Entangled two atoms through different couplings and the thermal noise

The entanglement of two atoms is studied when the two atoms are coupled to a single-mode thermal field with different couplings. The different couplings of two atoms are in favor of entanglement preparation: it not only makes the case of absence entanglement with same coupling appear entanglement, but also enhances the entanglement with the increasing of the relative difference of two couplings. We also show that the diversity of coupling can improved the critical temperature. If the optical cavity is leaky during the time evolution, the dissipative thermal environment is benefit to produce the entanglement.Comment: 4 pages, 4 figure

What Fraction of Gravitational Lens Galaxies Lie in Groups?

We predict how the observed variations in galaxy populations with environment affect the number and properties of gravitational lenses in different environments. Two trends dominate: lensing strongly favors early-type galaxies, which tend to lie in dense environments, but dense environments tend to have a larger ratio of dwarf to giant galaxies than the field. The two effects nearly cancel, and the distribution of environments for lens and non-lens galaxies are not substantially different (lens galaxies are slightly less likely than non-lens galaxies to lie in groups and clusters). We predict that about 20% of lens galaxies are in bound groups (defined as systems with a line-of-sight velocity dispersion sigma in the range 200 < sigma < 500 km/s), and another roughly 3% are in rich clusters (sigma > 500 km/s). Therefore at least roughly 25% of lenses are likely to have environments that significantly perturb the lensing potential. If such perturbations do not significantly increase the image separation, we predict that lenses in groups have a mean image separation that is about 0.2'' smaller than that for lenses in the field and estimate that 20-40 lenses in groups are required to test this prediction with significance. The tail of the distribution of image separations is already illuminating. Although lensing by galactic potential wells should rarely produce lenses with image separations theta >~ 6'', two such lenses are seen among 49 known lenses, suggesting that environmental perturbations of the lensing potential can be significant. Further comparison of theory and data will offer a direct probe of the dark halos of galaxies and groups and reveal the extent to which they affect lensing estimates of cosmological parameters.Comment: 32 pages, 6 embedded figures; accepted for publication in Ap

Unconditionally verifiable blind computation

Blind Quantum Computing (BQC) allows a client to have a server carry out a quantum computation for them such that the client's input, output and computation remain private. A desirable property for any BQC protocol is verification, whereby the client can verify with high probability whether the server has followed the instructions of the protocol, or if there has been some deviation resulting in a corrupted output state. A verifiable BQC protocol can be viewed as an interactive proof system leading to consequences for complexity theory. The authors, together with Broadbent, previously proposed a universal and unconditionally secure BQC scheme where the client only needs to be able to prepare single qubits in separable states randomly chosen from a finite set and send them to the server, who has the balance of the required quantum computational resources. In this paper we extend that protocol with new functionality allowing blind computational basis measurements, which we use to construct a new verifiable BQC protocol based on a new class of resource states. We rigorously prove that the probability of failing to detect an incorrect output is exponentially small in a security parameter, while resource overhead remains polynomial in this parameter. The new resource state allows entangling gates to be performed between arbitrary pairs of logical qubits with only constant overhead. This is a significant improvement on the original scheme, which required that all computations to be performed must first be put into a nearest neighbour form, incurring linear overhead in the number of qubits. Such an improvement has important consequences for efficiency and fault-tolerance thresholds.Comment: 46 pages, 10 figures. Additional protocol added which allows arbitrary circuits to be verified with polynomial securit

Brokered Graph State Quantum Computing

We describe a procedure for graph state quantum computing that is tailored to fully exploit the physics of optically active multi-level systems. Leveraging ideas from the literature on distributed computation together with the recent work on probabilistic cluster state synthesis, our model assigns to each physical system two logical qubits: the broker and the client. Groups of brokers negotiate new graph state fragments via a probabilistic optical protocol. Completed fragments are mapped from broker to clients via a simple state transition and measurement. The clients, whose role is to store the nascent graph state long term, remain entirely insulated from failures during the brokerage. We describe an implementation in terms of NV-centres in diamond, where brokers and clients are very naturally embodied as electron and nuclear spins.Comment: 5 pages, 3 figure

Structure and physical properties of the noncentrosymmetric superconductor Mo3 Al2 C

We have synthesized polycrystalline samples of the noncentrosymmetric superconductor Mo3 Al2 C by arc and RF melting, measured its transport, magnetic and thermodynamic properties, and computed its band structure. Experimental results indicate a bulk superconducting transition at Tc ∼9.2 K while the density of states at the Fermi surface is found to be dominated by Mod orbitals. Using the measured values for the lower critical field Hc1, upper critical field Hc2, and the specific heat C, we estimated the thermodynamic critical field Hc(0), coherence length ξ (0), penetration depth λ (0), and the Ginzburg-Landau parameter κ (0). The specific-heat jump at Tc, ΔC/γ Tc =2.14, suggests that Mo3 Al 2 C is moderately to strongly coupled, consistent with the fast opening of the gap, as evidenced by the rapid release of entropy below Tc from our electronic specific-heat measurements. Above 2 K the electronic specific heat exhibits the power-law behavior, suggesting that synthesis of single crystals and measurements at lower temperature are needed to establish whether the gap is anisotropic. The estimated value of the upper critical field H c2 (0) is close to the calculated Pauli limit, therefore further studies are needed to determine whether the absence of an inversion center results in a significant admixture of the triplet component of the order parameter. © 2010 The American Physical Society

How the Kano model contributes to Kansei engineering in services

Recent studies show that products and services hold great appeal if they are attractively designed to elicit emotional feelings from customers. Kansei engineering (KE) has good potential to provide a competitive advantage to those able to read and translate customer affect and emotion in actual product and services. This study introduces an integrative framework of the Kano model and KE, applied to services. The Kano model was used and inserted into KE to exhibit the relationship between service attribute performance and customer emotional response. Essentially, the Kano model categorises service attribute quality into three major groups (must-be [M], one-dimensional [O] and attractive [A]). The findings of a case study that involved 100 tourists who stayed in luxury 4- and 5-star hotels are presented. As a practical matter, this research provides insight on which service attributes deserve more attention with regard to their significant impact on customer emotional needs. Statement of Relevance: Apart from cognitive evaluation, emotions and hedonism play a big role in service encounters. Through a focus on delighting qualities of service attributes, this research enables service providers and managers to establish the extent to which they prioritise their improvement efforts and to always satisfy their customer emotions beyond expectation. Keywords: Kansei engineering, emotional feelings, Kano model, service

Effect of under-reinforcement on the flexural strength of corroded beams

Reinforced concrete beams are normally designed as under-reinforced to provide ductile behaviour i.e. the tensile moment of resistance, Mt(0) is less than the moment of resistance of the compressive zone, Mc. The degree of under-reinforcement (Mt(0)/Mc ratio) can depend upon the preferences of the designer in complying with design and construction constraints, codes and availability of steel reinforcement diameters and length. Mt(0)/Mc is further influenced during service life by corrosion which decreases Mt(0). The paper investigates the influence of Mt(0)/Mc on the residual flexural strength of corroded beams and determines detailing parameters (e.g. size and percentage of steel reinforcement, cover) on Mt(0)/Mc. Corroded reinforced concrete beams (100 mm · 150 mm deep) with varying Mt(0)/Mc ratios were tested in flexure. The results of the investigation were combined with the results of similar work by other researchers and show that beams with lower Mt(0)/Mc ratios suffer lower flexural strength loss when subjected to tensile reinforcement corrosion. Cover to the main steel does not directly influence Mt(0)/Mc and, thus, the residual flexural strength of corroded beams is not normally affected by increased cover. A simplified expression for estimating the residual strength of corroded beams is also given

Teleportation-based realization of an optical quantum two-qubit entangling gate

In recent years, there has been heightened interest in quantum teleportation, which allows for the transfer of unknown quantum states over arbitrary distances. Quantum teleportation not only serves as an essential ingredient in long-distance quantum communication, but also provides enabling technologies for practical quantum computation. Of particular interest is the scheme proposed by Gottesman and Chuang [Nature \textbf{402}, 390 (1999)], showing that quantum gates can be implemented by teleporting qubits with the help of some special entangled states. Therefore, the construction of a quantum computer can be simply based on some multi-particle entangled states, Bell state measurements and single-qubit operations. The feasibility of this scheme relaxes experimental constraints on realizing universal quantum computation. Using two different methods we demonstrate the smallest non-trivial module in such a scheme---a teleportation-based quantum entangling gate for two different photonic qubits. One uses a high-fidelity six-photon interferometer to realize controlled-NOT gates and the other uses four-photon hyper-entanglement to realize controlled-Phase gates. The results clearly demonstrate the working principles and the entangling capability of the gates. Our experiment represents an important step towards the realization of practical quantum computers and could lead to many further applications in linear optics quantum information processing.Comment: 10 pages, 6 figure