Mohamed Ridza Wahiddin

Classical information entropy and phase distributions of optical fields

The Wehrl phase distribution is defined as a phase density of the Wehrl classical information entropy. The new measure is applied to describe the quantum phase properties of some optical fields including Fock states, coherent and squeezed states, and superposition of chaotic and coherent fields. The Wehrl phase distribution is compared with both the conventional Wehrl entropy and Husimi phase distribution (the marginal Husimi Q-function). It is shown that the Wehrl phase distribution is a good measure of the phase-space uncertainty (noise), phase locking and phase bifurcation effects. It is also demonstrated that the Wehrl phase distribution properly describes phase randomization processes, and thus can be used in a description of the quantum optical phase.

Exact solution of an Ising model with competing interactions on a Cayley tree

The exact solution of an Ising model with competing restricted interactions on the Cayley tree, and in the absence of an external field is presented. A critical curve is defined where it is possible to get phase transitions above it, and a single Gibbs state is obtained elsewhere.

Generation of three-qubit entangled W state by nonlinear optical state truncation

We propose an alternative scheme to generate the W state via optical state truncation using quantum scissors. In particular, these states may be generated through three-mode optical state truncation in a Kerr nonlinear coupler. The more general three-qubit state may also be produced if the system is driven by external classical fields.

Soliton interaction and switching in a coupler with third order dispersion and Raman effect

The interaction and switching of optical solitons in a nonlinear directional coupler are investigated analytically and numerically. The influence of the coupling-coefficient dispersion, the third order dispersion and the Raman effect in fibers on these processes are reported. Coupled soliton states are found, and their stability is checked numerically. Switching characteristics of solitons in directional couplers are studied.

Generation of even and odd coherent states in the intensity dependent Jaynes-Cummings model

Abstract We study the evolution of the wavefunction in the intensity dependent Jaynes—Cummings model. It is shown that apart from the periodic revivals indicated by the dynamics of inversion, half-time revivals of the wavefunction take place in the limit of [nbar] ≫ 1. The decoupled atomic state is a superposition of the upper and lower levels and is independent of the initial atomic condition. The decoupled field state is an even or odd coherent state with a spiked distribution function, depending on the initial atomic state.

An ising model with three competing interactions on a Cayley tree

In this paper we consider an Ising model with three competing restricted interactions on the Cayley tree J2(J3). The translation invariant and periodic Gibbs measures for these models are investigated and the problem of the phase transition in these classes is solved.

Single-atom entropy squeezing for two two-level atoms interacting with a single-mode radiation field

In this paper we consider a system of two two-level atoms interacting with a single-mode quantized electromagnetic field in a lossless resonant cavity via l-photon-transition mechanism. The field and the atoms are initially prepared in the coherent state and the excited atomic states, respectively. For this system we investigate the entropy squeezing, the atomic variances, the von Neumann entropy and the atomic inversions for the single-atom case. Also we comment on the relationship between spin squeezing and linear entropy. We show that the amounts of the nonclassical effects exhibited in the entropy squeezing for the present system are less than those produced by the standard Jaynes–Cummings model. The entropy squeezing can give information on the corresponding von Neumann entropy. Also the nonclassical effects obtained from the asymmetric atoms are greater than those obtained from the symmetric ones. Finally, the entropy squeezing gives better information than the atomic variances only for the asymmetric atoms.

Dispersion-managed solitons in a periodically and randomly inhomogeneous birefringent optical fiber

The propagation of dispersion-managed vector solitons in optical fibers with periodic and random birefringence is studied. With the help of a variational approach, the equations that describe the evolution of pulse parameters are derived. Numerical modeling is performed for variational equations and for fully coupled periodic and stochastic nonlinear Schrodinger equations. It is shown that variational equations can be effectively used to describe the averaged dynamics of dispersion-managed vector solitons with stochastic perturbations. It is shown, analytically and numerically, that dispersion-managed (DM) solitons have the same resistance to random birefringence as do ordinary solitons. The dependence of the mean decay length of a DM vector soliton on the strength of random birefringence and on the energy of the initial pulse is found.

Quantum phase properties of two-mode Jaynes–Cummings model for Schrödinger-cat states: interference and entanglement

Abstract In this paper, we investigate the quantum phase properties for the coherent superposition states (Schrodinger-cat states) for two-mode multiphoton Jaynes–Cummings model in the framework of the Pegg–Barnett formalism. We also demonstrate the behavior of the Wigner ( W ) function at the phase space origin. We obtain many interesting results such as the existence of a clear relationship between the revival-collapse phenomenon occurring in the atomic inversion (as well as in the evolution of the W function) and the behavior of the phase distribution of both the single-mode and two-mode cases. Furthermore, we find that the phase variances of the single-mode case can exhibit revival-collapse phenomenon about the long-time behavior. We show that such behavior occurs for interaction time several times smaller than that of the single-mode Jaynes–Cummings model.

Analysis of the master equation for the Dicke model in squeezed vacua

The master equation for the reduced atomic density operator for the Dicke model (Na 2-level atoms on the same single site) interacting with a broad-band squeezed vacuum state field is derived using operator reaction field theory. The analysis through reaction field theory is presented first of all for the normal vacuum and then for the squeezed vacuum, both within the Markov and Born approximations. In the case of the squeezed vacuum field a statistical decorrelation between matter and field variables is also necessarily adopted in order to close the system of equations: this is also the case for the broad-band black-body field, and the theory contrasts with that which employs projection operator techniques and uses weak coupling. Models involving a both axially symmetrical and wholly isotropic distribution of the squeezed vacuum modes are compared.