Universal Quantum Degeneracy Point for Superconducting Qubits

The quantum degeneracy point approach [D. Vion et al., Science 296, 886 (2002)] effectively protects superconducting qubits from low-frequency noise that couples with the qubits as transverse noise. However, low-frequency noise in superconducting qubits can originate from various mechanisms and can couple with the qubits either as transverse or as longitudinal noise. Here, we present a quantum circuit containing a universal quantum degeneracy point that protects an encoded qubit from arbitrary low-frequency noise. We further show that universal quantum logic gates can be performed on the encoded qubit with high gate fidelity. The proposed scheme is robust against small parameter spreads due to fabrication errors in the superconducting qubits.Comment: 7 pages, 4 figure

The ground state entanglement in the XXZXXZ model

In this paper, we investigate spin entanglement in the $XXZ$ model defined on a $d$-dimensional bipartite lattice. The concurrence, a measure of the entanglement between two spins, is analyzed. We prove rigorously that the ground state concurrence reaches maximum at the isotropic point. For dimensionality $d \ge 2$, the concurrence develops a cusp at the isotropic point and we attribute it to the existence of magnetic long-range order.Comment: 5 pages, 2 figure

CD133, Stem Cells, and Cancer Stem Cells: Myth or Reality?

CD133, a member of the prominin family, is found in a variety of tissues with at least three variants. The function of CD133 is not well understood, but its expression is subject to changes in the microenvironment cues including bioenergetic stress. Knockout of CD133 does not affect renewal, but mammary gland branching. A point mutation of CD133 (R733C) leads to retinal disorder. CD133 is found in embryonic stem cells, normal tissue stem cells, stem cell niches, and circulating endothelial progenitors as well as cancer stem cells. Maintenance of stemness in cancer may be attributable to asymmetric cell division in association with a set of embryonic expression signatures in CD133+ tumor cells. CD133 could enrich cancer stem cells, which are associated with chemo- and radiation resistance phenotype. High CD133 is associated with poor survival in a variety of solid tumors, including lung, colon, prostate, etc. Monitoring CD133+ cells in peripheral blood, and targeting CD133 in cancer, may further predict and improve the clinical outcomes

Toward better data veracity in mobile cloud computing: A context-aware and incentive-based reputation mechanism

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.As a promising next-generation computing paradigm, Mobile Cloud Computing (MCC) enables the large-scale collection and big data processing of personal private data. An important but often overlooked V of big data is data veracity, which ensures that the data used are trusted, authentic, accurate and protected from unauthorized access and modification. In order to realize the veracity of data in MCC, specific trust models and approaches must be developed. In this paper, a Category-based Context-aware and Recommendation incentive-based reputation Mechanism (CCRM) is proposed to defend against internal attacks and enhance data veracity in MCC. In the CCRM, innovative methods, including a data category and context sensing technology, a security relevance evaluation model, and a Vickrey-Clark-Groves (VCG)-based recommendation incentive scheme, are integrated into the process of reputation evaluation. Cost analysis indicates that the CCRM has a linear communication and computation complexity. Simulation results demonstrate the superior performance of the CCRM compared to existing reputation mechanisms under internal collusion attacks and bad mouthing attacks.This work is supported by the National Natural Science Foundation of China (61363068, 61472083, 61671360), the Pilot Project of Fujian Province (formal industry key project) (2016Y0031), the Foundation of Science and Technology on Information Assurance Laboratory (KJ-14-109) and the Fujian Provincial Key Laboratory of Network Security and Cryptology Research Fund

Distribution of biomass and diversity of Stipa bungeana community to climatic factors in the Loess Plateau of northwestern China

Based on 28 year field data of Stipa bungeana community in arid, semi-arid, semi-humid areas of the Loess Plateau of Northwestern China, we studied species diversity and above ground biomass of S. bungeana community, analyzed the responses of above ground biomass to climate in different areas, and built a model of relationship between biomass and climatic factors. Results showed that there were significant differences for species diversity and above ground biomass among different sampling area. The species diversity range of S. bungeana was from 8.5 - 30.8 (ind/m2), and above ground biomass range was from 407.3 - 817.3 (g/m2) among studied area. The optimal distribution altitude range for S. bungeana is 1400 - 2000 m in arid area, 1200 - 1900 m in semi-arid area, and 600 - 1600 m in semi-humid area. Results also showed that the growth of S. bungeana was affected by different climatic factors, with rainfall as the major factor. Meanwhile, there was a close relationship between monthly biomass and rainfall during the growth stage. The models of monthly biomass and climate were built to compare the results and reveal the relationship between climatic factors and the growth of S. bungeana community.Key words: Stipa bungeana community, biomass model, species diversity, climatic factor, Loess Plateau

Uptake, sequestration and tolerance of cadmium at cellular levels in the hyperaccumulator plant species Sedum alfredii.

Sedum alfredii is one of a few plant species known to hyperaccumulate cadmium (Cd). Uptake, localization, and tolerance of Cd at cellular levels in shoots were compared in hyperaccumulating (HE) and non-hyperaccumulating (NHE) ecotypes of Sedum alfredii. X-ray fluorescence images of Cd in stems and leaves showed only a slight Cd signal restricted within vascular bundles in the NHEs, while enhanced localization of Cd, with significant tissue- and age-dependent variations, was detected in HEs. In contrast to the vascular-enriched Cd in young stems, parenchyma cells in leaf mesophyll, stem pith and cortex tissues served as terminal storage sites for Cd sequestration in HEs. Kinetics of Cd transport into individual leaf protoplasts of the two ecotypes showed little difference in Cd accumulation. However, far more efficient storage of Cd in vacuoles was apparent in HEs. Subsequent analysis of cell viability and hydrogen peroxide levels suggested that HE protoplasts exhibited higher resistance to Cd than those of NHE protoplasts. These results suggest that efficient sequestration into vacuoles, as opposed to rapid transport into parenchyma cells, is a pivotal process in Cd accumulation and homeostasis in shoots of HE S. alfredii. This is in addition to its efficient root-to-shoot translocation of Cd

Breakdown effect of periodic perturbations to the robustness of topological phase\\ in a gyromagnetic photonic crystal

In the known field of topological photonics, what remains less so is the breakdown effect of topological phases deteriorated by perturbation. In this paper, we investigate the variance on topological invariants for a periodic Kekul\'e medium perturbed in unit cells, which was a gyromagnetic photonic crystal holding topological phases induced by \emph{synchronized rotation} of unit cells. Two parameters for geometric and material perturbation are respectively benchmarked to characterise the topological degradation. Our calculation demonstrates that such a periodic perturbation easily destructs the topological phase, and thus calls for further checkups on robustness under such unit-cell-perturbation in realization.Comment: 9 pages, 6 figures, 1 table, re-submitted to Phys. Lett.