetic flux noise leading high spin sensitivity
International Nuclear Information System (INIS)
This doctoral thesis was aimed at establishing a set-up with high-temperature superconductor (HTS) radio-frequency (rf) superconducting quantum interference device (SQUID) technology for the detection of magnetic nanoparticles and in particular for testing applications of magnetic nanoparticle immunoassays. It was part of the EU-project ''Biodiagnostics'' running from 2005 to 2008. The method of magnetic binding assays was developed as an alternative to other methods of concentration determination like enzyme linked immunosorbent assay (ELISA), or fluorescent immunoassay. The ELISA has sensitivities down to analyte-concentrations of pg/ml. Multiple incubation and washing steps have to be performed for these techniques, the analyte has to diffuse to the site of binding. The magnetic assay uses magnetic nanoparticles as markers for the substance to be detected. It is being explored by current research and shows similar sensitivity compared to ELISA but in contrast - does not need any washing and can be read out directly after binding - can be applied in solution with opaque media, e.g. blood or muddy water - additionally allows magnetic separation or concentration - in combination with small magnetoresistive or Hall sensors, allows detection of only a few particles or even single beads. For medical or environmental samples, maybe opaque and containing a multitude of substances, it would be advantageous to devise an instrument, which allows to be read out quickly and with high sensitivity. Due to the mentioned items the magnetic assay might be a possibility here.
Energy Technology Data Exchange (ETDEWEB)
Pretzell, Alf
2012-07-01
This doctoral thesis was aimed at establishing a set-up with high-temperature superconductor (HTS) radio-frequency (rf) superconducting quantum interference device (SQUID) technology for the detection of magnetic nanoparticles and in particular for testing applications of magnetic nanoparticle immunoassays. It was part of the EU-project ''Biodiagnostics'' running from 2005 to 2008. The method of magnetic binding assays was developed as an alternative to other methods of concentration determination like enzyme linked immunosorbent assay (ELISA), or fluorescent immunoassay. The ELISA has sensitivities down to analyte-concentrations of pg/ml. Multiple incubation and washing steps have to be performed for these techniques, the analyte has to diffuse to the site of binding. The magnetic assay uses magnetic nanoparticles as markers for the substance to be detected. It is being explored by current research and shows similar sensitivity compared to ELISA but in contrast - does not need any washing and can be read out directly after binding - can be applied in solution with opaque media, e.g. blood or muddy water - additionally allows magnetic separation or concentration - in combination with small magnetoresistive or Hall sensors, allows detection of only a few particles or even single beads. For medical or environmental samples, maybe opaque and containing a multitude of substances, it would be advantageous to devise an instrument, which allows to be read out quickly and with high sensitivity. Due to the mentioned items the magnetic assay might be a possibility here.
International Nuclear Information System (INIS)
In this article, we describe an ultrahigh vacuum (UHV) compatible superconducting quantum interference device (SQUID) magnetometer system for investigations of surface, interface, and thin film magnetism. This system provides a new capability for a commercial SQUID magnetometer to characterize freshly deposited thin film samples transported from a separate molecular-beam epitaxy deposition facility without breaking vacuum. Magnetic measurements can be performed over a wide range of temperatures down to 4.2 K in applied magnetic fields as high as 1 T, and under a variable vacuum environment in which pressures as low as 10-10 Torr can be achieved. The combination of the extremely high sensitivity of the SQUID for magnetic measurements with UHV analysis techniques offers the unique capability for films to be prepared, processed, and characterized repeatedly without substantial contamination. The capabilities of the UHV-SQUID magnetometer system are demonstrated by in situ measurements of the magnetic properties of Co/CoO bilayered thin films grown on Si(100) single-crystal substrates by electron-beam evaporation. copyright 1995 American Institute of Physics
Giriat, Gaétan; Wang, Weiwei; Attfield, J. Paul; Huxley, Andrew D.; Kamenev, Konstantin V.
2010-07-01
We have developed a miniature diamond anvil cell for magnetization measurements in a widely used magnetic property measurement system commercial magnetometer built around a superconducting quantum interference device. The design of the pressure cell is based on the turnbuckle principle in which force can be created and maintained by rotating the body of the device while restricting the counterthreaded end-nuts to translational movement. The load on the opposed diamond anvils and the sample between them is generated using a hydraulic press. The load is then locked by rotating the body of the cell with respect to the end-nuts. The dimensions of the pressure cell have been optimized by use of finite element analysis. The cell is approximately a cylinder 7 mm long and 7 mm in diameter and weighs only 1.5 g. Due to its small size the cell thermalizes rapidly. It is capable of achieving pressures in excess of 10 GPa while allowing measurements to be performed with the maximum sensitivity of the magnetometer. The performance of the pressure cell is illustrated by a high pressure magnetic study of Mn3[Cr(CN)6]2ṡxH2O Prussian blue analog up to 10.3 GPa.
Advances in biomagnetic research using high- T{sub c} superconducting quantum interference devices
Energy Technology Data Exchange (ETDEWEB)
Yang, Hong-Chang [Department of Physics/Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan (China); Horng, Herng-Er; Yang, S Y [Institute of Electro-Optical Science and Technology, National Taiwan Normal University, Taipei 116, Taiwan (China); Liao, Shu-Hsien, E-mail: hcyang@phys.ntu.edu.t [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China)
2009-09-15
This review reports the advances of biomagnetic research using high- T{sub c} superconducting quantum interference devices (SQUIDs). It especially focuses on SQUID-detected magnetocardiography (MCG), magnetically labeled immunoassays (MLIs) as well as nuclear magnetic resonance and imaging (NMR/MRI). The progress in MCG that scientists have made and the encountered challenges are discussed here. This study includes the early detection of the electromagnetic change in cardiac activity in animal studies of hypercholesterolemic rabbits, which suggests the possibility of early diagnosis of cardiac disease in clinical applications. The progress on MLIs using measurements of remanence, magnetic relaxation and magnetic susceptibility reduction is presented. The wash-free immunomagnetic reduction shows both high sensitivity and high specificity. NMR/MRI of high spectral resolution and of high signal-to-noise ratio are addressed and discussed. The proton-phosphate J-coupling of trimethyl phosphate ((CH{sub 3}){sub 3}PO{sub 4}) in one shot in microtesla fields is demonstrated. The prospects of biomagnetic applications are addressed. (topical review)
Vettoliere, A.; Granata, C.; Ruggiero, B.; Russo, M.
Magnetometers based on Superconducting Quantum Interference Device (SQUID) are widely employed in high sensitivity magnetometry. In particular, new multichannel systems for biomagnetic applications require many sensors which are very close to each other giving the crosstalk disturbance between the neighboring channel. Here, we present experimental results about a fully integrated dc-SQUID magnetometer, based on niobium technology, having a suitable design which allows to reduce crosstalk due to both the feedback coil and wires. The crosstalk level measurements relative to a particular arrangement of sensors are reported. In such configuration, four magnetometers are placed over a square board 30 mm in side with a distance between their sensor centers of 14 mm. The measurements have been performed in a 4He cryostat at T = 4.2 K in a flux-locked loop configuration using a readout electronics with a direct coupled scheme. The experimental data have shown a substantial reduction of crosstalk among neighboring sensors with respect to a traditional feedback coil. Furthermore, the field noise measurements have ensured that the new pickup and feedback coils design does not introduce any noise level degradation.
Graf zu Eulenburg, A
1999-01-01
the best balance and gradient sensitivity at 1kHz were 3x10 sup - sup 3 and 222fT/(cm sq root Hz))) respectively. The measured spatial response to a current carrying wire was in good agreement with a theoretical model. A significant performance improvement was obtained with the development of a single layer gradiometer with 13mm baseline, fabricated on 30x10mm sup 2 bicrystals. For such a device, the gradient sensitivity at 1kHz was 50fT/(cm sq root Hz)) and the gradiometer was used successfully for unshielded magnetocardiography. A parasitic effective area compensation scheme was employed with two neighbouring SQUIDs coupled in an opposite sense to the same gradiometer loop. This improved the balance from the intrinsic value of 10 sup - sup 3 to 3x10 sup - sup 5. This thesis describes several aspects of the development of gradiometers using high temperature Superconducting Quantum Interference Devices (SQUID). The pulsed laser deposition of thin films of YBa sub 2 Cu sub 3 O sub 7 sub - subdelta (YBCO) on Sr...
Interference effects in a double quantum dot system with inter-dot Coulomb correlations
International Nuclear Information System (INIS)
Electron transport through a double quantum dot system is studied with the use of the Green function formalism based on the equation of motion method, and an interplay between interference and Coulomb blockade effects due to inter-dot correlations is discussed. A double structure with two Fano resonances (or antiresonances) is found in the conductance spectrum. Fano features are weakly influenced by the presence of Coulomb interaction but the conductance is strongly suppressed in the energy region with the Fermi level in the leads close to the aligned levels of both dots. This Coulomb blockade effect takes place when the coupling between the dots is of repulsive character. On the other hand, the conductance of an artificial molecule with attractive inter-dot coupling is only slightly modified in this energy region. As a sign of the coupling can be easily changed in a presence of an external magnetic field by changes of the magnetic flux there is the possibility to control variations of the conductance, which may be important from the application point of view
International Nuclear Information System (INIS)
In this paper we analyze the influence of the coupled energy sensitivity ϵc(f) of a superconducting quantum interference device (SQUID) on the energy resolution of metallic magnetic calorimeters. From this, we derive an upper limit on the readout noise that still allows for the readout of detectors with sub-eV energy resolution. Furthermore, we present two dc-SQUID designs, namely a first-stage SQUID and an N-SQUID series array, that are suited for the readout of high-resolution detectors. We show that fabricated SQUIDs have a noise performance that is competitive to the best state-of-the-art dc-SQUIDs. For the first-stage SQUIDs, we found a correlation between the 1/f noise exponent α and the 1/f noise prefactor ϵ1/f (1 Hz). Using both kind of SQUIDs we have built a two-stage dc-SQUID configuration. We show that this setup allows for the readout of x-ray detectors with a resolving power E/ΔEFWHM>3000. (paper)
Parasitic effects in superconducting quantum interference device-based radiation comb generators
International Nuclear Information System (INIS)
We study several parasitic effects on the implementation of a Josephson radiation comb generator based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. This system can be used as a radiation generator similarly to what is done in optics and metrology, and allows one to generate up to several hundreds of harmonics of the driving frequency. First we take into account how the assumption of a finite loop geometrical inductance and junction capacitance in each SQUID may alter the operation of the devices. Then, we estimate the effect of imperfections in the fabrication of an array of SQUIDs, which is an unavoidable source of errors in practical situations. We show that the role of the junction capacitance is, in general, negligible, whereas the geometrical inductance has a beneficial effect on the performance of the device. The errors on the areas and junction resistance asymmetries may deteriorate the performance, but their effect can be limited to a large extent by a suitable choice of fabrication parameters
Energy Technology Data Exchange (ETDEWEB)
Granata, Carmine, E-mail: c.granata@cib.na.cnr.it [Istituto di Cibernetica “E. Caianiello” del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Napoli) (Italy); Vettoliere, Antonio [Istituto di Cibernetica “E. Caianiello” del Consiglio Nazionale delle Ricerche, I-80078 Pozzuoli (Napoli) (Italy); Fretto, Matteo; Leo, Natascia De; Vincenzo, Lacquaniti [Istituto Nazionale di Ricerca Metrologica, Torino (Italy)
2015-06-15
The ultra high sensitivity exhibited by Superconducting Quantum Interference Device (SQUIDs) could be the key to explore new field of nanoscience such as the investigation of small cluster of elementary magnetic moments. In this paper, an ultra high sensitive niobium nanoSQUID based on submicron Josephson tunnel junction is presented. It has been fabricated in a vertical configuration by using a three-dimensional focused ion beam sculpting technique. In such a configuration, the nanosensor loop (area of 0.25 μm{sup 2}) is perpendicular to the substrate plane allowing to drastically reduce the spurious effects of the external magnetic field employed to excite the nano-objects under investigation. Main device characteristics have been measured at T=4.2 K by using a low noise readout electronics. Due to high voltage responsivity, the nanosensor has exhibited a spectral density of the magnetic flux noise as low as 1.6 μΦ{sub 0}/Hz{sup 1/2}. - Highlights: • Magnetic nano-sensor including sub-micrometric Josephson tunnel junctions. • Vertical design that reduces the parasitic effect of exciting magnetic field. • Non-hysteretic behavior allowing the use as magnetic flux-to-voltage transducer. • High intrinsic responsivity due to high current modulation depth. • Low intrinsic magnetic flux noise leading high spin sensitivity.
Dobbs, M A; Lueker, M; Aird, K A; Bender, A N; Benson, B A; Bleem, L E; Carlstrom, J E; Chang, C L; Cho, H-M; Clarke, J; Crawford, T M; Crites, A T; Flanigan, D I; de Haan, T; George, E M; Halverson, N W; Holzapfel, W L; Hrubes, J D; Johnson, B R; Joseph, J; Keisler, R; Kennedy, J; Kermish, Z; Lanting, T M; Lee, A T; Leitch, E M; Luong-Van, D; McMahon, J J; Mehl, J; Meyer, S S; Montroy, T E; Padin, S; Plagge, T; Pryke, C; Richards, P L; Ruhl, J E; Schaffer, K K; Schwan, D; Shirokoff, E; Spieler, H G; Staniszewski, Z; Stark, A A; Vanderlinde, K; Vieira, J D; Vu, C; Westbrook, B; Williamson, R
2012-07-01
A technological milestone for experiments employing transition edge sensor bolometers operating at sub-Kelvin temperature is the deployment of detector arrays with 100s-1000s of bolometers. One key technology for such arrays is readout multiplexing: the ability to read out many sensors simultaneously on the same set of wires. This paper describes a frequency-domain multiplexed readout system which has been developed for and deployed on the APEX-SZ and South Pole Telescope millimeter wavelength receivers. In this system, the detector array is divided into modules of seven detectors, and each bolometer within the module is biased with a unique ∼MHz sinusoidal carrier such that the individual bolometer signals are well separated in frequency space. The currents from all bolometers in a module are summed together and pre-amplified with superconducting quantum interference devices operating at 4 K. Room temperature electronics demodulate the carriers to recover the bolometer signals, which are digitized separately and stored to disk. This readout system contributes little noise relative to the detectors themselves, is remarkably insensitive to unwanted microphonic excitations, and provides a technology pathway to multiplexing larger numbers of sensors. PMID:22852677
Detection of bacteria in suspension using a superconducting Quantum interference device
Energy Technology Data Exchange (ETDEWEB)
Grossman, H.L.; Myers, W.R.; Vreeland, V.J.; Alper, J.D.; Bertozzi, C.R.; Clarke, J.
2003-06-09
We demonstrate a technique for detecting magnetically-labeled Listeria monocytogenes and for measuring the binding rate between antibody-linked magnetic particles and bacteria. This assay, which is both sensitive and straightforward to perform, can quantify specific bacteria in a sample without the need to immobilize the bacteria or wash away unbound magnetic particles. In the measurement, we add 50 nm diameter superparamagnetic particles, coated with antibodies, to a liquid sample containing L. monocytogenes. We apply a pulsed magnetic field to align the magnetic dipole moments and use a high transition temperature Superconducting Quantum Interference Device (SQUID), an extremely sensitive detector of magnetic flux, to measure the magnetic relaxation signal when the field is turned off. Unbound particles randomize direction by Brownian rotation too quickly to be detected. In contrast, particles bound to L. monocytogenes are effectively immobilized and relax in about 1 s by rotation of the internal dipole moment. This Neel relaxation process is detected by the SQUID. The measurements indicate a detection limit of (5.6 {+-} 1.1) x 10{sup 6} L. monocytogenes for a 20 {micro}L sample volume. If the sample volume were reduced to 1 nL, we estimate that the detection limit could be improved to 230 {+-} 40 L. monocytogenes cells. Time-resolved measurements yield the binding rate between the particles and bacteria.
Rigorous quantum field theory functional integrals over the p-adics I: anomalous dimensions
Abdesselam, Abdelmalek; Guadagni, Gianluca
2013-01-01
In this article we provide the complete proof of the result announced in arXiv:1210.7717 about the construction of scale invariant non-Gaussian generalized stochastic processes over three dimensional p-adic space. The construction includes that of the associated squared field and our result shows this squared field has a dynamically generated anomalous dimension which rigorously confirms a prediction made more than forty years ago, in an essentially identical situation, by K. G. Wilson. We also prove a mild form of universality for the model under consideration. Our main innovation is that our rigourous renormalization group formalism allows for space dependent couplings. We derive the relationship between mixed correlations and the dynamical systems features of our extended renormalization group transformation at a nontrivial fixed point. The key to our control of the composite field is a partial linearization theorem which is an infinite-dimensional version of the Koenigs Theorem in holomorphic dynamics. Th...
DEFF Research Database (Denmark)
Nozaki, Daijiro; Avdoshenko, Stanislav M.; Sevincli, Haldun; Gutierrez, Rafael; Cuniberti, Gianaurelio
2013-01-01
Recently the interest in quantum interference (QI) phenomena in molecular devices (molecular junctions) has been growing due to the unique features observed in the transmission spectra. In order to design single molecular devices exploiting QI effects as desired, it is necessary to provide simple...... rules for predicting the appearance of QI effects such as anti-resonances or Fano line shapes and for controlling them. In this study, we derive a transmission function of a generic molecular junction with a side group (T-shaped molecular junction) using a minimal toy model. We developed a simple method...... to predict the appearance of quantum interference, Fano resonances or anti- resonances, and its position in the conductance spectrum by introducing a simple graphical representation (parabolic model). Using it we can easily visualize the relation between the key electronic parameters and the...
Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru
2016-05-01
Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large
Liu, Shaopeng; Yang, Wen-Xing; Chuang, You-Lin; Chen, Ai-Xi; Liu, Ang; Huang, Yan; Lee, Ray-Kuang
2014-11-17
We propose and analyze an efficient way to enhance four-wave mixing (FWM) signals in a four-subband semiconductor quantum well via Fano-type interference. By using Schrödinger-Maxwell formalism, we derive explicitly analytical expressions for the input probe pulse and the generated FWM field in linear regime under the steady-state condition. With the aid of interference between two excited subbands tunneling to the common continuum, the efficiency to generate FWM field is found to be significantly enhanced, up to 35%. More interestingly, a linear growth rate in the FWM efficiency is demonstrated as the strength of Fano-type interference increases in presence of the continuum states, which can be maintained for a certain propagation distance (i.e., 50μm). PMID:25402157
García-Vela, Alberto; Henriksen, Niels E
2016-02-14
The role played by quantum interference in the laser phase modulation coherent control of photofragment distributions in the weak-field regime is investigated in detail in this work. The specific application involves realistic wave packet calculations of the transient vibrational populations of the Br2(B,vf) fragment produced upon predissociation of the Ne-Br2(B) complex, which is excited to a superposition of overlapping resonance states using different fixed bandwidth pulses where the linear chirps are varied. The postpulse transient phase modulation effects observed on fragment populations for a long time window are explained in terms of the mechanism of interference between overlapping resonances. A detailed description of how the interference mechanism affects the magnitude and the time window of the phase control effects is also provided. In the light of the results, the conditions to maximize phase modulation control on fragment distributions are discussed. PMID:26799495
The Third Law of Quantum Thermodynamics in the Presence of Anomalous Couplings
Institute of Scientific and Technical Information of China (English)
WANG Chun-Yang; BAO Jing-Dong
2008-01-01
The quantum thermodynamic functions of a hormonic oscillator coupled to a heat bath through velocity dependent coupling are obtained analytically.It is shown that both the free energy and the entropy decay fast with the temperature in relation to that of the usual coupling from.This implies that the veloeity-dependent coupling helps to ensure the third law of thermodynamics.
Varlet, Anastasia; Bischoff, Dominik; Simonet, Pauline; Watanabe, Kenji; Taniguchi, Takashi; Ihn, Thomas; Ensslin, Klaus; Mucha-Kruczyński, Marcin; Fal'ko, Vladimir I
2014-09-12
Bilayer graphene is a unique system where both the Fermi energy and the low-energy electron dispersion can be tuned. This is brought about by an interplay between trigonal warping and the band gap opened by a transverse electric field. Here, we drive the Lifshitz transition in bilayer graphene to experimentally controllable carrier densities by applying a large transverse electric field to a h-BN-encapsulated bilayer graphene structure. We perform magnetotransport measurements and investigate the different degeneracies in the Landau level spectrum. At low magnetic fields, the observation of filling factors -3 and -6 quantum Hall states reflects the existence of three maxima at the top of the valence-band dispersion. At high magnetic fields, all integer quantum Hall states are observed, indicating that deeper in the valence band the constant energy contours are singly connected. The fact that we observe ferromagnetic quantum Hall states at odd-integer filling factors testifies to the high quality of our sample. This enables us to identify several phase transitions between correlated quantum Hall states at intermediate magnetic fields, in agreement with the calculated evolution of the Landau level spectrum. The observed evolution of the degeneracies, therefore, reveals the presence of a Lifshitz transition in our system. PMID:25259994
Varlet, Anastasia; Bischoff, Dominik; Simonet, Pauline; Watanabe, Kenji; Taniguchi, Takashi; Ihn, Thomas; Ensslin, Klaus; Mucha-Kruczyński, Marcin; Fal'ko, Vladimir I.
2014-09-01
Bilayer graphene is a unique system where both the Fermi energy and the low-energy electron dispersion can be tuned. This is brought about by an interplay between trigonal warping and the band gap opened by a transverse electric field. Here, we drive the Lifshitz transition in bilayer graphene to experimentally controllable carrier densities by applying a large transverse electric field to a h-BN-encapsulated bilayer graphene structure. We perform magnetotransport measurements and investigate the different degeneracies in the Landau level spectrum. At low magnetic fields, the observation of filling factors -3 and -6 quantum Hall states reflects the existence of three maxima at the top of the valence-band dispersion. At high magnetic fields, all integer quantum Hall states are observed, indicating that deeper in the valence band the constant energy contours are singly connected. The fact that we observe ferromagnetic quantum Hall states at odd-integer filling factors testifies to the high quality of our sample. This enables us to identify several phase transitions between correlated quantum Hall states at intermediate magnetic fields, in agreement with the calculated evolution of the Landau level spectrum. The observed evolution of the degeneracies, therefore, reveals the presence of a Lifshitz transition in our system.
Institute of Scientific and Technical Information of China (English)
SUN Jiang; MI Xin; YU Zu-He; JIANG Qian; ZUO Zhan-Chun; WANG Yan-Bang; WU Ling-An; FU Pan-Ming
2004-01-01
@@ Quantum interference may lead to suppression and enhancement of the two-photon resonant nondegenerate fourwave mixing signal in a cascade four-level system. Such phenomena are demonstrated in Ba through inducing atomic coherence between the ground state 6s2 and the doubly excited autoionizing Rydberg state 6pnd. This method can be used as a new spectroscopic tool for measuring the transition dipole moment between two highly excited atomic states.
International Nuclear Information System (INIS)
Recently the interest in quantum interference (QI) phenomena in molecular devices (molecular junctions) has been growing due to the unique features observed in the transmission spectra. In order to design single molecular devices exploiting QI effects as desired, it is necessary to provide simple rules for predicting the appearance of QI effects such as anti-resonances or Fano line shapes and for controlling them. In this study, we derive a transmission function of a generic molecular junction with a side group (T-shaped molecular junction) using a minimal toy model. We developed a simple method to predict the appearance of quantum interference, Fano resonances or anti- resonances, and its position in the conductance spectrum by introducing a simple graphical representation (parabolic model). Using it we can easily visualize the relation between the key electronic parameters and the positions of normal resonant peaks and anti-resonant peaks induced by quantum interference in the conductance spectrum. We also demonstrate Fano and anti-resonance in T-shaped molecular junctions using a simple tight-binding model. This parabolic model enables one to infer on-site energies of T-shaped molecules and the coupling between side group and main conduction channel from transmission spectra.
Universal Fano factor and anomalous I-V characteristics in weakly interacting quantum dots
Souza, André Maurício Conceição de; Macedo, Antônio Murilo Santos
2005-01-01
We study interaction effects in quantum dots coupled to perfectly conducting leads via barriers of arbitrary transparencies and embedded in an electromagnetic environment characterized by a fixed external impedance. Combining a recently proposed renormalization group equation for the semiclassical regime of this system with an extended version of circuit theory, we study the Fano factor and the I-V characteristics in the low-temperature and low-energy regime. The Fano factor exhibits a sequen...
Efimov effect and anomalous transport properties of a quantum Lorentz gas
International Nuclear Information System (INIS)
The Lorentz gas is one of the simplest many-body systems which admits a detailed theoretical analysis still having a meaningful physical interpretation. The author studies a complication for the description of the equilibrium state of a gas due to the so called Efimov effect, being an anomaly of the quantum mechanical three-body system. In statistical mechanical studies concerning the thermodynamic properties of gases it is usually assumed that the constituents interact via short-range potentials, which excludes for instance the Coulomb gas. The author investigates the consequences of the effective long-range behaviour due to the Efimov effect in the three-body sub-systems for a binary gas mixture. In particular problems arise in the cluster expansion of the quantum mechanical partition function where it can readily be shown that the bound-state part of the three-particle contribution diverges logarithmically at the Efimov point. The question is whether this implies the divergence of the complete three particle contribution or not. Some aspects of the non-equilibrium behaviour of the quantum Lorentz gas are studied. (Auth.)
Nano Superconducting Quantum Interference device: A powerful tool for nanoscale investigations
Granata, Carmine; Vettoliere, Antonio
2016-02-01
The magnetic sensing at nanoscale level is a promising and interesting research topic of nanoscience. Indeed, magnetic imaging is a powerful tool for probing biological, chemical and physical systems. The study of small spin cluster, like magnetic molecules and nanoparticles, single electron, cold atom clouds, is one of the most stimulating challenges of applied and basic research of the next years. In particular, the magnetic nanoparticle investigation plays a fundamental role for the modern material science and its relative technological applications like ferrofluids, magnetic refrigeration and biomedical applications, including drug delivery, hyper-thermia cancer treatment and magnetic resonance imaging contrast-agent. Actually, one of the most ambitious goals of the high sensitivity magnetometry is the detection of elementary magnetic moment or spin. In this framework, several efforts have been devoted to the development of a high sensitivity magnetic nanosensor pushing sensing capability to the individual spin level. Among the different magnetic sensors, Superconducting QUantum Interference Devices (SQUIDs) exhibit an ultra high sensitivity and are widely employed in numerous applications. Basically, a SQUID consists of a superconducting ring (sensitive area) interrupted by two Josephson junctions. In the recent years, it has been proved that the magnetic response of nano-objects can be effectively measured by using a SQUID with a very small sensitive area (nanoSQUID). In fact, the sensor noise, expressed in terms of the elementary magnetic moment (spin or Bohr magneton), is linearly dependent on the SQUID loop side length. For this reason, SQUIDs have been progressively miniaturized in order to improve the sensitivity up to few spin per unit of bandwidth. With respect to other techniques, nanoSQUIDs offer the advantage of direct measurement of magnetization changes in small spin systems. In this review, we focus on nanoSQUIDs and its applications. In
Quantum-chemical approach to cohesive properties of metals: Anomalous behaviour of Be
International Nuclear Information System (INIS)
Calculations based upon the incremental scheme, i.e. an expansion of the total correlation energy in terms of one-body, two-body and higher-order contributions, have been performed on a variety of solids with band gaps. Metals require a special treatment. Via an embedding scheme, we can force localization in metallic-like model systems and can mimic the metallic band structure within finite fragments of the solid. This allows for a gradual delocalization towards the infinite crystal within the incremental scheme. Up to now we successfully applied the method to magnesium and group 12 elements where in all cases the ground-state properties agree very well with experiment.The beryllium crystal has the same hcp structure as Mg; the atoms are characterized by closed ns2 shells. At the same time Mg is almost free-electron-like whereas Be, although in general metallic, shows a lower density of states of almost entirely p character at the Fermi energy; that is the reason for the anomalous behavior of Be compared with other group 2 and 12 metals
International Nuclear Information System (INIS)
Anomalous X-ray diffraction was used for the investigation of shape and chemical composition of self-organized PbSe quantum dots covered by PbEuTe capping layers. From reciprocal-space maps of diffracted intensities measured at two energies of the primary radiation, we discriminated the contributions of the dot volumes and the surrounding crystal lattice to the diffracted intensity. We have found that the presence of Eu atoms suppresses the flattening of the dots during their overgrowth
Li, Yuanchang; West, Damien; Huang, Huaqing; Li, Jia; Zhang, S. B.; Duan, Wenhui
2015-11-01
The prospect of a Dirac half metal, a material which is characterized by a band structure with a gap in one spin channel but a Dirac cone in the other, is of both fundamental interest and a natural candidate for use in spin-polarized current applications. However, while the possibility of such a material has been reported based on model calculations [H. Ishizuka and Y. Motome, Phys. Rev. Lett. 109, 237207 (2012), 10.1103/PhysRevLett.109.237207], it remains unclear what material system might realize such an exotic state. Using first-principles calculations, we show that the experimentally accessible Mn-intercalated epitaxial graphene on SiC(0001) transits to a Dirac half metal when the coverage is >1 /3 monolayer. This transition results from an orbital-selective breaking of quasi-two-dimensional inversion symmetry, leading to symmetry breaking in a single spin channel which is robust against randomness in the distribution of Mn intercalates. Furthermore, the inclusion of spin-orbit interaction naturally drives the system into the quantum anomalous Hall (QAH) state. Our results thus not only demonstrate the practicality of realizing the Dirac half metal beyond a toy model, but also open up an avenue to the realization of the QAH effect.
Energy Technology Data Exchange (ETDEWEB)
Duong, Le Quy; Das, Tanmoy; Feng, Y. P.; Lin, Hsin, E-mail: nilnish@gmail.com [Graphene Research Centre and Department of Physics, National University of Singapore, Singapore 117546 (Singapore)
2015-05-07
We study the evolution of quantum anomalous Hall (QAH) effect for a Z{sub 2} topological insulator (TI) thin films in a proximity induced magnetic phase by a realistic layered k·p model with interlayer coupling. We examine three different magnetic configurations in which ferromagnetic (FM) layer(s) is added either from one side (FM-TI), from both sides (FM-TI-FM), or homogeneously distributed (magnetically doped) in a TI slab. We map out the thickness-dependent topological phase diagram under various experimental conditions. The critical magnetic exchange energy for the emergence of QAH effect in the latter two cases decreases monotonically with increasing number of quintuple layers (QLs), while it becomes surprisingly independent of the film thickness in the former case. The gap size of the emergent QAH insulator depends on the non-magnetic “parent” gap of the TI thin film and is tuned by the FM exchange energy, opening a versatile possibility to achieve room-temperature QAH insulator in various topological nanomaterials. Finally, we find that the emergent spin-texture in the QAH effect is very unconventional, non-“hedgehog” type; and it exhibits a chiral out-of-plane spin-flip texture within the same valence band which is reminiscent of dynamical “skyrmion” pattern, except our results are in the momentum space.
Anomalously large spin susceptibility enhancement in n-doped CdMnTe quantum wells
Energy Technology Data Exchange (ETDEWEB)
Ben Cheikh, Z. [Laboratoire Charles Coulomb, UMR 5221, Département Semi-conducteurs, Matériaux et Capteurs, Université Montpellier 2, France and Laboratoire de Physique des Matériaux: Structures et Propriétés, Faculté (Tunisia); Cronenberger, S.; Vladimirova, M.; Scalbert, D. [Laboratoire Charles Coulomb, UMR 5221, Departement Semi-conducteurs, Materiaux et Capteurs, Universite Montpellier 2 (France); Boujdaria, K. [Laboratoire de Physique des Matériaux: Structures et Propriétés, Faculté des Sciences de Bizerte, Université de Carthage, 7021 Zarzouna (Tunisia); Baboux, F.; Perez, F. [Institut des NanoSciences de Paris, CNRS/Université Paris 6, 4 place Jussieu, F-75005 Paris (France); Wojtowicz, T.; Karczewski, G. [Institute of Physics, Polish Academy of Sciences, 02-668 Warsaw (Poland)
2013-12-04
We report on time-resolved Kerr rotation (TRKR) experiments done on n-doped CdMnTe quantum wells (QWs), in the regime where strong coupling between the electron and the Mn spin-flip excitations shows up. It has been proposed previously to deduce the 2D electron gas spin susceptibility from the coupling energy between these spin excitations. Here we measure the coupling energy on a high mobility sample down to very low excitation density, and compare the results with spin-flip Raman scattering (SFRS) on the same sample. The electron spin polarizations measured by TRKR and SFRS are found in relatively good agreement. However the spin susceptibility measured by TRKR exceeds systematically the values predicted by many-body theory. This could be an indication that the two-oscillator model used to describe mixed electron-Mn spin excitations needs to be improved.
Anomalous Interlayer Transport of Quantum Hall Bilayers in the Strongly Josephson-Coupled Regime
Zhang, Ding; Dietsche, Werner; von Klitzing, Klaus
2016-05-01
We investigate Josephson coupling in a closely spaced quantum Hall bilayer. Reduction of the interlayer barrier from the widely used values of 10-12 nm to the present one of 8 nm leads to qualitatively different interlayer transport properties. The breakdown of interlayer coherence can be spatially confined in regions that are smaller than the device size. Such a spatial inhomogeneity depends crucially on the Josephson-coupling strength and can be removed by adding an in-plane magnetic field of about 0.5 T. At higher in-plane fields, the interlayer tunneling I -V curve develops unexpected overshoot features. These results challenge current theoretical understanding and suggest that our bilayer system has entered a previously unexplored regime.
A priori which-way information in quantum interference with unstable particles
International Nuclear Information System (INIS)
If an unstable particle used in a two-path interference experiment decays before reaching a detector, which-way information becomes available that reduces the detected interference fringe visibility V. Here we argue that even when an unstable particle does not decay while in the interferometer, a priori which-way information is still available in the form of path predictability P which depends on the particle's decay rate Γ. We further demonstrate that in a matter-wave Mach–Zehnder interferometer using an excited atom with an appropriately tuned cavity, P is related to V through the duality relation P2+V2=1. - Highlights: • Even undecayed unstable particles exhibit novel interference effects. • Interference is studied in a Mach–Zehnder interferometer with a cavity. • More which-way information is available when using unstable particles. • A relation between which-way information and interference is satisfied
DEFF Research Database (Denmark)
Il'ichev, E. V.; Andreev, A. V.; Jacobsen, Claus Schelde
1993-01-01
Experimental results on some radio-frequency superconducting quantum interference device (rf-SQUID) signal properties are presented. The quantum interferometer was made of ceramic YBa2Cu3O7−x and was due to a low critical current operated in the inductance or nonhysteretic mode. With bias current...
Energy Technology Data Exchange (ETDEWEB)
Myers, Whittier R.
2006-05-18
This dissertation describes magnetic resonance imaging (MRI) of protons performed in a precession field of 132 {micro}T. In order to increase the signal-to-noise ratio (SNR), a pulsed 40-300 mT magnetic field prepolarizes the sample spins and an untuned second-order superconducting gradiometer coupled to a low transition temperature superconducting quantum interference device (SQUID) detects the subsequent 5.6-kHz spin precession. Imaging sequences including multiple echoes and partial Fourier reconstruction are developed. Calculating the SNR of prepolarized SQUID-detected MRI shows that three-dimensional Fourier imaging yields higher SNR than slice-selection imaging. An experimentally demonstrated field-cycling pulse sequence and post-processing algorithm mitigate image artifacts caused by concomitant gradients in low-field MRI. The magnetic field noise of SQUID untuned detection is compared to the noise of SQUID tuned detection, conventional Faraday detection, and the Nyquist noise generated by conducting biological samples. A second-generation microtesla MRI system employing a low-noise SQUID is constructed to increase SNR. A 2.4-m cubic, eddy-current shield with 6-mm thick aluminum walls encloses the experiment to attenuate external noise. The measured noise is 0.75 fT Hz{sup -1/2} referred to the bottom gradiometer loop. Solenoids wound from 30-strand braided wire to decrease Nyquist noise and cooled by either liquid nitrogen or water polarize the spins. Copper wire coils wound on wooden supports produce the imaging magnetic fields and field gradients. Water phantom images with 0.8 x 0.8 x 10 mm{sup 3} resolution have a SNR of 6. Three-dimensional 1.6 x 1.9 x 14 mm{sup 3} images of bell peppers and 3 x 3 x 26 mm{sup 3} in vivo images of the human arm are presented. Since contrast based on the transverse spin relaxation rate (T{sub 1}) is enhanced at low magnetic fields, microtesla MRI could potentially be used for tumor imaging. The measured T{sub 1} of ex
International Nuclear Information System (INIS)
This thesis describes several aspects of the development of gradiometers using high temperature Superconducting Quantum Interference Devices (SQUID). The pulsed laser deposition of thin films of YBa2Cu3O7-δ (YBCO) on SrTiO3 substrates was analysed using the method of 'Experimental Design'. Optimised YBCO films had a critical temperature of 90.5K and a critical current density of 3.6MAcm-2. As a result of the 3D screw dislocation mediated growth mode of YBCO, all films showed a considerable surface roughness, between 5-17nm. In a second study, the pulsed laser deposition of NdBa2Cu3O7-δ (NBCO) on SrTiO3 substrates was investigated. The highest critical temperature was 90K. but the properties of the used NBCO bulk targets resulted in degraded properties after thin film patterning. Compared to YBCO, optimised NBCO films required a larger target-substrate separation during deposition and showed smoother surfaces with a roughness of at most 2nm. Both observations were attributed to a 2D layer-by-layer growth mode. dc-SQUIDs were fabricated and characterised from thin films of both materials incorporating bicrystal and step-edge junctions. The lowest white flux noise was 5μΦ0/√Hz for a 50pH YBCO device on a SrTiO3 bicrystal with a 24 deg misorientation angle. First order SQUID gradiometers were fabricated from single layers of YBCO. The baseline of these devices was 4mm and the best balance and gradient sensitivity at 1kHz were 3x10-3 and 222fT/(cm√Hz))) respectively. The measured spatial response to a current carrying wire was in good agreement with a theoretical model. A significant performance improvement was obtained with the development of a single layer gradiometer with 13mm baseline, fabricated on 30x10mm2 bicrystals. For such a device, the gradient sensitivity at 1kHz was 50fT/(cm√Hz)) and the gradiometer was used successfully for unshielded magnetocardiography. A parasitic effective area compensation scheme was employed with two neighbouring SQUIDs
International Nuclear Information System (INIS)
This thesis is concerned with the development of Superconducting Quantum Interference Device (SQUID) gradiometers based on the high temperature superconductor YBa2Cu3O7-δ (YBCO). A step-edge Josephson junction fabrication process was developed to produce sufficiently steep (>60 deg) step-edges such that junctions exhibited RSJ-like current-voltage characteristics. The mean ICRN product of a sample of twenty step-edge junctions was 130μV. Step-edge dc SQUIDs with inductances between 67pH and 114pH were fabricated. Generally the SQUIDs had an intrinsic white flux noise in the 10-30μΦ0/√Hz range, with the best device, a 70pH SQUID, exhibiting a white flux noise of 5μΦ0/√Hz. Different first-order SQUID gradiometer designs were fabricated from single layers of YBCO. Two single-layer gradiometer (SLG) designs were fabricated on 10x10mm2 substrates. The best balance and lowest gradient sensitivity measured for these devices were 1/300 and 308fT/cm√Hz (at 1 kHz) respectively. The larger baseline and larger flux capture area of the pick-up loops in a large area SLG design, fabricated on 30x10mm2 substrates, resulted in significant improvements in the balance and gradient field sensitivity with 1/1000 and 50fT/cm√Hz (at 1kHz) measured respectively. To reduce the uniform field effective area of SLOs and therefore reduce the direct pick-up of environmental field noise when operated unshielded, a novel gradiometric SQUID (G-SQUID) device was developed. Fabricated from a single layer of YBCO, the G-SQUIDs with inductances of 67pH, had small uniform field effective areas of approximately 2μm2 - more than two orders of magnitude smaller than the uniform field effective areas of conventional narrow linewidth SQUIDs of similar inductance. Two designs of G-SQUID were fabricated on 10x10mm2 substrates. Due to their small effective areas, when cooled unshielded these devices showed no increase in their white flux noise. The best balance achieved for a G-SQUID was
Energy Technology Data Exchange (ETDEWEB)
Graf zu Eulenburg, A
1999-07-01
This thesis describes several aspects of the development of gradiometers using high temperature Superconducting Quantum Interference Devices (SQUID). The pulsed laser deposition of thin films of YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) on SrTiO{sub 3} substrates was analysed using the method of 'Experimental Design'. Optimised YBCO films had a critical temperature of 90.5K and a critical current density of 3.6MAcm{sup -2}. As a result of the 3D screw dislocation mediated growth mode of YBCO, all films showed a considerable surface roughness, between 5-17nm. In a second study, the pulsed laser deposition of NdBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (NBCO) on SrTiO{sub 3} substrates was investigated. The highest critical temperature was 90K. but the properties of the used NBCO bulk targets resulted in degraded properties after thin film patterning. Compared to YBCO, optimised NBCO films required a larger target-substrate separation during deposition and showed smoother surfaces with a roughness of at most 2nm. Both observations were attributed to a 2D layer-by-layer growth mode. dc-SQUIDs were fabricated and characterised from thin films of both materials incorporating bicrystal and step-edge junctions. The lowest white flux noise was 5{mu}{phi}{sub 0}/{radical}Hz for a 50pH YBCO device on a SrTiO{sub 3} bicrystal with a 24 deg misorientation angle. First order SQUID gradiometers were fabricated from single layers of YBCO. The baseline of these devices was 4mm and the best balance and gradient sensitivity at 1kHz were 3x10{sup -3} and 222fT/(cm{radical}Hz))) respectively. The measured spatial response to a current carrying wire was in good agreement with a theoretical model. A significant performance improvement was obtained with the development of a single layer gradiometer with 13mm baseline, fabricated on 30x10mm{sup 2} bicrystals. For such a device, the gradient sensitivity at 1kHz was 50fT/(cm{radical}Hz)) and the gradiometer was used successfully for
International Nuclear Information System (INIS)
This dissertation describes magnetic resonance imaging (MRI) of protons performed in a precession field of 132 (micro)T. In order to increase the signal-to-noise ratio (SNR), a pulsed 40-300 mT magnetic field prepolarizes the sample spins and an untuned second-order superconducting gradiometer coupled to a low transition temperature superconducting quantum interference device (SQUID) detects the subsequent 5.6-kHz spin precession. Imaging sequences including multiple echoes and partial Fourier reconstruction are developed. Calculating the SNR of prepolarized SQUID-detected MRI shows that three-dimensional Fourier imaging yields higher SNR than slice-selection imaging. An experimentally demonstrated field-cycling pulse sequence and post-processing algorithm mitigate image artifacts caused by concomitant gradients in low-field MRI. The magnetic field noise of SQUID untuned detection is compared to the noise of SQUID tuned detection, conventional Faraday detection, and the Nyquist noise generated by conducting biological samples. A second-generation microtesla MRI system employing a low-noise SQUID is constructed to increase SNR. A 2.4-m cubic, eddy-current shield with 6-mm thick aluminum walls encloses the experiment to attenuate external noise. The measured noise is 0.75 fT Hz-1/2 referred to the bottom gradiometer loop. Solenoids wound from 30-strand braided wire to decrease Nyquist noise and cooled by either liquid nitrogen or water polarize the spins. Copper wire coils wound on wooden supports produce the imaging magnetic fields and field gradients. Water phantom images with 0.8 x 0.8 x 10 mm3 resolution have a SNR of 6. Three-dimensional 1.6 x 1.9 x 14 mm3 images of bell peppers and 3 x 3 x 26 mm3 in vivo images of the human arm are presented. Since contrast based on the transverse spin relaxation rate (T1) is enhanced at low magnetic fields, microtesla MRI could potentially be used for tumor imaging. The measured T1 of ex vivo normal and cancerous prostate
De Raedt, H; Michielsen, K
2005-01-01
We demonstrate that networks of locally connected processing units with a primitive learning capability exhibit behavior that is usually only attributed to quantum systems. We describe networks that simulate single-photon beam-splitter and Mach-Zehnder interferometer experiments on a causal, event-by-event basis and demonstrate that the simulation results are in excellent agreement with quantum theory. We also show that this approach can be generalized to simulate universal quantum computers.
Yu, Leo; Natarajan, Chandra M.; Horikiri, Tomoyuki; Langrock, Carsten; Pelc, Jason S.; Tanner, Michael G.; Abe, Eisuke; Maier, Sebastian; Schneider, Christian; Höfling, Sven; Kamp, Martin; Hadfield, Robert H.; Fejer, Martin M.; Yamamoto, Yoshihisa
2015-11-01
Practical quantum communication between remote quantum memories rely on single photons at telecom wavelengths. Although spin-photon entanglement has been demonstrated in atomic and solid-state qubit systems, the produced single photons at short wavelengths and with polarization encoding are not suitable for long-distance communication, because they suffer from high propagation loss and depolarization in optical fibres. Establishing entanglement between remote quantum nodes would further require the photons generated from separate nodes to be indistinguishable. Here, we report the observation of correlations between a quantum-dot spin and a telecom single photon across a 2-km fibre channel based on time-bin encoding and background-free frequency downconversion. The downconverted photon at telecom wavelengths exhibits two-photon interference with another photon from an independent source, achieving a mean wavepacket overlap of greater than 0.89 despite their original wavelength mismatch (900 and 911 nm). The quantum-networking operations that we demonstrate will enable practical communication between solid-state spin qubits across long distances.
Yu, Leo; Natarajan, Chandra M; Horikiri, Tomoyuki; Langrock, Carsten; Pelc, Jason S; Tanner, Michael G; Abe, Eisuke; Maier, Sebastian; Schneider, Christian; Höfling, Sven; Kamp, Martin; Hadfield, Robert H; Fejer, Martin M; Yamamoto, Yoshihisa
2015-01-01
Practical quantum communication between remote quantum memories rely on single photons at telecom wavelengths. Although spin-photon entanglement has been demonstrated in atomic and solid-state qubit systems, the produced single photons at short wavelengths and with polarization encoding are not suitable for long-distance communication, because they suffer from high propagation loss and depolarization in optical fibres. Establishing entanglement between remote quantum nodes would further require the photons generated from separate nodes to be indistinguishable. Here, we report the observation of correlations between a quantum-dot spin and a telecom single photon across a 2-km fibre channel based on time-bin encoding and background-free frequency downconversion. The downconverted photon at telecom wavelengths exhibits two-photon interference with another photon from an independent source, achieving a mean wavepacket overlap of greater than 0.89 despite their original wavelength mismatch (900 and 911 nm). The quantum-networking operations that we demonstrate will enable practical communication between solid-state spin qubits across long distances. PMID:26597223
Brown, Sandra E
2014-01-01
Free energy differences $\\Delta F:=F-F_{\\text{prism}}$ are computed for several isomers of water hexamer relative to the "prism" isomer using the self-consistent phonons method. %$\\Delta F:=F-F({prism})$ We consider the isotope effect defined by the quantity $\\delta F_{D_2O}:=\\Delta F_{\\rm D_2O}-\\Delta F_{\\rm H_2O}$, and the quantum effect, $\\delta F_{\\hbar=0}:=\\Delta F_{\\hbar=0}-\\Delta F_{\\rm H_2O}$, and evaluate them using different flexible water models. While both $\\delta F_{D_2O}$ and $\\delta F_{\\hbar=0}$ are found to be rather small for all of the potentials, they are especially small for two of the empirical models, q-TIP4P/F and TTM3-F, compared to q-SPC/Fw and the two {\\it abinitio}-based models, WHBB and HBB2-pol. This qualitative difference in the properties of different water models cannot be explained by one being "more accurate" than the other. We speculate as to whether the observed anomalies are caused by the special properties of water systems, or are an artifact of either the potential energ...
Anomalous Phase Shift of Quantum Oscillations in 3D Topological Semimetals
Wang, C. M.; Lu, Hai-Zhou; Shen, Shun-Qing
2016-08-01
Berry phase physics is closely related to a number of topological states of matter. Recently discovered topological semimetals are believed to host a nontrivial π Berry phase to induce a phase shift of ±1 /8 in the quantum oscillation (+ for hole and - for electron carriers). We theoretically study the Shubnikov-de Haas oscillation of Weyl and Dirac semimetals, taking into account their topological nature and inter-Landau band scattering. For a Weyl semimetal with broken time-reversal symmetry, the phase shift is found to change nonmonotonically and go beyond known values of ±1 /8 and ±5 /8 , as a function of the Fermi energy. For a Dirac semimetal or paramagnetic Weyl semimetal, time-reversal symmetry leads to a discrete phase shift of ±1 /8 or ±5 /8 . Different from the previous works, we find that the topological band inversion can lead to beating patterns in the absence of Zeeman splitting. We also find the resistivity peaks should be assigned integers in the Landau index plot. Our findings may account for recent experiments in Cd2 As3 and should be helpful for exploring the Berry phase in various 3D systems.
Spatially and spectrally resolved quantum path interference with chirped driving pulses
Preclíková, Jana; Lorek, Eleonora; Larsen, Esben Witting; Heyl, Christoph M; Paleček, David; Zigmantas, Donatas; Schafer, Kenneth J; Gaarde, Mette B; Mauritsson, Johan
2016-01-01
We measure spectrally and spatially resolved high-order harmonics generated in argon using chirped multi-cycle laser pulses. Using a very stable, high-repetition rate laser we are able to clearly observe the interference between light emitted from the two shortest trajectories and study this interference structure systematically. The interference structure is clearly observed over a large range of harmonic orders, ranging from harmonic 11, which is below the ionization threshold of argon, to harmonic 25. The interference pattern contains more information than just the relative phase of the light from the two trajectories, since it is both spatially and spectrally resolved. We can access this additional information by changing the chirp of the driving laser pulses which affects both the spatial and the spectral phases of the two trajectories differently, allowing us to reconstruct the dipole phase parameters for the short ($\\alpha_s$) and long ($\\alpha_l$) trajectories from the data. The reconstruction is done...
Quantum interference in laser-assisted photo-ionization excited by a femtosecond x-ray pulse
Institute of Scientific and Technical Information of China (English)
Ge Yu-Cheng
2008-01-01
The photoelectron energy spectra (PESs) excited by monochromatic femtosecond x-ray pulses in the presence of a femtosecond laser are investigated. APES is composed of a set of separate peaks, showing interesting comb-like structures. These structures result from the quantum interferences between photoelectron wave packets generated at different times. The width and the localization of each peak as well as the number of peaks are determined by all the laser and x-ray parameters. Most of peak heights of the PES are higher than the classical predictions.
International Nuclear Information System (INIS)
The well-known Fano-profiles appearing in differential photonionization cross sections when resonances are present can also be observed in the time-reversed process of photorecombination of highly charged ions, where direct and indirect processes leading to the same final quantum state of the ion and the photon field can interfere, thus producing asymmetric lines shapes. Experiments performed at the Heidelberg electron beam ion trap with Hg75+...78+ ions have delivered state-selective Fano parameters and accurate resonance energies
International Nuclear Information System (INIS)
Investigations of the quantum interference in laser-assisted photoionization by an attosecond extreme ultraviolet (xuv) pulse shows an approximately constant value for the total photoionizations for different laser intensities. The square of the full width at half maximum of a photoelectron energy spectrum (PES) linearly depends on the laser intensity. By determining the laser-related phase of each streaked electron and using a transfer equation with linear corrections, an analytically quick method is proposed for precisely reconstructing the xuv pulse intensity (chirp) from one (two) measured PES(s) with a theoretical root-mean-square temporal (energy) difference of less than 1 attosecond (0.1 eV).
Energy Technology Data Exchange (ETDEWEB)
Ge Yucheng; He Haiping [School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 (China)
2011-08-15
Investigations of the quantum interference in laser-assisted photoionization by an attosecond extreme ultraviolet (xuv) pulse shows an approximately constant value for the total photoionizations for different laser intensities. The square of the full width at half maximum of a photoelectron energy spectrum (PES) linearly depends on the laser intensity. By determining the laser-related phase of each streaked electron and using a transfer equation with linear corrections, an analytically quick method is proposed for precisely reconstructing the xuv pulse intensity (chirp) from one (two) measured PES(s) with a theoretical root-mean-square temporal (energy) difference of less than 1 attosecond (0.1 eV).
Directory of Open Access Journals (Sweden)
Jozsef Seres
2015-01-01
Full Text Available High-order harmonic generation is an important mechanism to generate coherent radiation in the few–100-eV spectral range with ultrashort laser pulses. Moreover, a closer inspection of the measured spectra provides unique information about the underlying physics and allows deriving guidelines for improvements. The long-range modulation of the spectral envelope is linked to phase matching, and we will show how to improve it with a double-pulse excitation scheme. Additionally, the spectrum contains only every fourth harmonic, which can be well explained by the quantum interference of multiple scattered electrons, and two dominant electron trajectories were selected by X-ray parametric interaction.
International Nuclear Information System (INIS)
For many decades, improvements in both theory and experiment of the fine structure of the n = 2 triplet P levels of helium have allowed for an increasingly precise determination of the fine-structure constant. Recently, it has been observed that quantum-mechanical interference between neighboring resonances can cause significant shifts, even if such neighboring resonances are separated by thousands of natural widths. The shifts depend in detail on the experimental method used for the measurement, as well as the specific experimental parameters employed. Here, we review how these shifts apply for the most precise measurements of the helium 23P fine-structure intervals
Interference of nematic quantum critical quasiparticles: a route to the octet model
Kim, Eun-Ah; Lawler, Michael J
2008-01-01
Repeated observations of inhomogeneity in cuperate superconductors[1-5] make one immediately question the existance of coherent quasiparticles(qp's) and the applicability of a momentum space picture. Yet, obversations of interference effects[6-9] suggest that the qp's maintain a remarkable coherence under special circumstances. In particular, quasi-particle interference (QPI) imaging using scanning tunneling spectroscopy revealed a highly unusual form of coherence: accumulation of coherence o...
Novel interference effects and a new Quantum phase in mesoscopic systems
Deo, P. Singha; Jayannavar, A. M.
2000-01-01
Mesoscopic systems have provided an opportunity to study quantum effects beyond the atomic realm. In these systems quantum coherence prevails over the entire sample. We discuss several novel effects related to persistent currents in open systems which do not have analogues in closed systems. Some phenomena arising simultaneously due to two non-classical effects namely, Aharonov-Bohm effect and quantum tunneling are presented. Simple analysis of sharp phase jumps observed in double-slit Aharon...
Institute of Scientific and Technical Information of China (English)
SONG Ke-Hui; ZHOU Zheng-Wei; GUO Guang-Can
2006-01-01
We present a scheme to realize geometric phase-shift gate for two superconducting quantum interference device (SQUID) qubits coupled to a single-mode microwave field. The geometric phase-shift gate operation is performed transitions during the gate operation. Thus, the docoherence due to energy spontaneous emission based on the levels of SQUIDs are suppressed. The gate is insensitive to the cavity decay throughout the operation since the cavity mode is displaced along a circle in the phase space, acquiring a phase conditional upon the two lower flux states of the SQUID qubits, and the cavity mode is still in the original vacuum state. Based on the SQUID qubits interacting with the cavity mode, our proposed approach may open promising prospects for quantum logic in SQUID-system.
Institute of Scientific and Technical Information of China (English)
CHEN Bao-Ju; CHEN Xiong-Wen; SHI Zhen-Gang; ZHU Xi-Xiang; SONG Ke-Hui; WU Shao-Quan
2007-01-01
We theoretically investigate the properties of the ground state of the strongly correlated T-shaped double quantum dots embedded in an Aharonov-Bohm ring in the Kondo regime by means of the one-impurity Anderson Hamiltonian.It is found that in this system,the persistent current depends sensitively on the parity and size of the ring.With the increase of interdot coupling,the persistent current is suppressed due to the enhancing Fano interference weakening the Kondo effect.Moreover,when the spin of quantum dot embedded in the aharonovBohm ring is screened,the persistent current peak is not affected by interdot coupling.Thus this model may be a new candidate for detecting Kondo screening cloud.
Energy Technology Data Exchange (ETDEWEB)
Gotoh, Hideki, E-mail: gotoh.hideki@lab.ntt.co.jp; Sanada, Haruki; Yamaguchi, Hiroshi; Sogawa, Tetsuomi [NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan)
2014-10-15
Optical nonlinear effects are examined using a two-color micro-photoluminescence (micro-PL) method in a coherently coupled exciton-biexciton system in a single quantum dot (QD). PL and photoluminescence excitation spectroscopy (PLE) are employed to measure the absorption spectra of the exciton and biexciton states. PLE for Stokes and anti-Stokes PL enables us to clarify the nonlinear optical absorption properties in the lowest exciton and biexciton states. The nonlinear absorption spectra for excitons exhibit asymmetric shapes with peak and dip structures, and provide a distinct contrast to the symmetric dip structures of conventional nonlinear spectra. Theoretical analyses with a density matrix method indicate that the nonlinear spectra are caused not by a simple coherent interaction between the exciton and biexciton states but by coupling effects among exciton, biexciton and continuum states. These results indicate that Fano quantum interference effects appear in exciton-biexciton systems at QDs and offer important insights into their physics.
International Nuclear Information System (INIS)
Optical nonlinear effects are examined using a two-color micro-photoluminescence (micro-PL) method in a coherently coupled exciton-biexciton system in a single quantum dot (QD). PL and photoluminescence excitation spectroscopy (PLE) are employed to measure the absorption spectra of the exciton and biexciton states. PLE for Stokes and anti-Stokes PL enables us to clarify the nonlinear optical absorption properties in the lowest exciton and biexciton states. The nonlinear absorption spectra for excitons exhibit asymmetric shapes with peak and dip structures, and provide a distinct contrast to the symmetric dip structures of conventional nonlinear spectra. Theoretical analyses with a density matrix method indicate that the nonlinear spectra are caused not by a simple coherent interaction between the exciton and biexciton states but by coupling effects among exciton, biexciton and continuum states. These results indicate that Fano quantum interference effects appear in exciton-biexciton systems at QDs and offer important insights into their physics
Li, Zheng; Medvedev, Nikita; Wang, Fenglin; Chapman, Henry N; Shih, Yanhua
2016-01-01
Using higher order coherence of thermal light sources, we can achieve enhancement of resolution of standard x-ray imaging techniques, such as x-ray diffraction and phase contrast imaging. The cost of implementing such schemes is minimal comparing to the schemes using entangled two-photon pairs. The proposed diffractive quan- tum crystallography using multipath interference of thermal light can be eventually free of radiation damage, because the diffraction pattern could be formed by using low energy photons of optical wavelength. Thus it is promising to apply the proposed quantum crystallography scheme to nanocrystalline or non-crystalline samples that are too difficult to be crystallized.
Energy Technology Data Exchange (ETDEWEB)
Pan, S. S., E-mail: sspan@issp.ac.cn, E-mail: ghli@issp.ac.cn; Li, F. D.; Liu, Q. W.; Xu, S. C.; Luo, Y. Y. [Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanostructures, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Li, G. H., E-mail: sspan@issp.ac.cn, E-mail: ghli@issp.ac.cn [Key Laboratory of Materials Physics, Anhui Key Laboratory of Nanomaterials and Nanostructures, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); School of Chemistry and Materials Science, University of Science and Technology of China, Hefei 230026 (China)
2015-05-07
SnO{sub 2} quantum dots (QDs) are potential materials for deep ultraviolet (DUV) light emitting devices. In this study, we report the temperature and excitation power-dependent exciton luminescence from SnO{sub 2} QDs. The exciton emission exhibits anomalous blue shift, accompanied with band width reduction with increasing temperature and excitation power above 300 K. The anomalous temperature dependences of the peak energy and band width are well interpreted by the strongly localized carrier thermal hopping process and Gaussian shape of band tails states, respectively. The localized wells and band tails at conduction minimum are considered to be induced by the surface oxygen defects and local potential fluctuation in SnO{sub 2} QDs.
Institute of Scientific and Technical Information of China (English)
CHEN Xiong-Wen; SHI Zhen-Gang; CHEN Bao-Ju; SONG Ke-Hui
2007-01-01
We analyse the transport properties of a coupled double quantum dot (DQD) device with one of the dots (QD1) coupled to metallic leads and the other (QD2) embedded in an Aharonov-Bhom (A-B) ring by means of the slave-boson mean-Geld theory. It is found that in this system, the Kondo resonance and the Fano interference exist simultaneously, the enhancing Kondo effect and the increasing hopping of the QD2-Ring destroy the localized electron state in the QD2 for the QD1-leads, and accordingly, the Fano interference between the DQD-leads and the QD1-leads are suppressed. Under some conditions, the Fano interference can be quenched fully and the single Kondo resonance of the QD1-leads comes into being. Moreover, when the magnetic flux of the A-B ring is zero, the influence of the parity of the A-B ring on the transport properties is very weak, but this inSuence becomes more obvious with non-zero magnetic flux. Thus this model may be a candidate for future device applications.
Quantum interference and the formation of trapping regions around a Schwarzschild black hole
International Nuclear Information System (INIS)
Astrophysical processes in vicinity of black holes involve a coupling of spacetime geometry and the quantum effects. Using the quantum potential approach we investigate the quantum dynamics of a massive particle around a Schwarzschild black hole. The analysis shows the existence of typical quantum effects near the black hole region. In particular the R-amplitude variation leads to the formation of fringe-like trapping regions around the black hole where the particle is more likely to be located. However due to the energy loss, which gains a local maxima in the trapping regions, the particle in-fall eventually occurs. The energy loss during such a process will show up in frequency and amplitude modulation in X-ray signals from accreting black holes and may confirm the existence of such trapping regions.
Electrochemical control of quantum interference in anthraquinone-based molecular switches
DEFF Research Database (Denmark)
Markussen, Troels; Schiøtz, Jakob; Thygesen, Kristian Sommer
2010-01-01
absent in the hydroquinone molecular bridge. A simple explanation of the interference effect is achieved by transforming the frontier molecular orbitals into localized molecular orbitals thereby obtaining a minimal tight-binding model describing the transport in the relevant energy range in terms of...
Quantum nonlocality of photon pairs in interference in a Mach-Zehnder interferometer
Czech Academy of Sciences Publication Activity Database
Trojek, P.; Peřina ml., Jan
2003-01-01
Roč. 53, č. 4 (2003), s. 335-349. ISSN 0011-4626 R&D Projects: GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z1010921 Keywords : entangled photon pairs * nonlocal interference * Mach-Zehender interferometer Subject RIV: BH - Optics, Masers, Lasers Impact factor: 0.263, year: 2003
Zhu, Laipan; Liu, Yu; Gao, Hansong; Qin, Xudong; Li, Yuan; Wu, Qing; Chen, Yonghai
2014-01-01
We observed an anomalous linear photogalvanic effect (ALPGE) in undoped InGaAs/AlGaAs multiple quantum well and studied its wavelength dependence in details. This effect is believed to originate from the optical momentum alignment effect and the inhomogeneity of light intensity. We find that the spot location with the maximum ALPGE current is wavelength independent. And the normalized ALPGE current decreasing at smaller wavelengths is attributed to the sharp decrease of the momentum and energy relaxation time. The electrical measurement of the spectra dependence of ALPGE is highly sensitive proving to be an effective method for detecting the momentum anisotropy of photoinduced carriers and band coupling. PMID:25258612
International Nuclear Information System (INIS)
We present experimental data on the state-selective quantum interference between different pathways of photorecombination, namely, radiative and dielectronic recombination, in the KLL resonances of highly charged mercury ions. The interference, observed for well resolved electronic states in the Heidelberg electron beam ion trap, manifests itself in the asymmetry of line shapes, characterized by ''Fano factors,'' which have been determined with unprecedented precision, as well as their excitation energies, for several strong dielectronic resonances
De Raedt, H.; De Raedt, K.; Michielsen, K.
2005-01-01
We demonstrate that networks of locally connected processing units with a primitive learning capability exhibit behavior that is usually only attributed to quantum systems. We describe networks that simulate single-photon beam-splitter and Mach-Zehnder interferometer experiments on a causal, event-b
Quantum interference effects in an ensemble of $^{229}$Th nuclei interacting with coherent light
Das, Sumanta; Keitel, Christoph H
2013-01-01
As a unique feature, the $^{229}$Th nucleus has an isomeric transition in the vacuum ultraviolet that can be accessed by optical lasers. The interference effects occurring in the interaction between coherent optical light and an ensemble of $^{229}$Th nuclei are investigated theoretically. We consider the scenario of nuclei doped in vacuum ultraviolet-vacuum ultraviolet transparent crystals and take into account the effect of different doping sites and therefore different lattice fields that broaden the nuclear transition width. This effect is shown to come in interplay with interference effects due to the hyperfine splitting of the ground and isomeric nuclear states. We investigate possible experimentally available situations involving two-, three- and four-level schemes of quadrupole sublevels of the ground and isomeric nuclear states coupling to one or two coherent fields. Specific configurations which offer clear signatures of the isomer excitation advantageous for the more precise experimental determinat...
Observation of Quantum Interferences via Light Induced Conical Intersections in Diatomic Molecules
Natan, Adi; Bucksbaum, Philip H
2015-01-01
We observe energy-dependent angle-resolved diffraction patterns in protons from strong-field dissociation of the molecular hydrogen ion H$_2^+$. The interference is a characteristic of dissociation around a laser-induced conical intersection (LICI), which is a point of contact between two surfaces in the dressed 2-dimensional Born-Oppenheimer potential energy landscape of a diatomic molecule in a strong laser field. The interference magnitude and angular period depend strongly on the energy difference between the initial state and the LICI, consistent with coherent diffraction around a cone-shaped potential barrier whose width and thickness depend on the relative energy of the initial state and the cone apex. These findings are supported by numerical solutions of the time-dependent Schr\\"{o}dinger equation for similar experimental conditions.
Observation of Quantum Interferences via Light-Induced Conical Intersections in Diatomic Molecules
Natan, Adi; Ware, Matthew R.; Prabhudesai, Vaibhav S.; Lev, Uri; Bruner, Barry D.; Heber, Oded; Bucksbaum, Philip H.
2016-04-01
We observe energy-dependent angle-resolved diffraction patterns in protons from strong-field dissociation of the molecular hydrogen ion H2+ . The interference is a characteristic of dissociation around a laser-induced conical intersection (LICI), which is a point of contact between two surfaces in the dressed two-dimensional Born-Oppenheimer potential energy landscape of a diatomic molecule in a strong laser field. The interference magnitude and angular period depend strongly on the energy difference between the initial state and the LICI, consistent with coherent diffraction around a cone-shaped potential barrier whose width and thickness depend on the relative energy of the initial state and the cone apex. These findings are supported by numerical solutions of the time-dependent Schrödinger equation for similar experimental conditions.
Novel interference effects and a new quantum phase in mesoscopic systems
Indian Academy of Sciences (India)
P Singha Deo; A M Jayannavar
2001-02-01
Mesoscopic systems have provided an opportunity to study quantum effects beyond the atomic realm. In these systems quantum coherence prevails over the entire sample. We discuss several novel effects related to persistent currents in open systems which do not have analogues in closed systems. Some phenomena arising simultaneously due to two non-classical effects namely, Aharonov–Bohm effect and quantum tunneling are presented. Simple analysis of sharp phase jumps observed in double-slit Aharonov–Bohm experiments is given. Some consequences of parity violation are elaborated. Finally, we brieﬂy describe the dephasing of Aharonov–Bohm oscillations in Aharonov–Bohm ring geometry due to spin-ﬂip scattering in one of the arms. Several experimental manifestations of these phenomena and their applications are given.
Chiao, R Y; Chiao, Raymond Y.; Speliotopoulos, Achilles D.
2003-01-01
An experiment in Low Earth Orbit (LEO) is proposed to measure components of the Riemann curvature tensor using atom interferometry. We show that the difference in the quantum phase $\\Delta\\phi$ of an atom that can travel along two intersecting geodesics is given by $mR_{0i0j}/\\hbar$ times the spacetime volume contained within the geodesics. Our expression for $\\Delta\\phi$ also holds for gravitational waves in the long wavelength limit.
Chiao, Raymond Y.; Speliotopoulos, Achilles D.
2003-01-01
An experiment in Low Earth Orbit (LEO) is proposed to measure components of the Riemann curvature tensor using atom interferometry. We show that the difference in the quantum phase $\\Delta\\phi$ of an atom that can travel along two intersecting geodesics is given by $mR_{0i0j}/\\hbar$ times the spacetime volume contained within the geodesics. Our expression for $\\Delta\\phi$ also holds for gravitational waves in the long wavelength limit.
de Bianchi, Massimiliano Sassoli
2013-01-01
The validity of the assertion that some recent double-slit interference experiments, conducted by Radin et al., would have tested the possible role of the experimenter's mind in the collapse of the quantum wave function, is questioned. It is emphasized that quantum mechanics doesn't need any psychophysical ingredient to explain the measurement processes, and therefore parapsychologists shouldn't resort to the latter to support the possibility of psychokinesis, but search for more convincing explanations.
International Nuclear Information System (INIS)
The electronic system of the organic superconductor κ-(BEDT-TTF)2I3 (BEDT-TTF=bis(ethylenedithiolo)tetrathi afulvalene) is identified as extremely two-dimensional (2D). The topology of the Fermi surface (FS) was investigated by means of Shubnikov-de Haas (SdH) as well as de Haas-van Alphen (dHvA) experiments focusing on the verification of the 2D character of the system. This two-dimensionality specially takes effect as soon as the magnetic field is oriented exactly perpendicular to the conducting planes (i.e. Θ=0 ). Under such conditions strong anomalous damping effects in the field and temperature dependence of quantum oscillation amplitudes are observed. These anomalous damping effects are discussed in terms of the occurrence of quasi-particle excitations with fractional statistics (QPFS) which may only occur in extremely 2D systems at high magnetic fields and low temperatures (i.e., only when ℎωC>>kBT). Taking up these requirements, the aim of this work is to quantify the extreme two-dimensionality of the electronic system of κ-(BEDT-TTF)2I3 and to show that the observed damping effects in fact are determined by the ratio ℎωC/kBT. These facts may support the interpretation of the observed damping effects of quantum oscillation amplitudes at high magnetic fields, low temperatures and Θ=0 as generated by the possible occurrence of such QPFS. (orig.)
International Nuclear Information System (INIS)
This study shows that the alternating current (AC) bias direct offset integrated technique (DOIT) reduces low-frequency noise without increasing the level of white noise in a high-Tc DC superconducting quantum interference device (SQUID). Additional positive feedback (APF), which can improve the effective flux-to-voltage transfer function, it used to reduce the equivalent flux noise due to the voltage noise of the preamplifier of the magnetometer. The use of APF combined with the AC bias DOIT reduced the noise of the magnetometer by factors of 1.5 at 100 Hz, 3.5 at 10 Hz, and 5.3 at 1 Hz when compared with noise levels obtained with the static current bias DOIT. (author)
Energy Technology Data Exchange (ETDEWEB)
Park, J-H; Stillwell, R L; Murphy, T P; Tozer, S W; Palm, E C [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, 32310-3706 (United States)], E-mail: palm@magnet.fsu.edu
2009-02-01
A commercially available SQUID (Superconducting QUantum Interference Device) DC magnetometer is often limited by its relatively high temperature ({>=} 1.9 K) and low magnetic field ({<=} 7 T) operating environment. The need for the lower temperature and higher field DC magnetization measurements keeps growing as more materials show interesting physical phenomena with relevant energy scales that require millikelvin temperatures. To meet these needs we have developed a SQUID DC magnetometer which operates in the top loading dilution refrigerator of a 16 T superconducting magnet. An essential part of this low temperature and high field SQUID magnetometer is a specialized probe which can adapt the SQUID electronics and low friction mechanical sample shaft. The details of magnetometer probe and preliminary testing results are described in this paper.
Institute of Scientific and Technical Information of China (English)
LI Sheng-Chang; YANG Wen-Xing; DUAN Wen-Shan
2008-01-01
An alternative scheme is proposed for the generation of n-qubit W states of superconducting quantum interference devices (SQUID) in cavity QED. In this scheme, Raman coupling of two lower flux states of SQUID system is achieved via a microwave pulse and the cavity mode. Conditioned on no photon leakage from the cavity, the n-qubit W state can be generated whether the effective coupling parameters of the SQUID to cavity mode and classical microwave fields are the same or different. Our strictly numerical simulations of the time evolution of the system including decay show that the success probability of our scheme is almost unity and the interaction time is on the order of 10-9 s. The scheme can also be used to generate the Schrfdinger cat states of multi-SQUID.
Institute of Scientific and Technical Information of China (English)
Zhang Bing; Xu Wei-Hua; Zhang Hui-Fang; Gao Jin-Yue
2004-01-01
A four-level system driven by two coherent fields is considered. It is shown that in the presence of an incoherent pump, the probe gain at a short wavelength can be achieved due to the quantum interference. Our density matrix calculation provides the conditions for probe amplification from different origins, including gain without population inversion on any state basis, gain with population inversion on the dressed-state basis, and gain with population inversion on the bare-state basis. Also, by controlling the Rabi frequency of the coupling field a total change from non-inversion to inversion can be achieved which does not depend on the intensity of the incoherent pump.
International Nuclear Information System (INIS)
We have prepared n-channel silicon field-effect transistors, which are capable of working at liquid helium temperatures (4.2 K) and used them in cooled preamplifiers for rf superconducting quantum interference device (SQUID) readout electronics. All metallizations of these transistors were made of niobium, to study the possibility of a further integration of a SQUID and FET on the same chip. Using the FETs in a cooled preamplifier together with a rf SQUID gradiometer, the flux noise of the system could be reduced by a factor of 3 compared to a room temperature low noise preamplifier. We have also performed calculations of a possible increase of the substrate temperature due to the power dissipation of the FET and have measured the cross talk between FET and SQUID. copyright 1995 American Institute of Physics
International Nuclear Information System (INIS)
We investigate the electron transport through a mesoscopic ring side-coupled with a quantum dot (QD) in the presence of Rashba spin-orbit (SO) interaction. It is shown that both the Fano resonance and the spin interference effects play important roles in the electron transport properties. As the QD level is around the Fermi energy, the total conductance shows a typical Fano resonance line shape. By applying an electrical gate voltage to the QD, the total transmission through the system can be strongly modulated. By threading the mesoscopic ring with a magnetic flux, the time-reversal symmetry of the system is broken, and a spin polarized current can be obtained even though the incident current is unpolarized.
Hsu, Liang-Yan; Rabitz, Herschel
2012-11-01
This work proposes a new type of optoelectronic switch, the phenyl-acetylene-macrocycle-based single-molecule transistor, which utilizes photon-assisted tunneling and destructive quantum interference. The analysis uses single-particle Green's functions along with Floquet theory. Without the optical field, phenyl-acetylene-macrocycle exhibits a wide range of strong antiresonance between its frontier orbitals. The simulations show large on-off ratios (over 10(4)) and measurable currents (~10(-11) A) enabled by photon-assisted tunneling in a weak optical field (~2 × 10(5) V/cm) and at a small source-drain voltage (~0.05 V). Field amplitude power scaling laws and a range of field intensities are given for operating one- and two-photon assisted tunneling in phenyl-acetylene-macrocycle-based single-molecule transistors. This development opens up a new direction for creating molecular switches. PMID:23215309
Dynamics of a neutron in electromagnetic fields and quantum phase interference
International Nuclear Information System (INIS)
The dynamics of a neutral spinning particle in electromagnetic fields is investigated. The interference with unpolarized neutron beams is reasonably interpreted as the observation of spin precession in electromagnetic fields which has a dynamical origin. It is shown that only for a particular choice of the initial polarization of the spin the conditions for the Aharonov-Casher topological phase shift and the scalar Aharonov-Bohm effect can be fulfilled. The recent experiment on the Aharonov-Casher phase shift with neutron interferometry can be considered as a test of a new anyon model, which is a result of spin precession in the local electric field. (orig.)
Fano interferences in the transport properties of triple quantum dot T-shaped systems
International Nuclear Information System (INIS)
We consider the transport and the noise characteristic in the case of a triple quantum dots T-shaped system where two of the dots form a two-level system and the other works in a detector-like setup. Our theoretical results are obtained using the equation of motion method for the case of zero on-site Coulomb interaction in the detector dot. The transport trough the T-shaped system can be controlled by varying the coupling between the two-level system dots or the coupling between the detector dot and the exterior electrodes. The Fano dips in the system's conductance can be observe both for strong (fast detector) and weak coupling (slow detector) between the detector dot and the external electrodes. Due to stronger electronic correlations the noise in the case of a slow detector are much higher. This setup may be of interest for the practical realization of qubit states in quantum dots systems.
Quantum interference and statistical fluctuations in deep inelastic heavy-ion reactions
International Nuclear Information System (INIS)
Starting from the general multi-channel formulation of the scattering matrix we perform the coarse-grain average of the cross section appropriate for the observed quantities in heavy-ion reactions. We keep full track of the geometrical factors for the coupling of partial waves and channel spin. Relating the diagonal part of the S-matrix product semiclassically to the statistical treatment in terms of phase space trajectories we are dealing with quantum fluctuations and statistical fluctuations on an even basis. Quantum corrections play a minor role if the underlying statistical model takes effects of the nonthermalized relative motion properly into account. This is true even for small energy losses. (orig.)
Institute of Scientific and Technical Information of China (English)
YANG Ya-Ping; Chen Hong; ZHU Shi-Yao
2000-01-01
The spontaneous emission from a V-type three-level atom embedded in a two-band photonic crystal is studied.Due to the quantum interference between the two transitions and existence of two bands, the populations in the upper levels display some novel behavior: anti-trapping, population oscillation, and population inversion.
Directory of Open Access Journals (Sweden)
Hideki Gotoh
2014-10-01
Full Text Available Optical nonlinear effects are examined using a two-color micro-photoluminescence (micro-PL method in a coherently coupled exciton-biexciton system in a single quantum dot (QD. PL and photoluminescence excitation spectroscopy (PLE are employed to measure the absorption spectra of the exciton and biexciton states. PLE for Stokes and anti-Stokes PL enables us to clarify the nonlinear optical absorption properties in the lowest exciton and biexciton states. The nonlinear absorption spectra for excitons exhibit asymmetric shapes with peak and dip structures, and provide a distinct contrast to the symmetric dip structures of conventional nonlinear spectra. Theoretical analyses with a density matrix method indicate that the nonlinear spectra are caused not by a simple coherent interaction between the exciton and biexciton states but by coupling effects among exciton, biexciton and continuum states. These results indicate that Fano quantum interference effects appear in exciton-biexciton systems at QDs and offer important insights into their physics.
Wang, Xiaofei; Liu, Xiaojie; Zhao, Xueyang; Yin, Haitao; Wan, Weilong; Feng, Li
2014-03-01
The spin polarized transport properties through an Aharonov-Bohm ring embedded with a double quantum dot-molecule in each arm with Rashba spin-orbit (RSO) interaction is theoretically studied in the framework of the equation of motion of Green's function. Based on molecular state representation, the anti-resonance phenomenon in the conductance spectrum is readily explained. We found that the position of antiresonant peaks in conductance spectrum is determined by the interdot coupling strengths. Moreover, the magnitude of conductance of each spin component can be manipulated by the Rashba spin orbit interaction strength. Especially only one spin component electron can be allowed to transport through this structure by modulating the strength of RSO interaction properly. PMID:24745284
Quantum interference in attosecond transient absorption of laser-dressed helium atoms
Chen, Shaohao; Gaarde, Mette B; Schafer, Kenneth J
2013-01-01
We calculate the transient absorption of an isolated attosecond pulse by helium atoms subject to a delayed infrared (\\ir) laser pulse. With the central frequency of the broad attosecond spectrum near the ionization threshold, the absorption spectrum is strongly modulated at the sub-\\ir-cycle level. Given that the absorption spectrum results from a time-integrated measurement, we investigate the extent to which the delay-dependence of the absorption yields information about the attosecond dynamics of the atom-field energy exchange. We find two configurations in which this is possible. The first involves multi photon transitions between bound states that result in interference between different excitation pathways. The other involves the modification of the bound state absorption lines by the IR field, which we find can result in a sub-cycle time dependence only when ionization limits the duration of the strong field interaction.
Quantum Interference between a Single-Photon Fock State and a Coherent State
Windhager, Armin; Suda, Martin; Pacher, Christoph; Peev, Momtchil; Poppe, Andreas
2010-01-01
We derive analytical expressions for the single mode quantum field state at the individual output ports of a beam splitter when a single-photon Fock state and a coherent state are incident on the input ports. The output states turn out to be a statistical mixture between a displaced Fock state and a coherent state. Consequently we are able to find an analytical expression for the corresponding Wigner function. Because of the generality of our calculations the obtained results are valid for al...
Energy Technology Data Exchange (ETDEWEB)
Henry, S. [University of Oxford, Department of Physics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Pozzo di Borgo, E. [UAPV, UMR1114 EMMAH, F-84914 Avignon, France and INRA, UMR1114 EMMAH, F-84914 Avignon (France); Cavaillou, A. [LSBB URL, UMS 3538 UNS/UAPV/CNRS La Grande Combe, F-84400 Rustrel (France)
2013-02-15
SQUIDs can be used to monitor the three vector components of the geomagnetic field to a high precision at very low frequencies, yet as they are susceptible to external interference, the accuracy to which they can track changes in the dc field over long periods has been unclear. We have carried out simultaneous measurements of the geomagnetic field recorded using two independent 3-axis SQUID magnetometers at the Laboratoire Souterrain a Bas Bruit (LSBB). We demonstrate a technique to take the difference between a linear transform of the three signals from one magnetometer, and a reference signal from the other, in order to account for any difference in alignment and calibration, and track local signals at a sub-nT level. We confirmed that both systems tracked the same signal with an RMS difference as low as 56pT over a period of 72 h. To our knowledge this is the first such demonstration of the long term accuracy of SQUID magnetometers for monitoring geomagnetic fields.
Quantum interference in a Cooper pair splitter: The three sites model
Domínguez, Fernando; Yeyati, Alfredo Levy
2016-01-01
New generation of Cooper pair splitters defined on hybrid nanostructures are devices with high tunable coupling parameters. Transport measurements through these devices revealed clear signatures of interference effects and motivated us to introduce a new model, called the 3-sites model. These devices provide an ideal playground to tune the Cooper pair splitting (CPS) efficiency on demand, and displays a rich variety of physical phenomena. In the present work we analyze theoretically the conductance of the 3-sites model in the linear and non-linear regimes and characterize the most representative features that arise by the interplay of the different model parameters. In the linear regime we find that the local processes typically exhibit Fano-shape resonances, while the CPS contribution exhibits Lorentzian-shapes. Remarkably, we find that under certain conditions, the transport is blocked by the presence of a dark state. In the non-linear regime we established a hierarchy of the model parameters to obtain the conditions for optimal efficiency.
Reprint of : Quantum interference in a Cooper pair splitter: The three sites model
Domínguez, Fernando; Yeyati, Alfredo Levy
2016-08-01
New generation of Cooper pair splitters defined on hybrid nanostructures are devices with high tunable coupling parameters. Transport measurements through these devices revealed clear signatures of interference effects and motivated us to introduce a new model, called the 3-sites model. These devices provide an ideal playground to tune the Cooper pair splitting (CPS) efficiency on demand, and displays a rich variety of physical phenomena. In the present work we analyze theoretically the conductance of the 3-sites model in the linear and non-linear regimes and characterize the most representative features that arise by the interplay of the different model parameters. In the linear regime we find that the local processes typically exhibit Fano-shape resonances, while the CPS contribution exhibits Lorentzian-shapes. Remarkably, we find that under certain conditions, the transport is blocked by the presence of a dark state. In the non-linear regime we established a hierarchy of the model parameters to obtain the conditions for optimal efficiency.
Quantum Interference in the Vibrational Relaxation of the O-H Stretch Overtone of Liquid H2O.
van der Post, Sietse T; Woutersen, Sander; Bakker, Huib J
2016-05-26
Using femtosecond two-color infrared pump-probe spectroscopy, we study the vibrational relaxation of the O-H stretch vibrations of liquid H2O after excitation of the overtone transition. The overtone transition has its maximum at 6900 cm(-1) (1.45 μm), which is a relatively high frequency in view of the central frequency of 3400 cm(-1) of the fundamental transition. The excitation of the overtone leads to a transient induced absorption of two-exciton states of the O-H stretch vibrations. When the overtone excitation frequency is tuned from 6600 to 7200 cm(-1), the vibrational relaxation time constant of the two-exciton states increases from 400 ± 50 fs to 540 ± 40 fs. These values define a limited range of relatively long relaxation time constants compared to the range of relaxation time constants of 250-550 fs that we recently observed for the one-exciton O-H stretch vibrational state of liquid H2O ( S. T. van der Post et al., Nature Comm. 2015 , 6 , 8384 ). We explain the high central frequency and the limited range of relatively long relaxation time constants of the overtone transition from the destructive quantum interference of the mechanical and electrical anharmonic contributions to the overtone transition probability. As a result of this destructive interference, the overtone transition of liquid H2O is dominated by molecules of which the O-H groups donate relatively weak hydrogen bonds to other H2O molecules. PMID:27070075
Czech Academy of Sciences Publication Activity Database
Peřina, Jan
2003-01-01
Roč. 48, č. 4 (2003), s. 99-103. ISSN 0447-6441 R&D Projects: GA MŠk LN00A015 Institutional research plan: CEZ:AV0Z1010921 Keywords : interference * quantum cryptography * quantum computing * quantum teleportation Subject RIV: BH - Optics, Masers, Lasers
Interference effects in the Si-Ge heterostructures with quantum wells of different width
International Nuclear Information System (INIS)
The effects of weak localization and interaction of charge carriers in a two p-type Si0.7Ge0.3/Si0.2Ge0.8/Si0.7Ge0.3 heterostructures with one and two subbands, respectively, occupy have been investigated. The weak localization effect of holes in conditions when the inelastic scattering time and spin orbit scattering time have close values was found in very weak magnetic fields. It is shown that splitting of the spin states occurs due to the influence of the perturbing potential (Rashba mechanism). The interaction effect which occurs due to Coulomb interaction with a scatter has been detected and analyzed in higher magnetic fields in case of one subband occupy. The dominant mechanism of scattering by Friedel oscillations of the charge carrier density, induced by the electric field of the impurity, is a dominant in the case of two subband occupy. In all regions the behavior of the interaction quantum correction is in good agreement with the modern theoretical predictions.
International Nuclear Information System (INIS)
We investigated and optimized the low-frequency noise characteristics of a preamplifier used for readout of direct current superconducting quantum interference devices (SQUIDs). When the SQUID output was detected directly using a room-temperature low-voltage-noise preamplifier, the low-frequency noise of a SQUID system was found to be dominated by the input current noise of the preamplifiers in case of a large dynamic resistance of the SQUID. To reduce the current noise of the preamplifier in the low-frequency range, we investigated the dependence of total preamplifier noise on the collector current and source resistance. When the collector current was decreased from 8.4 mA to 3 mA in the preamplifier made of 3 parallel SSM2220 transistor pairs, the low-frequency total voltage noise of the preamplifier (at 0.1 Hz) decreased by about 3 times for a source resistance of 30 Ω whereas the white noise level remained nearly unchanged. Since the relative contribution of preamplifier's input voltage and current noise is different depending on the dynamic resistance or flux-to-voltage transfer of the SQUID, the results showed that the total noise of a SQUID system at low-frequency range can be improved significantly by optimizing the preamplifier circuit parameters, mainly the collector current in case of low-noise bipolar transistor pairs
Hasdeo, Eddwi H.; Nugraha, Ahmad R. T.; Dresselhaus, Mildred S.; Saito, Riichiro
2016-08-01
Intensities of the first- and the second-order Raman spectra are calculated as a function of the Fermi energy. We show that the Kohn anomaly effect, i.e., phonon frequency renormalization, in the first-order Raman spectra originates from the phonon renormalization by the interband electron-hole excitation, whereas in the second-order Raman spectra, a competition between the interband and intraband electron-hole excitations takes place. By this calculation, we confirm the presence of different dispersive behaviors of the Raman peak frequency as a function of the Fermi energy for the first- and the second-order Raman spectra, as observed in some previous experiments. Moreover, the calculated results of the Raman intensity sensitively depend on the Fermi energy for both the first- and the second-order Raman spectra, indicating the presence of the quantum interference effect. The electron-phonon matrix element plays an important role in the intensity increase (decrease) of the combination (overtone) phonon modes as a function of the Fermi energy.
International Nuclear Information System (INIS)
Sensitive radio-frequency (rf) amplifiers based on dc Superconducting QUantum Interface Devices (SQUIDS) are available for frequencies up to 200 MHz. At 4.2 K, the gain and noise temperature of a typical tuned amplifier are 18.6 +- 0.5 dB and 1.7 +- 0.5 K at 93 MHz. These amplifiers are being applied to a series of novel experiments on nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR). The high sensitivity of these amplifiers was demonstrated in the observation of ''nuclear spin noise'', the emission of photons by 35Cl nuclei in a state of zero polarization. In the more conventional experiments in which one applies a large rf pulse to the spins, a Q-spoiler, consisting of a series array of Josephson junctions, is used to reduce the Q of the input circuit to a very low value during the pulse. The Q-spoiler enables the circuit to recover quickly after the pulse, and has been used in an NQR experiment to achieve a sensitivity of about 2 /times/ 1016 nuclear Bohr magnetons in a single free precession signal with a bandwidth of 10 kHz. In a third experiment, a sample containing 35Cl nuclei was placed in a capacitor and the signal detected electrically using a tuned SQUID amplifier and Q-spoiler. In this way, the electrical polarization induced by the precessing Cl nuclear quadrupole moments was detected: this is the inverse of the Stark effect in NQR. Two experiments involving NMR have been carried out. In the first, the 30 MHz resonance in 119Sn nuclei is detected with a tuned amplifier and Q-spoiler, and a single pulse resolution of 1018 nuclear Bohr magnetons in a bandwidth of 25 kHz has been achieved. For the second, a low frequency NMR system has been developed that uses an untuned input circuit coupled to the SQUID. The resonance in 195Pt nuclei has been observed at 55 kHz in a field of 60 gauss. 23 refs., 11 figs
Anomalous Magnetohydrodynamics
Giovannini, Massimo
2013-01-01
Anomalous symmetries induce currents which can be parallel rather than orthogonal to the hypermagnetic field. Building on the analogy with charged liquids at high magnetic Reynolds numbers, the persistence of anomalous currents is scrutinized for parametrically large conductivities when the plasma approximation is accurate. Different examples in globally neutral systems suggest that the magnetic configurations minimizing the energy density with the constraint that the helicity be conserved co...
Energy Technology Data Exchange (ETDEWEB)
Wagner, Konrad
2007-09-15
In the framework of the thesis presented here for the first time quantum interference effects in ferromagnetic semiconductors could be uniquely detected. For this wire and ring structures with line widths of few nanometers were fabricated and universal conductivity fluctuations and Aharonov-Bohm oscillations at very low temperatures (<20 mK) were studied. From the analysis of the temperature and length dependence of the fluctuations knowledge about the coherence length and the scattering processes connected with this could be obtained.
Superconducting quantum interference detector
International Nuclear Information System (INIS)
The detector is made of a lead foil whose surface is finished with mineral acids. Coiling the foil wh+ch is inductively bonded to a resonance oscillating circuit forms a system of Josephson tunnel contacts. The detector signal was experimentally shown to be many times higher than signals from niobium detectors with point contacts. The detector described is suitable for measuring voltages in the order of 10-14 to 10-15 V, currents of the same order, magnetic fields, etc. (J.B.)
Conradson, Steven D.; Andersson, David A.; Bagus, Paul S.; Boland, Kevin S.; Bradley, Joseph A.; Byler, Darrin D.; Clark, David L.; Conradson, Dylan R.; Espinosa-Faller, Francisco J.; Lezama Pacheco, Juan S.; Martucci, Mary B.; Nordlund, Dennis; Seidler, Gerald T.; Valdez, James A.
2016-05-01
Hypervalent UO2, UO2(+x) formed by both addition of excess O and photoexcitation, exhibits a number of unusual or often unique properties that point to it hosting a polaronic Bose-Einstein(-Mott) condensate. A more thorough analysis of the O X-ray absorption spectra of UO2, U4O9, and U3O7 shows that the anomalous increase in the width of the spectral features assigned to predominantly U 5f and 6d final states that points to increased dispersion of these bands occurs on the low energy side corresponding to the upper edge of the gap bordered by the conduction or upper Hubbard band. The closing of the gap by 1.5 eV is more than twice as much as predicted by calculations, consistent with the dynamical polaron found by structural measurements. In addition to fostering the excitation that is the proposed mechanism for the coherence, the likely mirroring of this effect on the occupied, valence side of the gap below the Fermi level points to increased complexity of the electronic structure that could be associated with the Fermi topology of BEC-BCS crossover and two band superconductivity.
DEFF Research Database (Denmark)
Unsleber, S.; McCutcheon, Dara; Dambach, M.;
We demonstrate the emission of highly indistinguishable photons from a quasiresonantly pumped coupled quantum dot–microcavity system operating in the regime of cavity quantum electrodynamics. Changing the sample temperature allows us to vary the quantum dot–cavity detuning, and on spectral...
International Nuclear Information System (INIS)
We have developed a scanning superconducting quantum interference device (SQUID) microscope system with interchangeable sensor configurations for imaging magnetic fields of room-temperature (RT) samples with submillimeter resolution. The low-critical-temperature (Tc) niobium-based monolithic SQUID sensors are mounted on the tip of a sapphire and thermally anchored to the helium reservoir. A 25 μm sapphire window separates the vacuum space from the RT sample. A positioning mechanism allows us to adjust the sample-to-sensor spacing from the top of the Dewar. We achieved a sensor-to-sample spacing of 100 μm, which could be maintained for periods of up to four weeks. Different SQUID sensor designs are necessary to achieve the best combination of spatial resolution and field sensitivity for a given source configuration. For imaging thin sections of geological samples, we used a custom-designed monolithic low-Tc niobium bare SQUID sensor, with an effective diameter of 80 μm, and achieved a field sensitivity of 1.5 pT/Hz1/2 and a magnetic moment sensitivity of 5.4x10-18 A m2/Hz1/2 at a sensor-to-sample spacing of 100 μm in the white noise region for frequencies above 100 Hz. Imaging action currents in cardiac tissue requires a higher field sensitivity, which can only be achieved by compromising spatial resolution. We developed a monolithic low-Tc niobium multiloop SQUID sensor, with sensor sizes ranging from 250 μm to 1 mm, and achieved sensitivities of 480-180 fT/Hz1/2 in the white noise region for frequencies above 100 Hz, respectively. For all sensor configurations, the spatial resolution was comparable to the effective diameter and limited by the sensor-to-sample spacing. Spatial registration allowed us to compare high-resolution images of magnetic fields associated with action currents and optical recordings of transmembrane potentials to study the bidomain nature of cardiac tissue or to match petrography to magnetic field maps in thin sections of geological
Gavrilyuk, S A; Polyutov, S P
2001-01-01
The obvious expressions for the rectified radiation forces, generated by the impact of weak interference optical fields of the arbitrary three-dimensional configuration on the resonance particles with the J = 0 -> J = 1 quantum transition, are obtained. It is shown that in contrast to the case of the monochromatic field there exist simple three-dimensional configurations of the biharmonic fields, whereby the ratio between the vortex and potential components of the rectified radiation force may be arbitrarily controlled by rearranging frequencies and polarization of the interference light waves. By such a rearrangement of the rectified radiation force there originate qualitatively different types of the vortex and vortex-free light-induced particles motion, which may lead to their three-dimensional spatial localization in the effective light lattice cells with the period significantly higher than the light wavelength. In particular, the stable rotational motion of the particles by closed orbits proves to be po...
Wu, C. C.; Hong, B. F.; Wu, B. H.; Yang, S. Y.; Horng, H. E.; Yang, H. C.; Tseng, W. Y. Isaac; Tseng, W. K.; Liu, Y. B.; Lin, L. C.; Lu, L. S.; Lee, Y. H.
2007-01-01
In this work, the authors used a superconducting quantum interference device (SQUID) magnetocardiography (MCG) system consisted of 64-channel low-transition-temperature SQUID gradiometers to detect the MCG signals of hepercholesterolemic rabbits. In addition, the MCG signals were recorded before and after the injection of magnetic nanoparticles into the rabbits' ear veins to investigate the effects of magnetic nanoparticles on the MCG signals. These MCG data were compared to those of normal rabbits to reveal the feasibility for early detection of the electromagnetic changes induced by hypercholesterolemia using MCG with the assistance of magnetic nanoparticle injection.
Martínez-Pérez, M J; Sesé, J; Luis, F; Drung, D; Schurig, T
2010-01-01
We report the experimental results that show the operation of superconducting quantum interference device (SQUID) microsusceptometers immersed in the (3)He-(4)He mixture inside the mixing chamber of a dilution refrigerator at high frequency (1 MHz) and down to very low temperatures (13 mK). The devices are based on highly sensitive and easy-to-use commercial SQUID sensors. The integrated susceptometers are fabricated by rerouting some connections of the SQUID's input circuit. Examples of measurements on molecular magnets Mn(12) and HoW(10) are shown. PMID:20113139
Anomalous Fano resonance of massive Dirac particle through a time-dependent barrier
Zhang, Cunxi; Liu, Jie; Fu, Libin
2015-06-01
As is well known Fano resonance arises from the interference between a localized state and a continuum state. Using the standard Floquet theory and the scattering matrix method, we study theoretically the massive Dirac particle transmission over a quantum barrier with an oscillating field. It is found that the massive relativistic particles can generate not only normal Fano resonance in the transmission due to the interference between a localized state (bound state) and the continuum state, but also anomalous Fano resonance due to the interference between a delocalized state (extended state) and the continuum state. The dependence of line shapes on driving parameters for these two kinds of Fano resonances is quite different. For normal Fano resonance the asymmetry parameter is approximately proportional to a power law of the amplitude of the oscillating field, while for the anomalous Fano resonance the asymmetry parameters change slightly with different oscillation amplitudes. In practice, the anomalous Fano resonance can be identified by observing asymmetry parameters in experiment.
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...
Effective actions for anomalous hydrodynamics
International Nuclear Information System (INIS)
We argue that an effective field theory of local fluid elements captures the constraints on hydrodynamic transport stemming from the presence of quantum anomalies in the underlying microscopic theory. Focussing on global current anomalies for an arbitrary flavour group, we derive the anomalous constitutive relations in arbitrary even dimensions. We demonstrate that our results agree with the constraints on anomaly governed transport derived hitherto using a local version of the second law of thermodynamics. The construction crucially uses the anomaly inflow mechanism and involves a novel thermofield double construction. In particular, we show that the anomalous Ward identities necessitate non-trivial interaction between the two parts of the Schwinger-Keldysh contour
Chen, Wei; Wang, Z. D.; Shen, R.; D. Y. Xing
2013-01-01
We propose an entanglement detector composed of two quantum spin Hall insulators and a side gate deposited on one of the edge channels. For an ac gate voltage, the differential noise contributed from the entangled electron pairs exhibits the nontrivial step structures, from which the spin entanglement concurrence can be easily obtained. The possible spin dephasing effects in the quantum spin Hall insulators are also included.
International Nuclear Information System (INIS)
The strong-field (multiphoton) process of above-threshold ionization (ATI) in laser-irradiated fullerene C60 is addressed theoretically within molecular strong-field approximation (SFA) applied in the so-called velocity-gauge (VG) formulation with respect to a strong electromagnetic interaction with incident laser field. The applied VG-SFA approach also essentially exploits the density-functional-theory (DFT) method for numerical composition of initial (laser-free) molecular wavefunction and respective the highest-occupied molecular orbital (HOMO) using the model LBα (van Leu wen-Baerends) intramolecular binding potential, which incorporates both the exchange and correlation model LSDA-potentials. According to the results of our DFT-SFA based numerical simulations (calculated for Ti:Sapphire laser radiation of wavelength λ = 800 nm and 35 fs pulse duration), the ionization of C60 reaches saturation at laser peak intensity I ≅ 2x1014 W/cm2, that is fairly well consistent with relevant experimental value. In addition, our findings proved to demonstrate at least two pronounced interference-related minima arising both in low-energy and high-energy domains of numerically calculated C60 photoelectron energy spectra (PES) due to destructive intramolecular (multislit) laser field-induced quantum interference, In particular, due to destructive interference in low-energy domain, the respective low-energy ATI photoelectron peaks are always highly suppressed that explains a high suppression in strong-field ionization of C60, thereby providing quite a clear and transparent physical interpretation within the molecular DFT-SFA presently applied. Whereas, the location of the high-energy interference minimum proved to be strongly dependent on the laser wavelength λ, in a full accordance with the theory prediction. (authors)
The role of quantum interference and partial redistribution in the solar Ba II D2 4554 A line
Smitha, H N; Stenflo, J O; Sampoorna, M
2014-01-01
The Ba II D2 line at 4554 A is a good example, where the F-state interference effects due to the odd isotopes produce polarization profiles, which are very different from those of the even isotopes that do not exhibit F-state interference. It is therefore necessary to account for the contributions from the different isotopes to understand the observed linear polarization profiles of this line. In this paper we present radiative transfer modeling with partial frequency redistribution (PRD), which is shown to be essential to model this line. This is because complete frequency redistribution (CRD) cannot reproduce the observed wing polarization. We present the observed and computed Q/I profiles at different limb distances. The theoretical profiles strongly depend on limb distance (\\mu) and the model atmosphere which fits the limb observations fails at other \\mu\\ positions.
Energy Technology Data Exchange (ETDEWEB)
Deeney, F.A., E-mail: f.a.deeney@ucc.ie [Physics Department, National University of Ireland, Cork (Ireland); O' Leary, J.P. [Physics Department, National University of Ireland, Cork (Ireland)
2012-07-30
The recently reported evidence for the existence of an unstable state of the dineutron has raised again the issues associated with this particle and with the related deuteron. For the dineutron there is the question of why it has no stable ground state, while for the deuteron the magnetic and electric properties are unusual. In this Letter we show how it is possible to explain these effects in a simple way, using only considerations of interference between the wave functions of two spin 1/2 particles in the same energy state. -- Highlights: ► We investigate the interference between the wave functions of two spin half particles. ► We show how the interference predicts a spin of ℏ for the ground state of the dineutron. ► Applying the theory to the deuteron shows that its spin is tilted slighted from that of the dineutron. ► The tilted spin shows the presence of an additional spin component normal to the principal one. ► The unusual features of the deuteron properties are simply explained by the theory.
Lin, Li-Hua
2010-05-01
We describe a scheme for the generation of macroscopic quantum-interference states for a collection of trapped ions by a single geometric phase operation. In the scheme the vibrational mode is displaced along a circle with the radius proportional to the number of ions in a certain ground electronic state. For a given interaction time, the vibrational mode returns to the original state, and the ionic system acquires a geometric phase proportional to the area of the circle, evolving from a coherent state to a superposition of two coherent states. The ions undergo no electronic transitions during the operation. Taking advantage of the inherent fault-tolerant feature of the geometric operation, our scheme is robust against decoherence.
Sim, Sangwan; Koirala, Nikesh; Brahlek, Matthew; Sung, Ji Ho; Park, Jun; Cha, Soonyoung; Jo, Moon-Ho; Oh, Seongshik; Choi, Hyunyong
2015-06-01
Asymmetric Fano resonance arises from quantum interference between discrete and continuum states. The characteristic asymmetry has attracted strong interests in understanding light-induced optoelectronic responses and corresponding applications. In conventional solids, however, the tunability of Fano resonance is generally limited by a material's intrinsic property. Topological insulators are unique states of matter embodying both conducting Dirac surface and underlying bulk. If it is possible to manipulate the two coexisting states, then it should form an ideal laboratory for realizing a tunable topological Fano system. Here, with the recently discovered topological phase transition in (Bi1-xI nx ) 2S e3 , we report tunable Fano interference phenomena. By engineering the spatial overlap between surface Dirac electrons (continuous terahertz transitions) and bulk phonon (discrete mode at ˜2 terahertz), we continuously tune, abruptly switch, and dynamically modulate the Fano resonance. Eliminating the topological surface via decreasing spin-orbit coupling―that is, across topological and nontopological phases, we find that the asymmetric Fano spectra return to the symmetric profile. Laser-excited ultrafast terahertz spectroscopy reveals that the controlled spatial overlap is responsible for the picosecond tunability of the Fano resonance, suggesting potentials toward optically controllable topological Fano systems.
International Nuclear Information System (INIS)
The multiconfiguration Dirac-Fock method has been used to study interference effects between direct and resonant photorecombination (i.e. radiative and dielectronic recombination) from the ground state 1s2S1/2 of H-like Ar17+ ions via doubly excited 2s21S0, 2s2p 3P0,1,2, 1P1 and 2p23P0,1,2, 1D2, 1S0 resonances of He-like Ar16+ ions combined with the Fano parameterization technique. In order to produce total photorecombination spectra, it is necessary to calculate the energy levels of the 1s of H-like Ar17+ ions, 1s2, 1s2l and 2l2l' (l,l' =0, 1) of He-like Ar16+ ions, the radiative and nonradiative properties of the doubly excited states of He-like Ar16+ ions, and the direct and resonant photorecombination cross sections from the 1s state of H-like Ar17+ ions into the ground state 1s2 and the single excited states of 1s2l (l=0, 1) of He-like Ar16+ ions, in detail. Based on good agreement between the present calculations and other available experimental and theoretical results, the interference profile determined by the so-called Fano parameters q and ρ2 is also shown. The results indicate that interference effects are remarkable at some resonances, especially near the doubly excited 2s2p 1P1 state of He-like Ar16+ ions, and strongly influence the intensity of the wing of the nonresonant background in the photorecombination of H-like Ar17+ ions through comparison between the final Fano and total radiative recombination to dielectronic recombination spectra.
Energy Technology Data Exchange (ETDEWEB)
Wan Jianjie; Dong Chenzhong, E-mail: dongcz@nwnu.edu.cn [College of Physics and Electronic Engineering, Northwest Normal University, 730070 Lanzhou (China)
2011-10-15
The multiconfiguration Dirac-Fock method has been used to study interference effects between direct and resonant photorecombination (i.e. radiative and dielectronic recombination) from the ground state 1s{sup 2}S{sub 1/2} of H-like Ar{sup 17+} ions via doubly excited 2s{sup 2} {sup 1}S{sub 0}, 2s2p {sup 3}P{sub 0,1,2}, {sup 1}P{sub 1} and 2p{sup 2} {sup 3}P{sub 0,1,} {sub 2}, {sup 1}D{sub 2}, {sup 1}S{sub 0} resonances of He-like Ar{sup 16+} ions combined with the Fano parameterization technique. In order to produce total photorecombination spectra, it is necessary to calculate the energy levels of the 1s of H-like Ar{sup 17+} ions, 1s{sup 2}, 1s2l and 2l2l' (l,l' =0, 1) of He-like Ar{sup 16+} ions, the radiative and nonradiative properties of the doubly excited states of He-like Ar{sup 16+} ions, and the direct and resonant photorecombination cross sections from the 1s state of H-like Ar{sup 17+} ions into the ground state 1s{sup 2} and the single excited states of 1s2l (l=0, 1) of He-like Ar{sup 16+} ions, in detail. Based on good agreement between the present calculations and other available experimental and theoretical results, the interference profile determined by the so-called Fano parameters q and {rho}{sup 2} is also shown. The results indicate that interference effects are remarkable at some resonances, especially near the doubly excited 2s2p {sup 1}P{sub 1} state of He-like Ar{sup 16+} ions, and strongly influence the intensity of the wing of the nonresonant background in the photorecombination of H-like Ar{sup 17+} ions through comparison between the final Fano and total radiative recombination to dielectronic recombination spectra.
Nyman, Peter
2011-01-01
The quantum-like representation algorithm (QLRA) was introduced by A. Khrennikov \\cite{K1,K2,K3,K4,K5} to solve the "inverse Born's rule problem", i.e. to construct a representation of probabilistic data - measured in any context of science - and represent this data by a complex or more general (A Clifford algebra is introduced for this more general representation) probability amplitude which matches a generalization of Born's rule. The outcome from QLRA will introduce the formula of total pr...
Phonon-Mediated Nonclassical Interference in Diamond
England, Duncan G.; Fisher, Kent A. G.; MacLean, Jean-Philippe W.; Bustard, Philip J.; Heshami, Khabat; Resch, Kevin J.; Sussman, Benjamin J.
2016-08-01
Quantum interference of single photons is a fundamental aspect of many photonic quantum processing and communication protocols. Interference requires that the multiple pathways through an interferometer be temporally indistinguishable to within the coherence time of the photon. In this Letter, we use a diamond quantum memory to demonstrate interference between quantum pathways, initially temporally separated by many multiples of the optical coherence time. The quantum memory can be viewed as a light-matter beam splitter, mapping a THz-bandwidth single photon to a variable superposition of the output optical mode and stored phononic mode. Because the memory acts both as a beam splitter and as a buffer, the relevant coherence time for interference is not that of the photon, but rather that of the memory. We use this mechanism to demonstrate nonclassical single-photon and two-photon interference between quantum pathways initially separated by several picoseconds, even though the duration of the photons themselves is just ˜250 fs .
Energy Technology Data Exchange (ETDEWEB)
Saari, M. M., E-mail: en19463@s.okayama-u.ac.jp; Sakai, K.; Kiwa, T.; Tsukada, K. [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Sasayama, T.; Yoshida, T. [Department of Electrical and Electronic Engineering, Kyushu University, Fukuoka 819-0395 (Japan)
2015-05-07
We developed a highly sensitive AC/DC magnetometer using a high-temperature superconductor superconducting quantum interference device for the evaluation of magnetic nanoparticles in solutions. Using the developed system, we investigated the distribution of magnetic moments of iron oxide multi-core particles of 100 nm at various iron concentrations that are lower than 96 μg/ml by analyzing the measured magnetization curves. Singular value decomposition and non-regularized non-negative least-squares methods were used during the reconstruction of the distribution. Similar distributions were obtained for all concentrations, and the iron concentration could be determined from the measured magnetization curves. The measured harmonics upon the excitation of AC and DC magnetic fields curves agreed well with the harmonics simulated based on the reconstructed magnetization curves, implying that the magnetization curves of magnetic nanoparticles were successfully obtained as we will show in the article. We compared the magnetization curves between multi-core particles of 100 nm and 130 nm, composed of 12-nm iron oxide nanoparticles. A distinctive magnetic property between the 100 nm and 130 nm particles in low-concentration solutions was successfully characterized. The distribution characteristic of magnetic moments suggests that the net magnetic moment in a multi-core particle is affected by the size of the magnetic cores and their degree of aggregation. Exploration of magnetic properties with high sensitivity can be expected using the developed system.
International Nuclear Information System (INIS)
Current experimental limits on the number of magnetic monopoles bound in matter are based on only a few dozen kilograms of material, and of the former experiments only a handful used superconducting-quantum-interference-device- (SQUID) based detection techniques. Furthermore, all previous searches for trapped monopoles used material formed or gathered from either the surface of the Earth or Moon, where ultramassive grand unified field theory monopoles would not be expected to stop. Using a new type of ultraefficient SQUID magnetometer which allows large volumes of room-temperature matter to pass directly through a superconducting loop, we examined a suite of high-pressure metamorphic rocks which had been buried at depths of up to 25 km and yet remained below the Curie temperature of the ferromagnetic minerals present. In addition, we also examined large volumes of manganese nodules and seawater, for a total mass of 643 kg of rock and 180 kg of seawater. No monopoles were found, suggesting that their cosmic abundance is either extremely low or they are not easily stopped or trapped by passage through a minimum of 25 km of the Earth's crust. We suggest that the next best place to look for monopoles is in cometary dust
International Nuclear Information System (INIS)
We developed a highly sensitive AC/DC magnetometer using a high-temperature superconductor superconducting quantum interference device for the evaluation of magnetic nanoparticles in solutions. Using the developed system, we investigated the distribution of magnetic moments of iron oxide multi-core particles of 100 nm at various iron concentrations that are lower than 96 μg/ml by analyzing the measured magnetization curves. Singular value decomposition and non-regularized non-negative least-squares methods were used during the reconstruction of the distribution. Similar distributions were obtained for all concentrations, and the iron concentration could be determined from the measured magnetization curves. The measured harmonics upon the excitation of AC and DC magnetic fields curves agreed well with the harmonics simulated based on the reconstructed magnetization curves, implying that the magnetization curves of magnetic nanoparticles were successfully obtained as we will show in the article. We compared the magnetization curves between multi-core particles of 100 nm and 130 nm, composed of 12-nm iron oxide nanoparticles. A distinctive magnetic property between the 100 nm and 130 nm particles in low-concentration solutions was successfully characterized. The distribution characteristic of magnetic moments suggests that the net magnetic moment in a multi-core particle is affected by the size of the magnetic cores and their degree of aggregation. Exploration of magnetic properties with high sensitivity can be expected using the developed system
Niu, Wei; Gao, Ming; Wang, Xuefeng; Song, Fengqi; Du, Jun; Wang, Xinran; Xu, Yongbing; Zhang, Rong
2016-01-01
Quantum interference effects (QIEs) dominate the appearance of low-temperature resistivity minimum in colossal magnetoresistance manganites. The T(1/2) dependent resistivity under high magnetic field has been evidenced as electron-electron (e-e) interaction. However, the evidence of the other source of QIEs, weak localization (WL), still remains insufficient in manganites. Here we report on the direct experimental evidence of WL in QIEs observed in the single-crystal La0.7Sr0.3MnO3 (LSMO) ultrathin films deposited by laser molecular beam epitaxy. The sharp cusps around zero magnetic field in magnetoresistance measurements is unambiguously observed, which corresponds to the WL effect. This convincingly leads to the solid conclusion that the resistivity minima at low temperatures in single-crystal manganites are attributed to both the e-e interaction and the WL effect. Moreover, the temperature-dependent phase-coherence length corroborates the WL effect of LSMO ultrathin films is within a two-dimensional localization theory. PMID:27181882
Wess-Zumino terms for reducible anomalous gauge theories
International Nuclear Information System (INIS)
Reducible off-shell anomalous gauge theories are studied in the framework of an extended Field-Antifield formalism by introducing new variables associated with the anomalous gauge degrees of freedom. The Wess-Zumino term for these theories is constructed and new gauge invariances appear. The quantum effects due to the extra variables are considered. (orig.)
DEFF Research Database (Denmark)
Popovski, Petar; Simeone, Osvaldo; Nielsen, Jimmy Jessen;
2015-01-01
traffic load and interference condition leads to performance gains. In this letter, a general network of multiple interfering two-way links is studied under the assumption of a balanced load in the two directions for each link. Using the notion of interference spin, we introduce an algebraic framework for...
Wave and Particle in Molecular Interference Lithography
Juffmann, Thomas; Geyer, Philipp; Major, Andras G; Deachapunya, Sarayut; Ulbricht, Hendrik; Arndt, Markus; 10.1103/PhysRevLett.103.263601
2010-01-01
The wave-particle duality of massive objects is a cornerstone of quantum physics and a key property of many modern tools such as electron microscopy, neutron diffraction or atom interferometry. Here we report on the first experimental demonstration of quantum interference lithography with complex molecules. Molecular matter-wave interference patterns are deposited onto a reconstructed Si(111) 7x7 surface and imaged using scanning tunneling microscopy. Thereby both the particle and the quantum wave character of the molecules can be visualized in one and the same image. This new approach to nanolithography therefore also represents a sensitive new detection scheme for quantum interference experiments.
Mineshige, S.; Kawabata, S.; Faniel, S.; Waugh, J.; Sekine, Y.; Koga, T.
2011-12-01
We present a semiclassical interpretation of the time-reversal spin interference (SI) observed in the square loop arrays made of In0.53Ga0.47As quantum wells [T. Koga , Phys. Rev. BPLRBAQ1098-012110.1103/PhysRevB.74.041302 74, 041302 (2006)]. The simulated amplitude of SI as a function of the Rashba parameter α captured characteristic features in the experimental results if γ≲8 eV Å3 is assumed for the bulk Dresselhaus spin-orbit constant γ. Our work proves the validity of the semiclassical approach to predict the effect of time-reversal quantum interference in mesoscopic systems and the values of the spin-orbit coefficients recently deduced from the weak localization/antilocalization experiment.
Yahya, Noorhana; Zakariah, Muhammad Hanis
2012-10-01
Electromagnetic (EM) waves transmitted by Horizontal Electric Dipole (HED) source to detect contrasts in subsurface resistivity termed Seabed Logging (SBL) is now an established method for hydrocarbon exploration. However, currently used EM wave detectors for SBL have several challenges including the sensitivity and its bulk size. This work exploits the benefit of superconductor technology in developing a magnetometer termed Superconducting Quantum Interference Device (SQUID) which can potentially be used for SBL. A SQUID magnetometer was fabricated using hexagon shape-niobium wire with YBa2Cu37O, (YBCO) as a barrier. The YBa2Cu37O, samples were synthesized by sol-gel method and were sintered using a furnace and conventional microwave oven. The YBCO gel was dried at 120 degrees C in air for 72 hours. It was then ground and divided into 12 parts. Four samples were sintered at 750 degrees C, 850 degrees C, 900 degrees C, and 950 degrees C for 12 hours in a furnace to find the optimum temperature. The other eight samples were sintered in a microwave with 1100 Watt (W) with a different sintering time, 5, 15, 45 minutes, 1 hour, 1 hour 15 minutes, 1 hour 30 minutes, 1 hour 45 minutes and 2 hours. A DEWAR container was designed and fabricated using fiberglass material. It was filled with liquid nitrogen (LN2) to ensure the superconducting state of the magnetometer. XRD results showed that the optimum sintering temperature for the formation of orthorhombic Y-123 phase was at 950 degrees C with the crystallite size of 67 nm. The morphology results from Field Emission Scanning Electron Microscopy (FESEM) showed that the grains had formed a rod shape with an average diameter of 60 nm. The fabricated SQUID magnetometer was able to show an increment of approximately 249% in the intensity of the EM waves when the source receiver offset was one meter apart. PMID:23421192
Indistinguishability interference
International Nuclear Information System (INIS)
Using directly the postulates of quantum theory, the existence of bosons and fermions, and only them, in nature is shown. The enhancement (boson) and inhibition (fermion) factors, are deduced from which the quantum distribution formulae follow directly, with no need of obscure normalisation arguments. The spin-statistics relation is illustrated by an analogy between the Stern-Gerlach and Young experiments. (author)
Interference of probabilities in dynamics
Energy Technology Data Exchange (ETDEWEB)
Zak, Michail, E-mail: michail.zak@gmail.com [Jet Propulsion Laboratory California Institute of Technology, Pasadena, CA 91109 (United States)
2014-08-15
A new class of dynamical systems with a preset type of interference of probabilities is introduced. It is obtained from the extension of the Madelung equation by replacing the quantum potential with a specially selected feedback from the Liouville equation. It has been proved that these systems are different from both Newtonian and quantum systems, but they can be useful for modeling spontaneous collective novelty phenomena when emerging outputs are qualitatively different from the weighted sum of individual inputs. Formation of language and fast decision-making process as potential applications of the probability interference is discussed.
Superconducting quantum-interference devices
Peters, P. N.; Holdeman, L. B.
1975-01-01
Published document discusses devices which are based on weak-link Josephson elements that join superconductors. Links can take numerous forms, and circuitry utilizing links can perform many varied functions with unprecedented sensitivity. Theoretical review of Josephson's junctions include tunneling junctions, point contact devices, microbridges, and proximity-effect devices.
Emergence of quantum mechanics from a sub-quantum statistical mechanics
Grössing, Gerhard
2014-07-01
A research program within the scope of theories on "Emergent Quantum Mechanics" is presented, which has gained some momentum in recent years. Via the modeling of a quantum system as a non-equilibrium steady-state maintained by a permanent throughput of energy from the zero-point vacuum, the quantum is considered as an emergent system. We implement a specific "bouncer-walker" model in the context of an assumed sub-quantum statistical physics, in analogy to the results of experiments by Couder and Fort on a classical wave-particle duality. We can thus give an explanation of various quantum mechanical features and results on the basis of a "21st century classical physics", such as the appearance of Planck's constant, the Schrödinger equation, etc. An essential result is given by the proof that averaged particle trajectories' behaviors correspond to a specific type of anomalous diffusion termed "ballistic" diffusion on a sub-quantum level. It is further demonstrated both analytically and with the aid of computer simulations that our model provides explanations for various quantum effects such as double-slit or n-slit interference. We show the averaged trajectories emerging from our model to be identical to Bohmian trajectories, albeit without the need to invoke complex wavefunctions or any other quantum mechanical tool. Finally, the model provides new insights into the origins of entanglement, and, in particular, into the phenomenon of a "systemic" non-locality.
Mineshige, S.; Kawabata, S.; Faniel, S.; Waugh, J.; Sekine, Y; Koga, T
2011-01-01
We present a semiclassical interpretation of the time-reversal spin interference (SI) observed in the square loop arrays made of In0.53Ga0.47As quantum wells [T. Koga et al., Phys. Rev. B 74, 041302 (2006)]. The simulated amplitude of SI as a function of the Rashba parameter α captured characteristic features in the experimental results if γ ≲ 8 eV Å3 is assumed for the bulk Dresselhaus spin-orbit constant γ. Our work proves the validity of the semiclassical approach to predict the effect of ...
Charge transport in manganites: Hopping conduction, the anomalous Hall effect, and universal scaling
International Nuclear Information System (INIS)
The low-temperature Hall resistivity ρxy of La2/3A1/3MnO3 single crystals (where A stands for Ca, Pb, and Ca, or Sr) can be separated into ordinary and anomalous contributions, giving rise to ordinary and anomalous Hall effects, respectively. However, no such decomposition is possible near the Curie temperature which, in these systems, is close to metal-to-insulator transition. Rather, for all of these compounds and to a good approximation, the ρxy data at various temperatures and magnetic fields collapse (up to an overall scale), on to a single function of the reduced magnetization m(equivalent to)M/Msat, the extremum of this function lying at m∼0.4. A mechanism for the anomalous Hall effect in the inelastic hopping regime, which reproduces these scaling curves, is identified. This mechanism, which is an extension of Holstein's model for the ordinary Hall effect in the hopping regime, arises from the combined effects of the double-exchange-induced quantal phase in triads of Mn ions and spin-orbit interactions. We identify processes that lead to the anomalous Hall effect for localized carriers and, along the way, analyze issues of quantum interference in the presence of phonon-assisted hopping. Our results suggest that, near the ferromagnet-to-paramagnet transition, it is appropriate to describe transport in manganites in terms of carrier hopping between states that are localized due to the combined effect of magnetic and nonmagnetic disorder. We attribute the qualitative variations in resistivity characteristics across manganite compounds to the differing strengths of their carrier self-trapping, and conclude that both disorder-induced localization and self-trapping effects are important for transport
Interference of spontaneously emitted photons
Beige, A; Pachos, J; Beige, Almut; Schoen, Christian; Pachos, Jiannis
2002-01-01
We discuss an experimental setup where two laser-driven atoms spontaneously emit photons and every photon causes a ``click'' at a point on a screen. By deriving the probability density for an emission into a certain direction from basic quantum mechanical principles we predict a spatial interference pattern. Similarities and differences with the classical double-slit experiment are discussed.
Interference of spontaneously emitted photons
Beige, Almut; Schoen, Christian; Pachos, Jiannis
2001-01-01
We discuss an experimental setup where two laser-driven atoms spontaneously emit photons and every photon causes a ``click'' at a point on a screen. By deriving the probability density for an emission into a certain direction from basic quantum mechanical principles we predict a spatial interference pattern. Similarities and differences with the classical double-slit experiment are discussed.
Dheur, Marie-Christine; Devaux, Eloïse; Ebbesen, Thomas W; Baron, Alexandre; Rodier, Jean-Claude; Hugonin, Jean-Paul; Lalanne, Philippe; Greffet, Jean-Jacques; Messin, Gaétan; Marquier, François
2016-03-01
Surface plasmon polaritons are electromagnetic waves coupled to collective electron oscillations propagating along metal-dielectric interfaces, exhibiting a bosonic character. Recent experiments involving surface plasmons guided by wires or stripes allowed the reproduction of quantum optics effects, such as antibunching with a single surface plasmon state, coalescence with a two-plasmon state, conservation of squeezing, or entanglement through plasmonic channels. We report the first direct demonstration of the wave-particle duality for a single surface plasmon freely propagating along a planar metal-air interface. We develop a platform that enables two complementary experiments, one revealing the particle behavior of the single-plasmon state through antibunching, and the other one where the interferences prove its wave nature. This result opens up new ways to exploit quantum conversion effects between different bosonic species as shown here with photons and polaritons. PMID:26998521
Al-Khalili, Jim
2003-01-01
In this lively look at quantum science, a physicist takes you on an entertaining and enlightening journey through the basics of subatomic physics. Along the way, he examines the paradox of quantum mechanics--beautifully mathematical in theory but confoundingly unpredictable in the real world. Marvel at the Dual Slit experiment as a tiny atom passes through two separate openings at the same time. Ponder the peculiar communication of quantum particles, which can remain in touch no matter how far apart. Join the genius jewel thief as he carries out a quantum measurement on a diamond without ever touching the object in question. Baffle yourself with the bizzareness of quantum tunneling, the equivalent of traveling partway up a hill, only to disappear then reappear traveling down the opposite side. With its clean, colorful layout and conversational tone, this text will hook you into the conundrum that is quantum mechanics.
Ramsey interference with single photons
Clemmen, Stéphane; Ramelow, Sven; Gaeta, Alexander L
2016-01-01
Interferometry using discrete energy levels in nuclear, atomic or molecular systems is the foundation for a wide range of physical phenomena and enables powerful techniques such as nuclear magnetic resonance, electron spin resonance, Ramsey-based spectroscopy and laser/maser technology. It also plays a unique role in quantum information processing as qubits are realized as energy superposition states of single quantum systems. Here, we demonstrate quantum interference of different energy states of single quanta of light in full analogy to energy levels of atoms or nuclear spins and implement a Ramsey interferometer with single photons. We experimentally generate energy superposition states of a single photon and manipulate them with unitary transformations to realize arbitrary projective measurements, which allows for the realization a high-visibility single-photon Ramsey interferometer. Our approach opens the path for frequency-encoded photonic qubits in quantum information processing and quantum communicati...
Anomalous Chiral Superfluidity
Lublinsky, Michael(Physics Department, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel); Zahed, Ismail
2009-01-01
We discuss both the anomalous Cartan currents and the energy-momentum tensor in a left chiral theory with flavour anomalies as an effective theory for flavored chiral phonons in a chiral superfluid with the gauged Wess-Zumino-Witten term. In the mean-field (leading tadpole) approximation the anomalous Cartan currents and the energy momentum tensor take the form of constitutive currents in the chiral superfluid state. The pertinence of higher order corrections and the Adler-Bardeen theorem is ...
Anomalous diffraction in hyperbolic materials
Alberucci, Alessandro; Boardman, Allan D; Assanto, Gaetano
2016-01-01
We demonstrate that light is subject to anomalous (i.e., negative) diffraction when propagating in the presence of hyperbolic dispersion. We show that light propagation in hyperbolic media resembles the dynamics of a quantum particle of negative mass moving in a two-dimensional potential. The negative effective mass implies time reversal if the medium is homogeneous. Such property paves the way to diffraction compensation, spatial analogue of dispersion compensating fibers in the temporal domain. At variance with materials exhibiting standard elliptic dispersion, in inhomogeneous hyperbolic materials light waves are pulled towards regions with a lower refractive index. In the presence of a Kerr-like optical response, bright (dark) solitons are supported by a negative (positive) nonlinearity.
Universal Braess paradox in open quantum dots
Barbosa, A. L. R.; Bazeia, D.; Ramos, J. G. G. S.
2014-10-01
We present analytical and numerical results that demonstrate the presence of the Braess paradox in chaotic quantum dots. The paradox that we identify, originally perceived in classical networks, shows that the addition of more capacity to the network can suppress the current flow in the universal regime. We investigate the weak localization term, showing that it presents the paradox encoded in a saturation minimum of the conductance, under the presence of hyperflow in the external leads. In addition, we demonstrate that the weak localization suffers a transition signal depending on the overcapacity lead and presents an echo on the magnetic crossover before going to zero due to the full time-reversal symmetry breaking. We also show that the quantum interference contribution can dominate the Ohm term in the presence of constrictions and that the corresponding Fano factor engenders an anomalous behavior.
Universal Braess paradox in open quantum dots.
Barbosa, A L R; Bazeia, D; Ramos, J G G S
2014-10-01
We present analytical and numerical results that demonstrate the presence of the Braess paradox in chaotic quantum dots. The paradox that we identify, originally perceived in classical networks, shows that the addition of more capacity to the network can suppress the current flow in the universal regime. We investigate the weak localization term, showing that it presents the paradox encoded in a saturation minimum of the conductance, under the presence of hyperflow in the external leads. In addition, we demonstrate that the weak localization suffers a transition signal depending on the overcapacity lead and presents an echo on the magnetic crossover before going to zero due to the full time-reversal symmetry breaking. We also show that the quantum interference contribution can dominate the Ohm term in the presence of constrictions and that the corresponding Fano factor engenders an anomalous behavior. PMID:25375575
International Nuclear Information System (INIS)
The most accurate measurements in physical sciences will be precision spectroscopic experiments which are based on the usage of most narrow lines in cooperation with interference phenomena. We present a novel experimental observation of 'a sharp absorption resonance line' with much more broad laser lights. The mechanism of such a novel phenomenon will be elucidated and its implications will be discussed
Institute of Scientific and Technical Information of China (English)
王治国; 高童童; 谭为
2012-01-01
基于对相位耦合机制的旁路微带线结构中类量子干涉行为的理论研究.通过格林函数框架下的界面响应理论,解析、计算了该结构中的波传播特性,得出了3种具有代表性的类量子干涉现象:两个谐振结构之间的干涉增强导致的反射加强,两者的干涉相消导致的类电磁诱导透明行为,以及谐振结构与波导结构的干涉导致的类Fano共振现象.引入相位耦合机制为结构中的波传播特性提供了更加丰富的调控手段,有望设计成新型调控器件.%The paper theoretically demonstrates the classical analog of quantum interference effects in microstrip system containing phase-coupled side-branch components. By employing the Interface Response Theory which is in the framework of Green's function method, the propagation properties of the system are analytically obtained, and three typical phenomena are presented. The first is the enhancement of reflection resulting from the constructive interference between two resonances; the second is the analogous electromag-netically induced transparency effect due to the destructive interference; and the third is the analogous Fano resonance based on the interference between resonances and propagating waves. The introduction of phase-coupling mechanism provides us great flexibility in manipulating wave propagations, which may pave a way to novel devices.
Institute of Scientific and Technical Information of China (English)
S. H. Kim
2006-01-01
We calculate the scattering cross section of an electron with respect to the spontaneously produced laser radiation in the first free-electron laser (FEL) with quantum-wiggler electrodynamics (QWD). The cross section is 1016 times the Thomson cross section, confirming the result obtained by a previous analysis of the experimental data. A QWD calculation show that spontaneous emission in an FEL using only an electric wiggler can be very strong while amplification through net stimulated emission is practically negligible.
González-Garciá, M Concepción
1999-01-01
We review the effects of new effective interactions on Higgs-boson phenomenology. New physics in the electroweak bosonic sector is expected to induce additional interactions between the Higgs doublet field and the electroweak gauge bosons, leading to anomalous Higgs couplings as well as anomalous gauge-boson self-interactions. Using a linearly realized SU(2)/sub L/*U(1)/sub Y/ invariant effective Lagrangian to describe the bosonic sector of the Standard Model, we review the effects of the new effective interactions on the Higgs- boson production rates and decay modes. We summarize the results from searches for the new Higgs signatures induced by the anomalous interactions in order to constrain the scale of new physics, in particular at CERN LEP and Fermilab Tevatron colliders. (43 refs).
Hughes, Richard J.; Alde, D. M.; Dyer, P.; Luther, G. G.; Morgan, G. L.; Schauer, M
1995-01-01
Quantum cryptography is a new method for secret communications offering the ultimate security assurance of the inviolability of a Law of Nature. In this paper we shall describe the theory of quantum cryptography, its potential relevance and the development of a prototype system at Los Alamos, which utilises the phenomenon of single-photon interference to perform quantum cryptography over an optical fiber communications link.
International Nuclear Information System (INIS)
The coherent control of field-free molecular orientation of CO with combined femtosecond single- and dual-color laser pulses has been theoretically studied. The effect of the delay time between the femtosecond single- and dual-color laser pulses is discussed, and the physical mechanism of the enhancement of molecular orientation with pre-alignment of the molecule is investigated. It is found that the basic mechanism is based on the creation of a rotational wave packet by the femtosecond single-color laser pulse. Furthermore, we investigate the interference between multiple rotational excitation pathways following pre-alignment with femtosecond single-color laser pulse. It is shown that such interference can lead to an enhancement of the orientation of CO molecule by a factor of 1.6. (atomic and molecular physics)
Energy Technology Data Exchange (ETDEWEB)
Lapas, Luciano C., E-mail: luciano.lapas@unila.edu.br [Universidade Federal da Integração Latino-Americana, Caixa Postal 2067, 85867-970 Foz do Iguaçu, Paraná (Brazil); Ferreira, Rogelma M. S., E-mail: rogelma.maria@gmail.com [Centro de Ciências Exatas e Tecnológicas, Universidade Federal do Recôncavo da Bahia, 44380-000 Cruz das Almas, Bahia (Brazil); Rubí, J. Miguel, E-mail: mrubi@ub.edu [Departament de Física Fonamental, Facultat de Física, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona (Spain); Oliveira, Fernando A., E-mail: fernando.oliveira@pq.cnpq.br [Instituto de Física and Centro Internacional de Física da Matéria Condensada, Universidade de Brasília, Caixa Postal 04513, 70919-970 Brasília, Distrito Federal (Brazil)
2015-03-14
We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton’s law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics.
Anomalous gauge boson interactions
International Nuclear Information System (INIS)
We discuss the direct measurement of the trilinear vector boson couplings in present and future collider experiments. The major goals of such experiments will be the confirmation of the Standard Model (SM) predictions and the search for signals of new physics. We review our current theoretical understanding of anomalous trilinear gauge-boson self interactions. If the energy scale of the new physics is ∼ 1 TeV, these low energy anomalous couplings are expected to be no larger than Ο(10-2). Constraints from high precision measurements at LEP and low energy charged and neutral current processes are critically reviewed
International Nuclear Information System (INIS)
We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton’s law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics
Lapas, Luciano C.; Ferreira, Rogelma M. S.; Rubí, J. Miguel; Oliveira, Fernando A.
2015-03-01
We analyze the temperature relaxation phenomena of systems in contact with a thermal reservoir that undergoes a non-Markovian diffusion process. From a generalized Langevin equation, we show that the temperature is governed by a law of cooling of the Newton's law type in which the relaxation time depends on the velocity autocorrelation and is then characterized by the memory function. The analysis of the temperature decay reveals the existence of an anomalous cooling in which the temperature may oscillate. Despite this anomalous behavior, we show that the variation of entropy remains always positive in accordance with the second law of thermodynamics.
Whirling waves in Interference experiments
Sinha, Urbasi; Sawant, Rahul; Samuel, Joseph; Sinha, Aninda; Sinha, Supurna
2014-03-01
In a double slit interference experiment, the wave function at the screen with both slits open is not exactly the sum of the wave functions with the slits individually open one at a time. The three scenarios represent three different boundary conditions and as such, the superposition principle should not be applicable. However, most well- known text books in quantum mechanics implicitly and/or explicitly use this assumption, the wave function hypothesis, which is only approximately true. In our present study, we have used the Feynman path integral formalism to quantify contributions from non-classical paths in interference experiments which provide a measurable deviation from the wave function hypothesis. A direct experimental demonstration for the existence of these non-classical paths is hard. We find that contributions from such paths can be significant and we propose simple three-slit interference experiments to directly confirm their existence. I will also describe some ongoing experimental efforts towards testing our theoretical findings.
Anomalous pion decay revisited
Battistel, O A; Nemes, M C; Hiller, B
1999-01-01
An implicit four dimensional regularization is applied to calculate the axial-vector-vector anomalous amplitude. The present technique always complies with results of Dimensional Regularization and can be easily applied to processes involving odd numbers of $\\gamma_5$ matrices. This is illustrated explicitely in the example of this letter.
Czech Academy of Sciences Publication Activity Database
Nagaosa, N.; Sinova, Jairo; Onoda, S.; MacDonald, A. H.; Ong, N. P.
2010-01-01
Roč. 82, č. 2 (2010), s. 1539-1592. ISSN 0034-6861 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 51.695, year: 2010
Interference effects in isolated Josephson junction arrays with geometric symmetries
Ivanov, D. A.; Ioffe, L. B.; Geshkenbein, V. B.; Blatter, G.
2001-01-01
As the size of a Josephson junction is reduced, charging effects become important and the superconducting phase across the link turns into a periodic quantum variable. Isolated Josephson junction arrays are described in terms of such periodic quantum variables and thus exhibit pronounced quantum interference effects arising from paths with different winding numbers (Aharonov-Casher effects). These interference effects have strong implications for the excitation spectrum of the array which are...
Burkhard, George F.
2010-05-31
Accurately measuring internal quantum efficiency requires knowledge of absorption in the active layer of a solar cell. The experimentally accessible total absorption includes significant contributions from the electrodes and other nonactive layers. We suggest a straightforward method for calculating the active layer contribution that minimizes error by subtracting optically-modeled electrode absorption from experimentally measured total absorption. (Figure Presented) © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Vertices for correlated electron systems with anomalous propagators
Czech Academy of Sciences Publication Activity Database
Janiš, Václav; Pokorný, Vladislav
2014-01-01
Roč. 3, č. 1 (2014), "66-1"-"66-10". ISSN 2278-3393 R&D Projects: GA ČR GCP204/11/J042 Institutional support: RVO:68378271 Keywords : interacting quantum dot * superconducting leads * diagrammatic perturbation expansion * anomalous vertex functions Subject RIV: BM - Solid Matter Physics ; Magnetism http://www.cognizure.com/sj.aspx?p=200638479
Glinka, Yuri D; Babakiray, Sercan; Johnson, Trent A; Lederman, David
2015-02-11
We report on a >100-fold enhancement of Raman responses from Bi2Se3 thin films if laser photon energy switches from 2.33 eV (532 nm) to 1.58 eV (785 nm), which is due to direct optical coupling to Dirac surface states (SS) at the resonance energy of ∼1.5 eV (a thickness-independent enhancement) and due to nonlinearly excited Dirac plasmon (a thickness-dependent enhancement). Owing to the direct optical coupling, we observed an in-plane phonon mode of hexagonally arranged Se-atoms associated with a continuous network of Dirac SS. This mode revealed a Fano lineshape for films interference between surface phonon and Dirac plasmon states. PMID:25614684
International Nuclear Information System (INIS)
We report the observation of a strong 2D band Raman in twisted bilayer graphene (tBLG) with large rotation angles under 638 nm and 532 nm visible laser excitations. The 2D band Raman intensity increased four-fold as opposed to the two-fold increase observed in single-layer graphene. The same tBLG samples also exhibited rotation-dependent G-line resonances and folded phonons under 364 nm UV laser excitation. We attribute this 2D band Raman enhancement to the constructive interference between two double-resonance Raman pathways, which were enabled by a nearly degenerate Dirac band in the tBLG Moiré superlattices. (paper)
Nonlocal Anomalous Hall Effect
Zhang, Steven S.-L.; Vignale, Giovanni
2016-04-01
The anomalous Hall (AH) effect is deemed to be a unique transport property of ferromagnetic metals, caused by the concerted action of spin polarization and spin-orbit coupling. Nevertheless, recent experiments have shown that the effect also occurs in a nonmagnetic metal (Pt) in contact with a magnetic insulator [yttrium iron garnet (YIG)], even when precautions are taken to ensure that there is no induced magnetization in the metal. We propose a theory of this effect based on the combined action of spin-dependent scattering from the magnetic interface and the spin-Hall effect in the bulk of the metal. At variance with previous theories, we predict the effect to be of first order in the spin-orbit coupling, just as the conventional anomalous Hall effect—the only difference being the spatial separation of the spin-orbit interaction and the magnetization. For this reason we name this effect the nonlocal anomalous Hall effect and predict that its sign will be determined by the sign of the spin-Hall angle in the metal. The AH conductivity that we calculate from our theory is in order of magnitude agreement with the measured values in Pt /YIG structures.
Quantum Physics Without Quantum Philosophy
Dürr, Detlef; Zanghì, Nino
2013-01-01
It has often been claimed that without drastic conceptual innovations a genuine explanation of quantum interference effects and quantum randomness is impossible. This book concerns Bohmian mechanics, a simple particle theory that is a counterexample to such claims. The gentle introduction and other contributions collected here show how the phenomena of non-relativistic quantum mechanics, from Heisenberg's uncertainty principle to non-commuting observables, emerge from the Bohmian motion of particles, the natural particle motion associated with Schrödinger's equation. This book will be of value to all students and researchers in physics with an interest in the meaning of quantum theory as well as to philosophers of science.
Sub-wavelength interference in macroscopic observation
International Nuclear Information System (INIS)
We study the generalized Young's double-slit interference for the beam produced in the spontaneous parametric down-conversion (SPDC). It has been found that the sub-wavelength interference can occur macroscopically in both the two-photon intensity measurement and the single-photon spatial intensity-correlation measurement. The former refers to the quantum entanglement and the latter originates from the thermal spatial correlation. We show the visibility and the strength of the interference fringe related to the SPDC interaction, which may provide a strong sub-wavelength lithography with a moderate visibility in practical application
Interference of Fano-Rashba conductance dips
International Nuclear Information System (INIS)
We study the interference of two tunable Rashba regions in a quantum wire with one propagating mode. The transmission dips (Fano-Rashba dips) of the two regions either cross or anti-cross, depending on the distance between the two regions. For large separations we find Fabry-Perot oscillations due to the interference of forwards and backwards propagating modes. At small separations overlapping evanescent modes play a prominent role, leading to an enhanced transmission and destroying the conductance dip. Analytical expressions in scattering matrix theory are given and the relevance of the interference effect in a device is discussed.