A study of excess energy and decoherence factor of a qubit coupled to a one dimensional periodically driven spin chain

We take a central spin model (CSM), consisting of a one dimensional environmental Ising spin chain and a single qubit connected globally to all the spins of the environment, to study numerically the excess energy (EE) of the environment and the logarithm of decoherence factor namely, dynamical fidelity susceptibility per site (DFSS), associated with the qubit under a periodic driving of the transverse field term of environment across its critical point using the Floquet technique. The coupling to the qubit, prepared in a pure state, with the transverse field of the spin chain yields two sets of EE corresponding to the two species of Floquet operators. In the limit of weak coupling, we derive an approximated expression of DFSS after an infinite number of driving period which can successfully estimate the low and intermediate frequency behavior of numerically obtained DFSS. Our main focus is to analytically investigate the effect of system-environment coupling strength on the EEs and DFSS and relate the behavior of DFSS to EEs as a function of frequency by plausible analytical arguments. We explicitly show that the low-frequency beating like pattern of DFSS is an outcome of two frequencies, causing the oscillations in the two branches of EEs, that are dependent on the coupling strength. In the intermediate frequency regime, dip structure observed in DFSS can be justified by the resonance peaks of EEs at those coupling parameter dependent frequencies; high frequency saturation value of EEs and DFSS are also connected to each other by the coupling strength.Comment: 12 pages, 10 figure

Image Registration Techniques: A Survey

Image Registration is the process of aligning two or more images of the same scene with reference to a particular image. The images are captured from various sensors at different times and at multiple view-points. Thus to get a better picture of any change of a scene or object over a considerable period of time image registration is important. Image registration finds application in medical sciences, remote sensing and in computer vision. This paper presents a detailed review of several approaches which are classified accordingly along with their contributions and drawbacks. The main steps of an image registration procedure are also discussed. Different performance measures are presented that determine the registration quality and accuracy. The scope for the future research are presented as well

Family planning success stories in Bangladesh and India

The Matlab Project in Bangladesh and the Kundam Project in India have demonstrated that a significant rise in contraceptive prevalence can occur in socioeconomic environments that are generally conducive to high fertility and mortality. The author describes the inputs and outputs of these two projects and tries to identify the factors underlying their success. Both projects are experimental in the sense that in each anintervention area is provided with special inputs that are not provided to a contiguous control area. The special inputs were different for the two projects. In the intervention area in Matlab, the project took responsibility for providing family planning and some rudimentary maternal and child health services that were considerably different from those provided in the national program. In Kundam, the project did not take responsibility for providing services in the intervention area, but rather tried to mobilize the community through various clubs and committees to take the most advantage of the government's family planning and other development programs. The success of the Matlab Project can be attributed to various aspects of the organizational system developed for delivering consumer-friendly services. The success of the Kundam Project can be attributed to various aspects of the system developed for community members'active participation in the program. The projects are not fully replicable because of inadequate human and financial resources, but the lessons learned from them should be useful in improving national programs. The Kundam Project is more realistic in the sense that it focuses on activities that supplement local activities of the national program rather than substitute for them (as in the Matlab Project). Thus the Kundam Project is more likely to be replicable than the Matlab Project.Health Monitoring&Evaluation,Adolescent Health,Reproductive Health,Early Child and Children's Health,ICT Policy and Strategies

Generation of concurrence between two qubits locally coupled to a one dimensional spin chain

We consider a generalized central spin model, consisting of two central qubits and an environmental spin chain (with periodic boundary condition) to which these central qubits are locally and weakly connected either at the same site or at two different sites separated by a distance $d$. Our purpose is to study the subsequent temporal generation of entanglement, quantified by concurrence, when initially the qubits are in an unentangled state. In the equilibrium situation, we show that the concurrence survives for a larger value of $d$ when the environmental spin chain is critical. Importantly, a common feature observed both in the equilibrium and the non-equilibrium situations while the latter is created by a sudden but global change of the environmental transverse field, is that the two qubits become maximally entangled for the critical quenching. Following a non-equilibrium evolution of the spin chain, our study for $d\neq 0$, indicates that there exists a threshold time above which concurrence attains a finite value. Additionally, we show that the number of independent decohering channels (DCs) is determined by $d$ as well as the local difference of the transverse field of the two underlying Hamiltonians governing the time evolution. The qualitatively similar behavior displayed by the concurrence for critical and off-critical quenches, as reported here, is characterized by analyzing the non-equilibrium evolution of these channels. The concurrence is maximum when the decoherence factor or the echo associated with the most rapidly DC decays to zero; on the contrary, the condition when the concurrence vanishes is determined non-trivially by the associated decay of one of the intermediate DCs. Analyzing the reduced density of a single qubit, we also explain the observation that the dephasing rate is always slower than the unentanglement rate.Comment: 11 pages and 11 figure