1,354 research outputs found
A quantum protocol to win the graph colouring game on all Hadamard graphs
This paper deals with graph colouring games, an example of pseudo-telepathy,
in which two provers can convince a verifier that a graph is -colourable
where is less than the chromatic number of the graph. They win the game if
they convince the verifier. It is known that the players cannot win if they
share only classical information, but they can win in some cases by sharing
entanglement. The smallest known graph where the players win in the quantum
setting, but not in the classical setting, was found by Galliard, Tapp and Wolf
and has 32,768 vertices. It is a connected component of the Hadamard graph
with . Their protocol applies only to Hadamard graphs where
is a power of 2. We propose a protocol that applies to all Hadamard graphs.
Combined with a result of Frankl, this shows that the players can win on any
induced subgraph of having 1609 vertices, with . Combined with a
result of Frankl and Rodl, our result shows that all sufficiently large
Hadamard graphs yield pseudo-telepathy games.Comment: 5pag
Configuration determination for chiral and polar crystals by anisotropic NMR shift
We propose a method to perform a configuration determination for chiral
and/or polar crystals by utilizing anisotropy of NMR shift. The chirality
(handedness) or polarity of a crystal, that is characterized by its sign, can
be extracted from the asymmetric magnetic-field angle dependence of NMR shift
in the appropriate plane, as the configuration is reflected in the off-diagonal
components of the shift tensor. This method is applicable to the triclinic,
monoclinic, and trigonal crystal structures among 230 crystallographic space
groups, and the appropriate planes to extract the asymmetric field-angle
dependence are tabulated for all relevant space groups. We discuss how to
determine the appropriate plane, and to identify each contribution of twin
domains, and so on, by using the specific examples of Te, IrSn and
RhSn, and the spontaneous symmetry-breaking phases of URhSn. We also
argue that an absolute-configuration determination is also possible in
accordance with the relation between chirality or polarity of crystal and the
sign of the relevant off-diagonal component of the shift tensor, provided by
theoretical evaluation of internal magnetic field from surrounding ions, and/or
by experimental input on the shape of the asymmetric etch pit on the cleaved
face of crystal.Comment: 12 pages, 7 figures, 5 table
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