On Sample Size Determination

One of the questions most frequently asked of a statistician is: How big should the sample be? Managers are anxious to obtain an answer to this fundamental question during the planning phase of the survey since it impacts directly on operational considerations such as the number of interviewers required. There is no magical solution and no perfect recipe for determining sample size. It is rather a process of compromise in which the precision requirements of the estimates are weighed against various operationalconstraints such as available budget, resources and time. In this article, we revisit to the estimate of sample size for various project characteristics. Examples for each are supported numerically

A Teaching Note for Model Selection and Validation

The model selection problem is always crucial for any decision making in statistical research and management. Among the choice of many competing models, how todecide the best is even more crucial for researchers. This small article is prepared as a teaching note for deciding an appropriate model for a real-life data set. We brieflydescribe some of the existing methods of model selection. The best model from the two competing models is decided based on the comparison of the limited expected valuefunction (LEVF) or loss elimination ratio (LER). A data set is analyzed through MINITAB software

Theory of high bias Coulomb Blockade in ultrashort molecules

We point out that single electron charging effects such as Coulomb Blockade (CB) and high-bias staircases play a crucial role in transport through single ultrashort molecules. A treatment of Coulomb Blockade through a prototypical molecule, benzene, is developed using a master-equation in its complete many-electron Fock space, evaluated through exact diagonalization or full Configuration Interaction (CI). This approach can explain a whole class of non-trivial experimental features including vanishing zero bias conductances, sharp current onsets followed by ohmic current rises, and gateable current levels and conductance structures, most of which cannot be captured even qualitatively within the traditional Self Consistent Field (SCF) approach coupled with perturbative transport theories. By comparing the two approaches, namely SCF and CB, in the limit of weak coupling to the electrode, we establish that the inclusion of strong-correlations within the molecule becomes critical in addressing the above experiments. Our approach includes on-bridge-correlations fully, and is therefore well-suited for describing transport through short molecules in the limit of weak coupling to electrodes.Comment: 19 pages 5 figure

Perfect Teleportation, Quantum state sharing and Superdense Coding through a Genuinely Entangled Five-qubit State

We investigate the usefulness of a recently introduced five qubit state by Brown \it et al. \normalfont \cite{Brown} for quantum teleportation, quantum state sharing and superdense coding. It is shown that this five-qubit state can be utilized for perfect teleportation of arbitrary single and two qubit systems. We devise various schemes for quantum state sharing of an arbitrary single and two particle state via cooperative teleportation. We later show that this state can be used for superdense coding as well. It is found that five classical bits can be sent by sending only three quantum bits.Comment: 8 Pages, added sections on state sharin

Custom-Designed HI-V Semiconductor Mimstmctures Wed to the Ultimate Physical Limit : U I ~ - L a y e r GaAs/AUs ~uperhtticesa nd Delta- (Monolayer) Doping in GaAs/Al,Ga,-As Structures

Two prototype artificially-layered semiconductor structures are presented in which the concept of microscopical structuring of solids is scaled to its ultimate physical limit normal to the crystal surface. In both the(G~AS),/(AIASm)~o no layer superlattice and in the delta- (or monolayer)doped G~AS/AI~G~,-s~truAcStu res, which have been grown by molecular beam epitaxy, the characteristic material lengths have reached a spatialextent nornlal to the surface of less than the lattice constant. The (GaAs),/(AIAs), ultrathin-layer superlattices exhibit novel optical properties due tothe indirect-gap nature ofthe constituent AlAs layers. The minority-carrier lifetimes can be tailored over four orders of magnitude by appropriately designing the superlattice configuration. This feature opens up new fieldsof application in lasers and in nonlinear photonic and optoelectronic devices. The narrow buried doping channel in delta-doped GaAslayers andin GaAs/AI,Gal-xAs structures leads to a significant improvement of the electrical properties. Based on this concept, non alloyed ohmic contacts,field-effect transistors with ;cry high transconductance, unpinned GaAs surfaces for MOS devices, and electron mobilities as high as 10' cm2v-'s-Ihave been fabricated