Some studies of the interaction between N-two level atoms and three level atom
Directory of Open Access Journals (Sweden)
D.A.M. Abo-Kahla
2016-07-01
Full Text Available In this paper, we present the analytical solution for the model that describes the interaction between a three level atom and two systems of N-two level atoms. The effect of the quantum numbers on the atomic inversion and the purity, for some special cases of the initial states, are investigated. We observe that the atomic inversion and the purity change remarkably by the change of the quantum numbers.
Squeezing in the interaction of radiation with two-level atoms
Bandyopadhyay, Abir; Rai, Jagdish
1995-01-01
We propose a simple experimental procedure to produce squeezing and other non-classical properties like photon antibunching of radiation, and amplification without population inversion. The method also decreases the uncertainties of the angular-momentum quadratures representing the two-level atomic system in the interaction of the two-level atoms with quantized radiation.
Theoretical treatment of the interaction between two-level atoms and periodic waveguides
Zang, Xiaorun
2015-01-01
Light transport in periodic waveguides coupled to a two-level atom is investigated. By using optical Bloch equations and a photonic modal formalism, we derive semi-analytical expressions for the scattering matrix of one atom trapped in a periodic waveguide. The derivation is general, as the expressions hold for any periodic photonic or plasmonic waveguides. It provides a basic building block to study collective effects arising from photon-mediated multi-atom interactions in periodic waveguides.
Semiclassical electrodynamics of alien atoms in interacting media II. Two-level systems
Elçi, Ahmet
1985-03-01
The previously developed self-consistent mean field theory of atoms entering an interacting medium is specialized to two-level alien atoms. It is shown that the medium may invert or split the original two levels, and that there is an intimate connection between the dressed atom spectrum and the statistical nature of the ensemble of alien atoms in the self-consistent mean field approximation. The optical susceptibility of alien atoms while inside the medium is calculated, and the lineshape and position of the optical resonance are shown to depend on the intensity of the optical field applied. There may be more than one phase possible for the atomic ensemble as a result of optical excitation.
Spectroscopic properties of a two-level atom interacting with a complex spherical nanoshell
Moroz, A
2004-01-01
Frequency shifts, radiative decay rates, the Ohmic loss contribution to the nonradiative decay rates, fluorescence yields, and photobleaching of a two-level atom radiating anywhere inside or outside a complex spherical nanoshell, i.e. a stratified sphere consisting of alternating silica and gold concentric spherical shells, are studied. The changes in the spectroscopic properties of an atom interacting with complex nanoshells are significantly enhanced, often more than two orders of magnitude, compared to the same atom interacting with a homogeneous dielectric sphere. The changes strongly depend on the nanoshell parameters and the atom position. When an atom approaches a metal shell,the radiative decay rates are strongly enhanced and they increase faster than the Ohmic loss contribution to the nonradiative decay rates. However, the majority of the emitted radiation does not escape to spatial infinity but instead is absorbed. The enhancement of the radiative decay rates in a close proximity of metal boundaries...
Effect of Phase Shifted Frequency Modulation on Two Level Atom-Field Interaction
Institute of Scientific and Technical Information of China (English)
K.V. Priyesh; Ramesh Babu Thayyullathil
2012-01-01
We have studied the effect of phase shifted frequency modulation on two level atom with field interaction using Jaynes-Cummings model. Here the frequency of the interacting field is sinusoidally varying with time with a constant phase. Due to the presence of phase in the frequency modulation, the variation of population inversion with time is different from the standard case. There are no exact collapses and revivals in the variation of population inversion but it oscillates sinusoidally with time. In coherent field atom interaction the population inversion behaves as in the case of Fock state atom interaction, when frequency modulation with a non zero phase is applied. The study done with squeezed field has shown the same behavior of the population inversion.
Information Entropy Squeezing of a Two-Level Atom Interacting with Two-Mode Coherent Fields
Institute of Scientific and Technical Information of China (English)
LIU Xiao-Juan; FANG Mao-Fa
2004-01-01
From a quantum information point of view we investigate the entropy squeezing properties for a two-level atom interacting with the two-mode coherent fields via the two-photon transition. We discuss the influences of the initial state of the system on the atomic information entropy squeezing. Our results show that the squeezed component number,squeezed direction, and time of the information entropy squeezing can be controlled by choosing atomic distribution angle,the relative phase between the atom and the two-mode field, and the difference of the average photon number of the two field modes, respectively. Quantum information entropy is a remarkable precision measure for the atomic squeezing.
Institute of Scientific and Technical Information of China (English)
Zeng Ke; Fang Mao-Fa
2005-01-01
The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investigated by using the quantum reduced entropy; the quantum entanglement between two two-level atoms, and that between a single two-level atom and a single-mode vacuum field are studied in terms of the quantum relative entropy. The influences of the atomic dipole-dipole interaction on the quantum entanglement of the system are also discussed. Our results show that three entangled states of two atoms-field, atom-atom, and atom-field can be prepared via two two-level atoms interacting with a single-mode vacuum field.
Interaction between two SU(1 , 1) quantum systems and a two-level atom
Abdalla, M. Sebawe; Khalil, E. M.; Obada, A. S.-F.
2016-07-01
We consider a two-level atom interacting with two coupled quantum systems that can be represented in terms of su(1 , 1) Lie algebra. The wave function that is obtained using the evolution operator for the atom is initially in a superposition state and the coupled su(1 , 1) systems in a pair coherent Barut-Girardello coherent state. We then discuss atomic inversion, where more periods of revivals are observed and compared with a single su(1 , 1) quantum system. For entanglement and squeezing phenomena, the atomic angles coherence and phase as well as the detuning are effective parameters. The second-order correlation function displays Bunching and anti-Bunching behavior.
Intrinsic decoherence in the interaction of two fields with a two-level atom
Energy Technology Data Exchange (ETDEWEB)
Juarez-Amaro, R. [Universidad Tecnologica de la Mixteca, Mexico (Mexico); INAOE, Puebla (Mexico); Escudero-Jimenez, J.L. [INAOE, Puebla (Mexico); Moya-Cessa, H.
2009-06-15
We study the interaction of a two-level atom and two fields, one of them classical. We obtain an effective Hamiltonian for this system by using a method recently introduced that produces a small rotation to the Hamiltonian that allows to neglect some terms in the rotated Hamiltonian. Then we solve a variation of the Schroedinger equation that models decoherence as the system evolves through intrinsic mechanisms beyond conventional quantum mechanics rather than dissipative interaction with an environment. (Abstract Copyright [2009], Wiley Periodicals, Inc.)
Graphene-like optical light field and its interaction with two-level atoms
Lembessis, V. E.; Courtial, Johannes; Radwell, N.; Selyem, A.; Franke-Arnold, S.; Aldossary, O. M.; Babiker, M.
2015-12-01
The theoretical basis leading to the creation of a light field with a hexagonal honeycomb structure resembling graphene is considered along with its experimental realization and its interaction with atoms. It is argued that associated with such a light field is an optical dipole potential which leads to the diffraction of the atoms, but the details depend on whether the transverse spread of the atomic wave packet is larger than the transverse dimensions of the optical lattice (resonant Kapitza-Dirac effect) or smaller (optical Stern-Gerlach effect). Another effect in this context involves the creation of gauge fields due to the Berry phase acquired by the atom moving in the light field. The experimental realization of the light field with a honeycomb hexagonal structure is described using holographic methods and we proceed to explore the atom diffraction in the Kapitza-Dirac regime as well as the optical Stern-Gerlach regime, leading to momentum distributions with characteristic but different hexagonal structures. The artificial gauge fields too are shown to have the same hexagonal spatial structure and their magnitude can be significantly large. The effects are discussed with reference to typical parameters for the atoms and the fields.
Intrinsic decoherence of entanglement of a single quantized field interacting with a two-level atom
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
How the mean photon number, the probability of excited state and intrinsic decoherence coefficient influence the time evolution of entanglement is unknown, when a single-mode quantized optic field and a two-level atom coupling system is governed by Milburn equation. The Jaynes-Cummings model is considered. A lower bound of concurrence is proposed to calculate the entanglement. Simulation results indicate that the entanglement of system increases following the increasing of intrinsic decoherence coefficient or the decreasing of the mean photon number. Besides that, the entanglement of system decreases, while the probability of exited state increases from 0 to 0.1, and increases, while the probability of exited state increases from 0.1 to 1.
Liu, Ju; Li, Zhi-Yuan
2014-11-17
One of the simplest models involving the atom-field interaction is the coupling of a single two-level atom with single-mode optical field. Under the rotating wave approximation, this problem is reduced to a form that can be solved exactly. But the approximation is only valid when the two levels are resonant or nearly resonant with the applied electromagnetic radiation. Here we present an analytical solution without the rotating wave approximation and applicable to general atom-field interaction far away from the resonance. We find that there exists remarkable influence of the initial phase of optical field on the Rabi oscillations and Rabi splitting, and this issue cannot be explored in the context of the rotating wave approximation. Due to the retention of the counter-rotating terms, higher-order harmonic appears during the Rabi splitting. The analytical solution suggests a way to regulate and control the quantum dynamics of a two-level atom and allows for exploring more essential features of the atom-field interaction.
Entanglement in a system of two two-level atoms interacting with a single-mode field
Institute of Scientific and Technical Information of China (English)
Jin Li-Juan; Fang Mao-Fa
2006-01-01
We investigate the entanglement in a system of two coupling atoms interacting with a single-mode field by means of quantum information entropy theory. The quantum entanglement between the two atoms and the coherent field is discussed by using the quantum reduced entropy, and the entanglement between the two coupling atoms is also investigated by using the quantum relative entropy. In addition, the influences of the atomic dipole-dipole interaction intensity and the average photon number of the coherent field on the degree of the entanglement is examined. The results show that the evolution of the degree of entanglement between the two atoms and the field is just opposite to that of the degree of entanglement between the two atoms. And the properties of the quantum entanglement in the system rely on the atomic dipole-dipole interaction and the average photon number of the coherent field.
Abdel-Khalek, S.; Berrada, K.; Alkhateeb, Sadah A.
2016-09-01
In this paper, we propose a useful quantum system to perform different tasks of quantum information and computational technologies. We explore the required optimal conditions for this system that are feasible with real experimental realization. We present an active way to control the variation of some measures of nonclassicality considering the time-dependent coupling and photon transition effects under a model that closely describes a realistic experimental scenario. We investigate qualitatively the quantum measures for a two-level atom system interacting with a quantum field initially defined in a coherent state in the framework of power-law potentials (PLPCSs). We study the nonlocal correlation in the whole system state using the negativity as a measure of entanglement in terms of the exponent parameter, number of photon transition, and phase damping effect. The influences of the different physical parameters on the statistical properties and purity of the field are also demonstrated during the time evolution. The results indicate that the preservation and enhancement of entanglement greatly benefit from the combination of the choice of the physical parameters. Finally, we explore an interesting relationship between the different quantum measures of non-classicality during the time evolution in the absence and presence of time-dependent coupling effect.
Institute of Scientific and Technical Information of China (English)
LUO Jin-Ming; LI Jia-Hua; XIE Xiao-Tao
2006-01-01
@@ Taking the intensity-dependent coupling between atoms and cavity mode into account, we investigate a system consisting of N homogeneously broadened two-level atoms interacting with the field inside a single-mode Fabry Perot cavity containing a nonlinear Kerr-like medium. We derive the steady-state bistable behaviour of the system, and further analyse in details the influence of several critical parameters on the bistable behaviour.
Zhang, Wen-Zhuo
2012-01-01
We derive a set of optical Bloch equations (OBEs) directly from the minimal-coupling Hamiltonian density of the bound-state quantum electrodynamics (bound-state QED). Such optical Bloch equations are beyond the former widely-used ones due to that there is no electric dipole approximation (EDA) on the minimal-coupling Hamiltonian density of the bound-state QED. Then our optical Bloch equations can describe a two-level atom interacting with a monochromatic light of arbitrary wavelength, which are suitable to study the spectroscopy and the Rabi oscillations of two-level atoms in X-ray laser beams since that the wavelength of X-ray is close to an atom to make the electric dipole approximation (EDA) invalid.
Energy Technology Data Exchange (ETDEWEB)
Dodonov, A.V., E-mail: adodonov@fis.unb.br [Instituto de Física, Universidade de Brasília, Caixa Postal 04455, 70910-900 Brasília, DF (Brazil); Dodonov, V.V., E-mail: vdodonov@fis.unb.br [Instituto de Física, Universidade de Brasília, Caixa Postal 04455, 70910-900 Brasília, DF (Brazil)
2011-11-21
We study numerically the evolution of the cavity electromagnetic field mode which is in resonance with an oscillating boundary (dynamical Casimir effect), taking into account the interaction between the field and a two-level atom, that may or not be continuously monitored by a coupled atomic excitation detector. We analyze the behavior of the field statistics and the quadrature squeezing properties in different regimes, demonstrating that at the expense of decreasing the number of produced photons and the degree of squeezing, one can create qualitatively new types of cavity field states. -- Highlights: ► We study the statistics of photons created in a cavity via dynamical Casimir effect. ► We take into account the interaction with a two-level atom placed inside the cavity. ► The field–atom dynamics is calculated numerically for the Rabi coupling. ► The interaction with a detector can totally change the statistics of created photons. ► The statistics can vary from weakly super-Poissonian to strong “hyper-Poissonian”.
Institute of Scientific and Technical Information of China (English)
Lu Daoming
2012-01-01
Using multipohton Tavis-Cummings model, the entanglement evolution of two coupling two-level atoms in Bell states interacting with a single-mode vacuum field is investigated by using negativity. The influences of coupling constants between atoms, the atomic initial states and the photon number of transition on the entanglement evolution of two coupling two-level atoms are discussed. The results obtained using the numerical method show that the entanglement of two atoms is related with coupling constants between atoms, the atomic initial states and the photon number of transition. The two-atom entanglement state will forever stay in the maximum entanglement state when the initial state is ｜β11 〉 . When the initial state of two atoms is ｜β 01 〉, the entanglement of two atoms displays periodic oscillation behavior. And its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition. On the other hand, when the initial state is ｜β 00 〉 or ｜β10 ）, the entanglement of two atoms displays quasiperiodic oscillation behavior and its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition.
Negative spontaneous emission by a moving two-level atom
Lannebère, Sylvain; Silveirinha, Mário G.
2017-01-01
In this paper we investigate how the dynamics of a two-level atom is affected by its interaction with the quantized near field of a plasmonic slab in relative motion. We demonstrate that for small separation distances and a relative velocity greater than a certain threshold, this interaction can lead to a population inversion, such that the probability of the excited state exceeds the probability of the ground state, corresponding to a negative spontaneous emission rate. It is shown that the developed theory is intimately related to a classical problem. The problem of quantum friction is analyzed and the differences with respect to the corresponding classical effect are highlighted.
Optical resonance and two-level atoms
Allen, L
1987-01-01
""Coherent and lucid…a valuable summary of a subject to which [the authors] have made significant contributions by their own research."" - Contemporary PhysicsOffering an admirably clear account of the basic principles behind all quantum optical resonance phenomena, and hailed as a valuable contribution to the literature of nonlinear optics, this distinguished work provides graduate students and research physicists probing fields such as laser physics, quantum optics, nonlinear optics, quantum electronics, and resonance optics an ideal introduction to the study of the interaction of electroma
Information Entropy. and Squeezing of Quantum Fluctuations in a Two-Level Atom
Institute of Scientific and Technical Information of China (English)
FANG Mao-Fa; ZHOU Peng; S. Swain
2000-01-01
We study the atomic squeezing in the language of the quantum information theory. A rigorous entropy uncertainty relation which suits for characterizing the squeezing of a two-level atoms is obtained, and a general definition of information entropy squeezing in the two-level atoms is given. The information entropy squeezing of two-level atoms interacting with a single-mode quantum field is examined. Our results show that the information entropy is a superior measure of the quantum uncertainty of atomic observable, also is a remarkable good precision measure of atomic squeezing. When the population difference of two-level atom is zero, the definition of atomic squeezing based on the Heisenberg uncertainty relation is trivial, while the definition of information entropy squeezing of the atom based on the entropy uncertainty relation is valid and can provide full information on the atomic squeezing in any cases.
Field correlations and effective two level atom-cavity systems
Rebic, S; Tan, S M
2004-01-01
We analyse the properties of the second order correlation functions of the electromagnetic field in atom-cavity systems that approximate two-level systems. It is shown that a recently-developed polariton formalism can be used to account for all the properties of the correlations, if the analysis is extended to include two manifolds - corresponding to the ground state and the states excited by a single photon - rather than just two levels.
Institute of Scientific and Technical Information of China (English)
2008-01-01
The time evolution of the field quantum entropy and entanglement in a system of multi-mode coherent light field resonantly interacting with a two-level atom by de-generating the multi-photon process is studied by utilizing the Von Neumann re-duced entropy theory,and the analytical expressions of the quantum entropy of the multimode field and the numerical calculation results for three-mode field inter-acting with the atom are obtained. Our attention focuses on the discussion of the influences of the initial average photon number,the atomic distribution angle and the phase angle of the atom dipole on the evolution of the quantum field entropy and entanglement. The results obtained from the numerical calculation indicate that: the stronger the quantum field is,the weaker the entanglement between the quan-tum field and the atom will be,and when the field is strong enough,the two sub-systems may be in a disentangled state all the time; the quantum field entropy is strongly dependent on the atomic distribution angle,namely,the quantum field and the two-level atom are always in the entangled state,and are nearly stable at maximum entanglement after a short time of vibration; the larger the atomic dis-tribution angle is,the shorter the time for the field quantum entropy to evolve its maximum value is; the phase angles of the atom dipole almost have no influences on the entanglement between the quantum field and the two-level atom. Entangled states or pure states based on these properties of the field quantum entropy can be prepared.
Institute of Scientific and Technical Information of China (English)
LIU WangYun; YANG ZhiYong; AN YuYing
2008-01-01
The time evolution of the field quantum entropy and entanglement in a system of multi-mode coherent light field resonantly interacting with a two-level atom by de-generating the multi-photon process is studied by utilizing the Von Neumann re-duced entropy theory, and the analytical expressions of the quantum entropy of the multimode field and the numerical calculation results for three-mode field inter-acting with the atom are obtained. Our attention focuses on the discussion of the influences of the initial average photon number, the atomic distribution angle and the phase angle of the atom dipole on the evolution of the quantum field entropy and entanglement. The results obtained from the numerical calculation indicate that: the stronger the quantum field is, the weaker the entanglement between the quan-tum field and the atom will be, and when the field is strong enough, the two sub-systems may be in a disentangled state all the time; the quantum field entropy is strongly dependent on the atomic distribution angle, namely, the quantum field and the two-level atom are always in the entangled state, and are nearly stable at maximum entanglement after a short time of vibration; the larger the atomic dis-tribution angle is, the shorter the time for the field quantum entropy to evolve its maximum value is; the phase angles of the atom dipole almost have no influences on the entanglement between the quantum field and the two-level atom. Entangled states or pure states based on these properties of the field quantum entropy can be prepared.
Abdalla, M. Sebawe; Khalil, E. M.; Obada, A. S.-F.
2017-01-01
In the present communication, we consider the problem of two quantum systems with the Kerr-like medium nonlinearity. The system is cast form of an interaction between two operators of the form su(1 , 1) Lie algebra and su(2) Lie algebra. We obtain the wave function via the evolution operator where we use the Heisenberg equations of motion to derive the constants of motion. We discuss the atomic inversion. It is found that the Kerr-like medium decreases the amplitude and increases the fluctuations. Also we consider different types of squeezing, it is shown that the entropy squeezing is pronounced in the second quadrature, but it shows a small amount in the first quadrature. For the variance squeezing, a small amount occurs in the presence of the Kerr-like medium. However, the normal squeezing occurs in the first quadrature where the squeezing is sensitive to both the Kerr-like medium parameter and the initial state. Furthermore, the degree of entanglement is examined through the linear entropy. It is shown that the function decreases besides rapid fluctuations. The correlation function displays nonclassical behavior in addition to an increase in the amplitude of the fluctuations.
The dynamic properties of the two-level entangled atom in an optical field
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The interaction of an optical field and one of the entangled atoms is analyzed in detail in this paper. Furthermore, the dynamic properties of the two-level entangled atom are manifested. The properties of the action are dependent on the initial state of the atom. After detecting the atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field influences the dynamic properties of the atom in the field.
Radiation Rate of a Two-Level Atom in a Spacetime with a Reflecting Boundary
Institute of Scientific and Technical Information of China (English)
LU Shi-Zhuan; YU Hong-Wei
2005-01-01
@@ We study a two-level atom in interaction with a real massless scalar quantum field in a spacetime with a reflecting boundary. We calculate the rate of change of the atomic energy for the atom. The presence of the boundary modifies the quantum fluctuations of the scalar field, which in turn modifies the rate of change of the atomic energy.It is found that the modifications induced by the presence of a boundary make the spontaneous radiation rate of an excited atom to oscillate near the boundary and this oscillatory behaviour may offer a possible opportunity for experimental tests for geometrical (boundary) effects in flat spacetime.
Coupling of effective one-dimensional two-level atoms to squeezed light
Clark, S; Clark, Stephen; Parkins, Scott
2002-01-01
A cavity QED system is analyzed which duplicates the dynamics of a two-level atom in free space interacting exclusively with broadband squeezed light. We consider atoms in a three or four-level Lambda-configuration coupled to a high-finesse optical cavity which is driven by a squeezed light field. Raman transitions are induced between a pair of stable atomic ground states via the squeezed cavity mode and coherent driving fields. An analysis of the reduced master equation for the atomic ground states shows that a three-level atomic system has insufficient parameter flexibility to act as an effective two-level atom interacting exclusively with a squeezed reservoir. However, the inclusion of a fourth atomic level, coupled dispersively to one of the two ground states by an auxiliary laser field, introduces an extra degree of freedom and enables the desired interaction to be realised. As a means of detecting the reduced quadrature decay rate of the effective two-level system, we examine the transmission spectrum o...
The Level-split of the Two-level Entangled Atom in an Optical Field
Institute of Scientific and Technical Information of China (English)
CAO Zhuoliang; HUANG Ting; GUO Guangcan; YI Youming
2002-01-01
The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field.
Quantum Otto engine of a two-level atom with single-mode fields.
Wang, Jianhui; Wu, Zhaoqi; He, Jizhou
2012-04-01
We establish a quantum Otto engine (QOE) of a two-level atom, which is confined in a one-dimensional (1D) harmonic trap and is coupled to single-mode radiation fields. Besides two adiabatic processes, the QOE cycle consists of two isochoric processes, along one of which the two-level atom as the working substance interacts with a single-mode radiation field. Based on the semigroup approach, we derive the time for completing any adiabatic process and then present a performance analysis of the heat engine model. Furthermore, we generalize the results to the performance optimization for a QOE of a single two-level atom trapped in a 1D power-law potential. Our result shows that the efficiency at maximum power output is dependent on the trap exponent θ but is independent of the energy spectrum index σ.
Quantum Otto engine of a two-level atom with single-mode fields
Wang, Jianhui; Wu, Zhaoqi; He, Jizhou
2012-04-01
We establish a quantum Otto engine (QOE) of a two-level atom, which is confined in a one-dimensional (1D) harmonic trap and is coupled to single-mode radiation fields. Besides two adiabatic processes, the QOE cycle consists of two isochoric processes, along one of which the two-level atom as the working substance interacts with a single-mode radiation field. Based on the semigroup approach, we derive the time for completing any adiabatic process and then present a performance analysis of the heat engine model. Furthermore, we generalize the results to the performance optimization for a QOE of a single two-level atom trapped in a 1D power-law potential. Our result shows that the efficiency at maximum power output is dependent on the trap exponent θ but is independent of the energy spectrum index σ.
Entropy Evolution of Coherend Field Interacting with Two-level Atom%相干光场与二能级原子的相互作用及场熵的演化
Institute of Scientific and Technical Information of China (English)
王建伟
2001-01-01
应用J-C模型研究了相干光场作用下二能级原子体系内部状态间的跃迁几率和相干光场场熵的演化，讨论了光场参数、耦合常数对跃迁几率和场熵演化的影响.%In this paper,evolution of the field entropy have been studied by use of the Jaynes-Cummings model, transition probability between every two levels if atom with coherent field interacting is also studied. The influence of field parameters and coupling constant on the transition probability and evolution of the field entropy are discussed.
Open-Loop Control in Quantum Optics: Two-Level Atom in Modulated Optical Field
Saifullah, Sergei
2008-01-01
The methods of mathematical control theory are widely used in the modern physics, but still they are less popular in quantum science. We will discuss the aspects of control theory, which are the most useful in applications to the real problems of quantum optics. We apply this technique to control the behavior of the two-level quantum particles (atoms) in the modulated external optical field in the frame of the so called "semi classical model", where quantum two-level atomic system (all other levels are neglected) interacts with classical electromagnetic field. In this paper we propose a simple model of feedforward (open-loop) control for the quantum particle system, which is a basement for further investigation of two-level quantum particle in the external one-dimensional optical field.
Spontaneously induced atom-radiation entanglement in an ensemble of two-level atoms
Tesfa, Sintayehu
2007-01-01
Analysis of the spontaneously induced correlation on atom-radiation entanglement in an ensemble of two-level atoms initially prepared in the upper level and placed in a cavity containing a squeezed radiation employing the method of evaluating the coherent-state propagator is presented. It is found that the cavity radiation exhibits squeezing which is directly attributed to the squeezed radiation in the cavity. The intensity of the cavity radiation increases with the squeeze parameter and inte...
Levitated nanoparticle as a classical two-level atom [Invited
Frimmer, Martin; Gieseler, Jan; Ihn, Thomas; Novotny, Lukas
2017-06-01
The center-of-mass motion of a single optically levitated nanoparticle resembles three uncoupled harmonic oscillators. We show how a suitable modulation of the optical trapping potential can give rise to a coupling between two of these oscillators, such that their dynamics are governed by a classical equation of motion that resembles the Schr\\"odinger equation for a two-level system. Based on experimental data, we illustrate the dynamics of this parametrically coupled system both in the frequency and in the time domain. We discuss the limitations and differences of the mechanical analogue in comparison to a true quantum mechanical system.
Temperature dependent quantum correlations in three dipolar coupled two-level atoms
Ahmed, Shaik
2016-01-01
We investigate the thermal entanglement characteristics of three dipole-coupled two-level atoms arranged in two different configurations - in a line with nearest neighbour coupling and in a closed loop with each atom interacting with both its neighbours. It is observed that in loop configuration, any one of the three atoms is indeed entangled with the other two atoms in the system, which are not mutually entangled, and further that this feature is specific to only the loop configuration, which is markedly absent in the line configuration. A detailed study of the quantum correlations demonstrated how these can be tuned by varying the temperature and the dipole dipole coupling strength, in both the configurations.
Dynamical decoherence in a cavity with a large number of two-level atoms
Frasca, M
2004-01-01
We consider a large number of two-level atoms interacting with the mode of a cavity in the rotating-wave approximation (Tavis-Cummings model). We apply the Holstein-Primakoff transformation to study the model in the limit of the number of two-level atoms, all in their ground state, becoming very large. The unitary evolution that we obtain in this approximation is applied to a macroscopic superposition state showing that, when the coherent states forming the superposition are enough distant, then the state collapses on a single coherent state describing a classical radiation mode. This appear as a true dynamical effect that could be observed in experiments with cavities.
Institute of Scientific and Technical Information of China (English)
邹旭波; 许晶波; 高孝纯; 符建
2001-01-01
We adopt a dynamical algebraic approach to study the system of a two-level atom moving in a quantized travelling light field and a gravitational field with a multiphoton interaction. The exact solution of the system is obtained and used to discuss the influence of the gravitational field on the collapses and revivals of atomic population, sub-Poissonian statistics.
Quantum averaging and resonances: two-level atom in a one-mode classical laser field
Directory of Open Access Journals (Sweden)
M. Amniat-Talab
2007-06-01
Full Text Available We use a nonperturbative method based on quantum averaging and an adapted from of resonant transformations to treat the resonances of the Hamiltonian of a two-level atom interacting with a one-mode classical field in Floquet formalism. We illustrate this method by extraction of effective Hamiltonians of the system in two regimes of weak and strong coupling. The results obtained in the strong-coupling regime, are valid in the whole range of the coupling constant for the one-photon zero-field resonance.
The excitation of a two-level atom by a propagating light pulse
Wang, Yimin; Scarani, Valerio
2010-01-01
State mapping between atoms and photons, and photon-photon interactions play an important role in scalable quantum information processing. We consider the interaction of a two-level atom with a quantized \\textit{propagating} pulse in free space and study the probability $P_e(t)$ of finding the atom in the excited state at any time $t$. This probability is expected to depend on (i) the quantum state of the pulse field and (ii) the overlap between the pulse and the dipole pattern of the atomic spontaneous emission. In the full three-dimensional vector model for the field, we show that the second effect is captured by a single parameter $\\Lambda\\in[0,8\\pi/3]$, obtained by weighing the numerical aperture with the dipole pattern. Then $P_e(t)$ can be obtained by solving time-dependent Heisenberg-Langevin equations. We provide detailed solutions for both single-photon states and coherent states and for various shapes of the pulse.
Regular and Chaotic Quantum Dynamics of Two-Level Atoms in a Selfconsistent Radiation Field
Konkov, L. E.; Prants, S. V.
1996-01-01
Dynamics of two-level atoms interacting with their own radiation field in a single-mode high-quality resonator is considered. The dynamical system consists of two second-order differential equations, one for the atomic SU(2) dynamical-group parameter and another for the field strength. With the help of the maximal Lyapunov exponent for this set, we numerically investigate transitions from regularity to deterministic quantum chaos in such a simple model. Increasing the collective coupling constant b is identical with 8(pi)N(sub 0)(d(exp 2))/hw, we observed for initially unexcited atoms a usual sharp transition to chaos at b(sub c) approx. equal to 1. If we take the dimensionless individual Rabi frequency a = Omega/2w as a control parameter, then a sequence of order-to-chaos transitions has been observed starting with the critical value a(sub c) approx. equal to 0.25 at the same initial conditions.
Solving the scattering of N photons on a two-level atom without computation
Roulet, Alexandre; Scarani, Valerio
2016-09-01
We propose a novel approach for solving the scattering of light onto a two-level atom coupled to a one-dimensional waveguide. First we express the physical quantity of interest in terms of Feynman diagrams and treat the atom as a non-saturable linear beamsplitter. By using the atomic response to our advantage, a relevant substitution is then made that captures the nonlinearity of the atom, and the final result is obtained in terms of simple integrals over the initial incoming wavepackets. The procedure is not limited to post-scattering quantities and allows for instance to derive the atomic excitation during the scattering event.
Clustering DTDs: An Interactive Two-Level Approach
Institute of Scientific and Technical Information of China (English)
周傲英; 钱卫宁; 钱海蕾; 张龙; 梁宇奇; 金文
2002-01-01
XML (eXtensible Markup Language) is a standard which is widely appliedin data representation and data exchange. However, as an important concept of XML, DTD(Document Type Definition) is not taken full advantage in current applications. In this paper, anew method for clustering DTDs is presented, and it can be used in XML document clustering.The two-level method clusters the elements in DTDs and clusters DTDs separately. Elementclustering forms the first level and provides element clusters, which are the generalization ofrelevant elements. DTD clustering utilizes the generalized information and forms the secondlevel in the whole clustering process. The two-level method has the following advantages: 1) Ittakes into consideration both the content and the structure within DTDs; 2) The generalizedinformation about elements is more useful than the separated words in the vector model; 3) Thetwo-level method facilitates the searching of outliers. The experiments show that this methodis able to categorize the relevant DTDs effectively.
Eigenmode expansion of the polarization for a spherical sample of two-level atoms
Energy Technology Data Exchange (ETDEWEB)
Friedberg, Richard [Physics Department, Columbia University, New York, NY 10027 (United States); Manassah, Jamal T., E-mail: jmanassah@gmail.co [HMS Consultants, Inc., PO Box 592, New York, NY 10028 (United States)
2009-12-07
We derive pseudo-orthogonality relations for both the magnetic and electric eigenmodes of a system of two-level atoms in a sphere configuration. We verify numerically that an arbitrary vector field can be reconstructed to a great accuracy from these eigenmode expansions. We apply this eigenmode analysis to explore superradiance from a sphere with initially uniform polarization.
Three-body entanglement induced by spontaneous emission in a three two-level atoms system
Institute of Scientific and Technical Information of China (English)
Liao Xiang-Ping; Fang Mao-Fa; Zheng Xiao-Juan; Cai Jian-Wu
2006-01-01
We study three-body entanglement induced by spontaneous emission in a three two-level atoms system by using the entanglement tensor approach. The results show that the amount of entanglement is strongly dependent on the initial state of the system and the species of atoms. The three-body entanglement is the result of the coherent superposition of the two-body entanglements. The larger the two-body entanglement is, the stronger the three-body entanglement is. On the other hand, if there exists a great difference in three two-body entanglement measures, the three-body entanglement is very weak. We also find that the maximum of the two-body entanglement obtained with nonidentical atoms is greater than that obtained with identical atoms via adjusting the difference in atomic frequency.
Entropy squeezing for a two-level atom in two-mode Raman coupled model with intrinsic decoherence
Institute of Scientific and Technical Information of China (English)
Zhang Jian; Shao Bin; Zou Jian
2009-01-01
In this paper,we investigate the entropy squeezing for a two-level atom interacting with two quantized fields through Raman coupling.We obtain the dynamical evolution of the total system under the influence of intrinsic decoherence when the two quantized fields are prepared in a two-mode squeezing vacuum state initially.The effects of the field squeezing factor,the two-level atomic transition frequency,the second field frequency and the intrinsic decoherence on the entropy squeezing are discussed.Without intrinsic decoherence,the increase of field squeezing factor can break the entropy squeezing.The two-level atomic transition frequency changes only the period of oscillation but not the strength of entropy squeezing.The influence of the second field frequency is complicated.With the intrinsic decoherence taken into consideration,the results show that the stronger the intrinsic decoherence is,the more quickly the entropy squeezing will disappear.The increase of the atomic transition frequency can hasten the disappearance of entropy squeezing.
Institute of Scientific and Technical Information of China (English)
何小灵; 杜四德; 周鲁卫; 汪启胜; 陈灏
2004-01-01
Tunnelling of a two-level atom is investigated in the two-photon mazer when the atom is initially prepared in a coherent superposition state and the cavity in various quantum states. For a strong coherent field, the tunnelling exhibits more regular oscillations but less remarkable switch effect than that in the one-photon mazer. It is discovered that in the presence of atomic coherence, the transmission probabilities in the ultracold regime are significantly different when the cavity field is initially in coherent, squeezed vacuum, even cat and odd cat states,respectively.
Surdutovich, G. I.; Ghiner, A. V.
2000-08-01
A famous model of a two-level atom interacting with the classical electromagnetic field is used to illustrate the fundamental problem of the relationship between the dynamical and relaxation processes under the interaction of radiation with a quantum-mechanical system and, as a result, to derive nonlinear Bloch-like equations. The presented considerations are based on the analysis of the balance of the fluxes of energy between atomic and field subsystems. It is shown that the generally accepted model of the exponential relaxation deduced for an isolated excited atom and inserted customarily into optical Bloch equations (OBE) describing atom in an external field always leads to a very strange result: spontaneous emission of an atom should be accompanied by the radiation of the coherent field into the external field's mode. Making use of only the energetic considerations, we found the relaxation mechanism (in the form of additional terms in the OBE) which, on the one hand, guarantees the fulfillment of the energetic balance and, on the other hand, allows to introduce arbitrary additional collision-like relaxation mechanism without violation of this balance. Note that these additional terms introduced into OBE from the energetic considerations in a remarkable manner exactly correspond to the renormalization of the external field with the allowance of the classical radiation damping (RD) effect. The revisited OBE may be used as the starting point for considering the dynamics of an atom by making allowance for the quantum properties of an external field.
Phase Dependence of Few-Cycle Pulsed Laser Propagation in a Two-Level Atom Medium
Institute of Scientific and Technical Information of China (English)
肖健; 王中阳; 徐至展
2002-01-01
The phase-dependent feature of few-cycle pulsed laser propagation in a resonant two-level atom medium is demonstrated by solving the full Maxwell-Bloch equations. Even in the perturbative region, the propagating carrier field and the corresponding spectra of the few-cycle pulsed laser are sensitive to the initial phase due to self-phase modulation. For the larger pulse area, the fact that the carrier-wave reshaping comes from the carrier wave Rabi flopping is also responsible for this sensitivity, and the phase-dependent feature is more evident.
SPECTRUM OF A FEW-CYCLE LASER PULSE PROPAGATING IN A TWO-LEVEL ATOM MEDIUM
Institute of Scientific and Technical Information of China (English)
肖健; 王中阳; 徐至展
2001-01-01
The spectrum evolution of a few-cycle optical pulse in a resonant two-level atom medium is studied theoretically by using the full Maxwell-Bloch equations. On the propagating pulse, significantly much faster oscillation components separated with the main pulse appear due to strong self-phase modulation and pulse reshaping. In this case, ideal selfinduced transparency cannot occur for a 2r pulse. The spectrum of the 4r pulse shows an evident oscillatory feature because of the continuum interference of the separate pulses. For larger pulse areas, continuum generation from near ultraviolet to infrared occurs.
Propagation of Few-Cycle Pulse Laser in Two-Level Atom Medium
Institute of Scientific and Technical Information of China (English)
肖健; 王中阳; 徐至展
2001-01-01
By comparing the numerical solutions of Maxwell-Bloch equations beyond and within the slowly-varying envelope approximation and the rotating-wave approximation for the propagation of a few-cycle pulse laser in a resonant two-level atom medium, we found that both the Rabi flopping and the refractive index, and subsequently the carrier and the propagation velocity of the few-cycle pulse, are closely connected with the time-derivative behaviour of the electric field. This is because the Rabi flopping is such that the soliton pulse splits during propagation and that a shorter pulse propagates faster than a broader one.
Phase Dependence of Fluorescence Spectrum of a Two-Level Atom in a Trichromatic Field
Institute of Scientific and Technical Information of China (English)
LI Jing-Yan; HU Xiang-Ming; LI Xiao-Xia; SHI Wen-Xing; XU Qing; GUO Hong-Ju
2005-01-01
@@ We examine the phase-dependent effects in resonance fluorescence of a two-level atom driven by a trichromatic modulated field. It is shown that the fluorescence spectrum depends crucially on the sum of relative phases of the sideband components compared to the central component, not simply on the respective phases. The appearance or disappearance of the central peak and the selective elimination of the sideband peaks are achieved simply by varying the sum phase. Once the sum phase is fixed, the spectrum keeps its features unchanged regardless of the respective relative phases.
Photon absorption and emission statistics of a two-level atom in a cavity
Energy Technology Data Exchange (ETDEWEB)
Lee, Chang J. [Sun Moon University, Asan (Korea, Republic of)
2012-03-15
The absorption and the emission of photons by an atom involves quantum jumps between states. We investigate the quantum jump statistics for the system of a two-level atom and a single-mode cavity field. We use the Jaynes-Cummings model for this problem, perform Monte Carlo numerical simulations, and give a detailed exact analysis on these simulations. These studies reveal that the waiting-time distribution (WTD) for photon absorptions (emissions) has a unique novel statistic, and that the photon absorption (emission) rate is not uniform, but counter-intuitively depends on the position in the Rabi cycle. The effects of the nonclassical nature of the field on the WTD is discussed.
Giant Cooperative Lamb Shift in a density-modulated slab of two-level atoms
Energy Technology Data Exchange (ETDEWEB)
Manassah, Jamal T., E-mail: jmanassah@gmail.co [Department of Electrical Engineering, City College of New York, NY 10031 (United States)
2010-04-19
A 'slab' of two-level atoms prepared in a superradiant Dicke state exhibits interesting enhancement of the Cooperative Decay Rate (CDR) when its density is modulated at the Bragg condition. In this Letter, complete analytical formulas are given, not only for CDR but also for the Cooperative Lamb Shift (CLS), both at and near the Bragg condition, as a function of the depth of modulation, the thickness of the slab, and the detuning from the Bragg condition. A major new result is that for detuning O(1/m) (where m=thickness/wavelength) the CLS takes on 'giant' values, proportional to m. The reason for this giant CLS is explored.
Controlling spontaneous emission of a two-level atom by hyperbolic metamaterials
Liu, Zheng; Jiang, Xunya
2012-01-01
Within the frame of quantum optics we analyze the properties of spontaneous emission of two-level atom in media with indefinite permittivity tensor where the geometry of the dispersion relation is characterized by an ellipsoid or a hyperboloid(hyperbolic medium). The decay rate is explicitly given with the orientation of the dipole transition matrix element taken into account. It indicates that for the ellipsoid case the intensity of the photons coupled into different modes can be tuned by changing the direction of the matrix element and for the hyperboloid case it is found that spontaneous emission in hyperbolic medium can be dramatically enhanced compared to the dielectric background. Moreover, spontaneous emission exhibit the strong directivity and get the maximum in the asymptote direction.
Temporal Bell-type inequalities for two-level Rydberg atoms coupled to a high-{ital Q} resonator
Energy Technology Data Exchange (ETDEWEB)
Huelga, S.F.; Marshall, T.W.; Santos, E. [Departamento de Fisica, Universidad de Oviedo, 33007 Oviedo (Spain)]|[Department of Mathematics, University of Manchester, Manchester M139PL, United Kingdom Departamento de Fisica Moderna, Universidad de Cantabria, 39005 Santander (Spain)
1996-09-01
Following the strategy of showing specific quantum effects by means of the violation of a classical inequality, a pair of Bell-type inequalities is derived on the basis of certain additional assumptions, whose plausibility is discussed in detail. Such inequalities are violated by the quantum mechanical predictions for the interaction of a two-level Rydberg atom with a single mode sustained by a high-{ital Q} resonator. The experimental conditions required in order to show the existence of forbidden values, according to a hidden variables formalism, in a real experiment are analyzed for various initial field statistics. In particular, the revival dynamics expected for the interaction with a coherent field leads to classically forbidden values, which would indicate a purely quantum effect. {copyright} {ital 1996 The American Physical Society.}
Atomic & Molecular Interactions
Energy Technology Data Exchange (ETDEWEB)
None
2002-07-12
The Gordon Research Conference (GRC) on Atomic & Molecular Interactions was held at Roger Williams University, Bristol, RI. Emphasis was placed on current unpublished research and discussion of the future target areas in this field.
Institute of Scientific and Technical Information of China (English)
李春先; 方卯发
2003-01-01
We study the squeezing for a two-level atom in the Jaynes-Cummings model with intensity-dependent coupling using quantum information entropy, and examine the influences of the initial state of the system on the squeezed component number and direction of the information entropy squeezing. Our results show that, the squeezed component number depends on the atomic initial distribution angle, while the squeezed direction is determined by both the phases of the atom and the field for the information entropy squeezing. Quantum information entropy is shown to be a remarkable precision measure for atomic squeezing.
Energy Technology Data Exchange (ETDEWEB)
Zhai, Hua [Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Zhang, Jialin, E-mail: jialinzhang@hunnu.edu.cn [Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn [Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications, Hunan Normal University, Changsha, Hunan 410081 (China); Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo 315211 (China)
2016-08-15
We study the geometric phase of a uniformly accelerated two-level atom coupled with vacuum fluctuations of electromagnetic fields in the presence of a perfectly reflecting plane. We find that the geometric phase difference between the accelerated and inertial atoms which can be observed by atom interferometry crucially depends on the polarizability of the atom and the distance to the boundary and it can be dramatically manipulated with anisotropically polarizable atoms. In particular, extremely close to the boundary, the phase difference can be increased by two times as compared to the case without any boundary. So, the detectability of the effects associated with acceleration using an atom interferometer can be significantly increased by the presence of a boundary using atoms with anisotropic polarizability.
Yang, Yiquan; Yu, Hongwei
2016-01-01
We investigate the entanglement dynamics of two uniformly accelerated atoms with the same acceleration perpendicular to their separation. The two-atom system is treated as an open system coupled with fluctuating electromagnetic fields in the Minkowski vacuum, and in the Born-Markov approximation the master equation that describes the completely positive time evolution of the two-atom system is derived. In particular, we investigate the phenomena of entanglement degradation, generation, revival and enhancement. As opposed to the scalar-field case, the entanglement dynamics is crucially dependent on the polarization directions of the atoms. For the two-atom system with certain acceleration and separation, the polarization directions of the atoms may determine whether entanglement generation, revival or enhancement happens, while for entanglement degradation, they affect the decay rate of entanglement. A comparison between the entanglement evolution of accelerated atoms and that of static ones immersed in a ther...
M Sakawa; Kato, K.
2009-01-01
This paper considers stochastic two-level linear programming problems. Using the concept of chance constraints and probability maximization, original problems are transformed into deterministic ones. An interactive fuzzy programming method is presented for deriving a satisfactory solution efficiently with considerations of overall satisfactory balance.
The dynamical Cooperative Lamb Shift in a system of two-level atoms in a slab-geometry
Energy Technology Data Exchange (ETDEWEB)
Friedberg, Richard [Department of Physics, Columbia University, New York, NY 10027 (United States); Manassah, Jamal T., E-mail: jmanassah@gmail.co [HMS Consultants, Inc., PO Box 592, New York, NY 10028 (United States)
2009-09-14
Using the eigenmode analysis, we compute the Cooperative Lamb Shift (CLS) as a function of time from the vector photon model for a system of two-level atoms in a slab-geometry for forward and backward emission in two initial states of weak excitation and complete inversion.
Directory of Open Access Journals (Sweden)
M. Corgini
2010-01-01
Full Text Available For a Bose atom system whose energy operator is diagonal in the so-called number operators and its ground state has an internal two-level structure with negative energies, exact expressions for the limit free canonical energy and pressure are obtained. The existence of non-conventional Bose-Einstein condensation has been also proved.
Controlled Single-Photon Emission from a Single Trapped Two-Level Atom
Darquié, B; Dingjan, J; Beugnon, J; Bergamini, S; Sortais, Y; Messin, G; Browaeys, A; Grangier, P; Darqui\\'{e}, Benoit; Jones, Matthew; Dingjan, Jos; Beugnon, Jerome; Bergamini, Silvia; Sortais, Yvan; Messin, Gaetan; Browaeys, Antoine; Grangier, Philippe
2005-01-01
By illuminating an individual rubidium atom stored in a tight optical tweezer with short resonant light pulses, we create an efficient triggered source of single photons with a well-defined polarization. The measured intensity correlation of the emitted light pulses exhibits almost perfect antibunching. Such a source of high rate, fully controlled single photon pulses has many potential applications for quantum information processing.
Institute of Scientific and Technical Information of China (English)
李鹏茂; 萨楚尔夫; 苏少龙
2015-01-01
Applying the method of coherent states orthogonalization expansion , the atomic population and the anti-bunching effect of the light field are studied in the system of interaction between a two -level atom and the SchrÖdinger cat state without rotating wave approximation ( RWA) .The results are compared with those in RWA . The influences of the original strength of the light field and two coherent phase angles on the atomic population and antibunching effect with RWA and without RWA are discussed respectively , and the antibunching effect in the weak coupling condition is also discussed without RWA .The results show that the atomic populations with RWA and without RWA have different properties with the different original strengths of the light field .As the original strength of the light field is smaller , the atomic populations with RWA and without RWA show the same properties , but with the increase of the original strength of the light field the population with RWA will show the collapse phe -nomenon .When the coupling strength is larger , the antibunching effects with RWA and without RWA have bigger difference .Without RWA the light field will appear bunching effect , whereas with RWA it will appear alternately the bunching effect and the antibunching effect with the increase of the original strength of light field .%在非旋波近似下，通过采用相干态正交化展开的方法，研究了薛定谔猫态光场与二能级原子相互作用系统中，原子的布局数和光场的反聚束效应，并与旋波近似下的结果进行了对比。在旋波近似与非旋波近似下，讨论了初始光场强度、相干态间的相位角以及失谐量对原子布局数和光场反聚束效应的影响；在非旋波近似下，讨论了强弱耦合情况下光场的反聚束效应。研究结果表明：旋波近似与非旋波近似下，原子的布局数随着初始光场强度的不同，表现出不同的特性；当初始光场强度较小时，
Controlled single-photon emission from a single trapped two-level atom.
Darquié, B; Jones, M P A; Dingjan, J; Beugnon, J; Bergamini, S; Sortais, Y; Messin, G; Browaeys, A; Grangier, P
2005-07-15
By illuminating an individual rubidium atom stored in a tight optical tweezer with short resonant light pulses, we created an efficient triggered source of single photons with a well-defined polarization. The measured intensity correlation of the emitted light pulses exhibits almost perfect antibunching. Such a source of high-rate, fully controlled single-photon pulses has many potential applications for quantum information processing.
Interaction of Lamb modes with two-level systems in amorphous nanoscopic membranes.
Energy Technology Data Exchange (ETDEWEB)
Kuhn, T.; Anghel, D. V.; Galperin, Y. M.; Manninen, M.; Materials Science Division; Univ. Jyvaskyla; National Inst. for Physics and Nuclear Engineering; Bogolivbov Lab. Theoretical Physics; Univ. Oslo; Russian Academy of Sciences
2007-01-01
Using a generalized model of interaction between a two-level system (TLS) and an arbitrary deformation of the material, we calculate the interaction of Lamb modes with TLSs in amorphous nanoscopic membranes. We compare the mean free paths of the Lamb modes of different symmetries and calculate the heat conductivity {kappa}. In the limit of an infinitely wide membrane, the heat conductivity is divergent. Nevertheless, the finite size of the membrane imposes a lower cutoff for the phonon frequencies, which leads to the temperature dependence {kappa}{alpha}T(a+b ln T). This temperature dependence is a hallmark of the TLS-limited heat conductance at low temperature.
Shuval-Sergeeva, E. V.; Zaitsev, A. I.
2008-03-01
When describing the phenomenon of bistability of optical response of an ultra thin layer consisting of two-level atoms it is important to take into account the local field correction. The account of the correction results in the improvement of existence conditions of bistability. One more bistable region is formed starting with certain value of local field parameter. Both effects are induced by the dynamical frequency shift.
Adiabatic approximation for a two-level atom in a light beam
Aftalion, Amandine
2011-01-01
Following the recent experimental realization of synthetic gauge magnetic forces, Jean Dalibard adressed the question whether the adiabatic ansatz could be math- ematically justified for a model of an atom in 2 internal states, shun by a quasi resonant laser beam. In this paper, we derive rigorously the asymptotic model guessed by the physicists, and show that this asymptotic analysis contains the in- formation about the presence of vortices. Surprisingly the main difficulties do not come from the nonlinear part but from the linear Hamiltonian. More precisely, the analysis of the nonlinear minimization problem and its asymptotic reduction to simpler ones, relies on an accurate partition of low and high frequencies (or mo- menta). This requires to reconsider carefully previous mathematical works about the adiabatic limit. Although the estimates are not sharp, this asymptotic analysis provides a good insight about the validity of the asymptotic picture, with respect to the size of the many parameters initially ...
Enhancing student learning of two-level quantum systems with interactive simulations
Kohnle, Antje; Campbell, Anna; Korolkova, Natalia; Paetkau, Mark J
2015-01-01
The QuVis Quantum Mechanics Visualization project aims to address challenges of quantum mechanics instruction through the development of interactive simulations for the learning and teaching of quantum mechanics. In this article, we describe evaluation of simulations focusing on two-level systems developed as part of the Institute of Physics Quantum Physics resources. Simulations are research-based and have been iteratively refined using student feedback in individual observation sessions and in-class trials. We give evidence that these simulations are helping students learn quantum mechanics concepts at both the introductory and advanced undergraduate level, and that students perceive simulations to be beneficial to their learning.
Grace, M; Kosut, R L; Lidar, D A; Rabitz, H; Walmsley, I A; Brif, Constantin; Grace, Matthew; Kosut, Robert L.; Lidar, Daniel A.; Rabitz, Herschel; Walmsley, Ian A.
2007-01-01
Methods of optimal control are applied to a model system of interacting two-level particles (e.g., spin-half atomic nuclei or electrons or two-level atoms) to produce high-fidelity quantum gates while simultaneously negating the detrimental effect of decoherence. One set of particles functions as the quantum information processor, whose evolution is controlled by a time-dependent external field. The other particles are not directly controlled and serve as an effective environment, coupling to which is the source of decoherence. The control objective is to generate target one- and two-qubit unitary gates in the presence of strong environmentally-induced decoherence and under physically motivated restrictions on the control field. The quantum-gate fidelity, expressed in terms of a novel state-independent distance measure, is maximized with respect to the control field using combined genetic and gradient algorithms. The resulting high-fidelity gates demonstrate the feasibility of precisely guiding the quantum ev...
Sohail, Amjad; Zhang, Yang; Zhang, Jun; Yu, Chang-Shui
2016-06-28
We analytically study the optomechanically induced transparency (OMIT) in the N-cavity system with the Nth cavity driven by pump, probing laser fields and the 1st cavity coupled to mechanical oscillator. We also consider that one atom could be trapped in the ith cavity. Instead of only illustrating the OMIT in such a system, we are interested in how the number of OMIT windows is influenced by the cavities and the atom and what roles the atom could play in different cavities. In the resolved sideband regime, we find that, the number of cavities precisely determines the maximal number of OMIT windows. It is interesting that, when the two-level atom is trapped in the even-labeled cavity, the central absorptive peak (odd N) or dip (even N) is split and forms an extra OMIT window, but if the atom is trapped in the odd-labeled cavity, the central absorptive peak (odd N) or dip (even N) is only broadened and thus changes the width of the OMIT windows rather than induces an extra window.
Evolution of optical force on two-level atom by ultrashort time-domain dark hollow Gaussian pulse
Cao, Xiaochao; Wang, Zhaoying; Lin, Qiang
2017-09-01
Based on the analytical expression of the ultrashort time-domain dark hollow Gaussian (TDHG) pulse, the optical force on two-level atoms induced by a TDHG pulse is calculated in this paper. The phenomena of focusing or defocusing of the light force is numerical analyzed for different detuning, various duration time, and different order of the ultrashort pulse. The transverse optical force can change from a focusing force to a defocusing force depending on the spatial-temporal coupling effect as the TDHG pulses propagating in free space. Our results also show that the initial phase of the TDHG pulse can significantly changes the envelope of the optical force.
Firth, W J; Labeyrie, G; Camara, A; Gomes, P; Ackemann, T
2016-01-01
We explore various models for the pattern forming instability in a laser-driven cloud of cold two-level atoms with a plane feedback mirror. Focus is on the combined treatment of nonlinear propagation in a diffractively thick medium and the boundary condition given by feedback. The combined presence of purely transverse transmission gratings and reflection gratings on wavelength scale is addressed. Different truncation levels of the Fourier expansion of the dielectric susceptibility in terms of these gratings are discussed and compared to literature. A formalism to calculate the exact solution for the homogenous state in presence of absorption is presented. The relationship between the counterpropagating beam instability and the feedback instability is discussed. Feedback reduces the threshold by a factor of two under optimal conditions. Envelope curves which bound all possible threshold curves for varying mirror distances are calculated. The results are comparing well to experimental results regarding the obs...
Zhang, Dasen; Zhang, Zhiming
2017-01-01
We study the spatiotemporal structure of the biphoton entangled state generated by the four-wave mixing (FWM) process in a cold two-level atomic ensemble. We analyze, for the first time, the X-like shaped structure of the biphoton entangled state and the geometry of the biphoton correlation for different lengths and densities of the cold atomic ensemble. The propagation equations of the photon pairs generated from FWM process are derived in a spatiotemporal framework. By means of the input-output relations of the propagation equations, the biphoton amplitude function is obtained in a spatiotemporal domain. In the given frequency range, the biphoton amplitude displays an X-like shaped geometry, nonfactorizable in the space-time domain. Such an X-like shaped spatiotemporal structure is caused by the phase matching and the FWM gain. The former leads to the X-like shaped envelope of the biphoton correlation, while the latter gives rise to the oscillations around the X-like shaped envelope. PMID:28218235
Zhang, Dasen; Zhang, Zhiming
2017-02-20
We study the spatiotemporal structure of the biphoton entangled state generated by the four-wave mixing (FWM) process in a cold two-level atomic ensemble. We analyze, for the first time, the X-like shaped structure of the biphoton entangled state and the geometry of the biphoton correlation for different lengths and densities of the cold atomic ensemble. The propagation equations of the photon pairs generated from FWM process are derived in a spatiotemporal framework. By means of the input-output relations of the propagation equations, the biphoton amplitude function is obtained in a spatiotemporal domain. In the given frequency range, the biphoton amplitude displays an X-like shaped geometry, nonfactorizable in the space-time domain. Such an X-like shaped spatiotemporal structure is caused by the phase matching and the FWM gain. The former leads to the X-like shaped envelope of the biphoton correlation, while the latter gives rise to the oscillations around the X-like shaped envelope.
Institute of Scientific and Technical Information of China (English)
Liu Xiao-Juan; Zhou Yuan-Jun; Fang Mao-Fa
2009-01-01
From the viewpoint of quantum information, this paper proposes a concept and a definition of the atomic optimal entropy squeezing sudden generation (AOESSG) for the system of an effective two-level moving atom which entangles with the two-mode coherent fields. It also researches the relationship between the AOESSG and entanglement sudden death of the atom-fields, and discusses the influences of atomic initial state on the AOESSG and obtains the system parameter which controls the AOESSG.
Canyon of current suppression in an interacting two-level quantum dot
DEFF Research Database (Denmark)
Karlström, O; Pedersen, Jonas Nyvold; Samuelsson, P
2011-01-01
Motivated by the recent discovery of a canyon of conductance suppression in a two-level equal-spin quantum dot system [Phys. Rev. Lett. 104, 186804 (2010)], the transport through this system is studied in detail. At low bias and low temperature a strong current suppression is found around...... quantum rate equations. The simulations allow for the prediction of how the suppression is affected by the couplings, the charging energy, the position of the energy levels, the applied bias, and the temperature. We find that, away from electron-hole symmetry, the parity of the couplings is essential...
Nemati Aram, Tahereh; Anghel-Vasilescu, Petrutza; Asgari, Asghar; Ernzerhof, Matthias; Mayou, Didier
2016-09-28
We present a novel simple model to describe molecular photocells where the energy conversion process takes place by a single molecular donor-acceptor complex attached to electrodes. By applying quantum scattering theory, an open quantum system method, the coherent molecular photocell is described by a wave function. We analyze photon absorption, energy conversion, and quantum yield of a molecular photocell by considering the effects of electron-hole interaction and non-radiative recombination. We model the exciton creation, dissociation, and subsequent effects on quantum yield in the energy domain. We find that depending on the photocell structure, the electron-hole interaction can normally decrease or abnormally increase the cell efficiency. The proposed model helps to understand the mechanisms of molecular photocells, and it can be used to optimize their yield.
Fidelity decay in interacting two-level boson systems: Freezing and revivals
Benet, Luis; Hernández-Quiroz, Saúl; Seligman, Thomas H.
2011-05-01
We study the fidelity decay in the k-body embedded ensembles of random matrices for bosons distributed in two single-particle states, considering the reference or unperturbed Hamiltonian as the one-body terms and the diagonal part of the k-body embedded ensemble of random matrices and the perturbation as the residual off-diagonal part of the interaction. We calculate the ensemble-averaged fidelity with respect to an initial random state within linear response theory to second order on the perturbation strength and demonstrate that it displays the freeze of the fidelity. During the freeze, the average fidelity exhibits periodic revivals at integer values of the Heisenberg time tH. By selecting specific k-body terms of the residual interaction, we find that the periodicity of the revivals during the freeze of fidelity is an integer fraction of tH, thus relating the period of the revivals with the range of the interaction k of the perturbing terms. Numerical calculations confirm the analytical results.
Fidelity decay in interacting two-level boson systems: Freezing and revivals
Benet, Luis; Seligman, Thomas H
2011-01-01
We study the fidelity decay in the $k$-body embedded ensembles of random matrices for bosons distributed in two single-particle states, considering the reference or unperturbed Hamiltonian as the one-body terms and the diagonal part of the $k$-body embedded ensemble of random matrices, and the perturbation as the residual off-diagonal part of the interaction. We calculate the ensemble-averaged fidelity with respect to an initial random state within linear response theory to second order on the perturbation strength, and demonstrate that it displays the freeze of the fidelity. During the freeze, the average fidelity exhibits periodic revivals at integer values of the Heisenberg time $t_H$. By selecting specific $k$-body terms of the residual interaction, we find that the periodicity of the revivals during the freeze of fidelity is an integer fraction of $t_H$, thus relating the period of the revivals with the range of the interaction $k$ of the perturbing terms. Numerical calculations confirm the analytical re...
Energy Technology Data Exchange (ETDEWEB)
Friedberg, Richard [Physics Department, Columbia University, New York, NY 10027 (United States); Manassah, Jamal T., E-mail: jmanassah@gmail.co [HMS Consultants, Inc., P.O. Box 592, New York, NY 10028 (United States)
2010-04-05
We give the analytic expressions for the initial Cooperative Decay Rate and Cooperative Lamb Shift for a spherical cloud of two-level atoms for the cases of uniform and Gaussian number density distributions. We derive these expressions in both scalar and vector models for the cases when the system's initial polarization is uniform and when it is coherently phased.
Yu, Min; Fang, Mao-Fa
2016-10-01
We investigate the entropy squeezing of a two-level atom coupled to a dissipative cavity under two different controls: In the first case, quantum-jump-based feedback is alone applied, whereas in the second case we consider the combined effect of quantum-jump-based feedback and classical driving, in which we provide a scheme to generate and protect steady and optimal entropy squeezing of the two-level atom. The results show that the entropy squeezing of atomic polarization components greatly depends on the control of quantum-jump-based feedback and classical driving. Under the condition of designing proper quantum-jump-based feedback parameters, the entropy squeezing can be generated and protected. Furthermore, when both quantum-jump-based feedback and classical driving are simultaneously applied, steady and optimal entropy squeezing of the two-level atom can be obtained even though there is initially no entropy squeezing, which is explained by making use of the steady-state solution of the atom.
Kale, Y. B.; Tiwari, V. B.; Mishra, S. R.; Singh, S.; Rawat, H. S.
2016-12-01
We report electromagnetically induced absorption (EIA) and transparency (EIT) resonances of sub-natural linewidth in degenerate two level systems (DTLSs) of metastable 84Kr (84Kr*) and 83Kr (83Kr*) atoms. Using the spectrally narrow EIA signals obtained corresponding to the closed hyperfine transition 4p55s[3/2]2(F=13/2) to 4p55p[5/2]3(F‧ = 15 / 2) in 83Kr* atom, we have measured the Landé g-factor (gF) for the lower hyperfine level involved in this transition by application of small values of magnetic field of few Gauss.
Atoms and Molecules Interacting with Light
van der Straten, Peter; Metcalf, Harold
2016-02-01
Part I. Atom-Light Interaction: 1. The classical physics pathway; Appendix 1.A. Damping force on an accelerating charge; Appendix 1.B. Hanle effect; Appendix 1.C. Optical tweezers; 2. Interaction of two-level atoms and light; Appendix 2.A. Pauli matrices for motion of the bloch vector; Appendix 2.B. The Ramsey method; Appendix 2.C. Echoes and interferometry; Appendix 2.D. Adiabatic rapid passage; Appendix 2.E Superposition and entanglement; 3. The atom-light interaction; Appendix 3.A. Proof of the oscillator strength theorem; Appendix 3.B. Electromagnetic fields; Appendix 3.C. The dipole approximation; Appendix 3.D. Time resolved fluorescence from multi-level atoms; 4. 'Forbidden' transitions; Appendix 4.A. Higher order approximations; 5. Spontaneous emission; Appendix 5.A. The quantum mechanical harmonic oscillator; Appendix 5.B. Field quantization; Appendix 5.C. Alternative theories to QED; 6. The density matrix; Appendix 6.A. The Liouville-von Neumann equation; Part II. Internal Structure: 7. The hydrogen atom; Appendix 7.A. Center-of-mass motion; Appendix 7.B. Coordinate systems; Appendix 7.C. Commuting operators; Appendix 7.D. Matrix elements of the radial wavefunctions; 8. Fine structure; Appendix 8.A. The Sommerfeld fine-structure constant; Appendix 8.B. Measurements of the fine structure 9. Effects of the nucleus; Appendix 9.A. Interacting magnetic dipoles; Appendix 9.B. Hyperfine structure for two spin =2 particles; Appendix 9.C. The hydrogen maser; 10. The alkali-metal atoms; Appendix 10.A. Quantum defects for the alkalis; Appendix 10.B. Numerov method; 11. Atoms in magnetic fields; Appendix 11.A. The ground state of atomic hydrogen; Appendix 11.B. Positronium; Appendix 11.C. The non-crossing theorem; Appendix 11.D. Passage through an anticrossing: Landau-Zener transitions; 12. Atoms in electric fields; 13. Rydberg atoms; 14. The helium atom; Appendix 14.A. Variational calculations; Appendix 14.B. Detail on the variational calculations of the ground state
Entropy of Field Interacting With Two Atoms in Bell State
Institute of Scientific and Technical Information of China (English)
JIAO Zhi-Yong; MA Jun-Mao; LI Ning; FU Xia
2009-01-01
In this paper, we investigate entropy properties of the single-mode coherent optical field interacting with the two two-level atoms initially in one of the four Bell states. It is found that the different initial states of the two atoms lead to different evolutions of field entropy and the intensity of the field plays an important role for the evolution properties of field entropy.
Atoms and molecules interacting with light atomic physics for the laser era
Straten, Peter van der
2016-01-01
This in-depth textbook with a focus on atom-light interactions prepares students for research in a fast-growing and dynamic field. Intended to accompany the laser-induced revolution in atomic physics, it is a comprehensive text for the emerging era in atomic, molecular and optical science. Utilising an intuitive and physical approach, the text describes two-level atom transitions, including appendices on Ramsey spectroscopy, adiabatic rapid passage and entanglement. With a unique focus on optical interactions, the authors present multi-level atomic transitions with dipole selection rules, and M1/E2 and multiphoton transitions. Conventional structure topics are discussed in some detail, beginning with the hydrogen atom and these are interspersed with material rarely found in textbooks such as intuitive descriptions of quantum defects. The final chapters examine modern applications and include many references to current research literature. The numerous exercises and multiple appendices throughout enable advanc...
Institute of Scientific and Technical Information of China (English)
肖健; 王中阳; 徐至展
2002-01-01
We have studied the spectral behaviour of few-cycle soliton pulses in a non-resonant two-level atom medium by solving the full Maxwell-Bloch equations. It is demonstrated further that the carrier effects play an important role in the propagation of the few-cycle pulse laser. When the frequency detuning is not very large, both the population distribution and the refractive index of the medium follow the oscillatory carrier field instantaneously; in this case,carrier-wave compression or carrier shock occurs, and a supercontinuum broader than that in the resonant medium may be generated. When the frequency detuning is large, the carrier shock is weak and the spectrum is not continuous, only showing an odd harmonic radiation.
Manipulating nanoscale atom-atom interactions with cavity QED
Pal, Arpita; Deb, Bimalendu
2016-01-01
We theoretically explore manipulation of interactions between excited and ground state atoms at nanoscale separations by cavity quantum electrodynamics (CQED). We develop an adiabatic molecular dressed state formalism and show that it is possible to generate Fano-Feshbach resonances between ground and long-lived excited-state atoms inside a cavity. The resonances are shown to arise due to non-adiabatic coupling near a pseudo-crossing between the dressed state potentials. We illustrate our results with a model study using fermionic $^{171}$Yb atoms in a two-modal cavity. Our study is important for manipulation of interatomic interactions at low energy by cavity field.
Effect of pairwise dipole–dipole interaction among three-atom systems
Indian Academy of Sciences (India)
P Anantha Lakshmi; Ashoka Vudayagiri; Shaik Ahmed
2014-08-01
We present an analysis of a system of three two-level atoms interacting with one another through dipole–dipole interaction. The interaction manifests between the excited state of one of the atoms and the ground state of its nearest neighbour. Steady-state populations of the density matrix elements are presented and are compared with a situation when only two atoms are present. It can be noticed that the third atom modifies the behaviour of the three atoms. Two configurations are analysed, one in which the three atoms are in a line, with no interaction between atoms at the end points and the other in which the atoms form a closed loop with one atom interacting with both its neighbours.
Entanglement Swapping: Entangling Atoms That Never Interacted
Guerra, E S
2005-01-01
In this paper we discuss four different proposals of entangling atomic states of particles which have never interacted. The experimental realization proposed makes use of the interaction of Rydberg atoms with a micromaser cavity prepared in either a coherent state or in a superposition of the zero and one field Fock states. We consider atoms in either a three-level cascade or lambda configuration
Van der Waals Interactions among Alkali Rydberg Atoms with Excitonic States
Zoubi, Hashem
2015-01-01
We investigate the influence of the appearance of excitonic states on van der Waals interactions among two Rydberg atoms. The atoms are assumed to be in different Rydberg states, e.g., in the $|ns\\rangle$ and $|np\\rangle$ states. The resonant dipole-dipole interactions yield symmetric and antisymmetric excitons, with energy splitting that give rise to new resonances as the atoms approach each other. Only far from these resonances the van der Waals coefficients, $C_6^{sp}$, can be defined. We calculate the $C_6$ coefficients for alkali atoms and present the results for lithium by applying perturbation theory. At short interatomic distances of several $\\mu m$, we show that the widely used simple model of two-level systems for excitons in Rydberg atoms breaks down, and the correct representation implies multi-level atoms. Even though, at larger distances one can keep the two-level systems but in including van der Waals interactions among the atoms.
Resonant interaction modified by the atomic environment
Energy Technology Data Exchange (ETDEWEB)
Sainz, I; Klimov, A B; Chumakov, S M [Departamento de Fisica, Universidad de Guadalajara, Revolucion 1500, 44410, Guadalajara, Jal. (Mexico)
2003-04-01
The dynamics of a resonant atom interacting with a quantum cavity field in the presence of many off-resonant atoms is studied. In the framework of the effective Hamiltonian approach we show that the results of elimination of non-resonant transitions are (a) a dynamical Stark shift of the field frequency, dependent on the populations of non-resonant atoms, (b) dependence of the coupling constant between the resonant atom and the field on the populations of non-resonant atoms, and (c) an effective dipole-dipole interaction between non-resonant atoms. Two effects (the coherent influence and dephasing) of the off-resonant environment on the dynamics of the resonant atom are discussed.
Atomic Spectrum in Ramsey Separated Oscillating Fields with Three Interaction Regions
Institute of Scientific and Technical Information of China (English)
CHEN Jingbiao; WANG Fengzhi; YANG Donghai; WANG YiQiu
2001-01-01
Comparing with the situation of Ramsey separated oscillating fields used in Cesium atomic beam frequency standard, the transition probability spectrum of two-level atoms in the Ramsey separated oscillating fields with three interaction regions has been derived under the condition of near resonance. The new characteristic of atomic spectrum with excessive microwave power was analyzed in detail. Meantime, the predicted new characteristic of atomic spectrum was confirmed by numerical method in this paper.
Super-Coulombic atom-atom interactions in hyperbolic media
Cortes, Cristian L
2016-01-01
Dipole-dipole interactions which govern phenomena like cooperative Lamb shifts, superradiant decay rates, Van der Waals forces, as well as resonance energy transfer rates are conventionally limited to the Coulombic near-field. Here, we reveal a class of real-photon and virtual-photon long-range quantum electrodynamic (QED) interactions that have a singularity in media with hyperbolic dispersion. The singularity in the dipole-dipole coupling, referred to as a Super-Coulombic interaction, is a result of an effective interaction distance that goes to zero in the ideal limit irrespective of the physical distance. We investigate the entire landscape of atom-atom interactions in hyperbolic media and propose practical implementations with phonon-polaritonic hexagonal boron nitride in the infrared spectral range and plasmonic super-lattice structures in the visible range. Our work paves the way for the control of cold atoms in hyperbolic media and the study of many-body atomic states where optical phonons mediate qua...
Nagaoka's atomic model and hyperfine interactions.
Inamura, Takashi T
2016-01-01
The prevailing view of Nagaoka's "Saturnian" atom is so misleading that today many people have an erroneous picture of Nagaoka's vision. They believe it to be a system involving a 'giant core' with electrons circulating just outside. Actually, though, in view of the Coulomb potential related to the atomic nucleus, Nagaoka's model is exactly the same as Rutherford's. This is true of the Bohr atom, too. To give proper credit, Nagaoka should be remembered together with Rutherford and Bohr in the history of the atomic model. It is also pointed out that Nagaoka was a pioneer of understanding hyperfine interactions in order to study nuclear structure.
Preparation of Multicomponent Schr(o)dinger Cat States Through Resonant Atom-Field Interaction
Institute of Scientific and Technical Information of China (English)
ZHENG Shi-Biao
2005-01-01
A simple method is presented for generating multicomponent Schrodinger cat states through resonant atom-field interactions. In the scheme n two-level atoms, initially in ground states, are sent through a resonant cavity filled with a strong coherent field sequentially. Then state-selective measurements are performed on the atoms. The detections of the atoms in ground states collapse the cavity field onto a superposition of 2n coherent states. This is the first way for producing superpositions of many coherent states through resonant atom-field interaction.
Directory of Open Access Journals (Sweden)
Tarek H. M. Abou-El-Enien
2015-04-01
Full Text Available This paper extended TOPSIS (Technique for Order Preference by Similarity Ideal Solution method for solving Two-Level Large Scale Linear Multiobjective Optimization Problems with Stochastic Parameters in the righthand side of the constraints (TL-LSLMOP-SPrhs of block angular structure. In order to obtain a compromise ( satisfactory solution to the (TL-LSLMOP-SPrhs of block angular structure using the proposed TOPSIS method, a modified formulas for the distance function from the positive ideal solution (PIS and the distance function from the negative ideal solution (NIS are proposed and modeled to include all the objective functions of the two levels. In every level, as the measure of ―Closeness‖ dp-metric is used, a k-dimensional objective space is reduced to two –dimentional objective space by a first-order compromise procedure. The membership functions of fuzzy set theory is used to represent the satisfaction level for both criteria. A single-objective programming problem is obtained by using the max-min operator for the second –order compromise operaion. A decomposition algorithm for generating a compromise ( satisfactory solution through TOPSIS approach is provided where the first level decision maker (FLDM is asked to specify the relative importance of the objectives. Finally, an illustrative numerical example is given to clarify the main results developed in the paper.
Entropy for the Quantized Field in the Atom-Field Interaction: Initial Thermal Distribution
Directory of Open Access Journals (Sweden)
Luis Amilca Andrade-Morales
2016-09-01
Full Text Available We study the entropy of a quantized field in interaction with a two-level atom (in a pure state when the field is initially in a mixture of two number states. We then generalise the result for a thermal state; i.e., an (infinite statistical mixture of number states. We show that for some specific interaction times, the atom passes its purity to the field and therefore the field entropy decreases from its initial value.
Strong interaction physics from hadronic atoms
Batty, C. J.; Friedman, E.; Gal, A.
1997-08-01
Hadronic atoms provide a unique laboratory for studying strong interactions and nuclear medium effects at zero kinetic energy. Previous results from analyses of strong-interaction data consisting of level shifts, widths and yields in π-, K -, p¯ and ∑ - atoms are reviewed. Recent results from fits to comprehensive sets of data in terms of density-dependent optical potentials that respect the low-density limit, where the interaction tends to the free hadron nucleon value, are discussed. The importance of using realistic nuclear density distributions is highlighted. The introduction of density dependence in most cases significantly improves the fit to the data and leads to some novel results. For K - atoms, a substantial attraction of order 200 MeV in nuclear matter is suggested, with interesting repercussions for K¯ condensation and the evolution of strangeness in high-density stars. For p¯ atoms it is found that a reasonable p-wave strength can be accommodated in the fitted optical potential, in agreement with the energy dependence observed for some low-energy p¯N reactions. For ∑ - atoms, the fitted potential becomes repulsive inside the nucleus, implying that Σ hyperons generally do not bind in nuclei in agreement with recent measurements. This repulsion significantly affects calculated masses of neutron stars.
Atom-Light Interactions in Photonic Crystals
Goban, A; Yu, S -P; Hood, J D; Muniz, J A; Lee, J H; Martin, M J; McClung, A C; Choi, K S; Chang, D E; Painter, O; Kimble, H J
2013-01-01
The integration of nanophotonics and atomic physics has been a long-sought goal that would open new frontiers for optical physics. Here, we report the development of the first integrated optical circuit with a photonic crystal capable of both localizing and interfacing atoms with guided photons in the device. By aligning the optical bands of a photonic crystal waveguide (PCW) with selected atomic transitions, our platform provides new opportunities for novel quantum transport and many-body phenomena by way of photon-mediated atomic interactions along the PCW. From reflection spectra measured with average atom number N = 1.1$\\pm$0.4, we infer that atoms are localized within the PCW by Casimir-Polder and optical dipole forces. The fraction of single-atom radiative decay into the PCW is $\\Gamma_{\\rm 1D}/\\Gamma'$ = 0.32$\\pm$0.08, where $\\Gamma_{1D}$ is the rate of emission into the guided mode and $\\Gamma'$ is the decay rate into all other channels. $\\Gamma_{\\rm 1D}/\\Gamma'$ is quoted without enhancement due to a...
Long-range interactions between Rydberg atoms
Deiglmayr, Johannes
2016-10-01
We present an overview over theoretical models to describe adiabatic potential-energy curves, experimental excitation spectra, and electronic and nuclear dynamics in interacting Rydberg-atom pairs at large internuclear separations. The potential-energy curves and molecular wavefunctions are determined from the multipole expansion of the static Coulomb interaction which is evaluated numerically in a product basis of atomic orbitals. The convergence of this approach both in the truncation of the multipole expansion as well as in the size of the product basis is discussed, and the comparison of simulated excitation spectra is established as a useful criterium to test the convergence of the calculation. We finally discuss the dynamics of electronic and nuclear motions of pairs of Rydberg atoms, focusing on the stability of ultralong range Rydberg molecules with respect to autoionization.
Anisotropic Interactions between Cold Rydberg Atoms
2015-09-28
AFRL-AFOSR-CL-TR-2015-0002 Anisotropic interactions between cold Rydberg atoms Luis Marcassa INSTITUTO DE FISICA DE SAO CARLOS Final Report 09/28...problem with the report +551633739806 Organization / Institution name Instituto de Fisica de Sao Carlos Grant/Contract Title The full title of the
Directory of Open Access Journals (Sweden)
Souza Alessandra A.
2000-01-01
Full Text Available Molecular markers were used to estimate the effect of mineral nitrogen on the phenotypic expression of quantitative trait loci (QTL controlling the number of Rhizobium nodules (NN and resistance to Xanthomonas axonopodis pv. phaseoli in the common bean. Recombinant inbred lines derived from a BAT-93 x Jalo EEP558 cross were grown in a greenhouse in the absence or presence (5 mM NH4NO3 of nitrogen. Resistance to Xanthomonas was assessed as diseased leaf area (DLA and the number of nodules was obtained by direct counting. Analyses of variance were used to detect significant associations between 85 marker loci from 12 linkage groups (LG and quantitative traits. In the absence of nitrogen, 15 and 11 markers, distributed over 7 and 5 LG, showed a significant association with NN and DLA, respectively. The combined percentage of phenotypic variance explained by the marker-loci and QTL associations was 34% for NN and 42% for DLA. In the presence of nitrogen, there were only five significant associations for NN and eight for DLA, which explained 28 and 26% of the total phenotypic variance, respectively. The effects of some QTL were detected only at a certain level of nitrogen. The contribution of parental alleles at two NN QTL was dependent on the level of nitrogen. Four QTL were associated with both the number of Rhizobium nodules and resistance to Xanthomonas, suggesting a common genetic control of responses to bacterial infections in the common bean. Despite the dramatic environmental interactions noted with some QTL, in other cases the phenotypic effects were not affected by the amount of nitrogen. The stability of the latter QTL may be relevant when breeding cultivars adapted to variable soil fertility.
Atomic hydrogen interaction with Ru(1010).
Vesselli, E; Comelli, G; Rosei, R
2004-05-01
The interaction of atomic hydrogen with clean and deuterium precovered Ru(1010) was studied by means of temperature-programmed desorption (TPD) spectroscopy. Compared to molecular hydrogen experiments, after exposure of the clean surface to gas-phase atomic hydrogen at 90 K, two additional peaks grow in the desorption spectra at 115 and 150 K. The surface saturation coverage, determined by equilibrium between abstraction and adsorption reactions, is 2.5 monolayers. Preadsorbed deuterium abstraction experiments with gas-phase atomic hydrogen show that a pure Eley-Rideal mechanism is not involved in the process, while a hot atom (HA) kinetics describes well the reaction. By least-squares fitting of the experimental data, a simplified HA kinetic model yields an abstraction cross section value of 0.5 +/- 0.2 angstroms2. The atomic hydrogen interaction with an oxygen precovered surface was also studied by means of both TPD and x-ray photoelectron spectroscopy: oxygen hydrogenation and water production take place already at very low temperature (90 K).
Bright Solitons in an Atomic Tunnel Array with Either Attractive or Repulsive Atom-Atom Interactions
Institute of Scientific and Technical Information of China (English)
YANG Xiao-Xue; YOU Jun; WU Ying
2004-01-01
@@ Taking a coherent state representation, we derive the nonlinear Schrodinger-type differential-difference equations from the quantized model of an array of traps containing Bose-Einstein condensates and linked by the tunnelling process among the adjacent traps. It is shown that no matter whether two-body interactions among atoms are repulsive or attractive, a nearly uniform atom distribution can evolve into a bright soliton-type localized ensemble of atoms and a lump of atom distribution can also be smeared out by redistributing atoms among traps under appropriate initial phase differences of atoms in adjacent traps. These two important features originate from the tailoring effect of the initial phase conditions in coherent tunnelling processes, which differs crucially from the previous tailoring effect coming mainly from the periodicity of optical lattices.
Institute of Scientific and Technical Information of China (English)
QIAN Yi; XU Jing-Bo
2011-01-01
We investigate the quantum discord dynamics of two effective two-level atoms independently interacting with two quantized field modes through a Raman interaction in the presence of phase decoherence.The influence of the phase decoherence and detuning on the evolution of the quantum discord and entanglement between two atoms is discussed.It is found that the quantum discord is more robust than the entanglement under the phase decoherence,and the amount of discord and entanglement between two atoms can be increased by adjusting the detuning.
Effective potentials for atom-atom interaction at low temperatures
Gao, Bo
2002-01-01
We discuss the concept and design of effective atom-atom potentials that accurately describe any physical processes involving only states around the threshold. The existence of such potentials gives hope to a quantitative, and systematic, understanding of quantum few-atom and quantum many-atom systems at relatively low temperatures.
Qureshi, Muhammad Mohsin; Rehman, Hafeez Ur; Noh, Heung-Ryoul; Kim, Jin-Tae
2016-05-01
We have investigated ultra-narrow EIA spectral features with respect to variations of polarizations and powers of pump laser beam in a degenerate two-level system of the transition of 85 Rb D2 transition line. Polarizations of the probe laser beam in two separate experiments were fixed at right circular and horizontal linear polarizations, respectively while the polarizations of the pump lasers were varied from initial polarizations same as the probe laser beams to orthogonal to probe polarizations. One homemade laser combined with AOMs was used to the pump and probe laser beams instead of two different lasers to overcome broad linewidths of the homemade lasers. Theoretically, probe absorption coefficients have been calculated from optical Bloch equations of the degenerate two level system prepared by a pump laser beam. In the case of the circular polarization, EIA signal was obtained as expected theoretically although both pump and probe beams have same polarization. The EIA signal become smaller as power increases and polarizations of the pump and probe beams were same. When the polarization of the pump beam was linear polarization, maximum EIA signal was obtained theoretically and experimentally. Experimental EIA spectral shapes with respect to variations of the pump beam polarization shows similar trends as the theoretical results.
Strong interaction studies with kaonic atoms
Marton, J; Beer, G; Berucci, C; Bosnar, D; Bragadireanu, A M; Cargnelli, M; Clozza, A; Curceanu, C; d'Uffizi, A; Fiorini, C; Ghio, F; Guaraldo, C; Hayano, R; Iliescu, M; Ishiwatari, T; Iwasaki, M; Sandri, P Levi; Okada, S; Pietreanu, D; Piscicchia, K; Ponta, T; Quaglia, R; Vidal, A Romero; Sbardella, E; Scordo, A; Shi, H; Sirghi, D L; Sirghi, F; Tatsuno, H; Doce, O Vazquez; Widmann, E; Zmeskal, J
2016-01-01
The strong interaction of antikaons with nucleons and nuclei in the low-energy regime represents an active research field connected intrinsically with few-body physics. There are important open questions like the question of antikaon nuclear bound states. A unique and rather direct experimental access to the antikaon-nucleon scattering lengths is provided by precision X-ray spectroscopy of transitions in low-lying states of light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment at the electron-positron collider DAFNE of LNF-INFN we measured the most precise values of the strong interaction observables, i.e. the strong interaction on the 1s ground state of the electromagnetically bound kaonic hydrogen atom leading to a hadronic shift and a hadronic broadening of the 1s state. The SIDDHARTA result triggered new theoretical work which achieved major progress in the understanding of the low-energy strong interaction with strangeness. Antikaon-nucleon scattering lengths have been calculated ...
Strong interaction studies with kaonic atoms
Marton, J; Beer, G; Berucci, C; Bosnar, D; Bragadireanu, A M; Cargnelli, M; Clozza, A; Curceanu, C; d'Uffizi, A; Fiorini, C; Ghio, F; Guaraldo, C; Hayano, R; Iliescu, M; Ishiwatari, T; Iwasaki, M; Sandri, P Levi; Okada, S; Pietreanu, D; Piscicchia, K; Ponta, T; Quaglia, R; Vidal, A Romero; Sbardella, E; Scordo, A; Shi, H; Sirghi, D L; Sirghi, F; Tatsuno, H; Doce, O Vazquez; Widmann, E; Zmeskal, J
2015-01-01
The strong interaction of antikaons (K-) with nucleons and nuclei in the low energy regime represents an active research field connected intrinsically with few-body physics. There are important open questions like the question of antikaon nuclear bound states - the prototype system being K-pp. A unique and rather direct experimental access to the antikaon-nucleon scattering lengths is provided by precision X-ray spectroscopy of transitions in low-lying states of light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment at the electron-positron collider DA?NE of LNF-INFN we measured the most precise values of the strong interaction observables, i.e. the strong interaction on the 1s ground state of the electromagnetically bound K-p atom leading to a hadronic shift and a hadronic broadening of the 1s state. The SIDDHARTA result triggered new theoretical work which achieved major progress in the understanding of the low-energy strong interaction with strangeness. Antikaon-nucleon scattering le...
Cai, Huabing; Ren, Zhongzhou
2017-09-01
We investigate the rate of change of energy for a static two-level atom interacting with a massless quantum scalar field in global monopole spacetime and separately calculate the contributions of thermal fluctuations and radiation reaction. We discuss two different kinds of atom-field interactions separately. The behaviors of the atomic transition rates are analyzed in different circumstances such as near distance and big solid angle deficit. Moreover, we compare the results with those in Minkowski spacetime so as to reveal the effects of the global monopole. In general, as the atom-monopole distance increases, the transition rates oscillate around the results in Minkowski spacetime and the amplitude of oscillation gradually decreases. The oscillation is more severe for larger solid angle deficit. Our works suggest that the transition rates can profoundly change with different atom-field interactions and different types of scalar field.
Grinberg, Horacio
2008-12-18
The interaction of a two-level cyclic XY n-spin model with a two-mode cavity field involving two-photon transitions is investigated through a generalized Jaynes-Cummings model in the rotating-wave approximation. The two-photon interacting Hamiltonian becomes from the replacement of each single-mode field in the one-photon interacting Hamiltonian with the second-harmonic generation. It was assumed that initially the correlated field modes are in disentangled coherent states having the same photon distribution and that the spin system is in an excited state. At any time t > 0, the spin system and the field are in an entangled state, in this case, via a unitary time evolution operator. Thus, the spontaneous decay of a spin level was treated by considering the interaction of the two-level spin system with the modes of the universe in the vacuum state. The different cases of interest, characterized in terms of a detuning parameter for each mode, which emerge from nonvanishing commutation relations, were analytically implemented and numerically discussed for various values of the initial mean photon number and spin-photon coupling constants. Photon distribution, time evolution of the spin population inversion, as well as the statistical properties of the field leading to the possible production of nonclassical states, such as antibunched light, violations of the Cauchy-Schwartz inequality, and second- and fourth-order squeezing, are examined. The case of zero detuning of both modes was treated in terms of a linearization of the expansion of the time evolution operator, while in other three cases, the computations were conducted via second- and third-order Dyson perturbation expansion of the time evolution operator matrix elements for the excited and ground states of the spin system, respectively.
Nanoindentation: Toward the sensing of atomic interactions
Fraxedas, J.; Garcia-Manyes, S.; Gorostiza, P.; Sanz, F.
2002-04-01
The mechanical properties of surfaces of layered materials (highly oriented pyrolytic graphite, InSe, and GaSe) and single-crystal ionic materials (NaCl, KBr, and KCl) have been investigated at the nanometer scale by using nanoindentations produced with an atomic force microscope with ultrasharp tips. Special attention has been devoted to the elastic response of the materials before the onset of plastic yield. A new model based on an equivalent spring constant that takes into account the changes in in-plane interactions on nanoindentation is proposed. The results of this model are well correlated with those obtained by using the Debye model of solid vibrations.
Strong interaction studies with kaonic atoms
Directory of Open Access Journals (Sweden)
Marton J.
2016-01-01
Full Text Available The strong interaction of antikaons (K− with nucleons and nuclei in the low-energy regime represents an active research field connected intrinsically with few-body physics. There are important open questions like the question of antikaon nuclear bound states - the prototype system being K−pp. A unique and rather direct experimental access to the antikaon-nucleon scattering lengths is provided by precision X-ray spectroscopy of transitions in low-lying states of light kaonic atoms like kaonic hydrogen isotopes. In the SIDDHARTA experiment at the electron-positron collider DAΦNE of LNF-INFN we measured the most precise values of the strong interaction observables, i.e. the strong interaction on the 1s ground state of the electromagnetically bound K−p atom leading to a hadronic shift ϵ1s and a hadronic broadening Γ1s of the 1s state. The SIDDHARTA result triggered new theoretical work which achieved major progress in the understanding of the low-energy strong interaction with strangeness. Antikaon-nucleon scattering lengths have been calculated constrained by the SIDDHARTA data on kaonic hydrogen. For the extraction of the isospin-dependent scattering lengths a measurement of the hadronic shift and width of kaonic deuterium is necessary. Therefore, new X-ray studies with the focus on kaonic deuterium are in preparation (SIDDHARTA2. Many improvements in the experimental setup will allow to measure kaonic deuterium which is challenging due to the anticipated low X-ray yield. Especially important are the data on the X-ray yields of kaonic deuterium extracted from a exploratory experiment within SIDDHARTA.
Liu, Tang-Kun; Tao, Yu; Shan, Chuan-Jia; Liu, Ji-bing
2017-10-01
Using the three criterions of the concurrence, the negative eigenvalue and the geometric quantum discord, we investigate the quantum entanglement and quantum correlation dynamics of two two-level atoms interacting with the coherent state optical field. We discuss the influence of different photon number of the mean square fluctuations on the temporal evolution of the concurrence, the negative eigenvalue and the geometric quantum discord between two atoms when the two atoms are initially in specific three states. The results show that different photon number of the mean square fluctuations can lead to different effects of quantum entanglement and quantum correlation dynamics.
Liu, Tang-Kun; Tao, Yu; Shan, Chuan-Jia; Liu, Ji-bing
2017-08-01
Using the three criterions of the concurrence, the negative eigenvalue and the geometric quantum discord, we investigate the quantum entanglement and quantum correlation dynamics of two two-level atoms interacting with the coherent state optical field. We discuss the influence of different photon number of the mean square fluctuations on the temporal evolution of the concurrence, the negative eigenvalue and the geometric quantum discord between two atoms when the two atoms are initially in specific three states. The results show that different photon number of the mean square fluctuations can lead to different effects of quantum entanglement and quantum correlation dynamics.
Atom-atom interactions around the band edge of a photonic crystal waveguide.
Hood, Jonathan D; Goban, Akihisa; Asenjo-Garcia, Ana; Lu, Mingwu; Yu, Su-Peng; Chang, Darrick E; Kimble, H J
2016-09-20
Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. Coupling a quantum emitter to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for tuning these interactions. In particular, the cross-over from propagating fields [Formula: see text] outside the bandgap to localized fields [Formula: see text] within the bandgap should be accompanied by a transition from largely dissipative atom-atom interactions to a regime where dispersive atom-atom interactions are dominant. Here, we experimentally observe this transition by shifting the band edge frequency of the PCW relative to the [Formula: see text] line of atomic cesium for [Formula: see text] atoms trapped along the PCW. Our results are the initial demonstration of this paradigm for coherent atom-atom interactions with low dissipation into the guided mode.
Effects of a uniform acceleration on atom-field interactions
Marino, Jamir; Noto, Antonio; Passante, Roberto; Rizzuto, Lucia; Spagnolo, Salvatore
2014-01-01
We review some quantum electrodynamical effects related to the uniform acceleration of atoms in vacuum. After discussing the energy level shifts of a uniformly accelerated atom in vacuum, we investigate the atom-wall Casimir-Polder force for accelerated atoms, and the van der Waals/Casimir-Polder interaction between two accelerated atoms. The possibility of detecting the Unruh effect through these phenomena is also discussed in detail.
Effects of a uniform acceleration on atom-field interactions
Marino, Jamir; Passante, Roberto; Rizzuto, Lucia; Spagnolo, Salvatore
2014-01-01
We review some quantum electrodynamical effects related to the uniform acceleration of atoms in vacuum. After discussing the energy level shifts of a uniformly accelerated atom in vacuum, we investigate the atom-wall Casimir-Polder force for accelerated atoms, and the van der Waals/Casimir-Polder interaction between two accelerated atoms. The possibility of detecting the Unruh effect through these phenomena is also discussed in detail.
Preparation of Entangled Atomic States Through Resonant Atom-Field Interaction
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A scheme is proposed for the generation of two-atom maximally entangled states and multi-atom maximally entangled states of W class. The scheme is based on the simultaneous resonant interaction of atoms with a single-mode cavity field. It does not require accurate adjustment of the interaction time. The time needed to complete the generation does not increase with the number of the atom.
Institute of Scientific and Technical Information of China (English)
刘堂昆; 张康隆; 陶宇; 单传家; 刘继兵
2016-01-01
The temporal evolution of the degree of entanglement between two atoms in a system of the binomial optical field interacting with two arbitrary entangled atoms is investigated. The influence of the strength of the dipole–dipole interaction between two atoms, probabilities of the Bernoulli trial, and particle number of the binomial optical field on the temporal evolution of the atomic entanglement are discussed. The result shows that the two atoms are always in the entanglement state. Moreover, if and only if the two atoms are initially in the maximally entangled state, the entanglement evolution is not affected by the parameters, and the degree of entanglement is always kept as 1.
Description of Atom-Field Interaction via Quantized Caldirola-Kanai Hamiltonian
Daneshmand, Roohollah; Tavassoly, Mohammad Kazem
2017-01-01
In this paper we outline an approach to the study of atom-field interacting systems, where the Hamiltonian of the field is simply inspired from the quantized Caldirola-Kanai Hamiltonian. As a simple physical realization of the model, the interaction between a two-level atom with such a single-mode field is studied. The explicit form of the atom-field entangled state associated with the considered system is analytically deduced and the dynamics of a few of its physical properties is numerically evaluated. To achieve the latter purposes, the temporal behavior of the degree of entanglement, atomic population inversion as well as sub-Poissonian statistics and quadrature squeezing of the field are evaluated. Moreover, the effects of the intensity of initial field and the damping parameter within the Caldirola-Kanai Hamiltonian on the above-mentioned criteria are investigated. As is shown, by adjusting the latter evolved parameters one can appropriately tune the discussed physical quantities.
Chaos and flights in the atom-photon interaction in cavity QED
Prants, S. V.; Edelman, M.; Zaslavsky, G. M.
2002-10-01
We study dynamics of the atom-photon interaction in cavity quantum electrodynamics, considering a cold two-level atom in a single-mode high-finesse standing-wave cavity as a nonlinear Hamiltonian system with three coupled degrees of freedom: translational, internal atomic, and the field. The system proves to have different types of motion including Lévy flights and chaotic walkings of an atom in a cavity. The corresponding equations of motion for expectation values of the atom and field variables have two characteristic time scales: fast Rabi oscillations of the internal atomic and field quantities and slow translational oscillations of the center of the atom mass. It is shown that the translational motion, related to the atom recoils, is governed by an equation of a parametric nonlinear pendulum with a frequency modulated by the Rabi oscillations. This type of dynamics is chaotic with some width of the stochastic layer that is estimated analytically. The width is fairly small for realistic values of the control parameters, the normalized detuning δ and atomic recoil frequency α. We consider the Poincaré sections of the dynamics, compute the Lyapunov exponents, and find a range of the detuning, |δ|ballistic motion of the atom and the other corresponding to small oscillations in a potential well, are found. These flights influence statistical properties of the atom-photon interaction such as distribution of Poincaré recurrences and moments of the atom position x. The simulation shows different regimes of motion, from slightly abnormal diffusion with ~τ1.13 at δ=1.2 to a superdiffusion with ~τ2.2 at δ=1.92 that corresponds to a superballistic motion of the atom with an acceleration. The obtained results can be used to find new ways to manipulate atoms, to cool and trap them by adjusting the detuning δ.
Institute of Scientific and Technical Information of China (English)
王菊霞
2013-01-01
The process of two - atom interacting with light field under considering atom - atom coupling and intensity - dependent coppling are investigated by mean of full quantum theory. The analysis law of evolutionary process of atomical fidelity is obtained. It is found that the variation of atomical fidelity with time presents the oscillation characteristics. Trie light field could revert to the initial coherent state at some microtime and the value of atomical fidelity less than 1 during most of interacting process, that is, both light fields and atoms are in complex entangled states. The above mentioned show that the interaction between atoms and light fields may leads to maintaining or cancaling the initial entanglement states.%利用全量子理论,分析了原子耦合时双原子与光场依赖于强度耦合的相互作用,得出了原子保真度演化过程的解析规律,结果表明:原子的保真度随时间的变化呈现出振荡性,而且在某些瞬时光场恢复为初始的相干态,其它更多的相互作用期间原子的保真度值小于1,即原子与光场处于复杂的纠缠状态,说明原子与光场的相互作用使得初始的纠缠态既可能保持也可能消纠缠.
Positron Interactions with Atoms and Ions
Bhatia, Anand K.
2012-01-01
Dirac, in 1928, combining the ideas of quantum mechanics and the ideas of relativity invented the well-known relativistic wave equation. In his formulation, he predicted an antiparticle of the electron of spin n-bar/2. He thought that this particle must be a proton. Dirac published his interpretation in a paper 'A theory of electrons and protons.' It was shown later by the mathematician Hermann Weyl that the Dirac theory was completely symmetric between negative and positive particles and the positive particle must have the same mass as that of the electron. In his J. Robert Oppenheimer Memorial Prize Acceptance Speech, Dirac notes that 'Blackett was really the first person to obtain hard evidence for the existence of a positron but he was afraid to publish it. He wanted confirmation, he was really over cautious.' Positron, produced by the collision of cosmic rays in a cloud chamber, was detected experimentally by Anderson in 1932. His paper was published in Physical Review in 1933. The concept of the positron and its detection were the important discoveries of the 20th century. I have tried to discuss various processes involving interactions of positrons with atoms and ions. This includes scattering, bound states and resonances. It has not been possible to include the enormous work which has been carried out during the last 40 or 50 years in theory and measurements.
Interacting Atomic Interferometry for Rotation Sensing Approaching the Heisenberg Limit
Ragole, Stephen; Taylor, Jacob M.
2016-11-01
Atom interferometers provide exquisite measurements of the properties of noninertial frames. While atomic interactions are typically detrimental to good sensing, efforts to harness entanglement to improve sensitivity remain tantalizing. Here we explore the role of interactions in an analogy between atomic gyroscopes and SQUIDs, motivated by recent experiments realizing ring-shaped traps for ultracold atoms. We explore the one-dimensional limit of these ring systems with a moving weak barrier, such as that provided by a blue-detuned laser beam. In this limit, we employ Luttinger liquid theory and find an analogy with the superconducting phase-slip qubit, in which the topological charge associated with persistent currents can be put into superposition. In particular, we find that strongly interacting atoms in such a system could be used for precision rotation sensing. We compare the performance of this new sensor to an equivalent noninteracting atom interferometer, and find improvements in sensitivity and bandwidth beyond the atomic shot-noise limit.
Berry phase in a generalized nonlinear two-level system
Institute of Scientific and Technical Information of China (English)
Liu Ji-Bing; Li Jia-Hua; Song Pei-Jun; Li Wei-Bin
2008-01-01
In this paper,we investigate the behaviour of the geometric phase of a more generalized nonlinear system composed of an effective two-level system interacting with a single-mode quantized cavity field.Both the field nonlinearity and the atom-field coupling nonlinearity are considered.We find that the geometric phase depends on whether the index k is an odd number or an even number in the resonant case.In addition,we also find that the geometric phase may be easily observed when the field nonlinearity is not considered.The fractional statistical phenomenon appears in this system if the strong nonlinear atom-field coupling is considered.We have also investigated the geometric phase of an effective two-level system interacting with a two-mode quantized cavity field.
Spin-sensitive atom mirror via spin-orbit interaction
Zhou, Lu; Zheng, Ren-Fei; Zhang, Weiping
2016-11-01
Based on the spin-orbit coupling recently implemented in a neutral cold-atom gas, we propose a scheme to realize spin-dependent scattering of cold atoms. In particular we consider a matter wave packet of cold-atom gas impinging upon a step potential created by the optical light field, inside of which the atoms are subject to spin-orbit interaction. We show that the proposed system can act as a spin polarizer or spin-selective atom mirror for the incident atomic beam. The principle and the operating parameter regime of the system are carefully discussed.
Gavryusev, Vladislav; Ferreira-Cao, Miguel; Kekić, Armin; Zürn, Gerhard; Signoles, Adrien
2016-12-01
The Interaction Enhanced Imaging technique allows to detect the spatial distribution of strongly interacting impurities embedded within a gas of background atoms used as a contrast medium [1]. Here we present a detailed study of this technique, applied to detect Rydberg P states. We experimentally realize fast and efficient three-photon excitation of P states, optimized according to the results of a theoretical effective two-level model. Few Rydberg P-state atoms, prepared in a small cloud with dimensions comparable to the blockade radius, are detected with a good sensitivity by averaging over 50 shots. The main aspects of the technique are described with a hard-sphere model, finding good agreement with experimental data. This work paves the way to a non-destructive optical detection of single Rydberg atoms with high spatial and temporal resolution.
Whittaker, K A; Hughes, I G; Sargsyan, A; Sarkisyan, D; Adams, C S
2015-01-01
We measure the resonance line shape of atomic vapor layers with nanoscale thickness confined between two sapphire windows. The measurement is performed by scanning a probe laser through resonance and collecting the scattered light. The line shape is dominated by the effects of Dicke narrowing, self-broadening, and atom-surface interactions. By fitting the measured line shape to a simple model we discuss the possibility to extract information about the atom-surface interaction.
Controllable interactions between Rydberg atoms and ultracold plasmas
Energy Technology Data Exchange (ETDEWEB)
Pillet, P; Vogt, T; Viteau, M; Chotia, A; Zhao, J; Comparat, D; Gallagher, T F; Tate, D [Laboratoire Aime Cotton, CNRS, Univ Paris-Sud, Bat.505, Campus d' Orsay, 91405 Orsay cedex (France); Gaetan, A; Miroshnychenko, Y; Wilk, T; Browaeys, A; Grangier, P, E-mail: pierre.pillet@lac.u-psud.f [Laboratoire Charles Fabry de l' Institut d' Optique CNRS, Univ Paris-Sud, Campus Polytechnique, RD 128, 91127 Palaiseau cedex (France)
2009-11-15
We discuss the control of dipole-dipole interactions in a frozen assembly of Rydberg atoms. We report the evidence of dipole blockade of the Rydberg excitation for two configurations: dipole blockade induced by electric field and dipole blockade in Foerster resonance. We demonstrate that two individual atoms separated by {approx} 4 {mu}m can act as a collective dipole if their interaction is strong enough to be in the dipole blockade regime. This observation is crucial for the quantum entanglement of two or more atoms using dipole-dipole interaction. The dipole-dipole interactions between Rydberg atoms are also responsible for Penning ionization leading to the formation of an ultracold plasma. We have demonstrated that Penning ionization of np Rydberg cesium atoms can be prevented by considering repulsive dipole-dipole interactions.
Master equation with quantized atomic motion including dipole-dipole interactions
Damanet, François; Braun, Daniel; Martin, John
2016-05-01
We derive a markovian master equation for the internal dynamics of an ensemble of two-level atoms including all effects related to the quantization of their motion. Our equation provides a unifying picture of the consequences of recoil and indistinguishability of atoms beyond the Lamb-Dicke regime on both their dissipative and conservative dynamics, and is relevant for experiments with ultracold trapped atoms. We give general expressions for the decay rates and the dipole-dipole shifts for any motional states, and we find analytical formulas for a number of relevant states (Gaussian states, Fock states and thermal states). In particular, we show that the dipole-dipole interactions and cooperative photon emission can be modulated through the external state of motion. The effects predicted should be experimentally observable with Rydberg atoms. FD would like to thank the F.R.S.-FNRS for financial support. FD is a FRIA Grant holder of the Fonds de la Recherche Scientifique-FNRS.
Enhanced Quantum Reflection of Ultracold Atoms with Strong Interatomic Interaction
Institute of Scientific and Technical Information of China (English)
LIU Min; ZHAN Ming-Sheng
2008-01-01
We calculate the reflection probability for ultracold alkali atoms incident on a solid surface. By considering the interatomic interaction and using the WKB method, it is shown that the repulsive interaction between atoms has the effect of increasing the reflection probability. The increasing amplitude is related with the interatomic interaction and the depth of atom-surface potential. In addition, we also perform a numerical calculation to testify the effect of the interatomic interaction, and the analytic result is proven by the numerical result.
Spontaneous emission of two interacting atoms near an interface
Institute of Scientific and Technical Information of China (English)
Dehua Wang
2009-01-01
The spontaneous emission rate of two interacting excited atoms near a dielectric interface is studied using the photon closed-orbit theory and the dipole image method.The total emission rate of one atom during the emission process is calculated as a function of the distance between the atom and the interface.The results suggest that the spontaneous emission rate depends not only on the atomic-interface distances,but also on the orientation of the two atomic dipoles and the initial distance between the two atoms.The oscillation in the spontaneous emission rate is caused by the interference between the outgoing electromagnetic wave emitted from one atom and other waves arriving at this atom after traveling along various classical orbits.Each peak in the Fourier transformed spontaneous emission rate corresponds with one action of photon classical orbit.
Interaction-Free Effects Between Distant Atoms
Aharonov, Yakir; Elitzur, Avshalom C; Smolin, Lee
2016-01-01
A gedankenexperiment is presented where an excited and a ground-state atom are positioned such that, within the former's half-life time, they exchange a photon with 50% probability. A measurement of their energy state will therefore indicate in 50% of the cases that no photon was exchanged. Yet other measurements would reveal that, by the mere possibility of exchange, the two atoms become entangled. Consequently, the "no exchange" result, apparently precluding entanglement, is non-locally established between the atoms by this very entanglement. When densely repeated several times, this result gives rise to the Quantum Zeno effect as well, again exerted between distant atoms without photon exchange. We discuss these experiments as variants of IFM, now generalized for both spatial and temporal uncertainties. We next employ weak measurements for a sharper and simpler elucidation of the paradox. Interpretational issues are discussed in the conclusion, and a resolution is offered within the Two-State Vector Formal...
Interaction between atoms and slow light: a design study
Zang, Xiaorun; Faggiani, Rémi; Gill, Christopher; Petrov, Plamen G; Hugonin, Jean-Paul; Bernon, Simon; Bouyer, Philippe; Boyer, Vincent; Lalanne, Philippe
2015-01-01
The emerging field of on-chip integration of nanophotonic devices and cold atoms offers extremely-strong and pure light-matter interaction schemes, which may have profound impact on quantum information science. In this context, a longstanding obstacle is to achieve strong interaction between single atoms and single photons, while at the same time trap atoms in vacuum at large separation distances from dielectric surfaces. In this letter, we study new waveguide geometries that challenge these conflicting objectives. The designed photonic crystal waveguide is expected to offer a good compromise, which additionally allow for easy manipulation of atomic clouds around the structure.
Atom-atom interactions around the band edge of a photonic crystal waveguide
Hood, Jonathan D.; Goban, Akihisa; Asenjo-Garcia, Ana; Lu, Mingwu; Yu, Su-Peng; Chang, Darrick E.; Kimble, H. J.
2016-09-01
Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. Coupling a quantum emitter to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for tuning these interactions. In particular, the cross-over from propagating fields E(x)∝e±ikxxE(x)∝e±ikxx outside the bandgap to localized fields E(x)∝e-κx|x|E(x)∝e-κx|x| within the bandgap should be accompanied by a transition from largely dissipative atom-atom interactions to a regime where dispersive atom-atom interactions are dominant. Here, we experimentally observe this transition by shifting the band edge frequency of the PCW relative to the D1D1 line of atomic cesium for N¯=3.0±0.5N¯=3.0±0.5 atoms trapped along the PCW. Our results are the initial demonstration of this paradigm for coherent atom-atom interactions with low dissipation into the guided mode.
“Hard probes” of strongly-interacting atomic gases
Energy Technology Data Exchange (ETDEWEB)
Nishida, Yusuke [Los Alamos National Laboratory
2012-06-18
We investigate properties of an energetic atom propagating through strongly interacting atomic gases. The operator product expansion is used to systematically compute a quasiparticle energy and its scattering rate both in a spin-1/2 Fermi gas and in a spinless Bose gas. Reasonable agreement with recent quantum Monte Carlo simulations even at a relatively small momentum k/kF > 1.5 indicates that our large-momentum expansions are valid in a wide range of momentum. We also study a differential scattering rate when a probe atom is shot into atomic gases. Because the number density and current density of the target atomic gas contribute to the forward scattering only, its contact density (measure of short-range pair correlation) gives the leading contribution to the backward scattering. Therefore, such an experiment can be used to measure the contact density and thus provides a new local probe of strongly interacting atomic gases.
Rydberg atom interactions from 300 K to 300 K
Pillet, P.; Gallagher, T. F.
2016-09-01
Cold Rydberg atoms provide novel approaches to many-body problems and quantum simulation. To introduce the recent work presented in this special issue, we present here a quick history of a half-century research activity in the Rydberg-atom field, focusing our attention on the giant interactions between Rydberg atoms and other atoms. These interactions are the origin of many effects observed with Rydberg atoms: pressure shifts, dipole-dipole energy transfer, and avalanche-ionization. These effects have led to evidence of new bound chemical states, such as trilobites states, many-body effects in frozen Rydberg gases, and the spontaneous formation of ultra-cold plasmas. They open exciting new prospects at the intersection of atomic physics, condensed matter physics, and plasma physics.
Reactive Collisions and Interactions of Ultracold Dipolar Atoms
2014-10-29
rotate and vibrate and where the atomic Zeeman states are coupled by the anisotropic interactions. The calculations were performed with the symmetrized...calculation for Dy atoms can be found in [10] and for Er in [11]. A first-principle coupled-channel model allowed us to calculate anisotropy- induced mag- netic... vibrational levels due to the presence of the third atom . In addition, we studied the dynamic polarizability of the N = 0 and N = 1 rotational levels of the
Intrinsic Decoherence of a Two-Atom System with Dipole-Dipole Interaction
Institute of Scientific and Technical Information of China (English)
QI Lin-Na; ZHU Ai-Dong; ZHANG Shou
2008-01-01
@@ We investigate the effect of dipole-dipole interaction on the intrinsic decoherence of a system which consists of two two-level atoms and an optical cavity. The entanglement of the system is calculated by making use of concurrence. Our results show that the appropriate choice for the coupling constant Ω of dipole-dipole interaction can restrain the intrinsic decoherence of the system. We also find a special phenomenon. No matter what the value of γ is, the concurrence of system slowly increases and cannot exceed 0.71 when Ω= 1.
Study on the fine control of atoms by coherent interaction
Energy Technology Data Exchange (ETDEWEB)
Han, Jae Min; Rho, S. P.; Park, H. M.; Lee, K. S.; Rhee, Y. J.; Yi, J. H.; Jeong, D. Y.; Jung, E. C.; Choe, A. S.; Lee, J. M
1998-01-01
The basic research on the control of atoms using the coherent interaction, such as the development of the generator of the thermal atomic beam with high directionality, the photodeflection of atomic beam and the coherent excitation of atoms, has been performed. Yb atomic beam with small divergence was generated and the deflection mechanism of the atomic beam was studied by using a broad band dye laser and a narrow band laser. It has been proved that the single mode dye laser with narrow bandwidth was suitable for deflection of atoms but the frequency locking system was indispensable. And the apparatus for intermodulated optogalvanic (IMOG) experiment was developed and the high resolution optogalvanic spectroscopy was studied for laser frequency stabilization. (author). 74 refs., 1 tab., 26 figs
Study on the fine control of atoms by coherent interaction
Energy Technology Data Exchange (ETDEWEB)
Han, Jae Min; Rho, S. P.; Park, H. M.; Lee, K. S.; Rhee, Y. J.; Yi, J. H.; Jeong, D. Y.; Ko, K. H.; Lee, J. M.; Kim, M.K
2000-01-01
Study on one dimensional atom cooling and trapping process which is basic to the development of atom manipulation technology has been performed. A Zeeman slower has been designed and manufactured for efficient cooling of atoms. The speed of atoms finally achieved is as slow as 15 m/s with proper cooling conditions. By six circularly-polarized laser beams and quadrupole magnetic field, the atoms which have been slowed down by zeeman slower have been trapped in a small spatial region inside MOT. The higher the intensity of the slowing laser is the more is the number of atoms slowed and the maximum number of atoms trapped has been 10{sup 8}. The atoms of several tens of {mu}K degree have been trapped by controlling the intensity of trapping laser and intensity gradient of magnetic field. EIT phenomena caused by atomic coherent interaction has been studied for the development of atom optical elements. For the investigation of the focusing phenomena induced by the coherent interaction, experimental measurements and theoretical analysis have been performed. Spatial dependency of spectrum and double distribution signal of coupling laser have been obtained. The deflection of laser beams utilizing the EIT effects has also been considered. (author)
Processus d'interaction entre photons et atomes
Fellot, Dominique
1996-01-01
This work expounds the basic force interactions between photons and atoms, as well as an analysis of more complex processes. Various theoretical methods are introduced and illustrated with simple systems that help broach that subject.
Collisional interaction between metastable neon atoms
Energy Technology Data Exchange (ETDEWEB)
Drunen, Wouter Johannes van
2008-07-07
In this thesis, the study of cold gases of neon atoms in different metastable states is described. It contains measurements of the collisional parameters for both the 3s[3/2]{sub 2} and the 3s'[1/2]{sub 0} metastable state and the dependence of the inelastic loss on external fields. Furthermore, the investigation of frequency dependent laser-induced collisions, and the possibility to excite photoassociation resonances is presented. For the measurements described here, neon atoms have been confined in a magnetooptical trap, in a magnetostatic trap, or in an optical dipole trap, respectively. By laser cooling inside the magnetic trap, atomic samples with more than 95 percent occupation of the magnetic substate m{sub J} = +2 could be prepared. They have a typical temperature of 0.5 mK, central densities up to 10{sup 11} cm{sup -3}, and a central phase-space density of up to 2.2.10{sup -7}. After loading the optical dipole trap from the magnetic trap, 2.5.10{sup 6} atoms with typical temperatures of 0.1 mK, and central densities up to 5.10{sup 10} cm{sup -3} were trapped. By evaporative cooling of the atoms in the magnetic trap we could increase the phase-space density by a factor of 200 to 5.10{sup -5}. Investigating the frequency dependence of laser-induced collisions did not reveal an experimental signature for the excitation of photoassociation resonances. For the {sup 3}D{sub 3} line a frequency dependence of laser enhanced Penning ionization was observed. Measurement of the two-body loss coefficient as function of the magnetic field showed a field dependence of the inelastic loss. These losses increase towards both small and large offset fields. The implementation of an optical dipole trap allowed us to trap the {sup 3}P{sub 0} metastable state. From the trap loss measurements we determined the two-body loss coefficient of the {sup 3}P{sub 0} metastable state for both bosonic isotopes {sup 20}Ne and {sup 22}Ne. For {sup 20}Ne we obtained {beta}=6{sup +5}{sub
Controlled long-range interactions between Rydberg atoms and ions
Secker, T.; Gerritsma, R.; Glaetzle, A. W.; Negretti, A.
2016-07-01
We theoretically investigate trapped ions interacting with atoms that are coupled to Rydberg states. The strong polarizabilities of the Rydberg levels increase the interaction strength between atoms and ions by many orders of magnitude, as compared to the case of ground-state atoms, and may be mediated over micrometers. We calculate that such interactions can be used to generate entanglement between an atom and the motion or internal state of an ion. Furthermore, the ion could be used as a bus for mediating spin-spin interactions between atomic spins in analogy to much employed techniques in ion-trap quantum simulation. The proposed scheme comes with attractive features as it maps the benefits of the trapped-ion quantum system onto the atomic one without obviously impeding its intrinsic scalability. No ground-state cooling of the ion or atom is required and the setup allows for full dynamical control. Moreover, the scheme is to a large extent immune to the micromotion of the ion. Our findings are of interest for developing hybrid quantum information platforms and for implementing quantum simulations of solid-state physics.
Controlled long-range interactions between Rydberg atoms and ions
Secker, Thomas; Glaetzle, Alexander W; Negretti, Antonio
2016-01-01
We theoretically investigate trapped ions interacting with atoms that are coupled to Rydberg states. The strong polarizabilities of the Rydberg levels increases the interaction strength between atoms and ions by many orders of magnitude, as compared to the case of ground state atoms, and may be mediated over micrometers. We calculate that such interactions can be used to generate entanglement between an atom and the motion or internal state of an ion. Furthermore, the ion could be used as a bus for mediating spin-spin interactions between atomic spins in analogy to much employed techniques in ion trap quantum simulation. The proposed scheme comes with attractive features as it maps the benefits of the trapped ion quantum system onto the atomic one without obviously impeding its intrinsic scalability. No ground state cooling of the ion or atom is required and the setup allows for full dynamical control. Moreover, the scheme is to a large extent immune to the micromotion of the ion. Our findings are of interest...
Chaos and flights in the atom-photon interaction in cavity QED.
Prants, S V; Edelman, M; Zaslavsky, G M
2002-10-01
We study dynamics of the atom-photon interaction in cavity quantum electrodynamics, considering a cold two-level atom in a single-mode high-finesse standing-wave cavity as a nonlinear Hamiltonian system with three coupled degrees of freedom: translational, internal atomic, and the field. The system proves to have different types of motion including Lévy flights and chaotic walkings of an atom in a cavity. The corresponding equations of motion for expectation values of the atom and field variables have two characteristic time scales: fast Rabi oscillations of the internal atomic and field quantities and slow translational oscillations of the center of the atom mass. It is shown that the translational motion, related to the atom recoils, is governed by an equation of a parametric nonlinear pendulum with a frequency modulated by the Rabi oscillations. This type of dynamics is chaotic with some width of the stochastic layer that is estimated analytically. The width is fairly small for realistic values of the control parameters, the normalized detuning delta and atomic recoil frequency alpha. We consider the Poincaré sections of the dynamics, compute the Lyapunov exponents, and find a range of the detuning, |delta| less, similar 3, where chaos is prominent. It is demonstrated how the atom-photon dynamics with a given value of alpha depends on the values of delta and initial conditions. Two types of Lévy flights, one corresponding to the ballistic motion of the atom and the other corresponding to small oscillations in a potential well, are found. These flights influence statistical properties of the atom-photon interaction such as distribution of Poincaré recurrences and moments of the atom position x. The simulation shows different regimes of motion, from slightly abnormal diffusion with approximately tau(1.13) at delta=1.2 to a superdiffusion with approximately tau(2.2) at delta=1.92 that corresponds to a superballistic motion of the atom with an acceleration. The
Photon-mediated interactions between distant artificial atoms.
van Loo, Arjan F; Fedorov, Arkady; Lalumière, Kevin; Sanders, Barry C; Blais, Alexandre; Wallraff, Andreas
2013-12-20
Photon-mediated interactions between atoms are of fundamental importance in quantum optics, quantum simulations, and quantum information processing. The exchange of real and virtual photons between atoms gives rise to nontrivial interactions, the strength of which decreases rapidly with distance in three dimensions. Here, we use two superconducting qubits in an open one-dimensional transmission line to study much stronger photon-mediated interactions. Making use of the possibility to tune these qubits by more than a quarter of their transition frequency, we observe both coherent exchange interactions at an effective separation of 3λ/4 and the creation of super- and subradiant states at a separation of one photon wavelength λ. In this system, collective atom-photon interactions and applications in quantum communication may be explored.
Interaction of dopant atoms with stacking faults in silicon
Ohno, Yutaka; Tokumoto, Yuki; Taneichi, Hiroto; Yonenaga, Ichiro; Togase, Kensuke; Nishitani, Sigeto R.
2012-08-01
The width of a stacking fault ribbon bound by a pair of partial dislocations in silicon crystals was unchanged when boron and gallium atoms of p-type dopant were agglomerated nearby the ribbon by annealing, even though the width increased when n-type dopant atoms were agglomerated as previously reported [Y. Ohno, Y. Tokumoto, I. Yonenaga, Thin Solid Films, accepted for publication]. The origin of the width-increase in n-type crystals was proposed as the reduction of the stacking fault energy, from 58±5 down to 46±5 mJ/m2, due to an electronic interaction between the ribbon and the n-type dopant atoms, and the interaction energy was estimated to be 0.15±0.05 eV. On the other hand, the interaction of p-type dopant atoms with stacking faults was not detected.
Interaction-induced decoherence of atomic BLOCH oscillations.
Buchleitner, Andreas; Kolovsky, Andrey R
2003-12-19
We show that the energy spectrum of the Bose-Hubbard model amended by a static field exhibits Wigner-Dyson level statistics. In itself a characteristic signature of quantum chaos, this induces the irreversible decay of Bloch oscillations of cold, interacting atoms loaded into an optical lattice, and provides a Hamiltonian model for interaction-induced decoherence.
Resolved Atomic Interaction Sidebands in an Optical Clock Transition
2011-06-24
interrogated by a linearly polarized laser with bare Rabi frequency B and detuning from the atomic resonance . The Pauli exclusion principle forces...are populated. The population of transverse modes is accounted for as a renormalization of the interaction parameter. The interaction part of the
Badshah, Fazal; Basit, Abdul; Ali, Hamad; Ge, Guo-Qin
2017-02-01
We study the tunneling and traversal time of ultracold two-level atoms through a high quality microwave cavity containing N - 1 ground state atoms. The phase time of tunneling may be considered as a measure of the time required to traverse the cavity which exhibits both super and subclassical traversal behaviors. Here we examine that superclassical phase time behavior suppresses with the increase in the number of motionless ground state atoms inside the cavity. It happens due to the multipartite influence in the interaction that traps the incident atom into its upper state such that it does not observe any induced potential. Accordingly, for larger atomic samples, the incident atoms in the initial excited states get perfect transmission and tunnel through the cavity nearly with the same speed as they would have moved through a free space. This is true for any width of potential and the particle’s speed provided that the center-of-mass energy of the incident particle lies in the classically forbidden range.
Influence of dissipation on two-atom dispersion interactions
Barcellona, Pablo; Buhmann, Stefan Yoshi
2015-03-01
We consider the dispersion interaction between two neutral, ground-state atoms at zero and finite temperature by means of a dynamical approach. Our result differs from the previous ones obtained with time-independent perturbation theory because it correctly accounts for the influence of dissipation via the atomic decay rates. Modern measurements of Casimir force seem to suggest a suppressed influence of dissipation. Our new result shows similar features and can hence help resolve the Drude-plasma debate. We also consider the interaction between a ground-state atom and an excited atom. There are discordant results in the literature for the retarded potential: one oscillating and one monotonous. Our dynamical result uniquely leads to the oscillating result when taking into account the decay rates. This work was supported by the DFG (Grant BU 1803/3-1).
Estimation of atomic interaction parameters by quantum measurements
DEFF Research Database (Denmark)
Kiilerich, Alexander Holm; Mølmer, Klaus
Quantum systems, ranging from atomic systems to field modes and mechanical devices are useful precision probes for a variety of physical properties and phenomena. Measurements by which we extract information about the evolution of single quantum systems yield random results and cause a back action...... strategies, we address the Fisher information and the Cramér-Rao sensitivity bound. We investigate monitoring by photon counting, homodyne detection and frequent projective measurements respectively, and exemplify by Rabi frequency estimation in a driven two-level system....
Nanoscale light-matter interactions in atomic cladding waveguides.
Stern, Liron; Desiatov, Boris; Goykhman, Ilya; Levy, Uriel
2013-01-01
Alkali vapours, such as rubidium, are being used extensively in several important fields of research such as slow and stored light nonlinear optics quantum computation, atomic clocks and magnetometers. Recently, there is a growing effort towards miniaturizing traditional centimetre-size vapour cells. Owing to the significant reduction in device dimensions, light-matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for nonlinear interactions. Here, taking advantage of the mature platform of silicon photonics, we construct an efficient and flexible platform for tailored light-vapour interactions on a chip. Specifically, we demonstrate light-matter interactions in an atomic cladding waveguide, consisting of a silicon nitride nano-waveguide core with a rubidium vapour cladding. We observe the efficient interaction of the electromagnetic guided mode with the rubidium cladding and show that due to the high confinement of the optical mode, the rubidium absorption saturates at powers in the nanowatt regime.
Scalar-pseudoscalar interaction in the francium atom
Skripnikov, L. V.; Maison, D. E.; Mosyagin, N. S.
2017-02-01
Fr atom can be successively used to search for the atomic permanent electric dipole moment (EDM) [Hyperfine Interact. 236, 53 (2015), 10.1007/s10751-015-1193-1; J. Phys.: Conference Series 691, 012017 (2016), 10.1088/1742-6596/691/1/012017]. It can be induced by the permanent electron EDM predicted by modern extensions of the standard model to be nonzero at the level accessible by the new generation of EDM experiments. We consider another mechanism of the atomic EDM generation in Fr. This is caused by the scalar-pseudoscalar nucleus-electron neutral current interaction with the dimensionless strength constant kT ,P. Similar to the electron EDM this interaction violates both spatial parity and time-reversal symmetries and can also induce permanent atomic EDM. It was shown in [Phys. Rev. D 89, 056006 (2014), 10.1103/PhysRevD.89.056006] that the scalar-pseudoscalar contribution to the atomic EDM can dominate over the direct contribution from the electron EDM within the standard model. We report high-accuracy combined all-electron and two-step relativistic coupled cluster treatment of the effect from the scalar-pseudoscalar interaction in the Fr atom. Up to the quadruple cluster amplitudes within the coupled cluster method with single, double, triple, and noniterative quadruple amplitudes, CCSDT(Q), were included in correlation treatment. This calculation is required for the interpretation of the experimental data in terms of kT ,P. The resulted EDM of the Fr atom expressed in terms of kT ,P is dFr=kT ,P4.50 ×10-18e cm , where e is the (negative) charge of the electron. The value of the ionization potential of the 2S1 /2 ground state of Fr calculated within the same methods is in very good agreement with the experimental datum.
Institute of Scientific and Technical Information of China (English)
DongChuan-Hua
2003-01-01
The interactions between coulpled atoms and a single mode of a quantized electromagnetic field, which involve the terms originating from the dipole interactions, are discussed. In the usual Jaynes-Cummings model for coupled atoms, the terms of non-conservation of energy originating from dipole interactions are neglected, however, we take them into consideration in this paper. The effects of these terms on the evolutions of quantum statistic properties and squeezing of the field, the squeezing of atomic dipole moments and atomic population inversion are investigated. It has been shown that the coupling between atoms modulates these evolutions of fields and atoms. The terms of non-conservation of energy affect these evolutions of field and atoms slightly. They also have effects on the squeezing of the field, the squeezing of atomic dipole and atomic population inversions. The initial states of atoms also affect these properties.
Institute of Scientific and Technical Information of China (English)
董传华
2003-01-01
The interactions between coupled atoms and a single mode of a quantized electromagnetic field, which involve the terms originating from the dipole interactions, are discussed. In the usual Jaynes Cummings model for coupled atoms,the terms of non-conservation of energy originating from dipole interactions are neglected, however, we take them into consideration in this paper. The effects of these terms on the evolutions of quantum statistic properties and squeezing of the field, the squeezing of atomic dipole moments and atomic population inversion are investigated. It has been shown that the coupling between atoms modulates these evolutions of fields and atoms. The terms of non-conservation of energy affect these evolutions of fields and atoms slightly. They also have effects on the squeezing of the field, the squeezing of atomic dipole and atomic population inversions. The initial states of atoms also affect these properties.
Nagaoka’s atomic model and hyperfine interactions
INAMURA, Takashi T.
2016-01-01
The prevailing view of Nagaoka’s “Saturnian” atom is so misleading that today many people have an erroneous picture of Nagaoka’s vision. They believe it to be a system involving a ‘giant core’ with electrons circulating just outside. Actually, though, in view of the Coulomb potential related to the atomic nucleus, Nagaoka’s model is exactly the same as Rutherford’s. This is true of the Bohr atom, too. To give proper credit, Nagaoka should be remembered together with Rutherford and Bohr in the history of the atomic model. It is also pointed out that Nagaoka was a pioneer of understanding hyperfine interactions in order to study nuclear structure. PMID:27063182
Counting atoms using interaction blockade in an optical superlattice.
Cheinet, P; Trotzky, S; Feld, M; Schnorrberger, U; Moreno-Cardoner, M; Fölling, S; Bloch, I
2008-08-29
We report on the observation of an interaction blockade effect for ultracold atoms in optical lattices, analogous to the Coulomb blockade observed in mesoscopic solid state systems. When the lattice sites are converted into biased double wells, we detect a discrete set of steps in the well population for increasing bias potentials. These correspond to tunneling resonances where the atom number on each side of the barrier changes one by one. This allows us to count and control the number of atoms within a given well. By evaluating the amplitude of the different plateaus, we can fully determine the number distribution of the atoms in the lattice, which we demonstrate for the case of a superfluid and Mott insulating regime of 87Rb.
Evanescent light-matter Interactions in Atomic Cladding Wave Guides
Stern, Liron; Goykhman, Ilya; Levy, Uriel
2012-01-01
Alkali vapors, and in particular rubidium, are being used extensively in several important fields of research such as slow and stored light non-linear optics3 and quantum computation. Additionally, the technology of alkali vapors plays a major role in realizing myriad industrial applications including for example atomic clocks magentometers8 and optical frequency stabilization. Lately, there is a growing effort towards miniaturizing traditional centimeter-size alkali vapor cells. Owing to the significant reduction in device dimensions, light matter interactions are greatly enhanced, enabling new functionalities due to the low power threshold needed for non-linear interactions. Here, taking advantage of the mature Complimentary Metal-Oxide-Semiconductor (CMOS) compatible platform of silicon photonics, we construct an efficient and flexible platform for tailored light vapor interactions on a chip. Specifically, we demonstrate light matter interactions in an atomic cladding wave guide (ACWG), consisting of CMOS ...
Collective polaritonic modes in an array of two-level quantum emitters coupled to optical nanofiber
Kornovan, D F; Petrov, M I
2016-01-01
In this paper we develop a microscopic analysis of the light scattering on a periodic two-level atomic array coupled to an optical nanofiber. We extend the scattering matrix approach for two-level system interaction with nanofiber fundamental waveguiding mode HE_{11}, that allows us modeling the scattering spectra. We support these results considering the dispersion of the polaritonic states formed by the superposition of the fundamental mode of light HE_{11} and the atomic chain states. To illustrate our approach we start with considering a simple model of light scattering over atomic array in the free space. We discuss the Bragg diffraction at the atomic array and show that the scattering spectrum is defined by the non-symmetric coupling of two-level system with nanofiber and vacuum modes. The proposed method allows considering two-level systems interaction with full account for dipole-dipole interaction both via near fields and long-range interaction owing to nanofiber mode coupling.
Interaction of Hg Atom with Bare Si(111) Surface
Institute of Scientific and Technical Information of China (English)
LIU Yong-Jun; LIU Ying
2006-01-01
To evaluate the interaction between Hg atom and bare Si(111) surface, three types of silicon cluster models of Si4H7, Si7H10 and Si16H20 together with their Hg complexes were studied by using hybrid (U)B3LYP density functional theory method. Optimized geometries and energies for Hg atom on different adsorption sites indicate that: 1) the binding energies at different adsorption sites are small (ranging from ～3 to 8 kJ/mol dependent on the adsorption sites), suggesting a weak interaction between Hg atom and silicon surface; 2) the most favorable adsorption site is the on top (T) site. By analyzing their natural bonding orbitals, the possible reason of this difference is suggested.
2004 Atomic and Molecular Interactions Gordon Research Conference
Energy Technology Data Exchange (ETDEWEB)
Dr. Paul J. Dagdigian
2004-10-25
The 2004 Gordon Research Conference on Atomic and Molecular Interactions was held July 11-16 at Colby-Sawyer College, New London, New Hampshire. This latest edition in a long-standing conference series featured invited talks and contributed poster papers on dynamics and intermolecular interactions in a variety of environments, ranging from the gas phase through surfaces and condensed media. A total of 90 conferees participated in the conference.
Time-domain Ramsey interferometry with interacting Rydberg atoms
Sommer, Christian; Pupillo, Guido; Takei, Nobuyuki; Takeda, Shuntaro; Tanaka, Akira; Ohmori, Kenji; Genes, Claudiu
2016-11-01
We theoretically investigate the dynamics of a gas of strongly interacting Rydberg atoms subject to a time-domain Ramsey interferometry protocol. The many-body dynamics is governed by an Ising-type Hamiltonian with long-range interactions of tunable strength. We analyze and model the contrast degradation and phase accumulation of the Ramsey signal and identify scaling laws for varying interrogation times, ensemble densities, and ensemble dimensionalities.
Atomic Force Microscopy of dynamic protein DNA interactions
Noort, van Simon Johannes Theodorus
1999-01-01
In this thesis a dedicated Atomic Force Microscopy (AFM) setup is used for imaging biochemical reactions with molecular resolution. The basis for the high resolution of AFM is the combination of a small probe, close proximity to the sample and a short-range interaction between the probe and the samp
Measurement of strong interaction effects in antiprotonic helium atoms
Energy Technology Data Exchange (ETDEWEB)
Davies, J.D.; Gorringe, T.P.; Lowe, J.; Nelson, J.M.; Playfer, S.M.; Pyle, G.J.; Squier, G.T.A. (Birmingham Univ. (UK). Dept. of Physics); Baker, C.A.; Batty, C.J.; Clark, S.A.
1984-09-27
The strong interaction shift and width for the 2 p level and the width for the 3d level have been measured for antiprotonic helium atoms. The results are compared with optical model calculations. The possible existence of strongly bound antiproton states in nuclei is discussed.
Bio-Molecular Interactions Measured by Atomic Force Microscopy
Willemsen, O.H.; Snel, M.M.E.; Cambi, A.; Cambi, Alessandra; Greve, Jan; de Grooth, B.G.; Figdor, Carl
2000-01-01
Atomic force microscopy (AFM) is nowadays frequently applied to determine interaction forces between biological molecules. Starting with the detection of the first discrete unbinding forces between ligands and receptors by AFM only several years ago, measurements have become more and more
"Material interactions": from atoms & bits to entangled practices
DEFF Research Database (Denmark)
Vallgårda, Anna
and intellectually stimulating panel moderated by Prof. Mikael Wiberg consisting of a number of scholars with a well-developed view on digital materialities to fuel a discussion on material interactions - from atoms & bits to entangled practices. These scholars include: Prof. Hiroshi Ishii, Prof. Paul Dourish...
Two interacting atoms in a cavity: Entanglement vs decoherence
Torres, J M; Seligman, T H
2009-01-01
We address the problem of two interacting atoms of different species inside a cavity and find the explicit solutions of the corresponding eigenvalue problem. Closed expressions for concurrence and purity as a function of time when the cavity is prepared in a number state are found. The behavior in the concurrence-purity plane is discussed.
Collective Dipole-Dipole Interactions in an Atomic Array
Sutherland, R T
2016-01-01
The coherent dipole-dipole interactions of atoms in an atomic array are studied. It is found that the excitation probability of an atom in an array parallel to the direction of laser propagation ($\\boldsymbol{\\hat{k}}$) will either grow or decay logarithmically along $\\boldsymbol{\\hat{k}}$, depending on the detuning of the laser. The symmetry of the system for atomic separations of $\\delta r = j\\lambda/2$, where $j$ is an integer, causes the excitation distribution and scattered radiation to abruptly become symmetric about the center of the array. For atomic separations of $\\delta r < \\lambda/2$, the appearance of a collection of extremely subradiant states ($\\Gamma\\sim 0$), disrupts the described trend. In order to interpret the results from a finite array of atoms, a band structure calculation in the $N\\rightarrow \\infty$ limit is conducted where the decay rates and the Collective Lamb Shifts of the eigenmodes along the Brillouin zone are shown. Finally, the band structure of an array strongly affects it...
Retardation effects in induced atomic dipole-dipole interactions
Graham, S D
2016-01-01
We present mean-field calculations of azimuthally averaged retarded dipole-dipole interactions in a Bose-Einstein condensate induced by a laser, at both long and short wavelengths. Our calculations demonstrate that dipole-dipole interactions become significantly stronger at shorter wavelengths, by as much as 30-fold, due to retardation effects. This enhancement, along with inclusion of the dynamic polarizability, indicate a method of inducing long-range interatomic interactions in neutral atom condensates at significantly lower intensities than previously realized.
Jiang, Li; Zhang, Guo-Feng
2017-03-01
By using the effective non-Markovian measure (Breuer et al., Phys. Rev. Lett. 103, 210401 2009) we investigate non-Markovian dynamics of a pair of two-level atoms (TLAs) system, each of which interacting with a local reservoir. We show that subsystem dynamics can be controlled by manipulating the coupling between TLAs, temperature and relaxation rate of the atoms. Moreover, the correlation between non-Markovianity of subsystem and entanglement between the subsystem and the structured bath is investigated, the results show that the emergence of non-Markovianity has a negative effect on the entanglement.
Propagation of light through small clouds of cold interacting atoms
Jennewein, S; Greffet, J -J; Browaeys, A
2015-01-01
We demonstrate experimentally that a cloud of cold atoms with a size comparable to the wavelength of light can induce large group delays on a laser pulse when the laser is tightly focused on it and is close to an atomic resonance. Delays as large as -10 ns are observed, corresponding to "superluminal" propagation with negative group velocities as low as -300 m/s. Strikingly, this large delay is associated with a moderate extinction owing to the very small size of the cloud and to the light-induced interactions between atoms. It implies that a large phase shift is imprinted on the continuous laser beam, and opens interesting perspectives for applications to quantum technologies.
A Waveguide Platform for Collective Light-Atom Interaction
DEFF Research Database (Denmark)
Sørensen, Heidi Lundgaard
In this work a tapered optical fiber is studied as a waveguide platform for efficient collective light-atom interaction. We present an allcomputer controlled heat-and-pull setup with which a standard optical fiber can reproducible be tapered down to sub-micron waist size. The resulting fiber shape...... is compared against a prediction derived from a numerical model build upon an easy experimental calibration of the viscosity profile within the heater. Very good agreement between the modeled and measured fiber shape is found. We next study the coherent back-scattering off atoms confined as two one......-dimensional strings in the evanescent field of a tapered optical fiber. By applying a near-resonant standing wave field, the atoms are arranged into a periodic Bragg structure in close analogy to a photo-refractive medium with a refractive index grating. We observe more than 10% power reflection off about 1000...
Institute of Scientific and Technical Information of China (English)
Liu Tang-Kun
2006-01-01
The field entropy can be regarded as a measurement of the degree of entanglement between the light field and the atoms of a system which is composed of two-level atoms initially in an entangled state interacting with the Schr(o)dinger cat state. The influences of the strength of light field and the phase angle between the two coherent states on the field entropy are discussed by using numerical calculations. The result shows that when the strength of light field is large enough the field entropy is not zero and the degrees of entanglement between the atoms and the three different states of the light fields are equal. When the strength of the light field is small, the degree of entanglement is maximum in a system of the two entangled atoms interacting with an odd coherent state; it is intermediate for a system of the two entangled atoms interacting with the Yurke-Stoler coherent state, and it is minimum in a system of the two entangled atoms interacting with an even coherent state.
Atomic size zone interaction potential between two ground-state cold atoms
Wang, Zhaoying; Wu, Yunhan
2016-01-01
The complex-source-point model are already used in the exact solution for the urtrashort pulse and nonparaxial beam. In this letter we have used the complex-source-point model to deduce the interaction potential equation for the separation R between two atoms which is comparable with the size of the atoms. We show the result and the characteristics of the numerical calculation. Since the singular point around R=0 is removed by using the complex-source-point model, so that we can obtain the result force around R=0. With the decreasing of the distance between two atoms, the force switches from the electromagnetic force to the strong force by use our equation.
String order via Floquet interactions in atomic systems
Lee, Tony E.; Joglekar, Yogesh N.; Richerme, Philip
2016-08-01
We study the transverse-field Ising model with interactions that are modulated in time. In a rotating frame, the system is described by a time-independent Hamiltonian with many-body interactions, similar to the cluster Hamiltonians of measurement-based quantum computing. In one dimension, there is a three-body interaction, which leads to string order instead of conventional magnetic order. We show that the string order is robust to power-law interactions that decay with the cube of distance. In two and three dimensions, there are five- and seven-body interactions. We discuss adiabatic preparation of the ground state as well as experimental implementation with trapped ions, Rydberg atoms, and polar molecules.
D-state Rydberg electrons interacting with ultracold atoms
Energy Technology Data Exchange (ETDEWEB)
Krupp, Alexander Thorsten
2014-10-02
This thesis was established in the field of ultracold atoms where the interaction of highly excited D-state electrons with rubidium atoms was examined. This work is divided into two main parts: In the first part we study D-state Rydberg molecules resulting from the binding of a D-state Rydberg electron to a ground state rubidium atom. We show that we can address specific rovibrational molecular states by changing our laser detuning and thus create perfectly aligned axial or antialigned toroidal molecules, in good agreement with our theoretical calculations. Furthermore the influence of the electric field on the Rydberg molecules was investigated, creating novel states which show a different angular dependence and alignment. In the second part of this thesis we excite single D-state Rydberg electrons in a Bose-Einstein condensate. We study the lifetime of these Rydberg electrons, the change of the shape of our condensate and the atom losses in the condensate due to this process. Moreover, we observe quadrupolar shape oscillations of the whole condensate created by the consecutive excitation of Rydberg atoms and compare all results to previous S-state measurements. In the outlook we propose a wide range of further experiments including the proposal of imaging a single electron wavefunction by the imprint of its orbit into the Bose-Einstein condensate.
Atom-scale molecular interactions in lipid raft mixtures
DEFF Research Database (Denmark)
Niemelä, Perttu S; Hyvönen, Marja T; Vattulainen, Ilpo
2009-01-01
We review the relationship between molecular interactions and the properties of lipid environments. A specific focus is given on bilayers which contain sphingomyelin (SM) and sterols due to their essential role for the formation of lipid rafts. The discussion is based on recent atom-scale molecul....... As a particularly intriguing example of this, the lateral pressure profiles of raft-like and non-raft systems indicate that the lipid composition of membrane domains may have a major impact on membrane protein activation.......We review the relationship between molecular interactions and the properties of lipid environments. A specific focus is given on bilayers which contain sphingomyelin (SM) and sterols due to their essential role for the formation of lipid rafts. The discussion is based on recent atom-scale molecular...
Super-Coulombic atom–atom interactions in hyperbolic media
Cortes, Cristian L.; Jacob, Zubin
2017-01-01
Dipole–dipole interactions, which govern phenomena such as cooperative Lamb shifts, superradiant decay rates, Van der Waals forces and resonance energy transfer rates, are conventionally limited to the Coulombic near-field. Here we reveal a class of real-photon and virtual-photon long-range quantum electrodynamic interactions that have a singularity in media with hyperbolic dispersion. The singularity in the dipole–dipole coupling, referred to as a super-Coulombic interaction, is a result of an effective interaction distance that goes to zero in the ideal limit irrespective of the physical distance. We investigate the entire landscape of atom–atom interactions in hyperbolic media confirming the giant long-range enhancement. We also propose multiple experimental platforms to verify our predicted effect with phonon–polaritonic hexagonal boron nitride, plasmonic super-lattices and hyperbolic meta-surfaces as well. Our work paves the way for the control of cold atoms above hyperbolic meta-surfaces and the study of many-body physics with hyperbolic media. PMID:28120826
Thermoelectricity in a junction between interacting cold atomic Fermi gases
Sekera, Tibor; Bruder, Christoph; Belzig, Wolfgang
2016-09-01
A gas of interacting ultracold fermions can be tuned into a strongly interacting regime using a Feshbach resonance. Here, we theoretically study quasiparticle transport in a system of two reservoirs of interacting ultracold fermions on the BCS side of the BCS-BEC crossover coupled weakly via a tunnel junction. Using the generalized BCS theory, we calculate the time evolution of the system that is assumed to be initially prepared in a nonequilibrium state characterized by a particle number imbalance or a temperature imbalance. A number of characteristic features like sharp peaks in quasiparticle currents or transitions between the normal and superconducting states are found. We discuss signatures of the Seebeck and the Peltier effects and the resulting temperature difference of the two reservoirs as a function of the interaction parameter (kFa ) -1. The Peltier effect may lead to an additional cooling mechanism for ultracold fermionic atoms.
Yin, Z; Yin, Zhang-qi; Li, Fu-li
2007-01-01
A system consisting of two single-mode cavities spatially separated and connected by an optical fibre and multi two-level atoms trapped in the cavities is considered. If the atoms resonantly and collectively interact with the local cavity fields but there is no direct interaction between the atoms, we show that an ideal quantum state transfer, and highly reliable quantum swap, entangling and controlled-Z gates can be deterministically realized between the distant cavities. We find that the operation of the state-transfer, and swap, entangling and controlled-Z gates can be greatly speeded up as number of the atoms in the cavities increases. We also notice that the effects of spontaneous emission of atoms and photon leakage out of cavity on the quantum processes can also be greatly diminished in the multi-atom case.
Theory of noncontact friction for atom-surface interactions
Jentschura, U D; DeKieviet, M
2016-01-01
The noncontact (van der Waals) friction is an interesting physical effect which has been the subject of controversial scientific discussion. The "direct" friction term due to the thermal fluctuations of the electromagnetic field leads to a friction force proportional to 1/Z^5 where Z is the atom-wall distance). The "backaction" friction term takes into account the feedback of thermal fluctuations of the atomic dipole moment onto the motion of the atom and scales as 1/Z^8. We investigate noncontact friction effects for the interactions of hydrogen, ground-state helium and metastable helium atoms with alpha-quartz (SiO_2), gold (Au) and calcium difluorite (CaF_2). We find that the backaction term dominates over the direct term induced by the thermal electromagnetic fluctuations inside the material, over wide distance ranges. The friction coefficients obtained for gold are smaller than those for SiO_2 and CaF_2 by several orders of magnitude.
Frémont, F.; Belyaev, A. K.
2017-02-01
Cross sections for producing H(nl) excited state atoms in H(1s) + He(1s2) collisions are calculated using the CTMC method, at impact energies ranging from 20 eV to 100 keV. The role of the electron correlation is studied. In the first step, the interactions between each pair of the three electrons are neglected. This leads to disagreement of the calculated total cross section for producing H(2l) atoms with previous experimental and theoretical results. In a second step, the electron–electron interaction is taken into account in a rigorous way, that is, in the form of the pure Coulomb potential. To make sure that the He target is stable before the collision, phenomenological potentials for the electron–helium-nucleus interactions that simulate the Heisenberg principle are included in addition to the Coulomb potential. The excitation cross section calculated in the frame of this model is in remarkable agreement with previous data in the range between 200 eV and 5 keV. At other energies, discrepancies are revealed, but only by a factor of less than 2 at high energies. The present results show the decisive role of the electron–electron interaction during collisions. In addition, they demonstrate the ability of classical mechanics to take into account the effects of the electron correlation.
Interaction of atomic oxygen with a graphite surface
Mateljevic, Natasa
This project was a part of the Multi University Research Initiative (MURI) Center for Materials Chemistry in the Space Environment which seeks to develop a quantitative and predictive understanding of how materials degrade or become passivated in the space environment. This is a critical research area for the Department of Defense (DoD) and National Aeronautics and Space Administration (NASA) given the large and increasing dependence on satellites and manned spacecrafts that reside in, or pass through, the low-Earth orbit (LEO) space environment. In this work, we completed three separate projects. First, we carried out ab initio electronic structure studies of the interaction of oxygen atoms with graphite surfaces. The (O3 P) ground state of oxygen interacts weakly with the graphite surface while the excited (O1D) state interacts more strongly with a binding energy sufficient for a high coverage of oxygen to be maintained on the surface. Thus, it requires a transition from O(3P) to O(1D) in order for oxygen to strongly bind. Since graphite is a semi-metal, it requires a vanishingly small energy to remove an electron of up spin from just below the Fermi level, and replace it with a down spin electron just above the Fermi level; spin-orbit interaction is not required to switch the state of the oxygen atom. We have examined this complexity for the first time and developed guidelines for properly describing chemical reactivity on graphite surfaces. The second project is a kinetic Monte Carlo study of the erosion of graphite by energetic oxygen atoms in LEO and in the laboratory. These simulations, in conjunction with experiments by our MURI collaborators, reveal new insights about reaction pathways. Finally, we have developed a new model for accommodation of energy and momentum in collisions of gases with highly corrugated surfaces. This model promises to be valuable in simulating frictional heating and drag of objects moving through the atmosphere.
Study on the fine control of atoms by coherent interaction
Energy Technology Data Exchange (ETDEWEB)
Min, Han Jae; Rho, S. P.; Park, H. M.; Lee, K. S.; Rhee, Y. J.; Yi, J. H.; Jeong, D. Y.; Jung, E. C.; Choe, A. S.; Lee, J. M
1999-01-01
The doppler-free saturation spectroscopy of Na atoms has been performed and the proper conditions for the frequency stabilization of narrow band cw dye lasers, which was used as laser sources for the laser cooling and trapping, have been obtained as follows : a) optimum pressure of a Na vapor cell: 10 mTorr b) intensity of a pump laser : a few {mu}W c) intensity of a probe laser : 1/10 of that of a pump laser. EIT (Electromagnetically Induced Transparency) generated by coherent laser-atom interactions was investigated experimentally and analyzed theoretically. The absorption of a probe laser could be remarkably reduced more than 90 % due to EIT effect. The EIT spectrum as narrow as 6 MHz which is even narrower than the natural linewidth of an excited state could be obtained under proper conditions.
Atoms and Ions Interacting with Particles and Fields: Final Report
Energy Technology Data Exchange (ETDEWEB)
Robicheaux, Francis [Auburn Univ., AL (United States)
2014-09-18
This grant supported research in basic atomic, molecular and optical physics related to the interactions of atoms with particles and fields. The duration of the grant was the 10 year period from 8/2003 to 8/2013. All of the support from the grant was used to pay salaries of the PI, postdocs, graduate students, and undergraduates and travel to conferences and meetings. The results were in the form of publications in peer reviewed journals. There were 65 peer reviewed publications over these 10 years with 8 of the publications in Physical Review Letters; all of the other articles were in respected peer reviewed journals (Physical Review A, New Journal of Physics, Journal of Physics B, ...). I will disuss the results for the periods of time relevant for each grant period.
The emission properties of an atom inside a cavity when manipulating the atoms outside the cavity
Institute of Scientific and Technical Information of China (English)
ZHANG Wen; YE Liu; XIONG Kuang-wei; ZHANG Jin
2003-01-01
Considering three two-level atoms initially in the GHZ state, then one atom of them is put into an initially empty cavity and made resonant interaction. It is shown that the emission properties of the atom inside the cavity can be affected only when both of the atoms outside the cavity have been manipulated. This conclusion can also be generalized to n two-level atoms.
Artificial abelian gauge potentials induced by dipole-dipole interactions between Rydberg atoms
Cesa, A
2013-01-01
We analyze the influence of dipole-dipole interactions between Rydberg atoms on the generation of abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field, we show that the combined atom-atom and atom-field interactions give rise to new, non-uniform, artificial gauge potentials. We identify the mechanism responsible for the emergence of these gauge potentials. Analytical expressions for the latter indicate that the strongest artificial magnetic fields are reached in the regime intermediate between the dipole blockade regime and the regime in which the atoms are sufficiently far apart such that atom-light interaction dominates over atom-atom interactions. We discuss the differences and similarities of artificial gauge fields originating from resonant dipole-dipole and van der Waals interactions. We also give an estimation of experimentally attainable artificial magnetic fields resulting from this mechanism.
Institute of Scientific and Technical Information of China (English)
Liu Tang-Kun
2007-01-01
By the negative eigenvalues of partial transposition of density matrix, this paper investigates the time evolution of entanglement of the two entangled atoms in the system of two atoms interacting with Schr(o)dinger cat state. The result shows that the two atoms are always in the entanglement state, and the degree of entanglement between the two atoms exhibits ordinary collapses and revivals at 0.2 degree of entanglement, when the light field is large enough. On the other hand, the reinforcement of three different light fields on the degree of entanglement between two atoms is not evident.
Energy Technology Data Exchange (ETDEWEB)
Jiang, Jun, E-mail: phyjiang@yeah.net [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Cheng, Yongjun, E-mail: cyj83mail@gmail.com [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150080 (China); Bromley, M.W.J., E-mail: brom@physics.uq.edu.au [School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4075 (Australia)
2015-01-15
Effective oscillator strength distributions are systematically generated and tabulated for the alkali atoms, the alkaline-earth atoms, the alkaline-earth ions, the rare gases and some miscellaneous atoms. These effective distributions are used to compute the dipole, quadrupole and octupole static polarizabilities, and are then applied to the calculation of the dynamic polarizabilities at imaginary frequencies. These polarizabilities can be used to determine the long-range C{sub 6}, C{sub 8} and C{sub 10} atom–atom interactions for the dimers formed from any of these atoms and ions, and we present tables covering all of these combinations.
Light interacting with atomic ensembles: collective, cooperative and mesoscopic effects
Guerin, W; Kaiser, R
2016-01-01
Cooperative scattering has been the subject of intense research in the last years. In this article, we discuss the concept of cooperative scattering from a broad perspective. We briefly review the various collective effects that occur when light interacts with an ensemble of atoms. We show that some effects that have been recently discussed in the context of "single-photon superradiance", or cooperative scattering in the linear-optics regime, can also be explained by "standard optics", i.e., using macroscopic quantities such as the susceptibility or the diffusion coefficient. We explain why some collective effects depend on the atomic density, and others on the optical depth. In particular, we show that, for a large and dilute atomic sample driven by a far-detuned laser, the decay of the fluorescence, which exhibits superradiant and subradiant dynamics, depends only on the on-resonance optical depth. We also discuss the link between concepts that are independently studied in the quantum-optics community and i...
Excitation dynamics of interacting Rydberg atoms in small lattices
Energy Technology Data Exchange (ETDEWEB)
Wu, G., E-mail: gwu@physnet.uni-hamburg.de [Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Physikalisches Institut, Universität Heidelberg, Im Neuenheimer Feld 226, 69120 Heidelberg (Germany); Kurz, M.; Liebchen, B. [Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); Schmelcher, P. [Zentrum für Optische Quantentechnologien, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany); The Hamburg Centre for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg (Germany)
2015-01-23
We study the Rydberg excitation dynamics of laser-driven atoms confined in a one-dimensional three-site lattice with open boundary conditions. Different regular excitation patterns are obtained within various parameter regimes. In the case of a weak Rydberg–Rydberg interaction, the excitation probability possesses a nodal structure which is characterized by an envelope with a period inversely proportional to the interaction. For strong Rydberg interaction we observe dipole blockade and antiblockade effects and an appropriate detuning leads to an overall oscillatory behavior of the Rydberg probability density which is modulated only by small oscillations. Besides an exact diagonalization procedure we study the system by performing first and second order perturbation theory as well as a spectral analysis. - Highlights: • We study Rydberg excitation in small 1-d lattices. • For weak Rydberg interaction, the excitation probability possesses an envelope structure. • For strong Rydberg interaction, we observe dipole blockade and antiblockade effects. • A specific detuning leads to degeneracy and regular oscillatory behavior of the Rydberg density.
The electron-atom interaction in partially ionized dense plasmas
Energy Technology Data Exchange (ETDEWEB)
Omarbakiyeva, Yu A; Ramazanov, T S; Roepke, G [IETP, Al Farabi Kazakh National University, Tole Bi 96a, Almaty 050012 (Kazakhstan)], E-mail: yultuz@physics.kz
2009-05-29
The electron-atom interaction is considered in dense partially ionized plasmas. The separable potential is constructed from scattering data using effective radius theory. Parameters of the interaction potential were obtained from phase shifts, scattering length and effective radius. The binding energy of the electron in the H{sup -} ion is determined for the singlet channel on the basis of the reconstructed separable potential. In dense plasmas, the influence of the Pauli exclusion principle on the phase shifts and the binding energy is considered. Due to the Pauli blocking, the binding energy vanishes at the Mott density. At that density the behavior of the phase shifts is drastically changed. This leads to modifications of macroscopic properties such as composition and transport coefficients.
The interaction of atoms with LiF(001) revisited
Miraglia, J E
2016-01-01
Pairwise additive potentials for multielectronic atoms interacting with a LiF(001) surface are revisited by including an improved description of the electron density associated with the different lattice sites, as well as non-local electron density contributions. Within this model, the electron distribution around each ionic site of the crystal is described by means of an onion approach that accounts for the influence of the Madelung potential. From such densities, binary interatomic potentials are then derived by using well-known non-local functionals for the kinetic, exchange and correlation terms. Rumpling and long-range contributions due to projectile polarization and van der Waals forces are also included in an analogous fashion. We apply this pairwise additive approximation to evaluate the interaction potential between closed-shell - He, Ne, Ar, Kr, and Xe - and open-shell - N, S, and Cl - atoms and the LiF surface, analyzing the relative importance of the different contributions. The performance of the...
Atom-light interactions in quasi-one-dimensional nanostructures: A Green's-function perspective
Asenjo-Garcia, A.; Hood, J. D.; Chang, D. E.; Kimble, H. J.
2017-03-01
Based on a formalism that describes atom-light interactions in terms of the classical electromagnetic Green's function, we study the optical response of atoms and other quantum emitters coupled to one-dimensional photonic structures, such as cavities, waveguides, and photonic crystals. We demonstrate a clear mapping between the transmission spectra and the local Green's function, identifying signatures of dispersive and dissipative interactions between atoms. We also demonstrate the applicability of our analysis to problems involving three-level atoms, such as electromagnetically induced transparency. Finally we examine recent experiments, and anticipate future observations of atom-atom interactions in photonic band gaps.
Interaction of Photon Vortex Beams with Atomic Matter
Solyanik, Maria; Afanasev, Andrei; Carlson, Carl E.
2017-01-01
In our work we consider helical Bessel beams' (BB's) propagation and interaction with isotropic matter. Dynamical properties of the beams with non-zero orbital angular momentum (OAM), which are determined by spatial degrees of freedom and polarization, modify the fundamental processes in light-matter interactions. Circular dichroism of BBs propagating in hydrogen gas was considered within the frame of studying the vortex beams' attenuation due to photoabsorption in hydrogen gas. In this case, the phenomenon is due to the topology of the wave front, contrary to the zero OAM case, when the change in polarization state is due to matter inhomogeneity. The effect of circular dichroism has been predicted by calculating the beam ellipticity evolution when traversing an isotropic target. According to our results, the BBs' transverse ellipticity profile has a structure of concentric circular maxima which correspond to minima of the intensity. The characteristic polarization singularity arises on the beam axis as the result of interaction with matter. It is shown, that even for the case of the paraxial approximation the effect of circular dichroism takes place. These signatures can be used for theoretical and experimental analysis of the interactions of optical vortices with atomic matter.
Teleportation of Atomic States for Atoms in a Lambda Configuration
Guerra, E S
2004-01-01
In this article we discuss a scheme of teleportation of atomic states making use of three-level lambda atoms. The experimental realization proposed makes use of cavity QED involving the interaction of Rydberg atoms with a micromaser cavity prepared in a coherent state. We start presenting a scheme to prepare atomic EPR states involving two-level atoms via the interaction of these atoms with a cavity. In our scheme the cavity and some atoms play the role of auxiliary systems used to achieve the teleportation.
Interaction between polystyrene spheres by atomic force microscopy
Looi, L
2002-01-01
The interaction between a single polystyrene particle and a polystyrene substrate has been previously reported by a number of investigators. However, the effects of relative humidity, applied load and contact time on the adhesion of polystyrene surfaces have not been investigated and these effects are poorly understood. It is the primary aim of the current work to characterise the effect of the aforementioned parameters on the adhesion of polystyrene surfaces using atomic force microscopy. The polystyrene used in this study contained 1% of di-vinyl benzene as a cross-linking agent. From the work conducted using the custom-built instrument, the dependency of adhesion forces on the relative humidity is greatest at relative humidities above 60% where capillary forces cause a sharp increase in adhesion with increasing relative humidity. Hysteresis was observed in the solid-solid contact gradient of the accompanying force curves, suggesting non-elastic behaviour at the contact area of the surfaces
Long-range interactions of excited He atoms with ground-state noble-gas atoms
Zhang, J.-Y.
2013-10-09
The dispersion coefficients C6, C8, and C10 for long-range interactions of He(n1,3S) and He(n1,3P), 2≤n≤10, with the ground-state noble-gas atoms Ne, Ar, Kr, and Xe are calculated by summing over the reduced matrix elements of multipole transition operators. The large-n expansions for the sums over the He oscillator strength divided by the corresponding transition energy are presented for these series. Using the expansions, the C6 coefficients for the systems involving He(131,3S) and He(131,3P) are calculated and found to be in good agreement with directly calculated values.
Atom interaction propensities of oxygenated chemical functions in crystal packings
Directory of Open Access Journals (Sweden)
Christian Jelsch
2017-03-01
Full Text Available The crystal contacts of several families of hydrocarbon compounds substituted with one or several types of oxygenated chemical groups were analyzed statistically using the Hirshfeld surface methodology. The propensity of contacts to occur between two chemical types is described with the contact enrichment descriptor. The systematic large enrichment ratios of some interactions like the O—H...O hydrogen bonds suggests that these contacts are a driving force in the crystal packing formation. The same statement holds for the weaker C—H...O hydrogen bonds in ethers, esters and ketones, in the absence of polar H atoms. The over-represented contacts in crystals of oxygenated hydrocarbons are generally of two types: electrostatic attractions (hydrogen bonds and hydrophobic interactions. While Cl...O interactions are generally avoided, in a minority of chloro-oxygenated hydrocarbons, significant halogen bonding does occur. General tendencies can often be derived for many contact types, but outlier compounds are instructive as they display peculiar or rare features. The methodology also allows the detection of outliers which can be structures with errors. For instance, a significant number of hydroxylated molecules displaying over-represented non-favorable oxygen–oxygen contacts turned out to have wrongly oriented hydroxyl groups. Beyond crystal packings with a single molecule in the asymmetric unit, the behavior of water in monohydrate compounds and of crystals with Z′ = 2 (dimers are also investigated. It was found in several cases that, in the presence of several oxygenated chemical groups, cross-interactions between different chemical groups (e.g. water/alcohols; alcohols/phenols are often favored in the crystal packings. While some trends in accordance with common chemical principles are retrieved, some unexpected results can however appear. For example, in crystals of alcohol–phenol compounds, the strong O—H...O hydrogen bonds between
Zhou, Wenting; Rizzuto, Lucia
2016-01-01
We investigate the resonance interaction energy between two uniformly accelerated identical atoms, interacting with the scalar field or the electromagnetic field in the vacuum state, in the reference frame coaccelerating with the atoms. We assume that one atom is excited and the other in the ground state, and that they are prepared in their correlated symmetric or antisymmetric state. Using perturbation theory, we separate, at the second order in the atom-field coupling, the contributions of vacuum fluctuations and radiation reaction field to the energy shift of the interacting system. We show that only the radiation reaction term contributes to the resonance interaction between the two atoms, while Unruh thermal fluctuations, related to the vacuum fluctuations contribution, do not affect the resonance interatomic interaction. We also show that the resonance interaction between two uniformly accelerated atoms, recently investigated in the comoving (locally inertial) frame, can be recovered in the coaccelerate...
Noble gas, alkali and alkaline atoms interacting with a gold surface
Łach, Grzegorz; Jentschura, Ulrich D; 10.1142/S0217751X1004961X
2013-01-01
The attractive branch of the interaction potentials with the surface of gold have been computed for a large variety of atomic systems: the hydrogen atom, noble gases (He, Ne, Ar, Kr, Xe), alkali atoms (Li, Na, K, Rb, Cs) and alkaline atoms (Be, Mg, Ca, Sr, Ba). The results include highly accurate dynamic polarizabilities for the helium atom calculated using a variational method and explicitly correlated wavefunctions. For other atoms considered we used the data available in the literature. The interaction potentials include both the effects of retardation of the electromagnetic interactions and a realistic representation of the optical response function of gold (beyond the approximation of a perfect conductor). An explicit comparison of our result to the interaction between an atom and a perfect conductor is given.
Li, Z K; Fu, H. M.; Sha, P. F.; Zhu, Z. W.; A. M. Wang; Li, H.; Zhang, H. W.; Zhang, H. F.; Hu, Z. Q.
2015-01-01
The interaction between active element Zr and W damages the W fibers and the interface and decreases the mechanical properties, especially the tensile strength of the W fibers reinforced Zr-based bulk metallic glass composites (BMGCs). From the viewpoint of atomic interaction, the W-Zr interaction can be restrained by adding minor elements that have stronger interaction with W into the alloy. The calculation about atomic interaction energy indicates that Ta and Nb preferred to segregate on th...
Kaonic atoms – studies of the strong interaction with strangeness
Directory of Open Access Journals (Sweden)
Marton J.
2014-01-01
Full Text Available The strong interaction of charged antikaons (K− with nucleons and nuclei in the low-energy regime is a fascinating topic. The antikaon plays a peculiar role in hadron physics due to the strong attraction antikaon-nucleon which is a key question for possible kaonic nuclear bound states. A rather direct experimental access to the antikaon-nucleon scattering lengths is provided by precision X-ray spectroscopy of transitions to low-lying states in light kaonic atoms like kaonic hydrogen and deuterium. After the successful completion of precision measurements on kaonic hydrogen and helium isotopes by SIDDHARTA at DAΦNE/LNF, new X-ray studies with the focus on kaonic deuterium are in preparation (SIDDHARTA2. In the future with kaonic deuterium data the antikaon-nucleon isospin-dependent scattering lengths can be extracted for the first time. An overview of the experimental results of SIDDHARTA and an outlook to future perspectives in the SIDDHARTA2 experiments in this frontier research field will be given.
Measurement of van-der-Waals interaction by atom trajectory imaging
Thaicharoen, N; Raithel, G
2015-01-01
We study the repulsive van der Waals interaction of cold rubidium $70S_{1/2}$ Rydberg atoms by analysis of time-delayed pair correlation functions. After excitation, Rydberg atoms are allowed to accelerate under the influence of the van der Waals force. Their positions are then measured using a single-atom imaging technique. From the average pair correlation function of the atom positions we obtain the initial atom-pair separation and the terminal velocity, which yield the van der Waals interaction coefficient $C_{6}$. The measured $C_{6}$ value agrees well with calculations. The experimental method has been validated by simulations. The data hint at anisotropy in the overall expansion, caused by the shape of the excitation volume. Our measurement implies that the interacting entities are individual Rydberg atoms, not groups of atoms that coherently share a Rydberg excitation.
Controlling interactions between highly magnetic atoms with Feshbach resonances.
Kotochigova, Svetlana
2014-09-01
This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic (7)S3 chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on dysprosium and erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P-states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.
Controlling interactions between highly-magnetic atoms with Feshbach resonances
Kotochigova, Svetlana
2014-01-01
This paper reviews current experimental and theoretical progress in the study of dipolar quantum gases of ground and meta-stable atoms with a large magnetic moment. We emphasize the anisotropic nature of Feshbach resonances due to coupling to fast-rotating resonant molecular states in ultracold s-wave collisions between magnetic atoms in external magnetic fields. The dramatic differences in the distribution of resonances of magnetic $^7$S$_3$ chromium and magnetic lanthanide atoms with a submerged 4f shell and non-zero electron angular momentum is analyzed. We focus on Dysprosium and Erbium as important experimental advances have been recently made to cool and create quantum-degenerate gases for these atoms. Finally, we describe progress in locating resonances in collisions of meta-stable magnetic atoms in electronic P states with ground-state atoms, where an interplay between collisional anisotropies and spin-orbit coupling exists.
Rizzuto, Lucia; Marino, Jamir; Noto, Antonio; Spagnolo, Salvatore; Passante, Roberto
2016-01-01
We study the resonance interaction between two uniformly accelerated identical atoms, one excited and the other in the ground state, prepared in a correlated (symmetric or antisymmetric) state and interacting with the scalar field in the vacuum state. Because the two atoms are in a correlated state, the interaction is a second-order effect in the atom-field coupling. We separate the contributions of vacuum fluctuations and radiation reaction to the resonance energy shift of the system, and show that only radiation reaction contributes, while Unruh thermal fluctuations do not affect the resonant interatomic interaction. We also find that beyond a characteristic length scale associated to the breakdown of a local inertial description of the two-atom system, non-thermal effects in the radiation reaction correction change the distance-dependence of the resonance interaction. Finally, we generalize our model to the case of atoms interacting with the electromagnetic field, and shown that new features appear in the ...
Donaire, M.
2016-05-01
I revisit the problem of the interaction between two dissimilar atoms with one atom in an excited state, recently addressed by Berman [Phys. Rev. A 91, 042127 (2015), 10.1103/PhysRevA.91.042127], Donaire et al. [Phys. Rev. Lett. 115, 033201 (2015), 10.1103/PhysRevLett.115.033201], and Milonni and Rafsanjani [Phys. Rev. A 92, 062711 (2015), 10.1103/PhysRevA.92.062711], for which precedent approaches have given conflicting results. In the first place, I discuss to what extent these works provide equivalent results. I show that the phase-shift rate of the two-atom wave function computed by Berman, the van der Waals potential of the excited atom by Donaire et al., and the level shift of the excited atom by Milonni and Rafsanjani possess equivalent expressions in the quasistationary approximation. In addition, I show that the level shift of the ground-state atom computed by Milonni and Rafsanjani is equivalent to its van der Waals potential. A diagrammatic representation of all those quantities is provided. The equivalences among them are, however, not generic. In particular, it is found that for the case of the interaction between two identical atoms excited, the phase-shift rate and the van der Waals potentials differ. Concerning the conflicting results of previous approaches in regards to the spatial oscillation of the interactions, I conclude, in agreement with Berman and with Milonni and Rafsanjani, that they refer to different physical quantities. The impacts of free-space dissipation and finite excitation rates on the dynamics of the potentials are analyzed. In contrast with Milonni and Rafsanjani, the oscillatory versus monotonic spatial forms of the potentials of each atom are found not to be related to the reversible versus irreversible nature of the excitation transfer involved.
Atom-light interactions in quasi-1D nanostructures: a Green's function perspective
Asenjo-Garcia, A; Chang, D E; Kimble, H J
2016-01-01
Based on a formalism that describes atom-light interactions in terms of the classical electromagnetic Green's function, we study the optical response of atoms and other quantum emitters coupled to one-dimensional photonic structures, such as cavities, waveguides, and photonic crystals. We demonstrate a clear mapping between the transmission spectra and the local Green's function that allows to identify signatures of dispersive and dissipative interactions between atoms, gaining insight into recent experiments.
Institute of Scientific and Technical Information of China (English)
胡正峰; 杜春光; 李代军; 李师群
2002-01-01
We investigate electromagnetically induced transparency and slow group velocity of light in ultracold Bose gas with a two-photon Raman process. The properties of electromagnetically induced transparency and light speed can be changed by controlling the atomic interaction. Atomic interaction can be used as a knob to control the optical properties of atomic media. This can be realized in experiment by using the Feshbach resonance technique.
Non-integer Quantum Transition, a True Non-perturbation Effect in Laser-Atom Interaction
Institute of Scientific and Technical Information of China (English)
ZHANG Qi-Ren
2007-01-01
We show that in the quantum transition of an atom interacting with an intense laser of circular frequencyω, the energy difference between the initial and the final states of the atom is not necessarily an integer multiple of the quantum energy (h)ω. This kind of non-integer transition is a true non-perturbation effect in laser-atom interaction.
Concentration of Unknown Atomic Entangled States via Entanglement Swapping through Raman Interaction
Institute of Scientific and Technical Information of China (English)
ZOU Jin-Hua; HU Xiang-Ming
2008-01-01
We show that entanglement concentration of unknown atomic entangled states is achieved via the implementation of entanglement swapping based on Raman interaction in cavity QED. A maximally entangled state is obtained from a pair of partially entangled states probabilistically. Due to Raman interaction of two atoms with a cavity mode and an external driving field, the influence of atomic spontaneous emission has been eliminated. Because of the virtual excitation of the cavity mode, the decoherence of cavity decay and thermal field is neglected.
Fidelity of quantum state for interacting system of light field and atomic Bose-Einstein condensate
Institute of Scientific and Technical Information of China (English)
Chunjia Huang; Ming Zhou; Fanzhi Kong; Jiayuan Fang; Kewei Mo
2005-01-01
@@ The evolution characteristics of quantum state fidelity in an interacting system of single-mode light field and atomic Bose-Einstein condensate have been studied and the influence of the initial light field intensity and the interaction among atoms of Bose-Einstein condensate on the quantum state fidelity respectively have been discussed.
Interactions of Pb and Te atoms with graphene.
Gong, Chuncheng; Robertson, Alex W; He, Kuang; Ford, Camden; Watt, Andrew A R; Warner, Jamie H
2014-05-28
PbTe nanocrystals were deposited onto the surface of graphene and used as a reservoir of Pb and Te atoms. Electron beam irradiation at 80 kV caused Pb and Te atoms to mobilize and disperse across the surface of graphene. We studied the dynamics of these atoms in real time using aberration-corrected transmission electron microscopy. The Pb and Te atoms were found to attach to the surface layer of amorphous carbon that resides upon the graphene, as well as its edge. Pb and Te atoms were not found residing on pristine graphene, but were found to bond to the free edge states along graphene hole edges. Small PbTe nanoclusters tended to only form on the surface of the amorphous carbon regions and not on pristine graphene.
Atom–atom interactions around the band edge of a photonic crystal waveguide
Hood, Jonathan D.; Goban, Akihisa; Asenjo-Garcia, Ana; Lu, Mingwu; Yu, Su-Peng; Chang, Darrick E.; Kimble, H. J.
2016-01-01
Tailoring the interactions between quantum emitters and single photons constitutes one of the cornerstones of quantum optics. Coupling a quantum emitter to the band edge of a photonic crystal waveguide (PCW) provides a unique platform for tuning these interactions. In particular, the cross-over from propagating fields E(x)∝e±ikxx outside the bandgap to localized fields E(x)∝e−κx|x| within the bandgap should be accompanied by a transition from largely dissipative atom–atom interactions to a regime where dispersive atom–atom interactions are dominant. Here, we experimentally observe this transition by shifting the band edge frequency of the PCW relative to the D1 line of atomic cesium for N¯=3.0±0.5 atoms trapped along the PCW. Our results are the initial demonstration of this paradigm for coherent atom–atom interactions with low dissipation into the guided mode. PMID:27582467
Institute of Scientific and Technical Information of China (English)
刘洪毓
2007-01-01
Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what
Institute of Scientific and Technical Information of China (English)
陈昌永
2002-01-01
A scheme for preparation of the many-atom entangled state via the resonant interaction of quantized cavity with atom is presented.It is injected an two-level atom initially prepared in the superposition of the ground state and excited state through the cavity prepared in the vacuum state.The atom passing through the cavity creates atom-field entanglement.The other two-level atoms prepared in the ground states are injected into the cavity at different angles,respectively.After the interaction with the cavity field,the many-atom entangled state is produced and the cavity field is still in the vacuum state.Comparing with the existing schemes,ours is easier to realize experimently.%提出了一个利用量子腔场与原子的共振相互作用制备多原子缠结态的方案.首先将一个初态制备在基态和激发态的叠加态的二能级原子注入一个真空态腔场中.原子通过腔时产生原子-场缠结.制备于基态的其它二能级原子分别以不同角度注入腔场,在与腔场相互作用时可制得多原子缠结态,而空腔仍然保持在真空态.与现存的方案比较,该方案在实验上更容易实现.
Van der Waals and resonance interactions between accelerated atoms in vacuum and the Unruh effect
Lattuca, M.; Marino, J.; Noto, A.; Passante, R.; Rizzuto, L.; Spagnolo, S.; Zhou, W.
2017-08-01
We discuss different physical effects related to the uniform acceleration of atoms in vacuum, in the framework of quantum electrodynamics. We first investigate the van der Waals/Casimir-Polder dispersion and resonance interactions between two uniformly accelerated atoms in vacuum. We show that the atomic acceleration significantly affects the van der Waals force, yielding a different scaling of the interaction with the interatomic distance and an explicit time dependence of the interaction energy. We argue how these results could allow for an indirect detection of the Unruh effect through dispersion interactions between atoms. We then consider the resonance interaction between two accelerated atoms, prepared in a correlated Bell-type state, and interacting with the electromagnetic field in the vacuum state, separating vacuum fluctuations and radiation reaction contributions, both in the free-space and in the presence of a perfectly reflecting plate. We show that nonthermal effects of acceleration manifest in the resonance interaction, yielding a change of the distance dependence of the resonance interaction energy. This suggests that the equivalence between temperature and acceleration does not apply to all radiative properties of accelerated atoms. To further explore this aspect, we evaluate the resonance interaction between two atoms in non inertial motion in the coaccelerated (Rindler) frame and show that in this case the assumption of an Unruh temperature for the field is not required for a complete equivalence of locally inertial and coaccelerated points of views.
Theory of light-matter interactions in cascade and diamond type atomic ensembles
Jen, Hsiang-Hua
2011-01-01
In this thesis, we investigate the quantum mechanical interaction of light with matter in the form of a gas of ultracold atoms: the atomic ensemble. We present a theoretical analysis of two problems, which involve the interaction of quantized electromagnetic fields (called signal and idler) with the atomic ensemble (i) cascade two-photon emission in an atomic ladder configuration, and (ii) photon frequency conversion in an atomic diamond configuration. The motivation of these studies comes from potential applications in long-distance quantum communication where it is desirable to generate quantum correlations between telecommunication wavelength light fields and ground level atomic coherences. We develop a theory of correlated signal-idler pair correlation. The analysis is complicated by the possible generation of multiple excitations in the atomic ensemble. An analytical treatment is given in the limit of a single excitation assuming adiabatic laser excitations. The analysis predicts superradiant timescales ...
Nonvolatile optical memory via recoil-induced resonance in a pure two-level system
de Almeida, A. J. F.; Maynard, M.-A.; Banerjee, C.; Felinto, D.; Goldfarb, F.; Tabosa, J. W. R.
2016-12-01
We report on the storage of light via the phenomenon of recoil-induced resonance in a pure two-level system of cold cesium atoms. We use a strong coupling beam and a weak probe beam to couple different external momentum states of the cesium atom via two-photon Raman interaction which leads to the storage of the optical information of the probe beam. We have also measured the probe transmission spectrum, as well as the light storage spectrum which reveals very narrow subnatural resonance features showing absorption and gain. We have demonstrated that this memory presents the unique property of being insensitive to the reading process, which does not destroy the stored information leading to a memory lifetime limited only by the atomic thermal motion.
Van der Waals interactions and the limits of isolated atom models at interfaces.
Kawai, Shigeki; Foster, Adam S; Björkman, Torbjörn; Nowakowska, Sylwia; Björk, Jonas; Canova, Filippo Federici; Gade, Lutz H; Jung, Thomas A; Meyer, Ernst
2016-05-13
Van der Waals forces are among the weakest, yet most decisive interactions governing condensation and aggregation processes and the phase behaviour of atomic and molecular matter. Understanding the resulting structural motifs and patterns has become increasingly important in studies of the nanoscale regime. Here we measure the paradigmatic van der Waals interactions represented by the noble gas atom pairs Ar-Xe, Kr-Xe and Xe-Xe with a Xe-functionalized tip of an atomic force microscope at low temperature. Individual rare gas atoms were fixed at node sites of a surface-confined two-dimensional metal-organic framework. We found that the magnitude of the measured force increased with the atomic radius, yet detailed simulation by density functional theory revealed that the adsorption induced charge redistribution strengthened the van der Waals forces by a factor of up to two, thus demonstrating the limits of a purely atomic description of the interaction in these representative systems.
Graphene as a flexible template for controlling magnetic interactions between metal atoms
Lee, Sungwoo; Kim, Dongwook; Robertson, Alex W.; Yoon, Euijoon; Hong, Suklyun; Ihm, Jisoon; Yu, Jaejun; Warner, Jamie H.; Lee, Gun-Do
2017-03-01
Metal-doped graphene produces magnetic moments that have potential application in spintronics. Here we use density function theory computational methods to show how the magnetic interaction between metal atoms doped in graphene can be controlled by the degree of flexure in a graphene membrane. Bending graphene by flexing causes the distance between two substitutional Fe atoms covalently bonded in graphene to gradually increase and these results in the magnetic moment disappearing at a critical strain value. At the critical strain, a carbon atom can enter between the two Fe atoms and blocks the interaction between relevant orbitals of Fe atoms to quench the magnetic moment. The control of interactions between doped atoms by exploiting the mechanical flexibility of graphene is a unique approach to manipulating the magnetic properties and opens up new opportunities for mechanical-magnetic 2D device systems.
Graphene as a flexible template for controlling magnetic interactions between metal atoms.
Lee, Sungwoo; Kim, Dongwook; Robertson, Alex W; Yoon, Euijoon; Hong, Suklyun; Ihm, Jisoon; Yu, Jaejun; Warner, Jamie H; Lee, Gun-Do
2017-03-01
Metal-doped graphene produces magnetic moments that have potential application in spintronics. Here we use density function theory computational methods to show how the magnetic interaction between metal atoms doped in graphene can be controlled by the degree of flexure in a graphene membrane. Bending graphene by flexing causes the distance between two substitutional Fe atoms covalently bonded in graphene to gradually increase and these results in the magnetic moment disappearing at a critical strain value. At the critical strain, a carbon atom can enter between the two Fe atoms and blocks the interaction between relevant orbitals of Fe atoms to quench the magnetic moment. The control of interactions between doped atoms by exploiting the mechanical flexibility of graphene is a unique approach to manipulating the magnetic properties and opens up new opportunities for mechanical-magnetic 2D device systems.
Long-range interactions of excited He atoms with the alkaline earth atoms Mg, Ca, and Sr
Zhang, J.-Y.
2013-04-05
Dispersion coefficients for the long-range interactions of the first four excited states of He, i.e., He(2 1, 3 S) and He(2 1, 3 P), with the low-lying states of the alkaline earth atoms Mg, Ca, and Sr are calculated by summing over the reduced matrix elements of multipole transition operators.
Sagué, G; Vetsch, E; Alt, W; Meschede, D; Rauschenbeutel, A
2007-10-19
The strong evanescent field around ultrathin unclad optical fibers bears a high potential for detecting, trapping, and manipulating cold atoms. Introducing such a fiber into a cold-atom cloud, we investigate the interaction of a small number of cold cesium atoms with the guided fiber mode and with the fiber surface. Using high resolution spectroscopy, we observe and analyze light-induced dipole forces, van der Waals interaction, and a significant enhancement of the spontaneous emission rate of the atoms. The latter can be assigned to the modification of the vacuum modes by the fiber.
Entanglement and Its Dynamics with Atomic Spontaneous Decay
Institute of Scientific and Technical Information of China (English)
H. A. Hessian; A. -B. A. Mohamed
2008-01-01
The atomic decay for a two-level atom interacting with a single mode of electromagnetic field is considered. For a chosen initial state, the exact solution of the master equation is found. Therefore, effect of the atomic damping on entanglement (purity loss), degree of entanglement by the negativity, mutual information and atomic coherence through the master equation are studied.
Atom lens without chromatic aberrations
Efremov, Maxim A; Schleich, Wolfgang P
2012-01-01
We propose a lens for atoms with reduced chromatic aberrations and calculate its focal length and spot size. In our scheme a two-level atom interacts with a near-resonant standing light wave formed by two running waves of slightly different wave vectors, and a far-detuned running wave propagating perpendicular to the standing wave. We show that within the Raman-Nath approximation and for an adiabatically slow atom-light interaction, the phase acquired by the atom is independent of the incident atomic velocity.
Quantum Correlation of Two Entangled Atoms Interacting with the Binomial Optical Field
Liu, Tang-Kun; Tao, Yu; Shan, Chuan-Jia; Liu, Ji-bing
2016-10-01
Quantum correlations of two atoms in a system of two entangled atoms interacting with the binomial optical field are investigated. In eight different initial states of the two atoms, the influence of the strength of the dipole-dipole interaction, probabilities of a the Bernoulli trial and particle number of the binomial optical field on the temporal evolution of the geometrical quantum discord between two atoms are discussed. The result shows that two atoms always exist the correlation for different parameters. In addition, when and only when the two atoms are initially in the maximally entangled state, the temporal evolution of geometrical quantum discord is not affected by the parameters, and always keep in the degree of geometrical quantum discord that is a fixed value.
Scattering approach to dispersive atom-surface interactions
Energy Technology Data Exchange (ETDEWEB)
Dalvit, Diego [Los Alamos National Laboratory; Messina, Riccardo [LAB KASTLER BROSSEL; Maia Neto, Paulo [INSTITUTO DE FISICA UFRJ; Lambrecht, Astrid [LAB KASTLER BROSSEL; Reynaud, Serge [LAB KASTLER BROSSEL
2009-01-01
We develop the scattering approach for the dispersive force on a ground state atom on top of a corrugated surface. We present explicit results to first order in the corrugation amplitude. A variety of analytical results are derived in different limiting cases, including the van der Waals and Casimir-Polder regimes. We compute numerically the exact first-order dispersive potential for arbitrary separation distances and corrugation wavelengths, for a Rubidium atom on top of a silicon or gold corrugated surface. We consider in detail the correction to the proximity force approximation, and present a very simple approximation algorithm for computing the potential.
Atomic forces between noble gas atoms, alkali ions, and halogen ions for surface interactions
Wilson, J. W.; Outlaw, R. A.; Heinbockel, J. H.
1988-01-01
The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base developed from analysis of the two-body potential data, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas surfaces and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.
Van der Waals and Casimir interactions between atoms and carbon nanotubes
Klimchitskaya, G. L.(Central Astronomical Observatory at Pulkovo of the Russian Academy of Sciences, 196140, St. Petersburg, Russia); Blagov, E. V.; Mostepanenko, V. M.
2008-01-01
The van der Waals and Casimir interactions of a hydrogen atom (molecule) with a single-walled and a multiwalled carbon nanotubes are compared. It is shown that the macroscopic concept of graphite dielectric permittivity is already applicable for nanotubes with only two or three walls. The absorption of hydrogen atoms by a nanotube at separations below one nanometer is considered. The lateral force due to exchange repulsion moves the atom to a position above the cell center, where it is absorb...
Interference of Atomic Bose-Einstein Condensate Interacting with Laser Field
Institute of Scientific and Technical Information of China (English)
YU Zhao-Xian; JIAO Zhi-Yong; SUN Jin-Zuo
2004-01-01
Interference of an atomic Bose-Einstein condensate interacting with a laser field in a double-well potential with dissipation is investigated. If properly selecting the laser field and the initial states of the atoms in the two wells,we find that the intensity exhibits revivals and collapses. The fidelity of interference is affected by the total number of atoms in the two wells and dissipation.
Entanglement and coherence of a three-level atom in Λ configuration interacting with two fields
Institute of Scientific and Technical Information of China (English)
Zhang Jian-Song; Xu Jing-Bo
2009-01-01
We investigate the entanglement of a three-level atom in A configuration interacting with two quantized field modes by using logarithmic negativity. Then, we study the relationship of the atomic coherence and the entanglement between two fields which are initially prepared in vacuum or thermal states. We find that if the two fields are prepared in thermal states, the atomic coherence can induce the entanglement between two thermal fields. However, there is no coherence-induced entanglement between two vacuum fields.
Santhanam, K S V; Chen, Xu; Gupta, S
2014-04-01
Ab initio studies of ferromagnetic atom interacting with carbon nanotubes have been reported in the literature that predict when the interaction is strong, a higher hybridization with confinement effect will result in spin polarization in the ferromagnetic atom. The spin polarization effect on the thermal oxidation to form its oxide is modeled here for the ferromagnetic atom and its alloy, as the above studies predict the 4s electrons are polarized in the atom. The four models developed here provide a pathway for distinguishing the type of interaction that exists in the real system. The extent of spin polarization in the ferromagnetic atom has been examined by varying the amount of carbon nanotubes in the composites in the thermogravimetric experiments. In this study we report the experimental results on the CoNi alloy which appears to show selective spin polarization. The products of the thermal oxidation has been analyzed by Fourier Transform Infrared Spectroscopy.
Quantum Statistical Behaviors of Interaction of an Atomic Bose-Einstein Condensate with Laser
Institute of Scientific and Technical Information of China (English)
YU Zhao-Xian; JIAO Zhi-Yong
2001-01-01
We have investigated quantum statistical behaviors of photons and atoms in interaction of an atomic Bose Einstein condensate with quantized laser field. When the quantized laser field is initially prepared in a superposition state which exhibits holes in its photon-number distribution, while the atomic field is initially in a Fock state, it is found that there is energy exchange between photons and atoms. For the input and output states, the photons and atoms may exhibit the sub-Poissonian distribution. The input and output laser fields may exhibit quadrature squeezing, but for the atomic field, only the output state exhibits quadrature squeezing. It is shown that there exists the violation of the Cauchy-Schwartz inequality, which means that the correlation between photons and atoms is nonclassical.``
Estimation of atomic interaction parameters by photon counting
DEFF Research Database (Denmark)
Kiilerich, Alexander Holm; Mølmer, Klaus
2014-01-01
Detection of radiation signals is at the heart of precision metrology and sensing. In this article we show how the fluctuations in photon counting signals can be exploited to optimally extract information about the physical parameters that govern the dynamics of the emitter. For a simple two......-level emitter subject to photon counting, we show that the Fisher information and the Cram\\'er- Rao sensitivity bound based on the full detection record can be evaluated from the waiting time distribution in the fluorescence signal which can, in turn, be calculated for both perfect and imperfect detectors...
Estimation of atomic interaction parameters by photon counting
DEFF Research Database (Denmark)
Kiilerich, Alexander Holm; Mølmer, Klaus
2014-01-01
Detection of radiation signals is at the heart of precision metrology and sensing. In this article we show how the fluctuations in photon counting signals can be exploited to optimally extract information about the physical parameters that govern the dynamics of the emitter. For a simple two......-level emitter subject to photon counting, we show that the Fisher information and the Cram\\'er- Rao sensitivity bound based on the full detection record can be evaluated from the waiting time distribution in the fluorescence signal which can, in turn, be calculated for both perfect and imperfect detectors...
Taber, Keith S.
2013-01-01
Comparing the atom to a "tiny solar system" is a common teaching analogy, and the extent to which learners saw the systems as analogous was investigated. English upper secondary students were asked parallel questions about the physical interactions between the components of a simple atomic system and a simple solar system to investigate…
Taber, Keith S.
2013-01-01
Comparing the atom to a "tiny solar system" is a common teaching analogy, and the extent to which learners saw the systems as analogous was investigated. English upper secondary students were asked parallel questions about the physical interactions between the components of a simple atomic system and a simple solar system to investigate…
Engineering the Dynamics of Effective Spin-Chain Models for Strongly Interacting Atomic Gases
DEFF Research Database (Denmark)
Volosniev, A. G.; Petrosyan, D.; Valiente, M.
2015-01-01
We consider a one-dimensional gas of cold atoms with strong contact interactions and construct an effective spin-chain Hamiltonian for a two-component system. The resulting Heisenberg spin model can be engineered by manipulating the shape of the external confining potential of the atomic gas. We...
Li, Z. K.; Fu, H. M.; Sha, P. F.; Zhu, Z. W.; Wang, A. M.; Li, H.; Zhang, H. W.; Zhang, H. F.; Hu, Z. Q.
2015-03-01
The interaction between active element Zr and W damages the W fibers and the interface and decreases the mechanical properties, especially the tensile strength of the W fibers reinforced Zr-based bulk metallic glass composites (BMGCs). From the viewpoint of atomic interaction, the W-Zr interaction can be restrained by adding minor elements that have stronger interaction with W into the alloy. The calculation about atomic interaction energy indicates that Ta and Nb preferred to segregate on the W substrate surface. Sessile drop experiment proves the prediction and corresponding in-situ coating appears at the interface. Besides, the atomic interaction mechanism was proven to be effective in many other systems by the sessile drop technique. Considering the interfacial morphology, Nb was added into the alloy to fabricate W/Zr-based BMGCs. As expected, the Nb addition effectively suppressed the W-Zr reaction and damage to W fibers. Both the compressive and tensile properties are improved obviously.
A constructive model potential method for atomic interactions
Bottcher, C.; Dalgarno, A.
1974-01-01
A model potential method is presented that can be applied to many electron single centre and two centre systems. The development leads to a Hamiltonian with terms arising from core polarization that depend parametrically upon the positions of the valence electrons. Some of the terms have been introduced empirically in previous studies. Their significance is clarified by an analysis of a similar model in classical electrostatics. The explicit forms of the expectation values of operators at large separations of two atoms given by the model potential method are shown to be equivalent to the exact forms when the assumption is made that the energy level differences of one atom are negligible compared to those of the other.
Propagation of light through small clouds of cold interacting atoms
Jennewein, S.; Sortais, Y. R. P.; Greffet, J.-J.; Browaeys, A.
2016-11-01
We demonstrate experimentally that a dense cloud of cold atoms with a size comparable to the wavelength of light can induce large group delays on a laser pulse when the laser is tightly focused on it and is close to an atomic resonance. Delays as large as -10 ns are observed, corresponding to "superluminal" propagation with negative group velocities as low as -300 m /s . Strikingly, this large delay is associated with a moderate extinction owing to the very small size of the dense cloud. It implies that a large phase shift is imprinted on the continuous laser beam. Our system may thus be useful for applications to quantum technologies, such as variable delay line for individual photons or phase imprint between two beams at the single-photon level.
Bose-Einstein condensation temperature of weakly interacting atoms
Yukalov, V. I.; Yukalova, E. P.
2017-07-01
The critical temperature of Bose-Einstein condensation essentially depends on internal properties of the system as well as on the geometry of a trapping potential. The peculiarities of defining the phase transition temperature of Bose-Einstein condensation for different systems are reviewed, including homogenous Bose gas, trapped Bose atoms, and bosons in optical lattices. The method of self-similar approximants, convenient for calculating critical temperature, is briefly delineated.
Engineering the Dynamics of Effective Spin-Chain Models for Strongly Interacting Atomic Gases
DEFF Research Database (Denmark)
Volosniev, A. G.; Petrosyan, D.; Valiente, M.
2015-01-01
We consider a one-dimensional gas of cold atoms with strong contact interactions and construct an effective spin-chain Hamiltonian for a two-component system. The resulting Heisenberg spin model can be engineered by manipulating the shape of the external confining potential of the atomic gas. We...... find that bosonic atoms offer more flexibility for tuning independently the parameters of the spin Hamiltonian through interatomic (intra-species) interaction which is absent for fermions due to the Pauli exclusion principle. Our formalism can have important implications for control and manipulation...
Nonlinear interaction of meta-atoms through optical coupling
Energy Technology Data Exchange (ETDEWEB)
Slobozhanyuk, A. P.; Kapitanova, P. V.; Filonov, D. S.; Belov, P. A. [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Powell, D. A. [Nonlinear Physics Centre and Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Australian National University, Canberra, ACT 0200 (Australia); Shadrivov, I. V.; Kivshar, Yu. S. [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Nonlinear Physics Centre and Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), Australian National University, Canberra, ACT 0200 (Australia); Lapine, M., E-mail: mlapine@physics.usyd.edu.au [National Research University of Information Technologies, Mechanics and Optics (ITMO), St. Petersburg 197101 (Russian Federation); Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), School of Physics, University of Sydney, New South Wales 2006 (Australia); McPhedran, R. C. [Centre for Ultrahigh-bandwidth Devices for Optical Systems (CUDOS), School of Physics, University of Sydney, New South Wales 2006 (Australia)
2014-01-06
We propose and experimentally demonstrate a multi-frequency nonlinear coupling mechanism between split-ring resonators. We engineer the coupling between two microwave resonators through optical interaction, whilst suppressing the direct electromagnetic coupling. This allows for a power-dependent interaction between the otherwise independent resonators, opening interesting opportunities to address applications in signal processing, filtering, directional coupling, and electromagnetic compatibility.
The Master Equation for Two-Level Accelerated Systems at Finite Temperature
Tomazelli, J. L.; Cunha, R. O.
2016-10-01
In this work, we study the behaviour of two weakly coupled quantum systems, described by a separable density operator; one of them is a single oscillator, representing a microscopic system, while the other is a set of oscillators which perform the role of a reservoir in thermal equilibrium. From the Liouville-Von Neumann equation for the reduced density operator, we devise the master equation that governs the evolution of the microscopic system, incorporating the effects of temperature via Thermofield Dynamics formalism by suitably redefining the vacuum of the macroscopic system. As applications, we initially investigate the behaviour of a Fermi oscillator in the presence of a heat bath consisting of a set of Fermi oscillators and that of an atomic two-level system interacting with a scalar radiation field, considered as a reservoir, by constructing the corresponding master equation which governs the time evolution of both sub-systems at finite temperature. Finally, we calculate the energy variation rates for the atom and the field, as well as the atomic population levels, both in the inertial case and at constant proper acceleration, considering the two-level system as a prototype of an Unruh detector, for admissible couplings of the radiation field.
Corsini, Eric P.
The quest to expand the limited sensorial domain, in particular to bridge the inability to gauge magnetic fields near and far, has driven the fabrication of remedial tools. The interaction of ferromagnetic material with a magnetic field had been the only available technique to gauge that field for several millennium. The advent of electricity and associated classical phenomena captured in the four Maxwell equations, were a step forward. In the early 1900s, the model of quantum mechanics provided a two-way leap forward. One came from the newly understood interaction of light and matter, and more specifically the three-way coupling of photons, atoms' angular momenta, and magnetic field, which are the foundations of atomic magnetometry. The other came from magnetically sensitive quantum effects in a fabricated energy-ladder form of matter cooled to a temperature below that of the energy steps; these quantum effects gave rise to the superconducting quantum interference device (SQUID). Research using atomic magnetometers and SQUIDs has resulted in thousands of publications, text books, and conferences. The current status in each field is well described in Refs. [48,49,38,42] and all references therein. In this work we develop and investigate techniques and applications pertaining to atomic magnetometry. [Full text: eric.corsini gmail.com].
Paul, Saurabh; Johnson, P. R.; Tiesinga, Eite
2016-04-01
We show that, for ultracold neutral bosonic atoms held in a three-dimensional periodic potential or optical lattice, a Hubbard model with dominant, attractive three-body interactions can be generated. In fact, we derive that the effect of pairwise interactions can be made small or zero starting from the realization that collisions occur at the zero-point energy of an optical lattice site and the strength of the interactions is energy dependent from effective-range contributions. We determine the strength of the two- and three-body interactions for scattering from van der Waals potentials and near Fano-Feshbach resonances. For van der Waals potentials, which for example describe scattering of alkaline-earth atoms, we find that the pairwise interaction can only be turned off for species with a small negative scattering length, leaving the 88Sr isotope a possible candidate. Interestingly, for collisional magnetic Feshbach resonances this restriction does not apply and there often exist magnetic fields where the two-body interaction is small. We illustrate this result for several known narrow resonances between alkali-metal atoms as well as chromium atoms. Finally, we compare the size of the three-body interaction with hopping rates and describe limits due to three-body recombination.
Multimode Kapitza-Dirac interferometer on Bose-Einstein condensates with atomic interactions
He, Tianchen; Niu, Pengbin
2017-03-01
The dynamics of multimode interferometers for Bose Einstein condensation (BEC) with atomic interactions confined to a harmonic trap is investigated. At the initial time t = 0, several spatially addressable wave packets (modes) with different momenta are created by the first Kapitza-Dirac pulse. These modes are coherently recombined by the harmonic potential with atomic interactions. The second Kapitza-Dirac pulse splits the evolved modes a second time and separates them along different paths for a second time. The signal to noise ratio is numerically calculated by the Fisher information and the Cramér-Rao lower bound. We find that the small atomic interactions decrease the measurement accuracy for current atom interferometers when measuring the gravitational acceleration. Its impact on measurement precision can be reduced by improving the Kapitza-Dirac strength.
Parrish, Robert M; Sherrill, C David
2014-07-28
We develop a physically-motivated assignment of symmetry adapted perturbation theory for intermolecular interactions (SAPT) into atom-pairwise contributions (the A-SAPT partition). The basic precept of A-SAPT is that the many-body interaction energy components are computed normally under the formalism of SAPT, following which a spatially-localized two-body quasiparticle interaction is extracted from the many-body interaction terms. For electrostatics and induction source terms, the relevant quasiparticles are atoms, which are obtained in this work through the iterative stockholder analysis (ISA) procedure. For the exchange, induction response, and dispersion terms, the relevant quasiparticles are local occupied orbitals, which are obtained in this work through the Pipek-Mezey procedure. The local orbital atomic charges obtained from ISA additionally allow the terms involving local orbitals to be assigned in an atom-pairwise manner. Further summation over the atoms of one or the other monomer allows for a chemically intuitive visualization of the contribution of each atom and interaction component to the overall noncovalent interaction strength. Herein, we present the intuitive development and mathematical form for A-SAPT applied in the SAPT0 approximation (the A-SAPT0 partition). We also provide an efficient series of algorithms for the computation of the A-SAPT0 partition with essentially the same computational cost as the corresponding SAPT0 decomposition. We probe the sensitivity of the A-SAPT0 partition to the ISA grid and convergence parameter, orbital localization metric, and induction coupling treatment, and recommend a set of practical choices which closes the definition of the A-SAPT0 partition. We demonstrate the utility and computational tractability of the A-SAPT0 partition in the context of side-on cation-π interactions and the intercalation of DNA by proflavine. A-SAPT0 clearly shows the key processes in these complicated noncovalent interactions, in
Retarded Boson-Fermion interaction in atomic systems
Indian Academy of Sciences (India)
Sambhu N Datta
2007-09-01
The retarded interaction between an electron and a spin-0 nucleus, that has been derived from electro-dynamical perturbation theory is discussed here. A brief account of the derivation is given. The retarded form is correct through order 2/2. Use of the relative coordinates leads to an effective oneelectron operator that can be used through all orders of perturbation theory. A few unitary transformations give rise to the interaction that is valid in the non-relativistic limit.
Two-Level Semantics and Abstract Interpretation
DEFF Research Database (Denmark)
Nielson, Flemming
1989-01-01
Two-level semantics is a variant of Scott/Strachey denotational semantics in which the concept of binding time is treated explicitly. This is done by formally distinguishing between those computations that take place at run-time and those that take place at compile-time. Abstract interpretation...... unique flavour is the insistence on formal proofs of correctness and the methods used to establish these. This paper develops a theory of abstract interpretation for two-level denotational definitions. There are three ingredients in this. First a framework for proving the correctness of analyses...
Metal-graphene interaction studied via atomic resolution scanning transmission electron microscopy.
Zan, Recep; Bangert, Ursel; Ramasse, Quentin; Novoselov, Konstantin S
2011-03-09
Distributions and atomic sites of transition metals and gold on suspended graphene were investigated via high-resolution scanning transmission electron microscopy, especially using atomic resolution high angle dark field imaging. All metals, albeit as singular atoms or atom aggregates, reside in the omni-present hydrocarbon surface contamination; they do not form continuous films, but clusters or nanocrystals. No interaction was found between Au atoms and clean single-layer graphene surfaces, i.e., no Au atoms are retained on such surfaces. Au and also Fe atoms do, however, bond to clean few-layer graphene surfaces, where they assume T and B sites, respectively. Cr atoms were found to interact more strongly with clean monolayer graphene, they are possibly incorporated at graphene lattice imperfections and have been observed to catalyze dissociation of C-C bonds. This behavior might explain the observed high frequency of Cr-cluster nucleation, and the usefulness as wetting layer, for depositing electrical contacts on graphene.
Atomic coherence control on the entanglement of two atoms in two-photon processes
Institute of Scientific and Technical Information of China (English)
Hu Yao-Hua; Fang Mao-Fa; Wu Qin
2007-01-01
Considering two identical two-level atoms interacting with a single-mode thermal field through two-photon processes, this paper studies the atomic coherence control on the entanglement between two two-level atoms, and finds that the entanglement is greatly enhanced due to the initial atomic coherence. The results show that the entanglement can be manipulated by changing the initial parameters of the system, such as the superposition coefficients and the relative phases of the initial atomic coherent state and the mean photon number of the cavity field.
Molecular mechanics on bonding and non-bonding interactions in (atom@C60)
Institute of Scientific and Technical Information of China (English)
朱传宝; 徐志谨; 严继民
1997-01-01
The interactions between the embedded atom X (X=Li,Na,K,Rb,Cs; F,Cl,Br,I) and C60cage in the endohedral-form complexes (X@C60) are calculated and discussed according to molecular mechanics from the point of view of the bonding and non-bonding.It is found from the computational results that for atoms with radii larger than Li’s,their locations with the minimum interaction in (X@C60) are at the cage center,while atom Li has an off-center location with the minimum interaction deviation of-0.05 nm,and the cage-environment in C60 can be regarded as sphero-symmetry in the region with radius r of ~0.2 nm.It is shown that the interaction between X and C60 cage is of non-bonding characteristic,and this non-bonding interaction is not purely electrostatic.The repulsion and dispersion in non-bonding interactions should not be neglected,which make important contribution to the location with minimum interaction of X,at center or off center.Some rules about the variations of interactions with atomic radii have been ob
Spin Diffusion in Trapped Clouds of Cold Atoms with Resonant Interactions
DEFF Research Database (Denmark)
Bruun, Georg; Pethick, Christhopher
2011-01-01
We show that puzzling recent experimental results on spin diffusion in a strongly interacting atomic gas may be understood in terms of the predicted spin diffusion coefficient for a generic strongly interacting system. Three important features play a central role: (a) Fick’s law for diffusion must...
The Multiphoton Interaction of Lambda Model Atom and Two-Mode Fields
Liu, Tang-Kun
1996-01-01
The system of two-mode fields interacting with atom by means of multiphotons is addressed, and the non-classical statistic quality of two-mode fields with interaction is discussed. Through mathematical calculation, some new rules of non-classical effects of two-mode fields which evolue with time, are established.
van Hoogmoed, CG; Dijkstra, RJB; van der Mei, HC; Busscher, HJ
Although interactive forces, influenced by environmental conditions, between oral bacteria and tooth surfaces are important for the development of plaque, they have never been estimated. It is hypothesized that interactive forces, as measured by atomic force microscopy, between enamel with or
Strong spin-orbit interaction of light on the surface of atomically thin crystals
Liu, Mengxia; Cai, Liang; Chen, Shizhen; Liu, Yachao; Luo, Hailu; Wen, Shuangchun
2017-06-01
The photonic spin Hall effect (SHE) can be regarded as a direct optical analogy of the SHE in electronic systems where a refractive index gradient plays the role of an electric potential. However, it has been demonstrated that the effective refractive index fails to adequately explain the light-matter interaction in atomically thin crystals. In this paper, we examine the spin-orbit interaction on the surface of the freestanding atomically thin crystals. We find that it is not necessary to involve the effective refractive index to describe the spin-orbit interaction and the photonic SHE in the atomically thin crystals. The strong spin-orbit interaction and giant photonic SHE are predicted, which can be explained as the large polarization rotation of plane-wave components in order to satisfy the transversality of photon polarization.
Long-range interactions between the alkali-metal atoms and alkaline earth ions
Kaur, Jasmeet; Arora, Bindiya; Sahoo, B K
2014-01-01
Accurate knowledge of interaction potentials among the alkali atoms and alkaline earth ions is very useful in the studies of cold atom physics. Here we carry out theoretical studies of the long-range interactions among the Li, Na, K, and Rb alkali atoms with the Ca$^+$, Ba$^+$, Sr$^+$, and Ra$^+$ alkaline earth ions systematically which are largely motivated by their importance in a number of applications. These interactions are expressed as a power series in the inverse of the internuclear separation $R$. Both the dispersion and induction components of these interactions are determined accurately from the algebraic coefficients corresponding to each power combination in the series. Ultimately, these coefficients are expressed in terms of the electric multipole polarizabilities of the above mentioned systems which are calculated using the matrix elements obtained from a relativistic coupled-cluster method and core contributions to these quantities from the random phase approximation. We also compare our estim...
Maxwell, Peter I; Popelier, Paul L A
2017-11-05
Accurate description of the intrinsic preferences of amino acids is important to consider when developing a biomolecular force field. In this study, we use a modern energy partitioning approach called Interacting Quantum Atoms to inspect the cause of the φ and ψ torsional preferences of three dipeptides (Gly, Val, and Ile). Repeating energy trends at each of the molecular, functional group, and atomic levels are observed across both (1) the three amino acids and (2) the φ/ψ scans in Ramachandran plots. At the molecular level, it is surprisingly electrostatic destabilization that causes the high-energy regions in the Ramachandran plot, not molecular steric hindrance (related to the intra-atomic energy). At the functional group and atomic levels, the importance of key peptide atoms (Oi-1 , Ci , Ni , Ni+1 ) and some sidechain hydrogen atoms (Hγ ) are identified as responsible for the destabilization seen in the energetically disfavored Ramachandran regions. Consistently, the Oi-1 atoms are particularly important for the explanation of dipeptide intrinsic behavior, where electrostatic and steric destabilization unusually complement one another. The findings suggest that, at least for these dipeptides, it is the peptide group atoms that dominate the intrinsic behavior, more so than the sidechain atoms. © 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc. © 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.
Expectations of two-level telegraph noise
Fern, J
2006-01-01
We find expectation values of functions of time integrated two-level telegraph noise. Expectation values of this noise are evaluated under simple control pulses. Both the Gaussian limit and $1/f$ noise are considered. We apply the results to a specific superconducting quantum computing example, which illustrates the use of this technique for calculating error probabilities.
Singh, Sukhjit; Sahoo, B K; Arora, Bindiya
2016-01-01
We report the dispersion coefficients for the interacting inert gas atoms with the alkali ions, alkaline earth ions and alkali atoms with their singly charged ions. We use our relativistic coupled-cluster method to determine dynamic dipole and quadrupole polarizabilities of the alkali atoms and singly ionized alkaline earth atoms, whereas a relativistic random phase approximation approach has been adopted to evaluate these quantities for the closed-shell configured inert gas atoms and the singly and doubly ionized alkali and alkaline earth atoms, respectively. Accuracies of these results are adjudged from the comparison of their static polarizability values with their respective experimental results. These polarizabilities are further compared with the other theoretical results. Reason for the improvement in the accuracies of our estimated dispersion coefficients than the data listed in [At. Data and Nucl. Data Tables 101, 58 (2015)] are discussed. Results for some of the atom-ion interacting systems were not...
On the interaction between radiation-induced defects and foreign interstitial atoms in {alpha}-iron
Energy Technology Data Exchange (ETDEWEB)
Nikolaev, Alexander L., E-mail: nikolaev@imp.uran.ru [Institute of Metal Physics, Russian Academy of Sciences Ural Branch 18, S. Kovalevskaya St., Ekaterinburg 620990 (Russian Federation); Kurennykh, Tatiana E. [Institute of Metal Physics, Russian Academy of Sciences Ural Branch 18, S. Kovalevskaya St., Ekaterinburg 620990 (Russian Federation)
2011-07-31
Interaction between Frenkel pair (FP) defects and nitrogen atoms in {alpha}-iron has been investigated by means of resistivity recovery method. Both FP defects are attracted to nitrogen atoms. Dissociation of self-interstitial atoms from nitrogen atoms is observed at 165 K while that of vacancies at 250 K. The binding energies of FP defects with nitrogen are both about 0.1-0.15 eV. A weak RR stage is observed at 340 K assigned to the presence of carbon in concentration of about 1 appm. Analysis of its features leads to a conclusion on a dissociation (binding) energy of vacancy-carbon atom pairs of about 0.9 (0.35) eV.
Interactions between C and Cu atoms in single-layer graphene: direct observation and modelling.
Kano, Emi; Hashimoto, Ayako; Kaneko, Tomoaki; Tajima, Nobuo; Ohno, Takahisa; Takeguchi, Masaki
2016-01-07
Metal doping into the graphene lattice has been studied recently to develop novel nanoelectronic devices and to gain an understanding of the catalytic activities of metals in nanocarbon structures. Here we report the direct observation of interactions between Cu atoms and single-layer graphene by transmission electron microscopy. We document stable configurations of Cu atoms in the graphene sheet and unique transformations of graphene promoted by Cu atoms. First-principles calculations based on density functional theory reveal a reduction of energy barrier that caused rotation of C-C bonds near Cu atoms. We discuss two driving forces, electron irradiation and in situ heating, and conclude that the observed transformations were mainly promoted by electron irradiation. Our results suggest that individual Cu atoms can promote reconstruction of single-layer graphene.
Berkout, Vadym D; Doroshenko, Vladimir M
2008-12-01
Fragmentation of phosphorylated peptide ions via interaction with electronically excited metastable argon atoms was studied in a linear trap - time-of-flight mass spectrometer. Doubly charged ions of phosphorylated peptides from an Enolase digest were produced by electrospray ionization and subjected to a metastable atom beam in the linear trap. The metastable argon atoms were generated using a glow-discharge source. An intensive series of c- and z- ions were observed in all cases, with the phosphorylation group intact. The formation of molecular radical cations with reduced charge indicated that an electron transfer from a highly excited metastable state of argon to the peptide cation occurred. Additionally, singly charged Bradykinin, Substance P and Fibrinopeptide A molecular ions were fragmented via interaction with electronically excited metastable helium atoms. The fragmentation mechanism was different in this case and involved Penning ionization.
Long-range interactions between excited helium and alkali-metal atoms
Zhang, J.-Y.
2012-12-03
The dispersion coefficients for the long-range interaction of the first four excited states of He, i.e., He(2 1,3S) and He(2 1,3P), with the low-lying states of the alkali-metal atoms Li, Na, K, and Rb are calculated by summing over the reduced matrix elements of the multipole transition operators. For the interaction between He and Li the uncertainty of the calculations is 0.1–0.5%. For interactions with other alkali-metal atoms the uncertainty is 1–3% in the coefficient C5, 1–5% in the coefficient C6, and 1–10% in the coefficients C8 and C10. The dispersion coefficients Cn for the interaction of He(2 1,3S) and He(2 1,3P) with the ground-state alkali-metal atoms and for the interaction of He(2 1,3S) with the alkali-metal atoms in their first 2P states are presented in this Brief Report. The coefficients for other pairs of atomic states are listed in the Supplemental Material.
Topcu, Turker
2015-01-01
We investigate the effect of series perturbation on the second order dipole-dipole interactions between strontium atoms in $5sns({^1}S_0)$ and $5snp({^1}P_1)$ Rydberg states as a means of engineering long-range interactions between atoms in a way that gives an exceptional level of control over the strength and the sign of the interaction by changing $n$. We utilize experimentally available data to estimate the importance of perturber states at low $n$, and find that van der Waals interaction between two strontium atoms in the $5snp({^1}P_1)$ states shows strong peaks outside the usual hydrogenic $n^{11}$ scaling. We identify this to be the result of the perturbation of $5snd({^1}D_2)$ intermediate states by the $4d^2({^1}D_2)$ and $4dn's({^1}D_2)$ states in the $n<20$ range. This demonstrates that divalent atoms in general present a unique advantage for creating substantially stronger or weaker interaction strengths than those can be achieved using alkali metal atoms due to their highly perturbed spectra t...
Improved limits on interactions of low-mass spin-0 dark matter from atomic clock spectroscopy
Stadnik, Y. V.; Flambaum, V. V.
2016-08-01
Low-mass (sub-eV) spin-0 dark matter particles, which form a coherently oscillating classical field ϕ =ϕ0cos(mϕt ) , can induce oscillating variations in the fundamental constants through their interactions with the standard model sector. We calculate the effects of such possible interactions, which may include the linear interaction of ϕ with the Higgs boson, on atomic and molecular transitions. Using recent atomic clock spectroscopy measurements, we derive limits on the linear interaction of ϕ with the Higgs boson, as well as its quadratic interactions with the photon and light quarks. For the linear interaction of ϕ with the Higgs boson, our derived limits improve on existing constraints by up to 2-3 orders of magnitude.
Improved limits on interactions of low-mass spin-0 dark matter from atomic clock spectroscopy
Stadnik, Y V
2016-01-01
Low-mass (sub-eV) spin-0 dark matter particles, which form a coherently oscillating classical field $\\phi = \\phi_0 \\cos(m_\\phi t)$, can induce oscillating variations in the fundamental constants through their interactions with the Standard Model sector. We calculate the effects of such possible interactions, which may include the linear interaction of $\\phi$ with the Higgs boson, on atomic and molecular transitions. Using recent atomic clock spectroscopy measurements, we derive new limits on the linear interaction of $\\phi$ with the Higgs boson, as well as its quadratic interactions with the photon and light quarks. For the linear interaction of $\\phi$ with the Higgs boson, our derived limits improve on existing constraints by up to $2-3$ orders of magnitude.
Modelling laser-atom interactions in the strong field regime
Galstyan, A; Mota-Furtado, F; O'Mahony, P F; Janssens, N; Jenkins, S D; Chuluunbaatar, O; Piraux, B
2016-01-01
We consider the ionisation of atomic hydrogen by a strong infrared field. We extend and study in more depth an existing semi-analytical model. Starting from the time-dependent Schroedinger equation in momentum space and in the velocity gauge we substitute the kernel of the non-local Coulomb potential by a sum of N separable potentials, each of them supporting one hydrogen bound state. This leads to a set of N coupled one-dimensional linear Volterra integral equations to solve. We analyze the gauge problem for the model, the different ways of generating the separable potentials and establish a clear link with the strong field approximation which turns out to be a limiting case of the present model. We calculate electron energy spectra as well as the time evolution of electron wave packets in momentum space. We compare and discuss the results obtained with the model and with the strong field approximation and examine in this context, the role of excited states.
Classical-field description of the quantum effects in the light-atom interaction
Rashkovskiy, Sergey A
2016-01-01
In this paper I show that light-atom interaction can be described using purely classical field theory without any quantization. In particular, atom excitation by light that accounts for damping due to spontaneous emission is fully described in the framework of classical field theory. I show that three well-known laws of the photoelectric effect can also be derived and that all of its basic properties can be described within classical field theory.
Tuning Casimir-Polder interactions in atom-metamaterial hybrid devices
Chan, Eng Aik; Adamo, Giorgio; Laliotis, Athanasios; Ducloy, Martial; Wilkowski, David
2016-01-01
We report on the coupling of a surface plasmonic mode with a thermal vapor of cesium atoms. The plasmonic resonance is created using a nano-structured metallic surface. By changing the geometrical properties of the metamaterial, we tune the plasmonic resonance wavelength with respect to the D2 line of cesium. When the two resonances are close, we observe a strong modification of the Casimir-Polder interaction accompanied by a change of the atomic lifetime. A proper tuning leads to an almost suppression of the frequency shift of the cesium transition. This result paves the way for precision atomic spectroscopy in the vicinity of a material surface.
Periodic trends governing the interactions between impurity atoms [H-Ar] and (alpha)-U
Energy Technology Data Exchange (ETDEWEB)
Taylor, Christopher David [Los Alamos National Laboratory
2008-01-01
The binding energies, geometries, charges and electronic structures of a series of impurity atoms [H-Ar] interacting with the {alpha}-U lattice in various configurations were assessed by means of density functional theory calculations. Periodic trends governing the binding energy were highlighted and related to the electronic properties of the impurity atoms, with some consideration given to the band-structure of {alpha}-U. The strongest bound impurity atoms include [C, N, O] and [Si, P, S]. The general trends in the binding energy can be reproduced by a simple parameterisation in terms of the electronegativity (charge-transfer) and covalent radius (elasticity theory) of the impurity atom. The strongest bound atoms deviate from this model, due to their ability to bind with an optimum mixture of covalency and ionicity. This last point is evidenced by the partial overlap of the impurity atom p-band with the hybrid d-/f-band of {alpha}-U. It is expected that the trends and general behaviour reported in this work can be extended to the interactions of impurity atoms with other metallic systems.
Study of mesoscopic clouds of cold atoms in the interacting regime
Bourgain, Ronan; Fuhrmanek, Andreas; Pellegrino, Joseph; R. P Sortais, Yvan; Browaeys, Antoine
2012-06-01
We present studies on cold and dense atomic ^87Rb clouds containing N˜2-100 interacting atoms. We produced such mesoscopic ensembles by loading a microscopic optical dipole trap from a MOT. Due to 2-body light-assisted collisions, we have found that in steady state such ensembles exhibit reduced number fluctuations with respect to a Poisson distribution. For N >=2, we measured a reduction Fano factor F=0.72±0.07 consistent with the value F=3/4 predicted at large N by a general stochastic model [1,2]. To enhance interactions between the atoms, we are following two tracks. Firstly we evaporatively cooled a few hundreds of trapped atoms and obtained ˜10 atoms close to quantum degeneracy (nλdB^3˜1) in the microscopic trap. In this regime s-wave interactions dominate (n=2 10^14 at.cm-3). Secondly we sent near resonant light (λp) on the small cloud (size l). When lGrangier, A. Browaeys, Phys. Rev. A 82, 023623 (2010).[0pt] [2] Y.R.P. Sortais, A. Fuhrmanek, R. Bourgain, A. Browaeys, ``Sub-Poissonian atom number fluctuations using light-assisted collisions,'' arXiv:1111.5203 (2011).
Yu, Yue; Luo, Zhuxi; Wang, Ziqiang
2014-07-30
We show that the dipole-dipole coupling between Wannier modes in cigar-shaped Bose-Einstein condensates (BECs) is significantly enhanced while the short-range coupling is strongly suppressed. As a result, the dipole-dipole interaction can become the dominant interaction between ultracold alkali Bose atoms. In the long length limit of a cigar-shaped BEC, the resulting effective one-dimensional models possess an effective inverse squared interacting potential, the Calogero-Sutherland potential, which plays a fundamental role in many fields of contemporary physics; but its direct experimental realization has been a challenge for a long time. We propose to realize the Calogero-Sutherland model in ultracold alkali Bose atoms and study the effects of the dipole-dipole interaction.
Institute of Scientific and Technical Information of China (English)
王中结; 陆同兴; 路轶群
2001-01-01
In this paper the model of two-level atomic momentum spread in amplitude- and phase-modulated standing light wave was investigated. this is a nonlinear quantum pendulum driven by a time-dependent perterbation with two frequencies. This system shows chaotic behaviour in the classical limit. The system exists the characteristic of dynamical localization for the same parameters as that in the classical model correspoinding to it. Localization length of the system with two incommensurate perturbing frequency is much larger than that of the system with one perturbing frequency.%分析了二能级原子在振幅相位调制驻波场作用下动量扩散模型，这是一个双频参数激励的非线性量子单摆模型。这个系统在经典极限下表现混沌行为，在相同参数条件下，这个系统具有动力学局域特征，具有两个不可约频率扰动的系统的局域长度要比单个频率扰动时大得多。
Institute of Scientific and Technical Information of China (English)
Shao Xiao-Qiang; Chen Li; Zhang Shou
2009-01-01
This paper proposes two schemes for implementing three-qubit Toffoli gate with an atom (as target qubit) sent through a two-mode cavity (as control qubits). The first scheme is based on the large-detuning atom-cavity field interaction and the second scheme is based on the resonant atom-field interaction. Both the situations with and without cavity decay and atomic spontaneous emission are considered. The advantages and the experimental feasibility of these two schemes are discussed.
Two-Level Semantics and Abstract Interpretation
DEFF Research Database (Denmark)
Nielson, Flemming
1989-01-01
Two-level semantics is a variant of Scott/Strachey denotational semantics in which the concept of binding time is treated explicitly. This is done by formally distinguishing between those computations that take place at run-time and those that take place at compile-time. Abstract interpretation...... is concerned with the (preferably automatic) analysis of programs. The main purpose of these analyses is to find information that may assist in the efficient implementation of the programs. Abstract interpretation is thus related to data flow analysis, partial evaluation and other program analysis methods. Its...... unique flavour is the insistence on formal proofs of correctness and the methods used to establish these. This paper develops a theory of abstract interpretation for two-level denotational definitions. There are three ingredients in this. First a framework for proving the correctness of analyses...
Energy Technology Data Exchange (ETDEWEB)
Liu, S.M.; Rodgers, W.E.; Knuth, E.L.
1975-06-01
Interactions of satellite-speed helium atoms with practical satellite surfaces were investigated experimentally, and spatial distributions of satellite-speed helium beams scattered from four different engineering surfaces were measured. The 7000-m/s helium beams were produced using an arc-heated supersonic molecular beam source. The test surfaces included cleaned 6061-T6 aluminum plate, anodized aluminum foil, white paint, and quartz surfaces. Both in-plane (in the plane containing the incident beam and the surface normal) and out-of-plane spatial distributions of reflected helium atoms were measured for six different incidence angles (0, 15, 30, 45, 60, and 75 deg from the surface normal). It was found that a large fraction of the incident helium atoms were scattered back in the vicinity of the incoming beam, particularly in the case of glancing incidence angles. This unexpected scattering feature results perhaps from the gross roughness of these test surfaces. This prominent backscattering could yield drag coefficients which are higher than for surfaces with either forward-lobed or diffusive (cosine) scattering patterns. (auth)
Atoms and Forces of Interaction Between Elementary Particles in the Expanding Universe
Gorbatenko, M V
2011-01-01
The earlier developed algorithm for constructing a self-conjugate Hamiltonian in the representation for Dirac particles interacting with a general gravitational field is extended to the case of electromagnetic fields. This Hamiltonian is applied to the case when the gravitational field describes the spatially flat Friedmann model, and the electromagnetic field is the Coulomb potential extended to the case of this model. The analysis of atomic systems and electromagnetic forces of interaction under the conditions of spatially flat expansion of the universe has demonstrated that the system of atomic levels does not change with cosmological time. Spectral lines of atoms in the spatially flat Friedmann model are identical at different points of cosmological time. In this case the redshift is stipulated entirely by the growth of wavelength of photons at movement in the expending universe. At the same time force of interaction between elementary particles can change with expansion of the universe.
Dispersion coefficients for the interaction of Cs atom with different material media
Kaur, Kiranpreet; Kaur, Jasmeet; Sahoo, B. K.; Arora, Bindiya
2016-10-01
Motivated by a large number of applications, the dispersion (C3) coefficients for the interaction of a Cs atom with different material media such as Au (metal), Si (semiconductor) and various dielectric surfaces like vitreous SiO2, SiNx, sapphire and YAG are determined using accurate values of the dynamic polarizabilities of the Cs atom obtained employing the relativistic coupled-cluster approach and the dynamic dielectric constants of the walls. Moreover, we also give the retardation function in the graphical representation as functions of separation distances to describe the interaction potentials between the Cs atom with the above considered material media. For the easy access to the interaction potentials at a given distance of separation, we give a simple working functional fitting form for the retardation functions in terms of four fitting parameters that are quoted for the respective medium.
Stable BLOCH oscillations of cold atoms with time-dependent interaction.
Gaul, C; Lima, R P A; Díaz, E; Müller, C A; Domínguez-Adame, F
2009-06-26
We investigate Bloch oscillations of interacting cold atoms in a mean-field framework. In general, atom-atom interaction causes dephasing and destroys Bloch oscillations. Here we show that Bloch oscillations are persistent if the interaction is modulated harmonically with suitable frequency and phase. For other modulations, Bloch oscillations are rapidly damped. We explain this behavior in terms of collective coordinates whose Hamiltonian dynamics permits one to predict a whole family of stable solutions. In order to describe also the unstable cases, we carry out a stability analysis for Bogoliubov excitations. Using Floquet theory, we are able to predict the unstable modes as well as their growth rate, found to be in excellent agreement with numerical simulations.
The two-atom Jaynes-Cummings model's dynamic properties
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The model of two two-level atoms interact with a single-mode cavity was investigated. The formulation of the time evolution operator for the two-atom Jaynes-Cummings model is pressented by the bare-states approach. Besides, the time evolution of the two-atom common population probabilities is studied, and some novel features are obtained.
Hernandez, R A Vargas
2015-01-01
We show that Zeeman excitations in an ensemble of highly magnetic atoms trapped in an optical lattice lead to interacting Frenkel excitons described by a tunable $t$-$V$ model. The dispersion of the excitons and the interactions between excitons can be tuned in a wide range by transferring atoms to different Zeeman states. We show that these parameters are insensitive to an external magnetic field, which leads to an interesting possibility of engineering lattice models with significant particle-non-conserving terms. We consider the coupling of the Zeeman excitations to the translational motion of atoms in the lattice and show that the resulting Hamiltonian is equivalent to a polaron Hamiltonian, where the mathematical form of the particle - phonon interaction can be tuned by transferring atoms to different Zeeman states. We calculate the model parameters for the specific system of Dy atoms on an optical lattice with the lattice site separation 266 nm and show that the exciton interaction parameters can be tun...
Quantum logic gates with two-level trapped ions beyond Lamb-Dicke limit
Institute of Scientific and Technical Information of China (English)
Zheng Xiao-Juan; Luo Yi-Min; Cai Jian-Wu
2009-01-01
In the system with two two-level ions confined in a linear trap,this paper presents a simple scheme to realize the quantum phase gate(QPG)and the swap gate beyond the Lamb-Dicke(LD)limit.These two-qubit quantum logic gates only involve the internal states of two trapped ions.The scheme does not use the vibrational mode as the data bus and only requires a single resonant interaction of the ions with the lasers.Neither the LD approximation nor the auxiliary atomic level is needed in the proposed scheme.Thus the scheme is simple and the interaction time is very short,which is important in view of decoherence.The experimental feasibility for achieving this scheme is also discussed.
Institute of Scientific and Technical Information of China (English)
ZHANG Cai-hua; Sachuerfu; Gerile
2011-01-01
The field entropy of the system with two moving atoms interacting with the coherent state is investigated by means of the full quantum theory.Under the different initial states with two atoms,the influences of the light field intensity and the atomic motion on the field entropy are discussed.The results indicate that the motion of the atoms leads to strict periodicity in the field entropy evolution.When the two atoms are in the Bell state initially,the system is in a completely disentangled state.For the atoms initially at other Bell states,the field periodically entangles with the atoms.
Hochstuhl, David
2012-01-01
We introduce the time-dependent restricted active space Configuration Interaction method to solve the time-dependent Schr\\"odinger equation for many-electron atoms, and particularly apply it to the treatment of photoionization processes in atoms. The method is presented in a very general formulation and incorporates a wide range of commonly used approximation schemes, like the single-active electron approximation, time-dependent Configuration Interaction with single-excitations, or the time-dependent R-matrix method. We proof the applicability of the method by calculating the photoionization cross sections of Helium and Beryllium.
Model for Interaction Between Photon and Cold Atom in QED Cavity
Institute of Scientific and Technical Information of China (English)
ZHANG Li; WANG Cheng; LI Yan-Min; RUAN Sheng-Ping; XUAN Li
2004-01-01
A model has been established for the interaction between a single-mode optical field and a 2-energy-level cold atom with exact analytic solutions given. The processes of momentum and energy exchanges between the optical field and the cold atom due to the interaction between them are discussed in detail, and a formula has been given for the variation of momentum and energy exchange volumes with time t in dress state while both the effects of photon recoil and Doppler effect are taken into consideration.
Institute of Scientific and Technical Information of China (English)
GU Xiao-Yan; CHEN Chang-Yong; SUN Jian-Qiang
2008-01-01
We propose a potentially practical scheme to implement an approximate three-qubit Toffoli gate by a single resonant interaction in dissipative cavity QED in which the cavity mode decay and atomic spontaneous emission are considered. The scheme does not require two-qubit controlled-NOT gates but uses a three-qubit phase gate and two Hadamard gates, where the approximate phase gate can be implemented by only a single dissipative resonant interaction of atoms with the cavity mode. Discussions are made for the advantages and the experimental feasibility of our scheme.
Wang, Shuai; Takahashi, Keisuke; Hashimoto, Naoyuki; Isobe, Shigehito; Ohnuki, Somei
2013-01-01
Effect of hydrogen in body-centered cubic iron is explored by using the density function theory. Hydrogen atoms increase the concentration of free electrons in the simulation cell and have bonding interaction with Fe atom. Caused by anisotropic strain components of hydrogen atoms in the tetrahedral sites, elastic interaction for hydrogen with screw dislocation has been found. The dependence of hydrogen-screw dislocation interaction on hydrogen concentration is confirmed by repeated stress rel...
Study of the scalar-pseudoscalar interaction in the francium atom
Skripnikov, L V; Mosyagin, N S
2016-01-01
Fr atom can be successively used to search for the atomic permanent electric dipole moment (EDM) [Hyperfine Interactions 236, 53 (2015); Journal of Physics: Conference Series 691, 012017 (2016)]. It can be induced by the permanent electron EDM predicted by modern extensions of the standard model to be nonzero at the level accessible by the new generation of EDM experiments. We consider another mechanism of the atomic EDM generation in Fr. This is caused by the scalar-pseudoscalar nucleus-electron neutral current interaction with the dimensionless strength constant, $k_{T,P}$. Similar to the electron EDM this interaction violates both spatial parity and time-reversal symmetries and can also induce permanent atomic EDM. It was shown in [Phys. Rev. D 89, 056006 (2014)] that the scalar-pseudoscalar contribution to the atomic EDM can dominate over the direct contribution from the electron EDM within the standard model. We report high-accuracy combined all-electron and two-step relativistic coupled cluster treatmen...
Competition between finite-size effects and dipole-dipole interactions in few-atom systems
Damanet, François; Martin, John
2016-11-01
In this paper, we study the competition between finite-size effects (i.e. discernibility of particles) and dipole-dipole interactions in few-atom systems coupled to the electromagnetic field in vacuum. We consider two hallmarks of cooperative effects, superradiance and subradiance, and compute for each the rate of energy radiated by the atoms and the coherence of the atomic state during the time evolution. We adopt a statistical approach in order to extract the typical behaviour of the atomic dynamics and average over random atomic distributions in spherical containers with prescribed {k}0R with k 0 the radiation wavenumber and R the average interatomic distance. Our approach allows us to highlight the tradeoff between finite-size effects and dipole-dipole interactions in superradiance/subradiance. In particular, we show the existence of an optimal value of {k}0R for which the superradiant intensity and coherence pulses are the less affected by dephasing effects induced by dipole-dipole interactions and finite-size effects.
Interaction of epitaxial silicene with overlayers formed by exposure to Al atoms and O2 molecules.
Friedlein, R; Van Bui, H; Wiggers, F B; Yamada-Takamura, Y; Kovalgin, A Y; de Jong, M P
2014-05-28
As silicene is not chemically inert, the study and exploitation of its electronic properties outside of ultrahigh vacuum environments require the use of insulating capping layers. In order to understand if aluminum oxide might be a suitable encapsulation material, we used high-resolution synchrotron photoelectron spectroscopy to study the interactions of Al atoms and O2 molecules, as well as the combination of both, with epitaxial silicene on thin ZrB2(0001) films grown on Si(111). The deposition of Al atoms onto silicene, up to the coverage of about 0.4 Al per Si atoms, has little effect on the chemical state of the Si atoms. The silicene-terminated surface is also hardly affected by exposure to O2 gas, up to a dose of 4500 L. In contrast, when Al-covered silicene is exposed to the same dose, a large fraction of the Si atoms becomes oxidized. This is attributed to dissociative chemisorption of O2 molecules by Al atoms at the surface, producing reactive atomic oxygen species that cause the oxidation. It is concluded that aluminum oxide overlayers prepared in this fashion are not suitable for encapsulation since they do not prevent but actually enhance the degradation of silicene.
Interaction of laser-cooled 87Rb atoms with higher order modes of an optical nanofibre
Kumar, Ravi; Gokhroo, Vandna; Deasy, Kieran; Maimaiti, Aili; Frawley, Mary C.; Phelan, Ciarán; Chormaic, Síle Nic
2015-01-01
Optical nanofibres are used to confine light to sub-wavelength regions and are very promising tools for the development of optical fibre-based quantum networks using cold, neutral atoms. To date, experimental studies on atoms near nanofibres have focussed on fundamental fibre mode interactions. In this work, we demonstrate the integration of a few-mode optical nanofibre into a magneto-optical trap for 87Rb atoms. The nanofibre, with a waist diameter of ∼700 nm, supports both the fundamental and first group of higher order modes (HOMs) and is used for atomic fluorescence and absorption studies. In general, light propagating in higher order fibre modes has a greater evanescent field extension around the waist in comparison with the fundamental mode. By exploiting this behaviour, we demonstrate that the detected signal of fluorescent photons emitted from a cloud of cold atoms centred at the nanofibre waist is larger if HOMs are also included. In particular, the signal from HOMs appears to be about six times larger than that obtained for the fundamental mode. Absorption of on-resonance, HOM probe light by the laser-cooled atoms is also observed. These advances should facilitate the realization of atom trapping schemes based on HOM interference.
Interaction and dynamics of add-atoms with 2-dimensional structures
The interaction and dynamics of add-atoms with graphene, graphene-derivate structures and, later, MoSi$_2$, two-dimensional – single and few – atomic layers will be studied with the Perturbed Angular Correlation – PAC – technique. Graphene is also envisaged as new platform for growing semiconductor nanostructure devices, such as quantum dots and as a particularly powerful catalyst. Understanding nucleation of nanostructures and clusters on graphene and related phases in wet conditions as they are used in chemical methods in research and industry require complementary studies. These systems will therefore be studied systematically using radioactive probe atoms attaching via a transfer media (e.g., water in catalysis process) or being deposited with soft-landing techniques under vacuum and UHV conditions, as put in place at the ASPIC setup at ISOLDE. The hyperfine fields obtained under different environments are expected to reveal basic information on the rich atomic and physical mechanisms associated w...
Nonlinear Zeno dynamics due to atomic interactions in Bose–Einstein condensate
Energy Technology Data Exchange (ETDEWEB)
Navarro, V.G.; Shchesnovich, V.S., E-mail: valery@ufabc.edu.br
2014-12-01
We show that nonlinear interactions induce both the Zeno and anti-Zeno effects in the generalized Bose–Josephson model (with the on-site interactions and the second-order tunneling) describing Bose–Einstein condensate in double-well trap subject to particle removal from one of the wells. We find that the on-site interactions induce only the Zeno effect, which appears at long evolution times, whereas the second-order tunneling leads to a strong decay of the atomic population at short evolution times, reminiscent of the anti-Zeno effect, and destroys the nonlinear Zeno effect due to the on-site interactions at long times.
Atomic Oxygen Interactions With Silicone Contamination on Spacecraft in Low Earth Orbit Studied
Banks, Bruce A.
2001-01-01
Silicones have been widely used on spacecraft as potting compounds, adhesives, seals, gaskets, hydrophobic surfaces, and atomic oxygen protective coatings. Contamination of optical and thermal control surfaces on spacecraft in low Earth orbit (LEO) has been an ever-present problem as a result of the interaction of atomic oxygen with volatile species from silicones and hydrocarbons onboard spacecraft. These interactions can deposit a contaminant that is a risk to spacecraft performance because it can form an optically absorbing film on the surfaces of Sun sensors, star trackers, or optical components or can increase the solar absorptance of thermal control surfaces. The transmittance, absorptance, and reflectance of such contaminant films seem to vary widely from very transparent SiOx films to much more absorbing SiOx-based films that contain hydrocarbons. At the NASA Glenn Research Center, silicone contamination that was oxidized by atomic oxygen has been examined from LEO spacecraft (including the Long Duration Exposure Facility and the Mir space station solar arrays) and from ground laboratory LEO simulations. The findings resulted in the development of predictive models that may help explain the underlying issues and effects. Atomic oxygen interactions with silicone volatiles and mixtures of silicone and hydrocarbon volatiles produce glassy SiOx-based contaminant coatings. The addition of hydrocarbon volatiles in the presence of silicone volatiles appears to cause much more absorbing (and consequently less transmitting) contaminant films than when no hydrocarbon volatiles are present. On the basis of the LDEF and Mir results, conditions of high atomic oxygen flux relative to low contaminant flux appear to result in more transparent contaminant films than do conditions of low atomic oxygen flux with high contaminant flux. Modeling predictions indicate that the deposition of contaminant films early in a LEO flight should depend much more on atomic oxygen flux than
Far-field resonance fluorescence from a dipole-interacting laser-driven cold atomic gas
Jones, Ryan; Saint, Reece; Olmos, Beatriz
2017-01-01
We analyze the temporal response of the fluorescence light that is emitted from a dense gas of cold atoms driven by a laser. When the average interatomic distance is comparable to the wavelength of the photons scattered by the atoms, the system exhibits strong dipolar interactions and collective dissipation. We solve the exact dynamics of small systems with different geometries and show how these collective features are manifest in the scattered light properties such as the photon emission rate, the power spectrum and the second-order correlation function. By calculating these quantities beyond the weak (linear) driving limit, we make progress in understanding the signatures of collective behavior in these many-body systems. Furthermore, we shed light on the role of disorder and averaging on the resonance fluorescence, of direct relevance for recent experimental efforts that aim at the exploration of many-body effects in dipole-dipole interacting gases of atoms.
Quantum computing with atomic qubits and Rydberg interactions: Progress and challenges
Saffman, Mark
2016-01-01
We present a review of quantum computation with neutral atom qubits. After an overview of architectural options we examine Rydberg mediated gate protocols and fidelity for two- and multi-qubit interactions. We conclude with a summary of the current status and give an outlook for future progress.
Dispersion Interactions between Rare Gas Atoms: Testing the London Equation Using ab Initio Methods
Halpern, Arthur M.
2011-01-01
A computational chemistry experiment is described in which students can use advanced ab initio quantum mechanical methods to test the ability of the London equation to account quantitatively for the attractive (dispersion) interactions between rare gas atoms. Using readily available electronic structure applications, students can calculate the…
Lisowski, W.; Keim, E.G.; Berg, van den A.H.J.; Smithers, M.A.
2005-01-01
The interaction of atomic (D) and molecular (D2) deuterium, as present in a (D + D2) gas mixture, with single-wall carbon nanotubes (SWNTs) has been studied by means of a combination of scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The SWNT samp
Fundamental symmetries and interactions studied with radioactive isotopes in atom traps
Wilschut, H.W.E.M.; Gacsi, Z; Dombradi, Z; Krasznahorkay, A
2005-01-01
The structure of certain nuclei and atoms allow one to study fundamental symmetries and interactions. In this review we consider the search for Time-Reversal invariance Violation (TRV). We consider two options: TRV in beta decay or the search for the forbidden Electric Dipole Moment (EDM). In both c
Influence of atomic force microscope tip-sample interaction on the study of scaling behavior
Aue, J.; de Hosson, J.T.M.
1997-01-01
Images acquired with atomic force microscopy are based on tip-sample interaction. It is shown that using scanning probe techniques for determining scaling parameters of a surface leads to an underestimate of the actual scaling dimension, due to the dilation of tip and surface. How much we underestim
Quantum Statistical Properties of Binomial Field Interacting with Two Entangled Atoms
Institute of Scientific and Technical Information of China (English)
JIAO Zhi-Yong; MA Jun-Mao; SHANG Yong-Tao; LI Ning; FU Xia
2008-01-01
Quantum statistical properties of the binomial field interacting with the two entangled atoms are investi-gated for the different initial conditions. It is found that the sub-Poissonian distribution and the antibunching effect can be presented for the certain ranges of the involved parameters.
Energy Technology Data Exchange (ETDEWEB)
Benmore, C.J.; Egelstaff, P.A. [Guelph Univ., ON (Canada). Dept. of Physics; Formisano, F.; Barocchi, F. [Dipartimento di Fisica, Universita di Firenze, largo E.Fermi 2, 50125 Firenze (Italy)]|[Istituto Nazionale di Fisica della Materia, Unita di ricerca di Firenze, largo E.Fermi 2, 50125 Firenze (Italy); Magli, R. [Istituto Nazionale di Fisica della Materia, Unita di ricerca di Firenze, largo E.Fermi 2, 50125 Firenze (Italy)]|[Dipartimento di Energetica ``S.Stecco``, Universita di Firenze, via di S.Marta 3, 50139 Firenze (Italy); Bafile, U. [Istituto di Elettronica Quantistica, Consiglio Nazionale delle Ricerche, via Panciatichi 56/30, Firenze 50127 (Italy); Robinson, R.A. [Los Alamos National Laboratory, LANSCE, Los Alamos, NM 87545 (United States); Verkerk, P. [Interfacultair Reactor Instituut, Technische Universiteit Delft, Mekelweg 15, 2629 JB Delft (Netherlands)
1997-06-01
The first direct determination of the London dispersive contribution to the long-range interaction energy of pairs of krypton atoms is discussed. The result, obtained using a SANS technique, is in good agreement with previous estimates present in literature. (orig.).
Coherent Atom-Phonon Interaction through Mode Field Coupling in Hybrid Optomechanical Systems
Cotrufo, Michele; Verhagen, Ewold
2016-01-01
We propose a novel type of optomechanical coupling which enables a tripartite interaction between a quantum emitter, an optical mode and a macroscopic mechanical oscillator. The interaction uses a mechanism we term mode field coupling: mechanical displacement modifies the spatial distribution of the optical mode field, which in turn modulates the atom-photon coupling rate. In properly designed multimode optomechanical systems, we can achieve situations in which mode field coupling is the only possible interaction pathway for the system. This enables, for example, swapping of a single excitation between emitter and phonon, creation of nonclassical states of motion and mechanical ground-state cooling in the bad-cavity regime. Importantly, the emitter-phonon coupling rate can be enhanced through an optical drive field, allowing active control of strong atom-phonon coupling for realistic experimental parameters.
Precision X-ray spectroscopy of kaonic atoms as a probe of low-energy kaon-nucleus interaction
Shi, H; Beer, G; Bellotti, G; Berucci, C; Bragadireanu, A M; Bosnar, D; Cargnelli, M; Curceanu, C; Butt, A D; d'Uffizi, A; Fiorini, C; Ghio, F; Guaraldo, C; Hayano, R S; Iliescu, M; Ishiwatari, T; Iwasaki, M; Sandri, P Levi; Marton, J; Okada, S; Pietreanu, D; Piscicchia, K; Vidal, A Romero; Sbardella, E; Scordo, A; Sirghi, D L; Sirghi, F; Tatsuno, H; Doce, O Vazquez; Widmann, E; Zmeskal, J
2016-01-01
In the exotic atoms where one atomic $1s$ electron is replaced by a $K^{-}$, the strong interaction between the $K^{-}$ and the nucleus introduces an energy shift and broadening of the low-lying kaonic atomic levels which are determined by only the electromagnetic interaction. By performing X-ray spectroscopy for Z=1,2 kaonic atoms, the SIDDHARTA experiment determined with high precision the shift and width for the $1s$ state of $K^{-}p$ and the $2p$ state of kaonic helium-3 and kaonic helium-4. These results provided unique information of the kaon-nucleus interaction in the low energy limit.
Interaction of slow and highly charged ions with surfaces: formation of hollow atoms
Energy Technology Data Exchange (ETDEWEB)
Stolterfoht, N.; Grether, M.; Spieler, A.; Niemann, D. [Hahn-Meitner Institut, Berlin (Germany). Bereich Festkoerperphysik; Arnau, A.
1997-03-01
The method of Auger spectroscopy was used to study the interaction of highly charged ions with Al and C surfaces. The formation of hollow Ne atoms in the first surface layers was evaluated by means of a Density Functional theory including non-linear screening effects. The time-dependent filling of the hollow atom was determined from a cascade model yielding information about the structure of the K-Auger spectra. Variation of total intensities of the L- and K-Auger peaks were interpreted by the cascade model in terms of attenuation effects on the electrons in the solid. (author)
Dzuba, V A; Harabati, C; Flambaum, V V
2016-01-01
A version of the configuration interaction (CI) method is developed which treats highly excited many-electron basis states perturbatively, so that their inclusion does not affect the size of the CI matrix. This removes, at least in principle, the main limitation of the CI method in dealing with many-electron atoms or ions. We perform calculations of the spectra of iodine and its ions, tungsten, and ytterbium as examples of atoms with open $s$, $p$, $d$ and $f$-shells. Good agreement of the calculated data with experiment illustrates the power of the method. Its advantages and limitations are discussed.
Two-level leader-follower organization in pigeon flocks
Chen, Zhiyong; Zhang, Hai-Tao; Chen, Xi; Chen, Duxin; Zhou, Tao
2015-10-01
The most attractive trait of collective animal behavior is the emergence of highly ordered structures (Cavagna A., Giardina I. and Ginelli F., Phys. Rev. Lett., 110 (2013) 168107). It has been conjectured that the interaction mechanism in pigeon flock dynamics follows a hierarchical leader-follower influential network (Nagy M., Ákos Z., Biro D. and Vicsek T., Nature, 464 (2010) 890). In this paper, a new observation is reported that shows that pigeon flocks actually adopt a much simpler two-level interactive network composed of one leader and some followers. By statistically analyzing the same experimental dataset, we show that for a certain period of time a sole leader determines the motion of the flock while the remaining birds are all followers directly copying the leader's direction with specific time delays. This simple two-level despotic organization is expected to save both motional energy and communication cost, while retaining agility and robustness of the whole group. From an evolutionary perspective, our results suggest that a two-level organization of group flight may be more efficient than a multilevel topology for small pigeon flocks.
Engaging the Terminal: Promoting Halogen Bonding Interactions with Uranyl Oxo Atoms.
Carter, Korey P; Kalaj, Mark; Surbella, Robert G; Ducati, Lucas C; Autschbach, Jochen; Cahill, Christopher L
2017-07-13
Engaging the nominally terminal oxo atoms of the linear uranyl (UO2(2+) ) cation in non-covalent interactions represents both a significant challenge and opportunity within the field of actinide hybrid materials. An approach has been developed for promoting oxo atom participation in a range of non-covalent interactions, through judicious choice of electron donating equatorial ligands and appropriately polarizable halogen-donor atoms. As such, a family of uranyl hybrid materials was generated based on a combination of 2,5-dihalobenzoic acid and aromatic, chelating N-donor ligands. Delineation of criteria for oxo participation in halogen bonding interactions has been achieved by preparing materials containing 2,5-dichloro- (25diClBA) and 2,5-dibromobenzoic acid (25diBrBA) coupled with 2,2'-bipyridine (bipy) (1 and 2), 1,10-phenanthroline (phen) (3-5), 2,2':6',2''-terpyridine (terpy) (6-8), or 4'-chloro-2,2':6',2''-terpyridine (Cl-terpy) (9-10), which have been characterized through single crystal X-ray diffraction, Raman, Infrared (IR), and luminescence spectroscopy, as well as through density functional calculations of electrostatic potentials. Looking comprehensively, these results are compared with recently published analogues featuring 2,5-diiodobenzoic acid which indicate that although inclusion of a capping ligand in the uranyl first coordination sphere is important, it is the polarizability of the selected halogen atom that ultimately drives halogen bonding interactions with the uranyl oxo atoms. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Two-level tunneling systems in amorphous alumina
Lebedeva, Irina V.; Paz, Alejandro P.; Tokatly, Ilya V.; Rubio, Angel
2014-03-01
The decades of research on thermal properties of amorphous solids at temperatures below 1 K suggest that their anomalous behaviour can be related to quantum mechanical tunneling of atoms between two nearly equivalent states that can be described as a two-level system (TLS). This theory is also supported by recent studies on microwave spectroscopy of superconducting qubits. However, the microscopic nature of the TLS remains unknown. To identify structural motifs for TLSs in amorphous alumina we have performed extensive classical molecular dynamics simulations. Several bistable motifs with only one or two atoms jumping by considerable distance ~ 0.5 Å were found at T=25 K. Accounting for the surrounding environment relaxation was shown to be important up to distances ~ 7 Å. The energy asymmetry and barrier for the detected motifs lied in the ranges 0.5 - 2 meV and 4 - 15 meV, respectively, while their density was about 1 motif per 10 000 atoms. Tuning of motif asymmetry by strain was demonstrated with the coupling coefficient below 1 eV. The tunnel splitting for the symmetrized motifs was estimated on the order of 0.1 meV. The discovered motifs are in good agreement with the available experimental data. The financial support from the Marie Curie Fellowship PIIF-GA-2012-326435 (RespSpatDisp) is gratefully acknowledged.
Cheng, Guang-Ling; Cong, Lu; Chen, Ai-Xi
2016-04-01
A scheme for two-dimensional (2D) electromagnetically induced grating via spatial gain and phase modulation is presented in a two-level atomic system. Based on the interactions of two orthogonal standing-wave fields, the atom could diffract the weak probe beam into high-order directions and a 2D diffraction grating is generated. It is shown that the diffraction efficiency of the grating can be efficiently manipulated by controlling the Rabi frequencies of control fields, the detunings of the control and probe fields, and interaction length. Different from 2D cross-grating via electromagnetically induced transparency in a four-level atomic system, the present scheme results from the spatial modulation of gain and phase in a simple two-level system, which could lead to 2D gain-phase grating with larger diffraction intensities in the diffraction directions. The studies we present may have potential applications in developing photon devices for optical-switching, optical imaging and quantum information processing.
Molecular dynamics study of the interactions of incident N or Ti atoms with the TiN(001) surface
Energy Technology Data Exchange (ETDEWEB)
Xu, Zhenhai [National Key Laboratory for Precision Hot Processing of Metals & School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Centre for Precision Manufacturing, Department of Design, Manufacture and Engineering Management, The University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Zeng, Quanren [Centre for Precision Manufacturing, Department of Design, Manufacture and Engineering Management, The University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Yuan, Lin [National Key Laboratory for Precision Hot Processing of Metals & School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Qin, Yi [Centre for Precision Manufacturing, Department of Design, Manufacture and Engineering Management, The University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Chen, Mingjun [School of Mechatronics Engineering, Harbin Institute of Technology, Harbin 150001 (China); Shan, Debin, E-mail: d.b.shan@gmail.com [National Key Laboratory for Precision Hot Processing of Metals & School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)
2016-01-01
Graphical abstract: - Highlights: • Interactions of incident N or Ti atoms with TiN(001) surface are studied by CMD. • The impact position of incident N on the surface determines the interaction modes. • Adsorption could occur due to the atomic exchange process. • Resputtering and reflection may simultaneously occur. • The initial sticking coefficient of N on TiN(001) is much smaller than that of Ti. - Abstract: The interaction processes between incident N or Ti atoms and the TiN(001) surface are simulated by classical molecular dynamics based on the second nearest-neighbor modified embedded-atom method potentials. The simulations are carried out for substrate temperatures between 300 and 700 K and kinetic energies of the incident atoms within the range of 0.5–10 eV. When N atoms impact against the surface, adsorption, resputtering and reflection of particles are observed; several unique atomic mechanisms are identified to account for these interactions, in which the adsorption could occur due to the atomic exchange process while the resputtering and reflection may simultaneously occur. The impact position of incident N atoms on the surface plays an important role in determining the interaction modes. Their occurrence probabilities are dependent on the kinetic energy of incident N atoms but independent on the substrate temperature. When Ti atoms are the incident particles, adsorption is the predominant interaction mode between particles and the surface. This results in the much smaller initial sticking coefficient of N atoms on the TiN(001) surface compared with that of Ti atoms. Stoichiometric TiN is promoted by N/Ti flux ratios larger than one.
Interaction-induced decay of a heteronuclear two-atom system
Xu, Peng; Yang, Jiaheng; Liu, Min; He, Xiaodong; Zeng, Yong; Wang, Kunpeng; Wang, Jin; Papoular, D. J.; Shlyapnikov, G. V.; Zhan, Mingsheng
2015-01-01
Two-atom systems in small traps are of fundamental interest for understanding the role of interactions in degenerate cold gases and for the creation of quantum gates in quantum information processing with single-atom traps. One of the key quantities is the inelastic relaxation (decay) time when one of the atoms or both are in a higher hyperfine state. Here we measure this quantity in a heteronuclear system of 87Rb and 85Rb in a micro optical trap and demonstrate experimentally and theoretically the presence of both fast and slow relaxation processes, depending on the choice of the initial hyperfine states. This experimental method allows us to single out a particular relaxation process thus provides an extremely clean platform for collisional physics studies. Our results have also implications for engineering of quantum states via controlled collisions and creation of two-qubit quantum gates. PMID:26199051
Zhang, Hong; Smith, Sean C; Nanbu, Shinkoh; Nakamura, Hiroki
2009-04-08
In this work we study the transmission of atomic hydrogen across a fluorinated boron-substituted coronene radical (C(19)H(12)BF(6)) as a model for partially fluorinated and boron-doped nanotubes or fullerenes. Complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) methods are employed to calculate the potential energy surfaces for both ground and excited electronic states, and one-dimensional R-matrix propagation is utilized to investigate the transmission/reflection dynamics of atomic hydrogen, through the central six-member ring of the fluorinated boron-substituted coronene radical. The quantum scattering includes resonance effects as well as non-adiabatic transitions between the ground and excited electronic states. Within the sudden approximation, both centre and off-centre approach trajectories have been investigated. Implications for atomic hydrogen encapsulation by carbon nanotube and fullerene are discussed.
Evaluation and Comparison of the Configuration Interaction Calculations for Complex Atoms
Directory of Open Access Journals (Sweden)
Charlotte Froese Fischer
2014-03-01
Full Text Available Configuration interaction (CI methods are the method of choice for the determination of wave functions for complex atomic systems from which a variety of atomic properties may be computed. When applied to highly ionized atoms, where few, if any, energy levels from observed wavelengths are available, the question arises as to how a calculation may be evaluated. Many different codes are available for such calculations. Agreement between the results from different codes in itself is not a check on accuracy, but may be due to a similarity in the computational procedures. This paper reviews basic theory, which, when applied in a systematic manner, can be the basis for the evaluation of accuracy. Results will be illustrated in the study of 4s24p5 (odd and 4s24p44d (even levels in W39+ and the transitions between them.
Few-body Cs Rydberg Atom Interactions in a 1064 nm Dipole Trap
Booth, Donald; Tallant, Jonathan; Marangoni, Bruno; Marcassa, Luis; Shaffer, James
2011-05-01
In studying few-body physics, the number density of atoms is an important parameter in achieving a good signal to noise ratio. We have recently improved our apparatus by implementing a crossed 1064 nm far off-resonance trap (FORT), which enables us to trap atoms at three orders of magnitude greater density than our MOT. Future directions for the apparatus, which include the study of anisotropic interactions among Rydberg atoms in the dipole trap, three-body recombination, ``trilobite-like'' molecules, and the detection of ultra-long range Rydberg macrodimers in Cs, will be described. Our presentation will focus on data on three-body recombination and long-range Rydberg ``trilobite-like'' molecules. We acknowledge funding from ARO (W911NF-08-1-0257), NSF (PHY-0855324) and NSF (OISE-0756321).
NATO Advanced Study Institute on Laser Interactions with Atoms, Solids,and Plasmas
1994-01-01
The aim of this NATO Advanced Study Institute was to bring together scientists and students working in the field of laser matter interactions in order to review and stimulate developmentoffundamental science with ultra-short pulse lasers. New techniques of pulse compression and colliding-pulse mode-locking have made possible the construction of lasers with pulse lengths in the femtosecond range. Such lasers are now in operation at several research laboratories in Europe and the United States. These laser facilities present a new and exciting research direction with both pure and applied science components. In this ASI the emphasis is on fundamental processes occurring in the interaction of short laser pulses with atoms, molecules, solids, and plasmas. In the case of laser-atom (molecule) interactions, high power lasers provide the first access to extreme high-intensity conditions above 10'8 Watts/em', a new frontier for nonlinear interaction of photons with atoms and molecules. New phenomena observed include ...
Directory of Open Access Journals (Sweden)
Noriyoshi Isozumi
2012-06-01
Full Text Available In organic molecules a divalent sulfur atom sometimes adopts weak coordination to a proximate heteroatom (X. Such hypervalent nonbonded S···X interactions can control the molecular structure and chemical reactivity of organic molecules, as well as their assembly and packing in the solid state. In the last decade, similar hypervalent interactions have been demonstrated by statistical database analysis to be present in protein structures. In this review, weak interactions between a divalent sulfur atom and an oxygen or nitrogen atom in proteins are highlighted with several examples. S···O interactions in proteins showed obviously different structural features from those in organic molecules (i.e., π_{O} → σ_{S}* versus n_{O} → σ_{S}* directionality. The difference was ascribed to the HOMO of the amide group, which expands in the vertical direction (π_{O} rather than in the plane (n_{O}. S···X interactions in four model proteins, phospholipase A_{2} (PLA_{2}, ribonuclease A (RNase A, insulin, and lysozyme, have also been analyzed. The results suggested that S···X interactions would be important factors that control not only the three-dimensional structure of proteins but also their functions to some extent. Thus, S···X interactions will be useful tools for protein engineering and the ligand design.
Partial as Well as Total Photon Interaction Effective Atomic Numbers for Some Concretes
Directory of Open Access Journals (Sweden)
Tejbir Singh
2013-08-01
Full Text Available Photon interaction effective atomic number (Zeff for partial as well as total photon interaction processes has been computed using logarithmic interpolation method for seven different concretes viz. (i Ordinary, (ii Hematite - Serpentine, (iii Ilmenite - Limonite, (iv Basalt - magnetite, (v Ilmenite, (vi Steel - scrap and (vii Steel - magnetite concrete in the wide energy range from 10.0 keV to 100 GeV. It has been concluded that this method has an advantage over the atomic to electronic cross-section ratio method especially for mixtures in the intermediate energy level. However, due to lack of experimental data in the higher energy region, it is difficult to discuss, its validity in these energy regions.
Long-Range Atom--Wall Interactions and Mixing Terms: Metastable Hydrogen
Jentschura, U D
2015-01-01
We investigate the interaction of metastable 2S hydrogen atoms with a perfectly conducting wall, including parity-breaking S-P mixing terms (with full account of retardation). The neighboring 2P_1/2 and 2P_3/2 levels are found to have a profound effect on the transition from the short-range, nonrelativistic regime, to the retarded form of the Casimir-Polder interaction. The corresponding P state admixtures to the metastable 2S state are calculated. We find the long-range asymptotics of the retarded Casimir-Polder potentials and mixing amplitudes, for general excited states, including a fully quantum electrodynamic treatment of the dipole-quadrupole mixing term. The decay width of the metastable 2S state is roughly doubled even at a comparatively large distance of 918 atomic units (Bohr radii) from the perfect conductor. The magnitude of the calculated effects is compared to the unexplained Sokolov effect.
Spin-orbit interactions and quantum spin dynamics in cold ion-atom collisions
Tscherbul, Timur V; Buchachenko, Alexei A
2015-01-01
We present accurate ab initio and quantum scattering calculations on a prototypical hybrid ion-atom system Yb$^+$-Rb, recently suggested as a promising candidate for the experimental study of open quantum systems, quantum information processing, and quantum simulation. We identify the second-oder spin-orbit (SO) interaction as the dominant source of hyperfine relaxation and decoherence in cold Yb$^+$-Rb collisions. Our results are in good agreement with recent experimental observations [L. Ratschbacher et al., Phys. Rev. Lett. 110, 160402 (2013)] of hyperfine relaxation rates of trapped Yb$^+$ immersed in an ultracold Rb gas. The calculated rates are 4 times smaller than predicted by the Langevin capture theory and display a weak $T^{-0.3}$ temperature dependence, indicating significant deviations from statistical behavior. Our analysis underscores the deleterious nature of the SO interaction and implies that light ion-atom combinations such as Yb$^+$-Li should be used to minimize hyperfine relaxation and dec...
Solving the self-interaction problem in Kohn-Sham density functional theory: Application to atoms
Däne, M.; Gonis, A.; Nicholson, D. M.; Stocks, G. M.
2015-04-01
In previous work, we proposed a computational methodology that addresses the elimination of the self-interaction error from the Kohn-Sham formulation of the density functional theory. We demonstrated how the exchange potential can be obtained, and presented results of calculations for atomic systems up to Kr carried out within a Cartesian coordinate system. In this paper, we provide complete details of this self-interaction free method formulated in spherical coordinates based on the explicit equidensity basis ansatz. We prove analytically that derivatives obtained using this method satisfy the Virial theorem for spherical orbitals, where the problem can be reduced to one dimension. We present the results of calculations of ground-state energies of atomic systems throughout the periodic table carried out within the exchange-only mode.
Demonstration of strong Rydberg blockade in three-atom systems with anisotropic interactions
Barredo, Daniel; Labuhn, Henning; Béguin, Lucas; Vernier, Aline; Nogrette, Florence; Lahaye, Thierry; Browaeys, Antoine
2014-01-01
We study the Rydberg blockade in a system of three atoms arranged in different 2D geometries (linear and triangular configurations). In the strong blockade regime, we observe high-contrast, coherent collective oscillations of the single excitation probability, and an almost perfect van der Waals blockade. Our data is consistent with a total population in doubly and triply excited states below 2%. In the partial blockade regime, we directly observe the anisotropy of the van der Waals interactions between $|nD\\rangle$ Rydberg states in the triangular configuration. A simple model, that only uses independently measured two-body van der Waals interactions, fully reproduces the dynamics of the system without any adjustable parameter. These results are extremely promising for scalable quantum information processing and quantum simulation with neutral atoms.
Rabi noise spectroscopy of individual two-level tunneling defects
Matityahu, Shlomi; Lisenfeld, Jürgen; Bilmes, Alexander; Shnirman, Alexander; Weiss, Georg; Ustinov, Alexey V.; Schechter, Moshe
2017-06-01
Understanding the nature of two-level tunneling defects is important for minimizing their disruptive effects in various nanodevices. By exploiting the resonant coupling of these defects to a superconducting qubit, one can probe and coherently manipulate them individually. In this work, we utilize a phase qubit to induce Rabi oscillations of single tunneling defects and measure their dephasing rates as a function of the defect's asymmetry energy, which is tuned by an applied strain. The dephasing rates scale quadratically with the external strain and are inversely proportional to the Rabi frequency. These results are analyzed and explained within a model of interacting defects, in which pure dephasing of coherent high-frequency (gigahertz) defects is caused by interaction with incoherent low-frequency thermally excited defects. Our analysis sets an upper bound for the relaxation rates of thermally excited defects interacting strongly with strain fields.
Institute of Scientific and Technical Information of China (English)
Lin Xiu; Li Hong-Cai; Yang Rong-Can; Huang Zhi-Ping
2007-01-01
This paper proposes a scheme for realizing entanglement swapping in cavity QED. The scheme is based on the resonant interaction of a two-mode cavity field with a A-type three-level atom. In contrast with the previously proposed schemes, the present scheme is ascendant, since the fidelity is 1.0 and the joint measurement isn't needed. And the scheme is experimentally feasible based on the current cavity QED technique.
Torres, J. M.; Sadurní, E.; Seligman, T. H.
2010-05-01
We address the problem of two interacting atoms of different species inside a cavity and find the explicit solutions of the corresponding eigenvalues and eigenfunctions using a new variant. This model encompasses various commonly used models. By way of example we obtain closed expressions for concurrence and purity as a function of time for the case where the cavity is prepared in a number state. We discuss the behaviour of these quantities and their relative behaviour in the concurrence-purity plane.
Interaction-based nonlinear quantum metrology with a cold atomic ensemble
2014-01-01
In this manuscript we present an experimental and theoretical investigation of quantum-noise-limited measurement by nonlinear interferometry, or from another perspective, quantum-noise-limited interaction-based measurement. The experimental work is performed using a polarization-based quantum interface between propagating light pulses and cold rubidium-87 atoms trapped in an optical dipole trap. We first review the theory of quantum metrology and estimation theory, and we describe theor...
Remote atomic information concentration without Bell-state measurement
Institute of Scientific and Technical Information of China (English)
Wu Zhen-Zhen; Fang Mao-Fa
2006-01-01
This paper proposes a scheme for information concentration of two remote two-level atoms in cavity QED. This scheme does not involve the Bell-state measurement. During the interaction between atom and cavity, the cavity frequency is large-detuned from the atomic transition frequency, thus the scheme is insensitive to both the cavity decay and the thermal field. This idea can directly be generalized in the case of multi-atom information concentration.
Wang, Hongtao
2012-01-01
Interaction between single noble metal atoms and graphene edges has been investigated via aberration-corrected and monochromated transmission electron microscopy. A collective motion of the Au atom and the nearby carbon atoms is observed in transition between energy-favorable configurations. Most trapping and detrapping processes are assisted by the dangling carbon atoms, which are more susceptible to knock-on displacements by electron irradiation. Thermal energy is lower than the activation barriers in transition among different energy-favorable configurations, which suggests electron-beam irradiation can be an efficient way of engineering the graphene edge with metal atoms. © 2012 The Royal Society of Chemistry.
Shantappa, A.; Hanagodimath, S. M.
2014-01-01
Effective atomic numbers, electron densities of some vitamins (Retinol, Riboflavin, Niacin, Biotin, Folic acid, Cobalamin, Phylloquinone and Flavonoids) composed of C, H, O, N, Co, P and S have been calculated for total and partial photon interactions by the direct method for energy range 1 keV-100 GeV by using WinXCOM and kinetic energy released in matter (Kerma) relative to air is calculated in energy range of 1 keV-20 MeV. Change in effective atomic number and electron density with energy is calculated for all photon interactions. Variation of photon mass attenuation coefficients with energy are shown graphically only for total photon interaction. It is observed that change in mass attenuation coefficient with composition of different chemicals is very large below 100 keV and moderate between 100 keV and 10 MeV and negligible above 10 MeV. Behaviour of vitamins is almost indistinguishable except biotin and cobalamin because of large range of atomic numbers from 1(H) to 16 (S) and 1(H) to 27(Co) respectively. K a value shows a peak due to the photoelectric effect around K-absorption edge of high- Z constituent of compound for biotin and cobalamin.
Long-range interacting many-body systems with alkaline-earth-metal atoms
Olmos, B; Singh, Y; Schreck, F; Bongs, K; Lesanovsky, I
2012-01-01
Alkaline-earth-metal atoms exhibit long-range dipolar interactions, which are generated via the coherent exchange of photons on the 3P_0-3D_1-transition of the triplet manifold. In case of bosonic strontium, which we discuss here, this transition has a wavelength of 2.7 \\mu m and a dipole moment of 2.46 Debye, and there exists a magic wavelength permitting the creation of optical lattices that are identical for the states 3P_0 and 3D_1. This interaction enables the realization and study of mixtures of hard-core lattice bosons featuring long-range hopping, with tuneable disorder and anisotropy. We derive the many-body Master equation, investigate the dynamics of excitation transport and analyze spectroscopic signatures stemming from coherent long-range interactions and collective dissipation. Our results show that lattice gases of alkaline-earth-metal atoms permit the creation of long-lived collective atomic states and constitute a simple and versatile platform for the exploration of many-body systems with lon...
Sagu'e, G; Meschede, D; Rauschenbeutel, A; Vetsch, E
2007-01-01
The strong evanescent field around ultra-thin unclad optical fibers bears a high potential for detecting, trapping, and manipulating cold atoms. Introducing such a fiber into a cold atom cloud, we investigate the interaction of a small number of cold Caesium atoms with the guided fiber mode and with the fiber surface. Using high resolution spectroscopy, we observe and analyze light-induced dipole forces, van der Waals interaction, and a significant enhancement of the spontaneous emission rate of the atoms. The latter can be assigned to the modification of the vacuum modes by the fiber.
Institute of Scientific and Technical Information of China (English)
Liao Xiang-Ping; Fang Mao-Fa; Cai Jian-Wu; Zheng Xiao-Juan
2008-01-01
This paper studies entanglement between two dipole-dipole coupled atoms interacting with a thermal field via a two-photon process. It shows that the entanglement is dependent on the mean photon number of the thermal field and the dipole-dipole interaction. The results also show that the atom-atom entanglement through the two-photon process is larger than that through the one-photon process and a remarkable amount of entanglement between the atoms still remains at certain times even for a very highly noisy thermal field.
Effects of the Lorentz invariance violation in Coulomb interaction in nuclei and atoms
Flambaum, V V
2016-01-01
Anisotropy in the speed of light (studied in the Michelson-Morley experiment ) generates anisotropy in the Coulomb interaction. This anisotropy manifests itself in the nuclear and atomic experiments. The experimental results for 21Ne are used to improve the limits on the tensor components characterising the asymmetry of the speed of light and the Coulomb interaction (violation of the Lorentz symmetry in the photon sector) by 7 orders of magnitude in comparison with previous experiments: the speed of light is isotropic to a part in 10E-28.
Effects of the Lorentz Invariance Violation on Coulomb Interactions in Nuclei and Atoms
Flambaum, V. V.; Romalis, M. V.
2017-04-01
Anisotropy in the speed of light that has been constrained by Michelson-Morley-type experiments also generates anisotropy in the Coulomb interactions. This anisotropy can manifest itself as an energy anisotropy in nuclear and atomic experiments. Here the experimental limits on Lorentz violation in Ne2110 are used to improve the limits on Lorentz symmetry violations in the photon sector, namely, the anisotropy of the speed of light and the Coulomb interactions, by 7 orders of magnitude in comparison with previous experiments: the speed of light is isotropic to a part in 10-28.
Limits on Lorentz Invariance Violation from Coulomb Interactions in Nuclei and Atoms.
Flambaum, V V; Romalis, M V
2017-04-07
Anisotropy in the speed of light that has been constrained by Michelson-Morley-type experiments also generates anisotropy in the Coulomb interactions. This anisotropy can manifest itself as an energy anisotropy in nuclear and atomic experiments. Here the experimental limits on Lorentz violation in _{10}^{21}Ne are used to improve the limits on Lorentz symmetry violations in the photon sector, namely, the anisotropy of the speed of light and the Coulomb interactions, by 7 orders of magnitude in comparison with previous experiments: the speed of light is isotropic to a part in 10^{28}.
Spin Diffusion in Trapped Clouds of Cold Atoms with Resonant Interactions
DEFF Research Database (Denmark)
Bruun, Georg Morten; Pethick, C. J.
2011-01-01
We show that puzzling recent experimental results on spin diffusion in a strongly interacting atomic gas may be understood in terms of the predicted spin diffusion coefficient for a generic strongly interacting system. Three important features play a central role: (a) Fick’s law for diffusion mus...... be modified to allow for the trapping potential; (b) the diffusion coefficient is inhomogeneous, due to the density variations in the cloud; and (c) the diffusion approximation fails in the outer parts of the cloud, where the mean free path is long....
Gerchikov, L.; Guillemin, R.; Simon, M.; Sheinerman, S.
2017-06-01
A concrete mechanism of angular-momentum transfer in photoionization process is proposed for electron photoemission from deep inner atomic shells. It is demonstrated that the leading contribution to angular-momentum transfer is provided by postcollision interaction of the photoelectrons and Auger electrons. The standard theoretical approach to postcollision interaction has been considerably improved by taking into account angular-momentum transfer. The theory developed is applied to the photoionization of 1 s2 shell in Ar. Calculations show the noticeable influence of angular-momentum transfer on the photoelectron angular distribution.
Quantum computing with atomic qubits and Rydberg interactions: progress and challenges
Saffman, M.
2016-10-01
We present a review of quantum computation with neutral atom qubits. After an overview of architectural options and approaches to preparing large qubit arrays we examine Rydberg mediated gate protocols and fidelity for two- and multi-qubit interactions. Quantum simulation and Rydberg dressing are alternatives to circuit based quantum computing for exploring many body quantum dynamics. We review the properties of the dressing interaction and provide a quantitative figure of merit for the complexity of the coherent dynamics that can be accessed with dressing. We conclude with a summary of the current status and an outlook for future progress.
Atomic Force Microscopy Study of the Interactions of Indolicidin with Model Membranes and DNA.
Fojan, Peter; Gurevich, Leonid
2017-01-01
The cell membrane is the first barrier and quite often the primary target that antimicrobial peptides (AMPs) have to destroy or penetrate to fulfill their mission. Upon penetrating through the membrane, the peptides can further attack intracellular targets, in particular DNA. Studying the interaction of an antimicrobial peptide with a cell membrane and DNA holds keys to understanding its killing mechanisms. Commonly, these interactions are studied by using optical or scanning electron microscopy and appropriately labeled peptides. However, labeling can significantly affect the hydrophobicity, conformation, and size of the peptide, hence altering the interaction significantly. Here, we describe the use of atomic force microscopy (AFM) for a label-free study of the interactions of peptides with model membranes under physiological conditions and DNA as a possible intracellular target.
Simplified approach to double jumps for fluorescing dipole-dipole interacting atoms
Hannstein, V; Hannstein, Volker; Hegerfeldt, Gerhard C.
2006-01-01
A simplified scheme for the investigation of cooperative effects in the quantum jump statistics of small numbers of fluorescing atoms and ions in a trap is presented. It allows the analytic treatment of three dipole-dipole interacting four-level systems which model the relevant level scheme of Ba+ ions. For the latter, a huge rate of double and triple jumps was reported in a former experiment and the huge rate was attributed to the dipole-dipole interaction. Our theoretical results show that the effect of the dipole-dipole interaction on these rates is at most 5% and that for the parameter values of the experiment there is practically no effect. Consequently it seems that the dipole-dipole interaction can be ruled out as a possible explanation for the huge rates reported in the experiment.
Institute of Scientific and Technical Information of China (English)
YU Zhao-Xian; JIAO Zhi-Yong
2002-01-01
We present a theoretical treatment of dynamics of an atomic Bose-Einstein condensation interacting witha single-mode quantized travelling-wave laser field in a double-well potential. When the atom-field system is initiallyin a coherent state, expressions for the energy exchange between atoms and photons are derived. It is revealed thatatoms in the two wells can be in a self-trapping state when the tunnelling frequency satisfies two specific conditions,in which the resonant and far off-resonant cases are included. It is found that there is an alternating current with twodifferent sinusoidal oscillations between the two wells, but no dc characteristic of the atomic tunnelling current occurs.It should be emphasized that when without the laser field, both the population difference and the atomic tunnellingcurrent are only a single oscillation. But they will respectively become a superposition of two oscillations with differentoscillatory frequencies in the presence of the laser field. For the two oscillations of the population difference, one alwayshas an increment in the oscillatory frequency, the other can have an increment or a decrease under different cases. Theseconclusions are also suitable to those of the atomic tunnelling current. As a possible application, by measurement of theatomic tunnelling current between the two wells, the number of Bose-condensed atoms can be evaluated. lBy properlyselecting the laser field, the expected atomic tunnelling current can be obtained too.
Spin Accumulation of Spinor Atoms in Optical Lattices
Institute of Scientific and Technical Information of China (English)
LI Hong; JIANG Zhan-Feng
2007-01-01
We obtain an effective spin correlation Hamiltonian describing the interaction of light with a two-level atom, then we investigate the classical trajectory of the two-level atom system by numerical integration of the Heisenberg equation of motion. Our results show that the spin accumulation is a very popular phenomenon as long as the spin character cannot be ignored in the Hamiltonian. We propose experimental protocol to observe this new phenomenon in further experiments.
Taninaka, Atsushi; Yoshida, Shoji; Kanazawa, Ken; Hayaki, Eiko; Takeuchi, Osamu; Shigekawa, Hidemi
2016-06-16
Scanning tunneling microscopy/spectroscopy (STM/STS) was carried out to investigate the structures of Mn atoms deposited on a GaAs(110) surface at room temperature to directly observe the characteristics of interactions between Mn atoms in GaAs. Mn atoms were paired with a probability higher than the random distribution, indicating an attractive interaction between them. In fact, re-pairing of unpaired Mn atoms was observed during STS measurement. The pair initially had a new structure, which was transformed during STS measurement into one of those formed by atom manipulation at 4 K. Mn atoms in pairs and trimers were aligned in the direction, which is theoretically predicted to produce a high Curie temperature.
Interaction of laser-cooled $^{87}$Rb atoms with higher order modes of an optical nanofiber
Kumar, Ravi; Maimaiti, Aili; Deasy, Kieran; Frawley, Mary C; Chormaic, Síle Nic
2013-01-01
Optical nanofibers can be used to confine light to submicron regions and are very promising for the realization of optical fiber-based quantum networks using cold, neutral atoms. Light propagating in the higher order modes of a nanofiber has a greater evanescent field extension around the waist in comparison with the fundamental mode, leading to a stronger interaction with the surrounding environment. In this work, we report on the integration of a few-mode, optical nanofiber, with a waist diameter of ~700 nm, into a magneto-optical trap for $^{87}$Rb atoms. The nanofiber is fabricated from 80 $\\mu$m diameter fiber using a brushed hydrogen-oxygen flame pulling rig. We show that absorption by laser-cooled atoms around the waist of the nanofiber is stronger when probe light is guided in the higher order modes than in the fundamental mode. As predicted by Masalov and Minogin*, fluorescent light from the atoms coupling in to the nanofiber through the waist has a higher pumping rate (5.8 times) for the higher-orde...
Phase transitions due to interaction between photons and atoms in a cavity system
Shirai, Tatsuhiko; Miyashita, Seiji
2012-01-01
We survey phenomena of a cavity system in which many atoms coherently interact with a single quantized photon mode driven by the AC external field in a dissipative environment. It has been known that a strongly external field causes the so-called optical bistability which is a non-equilibrium phase transition for the balance of excitation and dissipation. On the other hand, a strong interaction causes the Dicke transition, which is a phase transition with a spontaneous appearance of excitations of atoms and photons in the equilibrium system as a consequence of the cooperative phenomena. We study the phenomena in full range of the strength of the interaction and the external field, and present a phase diagram of the stationary state. For the strong interaction region, in order to realize the ground state, appropriate form of the dissipative mechanism in the master equation is necessary instead of the conventional Lindblad form. We provide such an extended master equation. Moreover, the rotating wave approximat...
Interactions between synaptic vesicle fusion proteins explored by atomic force microscopy.
Yersin, A; Hirling, H; Steiner, P; Magnin, S; Regazzi, R; Hüni, B; Huguenot, P; De los Rios, P; Dietler, G; Catsicas, S; Kasas, S
2003-07-22
Measuring the biophysical properties of macromolecular complexes at work is a major challenge of modern biology. The protein complex composed of vesicle-associated membrane protein 2, synaptosomal-associated protein of 25 kDa, and syntaxin 1 [soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) complex] is essential for docking and fusion of neurotransmitter-filled synaptic vesicles with the presynaptic membrane. To better understand the fusion mechanisms, we reconstituted the synaptic SNARE complex in the imaging chamber of an atomic force microscope and measured the interaction forces between its components. Each protein was tested against the two others, taken either individually or as binary complexes. This approach allowed us to determine specific interaction forces and dissociation kinetics of the SNAREs and led us to propose a sequence of interactions. A theoretical model based on our measurements suggests that a minimum of four complexes is probably necessary for fusion to occur. We also showed that the regulatory protein neuronal Sec1 injected into the atomic force microscope chamber prevented the complex formation. Finally, we measured the effect of tetanus toxin protease on the SNARE complex and its activity by on-line registration during tetanus toxin injection. These experiments provide a basis for the functional study of protein microdomains and also suggest opportunities for sensitive screening of drugs that can modulate protein-protein interactions.
Taber, Keith S.
2013-08-01
Comparing the atom to a `tiny solar system' is a common teaching analogy, and the extent to which learners saw the systems as analogous was investigated. English upper secondary students were asked parallel questions about the physical interactions between the components of a simple atomic system and a simple solar system to investigate how they understood the forces acting within the two systems. A sample of just over 100 across the 15-18 age range responded to a pencil-and-paper instrument that asked about four aspects of the two systems. It was found that for both systems, about four fifths of students expected forces to decrease with increasing distance; but that only a little over half expected there to be interactions between the minor constituents (electrons and planets). Most students failed to apply Newton's third law to either system. There was a considerable difference in the extent to which respondents were able to identify the type of force acting in the systems (nearly all for the solar system, but only a small proportion in the case of the atom). The findings are considered in terms of both the limitations of students' understanding of the basic physics and possible implications for the use of the teaching analogy.
Zeltzer, Gabriel
In condensed matter systems the spatial limit is given by the fundamental atomic and molecular interactions. Controlling matter at these length scales hold promise in both fundamental scientific research as well as applications in nanotechnology and related fields such as electronics, biochemistry and medicine. Atomic and molecular manipulation on surfaces has opened a new realm of possibilities where materials can be engineered at the spatial limit and artificial structures can be constructed with a bottom-up approach, one building block at a time. This thesis describes nanostructures assembled from CO molecules on Cu(111) using a custom-built low-temperature ultra-high vacuum (UHV) scanning tunneling microscope (STM). The design and performance of the atom-manipulation apparatus that has enabled these experiments is presented. The control of electronic and vibronic states is demonstrated in several coherent quantum geometries and interactions between these two degrees of freedom are investigated. This work has revealed a virtual vibron process where non-local vibrons are synthesized and focused using a two-dimensional electron gas as a propagation medium and molecular oscillators as a source. Analysis of higher order harmonic modes of quartz tuning fork sensors is presented in the context of high frequency optical homodyne interferometric detection of subnanometer oscillatory motion. Further developments which could expand upon the work presented herein, in which STM may be combined with quantum force sensing through the use of quartz tuning forks, are suggested.
Direct measurement of the van der Waals interaction between two single atoms
Béguin, Lucas; Chicireanu, Radu; Lahaye, Thierry; Browaeys, Antoine
2013-01-01
We report on the direct measurement of the van der Waals interaction between two isolated, single Rydberg atoms separated by a controlled distance of a few micrometers. By working in a regime where the single-atom Rabi frequency of the laser used for excitation to the Rydberg state is comparable to the interaction energy, we observe a \\emph{partial} Rydberg blockade, whereby the time-dependent populations of the various two-atom states exhibit coherent oscillations with several frequencies. A quantitative comparison of the data with a simple model based on the optical Bloch equations allows us to extract the van der Waals energy, and to observe its characteristic $C_6/R^6$ dependence. The magnitude of the measured $C_6$ coefficient agrees well with an \\emph{ab-initio} theoretical calculation, and we observe its dramatic increase with the principal quantum number $n$ of the Rydberg state. Our results not only allow to test an important physical law, but also demonstrate a degree of experimental control which o...
Institute of Scientific and Technical Information of China (English)
YUZhao－Xian; JIAOZhi－Yong
2002-01-01
We present a theoretical treatment of dynamics of an atomic Bose-Einstein condensation interacting with a single-mode quantized travelling-wave laser field in a double-well potential.When the atom-field system is initially in a coherent state,expressions for the energy exchange between atoms and photons are derived.It is revealed that atoms in the two wells can be in a self-trapping state when the tunnelling frequency satisfies two specific conditions,in which the resonant and far off-resonant cases are included.It is found that there is an alternating current with two different sinusoidal oscillations between the two wells,but no dc characteristic of the atomic tunnelling current occurs.It should be emphasized that when without the laser field,both the population difference and the atomic tunnelling current are only a single oscillation.But they will respectively become a superposition of two oscillations with different oscillatory frequencies in the presence of the laser field.For the two oscillations of the population difference,one always has an increment in the oscillatory frequency,the other can have an increment or a decrease under different cases.These conclusions are also suitable to those of the atomic tunnelling current.As a possible application,by measurement of the atomic tunnelling current between the two wells,the number of Bose-condensed atoms can be evaluated.By poperly selecting the laser field,the expected atomic tunnelling current can be obtained too.
Probing the short range spin dependent interactions by polarized {sup 3}He atom beams
Energy Technology Data Exchange (ETDEWEB)
Yan, H. [China Academy of Engineering Physics, Institute of Nuclear Physics and Chemistry, Mianyang, Sichuan (China); Indiana University, Center for Exploration of Energy and Matter, Bloomington, IN (United States); Sun, G.A.; Gong, J.; Pang, B.B.; Wang, Y.; Yang, Y.W.; Zhang, J.; Zhang, Y. [China Academy of Engineering Physics, Institute of Nuclear Physics and Chemistry, Mianyang, Sichuan (China)
2014-10-15
Experiments using polarized {sup 3}He atom beams to search for short range spin dependent forces are proposed. High intensity, high polarization, small beam size {sup 3}He atom beams have been successfully produced and used in surface science researches. By incorporating background reduction designs as combination shielding by μ-metal and superconductor and double beam paths, the precision of spin rotation angle per unit length could be improved by a factor of ∝ 10{sup 4}. By this precision, in combination with a high density and low magnetic susceptibility sample source mass, and reversing one beam path if necessary, sensitivities on three different types of spin dependent interactions could be improved by as much as ∝ 10{sup 2} to ∝ 10{sup 8} over the current experiments at the millimeter range. (orig.)
Three-body bound states in dipole-dipole interacting Rydberg atoms
Kiffner, Martin; Jaksch, Dieter
2013-01-01
We show that the dipole-dipole interaction between three identical Rydberg atoms can give rise to bound trimer states. The microscopic origin of these states is fundamentally different from Efimov physics. Two stable trimer configurations exist where the atoms form the vertices of an equilateral triangle in a plane perpendicular to a static electric field. The triangle edge length typically exceeds $R\\approx 2\\,\\mu\\text{m}$, and each configuration is two-fold degenerate due to Kramers' degeneracy. The depth of the potential wells and the triangle edge length can be controlled by external parameters. We establish the Borromean nature of the trimer states, analyze the quantum dynamics in the potential wells and describe methods for their production and detection.
Electron dynamics in the carbon atom induced by spin-orbit interaction
Rey, H F
2014-01-01
We use R-Matrix theory with Time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number $M_L$=0 and $M_L$=1 at a laser wavelength of 390 nm and peak intensity of 10$^{14}$ W cm$^{-2}$. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for $M_L$. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with $M_L=0$, the dynamics with respect to time delay of an ionizing probe pulse modelled using RMT theory is found to be in good agreement with available experimental data.
Rey, H. F.; van der Hart, H. W.
2014-09-01
We use R-matrix theory with time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number ML=0 and ML=1 at a laser wavelength of 390 nm and peak intensity of 1014W/cm2. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for ML. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with ML=0, the dynamics with respect to time delay of an ionizing probe pulse modeled by using RMT theory is found to be in good agreement with available experimental data.
Laser-material interaction during atom probe tomography of oxides with embedded metal nanoparticles
Shinde, D.; Arnoldi, L.; Devaraj, A.; Vella, A.
2016-10-01
Oxide-supported metal nano-particles are of great interest in catalysis but also in the development of new large-spectrum-absorption materials. The design of such nano materials requires three-dimensional characterization with a high spatial resolution and elemental selectivity. The laser assisted Atom Probe Tomography (La-APT) presents both these capacities if an accurate understanding of laser-material interaction is developed. In this paper, we focus on the fundamental physics of field evaporation as a function of sample geometry, laser power, and DC electric field for Au nanoparticles embedded in MgO. By understanding the laser-material interaction through experiments and a theoretical model of heat diffusion inside the sample after the interaction with laser pulse, we point out the physical origin of the noise and determine the conditions to reduce it by more than one order of magnitude, improving the sensitivity of the La-APT for metal-dielectric composites.
Systematics of ground state multiplets of atomic nuclei in the delta-interaction approach
Energy Technology Data Exchange (ETDEWEB)
Imasheva, L. T.; Ishkhanov, B. S.; Stepanov, M. E., E-mail: stepanov@depni.sinp.msu.ru [Moscow State University, Faculty of Physics (Russian Federation); Tretyakova, T. Yu. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)
2015-12-15
Pairing forces between nucleons in an atomic nucleus strongly influence its structure. One of the manifestations of pair interaction is the ground state multiplet (GSM) formation in the spectrum of low-lying excited states of even–even nuclei. The value of GSM splitting is determined by the value of pair interaction of nucleons; for each isotope, it can be estimated on the basis of experimental nuclear masses. The quality of this estimate is characterized by the degree of reproduction of GSM levels in the nucleus. The GSM systematics in even–even nuclei with a pair of identical nucleons in addition to the filled nuclear core is considered on the basis of delta interaction.
Convergence of CI single center calculations of positron-atom interactions
Mitroy, J
2006-01-01
The Configuration Interaction (CI) method using orbitals centered on the nucleus has recently been applied to calculate the interactions of positrons interacting with atoms. Computational investigations of the convergence properties of binding energy, phase shift and annihilation rate with respect to the maximum angular momentum of the orbital basis for the e^+Cu and PsH bound states, and the e^+-H scattering system were completed. The annihilation rates converge very slowly with angular momentum, and moreover the convergence with radial basis dimension appears to be slower for high angular momentum. A number of methods of completing the partial wave sum are compared, an approach based on a Delta X_J = a/(J + 1/2)^n + b/(J + 1/2)^(n+1) form (with n = 4 for phase shift (or energy) and n = 2 for the annihilation rate) seems to be preferred on considerations of utility and underlying physical justification.
Probing the interactions between lignin and inorganic oxides using atomic force microscopy
Wang, Jingyu; Qian, Yong; Deng, Yonghong; Liu, Di; Li, Hao; Qiu, Xueqing
2016-12-01
Understanding the interactions between lignin and inorganic oxides has both fundamental and practical importance in industrial and energy fields. In this work, the specific interactions between alkali lignin (AL) and three inorganic oxide substrates in aqueous environment are quantitatively measured using atomic force microscopy (AFM). The results show that the average adhesion force between AL and metal oxide such as Al2O3 or MgO is nearly two times bigger than that between AL and nonmetal oxide such as SiO2 due to the electrostatic difference and cation-π interaction. When 83% hydroxyl groups of AL is blocked by acetylation, the adhesion forces between AL and Al2O3, MgO and SiO2 decrease 43, 35 and 75% respectively, which indicate hydrogen bonds play an important role between AL and inorganic oxides, especially in AL-silica system.
Taber, Keith S.
2013-01-01
Comparing the atom to a "tiny solar system" is a common teaching analogy, and the extent to which learners saw the systems as analogous was investigated. English upper secondary students were asked parallel questions about the physical interactions between the components of a simple atomic system and a simple solar system to investigate…
A scheme for teleporting Schrdinger-cat states via the dispersive atom-cavity-field interaction
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
A proposal is presented for teleporting Schrding-cat states. The process of the teleportation is achieved through the dispersive atom-cavity-field interaction. In this proposal, only measurement on the cavity field and on the singlet atomic states are used.
GPGPU Approach: Simulation of the Interaction of Heavy Interstellar Atoms with the Heliosphere
DeStefano, A.
2014-12-01
Running simulations is an involved process taking many hours of computational time to complete. With the advent of cluster computing and parallel processing, problems may be solved in much less time compared to those run in serial. Specifically, NVIDIA released the parallel computing platform CUDA in 2007 giving researchers and programmers access to the GPU to solve generalized problems, and not those of just images.In current research, code has previously been developed to study the interaction of the heliosphere and heavy atoms from the local interstellar medium.Ionized species of hydrogen, helium and other heavy atoms are deflected by the heliosphere where as the neutral species are relatively unimpeded. Charge exchange of these neutral particles may occur between ionized species originating from the solar wind or other populations of pickup ions (PUI) modifying the shape and properties of the heliosphere, compared to one without neutrals. The details of the charge exchange interaction are element dependent and need to be investigated one by one. Current research has studied the interaction of local interstellar hydrogen with the heliosphere quite extensively with theory, simulations and modeling.Since hydrogen is the most abundant element care must be taken when coupling MHD equations with the charge exchange interactions. Simulation code has been developed to account for this dynamic problem and they have shown that the shape of the heliosphere is affected by this. Interstellar atoms heavier than hydrogen interacting with the heliosphere has been looked at as well, but not nearly with as much detail or sophisticated models as hydrogen. The heavy atom data collected by IBEX has in this sense been under-utilized by models.Previously, the simulation was computed with the use of MPI (Message Passing Interface) for parallelization. This approach provided a decrease in computational time. However, CUDA enables the programmer to take advantage of the computer
Communie, Guillaume; Habchi, Johnny; Yabukarski, Filip; Blocquel, David; Schneider, Robert; Tarbouriech, Nicolas; Papageorgiou, Nicolas; Ruigrok, Rob W H; Jamin, Marc; Jensen, Malene Ringkjøbing; Longhi, Sonia; Blackledge, Martin
2013-01-01
Hendra virus (HeV) is a recently emerged severe human pathogen that belongs to the Henipavirus genus within the Paramyxoviridae family. The HeV genome is encapsidated by the nucleoprotein (N) within a helical nucleocapsid. Recruitment of the viral polymerase onto the nucleocapsid template relies on the interaction between the C-terminal domain, N(TAIL), of N and the C-terminal X domain, XD, of the polymerase co-factor phosphoprotein (P). Here, we provide an atomic resolution description of the intrinsically disordered N(TAIL) domain in its isolated state and in intact nucleocapsids using nuclear magnetic resonance (NMR) spectroscopy. Using electron microscopy, we show that HeV nucleocapsids form herringbone-like structures typical of paramyxoviruses. We also report the crystal structure of XD of P that consists of a three-helix bundle. We study the interaction between N(TAIL) and XD using NMR titration experiments and provide a detailed mapping of the reciprocal binding sites. We show that the interaction is accompanied by α-helical folding of the molecular recognition element of N(TAIL) upon binding to a hydrophobic patch on the surface of XD. Finally, using solution NMR, we investigate the interaction between intact nucleocapsids and XD. Our results indicate that monomeric XD binds to N(TAIL) without triggering an additional unwinding of the nucleocapsid template. The present results provide a structural description at the atomic level of the protein-protein interactions required for transcription and replication of HeV, and the first direct observation of the interaction between the X domain of P and intact nucleocapsids in Paramyxoviridae.
Chen, Ching-Tai; Peng, Hung-Pin; Jian, Jhih-Wei; Tsai, Keng-Chang; Chang, Jeng-Yih; Yang, Ei-Wen; Chen, Jun-Bo; Ho, Shinn-Ying; Hsu, Wen-Lian; Yang, An-Suei
2012-01-01
Protein-protein interactions are key to many biological processes. Computational methodologies devised to predict protein-protein interaction (PPI) sites on protein surfaces are important tools in providing insights into the biological functions of proteins and in developing therapeutics targeting the protein-protein interaction sites. One of the general features of PPI sites is that the core regions from the two interacting protein surfaces are complementary to each other, similar to the interior of proteins in packing density and in the physicochemical nature of the amino acid composition. In this work, we simulated the physicochemical complementarities by constructing three-dimensional probability density maps of non-covalent interacting atoms on the protein surfaces. The interacting probabilities were derived from the interior of known structures. Machine learning algorithms were applied to learn the characteristic patterns of the probability density maps specific to the PPI sites. The trained predictors for PPI sites were cross-validated with the training cases (consisting of 432 proteins) and were tested on an independent dataset (consisting of 142 proteins). The residue-based Matthews correlation coefficient for the independent test set was 0.423; the accuracy, precision, sensitivity, specificity were 0.753, 0.519, 0.677, and 0.779 respectively. The benchmark results indicate that the optimized machine learning models are among the best predictors in identifying PPI sites on protein surfaces. In particular, the PPI site prediction accuracy increases with increasing size of the PPI site and with increasing hydrophobicity in amino acid composition of the PPI interface; the core interface regions are more likely to be recognized with high prediction confidence. The results indicate that the physicochemical complementarity patterns on protein surfaces are important determinants in PPIs, and a substantial portion of the PPI sites can be predicted correctly with
Blanter, M. S.; Dmitriev, V. V.; Mogutnov, B. M.; Ruban, A. V.
2017-02-01
The pairwise interaction energies of O-O and N-N in bcc metals of group VB, which were calculated earlier using first-principles methods, have been employed to analyze the effect of the interatomic interactions on the configurational contribution to the thermodynamic activity. The strong effect of interstitial- interstitial interaction has been shown. The configurational contribution grows in the row (Nb-N) → (V-N) → (Ta-N) → (Nb-O) → (V-O) → (Ta-O), which is caused by a weakening of the mutual attraction of interstitial atoms in these solid solutions. The strong repulsion that characterizes the majority of coordination shells only weakly affects the thermodynamic activity. The character of the temperature dependence of the configurational contribution is defined by the strength of the mutual attraction of the interstitial atoms, i.e., upon strong attraction, the contribution increases with increasing temperature (Nb-N, V-N, Ta-N, and Nb-O) and, upon weak attraction, it decreases (V-O and Ta-O).
Directory of Open Access Journals (Sweden)
S. Abdel-Khalek
2013-01-01
Full Text Available We study the dynamics of the atomic inversion, scaled atomic Wehrl entropy, and marginal atomic Q-function for a single two-level atom interacting with a one-mode cavity field taking in the presence of atomic damping. We obtain the exact solution of the master equation in the interaction picture using specific initial conditions. We examine the effects of atomic damping parameter and number of multiphoton transition on the scaled atomic Wehrl entropy, atomic Q-function, and their marginal distribution. We observe an interesting monotonic relation between the different physical quantities in the case of different values of the number of photon transition during the time evolution.
Zhuang, Chunqiang; Liu, Lei
2017-08-01
The understanding of fundamental issues related to friction at the atomic scale remains a great challenge due to the large difference between macroscopic and microscopic frictional behaviors. Here based on first-principles calculations, the applicability of macroscopic friction laws to the atomic scale is studied. The underlying mechanism that governs friction behavior is also explored. A completely new perspective of understanding the friction at the atomic scale is presented according to the observation of the applicability of friction law at the atomic scale and the variations of interaction potential induced by the number of layer and normal load.
Probing molecular interaction between transferrin and anti-transferrin by atomic force microscope
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
The interaction between transferrin (Tf) and its antibody was investigated by atomic force microscope. Tf-antibody was immobilized on the Au-coated glass slide, and the specific combination between antibody and antigen was also characterized by AFM. The results showed that holo-transferrin was jogged with anti-transferrin, and binded anti-tran- sferrin more tightly than apo-transferrin. The force- distance curves revealed that the affinity of anti-trans- ferrin and holo-transferrin was much stronger than that of apo-transferrin.
Institute of Scientific and Technical Information of China (English)
吴晓华; 刘望夷; 欧阳振乾; 李民乾
1997-01-01
The interaction between ribosome-inactivating proteins (RIPs) and supercoiled DNA was observed with an atomic force microscope (AFM). It was found that RIPs can bind to both supercoiled DNA and the unwound double stranded loop region in supercoiled DNA. The RIPs hound to the supercoils can induce the conformational change of supercoiled DNA. Furthermore, the supercoiled DNA was relaxed and cleaved into nick or linear form by RIPs. It indicated that RIP seemed to be a supercoil-dependent DNA binding protein and exhibited the activity of su-percoil-dependent DNA endonuclease.
Molecular ions in ultracold atomic gases: computed electronic interactions for \\MgHion with Rb
Tacconi, Mario
2007-01-01
The electronic structures of the manifold of potential energy surfaces generated in the lower energy range by the interaction of the MgH$^+$(X$^1\\Sigma^+$) cationic molecule with Rb($^2$S), neutral atom are obtained over a broad range of Jacobi coordinates from strongly correlated \\emph{ab initio} calculations which use a Multireference (MR) wavefunction within a Complete Active Space (CAS) approach. The relative features of the lowest five surfaces are analyzed in terms of possible collisional outcomes when employed to model the ultracold dynamics of ionic molecular partners.
Interaction of atomic hydrogen with anthracene and polyacene from density functional theory
Ferullo, Ricardo M.; Castellani, Norberto J.; Belelli, Patricia G.
2016-03-01
The interaction of atomic hydrogen with two linear polycyclic aromatic hydrocarbons (PAHs), anthracene and polyacene (the polymer of benzene), was studied within the density functional theory (DFT). Using a proper dispersion-corrected method (DFT-D) the preferential physisorption sites were explored. The activation barrier for the bond formation between a peripheral C and the incoming H was calculated to be 58.5 and 34.1 meV with pure DFT on anthracene and polyacene at its antiferromagnetic ground state, respectively. DFT-D, although improves the description of the physisorbed state, tends to underestimate the chemisorption barriers due an artifact arising from the dispersion correction.
Two interacting atoms in a cavity: exact solutions, entanglement and decoherence
Energy Technology Data Exchange (ETDEWEB)
Torres, J M; SadurnI, E; Seligman, T H, E-mail: mau@fis.unam.m [Instituto de Ciencias FIsicas, Universidad Nacional Autonoma de Mexico, CP 62210 Cuernavaca, Morelos (Mexico)
2010-05-14
We address the problem of two interacting atoms of different species inside a cavity and find the explicit solutions of the corresponding eigenvalues and eigenfunctions using a new variant. This model encompasses various commonly used models. By way of example we obtain closed expressions for concurrence and purity as a function of time for the case where the cavity is prepared in a number state. We discuss the behaviour of these quantities and their relative behaviour in the concurrence-purity plane. (fast track communication)
px+ipy superfluid from s-wave interactions of fermionic cold atoms.
Zhang, Chuanwei; Tewari, Sumanta; Lutchyn, Roman M; Das Sarma, S
2008-10-17
Two-dimensional (p(x)+ip(y)) superfluids or superconductors offer a playground for studying intriguing physics such as quantum teleportation, non-Abelian statistics, and topological quantum computation. Creating such a superfluid in cold fermionic atom optical traps using p-wave Feshbach resonance is turning out to be challenging. Here we propose a method to create a p(x)+ip(y) superfluid directly from an s-wave interaction making use of a topological Berry phase, which can be artificially generated. We discuss ways to detect the spontaneous Hall mass current, which acts as a diagnostic for the chiral p-wave superfluid.
Arora, Bindiya; Sahoo, B K
2013-01-01
We evaluate separation dependent van der Waal dispersion ($C_3$) coefficients for the interactions of the Li, Na, K and Rb alkali atoms with a graphene layer and with a single walled carbon nanotube (CNT) using the hydrodynamic and Dirac models. The results from both the models are evaluated using accurate values of the dynamic polarizabilities of the above atoms. Accountability of these accurate values of dynamical polarizabilities of the alkali atoms in determination of the above $C_3$ coefficients are accentuated by comparing them with the coefficients evaluated using the dynamic dipole polarizabilities estimated from the single oscillator approximation which are typically employed in the earlier calculations. For practical description of the atom-surface interaction potentials the radial dependent $C_3$ coefficients are given for a wide range of separation distances between the ground states of the considered atoms and the wall surfaces and also for different values of nanotube radii. The coefficients for...
Interaction of atomic hydrogen with pico- and femtosecond laser pulses. Technical report
Energy Technology Data Exchange (ETDEWEB)
Parker, J.S.
1989-12-01
This thesis presents a theoretical study of the interaction of atomic hydrogen with coherent laser pulses in the 5 femtosecond to 10 picosecond range, in the weak-field limit, and in intense fields. We approach the problem in the weak-field limit by studying the relationship between the Fourier relation of the laser pulse (Delta omega Delta t) and the (Delta E Delta t) relation of the atomic Rydberg wave packet generated by the laser pulse. A derivation of the wave packet based on the WKB approximation is given, permitting the quantity Delta t to be derived for the quantum state, with the conclusion that under certain circumstances a transform-limited laser pulse (satisfying Delta omega Delta t = 1/2) can generate a transform-limited electron (satisfying Delta E Delta t/h = 1/2). A population-trapping effect is found numerically and modeled theoretically. Despite the high field intensities, population representing the excited electron is recaptured from the ionization continuum by bound states during the excitation. Population returns to the atom with just the right phase to strongly inhibit ionization. A theory is presented that models this effect for a variety of laser pulse shapes, with and without the rotating-wave approximation. The numerical integration reveals that a certain amount of above-threshold ionization (ATI) occurs.
Razvag, Yair; Gutkin, Vitaly; Reches, Meital
2013-08-13
This article describes single-molecule force spectroscopy measurements of the interaction between individual amino acid residues and inorganic surfaces in an aqueous solution. In each measurement, there is an amino acid residue, lysine, glutamate, phenylalanine, leucine, or glutamine, and each represents a class of amino acids (positively or negatively charged, aromatic, nonpolar, and polar). Force-distance curves measured the interaction of the individual amino acid bound to a silicon atomic force microscope (AFM) tip with a silcon substrate, cut from a single-crystal wafer, or mica. Using this method, we were able to measure low adhesion forces (below 300 pN) and could clearly determine the strength of interactions between the individual amino acid residues and the inorganic substrate. In addition, we observed how changes in the pH and ionic strength of the solution affected the adsorption of the residues to the substrates. Our results pinpoint the important role of hydrophobic interactions among the amino acids and the substrate, where hydrophobic phenylalanine exhibited the strongest adhesion to a silicon substrate. Additionally, electrostatic interactions also contributed to the adsorption of amino acid residues to inorganic substrates. A change in the pH or ionic strength values of the buffer altered the strength of interactions among the amino acids and the substrate. We concluded that the interplay between the hydrophobic forces and electrostatic interactions will determine the strength of adsorption among the amino acids and the surface. Overall, these results contribute to our understanding of the interaction at the organic-inorganic interface. These results may have implications for our perception of the specificity of peptide binding to inorganic surfaces. Consequently, it would possibly lead to a better design of composite materials and devices.
Aspects of the theory of atoms and coherent matter and their interaction with electromagnetic fields
Energy Technology Data Exchange (ETDEWEB)
Nilsen, Halvor Moell
2002-07-01
In the present work I have outlined and contributed to the time-dependent theory of the interaction between atoms and electromagnetic fields and the theory of Bose-Einstein condensates. New numerical methods and algorithms have been developed and applied in practice. Calculations have exhibited certain new dynamical features. All these calculations are in a regime where the applied field is of the same magnitude as the atomic field. In the case of BEC we have investigated the use of time-dependent methods to calculate the excitation frequencies. We also investigated the possibility of nonlinear coupling for a scissors mode and found no such contributions to damping which is consistent with other studies . Special emphasis has also been paid to the gyroscopic motion of rotating BEC where several models were investigated. Briefly, the main conclusions are: (1) Rydberg wave packets appear for direct excitations of Rydberg atoms for long pulses. (2) The survival of just a few states is decided by symmetry of the Hamiltonian. (3) For few cycle intense pulses classical and quantum mechanics show remarkable similarity. (4) Time-dependent methods for finding excitation frequencies have been shown to be very efficient. (5) New dynamical features is shown in gyroscopic motion of BEC. (6) It was shown that no nonlinear mixing of scissors modes occur in the standard Gross-Pitaevskii regime. As mentioned in the introduction, this work is a part of very active research fields and new progress is constantly reported. Thus, the present work cannot be concluded as a closed loop. The fast development of grid based numerical solutions for atoms in intense fields will surely make great contribution to solve many of today's problems. It is a very important area of research to understand both nonperturbative atomic response and highly nonlinear optics. In the field of Bose-Einstein condensation the new experimental achievements constantly drive the field forward. The new
Li, Yan; Yan, Xiu-ping
2015-09-01
Trace metals may be adopted by biological systems to assist in the syntheses and metabolic functions of genes (DNA and RNA) and proteins in the environment. These metals may be beneficial or may pose a risk to humans and other life forms. Novel hybrid techniques are required for studies on the interaction between different metal species and biomolecules, which is significant for biology, biochemistry, nutrition, agriculture, medicine, pharmacy, and environmental science. In recent years, our group dwells on new hyphenated techniques based on capillary electrophoresis (CE), electrothermal atomic absorption spectrometry (ETAAS), and inductively coupled plasma mass spectroscopy (ICP-MS), and their application for different metal species interaction with biomolecules such as DNA, HSA, and GSH. The CE-ETAAS assay and CE-ICP-MS assay allow sensitively probing the level of biomolecules such as DNA damage by different metal species and extracting the kinetic and thermodynamic information on the interactions of different metal species with biomolecules, provides direct evidences for the formation of different metal species--biomolecule adducts. In addition, the consequent structural information were extracted from circular dichroism (CD) and X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The present works represent the most complete and extensive study to date on the interactions between different metal species with biomolecules, and also provide new evidences for and insights into the interactions of different metal species with biomolecules for further understanding of the toxicological effects of metal species.
Energy Technology Data Exchange (ETDEWEB)
Zwier, Timothy
2012-07-20
At the 2012 Atomic and Molecular Interactions Gordon Conference, there will be talks in several broadly defined and partially overlapping areas: Intramolecular and single-collision reaction dynamics; Photophysics and photochemistry of excited states; Clusters, aerosols and solvation; Interactions at interfaces; Conformations and folding of large molecules; Interactions under extreme conditions of temperature and pressure. The theme of the Gordon Research Seminar on Atomic & Molecular Interactions, in keeping with the tradition of the Atomic and Molecular Interactions Gordon Research Conference, is far-reaching and involves fundamental research in the gas and condensed phases along with application of these ideas to practical chemical fields. The oral presentations, which will contain a combination of both experiment and theory, will focus on four broad categories: Ultrafast Phenomena; Excited States, Photoelectrons, and Photoions; Chemical Reaction Dynamics; Biomolecules and Clusters.
Nonlinear Dynamics of Cantilever-Sample Interactions in Atomic Force Microscopy
Cantrell, John H.; Cantrell, Sean A.
2010-01-01
The interaction of the cantilever tip of an atomic force microscope (AFM) with the sample surface is obtained by treating the cantilever and sample as independent systems coupled by a nonlinear force acting between the cantilever tip and a volume element of the sample surface. The volume element is subjected to a restoring force from the remainder of the sample that provides dynamical equilibrium for the combined systems. The model accounts for the positions on the cantilever of the cantilever tip, laser probe, and excitation force (if any) via a basis set of set of orthogonal functions that may be generalized to account for arbitrary cantilever shapes. The basis set is extended to include nonlinear cantilever modes. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a matrix iteration procedure. The effects of oscillatory excitation forces applied either to the cantilever or to the sample surface (or to both) are obtained from the solution set and applied to the to the assessment of phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) modalities. The influence of bistable cantilever modes of on AFM signal generation is discussed. The effects on the cantilever-sample surface dynamics of subsurface features embedded in the sample that are perturbed by surface-generated oscillatory excitation forces and carried to the cantilever via wave propagation are accounted by the Bolef-Miller propagating wave model. Expressions pertaining to signal generation and image contrast in A-AFM are obtained and applied to amplitude modulation (intermittent contact) atomic force microscopy and resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM). The influence of phase accumulation in A-AFM on image contrast is discussed, as is the effect of hard contact and maximum nonlinearity regimes of A-AFM operation.
P ,T -odd electron-nucleus interaction in atomic systems as an exchange by Higgs bosons
Chubukov, D. V.; Labzowsky, L. N.
2016-06-01
Scalar-pseudoscalar P ,T -odd interaction between the electron and the nucleus in atomic systems is constructed within the standard model as an exchange by Higgs boson. The necessary P - and T -violating contribution is obtained at the three-loop level on the basis of Cabibbo-Kobayashi-Maskawa matrix. This contribution, unlike the corresponding contribution to the electron electric dipole moment (EDM), does not vanish since the "Higgs charges" of quarks, contrary to their electric charges, are flavor dependent. Order-of-magnitude estimates of the effect expressed as an "equivalent" electron EDM give the values within the range deeqv˜10-40-10-45e cm , depending on the known different estimates for the electron EDM. This can be compared with the known "benchmark" two-photon P ,T -odd electron-nucleus interaction effect, which provides deeqv˜10-38e cm .
Energy Technology Data Exchange (ETDEWEB)
Bross, David H.; Parmar, Payal; Peterson, Kirk A., E-mail: kipeters@wsu.edu [Department of Chemistry, Washington State University, Pullman, Washington 99164-4630 (United States)
2015-11-14
The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set limit using new all-electron correlation consistent basis sets. The latter was carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons has been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. The final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV) and thus more reliable than the current experimental values of IP{sub 3} through IP{sub 6}.
Indium-defect interactions in FCC and BCC metals studied using the modified embedded atom method
Zacate, M. O.
2016-12-01
With the aim of developing a transferable potential set capable of predicting defect formation, defect association, and diffusion properties in a wide range of intermetallic compounds, the present study was undertaken to test parameterization strategies for determining empirical pair-wise interaction parameters in the modified embedded atom method (MEAM) developed by Baskes and coworkers. This report focuses on indium-solute and indium-vacancy interactions in FCC and BCC metals, for which a large set of experimental data obtained from perturbed angular correlation measurements is available for comparison. Simulation results were found to be in good agreement with experimental values after model parameters had been adjusted to reproduce as best as possible the following two sets of quantities: (1) lattice parameters, formation enthalpies, and bulk moduli of hypothetical equiatomic compounds with the NaCl crystal structure determined using density functional theory and (2) dilute solution enthalpies in metals as predicted by Miedema's semi-empirical model.
Bross, David H.; Parmar, Payal; Peterson, Kirk A.
2015-11-01
The first 6 ionization potentials (IPs) of the uranium atom have been calculated using multireference configuration interaction (MRCI+Q) with extrapolations to the complete basis set limit using new all-electron correlation consistent basis sets. The latter was carried out with the third-order Douglas-Kroll-Hess Hamiltonian. Correlation down through the 5s5p5d electrons has been taken into account, as well as contributions to the IPs due to the Lamb shift. Spin-orbit coupling contributions calculated at the 4-component Kramers restricted configuration interaction level, as well as the Gaunt term computed at the Dirac-Hartree-Fock level, were added to the best scalar relativistic results. The final ionization potentials are expected to be accurate to at least 5 kcal/mol (0.2 eV) and thus more reliable than the current experimental values of IP3 through IP6.
Atomic Ensemble Effects and Non-Covalent Interactions at the Electrode–Electrolyte Interface
Directory of Open Access Journals (Sweden)
Angel Cuesta
2016-09-01
Full Text Available Cyanide-modified Pt(111 electrodes have been recently employed to study atomic ensemble effects in electrocatalysis. This work, which will be briefly reviewed, reveals that the smallest site required for methanol dehydrogenation and formic acid dehydration is composed of three contiguous Pt atoms. By blocking these trigonal sites, the specific adsorption of anions, such as sulfate and phosphate, can be inhibited, thus increasing the rate of oxygen reduction reaction by one order of magnitude or more. Moreover, alkali metal cations affect hydrogen adsorption on cyanide-modified Pt(111. This effect is attributed to the non-covalent interactions at the electrical double layer between specifically adsorbed anions or dipoles and the alkali metal cations. A systematic investigation is conducted on the effect of the concentration of alkali metal cations. Accordingly, a simple model that reproduces the experimental observations accurately and enables the understanding of the trends in the strength of the interaction between M+ and CNad when moving from Li+ to Cs+, as well as the deviations from the expected trends, is developed. This simple model can also explain the occurrence of super-Nernstian shifts of the equilibrium potential of interfacial proton-coupled electron transfers. Therefore, the model can be generally applied to explain quantitatively the effect of cations on the properties of the electrical double layer. The recently reported effects of alkali metal cations on several electrocatalytic reactions must be mediated by the interaction between these cations and chemisorbed species. As these interactions seem to be adequately and quantitatively described by our model, we expect the model to also be useful to describe, explain, and potentially exploit these effects.
Baselt, David Randall
This thesis describes the construction of an atomic force microscope and its application to the study of tip -sample interactions, primarily through the use of friction and hardness (elasticity) imaging. Part one describes the atomic force microscope, which consists of a scanned-cantilever stage (chapter 2); a versatile digital signal processor-based control system with self-optimizing feedback, lock-in amplifier emulation (for hardness imaging), and macro programmability (chapter 3); and image processing software (chapter 4). Part two describes a number of results that have helped to characterize the tip-sample interaction and the contact imaging modes used for its study. Meniscus forces act laterally as well as normally, and that they vary with position (chapter 5). Friction measurements couple with scanner position and feedback, and the meniscus effects friction images (chapter 6). Sliding of the tip over the sample surface introduces slope-dependence into hardness measurements (chapter 7). Dull tips can create prominent topography artifacts even on very flat surfaces (chapter 8). In an investigation of collagen fibrils, AFM has revealed the characteristic 65 nm banding pattern, a second, minor banding pattern, and microfibrils that run along the fibril axis. The distribution of proteoglycans along the fibrils creates a characteristic pattern in friction images. Although imaging in water reduces interaction forces, water can also make biological samples more sensitive to force. However, for robust biological samples imaged in air, tip shape presents a greater obstacle than tip -sample interaction forces to obtaining high-resolution images. Tip contamination increases tip-sample friction and can occasionally improve resolution (chapter 9). For a separate project I have designed a general -purpose nearfield scanning optical microscope (chapter 10).
Density functional theory study of nitrogen atoms and molecules interacting with Fe(1 1 1) surfaces
Nosir, M. A.; Martin-Gondre, L.; Bocan, G. A.; Díez Muiño, R.
2016-09-01
We present Density functional theory (DFT) calculations for the investigation of the structural relaxation of Fe(1 1 1), as well as for the study of the interaction of nitrogen atoms and molecules with this surface. We perform spin polarized DFT calculations using VASP (Vienna Ab-initio Simulation Package) code. We use the supercell approach and up to 19 slab layers for the relaxation of the Fe(1 1 1) surface. We find a contraction of the first two interlayer distances with a relative value of Δ12 = - 7.8 % and Δ23 = - 21.7 % with respect to the bulk reference. The third interlayer distance is however expanded with a relative change of Δ34 = 9.7 % . Early experimental studies of the surface relaxation using Low Energy Electron Diffraction (LEED) and Medium Energy Ion Scattering (MEIS) showed contradictory results, even on the relaxation general trend. Our current theoretical results support the LEED conclusions and are consistent qualitatively with other recent theoretical calculations. In addition, we study the interaction energy of nitrogen atoms and molecules on the Fe(1 1 1) surface. The nitrogen atoms are adsorbed in the hollow site of the unit cell, with an adsorption energy consistent with the one found in previous studies. In addition, we find the three molecularly adsorbed states that are observed experimentally. Two of them correspond to the adsorbed molecule oriented normal to the surface and a third one corresponds to the molecule adsorbed parallel to the surface. We conclude that our results are accurate enough to be used to build a full six-dimensional potential energy surface for the N2 system.
Interactions between solute atoms in Fe-Si-Al-C alloys as studied by mechanical spectroscopy
Energy Technology Data Exchange (ETDEWEB)
Sinning, H.-R., E-mail: hr.sinning@tu-bs.de [Institut fuer Werkstoffe, Technische Universitaet Braunschweig, Braunschweig (Germany); Golovin, I.S. [Physics of Metals Department, Moscow Institute of Steel and Alloys, Moscow (Russian Federation); Physics of Metals and Materials Science Department, Tula State University, Tula (Russian Federation); Strahl, A. [Institut fuer Fachdidaktik der Naturwissenschaften, TU Braunschweig (Germany); Sokolova, O.A. [Physics of Metals and Materials Science Department, Tula State University, Tula (Russian Federation); Sazonova, T. [Institut fuer Werkstoffe, Technische Universitaet Braunschweig, Braunschweig (Germany)
2009-09-15
In Fe-Si-Al-C alloys, point-defect relaxation includes both the interstitial carbon Snoek-type relaxation, split into a 'pure iron' (Fe-C-Fe) Snoek peak and an 'interstitial-substitutional' (Fe-C-Me; Me = Al, Si) peak, and the substitutional Zener relaxation. The influence of Al and Si, with varying Al/Si ratio, on these effects is used to study the qualitative characteristics of substitutional-interstitial (Si-C, Al-C) and substitutional-substitutional (Al-Al, Si-Si, Al-Si) interactions in these alloys. Concerning the latter, there is a mutual compensation of the elastic distortion fields, produced in the Fe matrix by the relatively bigger Al and smaller Si atoms, respectively, which largely suppresses the Zener relaxation in the ternary Fe-Si-Al alloys, probably without affecting the elastic dipole strength of interstitial carbon. From the kinetic behavior of the two components of the Snoek-type relaxation, it is concluded that the substitutional-interstitial interaction is generally attractive and sufficient for modifying the distribution of the C atoms, but not for trapping to become dominant.
Precision Tests of the Electroweak Interaction using Trapped Atoms and Ions
Energy Technology Data Exchange (ETDEWEB)
Melconian, Daniel George [Texas A & M Univ., College Station, TX (United States)
2017-06-21
The objective of the proposed research is to study fundamental aspects of the electroweak interaction via precision measurements in beta decay to test our current understanding of fundamental particles and forces as contained in the so-called "Standard Model" of particle physics. By comparing elegant experiments to rigorous theoretical predictions, we will either confirm the Standard Model to a higher degree and rule out models which seek to extend it, or find evidence of new physics and help guide theorists in developing the New Standard Model. The use of ion and neutral atom traps at radioactive ion beam facilities has opened up a new vista in precision low-energy nuclear physics experiments. Traps provide an ideal source of decaying atoms: they can be extremely cold (~1 mK); they are compact (~1 mm^3); and perhaps most importantly, the daughter particles escape with negligible distortions to their momenta in a scattering-free, open environment. The project is taking advantage of these technologies and applying them to precision beta-decay studies at radioactive beam facilities. The program consists of two complementary efforts: 1) Ion traps are an extremely versatile tool for purifying, cooling and bunching low-energy beams of short-lived nuclei. A large-bore (210~mm) superconducting 7-Tesla solenoid is at the heart of a Penning trap system for which there is a dedicated beamline at T-REX, the upgraded radioactive beam facility at the Cyclotron Institute, Texas A&M University. In addition to providing a general-purpose decay station, the flagship program for this system is measuring the ft-values and beta-neutrino correlation parameters from isospin T=2 superallowed beta-delayed proton decays, complimenting and expanding the already strong program in fundamental interactions at the Institute. 2) A magneto-optical trap is being used at the TRIUMF Neutral Atom Trap facility to observe the (un)polarized angular distribution parameters of isotopes of potassium. We
On the dependence of the two-level source function on its radiation field.
Steinitz, R.; Shine, R. A.
1973-01-01
The consequences of the universally made assumption that the stimulated emission profile is identical to the absorption profile are quantitatively investigated for a two-level atom with Doppler redistribution. The nonlinear terms arising in the source function are evaluated iteratively. We find that the magnitude of the effects is probably completely negligible for visible and UV solar lines.
West, Aaron C; Schmidt, Michael W; Gordon, Mark S; Ruedenberg, Klaus
2017-02-09
A general intrinsic energy resolution has been formulated for strongly correlated wave functions in the full molecular valence space and its subspaces. The information regarding the quasi-atomic organization of the molecular electronic structure is extracted from the molecular wave function without introducing any additional postulated model state wave functions. To this end, the molecular wave function is expressed in terms of quasi-atomic molecular orbitals, which maximize the overlap between subspaces of the molecular orbital space and the free-atom orbital spaces. As a result, the molecular wave function becomes the superposition of a wave function representing the juxtaposed nonbonded quasi-atoms and a wave function describing the interatomic electron migrations that create bonds through electron sharing. The juxtaposed nonbonded quasi-atoms are shown to consist of entangled quasi-atomic states from different atoms. The binding energy is resolved as a sum of contributions that are due to quasi-atom formation, quasiclassical electrostatic interactions, and interatomic interferences caused by electron sharing. The contributions are further resolved according to orbital interactions. The various transformations that generate the analysis are determined by criteria that are independent of the working orbital basis used for calculating the molecular wave function. The theoretical formulation of the resolution is quantitatively validated by an application to the C2 molecule.
2008 Atomic and Molecular Interactions GRC-July 6-11, 2008
Energy Technology Data Exchange (ETDEWEB)
Arthur Suits
2009-06-03
The Atomic and Molecular Interactions Gordon Conferences is justifiably recognized for its broad scope, touching on areas ranging from fundamental gas phase and gas-condensed matter collision dynamics, to laser-molecule interactions, photophysics, and unimolecular decay processes. The meeting has traditionally involved scientists engaged in fundamental research in gas and condensed phases and those who apply these concepts to systems of practical chemical and physical interest. A key tradition in this meeting is the strong mixing of theory and experiment throughout. The program for 2008 conference continues these traditions. At the 2008 AMI GRC, there will be talks in 5 broadly defined and partially overlapping areas of intermolecular interactions and chemical dynamics: (1) Photoionization and Photoelectron Spectroscopy; (2) Molecules in Strong Fields; (3) Photodissociation Dynamics; (4) Astrochemistry; and (5) Reaction Dynamics. These areas encompass many of the most productive and exciting areas of chemical physics, including both reactive and nonreactive processes, intermolecular and intramolecular energy transfer, and photodissociation and unimolecular processes. Gas phase dynamics, van der Waals and cluster studies, laser-matter interactions and multiple potential energy surface phenomena will all be discussed. Limited funds are available to support attendance for students and post-docs. Advisors should email the conference chair requesting such support, and the students should apply online as usual.
High Intensity Femtosecond XUV Pulse Interactions with Atomic Clusters: Final Report
Energy Technology Data Exchange (ETDEWEB)
Ditmire, Todd [Univ. of Texas, Austin, TX (United States). Center for High Energy Density Science
2016-10-12
We propose to expand our recent studies on the interactions of intense extreme ultraviolet (XUV) femtosecond pulses with atomic and molecular clusters. The work described follows directly from work performed under BES support for the past grant period. During this period we upgraded the THOR laser at UT Austin by replacing the regenerative amplifier with optical parametric amplification (OPA) using BBO crystals. This increased the contrast of the laser, the total laser energy to ~1.2 J , and decreased the pulse width to below 30 fs. We built a new all reflective XUV harmonic beam line into expanded lab space. This enabled an increase influence by a factor of 25 and an increase in the intensity by a factor of 50. The goal of the program proposed in this renewal is to extend this class of experiments to available higher XUV intensity and a greater range of wavelengths. In particular we plan to perform experiments to confirm our hypothesis about the origin of the high charge states in these exploding clusters, an effect which we ascribe to plasma continuum lowering (ionization potential depression) in a cluster nano-plasma. To do this we will perform experiments in which XUV pulses of carefully chosen wavelength irradiate clusters composed of only low-Z atoms and clusters with a mixture of this low-Z atom with higher Z atoms. The latter clusters will exhibit higher electron densities and will serve to lower the ionization potential further than in the clusters composed only of low Z atoms. This should have a significant effect on the charge states produced in the exploding cluster. We will also explore the transition of explosions in these XUV irradiated clusters from hydrodynamic expansion to Coulomb explosion. The work proposed here will explore clusters of a wider range of constituents, including clusters from solids. Experiments on clusters from solids will be enabled by development we performed during the past grant period in which we constructed and
Chu, X.; Dalgarno, A.; Groenenboom, G.C.
2007-01-01
The dynamic scalar and tensor polarizabilities of the rare-earth-metal atoms are calculated with time-dependent density functional theory. The frequency-dependent polarizabilities at imaginary frequencies are used to determine the isotropic and orientation-dependent van der Waals coefficients for th
The role of hydrogen atoms in interactions involving imidazolium-based ionic liquids
Kempter, V.; Kirchner, B.
2010-05-01
In the first part of this report experimental results are discussed which focus onto the importance of hydrogen atoms in the interaction of imidazolium-based ionic liquids. These include examples for the cation-anion interaction in neat ionic liquids as well as the interactions between ionic liquids and their molecular environment, water in particular. Most of the studies emphasize the importance of the C(2)-H group of the imidazolium ring for the intra- and intermolecular interactions; commonly, the interactions of the type C-H … X (X =: O, halide) are attributed to "hydrogen bonding". In the second part it is analyzed whether these interactions and their consequences fulfill the criteria set by standard definitions of hydrogen bonding. Two cation-anion co-conformations at the C(2)-H group are found. One co-conformer (in-plane) often resembles a hydrogen bond while the other one (on-top) points to a non-hydrogen bonding behavior. Furthermore, the degree of hydrogen bonding for the in-plane structure is very dependent on the anion. Spatial distribution functions show that, in general, both co-conformations are occupied. However, the question of how long a particular co-conformer is populated in the liquid state has yet to be answered. Therefore, it is concluded that the term "hydrogen bond" should, at present, be treated with care to characterize the cation-anion contacts, because of the above-mentioned difficulties. Once more it must be stressed that oversimplifications and generalizations, even for this subclass of ionic liquids have to be avoided, because these liquids are more complicated than it appears from first sight.
Energy Technology Data Exchange (ETDEWEB)
Mironchuk, E. S.; Narits, A. A.; Lebedev, V. S., E-mail: vlebedev@sci.lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)
2015-11-15
The resonant mechanism of interaction of alkaline-earth atoms having a low electron affinity to Rydberg atoms in circular (l = vertical bar m vertical bar = n–1) and near-circular states has been studied. To describe the dynamics of resonant processes accompanied by nonadiabatic transitions between ionic and Rydberg covalent terms of a quasimolecule, an approach based on the integration of coupled equations for the probability amplitudes has been developed taking into account the possibility of the decay of an anion in the Coulomb field of the positive ionic core of a highly excited atom. The approach involves the specific features of the problem associated with the structure of the wavefunction of a Rydberg electron in states with high orbital angular momenta l ∼ n–1. This approach provides a much more accurate description of the dynamics of electronic transitions at collisions between atoms than that within the modified semiclassical Landau–Zener model. In addition, this approach makes it possible to effectively take into account many channels of the problem. The cross sections for resonant quenching of Rydberg states of the Li(nlm) atom with given principal n, orbital l = n–1, and magnetic m quantum numbers at thermal collisions with the Ca(4s{sup 2}) and Sr(5s{sup 2}) atoms have been calculated. The dependences of the results on n, m, and angle α between the relative velocity of the atoms and the normal to the plane of the orbit of the Rydberg electron have been obtained. The influence of orientational effects on the efficiency of the collisional destruction of circular and near-circular states has been studied. The results indicate a higher stability of such states to their perturbations by neutral particles as compared to usually studied nl states with low values of l (l ≪ n)
Mironchuk, E. S.; Narits, A. A.; Lebedev, V. S.
2015-11-01
The resonant mechanism of interaction of alkaline-earth atoms having a low electron affinity to Rydberg atoms in circular ( l = | m| = n-1) and near-circular states has been studied. To describe the dynamics of resonant processes accompanied by nonadiabatic transitions between ionic and Rydberg covalent terms of a quasimolecule, an approach based on the integration of coupled equations for the probability amplitudes has been developed taking into account the possibility of the decay of an anion in the Coulomb field of the positive ionic core of a highly excited atom. The approach involves the specific features of the problem associated with the structure of the wavefunction of a Rydberg electron in states with high orbital angular momenta l ~ n-1. This approach provides a much more accurate description of the dynamics of electronic transitions at collisions between atoms than that within the modified semiclassical Landau-Zener model. In addition, this approach makes it possible to effectively take into account many channels of the problem. The cross sections for resonant quenching of Rydberg states of the Li( nlm) atom with given principal n, orbital l = n-1, and magnetic m quantum numbers at thermal collisions with the Ca(4 s 2) and Sr(5 s 2) atoms have been calculated. The dependences of the results on n, m, and angle α between the relative velocity of the atoms and the normal to the plane of the orbit of the Rydberg electron have been obtained. The influence of orientational effects on the efficiency of the collisional destruction of circular and near-circular states has been studied. The results indicate a higher stability of such states to their perturbations by neutral particles as compared to usually studied nl states with low values of l ( l ≪ n).
Grimme, Stefan; Brandenburg, Jan Gerit; Bannwarth, Christoph; Hansen, Andreas
2015-08-01
A density functional theory (DFT) based composite electronic structure approach is proposed to efficiently compute structures and interaction energies in large chemical systems. It is based on the well-known and numerically robust Perdew-Burke-Ernzerhoff (PBE) generalized-gradient-approximation in a modified global hybrid functional with a relatively large amount of non-local Fock-exchange. The orbitals are expanded in Ahlrichs-type valence-double zeta atomic orbital (AO) Gaussian basis sets, which are available for many elements. In order to correct for the basis set superposition error (BSSE) and to account for the important long-range London dispersion effects, our well-established atom-pairwise potentials are used. In the design of the new method, particular attention has been paid to an accurate description of structural parameters in various covalent and non-covalent bonding situations as well as in periodic systems. Together with the recently proposed three-fold corrected (3c) Hartree-Fock method, the new composite scheme (termed PBEh-3c) represents the next member in a hierarchy of "low-cost" electronic structure approaches. They are mainly free of BSSE and account for most interactions in a physically sound and asymptotically correct manner. PBEh-3c yields good results for thermochemical properties in the huge GMTKN30 energy database. Furthermore, the method shows excellent performance for non-covalent interaction energies in small and large complexes. For evaluating its performance on equilibrium structures, a new compilation of standard test sets is suggested. These consist of small (light) molecules, partially flexible, medium-sized organic molecules, molecules comprising heavy main group elements, larger systems with long bonds, 3d-transition metal systems, non-covalently bound complexes (S22 and S66×8 sets), and peptide conformations. For these sets, overall deviations from accurate reference data are smaller than for various other tested DFT methods
Grimme, Stefan; Brandenburg, Jan Gerit; Bannwarth, Christoph; Hansen, Andreas
2015-08-07
A density functional theory (DFT) based composite electronic structure approach is proposed to efficiently compute structures and interaction energies in large chemical systems. It is based on the well-known and numerically robust Perdew-Burke-Ernzerhoff (PBE) generalized-gradient-approximation in a modified global hybrid functional with a relatively large amount of non-local Fock-exchange. The orbitals are expanded in Ahlrichs-type valence-double zeta atomic orbital (AO) Gaussian basis sets, which are available for many elements. In order to correct for the basis set superposition error (BSSE) and to account for the important long-range London dispersion effects, our well-established atom-pairwise potentials are used. In the design of the new method, particular attention has been paid to an accurate description of structural parameters in various covalent and non-covalent bonding situations as well as in periodic systems. Together with the recently proposed three-fold corrected (3c) Hartree-Fock method, the new composite scheme (termed PBEh-3c) represents the next member in a hierarchy of "low-cost" electronic structure approaches. They are mainly free of BSSE and account for most interactions in a physically sound and asymptotically correct manner. PBEh-3c yields good results for thermochemical properties in the huge GMTKN30 energy database. Furthermore, the method shows excellent performance for non-covalent interaction energies in small and large complexes. For evaluating its performance on equilibrium structures, a new compilation of standard test sets is suggested. These consist of small (light) molecules, partially flexible, medium-sized organic molecules, molecules comprising heavy main group elements, larger systems with long bonds, 3d-transition metal systems, non-covalently bound complexes (S22 and S66×8 sets), and peptide conformations. For these sets, overall deviations from accurate reference data are smaller than for various other tested DFT methods
Energy Technology Data Exchange (ETDEWEB)
Grimme, Stefan, E-mail: grimme@thch.uni-bonn.de; Brandenburg, Jan Gerit; Bannwarth, Christoph; Hansen, Andreas [Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie, Rheinische Friedrich-Wilhelms Universität Bonn, Beringstraße 4, 53115 Bonn (Germany)
2015-08-07
A density functional theory (DFT) based composite electronic structure approach is proposed to efficiently compute structures and interaction energies in large chemical systems. It is based on the well-known and numerically robust Perdew-Burke-Ernzerhoff (PBE) generalized-gradient-approximation in a modified global hybrid functional with a relatively large amount of non-local Fock-exchange. The orbitals are expanded in Ahlrichs-type valence-double zeta atomic orbital (AO) Gaussian basis sets, which are available for many elements. In order to correct for the basis set superposition error (BSSE) and to account for the important long-range London dispersion effects, our well-established atom-pairwise potentials are used. In the design of the new method, particular attention has been paid to an accurate description of structural parameters in various covalent and non-covalent bonding situations as well as in periodic systems. Together with the recently proposed three-fold corrected (3c) Hartree-Fock method, the new composite scheme (termed PBEh-3c) represents the next member in a hierarchy of “low-cost” electronic structure approaches. They are mainly free of BSSE and account for most interactions in a physically sound and asymptotically correct manner. PBEh-3c yields good results for thermochemical properties in the huge GMTKN30 energy database. Furthermore, the method shows excellent performance for non-covalent interaction energies in small and large complexes. For evaluating its performance on equilibrium structures, a new compilation of standard test sets is suggested. These consist of small (light) molecules, partially flexible, medium-sized organic molecules, molecules comprising heavy main group elements, larger systems with long bonds, 3d-transition metal systems, non-covalently bound complexes (S22 and S66×8 sets), and peptide conformations. For these sets, overall deviations from accurate reference data are smaller than for various other tested DFT
Entropy squeezing of the field interacting with a nearly degenerate V-type three-level atom
Institute of Scientific and Technical Information of China (English)
Zhou Qing-Chun; Zhu Shi-Ning
2005-01-01
The position- and momentum-entopic squeezing properties of the optical field in the system of a nearly degenerate three-level atom interacting with a single-mode field are investigated. Calculation results indicate that when the field is initially in the vacuum state, it may lead to squeezing of the position entropy or the momentum entropy of the field if the atom is prepared properly. The effects of initial atomic state and the splitting of the excited levels of the atom on field entropies are discussed in this case. When the initial field is in a coherent state, we find that position-entropy squeezing of the field is present even if the atom is prepared in the ground state. By comparing the variance squeezing and entropy squeezing of the field we confirm that entropy is more sensitive than variance in measuring quantum fluctuations.
Dynamics of bell-nonlocality for two atoms interacting with a vacuum multi-mode noise field
Liu, Yu-Jie; Zheng, Li; Han, Dong-Mei; Lü, Huan-Lin; Zheng, Tai-Yu
2016-06-01
We investigate the internal-state Bell nonlocal entanglement dynamics, as measured by CHSH inequality of two atoms interacting with a vacuum multi-mode noise field by taking into account the spatial degrees of freedom of the two atoms. The dynamics of Bell nonlocality of the atoms with the atomic internal states being initially in a Werner-type state is studied, by deriving the analytical solutions of the Schrödinger equation, and tracing over the degrees of freedom of the field and the external motion of the two atoms. In addition, through comparison with entanglement as measured by concurrence, we find that the survival time of entanglement is much longer than that of the Bell-inequality violation. And the comparison of the quantum correlation time between two Werner-type states is discussed.
Institute of Scientific and Technical Information of China (English)
Rong Zhang; Wen-juan Wu; Jing-man Huang; Xin Meng
2011-01-01
All-atom molecular dynamics (MD) simulation and the NMR spectra are used to investigate the interactions in N-glycylglycine aqueous solution.Different types of atoms exhibit different capability in forming hydrogen bonds by the radial distribution function analysis.Some typical dominant aggregates are found in different types of hydrogen bonds by the statistical hydrogen-bonding network.Moreover,temperature-dependent NMR are used to compare with the results of the MD simulations.The chemical shifts of the three hydrogen atoms all decrease with the temperature increasing which reveals that the hydrogen bonds are dominant in the glycylglycine aqueous solution.And the NMR results show agreement with the MD simulations.All-atom MD simulations and NMR spectra are successful in revealing the structures and interactions in the N-glycylglycine-water mixtures.
Institute of Scientific and Technical Information of China (English)
CHEN Chang-Yong
2006-01-01
A scheme for approximately and conditionally teleporting an unknown atomic state via two-photon interaction in cavity QED is proposed. It is the extension of the scheme of Ref. [11] [Phys. Rev. A 69 (2004) 064302], which is based on Jaynes-Cummings model in QED and where only a time point of system evolution and the corresponding fidelity implementing the teleportation are given. In our scheme, the two-photon interaction Jaynes-Cummings model is used to realize the approximate and conditional teleportation. Our scheme does not involve the Bell-state measurement and an additional atom, only requiring two atoms and one single-mode cavity. The fidelity of the scheme is higher than that of Ref. [11]. The scheme may be generalized to not only the teleportation of the state of a cavity mode to another mode by means of a single atom but also the teleportation of the state of a trapped ion.
Structured Learning of Two-Level Dynamic Rankings
Raman, Karthik; Shivaswamy, Pannaga
2011-01-01
For ambiguous queries, conventional retrieval systems are bound by two conflicting goals. On the one hand, they should diversify and strive to present results for as many query intents as possible. On the other hand, they should provide depth for each intent by displaying more than a single result. Since both diversity and depth cannot be achieved simultaneously in the conventional static retrieval model, we propose a new dynamic ranking approach. Dynamic ranking models allow users to adapt the ranking through interaction, thus overcoming the constraints of presenting a one-size-fits-all static ranking. In particular, we propose a new two-level dynamic ranking model for presenting search results to the user. In this model, a user's interactions with the first-level ranking are used to infer this user's intent, so that second-level rankings can be inserted to provide more results relevant for this intent. Unlike for previous dynamic ranking models, we provide an algorithm to efficiently compute dynamic ranking...
da Silva, Aline C N; Deda, Daiana K; Bueno, Carolina C; Moraes, Ariana S; Da Roz, Alessandra L; Yamaji, Fabio M; Prado, Rogilene A; Viviani, Vadim; Oliveira, Osvaldo N; Leite, Fábio L
2014-09-01
The development of sensitive methodologies for detecting agrochemicals has become important in recent years due to the increasingly indiscriminate use of these substances. In this context, nanosensors based on atomic force microscopy (AFM) tips are useful because they provide higher sensitivity with operation at the nanometer scale. In this paper we exploit specific interactions between AFM tips functionalized with the enzyme acetolactate synthase (ALS) to detect the ALS-inhibitor herbicides metsulfuron-methyl and imazaquin. Using atomic force spectroscopy (AFS) we could measure the adhesion force between tip and substrate, which was considerably higher when the ALS-functionalized tip (nanobiosensor) was employed. The increase was approximately 250% and 160% for metsulfuron-methyl and imazaquin, respectively, in comparison to unfunctionalized probes. We estimated the specific enzyme-herbicide force by assuming that the measured force comprises an adhesion force according to the Johnson-Kendall-Roberts (JKR) model, the capillary force and the specific force. We show that the specific, biorecognition force plays a crucial role in the higher sensitivity of the nanobiosensor, thus opening the way for the design of similarly engineered tips for detecting herbicides and other analytes.
Dynamics of gas-surface interactions atomic-level understanding of scattering processes at surfaces
Díez Muniño, Ricardo
2013-01-01
This book gives a representative survey of the state of the art of research on gas-surface interactions. It provides an overview of the current understanding of gas surface dynamics and, in particular, of the reactive and non-reactive processes of atoms and small molecules at surfaces. Leading scientists in the field, both from the theoretical and the experimental sides, write in this book about their most recent advances. Surface science grew as an interdisciplinary research area over the last decades, mostly because of new experimental technologies (ultra-high vacuum, for instance), as well as because of a novel paradigm, the ‘surface science’ approach. The book describes the second transformation which is now taking place pushed by the availability of powerful quantum-mechanical theoretical methods implemented numerically. In the book, experiment and theory progress hand in hand with an unprecedented degree of accuracy and control. The book presents how modern surface science targets the atomic-level u...
Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo
2014-09-16
Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles.
Direct force measurement of single DNA-peptide interactions using atomic force microscopy.
Chung, Ji W; Shin, Dongjin; Kwak, June M; Seog, Joonil
2013-06-01
The selective interactions between DNA and miniature (39 residues) engineered peptide were directly measured at the single-molecule level by using atomic force microscopy. This peptide (p007) contains an α-helical recognition site similar to leucine zipper GCN4 and specifically recognizes the ATGAC sequence in the DNA with nanomolar affinity. The average rupture force was 42.1 pN, which is similar to the unbinding forces of the digoxigenin-antidigoxigenin complex, one of the strongest interactions in biological systems. The single linear fit of the rupture forces versus the logarithm of pulling rates showed a single energy barrier with a transition state located at 0.74 nm from the bound state. The smaller koff compared with that of other similar systems was presumably due to the increased stability of the helical structure by putative folding residues in p007. This strong sequence-specific DNA-peptide interaction has a potential to be utilized to prepare well-defined mechanically stable DNA-protein hybrid nanostructures.
Laser-material interaction during atom probe tomography of oxides with embedded metal nanoparticles
Energy Technology Data Exchange (ETDEWEB)
Shinde, D.; Arnoldi, L.; Devaraj, A.; Vella, A.
2016-10-28
Oxide-supported metal nano-particles are of great interest in catalysis but also in the development of new large-spectrum-absorption materials. The design of such nano materials requires three-dimensional characterization with a high spatial resolution and elemental selectivity. The laser assisted Atom Probe Tomography (La-APT) presents both these capacities if an accurate understanding of laser-material interaction is developed. In this paper, we focus on the fundamental physics of field evaporation as a function of sample geometry, laser power, and DC electric field for Au nanoparticles embedded in MgO. By understanding the laser-material interaction through experiments and a theoretical model of heat diffusion inside the sample after the interaction with laser pulse, we point out the physical origin of the noise and determine the conditions to reduce it by more than one order of magnitude, improving the sensitivity of the La-APT for metal-dielectric composites. Published by AIP Publishing.
An Atomic Force Microscopy Study of the Interactions Involving Polymers and Silane Networks
Directory of Open Access Journals (Sweden)
Rodrigo L. Oréfice
1998-12-01
Full Text Available ABSTRACT: Silane coupling agents have been frequently used as interfacial agents in polymer composites to improve interfacial strength and resistance to fluid migration. Although the capability of these agents in improving properties and performance of composites has been reported, there are still many uncertainties regarding the processing-structure-property relationships and the mechanisms of coupling developed by silane agents. In this work, an Atomic Force Microscope (AFM was used to measure interactions between polymers and silica substrates, where silane networks with a series of different structures were processed. The influence of the structure of silane networks on the interactions with polymers was studied and used to determine the mechanisms involved in the coupling phenomenon. The AFM results showed that phenomena such as chain penetration, entanglements, intersegment bonding, chain conformation in the vicinities of rigid surfaces were identified as being relevant for the overall processes of adhesion and adsorption of polymeric chains within a silane network. AFM adhesion curves showed that penetration of polymeric chains through a more open silane network can lead to higher levels of interactions between polymer and silane agents.
Nonclasssical Properties in Two-Mode Fields Resonantly Interacting with a Three-Level [Ⅰ]-Type Atom
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
Some noclassical properties in electromagnetic Reid are investigated for the interaction of two-modes initially taken in coherent-state representation with the three-level [Ⅰ]-type atom, such as squeezing properties and violation of the Cauchy-Schwartz inequality. The enhancement of Geld squeezing is found by selective atomic measurement. The Cauchy-Schwartz inequality is violated by the application of the classical Geld followed by detection in excited state.
Shifted Tietz-Wei oscillator for simulating the atomic interaction in diatomic molecules
Falaye, Babatunde J; Hamzavi, Majid
2015-01-01
The shifted Tietz-Wei (sTW) oscillator is as good as traditional Morse potential in simulating the atomic interaction in diatomic molecules. By using the Pekeris-type approximation to deal with the centrifugal term, we obtain the bound-state solutions of the radial Schr\\"odinger equation with this typical molecular model via the exact quantization rule (EQR). The energy spectrum for a set of diatomic molecules ($NO \\left(a^4\\Pi_i\\right)$, $NO \\left(B^2\\Pi_r\\right)$, $NO \\left(L'^2\\phi\\right)$, $NO \\left(b^4\\Sigma^{-}\\right)$, $ICl\\left(X^1\\Sigma_g^{+}\\right)$, $ICl\\left(A^3\\Pi_1\\right)$ and $ICl\\left(A'^3\\Pi_2\\right)$ for arbitrary values of $n$ and $\\ell$ quantum numbers are obtained. For the sake of completeness, we study the corresponding wavefunctions using the formula method.
The thermal Casimir-Polder interaction of an atom with spherical plasma shell
Khusnutdinov, Nail R
2012-01-01
The van der Waals and Casimir-Polder interaction energy of an atom with an infinitely thin sphere with finite conductivity is investigated in the framework of the hydrodynamic approach at finite temperature. The Lifshits approach is used to find the free energy. We find the close expression for the free energy and make the analysis of it for i) high and low temperatures, ii) large radii of sphere and ii) short distance from sphere. At low temperatures the thermal part of the free energy tends to zero as forth power of the temperature while for high temperatures it is proportional to the first degree of the temperature. We show that the entropy of this system is positive for small radii of sphere and it becomes negative at low temperatures and for large radii of the sphere.
Optical Control of the Resonant Dipole-Dipole Interaction between Rydberg Atoms
de Léséleuc, Sylvain; Barredo, Daniel; Lienhard, Vincent; Browaeys, Antoine; Lahaye, Thierry
2017-08-01
We report on the local control of the transition frequency of a spin 1 /2 encoded in two Rydberg levels of an individual atom by applying a state-selective light shift using an addressing beam. With this tool, we first study the spectrum of an elementary system of two spins, tuning it from a nonresonant to a resonant regime, where "bright" (super-radiant) and "dark" (subradiant) states emerge. We observe the collective enhancement of the microwave coupling to the bright state. We then show that after preparing an initial single spin excitation and letting it hop due to the spin-exchange interaction, we can freeze the dynamics at will with the addressing laser, while preserving the coherence of the system. In the context of quantum simulation, this scheme opens exciting prospects for engineering inhomogeneous X Y spin Hamiltonians or preparing spin-imbalanced initial states.
Variation of phosphorus atom state in silicon lattice at interaction with radiation defects
Bolotov, V V; Smirnov, L S
2002-01-01
The interaction of radiation defects with phosphorus atoms in silicon crystals is investigated under conditions of a different degree of supersaturation with respect to the equilibrium concentration of impurities point defects at electron irradiation and annealing. It is shown that the dose dependences of the variation of the phosphorus concentration in interstitials (P sub s) flattens out on saturation sections. The saturation level is defined by irradiation temperature. The stages of the P sub s concentration recovery at annealing correlate with temperature ranges of vacancy complex dissociation. The results obtained confirm the presence of two processes: the radiation-induced decay of the supersaturated impurity solution at point defect generation and ionization; the saturation of interstitial impurity in vacancies at sufficiently high temperature
Yang, Yong; Wang, Hong; Erie, Dorothy A
2003-02-01
Atomic force microscopy (AFM) has been applied in many biological investigations in the past 15 years. This review focuses on the application of AFM for quantitatively characterizing the structural and thermodynamic properties of protein-protein and protein-nucleic acid complexes. AFM can be used to determine the stoichiometries and association constants of multiprotein assemblies and to quantify changes in conformations of proteins and protein-nucleic acid complexes. In addition, AFM in solution permits the observation of the dynamic properties of biomolecular complexes and the measurement of intermolecular forces between biomolecules. Recent advances in cryogenic AFM, AFM on two-dimensional crystals, carbon nanotube probes, solution imaging, high-speed AFM, and manipulation capabilities enhance these applications by improving AFM resolution and the dynamic and operative capabilities of the AFM. These developments make AFM a powerful tool for investigating the biomolecular assemblies and interactions that govern gene regulation.
Van der Waals-Casimir-Polder interaction of an atom with a composite surface
Eizner, Elad; Henkel, Carsten
2012-01-01
We study the dispersion interaction of the van der Waals and Casimir-Polder (vdW-CP) type between a neutral atom and the surface of a metal by allowing for nonlocal electrodynamics, i.e. electron diffusion. We consider two models: (i) bulk diffusion, and (ii) diffusion in a surface charge layer. In both cases the transition to a semiconductor is continuous as a function of the conductivity, unlike the case of a local model. The relevant parameter is the electric screening length and depends on the carrier diffusion constant. We find that for distances comparable to the screening length, vdW-CP data can distinguish between bulk and surface diffusion, hence it can be a sensitive probe for surface states.
A Partitioned Correlation Function Interaction approach for describing electron correlation in atoms
Verdebout, S; Jönsson, P; Gaigalas, G; Fischer, C Froese; Godefroid, M
2013-01-01
Traditional multiconfiguration Hartree-Fock (MCHF) and configuration interaction (CI) methods are based on a single orthonormal orbital basis (OB). For atoms with complicated shell structures, a large OB is needed to saturate all the electron correlation effects. The large OB leads to massive configuration state function (CSF) expansions that are difficult to handle. We show that it is possible to relax the orthonormality restriction on the OB and break down the originally large calculations to a set of smaller ones that can be run in parallel. Each calculation determines a partitioned correlation function (PCF) that accounts for a specific correlation effect. The PCFs are built on optimally localized orbital sets and are added to a zero-order multireference (MR) function to form a total wave function. The mixing coefficients of the PCFs are fixed from a small generalized eigenvalue problem. The required matrices are computed using a biorthonormal transformation technique. The new method, called partitioned c...
Theory of metal atom-water interactions and alkali halide dimers
Jordan, K. D.; Kurtz, H. A.
1982-01-01
Theoretical studies of the interactions of metal atoms with water and some of its isoelectronic analogs, and of the properties of alkali halides and their aggregates are discussed. Results are presented of ab initio calculations of the heats of reaction of the metal-water adducts and hydroxyhydrides of Li, Be, B, Na, Mg, and Al, and of the bond lengths and angles an; the heats of reaction for the insertion of Al into HF, H2O, NH3, H2S and CH3OH, and Be and Mg into H2O. Calculations of the electron affinities and dipole moments and polarizabilities of selected gas phase alkali halide monomers and dimers are discussed, with particular attention given to results of calculations of the polarizability of LiF taking into account electron correlation effects, and the polarizability of the dimer (LiF)2.
Hamdi, I; Yarovitski, A; Dutier, G; Maurin, I; Saltiel, S; Li, Y; Lezama, A; Vartapetyan, T; Sarkisyan, D; Gorza, M P; Fichet, M; Bloch, D; Ducloy, M; Hamdi, Ismah\\`{e}ne; Todorov, Petko; Yarovitski, Alexander; Dutier, Gabriel; Maurin, Isabelle; Saltiel, Solomon; Li, Yuanyuan; Lezama, Arturo; Varzhapetyan, Tigran; Sarkisyan, David; Gorza, Marie-Pascale; Fichet, Mich\\`{e}le; Bloch, Daniel; Ducloy, Martial
2005-01-01
The high sensitivity of Laser Spectroscopy has made possible the exploration of atomic resonances in newly designed "nanometric" gas cells, whose local thickness varies from 20nm to more than 1000 nm. Following the initial observation of the optical analogous of the coherent Dicke microwave narrowing, the newest prospects include the exploration of long-range atom surface van der Waals interaction with spatial resolution in an unprecedented range of distances, modification of atom dielectric resonant coupling under the influence of the coupling between the two neighbouring dielectric media, and even the possible modification of interatomic collisions processes under the effect of confinement.
Institute of Scientific and Technical Information of China (English)
Lu Dao-Ming
2011-01-01
Considering three two-level atoms initially in the W or Greenberger-Horne-Zeilinger (GHZ) state, one of the three atoms is put into an initially coherent light cavity and made to resonantly interact with the cavity. The two-atom entanglement evolution outside the cavity is investigated. The influences of state-selective measurement of the atom inside the cavity and strength of the light field on the two-atom entanglement evolution outside the cavity are discussed. The results obtained from the numerical method show that the two-atom entanglement outside the cavity is strengthened through state-selective measurement of the atom inside the cavity. In addition, the strength of the light field also influences the two-atom entanglement properties.
Ghezali, S.; Taleb, A.
2008-09-01
A research project at the "Laboratoire d'électronique quantique" consists in a theoretical study of the reflection and diffraction phenomena via an atomic mirror. This poster presents the principle of an atomic mirror. Many groups in the world have constructed this type of atom optics experiments such as in Paris-Orsay-Villetaneuse (France), Stanford-Gaithersburg (USA), Munich-Heidelberg (Germany), etc. A laser beam goes into a prism with an incidence bigger than the critical incidence. It undergoes a total reflection on the plane face of the prism and then exits. The transmitted resulting wave out of the prism is evanescent and repulsive as the frequency detuning of the laser beam compared to the atomic transition δ = ωL-ω0 is positive. The cold atomic sample interacts with this evanescent wave and undergoes one or more elastic bounces by passing into backward points in its trajectory because the atoms' kinetic energy (of the order of the μeV) is less than the maximum of the dipolar potential barrier ℏΩ2/Δ where Ω is the Rabi frequency [1]. In fact, the atoms are cooled and captured in a magneto-optical trap placed at a distance of the order of the cm above the prism surface. The dipolar potential with which interact the slow atoms is obtained for a two level atom in a case of a dipolar electric transition (D2 Rubidium transition at a wavelength of 780nm delivered by a Titane-Saphir laser between a fundamental state Jf = l/2 and an excited state Je = 3/2). This potential is corrected by an attractive Van der Waals term which varies as 1/z3 in the Lennard-Jones approximation (typical atomic distance of the order of λ0/2π where λ0 is the laser wavelength) and in 1/z4 if the distance between the atom and its image in the dielectric is big in front of λ0/2π. This last case is obtained in a quantum electrodynamic calculation by taking into account an orthornormal base [2]. We'll examine the role of spontaneous emission for which the rate is inversely
Influence of the virtual photon field on the squeezing properties of an atom laser
Institute of Scientific and Technical Information of China (English)
Zhao Jian-Gang; Sun Chang-Yong; Wen Ling-Hua; Liang Bao-Long
2009-01-01
This paper investigates the squeezing properties of an atom laser without rotating-wave approximation in the system of a binomial states field interacting with a two-level atomic Bose-Einstein condensate. It discusses the influences of atomic eigenfrequency, the interaction intensity between the optical field and atoms, parameter of the binomial states field and virtual photon field on the squeezing properties. The results show that two quadrature components of an atom laser can be squeezed periodically. The duration and the degree of squeezing an atom laser have something to do with the atomic eigenfrequency and the parameter of the binomial states field, respectively. The collapse and revival frequency of atom laser fluctuation depends on the interaction intensity between the optical field and atoms. The effect of the virtual photon field deepens the depth of squeezing an atom laser.
Quantum dynamics of a driven two-level molecule with variable dephasing
Grandi, Samuele; Major, Kyle D.; Polisseni, Claudio; Boissier, Sebastien; Clark, Alex S.; Hinds, E. A.
2016-12-01
The longitudinal (Γ1) and transverse (Γ2) decay rates of a two-level quantum system have a profound influence on its evolution. Atomic systems with Γ2=1/2 Γ1 have been studied extensively, but with the rise of solid-state quantum devices it is also important to consider the effect of stronger transverse relaxation due to interactions with the solid environment. Here we study the quantum dynamics of a single organic dye molecule driven by a laser. We measure the variation of Γ2 with temperature and determine the activation energy for thermal dephasing of the optical dipole. Then we measure the second-order correlation function g(2 )(τ ) of the light emitted by the molecule for various ratios Γ2/Γ1 and saturation parameters S . We show that the general solution to the optical Bloch equations accurately describes the observed quantum dynamics over a wide range of these parameters, and we discuss the limitations of the various approximate expressions for g(2 )(τ ) that appear in the literature.
Fundamentals of PV Efficiency Interpreted by a Two-Level Model
Alam, Muhammad A
2012-01-01
Elementary physics of photovoltaic energy conversion in a two-level atomic PV is considered. We explain the conditions for which the Carnot efficiency is reached and how it can be exceeded! The loss mechanisms - thermalization, angle entropy, and below-bandgap transmission - explain the gap between Carnot efficiency and the Shockley-Queisser limit. Wide varieties of techniques developed to reduce these losses (e.g., solar concentrators, solar-thermal, tandem cells, etc.) are reinterpreted by using a two level model. Remarkably, the simple model appears to capture the essence of PV operation and reproduce the key results and important insights that are known to the experts through complex derivations.
Weyl spin-orbit-coupling-induced interactions in uniform and trapped atomic quantum fluids
Gupta, Reena; Singh, G. S.; Bosse, Jürgen
2013-11-01
We establish through analytical and numerical studies of thermodynamic quantities for noninteracting atomic gases that the isotropic three-dimensional spin-orbit coupling, the Weyl coupling, induces interaction which counters “effective” attraction (repulsion) of the exchange symmetry present in zero-coupling Bose (Fermi) gas. The exact analytical expressions for the grand potential and hence for several thermodynamic quantities have been obtained for this purpose in both uniform and trapped cases. It is enunciated that many interesting features of spin-orbit-coupled systems revealed theoretically can be understood in terms of coupling-induced modifications in statistical interparticle potential. The temperature dependence of the chemical potential, specific heat, and isothermal compressibility for a uniform Bose gas is found to have signature of the incipient Bose-Einstein condensation in the very weak coupling regime although the system does not really go in the Bose-condensed phase. The transition temperature in the harmonically trapped case decreases with an increase of coupling strength consistent with the weakening of the statistical attractive interaction. Anomalous behavior of some thermodynamic quantities, partly akin to that in dimensions less than two, appears for uniform fermions as soon as the Fermi level goes down the Dirac point on increasing the coupling strength. It is suggested that the fluctuation-dissipation theorem can be utilized to verify anomalous behaviors from studies of long-wavelength fluctuations in bunching and antibunching effects.
The Fueling Diagram: Linking Galaxy Molecular-to-Atomic Gas Ratios to Interactions and Accretion
Stark, David V; Wei, Lisa H; Baker, Andrew J; Leroy, Adam K; Eckert, Kathleen D; Vogel, Stuart N
2013-01-01
To assess how external factors such as local interactions and fresh gas accretion influence the global ISM of galaxies, we analyze the relationship between recent enhancements of central star formation and total molecular-to-atomic (H2/HI) gas ratios, using a broad sample of field galaxies spanning early-to-late type morphologies, stellar masses of 10^(7.2-11.2) Msun, and diverse stages of evolution. We find that galaxies occupy several loci in a "fueling diagram" that plots H2/HI vs. mass-corrected blue-centeredness, a metric tracing the degree to which galaxies have bluer centers than the average galaxy at their stellar mass. Spiral galaxies show a positive correlation between H2/HI and mass-corrected blue-centeredness. When combined with previous results linking mass-corrected blue-centeredness to external perturbations, this correlation suggests a link between local galaxy interactions and molecular gas inflow/replenishment. Intriguingly, E/S0 galaxies show a more complex picture: some follow the same cor...
Unraveling protein-protein interactions in clathrin assemblies via atomic force spectroscopy.
Jin, Albert J; Lafer, Eileen M; Peng, Jennifer Q; Smith, Paul D; Nossal, Ralph
2013-03-01
Atomic force microscopy (AFM), single molecule force spectroscopy (SMFS), and single particle force spectroscopy (SPFS) are used to characterize intermolecular interactions and domain structures of clathrin triskelia and clathrin-coated vesicles (CCVs). The latter are involved in receptor-mediated endocytosis (RME) and other trafficking pathways. Here, we subject individual triskelia, bovine-brain CCVs, and reconstituted clathrin-AP180 coats to AFM-SMFS and AFM-SPFS pulling experiments and apply novel analytics to extract force-extension relations from very large data sets. The spectroscopic fingerprints of these samples differ markedly, providing important new information about the mechanism of CCV uncoating. For individual triskelia, SMFS reveals a series of events associated with heavy chain alpha-helix hairpin unfolding, as well as cooperative unraveling of several hairpin domains. SPFS of clathrin assemblies exposes weaker clathrin-clathrin interactions that are indicative of inter-leg association essential for RME and intracellular trafficking. Clathrin-AP180 coats are energetically easier to unravel than the coats of CCVs, with a non-trivial dependence on force-loading rate.
Atomic resolution model of the antibody Fc interaction with the complement C1q component.
Schneider, Sebastian; Zacharias, Martin
2012-05-01
The globular C1q heterotrimer is a subunit of the C1 complement factor. Binding of the C1q subunit to the constant (Fc) part of antibody molecules is a first step and key event of complement activation. Although three-dimensional structures of C1q and antibody Fc subunits have been determined experimentally no atomic resolution structure of the C1q-Fc complex is known so far. Based on systematic protein-protein docking searches and Molecular Dynamics simulations a structural model of the C1q-IgG1-Fc-binding geometry has been obtained. The structural model is compatible with available experimental data on the interaction between the two partner proteins. It predicts a binding geometry that involves mainly the B-subunit of the C1q-trimer and both subunits of the IgG1-Fc-dimer with small conformational adjustments with respect to the unbound partners to achieve high surface complementarity. In addition to several charge-charge and polar contacts in the rim region of the interface it also involves nonpolar contacts between the two proteins and is compatible with the carbohydrate moiety of the Fc subunit. The model for the complex structure provides a working model for rationalizing available biochemical data on this important interaction and can form the basis for the design of Fc variants with a greater capacity to activate the complement system for example on binding to cancer cells or other target structures.
Directory of Open Access Journals (Sweden)
A Ruggeri
2009-12-01
Full Text Available The extracellular matrix of unfixed, unstained rat corneal stroma, visualized with high-resolution scanning electron microscopy and atomic force microscopy after minimal preliminary treatment, appears composed of straight, parallel, uniform collagen fibrils regularly spaced by a three-dimensional, irregular network of thin, delicate proteoglycan filaments. Rat tail tendon, observed under identical conditions, appears instead made of heterogeneous, closely packed fibrils interwoven with orthogonal proteoglycan filaments. Pre-treatment with cupromeronic blue just thickens the filaments without affecting their spatial layout. Digestion with chondroitinase ABC rids the tendon matrix of all its interconnecting filaments while the corneal stroma architecture remains virtually unaffected, its fibrils always being separated by an evident interfibrillar spacing which is never observed in tendon. Our observations indicate that matrix proteoglycans are responsible for both the highly regular interfibrillar spacing which is distinctive of corneal stroma, and the strong interfibrillar binding observed in tendon. These opposite interaction patterns appear to be distinctive of different proteo- glycan species. The molecular details of proteoglycan interactions are still incompletely understood and are the subject of ongoing research.
Hsueh, Carlin
Nanotechnology has a unique and relatively untapped utility in the fields of medicine and dentistry at the level of single-biopolymer and -molecule diagnostics. In recent years atomic force microscopy (AFM) has garnered much interest due to its ability to obtain atomic-resolution of molecular structures and probe biophysical behaviors of biopolymers and proteins in a variety of biologically significant environments. The work presented in this thesis focuses on the nanoscale manipulation and observation of biopolymers to develop an innovative technology for personalized medicine while understanding complex biological systems. These studies described here primarily use AFM to observe biopolymer interactions with proteins and its surroundings with unprecedented resolution, providing a better understanding of these systems and interactions at the nanoscale. Transcriptional profiling, the measure of messenger RNA (mRNA) abundance in a single cell, is a powerful technique that detects "behavior" or "symptoms" at the tissue and cellular level. We have sought to develop an alternative approach, using our expertise in AFM and single molecule nanotechnology, to achieve a cost-effective high throughput method for sensitive detection and profiling of subtle changes in transcript abundance. The technique does not require amplification of the mRNA sample because the AFM provides three-dimensional views of molecules with unprecedented resolution, requires minimal sample preparation, and utilizes a simple tagging chemistry on cDNA molecules. AFM images showed collagen polymers in teeth and of Drebrin-A remodeling of filamentous actin structure and mechanics. AFM was used to image collagen on exposed dentine tubules and confirmed tubule occlusion with a desensitizing prophylaxis paste by Colgate-Palmolive. The AFM also superseded other microscopy tools in resolving F-actin helix remodeling and possible cooperative binding by a neuronal actin binding protein---Drebrin-A, an
McNamee, Cathy E; Butt, Hans-Jürgen; Higashitani, Ko; Vakarelski, Ivan U; Kappl, Michael
2009-10-06
Atomic force microscopy was used to study the adsorption of the surfactant octadecyl trimethyl ammonium chloride (C18TAC) at a low concentration (0.03 mM) to negatively charged surfaces in water. Atomic force microscopy tips were functionalized with dimethyloctadecyl(3-tripropyl)ammonium chloride (C18TAC-si) or N-trimethoxysilylpropyl-N,N,N-trimethylammomium chloride (hydrophilpos-si) to facilitate imaging of the adsorbed surfactant without artifacts. Tapping mode images and force measurements revealed C18TAC patches, identified as partial surfactant bilayers or hemimicelles. The forces controlling the adsorption process of the C18TAC to a negatively charged surface were investigated by measuring the forces between a C18TAC-si or a hydrophilpos-si tip and a silica surface in the presence of varying concentrations of either NaCl or NaNO3. Screening of forces with an increasing NaCl concentration was observed for the C18TAC-si and hydrophilpos-si tips, proving an electrostatic contribution. Screening was also observed for the hydrophilpos-si tip in NaNO3, whereas a long-range attraction was observed for the C18TAC-si tip for all NaNO3 concentrations. These results indicate that screening of the forces for the C18TAC-si tip depended on the type and/or size of the anion, possibly due to a different probability of the anions to enter the silane layers. The interaction of C18TAC patches with C18TAC-si tips in the presence of NaCl and the interaction of the patches with hydrophilpos-si tips in either NaCl or NaNO3 were repulsive and independent of the number of force curves measured, indicating a stable, positively charged C18TAC patch. However, the forces measured between the patches and a C18TAC-si tip in NaNO3 depended on the number of force curves measured, indicating a change in patch structure induced by the first interaction.
Jafari, Rahim; Sadeghi, Mehdi; Mirzaie, Mehdi
2016-05-01
The approaches taken to represent and describe structural features of the macromolecules are of major importance when developing computational methods for studying and predicting their structures and interactions. This study attempts to explore the significance of Delaunay tessellation for the definition of atomic interactions by evaluating its impact on the performance of scoring protein-protein docking prediction. Two sets of knowledge-based scoring potentials are extracted from a training dataset of native protein-protein complexes. The potential of the first set is derived using atomic interactions extracted from Delaunay tessellated structures. The potential of the second set is calculated conventionally, that is, using atom pairs whose interactions were determined by their separation distances. The scoring potentials were tested against two different docking decoy sets and their performances were compared. The results show that, if properly optimized, the Delaunay-based scoring potentials can achieve higher success rate than the usual scoring potentials. These results and the results of a previous study on the use of Delaunay-based potentials in protein fold recognition, all point to the fact that Delaunay tessellation of protein structure can provide a more realistic definition of atomic interaction, and therefore, if appropriately utilized, may be able to improve the accuracy of pair potentials.
Two-Level Fingerprinting Codes: Non-Trivial Constructions
Rochanakul, Penying
2011-01-01
We extend the concept of two-level fingerprinting codes, introduced by Anthapadmanabhan and Barg (2009) in context of traceability (TA) codes, to other types of fingerprinting codes, namely identifiable parent property (IPP) codes, secure-frameproof (SFP) codes, and frameproof (FP) codes. We define and propose the first explicit non-trivial construction for two-level IPP, SFP and FP codes.
Random-Defect Laser: Manipulating Lossy Two-Level Systems to Produce a Circuit with Coherent Gain
Rosen, Yaniv J.; Khalil, Moe S.; Burin, Alexander L.; Osborn, Kevin D.
2016-04-01
We demonstrate a laser using material defects known for deleterious microwave absorption in quantum computing. These defects are two-level atomic tunneling systems (TSs), which are manipulated using a uniform swept dc electric field and two ac pump fields. The swept field changes the TS energies. TSs first pass through degeneracy with pump photons, which invert (excite) them with a high probability using rapid adiabatic passage. Population inversion is accomplished in spite of a broad distribution of TS parameters. Afterwards the TSs are brought to degeneracy with the resonator where they emit photons. The emission is found to be dependent on individual cavity-TS interactions, and the narrowing linewidth at increasing photon occupancy indicates stimulated emission. Characterization with a microwave probe shows a transition from ordinary defect loss to negligible microwave absorption, and ultimately to coherent amplification. Thus, instead of absorbing microwave energy, the TSs can be tuned to reduce loss and even amplify signals.
Arafat, A Syed Yasir; Arun, A; Ilamathi, M; Asha, J; Sivashankari, P R; D'Souza, Cletus J M; Sivaramakrishnan, V; Dhananjaya, B L
2014-03-01
5' Nucleotidase (5' NUC) is a ubiquitously distributed enzyme known to be present in snake venoms (SV) that is responsible primarily for causing dysregulation of physiological homeostasis in humans by inducing anticoagulant effects and by inhibiting platelet aggregation. It is also known to act synergistically with other toxins to exert a more pronounced anti-coagulant effect during envenomation. Its structural and functional role is not yet ascertained clearly. The 3D structure of snake venom 5' nucleotidase (SV-5' NUC) is not yet known and was predicted by us for the first time using a comparative homology modeling approach using Demansia vestigiata protein sequence. The accuracy and stability of the predicted SV-5' NUC structure were validated using several computational approaches. Key interactions of SV-5' NUC were studied using experimental studies/molecular docking analysis of the inhibitors vanillin, vanillic acid and maltol. All these inhibitors were found to dock favorably following pharmacologically relevant absorption, distribution, metabolism and excretion (ADME) profiles. Further, atomic level docking interaction studies using inhibitors of the SV-5' NUC active site revealed amino acid residues Y65 and T72 as important for inhibitor-(SV-5' NUC) interactions. Our in silico analysis is in good agreement with experimental inhibition results of SV-5' NUC with vanillin, vanillic acid and maltol. The present study should therefore play a guiding role in the experimental design of new SV-5' NUC inhibitors for snake bite management. We also identified a few pharmacophoric features essential for SV-5' NUC inhibitory activity that can be utilized further for the discovery of putative anti-venom agents of therapeutic value for snake bite management.
Sherlock, David J.; Chandrasekaran, A.; Prakasha, T. K.; Day, Roberta O.; Holmes, Robert R.
1998-01-12
New bicyclic tetraoxyphosphoranes all containing a six-membered oxaphosphorinane ring, C(6)H(8)(CH(2)O)(2)P(OC(12)H(8))(OXyl) (1), (C(6)H(4)O)(2)P(OC(12)H(8))(OXyl) (2), CH(2)[(t-Bu)(2)C(6)H(2)O](2)P(OC(12)H(8))(OXyl) (3), O(2)S[(t-Bu)MeC(6)H(2)O](2)P(OC(12)H(8))(OXyl) (4), and S[(t-Bu)MeC(6)H(2)O](2)P(OC(12)H(8))(OXyl) (5), were synthesized by the oxidative addition reaction of the cyclic phosphine P(OC(12)H(8))(OXyl) (6) with an appropriate diol in the presence of N-chlorodiisopropylamine. X-ray analysis revealed trigonal bipyramidal (TBP) geometries for 1-4 where the dioxa ring varied in size from six- to eight-membered. With a sulfur donor atom as part of an eight-membered ring in place of a potential oxygen donor atom of a sulfone group as in 4, the X-ray study of 5 showed the formation of a hexacoordinated structure via a P-S interaction. Ring constraints are evaluated to give an order of conformational flexibility associated with the (TBP) tetraoxyphosphoranes 4 > 3 approximately 1 > 2 which parallels the degree of shielding from (31)P NMR chemical shifts: 4 > 3 > 1 > 2. The six- and seven-membered dioxa rings in 1 and 2, respectively, are positioned at axial-equatorial sites, whereas the eight-membered dioxa ring in 3 and 4 occupies diequatorial sites of a TBP. V-T (1)H NMR data give barriers to xylyl group rotation about the C-OXyl bond. The geometry of 5 is located along a coordinate from square pyramidal toward octahedral to the extent of 60.7%. Achieving hexacoordination in bicyclic tetraoxyphosphoranes of reduced electrophilicity relative to bicyclic pentaoxyphosphoranes appears to be dependent on the presence of a sufficiently strong donor atom.
Blagov, E V; Mostepanenko, V M
2005-01-01
The Lifshitz theory of the van der Waals force is extended for the case of an atom (molecule) interacting with a plane surface of an uniaxial crystal or with a long solid cylinder or cylindrical shell made of isotropic material or uniaxial crystal. For a microparticle near a semispace or flat plate made of an uniaxial crystal the exact expressions for the free energy of the van der Waals and Casimir-Polder interaction are presented. An approximate expression for the free energy of microparticle- cylinder interaction is obtained which becomes precise for microparticle-cylinder separations much smaller than cylinder radius. The obtained expressions are used to investigate the van der Waals interaction between hydrogen atoms (molecules) and graphite plates or multiwall carbon nanotubes. To accomplish this the behavior of graphite dielectric permittivities along the imaginary frequency axis is found using the optical data for the complex refractive index of graphite for the ordinary and extraordinary rays. It is ...
Yang, Chui-Ping
2012-01-01
We propose a method to generate a GHZ entangled state of n photons in n microwave cavities (or resonators) via resonant interaction to a single superconducting qubit. By performing local operations on a qubit (e.g., a solid-state qubit, an atom, etc.) placed in each cavity, the created GHZ states of n photons can be transferred to qubits for storage. The proposed scheme greatly reduces effect of decoherence since only resonant qubit-cavity interaction and resonant qubit-pulse interaction are involved, and no measurement is required. In addition, we show that the method can be applied to create a GHZ state of photons in multiple cavities via an atom through resonant interaction with no measurement needed.
Directory of Open Access Journals (Sweden)
Armend Gazmeno Håti
Full Text Available Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g. viscosity, gelation and ion binding. Here, the interactions between epimerases AlgE4 and AlgE6 and alginate substrates as well as epimerization products were determined. The interactions of the various epimerase-polysaccharide pairs were determined over an extended range of force loading rates by the combined use of optical tweezers and atomic force microscopy. When studying systems that in nature are not subjected to external forces the access to observations obtained at low loading rates, as provided by optical tweezers, is a great advantage since the low loading rate region for these systems reflect the properties of the rate limiting energy barrier. The AlgE epimerases have a modular structure comprising both A and R modules, and the role of each of these modules in the epimerization process were examined through studies of the A- module of AlgE6, AlgE6A. Dynamic strength spectra obtained through combination of atomic force microscopy and the optical tweezers revealed the existence of two energy barriers in the alginate-epimerase complexes, of which one was not revealed in previous AFM based studies of these complexes. Furthermore, based on these spectra estimates of the locations of energy transition states (xβ, lifetimes in the absence of external perturbation (τ0 and free energies (ΔG# were determined for the different epimerase-alginate complexes. This is the first determination of ΔG# for these complexes. The values determined were up to 8 kBT for the outer barrier, and smaller values for the inner barriers. The size of the free energies determined are consistent with the interpretation that the enzyme and substrate are thus not tightly locked at all times but are able to relocate
Håti, Armend Gazmeno; Aachmann, Finn Lillelund; Stokke, Bjørn Torger; Skjåk-Bræk, Gudmund; Sletmoen, Marit
2015-01-01
Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g. viscosity, gelation and ion binding. Here, the interactions between epimerases AlgE4 and AlgE6 and alginate substrates as well as epimerization products were determined. The interactions of the various epimerase-polysaccharide pairs were determined over an extended range of force loading rates by the combined use of optical tweezers and atomic force microscopy. When studying systems that in nature are not subjected to external forces the access to observations obtained at low loading rates, as provided by optical tweezers, is a great advantage since the low loading rate region for these systems reflect the properties of the rate limiting energy barrier. The AlgE epimerases have a modular structure comprising both A and R modules, and the role of each of these modules in the epimerization process were examined through studies of the A- module of AlgE6, AlgE6A. Dynamic strength spectra obtained through combination of atomic force microscopy and the optical tweezers revealed the existence of two energy barriers in the alginate-epimerase complexes, of which one was not revealed in previous AFM based studies of these complexes. Furthermore, based on these spectra estimates of the locations of energy transition states (xβ), lifetimes in the absence of external perturbation (τ0) and free energies (ΔG#) were determined for the different epimerase-alginate complexes. This is the first determination of ΔG# for these complexes. The values determined were up to 8 kBT for the outer barrier, and smaller values for the inner barriers. The size of the free energies determined are consistent with the interpretation that the enzyme and substrate are thus not tightly locked at all times but are able to relocate. Together with the
Håti, Armend Gazmeno; Aachmann, Finn Lillelund; Stokke, Bjørn Torger; Skjåk-Bræk, Gudmund; Sletmoen, Marit
2015-01-01
Mannuronan C-5 epimerases are a family of enzymes that catalyze epimerization of alginates at the polymer level. This group of enzymes thus enables the tailor-making of various alginate residue sequences to attain various functional properties, e.g. viscosity, gelation and ion binding. Here, the interactions between epimerases AlgE4 and AlgE6 and alginate substrates as well as epimerization products were determined. The interactions of the various epimerase–polysaccharide pairs were determined over an extended range of force loading rates by the combined use of optical tweezers and atomic force microscopy. When studying systems that in nature are not subjected to external forces the access to observations obtained at low loading rates, as provided by optical tweezers, is a great advantage since the low loading rate region for these systems reflect the properties of the rate limiting energy barrier. The AlgE epimerases have a modular structure comprising both A and R modules, and the role of each of these modules in the epimerization process were examined through studies of the A- module of AlgE6, AlgE6A. Dynamic strength spectra obtained through combination of atomic force microscopy and the optical tweezers revealed the existence of two energy barriers in the alginate-epimerase complexes, of which one was not revealed in previous AFM based studies of these complexes. Furthermore, based on these spectra estimates of the locations of energy transition states (xβ), lifetimes in the absence of external perturbation (τ0) and free energies (ΔG#) were determined for the different epimerase–alginate complexes. This is the first determination of ΔG# for these complexes. The values determined were up to 8 kBT for the outer barrier, and smaller values for the inner barriers. The size of the free energies determined are consistent with the interpretation that the enzyme and substrate are thus not tightly locked at all times but are able to relocate. Together with the
Two-level cervical disc replacement: perspectives and patient selection
Directory of Open Access Journals (Sweden)
Narain AS
2017-02-01
Full Text Available Ankur S Narain, Fady Y Hijji, Daniel D Bohl, Kelly H Yom, Krishna T Kudaravalli, Kern Singh Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL, USA Introduction: Cervical disc replacement (CDR is an emerging treatment option for cervical degenerative disease. Postulated benefits of cervical disc replacement compared to anterior cervical discectomy and fusion include preserved motion at the operative segments and decreased motion at adjacent levels. Multiple studies have been performed investigating the outcomes of CDR in single-level pathology. The investigation of the use of CDR in two-level pathology is an emerging topic within the literature.Purpose: To critically evaluate the literature regarding two-level CDR in order to determine its utility compared to two-level cervical arthrodesis. Patient selection factors including indications and contraindications will also be explored.Methods: The PubMed database was searched for all articles published on the subject of two-level CDR up until October 2016. Studies were classified by publication year, study design, sample size, follow-up interval, and conflict of interest. Outcomes were recorded from each study, and included data on patient-reported outcomes, radiographic measurements, range of motion, peri- and postoperative complications, heterotopic ossification, adjacent segment disease, reoperation rate, and total intervention cost. Results: Fourteen studies were included in this review. All studies demonstrated at least noninferiority of two-level CDR compared to both two-level arthrodesis and single-level CDR. Patient selection in two-level CDR is driven by the inclusion and exclusion criteria presented in prospective, randomized controlled trials. The most common indication is subaxial degenerative disc disease over two contiguous levels presenting with radiculopathy or myelopathy. Furthermore, costs analyses trended toward at least noninferiority of two-level
Use of a PhET Interactive Simulation in General Chemistry Laboratory: Models of the Hydrogen Atom
Clark, Ted M.; Chamberlain, Julia M.
2014-01-01
An activity supporting the PhET interactive simulation, Models of the Hydrogen Atom, has been designed and used in the laboratory portion of a general chemistry course. This article describes the framework used to successfully accomplish implementation on a large scale. The activity guides students through a comparison and analysis of the six…
Aguiar, Joana G.; Correia, Paulo R. M.
2016-01-01
In this paper, we explore the use of concept maps (Cmaps) as instructional materials prepared by teachers, to foster the understanding of chemistry. We choose fireworks as a macroscopic event to teach basic chemical principles related to the Bohr atomic model and matter-energy interaction. During teachers' Cmap navigation, students can experience…
Use of a PhET Interactive Simulation in General Chemistry Laboratory: Models of the Hydrogen Atom
Clark, Ted M.; Chamberlain, Julia M.
2014-01-01
An activity supporting the PhET interactive simulation, Models of the Hydrogen Atom, has been designed and used in the laboratory portion of a general chemistry course. This article describes the framework used to successfully accomplish implementation on a large scale. The activity guides students through a comparison and analysis of the six…
Dynamics of Two-Level Trapped Ion in a Standing Wave Laser in Noncommutative Space
Institute of Scientific and Technical Information of China (English)
YANG Xiao-Xue; WU Ying
2007-01-01
We study the dynamics of a two-level trapped ion in a standing wave electromagnetic field in two-dimensional (2D) noncommutative spaces in the Lamb-Dicke regime under the rotating wave approximation. We obtain the explicit analytical expressions for the energy spectra, energy eigenstates, unitary time evolution operator, atomic inversion, and phonon number operators. The Rabi oscillations, the collapse, and revivals in the average atomic inversion and the average phonon number are explicitly shown to contain the information of the parameter of the space noncommutativity,which sheds light on proposing new schemes based on the dynamics of trappedion to test the noncommutativity.
Kucheryaev, YA; Pal'chikov, VG; Pchelin, YA; Sokolov, YL; Yakovlev, VP
2005-01-01
The interference of the 2P state of the hydrogen atom due to unknown long-range interaction with the metal surface (Sokolov effect) has been studied by an atomic interferometer. In contrast to previous experiments, where an atomic beam passed through slits in metal plates, a beam in the presented ex
The Two-level Management System of University and School
Institute of Scientific and Technical Information of China (English)
Yang Xu
2013-01-01
With the development of our country's higher e-ducation, the school also presents the great-leap-forward devel-opment trend. The previous denotative development has changed into the way of connotative development. The two-level management system of university and school is the most common management mode in many colleges. This paper intro-duces the advantage of this mode in the objective view, analyzes the problems existing in the practice operation, put forward countermeasures to improve the two-level management and proposes a method to build the two-level management system.
Measurement of the parity nonconserving neutral weak interaction in atomic thallium
Energy Technology Data Exchange (ETDEWEB)
Bucksbaum, P.H.
1980-11-01
This thesis describes an experiment to measure parity nonconservation in atomic thallium. A frequency doubled, flashlamp pumped tunable dye laser is used to excite the 6P/sub 1/2/(F = 0) ..-->.. 7P/sub 1/2/(F = 1) transition at 292.7 nm, with circularly polarized light. An electrostatic field E of 100 to 300 V/cm causes this transition to occur via Stark induced electric dipole. Two field free transitions may also occur: a highly forbidden magnetic dipole M, and a parity nonconserving electric dipole epsilon/sub P/. The latter is presumed to be due to the presence of a weak neutral current interaction between the 6p valence electron and the nucleus, as predicted by gauge theories which unite the electromagnetic and weak interactions. Both M and epsilon/sub P/ interfere with the Stark amplitude ..beta..E to produce a polarization of the 7P/sub 1/2/ state. This is measured with a circularly polarized infrared laser beam probe, tuned to the 7P/sub 1/2/ ..-->.. 8S/sub 1/2/ transition. This selectively excites m/sub F/ = +1 or -1 components of the 7P/sub 1/2/ state, and the polarization is seen as an asymmetry in 8S ..-->.. 6P/sub 3/2/ fluorescence when the probe helicity is reversed. The polarization due to M is ..delta../sub M/ = -2M/(BETAE). It is used to calibrate the analyzing efficiency. The polarization due to epsilon/sub P/ is ..delta../sub P/ = 2i epsilon/sub P//(..beta..E), and can be distinguished from ..delta../sub M/ by its properties under reversal of the 292.7 nm photon helicity and reversal of the laser direction. A preliminary measurement yielded a parity violation in agreement with the gauge theory of Weinberg and Salam.
Modes of Escherichia coli Dps Interaction with DNA as Revealed by Atomic Force Microscopy.
Directory of Open Access Journals (Sweden)
Vladislav V Melekhov
Full Text Available Multifunctional protein Dps plays an important role in iron assimilation and a crucial role in bacterial genome packaging. Its monomers form dodecameric spherical particles accumulating ~400 molecules of oxidized iron ions within the protein cavity and applying a flexible N-terminal ends of each subunit for interaction with DNA. Deposition of iron is a well-studied process by which cells remove toxic Fe2+ ions from the genetic material and store them in an easily accessible form. However, the mode of interaction with linear DNA remained mysterious and binary complexes with Dps have not been characterized so far. It is widely believed that Dps binds DNA without any sequence or structural preferences but several lines of evidence have demonstrated its ability to differentiate gene expression, which assumes certain specificity. Here we show that Dps has a different affinity for the two DNA fragments taken from the dps gene regulatory region. We found by atomic force microscopy that Dps predominantly occupies thermodynamically unstable ends of linear double-stranded DNA fragments and has high affinity to the central part of the branched DNA molecule self-assembled from three single-stranded oligonucleotides. It was proposed that Dps prefers binding to those regions in DNA that provide more contact pads for the triad of its DNA-binding bundle associated with one vertex of the protein globule. To our knowledge, this is the first study revealed the nucleoid protein with an affinity to branched DNA typical for genomic regions with direct and inverted repeats. As a ubiquitous feature of bacterial and eukaryotic genomes, such structural elements should be of particular care, but the protein system evolutionarily adapted for this function is not yet known, and we suggest Dps as a putative component of this system.
Two-Photon Collective Atomic Recoil Lasing
Directory of Open Access Journals (Sweden)
James A. McKelvie
2015-11-01
Full Text Available We present a theoretical study of the interaction between light and a cold gasof three-level, ladder conﬁguration atoms close to two-photon resonance. In particular, weinvestigate the existence of collective atomic recoil lasing (CARL instabilities in differentregimes of internal atomic excitation and compare to previous studies of the CARL instabilityinvolving two-level atoms. In the case of two-level atoms, the CARL instability is quenchedat high pump rates with signiﬁcant atomic excitation by saturation of the (one-photoncoherence, which produces the optical forces responsible for the instability and rapid heatingdue to high spontaneous emission rates. We show that in the two-photon CARL schemestudied here involving three-level atoms, CARL instabilities can survive at high pump rateswhen the atoms have signiﬁcant excitation, due to the contributions to the optical forces frommultiple coherences and the reduction of spontaneous emission due to transitions betweenthe populated states being dipole forbidden. This two-photon CARL scheme may form thebasis of methods to increase the effective nonlinear optical response of cold atomic gases.
Sulphur Atoms from Methionines Interacting with Aromatic Residues Are Less Prone to Oxidation
Aledo, Juan C.; Cantón, Francisco R.; Veredas, Francisco J.
2015-01-01
Methionine residues exhibit different degrees of susceptibility to oxidation. Although solvent accessibility is a relevant factor, oxidation at particular sites cannot be unequivocally explained by accessibility alone. To explore other possible structural determinants, we assembled different sets of oxidation-sensitive and oxidation-resistant methionines contained in human proteins. Comparisons of the proteins containing oxidized methionines with all proteins in the human proteome led to the conclusion that the former exhibit a significantly higher mean value of methionine content than the latter. Within a given protein, an examination of the sequence surrounding the non-oxidized methionine revealed a preference for neighbouring tyrosine and tryptophan residues, but not for phenylalanine residues. However, because the interaction between sulphur atoms and aromatic residues has been reported to be important for the stabilization of protein structure, we carried out an analysis of the spatial interatomic distances between methionines and aromatic residues, including phenylalanine. The results of these analyses uncovered a new determinant for methionine oxidation: the S-aromatic motif, which decreases the reactivity of the involved sulphur towards oxidants. PMID:26597773
Fermi and Coulomb correlation effects upon the interacting quantum atoms energy partition
Ruiz, Isela; Holguín-Gallego, Fernando José; Francisco, Evelio; Pendás, Ángel Martín; Rocha-Rinza, Tomás
2016-01-01
The Interacting Quantum Atoms (IQA) electronic energy partition is an important method in the field of quantum chemical topology which has given important insights of different systems and processes in physical chemistry. There have been several attempts to include Electron Correlation (EC) in the IQA approach, for example, through DFT and Hartree-Fock/Coupled-Cluster (HF/CC) transition densities. This work addresses the separation of EC in Fermi and Coulomb correlation and its effect upon the IQA analysis by taking into account spin-dependent one- and two-electron matrices $D^{\\mathrm{HF/CC}}_{p\\sigma q \\sigma}$ and $d^{\\mathrm{HF/CC}}_{p\\sigma q\\sigma r\\tau s\\tau}$ wherein $\\sigma$ and $\\tau$ represent either of the $\\alpha$ and $\\beta$ spin projections. We illustrate this approach by considering BeH$_2$,BH, CN$^-$, HF, LiF, NO$^+$, LiH, H$_2$O$\\cdots$H$_2$O and C$_2$H$_2$, which comprise non-polar covalent, polar covalent, ionic and hydrogen bonded systems. The same and different spin contributions to ($i$...
Moscetti, Ilaria; Teveroni, Emanuela; Moretti, Fabiola; Bizzarri, Anna Rita; Cannistraro, Salvatore
Murine double minute 2 (MDM2) and 4 (MDM4) are known as the main negative regulators of p53, a tumor suppressor. They are able to form heterodimers that are much more effective in the downregulation of p53. Therefore, the MDM2-MDM4 complex could be a target for promising therapeutic restoration of p53 function. To this aim, a deeper understanding of the molecular mechanisms underlining the heterodimerization is needed. The kinetic and thermodynamic characterization of the MDM2-MDM4 complex was performed with two complementary approaches: atomic force spectroscopy and surface plasmon resonance. Both techniques revealed an equilibrium dissociation constant (KD ) in the micromolar range for the MDM2-MDM4 heterodimer, similar to related complexes involved in the p53 network. Furthermore, the MDM2-MDM4 complex is characterized by a relatively high free energy, through a single energy barrier, and by a lifetime in the order of tens of seconds. New insights into the MDM2-MDM4 interaction could be highly important for developing innovative anticancer drugs focused on p53 reactivation.
Destefano, Anthony; Heerikhuisen, Jacob
2015-04-01
Fully 3D particle simulations can be a computationally and memory expensive task, especially when high resolution grid cells are required. The problem becomes further complicated when parallelization is needed. In this work we focus on computational methods to solve these difficulties. Hilbert curves are used to map the 3D particle space to the 1D contiguous memory space. This method of organization allows for minimized cache misses on the GPU as well as a sorted structure that is equivalent to an octal tree data structure. This type of sorted structure is attractive for uses in adaptive mesh implementations due to the logarithm search time. Implementations using the Message Passing Interface (MPI) library and NVIDIA's parallel computing platform CUDA will be compared, as MPI is commonly used on server nodes with many CPU's. We will also compare static grid structures with those of adaptive mesh structures. The physical test bed will be simulating heavy interstellar atoms interacting with a background plasma, the heliosphere, simulated from fully consistent coupled MHD/kinetic particle code. It is known that charge exchange is an important factor in space plasmas, specifically it modifies the structure of the heliosphere itself. We would like to thank the Alabama Supercomputer Authority for the use of their computational resources.
Elemental Analysis of Nanomaterial Using Photon-Atom Interaction Based EDXRF Technique
Directory of Open Access Journals (Sweden)
Sanjeev Kumar
2013-08-01
Full Text Available Presence of trace amount of foreign impurities (both metallic and non-metallic in standard salts used for sample preparation and during the synthesis process can alter the physical and chemical behavior of the pure and doped nano-materials. Therefore, it becomes important to determine concentration of various elements present in synthesized nano-material sample. In present work, the elemental and compositional analysis of nano-materials synthesized using various methods has been performed using photon-atom interaction based energy dispersive x-ray fluorescence (EDXRF technique. This technique due to its multielement analytical capability, lower detection limit, capability to analyze metals and non-metals alike and almost no sample preparation requirements can be utilized for analysis of nano-materials. The EDXRF spectrometer involves a 2.4 kW Mo anode x-ray tube (Pananalytic, Netherland equipped with selective absorbers as an excitation source and an LEGe detector (FWHM = 150 eV at 5.895 keV, Canberra, US coupled with PC based multichannel analyzer used to collect the fluorescentx-ray spectra. The analytical results showed good agreements with the expected values calculated on the basis of the precursor used in preparation of nano-materials.
Jian, Jhih-Wei; Elumalai, Pavadai; Pitti, Thejkiran; Wu, Chih Yuan; Tsai, Keng-Chang; Chang, Jeng-Yih; Peng, Hung-Pin; Yang, An-Suei
2016-01-01
Predicting ligand binding sites (LBSs) on protein structures, which are obtained either from experimental or computational methods, is a useful first step in functional annotation or structure-based drug design for the protein structures. In this work, the structure-based machine learning algorithm ISMBLab-LIG was developed to predict LBSs on protein surfaces with input attributes derived from the three-dimensional probability density maps of interacting atoms, which were reconstructed on the query protein surfaces and were relatively insensitive to local conformational variations of the tentative ligand binding sites. The prediction accuracy of the ISMBLab-LIG predictors is comparable to that of the best LBS predictors benchmarked on several well-established testing datasets. More importantly, the ISMBLab-LIG algorithm has substantial tolerance to the prediction uncertainties of computationally derived protein structure models. As such, the method is particularly useful for predicting LBSs not only on experimental protein structures without known LBS templates in the database but also on computationally predicted model protein structures with structural uncertainties in the tentative ligand binding sites. PMID:27513851
Interactions and low energy collisions between an alkali ion and an alkali atom of different nucleus
Rakshit, Arpita; Berriche, Hamid; Deb, Bimalendu
2015-01-01
We study theoretically interaction potentials and low energy collisions between different alkali atoms and alkali ions. Specifically, we consider systems like X + Y$^{+}$, where X(Y$^{+})$ is either Li(Cs$^+$) or Cs((Li$^+$), Na(Cs$^+$) or Cs(Na$^+$) and Li(Rb$^+$) or Rb(Li$^+$). We calculate the molecular potentials of the ground and first two excited states of these three systems using pseudopotential method and compare our results with those obtained by others. We calculate ground-state scattering wave functions and cross sections of these systems for a wide range of energies. We find that, in order to get convergent results for the total scattering cross sections for energies of the order $1$ K, one needs to take into account at least 60 partial waves. In the low energy limit ($< 1 \\mu$K), elastic scattering cross sections exhibit Wigner law threshold behavior while in the high energy limit the cross sections go as $E^{-1/3}$. We discuss qualitatively the possibilities of forming cold molecular ion by ...
Sulphur Atoms from Methionines Interacting with Aromatic Residues Are Less Prone to Oxidation
Aledo, Juan C.; Cantón, Francisco R.; Veredas, Francisco J.
2015-11-01
Methionine residues exhibit different degrees of susceptibility to oxidation. Although solvent accessibility is a relevant factor, oxidation at particular sites cannot be unequivocally explained by accessibility alone. To explore other possible structural determinants, we assembled different sets of oxidation-sensitive and oxidation-resistant methionines contained in human proteins. Comparisons of the proteins containing oxidized methionines with all proteins in the human proteome led to the conclusion that the former exhibit a significantly higher mean value of methionine content than the latter. Within a given protein, an examination of the sequence surrounding the non-oxidized methionine revealed a preference for neighbouring tyrosine and tryptophan residues, but not for phenylalanine residues. However, because the interaction between sulphur atoms and aromatic residues has been reported to be important for the stabilization of protein structure, we carried out an analysis of the spatial interatomic distances between methionines and aromatic residues, including phenylalanine. The results of these analyses uncovered a new determinant for methionine oxidation: the S-aromatic motif, which decreases the reactivity of the involved sulphur towards oxidants.
The atom-surface interaction potential for He-NaCl: A model based on pairwise additivity
Hutson, Jeremy M.; Fowler, P. W.
1986-08-01
The recently developed semi-empirical model of Fowler and Hutson is applied to the He-NaCl atom-surface interaction potential. Ab initio self-consistent field calculations of the repulsive interactions between He atoms and in-crystal Cl - and Na + ions are performed. Dispersion coefficients involving in-crystal ions are also calculated. The atom-surface potential is constructed using a model based on pairwise additivity of atom-ion forces. With a small adjustment of the repulsive part, this potential gives good agreement with the experimental bound state energies obtained from selective adsorption resonances in low-energy atom scattering experiments. Close-coupling calculations of the resonant scattering are performed, and good agreement with the experimental peak positions and intensity patterns is obtained. It is concluded that there are no bound states deeper than those observed in the selective adsorption experiments, and that the well depth of the He-NaCl potential is 6.0 ± 0.2 meV.
External Heavy-Atom Effect via Orbital Interactions Revealed by Single-Crystal X-ray Diffraction.
Sun, Xingxing; Zhang, Baicheng; Li, Xinyang; Trindle, Carl O; Zhang, Guoqing
2016-07-28
Enhanced spin-orbit coupling through external heavy-atom effect (EHE) has been routinely used to induce room-temperature phosphorescence (RTP) for purely organic molecular materials. Therefore, understanding the nature of EHE, i.e., the specific orbital interactions between the external heavy atom and the luminophore, is of essential importance in molecular design. For organic systems, halogens (e.g., Cl, Br, and I) are the most commonly seen heavy atoms serving to realize the EHE-related RTP. In this report, we conduct an investigation on how heavy-atom perturbers and aromatic luminophores interact on the basis of data obtained from crystallography. We synthesized two classes of molecular systems including N-haloalkyl-substituted carbazoles and quinolinium halides, where the luminescent molecules are considered as "base" or "acid" relative to the heavy-atom perturbers, respectively. We propose that electron donation from a π molecular orbital (MO) of the carbazole to the σ* MO of the C-X bond (π/σ*) and n electron donation to a π* MO of the quinolinium moiety (n/π*) are responsible for the EHE (RTP) in the solid state, respectively.
Photon statistical properties of the cavity field in the two-atom Jaynes-Cummings model
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
The model that two two-level atoms interact with a singel-mode cavity is studied. The exact solution of the time evolution operator for the two-atom Jaynes-Cummings model is presented by the bare-states approach. Furthermore, we investigate the dynamical properties of the photon statistics of the cavity field, and obtain a number of novel features.
Tomza, Michał
2015-01-01
The Ca$^+$, Sr$^+$, Ba$^+$, and Yb$^+$ ions immersed in an ultracold gas of the Cr atoms are proposed as experimentally feasible heteronuclear systems in which ion-atom interactions at ultralow temperatures can be controlled with magnetically tunable Feshbach resonances without charge transfer and radiative losses. \\textit{Ab initio} techniques are applied to investigate electronic-ground-state properties of the (CaCr)$^+$, (SrCr)$^+$, (BaCr)$^+$, and (YbCr)$^+$ molecular ions. The potential energy curves, permanent electric dipole moments, and static electric dipole polarizabilities are computed. The spin restricted open-shell coupled cluster method restricted to single, double, and noniterative triple excitations, RCCSD(T), and the multireference configuration interaction method restricted to single and double excitations, MRCISD, are employed. The scalar relativistic effects are included within the small-core energy-consistent pseudopotentials. The leading long-range induction and dispersion interaction co...
Cantrell, John H., Jr.; Cantrell, Sean A.
2008-01-01
A comprehensive analytical model of the interaction of the cantilever tip of the atomic force microscope (AFM) with the sample surface is developed that accounts for the nonlinearity of the tip-surface interaction force. The interaction is modeled as a nonlinear spring coupled at opposite ends to linear springs representing cantilever and sample surface oscillators. The model leads to a pair of coupled nonlinear differential equations that are solved analytically using a standard iteration procedure. Solutions are obtained for the phase and amplitude signals generated by various acoustic-atomic force microscope (A-AFM) techniques including force modulation microscopy, atomic force acoustic microscopy, ultrasonic force microscopy, heterodyne force microscopy, resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), and the commonly used intermittent contact mode (TappingMode) generally available on AFMs. The solutions are used to obtain a quantitative measure of image contrast resulting from variations in the Young modulus of the sample for the amplitude and phase images generated by the A-AFM techniques. Application of the model to RDF-AFUM and intermittent soft contact phase images of LaRC-cp2 polyimide polymer is discussed. The model predicts variations in the Young modulus of the material of 24 percent from the RDF-AFUM image and 18 percent from the intermittent soft contact image. Both predictions are in good agreement with the literature value of 21 percent obtained from independent, macroscopic measurements of sheet polymer material.
Reichel, Jakob
2010-01-01
This book provides a stimulating and multifaceted picture of a rapidly developing field. The first part reviews fundamentals of atom chip research in tutorial style, while subsequent parts focus on the topics of atom-surface interaction, coherence on atom chips, and possible future directions of atom chip research. The articles are written by leading researchers in the field in their characteristic and individual styles.
Institute of Scientific and Technical Information of China (English)
JIANG ZhiQuan; HUANG WeiXin; BAO XinHe
2007-01-01
Employing hot tungsten filament to thermal dissociate molecular hydrogen, we generated gas phase atomic hydrogen under ultra-high vacuum (UHV) conditions and investigated its interaction with Pt(111) surface. Thermal desorption spectroscopy (TDS) results demonstrate that adsorption of molecular hydrogen on Pt(111) forms surface Had species whereas adsorption of atomic hydrogen forms not only surface Had species but also bulk Had species. Bulk Had species is more thermal-unstable than surface Had species on Pt(111), suggesting that bulk Had species is more energetic. This kind of weakly- adsorbed bulk Had species might be the active hydrogen species in the Pt-catalyzed hydrogenation reactions.
DEFF Research Database (Denmark)
Ruban, Andrei; Simak, S.I.; Korzhavyi, P.A.
2002-01-01
-electron potential and energy. In the case of a random alloy such interactions can be accounted for only by lifting the atomic-sphere and single-site approximations, in order to include the polarization due to local environment effects. Nevertheless, a simple parametrization of the screened Coulomb interactions...... for the ordinary single-site methods, including the generalized perturbation method, is still possible. We obtained such a parametrization for bulk and surface NiPt alloys, which allows one to obtain quantitatively accurate effective interactions in this system....
Indian Academy of Sciences (India)
E K Bashkirov; M S Mastyugin
2015-01-01
Considering two artificial identical atoms interacting with two-mode thermal field through non-degenerate two-photon transitions, this paper studies the influence of atomic coherence and dipole–dipole interaction on the entanglement of two qubits. It is found that the entanglement is greatly enhanced by these mechanisms.
Atom-molecule equilibration in a degenerate Fermi gas with resonant interactions
DEFF Research Database (Denmark)
Williams, J. E.; Nikuni, T.; Nygaard, Nicolai;
2004-01-01
We present a nonequilibrium kinetic theory describing atom-molecule population dynamics in a two-component Fermi gas with a Feshbach resonance. Key collision integrals emerge that govern the relaxation of the atom-molecule mixture to chemical and thermal equilibrium. Our focus is on the pseudogap...
Preparation of Multi—Atom Entangled States with a Single Cavity in a Thermal State
Institute of Scientific and Technical Information of China (English)
ZHENGShi－Biao
2002-01-01
A scheme is suggested for the generation of multi-atom maximally entangled states with a cavity in a thermal state,In this scheme several appropriately prepared two-level atoms are simultaneously sent through the nonresonant cavity.We divide the whole atom-cavity interaction time into two equal parts.At the end of the first part a π pulse is applied to the atome using a classical field.Then the photon-number-dependent shifts on the atomic states are cancelled and the atomic system finally evoloves to a maximally entangled state.
Preparation of Multi-Atom Entangled States with a Single Cavity in a Thermal State
Institute of Scientific and Technical Information of China (English)
ZHENG Shi-Biao
2002-01-01
A scheme is suggested for the generation of multi-atom maximally entangled states with a cavity in a thermalstate. In this scheme several appropriately prepared two-level atoms are simultaneously sent through the nonresonantcavity. We divide the whole atom-cavity interaction time into two equal parts. At the end of the first part a π pulse isapplied to the atoms using a classical field. Then the photon-number-dependent shifts on the atomic states are cancelledand the atomic system finally evolves to a maximally entangled state.
Low frequency critical current noise and two level system defects in Josephson junctions
Nugroho, Christopher Daniel
The critical current in a Josephson junction is known to exhibit a 1/falpha low frequency noise. Implemented as a superconducting qubit, this low frequency noise can lead to decoherence. While the 1/f noise has been known to arise from an ensemble of two level systems connected to the tunnel barrier, the precise microscopic nature of these TLSs remain a mystery. In this thesis we will present measurements of the 1/f alpha low frequency noise in the critical current and tunneling resistance of Al-AlOx-Al Josephson junctions. Measurements in a wide range of resistively shunted and unshunted junctions confirm the equality of critical current and tunneling resistance noise. That is the critical current fluctuation corresponds to fluctuations of the tunneling resistance. In not too small Al-AlOx-Al junctions we have found that the fractional power spectral density scales linearly with temperature. We confirmed that the 1/falpha power spectrum is the result of a large number of two level systems modulating the tunneling resistance. At small junction areas and low temperatures, the number of thermally active TLSs is insufficient to integrate out a featureless 1/ f spectral shape. By analyzing the spectral variance in small junction areas, we have been able to deduce the TLS defect density, n ≈ 2.53 per micrometer squared per Kelvin spread in the TLS energy per factor e in the TLS lifetimes. This density is consistent with the density of tunneling TLSs found in glassy insulators, as well as the density deduced from coherent TLSs interacting at qubit frequencies. The deduced TLS density combined with the magnitude of the 1/f power spectral density in large area junctions, gives an average TLS effective area, A ˜ 0.3 nanometer squared. In ultra small tunnel junctions, we have studied the time-domain dynamics of isolated TLSs. We have found a TLS whose dynamics is described by the quantum tunneling between the two localized wells, and a one-phonon absorption
Parity violation in atomic cesium and alternatives to the standard model of electroweak interactions
Energy Technology Data Exchange (ETDEWEB)
Bouchiat, C.; Piketty, C.A. (Ecole Normale Superieure, 75 - Paris (France). Lab. de Physique Theorique)
1983-08-18
We study the implications of the recent observation of a parity violation in atomic cesium. After a discussion of the uncertainties associated with the atomic physics calculations we derive conservative bounds for the weak charge Qsub(W). These bounds are used to put constraints on alternatives to the standard electroweak model, involving an 'extra U(1)' gauge group. We analyze the possibility that the extra gauge boson might be very light and give, as a by-product, the typical range of momentum transfer explored in atomic parity violation experiments.
Willden, Jeff
2001-01-01
"Bohr's Atomic Model" is a small interactive multimedia program that introduces the viewer to a simplified model of the atom. This interactive simulation lets students build an atom using an atomic construction set. The underlying design methodology for "Bohr's Atomic Model" is model-centered instruction, which means the central model of the…
Energy Technology Data Exchange (ETDEWEB)
Gramich, Vera; Ankerhold, Joachim [Institut fuer Theoretische Physik, Universitaet Ulm, Albert-Einstein-Allee 11, 89069 Ulm (Germany); Solinas, Paolo; Moettoenen, Mikko [Department of Applied Physics/COMP, Aalto University, P.O. Box 14100, FI-00076 Aalto (Finland); Low Temperature Laboratory, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland); Pekola, Jukka [Low Temperature Laboratory, Aalto University, P.O. Box 13500, FI-00076 Aalto (Finland)
2012-07-01
Realistic quantum systems are never completely isolated. Even a single atom in zero-temperature vacuum is influenced by the zero-point fluctuations of the electromagnetic field which in turn induces a shift of its transition frequencies known as the Lamb shift. Cavity quantum electrodynamics (QED) provides a particularly convenient setup to observe this shift since the restricted geometries of the cavities allow the atoms to interact only with the fluctuations of single harmonic fields. In contrast to single-frequency environments, typical reservoirs for mesoscopic solid-state devices are characterized by broadband spectral distributions in thermal equilibrium. Within weak-coupling master equations even explicit expressions for the reservoir-induced frequency shifts can be derived, while associated experimental observations are still missing. To fill this gap, we discuss and analyze a theoretical proposal to retrieve the Lamb shift for a superconducting two-level system embedded in an Ohmic environment. Moreover, we present a possible way to measure the Lamb shift in a circuit containing a Cooper pair sluice.
Uniformity pattern and related criteria for two-level factorials
Institute of Scientific and Technical Information of China (English)
FANG; Kaitai; QIN; Hong
2005-01-01
In this paper,the study of projection properties of two-level factorials in view of geometry is reported.The concept of uniformity pattern is defined.Based on this new concept,criteria of uniformity resolution and minimum projection uniformity are proposed for comparing two-level factorials.Relationship between minimum projection uniformity and other criteria such as minimum aberration,generalized minimum aberration and orthogonality is made explict.This close relationship raises the hope of improving the connection between uniform design theory and factorial design theory.Our results provide a justification of orthogonality,minimum aberration,and generalized minimum aberration from a natural geometrical interpretation.
van der Waals interaction of a neutral atom with the surface of a metal or dielectric nanosphere
Energy Technology Data Exchange (ETDEWEB)
Schmidt, Regine; Chormaic, Sile Nic [Photonics Centre, Tyndall National Institute, Prospect Row, Cork (Ireland); Minogin, Vladimir G, E-mail: s.nicchormaic@ucc.ie [Institute of Spectroscopy Russ. Ac. of Sciences, 142190 Troitsk, Moscow region (Russian Federation)
2011-01-14
We analyse the van der Waals interaction of a neutral atom with the internal and external surfaces of either a metal or dielectric nanosphere. We derive closed analytical equations for the van der Waals interaction energy using an electrostatic approximation and show that the energy increases or decreases as a function of the atom's distance from the surface, depending on the surface curvature. For concave spherical surfaces, the van der Waals energy can increase by up to a factor of 6, while for convex surfaces it decreases by as much as a factor of 2, when compared to that obtained for a flat surface. The derived analytical equations are very simple and can be used for a comparison between theory and experimental measurements of the van der Waals constant, C{sub 3}.
Institute of Scientific and Technical Information of China (English)
Rong Zhang; Zai-you Tan; San-lai Luo
2008-01-01
N,N-dimethylacetamide (DMA) has been investigated extensively in studying models of peptide bonds. An all-atom MD simulation and the NMR spectra were performed to investigate the interactions in the DMA- water system. The radial distribution functions (RDFs) and the hydrogen-bonding network were used in MD simulations. There are strong hydrogen bonds and weak C-H…O contacts in the mixtures, as shown by the analysis of the RDFs. The insight structures in the DMA-water mixtures can be classified into different regions by the analysis of the hydrogen-bonding network. Chemical shifts of the hydrogen atom of water molecule with concentration and temperatures are adopted to study the interactions in the mixtures. The results of NMR spectra show good agreement with the statistical results of hydrogen bonds in MD simulations.
Boström, Mathias; Brevik, Iver; Parsons, Drew F; Sernelius, Bo E
2012-01-01
We demonstrate that Casimir-Polder energies between noble gas atoms (dissolved in water) and oil-water interfaces are highly surface specific. Both repulsion (e.g. hexane) and attraction (e.g. glycerol and cyclodecane) is found with different oils. For several intermediate oils (e.g. hexadecane, decane, and cyclohexane) both attraction and repulsion can be found in the same system. Near these oil-water interfaces the interaction is repulsive in the non-retarded limit and turns attractive at larger distances as retardation becomes important. These highly surface specific interactions may have a role to play in biological systems where the surface may be more or less accessible to dissolved atoms.
QPROP: A Schrödinger-solver for intense laser atom interaction
Bauer, Dieter; Koval, Peter
2006-03-01
The QPROP package is presented. QPROP has been developed to study laser-atom interaction in the nonperturbative regime where nonlinear phenomena such as above-threshold ionization, high order harmonic generation, and dynamic stabilization are known to occur. In the nonrelativistic regime and within the single active electron approximation, these phenomena can be studied with QPROP in the most rigorous way by solving the time-dependent Schrödinger equation in three spatial dimensions. Because QPROP is optimized for the study of quantum systems that are spherically symmetric in their initial, unperturbed configuration, all wavefunctions are expanded in spherical harmonics. Time-propagation of the wavefunctions is performed using a split-operator approach. Photoelectron spectra are calculated employing a window-operator technique. Besides the solution of the time-dependent Schrödinger equation in single active electron approximation, QPROP allows to study many-electron systems via the solution of the time-dependent Kohn-Sham equations. Program summaryProgram title:QPROP Catalogue number:ADXB Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADXB Program obtainable from:CPC Program Library, Queen's University of Belfast, N. Ireland Computer on which program has been tested:PC Pentium IV, Athlon Operating system:Linux Program language used:C++ Memory required to execute with typical data:Memory requirements depend on the number of propagated orbitals and on the size of the orbitals. For instance, time-propagation of a hydrogenic wavefunction in the perturbative regime requires about 64 KB RAM (4 radial orbitals with 1000 grid points). Propagation in the strongly nonperturbative regime providing energy spectra up to high energies may need 60 radial orbitals, each with 30000 grid points, i.e. about 30 MB. Examples are given in the article. No. of bits in a word:Real and complex valued numbers of double precision are used No. of lines in distributed program
Population Dynamics in Cold Gases Resulting from the Long-Range Dipole-Dipole Interaction
Mandilara, A; Pillet, P
2009-01-01
We consider the effect of the long range dipole-dipole interaction on the excitation exchange dynamics of cold two-level atomic gase in the conditions where the size of the atomic cloud is large as compared to the wavelength of the dipole transition. We show that this interaction results in population redistribution across the atomic cloud and in specific spectra of the spontaneous photons emitted at different angles with respect to the direction of atomic polarization.
D'Incao, Jose P.; Willians, Jason R.
2015-05-01
Precision atom interferometers (AI) in space are a key element for several applications of interest to NASA. Our proposal for participating in the Cold Atom Laboratory (CAL) onboard the International Space Station is dedicated to mitigating the leading-order systematics expected to corrupt future high-precision AI-based measurements of fundamental physics in microgravity. One important focus of our proposal is to enhance initial state preparation for dual-species AIs. Our proposed filtering scheme uses Feshbach molecular states to create highly correlated mixtures of heteronuclear atomic gases in both their position and momentum distributions. We will detail our filtering scheme along with the main factors that determine its efficiency. We also show that the atomic and molecular heating and loss rates can be mitigated at the unique temperature and density regimes accessible on CAL. This research is supported by the National Aeronautics and Space Administration.
DEFF Research Database (Denmark)
Loft, N. J. S.; Marchukov, O. V.; Petrosyan, D.
2016-01-01
We have developed an efficient computational method to treat long, one-dimensional systems of strongly-interacting atoms forming self-assembled spin chains. Such systems can be used to realize many spin chain model Hamiltonians tunable by the external confining potential. As a concrete...... demonstration, we consider quantum state transfer in a Heisenberg spin chain and we show how to determine the confining potential in order to obtain nearly-perfect state transfer....
Nanowire photonic crystal waveguides for single-atom trapping and strong light-matter interactions
Yu, S -P; Muniz, J A; Martin, M J; Norte, Richard; Hung, C -L; Meenehan, Seán M; Cohen, Justin D; Painter, Oskar; Kimble, H J
2014-01-01
We present a comprehensive study of dispersion-engineered nanowire photonic crystal waveguides suitable for experiments in quantum optics and atomic physics with optically trapped atoms. Detailed design methodology and specifications are provided, as are the processing steps used to create silicon nitride waveguides of low optical loss in the near-IR. Measurements of the waveguide optical properties and power-handling capability are also presented.
Gao, W; Cheng, H; Zhang, S S; Liu, H P
2015-01-01
We have investigated the wave-function feature of Rydberg sodium in a uniform electric field and found that the core-induced interaction of non-hydrogenic atom in electric field can be directly visualized in the wave-function. As is well known, the hydrogen atom in electric field can be separated in parabolic coordinates (\\eta, \\xi), whose eigen-function can show a clear pattern towards negative and positive directions corresponding to the so-called red and blue states without ambiguity, respectively. It can be served as a complete orthogonal basis set to study the core-induced interaction of non-hydrogenic atom in electric field. Owing to complete different patterns of the probability distribution for red and blue states, the interaction can be visualized in the wave-function directly via superposition. Moreover, the constructive and destructive interferences between red and blue states are also observed in the wave-function, explicitly explaining the experimental measurement for the spectral oscillator stre...
Potential energy curves for the interaction of Ag(5s) and Ag(5p) with noble gas atoms
Loreau, J; Dalgarno, A
2013-01-01
We investigate the interaction of ground and excited states of a silver atom with noble gases (NG), including helium. Born-Oppenheimer potential energy curves are calculated with quantum chemistry methods and spin-orbit effects in the excited states are included by assuming a spin-orbit splitting independent of the internuclear distance. We compare our results with experimentally available spectroscopic data, as well as with previous calculations. Because of strong spin-orbit interactions, excited Ag-NG potential energy curves cannot be fitted to Morse-like potentials. We find that the labeling of the observed vibrational levels has to be shifted by one unit.
Single-photon frequency conversion via interaction with a three-level atom coupled to a microdisk
Akbari, M.; Andrianov, S. N.; Kalachev, A. A.
2017-02-01
The frequency conversion of light has proved to be an important instrument for communication, spectroscopy, imaging and information processing. We theoretically study the frequency conversion of a single photon via its interaction with a Λ -type atom coupled to a microdisk. We show that the frequency conversion efficiency approaches unity even in the case of an interaction between clockwise and counterclockwise modes in the microdisk due to surface imperfections. By the use of the Schrieffer-Wolff transformation, we get an effective Hamiltonian that allows us to investigate the dynamics of the system and obtain time and probability of frequency conversion in different conditions.
Phase-dependent inversionless gain in a four-level atomic system with a closed interaction loop
Institute of Scientific and Technical Information of China (English)
Xu Wei-Hua; Wu Jin-Hui; Gao Jin-Yue
2007-01-01
A four-level atomic system with a closed interaction loop connected by two coherent driving fields and a microwave field is investigated. The results show that inversionless gain can be achieved on a higher frequency transition outside the closed interaction loop, and the gain behaviour can be modulated by the phase of the closed loop as well as the amplitude of the microwave field. The phase sensitivity property in such a scheme is similar to that in an analogous configuration with spontaneously generated coherence, but it is beyond the rigorous condition of near-degenerate levels with non-orthogonal dipole moments. Therefore this scheme is much more convenient in experimental realization.