K. Berrada

Entanglement generation from deformed spin coherent states using a beam splitter

Using the linear entropy as a measure of entanglement, we investigate the effect of a beam splitter on the Perelomov coherent states for the q-deformed Uq(su(2)) algebra. We distinguish two cases: in the classical q → 1 limit, we find that the states become Glauber coherent states as the spin tends to infinity; whereas for q ≠ 1, the states, contrary to the earlier case, become entangled as they pass through a beam splitter. The entanglement strongly depends on the q-deformation parameter and the amplitude Z of the state.

Concurrence in the framework of coherent states

The concurrence of a two-qubit nonorthogonal pure state is determined through the construction of this state in the language of spin coherent states. The generalization of this method to the case of a class of mixed states is given. The concurrence in this case is nothing but a function of the amplitude of the spin coherent states, it is shown also that probability present an interesting behavior.

Beam splitting and entanglement generation: excited coherent states

We study the mathematical properties of the excited coherent states, which are obtained through actions of a photon creation operator of the mode optical field on its corresponding coherent state, by analyzing the minimal set of Klauder’s coherent states. Using linear entropy as a measure of entanglement, we investigate in detail the entanglement generated via a beam splitter when an excited coherent state is injected on one input mode and vacuum state is injected on the other one. Finally, we examine the physical properties of the excited coherent states through the Mandel’s parameter and the Wehrl entropy and we give the correlation between these parameters and the entanglement of the output state.

Entanglement generation with deformed Barut-Girardello coherent states as input states in an unitary beam splitter

Using linear entropy as a measure of entanglement, we investigate the entanglement generated via a beam splitter using deformed Barut-Girardello coherent states. We show that the degree of entanglement depends strongly on the q-deformation parameter and amplitude Z of the states. We compute the Mandel Q parameter to examine the quantum statistical properties of these coherent states and make a comparison with the Glauber coherent states. It is shown that these states are useful in describing the states of real and ideal lasers by a proper choice of their characterizing parameters, using an alteration of the Holstein-Primakoff realization.

Geometric phase and entanglement for a single qubit interacting with deformed-states superposition

The geometric phase and quantum entanglement for a nonlinear field-atom system are described quantitatively in terms of different parameters. Specifically, considering a deformed Schrödinger cat interacting with a qubit and taking into account the time dependent of the system coupling. The results show that the initial state setting, atomic motion, photon number and deformation play important roles in the evolution of the system dynamics, nonlocal correlation and geometric phase. An interesting correlation between the entanglement and geometric phase is observed during the time evolution. The presented system is very useful to generate and maintain high amount of entanglement through controlling the phase variation of the system under consideration. We test this observation with experimentally accessible parameters and some new aspects are obtained.

Quantum and Classical Quantifiers for Atom-Nonlinear Field System under Decoherence

The entanglement and coherence of a single qubit and deformed bosonic field inside a phase-damped cavity are discussed. In the classical q → 1 limit, analytic results under certain parametric conditions are obtained. The influence of deformation and dissipation on the negativity, Wehrl entropy, atomic Wehrl entropy and marginal distribution is studied. An interesting relation between the entanglement, deformation and decoherence effects is observed.

Nonlocal correlations for manifold quantum systems: Entanglement of two-spin states

In this paper, we study the bipartite entanglement of spin coherent states in the case of pure and mixed states. By a proper choice of the subsystem spins, the entanglement for large class of quantum systems is investigated. We generalize the result to the case of bipartite mixed states using a simplified expression of concurrence in Wootters’ measure of the bipartite entanglement. It is found that in some cases, the maximal entanglement of mixed states in the context of su(2) algebra can be detected. Our observations may have important implications in exploiting these states in quantum information theory.

Bipartite entanglement of nonlinear quantum systems in the context of the q-Heisenberg Weyl algebra

In this paper, we study in detail the degree of entanglement of bipartite system states in the context of q-Heisenberg-Wely algebra. We examine the entanglement properties for two systems of arbitrary deformation parameters q1 and q2, defined in entanglement of entangled deformed bosonic coherent states of each of the deformation parameters. For a particular choice of the parameters that specify the coherent states, we give conditions under which bipartite entangled coherent states become maximally entangled. We generalize this formalism to the case of bipartite mixed states using a simplified expression of concurrence in Wootters’ measure of the bipartite entanglement.

Geometric phase and entanglement of Raman photon pairs in the presence of photonic band gap

Robustness of the geometric phase (GP) with respect to different noise effects is a basic condition for an effective quantum computation. Here, we propose a useful quantum system with real physical parameters by studying the GP of a pair of Stokes and anti-Stokes photons, involving Raman emission processes with and without photonic band gap (PBG) effect. We show that the properties of GP are very sensitive to the change of the Rabi frequency and time, exhibiting collapse phenomenon as the time becomes significantly large. The system allows us to obtain a state which remains with zero GP for longer times. This result plays a significant role to enhance the stabilization and control of the system dynamics. Finally, we investigate the nonlocal correlation (entanglement) between the pair photons by taking into account the effect of different parameters. An interesting correlation between the GP and entanglement is observed showing that the PBG stabilizes the fluctuations in the system and makes the entanglement more robust against the change of time and frequency.

Quantum Quantifiers for an Atom System Interacting with a Quantum Field Based on Pseudoharmonic Oscillator States

We develop a useful model considering an atom-field system interaction in the framework of pseudoharmonic oscillators. We examine qualitatively the different physical quantities for a two-level atom (TLA) system interacting with a quantized coherent field in the context of photon-added coherent states of pseudoharmonic oscillators. Using these coherent states, we solve the model that exhibits the interaction between the TLA and field associated with these kinds of potentials. We analyze the temporal evolution of the entanglement, statistical properties, geometric phase and squeezing entropies. Finally, we show the relationship between the physical quantities and their dynamics in terms of the physical parameters.