3,792 research outputs found
Two stage superconducting quantum interference device amplifier in a high-Q gravitational wave transducer
We report on the total noise from an inductive motion transducer for a
gravitational-wave antenna. The transducer uses a two-stage SQUID amplifier and
has a noise temperature of 1.1 mK, of which 0.70 mK is due to back-action noise
from the SQUID chip. The total noise includes thermal noise from the transducer
mass, which has a measured Q of 2.60 X 10^6. The noise temperature exceeds the
expected value of 3.5 \mu K by a factor of 200, primarily due to voltage noise
at the input of the SQUID. Noise from flux trapped on the chip is found to be
the most likely cause.Comment: Accepted by Applied Physics Letters tentatively scheduled for March
13, 200
Quartz crystal microbalance use in biological studies
Design, development, and applications of quartz crystal microbalance are discussed. Two types of crystals are used. One serves as reference and other senses changes in mass. Specific application to study of bacterial spores is described
Corporate social responsibility performance and outsourcing: The case of the Bangladesh tragedy
Multinational firms frequently outsource the manufacturing of their products to factories in less- developed countries to take advantage of much lower labor costs. A tragic disaster occurred in Bangladesh in April 2013 when a clothing factory building collapsed, killing more than a thousand workers. Subsequently, textile companies in the U.S. and in Europe who outsource their manufacturing in Bangladesh had to decide whether to commit to better working conditions by signing one of two worker safety agreements (WSAs) born in the after-math of the tragedy. Although many firms signed one of these agreements, many more did not. This study explores the relationship between an actual corporate social responsibility (CSR) commitment and firm performance, using a sample of companies who signed one of the WSAs after the Bangladesh disaster and those who did not. The results suggest that the decision to sign is positively associated with social visibility, prior CSR performance, and impact in stock price after the tragedy. Regarding subsequent performance, investors favorably responded to the news of firms’ signing on to the WSA agreement
Instructional Case: Can Management Accounting Help Aid Associations Make Tough Choices in Haiti?
Based on an actual situation, this case explores the use of management accounting analysis in a difficult make-or-buy decision in the real world of humanitarian aid. An aid organization produces a specially designed, highly nutritious peanut butter medicine to save the lives of Haiti’s malnourished children. The challenge is deciding whether to source the peanuts from Haitian farmers and pay more or from foreign suppliers and pay less. Students perform both quantitative and qualitative cost-benefit, break-even, operating leverage, and product costing analysis. Performance measurement, incentive issues, short-term versus long-term thinking, micro and macroeconomics, and ethical issues are also considered. The case is best suited for cost accounting and managerial (particularly MBA managerial) accounting courses
Comparison of coherence times in three dc SQUID phase qubits
We report measurements of spectroscopic linewidth and Rabi oscillations in
three thin-film dc SQUID phase qubits. One device had a single-turn Al loop,
the second had a 6-turn Nb loop, and the third was a first order gradiometer
formed from 6-turn wound and counter-wound Nb coils to provide isolation from
spatially uniform flux noise. In the 6 - 7.2 GHz range, the spectroscopic
coherence times for the gradiometer varied from 4 ns to 8 ns, about the same as
for the other devices (4 to 10 ns). The time constant for decay of Rabi
oscillations was significantly longer in the single-turn Al device (20 to 30
ns) than either of the Nb devices (10 to 15 ns). These results imply that
spatially uniform flux noise is not the main source of decoherence or
inhomogenous broadening in these devices.Comment: 4 pages, 5 figures, accepted for publication in IEEE Trans. Appl.
Supercon
- and -spin relaxation time limitations of phosphorous donor electrons near crystalline silicon to silicon dioxide interface defects
A study of donor electron spins and spin--dependent electronic transitions
involving phosphorous (P) atoms in proximity of the (111) oriented
crystalline silicon (c-Si) to silicon dioxide (SiO) interface is
presented for [P] = 10 and [P] =
10 at about liquid He temperatures (
). Using pulsed electrically detected magnetic
resonance (pEDMR), spin--dependent transitions between the \Phos donor state
and two distinguishable interface states are observed, namely (i) \Pb centers
which can be identified by their characteristic anisotropy and (ii) a more
isotropic center which is attributed to E defects of the \sio bulk
close to the interface. Correlation measurements of the dynamics of
spin--dependent recombination confirm that previously proposed transitions
between \Phos and the interface defects take place. The influence of these
electronic near--interface transitions on the \Phos donor spin coherence time
as well as the donor spin--lattice relaxation time is then
investigated by comparison of spin Hahn--echo decay measurements obtained from
conventional bulk sensitive pulsed electron paramagnetic resonance and surface
sensitive pEDMR, as well as surface sensitive electrically detected inversion
recovery experiments. The measurements reveal that both and of
\Phos donor electrons spins in proximity of energetically lower interface
states at K are reduced by several orders of magnitude
Strong-field effects in the Rabi oscillations of the superconducting phase qubit
Rabi oscillations have been observed in many superconducting devices, and
represent prototypical logic operations for quantum bits (qubits) in a quantum
computer. We use a three-level multiphoton analysis to understand the behavior
of the superconducting phase qubit (current-biased Josephson junction) at high
microwave drive power. Analytical and numerical results for the ac Stark shift,
single-photon Rabi frequency, and two-photon Rabi frequency are compared to
measurements made on a dc SQUID phase qubit with Nb/AlOx/Nb tunnel junctions.
Good agreement is found between theory and experiment.Comment: 4 pages, 4 figures, accepted for publication in IEEE Trans. Appl.
Supercon
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