International Journal of Modern Physics B

We review how to rely on the quantum entanglement idea of Einstein–Podolsky–Rosen and the developed Dirac's symbolic method to set up two kinds of entangled state representations for describing the motion and states of an electron in uniform magnetic field. The entangled states can be employed for conveniently expressing Landau wave function and Laughlin wave function with a fresh look. We analyze the entanglement involved in electron's coordinates (or momenta) eigenstates, and in the angular momentum-orbit radius entangled state. Various applications of these two representations, such as in developing angular momentum theory, squeezing mechanism, Wigner function and tomography theory for this system are presented. Thus the present review systematically summarizes a distinct approach for tackling this physical system.

We investigate 2-dimensional spatial optical solitons in media exhibiting a large nonlocal response coupled with a self-focusing nonlinearity. To this extent, with reference to a specific system in undoped nematic liquid crystals, we develop a general theory of spatial solitons in media with an arbitrary degree of nonlocality and carry out experimental observations to validate the model. The remarkable agreement between predictions and data yields evidence of narrow-waist solitons, revealing an important connection between nonparaxiality and nonlocality and emphasizing the role of nonlocality.

We propose a model for two identical granular fluids separated by a piston that can present clustering (volume tending to zero) for a range of parameters. This model is based on point granular particles. For a convenient range of parameters, a granular fluid-cluster collapse is then possible and permits us to get an insight on the physics of granular clusters based on the behavior of the fluid phase itself.

X-ray absorption measurements have been made on CuL₃ and O K-edge on BSCCO (2212) single crystals annealed under two different conditions at 1 bar O₂ (under-doped) and another annealed in 1:4 ratio of O₂: Ar (optimally doped) using the F. Y. detection technique. Our results clearly indicate that hole density decreases while going towards c-axis from the ab plane. Our results shows that the doping holes have predominantly x, y symmetry compared to those having p_z symmetry. The T_c for both the crystals does not depend on the density of doping holes in the apical oxygen. However, the matter needs to be further explored.

X-ray absorption measurements have been made at the CuL₃ and O K-edge on (Hg_0.5Bi_0.5)Sr₂(Ca_1-xPr_x)Cu₂O_7-δ (x=0.35,0.50) and (Hg_0.5Bi_0.5)Sr₂(Ca_0.65Nd_0.35)-Cu₂O_7-δ superconducting systems. Our results clearly indicate that hole density decreases with increase in Pr content. The values of T_c for Pr and Nd (x=0.35) systems are the same but the itinerant hole density is found to be larger in the latter case. In view of the fact that the density of holes depends more upon diamagnetic fraction than the T_c in these superconducting systems, we can conclude that superconducting properties are different for these two cases.

The low-temperature thermodynamics of a one-dimensional electron gas on a disordered lattice, which comes to existence when the inter-electron distances exceed noticeably the inter-site ones, has been studied. An efficient computer procedure, based on the presentation of the partition function as a product of random transfer-matrixes, has been developed for calculations of thermodynamic characteristics of the system under consideration. The lattice structures were varied from completely chaotic up to the strictly regular one. It has been established that for any degree of disorder the entropy and heat capacity of the system tend to zero linearly as the temperature is reduced. The conclusion about the gapless character of the elementary excitations spectrum has been made. An instability of one-dimensional electron gas on a disordered lattice has been revealed: under conditions of vanishingly small disordering of the lattice, the long-range order in the systems under consideration is broken by frustrations that are one-dimensional analogues of the frustrations in two- and three-dimensional spin glasses.

The activation energy E (eV) of the first-order thermoluminescence (TL) glow peak is currently obtained using a two heating rates method. However, this method having the common drawback, that it assumes the first-order kinetics in the luminescence process. In the present work, an equation is suggested to determine the activation energy E (eV) of any glow peak, independent on the kinetics order of the process. To apply this method, three heating rates (β₁,β₂,β₃), the corresponding peak temperatures (T₁,T₂,T₃) and intensities (I₁,I₂,I₃) of the isolated glow peaks are required. The applicability of the suggested method is demonstrated here by taking some numerically computed first-, second- and general-order TL glow peaks.

The polaronic correction to the ground-state energy of the electron confined in a cylindrical quantum dot (QD) subject to electric and magnetic fields along the growth axis has been investigated. Using a combinative approach of perturbative theory and variational wavefunction, calculations are performed for an infinitely deep confinement potential outside the QD within the effective mass and adiabatic approximation. We have treated the system by taking into consideration the interaction of the electron with the confined longitudinal optical (LO) phonons as well as the side surface (SSO) and the top surface (TSO) optical phonons.^1,2 The ground-state energy shift is obtained as a function of the cylindrical radius and the strength of electric and magnetic fields. The results show that the magnetic field heavily enhances the three types of phonon mode contribution to the correction of the electron ground-state energy while the electric field only improves the contribution of surface phonons (SSO and TSO) but decreases the contribution of LO phonons.

We study the interaction of a moving four-level atom with a single mode cavity field. Involving intensity dependent coupling, the atom-field wave function and the reduced density matrix of the field are obtained when the atom is initially prepared in a coherent superposition of the upper and ground states and the field is initially in a coherent state. The influence of the intensity dependent atom-field coupling and of the detuning on the collapse and revival phenomenon of the time evolution of statistical aspects, such as the mean photon number, the second-order correlation function of the field, the momentum increment and momentum diffusion, are investigated. It is found that, for the nonresonant case, the detuning between the field and the atom has a significant influence which leads to increasing the collapse time with decreasing amplitude. Numerical computations and discussion of the results are presented.

Glasses of the xCuO·(100-x)[2B₂O₃·Ag₂O] system, with 0<x≤30 mol%, were investigated by means of EPR and magnetic susceptibility measurements. The influence of a gradual increase in CuO content on the glass structure and magnetic interactions that involved copper ions, have been discussed. EPR absorption spectra show Cu²⁺ ions in axially distorted octahedral environments. Both EPR and magnetic measurements data pointed out the simultaneous presence in the glasses with x>5 mol% of Cu²⁺ and Cu⁺ ionic species. The Curie behavior of magnetic susceptibility indicates the absence of the superexchange interactions in these glasses.

We present in this work a theory of magnetization (M) in diluted magnetic semiconductors and express it as sum of contributions due to magnetic impurities (M_i) and band effects which include lattice diamagnetism (M_dia) and spin density due to carriers (M_c). In addition to the contribution of isolated magnetic ions (M_s), M_i includes the contributions of three types of small clusters: pairs (M_p), open triplets (M_ot) and closed triplets (M_ct). The contributions due to impurity spin interactions were calculated using modified Heisenberg's Hamiltonian as applicable to these clusters within the nearest neighbor interaction approximation. The band effects include contributions due to lattice diamagnetism and spin density due to carriers. The lattice diamagnetism χ_dia was calculated using a two band model for the host system and a modified one for the alloy systems. χ_dia for the host system compare well with the available experimental results. M_c was calculated using a formula derived from first principles for an interacting electronic system. This is modified to calculate M_c in the p-type Pb_1-xMn_xTe and Pb_1-xEu_xTe. Although the band effects are found to be small in the context of analyzing magnetization, they are intrinsically important in the sense that these quantities shed light on the nature of mechanisms contributing to lattice diamagnetism and the carrier spin densities in these systems.

Phase synchronization of a chaotic oscillator that is driven by two chaotic signals is investigated. The anti-biased PS in the presence of biased coupling is found, i.e., the response oscillator can be phase synchronized by the drive with a weaker coupling rather than the stronger driver. The mechanism for this behavior is explored. In the non-PS region, alternating phase-locking is observed.

We show how a non-local quantum CNOT with (N-1)-target operation can be implemented with unit fidelity and unit probability by using a N-qubit maximally entangled GHZ state as quantum channel. We also put forward two schemes for probabilistic implementing the operation with unit fidelity by employing a partially entangled pure GHZ state as quantum channel. The overall physical resources required for accomplishing these schemes are different, and the successful implementation probabilities are also different. We also point out the non-local CNOT with (N-1)-target operation can be used as a purification protocol to concentrate entanglement from an ensemble of partially entangled GHZ states into a subensemble of maximally entangled ones.