Dynamics of the Driven Jaynes-Cummings Model

We study the dynamical features of the Jaynes-Cummings model with the atomdriven by an external classical field in the case that the cavity field is initially in a Fock state.We find the dynamical variables by using dressed states in the bare atom representation. Weshow that the dynamical behavior of the cavity field can be strongly modified by the externalclassical field. We also find that the cavity field is super-Poissonian after some interaction timeif the external field is strong enough.     

An ampere-like law for displacement vector field and near-field optical microscopy

We make up a novel and simple theory for near field and near-field optical microscopy (NOM). Our theory is composed of two parts. The first is a formulation to calculate the scattered near field of light by a small dielectric. We state that a wavenumber-vector-independent picture appears in the theory of the near field, and we find that this is expressed by an Ampere-like law for the displacement vector field. The second part is a formulation of field intensity for far field observation and near field observation from a unified point of view. We suggest a theoretical formula for the field intensity corresponding to the NOM image and demonstrate how to understand the relation between the near field and this image.     

Quantum state transfer from light beams to atomic ensembles

We show the equivalence between an ensemble of two-level atoms driven by a squeezed vacuum field, and a harmonic oscillator coupled to a squeezed field. We give the conditions for optimal squeezing transfer from the field to the atomic ensemble. We show that EPR-type correlations are created between the atomic ensemble and the incoming field. Received 23 January 2001     

Dynamic behaviour of a single—Cooper—pair box in a single—mode quantized field with dissipation

We study the quantum dynamics of a single-Cooper-pair box biased by a classical voltage and also irradiated by a single-mode quantized field.We demonstrate that under the weak damping,the collapse-revival phenomena can exist in this system.We also demonstrate that the revivals of oscillations are sensitive to the initial coherent field and the damping rate of the single-mode quantized field.     

Multi-window transparency and fast–slow light switching in a quadratically coupled optomechanical system assisted with three-level atoms

We study theoretically the features of the output field of a quadratically coupled optomechanical system assisted with three-level atoms. In this system, the atoms interact with the cavity field and are driven by a classical field, and the cavity is driven by a strong coupling field and a weak signal field. We find that there exists a multi-window transparency phenomenon. The width of the transparent windows can be adjusted by controlling the system parameters, including the number of the atoms, the powers of the lasers driving the atoms and driving the cavity, and the environment temperature.We also find that a tunable switch from fast light to slow light can be realized in this system.     

Conformal invariance and spontaneous symmetry breaking

We study the spontaneous symmetry breaking in a conformally invariant gravitational theory. We particularly emphasize on the nonminimal coupling of matter fields to gravity. By the nonminimal coupling we consider a local distinction between the conformal frames of metric of matter fieldsand the metric explicitly entering the vacuum sector. We suppose that these two frames are conformally related by a dilaton field. We show that the imposition of a condition on the variable mass term of a scalar field may lead to the spontaneous symmetry breaking. In this way the scalar field may imitate the Higgs field behavior. Attributing a constant configuration to the ground state of the Higgs field, a Higgs conformal frame is specified. We define the Higgs conformal frame as a cosmological frame which describes the large scale characteristics of the observed universe. In the cosmological frame the gravitational coupling acquires a correct value and one no longer deals with the vacuum energy problem. We then study a more general case by considering a variable configuration for the ground state of Higgs field. In this case we introduce a cosmological solution of themodel.     

Observation of dressed excitonic states in a single quantum dot

We report the observation of dressed states of a quantum dot. The optically excited exciton and biexciton states of the quantum dot are coupled by a strong laser field and the resulting spectral signatures are measured using differential transmission of a probe field. We demonstrate that the anisotropic electron-hole exchange interaction induced splitting between the x- and y-polarized excitonic states can be completely erased by using the ac-Stark effect induced by the coupling field, without causing any appreciable broadening of the spectral lines. We also show that by varying the polarization and strength of a resonant coupling field, we can effectively change the polarization axis of the quantum dot.     

Significant reduction of the triggering electric field for half-metallicity in hydrogenated carbon nanotubes by optimized field direction

We have investigated the half-metallicity in hydrogenated carbon nanotubes under an electric field as a function of the electric field direction by using the density functional theory calculation. We found that the electric field required for the half-metallicity can be significantly reduced by controlling the field direction and the reduction rate increases with the nanotube diameter. The field direction effect can be understood in a simple model based on the electrostatic potential difference between the spatially-separated edges.     

Guiding and trapping of electron spin waves in atomic hydrogen gas

We present a high magnetic field study of electron spin waves in atomic hydrogen gas compressed to high densities of ～10(18) cm(-3) at temperatures ranging from 0.26 to 0.6 K. We observed a variety of spin wave modes caused by the identical spin rotation effect with strong dependence on the spatial profile of the polarizing magnetic field. We demonstrate confinement of these modes in regions of strong magnetic field and manipulate their spatial distribution by changing the position of the field maximum.     

Hamiltonian Anomalies from Extended Field Theories

We develop a proposal by Freed to see anomalous field theories as relative field theories, namely field theories taking value in a field theory in one dimension higher, the anomaly field theory. We show that when the anomaly field theory is extended down to codimension 2, familiar facts about Hamiltonian anomalies can be naturally recovered, such as the fact that the anomalous symmetry group admits only a projective representation on the Hilbert space, or that the latter is really an abelian bundle gerbe over the moduli space. We include in the discussion the case of non-invertible anomaly field theories, which is relevant to six-dimensional (2, 0) superconformal theories. In this case, we show that the Hamiltonian anomaly is characterized by a degree 2 non-abelian group cohomology class, associated to the non-abelian gerbe playing the role of the state space of the anomalous theory. We construct Dai-Freed theories, governing the anomalies of chiral fermionic theories, and Wess-Zumino theories, governing the anomalies of Wess-Zumino terms and self-dual field theories, as extended field theories down to codimension 2.     

Fluctuation polarimetry

We examine the relationship between the strength of the intensity fluctuations and the polarimetric properties of a random electromagnetic field composed of a Gaussian, random field, and nonrandom field, and we present a method for determining the state of polarization of the Gaussian random field. The approach relies on incoherently mixing a Gaussian random field with a controllable reference field and measuring the intensity fluctuations of their superposition. We demonstrate that by controlling the reference field, the full polarimetric information about the Gaussian random field can be uniquely determined.     

Nonlinear TM modes in cylindrical liquid crystal waveguide

We consider a nonlinear cylindrical fiber with a nematic liquid crystal (LC) core having initially the escaped configuration and subject to the action of a normal mode propagating electromagnetic field of arbitrary intensity. We derive a set of coupled equations governing the nonlinear dynamics of the electromagnetic field and the confined LC. We solve numerically these coupled equations and find simultaneously the distorted textures of the nematic inside the cylinder and the Transverse Magnetic modes in the guide. We analyze the dependence of these solutions on the electromagnetic field intensity by assuming consistently soft boundary conditions. We have found a dramatic correlation in the spatial distribution of the nematic's configuration and the Transverse Magnetic modes. Thus, the director adopts configurations completely guided by the specific mode involved. We show that the cut-off frequencies and dispersion relations can be tuned by varying the intensity of the electromagnetic propagating field.     

Controlling the optical bistability in a Λ-type atomic system via incoherent pump field

We investigated optical bistability (OB) and the absorption properties of a weak probe field in a three-level Λ-type atomic system confined in a unidirectional ring cavity via incoherent pump field. We found that the threshold of OB and the probe field absorption can be controlled by the rate of incoherent pump field. No laser field was used in the pumping processes.     

Diffraction method for recording optical wave fields

We propose a method for recording an optical wave field that is based on diffraction of the optical wave field by two screens that are complementary to each other. We show that the new method ensures the measurement of the phase of the wave field with a high accuracy and spatial resolution. An optical scheme for implementing the diffraction method and an algorithm for reconstructing the phase of the wave field from the measurement data are developed. We perform a computer simulation of the experiment on recording the optical wave field based on the method proposed.     

Collapse and revival of a single—Cooper—pair box in a single—mode quantized field

We study the quantum dynamics of a single-Cooper-pair box biased by a classical voltage and also irradiated by a single-mode quantized field. We demonstrate that under weak damping of the quantized field, the collapse-revival phenomena can exist in this system, and the oscillations of the collapse and revival depend sensitively on the initial state of the single-mode quantized field and the damping rate κ. We also demonstrate that this system can show the beats phenomena.     

Features of sound propagation in the ocean with fine-structure inhomogeneities

We analyze the results of an experiment using an explosive sound source in the tropical part of the Indian Ocean. We consider the time structure of sound signals in geometric shadow zones to a distance of 270 km and the scheme of how the sound field in the shadow zone is formed by rays reflected from horizontally extended fine-structured sound velocity layers. From the results of calculation using a wave program that realizes the method of psuedodifferential parabolic equations, we analyze the influence of signal scattering by fine-structure sound velocity inhomogeneities on the sound field distribution in a waveguide. We show that the field formed by spots of light in each of the shadow zones is generated by a regular field and propagates in parallel to it, taking energy from the regular zone in the near field and in each subsequent convergence zone. This mechanism causes an additional decrease in the field in illuminated zones, which can be interpreted as additional attenuation of the regular sound field.     

Dilation analyticity in constant electric field

We extend the analysis of Paper I from two body dilation analytic systems in constant electric field toN-body systems in constant electric field. Particular attention is paid to what happens to isolated eigenvalues of an atomic or molecular system in zero field when the field is turned on. We prove that the corresponding eigenvalue of the complex scaled Hamiltonian is stable and becomes a resonance. We study analyticity properties of the levels as a function of the field and also Borel summability.Research partially supported by USNSF grant MCS 78-00101Research partially supported by USNSF grant MCS 78-01885     

外场驱动对双原子Tavis-Cummings模型中原子和腔场性质的影响

研究受外部经典场驱动的双原子Tavis-Cummings模型中原子和腔场的特性. 分析了腔场初态为相干态的情况,求出外场驱动下原子系统粒子布居差、光场的平均光子数和Mandel Q参数，并进行了数值分析. 特别讨论了外部驱动场对此模型中原子和腔场性质的影响.     

Enhancement of nonlinear susceptibility in a four-level tripod scheme

We propose a scheme for the enhancement of nonlinear susceptibility in a four-level tripod-type atomic system in the presence of a microwave field. With a microwave field, nonlinear susceptibility can be enhanced. Nonlinearity can also be ulteriorly enhanced by controlling the coupling field under the optimal intensity of the microwave field. The physical mechanism of the obtained giant nonlinear susceptibility is mainly based on interactions between microwave field and coupling fields. We present a physical understanding of our numerical results using a dressed-state approach and an analytical explanation.     

Geometric nature of the environment-induced Berry phase and geometric dephasing

We investigate the geometric phase or Berry phase acquired by a spin half which is both subject to a slowly varying magnetic field and weakly coupled to a dissipative environment (either quantum or classical). We study how this phase is modified by the environment and find that the modification is of a geometric nature. While the original Berry phase (for an isolated system) is the flux of a monopole field through the loop traversed by the magnetic field, the environment-induced modification of the phase is the flux of a quadrupolelike field. We find that the environment-induced phase is complex, and its imaginary part is a geometric contribution to dephasing. Its sign depends on the direction of the loop. Unlike the Berry phase, this geometric dephasing is gauge invariant for open paths of the magnetic field.