Controllable binding of polar molecules and meta-stability of 1-D gases with attractive dipole forces

We explore one-dimensional (1-D) samples of ultracold polar molecules with attractive dipole-dipole interactions and show the existence of a repulsive barrier due to a strong quadrupole interaction between molecules. This barrier can stabilize a gas of ultracold KRb molecules and even lead to long-range wells supporting bound states between molecules. The properties of these wells can be controlled by external electric fields, allowing the formation of long polymer-like chains of KRb, and studies of quantum phase transitions by varying the effective interaction between molecules. We discuss the generalization of those results to other systems

Empowering Distributed Solar PV Energy for Malaysian Rural Housing: Towards Energy Security and Equitability of Rural Communities

This paper illustrates on how Malaysia's development landscapes has been poweredby cheap oil and gas making it dependent and addicted on using large amounts of fossil fuels. As acountry that is primarily depended on fossil fuels for generating power supply, Malaysia needs tocogitate of long-term energy security due to fossil fuel depletion and peak oil issues. Loss of theseresources could leadto thereduction of power generation capacitywhich will threaten the stabilityof the electricity supply in Malaysia. This could potentially influence in an increase in electricitycosts which lead to a phase of power scarcity and load shedding for the country. With the risk ofinterrupted power supplies, rural households, especially those of low-income groups areparticularly vulnerable to the post-effects of a power outage and an inequitable distribution to thepeople. Distributed generation of electricity by solar PVs diminishes the vulnerability of thesehouseholds and can also offer an income to them by feeding the power supply to the national gridthrough Feed-in Tariff scheme. At the moment, the deployment of solar PV installations is still inthe introductory stage in Malaysia, where roof-mounted PV panels are only available to commercialand urban residential buildings. This is due to the lack of a suitable renewable energy policy forrural households and the high cost of the solar PV technology. This paper will put forward ananalysis for incorporating solar photovoltaic on roofs of rural houses by identifying the energyconsumption of these households and the extent to which PVs can alleviate electricity insecurity.The results present significant potential for distributed PV power generation in rural areas inMalaysia which shown a considerable amount of electricity needed to be harvested from roofmountedsolar PV for rural people in Malaysia

Bistable light detectors with nonlinear waveguide arrays

Bistability induced by nonlinear Kerr effect in arrays of coupled waveguides is studied and shown to be a means to conceive light detectors that switch under excitation by a weak signal. The detector is obtained by coupling two single 1D waveguide to an array of coupled waveguides with adjusted indices and coupling. The process is understood by analytical description in the conservative and continuous case and illustrated by numerical simulations of the model with attenuation.Comment: Phys. Rev. Lett., v.94, (2005, to be published

Symmetry breaking and manipulation of nonlinear optical modes in an asymmetric double-channel waveguide

We study light-beam propagation in a nonlinear coupler with an asymmetric double-channel waveguide and derive various analytical forms of optical modes. The results show that the symmetry-preserving modes in a symmetric double-channel waveguide are deformed due to the asymmetry of the two-channel waveguide, yet such a coupler supports the symmetry-breaking modes. The dispersion relations reveal that the system with self-focusing nonlinear response supports the degenerate modes, while for self-defocusingmedium the degenerate modes do not exist. Furthermore, nonlinear manipulation is investigated by launching optical modes supported in double-channel waveguide into a nonlinear uniform medium.Comment: 10 page

Universal Leakage Elimination

``Leakage'' errors are particularly serious errors which couple states within a code subspace to states outside of that subspace thus destroying the error protection benefit afforded by an encoded state. We generalize an earlier method for producing leakage elimination decoupling operations and examine the effects of the leakage eliminating operations on decoherence-free or noiseless subsystems which encode one logical, or protected qubit into three or four qubits. We find that by eliminating the large class of leakage errors, under some circumstances, we can create the conditions for a decoherence free evolution. In other cases we identify a combination decoherence-free and quantum error correcting code which could eliminate errors in solid-state qubits with anisotropic exchange interaction Hamiltonians and enable universal quantum computing with only these interactions.Comment: 14 pages, no figures, new version has references updated/fixe

A Parametrization of Bipartite Systems Based on SU(4) Euler Angles

In this paper we give an explicit parametrization for all two qubit density matrices. This is important for calculations involving entanglement and many other types of quantum information processing. To accomplish this we present a generalized Euler angle parametrization for SU(4) and all possible two qubit density matrices. The important group-theoretical properties of such a description are then manifest. We thus obtain the correct Haar (Hurwitz) measure and volume element for SU(4) which follows from this parametrization. In addition, we study the role of this parametrization in the Peres-Horodecki criteria for separability and its corresponding usefulness in calculating entangled two qubit states as represented through the parametrization.Comment: 23 pages, no figures; changed title and abstract and rewrote certain areas in line with referee comments. To be published in J. Phys. A: Math. and Ge