Rheological study of structural transitions in triblock copolymers in a liquid crystal solvent

Rheological properties of triblock copolymers dissolved in a nematic liquid crystal (LC) solvent demonstrate that their microphase separated structure is heavily influenced by changes in LC order. Nematic gels were created by swelling a well-defined, high molecular weight ABA block copolymer with the small-molecule nematic LC solvent 4-pentyl-4-cyanobiphenyl (5CB). The B midblock is a side-group liquid crystal polymer (SGLCP) designed to be soluble in 5CB and the A endblocks are polystyrene, which is LC-phobic and microphase separates to produce a physically cross-linked, thermoreversible, macroscopic polymer network. At sufficiently low polymer concentration a plateau modulus in the nematic phase, characteristic of a gel, abruptly transitions to terminal behavior when the gel is heated into its isotropic phase. In more concentrated gels, endblock aggregates persist into the isotopic phase. Dramatic changes in network structure are observed over small temperature windows (as little as 1 °C) due to tccche rapidly changing LC order near the isotropization point. The discontinuous change in solvent quality produces an abrupt change in viscoelastic properties for three polymers having different pendant mesogenic groups and matched block lengths

Aperiodic Quantum Random Walks

We generalize the quantum random walk protocol for a particle in a one-dimensional chain, by using several types of biased quantum coins, arranged in aperiodic sequences, in a manner that leads to a rich variety of possible wave function evolutions. Quasiperiodic sequences, following the Fibonacci prescription, are of particular interest, leading to a sub-ballistic wavefunction spreading. In contrast, random sequences leads to diffusive spreading, similar to the classical random walk behaviour. We also describe how to experimentally implement these aperiodic sequences.Comment: 4 pages and 4 figure

Effects of non-local initial conditions in the Quantum Walk on the line

We report an enhancement of the decay rate of the survival probability when non-local initial conditions in position space are considered in the Quantum Walk on the line. It is shown how this interference effect can be understood analytically by using previously derived results. Within a restricted position subspace, the enhanced decay is correlated with a maximum asymptotic entanglement level while the normal decay rate corresponds to initial relative phases associated to a minimum entanglement level.Comment: 5 pages, 1 figure, Elsevier style, to appear in Physica

Children’s tolerance of word-form variation

How much morphological variation can children tolerate when identifying familiar words? This is an important question in the context of the acquisition of richly inflected languages where identical word forms occur far less frequently than in English. To address this question, we compared children’s (N = 96, mean age 4;1, range 2;11–5;1) and adults’ (N = 96, mean age 21 years) tolerance of word-onset modifications (e.g., for stug: wug and wastug) and pseudoaffixes (e.g., kostug and stugko) in a labelextension task. Word-form modifications were repeated within each experiment to establish productive inflectional patterns. In two experiments, children and adults exhibited similar strategies: they were more tolerant of prefixes (wastug) than substitutions of initial consonants (wug), and more tolerant of suffixes (stugko) than prefixes (kostug). The findings point to word-learning strategies as being flexible and adaptive to morphological patterns in languages

The Bose-Hubbard model is QMA-complete

The Bose-Hubbard model is a system of interacting bosons that live on the vertices of a graph. The particles can move between adjacent vertices and experience a repulsive on-site interaction. The Hamiltonian is determined by a choice of graph that specifies the geometry in which the particles move and interact. We prove that approximating the ground energy of the Bose-Hubbard model on a graph at fixed particle number is QMA-complete. In our QMA-hardness proof, we encode the history of an n-qubit computation in the subspace with at most one particle per site (i.e., hard-core bosons). This feature, along with the well-known mapping between hard-core bosons and spin systems, lets us prove a related result for a class of 2-local Hamiltonians defined by graphs that generalizes the XY model. By avoiding the use of perturbation theory in our analysis, we circumvent the need to multiply terms in the Hamiltonian by large coefficients

Conditional Quantum Walk and Iterated Quantum Games

Iterated bipartite quantum games are implemented in terms of the discrete-time quantum walk on the line. Our proposal allows for conditional strategies, as two rational agents make a choice from a restricted set of two-qubit unitary operations. Several frequently used classical strategies give rise to families of corresponding quantum strategies. A quantum version of the Prisoner's Dilemma in which both players use mixed strategies is presented as a specific example. Since there are now quantum walk physical implementations at a proof-of principle stage, this connection may represent a step towards the experimental realization of quantum games.Comment: Revtex 4, 6 pages, 3 figures. Expanded version with one more figure and updated references. Abstract was rewritte

Asymptotic entanglement in 1D quantum walks with a time-dependent coined

Discrete-time quantum walk evolve by a unitary operator which involves two operators a conditional shift in position space and a coin operator. This operator entangles the coin and position degrees of freedom of the walker. In this paper, we investigate the asymptotic behavior of the coin position entanglement (CPE) for an inhomogeneous quantum walk which determined by two orthogonal matrices in one-dimensional lattice. Free parameters of coin operator together provide many conditions under which a measurement perform on the coin state yield the value of entanglement on the resulting position quantum state. We study the problem analytically for all values that two free parameters of coin operator can take and the conditions under which entanglement becomes maximal are sought.Comment: 23 pages, 4 figures, accepted for publication in IJMPB. arXiv admin note: text overlap with arXiv:1001.5326 by other author

Crystal structure of bis(1,3-bis[{4-methyl-pyridin-2-yl}amido]-1,1,3,3-tetramethyldisiloxane)dichromium dichloride, [(C16H24N4OSi2)CrCl]2

C32H48Cl2Cr2N8O2Si=, monoclinic, P121/n1 (no. 14), a = 12.416(2) Å, b = 13.668(3) Å, c = 13.172(3) Å, β = 113.83(3)°, V= 2044.8 A3, Z = 2, Rgt(F) = 0.052, wRref(F2) = 0.110, T = 200 K. © 2014 Oldenbourg Wissenschaftsverlag GmbH, Rosenheimer Str. 145, 81671 München. All rights reserved

Fast Universal Quantum Computation with Railroad-switch Local Hamiltonians

We present two universal models of quantum computation with a time-independent, frustration-free Hamiltonian. The first construction uses 3-local (qubit) projectors, and the second one requires only 2-local qubit-qutrit projectors. We build on Feynman's Hamiltonian computer idea and use a railroad-switch type clock register. The resources required to simulate a quantum circuit with L gates in this model are O(L) small-dimensional quantum systems (qubits or qutrits), a time-independent Hamiltonian composed of O(L) local, constant norm, projector terms, the possibility to prepare computational basis product states, a running time O(L log^2 L), and the possibility to measure a few qubits in the computational basis. Our models also give a simplified proof of the universality of 3-local Adiabatic Quantum Computation.Comment: Added references to work by de Falco et al., and realized that Feynman's '85 paper already contained the idea of a switch in i