Fusing atomic WW states via quantum Zeno dynamics

We propose a scheme for preparation of large-scale entangled $W$ states based on the fusion mechanism via quantum Zeno dynamics. By sending two atoms belonging to an $n$-atom $W$ state and an $m$-atom $W$ state, respectively, into a vacuum cavity (or two separate cavities), we may obtain a ($n+m-2$)-atom $W$ state via detecting the two-atom state after interaction. The present scheme is robust against both spontaneous emission of atoms and decay of cavity, and the feasibility analysis indicates that it can also be realized in experiment.Comment: 28 pages, 6 figure

Conversion of entangled states with nitrogen-vacancy centers coupled to microtoroidal resonators

We propose efficient schemes for converting three-photon, four-photon and five-photon GHZ state to a $W$ state or Dicke state, respectively with the nitrogen-vacancy (N-V) centers via single-photon input-output process and cross-Kerr nonlinearities. The total success probability can be improved by iterating the conversion process for the case of three-photon and five-photon while it does not require iteration for converting four-photon GHZ state to a $W$ state. The analysis of feasibility shows that our scheme is feasible for current experimental technology.Comment: 11 pages, 6 figure

Four-Dimensional Topological Insulators with Nodal-Line Boundary States

Conventional topological insulators and superconductors have topologically protected nodal points on their boundaries, and the recent interests in nodal-line semimetals only concerned bulk band structures. Here, we present a novel four-dimensional topological insulator protected by an anti-unitary reflection symmetry, whose boundary band has a single $PT$-symmetric nodal line with double topological charges. Inspired by the recent experimental realization of the four-dimensional quantum Hall effect, we also propose a cold-atom system which realizes the novel topological insulator with tunable parameters as extra dimensions.Comment: 5 pages and 3 figures for main text, 10 pages and 2 figures for supplemental materia

Geometric Quantization of free fields in space of motions

Via K$\ddot{a}$hker polarization we geometrically quantize free fields in the spaces of motions, namely the space of solutions of equations of motion. We obtain the correct results just as that given by the canonical quantization. Since we follow the method of covariant symplectic current proposed by Crnkovic, Witten and Zuckerman et al, the canonical commutator we obtained are naturally invariant under proper Lorentz transformation and the discrete parity and time transverse transformations, as well as the equations of motion.Comment: Latex, 14 page

Classical Geometric Interaction- picture-like Description

In order to get the classical analogue of quantum interaction picture in classical symplectic geometric description, the space of solutions of free equations of motion is suggested to replace the phase space in $T^{*}Q$ description or the space of motions in usual classical symplectic geometric description. The way to determine measured values of observables in this scheme is worked out.Comment: 8 pages, no figures, changed muc

Enhanced exciton transmission by quantum-jump-based feedback

With rotating-wave approximation (RWA), we show in this paper that exciton transmission in a one-dimensional two-level molecule chain embedded in a cavity can be enhanced or suppressed by strong cavity-chain couplings. This exciton transmission is closely related to the number of molecules and the distribution of molecular exciton energy. In addition, we propose a proposal to enhance the exciton transmission by quantum-jump-based feedback. These results may find applications in experiments of exciton transmission in organic materials.Comment: 8 pages, 8 figure

Engineering the coupling between Majorana bound states

We study the coupling between Majorana bound states (CMBS), which is mediated by a topologically trivial chain in the presence of pairing coupling and long-range coupling. The results show that CMBS can be enhanced by the pairing coupling and long-range coupling of the trivial chain. When driving the trivial chain by periodic driving field, we deduce the analytical expressions of CMBS in the high-frequency limit, and demonstrate that CMBS can be modulated by the frequency and amplitude of driving field. Finally we exhibit the application of tunable CMBS in realizing quantum logic gates.Comment: 8 pages, 8 figure

Strategic Asset Seeking and Innovation Performance: The Role of Innovation Capabilities and Host Country Institutions

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Ground-state blockade of Rydberg atoms and application in entanglement generation

We propose a mechanism of ground-state blockade between two $N$-type Rydberg atoms in virtue of Rydberg-antiblockade effect and Raman transition. Inspired by the quantum Zeno effect, the strong Rydberg antiblockade interaction plays a role in frequently measuring one ground state of two, leading to a blockade effect for double occupation of the corresponding quantum state. By encoding the logic qubits into the ground states, we efficiently avoid the spontaneous emission of the excited Rydberg state, and maintain the nonlinear Rydberg-Rydberg interaction at the same time. As applications, we discuss in detail the feasibility of preparing two-atom and three-atom entanglement with ground-state blockade in closed system and open system, respectively, which shows that a high fidelity of entangled state can be obtained with current experimental parameters

Variability and spectral variation of 3C 66A

3C 66A was monitored by the BATC(Beijing-Arizona-Taipei-Connecticut) telescope from 2005 to 2008,1994 observations were obtained on 89 nights. Detailed research and analysis was performed on these observations in this paper. A long term burst occurred in the whole light curve. No intra-day variability was claimed in our campaign by intra-night light curve analysis. Time lag of shorter wavelenth preceding longer wavelength was shown by correlation analysis. The results showed that the optical spectral shape turned flatter when the source brightened, and the spectral variability indicator was bigger on shorter time-scale as determined by the color indices variation analysis.Comment: 11 pages, 6 figures. arXiv admin note: text overlap with arXiv:1001.5206 by other author