2,377 research outputs found
Cellular-automaton decoders with provable thresholds for topological codes
We propose a new cellular automaton (CA), the Sweep Rule, which generalizes
Toom's rule to any locally Euclidean lattice. We use the Sweep Rule to design a
local decoder for the toric code in dimensions, the Sweep Decoder,
and rigorously establish a lower bound on its performance. We also numerically
estimate the Sweep Decoder threshold for the three-dimensional toric code on
the cubic and body-centered cubic lattices for phenomenological phase-flip
noise. Our results lead to new CA decoders with provable error-correction
thresholds for other topological quantum codes including the color code.Comment: 4+8 pages, 5 figure
Efficient color code decoders in dimensions from toric code decoders
We introduce an efficient decoder of the color code in dimensions,
the Restriction Decoder, which uses any -dimensional toric code decoder
combined with a local lifting procedure to find a recovery operation. We prove
that the Restriction Decoder successfully corrects errors in the color code if
and only if the corresponding toric code decoding succeeds. We also numerically
estimate the Restriction Decoder threshold for the color code in two and three
dimensions against the bit-filp and phase-flip noise with perfect syndrome
extraction. We report that the 2D color code threshold on the square-octagon lattice is on a par with the toric code threshold
on the square lattice.Comment: 28 pages, 8 figure
LSST: Comprehensive NEO Detection, Characterization, and Orbits
(Abridged) The Large Synoptic Survey Telescope (LSST) is currently by far the
most ambitious proposed ground-based optical survey. Solar System mapping is
one of the four key scientific design drivers, with emphasis on efficient
Near-Earth Object (NEO) and Potentially Hazardous Asteroid (PHA) detection,
orbit determination, and characterization. In a continuous observing campaign
of pairs of 15 second exposures of its 3,200 megapixel camera, LSST will cover
the entire available sky every three nights in two photometric bands to a depth
of V=25 per visit (two exposures), with exquisitely accurate astrometry and
photometry. Over the proposed survey lifetime of 10 years, each sky location
would be visited about 1000 times. The baseline design satisfies strong
constraints on the cadence of observations mandated by PHAs such as closely
spaced pairs of observations to link different detections and short exposures
to avoid trailing losses. Equally important, due to frequent repeat visits LSST
will effectively provide its own follow-up to derive orbits for detected moving
objects. Detailed modeling of LSST operations, incorporating real historical
weather and seeing data from LSST site at Cerro Pachon, shows that LSST using
its baseline design cadence could find 90% of the PHAs with diameters larger
than 250 m, and 75% of those greater than 140 m within ten years. However, by
optimizing sky coverage, the ongoing simulations suggest that the LSST system,
with its first light in 2013, can reach the Congressional mandate of cataloging
90% of PHAs larger than 140m by 2020.Comment: 10 pages, color figures, presented at IAU Symposium 23
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