We present the design, fabrication, and experimental implementation of surface ion traps with Y-shaped junctions. The traps are designed to minimize the pseudopotential variations in the junction region at the symmetric intersection of three linear segments. We experimentally demonstrate robust linear and junction shuttling with greater than 10 6 round-trip shuttles without ion loss. By minimizing the direct line of sight between trapped ions and dielectric surfaces, negligible day-to-day and trap-to-trap variations are observed. In addition to high-fidelity single-ion shuttling, multiple-ion chains survive splitting, ion-position swapping, and recombining routines. The development of two-dimensional trapping structures is an important milestone for ion-trap quantum computing and quantum simulations. arXiv:1105.1834v1 [quant-ph]

We report the results of a computer simulation of the evolution of structure in a two component fluid consisting of a liquid phase and a dispersed colloidal phase subjected to a uniaxial field. Our primary objective is to understand the mechanism and kinetics of coarsening and the emergence of crystallinity. Using an efficient, linear-N simulation method we report studies of systems of N=10 000 particles over the concentration range of 10–50 vol %. We present a variety of methods of characterizing the structures that emerge, including the anisotropy of the conductivity, capacitance and dipolar interaction energy, the two-dimensional pair correlation function, principal moments of the gyration tensor, velocity correlation functions, microcrystallinity and coordination number, and the optical attenuation length. We conclude that athermal coarsening is effectively driven by the presence of defect structures and that as the concentration increases, the structures progressively lose the well-known “chain” anisotropy evinced at low concentration.

Articles you may be interested inThe effect of an external magnetic field on the structure of liquid water using molecular dynamics simulation Monte Carlo simulation of polymer chain collapse in an athermal solventWe report the results of a computer simulation of the evolution of structure in a two component fluid consisting of a liquid phase and a dispersed colloidal phase subjected to a biaxial field. A biaxial field, such as a rotating field, can induce the organization of polarizable particles into two-dimensional sheets, in contrast with the essentially one-dimensional columns formed in a uniaxial field. Our primary objective is to explore the kinetics of coarsening, the emergence of structure, and the anisotropy in materials properties. Using an efficient, linear-N simulation method we report studies of systems of Nϭ10 000 particles over the concentration range of ϭ10-50 vol %. We present a variety of methods of characterizing the structures that emerge, including the two dimensional pair correlation, velocity correlations, microcrystallinity, optical attenuation, dipolar interaction energy, conductivity, and permittivity. The anisotropies that we compute are generally inverted relative to those found in materials structured by a uniaxial field.

Through simulation and experiment we demonstrate that when a magnetic field is applied to a suspension of magnetic particles, the optical attenuation length along the direction of the field increases dramatically, due to the formation of chainlike structures that allow the transmission of light between the strongly absorbing particles. This phenomenon is interesting for two reasons; first, there might be practical applications for this effect, such as optical-fiber-based magnetic field sensors, and second, measuring the time evolution of the optical attenuation length enables us to determine the kinetics of structure formation, which can be compared to the predictions of simulation and theory. In agreement with both simulation and theory, the optical attenuation length increases as a power of time, but much less light is actually transmitted than expected, especially at higher particle concentrations. We conclude that particle roughness, which is not included in either theory or simulation, plays a significant role in structural development, by pinning structures into local minima.

Articles you may be interested inEffect of temperature gradient on high-frequency dielectric permittivity in quantum-well superlattice structures AIP Conf.When a suspension of colloidal particles is subjected to a strong electric or magnetic field, the induced dipolar interactions will cause the particles to form organized structures, provided a sufficient permittivity or permeability mismatch exists, respectively, between the particles and the suspending liquid. A uniaxial field will produce uniaxial structures, and a biaxial field, such as a rotating field, will produce biaxial structures, and either of these structures can be pinned by polymerizing the continuous phase to produce field-structured composites. We have previously reported on the coarsening of field-structured composites in the absence of thermal effects, i.e., Brownian motion. Athermal simulations are primarily valid in describing the deep quenches that occur when the induced dipolar interactions between particles greatly exceed k B T. However, deep quenches can lead to kinetic structures that are far from equilibrium. By introducing Brownian motion we have shown that structures with significantly greater anisotropy and crystallinity can form. These structures have enhanced material properties, such as the conductivity, permittivity, and optical attenuation. Careful anneals at certain fixed fields, or at continuously increasing fields, should produce more anisotropic structures than the deep quenches we have used to synthesize real materials.