Integrated optics architecture for trapped-ion quantum information processing

Standard schemes for trapped-ion quantum information processing (QIP) involve the manipulation of ions in a large array of interconnected trapping potentials. The basic set of QIP operations, including state initialization, universal quantum logic, and state detection, is routinely executed within a single array site by means of optical operations, including various laser excitations as well as the collection of ion fluorescence. Transport of ions between array sites is also routinely carried out in microfabricated trap arrays. However, it is still not possible to perform optical operations in parallel across all array sites. The lack of this capability is one of the major obstacles to scalable trapped-ion QIP and presently limits exploitation of current microfabricated trap technology. Here we present an architecture for scalable integration of optical operations in trapped-ion QIP. We show theoretically that diffractive mirrors, monolithically fabricated on the trap array, can efficiently couple light between trap array sites and optical waveguide arrays. Integrated optical circuits constructed from these waveguides can be used for sequencing of laser excitation and fluorescence collection. Our scalable architecture supports all standard QIP operations, as well as photon-mediated entanglement channels, while offering substantial performance improvements over current techniques.Griffith Sciences, School of Natural SciencesNo Full Tex

Elasticities of road traffic and fuel consumption with respect to price and income: A review

This paper gives the main results of a literature review of new empirical studies, published since 1990, updating work on the effects of price and income on fuel consumption, traffic levels, and where available other indicators including fuel efficiency and car ownership. The results are broadly consistent with several earlier reviews, though not always with current practice. The work was carried out as one of two parallel 'blind' literature reviews, the other being summarized in a companion paper by Graham and Glaister: the results are broadly, though not in every respect, consistent. © 2004 Taylor and Francis Ltd