Stimulated quantum phase slips from weak electromagnetic radiations in superconducting nanowires

We study the rate of quantum phase slips in an ultranarrow superconducting nanowire exposed to weak electromagnetic radiations. The superconductor is in the dirty limit close to the superconducting-insulating transition, where fluxoids move in strong dissipation. We use a semiclassical approach and show that external radiation stimulates a significant enhancement in the probability of quantum phase slips. This can help to outline a new type of detector for microwave to submillimetre radiations based on stimulated quantum phase slip phenomenon.Comment: 10 pages, 9 figure

Efficient implementation of linear programming decoding

While linear programming (LP) decoding provides more flexibility for finite-length performance analysis than iterative message-passing (IMP) decoding, it is computationally more complex to implement in its original form, due to both the large size of the relaxed LP problem, and the inefficiency of using general-purpose LP solvers. This paper explores ideas for fast LP decoding of low-density parity-check (LDPC) codes. We first prove, by modifying the previously reported Adaptive LP decoding scheme to allow removal of unnecessary constraints, that LP decoding can be performed by solving a number of LP problems that contain at most one linear constraint derived from each of the parity-check constraints. By exploiting this property, we study a sparse interior-point implementation for solving this sequence of linear programs. Since the most complex part of each iteration of the interior-point algorithm is the solution of a (usually ill-conditioned) system of linear equations for finding the step direction, we propose a preconditioning algorithm to facilitate iterative solution of such systems. The proposed preconditioning algorithm is similar to the encoding procedure of LDPC codes, and we demonstrate its effectiveness via both analytical methods and computer simulation results.Comment: 44 pages, submitted to IEEE Transactions on Information Theory, Dec. 200

Caffeine as A Catalyst for A Four-Component Synthesis of Dihydropyrano [2, 3-C]Pyrazoles in Water

We describe a one-pot four component synthesis of pyrano[2,3-c]pyrazoles from hydrazine hydrate or phenyl hydrazine, ethyl acetoacetate, an aldehyde, and malononitrile in the presence of catalytic amounts of a caffeine as a green catalyst in water at 50 ºC. The present protocol offers the advantages of a clean reaction, a short reaction time, a high product yield, and an environmentally-friendly, easily-purified, and economically-available catalyst