4,010 research outputs found
Development of a semipurified diet for the adult pocket mouse /Perognathus/
Semipurified diet effect on adult pocket mic
Damage Valuation of Indirect Expropriation in Public Services
damage valuation, expropriation, public services, contracting, privatization
Integrating process and factor understanding of environmental innovation by water utilities
Innovations in technology and organisations are central to enabling the water sector to adapt to major environmental changes such as climate change, land degradation or drinking water pollution. While there are literatures on innovation as a process and on the factors that influence it, there is little research that integrates these. Development of such an integrated understanding of innovation is central to understanding how policy makers and organisations can stimulate and direct environmental innovation. In the research reported here a framework is developed that enables such an integrated analysis of innovation process and factors. From research interviews and the literature twenty factors were identified that affect the five stages of the environmental innovation process in English and Welsh water utilities. The environmental innovations investigated are measures taken by water utilities to reduce or prevent pollution in drinking water catchments rather than technical measures to treat water. These Source Control Interventions are similar to other environmental innovations, such as ecosystem and species conservation, in that they emphasise the mix of technology, management and engagement with multiple actors. Results show that in water utilities direct performance regulation and regulation that raises awareness of a ‘performance’ gap as a ‘problem’ can stimulate innovation, but only under particular organisational, natural physical and regulatory conditions. The integrated framework also suggests that while flexible or framework legislation (e.g. Water Framework Directive) does not stimulate innovation in itself, it has shaped the option spaces and characteristics of innovations selected towards source control instead of technical end-of-pipe solutions
Cool for Cats
The iconic Schr\"odinger's cat state describes a system that may be in a
superposition of two macroscopically distinct states, for example two clearly
separated oscillator coherent states. Quite apart from their role in
understanding the quantum classical boundary, such states have been suggested
as offering a quantum advantage for quantum metrology, quantum communication
and quantum computation. As is well known these applications have to face the
difficulty that the irreversible interaction with an environment causes the
superposition to rapidly evolve to a mixture of the component states in the
case that the environment is not monitored. Here we show that by engineering
the interaction with the environment there exists a large class of systems that
can evolve irreversibly to a cat state. To be precise we show that it is
possible to engineer an irreversible process so that the steady state is close
to a pure Schr\"odinger's cat state by using double well systems and an
environment comprising two-photon (or phonon) absorbers. We also show that it
should be possible to prolong the lifetime of a Schr\"odinger's cat state
exposed to the destructive effects of a conventional single-photon decohering
environment. Our protocol should make it easier to prepare and maintain
Schr\"odinger cat states which would be useful in applications of quantum
metrology and information processing as well as being of interest to those
probing the quantum to classical transition.Comment: 10 pages, 7 figures. Significantly updated version with supplementary
informatio
Freezing distributed entanglement in spin chains
We show how to freeze distributed entanglement that has been created from the
natural dynamics of spin chain systems. The technique that we propose simply
requires single-qubit operations and isolates the entanglement in specific
qubits at the ends of branches. Such frozen entanglement provides a useful
resource, for example for teleportation or distributed quantum processing. The
scheme can be applied to a wide range of systems -- including actual spin
systems and alternative qubit embodiments in strings of quantum dots, molecules
or atoms.Comment: 5 pages, to appear in Phys. Rev. A (Rapid Communication
Some Remarks on Quantum Coherence
There are many striking phenomena which are attributed to
``quantum coherence''. It is natural to wonder if there are new quantum
coherence effects waiting to be discovered which could lead to interesting
results and perhaps even practical applications. A useful starting point for
such discussions is a definition of ``quantum coherence''. In this article I
give a definition of quantum coherence and use a number of illustrations to
explore the implications of this definition. I point to topics of current
interest in the fields of cosmology and quantum computation where questions of
quantum coherence arise, and I emphasize the impact that interactions with the
environment can have on quantum coherence.Comment: 25 pages plain LaTeX, no figures. More references have been added and
typos have been corrected. Journal of Modern Optics, in press.
Imperial/TP/93-94/1
Selective spin coupling through a single exciton
We present a novel scheme for performing a conditional phase gate between two
spin qubits in adjacent semiconductor quantum dots through delocalized single
exciton states, formed through the inter-dot Foerster interaction. We consider
two resonant quantum dots, each containing a single excess conduction band
electron whose spin embodies the qubit. We demonstrate that both the two-qubit
gate, and arbitrary single-qubit rotations, may be realized to a high fidelity
with current semiconductor and laser technology.Comment: 5 pages, 3 figures; published version, equation formatting improved,
references adde
Entanglement of superconducting charge qubits by homodyne measurement
We present a scheme by which projective homodyne measurement of a microwave
resonator can be used to generate entanglement between two superconducting
charge qubits coupled to this resonator. The non-interacting qubits are
initialised in a product of their ground states, the resonator is initialised
in a coherent field state, and the state of the system is allowed to evolve
under a rotating wave Hamiltonian. Making a homodyne measurement on the
resonator at a given time projects the qubits into an state of the form (|gg> +
exp(-i phi)|ee>)/sqrt(2). This protocol can produce states with a fidelity as
high as required, with a probability approaching 0.5. Although the system
described is one that can be used to display revival in the qubit oscillations,
we show that the entanglement procedure works at much shorter timescales.Comment: 17 pages, 7 figure
Generalized Toffoli gates using qudit catalysis
We present quantum networks for a n-qubit controlled gate C^{n-1}(U) which
use a higher dimensional (qudit) ancilla as a catalyser. In its simplest form
the network has only n two-particle gates (qubit-qudit) -- this is the minimum
number of two-body interactions needed to couple all n+1 subsystems (n qubits
plus one ancilla). This class of controlled gates includes the generalised
Toffoli gate C^{n-1}(X) on n qubits, which plays an important role in several
quantum algorithms and error correction. A particular example implementing this
model is given by the dispersive limit of a generalised Jaynes-Cummings
Hamiltonian of an effective spin-s interacting with a cavity mode.Comment: 5 pages, 3 fig
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