Designing short robust NOT gates for quantum computation

Composite pulses, originally developed in Nuclear Magnetic Resonance (NMR), have found widespread use in experimental quantum information processing (QIP) to reduce the effects of systematic errors. Most pulses used so far have simply been adapted from existing NMR designs, and while techniques have been developed for designing composite pulses with arbitrary precision the results have been quite complicated and have found little application. Here I describe techniques for designing short but effective composite pulses to implement robust NOT gates, bringing together existing insights from NMR and QIP, and present some novel composite pulses.Comment: 12 pages RevTex including 7 figures; in press at Phys Rev

Robust quantum information processing with techniques from liquid state NMR

While Nuclear Magnetic Resonance (NMR) techniques are unlikely to lead to a large scale quantum computer they are well suited to investigating basic phenomena and developing new techniques. Indeed it is likely that many existing NMR techniques will find uses in quantum information processing. Here I describe how the composite rotation (composite pulse) method can be used to develop quantum logic gates which are robust against systematic errors.Comment: 11 pages including 4 figures in rspublic format. Article submitted for proceeding of the Discussion Meeting on Practical Realisations of Quantum Information Processing, held at the Royal Society, Nov. 13-14, 200

Detecting LISA sources using time-frequency techniques

The planned Laser Interferometer Space Antenna (LISA) will detect gravitational wave signals from a wide range of sources. However, disentangling individual signals from the source-dominated data stream is a challenging problem and the focus of much current research. The problems are particularly acute for detection of extreme mass ratio inspirals (EMRIs), for which the instantaneous signal amplitude is an order of magnitude below the level of the instrumental noise, and the parameter space of possible signals is too large to permit fully-coherent matched filtering. One possible approach is to attempt to identify sources in a time-frequency spectrogram of the LISA data. This is a computationally cheap method that may be useful as a first stage in a hierarchical analysis. Initial results, evaluated using a significantly simplified model of the LISA data stream, suggest that time-frequency techniques might be able to detect the nearest few tens of EMRI events. In this proceedings article, we briefly outline the methods that have so far been applied to the problem, initial results and possible future directions for the research.Comment: 3 pages; to appear in Proceedings of the Eleventh Marcel Grossmann meetin

Design study of a thermocouple power sensor as a monolithic fin-line

Making traceable power measurements above 110 GHz using current measurement technologies is challenging. We investigate a design of power sensor consisting of a thermocouple-based integrated circuit (IC) mounted as a finline component in WR-6 waveguide. The design is original in that it contains an antenna, terminating resistor and thermocouples on-chip. We detail the design and report results from simulations and measurements made on a two-port 16:1 scale model. Our design of scale model provides both insertion and reflection loss measurements. Electromagnetic simulation and easily-calibrated model measurements confirm that the short antenna fins feasible on a monolithic microwave integrated circuit (MMIC) can achieve acceptable specifications. The design proves to be relatively insensitive to the value of the terminating resistance or the size of the antenna fins

Feeding selectivity of brown trout (Salmo trutta) in Loch Ness, Scotland

The aim of this study was to compare statistically the zooplankton assemblage ingested by brown trout (Salmo trutta) in Loch Ness with that of the zooplankton in the water column. This would allow the examination of the apparent paradox that very few copepods appear to be consumed by trout at a time of year when they are numerous and readily available as food. The investigation was limited to the crustacean zooplankters, since the Rotifera are generally so small that they are only of interest to fish in the first few days of life. 25 trout were obtained from anglers, and the stomach contents of non-"ferox" animals analysed. Samples of pelagic zooplankton were obtained approximately monthly from 30-m vertical net-hauls (mesh size 100 km). It is concluded that the variation in dietary composition with trout wet weight indicates an ontogenetic habitat shift producing spatial separation of young and older individuals

Scaling of Electrode-Electrolyte Interface Model Parameters In Phosphate Buffered Saline

We report how the impedance presented by a platinum electrode scales with the concentration of phosphate buffered saline (PBS). We find that the constant phase element of the model scales with approximately the log of concentration, whereas the resistivity is inversely proportional. Using a novel DC measurement technique we show that the Faradaic response of a platinum electrode, and thus the safe exposure limit, does not scale with concentration below 900mV overpotential across a pair of electrodes. We compare objective measurements made in saline to those made in the spinal cavity of live sheep. We comment upon the appropriateness of using PBS as a substitute for living sheep

The energy efficiency of 8-bit low-power microcontrollers

We have measured the energy cost of processing, sleeping, non-volatile memory writes and ADC measurements of six 8-bit microprocessors from three manufacturers. These measurements compare the chips directly to one another and reveal ideal operating points which can be used to reduce energy consumption