29,371 research outputs found
Teleportation of the one-qubit state in decoherence environments
We study standard quantum teleportation of one-qubit state for the situation
in which the channel is subject to decoherence, and where the evolution of the
channel state is ruled by a master equation in the Lindblad form. A detailed
calculation reveals that the quality of teleportation is determined by both the
entanglement and the purity of the channel state, and only the optimal matching
of them ensures the highest fidelity of standard quantum teleportation. Also
our results demonstrated that the decoherence induces distortion of the Bloch
sphere for the output state with different rates in different directions, which
implies that different input states will be teleported with different
fidelities.Comment: 17 pages, 10 figure
Infrared optical absorption spectra of CuO single crystals: Fermion-spinon band and dimensional crossover of the antiferromagnetic order
We have obtained mid-infrared optical absorption spectra of the S=1/2 quasi
one-dimensional CuO using polarized transmission measurement and interpreted
the spectra in terms of phonon assisted magnetic excitations. When the electric
field is parallel to the main antiferromagnetic direction a Delta shaped peak
is observed with the maximum at 0.23eV which is attributed to spinons along
Cu-O chains. At low temperatures in the antiferromagnetic phase another peak
appears at 0.16eV which is attributed to two-magnon absorption but the spinon
peak remains. This behavior is interpreted as due to a dimensional crossover
where the low temperature three-dimensional magnetic phase keeps short range
characteristics of a one-dimensional magnet.Comment: 5 pages, 5 figure
Dynamic Creation and Annihilation of Metastable Vortex Phase as a Source of Excess Noise
The large increase in voltage noise, commonly observed in the vicinity of the
peak-effect in superconductors, is ascribed to a novel noise mechanism. A
strongly pinned metastable disordered vortex phase, which is randomly generated
at the edges and annealed into ordered phase in the bulk, causes large
fluctuations in the integrated critical current of the sample. The excess noise
due to this dynamic admixture of two distinct phases is found to display
pronounced reentrant behavior. In the Corbino geometry the injection of the
metastable phase is prevented and, accordingly, the excess noise disappearsComment: 5 pages 3 figures. Accepted for publication in Europhysics letter
Melting of Charge/Orbital Ordered States in NdSrMnO: Temperature and Magnetic Field Dependent Optical Studies
We investigated the temperature ( 15 290 K) and the magnetic
field ( 0 17 T) dependent optical conductivity spectra of a
charge/orbital ordered manganite, NdSrMnO. With variation
of and , large spectral weight changes were observed up to 4.0 eV. These
spectral weight changes could be explained using the polaron picture.
Interestingly, our results suggested that some local ordered state might remain
above the charge ordering temperature, and that the charge/orbital melted state
at a high magnetic field (i.e. at 17 T and 4.2 K) should be a three
dimensional ferromagnetic metal. We also investigated the first order phase
transition from the charge/orbital ordered state to ferromagnetic metallic
state using the - and % -dependent dielectric constants . In
the charge/orbital ordered insulating state, was positive and
. With increasing and , was
increased up to the insulator-metal phase boundaries. And then,
abruptly changed into negative and , which was
consistent with typical responses of a metal. Through the analysis of using an effective medium approximation, we found that the melting
of charge/orbital ordered states should occur through the percolation of
ferromagnetic metal domains.Comment: submitted to Phys. Rev.
PHO1 Exports Phosphate from the Chalazal Seed Coat to the Embryo in Developing Arabidopsis Seeds.
Seed production requires the transfer of nutrients from the maternal seed coat to the filial endosperm and embryo. Because seed coat and filial tissues are symplasmically isolated, nutrients arriving in the seed coat via the phloem must be exported to the apoplast before reaching the embryo. Proteins implicated in the transfer of inorganic phosphate (Pi) from the seed coat to the embryo are unknown despite seed P content being an important agronomic trait. Here we show that the Arabidopsis Pi exporters PHO1 and PHOH1 are expressed in the chalazal seed coat (CZSC) of developing seeds. PHO1 is additionally expressed in developing ovules. Phosphorus (P) content and Pi flux between the seed coat and embryo were analyzed in seeds from grafts between WT roots and scions from either pho1, phoh1, or the pho1 phoh1 double mutant. Whereas P content and distribution between the seed coat and embryo in fully mature dry seeds of these mutants are similar to the WT, at the mature green stage of seed development the seed coat of the pho1 and pho1 phoh1 mutants, but not of the phoh1 mutant, retains approximately 2-fold more P than its WT control. Expression of PHO1 under a CZSC-specific promoter complemented the seed P distribution phenotype of the pho1 phoh1 double mutant. CZSC-specific down-expression of PHO1 also recapitulated the seed P distribution phenotype of pho1. Together, these experiments show that PHO1 expression in the CZSC is important for the transfer of P from the seed coat to the embryo in developing seeds
Infrared Hall conductivity of NaCoO
We report infrared Hall conductivity of
NaCoO thin films determined from Faraday rotation angle
measurements. exhibits two types of hole
conduction, Drude and incoherent carriers. The coherent Drude carrier shows a
large renormalized mass and Fermi liquid-like behavior of Hall scattering rate,
. The spectral weight is suppressed and disappears at T
= 120K. The incoherent carrier response is centered at mid-IR frequency and
shifts to lower energy with increasing T. Infrared Hall constant is positive
and almost independent of temperature in sharp contrast with the dc-Hall
constant.Comment: 5 Pages, 5 Figures. Author list corrected in metadata only, paper is
unchange
Dimensional Crossover driven by Magnetic Ordering in Optical Conductivity of Pr_{1/2}Sr_{1/2}MnO_3
We investigated optical properties of Pr_{0.5}Sr_{0.5}MnO_3, which has the
A-type antiferromagnetic ordering at a low temperature. We found that T-
dependence of spectral weight transfer shows a clear correlation with the
magnetic phase transition. In comparison with the optical conductivity results
of Nd_{0.5}Sr_{0.5}MnO_3, which has the CE-type antiferromagnetic charge
ordering, we showed that optical properties of Pr_{0.5}Sr_{0.5}MnO_3 near the
Neel temperature could be explained by a crossover from 3D to 2D metals.
Details of spectral weight changes are consistent with the polaron picture.Comment: 11 pages, 4 figures, submitted to PRL at June
Bias Dependent 1/f Conductivity Fluctuations in Low-Doped LaCaMnO Manganite Single Crystals
Low frequency noise in current biased LaCaMnO single
crystals has been investigated in a wide temperature range from 79 K to 290 K.
Despite pronounced changes in magnetic properties and dissipation mechanisms of
the sample with changing temperature, the noise spectra were found to be always
of the 1/f type and their intensity (except the lowest temperature studied)
scaled as a square of the bias. At liquid nitrogen temperatures and under bias
exceeding some threshold value, the behavior of the noise deviates from the
quasi-equilibrium modulation noise and starts to depend in a non monotonic way
on bias. It has been verified that the observed noise obeys Dutta and Horn
model of 1/f noise in solids. The appearance of nonequilibrium 1/f noise and
its dependence on bias have been associated with changes in the distribution of
activation energies in the underlying energy landscape. These changes have been
correlated with bias induced changes in the intrinsic tunneling mechanism
dominating dissipation in LaCaMnO at low temperatures.Comment: Accepted for publication in the Journal of Applied Physic
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