Kerr-like Medium Research Articles

ENTANGLEMENT OF A GENERAL FORMALISM Λ-TYPE THREE-LEVEL ATOM INTERACTING WITH A SINGLE-MODE FIELD IN THE PRESENCE OF NONLINEARITIES

We investigate the evolution of the atomic quantum entropy and the atom–field entanglement in a system of a Λ-configuration three-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom–field coupling. With the derivation of the unitary operator within the frame of the dressed state and the exact results for the state of the system, we perform a careful investigation of the temporal evolution of the entropy. A factorization of the initial density operator is assumed, considering the field to be initially in a squeezed coherent or binomial state. The effects of the mean photon number, detuning, Kerr-like medium, and the intensity-dependent coupling functional on the entropy are analyzed.

ENTANGLEMENT OF A GENERAL FORMALISM Ξ-TYPE THREE-LEVEL ATOM INTERACTING WITH A SINGLE-MODE FIELD IN THE PRESENCE OF NONLINEARITIES

We investigate the evolution of the atomic quantum entropy and the atom-field entanglement in a system of a Ξ-configuration three-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling. With the derivation of the unitary operator within the frame of the dressed state and the exact results for the state of the system, we perform a careful investigation of the temporal evolution of the entropy. A factorization of the initial density operator is assumed, considering the field to be initially in a squeezed coherent or binomial state. The effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy are analyzed.

Entanglement in a system of an [formula omitted]-type three-level atom interacting with a non-correlated two-mode cavity field in the presence of nonlinearities

We investigate the evolution of the atomic quantum entropy and the atom-field entanglement in a system of an Ξ-configuration three-level atom interacting with a two-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling. With the derivation of the unitary operator within the frame of the dressed state and the exact results for the state of the system we perform a careful investigation of the temporal evolution of the entropy. A factorization of the initial density operator will be assumed, considering the field to be initially in a non-correlated two-mode squeezed coherent or binomial states. The effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy will be analyzed.

Tripartite entanglement dynamics for an atom interacting with nonlinear couplers

In this communication we introduce a new model which represents the interaction between an atom and two fields injected simultaneously within a cavity including the nonlinear couplers. By using the canonical transformation the model can be regarded as a generalization of several well-known models. We calculate and discuss entanglement between the tripartite system of one atom and the two cavity modes. For a short interaction time, similarities between the behavior based on our solution compared with the other simulation based on a numerical linear algebra solution of the original Hamiltonian with truncated Fock bases for each mode, is shown. For a specific value of the Kerr-like medium defined in this letter, we find that the entanglement, as measured by concurrence, may terminate abruptly in a finite time.

Berry phase in a two-atom Jaynes–Cummings model with Kerr medium

The Jaynes–Cummings model (JCM) is an very important model for describing interaction between quantized electromagnetic fields and atoms in cavity quantum electrodynamics (QED). This model is generalized in many different directions since it predicts many novel quantum effects that can be verified by modern physics experimental technologies. In this paper, the Berry phase and entropy of the ground state for arbitrary photon number n of a two-atom Jaynes–Cummings model with Kerr-like medium are investigated. It is found that there is some correspondence between their images, especially the existence of a curve in the Δ–ε plane along which the energy, Berry phase and entropy all reach their special values. So it is available for detecting entanglement by applying Berry phase.

Pseudo-invariant Eigen-operator of a System About Three-Level Atom in Presence of a Kerr-Like Medium

A system of a three-level atom interacting with single mode cavity field through multi-photon transition in the presence of a Kerr-like medium is proposed, and its pseudo-invariant eigen-operator (PIEO) and energy-level gap are presented under one-order approximation.

Entanglement of a general formalism Λ-type three-level atom interacting with a non-correlated two-mode cavity field in the presence of nonlinearities

We investigate the evolution of the atomic quantum entropy and the atom–field entanglement in a system of a Λ-configuration three-level atom interacting with a two-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom–field coupling. With the derivation of the unitary operator within the frame of the dressed state and the exact results for the state of the system we perform a careful investigation of the temporal evolution of the entropy. A factorization of the initial density operator is assumed, considering the field to be initially in a non-correlated two-mode squeezed coherent or binomial state. The effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy are analysed.

Entanglement of a General Formalism V-Type Three-Level Atom Interacting with a Single-Mode Field in the Presence of Nonlinearities

We investigate the evolution of the atomic quantum entropy and the atom-field entanglement in a system of a V-configuration three-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling. With the derivation of the unitary operator within the frame of the dressed state and the exact results for the state of the system we perform a careful investigation of the temporal evolution of the entropy. A factorization of the initial density operator is assumed, considering the field to be initially in a squeezed coherent or binomial state. The effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy are analyzed.

The investigation of an electrically stabilized optical spatial soliton induced in a nematic liquid crystal

A spatial soliton is induced between two optical fibres in a liquid crystal medium and the associated optical power transmitted is measured. The signal/noise (S/N) ratio of the device is estimated and then improved by applying an extra voltage along the propagation axis. Besides this applicative result, which is the first step towards realistic optical switches, we show that the response curve of such a coupler gives information on the soliton propagation regime in a highly nonlocal medium, namely the longitudinal structure of the soliton envelope. In addition, it is shown that the extra voltage allows control of the nonlocality, approaching a Kerr-like medium for strong voltage.

Reducing four-level two-mode Hamiltonian to an effective two-level Hamiltonian with the addition of kerr-like medium

We consider a two-mode quantized field described in a coherent state interacting with a four-level atom. An effective Hamiltonian is obtained by adiabatically eliminating the intermediate two levels in a cascade process. The influence of the Stark shifts and the Kerr-like medium on the atomic inversion are examined, as well as on the field entropy, atomic purity and Mandel's Q-parameter. The results of the calculations are illustrated numerically.

A moving four-level N-type atom interacting with cavity fields

We study the non-resonant interaction of a moving four-level N-type atom with cavity fields in the presence of a nonlinear Kerr-like medium. The exact solutions of the considered models are obtained when the atom is initially in an upper state, while the field is in a coherent state. We derive an expression for the occupation numbers of the photon state. Also, the momentum increment of the atomic system is obtained. The influence of the detuning parameters or the Kerr medium on the evolution time of the momentum increment is examined numerically. The existence of the detuning parameters leads to the retraction of the revivals for the three atomic systems. On the other hand, the presence of the Kerr medium is conducive to increasing the regularity and periodicity of the collapse–revival phenomenon for the one- and two-mode systems, while chaotic behaviour occurs for the three-mode system.

Eigenstates and spectrum properties of a resonant field in a Kerr-like medium

We investigate the energy eigenvalues and eigenstates of a resonant field in a Kerr-like medium by an efficient method. All the energy eigenvalues and eigenstates can be obtained for an arbitrary total particle number N and other parameters involved in the system. We show that the eigenstates can be explicitly expressed analytically in terms of a single parameter γ whose values are determined by the roots of a polynomial of the order of at most 1 + int(N/2) with int(x) being x's integer part. By studying the spectra, the erratic level crossings appear apparent when N ⩾ 40 and γ over critical values.

Entropies and Entanglement for Initial Mixed State in the Multi-quanta JC Model with the Stark Shift and Kerr-like Medium

In this paper, we study the time evolution of the entropies and the degree of entanglement in the mixed state for a multi-quanta JC model taking into consideration Stark shift and Kerr-like medium effect, we use a numerical method to investigate the time evolution of the partial entropy of the atom and field subsystem. This is done in the framework of the multi-quanta presses JC model with both the Stark shift and Kerr-like medium effect added. Furthermore, we examine the effect of the superposition states and a statistical mixture of coherent states as an initial field on the entropies and entanglement. Our results show that the setting of the initial state play an important role in the evolution of the sub-entropies and entanglement.

Cavity Field Spectra of a Cascade Three-Level Atom Interacting witha Single-Mode Field with Kerr-Like Medium

The cavity field spectrum of a cascadethree-level atom interacting with single-mode field with Kerr-like medium inthe cavity is investigated. The numerical results for the initial field inpure number state, coherent state and squeezed vacuum state arecalculated, respectively. It is found that the Kerr-like medium affects thespectral structure even though the initial field is in vacuum when theatom is in upper level. In the case of strong input field, the number statespectrum shows two peaks with different heights; and the superposition statespectrum shows a multi-peak structure with an equal distance of twoneighboring peaks. The spectral ``central frequency" shifts away from theresonant frequency with the increasing of average photon number.

Squeezing properties of the Kerr-down conversion system

In this Letter we describe a new two-mode system, which consists of Kerr-like medium and down conversion process, called the Kerr-down conversion system. Under a certain condition we can obtain an exact solution of the dynamical equations of motion. For this system we investigate different kinds of quadrature squeezing, e.g., single-mode, two-mode and sum-squeezing. Also we give a more general definition of the principal squeezing. We show that the amounts of nonclassical effects produced by the Kerr-like and down-conversion processes separately are greater than those obtained from the Kerr-down conversion system where both the processes are in competition.

Entropy squeezing of time dependent single-mode Jaynes–Cummings model in presence of non-linear effect

A general Hamiltonian for a system which consists of a two-level atom interacting with electromagnetic field is considered. Besides the Stark shift the model includes multi-photon process as well as a non-linear Kerr-like medium effect. Furthermore the field and the atom are assumed to be coupled with modulated coupling parameter which depends explicitly on time. Under an approximation where fast oscillations are ignored, an exact solution for the wave function in Schrödinger picture is given. The atomic inversion as well as the entropy squeezing are considered and it has been shown that existence of the time dependent coupling parameter leads to a time delaying in the interaction which is twice the delay time for the independent case.

Population Dynamics and Emission Spectrum of a Cascade Three-Level Jaynes–Cummings Model with Intensity-Dependent Coupling in a Kerr-like Medium

By using the method of eigenvectors, the atomic populations and emissionspectrum are investigated in a system that consists of a cascade three-levelatom resonantly interacting with a single-mode field in a Kerr-like medium.The atom and the field are assumed to be initially in the upper atomic stateand the Fock state, respectively. Results for models withintensity-dependent coupling and with intensity-independent coupling arecompared. It is found that both population dynamics and emission spectrumshow no indications of atom-field decoupling in the strong field limit ifthe intensity-dependent coupling is taken into account.

Effect of Kerr-like medium on a two-level atom in interaction with bimodal oscillators

In this article we study the effect of the Kerr-like medium on a system consisting of two-level atom and two fields injected simultaneously within perfect cavity. We assume that in the presence of the nonlinear Kerr coupler, the atom interacts with each field separately. The present system can be regarded as a co-directional nonlinear coupler composed of two Kerr nonlinear waveguides, where the atom–field interaction plays the role of the energy exchange between the waveguides. The system includes two effective different coupling parameters λ1 and λ2, such that each coupling connects the atom with one of the field mode. Moreover, it includes two different susceptibility factors, one represents self-coupling while the other is responsible for cross-action processes. Under certain conditions, the exact solution of the wavefunction in the Schrödinger picture is obtained and the Husimi quasidistribution is derived. A consideration of some physical phenomena, such as collapses and revivals is given, and the degree of entanglement is also discussed. The system is found to be sensitive to the variation of both mean photon numbers as well as to the Kerr-like medium.

Pattern formation and direct measurement of the spatial resolution in a photorefractive liquid crystal light valve

In a photorefractive liquid crystal light valve, acting as a Kerr-like nonlinear optical medium, we show the appearance of optical patterns induced by a single mirror feedback. The spatial wavelength of the patterns scales with the distance between the mirror and the valve and the contrast of the patterns decreases for decreasing this distance. We use these properties to setup a new optical scheme for the measurement of the spatial resolution of the nonlinear device.

Squeezing and higher-order squeezing of photon-added coherent states propagating in a Kerr-like medium

We investigate the squeezing and higher-order squeezing properties of photon-added coherent states propagating through a Kerr-like medium, particularly close to instants of revivals and fractional revivals of the state. The Wigner functions at these instants are obtained, and the extent of non-classicality quantified.