121 research outputs found
Development of a KSC test and flight engineering oriented computer language, Phase 1
Ten, primarily test oriented, computer languages reviewed during the phase 1 study effort are described. Fifty characteristics of ATOLL, ATLAS, and CLASP are compared. Unique characteristics of the other languages, including deficiencies, problems, safeguards, and checking provisions are identified. Programming aids related to these languages are reported, and the conclusions resulting from this phase of the study are discussed. A glossary and bibliography are included. For the reports on phase 2 of the study, see N71-35027 and N71-35029
Threshold Error Penalty for Fault Tolerant Computation with Nearest Neighbour Communication
The error threshold for fault tolerant quantum computation with concatenated
encoding of qubits is penalized by internal communication overhead. Many
quantum computation proposals rely on nearest-neighbour communication, which
requires excess gate operations. For a qubit stripe with a width of L+1
physical qubits implementing L levels of concatenation, we find that the error
threshold of 2.1x10^-5 without any communication burden is reduced to 1.2x10^-7
when gate errors are the dominant source of error. This ~175X penalty in error
threshold translates to an ~13X penalty in the amplitude and timing of gate
operation control pulses.Comment: minor correctio
Levels of adenosine deaminase in some experimental animal tumours and the possible therapeutic effect of the ADA inhibitor 2-deoxy-coformycin.
The intracellular adenosine deaminase activities (ADA) in 12 different experimental animal tumours were measured. Unlike the leukaemic lymphoblasts of man, those of two spontaneous rat leukaemias did not have elevated levels of the enzyme. Very high levels were found in a rat plasma-cell tumour (IR 461) and an attempt was made to treat such tumours with the specific enzyme inhibitor, 2-deoxy-coformycin. The shortage of this drug prevented a systematic study, but a daily dose of 8 mg/kg had a significant inhibitory effect on the growth of tumours
Development of a test and flight engineering oriented language. Phase 1: Oral presentation material
The material used in an oral presentation of the phase 1 study effort is given. Phase 1 was directed at the examination of existing related languages and their applications
Single-Gate Accumulation-Mode InGaAs Quantum Dot with a Vertically Integrated Charge Sensor
We report on the fabrication and characterization of a few-electron quantum
dot controlled by a single gate electrode. Our device has a double-quantum-well
design, in which the doping controls the occupancy of the lower well while the
upper well remains empty under the free surface. A small air-bridged gate
contacts the surface, and is positively biased to draw laterally confined
electrons into the upper well. Electrons tunneling between this
accumulation-mode dot and the lower well are detected using a quantum point
contact (QPC), located slightly offset from the dot gate. The charge state of
the dot is measured by monitoring the differential transconductance of the QPC
near pinch-off. Addition spectra starting with N=0 were observed as a function
of gate voltage. DC sensitivity to single electrons was determined to be as
high as 8.6%, resulting in a signal-to-noise ratio of ~9:1 with an equivalent
noise bandwidth of 12.1 kHz. Analysis of random telegraph signals associated
with the zero to one electron transition allowed a measurement of the lifetimes
for the filled and empty states of the one-electron dot: 0.38 ms and 0.22 ms,
respectively, for a device with a 10 nm AlInAs tunnel barrier between the two
wells.Comment: 3 pages, 3 figure
A Hybrid Monte Carlo Method for Surface Growth Simulations
We introduce an algorithm for treating growth on surfaces which combines
important features of continuum methods (such as the level-set method) and
Kinetic Monte Carlo (KMC) simulations. We treat the motion of adatoms in
continuum theory, but attach them to islands one atom at a time. The technique
is borrowed from the Dielectric Breakdown Model. Our method allows us to give a
realistic account of fluctuations in island shape, which is lacking in
deterministic continuum treatments and which is an important physical effect.
Our method should be most important for problems close to equilibrium where KMC
becomes impractically slow.Comment: 4 pages, 5 figure
Linear theory of unstable growth on rough surfaces
Unstable homoepitaxy on rough substrates is treated within a linear continuum
theory. The time dependence of the surface width is governed by three
length scales: The characteristic scale of the substrate roughness, the
terrace size and the Ehrlich-Schwoebel length . If (weak step edge barriers) and ,
then displays a minimum at a coverage , where the initial surface width is reduced by a factor
. The r\^{o}le of deposition and diffusion noise is analyzed. The
results are applied to recent experiments on the growth of InAs buffer layers
[M.F. Gyure {\em et al.}, Phys. Rev. Lett. {\bf 81}, 4931 (1998)]. The overall
features of the observed roughness evolution are captured by the linear theory,
but the detailed time dependence shows distinct deviations which suggest a
significant influence of nonlinearities
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