13,458 research outputs found
Fully fault tolerant quantum computation with non-deterministic gates
In certain approaches to quantum computing the operations between qubits are
non-deterministic and likely to fail. For example, a distributed quantum
processor would achieve scalability by networking together many small
components; operations between components should assumed to be failure prone.
In the logical limit of this architecture each component contains only one
qubit. Here we derive thresholds for fault tolerant quantum computation under
such extreme paradigms. We find that computation is supported for remarkably
high failure rates (exceeding 90%) providing that failures are heralded,
meanwhile the rate of unknown errors should not exceed 2 in 10^4 operations.Comment: 5 pages, 3 fig
Measurement-based approach to entanglement generation in coupled quantum dots
Measurements provide a novel mechanism for generating the entanglement
resource necessary for performing scalable quantum computation. Recently, we
proposed a method for performing parity measurements in a coupled quantum dot
system. In this paper we generalise this scheme and perform a comprehensive
analytic and numerical study of environmental factors. We calculate the effects
of possible error sources including non-ideal photon detectors, ineffective
spin-selective excitation and dot distinguishability (both spatial and
spectral). Furthermore, we present an experimental approach for verifying the
success of the parity measurement
Optimized imaging using non-rigid registration
The extraordinary improvements of modern imaging devices offer access to data
with unprecedented information content. However, widely used image processing
methodologies fall far short of exploiting the full breadth of information
offered by numerous types of scanning probe, optical, and electron
microscopies. In many applications, it is necessary to keep measurement
intensities below a desired threshold. We propose a methodology for extracting
an increased level of information by processing a series of data sets
suffering, in particular, from high degree of spatial uncertainty caused by
complex multiscale motion during the acquisition process. An important role is
played by a nonrigid pixel-wise registration method that can cope with low
signal-to-noise ratios. This is accompanied by formulating objective quality
measures which replace human intervention and visual inspection in the
processing chain. Scanning transmission electron microscopy of siliceous
zeolite material exhibits the above-mentioned obstructions and therefore serves
as orientation and a test of our procedures
GMC Collisions as Triggers of Star Formation. V. Observational Signatures
We present calculations of molecular, atomic and ionic line emission from
simulations of giant molecular cloud (GMC) collisions. We post-process
snapshots of the magneto-hydrodynamical simulations presented in an earlier
paper in this series by Wu et al. (2017) of colliding and non-colliding GMCs.
Using photodissociation region (PDR) chemistry and radiative transfer we
calculate the level populations and emission properties of CO ,
[CI] at m, [CII] m and [OI]
transition at m. From integrated
intensity emission maps and position-velocity diagrams, we find that
fine-structure lines, particularly the [CII] m, can be used as a
diagnostic tracer for cloud-cloud collision activity. These results hold even
in more evolved systems in which the collision signature in molecular lines has
been diminished.Comment: 10 pages, 7 figures, accepted for publication in ApJ, comments
welcom
Nonproductive Events in Ring-Closing Metathesis Using Ruthenium Catalysts
The relative TONs of productive and nonproductive metathesis reactions of diethyl diallylmalonate are compared for eight different ruthenium-based catalysts. Nonproductive cross metathesis is proposed to involve a chain-carrying ruthenium methylidene. A second more-challenging substrate (dimethyl allylmethylallylmalonate) that forms a trisubstituted olefin product is used to further delineate the effect of catalyst structure on the relative efficiencies of these processes. A steric model is proposed to explain the observed trends
- …