6,886 research outputs found
Random subspaces for encryption based on a private shared Cartesian frame
A private shared Cartesian frame is a novel form of private shared
correlation that allows for both private classical and quantum communication.
Cryptography using a private shared Cartesian frame has the remarkable property
that asymptotically, if perfect privacy is demanded, the private classical
capacity is three times the private quantum capacity. We demonstrate that if
the requirement for perfect privacy is relaxed, then it is possible to use the
properties of random subspaces to nearly triple the private quantum capacity,
almost closing the gap between the private classical and quantum capacities.Comment: 9 pages, published versio
A Survey of Mucilaginous Testa in \u3ci\u3eChamaesyce\u3c/i\u3e
Seeds of Chamaesyce were studied for presence of mucilaginous testa. Samples were selected to represent all major systematic sections within the genus. Observations were made with a dissecting microscope following brief hydration of seeds; additional SEM observations of both intact and fractured dry seeds were made for selected species. With few exceptions, most of Boissier\u27s subsections test positively for seed mucilage; however, mucilage is generally absent in subsections Gymnadeniae and Sclerophyllae , for which absence of mucilage is regarded as secondary loss from mucilagionus ancestors. Although mucilage production is associated with a well-defined subepidermal layer of macroesclereids, it is the surface layer of cells that actually secrete mucilage. Mucilage secreting cells and macroesclereids of mature testa are interpretted to develop from the epidermal layers of outer and inner integuments, respectively. Seed mucilages may play a role in seed hydration and/or seed dispersal
Random quantum codes from Gaussian ensembles and an uncertainty relation
Using random Gaussian vectors and an information-uncertainty relation, we
give a proof that the coherent information is an achievable rate for
entanglement transmission through a noisy quantum channel. The codes are random
subspaces selected according to the Haar measure, but distorted as a function
of the sender's input density operator. Using large deviations techniques, we
show that classical data transmitted in either of two Fourier-conjugate bases
for the coding subspace can be decoded with low probability of error. A
recently discovered information-uncertainty relation then implies that the
quantum mutual information for entanglement encoded into the subspace and
transmitted through the channel will be high. The monogamy of quantum
correlations finally implies that the environment of the channel cannot be
significantly coupled to the entanglement, and concluding, which ensures the
existence of a decoding by the receiver.Comment: 9 pages, two-column style. This paper is a companion to
quant-ph/0702005 and quant-ph/070200
Wood Anatomy and Relationships of Neowawraea (Euphorbiaceae)
Wood anatomy of three specimens of Neowawraea phyllanthoides Rock, a rare and endangered member of Euphorbiaceae endemic to the Hawaiian Islands, is described and compared with woods of other genera of subfamily Phyllanthoideae. Neowawraea has often been associated or synonymized with Drypetes Vahl. Wood of Neowawraea is diffuse porous, perforation plates are simple, imperforate tracheary elements are thin-walled septate fiber-tracheids, rays are heterocellular and crystalliferous, and axial xylem parenchyma is restricted to a few scanty paratracheal and terminal cells. In several respects these results differ from earlier published descriptions of the wood of this taxon; these earlier descriptions are shown to be in error. Further, as described here, wood of Neowawraea differs greatly from that of Drypetes. Accordingly, generic status for Neowawraea is warranted on anatomical grounds and relationship with certain genera of tribe Phyllantheae such as Breynia Forst., Glochidion Forst., or Phyllanthus L. is favored over relationship with Drypetes
Orbital transfer vehicle oxygen turbopump technology. Volume 1: Design, fabrication, and hydrostatic bearing testing
The design, fabrication, and initial testing of a rocket engine turbopump (TPA) for the delivery of high pressure liquid oxygen using hot oxygen for the turbine drive fluid are described. This TPA is basic to the dual expander engine which uses both oxygen and hydrogen as working fluids. Separate tasks addressed the key issue of materials for this TPA. All materials selections emphasized compatibility with hot oxygen. The OX TPA design uses a two-stage centrifugal pump driven by a single-stage axial turbine on a common shaft. The design includes ports for three shaft displacement/speed sensors, various temperature measurements, and accelerometers
A Comparison of the High-Frequency Magnetic Fluctuations in Insulating and Superconducting La2-xSrxCuO4
Inelastic neutron scattering performed at a spallation source is used to make
absolute measurements of the dynamic susceptibility of insulating La2CuO4 and
superconducting La2-xSrxCuO4 over the energy range 15<EN<350 meV. The effect of
Sr doping on the magnetic excitations is to cause a large broadening in
wavevector and a substantial change in the spectrum of the local spin
fluctuations. Comparison of the two compositions reveals a new energy scale of
22 meV in La1.86Sr0.14CuO4.Comment: RevTex, 7 Pages, 4 postscript figure
Relativistically covariant state-dependent cloning of photons
The influence of the relativistic covariance requirement on the optimality of
the symmetric state-dependent 1 -> 2 cloning machine is studied. Namely, given
a photonic qubit whose basis is formed from the momentum-helicity eigenstates,
the change to the optimal cloning fidelity is calculated taking into account
the Lorentz covariance unitarily represented by Wigner's little group. To
pinpoint some of the interesting results, we found states for which the optimal
fidelity of the cloning process drops to 2/3 which corresponds to the fidelity
of the optimal classical cloner. Also, an implication for the security of the
BB84 protocol is analyzed.Comment: corrected, rewritten and accepted in PR
No Evidence for Orbital Loop Currents in Charge Ordered YBaCuO from Polarized Neutron Diffraction
It has been proposed that the pseudogap state of underdoped cuprate
superconductors may be due to a transition to a phase which has circulating
currents within each unit cell. Here, we use polarized neutron diffraction to
search for the corresponding orbital moments in two samples of underdoped
YBaCuO with doping levels and 0.123. In contrast to
some other reports using polarized neutrons, but in agreement with nuclear
magnetic resonance and muon spin rotation measurements, we find no evidence for
the appearance of magnetic order below 300 K. Thus, our experiment suggests
that such order is not an intrinsic property of high-quality cuprate
superconductor single crystals. Our results provide an upper bound for a
possible orbital loop moment which depends on the pattern of currents within
the unit cell. For example, for the CC- pattern proposed by Varma,
we find that the ordered moment per current loop is less than 0.013 for
.Comment: Comments in arXiv:1710.08173v1 fully addresse
- …