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For the interaction between a two-level atom and the radiation field in the dipole and the rotating wave approximations, namely, the Jaynes-Cummings model, we obtain a closed form for the atomic Wehrl entropy in terms of the Bloch sphere radius. This explains analytically why the atomic Wehrl entropy has an identical behavior to that of the von Neumann entropy. [ABSTRACT FROM AUTHOR]

In this paper, we study the interaction between two two-level atoms and two nondegenerate cavity modes when the atoms and the field are initially in the atomic superposition states and the pair-coherent state (PCS), respectively. We investigate the atomic inversions, tangles and joint probability distribution. We show that the system can generate long-living entanglement by controlling the values of the interaction parameters. Also we show generally that for obtaining a large amount of entanglement from two qubits interacting with a maximally entangled two-mode state one has to prepare the qubits initially in the decoupled states. Moreover, the system - at certain values of interaction parameters - can generate different types of nonclassical states, such as the mth-photon PCS, statistical mixtures of PCSs and superposition of PCS. [ABSTRACT FROM AUTHOR]

For the multiphoton intensity-dependent Jaynes–Cummings model (JCM) described by a two-level atom interacting with a radiation field, we prove that there is a relationship between the atomic inversion and the quadrature squeezing. We give the required condition to obtain best information from this relation. Also we show that this relation is only sensitive to large values of the detuning parameter. Furthermore, we discuss briefly such relation for the off-resonance standard JCM. [ABSTRACT FROM AUTHOR]

In this paper we derive the quantum statistical and dynamical properties of nonlinear optical couplers composed of two nonlinear waveguides operating by second subharmonic generation, which are coupled linearly through evanescent waves and nonlinearly through non-degenerate optical parametric interaction. Main attention is paid to generation and transmission of non-classical light, based on a discussion of the squeezing phenomenon, the normalized second-order correlation function and quasiprobability distribution functions. Initially coherent, number and thermal states of optical beams are considered. In particular, results are discussed with dependence on the strength of the nonlinear coupling relatively to the linear coupling. We show that if the Fock state |1> enters the first waveguide and the vacuume state |0> enters the second waveguide, the coupler can serve as a generator of squeezed vacuum state governed by the coupler parameters. Further, if thermal fields enter initially the waveguides the coupler plays a similar role as a microwave Josephson-junction parametric amplifier to generate squeezed thermal light. [ABSTRACT FROM AUTHOR]

The effect of thermal noise is studied on the statistical behaviour of the superposition of squeezed and displaced number states. In our analysis we have employed the s-parametrized characteristic function. For such superposition states exact expressions for quasiprobability distribution functions, normalized second-order correlation function, photon-number distribution and phase space distribution are obtained and discussed in detail. [ABSTRACT FROM AUTHOR]