Stationary entanglement between macroscopic mechanical oscillators

We show that the optomechanical coupling between an optical cavity mode and two movable cavity mirrors is able to entangle two different macroscopic oscillation modes of the mirrors. This continuous variable entanglement is maintained by the light bouncing between the mirrors and is robust against thermal noise. In fact, it could be experimentally demonstrated using present technology. Received 2 September 2002 / Received in final form 10 October 2002 Published online 7 January 2003     

1/N-Expansion for the Dicke model and the decoherence program

An analysis of the Dicke model, N two-level atoms interacting with a single radiation mode, is done using the Holstein-Primakoff transformation. The main aim of the paper is to show that, changing the quantization axis with respect to the common usage, it is possible to prove a general result either for N or the coupling constant going to infinity for the exact solution of the model. This completes the analysis, known in the current literature, with respect to the same model in the limit of N and volume going to infinity, keeping the density constant. For the latter the proper axis of quantization is given by the Hamiltonian of the two-level atoms and for the former the proper axis of quantization is defined by the interaction. The relevance of this result relies on the observation that a general measurement apparatus acts using electromagnetic interaction and so, one can state that the thermodynamic limit is enough to grant the appearance of classical effects. Indeed, recent experimental results give first evidence that superposition states disappear interacting with an electromagnetic field having a large number of photons.     

Synthesis of single crystalline layered lithium manganese oxide nanorods

Single-crystalline layered lithium manganese oxide nanorods were prepared via a low-temperature molten salt synthesis method. The material was investigated by a variety of techniques, including X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS).     

Tip-induced local anodic oxidation on p-GaAs surface with non-contact atomic force microscopy

Nano-sized oxide structures resulted from localized electrochemical oxidation induced by a negatively biased atomic force microscopy (AFM) tip operated with the non-contact mode were fabricated on p-GaAs(1 0 0) surface. The geometrical characteristics of the oxide patterns and their dependences on various fabrication parameters, e.g., the anodization time, the biased voltages, the tip scanning rates, as well as the formation mechanism and relevant growth kinetics are investigated. Results indicate that the height of the protruded oxide dots grow exponentially as a function of time in the initial stage of oxidation and soon reaches a maximum height depending linearly with the anodized voltages, in according with the behaviors predicted by space charge limited local oxidation mechanism. In addition, selective micro-Auger analysis of the anodized region reveals the formation of Ga(As)O_x, indicating the prominent role played by the field-induced nanometer-size water meniscus in producing the nanometer-scale oxide dots and bumps on p-GaAs(1 0 0) surface.     

Geometric phase in a composite system subjected to decoherence

In this paper, we investigate the geometric phase of a composite system which is composed of two spin- particles driven by a time-varying magnetic field. Firstly, we consider the special case that only one subsystem driven by time-varying magnetic field. Using the quantum jump approach, we calculate the geometric phase associated with the adiabatic evolution of the system subjected to decoherence. The results show that the lowest order corrections to the phase in the no-jump trajectory is only quadratic in decoherence coefficient. Then, both subsystem driven by time-varying magnetic field is considered, we show that the geometric phase is related to the exchange-interaction coefficient and polar angle of the magnetic field.     

Qubit disentanglement in local squeezed reservoirs

We consider the influence of the local squeezed vacuum fields on two initially entangled two-qubit system. By considering the upper bound of entanglement under time evolution, we find that the decay of the quantum entanglement shows different behavior for different time scales (t?max{(2βA)⁻¹,(2βB)⁻¹}$t?\max \{{(2{\beta }_A)}^{\mathrm{-1}},{(2{\beta }_B)}^{\mathrm{-1}}\}$ and t?min{(2βA)⁻¹,(2βB)⁻¹}$t?\min \{{(2{\beta }_A)}^{\mathrm{-1}},{(2{\beta }_B)}^{\mathrm{-1}}\}$). The relative phase of the squeezing environment can also affect the entanglement dynamics profoundly.     

On quantum kinetic equation for hierarchic systems

The energy dissipation in a gas of structured objects, e.g. molecules, is considered. It is shown that the macroscopic irreversibility of the kinetic processes can be considered as a consequence of the microscopic operator ordering. Our approach is free of any special assumptions on the space-time geometry, except for the general region causality assumptions [J.C. Christensen, L. Crane, J. Math. Phys. 46 (2005) 122502], it can be applied to a wide variety of processes, from the cosmological processes at Big Bang stage till the energy dissipation in molecular gases.     

Quantum Tricritical Point in the Spin-Boson Model with an Ohmic Bath

The dynamics of the spin-boson model with an Ohmic bath at finite temperature is studied by a variational calculation. Numerical solution of the self-consistent equation derived from the variational method shows that the transition from incoherent to coherent phases is discontinuous. It indicates that （T = 0, s = 1） is a tricritical point, i.e. the transition changes from continuous to discontinuous by tuning from T = 0 to T≠ 0. The discontinuous transition at finite temperature is analysed by Landau theory and the relation to the experimental observation on the coherent state is also discussed.     

Supramolecular motif and macroscopic pattern in alpha-methylferrocenemethanol films cast from organic solution

The macroscopic patterns were formed in alpha-methylferrocenemethanol films cast from organic solutions. The macroscopic pattern was composed of concentric rings in the solid film. The concentric rings consist of convex ridges and concave valleys; the ordered phase constitutes the convex ridges, while the concave valleys barely contain anything. It has been found that, as for the solvent which can form hydrogen bonding with the solute and has suitable evaporation rate, macroscopic pattern could be observed in the solid film; while as for the solvent that cannot form hydrogen bonding with the solute, no macroscopic pattern would appear. It was suggested that, intermolecular hydrogen bonding and aromatic π stacking interactions of the solute is responsible for the formation of the microscopic crystalline structure; while the hydrogen bonding between the solute and the solvent, and the solvent-evaporation-induced crystallization process, as well as the solvent-evaporation-induced convections are responsible for the formation of the macroscopic pattern. The results could offer a facile way to the electronic material films with well-defined spatial alignment.     

Analytical Solution and Production of Coherent State of the Generalized Dissipative Two-Mode Optical System

We obtain the analytical solution to the master equation in the photon number representation by using algebraic dynamical method in the nonautonomous case. Based on the solution we find that a two-mode coherent sate can be produced within dissipative background, and the averaged photon number for each mode is related to the damping constant, external field amplitude and coupling constant between two modes.