Quantum information processing using strongly-dipolar coupled nuclear spins

Dipolar coupled homonuclear spins present challenging, yet useful systems for quantum information processing. In such systems, eigenbasis of the system Hamiltonian is the appropriate computational basis and coherent control can be achieved by specially designed strongly modulating pulses. In this letter we describe the first experimental implementation of the quantum algorithm for numerical gradient estimation on the eigenbasis of a four spin system.Comment: 5 pages, 5 figures, Accepted in PR

Metastability and uniqueness of vortex states at depinning

We present results from numerical simulations of transport of vortices in the zero-field cooled (ZFC) and the field-cooled (FC) state of a type-II superconductor. In the absence of an applied current $I$, we find that the FC state has a lower defect density than the ZFC state, and is stable against thermal cycling. On the other hand, by cycling $I$, surprisingly we find that the ZFC state is the stable state. The FC state is metastable as manifested by increasing $I$ to the depinning current $I_{c}$, in which case the FC state evolves into the ZFC state. We also find that all configurations acquire a unique defect density at the depinning transition independent of the history of the initial states.Comment: 4 pages, 4 figures. Problem of page size correcte

FEASIBILTY ANALYSIS OF WALKING OF PASSIVE DYNAMIC BIPED ROBOT

  Passive dynamic walking is an essential development for the biped robots. So the focus of our work is a systematic analysis of the passive walk of a planar biped robot on an inclined slope. The dynamics of passive biped robot is only caused of gravity. The biped robot with two point masses at kneeless legs and a third point mass at the hip-joint is kinematically equivalent to a double pendulum. In this paper, we represent a general method for developing the equations of motion and impact equations for the study of multi-body systems, as in bipedal models. The solution of this system depends on the initial conditions. But it is difficult to find the proper initial conditions for which the system has solutions, in other words, the initial conditions for which the robot can walk. In this paper, we describe the cell mapping method which able to compute the feasible initial conditions for which the biped robot can move forward on the inclined ramp. The results of this method described the region of feasible initial conditions is small and bounded. Moreover, the results of cell mapping method give the fixed of Poincare map which explains the symmetric gait cycle of the robot and describe the orientation of legs of robot

Evolution of Quantum Discord and its Stability in Two-Qubit NMR Systems

We investigate evolution of quantum correlations in ensembles of two-qubit nuclear spin systems via nuclear magnetic resonance techniques. We use discord as a measure of quantum correlations and the Werner state as an explicit example. We first introduce different ways of measuring discord and geometric discord in two-qubit systems and then describe the following experimental studies: (a) We quantitatively measure discord for Werner-like states prepared using an entangling pulse sequence. An initial thermal state with zero discord is gradually and periodically transformed into a mixed state with maximum discord. The experimental and simulated behavior of rise and fall of discord agree fairly well. (b) We examine the efficiency of dynamical decoupling sequences in preserving quantum correlations. In our experimental setup, the dynamical decoupling sequences preserved the traceless parts of the density matrices at high fidelity. But they could not maintain the purity of the quantum states and so were unable to keep the discord from decaying. (c) We observe the evolution of discord for a singlet-triplet mixed state during a radio-frequency spin-lock. A simple relaxation model describes the evolution of discord, and the accompanying evolution of fidelity of the long-lived singlet state, reasonably well.Comment: 9 pages, 7 figures, Phys. Rev. A (in press

POLYMER GRAFTING AND APPLICATIONS IN PHARMACEUTICAL DRUG DELIVERY SYSTEMS - A BRIEF REVIEW

  Selection of proper polymer system is a critical step involved in the formulation of dosage form. Type of polymer/s incorporated in pharmaceutical formulation majorly decides the stability of formulation and drug itself, mechanism, and rate of drug release. Pharmaceutical and biological therapeutics are suffered from disadvantages such as short half-lives, poor bioavailability, and physical and chemical instability. Delivery of drugs to target site at a specific concentration for a specific time can be successfully achieved by the use of suitable polymer/s. Thus, it is not necessary that available polymer till the date should have all ideal properties with respect to above. This makes a demand of tailored polymers with desired features and introduces concept of grafting for making new polymers to be used in dosage forms. Grafting can be achieved by various techniques described herein and can be analyzed by various modern analytical techniques including infrared, NMR, X-ray diffractometer, and differential scanning calorimeter. These grafted polymers offer many applications in terms of site drug/biological carrying capacity, tailored physicochemical properties based dosage form modifications and with desired features, and also to deliver therapeutics at specific sites. Considering these advantages, a number of applications of grafted polymers developed and many patents were filed in this area till the date. This review highlights the basic concept of grafting and its various techniques and their significant pharmaceutical applications

A Distributed Weighted Voting Approach for Accurate Eye Center Estimation

This paper proposes a novel approach for accurate estimation of eye center in face images. A distributed voting based approach in which every pixel votes is adopted for potential eye center candidates. The votes are distributed over a subset of pixels which lie in a direction which is opposite to gradient direction and the weightage of votes is distributed according to a novel mechanism.  First, image is normalized to eliminate illumination variations and its edge map is generated using Canny edge detector. Distributed voting is applied on the edge image to generate different eye center candidates. Morphological closing and local maxima search are used to reduce the number of candidates. A classifier based on spatial and intensity information is used to choose the correct candidates for the locations of eye center. The proposed approach was tested on BioID face database and resulted in better Iris detection rate than the state-of-the-art. The proposed approach is robust against illumination variation, small pose variations, presence of eye glasses and partial occlusion of eyes.Defence Science Journal, 2013, 63(3), pp.292-297, DOI:http://dx.doi.org/10.14429/dsj.63.276

Factorizing Numbers with the Gauss Sum Technique: NMR Implementations

Several physics-based algorithms for factorizing large number were recently published. A notable recent one by Schleich et al. uses Gauss sums for distinguishing between factors and non-factors. We demonstrate two NMR techniques that evaluate Gauss sums and thus implement their algorithm. The first one is based on differential excitation of a single spin magnetization by a cascade of RF pulses. The second method is based on spatial averaging and selective refocusing of magnetization for Gauss sums corresponding to factors. All factors of 16637 and 52882363 are successfully obtained.Comment: 4 pages, 4 figures; Abstract and Conclusion are slightly modified. References added and formatted with Bibte