Parallel Implementation of the Discrete Green's Function Formulation of the FDTD Method on a Multicore Central Processing Unit

Parallel implementation of the discrete Green's function formulation of the finite-difference time-domain (DGF-FDTD) method was developed on a multicore central processing unit. DGF-FDTD avoids computations of the electromagnetic field in free-space cells and does not require domain termination by absorbing boundary conditions. Computed DGF-FDTD solutions are compatible with the FDTD grid enabling the perfect hybridization of FDTD with the use of time-domain integral equation methods. The developed implementation can be applied to simulations of antenna characteristics. For the sake of example, arrays of Yagi-Uda antennas were simulated with the use of parallel DGF-FDTD. The efficiency of parallel computations was investigated as a function of the number of current elements in the FDTD grid. Although the developed method does not apply the fast Fourier transform for convolution computations, advantages stemming from the application of DGF-FDTD instead of FDTD can be demonstrated for one-dimensional wire antennas when simulation results are post-processed by the near-to-far-field transformation

Applications of Integrated Magnetic Microtraps

Lithographically fabricated circuit patterns can provide magnetic guides and microtraps for cold neutral atoms. By combining several such structures on the same ceramic substrate, we have realized the first ``atom chips'' that permit complex manipulations of ultracold trapped atoms or de Broglie wavepackets. We show how to design magnetic potentials from simple conductor patterns and we describe an efficient trap loading procedure in detail. Applying the design guide, we describe some new microtrap potentials, including a trap which reaches the Lamb-Dicke regime for rubidium atoms in all three dimensions, and a rotatable Ioffe-Pritchard trap, which we also demonstrate experimentally. Finally, we demonstrate a device allowing independent linear positioning of two atomic clouds which are very tightly confined laterally. This device is well suited for the study of one-dimensional collisions.Comment: 10 pages, 17 figure

Program user's manual for optimizing the design of a liquid or gaseous propellant rocket engine with the automated combustor design code AUTOCOM

This computer program manual describes in two parts the automated combustor design optimization code AUTOCOM. The program code is written in the FORTRAN 4 language. The input data setup and the program outputs are described, and a sample engine case is discussed. The program structure and programming techniques are also described, along with AUTOCOM program analysis

Coherence in Microchip Traps

We report the coherent manipulation of internal states of neutral atoms in a magnetic microchip trap. Coherence lifetimes exceeding 1 s are observed with atoms at distances of $5-130 \mu$m from the microchip surface. The coherence lifetime in the chip trap is independent of atom-surface distance within our measurement accuracy, and agrees well with the results of similar measurements in macroscopic magnetic traps. Due to the absence of surface-induced decoherence, a miniaturized atomic clock with a relative stability in the $10^{-13}$ range can be realized. For applications in quantum information processing, we propose to use microwave near-fields in the proximity of chip wires to create potentials that depend on the internal state of the atoms.Comment: Revised version, accepted for publication in Phys. Rev. Lett., 4 pages, 4 figure

Creating Ioffe-Pritchard micro-traps from permanent magnetic film with in-plane magnetization

We present designs for Ioffe-Pritchard type magnetic traps using planar patterns of hard magnetic material. Two samples with different pattern designs were produced by spark erosion of 40 $\mu$m thick FePt foil. The pattern on the first sample yields calculated axial and radial trap frequencies of 51 Hz and 6.8 kHz, respectively. For the second sample the calculated frequencies are 34 Hz and 11 kHz. The structures were used successfully as a magneto-optical trap for $^{87}$Rb and loaded as a magnetic trap. A third design, based on lithographically patterned 250 nm thick FePt film on a Si substrate, yields an array of 19 traps with calculated axial and radial trap frequencies of 1.5 kHz and 110 kHz, respectively.Comment: 8 pages, 5 figures Revised and accepted for EPJD, improved picture

Microwave potentials and optimal control for robust quantum gates on an atom chip

We propose a two-qubit collisional phase gate that can be implemented with available atom chip technology, and present a detailed theoretical analysis of its performance. The gate is based on earlier phase gate schemes, but uses a qubit state pair with an experimentally demonstrated, very long coherence lifetime. Microwave near-fields play a key role in our implementation as a means to realize the state-dependent potentials required for conditional dynamics. Quantum control algorithms are used to optimize gate performance. We employ circuit configurations that can be built with current fabrication processes, and extensively discuss the impact of technical noise and imperfections that characterize an actual atom chip. We find an overall infidelity compatible with requirements for fault-tolerant quantum computation