The Role and Effectiveness of Parish Councils in Gloucestershire: Adapting to New Modes of Rural Community Governance.

This thesis examines the changing roles of rural parish councils in the context of the Government White Paper on Rural England (DEFRA, November 2000). This suggested that new responsibilities should be given to Parish Councils within rural policy and planning frameworks. Concepts such as ‘Partnership’, 'Parish Plans' and ‘Quality Parish Councils' were mooted as possible vehicles to promote greater community participation and increased local 'empowerment' in the governance of rural communities. The proposals for parish councils are part of a new 'integrated approach' to rural planning which seeks to combine the state and voluntary sectors through the ideals of partnership. The research examines the appropriateness and willingness of parish councils in Gloucestershire to fulfill the new responsibilities set down in the Rural White Paper and the key they have as ‘agents’ of government. It explores and assesses how far they have adjusted to the new forms of governance set out by the White Paper, and considers how they have adapted alongside greater voluntary and community activity, focussing in particular on the new forms of partnership distributed across the countryside. The research found that the effectiveness of parish councils in Gloucestershire is extremely varied and often piecemeal in nature, influenced by a wide variety of social, economic and geographical factors. Both individual decisions and wider structural factors, including the opportunities provided by self-interest, influence the variations in the type and level of participation in community leadership. In Gloucestershire, the emergence of new organisations and actors in rural community governance has generated only a moderate shift in the way parish councils operate. Parish councils consider that they have very little influence in the broader sphere of rural governance structures. Recent government legislation regarding community involvement, partnership and participation has been slow to filter down to a large number of parish councils in the county. The geography of partnership initiatives across the UK has emerged as a very uneven map of rural governance. This “map” is mirrored in the incidence of effective partnerships within rural politics in Gloucestershire. Indeed the complex nature of participation in community governance and leadership revealed by the research confirms the need for further examination of the shift from “joined up” to “joining up” partnerships, and the incidence of partnership marginalisation felt across many parish councils in the county. Some signposts for future research are also identified

Minimum cbits for remote preperation and measurement of a qubit

We show that a qubit chosen from equatorial or polar great circles on a Bloch spehere can be remotely prepared with one cbit from Alice to Bob if they share one ebit of entanglement. Also we show that any single particle measurement on an arbitrary qubit can be remotely simulated with one ebit of shared entanglement and communication of one cbit.Comment: Latex, 7 pages, minor changes, references adde

Entanglement required in achieving entanglement-assisted channel capacities

Entanglement shared between the two ends of a quantum communication channel has been shown to be a useful resource in increasing both the quantum and classical capacities for these channels. The entanglement-assisted capacities were derived assuming an unlimited amount of shared entanglement per channel use. In this paper, bounds are derived on the minimum amount of entanglement required per use of a channel, in order to asymptotically achieve the capacity. This is achieved by introducing a class of entanglement-assisted quantum codes. Codes for classes of qubit channels are shown to achieve the quantum entanglement-assisted channel capacity when an amount of shared entanglement per channel given by, E = 1 - Q_E, is provided. It is also shown that for very noisy channels, as the capacities become small, the amount of required entanglement converges for the classical and quantum capacities.Comment: 9 pages, 2 figures, RevTex

Physical Complexity of Symbolic Sequences

A practical measure for the complexity of sequences of symbols (``strings'') is introduced that is rooted in automata theory but avoids the problems of Kolmogorov-Chaitin complexity. This physical complexity can be estimated for ensembles of sequences, for which it reverts to the difference between the maximal entropy of the ensemble and the actual entropy given the specific environment within which the sequence is to be interpreted. Thus, the physical complexity measures the amount of information about the environment that is coded in the sequence, and is conditional on such an environment. In practice, an estimate of the complexity of a string can be obtained by counting the number of loci per string that are fixed in the ensemble, while the volatile positions represent, again with respect to the environment, randomness. We apply this measure to tRNA sequence data.Comment: 12 pages LaTeX2e, 3 postscript figures, uses elsart.cls. Substantially improved and clarified version, includes application to EMBL tRNA sequence dat

Reversibility of continuous-variable quantum cloning

We analyze a reversibility of optimal Gaussian $1\to 2$ quantum cloning of a coherent state using only local operations on the clones and classical communication between them and propose a feasible experimental test of this feature. Performing Bell-type homodyne measurement on one clone and anti-clone, an arbitrary unknown input state (not only a coherent state) can be restored in the other clone by applying appropriate local unitary displacement operation. We generalize this concept to a partial LOCC reversal of the cloning and we show that this procedure converts the symmetric cloner to an asymmetric cloner. Further, we discuss a distributed LOCC reversal in optimal $1\to M$ Gaussian cloning of coherent states which transforms it to optimal $1\to M'$ cloning for $M'<M$. Assuming the quantum cloning as a possible eavesdropping attack on quantum communication link, the reversibility can be utilized to improve the security of the link even after the attack.Comment: 7 pages, 5 figure

Asymmetric quantum telecloning of d-level systems and broadcasting of entanglement to different locations using the "many-to-many" communication protocol

We propose a generalization of quantum teleportation: the so-called many-to-many quantum communication of the information of a d-level system from N spatially separated senders to M>N receivers situated at different locations. We extend the concept of asymmetric telecloning from qubits to d-dimensional systems. We investigate the broadcasting of entanglement by using local 1->2 optimal universal asymmetric Pauli machines and show that the maximal fidelities of the two final entangled states are obtained when symmetric machines are applied. Cloning of entanglement is studied using a nonlocal optimal universal asymmetric cloning machine and we show that the symmetric machine optimally copies the entanglement. The "many-to-many" teleportation scheme is applied in order to distribute entanglement shared between two observers to two pairs of spatially separated observers.Comment: 17 pages, 1 figur

Multipartite Classical and Quantum Secrecy Monotones

In order to study multipartite quantum cryptography, we introduce quantities which vanish on product probability distributions, and which can only decrease if the parties carry out local operations or carry out public classical communication. These ``secrecy monotones'' therefore measure how much secret correlations are shared by the parties. In the bipartite case we show that the mutual information is a secrecy monotone. In the multipartite case we describe two different generalisations of the mutual information, both of which are secrecy monotones. The existence of two distinct secrecy monotones allows us to show that in multipartite quantum cryptography the parties must make irreversible choices about which multipartite correlations they want to obtain. Secrecy monotones can be extended to the quantum domain and are then defined on density matrices. We illustrate this generalisation by considering tri-partite quantum cryptography based on the Greenberger-Horne-Zeilinger (GHZ) state. We show that before carrying out measurements on the state, the parties must make an irreversible decision about what probability distribution they want to obtain

A small universe after all?

The cosmic microwave background radiation allows us to measure both the geometry and topology of the universe. It has been argued that the COBE-DMR data already rule out models that are multiply connected on scales smaller than the particle horizon. Here we show the opposite is true: compact (small) hyperbolic universes are favoured over their infinite counterparts. For a density parameter of Omega_o=0.3, the compact models are a better fit to COBE-DMR (relative likelihood ~20) and the large-scale structure data (sigma_8 increases by ~25%).Comment: 4 pages, RevTeX, 7 Figure

Positive Maps Which Are Not Completely Positive

The concept of the {\em half density matrix} is proposed. It unifies the quantum states which are described by density matrices and physical processes which are described by completely positive maps. With the help of the half-density-matrix representation of Hermitian linear map, we show that every positive map which is not completely positive is a {\em difference} of two completely positive maps. A necessary and sufficient condition for a positive map which is not completely positive is also presented, which is illustrated by some examples.Comment: 4pages,The Institute of Theoretical Physics, Academia Sinica, Beijing 100080, P.R. Chin

Photon losses depending on polarization mixedness

We introduce a quantum channel describing photon losses depending on the degree of polarization mixedness. This can be regarded as a model of quantum channel with correlated errors between discrete and continuous degrees of freedom. We consider classical information over a continuous alphabet encoded on weak coherent states as well as classical information over a discrete alphabet encoded on single photons using dual rail representation. In both cases we study the one-shot capacity of the channel and its behaviour in terms of correlation between losses and polarization mixedness