Transport of Entanglement Through a Heisenberg-XY Spin Chain

The entanglement dynamics of spin chains is investigated using Heisenberg-XY spin Hamiltonian dynamics. The various measures of two-qubit entanglement are calculated analytically in the time-evolved state starting from initial states with no entanglement and exactly one pair of maximally-entangled qubits. The localizable entanglement between a pair of qubits at the end of chain captures the essential features of entanglement transport across the chain, and it displays the difference between an initial state with no entanglement and an initial state with one pair of maximally-entangled qubits.Comment: 5 Pages. 3 Figure

Enhancing the photomixing efficiency of optoelectronic devices in the terahertz regime

A method to reduce the transit time of majority of carriers in photomixers and photo detectors to $< 1$ ps is proposed. Enhanced optical fields associated with surface plasmon polaritons, coupled with velocity overshoot phenomenon results in net decrease of transit time of carriers. As an example, model calculations demonstrating $> 280\times$ (or $\sim$2800 and 31.8 $\mu$W at 1 and 5 THz respectively) improvement in THz power generation efficiency of a photomixer based on Low Temperature grown GaAs are presented. Due to minimal dependence on the carrier recombination time, it is anticipated that the proposed method paves the way for enhancing the speed and efficiency of photomixers and detectors covering UV to far infrared communications wavelengths (300 to 1600 nm).Comment: 5 pages, 4 figure

A Novel Approach to Compute the Handover Probabilities Based on Mobility in WPAN

A novel approach has been presented to compute the probabilities of unsuccessful handovers based number of free channels available in the target AP and number of free channels available plus based on the mobility of mobile device. The number of free channels in the AP is 16 and the mobility of the mobile device in the 8 different directions is considered. The directions of movement are 0, 45, 90, 135, 180, 215, 270 and 315 that a mobile can take a turn to. If the mobile device is handed over to the target AP based on the movement of the mobile device, then the proposed model can be used to compute the probabilities of the unsuccessful handover if the number of free channels in the target AP is different than expected with respect to the host AP. The probabilities of the incorrect decision is plotted for the cases of mobile device moving in a direction normal to the boundary and moving along the boundary are plotted