Electronic and phononic Raman scattering in detwinned YBa2_2Cu3_3O6.95_{6.95} and Y0.85_{0.85}Ca0.15_{0.15}Ba2_2Cu3_3O6.95_{6.95}: s-wave admixture to the dx2−y2d_{x^2-y^2}-wave order parameter

Inelastic light (Raman) scattering has been used to study electronic excitations and phonon anomalies in detwinned, slightly overdoped YBa$_2$Cu$_3$O$_{6.95}$ and moderately overdoped Y$_{0.85}$Ca$_{0.15}$Ba$_2$Cu$_3$O$_{6.95}$ single crystals. In both samples modifications of the electronic pair-breaking peaks when interchanging the a- and b-axis were observed. The lineshapes of several phonon modes involving plane and apical oxygen vibrations exhibit pronounced anisotropies with respect to the incident and scattered light field configurations. Based on a theoretical model that takes both electronic and phononic contributions to the Raman spectra into account, we attribute the anisotropy of the superconductivity-induced changes in the phonon lineshapes to a small s-wave admixture to the $d_{x^2-y^2}$ pair wave-function. Our theory allows us to disentangle the electronic Raman signal from the phononic part and to identify corresponding interference terms. We argue that the Raman spectra are consistent with an s-wave admixture with an upper limit of 20 percent.Comment: accepted in Phys. Rev. B, 11 page

Efficient qubit detection using alkali earth metal ions and a double STIRAP process

We present a scheme for robust and efficient projection measurement of a qubit consisting of the two magnetic sublevels in the electronic ground state of alkali earth metal ions. The scheme is based on two stimulated Raman adiabatic passages (STIRAP) involving four partially coherent laser fields. We show how the efficiency depends on experimentally relevant parameters: Rabi frequencies, pulse widths, laser linewidths, one- and two-photon detunings, residual laser power, laser polarization and ion motion.Comment: 14 pages, 15 figure

Boundary effects in finite size plasmonic crystals: Focusing and routing of plasmonic beams for optical communications

Plasmonic crystals, which consist of periodic arrangements of surface features at a metal-dielectric interface, allow the manipulation of optical information in the form of surface plasmon polaritons. Here we investigate the excitation and propagation of plasmonic beams in and around finite size plasmonic crystals at telecom wavelengths, highlighting the effects of the crystal boundary shape and illumination conditions. Significant differences in broad plasmonic beam generation by crystals of different shapes are demonstrated, while for narrow beams, the propagation onto the smooth metal film is less sensitive to the crystal boundary shape. We show that by controlling the boundary shape, the size and the excitation beam parameters, directional control of propagating plasmonic modes and associated beam parameters such as angular beam splitting, focusing power and beam width can be efficiently achieved. This provides a promising route for robust and alignment-independent integration of plasmonic crystals with optical communication components

A High Speed Hardware Scheduler for 1000-port Optical Packet Switches to Enable Scalable Data Centers

Meeting the exponential increase in the global demand for bandwidth has become a major concern for today's data centers. The scalability of any data center is defined by the maximum capacity and port count of the switching devices it employs, limited by total pin bandwidth on current electronic switch ASICs. Optical switches can provide higher capacity and port counts, and hence, can be used to transform data center scalability. We have recently demonstrated a 1000-port star-coupler based wavelength division multiplexed (WDM) and time division multiplexed (TDM) optical switch architecture offering a bandwidth of 32 Tbit/s with the use of fast wavelength-tunable transmitters and high-sensitivity coherent receivers. However, the major challenge in deploying such an optical switch to replace current electronic switches lies in designing and implementing a scalable scheduler capable of operating on packet timescales. In this paper, we present a pipelined and highly parallel electronic scheduler that configures the high-radix (1000-port) optical packet switch. The scheduler can process requests from 1000 nodes and allocate timeslots across 320 wavelength channels and 4000 wavelength-tunable transceivers within a time constraint of 1μs. Using the Opencell NanGate 45nm standard cell library, we show that the complete 1000-port parallel scheduler algorithm occupies a circuit area of 52.7mm2, 4-8x smaller than that of a high-performance switch ASIC, with a clock period of less than 8ns, enabling 138 scheduling iterations to be performed in 1μs. The performance of the scheduling algorithm is evaluated in comparison to maximal matching from graph theory and conventional software-based wavelength allocation heuristics. The parallel hardware scheduler is shown to achieve similar matching performance and network throughput while being orders of magnitude faster

Evaluating greenhouse tomato and pepper input efficiency use in Kosovo

Non-Peer ReviewedDeterminants of vegetable production input efficiency affect a Kosovar farmer's decision to contribute to the agricultural sector. This study evaluates the input efficiency of greenhouse tomato and pepper farms in Kosovo. Using data collected from farm surveys, we conducted an input-oriented data envelopment analysis (DEA) to empirically assess input efficiency. Second, linear regression analysis was used to investigate what farm variables predict greenhouse tomato and pepper technical efficiency (TE). The DEA results indicated that, among the seven regions in Kosovo, Prizren emerged as the most efficient greenhouse tomato-producing region with a mean efficiency of 0.83 (on a scale of 0 to 1.00). Prishtina followed with a mean efficiency of 0.80. In the production of greenhouse peppers, Prishtina was the most efficient region with a mean efficiency of 0.99. Ferizaj followed with a mean efficiency of 0.93. Conclusions about farm characteristics that explain differences in efficiency were sensitive to model specification. Nevertheless, depending on the structural and operational characteristics of the greenhouse tomato and pepper farms, there is an opportunity for the technically inefficient farms and regions to improve their use of inputs