6,779 research outputs found
Quantum dynamics of a dc-SQUID coupled to an asymmetric Cooper pair transistor
We present a theoretical analysis of the quantum dynamics of a
superconducting circuit based on a highly asymmetric Cooper pair transistor
(ACPT) in parallel to a dc-SQUID. Starting from the full Hamiltonian we show
that the circuit can be modeled as a charge qubit (ACPT) coupled to an
anharmonic oscillator (dc-SQUID). Depending on the anharmonicity of the SQUID,
the Hamiltonian can be reduced either to one that describes two coupled qubits
or to the Jaynes-Cummings Hamiltonian. Here the dc-SQUID can be viewed as a
tunable micron-size resonator. The coupling term, which is a combination of a
capacitive and a Josephson coupling between the two qubits, can be tuned from
the very strong- to the zero-coupling regimes. It describes very precisely the
tunable coupling strength measured in this circuit and explains the
'quantronium' as well as the adiabatic quantum transfer read-out.Comment: 20 page
Wrong Means to an Unjust End? The Eleventh Circuit’s Decision in First Vagabonds Church of God
In 2005, Orlando Food Not Bombs (OFNB), a conglomeration of political activists who advocate a “right to food,” began conducting “food-sharing events” once a week in downtown Orlando, Florida. OFNB distributed free vegan meals in Lake Eola Park to the hungry and homeless. Soon, however, the City began receiving complaints related to the number of homeless individuals who would disperse into adjacent neighborhoods following the events. In response, the City enacted the Large Group Feeding Ordinance, which required a permit for any feeding event likely to attract twenty-five or more people
Wrong Means to an Unjust End? The Eleventh Circuit’s Decision in First Vagabonds Church of God
In 2005, Orlando Food Not Bombs (OFNB), a conglomeration of political activists who advocate a “right to food,” began conducting “food-sharing events” once a week in downtown Orlando, Florida. OFNB distributed free vegan meals in Lake Eola Park to the hungry and homeless. Soon, however, the City began receiving complaints related to the number of homeless individuals who would disperse into adjacent neighborhoods following the events. In response, the City enacted the Large Group Feeding Ordinance, which required a permit for any feeding event likely to attract twenty-five or more people
Decoherence processes in a current biased dc SQUID
A current bias dc SQUID behaves as an anharmonic quantum oscillator
controlled by a bias current and an applied magnetic flux. We consider here its
two level limit consisting of the two lower energy states | 0 \right> and |
1 \right>. We have measured energy relaxation times and microwave absorption
for different bias currents and fluxes in the low microwave power limit.
Decoherence times are extracted. The low frequency flux and current noise have
been measured independently by analyzing the probability of current switching
from the superconducting to the finite voltage state, as a function of applied
flux. The high frequency part of the current noise is derived from the
electromagnetic environment of the circuit. The decoherence of this quantum
circuit can be fully accounted by these current and flux noise sources.Comment: 4 pages, 4 figure
Nanosecond quantum state detection in a current biased dc SQUID
This article presents our procedure to measure the quantum state of a dc
SQUID within a few nanoseconds, using an adiabatic dc flux pulse. Detection of
the ground state is governed by standard macroscopic quantum theory (MQT), with
a small correction due to residual noise in the bias current. In the two level
limit, where the SQUID constitutes a phase qubit, an observed contrast of 0.54
indicates a significant loss in contrast compared to the MQT prediction. It is
attributed to spurious depolarization (loss of excited state occupancy) during
the leading edge of the adiabatic flux measurement pulse. We give a simple
phenomenological relaxation model which is able to predict the observed
contrast of multilevel Rabi oscillations for various microwave amplitudes.Comment: 10 pages, 8 figure
Beyond Node Degree: Evaluating AS Topology Models
This is the accepted version of 'Beyond Node Degree: Evaluating AS Topology Models', archived originally at arXiv:0807.2023v1 [cs.NI] 13 July 2008.Many models have been proposed to generate Internet Autonomous System (AS) topologies, most of which make structural assumptions about the AS graph. In this paper we compare AS topology generation models with several observed AS topologies. In contrast to most previous works, we avoid making assumptions about which topological properties are important to characterize the AS topology. Our analysis shows that, although matching degree-based properties, the existing AS topology generation models fail to capture the complexity of the local interconnection structure between ASs. Furthermore, we use BGP data from multiple vantage points to show that additional measurement locations significantly affect local structure properties, such as clustering and node centrality. Degree-based properties, however, are not notably affected by additional measurements locations. These observations are particularly valid in the core. The shortcomings of AS topology generation models stems from an underestimation of the complexity of the connectivity in the core caused by inappropriate use of BGP data
Effect of spin orbit scattering on the magnetic and superconducting properties of nearly ferromagnetic metals: application to granular Pt
We calculate the effect of scattering on the static, exchange enhanced, spin
susceptibility and show that in particular spin orbit scattering leads to a
reduction of the giant moments and spin glass freezing temperature due to
dilute magnetic impurities. The harmful spin fluctuation contribution to the
intra-grain pairing interaction is strongly reduced opening the way for BCS
superconductivity. We are thus able to explain the superconducting and magnetic
properties recently observed in granular Pt as due to scattering effects in
single small grains.Comment: 9 pages 3 figures, accepted for publication in Phys. Rev. Letter
Effect of Soil Chemistry on Microbial Biodiversity and Functionality in Grassland and Tilled Soils
Microorganisms are excellent indicators of soil health, because of their rapid response to environmental change. Traditional microbiology is ineffective for the study of soil, as \u3c 1% of microorganisms are currently culturable (Torsvik et al., 1996). Nucleic acid based methods, however, allow rapid detection of organisms, or particular genes, directly from soil samples. This work investigated, using polymerase chain reaction (PCR)-based approaches, the relationship between key chemical properties and bacterial biodiversity in grassland and tilled soils, with particular emphasis on the abundance and diversity of ammonium oxidisers
Caracterização de bactérias e fungos envolvidos na degradação de sulfentrazona em solos.
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