26,247 research outputs found

    Multi-party Quantum Computation

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    We investigate definitions of and protocols for multi-party quantum computing in the scenario where the secret data are quantum systems. We work in the quantum information-theoretic model, where no assumptions are made on the computational power of the adversary. For the slightly weaker task of verifiable quantum secret sharing, we give a protocol which tolerates any t < n/4 cheating parties (out of n). This is shown to be optimal. We use this new tool to establish that any multi-party quantum computation can be securely performed as long as the number of dishonest players is less than n/6.Comment: Masters Thesis. Based on Joint work with Claude Crepeau and Daniel Gottesman. Full version is in preparatio

    Small Pseudo-Random Families of Matrices: Derandomizing Approximate Quantum Encryption

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    A quantum encryption scheme (also called private quantum channel, or state randomization protocol) is a one-time pad for quantum messages. If two parties share a classical random string, one of them can transmit a quantum state to the other so that an eavesdropper gets little or no information about the state being transmitted. Perfect encryption schemes leak no information at all about the message. Approximate encryption schemes leak a non-zero (though small) amount of information but require a shorter shared random key. Approximate schemes with short keys have been shown to have a number of applications in quantum cryptography and information theory. This paper provides the first deterministic, polynomial-time constructions of quantum approximate encryption schemes with short keys. Previous constructions (quant-ph/0307104) are probabilistic--that is, they show that if the operators used for encryption are chosen at random, then with high probability the resulting protocol will be a secure encryption scheme. Moreover, the resulting protocol descriptions are exponentially long. Our protocols use keys of the same length as (or better length than) the probabilistic constructions; to encrypt nn qubits approximately, one needs n+o(n)n+o(n) bits of shared key. An additional contribution of this paper is a connection between classical combinatorial derandomization and constructions of pseudo-random matrix families in a continuous space.Comment: 11 pages, no figures. In Proceedings of RANDOM 2004, Cambridge, MA, August 200

    A Decision-Support Framework For Using Value Capture to Fund Public Transit: Lessons From Project-Specific Analyses, Research Report 11-14

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    Local and state governments provide 75 percent of transit funds in the United States. With all levels of governments under significant fiscal stress, any new transit funding mechanism is welcome. Value capture (VC) is one such mechanism. Based on the “benefits received” principle, VC involves the identification and capture of public infrastructure-led increase in land value. While the literature has extensively demonstrated the property-value impacts of transit investments and has empirically simulated the potential magnitude of VC revenues for financing transit facilities, very little research has examined the suitability of VC mechanisms for specific transit projects. This report aims to fill this research gap by examining five VC mechanisms in depth: tax-increment financing (TIF), special assessment districts (SADs), transit impact fees, joint developments, and air rights. The report is intended to assist practitioners in gauging the legal, financial, and administrative suitability of VC mechanisms for meeting project-specific funding requirements

    Wildlife tourism in Scotland – the example of grouse shooting

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    Wildlife tourism in Scotland has seen a recent increase in profile, with two reports providing new figures on the economic value of the activity. The reports, by the Scottish Government and Scottish Natural Heritage (SNH), seem likely to generate policy responses to further develop the sector

    Bayesian Modelling of Direct and Indirect Effects of Marine Reserves on Fishes : A thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Statistics at Massey University, Albany, New Zealand.

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    This thesis reviews and develops modern advanced statistical methodology for sampling and modelling count data from marine ecological studies, with specific applications to quantifying potential direct and indirect effects of marine reserves on fishes in north eastern New Zealand. Counts of snapper (Pagrus auratus: Sparidae) from baited underwater video surveys from an unbalanced, multi-year, hierarchical sampling programme were analysed using a Bayesian Generalised Linear Mixed Model (GLMM) approach, which allowed the integer counts to be explicitly modelled while incorporating multiple fixed and random effects. Overdispersion was modelled using a zero-inflated negative-binomial error distribution. A parsimonious method for zero inflation was developed, where the mean of the count distribution is explicitly linked to the probability of an excess zero. Comparisons of variance components identified marine reserve status as the greatest source of variation in counts of snapper above the legal size limit. Relative densities inside reserves were, on average, 13-times greater than outside reserves. Small benthic reef fishes inside and outside the same three reserves were surveyed to evaluate evidence for potential indirect effects of marine reserves via restored populations of fishery-targeted predators such as snapper. Sites for sampling were obtained randomly from populations of interest using spatial data and geo-referencing tools in R—a rarely used approach that is recommended here more generally to improve field-based ecological surveys. Resultant multispecies count data were analysed with multivariate GLMMs implemented in the R package MCMCglmm, based on a multivariate Poisson lognormal error distribution. Posterior distributions for hypothesised effects of interest were calculated directly for each species. While reserves did not appear to affect densities of small fishes, reserve-habitat interactions indicated that some endemic species of triplefin (Tripterygiidae) had different associations with small-scale habitat gradients inside vs outside reserves. These patterns were consistent with a behavioural risk effect, where small fishes may be more strongly attracted to refuge habitats to avoid predators inside vs outside reserves. The approaches developed and implemented in this thesis respond to some of the major current statistical and logistic challenges inherent in the analysis of counts of organisms. This work provides useful exemplar pathways for rigorous study design, modelling and inference in ecological systems

    A Decision-Support Framework For Using Value Capture to Fund Public Transit: Lessons From Project-Specific Analyses

    Get PDF
    Local and state governments provide 75 percent of transit funds in the United States. With all levels of governments under significant fiscal stress, any new transit funding mechanism is welcome. Value capture (VC) is one such mechanism. Based on the “benefits received” principle, VC involves the identification and capture of public infrastructure-led increase in land value. While the literature has extensively demonstrated the property-value impacts of transit investments and has empirically simulated the potential magnitude of VC revenues for financing transit facilities, very little research has examined the suitability of VC mechanisms for specific transit projects. This report aims to fill this research gap by examining five VC mechanisms in depth: tax-increment financing (TIF), special assessment districts (SADs), transit impact fees, joint developments, and air rights. The report is intended to assist practitioners in gauging the legal, financial, and administrative suitability of VC mechanisms for meeting project-specific funding requirements
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