A conditional quantum phase gate between two 3-state atoms

We propose a scheme for conditional quantum logic between two 3-state atoms that share a quantum data-bus such as a single mode optical field in cavity QED systems, or a collective vibrational state of trapped ions. Making use of quantum interference, our scheme achieves successful conditional phase evolution without any real transitions of atomic internal states or populating the quantum data-bus. In addition, it only requires common addressing of the two atoms by external laser fields.Comment: 8 fig

Observation of momentum-confined in-gap impurity state in Ba0.6_{0.6}K0.4_{0.4}Fe2_2As2_2: evidence for anti-phase s±s_{\pm} pairing

We report the observation by angle-resolved photoemission spectroscopy of an impurity state located inside the superconducting gap of Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ and vanishing above the superconducting critical temperature, for which the spectral weight is confined in momentum space near the Fermi wave vector positions. We demonstrate, supported by theoretical simulations, that this in-gap state originates from weak non-magnetic scattering between bands with opposite sign of the superconducting gap phase. This weak scattering, likely due to off-plane Ba/K disorders, occurs mostly among neighboring Fermi surfaces, suggesting that the superconducting gap phase changes sign within holelike (and electronlike) bands. Our results impose severe restrictions on the models promoted to explain high-temperature superconductivity in these materials.Comment: 8 pages, 5 figures. Accepted for publication in Physical Review

Suppression of the superconducting energy gap in intrinsic Josephson junctions of Bi2Sr2CaCu2O8+δ\mathbf{Bi_2Sr_2CaCu_2O_{8+\delta}} single crystals

We have observed back-bending structures at high bias current in the current-voltage curves of intrinsic Josephson junctions. These structures may be caused by nonequilibrium quasiparticle injection and/or Joule heating. The energy gap suppression varies considerably with temperature. Different levels of the suppression are observed when the same level of current passes through top electrodes of different sizes. Another effect which is seen and discussed, is a super-current ``reentrance'' of a single intrinsic Josephson junction with high bias current.Comment: accepted by Supercond. Sci. and Tech., 200

Acoustic black holes from supercurrent tunneling

We present a version of acoustic black holes by using the principle of the Josephson effect. We find that in the case two superconductors $A$ and $B$ are separated by an insulating barrier, an acoustic black hole may be created in the middle region between the two superconductors. We discuss in detail how to describe an acoustic black hole in the Josephson junction and write the metric in the langauge of the superconducting electronics. Our final results infer that for big enough tunneling current and thickness of the junction, experimental verification of the Hawking temperature could be possible.Comment: 15pages,1 figure, to appear in IJMP

Resonant peak splitting for ballistic conductance in magnetic superlattices

We investigate theoretically the resonant splitting of ballistic conductance peaks in magnetic superlattices. It is found that, for magnetic superlattices with periodically arranged $n$ identical magnetic-barriers, there exists a general $(n-1)$-fold resonant peak splitting rule for ballistic conductance, which is the analogy of the $(n-1)$-fold resonant splitting for transmission in $n$-barrier electric superlattices (R. Tsu and L. Esaki, Appl. Phys. Lett. {\bf 22}, 562 (1973)).Comment: 9 pages, 3 figures, latex forma

Quantum logic between atoms inside a high Q optical cavity

We propose a protocol for conditional quantum logic between two 4-state atoms inside a high Q optical cavity. The process detailed in this paper utilizes a direct 4-photon 2-atom resonant process and has the added advantage of commonly addressing the two atoms when they are inside the high Q optical cavity.Comment: 8 pages, 3 figs. submitte

Development of Chengdu and sustainable utilization of the ancient Dujiangyan Water-Conservancy Project

The Dujiangyan Water-Conservancy Project is a great water irrigation works in Chinese cultural history, which led the Min River water to the vast Chengdu Plain, and created fertile and pretty "land of abundance". Now Chengdu is facing increased water demand stress due mainly to rapid urbanization. This paper first analyses the available water resources of Chengdu based on historical hydrological data from 1964 to 2008. The results show that the average annual water resources were 8.9 billion m3 in 1986 and 7.9 billion m3 in 2008 under various environmental conditions. The future tendency of water demand in city development planning is predicted by the Policy Dialogue Model (PODIUM). Finally, the strategies for water resources exploitation accompanying the sustainable development pattern are studied. The result illustrates that rational and careful management are required to balance the gap between water supply and deman

Entanglement, quantum phase transition and scaling in XXZ chain

Motivated by recent development in quantum entanglement, we study relations among concurrence $C$, SU$_q$(2) algebra, quantum phase transition and correlation length at the zero temperature for the XXZ chain. We find that at the SU(2) point, the ground state possess the maximum concurrence. When the anisotropic parameter $\Delta$ is deformed, however, its value decreases. Its dependence on $\Delta$ scales as $C=C_0-C_1(\Delta-1)^2$ in the XY metallic phase and near the critical point (i.e. $1<\Delta<1.3$) of the Ising-like insulating phase. We also study the dependence of $C$ on the correlation length $\xi$, and show that it satisfies $C=C_0-1/2\xi$ near the critical point. For different size of the system, we show that there exists a universal scaling function of $C$ with respect to the correlation length $\xi$.Comment: 4 pages, 3 figures. to appear in Phys. Rev.