Full quantum theory of control-not gate in ion-trap quantum computation

We investigate the exact effect on ion trap quantum computation after field quantization. First an exact expression of failure probability from field quantization after many CNOT operations in Cirac-Zoller scheme is given. It is proportional to operation number and the amplitude of $|1\rangle_x |0\rangle_y$ or $|1\rangle_x |1\rangle_y$ in initial state, and inverse proportional to mean number of photons and amplitude of $|0\rangle_x |0\rangle_y$ or $|0\rangle_x |1\rangle_y$ in initial state. Then we calculate the failure probability when the limitation to mean number of photons in sideband transition is considered. When the initial state is $|1\rangle_x |0\rangle_y$ or $|1\rangle_x |1\rangle_y$, after about $10^2$ times of CNOT operations, failure probability is no less than $10^{-2}$, while $10^{-2}$ is the known maximum threshold in fault-tolerant quantum computation. Then when the initial state is $|1\rangle_x |0\rangle_y$ or $|1\rangle_x |1\rangle_y$, the number of CNOT gates on the same pair of physical qubits should be no more than $10^2$ in one error-correction period, or else the computation cannot be implemented reliably. This conclusion can help to determine the number of CNOT operations between coding and decoding in one error-correction period in fault-tolerant quantum computation.Comment: 23 pages, 6 figure

L2L^2 Forms and Ricci flow with bounded curvature on Complete Non-compact manifolds

In this paper, we study the evolution of $L^2$ one forms under Ricci flow with bounded curvature on a non-compact Rimennian manifold. We show on such a manifold that the $L^2$ norm of a smooth one form with compact support is non-increasing along the Ricci flow with bounded curvature. The $L^{\infty}$ norm is showed to have monotonicity property too. Then we use $L^{\infty}$ cohomology of one forms with compact support to study the singularity model for the Ricci flow on $S^1\times \mathbb{R}^{n-1}$.Comment: 11 page

Application of EOS-ELM with binary Jaya-based feature selection to real-time transient stability assessment using PMU data

Recent studies show that pattern-recognition-based transient stability assessment (PRTSA) is a promising approach for predicting the transient stability status of power systems. However, many of the current well-known PRTSA methods suffer from excessive training time and complex tuning of parameters, resulting in inefficiency for real-time implementation and lacking the online model updating ability. In this paper, a novel PRTSA approach based on an ensemble of OS-extreme learning machine (EOSELM) with binary Jaya (BinJaya)-based feature selection is proposed with the use of phasor measurement units (PMUs) data. After briefly describing the principles of OS-ELM, an EOS-ELM-based PRTSA model is built to predict the post-fault transient stability status of power systems in real time by integrating OS-ELM and an online boosting algorithm, respectively, as a weak classifier and an ensemble learning algorithm. Furthermore, a BinJaya-based feature selection approach is put forward for selecting an optimal feature subset from the entire feature space constituted by a group of system-level classification features extracted from PMU data. The application results on the IEEE 39-bus system and a real provincial system show that the proposal has superior computation speed and prediction accuracy than other state-of-the-art sequential learning algorithms. In addition, without sacrificing the classification performance, the dimension of the input space has been reduced to about one-third of its initial value.Comment: Accepted by IEEE Acces

Research on Information Security Enhancement Approaches and the Applications on HCI Systems

With rapid development of computer techniques, the human computer interaction scenarios are becoming more and more frequent. The development history of the human-computer interaction is from a person to adapt to the computer to the computer and continually adapt to the rapid development. Facing the process of human-computer interaction, information system daily operation to produce huge amounts of data, how to ensure human-computer interaction interface clear, generated data safe and reliable, has become a problem to be solved in the world of information. To deal with the challenging, we propose the information security enhancement approaches and the core applications on HCI systems. Through reviewing the other state-of-the-art methods, we propose the data encryption system to deal with the issues that uses mixed encryption system to make full use of the symmetric cipher algorithm encryption speed and encryption intensity is high while the encryption of large amounts of data efficiently. Our method could enhance the general safety of the HCI system, the experimental result verities the feasibility and general robustness of our approach

Optimized spin-injection efficiency and spin MOSFET operation based on low-barrier ferromagnet/insulator/n-Si tunnel contact

We theoretically investigate the spin injection in different FM/I/n-Si tunnel contacts by using the lattice NEGF method. We find that the tunnel contacts with low barrier materials such as TiO$_2$ and Ta$_{2}$O$_{5}$, have much lower resistances than the conventional barrier materials, resulting in a wider and attainable optimum parameters window for improving the spin injection efficiency and MR ratio of a vertical spin MOSFET. Additionally, we find the spin asymmetry coefficient of TiO$_2$ tunnel contact has a negative value, while that of Ta$_{2}$O$_{5}$ contact can be tuned between positive and negative values, by changing the parameters

Optical Absorption Spectra of Electrically Gated Bilayer Graphene

The electronic structure and optical response of electrically gated bilayer graphene are studied by first-principles approaches. We have obtained the induced band gap that is in good agreement with experiment when the applied electric field is less than 1.5 V/nm. The infrared optical absorbance is calculated within the single-particle excitation picture and its fine structures are presented. In addition, the calculated infrared optical absorbance is found to be strongly depending on stacking styles of bilayer graphene and the polarization direction of the incident light, which provides efficient ways to identify the electric-field intensity and stacking styles in experiment. Finally, many-electron effects are discussed.Comment: 7 pages and 6 figure

A new complete Calabi-Yau metric on C3\mathbb{C}^3

Motivated by the study of collapsing Calabi-Yau threefolds with a Lefschetz K3 fibration, we construct a complete Calabi-Yau metric on $\mathbb{C}^3$ with maximal volume growth, which in the appropriate scale is expected to model the collapsing metric near the nodal point. This new Calabi-Yau metric has singular tangent cone at infinity, and its Riemannian geometry has certain non-standard features near the singularity of the tangent cone $\mathbb{C}^2/\mathbb{Z}_2 \times \mathbb{C}$, which are more typical of adiabatic limit problems. The proof uses an existence result in H-J. Hein's PhD thesis to perturb an asymptotic approximate solution into an actual solution, and the main difficulty lies in correcting the slowly decaying error terms

Full quantum treatment of Rabi oscillation driven by a pulse train and its application in ion-trap quantum computation

Rabi oscillation of a two-level system driven by a pulse train is a basic process involved in quantum computation. We present a full quantum treatment of this process and show that the population inversion of this process collapses exponentially, has no revival phenomenon, and has a dual-pulse structure in every period. As an application, we investigate the properties of this process in ion-trap quantum computation. We find that in the Cirac--Zoller computation scheme, when the wavelength of the driving field is of the order $10^{-6}$ m, the lower bound of failure probability is of the order $10^{-2}$ after about $10^2$ controlled-NOT gates. This value is approximately equal to the generally-accepted threshold in fault-tolerant quantum computation.Comment: 22 pages, 5 figur

Universal Correlation between Critical Temperature of Superconductivity and band structure features

The critical temperature (${T}_\text{c}$) of superconductors varies a lot. The factors governing the ${T}_\text{c}$ may hold key clues to understand the nature of the superconductivity. Thereby, ${T}_\text{c}$-involved correlations, such as Matthias laws, Uemura law, and cuprates doping phase diagrams, have been of great concern. However, the electronic interaction being responsible for the carriers pairing in high-${T}_\text{c}$ superconductors is still not clear, which calls for more comprehensive analyses of the experimental data in history. In this work, we propose a novel perspective for searching material gene parameters and ${T}_\text{c}$-involved correlations. By exploring holistic band structure features of diverse superconductors, we found a universal correlation between the ${T}_\text{c}$ maxima and the electron energy levels for all kinds of superconducting materials. It suggests that the ${T}_\text{c}$ maxima are determined by the energy level of secondary-outer orbitals, rather than the band structure nearby the Fermi level. The energy level of secondary-outer orbitals is a parameter corresponding to the ratio of atomic orbital hybridization, implying that the fluctuation of the orbital hybridization is another candidate of pairing glue

Quantum no-key protocol for direct and secure transmission of quantum and classical messages

We present a quantum no-key protocol for direct and secure transmission of quantum and classical messages based on simple Boolean function computation with several quantum gates and Shamir's interactive idea of classical message encryption. This protocol has inherent personal identification and message authentication. It probably is the first quantum protocol that can resist the man-in-the-middle attack by itself