1,830 research outputs found
Schur-Weyl Duality for the Clifford Group with Applications: Property Testing, a Robust Hudson Theorem, and de Finetti Representations
Schur-Weyl duality is a ubiquitous tool in quantum information. At its heart
is the statement that the space of operators that commute with the tensor
powers of all unitaries is spanned by the permutations of the tensor factors.
In this work, we describe a similar duality theory for tensor powers of
Clifford unitaries. The Clifford group is a central object in many subfields of
quantum information, most prominently in the theory of fault-tolerance. The
duality theory has a simple and clean description in terms of finite
geometries. We demonstrate its effectiveness in several applications:
(1) We resolve an open problem in quantum property testing by showing that
"stabilizerness" is efficiently testable: There is a protocol that, given
access to six copies of an unknown state, can determine whether it is a
stabilizer state, or whether it is far away from the set of stabilizer states.
We give a related membership test for the Clifford group.
(2) We find that tensor powers of stabilizer states have an increased
symmetry group. We provide corresponding de Finetti theorems, showing that the
reductions of arbitrary states with this symmetry are well-approximated by
mixtures of stabilizer tensor powers (in some cases, exponentially well).
(3) We show that the distance of a pure state to the set of stabilizers can
be lower-bounded in terms of the sum-negativity of its Wigner function. This
gives a new quantitative meaning to the sum-negativity (and the related mana)
-- a measure relevant to fault-tolerant quantum computation. The result
constitutes a robust generalization of the discrete Hudson theorem.
(4) We show that complex projective designs of arbitrary order can be
obtained from a finite number (independent of the number of qudits) of Clifford
orbits. To prove this result, we give explicit formulas for arbitrary moments
of random stabilizer states.Comment: 60 pages, 2 figure
Rabbit reticulocyte double-stranded RNA-activated protein kinase and the hemin-controlled translational repressor phosphorylate the same Mr 1500 peptide of eukaryotic initiation factor 2α
A BVRcIc Survey of W Ursae Majoris Binaries
We report on a BVRcIc survey of field W Ursae Majoris binary stars and
present accurate colors for 606 systems that have been observed on at least
three photometric nights from a robotic observatory in southern Arizona.
Comparison with earlier photometry for a subset of the systems shows good
agreement. We investigate two independent methods of determining the
interstellar reddening, although both have limitations that can render them
less effective than desired. A subset of 101 systems shows good agreement
between the two reddening methods.Comment: 10 pages, 6 figures, accepted for publication in A
The Ultrastructure of the Skin of Human Embryos III. The Formation of the Nail in 16–18 Weeks Old Embryos**From the Department of Dermatology, Tufts University School of Medicine, and the Dermatology Research Laboratories, New England Medical Center Hospitals and Boston City Hospital, Boston, Massachusetts.
The non-abelian Born-Infeld action at order F^6
To gain insight into the non-abelian Born-Infeld (NBI) action, we study
coinciding D-branes wrapped on tori, and turn on magnetic fields on their
worldvolume. We then compare predictions for the spectrum of open strings
stretching between these D-branes, from perturbative string theory and from the
effective NBI action. Under some plausible assumptions, we find corrections to
the Str-prescription for the NBI action at order F^6. In the process we give a
way to classify terms in the NBI action that can be written in terms of field
strengths only, in terms of permutation group theory.Comment: LaTeX, 31 pages, 30 figure
The Cyborg Astrobiologist: Testing a Novelty-Detection Algorithm on Two Mobile Exploration Systems at Rivas Vaciamadrid in Spain and at the Mars Desert Research Station in Utah
(ABRIDGED) In previous work, two platforms have been developed for testing
computer-vision algorithms for robotic planetary exploration (McGuire et al.
2004b,2005; Bartolo et al. 2007). The wearable-computer platform has been
tested at geological and astrobiological field sites in Spain (Rivas
Vaciamadrid and Riba de Santiuste), and the phone-camera has been tested at a
geological field site in Malta. In this work, we (i) apply a Hopfield
neural-network algorithm for novelty detection based upon color, (ii) integrate
a field-capable digital microscope on the wearable computer platform, (iii)
test this novelty detection with the digital microscope at Rivas Vaciamadrid,
(iv) develop a Bluetooth communication mode for the phone-camera platform, in
order to allow access to a mobile processing computer at the field sites, and
(v) test the novelty detection on the Bluetooth-enabled phone-camera connected
to a netbook computer at the Mars Desert Research Station in Utah. This systems
engineering and field testing have together allowed us to develop a real-time
computer-vision system that is capable, for example, of identifying lichens as
novel within a series of images acquired in semi-arid desert environments. We
acquired sequences of images of geologic outcrops in Utah and Spain consisting
of various rock types and colors to test this algorithm. The algorithm robustly
recognized previously-observed units by their color, while requiring only a
single image or a few images to learn colors as familiar, demonstrating its
fast learning capability.Comment: 28 pages, 12 figures, accepted for publication in the International
Journal of Astrobiolog
Image Compression for Geological Mapping and Novelty Detection
We describe an image-comparison technique of Heidemann and Ritter [4,5] that
uses image compression, and is capable of: (i) detecting novel textures in a
series of images, as well as of: (ii) alerting the user to the similarity of a
new image to a previously-observed texture. This image-comparison technique
has been implemented and tested using our Astrobiology Phone-cam system, which
employs Bluetooth communication to send images to a local laptop server in the
field for the image-compression analysis. We tested the system in a field site
displaying a heterogeneous suite of sandstones, limestones, mudstones and
coalbeds. Some of the rocks are partly covered with lichen. The imagematching
procedure of this system performed very well with data obtained through our
field test, grouping all images of yellow lichens together and grouping all
images of a coal bed together, and giving a 91% accuracy for similarity
detection. Such similarity detection could be employed to make maps of
different geological units. The novelty-detection performance of our system
was also rather good (a 64% accuracy). Such novelty detection may become
valuable in searching for new geological units, which could be of
astrobiological interest. By providing more advanced capabilities for
similarity detection and novelty detection, this image-compression technique
could be useful in giving more scientific autonomy to robotic planetary
rovers, and in assisting human astronauts in their geological exploration
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