6,851 research outputs found
Coherence-Preserving Quantum Bits
Real quantum systems couple to their environment and lose their intrinsic
quantum nature through the process known as decoherence. Here we present a
method for minimizing decoherence by making it energetically unfavorable. We
present a Hamiltonian made up solely of two-body interactions between four
two-level systems (qubits) which has a two-fold degenerate ground state. This
degenerate ground state has the property that any decoherence process acting on
an individual physical qubit must supply energy from the bath to the system.
Quantum information can be encoded into the degeneracy of the ground state and
such coherence-preserving qubits will then be robust to local decoherence at
low bath temperatures. We show how this quantum information can be universally
manipulated and indicate how this approach may be applied to a quantum dot
quantum computer.Comment: 5 pages, 1 figur
On SIC-POVMs in Prime Dimensions
The generalized Pauli group and its normalizer, the Clifford group, have a
rich mathematical structure which is relevant to the problem of constructing
symmetric informationally complete POVMs (SIC-POVMs). To date, almost every
known SIC-POVM fiducial vector is an eigenstate of a "canonical" unitary in the
Clifford group. I show that every canonical unitary in prime dimensions p > 3
lies in the same conjugacy class of the Clifford group and give a class
representative for all such dimensions. It follows that if even one such
SIC-POVM fiducial vector is an eigenvector of such a unitary, then all of them
are (for a given such dimension). I also conjecture that in all dimensions d,
the number of conjugacy classes is bounded above by 3 and depends only on d mod
9, and I support this claim with computer computations in all dimensions < 48.Comment: 6 pages, no figures. v3 Refs added, improved discussion of previous
work. Ref to a proof of the main conjecture also adde
Arkansas Wheat Cultivar Performance Tests 2010-2011
Wheat cultivar performance tests are conducted each year in Arkansas by the Arkansas Agricultural Experiment Station, Department of Crop, Soil and Environmental Sciences. The tests provide information to companies developing cultivars and/or marketing seed within the state and aid the Arkansas Cooperative Extension Service in formulating cultivar recommendations for small-grain producers
Mutations in shaking-B prevent electrical synapse formation in the Drosophila giant fiber system
The giant fiber system (GFS) is a simple network of neurons that mediates visually elicited escape behavior in Drosophila. The giant fiber (GF), the major component of the system, is a large, descending interneuron that relays visual stimuli to the motoneurons that innervate the tergotrochanteral jump muscle (TTM) and dorsal longitudinal flight muscles (DLMs). Mutations in the neural transcript from the shaking-B locus abolish the behavioral response by disrupting transmission at some electrical synapses in the GFS. This study focuses on the role of the gene in the development of the synaptic connections. Using an enhancer-trap line that expresses lacZ in the GFs, we show that the neurons develop during the first 30 hr of metamorphosis. Within the next 15 hr, they begin to form electrical synapses, as indicated by the transfer of intracellularly injected Lucifer yellow. The GFs dye-couple to the TTM motoneuron between 30 and 45 hr of metamorphosis, to the peripherally synapsing interneuron that drives the DLM motoneurons at approximately 48 hr, and to giant commissural interneurons in the brain at approximately 55 hr. Immunocytochemistry with shaking-B peptide antisera demonstrates that the expression of shaking-B protein in the region of GFS synapses coincides temporally with the onset of synaptogenesis; expression persists thereafter. The mutation shak-B2, which eliminates protein expression, prevents the establishment of dye coupling shaking-B, therefore, is essential for the assembly and/or maintenance of functional gap junctions at electrical synapses in the GFS
Interactions of Bacillus Mojavensis and Fusarium Verticillioides With a Benzoxazolinone (Boa) and Its Transformation Product, Apo
En:Journal of Chemical Ecology (2007, vol. 33, n. 10, p. 1885-1897)The benzoxazolinones, specifically benzoxazolin-2(3H)-one (BOA), are important transformation products of the benzoxazinones that can serve as allelochemicals providing resistance to maize from pathogenic bacteria, fungi, and insects. However, maize pathogens such as Fusarium verticillioides are capable of detoxifying the benzoxazolinones to 2-aminophenol (AP), which is converted to the less toxic N-(2-hydroxyphenyl) malonamic acid (HPMA) and 2-acetamidophenol (HPAA). As biocontrol strategies that utilize a species of endophytic bacterium, Bacillus mojavensis, are considered efficacious as a control of this Fusarium species, the in vitro transformation and effects of BOA on growth of this bacterium was examined relative to its interaction with strains of F. verticillioides. The results showed that a red pigment was produced and accumulated only on BOA-amended media when wild type and the progeny of genetic crosses of F. verticillioides are cultured in the presence of the bacterium. The pigment was identified as 2-amino-3H-phenoxazin-3-one (APO), which is a stable product. The results indicate that the bacterium interacts with the fungus preventing the usual transformation of AP to the nontoxic HPMA, resulting in the accumulation of higher amounts of APO than when the fungus is cultured alone. APO is highly toxic to F. verticillioides and other organisms. Thus, an enhanced biocontrol is suggested by this in vitro study.
=580 $aEn:Journal of Chemical Ecolog
Direct experimental evidence of free fermion antibunching
Fermion antibunching was observed on a beam of free noninteracting neutrons.
A monochromatic beam of thermal neutrons was first split by a graphite single
crystal, then fed to two detectors, displaying a reduced coincidence rate. The
result is a fermionic complement to the Hanbury Brown and Twiss effect for
photons.Comment: 4 pages, 2 figure
Universal Quantum Computation with the Exchange Interaction
Experimental implementations of quantum computer architectures are now being
investigated in many different physical settings. The full set of requirements
that must be met to make quantum computing a reality in the laboratory [1] is
daunting, involving capabilities well beyond the present state of the art. In
this report we develop a significant simplification of these requirements that
can be applied in many recent solid-state approaches, using quantum dots [2],
and using donor-atom nuclear spins [3] or electron spins [4]. In these
approaches, the basic two-qubit quantum gate is generated by a tunable
Heisenberg interaction (the Hamiltonian is between spins and ), while the one-qubit gates require the control
of a local Zeeman field. Compared to the Heisenberg operation, the one-qubit
operations are significantly slower and require substantially greater materials
and device complexity, which may also contribute to increasing the decoherence
rate. Here we introduce an explicit scheme in which the Heisenberg interaction
alone suffices to exactly implement any quantum computer circuit, at a price of
a factor of three in additional qubits and about a factor of ten in additional
two-qubit operations. Even at this cost, the ability to eliminate the
complexity of one-qubit operations should accelerate progress towards these
solid-state implementations of quantum computation.Comment: revtex, 2 figures, this version appeared in Natur
Export Tourism Input-Output Multipliers for Ireland. Quarterly Economic Commentary Special Article, May 1982
This paper focuses on some difficulties involved in the interpretation of
earlier studies and goes on to calculate upper bound estimates of some of the
principal economic effects of Irish export tourism in 1976. The 1976 input-output
data of Henry (1980) form the basis for the calculations herein
Beings in their own right? Exploring Children and young people's sibling and twin relationships in the Minority World
This paper examines the contributions that the sociological study of sibship and twinship in the Minority World can make to childhood studies. It argues that, in providing one forum within which to explore children and young people's social relationships, we can add to our understanding of children and young people's interdependence and develop a more nuanced understanding of agency. As emergent subjects, children, young people and adults are in a process of âbecomingâ. However, this does not mean that they can âbecomeâ anything they choose to. The notion of negotiated interdependence (Punch 2002) is useful in helping us to grasp the contingent nature of children and young people's agency
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