Experimental implementation of high-fidelity unconventional geometric quantum gates using NMR interferometer

Following a key idea of unconventional geometric quantum computation developed earlier [Phys. Rev. Lett. 91, 197902 (2003)], here we propose a more general scheme in such an intriguing way: $\gamma_{d}=\alpha_{g}+\eta \gamma _{g}$, where $\gamma_{d}$ and $\gamma_{g}$ are respectively the dynamic and geometric phases accumulated in the quantum gate operation, with $\eta$ as a constant and $\alpha_{g}$ being dependent only on the geometric feature of the operation. More arrestingly, we demonstrate the first experiment to implement a universal set of such kind of generalized unconventional geometric quantum gates with high fidelity in an NMR system.Comment: 4 pages, 3 figure

A universal quantum estimator

Almost all computational tasks in the modem computer can be designed from basic building blocks. These building blocks provide a powerful and efficient language for describing algorithms. In quantum computers, the basic building blocks are the quantum gates. In this tutorial, we will look at quantum gates that act on one and two qubits and briefly discuss how these gates can be used in quantum networks

MapSense: Mitigating Inconsistent WiFi Signals using Signal Patterns and Pathway Map for Indoor Positioning

The indoor positioning technology plays a significant role in the scenarios of the Internet of Things (IoT) which require indoor location context. In this paper, the WiFi signals under modern enterprise WiFi infrastructure, signal patterns between coexisting access points (APs) and signals’ correlation with indoor pathway map are investigated to address the problem of inconsistent WiFi signal observations. The sibling signal patterns (SSP) are defined for the first time and processed to generate Beacon APs which have higher confidence in positioning. The spatial signal patterns are used to bring the estimated location into a limited area through signal coverage constraint (SCC). A positioning scheme using SSP and SCC is proposed and shows improved positioning accuracy. The proposed scheme is fully designed, implemented and evaluated in a real-world environment, revealing its effectiveness and efficiency

Composite fermions in a long-range random magnetic field: Quantum Hall effect versus Shubnikov-de Haas oscillations

We study transport in a smooth random magnetic field, with emphasis on composite fermions (CF) near half-filling of the Landau level. When either the amplitude of the magnetic field fluctuations or its mean value $\bar B$ is large enough, the transport is of percolating nature. While at $\bar{B}=0$ the percolation effects enhance the conductivity $\sigma_{xx}$, increasing $\bar B$ (which corresponds to moving away from half-filling for the CF problem) leads to a sharp falloff of $\sigma_{xx}$ and, consequently, to the quantum localization of CFs. We demonstrate that the localization is a crucial factor in the interplay between the Shubnikov-de Haas and quantum Hall oscillations, and point out that the latter are dominant in the CF metal.Comment: 4 pages, RevTe

Effective Mass of the Four Flux Composite Fermion at ν=1/4\nu = 1/4

We have measured the effective mass ($m^*$) of the four flux composite fermion at Landau level filling factor $\nu = 1/4$ ($^4$CF), using the activation energy gaps at the fractional quantum Hall effect (FQHE) states $\nu$ = 2/7, 3/11, and 4/15 and the temperature dependence of the Shubnikov-de Haas (SdH) oscillations around $\nu = 1/4$. We find that the energy gaps show a linear dependence on the effective magnetic field $B_{eff}$ ($\equiv B-B_{\nu=1/4}$), and from this linear dependence we obtain $m^* = 1.0 m_e$ and a disorder broadening $\Gamma \sim$ 1 K for a sample of density $n = 0.87 \times 10^{11}$ /cm$^2$. The $m^*$ deduced from the temperature dependence of the SdH effect shows large differences for $\nu > 1/4$ and $\nu < 1/4$. For $\nu > 1/4$, $m^* \sim 1.0 m_e$. It scales as $\sqrt{B_{\nu}}$ with the mass derived from the data around $\nu =1/2$ and shows an increase in $m^*$ as $\nu \to 1/4$, resembling the findings around $\nu =1/2$. For $\nu < 1/4$, $m^*$ increases rapidly with increasing $B_{eff}$ and can be described by $m^*/m_e = -3.3 + 5.7 \times B_{eff}$. This anomalous dependence on $B_{eff}$ is precursory to the formation of the insulating phase at still lower filling.Comment: 5 pages, 3 figure

Stripe State in the Lowest Landau Level

The stripe state in the lowest Landau level is studied by the density matrix renormalization group (DMRG) method. The ground state energy and pair correlation functions are systematically calculated for various pseudopotentials in the lowest Landau level. We show that the stripe state in the lowest Landau level is realized only in a system whose width perpendicular to the two-dimensional electron layer is smaller than the order of magnetic length.Comment: 4 pages, 6 figures, to appear in J. Phys. Soc. Jpn. vol.73 No.1 (2004

An extensible product structure model for product lifecycle management in the make-to-order environment

This paper presents a product structure model with a semantic representation technique that make the product structure extensible for developing product lifecycle management (PLM) systems that is flexible for make-to-order environment. In the make-to-order business context, each product could have a number of variants with slightly different constitutions to fulfill different customer requirements. All the variants of a family have common characteristics and each variant has its specific features. A master-variant pattern is proposed for building the product structure model to explicitly represent common characteristics and specific features of individual variants. The model is capable of enforcing the consistency of a family structure and its variant structure, supporting multiple product views, and facilitating the business processes. A semantic representation technique is developed that enables entity attributes to be defined and entities to be categorized in a neutral and semantic format. As a result, entity attributes and entity categorization can be redefined easily with its configurable capability for different requirements of the PLM systems. An XML-based language is developed for semantically representing entities and entity categories. A prototype as a proof-of-concept system is presented to illustrate the capability of the proposed extensible product structure model

Coexistence of localized and itinerant electrons in BaFe2X3 (X = S and Se) revealed by photoemission spectroscopy

We report a photoemission study at room temperature on BaFe2X3 (X = S and Se) and CsFe2Se3 in which two-leg ladders are formed by the Fe sites. The Fe 2p core-level peaks of BaFe2X3 are broad and exhibit two components, indicating that itinerant and localized Fe 3d sites coexist similar to KxFe2-ySe2. The Fe 2p core-level peak of CsFe2Se3 is rather sharp and is accompanied by a charge-transfer satellite. The insulating ground state of CsFe2Se3 can be viewed as a Fe2+ Mott insulator in spite of the formal valence of +2.5. The itinerant versus localized behaviors can be associated with the stability of chalcogen p holes in the two-leg ladder structure.Comment: 5 pages, 5 figures, Accepted in publication for Physical Review

A CENTER OF A POLYTOPE: AN EXPOSITORY REVIEW AND A PARALLEL IMPLEMENTATION

ABSTRACT. The solution space of the rectangular linear system Az b, subject to x&gt; 0, is called a polytope. An attempt is made to provide a deeper geometric insight, with numerical examples, into the condensed paper by Lord, et al. [1], that presents an algorithm to compute a center of a polytope. The algorithm is readily adopted for either sequential or parallel computer implementation. The computed center provides an initial feasible solution (interior point) of a linear programming problem. KEY WORDS AND PHRASES. Center of a polytope, consistency check, Euclidean distance, initial feasible solution, linear programming, Moore-Penrose inverse, nonnegative solution