2,837 research outputs found
Development and performance of pulse-width-modulated static inverter and converter modules
Pulse-width-modulated inverter and converter modules are being developed for modular aerospace electrical power systems. The modules, rate 2.5 kilowatts per module and 10-minute - 150-percent overload, operate from 56 volts dc. The converter module provides two output voltages: a nominal link voltage of 200 volts dc when used with the inverter, and 150 volts dc to a load bus when used separately. The inverter module output is 400-hertz, sinusoidal, three-phase, 120/208 volts. Tests of breadboard models with standard parts and integrated circuits show rated power efficiencies of 71.4 and 85.1 percent and voltage regulation of 5 and 3.1 percent for inverter and converter modules, respectively. Sine-wave output distortion is 0.74 percent
An Assessment of Economic Considerations for Industrial Hemp Production
United States farm policy and programs are governed by the Farm Bill. The 2014 Farm Bill allows for the legal production and research of industrial hemp as long as it meets the standards outlined in the Farm Bill. Although it has a wide range of uses (upwards of 25,000 products use hemp), there is a lack of recent information regarding the economic feasibility of hemp production for the private agricultural sector. Through an extensive search of existing literature, information was gathered to construct an enterprise budget for industrial hemp. Data from the enterprise budget were used in a constrained linear programming model to compare how introducing industrial hemp production could change crop allocations in all 75 counties of Arkansas When industrial hemp was introduced, the total number of acres farmed increased by 2.8% to 4.4%, the statewide profit increased by 0.3% to 18.2%, and rice was the only crop that increased in acreage by 5%. While these results suggest that industrial hemp may be an economically promising crop, there are still hurdles to overcome. The lack of clearance (permitting) by the Drug Enforcement Agency and the absence of hemp processing facilities in the United States are clear roadblocks to hemp production. Once permitting hurdles are overcome, additional research will be needed to identify optimal locations for processing facilities and target markets for hemp goods
Conditional linear-optical measurement schemes generate effective photon nonlinearities
We provide a general approach for the analysis of optical state evolution
under conditional measurement schemes, and identify the necessary and
sufficient conditions for such schemes to simulate unitary evolution on the
freely propagating modes. If such unitary evolution holds, an effective photon
nonlinearity can be identified. Our analysis extends to conditional measurement
schemes more general than those based solely on linear optics.Comment: 16 pages, 2 figure
Experimental Controlled-NOT Logic Gate for Single Photons in the Coincidence Basis
We report a proof-of-principle demonstration of a probabilistic
controlled-NOT gate for single photons. Single-photon control and target qubits
were mixed with a single ancilla photon in a device constructed using only
linear optical elements. The successful operation of the controlled-NOT gate
relied on post-selected three-photon interference effects which required the
detection of the photons in the output modes.Comment: 4 pages, 4 figures; minor change
Photon number resolution using a time-multiplexed single-photon detector
Photon number resolving detectors are needed for a variety of applications
including linear-optics quantum computing. Here we describe the use of
time-multiplexing techniques that allows ordinary single photon detectors, such
as silicon avalanche photodiodes, to be used as photon number-resolving
detectors. The ability of such a detector to correctly measure the number of
photons for an incident number state is analyzed. The predicted results for an
incident coherent state are found to be in good agreement with the results of a
proof-of-principle experimental demonstration.Comment: REVTeX4, 6 pages, 8 eps figures, v2: minor changes, v3: changes in
response to referee report, appendix added, 1 reference adde
Heralded generation of entangled photon pairs
Entangled photons are a crucial resource for quantum communication and linear
optical quantum computation. Unfortunately, the applicability of many
photon-based schemes is limited due to the stochastic character of the photon
sources. Therefore, a worldwide effort has focused in overcoming the limitation
of probabilistic emission by generating two-photon entangled states conditioned
on the detection of auxiliary photons. Here we present the first heralded
generation of photon states that are maximally entangled in polarization with
linear optics and standard photon detection from spontaneous parametric
down-conversion. We utilize the down-conversion state corresponding to the
generation of three photon pairs, where the coincident detection of four
auxiliary photons unambiguously heralds the successful preparation of the
entangled state. This controlled generation of entangled photon states is a
significant step towards the applicability of a linear optics quantum network,
in particular for entanglement swapping, quantum teleportation, quantum
cryptography and scalable approaches towards photonics-based quantum computing
Heralded Two-Photon Entanglement from Probabilistic Quantum Logic Operations on Multiple Parametric Down-Conversion Sources
An ideal controlled-NOT gate followed by projective measurements can be used
to identify specific Bell states of its two input qubits. When the input qubits
are each members of independent Bell states, these projective measurements can
be used to swap the post-selected entanglement onto the remaining two qubits.
Here we apply this strategy to produce heralded two-photon polarization
entanglement using Bell states that originate from independent parametric
down-conversion sources, and a particular probabilistic controlled-NOT gate
that is constructed from linear optical elements. The resulting implementation
is closely related to an earlier proposal by Sliwa and Banaszek
[quant-ph/0207117], and can be intuitively understood in terms of familiar
quantum information protocols. The possibility of producing a ``pseudo-demand''
source of two-photon entanglement by storing and releasing these heralded pairs
from independent cyclical quantum memory devices is also discussed.Comment: 5 pages, 4 figures; submitted to IEEE Journal of Selected Topics in
Quantum Electronics, special issue on "Quantum Internet Technologies
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