Electron localization in an asymmetric double quantum well nanostructure
Energy Technology Data Exchange (ETDEWEB)
Hamedi, Hamid Reza, E-mail: Hamid.r.Hamedi@gmail.com
2014-05-01
The localization behavior of an asymmetric coupled quantum well (CQW) driven by two orthogonal standing-wave lasers based on intersubband transitions is investigated. We have shown that the precision of localization of the electron depends on different controlling parameters in the medium. We find that the high-spatial- resolution and high-precision-localization of the electron can be achieved through proper adjustment of the standing-wave fields. This scheme manifests a high controllability for the formation of the electron localization through different parameters such as frequency detuning and intensity of fields and level splitting energy between the bonding and anti-bonding states.
Asymmetric double quantum well structure as a tunable detector in the far-infrared range
Shin, U; Park, M J; Lee, S J
1999-01-01
The eigenvalues and the wave functions of GaAs/Al sub x Ga sub 1 sub - sub x As asymmetric double quantum well structure have been calculated by using of complex energy method. Based on theoretical calculations, tuning ranges from 9 to 14 mu m are predicted for the proposed asymmetric coupled-quantum-well structure. In addition we calculated the energy eigenvalues and the wave functions of an electron in GaAs/Al sub x Ga sub 1 sub - sub x As single quantum well structure (including delta-perturbation). the variation in E sub 1 , the ground state energy eigenvalue of the electron, depends on the strength and position of the perturbation within the well.
Christopher, Heike; Kovalchuk, Evgeny V; Wenzel, Hans; Bugge, Frank; Weyers, Markus; Wicht, Andreas; Peters, Achim; Tränkle, Günther
2017-07-01
We present a compact, mode-locked diode laser system designed to emit a frequency comb in the wavelength range around 780 nm. We compare the mode-locking performance of symmetric and asymmetric double quantum well ridge-waveguide diode laser chips in an extended-cavity diode laser configuration. By reverse biasing a short section of the diode laser chip, passive mode-locking at 3.4 GHz is achieved. Employing an asymmetric double quantum well allows for generation of a mode-locked optical spectrum spanning more than 15 nm (full width at -20 dB) while the symmetric double quantum well device only provides a bandwidth of ∼2.7 nm (full width at -20 dB). Analysis of the RF noise characteristics of the pulse repetition rate shows an RF linewidth of about 7 kHz (full width at half-maximum) and of at most 530 Hz (full width at half-maximum) for the asymmetric and symmetric double quantum well devices, respectively. Investigation of the frequency noise power spectral density at the pulse repetition rate shows a white noise floor of approximately 2100 Hz2/Hz and of at most 170 Hz2/Hz for the diode laser employing the asymmetric and symmetric double quantum well structures, respectively. The pulse width is less than 10 ps for both devices.
Afalla, Jessica; Ohta, Kaoru; Tokonami, Shunrou; Prieto, Elizabeth Ann; Catindig, Gerald Angelo; Cedric Gonzales, Karl; Jaculbia, Rafael; Vasquez, John Daniel; Somintac, Armando; Salvador, Arnel; Estacio, Elmer; Tani, Masahiko; Tominaga, Keisuke
2017-11-01
Two asymmetric double quantum wells of different coupling strengths (barrier widths) were grown via molecular beam epitaxy, both samples allowing tunneling. Photoluminescence was measured at 10 and 300 K to provide evidence of tunneling, barrier dependence, and structural uniformity. Carrier dynamics at room temperature was investigated by optical pump terahertz probe (OPTP) spectroscopy. Carrier population decay rates were obtained and photoconductivity spectra were analyzed using the Drude model. This work demonstrates that carrier, and possibly tunneling dynamics in asymmetric double quantum well structures may be studied at room temperature through OPTP spectroscopy.
Hamedi, H. R.
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.
Time Asymmetric Quantum Mechanics
Directory of Open Access Journals (Sweden)
Arno R. Bohm
2011-09-01
Full Text Available The meaning of time asymmetry in quantum physics is discussed. On the basis of a mathematical theorem, the Stone-von Neumann theorem, the solutions of the dynamical equations, the Schrödinger equation (1 for states or the Heisenberg equation (6a for observables are given by a unitary group. Dirac kets require the concept of a RHS (rigged Hilbert space of Schwartz functions; for this kind of RHS a mathematical theorem also leads to time symmetric group evolution. Scattering theory suggests to distinguish mathematically between states (defined by a preparation apparatus and observables (defined by a registration apparatus (detector. If one requires that scattering resonances of width Γ and exponentially decaying states of lifetime τ=h/Γ should be the same physical entities (for which there is sufficient evidence one is led to a pair of RHS's of Hardy functions and connected with it, to a semigroup time evolution t_0≤t<∞, with the puzzling result that there is a quantum mechanical beginning of time, just like the big bang time for the universe, when it was a quantum system. The decay of quasi-stable particles is used to illustrate this quantum mechanical time asymmetry. From the analysis of these processes, we show that the properties of rigged Hilbert spaces of Hardy functions are suitable for a formulation of time asymmetry in quantum mechanics.
Asymmetric Quantum Codes on Toric Surfaces
DEFF Research Database (Denmark)
Hansen, Johan P.
2017-01-01
Asymmetric quantum error-correcting codes are quantum codes defined over biased quantum channels: qubit-flip and phase-shift errors may have equal or different probabilities. The code construction is the Calderbank-Shor-Steane construction based on two linear codes. We present families of toric...... surfaces, toric codes and associated asymmetric quantum error-correcting codes....
Singh, Madhav K.; Jha, Pradeep K.; Bhattacherjee, Aranya B.
2017-09-01
In this article, we study the spin and tunneling dynamics as a function of magnetic field in a one-dimensional GaAs double quantum dot with both the Dresselhaus and Rashba spin-orbit coupling. In particular, we consider different spatial widths for the spin-up and spin-down electronic states. We find that the spin dynamics is a superposition of slow as well as fast Rabi oscillations. It is found that the Rashba interaction strength as well as the external magnetic field strongly modifies the slow Rabi oscillations which is particularly useful for implementing solid state selective spin transport device.
Energy Technology Data Exchange (ETDEWEB)
Rodríguez-Magdaleno, K.A.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calz. Solidaridad Esq. Paseo a La Bufa S/N. C.P. 98060 Zacatecas (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca, Morelos (Mexico); Física Teórica y Aplicada, Escuela de Ingeniería de Antioquia, AA 7516 Medellín (Colombia); Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Grupo de Materia Condensada-UdeA, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia)
2014-03-15
In this work, the conduction band electron states and the associated intersubband-related linear and nonlinear optical absorption coefficient and relative refractive index change are calculated for an asymmetric double n-type δ-doped quantum well in a GaAs-matrix. The effects of an external applied static electric field are included. Values of the two-dimensional impurities density (N{sub 2d}) of each single δ-doped quantum well are taken to vary within the range of 1.0×10{sup 12} to 7.0×10{sup 12} cm{sup −2}, consistent with the experimental data growth regime. The optical responses are reported as a function of the δ-doped impurities density and the applied electric field. It is shown that single electron states and the related optical quantities are significantly affected by the structural asymmetry of the double δ-doped quantum well system. In addition, a brief comparison with the free-carrier-related optical response is presented. -- Highlights: • Nonlinear optics in asymmetric double n-type δ-doped quantum well in a GaAs-matrix. • The system is considered under external applied electric field in growth direction. • The 2D impurity density is consistent with the experimental data growth regime. • The optical quantities are significantly affected by the structural asymmetry of the system.
DEFF Research Database (Denmark)
Sherman, D.; Yodh, J. S.; Albrecht, S. M.
2016-01-01
Epitaxial semiconductor-superconductor hybrid materials are an excellent basis for studying mesoscopic and topological superconductivity, as the semiconductor inherits a hard superconducting gap while retaining tunable carrier density. Here, we investigate double-quantum-dot devices made from InA...... that the individual dots host weakly hybridized Majorana modes....
Spectral inequalities for the quantum asymmetric top
Energy Technology Data Exchange (ETDEWEB)
Bourget, Alain; McMillen, Tyler [Department of Mathematics, California State University (Fullerton), McCarthy Hall 154, Fullerton, CA 92834 (United States)], E-mail: abourget@fullerton.edu, E-mail: tmcmillen@fullerton.edu
2009-03-06
We consider the spectrum of the quantum asymmetric top. Unlike in the case when two or three moments of inertia are equal, when the moments of inertia are distinct all degeneracy in the spectrum of the operator is removed. We derive inequalities for the spectra based on recent results on the interlacing of Van Vleck zeros.
Energy Technology Data Exchange (ETDEWEB)
Rojas-Briseño, J.G.; Martínez-Orozco, J.C.; Rodríguez-Vargas, I. [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo la Bufa S/N, C.P. 98060, Zacatecas, Zac. (Mexico); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia); Duque, C.A., E-mail: cduque@fisica.udea.edu.co [Instituto de Física, Universidad de Antioquia, AA 1226, Medellín (Colombia)
2013-09-01
In this work we are reporting the energy level spectrum for a quantum system consisting of an n-type double δ-doped quantum well with a Schottky barrier potential in a Gallium Arsenide matrix. The calculated states are taken as the basis for the evaluation of the linear and third-order nonlinear contributions to the optical absorption coefficient and to the relative refractive index change, making particular use of the asymmetry of the potential profile. These optical properties are then reported as a function of the Schottky barrier height (SBH) and the separation distance between the δ-doped quantum wells. Also, the effects of the application of hydrostatic pressure are studied. The results show that the amplitudes of the resonant peaks are of the same order of magnitude of those obtained in the case of single δ-doped field effect transistors; but tailoring the asymmetry of the confining potential profile allows the control the resonant peak positions.
Directory of Open Access Journals (Sweden)
Élder Mantovani Lopes
2010-12-01
Full Text Available The progress of the semiconductor growth techniques allows the opportunity to produce new semiconductors devices that may contribute to the development of the nanotechnology. The fabrication of semiconductor heterostructures with high quality allows the obtaining of new effects based on the quantum properties of those systems, which have stimulated great technological interest, especially on the optoelectronic and telecommunications fields. In this work some basic concepts related to one of those heterostructures are discussed: the Coupled Double Quantum Well (CDQW. The deduction of the expression for the determination of the energy levels in CDQWs is presented in details. The results obtained through this expression are compared with experimental results obtained through photoluminescence (PL measurements, complementing the work.
Li, Ying; Holloway, Gregory W.; Benjamin, Simon C.; Briggs, G. Andrew D.; Baugh, Jonathan; Mol, Jan A.
2017-08-01
Memristive systems are generalizations of memristors, which are resistors with memory. In this paper, we present a quantum description of quantum dot memristive systems. Using this model we propose and experimentally demonstrate a simple and practical scheme for realizing memristive systems with quantum dots. The approach harnesses a phenomenon that is commonly seen as a bane of nanoelectronics, i.e., switching of a trapped charge in the vicinity of the device. We show that quantum dot memristive systems have hysteresis current-voltage characteristics and quantum jump-induced stochastic behavior. While our experiment requires low temperatures, the same setup could, in principle, be realized with a suitable single-molecule transistor and operated at or near room temperature.
Bound states in a hyperbolic asymmetric double-well
Energy Technology Data Exchange (ETDEWEB)
Hartmann, R. R., E-mail: richard.hartmann@dlsu.edu.ph [Physics Department, De La Salle University, 2401 Taft Avenue, Manila (Philippines)
2014-01-15
We report a new class of hyperbolic asymmetric double-well whose bound state wavefunctions can be expressed in terms of confluent Heun functions. An analytic procedure is used to obtain the energy eigenvalues and the criterion for the potential to support bound states is discussed.
Asymptotic behavior of observables in the asymmetric quantum Rabi model
Semple, J.; Kollar, M.
2018-01-01
The asymmetric quantum Rabi model with broken parity invariance shows spectral degeneracies in the integer case, that is when the asymmetry parameter equals an integer multiple of half the oscillator frequency, thus hinting at a hidden symmetry and accompanying integrability of the model. We study the expectation values of spin observables for each eigenstate and observe characteristic differences between the integer and noninteger cases for the asymptotics in the deep strong coupling regime, which can be understood from a perturbative expansion in the qubit splitting. We also construct a parent Hamiltonian whose exact eigenstates possess the same symmetries as the perturbative eigenstates of the asymmetric quantum Rabi model in the integer case.
Guided Modes in a Double-Well Asymmetric Potential of a Graphene Waveguide
Directory of Open Access Journals (Sweden)
Yi Xu
2016-12-01
Full Text Available The analogy between the electron wave nature in graphene electronics and the electromagnetic waves in dielectrics has suggested a series of optical-like phenomena, which is of great importance for graphene-based electronic devices. In this paper, we propose an asymmetric double-well potential on graphene as an electronic waveguide to confine the graphene electrons. The guided modes in this graphene waveguide are investigated using a modified transfer matrix method. It is found that there are two types of guided modes. The first kind is confined in one well, which is similar to the asymmetric quantum well graphene waveguide. The second kind can appear in two potential wells with double-degeneracy. Characteristics of all the possible guide modes are presented.
Distribution of quantum Fisher information in asymmetric cloning machines.
Xiao, Xing; Yao, Yao; Zhou, Lei-Ming; Wang, Xiaoguang
2014-12-08
An unknown quantum state cannot be copied and broadcast freely due to the no-cloning theorem. Approximate cloning schemes have been proposed to achieve the optimal cloning characterized by the maximal fidelity between the original and its copies. Here, from the perspective of quantum Fisher information (QFI), we investigate the distribution of QFI in asymmetric cloning machines which produce two nonidentical copies. As one might expect, improving the QFI of one copy results in decreasing the QFI of the other copy. It is perhaps also unsurprising that asymmetric phase-covariant cloning outperforms universal cloning in distributing QFI since a priori information of the input state has been utilized. However, interesting results appear when we compare the distributabilities of fidelity (which quantifies the full information of quantum states), and QFI (which only captures the information of relevant parameters) in asymmetric cloning machines. Unlike the results of fidelity, where the distributability of symmetric cloning is always optimal for any d-dimensional cloning, we find that any asymmetric cloning outperforms symmetric cloning on the distribution of QFI for d ≤ 18, whereas some but not all asymmetric cloning strategies could be worse than symmetric ones when d > 18.
Eigenstate localization in an asymmetric coupled quantum well pair
DEFF Research Database (Denmark)
Mialitsin, Aleksej; Schmult, Stefan; Solov'yov, Ilia
2012-01-01
Optical pumping of a type-I/type-II coupled asymmetric quantum well pair induces a spatially separated two dimensional charge carriers plasma in the well’s wide and narrow parts. Treating the two coupled wells as a single system we find that the eigenstate probability distribution localizes...
Some Families of Asymmetric Quantum MDS Codes Constructed from Constacyclic Codes
Huang, Yuanyuan; Chen, Jianzhang; Feng, Chunhui; Chen, Riqing
2017-10-01
Quantum maximal-distance-separable (MDS) codes that satisfy quantum Singleton bound with different lengths have been constructed by some researchers. In this paper, seven families of asymmetric quantum MDS codes are constructed by using constacyclic codes. We weaken the case of Hermitian-dual containing codes that can be applied to construct asymmetric quantum MDS codes with parameters [[n,k,dz/dx
Double-partition Quantum Cluster Algebras
DEFF Research Database (Denmark)
Jakobsen, Hans Plesner; Zhang, Hechun
2012-01-01
A family of quantum cluster algebras is introduced and studied. In general, these algebras are new, but sub-classes have been studied previously by other authors. The algebras are indexed by double parti- tions or double flag varieties. Equivalently, they are indexed by broken lines L. By grouping...... together neighboring mutations into quantum line mutations we can mutate from the cluster algebra of one broken line to another. Compatible pairs can be written down. The algebras are equal to their upper cluster algebras. The variables of the quantum seeds are given by elements of the dual canonical basis....
Electronic properties of asymmetrical quantum dots dressed by laser field
Energy Technology Data Exchange (ETDEWEB)
Kibis, O.V. [Department of Applied and Theoretical Physics, Novosibirsk State Technical University, Karl Marx Avenue 20, 630092 Novosibirsk (Russian Federation); Slepyan, G.Ya.; Maksimenko, S.A. [Institute for Nuclear Problems, Belarus State University, Bobruyskaya St. 11, 220050 Minsk (Belarus); Hoffmann, A. [Institut fuer Festkoerperphysik, Technische Universitaet Berlin, Hardenbergstrasse 36, 10623 Berlin (Germany)
2012-05-15
In the present paper, we demonstrate theoretically that the strong non-resonant interaction between asymmetrical quantum dots (QDs) and a laser field results in harmonic oscillations of their band gap. It is shown that such oscillations change the spectrum of elementary electron excitations in QDs: in the absence of the laser pumping there is only one resonant electron frequency, but QDs dressed by the laser field have a set of electron resonant frequencies. One expects that this modification of elementary electron excitations in QDs can be observable in optical experiments. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Quantum efficiency of a double quantum dot microwave photon detector
Wong, Clement; Vavilov, Maxim
Motivated by recent interest in implementing circuit quantum electrodynamics with semiconducting quantum dots, we study charge transfer through a double quantum dot (DQD) capacitively coupled to a superconducting cavity subject to a microwave field. We analyze the DQD current response using input-output theory and determine the optimal parameter regime for complete absorption of radiation and efficient conversion of microwave photons to electric current. For experimentally available DQD systems, we show that the cavity-coupled DQD operates as a photon-to-charge converter with quantum efficiencies up to 80% C.W. acknowledges support by the Intelligence Community Postdoctoral Research Fellowship Program.
No fermion doubling in quantum geometry
Energy Technology Data Exchange (ETDEWEB)
Gambini, Rodolfo [Instituto de Física, Facultad de Ciencias, Iguá 4225, esq. Mataojo, 11400 Montevideo (Uruguay); Pullin, Jorge, E-mail: pullin@lsu.edu [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803-4001 (United States)
2015-10-07
In loop quantum gravity the discrete nature of quantum geometry acts as a natural regulator for matter theories. Studies of quantum field theory in quantum space–times in spherical symmetry in the canonical approach have shown that the main effect of the quantum geometry is to discretize the equations of matter fields. This raises the possibility that in the case of fermion fields one could confront the usual fermion doubling problem that arises in lattice gauge theories. We suggest, again based on recent results on spherical symmetry, that since the background space–times will generically involve superpositions of states associated with different discretizations the phenomenon may not arise. This opens a possibility of incorporating chiral fermions in the framework of loop quantum gravity.
Quantum capacitance of double-layer graphene
Parhizgar, Fariborz; Qaiumzadeh, Alireza; Asgari, Reza
2017-08-01
We study the ground-state properties of a double-layer graphene system with the Coulomb interlayer electron-electron interaction modeled within the random-phase approximation. We first obtain an expression of the quantum capacitance of a two-layer system. In addition, we calculate the many-body exchange-correlation energy and quantum capacitance of the hybrid double-layer graphene system at zero temperature. We show an enhancement of the majority density layer thermodynamic density of states owing to an increasing interlayer interaction between two layers near the Dirac point. The quantum capacitance near the neutrality point behaves like a square root of the total density α √{n } where the coefficient α decreases by increasing the charge-density imbalance between two layers. Furthermore, we show that the quantum capacitance changes linearly by the gate voltage. Our results can be verified by current experiments.
Detection of entanglement in asymmetric quantum networks and multipartite quantum steering.
Cavalcanti, D; Skrzypczyk, P; Aguilar, G H; Nery, R V; Ribeiro, P H Souto; Walborn, S P
2015-08-03
The future of quantum communication relies on quantum networks composed by observers sharing multipartite quantum states. The certification of multipartite entanglement will be crucial to the usefulness of these networks. In many real situations it is natural to assume that some observers are more trusted than others in the sense that they have more knowledge of their measurement apparatuses. Here we propose a general method to certify all kinds of multipartite entanglement in this asymmetric scenario and experimentally demonstrate it in an optical experiment. Our results, which can be seen as a definition of genuine multipartite quantum steering, give a method to detect entanglement in a scenario in between the standard entanglement and fully device-independent scenarios, and provide a basis for semi-device-independent cryptographic applications in quantum networks.
Energy levels of double triangular graphene quantum dots
Energy Technology Data Exchange (ETDEWEB)
Liang, F. X.; Jiang, Z. T., E-mail: ztjiang616@hotmail.com; Zhang, H. Y.; Li, S. [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); Lv, Z. T. [School of Physics, Beijing Institute of Technology, Beijing 100081 (China); School of Physical Science and Information Engineering, Liaocheng University, Liaocheng 252059 (China)
2014-09-28
We investigate theoretically the energy levels of the coupled double triangular graphene quantum dots (GQDs) based on the tight-binding Hamiltonian model. The double GQDs including the ZZ-type, ZA-type, and AA-type GQDs with the two GQDs having the zigzag or armchair boundaries can be coupled together via different interdot connections, such as the direct coupling, the chains of benzene rings, and those of carbon atoms. It is shown that the energy spectrum of the coupled double GQDs is the amalgamation of those spectra of the corresponding two isolated GQDs with the modification triggered by the interdot connections. The interdot connection is inclined to lift up the degeneracies of the energy levels in different degree, and as the connection changes from the direct coupling to the long chains, the removal of energy degeneracies is suppressed in ZZ-type and AA-type double GQDs, which indicates that the two coupled GQDs are inclined to become decoupled. Then we consider the influences on the spectra of the coupled double GQDs induced by the electric fields applied on the GQDs or the connection, which manifests as the global spectrum redistribution or the local energy level shift. Finally, we study the symmetrical and asymmetrical energy spectra of the double GQDs caused by the substrates supporting the two GQDs, clearly demonstrating how the substrates affect the double GQDs' spectrum. This research elucidates the energy spectra of the coupled double GQDs, as well as the mechanics of manipulating them by the electric field and the substrates, which would be a significant reference for designing GQD-based devices.
DEFF Research Database (Denmark)
Zubov, F. I.; Zhukov, A. E.; Shernyakov, Yu M.
2014-01-01
The effect of asymmetric barriers on the light-current characteristic (LCC) of a quantum well laser was studied theoretically and experimentally. It is shown that the utilization of asymmetric barriers in a waveguide prevents the nonlinearity of LCC and, consequently, allows rising of the maximum...
A double quantum well single charge electrometer
Robinson, Hans D.; Bandaru, Prabhakar; Kosaka, Hideo; Yablonovitch, Eli; Caflisch, Russel E.; Anderson, Chris; Gyure, Mark F.; Croke, Edward T.
2002-03-01
In recent years, quantum point contacts and single electron transistors have been shown to be useful as extremely sensitive ( 10-5 e/Hz^1/2) charge sensors. In this talk, we present experimental and numerical results on a new device, based on an InP/InGaAs double quantum well structure, where the charge sensitive channel is realized in the lower quantum well, while a single electron is confined in a quantum dot in the upper well. If the spacer between the wells is made thin enough, then the channel plays the dual role of both supplying the trapped charges and detecting them. We show that it is possible to spin polarize the sensing channel, and that this property will make it possible to read out the spin of the trapped electron. (See the talk by Mark Gyure for further details on this topic.) The spacer can also be made sufficiently wide that tunneling between the wells does not take place, and the device can then be used as a coherent single photon detector.
Double quantum dots defined in bilayer graphene
Żebrowski, D. P.; Peeters, F. M.; Szafran, B.
2017-07-01
Artificial molecular states of double quantum dots defined in bilayer graphene are studied with the atomistic tight-binding method and its low-energy continuum approximation. We indicate that the extended electron wave functions have opposite parities on sublattices of the layers and that the ground-state wave-function components change from bonding to antibonding with the interdot distance. In the weak-coupling limit, the one most relevant for quantum dots defined electrostatically, the signatures of the interdot coupling include, for the two-electron ground state, formation of states with symmetric or antisymmetric spatial wave functions split by the exchange energy. In the high-energy part of the spectrum the states with both electrons in the same dot are found with the splitting of energy levels corresponding to simultaneous tunneling of the electron pair from one dot to the other.
Double quantum dots in carbon nanotubes
von Stecher, Javier; Wunsch, Bernhard; Lukin, Mikhail; Demler, Eugene; Rey, Ana Maria
2010-03-01
We study the behavior of few-electrons confined in a double-well quantum dot in semiconducting carbon nanotubes. These carbon nanostructures exhibit richer physics than GaAs ones due to the additional valley degree of freedom. We calculate and characterize the low energy eigenstates in the presence of a magnetic field and double-well detuning. Spin-orbit coupling lifts the spin and valley degeneracy and, in the presence of exchange interactions, leads, at small detunings and weak magnetic fields, to a spin-valley antisymmetric two-electron ground state which is not a pure spin-singlet state. At large detuning, the strong Coulomb interactions accessible in carbon nanotubes can substantially modify the non-interacting eigenstates via higher orbital-level mixing. The latter manifest in current transport experiments by the disappearance of the Pauli blockade.
Directory of Open Access Journals (Sweden)
Zhao Yi Fan
2016-01-01
Full Text Available paper presents a new use of double queues asymmetric gated service polling system in the intelligent traffic light control system.Usually there are more vehicles in main road than minor road,so there are more green light time be needed in the main road.From the computer simulation and theory analysis,we can find that the application of double queues asymmetric gated service polling theory in intelligent traffic system can balance intersections load and set suitable passing time for vehicles to assure the roads open.
Zhao Yi Fan; Ding Hong Wei; Wang Meng Yao; Liang Zhu Guan
2016-01-01
paper presents a new use of double queues asymmetric gated service polling system in the intelligent traffic light control system.Usually there are more vehicles in main road than minor road,so there are more green light time be needed in the main road.From the computer simulation and theory analysis,we can find that the application of double queues asymmetric gated service polling theory in intelligent traffic system can balance intersections load and set suitable passing time for vehicles t...
Andreev molecules in semiconductor nanowire double quantum dots
Su, Zhaoen; Tacla, Alexandre B.; Hocevar, Moïra; Car, Diana; Plissard, Sébastien R.; Bakkers, E.P.A.M.; Daley, Andrew J.; Pekker, David; Frolov, Sergey M.
2017-01-01
Chains of quantum dots coupled to superconductors are promising for the realization of the Kitaev model of a topological superconductor. While individual superconducting quantum dots have been explored, control of longer chains requires understanding of interdot coupling. Here, double quantum
Enhanced confinement energy in strained asymmetric T-shaped quantum wires
DEFF Research Database (Denmark)
Jensen, Jacob Riis; Hvam, Jørn Märcher; Langbein, W.
2001-01-01
A new type of T-shaped quantum wire, based on a sri strained asymmetric structure, has been grown and characterised. A narrow GaAs well is overgrown on an multi quantum well structure consisting of wide InAlGaAs c ells with Al0.3Ga0.7As barriers. Since the lattice constants of the InAlGaAs wells ......-10 meV is found for In molefractions of 10% and 15%, in the multi quantum wells. For an In mole fraction of 20% no quantum wire states are observed, probably due to dislocation formation in the overgrown layers....
The effect of hydrogen-like impurity on RbCl asymmetric quantum dot qubit
Liang, Z.-H.; Qi, B.; Xiao, J.-L.
2015-12-01
We study the eigenenergies and eigenfunctions of the ground and the first excited states of an electron, which is strongly coupled to longintudinal-optical phonon in an asymmetric quantum dot with a hydrogen-like impurity by using variational method of Pekar type. A single qubit can be realized in this two-level quantum system. The electron probability density oscillates in the asymmetric quantum dot with a certain period of T 0 = 10.958 fs when the electron is in the superposition state of the ground and the first excited states. Moreover, due to the presence of the different harmonic potentials, the dependence way of the probability density of the electron on the coordinate of z is different from that on the coordinates of x and y. It is found that the oscillating period increases with decreasing Coulombic impurity potential and the polaron radius.
A Portable Double-Slit Quantum Eraser with Individual Photons
Dimitrova, T. L.; Weis, A.
2011-01-01
The double-slit experiment has played an important role in physics, from supporting the wave theory of light, via the discussions of the wave-particle duality of light (and matter) to the foundations of modern quantum optics. Today it keeps playing an active role in the context of quantum optics experiments involving single photons. In this paper,…
Asymmetric quantum-well structures for AlGaN/GaN/AlGaN resonant tunneling diodes
Yang, Lin'an; Li, Yue; Wang, Ying; Xu, Shengrui; Hao, Yue
2016-04-01
Asymmetric quantum-well (QW) structures including the asymmetric potential-barrier and the asymmetric potential-well are proposed for AlGaN/GaN/AlGaN resonant tunneling diodes (RTDs). Theoretical investigation gives that an appropriate decrease in Al composition and thickness for emitter barrier as well as an appropriate increase of both for collector barrier can evidently improve the negative-differential-resistance characteristic of RTD. Numerical simulation shows that RTD with a 1.5-nm-thick GaN well sandwiched by a 1.3-nm-thick Al0.15Ga0.85N emitter barrier and a 1.7-nm-thick Al0.25Ga0.75N collector barrier can yield the I-V characteristic having the peak current (Ip) and the peak-to-valley current ratio (PVCR) of 0.39 A and 3.6, respectively, about double that of RTD with a 1.5-nm-thick Al0.2Ga0.8N for both barriers. It is also found that an introduction of InGaN sub-QW into the diode can change the tunneling mode and achieve higher transmission coefficient of electron. The simulation demonstrates that RTD with a 2.8-nm-thick In0.03Ga0.97N sub-well in front of a 2.0-nm-thick GaN main-well can exhibit the I-V characteristic having Ip and PVCR of 0.07 A and 11.6, about 7 times and double the value of RTD without sub-QW, respectively. The purpose of improving the structure of GaN-based QW is to solve apparent contradiction between the device structure and the device manufacturability of new generation RTDs for sub-millimeter and terahertz applications.
A portable double-slit quantum eraser with individual photons
Energy Technology Data Exchange (ETDEWEB)
Dimitrova, T L [Physics Faculty, University of Plovdiv ' Paissi Hilendarski' , Tzar Assen Str. 24, BG-4000 Plovdiv (Bulgaria); Weis, A, E-mail: doradimitrova@uni-plovdiv.bg [Physics Department, University of Fribourg, Chemin du Musee 3, CH-1700 Fribourg (Switzerland)
2011-11-15
The double-slit experiment has played an important role in physics, from supporting the wave theory of light, via the discussions of the wave-particle duality of light (and matter) to the foundations of modern quantum optics. Today it keeps playing an active role in the context of quantum optics experiments involving single photons. In this paper, we present a truly portable double-slit apparatus which demonstrates both the wave-particle duality of light and the phenomenon of quantum erasing. The device can be operated either with strong laser light and screen projection, or with individual photons, in which case quantum interference and quantum erasing are detected by a photomultiplier whose pulses are rendered acoustically by means of a loudspeaker. Alternatively, the phenomena can be displayed using multimedia projection of oscilloscope traces.
Dispersive microwave readout of a silicon double quantum dot
Schmidt, Andrew; Henry, Edward; House, M. G.; Wang, Y. T.; Lo, C. C.; Li, H.; Greenman, L.; Pan, H.; Xiao, M.; Whaley, K. B.; Jiang, H. W.; Yablonovitch, E.; Bokor, J.; Siddiqi, I.
2012-02-01
Microwave resonators coupled to quantum systems have been used for fast dispersive measurement in several different architectures in solid state and atomic physics. The electronic states of a semiconductor quantum dot represent a promising candidate for quantum information processing. Our work is geared toward developing a fast, non-demolition readout of a semiconductor qubit as realized in silicon by coupling to a superconducting resonant circuit. We report progress on a novel design of a lateral double quantum dot with a unique accumulation gate that allows for control of the spatial location of the 2DEG on the device, allowing the lossy 2DEG to be decoupled from the resonator.
Mid/far-infrared photo-detectors based on graphene asymmetric quantum wells
Ben Salem, E.; Chaabani, R.; Jaziri, S.
2016-09-01
We conducted a theoretical study on the electronic properties of a single-layer graphene asymmetric quantum well. Quantification of energy levels is limited by electron-hole conversion at the barrier interfaces and free-electron continuum. Electron-hole conversion at the barrier interfaces can be controlled by introducing an asymmetry between barriers and taking into account the effect of the interactions of the graphene sheet with the substrate. The interaction with the substrate induces an effective mass to carriers, allowing observation of Fabry-Pérot resonances under normal incidence and extinction of Klein tunneling. The asymmetry, between barriers creates a transmission gap between confined states and free-electron continuum, allowing the large graphene asymmetric quantum well to be exploited as a photo-detector operating at mid- and far-infrared frequency regimes.
Sang, Ming-huang; Nie, Li-ping
2017-11-01
We demonstrate that a seven-particle entangled state can be used to realize the deterministic asymmetric bidirectional controlled quantum information transmission by performing only Bell-state measurement and two-particle projective measurement and single-particle measurement. In our protocol, Alice can teleport an arbitrary unknown single-particle state to Bob and at the same time Bob can remotely prepare an arbitrary known two-particle state for Alice via the control of the supervisor Charlie.
A prototype silicon double quantum dot with dispersive microwave readout
Schmidt, A. R.; Henry, E.; Lo, C. C.; Wang, Y.-T.; Li, H.; Greenman, L.; Namaan, O.; Schenkel, T.; Whaley, K. B.; Bokor, J.; Yablonovitch, E.; Siddiqi, I.
2014-07-01
We present a unique design and fabrication process for a lateral, gate-confined double quantum dot in an accumulation mode metal-oxide-semiconductor (MOS) structure coupled to an integrated microwave resonator. All electrostatic gates for the double quantum dot are contained in a single metal layer, and use of the MOS structure allows for control of the location of the two-dimensional electron gas via the location of the accumulation gates. Numerical simulations of the electrostatic confinement potential are performed along with an estimate of the coupling of the double quantum dot to the microwave resonator. Prototype devices are fabricated and characterized by transport measurements of electron confinement and reflectometry measurements of the microwave resonator.
A prototype silicon double quantum dot with dispersive microwave readout
Energy Technology Data Exchange (ETDEWEB)
Schmidt, A. R., E-mail: andrewrobertschmidt@gmail.com; Henry, E.; Namaan, O.; Siddiqi, I., E-mail: irfan-siddiqi@berkeley.edu [Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720 (United States); Lo, C. C.; Wang, Y.-T.; Bokor, J.; Yablonovitch, E. [Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720 (United States); Li, H. [Department of Physics, University of California, Berkeley, California 94720 (United States); Department of Chemistry, University of California, Berkeley, California 94720 (United States); Greenman, L.; Whaley, K. B. [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Schenkel, T. [Accelerator and Fusion Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2014-07-28
We present a unique design and fabrication process for a lateral, gate-confined double quantum dot in an accumulation mode metal-oxide-semiconductor (MOS) structure coupled to an integrated microwave resonator. All electrostatic gates for the double quantum dot are contained in a single metal layer, and use of the MOS structure allows for control of the location of the two-dimensional electron gas via the location of the accumulation gates. Numerical simulations of the electrostatic confinement potential are performed along with an estimate of the coupling of the double quantum dot to the microwave resonator. Prototype devices are fabricated and characterized by transport measurements of electron confinement and reflectometry measurements of the microwave resonator.
Tuning terahertz transitions in a double-gated quantum ring
Collier, T. P.; Saroka, V. A.; Portnoi, M. E.
2017-12-01
We theoretically investigate the optical functionality of a semiconducting quantum ring manipulated by two electrostatic lateral gates used to induce a double quantum well along the ring. The well parameters and corresponding interlevel spacings, which lie in the THz range, are highly sensitive to the gate voltages. Our analysis shows that selection rules for interlevel dipole transitions, caused by linearly polarized excitations, depend on the polarization vector angle with respect to the gates. In striking difference from the conventional symmetric double well potential, the ring geometry permits polarization-dependent transitions between the ground and second excited states, allowing the use of this structure in a three-level lasing scheme.
Guo, Xiao; Wang, Sheng; Peng, Lian-Mao
2017-10-01
Electrostatic properties of asymmetrically contacted carbon nanotube barrier-free bipolar diode photodetector are studied by solving the Poisson equation self-consistently with equilibrium carrier statistics. For electric field parallel to tube's axis, the maximum electric field occurs near contact but decays rapidly in a few nanometers, followed by a slowly increasing trend when it extends to the center of channel. By considering the field ionization and the diffusion effect of exciton, a model of estimation on quantum efficiency for the device is made. We find that the quantum efficiency increases with increasing exciton lifetime, decreasing diffusion constant and channel length. For devices with a channel length shorter than 50 nm, the contribution of field ionization to the quantum efficiency can reach 60%.
Directory of Open Access Journals (Sweden)
Xiao Guo
2017-10-01
Full Text Available Electrostatic properties of asymmetrically contacted carbon nanotube barrier-free bipolar diode photodetector are studied by solving the Poisson equation self-consistently with equilibrium carrier statistics. For electric field parallel to tube’s axis, the maximum electric field occurs near contact but decays rapidly in a few nanometers, followed by a slowly increasing trend when it extends to the center of channel. By considering the field ionization and the diffusion effect of exciton, a model of estimation on quantum efficiency for the device is made. We find that the quantum efficiency increases with increasing exciton lifetime, decreasing diffusion constant and channel length. For devices with a channel length shorter than 50 nm, the contribution of field ionization to the quantum efficiency can reach 60%.
Tunable RKKY interaction in a double quantum dot nanoelectromechanical device
Parafilo, A. V.; Kiselev, M. N.
2018-01-01
We propose a realization of mechanically tunable Ruderman-Kittel-Kasuya-Yosida interaction in a double quantum dot nanoelectromechanical device. The coupling between spins of two quantum dots suspended above a metallic plate is mediated by conduction electrons. We show that the spin-mechanical interaction can be driven by a slow modulation of charge density in the metallic plate. We propose to use Stückelberg oscillations as a sensitive tool for detection of the spin and charge states of the coupled quantum dots. Theory of mechanical back action induced by a dynamical spin-spin interaction is discussed.
Fabrication of the asymmetric double-sided concave microlens arrays by femtosecond laser
Zhang, Fan; Yang, Qing; Bian, Hao; Chen, Feng
2017-02-01
In the last decades, fabrication of microlens array in materials with high-damage threshold has attracted increasing interest, especially in the application of high-power laser. In this paper, we propose an advanced strategy to efficiently fabricate microlens array on the surface of glass using a single-pulsed femtosecond laser wet etch process, which is a combination of high-speed laser scanning and the subsequent chemical etch with HF solution. Based on this method, double-sided microlens array, non-regular arrays consisting of close-packed concave microlens array on one side and regular concave MLA on the other side, were fabricated on the 1cm*1cm glass. Especially over one million microlenses could be acquired within an hour, exhibiting great superiority in practical application. Moreover, the optical properties of the asymmetric double-sided MLA were experimentally characterized, and the experimental results reveal the good light homogenization performance.
Andreev molecules in semiconductor nanowire double quantum dots.
Su, Zhaoen; Tacla, Alexandre B; Hocevar, Moïra; Car, Diana; Plissard, Sébastien R; Bakkers, Erik P A M; Daley, Andrew J; Pekker, David; Frolov, Sergey M
2017-09-19
Chains of quantum dots coupled to superconductors are promising for the realization of the Kitaev model of a topological superconductor. While individual superconducting quantum dots have been explored, control of longer chains requires understanding of interdot coupling. Here, double quantum dots are defined by gate voltages in indium antimonide nanowires. High transparency superconducting niobium titanium nitride contacts are made to each of the dots in order to induce superconductivity, as well as probe electron transport. Andreev bound states induced on each of dots hybridize to define Andreev molecular states. The evolution of these states is studied as a function of charge parity on the dots, and in magnetic field. The experiments are found in agreement with a numerical model.Quantum dots in a nanowire are one possible approach to creating a solid-state quantum simulator. Here, the authors demonstrate the coupling of electronic states in a double quantum dot to form Andreev molecule states; a potential building block for longer chains suitable for quantum simulation.
Secure entanglement distillation for double-server blind quantum computation.
Morimae, Tomoyuki; Fujii, Keisuke
2013-07-12
Blind quantum computation is a new secure quantum computing protocol where a client, who does not have enough quantum technologies at her disposal, can delegate her quantum computation to a server, who has a fully fledged quantum computer, in such a way that the server cannot learn anything about the client's input, output, and program. If the client interacts with only a single server, the client has to have some minimum quantum power, such as the ability of emitting randomly rotated single-qubit states or the ability of measuring states. If the client interacts with two servers who share Bell pairs but cannot communicate with each other, the client can be completely classical. For such a double-server scheme, two servers have to share clean Bell pairs, and therefore the entanglement distillation is necessary in a realistic noisy environment. In this Letter, we show that it is possible to perform entanglement distillation in the double-server scheme without degrading the security of blind quantum computing.
Optical properties of magnetoexcitons in double quantum dots
Schillak, Piotr; Czajkowski, Gerard
2015-10-01
Here we investigate the influence of a constant magnetic field on the energy levels and optical properties of excitons in a double quantum disk (quantum molecule). Taking into account the cylindrical symmetry of the double disk we calculate the wave functions and excitonic energies when the external constant magnetic field is applied along the symmetry axis. Having the eigenfunctions and eigenvalues and using the long-wave approximation we can compute all the optical functions. The double quantum dot is considered as one system rather than two interacting dots separated by narrow barrier. The screened Coulomb interaction between an electron and a hole is assumed. Since in the given structure the separation of the relative- and center-of-mass motion of the electron and the hole is not possible, we use an approach where the six-dimensional eigenvalue problem is transformed into the equivalent eigenvalue problem given by the system of the coupled two-dimensional second order differential equations. The so obtained differential equations are solved numerically. As an example, we give detailed results for a InP/InGaP double quantum dot. Satisfactory agreement with the available experimental data is obtained.
The Effect of Electric Field on RbCl Asymmetric Gaussian Potential Quantum Well Qubit
Xiao, Jing-Lin
2016-01-01
We calculate the time evolution and the coordinate change of the quantum mechanical electronic state by using variational method of Pekar type (VMPT) in the presence of strong electron-LO-phonon coupling. The electron is confined in an asymmetric Gaussian potential quantum well (AGPQW) subjected to an applied electric field. The eigenenergies and the eigenfunctions of the ground and the first excited states (GFES) are calculated. A single qubit can be realized in this two-level quantum system. The electron's probability density oscillates in the AGPQW with a certain period of T 0 = 22.511 fs when the electron is in the superposition state of the GFES. We show that due to the presence of the asymmetrical Gaussian potential in the growth direction of the QW, the electron's probability density shows one peak in the range of the coordinate z > 0, whereas it equals to zero in the range of z 0.24 nm. It has a minimum when R = 0.24 nm.
DEFF Research Database (Denmark)
Thirstrup, Carsten
1995-01-01
The effect of excitons in GaInAs-InP coupled asymmetric quantum wells on the refractive index modulation, is analyzed numerically using a model based on the effective mass approximation. It is shown that two coupled quantum wells brought in resonance by an applied electric field will, due...... to the reduction in the exciton oscillator strengths, have a modulation of the refractive index which is more than one order of magnitude larger than in a similar quantum well structure based on the quantum confined Stark effect, but with no coupling between the quantum wells. Calculations show that combining...
Valley blockade in a silicon double quantum dot
Perron, Justin K.; Gullans, Michael J.; Taylor, Jacob M.; Stewart, M. D.; Zimmerman, Neil M.
2017-11-01
Electrical transport in double quantum dots (DQDs) illuminates many interesting features of the dots' carrier states. Recent advances in silicon quantum information technologies have renewed interest in the valley states of electrons confined in silicon. Here we show measurements of dc transport through a mesa-etched silicon double quantum dot. Comparing bias triangles (i.e., regions of allowed current in DQDs) at positive and negative bias voltages we find a systematic asymmetry in the size of the bias triangles at the two bias polarities. Asymmetries of this nature are associated with blocked tunneling events due to the occupation of a metastable state. Several features of our data lead us to conclude that the states involved are not simple spin states. Rather, we develop a model based on selective filling of valley states in the DQD that is consistent with all of the qualitative features of our data.
Coupling effects on photoluminescence of exciton states in asymmetric quantum dot molecules.
Fino, Nelson R; Camacho, Angela S; Ramírez, Hanz Y
2014-01-01
We present a theoretical study of photoluminescence from exciton states in InAs/GaAs asymmetric dot pairs, where interdot coupling is reached via magnetic field in the Faraday configuration. Electronic structure is obtained by finite element calculations, and Coulomb effects are included using a perturbative approach. According to our simulated spectra, bright excited states may become optically accessible at low temperatures in hybridization regimes where intermixing with the ground state is achieved. Our results show effective magnetic control on the energy, polarization and intensity of emitted light, and suggest these coupled nanostructures as relevant candidates for implementation of quantum optoelectronic devices.
Simulating electron spin entanglement in a double quantum dot
Rodriguez-Moreno, M. A.; Hernandez de La Luz, A. D.; Meza-Montes, Lilia
2011-03-01
One of the biggest advantages of having a working quantum-computing device when compared with a classical one, is the exponential speedup of calculations. This exponential increase is based on the ability of a quantum system to create and operate on entangled states. In order to study theoretically the entanglement between two electron spins, we simulate the dynamics of two electron spins in an electrostatically-defined double quantum dot with a finite barrier height between the dots. Electrons are initially confined to separated quantum dots. Barrier height is varied and the spin entanglement as a function of this variation is investigated. The evolution of the system is simulated by using a numerical approach for solving the time-dependent Schrödinger equation for two particles. Partially supported by VIEP-BUAP.
Electronic structure of double Ge quantum dots in Si
Yakimov, A. I.
2012-09-01
Theoretical investigations of the electronic structure of elastically stressed double Ge quantum dots in Si performed in the six-band kp approximation with the Bir-Pikus Hamiltonian and with the configuration interaction method are reviewed. The existence of the antibonding ground state of holes has been revealed. It has been found that, when quantum dots approach each other, the exchange energy of two-particle states has a minimum at the point of the intersection of bonding and antibonding levels; the singlet and triplet states at this point are degenerate. For the lowest spin singlet, it has been revealed that Coulomb correlations in the motion of two holes are manifested in the localization of the two-particle wavefunction at opposite quantum dots when the distance between the dots increases. It has been shown that the degree of entanglement of the singlet quantum states reaches 50% in the case of the manifestation of such spatial correlations.
Perturbative quantum gravity in double field theory
Energy Technology Data Exchange (ETDEWEB)
Boels, Rutger H.; Horst, Christoph [II. Institut für Theoretische Physik, Universität Hamburg,Luruper Chaussee 149, D- 22761 Hamburg (Germany)
2016-04-19
We study perturbative general relativity with a two-form and a dilaton using the double field theory formulation which features explicit index factorisation at the Lagrangian level. Explicit checks to known tree level results are performed. In a natural covariant gauge a ghost-like scalar which contributes even at tree level is shown to decouple consistently as required by perturbative unitarity. In addition, a lightcone gauge is explored which bypasses the problem altogether. Using this gauge to study BCFW on-shell recursion, we can show that most of the D-dimensional tree level S-matrix of the theory, including all pure graviton scattering amplitudes, is reproduced by the double field theory. More generally, we argue that the integrand may be reconstructed from its single cuts and provide limited evidence for off-shell cancellations in the Feynman graphs. As a straightforward application of the developed technology double field theory-like expressions for four field string corrections are derived.
QCAD simulation and optimization of semiconductor double quantum dots
Energy Technology Data Exchange (ETDEWEB)
Nielsen, Erik; Gao, Xujiao; Kalashnikova, Irina; Muller, Richard Partain; Salinger, Andrew Gerhard; Young, Ralph Watson
2013-12-01
We present the Quantum Computer Aided Design (QCAD) simulator that targets modeling quantum devices, particularly silicon double quantum dots (DQDs) developed for quantum qubits. The simulator has three di erentiating features: (i) its core contains nonlinear Poisson, e ective mass Schrodinger, and Con guration Interaction solvers that have massively parallel capability for high simulation throughput, and can be run individually or combined self-consistently for 1D/2D/3D quantum devices; (ii) the core solvers show superior convergence even at near-zero-Kelvin temperatures, which is critical for modeling quantum computing devices; (iii) it couples with an optimization engine Dakota that enables optimization of gate voltages in DQDs for multiple desired targets. The Poisson solver includes Maxwell- Boltzmann and Fermi-Dirac statistics, supports Dirichlet, Neumann, interface charge, and Robin boundary conditions, and includes the e ect of dopant incomplete ionization. The solver has shown robust nonlinear convergence even in the milli-Kelvin temperature range, and has been extensively used to quickly obtain the semiclassical electrostatic potential in DQD devices. The self-consistent Schrodinger-Poisson solver has achieved robust and monotonic convergence behavior for 1D/2D/3D quantum devices at very low temperatures by using a predictor-correct iteration scheme. The QCAD simulator enables the calculation of dot-to-gate capacitances, and comparison with experiment and between solvers. It is observed that computed capacitances are in the right ballpark when compared to experiment, and quantum con nement increases capacitance when the number of electrons is xed in a quantum dot. In addition, the coupling of QCAD with Dakota allows to rapidly identify which device layouts are more likely leading to few-electron quantum dots. Very efficient QCAD simulations on a large number of fabricated and proposed Si DQDs have made it possible to provide fast feedback for design
Vertically coupled double quantum rings at zero magnetic field
Malet, F.; Barranco, M.; Lipparini, E.; Mayol, R.; Pi, M.; Climente, J. I.; Planelles, J.
2006-06-01
Within local-spin-density functional theory, we have investigated the “dissociation” of few-electron circular vertical semiconductor double quantum ring artificial molecules at zero magnetic field as a function of inter-ring distance. In a first step, the molecules are constituted by two identical quantum rings. When the rings are quantum mechanically strongly coupled, the electronic states are substantially delocalized, and the addition energy spectra of the artificial molecule resemble those of a single quantum ring in the few-electron limit. When the rings are quantum mechanically weakly coupled, the electronic states in the molecule are substantially localized in one ring or the other, although the rings can be electrostatically coupled. The effect of a slight mismatch introduced in the molecules from nominally identical quantum wells, or from changes in the inner radius of the constituent rings, induces localization by offsetting the energy levels in the quantum rings. This plays a crucial role in the appearance of the addition spectra as a function of coupling strength particularly in the weak coupling limit.
Asymmetric and double-cathode-pad wire chambers for the LHCb muon system
Kachtchouk, A; Riegler, W; Schmidt, B; Schneider, T; Souvorov, V
2005-01-01
We present results from two types of Multi-Wire Proportional Chambers (MWPCs) with wire pitch of 1.5 mm and cathode–cathode distance of 5 mm intended for triggering purposes in the LHCb experiment. Both prototypes use cathode readout because this allows arbitrary segmentation in order to achieve the required granularity. One MWPC prototype uses a symmetric wire–cathode distance (2.5/2.5 mm) with double cathode readout, which doubles the signal compared to reading only one cathode. The second prototype uses an asymmetric wire–cathode distance (1.25/3.75 mm) with single cathode readout which also doubles the signal and in addition reduces the width of the induced charge distribution and therefore reduces the crosstalk for small cathode pads. We also performed a dedicated optimization of readout traces and guard traces in order to reduce the pad–pad crosstalk. Both prototypes show a few hundred volts of operating plateau defined as the region with 99% efficiency in a 20 ns time window. Close to the plate...
Asymmetric quantum-well structures for AlGaN/GaN/AlGaN resonant tunneling diodes
Energy Technology Data Exchange (ETDEWEB)
Yang, Lin' an, E-mail: layang@xidian.edu.cn; Li, Yue; Wang, Ying; Xu, Shengrui; Hao, Yue [State Key Discipline Laboratory of Wide Bandgap Semiconductor Technology, School of Microelectronics, Xidian University, Xi' an 710071 (China)
2016-04-28
Asymmetric quantum-well (QW) structures including the asymmetric potential-barrier and the asymmetric potential-well are proposed for AlGaN/GaN/AlGaN resonant tunneling diodes (RTDs). Theoretical investigation gives that an appropriate decrease in Al composition and thickness for emitter barrier as well as an appropriate increase of both for collector barrier can evidently improve the negative-differential-resistance characteristic of RTD. Numerical simulation shows that RTD with a 1.5-nm-thick GaN well sandwiched by a 1.3-nm-thick Al{sub 0.15}Ga{sub 0.85}N emitter barrier and a 1.7-nm-thick Al{sub 0.25}Ga{sub 0.75}N collector barrier can yield the I-V characteristic having the peak current (Ip) and the peak-to-valley current ratio (PVCR) of 0.39 A and 3.6, respectively, about double that of RTD with a 1.5-nm-thick Al{sub 0.2}Ga{sub 0.8}N for both barriers. It is also found that an introduction of InGaN sub-QW into the diode can change the tunneling mode and achieve higher transmission coefficient of electron. The simulation demonstrates that RTD with a 2.8-nm-thick In{sub 0.03}Ga{sub 0.97}N sub-well in front of a 2.0-nm-thick GaN main-well can exhibit the I-V characteristic having Ip and PVCR of 0.07 A and 11.6, about 7 times and double the value of RTD without sub-QW, respectively. The purpose of improving the structure of GaN-based QW is to solve apparent contradiction between the device structure and the device manufacturability of new generation RTDs for sub-millimeter and terahertz applications.
Useinov, Arthur
2012-06-01
In this paper, we study the value of the tunnel magnetoresistance (TMR) as a function of the applied voltage in double barrier magnetic tunnel junctions (DMTJs) with the left and right ferromagnetic (FM) layers being pinned and numerically estimate the possible difference of the TMR curves for negative and positive voltages in the homojunctions (equal barriers and electrodes). DMTJs are modeled as two single barrier junctions connected in series with consecutive tunneling (CST). We investigated the asymmetric voltage behavior of the TMR for the CST in the range of a general theoretical model. Significant asymmetries of the experimental curves, which arise due to different annealing regimes, are mostly explained by different heights of the tunnel barriers and asymmetries of spin polarizations in magnetic layers. © (2012) Trans Tech Publications.
Useinov, Arthur
2011-10-22
In this paper we study the asymmetric voltage behavior (AVB) of the tunnel magnetoresistance (TMR) for single and double barrier magnetic tunnel junctions (MTJs) in range of a quasi-classical free electron model. Numerical calculations of the TMR-V curves, output voltages and I-V characteristics for negative and positive values of applied voltages were carried out using MTJs with CoFeB/MgO interfaces as an example. Asymmetry of the experimental TMR-V curves is explained by different values of the minority and majority Fermi wave vectors for the left and right sides of the tunnel barrier, which arises due to different annealing regimes. Electron tunneling in DMTJs was simulated in two ways: (i) Coherent tunneling, where the DMTJ is modeled as one tunnel system and (ii) consecutive tunneling, where the DMTJ is modeled by two single barrier junctions connected in series. © 2012 Elsevier B.V. All rights reserved.
Quantum Entanglement in Double Quantum Systems and Jaynes-Cummings Model.
Jakubczyk, Paweł; Majchrowski, Klaudiusz; Tralle, Igor
2017-12-01
In the paper, we proposed a new approach to producing the qubits in electron transport in low-dimensional structures such as double quantum wells or double quantum wires (DQW). The qubit could arise as a result of quantum entanglement of two specific states of electrons in DQW structure. These two specific states are the symmetric and antisymmetric (with respect to inversion symmetry) states arising due to tunneling across the structure, while entanglement could be produced and controlled by means of the source of nonclassical light. We examined the possibility to produce quantum entanglement in the framework of Jaynes-Cummings model and have shown that at least in principle, the entanglement can be achieved due to series of "revivals" and "collapses" in the population inversion due to the interaction of a quantized single-mode EM field with a two-level system.
Multi-bit dark state memory: Double quantum dot as an electronic quantum memory
Aharon, Eran; Pozner, Roni; Lifshitz, Efrat; Peskin, Uri
2016-12-01
Quantum dot clusters enable the creation of dark states which preserve electrons or holes in a coherent superposition of dot states for a long time. Various quantum logic devices can be envisioned to arise from the possibility of storing such trapped particles for future release on demand. In this work, we consider a double quantum dot memory device, which enables the preservation of a coherent state to be released as multiple classical bits. Our unique device architecture uses an external gating for storing (writing) the coherent state and for retrieving (reading) the classical bits, in addition to exploiting an internal gating effect for the preservation of the coherent state.
Dephasing and hyperfine interaction in carbon nanotubes double quantum dots
DEFF Research Database (Denmark)
Reynoso, Andres Alejandro; Flensberg, Karsten
2012-01-01
We study theoretically the return probability experiment, which is used to measure the dephasing time T-2*, in a double quantum dot (DQD) in semiconducting carbon nanotubes with spin-orbit coupling and disorder-induced valley mixing. Dephasing is due to hyperfine interaction with the spins of the C...... with these for DQDs in clean nanotubes, whereas the disorder effect is always relevant when the magnetic field is perpendicular to the nanotube axis....
Decoherence in a double-slit quantum eraser
Torres-Ruiz, F. A.; Lima, G.; Delgado, A.; Pádua, S.; Saavedra, C.
2010-04-01
We study and experimentally implement a double-slit quantum eraser in the presence of a controlled decoherence mechanism. A two-photon state, produced in a spontaneous parametric down-conversion process, is prepared in a maximally entangled polarization state. A birefringent double slit is illuminated by one of the down-converted photons, and it acts as a single-photon two-qubits controlled-not gate that couples the polarization with the transversal momentum of these photons. The other photon, which acts as a which-path marker, is sent through a Mach-Zehnder-like interferometer. When the interferometer is partially unbalanced, it behaves as a controlled source of decoherence for polarization states of down-converted photons. We show the transition from wavelike to particle-like behavior of the signal photons crossing the double slit as a function of the decoherence parameter, which depends on the length path difference at the interferometer.
Computer-automated tuning of semiconductor double quantum dots into the single-electron regime
Energy Technology Data Exchange (ETDEWEB)
Baart, T. A.; Vandersypen, L. M. K. [QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Eendebak, P. T. [QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft (Netherlands); Netherlands Organisation for Applied Scientific Research (TNO), P.O. Box 155, 2600 AD Delft (Netherlands); Reichl, C.; Wegscheider, W. [Solid State Physics Laboratory, ETH Zürich, 8093 Zürich (Switzerland)
2016-05-23
We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.
Computer-automated tuning of semiconductor double quantum dots into the single-electron regime
Baart, T.A.; Eendebak, P.T.; Reichl, C.; Wegscheider, W.; Vandersypen, L.M.K.
2016-01-01
We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the
DEFF Research Database (Denmark)
Zubov, F.I.; Maximov, M.V.; Shernyakov, Yu.M.
2015-01-01
An AlGaAs/GaAs quantum well (QW) laser is fabricated with GaInP and AlGaInAs asymmetric barrier layers (ABLs) and its light–current characteristic (LCC) is compared with that of a reference conventional QW laser without ABLs. It was found that the use of the ABLs suppresses the sublinearity...
Some double resonance and multiple quantum NMR studies in solids
Energy Technology Data Exchange (ETDEWEB)
Wemmer, D.E.
1978-08-01
The first section of this work presents the theory and experimental applications to analysis of molecular motion of chemical shielding lineshapes obtained with high resolution double resonance NMR techniques. Analysis of /sup 13/C powder lineshapes in hexamethylbenzene (HMB) and decamethylferrocene (DMFe) show that these molecules reorient in a jumping manner about the symmetry axis. Analysis of proton chemical shielding lineshapes of residual protons in heavy ice (D/sub 2/O) show that protons are exchanged among the tetrahedral positions of neighboring oxygen atoms, consistent with motion expected from defect migration. The second section describes the application of Fourier Transform Double Quantum NMR to measurement of chemical shielding of deuterium in powder samples. Studies of partially deuterated benzene and ferrocene give equal shielding anisotropies, ..delta..sigma = -6.5 ppM. Theoretical predictions and experimental measurements of dipolar couplings between deuterons using FTDQ NMR are presented. Crystals of BaClO/sub 3/.D/sub 2/O, ..cap alpha..,..beta.. d-2 HMB and ..cap alpha..,..beta..,..gamma.. d-3 HMB were studied, as were powders of d-2 HMB and anisic acid. The third section discusses general multiple quantum spectroscopy in dipolar coupled spin systems. Theoretical description is made for creation and detection of coherences between states without quantum number selection rules ..delta..m = +-1. Descriptions of techniques for partial selectivity of order in preparation and detection of multiple quantum coherences are made. The effects on selectivity and resolution of echo pulses during multiple quantum experiments are discussed. Experimental observation of coherences up to order 6 have been made in a sample of benzene dissolved in a liquid crystal. Experimental verifications of order selection and echo generation have been made.
Afzal, Muhammad Imran; Lee, Yong Tak
2016-01-01
Von Neumann and Wigner theorized bounding of asymmetric eigenstates and anti-crossing of symmetric eigenstates. Experiments have shown that owing to anti-crossing and similar radiation rates, graphene-like resonance of inhomogeneously strained photonic eigenstates can generate pseudomagnetic field, bandgaps and Landau levels, while dissimilar rates induce non-Hermicity. Here, we showed experimentally higher-order supersymmetry and quantum phase transitions by resonance between similar one dimensional lattices. The lattices consisted of inhomgeneously strain-like phases of triangular solitons. The resonance created two dimensional inhomogeneously deformed photonic graphene. All parent eigenstates are annihilated. Where eigenstates of mildly strained solitons are annihilated with similar (power law) rates through one tail only and generated Hermitianally bounded eigenstates. The strongly strained solitons, positive defects are annihilated exponentially through both tails with dissimilar rates. Which bounded eig...
The properties of an asymmetric Gaussian potential quantum well qubit in RbCl crystal
Sun, Yong; Miao, Xiujuan; Ding, Zhaohua; Xiao, Jinglin
2017-04-01
With the circumstance of the electron strongly coupled to LO-phonon and using the variational method of Pekar type (VMPT), we study the eigenenergies and the eigenfunctions (EE) of the ground and the first excited states (GFES) in a RbCl crystal asymmetric Gaussian potential quantum well (AGPQW). It concludes: (i) Two-energy-level of the AGPQW may be seen as a qubit. (ii) When the electron located in the superposition state of the two-energy-level system, the time evolution and the coordinate changes of the electron probability density oscillated periodically in the AGPQW with every certain period {T}0=22.475 fs. (iii) Due to the confinement that is a two dimensional x-y plane symmetric structure in the AGPQW and the asymmetrical Gaussian potential (AGP) in the AGPQW growth direction, the electron probability density presents only one peak configuration located in the coordinate of z > 0, whereas it is zero in the range of z 0.24 nm and it takes a minimum value in R = 0.24 nm. Project supported by the National Natural Science Foundation of China (No. 11464033) and the Mongolia University for Nationalities Fund (No.NMDYB1445).
Wei, Hai-Rui; Deng, Fu-Guo
2013-07-29
We investigate the possibility of achieving scalable photonic quantum computing by the giant optical circular birefringence induced by a quantum-dot spin in a double-sided optical microcavity as a result of cavity quantum electrodynamics. We construct a deterministic controlled-not gate on two photonic qubits by two single-photon input-output processes and the readout on an electron-medium spin confined in an optical resonant microcavity. This idea could be applied to multi-qubit gates on photonic qubits and we give the quantum circuit for a three-photon Toffoli gate. High fidelities and high efficiencies could be achieved when the side leakage to the cavity loss rate is low. It is worth pointing out that our devices work in both the strong and the weak coupling regimes.
Electron transport in coupled double quantum wells and wires
Energy Technology Data Exchange (ETDEWEB)
Harff, N.E.; Simmons, J.A.; Lyo, S.K. [and others
1997-04-01
Due to inter-quantum well tunneling, coupled double quantum wells (DQWs) contain an extra degree of electronic freedom in the growth direction, giving rise to new transport phenomena not found in single electron layers. This report describes work done on coupled DQWs subject to inplane magnetic fields B{sub {parallel}}, and is based on the lead author`s doctoral thesis, successfully defended at Oregon State University on March 4, 1997. First, the conductance of closely coupled DQWs in B{sub {parallel}} is studied. B{sub {parallel}}-induced distortions in the dispersion, the density of states, and the Fermi surface are described both theoretically and experimentally, with particular attention paid to the dispersion anticrossing and resulting partial energy gap. Measurements of giant distortions in the effective mass are found to agree with theoretical calculations. Second, the Landau level spectra of coupled DQWs in tilted magnetic fields is studied. The magnetoresistance oscillations show complex beating as Landau levels from the two Fermi surface components cross the Fermi level. A third set of oscillations resulting from magnetic breakdown is observed. A semiclassical calculation of the Landau level spectra is then performed, and shown to agree exceptionally well with the data. Finally, quantum wires and quantum point contacts formed in DQW structures are investigated. Anticrossings of the one-dimensional DQW dispersion curves are predicted to have interesting transport effects in these devices. Difficulties in sample fabrication have to date prevented experimental verification. However, recently developed techniques to overcome these difficulties are described.
Elastic-plastic defect interaction in (asymmetrical double edge notched tension specimens
Directory of Open Access Journals (Sweden)
Kaveh Samadian
2017-02-01
Full Text Available Interaction of defects tends to intensify their crack driving force response compared to the situation where these defects act independently. The interaction between multiple defects is addressed in engineering critical assessment standards like BS7910 and ASME B&PV Section XI. Nonetheless, the accuracy of these rules is open to debate since all of them are based on re-characterization procedures which in essence introduce conservativeness. The authors have developed a fully parametric finite element (FE model able to generate multiple notches in different topologies, in order to investigate their interaction effect. An experimental validation study is conducted to verify the FE model in terms of CTOD response and surface strain distribution. To that end, symmetrically and asymmetrically double edge notched tension specimens are tensile tested and their deformation monitored by means of 3D digital image correlation. In this study the CTOD is opted as a local criterion to evaluate the interaction between notches. These results are compared with an evaluation of strain patterns on a specimen’s surface, as a global interaction evaluation. Through this comparison a deeper understanding is gained to allow us to develop a novel approach to address flaw interaction. Moreover, the validation of the FE model allows future studies of interaction between other defect types (e.g., semi-elliptical, surface breaking in plate-like geometries.
Anyons are not energy eigenspaces of quantum double Hamiltonians
Kómár, Anna; Landon-Cardinal, Olivier
2017-11-01
Kitaev's quantum double models, including the toric code, are canonical examples of quantum topological models on a two-dimensional spin lattice. Their Hamiltonian defines the ground space by imposing an energy penalty to any nontrivial flux or charge, but does not distinguish among those. We generalize this construction by introducing a family of Hamiltonians made of commuting four-body projectors that provide an intricate splitting of the Hilbert space by discriminating among nontrivial charges and fluxes. Our construction highlights that anyons are not in one-to-one correspondence with energy eigenspaces, a feature already present in Kitaev's construction. This discrepancy is due to the presence of local degrees of freedom in addition to topological ones on a lattice.
Out-of-Equilibrium Kondo Effect in Double Quantum Dots
Energy Technology Data Exchange (ETDEWEB)
Aguado, Ramon; Langreth, David C.
2000-08-28
The out-of-equilibrium transport properties of a double quantum dot system in the Kondo regime are studied theoretically by means of a two-impurity Anderson Hamiltonian with interimpurity hopping. The Hamiltonian is solved by means of a nonequilibrium generalization of the slave-boson mean-field theory. It is demonstrated that measurements of the differential conductance dI/dV , for appropriate values of voltages and tunneling couplings, can give a direct observation of the coherent superposition between the many-body Kondo states of each dot. For large voltages and arbitrarily large interdot tunneling, there is a critical voltage above which the physical behavior of the system again resembles that of two decoupled quantum dots. (c) 2000 The American Physical Society.
Asymmetric adiabatic couplers for fully-integrated broadband quantum-polarization state preparation.
Chung, Hung-Pin; Huang, Kuang-Hsu; Wang, Kai; Yang, Sung-Lin; Yang, Shih-Yuan; Sung, Chun-I; Solntsev, Alexander S; Sukhorukov, Andrey A; Neshev, Dragomir N; Chen, Yen-Hung
2017-12-04
Spontaneous parametric down-conversion (SPDC) is a widely used method to generate entangled photons, enabling a range of applications from secure communication to tests of quantum physics. Integrating SPDC on a chip provides interferometric stability, allows to reduce a physical footprint, and opens a pathway to true scalability. However, dealing with different photon polarizations and wavelengths on a chip presents a number of challenging problems. In this work, we demonstrate an on-chip polarization beam-splitter based on z-cut titanium-diffused lithium niobate asymmetric adiabatic couplers (AAC) designed for integration with a type-II SPDC source. Our experimental measurements reveal unique polarization beam-splitting regime with the ability to tune the splitting ratios based on wavelength. In particular, we measured a splitting ratio of 17 dB over broadband regions (>60 nm) for both H- and V-polarized lights and a specific 50%/50% splitting ratio for a cross-polarized photon pair from the AAC. The results show that such a system can be used for preparing different quantum polarization-path states that are controllable by changing the phase-matching conditions in the SPDC over a broad band. Furthermore, we propose a fully integrated electro-optically tunable type-II SPDC polarization-path-entangled state preparation circuit on a single lithium niobate photonic chip.
Hamedi, H. R.
2014-09-01
The transient and steady-state dispersion and absorption properties of a three-subband asymmetric semiconductor quantum well system are investigated. In the steady-state regime, it is shown that by increasing the strength of Fano-interference as well as enhancement of energy splitting of two excited states the slope of dispersion changes from negative to positive which is corresponding to a switch between superluminal to subluminal light propagation. At the same time, the probe absorption reduces at telecommunication wavelength λ = 1550 nm. The influence of incoherent pumping fields on time-dependent susceptibility is then discussed. It is found that due to more transfer of population to the upper levels, increasing the rate of incoherent pump field leads to the reduction of probe absorption. In addition, it is realized that incoherent pumping has a major role in converting fast to slow propagation of light at long wavelength. We also introduce an extra controllability for the light pulse to be slow downed at Telecom wavelength just through the quantum interference arising from incoherent pumping fields. The obtained results may be practical in telecommunication applications.
Non-equilibrium Kondo effect in double quantum dot
Energy Technology Data Exchange (ETDEWEB)
Kiselev, M.N. E-mail: kiselev@physik.uni-wuerzburg.de; Kikoin, K.A.; Molenkamp, L.W
2004-05-01
We investigate theoretically a non-equilibrium transport through a double quantum dot (DQD) in a parallel geometry. It is shown that the resonance Kondo tunneling through a parallel DQD with even occupation and singlet ground state may arise at a strong bias, which compensates the energy of singlet/triplet excitation. Using the renormalization group technique we derive scaling equations and calculate the differential conductance as a function of an auxiliary DC-bias for parallel DQD being in a regime described by SO(4) symmetry.
Quantum efficiency of a single microwave photon detector based on a semiconductor double quantum dot
Wong, Clement H.; Vavilov, Maxim G.
2017-01-01
Motivated by recent interest in implementing circuit quantum electrodynamics with semiconducting quantum dots, we consider a double quantum dot (DQD) capacitively coupled to a superconducting resonator that is driven by the microwave field of a superconducting transmission line. We analyze the DQD current response using input-output theory and show that the resonator-coupled DQD is a sensitive microwave single photon detector. Using currently available experimental parameters of DQD-resonator coupling and dissipation, including the effects of 1 /f charge noise and phonon noise, we determine the parameter regime for which incident photons are completely absorbed and near-unit ≳98 % efficiency can be achieved. We show that this regime can be reached by using very high quality resonators with quality factor Q ≃105 .
Magnetotransport in HgTe double quantum well
Suslov, A. V.; Yakunin, M. V.; Popov, M. R.; Novik, E. G.; Dvoretsky, S. A.; Mikhailov, N. N.
We present a study of a double quantum well (DQW) made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands, than is known for HgTe single quantum wells (QW). Thus, the critical field Bc for opening the gap in the energy spectrum shifts towards much higher fields with respect to Bc in single QWs. The accompanying specific features in magnetotransport, such as multiple inversions in ρxy(B), zero-filling-factor state with a concomitant manifestation of its insulator character in ρxx(B), etc., also move towards higher fields, where the quantum Hall regime is well realized. The overlap can be regulated by a gate voltage Vg and the coexisting electrons and holes were found in the whole investigated range of positive and negative Vg. The electron density n remains almost constant in the whole range of investigated Vg, while the hole density p drops down passing through the charge-neutrality point. This difference between n and p stems from an order of magnitude larger density of states for holes than for electrons. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW. Supported by FASO (theme Spin 01201463330), RFBR (Project 17-02-00330), the RAS Ural division complex program (Project 15-9-2-21), NSF Cooperative Agreement DMR-1157490 and the State of Florida.
Double parton scattering in the CGC: Double quark production and effects of quantum statistics
Kovner, Alex; Rezaeian, Amir H.
2017-10-01
We consider forward inclusive production of two quarks in the high energy p-A collisions in the color-glass-condensate formalism. We demonstrate that the production cross section is determined by the convolution of the proton generalized double transverse momentum-dependent distribution functions with two independent eikonal scattering amplitudes: the product of two dipoles and a quadrupole. We explicitly demonstrate that the quadrupole amplitude term accounts for all the (initial and final state) effects of quantum statistics for identical fermions, and the correlations due to these effects. We also demonstrate that the effects due to quantum statistics (entirely encoded in the quadrupole) are parametrically leading contributions to the correlated particle production at large Nc. For nonidentical quarks the quadrupole term also leads to correlated production which (barring accidental cancellations) has characteristics similar to the Hanbury Brown-Twiss effect.
Double-β decay matrix elements from lattice quantum chromodynamics
Tiburzi, Brian C.; Wagman, Michael L.; Winter, Frank; Chang, Emmanuel; Davoudi, Zohreh; Detmold, William; Orginos, Kostas; Savage, Martin J.; Shanahan, Phiala E.; Nplqcd Collaboration
2017-09-01
A lattice quantum chromodynamics (LQCD) calculation of the nuclear matrix element relevant to the n n →p p e e ν¯eν¯e transition is described in detail, expanding on the results presented in Ref. [P. E. Shanahan et al., Phys. Rev. Lett. 119, 062003 (2017), 10.1103/PhysRevLett.119.062003]. This matrix element, which involves two insertions of the weak axial current, is an important input for phenomenological determinations of double-β decay rates of nuclei. From this exploratory study, performed using unphysical values of the quark masses, the long-distance deuteron-pole contribution to the matrix element is separated from shorter-distance hadronic contributions. This polarizability, which is only accessible in double-weak processes, cannot be constrained from single-β decay of nuclei, and is found to be smaller than the long-distance contributions in this calculation, but non-negligible. In this work, technical aspects of the LQCD calculations, and of the relevant formalism in the pionless effective field theory, are described. Further calculations of the isotensor axial polarizability, in particular near and at the physical values of the light-quark masses, are required for precise determinations of both two-neutrino and neutrinoless double-β decay rates in heavy nuclei.
DEFF Research Database (Denmark)
Zhukov, A. E.; Asryan, L. V.; Shernyakov, Yu. M.
2012-01-01
The temperature sensitivity of the threshold-current density in quantum-well lasers is studied and the factors affecting the characteristic temperature and its dependence on optical losses are analyzed. It is shown that the inclusion of asymmetric potential barriers (one barrier on each side...... of the quantum well), which prevent the formation of bipolar carrier population in the waveguide region and lead to weakening of the temperature dependences of the transparency-current density, the gain-saturation parameter and, consequently, to a higher characteristic temperature for both long- and short...
The Double-Well Potential in Quantum Mechanics: A Simple, Numerically Exact Formulation
Jelic, V.; Marsiglio, F.
2012-01-01
The double-well potential is arguably one of the most important potentials in quantum mechanics, because the solution contains the notion of a state as a linear superposition of "classical" states, a concept which has become very important in quantum information theory. It is therefore desirable to have solutions to simple double-well potentials…
Spin transport properties in a double quantum ring with Rashba spin-orbit interaction
Naeimi, Azadeh S.; Eslami, Leila; Esmaeilzadeh, Mahdi; Abolhassani, Mohammad Reza
2013-01-01
We study spin-resolved electron transport in a double quantum ring in the presence of Rashba spin-orbit interaction and a magnetic flux using quantum waveguide theory. We show that, at the proper values of the system parameters such as the Rashba coupling constant, the radius of the rings, and the angle between the leads, the double quantum ring can act as a perfect electron spin-inverter with very high efficiency. Also, the double quantum ring can work as a spin switch. The spin polarization of transmitted electrons can be controlled and changed from -1 to +1 by using a magnetic flux.
Kondo physics in double quantum dot based Cooper pair splitters
Wrześniewski, Kacper; Weymann, Ireneusz
2017-11-01
The Andreev transport properties of double quantum dot based Cooper pair splitters with one superconducting and two normal leads are studied theoretically in the Kondo regime. The influence of the superconducting pairing correlations on the local density of states, Andreev transmission coefficient, and Cooper pair splitting efficiency is thoroughly analyzed. It is shown that finite superconducting pairing potential quickly suppresses the SU(2 ) Kondo effect, which can however reemerge for relatively large values of coupling to superconductor. In the SU(4 ) Kondo regime, a crossover from the SU(4 ) to the SU(2 ) Kondo state is found as the coupling to superconductor is enhanced. The analysis is performed by means of the density-matrix numerical renormalization group method.
Wei, Hai-Rui; Deng, Fu-Guo
2014-12-18
Quantum logic gates are the key elements in quantum computing. Here we investigate the possibility of achieving a scalable and compact quantum computing based on stationary electron-spin qubits, by using the giant optical circular birefringence induced by quantum-dot spins in double-sided optical microcavities as a result of cavity quantum electrodynamics. We design the compact quantum circuits for implementing universal and deterministic quantum gates for electron-spin systems, including the two-qubit CNOT gate and the three-qubit Toffoli gate. They are compact and economic, and they do not require additional electron-spin qubits. Moreover, our devices have good scalability and are attractive as they both are based on solid-state quantum systems and the qubits are stationary. They are feasible with the current experimental technology, and both high fidelity and high efficiency can be achieved when the ratio of the side leakage to the cavity decay is low.
Resonant Tunneling in Photonic Double Quantum Well Heterostructures
Directory of Open Access Journals (Sweden)
Cox Joel
2010-01-01
Full Text Available Abstract Here, we study the resonant photonic states of photonic double quantum well (PDQW heterostructures composed of two different photonic crystals. The heterostructure is denoted as B/A/B/A/B, where photonic crystals A and B act as photonic wells and barriers, respectively. The resulting band structure causes photons to become confined within the wells, where they occupy discrete quantized states. We have obtained an expression for the transmission coefficient of the PDQW heterostructure using the transfer matrix method and have found that resonant states exist within the photonic wells. These resonant states occur in split pairs, due to a coupling between degenerate states shared by each of the photonic wells. It is observed that when the resonance energy lies at a bound photonic state and the two photonic quantum wells are far away from each other, resonant states appear in the transmission spectrum of the PDQW as single peaks. However, when the wells are brought closer together, coupling between bound photonic states causes an energy-splitting effect, and the transmitted states each have two peaks. Essentially, this means that the system can be switched between single and double transparent states. We have also observed that the total number of resonant states can be controlled by varying the width of the photonic wells, and the quality factor of transmitted peaks can be drastically improved by increasing the thickness of the outer photonic barriers. It is anticipated that the resonant states described here can be used to develop new types of photonic-switching devices, optical filters, and other optoelectronic devices.
Bose condensation of interwell excitons in double quantum wells
Larionov, A V; Ni, P A; Dubonos, S V; Hvam, I; Soerensen, K
2002-01-01
The luminescence of the interwell excitons in the GaAs/AlGaAs double quantum wells, containing large-scale fluctuations of the random potential in the heteroboundary planes, is studied. The properties of the excitons, wherein the excited electron and hole are spatially separated between the neighboring quantum wells by the density and temperature variation within the domain limits of the scale below one micron, are investigated. The interwell excitons by low pumping (below 50 mW) are strongly localized due to the small-scale fluctuations of the random potential. The localized excitons line grows by increase in the resonance excitation capacity through the threshold method. With the temperature growth this line disappears in the spectrum (T sub c <= 3.4 K). The above phenomenon is related to the Bose-Einstein condensation in the quasi-two-dimensional system of the interwell excitons. The critical values of the exciton density and temperature in the studied temperature range (1.5-3.4 K) grow according to the...
Finite coupling effects in double quantum dots near equilibrium
Xu, Xiansong; Thingna, Juzar; Wang, Jian-Sheng
2017-01-01
A weak coupling quantum master equation provides reliable steady-state results only in the van Hove limit, i.e., when the system-lead coupling approaches zero. Recently, J. Thingna et al. [Phys. Rev. E 88, 052127 (2013), 10.1103/PhysRevE.88.052127] proposed an alternative approach, based on an analytic continuation of the Redfield solution, to evaluate the steady-state reduced density matrix up to second order in the system-bath coupling. The approach provides accurate results for harmonic oscillator and spin-bosonic systems. We apply this approach to study steady-state fermionic systems and the calculation on an exactly solvable double quantum dot system shows that the method is rigorously valid up to second order in system-lead coupling only near equilibrium, i.e., linear response regime. We further compare to the Redfield and the secular Redfield (Lindblad-type) master equations that are inaccurate in all parameter regimes. Lastly, we consider the nontrivial problem of strong Coulomb interaction and illustrate the interplay between system-lead coupling, interdot tunneling, and Coulomb strength that can be captured only via the analytic continuation method.
Sayer, Ryan; Maries, Alexandru; Singh, Chandralekha
2017-01-01
Learning quantum mechanics is challenging, even for upper-level undergraduate and graduate students. Research-validated interactive tutorials that build on students' prior knowledge can be useful tools to enhance student learning. We have been investigating student difficulties with quantum mechanics pertaining to the double-slit experiment in…
Han, Kihwan; Yeo, Hyeonjung; Choi, Tae Hyun; Son, Daegu; Kim, Jun Hyung
2010-03-01
One of the most common complications of double eyelid operations is asymmetry. To reduce asymmetry, we fixed the dermis to the tarsal plate at the same level as the skin incision, and objectively evaluated the symmetry of the height using photogrammetry.Of 30 patients who had double eyelid operations by the intratarsal fixation technique, 15 patients completed a minimum follow-up of 6 months. After the skin incision and removal of the orbicularis oculi muscle and the orbital fat, the pretarsal fat pad was excised to expose the superior portion of the tarsal plate. The 3 fixation points were marked on the tarsal plate at the same level with the skin incision using a spreading caliper. The dermis was fixed to the marked points of the tarsal plate and the skin was closed.The height of the double eyelid was measured by clinical photography at 4 points when the eyes were opened and at 3 points when the eyes were closed. The height proportional index at each point was obtained by dividing the height of the left double eyelid by that of the right double eyelid. We compared each height proportional index with "1" to evaluate the symmetry of both double eyelids using a paired t test.The follow-up period was an average of 9.0 months. The mean height proportional indices were 0.97 (a), 0.96 (b), 0.98 (c), 1.08 (d), 0.97 (e), 1.02 (f), and 1.13 (g). According to a paired t test, the height of the left double eyelid was not different from that of the right double eyelid.Intratarsal fixation, along with other previously known methods, decreases asymmetric double eyelids.
Adaptive double chain quantum genetic algorithm for constrained optimization problems
Directory of Open Access Journals (Sweden)
Haipeng Kong
2015-02-01
Full Text Available Optimization problems are often highly constrained and evolutionary algorithms (EAs are effective methods to tackle this kind of problems. To further improve search efficiency and convergence rate of EAs, this paper presents an adaptive double chain quantum genetic algorithm (ADCQGA for solving constrained optimization problems. ADCQGA makes use of double-individuals to represent solutions that are classified as feasible and infeasible solutions. Fitness (or evaluation functions are defined for both types of solutions. Based on the fitness function, three types of step evolution (SE are defined and utilized for judging evolutionary individuals. An adaptive rotation is proposed and used to facilitate updating individuals in different solutions. To further improve the search capability and convergence rate, ADCQGA utilizes an adaptive evolution process (AEP, adaptive mutation and replacement techniques. ADCQGA was first tested on a widely used benchmark function to illustrate the relationship between initial parameter values and the convergence rate/search capability. Then the proposed ADCQGA is successfully applied to solve other twelve benchmark functions and five well-known constrained engineering design problems. Multi-aircraft cooperative target allocation problem is a typical constrained optimization problem and requires efficient methods to tackle. Finally, ADCQGA is successfully applied to solving the target allocation problem.
Wen, Pengyan; Liu, Jianping; Zhang, Shuming; Zhang, Liqun; Ikeda, Masao; Li, Deyao; Tian, Aiqin; Zhang, Feng; Cheng, Yang; Zhou, Wei; Yang, Hui
2017-11-01
The temperature, power, and voltage dependent photoluminescence spectra are studied in InGaN/GaN double quantum well blue laser diodes. Emissions from the two quantum wells can be distinguished at low temperature at low excitation power density due to the different built-in electric field in the two quantum wells. This finding is utilized to study the degradation of InGaN/GaN blue laser diodes. Two peaks are observed for the non-aged laser diode (LD), while one peak for the aged LD which performed 3200 h until no laser output is detected. The disappearance of the high energy peak in the photoluminescence spectra indicates a heavier degradation of the quantum well on the p-side, which agrees with our previous observation that both the linewidth and the potential fluctuation of InGaN quantum wells (QWs) reduced for the aged LDs.
Enhanced Kerr nonlinearity in a tunnel-coupled double quantum wells
Asadpour, S. H.; Hamedi, Hamid Reza; Eslami-Majd, A.; Sahrai, Mostafa
2011-11-01
The giant Kerr nonlinearity in an asymmetric coupled quantum well (CQW) driven by probe and control laser fields based on intersubband transitions is investigated. The effect of controlling parameters such as intensity of coupling field and electron tunneling on nonlinear behavior of the system is then discussed. It is shown that the enhanced Kerr nonlinearity with reduced linear and nonlinear absorption can be achieved.
A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures
Energy Technology Data Exchange (ETDEWEB)
Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.
1998-12-14
We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.
Low strain quantum dots in a double well infrared detector
Shenoi, R. V.; Hou, J.; Sharma, Y.; Shao, J.; Vandervelde, T. E.; Krishna, S.
2008-08-01
We report the fabrication of low strain quantum-dots-in-a-double-well (DDWELL) infrared photodetector where the net strain on the system has been reduced by limiting the total indium content in the system. The detector consists of InAs dots embedded in In0.15Ga0.85As and GaAs wells with a Al0.1Ga0.9As barrier, as opposed to In0.15Ga0.85As wells and a GaAs barrier in standard dots-in-a-well (DWELL) detector. The structure was a result of multilevel optimization involving the dot, well layers above and below the dot for achieving the desired wavelength response and higher absorption, and the thickness of the barriers for reduction in dark current. Detector structures grown using solid source molecular beam epitaxy (MBE) were processed and characterized. The reduction in total strain has enabled the growth of higher number of active region layers resulting in enhanced absorption of light. The detector shows dual color response with peaks in the mid-wave infrared (MWIR) and the long-wave infrared (LWIR) region. A peak detectivity of 6.7×1010 cm.√ Hz/W was observed at 8.7μm. The detector shows promise in raising the operating temperature of DWELL detectors, thereby enabling cheaper operation.
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.
Wang, Wen-Yuan; Dou, Fu-Quan; Duan, Wen-Shan
2018-02-01
We investigate the macroscopic quantum self-trapping (MQST) phenomenon of a spin–orbit-coupled Bose–Einstein condensate (BEC) in a double-well potential, emphasizing the critical behavior at the transition to MQST. We show that as the nonlinear parameter characterizing the atomic interaction increases, the spin–orbit-coupled BEC appears as MQST, manifesting an asymmetric distribution of the atom in two wells. Then, the effect of the initial condition on the critical behavior at the transition to MQST is given. Analytic expressions for the dependence of the transition parameters on the system parameters and the initial condition are derived, which are in agreement with our numerical simulations.
Efficient 2D double-quantum solid-state NMR spectroscopy with large spectral widths.
Märker, Katharina; Hediger, Sabine; De Paëpe, Gaël
2017-08-10
2D double-quantum single-quantum correlation spectra with arbitrary spectral widths can be recorded with SR26 and related supercycled recoupling sequences when applying Supercycle-Timing-Compensation (STiC) phase shifts. This concept widely extends the applicability of supercycled sequences, most importantly for obtaining long-range distance constraints for structure determination with solid-state NMR.
Robustness of Charge-Qubit Cluster States to Double Quantum Point Contact Measurement
Tanamoto, Tetsufumi
2010-01-01
We theoretically investigate the robustness of cluster states in charge qubit system based on quantum dot (QD) and double quantum point contact (DQPC). Trap state is modeled by an island structure in DQPC and represents a dynamical fluctuation. We found that the dynamical fluctuations affect the cluster states more than static fluctuation caused by QD size fluctuation.
Improvement of power characteristics in 850 nm quantum well laser with asymmetric barriers
DEFF Research Database (Denmark)
Zubov, F.I.; Maximov, M.V.; Shernyakov, YuM.
2015-01-01
Power and spectral characteristics of lasers with asymmetric barrier layers (ABLs) and a wide waveguide are studied. The use of ABLs reduces the saturation of light-current characteristic, associated with the parasitic recombination in the waveguide....
Directory of Open Access Journals (Sweden)
Pengqin Shi
2016-09-01
Full Text Available Based on the time-nonlocal particle number-resolved master equation, we investigate the sequential electron transport through the interacting double quantum dots. Our calculations show that there exists the effect of energy renormalization in the dispersion of the bath interaction spectrum and it is sensitive to the the bandwidth of the bath. This effect would strongly affect the stationary current and its zero-frequency shot noise for weak inter-dot coherent coupling strength, but for strong inter-dot coupling regime, it is negligible due to the strong intrinsic Rabi coherent dynamics. Moreover, the possible observable effects of the energy renormalization in the noise spectrum are also investigated through the Rabi coherence signal. Finally, the non-Markovian effect is manifested in the finite-frequency noise spectrum with the appearance of quasisteps, and the magnitude of these quasisteps are modified by the dispersion function.
Directory of Open Access Journals (Sweden)
Myunghwan Ryu
2016-01-01
Full Text Available We investigate the electrical characteristics of a double-gate-all-around (DGAA transistor with an asymmetric channel width using three-dimensional device simulation. The DGAA structure creates a silicon nanotube field-effect transistor (NTFET with a core-shell gate architecture, which can solve the problem of loss of gate controllability of the channel and provides improved short-channel behavior. The channel width asymmetry is analyzed on both sides of the terminals of the transistors, i.e., source and drain. In addition, we consider both n-type and p-type DGAA FETs, which are essential to forming a unit logic cell, the inverter. Simulation results reveal that, according to the carrier types, the location of the asymmetry has a different effect on the electrical properties of the devices. Thus, we propose the N/P DGAA FET structure with an asymmetric channel width to form the optimal inverter. Various electrical metrics are analyzed to investigate the benefits of the optimal inverter structure over the conventional inverter structure. Simulation results show that 27% delay and 15% leakage power improvement are enabled in the optimum structure.
Spin magneto-transport in a Rashba-Dresselhaus quantum channel with single and double finger gates
Tang, Chi-Shung; Keng, Jia-An; Abdullah, Nzar Rauf; Gudmundsson, Vidar
2017-05-01
We address spin-resolved electronic transport properties in a Rashba-Dresselhaus quantum channel in the presence of an in-plane magnetic field. The strong Rashba-Dresselhaus effect induces an asymmetric spin-splitting energy spectrum with a spin-orbit-Zeeman gap. This asymmetric fact in energy spectrum may result in various quantum dynamic features in conductance due to the presence of finger gates. This asymmetric spin-splitting energy spectrum results in a bound state in continuum for electrons within ultralow energy regime with binding energies in order of 10-1 meV.
Directory of Open Access Journals (Sweden)
JunÃ¢Â€Â™ichi Kobayashi
2005-01-01
Full Text Available Asymmetric synthesis of double bond isomers ( -2 (Ã¢ÂˆÂ†15Ã¢Â€Â™,16Ã¢Â€Â™ and ( -3 (Ã¢ÂˆÂ†14Ã¢Â€Â™,15Ã¢Â€Â™ ofthe structure (1 (Ã¢ÂˆÂ†16Ã¢Â€Â™,17Ã¢Â€Â™ proposed for pyrinodemin A, a cytotoxic bis-pyridine alkaloidwith a unique cis-cyclopent[c]isoxazolidine moiety from a marine sponge, has beenaccomplished. Pyrinodemin A was indicated to be a 1:1 racemic mixture of 2 fromcomparison of C18 and chiral HPLC analysis for pyrinodemin A and the syntheticcompounds as well as ESIMS data of oxidative degradation products of pyrinodemin A.
Hagar, Amit
Among the alternatives of non-relativistic quantum mechanics (NRQM) there are those that give different predictions than quantum mechanics in yet-untested circumstances, while remaining compatible with current empirical findings. In order to test these predictions, one must isolate one's system from environmental induced decoherence, which, on the standard view of NRQM, is the dynamical mechanism that is responsible for the 'apparent' collapse in open quantum systems. But while recent advances in condensed-matter physics may lead in the near future to experimental setups that will allow one to test the two hypotheses, namely genuine collapse vs. decoherence, hence make progress toward a solution to the quantum measurement problem, those philosophers and physicists who are advocating an information-theoretic approach to the foundations of quantum mechanics are still unwilling to acknowledge the empirical character of the issue at stake. Here I argue that in doing so they are displaying an unwarranted double standard.
Fast coherent manipulation of three-electron states in a double quantum dot.
Shi, Zhan; Simmons, C B; Ward, Daniel R; Prance, J R; Wu, Xian; Koh, Teck Seng; Gamble, John King; Savage, D E; Lagally, M G; Friesen, Mark; Coppersmith, S N; Eriksson, M A
2014-01-01
An important goal in the manipulation of quantum systems is the achievement of many coherent oscillations within the characteristic dephasing time T2(*). Most manipulations of electron spins in quantum dots have focused on the construction and control of two-state quantum systems, or qubits, in which each quantum dot is occupied by a single electron. Here we perform quantum manipulations on a system with three electrons per double quantum dot. We demonstrate that tailored pulse sequences can be used to induce coherent rotations between three-electron quantum states. Certain pulse sequences yield coherent oscillations fast enough that more than 100 oscillations are visible within a T2(*) time. The minimum oscillation frequency we observe is faster than 5 GHz. The presence of the third electron enables very fast rotations to all possible states, in contrast to the case when only two electrons are used, in which some rotations are slow.
Local Gate Control of a Carbon Nanotube Double Quantum Dot
2016-04-04
candidates for elu- cidating surface phenomena. Here, we used Car -Parrinello molecular dynamics (CPMD) (13, 14) to investigate the properties of the aqueous...This ability to control electron interactions in the quantum regime in a molecular conductor is important for applications such as quantum...fabricated in semiconductor heterostructures (21, 26). Such similarities suggest that more complex quantum devices formed from molecular conductors such as
A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor
DEFF Research Database (Denmark)
Hu, Yongjie; Churchill, Hugh; Reilly, David
2007-01-01
Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation......: the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top gate-defined double quantum dot based on Ge/Si heterostructure nanowires with fully tunable coupling between the dots...... and to the leads. We also demonstrate a novel approach to charge sensing in a one-dimensional nanostructure by capacitively coupling the double dot to a single dot on an adjacent nanowire. The double quantum dot and integrated charge sensor serve as an essential building block required to form a solid-state spin...
Shifted one-parameter supersymmetric family of quartic asymmetric double-well potentials
Energy Technology Data Exchange (ETDEWEB)
Rosu, Haret C., E-mail: hcr@ipicyt.edu.mx [IPICYT, Instituto Potosino de Investigacion Cientifica y Tecnologica, Camino a la presa San José 2055, Col. Lomas 4a Sección, 78216 San Luis Potosí, S.L.P. (Mexico); Mancas, Stefan C., E-mail: mancass@erau.edu [Department of Mathematics, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114-3900 (United States); Chen, Pisin, E-mail: pisinchen@phys.ntu.edu.tw [Leung Center for Cosmology and Particle Astrophysics (LeCosPA) and Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)
2014-10-15
Extending our previous work (Rosu, 2014), we define supersymmetric partner potentials through a particular Riccati solution of the form F(x)=(x−c){sup 2}−1, where c is a real shift parameter, and work out the quartic double-well family of one-parameter isospectral potentials obtained by using the corresponding general Riccati solution. For these parametric double well potentials, we study how the localization properties of the two wells depend on the parameter of the potentials for various values of the shifting parameter. We also consider the supersymmetric parametric family of the first double-well potential in the Razavy chain of double well potentials corresponding to F(x)=1/2 sinh2x−2((1+√(2))sinh2x)/((1+√(2))cosh2x+1) , both unshifted and shifted, to test and compare the localization properties. - Highlights: • Quartic one-parameter DWs with an additional shift parameter are introduced. • Anomalous localization feature of their zero modes is confirmed at different shifts. • Razavy one-parameter DWs are also introduced and shown not to have this feature.
Kinetic analysis of the thermal isomerisation pathways in an asymmetric double azobenzene switch
Robertus, Jort; Reker, Siebren F.; Pijper, Thomas C.; Deuzeman, Albert; Browne, Wesley R.; Feringa, Ben L.
2012-01-01
Here we report a photochemical and kinetic study of the thermal relaxation reaction of a double azobenzene system, in which two azobenzene photochromic units are connected via a phenyl ring. Upon UV irradiation, three thermally unstable isomers are formed. Kinetic studies using arrayed H-1-NMR
Liu, Bao; Zhang, Feng-Yang; Song, Jie; Song, He-Shan
2015-06-29
We propose a direct measurement scheme to read out the geometric phase of a coupled double quantum dot system via a quantum point contact(QPC) device. An effective expression of the geometric phase has been derived, which relates the geometric phase of the double quantum dot qubit to the current through QPC device. All the parameters in our expression are measurable or tunable in experiment. Moreover, since the measurement process affects the state of the qubit slightly, the geometric phase can be protected. The feasibility of the scheme has been analyzed. Further, as an example, we simulate the geometrical phase of a qubit when the QPC device is replaced by a single electron transistor(SET).
Janjua, Bilal
2013-01-01
A novel design based on an asymmetrically graded-well, Al(a→b)Ga(1-a→1-b) N / Al(c)Ga(1-c) N,where b>c>a, to enhance the optical matrix element of radiative transitions in an AlGaN based UV-LED, is theoretically studied.
States of direct and indirect excitons in strained zinc-blende GaN/InGaN asymmetric quantum wells
Rojas-Briseño, J. G.; Martínez-Orozco, J. C.; Mora-Ramos, M. E.
2017-12-01
The total and binding energies of excitons in step-like asymmetric quantum wells made of zincblende GaN/InxlGa(1-xl)N/InxrGa(1-xr)N/GaN are theoretically reported. It is discussed how the asymmetry in the carrier confinement leads to singular behaviors in the exciton binding energy, allowing to observe both direct and indirect exciton states in the heterostructure. The study is carried out with the use of the effective mass approximation. The effects of strain are taken into account and a comparison of the results obtained for both strained and unstrained situations is presented. Exciton energy shows a decreasing behavior when the size of the effective confinement region is augmented. The total exciton energy as well as the binding energy are reported as functions of the indium concentration and quantum well width. In addition, the results of the calculation of the photoluminescence peak are presented. For this latter quantity, our results for the limiting case of a single zinc-blende GaN/InGaN quantum well show very good agreement with published experimental ones.
Martínez-Orozco, J. C.; Rojas-Briseño, J. G.; Rodríguez-Magdaleno, K. A.; Rodríguez-Vargas, I.; Mora-Ramos, M. E.; Restrepo, R. L.; Ungan, F.; Kasapoglu, E.; Duque, C. A.
2017-11-01
In this paper we are reporting the computation for the Nonlinear Optical Rectification (NOR) and the Second and Third Harmonic Generation (SHG and THG) related with electronic states of asymmetric double Si-δ-doped quantum well in a GaAs matrix when this is subjected to an in-plane (x-oriented) constant magnetic field effect. The work is performed in the effective mass and parabolic band approximations in order to compute the electronic structure for the system by a diagonalization procedure. The expressions for the nonlinear optical susceptibilities, χ0(2), χ2ω(2), and χ3ω(3), are those arising from the compact matrix density formulation and stand for the NOR, SHG, and THG, respectively. This asymmetric double δ-doped quantum well potential profile actually exhibits nonzero NOR, SHG, and THG responses which can be easily controlled by the in-plane (x-direction) externally applied magnetic field. In particular we find that for the chosen configuration the harmonic generation is in the far-infrared/THz region, thus and becoming suitable building blocks for photodetectors in this range of the electromagnetic spectra.
Progress towards microwave readout of a silicon double quantum dot
Schmidt, A. R.; Henry, E.; House, M.; Wang, Y. T.; Lo, C. C.; Li, H.; Greenman, L.; Pan, H.; Xiao, M.; Whaley, K. B.; Jiang, H.-W.; Yablonovitch, E.; Bokor, J.; Siddiqi, I.
2013-03-01
Microwave resonators coupled to quantum systems have been used for fast dispersive measurement in several different architectures in solid state and atomic physics. The electronic states of a semiconductor quantum dot represent a promising candidate for quantum information processing. Our work is geared toward developing a fast, non-demolition readout of a semiconductor qubit in silicon through coupling to a superconducting microwave resonator. We report progress on a novel design of a lateral This work is supported by the DARPA QuEST program.
Ruckle, L. J.; Belloni, M.; Robinett, R. W.
2012-01-01
The biharmonic oscillator and the asymmetric linear well are two confining power-law-type potentials for which complete bound-state solutions are possible in both classical and quantum mechanics. We examine these problems in detail, beginning with studies of their trajectories in position and momentum space, evaluation of the classical probability…
Temperature effects on excited state of strong-coupling polaron in an asymmetric RbCl quantum dot
Feng, Li-Qin; Li, Jing-Qi; Xiao, Jing-Lin
2015-01-01
On the condition of strong electron-LO phonon coupling in an asymmetric RbCl quantum dot (QD), the first excited state energy (FESE), the excitation energy (EE), and the transition frequency (TF) between the first excited ground states (FEGS) of the polaron are calculated by using the linear combination operator and the unitary transformation methods. The variation of the FESE, the EE and the TF with the temperature, the transverse and longitudinal confinement strengths (TLCS) of the QD are studied in detail. We find that the FESE, the EE and the TF decreases (increases) with increasing temperature when the temperature is in lower (higher) temperature regime. They are increasing functions of the TLCS. We find three ways to tune the FESE, the EE and the TF via controlling the temperature and the TLCS.
Fast response of the optical nonlinearity in a GaAs/AlGaAs asymmetric triple quantum well structure
Ahn, S H; Sawaki, N
1999-01-01
The time response of the optical nonlinear behavior in a GaAs/AlGaAs asymmetric triple quantum well structure is estimated by using a picosecond pump-probe method at 77 K. From the results of the transmission of the probe pulse as a function of the delay time at the excitation wavelengths, a rise time of 5 approx 10 ps and a fall time of 8 approx 16 ps are obtained. The nonlinear behavior is attributed to the triple resonance of the electronic states due to the build-up of the internal field induced by the separation of photo-excited electrons and holes. It is found that the rise time is determined by the tunneling transfer time of the electrons in the narrowest well to an adjacent well separated by a thin potential barrier.
Quantum Molecular Interaction Field Models of Substrate Enantioselection in Asymmetric Processes.
Kozlowski, Marisa C; Ianni, James C
2010-06-01
Computational models correlating substrate structure to enantioselection with asymmetric catalysts using the QMQSAR program are described. In addition to rapidly providing predictions that could be used to facilitate the screening of catalysts for novel substrates, the QMQSAR program identifies the portions of the substrate that most directly influence the enantioselectivity. The lack underlying relationship between all the substrates in one case, requires two quantitative structure selectivity relationships (QSSR) models to describe all of the experimental results.
Temporal mode sorting using dual-stage quantum frequency conversion by asymmetric Bragg scattering
DEFF Research Database (Denmark)
Christensen, Jesper Bjerge; Reddy, Dileep V.; McKinstrie, C. J.
2015-01-01
-mode interferometry [D. V. Reddy, Phys. Rev. A 91, 012323 (2015)], has been shown in the case of three-wave mixing to promise near-unity mode-sorting efficiency. Here we demonstrate that it is also possible to achieve high mode-sorting efficiency using four-wave mixing, if one pump pulse is long and the other short...... - a configuration we call asymmetrically-pumped Bragg scattering. (C) 2015 Optical Society of America...
Collective Behavior of a Spin-Aligned Gas of Interwell Excitons in Double Quantum Wells
DEFF Research Database (Denmark)
Larionov, A. V.; Bayer, M.; Hvam, Jørn Märcher
2005-01-01
The kinetics of a spin-aligned gas of interwell excitons in GaAs/AlGaAs double quantum wells (n–i–n heterostructure) is studied. The temperature dependence of the spin relaxation time for excitons, in which a photoexcited electron and hole are spatially separated between two adjacent quantum well...... is associated with indirect evidence of the coherence of the collective phase of interwell excitons at temperatures below the critical value....
A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor.
Hu, Yongjie; Churchill, Hugh O H; Reilly, David J; Xiang, Jie; Lieber, Charles M; Marcus, Charles M
2007-10-01
One proposal for a solid-state-based quantum bit (qubit) is to control coupled electron spins on adjacent semiconductor quantum dots. Most experiments have focused on quantum dots made from III-V semiconductors; however, the coherence of electron spins in these materials is limited by hyperfine interactions with nuclear spins. Ge/Si core/shell nanowires seem ideally suited to overcome this limitation, because the most abundant nuclei in Ge and Si have spin zero and the nanowires can be chemically synthesized defect-free with tunable properties. Here, we present a double quantum dot based on Ge/Si nanowires in which we can completely control the coupling between the dots and to the leads. We also demonstrate that charge on the double dot can be detected by coupling it capacitively to an adjacent nanowire quantum dot. The double quantum dot and integrated charge sensor serve as an essential building block to form a solid-state qubit free of nuclear spin.
Timing PSR J0453+1559: A likely asymmetric double neutron star system
Martinez, Jose; Stovall, K.; Freire, P.; Deneva, J. S.; Jenet, F.; McLaughlin, M.
2014-01-01
PSR J0453+1559 is a pulsar with a spin period of 45.7 ms discovered in the Arecibo All-Sky 327 MHz Drift Pulsar Survey. Subsequent observations of this source performed at the Arecibo Radio Observatory has revealed that it is in a binary system with an orbit period of 4.07 days with an eccentricity of 0.1125. The semi-major axis of the orbit is 14.5 light seconds, which implies, for a pulsar mass of 1.35 solar masses, a minimum and median companion mass of 1.0 and 1.2 solar masses respectively. This strongly suggests this is a new double neutron star (DNS) system. If confirmed, this would be the tenth DNS known in the Universe.
Impact of Lateral Straggle on the Analog/RF Performance of Asymmetric Gate Stack Double Gate MOSFET
Sivaram, Gollamudi Sai; Chakraborty, Shramana; Das, Rahul; Dasgupta, Arpan; Kundu, Atanu; Sarkar, Chandan K.
2016-09-01
This paper presents a systematic comparative study of Analog and RF performances of an underlapped double gate (U-DG) NMOSFET with Gate Stack (GS) for varying straggle lengths. Asymmetric underlap devices (A-U-DG) have been proposed as one of the remedies for reducing Short Channel Effects (SCE's) with the underlap being present towards the source for sub 20 nm devices. However, the Source to Drain (S/D) implant lateral diffusion leads to a variation in the effective underlap length. This paper investigates the impact of variation of straggle length on the Analog and RF parameters of the device. The RF performance is analyzed by considering the intrinsic capacitances (Cgd, Cgs), intrinsic resistances (Rgd, Rgs), transport delay (τm), inductance (Lsd), cutoff frequency (fT), and the maximum frequency of oscillations (fmax). The circuit performance of the devices are also studied. It is seen that the Analog and RF performances of the devices are improved by optimizing the S/D lateral straggle.
Sayer, Ryan; Maries, Alexandru; Singh, Chandralekha
2017-06-01
Learning quantum mechanics is challenging, even for upper-level undergraduate and graduate students. Research-validated interactive tutorials that build on students' prior knowledge can be useful tools to enhance student learning. We have been investigating student difficulties with quantum mechanics pertaining to the double-slit experiment in various situations that appear to be counterintuitive and contradict classical notions of particles and waves. For example, if we send single electrons through the slits, they may behave as a "wave" in part of the experiment and as a "particle" in another part of the same experiment. Here we discuss the development and evaluation of a research-validated Quantum Interactive Learning Tutorial (QuILT) which makes use of an interactive simulation to improve student understanding of the double-slit experiment and strives to help students develop a good grasp of foundational issues in quantum mechanics. We discuss common student difficulties identified during the development and evaluation of the QuILT and analyze the data from the pretest and post test administered to the upper-level undergraduate and first-year physics graduate students before and after they worked on the QuILT to assess its effectiveness. These data suggest that on average, the QuILT was effective in helping students develop a more robust understanding of foundational concepts in quantum mechanics that defy classical intuition using the context of the double-slit experiment. Moreover, upper-level undergraduates outperformed physics graduate students on the post test. One possible reason for this difference in performance may be the level of student engagement with the QuILT due to the grade incentive. In the undergraduate course, the post test was graded for correctness while in the graduate course, it was only graded for completeness.
Directory of Open Access Journals (Sweden)
Ryan Sayer
2017-05-01
Full Text Available Learning quantum mechanics is challenging, even for upper-level undergraduate and graduate students. Research-validated interactive tutorials that build on students’ prior knowledge can be useful tools to enhance student learning. We have been investigating student difficulties with quantum mechanics pertaining to the double-slit experiment in various situations that appear to be counterintuitive and contradict classical notions of particles and waves. For example, if we send single electrons through the slits, they may behave as a “wave” in part of the experiment and as a “particle” in another part of the same experiment. Here we discuss the development and evaluation of a research-validated Quantum Interactive Learning Tutorial (QuILT which makes use of an interactive simulation to improve student understanding of the double-slit experiment and strives to help students develop a good grasp of foundational issues in quantum mechanics. We discuss common student difficulties identified during the development and evaluation of the QuILT and analyze the data from the pretest and post test administered to the upper-level undergraduate and first-year physics graduate students before and after they worked on the QuILT to assess its effectiveness. These data suggest that on average, the QuILT was effective in helping students develop a more robust understanding of foundational concepts in quantum mechanics that defy classical intuition using the context of the double-slit experiment. Moreover, upper-level undergraduates outperformed physics graduate students on the post test. One possible reason for this difference in performance may be the level of student engagement with the QuILT due to the grade incentive. In the undergraduate course, the post test was graded for correctness while in the graduate course, it was only graded for completeness.
Double coupling: modeling subjectivity and asymmetric organization in social-ecological systems
Directory of Open Access Journals (Sweden)
David Manuel-Navarrete
2015-09-01
Full Text Available Social-ecological organization is a multidimensional phenomenon that combines material and symbolic processes. However, the coupling between social and ecological subsystem is often conceptualized as purely material, thus reducing the symbolic dimension to its behavioral and actionable expressions. In this paper I conceptualize social-ecological systems as doubly coupled. On the one hand, material expressions of socio-cultural processes affect and are affected by ecological dynamics. On the other hand, coupled social-ecological material dynamics are concurrently coupled with subjective dynamics via coding, decoding, personal experience, and human agency. This second coupling operates across two organizationally heterogeneous dimensions: material and symbolic. Although resilience thinking builds on the recognition of organizational asymmetry between living and nonliving systems, it has overlooked the equivalent asymmetry between ecological and socio-cultural subsystems. Three guiding concepts are proposed to formalize double coupling. The first one, social-ecological asymmetry, expands on past seminal work on ecological self-organization to incorporate reflexivity and subjectivity in social-ecological modeling. Organizational asymmetry is based in the distinction between social rules, which are symbolically produced and changed through human agents' reflexivity and purpose, and biophysical rules, which are determined by functional relations between ecological components. The second guiding concept, conscious power, brings to the fore human agents' distinctive capacity to produce our own subjective identity and the consequences of this capacity for social-ecological organization. The third concept, congruence between subjective and objective dynamics, redefines sustainability as contingent on congruent relations between material and symbolic processes. Social-ecological theories and analyses based on these three guiding concepts would support the
Double-resonance spectroscopy of InAs/GaAs self-assembled quantum dots
Murdin, B. N.; Hollingworth, A. R.; Barker, J. A.; Clarke, D. G.; Findlay, P. C.; Pidgeon, C. R.; Wells, J. P. R.; Bradley, I. V.; Malik, S.; Murray, R.
2000-01-01
We present far-/near-infrared double resonance measurements of self-assembled InAs/GaAs quantum dots. The far-infrared resonance is unambiguously associated with a bound-bound intraband transition in the neutral dots. The results show that the interband photoluminescence (PL) lines originate from
Correlation Effects on the Coupled Plasmon Modes of a Double Quantum Well
DEFF Research Database (Denmark)
Hill, N. P. R.; Nicholls, J. T.; Linfield, E. H.
1997-01-01
At temperatures comparable to the Fermi temperature, we have measured a plasmon enhanced Coulomb drag in a GaAs/AlGaAs double quantum well electron system. This measurement provides a probe of the many-body corrections to the coupled plasmon modes, and we present a detailed comparison between exp...
Optical analogue of 2D heteronuclear double-quantum NMR
Tollerud, Jonathan
2016-01-01
Heteronuclear multi-quantum spectroscopy is a powerful part of the NMR toolbox, commonly used to identify specific sequences of atoms in complex pulse sequences designed to determine the structure of complex molecules, including proteins. Optical coherent multidimensional spectroscopy (CMDS) is analogous to multidimensional NMR and many of the techniques of NMR have been adapted for application in the optical regime. This has been highly successful, with CMDS being used to understand energy transfer in photosynthesis and many body effects in semiconductor nanostructures amongst many other scientific breakthroughs. Experimental challenges have, however, prevented the translation of heteronuclear multi-quantum NMR to the optical regime, where capabilities to isolate signals in otherwise congested spectra, reduce acquisition times and enable more incisive probes of multi-particle correlations and complex electronic systems would have great benefit. Here we utilise a diffraction based pulseshaper to impose the tw...
Deterministic entanglement distillation for secure double-server blind quantum computation
Sheng, Yu-Bo; Zhou, Lan
2015-01-01
Blind quantum computation (BQC) provides an efficient method for the client who does not have enough sophisticated technology and knowledge to perform universal quantum computation. The single-server BQC protocol requires the client to have some minimum quantum ability, while the double-server BQC protocol makes the client's device completely classical, resorting to the pure and clean Bell state shared by two servers. Here, we provide a deterministic entanglement distillation protocol in a practical noisy environment for the double-server BQC protocol. This protocol can get the pure maximally entangled Bell state. The success probability can reach 100% in principle. The distilled maximally entangled states can be remaind to perform the BQC protocol subsequently. The parties who perform the distillation protocol do not need to exchange the classical information and they learn nothing from the client. It makes this protocol unconditionally secure and suitable for the future BQC protocol. PMID:25588565
Double-slit experiment with single wave-driven particles and its relation to quantum mechanics.
Andersen, Anders; Madsen, Jacob; Reichelt, Christian; Rosenlund Ahl, Sonja; Lautrup, Benny; Ellegaard, Clive; Levinsen, Mogens T; Bohr, Tomas
2015-07-01
In a thought-provoking paper, Couder and Fort [Phys. Rev. Lett. 97, 154101 (2006)] describe a version of the famous double-slit experiment performed with droplets bouncing on a vertically vibrated fluid surface. In the experiment, an interference pattern in the single-particle statistics is found even though it is possible to determine unambiguously which slit the walking droplet passes. Here we argue, however, that the single-particle statistics in such an experiment will be fundamentally different from the single-particle statistics of quantum mechanics. Quantum mechanical interference takes place between different classical paths with precise amplitude and phase relations. In the double-slit experiment with walking droplets, these relations are lost since one of the paths is singled out by the droplet. To support our conclusions, we have carried out our own double-slit experiment, and our results, in particular the long and variable slit passage times of the droplets, cast strong doubt on the feasibility of the interference claimed by Couder and Fort. To understand theoretically the limitations of wave-driven particle systems as analogs to quantum mechanics, we introduce a Schrödinger equation with a source term originating from a localized particle that generates a wave while being simultaneously guided by it. We show that the ensuing particle-wave dynamics can capture some characteristics of quantum mechanics such as orbital quantization. However, the particle-wave dynamics can not reproduce quantum mechanics in general, and we show that the single-particle statistics for our model in a double-slit experiment with an additional splitter plate differs qualitatively from that of quantum mechanics.
Wu, Q. Q.; Tan, Q. S.; Kuang, L. M.
2011-10-01
We propose a theoretical scheme to generate a controllable and switchable coupling between two double-quantum-dot (DQD) spin qubits by using a transmission line resonator (TLR) as a bus system. We study dynamical behaviors of quantum correlations described by entanglement correlation (EC) and discord correlation (DC) between two DQD spin qubits when the two spin qubits and the TLR are initially prepared in X-type quantum states and a coherent state, respectively. We demonstrate that in the EC death regions there exist DC stationary states in which the stable DC amplification or degradation can be generated during the dynamical evolution. It is shown that these DC stationary states can be controlled by initial-state parameters, the coupling, and detuning between qubits and the TLR. We reveal the full synchronization and anti-synchronization phenomena in the EC and DC time evolution, and show that the EC and DC synchronization and anti-synchronization depends on the initial-state parameters of the two DQD spin qubits. It is shown that the initial quantum correlation may be suppressed completely when the evolution time approaches to the infinity in the presence of dissipation. These results shed new light on dynamics of quantum correlations.
Double-time correlation functions of two quantum operations in open systems
Ban, Masashi
2017-10-01
A double-time correlation function of arbitrary two quantum operations is studied for a nonstationary open quantum system which is in contact with a thermal reservoir. It includes a usual correlation function, a linear response function, and a weak value of an observable. Time evolution of the correlation function can be derived by means of the time-convolution and time-convolutionless projection operator techniques. For this purpose, a quasidensity operator accompanied by a fictitious field is introduced, which makes it possible to derive explicit formulas for calculating a double-time correlation function in the second-order approximation with respect to a system-reservoir interaction. The derived formula explicitly shows that the quantum regression theorem for calculating the double-time correlation function cannot be used if a thermal reservoir has a finite correlation time. Furthermore, the formula is applied for a pure dephasing process and a linear dissipative process. The quantum regression theorem and the the Leggett-Garg inequality are investigated for an open two-level system. The results are compared with those obtained by exact calculation to examine whether the formula is a good approximation.
Janjua, Bilal
2014-04-01
We study the enhanced hole confinement by having a large bandgap AlGaN monolayer insertion (MLI) between the quantum well (QW) and the quantum barrier (QB). The numerical analysis examines the energy band alignment diagrams, using a self-consistent 6 × 6 k ·p method and, considering carrier distribution, recombination rates (Shockley-Reed-Hall, Auger, and radiative recombination rates), under equilibrium and forward bias conditions. The active region is based on AlaGa1-aN (barrier)/AlbGa1-bN (MLI)/AlcGa1-cN (well)/AldGa1-dN (barrier), where b > d > a > c. A large bandgap AlbGa1-bN mono layer, inserted between the QW and QB, was found to be effective in providing stronger hole confinement. With the proposed band engineering scheme, an increase of more than 30% in spatial overlap of carrier wavefunction was obtained, with a considerable increase in carrier density and direct radiative recombination rates. The single-QW-based UV-LED was designed to emit at 280 nm, which is an effective wavelength for water disinfection.
Anisotropic Pauli Spin Blockade of Holes in a GaAs Double Quantum Dot
Wang, Qingwen; Klochan, Oleh; Hung, Jo-Tzu; Culcer, Dimitrie; Farrer, Ian; Ritchie, David; Hamilton, Alex
Electrically defined semiconductor quantum dots are appealing systems for spin manipulation and quantum information processing. Thanks to the weak hyperfine interaction and the strong spin-orbit interaction, heavy-holes in GaAs are promising candidates for all-electrical spin manipulation. However, making stable quantum dots in GaAs has only become possible recently, mainly because of difficulties in device fabrication and device stability. Here we present electrical transport measurements of heavy-holes in a lateral double quantum dot based on a GaAs /AlxGa1 - x As heterostructure. We observe clear Pauli spin blockade and show that the lifting of the spin blockade by an external magnetic field is extremely anisotropic. Numerical calculations of heavy-hole transport through a double quantum dot in the presence of strong spin-orbit interaction demonstrate quantitative agreement with experimental results, which indicates that the observed anisotropy can be explained by the anisotropic hole g-factor and the surface Dresselhaus spin-orbit coupling.
Sequential double Auger decay in atoms: A quantum informatic analysis
Energy Technology Data Exchange (ETDEWEB)
Parida, S. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721302 (India); Chandra, N. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721302 (India)], E-mail: ncphy@phy.iitkgp.ernet.in
2009-05-04
We theoretically show that the process of inner-shell photoionization in an atom A, followed by the spontaneous sequential emission of two Auger electrons, produces various kinds of spin-entangled states of three flying electronic qubits. All properties of these states are completely pre-determined by the total spin quantum numbers of the electronic states of four atomic species (i.e., A, A{sup +{sup *}}, A{sup 2+{sup *}}, A{sup 3+}) participating in this process in the Russell-Saunders coupling. These tripartite states are readily characterized experimentally by measuring only energies of the three emitted electrons, without requiring any entanglement witness or other such protocols.
Quantum frequency doubling based on tripartite entanglement with cavities
Juan, Guo; Zhi-Feng, Wei; Su-Ying, Zhang
2016-02-01
We analyze the entanglement characteristics of three harmonic modes, which are the output fields from three cavities with an input tripartite entangled state at fundamental frequency. The entanglement properties of the input beams can be maintained after their frequencies have been up-converted by the process of second harmonic generation. We have calculated the parametric dependences of the correlation spectrum on the initial squeezing factor, the pump power, the transmission coefficient, and the normalized analysis frequency of cavity. The numerical results provide references to choose proper experimental parameters for designing the experiment. The frequency conversion of the multipartite entangled state can also be applied to a quantum communication network. Project supported by the National Natural Science Foundation of China (Grant No. 91430109), the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20111401110004), and the Natural Science Foundation of Shanxi Province, China (Grant No. 2014011005-3).
Fluctuation theorem for a double quantum dot coupled to a point-contact electrometer
Energy Technology Data Exchange (ETDEWEB)
Golubev, D. [Institut für Nanotechnologie, Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany); Utsumi, Y. [Department of Physics Engineering, Faculty of Engineering, Mie University, Tsu, Mie, 514-8507 (Japan); Marthaler, M. [Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Schön, G. [Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, 76128 Karlsruhe, Germany and Institut für Nanotechnologie, Karlsruhe Institute of Technology, 76021 Karlsruhe (Germany)
2013-12-04
Motivated by recent experiments on the real-time single-electron counting through a semiconductor GaAs double quantum dot (DQD) by a nearby quantum point contact (QPC), we develop the full-counting statistics of coupled DQD and QPC system. By utilizing the time-scale separation between the dynamics of DQD and QPC, we derive the modified master equation with tunneling rates depending on the counting fields, which fulfill the detailed fluctuation theorem. Furthermore, we derive universal relations between the non-linear corrections to the current and noise, which can be verified in experiments.
Quantum even spheres Sigma_q^2n from Poisson double suspension
Bonechi, F.; Ciccoli, N.; Tarlini, M.
2002-01-01
We define even dimensional quantum spheres Sigma_q^2n that generalize to higher dimension the standard quantum two-sphere of Podle's and the four-sphere Sigma_q^4 obtained in the quantization of the Hopf bundle. The construction relies on an iterated Poisson double suspension of the standard Podle's two-sphere. The Poisson spheres that we get have the same symplectic foliation consisting of a degenerate point and a symplectic plane and, after quantization, have the same C^*-...
Microwave spectroscopy on a double quantum dot with an on-chip Josephson oscillator
Energy Technology Data Exchange (ETDEWEB)
Holleitner, A.W.; Qin, H.; Simmel, F.; Irmer, B.; Kotthaus, J. P. [Center for NanoScience and Sektion Physik, Ludwig-Maximilians-Universitaet, Geschwister-Scholl-Platz 1, 80539 Muenchen (Germany); Blick, R.H. [Center for NanoScience and Sektion Physik, Ludwig-Maximilians-Universitaet, Geschwister-Scholl-Platz 1, 80539 Muenchen (Germany). E-mail: robert.blick at physik.uni-muenchen.de; Ustinov, A.V. [Physikalisches Institut III, Universitaet Erlangen-Nuernberg, Erwin-Rommel-Strasse 1, 91058 Erlangen (Germany); Eberl, K. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstrasse 1, 70569 Stuttgart (Germany)
2000-01-01
We present measurements on microwave spectroscopy on a double quantum dot with an on-chip microwave source. The quantum dots are realized in the two-dimensional electron gas of an AlGaAs/GaAs heterostructure and are weakly coupled in series by a tunnelling barrier forming an 'ionic' molecular state. We employ a Josephson oscillator formed by a long Nb/Al-AlO{sub x}/Nb junction as a microwave source. We find photon-assistedtunnelling sidebands induced by the Josephson oscillator, and compare the results with those obtained using an externally operated microwave source. (author)
String-nets, single and double-stranded quantum loop gases for non-Abelian anyons
Velenich, Andrea; Chamon, Claudio; Wen, Xiao-Gang
2009-01-01
String-net condensation can give rise to non-Abelian anyons whereas loop condensation usually gives rise to Abelian anyons. It has been proposed that generalized quantum loop gases with non-orthogonal inner products can produce non-Abelian anyons. We detail an exact mapping between the string-net and the generalized loop models and explain how the non-orthogonal products arise. We also introduce a loop model of double-stranded nets where quantum loops with an orthogonal inner product and loca...
Vibrational effects in charge transport through a molecular double quantum dot
Sowa, Jakub K.; Mol, Jan A.; Briggs, G. Andrew D.; Gauger, Erik M.
2017-02-01
Recent progress in the field of molecular electronics has revealed the fundamental importance of the coupling between the electronic degrees of freedom and specific vibrational modes. Considering the examples of a molecular dimer and a carbon nanotube double quantum dot, we here theoretically investigate transport through a two-site system that is strongly coupled to a single vibrational mode. Using a quantum master equation approach, we demonstrate that, depending on the relative positions of the two dots, electron-phonon interactions can lead to negative differential conductance and suppression of the current through the system. We also discuss the experimental relevance of the presented results and possible implementations of the studied system.
Aceituno, P.; Hernández-Cabrera, A.
2017-11-01
We study the multistable behavior of the intersubband optical absorption for InSb-based tunnel-coupled quantum wells. We consider four sublevels coming from the splitting of the two deepest levels due to the inversion asymmetry of the structure (Rashba effect), and a weak external in-plane magnetic field (Zeeman effect). Photoexcitation with an intense terahertz pump produces the redistribution of nonequilibrium electrons among the four spin sublevels. The redistribution produces a photoinduced self-consistent potential, giving rise to the renormalization of energy distance between sublevels. Depending on total electron concentration, magnetic field intensity, and pumping efficiency, we find different multistable behaviors in the intersubband optical absorption spectrum. Based on the matrix density, we describe the electron redistribution by means of a system of balance equations for electron concentrations.
Martineau-Corcos, Charlotte; Dědeček, Jiri; Taulelle, Francis
In this paper, we review and illustrate applications, reported in the literature or used in our group, of 27Al-27Al double-quantum single-quantum (DQ-SQ) MAS NMR experiments for the structural characterization of Al-containing microporous solids, namely zeolites, aluminophosphates and metal-organic frameworks. Information regarding the periodic frameworks or the localization of the various aluminum species in the materials are obtained from the analysis of the two-dimensional NMR spectra, which allows getting local structural details sometimes inaccessible from other characterization technique. An application of 27Al-27Al of the DQ-SQ experiment for the detection of aluminum pairing in zeolite is shown. Copyright © 2017 Elsevier Inc. All rights reserved.
Few electron double quantum dots in InAs/InP nanowire heterostructures.
Fuhrer, Andreas; Fröberg, Linus E; Pedersen, Jonas Nyvold; Larsson, Magnus W; Wacker, Andreas; Pistol, Mats-Erik; Samuelson, Lars
2007-02-01
We report on fabrication of double quantum dots in catalytically grown InAs/InP nanowire heterostructures. In the few-electron regime, starting with both dots empty, our low-temperature transport measurements reveal a clear shell structure for sequential charging of the larger of the two dots with up to 12 electrons. The resonant current through the double dot is found to depend on the orbital coupling between states of different radial symmetry. The charging energies are well described by a capacitance model if next-neighbor capacitances are taken into account.
Spin-valley resolved photon-assisted tunneling in carbon nanotube double quantum dots
Osika, E. N.; Szafran, B.
2017-05-01
We consider photon-assisted tunneling (PAT) and the Landau-Zener-Stueckelberg (LZS) interference for double quantum dots induced electrostatically along a semiconducting carbon nanotube. An atomistic tight-binding approach and the time-dependent configuration-interaction method are employed to describe systems of a few confined electrons and holes. We reproduce the patterns of the LZS interference recently observed for quantum double dots describing transport across hole-localized states. Moreover, we indicate that for charge configurations for which the ground state is Pauli-blocked, PAT can be used for resolution of the transitions that involve spin-flip or intervalley transitions without the spin-valley conserving background signal.
Charge Sensed Pauli Blockade in a Metal–Oxide–Semiconductor Lateral Double Quantum Dot
Energy Technology Data Exchange (ETDEWEB)
Nguyen, Khoi T.; Lilly, Michael P.; Nielsen, Erik; Bishop, Nathan; Rahman, Rajib; Young, Ralph; Wendt, Joel; Dominguez, Jason; Pluym, Tammy; Stevens, Jeffery; Lu, Tzu-Ming; Muller, Richard; Carroll, Malcolm S.
2013-12-11
We report Pauli blockade in a multielectron silicon metal–oxide–semiconductor double quantum dot with an integrated charge sensor. The current is rectified up to a blockade energy of 0.18 ± 0.03 meV. The blockade energy is analogous to singlet–triplet splitting in a two electron double quantum dot. Built-in imbalances of tunnel rates in the MOS DQD obfuscate some edges of the bias triangles. A method to extract the bias triangles is described, and a numeric rate-equation simulation is used to understand the effect of tunneling imbalances and finite temperature on charge stability (honeycomb) diagram, in particular the identification of missing and shifting edges. A bound on relaxation time of the triplet-like state is also obtained from this measurement.
A Ge/Si heterostructure nanowire-based double quantum dot with integrated charge sensor
Hu, Yongjie; Churchill, Hugh; Reilly, David; Xiang, Jie; Lieber, Charles; M. Marcus, Charles
2007-01-01
Coupled electron spins in semiconductor double quantum dots hold promise as the basis for solid-state qubits. To date, most experiments have used III-V materials, in which coherence is limited by hyperfine interactions. Ge/Si heterostructure nanowires seem ideally suited to overcome this limitation: the predominance of spin-zero nuclei suppresses the hyperfine interaction and chemical synthesis creates a clean and defect-free system with highly controllable properties. Here we present a top g...
Interaction-induced merging of Landau levels in an electron system of double quantum wells
Shashkin, A.A.; Dolgopolov, V.T.; Clark, J. W.; Shaginyan, V. R.; Zverev, M. V.; Khodel, V. A.
2015-01-01
We show that the disappearance of the chemical potential jumps over the range of perpendicular magnetic fields at fixed integer filling factor in a double quantum well with a tunnel barrier is caused by the interaction-induced level merging. The distribution function in the merging regime is special in that the probability to find an electron with energy equal to the chemical potential is different for the two merged levels.
Electron spin resonance and spin-valley physics in a silicon double quantum dot.
Hao, Xiaojie; Ruskov, Rusko; Xiao, Ming; Tahan, Charles; Jiang, HongWen
2014-05-14
Silicon quantum dots are a leading approach for solid-state quantum bits. However, developing this technology is complicated by the multi-valley nature of silicon. Here we observe transport of individual electrons in a silicon CMOS-based double quantum dot under electron spin resonance. An anticrossing of the driven dot energy levels is observed when the Zeeman and valley splittings coincide. A detected anticrossing splitting of 60 MHz is interpreted as a direct measure of spin and valley mixing, facilitated by spin-orbit interaction in the presence of non-ideal interfaces. A lower bound of spin dephasing time of 63 ns is extracted. We also describe a possible experimental evidence of an unconventional spin-valley blockade, despite the assumption of non-ideal interfaces. This understanding of silicon spin-valley physics should enable better control and read-out techniques for the spin qubits in an all CMOS silicon approach.
Input-output theory for spin-photon coupling in Si double quantum dots
Benito, M.; Mi, X.; Taylor, J. M.; Petta, J. R.; Burkard, Guido
2017-12-01
The interaction of qubits via microwave frequency photons enables long-distance qubit-qubit coupling and facilitates the realization of a large-scale quantum processor. However, qubits based on electron spins in semiconductor quantum dots have proven challenging to couple to microwave photons. In this theoretical work we show that a sizable coupling for a single electron spin is possible via spin-charge hybridization using a magnetic field gradient in a silicon double quantum dot. Based on parameters already shown in recent experiments, we predict optimal working points to achieve a coherent spin-photon coupling, an essential ingredient for the generation of long-range entanglement. Furthermore, we employ input-output theory to identify observable signatures of spin-photon coupling in the cavity output field, which may provide guidance to the experimental search for strong coupling in such spin-photon systems and opens the way to cavity-based readout of the spin qubit.
Energy Technology Data Exchange (ETDEWEB)
An, Xing-Tao, E-mail: anxt2005@163.com [School of Sciences, Hebei University of Science and Technology, Shijiazhuang, Hebei 050018 (China); Mu, Hui-Ying [Department of Chemistry and Environmental Engineering, Hebei Chemical and Pharmaceutical Vocational Technology College, Shijiazhuang, Hebei 050026 (China); Li, Yu-Xian [College of Physical Science and Information Engineering, Hebei Normal University, and Hebei Advanced Thin Films Laboratory, Shijiazhuang, Hebei 050016 (China); Liu, Jian-Jun [College of Physical Science and Information Engineering, Hebei Normal University, and Hebei Advanced Thin Films Laboratory, Shijiazhuang, Hebei 050016 (China); Physics Department, Shijiazhuang University, Shijiazhuang 050035 (China)
2011-10-31
A four-terminal parallel double quantum dots (QDs) device is proposed to generate and detect the spin polarization in QDs. It is found that the spin accumulation in QDs and the spin-polarized currents in the upper and down leads can be generated when a bias voltage is applied between the left and right leads. It is more interesting that the spin polarization in the QDs can be detected using the upper and down leads. Moreover, the direction and magnitude of the spin polarization in the QDs, and in the upper and down leads can be tuned by the energy levels of QDs and the bias. -- Highlights: → The spin polarization in the quantum dots can be generated and controlled. → The spin polarization in quantum dots can be detected by the nonferromagnetic leads. → The system our studied is a discrete level spin Hall system.
Design and measurement of a silicon double quantum dot qubit with dispersive microwave readout
Henry, Edward; Schmidt, Andrew; House, Mathew; Wang, Yao-Tseng; Lo, Cheuk; Pan, Hong; Xiao, Xin; Li, Hanhan; Greenman, Loren; Whaley, Birgitta; Jiang, Hongwen; Yablonovitch, Eli; Bokor, Jeffrey; Siddiqi, I.
2012-02-01
The electronic states of a semiconductor quantum dot are a promising candidate for quantum information processing. We describe a circuit QED qubit architecture in which a semiconductor qubit in silicon is capacitively coupled to a 6 GHz superconducting resonator. Silicon is an attractive material on account of the long electron spin lifetime. We discuss the design and operation of both the laterally defined double quantum dot qubit as well as the balanced coplanar stripline resonator. We focus in particular on the chip design and the specifics of the measurement setup, including both low and high frequency filtering. We also discuss the possibility of operating this device as a spin qubit by way of applying an inhomogeneous magnetic field.
String-nets, single- and double-stranded quantum loop gases for non-Abelian anyons
Energy Technology Data Exchange (ETDEWEB)
Velenich, Andrea; Chamon, Claudio [Physics Department, Boston University, 590 Commonwealth Avenue, Boston, MA 02215 (United States); Wen Xiaogang, E-mail: velenich@bu.ed [Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02215 (United States)
2010-04-30
String-nets and quantum loop gases are two prominent microscopic lattice models to describe topological phases. String-net condensation can give rise to both Abelian and non-Abelian anyons, whereas loop condensation usually produces Abelian anyons. It has been proposed, however, that generalized quantum loop gases with non-orthogonal inner products could support non-Abelian anyons. We detail an exact mapping between the string-net and these generalized loop models and explain how the non-orthogonal products arise. We also introduce an equivalent loop model of double-stranded nets where quantum loops with an orthogonal inner product and local interactions supports non-Abelian Fibonacci anyons. Finally, we emphasize the origin of the sign problem in systems with non-Abelian excitations and its consequences on the complexity of their ground state wavefunctions. (fast track communication)
DEFF Research Database (Denmark)
Larsen, Christian Albrekt; Vesan, Patrik
2012-01-01
It has been a general finding across Europe that very few job matches are facilitated by public employment services (PES).The article explains this failure by highlighting the existence of a double-sided asymmetric information problem on the labour market. It is argued that although a PES...... potentially reduces search costs, both employers and employees have strong incentives not to use PES. The reason is that employers try to avoid the ‘worst’ employees, and employees try to avoid the ‘worst’ employers. Therefore these services get caught in a low-end equilibrium that is almost impossible...
Tsukanov, A. V.; Kateev, I. Yu
2017-08-01
The concept of a quantum node consisting of a memory qubit and a frequency convertor is proposed and analysed. The memory qubit is presented by a semiconductor four-level double quantum dot (DQD) placed in an optical microresonator (MR). The DQD contains an electron in the quantised part of the conduction band and the MR can be populated by a certain number of photons. The DQD and MR states are controlled be applying the laser and electrostatic fields. The difference between the telecommunication frequency of the photon (transport qubit) supplied to the system through a waveguide and the frequency of the electronic transition in the DQD is compensated for using an auxiliary element, i.e. a frequency convertor based on a single quantum dot (QD). This design allows the electron - photon state of the hybrid system to be controlled by an appropriate variation of the field parameters and the switching between resonance and nonresonance DQD and MR interaction regimes. As an example, a GaAs DQD placed in a microdisk MR is studied. A numerical technique for modelling an optical spectrum of a microdisk MR with an additional layer (AL) deposited on its surface is developed. Using this technique, the effect of the AL on the MR eigenmode properties is investigated and the possibility of tuning its frequency to the QD electronic transition frequency by depositing an AL on the disk surface is demonstrated.
Entanglement of mixed quantum states for qubits and qudit in double photoionization of atoms
Energy Technology Data Exchange (ETDEWEB)
Chakraborty, M., E-mail: bminakshi@yahoo.com [Department of Physics, Asansol Girls’ College, Asansol 713304 (India); Sen, S. [Department of Physics, Triveni Devi Bhalotia College, Raniganj 713347 (India)
2015-08-15
Highlights: • We study tripartite entanglement between two electronic qubits and an ionic qudit. • We study bipartite entanglement between any two subsystems of a tripartite system. • We have presented a quantitative application of entangled properties in Neon atom. - Abstract: Quantum entanglement and its paradoxical properties are genuine physical resources for various quantum information tasks like quantum teleportation, quantum cryptography, and quantum computer technology. The physical characteristic of the entanglement of quantum-mechanical states, both for pure and mixed, has been recognized as a central resource in various aspects of quantum information processing. In this article, we study the bipartite entanglement of one electronic qubit along with the ionic qudit and also entanglement between two electronic qubits. The tripartite entanglement properties also have been investigated between two electronic qubits and an ionic qudit. All these studies have been done for the single-step double photoionization from an atom following the absorption of a single photon without observing spin orbit interaction. The dimension of the Hilbert space of the qudit depends upon the electronic state of the residual photoion A{sup 2+}. In absence of SOI, when Russell–Saunders coupling (L–S coupling) is applicable, dimension of the qudit is equal to the spin multiplicity of A{sup 2+}. For estimations of entanglement and mixedness, we consider the Peres–Horodecki condition, concurrence, entanglement of formation, negativity, linear and von Neumann entropies. In case of L–S coupling, all the properties of a qubit–qudit system can be predicted merely with the knowledge of the spins of the target atom and the residual photoion.
Jiang, Liyang; Sui, Yanwei; Qi, Jiqiu; Chang, Yuan; He, Yezeng; Meng, Qingkun; Wei, Fuxiang; Sun, Zhi; Jin, Yunxue
2017-12-01
In this paper, ultrathin reduced graphene oxide films on nickel foam were fabricated via a facile dip-coating method combined with thermal reduction. Hierarchical Ni-Co layered double hydroxide nanosheets with network structure were electrodeposited on the ultrathin reduced graphene oxide films in a simple three-electrode system. The thickness of Ni-Co layered double hydroxide nanosheets can be controlled through adjusting the deposition temperature. The as-prepared electrode exhibited excellent electrochemical performance with specific capacitance of 1454.2 F g-1 at a current density of 1 A g-1. An asymmetric supercapacitor device was designed with the as-prepared composites as positive electrode material and Nitrogen-doped reduced graphene oxide as negative electrode material. This device could be operated in a working voltage range of 0-1.8 V in 1 M KOH aqueous electrolyte, delivering a high energy density of 56.4 W h kg-1 at a power density of 882.5 W kg-1. One supercapacitor can power two LEDs with rated voltage of 1.8-2.0 V. After 10,000 consecutive charge-discharge tests at 10 A g-1, this asymmetric supercapacitor revealed an excellent cycle life with 98.3% specific capacitance retention. These excellent electrochemical performances make it become one of most promising candidates for high energy supercapacitor device.
Imaging Few-Electron Double Quantum Dots in InAs/InP Nanowires
Trodahl, Halvar J.; Boyd, Erin E.; Bleszynski, Ania; Westervelt, R. M.; Froberg, Linus E.; Samuelson, Lars
2007-03-01
InAs quantum dots formed in InAs/InP nanowire heterostructures are attractive candidates for nanoelectronics, spintronics and quantum information processing. Tunnel-coupled double InAs dots defined by InP barriers can be grown using chemical beam epitaxy; each dot can be small enough to hold just a few electrons. It is difficult to lithographically define gates small enough to individually address each dot. With use of a liquid-He cooled scanning probe microscope (SPM), the Coulomb blockade conductance of a single InAs quantum dot in an InAs/InP nanowire has been imaged, using the SPM tip as a movable gate [1]. This approach can individually tune the charge on each InAs dot in an InAs/InP nanowire. We plan to use this technique to investigate tunnel-coupled InAs double dots. [1] A. Bleszynski et al., 28th Int. Conf. on the Physics of Semiconductors, 2006.
Kurian, P; Dunston, G; Lindesay, J
2016-02-21
Macroscopic quantum effects in living systems have been studied widely in pursuit of fundamental explanations for biological energy transport and sensing. While it is known that type II endonucleases, the largest class of restriction enzymes, induce DNA double-strand breaks by attacking phosphodiester bonds, the mechanism by which simultaneous cutting is coordinated between the catalytic centers remains unclear. We propose a quantum mechanical model for collective electronic behavior in the DNA helix, where dipole-dipole oscillations are quantized through boundary conditions imposed by the enzyme. Zero-point modes of coherent oscillations would provide the energy required for double-strand breakage. Such quanta may be preserved in the presence of thermal noise by the enzyme's displacement of water surrounding the DNA recognition sequence. The enzyme thus serves as a decoherence shield. Palindromic mirror symmetry of the enzyme-DNA complex should conserve parity, because symmetric bond-breaking ceases when the symmetry of the complex is violated or when physiological parameters are perturbed from optima. Persistent correlations in DNA across longer spatial separations-a possible signature of quantum entanglement-may be explained by such a mechanism. Copyright © 2015 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Zheng, Mei C., E-mail: meizheng@princeton.edu; Gmachl, Claire F. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Liu, Peter Q. [Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544 (United States); Institute of Quantum Electronics, ETH Zürich, 8093 Zürich (Switzerland); Wang, Xiaojun; Fan, Jen-Yu; Troccoli, Mariano [AdTech Optics, Inc., City of Industry, California 91748 (United States)
2013-11-18
We report on the experimental demonstration of a widely tunable single mode quantum cascade laser with Asymmetric Mach-Zehnder (AMZ) interferometer type cavities with separately biased arms. Current and, consequently, temperature tuning of the two arms of the AMZ type cavity resulted in a single mode tuning range of 20 cm{sup −1} at 80 K in continuous-wave mode operation, a ten-fold improvement from the lasers under a single bias current. In addition, we also observed a five fold increase in the tuning rate as compared to the AMZ cavities controlled by one bias current.
Cai, Cong; Zhu, Rui
2017-11-01
In this work, transport properties of the nonadiabatically pumped double-quantum-well (DQW) structure are studied. Different from a single quantum well, band mixing in the DQW generates bonding and antibonding states, whose wave functions have different spatial symmetry. By applying a time-dependent electric potential to the two well regions simultaneously, Floquet sidebands are formed, which constitutes additional quantum tunneling paths. When one of the Floquet sidebands coincides with the bonding or antibonding quasibound states within the DQW structure, sharp Fano resonances are found in the transmission coefficients as well as in the differential shot noise spectra. While such Fano resonances originate from quantum interference, their shapes are strikingly different for transport via the bonding state and via the antibonding state. The Fano resonance via the even-parity bonding state shows a perfect transmission followed by a total reflection and the Fano resonance via the odd-parity antibonding state has a reversed symmetry and shows a total reflection before a perfect transmission.
Anomalous thermoelectric properties in double quantum dots coupled with Majorana bound states
Directory of Open Access Journals (Sweden)
Yi-Jie Zheng
2016-12-01
Full Text Available We discuss the transport properties of thermal electrons in double quantum dots that are coupled with Majorana bound states (MBSs corresponding to two model systems with T-type structure and series connection structure. It has been found that the thermoelectric figure of merit ZT in these model systems is suppressed when we consider the effects of the Majorana bound states. Here, ZT=GS2Tκ, where G is the electric conductance, S is the thermopower, T is the temperature and κ is the thermal conductance. The sign of the thermopower S changes from negative to positive when the energy levels of the quantum dots are less than μ while the sign of the thermopower S changes from positive to negative when the energy levels of the quantum dots are above μ in the model system of T-type structure, where μ is the chemical potential. As a result, the figure of merit ZT first decreases and then increases as the temperature kBT increases. This behavior is different from what is seen in the general quantum dot structure without MBSs. It is interesting to show that in the series connection structure, the thermopower S and ZT are robustness and do not vary with changes in εM when |εd|<λ, even if κ changes with εM.
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.
Controllable double tunneling induced transparency and solitons formation in a quantum dot molecule.
She, Yanchao; Zheng, Xuejun; Wang, Denglong; Zhang, Weixi
2013-07-15
We consider the coupling effect between interdot tunneling coupling and external optical control field to study the linear optical property and the formation of temporal optical solitons in a quantum dot molecules system, analytically. The results show that the double tunneling induced transparency (TIT) windows are appeared in the absorption curve of probe field because of the formation of dynamic Stark splitting and quantum destructive interference effect from the two upper levels. Interestingly, the width of the TIT window becomes wider with the increasing intensity of the optical control field. We also find that the Kerr nonlinear effect of the probe field can be modulated effectively through coherent control both the control field and the interdot tunneling coupling in this system. Meanwhile, we demonstrate that the formation of dark or bright solitons can be practical regulated by varying the intensity of the optical control field.
Electronic structures of GaAs/AlxGa1-xAs quantum double rings
Directory of Open Access Journals (Sweden)
Li Shu-Shen
2006-01-01
Full Text Available AbstractIn the framework of effective mass envelope function theory, the electronic structures of GaAs/AlxGa1-xAs quantum double rings (QDRs are studied. Our model can be used to calculate the electronic structures of quantum wells, wires, dots, and the single ring. In calculations, the effects due to the different effective masses of electrons and holes in GaAs and AlxGa1-xAs and the valence band mixing are considered. The energy levels of electrons and holes are calculated for different shapes of QDRs. The calculated results are useful in designing and fabricating the interrelated photoelectric devices. The single electron states presented here are useful for the study of the electron correlations and the effects of magnetic fields in QDRs.
Electron confinement and correlation in double quantum well single charge electrometers
Gyure, Mark F.; Caflisch, Russel E.; Anderson, Chris; Robinson, Hans D.; Croke, Edward T.; Yablonovitch, Eli
2002-03-01
Single electron transistors and other related device concepts have been proposed for use in a variety of quantum information processing applications. Central to the application of these devices is not only single electron confinement and sensitivity, but the ability to discriminate between the singlet and triplet states for indirect measurement of electron spin. In this talk, we will describe theoretical and numerical results for a new device based on InGaAs/InP double quantum well structures (see related talk by H.D. Robinson et al) that demonstrate that single electron confinement is achievable in this structure. In addition, we will discuss properties related to spin readout such as the the singlet-triplet energy splitting of two-electron states as well as the role of electron correlation effects in this device.
Photoluminescence study of InGaN/GaN double quantum wells with varying barrier widths
Ryu, M Y; Shin, E J; Lee, J I; Yu, S K; Oh, E S; Park, Y J; Park, H S; Kim, T I
2000-01-01
We report the results of photoluminescence (PL) and time-resolved PL studies on InGaN/GaN double quantum well (DQW) samples with different barrier widths. The barrier-width dependence of the PL emission energy and intensity are discussed. The PL as a function of excitation density can be well explained in terms of the quantum-confined Stark effect (QCSE). The temporal behavior of the PL was also studied. As the barrier width increases, the decay times tau sub 1 and tau sub 2 , decrease from 1.02 ns and 6.99 ns to 0.32 ns and 1.09 ns, respectively. The PL efficiency and the decay lifetime depend on the barrier width.
Dynamical entanglement formation and dissipation effects in two double quantum dots
Energy Technology Data Exchange (ETDEWEB)
Contreras-Pulido, L D [Centro de Investigacion CientIfica y de Educacion Superior de Ensenada, Apartado Postal 2732, Ensenada, BC 22860 (Mexico); Rojas, F [Departamento de Fisica Teorica, Centro de Ciencias de la Materia Condensada, Universidad Nacional Autonoma de Mexico, Ensenada, Baja California 22800 (Mexico)
2006-11-01
We study the static and dynamic formation of entanglement in charge states of a two double quantum dot array with two mobile electrons under the effect of an external driving field. We include dissipation via contact with a phonon bath. By using the density matrix formalism and an open quantum system approach, we describe the dynamical behaviour of the charge distribution (polarization), concurrence (measure of the degree of entanglement) and Bell state probabilities (two qubit states with maximum entanglement) of such a system, including the role of dot asymmetry and temperature effects. Our results show that it is possible to obtain entangled states as well as a most probable Bell state, which can be controlled by the driving field. We also evaluate how the entanglement formation based on charge states deteriorates as the temperature or asymmetry increases.
The quantum optical description of a double Mach-Zehnder interferometer
Ataman, Stefan
2014-01-01
In this paper we describe within the formalism of Quantum Optics (QO) a double Mach-Zehnder interferometer (MZI). For single photon Fock states this experimental setup is shown to exhibit a counter-intuitive behavior: for certain values of the path length difference of the first MZI, the singles photon-count statistics at the output detectors does not change, whatever the difference in path length for the second MZI. For simultaneously impinging light quanta, we show that this setup is able t...
Two-electron double quantum dot coupled to coherent photon and phonon fields
Sato, Yuya; Chen, Jason C. H.; Hashisaka, Masayuki; Muraki, Koji; Fujisawa, Toshimasa
2017-09-01
Two-electron states of a double quantum dot (DQD) under irradiation of coherent boson (photon and phonon) fields are studied by measuring spin-flip tunneling current in the Pauli spin blockade regime. This measurement scheme allows us to investigate Rabi splitting and associated boson dressed states particularly in the deep dispersive regime where the detuning δ ≡ℏ ω -EAB between the boson energy ℏ ω and energy spacing EAB of the two-level system is significantly large (δ ˜ℏ ω ), where the permanent dipole moment in the DQD plays a significant role in the hybridization.
Collective Behavior of Interwell Excitons in GaAs/AlGaAs Double Quantum Wells
DEFF Research Database (Denmark)
Larionov, A. V.; Timofeev, V. B.; Hvam, Jørn Märcher
2000-01-01
Photoluminescence spectra of interwell excitons in double GaAs/AlGaAs quantum wells (n-i-n structures) have been investigated (an interwell excition in these systems is an electron-hole pair spatially separated by a narrow AlAs barrier). Under resonance excitation by circular polarized light......, the luminescence line of interwell excitions exhibits a significant narrowing and a drastic increase in the degree of circular polarization of photoluminescence with increasing exciton concentration. It is found that the radiative recombination rate significantly increases under these conditions. This phenomenon...
Revealing the internal spin dynamics in a double quantum dot by periodic voltage modulation
Ptaszyński, Krzysztof
2017-11-01
This paper proposes the method to analyze the internal dynamics of nanoscopic systems by periodic modulation of the electrochemical potentials of the attached leads and measuring the time-averaged current. The idea is presented using the example of a double quantum dot coupled to one nonmagnetic and one spin-polarized lead. The current flowing through the molecule is shown to depend on both the frequency of the modulation and the exchange coupling between the electrons occupying the molecule. In particular, one can observe a pronounced oscillatory behavior of the current-frequency dependence, which reveals the coherent oscillations between the spin states of the system.
Quantum Faraday Effect in Double-Dot Aharonov-Bohm Ring
Kang, Kicheon
2011-01-01
We investigate Faraday's law of induction manifested in the quantum state of Aharonov-Bohm loops. In particular, we propose a flux-switching experiment for a double-dot AB ring to verify the phase shift induced by Faraday's law. We show that the induced {\\em Faraday phase} is geometric and nontopological. Our study demonstrates that the relation between the local phases of a ring at different fluxes is not arbitrary but is instead determined by Faraday's inductive law, which is in strong cont...
Relaxation and Dephasing in a Two-Electron 13C Nanotube Double Quantum Dot
DEFF Research Database (Denmark)
Churchill, H O H; Kuemmeth, Ferdinand; Harlow, J W
2009-01-01
We use charge sensing of Pauli blockade (including spin and isospin) in a two-electron 13C nanotube double quantum dot to measure relaxation and dephasing times. The relaxation time T1 first decreases with a parallel magnetic field and then goes through a minimum in a field of 1.4 T. We attribute...... both results to the spin-orbit-modified electronic spectrum of carbon nanotubes, which at high field enhances relaxation due to bending-mode phonons. The inhomogeneous dephasing time T2* is consistent with previous data on hyperfine coupling strength in 13C nanotubes....
Energy Technology Data Exchange (ETDEWEB)
Miranda, Guillermo L. [Fisica Teorica y Aplicada, Escuela de Ingenieria de Antioquia, A.A. 7516, Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque_echeverri@yahoo.es [Instituto de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia)
2012-10-15
The dependencies of the binding energies of the lowest four 1s-like exciton states in GaAs-(Ga,Al)As coupled double quantum wells (CDQW) on the geometric parameters of the system are theoretically studied. A variational approach, together with the parabolic band and effective mass approximations, were considered in order to perform the numerical calculations. It is shown that in the case of a symmetric system there is a degeneracy between the heavy-hole even and odd states and this degeneracy can be removed by the presence of a sufficiently narrow middle barrier. In contrast to this fact, the electron even and odd states are never degenerated. It is detected that, if the system is asymmetric, there will appear binding energies anticrossings between the heavy-hole states at the point of the asymmetric {yields} symmetric QW transition. - Highlights: Black-Right-Pointing-Pointer Study of 1s-like exciton states in double quantum wells. Black-Right-Pointing-Pointer Binding energy decreases with the presence of second well. Black-Right-Pointing-Pointer Binding energy of (2,2) state can be larger than (1,1) state. Black-Right-Pointing-Pointer Central barrier can remove degeneracy of states. Black-Right-Pointing-Pointer Anticrossing between states can be induced via symmetries.
Mizugaki, Yoshinao; Urai, Yoshiaki; Shimada, Hiroshi
2017-07-01
A double-flux-quantum amplifier (DFQA) is a voltage multiplier of quantum accuracy, which we have employed at the final stage of a single-flux-quantum (SFQ) digital-to-analog converter (DAC). We recently found that experimental input-output (IO) characteristics of DFQAs were always slightly different from numerical results assuming ideally-periodic SFQ pulse trains. That is, experimental IO characteristics obtained using an over-biasing method were gradually deteriorated near their maximum operation voltages. Numerical simulation including the over-biasing method at a finite temperature suggested that the difference was likely to be attributed to thermally-fluctuated intervals of input SFQ pulses.
Strong spin Seebeck effect in Kondo T-shaped double quantum dots.
Wójcik, K P; Weymann, I
2017-02-08
We investigate, taking a theoretical approach, the thermoelectric and spin thermoelectric properties of a T-shaped double quantum dot strongly coupled to two ferromagnetic leads, focusing on the transport regime in which the system exhibits the two-stage Kondo effect. We study the dependence of the (spin) Seebeck coefficient, the corresponding power factor and the figure of merit on temperature, leads' spin polarization and dot level position. We show that the thermal conductance fulfills a modified Wiedemann-Franz law, also in the regime of suppression of subsequent stages of the Kondo effect by the exchange field resulting from the presence of ferromagnets. Moreover, we demonstrate that the spin thermopower is enhanced at temperatures corresponding to the second stage of Kondo screening. Very interestingly, the spin-thermoelectric response of the system is found to be highly sensitive to the spin polarization of the leads. In some cases spin polarization of the order of 1% is sufficient for a strong spin Seebeck effect to occur. This is explained as a consequence of the interplay between the two-stage Kondo effect and the exchange field induced in the double quantum dot. Due to the possibility of tuning the exchange field by the choice of gate voltage, the spin thermopower may also be tuned to be maximal for desired spin polarization of the leads. All calculations are performed with the aid of the numerical renormalization group technique.
Shaker, Ahmed; Ossaimee, Mahmoud; Zekry, A.
2016-08-01
In this paper, a proposed structure based on asymmetrical double pockets SB-TFET with gate-drain underlap is presented. 2D extensive modeling and simulation, using Silvaco TCAD, were carried out to study the effect of both underlap length and pockets' doping on the transistor performance. It was found that the underlap from the drain side suppresses the ambipolar conduction and doesn't enhance the high-frequency characteristics. The enhancement of the high-frequency characteristics could be realized by increasing the doping of the drain pocket over the doping of the source pocket. An optimum choice was found which gives the conditions of minimum ambipolar conduction, maximum ON current and maximum cut-off frequency. These enhancements render the device more competitive as a nanometer transistor.
Pei, Peng-Xiang; Hu, Jing-Han; Chen, Ying; Sun, You; Qi, Jing
2017-06-01
In this paper, we have designed and synthesized a novel sensor L1 based on asymmetric double-azine derivatives, which showed both ;naked eye; recognition and fluorescence responses for CN- in DMSO/H2O (v/v = 4:1, pH = 7.20) solution. This simple sensor L1 could distinguish CN- from coexisting anions via the way of deprotonation and sensing mechanism of intramolecular charge transfer (ICT), and the minimum detection limit on fluorescence response of the sensor L1 towards CN- was down to 9.47 × 10- 7 M. Moreover, we have successfully utilized the sensor L1 to detect CN- in bitter almond. Test strips containing L1 were also prepared, which could act as a practical colorimetric tool to detect CN- in aqueous media.
2011-07-01
InGaAs and GaAs double wells with AlGaAs barriers, leading to a less strained InAs/ InGaAs /GaAs/ AlGaAs heterostructure...have been further advanced by embedding InAs QDs in InGaAs and GaAs double wells with AlGaAs barriers, leading to a less strained InAs/ InGaAs /GaAs... AlGaAs heterostructure. These lower strain quantum dots-in-a-double- well devices exhibit lower dark current than the previous generation DWELL
Energy Technology Data Exchange (ETDEWEB)
Baba, Shoji, E-mail: baba@meso.t.u-tokyo.ac.jp; Sailer, Juergen [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Deacon, Russell S. [Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); RIKEN Advanced Science Laboratory, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Oiwa, Akira [The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Shibata, Kenji [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); Department of Electronics and Intelligent Systems, Tohoku Institute of Technology, Sendai 982-8577 (Japan); Hirakawa, Kazuhiko [Institute of Industrial Science, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); JST CREST, 4-1-8 Hon-cho, Kawaguchi-shi, Saitama 332-0012 (Japan); Tarucha, Seigo [Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198 (Japan); INQIE, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505 (Japan); QPEC, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku 113-8656 (Japan)
2015-11-30
We report conductance and supercurrent measurements for InAs single and parallel double quantum dot Josephson junctions contacted with Nb or NbTiN superconducting electrodes. Large superconducting gap energy, high critical field, and large switching current are observed, all reflecting the features of Nb-based electrodes. For the parallel double dots, we observe an enhanced supercurrent when both dots are on resonance, which may reflect split Cooper pair tunneling.
Energy Technology Data Exchange (ETDEWEB)
Tagliaferri, M.L.V., E-mail: marco.tagliaferri@mdm.imm.cnr.it [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 53, 20125 Milano (Italy); Crippa, A. [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 53, 20125 Milano (Italy); De Michielis, M. [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Mazzeo, G.; Fanciulli, M. [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Via Cozzi 53, 20125 Milano (Italy); Prati, E. [Laboratorio MDM, CNR-IMM, Via C. Olivetti 2, 20864 Agrate Brianza (MB) (Italy); Istituto di Fotonica e Nanotecnologie, CNR, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)
2016-03-11
We report on the fabrication and the characterization of a tunable complementary-metal oxide semiconductor (CMOS) system consisting of two quantum dots and a MOS single electron transistor (MOSSET) charge sensor. By exploiting a compact T-shaped design and few gates fabricated by electron beam lithography, the MOSSET senses the charge state of either a single or double quantum dot at 4.2 K. The CMOS compatible fabrication process, the simplified control over the number of quantum dots and the scalable geometry make such architecture exploitable for large scale fabrication of multiple spin-based qubits in circuital quantum information processing. - Highlights: • Charge sensing of tunable, by position and number, quantum dots is demonstrated. • A compact T-shaped design with five gates at a single metalization level is proposed. • The electrometer is a silicon-etched nanowire acting as a disorder tolerant MOSSET.
Bahramiyan, H.
2018-01-01
In this work, we have investigated the effect of electric field and impurity position on nonlinear optical rectification of a double cone like quantum dot in the effective mass approximation and by using compact density-matrix formalism. We have calculated the energy levels and wave functions using finite element method (FEM) in the presence of impurity and influence of electric field. The results show that: (i) the binding energy changes with the impurity position and it is changed by the applied electric field, (ii) nonlinear optical rectification peak position of this system present the blue or red shift due to the applied electric field and changing the impurity position. (iii) for low electric field, impurity position plays an important role in electronic and optical properties, but for larger electric field, impurity position role becomes non-significant. (iv) the optical rectification changes due to the impurity position and the electric field are considerable.
6j symbols for the modular double, quantum hyperbolic geometry, and supersymmetric gauge theories
Energy Technology Data Exchange (ETDEWEB)
Teschner, J.; Vartanov, G.S.
2012-02-15
We revisit the definition of the 6j-symbols from the modular double of U{sub q}(sl(2,R)), referred to as b-6j symbols. Our new results are (i) the identification of particularly natural normalization conditions, and (ii) new integral representations for this object. This is used to briefly discuss possible applications to quantum hyperbolic geometry, and to the study of certain supersymmetric gauge theories. We show, in particular, that the b-6j symbol has leading semiclassical asymptotics given by the volume of a non-ideal tetrahedron. We furthermore observe a close relation with the problem to quantize natural Darboux coordinates for moduli spaces of flat connections on Riemann surfaces related to the Fenchel-Nielsen coordinates. Our new integral representations finally indicate a possible interpretation of the b-6j symbols as partition functions of three-dimensional N=2 supersymmetric gauge theories. (orig.)
Magnetospectroscopy of double HgTe/CdHgTe quantum wells
Energy Technology Data Exchange (ETDEWEB)
Bovkun, L. S.; Krishtopenko, S. S.; Ikonnikov, A. V., E-mail: antikon@ipmras.ru; Aleshkin, V. Ya.; Kadykov, A. M. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Ruffenach, S.; Consejo, C.; Teppe, F.; Knap, W. [Laboratoire Charles Coulomb (L2C), UMR CNRS 5221 and UM (France); Orlita, M.; Piot, B.; Potemski, M. [Laboratoire National des Champs Magnetiques Intenses (LNCMI-G), CNRS-UJF-UPS-INSA (France); Mikhailov, N. N.; Dvoretskii, S. A. [Russian Academy of Sciences, Siberian Branch, Rzhanov Institute of Semiconductor Physics (Russian Federation); Gavrilenko, V. I. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)
2016-11-15
The magnetoabsorption spectra in double HgTe/CdHgTe quantum wells (QWs) with normal and inverted band structures are investigated. The Landau levels in symmetric QWs with a rectangular potential profile are calculated based on the Kane 8 × 8 model. The presence of a tunnel-transparent barrier is shown to lead to the splitting of states and “doubling” of the main magnetoabsorption lines. At a QW width close to the critical one the presence of band inversion and the emergence of a gapless band structure, similar to bilayer graphene, are shown for a structure with a single QW. The shift of magnetoabsorption lines as the carrier concentration changes due to the persistent photoconductivity effect associated with a change in the potential profile because of trap charge exchange is detected. This opens up the possibility for controlling topological phase transitions in such structures.
Phase locking of a semiconductor double-quantum-dot single-atom maser
Liu, Y.-Y.; Hartke, T. R.; Stehlik, J.; Petta, J. R.
2017-11-01
We experimentally study the phase stabilization of a semiconductor double-quantum-dot (DQD) single-atom maser by injection locking. A voltage-biased DQD serves as an electrically tunable microwave frequency gain medium. The statistics of the maser output field demonstrate that the maser can be phase locked to an external cavity drive, with a resulting phase noise L =-99 dBc/Hz at a frequency offset of 1.3 MHz. The injection locking range, and the phase of the maser output relative to the injection locking input tone are in good agreement with Adler's theory. Furthermore, the electrically tunable DQD energy level structure allows us to rapidly switch the gain medium on and off, resulting in an emission spectrum that resembles a frequency comb. The free running frequency comb linewidth is ≈8 kHz and can be improved to less than 1 Hz by operating the comb in the injection locked regime.
Palasantzas, G; De Hosson, JTM
2003-01-01
We have investigated the influence of surface/interface roughness on the electrical conductivity in semiconducting thin films/quantum wells with double self-affine rough interface boundaries. The self-affine boundary roughness is characterized by the roughness exponent H, the in-plane correlation
Lasing of whispering-gallery modes in asymmetric waveguide GaInP micro-disks with InP quantum dots
Energy Technology Data Exchange (ETDEWEB)
Chu, Y. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)], E-mail: ychu@nd.edu; Mintairov, A.M.; He, Y.; Merz, J.L. [Department of Electrical Engineering, University of Notre Dame, Notre Dame, IN 46556 (United States); Kalyuzhnyy, N.A.; Lantratov, V.M.; Mintairov, S.A. [Ioffe Physical Technical Institute, St. Petersburg (Russian Federation)
2009-03-16
Using wafer bonding (WB) and wet oxidation (WO) techniques, GaInP microdisks having an asymmetric waveguide (diameters D=1-3 {mu}m) with embedded InP quantum dots (size/density {approx}100 nm/{approx}10{sup 9} cm{sup -2}) have been fabricated on Si and GaAs substrates, respectively. The TE{sub m,l} (m=28-12, l=1,2) and TM{sub m,l} (m=25-10, l=1-4) whispering gallery modes with quality factors Q{approx}2-5x10{sup 3} have been identified in photoluminescence spectra of these microdisks (MDs) in the spectral range 720-770 nm. Lasing thresholds of 6 (30) {mu}W and mode coupling constants 0.9 (0.7) have been demonstrated for WO (WB) MDs.
Large asymmetric Stark shift in GaxIn1-xAs/InP/InAsyP1-y composite quantum wells
Aneeshkumar, B.; Silov, A. Yu.; Leys, M. R.; Wolter, J. H.
2003-10-01
Strong asymmetric Stark shift in excess of 115 meV of the lowest energy transition has been experimentally observed in composite GaxIn1-xAs/InP/InAsyP1-y quantum-well system. In this structure, we can independently control the confinement of electrons and holes by controlling the strain. The photoexcited electrons and holes are confined in spatially separated regions without the application of an electric field. Due to the large asymmetry in the structure, we observed large blueshifts and redshifts of the absorption edge with an applied electric field. All our measurements agree with the calculations within the framework of the Bir-Pikus strain Hamiltonian.
Quantum transport in GaN/AlN double-barrier heterostructure nanowires.
Songmuang, R; Katsaros, G; Monroy, E; Spathis, P; Bougerol, C; Mongillo, M; De Franceschi, S
2010-09-08
We investigate electronic transport in n-i-n GaN nanowires with and without AlN double barriers. The nanowires are grown by catalyst-free, plasma-assisted molecular beam epitaxy enabling abrupt GaN/AlN interfaces as well as longitudinal n-type doping modulation. At low temperature, transport in n-i-n GaN nanowires is dominated by the Coulomb blockade effect. Carriers are confined in the undoped middle region, forming single or multiple islands with a characteristic length of approximately 100 nm. The incorporation of two AlN tunnel barriers causes confinement to occur within the GaN dot in between. In the case of a 6 nm thick dot and 2 nm thick barriers, we observe characteristic signatures of Coulomb-blockaded transport in single quantum dots with discrete energy states. For thinner dots and barriers, Coulomb-blockade effects do not play a significant role while the onset of resonant tunneling via the confined quantum levels is accompanied by a negative differential resistance surviving up to approximately 150 K.
Transport and current noise characteristics of a T-shape double-quantum-dot system
Energy Technology Data Exchange (ETDEWEB)
Brown, K; Tifrea, I [Department of Physics and Astronomy, California State University, Fullerton, CA 92834 (United States); Crisan, M [Department of Theoretical Physics, ' Babes-Bolyai' University, 40084 Cluj-Napoca (Romania)
2009-05-27
We consider the transport and the noise characteristics for the case of a T-shape double-quantum-dot system using the equation of motion method. Our theoretical results, obtained in an approximation equivalent to the Hartree-Fock approximation, account for non-zero on-site Coulomb interaction in both the detector and side dots. The existence of a non-zero Coulomb interaction implies an additional two resonances in the detector's dot density of states and thereafter affects the electronic transport properties of the system. The system's conductance presents two Fano dips as a function of the energy of the localized electronic level in the side dot. The Fano dips in the system's conductance can be observed for both strong (fast detector) and weak coupling (slow detector) between the detector dot and the external electrodes. Due to stronger electronic correlations, the noise characteristics 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 dot systems.
Rameez-ul-Islam; Ikram, Manzoor; Hasan Mujtaba, Abid; Abbas, Tasawar
2018-01-01
We propose an idea for symmetric measurements through the famous double slit experiment (DSE) in a new detection scenario. The interferometric setup is complemented here with quantum detectors that switch to an arbitrary superposition after interaction with the arms of the DSE. The envisioned schematics cover the full measurement range, i.e. from the weak to the strong projective situation with selectivity being a smoothly tunable open option, and suggests an alternative methodology for weak measurements based on information overlap from DSE paths. The results, though generally in agreement with the quantum paradigm, raise many questions over the nature of probabilities, the absurdity of the common language for phenomena’s description in the theory and the boundary separating the projective/non-projective measurements, and the related misconceived interpretations. Further, the results impose certain constraints over the hidden variable theories as well as on the repercussions of the weak measurements. Although described as a thought experiment, the proposal can equally be implemented experimentally under a prevailing research scenario.
Coupled-Double-Quantum-Dot Environmental Information Engines: A Numerical Analysis
Tanabe, Katsuaki
2016-06-01
We conduct numerical simulations for an autonomous information engine comprising a set of coupled double quantum dots using a simple model. The steady-state entropy production rate in each component, heat and electron transfer rates are calculated via the probability distribution of the four electronic states from the master transition-rate equations. We define an information-engine efficiency based on the entropy change of the reservoir, implicating power generators that employ the environmental order as a new energy resource. We acquire device-design principles, toward the realization of corresponding practical energy converters, including that (1) higher energy levels of the detector-side reservoir than those of the detector dot provide significantly higher work production rates by faster states' circulation, (2) the efficiency is strongly dependent on the relative temperatures of the detector and system sides and becomes high in a particular Coulomb-interaction strength region between the quantum dots, and (3) the efficiency depends little on the system dot's energy level relative to its reservoir but largely on the antisymmetric relative amplitudes of the electronic tunneling rates.
Iontsev, M. A.; Mukhin, S. I.; Fistul, M. V.
2016-11-01
We report a theoretical study of the ac response of superconducting quantum metamaterials (SQMs), i.e., an array of qubits (two-level systems) embedded in a low-dissipative resonator. By making use of a particular example of a SQM, namely the array of charge qubits capacitively coupled to the resonator, we obtain a second-order phase transition between an incoherent (the high-temperature phase) and coherent (the low-temperatures phase) state of photons. This phase transition in many aspects resembles the paramagnetic-ferromagnetic phase transition. The critical temperature of the phase transition, T, is determined by the energy splitting of two-level systems δ , number of qubits in the array N , and the strength of the interaction η between qubits and photons in the cavity. We obtain that the photon states manifest themselves by resonant drops in the frequency-dependent transmission D (ω ) of electromagnetic waves propagating through a transmission line weakly coupled to the SQM. At high temperatures the D (ω ) displays a single resonant drop, and at low temperatures a peculiar double-resonance response has to be observed. The physical origin of such a resonant splitting is the quantum oscillations between two coherent states of photons of different polarizations.
Thermodynamic Properties of a Double Ring-Shaped Quantum Dot at Low and High Temperatures
Khordad, R.; Sedehi, H. R. Rastegar
2018-02-01
In this work, we study thermodynamic properties of a GaAs double ring-shaped quantum dot under external magnetic and electric fields. To this end, we first solve the Schrödinger equation and obtain the energy levels and wave functions, analytically. Then, we calculate the entropy, heat capacity, average energy and magnetic susceptibility of the quantum dot in the presence of a magnetic field using the canonical ensemble approach. According to the results, it is found that the entropy is an increasing function of temperature. At low temperatures, the entropy increases monotonically with raising the temperature for all values of the magnetic fields and it is independent of the magnetic field. But, the entropy depends on the magnetic field at high temperatures. The entropy also decreases with increasing the magnetic field. The heat capacity and magnetic susceptibility show a peak structure. The heat capacity reduces with increasing the magnetic field at low temperatures. The magnetic susceptibility shows a transition between diamagnetic and paramagnetic below for T<4 K. The transition temperature depends on the magnetic field.
Investigation of multi-stack quantum dots-in-double-well infrared detectors
Kutty, M. N.; Sharma, Y. D.; Barve, A.; Shao, J.; Plis, E.; Shenoi, R. V.; Krishna, S.; Lee, S. J.; Noh, S. K.
2009-08-01
We report on the performance of multi-stack quantum dots in a well (DWELL) detectors. Present-day QD detectors are limited by low responsivity and quantum efficiency (QE). This can be attributed to the low absorption efficiency of these structures due to the small number of QD stacks in the detector. In this paper we examine the effect of the number of stacks on the performance of the detector. In particular, we investigate the InAs/GaAs/AlGaAs D-DWELL (Dots-in-double-well) design, which has a lower strain per DWELL stack than the InAs/InGaAs/GaAs DWELLs thereby enabling the growth of many more stacks in the detector. The purpose of the study detailed in this paper is to examine the effects of varying the number of stacks in the InAs/InGaAs/GaAs/AlGaAs D-DWELL detector, on its device performance. The numbers of stacks grown using solid source molecular beam epitaxy (MBE), were 15, 30, 40, 50, and 60. Once fabricated as single pixel devices, we carried-out a series of device measurements such as spectral response, dark current, total current, responsivity along with computing the photoconductive gain and the activation energies. The goal of these experiments is to not only study the single pixel detector performance with varying number of stacks in a D-DWELL structure, but to also understand the effect of the transport mechanism in these devices.
Waiting time distribution revealing the internal spin dynamics in a double quantum dot
Ptaszyński, Krzysztof
2017-07-01
Waiting time distribution and the zero-frequency full counting statistics of unidirectional electron transport through a double quantum dot molecule attached to spin-polarized leads are analyzed using the quantum master equation. The waiting time distribution exhibits a nontrivial dependence on the value of the exchange coupling between the dots and the gradient of the applied magnetic field, which reveals the oscillations between the spin states of the molecule. The zero-frequency full counting statistics, on the other hand, is independent of the aforementioned quantities, thus giving no insight into the internal dynamics. The fact that the waiting time distribution and the zero-frequency full counting statistics give a nonequivalent information is associated with two factors. Firstly, it can be explained by the sensitivity to different timescales of the dynamics of the system. Secondly, it is associated with the presence of the correlation between subsequent waiting times, which makes the renewal theory, relating the full counting statistics and the waiting time distribution, no longer applicable. The study highlights the particular usefulness of the waiting time distribution for the analysis of the internal dynamics of mesoscopic systems.
Transport and current noise characteristics of a T-shape double-quantum-dot system.
Brown, K; Crisan, M; Tifrea, I
2009-05-27
We consider the transport and the noise characteristics for the case of a T-shape double-quantum-dot system using the equation of motion method. Our theoretical results, obtained in an approximation equivalent to the Hartree-Fock approximation, account for non-zero on-site Coulomb interaction in both the detector and side dots. The existence of a non-zero Coulomb interaction implies an additional two resonances in the detector's dot density of states and thereafter affects the electronic transport properties of the system. The system's conductance presents two Fano dips as a function of the energy of the localized electronic level in the side dot. The Fano dips in the system's conductance can be observed for both strong (fast detector) and weak coupling (slow detector) between the detector dot and the external electrodes. Due to stronger electronic correlations, the noise characteristics 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 dot systems.
SU(4)-SU(2) crossover and spin-filter properties of a double quantum dot nanosystem
Lopes, V.; Padilla, R. A.; Martins, G. B.; Anda, E. V.
2017-06-01
The SU(4)-SU(2) crossover, driven by an external magnetic field h , is analyzed in a capacitively coupled double quantum dot device connected to independent leads. As one continuously charges the dots from empty to quarter filled, by varying the gate potential Vg, the crossover starts when the magnitude of the spin polarization of the double quantum dot, as measured by - , becomes finite. Although the external magnetic field breaks the SU(4) symmetry of the Hamiltonian, the ground state preserves it in a region of Vg, where - =0 . Once the spin polarization becomes finite, it initially increases slowly until a sudden change occurs, in which (polarization direction opposite to the magnetic field) reaches a maximum and then decreases to negligible values abruptly, at which point an orbital SU(2) ground state is fully established. This crossover from one Kondo state, with emergent SU(4) symmetry, where spin and orbital degrees of freedom all play a role, to another, with SU(2) symmetry, where only orbital degrees of freedom participate, is triggered by a competition between g μBh , the energy gain by the Zeeman-split polarized state and the Kondo temperature TKS U (4 ), the gain provided by the SU(4) unpolarized Kondo-singlet state. At fixed magnetic field, the knob that controls the crossover is the gate potential, which changes the quantum dots occupancies. If one characterizes the occurrence of the crossover by Vgmax, the value of Vg where reaches a maximum, one finds that the function f relating the Zeeman splitting, Bmax, which corresponds to Vgmax, i.e., Bmax=f (Vgmax) , has a similar universal behavior to that of the function relating the Kondo temperature to Vg. In addition, our numerical results show that near the SU(4) Kondo temperature and for relatively small magnetic fields the device has a ground state that restricts the electronic population at the dots to be spin polarized along the magnetic field. These two facts introduce very efficient spin
Moreno, Diego V; González, Sergio A; Reyes, Andrés
2011-01-14
Nuclear quantum effects (NQE) on the geometry, energy, and electronic structure of the [CN·L·NC](-) complex (L = H, D, T) are investigated with the recently developed APMO/MP2 code. This code implements the nuclear molecular orbital approach (NMO) at the Hartree-Fock (HF) and MP2 levels of theory for electrons and quantum nuclei. In a first study, we examined the H/D/T isotope effects on the geometry and electronic structure of the CNH molecule at NMO/HF and NMO/MP2 levels of theory. We found that when increasing the hydrogen nuclear mass there is a reduction of the R(N-H) bond distance and an increase of the electronic population on the hydrogen atom. Our calculated bond distances are in good agreement with experimental and other theoretical results. In a second investigation, we explored the hydrogen NQE on the geometry of [CNHNC](-) complex at the NMO/HF and NMO/MP2 levels of theory. We discovered that while a NMO/HF calculation presented an asymmetric hydrogen bond, the NMO/MP2 calculation revealed a symmetric H-bond. We also examined the H/D/T isotope effects on the geometry and stabilization energy of the [CNHNC](-) complex. We noted that gradual increases in hydrogen mass led to reductions of the R(NN) distance and destabilization of the hydrogen bond (H-bond). A discussion of these results is given in terms of the hydrogen nuclear delocalization effects on the electronic structure and energy components. To the best of our knowledge, this is the first ab initio NMO study that reveals the importance of including nuclear quantum effects in conventional electronic structure calculations for an enhanced description of strong-low-barrier H-bonded systems.
Directory of Open Access Journals (Sweden)
Pedram Shokouh
2013-01-01
Full Text Available The present trial aimed to investigate the effects of pioglitazone on the serum level of asymmetric dimethylarginine (ADMA, a marker of endothelial function, and some indices of inflammation and glucose and lipid metabolism in nondiabetic metabolic syndrome patients. 104 eligible participants (57% female; age between 20 and 70 were enrolled in a double-blind placebo-controlled trial and were randomized to receive either pioglitazone (uptitrated to 30 mg/day or matching placebo for 24 weeks. Participants were clinically examined and a blood sample was obtained at baseline and at the end of the trial. Pioglitazone significantly improved C-reactive protein level irrespective of changes in insulin sensitivity. Compared with the placebo group, alanine and aspartate transaminases were decreased and high-density lipoprotein cholesterol was increased after treatment with pioglitazone. A considerably greater weight gain was also recorded in the intervention group. We failed to observe any significant changes in serum ADMA in either group and between groups with and without adjustment for age, sex, and components of the metabolic syndrome. In a nutshell, pioglitazone seems to have positive effects on lipid profile, liver transaminases, and systemic inflammation. However, its previously demonstrated endothelial function-improving properties do not seem to be mediated by ADMA.
Cornaglia, P. S.
2008-06-01
In a recent paper [Physica E 39 (2007) 214, arXiv:0708.1842v1] Crisan, Grosu, and Tifrea revisited the problem of the conductance through a double-quantum-dot molecule connected to electrodes in a T-shape configuration. The authors obtained an expression for the conductance that disagrees with previous results in the literature. We point out an error in their derivation of the conductance formula and show that it gives unphysical results even for non-interacting quantum dots.
Deng, Guang-Wei; Wei, Da; Johansson, J R; Zhang, Miao-Lei; Li, Shu-Xiao; Li, Hai-Ou; Cao, Gang; Xiao, Ming; Tu, Tao; Guo, Guang-Can; Jiang, Hong-Wen; Nori, Franco; Guo, Guo-Ping
2015-09-18
We use an on-chip superconducting resonator as a sensitive meter to probe the properties of graphene double quantum dots at microwave frequencies. Specifically, we investigate the charge dephasing rates in a circuit quantum electrodynamics architecture. The dephasing rates strongly depend on the number of charges in the dots, and the variation has a period of four charges, over an extended range of charge numbers. Although the exact mechanism of this fourfold periodicity in dephasing rates is an open problem, our observations hint at the fourfold degeneracy expected in graphene from its spin and valley degrees of freedom.
Forming double layer-encapsulated quantum dots for bio-imaging and cell targeting
Fahmi, Mochamad Zakki; Chang, Jia-Yaw
2013-01-01
We report a simple and effective approach for the preparation of double layer-encapsulated quantum dots (DL-Qdots) composed of alkyl-capping ligands to interdigitate with hydrophobic, protective agents on the surface of AgInS2/ZnS quantum dots (Qdots), which allow phase transfer of hydrophobic Qdots from the organic phase into the aqueous phase. The alkyl-capping ligands consist of a hydrophobic, aliphatic chain and different functional terminal groups (e.g., carboxyl, amine, hydroxyl, and thiol groups) that can serve as reactive sites to chemically couple with other materials. The resulting DL-Qdots bearing various functional groups retain good fluorescence properties and show excellent solubility as well as stability over a range of pH in the aqueous phase. Cytotoxicity studies of DL-Qdots bearing carboxyl groups (DL-Qdots-COOH) were carried out against human cervical (HeLa) cancer cells to elicit no apparent toxicity even at high concentrations of 300 μg mL-1 and 24 h of incubation. To demonstrate their potential biomedical application, DL-Qdots-COOH were further conjugated with folate for staining in HeLa, human liver carcinoma (HepG2), and human breast (MCF-7) cancer cells. Confocal imaging characterization revealed that folate-conjugated DL-Qdots could target most specifically and effectively HeLa cells via folate receptor-mediated targeted delivery compared to HepG2 and MCF-7 cells. The generality and simplicity of this newly developed strategy can possibly be extended to a large variety of hydrophobic Qdots and nanocrystals whose surface protective agents have a long aliphatic chain.
Directory of Open Access Journals (Sweden)
A. Stockklauser
2017-03-01
Full Text Available The strong coupling limit of cavity quantum electrodynamics (QED implies the capability of a matterlike quantum system to coherently transform an individual excitation into a single photon within a resonant structure. This not only enables essential processes required for quantum information processing but also allows for fundamental studies of matter-light interaction. In this work, we demonstrate strong coupling between the charge degree of freedom in a gate-defined GaAs double quantum dot (DQD and a frequency-tunable high impedance resonator realized using an array of superconducting quantum interference devices. In the resonant regime, we resolve the vacuum Rabi mode splitting of size 2g/2π=238 MHz at a resonator linewidth κ/2π=12 MHz and a DQD charge qubit decoherence rate of γ_{2}/2π=40 MHz extracted independently from microwave spectroscopy in the dispersive regime. Our measurements indicate a viable path towards using circuit-based cavity QED for quantum information processing in semiconductor nanostructures.
Energy Technology Data Exchange (ETDEWEB)
Altin, E. [Inonu University, Scientific and Technological Research Center, Malatya (Turkey); Anadolu University, Department of Physics, Eskisehir (Turkey); Hostut, M. [Akdeniz University, Department of Secondary Education of Science and Maths., Division of Physics Education, Antalya (Turkey); Ergun, Y. [Anadolu University, Department of Physics, Eskisehir (Turkey)
2011-12-15
In this study, we investigate dark current voltage characteristics of GaAs/AlGaAs staircase-like asymmetric multiquantum well structure at various temperatures experimentally. The activation energy is calculated by using Arrhenius plots at different voltages. It is found that the activation energy decreased with increasing electric field. This result is evaluated using a barrier lowering effect which is a combination of geometrical and Poole-Frenkel effects. Measured dark current density-voltage (J-V) characteristics compared with the Levine model, 3D carrier drift model and the emission capture model. The best agreement with the experimental results of dark current densities is obtained by the Levine model. (orig.)
Photoluminescence from quantum dots in cubic GaN/InGaN/GaN double heterostructures
Husberg, O.; Khartchenko, A.; As, D. J.; Vogelsang, H.; Frey, T.; Schikora, D.; Lischka, K.; Noriega, O. C.; Tabata, A.; Leite, J. R.
2001-08-01
We have measured photoluminescence spectra of molecular-beam-epitaxy-grown cubic GaN/InxGa1-xN/GaN double heterostructures with x between 0.09 and 0.33. We observe a luminescence peak at about 2.3-2.4 eV which is almost independent of the InGaN layer composition. High-resolution x-ray diffraction measurements revealed a pseudomorphic In-rich phase with x=0.56±0.02 embedded in the InGaN layers. Including strain effects we calculate a gap energy Eg=2.13 eV of this phase. In cubic InGaN, spontaneous polarization and strain-induced piezoelectric fields are negligible. Therefore, the observed difference between the luminescence energy and the gap of the In-rich phase is assumed to be due to the localization of excitons at quantum-dot-like structures with a size of about 15 nm.
Ultrafast double-quantum NMR spectroscopy with optimized sensitivity for the analysis of mixtures.
Rouger, Laetitia; Gouilleux, Boris; Pourchet-Gellez, Mariane; Dumez, Jean-Nicolas; Giraudeau, Patrick
2016-03-07
Ultrafast (UF) 2D NMR enables the acquisition of 2D spectra within a single-scan. This methodology has become a powerful analytical tool, used in a large array of applications. However, UF NMR spectroscopy still suffers from the need to compromise between sensitivity, spectral width and resolution. With the commonly used UF-COSY pulse sequence, resolution issues are compounded by the presence of strong auto-correlation signals, particularly in the case of samples with high dynamic ranges. The recently proposed concept of UF Double Quantum Spectroscopy (DQS) allows a better peak separation as it provides a lower spectral peak density. This paper presents the detailed investigation of this new NMR tool in an analytical chemistry context. Theoretical calculations and numerical simulations are used to characterize the modulation of peak intensities as a function of pulse-sequence parameters, and thus enable a significant enhancement of the sensitivity. The analytical comparison of UF-COSY and UF-DQS shows similar performances, however the ultrafast implementation of the DQS approach is found to have some sensitivity advantages over its conventional counterpart. The analytical performance of the pulse sequence is illustrated by the quantification of taurine in complex mixtures (homemade and commercial energy drinks). The results demonstrate the high potential of this experiment, which forms a valuable alternative to UF-COSY spectra when the latter are characterized by strong overlaps and high dynamic ranges.
Spin-Filtering Transport in Double Parallel Quantum Wires on a Graphene Sheet
Yang, Fu-Bin; Cheng, Yan; Liu, Fu-Ti; Chen, Xiang-Rong; Cai, Ling-Cang
2015-03-01
We theoretically investigate the spin filtering transport of double parallel quantum wires (QWs) side-coupled to a graphene sheet and sandwiched between two ferromagnetic (FM) leads. The dependences of the wire-graphene coupling strength, wire-wire coupling strength, as well as the spin polarization of the ferromagnetic leads are studied. It is found that the wire-graphene coupling strength tends to reduce the current and the wire-wire coupling strength can first reinforce and then decrease the current. The spin polarization strength has an enhanced (identical) effect on the current under the parallel (anti-parallel) alignment of the FM leads, which gives rise to an obvious spin-filter and tunnel magnetoresistance (TMR) effect. Our results suggest that such a theoretical model can stimulate some experimental investigations about the spin-filter devices. Supported by the National Natural Science Foundation of China under Grant Nos. 11174214, 11204192, the NSAF Joint Fund Jointly set up by the National Natural Science Foundation of China and the Chinese Academy of Engineering Physics under Grant Nos. U1230201 and U1430117
Energy Technology Data Exchange (ETDEWEB)
Adelerhof, D.J.; Kawai, J.; Uehara, G.; Kado, H. [Electrotechnical Laboratory, 1-1-4 Umezono, Tsukuba 303 (Japan)
1995-03-01
Double relaxation oscillation superconducting quantum interference devices (SQUIDs) (DROSs) based on Nb/AlO{sub {ital x}} tunnel junctions have been fabricated and characterized. The estimated relaxation frequencies range from 400 MHz up to 14 GHz. Transfer coefficients from flux to voltage of 2 up to 7 mV/{phi}{sub 0} have been obtained. Both the intrinsic flux noise and the performance in a flux-locked loop with direct-voltage readout have been determined. Special attention is paid to the effect of damping resistors on the sensitivity of DROSs. The intrinsic sensitivity improves with increasing relaxation frequency, leveling off to a value of 13{ital h} at relaxation frequencies above 2--3 GHz for SQUID inductances of about 30 pH. This sensitivity is very close to the theoretical maximum sensitivity of 6{ital h} of a comparable standard type dc SQUID. In a flux-locked loop based on direct-voltage readout, a noise level of 0.55 {mu}{phi}{sub 0}/{radical}Hz corresponding to an energy sensitivity of 34{ital h} has been obtained for a DROS with a SQUID inductance of 29 pH. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.
Bao, Jianfeng; Cui, Xiaohong; Huang, Yuqing; Zhong, Jianhui; Chen, Zhong
2015-08-01
High-resolution 1H magnetic resonance spectroscopy (MRS) is generally inaccessible in red bone marrow (RBM) tissues using conventional MRS techniques. This is because signal from these tissues suffers from severe inhomogeneity in the main static B0 field originated from the intrinsic honeycomb structures in trabecular bone. One way to reduce effects of B0 field inhomogeneity is by using the intermolecular double quantum coherence (iDQC) technique, which has been shown in other systems to obtain signals insensitive to B0 field inhomogeneity. In the present study, we employed an iDQC approach to enhance the spectral resolution of RBM. The feasibility and performance of this method for achieving high resolution MRS was verified by experiments on phantoms and pig vertebral bone samples. Unsaturated fatty acid peaks which overlap in the conventional MRS were well resolved and identified in the iDQC spectrum. Quantitative comparison of fractions of three types of fatty acids was performed between iDQC spectra on the in situ RMB and conventional MRS on the extracted fat from the same RBM. Observations of unsaturated fatty acids with iDQC MRS may provide valuable information and may hold potential in diagnosis of diseases such as obesity, diabetes, and leukemia.
Sub-Poissonian photon emission in coupled double quantum dots-cavity system
Ye, Han; Peng, Yi-Wei; Yu, Zhong-Yuan; Zhang, Wen; Liu, Yu-Min
2015-11-01
In this work, we theoretically analyze the few-photon emissions generated in a coupled double quantum dots (CDQDs)-single mode microcavity system, under continuous wave and pulse excitation. Compared with the uncoupled case, strong sub-Poissonian character is achieved in a CDQDs-cavity system at a certain laser frequency. Based on the proposed scheme, single photon generation can be obtained separately under QD-cavity resonant condition and off-resonant condition. For different cavity decay rates, we reveal that laser frequency detunings of minimum second-order autocorrelation function are discrete and can be divided into three regions. Moreover, the non-ideal situation where two QDs are not identical is discussed, indicating the robustness of the proposed scheme, which possesses sub-Poissonian character in a large QD difference variation range. Project supported by the National Natural Science Foundation of China (Grant Nos. 61372037 and 61401035), the Beijing Excellent Ph.D. Thesis Guidance Foundation, China (Grant No. 20131001301), and the Fund of State Key Laboratory of Information Photonics and Optical Communications (Beijing University of Posts and Telecommunications), China (Grant No. IPOC2015ZC05).
Energy Technology Data Exchange (ETDEWEB)
Hamedi, H. R., E-mail: hamid.r.hamedi@gmail.com, E-mail: hamid.hamedi@tfai.vu.lt [Institute of Theoretical Physics and Astronomy, Vilnius University Sauletekio 3 LT-10222 Vilnius (Lithuania)
2016-05-14
The problem of pulse propagation is theoretically investigated through a coupled semiconductor-double-quantum-dot (SDQD) nanostructure. Solving the coupled Maxwell–Bloch equations for the SDQD and field simultaneously, the dynamic control of pulse propagation through the medium is numerically explored. It is found that when all the control fields are in exact resonance with their corresponding transitions, a weak Gaussian-shaped probe pulse is transmitted through the medium nearly without any significant absorption and losses so that it can preserve its shape for quite a long propagation distance. In contrast, when one of the control fields is not in resonance with its corresponding transition, the probe pulse will be absorbed by the QD medium after a short distance. Then we consider the probe pulses with higher intensities. It is realized that an intense probe pulse experiences remarkable absorption and broadening during propagation. Finally, we demonstrate that this SDQD system can be employed as an optically controllable switch for the wave propagation to transit from an absorbing phase to a perfect transparency for the probe field. The required time for such switch is also estimated through realistic values.
Hamedi, H. R.
2016-05-01
The problem of pulse propagation is theoretically investigated through a coupled semiconductor-double-quantum-dot (SDQD) nanostructure. Solving the coupled Maxwell-Bloch equations for the SDQD and field simultaneously, the dynamic control of pulse propagation through the medium is numerically explored. It is found that when all the control fields are in exact resonance with their corresponding transitions, a weak Gaussian-shaped probe pulse is transmitted through the medium nearly without any significant absorption and losses so that it can preserve its shape for quite a long propagation distance. In contrast, when one of the control fields is not in resonance with its corresponding transition, the probe pulse will be absorbed by the QD medium after a short distance. Then we consider the probe pulses with higher intensities. It is realized that an intense probe pulse experiences remarkable absorption and broadening during propagation. Finally, we demonstrate that this SDQD system can be employed as an optically controllable switch for the wave propagation to transit from an absorbing phase to a perfect transparency for the probe field. The required time for such switch is also estimated through realistic values.
Spin polarized current in a double quantum dot with time-dependent interdot tunneling
Cota, Ernesto; Mireles, Francisco; Rojas, Fernando; Ulloa, Sergio E.
2006-03-01
A bipolar spin filter has been proposed using a few-electron double quantum dot (DQD) in a `hanging-dot' configuration [1], and tunable by controlling the molecular hybridization (interdot tunneling) between dots. The bipolar nature of the electron spin current arises from a singlet-triplet transition in the ground state of the two-electron DQD. The transition occurs due to the competition among Zeeman energy, exchange interaction and interdot coupling, favoring a lower (higher) energy for the triplet (singlet) configuration in the weak (large) interdot tunneling regime. In this work we use a density matrix equation to study the dynamical behavior of the DQD, by considering the adiabatic variation of the interdot tunneling in time. We report on the spin-polarized current through the DQD as a function of the relevant physical parameters. A bipolar spin filtering effect in the time domain is observed to arise on time scales smaller than the relevant coherent and spin relaxation times in typical QDs. Spin-orbit coupling is included in our approach but found to not significantly affect our results. [1] F. Mireles, E. Cota, F. Rojas and S.E. Ulloa, submitted.
Monteros, A. L.; Uppal, G. S.; McMillan, S. R.; Crisan, M.; Tifrea, I.
2014-01-01
We investigate the thermoelectric properties of a T-shaped double quantum dot system described by a generalized Anderson Hamiltonian. The system's electrical conduction (G) and the fundamental thermoelectric parameters such as the Seebeck coefficient ($S$) and the thermal conductivity ($\\kappa$), along with the system's thermoelectric figure of merit (ZT) are numerically estimated based on a Green's function formalism that includes contributions up to the Hartree-Fock level. Our results accou...
Asghar, Haroon; McInerney, John G
2017-09-15
We demonstrate an asymmetric dual-loop feedback method to suppress external cavity side-modes induced in self-mode-locked quantum-dash lasers with conventional single- and dual-loop feedback. In this Letter, we report optimal suppression of spurious tones by optimizing the delay in the second loop. We observed that asymmetric dual-loop feedback, with large (∼8×) disparity in loop lengths, gives significant suppression in external-cavity side-modes and produces flat radio frequency (RF) spectra close to the main peak with a low timing jitter, compared to single-loop feedback. Significant reduction in RF linewidth and timing jitter was produced by optimizing the delay time in the second feedback loop. Experimental results based on this feedback configuration validate predictions of recently published numerical simulations. This asymmetric dual-loop feedback scheme provides simple, efficient, and cost-effective stabilization of optoelectronic oscillators based on mode-locked lasers.
Constable, E.; Ballou, R.; Robert, J.; Decorse, C.; Brubach, J.-B.; Roy, P.; Lhotel, E.; Del-Rey, L.; Simonet, V.; Petit, S.; deBrion, S.
2017-01-01
The origin of quantum fluctuations responsible for the spin liquid state in Tb2Ti2O7 has remained a long-standing problem. By synchrotron-based terahertz measurements, we show evidence of strong coupling between the magnetic and lattice degrees of freedom that provides a path to the quantum melting process. As revealed by hybrid crystal electric field-phonon excitations that appear at 0.67 THz below 200 K, and around 0.42 THz below 50 K, the double vibronic process is unique for Tb3 + in the titanate family due to adequate energy matching and strong quadrupolar moments. The results suggest that lattice motion can indeed be the driving force behind spin flips within the hybridized ground and first excited states, promoting quantum terms in the effective Hamiltonian that describes Tb2Ti2O7 .
Velenich, Andrea; Chamon, Claudio; Wen, Xiao-Gang
2010-04-01
String-nets and quantum loop gases are two prominent microscopic lattice models to describe topological phases. String-net condensation can give rise to both Abelian and non-Abelian anyons, whereas loop condensation usually produces Abelian anyons. It has been proposed, however, that generalized quantum loop gases with non-orthogonal inner products could support non-Abelian anyons. We detail an exact mapping between the string-net and these generalized loop models and explain how the non-orthogonal products arise. We also introduce an equivalent loop model of double-stranded nets where quantum loops with an orthogonal inner product and local interactions supports non-Abelian Fibonacci anyons. Finally, we emphasize the origin of the sign problem in systems with non-Abelian excitations and its consequences on the complexity of their ground state wavefunctions.
Energy Technology Data Exchange (ETDEWEB)
Koerting, V., E-mail: koerting@nbi.d [Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Niels Bohr Institute, Universitetsparken, DK-2100 Copenhagen (Denmark); The Niels Bohr International Academy, The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Fritsch, P. [Physics Department, Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Ludwig-Maximilians-Universitaet, Theresienstrasse 37, 80333 Munich (Germany); Kehrein, S., E-mail: stefan.kehrein@physik.lmu.d [Physics Department, Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Ludwig-Maximilians-Universitaet, Theresienstrasse 37, 80333 Munich (Germany)
2011-05-15
Since the experimental realization of Kondo physics in quantum dots, its far-from-equilibrium properties have generated considerable theoretical interest. This is due to the interesting interplay of non-equilibrium physics and correlation effects in this model, which has now been analyzed using several new theoretical methods that generalize renormalization techniques to non-equilibrium situations. While very good agreement between these methods has been found for the spin-1/2 Kondo model, it is desirable to have a better understanding of their applicability for more complicated impurity models. In this paper the differences and commons between two such approaches, namely the flow equation method out of equilibrium and the frequency-dependent poor man's scaling approach are presented for the non-equilibrium double quantum dot system. This will turn out to be a particularly suitable testing ground while being experimentally interesting in its own right. An outlook is given on the quantum critical behavior of the double quantum dot system and its accessibility with the two methods.
On the relation between the modular double of U{sub q}(sl(2,R)) and the quantum Teichmueller theory
Energy Technology Data Exchange (ETDEWEB)
Nidaiev, Iurii; Teschner, Joerg
2013-02-15
We exhibit direct relations between the modular double of U{sub q}(sl(2,R)) and the quantum Teichmueller theory. Explicit representations for the fusion- and braiding operations of the quantum Teichmueller theory are immediate consequences. Our results include a simplified derivation of the Clebsch-Gordan decomposition for the principal series of representation of the modular double of U{sub q}(sl(2,R)).
Menéndez-Miranda, Mario; Encinar, Jorge Ruiz; Costa-Fernández, José M; Sanz-Medel, Alfredo
2015-11-27
Hyphenation of asymmetric flow field-flow fractionation (AF4) to an on-line elemental detection (inductively coupled plasma-mass spectrometry, ICP-MS) is proposed as a powerful diagnostic tool for quantum dots bioconjugation studies. In particular, conjugation effectiveness between a "model" monoclonal IgG antibody (Ab) and CdSe/ZnS core-shell Quantum Dots (QDs), surface-coated with an amphiphilic polymer, has been monitored here by such hybrid AF4-ICP-MS technique. Experimental conditions have been optimized searching for a proper separation between the sought bioconjugates from the eventual free reagents excesses employed during the bioconjugation (QDs and antibodies). Composition and pH of the carrier have been found to be critical parameters to ensure an efficient separation while ensuring high species recovery from the AF4 channel. An ICP-MS equipped with a triple quadropole was selected as elemental detector to enable sensitive and reliable simultaneous quantification of the elemental constituents, including sulfur, of the nanoparticulated species and the antibody. The hyphenated technique used provided nanoparticle size-based separation, elemental detection, and composition analysis capabilities that turned out to be instrumental in order to investigate in depth the Ab-QDs bioconjugation process. Moreover, the analytical strategy here proposed allowed us not only to clearly identify the bioconjugation reaction products but also to quantify nanoparticle:antibodies bioconjugation efficiency. This is a key issue in future development of analytical and bioanalytical photoluminescent QDs applications. Copyright © 2015 Elsevier B.V. All rights reserved.
Vertically coupled double-microdisk lasers composed of InGaAs quantum dots-in-a-well active layers
Hsing, J. Y.; Tzeng, T. E.; Lay, T. S.; Shih, M. H.
2017-05-01
We report the epitaxy, fabrication, and measurement of vertically coupled double-microdisk lasers using InGaAs quantum dots-in-a-well as the optical gain material. The bonding and anti-bonding photonic molecule laser modes are simultaneously observed at room temperature (T = 300 K). The optical coupling is confirmed by measuring the double disks for three different air gaps of 100 nm, 200 nm, and 480 nm, respectively. The coupling strengths for the photonic molecule bonding mode MB1,9 and anti-bonding mode MA1,9 between the adjacent microdisks are equal to 17.4 THz for 100 nm air gap, and 5.2 THz for 200 nm air gap, respectively. The refractive index sensing experiments show the lasing wavelength sensitivity of 60 nm/RIU for the vertically coupled double-microdisk laser of 100 nm air gap.
Lange, Heiko; Huenerbein, Robert; Fröhlich, Roland; Grimme, Stefan; Hoppe, Dieter
2008-01-04
The title compounds were generated by deprotonation of different benzyl-type carbamates with sec-butyllithium in the presence of chiral diamines (-)-sparteine or diisopropyl and di-tert-butyl bis(oxazoline)s. These lithiated species exhibit configurational lability at -78 degrees C. In the case of the chiral di-tert-butyl bis(oxazoline), the equilibrium of the epimeric complexes can be used synthetically to obtain highly enantioenriched secondary benzyl carbamates. The enantiodetermining step was proven to be a dynamic thermodynamic resolution. The absolute configurations of the products were determined, and the stereochemical pathways of selected substitution reactions were thus elucidated. High-level quantum chemical investigations were performed to gain insight into the experimentally investigated system. To obtain an accuracy for the energy difference (delta deltaH) between two epimeric complexes of about 0.5 kcal mol(-1) as well as the correct sign, a theoretical procedure was established. It included geometry optimization at the dispersion-corrected DFT level, computation of zero-point vibrational energies, and single-point SCS-MP2 energy calculations with large atomic-orbital basis sets.
Partial hybridisation of electron-hole states in an InAs/GaSb double quantum well heterostructure
Knox, C. S.; Morrison, C.; Herling, F.; Ritchie, D. A.; Newell, O.; Myronov, M.; Linfield, E. H.; Marrows, C. H.
2017-10-01
InAs/GaSb coupled quantum well heterostructures are important semiconductor systems with applications ranging from spintronics to photonics. Most recently, InAs/GaSb heterostructures have been identified as candidate two-dimensional topological insulators, predicted to exhibit helical edge conduction via fully spin-polarised carriers. We study an InAs/GaSb double quantum well heterostructure with an AlSb barrier to decouple partially the 2D electrons and holes, and find conduction consistent with a 2D hole gas, with an effective mass of 0.235 ± 0.005 m 0, existing simultaneously with hybridised carriers with an effective mass of 0.070 ± 0.005 m 0, where m 0 is the bare electron mass.
Ting, David Z.-Y; Soibel, Alexander; Khoshakhlagh, Arezou; Keo, Sam A.; Nguyen, Jean; Hoglund, Linda; Mumolo, Jason M.; Liu, John K.; Rafol, Sir B.; Hill, Cory J.;
2012-01-01
The InAs/GaSb type-II superlattice based complementary barrier infrared detector (CBIRD) has already demonstrated very good performance in long-wavelength infrared (LWIR) detection. In this work, we describe results on a modified CBIRD device that incorporates a double tunnel junction contact designed for robust device and focal plane array processing. The new device also exhibited reduced turn-on voltage. We also report results on the quantum dot barrier infrared detector (QD-BIRD). By incorporating self-assembled InSb quantum dots into the InAsSb absorber of the standard nBn detector structure, the QD-BIRD extend the detector cutoff wavelength from approximately 4.2 micrometers to 6 micrometers, allowing the coverage of the mid-wavelength infrared (MWIR) transmission window. The device has been observed to show infrared response at 225 K.
Quantum dynamics of a binary mixture of BECs in a double-well potential: a Holstein-Primakoff approach
Energy Technology Data Exchange (ETDEWEB)
Citro, Roberta; Naddeo, Adele [Dipartimento di Fisica ' E. R. Caianiello' , Universita degli Studi di Salerno, Via Ponte Don Melillo, 84084 Fisciano (Saudi Arabia) (Italy); Orignac, Edmond, E-mail: citro@sa.infn.it, E-mail: naddeo@sa.infn.it, E-mail: Edmond.Orignac@ens-lyon.fr [Laboratoire de Physique, CNRS-UMR5672, Ecole Normale Superieure de Lyon, 46, Allee d' Italie, 69364 Lyon Cedex 07 (France)
2011-06-14
We study the quantum dynamics of a binary mixture of Bose-Einstein condensates (BECs) in a double-well potential starting from a two-mode Bose-Hubbard Hamiltonian. Focussing on the regime where the number of atoms is very large, a mapping onto an SU(2) spin problem together with a Holstein-Primakoff transformation is performed. The quantum evolution of the number difference of bosons between the two wells is investigated for different initial conditions, which range from the case of a small imbalance between the two wells to a coherent spin state. The results show an instability towards a phase separation above a critical positive value of the interspecies interaction while the system evolves towards a coherent tunnelling regime for negative interspecies interactions. A comparison with a semiclassical approach is discussed together with some implications on the experimental realization of phase separation with cold atoms.
Karaaslan, Y.; Gisi, B.; Sakiroglu, S.; Kasapoglu, E.; Sari, H.; Sokmen, I.
2018-02-01
We study the influence of electric field on the electronic energy band structure, zero-temperature ballistic conductivity and optical properties of double quantum wire. System described by double-well anharmonic confinement potential is exposed to a perpendicular magnetic field and Rashba and Dresselhaus spin-orbit interactions. Numerical results show up that the combined effects of internal and external agents cause the formation of crossing, anticrossing, camel-back/anomaly structures and the lateral, downward/upward shifts in the energy dispersion. The anomalies in the energy subbands give rise to the oscillation patterns in the ballistic conductance, and the energy shifts bring about the shift in the peak positions of optical absorption coefficients and refractive index changes.
Double-slit experiment with single wave-driven particles and its relation to quantum mechanics
DEFF Research Database (Denmark)
Andersen, Anders Peter; Madsen, Jacob; Reichelt, Christian Günther
2015-01-01
even though it is possible to determine unambiguously which slit the walking droplet passes. Here we argue, however, that the single-particle statistics in such an experiment will be fundamentally different from the single-particle statistics of quantum mechanics. Quantum mechanical interference takes...... results, in particular the long and variable slit passage times of the droplets, cast strong doubt on the feasibility of the interference claimed by Couder and Fort. To understand theoretically the limitations of wave-driven particle systems as analogs to quantum mechanics, we introduce a Schro......¨dinger equation with a source term originating from a localized particle that generates a wave while being simultaneously guided by it. We show that the ensuing particle-wave dynamics can capture some characteristics of quantum mechanics such as orbital quantization. However, the particle-wave dynamics can...
de Bianchi, Massimiliano Sassoli
2012-01-01
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 e...
de Bianchi, Massimiliano Sassoli
2013-03-01
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.
Energy Technology Data Exchange (ETDEWEB)
Balagula, R. M., E-mail: rmbal@spbstu.ru; Vinnichenko, M. Ya., E-mail: mvin@spbstu.ru; Makhov, I. S.; Firsov, D. A.; Vorobjev, L. E. [Peter the Great Saint-Petersburg Polytechnic University (Russian Federation)
2016-11-15
The effect of a lateral electric field on the mid-infrared absorption and interband photoluminescence spectra in double tunnel-coupled GaAs/AlGaAs quantum wells is studied. The results obtained are explained by the redistribution of hot electrons between quantum wells and changes in the space charge in the structure. The hot carrier temperature is determined by analyzing the intersubband light absorption and interband photoluminescence modulation spectra under strong lateral electric fields.
Spin-orbit effects in carbon-nanotube double quantum dots
DEFF Research Database (Denmark)
Weiss, S; Rashba, E I; Kuemmeth, Ferdinand
2010-01-01
between the dots. For the two-electron regime, the detailed structure of the spin-orbit split energy spectrum is investigated as a function of detuning between the quantum dots in a 22-dimensional Hilbert space within the framework of a single-longitudinal-mode model. We find a competing effect...
Suppression of Zeeman Gradients by Nuclear Polarization in Double Quantum Dots
Frolov, S.M.; Danon, J.; Nadj-Perge, S.; Zuo, K.; Van Tilburg, J.W.W.; Pribiag, V.S.; Van den Berg, J.W.G.; Bakkers, E.P.A.M.; Kouwenhoven, L.P.
2012-01-01
We use electric dipole spin resonance to measure dynamic nuclear polarization in InAs nanowire quantum dots. The resonance shifts in frequency when the system transitions between metastable high and low current states, indicating the presence of nuclear polarization. We propose that the low and the
Peguiron, J.
1997-01-01
In this thesis, ratchet systems operating in the quantum regime are investigated. Ratchet systems, also known as Brownian motors, are periodic systems presenting an intrinsic asymmetry which can be exploited to extract work out of unbiased forces. As a model for ratchet systems, we consider the motion of a particle in a one-dimensional periodic and asymmetric potential, interacting with a thermal environment, and subject to an unbiased driving force. In quantum ratchets, intrinsic quantum flu...
Double quantum 1H MAS NMR studies of hydrogen-bonded protons and water dynamics in materials.
Alam, Todd M; Nyman, May; McIntyre, Sarah K
2007-03-15
Two-dimensional double quantum (DQ) 1H MAS NMR was used to investigate different proton environments in a series of alkali (Na, K, Rb, Cs) [Nb6O19]8- Lindqvist salts, with the water and hydrogen-bound intercluster protons being clearly resolved. Through the analysis of the DQ 1H NMR spinning sideband pattern, it is possible to extract both the mean and distribution of the motionally averaged intramolecular homonuclear 1H-1H dipolar coupling for the different water environments and the intercluster protons. Motional order parameters for the water environments were then calculated from the averaged dipolar couplings. The influence of additional intermolecular dipolar couplings due to multispin interactions were simulated and discussed.
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.
DEFF Research Database (Denmark)
Timofeev, V.B.; Larionov, A.V.; Ioselevich, A.S.
1998-01-01
The interwell radiative recombination from biased double quantum wells (DQW) in pin GaAs/AlGaAs heterostructures is investigated at different temperatures and external electrical fields. The luminescence line of interwell recombination of spatially separated electron-hole pairs exhibits systemati...
Phase diagram of a two-dimensional liquid in GaAs/AlxGa1-xAs biased double quantum wells
DEFF Research Database (Denmark)
Timofeev, V. B.; Larionov, A. V.; Alessi, M. G.
2000-01-01
Photoluminescence (PL) and PL excitation (PLE) measurements have been performed in GaAs/AlxGa1-xAs biased double quantum well heterostructures. The recombination of electrons, e, with holes, h, located in the same or in two adjacent wells, has been investigated for different exciting power...
Electron-nuclear interaction in 13C nanotube double quantum dots
DEFF Research Database (Denmark)
Churchill, H O H; Bestwick, A J; Harlow, J W
2009-01-01
For coherent electron spins, hyperfine coupling to nuclei in the host material can either be a dominant source of unwanted spin decoherence or, if controlled effectively, a resource enabling storage and retrieval of quantum information. To investigate the effect of a controllable nuclear environm......For coherent electron spins, hyperfine coupling to nuclei in the host material can either be a dominant source of unwanted spin decoherence or, if controlled effectively, a resource enabling storage and retrieval of quantum information. To investigate the effect of a controllable nuclear...... processing and memory: the 13C nuclei differ from those in the substrate, are naturally confined to one dimension, lack quadrupolar coupling and have a readily controllable concentration from less than one to 10^5 per electron....
Energy Technology Data Exchange (ETDEWEB)
Vernek, E. [Instituto de Física, Universidade Federal de Uberlândia, Uberlândia, MG 38400-902 (Brazil); Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos-SP 13560-970 (Brazil); Büsser, C. A. [Department of Physics and Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München, D-80333 München (Germany); Anda, E. V. [Departamento de Física, Pontifícia Universidade Católica, Rio de Janeiro-RJ (Brazil); Feiguin, A. E. [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Martins, G. B., E-mail: martins@oakland.edu [Department of Physics, Oakland University, Rochester, Michigan 48309 (United States); Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)
2014-03-31
A double quantum dot device, connected to two channels that only interact through interdot Coulomb repulsion, is analyzed using the numerical renormalization group technique. Using a two-impurity Anderson model, and realistic parameter values [S. Amasha, A. J. Keller, I. G. Rau, A. Carmi, J. A. Katine, H. Shtrikman, Y. Oreg, and D. Goldhaber-Gordon, Phys. Rev. Lett. 110, 046604 (2013)], it is shown that, by applying a moderate magnetic field and independently adjusting the gate potential of each quantum dot at half-filling, a spin-orbital SU(2) Kondo state can be achieved where the Kondo resonance originates from spatially separated parts of the device. Our results clearly link this spatial separation effect to currents with opposing spin polarizations in each channel, i.e., the device acts as a spin filter. In addition, an experimental probe of this polarization effect is suggested, pointing to the exciting possibility of experimentally probing the internal structure of an SU(2) Kondo state.
Generation of vector beams using a double-wedge depolarizer: Non-quantum entanglement
Samlan, C. T.; Viswanathan, Nirmal K.
2016-07-01
Propagation of horizontally polarized Gaussian beam through a double-wedge depolarizer generates vector beams with spatially varying state of polarization. Jones calculus is used to show that such beams are maximally nonseparable on the basis of even (Gaussian)-odd (Hermite-Gaussian) mode parity and horizontal-vertical polarization state. The maximum nonseparability in the two degrees of freedom of the vector beam at the double wedge depolarizer output is verified experimentally using a modified Sagnac interferometer and linear analyser projected interferograms to measure the concurrence 0.94±0.002 and violation of Clauser-Horne-Shimony-Holt form of Bell-like inequality 2.704±0.024. The investigation is carried out in the context of the use of vector beams for metrological applications.
Iontsev, M. A.; Mukhin, S. I.; Fistul, M. V.
2016-01-01
We report a theoretical study of ac response of superconducting quantum metamaterials (SQMs), i.e. an array of qubits (two-levels system) embedded in the low-dissipative resonator. By making use of a particular example of SQM, namely the array of charge qubits capacitively coupled to the resonator, we obtain a second-order phase transition between an incoherent (the high-temperature phase) and coherent (the low-temperatures phase) states of photons. This phase transition in many aspects resem...
Asymmetry of single-particle hole states in a strained Ge/Si double quantum dot
Yakimov, A. I.; Bloshkin, A. A.; Dvurechenskii, A. V.
2008-10-01
A six-band kṡp formalism was used to study single-particle hole states of two vertically aligned pyramidal Ge quantum dots embedded in Si and separated by a distance tSi . The elastic strain due to the lattice mismatch between Ge and Si was included into the problem via Bir-Pikus Hamiltonian. The three-dimensional spatial strain distribution was obtained by finite element method. We found that at small interdot separation (tSi3.5nm , σAS becomes the ground state of the system, replacing σS .
DPS in CGC: Double Quark Production and Effects of Quantum Statistics
Kovner, Alex; Rezaeian, Amir H.
2017-01-01
We consider forward inclusive production of two quarks in the high energy p-A collisions in the CGC formalism. We demonstrate that the production cross-section is determined by the convolution of the proton generalized double transverse momentum-dependent distribution (2GTMD) functions with two independent eikonal scattering amplitudes: the product of two dipoles and a quadrupole. We explicitly demonstrate that the quadrupole amplitude term accounts for all the (initial and final state) effec...
Chen, Zhangjin; Liang, Yaqiu; Lin, C D
2010-06-25
Based on the full quantal recollision model and field-free electron impact ionization theory, we calculate the correlated momentum spectra of the two outgoing electrons in strong field nonsequential double ionization (NSDI) of helium to compare with recent experiments. By analyzing the relative strength of binary versus recoil collisions exhibited in the photoelectron spectra, we confirm that the observed fingerlike structure in the experiment is a consequence of the Coulomb interaction between the two emitted electrons. Our result supports the recollision mechanism of strong field NSDI at the most fundamental level.
Tiutiunnyk, A.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. M.; Restrepo, R. L.; Ungan, F.; Martínez-Orozco, J. C.; Kasapoglu, E.; Duque, C. A.
2017-02-01
In this work we shall present a study of inelastic light scattering involving inter-subband electron transitions in coupled GaAs-(Ga,Al)As quantum wells. Calculations include the electron related Raman differential cross section and Raman gain. The effects of an external nonresonant intense laser field are used in order to tune these output properties. The confined electron states will be described by means of a diagonalization procedure within the effective mass and parabolic band approximations. It is shown that the application of the intense laser field can produce values of the intersubband electron Raman gain above 400 cm-1. The system proposed here is an alternative choice for the development of AlxGa1-xAs semiconductor laser diodes that can be tuned via an external nonresonant intense laser field.
Senokos, E.; Reguero, V.; Palma, J.; Vilatela, J. J.; Marcilla, Rebeca
2016-02-01
In this work we present a combined electrochemical and mechanical study of mesoporous electrodes based on CNT fibres in the context of electric double layer capacitors. We show that through control of the synthetic and assembly processes of the fibres, it is possible to obtain an active material that combines a surface area of 250 m2 g-1, high electrical conductivity (3.5 × 105 S m-1) and mechanical properties in the high-performance range including toughness (35 J g-1) comparable to that of aramid fibre (e.g. Kevlar). These properties are a consequence of the predominant orientation of the CNTs, observed by wide- and small-angle X-ray diffraction, and to the exceptionally long CNT length on the millimetre scale. Cyclic voltammetry measurements in a three-electrode configuration and using 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR14TFSI) ionic liquid electrolyte, show that the CNT fibres have a large quantum capacitance, evidenced by the near linear dependence of geometric capacitance (and conductivity) on potential bias. This reflects the low dimensionality of the CNT building blocks, which were purposely synthesised to have 1-5 layers and a high degree of graphitization. From the charge-discharge measurements of supercapacitor devices with symmetric CNT fibre electrodes we obtain power and energy densities as high as 58 kW kg-1 and 14 Wh kg-1, respectively. These record-high values for CNT fibre-based supercapacitors, are a consequence of the low equivalent series resistance due to the high conductivity of the fibres, the large contribution from quantum capacitance, and the wide stability window of the ionic liquid (3.5 V). Cycle life experiments demonstrate stable capacitance and energy retention over 10 000 cycles of charge-discharge at 3.5 V.In this work we present a combined electrochemical and mechanical study of mesoporous electrodes based on CNT fibres in the context of electric double layer capacitors. We show that through
Energy Technology Data Exchange (ETDEWEB)
Atanasov, Atanas Todorov, E-mail: atanastod@abv.bg [Department of Physics and Biophysics, Faculty of Medicine, Trakia University, 11 Armeiska Str., 6000 Stara Zagora (Bulgaria)
2014-10-06
The scaling of physical and biological characteristics of the living organisms is a basic method for searching of new biophysical laws. In series of previous studies the author showed that in Poikilotherms, Mammals and Aves, the volume to surface ratio V×S{sup −1} (m) of organisms is proportional to their generation time T{sub gt}(s) via growth rate v (m s{sup −1}): V×S{sup −1} = v{sub gr}×T{sup r}. The power and the correlation coefficients are near to 1.0. Aim of this study is: i) to prove with experimental data the validity of the above equation for Unicellular organisms and ii) to show that perhaps, the cells are quantum-mechanical systems. The data for body mass M (kg), density ρ (kg/m{sup 3}), minimum and maximum doubling time T{sub dt} (s) for 50 unicellular organisms are assembled from scientific sources, and the computer program ‘Statistics’ is used for calculations. In result i) the analytical relationship from type: V×S{sup −1} = 4.46⋅10{sup −11}×T{sub dt} was found, where v{sub gr} = 4.46×10{sup −11} m/s and ii) it is shown that the products between cell mass M, cell length expressed by V/S ratio and growth rate v{sub gr} satisfied the Heisenberg uncertainty principle i.e. the inequalities V/S×M×v{sub gr}>h/2π and T{sub dt}×M×v{sub gr}{sup 2}>h/2π are valid, where h= 6.626×10{sup −34} J⋅s is the Planck constant. This rise the question: do cells appear quantum-mechanical systems?.
Korsch, H J
2003-01-01
The complex energy resonances of a double delta potential well in a constant (Stark) field are studied. Varying the two system parameters (well distance and field strength) we investigate the behaviour of the resonance energies and wavefunctions both analytically and numerically. Different crossing scenarios for the real and imaginary parts of two resonance energies are observed and compared with a simple two-state model. In addition, a point in parameter space where both the real and imaginary parts of the two energies degenerate, an exceptional point, is found. Varying the system parameters around this exceptional point, the behaviour of energies and wavefunctions is discussed and the corresponding geometric phases, or Berry phases, for this non-Hermitian system are considered.
Malon, Michal; Pandey, Manoj Kumar; Nishiyama, Yusuke
2017-08-31
1H double quantum (DQ)/1H single quantum (SQ) correlation solid-state NMR spectroscopy is widely used to obtain internuclear 1H-1H proximities, especially at fast magic-angle spinning (MAS) rate (>60 kHz). However, to date, 1H signals are not well-resolved because of intense 1H-1H homonuclear dipolar interactions even at the attainable maximum MAS frequencies of ∼100 kHz and/or under 1H-1H homonuclear dipolar decoupling irradiations. Here we introduce novel three-dimensional (3D) experiments to resolve the 1H DQ/1H SQ correlation peaks using the additional 13C dimension. Although the low natural abundance of 13C (1.1%) significantly reduces the sensitivities, the 1H indirect measurements alleviate this issue and make this experiment possible even in naturally abundant samples. The two different implementations of 13C/1H DQ/1H SQ correlations and 1H DQ/13C/1H SQ correlations are discussed and demonstrated using l-histidine·HCl·H2O at natural abundance to reveal the local 1H-1H networks near each 13C. In addition, the complete 1H resonance assignments are achieved from a single 3D 13C/1H DQ/1H SQ experiment. We have also demonstrated the applicability of our proposed method on a biologically relevant molecule, capsaicin.
Minimal asymmetric dark matter
Directory of Open Access Journals (Sweden)
Sofiane M. Boucenna
2015-09-01
Full Text Available In the early Universe, any particle carrying a conserved quantum number and in chemical equilibrium with the thermal bath will unavoidably inherit a particle–antiparticle asymmetry. A new particle of this type, if stable, would represent a candidate for asymmetric dark matter (DM with an asymmetry directly related to the baryon asymmetry. We study this possibility for a minimal DM sector constituted by just one (generic SU(2L multiplet χ carrying hypercharge, assuming that at temperatures above the electroweak phase transition an effective operator enforces chemical equilibrium between χ and the Higgs boson. We argue that limits from DM direct detection searches severely constrain this scenario, leaving as the only possibilities scalar or fermion multiplets with hypercharge y=1, preferentially quintuplets or larger SU(2 representations, and with a mass in the few TeV range.
Energy Technology Data Exchange (ETDEWEB)
Lopez, S.Y. [Grupo de Educacion en Ciencias Experimentales y Matematicas-GECEM, Facultad de Educacion, Universidad de Antioquia, AA 1226 Medellin (Colombia); Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, CP 62209, Cuernavaca, Morelos (Mexico); Duque, C.A., E-mail: cduque@fisica.udea.edu.c [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia)
2009-12-15
The photoluminescence energy transitions in GaAs-Ga{sub 1-x}Al{sub x}As coupled double quantum wells are presented by considering the simultaneous effects of applied electric and magnetic fields and hydrostatic pressure. Calculations have been made in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electric field is taken to be oriented along the growth direction of the heterostructure whereas for the magnetic field both in-plane and in-growth directions have been considered. The results show that the hydrostatic pressure and the applied electric field are two useful tools to tune the direct and indirect exciton transitions in such heterostructures. Our results are in good agreement with previous experimental findings in double quantum wells under applied electric field and hydrostatic pressure.
Donor states in a semimagnetic Cd1 -xinMnxin Te /Cd1 -xoutMnxout Te Double Quantum Well
Kalpana, Panneer Selvam; Nithiananthi, Perumal; Jayakumar, Kalyanasundaram
2017-02-01
The theoretical investigation has been carried out on the binding energy of donor associated with the electrons confined in a Cd1 -xinMnxin Te /Cd1 -xoutMnxout Te Double Quantum Well (DQW) as a function of central barrier width for various well dimensions and impurity locations in the barrier and the well. The magnetic field can act as a tool to continuously change the interwell coupling inside this DQW systems and its effect on donor binding has also been studied. Moreover, the polaronic corrections, which is due to the strong exchange interaction between the magnetic moment of Mn2+ ion and the spin of the confined carrier, to the binding energy of the hydrogenic donor impurity has also been estimated with and without the application of magnetic field. The binding energy of the donor impurity is determined by solving the Schrodinger equation variationally in the effective mass approximation and the effect due to Bound Magnetic Polaron (BMP) is included using mean field theory with the modified Brillouin function. The results are reported and discussed.
Naumova, Anna; Tschierske, Carsten; Saalwächter, Kay
In recent years, the analysis of proton double-quantum NMR build-up curves has become an important tool to quantify anisotropic mobility in different kinds of soft materials such as polymer networks or liquid crystals. In the former case, such data provides a measure of orientation-dependent residual (time-averaged) dipolar couplings arising from anisotropic segmental motions, informing about the length and the state of local stretching of the network chains. Previous studies of macroscopically ordered, i.e. stretched, networks were subject to the limitation that a detailed build-up curve analysis on the basis of a universal "Abragam-like" (A-l) build-up function valid for a proton multi-spin system was only possible for an isotropic orientation-averaged response. This situation is here remedied by introducing a generic orientation-dependent build-up function for an anisotropically mobile protonated molecular segment. We discuss an application to the modeling of data for a stretched network measured at different orientations with respect to the magnetic field, and present a validation by fitting data of different liquid-crystal molecules oriented in the magnetic field. Copyright © 2017 Elsevier Inc. All rights reserved.
Nayak, Chittaranjan; Aghajamali, Alireza; Saha, Ardhendu
2017-11-01
Theoretically, the transmission properties of a symmetric double-negative metamaterial one-dimensional photonic crystal containing an extrinsic random layer thickness magnetized cold plasma photonic quantum-well defect structure have been investigated. From the numerical results performed by characteristics matrix method, it is found that, such type of structure possesses a transmission peak within the zero-nbar gap. To design a tunable microwave filter, the effects of many parameters such as randomness of layer thickness of the multilayer defect in terms of standard deviation (σ), strength of external magnetic field (B) and electron density of magnetized cold plasma (ne) on transmission peak is discussed. Our findings show that the histogram for the central frequency of the transmission peaks becomes wider with respect to smaller values of σ. In addition, in the case of B, our investigations also reveal that the histogram shifts to the higher frequency range and vice versa while considering the case of ne . These findings help to design a tunable filter for different microwave applications.
Cheng, Qifa; Xu, Jing; Wang, Tao; Fan, Ling; Ma, Ruifang; Yu, Xinzhi; Zhu, Jian; Xu, Zhi; Lu, Bingan
2017-11-01
Photoelectrocatalysis (PEC) has been demonstrated as a promising technique for hydrogen production. However, the high over-potential and high recombination rate of photo-induced electron-hole pairs lead to poor hydrogen production efficiency. In order to overcome these problems, TiO2 and Au dual quantum dots (QDs) on three-dimensional graphene flowers (Au@TiO2@3DGFs) was synthesized by an electro-deposition strategy. The combination of Au and TiO2 modulates the band gap of TiO2, shifts the absorption to visible lights and improves the utilization efficiency of solar light. Simultaneously, the size-quantization TiO2 on 3DGFs not only achieves a larger specific surface area over conventional nanomaterials, but also promotes the separation of the photo-induced electron-hole pairs. Besides, the 3DGFs as a scaffold for QDs can provide more active sites and stable structure. Thus, the newly-developed Au@TiO2@3DGFs composite exhibited an impressive PEC activity and excellent durability. Under -240 mV potential (vs. RHE), the photoelectric current density involved visible light illumination (100 mW cm-2) reached 90 mA cm-2, which was about 3.6 times of the natural current density (without light, only 25 mA cm-2). It worth noting that the photoelectric current density did not degrade and even increased to 95 mA cm-2 over 90 h irradiation, indicating an amazing chemical stability.
González-Fernández, J. V.; Herrera-Jasso, R.; Ulloa-Castillo, N. A.; Ortega-Gallegos, J.; Castro-García, R.; Lastras-Martínez, L. F.; Lastras-Martínez, A.; Balderas-Navarro, R. E.; Mozume, T.; Gozu, S.
2016-12-01
We report on photoreflectance anisotropy (PRA) spectroscopy of InGaAs/AlAs/AlAsSb coupled double quantum wells (CDQWs) with extremely thin coupling AlAs barriers grown by molecular beam epitaxy (MBE), with no intentional doping. By probing the in-plane interfacial optical anisotropies (OAs), it is shown that PRA spectroscopy has the ability to detect and distinguish semiconductor layers with quantum dimensions, as the anisotropic photoreflectance (PR) signal stems entirely from buried quantum wells (QWs). In order to account for the experimental PRA spectra, a theoretical model at k = 0, based on a linear electro-optic effect through a piezoelectric shear strain, has been employed to quantify the internal electric fields across the QWs. The dimensionalities of the PR lineshapes were tested by using reciprocal (Fourier) space analysis. Such a complementary test is used in order to correctly employ the PRA model developed here.
Hwang, Won Young; Koh, In Gyu; Han, Yeong Deok
1997-01-01
We show that a secure quantum protocol for coin tossing exist. The existence of quantum coin tossing support the conjecture of D.Mayers [Phys.Rev.Lett. 78, 3414(1997)] that only asymmetrical tasks as quantum bit commitment are impossible.
Torchynska, T. V.; Casas Espinola, J. L.; Jaramillo Gómez, J. A.; Douda, J.; Gazarian, K.
2013-06-01
Double core CdSeTe/ZnS quantum dots (QDs) with emission at 800 nm (1.60 eV) have been studied by photoluminescence (PL) and Raman scattering methods in the non-conjugated state and after the conjugation to the Pseudo rabies virus (PRV) antibodies. The transformation of PL spectra, stimulated by the electric charge of antibodies, has been detected for the bioconjugated QDs. Raman scattering spectra are investigated with the aim to reveal the CdSeTe core compositions. The double core QD energy diagrams were designed that help to analyze the PL spectra and their transformation at the bioconjugation. It is revealed that the interface in double core QDs has the type II quantum well character that permits to explain the near IR optical transition (1.60 eV) in the double core QDs. It is shown that the essential transformation of PL spectra is useful for the study of QD bioconjugation with specific antibodies and can be a powerful technique in early medical diagnostics.
Energy Technology Data Exchange (ETDEWEB)
Yablonsky, A. N., E-mail: yablonsk@ipmras.ru; Zhukavin, R. Kh.; Bekin, N. A.; Novikov, A. V.; Yurasov, D. V.; Shaleev, M. V. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)
2016-12-15
For SiGe/Si(001) epitaxial structures with two nonequivalent SiGe quantum wells separated by a thin Si barrier, the spectral and time characteristics of interband photoluminescence corresponding to the radiative recombination of excitons in quantum wells are studied. For a series of structures with two SiGe quantum wells different in width, the characteristic time of tunneling of charge carriers (holes) from the narrow quantum well, distinguished by a higher exciton recombination energy, to the wide quantum well is determined as a function of the Si barrier thickness. It is shown that the time of tunneling of holes between the Si{sub 0.8}5Ge{sub 0.15} layers with thicknesses of 3 and 9 nm steadily decreases from ~500 to <5 ns, as the Si barrier thickness is reduced from 16 to 8 nm. At intermediate Si barrier thicknesses, an increase in the photoluminescence signal from the wide quantum well is observed, with a characteristic time of the same order of magnitude as the luminescence decay time of the narrow quantum well. This supports the observation of the effect of the tunneling of holes from the narrow to the wide quantum well. A strong dependence of the tunneling time of holes on the Ge content in the SiGe layers at the same thickness of the Si barrier between quantum wells is observed, which is attributed to an increase in the effective Si barrier height.
On New Phenomena of Photon from Modified Double Slit Experiment
Liu, Haisheng
2011-03-01
A modified double slit experiment of light was implemented. In the experiment, a spatial shape filter is used to manipulate the shape of cross section of laser beam. When this modified laser beam was shined on the double slit, the intensity distribution of laser beam on double slit is asymmetrical. In this way, the laser light was directed to pass through only one or two slits of double slit in different sections. So the which-way information is predetermined before the photons pass through the slits. At the same time, the visible interference pattern can be observed on a monitor screen after the double slit. A couple of new phenomena had been observed from this experiment. The results of this experiment raise questions about Wave-Particle Duality model of quantum theory, which is the foundation for the Copenhagen explanation that is generally regarded as the principal interpretation of quantum theory. As the observed properties from this experiment cannot be fully explained using the quantum theory, especially the Copenhagen explanation, a new model of photon is proposed. The new model for photon should be also applicable to all other micro entities, according to L. de Broglie assumption.
2006-11-01
that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy
Charged excitonic complexes in GaAs/Al0.35Ga0.65As p-i-n double quantum wells
DEFF Research Database (Denmark)
Timofeev, V. B.; Larionov, A. V.; Alessi, M. Grassi
1999-01-01
Photoluminescence (PL) and PL excitation measurements (PLE) have been performed in GaAs/AlxGa1-xAs double quantum well (QW) structures under different applied electric fields. An emission due to charged excitons (trions) has been identified in the PL spectra similar to 3 meV below the heavy-hole ......, as shown by (i) an analysis of the PL polarization for resonant excitation of the heavy- and the light-exciton ground state, and (ii) the analysis of the Zeeman effect for the trion PL band in the Faraday geometry, i.e., for a magnetic field normal to the QW's....
Tsai, Chia-Lung; Chen, Yen-Jen
2015-10-19
The feasibility of using InGaN LEDs grown with asymmetric barrier layer (ABL) as transmitters in visible light communications is investigated experimentally. Compared with normal LEDs, the improvement in the spontaneous emission rate due to enhanced carrier localization and better uniformity of carrier distribution in ABL-containing MQWs leads to the fabricated LEDs can exhibit a 32.6% (@ 350 mA) increase in emission intensity and a 10.5% increase in modulation bandwidth. After eliminating the slow-responding phosphorescent components emitting from the phosphor-converted white LEDs, an open eye-diagram at 180 Mb/s is demonstrated over a distance of 100 cm in directed line-of-sight optical links. With the use of proposed LEDs, real-time transmissions of digital TV signals over a moderate distance (~100 cm) in free space is shown to be available in a 150 Mbit/s white LED-based optical link with conventional on-off keying modulation.
Eliav, Uzi; Komlosh, Michal E; Basser, Peter J; Navon, Gil
2014-01-01
To test the potential of combining double quantum and magnetization transfer filtered ultra-short echo time (DQF-MT-UTE) MRI to obtain information about the macromolecular composition and characteristics of connective tissues. A DQF-MT-UTE pulse sequence was implemented on a 14.1 T AVANCE III Bruker spectrometer equipped with a Bruker micro2.5-imaging gradient system to obtain images of porcine annulus fibrosus. The DQF-MT-UTE MRI of the annulus fibrosus of porcine intervertebral disc, where the creation time of the double quantum coherence filtering (DQF) was on a time scale appropriate for excitation of macromolecules, showed stronger signal from the outer layers of the disc than from the inner layers closer to the nucleus pulposus. Similarly, spectroscopic studies showed the same trend in the efficiency of the magnetization transfer (MT) from collagen to water. DQF-MT filtered UTE MRI of the annulus fibrosus provides new contrast parameters that depend on the concentration of the collagen and on the rate and efficiency of MT of its protons to water. The latter parameters appear to be different for collagen types I and II in the annulus fibrosus. Copyright © 2013 Wiley Periodicals, Inc.
Eliav, Uzi; Komlosh, Michal E.; Basser, Peter J.; Navon, Gil
2013-01-01
Purpose To test the potential of combining double quantum and magnetization transfer filtered ultra-short echo time (DQF-MT-UTE) MRI to obtain information about the macromolecular composition and characteristics of connective tissues. Methods A DQF-MT-UTE pulse sequence was implemented on a 14.7T AVANCE III Bruker spectrometer equipped with a Bruker micro2.5-imaging gradient system to obtain images of porcine annulus fibrosus. Results The DQF-MT-UTE MRI of the annulus fibrosus of porcine intervertebral disc, where the creation time of the double quantum coherence filtering (DQF) was on a time scale appropriate for excitation of macromolecules, showed stronger signal from the outer layers of the disc than from the inner layers closer to the nucleus pulposus. Similarly, spectroscopic studies showed the same trend in the efficiency of the magnetization transfer (MT) from collagen to water. Conclusion DQF-MT filtered UTE MRI of the annulus fibrosus provides new contrast parameters that depend on the concentration of the collagen and on the rate and efficiency of MT of its protons to water. The latter parameters appear to be different for collagen types I and II in the annulus fibrosus. PMID:23413021
Persistent photoeffects in p-i-n GaAs/AlGaAs heterostructures with double quantum wells
DEFF Research Database (Denmark)
Dorozhkin, S.I.; Timofeev, V.B.; Hvam, Jørn Märcher
2001-01-01
Abrupt changes in the capacitance between the p and n regions were observed in a planar p-i-n GaAs/AlGaAs heterostructure with two tunneling-coupled quantum wells exposed to laser irradiation (lambda = 633 nm). These changes can be caused by variations in both temperature (in the vicinity of T si...
Energy Technology Data Exchange (ETDEWEB)
Yablonsky, A. N., E-mail: yablonsk@ipm.sci-nnov.ru; Morozov, S. V.; Gaponova, D. M.; Aleshkin, V. Ya. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation); Shengurov, V. G.; Zvonkov, B. N.; Vikhrova, O. V.; Baidus’, N. V. [Lobachevsky State University of Nizhny Novgorod (Russian Federation); Krasil’nik, Z. F. [Russian Academy of Sciences, Institute for Physics of Microstructures (Russian Federation)
2016-11-15
We report the observation of stimulated emission in heterostructures with double InGaAs/GaAsSb/GaAs quantum wells, grown on Si(001) substrates with the application of a relaxed Ge buffer layer. Stimulated emission is observed at 77 K under pulsed optical pumping at a wavelength of 1.11 μm, i.e., in the transparency range of bulk silicon. In similar InGaAs/GaAsSb/GaAs structures grown on GaAs substrates, room-temperature stimulated emission is observed at 1.17 μm. The results obtained are promising for integration of the structures into silicon-based optoelectronics.
Shepherd, James J; Scuseria, Gustavo E
2016-01-01
Over the past few years pair coupled cluster doubles (pCCD) has shown promise for the description of strong correlation. This promise is related to its apparent ability to match results from doubly occupied configuration interaction (DOCI), even though the latter method has exponential computational cost. Here, by modifying the full configuration interaction quantum Monte Carlo (FCIQMC) algorithm to sample only the seniority zero sector of Hilbert space, we show that the DOCI and pCCD energies are in agreement for a variety of 2D Hubbard models, including for systems well out of reach for conventional configuration interaction algorithms. Our calculations are aided by the sign problem being much reduced in the seniority zero space compared with the full space. We present evidence for this, and then discuss the sign problem in terms of the wave function of the system which appears to have a simplified sign structure.
Energy Technology Data Exchange (ETDEWEB)
Majumdar, Amlan, E-mail: amajumd@us.ibm.com [IBM Research Division, T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States)
2015-05-28
We present first-principle analytical derivations and numerically modeled data to show that the gate capacitance per unit gate area C{sub G} of extremely thin undoped-channel single-gate and double-gate field-effect transistor geometries in the extreme quantum limit with single-subband occupancy can be written as 1/C{sub G} = 1/C{sub OX} + N{sub G}/C{sub DOS} + N{sub G}/ηC{sub WF}, where N{sub G} is the number of gates, C{sub OX} is the oxide capacitance per unit area, C{sub DOS} is the density-of-states capacitance per unit area, C{sub WF} is the wave function spreading capacitance per unit area, and η is a constant on the order of 1.
Energy Technology Data Exchange (ETDEWEB)
Miranda, Guillermo L. [Fisica Teorica y Aplicada, Escuela de Ingenieria de Antioquia, A.A. 7516 Medellin (Colombia); Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia); Mora-Ramos, Miguel E., E-mail: memora@uaem.mx [Fisica Teorica y Aplicada, Escuela de Ingenieria de Antioquia, A.A. 7516 Medellin (Colombia); Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209 Cuernavaca, Morelos (Mexico); Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia); Duque, Carlos A. [Instituto de Fisica, Universidad de Antioquia, AA 1226 Medellin (Colombia)
2013-01-15
In this work the variations of the exciton-related optical absorption and the change of the refractive index in a GaAs-(Ga,Al)As double quantum well as functions of the geometric parameters of the heterostructure are investigated. The variational method is applied within the framework of the parabolic band and effective mass approximations, in order to obtain the 1s-like exciton energy spectrum. The outcome for the related optical coefficients shows a quenched and redshifted light absorption as a result of the increment in the inner barrier and right-hand well widths, with the possibility of an enhancement of the excitonic contribution to the relative change in the refractive index.
Khordad, R.
2017-10-01
In this work, we analytically study the effects of the Rashba spin-orbit interaction (SOI) and magnetic field on energy levels and optical properties of a double ring-shaped quantum dot. For this purpose, we first solve the Schrödinger equation and obtain the energy eigenvalues and the wave functions. Then, we use analytical expressions for optical properties obtained by the compact-density matrix formalism. We calculate the total refractive index change and total absorption in the presence of applied magnetic field and Rashba SOI. It is found that the energy levels strongly depend on the combined effects of the Rashba SOI and the applied magnetic field. The energy levels split into two branches, spin-up and spin-down states, due to the Rashba spin-obit interaction. The peak positions of both optical properties shift towards higher energies with increasing the magnetic field and Rashba parameter.
Energy Technology Data Exchange (ETDEWEB)
Eslami, Leila, E-mail: Leslami@iust.ac.ir; Esmaeilzadeh, Mahdi, E-mail: mahdi@iust.ac.ir [Department of Physics, Iran University of Science and Technology, Tehran 16846 (Iran, Islamic Republic of)
2014-02-28
Spin-dependent electron transport in an open double quantum ring, when each ring is made up of four quantum dots and threaded by a magnetic flux, is studied. Two independent and tunable gate voltages are applied to induce Rashba spin-orbit effect in the quantum rings. Using non-equilibrium Green's function formalism, we study the effects of electron-electron interaction on spin-dependent electron transport and show that although the electron-electron interaction induces an energy gap, it has no considerable effect when the bias voltage is sufficiently high. We also show that the double quantum ring can operate as a spin-filter for both spin up and spin down electrons. The spin-polarization of transmitted electrons can be tuned from −1 (pure spin-down current) to +1 (pure spin-up current) by changing the magnetic flux and/or the gates voltage. Also, the double quantum ring can act as AND and NOR gates when the system parameters such as Rashba coefficient are properly adjusted.
Energy Technology Data Exchange (ETDEWEB)
Fan, Yao; Liu, Li; Sun, Donglei; Lan, Hanyue [The Modernization Engineering Technology Research Center of Ethnic Minority Medicine of Hubei Province, College of Pharmacy, South-Central University for Nationalities, Wuhan 430074 (China); Fu, Haiyan, E-mail: fuhaiyan@mail.scuec.edu.cn [The Modernization Engineering Technology Research Center of Ethnic Minority Medicine of Hubei Province, College of Pharmacy, South-Central University for Nationalities, Wuhan 430074 (China); Yang, Tianming, E-mail: tmyang@mail.scuec.edu.cn [The Modernization Engineering Technology Research Center of Ethnic Minority Medicine of Hubei Province, College of Pharmacy, South-Central University for Nationalities, Wuhan 430074 (China); She, Yuanbin, E-mail: sheyb@zjut.edu.cn [State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310032 (China); Ni, Chuang [The Modernization Engineering Technology Research Center of Ethnic Minority Medicine of Hubei Province, College of Pharmacy, South-Central University for Nationalities, Wuhan 430074 (China)
2016-04-15
As a popular detection model, the fluorescence “turn-off” sensor based on quantum dots (QDs) has already been successfully employed in the detections of many materials, especially in the researches on the interactions between pesticides. However, the previous studies are mainly focused on simple single track or the comparison based on similar concentration of drugs. In this work, a new detection method based on the fluorescence “turn-off” model with water-soluble ZnCdSe and CdSe QDs simultaneously as the fluorescent probes is established to detect various pesticides. The fluorescence of the two QDs can be quenched by different pesticides with varying degrees, which leads to the differences in positions and intensities of two peaks. By combining with chemometrics methods, all the pesticides can be qualitative and quantitative respectively even in real samples with the limit of detection was 2 × 10{sup −8} mol L{sup −1} and a recognition rate of 100%. This work is, to the best of our knowledge, the first report on the detection of pesticides based on the fluorescence quenching phenomenon of double quantum dots combined with chemometrics methods. What's more, the excellent selectivity of the system has been verified in different mediums such as mixed ion disruption, waste water, tea and water extraction liquid drugs. - Highlights: • A new model based on double QDs is established for pesticide residues detection. • The fluorescent data array sensor is coupled with chmometrics methods. • The sensor can be highly sensitive and selective detection in actual samples.
Fan, Yao; Liu, Li; Sun, Donglei; Lan, Hanyue; Fu, Haiyan; Yang, Tianming; She, Yuanbin; Ni, Chuang
2016-04-15
As a popular detection model, the fluorescence "turn-off" sensor based on quantum dots (QDs) has already been successfully employed in the detections of many materials, especially in the researches on the interactions between pesticides. However, the previous studies are mainly focused on simple single track or the comparison based on similar concentration of drugs. In this work, a new detection method based on the fluorescence "turn-off" model with water-soluble ZnCdSe and CdSe QDs simultaneously as the fluorescent probes is established to detect various pesticides. The fluorescence of the two QDs can be quenched by different pesticides with varying degrees, which leads to the differences in positions and intensities of two peaks. By combining with chemometrics methods, all the pesticides can be qualitative and quantitative respectively even in real samples with the limit of detection was 2 × 10(-8) mol L(-1) and a recognition rate of 100%. This work is, to the best of our knowledge, the first report on the detection of pesticides based on the fluorescence quenching phenomenon of double quantum dots combined with chemometrics methods. What's more, the excellent selectivity of the system has been verified in different mediums such as mixed ion disruption, waste water, tea and water extraction liquid drugs. Copyright © 2016 Elsevier B.V. All rights reserved.
The Schrödinger equation with friction from the quantum trajectory perspective.
Garashchuk, Sophya; Dixit, Vaibhav; Gu, Bing; Mazzuca, James
2013-02-07
Similarity of equations of motion for the classical and quantum trajectories is used to introduce a friction term dependent on the wavefunction phase into the time-dependent Schrödinger equation. The term describes irreversible energy loss by the quantum system. The force of friction is proportional to the velocity of a quantum trajectory. The resulting Schrödinger equation is nonlinear, conserves wavefunction normalization, and evolves an arbitrary wavefunction into the ground state of the system (of appropriate symmetry if applicable). Decrease in energy is proportional to the average kinetic energy of the quantum trajectory ensemble. Dynamics in the high friction regime is suitable for simple models of reactions proceeding with energy transfer from the system to the environment. Examples of dynamics are given for single and symmetric and asymmetric double well potentials.
Quantum Correlations Evolution Asymmetry in Quantum Channels
Li, Meng; Huang, Yun-Feng; Guo, Guang-Can
2017-03-01
It was demonstrated that the entanglement evolution of a specially designed quantum state in the bistochastic channel is asymmetric. In this work, we generalize the study of the quantum correlations, including entanglement and quantum discord, evolution asymmetry to various quantum channels. We found that the asymmetry of entanglement and quantum discord only occurs in some special quantum channels, and the behavior of the entanglement evolution may be quite different from the behavior of the quantum discord evolution. To quantum entanglement, in some channels it decreases monotonously with the increase of the quantum channel intensity. In some other channels, when we increase the intensity of the quantum channel, it decreases at first, then keeps zero for some time, and then rises up. To quantum discord, the evolution becomes more complex and you may find that it evolutes unsmoothly at some points. These results illustrate the strong dependence of the quantum correlations evolution on the property of the quantum channels. Supported by the National Natural Science Foundation of China under Grant Nos. 61327901, 61490711, 61225025, 11474268, and the Fundamental Research Funds for the Central Universities under Grant No. WK2470000018
Energy Technology Data Exchange (ETDEWEB)
Ngaojampa, C.; Nimmanpipug, P. [Computer Simulation and Modeling Laboratory (CSML), Department of Chemistry and Center for Innovation Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Yu, L.D., E-mail: yuld@fnrf.science.cmu.ac.t [Plasma and Beam Physics Research Facility, Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand); Anuntalabhochai, S. [Molecular Biology Laboratory, Department of Biology, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Lee, V.S., E-mail: vannajan@gmail.co [Computer Simulation and Modeling Laboratory (CSML), Department of Chemistry and Center for Innovation Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Si Ayutthaya Road, Bangkok 10400 (Thailand)
2011-02-15
In order to promote understanding of the fundamentals of ultra-low-energy ion interaction with DNA, molecular dynamics simulations using combined quantum-mechanics/molecular-mechanics of poly-AT and poly-GC A-DNA double strands irradiated by <200 eV carbon ions were performed to investigate the molecular implications of mutation bias. The simulations were focused on the responses of the DNA backbones and nitrogenous bases to irradiation. Analyses of the root mean square displacements of the backbones and non-hydrogen atoms of base rings of the simulated DNA structure after irradiation revealed a potential preference of DNA double strand separation, dependent on the irradiating energy. The results show that for the backbones, the large difference in the displacement between poly-GC and poly-AT in the initial time period could be the reason for the backbone breakage; for the nitrogenous base pairs, A-T is 30% more sensitive or vulnerable to ion irradiation than G-C, demonstrating a preferential, instead of random, effect of irradiation-induced mutation.
Asymmetric Divisions in Oogenesis.
Bilinski, Szczepan M; Kubiak, Jacek Z; Kloc, Malgorzata
In the majority of animals, the oocyte/egg is structurally, molecularly, and functionally asymmetric. Such asymmetry is a prerequisite for a flawless fertilization and faithful segregation of maternal determinants during subsequent embryonic development. The oocyte asymmetry develops during oogenesis and must be maintained during consecutive and obligatorily asymmetric oogonial divisions, which depending on the species lead to the formation of either oocyte alone or oocyte and nurse cell complex. In the following chapter, we summarize current knowledge on the asymmetric oogonial divisions in invertebrate (insects) and vertebrate (Xenopus) species.
Energy Technology Data Exchange (ETDEWEB)
Parani, Sundararajan [University of Madras, Department of Inorganic Chemistry (India); Bupesh, Giridharan [Bharath University, Central Research Laboratory, Sree Balaji Medical College and Hospital (India); Manikandan, Elayaperumal [Thiruvalluvar University, Department of Physics, TUCAS, Thennangur-604408 (India); Pandian, Kannaiyan [University of Madras, Department of Inorganic Chemistry (India); Oluwafemi, Oluwatobi Samuel, E-mail: oluwafemi.oluwatobi@gmail.com [University of Johannesburg, Department of Applied Chemistry (South Africa)
2016-11-15
Water-soluble, mercaptosuccinic acid (MSA)-capped CdTe/CdS/ZnS core/double shell quantum dots (QDs) were prepared by successive growth of CdS and ZnS shells on the as-synthesized CdTe/CdS{sub thin} core/shell quantum dots. The formation of core/double shell structured QDs was investigated by ultraviolet-visible (UV–Vis) absorption and photoluminescence (PL) spectroscopy, PL decay studies, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The core/double shell QDs exhibited good photoluminescence quantum yield (PLQY) which is 70% higher than that of the parent core/shell QDs, and they are stable for months. The average particle size of the core/double shell QDs was ∼3 nm as calculated from the transmission electron microscope (TEM) images. The cytotoxicity of the QDs was evaluated on a variety of cancer cells such as HeLa, MCF-7, A549, and normal Vero cells by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) cell viability assay. The results showed that core/double shell QDs were less toxic to the cells when compared to the parent core/shell QDs. MCF-7 cells showed proliferation on incubation with QDs, and this is attributed to the metalloestrogenic activity of cadmium ions released from QDs. The core/double shell CdTe/CdS/ZnS (CSS) QDs were conjugated with transferrin and successfully employed for the biolabeling and fluorescent imaging of HeLa cells. These core/double shell QDs are highly promising fluorescent probe for cancer cell labeling and imaging applications.
Larionov, A V; Hvam, J; Soerensen, K
2002-01-01
The time evolution and kinetics of the photoluminescence (PL) spectra of the interwall excitons under the pulse resonant excitation of the interwall excitons are studied in the GaAs/AlGaAs binary quantum well. It is established, that the collective exciton phase originates with the time delay relative to the exciting pulse (several nanoseconds), which is conditioned by the density and temperature relaxation to the equilibrium values.The origination of the collective phase of the interwall excitons is accompanied by the strong narrowing of the corresponding photoluminescence line, the superlinear growth of its intensity and large time of change in the degree of the circular polarization.The collective exciton phase originates at the temperatures < 6 K and the interwall excitons densities 3 x 10 sup 1 sup 0 cm sup - sup 2
Carrier mobility in double-helix DNA and RNA: A quantum chemistry study with Marcus-Hush theory.
Wu, Tao; Sun, Lei; Shi, Qi; Deng, Kaiming; Deng, Weiqiao; Lu, Ruifeng
2016-12-21
Charge mobilities of six DNAs and RNAs have been computed using quantum chemistry calculation combined with the Marcus-Hush theory. Based on this simulation model, we obtained quite reasonable results when compared with the experiment, and the obtained charge mobility strongly depends on the molecular reorganization and electronic coupling. Besides, we find that hole mobilities are larger than electron mobilities no matter in DNAs or in RNAs, and the hole mobility of 2L8I can reach 1.09 × 10 -1 cm 2 V -1 s -1 which can be applied in the molecular wire. The findings also show that our theoretical model can be regarded as a promising candidate for screening DNA- and RNA-based molecular electronic devices.
Energy Technology Data Exchange (ETDEWEB)
Lopes, E.M., E-mail: eldermantovani@yahoo.com.br [Departamento de Física, Química e Biologia, Universidade Estadual Paulista, C. P. 266, Presidente Prudente, São Paulo 17700-000 (Brazil); César, D.F. [Departamento de Física, Universidade Federal de São Carlos, C. P. 676, São Carlos, São Paulo (Brazil); Franchello, F.; Duarte, J.L.; Dias, I.F.L.; Laureto, E. [Departamento de Física, Universidade Estadual de Londrina, C. P. 6001, Londrina, Paraná (Brazil); Elias, D.C.; Pereira, M.V.M.; Guimarães, P.S.S. [Departamento de Física, Instituto de Ciências Exatas, Universidade Federal de Minas Gerais, C. P. 702, Belo Horizonte, Minas Gerais (Brazil); Quivy, A.A. [Laboratório de Novos Materiais Semicondutores, Instituto de Física, Universidade de São Paulo, C. P. 66318, São Paulo (Brazil)
2013-12-15
This paper discusses the theoretical and experimental results obtained for the excitonic binding energy (E{sub b}) in a set of single and coupled double quantum wells (SQWs and CDQWs) of GaAs/AlGaAs with different Al concentrations (Al%) and inter-well barrier thicknesses. To obtain the theoretical E{sub b} the method proposed by Mathieu, Lefebvre and Christol (MLC) was used, which is based on the idea of fractional-dimension space, together with the approach proposed by Zhao et al., which extends the MLC method for application in CDQWs. Through magnetophotoluminescence (MPL) measurements performed at 4 K with magnetic fields ranging from 0 T to 12 T, the diamagnetic shift curves were plotted and adjusted using two expressions: one appropriate to fit the curve in the range of low intensity fields and another for the range of high intensity fields, providing the experimental E{sub b} values. The effects of increasing the Al% and the inter-well barrier thickness on E{sub b} are discussed. The E{sub b} reduction when going from the SQW to the CDQW with 5 Å inter-well barrier is clearly observed experimentally for 35% Al concentration and this trend can be noticed even for concentrations as low as 25% and 15%, although the E{sub b} variations in these latter cases are within the error bars. As the Zhao's approach is unable to describe this effect, the wave functions and the probability densities for electrons and holes were calculated, allowing us to explain this effect as being due to a decrease in the spatial superposition of the wave functions caused by the thin inter-well barrier. -- Highlights: • Magnetophotoluminescence results from coupled double quantum wells are reported. • Theoretical and experimental values for excitonic binding energy (E{sub b}) are obtained. • The effects of increasing the inter-well barrier height and thickness on E{sub b} are discussed. • An E{sub b} reduction is observed when going from zero to the 5 Å inter-well barrier
Shadman, Abir; Rahman, Ehsanur; Khosru, Quazi D. M.
2017-11-01
To reduce the thermal budget and the short channel effects in state of the art CMOS technology, Junctionless field effect transistor (JLFET) has been proposed in the literature. Numerous experimental, modeling, and simulation based works have been done on this new FET with bulk materials for various geometries until now. On the other hand, the two-dimensional layered material is considered as an alternative to current Si technology because of its ultra-thin body and high mobility. Very recently few simulation based works have been done on monolayer molybdenum disulfide based JLFET mainly to show the advantage of JLFET over conventional FET. However, no comprehensive simulation-based work has been done for double gate JLFET keeping in mind the prominent transition metal dichalcogenides (TMDC) to the authors' best knowledge. In this work, we have studied quantum ballistic drain current-gate voltage characteristics of such FETs within non-equilibrium Green's function (NEGF) framework. Our simulation results reveal that all these TMDC materials are viable options for implementing state of the art Junctionless MOSFET with emphasis on their performance at short gate lengths. Besides evaluating the prospect of TMDC materials in the digital logic application, the performance of Junctionless Double Gate trilayer TMDC heterostructure FET for the label-free electrical detection of biomolecules in dry environment has been investigated for the first time to the authors' best knowledge. The impact of charge neutral biomolecules on the electrical characteristics of the biosensor has been analyzed under dry environment situation. Our study shows that these materials could provide high sensitivity in the sub-threshold region as a channel material in nano-biosensor, a trend demonstrated by silicon on insulator FET sensor in the literature. Thus, going by the trend of replacing silicon with these novel materials in device level, TMDC heterostructure could be a viable alternative to
Electrical and Optical Studies of Double Barrier Structures
White, Christopher Richard Hardy
Available from UMI in association with The British Library. Requires signed TDF. This thesis uses a combination of electrical and optical spectroscopy measurements to examine in detail the electronic properties of a series of n-type GaAs/(AlGa)As double barrier resonant tunnelling devices with relatively narrow well widths. The current-voltage characteristics show peak to alley ratios as high as 40:1. The application of a magnetic field parallel to the current flow produces magneto-oscillations in the transport properties which allow the sheet charge density in the accumulation layer to be determined. The sheet charge density in the quantum well is determined from the photoluminescence spectra measured in zero and finite magnetic field, with the magnetic field applied parallel to the current flow. The buildup of space charge in the quantum well in these structures leads to intrinsic bistability in the current and in the photoluminescence intensity. In an 'asymmetric' sample, with tunnel barriers of different widths, a new kind of bistability is observed, in which the off-resonance current exceeds the on-resonance current. Electroluminescence is observed in this asymmetric sample when it is operated at high voltages. The electroluminescence is a result of the recombination between electrons and holes, where the holes have been created by high energy electrons undergoing impact ionisation in the high field collector region of the device. The careful analysis of the electroluminescence intensity allows us to deduce the electron impact ionisation coefficient in GaAs at 4.2K. The electroluminescence shows a very pronounced hysteresis and corresponds to a new type of optoelectronic bistability. A symmetric sample, with tunnel barriers of equal width, which has a 'window' layer in the region between the double barriers and the top electrical contact has been investigated. The window layer is a region of material whose bandgap is greater than the quantum well recombination
Yan, Yun-Jing; He, Xi-Wen; Li, Wen-You; Zhang, Yu-Kui
2017-05-15
A novel fluorescent sensor nitrogen-doped graphene quantum dots (N-GQDs)/SiO 2 /molecular imprinting polymer（N-GQDs/SiO 2 /MIP）was fabricated by surface imprinting and epitope imprinting to recognize and detect the target protein cytochrome c (Cyt C) with fluorescence quenching. In the polymerization process, the C- and N-terminal nonapeptides of Cyt C were selected as the double templates which were fixed by functional monomer (zinc acrylate) through metal chelation and steady six-membered ring. The linear range of fluorescence quenching for this receptor towards Cyt C was 0.20-60μM, and the detection limit was 0.11μM. The precision for six times replicate determination of Cyt C at 30μM was 1.20%, and the imprinting factor (IF) was 3.06. The recoveries of the material to Cyt C in urine were 99.3-114.0%. In brief, this work proposed a strategy to prepare a new type fluorescent imprinting polymer based on N-GQDs and provided an attractive perspective for the detection of protein by using the combination of N-GQDs and molecular imprinting technique. Copyright © 2016 Elsevier B.V. All rights reserved.
Maruyoshi, Keisuke; Iuga, Dinu; Watts, Abigail E; Hughes, Colan E; Harris, Kenneth D M; Brown, Steven P
2017-11-01
The lower detection limit for 2 distinct crystalline phases by 1H magic-angle spinning (MAS) solid-state nuclear magnetic resonance (NMR) is investigated for a minority amount of cimetidine (anhydrous polymorph A) in a physical mixture with the anhydrous HCl salt of cimetidine. Specifically, 2-dimensional 1H double-quantum (DQ) MAS NMR spectra of polymorph A and the anhydrous HCl salt constitute fingerprints for the presence of each of these solid forms. For solid-state NMR data recorded at a 1H Larmor frequency of 850 MHz and a MAS frequency of 30 kHz on ∼10 mg of sample, it is shown that, by following the pair of cross-peaks at a 1H DQ frequency of 7.4 + 11.6 = 19.0 ppm that are unique to polymorph A, the level of detection for polymorph A in a physical mixture with the anhydrous HCl salt is a concentration of 1% w/w. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.
Liu, Peng; Zhang, Jingxue; Wang, Dunyou
2017-06-07
A double-inversion mechanism of the F - + CH 3 I reaction was discovered in aqueous solution using combined multi-level quantum mechanics theories and molecular mechanics. The stationary points along the reaction path show very different structures to the ones in the gas phase due to the interactions between the solvent and solute, especially strong hydrogen bonds. An intermediate complex, a minimum on the potential of mean force, was found to serve as a connecting-link between the abstraction-induced inversion transition state and the Walden-inversion transition state. The potentials of mean force were calculated with both the DFT/MM and CCSD(T)/MM levels of theory. Our calculated free energy barrier of the abstraction-induced inversion is 69.5 kcal mol -1 at the CCSD(T)/MM level of theory, which agrees with the one at 72.9 kcal mol -1 calculated using the Born solvation model and gas-phase data; and our calculated free energy barrier of the Walden inversion is 24.2 kcal mol -1 , which agrees very well with the experimental value at 25.2 kcal mol -1 in aqueous solution. The calculations show that the aqueous solution makes significant contributions to the potentials of mean force and exerts a big impact on the molecular-level evolution along the reaction pathway.
Energy Technology Data Exchange (ETDEWEB)
Tang, Yanqun; Wang, Ruirui; Yang, Ye; Yan, Dongpeng; Xiang, Xu
2016-08-03
The water oxidation half-reaction is considered to be a bottleneck for achieving highly efficient solar-driven water splitting due to its multiproton-coupled four-electron process and sluggish kinetics. Herein, a triadic photoanode consisting of dual-sized CdTe quantum dots (QDs), Co-based layered double hydroxide (LDH) nanosheets, and BiVO4 particles, that is, QD@LDH@BiVO4, was designed. Two sets of consecutive Type-II band alignments were constructed to improve photogenerated electron-hole separation in the triadic structure. The efficient charge separation resulted in a 2-fold enhancement of the photocurrent of the QD@LDH@BiVO4 photoanode. A significantly enhanced oxidation efficiency reaching above 90% in the low bias region (i.e., E < 0.8 V vs RHE) could be critical in determining the overall performance of a complete photoelectrochemical cell. The faradaic efficiency for water oxidation was almost 90%. The conduction band energy of QDs is -1.0 V more negative than that of LDH, favorable for the electron injection to LDH and enabling a more efficient hole separation. The enhanced photon-to-current conversion efficiency and improved water oxidation efficiency of the triadic structure may result from the non-negligible contribution of hot electrons or holes generated in QDs. Such a band-matching and multidimensional triadic architecture could be a promising strategy for achieving high-efficiency photoanodes by sufficiently utilizing and maximizing the functionalities of QDs.
Rahmanian, Omid; Dinari, Mohammad; Abdolmaleki, Mahmood Karimi
2018-01-01
Novel carbon quantum dots/zinc aluminum layered double hydroxide (CQD/ZnAl-LDH) composite was prepared through the precipitation of metal nitrates in the presence of CQD by a facile and simple method and further applied to remove excessive Cd(II) ions from water. The chemical composition and morphology of the CQDs/ZnAl-LDH hybrid was investigated by Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, and Energy-dispersive X-ray spectroscopy. Batch studies were done to evaluate the effects of the adsorption of Cd(II) by CQDs/ZnAl-LDH to optimize the major parameters such as pH, contact time, and initial concentration. The maximum uptake capacity of Cd(II) on CQDs/ZnAl-LDH was only 12.60 mg/g at 20 min due to the available exterior sites on the adsorbent. The adsorption kinetics and isotherms of Cd(II) on CQDs/ZnAl-LDH were also investigated. The experimental data indicated that the adsorption kinetics and adsorption isotherms of Cd(II) on CQDs/ZnAl-LDH were well-fitted by the pseudo-second-order kinetic model and the Freundlich isotherm model, respectively.
Samuei, Sara; Fakkar, Jila; Rezvani, Zolfaghar; Shomali, Ashkan; Habibi, Biuck
2017-03-15
In the present work, a novel nanocomposite based on the graphene quantum dots and CoNiAl-layered double-hydroxide was successfully synthesized by co-precipitation method. To achieve the morphological, structural and compositional information, the resulted nanocomposite was characterized by scanning electron microscopy X-ray diffraction, thermal gravimetric analysis, Fourier transform infrared spectroscopy, and photoluminescence. Then, the nanocomposite was used as a modifier to fabricate a modified carbon paste electrode as a non-enzymatic sensor for glucose determination. Electrochemical behavior and determination of glucose at the nanocomposite modified carbon paste electrode were investigated by cyclic voltammetry and chronoamperometry methods, respectively. The prepared sensor offered good electrocatalytic properties, fast response time, high reproducibility and stability. At the optimum conditions, the constructed sensor exhibits wide linear range; 0.01-14.0 mM with a detection limit of 6 μM (S/N = 3) and high sensitivity of 48.717 μAmM-1. Finally, the sensor was successfully applied to determine the glucose in real samples which demonstrated its applicability. Copyright © 2017 Elsevier Inc. All rights reserved.
Enhancing molecule fluorescence with asymmetrical plasmonic antennas.
Lu, Guowei; Liu, Jie; Zhang, Tianyue; Shen, Hongming; Perriat, Pascal; Martini, Matteo; Tillement, Olivier; Gu, Ying; He, Yingbo; Wang, Yuwei; Gong, Qihuang
2013-07-21
We propose and justify by the finite-difference time-domain method an efficient strategy to enhance the spontaneous emission of a fluorophore with a multi-resonance plasmonic antenna. The custom-designed asymmetrical antenna consists of two plasmonic nanoparticles with different sizes and is able to couple efficiently to free space light through multiple localized surface plasmon resonances. This design simultaneously permits a large near-field excitation near the antenna as well as a high quantum efficiency, which results in an unusual and significant enhancement of the fluorescence of a single emitter. Such an asymmetrical antenna presents intrinsic advantages over single particle or dimer based antennas made using two identical nanostructures. This promising concept can be exploited in the large domain of light-matter interaction processes involving multiple frequencies.
Li, Jiahua; Yu, Rong; Wu, Ying
2016-12-01
Optical Fano resonances are an increasingly important line-shape engineering tool with applications ranging from high-sensitivity sensing and ultrasmall lasers to low-power optical switching or modulating. Here we demonstrate a fully on-chip resonant nanostructure on a photonic crystal molecule platform exhibiting typical double- and Ramsey-Fano resonances, which can be actively controlled by the modification of the blockade transmittance in the waveguide. First, we investigate the transmission spectrum of a coupled double-cavity setting, showing a kind of double-Fano resonance line shape which consists of an asymmetric low-frequency Fano (LF) resonance and a high-frequency Fano (HF) resonance. At the same time, we elucidate the influences of various physical quantities on the generated LF and HF resonances. Second, and more interestingly, we reveal the occurrence of the Ramsey-Fano resonance profile by extending a double-cavity arrangement to a coupled-cavity-array arrangement. This Ramsey-Fano resonance can be attributed to the multiple quantum interference among a variety of light pathways. Finally, as an application, we discuss how to use an asymmetric double-Fano resonance line shape, which features the steep spectral slope, to improve the sensing performance. Our obtained results may stimulate future experimental efforts in controlling the double- and Ramsey-Fano resonance line shapes of this system more accurately.
Fleming, J.G.; Smith, B.K.
1995-10-10
A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.
Quantum Cryptography: a direct approach
Directory of Open Access Journals (Sweden)
MENDES, A. J. B.
2011-06-01
Full Text Available This study aims to answer directly to four questions relating to knowledge of what Quantum Cryptography is. The text is developed through a historical overview of the encryption of messages, reaching asymmetric encryption, a solution to the problem of production and distribution of keys. Afterwards, inserted in a quantum scope, it defines and exemplifies protocols of quantum cryptography, showing, in conclusion, the responses required.
Pesic, Peter
2003-10-01
The separateness and connection of individuals is perhaps the central question of human life: What, exactly, is my individuality? To what degree is it unique? To what degree can it be shared, and how? To the many philosophical and literary speculations about these topics over time, modern science has added the curious twist of quantum theory, which requires that the elementary particles of which everything consists have no individuality at all. All aspects of chemistry depend on this lack of individuality, as do many branches of physics. From where, then, does our individuality come? In Seeing Double, Peter Pesic invites readers to explore this intriguing set of questions. He draws on literary and historical examples that open the mind (from Homer to Martin Guerre to Kafka), philosophical analyses that have helped to make our thinking and speech more precise, and scientific work that has enabled us to characterize the phenomena of nature. Though he does not try to be all-inclusive, Pesic presents a broad range of ideas, building toward a specific point of view: that the crux of modern quantum theory is its clash with our ordinary concept of individuality. This represents a departure from the usual understanding of quantum theory. Pesic argues that what is bizarre about quantum theory becomes more intelligible as we reconsider what we mean by individuality and identity in ordinary experience. In turn, quantum identity opens a new perspective on us. Peter Pesic is a Tutor and Musician-in-Residence at St. John's College, Santa Fe, New Mexico. He has a Ph.D. in physics from Stanford University.
Asymmetrical international attitudes
Van Oudenhoven, JP; Askevis-Leherpeux, F; Hannover, B; Jaarsma, R; Dardenne, B
2002-01-01
In general, attitudes towards nations have a fair amount of reciprocity: nations either like each other are relatively indifferent to each other or dislike each other Sometimes, however international attitudes are asymmetrical. In this study, we use social identity theory in order to explain
Indian Academy of Sciences (India)
Home; Journals; Resonance – Journal of Science Education; Volume 7; Issue 6. How Is Nature Asymmetric? - Discrete Symmetries in Particle Physics and their Violation ... Indian Institute of Technology, Chennai. Aligarh Muslim University. University of Rajasthan, Jaipur. Indian Institute of Science, Bangalore 560012, India.
Highly asymmetric rice genomes
Directory of Open Access Journals (Sweden)
Chen Jian-Qun
2007-06-01
Full Text Available Abstract Background Individuals in the same species are assumed to share the same genomic set. However, it is not unusual to find an orthologous gene only in small subset of the species, and recent genomic studies suggest that structural rearrangements are very frequent between genomes in the same species. Two recently sequenced rice genomes Oryza sativa L. var. Nipponbare and O. sativa L. var. 93-11 provide an opportunity to systematically investigate the extent of the gene repertoire polymorphism, even though the genomic data of 93-11 derived from whole-short-gun sequencing is not yet as complete as that of Nipponbare. Results We compared gene contents and the genomic locations between two rice genomes. Our conservative estimates suggest that at least 10% of the genes in the genomes were either under presence/absence polymorphism (5.2% or asymmetrically located between genomes (4.7%. The proportion of these "asymmetric genes" varied largely among gene groups, in which disease resistance (R genes and the RLK kinase gene group had 11.6 and 7.8 times higher proportion of asymmetric genes than housekeeping genes (Myb and MADS. The significant difference in the proportion of asymmetric genes among gene groups suggests that natural selection is responsible for maintaining genomic asymmetry. On the other hand, the nucleotide diversity in 17 R genes under presence/absence polymorphism was generally low (average nucleotide diversity = 0.0051. Conclusion The genomic symmetry was disrupted by 10% of asymmetric genes, which could cause genetic variation through more unequal crossing over, because these genes had no allelic counterparts to pair and then they were free to pair with homologues at non-allelic loci, during meiosis in heterozygotes. It might be a consequence of diversifying selection that increased the structural divergence among genomes, and of purifying selection that decreased nucleotide divergence in each R gene locus.
Liu, Yuqian; Ye, Mingfu; Ge, Qinyu; Qu, Xiaojun; Guo, Qingsheng; Hu, Xianyun; Sun, Qingjiang
2016-02-02
We have developed a proof-of-concept quantum dot-ligand (QD-L) system for visual selective detection of nucleic acids, in combination with a ratiometric fluorescence technique. This system comprises a dual-emission QDs nanohybrid formed by embedding a red-emission QD (rQD) in a silica nanoparticle and electrostatically assembling green-emission QDs (gQDs) onto the silica surface, as the signal displaying unit, and a hydrophobic compound, dipyrido[3,2-a:2',3'-c]phenazine (dppz), attached onto the gQDs surface via phase transfer, as the ligand as well as fluorescence quencher of gQDs. This system is successfully used for quantification of double-stranded DNA (dsDNA). Because of its avid binding with dppz, dsDNA can break up the QD-L system, displacing the dppz ligand from the gQDs surface and restoring the gQDs emission. Since the red emission of embedded rQDs stays constant, variations of the dual-emission intensity ratios display continuous color changes from orange to bright green, which can be clearly observed by the naked eye. More importantly, this system is advantageous in terms of specificity over a QD ionic conjugate, because the electrical neutrality of dppz excludes its nonspecific electrostatic association with dsDNA. The QD-L system also is capable of detecting single-nucleotide polymorphism, exhibiting sequence-specific ratiometric fluorescence as a QD-bioconjugate does, but possessing the obvious advantage in terms of low cost, with the avoidance of modification, labeling, and purification processes. Therefore, the QD-L system provides an extremely simple but general strategy for detecting nucleic acids in a facile, sensitive, and specific manner.
National Research Council Canada - National Science Library
Ukaji, Yutaka; Shimizu, Yuuko; Kenmoku, Yuuichi; Ahmed, Alauddin; Inomata, Katsuhiko
1997-01-01
The catalytic asymmetric addition reaction of dialkylzinc to carbon-nitrogen double bond in 3,4-dihydroisoquinoline N-oxide derivatives was achieved by utilizing a catalytic amount of dicyclopentyl (R,R...
Ion pumping in nanochannels using an asymmetric electrode array
Sparreboom, Wouter; Cucu, C.F.; Eijkel, Jan C.T.; van den Berg, Albert; Locascio, L.E.; Gaitan, M.; Paegel, B.M.; Ross, D.J.; Vreeland, W.N.
2008-01-01
We demonstrate an ion pump, consisting of a nanochannel with an AC driven asymmetric electrode array. Our system enables us to actively pump ions using a low driving voltage. In all experiments the electrical double layers are overlapping. Via viscous coupling ion pumping is accompanied by liquid
Asymmetric extractions in orthodontics
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Camilo Aquino Melgaço
2012-04-01
Full Text Available INTRODUCTION: Extraction decisions are extremely important in during treatment planning. In addition to the extraction decision orthodontists have to choose what tooth should be extracted for the best solution of the problem and the esthetic/functional benefit of the patient. OBJECTIVE: This article aims at reviewing the literature relating the advantages, disadvantages and clinical implications of asymmetric extractions to orthodontics. METHODS: Keywords were selected in English and Portuguese and the EndNote 9 program was used for data base search in PubMed, Web of Science (WSc and LILACS. The selected articles were case reports, original articles and prospective or retrospective case-control studies concerning asymmetrical extractions of permanent teeth for the treatment of malocclusions. CONCLUSION: According to the literature reviewed asymmetric extractions can make some specific treatment mechanics easier. Cases finished with first permanent molars in Class II or III relationship in one or both sides seem not to cause esthetic or functional problems. However, diagnosis knowledge and mechanics control are essential for treatment success.
Asymmetric Evolutionary Games.
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Alex McAvoy
2015-08-01
Full Text Available Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner's Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games.
Asymmetric Evolutionary Games.
McAvoy, Alex; Hauert, Christoph
2015-08-01
Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner's Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games.
Energy Technology Data Exchange (ETDEWEB)
Huebel, A.
2007-11-22
In this work, a double quantum dot system is studied whose two dots are electrically insulated from one another and contacted independently with two leads. The geometry is optimized to maximize the capacitive interaction between the dots. The samples are characterized by electrical transport measurements in a dilution refrigerator. It is then studied at different tunnel couplings how the capacitive interaction influences the electrical transport in equilibrium. Under certain conditions correlated tunnel processes can be observed. A simple model is derived that serves to understand these processes. The double quantum dot system is defined in lateral arrangement by reactive ion etching of a two-dimensional electron system located only 50 nm below the surface of a GaAs-AlGaAs heterostructure. The samples are characterized in a dilution refrigerator at 25 mK near the common pinch-off point of all four tunnel barriers. A measurement of the differential equilibrium conductances of both quantum dots as a function of two gate voltages yields a honeycomb-like charge stability diagram. The most important sample characteristic is the ratio between the interaction capacitance and the total capacitance of a single quantum dot. For the optimized sample, this ratio turns out to be larger than one third near the common pinch-off point, with a single-dot charging energy of up to 800 {mu}eV. At more positive gate voltages, the capacitances between the quantum dots and their leads increase more and more, thereby diminishing the charging energy. It is shown for the optimized sample that all capacitance coefficients except the dot-lead capacitances are constant to within considerable accuracy over several Coulomb blockade oscillations. In order to measure correlated electrical transport in equilibrium, special parameter regions are examined in which the charges of both quantum dots cannot fluctuate independently of each other. An analytical formula is derived that describes the
Hobson, Art
2012-01-01
Nonlocality arises from the unified "all or nothing" interactions of a spatially extended field quantum such as a photon or an electron. In the double-slit experiment with light, for example, each photon comes through both slits and arrives at the viewing screen as an extended but unified energy bundle or "field quantum." When the photon interacts…
Energy Technology Data Exchange (ETDEWEB)
Odhiambo Oyoko, H. [Department of Physics, Westville Campus, University of KwaZulu-Natal, Private Bag X 54001, Durban 4000 (South Africa); Porras-Montenegro, N. [Departamento de Fisica, Universidad del Valle, AA 25360, Cali (Colombia); Lopez, S.Y. [Facultad de Educacion, Universidad de Antioquia, AA 1226, Medellin (Colombia); Duque, C.A. [Instituto de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia)
2007-07-01
Using a variational technique within the effective mass approximation we have carried out a comparative study of the effect of hydrostatic pressure and temperature on the shallow-impurity related optical absorption spectra in GaAs-Ga{sub 1-x}Al{sub x}As single and double quantum wells. The results show a pressure dependent read-shift and a temperature dependent blue-shift in the optical absorption spectra. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Directory of Open Access Journals (Sweden)
Nikolay M. Bogoliubov
2009-04-01
Full Text Available The basic model of the non-equilibrium low dimensional physics the so-called totally asymmetric exclusion process is related to the 'crystalline limit' (q → ∞ of the SU_q(2 quantum algebra. Using the quantum inverse scattering method we obtain the exact expression for the time-dependent stationary correlation function of the totally asymmetric simple exclusion process on a one dimensional lattice with the periodic boundary conditions.
Wu, Shuxing; Hui, Kwan San; Hui, Kwun Nam; Kim, Kwang Ho
2017-01-18
Achieving high energy density while retaining high power density is difficult in electrical double-layer capacitors and in pseudocapacitors considering the origin of different charge storage mechanisms. Rational structural design became an appealing strategy in circumventing these trade-offs between energy and power densities. A hybrid structure consists of chemically converted graphene-encapsulated carbon@nickel-aluminum layered double hydroxide core-shell spheres as spacers among graphene layers (G-CLS) used as an advanced electrode to achieve high energy density while retaining high power density for high-performance supercapacitors. The merits of the proposed architecture are as follows: (1) CLS act as spacers to avoid the close restacking of graphene; (2) highly conductive carbon sphere and graphene preserve the mechanical integrity and improve the electrical conductivity of LDHs hybrid. Thus, the proposed hybrid structure can simultaneously achieve high electrical double-layer capacitance and pseudocapacitance resulting in the overall highly active electrode. The G-CLS electrode exhibited high specific capacitance (1710.5 F g -1 at 1 A g -1 ) under three-electrode tests. An ASC fabricated using the G-CLS as positive electrode and reduced graphite oxide as negative electrode demonstrated remarkable electrochemical performance. The ASC device operated at 1.4 V and delivered a high energy density of 35.5 Wh kg -1 at a 670.7 W kg -1 power density at 1 A g -1 with an excellent rate capability as well as a robust long-term cycling stability of up to 10 000 cycles.
Asymmetric fluorocyclizations of alkenes.
Wolstenhulme, Jamie R; Gouverneur, Véronique
2014-12-16
CONSPECTUS: The vicinal fluorofunctionalization of alkenes is an attractive transformation that converts feedstock olefins into valuable cyclic fluorinated molecules for application in the pharmaceutical, agrochemical, medical, and material sectors. The challenges associated with asymmetric fluorocyclizations induced by F(+) reagents are distinct from other types of halocyclizations. Processes initiated by the addition of an F(+) reagent onto an alkene do not involve the reversible formation of bridged fluoronium ions but generate acyclic β-fluorocationic intermediates. This mechanistic feature implies that fluorocyclizations are not stereospecific. A discontinuity exists between the importance of this class of fluorocyclization and the activation modes currently available to implement successful catalysis. Progress toward fluorocyclization has been achieved by investing in neutral and cationic [NF] reagent development. The body of work on asymmetric fluorination using chiral cationic [NF](+) reagents prepared by fluorine transfer from the dicationic [NF](2+) reagent Selectfluor to quinuclidines, inspired the development of asymmetric F(+)-induced fluorocyclizations catalyzed by cinchona alkaloids; for catalysis, the use of N-fluorobenzenesulfonimide, which is less reactive than Selectfluor, ensures that the achiral F(+) source remains unreactive toward the alkene. These organocatalyzed enantioselective fluorocyclizations can be applied to indoles to install the fluorine on a quaternary benzylic stereogenic carbon center and to afford fluorinated analogues of natural products featuring the hexahydropyrrolo[2,3-b]indole or the tetrahydro-2H-furo[2,3-b]indole skeleton. In an alternative approach, the poor solubility of dicationic Selectfluor bis(tetrafluoroborate) in nonpolar solvent was exploited with anionic phase transfer catalysis as the operating activation mode. Exchange of the tetrafluoroborate ions of Selectfluor with bulky lipophilic chiral anions (e
Kendon, Vivien M; Nemoto, Kae; Munro, William J
2010-08-13
We briefly review what a quantum computer is, what it promises to do for us and why it is so hard to build one. Among the first applications anticipated to bear fruit is the quantum simulation of quantum systems. While most quantum computation is an extension of classical digital computation, quantum simulation differs fundamentally in how the data are encoded in the quantum computer. To perform a quantum simulation, the Hilbert space of the system to be simulated is mapped directly onto the Hilbert space of the (logical) qubits in the quantum computer. This type of direct correspondence is how data are encoded in a classical analogue computer. There is no binary encoding, and increasing precision becomes exponentially costly: an extra bit of precision doubles the size of the computer. This has important consequences for both the precision and error-correction requirements of quantum simulation, and significant open questions remain about its practicality. It also means that the quantum version of analogue computers, continuous-variable quantum computers, becomes an equally efficient architecture for quantum simulation. Lessons from past use of classical analogue computers can help us to build better quantum simulators in future.
Asymmetric strand segregation: epigenetic costs of genetic fidelity?
Directory of Open Access Journals (Sweden)
Diane P Genereux
2009-06-01
Full Text Available Asymmetric strand segregation has been proposed as a mechanism to minimize effective mutation rates in epithelial tissues. Under asymmetric strand segregation, the double-stranded molecule that contains the oldest DNA strand is preferentially targeted to the somatic stem cell after each round of DNA replication. This oldest DNA strand is expected to have fewer errors than younger strands because some of the errors that arise on daughter strands during their synthesis fail to be repaired. Empirical findings suggest the possibility of asymmetric strand segregation in a subset of mammalian cell lineages, indicating that it may indeed function to increase genetic fidelity. However, the implications of asymmetric strand segregation for the fidelity of epigenetic information remain unexplored. Here, I explore the impact of strand-segregation dynamics on epigenetic fidelity using a mathematical-modelling approach that draws on the known molecular mechanisms of DNA methylation and existing rate estimates from empirical methylation data. I find that, for a wide range of starting methylation densities, asymmetric -- but not symmetric -- strand segregation leads to systematic increases in methylation levels if parent strands are subject to de novo methylation events. I found that epigenetic fidelity can be compromised when enhanced genetic fidelity is achieved through asymmetric strand segregation. Strand segregation dynamics could thus explain the increased DNA methylation densities that are observed in structured cellular populations during aging and in disease.
Asymmetric Flexible Supercapacitor Stack
National Research Council Canada - National Science Library
Leela Mohana Reddy, A; Estaline Amitha, F; Jafri, Imran; Ramaprabhu, S
2008-01-01
Electrical double layer supercapacitor is very significant in the field of electrical energy storage which can be the solution for the current revolution in the electronic devices like mobile phones...
Catalytic asymmetric fluorinations.
Bobbio, Carla; Gouverneur, Véronique
2006-06-07
The appearance of structurally diverse fluorinating reagents displaying a large spectrum of reactivity has been critical to the development of the catalytic asymmetric fluorination processes known to date. In this article, we discuss how this area of research emerged and which strategies have allowed for the successful development of both nucleophilic and electrophilic catalytic enantioselective fluorinations. We also present the fundamental understanding of catalytic activity and enantioselectivity for the most efficient processes and highlight the first synthetic application with the preparation of a complex fluorinated target.
Morrison, James
1984-01-01
Asymmetric Synthesis, Volume 4: The Chiral Carbon Pool and Chiral Sulfur, Nitrogen, Phosphorus, and Silicon Centers describes the practical methods of obtaining chiral fragments. Divided into five chapters, this book specifically examines initial chiral transmission and extension. The opening chapter describes the so-called chiral carbon pool, the readily available chiral carbon fragments used as building blocks in synthesis. This chapter also provides a list of 375 chiral building blocks, along with their commercial sources, approximate prices, and methods of synthesis. Schemes involving
Asymmetric Organocatalytic Cycloadditions
DEFF Research Database (Denmark)
Mose, Rasmus
2016-01-01
were pioneered by Otto Paul Hermann Diels and Kurt Alder who discovered what later became known as the Diels Alder reaction. The Diels Alder reaction is a [4+2] cycloaddition in which a π4 component reacts with a π2 component via a cyclic transition state to generate a 6 membered ring. This reaction...... undergo cascade reactions with different electron deficient dienophiles in Diels Alder – nucleophilic ring closing reactions. This methodology opens up for the direct asymmetric formation of hydroisochromenes and hydroisoquinolines which may possess interesting biological activities. It is also...
Chiral fullerenes from asymmetric catalysis.
Maroto, Enrique E; Izquierdo, Marta; Reboredo, Silvia; Marco-Martínez, Juan; Filippone, Salvatore; Martín, Nazario
2014-08-19
Fullerenes are among the most studied molecules during the last three decades, and therefore, a huge number of chemical reactions have been tested on these new carbon allotropes. However, the aim of most of the reactions carried out on fullerenes has been to afford chemically modified fullerenes that are soluble in organic solvents or even water in the search for different mechanical, optical, or electronic properties. Therefore, although a lot of effort has been devoted to the chemical functionalization of these molecular allotropes of carbon, important aspects in the chemistry of fullerenes have not been properly addressed. In particular, the synthesis of chiral fullerenes at will in an efficient manner using asymmetric catalysis has not been previously addressed in fullerene science. Thus, despite the fact that the chirality of fullerenes has always been considered a fundamental issue, the lack of a general stereoselective synthetic methodology has restricted the use of enantiopure fullerene derivatives, which have usually been obtained only after highly expensive HPLC isolation on specific chiral columns or prepared from a pool of chiral starting materials. In this Account, we describe the first stereodivergent catalytic enantioselective syntheses in fullerene science, which have allowed the highly efficient synthesis of enantiomerically pure derivatives with total control of the stereochemical result using metallic catalysts and/or organocatalysts under very mild conditions. Density functional theory calculations strongly support the experimental findings for the assignment of the absolute configuration of the new stereocenters, which has also been ascertained by application of the sector rule and single-crystal X-ray diffraction. The use of the curved double bond of fullerene cages as a two-π-electron component in a variety of stereoselective cycloaddition reactions represents a challenging goal considering that, in contrast to most of the substituted
Reuveni, Shlomi; Eliazar, Iddo; Yechiali, Uri
2011-10-01
We introduce and explore the asymmetric inclusion process (ASIP), an exactly solvable bosonic counterpart of the fermionic asymmetric exclusion process (ASEP). In both processes, random events cause particles to propagate unidirectionally along a one-dimensional lattice of n sites. In the ASEP, particles are subject to exclusion interactions, whereas in the ASIP, particles are subject to inclusion interactions that coalesce them into inseparable clusters. We study the dynamics of the ASIP, derive evolution equations for the mean and probability generating function (PGF) of the sites' occupancy vector, obtain explicit results for the above mean at steady state, and describe an iterative scheme for the computation of the PGF at steady state. We further obtain explicit results for the load distribution in steady state, with the load being the total number of particles present in all lattice sites. Finally, we address the problem of load optimization, and solve it under various criteria. The ASIP model establishes bridges between statistical physics and queueing theory as it represents a tandem array of queueing systems with (unlimited) batch service, and a tandem array of growth-collapse processes.
Indian Academy of Sciences (India)
These particles typically carry electric charge as do the charged leptons and also additional quantum numbers called ... only in the sign of their electric charge, while their masses are equal. Many successful ... In this manner C P violation could possibly hold one of the keys to the origin of the matter- antimatter asymmetry in ...
Crystallization in mass and charge asymmetric bilayers
Bonitz, Michael; Ludwig, Patrick; Filinov, Alexei; Lozovik, Yurii; Stolz, Heinrich
2007-11-01
We consider Coulomb crystal formation in quantum electron-ion (hole) bilayers. Varying the mass ratio M of ions and electrons between 1 and 100 for a fixed layer separation d at low temperature and high density, one can tune the hole behavior from delocalized (quantum) to localized (quasi-classical) while the electrons remain delocalized all the time. While in 3D plasmas [1], ions crystallize if the mass ratio exceeds a critical value of Mcr˜80, in bilayers Mcr can be drastically reduced by properly choosing d and the in-layer particle density. The complicated overlap of correlation and quantum effects of both, electrons and holes, is fully taken care of by performing first-principle path integral Monte Carlo simulations. [1] M. Bonitz, V.S. Filinov, V.E. Fortov. P.R. Levashov, and H. Fehske, Phys. Rev. Lett. 95, 235006 (2005) and J. Phys. A: Math. Gen. 39, 4717 (2006). [2] P. Ludwig, A. Filinov, Yu. Lozovik, H. Stolz, and M. Bonitz, Crystallization in mass-asymmetric electron-hole bilayers, Contrib. Plasma Phys. (2007), ArXiv: cond-mat/0611556
New mechanistic aspects of the asymmetric homogeneous hydrogenation of alkenes.
Brown, J M; Giernoth, R
2000-11-01
Progress in homogeneous catalysis depends upon an understanding of the reaction mechanism; in asymmetric catalysis this entails an insight into the origins of enantioselectivity. Significant advances have been made in the area of alkene reduction catalyzed by rhodium or ruthenium complexes, which has been in tandem with the development of new, more effective ligands for the reaction. The combination of quantum chemical calculations and direct spectroscopic observation of catalytic intermediates has proved powerful in this regard.
Symmetric Decomposition of Asymmetric Games.
Tuyls, Karl; Pérolat, Julien; Lanctot, Marc; Ostrovski, Georg; Savani, Rahul; Leibo, Joel Z; Ord, Toby; Graepel, Thore; Legg, Shane
2018-01-17
We introduce new theoretical insights into two-population asymmetric games allowing for an elegant symmetric decomposition into two single population symmetric games. Specifically, we show how an asymmetric bimatrix game (A,B) can be decomposed into its symmetric counterparts by envisioning and investigating the payoff tables (A and B) that constitute the asymmetric game, as two independent, single population, symmetric games. We reveal several surprising formal relationships between an asymmetric two-population game and its symmetric single population counterparts, which facilitate a convenient analysis of the original asymmetric game due to the dimensionality reduction of the decomposition. The main finding reveals that if (x,y) is a Nash equilibrium of an asymmetric game (A,B), this implies that y is a Nash equilibrium of the symmetric counterpart game determined by payoff table A, and x is a Nash equilibrium of the symmetric counterpart game determined by payoff table B. Also the reverse holds and combinations of Nash equilibria of the counterpart games form Nash equilibria of the asymmetric game. We illustrate how these formal relationships aid in identifying and analysing the Nash structure of asymmetric games, by examining the evolutionary dynamics of the simpler counterpart games in several canonical examples.
Directory of Open Access Journals (Sweden)
I. Cabrera-Munguia
2015-04-01
Full Text Available A 6-parametric asymptotically flat exact solution, describing a two-body system of asymmetric black dyons, is studied. The system consists of two unequal counterrotating Kerr–Newman black holes, endowed with electric and magnetic charges which are equal but opposite in sign, separated by a massless strut. The Smarr formula is generalized in order to take into account their contribution to the mass. The expressions for the horizon half-length parameters σ1 and σ2, as functions of the Komar parameters and of the coordinate distance, are displayed, and the thermodynamic properties of the two-body system are studied. Furthermore, the seven physical parameters satisfy a simple algebraic relation which can be understood as a dynamical scenario, in which the physical properties of one body are affected by the ones of the other body.
Asymmetric Realized Volatility Risk
Directory of Open Access Journals (Sweden)
David E. Allen
2014-06-01
Full Text Available In this paper, we document that realized variation measures constructed from high-frequency returns reveal a large degree of volatility risk in stock and index returns, where we characterize volatility risk by the extent to which forecasting errors in realized volatility are substantive. Even though returns standardized by ex post quadratic variation measures are nearly Gaussian, this unpredictability brings considerably more uncertainty to the empirically relevant ex ante distribution of returns. Explicitly modeling this volatility risk is fundamental. We propose a dually asymmetric realized volatility model, which incorporates the fact that realized volatility series are systematically more volatile in high volatility periods. Returns in this framework display time varying volatility, skewness and kurtosis. We provide a detailed account of the empirical advantages of the model using data on the S&P 500 index and eight other indexes and stocks.
Families of asymmetric periodic solutions in the restricted four-body problem
Papadakis, K. E.
2016-12-01
Very recently, we presented five of the basic families of the network of periodic orbits of the restricted four-body problem which are simple, i.e. one intersection with the horizontal x-axis at the half period, symmetric with respect to the same axis and asymmetric with respect to the vertical y-axis. In the present work, using these families, we found series of asymmetric critical orbits for various values of the primaries m2 and m3. From these critical orbits we calculate and present five new families of simple periodic orbits which are asymmetric with respect to both the x- and y-axis. Additionally, we describe a grid method in the (x0, dot{x}0) plane and we obtain initial conditions for new asymmetric double-periodic orbits. We determine ten families of asymmetric double-periodic orbits from the bifurcations of the previous five asymmetric families using the special generating horizontally critical periodic orbits. The stability of each calculated asymmetric periodic orbit is also studied. Characteristic curves as well as stability diagrams of these families are illustrated. In the last section we present the evolution of the five basic families of simple asymmetric periodic orbits when the primaries are the Sun the Jupiter and the 2797 Teucer Asteroid.
Quantum cluster algebra structures on quantum nilpotent algebras
Goodearl, K R
2017-01-01
All algebras in a very large, axiomatically defined class of quantum nilpotent algebras are proved to possess quantum cluster algebra structures under mild conditions. Furthermore, it is shown that these quantum cluster algebras always equal the corresponding upper quantum cluster algebras. Previous approaches to these problems for the construction of (quantum) cluster algebra structures on (quantized) coordinate rings arising in Lie theory were done on a case by case basis relying on the combinatorics of each concrete family. The results of the paper have a broad range of applications to these problems, including the construction of quantum cluster algebra structures on quantum unipotent groups and quantum double Bruhat cells (the Berenstein-Zelevinsky conjecture), and treat these problems from a unified perspective. All such applications also establish equality between the constructed quantum cluster algebras and their upper counterparts.
Boroumand, Samira; Chamjangali, Mansour Arab; Bagherian, Ghadamali
2017-03-01
A simple and sensitive double injection/single detector flow injection analysis (FIA) method is proposed for the simultaneous kinetic determination of ascorbic acid (AA) and uric acid (UA). This method is based upon the difference between the rates of the AA and UA reactions with Fe3 + in the presence of 1, 10-phenanthroline (phen). The absorbance of Fe2 +/1, 10-phenanthroline (Fe-phen) complex obtained as the product was measured spectrophotometrically at 510 nm. To reach a good accuracy in the differential kinetic determination via the mathematical manipulations of the transient signals, different criteria were considered in the selection of the optimum conditions. The multi criteria decision making (MCDM) approach was applied for the selection of the optimum conditions. The importance weights of the evaluation criteria were determined using the analytic hierarchy process, entropy method, and compromised weighting (CW). The experimental conditions (alternatives) were ranked by the technique for order preference by similarity to an ideal solution. Under the selected optimum conditions, the obtained analytical signals were linear in the ranges of 0.50-5.00 and 0.50-4.00 mg L- 1 for AA and UA, respectively. The 3σ detection limits were 0.07 mg L- 1 for AA and 0.12 mg L- 1 for UA. The relative standard deviations for four replicate determinations of AA and UA were 2.03% and 3.30% respectively. The method was also applied for the analysis of analytes in the blood serum, Vitamine C tablets, and tap water with satisfactory results.
Asymmetric bifurcated halogen bonds.
Novák, Martin; Foroutan-Nejad, Cina; Marek, Radek
2015-03-07
Halogen bonding (XB) is being extensively explored for its potential use in advanced materials and drug design. Despite significant progress in describing this interaction by theoretical and experimental methods, the chemical nature remains somewhat elusive, and it seems to vary with the selected system. In this work we present a detailed DFT analysis of three-center asymmetric halogen bond (XB) formed between dihalogen molecules and variously 4-substituted 1,2-dimethoxybenzene. The energy decomposition, orbital, and electron density analyses suggest that the contribution of electrostatic stabilization is comparable with that of non-electrostatic factors. Both terms increase parallel with increasing negative charge of the electron donor molecule in our model systems. Depending on the orientation of the dihalogen molecules, this bifurcated interaction may be classified as 'σ-hole - lone pair' or 'σ-hole - π' halogen bonds. Arrangement of the XB investigated here deviates significantly from a recent IUPAC definition of XB and, in analogy to the hydrogen bonding, the term bifurcated halogen bond (BXB) seems to be appropriate for this type of interaction.
Duality and Recycling Computing in Quantum Computers
Long, Gui Lu; Liu, Yang
2007-01-01
Quantum computer possesses quantum parallelism and offers great computing power over classical computer \\cite{er1,er2}. As is well-know, a moving quantum object passing through a double-slit exhibits particle wave duality. A quantum computer is static and lacks this duality property. The recently proposed duality computer has exploited this particle wave duality property, and it may offer additional computing power \\cite{r1}. Simply put it, a duality computer is a moving quantum computer pass...
Magnetically Modified Asymmetric Supercapacitors Project
National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is for the development of an asymmetric supercapacitor that will have improved energy density and cycle life....
Doitomi, Kazuki; Xu, Kai; Hirao, Hajime
2017-03-14
We applied QM/MM calculations to the asymmetric ring-opening reaction of cyclohexene oxide with aniline catalyzed by a two-dimensional metal-organic framework (MOF) that contains a Cu-paddlewheel (Cu-PDW) unit, aiming to elucidate the reaction mechanism and to identify the factors that determine the enantioselectivity of the reaction. Our QM/MM calculations show that the reaction consists of two major steps. In the first step, ring-opening of the epoxide moiety occurs that leads to an intermediate having an alkoxide ion, and the strong binding of the alkoxide to the Cu(ii) center results in cleavage of one of the four coordination bonds of the copper with carboxylate ligands. In the second step of the reaction, there is a proton transfer from aniline to a distant site-i.e., the alkoxide oxygen atom-to form the β-amino alcohol product, and the carboxylate ligands of the Cu-PDW unit assist this process. The first ring-opening step was calculated as the rate-limiting step, and the enantioselectivity arises from different degrees of CH-π interactions between aniline and a naphthol group in the transition states. The transition state for the ring-opening step in the formation of the (R,R)-isomer is stabilized by CH-π interactions, whereas such interactions are absent in the transition state for the (S,S)-isomer formation. Interestingly, QM/MM calculations also show that the Cu-PDW unit does not maintain a symmetric geometry during the reaction but rather is flexible enough to detach a carboxylate ligand from the copper center, thereby facilitating the reaction. These results illuminate the utility of multiscale QM/MM computations in identifying critical factors determining the reactivity and selectivity of MOF-catalyzed reactions.
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.
Multicatalyst system in asymmetric catalysis
Zhou, Jian
2014-01-01
This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis. Helps organic chemists perform more efficient catalysis with step-by-step methods Overviews new concepts and progress for greener and economic catalytic reactions Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance
Asymmetric Ion-Pairing Catalysis
Brak, Katrien
2014-01-01
Charged intermediates and reagents are ubiquitous in organic transformations. The interaction of these ionic species with chiral neutral, anionic, or cationic small molecules has emerged as a powerful strategy for catalytic, enantioselective synthesis. This review describes developments in the burgeoning field of asymmetric ion-pairing catalysis with an emphasis on the insights that have been gleaned into the structural and mechanistic features that contribute to high asymmetric induction. PMID:23192886
Picosecond Carrier Spin Relaxation in In0.8Ga0.2As/AlAs/AlAs0.56Sb0.44 Coupled Double Quantum Wells
Yamaguchi, Ryo; Gozu, Shin-ichiro; Mozume, Teruo; Oyanagi, Yoshitsugu; Uemura, Mitsunori; Tackeuchi, Atsushi
2013-04-01
The carrier spin relaxation of In0.8Ga0.2As/AlAs/AlAs0.56Sb0.44 coupled double quantum wells is investigated by spin-dependent pump and probe reflectance measurements with a high time resolution of 200 fs. The observed fast spin relaxation time of 9 ps at room temperature indicates high potential for applications to high-speed optical devices. A negative temperature dependence of spin relaxation time is observed between 100 K and room temperature. The spin relaxation is found to be governed by the Bir-Aronov-Pikus process between 10 and 100 K and by the D'yakonov-Perel' and Elliott-Yafet processes between 100 K and room temperature.
Asymmetric Gepner models (revisited)
Energy Technology Data Exchange (ETDEWEB)
Gato-Rivera, B. [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)] [Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain); Schellekens, A.N., E-mail: t58@nikhef.n [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)] [Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain)] [IMAPP, Radboud Universiteit, Nijmegen (Netherlands)
2010-12-11
We reconsider a class of heterotic string theories studied in 1989, based on tensor products of N=2 minimal models with asymmetric simple current invariants. We extend this analysis from (2,2) and (1,2) spectra to (0,2) spectra with SO(10) broken to the Standard Model. In the latter case the spectrum must contain fractionally charged particles. We find that in nearly all cases at least some of them are massless. However, we identify a large subclass where the fractional charges are at worst half-integer, and often vector-like. The number of families is very often reduced in comparison to the 1989 results, but there are no new tensor combinations yielding three families. All tensor combinations turn out to fall into two classes: those where the number of families is always divisible by three, and those where it is never divisible by three. We find an empirical rule to determine the class, which appears to extend beyond minimal N=2 tensor products. We observe that distributions of physical quantities such as the number of families, singlets and mirrors have an interesting tendency towards smaller values as the gauge groups approaches the Standard Model. We compare our results with an analogous class of free fermionic models. This displays similar features, but with less resolution. Finally we present a complete scan of the three family models based on the triply-exceptional combination (1,16{sup *},16{sup *},16{sup *}) identified originally by Gepner. We find 1220 distinct three family spectra in this case, forming 610 mirror pairs. About half of them have the gauge group SU(3)xSU(2){sub L}xSU(2){sub R}xU(1){sup 5}, the theoretical minimum, and many others are trinification models.
Asymmetric Flexible Supercapacitor Stack
2008-01-01
Electrical double layer supercapacitor is very significant in the field of electrical energy storage which can be the solution for the current revolution in the electronic devices like mobile phones, camera flashes which needs flexible and miniaturized energy storage device with all non-aqueous components. The multiwalled carbon nanotubes (MWNTs) have been synthesized by catalytic chemical vapor deposition technique over hydrogen decrepitated Mischmetal (Mm) based AB3alloy hydride. The polymer dispersed MWNTs have been obtained by insitu polymerization and the metal oxide/MWNTs were synthesized by sol-gel method. Morphological characterizations of polymer dispersed MWNTs have been carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM and HRTEM). An assymetric double supercapacitor stack has been fabricated using polymer/MWNTs and metal oxide/MWNTs coated over flexible carbon fabric as electrodes and nafion®membrane as a solid electrolyte. Electrochemical performance of the supercapacitor stack has been investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
Asymmetric Flexible Supercapacitor Stack
Directory of Open Access Journals (Sweden)
Leela Mohana Reddy A
2008-01-01
Full Text Available AbstractElectrical double layer supercapacitor is very significant in the field of electrical energy storage which can be the solution for the current revolution in the electronic devices like mobile phones, camera flashes which needs flexible and miniaturized energy storage device with all non-aqueous components. The multiwalled carbon nanotubes (MWNTs have been synthesized by catalytic chemical vapor deposition technique over hydrogen decrepitated Mischmetal (Mm based AB3alloy hydride. The polymer dispersed MWNTs have been obtained by insitu polymerization and the metal oxide/MWNTs were synthesized by sol-gel method. Morphological characterizations of polymer dispersed MWNTs have been carried out using scanning electron microscopy (SEM, transmission electron microscopy (TEM and HRTEM. An assymetric double supercapacitor stack has been fabricated using polymer/MWNTs and metal oxide/MWNTs coated over flexible carbon fabric as electrodes and nafion®membrane as a solid electrolyte. Electrochemical performance of the supercapacitor stack has been investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
Fialko, O; Hallwood, D W
2012-02-24
We present a theoretical and numerical analysis of a quantum system that is capable of functioning as a heat engine. This system could be realized experimentally using cold bosonic atoms confined to a double well potential that is created by splitting a harmonic trap with a focused laser. The system shows thermalization, and can model a reversible heat engine cycle. This is the first demonstration of the operation of a heat engine with a finite quantum heat bath.
Fialko, O.; Hallwood, D.
2011-01-01
We present a theoretical and numerical analysis of a quantum system that is capable of functioning as a heat engine. This system could be realized experimentally using cold bosonic atoms confined to a double well potential that is created by splitting a harmonic trap with a focused laser. The system shows thermalization, and can model a reversible heat engine cycle. This is the first demonstration of the operation of a heat engine with a finite quantum heat bath.
Energy Technology Data Exchange (ETDEWEB)
Markmann, Sergej, E-mail: sergej.markmann@ruhr-uni-bochum.de; Nong, Hanond, E-mail: nong.hanond@ruhr-uni-bochum.de; Hekmat, Negar; Jukam, Nathan [AG Terahertz Spektroskopie und Technologie, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Pal, Shovon [AG Terahertz Spektroskopie und Technologie, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Scholz, Sven; Kukharchyk, Nadezhda; Ludwig, Arne; Wieck, Andreas D. [Lehrstuhl für Angewandte Festkörperphysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany); Dhillon, Sukhdeep; Tignon, Jérôme [Laboratoire Pierre Aigrain, Ecole Normale Supérieure, UMR 8551 CNRS, UPMC, Univ. Paris 6, 75005 Paris (France); Marcadet, Xavier [Alcatel-Thales III-V Lab, Route Départementale 128, 91767 Palaiseau Cedex (France); Bock, Claudia; Kunze, Ulrich [Lehrstuhl für Werkstoffe und Nanoelektronik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)
2015-09-14
We demonstrate by injection seeding that the spectral emission of a terahertz (THz) quantum cascade laser (QCL) can be modified with broad-band THz pulses whose bandwidths are greater than the QCL bandwidth. Two broad-band THz pulses delayed in time imprint a modulation on the single THz pulse spectrum. The resulting spectrum is used to injection seed the THz QCL. By varying the time delay between the THz pulses, the amplitude distribution of the QCL longitudinal modes is modified. By applying this approach, the QCL emission is reversibly switched from multi-mode to single mode emission.
Lee, Jaehoon; Wilczek, Frank
2013-11-27
Motivated by the problem of identifying Majorana mode operators at junctions, we analyze a basic algebraic structure leading to a doubled spectrum. For general (nonlinear) interactions the emergent mode creation operator is highly nonlinear in the original effective mode operators, and therefore also in the underlying electron creation and destruction operators. This phenomenon could open up new possibilities for controlled dynamical manipulation of the modes. We briefly compare and contrast related issues in the Pfaffian quantum Hall state.
Mesoscopic quantum coherence in an optical lattice
Haycock; Alsing; Deutsch; Grondalski; Jessen
2000-10-16
We observe the quantum coherent dynamics of atomic spinor wave packets in the double-well potentials of a far-off-resonance optical lattice. With appropriate initial conditions the system Rabi oscillates between the left and right localized states of the ground doublet, and at certain times the wave packet corresponds to a coherent superposition of these mesoscopically distinct quantum states. The atom/optical double-well potential is a flexible and powerful system for further study of quantum coherence, quantum control, and the quantum/classical transition.
Quantum cloning machines and the applications
Fan, Heng; Wang, Yi-Nan; Jing, Li; Yue, Jie-Dong; Shi, Han-Duo; Zhang, Yong-Liang; Mu, Liang-Zhu
2014-11-01
No-cloning theorem is fundamental for quantum mechanics and for quantum information science that states an unknown quantum state cannot be cloned perfectly. However, we can try to clone a quantum state approximately with the optimal fidelity, or instead, we can try to clone it perfectly with the largest probability. Thus various quantum cloning machines have been designed for different quantum information protocols. Specifically, quantum cloning machines can be designed to analyze the security of quantum key distribution protocols such as BB84 protocol, six-state protocol, B92 protocol and their generalizations. Some well-known quantum cloning machines include universal quantum cloning machine, phase-covariant cloning machine, the asymmetric quantum cloning machine and the probabilistic quantum cloning machine. In the past years, much progress has been made in studying quantum cloning machines and their applications and implementations, both theoretically and experimentally. In this review, we will give a complete description of those important developments about quantum cloning and some related topics. On the other hand, this review is self-consistent, and in particular, we try to present some detailed formulations so that further study can be taken based on those results.
Quantum cloning machines and the applications
Energy Technology Data Exchange (ETDEWEB)
Fan, Heng, E-mail: hfan@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Collaborative Innovation Center of Quantum Matter, Beijing 100190 (China); Wang, Yi-Nan; Jing, Li [School of Physics, Peking University, Beijing 100871 (China); Yue, Jie-Dong [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Shi, Han-Duo; Zhang, Yong-Liang; Mu, Liang-Zhu [School of Physics, Peking University, Beijing 100871 (China)
2014-11-20
No-cloning theorem is fundamental for quantum mechanics and for quantum information science that states an unknown quantum state cannot be cloned perfectly. However, we can try to clone a quantum state approximately with the optimal fidelity, or instead, we can try to clone it perfectly with the largest probability. Thus various quantum cloning machines have been designed for different quantum information protocols. Specifically, quantum cloning machines can be designed to analyze the security of quantum key distribution protocols such as BB84 protocol, six-state protocol, B92 protocol and their generalizations. Some well-known quantum cloning machines include universal quantum cloning machine, phase-covariant cloning machine, the asymmetric quantum cloning machine and the probabilistic quantum cloning machine. In the past years, much progress has been made in studying quantum cloning machines and their applications and implementations, both theoretically and experimentally. In this review, we will give a complete description of those important developments about quantum cloning and some related topics. On the other hand, this review is self-consistent, and in particular, we try to present some detailed formulations so that further study can be taken based on those results.
Asymmetric distances for binary embeddings.
Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana
2014-01-01
In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes that binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances that are applicable to a wide variety of embedding techniques including locality sensitive hashing (LSH), locality sensitive binary codes (LSBC), spectral hashing (SH), PCA embedding (PCAE), PCAE with random rotations (PCAE-RR), and PCAE with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques.
Asymmetric cation-binding catalysis
DEFF Research Database (Denmark)
Oliveira, Maria Teresa; Lee, Jiwoong
2017-01-01
The employment of metal salts is quite limited in asymmetric catalysis, although it would provide an additional arsenal of safe and inexpensive reagents to create molecular functions with high optical purity. Cation chelation by polyethers increases the salts' solubility in conventional organic...... solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation-binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL-based polyethers. Alkali metal salts, namely KF...... and KCN, are selectively bound to the catalyst, providing exceptionally high enantioselectivities for kinetic resolutions, elimination reactions (fluoride base), and Strecker synthesis (cyanide nucleophile). Asymmetric cation-binding catalysis was recently expanded to silicon-based reagents, enabling...
Dark soliton scattering in symmetric and asymmetric double potential barriers
Tsitoura, F.; Anastassi, Z. A.; Marzuola, J. L.; Kevrekidis, P. G.; Frantzeskakis, D. J.
2017-08-01
Motivated by the recent theoretical study of (bright) soliton diode effects in systems with multiple scatterers, as well as by experimental investigations of soliton-impurity interactions, we consider some prototypical case examples of interactions of dark solitons with a pair of scatterers. In a way fundamentally opposite to the case of bright solitons (but consonant to their ;anti-particle character;), we find that dark solitons accelerate as they pass the first barrier and hence cannot be trapped by a second equal-height barrier. A pair of unequal barriers may lead to reflection from the second one, however trapping in the inter-barrier region cannot occur. We also give some examples of dynamical adjusting of the barriers to trap the dark soliton in the inter-barrier region, yet we show that this can only occur over finite time horizons, with the dark soliton always escaping eventually, contrary again to what is potentially the case with bright solitons.
Li, Shu-shen; Long, Gui-Lu; Bai, Feng-Shan; Feng, Song-Lin; Zheng, Hou-Zhi
2001-01-01
Quantum computing is a quickly growing research field. This article introduces the basic concepts of quantum computing, recent developments in quantum searching, and decoherence in a possible quantum dot realization.
Energy Technology Data Exchange (ETDEWEB)
Loginova, Y.F. [Laboratory of Physical Biochemistry, A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow 119071 (Russian Federation); Dezhurov, S.V. [Trial Center For Science and Technology ' Nanotech-Dubna' , Dubna, Moscow Region 141983 (Russian Federation); Zherdeva, V.V.; Kazachkina, N.I. [Laboratory of Physical Biochemistry, A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow 119071 (Russian Federation); Wakstein, M.S. [Trial Center For Science and Technology ' Nanotech-Dubna' , Dubna, Moscow Region 141983 (Russian Federation); Savitsky, A.P., E-mail: apsavitsky@inbi.ras.ru [Laboratory of Physical Biochemistry, A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow 119071 (Russian Federation)
2012-03-02
Highlights: Black-Right-Pointing-Pointer New QDs coated with combination of polythiol ligands and silica shell were synthesized. Black-Right-Pointing-Pointer We examine the QDs stability in digestive tract of mice after per os administration. Black-Right-Pointing-Pointer The polymer/silica shell prevents QDs degradation and fluorescence quenching in vivo. -- Abstract: CdSe-core, ZnS-capped semiconductor quantum dots (QDs) are of great potential for biomedical applications. However, applications in the gastrointestinal tract for in vivo imaging and therapeutic purposes are hampered by their sensitivity to acidic environments and potential toxicity. Here we report the use of coatings with a combination of polythiol ligands and silica shell (QDs PolyT-APS) to stabilize QDs fluorescence under acidic conditions. We demonstrated the stability of water-soluble QDs PolyT-APS both in vitro, in strong acidic solutions, and in vivo. The biodistribution, stability and photoluminescence properties of QDs in the gastrointestinal tract of mice after per os administration were assessed. We demonstrated that QDs coated with current traditional materials - mercapto compounds (QDs MPA) and pendant thiol group (QDs PolyT) - are not capable of protecting QDs from chemically induced degradation and surface modification. Polythiol ligands and silica shell quantum dots (QDs PolyT-APS) are suitable for biological and biomedical applications in the gastrointestinal tract.
Double-Barrier Resonant Tunneling in Three and Two Dimensions
Zaslavsky, Alexander
Double-barrier resonant tunneling devices have attracted great scientific interest, both as novel physical systems based on strong size quantization that exhibit unusual transport behavior and also as a promising class of semiconductor structures for high-speed electronic devices. This thesis describes the physics of transport in double-barrier structures fabricated by conventional planar growth, where the fundamental process involves tunneling from three-dimensional (3D) into two-dimensional (2D) densities of electronic states, as well as in novel 2D double-barrier structures fabricated by regrowth, where 2D electrons tunnel into well-separated ID quantum wire subbands. A brief introduction to the basic theory of resonant tunneling and the results of low-temperature I(V) transport measurements on high -quality planar double-barrier devices is presented in Chapter 1. Chapter 2 examines the bistable I(V) characteristic observed in specially designed asymmetric devices, with the intrinsic nature of this effect confirmed by parallel field magnetotunneling measurements. In Chapter 3 transverse field magnetotunneling is employed to experimentally verify the energy and transverse momentum selection rules that govern transport in resonant tunneling devices. Chapter 4 focuses on the fabrication of 2D resonant tunneling devices by liquid phase epitaxial regrowth on patterned substrates. A brief overview of liquid phase epitaxy and two different in-situ patterning techniques--selective meltback and cleaving inside the chamber--are presented. The measurements of the 2D device fabricated by regrowth on cleaved substrates are presented and analyzed in Chapter 5. The new possibilities opened up by the cleaved substrate regrowth techniques are also discussed, including the realization of an edge -regrown superlattice with novel high-field transport characteristics.
Does asymmetric correlation affect portfolio optimization?
Fryd, Lukas
2017-07-01
The classical portfolio optimization problem does not assume asymmetric behavior of relationship among asset returns. The existence of asymmetric response in correlation on the bad news could be important information in portfolio optimization. The paper applies Dynamic conditional correlation model (DCC) and his asymmetric version (ADCC) to propose asymmetric behavior of conditional correlation. We analyse asymmetric correlation among S&P index, bonds index and spot gold price before mortgage crisis in 2008. We evaluate forecast ability of the models during and after mortgage crisis and demonstrate the impact of asymmetric correlation on the reduction of portfolio variance.
Hydroxamic acids in asymmetric synthesis.
Li, Zhi; Yamamoto, Hisashi
2013-02-19
Metal-catalyzed stereoselective reactions are a central theme in organic chemistry research. In these reactions, the stereoselection is achieved predominantly by introducing chiral ligands at the metal catalyst's center. For decades, researchers have sought better chiral ligands for asymmetric catalysis and have made great progress. Nevertheless, to achieve optimal stereoselectivity and to catalyze new reactions, new chiral ligands are needed. Because of their high metal affinity, hydroxamic acids play major roles across a broad spectrum of fields from biochemistry to metal extraction. Dr. K. Barry Sharpless first revealed their potential as chiral ligands for asymmetric synthesis in 1977: He published the chiral vanadium-hydroxamic-acid-catalyzed, enantioselective epoxidation of allylic alcohols before his discovery of Sharpless asymmetric epoxidation, which uses the titanium-tartrate complex as the chiral reagent. However, researchers have reported few highly enantioselective reactions using metal-hydroxamic acid as catalysts since then. This Account summarizes our research on metal-catalyzed asymmetric epoxidation using hydroxamic acids as chiral ligands. We designed and synthesized a series of new hydroxamic acids, most notably the C2-symmetric bis-hydroxamic acid (BHA) family. V-BHA-catalyzed epoxidation of allylic and homoallylic alcohols achieved higher activity and stereoselectivity than Sharpless asymmetric epoxidation in many cases. Changing the metal species led to a series of unprecedented asymmetric epoxidation reactions, such as (i) single olefins and sulfides with Mo-BHA, (ii) homoallylic and bishomoallylic alcohols with Zr- and Hf-BHA, and (iii) N-alkenyl sulfonamides and N-sulfonyl imines with Hf-BHA. These reactions produce uniquely functionalized chiral epoxides with good yields and enantioselectivities.
Quantum cluster algebras and quantum nilpotent algebras
Goodearl, Kenneth R.; Yakimov, Milen T.
2014-01-01
A major direction in the theory of cluster algebras is to construct (quantum) cluster algebra structures on the (quantized) coordinate rings of various families of varieties arising in Lie theory. We prove that all algebras in a very large axiomatically defined class of noncommutative algebras possess canonical quantum cluster algebra structures. Furthermore, they coincide with the corresponding upper quantum cluster algebras. We also establish analogs of these results for a large class of Poisson nilpotent algebras. Many important families of coordinate rings are subsumed in the class we are covering, which leads to a broad range of applications of the general results to the above-mentioned types of problems. As a consequence, we prove the Berenstein–Zelevinsky conjecture [Berenstein A, Zelevinsky A (2005) Adv Math 195:405–455] for the quantized coordinate rings of double Bruhat cells and construct quantum cluster algebra structures on all quantum unipotent groups, extending the theorem of Geiß et al. [Geiß C, et al. (2013) Selecta Math 19:337–397] for the case of symmetric Kac–Moody groups. Moreover, we prove that the upper cluster algebras of Berenstein et al. [Berenstein A, et al. (2005) Duke Math J 126:1–52] associated with double Bruhat cells coincide with the corresponding cluster algebras. PMID:24982197
Quantum cluster algebras and quantum nilpotent algebras.
Goodearl, Kenneth R; Yakimov, Milen T
2014-07-08
A major direction in the theory of cluster algebras is to construct (quantum) cluster algebra structures on the (quantized) coordinate rings of various families of varieties arising in Lie theory. We prove that all algebras in a very large axiomatically defined class of noncommutative algebras possess canonical quantum cluster algebra structures. Furthermore, they coincide with the corresponding upper quantum cluster algebras. We also establish analogs of these results for a large class of Poisson nilpotent algebras. Many important families of coordinate rings are subsumed in the class we are covering, which leads to a broad range of applications of the general results to the above-mentioned types of problems. As a consequence, we prove the Berenstein-Zelevinsky conjecture [Berenstein A, Zelevinsky A (2005) Adv Math 195:405-455] for the quantized coordinate rings of double Bruhat cells and construct quantum cluster algebra structures on all quantum unipotent groups, extending the theorem of Geiß et al. [Geiß C, et al. (2013) Selecta Math 19:337-397] for the case of symmetric Kac-Moody groups. Moreover, we prove that the upper cluster algebras of Berenstein et al. [Berenstein A, et al. (2005) Duke Math J 126:1-52] associated with double Bruhat cells coincide with the corresponding cluster algebras.
DEFF Research Database (Denmark)
Pedersen, Jesper Goor; Zhang, Lei; Gilbert, M.J.
2010-01-01
We explore exchange coupling of a pair of spins in a double dot and in an optical lattice, using the frequency of exchanges in a bosonic path integral, evaluated using Monte Carlo simulation. The algorithm gives insights into the role of correlation through visualization of two-particle probabili...... densities, instantons, and the correlation hole. We map the problem to the Hubbard model and see that exchange and correlation renormalize the model parameters, dramatically reducing the effective on-site repulsion at larger separations...
Simulation of continuous variable quantum games without entanglement
Li, Shang-Bin
2011-07-01
A simulation scheme of quantum version of Cournot's duopoly is proposed, in which there is a new Nash equilibrium that may also be Pareto optimal without any entanglement involved. The unique property of this simulation scheme is decoherence-free against the symmetric photon loss. Furthermore, we analyze the effects of the asymmetric information on this simulation scheme and investigate the case of asymmetric game caused by asymmetric photon loss. A second-order phase transition-like behavior of the average profits of firms 1 and 2 in a Nash equilibrium can be observed with the change of the degree of asymmetry of the information or the degree of 'virtual cooperation'. It is also found that asymmetric photon loss in this simulation scheme plays a similar role as that with the asymmetric entangled states in the quantum game.
Simulation of continuous variable quantum games without entanglement
Energy Technology Data Exchange (ETDEWEB)
Li Shangbin, E-mail: stephenli74@yahoo.com.cn [Research and Development Department of Amertron Optoelectronic (Kunshan) Ltd, Jingde Road 28, Kunshan, Suzhou (China)
2011-07-22
A simulation scheme of quantum version of Cournot's duopoly is proposed, in which there is a new Nash equilibrium that may also be Pareto optimal without any entanglement involved. The unique property of this simulation scheme is decoherence-free against the symmetric photon loss. Furthermore, we analyze the effects of the asymmetric information on this simulation scheme and investigate the case of asymmetric game caused by asymmetric photon loss. A second-order phase transition-like behavior of the average profits of firms 1 and 2 in a Nash equilibrium can be observed with the change of the degree of asymmetry of the information or the degree of 'virtual cooperation'. It is also found that asymmetric photon loss in this simulation scheme plays a similar role as that with the asymmetric entangled states in the quantum game.
Asymmetric hydrogenation using monodentate phosphoramidite ligands
Minnaard, Adriaan J.; Feringa, Ben L.; Lefort, Laurent; De Vries, Johannes G.
2007-01-01
Monodentate phosphoramidites are excellent ligands for Rh-catalyzed asymmetric hydrogenations of substituted olefins. Enantioselectivities between 95 and 99% were obtained in the asymmetric hydrogenation of protected alpha- and beta-dehydroamino acids and esters, itaconic acid and esters, aromatic
Quantum circuits for cryptanalysis
Amento, Brittanney Jaclyn
Finite fields of the form F2 m play an important role in coding theory and cryptography. We show that the choice of how to represent the elements of these fields can have a significant impact on the resource requirements for quantum arithmetic. In particular, we show how the Gaussian normal basis representations and "ghost-bit basis" representations can be used to implement inverters with a quantum circuit of depth O(mlog(m)). To the best of our knowledge, this is the first construction with subquadratic depth reported in the literature. Our quantum circuit for the computation of multiplicative inverses is based on the Itoh-Tsujii algorithm which exploits the property that, in a normal basis representation, squaring corresponds to a permutation of the coefficients. We give resource estimates for the resulting quantum circuit for inversion over binary fields F2 m based on an elementary gate set that is useful for fault-tolerant implementation. Elliptic curves over finite fields F2 m play a prominent role in modern cryptography. Published quantum algorithms dealing with such curves build on a short Weierstrass form in combination with affine or projective coordinates. In this thesis we show that changing the curve representation allows a substantial reduction in the number of T-gates needed to implement the curve arithmetic. As a tool, we present a quantum circuit for computing multiplicative inverses in F2m in depth O(m log m) using a polynomial basis representation, which may be of independent interest. Finally, we change our focus from the design of circuits which aim at attacking computational assumptions on asymmetric cryptographic algorithms to the design of a circuit attacking a symmetric cryptographic algorithm. We consider a block cipher, SERPENT, and our design of a quantum circuit implementing this cipher to be used for a key attack using Grover's algorithm as in [18]. This quantum circuit is essential for understanding the complexity of Grover's algorithm.
Asymmetric Synthesis via Chiral Aziridines
DEFF Research Database (Denmark)
Tanner, David Ackland; Harden, Adrian; Wyatt, Paul
1996-01-01
A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines)]. In the b...
Structure of asymmetrical peptide dendrimers
Okrugin, B.M.; Neelov, I.M.; Leermakers, F.A.M.; Borisov, Oleg V.
2017-01-01
Structural properties of asymmetric peptide dendrimers up to the 11th generation are studied on the basis of the self-consistent field Scheutjens-Fleer numerical approach. It is demonstrated that large scale properties such as, e.g., the gyration radius, are relatively weakly affected by the
Quantum Distinction: Quantum Distinctiones!
Zeps, Dainis
2009-01-01
10 pages; How many distinctions, in Latin, quantum distinctiones. We suggest approach of anthropic principle based on anthropic reference system which should be applied equally both in theoretical physics and in mathematics. We come to principle that within reference system of life subject of mathematics (that of thinking) should be equated with subject of physics (that of nature). For this reason we enter notions of series of distinctions, quantum distinction, and argue that quantum distinct...
Hidden worlds in quantum physics
Gouesbet, Gérard
2014-01-01
The past decade has witnessed a resurgence in research and interest in the areas of quantum computation and entanglement. This new book addresses the hidden worlds or variables of quantum physics. Author Gérard Gouesbet studied and worked with a former student of Louis de Broglie, a pioneer of quantum physics. His presentation emphasizes the history and philosophical foundations of physics, areas that will interest lay readers as well as professionals and advanced undergraduate and graduate students of quantum physics. The introduction is succeeded by chapters offering background on relevant concepts in classical and quantum mechanics, a brief history of causal theories, and examinations of the double solution, pilot wave, and other hidden-variables theories. Additional topics include proofs of possibility and impossibility, contextuality, non-locality, classification of hidden-variables theories, and stochastic quantum mechanics. The final section discusses how to gain a genuine understanding of quantum mec...
Hobson, Art
2011-01-01
An earlier paper introduces quantum physics by means of four experiments: Youngs double-slit interference experiment using (1) a light beam, (2) a low-intensity light beam with time-lapse photography, (3) an electron beam, and (4) a low-intensity electron beam with time-lapse photography. It's ironic that, although these experiments demonstrate…
Quantum information processing : science & technology.
Energy Technology Data Exchange (ETDEWEB)
Horton, Rebecca; Carroll, Malcolm S.; Tarman, Thomas David
2010-09-01
Qubits demonstrated using GaAs double quantum dots (DQD). The qubit basis states are the (1) singlet and (2) triplet stationary states. Long spin decoherence times in silicon spurs translation of GaAs qubit in to silicon. In the near term the goals are: (1) Develop surface gate enhancement mode double quantum dots (MOS & strained-Si/SiGe) to demonstrate few electrons and spin read-out and to examine impurity doped quantum-dots as an alternative architecture; (2) Use mobility, C-V, ESR, quantum dot performance & modeling to feedback and improve upon processing, this includes development of atomic precision fabrication at SNL; (3) Examine integrated electronics approaches to RF-SET; (4) Use combinations of numerical packages for multi-scale simulation of quantum dot systems (NEMO3D, EMT, TCAD, SPICE); and (5) Continue micro-architecture evaluation for different device and transport architectures.
Mahyuddin, M. B. H.; Latiff, A. A.; Rusdi, M. F. M.; Irawati, N.; Harun, S. W.
2017-08-01
This paper demonstrates the integration of quantum dot (QD) cadmium selenide (CdSe) nanoparticles, which is embedded into polymethyl methacrylate (PMMA) film into an ytterbium-doped fiber laser (YDFL) cavity to produce Q-switched and mode-locked fiber lasers. The QD CdSe based film functions as a saturable absorber (SA). For Q-switching operation, stable pulse is generated within 970-1200 mW pump power, with tunable repetition rate and pulse width of 24.5-40.5 kHz and 6.8-3.7 μs, respectively. Maximum pulse energy and peak power are obtained about 1.1 μJ and 0.28 W, respectively. As we tune the polarization state of the laser cavity and use a single QD CdSe film, the mode-locking operation could also be generated within 310-468 mW pump power with repetition rate of 14.5 MHz and pulse width of 3.5 ps. Maximum pulse energy and peak power are obtained about 2 nJ and 0.11 W, respectively. These results may contribute to continuous research work on laser pulse generation, providing new opportunities of CdSe material in photonics applications.
Wang, Jing; Han, Heyou; Jiang, Xiaochun; Huang, Liang; Chen, Lina; Li, Na
2012-06-05
Near-infrared electrochemiluminescence (NIR ECL) from quantum dots (QDs) has aroused particular attention. However, whether it is possible to achieve NIR ECL sensing has remained an open question. In this article, we reported a NIR ECL immunosensor with amplification techniques for ultrasensitive and selective determination of biomarker. In this sensing platform, NIR-emitting CdTe/CdS core(small)/shell(thick) QDs were first selected as NIR ECL emitters. The NIR ECL nanoprobe (SiO(2)-QD-Ab2) was designed by covalent assembly of goat antihuman IgG antibody (Ab2) on CdTe/CdS QDs tagged silica nanospheres. Gold nanoparticle-graphene nanosheet (Au-GN) hybrids were prepared by a sonication-induced self-assembly and served as an effective matrix for initial antibodies (Ab1) attachment. After a sandwich immunoreaction, the functionalized silica nanosphere labels were captured onto the glass carbon electrode surface. Integrating the dual amplification from the promoting electron transfer rate of Au-GN hybrids and the increasing QD loading of SiO(2)-QD-Ab2 labels, the NIR ECL response from CdTe/CdS QDs enhanced 16.8-fold compared to the unamplified protocol and successfully fulfilled the ultrasensitive detection of human IgG (HIgG) with a detection limit of 87 fg mL(-1). Moreover, as a practical application, the proposed immunosensor was used to monitor HIgG level in human serum with satisfactory results obtained.
Energy Technology Data Exchange (ETDEWEB)
Suzuki, Atsushi, E-mail: suzuki@mat.usp.ac.jp; Oku, Takeo
2016-09-01
Graphical abstract: - Highlights: • Electron density distributions were delocalized on the phthalocyanine rings. • The chemical shift was separated by the nuclear quadrupole interaction based on the EFG and η. • The magnetic parameters were dependent on the perturbation of the crystal field. • The vibration modes were shifted by the asymmetrical structure. - Abstract: The effects of the central metal in double-decker metal phthalocyanine on the electronic structure, magnetic properties, and infrared and Raman spectra of the complex were investigated. Electron density distributions were delocalized on the phthalocyanine rings. The narrow energy gap and infrared peaks observed in the ultra-violet–visible–near infrared spectra of the systems were attributed to phthalocyanine ring–ring interactions the between overlapping π-orbitals on each ring. The chemical shift behavior of the phthalocyanine rings was separated by the deformation of their structure owing to nuclear magnetic interaction of the nuclear quadrupole interaction as determined by the electronic field gradient and asymmetric parameters. The magnetic parameters of principle g-tensors were dependent on the perturbation of the crystal field by the hybridization of the d-spin in the central metal conjugated with nitrogen ligands. In the case of the vanadyl system, the IR vibration modes were shifted by the soft vibration mode for resolving the symmetrical structure. Inactive Raman vibration modes arose from no-polarization on the phthalocyanine rings. Double-decker metal phthalocyanines have great advantages for the control of the magnetic mechanism for quantum spin entanglement in the relaxation process.
Cyclodextrins in Asymmetric and Stereospecific Synthesis
Directory of Open Access Journals (Sweden)
Fliur Macaev
2015-09-01
Full Text Available Since their discovery, cyclodextrins have widely been used as green and easily available alternatives to promoters or catalysts of different chemical reactions in water. This review covers the research and application of cyclodextrins and their derivatives in asymmetric and stereospecific syntheses, with their division into three main groups: (1 cyclodextrins promoting asymmetric and stereospecific catalysis in water; (2 cyclodextrins’ complexes with transition metals as asymmetric and stereospecific catalysts; and (3 cyclodextrins’ non-metallic derivatives as asymmetric and stereospecific catalysts. The scope of this review is to systematize existing information on the contribution of cyclodextrins to asymmetric and stereospecific synthesis and, thus, to facilitate further development in this direction.
A Note on Asymmetric Thick Branes
Directory of Open Access Journals (Sweden)
D. Bazeia
2014-01-01
Full Text Available We study asymmetric thick braneworld scenarios, generated after adding a constant to the superpotential associated with the scalar field. We study in particular models with odd and even polynomial superpotentials, and we show that asymmetric brane can be generated irrespective of the potential being symmetric or asymmetric. We study in addition the nonpolynomial sine-Gordon like model, also constructed with the inclusion of a constant in the standard superpotential, and we investigate gravitational stability of the asymmetric brane. The results suggest robustness of the new braneworld scenarios and add further possibilities of the construction of asymmetric branes.
Scaling of cross-sections for asymmetric (e, 3e) process on helium ...
Indian Academy of Sciences (India)
Home; Journals; Pramana – Journal of Physics; Volume 63; Issue 5. Scaling of ... An approximate simple scaling law is obtained for asymmetric (, 3) process on helium-like ions for double ionization by fast electrons. ... The scaling law becomes increasingly accurate as the target nuclear charge and the energy increase.
Shi, Bei; Lau, Kei May
2016-01-01
The effects of a double-cap procedure on the optical properties of an InAs/InAlGaAs quantum dots (QDs) system grown by metal-organic chemical vapor deposition (MOCVD) have been investigated by atomic force microscopy (AFM) and room temperature photoluminescence (RT-PL) spectroscopy. An optimized QD growth condition has been achieved, with an areal density of 4.6×1010 cm-2. It was found that the thickness and lattice constant of the high temperature second cap layer (SCL) were crucial for improving the integrated PL intensity and line-width of the 1.55 μm emission from the InAs/InAlGaAs QD system grown on a semi-insulating InP (100) substrate. With fine-tuned SCL thickness and lattice constant, the optical performance of the five-stack QDs was enhanced. The improvements can be attributed to the smooth growth front, observed from the AFM images, and the well-balanced stress engineering.
Silicon Quantum Dots for Quantum Information Processing
2013-11-01
16 2.2.2 Si/SiGe Heterostructures . . . . . . . . . . . . . . . . . . . 18 2.2.3 Silicon Nanowires ...Recently, silicon MOS, silicon/silicon- germanium (Si/SiGe) heterostructures and silicon nanowire architectures have also achieved spin manipulation and...Churchill, D. J. Reilly, J. Xiang, C. M. Lieber, and C. M. Marcus. A Ge/Si heterostructure nanowire -based double quantum dot with integrated charge
Geodesics in Asymmetric Metric Spaces
Directory of Open Access Journals (Sweden)
Mennucci Andrea C. G.
2014-01-01
Full Text Available In a recent paper [17] we studied asymmetric metric spaces; in this context we studied the length of paths, introduced the class of run-continuous paths; and noted that there are different definitions of “length spaces” (also known as “path-metric spaces” or “intrinsic spaces”. In this paper we continue the analysis of asymmetric metric spaces.We propose possible definitions of completeness and (local compactness.We define the geodesics using as admissible paths the class of run-continuous paths.We define midpoints, convexity, and quasi-midpoints, but without assuming the space be intrinsic.We distinguish all along those results that need a stronger separation hypothesis. Eventually we discuss how the newly developed theory impacts the most important results, such as the existence of geodesics, and the renowned Hopf-Rinow (or Cohn-Vossen theorem.
Electron Jet of Asymmetric Reconnection
Khotyaintsev, Yu. V.; Graham, D. B.; Norgren, C.; Eriksson, E.; Li, W.; Johlander, A.; Vaivads, A.; Andre, M.; Pritchett, P. L.; Retino, A.;
2016-01-01
We present Magnetospheric Multiscale observations of an electron-scale current sheet and electron outflow jet for asymmetric reconnection with guide field at the subsolar magnetopause. The electron jet observed within the reconnection region has an electron Mach number of 0.35 and is associated with electron agyrotropy. The jet is unstable to an electrostatic instability which generates intense waves with E(sub parallel lines) amplitudes reaching up to 300 mV/m and potentials up to 20% of the electron thermal energy. We see evidence of interaction between the waves and the electron beam, leading to quick thermalization of the beam and stabilization of the instability. The wave phase speed is comparable to the ion thermal speed, suggesting that the instability is of Buneman type, and therefore introduces electron-ion drag and leads to braking of the electron flow. Our observations demonstrate that electrostatic turbulence plays an important role in the electron-scale physics of asymmetric reconnection.
Coulomb Impurity Potential RbCl Quantum Pseudodot Qubit
Ma, Xin-Jun; Qi, Bin; Xiao, Jing-Lin
2015-08-01
By employing a variational method of Pekar type, we study the eigenenergies and the corresponding eigenfunctions of the ground and the first-excited states of an electron strongly coupled to electron-LO in a RbCl quantum pseudodot (QPD) with a hydrogen-like impurity at the center. This QPD system may be used as a two-level quantum qubit. The expressions of electron's probability density versus time and the coordinates, and the oscillating period versus the Coulombic impurity potential and the polaron radius have been derived. The investigated results indicate ① that the probability density of the electron oscillates in the QPD with a certain oscillating period of , ② that due to the presence of the asymmetrical potential in the z direction of the RbCl QPD, the electron probability density shows double-peak configuration, whereas there is only one peak if the confinement is a two-dimensional symmetric structure in the xy plane of the QPD, ③ that the oscillation period is a decreasing function of the Coulombic impurity potential, whereas it is an increasing one of the polaron radius.
Asymmetric information and macroeconomic dynamics
Hawkins, Raymond J.; Aoki, Masanao; Roy Frieden, B.
2010-09-01
We show how macroeconomic dynamics can be derived from asymmetric information. As an illustration of the utility of this approach we derive the equilibrium density, non-equilibrium densities and the equation of motion for the response to a demand shock for productivity in a simple economy. Novel consequences of this approach include a natural incorporation of time dependence into macroeconomics and a common information-theoretic basis for economics and other fields seeking to link micro-dynamics and macro-observables.
Comprehensive asymmetric dark matter model
Lonsdale, Stephen J.; Volkas, Raymond R.
2018-01-01
Asymmetric dark matter (ADM) is motivated by the similar cosmological mass densities measured for ordinary and dark matter. We present a comprehensive theory for ADM that addresses the mass density similarity, going beyond the usual ADM explanations of similar number densities. It features an explicit matter-antimatter asymmetry generation mechanism, has one fully worked out thermal history and suggestions for other possibilities, and meets all phenomenological, cosmological and astrophysical...
Ball, Justin
2016-01-01
Bulk toroidal rotation has proven capable of stabilising both dangerous MHD modes and turbulence. In this thesis, we explore a method to drive rotation in large tokamaks: up-down asymmetry in the magnetic equilibrium. We seek to maximise this rotation by finding optimal up-down asymmetric flux surface shapes. First, we use the ideal MHD model to show that low order external shaping (e.g. elongation) is best for creating up-down asymmetric flux surfaces throughout the device. Then, we calculate realistic up-down asymmetric equilibria for input into nonlinear gyrokinetic turbulence analysis. Analytic gyrokinetics shows that, in the limit of fast shaping effects, a poloidal tilt of the flux surface shaping has little effect on turbulent transport. Since up-down symmetric surfaces do not transport momentum, this invariance to tilt implies that devices with mirror symmetry about any line in the poloidal plane will drive minimal rotation. Accordingly, further analytic investigation suggests that non-mirror symmetri...
Hartle, James B.
2018-01-01
A quantum theory of the universe consists of a theory of its quantum dynamics and a theory of its quantum state The theory predicts quantum multiverses in the form of decoherent sets of alternative histories describing the evolution of the universe's spacetime geometry and matter content. These consequences follow: (a) The universe generally exhibits different quantum multiverses at different levels and kinds of coarse graining. (b) Quantum multiverses are not a choice or an assumption but ar...
Traub, Joseph F.
2014-01-01
The aim of this thesis was to explain what quantum computing is. The information for the thesis was gathered from books, scientific publications, and news articles. The analysis of the information revealed that quantum computing can be broken down to three areas: theories behind quantum computing explaining the structure of a quantum computer, known quantum algorithms, and the actual physical realizations of a quantum computer. The thesis reveals that moving from classical memor...
The application of asymmetric entangled states in quantum games
Energy Technology Data Exchange (ETDEWEB)
Li Ye [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Qin Gan [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Zhou Xianyi [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Du Jiangfeng [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China) and Hefei National Laboratory for Physical Sciences at Microscale, Hefei 230026 (China) and Fachbereich Physik, Universitaet Dortmund, 44221 Dortmund (Germany)]. E-mail: djf@ustc.edu.cn
2006-07-17
We propose a more general entangling operator in the quantization of Cournot model. It is discovered that the total profit at the Nash equilibrium always achieves maximum once the von Neumann entropy tends to infinity. Moreover, the asymmetry introduced here would cause some 'encouraging' and 'suppressing' effect on players' profit.
Nonlinear Dynamics In Quantum Physics -- Quantum Chaos and Quantum Instantons
Kröger, H.
2003-01-01
We discuss the recently proposed quantum action - its interpretation, its motivation, its mathematical properties and its use in physics: quantum mechanical tunneling, quantum instantons and quantum chaos.
Scanning gate microscopy of ultra clean carbon nanotube quantum dots
Xue, Jiamin; Dhall, Rohan; Cronin, Stephen B.; LeRoy, Brian J.
2015-01-01
We perform scanning gate microscopy on individual suspended carbon nanotube quantum dots. The size and position of the quantum dots can be visually identified from the concentric high conductance rings. For the ultra clean devices used in this study, two new effects are clearly identified. Electrostatic screening creates non-overlapping multiple sets of Coulomb rings from a single quantum dot. In double quantum dots, by changing the tip voltage, the interactions between the quantum dots can b...
Directory of Open Access Journals (Sweden)
A. Berthelot
2010-01-01
We emphasize the generality and the versatility of our model where the inclusion of asymmetric jump processes appears as an essential extension for the understanding of semiconductor quantum dot physics.
LG tools for asymmetric wargaming
Stilman, Boris; Yakhnis, Alex; Yakhnis, Vladimir
2002-07-01
Asymmetric operations represent conflict where one of the sides would apply military power to influence the political and civil environment, to facilitate diplomacy, and to interrupt specified illegal activities. This is a special type of conflict where the participants do not initiate full-scale war. Instead, the sides may be engaged in a limited open conflict or one or several sides may covertly engage another side using unconventional or less conventional methods of engagement. They may include peace operations, combating terrorism, counterdrug operations, arms control, support of insurgencies or counterinsurgencies, show of force. An asymmetric conflict can be represented as several concurrent interlinked games of various kinds: military, transportation, economic, political, etc. Thus, various actions of peace violators, terrorists, drug traffickers, etc., can be expressed via moves in different interlinked games. LG tools allow us to fully capture the specificity of asymmetric conflicts employing the major LG concept of hypergame. Hypergame allows modeling concurrent interlinked processes taking place in geographically remote locations at different levels of resolution and time scale. For example, it allows us to model an antiterrorist operation taking place simultaneously in a number of countries around the globe and involving wide range of entities from individuals to combat units to governments. Additionally, LG allows us to model all sides of the conflict at their level of sophistication. Intelligent stakeholders are represented by means of LG generated intelligent strategies. TO generate those strategies, in addition to its own mathematical intelligence, the LG algorithm may incorporate the intelligence of the top-level experts in the respective problem domains. LG models the individual differences between intelligent stakeholders. The LG tools make it possible to incorporate most of the known traits of a stakeholder, i.e., real personalities involved in
High power, 1060-nm diode laser with an asymmetric hetero-waveguide
Energy Technology Data Exchange (ETDEWEB)
Li, T; Zhang, Yu [National Key Lab. On High Power Diode Laser,Changchun University of Science and Technology,Changchun, 130033 (China); Hao, E [College of Physics, Jilin University, Changchun, 130021 (China)
2015-07-31
By introducing an asymmetric hetero-waveguide into the epitaxial structure of a diode laser, a 6.21-W output is achieved at a wavelength of 1060 nm. A different design in p- and n-confinement, based on optimisation of energy bands, is used to reduce voltage loss and meet the requirement of high power and high wall-plug efficiency. A 1060-nm diode laser with a single quantum well and asymmetric hetero-structure waveguide is fabricated and analysed. Measurement results show that the asymmetric hetero-structure waveguide can be efficiently used for reducing voltage loss and improving the confinement of injection carriers and wall-plug efficiency. (lasers)
Ma, Peng-Cheng; Chen, Gui-Bin; Li, Xiao-Wei; Zhan, You-Bang
2017-09-01
We present two schemes for asymmetric controlled bidirectional remote state preparation (CBRSP) with real and complex coefficients via seven- and ten-qubit entangled states, respectively, as the quantum channel. In these schemes, two distant parties—Alice and Bob—are not only senders but also receivers: Alice wants to remotely prepare a single-qubit state at Bob’s site; at the same time, Bob wishes to help Alice remotely prepare a two-qubit state. It is shown that the asymmetric CBRSP be can be completed successfully only if the two senders and the controller collaborate with each other. We demonstrate that, in our schemes, the total success probability of the asymmetric CBRSP can reach 1, that is, the schemes are deterministic.
Loan sales under asymmetric information
Vargas Martínez, Mónica
2010-01-01
Loans are illiquid assets that can be sold in a secondary market even that buyers have no certainty about their quality. I study a model in which a lender has access to new investment opportunities when all her assets are illiquid. To raise funds, the lender may either borrow using her assets as collateral, or she can sell them in a secondary market. Given asymmetric information about assets quality, the lender cannot recover the total value of her assets. There is then a role for the governm...
Voltage Tunable Multicolor GaAs/AlGaAs Coupled Quantum Well Infrared Photodetector
Choi, Jae Kyu; Eason, David; Strasser, Gottfried; Vagidov, Nizami; Mitin, Vladimir
2011-03-01
Tunable quantum well infrared photodetectors (QWIP) has attracted attention because of the mature growth technique of GaAs/AlGaAs quantum wells and their diverse applications such as remote temperature sensing, chemical analysis, military applications, and so on. We have designed, grown, and characterized a voltage tunable multicolor QWIP for the long wavelength infrared detection (7.5 -- 12.4 μ m). The QWIP structure was grown by MBE, and the device is designed to have bound to bound and bound to quasi-continuum transitions in an asymmetrically doped double quantum well. At zero bias we observed several distinctive spectral lines in photoresponse. The device demonstrates strong dependence on a magnitude and a polarity of the bias that is confirmed by the shift of energy levels in the electric field calculated by nextnano 3 software. In particular, switching bias from +3V to -5V we change the photoresponse of our detector from 8.39 μ m to 10.21 μ m.
Holomorphic anomaly and quantum mechanics
Codesido, Santiago; Mariño, Marcos
2018-02-01
We show that the all-orders WKB periods of one-dimensional quantum mechanical oscillators are governed by the refined holomorphic anomaly equations of topological string theory. We analyze in detail the double-well potential and the cubic and quartic oscillators, and we calculate the WKB expansion of their quantum free energies by using the direct integration of the anomaly equations. We reproduce in this way all known results about the quantum periods of these models, which we express in terms of modular forms on the WKB curve. As an application of our results, we study the large order behavior of the WKB expansion in the case of the double well, which displays the double factorial growth typical of string theory.
Spin superconductors in double-layer ferromagnetic graphene
Chen, Hua; Sun, Qingfeng; Xie, X. C.
2015-03-01
We study double-layer ferromagnetic graphene with asymmetric gate voltage applied on top and bottom layers. By employing general random phase approximation (GRPA), the interaction dressed susceptibility shows that the leading instability is of Stoner type: the Hubbard interaction drives the electron-hole (e-h) pairs condense and leads to the coherence between top and bottom layers. These e-h excitons are charge neutral but spin polarized, and their condensation can be viewed as a spin superconductor. The Goldstone mode associated with spontaneous symmetry breaking is revealed by calculating the dynamical susceptibility. An in-plane magnetic field couples the intra-spin component to the Goldstone mode and induces a zero bias voltage tunneling peak, realizing an analogue of tunneling current in bilayer quantum Hall systems. The inter-layer tunneling current is calculated by following linear response theory, which recovers the results of Fermi's golden rule. As a complementary of susceptibility calculation, mean field approximation, which ignores fluctuations, is also applied. It precisely recovers the critical Coulomb interaction as predicted by GRPA results and comfirms the existence of symmetry breaking ground states as a saddle point solution.
Pseudomorphic Bipolar Quantum Resonant-Tunneling Transistor
National Research Council Canada - National Science Library
Seabaugh, Alan C; Frensley, William R; Randall, John N; Reed, Mark A; Farrington, Dewey L; Matyi, Richard J
1989-01-01
...+ InGaAs quantum well of a double-barrier resonant-tunneling structure. The heterojunction transistor consists of an n-GaAs emitter and collector, undoped AlAs tunnel barriers, and a pseudomorphic p...
Lanzagorta, Marco
2011-01-01
This book offers a concise review of quantum radar theory. Our approach is pedagogical, making emphasis on the physics behind the operation of a hypothetical quantum radar. We concentrate our discussion on the two major models proposed to date: interferometric quantum radar and quantum illumination. In addition, this book offers some new results, including an analytical study of quantum interferometry in the X-band radar region with a variety of atmospheric conditions, a derivation of a quantum radar equation, and a discussion of quantum radar jamming.This book assumes the reader is familiar w
Asymmetric liberations in exterior resonances
Beauge, C.
1994-10-01
The purpose of this paper is to present a general analysis of the planar circular restricted problem of three bodies in the case of exterior mean-motion resonances. Particularly, our aim is to map the phase space of various commensurabilities and determine the singular solutions of the averaged system, comparing them to the well-known case of interior resonances. In some commensurabilities (e.g. 1/2, 1/3) we show the existence of asymmetric librations; that is, librations in which the stationary value of the critical angle theta = (p+q) lambda1-p lambda-q pi is not equal to either zero or pi. The origin, stability and morphogenesis of these solutions are discussed and compared to symmetric librations. However, in some other resonances (e.g. 2/3, 3/4), these fixed points of the mean system seem to be absent. Librations in such cases are restricted to theta = O mod(pi). Asymmetric singular solutions of the plane circular problem are unknown in the case of interior resonances and cannot be reproduced by the reduced Andoyer Hamiltonian known as the Second Fundamental Model for Resonance. However, we show that the extended version of this Hamiltonian function, in which harmonics up to order two are considered, can reproduce fairly well the principal topological characteristics of the phase space and thereby constitutes a simple and useful analytical approximation for these resonances.
Asymmetric Laguerre-Gaussian beams
Kovalev, A. A.; Kotlyar, V. V.; Porfirev, A. P.
2016-06-01
We introduce a family of asymmetric Laguerre-Gaussian (aLG) laser beams. The beams have been derived via a complex-valued shift of conventional LG beams in the Cartesian plane. While propagating in a uniform medium, the first bright ring of the aLG beam becomes less asymmetric and the energy is redistributed toward peripheral diffraction rings. The projection of the orbital angular momentum (OAM) onto the optical axis is calculated. The OAM is shown to grow quadratically with increasing asymmetry parameter of the aLG beam, which equals the ratio of the shift to the waist radius. Conditions for the OAM becoming equal to the topological charge have been derived. For aLG beams with zero radial index, we have deduced an expression to define the intensity maximum coordinates and shown the crescent-shaped intensity pattern to rotate during propagation. Results of the experimental generation and rotation of aLG beams agree well with theoretical predictions.
Thin lenses of asymmetric power
Directory of Open Access Journals (Sweden)
W. F. Harris
2009-12-01
Full Text Available It is generally supposed that thin systems, including refracting surfaces and thin lenses, have powers that are necessarily symmetric. In other words they have powers which can be represented assymmetric dioptric power matrices and in the familar spherocylindrical form used in optometry and ophthalmology. This paper shows that this is not correct and that it is indeed possible for a thin system to have a power that is not symmetric and which cannot be expressed in spherocylindrical form. Thin systems of asymmetric power are illustratedby means of a thin lens that is modelled with small prisms and is chosen to have a dioptric power ma-trix that is antisymmetric. Similar models can be devised for a thin system whose dioptric power matrix is any 2 2 × matrix. Thus any power, symmetric, asymmetric or antisymmetric, is possible for a thin system. In this sense our understanding of the power of thin systems is now complete.
DEFF Research Database (Denmark)
Zubov, F. I.; Zhukov, A. E.; Shernyakov, Yu M.
2015-01-01
Current-voltage and light-current characteristics of quantum-well lasers have been studied at high drive currents. The introduction of asymmetric barrier layers adjacent to the active region caused a significant suppression of the nonlinearity in the light-current characteristic and an increase...... in the external differential efficiency. As a result, the maximum wallplug efficiency increased by 9%, while the output optical power increased by 29%....
Controlled Photon Switch Assisted by Coupled Quantum Dots
Luo, Ming-Xing; Ma, Song-Ya; Chen, Xiu-Bo; Wang, Xiaojun
2015-01-01
Quantum switch is a primitive element in quantum network communication. In contrast to previous switch schemes on one degree of freedom (DOF) of quantum systems, we consider controlled switches of photon system with two DOFs. These controlled photon switches are constructed by exploring the optical selection rules derived from the quantum-dot spins in one-sided optical microcavities. Several double controlled-NOT gate on different joint systems are greatly simplified with an auxiliary DOF of the controlling photon. The photon switches show that two DOFs of photons can be independently transmitted in quantum networks. This result reduces the quantum resources for quantum network communication. PMID:26095049
Quantum CPU and Quantum Simulating
Wang, An Min
1999-01-01
Making use of an universal quantum network or QCPU proposed by me [6], some special quantum networks for simulating some quantum systems are given out. Specially, it is obtained that the quantum network for the time evolution operator which can simulate, in general, Schr\\"odinger equation.
Quantum Computer Games: Quantum Minesweeper
Gordon, Michal; Gordon, Goren
2010-01-01
The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical…
Gaussian Hypothesis Testing and Quantum Illumination.
Wilde, Mark M; Tomamichel, Marco; Lloyd, Seth; Berta, Mario
2017-09-22
Quantum hypothesis testing is one of the most basic tasks in quantum information theory and has fundamental links with quantum communication and estimation theory. In this paper, we establish a formula that characterizes the decay rate of the minimal type-II error probability in a quantum hypothesis test of two Gaussian states given a fixed constraint on the type-I error probability. This formula is a direct function of the mean vectors and covariance matrices of the quantum Gaussian states in question. We give an application to quantum illumination, which is the task of determining whether there is a low-reflectivity object embedded in a target region with a bright thermal-noise bath. For the asymmetric-error setting, we find that a quantum illumination transmitter can achieve an error probability exponent stronger than a coherent-state transmitter of the same mean photon number, and furthermore, that it requires far fewer trials to do so. This occurs when the background thermal noise is either low or bright, which means that a quantum advantage is even easier to witness than in the symmetric-error setting because it occurs for a larger range of parameters. Going forward from here, we expect our formula to have applications in settings well beyond those considered in this paper, especially to quantum communication tasks involving quantum Gaussian channels.
Gaussian Hypothesis Testing and Quantum Illumination
Wilde, Mark M.; Tomamichel, Marco; Lloyd, Seth; Berta, Mario
2017-09-01
Quantum hypothesis testing is one of the most basic tasks in quantum information theory and has fundamental links with quantum communication and estimation theory. In this paper, we establish a formula that characterizes the decay rate of the minimal type-II error probability in a quantum hypothesis test of two Gaussian states given a fixed constraint on the type-I error probability. This formula is a direct function of the mean vectors and covariance matrices of the quantum Gaussian states in question. We give an application to quantum illumination, which is the task of determining whether there is a low-reflectivity object embedded in a target region with a bright thermal-noise bath. For the asymmetric-error setting, we find that a quantum illumination transmitter can achieve an error probability exponent stronger than a coherent-state transmitter of the same mean photon number, and furthermore, that it requires far fewer trials to do so. This occurs when the background thermal noise is either low or bright, which means that a quantum advantage is even easier to witness than in the symmetric-error setting because it occurs for a larger range of parameters. Going forward from here, we expect our formula to have applications in settings well beyond those considered in this paper, especially to quantum communication tasks involving quantum Gaussian channels.
Asymmetric Warfare and the Will to Win
National Research Council Canada - National Science Library
Herrera, Cary
2001-01-01
This thesis explores the will to win in asymmetric war. Asymmetric war, in which one side has an overwhelming advantage over its opponent, will likely be the war of the future for the United States in the post-Cold War uni-polar world...
Renewable resource management under asymmetric information
DEFF Research Database (Denmark)
Jensen, Frank; Andersen, Peder; Nielsen, Max
2013-01-01
Asymmetric information between fishermen and the regulator is important within fisheries. The regulator may have less information about stock sizes, prices, costs, effort, productivity and catches than fishermen. With asymmetric information, a strong analytical tool is principal-agent analysis. I...
Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach
Chauhan, Pankaj; Chimni, Swapandeep Singh
2012-01-01
Summary Ball-milling and pestle and mortar grinding have emerged as powerful methods for the development of environmentally benign chemical transformations. Recently, the use of these mechanochemical techniques in asymmetric organocatalysis has increased. This review highlights the progress in asymmetric organocatalytic reactions assisted by mechanochemical techniques.
Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach
Chauhan, Pankaj
2012-01-01
Summary Ball-milling and pestle and mortar grinding have emerged as powerful methods for the development of environmentally benign chemical transformations. Recently, the use of these mechanochemical techniques in asymmetric organocatalysis has increased. This review highlights the progress in asymmetric organocatalytic reactions assisted by mechanochemical techniques. PMID:23243475
Worst Asymmetrical Short-Circuit Current
DEFF Research Database (Denmark)
Arana Aristi, Iván; Holmstrøm, O; Grastrup, L
2010-01-01
In a typical power plant, the production scenario and the short-circuit time were found for the worst asymmetrical short-circuit current. Then, a sensitivity analysis on the missing generator values was realized in order to minimize the uncertainty of the results. Afterward the worst asymmetrical...
Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach
Directory of Open Access Journals (Sweden)
Pankaj Chauhan
2012-12-01
Full Text Available Ball-milling and pestle and mortar grinding have emerged as powerful methods for the development of environmentally benign chemical transformations. Recently, the use of these mechanochemical techniques in asymmetric organocatalysis has increased. This review highlights the progress in asymmetric organocatalytic reactions assisted by mechanochemical techniques.
Quantum Thermodynamics with Degenerate Eigenstate Coherences
Directory of Open Access Journals (Sweden)
Gregory Bulnes Cuetara
2016-12-01
Full Text Available We establish quantum thermodynamics for open quantum systems weakly coupled to their reservoirs when the system exhibits degeneracies. The first and second law of thermodynamics are derived, as well as a finite-time fluctuation theorem for mechanical work and energy and matter currents. Using a double quantum dot junction model, local eigenbasis coherences are shown to play a crucial role on thermodynamics and on the electron counting statistics.
Quantum transport in carbon nanotubes
DEFF Research Database (Denmark)
Laird, Edward A.; Kuemmeth, Ferdinand; Steele, Gary A.
2015-01-01
modifies their transport behaviour. Interaction between electrons inside and outside a quantum dot is manifested in SU(4) Kondo behavior and level renormalization. Interaction within a dot leads to Wigner molecules and more complex correlated states. This review takes an experimental perspective informed...... and valley degrees of freedom. This review describes the modern understanding of transport through nanotube devices. Unlike conventional semiconductors, electrons in nanotubes have two angular momentum quantum numbers, arising from spin and from valley freedom. We focus on the interplay between the two....... In single quantum dots defined in short lengths of nanotube, the energy levels associated with each degree of freedom, and the spin-orbit coupling between them, are revealed by Coulomb blockade spectroscopy. In double quantum dots, the combination of quantum numbers modifies the selection rules of Pauli...
Geometric reduction of dynamical nonlocality in nanoscale quantum circuits
Strambini, Elia; Makarenko, K.S.; Makarenko, K.S.; Abulizi, G.; de Jong, Machiel Pieter; van der Wiel, Wilfred Gerard
2016-01-01
Nonlocality is a key feature discriminating quantum and classical physics. Quantum-interference phenomena, such as Young’s double slit experiment, are one of the clearest manifestations of nonlocality, recently addressed as dynamical to specify its origin in the quantum equations of motion. It is
Asymmetric Digital Subscriber Line (ADSL
Directory of Open Access Journals (Sweden)
Slavko Šarić
2012-10-01
Full Text Available ADSL (Asymmetric Digital Subscriber Line is a technologythat allows transmission at 8.488 Mbps over the existingtelephone copper line (speed range depending on the distance.ADSL circuit connects the ADSL modems by twisted-pairtelephone lines creating three infonnation channels: high speedsimplex (maximum 9 Mbps, medium speed duplex channel(maximum 2 Mbps and plain old telephone service channel.ADSL technology supports up to seven synchronous channelsthat can be configured to meet the needs of the end user.One could simultaneously view four movies stored in MPEG 1fonnat on separate television sets (MPEG 1 transmitted at 1.5Mbps, hold a video-conference (transmitted at 348 kbps,download data files from a server at 128 kbps via ISDN andeven receive a telephone call.
Research on asymmetric searchable encryption
Yu, Zonghua; Wu, Yudong
2017-05-01
Cloud server side to ease the user's local storage pressure at the same time, there are hidden data on the hidden dangers, the user often choose to upload the data in the form of cipher text to the cloud server. However, the classic data encryption and decryption algorithms are not provided search function, affecting the user's efficiency. To this end, an asymmetric searchable encryption scheme is proposed. The scheme can be used for any person can generate a trapdoor, cipher text can be free modified, the key pair generated by the user themselves, encrypt the identity, S-shaped virtual and other five loopholes to improve. The analysis results show that the scheme solves the above five vulnerabilities in the original scheme, so that the information semantics of both parties of communication can be guaranteed.
Short-channel drain current model for asymmetric heavily / lightly doped DG MOSFETs
Dutta, Pradipta; Syamal, Binit; Koley, Kalyan; Dutta, Arka; Sarkar, C. K.
2017-08-01
The paper presents a drain current model for double gate metal oxide semiconductor field effect transistors (DG MOSFETs) based on a new velocity saturation model that accounts for short-channel velocity saturation effect independently in the front and the back gate controlled channels under asymmetric front and back gate bias and oxide thickness. To determine the front and the back-channel velocity saturation, drain-induced barrier lowering is evaluated by effective gate voltages at the front and back gates obtained from surface potential at the threshold condition after considering symmetric and asymmetric front and back oxide thickness. The model also incorporates surface roughness scattering and ionized impurity scattering to estimate drain current for heavily / lightly doped channel for short-channel asymmetric DG MOSFET and a good agreement has been achieved with TCAD simulations, with a relative error of around 3-7%.
Chattaraj, Pratim Kumar
2010-01-01
The application of quantum mechanics to many-particle systems has been an active area of research in recent years as researchers have looked for ways to tackle difficult problems in this area. The quantum trajectory method provides an efficient computational technique for solving both stationary and time-evolving states, encompassing a large area of quantum mechanics. Quantum Trajectories brings the expertise of an international panel of experts who focus on the epistemological significance of quantum mechanics through the quantum theory of motion.Emphasizing a classical interpretation of quan
Bialynicki-Birula, I; Ter Haar, D
1975-01-01
Quantum Electrodynamics focuses on the formulation of quantum electrodynamics (QED) in its most general and most abstract form: relativistic quantum field theory. It describes QED as a program, rather than a closed theory, that rests on the theory of the quantum Maxwellian field interacting with given (external) classical sources of radiation and on the relativistic quantum mechanics of electrons interacting with a given (external) classical electromagnetic field.Comprised of eight chapters, this volume begins with an introduction to the fundamental principles of quantum theory formulated in a
Blaise, Paul
2011-01-01
An invaluable reference for an overall but simple approach to the complexity of quantum mechanics viewed through quantum oscillators Quantum oscillators play a fundamental role in many areas of physics; for instance, in chemical physics with molecular normal modes, in solid state physics with phonons, and in quantum theory of light with photons. Quantum Oscillators is a timely and visionary book which presents these intricate topics, broadly covering the properties of quantum oscillators which are usually dispersed in the literature at varying levels of detail and often combined with other p
Bradley, Jonathan P; Tripon, Carmen; Filip, Claudiu; Brown, Steven P
2009-08-28
The build-up of intensity-as a function of the number, n(rcpl), of POST-C7 elements used for the excitation and reconversion of double-quantum (DQ) coherence (DQC)-is analysed for the fifteen distinct DQ correlation peaks that are observed experimentally for the eight separate (1)H resonances in a (1)H (500 MHz) DQ CRAMPS solid-state (12.5 kHz MAS) NMR spectrum of the dipeptide beta-AspAla (S. P. Brown, A. Lesage, B. Elena, and L. Emsley, J. Am. Chem. Soc., 2004, 126, 13230). The simulation in SPINEVOLUTION (M. Veshtort and R. G. Griffin, J. Magn. Reson., 2006, 178, 248) of t(1) ((1)H DQ evolution) FIDs for clusters of eight dipolar-coupled protons gives separate simulated (1)H DQ build-up curves for the CH(2)(a), CH(2)(b), CH(Asp), CH(Ala), NH and OH (1)H single-quantum (SQ) (1)H resonances. An analysis of both the simulated and experimental (1)H DQ build-up leads to the following general observations: (i) considering the build-up of (1)H DQ peaks at a particular SQ frequency, maximum intensity is observed for the DQC corresponding to the shortest H-H distance; (ii) for the maximum intensity (1)H DQ peak at a particular SQ frequency, the recoupling time for the observed maximum intensity depends on the corresponding H-H distance, e.g., maximum intensity for the CH(2)(a)-CH(2)(b) (H-H distance = 1.55 A) and OH-CH(Asp) (H-H distance = 2.49 A) DQ peaks is observed at n(rcpl) = 2 and 3, respectively; (iii) for DQ peaks involving a CH(2) proton at a non-CH(2) SQ frequency, there is much reduced intensity and a maximum intensity at a short recoupling time; (iv) for the other lower intensity (1)H DQ peaks at a particular SQ frequency, maximum intensity is observed for the same (or close to the same) recoupling time, but the relative intensity of the DQ peaks is a reliable indicator of the relative H-H distance-the ratio of the maximum intensities for the peaks at the CH(Ala) SQ frequency due to the two DQCs with the NH and OH protons are found to be approximately in the
Simplifying quantum double Hamiltonians using perturbative gadgets
Koenig, Robert
2009-01-01
Perturbative gadgets were originally introduced to generate effective k-local interactions in the low-energy sector of a 2-local Hamiltonian. Extending this idea, we present gadgets which are specifically suited for realizing Hamiltonians exhibiting non-abelian anyonic excitations. At the core of our construction is a perturbative analysis of a widely used hopping-term Hamiltonian. We show that in the low-energy limit, this Hamiltonian can be approximated by a certain ordered p...
Quantum robots and quantum computers
Energy Technology Data Exchange (ETDEWEB)
Benioff, P.
1998-07-01
Validation of a presumably universal theory, such as quantum mechanics, requires a quantum mechanical description of systems that carry out theoretical calculations and systems that carry out experiments. The description of quantum computers is under active development. No description of systems to carry out experiments has been given. A small step in this direction is taken here by giving a description of quantum robots as mobile systems with on board quantum computers that interact with different environments. Some properties of these systems are discussed. A specific model based on the literature descriptions of quantum Turing machines is presented.
Energy Technology Data Exchange (ETDEWEB)
Zurek, Wojciech H [Los Alamos National Laboratory
2008-01-01
Quantum Darwinism - proliferation, in the environment, of multiple records of selected states of the system (its information-theoretic progeny) - explains how quantum fragility of individual state can lead to classical robustness of their multitude.
Gisin, Nicolas; Ribordy, Grégoire; Tittel, Wolfgang; Zbinden, Hugo
2002-01-01
Quantum cryptography could well be the first application of quantum mechanics at the individual quanta level. The very fast progress in both theory and experiments over the recent years are reviewed, with emphasis on open questions and technological issues.
Quantum metamaterials as a tool for investigating the quantum-classical transition
Saveliev, Sergey; Zagoskin, Alexandre; Everitt, Mark; Wilson, Richard
2012-02-01
Quantum metamaterials are optical media comprised of individually controllable unit elements (e.g., qubits), which maintain quantum coherence for periods sufficient for an electromagnetic wave to pass through the system. They represent macroscopic, spatially extended quantum scatterers, which can be put in a superposition of states with different properties (e.g., different refractive indexes) and can thus provide new ways of testing different scenarios of quantum-classical transition. We consider an inverse of the classic double-slit experiment, where a classical electromagnetic wave is scattered by a quantum metamaterial in a superposition of states, and discuss the possibilities of its experimental realization.
Telegraph noise in coupled quantum dot circuits induced by a quantum point contact.
Taubert, D; Pioro-Ladrière, M; Schröer, D; Harbusch, D; Sachrajda, A S; Ludwig, S
2008-05-02
Charge detection utilizing a highly biased quantum point contact has become the most effective probe for studying few electron quantum dot circuits. Measurements on double and triple quantum dot circuits is performed to clarify a back action role of charge sensing on the confined electrons. The quantum point contact triggers inelastic transitions, which occur quite generally. Under specific device and measurement conditions these transitions manifest themselves as bounded regimes of telegraph noise within a stability diagram. A nonequilibrium transition from artificial atomic to molecular behavior is identified. Consequences for quantum information applications are discussed.
Esteban Guevara Hidalgo
2006-01-01
The relationships between game theory and quantum mechanics let us propose certain quantization relationships through which we could describe and understand not only quantum but also classical, evolutionary and the biological systems that were described before through the replicator dynamics. Quantum mechanics could be used to explain more correctly biological and economical processes and even it could encloses theories like games and evolutionary dynamics. This could make quantum mechanics a...
A mean-field theory on the differential capacitance of asymmetric ionic liquid electrolytes.
Han, Yining; Huang, Shanghui; Yan, Tianying
2014-07-16
The size of ions significantly influences the electric double layer structure of room temperature ionic liquid (IL) electrolytes and their differential capacitance (Cd). In this study, we extended the mean-field theory (MFT) developed independently by Kornyshev (2007J. Phys. Chem. B 111 5545-57) and Kilic, Bazant, and Ajdari (2007 Phys. Rev. E 75 021502) (the KKBA MFT) to take into account the asymmetric 1:1 IL electrolytes by introducing an additional parameter ξ for the anion/cation volume ratio, besides the ionic compressibility γ in the KKBA MFT. The MFT of asymmetric ions becomes KKBA MFT upon ξ = 1, and further reduces to Gouy-Chapman theory in the γ → 0 limit. The result of the extended MFT demonstrates that the asymmetric ILs give rise to an asymmetric Cd, with the higher peak in Cd occurring at positive polarization for the smaller anionic size. At high potential, Cd decays asymptotically toward KKBA MFT characterized by γ for the negative polarization, and characterized by ξγ for the positive polarization, with inverse-square-root behavior. At low potential, around the potential of zero charge, the asymmetric ions cause a higher Cd, which exceeds that of Gouy-Chapman theory.
S. Fehr (Serge)
2010-01-01
textabstractQuantum cryptography makes use of the quantum-mechanical behavior of nature for the design and analysis of cryptographic schemes. Optimally (but not always), quantum cryptography allows for the design of cryptographic schemes whose security is guaranteed solely by the laws of nature.
Modelling asymmetric growth in crowded plant communities
DEFF Research Database (Denmark)
Damgaard, Christian
2010-01-01
A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size......-asymmetric growth part, where growth is assumed to be proportional to a power function of the size of the individual, and a term that reduces the relative growth rate as a decreasing function of the individual plant size and the competitive interactions from other plants in the neighbourhood....
Nondeterministic self-assembly with asymmetric interactions
Tesoro, S.; Göpfrich, K.; Kartanas, T.; Keyser, U. F.; Ahnert, S. E.
2016-08-01
We investigate general properties of nondeterministic self-assembly with asymmetric interactions, using a computational model and DNA tile assembly experiments. By contrasting symmetric and asymmetric interactions we show that the latter can lead to self-limiting cluster growth. Furthermore, by adjusting the relative abundance of self-assembly particles in a two-particle mixture, we are able to tune the final sizes of these clusters. We show that this is a fundamental property of asymmetric interactions, which has potential applications in bioengineering, and provides insights into the study of diseases caused by protein aggregation.
"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…
DEFF Research Database (Denmark)
Clausen, Lisbeth
2017-01-01
There are two main streams of understanding intercultural communication. The “classic” transmission models include the basic elements of communication involved in sending messages from a sender to a receiver. These models enable analysis of all communication elements and effects by focusing...... on sameness in communication. In contrast, Muneo Jay Yoshikawa's “double-swing” model of intercultural communication between the East and West is based on an eastern understanding of dialogue, collaborative communication, and co-creation of meaning. The double-swing model enables an understanding...... of communication as an ongoing encounter where both sender and receiver have mutual respect. It has four modes of communication: the ethnocentric, the dialectic, the control, and the dialogic. Both models have something to offer intercultural communication, but the double-swing model enables a worldview...
Scaling of cross-sections for asymmetric (e,3e) process on helium ...
Indian Academy of Sciences (India)
Abstract. An approximate simple scaling law is obtained for asymmetric (e, 3e) process on helium-like ions for double ionization by fast electrons. It is based on the equation. (Z 3/π) exp[−Z (r1 + r2)], Z = Z − (5/16) for ground state wave function of helium- like ions and Z 2 scaling of energies. The scaling law is found to work ...
Song, Yi; Ni, Jiang-Li; Wang, Zhang-Yin; Lu, Yan; Han, Lian-Fang
2017-10-01
We present a new scheme for deterministically realizing the mutual interchange of quantum information between two distant parties via selected quantum states as the shared entangled resource. We first show the symmetric bidirectional remote state preparation (BRSP), where two single-qubit quantum states will be simultaneously exchanged in a deterministic manner provided that each of the users performs single-qubit von Neumann measurements with proper measurement bases as well as appropriate unitary operations, depending essentially on the outcomes of the prior measurements. Then we consider to extend the symmetric protocol to an asymmetric case, in which BRSP of a general single-qubit state and an arbitrary two-qubit state is investigated successfully. The necessary quantum operations and the employed quantum resources are feasible according to the present technology, resulting in that this protocol may be realizable in the realm of current physical experiment.
Modeling of asymmetrical boost converters
Directory of Open Access Journals (Sweden)
Eliana Isabel Arango Zuluaga
2014-01-01
Full Text Available The asymmetrical interleaved dual boost (AIDB is a fifth-order DC/DC converter designed to interface photovoltaic (PV panels. The AIDB produces small current harmonics to the PV panels, reducing the power losses caused by the converter operation. Moreover, the AIDB provides a large voltage conversion ratio, which is required to step-up the PV voltage to the large dc-link voltage used in grid-connected inverters. To reject irradiance and load disturbances, the AIDB must be operated in a closed-loop and a dynamic model is required. Given that the AIDB converter operates in Discontinuous Conduction Mode (DCM, classical modeling approaches based on Continuous Conduction Mode (CCM are not valid. Moreover, classical DCM modeling techniques are not suitable for the AIDB converter. Therefore, this paper develops a novel mathematical model for the AIDB converter, which is suitable for control-pur-poses. The proposed model is based on the calculation of a diode current that is typically disregarded. Moreover, because the traditional correction to the second duty cycle reported in literature is not effective, a new equation is designed. The model accuracy is contrasted with circuital simulations in time and frequency domains, obtaining satisfactory results. Finally, the usefulness of the model in control applications is illustrated with an application example.
Modeling of asymmetrical boost converters
Directory of Open Access Journals (Sweden)
Eliana Isabel Arango Zuluaga
2014-03-01
Full Text Available The asymmetrical interleaved dual boost (AIDB is a fifth-order DC/DC converter designed to interface photovoltaic (PV panels. The AIDB produces small current harmonics to the PV panels, reducing the power losses caused by the converter operation. Moreover, the AIDB provides a large voltage conversion ratio, which is required to step-up the PV voltage to the large dc-link voltage used in grid-connected inverters. To reject irradiance and load disturbances, the AIDB must be operated in a closed-loop and a dynamic model is required. Given that the AIDB converter operates in Discontinuous Conduction Mode (DCM, classical modeling approaches based on Continuous Conduction Mode (CCM are not valid. Moreover, classical DCM modeling techniques are not suitable for the AIDB converter. Therefore, this paper develops a novel mathematical model for the AIDB converter, which is suitable for control-pur-poses. The proposed model is based on the calculation of a diode current that is typically disregarded. Moreover, because the traditional correction to the second duty cycle reported in literature is not effective, a new equation is designed. The model accuracy is contrasted with circuital simulations in time and frequency domains, obtaining satisfactory results. Finally, the usefulness of the model in control applications is illustrated with an application example.
Zurek, Wojciech Hubert
2009-03-01
Quantum Darwinism describes the proliferation, in the environment, of multiple records of selected states of a quantum system. It explains how the quantum fragility of a state of a single quantum system can lead to the classical robustness of states in their correlated multitude; shows how effective `wave-packet collapse' arises as a result of the proliferation throughout the environment of imprints of the state of the system; and provides a framework for the derivation of Born's rule, which relates the probabilities of detecting states to their amplitudes. Taken together, these three advances mark considerable progress towards settling the quantum measurement problem.
Moulick, Subhayan Roy; Panigrahi, Prasanta K.
2016-06-01
We propose the idea of a quantum cheque scheme, a cryptographic protocol in which any legitimate client of a trusted bank can issue a cheque, that cannot be counterfeited or altered in anyway, and can be verified by a bank or any of its branches. We formally define a quantum cheque and present the first unconditionally secure quantum cheque scheme and show it to be secure against any no-signalling adversary. The proposed quantum cheque scheme can been perceived as the quantum analog of Electronic Data Interchange, as an alternate for current e-Payment Gateways.
Basin boundaries in asymmetric vibrations of a circular plate
Park, H. D.; Lee, W. K.
2008-08-01
In order to investigate further nonlinear asymmetric vibrations of a clamped circular plate under a harmonic excitation, we reexamine a primary resonance, studied by Yeo and Lee [Corrected solvability conditions for non-linear asymmetric vibrations of a circular plate, Journal of Sound and Vibration 257 (2002) 653-665] in which at most three stable steady-state responses (one standing wave and two traveling waves) are observed to exist. Further examination, however, tells that there exist at most five stable steady-state responses: one standing wave and four traveling waves. Two of the traveling waves lose their stability by Hopf bifurcation and have a sequence of period-doubling bifurcations leading to chaos. When the system has five attractors: three equilibrium solutions (one standing wave and two traveling waves) and two chaotic attractors (two modulated traveling waves), the basin boundaries of the attractors on the principal plane are obtained. Also examined is how basin boundaries of the modulated motions (quasi-periodic and chaotic motions) evolve as a system parameter varies. The basin boundaries of the modulated motions turn out to have the fractal nature.
An asymmetric mesoscopic model for single bulges in RNA
de Oliveira Martins, Erik; Weber, Gerald
2017-10-01
Simple one-dimensional DNA or RNA mesoscopic models are of interest for their computational efficiency while retaining the key elements of the molecular interactions. However, they only deal with perfectly formed DNA or RNA double helices and consider the intra-strand interactions to be the same on both strands. This makes it difficult to describe highly asymmetric structures such as bulges and loops and, for instance, prevents the application of mesoscopic models to determine RNA secondary structures. Here we derived the conditions for the Peyrard-Bishop mesoscopic model to overcome these limitations and applied it to the calculation of single bulges, the smallest and simplest of these asymmetric structures. We found that these theoretical conditions can indeed be applied to any situation where stacking asymmetry needs to be considered. The full set of parameters for group I RNA bulges was determined from experimental melting temperatures using an optimization procedure, and we also calculated average opening profiles for several RNA sequences. We found that guanosine bulges show the strongest perturbation on their neighboring base pairs, considerably reducing the on-site interactions of their neighboring base pairs.
Asymmetrical Warfare, Transformation, and Foreign Language Capability
National Research Council Canada - National Science Library
Porter, Clifford F
2006-01-01
.... There is no doubt that the current global war on terrorism is an asymmetrical war against an unpredictable enemy rather than the predictable or symmetrical threats against self-important dictators or the Soviet Union...
Asymmetric cryptography based on wavefront sensing.
Peng, Xiang; Wei, Hengzheng; Zhang, Peng
2006-12-15
A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.
Congenital asymmetric crying face: a case report
Directory of Open Access Journals (Sweden)
Semra Kara
2011-12-01
Full Text Available Congenital asymmetric crying face is an anomalia caused by unilateral absence or weakness of depressor anguli oris muscle The major finding of the disease is the absence or weakness in the outer and lower movement of the commissure during crying. The other expression muscles are normal and the face is symmetric at rest. The asymmetry in congenital asymmetric crying face is most evident during infancy but decreases by age. Congenital asymmetric crying face can be associated with cervicofacial, musclebone, respiratory, genitourinary and central nervous system anomalia. It is diagnosed by physical examination. This paper presents a six days old infant with Congenital asymmetric crying face and discusses the case in terms of diagnosis and disease features.
Modeling Asymmetric Volatility In Oil Prices
National Research Council Canada - National Science Library
Syed Aun Hassan
2011-01-01
.... The paper uses daily crude oil price data for the past 10 years to test and model the oil price volatility by fitting different variations of GARCH including a univariate asymmetric GARCH model to the series...
Asymmetric dense matter in holographic QCD
Directory of Open Access Journals (Sweden)
Shin Ik Jae
2012-02-01
Full Text Available We study asymmetric dense matter in holographic QCD.We construct asymmetric dense matter by considering two quark flavor branes with dierent quark masses in a D4/D6/D6 model. To calculate the symmetry energy in nuclear matter, we consider two quarks with equal masses and observe that the symmetry energy increases with the total charge showing the stiff dependence. This behavior is universal in the sense that the result is independent of parameters in the model. We also study strange (or hyperon matter with one light and one intermediate mass quarks. In addition to the vacuum properties of asymmetric matter, we calculate meson masses in asymmetric dense matter and discuss our results in the light of in-medium kaon masses.
DEFF Research Database (Denmark)
Taherkhani, Masoomeh; Gregersen, Niels; Willatzen, Morten
2017-01-01
The exciton oscillator strength (OS) in type-II quantum dot (QD) nanowires is calculated by using a fast and efficient method. We propose a new structure in Double-Well QD (DWQD) nanowire that considerably increases OS of type-II QDs which is a key parameter in optical quantum gating in the stimu...... in the stimulated Raman adiabatic passage (STIRAP) process [1] for implementing quantum gates....
Asymmetric electroresistance of cluster glass state in manganites
Lourembam, James
2014-03-31
We report the electrostatic modulation of transport in strained Pr0.65(Ca0.75Sr0.25)0.35MnO3 thin films grown on SrTiO3 by gating with ionic liquid in electric double layer transistors (EDLT). In such manganite films with strong phase separation, a cluster glass magnetic state emerges at low temperatures with a spin freezing temperature of about 99 K, which is accompanied by the reentrant insulating state with high resistance below 30 K. In the EDLT, we observe bipolar and asymmetric modulation of the channel resistance, as well as an enhanced electroresistance up to 200% at positive gate bias. Our results provide insights on the carrier-density-dependent correlated electron physics of cluster glass systems.
Designing Asymmetric Multiferroics with Strong Magnetoelectric Coupling
Lu, X. Z.; Xiang, H. J.
2014-01-01
Multiferroics offer exciting opportunities for electric-field control of magnetism. Unfortunately, single-phase multiferroics suitable for such applications at room temperature has not been discovered. Here, we propose the concept of a new type of multiferroics, namely, "asymmetric multiferroic". In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from ...
Stable Bound States of Asymmetric Dark Matter
Wise, Mark B.; Zhang, Yue
2014-01-01
The simplest renormalizable effective field theories with asymmetric dark matter bound states contain two additional gauge singlet fields one being the dark matter and the other a mediator particle that the dark matter annihilates into. We examine the physics of one such model with a Dirac fermion as the dark matter and a real scalar mediator. For a range of parameters the Yukawa coupling of the dark matter to the mediator gives rise to stable asymmetric dark matter bound states. We derive pr...
KINEMATIC DETECTION OF THE DOUBLE NUCLEUS IN M31
GERSSEN, J; KUIJKEN, K; MERRIFIELD, MR
1995-01-01
Using a spectrum obtained under moderate (similar to 1 arcsec) seeing, we show that the double nucleus in M31 produces a strong kinematic signature even though the individual components are not spatially resolved. The signature consists of a significant asymmetric wing in the stellar velocity
Characteristics of Braced Excavation under Asymmetrical Loads
Directory of Open Access Journals (Sweden)
Changjie Xu
2013-01-01
Full Text Available Numerous excavation practices have shown that large discrepancies exist between field monitoring data and calculated results when the conventional symmetry-plane method (with half-width is used to design the retaining structure under asymmetrical loads. To examine the characteristics of a retaining structure under asymmetrical loads, we use the finite element method (FEM to simulate the excavation process under four different groups of asymmetrical loads and create an integrated model to tackle this problem. The effects of strut stiffness and wall length are also investigated. The results of numerical analysis clearly imply that the deformation and bending moment of diaphragm walls are distinct on different sides, indicating the need for different rebar arrangements when the excavation is subjected to asymmetrical loads. This study provides a practical approach to designing excavations under asymmetrical loads. We analyze and compare the monitoring and calculation data at different excavation stages and find some general trends. Several guidelines on excavation design under asymmetrical loads are drawn.
Resonance scattering in quantum wells with nanocenters
Satanin, A M
2002-01-01
The study on the Fano resonances is carried out in the 2D systems and their contribution to the residual resistance is calculated. The quantum well, the states whereof interfere with the nanocenters, for example, with the delta-layer donor states or with the quantum points states, is considered as a model. It is shown, that the states, localized on the state centers, lead to the appearance of additional asymmetric peaks in the resistance dependence on the Fermi energy. It is also shown, that the finite radius nanocenters in the 2D electron layers may lead to origination of the Fano resonances in the scattering cross section
Quantum coherence versus quantum uncertainty
Luo, Shunlong; Sun, Yuan
2017-08-01
The notion of measurement is of both foundational and instrumental significance in quantum mechanics, and coherence destroyed by measurements (decoherence) lies at the very heart of quantum to classical transition. Qualitative aspects of this spirit have been widely recognized and analyzed ever since the inception of quantum theory. However, axiomatic and quantitative investigations of coherence are attracting great interest only recently with several figures of merit for coherence introduced [Baumgratz, Cramer, and Plenio, Phys. Rev. Lett. 113, 140401 (2014), 10.1103/PhysRevLett.113.140401]. While these resource theoretic approaches have many appealing and intuitive features, they rely crucially on various notions of incoherent operations which are sophisticated, subtle, and not uniquely defined, as have been critically assessed [Chitambar and Gour, Phys. Rev. Lett. 117, 030401 (2016), 10.1103/PhysRevLett.117.030401]. In this paper, we elaborate on the idea that coherence and quantum uncertainty are dual viewpoints of the same quantum substrate, and address coherence quantification by identifying coherence of a state (with respect to a measurement) with quantum uncertainty of a measurement (with respect to a state). Consequently, coherence measures may be set into correspondence with measures of quantum uncertainty. In particular, we take average quantum Fisher information as a measure of quantum uncertainty, and introduce the corresponding measure of coherence, which is demonstrated to exhibit desirable properties. Implications for interpreting quantum purity as maximal coherence, and quantum discord as minimal coherence, are illustrated.
Asymmetric Bessel-Gauss beams.
Kotlyar, V V; Kovalev, A A; Skidanov, R V; Soifer, V A
2014-09-01
We propose a three-parameter family of asymmetric Bessel-Gauss (aBG) beams with integer and fractional orbital angular momentum (OAM). The aBG beams are described by the product of a Gaussian function by the nth-order Bessel function of the first kind of complex argument, having finite energy. The aBG beam's asymmetry degree depends on a real parameter c≥0: at c=0, the aBG beam is coincident with a conventional radially symmetric Bessel-Gauss (BG) beam; with increasing c, the aBG beam acquires a semicrescent shape, then becoming elongated along the y axis and shifting along the x axis for c≫1. In the initial plane, the intensity distribution of the aBG beams has a countable number of isolated optical nulls on the x axis, which result in optical vortices with unit topological charge and opposite signs on the different sides of the origin. As the aBG beam propagates, the vortex centers undergo a nonuniform rotation with the entire beam about the optical axis (c≫1), making a π/4 turn at the Rayleigh range and another π/4 turn after traveling the remaining distance. At different values of the c parameter, the optical nulls of the transverse intensity distribution change their position, thus changing the OAM that the beam carries. An isolated optical null on the optical axis generates an optical vortex with topological charge n. A vortex laser beam shaped as a rotating semicrescent has been generated using a spatial light modulator.
Ding, Si-Jing; Li, Xiaoguang; Nan, Fan; Zhong, Yu-Ting; Zhou, Li; Xiao, Xudong; Wang, Qu-Quan; Zhang, Zhenyu
2017-10-01
Recent intense effort has been devoted to exploring different manifestations of resonant excitations of strongly coupled plasmons and excitons, but so far such studies have been limited to situations where the Fano- or Rabi-type spectra are largely symmetric at zero detuning. Using a newly developed full quantum mechanical model, here we reveal the existence of a highly asymmetric spectroscopic regime for both the Rabi splitting and transparency dip. The asymmetric nature is inherently tied to the non-negligible exciton absorbance and is caused by substantial interference-induced energy repartitioning of the resonance peaks. This theoretical framework can be exploited to reveal the quantum behaviors of the two excitation entities with varying mutual coupling strengths in both linear and nonlinear regimes. We also use prototypical systems of rhodamine molecules strongly coupled with AuAg alloyed nanoparticles and well-devised control experiments to demonstrate the validity and tunability of the energy repartitioning and correlated electronic state occupations, as captured by the variations in the asymmetric spectroscopy and corresponding nonlinear absorption coefficient as a function of the Au:Ag ratio. The present study helps to substantially enrich our microscopic understanding of strongly coupled plasmon-exciton systems.
Quantum games as quantum types
Delbecque, Yannick
In this thesis, we present a new model for higher-order quantum programming languages. The proposed model is an adaptation of the probabilistic game semantics developed by Danos and Harmer [DH02]: we expand it with quantum strategies which enable one to represent quantum states and quantum operations. Some of the basic properties of these strategies are established and then used to construct denotational semantics for three quantum programming languages. The first of these languages is a formalisation of the measurement calculus proposed by Danos et al. [DKP07]. The other two are new: they are higher-order quantum programming languages. Previous attempts to define a denotational semantics for higher-order quantum programming languages have failed. We identify some of the key reasons for this and base the design of our higher-order languages on these observations. The game semantics proposed in this thesis is the first denotational semantics for a lambda-calculus equipped with quantum types and with extra operations which allow one to program quantum algorithms. The results presented validate the two different approaches used in the design of these two new higher-order languages: a first one where quantum states are used through references and a second one where they are introduced as constants in the language. The quantum strategies presented in this thesis allow one to understand the constraints that must be imposed on quantum type systems with higher-order types. The most significant constraint is the fact that abstraction over part of the tensor product of many unknown quantum states must not be allowed. Quantum strategies are a new mathematical model which describes the interaction between classical and quantum data using system-environment dialogues. The interactions between the different parts of a quantum system are described using the rich structure generated by composition of strategies. This approach has enough generality to be put in relation with other
The effect of magnetic field on RbCl quantum pseudodot qubit
Xiao, Jing-Lin
2015-07-01
Under the condition of strong electron-LO-phonon coupling in a RbCl quantum pseudodot (QPD) with an applied magnetic field (MF), the eigenenergies and the eigenfunctions of the ground and the first excited states (GFES) are obtained by using a variational method of the Pekar type (VMPT). A single qubit can be realized in this two-level quantum system. The electron’s probability density oscillates in the RbCl QPD with a certain period of T0 = 7.933 fs when the electron is in the superposition state of the GFES. The results indicate that due to the presence of the asymmetrical structure in the z direction of the RbCl QPD, the electron’s probability density shows double-peak configuration, whereas there is only peak if the confinement is a symmetric structure in the x and y directions of the RbCl QPD. The oscillating period is an increasing function of the cyclotron frequency and the polaron radius, whereas it is a decreasing one of the chemical potential of the two-dimensional electron gas and the zero point of the pseudoharmonic potential (PP).
Polarized heat current generated by quantum pumping in two-dimensional topological insulators
Ronetti, F.; Carrega, M.; Ferraro, D.; Rech, J.; Jonckheere, T.; Martin, T.; Sassetti, M.
2017-03-01
We consider the transport properties of a two-dimensional topological insulator in a double quantum point contact geometry in the presence of a time-dependent external field. In the proposed setup an external gate is placed above a single constriction and it couples only with electrons belonging to the top edge. This asymmetric configuration and the presence of an ac signal allow for a quantum pumping mechanism, which, in turn, can generate finite heat and charge currents in an unbiased device configuration. A microscopic model for coupling with the external time-dependent gate potential is developed and the induced finite heat and charge currents are investigated. We demonstrate that in the noninteracting case, heat flow is associated with a single spin component, due to the helical nature of the edge states, and therefore a finite and polarized heat current is obtained in this configuration. The presence of e -e interchannel interactions strongly affects the current signal, lowering the degree of polarization of the system. Finally, we also show that separate heat and charge flows can be achieved, varying the amplitude of the external gate.
Kobayashi, Toyoharu; Hasegawa, Futoshi; Hirose, Yoshikatsu; Tanaka, Katsunori; Mori, Hajime; Katsumura, Shigeo
2012-02-17
The asymmetric one-pot 6π-azaelectrocyclization of alkenyl vinyl stannane, ethyl (Z)-2-iodo-4-oxobutenoate, and (-)-7-isopropyl-cis-aminoindanol in the presence of a Pd(0) catalyst stereoselectively produced the tetracyclic aminoacetal compounds, resulting from the four-bond formation accompanying by controlling the stereochemistry at the two asymmetric centers. The produced cyclic aminoacetals can be regarded as synthetic precursors of substituted chiral piperidines, and the syntheses of 2,4- and 2,4,6-substituted piperidines were realized from the obtained aminoacetals by the stereoselective hydrogenation of the double bond conjugated with the C-4 ester group and alkylation at the aminoacetal moiety. In addition, the stereoselective synthesis of an indolizidine alkaloid, (-)-dendroprimine, and its three stereoisomers, (+)-7-epidendroprimine, (+)-5-epidendroprimine, and (+)-5,7-epidendroprimine, were achieved.
Chiral Aminophosphines as Catalysts for Enantioselective Double-Michael Indoline Syntheses
Directory of Open Access Journals (Sweden)
Ohyun Kwon
2012-05-01
Full Text Available The bisphosphine-catalyzed double-Michael addition of dinucleophiles to electron-deficient acetylenes is an efficient process for the synthesis of many nitrogen-containing heterocycles. Because the resulting heterocycles contain at least one stereogenic center, this double-Michael reaction would be even more useful if an asymmetric variant of the reaction were to be developed. Aminophosphines can also facilitate the double-Michael reaction and chiral amines are more readily available in Nature and synthetically; therefore, in this study we prepared several new chiral aminophosphines. When employed in the asymmetric double-Michael reaction between ortho-tosylamidophenyl malonate and 3-butyn-2-one, the chiral aminophosphines produced indolines in excellent yields with moderate asymmetric induction.
Energy Technology Data Exchange (ETDEWEB)
Gratia, Pierre [Department of Physics, University of Chicago,South Ellis Avenue, Chicago, IL 60637 (United States); Hu, Wayne [Department of Astronomy and Astrophysics, University of Chicago,South Ellis Avenue, Chicago, IL 60637 (United States); Enrico Fermi Institute and Kavli Institute for Cosmological Physics, University of Chicago,South Ellis Avenue, Chicago, IL 60637 (United States); Joyce, Austin [Enrico Fermi Institute and Kavli Institute for Cosmological Physics, University of Chicago,South Ellis Avenue, Chicago, IL 60637 (United States); Ribeiro, Raquel H. [School of Physics and Astronomy, Queen Mary University of London,Mile End Road, London, E1 4NS (United Kingdom)
2016-06-15
Attempts to modify gravity in the infrared typically require a screening mechanism to ensure consistency with local tests of gravity. These screening mechanisms fit into three broad classes; we investigate theories which are capable of exhibiting more than one type of screening. Specifically, we focus on a simple model which exhibits both Vainshtein and kinetic screening. We point out that due to the two characteristic length scales in the problem, the type of screening that dominates depends on the mass of the sourcing object, allowing for different phenomenology at different scales. We consider embedding this double screening phenomenology in a broader cosmological scenario and show that the simplest examples that exhibit double screening are radiatively stable.
Levy, Amikam; Diósi, Lajos; Kosloff, Ronnie
2016-05-01
In this work we present the concept of a quantum flywheel coupled to a quantum heat engine. The flywheel stores useful work in its energy levels, while additional power is extracted continuously from the device. Generally, the energy exchange between a quantum engine and a quantized work repository is accompanied by heat, which degrades the charging efficiency. Specifically when the quantum harmonic oscillator acts as a work repository, quantum and thermal fluctuations dominate the dynamics. Quantum monitoring and feedback control are applied to the flywheel in order to reach steady state and regulate its operation. To maximize the charging efficiency one needs a balance between the information gained by measuring the system and the information fed back to the system. The dynamics of the flywheel are described by a stochastic master equation that accounts for the engine, the external driving, the measurement, and the feedback operations.
Braun, Daniel; Giraud, Olivier; Braun, Peter A.
2010-03-01
We introduce and study a measure of ``quantumness'' of a quantum state based on its Hilbert-Schmidt distance from the set of classical states. ``Classical states'' were defined earlier as states for which a positive P-function exists, i.e. they are mixtures of coherent states [1]. We study invariance properties of the measure, upper bounds, and its relation to entanglement measures. We evaluate the quantumness of a number of physically interesting states and show that for any physical system in thermal equilibrium there is a finite critical temperature above which quantumness vanishes. We then use the measure for identifying the ``most quantum'' states. Such states are expected to be potentially most useful for quantum information theoretical applications. We find these states explicitly for low-dimensional spin-systems, and show that they possess beautiful, highly symmetric Majorana representations. [4pt] [1] Classicality of spin states, Olivier Giraud, Petr Braun, and Daniel Braun, Phys. Rev. A 78, 042112 (2008)
Khan, Shabbir A
2013-01-01
Quantum plasma physics is a rapidly evolving research field with a very inter-disciplinary scope of potential applications, ranging from nano-scale science in condensed matter to the vast scales of astrophysical objects. The theoretical description of quantum plasmas relies on various approaches, microscopic or macroscopic, some of which have obvious relation to classical plasma models. The appropriate model should, in principle, incorporate the quantum mechanical effects such as diffraction, spin statistics and correlations, operative on the relevant scales. However, first-principle approaches such as quantum Monte Carlo and density functional theory or quantum-statistical methods such as quantum kinetic theory or non-equilibrium Green's functions require substantial theoretical and computational efforts. Therefore, for selected problems, alternative simpler methods have been put forward. In particular, the collective behavior of many-body systems is usually described within a self-consistent scheme of parti...
Gilbert, Gerald; Hamrick, Michael
2013-01-01
This book provides a detailed account of the theory and practice of quantum cryptography. Suitable as the basis for a course in the subject at the graduate level, it crosses the disciplines of physics, mathematics, computer science and engineering. The theoretical and experimental aspects of the subject are derived from first principles, and attention is devoted to the practical development of realistic quantum communications systems. The book also includes a comprehensive analysis of practical quantum cryptography systems implemented in actual physical environments via either free-space or fiber-optic cable quantum channels. This book will be a valuable resource for graduate students, as well as professional scientists and engineers, who desire an introduction to the field that will enable them to undertake research in quantum cryptography. It will also be a useful reference for researchers who are already active in the field, and for academic faculty members who are teaching courses in quantum information s...
Busch, Paul; Pellonpää, Juha-Pekka; Ylinen, Kari
2016-01-01
This is a book about the Hilbert space formulation of quantum mechanics and its measurement theory. It contains a synopsis of what became of the Mathematical Foundations of Quantum Mechanics since von Neumann’s classic treatise with this title. Fundamental non-classical features of quantum mechanics—indeterminacy and incompatibility of observables, unavoidable measurement disturbance, entanglement, nonlocality—are explicated and analysed using the tools of operational quantum theory. The book is divided into four parts: 1. Mathematics provides a systematic exposition of the Hilbert space and operator theoretic tools and relevant measure and integration theory leading to the Naimark and Stinespring dilation theorems; 2. Elements develops the basic concepts of quantum mechanics and measurement theory with a focus on the notion of approximate joint measurability; 3. Realisations offers in-depth studies of the fundamental observables of quantum mechanics and some of their measurement implementations; and 4....
Stapp, Henry
2009-01-01
Robert Griffiths has recently addressed, within the framework of a 'consistent quantum theory' that he has developed, the issue of whether, as is often claimed, quantum mechanics entails a need for faster-than-light transfers of information over long distances. He argues that the putative proofs of this property that involve hidden variables include in their premises some essentially classical-physics-type assumptions that are fundamentally incompatible with the precepts of quantum physics. O...
Quantum information and computation
Bub, Jeffrey
2005-01-01
This article deals with theoretical developments in the subject of quantum information and quantum computation, and includes an overview of classical information and some relevant quantum mechanics. The discussion covers topics in quantum communication, quantum cryptography, and quantum computation, and concludes by considering whether a perspective in terms of quantum information sheds new light on the conceptual problems of quantum mechanics.
Barnett, Stephen M
2009-01-01
Quantum information- the subject- is a new and exciting area of science, which brings together physics, information theory, computer science and mathematics. "Quantum Information"- the book- is based on two successful lecture courses given to advanced undergraduate and beginning postgraduate students in physics. The intention is to introduce readers at this level to the fundamental, but offer rather simple, ideas behind ground-breaking developments including quantum cryptography,teleportation and quantum computing. The text is necessarily rather mathematical in style, but the mathema
Vogel, Werner
2006-01-01
This is the third, revised and extended edition of the acknowledged "Lectures on Quantum Optics" by W. Vogel and D.-G. Welsch.It offers theoretical concepts of quantum optics, with special emphasis on current research trends. A unified concept of measurement-based nonclassicality and entanglement criteria and a unified approach to medium-assisted electromagnetic vacuum effects including Van der Waals and Casimir Forces are the main new topics that are included in the revised edition. The rigorous development of quantum optics in the context of quantum field theory and the attention to details makes the book valuable to graduate students as well as to researchers
Exploring the Physics of Semiconductor Quantum Dots using Circuit Quantum Electrodynamics
Stockklauser, Anna; Maisi, Ville; Ihn, Thomas; Ensslin, Klaus; Wallraff, Andreas
2015-03-01
Semiconductor quantum dots and superconducting qubits both possess excitations in the microwave domain for which a wide range of novel approaches to create, store, manipulate and detect individual photons have been developed. A key ingredient are coplanar waveguide resonators in which the field energy of an excitation is distributed over a small mode volume. This feature creates sizable electromagnetic fields at the level of individual microwave photons mediating strong electromagnetic interactions with a variety of quantum systems. In an approach known as circuit quantum electrodynamics (QED) we both probe fundamental quantum optical effects and demonstrate basic features of quantum information processing. In this presentation, I will discuss experiments exploring the physics of semiconductor quantum dots in the context of circuit QED. We investigate the coherent dipole coupling of double dots to microwave photons and detect radiation emitted from the dots in inelastic electron tunneling processes. This approach may allow us to explore quantum coherent interfaces between semiconducting and superconducting qubits.
Asymmetrical soft palate cleft repair: preliminary results.
Bütow, K-W; Engelbrecht, H; Naidoo, S
2014-06-01
The reconstructions of the asymmetrical soft palate cleft is a surgical challenge when it comes to achieving symmetry and optimal soft palate muscular function. Three different versions of the intravelar veloplasty have been used: the intravelar veloplasty (1969) (type I), the modification according to anatomical defects (1991) (type II), and the modification using part of Sommerlad's technique and part of Ivanov's technique (2008) (type III). The perioperative outcomes of the type II and type III intravelar veloplasty were assessed and compared in asymmetrical cleft cases. Two hundred and seventy-seven soft palate clefts were reconstructed: 153 type II and 124 type III. Of these, 49 were asymmetrical (17.7%); 23 underwent the type II procedure and 26 the type III procedure. Of the type II procedure cases, 30.4% remained asymmetrical postoperatively compared to 3.8% of the type III cases. The uvula appeared subjectively atrophic in 47.8% of the type II cases and in 7.7% of type III cases. Oro-nasal fistula occurred in 13.0% of the type II cases and 3.8% of the type III cases. Speech results will only be assessed after 4 years of age. The type III modified intravelar veloplasty has had a major beneficial impact on patients who had an asymmetrical soft palate cleft. Copyright © 2014. Published by Elsevier Ltd.
Control of apoptosis by asymmetric cell division.
Hatzold, Julia; Conradt, Barbara
2008-04-08
Asymmetric cell division and apoptosis (programmed cell death) are two fundamental processes that are important for the development and function of multicellular organisms. We have found that the processes of asymmetric cell division and apoptosis can be functionally linked. Specifically, we show that asymmetric cell division in the nematode Caenorhabditis elegans is mediated by a pathway involving three genes, dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail, that directly control the enzymatic machinery responsible for apoptosis. Interestingly, the MIDA1-like protein GlsA of the alga Volvox carteri, as well as the Snail-related proteins Snail, Escargot, and Worniu of Drosophila melanogaster, have previously been implicated in asymmetric cell division. Therefore, C. elegans dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail may be components of a pathway involved in asymmetric cell division that is conserved throughout the plant and animal kingdoms. Furthermore, based on our results, we propose that this pathway directly controls the apoptotic fate in C. elegans, and possibly other animals as well.
Control of apoptosis by asymmetric cell division.
Directory of Open Access Journals (Sweden)
Julia Hatzold
2008-04-01
Full Text Available Asymmetric cell division and apoptosis (programmed cell death are two fundamental processes that are important for the development and function of multicellular organisms. We have found that the processes of asymmetric cell division and apoptosis can be functionally linked. Specifically, we show that asymmetric cell division in the nematode Caenorhabditis elegans is mediated by a pathway involving three genes, dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail, that directly control the enzymatic machinery responsible for apoptosis. Interestingly, the MIDA1-like protein GlsA of the alga Volvox carteri, as well as the Snail-related proteins Snail, Escargot, and Worniu of Drosophila melanogaster, have previously been implicated in asymmetric cell division. Therefore, C. elegans dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail may be components of a pathway involved in asymmetric cell division that is conserved throughout the plant and animal kingdoms. Furthermore, based on our results, we propose that this pathway directly controls the apoptotic fate in C. elegans, and possibly other animals as well.
A sampling theory for asymmetric communities.
Noble, Andrew E; Temme, Nico M; Fagan, William F; Keitt, Timothy H
2011-03-21
We introduce the first analytical model of asymmetric community dynamics to yield Hubbell's neutral theory in the limit of functional equivalence among all species. Our focus centers on an asymmetric extension of Hubbell's local community dynamics, while an analogous extension of Hubbell's metacommunity dynamics is deferred to an appendix. We find that mass-effects may facilitate coexistence in asymmetric local communities and generate unimodal species abundance distributions indistinguishable from those of symmetric communities. Multiple modes, however, only arise from asymmetric processes and provide a strong indication of non-neutral dynamics. Although the exact stationary distributions of fully asymmetric communities must be calculated numerically, we derive approximate sampling distributions for the general case and for nearly neutral communities where symmetry is broken by a single species distinct from all others in ecological fitness and dispersal ability. In the latter case, our approximate distributions are fully normalized, and novel asymptotic expansions of the required hypergeometric functions are provided to make evaluations tractable for large communities. Employing these results in a bayesian analysis may provide a novel statistical test to assess the consistency of species abundance data with the neutral hypothesis. Copyright © 2010 Elsevier Ltd. All rights reserved.
DEFF Research Database (Denmark)
Norrby, Per-Ola; Brandt, Peter; Rein, Tobias
1999-01-01
A new method for creating a transition-state force field, based on quantum chemical normal-mode analysis, is described. The force field was used to rationalize the experimentally observed product selectivities in asymmetric Horner-Wadsworth-Emmons reactions between some chiral phosphonates...
Quantum physics without quantum philosophy
Energy Technology Data Exchange (ETDEWEB)
Duerr, Detlef [Muenchen Univ. (Germany). Mathematisches Inst.; Goldstein, Sheldon [Rutgers State Univ., Piscataway, NJ (United States). Dept. of Mathematics; Zanghi, Nino [Genova Univ. (Italy); Istituto Nazionale Fisica Nucleare, Genova (Italy)
2013-02-01
Integrates and comments on the authors' seminal papers in the field. Emphasizes the natural way in which quantum phenomena emerge from the Bohmian picture. Helps to answer many of the objections raised to Bohmian quantum mechanics. Useful overview and summary for newcomers and students. 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 Schroedinger'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.
Quantum computer games: quantum minesweeper
Gordon, Michal; Gordon, Goren
2010-07-01
The computer game of quantum minesweeper is introduced as a quantum extension of the well-known classical minesweeper. Its main objective is to teach the unique concepts of quantum mechanics in a fun way. Quantum minesweeper demonstrates the effects of superposition, entanglement and their non-local characteristics. While in the classical minesweeper the goal of the game is to discover all the mines laid out on a board without triggering them, in the quantum version there are several classical boards in superposition. The goal is to know the exact quantum state, i.e. the precise layout of all the mines in all the superposed classical boards. The player can perform three types of measurement: a classical measurement that probabilistically collapses the superposition; a quantum interaction-free measurement that can detect a mine without triggering it; and an entanglement measurement that provides non-local information. The application of the concepts taught by quantum minesweeper to one-way quantum computing are also presented.
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.
Excitonic superfluid phase in double bilayer graphene
Li, J. I. A.; Taniguchi, T.; Watanabe, K.; Hone, J.; Dean, C. R.
2017-08-01
A spatially indirect exciton is created when an electron and a hole, confined to separate layers of a double quantum well system, bind to form a composite boson. Such excitons are long-lived, and in the limit of strong interactions are predicted to undergo a Bose-Einstein condensate-like phase transition into a superfluid ground state. Here, we report evidence of an exciton condensate in the quantum Hall effect regime of double-layer structures of bilayer graphene. Interlayer correlation is identified by quantized Hall drag at matched layer densities, and the dissipationless nature of the phase is confirmed in the counterflow geometry. A selection rule for the condensate phase is observed involving both the orbital and valley indices of bilayer graphene. Our results establish double bilayer graphene as an ideal system for studying the rich phase diagram of strongly interacting bosonic particles in the solid state.
Chiral quantum dot based materials
Govan, Joseph; Loudon, Alexander; Baranov, Alexander V.; Fedorov, Anatoly V.; Gun'ko, Yurii
2014-05-01
Recently, the use of stereospecific chiral stabilising molecules has also opened another avenue of interest in the area of quantum dot (QD) research. The main goal of our research is to develop new types of technologically important quantum dot materials containing chiral defects, study their properties and explore their applications. The utilisation of chiral penicillamine stabilisers allowed the preparation of new water soluble white emitting CdS quantum nanostructures which demonstrated circular dichroism in the band-edge region of the spectrum. It was also demonstrated that all three types of QDs (D-, L-, and Rac penicillamine stabilised) show very broad emission bands between 400 and 700 nm due to defects or trap states on the surfaces of the nanocrystals. In this work the chiral CdS based quantum nanostructures have also been doped by copper metal ions and new chiral penicilamine stabilized CuS nanoparticles have been prepared and investigated. It was found that copper doping had a strong effect at low levels in the synthesis of chiral CdS nanostructures. We expect that this research will open new horizons in the chemistry of chiral nanomaterials and their application in biotechnology, sensing and asymmetric synthesis.
Asymmetric microscope. Fusho no kenbisho [exclamation point
Energy Technology Data Exchange (ETDEWEB)
Inoue, Tadashi. (Tokyo Institute of Technology, Tokyo (Japan))
1999-07-01
It is difficult for a conventional optical analysis means to determine the configuration of a substance with an ultra low optical purity. Recently, an asymmetric microscope has been reported as a new concept for solving the above-mentioned problem. Specifically, a product with slight asymmetry is obtained by using the substance with an ultra low optical purity as the chiral initiation, and then the asymmetry of the product is amplified dramatically due to the asymmetric autocatalysis, thus obtaining a product having a high optical purity. A new means is to determine the configuration of the original substance having the low optical purity from the configuration of the substance having the high optical purity. According to this method, the chirality of the substance having the low optical purity is transcribed to alkanol, and the chirality is amplified due to the asymmetric autocatalysis, thus the absolute configuration of the original compound can be determined from the absolute configuration of the final product. (NEDO)
Multi-agent Bargaining under Asymmetric Information
DEFF Research Database (Denmark)
Asplund, Marcus; Genesove, David
information aspect is due to partly unobserved individual valuations of an elevator. We tailor Hellwig (2003) to the features of the retrofitting problem and use this to predict which building characteristics should make it easier for owners to agree. Data from Copenhagen broadly support the model......It is well know that asymmetric information might lead to underprovision of public goods. To test the theoretical prediction, we study the decision to retrofit an elevator into an old apartment building, in which each owner has to agree on how the investment cost is split. The asymmetric......'s predictions. We use transaction data to estimate the market value of an elevator and conclude that for approximately 30-40 percent of the buildings without an elevator the aggregate increase in value exceeds the investment cost....
Asymmetric synthesis II more methods and applications
Christmann, Mathias
2012-01-01
After the overwhelming success of 'Asymmetric Synthesis - The Essentials', narrating the colorful history of asymmetric synthesis, this is the second edition with latest subjects and authors. While the aim of the first edition was mainly to honor the achievements of the pioneers in asymmetric syntheses, the aim of this new edition was bringing the current developments, especially from younger colleagues, to the attention of students. The format of the book remained unchanged, i.e. short conceptual overviews by young leaders in their field including a short biography of the authors. The growing multidisciplinary research within chemistry is reflected in the selection of topics including metal catalysis, organocatalysis, physical organic chemistry, analytical chemistry, and its applications in total synthesis. The prospective reader of this book is a graduate or undergraduate student of advanced organic chemistry as well as the industrial chemist who wants to get a brief update on the current developments in th...
Steffen, Matthias
Solving computational problems require resources such as time, memory, and space. In the classical model of computation, computational complexity theory has categorized problems according to how difficult it is to solve them as the problem size increases. Remarkably, a quantum computer could solve certain problems using fundamentally fewer resources compared to a conventional computer, and therefore has garnered significant attention. Yet because of the delicate nature of entangled quantum states, the construction of a quantum computer poses an enormous challenge for experimental and theoretical scientists across multi-disciplinary areas including physics, engineering, materials science, and mathematics. While the field of quantum computing still has a long way to grow before reaching full maturity, state-of-the-art experiments on the order of 10 qubits are beginning to reach a fascinating stage at which they can no longer be emulated using even the fastest supercomputer. This raises the hope that small quantum computer demonstrations could be capable of approximately simulating or solving problems that also have practical applications. In this talk I will review the concepts behind quantum computing, and focus on the status of superconducting qubits which includes steps towards quantum error correction and quantum simulations.
Baaquie, Belal E.
2004-11-01
Financial mathematics is currently almost completely dominated by stochastic calculus. Presenting a completely independent approach, this book applies the mathematical and conceptual formalism of quantum mechanics and quantum field theory (with particular emphasis on the path integral) to the theory of options and to the modeling of interest rates. Many new results, accordingly, emerge from the author's perspective.
Hallman, Tyler A; Brooks, Marjorie L
2015-11-01
Climate projections over the next century include disproportionately warmer nighttime temperatures ("asymmetrical warming"). Cool nighttime temperatures lower metabolic rates of aquatic ectotherms. In contaminated waters, areas with cool nights may provide thermal refugia from high rates of daytime contaminant uptake. We exposed Cope's gray tree frogs (Hyla chrysoscelis), southern leopard frogs (Lithobates sphenocephalus), and spotted salamanders (Ambystoma maculatum) to five concentrations of a mixture of cadmium, copper, and lead under three to four temperature regimes, representing asymmetrical warming. At concentrations with intermediate toxicosis at test termination (96 h), temperature effects on acute toxicity or escape distance were evident in all study species. Asymmetrical warming (day:night, 22:20 °C; 22:22 °C) doubled or tripled mortality relative to overall cooler temperatures (20:20 °C) or cool nights (22:18 °C). Escape distances were 40-70% shorter under asymmetrical warming. Results suggest potentially grave ecological impacts from unexpected toxicosis under climate change. Copyright © 2015 Elsevier Ltd. All rights reserved.
Kiefer, Claus
2012-01-01
The search for a quantum theory of the gravitational field is one of the great open problems in theoretical physics. This book presents a self-contained discussion of the concepts, methods and applications that can be expected in such a theory. The two main approaches to its construction - the direct quantisation of Einstein's general theory of relativity and string theory - are covered. Whereas the first attempts to construct a viable theory for the gravitational field alone, string theory assumes that a quantum theory of gravity will be achieved only through a unification of all the interactions. However, both employ the general method of quantization of constrained systems, which is described together with illustrative examples relevant for quantum gravity. There is a detailed presentation of the main approaches employed in quantum general relativity: path-integral quantization, the background-field method and canonical quantum gravity in the metric, connection and loop formulations. The discussion of stri...