Shao-Hua Pan

Entangled coherent states for systems with SU(2) and SU(1,1) symmetries

Entangled SU(2) and SU(1,1) coherent states are developed as superpositions of multiparticle SU(2) and SU(1,1) coherent states. In certain cases, these are coherent states with respect to generalized su(2) and su(1,1) generators, and multiparticle parity states arise as a special case. As a special example of entangled SU(2) coherent states, entangled binomial states are introduced and these entangled binomial states enable the contraction from entangled SU(2) coherent states to entangled harmonic oscillator coherent states. Entangled SU(2) coherent states are discussed in the context of pairs of qubits. We also introduce the entangled negative binomial states and entangled squeezed states as examples of entangled SU(1,1) coherent states. A method for generating the entangled SU(2) and SU(1,1) coherent states is discussed and degrees of entanglement calculated. Two types of SU(1,1) coherent states are discussed in each case: Perelomov coherent states and Barut-Girardello ∗Email: barry.sanders@mq.edu.auEntangled SU(2) and SU(1,1) coherent states are developed as superpositions of multiparticle SU(2) and SU(1,1) coherent states. As a special example of entangled SU(2) coherent states, entangled binomial states are introduced and these entangled binomial states enable the contraction from entangled SU(2) coherent states to entangled harmonic oscillator coherent states. Entangled SU(2) coherent states are discussed in the context of pairs of qubits. We also introduce the entangled negative binomial states and entangled squeezed states as examples of entangled SU(1,1) coherent states. A method for generating the entangled SU(2) and SU(1,1) coherent states is discussed and degrees of entanglement calculated. Two types of SU(1,1) coherent states are discussed in each case: Perelomov coherent states and Barut-Girardello coherent states.

Second-harmonic generation in BaTiO3 films doped with cerium

Second-harmonic generation of 1.064 μm incident light was measured on BaTiO3 thin films, both a-axis and c-axis oriented, undoped and doped with cerium, prepared by pulsed laser deposition. The dependence of second-harmonic generation (SHG) coefficients of these films on the incidence angle and the polarization direction of the fundamental beam were investigated. The effective SHG coefficients was enhanced greatly when the films were doped with cerium.

A new direct process to prepare YBa2Cu3O7−δ films on biaxially textured Ag{110}〈211〉

YBa2Cu3O7-delta (YBCO) films were successfully prepared on biaxially textured Ag(110)(211) substrates by using pulsed laser deposition. X-ray diffraction results showed that the degree of preferential orientation of Ag(110)(211) substrates varied with increasing annealing temperature. With a thin template layer deposited at low temperature, YBCO film with c-axis orientation and in-plane biaxial alignment could be obtained at high deposition temperature. Scanning electron microscopy observation revealed that YBCO grains enlarged, but Ag grains on the surface of the YBCO films became smaller with increasing deposition temperature. At optimal deposition: conditions, Ag atoms diffuse into the YBCO grain boundaries, and then fill in the weak-link regions in the YBCO film, resulting in the easier conduction. J(c) value of 5 x 10(5) A/cm(2) was obtained at 77 K and zero magnetic field for the best YBCO film in our work

Fabrication and characteristics of CeO2 films on Si(1 0 0) substrates by pulsed laser deposition

A detailed investigation about the dependence of film orientation on deposition temperature and ambient oxygen pressure has been carried out for CeO2 films on Si(1 0 0) substrates using pulsed laser deposition. It has been found that the CeO2 film orientation varies with increasing oxygen pressure at 750 degrees C deposition temperature. In addition, the recovery of preferential orientation of CeO2 films grown at 20 Pa ambient oxygen pressure with increasing deposition temperature has also been found for the first time. X-ray photoelectron spectroscopy (XPS) measurements confirm that stoichiometric CeO2 films can be grown at lower oxygen pressure(similar to 5 x 10(-3) Pa). HRTEM result also indicates that the CeO2 films grown at low oxygen pressure are of high crystallinity

Effects of multi-surface modification on Curie temperature of ferroelectric films

Within the framework of mean field theory, we study the effects of multi-surface modification on the Curie temperature of ferroelectric films using the transverse Ising model. The general nonlinear equations for Curie temperature of multi-surface ferroelectric films with arbitrary exchange constants and transverse fields are derived by the transfer matrix method. As an example, we consider an (l, n, l) film consisting of l top surface layers, n bulk layers and l bottom surface layers. Two types of surface modification, modifications of a surface exchange constant and a surface transverse field, are taken into account. The dependence of Curie temperature on the surface layer numbers, bulk layer numbers, surface exchange constants, surface transverse fields and bulk transverse fields is discussed.

Third-order optical nonlinear properties of amorphous Si/SiO2 superlattices fabricated by magnetron sputtering

Abstract The nonlinear optical response of amorphous Si/SiO2 superlattices fabricated by magnetron sputtering are studied using the Z-scan technique. The real and imaginary parts of the third-order optical nonlinearity χ(3) have been measured at 532 nm and found to be 6.392×10−7 esu and −9.814×10−7 esu, respectively. The results indicate an enhancement over crystalline silicon and porous silicon, which may be attractive for potential application in electro-optic devices.

Magnetization profiles of ferromagnetic Ising films in a transverse field

Within the framework of the mean field theory, we study the magnetization profiles of ferromagnetic Ising films in a transverse field. By the transfer matrix method, we first derive a general nonlinear equation for phase transition temperatures and then calculate the magnetization profiles of the system. The method proposed here can be applied to ferromagnetic films with arbitrary surface layer number, bulk layer number, exchange interaction constants and transverse fields.

Quantum Fluctuations of a Mesoscopic RLC Circuit in a Displaced Squeezed Fock State

Starting from the equation of motion for a circuit including resistor, inductor and capacitor (RLC), we study the quantum fluctuations of charge and magnetic flux of a mesoscopic RLC circuit in a displaced squeezed Fock state. It is found that the fluctuations of charge and magnetic flux do not depend on the displacement parameter and there exist squeezing effects between them. We also show how to generate the displaced squeezed Fock state in the RLC circuit.

Structural characteristics of CeO2 films grown on biaxially textured nickel (001)

Preferential (001) orientation CeO2 films have been successfully grown on biaxially textured Ni substrates using ion beam assisted pulsed laser deposition. The x-ray diffraction (XRD) patterns for the CeO2 films and target have been measured. The in-plane lattice constants have been derived from the data of XRD. It was found that the in-plane lattice constants of the films increase with increasing deposition temperature. A reasonable explanation based on the difference of the linear thermal expansion coefficient between the CeO2 film and Ni substrate was proposed. Moreover, Raman spectra of the films and target have been recorded. It was shown that the oxygen deficiency in the CeO2 samples has a great effect on the full width at half maximum of the Raman lines. According to the relation between the Gruneisen shift and the lattice contraction, we have obtained the theoretical Raman shifts which are in good agreement with the experimental results.

Properties of YBa2Cu3Ox−δ films on textured Ag tapes

Abstract Two types of biaxial textured tape, Ag{110}〈112〉 and Ag{100}〈001〉, have been produced by different rolling and recrystallization from a pure (>99.95%) Ag plate. YBa 2 Cu 3 O 7− δ (YBCO) films were then prepared on the Ag tapes by use of pulsed laser deposition (PLD). DC transport measurement revealed that the films on Ag{110}〈112〉 tape have a critical current density ( J c ) in the range of 4–6×10 5 A/cm 2 (77 K, 0 T), while the J c values of YBCO films on Ag{100}〈001〉 tape, prepared under the same conditions, were lower. Accordingly, X-ray diffraction (XRD) produced sharp spots in the pole-figure of YBCO on the Ag{110}〈112〉 tape, which confirms the presence of a texture in the YBCO film. The pole-figure of the YBCO film on Ag{100}〈001〉 did not show a preferred in-plane orientation.