1,173 research outputs found
A Necessary And Sufficient Condition of Distillability with unite fidelity from Finite Copies of a Mixed State: The Most Efficient Purification Protocol
It is well known that any entangled mixed state in systems can
be purified via infinite copies of the mixed state. But can one distill a pure
maximally entangled state from finite copies of a mixed state in any bipartite
system by local operation and classical communication? This is more meaningful
in practical application. We give a necessary and sufficient condition of this
distillability. This condition can be expressed as: there exists
distillable-subspaces. According to this condition, one can judge whether a
mixed state is distillable or not easily. We also analyze some properties of
distillable-subspaces, and discuss the most efficient purification protocols.
Finally, we discuss the distillable enanglement of two-quibt system for the
case of finite copies.Comment: a revised versio
Entanglement and Berry Phase in a dimensional Yang-Baxter system
Based on the method which is given in Ref. [Sun et.al. arXiv:0904.0092v1], we
present another unitary matrix, solution of the
Yang-Baxter Equation, is obtained in this paper. The entanglement properties of
matrix is investigated, and the arbitrary degree of entanglement
for two-qutrit entangled states can be generated via -matrix acting
on the standard basis. A Yang-Baxter Hamiltonian can be constructed from
unitary matrix. Then the geometric properties of this system is
studied. The results showed that the Berry phase of this system can be
represented under the framework of SU(2) algebra.Comment: 6 page
Neutron Transfer Dynamics and Doorway to Fusion in Time-Dependent Hartree-Fock Theory
We analyze the details of mass exchange in the vicinity of the Coulomb
barrier for heavy-ion collisions involving neutron-rich nuclei using the
time-dependent Hartree-Fock (TDHF) theory. We discuss the time-dependence of
transfer and show that the potential barriers seen by individual
single-particle states can be considerably different than the effective barrier
for the two interacting nuclei having a single center-of-mass. For this reason
we observe a substantial transfer probability even at energies below the
effective barrier.Comment: 6 pages, 9 figure
Demonstration of large ionization coefficient ratio in AlAs0.56Sb0.44 lattice matched to InP
The electron and hole avalanche multiplication characteristics have been measured in bulk AlAs0.56Sb0.44 p-i-n and n-i-p homojunction diodes, lattice matched to InP, with nominal avalanche region thicknesses of ~0.6 μm, 1.0 μm and 1.5 μm. From these and data from two much thinner devices, the bulk electron and hole impact ionization coefficients (α and β respectively), have been determined over an electric-field range from 220-1250 kV/cm for α and from 360-1250 kV/cm for β for the first time. The α/β ratio is found to vary from 1000 to 2 over this field range, making it the first report of a wide band-gap III-V semiconductor with ionization coefficient ratios similar to or larger than that observed in silicon
Relations between entanglement, Bell-inequality violation and teleportation fidelity for the two-qubit X states
Based on the assumption that the receiver Bob can apply any unitary
transformation, Horodecki {\it et al.} [Phys. Lett. A {\bf 222}, 21 (1996)]
proved that any mixed two spin-1/2 state which violates the Bell-CHSH
inequality is useful for teleportation. Here, we further show that any X state
which violates the Bell-CHSH inequality can also be used for nonclassical
teleportation even if Bob can only perform the identity or the Pauli rotation
operations. Moreover, we showed that the maximal difference between the two
average fidelities achievable via Bob's arbitrary transformations and via the
sole identity or the Pauli rotation is 1/9.Comment: 5 pages, to be published in "Quantum Information Processing
Pedagogical demonstration of twitter data analysis: A case study of world AIDS day, 2014
As a pedagogical demonstration of Twitter data analysis, a case study of HIV/AIDS-related tweets around World AIDS Day, 2014, was presented. This study examined if Twitter users from countries with various income levels responded differently to World AIDS Day. The performance of support vector machine (SVM) models as classifiers of relevant tweets was evaluated. A manual coding of 1,826 randomly sampled HIV/AIDS-related original tweets from November 30 through December 2, 2014 was completed. Logistic regression was applied to analyze the association between the World Bank-designated income level of users’ self-reported countries and Twitter contents. To identify the optimal SVM model, 1278 (70%) of the 1826 sampled tweets were randomly selected as the training set, and 548 (30%) served as the test set. Another 180 tweets were separately sampled and coded as the held-out dataset. Compared with tweets from low-income countries, tweets from the Organization for Economic Cooperation and Development countries had 60% lower odds to mention epidemiology (adjusted odds ratio, aOR = 0.404; 95% CI: 0.166, 0.981) and three times the odds to mention compassion/support (aOR = 3.080; 95% CI: 1.179, 8.047). Tweets from lower-middle-income countries had 79% lower odds than tweets from low-income countries to mention HIV-affected sub-populations (aOR = 0.213; 95% CI: 0.068, 0.664). The optimal SVM model was able to identify relevant tweets from the held-out dataset of 180 tweets with an accuracy (F1 score) of 0.72. This study demonstrated how students can be taught to analyze Twitter data using manual coding, regression models, and SVM models
Understorey plant community and light availability in conifer plantations and natural hardwood forests in Taiwan
Questions: What are the effects of replacing mixed species natural forests with Cryptomeria japonica plantations on understorey plant functional and species diversity? What is the role of the understorey light environment in determining understorey diversity and community in the two types of forest?
Location: Subtropical northeast Taiwan.
Methods: We examined light environments using hemispherical photography, and diversity and composition of understorey plants of a 35‐yr C. japonica plantation and an adjacent natural hardwood forest.
Results: Understorey plant species richness was similar in the two forests, but the communities were different; only 18 of the 91 recorded understorey plant species occurred in both forests. Relative abundance of plants among different functional groups differed between the two forests. Relative numbers of shade‐tolerant and shade‐intolerant seedling individuals were also different between the two forest types with only one shade‐intolerant seedling in the plantation compared to 23 seedlings belonging to two species in the natural forest. In the natural forest 11 species of tree seedling were found, while in the plantation only five were found, and the seedling density was only one third of that in the natural forest. Across plots in both forests, understorey plant richness and diversity were negatively correlated with direct sunlight but not indirect sunlight, possibly because direct light plays a more important role in understorey plant growth.
Conclusions: We report lower species and functional diversity and higher light availability in a natural hardwood forest than an adjacent 30‐yr C. japonica plantation, possibly due to the increased dominance of shade‐intolerant species associated with higher light availability. To maintain plant diversity, management efforts must be made to prevent localized losses of shade‐adapted understorey plants
Tunneling Conductance and Coulomb Blockade Peak Splitting of Two Quantum Dots Connected by a Quantum Point Contact
By using bosonization method and unitary transformation, we give a general
relation between the dimensionless tunneling conductance and the fractional
Coulomb blockade conductance peak splitting which is valid both for weak and
strong transmission between two quantum dots, and show that the tunneling
conductance has a linear temperature dependence in the low energy and low
temperature limit.Comment: 12 pages, Revtex, no figures, to appear in Phys. Rev.
Cyclin D1 acts as a barrier to pluripotent reprogramming by promoting neural progenitor fate commitment
AbstractA short G1 phase is a characteristic feature of the cell cycle structure of pluripotent cells, and is reestablished during Yamanaka factor-mediated pluripotent reprogramming. How cell cycle control is adjusted to meet the requirements of pluripotent cell fate commitment during reprogramming is less well understood. Elevated levels of cyclin D1 were initially found to impair pluripotency maintenance. The current work further identified Cyclin D1 to be capable of transcriptionally upregulating Pax6, which promoted reprogramming cells to commit to a neural progenitor fate rather than a pluripotent cell fate. These findings explain the importance of reestablishment of G1-phase restriction in pluripotent reprogramming
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